EP0712464A1

EP0712464A1 - Piston pump

Info

Publication number: EP0712464A1
Application number: EP95920733A
Authority: EP
Inventors: Manfred Ruoff; Helmut Rembold; Ernst Linder
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-06-08
Filing date: 1995-05-27
Publication date: 1996-05-22
Anticipated expiration: 2015-05-27
Also published as: DE59500473D1; ES2106643T3; US5626466A; WO1995033924A1; KR960702888A; JPH09501481A; EP0712464B1; DE4419927A1

Abstract

Proposed is a piston pump which is intended for the provision of fuel at high pressure, in particular petrol with low self-lubricating characteristics, a cam (12) driven to rotate being fitted as the pump-piston actuator in order to avoid wear on the drive side, the drive motion being imparted to the pump piston (38) by the cam by means of a flexible transmission element (53).

Description

Piston pump

State of the art

The invention is based on a radial piston pump according to the claim 1, as is already known from DE-Al-37 01 857. There, an annular device is provided as the actuating element, which is mounted on one side of its axial extension on a ball bearing, which in turn is fixed on an eccentric at the free end of a drive shaft. The known ring device overlaps a support-shaped housing part into which the pump cylinders are incorporated, with pump pistons emerging radially outwards, which come into contact with the ring device via cup-like designs. When the eccentric is driven, the ring device carries out a wobbling eccentric movement, in the course of which the pump pistons are moved alternately inwards or outwards and thereby perform their suction and delivery strokes. In this embodiment of a radial piston pump, the transferdoric movements between the actuating element and the pump piston are relatively small compared to known designs in which the pump pistons slide over centrally located cam tracks, but these are not completely prevented in the known embodiment. In particular, depending on the rotational position of the ring device, the pump pistons assume positions in which they are not perpendicular to the inner surface of the driving ring device. This nevertheless results in transverse forces at the point of contact of the pump piston with the ring device and sliding friction gene, because of the design, the surface of the ring device shifts in relation to the pump piston. The known radial piston pump is intended in particular for supplying a hydraulic anti-lock braking system, pressure medium which has more lubricating properties within limits can be selected as the conveying medium. However, if such a pump is to be used to generate pressure from media which have only little or no lubricating properties, such as, for example, For example, gasoline, high sliding friction is to be expected in the contact areas between the pump pistons, which leads on the one hand to an increased power loss when driving the radial piston pump and on the other hand to increased wear. Due to material removal and seizure processes in the event of high suction on the drive side of the pump pistons, a considerably restricted service life is to be expected here. Pumps that are exposed to petrol in this area behave as if they are lubricated and run dry.

Advantages of the invention

The radial piston pump according to the invention with the characterizing features of claim 1 has the advantage that sliding friction between the pump piston and its actuating element is completely switched off by the drive of the pump piston via a flexible transmission element. There is no sliding friction and thus loss of friction and wear are avoided. The pump is thus very well suited for the delivery of fuel, in particular gasoline, which is delivered under high pressure to a pressure accumulator, from where the fuel of a fuel injector is electrically controlled is supplied, via which the fuel is injected into an internal combustion engine.

The configuration according to claim 4 results in particular in the advantage that a longitudinally symmetrical quadrilateral is formed by the transmission element and the transmission part together with the ring-shaped part that can be formed into a parallelogram without the presence of ring joints which are subject to sliding friction. Because the ring-shaped part is rotatably mounted on the eccentric, the assignment of the transmission part orientation and orientation of the ring-shaped element which is intended for one another is maintained when the latter is deflected via the eccentric. The configuration according to claim 6 results in a construction that is particularly simple to implement, the parts of the transmission element running parallel to one another being able to be placed in end grooves of a part receiving the pump cylinder. In a particularly advantageous manner, according to claim 8, a deflection arrangement is provided on the ring-shaped part for producing the parallel course of the parts of the transmission element, which arrangement cooperates with the transmission part. In this case, according to patent claim 13, circular-cylindrical surface parts are provided on the contact areas of the parts of the transmission element, on which the two parts of the transmission element can unwind or wind up when the transmission part is displaced relative to the annular part. The transmission element advantageously consists of flat strip material according to claims 15 and 16, which has great flexibility in the direction of the deformation plane with a high transmission cross-section and thus resilience. Another advantageous embodiment According to claim 17, the storage of the annular part on the eccentric from the rest of the gasoline-filled housing is separated and sealed. Good storage conditions are thus achieved, while avoiding a dry running possible due to the action of the gasoline, as mentioned at the beginning. In a modification to this, a bellows enclosing the bearing and the end of the eccentric is provided and, according to claim 21, a device is provided through which lubricant can be introduced into the region of the bearing of the ring-shaped part on the eccentric which is encapsulated by the gasoline-filled interior. According to claim 13, pressure lubrication can also be realized, since the spring clamped between the outside of the bottom and the housing wall, the axial position of the annular part is secured against the inflowing lubricant pressure.

Further advantages of the embodiments of the invention listed in the subclaims can be found in the description below.

drawing

Four exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the description below. 1 shows a longitudinal section through the radial piston pump according to the invention in a first exemplary embodiment, FIG. 2 shows a section along the line II-II from FIG. 1 through the first exemplary embodiment, FIG. 3 shows a partial view analogous to the section from FIG. 2 for a second exemplary embodiment, Figure 4 shows a third embodiment with a single band 5 shows an axial view of the exemplary embodiment according to FIG. 4, FIG. 6 shows a modified form of the sealing of the bearing on the eccentric using the exemplary embodiment according to FIG. 4, FIG. 7 shows a fourth exemplary embodiment with a two-part part lying along the axis of the drive shaft Transmission element, FIG. 8 shows a fifth exemplary embodiment with a part-ring-shaped part for fastening the transmission element, and FIG. 9 shows a section perpendicular to FIG. 8, showing the drive shaft.

Description of the embodiments

The radial piston pump shown in FIG. 1 has a pump housing 1 in which a drive shaft 2 of the radial piston pump is mounted. At one end protruding from the pump housing, a drive gear 4 is fastened to the drive shaft. The shaft is supported by means of two ball bearings 5, which are sealed to the outside and to an interior 6 of the radial piston pump by seals 7, so that no fuel can escape from the interior 6, which is filled with gasoline, along the drive shaft to the ball bearings .

At its end protruding into the interior 6, the drive shaft has a peg-shaped eccentric 12 which is eccentric to the central axis 11 of the drive shaft, with the eccentricity e shown in FIG. On the eccentric a roller bearing 14 is arranged, which is a needle bearing in the example shown, the z. B. has only a needle cage and a liner and axially between a shoulder 15 and a locking ring 16 with Is secured. On the needle bearing a ring-shaped part 20 is mounted, which in the present case is pot-shaped with a bottom 21 which is opposite the end face 17 of the eccentric 12 and there by a compression spring 22 which engages on the outside of the bottom and which is attached to a housing cover

23 is supported in contact with the inside of the floor on a ball

24 is held, which is inserted into an outlet opening 18 of a lubricant channel 10 running axially through the eccentric 12. The lubricant channel 10 enters the drive shaft radially in the area between the two ball bearings 5 and is supplied with lubricant from a lubricant source (not shown) by a lubricant feed opening 9 which opens into the annular groove 8 arranged between the two ball bearings . Grease or lubricating oil which is supplied under pressure can be used as the lubricant. In the latter case in particular, the compression spring 22 is required to hold the annular part 20 in its intended position, which is predetermined by the ball 24. When lubricated with grease, there are no significant axial forces. In this case, the compression spring can be replaced by a ball, which secures the position of the ring-shaped part against axial accelerations transmitted from the internal combustion engine.

The annular part 20 has on its side facing away from the base 21 a diameter widening 25 which serves to receive a shaft seal 26. A closed space is thus formed between this shaft seal and the interior of the cup-shaped annular part, which is filled with lubricant for lubricating the needle bearing 14. Instead of a needle bearing, a plain bearing can also be used, which can also be used with a suitable material pairing Dry bearing can be formed, then a corresponding lubricant supply and shaft seal can be dispensed with.

The interior 6 is formed by a cup-shaped recess in the pump housing 1 and, with its cylindrical wall 28, comprises the eccentric 12 and the annular part in the circumferential direction. On the face side, the interior 6 is closed by the cover 23, which is also cup-shaped and encloses the housing 1 with its cylindrical wall 30 to form an annular space 31, for the tight sealing of the annular space 31 to the outside with the end of its cylindrical wall in one Front ring groove 32 of the pump housing 1 engages and there forms a tight connection to the outer boundary ring wall of the front ring groove 32 via a seal 33 which is inserted in an outer ring groove of the cylindrical wall 30. Since there is a higher pressure than the atmospheric ambient pressure in the operation of the radial piston pump in the annular space 33, the pressure difference between the annular space 31 and the environment supports the tight contact of the cylindrical wall 30 with the seal 33 on the cylindrical wall of the Ring groove 32.

In the annular web 34 of the pump housing formed between the pump interior 6 and the annular space 31, pump cylinder bores 36 are arranged, which are designed as cylindrical blind bores arranged radially to the central axis 11 starting from the annular space 31. In the example shown, three such cylinder bores 36 are arranged at a uniform angular distance from one another. They each hold a pump piston 38, which has an axially extended end on its part projecting outward into the annular space 31 Has pin 39 on which a transmission part 40 with its bore 41 is placed. The transmission part is prismatic and mushroom-shaped in cross-section with a lower flat surface 42, which comes into contact with the remaining end face of the pump piston, with an upper curved surface 43 with a large radius and with a curved surface 44 adjoining this surface with a small radius. With regard to a plane passing through the pump piston axis and the central axis 11, the transmission part is constructed symmetrically.

A compression spring 46 is arranged within the cylinder bore 36 and is supported in an axial blind hole 47 in the pump piston 38. The pump piston includes a pump working chamber 48 in the cylinder bore, which is supplied with pressure medium, in this case gasoline, via a radial bore 49, which is controlled by the outer surface of the pump piston, during the suction stroke of the pump piston. During the pressure stroke of the pump piston, the radial bore is closed and the enclosed pressure medium is fed via a pressure channel 50 leading from the bottom of the cylinder bore 36, which contains a check valve 51 opening in the outflow direction, to a pressure accumulator from which, for example, fuel injection nozzles are supplied with fuel which but is not shown in more detail here.

The pump piston is driven by the eccentric 12. For this purpose, a flexible transmission element 53 is provided between the pump piston and the annular part 20 mounted rotatably on the eccentric. In the example shown in FIGS. 1 and 2, this consists of tape material, preferably made of steel strip, which is placed over the curved surface 43 with a large radius of the transmission element 40 and is penetrated there in the region of a form-fitting opening 54 by the pin 39 as a counterpart of a form-fitting connection. The transmission element is thus secured against displacement on the transmission part. The transmission element leads in two mutually parallel parts 55 after deflection on the curved surface 44 with a smaller radius through end-side recesses 56 of the ring web 34 to the annular part 20. There, the mutually parallel parts 55 of the transmission element 53 are attached to cylindrical pins 58, which are inserted into the annular part 20 parallel to the eccentric axis, are deflected and then follow the cylindrical outer surface of the annular part 20 between the two cylindrical pins 58 until their ends, which also have positive-locking openings 59, form-fit into a corresponding, engage radially in the annular part inserted form-fitting pin. The cylindrical pins 58 have the same radius as the curved surfaces 44 of the transmission part with a small radius, the distance between the centers of curvature of this surface being the same as the distance between the axes of the cylindrical pins. In this way, the transfer element in the form of a flat ribbon, which has been folded over in this way, forms a rectangle consisting of the two mutually parallel sides of the parts 55 of the transfer element and the imaginary connection between the centers of curvature of the curved surfaces with a small radius 44 of the transfer part and the imaginary connection between the axes of the cylinder pins 58, which imaginary connections are parallel to each other. The mutually parallel parts 55 are seen in the direction of rotation of the eccentric in front and behind the pump piston, what z. B. is also fulfilled in that they lie in a common radial plane to the axis of the drive shaft.

The annular space 31 is hydraulically connected to the inner space 6 via the end recesses, which are provided parallel to the pump piston on the left and right of the latter. The interior is supplied with fuel via a filling opening 61, which can then be supplied to the pump working space 48 via the radial bore 49 opening into the front recess.

In operation, the center point of the eccentric pin moves in a circle around the central axis 11 of the drive shaft and in doing so conveys the ring-shaped element 20. Starting from the position of the one pump piston 38 in FIG. 2, in which the axis 62 of the eccentric is in relation to the upper pump piston 38 and the delivery bottom dead center position, the pump piston 38 is subsequently moved inward as the eccentric continues to rotate in the direction of the arrow. The ring-shaped part 20 moves from its shown central position to the right, so that a parallelogram is now formed from the rectangle formed by the transmission element 53 and the transmission part 40. The rotational position of the annular element is maintained so that the connection between the axes of the cylindrical pins 58 is further parallel to the transmission part. The left part 55 of the transmission element must lie somewhat on the left curved surface 44 of the transmission part and unwind from the cylinder pin 58 located underneath. Correspondingly mutually, this process takes place in the other of the parallel parts 55. As a result, the pump piston 38 executes its pressure stroke and conveys it from there closed pump working chamber 48 the pressure medium in the pressure channel 50. Meanwhile, the pump piston adjacent in the direction of rotation executes an outward movement corresponding to its suction stroke, while the pump piston adjacent to the pump piston 38 in the opposite direction of rotation is approximately at the end of its pressure stroke. The actuating devices of the pump pistons, consisting of the annular part 20 and the respective transmission element 53 and the transmission part 40, do not influence one another, as can easily be seen. In this way, the movements of the eccentric are transmitted to the pump pistons without sliding friction and friction losses. The radii of the same size, on which the parallel parts unwind or wind up, guarantee exact parallel guidance without relative sliding movement to one another and with very low real pressures. The ring-shaped element does not perform any rotational movement with respect to the axis 62 of the eccentric, rather the eccentric moves even under the ring-shaped part. The deflection of the mutually parallel parts 55 from the rectangular shape to the parallelogram results in a gentler start-up of the respective pump piston delivery stroke, which is advantageous for reducing pressure pulsations and reducing noise. This special actuation device of the pump pistons makes it possible to operate the radial piston pump surrounded by gasoline with the least possible wear. In contrast, the successive running portions, the annular portion and the eccentric ^'12 are housed 6 getrenn¬ th space within a closed, filled from the fuel interior, so that here also the wear is kept low and a high durability of the radial piston pump with drive is achieved with gasoline as a pressure medium. Because the annular part 20 does not movement, but only a circular movement around the central axis 6, it is possible for it to be held in position with the aid of the compression spring against axial accelerations which are transmitted by the internal combustion engine.

In the foregoing, the two parallel parts 55 of the transmission element 53 are two individual tapes, which in the area of the pin 39 and the pin 60 overlap each other, each have the positive-locking opening 54 and 59 and are welded together for securing. Other types of connection are also possible, such as folding, screwing and the like. An infinity band is also advantageous, which is manufactured to the exact required length and thus has a ring shape without the overlaps shown. When selecting the material for the transmission element, a flat strip made of metal is advantageous. Because of its inherent elasticity, this is not as easily deformable as a non-steel material, but the energy invested for the deformation is recovered almost completely in the course of the successive work steps. Is instead of steel z. B. uses a transmission element made of textile tape, a loss of performance due to internal heating of the material during its deformation must be expected. Thanks to ribbon material, it is also easily conceivable to use other cross-sectional shapes of the transmission element, even if ribbon in the present case has advantages due to the geometrical guidance and its high flexibility in the circumferential direction to the ring-shaped part. During operation, the interior 31 or 6 of the radial piston pump is supplied with a fuel by a prefeed pump, which is approximately below 3-5 bar and by the radial piston pump z. B. is brought to pressures greater than 100 bar.

In a modification of the embodiment shown in FIGS. 1 and 2, the transmission element can also be formed from two flat strips 755 according to FIG. 7 lying parallel to one another and next to one another, with their plane pointing in the circumferential direction, both of which, on the one hand, on the annular part 720, . B. are attached to a radially projecting rib 769 corresponding to the rib 249 of Figure 4 and on the other hand are attached to a bridge-like part 740 serving as a transfer part. This acts on the pump piston 738 located between the flat belts. The flat strips are guided through a corresponding recess 756 through the housing separating the interior 6 from the annular space 31. They can also be easily deformed following the deflection of the ring-shaped element and transmit the axial forces symmetrically to the pump piston.

A modification of the embodiment shown in FIGS. 1 and 2 can also be seen in FIG. 3. There, the transmission element 153, which is built from a single piece, is placed with a corresponding guide over the transmission part 140 and deflected via deflection pieces 158 on the side of the ring-shaped part 120 in such a way that, in turn, two mutually parallel parts 155 in the intermediate region between the transmission part 140 and the annular part 120 arise. The deflecting part is again preferably cylindrical in cross-section and has a central transverse bore 66 through which a transverse bolt 67 is drawn perpendicular to the band plane and the deflecting part 158 and which extends through a corresponding bore 68 in a radially projecting rib 69 of the annular part 120 is guided. The end of the transmission element 153 is clamped between this rib and the deflection part 158 and folded onto the end face 70 of the rib 69. This results in a very good interlocking connection between the ends of the transmission element 53 and the annular part 120, the ends of this transmission element 153 for the passage of the bolt 67 being broken through twice.

In the above, the greatest possible distance was chosen between the linkage on the pump piston and the linkage on the ring-shaped part, with the result that the transmission element 53 or 153 is not deformed very much. If one wants to allow a larger deformation, the radial piston pump according to the invention can also be designed according to FIG. 4. In this case, the pump piston 238 is designed as a piston which is guided in a corresponding cylinder bore 236 designed as a stepped bore. The part 72 of the stepped piston 238 which is larger in diameter serves as the actual pump piston which, together with its part 73 having a smaller diameter, encloses the pump working chamber 248 in the larger bore 74. A compression spring 246 is arranged in this, which moves the pump piston back during its suction stroke movement. In this exemplary embodiment, such a spring can also act as a tension spring on the outside of the pump piston, as shown in FIG. 5. The pump working chamber 248 is in turn supplied with fuel via a suction line 75 which, if control by the pump piston itself is no longer present, now contains a filling check valve 76. Via a corresponding pressure channel 250 and the delivery pressure valve 251, the compressed fuel is delivered to the reservoir (not shown). To drive the pump piston, the stepped piston part 73, which is smaller in diameter and projects into the interior 206 on the side facing away from the pump working space 248, is connected there to a transmission element 253 which is modified compared to the above exemplary embodiments. This consists of a leaf-shaped part which is connected on the one hand at the end of the stepped piston part 73, which is smaller in diameter, and on the other end is connected to a rib 269 which projects radially from the annular part 220 in the axial direction. In the exemplary embodiment shown, the annular part 220 is now supported by a ball bearing 77 on the eccentric 12, which bearing can absorb both radial and axial forces, so that no axial securing of the annular part 22 is required. Otherwise, however, this is carried out in the same way as the ring-shaped part 20 from FIG. 1 in such a way that it is cup-shaped with a lip seal 226 that closes off the interior of the cup-shaped part.

Figure 5 shows a modification of Figure 4, the axial plan view of this embodiment, from which it can be seen that the leaf-shaped transmission element 253 can deform according to the offset e of the eccentric 12. The pump piston is shown schematically there by a tension spring 78, which is suspended from the housing, acted radially outwards. In a modification, the transmission element 253 ′ can also be fastened to the peripheral surface of the annular part 220 instead of to a rib 269, as shown in FIG. 5. 6 finally shows a modified form of the exemplary embodiment according to FIG. 4, in which the ring-shaped element 320 has only a ring shape with radially projecting ribs 369, to which the sheet-shaped transmission elements 253 already known from FIG. 4 are fastened for actuation of the step-shaped piston 238. To seal the bearing point of the annular element 320, a bellows 79 is now clamped between the ball bearing 77 of FIG. 4 and the annular element 320, which is bag-shaped and with its outer ends tightly connected to the flanges 81 with the Exit of the drive shaft 2 surrounding the end wall of the pump housing is connected. The outlet of the drive shaft 2, the eccentric 12, the ball bearing 77 and a fastening element 82, which has a threaded bore, into which the end of a screw 83 can be screwed, which is through the housing wall 84 of the pump housing in a bore, is then located within the bag-shaped bellows 85 is passed, passes through an opening in the bottom of the bag-shaped bellows and, when screwed into the fastening element 58, clamps the adjacent part of the bag-shaped bellows between the latter and the housing wall, sealing the interior of the bellows tightly.

However, this solution has the disadvantage that mass balancing, as provided in the exemplary embodiment according to FIG. 1, cannot be used. In order to avoid unbalance due to the eccentric position of the eccentric and the mass parts running on it, a weight compensation is provided, in the form of a mass part 86 as a compensating mass, which initially as a radially extending part 87 and then as Part 88 running axially parallel, which overlaps the annular element 20, is arranged diametrically to the eccentricity of the eccentric. However, if the mass sitting on the eccentric can be reduced by using a plain bearing instead of a roller bearing, which at the same time also has dry running properties in such a way that it can be flushed with petrol, then the mass of the annular part can can also be significantly reduced by omitting the shaft seal 26 and such a mass balance is not required.

FIG. 8 shows a fifth exemplary embodiment as a section perpendicular to the view of the drive shaft 802 of this exemplary embodiment shown in FIG. 9. This embodiment is suitable for a series arrangement of several pump pistons, for which purpose the drive shaft 802 is supported on both sides with eccentrics 812 arranged between them. These are either separated from one another by bearings 90, as shown on the left half of FIG. 9, or by intermediate disks 89, as shown on the right half. Bearing shells 820 are supported on the eccentrics 812 by means of semi-cylindrical bearing surfaces 887, each of which forms a bearing surface 888 for a transmission element 853 with its rounded outer surface opposite the bearing surface. This is subsequently designed in the same way as the transmission element 53 from FIG. 2. After leaving the bearing shell, it branches at its rounded outer edge into two mutually parallel parts 855 which are formed by recesses 856 inside the housing lead through to the transmission part 840, which is designed in the same way as that of FIG. 2 and which, as in FIG. 2, acts on a pump piston 38. against the force of a compression spring 46 which is arranged in the pump working space 48. The transmission element 853 can be designed as a continuous band or at one point joined together, the outer contour of the bearing shell 820 at the position area of the transmission element being designed analogously to the outer contour of the transmission part 840. The compression spring 46 ensures that the transmission element 853 is always tensioned and the bearing shell 820 with its open bearing surface is constantly held on the eccentric 812 so that it can carry out the required drive on the pump piston by adjusting the eccentric.

The pump working space 48, which is enclosed by the pump piston in the housing part lying between the recesses 856, is in turn supplied with fuel by a filling check valve 876 and a suction line 875, which is then brought to high pressure via the check valve 851 and the pressure channel 850 is discharged. The check valves are accommodated in blind bores in the housing, which blind bores are closed by plugs 190.

It can be seen from FIG. 9 that the bearing shells 820 are guided axially, either between the housing wall and an intermediate bearing 90 or between two intermediate bearings in the central region of the drive shaft 802 or by means of intermediate discs 89 or 89 provided on the drive shaft 802 between the eccentrics 820 the housing wall. This arrangement also results in a very compact unit with small moving masses due to the semi-annular bearing shells. The embodiments of the piston pump according to the invention described here can also be used as a hydraulic drive machine in that, in a kinematic reversal, pressure medium is supplied to the pump work space from a high-pressure source in a controlled manner until the pump piston, now serving as the work piston, extends its working stroke has led, which he transmits via the eccentric 12 to the shaft 2, which is now an output shaft in the sense of a crankshaft, via the transmission elements 53, 55 and at the same time drives out another pump piston for its return stroke. After reaching its top dead center, the pressure medium supply to the work space is interrupted and a relief line to a relief space is opened so that the pump piston can move through one or more of the other pump pistons via the eccentric and the transmission element, whereby it can execute its return stroke the amount of pressure medium present in the work area conveys into the open relief line.

Claims

Expectations

1. Piston pump with at least one radially to a central axis (11) of a drive shaft (2) in a pump housing

(1) arranged pump cylinder (36, 236), in which a pump piston (38, 238) is driven by an actuating device to its pressure stroke to the central axis (11), the actuating element on one of the drive shaft

(2) driven eccentric (12) is mounted, characterized in that the actuating device consists of an at least partially annular part (20, 820) which is rotatably mounted on the eccentric and a transmission element which is flexible in the circumferential direction and connected to it on the one hand and to the pump piston (53, 153, 253).

2. Piston pump according to claim 1, characterized in that the pump piston is acted upon axially outwards by a return spring (60, 246, 78, 860).

3. Piston pump according to claim 2, characterized in that the pump piston is designed as a stepped piston (238) and with its smaller diameter part (73) through the smaller diameter bore of a pump piston receiving stepped cylinder bore (236) radially inwards ¬ NEN exits an interior space (6) surrounded by the pump housing and is connected there to the transmission element (253)

(Figures 5 and 6).

4. Piston pump according to claim 2, characterized in that the transmission element consists of two parallel ver there are running parts (55, 155) which engage a transmission part (40, 140) which is connected to the pump piston (38) arranged between the parts of the transmission element which run parallel to one another (FIGS. 1 to 3 and 8) .

5. Piston pump according to claim 4, characterized in that the at least partially ring-shaped part is a semi-annular, with a semi-cylindrical bearing surface (87) provided bearing shell

(820), which on the side opposite the bearing surface (87) has a rounded bearing surface (88) for the transmission element (853), the bearing shell with its bearing surface (87) by the return spring (860) on the eccentric (12) is held.

6. Piston pump according to claim 5, characterized in that the drive shaft has at least one between two intermediate disks (89) or bearings of the drive shaft Exzen¬ ter (812), between which washers and / or axial boundary wall of the bearing, the bearing shell axially is.

7. Piston pump according to claim 4 or 5, characterized gekennzeich¬ net that the mutually parallel parts of the transmission element are arranged in a common, axially directed plane.

8. Piston pump according to claim 4 or 5, characterized gekennzeich¬ net that the mutually parallel parts (55, 155) of the transmission element in the direction of rotation of the eccentric (12) seen in front of and behind the pump piston (38) on the transmission part (40, 140) attack (Figures 1 to 3 and 8).

9. Piston pump according to claim 7 or 8, characterized gekennzeich¬ net that the mutually parallel parts (55, 155) of the transmission element are each connected as individual parts with the transmission part and the annular part (Figures 2 and 7).

10. Piston pump according to claim 7 or 8, characterized gekennzeich¬ net that the transmission element via a deflection arrangement

(58, 158) on the annular part (20, 120) and over the transmission part (40, 140) with at least one fixing device (54, 39, 60, 59, 67, 68, 69) against longitudinal displacement of the transmission element on one of the parts, the annular part or the transmission part.

11. Piston pump according to claim 10, characterized in that the transmission element (153) is formed by a single part.

12. Piston pump according to claim 10, characterized in that the transmission element is a ring element.

13. Piston pump according to claim 9 or 10, characterized gekenn¬ characterized in that the mutually parallel parts (55, 155) of the transmission element at their ends have a form-locking part (54, 59) with which they in corresponding form-locking parts (39, 60) engage on the transmission part (40) on the one hand and on the annular part (20) on the other hand.

14. Piston pump according to claim 13, characterized in that the form-fitting parts form a hole-pin connection.

15. Piston pump according to claim 10 to 14, characterized gekenn¬ characterized in that the transmission part (40) is formed prismatic with mushroom-shaped cross section and with rounded edges over which the transmission element is guided, and the annular part pin (58) as a deflection arrangement between which the mutually parallel parts (55) of the transmission element rest with their ends having the form-fitting parts on the ring-shaped part and there form-fit connection with the ring-shaped part.

16. Piston pump according to claim 15, characterized in that the rounding (44) on the transmission part in cross section forms a pitch circle, the diameter of which is the same size as the diameter of the deflection device formed from cylindrical bolts (58).

17. Piston pump according to claim 3, characterized in that the transmission element consists of flat strip material with a strip plane which is perpendicular to the longitudinal direction of the central axis.

18. Piston pump according to claim 1 to 16, characterized gekennzeich¬ net that the transmission element consists of flat strip material with a strip plane which lies in the longitudinal direction to the central axis.

19. Piston pump according to claim 3 or 4, characterized gekennzeich¬ net that the annular part (20) on one axial side of the annular part ver¬ closing the end, the eccentric (12) has front end (21) and on the other Axial side has a sealing element (26) which interacts with the eccentric.

20. Piston pump according to claim 1, characterized in that on the drive shaft (2) diametrically to the eccentric (12) a partially parallel to this compensating mass part (88) is arranged.

21. Piston pump according to claim 3 or 4, characterized gekennzeich¬ net that a bellows (79) tightly enclosing the eccentric is connected to the annular part.

22. Piston pump according to claim 21, characterized in that the bellows between the annular part (320) and roller bearing (77) is clamped and on the one hand is tightly connected to the outlet of the drive shaft surrounding the pump housing and on the other hand with one of the end of the eccentric opposite Housing wall is connected.

23. Piston pump according to claim 18, characterized in that a lubricant outlet opening (18) is provided on the end face of the eccentric, in which a ball (24) is mounted, on which the bottom of the annular part (20) by a between the Outside of the floor and a housing wall clamped spring (22) is held.

24. Piston pump according to one of the preceding claims, characterized in that the piston pump has a controlled pressure medium inlet from a high pressure source to the pump work chamber (48) and a controlled pressure medium outlet to a relief chamber and is operated as a hydraulic drive machine.