High-pressure fuel pump for a fuel injection system of an internal combustion engine

Abstract

The invention relates to a high-pressure fuel pump (22) for a fuel injection system (10) of an internal combustion engine, said fuel pump comprising a pump housing (40) and a pump cover (42) which is mounted on the pump housing (40) and which, together with the pump housing (40), delimits a low-pressure chamber (44), wherein a recess (58) is formed in the pump housing (40), in which recess a pressure-limiting valve (56) is located, wherein the recess (58) is fluidically connected to the low-pressure chamber (44) via a channel (72), wherein the channel (72) has the same or a larger cross-section at its end facing the low-pressure chamber (44) than at its end facing the recess (58).

Description

State of the art

[0001] The invention relates to a high-pressure fuel pump for a fuel injection system of an internal combustion engine according to the preamble of claim 1.

[0002] Such a high-pressure fuel pump is known, for example, from DE 10 2018 211 237 A1. This high-pressure fuel pump comprises a pump housing and a pump cover mounted thereon with a low-pressure chamber. A pressure relief valve is arranged in a recess formed in the pump housing, wherein the recess is fluidly connected to a delivery chamber in which a piston rotates. Another fuel pump is also known from DE 103 27 411 A1. In such high-pressure fuel pumps, excessive wear and cavitation erosion can occur on the pressure relief valve.

[0003] Other high-pressure fuel pumps are known from DE 10 2019 203 967 A1 and US 2008 / 0156 294 A1. Disclosure of the invention

[0004] The problem underlying the invention is solved by a high-pressure fuel pump having the features of claim 1. Advantageous developments of the invention are mentioned in the subclaims.

[0005] According to the invention, a high-pressure fuel pump for a fuel injection system of an internal combustion engine is proposed. The high-pressure fuel pump comprises a pump housing and a pump cover mounted on the pump housing (which may not be detachable from the pump housing without damage), which, together with the pump housing, defines a low-pressure chamber. A recess is formed in the pump housing, in which a pressure relief valve is arranged. The recess is fluidly connected to the low-pressure chamber via a channel, wherein the channel has the same or a larger cross-section at its end facing the low-pressure chamber than at its end facing the recess with the pressure relief valve.

[0006] In this way, the pressure relief valve is connected to the low-pressure chamber or the low-pressure damper of the high-pressure fuel pump located in the low-pressure chamber. This connection reduces pressure pulsations / volume flows on the pressure relief valve spring, thus reducing wear and cavitation erosion on the pressure relief valve. Furthermore, cavitation erosion caused by steam in the delivery chamber and the "breathing" of the valve body can be prevented. Furthermore, the back pressures that occur in the high-pressure system in the event of a full delivery fault can be reduced, and the pump's volumetric efficiency can be increased. The possible tapering of the channel cross-section can potentially achieve acoustic advantages, as this allows the natural frequency of the recess to be modified.

[0007] It has been recognized that wear in conventional high-pressure fuel pumps can be caused by axial and radial movement of the spring retainer, as well as by the "breathing" of the valve body due to alternating pressure build-up / decrease in the delivery chamber. It has also been recognized that cavitation erosion can be caused by valve opening (due to movement of the spring retainer) and steam generated in the delivery chamber during the suction phases. The movement of the spring retainer can be caused by axial and radial oscillation of the spring due to pressure pulsations / volume flows in the delivery chamber. These issues can be avoided with the proposed high-pressure fuel pump.

[0008] The present high-pressure fuel pump is, in particular, a piston pump. Such a pump has a delivery chamber and a piston arranged therein, which can be driven in an oscillating manner.

[0009] The channel fluidically connecting the recess to the low-pressure chamber is formed in a wall of the pump housing, which defines the low-pressure chamber toward the pump housing and separates the low-pressure chamber from the recess. The channel can extend, in particular, in a straight line along a central longitudinal direction. The recess is fluidly connected to an outlet of the high-pressure fuel pump (i.e., to the high-pressure side), at which, for example, a connecting flange can be provided. An outlet valve can be arranged parallel to the pressure-limiting valve.

[0010] The pressure relief valve can have several functions. Firstly, the pressure relief valve can ensure that the pressure in the rail does not exceed a specified value (e.g., in the event of pressure overshoots or during hot shutoff). This ensures that the permissible load on the affected components is not exceeded. As long as the pressure in the rail is below the maximum permissible value, the pressure relief valve must seal off the low-pressure system or the discharge chamber to prevent pressure loss in the rail. The pressure relief valve can have a valve body, a ball, a spring retainer, and / or a spring.

[0011] According to a further development, the central longitudinal axis of the channel and the central longitudinal axis of the low-pressure chamber and the central longitudinal axis of the pump housing can be arranged parallel to each other or congruent with each other. This allows a central arrangement of the channel with respect to the pump housing or the low-pressure chamber. This contributes to a good connection of the pressure relief valve to the low-pressure damper. Pressure pulsations at the pressure relief valve and movements of the pressure relief valve spring can be further reduced.

[0012] According to a further development, the cross-section of the channel can increase conically along the central longitudinal axis of the channel toward the low-pressure chamber. This can achieve acoustic advantages, as it allows the natural frequency of the recess to be modified.

[0013] According to a further development, the channel can have a first axial channel section and a second axial channel section, wherein the second channel section faces the low-pressure chamber and has a larger cross-section than the first channel section. This also allows the excitation of the vibrations to be dampened, thus achieving acoustic advantages. In other words, the channel is designed as a stepped channel, e.g., a stepped bore, which widens toward the low-pressure chamber or whose larger cross-section (e.g., larger diameter) faces the low-pressure chamber.

[0014] According to a further development, a delivery chamber can be provided in which a piston runs, wherein the wall separating the delivery chamber and the recess in which the pressure relief valve is arranged is designed to be channel-free. This contributes to a good connection of the pressure relief valve to the low-pressure chamber or the low-pressure damper arranged in the low-pressure chamber. There is no direct flow connection from the delivery chamber to the recess via the wall.

[0015] According to a further development, the central longitudinal axis of the recess for the pressure relief valve can be oriented orthogonally to the central longitudinal axis of the pump housing. This contributes to a compact design of the high-pressure fuel pump, as a low overall height can be achieved.

[0016] Possible embodiments of the invention are explained below with reference to the accompanying drawings, wherein identical or functionally equivalent elements are provided with identical reference numerals. They show: Fig. 1 is a schematic representation of a fuel system for an internal combustion engine; and Fig. 2 is a longitudinal section of an embodiment of the high-pressure fuel pump.

[0017] Figure 1 shows a schematic representation of a fuel injection system 10 for an internal combustion engine. Fuel is supplied from a fuel tank 12 via a suction line 14 by means of a pre-feed pump 16 into a low-pressure line 18 and from there to a low-pressure connection 20 (inlet 20) of a high-pressure fuel pump 22.

[0018] A fuel, e.g., gasoline, is compressed to a high pressure in the high-pressure fuel pump 22 and fed through a high-pressure connection 24 (outlet 24) via a high-pressure rail 25 and a high-pressure injector 26 to a combustion chamber 28 of the internal combustion engine. There, the fuel can be mixed with air supplied via an intake manifold 30 and ignited, e.g., by a spark generated by a spark plug.

[0019] Optionally, a portion of the fuel supplied via the low-pressure connection 20 of the high-pressure fuel pump 22 can, after flowing through the high-pressure fuel pump 22 without compression, be led out of the high-pressure fuel pump 22 again through a further low-pressure connection 32 and into the intake manifold 30 via a low-pressure injector 34. There, this portion of the fuel can mix with the supplied air before the mixture reaches the combustion chamber 28.

[0020] The high-pressure fuel pump 22 is designed as a piston pump, wherein a piston 36 can be driven, for example, by means of a cam disk 38 (direction of movement oriented vertically in the drawing).

[0021] The high-pressure fuel pump 22 will be described below with reference to Figure 2 explained in more detail.

[0022] The high-pressure fuel pump 22 has a pump housing 40 on or in which the components of the high-pressure fuel pump 22 are arranged. A pump cover 42 is mounted on the pump housing 40, in particular in a manner that cannot be removed without destruction. The pump cover 42 can be connected, for example, welded, to the pump housing 40. The pump cover 42, together with the pump housing 40, defines a low-pressure chamber 44. A low-pressure damper 45 is arranged in the low-pressure chamber 44.

[0023] A connection piece (inlet piece) is mounted on the side of the pump housing 40 at the inlet 20 (in Fig.2(not shown). The inlet 20 or the inlet-side connection piece is fluidly connected to the low-pressure chamber 44 via a connecting channel (not shown). The low-pressure chamber 44 is fluidly connected to the delivery chamber 50, in which the piston 36 is arranged, via a further connecting channel (not shown). This allows fuel to be guided from the low-pressure chamber 44 into the delivery chamber 50.

[0024] A connection piece 52 (outlet piece 52) is attached to the side of the pump housing 40 at the outlet 24. An outlet valve 54 and a pressure relief valve 56 are also provided at the outlet 24. The pressure relief valve 56 is arranged in a recess 58 formed in the pump housing 40. The outlet valve 54 is arranged in a recess 60 formed in the pump housing 40.

[0025] In the example, the recesses 58, 60 are oriented parallel to each other and are fluidly connected to the outlet 24 and the connecting piece 52, respectively. The outlet valve 54 is also fluidly connected to the delivery chamber 50 via a passage 62. The pressure relief valve 56 consists in particular of several components and can, for example, have a valve body 64, a ball 66, a spring receptacle 68 and / or a spring 70 (see enlarged partial section in Fig.2 ).

[0026] The recess 58, in which the pressure relief valve 56 is arranged, is fluidly connected to the low-pressure chamber 44 via a channel 72. The channel 72 is formed in a wall 74 of the pump housing 40, which delimits the low-pressure chamber 44 toward the pump housing 40 and separates the low-pressure chamber 44 from the recess 58.

[0027] The channel 72 extends, in particular, in a straight line along a central longitudinal axis 76. The channel 72 has the same or a larger cross-section at its end facing the low-pressure chamber 44 than at its end facing the recess 58 with the pressure relief valve 56.

[0028] In the example, the central longitudinal axis 76 of the channel 72 and the central longitudinal axis 77 of the low-pressure chamber 44 and / or the central longitudinal axis 78 of the pump housing 40 are arranged parallel to one another or congruent to one another.

[0029] In the example, the channel 72 has a first axial channel section 80 and a second axial channel section 82, wherein the second channel section 82 faces the low-pressure chamber 44 and has a larger cross-section than the first channel section 80. In the example, the channel 72 is designed as a stepped channel in the form of a stepped bore that widens towards the low-pressure chamber 44 (smaller diameter in the first channel section 80 than in the second channel section 82). In embodiments not shown, the cross-section of the channel 72 can taper along the central longitudinal axis 76 of the channel 72 towards the low-pressure chamber 44.

[0030] The delivery chamber 50, in which the piston 36 runs, is separated from the recess 58, in which the pressure relief valve 56 is arranged, by a wall 84. The wall 84 is designed without any channels. In other words, there is no direct flow connection between the delivery chamber 50 and the recess 58 through the wall 84.

[0031] The central longitudinal axis 86 of the recess 58 for the pressure relief valve 56 is oriented orthogonally to the central longitudinal axis 78 of the pump housing 40.

[0032] By an upward movement of the piston 36, the medium (fuel) located in the delivery chamber 50 is displaced and conveyed via the outlet valve 54, which opens away from the delivery chamber 50, and the outlet 24 or the connecting piece 52, for example, to a high-pressure rail 25. The pressure relief valve 56 is connected antiparallel to the outlet valve 54 (opposite opening direction) to prevent excessively high pressures in the high-pressure area of ​​the fuel system 10.

Claims

1. High-pressure fuel pump (22) for a fuel injection system (10) of an internal combustion engine, having a pump housing (40) and a pump cover (42) mounted on the pump housing (40), which, together with the pump housing (40), delimits a low-pressure chamber (44), wherein a recess (58) is formed in the pump housing (40) in which a pressure-limiting valve (56) is arranged, wherein the recess (58) is fluidically connected to the low-pressure chamber (44) via a channel (72), wherein the channel (72) has, at its end facing the low-pressure chamber (44), the same or a larger cross section than at its end facing the recess (58) and characterized in that the central longitudinal axis (76) of the channel (72) and the central longitudinal axis (77) of the low-pressure chamber (44) are congruent to one another.

2. High-pressure fuel pump (22) according to Claim 1, characterized in that the central longitudinal axis (76) of the channel (72) and the central longitudinal axis (78) of the pump housing (40) are arranged parallel to one another or are congruent to one another.

3. High-pressure fuel pump (22) according to Claim 1 or 2, characterized in that the cross section of the channel (72) along the central longitudinal axis (76) of the channel (72) increases conically towards the low-pressure chamber (44).

4. High-pressure fuel pump (22) according to Claim 1 or 2, characterized in that the channel (72) has a first axial channel portion (80) and a second axial channel portion (82), wherein the second channel portion (82) faces the low-pressure chamber (44) and has a larger cross section than the first channel portion (80).

5. High-pressure fuel pump (22) according to one of the preceding claims, characterized in that a delivery chamber (50) is provided in which a piston (36) runs, wherein the wall (84), which separates the delivery chamber (50) and the recess (58), in which the pressure-limiting valve (56) is arranged, from one another, has a channel-free design.

6. High-pressure fuel pump (22) according to one of the preceding claims, characterized in that the central longitudinal axis (86) of the recess (58) for the pressure-limiting valve (56) is oriented orthogonally to the central longitudinal axis (78) of the pump housing (40).

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