WO2006008051A1

WO2006008051A1 - Pump

Info

Publication number: WO2006008051A1
Application number: PCT/EP2005/007628
Authority: WO
Inventors: Michael Robohm
Original assignee: Bosch Rexroth Ag
Priority date: 2004-07-21
Filing date: 2005-07-13
Publication date: 2006-01-26
Also published as: DE102004035188A1

Abstract

The invention relates to a pump, particularly a diesel injection pump, wherein a pump piston is actuated via an oscillation cylinder. The oscillation cylinder and pump piston form a pressure translator whose transmission ratio determines the maximum adjustable conveying pressure.

Description

description

pump

The invention relates to a pump via which a pressure medium, for example diesel fuel, water of a high pressure pump for Wasserstrahlscnneiden or the pressure medium (oil, water) of a hydroforming press with the required high pressure can be acted upon.

Modern diesel engines for passenger cars usually employ pump-nozzle systems or common-rail systems. In larger engines, such as marine engines, construction machinery, etc. simpler systems are used in which, for example, the diesel injection pump is driven ange¬ directly from an engine camshaft. Especially in diesel engines, these pumps are usually carried out with a diesel pressure limiting and a flow control.

The invention has for its object to provide a pump of the type mentioned, which allows verrin¬ gertem device complexity simple flow control.

This object is achieved by a pump having the features of patent claim 1.

According to the invention, the pump is designed as a pressure booster, wherein a pump piston is actuated via a hydraulically controlled oscillating cylinder. The area ratio between the working piston of the oscillating cylinder and the pumping piston determines the ratio of the ratio of the pressure booster. The control of the working piston via a control piston which is guided axially displaceably in the working piston. inventions According to the control piston has an end portion which comes into contact with a housing-fixed stop in the region of a dead center of the working piston and is thereby adjusted so that the return movement of the working piston takes place in the opposite direction.

The constructed as a pressure booster pump does not require a stepped piston and is therefore constructed much simpler than conventional pumps.

Oscillating cylinders are already known as such. Thus, WO 97/08464 shows an oscillating cylinder, in which the extendable working piston is used for actuating machine elements. The actuation of the working piston takes place via a control piston which is guided in the axial distance to the working piston in the oscillating cylinder. By means of the control piston, a larger end face of the working piston designed as a differential piston can be acted upon either with tank pressure or with high pressure in order to produce the retraction or extension of the working piston. Its smaller annular surface is subjected to the high pressure when retracting the working piston, the connection to the high pressure is shut off via the control piston and the pressure medium is displaced towards the tank via a nozzle 26 that is always open, so that the annular surface is depressurized.

A disadvantage of this known oscillating cylinder, on the one hand, the large space, since the working piston and the control piston are arranged axially one behind the other. Furthermore, due to the constant opening of the nozzle towards the tank, a loss of control oil occurs.

US 3,154,923 discloses an oscillating cylinder used in machine tools and one still Having more complex structure than the above-described embodiment.

In DE 198 20 102 B4, an oscillating cylinder is shown, in which the control piston is integrated into the working piston. The switching of the control piston in the dead center is effected by picking up a control pressure between a nozzle, of which a nozzle is controlled on reaching the dead center of the Arbeistkolbens.

The integration of the control valve with the Steuerkanä¬ len and the two nozzles connected in series can be carried out only with great effort.

For the sake of good order, it should be noted that the abovementioned publications contain no indication that the known oscillating cylinders are used to drive a pump piston.

The main advantage of the invention is that on the one hand, the pump can be made very compact, since the control piston is integrated into the working piston. Due to the mechanical reversal at at least one dead center, the channel guide within the Ar¬ beitskolbens compared to the above-described prior art can be significantly simplified.

A further advantage of the pump according to the invention, designed as a pressure booster, is that the adjustable maximum pressure is determined firstly by the transmission ratio and secondly by the high pressure acting on the oscillating cylinder. If the pressure of the pressure medium acting on the pump piston exceeds a predetermined level, then the effective hydraulic pressure is insufficient to move the working piston further in the pressure buildup direction - it stops until the pressure of the pressure medium has dropped and then continues in the direction of its dead center. A Maxi¬ maldruckbegrenzung for funded by the pump piston pressure medium is therefore - in contrast to conventional diesel injection pumps not required.

In a particularly preferred embodiment, the pressure medium is sucked into a pump chamber via a suction valve and pressurized out of the pump chamber via a pressure valve and the pressure connection. The valves are preferably designed as check valves.

In a particularly preferred embodiment, the control piston has an end portion which can be brought into contact with a housing wall at the dead center of the working piston.

The control piston guided in the working piston preferably has a tank and a pressure control edge, by means of which a working surface of the working piston effective in the direction of extension or pressure buildup can be acted upon by hydraulic tank pressure or hydraulic high pressure during the stroke of the working piston. That In contrast to the embodiment disclosed in WO 97/08464, the connection to the hydraulic tank is opened or closed via a control edge, so that the control oil losses are minimal.

An effective surface area of the working piston which acts in the direction of entry or suction is always subjected to hydraulic tank pressure in a particularly simply constructed embodiment, so that only the control pressure which acts on the pressure surface effective in the direction of extension must be reversed via the control valve. In a particularly simple embodiment, the pump piston is biased by a spring into contact with the working piston. In this construction, the hydraulic part is sealed off from the pump part accommodating the pump piston via a bellows or the like which is sealingly supported on the working piston side end portion of the pump piston and on an adjacent end wall of the pump part.

The space encompassed by the bellows is preferably connected to a pressure medium tank.

A further advantage of the solution according to the invention is that apart from the seal between the pumping part and the hydraulic part, no moving parts have to be sealed to the outside by the bellows.

The working piston is advantageously designed with a control edge, via which a connection to the hydraulic high pressure or the hydraulic tank can be opened in the region of the second dead center, so that a pump piston-side spring chamber of the control piston is acted upon either with high hydraulic pressure or with hydraulic tank pressure. This control edge is preferably formed by a shell opening, which opens into the spring chamber.

In this spring chamber, in a preferred embodiment, a control spring is accommodated, via which the control piston is biased into a basic position within the working piston.

The entire system with pump piston, working piston and control piston is biased by a pump spring and the vorge mentioned control spring in a basic position, in the pump piston and the working piston are retracted and the control piston rests on the housing-side stop.

Preferably, the tank and the Drucksteuerkan¬ te are formed on a control collar of the control piston, wherein the control edges are each carried out with respect to housing-fixed control edges with negative coverage, so that a stop ^'of the working piston is avoided in the dead centers.

The pump according to the invention is preferably designed as a diesel injection pump, diesel fuel being used as the pressure medium.

To damp pulsations of the pressure medium, a hydraulic accumulator can be provided in a high-pressure line.

Other advantageous developments of the invention are the subject of further subclaims.

In the following, a preferred embodiment of the invention is explained in more detail with reference to schematic drawings. Show it:

FIG. 1 is a schematic diagram of a diesel injection pump according to the invention, which is designed as a pressure booster and FIG

Figures 2 to 5 each Figure 1 corresponding Dar¬ settings of the pump in different operating positions.

1 is a greatly simplified longitudinal section through a diesel injection pump 1. This has a pumping or diesel part 2 and a hydraulic part 4, which together form a pressure booster.

The diesel part 2 has a low-pressure connection ND which is connected to a prefeed pump and a high-pressure diesel connection HD, which are connected to a pump chamber 6 via a suction channel 8 or a high-pressure channel 10. A suction valve 12 designed as a check valve is arranged in the suction channel 8 and a pressure valve 14 is arranged in the high-pressure channel 10 accordingly. In a guide bore 17 of a pump housing 16 of the diesel part 2, a pump piston 18 is guided axially displaceable, which dips with its free end portion in the pump chamber 6. At this end portion of the pump piston 18 carries a stop ring 20, which limits the stroke of the pump piston 18 by running on a pump chamber 6 in the axial direction delimiting annular end face 22. At a distance from the annular end face 22, a tank space 24 is formed in the pump housing 16 which is connected via a tank channel 26 to a tank connection TD of the diesel part 2.

At the right in Figure 1 end face of the diesel part 2, a guide projection 28 is formed, which is penetrated by a guide bore 17. The pump piston 18 extends through this axial projection 28 and immersed in a pressure chamber 30 of a housing 32 of the hydraulic part 4 a. _, At this end portion of the pumping piston 18, a spring plate 34 is supported in the axial direction, against which a pump spring 36 engages, which is supported with its other end section on a graduation 38 of the pump housing 16.

On the end face of the axial projection 28, a bellows 40 is sealingly mounted, which is fastened near the Federtel¬ ler 34 on the outer circumference of the pump piston 18. The bellows 40 thus seals the guide bore 17th and the pump chamber 6 with respect to the pressure chamber 30 from. The space enclosed by the bellows 40 is connected via a channel 44 to the tank space 24 and thus to the tank connection TD. Thus, leakage can be dissipated via the tank space 24 and the tank connection TD, which reaches from the pump space 6 or from the space 42 into the tank space.

Through the pump spring 36, the pump piston 18 is biased against a working piston 46 which is guided axially displaceable bar in an axial bore 48 of the housing 32 of the Hydrau¬ likteils 4.

In the illustrated embodiment, the Ar¬ beitskolben 46 at its left in Figure 1 end portion an insert 50, against which the pump piston 18 is preloaded vorstsei¬ term. The opening in the pressure chamber 30 Axial¬ bore 48 is extended in the radial direction to a tank annulus 52, a pressure ring chamber 54 and a groove 56 which is disposed between the tank annulus 52 and the pressure chamber 30. The pressure ring space 54 is connected via a pressure channel 58 with a hydraulic pressure port P and the tank annulus 52 is connected via a drain channel 60 to a hydraulic tank connection T of the hydraulic part 4. The groove 56 is connected via a connecting channel 62 with the pressure channel 58 in connection. From the drainage channel 60 branches off a branch channel 64, which opens into the pressure chamber 30. The right in Figure 1 end face of the working piston 46 defines in the axial direction together with a bottom surface 68 of the axial bore 48 a working space 66th

The working piston 46 is designed as a sleeve-shaped Hohlkol¬ ben, in the inner bore 70 a Steuerkol¬ ben 72 is guided axially displaceable. This has an approximately centrally arranged control collar 74 whose annular end surfaces a tank control edge 76 and a pressure control edge 78 limit.

On both sides of the control collar 74, two guide collars 80, 82 are formed on the control piston 72, via which the control piston 72 is guided on the ümfangswänden the inner bore 70.

The left in Figure 1 end portion of the control piston 72 is radially set back and immersed in a spring chamber 84 which is bounded in the axial direction on the one hand by the insert 50 and on the other hand by the annular shoulder and the Stirn¬ surface of the guide collar 80. At the left annular end surface of the guide collar 80, a spring plate is arranged, on which a control spring 8β attacks, which is supported on the insert 50.

In the jacket of the working piston 46, a Schrägboh¬ tion 88 is formed, via which - in the illustrated relative position of the working piston 46- the groove 56 is connected to the spring chamber 84, so that in this then accordingly the pressure at the hydraulic pressure port P is present.

In the mantle of the working piston 46, two openings 90, 92 are also provided, which are always in coincidence with the tank annulus 52 and the pressure annulus 54 during the stroke of the working piston 46.

The axial bore 70 is widened in the radial direction in the region of the control collar 82, so that two control edges 94, 96 fixed to the housing are created, which interact with the tank control edge 76 or the pressure control edge 78. The axial distance of the two housing-fixed Steuerkan¬ th 94, 96 is slightly larger than the axial length of the Steu¬ erbunds 90 formed so that it is designed with negative coverage. The space forming the two housing-fixed control edges 94, 96 is connected to the work space 66 via a longitudinal channel 98. In addition, a stop 100 is formed in the axial bore 70, onto which the radial collar 82 runs with an axial displacement to the right within the working piston 46 and thus limits the stroke of the control piston 72. The right in Figure 1 end portion of the control piston 72 is formed by a subsequent to the control collar 82 radially recessed Kolben¬ rod 102 whose axial length is slightly larger than the distance of the stop 100 from the right (Figure 1) end face of the working piston 46, so in that the piston rod 102 protrudes from the working piston 46 into the working chamber 66 when the control collar 82 bears against the stop 100.

As mentioned, this construction forms a Druck¬ translator whose transmission ratio of the ratio D / d depends, where D is the diameter of the working piston 46 and d is the diameter of the pump piston 18. In the illustrated embodiment, the Durchmesser¬ ratio D / d should be approximately chosen so that at a pressure of about 300 bar in the working space 66 ^' a maximum Förder¬ pressure at the high pressure port HD of about 1400 bar is generated

For a better understanding of the function of designed as a pressure booster diesel injection pump 1 will be explained.

It is assumed that the pump piston 18 has just performed a delivery stroke and is in the lower dead center or already in the first phase of the piston return. This relative position is shown in FIG. The pump room 6 is kept to a minimum. petted and. The diesel fuel is conveyed to the injection system via the pressure valve 14 and the diesel high-pressure connection. In this case, a control oil cross section is opened via the pressure control edge 78 and the housing-fixed control edge 96, via which the hydraulic pressure connection P via the pressure channel 58, the pressure ring space 54, the opening 92, the annular space between the guide collar 82 and the control collar 90 and over the Longitudinal channel 98 is connected to the working space 66, so that initially acts on the right in Figure 1 end faces of the working piston 46 and the control piston 72, the hydraulic pressure. At the same time, however, the oblique bore 88 is in register with the groove 56, so that the spring chamber 84 is also acted upon by the oblique bore 88, the groove 56 and the connecting channel 62 with the hydraulic pressure. The end faces of the control piston 72 are thus druckausge¬, so that it is shifted by the force of the control spring 86 from the position shown in Figure 1 to the right and in accordance with the Drucksteuerkan¬ te 78 the connection to the hydraulic port P is zugesteuert while on the Tank control edge 76 in Zusammenwir¬ ken with the housing-fixed control edge 94 a connection from the hydraulic tank connection T via the drain passage 60, the opening 90, the annular space between the guide collar 80 and the control collar 90, the controlled cross-section between the control edges 76, 94 and the Verbin¬ Duct 98 is opened with the working space 66 - the right in Figure 1 end face of the working piston 46 is thus acted upon by hydraulic tank pressure. Since the pressure chamber 30 is always connected to the hydraulic 1iktankanschluss T via the branch channel 64, the Hydraulik¬ tank pressure acts on the left end face of the working piston 46 - the working piston is pressure balanced and is by the force of the pump spring 36, via the pump piston 18th transferred to the piston 46 is moved in the illustration of Figure 1 to the right. Due to the slightly negative coverage of the control collar 90 with the two housing-fixed control edges 94, 96 prevents the working piston 46 stops in the area of the dead center when reversing. As a result of the movement of the pumping piston 18 and the working piston 46 to the right in FIG. 1, the pump chamber 6 is enlarged and accordingly diesel fuel is sucked in via the diesel low-pressure connection ND with prefetching pressure via the opening suction valve 12. This prefeed pressure acts on the left in Figure 1 end face of the pump piston 18 and thus supports the action of the pump spring 36, so that the pump piston 18 is accelerated.

As shown in FIG. 2, after a certain stroke, the overlap between the oblique bore 88 and the groove 56 is canceled, so that the control oil connection between the spring chamber 84 and the connecting channel 62 leading to the hydraulic pressure connection P is controlled. After a further stroke, the oblique bore 88 comes into coincidence with the tank annulus 54, so that correspondingly the spring chamber 84 is vented to the hydraulic tank connection T. However, the spool 72 remains in its relative position with respect to the power piston 46 because the spool 74 continues to be urged against the stop 100 by the force of the control spring 86. The working space 66 is acted upon in this phase by the opened cross-section between the tank control edge 76 and the housing-fixed control edge 94 with tank pressure - the suction stroke of the pump piston 18 continues.

As shown in Figure 3, the piston rod 102 of the Steuerkolbehs 72 runs after another stroke on the bottom surface 68, so that the control piston 72 can not move to the right, while the working piston 46 and the pump piston 18 continues to the right ( Figure 3) move. By Relatiwerschiebung The connection to the hydraulic tank connection T is then fed via the tank control edge 76 between the working piston 46 and the control piston 72 and, as a result, the movement of the working piston 46 is decelerated. This braking alone by closing the tank connection should be caused by the increase in pressure in the decreasing work space 66. It was found that the noise emissions during the Umsteuer¬ processes can be reduced by this deceleration. The pressure control edge 78 begins - as shown in Figure 3 - aufzusteuern the connection between the working space 66 and the hydraulic pressure P, so that the pressure in the working chamber 66 increases, the negative coverage of Steuer¬ piston 74 ensures that this movement is not is interrupted. Due to the increasing pressure in the working chamber 66, the control piston 72 is displaced to the left against the force of the control spring 86, so that the opening cross section to the hydraulic pressure connection is further opened. The working piston 46 continues to move to the right (FIG. 3) until the pressure force acting on its right-hand end face is greater than the force acting on the pump piston 18 from the diesel advance pressure and the force of the pump spring 36. In the embodiment, this is at a pressure reached about 10 bar in Ar¬ beitsraum 66. As a result, the working piston 46 and the pump piston 18 are accelerated to the left from the dead center position shown in FIG. 3 - the delivery stroke of the diesel injection pump begins (see FIG. 4). The cross section opened by the pressure control edge 78 has reached its maximum value, since the control piston 72 has accumulated on the insert 50 with its left end section. The spring chamber 84 is further connected via the oblique bore 88 with the hydraulic tank connection T. The pressure in the working space 66 rises to its maximum value, which is for example 300 bar. As stated above, the maximum diesel fuel consumption is pressure then about 1400 bar. The diesel fuel is delivered via the open pressure valve 14 to the injection system of the engine. To even out the pulsation of the diesel injection pump, a reservoir is connected in the delivery line connected to the high-pressure diesel connection HD.

If, for some reason, the diesel pressure should exceed a predetermined maximum value, then the hydraulic pressure applied to the hydraulic pressure port P could not move the working piston 46 further against this excessive pressure - the working piston 46 would stop until the excessive pressure in the pressure chamber 6 was reduced would be and only then move on simply because of vorbeschrie¬ surrounded pressure conditions. The maximum delivery pressure is thus limited in a very simple manner.

Shortly before reaching the dead center shown in FIG. 5, in which the pressure chamber 6 has its minimum volume, the oblique bore 88 overlaps the groove 56, so that the spring chamber 84 is connected to the hydraulic pressure port P. This pressure also acts on the right in Figure 5 end face of the control piston 72 so that it is moved by the force of the control spring 86 to the right with respect to the working piston 46. In this case, the pressure control edge 78 controls the connection between the hydraulic pressure connection P and the working space 66, while the connection to the hydraulic tank connection T is opened by the tank control edge 76. is, so that in the working space 66 of the tank pressure is applied. The still present in the pressure chamber 6 high pressure then acts to the right on the pump piston 18 and the piston 46, so that they are braked and zurückbe¬ moved - the cycle begins - as in Figure 1 darge¬ - from the front. As mentioned, the above-described force translator can be used for pressurizing other media and can be used, for example, in a hydroforming press or for waterjet cutting.

Disclosed is a pump, in particular a diesel injection pump, in which a pump piston is actuated via an oscillating cylinder. Oscillating cylinder and pump piston form a pressure booster whose Übersetzungs¬ ratio determines the maximum adjustable delivery pressure be¬.

LIST OF REFERENCE NUMBERS

1 pump

2 diesel part

4 hydraulic unit1

6 pump room

8 suction channel

10 high pressure channel

12 suction valve

14 pressure valve

16 pump housings

17 guide bore

18 pump pistons

20 stop ring

22 ring end face

24 tank room

26 tank channel

28 Axial projection 0 Pressure chamber 2 Housing 4 Spring plate 6 Pump spring 8 Graduation 0 Bellows 2 Room 4 Channel 6 Working piston 8 Axial bore 0 Insert 2 Tank ring space 4 Pressure ring space 6 Groove 8 Pressure channel 0 Drain channel 2 Connection channel 4 Branch channel working space

floor area

internal bore

spool

control collar

Tank control edge

Pressure control edge

guide collar

spring chamber

control spring

oblique bore

breakthrough

control edge

longitudinal channel

attack

piston rod

Claims

claims

1. Pump with a pump piston (18), through the stroke of a pressure medium via a low-pressure connection (ND) in a pump chamber (6) sucked and pressurized via a high pressure port (HD) from the pump room

(6) is conveyed, wherein the pump piston (18) via a hydraulic oscillating cylinder of a hydraulic part (4) is driven, which has a working piston (46) whose at least one active surface via a control valve (72) alternately with hydraulic high pressure or Hydrauliknieder¬ pressure acted upon is, wherein a control piston (72) of the control valve in the working piston (46) is integrated and at least one dead center of the working piston (46) by means of a housing-fixed stopper (68) is switchable.

2. Pump according to claim 1, wherein the control piston (72) has a piston rod (102) which protrudes at the dead center from the working piston (46) and in abutment with a housing wall (68) can be brought.

3. Pump according to claim 1 or 2, wherein the Steu¬ erkolben (72) has a tank control edge (76) and a pressure control edge (78) via which during a stroke of the working piston (46) has a connection between one of the pressure build-up direction effective active surface of the working piston (46) limited pressure chamber 66 with a hydraulic tank pressure or hydraulic supply pressure leading the connection (T, P) of the hydraulic part (4) is connectable.

4. Pump according to claim 3, wherein the section of the effective effective in the suction effective area of the Working piston (46) limited pressure chamber (30) is acted upon Hy¬ drauliktankdruck.

5. Pump according to claim 4, wherein the pump piston in the pressure chamber (30) is immersed and biased by a pump spring (36) against the working piston (46).

6. Pump according to claim 5, with a bellows (40) which surrounds the pump piston (18) sealingly and is supported on a pressure chamber (30) delimiting end wall of a pump part (2).

7. Pump according to claim 6, wherein the bellows from Falten¬ (40) encompassed space with a tank connection (TD) is connected.

8. Pump according to one of the preceding claims, wherein the working piston (46) has a control edge (88) via which in the region of the second dead center a connec tion to the hydraulic pressure port (P) and after a stroke a connection to the hydraulic tank connection (T) tax Is ¬ bar, so that a pump-side spring chamber (84) for the control piston (72) with hydraulic tank pressure or hydraulic pressure can be acted upon.

9. Pump according to claim 8, wherein the control edge is formed by a sheath opening (88) of the working piston (46).

10. Pump according to claim 8 or 9, wherein the spring chamber (84) a control piston (72) acting on the control spring (86) is received.

11. Pump according to claim 5 and 10, wherein the pump piston (18) and the control piston (72) via the Pumpenfe¬ the (36) and the control spring (86) in a basic position are biased, in which the pump piston (18) pulled back and the control piston (72) is extended in the direction of its stop position.

12. Pump according to one of the preceding claims, wherein a the tank and pressure control edge (76, 78) ausbil¬ dender control collar (74) of the control piston (72) with negati¬ ver cover with respect to the associated housing-most control edges (94, 96) is executed.

13. A pump according to any one of the preceding claims, wherein between the pressure chamber (6) and the low pressure port

(KD) a suction valve (12) and between the pressure chamber (6) and high pressure port (HD), a pressure valve (14 are provided.