WO2013137422A2 - Electric tool and charging apparatus for electric tool - Google Patents

Electric tool and charging apparatus for electric tool Download PDF

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Publication number
WO2013137422A2
WO2013137422A2 PCT/JP2013/057326 JP2013057326W WO2013137422A2 WO 2013137422 A2 WO2013137422 A2 WO 2013137422A2 JP 2013057326 W JP2013057326 W JP 2013057326W WO 2013137422 A2 WO2013137422 A2 WO 2013137422A2
Authority
WO
WIPO (PCT)
Prior art keywords
charging
electric tool
output
motor
power supply
Prior art date
Application number
PCT/JP2013/057326
Other languages
French (fr)
Other versions
WO2013137422A3 (en
Inventor
Yuki Horie
Nobuhiro Takano
Kazuhiko Funabashi
Tomomasa Nishikawa
Yukihiro Shima
Takao Aradachi
Original Assignee
Hitachi Koki Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Koki Co., Ltd. filed Critical Hitachi Koki Co., Ltd.
Publication of WO2013137422A2 publication Critical patent/WO2013137422A2/en
Publication of WO2013137422A3 publication Critical patent/WO2013137422A3/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/342—The other DC source being a battery actively interacting with the first one, i.e. battery to battery charging

Definitions

  • the present invention relates to an electric tool in which a motor is driven by a built- in secondary battery and, more particularly, to an electric tool which includes a built-in secondary battery and can be charged by a dry cell and a charging device for the electric tool.
  • JP 2006-294310 A discloses a so- called gun-type electric tool in which a motor and a power transmission mechanism are disposed coaxially in a cylindrical body part of a housing and a battery is accommodated in a grip part which extends downward from the rear of the body part.
  • a clutch mechanism as the power transmission mechanism is accommodated in the body part of the housing and, the motor, the power transmission mechanism and an output shaft are arranged side-by-side on the same axis.
  • the battery is a pack type which is detachably attached to the electric tool and is mounted to protrude below the grip part.
  • the battery is the pack type which is detachably attached to the electric tool as disclosed in JP 2006-294310 A, it is possible to realize the electric tool in which the battery can be easily replaced and a predetermined fastening torque is achieved.
  • the heavy battery pack is mounted below the grip part, it is inevitable that the size of the electric tool itself becomes larger. Further, since the battery pack is charged by a dedicated charging device, charging locations have been limited.
  • the present invention has been made to solve the above-described problems and an object of the present invention is to provide an electric tool which has no limitation for usage locations (charging locations). Further, the present invention provides an electric tool which is configured so that a small secondary battery is integrated in and thus an overall length is compact. Another object of the present invention is to provide an electric tool which includes a built-in secondary battery and can be charged by a dry cell and a charging device for the electric tool.
  • Yet another object of the present invention is to provide an electric tool which can be operated without trouble even while being charged by the dry cell and a charging device for the electric tool.
  • An electric tool comprising:
  • a second power supply which is configured to be connected and disconnected from the first power supply and is configured to charge the first power supply in a state where the second power supply is connected to the first power supply.
  • the second power supply is detachably attached to the housing.
  • the housing includes an accommodation part accommodating the motor and a handle part extending from the accommodation part,
  • the first power supply is accommodated in the handle part and,
  • the second power supply is detachably attached to a lower side of the handle part.
  • connection terminal exposed to an outside of the housing and connected to the second power supply
  • a charging stop signal is output from the connection terminal in conjunction with an operation of the switch.
  • the charging stop signal is output when the detection circuit detects the operation of the switch.
  • a current detection part configured to detect current which is flowing in the motor
  • connection terminal exposed to an outside of the housing and connected to the second power supply
  • a charging stop signal is output from the connection terminal in accordance with the current value detected by the current detection part.
  • the second power supply includes a dry cell and a booster circuit for boosting an output of the dry cell
  • the first power supply is charged by the output of the booster circuit.
  • the first power supply includes a secondary cell and a protective circuit configured to output a protective signal for protecting the secondary cell
  • the second power supply includes a charging circuit configured to charge the first power supply
  • the protective signal from the protective circuit is input to the charging circuit.
  • An electric tool comprising:
  • a trigger switch configured to control a rotation of the motor
  • a deceleration mechanism configured to decelerate the rotation of the motor
  • a power transmission mechanism configured to drive an output shaft continuously or intermittently by the output of the deceleration mechanism
  • a built-in secondary battery configured to supply drive power to the motor; a housing accommodating the motor, the trigger switch, the deceleration mechanism, the power transmission mechanism and the built-in secondary batter;
  • connection terminal configured to be connected to an external charging device to charge the secondary battery
  • the charging stop signal is output to the charging device via the connection terminal.
  • the electric tool according to (11) or (12) further comprising a protective circuit configured to protect charging or/and discharging of the secondary battery,
  • the charging stop signal is output when the charging or discharging of the secondary battery is shut-off by the protective circuit.
  • a charging device connected to the connection terminal of the electric tool according to any one of (11) to (14) and supplying power to the electric tool to charge the secondary battery,
  • the charging device monitors the charging stop signal and shuts off the charging of the electric tool when the charging stop signal is output.
  • a booster circuit configured to boost an output voltage of the dry cell which is set in the dry cell holder
  • a housing accommodating the dry cell holder and the booster circuit; and a connector extended from the housing and configured to be connected to the connection terminal.
  • the charging device according to (18) further comprising a constant current circuit configured to maintain constant charging current.
  • a booster circuit configured to boost an output voltage of the secondary cell of the charging device
  • the charging current to the electric tool is shut-off if the current detection circuit detects a current more than the constant charging current.
  • a charging device configured to be connected to a charging terminal of an electric tool in which a secondary battery for driving a motor is integrated and supply power to charge the second battery, the charging device comprising:
  • a current detection circuit configured to monitor charging current to monitor whether or not the motor of the electric tool is started during the charging
  • a output stop circuit configured to stop the supply of power when the current detection circuit detects that the motor is started.
  • a charging system comprising:
  • a charging device configured to charge the secondary battery
  • the electric tool includes a switch for driving the motor and
  • the charging device includes a charge stopping part which stops the charging of the secondary battery in conjunction with an operation of the switch.
  • the second power supply is detachably attached to the housing, it is possible to remove the second power supply when not need.
  • the second power supply since the second power supply is detachably attached to the lower side of the housing, the second power supply does not disturb the work of the electric tool.
  • the second power supply is detachably attached to the lower side of the handle part, it is possible to accommodate the first power supply at a dead space in the handle part. Accordingly, the size of the electric tool is not increased and the second power supply does not disturb the work of the electric tool.
  • the charging stop signal is output from the connection terminal in conjunction with an operation of the switch, it is possible to stop the charging from an external charging device when the charging is performed using the external charging device and thus it is possible to protect the electric tool when equipment such as a dry cell which has a limited discharge current value is used as the power supply of the external charging device. Further, it is possible to prevent that the service life of the dry cell is degraded when the dry cell is used as the power supply of the external charging device.
  • the electric tool further includes the detection circuit for detecting the operation of the switch and the charging stop signal is output when the detection circuit detects the operation of the switch
  • the detection circuit can also be used in a charging stop control of the second battery and a stop control at the time of discharge error. Accordingly, it is possible to perform a charging control with more improved reliability.
  • the charging device can detect independently whether the motor has been started or not. Accordingly, the electric tool which has no function to output the charging stop signal can be charged using the charging device with confidence.
  • the first power supply can be charged by the dry cell and thus usage of the electric tool is spread.
  • the first power supply includes the protective circuit and the protective signal from the protective circuit is input to the charging circuit, it is possible to effectively protect the secondary cell.
  • the protective signal from the protective circuit and the charging stop signal are output from the same output terminal, it is possible to charge the electric tool by the dry cell without increasing the number of the terminals. Accordingly, usage of the electric tool can be further spread.
  • the charging stop signal is generated when the motor is rotated and the charging stop signal is output to the external charging device via the connection terminal, it is possible to stop the charging from an external charging device when the charging is performed using the external charging device and thus it is possible to protect the electric tool when equipment such as a dry cell which has a limited discharge current value is used as the power supply of the external charging device. Further, it is possible to prevent that the service life of the dry cell is degraded when the dry cell is used as the power supply of the external charging device.
  • the charging stop signal is output in conjunction with the output of the trigger switch, it is possible to reliably detect a state where a high current is flowing, such as during rotation of the motor. Accordingly, the charging stop signal with good precision can be output to the external charging device.
  • the electric tool further includes the protective circuit for protecting charging or/and discharging of the secondary battery and the charging stop signal is output when the charging or discharging of the secondary battery is shut-off by the protective circuit
  • the charging stop signal can be used not only in the charging control during rotation of the motor but also in the charging stop control of the second battery and the stop control at the time of discharge error. Accordingly, it is possible to perform a charging control with more improved reliability.
  • the built-in secondary battery is one or more 14500 sized lithium ion cells, it is possible to form a compact housing and thus it is possible to realize a compact and lightweight electric tool which is convenient to use.
  • the external charging device since the external charging device is used which monitors the charging stop signal and shuts off the charging of the electric tool when the charging stop signal is output, it is possible to prevent a high current from flowing to the electric tool from the charging device and thus a stable charging can be performed. Further, since it is possible to avoid a rapid discharge due to the high current when a battery such as a dry cell is used as the power supply of the charging device, degradation in the service life of the cell and reduction in the capacity of the cell can be prevented.
  • the charging device further includes the booster circuit for boosting the output voltage of the dry cell which is set in the dry cell holder, the electric tool can be easily charged using commercially available dry cells. Accordingly, it is possible to charge the electric tool even where there is no AC power.
  • the charging device further includes the housing accommodating the dry cell holder and the booster circuit and the connector is connected to the connection terminal and attached to extend from the housing, the charging device using the dry cells can be directly mounted on the electric tool. Accordingly, the electric tool can be easily handled and used in a state where the charging device is plugged therein.
  • the charging device since the charging device further includes the constant current circuit for maintaining the constant charging current, a rechargeable battery such as a nickel-hydrogen secondary cell of which voltage is lower than that of the dry cell can be used as the power supply of the charging device.
  • a rechargeable battery such as a nickel-hydrogen secondary cell of which voltage is lower than that of the dry cell can be used as the power supply of the charging device.
  • the electric tool since the output of the booster circuit for boosting the output voltage of the secondary cell is supplied to the electric tool, the electric tool can be easily charged using the secondary cell of which voltage is low. Accordingly, it is possible to charge the electric tool even where there is no AC power.
  • the charging device since the charging current to the electric tool is shut-off when the current detection circuit detects an over-charge condition, the charging device can detect independently that the charging state is abnormal and whether the motor has been started or not. Accordingly, the electric tool which has no function to output the charging stop signal can be charged using the charging device with confidence. Further, it is possible to stop charging when the motor is started, even if the function of the electric tool to output the charging stop signal is failed. Accordingly, reliability is improved.
  • the charging system includes the electric tool in which the motor and the secondary battery for driving the motor are integrated and the charging device for charging the secondary battery, the electric tool includes the switch for driving the motor and the charging device includes the charge stopping part which stops the charging of the secondary battery in conjunction with the operation of the switch.
  • Fig. 1 is a longitudinal sectional view showing an internal structure of an electric tool (impact driver 1) according to a first embodiment of the present invention, in a state before a charger 50 is mounted thereon.
  • Fig. 2 is a longitudinal sectional view showing the internal structure of the electric tool (impact driver 1) according to the first embodiment of the present invention, in a state where the charger 50 is mounted thereon.
  • Fig. 3 is a circuit diagram of the impact driver 1 and the charger 50 shown in Fig. 1.
  • Fig. 4 is an operation time chart of the impact driver 1 and the charger 50 shown in
  • Fig. 5 is a circuit diagram of an impact driver 101 and a charger 150 according to a second embodiment of the present invention.
  • Fig. 6 is a circuit diagram of an impact driver 1 and a charger 250 according to a third embodiment of the present invention.
  • Fig. 1 is a view showing an internal structure of an impact driver 1 as an example of an electric tool according to the present invention.
  • the impact driver 1 drives a striking mechanism 20 using a rechargeable battery 4 as a power supply (first power supply) and using a motor 5 as a drive source.
  • the impact driver 1 performs works such as screwing, bolting and drilling by giving a rotational force and a striking force to an output shaft 31 to transmit a rotational striking force continuously or intermittently to a tip tool (not shown) such as a driver bit.
  • a housing in order to minimize the size of the electric tool, a housing has L-shape as seen from the side and thus an overall length of the housing becomes compact.
  • the housing includes a housing body 2 formed from polymer resin such as plastic and a hammer case 3 attached to protrude forward from the housing body 2.
  • the motor 5 is a DC brush motor and rotated by electric energy of the battery 4.
  • an output shaft 5a of the motor 5 is arranged at a motor accommodation part in the housing body 2 in such a way that the output shaft 5 a is not coaxial with the rotating axes (output rotating axes) of the striking mechanism 20 and the output shaft 31 but shifted downward.
  • a second pinion 12 and a third pinion 13 can be arranged above a first pinion 11 which is provided in the output shaft 5a.
  • the rotation number of the motor 5 can be reduced to a predetermined reduction ratio. In this way, a deceleration mechanism to rotate a drive shaft 14 can be realized.
  • the drive shaft 14 are held by two bearing 15, 16 before and after the third pinion 13.
  • the bearings 15, 16 are held together by a solid part (resin part integrally molded of synthetic resin) formed on an inner wall of the housing body 2, the bearing 15 is arranged at a position not to interfere with a cylindrical part of the motor 5. Accordingly, the motor 5 and the deceleration mechanism can be effectively placed in the small housing body 2 and rigidity of a rotary drive system can be increased.
  • the output shaft 31 is placed not in series with the output shaft 5 a of the motor 5 but side-by-side in parallel with the output shaft 5a of the motor 5 in a vertical direction, it is possible to secure a sufficient space for the bearings 15, 16 even within the limited housing dimensions and thus ball bearings with a relatively large diameter can be used. Accordingly, rigidity of the output rotating shaft can be sufficiently enhanced.
  • a forward/re verse selector switch 8 is provided above the motor 5 and also at the rear of the bearing 15 and switches rotation direction of the motor 5.
  • the rotation direction of the motor 5 can be set to a positive rotation direction (fastening direction of a screw or bolt) and a negative rotation direction (loosening direction of the screw or bolt).
  • the forward/reverse selector switch 8 is a three-contact type switch which has a lock position (a position in which the motor 5 does not rotate even when a trigger 6 is pulled), in addition to a positive rotation position and a negative rotation position.
  • the battery 4, a trigger switch 7, the trigger 6 and a protective circuit 41 are accommodated in a grip part (handle part) 2b which is located in the housing body 2 and also below the motor 5.
  • the protective circuit 41 is provided with a connection terminal 12 to which a connector 54 of an external charger 50 is connected.
  • the battery 4 is a 14500 sized lithium ion cell, for example. In the present embodiment, two lithium ion cells are accommodated side-by-side in parallel in a traverse direction (left-right direction) and rated voltage of the series connection thereof is 7.2 V. In Fig. 1 , the batteries 4 arranged in parallel are shown as seen from the right beside and thus only a single battery 4 is visible.
  • the 14500 sized battery 4 has the same size as a so-called A A battery and has a diameter of 14 mm and a length of 50 mm. Accordingly, the battery is sufficiently short enough to be accommodated in the grip part 2b which is gripped by an operator. As a result, the battery 4 can be sufficiently accommodated, even if the motor 5 is offset downward from the output shaft 31 and thus a space within the grip part 2b of the housing body 2 is squeezed, as in the arrangement of the present embodiment. Meanwhile, the number of the batteries 4 to be used is arbitrary and one to four batteries may be arranged in accordance with the required fastening torque of the output shaft 31 and the work duration, etc. Further, the batteries 4 may be connected in series or in parallel, or a combination of the series connection and the parallel connection may be employed.
  • the trigger switch 7 is a limit switch having a lever 7a. As the trigger 6 is pulled by an operator, the lever 7a is pressed to move a plunger 7b and thus ON-state is achieved. Meanwhile, although two-stage on/off switch is used as the trigger switch 7 in the present embodiment, a variable switch which is capable of steplessly changing the rotation number of the motor 5 may be used or a small switch having other shape may be used.
  • the protective circuit 41 is vertically placed between the trigger switch 7 and the batteries 4. A control circuit is mounted on the protective circuit 41.
  • the control circuit performs controls such as monitoring of the batteries 4 which supplies power to the motor 5, interruption of the supply of power to the motor 5 due to an abnormal temperature or over-discharge prevention, etc., and interruption of the supply of power from the charger 50 due to the over-charge prevention.
  • a hexagonal shaft 14a having a hexagonal cross-sectional shape is provided at a front end of the drive shaft 14 and fitted into a hexagonal hole 21a which is provided at a rear end of a spindle 21.
  • a rotational force of the motor 5 is transmitted to the spindle 21 and thus the spindle 21 is rotated in a predetermined speed.
  • the spindle 21 and a hammer 26 are connected to each other by a cam mechanism.
  • the cam mechanism includes a V-shaped spindle cam groove formed at an outer peripheral surface of the spindle 21, a hammer cam groove formed at an inner peripheral surface of the hammer 26 and balls 27 disposed between the spindle cam groove and the hammer cam groove.
  • the hammer 26 is normally urged forward by a spring 23.
  • the hammer 26 When stationary, the hammer 26 is located at a position which is spaced apart from an end surface of an anvil 28 by engagement of the ball 27 and the cam grooves.
  • a rear portion of the spring 23 is held by a pressing member 22 and a front portion thereof is held by a washer 24.
  • An O-ring 25 is disposed between a front side of the washer 24 and the hammer 26 to reduce vibration transmitted to the electric tool at the time of striking.
  • Convex portions (not shown) are symmetrically formed, respectively at two locations on the rotation planes of the hammer 26 and the anvil 28 which face each other.
  • One-touch type mounting part 30 is provided at a leading end (front end) of the output shaft 31.
  • the mounting part 30 is configured so that a hexagonal hole 31 a having a hexagonal cross-sectional shape is provided in the output shaft 31 , a ball 32 which is movable in a radial direction is provided in the hexagonal hole 31a and an outer peripheral side of the ball is pressed by a sleeve 33.
  • the sleeve 33 is movable back and forth along an axial direction of the output shaft 31. Further, the sleeve 33 is formed with a protrusion for restricting the movement of the ball 32 outward in a radial direction and is urged axially rearward by a spring 34.
  • a washer 35 is inserted to a front side of the spring 34.
  • the washer 35 is fixed by a stop ring (C-shaped washer) 36 which is fitted into an annular groove provided at the output shaft.
  • the rotation of the spindle is transmitted to the hammer 26 via a cam mechanism. While the hammer 26 does not make a half-turn, a convex portion of the hammer 26 is engaged with a convex portion of the anvil 28 to rotate the anvil 28. In a case where the relative rotation occurs between the spindle 21 and the hammer 26 by an engagement reaction force at that time, the hammer 26 starts to retreat toward the motor 5 while compressing the spring 23 along the spindle cam groove of the cam mechanism.
  • the hammer 26 As the convex portion of the hammer 26 gets beyond the convex portion of the anvil 28 by the retreating movement of the hammer 26 and thus engagement between these convex portions is released, the hammer 26 is rapidly accelerated in a rotation direction and also in a forward direction by the action of the cam mechanism and elastic energy accumulated in the spring 23, in addition to the rotational force of the spindle 21. Further, the hammer 26 is moved in the forward direction by an urging force of the spring 23 and thus the convex portion of the hammer is again engaged with the convex portion of the anvil 28. In this way, the hammer 26 starts to rotate integrally with the anvil 28.
  • the output shaft 31 is rotatably held by a metal 29 which is placed at an inner peripheral surface of the hammer case 3.
  • the housing body 2 is produced to be divided into left and right by a vertical plane passing through the output rotating axis.
  • the hammer case 3 has an approximately cylindrical shape and is formed at its rear end with a rib 3 a.
  • a continuous groove portion 2c is circumferentially provided at an inner peripheral side of the housing body 2.
  • the hammer case 3 is fixed by fitting the rib 3a into the groove portion 2c.
  • Fig. 1 shows a left housing portion of the housing body 2 and a plurality of screw bosses 19 are formed at the housing body 2.
  • a right housing portion (not shown) of the housing body 2 is paired with the left housing portion and is formed with screw holes.
  • the right housing portion is fixed by a plurality of screws (not shown).
  • the charger 50 is a charging device for charging the battery 4 of the impact driver 1.
  • the charger 50 shown in Fig. 1 is adapted to charge the battery 4 by a power supply (second power supply) which uses commercially available dry cells 50.
  • a power supply second power supply
  • approximately two to four AA alkaline batteries are used as the dry cell 52 and are configured as a pack type. In this way, the dry cell is detachably attached to a main body of the electric tool.
  • the charger 50 which is non-replaceable itself may be manufactured as a disposable.
  • a charging circuit 51 is provided at the charger 50 and thus the charging of the battery 4 is controlled.
  • the charger 50 is accommodated in the housing 53 which covers the dry cell and the charging circuit 51.
  • the connector 54 which is connected to the connection terminal 12 is attached to extend from the housing 53.
  • the connector 54 is connected to the connection terminal 12 via a through- hole 2d in the direction of arrow.
  • Fig. 2 is a longitudinal sectional view showing the internal structure of the electric tool (impact driver 1) according to the first embodiment of the present invention, in a state where the charger 50 is mounted thereon.
  • a charging system includes the impact driver 1 in which the secondary battery is integrated and the charger (charging device) 50 which charges the secondary battery.
  • the overall length of the charger 50 is sufficiently short and thus the electric tool is sufficiently compact even in a state where the charger is attached to a lower side of the grip part 2b of the housing body 2.
  • the axis 45 of the cylindrical dry cell 52 included in the charger 50 is substantially parallel to the axis of the motor 5 and the axis of the output shaft 31.
  • the cordless impact driver 1 it is possible to realize the electric tool (impact driver) which achieves a significant reduction in size and weight without lowering the fastening torque value by the output shaft 31. Thereby, it is easy to carry the electric tool and also it is remarkably easier to work in a confined area.
  • Fig. 3 is a circuit diagram of the impact driver 1 and the charger 50 according to the present embodiment.
  • the connection terminal 12 (see Fig. 1) of the impact driver 1 which is a main body of the electric tool is provided with three terminals for connecting the charger 50 from the outside, that is, a plus terminal 42, a minus terminal 43 and a stop signal output terminal 44.
  • the impact driver 1 is provided with the motor 5 which is connected to the plus terminal 42 and the minus terminal 43 via the trigger switch 7.
  • a trigger detection circuit 11 detects whether the trigger switch 7 is turned on or not and the detection results are output to a stop signal output terminal 44.
  • the motor 5 is driven by the battery 4 which is accommodated in the impact driver 1.
  • the battery 4 is a rechargeable secondary cell such as lithium ion cell, for example.
  • the protective circuit 41 monitors the over-charge condition and the over-discharge condition of the battery 4 to prevent deterioration of the battery 4, thereby extending the service life of the battery 4.
  • the stop signal output terminal 44 is connected to the protective circuit 41 and thus the protective circuit 41 outputs a stop charging signal (that is, predetermined voltage) to the stop signal output terminal 44 regardless of the on/off state of the trigger switch 7. This serves as a charge stopping part.
  • the charger 50 is a charging device for charging the battery 4 of the impact driver 1 using the dry cell 52.
  • the electric tool such as the impact driver 1 uses a dedicated charger which uses a commercial power supply.
  • the charger 50 charges the battery 4 using a widely available dry cell 52.
  • the charger 50 is provided with a cell box 52a in which a plurality of dry cells is provided.
  • the type and number of the dry cell 52 can be arbitrarily selected according to the voltage or capacity of the battery 4, approximately two to four AA alkaline batteries can be used as the dry cell 52 when the battery 4 is composed of two 14500 sized lithium ion cells.
  • the charger 50 mainly includes a booster circuit and an output stop circuit.
  • the booster circuit part includes a diode 59, an inductor 58, a FET 62, resistors 60, 61, 64, 65, a boost control IC 55 and an electrolytic capacitor 71.
  • the IC 55 switches the FET 62 to perform a boosting operation.
  • the booster circuit inputs a value obtained by dividing the output voltage at the resistors 64, 65 to the boost control IC 55 and this value is compared with a reference value stored in the IC 55.
  • the switching of the FET 62 is feedback controlled so that the input voltage value (divided value) is equal to the reference value.
  • the voltage boosted by the switching is rectified at the diode 59 and the electrolytic capacitor 71.
  • a diode 57 serves to prevent reverse current in order to protect the dry cell.
  • the output stop circuit part of the charger 50 includes a resistor 66, a transistor 67, a FET 68, and resistors 69, 70.
  • the output stop circuit is a circuit which receives a signal from the stop signal output terminal 44 of the impact driver 1 and thus stops the supply of the charging current.
  • the base of the transistor 67 drops to a ground level when a source and drain of the FET 68 are in a conductive-state by a high signal from the stop signal output terminal 44 and thus the transistor 67 is turned on.
  • As the transistor 67 is turned on an emitter and a collector of the transistor 67 are in a conductive-state and a voltage value divided by the resistors 64, 66, 65 is input to the boost control IC 55.
  • the resistor 66 Since the resistor 66 is connected in parallel with the resistor 64, the resistance value (combined resistance of the resistor 64 and the resistor 66) of the upper stage is decreased and the divided value of the combined resistance and the resistor 65 is increased. Since the boost control IC 55 controls the FET 62 so that the reference value is constant, the output voltage boosted is set lower than when the transistor 67 is turned off. Charging is stopped by setting the voltage value at that time lower than the voltage of the battery 4 in the tool main body. Further, since the diode 59 is provided, there is no case that current is flowing from the battery 4 in the tool main body toward the charger 50. The electrolytic capacitor 71 is intended to stabilize the output voltage of the booster circuit.
  • a boost voltage (output voltage) Voutl during normal charging (FET68 is turned-off) with no stop signal is represented as (l+R64/R65)xVa
  • a boost voltage Vout2 during charging stop (FET68 is turned-on) with stop signal is represented as (l+(R64xR66/( R64+R66))x(l/R65))xVa.
  • R resistance value
  • Voutl is represented as 2xVa
  • Vout2 is represented as 3/2 Va. That is, the boost voltage is lower during the charging stop with stop signal than during the normal charging with no stop signal. Accordingly, it is possible to stop the charging state of the battery 4 by setting the boost voltage at this time lower than the cell voltage of the battery 4.
  • the connector 54 (see Fig. 1) of the charger 50 is provided with three connection terminals. Specifically, a plus terminal 72 is connected to the plus terminal 42 of the impact driver 1, a minus terminal 73 is connected to the minus terminal 43 and a stop signal input terminal 74 is connected to the stop signal output terminal 44.
  • the connector 54 it is important that the connector 54 (see Fig. 1) has directionality in the plugging direction. Also, it is important that the plus terminal 72 has a shape which cannot be physically plugged in the terminals other than the plus terminal 42 of the impact driver 1.
  • Fig. 4 is a time chart showing the operation of the charger 50. Each graph of Figs. 4 shows horizontal axes as the same time axis. Fig. 4 shows a state where charging has been performed using the charger 50 from time 0 to T7 and three fastening works has been performed using the impact driver 1 during the charging. Fig. 4 shows a trigger signal 81 of the trigger switch 7 in response to the operation of the trigger 6.
  • ON indicates a state where the trigger 6 is pulled
  • OFF indicates a state where the trigger 6 is released.
  • the trigger 6 is pulled at time Tl to operate the impact driver 1 and the trigger 6 is released at time T2.
  • the trigger 6 is pulled at times T3, T5 and the trigger 6 is released at times T4, T6.
  • Fig. 4 shows a stop signal 82 which is supplied to the charger 50 from the impact driver 1 via the stop signal output terminal 44 and the stop signal input terminal 74 of Fig. 3.
  • a vertical axis of Fig. 4 represents a voltage (unit: V).
  • High indicates a predetermined voltage and Low indicates zero voltage.
  • the stop signal becomes High.
  • Fig. 4 shows a charging current 83 which is output from the plus terminal 72 and the minus terminal 73 of the charger 50 and a vertical axis thereof represents a current value (unit: A).
  • the charging current 83 which is supplied to the impact driver 1 from the charger 50 is shut-off while the trigger 6 is pulled.
  • a gate signal of the FET 68 becomes high when the charger 50 receives a stop signal via the stop signal input terminal 74 in the circuit of Fig. 3 and thus the source and drain are in a conductive-state.
  • the base of the transistor 67 drops to the ground and thus the boost voltage becomes lower than the battery voltage. In this way, the charging is stopped.
  • the dry cell has a trend that the capacity which can be extracted becomes smaller as the discharge current is larger.
  • Fig. 4 shows a voltage 84 of the battery 4 (lithium ion cell) which is integrated in the impact driver 1.
  • a vertical axis of Fig. 4 represents a voltage (unit: V).
  • the voltage 84 of the lithium ion cell is gradually increased over time.
  • the trigger 6 is pulled between time Tl and T2, between time T3 and T4 and between the time T5 and T6 and thus the motor 5 of the impact driver 1 is rotated, the battery 4 is discharged and the voltage 84 is decreased over time. Further, at this time, the supply of charging power from the charger 50 is shut-off.
  • the charging is ended at time T7 when the charging is sufficiently completed.
  • an operator can detach the charger 50 from the impact driver 1.
  • the charging end may be determined in such a way that a stop signal is emitted when the protective circuit 41 (see Fig. 3) of the impact driver 1 detects the fully charged state or the charging is stopped when a current detection circuit (not shown) detects that the charging current is lower than a final charging current.
  • other charging end control may be used.
  • the charger 50 since the charger 50 includes the dry cell and the booster circuit in the present embodiment, the charger can be easily used even where there is no AC power. Accordingly, it is possible to realize a small portable charger. Further, if AA battery is used as the dry cell, the dry cell is relatively inexpensive and can be easily available.
  • the housing 53 of the charger 50 is small enough compared to the electric tool, an operator can perform works using the electric tool in a state where the charger 50 is plugged in the electric tool. Even in this state, since the charging from the charger 50 is shut-off when the motor of the electric tool is running, it is possible to eliminate occurrence of discharge state of high current in the dry cell. Accordingly, an effective charging using the dry cell can be realized.
  • a circuit of an impact driver 101 and a charger 150 according to a second embodiment of the present invention will be described with reference to Fig. 5.
  • a stop signal output function of the impact driver 101 is omitted and the connection of the impact driver 101 and the charger 150 is done by only two sets of plus terminals 172, 142 and minus terminals 173, 143.
  • a circuit configuration of the charger 150 has been studied.
  • Other functions of a protective circuit 141 of the impact driver 101 are the same as the protective circuit 41 described in the first embodiment, except that a stop signal output function has been omitted from the protective circuit 141.
  • a voltage may be monitored by the protective circuit 141 and a charging stop signal may be output to the charger 150 side when the over-charge is detected.
  • the circuit configuration of the charger 150 basically includes a booster circuit and a constant current circuit. However, when a current value from the constant current circuit is detected and the detected current value exceeds a predetermined current value, that is, when it is determined that high current is temporarily flowing from the charger 150 side toward the impact driver 101 due to an activation of a motor in a side (impact driver 101) to be charged, the charger 150 is configured to shut-off the charging current.
  • a charging circuit 151 of Fig. 5 will be denoted by the same reference numeral as that of the charging circuit 51 of Fig. 3 and the duplicated explanation thereof will be omitted.
  • the constant current circuit part of the second embodiment includes a constant current circuit 156, a diode 159 and resistors 163, 164, 165. Further, a current detection circuit using an operational amplifier 168 is provided at a rear end side of the constant current circuit 156. The operational amplifier 168 determines whether the current value of the constant current circuit 156 exceeds a predetermined value or not, by inputting a voltage value corresponding to a current value of the constant current circuit 156 and comparing the voltage value and a divided voltage potential corresponding to a reference current value of Vcc divided at the resistors 166, 167.
  • the operational amplifier 168 when the current value exceeds the predetermined value, the operational amplifier 168 causes a FET 174 to make a gate potential of a FET 169 to High and thus a source and drain of the FET 169 are in a non-conductive state. In this way, the supply of charging current to the impact driver 101 is shut-off.
  • a resistor 176 is inserted between the drain and gate of the FET 169 and a resistor 175 is inserted between the source and gate of the FET 174.
  • the operational amplifier 168 is used as an example of a circuit determining whether the current value of the constant current circuit 156 exceeds a predetermined value or not. However, control using a microcomputer may be used.
  • the FET 16 when it is detected by the impact driver 101 that the trigger is pulled and the charging current is suddenly increased, immediately, the FET 16 is shut-off. Accordingly, charging can be automatically stopped even if the stop signal is not received from the electric tool. Further, since the charging current is returned to a normal current value when a fastening work of the impact driver 1 is completed, the operational amplifier 168 causes the FET 169 to be operated again and thus charging can be resumed. Meanwhile, it is also desirable to realize double charging stop control by adding an over-current detection circuit using the operational amplifier 168 of the second embodiment to the first charging circuit 51.
  • the third embodiment has a configuration that a constant current circuit 256 and a shunt resistor 263 are added to the first embodiment and other configuration thereof is the same as the first embodiment. Accordingly, a description of the same configuration as that of the first embodiment will be omitted. Further, the signal, the charging current and the cell voltage waveform are respectively the same as those shown in Fig. 4 and thus a description thereof is omitted.
  • the constant current circuit part of the charger 250 includes the shunt resistor 263 connected to a charging path of the dry cell 52 and the battery 4 and the constant current circuit 256 detecting the charging current from the voltage applied to the shunt resistor 263.
  • the constant current circuit 256 is a known circuit which includes a dedicated IC or an operational amplifier.
  • a boost voltage output voltage becomes lower than the voltage of the battery 4 when a trigger signal (charging stop signal) is input to the charger 250 from the electric tool 1 and the charging is stopped when the electric tool is used.
  • the third embodiment is different from the first embodiment in that the constant current circuit 256 is provided for maintaining a constant charging current.
  • the shunt resistor 263 detects the charging current and the constant current circuit 256 performs a feedback control so that the charging current becomes constant.
  • the constant current circuit 256 is not provided in the first embodiment, the battery 4 is charged with maximum charging current which can be supplied by the dry cell 52 when the battery 4 is charged by the configuration of the first embodiment.
  • the dry cell 52 has a trend that the capacity which can be extracted becomes smaller as the discharge current is larger, that is, maximum capacity of the dry cell 52 cannot be extracted. Accordingly, since the discharge current of the dry cell 52 can be suppressed by controlling the charging current to a constant value by the constant current circuit 256, it is possible to maximally utilize the dry cell 52.
  • the charger 250 of the present embodiment is configured to perform the constant current control.
  • the lithium ion cell is generally charged by a constant current/constant voltage control
  • the boost circuit part corresponds to the constant voltage control part and the constant current circuit corresponds to the constant current control part.
  • the battery 4 is charged by the constant current control.
  • the boost circuit part may maintain (also in a section of the constant current control) the charging voltage and thus the charging current may be gradually decreased.
  • the charging may be stopped when the constant current circuit 256 detects that the charging current after a lapse of a predetermined time from the time T7 becomes lower than a charging stop current value (fully charge current value).
  • the charging may be stopped by turning off the switching operation of the FET 62.
  • a power supply using a nickel-hydrogen dry cell or other secondary cell as the second power supply to charge the battery 4, instead of the dry cell (primary cell).
  • the present invention is not limited to the above-described embodiments and can be variously changed in a range not departing from the spirit thereof.
  • the present invention is not limited to the impact driver and may be applied to other electric tools in which a small-size secondary battery of 14500 size is integrated.
  • a small-size secondary battery of 14500 size such as AA batteries
  • electric energy is 3.96 Wh when two 14500 sized lithium cells (respectively, 3.6 V, 0.55 Ah) are integrated.
  • the present invention is characterized by using a secondary battery of the same size as AA batteries, in particular, integrating the secondary battery in the electric tool.
  • the equipment to be charged is the electric tool and current of the electric tool is varied depending on load condition.
  • the dry cell has a trend that discharge capacity is varied depending on the discharge current, that is, the capacity becomes smaller as the discharge current is larger, the constant current circuit is provided in the charger to control the discharge current to a constant value.
  • charging is stopped while the electric tool is driven.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Secondary Cells (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Portable Power Tools In General (AREA)

Abstract

An electric tool includes: a rechargeable first power supply; an a second power supply which is configured to be connected and disconnected from the first power supply and is configured to charge the first power supply in a state where the second power supply is connected to the first power supply.

Description

DESCRIPTION
TITLE OF INVENTION
ELECTRIC TOOL AND CHARGING APPARATUS FOR ELECTRIC TOOL
TECHNICAL FIELD
The present invention relates to an electric tool in which a motor is driven by a built- in secondary battery and, more particularly, to an electric tool which includes a built-in secondary battery and can be charged by a dry cell and a charging device for the electric tool.
BACKGROUND ART
A handheld electric tool, especially, a cordless electric tool which is driven by the electric energy accumulated in a battery is widely used. In the cordless electric tool, it is required to secure a given running time and a given output and further miniaturization of the electric tool itself is strongly demanded. For example, JP 2006-294310 A discloses a so- called gun-type electric tool in which a motor and a power transmission mechanism are disposed coaxially in a cylindrical body part of a housing and a battery is accommodated in a grip part which extends downward from the rear of the body part. In the conventional electric tool, a clutch mechanism as the power transmission mechanism is accommodated in the body part of the housing and, the motor, the power transmission mechanism and an output shaft are arranged side-by-side on the same axis. The battery is a pack type which is detachably attached to the electric tool and is mounted to protrude below the grip part.
SUMMARY
If the battery is the pack type which is detachably attached to the electric tool as disclosed in JP 2006-294310 A, it is possible to realize the electric tool in which the battery can be easily replaced and a predetermined fastening torque is achieved. However, since the heavy battery pack is mounted below the grip part, it is inevitable that the size of the electric tool itself becomes larger. Further, since the battery pack is charged by a dedicated charging device, charging locations have been limited.
The present invention has been made to solve the above-described problems and an object of the present invention is to provide an electric tool which has no limitation for usage locations (charging locations). Further, the present invention provides an electric tool which is configured so that a small secondary battery is integrated in and thus an overall length is compact. Another object of the present invention is to provide an electric tool which includes a built-in secondary battery and can be charged by a dry cell and a charging device for the electric tool.
Yet another object of the present invention is to provide an electric tool which can be operated without trouble even while being charged by the dry cell and a charging device for the electric tool.
Representative aspects of the invention disclosed herein are as follows.
(1) An electric tool comprising:
a rechargeable first power supply; and
a second power supply which is configured to be connected and disconnected from the first power supply and is configured to charge the first power supply in a state where the second power supply is connected to the first power supply.
(2) The electric tool according to (1), further comprising:
a motor driven by the first power supply; and
a housing for housing the motor,
wherein the second power supply is detachably attached to the housing.
(3) The electric tool according to (2), wherein the second power supply is detachably attached to a lower side of the housing.
(4) The electric tool according to (3), wherein
the housing includes an accommodation part accommodating the motor and a handle part extending from the accommodation part,
the first power supply is accommodated in the handle part and,
the second power supply is detachably attached to a lower side of the handle part.
(5) The electric tool according to (2) further comprising:
a switch configured to control rotation of the motor; and
a connection terminal exposed to an outside of the housing and connected to the second power supply,
wherein a charging stop signal is output from the connection terminal in conjunction with an operation of the switch. (6) The electric tool according to (5) further comprising a detection circuit configured to detect the operation of the switch,
wherein the charging stop signal is output when the detection circuit detects the operation of the switch.
(7) The electric tool according to (2), further comprising:
a current detection part configured to detect current which is flowing in the motor, and
a connection terminal exposed to an outside of the housing and connected to the second power supply,
wherein a charging stop signal is output from the connection terminal in accordance with the current value detected by the current detection part.
(8) The electric tool according to any one of (1) to (7), wherein
the second power supply includes a dry cell and a booster circuit for boosting an output of the dry cell, and
the first power supply is charged by the output of the booster circuit.
(9) The electric tool according to any one of (6) to (8), wherein
the first power supply includes a secondary cell and a protective circuit configured to output a protective signal for protecting the secondary cell,
the second power supply includes a charging circuit configured to charge the first power supply, and
the protective signal from the protective circuit is input to the charging circuit.
(10) The electric tool according to any one of (5) to (9), wherein the protective signal from the protective circuit and the charging stop signal are output from the same output terminal.
(11) An electric tool comprising:
a motor;
a trigger switch configured to control a rotation of the motor;
a deceleration mechanism configured to decelerate the rotation of the motor;
a power transmission mechanism configured to drive an output shaft continuously or intermittently by the output of the deceleration mechanism;
a built-in secondary battery configured to supply drive power to the motor; a housing accommodating the motor, the trigger switch, the deceleration mechanism, the power transmission mechanism and the built-in secondary batter; and
a connection terminal configured to be connected to an external charging device to charge the secondary battery,
wherein a charging stop signal is generated when the motor is rotated, and
wherein the charging stop signal is output to the charging device via the connection terminal.
(12) The electric tool according to (11), wherein the charging stop signal is output in conjunction with the output of the trigger switch.
(13) The electric tool according to (11) or (12) further comprising a protective circuit configured to protect charging or/and discharging of the secondary battery,
wherein the charging stop signal is output when the charging or discharging of the secondary battery is shut-off by the protective circuit.
(14) The electric tool according to (11), wherein the secondary battery is one or more 14500 sized lithium ion cells.
(15) A charging device connected to the connection terminal of the electric tool according to any one of (11) to (14) and supplying power to the electric tool to charge the secondary battery,
wherein the charging device monitors the charging stop signal and shuts off the charging of the electric tool when the charging stop signal is output.
(16) The charging device according to (15), wherein the charging device resumes charging when the output stop state of the charging stop signal has been released.
(17) The charging device according to (16) further comprising:
a dry cell holder; and
a booster circuit configured to boost an output voltage of the dry cell which is set in the dry cell holder,
wherein the output of the booster circuit is supplied to the electric tool.
( 18) The charging device according to ( 17) further comprising:
a housing accommodating the dry cell holder and the booster circuit; and a connector extended from the housing and configured to be connected to the connection terminal.
(19) The charging device according to (18) further comprising a constant current circuit configured to maintain constant charging current.
(20) The charging device according to (16) further comprising:
a secondary cell; and
a booster circuit configured to boost an output voltage of the secondary cell of the charging device,
wherein the output of the booster circuit is supplied to the electric tool.
(21) The charging device according to (19) further comprising a current detection circuit configured to monitor charging current,
wherein the charging current to the electric tool is shut-off if the current detection circuit detects a current more than the constant charging current.
(22) A charging device configured to be connected to a charging terminal of an electric tool in which a secondary battery for driving a motor is integrated and supply power to charge the second battery, the charging device comprising:
a current detection circuit configured to monitor charging current to monitor whether or not the motor of the electric tool is started during the charging; and
a output stop circuit configured to stop the supply of power when the current detection circuit detects that the motor is started.
(23) The charging device according to (22), wherein the supply of power is resumed when the current detection circuit detects that the motor is stopped.
(24) A charging system comprising:
an electric tool in which a motor and a secondary battery for driving the motor are housed; and
a charging device configured to charge the secondary battery,
wherein the electric tool includes a switch for driving the motor and,
wherein the charging device includes a charge stopping part which stops the charging of the secondary battery in conjunction with an operation of the switch. According to the aspect described in (1), since the second power supply is provided to be connected or disconnected from the first power supply and can charge the first power supply in a connection state, it is possible to provide the electric tool in which the first power supply can be charged from the second power supply.
According to the aspect described in (2), since the second power supply is detachably attached to the housing, it is possible to remove the second power supply when not need.
According to the aspect described in (3), since the second power supply is detachably attached to the lower side of the housing, the second power supply does not disturb the work of the electric tool.
According to the aspect described in (4), since the second power supply is detachably attached to the lower side of the handle part, it is possible to accommodate the first power supply at a dead space in the handle part. Accordingly, the size of the electric tool is not increased and the second power supply does not disturb the work of the electric tool.
According to the aspect described in (5), since the charging stop signal is output from the connection terminal in conjunction with an operation of the switch, it is possible to stop the charging from an external charging device when the charging is performed using the external charging device and thus it is possible to protect the electric tool when equipment such as a dry cell which has a limited discharge current value is used as the power supply of the external charging device. Further, it is possible to prevent that the service life of the dry cell is degraded when the dry cell is used as the power supply of the external charging device.
According to the aspect described in (6), since the electric tool further includes the detection circuit for detecting the operation of the switch and the charging stop signal is output when the detection circuit detects the operation of the switch, the detection circuit can also be used in a charging stop control of the second battery and a stop control at the time of discharge error. Accordingly, it is possible to perform a charging control with more improved reliability.
According to the aspect described in (7), since the charging stop signal is output from the connection terminal in accordance with the current value detected by the current detection part, the charging device can detect independently whether the motor has been started or not. Accordingly, the electric tool which has no function to output the charging stop signal can be charged using the charging device with confidence.
According to the aspect described in (8), since the dry cell is used as the second power supply and the first power supply is charged by the output of the booster circuit, the first power supply can be charged by the dry cell and thus usage of the electric tool is spread.
According to the aspect described in (9), since the first power supply includes the protective circuit and the protective signal from the protective circuit is input to the charging circuit, it is possible to effectively protect the secondary cell.
According to the aspect described in (10), since the protective signal from the protective circuit and the charging stop signal are output from the same output terminal, it is possible to charge the electric tool by the dry cell without increasing the number of the terminals. Accordingly, usage of the electric tool can be further spread.
According to the aspect described in (11), since the charging stop signal is generated when the motor is rotated and the charging stop signal is output to the external charging device via the connection terminal, it is possible to stop the charging from an external charging device when the charging is performed using the external charging device and thus it is possible to protect the electric tool when equipment such as a dry cell which has a limited discharge current value is used as the power supply of the external charging device. Further, it is possible to prevent that the service life of the dry cell is degraded when the dry cell is used as the power supply of the external charging device.
According to the aspect described in (12), since the charging stop signal is output in conjunction with the output of the trigger switch, it is possible to reliably detect a state where a high current is flowing, such as during rotation of the motor. Accordingly, the charging stop signal with good precision can be output to the external charging device.
According to the aspect described in (13), since the electric tool further includes the protective circuit for protecting charging or/and discharging of the secondary battery and the charging stop signal is output when the charging or discharging of the secondary battery is shut-off by the protective circuit, the charging stop signal can be used not only in the charging control during rotation of the motor but also in the charging stop control of the second battery and the stop control at the time of discharge error. Accordingly, it is possible to perform a charging control with more improved reliability.
According to the aspect described in (14), since the built-in secondary battery is one or more 14500 sized lithium ion cells, it is possible to form a compact housing and thus it is possible to realize a compact and lightweight electric tool which is convenient to use.
According to the aspect described in (15), since the external charging device is used which monitors the charging stop signal and shuts off the charging of the electric tool when the charging stop signal is output, it is possible to prevent a high current from flowing to the electric tool from the charging device and thus a stable charging can be performed. Further, since it is possible to avoid a rapid discharge due to the high current when a battery such as a dry cell is used as the power supply of the charging device, degradation in the service life of the cell and reduction in the capacity of the cell can be prevented.
According to the aspect described in (16), since the charging device resumes charging when the output stop state of the charging stop signal has been released, it is possible to effectively perform charging while using the electric tool.
According to the aspect described in (17), since the charging device further includes the booster circuit for boosting the output voltage of the dry cell which is set in the dry cell holder, the electric tool can be easily charged using commercially available dry cells. Accordingly, it is possible to charge the electric tool even where there is no AC power.
According to the aspect described in (18), since the charging device further includes the housing accommodating the dry cell holder and the booster circuit and the connector is connected to the connection terminal and attached to extend from the housing, the charging device using the dry cells can be directly mounted on the electric tool. Accordingly, the electric tool can be easily handled and used in a state where the charging device is plugged therein.
According to the aspect described in (19), since the charging device further includes the constant current circuit for maintaining the constant charging current, a rechargeable battery such as a nickel-hydrogen secondary cell of which voltage is lower than that of the dry cell can be used as the power supply of the charging device.
According to the aspect described in (20), since the output of the booster circuit for boosting the output voltage of the secondary cell is supplied to the electric tool, the electric tool can be easily charged using the secondary cell of which voltage is low. Accordingly, it is possible to charge the electric tool even where there is no AC power.
According to the aspect described in (21), since the charging current to the electric tool is shut-off when the current detection circuit detects an over-charge condition, the charging device can detect independently that the charging state is abnormal and whether the motor has been started or not. Accordingly, the electric tool which has no function to output the charging stop signal can be charged using the charging device with confidence. Further, it is possible to stop charging when the motor is started, even if the function of the electric tool to output the charging stop signal is failed. Accordingly, reliability is improved.
According to the aspect described in (22), since it is monitored whether the motor of the electric tool is started or not during the charging by monitoring charging current in the charging device and the charging device is controlled in such a way that the supply of power is stopped when it is detected that the motor is started and the supply of power is resumed when it is detected that the motor is stopped, an over-discharge condition is not caused in the charging device. Accordingly, it is possible to prevent that the service life of the dry cell is degraded, even if a power supply such as the dry cell of which capacity is varied depending on a discharge current is used.
According to the aspect described in (23), since the supply of power is resumed when it is detected that the motor is stopped, it is possible to effectively perform charging while using the electric tool.
According to the aspect described in (24), the charging system includes the electric tool in which the motor and the secondary battery for driving the motor are integrated and the charging device for charging the secondary battery, the electric tool includes the switch for driving the motor and the charging device includes the charge stopping part which stops the charging of the secondary battery in conjunction with the operation of the switch. By this configuration, it is possible to protect the electric tool when equipment such as the dry cell which has a limited discharge current value is used as the power supply of the external charging device. Further, it is possible to prevent that the service life of the dry cell is degraded when the dry cell is used as the power supply of the external charging device.
The foregoing and other objects and features of the present invention will be apparent from the detailed description below and accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a longitudinal sectional view showing an internal structure of an electric tool (impact driver 1) according to a first embodiment of the present invention, in a state before a charger 50 is mounted thereon.
Fig. 2 is a longitudinal sectional view showing the internal structure of the electric tool (impact driver 1) according to the first embodiment of the present invention, in a state where the charger 50 is mounted thereon.
Fig. 3 is a circuit diagram of the impact driver 1 and the charger 50 shown in Fig. 1.
Fig. 4 is an operation time chart of the impact driver 1 and the charger 50 shown in
Fig. 1.
Fig. 5 is a circuit diagram of an impact driver 101 and a charger 150 according to a second embodiment of the present invention.
Fig. 6 is a circuit diagram of an impact driver 1 and a charger 250 according to a third embodiment of the present invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[First Embodiment]
Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following drawings, the same or similar reference numerals are applied to the same or similar parts and elements, and the duplicated description thereof will be omitted. Further, as used herein, a front-rear direction and an upper-lower direction are referred to the directions indicated in the drawings. Fig. 1 is a view showing an internal structure of an impact driver 1 as an example of an electric tool according to the present invention.
The impact driver 1 drives a striking mechanism 20 using a rechargeable battery 4 as a power supply (first power supply) and using a motor 5 as a drive source. The impact driver 1 performs works such as screwing, bolting and drilling by giving a rotational force and a striking force to an output shaft 31 to transmit a rotational striking force continuously or intermittently to a tip tool (not shown) such as a driver bit. In the present embodiment, in order to minimize the size of the electric tool, a housing has L-shape as seen from the side and thus an overall length of the housing becomes compact. The housing includes a housing body 2 formed from polymer resin such as plastic and a hammer case 3 attached to protrude forward from the housing body 2.
The motor 5 is a DC brush motor and rotated by electric energy of the battery 4. In the present embodiment, an output shaft 5a of the motor 5 is arranged at a motor accommodation part in the housing body 2 in such a way that the output shaft 5 a is not coaxial with the rotating axes (output rotating axes) of the striking mechanism 20 and the output shaft 31 but shifted downward. By taking such an arrangement of the motor 5, a second pinion 12 and a third pinion 13 can be arranged above a first pinion 11 which is provided in the output shaft 5a. And, by appropriately setting the gear number of these pinions, the rotation number of the motor 5 can be reduced to a predetermined reduction ratio. In this way, a deceleration mechanism to rotate a drive shaft 14 can be realized. At this time, the drive shaft 14 are held by two bearing 15, 16 before and after the third pinion 13. Although the bearings 15, 16 are held together by a solid part (resin part integrally molded of synthetic resin) formed on an inner wall of the housing body 2, the bearing 15 is arranged at a position not to interfere with a cylindrical part of the motor 5. Accordingly, the motor 5 and the deceleration mechanism can be effectively placed in the small housing body 2 and rigidity of a rotary drive system can be increased. Further, since the output shaft 31 is placed not in series with the output shaft 5 a of the motor 5 but side-by-side in parallel with the output shaft 5a of the motor 5 in a vertical direction, it is possible to secure a sufficient space for the bearings 15, 16 even within the limited housing dimensions and thus ball bearings with a relatively large diameter can be used. Accordingly, rigidity of the output rotating shaft can be sufficiently enhanced.
A forward/re verse selector switch 8 is provided above the motor 5 and also at the rear of the bearing 15 and switches rotation direction of the motor 5. By operating the forward/reverse selector switch 8, the rotation direction of the motor 5 can be set to a positive rotation direction (fastening direction of a screw or bolt) and a negative rotation direction (loosening direction of the screw or bolt). Preferably, the forward/reverse selector switch 8 is a three-contact type switch which has a lock position (a position in which the motor 5 does not rotate even when a trigger 6 is pulled), in addition to a positive rotation position and a negative rotation position.
The battery 4, a trigger switch 7, the trigger 6 and a protective circuit 41 are accommodated in a grip part (handle part) 2b which is located in the housing body 2 and also below the motor 5. The protective circuit 41 is provided with a connection terminal 12 to which a connector 54 of an external charger 50 is connected. The battery 4 is a 14500 sized lithium ion cell, for example. In the present embodiment, two lithium ion cells are accommodated side-by-side in parallel in a traverse direction (left-right direction) and rated voltage of the series connection thereof is 7.2 V. In Fig. 1 , the batteries 4 arranged in parallel are shown as seen from the right beside and thus only a single battery 4 is visible. The 14500 sized battery 4 has the same size as a so-called A A battery and has a diameter of 14 mm and a length of 50 mm. Accordingly, the battery is sufficiently short enough to be accommodated in the grip part 2b which is gripped by an operator. As a result, the battery 4 can be sufficiently accommodated, even if the motor 5 is offset downward from the output shaft 31 and thus a space within the grip part 2b of the housing body 2 is squeezed, as in the arrangement of the present embodiment. Meanwhile, the number of the batteries 4 to be used is arbitrary and one to four batteries may be arranged in accordance with the required fastening torque of the output shaft 31 and the work duration, etc. Further, the batteries 4 may be connected in series or in parallel, or a combination of the series connection and the parallel connection may be employed.
The trigger switch 7 is a limit switch having a lever 7a. As the trigger 6 is pulled by an operator, the lever 7a is pressed to move a plunger 7b and thus ON-state is achieved. Meanwhile, although two-stage on/off switch is used as the trigger switch 7 in the present embodiment, a variable switch which is capable of steplessly changing the rotation number of the motor 5 may be used or a small switch having other shape may be used. The protective circuit 41 is vertically placed between the trigger switch 7 and the batteries 4. A control circuit is mounted on the protective circuit 41. The control circuit performs controls such as monitoring of the batteries 4 which supplies power to the motor 5, interruption of the supply of power to the motor 5 due to an abnormal temperature or over-discharge prevention, etc., and interruption of the supply of power from the charger 50 due to the over-charge prevention.
A hexagonal shaft 14a having a hexagonal cross-sectional shape is provided at a front end of the drive shaft 14 and fitted into a hexagonal hole 21a which is provided at a rear end of a spindle 21. By such a connection condition, a rotational force of the motor 5 is transmitted to the spindle 21 and thus the spindle 21 is rotated in a predetermined speed. The spindle 21 and a hammer 26 are connected to each other by a cam mechanism. The cam mechanism includes a V-shaped spindle cam groove formed at an outer peripheral surface of the spindle 21, a hammer cam groove formed at an inner peripheral surface of the hammer 26 and balls 27 disposed between the spindle cam groove and the hammer cam groove.
The hammer 26 is normally urged forward by a spring 23. When stationary, the hammer 26 is located at a position which is spaced apart from an end surface of an anvil 28 by engagement of the ball 27 and the cam grooves. A rear portion of the spring 23 is held by a pressing member 22 and a front portion thereof is held by a washer 24. An O-ring 25 is disposed between a front side of the washer 24 and the hammer 26 to reduce vibration transmitted to the electric tool at the time of striking. Convex portions (not shown) are symmetrically formed, respectively at two locations on the rotation planes of the hammer 26 and the anvil 28 which face each other. One-touch type mounting part 30 is provided at a leading end (front end) of the output shaft 31. The mounting part 30 is configured so that a hexagonal hole 31 a having a hexagonal cross-sectional shape is provided in the output shaft 31 , a ball 32 which is movable in a radial direction is provided in the hexagonal hole 31a and an outer peripheral side of the ball is pressed by a sleeve 33. The sleeve 33 is movable back and forth along an axial direction of the output shaft 31. Further, the sleeve 33 is formed with a protrusion for restricting the movement of the ball 32 outward in a radial direction and is urged axially rearward by a spring 34. A washer 35 is inserted to a front side of the spring 34. The washer 35 is fixed by a stop ring (C-shaped washer) 36 which is fitted into an annular groove provided at the output shaft. By such a configuration, it is possible to insert or pull out the tip tool from the hexagonal hole 31a of the output shaft 31 while pulling the sleeve 33 axially forward.
As the spindle 21 is rotationally driven, the rotation of the spindle is transmitted to the hammer 26 via a cam mechanism. While the hammer 26 does not make a half-turn, a convex portion of the hammer 26 is engaged with a convex portion of the anvil 28 to rotate the anvil 28. In a case where the relative rotation occurs between the spindle 21 and the hammer 26 by an engagement reaction force at that time, the hammer 26 starts to retreat toward the motor 5 while compressing the spring 23 along the spindle cam groove of the cam mechanism.
As the convex portion of the hammer 26 gets beyond the convex portion of the anvil 28 by the retreating movement of the hammer 26 and thus engagement between these convex portions is released, the hammer 26 is rapidly accelerated in a rotation direction and also in a forward direction by the action of the cam mechanism and elastic energy accumulated in the spring 23, in addition to the rotational force of the spindle 21. Further, the hammer 26 is moved in the forward direction by an urging force of the spring 23 and thus the convex portion of the hammer is again engaged with the convex portion of the anvil 28. In this way, the hammer 26 starts to rotate integrally with the anvil 28. At this time, since a powerful rotational striking force is applied to the anvil 28, the rotational striking force is transmitted to a member to be fastened such as a screw via the tip tool (not shown) mounted to the output shaft 31 integrally formed with the anvil 28. And then, the same operation is repeated and thus the rotational striking force is repeatedly and intermittently transmitted to the member to be fastened from the tip tool.
The output shaft 31 is rotatably held by a metal 29 which is placed at an inner peripheral surface of the hammer case 3. The housing body 2 is produced to be divided into left and right by a vertical plane passing through the output rotating axis. The hammer case 3 has an approximately cylindrical shape and is formed at its rear end with a rib 3 a. A continuous groove portion 2c is circumferentially provided at an inner peripheral side of the housing body 2. The hammer case 3 is fixed by fitting the rib 3a into the groove portion 2c. Fig. 1 shows a left housing portion of the housing body 2 and a plurality of screw bosses 19 are formed at the housing body 2. A right housing portion (not shown) of the housing body 2 is paired with the left housing portion and is formed with screw holes. The right housing portion is fixed by a plurality of screws (not shown).
The charger 50 is a charging device for charging the battery 4 of the impact driver 1. Although an external fast charger using AC power is typically used, the charger 50 shown in Fig. 1 is adapted to charge the battery 4 by a power supply (second power supply) which uses commercially available dry cells 50. In the present embodiment, approximately two to four AA alkaline batteries are used as the dry cell 52 and are configured as a pack type. In this way, the dry cell is detachably attached to a main body of the electric tool. Although it is economical that the dry cell 52 can be replaced with respect to a housing 53, the charger 50 which is non-replaceable itself may be manufactured as a disposable. A charging circuit 51 is provided at the charger 50 and thus the charging of the battery 4 is controlled. The charger 50 is accommodated in the housing 53 which covers the dry cell and the charging circuit 51. The connector 54 which is connected to the connection terminal 12 is attached to extend from the housing 53. The connector 54 is connected to the connection terminal 12 via a through- hole 2d in the direction of arrow.
Fig. 2 is a longitudinal sectional view showing the internal structure of the electric tool (impact driver 1) according to the first embodiment of the present invention, in a state where the charger 50 is mounted thereon. In the present embodiment, a charging system includes the impact driver 1 in which the secondary battery is integrated and the charger (charging device) 50 which charges the secondary battery. It is understood from Fig. 2 that the overall length of the charger 50 is sufficiently short and thus the electric tool is sufficiently compact even in a state where the charger is attached to a lower side of the grip part 2b of the housing body 2. In the present embodiment, the axis 45 of the cylindrical dry cell 52 included in the charger 50 is substantially parallel to the axis of the motor 5 and the axis of the output shaft 31. By this arrangement, an operator can perform works using the impact driver 1 in a state where the charger 50 is plugged in the impact driver.
In the cordless impact driver 1 according to the present embodiment, it is possible to realize the electric tool (impact driver) which achieves a significant reduction in size and weight without lowering the fastening torque value by the output shaft 31. Thereby, it is easy to carry the electric tool and also it is remarkably easier to work in a confined area.
Fig. 3 is a circuit diagram of the impact driver 1 and the charger 50 according to the present embodiment. The connection terminal 12 (see Fig. 1) of the impact driver 1 which is a main body of the electric tool is provided with three terminals for connecting the charger 50 from the outside, that is, a plus terminal 42, a minus terminal 43 and a stop signal output terminal 44. The impact driver 1 is provided with the motor 5 which is connected to the plus terminal 42 and the minus terminal 43 via the trigger switch 7. In the impact driver 1 according to the present embodiment, a trigger detection circuit 11 detects whether the trigger switch 7 is turned on or not and the detection results are output to a stop signal output terminal 44. For example, when the trigger 6 is pulled and thus the trigger switch 7 is turned on, a predetermined voltage is output to the stop signal output terminal 44. And, when the trigger 6 is returned and thus the trigger switch 7 is turned off, the output voltage to the stop signal output terminal 44 becomes zero. The motor 5 is driven by the battery 4 which is accommodated in the impact driver 1. The battery 4 is a rechargeable secondary cell such as lithium ion cell, for example. The protective circuit 41 monitors the over-charge condition and the over-discharge condition of the battery 4 to prevent deterioration of the battery 4, thereby extending the service life of the battery 4. In the present embodiment, the stop signal output terminal 44 is connected to the protective circuit 41 and thus the protective circuit 41 outputs a stop charging signal (that is, predetermined voltage) to the stop signal output terminal 44 regardless of the on/off state of the trigger switch 7. This serves as a charge stopping part.
The charger 50 is a charging device for charging the battery 4 of the impact driver 1 using the dry cell 52. Typically, the electric tool such as the impact driver 1 uses a dedicated charger which uses a commercial power supply. However, under an environment where it is difficult to charge using the commercial power supply, the charger 50 charges the battery 4 using a widely available dry cell 52. The charger 50 is provided with a cell box 52a in which a plurality of dry cells is provided. Although the type and number of the dry cell 52 can be arbitrarily selected according to the voltage or capacity of the battery 4, approximately two to four AA alkaline batteries can be used as the dry cell 52 when the battery 4 is composed of two 14500 sized lithium ion cells.
The charger 50 mainly includes a booster circuit and an output stop circuit. The booster circuit part includes a diode 59, an inductor 58, a FET 62, resistors 60, 61, 64, 65, a boost control IC 55 and an electrolytic capacitor 71. The IC 55 switches the FET 62 to perform a boosting operation. By using the booster circuit in this way, a higher-voltage second cell can be charged from a low-voltage dry cell 52. The booster circuit inputs a value obtained by dividing the output voltage at the resistors 64, 65 to the boost control IC 55 and this value is compared with a reference value stored in the IC 55. And then, the switching of the FET 62 is feedback controlled so that the input voltage value (divided value) is equal to the reference value. The voltage boosted by the switching is rectified at the diode 59 and the electrolytic capacitor 71. A diode 57 serves to prevent reverse current in order to protect the dry cell.
The output stop circuit part of the charger 50 includes a resistor 66, a transistor 67, a FET 68, and resistors 69, 70. The output stop circuit is a circuit which receives a signal from the stop signal output terminal 44 of the impact driver 1 and thus stops the supply of the charging current. The base of the transistor 67 drops to a ground level when a source and drain of the FET 68 are in a conductive-state by a high signal from the stop signal output terminal 44 and thus the transistor 67 is turned on. As the transistor 67 is turned on, an emitter and a collector of the transistor 67 are in a conductive-state and a voltage value divided by the resistors 64, 66, 65 is input to the boost control IC 55. Since the resistor 66 is connected in parallel with the resistor 64, the resistance value (combined resistance of the resistor 64 and the resistor 66) of the upper stage is decreased and the divided value of the combined resistance and the resistor 65 is increased. Since the boost control IC 55 controls the FET 62 so that the reference value is constant, the output voltage boosted is set lower than when the transistor 67 is turned off. Charging is stopped by setting the voltage value at that time lower than the voltage of the battery 4 in the tool main body. Further, since the diode 59 is provided, there is no case that current is flowing from the battery 4 in the tool main body toward the charger 50. The electrolytic capacitor 71 is intended to stabilize the output voltage of the booster circuit. Specifically, when the resistance values of the resistors 64, 66, 65 are respectively represented as R64, R66, R65, a boost voltage (output voltage) Voutl during normal charging (FET68 is turned-off) with no stop signal is represented as (l+R64/R65)xVa and a boost voltage Vout2 during charging stop (FET68 is turned-on) with stop signal is represented as (l+(R64xR66/( R64+R66))x(l/R65))xVa. Herein, when each resistance value is represented as R (identical), Voutl is represented as 2xVa and Vout2 is represented as 3/2 Va. That is, the boost voltage is lower during the charging stop with stop signal than during the normal charging with no stop signal. Accordingly, it is possible to stop the charging state of the battery 4 by setting the boost voltage at this time lower than the cell voltage of the battery 4.
The connector 54 (see Fig. 1) of the charger 50 is provided with three connection terminals. Specifically, a plus terminal 72 is connected to the plus terminal 42 of the impact driver 1, a minus terminal 73 is connected to the minus terminal 43 and a stop signal input terminal 74 is connected to the stop signal output terminal 44. Herein, it is important that the connector 54 (see Fig. 1) has directionality in the plugging direction. Also, it is important that the plus terminal 72 has a shape which cannot be physically plugged in the terminals other than the plus terminal 42 of the impact driver 1.
Fig. 4 is a time chart showing the operation of the charger 50. Each graph of Figs. 4 shows horizontal axes as the same time axis. Fig. 4 shows a state where charging has been performed using the charger 50 from time 0 to T7 and three fastening works has been performed using the impact driver 1 during the charging. Fig. 4 shows a trigger signal 81 of the trigger switch 7 in response to the operation of the trigger 6. Herein, ON indicates a state where the trigger 6 is pulled and OFF indicates a state where the trigger 6 is released. In Fig. 4, the trigger 6 is pulled at time Tl to operate the impact driver 1 and the trigger 6 is released at time T2. Similarly, the trigger 6 is pulled at times T3, T5 and the trigger 6 is released at times T4, T6.
Fig. 4 shows a stop signal 82 which is supplied to the charger 50 from the impact driver 1 via the stop signal output terminal 44 and the stop signal input terminal 74 of Fig. 3. A vertical axis of Fig. 4 represents a voltage (unit: V). In Fig. 4, High indicates a predetermined voltage and Low indicates zero voltage. Here, since the trigger 6 is pulled between time Tl and T2, between time T3 and T4 and between time T5 and T6 and thus the motor 5 of the impact driver 1 is rotated, the stop signal becomes High. Fig. 4 shows a charging current 83 which is output from the plus terminal 72 and the minus terminal 73 of the charger 50 and a vertical axis thereof represents a current value (unit: A). However, the charging current 83 which is supplied to the impact driver 1 from the charger 50 is shut-off while the trigger 6 is pulled. In accordance with the shut-off of the charging current 83, a gate signal of the FET 68 becomes high when the charger 50 receives a stop signal via the stop signal input terminal 74 in the circuit of Fig. 3 and thus the source and drain are in a conductive-state. As a result, the base of the transistor 67 drops to the ground and thus the boost voltage becomes lower than the battery voltage. In this way, the charging is stopped. The dry cell has a trend that the capacity which can be extracted becomes smaller as the discharge current is larger. In this regard, since there is a case where a large current flows in response to the start-up current or load when the impact driver 1 is driven, the charging is stopped while the trigger 6 is operated and thus it is possible to utilize sufficiently the capacity of the dry cell without degrading the service life of the dry cell.
Fig. 4 shows a voltage 84 of the battery 4 (lithium ion cell) which is integrated in the impact driver 1. A vertical axis of Fig. 4 represents a voltage (unit: V). In Fig. 4, since the charging is performed by the charger 50 between the time 0 and Tl, between time T2 and T3, between time T and T5 and between time T6 and T7, the voltage 84 of the lithium ion cell is gradually increased over time. Meanwhile, since the trigger 6 is pulled between time Tl and T2, between time T3 and T4 and between the time T5 and T6 and thus the motor 5 of the impact driver 1 is rotated, the battery 4 is discharged and the voltage 84 is decreased over time. Further, at this time, the supply of charging power from the charger 50 is shut-off. And then, the charging is ended at time T7 when the charging is sufficiently completed. As the charging is ended, an operator can detach the charger 50 from the impact driver 1. The charging end may be determined in such a way that a stop signal is emitted when the protective circuit 41 (see Fig. 3) of the impact driver 1 detects the fully charged state or the charging is stopped when a current detection circuit (not shown) detects that the charging current is lower than a final charging current. In addition, other charging end control may be used.
As described above, since the charger 50 includes the dry cell and the booster circuit in the present embodiment, the charger can be easily used even where there is no AC power. Accordingly, it is possible to realize a small portable charger. Further, if AA battery is used as the dry cell, the dry cell is relatively inexpensive and can be easily available. In addition, since the housing 53 of the charger 50 is small enough compared to the electric tool, an operator can perform works using the electric tool in a state where the charger 50 is plugged in the electric tool. Even in this state, since the charging from the charger 50 is shut-off when the motor of the electric tool is running, it is possible to eliminate occurrence of discharge state of high current in the dry cell. Accordingly, an effective charging using the dry cell can be realized.
[Second Embodiment]
Next, a circuit of an impact driver 101 and a charger 150 according to a second embodiment of the present invention will be described with reference to Fig. 5. In the second embodiment, a stop signal output function of the impact driver 101 is omitted and the connection of the impact driver 101 and the charger 150 is done by only two sets of plus terminals 172, 142 and minus terminals 173, 143. Further, in order to realize the controls shown in Figs. 4 (1), (3), (4), a circuit configuration of the charger 150 has been studied. Other functions of a protective circuit 141 of the impact driver 101 are the same as the protective circuit 41 described in the first embodiment, except that a stop signal output function has been omitted from the protective circuit 141. In order to prevent over-charge, a voltage may be monitored by the protective circuit 141 and a charging stop signal may be output to the charger 150 side when the over-charge is detected.
The circuit configuration of the charger 150 basically includes a booster circuit and a constant current circuit. However, when a current value from the constant current circuit is detected and the detected current value exceeds a predetermined current value, that is, when it is determined that high current is temporarily flowing from the charger 150 side toward the impact driver 101 due to an activation of a motor in a side (impact driver 101) to be charged, the charger 150 is configured to shut-off the charging current. The same or similar element of a charging circuit 151 of Fig. 5 will be denoted by the same reference numeral as that of the charging circuit 51 of Fig. 3 and the duplicated explanation thereof will be omitted. The constant current circuit part of the second embodiment includes a constant current circuit 156, a diode 159 and resistors 163, 164, 165. Further, a current detection circuit using an operational amplifier 168 is provided at a rear end side of the constant current circuit 156. The operational amplifier 168 determines whether the current value of the constant current circuit 156 exceeds a predetermined value or not, by inputting a voltage value corresponding to a current value of the constant current circuit 156 and comparing the voltage value and a divided voltage potential corresponding to a reference current value of Vcc divided at the resistors 166, 167. Here, when the current value exceeds the predetermined value, the operational amplifier 168 causes a FET 174 to make a gate potential of a FET 169 to High and thus a source and drain of the FET 169 are in a non-conductive state. In this way, the supply of charging current to the impact driver 101 is shut-off. A resistor 176 is inserted between the drain and gate of the FET 169 and a resistor 175 is inserted between the source and gate of the FET 174. Meanwhile, in the circuit diagram of Fig. 5, the operational amplifier 168 is used as an example of a circuit determining whether the current value of the constant current circuit 156 exceeds a predetermined value or not. However, control using a microcomputer may be used.
As described above, in the second embodiment, when it is detected by the impact driver 101 that the trigger is pulled and the charging current is suddenly increased, immediately, the FET 16 is shut-off. Accordingly, charging can be automatically stopped even if the stop signal is not received from the electric tool. Further, since the charging current is returned to a normal current value when a fastening work of the impact driver 1 is completed, the operational amplifier 168 causes the FET 169 to be operated again and thus charging can be resumed. Meanwhile, it is also desirable to realize double charging stop control by adding an over-current detection circuit using the operational amplifier 168 of the second embodiment to the first charging circuit 51.
[Third Embodiment]
Next, a circuit of an impact driver 1 and a charger 250 according to a third embodiment of the present invention will be described with reference to Fig. 6. The third embodiment has a configuration that a constant current circuit 256 and a shunt resistor 263 are added to the first embodiment and other configuration thereof is the same as the first embodiment. Accordingly, a description of the same configuration as that of the first embodiment will be omitted. Further, the signal, the charging current and the cell voltage waveform are respectively the same as those shown in Fig. 4 and thus a description thereof is omitted. The constant current circuit part of the charger 250 includes the shunt resistor 263 connected to a charging path of the dry cell 52 and the battery 4 and the constant current circuit 256 detecting the charging current from the voltage applied to the shunt resistor 263. The constant current circuit 256 is a known circuit which includes a dedicated IC or an operational amplifier. In the third embodiment, similarly to the first embodiment, a boost voltage (output voltage) becomes lower than the voltage of the battery 4 when a trigger signal (charging stop signal) is input to the charger 250 from the electric tool 1 and the charging is stopped when the electric tool is used.
Meanwhile, the battery 4 is charged from the dry cell 52 when the trigger signal is not input from the electric tool 1. However, the third embodiment is different from the first embodiment in that the constant current circuit 256 is provided for maintaining a constant charging current. The shunt resistor 263 detects the charging current and the constant current circuit 256 performs a feedback control so that the charging current becomes constant. Since the constant current circuit 256 is not provided in the first embodiment, the battery 4 is charged with maximum charging current which can be supplied by the dry cell 52 when the battery 4 is charged by the configuration of the first embodiment. As described above, the dry cell 52 has a trend that the capacity which can be extracted becomes smaller as the discharge current is larger, that is, maximum capacity of the dry cell 52 cannot be extracted. Accordingly, since the discharge current of the dry cell 52 can be suppressed by controlling the charging current to a constant value by the constant current circuit 256, it is possible to maximally utilize the dry cell 52.
Meanwhile, the charger 250 of the present embodiment is configured to perform the constant current control. Although the lithium ion cell is generally charged by a constant current/constant voltage control, in the present embodiment, the boost circuit part corresponds to the constant voltage control part and the constant current circuit corresponds to the constant current control part. Accordingly, the battery 4 is charged by the constant current control. For example, as the cell voltage reaches a predetermined value at time T7 of Fig. 4, the boost circuit part may maintain (also in a section of the constant current control) the charging voltage and thus the charging current may be gradually decreased. The charging may be stopped when the constant current circuit 256 detects that the charging current after a lapse of a predetermined time from the time T7 becomes lower than a charging stop current value (fully charge current value). For example, the charging may be stopped by turning off the switching operation of the FET 62. Further, it is also possible to use a power supply using a nickel-hydrogen dry cell or other secondary cell as the second power supply to charge the battery 4, instead of the dry cell (primary cell).
Hereinabove, although the present invention has been described on the basis of the embodiment, the present invention is not limited to the above-described embodiments and can be variously changed in a range not departing from the spirit thereof. For example, although a case where the impact driver is employed as an example of the electric tool has been described in the present embodiment, the present invention is not limited to the impact driver and may be applied to other electric tools in which a small-size secondary battery of 14500 size is integrated. By integrating the small-size batteries of 14500 size such as AA batteries, it is possible to reduce the number of dry cells which are integrated in the charger. For example, electric energy is 3.96 Wh when two 14500 sized lithium cells (respectively, 3.6 V, 0.55 Ah) are integrated. In order to charge these lithium cells, it is sufficient to use only three dry cells (4.5 Wh; respectively, 1.5 V, lAh). Meanwhile, when two 18650 sized (diameter 18 mm, length 65 mm) lithium cells (respectively, 3.6 V, 1.5 Ah) which are widely used in the electric tool are integrated, the electric energy is 10.8 Wh and thus eight dry cells (12 Wh) are necessary in the charger side. Accordingly, not only the size of the electric tool but also the size of the charger is increased and thus it is inconvenient to use the electric tool. Accordingly, the present invention is characterized by using a secondary battery of the same size as AA batteries, in particular, integrating the secondary battery in the electric tool.
Further, in the present invention, the equipment to be charged is the electric tool and current of the electric tool is varied depending on load condition. Meanwhile, since the dry cell has a trend that discharge capacity is varied depending on the discharge current, that is, the capacity becomes smaller as the discharge current is larger, the constant current circuit is provided in the charger to control the discharge current to a constant value. In addition, charging is stopped while the electric tool is driven. By this configuration, a stable charging can be performed and it is possible to suppress the deterioration of the dry cell, even in the equipment such as the electric tool in which load is changed.
This application claims priority from Japanese Patent Application No. 2012-059499 filed on March 15, 2012, the entire contents of which are incorporated herein by reference.

Claims

1. An electric tool comprising:
a rechargeable first power supply; and
a second power supply which is configured to be connected and disconnected from the first power supply and is configured to charge the first power supply in a state where the second power supply is connected to the first power supply.
2. The electric tool according to claim 1, further comprising:
a motor driven by the first power supply; and
a housing for housing the motor,
wherein the second power supply is detachably attached to the housing.
3. The electric tool according to claim 2, wherein the second power supply is detachably attached to a lower side of the housing.
4. The electric tool according to claim 3, wherein
the housing includes an accommodation part accommodating the motor and a handle part extending from the accommodation part,
the first power supply is accommodated in the handle part and,
the second power supply is detachably attached to a lower side of the handle part.
5. The electric tool according to claim 2 further comprising:
a switch configured to control rotation of the motor; and
a connection terminal exposed to an outside of the housing and connected to the second power supply,
wherein a charging stop signal is output from the connection terminal in conjunction with an operation of the switch.
6. The electric tool according to claim 5 further comprising a detection circuit configured to detect the operation of the switch,
wherein the charging stop signal is output when the detection circuit detects the operation of the switch.
7. The electric tool according to claim 2, further comprising:
a current detection part configured to detect current which is flowing in the motor, and a connection terminal exposed to an outside of the housing and connected to the second power supply,
wherein a charging stop signal is output from the connection terminal in accordance with the current value detected by the current detection part.
8. The electric tool according to any one of claims 1 to 7, wherein
the second power supply includes a dry cell and a booster circuit for boosting an output of the dry cell, and
the first power supply is charged by the output of the booster circuit.
9. The electric tool according to any one of claims 6 to 8, wherein
the first power supply includes a secondary cell and a protective circuit configured to output a protective signal for protecting the secondary cell,
the second power supply includes a charging circuit configured to charge the first power supply, and
the protective signal from the protective circuit is input to the charging circuit.
10. The electric tool according to any one of claims 5 to 9, wherein the protective signal from the protective circuit and the charging stop signal are output from the same output terminal.
11. An electric tool comprising:
a motor;
a trigger switch configured to control a rotation of the motor;
a deceleration mechanism configured to decelerate the rotation of the motor;
a power transmission mechanism configured to drive an output shaft continuously or intermittently by the output of the deceleration mechanism;
a built-in secondary battery configured to supply drive power to the motor;
a housing accommodating the motor, the trigger switch, the deceleration mechanism, the power transmission mechanism and the built-in secondary batter; and
a connection terminal configured to be connected to an external charging device to charge the secondary battery,
wherein a charging stop signal is generated when the motor is rotated, and
wherein the charging stop signal is output to the charging device via the connection terminal.
12. The electric tool according to claim 11, wherein the charging stop signal is output in conjunction with the output of the trigger switch.
13. The electric tool according to claim 11 or 12 further comprising a protective circuit configured to protect charging or/and discharging of the secondary battery,
wherein the charging stop signal is output when the charging or discharging of the secondary battery is shut-off by the protective circuit.
14. The electric tool according to claim 11, wherein the secondary battery is one or more 14500 sized lithium ion cells.
15. A charging device connected to the connection terminal of the electric tool according to any one of claims 11 to 14 and supplying power to the electric tool to charge the secondary battery,
wherein the charging device monitors the charging stop signal and shuts off the charging of the electric tool when the charging stop signal is output.
16. The charging device according to claim 15, wherein the charging device resumes charging when the output stop state of the charging stop signal has been released.
17. The charging device according to claim 16 further comprising:
a dry cell holder; and
a booster circuit configured to boost an output voltage of the dry cell which is set in the dry cell holder,
wherein the output of the booster circuit is supplied to the electric tool.
18. The charging device according to claim 17 further comprising:
a housing accommodating the dry cell holder and the booster circuit; and
a connector extended from the housing and configured to be connected to the connection terminal.
19. The charging device according to claim 18 further comprising a constant current circuit configured to maintain constant charging current.
20. The charging device according to claim 16 further comprising:
a secondary cell; and a booster circuit configured to boost an output voltage of the secondary cell of the charging device,
wherein the output of the booster circuit is supplied to the electric tool.
21. The charging device according to claim 19 further comprising a current detection circuit configured to monitor charging current,
wherein the charging current to the electric tool is shut-off if the current detection circuit detects a current more than the constant charging current.
22. A charging device configured to be connected to a charging terminal of an electric tool in which a secondary battery for driving a motor is integrated and supply power to charge the second battery, the charging device comprising:
a current detection circuit configured to monitor charging current to monitor whether or not the motor of the electric tool is started during the charging; and
a output stop circuit configured to stop the supply of power when the current detection circuit detects that the motor is started.
23. The charging device according to claim 22, wherein the supply of power is resumed when the current detection circuit detects that the motor is stopped.
24. A charging system comprising:
an electric tool in which a motor and a secondary battery for driving the motor are housed; and
a charging device configured to charge the secondary battery,
wherein the electric tool includes a switch for driving the motor and,
wherein the charging device includes a charge stopping part which stops the charging of the secondary battery in conjunction with an operation of the switch.
PCT/JP2013/057326 2012-03-15 2013-03-08 Electric tool and charging apparatus for electric tool WO2013137422A2 (en)

Applications Claiming Priority (2)

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JP2012-059499 2012-03-15
JP2012059499A JP2013193136A (en) 2012-03-15 2012-03-15 Electric tool and charging apparatus for electric tool

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