EP1045965A1

EP1045965A1 - Fuel injection pump

Info

Publication number: EP1045965A1
Application number: EP99971490A
Authority: EP
Inventors: Stuart-William Nicol; Stephan Jonas
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-10-29
Filing date: 1999-10-13
Publication date: 2000-10-25
Anticipated expiration: 2019-10-13
Also published as: DE19849925A1; DE59909958D1; JP2002529637A; EP1045965B1; US6453880B1; WO2000026520A1

Abstract

Disclosed is a fuel injection pump having an injection timing mechanism whose piston (10) is impinged upon by a return spring (16) and a pressure controlled by a pilot valve (24) on one front face (12) and is constantly exposed to a pressurized fluid source on the other front face (13) preferably supplying a speed-dependent pressure. The pilot valve (24) is moved in positive fit by a control piston (29) actuated by a control pressure and alters the pressure exerted on one front face (12) in a first closed pressure chamber (14). The injection timing piston (10) is not exposed to higher setting pressures exerted on said piston crosswise in relation to its direction of movement.

Description

Fuel injection pump

State of the art

The invention is based on a fuel injection pump according to the preamble of the patent claim. In such a fuel injection pump known from DE 44 40 749, the injection adjusting piston encloses the first pressure chamber with its one end in the cylinder and encloses a spring chamber with its other end in the cylinder, which is relieved of pressure. The control slide, which can be actuated by a control piston, is provided in the injection adjustment piston. This control piston protrudes with its end into the second pressure chamber receiving the compression spring and acts on the control slide against the force of a return spring acting on the control slide. At the other end, the control piston has, in a part fixed to the housing and separated from the second pressure chamber, a piston, one side of which is acted upon by a control pressure which adjusts the control piston against a return spring, the control slide following the adjustment of the control piston under the action of its return spring. To adjust the injection adjustment piston, the first pressure chamber is acted upon by a pressure medium which is controlled by the adjustment of the control slide relative to the control piston and which is actuated via a radial bore in the

Injection adjuster piston is fed to the control spool. For this purpose, there is also a pressure medium inlet in the peripheral wall of the cylinder, which is constantly connected to a groove extending in the direction of adjustment of the control piston and from which the radial bore leads to the cylinder bore receiving the control slide. The spray adjustment piston is thus acted upon by the one-sided inflow of the pressure medium. A recess in the cylinder wall also provides a connection to an interior of the pump in which the cam drive is located. This engages with an actuating arm through this recess into a corresponding recess in the injection adjuster piston, so that it can bring about a rotation of the cam drive as part of its longitudinal movement. The injection adjustment piston is relieved of pressure on one side from this side. In this known pump, expensive means must be provided with which the one-sided loads on the injection adjustment piston are compensated for, so that there are no operational failures due to wear. In particular, if the injection adjustment piston is eccentrically connected to the associated cam drive, forces also occur from the side of the cam drive, which act as tilting moments on the injection adjustment piston and as a result lead to increased one-sided local pressures between the lateral surface of the injection adjustment piston and the one receiving it Cylinder guide. Advantages of the invention

The fuel injection pump according to the invention with the features of the characterizing feature ensures that the injection adjusting piston is only acted upon by the high signal pressure in the axial direction and is not exposed to force components which act in the radial direction and which trigger the above-mentioned risk. The force exerted on the injection adjusting piston by the second pressure chamber serves as a constant base load, which counteracts the restoring force in the first pressure chamber. The restoring forces of the restoring means in the first pressure chamber also act exclusively axially on the injection adjustment piston. Furthermore, the space accommodating the cam drive is designed as a relief space, so that in the area of the mechanical connection of the cam drive, which is realized as an actuation arm, likewise no high pressure acts radially on the injection adjustment piston. Thus, the spray adjustment piston is evenly loaded by its adjustment means. Accordingly, the frictional forces and thus the wear between the injection adjustment piston and its cylinder wall receiving it are reduced.

Advantageous developments of the subject matter of claim 1 are claimed in the subclaims. They are presented with their advantages in connection with the following description of an exemplary embodiment. drawing

Three exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the description below. 1 shows a first exemplary embodiment of the invention based on a section through the injection adjuster of a fuel injection pump of the radial piston type, of which only the cam ring of the cam drive of the pump piston of the fuel injection pump is shown, FIG. 2 shows a partial section through the

1 in a plane perpendicular to the illustration of FIG. 1, FIG. 3 a section through the injection adjustment piston along the line III-III, FIG. 4 a section through the injection adjustment piston along the line IV-IV, FIG. 5 a second exemplary embodiment of the invention with an alternative coupling of the control slide with the control piston and FIG. 6 shows a third embodiment of the invention with a modified control piston and a modified coupling of the control piston to the control slide.

description

Fuel injection pumps of the distributor type can either be used as a distributor as well

Axially driven pump pistons that serve pump pistons can be provided, or radial pistons can be provided that request radially into a delivery channel arranged in a distributor. In both cases, the pump pistons are driven by one of the drive shafts

Fuel injection pump actuated moving cam drive. A part of such a so-called radial piston pump is shown in section in FIG. 1. In such pumps, for. B. four pump pistons, not shown here, are provided are mounted so as to be displaceable in radial bores of the distributor, which run at the same angular distance from one another radially to the axis of the distributor. On one end, they enclose a common pump work space, which is filled with fuel in a known manner during the radial outward stroke of the pump piston and is connected via a pressure line to a distributor opening on the jacket surface of the distributor during a radial inward stroke, the distributor opening going out at the circumference of the distributor Controls injection lines, one of which is supplied with fuel brought to injection pressure when the pump pistons move inward. The distributor is driven in rotation by a drive shaft in such a way that on the one hand the distributor opening can perform its control function and on the other hand the

Pump pistons are moved in the circumferential direction along a cam track. This construction is not shown in detail here, since it is assumed to be generally known. Only part of the cam track 2 is shown, which is arranged on the inside of a cam ring 3 and which the pump pistons follow. The cam ring 3 represents the substantially stationary part of the cam drive of the pump piston, while the pump piston moving device, the z. B. can be a roller plunger of the pump piston leading ring or distributor, which is coupled to the drive shaft, represents the moving part of the cam drive. The outer circumference of the cam ring is mounted in a cylindrical recess 5 in the housing 6 of the fuel injection pump and can be rotated in a plane perpendicular to the drive axis of the fuel injection pump. The rotational position of the cam ring can now be related to the drive movement of the distributor change the time at which the pump pistons begin to stroke.

The injection adjustment piston is tightly displaceable in a cylinder 11 and encloses a first pressure chamber 14 with its one end side 12 with the closed end of the cylinder 11 and with its other end side 13 a second pressure chamber 15 in the cylinder 11, which is likewise closed there. In the first pressure chamber, a return spring 16 is arranged, one end of which is supported on a closure part 17 which closes the cylinder 11 and the other end of which is supported on one end face 12 of the injection adjustment piston 10 and is thus clamped, the injection adjustment piston with its other end face 13 in Bring contact to the wall 20 closing the cylinder 11 opposite or a stop arranged there. For rotation, the cam ring 3 has a coupling part in the form of a pin 7 protruding radially outwards from this, which through an opening 8 in the wall of the cylinder 11 from the interior 4 receiving the cam drive

Immersed fuel injection pump into a recess 9 of an injection adjusting piston 10.

A cylinder bore 22 is also provided in the injection adjustment piston 10, in the form of a blind bore lying eccentrically to the axis of the injection adjustment piston and starting from one end face 12. A control slide 24 used there closes with one

Slide end 25 with the end of the blind bore a third pressure chamber 23, which via a channel 26 opening on the lateral surface 27 of the injection adjustment piston, constantly with the Breakthrough 8 is connected to the pressure-relieved interior 4 of the fuel injection pump. At the other end, the control slide projects into the first pressure chamber 14 and is coupled there to a tappet 28 of a control piston 29.

This plunger has a spring plate 30 on which one end supports a control spring 31, the other end of which is supported on the closure part 17. The plunger is guided in a bore 32 of the closure part 17 lying coaxially to the axis of the injection adjustment piston and projects into a space in the form of a cylinder 33 which is arranged inside the closure part 17. There the tappet merges into a piston 34 which slides tightly in the cylinder and, on the side of the 1st pressure chamber 14, includes a working chamber 35 together with the tappet 28, which is supplied with pressure medium via a bore 36. The other side of the piston 34 is exposed to the pressure of a relief space. The pressure medium supplied to the working space 35 is kept at a control pressure which is essentially dependent on the speed, but can also be varied as a function of other parameters of the internal combustion engine, such as, for. B. depending on the load. The output pressure varied in this way is provided in a control pressure source, which is not shown here, in a known manner. at

Pressure increase in the working space 35, the plunger 28 is moved together with the piston 34 against the force of the control spring 31. So that the control slide 24 can follow the movement of the control piston 29 even without coupling by force fit, which is usually achieved by a weak spring, the control slide 24 is now coupled to the plunger 28 of the control piston 29 by a positive connection. This looks at the end of the spool and Plunger each have a congruent claw 38 in such a way that the claws can be brought into engagement with one another transversely to the movement of the control slide and the plunger and are coupled to one another in the adjusting direction essentially without play. The coupled state can be advantageously secured in that the spring plate 30 with a bore 39 leading both the end of the plunger 28 and with one that is offset

Control piston lying end of the control slide comprehensive recess 40 is provided, the spring plate is held under the action of the clamped control spring 31 in the position comprising the end of the control slide and in addition the end position of the spring plate on the plunger is secured by contact on the end of the control slide. This installation situation is shown in FIG. 4 using a sectional view along the line IV-IV.

The control spring 31 arranged coaxially to the return spring 16 in the first pressure chamber 14 is flushed by pressure medium, preferably pressure medium provided by the fuel, the pressure of which is set by the control slide. For this purpose, the control slide 24 has three annular collars separated by two grooves 42, of which a first annular collar 43 is arranged on the side of the 1st pressure chamber 14 and has a 1st control edge 45 to which a part of the control slide provided with a flow cross section 46 is attached then leads to the first pressure chamber 14. The flow is carried out in the form of a flattening 52, as can also be seen from the section in FIG. 3, but can also have a different shape. The middle collar

47 between the first collar 43 and the second collar

48 is used for hydraulic separation and guidance and has itself no tax function. The second collar 48 has a second control edge 49 on the side of the third pressure chamber 23.

In the injection adjusting piston there is also an inflow bore 50 on the other end 13 of the second pressure chamber 15 and an outlet bore 51 emerging on one end 12 of the injection adjusting piston in the first pressure chamber, which run parallel to the control slide and each have a short radial bore in the cylinder bore 22 of the spool mouth. The mouths of the inflow bore and the drain bore lie at an axial distance from one another which is smaller than the axial distance from the two control edges 49 and 45 from one another, so that both bores are closed in a central position of the control slide 24. As can be seen in FIG. 2, the inflow or outflow bore is then opened, depending on the position of the control slide relative to the injection adjustment piston, so that the 1st pressure chamber is connected to the pressure source of the 2nd pressure chamber or is relieved to the relief chamber 4. The pressure in the 1st pressure chamber is controlled accordingly and the pressure adjustment piston is adjusted by the pressure in the 2nd pressure chamber when a parameter changes with the additional action of the return spring until a connection to the 1st or 2. The pressure chamber is restored. Then the control slide closes both, the inlet bore 50 and the outlet bore 51 and the injection adjusting piston remains in the position reached. Then the

Control spool adjusted depending on changing operating parameters of control spool, this can be done to the right or left. Depending on the pressure in the 1st pressure chamber via the drain hole 51 and the channel 26 relieved or increased by the pressure medium supplied via the inlet bore with subsequent adjustment of the injection adjustment piston up to the equilibrium of forces.

The control slide 24 and the control piston 29 are, as far as the pressurization in the first pressure chamber 14 is concerned, in the equilibrium of forces, since both have the same diameter in the region of the first pressure chamber. The control pressure fed into the working space 33 can be derived from the pressure prevailing in the second pressure space, for example by connecting the working space 33 to the inlet to the second pressure space via a throttle and relieving it to the relief space via a variable discharge throttle. Instead of the variable throttle, a solenoid valve can be used, which is clocked or adjusted accordingly. This then takes place as a function of operating parameters that have not yet had an effect on the pressure of the pressure medium inlet to the second pressure chamber 15. The pressure in this pressure chamber is generated by the feed pump and is therefore speed-dependent. The rear of the piston 34 of the control piston is relieved of pressure, so that leakage quantities of pressure medium can flow off there. Fuel is used as the pressure medium, but a separate pressure oil circuit can also be used. In order to counter pressure fluctuations, a throttle 55 is arranged in an inlet line, which supplies the pressure medium from the feed pump of the fuel injection pump to the second pressure chamber 15 as a function of speed, which restricts the second pressure chamber 15 from the pump piston in the request phase when the cam ring impacts the shock is compliant. A second exemplary embodiment of the invention is shown in FIG. 5. This exemplary embodiment differs from the first exemplary embodiment in that the control slide 124 is now arranged coaxially with the injection adjustment piston 110, the recess 109 being less deep than the recess 9 in the exemplary embodiment according to FIG. Accordingly, the control slide 124 is now coaxial with the control piston 129, so that the connection between

Spool 124 and spool 129 can now be easily realized by a pin 57. For this purpose, the end of the control piston 129 located in the first pressure chamber 14 is pot-shaped, with a recess 58 into which the end 59 of the control slide 124 is immersed. Through the pot-shaped end 60 of the control piston 129, the pin 57 is guided transversely to the axes of the control slide 124 or the axis of the control piston 129 through corresponding bores. On the outer circumference, the pot-shaped part 60 has a collar 61, onto which a ring 62 is pushed or pressed, which lies in overlap with the ends of the cross pin 57. Thus the pin is secured against shifting. The ring also serves as a support for the control spring 131, which is now supported on the end face 12 of the injection adjustment piston 110 and is able to hold the ring 62 in its position. On the other hand, it is also possible to press the ring 62 onto the pot-shaped part 60. The outer jacket surface 63 of the cup-shaped part which then projects over the ring 62 serves for the radial guidance of the control spring 131.

In a departure from the embodiment according to FIG. 1, the control piston 129 no longer has any specially shaped plungers. The bore 32 receiving the control piston as Cylinder 33 formed by immersing one end of the spool 129. The other end of the control piston 129, which plunges into the first pressure chamber 14, is then used for coupling to the control slide 124. The rear region of the control piston provided in FIG. 1, which is connected to the relief chamber, is thus eliminated.

As in the exemplary embodiment according to FIG. 1, the control slide 124 and the control piston 129 have the same area exposed to the pressure in the first pressure chamber 14. However, the working direction of the control piston 129 is now reversed.

A third variant is now provided in FIG. 6 in a modification to the embodiment according to FIG. 5. Here too, spool 224 and spool 229 are in turn arranged coaxially with each other. The coupling of these two parts to one another takes place by means of a dovetail-like connection known per se. In a departure from FIG. 5, the control spring 231 is now displaced out of the first pressure chamber 14 into the cylinder 233. The cylinder 33 is enlarged compared to the diameter of the bore 32 so that it can receive the control spring 231, together with a head-like end 66 on which the control spring 231 is supported at one end. The other end is supported on the housing at the transition from the bore 232 into the cylinder 233. The cylinder 233 is again acted upon in the same way as in the exemplary embodiment according to FIG. 5 with control pressure which displaces the control piston 229 against the force of the control spring 231 toward the control slide 224. With the solution provided here, an injection adjuster of a fuel injection pump is achieved, the injection adjustment piston of which is no longer loaded on one side and across the adjustment direction by higher pressures. By means of the control slide arranged offset to the axis of the injection adjustment piston, the pin 7 can engage far into the injection adjustment piston 10, which reduces the generation of tilting moments on the injection adjustment piston.

Claims

Expectations

1. Fuel injection pump with a cam drive for at least pump pistons and one that serves to adjust the start of injection acting on the cam drive

Injection-adjusting piston (10) which delimits a first pressure chamber (14) with its one end face (12) in a cylinder (11) and delimits a second pressure chamber (15) with its other end face (13) in the cylinder (11) is acted upon by a pressure medium which adjusts the injection adjustment piston (10) counter to a restoring means arranged in the 1st pressure chamber (14) and with a control slide (24) which is displaceably arranged in a cylinder bore (22) and which can be actuated against the force of a control spring (31) is, and the spool (24) in the cylinder bore (22) with

Control edges (45, 49) controls a pressure medium inlet (50) to one of the pressure spaces (14, 15) or a pressure medium outlet (51) from one of the pressure spaces (14, 15) or closes both, characterized in that the second pressure space (15 ) is permanently connected to the pressure medium from a pressure source and the first pressure chamber (14) is only connected to the pressure medium inlet (50) controlled by the control slide (24) and connects the first pressure chamber (14) to the pressure source or to the first pressure chamber (14) with a relief space connecting pressure medium outlet (51) is connectable or completely closable.

2. Fuel injection pump according to claim 1, characterized in that as a return means in addition to that of

Control spool (24) controlled pressure a return spring (16) is provided.

3. Fuel injection pump according to claim 1 or 2, characterized in that the control pressure depending on the

Speed or in addition of other operating parameters of the internal combustion engine is set.

4. Fuel injection pump according to claim 3, characterized in that the second pressure chamber (15) is constant with the

Pressure side of a low-pressure fuel supply of the fuel injection pump serving pump is connected.

5. Fuel injection pump according to claim 4, characterized in that the delivery pressure of the delivery pump changes depending on the drive speed of the fuel pump.

6. Fuel injection pump according to claim 4, characterized in that a throttle (55) is arranged in the connection between the second pressure chamber (15) and the fuel pump.

7. Fuel injection pump according to one of claims 1 to 6, characterized in that the injection adjusting piston (10) on its jacket compartment has a receiving arm (7) serving recess (9) which is connected to the interior (4) fuel injection pump.

8. Fuel injection pump according to one of claims 1 to 7, characterized in that in the injection adjusting piston (10) in the axial direction from its one, to the 1st pressure chamber (14) adjacent end face (12) outgoing cylinder bore (22) is arranged, in which the control slide (24) is displaceable and there with the control edges (45, 49) depending on the position of the control slide (24)

Injection adjusting piston (10) controls the pressure medium inlet (50) to one of the pressure chambers (14, 15) or the pressure medium outlet (51) from one of the pressure chambers (14, 15) or closes both, the control slide (24) being actuated by a control piston (29) which has a surface which is acted upon by a control pressure against the force of a control spring (31) and is arranged in a space (35) which is arranged in a part (17) fixed to the housing and is separated from the cylinder (11) and the control slide (24 ) with its one end face (25) in the cylinder bore (22) encloses a third pressure chamber (23) which is permanently connected to the relief chamber, preferably a pump interior (4) of the fuel injection pump receiving the cam drive (3) of the fuel injection pump.

9. Fuel injection pump according to claim 8, characterized in that the control piston (28, 129, 229) with the control slide (24, 124, 224) is at least positively connected in the adjusting direction and one of the pressure in the 1st pressure chamber (14) exposed in the adjusting direction Has area which is the same size as the area of the control slide (24, 124, 224) exposed to the pressure in the 1st pressure chamber (14) in the adjusting direction.

10th Fuel fine injection pump according to claim 8 or 9, characterized in that the control slide (24, 124, 224) one The piston part has a pressure medium inlet (50) for

I. pressure chamber (14) controlling 1st control edge (45) and a pressure medium outlet (51) from the 1st pressure chamber (14) controlling 2nd control edge (49) to which control edges are used for pressure medium flow cross sections (52, 23) on Connect the control spool, the inlet of the pressure medium inlet (50) into the cylinder bore (22) and the outlet of the pressure medium outlet (51) from the cylinder bore (22) in the axial direction of the control spool.

II. A fuel injection pump according to claim 10, characterized in that the restoring means serve the pressure controlled by the control slide in the 1st pressure chamber (14) and a compression spring (16) which is supported in the 1st pressure chamber (14) between the injection adjustment piston (10) and the housing.

12. A fuel injection pump according to claim 11, characterized in that the control spring (31) of the control piston (29) is arranged in the first pressure chamber (14) and there between a spring plate (30) supported on the tappet (28) of the control piston (29). and the housing-fixed part (17) is clamped.

13. Fuel injection pump according to claim 11, characterized in that the control spring (31) of the control piston (29) is arranged in the 1st pressure chamber (14) and there between the control piston (29) and one end face (12) of the injection adjustment piston (10) is clamped.

14. Fuel injection pump according to claim 12 to 13, characterized in that the control piston (29) arranged in the fixed housing part (17) as a control cylinder immersed trained space and there separates a control work space from a relief space with a piston part.

15. Fuel injection pump according to claim 11, characterized in that the control piston (229) is immersed in the space (233) arranged in the housing-fixed part (17) and there by the control spring (231), which is located at one end on a shoulder ( 66) on the control piston (229) and at its other end on the housing-fixed part (17).

16. Fuel injection pump according to claim 9, characterized in that the positive connection between the control slide (24) and the control piston (29) consists of a claw connection, the control slide (24) in a to the axis of the injection piston (10) arranged offset cylinder bore (22) is led.

17. Fuel injection pump according to claim 9, characterized in that the positive connection between the control slide (24, 124, 224) and the control piston (29, 129, 229) consists of a pin connection (57).

18. Fuel injection pump according to claim 17, characterized in that the pin connection consists of a pot-shaped end (60) at one of the mutually adjacent ends of the control piston (129) or the control slide (124) into which the other end of the control slide (124) or of the control piston (129) is immersed and held there by a cross pin (57) which is guided through the wall of the pot-shaped end (60) and the end of the control slide (124) immersed there, which in turn is held by an outside on the pot-shaped end (60) deferred or Pressable ring (62) is fixed, which also serves as a support for the control spring (131) which is otherwise guided on the remaining pot-shaped part.

19. Fuel injection pump according to claim 18, characterized in that the ring (62) under the action of the control spring (131) in contact with an outer collar (61) of the pot-shaped end (60) (is held.