FUEL HIGH-PRESSURE PUMP

Description

State of the art

[0001] From the prior art, for example from EP 2 344 749 B1 of the applicant, a high-pressure fuel pump is already known, comprising an inlet for supplying fuel, an outlet for discharging compressed fuel, a pump housing, a pumping chamber arranged in the pump housing, a pump piston movable in the pump housing along a longitudinal direction and delimiting the pumping chamber, an inlet valve arranged between the inlet and the pumping chamber and opening towards the pumping chamber, an outlet valve arranged between the pumping chamber and the outlet and opening away from the pumping chamber, a high-pressure area extending fluidically between the outlet valve and the outlet, a low-pressure area extending fluidically between the inlet and the inlet valve, and a pressure relief valve that fluidly connects the high-pressure area to the low-pressure area and opens towards the low-pressure area.such that fuel flows from the high-pressure area to the low-pressure area when the pressure difference between fuel in the high-pressure area and fuel in the low-pressure area exceeds an opening pressure, is known.

[0002] According to the aforementioned state of the art, it is provided that an outlet of the pressure relief valve is connected to a receiving chamber belonging to the low-pressure area of ​​a pressure damper of the fuel high-pressure pump.

[0003] Another high-pressure fuel pump is known from US 2007 / 0286742 A1. Disclosure of the invention

[0004] The invention is based on the inventors' observation that the solution known from the prior art leads to a potentially excessive mechanical load on the pressure damper. Because pressure pulsations from the high-pressure area pass through the pressure relief valve into the receiving chamber and act upon the pressure damper, which is actually designed only for low pressure, wear and unwanted noise occur. Furthermore, the actual function of the pressure damper, which is to dampen pressure pulsations originating in the low-pressure area of ​​the high-pressure fuel pump, is impaired.

[0005] In order to minimize the mechanical stress and wear associated with the pressure limiting function of the high-pressure fuel pump, and also the noise generation, the invention provides that the pressure limiting valve fluidically connects the high-pressure area with an inlet valve area of ​​the low-pressure area and opens towards the inlet valve area, so that fuel flows from the high-pressure area into the inlet valve area when the pressure difference between fuel in the high-pressure area and fuel in the low-pressure area exceeds an opening pressure, wherein the inlet valve area of ​​the low-pressure area is geometrically located between the inlet valve and an electromagnetic actuator of the high-pressure fuel pump which acts on the inlet valve via a plunger.

[0006] The electromagnetic actuator of the high-pressure fuel pump can be a component comprising an actuator housing that is fixed to the pump housing, in particular by being screwed, pressed, or welded to the pump housing. The electromagnetic actuator can have a pump-mounted electrical coil and an electrical connection associated with it. For example, an armature that is displaceable according to the current applied to the coil and is mechanically coupled to a plunger can be provided. The plunger is thus displaceable, in particular by the electromagnetic actuator, to open or close the inlet valve, especially perpendicular to the longitudinal direction of the high-pressure fuel pump.

[0007] The electromagnetic actuator can, for example, be designed such that it only advances the plunger into a position opening the intake valve when the electrical coil is energized. Alternatively, the electromagnetic actuator can, for example, be designed such that it only allows the plunger to retract, so that the intake valve can close, when the electrical coil is energized.

[0008] According to the invention, the outlet valve is fixed in an outlet valve bore of the pump housing and the pressure relief valve is fixed in a pressure relief valve bore of the pump housing.

[0009] If the outlet valve bore and the pressure relief valve bore are geometrically parallel to each other, this has the advantage that machining, for example cutting, of the pump housing to produce the pressure relief valve bore and the outlet valve bore is made easier, since the machining can be carried out in the same direction and thus, for example, even with the same tool and / or simultaneously.

[0010] Secondly, this makes the installation of the high-pressure fuel pump easier, since the bores belonging to the pressure relief valve and the exhaust valve point in the same direction, and the pressure relief valve and the exhaust valve can therefore be installed in a simple way, for example with the same tool and / or simultaneously.

[0011] In a further development, it is provided that the outlet is designed as an outlet nozzle fixed to the pump housing. The outlet nozzle has, in particular, a tubular shape and can, for example, be welded or bolted to the pump housing and furthermore include means by which a high-pressure line can be tightly attached to it, for example, a thread or the like.

[0012] Furthermore, it may be provided that an outlet space is formed between the pump housing and the outlet nozzle. The outlet space can consist of, or encompass, the portion of the nozzle's interior facing the pump housing. The outlet space can also include a recess in the pump body covered by the outlet nozzle, and in particular, it can consist of these two sub-spaces. Alternatively, the outlet space can consist of the recess in the pump body covered by the outlet nozzle.

[0013] Further development may include the option of having both the outlet valve bore and the pressure relief valve bore originate from the outlet nozzle chamber. This reduces the number of parts comprising the high-pressure fuel pump and the number of sealing points required within the pump.

[0014] Alternatively, it can be provided that only the outlet valve bore extends from the outlet nozzle chamber, but not the pressure relief valve bore. This has the advantage that the cross-sectional area through which the fluid flows in the outlet nozzle chamber can be significantly reduced, and thus also the cross-section with which the outlet nozzle is attached to the pump body. This improves the reliability and pressure resistance with which the outlet nozzle can be attached to the pump housing, because the cross-sectional area with which the outlet nozzle is attached to the pump body is proportional to the force acting on the nozzle when high-pressure fuel is being pumped. The connection length along which the nozzle can be attached to the pump housing around its circumference, on the other hand, is only proportional to the square root of the cross-sectional area with which the outlet nozzle is attached to the pump body.The reduction in the cross-section with which the outlet nozzle is attached to the pump body, resulting from the measure that only the outlet valve bore extends from the outlet nozzle chamber, but not the pressure relief valve bore, thus increases the ratio of the connection length along which the nozzle can be attached to the pump housing around its circumference to the cross-section with which the outlet nozzle is attached to the pump body. This allows the outlet nozzle attachment to withstand higher pressures of the pumped fuel.

[0015] It can be further developed, for example, that the pressure relief valve bore is closed on its outlet side with a ball or a plug, with the outlet valve bore being connected to the pressure relief valve bore by a high-pressure connecting bore located in the high-pressure area. The fluidic communication between the outlet and the pressure relief valve then takes place solely within the pump housing via the high-pressure connecting bore.

[0016] At the same time, closing the pressure relief valve bore with a ball or a plug creates a simple and reliable sealing point.

[0017] According to the invention, the pressure limiting valve bore is connected to the inlet valve area by means of a low-pressure connecting bore located in the low-pressure area.

[0018] It may be designed so that the cross-section of the low-pressure connecting bore is smaller than the cross-section of the pressure-relieving valve bore. This allows the low-pressure connecting bore to act as a throttle, and pressure pulsations from the high-pressure area reach the inlet valve area only in a weakened form.

[0019] Additionally or alternatively, the low-pressure connection bore and the pressure relief valve bore may be angled relative to each other at an angle other than 0° in a projection along the longitudinal direction, and / or the low-pressure connection bore and the pressure relief valve bore may be angled relative to each other at an angle other than 0° in at least one projection perpendicular to the longitudinal direction. In these cases, more efficient use of the space available for internal contours within the pump housing or pump body is achieved.

[0020] The same effect is achieved by a further development in which the low-pressure connecting bore is angled in at least one projection perpendicular to the longitudinal direction at an angle other than 0° from the pressure limiting valve bore, such that the low-pressure connecting bore is directed towards the inlet valve with respect to the longitudinal direction and with respect to its direction from the pressure limiting valve bore to the inlet valve area.

[0021] Alternatively, the low-pressure connecting bore and the pressure relief valve bore can be designed to be coaxial. The two bores can then be created in a single drilling process, for example using a step drill.

[0022] Within the scope of the present invention, a bore (in particular, an outlet valve bore, a pressure relief valve bore, a low-pressure connecting bore, a high-pressure connecting bore, etc.) is understood to be, in particular, an internal contour of the pump housing or pump body that can be machined into the pump housing or pump body from the outside using a rotating twist drill. The bore thus has, in particular, axial symmetry, the axis of which corresponds to the axis of rotation of the twist drill. This axis of symmetry then indicates the direction in which the bore is oriented. The bore can, in principle, be a through bore through the pump housing or pump body, or a blind bore that terminates at a borehole base arranged in the pump housing or pump body.In the context of the present invention, the exit of a bore is the side of the bore that is first created by machining when the drill bit penetrates the pump housing or pump body. In the case of blind holes, this is always the side opposite the bottom of the bore. The opening of a bore is therefore the side of the bore opposite the exit if the bore encounters another internal contour of the pump housing or pump body there, or if it exits the pump housing or pump body. The bores of the present invention are, in particular, free of undercuts when viewed from their exit.

[0023] Within the scope of the present invention, the bore wall in a through bore is the inner contour represented by the through bore; in a blind bore, the bore wall is the part of the inner contour represented by the through bore that is not the bore bottom.

[0024] Within the scope of the present invention, the high-pressure area is understood to be the entire space that communicates directly with the outlet, in particular without any further intermediate valves, so that a uniform pressure is established in the high-pressure area, for example 500 bar during operation of the pump.

[0025] Within the scope of the present invention, the low-pressure area is understood to be the entire space that communicates directly with the inlet, in particular without any further intermediate valves, so that a uniform pressure is established in the low-pressure area, for example 5 bar during operation of the pump and with a low-pressure pump connected to the inlet.

[0026] In particular, the internal contours of the high-pressure fuel pump, through which fuel flows, ultimately consist of the low-pressure area, the pumping chamber, and the high-pressure area. These areas are separated from each other by the inlet valve, the outlet valve, and the pressure relief valve.

[0027] The fuel could be, for example, a fuel such as gasoline.

[0028] Where the invention refers to an angle other than 0°, this angle may be significantly different from 0°, for example, at least 2° or at least 5°. It may, for example, be an angle between 2° and 90°.

[0029] Exemplary embodiments of the invention are explained below with reference to the drawing. Figure 1 shows a simplified schematic representation of a fuel system for an internal combustion engine. Figure 2 shows a first embodiment of the invention. Figure 3 shows, in detail, an exemplary pressure relief valve as it appears in the embodiments according to Figure 2 or 4 can be used. Figure 4 shows a second embodiment of the invention.

[0030] Figure 1Figure 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-supply pump 6 and a low-pressure line 8 to a high-pressure fuel pump 10, designed as a piston pump, via an inlet port 20. An inlet valve 14 is fluidically located downstream of the inlet port 20. A low-pressure section 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 section 28 can be dampened by means of a pressure damper device. The inlet valve 14 can be forcibly opened by means of 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.

[0031] A pump piston 18 of the high-pressure fuel pump 10 can be moved up and down by means of a drive 36, in this case designed as a cam disk, along a longitudinal axis LA extending in the longitudinal direction, to which the pump piston 18 is axially symmetrical, which in the Figure 1 This is represented by a double arrow 40. Fluidically between the pumping chamber 16 and an outlet port 35 of the high-pressure fuel pump 10, an outlet valve 37 is arranged, which can open towards the outlet port 35 and a high-pressure accumulator 45 ("rail") located further downstream. Consequently, a high-pressure area 29 of the high-pressure fuel pump 10 extends fluidically between the outlet valve 37 and the outlet port 35.

[0032] The high-pressure section 29 and the low-pressure section 28 are directly connected via a pressure relief valve 22, which opens when a limit pressure is exceeded in the high-pressure section 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 towards the low-pressure section 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 The first embodiment of the invention shows a high-pressure fuel pump 10 in a sectional view.

[0034] The high-pressure fuel pump 10 has an inlet 11 designed as an inlet port 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 port 35. Without the interposition of valves, the outlet 34 communicates with the entire high-pressure section 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 pumping chamber 16 is also arranged, which is bounded by a pump piston 18 which can be displaced along a longitudinal direction LA.

[0037] The low-pressure area 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, include a filter bore in which a filter element is arranged that removes entrained solid particles above a minimum size from the fuel flowing through the filter bore.

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

[0040] The conveying chamber 16 is limited towards the low-pressure area 28 by an inlet valve 14, which opens towards the conveying 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 plunger 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 located between the inlet valve 14 and the actuator 30, an inlet valve section 28c of the low-pressure section 28 is formed in the pump housing. It communicates with the damping section 28a via the bore 28f visible in this cross-section.

[0043] The pumping chamber 16 is delimited towards the high-pressure area 29 by an outlet valve 37, which opens away from the pumping chamber 16 when a corresponding pressure differential is reached. 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 that interacts with a sealing seat 37.4, which is formed on a sealing seat part 37.2 that is fixed to the pump upstream of the valve element 37.1. 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 nozzle 35 and the pump housing 12 or the pump body 12a.

[0044] The pump piston 18 is designed as a stepped piston. It has a first section 18.1, facing the pumping chamber 16, with a larger diameter, and a second section 18.2, facing away from the pumping chamber, with a smaller diameter (relative to the diameter of the first section 18.1). A spacer is located between the first and second sections 18.1, 18.2. Figure 2 Vertical downward pointing ring step 18.3 formed.

[0045] A high-pressure seal 80 is arranged between the first section 18.1 and the pump housing 12, in which the pump piston 18 is slidable. The high-pressure seal 80 seals the pumping chamber 16 against the low-pressure area 28.

[0046] The high-pressure seal 80 can, for example, be a separate sealing ring, e.g., made of metal or plastic, as further explained in WO 19 015 862 A1 of the applicant. Alternatively, 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, as further explained in WO 06 069 819 A1 of the applicant.

[0047] A low-pressure seal 78 is arranged between the second section 18.2 and the seal carrier 60 mentioned above, separating the stage chamber 28d of the low-pressure area 28 from the chamber 100 located outside the high-pressure fuel pump 10. The pump piston 18 is slidable within the low-pressure seal 78.

[0048] The pump piston 18 is moved into the space provided by 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. Figure 2 Prestressed in the downward-pointing longitudinal direction LA.

[0049] The high-pressure fuel pump 10 according to the invention has a pressure relief valve 22 that fluidically connects the high-pressure area 29 with the low-pressure area 28 and opens towards the low-pressure area 28, so that fuel flows from the high-pressure area 29 into the low-pressure area 28 when the pressure difference between the fuel in the high-pressure area 29 and the fuel in the low-pressure area 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 described in more detail by way of example.

[0050] The pressure relief valve 22 is designed to fluidically connect the high-pressure area 29 with an inlet valve area 28c of the low-pressure area 28 and to open towards the inlet valve area 28c, so that fuel flows from the high-pressure area 29 into the inlet valve area 28c when the pressure difference between fuel in the high-pressure area 29 and fuel in the low-pressure area 28 exceeds an opening pressure, wherein the inlet valve area 28c of the low-pressure area 28 is geometrically located between the inlet valve 14 and an electromagnetic actuator 30 of the high-pressure fuel pump 10, which acts on the inlet valve 14 via a plunger 31.

[0051] The extent of the intake valve area 28c is in the Figure 2This is exemplified by a rectangle bounded by a dashed line. It could, for instance, be a cylindrical space (e.g., based on a vertical circular cylinder) whose bases are oriented parallel to the longitudinal direction LA and are only as large as necessary to allow a projection perpendicular to the longitudinal axis (e.g., in the Figure 2 horizontal direction), in which these base surfaces enclose the projection of the inlet valve 14 and the projection of the connection between pump housing 12 and actuator housing 30a. The height of the cylindrical space can be determined by the distance between the inlet valve 14 and the actuator 30 in the direction of this projection.

[0052] In the first embodiment, the pressure relief valve 22 is fixed in a pressure relief valve bore 22a of the pump housing 12, which is geometrically parallel to the outlet valve bore 37a.

[0053] According to the first embodiment, 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, from which both the outlet valve bore 37a and the pressure limiting valve bore 22a extend.

[0054] 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 chamber 35a arranged between the pump housing 12 and the outlet nozzle 35.

[0055] The (outer) diameter with which the outlet nozzle 35 is fixed to the pump housing in this arrangement is relatively large, for example at least as large as the sum of the diameter of the pressure relief valve bore 22a and the diameter of the outlet valve bore 37a, in particular even at least as large as 1.2 times this sum.

[0056] Furthermore, the pressure relief valve bore 22a is provided to be connected to the inlet valve area 28c by a low-pressure connecting bore 28b located in the low-pressure area 28. In this example, the cross-section of the low-pressure connecting bore 28b is smaller than the cross-section of the pressure relief valve bore 22a.

[0057] The cross-section of the pressure relief valve bore 22a can be smaller than the cross-section of the outlet valve bore 37a.

[0058] It may be provided that the low-pressure connecting bore 28b and the pressure-limiting valve bore 22a are angled away from each other in a projection along the longitudinal direction LA at an angle other than 0°, for example at least 20°.

[0059] It may be provided that the low-pressure connecting bore 28b and the pressure-limiting valve bore 22a are angled away from each other in at least one projection perpendicular to the longitudinal direction LA at an angle other than 0°, for example at least 20°.

[0060] In this example, this can be done by angled the low-pressure connecting bore 28b in at least one projection perpendicular to the longitudinal direction LA at an angle other than 0° from the pressure limiting valve bore 22a, such that the low-pressure connecting bore 28b is directed towards the inlet valve 14 with respect to the longitudinal direction LA and with respect to its direction from the pressure limiting valve bore 22a to the inlet valve area 28c.

[0061] Alternatively, as in the Figure 2As shown, the low-pressure connecting bore 28b and the pressure-relieving valve bore 22a are coaxial with each other. The entirety of the two bores 22a, 28b can then also be considered a stepped bore, the larger diameter portion of which is formed by the pressure-relieving valve bore 22a and the smaller diameter portion of which is formed by the low-pressure connecting bore 28b.

[0062] The pressure relief valve 22 from the Figure 2 (it could also be the one in the Figure 4 The pressure relief valve 22 shown is in the Figure 3The diagram is enlarged and shown as an example. It has a valve seat body 38 pressed into the pressure relief valve bore 22a or into a housing of the pressure relief valve 22, on which a conical valve seat 42 is formed. The pressure relief 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 retaining element 46, and the retaining element 46 is pressed in the closing direction by a coil spring 52. The coil spring 52 is supported on a housing of the pressure relief valve 22 or directly on the pump housing 12. The coil spring 52 rests against a radially outer region 464 of the retaining element 46. A radially inner region 465 of the retaining element 46 is received by the coil spring 52.The opening pressure of the pressure limiting valve 22 is defined by the stiffness of the spiral spring 52 and by the area effective at the pressure limiting valve, 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.

[0063] Referring once again to the first example and the coaxial arrangement of low-pressure connecting bore 28b and pressure-relieving valve bore 22a (see Figure 2 ), it can be provided that the spiral spring 52 is supported on an annular step 22.2 formed between the low-pressure connecting bore 28b and the pressure limiting valve bore 22a, pointing towards the pressure limiting valve bore 22a.

[0064] A second embodiment is described in the Figure 4The embodiment is shown in part in a sectional view. It differs from the first embodiment in that only the outlet valve bore 37a, but not the pressure relief valve bore 22a, extends from the outlet nozzle chamber 35a. Instead, in this embodiment, the pressure relief valve bore 22a is closed on the side of its outlet 22aa with a ball 56 or a plug 57, which is pressed into the pressure relief valve bore 22a, and the outlet valve bore 37a is connected to the pressure relief valve bore 22a by a high-pressure connecting bore 29a located in the high-pressure area 29.

[0065] It may be provided that the high-pressure connecting bore 29a originates from the damping area 28a and is closed on its outlet side 29aa with a ball 56 pressed into it or a plug 57 pressed into it.

[0066] The outlet nozzle 34 can be made smaller than in the first embodiment; for example, the (outer) diameter with which the outlet nozzle 35 is fixed to the pump housing 12 in this arrangement can be smaller than the sum of the diameter of the pressure relief valve bore 22a and the diameter of the outlet valve bore 37a, and in particular even smaller than 0.9 times this sum. The robustness of the connection of the outlet nozzle 35 to the pump housing 12 is increased in this way, because while the hydraulic forces acting on the outlet nozzle 35 are proportional to the cross-sectional area it covers, the connection length with which the outlet nozzle 35 is fixed to the pump housing 12 is only proportional to the circumference of the cross-sectional area it covers, i.e., proportional to the square root of the cross-sectional area it covers.

[0067] What has been said in the first embodiment with regard to the pressure limiting valve bore 22a, the outlet valve bore 37a and the low-pressure connecting bore 28b and the relations between these bores is also valid in this second embodiment.

[0068] The high-pressure connecting bore 29a can have a cross-section that is smaller than the respective cross-sections of the pressure-limiting valve bore 22a, the outlet valve bore 37a and the low-pressure connecting bore 28b, for example, each at most half the size.

[0069] Alternatively, the high-pressure connecting bore 29a can have a cross-section that is smaller than the respective cross-sections of the pressure-limiting valve bore 22a and the outlet valve bore 37a but larger than that of the low-pressure connecting bore 28b.

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 dispensing compressed fuel, with a pump housing (12), a delivery chamber (16) arranged in the pump housing (12), with a pump piston (18) which is movable in the pump housing (12) along a longitudinal direction (LA) and delimits the delivery chamber (16), with an inlet valve (14) which is arranged between the inlet (11) and the delivery chamber (16) and opens towards the delivery chamber (16), with an outlet valve (37) which is arranged 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, wherein the pressure-limiting valve (22) fluidically connects the high-pressure region (29) to an inlet valve region (28c) of the low-pressure region (28) and opens towards the inlet valve region (28c), so that fuel flows out of the high-pressure region (29) into the inlet valve region (28c) 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 inlet valve region (28c) of the low-pressure region (28) is located geometrically between the inlet valve (14) and an electromagnetic actuator (30) of the high-pressure fuel pump (10), the actuator acting upon the inlet valve (14) via a plunger (31), wherein the outlet valve (37) is fixed in an outlet valve bore (37a) of the pump housing (12), and wherein the pressure-limiting valve (22) is fixed in a pressure-limiting valve bore (22a) of the pump housing (12), wherein the pressure-limiting valve bore (22a) is connected to the inlet valve region (28c) by a low-pressure connection bore (28b) lying in the low-pressure region (28), characterized in that the low-pressure connection bore (28b) extends from the pressure-limiting valve bore (22a) as far as the inlet valve region (28c).

2. High-pressure fuel pump (10) according to Claim 1, wherein the electromagnetic actuator (30) has an actuator housing (30a), which is fixed to the pump housing (12), in particular is screwed, pressed or welded to the pump housing (12), and has an electric coil (30b) and an electrical connection (30c) connected to the latter, and can move the plunger (31) perpendicular to the longitudinal direction (LA) in order to open or close the inlet valve (14).

3. High-pressure fuel pump (10) according to Claim 1 or 2, wherein the outlet valve bore (37a) and the pressure-limiting valve bore (22a) are oriented geometrically parallel to each other.

4. High-pressure fuel pump (10) according to Claim 1, 2 or 3, wherein the outlet (34) is designed as an outlet connector (35) fixed to the pump housing (12), and an outlet connector space (35a) is formed between the pump housing (12) and the outlet connector (35), wherein the outlet valve bore (37a) and the pressure-limiting valve bore (22a) both start from the outlet connector space (35a).

5. High-pressure fuel pump (10) according to one of Claims 1 to 3, wherein the outlet (34) is designed as an outlet connector (35) fixed to the pump housing, and an outlet connector space (35a) is formed between the pump housing (12) and the outlet connector (35), wherein the outlet valve bore (37a) starts from the outlet connector space (35a) and the pressure-limiting valve bore (22a) does not start from the outlet connector space (35a), wherein the pressure-limiting valve bore (22a) is closed, on the side of its output (22aa), by a ball (56) or a plug (57), and wherein the outlet valve bore (37a) is connected to the pressure-limiting valve bore (22a) by a high-pressure connection bore (29a) lying in the high-pressure region (29).

6. High-pressure fuel pump (10) according to Claim 5, wherein the pump housing (12) comprises a pump body (12a) and a pump cover (12b) which are connected to each other, wherein a damping region (28a) belonging to the low-pressure region (28) is delimited by the pump body (12a) and the pump cover (12b), in which damping region at least one diaphragm damper (55) is arranged, wherein the high-pressure connection bore (29a) starts from the damping region (28a) and is closed on its output side (29aa) by a ball (56) or a plug (57).

7. High-pressure fuel pump (10) according to one of Claims 1 to 6, wherein the cross section of the low-pressure connection bore (28b) is smaller than the cross section of the pressure-limiting valve bore (22a).

8. High-pressure fuel pump (10) according to one of Claims 1 to 7, wherein the low-pressure connection bore (28b) and the pressure-limiting valve bore (22a) are angled from each other at an angle different from 0° in a projection along the longitudinal direction (LA).

9. High-pressure fuel pump (10) according to one of Claims one of Claims 1 to 8, wherein the low-pressure connection bore (28b) and the pressure-limiting valve bore (22a) are angled from each other at an angle different from 0° in at least one projection perpendicular to the longitudinal direction (LA).

10. High-pressure fuel pump (10) according to Claim 9, wherein the low-pressure connection bore (28b) in the at least one projection perpendicular to the longitudinal direction (LA) is angled from the pressure-limiting valve bore (22a) at an angle different from 0° in such a way that the low-pressure connection bore (28b) is oriented towards the inlet valve (14) in respect of the longitudinal direction (LA) and in respect of its direction facing from the pressure-limiting valve bore (22a) to the inlet valve region (28c).

11. High-pressure fuel pump (10) according to one of Claims 1 to 7, wherein the low-pressure connection bore (28b) and the pressure-limiting valve bore (22a) are coaxial to each other.

12. High-pressure fuel pump (10) according to one of Claims 1 to 11, wherein the pressure-limiting valve (22) has a valve-seat body (38) which is pressed into the pressure-limiting valve bore (22a) or into a housing of the pressure-limiting valve (22) and on which a conical valve seat (42) is formed, wherein the pressure-limiting valve (22) has a valve element (44) which has the shape of a ball and which comes into sealing contact with the valve seat (42), wherein the valve element (44) is pressed in the closing direction by a holding element (46), wherein the holding element (46) is pressed in the closing direction by a spiral spring (52), wherein the spiral spring (52) is supported on a housing of the pressure-limiting valve (22) or on the pump housing (12), wherein the spiral spring (52) bears on a radially outer region (464) of the holding element (46), wherein the spiral spring (46) receives a radially inner region (465) of the holding element (46).