EP1483503A1

EP1483503A1 - Fuel pump for an internal combustion engine

Info

Publication number: EP1483503A1
Application number: EP02779213A
Authority: EP
Inventors: Uwe Kuhn; Markus Nieslony; Rolf Pojar
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-01-11
Filing date: 2002-11-14
Publication date: 2004-12-08
Anticipated expiration: 2022-11-14
Also published as: US6951165B2; JP4418681B2; EP1483503B1; WO2003058064A1; US20040096337A1; DE50212815D1; DE10200792A1; JP2005514557A

Abstract

The invention relates to a fuel pump for an internal combustion engine, said fuel pump comprising a housing (14) in which a piston (16) is guided. Part of a working chamber is defined by the piston (16). An eccentric shaft or camshaft acts on the piston (16), at the opposite end thereof to the working chamber. A pre-stressing element (30) acts on the piston (16) against the eccentric shaft or camshaft. The aim of the invention is to reduce the production costs of the fuel pump. To this end, a supporting element (40) is provided, separate from the piston (16), said supporting element being connected to the end region (36) of the piston (16) which faces the eccentric shaft or camshaft. The pre-stressing element (30) is supported by said supporting element.

Description

Fuel umpe for an internal combustion engine

State of the art

The invention relates to a fuel pump for an internal combustion engine, with a housing, with at least one piston, with a work space which is delimited in some areas by the piston, with an eccentric or camshaft which acts on the piston at least indirectly at its end opposite the work space, and with a biasing element which acts on the piston against the eccentric or camshaft at least indirectly.

Such a fuel pump is known from the market, for example as a radial piston pump. A central eccentric shaft is mounted in a housing. A cam ring is placed on an eccentric section of the eccentric shaft. Flat surfaces are formed around the circumference of the cam ring, on which sliding shoes bear. The sliding shoes are connected to a cylindrical piston which, with its end opposite the eccentric shaft, delimits a working space. A compression spring presses the piston against the sliding block or the flat surface of the cam ring.

In the known fuel pump, three cylinders are provided, each of which has a corresponding piston and a corresponding working space. With a movement In the eccentric shaft, the piston is made to move back and forth, which compresses the fuel present in the work area and ejects it via appropriate valve devices, for example into a fuel rail ("rail") of an internal combustion engine.

In the fuel pump known from the market, the compression spring is supported on an end section of the piston which has a significantly larger diameter than the shaft of the piston. The end section and the piston skirt are in one piece and, for example, turned out of solid. To guide the compression spring and to reduce tension in the transition areas between the piston skirt and the end section, it is necessary to provide recesses and shoulders with different diameters. In connection with the associated large diameter differences, this leads to complex machining, which has a disadvantageous effect on the production costs for the fuel pump.

The object of the present invention is therefore to develop a fuel pump of the type mentioned in the introduction in such a way that it can be manufactured more cost-effectively.

This object is achieved in a fuel pump of the type mentioned at the outset in that a support element separate from the piston is provided, which is connected to the end region of the piston facing the eccentric or camshaft and on which the pretensioning element is supported.

Advantages of the invention

In the fuel pump according to the invention, the piston of the fuel pump is of significantly simpler construction. In the simplest case, it can consist of a simple straight cylinder that has no change in diameter. An elaborate one Machining the piston is therefore not necessary, which significantly reduces the cost of the fuel pump according to the invention.

The biasing element, usually a compression spring, which acts on the piston against the eccentric or camshaft, is supported in the fuel pump according to the invention via a separate support element which is firmly connected to the piston. The connection of the support element to the piston can be done in different ways: For example, it is possible to press on, shrink on, weld, glue and other fastening variants, which are explained in more detail below. Although an additional step is required to attach the support element to the piston, this is less expensive than the above-mentioned. machining of the piston.

Advantageous further developments of the inventive fuel pump ^¬ are specified in subclaims.

First, it is proposed that the support element comprises a support ring. Such is very easy to manufacture, which also benefits the cost of the fuel pump.

It is proposed that the lintel element is in two parts and comprises a support ring connected to the end region of the piston and an intermediate element pushed onto the piston between the prestressing element and the protection ring. This makes it possible to choose a material for the support ring that can be optimally attached to the piston. In contrast, a material can be selected for the intermediate element, which can be shaped in a simple manner in such a way that the prestressing element is optimally held and guided. This development thus additionally increases the functional reliability of the fuel pump according to the invention. In another development, it is proposed that the support element rests with a section on a retaining ring, which is received in some areas in a groove in the end region of the piston facing the eccentric or camshaft. This mounting option is very simple and can also be removed again by destroying the locking ring.

It is also proposed that the fuel pump comprise a guide sleeve which is movable with the piston and which cooperates with a guide section which is fixed to the housing. This takes into account the fact that transverse forces have to be dissipated into the pump housing during operation. Although these transverse forces can also be absorbed via the guidance of the piston in the housing, it is more advantageous, particularly for reasons of tightness, if the piston is only loaded in the axial direction. This is made possible by the guide sleeve according to the invention, since it derives the transverse forces from the eccentric or camshaft, bypassing the piston, directly from the guide section fixed to the housing. A fuel pump designed in this way therefore works with high efficiency.

Such a fuel pump can be produced inexpensively, in particular if the support element is in one piece with the guide sleeve.

The support element can also have a radially inwardly directed ring collar which is supported on a radially outwardly directed ring collar of the piston. The support element is thus pressed by the prestressing element with its ring collar against the corresponding ring collar of the piston. The connection of the support element to the piston which is created in this way enables the piston to be safely reset after a compression stroke without Lateral forces from the support element are introduced into the piston. This is particularly advantageous if the support element is in one piece with the guide sleeve.

Another advantageous embodiment of the fuel pump according to the invention provides that the fuel pump comprises a base part which bears on the end face of the piston facing the eccentric or camshaft. Such a base part also makes it possible to design the piston from a material which is optimal for its function as a compression stamp. On the other hand, it is possible to make the base part from a material which can absorb the relative movements which occur due to the rotation of the cam or eccentric shaft relative to the piston without being subjected to excessive wear. Furthermore, by means of appropriate material pairings, the frictional forces between the base part and the eccentric or camshaft can be reduced, which leads to lower transverse forces. This development therefore has additional advantages with regard to the function of the fuel pump according to the invention.

It is again preferred if the guide sleeve has a radially inwardly directed annular collar which. protrudes into an annular space lying between the support element and the base part. As a result, the guide sleeve is held securely in the axial direction, and at the same time the assembly of the fuel pump according to the invention is simple and thus also inexpensive.

It is also advantageous if the base part has a raised section which covers the supporting element axially in some areas, and the supporting element is firmly connected to the base part via the raised section. Such a base part is thus cup-shaped and is opposed to that by the raised section Support element automatically centered during assembly. The base part can be fastened to the support element, for example, by means of a locking ring which is inserted in grooves on the one hand m the jacket surface of the support element and on the other hand m the jacket surface of the raised section.

An advantageous development of the fuel pump according to the invention is also characterized in that the support element has at least one bend, which engages around the base part from the outside and holds it axially. Such a bend is simple to manufacture and facilitates assembly of the fuel pump as a whole, since the base part is captively connected to the support element.

drawing

Particularly preferred exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawing. The drawing shows:

1 shows a section through a region of a first exemplary embodiment of a radial piston fuel pump;

FIG. 2 shows a partial section through a detail of the fuel pump from FIG. 1;

FIG. 3 shows a partial section through components of a second exemplary embodiment of a fuel pump;

FIG. 4 shows a partial section through components of a third exemplary embodiment of a fuel pump;

FIG. 5 shows a partial section through components of a fourth exemplary embodiment of a fuel pump; FIG. 6 shows a section through components of a fifth exemplary embodiment of a fuel pump;

FIG. 7 shows an enlarged detail from FIG. 6; and

8 shows a section through components of a sixth embodiment of a fuel pump.

Description of the embodiments

In Fig. 1, a fuel pump bears the overall reference number 10. It is a radial piston pump with three cylinders 12a, 12b and 12c, only the components of the cylinder 12a being explained in detail below. In the drawing, only those components of the cylinder 12a are provided with reference numerals. The components of the cylinders 12b and 12c are identical to those of the cylinder 12a.

The radial piston pump 10 comprises a housing 14. A piston 16 is accommodated in an axially displaceable manner in a bore (without reference number). The piston 16 delimits a working space 18 with its upper end face in FIG. 1. An inlet valve 20 can connect the working space 18 to a fuel line (not shown). An outlet valve, also not shown, can connect the working space 18 to a fuel line and further to a high-pressure manifold (“rail”).

An eccentric shaft with an eccentric section 22 is mounted in the housing 14 of the radial piston pump 10. A cam ring 24 is placed on the eccentric section 22 and has a plane machined contact surface 26 in the area of the individual cylinders 12a-12c. A base part 28 designed as a sliding shoe becomes indirect and even closer way to be represented acted upon by a compression spring 30 against the contact surface 26. The compression spring 30 is received in an annular space 32 of the housing 14. This is delimited radially inwards by a pipe section-like guide section 34. In this piston 16 is in turn axially slidably and fluid-tight. The connection of the piston 16 to the base part 28 and the piston-side support of the compression spring 30 will now be explained in detail in connection with FIG. 2:

The piston 16 has an end region 36 which faces the eccentric section 22 or the cam ring 24 and which has a larger diameter than the rest of the piston 16. The end region 36 is received in regions in a complementary recess 38 in the base part 28. An annular disk-shaped support element 40 bears against a shoulder 41 formed between the piston shaft 39 and the end region 36 of the piston 16. The support element 40 has a radially inwardly extending holding section 42 and an axially extending guide section 44. These two sections 42 and 44 center the support element 40 with respect to the longitudinal axis of the piston 16.

In its radially outer region, the support element 40 has a groove-like depression 46, which extends in the circumferential direction and “opens” in the axial direction, in which the lower end of the compression spring 30 is received in FIG. 2. In this way, the compression spring 30 is also centered radially. At its radially outer edge, the support element 40 has a plurality of hook-like U bends 48 distributed over its circumference, which. encompass a shoulder 50, which is formed on the outer lateral surface of the base part 28, with some play. In this way, the base part 28 is held axially on the piston 16.

The radial piston pump 10 works as follows: By a Rotation of the eccentric shaft with the eccentric section 22 moves the center of the cam ring 24 along a circular path. As a result, the contact surfaces 26 of the cam ring 24 move on the one hand in the axial direction of the respective cylinders 12 and also laterally to the longitudinal axis of the respective cylinders 12. The piston 16 is moved into a via the base part 28 by the axial movement of the contact surfaces 26 and the restoring force of the compression spring 30 axial reciprocating movement. As a result, fuel is either sucked into the working space 18, or the fuel present in the working space 18 is compressed and expelled to the fuel collecting line.

3 shows a modification of the area of the piston 16 facing the eccentric section 22. Such wear. Elements and areas which have equivalent functions to those shown in FIGS. 1 and ^' 2 have the same reference numerals. They are not explained in detail again.

In contrast to the FIGS. 1 and 2, the end region 36 of the piston 16 shown in FIG. 3 has no other diameter than the shaft 39 of the piston 16. The piston 16 is therefore even easier to manufacture. Furthermore, the support element 40 is formed in two parts. It comprises a support ring 52 which is pressed onto the piston 16. In this way, the support ring 52 is fixed axially immovably on the piston 16. In Fig. 3 from above, an intermediate element 54 is pushed onto the piston 16, which is centered with a holding section 42 and a guide section 44 relative to the support ring 52.

In Figs. 2 and 3, there is a certain amount of play on the one hand between the support element 40 and on the other hand between the base part 28. In other exemplary embodiments, not shown, the base part is connected to the piston 16 without play. Due to the above-described movement of the contact surfaces 26 lateral to the longitudinal axis of the respective cylinder 12, lateral forces are also introduced into the base part 28 by the contact surface 26 due to the friction present. In the radial piston pump 10 above (FIGS. 1 and 2) or in the formation of the components according to FIG. 3, these lateral forces are introduced into the piston 16 and from this into the guide section 34 of the housing 14. In the following exemplary embodiments according to FIGS. 4-8 options are set out with which the piston 16 can be held free of lateral forces. It is again pointed out here that such components and parts which have functions equivalent to components and parts already described have the same reference numerals and are not explained again in detail.

In Figs. 4 and 5 embodiments are shown with a so-called "cup guide". This comprises a cup-shaped guide part 56, which rests with the outside of a base 58 on the contact surface 26 of the cam ring 24. The end region 36 of the piston 16 is supported on the inside of the base 58 of the cup-shaped guide part 56. A circumferential wall 60 of the cup-shaped guide part 56 is guided with its outside in a guide section 62 of the housing 14. Of the contact surface ^'26 in operation of the radial piston pump 10 in the bottom 58 of the cup-shaped guide member 56 introduced lateral forces are so discharged through the peripheral wall 60 directly into the guide portion 62 of the housing fourteenth The piston 16 thus remains free of lateral forces.

The support member is formed in FIG. 4 as a one-piece support ring 40 which is pressed onto the ^'piston 16. The end region 36 of the piston 16 has no changes in diameter. In the exemplary embodiment according to FIG. 5, the support element 40 is again in two parts a support ring 52, which is pressed onto the piston 16, and an intermediate element 54.

In the case of the figures 6 and 7 illustrated exemplary embodiment, the end region 36 of the piston 16 again has a larger diameter than the shaft 39 of the piston 16 and thus forms a radially outwardly directed annular collar 64. This annular collar 64 is on the one hand between a radially inwardly directed annular collar 66 Guide sleeve 68 and axially guided a base part 28 abutting the end face of the piston 16.

The base part 28 has on its radially outer edge a circumferential raised section 70 which covers the guide sleeve 68 in regions in the axial direction. As is apparent from Fig. ^'7, on the one hand on the inside of the raised portion 70 a peripheral groove 72 and the other hand on the outside of the guide sleeve 68 has a circumferential groove 74 are provided. A locking ring 76 is received on the one hand in the groove 72 and on the other hand in the groove 74, so that the guide sleeve 68 and the base part 28 are firmly connected to one another.

The guide sleeve 68 is slidably guided on a guide section 62 of the housing 14 in the axial direction. Thus, transverse forces which are introduced into the base part 28 via the contact surface 26 of the cam ring 24 are introduced into the guide section 62 of the housing 14 via the guide sleeve 68. As can be seen from FIG. 6, the guide section 62 is part of a bush 14a, which is shrunk into a housing region 14b. The guide sleeve 68 has a radially outwardly directed annular collar 44, on which the compression spring 30 is supported. In this way, the piston 16 is acted upon indirectly by the restoring force of the compression spring 30. The guide sleeve 68 thus also forms the support element 40 at the same time. Yet another embodiment is shown in FIG. 8. In this exemplary embodiment, the end region 36 of the piston 16 again has the same diameter as the shaft 39 of the piston 16. The support element 40 is designed as a support ring, the holding section 42 of which rests on a locking ring 78 which is in a circumferential groove (without reference number) in the end region 36 of the piston 16. Here, too, transverse forces are again kept away from the piston 16 by a guide sleeve 68 cooperating with a guide section 62 of the housing 14.

The base part 28 has an upper section 80 with a smaller diameter in FIG. 8 and a lower section 82 with a larger diameter in FIG. 8. The upper side of the section 80 of the base part 28 bears against the end face of the piston 16 facing it. Between the section 82 of the base part 28 and the support element 40 there is an annular space 84, into which an annular collar 66 of the guide sleeve 68, which is directed radially inward, projects. Furthermore, the radially outer edge of the section 82 of the base part 28 bears against the inner wall of the guide sleeve 68. In this way, transverse forces are also kept away from the piston 16 here. A roller 86 is also present between the base part 28 and the cam ring 24, which is not shown in FIG. 8. The lateral forces are minimized again by this.

Claims

Expectations

1. Fuel pump (10) for an internal combustion engine, with a housing (14), with at least one piston (16), with a working space (18) which is delimited in some areas by the piston (16), with an eccentric (22) or Camshaft, which acts on the piston (16) at least indirectly at its end (36) opposite the working chamber (18), and with a pretensioning element (30), which acts at least indirectly on the piston (16) against the eccentric (22) or camshaft , characterized in that a support element (40) separate from the piston (16) is provided, which is connected to the end region (36) of the piston (16) facing the eccentric (22) or camshaft and on which the prestressing element (30 ) supports.

2. Fuel pump (10) according to claim 1, characterized in that the support element (40) comprises a support ring (52).

3. Fuel pump (10) according to claim 2, characterized in that the support element (40) is in two parts and a with the end region (36) of the piston (16) connected support ring (52) and between the biasing element (30) and support ring (52 ) on the piston (16) pushed intermediate element (54).

4. Fuel pump (10) according to one of the preceding claims, characterized in that the support element (40) A section (42) bears against a retaining ring (78) which is received in some areas in a groove in the end area (36) of the piston (16) facing the eccentric (22) or camshaft.

5. Fuel pump (10) according to one of the preceding claims, characterized in that it comprises a guide sleeve (68) which is movable with the piston (16) and which cooperates with a guide section (62) fixed to the housing.

6. Fuel pump (10) according to claim 5, characterized in that the support element (40) with the guide sleeve (68) is in one piece.

7. Fuel pump (10) according to one of the preceding claims, characterized in that the support element (40) has a radially inwardly directed annular collar (66), which is supported on a radially outwardly directed annular collar (64) of the piston (16) ,

8. Fuel pump (10) according to one of the preceding claims, characterized in that it comprises a base part (28) which bears on the end face of the piston (16) facing the eccentric (22) or camshaft.

9. Fuel pump according to one of claims 5 to 7 together with claim 8, characterized in that the guide sleeve

(68) has a radially inwardly directed annular collar (66) which projects into an annular space (84) located between support element (40) and base part (28).

10. Fuel pump (10) according to one of claims 8 or 9, characterized in that the base part (28) has a raised portion (70) which covers the support element (40) axially in regions, and the support element (40) is firmly connected to the base part (28) via the raised section (70).

11. Fuel pump (10) according to claim 9, characterized in that the support element (40) has at least one bend (48) which engages around the base part (28) from the outside and holds it axially.