WO2009115357A1

WO2009115357A1 - Fuel pump

Info

Publication number: WO2009115357A1
Application number: PCT/EP2009/050751
Authority: WO
Inventors: Friedrich Boecking
Original assignee: Robert Bosch Gmbh
Priority date: 2008-03-17
Filing date: 2009-01-23
Publication date: 2009-09-24
Also published as: CN101978163A; EP2255089A1; EP2255089B1; DE102008000700A1

Abstract

A fuel pump (1) for a fuel injection system of air-compressing, self-igniting internal combustion engines comprises a first pump part (2) encompassing a gear pump, and a second pump part (3). The first pump part (2) is separated from the second pump part (3) by means of a housing part (16). A pump shaft (15) extends into the housing part (16) through an opening (22). A shaft sealing ring (31) which seals the first pump part (2) relative to the second pump part (3) is arranged in the opening (22). It is thus sufficient for the first pump part (2) to be covered by a cover (7) such that the first pump part (2) does not require a lid.

Description

description

Title fuel pump

State of the art

The invention relates to a fuel pump, in particular a pump arrangement with an external gear pump. Specifically, the invention relates to the field of fuel injection systems of air compressing, self-igniting internal combustion engines.

From DE 197 36 160 Al a pump arrangement for high-pressure fuel supply in fuel injection systems of internal combustion engines is known. The known pump arrangement is particularly suitable for a common rail injection system. The known pump arrangement comprises a radial piston pump with a drive shaft mounted in a pump housing and a low pressure pump upstream of the radial piston pump. The sealing between the designed as a gear pump low-pressure pump and the radial piston pump to the outside via sealing rings, wherein no additional seal is provided in the region of the drive train between the gear pump of the radial piston pump, since the internal lubrication of the radial piston pump via the conveyed medium fuel. As a result, leakage occurs in the region of the drive train from the gear pump into the interior of the radial piston pump.

The known from DE 197 36 160 Al pump arrangement has the disadvantage that a housing cover for the low pressure pump is required, which must be connected to the housing of the radial piston pump so that a reliable sealing effect is given. The structure of the known pump arrangement is therefore relatively complicated.

Disclosure of the invention

The fuel pump according to the invention with the features of claim 1 has the advantage that the structure of the fuel pump is simplified. Specifically, the Sealing of the first pump part can be simplified with the gear pump.

The measures listed in the dependent claims advantageous developments of the fuel pump specified in claim 1 are possible.

It is advantageous that the second pump part is configured as a high-pressure pump part, that the second pump part has a high-pressure pump housing and that the high-pressure pump housing comprises the housing part which separates the first pump part from the second pump part. In this case, the high-pressure pump part may have a radial piston pump, which is connected upstream of the gear pump of the first pump part. The first pump part can be attached in a relatively simple manner to the second pump part, for example, one or more pins or the like may be provided by means of which the first pump part is centered to the high-pressure pump housing of the second pump part. The requirements for the tightness are reduced, with a cover of the first pump part can be omitted. The first pump part may, for example, be surrounded by a relatively simply designed housing part, which is connected to the high-pressure pump housing.

Advantageously, the shaft sealing ring lies on its outer side on an inner surface of the opening, which is provided in the housing part separating the two pump parts. The inner surface of the opening is preferably designed as a cylinder jacket, so that it has a uniform curvature in the circumferential direction and a flat, in particular full-surface, concern of the shaft seal on the cylinder jacket-shaped inner surface of the opening is possible. As a result, a high sealing effect is achieved in the region between the inner surface of the opening and the outer side of the shaft sealing ring.

Furthermore, it is advantageous that the shaft sealing ring has on its inside an at least substantially circular sealing edge and that the shaft seal rests with its circular sealing edge on the pump shaft. As a result, a reliable seal in the region between the inside of the shaft sealing ring and the pump shaft is achieved even at relatively high speeds of the pump shaft. It is also advantageous that a clamping element is provided which presses the circular sealing edge of the shaft sealing ring circumferentially against the pump shaft. The clamping element thereby biases the shaft sealing ring with respect to the pump shaft, so that a high contact pressure in the radial direction is achieved on the pump shaft, which allows a high sealing effect. The clamping element can, for example, as a clamping ring be configured, which is elastically expanded in the shaft seal integrated. The clamping ring can be formed for example from a metal ring.

The first pump part may also have other elements in addition to one or more gears. For example, the first pump part may have a coupling, wherein the gear is operatively connected by means of the coupling with the pump shaft. The design of the pump shaft is adapted to the particular application. For example, the pump shaft may be designed as a polygonal shaft or as a camshaft.

Brief description of the drawings

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with corresponding reference numerals. It shows:

Fig. 1 is a side view of a fuel pump according to a

Embodiment of the invention and

Fig. 2 is a partial section through the fuel pump shown in Fig. 1 along the section line designated by Il.

Embodiments of the invention

Fig. 1 shows a fuel pump 1 in a side view according to a first embodiment of the invention. The fuel pump 1 can be designed in particular as a pump arrangement with an external gear pump for fuel injection systems of air-compressing, self-igniting internal combustion engines. A preferred use of the fuel pump 1 is for a fuel injection system with a fuel rail, a so-called common rail that stores diesel fuel under high pressure. However, the fuel pump 1 according to the invention is also suitable for other applications.

The fuel pump 1 has a first pump part 2 and a second pump part 3. In the illustrated side view, the second pump portion lies behind the first pump part 2 and is partially covered by the first pump part 2. At the second pump part 3, an intake manifold 4 is provided, via the fuel from a Tank or the like can be supplied. From the intake manifold 4, the fuel first passes through the second pump part 3 to a gear pump provided in the first pump part 2, which is connected upstream of a high-pressure pump provided in the second pump part 3. The first pump part 2 therefore has the function of a low-pressure pump, while the second pump part 3 mainly has the function of a high-pressure pump. The high-pressure pump of the second pump part 3 can be designed in particular as a radial piston pump.

The first pump part 2 has gears 5, 6, the position of which is illustrated in FIG. 1 by broken lines. The gears 5, 6 are covered by a cover 7, which is connected to fixed points 8A, 8B, 8C, 8D with a high-pressure pump housing 9 of the second pump part 3. The cover 7 preferably has essentially the function to cover the gears 5, 6 and possibly other components of the first pump part 2. However, the cover 7 has no special sealing means and is also provided with respect to the attachment to the high-pressure pump housing 9 with no special seal. The cover 7 is in particular not designed as a lid. Thus, the cover 7 can be easily manufactured. The first pump part 2 is thus designed without cover and thus also inexpensive to manufacture.

In Fig. 1, the position of a pump shaft 15 is also shown, which is illustrated by a broken line.

FIG. 2 shows a partial section through the fuel pump 1 shown in FIG. 1 along the section line designated by II. The cover 7 is connected to the fixing point 8 B with a housing part 16 of the high-pressure pump housing 9 of the second pump part 3. The connection can be made for example by means of a screw. The housing part 16 is in this embodiment part of the second pump part 3. The housing part 16 separates the first pump part 2 of the second pump part 3. In this case, the housing part 16 is disposed substantially between the pump parts 2, 3 of the fuel pump 1.

On the cover 7, a bearing pin 17 is formed, which has a bearing surface 18. On the bearing surface 18, a gear 19 is mounted, which is in engagement with a further gear 20 to form a gear pump.

The pump shaft 15 of the fuel pump 1 is inside the second pump part 3 stored and aligned axially with the gear 19. During operation of the fuel pump 1, the pump shaft 15 is driven so that it rotates about an axis 21. The pump shaft 15 protrudes through an opening 22 in the housing part 16. In this case, the pump shaft 15 protrudes partially into an adjacent to the housing part 16, bounded by the cover 7 space 23 of the first pump part 2. In the space 23, a clutch 24 is also arranged. An example designed as a two-flat end 25 of the pump shaft 15 is connected in a suitable manner with the coupling 24, so that via the coupling 24 is an operative connection between the pump shaft 15 and the gear 19. The end 25 of the pump shaft 15 is at least substantially in the space 23 of the first pump part. 2

On the housing part 16, an at least substantially cylindrical jacket-shaped inner surface 30 of the opening 22 is formed. The axis 21 of the pump shaft 15 is oriented at least substantially centrally to the cylinder jacket-shaped inner surface 30. In the opening 22, a shaft sealing ring 31 is arranged, which, viewed in the circumferential direction, has a profile opened on one side. In this embodiment, the profile is open to the second pump part 3. The shaft sealing ring 31 is configured such that an outer surface 32 of the shaft sealing ring 31, which is at least substantially cylindrical, is formed. The shaft sealing ring 31 rests flat on this outer surface 32 against the cylinder jacket-shaped inner surface 30 of the opening 22, so that a reliable sealing effect is provided in the region between the outer surface 32 of the shaft sealing ring 31 and the inner surface 30 of the opening 22.

Furthermore, the sealing ring has in profile a directed toward the pump shaft 15, triangular inner piece 33. The inner piece 33 of the shaft sealing ring 31 is designed such that a circular sealing edge 34 is provided on the shaft sealing ring 31, at which there is a contact between the shaft sealing ring 31 and the pump shaft 15. Thus, the shaft sealing ring 31 abuts circumferentially on the pump shaft 15 at the circular sealing edge 34. Furthermore, the shaft sealing ring 31 has a tensioning element designed as a clamping ring 35, which is inserted into the shaft sealing ring 31 which is open on one side in the profile. The clamping element 35 may be formed, for example, of a metal ring. The clamping element 35 is resiliently biased when introduced into the shaft sealing ring 31, wherein in the mounted state, which is shown in FIG. 2, a certain bias of the clamping element 35 of the shaft seal 31 continues. Thus, the sealing edge 34 is pressed against the pump shaft 15 on the inner piece 33 of the shaft sealing ring 31 by the bias of the clamping element 35. This results in a reliable seal between the shaft seal 31 and the pump shaft 15 in the region of the sealing edge 34th

Thus, the shaft seal 31 generates both in the region of its outer surface 32 to the housing part 16 out as well as in the region of its sealing edge 34 to the pump shaft 15 toward a reliable sealing effect. The shaft seal 31 therefore seals the second pump part 3 reliably relative to the first pump part 2. Thus, no or at most a slight leakage occurs from the second pump part 3 in the space 23 of the first pump part 2. This makes it possible for the first pump part 2 to be designed without seals, specifically that the first pump part 2 is designed to be cap-free. Therefore, a cover of the first pump part 2 with the cover 7 is sufficient.

The pump shaft 15 may be configured as a polygonal shaft or as a camshaft.

The fuel pump 1 of the embodiment of the invention has the advantage that the shaft seal 31 is integrated in the opening 22 of the housing part 16. The shaft seal 31 may be formed substantially of an elastic material, for example, an elastic plastic, wherein the clamping element 35 of the shaft seal 31 is preferably formed of a metallic material.

The invention is not limited to the described embodiments.

Claims

claims

1. A fuel pump (1), in particular pump arrangement with an external gear pump for fuel injection systems of air-compressing, self-igniting internal combustion engines, with a first pump part (2) having a gear pump, and at least a second pump part (3), wherein the first pump part (2) of the second pump part (3) is separated by means of at least one housing part (16) and wherein a pump shaft (15) projects through an opening (22) in the housing part (16), characterized in that in the opening (22) a shaft sealing ring (31 ) is arranged, which seals the first pump part (2) relative to the second pump part (3).

2. Fuel pump according to claim 1, characterized in that the second pump part (3) is designed as a high-pressure pump part, that the second pump part (3) has a high-pressure pump housing (9) and that the high-pressure pump housing (9) the housing part (16), which separates the first pump part (2) from the second pump part (3).

3. A fuel pump according to claim 1 or 2, characterized in that the shaft sealing ring (31) has an outer surface (32) and that the shaft seal (31) on its outer surface (32) at least indirectly on an inner surface (30) of the opening (22). is applied.

4. A fuel pump according to claim 3, characterized in that the inner surface (30) of the opening (22) on which the shaft seal (31) rests with its outer surface (32), at least substantially cylindrical jacket-shaped and that the shaft seal (31) flat against the cylinder jacket-shaped inner surface (30) of the opening (22).

5. Fuel pump according to one of claims 1 to 4, characterized in that the shaft seal (31) on an inner piece (33) has an at least substantially circular sealing edge (34) and that the shaft seal (31) with its circular sealing edge (34) on the pump shaft (15) is applied.

6. Fuel pump according to claim 5, characterized in that the shaft sealing ring (31) has a clamping element (35), in particular a clamping ring, and that the clamping element (35), the inner piece (33) of the shaft sealing ring (31) with the circular sealing edge (34 ) circumferentially against the pump shaft (15) presses.

7. A fuel pump according to claim 6, characterized in that the shaft seal (31) has a profile open on one side and that the clamping element (35) is inserted under a bias in the shaft seal (31).

8. Fuel pump according to one of claims 1 to 7, characterized in that the first pump part (2) is configured at least substantially seal-free.

9. A fuel pump according to claim 8, characterized in that the first pump part (2) is designed coverless.

10. Fuel pump according to one of claims 1 to 9, characterized in that the first pump part (2) has a coupling (24) and at least one gear (19), wherein the gear (19) by means of the coupling (24) with the pump shaft (15) is in operative connection.