High-pressure fuel pump

Abstract

High-pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising a fuel connection (11) for supplying fuel, an outlet (34) for discharging compressed fuel, a pump housing (12), a delivery chamber (16) arranged in the pump housing and delimited by a pump piston (18) displaceable in the pump housing (12), an inlet valve (14) arranged between the fuel connection (11) and the delivery chamber (16) and opening towards the delivery chamber (16), an outlet valve (20) arranged between the delivery chamber (16) and the outlet (34) and opening away from the delivery chamber (16), and a pressure relief valve (22) arranged between the delivery chamber (16) and the outlet (34) and opening towards the delivery chamber (16), wherein the pressure relief valve (22) has a valve seat body (38) on which a valve seat (42) is formed, wherein the Pressure relief valve (22) has a valve element (44),which comes into sealing contact with the valve seat (42), wherein the pressure relief valve (22) has a valve spring (52) which exerts a force acting in the direction of the valve seat (42) on the valve element (44), characterized in that the valve spring (52) is arranged on the side of the valve seat (42) opposite the delivery chamber (16).

Description

State of the art

[0001] High-pressure fuel pumps having the features of the preamble of claim 1 are already known from DE 10 2004 013 307 A1, DE 10 2019 202 271 A1, DE 10 2019 200 025 A1, DE 10 2018 218 919 A1, DE10 2018 209 033 A1 and DE 10 2021 203 663 A1 of the applicant.

[0002] Such high-pressure fuel pumps have become widespread in recent years, particularly in connection with the injection of fuels such as gasoline, ethanol and methanol. Disclosure of the invention

[0003] The present invention is based primarily on the finding that, during continuous operation of such high-pressure fuel pumps, functionally impairing wear phenomena can occur on the valve element and / or on the valve seat body of the pressure relief valve. These wear phenomena are caused by friction between the valve element and the valve seat body in the region of the valve seat. In particular, this wear can be accompanied by a drop in the opening pressure of the pressure relief valve. The high-pressure fuel pump is then only able to compress fuel to a high pressure to a limited extent.

[0004] The present invention is further based on the finding that this friction between the valve element and the valve seat body in the region of the valve seat is largely due to mechanical excitations of the valve spring, which are subsequently transmitted to the valve element and the valve seat body. These mechanical excitations of the valve spring can, for example, be lateral mechanical excitations.

[0005] It was further recognized that such excitations of the valve spring in the delivery chamber are particularly strong and can be caused at least in part by cavitation phenomena that can occur when the external pressure acting on the fuel falls below a vapor pressure of the fuel during suction phases of the pump.

[0006] According to the invention, the valve spring is arranged on the side of the valve seat opposite the delivery chamber. In other words, the valve spring is not arranged in the delivery chamber, but rather in the outlet-side area of ​​the high-pressure fuel pump, the high-pressure area, where the external pressure acting on the fuel is always high during operation of the high-pressure fuel pump.

[0007] As a result of this measure, no cavitation occurs in the area of ​​the valve spring, and the valve spring therefore experiences no significant mechanical stress. Wear on the valve element and / or the valve seat body of the pressure relief valve is thus reduced by the invention, and the function of the pressure relief valve and thus also of the high-pressure fuel pump is unaffected for a longer period.

[0008] Unlike the aforementioned prior art, the high-pressure fuel pump according to the invention eliminates the need to arrange the valve spring of the pressure relief valve within a dead volume of the delivery chamber. The dead volume of the delivery chamber can therefore be reduced, thus improving the delivery efficiency of the high-pressure fuel pump.

[0009] In one embodiment, the valve element comprises a sealing section that rests against the valve seat when the pressure relief valve is closed, and further comprises a transmission section that transmits a force emanating from the valve spring to the sealing section. The sealing section is then—figuratively speaking—drawn into the valve seat by the transmission section.

[0010] In order to achieve a good sealing effect, it can be provided that the sealing section as a whole or in a partial area has a spherical or conical shape, for example with the shape of a truncated cone that tapers in the direction away from the conveying chamber.

[0011] The transmission section can advantageously have a rod-shaped configuration, either entirely or in part, and extend through the valve seat body. In this way, it can effectively transmit forces between the sealing section arranged on the valve seat on the delivery chamber side and the valve spring arranged on the side of the valve seat opposite the delivery chamber.

[0012] The valve element can advantageously be composed of the spherical or conical part constituting the sealing section and the rod-shaped part constituting the transmission section, for example by welding two corresponding parts.

[0013] A sleeve, for example, a sleeve in the shape of a round disc with a central hole, can advantageously be fixed to the transmission section. Fixing can be achieved, for example, by pressing or screwing on, or by similar methods known per se.

[0014] Advantageously, the valve spring can then be clamped between the sleeve and the valve seat body.

[0015] In order to specifically adjust the force transmitted by the spring and thus the opening pressure of the pressure relief valve to predefined values, it can be provided that the force with which the spring is tensioned is determined while the sleeve is being fixed to the transmission section, and that the fixing of the sleeve to the transmission section is carried out based on the determined force in such a way that this force assumes a predetermined value. For example, the sleeve can be advanced until this force assumes a desired value, or depending on the result of a single initial force measurement, a certain advance of the sleeve can occur before it is finally fixed relative to the transmission section.

[0016] It is possible and advantageous to first pre-assemble a pressure relief valve assembly consisting of the valve seat body, the valve element, and the sleeve fixed to the valve element. The pressure relief valve assembly can then be fixed in a bore in the pump housing connected to the discharge chamber. This allows the functional properties of the pressure relief valve to be easily established and tested before installation in the pump housing.

[0017] The pre-assembled pressure relief valve assembly can then be fixed in a bore of the pump housing connected to the delivery chamber, for example by pressing the pressure relief valve assembly over an outer circumference of the valve seat body into the bore of the pump housing connected to the delivery chamber.

[0018] Exemplary embodiments of the invention are explained below with reference to the drawings. In the drawings: Fig. 1 a longitudinal section through a high-pressure fuel pump according to the invention, Fig. 2 an enlargement of the area of ​​the high-pressure fuel pump Fig. 1, in which the pressure relief valve is located.

[0019] In Fig. 1 shows a high-pressure fuel pump 10 for an internal combustion engine (not shown in detail). The high-pressure fuel pump 10 has a substantially cylindrical pump housing 12, in or on which the essential components of the high-pressure fuel pump 10 are arranged. Thus, the high-pressure fuel pump 10 has a fuel connection 11, an inlet and quantity control valve 14, a delivery piston 18 arranged in a delivery chamber 16 and capable of reciprocating motion by a drive shaft (not shown), an outlet valve 20, and a pressure relief valve 22.

[0020] In the housing 12, there is a first cylindrical channel 24 which extends coaxially to the delivery chamber 16 and the delivery piston 18 and which leads from the delivery chamber 16 to a second cylindrical channel 26 which is arranged at an angle of 90° to the first channel 24 and in which the pressure relief valve 22 is accommodated. A longitudinal axis of the pump housing 12 carries in Fig. 1 the reference numeral 28, a longitudinal axis of the second cylindrical channel 26 bears the reference numeral 29. In Fig. 1 a pressure damper 30 is arranged in the pump housing 12 at the top.

[0021] The longitudinal axis 29 of the second cylindrical channel 26 extends in the axial direction to which reference is made in the context of the invention with regard to the pressure relief valve 22 and its subcomponents.

[0022] During operation, the delivery piston 18 sucks in a fuel, for example a fuel such as gasoline, via the inlet and quantity control valve 14 into the delivery chamber 16 during a suction stroke. During a delivery stroke, the fuel in the delivery chamber 16 is compressed and expelled via the outlet valve 20, for example into a high-pressure region 32, for example to a fuel rail, where the fuel is stored under high pressure. An outlet 34 designed as an outlet nozzle is provided in the high-pressure region 32. The quantity of fuel expelled during a delivery stroke is adjusted by the electromagnetically actuated inlet and quantity control valve 14.

[0023] As already mentioned above, the pressure relief valve 22, when open, connects the high-pressure area 32 to the delivery chamber 16 of the high-pressure fuel pump 10. The pressure relief valve 22 opens when a pressure difference between the outlet-side high-pressure area 32 and the delivery chamber 16 of the high-pressure fuel pump 10 exceeds a limit value. The pressure relief valve 22 thus prevents the pressure in the outlet-side high-pressure area 32 from becoming excessively high. To implement this function, the opening pressure of the pressure relief valve 22 is selected accordingly and ensured for the service life of the high-pressure fuel pump.

[0024] The subcomponents of the pressure relief valve 22 according to the embodiment will now be described with additional reference to Fig. 2 explained in more detail.

[0025] The pressure relief valve 22 includes a sleeve-like valve seat body 38, which is pressed into the cylindrical channel 26. At the Fig. 2 On the right side of the valve seat body 38, a conical valve seat 42 is formed, which cooperates sealingly with a spherical sealing section 44a of the valve element 44.

[0026] The valve element 44 further comprises an approximately cylindrically shaped transmission section 44b which is welded to the sealing section 44a and which is guided through the valve seat body 38, i.e. in the Fig. 2 protrudes on the left side of the valve seat body 38.

[0027] In the example, on the end area facing away from the valve seat body 38 (in the Fig. 2 left) of the transmission section 44b, an approximately plate-shaped sleeve 46 is fixed by pressing. A valve spring 52 is clamped between the valve seat body 38 and the sleeve 46. The valve spring 52 causes a force that pulls the sealing section 44a of the valve element 44 into the sealing seat 42 of the valve seat body 38. If a pressure prevailing in the high-pressure area 32 of the high-pressure fuel pump 10 can overcome this force, then the valve element is displaced in the Fig. 2 to the right, the pressure relief valve 22 opens, and fuel from the high-pressure area 32 is diverted into the delivery chamber 16. In this way, the pressure in the high-pressure area 32 is limited by the pressure relief valve 22.

[0028] As already explained at the beginning, during operation, the pressure in the high-pressure region 32 of the high-pressure fuel pump 10 is always high, in particular higher than the vapor pressure of the fuel located in the high-pressure region 32. Therefore, unlike, for example, in the pumping chamber 16, cavitation certainly does not occur in the high-pressure region 32. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2004 013 307 A1

[0001] DE 10 2019 202 271 A1

[0001] DE 10 2019 200 025 A1

[0001] DE 10 2018 218 919 A1

[0001] DE 10 2018 209 033 A1

[0001] DE 10 2021 203 663 A1

[0001]

Claims

[1] High-pressure fuel pump (10) for a fuel system for an internal combustion engine, comprising a fuel connection (11) for supplying fuel, an outlet (34) for discharging compressed fuel, a pump housing (12), a delivery chamber (16) arranged in the pump housing and delimited by a pump piston (18) displaceable in the pump housing (12), an inlet valve (14) arranged between the fuel connection (11) and the delivery chamber (16) and opening towards the delivery chamber (16), an outlet valve (20) arranged between the delivery chamber (16) and the outlet (34) and opening away from the delivery chamber (16), and a pressure relief valve (22) arranged between the delivery chamber (16) and the outlet (34) and opening towards the delivery chamber (16), wherein the pressure relief valve (22) has a valve seat body (38) on which a valve seat (42) is formed, wherein the pressure relief valve (22) has a valve element (44),which comes into sealing contact with the valve seat (42), wherein the pressure relief valve (22) has a valve spring (52) which exerts a force acting in the direction of the valve seat (42) on the valve element (44), , characterized by that the valve spring (52) is arranged on the side of the valve seat (42) opposite the delivery chamber (16). [2] High-pressure fuel pump according to claim 1, characterized by that the valve element (44) has a sealing section (44a) which comes into contact with the valve seat (22) and further has a transmission section (44b) which transmits a force emanating from the valve spring (52) to the sealing section (44a). [3] High-pressure fuel pump according to claim 2, characterized by that the sealing section (44a) has a spherical or conical shape as a whole or in a partial area. [4] High-pressure fuel pump according to claim 2 or 3, characterized bythat the transmission section (44b) as a whole or in a partial area has a rod-shaped configuration and is guided through the valve seat body (38). [5] High-pressure fuel pump according to one of claims 2, 3 or 4, characterized by that the valve element (44) is composed of a spherical or conical part which represents the sealing section (44a) and a rod-shaped part which represents the transmission section (44b). [6] High-pressure fuel pump according to claim 5, characterized by that the spherical or conical part is connected to the rod-shaped part by welding. [7] High-pressure fuel pump according to one of claims 2 to 6, characterized by that a sleeve (46) is fixed on the transmission section (44b) and that the valve spring (52) is clamped between the sleeve (46) and the valve seat body (38). [8] Method for producing a high-pressure fuel pump (10) according to claim 7, wherein firstly a pressure relief valve assembly is pre-assembled, which consists of the valve seat body (38), the valve element (44) and the sleeve (46) fixed on the valve element, and wherein subsequently the pressure relief valve assembly is fixed in a bore (26) of the pump housing (12) connected to the delivery chamber (16). [9] Method according to claim 8, wherein the pressure relief valve assembly is fixed in the bore (26) of the pump housing (12) connected to the delivery chamber (16) by pressing the pressure relief valve assembly over an outer circumference of the valve seat body (38) in the bore (26) of the pump housing (12) connected to the delivery chamber (16). [10] Method, in particular according to one of claims 8 or 9, for producing a high-pressure fuel pump (10) according to claim 7, wherein it is provided that during the fixing of the sleeve (46) on the transmission section, the force with which the valve spring (52) is tensioned is determined, and that the fixing of the sleeve (46) on the transmission section (44b) is carried out based on the determination of the force in such a way that this force assumes a predetermined value.

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