Fuel high-pressure pump

Abstract

The high pressure fuel pump (10) has an inlet valve (14) and a pressure limiting valve (22) fluidly connecting a high pressure region (29) to an inlet valve region (28c) that is geometrically located between the inlet valve (14) and an electromagnetic actuator (30) of the high pressure fuel pump (10) that acts on the inlet valve (14) via a plunger (31).

Description

Technical Field

[0001] Background Art According to the prior art, for example, based on the European Patent No. 2344749 of the applicant, there is a fuel high-pressure pump, which has an inlet for supplying fuel, an outlet for discharging the compressed fuel, a pump casing, a pumping chamber disposed within the pump casing, a pump piston that defines this pumping chamber and is slidable longitudinally within the pump casing, an inlet valve disposed between the inlet and the pumping chamber and opening towards the pumping chamber, an outlet valve disposed between the pumping chamber and the outlet and opening in a direction away from the pumping chamber, a high-pressure region that fluidically extends between the outlet valve and the outlet, a low-pressure region that fluidically extends between the inlet and the inlet valve, and a pressure-limiting valve that fluidically connects the high-pressure region to the low-pressure region and opens towards the low-pressure region to allow fuel to flow out from the high-pressure region to the low-pressure region when the differential pressure between the fuel in the high-pressure region and the fuel in the low-pressure region exceeds the opening pressure. Such a fuel high-pressure pump is already known.

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

[0003] Disclosure of the Invention The present invention starts from the inventor's consideration that the known solution according to the prior art may cause a potentially excessive mechanical load on the pressure damper. The pressure pulsation reaches the receiving chamber from the high-pressure region through the pressure-limiting valve, where it loads the pressure damper, which was originally designed simply for low pressure, resulting in wear and unwanted sound wave formation in this pressure damper. Furthermore, the original function of this pressure damper, which is to attenuate the pressure pulsation whose pulsation source exists in the low-pressure region of the fuel high-pressure pump, is impaired.

[0004] Therefore, according to the present invention, in order to minimize the mechanical load or wear associated with the pressure limiting function of the fuel high-pressure pump, and furthermore to minimize the formation of sound waves, when the differential pressure 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 valve region of the low-pressure region and opens towards the inlet valve region to allow fuel to flow out from the high-pressure region to the inlet valve region. In this case, it is assumed that the inlet valve region of the low-pressure region is geometrically located between the inlet valve and the electromagnetic actuator of the fuel high-pressure pump that loads the inlet valve via the plunger.

[0005] The electromagnetic actuator of the fuel high-pressure pump may be a component having an actuator casing fixed to the pump casing, in particular, screwed, press-fitted, or welded to the pump casing. The electromagnetic actuator may have an electric coil for pump fixation, and may also have electric terminals connected to this electric coil. For example, a movable element that is slidable in response to energization of the coil may be provided, and this movable element is mechanically connected to the plunger. Therefore, the plunger is slidable by the electromagnetic actuator to open and close the inlet valve, particularly perpendicular to the longitudinal direction of the fuel high-pressure pump.

[0006] The electromagnetic actuator may be configured to advance the plunger to a position where the inlet valve is opened only when the electric coil is energized. Alternatively, the electromagnetic actuator may be configured to be able to retract the plunger only when the electric coil is energized, thereby closing the inlet valve in some cases.

[0007] It may be assumed that the outlet valve is fixed within the outlet valve hole of the pump casing and the pressure limiting valve is fixed within the pressure limiting valve hole of the pump casing.

[0008] Furthermore, if the outlet valve hole and the pressure limiting valve hole are geometrically parallel to each other, on the one hand, this provides the advantage that the machining of the pump casing for the production of the pressure limiting valve hole and the outlet valve hole, for example cutting, becomes easier. This is because this machining can be carried out in the same direction and thus, for example, can be carried out with the same tool and / or even simultaneously.

[0009] On the other hand, this facilitates the assembly of the fuel high-pressure pump. This is because the holes belonging to the pressure limiting valve and the holes belonging to the outlet valve can be oriented in the same direction, and thus the pressure limiting valve and the outlet valve can be easily attached, for example with the same tool and / or even simultaneously.

[0010] In a further configuration, the outlet is formed as an outlet pipe section fixed to the pump casing. The outlet pipe section particularly has a tubular basic shape and can, for example, be welded or screwed to the pump casing. Furthermore, the outlet pipe section itself can have means, for example threads, for tightly attaching a high-pressure pipeline to the outlet pipe section.

[0011] Furthermore, it may be assumed that an outlet pipe section chamber is formed between the pump casing and the outlet pipe section. The outlet pipe section chamber may, on the one hand, consist of or include the part of the inner chamber of the pipe section facing the pump casing. The outlet pipe section chamber may additionally include a recess in the pump body covered by the outlet pipe section, particularly consisting of both of these partial chambers. Alternatively, the outlet pipe section chamber may consist of a recess in the pump body covered by the outlet pipe section.

[0012] In a further configuration, it may be assumed that both the outlet valve hole and the pressure limiting valve hole originate from the outlet pipe section chamber. This reduces the number of components constituting the fuel high-pressure pump and the number of sealing locations required for the fuel high-pressure pump.

[0013] Alternatively, it may be assumed that only the outlet valve orifice originates from the outlet pipe piece chamber and the pressure limiting valve orifice does not originate from the outlet pipe piece chamber. This has the advantage that the cross-sectional area of the flow through the outlet pipe piece chamber can be significantly reduced, and thus the cross-sectional area of the outlet pipe piece attached to the pump body can also be reduced. This improves the certainty or pressure resistance of attaching the outlet pipe piece to the pump casing. This is because the cross-sectional area of the outlet pipe piece attached to the pump body is proportional to the force acting on the pipe piece when the fuel under high pressure is pumped. On the other hand, the coupling length by which the pipe piece can be attached to the pump casing along its circumference is only proportional to the square root of the cross-sectional area of the outlet pipe piece attached to the pump body. That is, due to the reduction in the cross-sectional area of the outlet pipe piece attached to the pump body associated with the measure that only the outlet valve orifice originates from the outlet pipe piece chamber and the pressure limiting valve orifice does not originate from the outlet pipe piece chamber, the ratio of the coupling length by which the pipe piece can be attached to the pump casing along its circumference to the cross-sectional area of the outlet pipe piece attached to the pump body increases. Therefore, the attachment portion of the outlet pipe piece can withstand a higher pressure of the pumped fuel.

[0014] For example, in addition to this, in a further configuration, it may be assumed that the pressure limiting valve orifice is closed by a ball or a plug on the side of its origin, and the outlet valve orifice is connected to the pressure limiting valve orifice by a high-pressure connection orifice located within the high-pressure region. In this case, the fluid communication between the outlet and the pressure limiting valve is effected only by the high-pressure connection orifice inside the pump casing. At the same time, the closure of the pressure limiting valve orifice by the ball or the plug realizes a simple and reliable sealing point.

[0015] In particular, it is assumed that the pressure limiting valve orifice is connected to the inlet valve region by a low-pressure connection orifice located in the low-pressure region.

[0016] It may be assumed that the cross-sectional area of the low-pressure connection orifice is smaller than the cross-sectional area of the pressure limiting valve orifice. Thereby, the low-pressure connection orifice functions as a throttle, and the pressure pulsation from the high-pressure region reaches the inlet valve region only after being attenuated.

[0017] Additionally or alternatively, it may be assumed that the low-pressure connection hole and the pressure-limiting valve hole are bent at an angle other than 0° with respect to each other in a projection view along the longitudinal direction, and / or that the low-pressure connection hole and the pressure-limiting valve hole are bent at an angle other than 0° with respect to each other in at least one projection view perpendicular to the longitudinal direction. In this case, an efficient use of the space provided for the inner contour in the pump casing or the pump body is achieved.

[0018] A similar effect can also be obtained by a further configuration, according to which it is assumed that in at least one projection view perpendicular to the longitudinal direction, the low-pressure connection hole is bent at an angle other than 0° with respect to the pressure-limiting valve hole such that the low-pressure connection hole is directed towards the inlet valve with respect to the longitudinal direction and with respect to the direction from the pressure-limiting valve hole towards the inlet valve region.

[0019] Alternatively, it may be assumed that the low-pressure connection hole and the pressure-limiting valve hole are coaxial with each other. In this case, for example, both holes can be formed by a single drilling process using a multi-grooved drill.

[0020] Within the scope 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 be the inner contours of the pump casing or the pump body that can be machined from the outside by cutting, particularly by a rotating spiral drill, into the pump casing or the pump body. Therefore, the holes particularly have axial symmetry, and the axis of symmetry corresponds to the axis of rotation of the spiral drill. In this case, this axis of symmetry defines the direction in which the hole is oriented. In this case, the hole may basically be a through-hole penetrating the pump casing or the pump body, or a blind hole terminating at a hole bottom disposed within the pump casing or the pump body. The starting point of the hole, within the scope of the present invention, is the side of the hole that is first formed by cutting when the drill enters the pump casing or the pump body. In the case of a blind hole, the starting point of the hole is always on the side opposite to the hole bottom. Therefore, when the hole reaches another inner contour of the pump casing or the pump body or exits from the pump casing or the pump body, the opening of the hole is on the side opposite to the starting point of the hole. The holes of the present invention particularly do not have an undercut when viewed from their starting point.

[0021] 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 the part of the inner contour formed by the through-hole that is not the hole bottom.

[0022] Within the scope of the present invention, the high-pressure region particularly means all spaces that communicate directly with the outlet without any other intervening valve, and thereby, a uniform pressure of, for example, 500 bar occurs in the high-pressure region during pump operation.

[0023] Within the scope of the present invention, the low-pressure region particularly means all spaces that communicate directly with the inlet without any other intervening valve, and thereby, a uniform pressure of, for example, 5 bar occurs in the low-pressure region during pump operation when a low-pressure pump is connected to the inlet.

[0024] In particular, the inner contour of the fuel high-pressure pump through which fuel flows ultimately consists of a low-pressure region, a pumping chamber, and a high-pressure region. These regions are separated from each other by an inlet valve, an outlet valve, and a pressure-limiting valve.

[0025] The fuel may be, for example, a fuel such as gasoline.

[0026] Within the scope of the present invention, when adjusted to an angle other than 0°, this angle may be an angle clearly different from 0°, that is, for example, an angle of at least 2° or at least 5°. For example, this angle may be an angle between 2° and 90°.

[0027] Exemplary embodiments of the present invention will be described below with reference to the drawings.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

[0029] Figure 1 shows a simplified schematic diagram of a fuel system 1 for an internal combustion engine, with other parts not shown. During operation of the fuel system 1, fuel is supplied from a fuel tank 2 via a suction line 4, through a feed pump 6 and a low-pressure line 8, to an inlet pipe section 20 of a fuel high-pressure pump 10 formed as a piston pump. Fluidically following the inlet pipe section 20, an inlet valve 14 is arranged. A low-pressure region 28 of the fuel high-pressure pump 10 is located fluidically between the inlet pipe section 20 and the inlet valve 14. Downstream of the inlet valve 14, a pumping chamber 16 of the fuel high-pressure pump 10 is located. Pressure pulsations in the low-pressure region 28 can be attenuated by a pressure attenuation device. The inlet valve 14 can in this case be forced open via an operating device formed as an electromagnetic actuator 30. The operating device, and thus the inlet valve 14, can be controlled via a control unit 32.

[0030] The pump piston 18 of the fuel high-pressure pump 10 can in this case move up and down along a longitudinal axis forming the axis of symmetry of the pump piston 18, extending in the longitudinal direction LA, as indicated by the double arrow 40 in Figure 1, by means of a drive device 36 formed as a cam disk. Fluidically between the pumping chamber 16 of the fuel high-pressure pump 10 and an outlet pipe section 35, an outlet valve 37 is arranged which can open towards the outlet pipe section 35 and a high-pressure accumulator 45 (a "rail") located further downstream. Thus, a high-pressure region 29 of the fuel high-pressure pump 10 extends fluidically between the outlet valve 37 and the outlet pipe section 35.

[0031] The high-pressure region 29 and the low-pressure region 28 are directly connected to each other via a pressure limiting valve 22 which opens when a boundary pressure in the high-pressure region 29 of the fuel high-pressure pump 10 or in the high-pressure accumulator 45 communicating with the high-pressure region is exceeded. The pressure limiting valve 22 is formed as a spring-loaded check valve and can open towards the low-pressure region 28 of the fuel high-pressure pump 10. In this way, the pressure that can be generated in the high-pressure accumulator 45 by the fuel high-pressure pump 10 is limited.

[0032] Figure 2 is a cross-sectional view showing a fuel high-pressure pump 10 as a first embodiment of the present invention.

[0033] The fuel high-pressure pump 10 has an inlet 11 formed as an inlet pipe piece 20. The inlet 11 communicates with the entire low-pressure region 28 of the fuel high-pressure pump 10 without an intervening valve.

[0034] The fuel high-pressure pump 10 has an outlet 34 formed as an outlet pipe piece 35. The outlet 34 communicates with the entire high-pressure region 29 of the fuel high-pressure pump 10 without an intervening valve.

[0035] The outlet pipe piece 35 and the inlet pipe piece 20 are fixed to the pump casing 12, and a pressure feed chamber 16 defined by a pump piston 18 slidable along the longitudinal direction LA is also arranged in the pump casing.

[0036] The low-pressure region 28 includes a damping chamber 28a connected to the inlet 11 via a fluid connection portion not visible in this cross-sectional view. This damping chamber is 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, and the diaphragm damper may have a flat and compressible can shape formed by two metal diaphragms.

[0037] The invisible fluid connection portion between the inlet 11 and the damping chamber 28a may have, for example, filter holes, and filter elements for removing entrained solid particles larger than the minimum size are arranged in the filter holes from the fuel flowing through the filter holes.

[0038] In the lower section of the pump body 12a in Figure 2, a seal support 60 is attached, 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 a through hole not visible in this cross-sectional view and penetrating the pump body 12a. Therefore, the stepped chamber is part of the low-pressure region 28.

[0039] The pressure chamber 16 is defined with respect to the low-pressure region 28 by an inlet valve 14 that opens toward the pressure chamber 16 under a corresponding differential pressure.

[0040] In order to control the delivery volume of the fuel high-pressure pump 10, the inlet valve 14 can be forcibly opened by a plunger 31 driven by an actuator 30. For this purpose, the actuator 30 has an actuator casing 30a fixed to the pump casing 12, in which an electromagnetic coil 30b is arranged, and power can be supplied to this electromagnetic coil via an electrical terminal 30c of the fuel high-pressure pump 10 that is accessible from the outside.

[0041] Inside the pump casing, an inlet valve region 28c of the low-pressure region 28 is geometrically formed between the inlet valve 14 and the actuator 30. The inlet valve region communicates with the damping region 28a via a hole 28f that is not visible in this cross-sectional view.

[0042] The pressure chamber 16 is defined with respect to the high-pressure region 29 by an outlet valve 37 that opens away from the pressure chamber 16 under a corresponding differential pressure. In this example, the outlet valve is arranged in an outlet valve hole 37a of the pump casing 12 or the pump body 12a. The outlet valve has a movable valve element 37.1, which cooperates with a seal seat 37.4 formed in a seal seat portion 37.2 arranged for pump fixation upstream of the valve element 37.1. The movability of the valve element 37.1 is restricted in the downstream direction via a corresponding plate 37.5 arranged for pump fixation. The outlet valve hole 37a starts from an outlet pipe piece chamber 35a located between the outlet pipe piece 35 and the pump casing 12 or the pump body 12a.

[0043] The pump piston 18 is formed as a stepped piston. The pump piston has a first section 18.1 facing the pumping chamber 16 with a relatively large diameter and a second section 18.2 directed in a direction away from the pumping chamber and having a relatively small diameter (relative to the diameter of the first section 18.1). A ring-shaped step 18.3 directed vertically downward in FIG. 2 is formed between the first section 18.1 and the second section 18.2.

[0044] A high-pressure seal 80 is arranged between the first section 18.1 and the pump casing 12, and within this high-pressure seal, the pump piston 18 is slidable. The high-pressure seal 80 seals and separates the pumping chamber 16 from the low-pressure region 28.

[0045] The high-pressure seal 80 may be, for example, a separate seal ring made of, for example, metal or plastic, as described in detail in the applicant's International Publication No. 19015862. On the other hand, the high-pressure seal 80 may be, for example, a narrow gap extending over a predetermined length between the pump piston 18 and the bush, or between the pump piston 18 and the pump casing 12, as described in detail in the applicant's International Publication No. 06069819.

[0046] A low-pressure seal 78 that separates the stepped chamber 28d of the low-pressure region 28 from the space 100 located outside the fuel high-pressure pump 10 is arranged between the second section 18.2 and the seal support 60 already described above. The pump piston 18 is slidable within the low-pressure seal 78.

[0047] The pump piston 18 is preloaded in the longitudinal direction LA directed downward in FIG. 2 via a spring receiver 19.1 fixed to the pump piston 18 and a pump spring 19.2 clamped between the spring receiver 19.1 and the seal support 60.

[0048] The fuel high-pressure 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 towards the low-pressure region 28 to allow fuel to flow out from the high-pressure region 29 to the low-pressure region 28 when the differential pressure between the fuel in the high-pressure region 29 and the fuel in the low-pressure region 28 exceeds the opening pressure. The arrangement of the pressure limiting valve 22 in the fuel high-pressure pump 10 according to the present invention will be further illustratively described below.

[0049] In this case, when the differential pressure 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 valve region 28c of the low-pressure region 28 and opens towards the inlet valve region 28c, allowing fuel to flow out from the high-pressure region 29 to the inlet valve region 28c. In this case, it is assumed that the inlet valve region 28c of the low-pressure region 28 is geometrically located between the inlet valve 14 and the electromagnetic actuator 30 that loads the inlet valve 14 via the plunger 31 of the fuel high-pressure pump 10.

[0050] The extent of the inlet valve region 28c is illustratively shown by the quadrilateral defined by the dashed-dotted line in FIG. 2. For example, the inlet valve region may be a cylindrical spatial region (e.g., based on a vertical cylinder), the bottom surface of this cylindrical spatial region is oriented parallel to the longitudinal direction LA, and its size is simply such that there is a projection view perpendicular to the longitudinal axis (e.g., the horizontal direction in FIG. 2) that surrounds the projection view of the inlet valve 14 and the projection view of the connection portion between the pump casing 12 and the actuator casing 30a. The height of this cylindrical spatial region may be defined by the distance between the inlet valve 14 and the actuator 30 in the direction of this projection view.

[0051] In the first embodiment, the pressure limiting valve 22 is fixed in the pressure limiting valve hole 22a of the pump casing 12 that is geometrically parallel to the outlet valve hole 37a.

[0052] According to the first embodiment, the outlet 34 is formed as an outlet pipe piece 35 fixed to the pump casing 12, and an outlet pipe piece chamber 35a is formed between the pump casing 12 and the outlet pipe piece 35. Both the outlet valve hole 37a and the pressure limiting valve hole 22a originate from the outlet pipe piece chamber.

[0053] Since the outlet pipe piece 35 extends, particularly in a lateral direction with respect to the flow direction, beyond the outlet of the pressure limiting valve hole 22a and beyond the outlet of the outlet valve hole 37a, the pressure limiting valve hole 22a and the outlet valve hole 37a communicate with each other via the outlet pipe piece chamber 35a arranged between the pump casing 12 and the outlet pipe piece 35.

[0054] In such an arrangement, the (outer) diameter fixing the outlet pipe piece 35 to the pump casing is, in this case, relatively large, for example, at least greater than the sum of the diameters of the pressure limiting valve hole 22a and the outlet valve hole 37a, and in particular, even at least 1.2 times the size of this sum.

[0055] Furthermore, the pressure limiting valve hole 22a is connected to the inlet valve region 28c by a low-pressure connection hole 28b located in the low-pressure region 28. In this case, in this example, the cross-section of the low-pressure connection hole 28b is smaller than the cross-section of the pressure limiting valve hole 22a.

[0056] The cross-section of the pressure limiting valve hole 22a may be smaller than the cross-section of the outlet valve hole 37a.

[0057] It may be assumed that the low-pressure connection hole 28b and the pressure limiting valve hole 22a are bent so as to form an angle other than 0°, for example, at least 20°, with respect to each other in a projection view along the longitudinal direction LA.

[0058] It may be assumed that the low-pressure connection hole 28b and the pressure limiting valve hole 22a are bent so as to form an angle other than 0°, for example, at least 20°, with respect to each other in at least one projection view perpendicular to the longitudinal direction LA.

[0059] In this embodiment, this bending can be performed such that the low-pressure connection hole 28b forms an angle other than 0° with respect to the pressure-limiting valve hole 22a in at least one projection view perpendicular to the longitudinal direction LA, and the low-pressure connection hole 28b is directed toward the inlet valve 14 with respect to the longitudinal direction LA and with respect to the direction from the pressure-limiting valve hole 22a toward the inlet valve region 28c.

[0060] Alternatively, as shown in FIG. 2, it may be assumed that the low-pressure connection hole 28b and the pressure-limiting valve hole 22a are coaxial with each other. The entirety of both holes 22a, 28b may be understood as a stepped hole in which a portion having a relatively large diameter is formed by the pressure-limiting valve hole 22a and a portion having a relatively small diameter is formed by the low-pressure connection hole 28b.

[0061] The pressure-limiting valve 22 in FIG. 2 (which may also be the pressure-limiting valve 22 shown in FIG. 4) is illustrated enlarged in FIG. 3. This pressure-limiting valve has a valve seat body 38 press-fitted into the pressure-limiting valve hole 22a or into the casing of the pressure-limiting valve 22, and a conical valve seat 42 is formed on this valve seat body. The pressure-limiting valve 22 further has a valve element 44 having the shape of a ball, and this valve element abuts tightly against the valve seat 42. The valve element 44 is pushed in the closing direction by a holding element 46, and the holding element 46 is pushed in the closing direction by a coil spring 52. The coil spring 52 is supported directly on the casing of the pressure-limiting valve 22 or on the pump casing 12. In this case, the coil spring 52 abuts against the radially outer region 464 of the holding element 46. The radially inner region 465 of the holding element 46 is accommodated by the coil spring 52. The opening pressure of the pressure-limiting valve 22 is defined via the stiffness of the coil spring 52 and via the area acting on the pressure-limiting valve, and thus, simultaneously, the maximum differential pressure that the fuel high-pressure pump 10 can generate between the inlet 11 and the outlet 34 is defined.

[0062] Again, with respect to the first embodiment and with respect to the coaxial arrangement of the low-pressure connection hole 28b and the pressure-limiting valve hole 22a (see FIG. 2), it may be assumed that the coil spring 52 is supported by a ring-shaped step portion 22.2 on the side of the pressure-limiting valve hole 22a formed between the low-pressure connection hole 28b and the pressure-limiting valve hole 22a.

[0063] The second embodiment is shown partially in cross-section in FIG. 4. The second embodiment differs from the first embodiment in that only the outlet valve hole 37a starts from the outlet pipe piece chamber 35a, while the pressure-limiting valve hole 22a does not start from the outlet pipe piece chamber 35a. Instead, in this embodiment, the pressure-limiting valve hole 22a is closed on the side of its outlet 22aa, in particular by a ball 56 press-fitted into the pressure-limiting valve hole 22a or a plug 57 press-fitted 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.

[0064] In this case, the high-pressure connection hole 29a starts from the attenuation region 28a, and it may be assumed that it is closed at its starting side 29aa by a ball 56 press-fitted into this high-pressure connection hole or a plug 57 press-fitted into the high-pressure connection hole.

[0065] The outlet pipe piece 34 may be formed smaller than in the first embodiment. For example, in such an arrangement, the (outer) diameter fixing the outlet pipe piece 35 to the pump casing 12 may be smaller than the sum of the diameter of the pressure-limiting valve hole 22a and the diameter of the outlet valve hole 37a, and may particularly be less than 0.9 times this sum. The robustness of the joint of the outlet pipe piece 35 in the pump casing 12 is thereby enhanced. This is because the hydraulic pressure acting on the outlet pipe piece 35 is proportional to the cross-sectional area covered by the outlet pipe piece, while the joint length fixing the outlet pipe piece 35 to the pump casing 12 is only proportional to the perimeter of the cross-section covered by the outlet pipe piece, that is, only proportional to the square root of the cross-sectional area covered by the outlet pipe piece.

[0066] In the first embodiment, what has been described above 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 this second embodiment.

[0067] The high-pressure connection hole 29a may have a cross-section that is smaller than the cross-sections of the pressure limiting valve hole 22a, the outlet valve hole 37a, and the low-pressure connection hole 28b, for example, at most half the size of each of them.

[0068] Alternatively, the high-pressure connection hole 29a may have a cross-section that is smaller than the cross-sections of the pressure limiting valve hole 22a and the outlet valve hole 37a, but larger than the cross-section of the low-pressure connection hole 28b.

Claims

Claim 1 A fuel high-pressure pump (10) for a fuel system for an internal combustion engine, an inlet (11) for supplying fuel, an outlet (34) for discharging 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 longitudinally (LA) within the pump casing (12), 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) and opening in a direction away from the pumping chamber (16), a high-pressure region (29) fluidly extending between the outlet valve (37) and the outlet (34), a low-pressure region (28) fluidly extending between the inlet (11) and the inlet valve (14), a pressure-limiting valve (22) that fluidly connects the high-pressure region (29) to the low-pressure region (28) and opens towards the low-pressure region (28) to allow fuel to flow out of the high-pressure region (29) into the low-pressure region (28) when the differential pressure between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds an opening pressure, comprising the pressure-limiting valve (22) fluidly 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) to allow fuel to flow out of the high-pressure region (29) into the inlet valve region (28c) when the differential pressure between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds an opening pressure, and the inlet valve region (28c) of the low-pressure region (28) is geometrically located between the inlet valve (14) and an electromagnetic actuator (30) of the fuel high-pressure pump (10) that loads the inlet valve (14) via a plunger (31), the outlet valve (37) is fixed within an outlet valve bore (37a) of the pump casing (12), and the pressure-limiting valve (22) is fixed within a pressure-limiting valve bore (22a) of the pump casing (12), The outlet (34) is formed as an outlet pipe piece (35) fixed to the pump casing (12). An outlet pipe piece chamber (35a) is formed between the pump casing (12) and the outlet pipe piece (35). The outlet valve hole (37a) starts from the outlet pipe piece chamber (35a), and the pressure limiting valve hole (22a) does not start from the outlet pipe piece chamber (35a). The pressure limiting valve hole (22a) is closed by a ball (56) or a plug body (57) on the side of its starting point (22aa). 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). Fuel high-pressure pump (10).

2. 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) belonging to the low-pressure region (28). At least one diaphragm damper (55) is arranged in the damping region. The high-pressure connection hole (29a) starts from the damping region (28a) and is closed by a ball (56) or a plug body (57) on the starting point side (29aa). The fuel high-pressure pump (10) according to claim 1.

3. A fuel high-pressure pump (10) for a fuel system of an internal combustion engine, An inlet (11) for supplying fuel, An outlet (34) for discharging compressed fuel, A pump casing (12), A pumping chamber (16) arranged in the pump casing (12), A pump piston (18) defining the pumping chamber (16) and slidable along the longitudinal direction (LA) in the pump casing (12), An inlet valve (14) arranged between the inlet (11) and the pumping chamber (16) and opening towards the pumping chamber (16), An outlet valve (37) arranged between the pumping chamber (16) and the outlet (34) and opening in a direction away from the pumping chamber (16), A high-pressure region (29) fluidly extending between the outlet valve (37) and the outlet (34), A low-pressure region (28) fluidly extending between the inlet (11) and the inlet valve (14), 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 out from the high-pressure region (29) to the low-pressure region (28) when the differential pressure between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds the opening pressure. Comprising When the differential pressure 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 valve region (28c) of the low-pressure region (28) and opens toward the inlet valve region (28c), allowing fuel to flow out from the high-pressure region (29) to the inlet valve region (28c). The inlet valve region (28c) of the low-pressure region (28) is geometrically located between the inlet valve (14) and the electromagnetic actuator (30) of the fuel high-pressure pump (10) that loads the inlet valve (14) via the plunger (31). The outlet valve (37) is fixed within the outlet valve hole (37a) of the pump casing (12), and the pressure limiting valve (22) is fixed within the pressure limiting valve hole (22a) of the pump casing (12). The pressure limiting valve hole (22a) is connected to the inlet valve region (28c) by a low-pressure connection hole (28b) located in the low-pressure region (28). A fuel high-pressure pump (10) in which the cross-section of the low-pressure connection hole (28b) is smaller than the cross-section of the pressure limiting valve hole (22a).

4. A fuel high-pressure pump (10) for a fuel system of an internal combustion engine, An inlet (11) for supplying fuel, An outlet (34) for discharging compressed fuel, A pump casing (12), A pumping chamber (16) disposed within the pump casing (12), A pump piston (18) that defines the pumping chamber (16) and is slidable along the longitudinal direction (LA) within the pump casing (12), An inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening toward the pumping chamber (16), An outlet valve (37) disposed between the pumping chamber (16) and the outlet (34) and opening in a direction away from the pumping chamber (16), A high-pressure region (29) that extends fluidly between the outlet valve (37) and the outlet (34), A low-pressure region (28) that extends fluidly between the inlet (11) and the inlet valve (14). 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 out from the high-pressure region (29) to the low-pressure region (28) when the differential pressure between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds the opening pressure. Comprising When the differential pressure 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 valve region (28c) of the low-pressure region (28) and opens toward the inlet valve region (28c), allowing fuel to flow out from the high-pressure region (29) to the inlet valve region (28c). The inlet valve region (28c) of the low-pressure region (28) is geometrically located between the inlet valve (14) and the electromagnetic actuator (30) of the fuel high-pressure pump (10) that loads the inlet valve (14) via the plunger (31). The outlet valve (37) is fixed within the outlet valve hole (37a) of the pump casing (12), and the pressure limiting valve (22) is fixed within the pressure limiting valve hole (22a) of the pump casing (12). The pressure limiting valve hole (22a) is connected to the inlet valve region (28c) by a low-pressure connection hole (28b) located in the low-pressure region (28). A fuel high-pressure pump (10) in which the low-pressure connection hole (28b) and the pressure limiting valve hole (22a) are bent at an angle other than 0° with respect to each other in a projection view along the longitudinal direction (LA). **Claim 5**: A fuel high-pressure pump (10) for a fuel system for an internal combustion engine, An inlet (11) for supplying fuel, An outlet (34) for discharging compressed fuel, A pump casing (12), A pumping chamber (16) disposed within the pump casing (12), A pump piston (18) that defines the pumping chamber (16) and is slidable along the longitudinal direction (LA) within the pump casing (12), An inlet valve (14) disposed between the inlet (11) and the pumping chamber (16) and opening toward the pumping chamber (16), An outlet valve (37) disposed between the pumping chamber (16) and the outlet (34) and opening in a direction away from the pumping chamber (16), A high-pressure region (29) that fluidly extends between the outlet valve (37) and the outlet (34). a low-pressure region (28) fluidly extending between the inlet (11) and the inlet valve (14); a pressure-limiting valve (22) that fluidly connects the high-pressure region (29) to the low-pressure region (28) and opens towards the low-pressure region (28) to allow fuel to flow out from the high-pressure region (29) to the low-pressure region (28) when the differential pressure between the fuel in the high-pressure region (29) and the fuel in the low-pressure region (28) exceeds the opening pressure; comprising; when the differential pressure 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 valve region (28c) of the low-pressure region (28) and opens towards the inlet valve region (28c), allowing fuel to flow out from the high-pressure region (29) to the inlet valve region (28c). The inlet valve region (28c) of the low-pressure region (28) is geometrically located between the inlet valve (14) and an electromagnetic actuator (30) of the fuel high-pressure pump (10) that loads the inlet valve (14) via a plunger (31); the outlet valve (37) is fixed in an outlet valve hole (37a) of the pump casing (12), and the pressure-limiting valve (22) is fixed in a pressure-limiting valve hole (22a) of the pump casing (12); the pressure-limiting valve hole (22a) is connected to the inlet valve region (28c) by a low-pressure connection hole (28b) located in the low-pressure region (28); the low-pressure connection hole (28b) and the pressure-limiting valve hole (22a) are bent at an angle other than 0° with respect to each other in at least one projection view perpendicular to the longitudinal direction (LA); in the at least one projection view perpendicular to the longitudinal direction (LA), the low-pressure connection hole (28b) is bent at an angle other than 0° with respect to the pressure-limiting valve hole (22a) such that the low-pressure connection hole (28b) is directed towards the inlet valve (14) with respect to the longitudinal direction (LA) and the direction from the pressure-limiting valve hole (22a) towards the inlet valve region (28c). Fuel high-pressure pump (10). Claim 6 The electromagnetic actuator (30) includes an actuator casing (30a) fixed to the pump casing (12), an electric coil (30b), an electric terminal (30c) connected to the electric coil, and the plunger (31) capable of sliding in a direction perpendicular to the longitudinal direction (LA) to open and close the inlet valve (14). The fuel high-pressure pump (10) according to any one of claims 1 and 3 to 5.

7. The outlet valve hole (37a) and the pressure limiting valve hole (22a) are geometrically parallel to each other. The fuel high-pressure pump (10) according to any one of claims 1 and 3 to 5.

8. The outlet (34) is formed as an outlet pipe piece (35) fixed to the pump casing (12). An outlet pipe piece chamber (35a) is formed between the pump casing (12) and the outlet pipe piece (35). Both the outlet valve hole (37a) and the pressure limiting valve hole (22a) originate from the outlet pipe piece chamber (35a). The fuel high-pressure pump (10) according to any one of claims 1 and 3 to 5.

9. The low-pressure connection hole (28b) and the pressure limiting valve hole (22a) are bent at an angle other than 0° with respect to each other in at least one projection view in a direction perpendicular to the longitudinal direction (LA). The fuel high-pressure pump (10) according to claim 3 or 4.

10. The low-pressure connection hole (28b) and the pressure limiting valve hole (22a) are coaxial with each other. The fuel high-pressure pump (10) according to any one of claims 3 to 5.

11. The pressure limiting valve (22) has a valve seat body (38) press-fitted into the pressure limiting valve hole (22a) or into the casing of the pressure limiting valve (22). A conical valve seat (42) is formed on the valve seat body. The pressure limiting valve (22) has the shape of a ball and has a valve element (44) that abuts tightly against the valve seat (42). The valve element (44) is pushed in the closing direction by a holding element (46). The holding element (46) is pushed in the closing direction by a coil spring (52). The coil spring (52) is supported by the casing of the pressure limiting valve (22) or by the pump casing (12). The coil spring (52) abuts against a radially outer region (464) of the holding element (46), and the coil spring (52) accommodates a radially inner region (465) of the holding element (46). The fuel high-pressure pump (10) according to any one of claims 1 and 3 to 5.

Images