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

Abstract

The present invention relates to a high-pressure fuel pump (22) for a fuel injection system (10) of an internal combustion engine, the high-pressure fuel pump having a pump housing (40) and a pump cover (42) mounted on the pump housing (40), the pump cover and the pump housing (40) defining a low-pressure chamber (44), wherein a groove (58) is formed in the pump housing (40) and a pressure limiting valve (56) is arranged in the groove, characterized in that the groove (58) is in flow communication with the low-pressure chamber (44) via a channel (72), wherein the channel (72) has the same cross-section at its end facing the low-pressure chamber (44) as at its end facing the groove (58) or has a larger cross-section than at its end facing the groove.

Description

Technical Field

[0001] This invention relates to a high-pressure fuel pump for a fuel injection system of an internal combustion engine. Background Technology

[0002] Such high-pressure fuel pumps are known, for example, by DE102018211237A1. This high-pressure fuel pump has a pump housing and a pump cover with a low-pressure chamber mounted thereon. A pressure-limiting valve is arranged in a recess constructed in the pump housing, wherein the recess is in flow communication with the delivery chamber where the piston operates. Another fuel pump is also known by DE10327411A1. In such high-pressure fuel pumps, unacceptable wear and cavitation may occur on the pressure-limiting valve. Summary of the Invention

[0003] The problem upon which this invention is based is solved by a high-pressure fuel pump according to the invention. Advantageous extensions of the invention are mentioned in the preferred embodiments.

[0004] According to the present invention, a high-pressure fuel pump for a fuel injection system of an internal combustion engine is provided, wherein the high-pressure fuel pump has a pump housing and a pump cover mounted on the pump housing (which can be non-destructively removed from the pump housing if necessary), the pump cover defining a low-pressure chamber together with the pump housing. A groove is formed in the pump housing, in which a pressure-limiting valve is arranged. The groove is in flow communication with the low-pressure chamber via a channel, wherein the channel has the same cross-section at its end facing the low-pressure chamber as at its end facing the groove with the pressure-limiting valve, or has a larger cross-section than at its end facing the groove with the pressure-limiting valve.

[0005] In this way, the pressure relief valve can be attached to the low-pressure chamber or to the low-pressure damper of the high-pressure fuel pump, which is located in the low-pressure chamber. This attachment reduces pressure pulsation / volume flow on the pressure relief valve's spring, thereby reducing wear and cavitation on the valve. Furthermore, cavitation caused by steam in the delivery chamber and the valve body's "breathing" can be avoided. Additionally, back pressure (staudruck) occurring in the high-pressure system under fault conditions of "full delivery" can be reduced, and the pump's delivery rate can be improved. The possible narrowing of the channel cross-section allows for acoustic advantages when necessary, as this alters the natural frequency of the groove.

[0006] It has been recognized that in conventional high-pressure fuel pumps, wear can be caused by axial and radial movement of the spring receiver and valve body "breathing" due to alternating pressure increases / decreases in the delivery chamber. It has also been recognized that cavitation can be caused by valve opening (due to the movement of the spring receiver) and steam generation in the delivery chamber during the suction phase. The movement of the spring receiver can be caused by axial and radial vibration of the spring due to pressure pulsations / volume flow in the delivery chamber. These issues can be avoided with the proposed high-pressure fuel pump.

[0007] Current high-pressure fuel pumps are, in particular, piston pumps. These pumps have a delivery chamber and a piston disposed therein, which can be driven to oscillate.

[0008] A channel for flow communication between the recess and the low-pressure chamber is constructed within the wall of the pump housing, which limits the low-pressure chamber toward the pump housing boundary and separates the low-pressure chamber from the recess. The channel may extend longitudinally along its center, particularly in a straight line. The recess is in flow communication with the outlet (i.e., the high-pressure side) of the high-pressure fuel pump, where a connecting flange may be provided, for example. The outlet valve may be arranged parallel to the pressure relief valve.

[0009] Pressure relief valves can have multiple functions. On one hand, they ensure that the pressure in the rail does not exceed a predetermined value (e.g., in the event of overpressure or thermal shutdown). This ensures that the allowable load on the components involved is not exceeded. Whenever the pressure in the rail is below the maximum allowable value, the pressure relief valve must seal relative to the low-pressure system or delivery chamber to prevent pressure loss in the rail. A pressure relief valve may include a valve body, a ball, a spring receiver, and / or a spring.

[0010] According to an extended embodiment, the central longitudinal axis of the channel and the central longitudinal axis of the low-pressure chamber and / or the central longitudinal axis of the pump housing can be arranged parallel to each other or coincident with each other. Thus, the channel can be arranged about the center of the pump housing or the low-pressure chamber. This facilitates proper attachment of the pressure relief valve to the low-pressure damper. Pressure pulsations on the pressure relief valve and the movement of the pressure relief valve spring can be further reduced.

[0011] According to one extension, the cross-section of the channel can be tapered towards the low-pressure chamber along the central longitudinal axis of the channel. This allows for acoustic advantages, as the natural frequency of the groove can be altered.

[0012] According to one extension, the channel may have a first axial channel segment and a second axial channel segment, wherein the second channel segment faces the low-pressure chamber and has a larger cross-section than the first channel segment. This can also dampen the excitation of vibrations, thereby achieving acoustic advantages. In other words, the channel is constructed as a stepped channel, such as a stepped aperture, where the channel widens towards the low-pressure chamber, or its larger cross-section (e.g., larger diameter) faces the low-pressure chamber.

[0013] According to an extended embodiment, a delivery chamber can be provided in which the piston operates, wherein the wall separating the delivery chamber and the recess in which the pressure-limiting valve is arranged is constructed without channels. This facilitates the efficient attachment of the pressure-limiting valve to the low-pressure chamber or to a low-pressure damper arranged within the low-pressure chamber. There is no direct flow communication from the delivery chamber to the recess via the wall.

[0014] According to one extended design, the central longitudinal axis of the groove for the pressure relief valve can be oriented orthogonally to the central longitudinal axis of the pump housing. This contributes to a compact configuration of the high-pressure fuel pump, as it allows for a low installation height. Attached Figure Description

[0015] In the following explanation, possible embodiments of the invention are illustrated with reference to the accompanying drawings, in which identical or functionally identical elements are provided with the same reference numerals. In the drawings:

[0016] Figure 1 A schematic diagram of a fuel system for an internal combustion engine is shown; and

[0017] Figure 2 A longitudinal cross-sectional view of an embodiment of the high-pressure fuel pump is shown. Detailed Implementation

[0018] Figure 1 A schematic diagram of a fuel injection system 10 for an internal combustion engine is shown. Fuel is supplied from the fuel tank 12 via the intake line 14 to the low-pressure line 18 by means of a pre-delivery pump 16, and from there to the low-pressure connector 20 (inlet 20) of the high-pressure fuel pump 22.

[0019] Fuel, such as gasoline, is compressed to high pressure in the fuel high-pressure pump 22 and supplied to the combustion chamber 28 of the internal combustion engine via high-pressure rail 25 and high-pressure injector 26 through high-pressure connector 24 (outlet 24). There, the fuel can be mixed with air supplied via intake pipe 30 and ignited, for example, by means of a spark generated by a spark plug.

[0020] Optionally, a portion of the fuel supplied via the low-pressure connector 20 of the high-pressure fuel pump 22, after flowing through the high-pressure fuel pump 22 without being compressed, can be introduced again from the high-pressure fuel pump 22 via another low-pressure connector 32 and through the low-pressure injector 34 into the intake pipe 30. There, this portion of the fuel can be mixed with the supplied air before the mixture reaches the combustion chamber 28.

[0021] The fuel high-pressure pump 22 is implemented as a piston pump, wherein the piston 36 can be driven, for example, by means of a cam disk 38 (the direction of movement is oriented vertically in the figure).

[0022] Below, refer to Figure 2 A more detailed explanation of the high-pressure fuel pump 22.

[0023] The high-pressure fuel pump 22 has a pump housing 40 on or within which components of the high-pressure fuel pump 22 are arranged. A pump cover 42 is mounted to the pump housing 40 in a manner that allows for non-destructive removal; it can be connected to the pump housing 40, for example, by welding. The pump cover 42, together with the pump housing 40, defines a low-pressure chamber 44. A low-pressure damper 45 is arranged within the low-pressure chamber 44.

[0024] On the side of the pump housing 40, a connecting pipe (inlet pipe) is installed on the inlet 20. Figure 2 (Not shown in the image). Inlet 20 or an inlet-side connecting pipe is in fluid communication with low-pressure chamber 44 via a connecting channel (not shown). Low-pressure chamber 44 is in fluid communication with delivery chamber 50, where piston 36 is arranged, via another connecting channel (not shown). Thus, fuel can be guided from low-pressure chamber 44 to delivery chamber 50.

[0025] On the side of the pump housing 40, a connecting pipe 52 (outlet pipe 52) is fixed to the outlet 24. An outlet valve 54 and a pressure relief valve 56 are also provided on the outlet 24. The pressure relief valve 56 is arranged in a recess 58 constructed in the pump housing 40. The outlet valve 54 is arranged in a recess 60 constructed in the pump housing 40.

[0026] In this example, grooves 58 and 60 are oriented parallel to each other and are in flow communication with outlet 24 or connecting pipe 52. Outlet valve 54 is also in flow communication with delivery chamber 50 via through-hole 62. Pressure relief valve 56 is particularly composed of multiple components and may, for example, have valve body 64, ball 66, spring receiver 68, and / or spring 70 (see...). Figure 2 (Enlarged portion of the local area).

[0027] The groove 58, in which the pressure limiting valve 56 is arranged, is in flow communication with the low-pressure chamber 44 via the channel 72. The channel 72 is constructed in the wall 74 of the pump housing 40, which limits the low-pressure chamber 44 toward the pump housing 40 and separates the low-pressure chamber 44 from the groove 58.

[0028] The channel 72 extends in a straight line along the central longitudinal axis 76. The end of the channel 72 facing the low-pressure chamber 44 has the same cross-section as or a larger cross-section than the end facing the groove 58 with the pressure relief valve 56.

[0029] In this example, the central longitudinal axis 76 of the channel 72, 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 each other or coincide with each other.

[0030] In this example, channel 72 has an axial first channel section 80 and an axial second 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 this example, channel 72 is constructed as a stepped channel in the form of a stepped aperture, which widens towards the low-pressure chamber 44 (the diameter in the first channel section 80 is smaller than the diameter in the second channel section 82). In an embodiment not shown, the cross-section of channel 72 may taper towards the low-pressure chamber 44 along the central longitudinal axis 76 of channel 72.

[0031] The delivery chamber 50, in which the piston 36 operates, is separated from the recess 58, where the pressure limiting valve 56 is arranged, by means of a wall 84. The wall 84 is constructed to be channelless. In other words, there is no flow communication between the delivery chamber 50 and the recess 58 through the wall 84.

[0032] The central longitudinal axis 86 of the groove 58 used for the pressure relief valve 56 is orthogonally oriented to the central longitudinal axis 78 of the pump housing 40.

[0033] By the upward movement of piston 36, the medium (fuel) located in delivery chamber 50 is compressed and delivered to high-pressure rail 25 via outlet valve 54, which is opened away from delivery chamber 50, and via outlet 24 or connecting pipe 52, for example. Pressure relief valve 56 is connected in the opposite parallel direction to outlet valve 54 (opposite opening direction) to prevent unacceptable high pressure from occurring in the high-pressure area of ​​fuel system 10.

Claims

1. A high-pressure fuel pump (22) for a fuel injection system (10) of an internal combustion engine, the high-pressure fuel pump having a pump housing (40) and a pump cover (42) mounted on the pump housing (40), the pump cover and the pump housing (40) together defining a low-pressure chamber (44), wherein, A groove (58) is constructed in the pump housing (40), and a pressure limiting valve (56) is arranged in the groove. The groove (58) is in flow communication with the low-pressure chamber (44) via a channel (72), wherein the channel (72) has the same cross-section at its end facing the low-pressure chamber (44) as at its end facing the groove (58) or has a larger cross-section than at its end facing the groove, wherein the central longitudinal axis (76) of the channel (72) and the central longitudinal axis (77) of the low-pressure chamber (44) coincide with each other.

2. The 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 each other or coincide with each other.

3. The high-pressure fuel pump (22) according to claim 1 or 2, characterized in that, The cross-section of the channel (72) tapers toward the low-pressure chamber (44) along the central longitudinal axis (76) of the channel (72).

4. The high-pressure fuel pump (22) according to claim 1 or 2, characterized in that, The channel (72) has an axial first channel section (80) and an axial second 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).

5. The high-pressure fuel pump (22) according to claim 1 or 2, characterized in that, A delivery chamber (50) is provided in which a piston (36) operates, wherein the wall (84) separating the delivery chamber (50) from the groove (58) in which the pressure relief valve (56) is arranged is constructed to be channelless.

6. The high-pressure fuel pump (22) according to claim 1 or 2, characterized in that, The central longitudinal axis (86) of the groove (58) for the pressure relief valve (56) is oriented orthogonally to the central longitudinal axis (78) of the pump housing (40).

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