EP3894687B1 - High-pressure fuel pump - Google Patents

Description

State of the art

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.

Such a high-pressure fuel pump is from the DE 10 2005 007 806 A1 known and includes a pump housing and a pressure relief valve.

This is accommodated in a recess in the pump housing. In an open state, the pressure relief valve connects a high-pressure outlet to a delivery chamber of the high-pressure fuel pump. The pressure relief valve opens when a pressure difference between the high-pressure outlet and the delivery chamber of the high-pressure fuel pump exceeds a limit value. The pressure relief valve therefore prevents the pressure in the high-pressure outlet from being unacceptably high. The pressure relief valve therefore essentially has two functions: on the one hand, to control the pressure from the high-pressure outlet when a maximum permissible pressure is exceeded, and on the other hand, to seal the high-pressure outlet and the components connected to it (e.g. a fuel rail) from the delivery chamber at a pressure below that maximum permissible pressure. WO 2018/164026 A1 and DE 10 2008 059638 A1 reveal high pressure fuel pumps.

Disclosure of the invention

The problem on which the invention is based is solved by a high-pressure fuel pump with the features of claim 1. Advantageous developments of the invention are specified in the subclaims.

The high-pressure fuel pump according to the invention is used to deliver fuel in a fuel injection system of an internal combustion engine. Gasoline or diesel is preferably used as fuel. The high-pressure fuel pump compresses the fuel to a high pressure and delivers it, for example, to a fuel rail to which injection devices are connected, which inject the fuel directly into assigned combustion chambers of the internal combustion engine. The high-pressure fuel pump includes a pressure relief valve. The pressure relief valve limits the pressure on or in a high-pressure outlet of the high-pressure fuel pump to a maximum permissible value. If the pressure prevailing there exceeds the opening pressure of the pressure relief valve, the pressure relief valve opens so that fuel is removed from the high pressure outlet.

The high-pressure fuel pump also includes a pump housing which has a drive-side end area. It goes without saying that the use of the term “front area” in no way means that the pump housing must have a rotationally symmetrical shape. Nevertheless, the pump housing as a whole has a longitudinal axis that runs parallel to a delivery piston. The drive-side end region is that end region of the pump housing that points towards a drive of the delivery piston. Such a drive usually includes a camshaft or an eccentric shaft.

According to the invention, it is proposed that the pressure relief valve is arranged in a discharge flow path in the pump housing, which opens into the drive-side end region of the pump housing just mentioned. In this way, wear-relevant pressure pulsations from a delivery chamber of the high-pressure fuel pump are avoided, as can occur when the discharge flow path opens into the delivery chamber. In addition, the dead volume in the delivery chamber of the high-pressure fuel pump is significantly reduced compared to a discharge flow path opening into the delivery chamber, whereby the degree of delivery of the high-pressure fuel pump can be increased. The housing strength of the high-pressure fuel pump can also be improved at critical points by rearranging the pressure relief valve in the pump housing of the high-pressure fuel pump be increased. Overall, this increases the efficiency of the high-pressure fuel pump and increases its reliability and service life.

According to the invention it is provided that it has a stepped delivery piston and that the discharge flow path opens into a step space in which the step of the delivery piston is arranged and which is formed on the drive-side end region of the pump housing. The step space is usually sealed from the drive and the lubricants present there by a seal holder and a piston seal and is connected via a flow path to a low-pressure area of the high-pressure fuel pump. The opening of the discharge flow path into the step space creates a reliable relief option for the high-pressure outlet in the event of an opening pressure relief valve, without the risk of fuel entering the drive and the lubricants present there.

According to the invention, a fluid space is formed between an upper end area of the pump housing opposite the drive-side end area and a hood-like housing cover carried by the upper end area, in which a membrane pressure damper is accommodated.

In a further development of the invention it is provided that the pressure relief valve is designed as a spring-loaded check valve.

This is inexpensive to produce and works reliably. It also has a small size.

In a further development of the invention it is provided that a longitudinal axis of the pressure relief valve is arranged parallel to a longitudinal axis of a delivery piston. In comparison to previous arrangements of the pressure relief valve (for example those arrangements in which the pressure relief valve is arranged radially or tangentially to the longitudinal axis of the delivery piston and thus also to the pump housing), this allows a reduction in the overall height of the high-pressure fuel pump, so that it can also be used in installation situations with cramped conditions space conditions can be used.

In a further development of the invention it is provided that the pressure relief valve is inserted into the discharge flow path from the mouth on the drive-side end region. This considerably simplifies the assembly of the pressure relief valve, since the front area on the drive side is usually very easily accessible.

In a further development of the invention it is provided that the pressure relief valve is held in a press fit in the discharge flow path. In this way, the pressure relief valve can be mounted and held easily and reliably.

In a further development of the invention it is provided that a section of the pressure relief valve, in particular a valve body, is formed by a section of the valve housing. For example, the valve body can be made directly from the housing material or incorporated directly into the housing. This reduces the number of components to be manufactured and joined or pressed, thereby simplifying production.

In a further development of the invention, it is provided that the high-pressure outlet is arranged laterally on the pump housing, viewed in an axial direction (i.e. in the direction of the longitudinal axis) of the pump housing, and that an outlet flow path, which leads from a delivery chamber to the high-pressure outlet, in the axial direction of the pump housing is arranged laterally from a section of the discharge flow path that opens into the high-pressure connection. This also allows the overall height of the high-pressure fuel pump to be reduced again.

In a further development of the invention it is provided that the discharge flow path comprises two at least approximately orthogonal and intersecting blind bores, one of which extends from the high-pressure outlet in a substantially radial or tangential direction of the pump housing, and the other of which extends from the drive side Front area extends in a substantially axial direction of the pump housing. Such blind holes can be easily realized, which means that the manufacturing costs of the high-pressure fuel pump can be kept low.

Figur 1

einen teilweisen Schnitt durch eine Kraftstoff-Hochdruckpumpe mit einem Druckbegrenzungsventil;

Figur 2

eine perspektivische Seitenansicht auf einen Hochdruckauslasses der Kraftstoff-Hochdruckpumpe von Figur 1; und

Figur 3

Komponenten des Druckbegrenzungsventils von Figur 1.

A possible embodiment of the invention is explained below with reference to the drawing. Show in the drawing:

Figure 1

a partial section through a high-pressure fuel pump with a pressure relief valve;

Figure 2

a perspective side view of a high-pressure outlet of the high-pressure fuel pump Figure 1 ; and

Figure 3

Components of the pressure relief valve from Figure 1 .

In Figure 1 a high-pressure fuel pump for an internal combustion engine, not shown, has the overall reference number 10. The high-pressure fuel pump 10 has an essentially cylindrical pump housing 12, in or on which the essential components of the high-pressure fuel pump 10 are arranged. The high-pressure fuel pump 10 has an inlet/quantity control valve 14, a delivery piston 22 which projects into a delivery chamber 18 with a first end region 16 and can be set in a back and forth movement at a second end region 20 by a drive shaft (not shown).

There is a flat area on the side of the pump housing 12, which forms a high-pressure outlet 24. This is about one outside the cutting plane of Figure 1 lying and therefore in Figure 1 Invisible outlet valve can be connected to the delivery chamber 18. An outlet connection 26 is attached to the high-pressure outlet 24. This is fluidly connected to a high-pressure region 28, which can be, for example, a fuel rail to which a plurality of injection devices are connected, which inject the fuel directly into assigned combustion chambers of the internal combustion engine.

Although the pump housing 12 is not exactly rotationally symmetrical, it nevertheless has a longitudinal axis 30. An in Figure 1 The upper end region 31 of the pump housing 12 carries a hood-like housing cover 32, to which an inlet connection 34 is attached, which is connected to a low-pressure region 36. The low-pressure area 36 can include, for example, an electric pre-feed pump. Between the upper end region 31 of the pump housing 12 and the housing cover 32, a fluid space (without reference number) is formed, in which a membrane pressure damper 38 is accommodated.

The delivery piston 22 is designed as a stepped piston with an in Figure 1 upper section with larger diameter and an in Figure 1 lower section with smaller diameter. A step or paragraph between the two Sections contributes in Figure 1 overall the reference number 40. As shown Figure 1 can be seen is located at the Figure 1 shown position of the delivery piston 22, the step 40 just outside of the pump housing 12, in a so-called "step space" 42, which is between an in Figure 1 lower drive-side end region 44 of the pump housing 12 and a seal holder 46 made as a sheet metal part, which is held in a press fit in a tubular fastening socket 48 of the pump housing 12 on its drive-side end region 44. The seal holder 46 carries a piston seal 50, which seals the step space 42 from the drive, not shown, which is arranged below the second end region 20 of the delivery piston 22.

In the pump housing 12 there is a discharge flow path 52, which in the present case is formed, for example, by two mutually orthogonal and intersecting blind holes 54 and 56. The blind hole 54 extends in a substantially radial direction of the pump housing 12 from the high-pressure outlet 24, and the blind hole 56 extends from the drive-side end region 44 in a substantially axial direction of the pump housing 12. The axial blind hole 56 is designed as a stepped bore a section (without reference number) with a larger diameter extending from the drive-side end region 44. A pressure relief valve 58 is arranged in this, which opens towards the drive-side end region 44.

The pressure relief valve 58 is designed as a spring-loaded check valve. It includes (see Figure 3 ) a valve element 60 designed as a valve ball, although other valve elements can of course also be used, for example a conical valve element. A valve spring 62, which in the present case is designed as a helical compression spring, carries on its in Figure 1 upper and in Figure 3 left end a ball holder 64 and acts on the valve element 60 against a valve body 66, on which a valve seat 68 which cooperates sealingly with the valve element 60 when the pressure relief valve 58 is closed is formed. The end of the valve spring 62 facing away from the valve body 66 is supported on a sleeve 70 which, like the valve body 66, is pressed into the blind hole 56, i.e. held there in a press fit.

You recognize it Figure 1 that a longitudinal axis (not shown) of the pressure relief valve 58 runs parallel to the longitudinal axis 30 of the pump housing 12. You can also recognize it Figure 1 that the components of the pressure relief valve 58 are inserted from the mouth on the drive-side end region 44 into the axial blind hole 56 of the discharge flow path 52.

Out of Figure 2 It can be seen that an outlet flow path 72, which leads from the delivery chamber 18 via the outlet valve already mentioned above to the high-pressure outlet 24, seen in the axial direction of the pump housing 12, to the side of the section opening into the high-pressure outlet 24, namely the radial blind hole 54, the discharge flow path 52 is arranged. The lateral offset contributes in Figure 1 the reference number 74. The exhaust valve is also in Figure 2 a spoke-shaped end plate 76 is visible. You recognize it Figure 2 also that the outlet flow path 72 opens into the overall circular high-pressure outlet 24 laterally in the middle but offset downwards, whereas the discharge flow path 52 with the radial blind hole 54 in Figure 2 laterally off-center on the left and slightly above the middle. It goes without saying that, in principle, other arrangements of the mouths of the outlet flow path 72 and the discharge flow path 52 are also possible.

During operation, fuel, for example gasoline or diesel, is sucked into the delivery chamber 18 via the inlet and quantity control valve 14 by the delivery piston 18 during a suction stroke. During a delivery stroke, the fuel located in the delivery chamber 18 is compressed and expelled into the high-pressure area 28 via the outlet valve and the outlet port 26. The amount of fuel that is ejected during a delivery stroke is adjusted by the electromagnetically actuated inlet and quantity control valve 14.

If there is an impermissible overpressure in the high-pressure area 28, the pressure relief valve 58 opens, allowing fuel to flow from the high-pressure area 28 into the step space 42. The step space 42 can be connected via flow paths (not shown here), for example to an area located upstream of the delivery space 18, which in turn is connected to the low-pressure area 36.

Claims (8)

1. High-pressure fuel pump (10) for a fuel injection system of an internal combustion engine, with a pump housing (12) which has a drive-side end region (44), a high-pressure outlet (24) and a pressure relief valve (58) which discharges fuel from the high-pressure outlet (24) in an open state, the pressure relief valve (58) being arranged in a discharge flow path (52) in the pump housing (12), which discharge flow path (52) opens into the drive-side end region (44) of the pump housing (12), the high-pressure fuel pump having a step conveying piston (22), the discharge flow path (52) opening into a step chamber (42), in which the step (40) of the conveying piston (22) is arranged and which is configured on the drive-side end region (44) of the pump housing (12), and a fluid chamber, in which a diaphragm pressure damper (38) is received, being configured between an upper end region (31), lying opposite the drive-side end region (44), of the pump housing (12) and a hood-like housing cover (32) which is supported by the upper end region (31) .
2. High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the pressure relief valve (58) is configured as a springloaded check valve.
3. High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that a longitudinal axis of the pressure relief valve (58) is arranged parallel to a longitudinal axis (30) of a conveying piston (22).
4. High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the pressure relief valve (58) or at least one part thereof is inserted from the orifice on the drive-side end region (44) into the discharge flow path (52).
5. High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the pressure relief valve (58) or at least one part thereof is held in the discharge flow path (52) in the press fit.
6. High-pressure fuel pump according to at least one of the preceding claims, characterized in that a portion of the pressure relief valve, in particular a valve body, is formed by a portion of the valve housing.
7. High-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the high-pressure outlet (24) is arranged laterally on the pump housing (12) as viewed in an axial direction of the pump housing (12), and in that an outlet flow path (72) which leads from the conveying chamber (18) to the high-pressure outlet (24) is arranged laterally, as viewed in the axial direction of the pump housing (12), from a portion of the discharge flow path (52) which opens into the high-pressure outlet (24).
8. High-pressure fuel pump (10) according to Claim 8, characterized in that the discharge flow path (52) comprises two orthogonal blind bores (52, 54) which intersect one another and of which one runs from the high-pressure outlet (24) in a substantially radial or tangential direction of the pump housing (12), and of which the other runs from the drive-side end region (44) in a substantially axial direction of the pump housing (12) .

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