EP1760312B1 - High pressure pump - Google Patents

Abstract

The high pressure pump has a displaceable control piston (25) guided in a longitudinal bore (24) of a passage (23) in the main piston (6). Fluid in the working chamber (8) acts on one side of the piston and fluid in the discharge chamber (22) on the other. The control piston ensures that the pressure in the discharge chamber increases with that in the working chamber, decompressing the sliding fit between the main piston and the stroke ring (12).

Description

The invention relates to a high pressure pump according to the preamble of claim 1, which is particularly suitable for use in a fuel injection system for internal combustion engines.

In the DE-A-197 05 205 and the corresponding US-A-6,077,056 a generic high-pressure pump for a fuel injection device for internal combustion engines is described, in which the piston of a piston pump unit is driven harmoniously by an eccentric drive. The piston carries at its end facing away from the working space of the piston pump unit end a sliding shoe, which rests with a sliding surface on a sliding bearing surface of a lifting ring. The cam ring is rotatably mounted on an eccentric pin of a drive shaft and is driven revolving, but not rotating. The drive shaft, the eccentric pin, the cam ring and the shoe are housed in a low-pressure space, which serves as a supply space for the medium to be conveyed, ie fuel. In the shoe a relief space is formed, which is open to the sliding bearing surface and via a passage which extends in the longitudinal direction of the pump piston, with the working space is in direct hydraulic communication. The discharge space is therefore filled with the fuel to be delivered.

During the delivery stroke of the piston pump unit, the piston or the sliding shoe fastened to it is pressed against the lifting ring by the pressure acting in the working space. At the same time there is also an increase in pressure with the Working space associated discharge space, whereby the forces acting on the shoe, directed away from the lifting ring force is increased. For a relief of the sliding bearing between the shoe and the cam ring is achieved. This hydrostatic relief of the sliding bearing leads to a reduction in the friction between the sliding surface on the shoe and the sliding bearing surface on the cam ring.

The lubrication of the sliding bearing between the shoe and the cam ring is effected by the fuel in the discharge chamber. The bearing between the eccentric pin and the cam ring is lubricated by the located in the low-pressure space fuel. However, fuel is known to have poor lubricating properties and therefore can only develop a limited lubricating effect.

The present invention is now based on the object to provide a high-pressure pump of the type mentioned for very high discharge pressures and large flow rates, the production costs are as low as possible and can meet the high demands on the reliability and life.

This object is achieved with a high pressure pump having the features of claim 1.

The inventive design of the high pressure pump significantly improved lubrication of the sliding bearing between the cam and the piston and also the bearing between the cam and the crank drive is possible. As a result, the risk of Anfressens this camp is greatly reduced even at high load, which contributes to increased reliability and a long life.

Preferred further developments of the high-pressure pump according to the invention form the subject of the dependent claims.

Fig. 1

in einem Längsschnitt eine erste Ausführungsform einer Hochdruckpumpe mit zwei Kolbenpumpeneinheiten,

Fig. 2 und 3

in einer der Fig. 1 entsprechenden Darstellung und in vergrössertem Massstab die eine der beiden Kolbenpumpeneinheiten mit dem Pumpenkolben in verschiedenen Arbeitsstellungen,

Fig. 4

einen Schnitt entlang der Linie A-A in Fig. 3, und

Fig. 5

in einer der Fig. 2 entsprechenden Darstellung eine zweite Ausführungsform einer Hochdruckpumpe.

In the following, embodiments of the subject invention will be explained in more detail with reference to the drawings. It shows purely schematically:

Fig. 1

in a longitudinal section a first embodiment of a high pressure pump with two piston pump units,

FIGS. 2 and 3

in one of the Fig. 1 corresponding representation and on an enlarged scale the one of the two piston pump units with the pump piston in different working positions,

Fig. 4

a section along the line AA in Fig. 3 , and

Fig. 5

in one of the Fig. 2 corresponding representation of a second embodiment of a high-pressure pump.

The in the Fig. 1 - 4th shown high-pressure pump 1, which is intended for use in a fuel injection system for internal combustion engines, has two diametrically opposed piston pump units 2, 2 '(plunger pump units), which are structurally identical and work in push-pull. Each piston pump unit 2, 2 'has a housing block 3, which is fixedly connected to a pump housing 4 and projects into the interior 5 of this pump housing 4. each Piston pump unit 2, 2 'has a piston 6 (plunger), which is guided with a tight sliding fit in a cylinder bore 7 in the housing block 3 linearly movable. The piston 6 bounded with an end face 6a a working space 8 and extends at its opposite end to a foot part 9. This foot part 9 has a flat sliding surface 10 which rests on a sliding bearing surface 11 which is provided on a cam ring 12. This cam ring 12 is common to both piston pump units 2, 2 '. For the harmonic driving of the piston 6 of the two piston pump units 2, 2 ', a crank drive 13 is provided, which has a drive shaft 14 shown in dashed lines and an eccentric element 15 fixedly connected thereto. The drive shaft 14 is rotated about its axis of rotation 14a (FIG. Fig. 1 ) driven circumferentially. The cam ring 13 is rotatably seated but not co-rotating on the eccentric element 15. The eccentric element 15 is provided with an eccentricity e (FIG. Fig. 1 ) arranged opposite to the axis of rotation 14a of the drive shaft 14. When rotating the drive shaft 14, the cam ring 12 is moved on the one hand parallel to the slide bearing surfaces 12 and on the other hand perpendicular to the axis of rotation 14a of the drive shaft 14, in each direction by the amount 2e. The cam ring 12 is thus displaced in operation relative to the foot part 9 of the piston 6 back and forth. The pistons 6 of the piston pump units 2, 2a execute a stroke, which is also 2e, ie twice the eccentricity e.

On the foot part 9 of the piston 6 sits a bearing ring 16 which serves as an abutment for a compression spring 17 which is supported on the housing block 3 at the other end. The compression spring 17 holds the associated piston 6 in constant contact with the cam ring 12th

In the housing block 3, an inlet line 18 is formed, which communicates via a pressure-controlled inlet valve 19 with the working space 8 ( Fig. 1 ). The inlet line 18 is connected to a supply line, not shown, which is connected to a liquid reservoir, ie in the present case with a fuel tank, for example via a prefeed pump. In the housing block 3, an outlet line 20 is further provided, which is connected via a pressure-controlled outlet valve 21 with the working space 8 ( Fig. 1 ). The outlet conduit 20 is connected to a high pressure space, eg the common rail of a fuel injection system.

In the region of the sliding surface 10, a relief space 22 is formed in the foot part 9 of the piston 6, which is open to the sliding bearing surface 11. In the longitudinal direction of the piston 6 extends a continuous, coaxial passage 23 which is open on the one hand to the working space 8 and on the other hand to the discharge space 22 (the passage 23 could also be desachsiert). To this passage 23, whose diameter changes, includes a longitudinal bore 24 in which a control piston 25 is slidably guided with a tight sliding fit, which serves as a pressure transmission element. The control piston 25 rests on a compression spring 26, which at the other end on a spring ring 27 (FIG. Fig. 2 ) is supported, which is held in the piston 6.

In the housing block 3, an annular groove 28 is formed, which extends around the piston 6 around and to the cylinder bore 7 is open. In the piston 6, a transverse bore 29 is present, which passes through the piston 6 and at both ends with the annular groove 28 in connection stands. To the annular groove 28, a drain line 30 is connected, which runs in the housing block 3 and which is connected to a return line, not shown, which leads to a collecting reservoir, which may be the fuel tank. In the annular groove 28 accumulates in a manner to be described, leakage liquid, which is returned via the drain line 30.

The eccentric element 15 is provided with a lubrication groove 31 which extends along a part of the circumference and is open towards the cam ring 12. The lubrication groove 31 is connected via a radial bore 32 in the eccentric element 15 with a feed channel 33 which extends in the direction of the axis of rotation 14a of the drive shaft 14 and which is connected via a lubricant pump, not shown, with a lubricant reservoir. About this feed channel 33, a lubricant, preferably lubricating oil, with a pressure of eg 2 - 6 bar supplied. In the cam ring 12 two connecting channels 34, 35 are formed, each of which leads from the inner surface 12 a of the cam ring 12 to one of the sliding bearing surfaces 11. The lubrication groove 31 which is permanently connected to the feed channel 33, however, is only in certain rotational positions of the eccentric element 15 with a connecting channel 34, 35 in connection, as that of the Fig. 1-3 is apparent.

Based on Fig. 1 - 4th Now, the operation of the high-pressure pump 1 will be described in more detail.

The FIG. 1 shows the rotational position of the eccentric element 15, in which the piston 6 is the one, in the figures upper piston pump unit 2 in the lower end position, ie, at the end of the suction stroke. The piston 6 of the other, lower piston pump unit 2 'has the end of Delivery stroke and thus reached its upper end position. The connection channels 34, 35 are not in connection with the lubrication groove 31 nor with the associated relief space 22.

Starting from this initial position, only the operation of the upper piston pump unit 2 will be described below. The operation of the other, lower piston pump unit 2 'is the same.

If the drive shaft 14 rotates counterclockwise, the delivery stroke for the piston 6 of the upper piston pump unit 2 begins, ie the piston 6 is moved in the direction of the arrow A (FIG. Fig. 2 ) moved upwards. During this delivery stroke, the inlet valve 19 is closed, which also applies to the outlet valve 21 at the beginning of the delivery stroke. The pressure in the working space 8 increases. The control piston 25, which is acted upon at its the working space 8 facing end face by the pressure of the liquid in the working space 8, is against the action of the compression spring 26 downward in the direction of arrow D in Fig. 2 emotional. This has the consequence that the pressure of the lubricant, which is located in the relief chamber 22 and in the region of the passage 23 located below the control piston 25, increases. As a result, a force is exerted on the piston 6, which is directed away from the cam ring 12 and counteracts the force exerted by the fluid in the working chamber 8 on the piston 6. In this way, a hydrostatic relief of the sliding surface 10 formed by the sliding surface 10 on the foot part 9 and the sliding bearing surface 11 on the cam ring 12, as in the already mentioned DE-A-197 05 205 and the corresponding US-A-6,077,056 is described. An optimal relief effect is achieved when the Diameter DA of the relief space 22 is slightly smaller than the diameter DP of the end face 6a of the piston 6, which faces the working space 8 (see Fig. 2 ).

In the Fig. 2 the situation is shown by a rotation of the drive shaft 14 by 90 °. The piston 6 has reached its center position during the delivery stroke. There is no connection between the lubrication groove 31 and the relief chamber 22 of the upper piston pump unit 2. In contrast, in the lower piston pump unit 2 ', not shown, the relief space 22 is connected to the lubrication groove 31. After the in Fig. 2 shown rotation of the drive shaft 14 by 90 ° takes the cam ring 12 its right end position, in the Fig. 4 shown by dashed lines and designated 12 '.

As soon as the pressure in the working space 8 in the course of the delivery stroke of the piston 6 reaches a value which is greater than the closing force of the outlet valve 21, this is opened and the liquid is expelled from the working space 8 into the outlet line 20 and then into the high-pressure space.

After a rotation of the drive shaft 14 from the in Fig. 1 shown position by 180 °, the delivery stroke of the piston 6 is completed. The piston 6 is now in the reverse direction, ie in the direction of arrow B ( Fig. 3 ) is moved downwards for the suction stroke. During this suction stroke, the exhaust valve 21 remains closed. During the downward movement of the piston 6 in the direction of the arrow B, a negative pressure arises in the working space 8, which has the consequence that the inlet valve 19 opens and liquid flows into the working space 8. The in the relief space 22 and the Region of the passage 23 below the control piston 28 prevailing pressure together with the compression spring 26 cause a displacement of the control piston 25 in the direction of arrow E (FIG. Fig. 3 ) up. In the Fig. 3 the situation is shown by a total of 270 ° after a rotation of the drive shaft 14. The piston 6 has reached its center position during the suction stroke. The cam ring 12 now assumes its left end position, in Fig. 4 is shown with solid lines. These Fig. 4 indicates that the cam ring 12 in the direction of the sliding bearing surface 11 performs a total stroke C, which is equal to 2e, so the double eccentricity e. In this in the Fig. 3 and 4 shown left end position of the cam ring 12 is now the connecting channel 34 in the cam ring 12 with the discharge chamber 22 and the lubrication 31 in conjunction. This means that via the feed channel 33, the radial bore 32, the lubrication groove 31 and the connecting channel 34 pressure oil can get into the discharge chamber 22. In this way, lubricant is replaced, which has been lost during the delivery stroke due to leakage along the sliding bearing surface 11 and along the outer surface of the control piston 25.

After a rotation of the drive shaft 14 by a total of 360 °, the piston 6 is at the end of the suction stroke and resumes in the Fig. 1 shown lower end position. The work cycle described starts from the beginning.

Although the piston 6 is guided with a tight sliding fit in the cylinder bore 7, through the gap between the piston 6 and the wall of the cylinder bore 7 on the one hand liquid, ie fuel, from the working space 8 and on the other hand lubricant, ie lubricating oil, from the interior. 5 the pump housing 4 pass. This leakage fluid is collected as a liquid-lubricant mixture, ie as a fuel-lubricating oil mixture, in the annular groove 28.

In addition, it is possible that liquid (fuel) from the working space 8 can pass over the upper portion of the passage 23 and through the very small gap between the control piston 25 and the wall of the longitudinal bore 24. This leakage liquid passes via the transverse bore 29 in the piston 6 also in the annular groove 28. In addition, lubricant (lubricating oil) from the discharge chamber 22 through the narrow gap between the control piston 25 and the wall of the longitudinal bore 24 pass. This leak lubricant also passes via the transverse bore 29 into the annular groove 28.

The mixture of liquid (fuel and lubricant (lubricating oil)) in the annular groove 28 is led away via the drain line 30 and is e.g. into the liquid reservoir, i. the fuel tank, returned.

Based on Fig. 3 and 4 Below is a variant of the in Fig. 1 and 2 described embodiment, in which in the foot part 9 of the piston 6 in the region of the sliding surface 10 in addition an annular groove 36 is formed, which is disposed coaxially to the relief space 22 and the sliding bearing surface 11 is open. This annular groove 36 communicates with a cam ring 12 formed in the sliding surface 10 toward open longitudinal groove 37 in conjunction. This longitudinal groove 37 is opposite the cutting plane of Fig. 3 (which is perpendicular to the axis of rotation 14a and in the middle of the cam ring 12) offset in the direction of the axis of rotation 14a of the drive shaft 14 and opens at both ends in the interior of the fifth of the pump housing 4 ( Fig. 4 ). The leakage liquid (lubricating oil) entering this annular groove 36 is returned to the interior 5 via the longitudinal groove 37.

By providing the annular groove 36, the pressure distribution along the sliding surface 10 or the sliding bearing surface 11 is changed from the relief space 22 in the radial direction to the outside, which has a favorable influence on the amount of leakage fluid.

The in the Fig. 5 shown second embodiment of a high-pressure pump 1 'differs from the first embodiment according to the Fig. 1 - 4th by another embodiment of the arranged in the piston 6 pressure transmission element. In this Fig. 5 , the representation of the Fig. 2 are identical, the same reference numerals are used for parts that are the same in both embodiments as in the Fig. 1 - 4th ,

In this second embodiment according to Fig. 5 the piston 6 consists of a guided in the cylinder bore 7 piston member 38 and a ring 39 which is fixedly connected to the working space 8 opposite end of the piston member 38 with this, for example by pressing or shrinking. The ring 39 rests with a sliding surface 10 on the sliding bearing surface 11 on the cam ring 12 and has a flange 40 on which the compression spring 17 is supported. This compression spring 17 ensures - as based on Fig. 1-3 described - that the ring 39 remains in contact with the cam ring 12. On the ring 39, the sliding surface 10 is formed. The flange 40 could also be formed as a separate part, analogous to the bearing ring 16 of Fig. 2 ,

Between the ring 39 and the piston member 38, an elastically deflectable membrane 41 is arranged along its edge region between the ring 39 and the piston member 38 is sealingly clamped. This serving as a pressure-transmitting element membrane 41 spans the limited by the inner annular wall 39a relief space 22 and separates this relief space 22 formed by a piston member 38 chamber 42. In this chamber 42 opens a longitudinal bore 43 which extends in the direction of the longitudinal axis of the piston member 38 and over which the chamber 42 communicates with the working space 8. The longitudinal bore 43 and the chamber 42 form the passage 23. The chamber 42 is filled with the liquid to be conveyed, ie with fuel.

The pressure in the chamber 42 changes in the same direction with the pressure in the working chamber 8. With increasing pressure in the chamber 42, the diaphragm 41 in the direction of pressurization down, ie to the sliding bearing surface 11 out, deflected. This leads to an increase in pressure in the lubricant-containing relief space 22 and thus to a hydrostatic pressure relief, as the basis of the Fig. 1 - 4th already described. Since the pressures on both sides of the diaphragm 41 are practically the same, the stress on the diaphragm 41 is low. This can thus be thin-walled and elastic.

In the variant according to Fig. 5 is the first embodiment according to the Fig. 1-3 existing annular groove 28 together with drain line 30 for collecting and removing leakage fluid is not shown, but can also be provided if necessary.

In a further variant, not shown, the membrane 41 is attached to the working space 8 facing end surface 6a of the piston 6. The attachment of the membrane 41 could by welding the same or, as in Fig. 5 , held with a screwed, pressed or shrunken holding part. The passage 23 is then below the membrane 41, it is filled with the lubricant and communicates directly with the relief space 22nd

The mode of action of in Fig. 5 illustrated embodiment corresponds to the basis of Fig. 1 - 4th described procedure.

The in connection with the Fig. 1-5 described embodiments of an inventive high-pressure pump 1, 1 'have the advantage that by arranging a pressure transmission element, ie a control piston 25 or a membrane 41, in the working space 8 and the discharge chamber 22 connecting passage 23, the media in the working space 8 and the discharge chamber 22 from each other be separated. This allows the use of a suitable lubricant in the region of the cam ring 12 and the crank drive 13, regardless of the medium to be pumped (fuel). In addition, the desired pressure relief of the sliding bearing, which is formed by the sliding surface 10 on the piston 6 and the sliding bearing surface 11 on the cam ring 12, achieved without great design effort.

It is understood that various variants of the embodiments shown are possible. Some of these variants are indicated below.

In a further embodiment, the piston 6 has no transverse bore 29. Due to the tight sliding fit and the present invention achieved pressure conditions on both sides of the control piston 25, the leakage of the working space 8 facing side in the discharge chamber 22 are kept very low.

It may also be possible to take measures to collect and remove leakage along the outside of the piston 6, i. be dispensed with the annular groove 28 and the drain line 30 in the housing block 3, if no appreciable leakage occurs due to the prevailing pressure conditions.

In a further variant, not shown, the control piston 25 has a larger diameter than in the Fig. 1-3 shown. The longitudinal bore 24 for guiding the control piston 25 in close sliding fit can be open towards the top in the direction of the working chamber 8. In this case, the narrower in cross section part of the passage 23 is again below the control piston 25 and communicates directly with the relief chamber 22. The control piston 25 is installed from above into the piston 6. A spring ring, analogous to the spring ring 27 according to Fig. 2 then prevents the spool from exiting above the end surface 6a. The longitudinal bore 24 can also be continuous in the piston 6. In this case, the remaining part of the passage 23 has the same diameter as the longitudinal bore 24. It is also conceivable to form the remaining portion of the passage 23 slightly larger than the diameter of the longitudinal bore 24.

Furthermore, there is also a need to keep the lubrication losses from the relief space 22 in the housing interior 5 low. One remedy for this is the execution of Fig. 3 and 4 shown (annular groove 36 and longitudinal groove 37). Are the flat sliding surface 10 of the Foot part 9 and the sliding surface 11 of the cam ring 12 not exactly to each other, for example, by a forced misalignment of the two sliding surfaces 10 and 11, the lubrication losses are negatively affected. Constructive measures to prevent such a condition may be: foot part 9 with a certain elasticity in such a way that the sliding surface 10 can adapt to the sliding surface 11 by a small elastic deformation of the foot part 9. A separation of foot part 9 and piston 6 into two parts, analogously as in the DE-A-197 05 205 and the corresponding US-A-6,077,056 in Fig. 4 is shown is also applicable. Also, the inner surface 12a of the cam ring 12, together with the associated surface of the Exenterelementes 15, in the direction of the rotation axis 14a slightly convex or even slightly longitudinal in the longitudinal and transverse directions. In this case, it is recommended to design the cam ring 12 in two parts for assembly reasons.

Instead of like in Fig. 1 shown two piston pump units 2, 2 ', only one piston pump unit 2 can be provided. Conversely, more than two piston pump units with corresponding sliding surfaces 11 of the cam ring 12 can be radially mounted, for example, 3 by 120 °, or 4 by 90 °, or 6 offset by 60 ° piston pump units with a common cam ring 12th

In addition, it is also possible, in the direction of the rotational axis 14a of the drive shaft 14, two or more individual piston pump units or two or more pairs of opposing, push-pull piston pump units 2, 2 'to be arranged one behind the other.

Although the described high-pressure pumps 1, 1 'are intended for use in fuel injection systems of internal combustion engines, in particular of diesel engines, these pumps can also be used in other fields.

It is also possible to dispense with the compression spring 26 and the spring ring 27 supporting this. In this case, the control piston 25 is moved solely by acting on the two end faces pressure forces.

Finally, it is also possible to form the control piston 25 with two different diameters. If the end face facing the working space 8 is then larger than the one facing the relief space, a pressure transmission takes place. In the opposite case, a pressure reduction. In these embodiments, it may be advantageous to form the control piston 25 of two separate parts, each with the appropriate diameter. If the holes with the correspondingly larger diameter and those with the corresponding smaller diameter are not precisely aligned, tolerance and friction problems can thus be prevented.

Claims (20)

1. A high pressure pump, in particular for a fuel injection system for internal combustion engines, having at least one piston pump unit (2, 2') which has a piston (6) guided in a cylinder bore (7) and delimiting a working chamber (8), having a crank drive (13) for driving the piston (6), having a stroke ring (12) which is arranged between the crank drive (13) and the piston (6) and which is mounted such that it is rotatable with respect to the crank drive (13) but does not rotate and which has a flat sliding bearing surface (11), on which the piston (6) is supported with a sliding surface (10), wherein
   a connecting duct (34, 35) is formed in the stroke ring (12), said connecting duct (34, 35) opens at one, first end into the sliding bearing surface (11) and is connected, independently of the medium to be delivered, to a fluid source by means of a fluid feed conduit (31, 32, 33) provided in the crank drive (13).
2. The high pressure pump as claimed in claim 1, wherein the crank drive (13) has an eccentric element (15) which is arranged on a rotatably driven drive shaft (14) and wherein the connecting duct (34, 35) opens at the other, second end into the inner surface (12a) of the stroke ring (12) which is in contact with the eccentric element (15) of the crank drive (13), and wherein a lubricating groove (31) forming part of the fluid feed conduit is provided on the circumference of the eccentric element (15), said lubricating groove (31) is open toward the outside and is connected to the lubricant source via a connecting line (32, 33) also forming part of the fluid feed conduit and running in the eccentric element (15) and in the drive shaft (14).
3. The high pressure pump as claimed in claim 2, wherein the lubricating groove (31) extends over part of the circumference of the eccentric element (15).
4. The high pressure pump as claimed in claim 1, further comprising a relief chamber (22) which is arranged in the region of the sliding surface (10), is open toward the sliding bearing surface (11) and is fluidically separated from the working chamber (8).
5. The high pressure pump as claimed in claim 4, wherein an annular groove (36) is formed in the piston (6), said annular groove (36) surrounds the relief chamber (22) and is open toward the sliding bearing surface (11).
6. The high pressure pump as claimed in claim 5, wherein the annular groove (36) is connected to a chamber (5) in which the crank drive (13) and the stroke ring (12) are accommodated.
7. The high pressure pump as claimed in claim 4, wherein the opening of the relief chamber (22) is completely surrounded by the sliding surface (10) of the piston (6), said sliding surface (10) acting together with the sliding bearing surface (11) of the stroke ring (12).
8. The high pressure pump as claimed in claim 6, wherein a longitudinal groove (37) is formed in the stroke ring (12) in the region of the sliding bearing surface (11), said longitudinal groove (37) is open toward the sliding surface (10) and opens into said chamber (5), is offset with respect to the relief chamber (22) in the direction of the axis of rotation (14a) of the drive shaft (14) and communicates with the annular groove (36).
9. The high pressure pump as claimed in claim 4, wherein the pressure medium in the relief chamber (22) is a lubricant, preferably lubricating oil.
10. The high pressure pump as claimed in one of claims 4 to 9, wherein the connecting duct (34, 35) opens into the sliding bearing surface (11) at a point such that it is connected to the relief chamber (22) only in specific positions of the stroke ring (12) with respect to the piston (6) and can be connected periodically to the lubricant feed conduit (31, 32, 33).
11. The high pressure pump as claimed in claim 10, wherein the lubricating groove (31) is arranged such that it is connected to the connecting duct (34, 35) in the stroke ring (12) when this connecting duct (34, 35) is connected to the relief chamber (22).
12. The high pressure pump as claimed in one of claims 4 to 11, wherein the relief chamber (22) is fluidically separated from the working chamber (8) by a pressure transmission element (25, 41) arranged in a passage (23) in the piston (6), said pressure transmission element (25, 41) is pressurized on one side by the medium to be delivered and on the opposite side by a pressure medium in the relief chamber (22) and can be displaced in the direction of the application of pressure under the action of pressure.
13. The high pressure pump as claimed in claim 12, wherein the pressure transmission element is a control piston (25) which can be displaced in a longitudinal bore (24) belonging to said passage (23) and is guided closely in a sliding manner.
14. The high pressure pump as claimed in claim 13, wherein the control piston (6) on its first end facing the relief chamber (22) is supported on a compression spring (26) which rests on an abutment at the other end.
15. The high pressure pump as claimed in claim 14, wherein said abutment is formed by a supporting element, in particular a spring ring (27), retained in the control piston (25).
16. The high pressure pump as claimed in claim 12, wherein the pressure transmission element is a diaphragm (41) which can be deflected elastically, covers the passage (23) and is fixed in a sealing manner in its edge region.
17. The high pressure pump as claimed in claim 16, wherein the piston (6) has a piston element (38) guided in the cylinder bore (7) and a ring (39) which is connected to the piston element (38) at the end of the latter facing away from the working chamber (8).
18. The high pressure pump as claimed in claim 17, wherein the diaphragm (41) is held firmly in its edge region between the piston element (38) and the ring (39).
19. The high pressure pump as claimed in one of claims 1 to 18, wherein an annular collecting groove (28) is formed in the wall of the cylinder bore (7), said annular collecting groove (28) is open toward the piston (6), is used to collect seepage which passes through the gap between the wall of the cylinder bore (7) and the piston (6) and to which a discharge conduit (30) is connected.
20. The high pressure pump as claimed in one of claims 1 to 19, wherein the high pressure pump (1, 1') is designed to deliver fuel, in particular diesel fuel.

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