High-Pressure Fuel Pump

Abstract

A high-pressure fuel pump has a pressure-limiting valve, which fluidically connects a high-pressure region to a low-pressure region and opens towards the low-pressure region. The pressure-limiting valve is disposed in a pressure-limiting valve bore, which is designed as a through bore through the pump body, extends from a damping region to a stepped chamber, and is closed on the side facing the damping region by a pressed-in closure. The pressure-limiting valve bore is a stepped bore having a larger diameter first portion, a smaller diameter second portion, and an annular step between the first and second portions The pressure-limiting valve has a valve seat body pressed into the pressure-limiting valve bore, and a valve element, which is pushed in the closing direction by a holding element, which is pushed in the closing direction by a spiral spring, which is supported on the annular step.

Claims

1. A high-pressure fuel pump for a fuel system for an internal combustion engine, the high-pressure fuel pump comprising: an inlet for supplying fuel; an outlet for discharging compressed fuel; a pump housing; a delivery chamber arranged in the pump housing; a pump piston which is displaceable in the pump housing along a longitudinal direction and delimits the delivery chamber; an inlet valve, which is disposed between the inlet and the delivery chamber and which opens towards the delivery chamber; an outlet valve, which is disposed between the delivery chamber and the outlet and which opens away from the delivery chamber; a high-pressure region, which extends fluidically between the outlet valve and the outlet; a low-pressure region, which extends fluidically between the inlet and the inlet valve; and a pressure-limiting valve configured such that, when a pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds an opening pressure, the pressure-limiting valve fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region to enable fuel to flow out of the high-pressure region into the low-pressure region, wherein the pump piston is a stepped piston having a first piston portion that points towards the delivery chamber and has a larger diameter, and a second piston portion that has a smaller diameter and points away from the delivery chamber, wherein a high-pressure seal, in which the pump piston is displaceable and which separates the delivery chamber from the low-pressure region, is arranged between the first piston portion and the pump housing, wherein a low-pressure seal, which separates the low-pressure region from the space outside the high-pressure fuel pump is disposed between the second piston portion and a seal carrier fixed to the pump housing, a stepped chamber of the low-pressure region being located between the seal carrier and the pump housing, wherein the pressure-limiting valve fluidically connects the high-pressure region to the stepped chamber of the low-pressure region and opening towards the stepped chamber, so that fuel flows out of the high-pressure region into the stepped chamber when the pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds the opening pressure, wherein 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, and at least one diaphragm damper is disposed in the damping region, wherein the pressure-limiting valve is disposed in a pressure-limiting valve bore formed as a through bore through the pump body, the pressure-limiting valve bore extending from the damping region to the stepped chamber and being closed on a side facing the damping region by a ball or plug pressed into the pressure-limiting valve bore, wherein the pressure-limiting valve bore is designed as a stepped bore having a first bore portion that has a larger bore diameter and points towards the damping region, a second bore portion that has a smaller bore diameter and points towards the stepped chamber, and an annular step formed between the first bore portion and the second bore portion, wherein the pressure-limiting valve comprises: a valve seat body pressed into the pressure-limiting valve bore and on which a tapered valve seat is formed; a valve element, which has a ball shape and which comes into sealing contact with the valve seat, the pressure-limiting valve configured such that the valve element is pressed in a closing direction by a holding element, which is pressed in the closing direction by a spiral spring, which is supported on the annular step.

2. The high-pressure fuel pump according to claim 1, wherein: the outlet valve is disposed in an outlet valve bore of the pump housing, and the outlet valve bore and the pressure-limiting valve bore intersect.

3. The high-pressure fuel pump according to claim 2, wherein; the outlet valve comprises: a movable valve element; a sealing seat part disposed upstream of the valve element, the sealing seat part being fixed in a pump-tight manner with a sealing seat part fixing portion; a sealing seat, which interacts with the valve element, formed on the sealing seat part; and a pump-proof counter plate disposed downstream of the valve element and fixed in a pump-tight manner with a counter plate fixing portion, the pump-proof counter plate being configured to enable mobility of the valve element in a downstream direction, and the pressure-limiting valve bore intersects the outlet valve bore between the sealing seat part fixing portion and the counter plate fixing portion.

4. The high-pressure fuel pump according to claim 1, wherein: the outlet is formed as an outlet port fixed to the pump housing and an outlet port chamber is defined between the pump housing and the outlet port, the outlet valve is fixed in an outlet valve bore of the pump housing, the outlet valve bore extends from the outlet port chamber, the pressure-limiting valve bore is connected to the outlet port chamber via a high-pressure connecting bore that is located in the high-pressure region and extends from the outlet port chamber.

5. The high-pressure fuel pump according to claim 4, wherein the outlet valve bore and the high-pressure connection bore are disposed parallel to each other and perpendicular to the longitudinal direction.

6. The high-pressure fuel pump according to claim 4, wherein the outlet valve bore and the high-pressure connection bore are each perpendicular to the longitudinal direction and are disposed at an angle different from 0? to each other.

7. The high-pressure fuel pump according to claim 2, wherein an imaginary center axis of the outlet valve bore intersects an imaginary center axis of the pump piston.

8. The high-pressure fuel pump according to claim 2, wherein an imaginary center axis of the outlet valve bore does not intersect an imaginary center axis of the pump piston.

9. A high-pressure fuel pump for a fuel system for an internal combustion engine, the high-pressure fuel pump comprising: an inlet for supplying fuel; an outlet for dispensing compressed fuel; a pump housing; a delivery chamber arranged in the pump housing; a pump piston, which is displaceable in the pump housing along a longitudinal direction and limits the delivery chamber; an inlet valve disposed between the inlet and the delivery chamber, the inlet valve opening towards the delivery chamber; an outlet valve disposed between the delivery chamber and the outlet, the outlet valve opening away from the delivery chamber; a high-pressure region fluidly extending between the outlet valve and the outlet; a low-pressure region fluidly extending between the inlet and the inlet valve; and a pressure-limiting valve configured such that, when a pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds an opening pressure, the pressure-limiting valve fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region to enable fuel to flow out of the high-pressure region into the low-pressure region, wherein the pump piston is formed as a stepped piston having a first piston portion that faces towards the delivery chamber and has a larger diameter, and a second piston portion that has a smaller diameter and faces away from the delivery chamber, wherein a high-pressure seal, in which the pump piston is displaceable, and which separates the delivery chamber from the low-pressure region is disposed between the first portion and the pump housing, wherein a low-pressure seal, which separates the low-pressure region from space outside the high-pressure fuel pump, is disposed between the second portion, and a seal carrier fixed to the pump housing, wherein a stepped chamber of the low-pressure region is disposed between the seal carrier and the pump housing, wherein the pressure-limiting valve fluidly connects the high-pressure region to the stepped chamber of the low-pressure region and opens toward the stepped chamber, such that fuel drains from the high-pressure region into the stepped chamber, when the pressure difference between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds an opening pressure, wherein the outlet valve is disposed in an outlet valve bore of the pump housing the outlet valve comprising: a movable valve element and a sealing seat part disposed upstream of the valve element, the sealing seat part being fixed in a pump-proof manner with a sealing seat part fixing portion; a sealing seat, which cooperates with the valve element, is formed on the sealing seat; and a pump-proof counter plate disposed downstream of the valve element and fixed in a pump-proof manner with a counter plate fixing portion, the pump-proof counter plate being configured to prevent mobility of the valve element in a downstream direction, and wherein the pressure-limiting valve is disposed in a pressure-limiting valve bore in the pump housing, the pressure-limiting valve bore extending in the longitudinal direction and, starting from the stepped chamber, opens into the outlet valve bore.

10. A high-pressure fuel pump for a fuel system for an internal combustion engine, the high-pressure fuel pump comprising: an inlet for supplying fuel; an outlet for dispensing compressed fuel; a pump housing; a delivery chamber arranged in the pump housing; a pump piston, which is displaceable in the pump housing along a longitudinal direction and limits the delivery chamber; an inlet valve disposed between the inlet and the delivery chamber, the inlet valve opening towards the delivery chamber; an outlet valve disposed between the delivery chamber and the outlet, the outlet valve opening away from the delivery chamber; a high-pressure region fluidly extending between the outlet valve and the outlet; a low-pressure region fluidly extending between the inlet and the inlet valve; and a pressure-limiting valve configured such that, when a pressure difference between fuel in the high-pressure region and fuel in the low-pressure region exceeds an opening pressure, the pressure-limiting valve fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region to enable fuel to flow out of the high-pressure region into the low-pressure region, wherein the pump piston is formed as a stepped piston having a first piston portion that faces towards the delivery chamber and has a larger diameter, and a second piston portion that has a smaller diameter and faces away from the delivery chamber, wherein a high-pressure seal, in which the pump piston is displaceable, and which separates the delivery chamber from the low-pressure region is disposed between the first portion and the pump housing, wherein a low-pressure seal, which separates the low-pressure region from space outside the high-pressure fuel pump, is disposed between the second portion, and a seal carrier fixed to the pump housing, wherein a stepped chamber of the low-pressure region is disposed between the seal carrier and the pump housing, wherein the pressure-limiting valve fluidly connects the high-pressure region to the stepped chamber of the low-pressure region and opens toward the stepped chamber, such that fuel drains from the high-pressure region into the stepped chamber, if when the pressure difference between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds an opening pressure, wherein the outlet valve is disposed in an outlet valve bore of the pump housing, wherein the pressure-limiting valve is disposed in a pressure-limiting valve bore in the pump housing, and extending in the longitudinal direction, the stepped chamber opening from the pressure-limiting valve bore into a high-pressure connecting bore in the pump housing, the pressure-limiting valve being disposed in the high-pressure region and oriented at an angle other than 0? to the outlet valve bore.

11. The high-pressure fuel pump according to claim 2, wherein the outlet valve bore and the pressure-limiting valve bore intersect at right angles.

12. The high-pressure fuel pump according to claim 9, wherein the pressure-limiting valve bore opens into the outlet valve bore between the sealing seat part fixing portion and the counter plate fixing portion.

13. The high-pressure fuel pump according to claim 10, wherein: the outlet is designed as an outlet port fixed to the pump housing, an outlet port chamber being formed between the pump housing and the outlet port, and the outlet valve bore and the high-pressure connecting bore both extend from the outlet port chamber.

Description

[0031] Embodiment examples of the invention are explained below with reference to the drawing. The drawings show:

[0032] FIG. 1 shows a simplified schematic diagram of a fuel system for an internal combustion engine.

[0033] FIG. 2 shows a first embodiment example of the invention.

[0034] FIG. 3 shows a detailed example of a pressure-limiting valve as it can be used in the embodiment examples shown.

[0035] FIG. 4 shows a second embodiment example of the invention.

[0036] FIG. 5 shows a third embodiment example of the invention.

[0037] FIG. 6 shows a fourth embodiment example of the invention.

[0038] FIG. 7 shows a fifth embodiment example of the invention.

[0039] FIG. 1 shows a fuel system 1 for an internal combustion engine not shown in a simplified schematic diagram. During operation of the fuel system 1, fuel is fed 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 port 20 to a high-pressure fuel pump 10 designed as a piston pump. An inlet valve 14 is fluidically arranged downstream of the inlet port 20. A low-pressure region 28 of the high-pressure fuel pump 10 is located fluidically between the inlet port 20 and the inlet valve 14. A 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 means of a pressure damping device. The inlet valve 14 can be forcibly opened via 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.

[0040] A pump piston 18 of the high-pressure fuel pump 10 can be moved up and down along a longitudinal axis running in the longitudinal direction LA, to which the pump piston 18 is axially symmetrical, by means of a drive 36 designed in the present case as a cam disk, which is shown in FIG. 1 by a double arrow 40. An outlet valve 37 is disposed fluidically between the delivery chamber 16 and an outlet port 35 of the high-pressure fuel pump 10, which can open towards the outlet port 35 and a high-pressure accumulator 45 (rail) located further downstream. As a result, a high-pressure region 29 of the high-pressure fuel pump 10 extends fluidically between the outlet valve 37 and the outlet port 35.

[0041] The high-pressure region 29 and the low-pressure region 28 are directly connected to each other 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 the high-pressure accumulator 45 communicating with it. The pressure-limiting valve 22 is designed as a spring-loaded check valve and can open towards 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.

[0042] FIG. 2 shows a sectional view of a high-pressure fuel pump 10 as a first embodiment example of the invention.

[0043] The high-pressure fuel pump 10 has an inlet 11 in the form of an inlet port 20. Without intermediate valves, the inlet 11 communicates with the entire low-pressure region 28 of the high-pressure fuel pump 10.

[0044] The high-pressure fuel pump 10 has an outlet 34 in the form of an outlet port 35. Without intermediate valves, the outlet 34 communicates with the entire high-pressure region 29 of the high-pressure fuel pump 10.

[0045] The outlet port 35 and the inlet port 20 are fixed to a pump housing 12, in which a delivery chamber 16 is also disposed, which is delimited by a pump piston 18 that can be displaced along a longitudinal direction LA.

[0046] 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 disposed in the damping chamber 28a, which can have the shape of a flat and compressible can formed by two metal diaphragms.

[0047] 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 disposed which frees a fuel flowing through the filter bore from entrained solid particles above a minimum size.

[0048] A seal carrier 60 is attached to the lower portion of the pump body 12a in FIG. 2 and a stepped chamber 28d is formed between the pump body 12a and the seal carrier 60. The stepped chamber 28d communicates with the damping chamber 28a via a through bore through the pump body 12a, which is not visible in this cross-section, and is therefore part of the low-pressure region 28.

[0049] The delivery chamber 16 is limited towards the low-pressure region 28 by an inlet valve 14, which opens towards the delivery chamber 16 when there is a corresponding pressure difference.

[0050] In order 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 disposed, which can be energized via an externally accessible electrical connection 30c of the high-pressure fuel pump 10.

[0051] Geometrically between the inlet valve 14 and the actuator 30, an inlet valve region 28c of the low-pressure region 28 is formed in the pump housing. It communicates with the damping region 28a via the bore 28f visible in this cross-section.

[0052] The delivery chamber 16 is limited towards the high-pressure region 29 by an outlet valve 37, which opens away from the delivery chamber 16 when there is a corresponding pressure difference. In this example, it is disposed 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 disposed upstream of the valve element 37.1 and fixed to the pump. The movement of the valve element 37.1 in the downstream direction is limited by a counter plate 37.5 that is fixed to the pump. The outlet valve bore 37a extends from an outlet port chamber 35a located between the outlet port 35 and the pump housing 12 or the pump body 12a.

[0053] The pump piston 18 is designed as a stepped piston. It has a first portion 18.1 pointing towards the delivery chamber 16 with a larger diameter and a second portion 18.2 pointing away from the delivery chamber with a smaller diameter (relative to the diameter of the first portion 18.1). Between the first and second portions 18.1, 18.2, an annular step 18.3 is formed, pointing vertically downwards in FIG. 2.

[0054] A high-pressure seal 80 is disposed between the first portion 18.1 and the pump housing 12, in which the pump piston 18 can be displaced. The high-pressure seal 80 separates the delivery chamber 16 from the low-pressure region 28.

[0055] The high-pressure seal 80 can, for example, be a separate sealing ring, e.g. made of metal or plastic, for example as explained in more detail in WO 19 015 862 A1 of the applicant. On the other hand, the high-pressure seal 80 can also be a narrow gap extending over a certain length between the pump piston 18 and a bushing or between the pump piston 18 and the pump housing 12, for example as explained in more detail in WO 06 069 819 A1 of the applicant.

[0056] A low-pressure seal 78 is disposed between the second portion 18.2 and the seal carrier 60 already mentioned above, which separates the stepped chamber 28d of the low-pressure region 28 from the space 100, which is located outside the high-pressure fuel pump 10. The pump piston 18 can be displaced in the low-pressure seal 78.

[0057] The pump piston 18 is pretensioned in the longitudinal direction LA, which is pointing downwards in FIG. 2, by means of 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.

[0058] The high-pressure fuel pump 10 according to the invention has a pressure-limiting valve 22 which fluidically connects the high-pressure region 29 to the low-pressure region 28 and opens towards the low-pressure region 28, so that fuel flows out of 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.

[0059] The pressure-limiting valve is shown in detail and by way of example in FIG. 3. It has a valve seat body 38 pressed into the pressure-limiting valve bore 22a or into a housing of the pressure-limiting valve 22, on which a tapered valve seat 42 is formed. The pressure-limiting valve 22 also has a valve element 44, which has the shape of a ball and which comes into sealing contact with the valve seat 42. The valve element 44 is pressed in the closing direction by a holding element 46 and the holding element 46 is pressed in the closing direction by a spiral spring 52. The spiral spring 52 is supported on a housing of the pressure-limiting valve 22 or directly on the pump housing 12. The spiral spring 52 is in contact with a radially outer region 464 of the holding element 46. A radially inner region 465 of the holding element 46 is accommodated by the spiral spring 52. The opening pressure of the pressure-limiting valve 22 is defined by the stiffness of the spiral spring 52 and by the effective area at the pressure-limiting valve 22, and thus also the maximum pressure difference that the high-pressure fuel pump 10 is able to generate between its inlet 11 and its outlet 34.

[0060] The arrangement of the pressure-limiting valve 22 in the high-pressure fuel pump 10 according to the invention will now be discussed further by way of example.

[0061] In the context of the invention (independent claim 1), it is provided that the pressure-limiting valve 22 fluidically connects the high-pressure region 29 to the stepped chamber 28d of the low-pressure region 28 and opens towards the stepped chamber 28d, so that fuel flows out of the high-pressure region 29 into the stepped chamber 28d when the pressure difference between fuel in the high-pressure region 29 and fuel in the low-pressure region 28 exceeds an opening pressure, and in that the pressure-limiting valve 22 is disposed in a pressure-limiting valve bore 22a formed as a through bore through the pump body 12b, wherein the pressure-limiting valve bore 22a extends from the damping region 28a to the stepped chamber 28d and is closed on the side facing the damping region 28a by a ball 56 pressed into the pressure-limiting valve bore 22a or a plug 57 pressed into the pressure-limiting valve bore 22a, wherein the pressure-limiting valve bore 22a is designed as a stepped bore, with a first portion 22.1, which has a larger diameter and points towards the damping region 28a, and a second portion 22.3, which has a smaller diameter and points towards the stepped chamber 28d, and with an annular step 22.2 formed between the first portion 22.1 and the second portion 22.3, and in that the above-mentioned spiral spring 52 of the pressure-limiting valve 22 is supported on the annular step 22.2 of the pressure-limiting valve bore 22a.

[0062] According to the first embodiment example of the invention (FIGS. 2 and 3), it is further provided that the outlet valve bore 37a and the pressure-limiting valve bore 22a intersect, in particular at right angles. In this example, the cut is made within the high-pressure region 29.

[0063] More precisely, the cut according to the first embodiment example of the invention is made such that the sealing seat part 37.2 is fixed in a pump-proof manner with a sealing seat part fixing portion 37.3 and that the counter plate 37.5 is fixed in a pump-proof manner with a counter plate fixing portion 37.6 and that the pressure-limiting valve bore 22a intersects the outlet valve bore 37a between the sealing seat part fixing portion 37.3 and the counter plate fixing portion 37.6.

[0064] In the example, it is provided that an imaginary central axis of the outlet valve bore 37a intersects an imaginary central axis of the pump piston 18, i.e. the longitudinal axis of the high-pressure fuel pump.

[0065] A second embodiment example of the invention is shown in FIG. 4 in part a) as a sectional view and in part b) as a top view of the semi-transparent pump body 12a. The second embodiment example differs from the first embodiment example in that it is not provided that the outlet valve bore 37a and the pressure-limiting valve bore 22a intersect. Instead, in the second embodiment example, it is provided that the pressure-limiting valve bore 22a is connected to the outlet port chamber 35a via a high-pressure connecting bore 29a located in the high-pressure region 29 and extending from the outlet port chamber 35a.

[0066] The outlet valve bore 37a and the high-pressure connection bore 29a are disposed at an angle different from 0?, in particular at an angle of at least 20?, relative to each other and in each case perpendicular to the longitudinal direction LA.

[0067] In particular, an imaginary central axis of the outlet valve bore 37a intersects an imaginary central axis of the pump piston 18.

[0068] A third embodiment example of the invention is shown in FIG. 5 in part a) as a sectional view and in part b) as a top view of the semi-transparent pump body 12a. The third embodiment example differs from the second embodiment example in that the outlet valve bore 37a and the high-pressure connection bore 29a are disposed parallel to each other.

[0069] In the example, these two bores 22a, 37a are disposed perpendicular to the longitudinal direction LA. An imaginary central axis of the outlet valve bore 37a does not or does not necessarily intersect an imaginary central axis of the pump piston 18.

[0070] A fourth embodiment example of the invention is designed according to the first secondary claim and is shown in a sectional view in FIG. 6. This is 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 delivery chamber 16 disposed in the pump housing, with a pump piston 18 which can be displaced in the pump housing 12 along a longitudinal direction LA, limiting the delivery chamber, having an inlet valve 14 disposed between the inlet 11 and the delivery chamber 16, which opens towards the delivery chamber 16, having an outlet valve 37 disposed between the delivery chamber 16 and the outlet 34, which opens away from the delivery chamber 16, having a high pressure region 29, which is fluidly extending between the outlet valve 20 and the outlet 34, having a low pressure region 28, which fluidly extends between the inlet 11 and the inlet valve 14, and having a pressure-limiting valve 22, fluidly connecting the high-pressure region 29 to the low-pressure region 28 and opening toward the low-pressure region 28, such that fuel drains from the high-pressure region 29 to the low-pressure region 28, if 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, wherein the pump piston 18 is formed as a stepped piston, having a first portion 18.1, facing towards the delivery chamber 16 and having a larger diameter, and having a second portion 18.2, having a smaller diameter and facing away from the delivery chamber 16, wherein a high-pressure seal 80 is disposed between the first portion 18.1 and the pump housing 12, in which the pump piston 18 can be displaced, and separating the delivery chamber 16 from the low-pressure region 28, wherein a low-pressure seal 78 is disposed between the second portion 18.2, and a seal carrier 60 fixed to the pump housing 12, separating the low-pressure region 28 from the space 100 outside the high-pressure fuel pump 10, wherein a stepped chamber 28d of the low-pressure region 28 is disposed between the seal carrier 60 and the pump housing 12, wherein the pressure-limiting valve 22 fluidly connects the high-pressure region 29 to the stepped chamber 28d of the low-pressure region and opens toward the stepped chamber 28d, such that fuel drains from the high-pressure region 29 into the stepped chamber 28d, if 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, wherein the outlet valve 37 is disposed in an outlet valve bore 37a of the pump housing 12 and has a movable valve element 37.1 and a sealing seat part 37.2 disposed upstream of the valve element 37.1, which is fixed in a pump-proof manner with a sealing seat part fixing portion 37.3, and on which a sealing seat 37.4 cooperating with the valve element 37.1 is formed, and a pump-proof counter plate 37.5 disposed downstream of the valve element 37.1, which is fixed in a pump-proof manner with a counter plate fixing portion 37.5 and which prevents the mobility of the valve element 37.1 in the downstream direction, wherein the pressure-limiting valve 37 is disposed in a pressure-limiting valve bore 37 in the pump housing 12, which extends in the longitudinal direction LA and, starting from the stepped chamber 28d, opens into the outlet valve bore 22a, namely between the sealing seat part fixing portion 37.3 and the counter plate fixing portion 37.6.

[0071] A fifth embodiment example of the invention is designed in accordance with the second secondary claim and is shown in FIG. 7 in part a) in a sectional view and in part b) by means of a top view of the pump body 12a shown semi-transparent. This is a 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, with a delivery chamber 16 disposed in the pump housing, with a pump piston 18 which can be displaced in the pump housing 12 along a longitudinal direction LA and which delimits the delivery chamber, with an inlet valve 14, which is disposed between the inlet 11 and the delivery chamber 16 and opens towards the delivery chamber 16, with an outlet valve 37, which is disposed between the delivery chamber 16 and the outlet 34 and 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, and with a pressure-limiting valve 22, which fluidically connects the high-pressure region 29 to the low-pressure region 28 and opens towards the low-pressure region 28, so that fuel flows out of 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, the pump piston 18 being designed as a stepped piston, with a first portion 18.1, which points towards the delivery chamber 16 and has a larger diameter, and with a second portion 18.2, which has a smaller diameter and faces away from the delivery chamber 16, a high-pressure seal 80 being disposed between the first portion 18.1 and the pump housing 12, in which the pump piston 18 is displaceable and which separates the delivery chamber 16 from the low-pressure region 28, a low-pressure seal 78 being disposed between the second portion 18.2 and a seal carrier 60 fixed to the pump housing 12, which seal separates the low-pressure region 28 from the space 100 outside the high-pressure fuel pump 10, wherein a stepped chamber 28d of the low-pressure region 28 is located between the seal carrier 60 and the pump housing 12, wherein the pressure-limiting valve 22 fluidically connects the high-pressure region 29 with the stepped chamber 28d of the low-pressure region and opens towards the stepped chamber 28d, so that fuel flows out of the high-pressure region 29 into the stepped chamber 28d, when the pressure difference between fuel in the high-pressure region 29 and fuel in the low-pressure region 28 exceeds an opening pressure, wherein the outlet valve 37 is disposed in an outlet valve bore 37a of the pump housing 12, wherein the pressure-limiting valve 22 is arranged in a pressure-limiting valve bore 22a in the pump housing 12, which extends in the longitudinal direction LA and, starting from the stepped chamber 28d, opens into a high-pressure connecting bore 29a in the pump housing 12, which is arranged in the high-pressure region 29 and which is oriented at an angle other than 0?, for example at an angle of 5? to 15?, to the outlet valve bore 37a, wherein in particular the outlet 34 is formed as an outlet port 35 fixed to the pump housing 12, wherein in particular an outlet port chamber 35a is formed between the pump housing 12 and the outlet port 35 and wherein in particular the outlet valve bore 37a and the high-pressure connection bore 29a both extend from the outlet port chamber 35a.