High-pressure fuel pump

Abstract

The invention relates to a high-pressure fuel pump (10) for a high-pressure fuel pump (10) for a fuel system for an internal combustion engine, having an inlet (11) for supplying fuel, having an outlet (34) for dispensing compressed fuel, having a pump housing (12), a pumping chamber (16) arranged in the pump housing (12), having a pump piston (18) that is displaceable in the pump housing (12) along a longitudinal direction (LA) and that delimits the pumping chamber (16), having an inlet valve (14) arranged between the inlet (11) and the pumping chamber (16), which inlet valve opens towards the pumping chamber (16), having a high-pressure region (29), which extends fluidically between the outlet valve (20) and the outlet (34), having a low-pressure region (28), which extends fluidically between the inlet (11) and the inlet valve (14), wherein the pump piston (18) has a groove (181) running around its circumference, in which groove a sealing ring (182) is fixed, which seals a gap between the pump housing (12) and the pump piston (18), wherein a contact length (k), with which the sealing ring (182) bears against the pump housing (13) in the longitudinal direction (LA), is less than 1 mm and / or is less than 10% of the maximum diameter (D) of the pump piston (18).

Description

[0001] Description

[0002] title

[0003] High-pressure fuel pump

[0004] State of the art

[0005] From the prior art, for example from DE 102004 063 074 B4 of the applicant, a high-pressure fuel pump with a pump housing, a delivery chamber arranged in the pump housing and a pump piston which is displaceable in a longitudinal direction in the pump housing and which delimits the delivery chamber is already known.

[0006] In the known high-pressure fuel pump, a liner in the pump housing is provided with a through-hole in which the piston is guided. The gap that inevitably remains between the pump piston and the pump housing, or between the pump piston and the liner, limits the delivery efficiency of the high-pressure fuel pump, especially when it oscillates at a comparatively low frequency.

[0007] Disclosure of the invention

[0008] The present invention is based primarily on the desire to improve the tightness between the pump piston and the pump housing and thus increase the delivery rate of the high-pressure fuel pump.

[0009] This is achieved by providing the pump piston with a groove running around its circumference in which a sealing ring (also known as a high-pressure seal) is fixed, which seals the gap between the pump housing and the pump piston.

[0010] The applicant has identified wear mechanisms of the sealing ring during operation of the high-pressure fuel pump and deduced that such wear can be minimized by providing that a contact length with which the sealing ring rests against the pump housing in the longitudinal direction is less than 1 mm and / or less than 10% of the maximum diameter of the pump piston.

[0011] In a further development, the contact length with which the sealing ring rests on 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.

[0012] The idea behind this is that if a 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 to a correspondingly small contact area, the friction work resulting from the operation of the pump and the corresponding wear of the sealing ring are also significantly reduced.

[0013] A lower limit for the contact length with which the sealing ring bears against the pump housing or against a bushing of the pump housing in the longitudinal direction can be given by the requirement of a sufficient sealing effect, e.g. by the contact length with which the sealing ring bears against the pump housing in the longitudinal direction being 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.

[0014] The contact length is preferably understood as the contact length when the pump is at a standstill, i.e. when there is no relative movement between the pump piston and the pump housing.

[0015] The inventors have recognized that wear on the sealing ring can be further reduced by providing that the thickness of the sealing ring increases in the radial direction in the longitudinal direction pointing away from the delivery chamber and / or that the sealing ring is thicker in the radial direction at its end pointing longitudinally away from the delivery chamber than at its end pointing longitudinally towards the delivery chamber. This can be achieved, for example, by the sealing ring having a conical or spherical outer contour towards the radial outside or by having a ring shoulder on the radial outside that points in the longitudinal direction away from the delivery chamber. A stepped design is also possible. Such structural designs of the sealing ring have the effect that the high pressure acting on the sealing ring from the delivery chamber results in a force that reduces the force with which the sealing ring is pressed against the pump housing.As a result, the friction work resulting from the operation of the high-pressure fuel pump and thus the wear of the sealing ring is also reduced.

[0016] The sealing ring may comprise or consist of a plastic. The sealing ring may, for example, be made of a plastic reinforced with fibers, such as carbon fibers and / or similar materials.

[0017] A pump piston which has a groove running around its circumference in which a sealing ring is fixed can be provided in a simple manner according to a further development of the invention in that the pump piston has two partial pistons mounted on one another in the longitudinal direction, between which the circumferential groove is formed.

[0018] In a further development, it can be provided that a disc spring is mounted between the two partial pistons, which acts on the sealing ring in the longitudinal direction pointing away from the delivery chamber so that it is reliably fixed in the circumferential groove.

[0019] The high-pressure fuel pump according to the invention is further provided with an inlet for supplying fuel, with an outlet for discharging compressed fuel, with an inlet valve arranged between the inlet and the delivery chamber, which opens towards the delivery chamber, with an outlet valve arranged between the delivery chamber and the outlet, which opens away from the delivery chamber, with a high-pressure region which extends fluidically between the outlet valve and the outlet, and with a low-pressure region which extends fluidically between the inlet and the inlet valve.

[0020] A particularly attractive development of the high-pressure fuel pump according to the invention in the context of the high-pressure seals described above provides that it has a pressure relief valve which fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region, so that fuel flows from the high-pressure region into the low-pressure region when the pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds an opening pressure, and that the pump housing comprises a pump body and a pump cover which are connected to one another, wherein the pump body and the pump cover delimit a damping region belonging to the low-pressure region, in which at least one diaphragm damper is arranged, and that the pressure relief valve fluidically connects the high-pressure region to the damping region and opens towards the damping region,so that fuel flows from the high-pressure area into the damping area when the pressure difference between the fuel in the high-pressure area and the fuel in the low-pressure area exceeds the opening pressure. Optionally, the outlet valve can be fixed in an outlet valve bore of the pump housing, the pressure relief valve can be fixed in a pressure relief valve bore of the pump housing, and the outlet valve bore and the pressure relief valve bore can extend in geometrically parallel planes perpendicular to the longitudinal direction.

[0021] Furthermore, it can be provided that the outlet valve bore and the pressure relief valve bore are oriented geometrically parallel to one another; and / or that the outlet is designed as an outlet nozzle fixed to the pump housing, and an outlet nozzle chamber is formed between the pump housing and the outlet nozzle, wherein the outlet valve bore and the pressure relief valve bore both extend from the outlet nozzle chamber; and / or that the pressure relief valve bore is connected to the damping region by a low-pressure connecting bore located in the low-pressure region.

[0022] These additional measures are already advantageous in themselves, since the pressure relief valve of the high-pressure fuel pump is separated from the delivery chamber and diverts into the low-pressure area, i.e. it is only exposed to significantly reduced pressure fluctuations and is therefore subject to significantly reduced wear.

[0023] However, these additional measures generally result in a significant reduction in the dead volume of the delivery chamber of the high-pressure fuel pump, so that a pronounced sudden increase in pressure occurs in the delivery chamber and thus also at the high-pressure seal or at the sealing ring.

[0024] A resulting reduction in the tightness of the

[0025] High pressure seal and resulting increased wear of the

[0026] However, high-pressure seals are avoided precisely by the properties of the high-pressure seal described above. The combined features of the invention and the further developments result in a durable high-pressure fuel pump with a high delivery rate over its service life.

[0027] The fuel can be, for example, a fuel such as gasoline. This naturally also includes synthesized liquid fuels. Naturally, the pump according to the invention is also capable of compressing fluid media other than fuels.

[0028] Exemplary embodiments of the invention are explained below with reference to the drawing.

[0029] Figure 1 shows a simplified schematic representation of a fuel system for an internal combustion engine.

[0030] Figure 2 shows a first embodiment of the invention. Figure 3 shows an enlarged detail of Figure 2. Figure 4 shows a second embodiment of the invention. Figure 5 shows schematic embodiments in parts a), b), and c).

[0031] Figure 1 shows a simplified schematic representation of a fuel system 1 for an internal combustion engine (not shown). During operation of the fuel system 1, fuel is supplied from a fuel tank 2 via a suction line 4 by means of a pre-feed pump 6 and a low-pressure line 8 via an inlet nozzle 20 to a high-pressure fuel pump 10 designed as a piston pump. An inlet valve 14 is fluidly arranged downstream of the inlet nozzle 20. A low-pressure region 28 of the high-pressure fuel pump 10 is located fluidically between the inlet nozzle 20 and the inlet valve 14. Downstream of the inlet valve 14 is a delivery chamber 16 of the high-pressure fuel pump 10. Pressure pulsations in the low-pressure region 28 can be dampened by means of a pressure damper device. The inlet valve 14 can be forcibly opened by an actuating device designed here as an electromagnetic actuator 30.The actuating device and thus the inlet valve 14 can be controlled via a control unit 32. A pump piston 18 of the high-pressure fuel pump 10 can be moved up and down by means of a drive 36, here designed as a cam disk, along a longitudinal axis extending in the longitudinal direction LA, to which the pump piston 18 is axially symmetrical, as shown in Figure 1 by a double arrow 40. An outlet valve 37 is arranged fluidically between the delivery chamber 16 and an outlet connection 35 of the high-pressure fuel pump 10, which can open toward the outlet connection 35 and a high-pressure accumulator 45 ("rail") located further downstream. Consequently, a high-pressure region 29 of the high-pressure fuel pump 10 extends fluidically between the outlet valve 37 and the outlet connection 35.

[0032] The high-pressure region 29 and the low-pressure region 28 are directly connected to one another via a pressure relief 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 the high-pressure accumulator 45 communicating with it. The pressure relief valve 22 is designed as a spring-loaded check 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 by the high-pressure fuel pump 10 in the high-pressure accumulator 45 is limited.

[0033] Figure 2 and Figure 3, which emerges from it by means of an enlarged detail and detail, show a high-pressure fuel pump 10 in a sectional view as a first embodiment of the invention.

[0034] The high-pressure fuel pump 10 has an inlet 11 designed as an inlet nozzle 20. Without the interposition of valves, the inlet 11 communicates with the entire low-pressure area 28 of the high-pressure fuel pump 10.

[0035] The high-pressure fuel pump 10 has an outlet 34 designed as an outlet nozzle 35. Without the interposition of valves, the outlet 34 communicates with the entire high-pressure area 29 of the high-pressure fuel pump 10.

[0036] The outlet nozzle 35 and the inlet nozzle 20 are fixed to a pump housing 12, in which a delivery chamber 16 is also arranged, which is delimited by a pump piston 18 displaceable along a longitudinal direction LA.

[0037] The low-pressure region 28 comprises a damper chamber 28a, which is connected to the inlet 11 via a fluidic connection not visible in this cross-section and which is formed between a pump body 12a of the pump housing 12 and a pump cover 12b of the pump housing 12. A diaphragm damper 55 is arranged in the damper chamber 28a, which can have the shape of a flat and compressible can formed by two metal diaphragms.

[0038] The non-visible fluidic connection between the inlet 11 and the damper chamber 28a can, for example, comprise a filter bore in which a filter element is arranged which frees a fuel flowing through the filter bore from entrained solid particles above a minimum size.

[0039] A seal carrier 60 is attached to the lower section of the pump body 12a in Figure 2, and a step chamber 28d is formed between the pump body 12a and the seal carrier 60. The step chamber 28d communicates with the damping chamber 28a via a through-bore through the pump body 12a (not visible in this cross-section) and is thus part of the low-pressure region 28.

[0040] The delivery chamber 16 is limited to the low-pressure area 28 by an inlet valve 14, which opens towards the delivery chamber 16 when there is a corresponding pressure difference.

[0041] To control the delivery rate of the high-pressure fuel pump 10, the inlet valve 14 can be forcibly opened by a tappet 31 driven by the actuator 30. For this purpose, the actuator 30 has an actuator housing 30a fixed to the pump housing 12, in which an electromagnetic coil 30b is arranged, which can be energized via an externally accessible electrical connection 30c of the high-pressure fuel pump 10.

[0042] Geometrically formed between the inlet valve 14 and the actuator 30 in the pump housing 12 is an inlet valve region 28c of the low-pressure region 28. It communicates with the damping region 28a via the bore 28f. The delivery chamber 16 is delimited towards the high-pressure region 29 by an outlet valve 37, which opens away from the delivery chamber 16 when a corresponding pressure difference exists. In this example, it is arranged in an outlet valve bore 37a of the pump housing 12 or the pump body 12a. It has a movable valve element 37.1, which interacts with a sealing seat 37.4, which is formed on a sealing seat part 37.2 arranged upstream of the valve element 37.1 and fixed to the pump. The mobility of the valve element 37.1 in the downstream direction is limited by a counterplate 37.5 arranged fixed to the pump. The outlet valve bore 37a extends from a bore formed between the outlet nozzle 35 and the pump housing 12 or.the outlet nozzle chamber 35a located in the pump body 12a.

[0043] The pump piston 18 is designed as a stepped piston. It has a first section 18.1 with a larger diameter, facing the pumping chamber 16, and a second section 18.2 with a smaller diameter (relative to the diameter of the first section 18.1), facing away from the pumping chamber. An annular step 18.3, pointing vertically downward in Figure 2, is formed between the first and second sections 18.1, 18.2.

[0044] In the present case, the pump body 12a consists of a receiving body 12a' and a bushing 80 pressed and / or caulked into it. The pump piston 18 is slidably arranged along its section 18.1 in the bushing 80. A narrow gap remains between the pump piston 18 and the bushing 80, resulting in a sealing effect, as explained in more detail, for example, in WO 06 069 819 A1 of the applicant.

[0045] Furthermore, the pump piston 18 is provided with a groove 181 extending around its circumference, in which a sealing ring 182 is fixed, which further seals the above-mentioned gap between the pump housing 12a or between the cylinder liner 80 and the pump piston 18. The sealing ring 182 thus forms a high-pressure seal.

[0046] The sealing ring 182 is designed such that its thickness d increases radially in the longitudinal direction LA pointing away from the conveying chamber 16, and that 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. It has a conical or spherical outer contour 182.3 radially outward, see also Figure 3.

[0047] The contact length k, with which the sealing ring 182 rests against the pump housing 12 or the liner 80 in the longitudinal direction LA, is 640 pm here, measured with the pump stationary. The diameter D of the pump piston 18 in section 18.1 is 8 mm in the example.

[0048] A low-pressure seal 78 is arranged between the second section 18.2 and the seal carrier 60 mentioned above, which separates the step chamber 28d of the low-pressure region 28 from the chamber 100 located outside the high-pressure fuel pump 10. The pump piston 18 is displaceable in the low-pressure seal 78.

[0049] The pump piston 18 is prestressed in the longitudinal direction LA pointing downwards in Figure 2 via a spring plate 19.1 fixed to the pump piston 18 and a pump spring 19.2 clamped between the spring plate 19.1 and the seal carrier 60.

[0050] The high-pressure fuel pump 10 according to the invention has a pressure relief valve 22 that fluidically connects the high-pressure region 29 to the low-pressure region 28 and opens toward the low-pressure region 28, so that fuel flows from the high-pressure region 29 into the low-pressure region 28 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 arrangement of the pressure relief valve 22 in the high-pressure fuel pump 10 according to the invention will now be discussed further by way of example.

[0051] In this example, it is provided that the pressure relief valve 22 is fixed in a pressure relief valve bore 22a of the pump housing 12 and that the outlet valve bore 37a and the pressure relief valve bore 22a extend in mutually geometrically parallel planes perpendicular to the longitudinal direction LA.

[0052] In the first embodiment according to Figure 2, the outlet valve bore 37a and the pressure relief valve bore 22a are even both oriented in a common plane which is parallel to the longitudinal direction LA, namely in the drawing plane of Figure 2.

[0053] In the first embodiment according to Figure 2, the outlet valve bore 37a and the pressure relief valve bore 22a are even oriented geometrically parallel to each other, namely in the horizontal direction in Figure 2.

[0054] In the illustration according to Figure 2, the outlet valve bore 37a is arranged on the side of the pressure relief valve bore 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 relief valve 22 and the damping area 28a is minimized.

[0055] It is further provided, by way of example, that in addition to the outlet valve bore 37a, the pressure relief valve bore 22a also extends from the outlet connection chamber 35a, and that the pressure relief valve bore 22a is connected to the damping region 28a by a low-pressure connecting bore 28b located in the low-pressure region 28 and oriented in the longitudinal direction LA. The low-pressure connecting bore 28b can, for example, be coaxial with a longitudinal axis of the high-pressure fuel pump 10 and / or coaxial with an axis of symmetry of the pump piston 18 and / or the diaphragm damper 55.

[0056] The outlet nozzle 35 extends in particular transversely to the flow direction over the outlet of the pressure relief valve bore 22a and over the outlet of the outlet valve bore 37a, so that the pressure relief valve bore 22a and the outlet valve bore 37a communicate with each other via the outlet nozzle space 35a arranged between the pump housing 12 and the outlet nozzle 35.

[0057] Figure 4 shows a detail of a second exemplary embodiment of the invention. It differs from the exemplary embodiment shown in Figures 2 and 3 in that the pump piston 18 has two partial pistons 18a, 18b mounted one on top of the other in the longitudinal direction, between which the circumferential groove 181 is formed. Furthermore, a disc spring 87 is mounted between the two partial pistons 18a, 18b, which acts on the sealing ring 182 in the longitudinal direction LA pointing away from the pumping chamber 16. In the example, the dimensions are: a = 3 mm; b = 2.3 mm; D = 8 mm; c = 5.8 mm.

[0058] In fields I, II, III, and IV shown in Figure 4, the fuel pressure acting on the sealing ring 182 is represented spatially resolved by a plurality of arrows, with long arrows symbolizing high fuel pressures and short arrows symbolizing low fuel pressures. The core concept of the present invention is evident: the transition from high fuel pressures to low fuel pressures occurs along short distances on the outer contour 182.3 of the sealing ring 182, so that the friction work resulting from the movement of the pump piston 18 and the resulting wear on the sealing ring 182 are minimized.

[0059] Figure 5 shows schematically embodiments in parts a), b) and c).

[0060] Common to embodiments a) and b) is that the thickness d of the sealing ring 182 decreases in the radial direction in the longitudinal direction pointing away from the delivery chamber 16, so that the sealing ring 182 is less thick 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 towards the delivery chamber 16 in the longitudinal direction LA. This design has the consequence that when the pump is in a delivery stroke, the pump piston 18 and with it the sealing ring 182 moves towards the delivery chamber 16 (upwards in the figures), the sealing edge pointing towards the delivery chamber 16 is pressed firmly onto the pump housing 12 or onto the bushing 80 by the high pressure prevailing in the delivery chamber 16 (e.g. 50 MPa) and the comparatively low counterpressure in the low-pressure region 28 (e.g. 0.5 MPa). This improves the sealing effect.However, the firm pressure also results in high friction work and high wear of the sealing ring 182, which may be undesirable under certain circumstances.

[0061] While the sealing ring 182 according to embodiment a) has an annular shoulder 182.4 pointing towards the conveying chamber 16, the sealing ring 182 according to embodiment b) is conical overall.

[0062] The embodiment c) in Figure 5 is characterized in that the thickness of the sealing ring 182 increases in the radial direction in the longitudinal direction pointing away from the delivery chamber 16, so that the sealing ring 182 is thicker in the radial direction at its end 182.2 pointing in the longitudinal direction away from the delivery chamber 16 than at its end 182.1 pointing in the longitudinal direction LA towards the delivery chamber 16. This design has the consequence that when the high-pressure fuel pump 10 is in a delivery stroke, the pump piston 18 and with it the sealing ring 182 moves towards the delivery chamber 16 (upwards in the figures), the sealing edge pointing towards the delivery chamber 16 is relieved of pressure by the high pressure prevailing in the delivery chamber 16 and the comparatively low counterpressure in the low-pressure region 28 on the pump housing 12 or on the cylinder bushing 80. As a result, a sealing effect may tend to be reduced or even eliminated.Such a reduction can be avoided by suitable design. However, the reduced pressure is accompanied by reduced resulting friction work and thus reduced wear on the sealing ring 182, thus extending its service life and the service life of the high-pressure fuel pump 10. The sealing ring 182 according to embodiment c) has a spherical outer contour 182.3 in its lower part (shown in Figure 5c).

Claims

Claims 1 . High-pressure fuel pump (10) for a fuel system for an internal combustion engine, with an inlet (11) for supplying fuel, with an outlet (34) for discharging compressed fuel, with a pump housing (12), a delivery chamber (16) arranged in the pump housing (12), with a pump piston (18) which is displaceable in the pump housing (12) along a longitudinal direction (LA) and delimits the delivery chamber (16), with an inlet valve (14) arranged between the inlet (11) and the delivery chamber (16) and which opens towards the delivery chamber (16), with an outlet valve (37) arranged between the delivery chamber (16) and the outlet (34) and which opens away from the delivery chamber (16), with a high-pressure region (29) which extends fluidically between the outlet valve (20) and the outlet (34), with a low-pressure region (28) which extends fluidically between the inlet (11) and the inlet valve (14), wherein the pump piston (18) has a groove (181) running around its circumference,in which a sealing ring (182) is fixed, which seals a gap between the pump housing (12) and the pump piston (18), wherein a contact length (k) with which the sealing ring (182) rests 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. High-pressure fuel pump (10) according to claim 1, wherein the thickness (d) of the sealing ring (182) increases in the radial direction in the longitudinal direction (LA) pointing away from the delivery chamber (16), so that the sealing ring (181) is in particular thicker 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 towards the delivery chamber (16) in the longitudinal direction (LA).

3. High-pressure fuel pump (10) according to claim 2, wherein the sealing ring (182) has a conical or spherical outer contour (182.3) radially outward or has a ring shoulder (182.4) radially outward, which points in the longitudinal direction (LA) away from the delivery chamber (16).

4. High-pressure fuel pump (10) according to one of the preceding claims, characterized in that it has a pressure relief valve (22) which fluidically connects the high-pressure region (29) with the low-pressure region (28). connects and opens towards the low-pressure region (28), so that fuel flows from the high-pressure region (29) into the low-pressure region (28) when the pressure difference between fuel in the high-pressure region (29) and fuel in the low-pressure region (28) exceeds an opening pressure. High-pressure fuel pump (10) according to one of the preceding claims, wherein the pump housing (12) comprises a pump body (12a) and a pump cover (12b) which are connected to one another, wherein the pump body (12a) and the pump cover (12b) delimit a damping region (28a) belonging to the low-pressure region (28), in which at least one diaphragm damper (55) is arranged.High-pressure fuel pump (10) according to claim 4 and claim 5, wherein the pressure relief valve (22) fluidically connects the high-pressure region (29) to the damping region (28a) and opens towards the damping region (28a) so that fuel flows from the high-pressure region (29) into the damping region (28a) when the pressure difference between fuel in the high-pressure region (29) and fuel in the low-pressure region (28) exceeds the opening pressure, wherein the outlet valve (37) is fixed in an outlet valve bore (37a) of the pump housing (12), wherein the pressure relief valve (22) is fixed in a pressure relief valve bore (22a) of the pump housing (12), and wherein the outlet valve bore (37a) and the pressure relief valve bore (22a) extend in mutually geometrically parallel planes perpendicular to the longitudinal direction (LA).The high-pressure fuel pump (10) according to claim 6, wherein the outlet valve bore (37a) and the pressure-limiting valve bore (22a) are oriented geometrically parallel to one another. The high-pressure fuel pump (10) according to one of claims 6 or 7, wherein the outlet (34) is designed as an outlet nozzle (35) fixed to the pump housing (12), and an outlet nozzle chamber (35a) is formed between the pump housing (12) and the outlet nozzle (35), wherein the outlet valve bore (37a) and the pressure-limiting valve bore (22a) are both separated from the outlet nozzle chamber. (35a). High-pressure fuel pump (10) according to one of claims 6 to 8, wherein the pressure relief valve bore (22a) is connected to the damping region (28a) by a low-pressure connecting bore (28b) located in the low-pressure region (28). High-pressure fuel pump (10) according to one of the preceding claims, wherein the sealing ring (182) is made of a plastic or of a fiber-reinforced plastic. High-pressure fuel pump (10) according to one of claims 5 to 10, wherein the pump body (12a) comprises a receiving body (12a') and a bushing (80) that is pressed and / or caulked into the receiving body (12a'), wherein the gap between the pump housing (12a) and the pump piston (18) is formed by a gap between the bushing (80) and the pump piston (18).High-pressure fuel pump (10) according to one of the preceding claims, wherein the pump piston (18) has two partial pistons (18a, 18b) mounted on one another in the longitudinal direction, between which the circumferential groove (181) is formed. High-pressure fuel pump (10) according to claim 12, wherein a disc spring (87) is mounted between the two partial pistons (18a, 18b), which acts on the sealing ring (182) in the longitudinal direction (LA) pointing away from the delivery chamber (16).

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