High-pressure fuel pump

Abstract

The invention relates to a high-pressure fuel pump (10) for a fuel system of an internal combustion engine, comprising an inlet (11) for supplying fuel, an outlet (34) for discharging compressed fuel, a pump housing (12), a delivery chamber (16) arranged in the pump housing (12), and a pump piston (18) which can be moved in the pump housing (12) in a longitudinal direction (LA) and delimits the delivery chamber (16), the invention relates to a pump (10) comprising an inlet (11), an outlet (34), a delivery chamber (16), an inlet valve (14) arranged between the inlet (11) and the delivery chamber (16), which is open towards the delivery chamber (16), an outlet valve (37) arranged between the delivery chamber (16) and the outlet (34), which is open away from the delivery chamber (16), a high-pressure region (29) fluidically extending between the outlet valve (20) and the outlet (34), the pump piston (18) has a groove (181) surrounding the periphery of the pump piston (18), a sealing ring (182) is fixed in the groove, the sealing ring seals a gap between the pump housing (12) and the pump piston (18), and the sealing ring (182) is arranged in the groove (181), so that the sealing ring (182) can seal the gap between the pump housing (12) and the pump piston (18), and the sealing ring (182) can seal the gap between the pump housing (12) and the pump piston (18). The contact length (k) of the sealing ring (182) in the longitudinal direction (LA) against the pump housing (13) is less than 1 mm and / or less than 10% of the maximum diameter (D) of the pump piston (18).

Description

Background Art

[0001] From the prior art, for example from DE 10 2004 063 074 B4 according to the applicant, a high-pressure fuel pump is known, which has a pump housing, a delivery chamber arranged in the pump housing, and a pump piston displaceable in the pump housing in the longitudinal direction, which delimits the delivery chamber.

[0002] In known high-pressure fuel pumps, the running bush of the pump housing is provided with a through-opening in which the piston is guided. The gaps that inevitably remain between the pump piston and the pump housing, or between the pump piston and the running bush, limit the volumetric efficiency of the high-pressure fuel pump, particularly when the high-pressure fuel pump vibrates at relatively low frequencies. Summary of the Invention

[0003] The present invention is primarily based on the desire to improve the seal between the pump piston and the pump housing and thereby increase the delivery rate of a high-pressure fuel pump.

[0004] This is achieved by providing the pump piston with a groove around its circumference, in which groove a sealing ring (also called a high-pressure seal) is fixed, which seals the gap between the pump housing and the pump piston.

[0005] The applicant has identified the wear mechanism of sealing rings during operation of high-pressure fuel pumps and has determined that this wear can be minimized by providing a contact length of the sealing ring against the pump housing in the longitudinal direction of less than 1 mm and / or less than 10% of the maximum diameter of the pump piston.

[0006] In a further development, the contact length of the sealing ring against the pump housing in the longitudinal direction can even be less than 0.7 mm and / or less than 7% of the maximum diameter of the pump piston.

[0007] The underlying knowledge is that if the pressure gradient between the high-pressure area and the low-pressure area of ​​the high-pressure fuel pump is limited to such a short contact length or a correspondingly small contact surface, the friction work generated during operation of the pump and the corresponding wear of the sealing rings are also significantly reduced.

[0008] The lower limit for the contact length of the sealing ring in the longitudinal direction against the pump housing or the running bushing of the pump housing can be derived from the requirement for a sufficient sealing effect, for example by virtue of the fact that the contact length of the sealing ring in the longitudinal direction against the pump housing is greater than 0.2 mm and / or greater than 2% of the maximum diameter of the pump piston; or even greater than 0.35 mm and / or greater than 3.5% of the maximum diameter of the pump piston.

[0009] The contact length is preferably understood to be the contact length when the pump is at rest, ie, at which there is no relative movement between the pump piston and the pump housing.

[0010] The inventors have recognized that wear on the sealing ring can be further reduced by increasing the radial thickness of the sealing ring in the longitudinal direction away from the delivery chamber and / or by making the sealing ring thicker at its end facing away from the delivery chamber than at its end facing toward the delivery chamber. This can be achieved, for example, by having the sealing ring have a conical or spherical outer contour radially outward or a radially outer annular flange with a longitudinal direction facing away from the delivery chamber. A stepped design is also possible. This structural design of the sealing ring results in the high pressure acting on the sealing ring from the side of the delivery chamber generating a force that reduces the force pressing the sealing ring against the pump housing. This also reduces the frictional work generated during operation of the high-pressure fuel pump and, consequently, wear on the sealing ring.

[0011] The sealing ring can comprise plastic or consist of plastic. The sealing ring can, for example, consist of plastic reinforced with fibers, such as carbon fibers and / or similar fibers.

[0012] According to one embodiment of the invention, a pump piston having a groove around its circumference, which secures the sealing ring, can be provided in a simple manner in that the pump piston has two partial pistons mounted on one another in the longitudinal direction, between which the circumferential groove is formed.

[0013] In a further development, provision can be made for this purpose that a disk spring is mounted between the two partial pistons, which disk spring loads the sealing ring in a longitudinal direction pointing away from the delivery chamber, so that the sealing ring is securely fixed in the circumferential groove.

[0014] The high-pressure fuel pump according to the present invention is further provided with an inlet for supplying fuel, an outlet for discharging compressed fuel, an inlet valve arranged between the inlet and the delivery chamber, the inlet valve opening toward the delivery chamber, an outlet valve arranged between the delivery chamber and the outlet, the outlet valve opening away from the delivery chamber, a high-pressure region extending fluidically between the outlet valve and the outlet, and a low-pressure region extending fluidically between the inlet and the inlet valve.

[0015] A particularly attractive embodiment of the high-pressure fuel pump according to the present invention, in the context of the high-pressure seal described above, provides that the high-pressure fuel pump includes a pressure-limiting valve that fluidically connects a high-pressure region with a low-pressure region and opens toward the low-pressure region, such that when the pressure differential between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds an opening pressure, fuel flows from the high-pressure region into the low-pressure region. The pump housing includes a pump body and a pump cover that are connected to each other, wherein the pump body and the pump cover delimit a vibration damping region belonging to the low-pressure region, in which at least one diaphragm damper is arranged. The pressure-limiting valve fluidically connects the high-pressure region with the vibration damping region and opens toward the vibration damping region, such that when the pressure differential between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds an opening pressure, fuel flows from the high-pressure region into the vibration damping region. The outlet valve can optionally be fixed in an outlet valve opening of the pump housing, the pressure-limiting valve can be fixed in a pressure-limiting valve opening of the pump housing, and the outlet valve opening and the pressure-limiting valve opening can extend in planes that are geometrically parallel to each other and perpendicular to the longitudinal direction.

[0016] Furthermore, it can be provided that the outlet valve hole and the pressure-limiting valve hole are oriented geometrically parallel to each other, and / or the outlet is constructed as an outlet pipe fixed to the pump housing, and an outlet pipe chamber is formed between the pump housing and the outlet pipe, wherein both the outlet valve hole and the pressure-limiting valve hole issue from the outlet pipe chamber; and / or the pressure-limiting valve hole is connected to the vibration damping area via a low-pressure connecting hole located in the low-pressure area.

[0017] These further measures are advantageous per se, since the pressure-limiting valve of the high-pressure fuel pump is separated from the delivery chamber and overflows into the low-pressure region, ie is subject only to significantly reduced pressure fluctuations and thus to significantly reduced wear.

[0018] However, these further measures usually result in a significant reduction in the dead volume of the delivery chamber of the high-pressure fuel pump, so that a very pronounced pressure increase occurs in the delivery chamber and therefore also at the high-pressure seal or sealing ring.

[0019] However, the resulting reduced tightness of the high-pressure seal and the resulting increased wear are avoided precisely by the above-described properties of the high-pressure seal. The sum of the features and developments according to the invention results in a durable high-pressure fuel pump with high volumetric efficiency over its service life.

[0020] The fuel may be a fuel such as gasoline. Of course, this also includes synthetic liquid fuels. Of course, the pump according to the present invention is also capable of compressing other fluid media except the fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Exemplary embodiments of the present invention are explained below with reference to the accompanying drawings.

[0022] Figure 1A simplified schematic diagram showing a fuel system for an internal combustion engine.

[0023] Figure 2 A first embodiment of the present invention is shown.

[0024] Figure 3 Show Figure 2 A partial enlarged view of .

[0025] Figure 4 A second embodiment of the present invention is shown.

[0026] FIG. 5 shows a schematic embodiment in parts a), b) and c). DETAILED DESCRIPTION

[0027] Figure 1 A simplified schematic diagram shows a fuel system 1 for an internal combustion engine (not shown). During operation of the fuel system 1, fuel is supplied from the fuel tank 2 via a suction line 4, a pre-feed pump 6, and a low-pressure line 8 via an inlet pipe 20 to a high-pressure fuel pump 10, which is designed as a piston pump. An inlet valve 14 is arranged fluidically downstream of the inlet pipe 20. A low-pressure region 28 of the high-pressure fuel pump 10 is fluidically located between the inlet pipe 20 and the inlet valve 14. The delivery chamber 16 of the high-pressure fuel pump 10 is located downstream of the inlet valve 14. Pressure pulsations in the low-pressure region 28 can be damped by a pressure damping device. The inlet valve 14 can be forcibly opened by an actuating device, which is designed here as an electromagnetic actuator 30. The actuating device, and thus the inlet valve 14, can be controlled by a control unit 32.

[0028] The pump piston 18 of the high-pressure fuel pump 10 can be moved up and down along a longitudinal axis extending in the longitudinal direction LA by means of a drive 36 embodied in the present case as a cam disk. Figure 1 The double arrow 40 indicates that the pump piston 18 is axially symmetrical about this longitudinal axis. An outlet valve 37 is arranged fluidically between the delivery chamber 16 of the high-pressure fuel pump 10 and the outlet connection piece 35 . The outlet valve 37 can be opened toward the outlet connection piece 35 and toward the high-pressure accumulator 45 ("rail") located further downstream. Consequently, the high-pressure region 29 of the high-pressure fuel pump 10 extends fluidically between the outlet valve 37 and the outlet connection piece 35 .

[0029] The high-pressure region 29 and the low-pressure region 28 are directly connected to one another via a pressure-limiting valve 22, which opens when a limit pressure is exceeded in the high-pressure region 29 of the high-pressure fuel pump 10 or in a high-pressure accumulator 45 connected thereto. The pressure-limiting valve 22 is designed as a spring-loaded nonreturn valve and can open toward the low-pressure region 28 of the high-pressure fuel pump 10. In this way, the pressure that can be generated in the high-pressure accumulator 45 by the high-pressure fuel pump 10 is limited.

[0030] Figure 2and through its partial magnification and detailed highlighting Figure 3 A cross-sectional view of a high-pressure fuel pump 10 as a first embodiment of the present invention is shown.

[0031] The high-pressure fuel pump 10 has an inlet 11 designed as an inlet connector 20 . The inlet 11 communicates with the entire low-pressure region 28 of the high-pressure fuel pump 10 without an intervening connecting valve.

[0032] The high-pressure fuel pump 10 has an outlet 34 designed as an outlet connection 35. The outlet 34 communicates with the entire high-pressure region 29 of the high-pressure fuel pump 10 without an intermediate connecting valve.

[0033] The outlet connector 35 and the inlet connector 20 are fastened to the pump housing 12 , in which the delivery chamber 16 is also arranged and is delimited by a pump piston 18 that is movable in the longitudinal direction LA.

[0034] The low-pressure region 28 comprises a damping chamber 28a, which is connected to the inlet 11 via a fluid connection (not visible in this cross section) and is formed between the pump body 12a of the pump housing 12 and the pump cover 12b of the pump housing 12. A diaphragm damper 55 is arranged in the damping chamber 28a, which can have the form of a flat, compressible pot consisting of two metal diaphragms.

[0035] The non-visible fluid connection between the inlet 11 and the damping chamber 28 a can, for example, comprise a filter aperture in which a filter element is arranged, which protects the fuel flowing through the filter aperture from entrained solid particles larger than a minimum size.

[0036] The seal carrier 60 is fastened to Figure 2 The step chamber 28 d is formed on the lower section of the pump body 12 a in the middle and between the pump body 12 a and the seal carrier 60. The step chamber 28 d is connected to the damping chamber 28 a via a through hole that is not visible in the cross section through the pump body 12 a and is therefore part of the low-pressure area 28.

[0037] The delivery chamber 16 is delimited toward the low-pressure region 28 by the inlet valve 14 , so that the inlet valve opens toward the delivery chamber 16 when a corresponding pressure difference exists.

[0038] In order to control the delivery rate of the high-pressure fuel pump 10, the inlet valve 14 can be forcibly opened by a plunger 31 driven by an actuator 30. For this purpose, the actuator 30 has an actuator housing 30a fixed to the pump housing 12, in which a solenoid 30b is arranged, which can be energized via an externally accessible electrical connection 30c of the high-pressure fuel pump 10.

[0039] Geometrically, an inlet valve region 28c of the low-pressure region 28 is formed in the pump housing 12 between the inlet valve 14 and the actuator 30. This inlet valve region communicates with the damping region 28a via a bore 28f.

[0040] The delivery chamber 16 is delimited toward the high-pressure region 29 by an outlet valve 37, which opens away from the delivery chamber 16 when a corresponding pressure differential exists. In this example, the outlet valve is arranged in an outlet valve opening 37a of the pump housing 12 or pump body 12a. The outlet valve comprises a movable valve element 37.1 that interacts with a sealing seat 37.4, which is formed on a sealing seat portion 37.2 that is fixedly arranged upstream of the valve element 37.1. The mobility of the valve element 37.1 in the downstream direction is limited by a counterplate 37.5 that is fixedly arranged to the pump. The outlet valve opening 37a originates from an outlet connection chamber 35a located between the outlet connection 35 and the pump housing 12 or pump body 12a.

[0041] The pump piston 18 is designed as a stepped piston. It has a first section 18.1 with a larger diameter facing the delivery chamber 16 and a second section 18.2 with a smaller diameter (relative to the diameter of the first section 18.1) pointing away from the delivery chamber. Figure 2 The annular step 18.3 is directed vertically downward.

[0042] In the present arrangement, the pump body 12a is composed of a receiving body 12a' and a running bushing 80 pressed and / or wedged into the receiving body. The pump piston 18 is arranged displaceably along its section 18.1 in the running bushing 80. A narrow gap remains between the pump piston 18 and the running bushing 80, thereby producing a sealing effect, as described in detail, for example, in WO 06 069 819 A1 of the applicant.

[0043] Furthermore, the pump piston 18 has a groove 181 around its circumference, in which a sealing ring 182 is fixed, which also seals the aforementioned gap between the pump housing 12a or between the running bush 80 and the pump piston 18. The sealing ring 182 thus forms a high-pressure seal.

[0044] The sealing ring 182 is designed such that its thickness d increases in the radial direction toward the longitudinal direction LA pointing away from the conveying chamber 16, and the sealing ring 182 is thicker in the radial direction at its end 182.2 pointing away from the conveying chamber 16 in the longitudinal direction LA than at its end 182.1 pointing toward the conveying chamber 16 in the longitudinal direction LA. The sealing ring has a conical or spherical outer contour 182.3 radially outward, see also Figure 3 .

[0045] The contact length k of the sealing ring 182 in the longitudinal direction LA against the pump housing 12 or the running bushing 80 is 640 μm, measured when the pump is at rest. In this example, the diameter D of the pump piston 18 in the section 18 . 1 is 8 mm.

[0046] Arranged between the second section 18 . 2 and the aforementioned seal carrier 60 is a low-pressure seal 78 which separates the step chamber 28 d of the low-pressure region 28 from a space 100 outside the high-pressure fuel pump 10 . The pump piston 18 is movable in the low-pressure seal 78 .

[0047] The pump piston 18 is urged toward the pump by means of a spring disk 19.1 fixed to the pump piston 18 and a pump spring 19.2 clamped between the spring disk 19.1 and the seal carrier 60. Figure 2 The preload is in the longitudinal direction LA pointing downward.

[0048] The high-pressure fuel pump 10 according to the present invention has a pressure-limiting valve 22 that fluidically connects a high-pressure region 29 to a low-pressure region 28 and opens toward the low-pressure region 28, so that when the pressure difference between the fuel in the high-pressure region 29 and the fuel in the low-pressure region 28 exceeds an opening pressure, fuel flows from the high-pressure region 29 into the low-pressure region 28. The arrangement of the pressure-limiting valve 22 in the high-pressure fuel pump 10 according to the present invention will now be discussed further by way of example.

[0049] In this example, it is provided that the pressure-limiting valve 22 is fixed in a pressure-limiting valve bore 22a of the pump housing 12 and that the outlet valve bore 37a and the pressure-limiting valve bore 22a extend in geometrically parallel planes perpendicular to the longitudinal direction LA.

[0050] In accordance with Figure 2 In the first embodiment, the outlet valve hole 37a and the pressure-limiting valve hole 22a are even in a common plane parallel to the longitudinal direction LA, that is, in Figure 2 Oriented in the drawing plane.

[0051] In accordance with Figure 2 In the first embodiment, the outlet valve hole 37a and the pressure limiting valve hole 22a are even geometrically parallel to each other, i.e., along Figure 2 Horizontal orientation in the .

[0052] In accordance with Figure 2 In the illustration of , the outlet valve hole 37a is arranged on the side of the pressure-limiting valve hole 22a facing away from the damping area 28a. In this way, the length of the flow path and thus the flow resistance between the pressure-limiting valve 22 and the damping area 28a are minimized.

[0053] Here, for example, it is provided that, in addition to the outlet valve opening 37a, the pressure-limiting valve opening 22a also originates from the outlet connecting chamber 35a, and that the pressure-limiting valve opening 22a is connected to the damping region 28a via a low-pressure connecting opening 28b oriented in the longitudinal direction LA in the low-pressure region 28. The low-pressure connecting opening 28b can, for example, be coaxial with the longitudinal axis of the high-pressure fuel pump 10 and / or with the axis of symmetry of the pump piston 18 and / or the diaphragm damper 55.

[0054] The outlet pipe 35 extends in particular transversely to the flow direction beyond the output end of the pressure-limiting valve bore 22a and the output end of the outlet valve bore 37a, so that the pressure-limiting valve bore 22a and the outlet valve bore 37a are connected to each other via an outlet pipe chamber 35a arranged between the pump housing 12 and the outlet pipe 35.

[0055] Figure 4 FIG2 shows a part of the second embodiment of the present invention. Figure 2 and Figure 3 The illustrated embodiment differs in that the pump piston 18 has two sub-pistons 18a, 18b mounted one above the other in the longitudinal direction, forming a circumferential groove 181 between the two sub-pistons. Furthermore, a disc spring 87 is mounted between the two sub-pistons 18a, 18b, which acts on a sealing ring 182 in the longitudinal direction LA pointing away from the delivery chamber 16. In the example, the dimensions are: a = 3 mm; b = 2.3 mm; D = 8 mm; and c = 5.8 mm.

[0056] exist Figure 4 In the illustrated regions I, II, III, and IV, the fuel pressure acting on sealing ring 182 is indicated by a plurality of arrows in a positionally resolved manner, with long arrows symbolically representing high fuel pressure and short arrows symbolically representing low fuel pressure. The core concept of the present invention is that the transition from high fuel pressure to low fuel pressure occurs over a short distance on outer contour 182.3 of sealing ring 182, thereby minimizing the friction work generated during the movement of pump piston 18 and the resulting wear on sealing ring 182.

[0057] FIG. 5 shows a schematic embodiment in parts a), b) and c).

[0058] Embodiments a) and b) share the fact that the thickness d of the sealing ring 182 decreases radially in the longitudinal direction, pointing away from the delivery chamber 16. This means that the sealing ring 182 is thinner in the radial direction at its end 182.2, pointing away from the delivery chamber 16 in the longitudinal direction LA, than at its end 182.1, pointing toward the delivery chamber 16 in the longitudinal direction LA. This configuration results in the pump piston 18 and its sealing ring 182 moving toward the delivery chamber 16 (upward in the drawing) during the delivery stroke. Due to the high pressure (e.g., 50 MPa) prevailing in the delivery chamber 16 and the relatively low back pressure (e.g., 0.5 MPa) in the low-pressure region 28, the sealing edge pointing toward the delivery chamber 16 is firmly pressed against the pump housing 12 or the running bushing 80. This improves the sealing effect. However, the resulting high frictional work and resulting high wear of the sealing ring 182 are also accompanied by this firm pressing, which can be particularly undesirable.

[0059] The sealing ring 182 according to embodiment a) has an annular collar 182 . 4 pointing toward the conveying chamber 16 , whereas the sealing ring 182 according to embodiment b) is of overall conical design.

[0060] The characteristic feature of embodiment c) in FIG. 5 is that the thickness of the sealing ring 182 increases radially in the longitudinal direction away from the delivery chamber 16 , such that the sealing ring 182 is thicker radially at its end 182 . 2 , which faces longitudinally away from the delivery chamber 16 , than at its end 182 . 1 , which faces longitudinally toward the delivery chamber 16 , in the longitudinal direction LA. This configuration results in the pump piston 18 and its sealing ring 182 moving toward the delivery chamber 16 (upward in the drawing) during the delivery stroke of the high-pressure fuel pump 10 . The sealing edge facing the delivery chamber 16 is relieved of the pressure acting on the pump housing 12 or the running bushing 80 due to the high pressure present in the delivery chamber 16 and the relatively low back pressure in the low-pressure region 28 . This can gradually reduce the sealing effect, or such a reduction can be avoided with a suitable design. However, the resulting reduced frictional work and, therefore, reduced wear of the sealing ring 182 , accompanied by reduced extrusion, results in a longer service life of the sealing ring and the high-pressure fuel pump 10 .

[0061] The sealing ring 182 according to embodiment c) is Figure 5c ) has a spherical outer contour 182.3 in the lower part.

Claims

1. A high-pressure fuel pump (10) for a fuel system of an internal combustion engine, comprising: an inlet (11) for supplying fuel, an outlet (34) for outputting the compressed fuel, Pump housing (12), a delivery chamber (16) arranged in the pump housing (12), a pump piston (18) which is movable in the longitudinal direction (LA) in the pump housing (12) and which delimits the delivery chamber (16), an inlet valve (14) arranged between the inlet (11) and the conveying chamber (16), the inlet valve opening toward the conveying chamber (16), an outlet valve (37) arranged between the conveying chamber (16) and the outlet (34), the outlet valve opening away from the conveying chamber (16), a high pressure region (29) extending fluidically between the outlet valve (20) and the outlet (34), A low pressure region (28) extending fluidically between the inlet (11) and the inlet valve (14), wherein The pump piston (18) has a groove (181) around its circumference, wherein a sealing ring (182) is fixed in the groove, wherein the sealing ring seals the gap between the pump housing (12) and the pump piston (18), wherein the contact length (k) of the sealing ring (182) against the pump housing (13) in the longitudinal direction (LA) is less than 1 mm and / or less than 10% of the maximum diameter (D) of the pump piston (18).

2. The high-pressure fuel pump (10) according to claim 1, wherein: The thickness (d) of the sealing ring (182) in the radial direction increases toward the longitudinal direction (LA) pointing away from the conveying chamber (16), so that the sealing ring (181) is thicker in the radial direction at its end (182.2) pointing away from the conveying chamber (16) in the longitudinal direction (LA) than at its end (182.1) pointing toward the conveying chamber (16) in the longitudinal direction (LA).

3. The high-pressure fuel pump (10) according to claim 2, wherein: The sealing ring (182) has a conical or spherical outer contour (182.3) radially outwardly or an annular collar (182.4) radially outwardly which points in a longitudinal direction (LA) away from the conveying chamber (16).

4. A high-pressure fuel pump (10) according to any one of the preceding claims, wherein: The high-pressure fuel pump has a pressure-limiting valve (22), which fluidically connects the high-pressure region (29) and the low-pressure region (28) and opens toward the low-pressure region (28), so that when the pressure difference between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds an opening pressure, the fuel flows out from the high-pressure region (29) into the low-pressure region (28).

5. A high-pressure fuel pump (10) according to any one of the preceding claims, wherein: The pump housing (12) comprises a pump body (12a) and a pump cover (12b) which are connected to each other, wherein a damping area (28a) belonging to the low-pressure area (28) is bounded by the pump body (12a) and the pump cover (12b), and at least one diaphragm damper (55) is arranged in the damping area.

6. The high-pressure fuel pump (10) according to claim 4 and claim 5, wherein: The pressure-limiting valve (22) fluidically connects the high-pressure region (29) with the damping region (28a) and opens toward the damping region (28a), so that when the pressure difference between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds an opening pressure, the fuel flows out of the high-pressure region (29) into the damping region (28a), wherein the outlet valve (37) is fixed in an outlet valve hole (37a) of the pump housing (12), wherein the pressure-limiting valve (22) is fixed in the pressure-limiting valve hole (22a) of the pump housing (12), and wherein the outlet valve hole (37a) and the pressure-limiting valve hole (22a) extend in planes that are geometrically parallel to each other and are perpendicular to the longitudinal direction (LA).

7. The high-pressure fuel pump (10) according to claim 6, wherein: The outlet valve opening (37a) and the pressure-limiting valve opening (22a) are oriented geometrically parallel to one another.

8. The high-pressure fuel pump (10) according to any one of claims 6 or 7, wherein: The outlet (34) is constructed as an outlet pipe (35) fixed to the pump housing (12), and an outlet pipe chamber (35a) is formed between the pump housing (12) and the outlet pipe chamber (35), wherein the outlet valve hole (37a) and the pressure limiting valve hole (22a) both start from the outlet pipe chamber (35a).

9. The high-pressure fuel pump (10) according to any one of claims 6 to 8, wherein: The pressure limiting valve hole (22a) is connected to the vibration damping area (28a) via a low-pressure connecting hole (28b) located in the low-pressure area (28).

10. A high-pressure fuel pump (10) according to any one of the preceding claims, wherein: The sealing ring (182) is made of plastic or of fiber-reinforced plastic.

11. The high-pressure fuel pump (10) according to any one of claims 5 to 10, wherein: The pump body (12a) comprises a receiving body (12a') and a running bushing (80) pressed into and / or wedged in the receiving body (12a'), wherein a gap between the pump housing (12a) and the pump piston (18) is formed by a gap between the running bushing (80) and the pump piston (18).

12. A high-pressure fuel pump (10) according to any one of the preceding claims, wherein: The pump piston (18) has two sub-pistons (18a, 18b) mounted on each other in the longitudinal direction, and a circumferential groove (181) is formed between the two sub-pistons.

13. The high-pressure fuel pump (10) according to claim 12, wherein: A disc spring (87) is mounted between the two partial pistons (18a, 18b) and acts on the sealing ring (182) in a longitudinal direction (LA) pointing away from the conveying chamber (16).

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