CN113167202A

CN113167202A - High-pressure fuel pump

Info

Publication number: CN113167202A
Application number: CN201980082246.9A
Authority: CN
Inventors: M·哈特韦格
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-12-13
Filing date: 2019-11-18
Publication date: 2021-07-23
Anticipated expiration: 2039-11-18
Also published as: EP3894687B1; EP3894687A1; CN113167202B; KR20210099585A; DE102018221702A1; WO2020120075A1; ES2976573T3

Abstract

The invention relates to a high-pressure fuel pump (10) for a fuel injection system of an internal combustion engine, comprising a pump housing (12) having an end-side region (44) on the drive side; a high-pressure outlet (24) and a pressure-limiting valve (58) which, in the open state, conducts fuel out of the high-pressure outlet (24). The invention proposes that the pressure-limiting valve (58) is arranged in a discharge flow path (52) in the pump housing (12), which discharge flow path opens into an end face region (44) of the pump housing (12) on the drive side.

Description

High-pressure fuel pump

Technical Field

The present 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.

Background

Such a high-pressure fuel pump is known from DE 102005007806 a1 and comprises a pump housing and a pressure limiting valve. The pressure limiting valve is accommodated in a recess of the pump housing. The pressure limiting valve connects the high-pressure outlet with the delivery chamber of the high-pressure fuel pump in the open state. In this case, the pressure limiting valve opens when the pressure difference between the high-pressure outlet and the delivery chamber of the high-pressure fuel pump exceeds a limit value. Thus, an inadmissibly high pressure is prevented in the high-pressure outlet by the pressure-limiting valve. The pressure limiting valve thus basically has two functions: on the one hand, the pressure of the high-pressure outlet is controlled to be reduced when the maximum permissible pressure is exceeded, and on the other hand, the high-pressure outlet and the component connected thereto (for example, a fuel rail) are sealed off from the delivery chamber when the pressure falls below the maximum permissible pressure.

Disclosure of Invention

The problem on which the invention is based is solved by a high-pressure fuel pump having the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

The high-pressure fuel pump according to the invention is used for delivering fuel in a fuel injection system of an internal combustion engine. Gasoline or diesel is preferably used as the fuel. The high-pressure fuel pump compresses the fuel to a high pressure and delivers the fuel, for example, to a fuel rail, to which injection devices are connected, which inject the fuel directly into the respective associated combustion chamber of the internal combustion engine. The high-pressure fuel pump comprises a pressure-limiting valve. The pressure at or in the high-pressure outlet of the high-pressure fuel pump is limited to a maximum permissible value by a pressure limiting valve. If the pressure prevailing there exceeds the opening pressure of the pressure-limiting valve, the pressure-limiting valve opens, so that fuel is conducted out of the high-pressure outlet.

The high-pressure fuel pump further comprises a pump housing having an end-side region on the drive side. Here, of course, the use of the term "end-side region" does not mean that the pump housing must have a rotationally symmetrical shape. The pump housing as a whole still has a longitudinal axis extending parallel to the delivery piston. In this connection, the end face region on the drive side is the end region of the pump housing which is directed toward the drive of the delivery piston. Such drive devices mostly comprise a camshaft or an eccentric shaft.

According to the invention, the pressure-limiting valve is arranged in a discharge flow path in the pump housing, which discharge flow path opens into the end region of the pump housing, which is just mentioned on the drive side. In this way, wear-related pressure pulsations from the delivery chamber of the high-pressure fuel pump, as may occur if the discharge flow path leads into the delivery chamber, are avoided. Furthermore, the dead volume (Totvolumen) in the delivery chamber of the high-pressure fuel pump is significantly reduced in relation to the discharge flow path into the delivery chamber, as a result of which the volumetric efficiency of the high-pressure fuel pump can be increased. The housing strength of the high-pressure fuel pump at critical points can also be increased by rearranging the pressure limiting valve in the pump housing of the high-pressure fuel pump. As a result, the efficiency of the high-pressure fuel pump is increased overall and the reliability and the service life of the high-pressure fuel pump are increased.

In one embodiment of the invention, it is provided that the high-pressure fuel pump has a stepped delivery piston, and the discharge flow path opens into a stepped chamber, in which the steps of the delivery piston are arranged and which is formed on the end face region of the pump housing on the drive side. The stepped chamber is mostly sealed off from the drive and the lubricant present there by a seal retainer and a piston seal and is connected via a flow path to a low-pressure region of the high-pressure fuel pump. By opening the discharge flow path into the step chamber, a reliable unloading possibility is provided for the high-pressure outlet when the pressure-limiting valve is open, without having to worry about the danger of fuel being used for the drive and lubricant being introduced there.

In one embodiment of the invention, it is provided that the pressure relief valve is designed as a spring-loaded check valve. Such a check valve can be produced inexpensively and works reliably. Furthermore, it has a small structural size.

In one embodiment of the invention, it is provided that the longitudinal axis of the pressure-limiting valve is arranged parallel to the longitudinal axis of the delivery piston. This allows a reduction in the overall height of the fuel high-pressure pump compared to previous arrangements of the pressure-limiting valve (for example, arrangements in which the pressure-limiting valve is arranged radially or tangentially relative to the longitudinal axis of the delivery piston and thus also relative to the pump housing), so that the fuel high-pressure pump can also be installed in installation situations with narrow spatial conditions.

In one embodiment of the invention, it is provided that the pressure-limiting valve is inserted into the discharge flow path from a passage on the end-side region on the drive side. The assembly of the pressure relief valve is thereby significantly simplified, since the end face region on the drive side is usually very easily accessible.

In one embodiment of the invention, it is provided that the pressure-limiting valve remains press-fitted in the discharge flow path. In this way, the pressure relief valve can be assembled and held simply and reliably.

In one embodiment of the invention, a section of the pressure relief valve, in particular the valve body, is formed by a section of the valve housing. For example, the valve body can be produced directly from the housing material or machined directly into the housing. This reduces the number of parts to be produced and joined or pressed together, thereby simplifying production.

In one embodiment of the invention, it is provided that the high-pressure outlet is arranged laterally of the pump housing, as seen in the axial direction of the pump housing (i.e. in the direction of the longitudinal axis), and that the outlet flow path leading from the delivery chamber to the high-pressure outlet is arranged laterally of the section of the discharge flow path leading into the high-pressure connection, as seen in the axial direction of the pump housing. This also reduces the overall height of the fuel high-pressure pump.

In one embodiment of the invention, it is provided that the discharge flow path comprises two at least approximately orthogonal and intersecting blind bores, wherein one blind bore extends from the high-pressure outlet in a substantially radial or tangential direction of the pump housing, and wherein the other blind bore extends from the end face region on the drive side in a substantially axial direction of the pump housing. Such a blind hole can be realized in a simple manner, as a result of which the production costs of the high-pressure fuel pump can be kept low.

Drawings

One possible embodiment of the present invention is explained below with reference to the drawings. The figures show:

FIG. 1 is a partial cross-section of a high pressure fuel pump having a pressure limiting valve;

FIG. 2 is a perspective side view of a high pressure outlet of the high pressure fuel pump of FIG. 1; and

fig. 3 parts of the pressure limiting valve of fig. 1.

Detailed Description

In fig. 1, a high-pressure fuel pump for an internal combustion engine, which is not shown in detail, is designated in its entirety by reference numeral 10. The high-pressure fuel pump 10 has a generally substantially cylindrical pump housing 12, in or on which the main components of the high-pressure fuel pump 10 are arranged. Namely the high-pressure fuel pump 10, has an inlet/quantity control valve 14, a delivery piston 22 which projects with a first end region 16 into a delivery chamber 18 and can be set in a reciprocating motion on a second end region 20 by a drive shaft, not shown.

At the side of the pump housing 12 there is a flattened portion which forms a high pressure outlet 24. This high-pressure outlet can be connected to the delivery chamber 18 via an outlet valve which is located outside the sectional plane of fig. 1 and is therefore not visible in fig. 1. An outlet connection 26 is fixed to the high-pressure outlet 24. The outlet connection is in fluid connection with a high-pressure region 28, which may be, for example, a fuel rail to which a plurality of injection devices are connected, which inject fuel directly into an associated combustion chamber of the internal combustion engine.

Although the pump housing 12 is not exactly rotationally symmetrical, it still has a longitudinal axis 30. In fig. 1, the upper end region 31 of the pump housing 12 carries a hood-shaped housing cover 32, to which an inlet connection 34 is fastened, which is connected to a low-pressure region 36. The low pressure region 36 may include, for example, an electric prefeed pump. A fluid chamber (no reference numeral) in which a diaphragm pressure damper 38 is accommodated is formed between the upper end region 31 of the pump housing 12 and the housing cover 32.

The delivery piston 22 is designed as a stepped piston having an upper section with a larger diameter in fig. 1 and a lower section with a smaller diameter in fig. 1. The step or shoulder between the two sections is generally indicated by reference numeral 40 in fig. 1. As can be seen from fig. 1, in the position of the delivery piston 22 shown in fig. 1, the step 40 is located almost outside the pump housing 12, in particular in a so-called "step chamber" 42, which is formed between an end region 44 of the pump housing 12 on the drive side, which is located in the lower position in fig. 1, and a seal retainer 46, which is produced as a sheet metal molding, which is held in a press fit in a tubular fastening socket 48 of the pump housing 12 on the end region 44 of the pump housing on the drive side. The seal holder 46 carries a piston seal 50 which seals the stepped chamber 42 against a drive device, not shown, which is arranged below the second end region 20 of the delivery piston 22.

In the pump housing 12, a discharge flow path 52 is present, which is formed in the present example by two

blind bores

54 and 56 which are orthogonal to one another and intersect. The blind hole 54 extends from the high-pressure outlet 24 in a substantially radial direction of the pump housing 12, and the blind hole 56 extends from the end-side region 44 on the drive side in a substantially axial direction of the pump housing 12. The axial blind hole 56 is embodied here as a stepped hole having a section (no reference numeral) of larger diameter, which starts from the end-side region 44 on the drive side. In this section, a pressure-limiting valve 58 is arranged, which opens toward the end-side region 44 on the drive side.

The pressure-limiting valve 58 is embodied as a spring-loaded check valve. It comprises a valve element 60 (see fig. 3) embodied as a valve ball, wherein, of course, other valve elements, for example conical valve elements, can also be used. The valve spring 62 is in the present case designed as a helical compression spring, which carries a ball retainer 64 at its upper end in fig. 1 and at its left end in fig. 3 and loads the valve element 60 against a valve body 66, on which a valve seat 68 is designed that interacts sealingly with the valve element 60 when the pressure-limiting valve 58 is closed. 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.

As can be seen in fig. 1, the longitudinal axis (not shown) of the pressure-limiting valve 58 extends parallel to the longitudinal axis 30 of the pump housing 12. It can also be seen from fig. 1 that the components of the pressure relief valve 58 are inserted from the opening on the end face region 44 on the drive side into the axial blind hole 56 of the discharge flow path 52.

As can be seen from fig. 2, the outlet flow path 72, which leads from the delivery chamber 18 via the above-mentioned outlet valve to the high-pressure outlet 24, is arranged laterally to the section of the discharge flow path 52 which leads into the high-pressure outlet 24, i.e. the radial blind bore 54, as viewed in the axial direction of the pump housing 12. The lateral displacement is indicated with reference numeral 74 in fig. 2. Also visible in fig. 2 is the spoke-like end plate 76 of the outlet valve. It can also be seen from fig. 2 that the outlet flow path 72 opens laterally centrally, but displaced downward, into the generally circular high-pressure outlet 24, while the outlet flow path 52 opens with the radial blind hole 54 laterally eccentrically to the left in fig. 2 and slightly above the center. Of course, other arrangements of the outlet flow path 72 and the through opening of the outlet flow path 52 are also possible in principle.

In operation, fuel, for example gasoline or diesel fuel, is drawn into the delivery chamber 18 by the delivery piston 18 through the inlet and the quantity control valve 14 during the suction stroke. During the delivery stroke, the fuel located in the delivery chamber 18 is compressed and discharged via the outlet valve and the outlet connection 26 into the high-pressure region 28. The quantity of fuel displaced in the delivery stroke is regulated by the solenoid-actuated inlet and the quantity control valve 14.

In the event of an inadmissible overpressure in the high-pressure region 28, the pressure-limiting valve 58 opens, as a result of which fuel can flow out of the high-pressure region 28 into the step chamber 42. The stepped chamber 42 can be connected via a flow path, not shown here, for example to a region upstream of the feed chamber 18, which in turn is connected to the low-pressure region 36.

Claims

1. A high-pressure fuel pump (10) for a fuel injection system of an internal combustion engine, having:

a pump housing (12) having an end-side region (44) on the drive side;

a high pressure outlet (24); and

a pressure-limiting valve (58) which, in the open state, conducts fuel out of the high-pressure outlet (24),

characterized in that the pressure-limiting valve (58) is arranged in a discharge flow path (52) in the pump housing (12), which discharge flow path opens into an end-side region (44) of the pump housing (12) on the drive side.

2. The high-pressure fuel pump (10) as claimed in claim 1, characterized in that it has a stepped delivery piston (22) and the discharge flow path (52) opens into a stepped chamber (42) in which a step (40) of the delivery piston (22) is arranged and which is formed on an end face region (44) of the pump housing (12) on the drive side.

3. The high-pressure fuel pump (10) as claimed in at least one of the preceding claims, characterized in that the pressure-limiting valve (58) is configured as a spring-loaded check valve.

4. The high-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the longitudinal axis of the pressure-limiting valve (58) is arranged parallel to the longitudinal axis (30) of the delivery piston (22).

5. The high-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the pressure-limiting valve (58) or at least a part thereof is inserted into the discharge flow path (52) from a passage on the drive-side end region (44).

6. The high-pressure fuel pump (10) according to at least one of the preceding claims, characterized in that the pressure-limiting valve (58) or at least a part thereof remains press-fitted in the discharge flow path (52).

7. The high-pressure fuel pump according to at least one of the preceding claims, characterized in that a section of the pressure-limiting valve, in particular a valve body, is formed by a section of the valve housing.

8. The 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 of the pump housing (12), seen in the axial direction of the pump housing (12), and an outlet flow path (72) leading from a delivery chamber (18) to the high-pressure outlet (24) is arranged laterally of a section of the discharge flow path (52) leading into the high-pressure outlet (24), seen in the axial direction of the pump housing (12).

9. The high-pressure fuel pump (10) according to claim 8, characterized in that the discharge flow path (52) comprises two orthogonal and intersecting blind bores (52, 54), wherein one blind bore extends from the high-pressure outlet (24) in a substantially radial or tangential direction of the pump housing (12), and wherein the other blind bore extends from the drive-side end region (44) in a substantially axial direction of the pump housing (12).