RECIPROCATING PUMP

Abstract

The invention relates to a reciprocating pump (1) comprising a roller tappet (2) and a pump plunger (10) that is operatively connected to the roller tappet (2). The roller tappet (2) has a roller support (3), a roller (4) and a pin (5). A first bearing eye (6) and a second bearing eye (7) are formed in the roller support (3), the pin (5) being supported in the first bearing eye (6) and in the second bearing eye (7). The roller (4) is rotatably mounted on the pin (5). The pin (5) is mounted more resiliently in the first bearing eye (6) than in the second bearing eye (7).

Claims

1. A reciprocating pump (1) comprising a roller tappet (2) and a pump plunger (10) that is operatively connected to the roller tappet (2), wherein the roller tappet (2) has a roller support (3), a roller (4) and a pin (5), wherein a first bearing eye (6) and a second bearing eye (7) are formed in the roller support (3), wherein the pin (5) is mounted in the first bearing eye (6) and in the second bearing eye (7) and wherein the roller (4) is arranged on the pin (5) in a rotatable manner, characterized in that the pin (5) is mounted more flexibly in the first bearing eye (6) than in the second bearing eye (7).

2. The reciprocating pump as claimed in claim 1, characterized in that the roller support (3) is arranged in a tappet housing (15).

3. The reciprocating pump (1) as claimed in claim 1, characterized in that the first bearing eye (6) has a first width (b6) and the second bearing eye (7) has a second width (b7), wherein the first width (b6) is smaller than the second width (b7).

4. The reciprocating pump (1) as claimed in claim 1, characterized in that a cutout (8) is formed in the first bearing eye (6).

5. The reciprocating pump (1) as claimed in claim 4, characterized in that the cutout (8) is a reduction of the wall thickness of the first bearing eye (6).

6. The reciprocating pump (1) as claimed in claim 4, characterized in that the first bearing eye (6) is expandable in a flexible manner.

7. The reciprocating pump (1) as claimed in claim 4, characterized in that the cutout (8) is a continuous slot, so that the first bearing eye (6) comprises two bearing legs that are separated from one another on one side.

8. The reciprocating pump (1) as claimed in claim 4, characterized in that the pin (5) is clamped into the first bearing eye (6) and pressed into the second bearing eye (7).

9. The reciprocating pump (1) as claimed in claim 4, characterized in that a further cutout is formed in the second bearing eye (7).

10. The reciprocating pump (1) as claimed in claim 9, characterized in that the further cutout is a reduction of the wall thickness of the second bearing eye (7).

11. The reciprocating pump (1) as claimed in claim 9, characterized in that the pin (5) is clamped into the first bearing eye (6) and into the second bearing eye (7).

12. A fuel injection system having a reciprocating pump (1) as claimed in claim 1.

13. The fuel injection system as claimed in claim 12, characterized in that the roller support (3) is arranged in a tappet housing (15).

14. The fuel injection system as claimed in claim 12, characterized in that the first bearing eye (6) has a first width (b6) and the second bearing eye (7) has a second width (b7), wherein the first width (b6) is smaller than the second width (b7).

15. The fuel injection system as claimed in claim 12, characterized in that a cutout (8) is formed in the first bearing eye (6).

16. The fuel injection system as claimed in claim 15, characterized in that the cutout (8) is a reduction of the wall thickness of the first bearing eye (6).

17. The fuel injection system as claimed in claim 15, characterized in that the first bearing eye (6) is expandable in a flexible manner.

18. The fuel injection system as claimed in claim 15, characterized in that the cutout (8) is a continuous slot, so that the first bearing eye (6) comprises two bearing legs that are separated from one another on one side.

19. The fuel injection system as claimed in claim 15, characterized in that the pin (5) is clamped into the first bearing eye (6) and pressed into the second bearing eye (7).

20. The fuel injection system as claimed in claim 15, characterized in that a further cutout is formed in the second bearing eye (7).

Description

BRIEF DESRIPTION OF THE DRAWINGS

[0018] FIG. 1 shows a reciprocating pump having a roller tappet.

[0019] FIG. 2 shows a side view of the roller tappet from FIG. 1.

[0020] FIG. 3 shows a roller tappet in a further embodiment.

DETAILED DESCRIPTION

[0021] FIG. 1 shows a reciprocating pump 1 having a pump housing 20. A camshaft 21, a roller tappet 2 and a pump plunger 10 are arranged in the pump housing 20. The roller tappet 2 comprises a tappet housing 15, a roller support 3, a roller 4 and a pin 5.

[0022] The roller support 3 is arranged in the tappet housing 15; in alternative embodiments, the tappet housing 15 and the roller support 3 can also be of one-piece design. The pin 5 is mounted in the roller support 3. For this purpose, a first bearing eye 6 having a first width b6 and a second bearing eye 7 having a second width b7 are formed in the roller support 3, the pin 5 being mounted or pressed into said eyes. The roller 4 is mounted on the pin 5 in a rotatable manner.

[0023] A cam 22 formed on the camshaft 21 interacts with the roller 4, such that the roller 4 rolls on the cam 22 whenever there is a rotation of the camshaft 21. On the side opposite to the cam 22, the roller support 3 is operatively connected to the pump plunger 10. A spring 25 pretensions the pump plunger 10, with a shim 26 in between, against the roller support 3.

[0024] FIG. 2 shows a side view of the roller tappet 2 from FIG. 1. The side view shows the roller support 3, the roller 4, the pin 5 and the first bearing eye 6. A cutout 8 is formed in the first bearing eye 6. The cutout 8 runs over the entire wall thickness of the first bearing eye 6 in the form of a continuous slot, so that the first bearing eye 6 is divided into a first bearing leg 6a and into a second bearing leg 6b, wherein the first bearing leg 6a is separated from the second bearing leg 6b on one side. An inner surface 6c of the first bearing eye 6, into which the pin 5 is clamped or pressed, is therefore of comparatively highly flexible design because of the cutout 8.

[0025] FIG. 3 shows the roller tappet 2 in a further embodiment. In contrast to the embodiment of FIG. 2, the cutout 8 in the first bearing eye 6 is not formed continuously over the entire wall thickness of the first bearing eye 8, but leads solely to a local reduction of the wall thickness of the first bearing eye 6 in this region. Consequently, in this exemplary embodiment, too, the inner surface 6c is of flexibly expandable design, that is to say the first bearing eye 6 is of comparatively soft design in the region of the cutout 8.

[0026] The reciprocating pump 1 functions as follows:

[0027] The camshaft 21 is driven by a drive unit (not shown), for example by a toothed belt connected to a combustion engine. As a result, the cam 22 performs a rotary movement and describes a cam path. The roller tappet 2, which is operatively connected to the cam 22 via the roller 4, performs a translatory upward and downward movement in the pump housing 20 because of the cam path, wherein the direction of the movement runs perpendicularly to the axis of the camshaft 21. Along with the roller tappet 2, the pump plunger 10 also performs the upward and downward movement and thereby compresses a fluid on the side opposite to the roller tappet 2 in a compression chamber (not shown). In this manner it is possible, for example, for the fuel of a fuel injection system to be brought into the reciprocating pump 1 under high pressure.

[0028] The reciprocating pump 1 is subjected to temperature variations during operation, which can result in linear expansions of the components. According to the invention, the connection between the pin 5 and the first bearing eye 6 is now of more flexible or softer design than the connection between the pin 5 and the second bearing eye 7. Consequently, under thermal loads, the pin 5 can perform a relative movement in its axial direction in relation to the first bearing eye 6. Thermal stresses in the pin 5 and in the roller support 3 are thus reduced or even avoided.

[0029] Here, the differing configurations of the stiffnesses of the connections in the two bearing eyes 6, 7 can be realized, for example, in the following manner: [0030] The oversize of the two interference fits between the pin 5 and the two bearing eyes 6, 7 is designed to be smaller in the first bearing eye 6 than in the second bearing eye 7. [0031] The friction force of the interference fit between the pin 5 and the first bearing eye 6 is smaller than the friction force of the interference fit between the pin 5 and the second bearing eye 7, for example, in that the first width b6 is smaller than the second width b7. [0032] The first bearing eye 6 is of softer design than the second bearing eye 7, for example due to the cutout 8.