WO1998054465A1

WO1998054465A1 - Radial piston pump

Info

Publication number: WO1998054465A1
Application number: PCT/DE1998/000500
Authority: WO
Inventors: Egon Eisenbacher; Franz Pawellek; Johann Schneider
Original assignee: Mannesmann Rexroth Ag
Priority date: 1997-05-27
Filing date: 1998-02-19
Publication date: 1998-12-03
Also published as: EP0985093B1; EP0985093A1

Abstract

The invention relates to a radial piston pump, of which at least one piston is housed in the pump casing, while the cylinder is moved by an eccentric shaft for fluid admission. This design principle enables coaxial arrangement of the intake and oulet valves at short distance of the crank housing, resulting in the flow of the fuel supply circuit being reduced to a minimum. Such a system is particularly suitable for high pressure gasoline pumps.

Description

description

Radial piston pump

The invention relates to a radial piston pump, in particular a high-pressure gasoline pump according to the preamble of claim 1.

Such radial piston pumps, for example known from DE 43 05 791 AI, are used, for example, as fuel pumps for internal combustion engines. The fuel delivery takes place via at least one radial piston, which is actuated by an eccentric of a shaft. Usually three such radial pistons are evenly distributed on the outer circumference of the eccentric shaft.

Each radial piston rests on the eccentric shaft via a sliding block and an eccentric ring. The eccentric ring is rotatably guided on the eccentric shaft and ensures secure guidance of the sliding block with minimal friction losses.

The cylinders for guiding the radial pistons are mounted in the pump housing and each have a suction and pressure valve, via which the fuel can be sucked out of the crank chamber or the pressurized fuel can be fed to the internal combustion engine.

Radial piston pumps of this type work quite satisfactorily when delivering fuels with a comparatively low vapor pressure, for example diesel fuel. When pumping more volatile fuels such as petrol, special measures to suppress the formation of vapor bubbles in the entire speed and temperature range of the engine are required. Since such fuels usually have a low have lower viscosity than diesel, the component tolerances should be designed to be relatively low to avoid leakage. Such leaks would reduce the efficiency of the pump and thus negatively affect engine performance.

In contrast, the invention has for its object to provide a radial piston pump that has a sufficient level of efficiency with minimal device complexity even when using low-viscosity fuels.

This object is solved by the features of claim 1.

The measure of arranging each radial piston of the pump to be stationary in the pump housing and of guiding the cylinders in an oscillating manner on the piston, i.e. By reversing the principle previously used, the filling process during the suction stroke of the cylinder can surprisingly be significantly improved compared to the conventional solution described at the beginning. The optimized filling behavior can be explained by the fact that during the suction movement of the cylinder (suction stroke) a liquid column in the area of the suction valve counteracts the movement of the cylinder due to its inertial forces and thus flows very quickly into the cylinder chamber when the suction valve is opened.

Another advantage of the solution according to the invention is that the standing piston makes it possible to arrange the two valves coaxially with one another.

In a preferred variant of the radial piston pump, the suction valve is formed on the shaft-side end section of the radially movable cylinder. In order to minimize the surface pressures and friction that occur, the cylinder can be supported on the eccentric shaft using a sliding block. It is preferred if a flattened eccentric ring is arranged between the sliding block and the eccentric shaft, which is rotatably mounted on the eccentric shaft and enables a flat contact of the sliding block due to its compensating movements.

In one design variant, the slide shoe is provided with a guide pin which dips into the cylinder bore, while the end faces of the cylinder are supported on a radially projecting guide flange of the slide shoe. This variant ensures reliable support of the sliding block with respect to the oscillating cylinder, so that tilting of the sliding block is almost impossible. The slide shoe can be attached to the cylinder in a particularly simple manner by pressing the guide pin into the cylinder bore, so that no fastening screw is required.

In an alternative variant, the sliding shoe can be provided with an annular shoulder which encompasses a circumferential recess in the cylinder.

The design effort is further minimized if the compression spring for prestressing the cylinder engages directly on one end section and is supported on the foot of the piston or the pump housing with the other end section. With this variant, separate spring plate parts can be saved, which are required for diesel pumps, for example.

As mentioned at the beginning, this construction allows the centric, coaxial arrangement of the two valves tile so that they can be fitted with high precision. Due to the coaxial orientation, the manufacturing effort for the formation of the bores is minimal.

The suction valve can, for example, be designed as a plate valve which is fastened in the cylinder.

In an alternative variant, the suction valve is formed by a slot control, a control slot being formed in the sliding shoe, which controls an opening in the eccentric ring.

The sliding block is preferably designed with an axial through opening, into which channels open, through which gasoline can be drawn in from the crankcase.

Both variants have the advantage in common that the suction valve is arranged in the cylinder and that the flow path from the crank chamber to the cylinder chamber is extremely short, so that the flow resistances are minimal and the filling behavior is further improved.

It is preferred that the pressure valve is designed as a ball valve in the piston, so that the entire unit comprising the piston, cylinder, suction and pressure valve can be preassembled, pretested and installed as a cartridge in the pump housing.

Due to the further development of designing the piston with a piston foot, the latter can accommodate the pressure valve and can be used for screwing to the pump housing. In an alternative variant, the piston is cylindrical and is fixed in the pump housing. This variant has the advantage that the manufacturing effort for producing the piston is minimal.

In an alternative design variant, the piston is pressed into a screw part, which in turn is screwed into the pump housing.

The radial piston pump according to the invention can be used particularly advantageously with low-viscosity fuels such as gasoline.

Further advantageous embodiments of the invention are the subject of the other subclaims.

Preferred exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. Show it:

1 shows a section through a radial piston pump in which the suction valve is designed as a plate valve,

FIG. 2 shows a section through a further exemplary embodiment of a radial piston pump, in which the suction valve is realized by a slot control,

Figure 3 shows a section through a third embodiment of a radial piston pump and

FIG. 4 shows a section through a fourth exemplary embodiment of a radial piston pump.

Figure 1 shows a section through a radial piston pump 1, the section being laid so that only one delivery unit 2 is visible. The radial piston pump 1 has a pump housing with a housing pot 4, which is closed by a housing flange 6. In the housing pot 4 are formed, for example, three cylinder receiving spaces 8, in each of which one of the conveyor units 2 is accommodated.

The conveyor units 2 are driven via an eccentric shaft 10, which is mounted in the housing pot 4 or housing flange 6 by means of slide bearings 12, 13. The sliding bearings are lubricated / cooled via a lubricant circuit, not shown.

The funding, in the present case gasoline, is fed via an input connection 14 into a crank chamber 16 formed between housing pot 4 and housing flange 6 with a predetermined admission pressure (1 to 3 bar) and, after pressure has been applied, is passed via an output connection 18 to the internal combustion engine.

The eccentric shaft 10 has a radially projecting eccentric 20, the center of which is offset by the eccentricity dimension e with respect to the axis of rotation 22 of the eccentric shaft 10.

The slide bearing 13 is pressed into a blind hole 24 in the housing flange 6. The other slide bearing 12 is located in a through bore of the housing cup 4, which is provided with a hub-shaped projection 26, from which an end section of the eccentric shaft 10 projects, which is provided with a coupling section 28 for the eccentric shaft drive.

In a radially widened part of the through bore of the housing pot 4, a shaft seal is arranged, which has a sealing ring 30 and a support ring 32. The seal (sealing ring 30, support ring 32) is fastened by means of a fastening ring 34, which is located in an internal annular groove in the through hole in hub-shaped projection 26 snaps so that the seal between the radial shoulder 36 of the through hole and the mounting ring 34 is fixed.

An eccentric ring 38 is rotatably mounted on the eccentric 20 of the eccentric shaft 10, the outer circumference of which is provided in the contact area with the conveyor unit 2 with a flattening which runs approximately perpendicular to the plane of the drawing in FIG. 1. The eccentric ring 38 is rotatably mounted on the eccentric 20, so that the flat maintains its orientation to the conveyor unit 2, so that a defined contact surface is created. A sliding bearing 39 can be provided between the eccentric ring 20 and the eccentric 20.

Due to the wobbling movement of the eccentric 20, the eccentric ring 38 performs a compensating movement, so that a relative displacement takes place approximately perpendicular to the plane of the drawing between the conveying unit 2 and the flattening. With regard to further details, reference is made to the following explanations.

The eccentric ring 38 is axially guided by two thrust washers 40, 41 flanking it, which are fastened in a radially widened part of the through bore of the housing pot 4 or the blind hole 24 of the housing flange 6. The mutually facing end faces of the thrust washers 40, 41 are designed as sliding surfaces for the end faces of the eccentric ring 38, which are also manufactured with high precision. The axial length of the eccentric 20 is selected to be slightly smaller than the axial length of the eccentric ring 38.

The housing pot 4 and the housing flange 6 delimit the crank chamber 16, from which the receiving spaces 8 for the conveyor units 2 extend in the axial direction. Each of these conveyor units 2 has a fixed piston 42, which is screwed radially into the housing pot 4 and on which an oscillatingly movable cylinder 44 is guided. The piston 42 is fastened by means of a piston foot 46 which is formed in one piece therewith and is screwed with its external thread into a corresponding receiving bore of the cylinder receiving space 8 in a sealing manner. The piston foot 46 is enlarged in the radial direction with respect to the piston 42. The cylinder 44 guided on the piston 42 has on its circumference an annular end face on which a compression spring 48 engages, the other end of which is supported on the piston foot 46. The cylinder 44 is biased by the compression spring 48 in the direction of the eccentric ring 38.

In the exemplary embodiment shown in FIG. 1, the cylinder 44 rests on the flat surface of the eccentric ring 38 via an annular sliding shoe 50. The end of the slide shoe 50 facing the cylinder 44 is immersed in a circumferential recess 52 of the cylinder 44. Since the sliding block 50 engages around the circumferential recess 52, a secure axial guidance of the sliding block 50 is ensured, so that the sliding block 50 cannot tilt during the compensating movement of the eccentric ring 38.

In the shaft-side end portion of the cylinder bore 54, a plate valve 56 is screwed, which consists of a plate 56 guided in the cylinder bore 54 with through holes 60 and a fastening screw 62, which is screwed into the cylinder bore 54 so far that the plate still has a movement in the axial direction Cylinder bore 54 can perform. The plate 56 can be assigned spring elements, not shown, for prestressing in the closed position. The contact surfaces for the plate 56 on the fastening screw 62 and in the cylinder bore 54 are tilsitzflachen executed. In the position shown, the through bores 60 are closed by the plate 56 resting against the seat of the fastening screw 62. The fastening screw 62 is provided with a through hole so that the gasoline can flow through the fastening screw 62 and the through holes when the plate 56 is lifted off into the cylinder space.

Instead of the fastening screw 62, the slide shoe 50 can also be used to fasten the plate 56.

The input connection 14 is connected to the crank chamber 16 via a bore system 64. The eccentric ring 38 has a slot 66 in the area of the flattened area, so that the gasoline can enter the cylinder space from the inlet connection 14 via the crank chamber 16, the slot 66, the through hole of the fastening screw 62 and the through hole 60 of the plate 56 in order to fill the latter .

As can also be seen from FIG. 1, the cylindrical piston 42 and the piston foot 46 are provided with an axial bore 68, into the upper end section of which the pressure valve 70 is screwed in FIG. In the exemplary embodiment shown, the pressure valve 70 is designed as a ball check valve, the spherical valve body 72 of which is resiliently biased against a valve seat in the axial bore 68. When the valve body 72 is lifted off, the pressurized gasoline (approx. 100 bar) can be guided via a connecting channel 74 to a circumferential groove 76 in the receiving bore for the housing flange 6. From there, the pressurized gasoline flows via a further channel 78 to the outlet connection 18. The construction shown in FIG. 1 has the advantage that the unit consisting of pressure valve 70, piston 72 and cylinder 44 and suction valve 56, 62 can be preassembled and then screwed into the pump housing as a cartridge or cartridge, so that the manufacturing and assembly effort is reduced to a minimum.

The construction described above has the further advantage that the flow paths from the crank chamber to the cylinder chamber are very short, so that the flow resistances are reduced to a minimum.

The part of the connecting channel 72 adjacent to the pressure valve 70 is formed approximately in the radial direction in the piston foot 46 and opens into a bore system in the housing pot 4, which is sealed to the outside by sealing plugs 80. Instead of the bore system consisting of several individual bores that merge into one another in the housing pot 4, a single oblique bore could also be introduced from the end face of the housing pot 4 (on the right in FIG. 1), so that the sealing plug 80 can be dispensed with.

During the suction stroke of the cylinder 24, i.e. during its downward movement from the position shown in FIG. 1 there is a liquid column below the plate 56 fastened in the cylinder 44, which counteracts the downward movement of the plate 56 and thus the cylinder 44 due to its inertia and thus the lifting of the plate 56 and the filling of the plate expanding cylinder space supports, so that the filling can be done faster and with less flow resistance.

The compensating movement of the eccentric ring 38 causes the gasoline located in the crank chamber 16 to swirl, so that possibly in the crank chamber occurring gas bubbles are swirled and cannot collect in one place.

Due to the design principle with the piston standing, the cylinder 44 can be guided and supported in a particularly simple manner, so that this design should also be superior to conventional solutions in terms of production technology. The wider slide shoe 50 enables a flat contact with the flattening of the eccentric ring 38, so that tilting movements or other undesired relative movements of the slide shoe 50 with respect to the support ring 38 are excluded.

FIG. 2 shows a further exemplary embodiment, which is identical to the previously described exemplary embodiment with regard to the pump housing structure with housing pot 4 and housing flange 6, the design and mounting of the eccentric shaft 10 with the eccentric ring 38 and the arrangement of the input and output connections 14, 18 , so that reference can be made to the relevant statements. The delivery unit 2 with the piston foot 46, the pressure valve 70, the piston 42 and the cylinder 44 axially movable thereon corresponds essentially to the above-described exemplary embodiment. Instead of the plate valve used as a suction valve in FIG. 1, however, the suction valve in the embodiment shown in FIG. 2 is realized by a slot control.

As in the exemplary embodiment described above, a slide shoe 82 is arranged between the cylinder 44 and the flattened area 84 of the eccentric ring 38 and has a T-shaped construction in the section shown in FIG. The slide shoe 82 has a guide pin 86 which dips into the cylinder bore 54. The part of the sliding shoe 82 resting on the flat 84 is as Guide flange 88 is formed, which is expanded in the radial direction with respect to the guide pin 86. The end face of the cylinder 44 rests on the annular end face of the guide flange 88 facing away from the flat 84.

The slide shoe 82 is provided with a control slot 90 which, in the relative position shown in FIG. 2, opens into the slot 66 of the eccentric ring 38. The dimensions of the control slot 90 are selected so that it opens or closes the slot 66 depending on the relative position of the eccentric ring 38 (compensating movement), so that the fluid connection from the crank chamber 16 to the cylinder chamber is opened or closed practically by the compensating movement of the eccentric ring 38. That In this exemplary embodiment, the provision of a separate valve body, such as, for example, the plate 56 in the exemplary embodiment according to FIG. 1, can be dispensed with, since its function can be taken over by the design of the control slot 90 and the slot 66. By means of such an embodiment, the manufacturing costs of the fuel pump according to the invention can be further reduced compared to the prior art, since the suction valve can be made with fewer components than the previously described solution.

To discharge leakages, a leakage bore, indicated in FIG. 2, can be formed between the crank chamber 16 and the receiving bore for the sealing ring 30, via which leakage fluid can be returned to the crankcase 16. In the embodiment shown in Figure 2, the end face of the guide pin 86 is provided on the outside with an undercut in which a seal 94 is located. In the exemplary embodiments described above, the piston 42 is provided with a piston foot 46, in which the pressure valve 70 and a connecting channel to the pressure line are formed. Furthermore, the piston 42 described above is provided with an external thread, via which it can be screwed into the housing pot 4. In the embodiment shown in Figure 3, the piston 42 is cylindrical with the substantially constant diameter. This variant has the advantage that the piston 42 can be precisely machined in a simple manner, for example by centerless grinding. Deviating from the construction principle described above, this cylindrical piston 42 is fixed by a suitable clamping device 100 in the joint between the housing cup 4 and the housing cover 6, which in this exemplary embodiment practically form a two-part pump housing with housing parts of approximately the same size.

To accommodate the piston 42, precisely manufactured receptacles 102 are formed or used in the contact areas in the housing pot 4 or in the housing cover 6, which allow the piston 42 to be fixed in position. Leaf springs, elastomers or other tensioning devices can be used as the clamping device 100. In the exemplary embodiment shown, clamping is carried out by means of tensioning screws 104, which are used to join the housing parts together. In the exemplary embodiment shown in FIG. 3, the piston 42 is supported essentially in the housing cover 6. In the parting line between a portion of the housing cover 6 encompassing the piston 42 and the housing pot 4, a circumferential, gas-tight seal 108 is provided, via which the cylinder receiving space 8 is sealed to the outside. The piston 42 is also provided with an axial bore 68, the pressure valve 70 being accommodated in the radially widened section of the axial bore 68 in FIG. 3, which in turn is designed as a check valve. The outlet of the pressure valve 70 is formed by a radial bore 110 of the piston 42, which opens into a through bore in the receptacle 102. This merges into a connection channel 112 on the housing side, which opens into a pressure line 114 which runs approximately perpendicular to the plane of the drawing and which is common to all three delivery units 2. From this pressure line 114, the pressurized gasoline is conveyed to the outlet connection of the pump.

An axially displaceable cylinder 44 is guided on the cylindrical piston 42, approximately in the same way as in the exemplary embodiment shown in FIG. This has a radial shoulder on which the compression spring 48 engages, which is supported on a spring plate 116 which bears against an end face of the cylinder receiving space 8. The axially movable cylinder 44 rests on the eccentric ring 38 over a slide shoe 50. In the lower area of the view according to FIG. 3 of the piston 42, a plate valve is mounted, the plate 56 of which is received in an axially movable manner on an enlarged part of the cylinder bore 54. The axial movement of the plate 56 in the opening direction is limited by a shoulder of the cylinder bore 54, while the plate 56 in the closed state rests on the fastening screw 62 designed as a valve seat on the end face. The plate 56 is biased into its closed position by a spring, not shown. When the plate 56 is lifted off, the gasoline can enter the cylinder bore 54 through the passage bore 60. The design of the plate valve thus corresponds essentially to that of the exemplary embodiment shown in FIG. 1.

FIG. 4 shows a further exemplary embodiment of a radial piston pump, which represents a modification of the construction shown in FIG. 2. In the exemplary embodiment shown in FIG. 4, the piston 42 and the cylinder 44 are also fastened in a housing pot 4 of the pump housing. The piston 42 is cylindrical and, with its upper end section in FIG. 4, is pressed into a receiving bore 120 of a screw part 122. The housing pot 4 is formed with a threaded receiving bore 124 for receiving the screw part 122. Instead of the press fit, the piston 42 can also be fastened in a different manner in the screw part 122, for example by screwing in, soldering, gluing, etc. The pump housing is sealed by an O-ring 126, which is received on the outer circumference of the screw part.

A support pin 128 extends from the bottom of the receiving bore 120 and plunges into an enlarged part of the axial bore 68 of the piston 42. The support pin 128 can be made in one piece with the screw part 122. The valve body 72 of the pressure valve 70 is biased against its valve seat 132 via a compression spring 130, which in turn is supported on the support pin 28. The pressurized fluid is guided via the radially extending connecting channel 74 via a manifold to the outlet connection of the radial piston pump, not shown.

The cylinder 44 guided on the projecting part of the cylindrical piston 42 is prestressed against the eccentric ring 38 by means of the compression spring 48, the sliding block 50 consisting of plastic being formed between the cylinder 44 and the eccentric ring 38. In which The exemplary embodiment shown in FIG. 4 is fastened in the cylinder bore by means of an interference fit 134 by means of an interference fit. An interference fit is formed between the guide pin 86 and the inner peripheral wall of the fitting bush 134. The radially projecting guide flange 88 bears against the lower end face of the cylinder 44 in FIG. 4.

The fitting sleeve 134 is axially extended beyond the guide pin 86 and forms an axial guide for the plate 56 of the plate valve. The plate 56 is biased by a spring 136 against the valve seat on the end face of the guide pin 36. The sliding block 50 has an axial through opening 138, in which open channels 140 which extend in the radial direction and which are formed in a star shape in the guide flange 88. The gasoline from the crank chamber 16 can enter the passage opening 138 through these channels 140.

In the exemplary embodiment shown in FIG. 4, the assembly and production outlay is reduced to a minimum by pressing the sliding block 50 into the cylinder 44 and pressing the piston 42 into the screw part 122, since no separate fastening means are provided for fixing these components have to. This practical example has proven to be particularly advantageous in practical operation. The risk of particle emissions due to breaking off threaded pieces is reduced to a minimum when using press fits for fastening the sliding block 50.

The radial piston pump according to the invention is characterized by an improved efficiency compared to conventional solutions with a simple construction. A radial piston pump is disclosed, in which at least one piston is arranged in a standing manner in a pump housing, while the cylinder can be driven by an eccentric shaft for fluid delivery. This design principle allows the suction and pressure valves to be designed coaxially with one another at a short distance from the crankcase, so that the flow paths for the conveying means are reduced to a minimum. Such a pump structure is particularly suitable for high-pressure gasoline pumps.

Claims

claims

1. Radial piston pump with an eccentric shaft (10) for driving at least one delivery unit (2) accommodated in a pump housing (4, 6), which has a piston (42, 46), a cylinder (44) and suction and pressure valves (56, 62 ; 70) for the conveying means, characterized in that the cylinder (44) is guided in a radial direction on the piston (42) and is supported on the eccentric shaft (10).

2. Radial piston pump according to claim 1, characterized in that the suction valve (56, 62) is arranged coaxially to the piston (42) at the shaft end of the cylinder (44).

3. Radial piston pump according to one of the preceding claims, characterized in that the cylinder (44) is biased towards the eccentric shaft via a compression spring (10) which engages a radial shoulder of the cylinder (44).

4. Radial piston pump according to one of the preceding claims, characterized in that the cylinder (44) via a sliding block (50, 82) on an eccentric ring (38) of the eccentric shaft (10) is supported.

5. Radial piston pump according to claim 4, characterized in that the sliding shoe is annular and surrounds a peripheral recess (52) of the cylinder (44).

6. A radial piston pump according to claim 4, characterized in that the sliding block (50) has a guide pin (86) which dips into the cylinder bore of the cylinder (44) and a radially projecting guide flange (88) on which an end face of the cylinder (44) is supported .

7. Radial piston pump according to claim 4 or 6, characterized in that the sliding block (50) with a in the cylinder bore of the cylinder (44) is immersed guide pin (86) which is pressed directly or indirectly into the cylinder bore.

8. Radial piston pump according to claim 4, 6 or 7, characterized by a control slot (90) of the slide shoe (82) through which the funding from the crank chamber (16) can be conveyed and through a slot (66) of the eccentric ring (38) openable is.

9. Radial piston pump according to one of the claims 4 to 7, characterized by a through opening of the

Sliding shoe (50) through which the conveying means can be guided to a suction valve, which is designed as a plate valve, the plate (56) of which is attached to the cylinder (44).

10. Radial piston pump according to claim 9, characterized in that the slide shoe (50) in the region of its bearing surface has at least one channel (140) which opens into the through opening of the slide shoe (50).

11. Radial piston pump according to one of the preceding claims, characterized in that the pressure valve (70) is arranged coaxially to the piston axis in the piston (46).

12. Radial piston pump according to one of claims 3 to 11, characterized in that the compression spring (48) is supported on the piston foot (46).

13. Radial piston pump according to one of the preceding claims, characterized in that the piston (42) has a radially expanded piston foot (46), via which it is fastened in the pump housing.

14. Radial piston pump according to one of claims 1 to 12, characterized in that the piston (42) is cylindrical and is fixed with an end portion in the pump housing (4, 6) by means of a clamping device.

15. Radial piston pump according to claim 14, characterized in that the piston (42) is fixed in the parting plane between the housing pot (4) and the housing flange (6).

16. Radial piston pump according to one of claims 1 to 12, characterized in that the piston (42) is pressed with a cylindrical portion in a screw part (122) which is screwed into the pump housing (4, 6).

17. Radial piston pump according to one of the preceding claims, characterized in that the delivery pressure is approximately 100 bar.