CA1096013A - Fuel injection system with switchable starting mode - Google Patents
Fuel injection system with switchable starting modeInfo
- Publication number
- CA1096013A CA1096013A CA287,881A CA287881A CA1096013A CA 1096013 A CA1096013 A CA 1096013A CA 287881 A CA287881 A CA 287881A CA 1096013 A CA1096013 A CA 1096013A
- Authority
- CA
- Canada
- Prior art keywords
- engine
- generators
- circuit
- thermistor
- fuel injection
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/04—Introducing corrections for particular operating conditions
- F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
- F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
- F02D41/064—Introducing corrections for particular operating conditions for engine starting or warming up for starting at cold start
Abstract
ABSTRACT OF THE DISCLOSURE
A multi-channel, sequentially timed fuel injection system for an internal combustion spark ignited engine employs a solenoid actuated injector valve for each cylinder controlled by the outputs of separate variable width pulse generators.
The pulse generators each employ a resistance-capacitance discharge timing circuit and a single thermistor, common to all the generators, sensitive to engine temperature is connected to the RC circuits of the generators in a first circuit con-figuration during starting of the engine which provides a wide range of fuel delivery rates for starting and in a second cir-cuit configuration during normal operation in which the various RC circuits are isolated from one another so that interaction.
of the variable width pulse generators does not occur as a result of the common thermistor connection during normal engine operation.
A multi-channel, sequentially timed fuel injection system for an internal combustion spark ignited engine employs a solenoid actuated injector valve for each cylinder controlled by the outputs of separate variable width pulse generators.
The pulse generators each employ a resistance-capacitance discharge timing circuit and a single thermistor, common to all the generators, sensitive to engine temperature is connected to the RC circuits of the generators in a first circuit con-figuration during starting of the engine which provides a wide range of fuel delivery rates for starting and in a second cir-cuit configuration during normal operation in which the various RC circuits are isolated from one another so that interaction.
of the variable width pulse generators does not occur as a result of the common thermistor connection during normal engine operation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to fuel injection systems for internal combustion engines and more particularly to a system for a multicylinder engine having a plurality of time pulse generators incorporating means for modifying the normal opera-tion of the system during start-up of the engine using a single temperature sensor common to all the generators.
1. Field of the Invention This invention relates to fuel injection systems for internal combustion engines and more particularly to a system for a multicylinder engine having a plurality of time pulse generators incorporating means for modifying the normal opera-tion of the system during start-up of the engine using a single temperature sensor common to all the generators.
2. Prior Art ~ 10Recent increases in the cost of fuel and government -~ regulations limiting the permissible quantities of atmosphere pollutants in engine exhaust emissions have increased interest in fuel injection systems as alternatives to conventional car-buretors or automobile engines. These fuel injection systems ; 15measure engine operating parameters such as manifold pressure and engine temperature and inject measured quantities of fuel, based on these conditions, to the engine cylinders~
My copending U.S. patent No. ~,058,70~ entitled "Control Computer for Fuel Injection System" discloses a fuel injection system wherein the quantity of fuel provided to the engine is controlled by an electrically energized injector valve connected to a constant pressure fuel supply. A number of engine sensorscontrolthe duration of pulses provided to the injectors by a number of variable width pulse generators, each serving one or more cylinders. One o the sensor signals :
indicates that the engine is being cranked for starting. When this signal is received the operation of the pulse generators are changed from their normal operating mode. During cold start the injectors then provide enriched fuel charges necessitated by the relatively cold temperature of the fuel and engine which minimizes the vaporization of the fuel charge. At other times ~6~3 '' .
the engine may be started while it is relatively hot and a smaller fuel charge, more commensurate with the quantity which would be supplied during normal engine operation will suffice.
Because of the relat-ively extreme temperature ` conditions which may occur during start-up, and the need for a relatively large fuel charge, the ratio between the ~,:
longest and shortest pulse duration which may be required during start-up is substantially larger than the ratio of pulse durations which may be required during normal opera-tion. The ratio between the maximum and minimum pulse durations, over the engine temperature range, required during starting may be ten times as large as the ratio required during normal engine operation over the same temperature range.
;~ Accordingly, some switching mechanism, triggered by the presence or absence of the starting signal, must be provided to switch the mode of operation of the pulse gen-~- erators to provide two widely different pulse ranges and such circuits have been proposed for systems employing a single pulse generator for all of the injections. An additional problem is encountered in systems of the type described in the aforesaid patent application, wherein a plurality of injector actuation circuits provide sequen-, 2S tial outputs during the engine cycle for different cylin-ders. During start-up operation the pulses that these multiple generators provide will not typically overlap despite the possible long duration of the pulses, hecause of the very low engine speed; however, during normal engine operation at higher speeds the pulses may overlap and if the overlapping generators employ any common com-ponents, such as a si.ngle temperature sensor, cross-modulation can occur resulting in pulse durations during these overlapping periods which are different from the periods produced when only a single generator is being actuated.
'' 96~)~3 One solution to the problem would be to provide separate sensors for each pulse generator, but this is an ex-pensive, awkward alternative. The present invention is accordingly directed toward a system which uses a single temperature sensor to control a plurality of pulse generators during both starting and normal engine operation and in which isolation is provided so that cross-modulation does not occur ` during the actuation of two or more generators during normal ` operation.
i 10 SUMMAR~ OF THE INVENTION
In accordance with this invention there is provided in a fuel injection system for a multi-cylinder engine, having ;~ a fuel source, electrically energized injectors associated with each cylinder, a plurality of variable width pulse generators .
controlling the injectors, and an electric circuit which is energized during the starting of the engine, the improvement comprising: a sensor disposed with respect to the engine to ; experience a temperature related to the engine temperature and having an electric property which has a specific value for each temperature and varies as a function of such temperature; and switching means, controlled by the start circuit for connecting the temperature sensor to all of the variable width pulse `; generators in either a first configuration during energization ~ of the start circuit, wherein changes in engine temperature ~ 25 effect a relatively great change in duration of the pulses generated, or in a second configuration, when the start circuit is not energized, wherein the output of the sensor controls the durations of the pulses provided by each of the generators, and the generators are connected to the sensor so that changes in engine temperature effect a relatively small change in pulse duration. Also, in accordance with this invention there is provided in a fuel injection system for a multi-cylinder . .
6~3 . engine having an electrically energized injector associated with each cylinder and a plurality of sequentially triggered variable : width pulse generators controlling the injectors, an electric circuit which is energized during the starting of the engine, ;. 5 a sensor disposed with respect to the engine to experience a temperature related to the engine temperature, the sensor having ` electric property which varies as a function of such temperature, and electric circuitry interconnecting the sensor and each of the variable width pulse generators, the circuitry being con-trolled by the condition of the start circuit or connecting the sensor to each of the pulse generators in a first configura-tion during energization of the start circuit, wherein the sensor is directly connected into the timing circuit, of each of the pulse generators, and a second configuration, when the start circuit is not energized, wherein the sensor is connected to each of the discharge circuits so that the operation of any discharge circuit does not effect the operation of any other discharge circuit.
The present invention broadly rela~tes to an injector pulse duration control circuit having a number of pulse genera-~; tors employing a single,common temperature sensor which is switched between a first configuration used during starting of ~: the engine, and a second configuration used during normal running operation. In the first configuration the pulse dura-tion may be controlled over the wide range required between : starting the engine while it is at cold temperature of about minus 20F, and starting an engine at normal operating tempera-: ` ture. During the running configuration the circuit provides a narrower range of pulse durations to insure an extremely .: 30 precise relationship between engine temperature and pulse dura-tion for a given set of the other engine operating parameters 1~ 13 and isolates the generators Erom each other so that no cross-f modulation will result when the outputs of two generators overlap.
,:. The switching between the starting and run modes pri-marily effects the interconnection between the engine tempera-ture sensor and the other pulse generator components. In a preferred embodiment of the invention, which will subsequently be disclosed in detail, the temperature sensor takes the form of ~; a thermistor supported to experience a temperature that varies . with the engine temperature. The current that flows through this variable resistance or the voltage across the resistance .' ~. -3b-~96~L3 ; when a controlled current is applied to it, provides the required electrical signal which varies with temperature.
The preferred embodiment of the invention employs resistance-capacitance discharge circuits in each pulse generator as the timing elements for the pulse -; duration. Each capacitor is initially charged to a voltage which varies with one or more engine operating parameters, such as manifold pressure and the like. On the receipt of a triggering signal generated in timed relation to the engine operation, the capacitor is then discharged through the resistance. The value of the resistance and/or the potential applied to the resistance, to which the capaci-tor discharges, may be controlled by other engine operat-ing parameters. The output pulse begins when the capaci-tor starts discharging and continues until it is dis-charged to a reference voltage.
In the preferred ernbodiment, during normal ; engine operation the thermistor is connected in series with the fixed resistances in the discharge path of the capacitors in each generator. A reference voltage is applied to the junction between the fixed resistor and the thermistor so that the two operate as a voltage divider - and thereby control the effective voltage to which the capacitor discharges and thus its rate of discharge. A
transistor acting as an emitter-follower couples the thermistor to separate discharge resistors in each of the pulse generated circuits to eliminate cross-channel coupl-ing. During engine start-up, the emitter-follower transistor is switched off so that its emitter-base 30 circuit acts as a diode connecting the thermistor to the -.
3L0~ 13 pulse generator discharge paths; the reference voltage is switched off; and a calibrating resistance is switched into shunting relationship with the thermistor. The -thermistor is then part of the discharge path to :~ 4A
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ground for the capacitors of the pulse generators.
In effect, the circuit switches the change in discharge time of the capacitor which a unit change of engine temperature produces, from a relatively high value during engine starting to a substantially lower value dur-ing normal runniny operation. The circuit thus achieves a wide range pulse duration during starting and a more pre-cise control of pulse duration, as a function of tempera-ture, during running from the same thermistor.
Other objectives, advantages and applications of the present invention will be made apparent by the follow-ing detailed description of a preferred embodiment of the invention. The description makes reference to the accom-panying drawings in which:
FIGURE 1 is a block diagram of a fuel injection system forming a preferred embodiment of the invention;
FIGURE 2 is a plot of ignition pulse duration versus engine temperature for starting and normal operat-ing conditions as produced by the system of FIGURE l;
FIGURE 3 is a detailed schematic diagram of a preferred embodiment of the pulse generator, thermistor, and switching circuit employed in the system of FIGU~E l;
; FIGURE 4 is an equivalent diagram of the ther-mistor-pulse generator interconnection during running operation; and FIGURE 5 is an equivalent diagram of the ther-mistor pulse generator interconnection during starting operation of the engine.
A single cylinder 10, of a multi cylinder engine, and the associated ignition systern and fuel injection sys-tem are illustrated in FIGURE 1.
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The fuel charge admitted to the cylinder 10 throuyh an .
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intake valve 12 is ignited by a spark plug 14. The spark plug 14 is energized by an electric pulse provided by the vehicle ignition system 16 which also provides igniting pulses to the spark plugs associated with the other engine cylinders (not shown) in timed relation to the operation of the engine.
Pulses from the ignition system 16 are also pro-vided to a trigger counter 20 so that each pulse advances the state of the counter. The counter has a plurality of output lines 22 which are sequentially energized as the ' counter is advanced by the pulses from the ignition system.
Typically, each of the counter output lines 22 will be high for the period between a particular pair of ignition pulses, once each engine cycle. Each of the lines 22 Eeeds a var-iable width pulse gnerator 24, and the termination of the signal from the counter 20 triggers the generation of a pulse by the particular generator.
sinyle one of the L)ulse cJenerators 24 is illus-trated in FIGURE 1 as connected to the solenoid coil 26 of a fuel injector 28, and the other pulse generators are con-,~ nected to the coils of injectors associated with the other engine cylinders (not shown). The injector 28 takes the form of a normally closed valve connected to a constant ~- pressure fuel source 30. When the coil 26 is energized by a pulse from the generator 24 the injector valve 28 is ;` opened and dispenses a volume of fuel to the area of the intake valve 12, externally of the cylinder 10. When the intake valve 12 opens, this fuel charge is admitted to the cylinder.
The quantity of fuel admitted is dependent upon the duration of the pulse from the generator 24. This pulse duration is controlled by a group of engine sensors 32, which provide outputs to each of the variable width pulse generators 24 as a function of engine operating parameters, such as manifold , ' .
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pressure atmospheric pressure, and the like. The pulse width is also controlled as a function of the condition of an enyine ter,lperature sensor 34, which preferably takes the form of a thermistor and is connected to each of the variable width pulse generators 24 by a mode switching circuit 36. The switching circuit connects the thermistor 34 to the variable width pulse generators 24 in a manner deter~nined by the presence or absence of a signal from a start circuit 38. A high signal from the start circuit indicates that the engine is being cranked and the absence of high output from the start circuit 38 is indicative of a normal mode of engine operation. In both modes of engine operation the resistivity of the thermistor 34, which is a function of engine temperature, controls the duration of the pulses provided by the yenerators 24.
In both modes an increase in engine temperature increases the resistance of the thermistor 34 and decreases the duration o the pulses froln the generators 24 and thus the quantity of fuel that is injected into the cylinders;
but the change in pulse duration produced by a given change of engine temperature is substantially higher during the starting mode than it is during the normal operating mode.
This is illustrated in FIGURE 2 which plots the injection pulse duration as a function of engine temperature for the - 25 start mode by line 40 and for the normal running mode by ; line 42. It will be noted that the slope of line 40 is much steeper than that of line 42 indicating the greater effect of a given temperature change on the injected fuel quantity during starting, considering all other engine parameters to be constant.
The preferred embodiment of the variable width 96~3 pulse generator 24 and a mode switching circuit 36 are illustrated in more detail in FIGURE 3. The triggering signals on line 22 ;
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take the form of negative-going pulses which are applied to the base of a PNP transistor 44 that has its emitter connected to the positive terminal of the power supply through a resistor 46.
The collector of transistor 44 is connected to ground through the sensor 32, which acts like a variable - voltage source, and is schematically designated as such.
Circuit 32 is controlled by various engine operating para-meters and in the preferred embodiment of the invention its potential is primarily a function of the engine mani-fold pressure. In alternative embodiments, other combina-tions of parameters could be used to determine the voltage provided by device 32.
The collector of transistor 44 is also connected to one terminal of a capacitor 50 which has its other ter-minal connected to the base of a second PNP transistor 52 and also to ground through a resistor 54 and the mode con-trol circuit 36. The emitter of transistor 52 is connected to the positive terminal of the power supply through resis-tance ~6 and its collector is connected to ground through a pair of resistances 56 and 58. The midpoint of these resistances is connected to a driver amplifier 60 which provides the output of the circuit and connects to the solenoid coil 26 of the injector 28.
In the absence of a negative-going pulse on line 22 from trigger circuit 20 the transistor 44 operates in a saturated conduction region. The transistor 52 is then ` also conductive and the voltage across the capacitor 50 is maintained su~stantially at zero. When the trigger cir-cuit 20 provides a negative-going pulse to the base of transistor 44, that transistor is switched out of conduc-68~
tion, allowing the capacitor 50 to ~e charyed to avoltage that is dependent upon the effective voltage . of the sensor circuit 32 and the emitter voltage of transistor 52.
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When the negative-going pulse to the base of transistor 44 terminates, that transistor immediately becomes conductive again and the voltage at the base of transistor 52 goes sharply positive by an amount propor-tional to the charge on the capacitor 50, turning offtransistor 52. The capacitor 50 then begins to discharge through the resistance 44 and the mode control circuit 36.
This discharge continues until the voltage across at the base of transistor 52 decays to a value substantially equal to the emitter voltage of transistor 52, causing transistor 52 to turn on, and to clamp the vol-tage on the capacitor.
In the mode control circuit 36, the discharc3e resistance 54 is connected to the emitter of a PNP trans~-istor 62 which has a shunting resistor 64 connected betweenits base and collector. The collector oE transistor 62 also connects to the collector of a NPN tansistor 66 which has its emitter grounded and its base connected to the start circuit through resistance 68 and to ground through a resistance 70. The base of transistor 62 is connected ` to ground through the thermistor 34 as well as through a resistance 72 and the emitter-collector circui-t of an NPN
transistor 74. The base of the transistor 7~ connects to the start circuit.
The base of the transistor 62 is also connected to the start circuit through a resistor 76 and a diode 7~.
The start circuit connection to the resistor 76 is normally high in the absence of energization of the start circui-t, : and drops to zero volts when the start circuit is energized.
3n This positive voltage acts as a reference voltage. The inputs provided by the start circuit to the bases of trans-~g6`~
istors 66 and 74 are normally at zero level, and go highwhen the start circuit is energized. Accordingly, in the absence of energization of the start circuit, .
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P-~2~ 960~L3 durin~ normal o~er~tion of th~ engine, transistor 66 is con-ductivc and shorts the collector o transistor 62 to ground so that transistor 62 is connectcd in an emitter-follower config-uration. When the start circuit is energized, during engine cranking, transistor 66 is turned off, opening the circuit between the collector of transistor 62 and ground. The resis--~ tor 54 is then connected to the thermistor through the emitter-base junction of transistor 62 ~hich acts as a diode. At the same time transistor 74 is turned on shunting the ther~istor 34 to ground through resistor 72 which acts to calibrate the thermistor. The reference voltage applied through resistor 76 and diode 78 is simultaneously removed.
During normal engine operation the transistor 62 acts as an emitter follower, connecting the resistor 54 to ground through the thermistor 34. The resistor 54 and thermis-tor 34 thus act as a voltage divider for the reference voltage applied through diode 78. The resistLvity of the thermistor 34 thus controls the voltage at the ernitter of transistor 62 and thùs the rate o discharge of the capacitor S0.
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During normal engine operation, paxticularly at high speeds, overlap may occur between the output signals from various of the pulse generators. The emitter follower connection of the transistor 62 effectively isolates the thermistors from the ~iring circuits so that no cross-modulation results from these overlaps. The emitter-follower configuration thus isoiates the ` variable width pulse generators from affecting one another during normal engine operation.
When the start pulse is received the transistor 62 is converted into an effective diode and the resistor 72 is shunted across the thermistor 34. The capacitox 50 then dis-charges to ground through the series combination of the resistor ., .
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54 and the effective resistance provided by the thermistor 34 and the calibrating resistor 72. ~hus the thermistor 34 affects the discharge rate of the capacitor 50 in sub-stantially different manners during normal and starting operation, but in both modes the rate of discharge is con-trolled as an inverse function of the resistance of ther-mistor 34.
~ ssuming that the resistance 54 is about 20,000 ohms and that the resistance of the thermistor may vary from practically zero at 250F to about 200,000 ohms at -20F. During starting operation the resistance of the discharge path for the capacitor 50 may vary by factor of 10 as a function of the engine temperature and thus the time constant of the R-C circuit is varied by a factor of 10. During norMal running operation the voltage to which the capacitor 50 discharges may vary by a factor of two as the thermistor undergoes the Eull temperature range.
FIGUR~ 4 illustrates the equivalent construction of the R-C circuit during normal engine operation while 20 FIGURE 5 illustrates the equivalent circuit during start- `
ing operation. It will be noted that the element 52 is illustrated as a transistor in FIGURE 4 and as a diode in FIGURE 5, its tunction during these two modes.
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" 11
My copending U.S. patent No. ~,058,70~ entitled "Control Computer for Fuel Injection System" discloses a fuel injection system wherein the quantity of fuel provided to the engine is controlled by an electrically energized injector valve connected to a constant pressure fuel supply. A number of engine sensorscontrolthe duration of pulses provided to the injectors by a number of variable width pulse generators, each serving one or more cylinders. One o the sensor signals :
indicates that the engine is being cranked for starting. When this signal is received the operation of the pulse generators are changed from their normal operating mode. During cold start the injectors then provide enriched fuel charges necessitated by the relatively cold temperature of the fuel and engine which minimizes the vaporization of the fuel charge. At other times ~6~3 '' .
the engine may be started while it is relatively hot and a smaller fuel charge, more commensurate with the quantity which would be supplied during normal engine operation will suffice.
Because of the relat-ively extreme temperature ` conditions which may occur during start-up, and the need for a relatively large fuel charge, the ratio between the ~,:
longest and shortest pulse duration which may be required during start-up is substantially larger than the ratio of pulse durations which may be required during normal opera-tion. The ratio between the maximum and minimum pulse durations, over the engine temperature range, required during starting may be ten times as large as the ratio required during normal engine operation over the same temperature range.
;~ Accordingly, some switching mechanism, triggered by the presence or absence of the starting signal, must be provided to switch the mode of operation of the pulse gen-~- erators to provide two widely different pulse ranges and such circuits have been proposed for systems employing a single pulse generator for all of the injections. An additional problem is encountered in systems of the type described in the aforesaid patent application, wherein a plurality of injector actuation circuits provide sequen-, 2S tial outputs during the engine cycle for different cylin-ders. During start-up operation the pulses that these multiple generators provide will not typically overlap despite the possible long duration of the pulses, hecause of the very low engine speed; however, during normal engine operation at higher speeds the pulses may overlap and if the overlapping generators employ any common com-ponents, such as a si.ngle temperature sensor, cross-modulation can occur resulting in pulse durations during these overlapping periods which are different from the periods produced when only a single generator is being actuated.
'' 96~)~3 One solution to the problem would be to provide separate sensors for each pulse generator, but this is an ex-pensive, awkward alternative. The present invention is accordingly directed toward a system which uses a single temperature sensor to control a plurality of pulse generators during both starting and normal engine operation and in which isolation is provided so that cross-modulation does not occur ` during the actuation of two or more generators during normal ` operation.
i 10 SUMMAR~ OF THE INVENTION
In accordance with this invention there is provided in a fuel injection system for a multi-cylinder engine, having ;~ a fuel source, electrically energized injectors associated with each cylinder, a plurality of variable width pulse generators .
controlling the injectors, and an electric circuit which is energized during the starting of the engine, the improvement comprising: a sensor disposed with respect to the engine to ; experience a temperature related to the engine temperature and having an electric property which has a specific value for each temperature and varies as a function of such temperature; and switching means, controlled by the start circuit for connecting the temperature sensor to all of the variable width pulse `; generators in either a first configuration during energization ~ of the start circuit, wherein changes in engine temperature ~ 25 effect a relatively great change in duration of the pulses generated, or in a second configuration, when the start circuit is not energized, wherein the output of the sensor controls the durations of the pulses provided by each of the generators, and the generators are connected to the sensor so that changes in engine temperature effect a relatively small change in pulse duration. Also, in accordance with this invention there is provided in a fuel injection system for a multi-cylinder . .
6~3 . engine having an electrically energized injector associated with each cylinder and a plurality of sequentially triggered variable : width pulse generators controlling the injectors, an electric circuit which is energized during the starting of the engine, ;. 5 a sensor disposed with respect to the engine to experience a temperature related to the engine temperature, the sensor having ` electric property which varies as a function of such temperature, and electric circuitry interconnecting the sensor and each of the variable width pulse generators, the circuitry being con-trolled by the condition of the start circuit or connecting the sensor to each of the pulse generators in a first configura-tion during energization of the start circuit, wherein the sensor is directly connected into the timing circuit, of each of the pulse generators, and a second configuration, when the start circuit is not energized, wherein the sensor is connected to each of the discharge circuits so that the operation of any discharge circuit does not effect the operation of any other discharge circuit.
The present invention broadly rela~tes to an injector pulse duration control circuit having a number of pulse genera-~; tors employing a single,common temperature sensor which is switched between a first configuration used during starting of ~: the engine, and a second configuration used during normal running operation. In the first configuration the pulse dura-tion may be controlled over the wide range required between : starting the engine while it is at cold temperature of about minus 20F, and starting an engine at normal operating tempera-: ` ture. During the running configuration the circuit provides a narrower range of pulse durations to insure an extremely .: 30 precise relationship between engine temperature and pulse dura-tion for a given set of the other engine operating parameters 1~ 13 and isolates the generators Erom each other so that no cross-f modulation will result when the outputs of two generators overlap.
,:. The switching between the starting and run modes pri-marily effects the interconnection between the engine tempera-ture sensor and the other pulse generator components. In a preferred embodiment of the invention, which will subsequently be disclosed in detail, the temperature sensor takes the form of ~; a thermistor supported to experience a temperature that varies . with the engine temperature. The current that flows through this variable resistance or the voltage across the resistance .' ~. -3b-~96~L3 ; when a controlled current is applied to it, provides the required electrical signal which varies with temperature.
The preferred embodiment of the invention employs resistance-capacitance discharge circuits in each pulse generator as the timing elements for the pulse -; duration. Each capacitor is initially charged to a voltage which varies with one or more engine operating parameters, such as manifold pressure and the like. On the receipt of a triggering signal generated in timed relation to the engine operation, the capacitor is then discharged through the resistance. The value of the resistance and/or the potential applied to the resistance, to which the capaci-tor discharges, may be controlled by other engine operat-ing parameters. The output pulse begins when the capaci-tor starts discharging and continues until it is dis-charged to a reference voltage.
In the preferred ernbodiment, during normal ; engine operation the thermistor is connected in series with the fixed resistances in the discharge path of the capacitors in each generator. A reference voltage is applied to the junction between the fixed resistor and the thermistor so that the two operate as a voltage divider - and thereby control the effective voltage to which the capacitor discharges and thus its rate of discharge. A
transistor acting as an emitter-follower couples the thermistor to separate discharge resistors in each of the pulse generated circuits to eliminate cross-channel coupl-ing. During engine start-up, the emitter-follower transistor is switched off so that its emitter-base 30 circuit acts as a diode connecting the thermistor to the -.
3L0~ 13 pulse generator discharge paths; the reference voltage is switched off; and a calibrating resistance is switched into shunting relationship with the thermistor. The -thermistor is then part of the discharge path to :~ 4A
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ground for the capacitors of the pulse generators.
In effect, the circuit switches the change in discharge time of the capacitor which a unit change of engine temperature produces, from a relatively high value during engine starting to a substantially lower value dur-ing normal runniny operation. The circuit thus achieves a wide range pulse duration during starting and a more pre-cise control of pulse duration, as a function of tempera-ture, during running from the same thermistor.
Other objectives, advantages and applications of the present invention will be made apparent by the follow-ing detailed description of a preferred embodiment of the invention. The description makes reference to the accom-panying drawings in which:
FIGURE 1 is a block diagram of a fuel injection system forming a preferred embodiment of the invention;
FIGURE 2 is a plot of ignition pulse duration versus engine temperature for starting and normal operat-ing conditions as produced by the system of FIGURE l;
FIGURE 3 is a detailed schematic diagram of a preferred embodiment of the pulse generator, thermistor, and switching circuit employed in the system of FIGU~E l;
; FIGURE 4 is an equivalent diagram of the ther-mistor-pulse generator interconnection during running operation; and FIGURE 5 is an equivalent diagram of the ther-mistor pulse generator interconnection during starting operation of the engine.
A single cylinder 10, of a multi cylinder engine, and the associated ignition systern and fuel injection sys-tem are illustrated in FIGURE 1.
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The fuel charge admitted to the cylinder 10 throuyh an .
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intake valve 12 is ignited by a spark plug 14. The spark plug 14 is energized by an electric pulse provided by the vehicle ignition system 16 which also provides igniting pulses to the spark plugs associated with the other engine cylinders (not shown) in timed relation to the operation of the engine.
Pulses from the ignition system 16 are also pro-vided to a trigger counter 20 so that each pulse advances the state of the counter. The counter has a plurality of output lines 22 which are sequentially energized as the ' counter is advanced by the pulses from the ignition system.
Typically, each of the counter output lines 22 will be high for the period between a particular pair of ignition pulses, once each engine cycle. Each of the lines 22 Eeeds a var-iable width pulse gnerator 24, and the termination of the signal from the counter 20 triggers the generation of a pulse by the particular generator.
sinyle one of the L)ulse cJenerators 24 is illus-trated in FIGURE 1 as connected to the solenoid coil 26 of a fuel injector 28, and the other pulse generators are con-,~ nected to the coils of injectors associated with the other engine cylinders (not shown). The injector 28 takes the form of a normally closed valve connected to a constant ~- pressure fuel source 30. When the coil 26 is energized by a pulse from the generator 24 the injector valve 28 is ;` opened and dispenses a volume of fuel to the area of the intake valve 12, externally of the cylinder 10. When the intake valve 12 opens, this fuel charge is admitted to the cylinder.
The quantity of fuel admitted is dependent upon the duration of the pulse from the generator 24. This pulse duration is controlled by a group of engine sensors 32, which provide outputs to each of the variable width pulse generators 24 as a function of engine operating parameters, such as manifold , ' .
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., .: ~ , 6~
pressure atmospheric pressure, and the like. The pulse width is also controlled as a function of the condition of an enyine ter,lperature sensor 34, which preferably takes the form of a thermistor and is connected to each of the variable width pulse generators 24 by a mode switching circuit 36. The switching circuit connects the thermistor 34 to the variable width pulse generators 24 in a manner deter~nined by the presence or absence of a signal from a start circuit 38. A high signal from the start circuit indicates that the engine is being cranked and the absence of high output from the start circuit 38 is indicative of a normal mode of engine operation. In both modes of engine operation the resistivity of the thermistor 34, which is a function of engine temperature, controls the duration of the pulses provided by the yenerators 24.
In both modes an increase in engine temperature increases the resistance of the thermistor 34 and decreases the duration o the pulses froln the generators 24 and thus the quantity of fuel that is injected into the cylinders;
but the change in pulse duration produced by a given change of engine temperature is substantially higher during the starting mode than it is during the normal operating mode.
This is illustrated in FIGURE 2 which plots the injection pulse duration as a function of engine temperature for the - 25 start mode by line 40 and for the normal running mode by ; line 42. It will be noted that the slope of line 40 is much steeper than that of line 42 indicating the greater effect of a given temperature change on the injected fuel quantity during starting, considering all other engine parameters to be constant.
The preferred embodiment of the variable width 96~3 pulse generator 24 and a mode switching circuit 36 are illustrated in more detail in FIGURE 3. The triggering signals on line 22 ;
' ' ~ , " ~;
~' `'';`
: 7~ `
: ~
; ~
,, , : .; ~ :
" . ... ... ..
~a~93~
take the form of negative-going pulses which are applied to the base of a PNP transistor 44 that has its emitter connected to the positive terminal of the power supply through a resistor 46.
The collector of transistor 44 is connected to ground through the sensor 32, which acts like a variable - voltage source, and is schematically designated as such.
Circuit 32 is controlled by various engine operating para-meters and in the preferred embodiment of the invention its potential is primarily a function of the engine mani-fold pressure. In alternative embodiments, other combina-tions of parameters could be used to determine the voltage provided by device 32.
The collector of transistor 44 is also connected to one terminal of a capacitor 50 which has its other ter-minal connected to the base of a second PNP transistor 52 and also to ground through a resistor 54 and the mode con-trol circuit 36. The emitter of transistor 52 is connected to the positive terminal of the power supply through resis-tance ~6 and its collector is connected to ground through a pair of resistances 56 and 58. The midpoint of these resistances is connected to a driver amplifier 60 which provides the output of the circuit and connects to the solenoid coil 26 of the injector 28.
In the absence of a negative-going pulse on line 22 from trigger circuit 20 the transistor 44 operates in a saturated conduction region. The transistor 52 is then ` also conductive and the voltage across the capacitor 50 is maintained su~stantially at zero. When the trigger cir-cuit 20 provides a negative-going pulse to the base of transistor 44, that transistor is switched out of conduc-68~
tion, allowing the capacitor 50 to ~e charyed to avoltage that is dependent upon the effective voltage . of the sensor circuit 32 and the emitter voltage of transistor 52.
. .
~0~6~
When the negative-going pulse to the base of transistor 44 terminates, that transistor immediately becomes conductive again and the voltage at the base of transistor 52 goes sharply positive by an amount propor-tional to the charge on the capacitor 50, turning offtransistor 52. The capacitor 50 then begins to discharge through the resistance 44 and the mode control circuit 36.
This discharge continues until the voltage across at the base of transistor 52 decays to a value substantially equal to the emitter voltage of transistor 52, causing transistor 52 to turn on, and to clamp the vol-tage on the capacitor.
In the mode control circuit 36, the discharc3e resistance 54 is connected to the emitter of a PNP trans~-istor 62 which has a shunting resistor 64 connected betweenits base and collector. The collector oE transistor 62 also connects to the collector of a NPN tansistor 66 which has its emitter grounded and its base connected to the start circuit through resistance 68 and to ground through a resistance 70. The base of transistor 62 is connected ` to ground through the thermistor 34 as well as through a resistance 72 and the emitter-collector circui-t of an NPN
transistor 74. The base of the transistor 7~ connects to the start circuit.
The base of the transistor 62 is also connected to the start circuit through a resistor 76 and a diode 7~.
The start circuit connection to the resistor 76 is normally high in the absence of energization of the start circui-t, : and drops to zero volts when the start circuit is energized.
3n This positive voltage acts as a reference voltage. The inputs provided by the start circuit to the bases of trans-~g6`~
istors 66 and 74 are normally at zero level, and go highwhen the start circuit is energized. Accordingly, in the absence of energization of the start circuit, .
~' ' '.
" ~
,.
P-~2~ 960~L3 durin~ normal o~er~tion of th~ engine, transistor 66 is con-ductivc and shorts the collector o transistor 62 to ground so that transistor 62 is connectcd in an emitter-follower config-uration. When the start circuit is energized, during engine cranking, transistor 66 is turned off, opening the circuit between the collector of transistor 62 and ground. The resis--~ tor 54 is then connected to the thermistor through the emitter-base junction of transistor 62 ~hich acts as a diode. At the same time transistor 74 is turned on shunting the ther~istor 34 to ground through resistor 72 which acts to calibrate the thermistor. The reference voltage applied through resistor 76 and diode 78 is simultaneously removed.
During normal engine operation the transistor 62 acts as an emitter follower, connecting the resistor 54 to ground through the thermistor 34. The resistor 54 and thermis-tor 34 thus act as a voltage divider for the reference voltage applied through diode 78. The resistLvity of the thermistor 34 thus controls the voltage at the ernitter of transistor 62 and thùs the rate o discharge of the capacitor S0.
.
During normal engine operation, paxticularly at high speeds, overlap may occur between the output signals from various of the pulse generators. The emitter follower connection of the transistor 62 effectively isolates the thermistors from the ~iring circuits so that no cross-modulation results from these overlaps. The emitter-follower configuration thus isoiates the ` variable width pulse generators from affecting one another during normal engine operation.
When the start pulse is received the transistor 62 is converted into an effective diode and the resistor 72 is shunted across the thermistor 34. The capacitox 50 then dis-charges to ground through the series combination of the resistor ., .
.
54 and the effective resistance provided by the thermistor 34 and the calibrating resistor 72. ~hus the thermistor 34 affects the discharge rate of the capacitor 50 in sub-stantially different manners during normal and starting operation, but in both modes the rate of discharge is con-trolled as an inverse function of the resistance of ther-mistor 34.
~ ssuming that the resistance 54 is about 20,000 ohms and that the resistance of the thermistor may vary from practically zero at 250F to about 200,000 ohms at -20F. During starting operation the resistance of the discharge path for the capacitor 50 may vary by factor of 10 as a function of the engine temperature and thus the time constant of the R-C circuit is varied by a factor of 10. During norMal running operation the voltage to which the capacitor 50 discharges may vary by a factor of two as the thermistor undergoes the Eull temperature range.
FIGUR~ 4 illustrates the equivalent construction of the R-C circuit during normal engine operation while 20 FIGURE 5 illustrates the equivalent circuit during start- `
ing operation. It will be noted that the element 52 is illustrated as a transistor in FIGURE 4 and as a diode in FIGURE 5, its tunction during these two modes.
.
" 11
Claims (10)
1. In a fuel injection system for a multi-cylinder engine, having a fuel source, electrically energized injectors associated with each cylinder, a plurality of variable width pulse generators controlling the injectors, and an electric circuit which is energized during the starting of the engine, the improvement comprising: a sensor disposed with respect to the engine to experience a temperature related to the engine temperature and having a electric property which has a specific value for each temperature and varies as a function of such temperature; and switching means, controlled by said start circuit for connecting said temperature sensor to all of the variable width pulse generators in either a first configuration during energization of said start circuit, wherein changes in engine temperature effect a relatively great change in duration of the pulses generated, or in a second configuration, when said start circuit is not energized, wherein the output of the sensor controls the durations of the pulses provided by each of the generators, and the generators are connected to the sensor so that changes in engine temperature effect a relatively small change in pulse duration.
2. The fuel injection system of claim 1 wherein said engine temperature sensor comprises a thermistor.
3. The fuel injection system of claim 1 wherein said variable width pulse generators each include a resistance-capacitance timing circuit and the manner of connection of the engine temperature sensor to the variable width pulse generators affects the discharge time of the timing circuit.
4. The fuel injection system of claim 3 wherein the resistance-capacitance timing circuits each include a capaci-tor, circuitry for charging the capacitor to a voltage which is a function of at least one engine operator parameter, and means for allowing discharge of the capacitor through the resistance.
5. The fuel injection system of claim 4 wherein said switching means connects said engine temperature sensor to each of the resistance-capacitance timing circuits during nor-mal engine operation, to control the voltage to which the capacitors discharge.
6. The fuel injection system of claim 5 wherein said engine temperature sensor comprises a thermistor and the variable width pulse generators each include a source of refer-ence voltage, a resistor connected to the source of reference voltage and means for connecting said resistors of each of said generators to said thermistor during normal engine operation to control the voltage to which the capacitor discharges.
7. The fuel injection system of claim 6 wherein said switching means connects said thermistor in the discharge paths of said capacitors, during energization of the starting circuit, so that the discharge current flows through said thermistor.
8. The fuel injection system of claim 6 wherein said means for connecting said resistors of each of said generators to said thermistor during normal engine operation comprises a transistor connected in an emitter-follower circuit so that the voltage across the thermistor is not affected by the activation of any of the generators.
9. The fuel injection system of claim 6 wherein said means for connecting said resistors of each of said generators to said thermistor during normal engine operation comprises a transistor having each of said resistors connected to its emitter, having a source of reference voltage connected to its base and having the thermistor connected between its base and ground, whereby the voltage drop across the thermistor is independent of the function of any of said generators fired.
10. In a fuel injection system for a multi-cylinder engine having an electrically energized injector associated with each cylinder and a plurality of sequentially triggered variable width pulse generators controlling the injectors, an electric circuit which is energized during the starting of the engine, a sensor disposed with respect to the engine to experience a temperature related to the engine temperature, the sensor having electric property which varies as a function of such temperature, and electric circuitry interconnecting the sensor and each of the variable width pulse generators, the circuitry being con-trolled by the condition of the start circuit for connecting the sensor to each of the pulse generators in a first configura-tion during energization of said start circuit, wherein said sensor is directly connected into the timing circuit of each of said pulse generators, and a second configuration, when said start circuit is not energized, wherein said sensor is connected to each of said discharge circuits so that the operation of any discharge circuit does not effect the operation of any other discharge circuit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US728,805 | 1976-10-01 | ||
| US05/728,805 US4132210A (en) | 1976-10-01 | 1976-10-01 | Fuel injection system with switchable starting mode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1096013A true CA1096013A (en) | 1981-02-17 |
Family
ID=24928340
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA287,881A Expired CA1096013A (en) | 1976-10-01 | 1977-09-30 | Fuel injection system with switchable starting mode |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4132210A (en) |
| JP (1) | JPS5344734A (en) |
| CA (1) | CA1096013A (en) |
| DE (1) | DE2743991A1 (en) |
| ES (1) | ES462777A1 (en) |
| FR (1) | FR2366458A2 (en) |
| GB (1) | GB1580729A (en) |
| IT (1) | IT1116339B (en) |
| SE (1) | SE7710960L (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4197767A (en) * | 1978-05-08 | 1980-04-15 | The Bendix Corporation | Warm up control for closed loop engine roughness fuel control |
| US4349000A (en) * | 1980-02-11 | 1982-09-14 | Brunswick Corporation | Control means for fuel injection in an internal combustion engine |
| US4391254A (en) * | 1981-12-11 | 1983-07-05 | Brunswick Corporation | Atomization compensation for electronic fuel injection |
| JPS5982545A (en) * | 1982-10-30 | 1984-05-12 | Aisan Ind Co Ltd | Start controller for fuel supply device |
| JPS60171999A (en) * | 1984-02-13 | 1985-09-05 | 小松フオ−クリフト株式会社 | Controller for speed of reaching of reaching forklift truck |
| JPS6172593U (en) * | 1984-10-15 | 1986-05-17 | ||
| JPS6172596U (en) * | 1984-10-15 | 1986-05-17 | ||
| JPS61277842A (en) * | 1985-06-01 | 1986-12-08 | Aisin Seiki Co Ltd | Solenoid valve control circuit |
| USRE34183E (en) * | 1986-02-05 | 1993-02-23 | Electromotive Inc. | Ignition control system for internal combustion engines with simplified crankshaft sensing and improved coil charging |
| JPS6362498U (en) * | 1986-10-11 | 1988-04-25 | ||
| SE462725B (en) * | 1988-12-06 | 1990-08-20 | Volvo Ab | CONTROL UNIT FOR AN INCORPORATING ENGINE FOR INCREASING THE LENGTH LENGTH DURING A PRE-DETERMINED TIME AFTER CALL |
| US6123241A (en) | 1995-05-23 | 2000-09-26 | Applied Tool Development Corporation | Internal combustion powered tool |
| US5549084A (en) * | 1995-11-13 | 1996-08-27 | Deere & Company | Fuel shut-off solenoid pull-in coil current limiter |
| US20070108249A1 (en) * | 2005-11-17 | 2007-05-17 | Moeller Larry M | Motor control for combustion nailer based on operating mode |
| CN101331005B (en) * | 2005-11-17 | 2010-11-03 | 伊利诺斯工具制品有限公司 | Variable ignition delay for combustion nailer |
| FR2957833B1 (en) * | 2010-03-23 | 2012-06-01 | Prospection & Inventions | MOTOR AND CARTRIDGE THERMISTOR FIXING APPARATUS |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2867200A (en) * | 1957-03-20 | 1959-01-06 | Bendix Aviat Corp | Auxiliary control means for pulse producing circuit |
| FR96024E (en) * | 1967-05-24 | 1972-05-19 | ||
| JPS50205B1 (en) * | 1969-10-22 | 1975-01-07 | ||
| US3809029A (en) * | 1970-01-09 | 1974-05-07 | Toyota Motor Co Ltd | Electric control apparatus for internal combustion engines |
| FR2073096A5 (en) * | 1970-01-22 | 1971-09-24 | Bosch | |
| US3771502A (en) * | 1972-01-20 | 1973-11-13 | Bendix Corp | Circuit for providing electronic warm-up enrichment fuel compensation which is independent of intake manifold pressure in an electronic fuel control system |
| DE2410090C2 (en) * | 1974-03-02 | 1986-07-31 | Robert Bosch Gmbh, 7000 Stuttgart | Switching device for the hot start of internal combustion engines with electronically controlled fuel injection |
| US3971354A (en) * | 1975-06-23 | 1976-07-27 | The Bendix Corporation | Increasing warm up enrichment as a function of manifold absolute pressure |
-
1976
- 1976-10-01 US US05/728,805 patent/US4132210A/en not_active Expired - Lifetime
-
1977
- 1977-09-29 GB GB40565/77A patent/GB1580729A/en not_active Expired
- 1977-09-29 ES ES462777A patent/ES462777A1/en not_active Expired
- 1977-09-30 IT IT69165/77A patent/IT1116339B/en active
- 1977-09-30 JP JP11780377A patent/JPS5344734A/en active Pending
- 1977-09-30 FR FR7729591A patent/FR2366458A2/en active Pending
- 1977-09-30 CA CA287,881A patent/CA1096013A/en not_active Expired
- 1977-09-30 SE SE7710960A patent/SE7710960L/en unknown
- 1977-09-30 DE DE19772743991 patent/DE2743991A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5344734A (en) | 1978-04-21 |
| DE2743991A1 (en) | 1978-04-06 |
| SE7710960L (en) | 1978-04-02 |
| IT1116339B (en) | 1986-02-10 |
| ES462777A1 (en) | 1978-12-16 |
| US4132210A (en) | 1979-01-02 |
| FR2366458A2 (en) | 1978-04-28 |
| GB1580729A (en) | 1980-12-03 |
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