High pressure fuel pump

Abstract

A high pressure fuel pump (10) comprising an inlet (11) formed as an inlet piece (20) fixed to a pump casing (12) and a pressure limiting valve (22) fluidly connecting a high pressure region (29) to a low pressure region (28) and opening towards the low pressure region (28), wherein the pressure limiting valve (22) opens towards an inlet piece chamber (28e).

Description

[Technical field]

[0001] Background technology Based on the prior art, for example on the basis of the applicant's EP 2 344 749, a high-pressure fuel pump is disclosed, which comprises an inlet for supplying fuel, an outlet for discharging compressed fuel, a pump casing, a pumping chamber arranged in the pump casing, a pump piston defining said pumping chamber and longitudinally slidable within the pump casing, 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 region extending fluidically between the outlet valve and the outlet, a high-pressure region extending fluidically between the inlet and the inlet valve, A high-pressure fuel pump is already known which has a low-pressure region located in the high-pressure region and a pressure limiting valve which fluidly connects the high-pressure region to the low-pressure region and opens towards the low-pressure region when the pressure difference between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds an opening pressure, the outlet valve being arranged in an outlet valve bore of the pump casing, the pressure limiting valve being arranged in a pressure limiting valve bore of the pump casing, the inlet being configured as an inlet stub fixed to the pump casing, and an inlet stub chamber of the low-pressure region being formed between the pump casing and the inlet stub.

[0002] According to the above-mentioned prior art, the outlet of the pressure limiting valve is connected to a receiving chamber of a pressure damper of the high-pressure fuel pump, which belongs to the low-pressure region.

[0003] Disclosure of the Invention The invention is based on the inventor's observation that the solutions known from the prior art lead to potentially excessive mechanical loading of the pressure damper, which is caused by pressure pulsations passing from the high pressure region through the pressure limiting valve into the receiving region, where they load the pressure damper, which was originally designed only for low pressure, leading to wear and the formation of undesirable sound waves in the pressure damper, and furthermore impairing the intended function of the pressure damper, which is to damp pressure pulsations whose source is in the low pressure region of the high pressure fuel pump.

[0004] Therefore, in order to minimize the mechanical load or wear associated with the pressure limiting function of the high-pressure fuel pump, and also the formation of acoustic waves, the present invention provides that when the pressure difference between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds the opening pressure, the pressure limiting valve fluidly connects the high-pressure region to the inlet pipe chamber of the low-pressure region and opens toward the inlet pipe chamber to allow fuel to flow from the high-pressure region to the inlet pipe chamber.

[0005] The inlet stub chamber may consist of or include, on the one hand, the part of the inner chamber of the stub facing the pump casing. Alternatively, the inlet stub chamber may consist of or include a recess in the pump body that is covered by the inlet stub. Furthermore, the inlet stub chamber may consist of or include both of these partial chambers.

[0006] In particular, it may be provided that the pressure limiting valve orifice and the outlet valve orifice are oriented geometrically parallel to one another.

[0007] On the one hand, this facilitates the machining, for example cutting, of the pump housing for the production of the pressure limiting valve orifice and the outlet valve orifice, since this can be carried out geometrically parallel to one another and thus, for example, with the same tool and / or even, for example, simultaneously.

[0008] On the other hand, this simplifies the assembly of the high-pressure fuel pump, since the bores associated with the pressure relief valve and the bores associated with the outlet valve are arranged parallel to one another, so that the pressure relief valve and the outlet valve can be mounted simply, for example with the same tool and / or for example simultaneously.

[0009] In a further embodiment, the outlet is configured as an outlet fitting which is fixed to the pump casing, which in particular has a tubular basic shape and can be welded or screwed to the pump casing, for example, and furthermore the outlet fitting itself can have means for tightly attaching the high-pressure line to it, for example a thread or the like.

[0010] It may further be provided that an outlet stub chamber is formed between the pump casing and the outlet stub. The outlet stub chamber may consist, on the one hand, of the part of the inner chamber of the stub facing the pump casing or may include this part. The outlet stub chamber may additionally include a recess in the pump body covered by the outlet stub, in particular it may consist of both of these partial chambers. Alternatively, the outlet stub chamber may consist of a recess in the pump body covered by the outlet stub.

[0011] In a further embodiment, it can be provided that both the outlet valve hole and the pressure limiting valve hole start from the outlet pipe chamber, which reduces the number of components that make up the high-pressure fuel pump and the number of sealing points required in the high-pressure fuel pump.

[0012] In a further configuration of the invention, it can be provided that the pressure limiting valve bore is connected to the inlet pipe piece chamber by a low pressure connection bore located in the low pressure region, so that the space provided for the pressure-limited fluid connection can be more optimally utilized.

[0013] The pressure limiting valve bore and the low-pressure connection bore can, for example, both be located in one plane, in particular perpendicular to the longitudinal direction, which facilitates the machining, for example cutting, of the pump housing for the production of the pressure limiting valve bore and the low-pressure connection bore, since this can be done in the same plane and thus, for example, with the same tool and / or even, for example, simultaneously.

[0014] The pump housing has a pump body and a pump cover connected to each other, which together define a damping area associated with the low-pressure area, in which at least one diaphragm damper is arranged, and the pump body is provided with a filter hole connecting the inlet section chamber to the damping chamber, in which a filter element is arranged through which the fuel flows from the inlet section chamber to the damping chamber, where it is possible for the low-pressure connection hole and the filter hole to intersect, so that in addition to the conventional function of directing the filtered fuel from the inlet section chamber to the damping chamber, the filter hole can also fulfill the further function of directing the amount of fuel controlled by the pressure limiting valve to the inlet section area. In a manner of speaking, a double function of the filter hole is provided.

[0015] Alternatively, it is also possible for only the outlet valve orifice to start from the outlet stub chamber, and for the pressure relief valve orifice not to start from the outlet stub chamber. This has the advantage that the through-flow cross section of the outlet stub chamber and therefore also the cross section of the attachment of the outlet stub to the pump body can be reduced. This improves the reliability or pressure resistance with which the outlet stub can be attached to the pump casing, since the cross section of the attachment of the outlet stub to the pump body is proportional to the force acting on the stub when fuel under high pressure is pumped through it. In contrast, the joint length over which the stub can be attached to the pump casing along its circumference is merely proportional to the square root of the cross section of the attachment of the outlet stub to the pump body. The reduction in the cross section of the outlet stub to the pump body, which is achieved by the fact that only the outlet valve hole starts from the outlet stub chamber and not the pressure limiting valve hole, increases the ratio of the joint length over which the stub can be attached to the pump casing along its circumference to the cross section of the outlet stub to the pump body, and the attachment of the outlet stub can therefore withstand a higher pressure of the pumped fuel.

[0016] For example, in a further configuration, it may be provided that the pressure limiting valve hole is closed at its origin by a ball or a plug, and the outlet valve hole is connected to the pressure limiting valve hole by a high-pressure connection hole located in the high-pressure region. In this case, the fluid communication between the outlet and the pressure limiting valve is only achieved by the high-pressure connection hole inside the pump casing. At the same time, a simple and reliable sealing point is realized by closing the pressure limiting valve hole by a ball or a plug.

[0017] For example, in a further embodiment, it may be provided that the pump housing has a pump body and a pump cover connected to one another, which together define a damping area associated with the low-pressure area, in which at least one diaphragm damper is arranged, and the high-pressure connection bore starts from the damping area and is closed at its start side by a ball or a plug, which allows a relatively short longitudinal extent of the high-pressure connection bore and also a simple and reliable sealing point.

[0018] In addition, in a further configuration, it can be provided that the pressure limiting valve hole is connected to the inlet pipe piece chamber by a low-pressure connection hole located in the low-pressure region, so that in this case too the space provided for the pressure-limited fluid connection can be more optimally utilized.

[0019] It is furthermore provided that both the pressure limiting valve bore and the low-pressure connection bore lie in one plane perpendicular to the longitudinal direction, with the result that the machining, e.g. cutting, of the pump housing for the production of the pressure limiting valve bore and the low-pressure connection bore is easier, since this can be carried out in the same plane and thus, e.g. with the same tool and / or even, e.g. simultaneously.

[0020] In addition, in a further embodiment, the pump body is provided with a filter bore connecting the inlet section chamber to the damping chamber, in which a filter element is arranged through which the fuel flows from the inlet section chamber to the damping chamber, the low-pressure connection bore and the filter bore can intersect, as a result of which the combination of features also has the advantage that the filter bore can fulfill a dual function, as already mentioned above.

[0021] In particular, it is provided that the outlet valve orifice and the pressure limiting valve orifice are oriented at a non-zero angle to one another, in particular at a right angle, which has the advantage that the available construction space can be well utilized.

[0022] In addition, in a further embodiment, it can be provided that the pump housing has a pump body and a pump cover connected to each other, which together define a damping region associated with the low-pressure region, in which at least one diaphragm damper is arranged, the pressure-limiting valve orifice is a blind hole starting from the damping region, from which a low-pressure connection located in the low-pressure region and opening into the inlet pipe chamber and a high-pressure connection located in the high-pressure region and opening into the outlet pipe chamber, and the pressure-limiting valve orifice is closed at its starting side by a ball or a plug. This measure results in the advantages already described.

[0023] In addition to this, in a further configuration the low pressure connection bore and the high pressure connection bore can also be oriented parallel to one another, which has the advantage that they can be provided, for example, simply and efficiently by machining the pump casing, for example with the same tool and / or for example simultaneously.

[0024] Alternatively, it may be provided that the low-pressure connection hole and the high-pressure connection hole are oriented at a non-0° angle to one another, in particular at a right angle, in which case the available construction space can be optimally utilized.

[0025] In the context of the present invention, holes (especially outlet valve holes, pressure limiting valve holes, low-pressure connection holes, high-pressure connection holes, etc.) are understood to mean the inner contour of the pump casing or pump body, which can be machined from the outside into the pump casing or pump body by cutting, in particular with a rotating spiral drill. The holes therefore have in particular axial symmetry, the axis of symmetry of which corresponds to the axis of rotation of the spiral drill. This axis of symmetry defines in this case the direction in which the holes are oriented. In this case, the holes can essentially be through-holes that pass through the pump casing or pump body, or blind holes that end in a hole bottom arranged in the pump casing or pump body. The start of the hole, in the context of the present invention, is the side of the hole that is first machined when the drill penetrates into the pump casing or pump body. In the case of a blind hole, the start of the hole is always on the side opposite the hole bottom. Thus, where the hole then leads to another inner contour of the pump casing or pump body or where it exits from the pump casing or pump body, the opening of the hole is on the opposite side to the hole's starting point. The hole of the invention in particular does not have an undercut when viewed from its starting point.

[0026] Within the scope of the present invention, in the case of a through hole, the hole wall is the inner contour formed by the through hole; in the case of a blind hole, the hole wall is that part of the inner contour formed by the through hole which is not the hole bottom.

[0027] In the context of the present invention, the high pressure area means all the spaces which are simply connected to the outlet, without any intervening separate valve, so that in the high pressure area a uniform pressure of, for example, 500 bar occurs during pump operation.

[0028] In the context of the present invention, the low pressure area means all the spaces which are simply connected to the inlet without any further intervening valve, so that in the low pressure area, during pump operation, a uniform pressure of, for example, 5 bar occurs with the low pressure pump connected to the inlet.

[0029] In particular, the inner contour of the high-pressure fuel pump, through which the fuel flows, ultimately consists of a low-pressure region, a pumping chamber and a high-pressure region, which are separated from one another by an inlet valve, an outlet valve and a pressure limiting valve.

[0030] The fuel may be, for example, a fuel such as gasoline.

[0031] In the scope of the present invention, when adjusted to an angle other than 0°, this angle may be an angle that is clearly different from 0°, i.e. for example an angle of at least 2° or at least 5°, for example an angle between 2° and 90°. [Brief description of the drawings]

[0032] [Figure 1] 1 is a simplified schematic diagram of a fuel system for an internal combustion engine. [Figure 2a] FIG. 1 illustrates a first embodiment of the present invention. [Figure 2b] FIG. 1 illustrates a first embodiment of the present invention. [Diagram 3] FIG. 13 is a detailed diagram illustrating a pressure limiting valve as may be used in an embodiment. [Figure 4] FIG. 13 illustrates a second embodiment of the present invention. [Figure 5a] FIG. 13 illustrates a third embodiment of the present invention. [Figure 5b] FIG. 13 illustrates a third embodiment of the present invention. [Figure 5c] FIG. 13 illustrates a third embodiment of the present invention. [Figure 6a] FIG. 13 is a diagram showing a fourth embodiment of the present invention. [Figure 6b] FIG. 13 is a diagram showing a fourth embodiment of the present invention. [Figure 6c] FIG. 13 is a diagram showing a fourth embodiment of the present invention. [Figure 7a] FIG. 13 is a diagram showing a fifth embodiment of the present invention. [Figure 7b] FIG. 13 is a diagram showing a fifth embodiment of the present invention. [Figure 7c]FIG. 13 is a diagram showing a fifth embodiment of the present invention. [Figure 8] FIG. 13 is a diagram showing a sixth embodiment of the present invention.

[0033] FIG. 1 shows a simplified schematic diagram of a fuel system 1 for an internal combustion engine, the rest of which is not shown. During operation of the fuel system 1, fuel is fed from a fuel tank 2 via a suction line 4, via a feed pump 6 and a low-pressure line 8 to an inlet end 20 of a high-pressure fuel pump 10, which is configured as a piston pump. An inlet valve 14 is arranged hydraulically downstream of the inlet end 20. A low-pressure area 28 of the high-pressure fuel pump 10 is located hydraulically between the inlet end 20 and the inlet valve 14. Downstream of the inlet valve 14 is the delivery chamber 16 of the high-pressure fuel pump 10. Pressure pulsations in the low-pressure area 28 can be damped by a pressure damping device. The inlet valve 14 can be forced open via an actuating device, which in this case is configured as an electromagnetic actuator 30. The actuating device and thus the inlet valve 14 can be controlled via a control unit 32.

[0034] The pump piston 18 of the high-pressure fuel pump 10 can be moved up and down along a longitudinal axis extending in the longitudinal direction LA and forming the axis of symmetry of the pump piston 18 by a drive 36 formed in this case as a cam disk, as indicated by a double-headed arrow 40 in Fig. 1. Between the pumping chamber 16 and the outlet end 35 of the high-pressure fuel pump 10, an outlet valve 37 is arranged fluidically, which can be opened towards the outlet end 35 and towards a high-pressure accumulator 45 ("rail") situated further downstream. The high-pressure region 29 of the high-pressure fuel pump 10 therefore extends fluidically between the outlet valve 37 and the outlet end 35.

[0035] The high pressure region 29 and the low pressure region 28 are directly connected to one another via a pressure limiting valve 22 which opens if a threshold pressure in the high pressure region 29 of the high pressure fuel pump 10 or in a high pressure accumulator 45 which communicates with the high pressure region is exceeded. The pressure limiting valve 22 is configured 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 which can be generated in the high pressure accumulator 45 by the high pressure fuel pump 10 is limited.

[0036] In FIG. 2, a high-pressure fuel pump 10 according to a first embodiment of the present invention is shown in cross section along the plane indicated as line aa in FIG. 2b, and in FIG. 2b, in cross section along the plane indicated as line bb in FIG. 2a.

[0037] The high-pressure fuel pump 10 has an inlet 11 which is configured as an inlet pipe 20. The inlet 11 communicates with the entire low-pressure region 28 of the high-pressure fuel pump 10 without the aid of an intervening valve.

[0038] The high-pressure fuel pump 10 has an outlet 34 which is configured as an outlet pipe 35. The outlet 34 communicates with the entire high-pressure region 29 of the high-pressure fuel pump 10 without the need for an intervening valve.

[0039] The outlet nozzle 35 and the inlet nozzle 20 are fixed to the pump casing 12, in which the pumping chamber 16 is also arranged, which is defined by a pump piston 18 which is slidable along the longitudinal direction LA.

[0040] The low pressure region 28 includes a damping chamber 28a which is connected to the inlet 11 via a fluid connection, the damping chamber being formed between the pump body 12a of the pump casing 12 and the pump cover 12b of the pump casing 12. A diaphragm damper 55 is arranged in the damping chamber 28a, which may have the shape of a flattened, compressible can formed by two metal diaphragms.

[0041] The fluid connection between the inlet 11 and the damping chamber 28a may, for example, have a filter hole in which a filter element is arranged that removes entrained solid particles above a minimum size from the fuel flowing through the filter hole.

[0042] In Fig. 2a, a seal support 60 is attached to the lower section of the pump body 12a, and a stepped chamber 28d is formed between the pump body 12a and the seal support 60. The stepped chamber 28d communicates with the damping chamber 28a through the pump body 12a via a stepped chamber hole 28g, which can be seen in Fig. 2b, and is therefore part of the low pressure region 28.

[0043] The pumping chamber 16 is delimited from a low-pressure region 28 by an inlet valve 14 which opens into the pumping chamber 16 under an appropriate pressure difference.

[0044] To control the pumping rate of the high-pressure fuel pump 10, the inlet valve 14 can be forced open by a plunger 31 driven by an actuator 30. For this purpose, the actuator 30 has an actuator casing 30a fixed to the pump casing 12, in which an electromagnetic coil 30b is arranged, which can be supplied with electricity via an electrical terminal 30c of the high-pressure fuel pump 10 that is accessible from the outside.

[0045] In the pump casing 12, geometrically between the inlet valve 14 and the actuator 30, an inlet valve area 28c of the low pressure area 28 is formed. The inlet valve area communicates with the damping area 28a via a hole 28f.

[0046] The pumping chamber 16 is delimited by an outlet valve 37 which opens away from the pumping chamber 16 with respect to the high pressure region 29 under a corresponding pressure difference. In this example, the outlet valve is arranged in an outlet valve bore 37a in the pump casing 12 or pump body 12a. The outlet valve has a movable valve element 37.1 which cooperates with a sealing seat 37.4 formed in a sealing seat 37.2 arranged on the pump stationary upstream of the valve element 37.1. The mobility of the valve element 37.1 is limited in the downstream direction via a counter plate 37.5 arranged on the pump stationary. The outlet valve bore 37a starts from an outlet stub chamber 35a which is located between the outlet stub 35 and the pump casing 12 or pump body 12a.

[0047] The pump piston 18 is configured as a stepped piston. It has a first section 18.1 with a relatively large 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. Between the first section 18.1 and the second section 18.2, a ring-shaped step 18.3 is formed which is oriented vertically downwards in FIG. 2a.

[0048] A high-pressure seal 80 is arranged between the first section 18.1 and the pump casing 12, in which the pump piston 18 can slide. The high-pressure seal 80 seals and separates the pumping chamber 16 from the low-pressure region 28.

[0049] The high-pressure seal 80 may for example be a separate sealing ring, for example made of metal or plastic, as for example described in detail in the applicant's WO 19015862. On the other hand, the high-pressure seal 80 may be a narrow gap extending over a certain length between the pump piston 18 and a bush or between the pump piston 18 and the pump casing 12, as for example described in detail in the applicant's WO 06069819.

[0050] Between the second section 18.2 and the already mentioned seal carrier 60, a low pressure seal 78 is arranged which separates the stepped chamber 28d of the low pressure region 28 from the space 100 located outside the high pressure fuel pump 10. The pump piston 18 is able to slide within the low pressure seal 78.

[0051] Via a spring retainer 19.1 fixed to the pump piston 18 and a pump spring 19.2 clamped between the spring retainer 19.1 and the seal support 60, the pump piston 18 is preloaded in a longitudinal direction LA, which is downwards in FIG. 2a.

[0052] The high pressure fuel pump 10 according to the present invention has a pressure limiting valve 22 that fluidly connects the high pressure region 29 to the low pressure region 28 and opens toward the low pressure region 28 to allow fuel to flow from the high pressure region 29 to 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 limiting valve 22 in the high pressure fuel pump 10 according to the present invention will be further exemplarily described below.

[0053] In this case, for example, the pressure limiting valve 22 is arranged in a pressure limiting valve bore 22a of the pump casing 12, the inlet 11 is formed as an inlet slit 20 fixed to the pump casing 12, and an inlet slit chamber 28e of the low pressure region 28 is formed between the pump casing 12 and the inlet slit 20, and when the pressure difference between the fuel in the high pressure region 29 and the fuel in the low pressure region 28 exceeds the opening pressure, the pressure limiting valve 22 fluidly connects the high pressure region 29 to the inlet slit chamber 28e of the low pressure region 28 and opens towards the inlet slit chamber 28e, allowing fuel to flow out from the high pressure region 29 to the inlet slit chamber 28e.

[0054] For example, the pressure limiting valve bore 22a is connected to the inlet pipe section chamber 28e by a low pressure connection bore 28b located in the low pressure region 28.

[0055] In the first exemplary embodiment according to FIG. 2, the outlet valve bore 37a and the pressure limiting valve bore 22a are oriented geometrically parallel to one another.

[0056] In the view according to FIG. 2a, the outlet valve hole 37a and the pressure limiting valve hole 22a are arranged in the drawing plane, i.e. the outlet valve hole 37a is arranged on the side of the pressure limiting valve hole 22a facing away from the damping region 28a.

[0057] In this case, it is further assumed, for example, that the pressure limiting valve hole 22a as well as the outlet valve hole 37a originates from the outlet pipe section chamber 35a and is connected to the inlet pipe section chamber 28e by a low-pressure connection hole 28b located in the low-pressure region 28 and oriented perpendicular to the longitudinal direction LA. The low-pressure connection hole 28b can, for example, be perpendicular to the longitudinal axis of the high-pressure fuel pump 10 and / or perpendicular to the axis of symmetry of the pump piston 18 and / or the diaphragm damper 55.

[0058] The outlet stub 35 extends, in particular transversely to the flow direction, beyond the outlet of the pressure limiting valve bore 22a and beyond the outlet of the outlet valve bore 37a, so that the pressure limiting valve bore 22a and the outlet valve bore 37a are connected to each other via the outlet stub chamber 35a which is arranged between the pump casing 12 and the outlet stub 35.

[0059] In such an arrangement, the (outer) diameter with which the outlet piece 35 is fixed to the pump casing is in this case relatively large, for example at least greater than the sum of the diameter of the pressure limiting valve hole 22a and the diameter of the outlet valve hole 37a, in particular even at least 1.2 times larger than this sum.

[0060] The cross-section of the pressure limiting valve hole 22a may be smaller than the cross-section of the outlet valve hole 37a.

[0061] The cross section of the low pressure connection hole 28b may be smaller than the cross section of the pressure limiting valve hole 22a, for example 5% to 35% smaller.

[0062] The pressure limiting valve bore 22a may also be designed as a blind bore into which the low-pressure connection bore 28b opens, i.e. preferably into the bore wall at a point remote from the bore bottom of the pressure limiting valve bore 22a.

[0063] In this case, it may be assumed that the axis of the pressure limiting valve hole 22a intersects with the axis of the low-pressure connection hole 28b, in particular at a right angle, at a crossing point at least a predetermined distance from the hole bottom of the pressure limiting valve hole 22a, which is defined as 0.6 times the diameter of the low-pressure connection hole 28b, in particular 1.5 times the diameter of the low-pressure connection hole 28b. The coil spring 52 of the pressure limiting valve 22 can in this case abut against the bottom of the pressure limiting valve hole 22a without intersecting the opening of the low-pressure connection hole 28b.

[0064] The pressure limiting valve hole 22a and the low pressure connection hole 28b may both be located in one plane, perpendicular to the longitudinal direction LA, for example in the drawing plane of FIG. 2a of FIG.

[0065] The pressure limiting valve 22 of FIG. 2 (which can also be the pressure limiting valve 22 shown in FIGS. 4 to 8 ) is illustrated enlarged in FIG. 3 . This pressure limiting valve has a valve seat body 38 which is pressed into the pressure limiting valve bore 22a or into the casing of the pressure limiting valve 22, on which a conical valve seat 42 is formed. The pressure limiting valve 22 further has a valve element 44 having the shape of a ball, which rests closely against the valve seat 42. The valve element 44 is pressed in the closing direction by a retaining element 46, which in turn is pressed in the closing direction by a coil spring 52. The coil spring 52 is supported on the casing of the pressure limiting valve 22 or directly on the pump casing 12. In this case, 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 accommodated by the coil spring 52. Through the stiffness of the coil spring 52 and through the area acting on the pressure limiting valve 22, the opening pressure of the pressure limiting valve 22 is determined and thus at the same time the maximum pressure difference that the high-pressure fuel pump 10 can generate between the inlet 11 and the outlet 34 is determined.

[0066] 4 shows a second embodiment of the invention in a partially sectional view. The second embodiment differs from the first embodiment in that only the outlet valve hole 37a starts from the outlet pipe section chamber 35a, but the pressure limiting valve hole 22a does not start from the outlet pipe section chamber 35a. Instead, in this embodiment, the pressure limiting valve hole 22a is closed at its start 22aa by a ball 56, in particular pressed into the pressure limiting valve hole 22a, or by a plug 57, in particular pressed into the pressure limiting valve hole 22a, and the outlet valve hole 37a is connected to the pressure limiting valve hole 22a by a high-pressure connection hole 29a located in the high-pressure region 29.

[0067] In this case, it may be assumed that the high-pressure connection hole 29a originates from the attenuation region 28a, and is closed at its origin side 29aa by a ball 56 pressed into the high-pressure connection hole or a plug 58 pressed into the high-pressure connection hole.

[0068] The outlet piece may be smaller than in the first embodiment, for example, the (outer) diameter of the fastening of the outlet piece 35 to the pump casing 12 in such an arrangement may be smaller than the sum of the diameters of the pressure limiting valve bores 22a and the outlet valve bores 37a, in particular even less than 0.9 times this sum. The robustness of the connection of the outlet piece 35 to the pump casing 12 is thereby increased, since the hydraulic pressure acting on the outlet piece 35 is proportional to the cross-sectional area covered by it, whereas the connection length of the fastening of the outlet piece 35 to the pump casing 12 is only proportional to the circumference of the cross-sectional area covered by it, i.e. only proportional to the square root of the cross-sectional area covered by it.

[0069] What has been said above in the first embodiment regarding the pressure limiting valve hole 22a, the outlet valve hole 37a and the low pressure connection hole 28b and the relationship between these holes also applies to the second embodiment.

[0070] The high pressure connection hole 29a may have a cross section smaller than, for example at most half the cross section of, the pressure limiting valve hole 22a, the outlet valve hole 37a and the low pressure connection hole 28b.

[0071] The axis of the high-pressure connection bore 29a and the axis of the pressure limiting valve bore 22a may intersect, in particular be perpendicular, with the intersection of these axes preferably being located at a distance of at least half, in particular the entire diameter, of the pressure limiting valve bore 22a from the outlet of the pressure limiting valve bore 22a and / or the intersection of these axes preferably being located at a distance of at least half, in particular the entire diameter, of the high-pressure connection bore 29b from the outlet of the high-pressure connection bore 29b, such that the pressure limiting valve bore 22a and / or the high-pressure connection bore 29b can be closed particularly simply at its starting side 29aa by a ball 56 pressed into the high-pressure connection or by a plug 58 pressed into the high-pressure connection.

[0072] In Figure 5 a third embodiment of the invention is shown in Figure 5 a by a first cross-sectional view along the axis of the pressure limiting valve hole 22a parallel to the longitudinal direction LA, in Figure 5 b by a second cross-sectional view along the axis of the pressure limiting valve hole 22a rotated around the axis of the pressure limiting valve hole 22a relative to Figure 5 a and in Figure 5 c by a plan view of the pump body 12a shown partly in a see-through view.

[0073] According to a third embodiment, the outlet valve bore 37a and the pressure limiting valve bore 22a are oriented at a non-0° angle, in particular at a right angle, to one another.

[0074] It is further assumed that the outlet 34 is configured as an outlet stub 35 fixed to the pump casing 12, an outlet stub chamber 35a is formed between the pump casing 12 and the outlet stub 35, the pump casing 12 has a pump body 12a and a pump cover 12b connected to each other, the pump body 12a and the pump cover 12b define a damping region 28a associated with the low-pressure region 28, in which at least one diaphragm damper 55 is arranged, the pressure limiting valve hole 22a is a blind hole starting from the damping region 28a, from which a low-pressure connection hole 28b located in the low-pressure region 28 and opening into the inlet stub chamber 28e and a high-pressure connection hole 29a located in the high-pressure region 29 and opening into the outlet stub chamber 35a are branched, and the pressure limiting valve hole 22a is closed at its starting side 22aa by a ball 56 or a plug 57.

[0075] It may be envisaged that the low pressure connection hole 28b and the high pressure connection hole 29a are oriented at a non-zero angle to each other, for example at least 20° or at a right angle (see FIG. 5c). Alternatively, the low pressure connection hole 28b and the high pressure connection hole 29a may be oriented geometrically parallel to each other (not shown).

[0076] A fourth embodiment of the invention is shown in FIG. 6 in a first partial cross-sectional view parallel to the longitudinal axis in FIG. 6a, in a second partial cross-sectional view rotated about the longitudinal axis with respect to the first cross-sectional view in FIG. 6b, and in a partial cross-sectional view perpendicular to the longitudinal direction LA in FIG. 6c.

[0077] In this case, the pump body 12a is provided with a filter hole 54a connecting the inlet pipe piece chamber 28e to the damping chamber 28a, and a filter element 54 is disposed within the filter hole to filter the fuel flowing from the inlet pipe piece chamber 28e to the damping chamber 28a. In this case, it is assumed that the low-pressure connection hole 28b and the filter hole 54a intersect.

[0078] 6b and 6c, it is assumed that the filter hole 54a is closed on the side of the inlet piece chamber 28e by a plug 57 or a ball 56. The fluid communication between the filter hole 54a and the inlet piece chamber 28e is in this case via the additional hole 54b, the opening of which is located near the bottom of the filter hole 54a.

[0079] Alternatively, the filter hole 54a may be formed unobstructed between the inlet pipe section 28e and the pressure limiting valve hole 22a (see the sixth embodiment in FIG. 8, which shows a view corresponding to the part in FIG. 6b). The additional hole 54b proposed in connection with the fourth embodiment can simply be omitted in the sixth embodiment, as shown.

[0080] A fifth embodiment of the invention is shown in FIG. 7 in a first partial cross-sectional view parallel to the longitudinal axis in FIG. 7a, in a second partial cross-sectional view rotated about the longitudinal axis with respect to the first cross-sectional view in FIG. 7b, and in a partial cross-sectional view perpendicular to the longitudinal direction LA in FIG. 7c.

[0081] This is a modified version of the second embodiment of the present invention described with reference to FIG. 4, but as in the fourth embodiment, a filter hole 54a is provided connecting the inlet pipe section chamber 28e to the damping chamber 28a, and a filter element 54 is arranged in the filter hole to filter the fuel flowing from the inlet pipe section chamber 54a to the damping chamber 28a. In this case, it is assumed that the low-pressure connection hole 28b and the filter hole 54a intersect.

Claims

1. A high pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising: an inlet (11) for supplying fuel; an outlet (34) for discharging the compressed fuel; A pump casing (12); a pumping chamber (16) disposed within the pump casing (12); a pump piston (18) defining the pumping chamber (16) and slidable within the pump casing (12) along a longitudinal direction (LA); an inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening towards the pumping chamber (16); an outlet valve (37) disposed between the pumping chamber (16) and the outlet (34), the outlet valve opening in a direction away from the pumping chamber (16); a high pressure region (29) fluidly extending between said outlet valve (37) and said outlet (34); a low pressure region (28) fluidly extending between said inlet (11) and said inlet valve (14); 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) to allow fuel to flow from the high pressure region (29) to the low pressure region (28) when a pressure difference between the fuel in the high pressure region (29) and the fuel in the low pressure region (28) exceeds an opening pressure; Equipped with the outlet valve (37) is arranged in an outlet valve hole (37a) of the pump casing (12), the pressure limiting valve (22) is arranged in a pressure limiting valve hole (22a) of the pump casing (12), the inlet (11) is formed as an inlet stub (20) fixed to the pump casing (12), an inlet stub chamber (28e) of the low pressure region (28) is formed between the pump casing (12) and the inlet stub (20), when a 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 pressure limiting valve (22) fluidly connects the high pressure region (29) to the inlet stub chamber (28e) of the low pressure region (28) and opens towards the inlet stub chamber (28e) to allow fuel to flow out of the high pressure region (29) into the inlet stub chamber (28e), 2. A high-pressure fuel pump, comprising: a pump casing, a pressure limiting valve hole, a pressure limiting valve hole, and a pressure limiting valve hole. The pressure limiting valve hole and the pressure limiting valve hole are connected to each other via a pressure limiting valve chamber and a pressure limiting valve hole.

2. 2. The high pressure fuel pump (10) according to claim 1, wherein the pressure limiting valve bore (22a) and the outlet valve bore (37a) are oriented geometrically parallel to one another.

3. A high pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising: an inlet (11) for supplying fuel; an outlet (34) for discharging the compressed fuel; A pump casing (12); a pumping chamber (16) disposed within the pump casing (12); a pump piston (18) defining the pumping chamber (16) and slidable within the pump casing (12) along a longitudinal direction (LA); an inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening towards the pumping chamber (16); an outlet valve (37) disposed between the pumping chamber (16) and the outlet (34), the outlet valve opening in a direction away from the pumping chamber (16); a high pressure region (29) fluidly extending between said outlet valve (37) and said outlet (34); a low pressure region (28) fluidly extending between said inlet (11) and said inlet valve (14); 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) to allow fuel to flow from the high pressure region (29) to the low pressure region (28) when a pressure difference between the fuel in the high pressure region (29) and the fuel in the low pressure region (28) exceeds an opening pressure; Equipped with the outlet valve (37) is arranged in an outlet valve hole (37a) of the pump casing (12), the pressure limiting valve (22) is arranged in a pressure limiting valve hole (22a) of the pump casing (12), the inlet (11) is formed as an inlet stub (20) fixed to the pump casing (12), an inlet stub chamber (28e) of the low pressure region (28) is formed between the pump casing (12) and the inlet stub (20), when a 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 pressure limiting valve (22) fluidly connects the high pressure region (29) to the inlet stub chamber (28e) of the low pressure region (28) and opens towards the inlet stub chamber (28e) to allow fuel to flow out of the high pressure region (29) into the inlet stub chamber (28e), the pressure limiting valve hole (22a) is connected to the inlet piece chamber (28e) by a low pressure connection hole (28b) located in the low pressure region (28); A high pressure fuel pump (10), wherein the pressure limiting valve hole (22a) and the low pressure connection hole (28b) are both located in a single plane perpendicular to the longitudinal direction (LA).

4. A high pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising: an inlet (11) for supplying fuel; an outlet (34) for discharging the compressed fuel; A pump casing (12); a pumping chamber (16) disposed within the pump casing (12); a pump piston (18) defining the pumping chamber (16) and slidable within the pump casing (12) along a longitudinal direction (LA); an inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening towards the pumping chamber (16); an outlet valve (37) disposed between the pumping chamber (16) and the outlet (34), the outlet valve opening in a direction away from the pumping chamber (16); a high pressure region (29) fluidly extending between said outlet valve (37) and said outlet (34); a low pressure region (28) fluidly extending between said inlet (11) and said inlet valve (14); 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) to allow fuel to flow from the high pressure region (29) to the low pressure region (28) when a pressure difference between the fuel in the high pressure region (29) and the fuel in the low pressure region (28) exceeds an opening pressure; Equipped with the outlet valve (37) is arranged in an outlet valve hole (37a) of the pump casing (12), the pressure limiting valve (22) is arranged in a pressure limiting valve hole (22a) of the pump casing (12), the inlet (11) is formed as an inlet stub (20) fixed to the pump casing (12), an inlet stub chamber (28e) of the low pressure region (28) is formed between the pump casing (12) and the inlet stub (20), when a 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 pressure limiting valve (22) fluidly connects the high pressure region (29) to the inlet stub chamber (28e) of the low pressure region (28) and opens towards the inlet stub chamber (28e) to allow fuel to flow out of the high pressure region (29) into the inlet stub chamber (28e), the pressure limiting valve hole (22a) is connected to the inlet piece chamber (28e) by a low pressure connection hole (28b) located in the low pressure region (28); 1. A high-pressure fuel pump according to claim 1, wherein the pump casing (12) has a pump body (12a) and a pump cover (12b) connected to each other, the pump body (12a) and the pump cover (12b) define a damping area (28a) associated with the low-pressure area (28), at least one diaphragm damper (55) is arranged in the damping area, the pump body (12a) is provided with a filter hole (54a) connecting the inlet pipe section chamber (28e) to the damping area (28a), a filter element (54) is arranged in the filter hole for filtering fuel flowing from the inlet pipe section chamber (28e) to the damping area (28a), and the low-pressure connection hole (28b) and the filter hole (54a) intersect.

5. A high pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising: an inlet (11) for supplying fuel; an outlet (34) for discharging the compressed fuel; A pump casing (12); a pumping chamber (16) disposed within the pump casing (12); a pump piston (18) defining the pumping chamber (16) and slidable within the pump casing (12) along a longitudinal direction (LA); an inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening towards the pumping chamber (16); an outlet valve (37) disposed between the pumping chamber (16) and the outlet (34), the outlet valve opening in a direction away from the pumping chamber (16); a high pressure region (29) fluidly extending between said outlet valve (37) and said outlet (34); a low pressure region (28) fluidly extending between said inlet (11) and said inlet valve (14); 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) to allow fuel to flow from the high pressure region (29) to the low pressure region (28) when a pressure difference between the fuel in the high pressure region (29) and the fuel in the low pressure region (28) exceeds an opening pressure; Equipped with the outlet valve (37) is arranged in an outlet valve hole (37a) of the pump casing (12), the pressure limiting valve (22) is arranged in a pressure limiting valve hole (22a) of the pump casing (12), the inlet (11) is formed as an inlet stub (20) fixed to the pump casing (12), an inlet stub chamber (28e) of the low pressure region (28) is formed between the pump casing (12) and the inlet stub (20), when a 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 pressure limiting valve (22) fluidly connects the high pressure region (29) to the inlet stub chamber (28e) of the low pressure region (28) and opens towards the inlet stub chamber (28e) to allow fuel to flow out of the high pressure region (29) into the inlet stub chamber (28e), 1. A high-pressure fuel pump, comprising: a pump casing, a pressure limiting valve hole, a pressure limiting valve hole, and a pressure connection hole located in the high-pressure region, the pressure limiting valve hole being connected to the pressure limiting valve hole by a high-pressure ...

6. 6. The high-pressure fuel pump according to claim 5, wherein the pump housing (12) has a pump body (12a) and a pump cover (12b) connected to each other, the pump body (12a) and the pump cover (12b) together define a damping area (28a) associated with the low-pressure area (28), in which at least one diaphragm damper (55) is arranged, and the high-pressure connection hole (29a) starts from the damping area (28a) and is closed on its starting side (29aa) by a ball (56) or a plug (57).

7. 7. The high pressure fuel pump (10) according to claim 6, wherein the pressure limiting valve bore (22a) is connected to the inlet piece chamber (28e) by a low pressure connection bore (28b) located in the low pressure region (28).

8. 8. The high pressure fuel pump (10) according to claim 7, wherein the pressure limiting valve bore (22a) and the low pressure connection bore (28b) are both located in one plane perpendicular to the longitudinal direction (LA).

9. 8. The high pressure fuel pump according to claim 7, wherein the pump body has a filter hole connecting the inlet piece chamber to the damping area, a filter element for filtering fuel flowing from the inlet piece chamber to the damping area is disposed in the filter hole, and the low pressure connection hole intersects with the filter hole.

10. A high pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising: an inlet (11) for supplying fuel; an outlet (34) for discharging the compressed fuel; A pump casing (12); a pumping chamber (16) disposed within the pump casing (12); a pump piston (18) defining the pumping chamber (16) and slidable within the pump casing (12) along a longitudinal direction (LA); an inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening towards the pumping chamber (16); an outlet valve (37) disposed between the pumping chamber (16) and the outlet (34), the outlet valve opening in a direction away from the pumping chamber (16); a high pressure region (29) fluidly extending between said outlet valve (37) and said outlet (34); a low pressure region (28) fluidly extending between said inlet (11) and said inlet valve (14); 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) to allow fuel to flow from the high pressure region (29) to the low pressure region (28) when a pressure difference between the fuel in the high pressure region (29) and the fuel in the low pressure region (28) exceeds an opening pressure; Equipped with the outlet valve (37) is arranged in an outlet valve hole (37a) of the pump casing (12), the pressure limiting valve (22) is arranged in a pressure limiting valve hole (22a) of the pump casing (12), the inlet (11) is formed as an inlet stub (20) fixed to the pump casing (12), an inlet stub chamber (28e) of the low pressure region (28) is formed between the pump casing (12) and the inlet stub (20), when a 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 pressure limiting valve (22) fluidly connects the high pressure region (29) to the inlet stub chamber (28e) of the low pressure region (28) and opens towards the inlet stub chamber (28e) to allow fuel to flow out of the high pressure region (29) into the inlet stub chamber (28e), A high pressure fuel pump (10), wherein the outlet valve hole (37a) and the pressure limiting valve hole (22a) are oriented at a non-zero angle to each other.

11. The outlet (34) is formed as an outlet piece (35) fixed to the pump casing (12), an outlet piece chamber (35a) is formed between the pump casing (12) and the outlet piece (35), the pump casing (12) has a pump body (12a) and a pump cover (12b) connected to each other, the pump body (12a) and the pump cover (12b) define a damping area (28a) associated with the low pressure area (28), and at least one diaphragm is disposed in the damping area.

11. The high-pressure fuel pump according to claim 10, further comprising a damper, the pressure limiting valve hole being a blind hole originating from the damping region, from which a low-pressure connection hole located in the low-pressure region and opening into the inlet piece chamber and a high-pressure connection hole located in the high-pressure region and opening into the outlet piece chamber, the pressure limiting valve hole being closed at its origin side by a ball or a plug.

12. 12. The high pressure fuel pump (10) according to claim 11, wherein the low pressure connection hole (28b) and the high pressure connection hole (29a) are oriented geometrically parallel to one another.

13. 12. The high pressure fuel pump (10) of claim 11, wherein the low pressure connection hole (28b) and the high pressure connection hole (29a) are oriented at a non-zero angle to each other.

14. The pressure limiting valve (22) has a valve seat body (38) which is pressed into the pressure limiting valve bore (22a) or into a casing of the pressure limiting valve (22), the valve seat body being formed with a conical valve seat (42), the pressure limiting valve (22) has a valve element (44) which has the shape of a ball and tightly abuts against the valve seat (42), the valve element (44) being pressed in the closing direction by a retaining element (46), the retaining element (46) being 11. The high pressure fuel pump (10) according to claim 1, wherein the pressure limiting valve (22) is biased in the closing direction by a coil spring (52), the coil spring (52) being supported on a casing of the pressure limiting valve (22) or on a pump casing (12), the coil spring (52) abutting a radially outer region (464) of the retaining element (46) and the coil spring (52) receiving a radially inner region (465) of the retaining element (46).

Images