PUMP, IN PARTICULAR HIGH-PRESSURE FUEL PUMP

Abstract

Disclosed is a pump, in particular a high-pressure fuel pump, comprising at least one pump element (10) that has a roller tappet (20) inside which a roller (42) is rotatably mounted on a bearing bolt (44) by means of a bearing sleeve (46), said roller (42) rolling off a cam (22) of an input shaft (24). The bearing sleeve (46) is made of a plastic material, especially polyether ether ketone (PEEK) or polyphthalamide (PPA).

Claims

1. A pump, having at least one pump element (10), which comprises a roller tappet (20), in which a roller (42), which rolls on a cam (22) of a drive shaft (24), is rotatably supported on a bearing pin (44) by a bearing bush (46), characterized in that the bearing bush (46) is made from a plastic material.

2. The pump as claimed in claim 1, characterized in that the bearing bush (46) is made from polyether ether ketone (PEEK).

3. The pump as claimed in claim 1, characterized in that the bearing bush (46) is made from polyphthalamide (PPA).

4. The pump as claimed in claim 1, characterized in that the bearing bush (46) is made from polyphenylene sulfide (PPS)

5. The pump as claimed in claim 1, characterized in that the bearing bush (46) is made from polyimide or polyamide imide.

6. The pump as claimed in claim 1, characterized in that at least one filler is added to the plastic material of the bearing bush (46) to improve the emergency running characteristics of the bearing bush (46) in the event of inadequate lubrication.

7. The pump as claimed in claim 6, characterized in that carbon fibers and/or glass fibers and/or potassium titanate and/or polyaramid, and/or titanium dioxide and/or zinc sulfide and/or graphite and/or polytetrafluoroethylene are used as filler.

8. The pump as claimed in claim 1, characterized in that the bearing bush (46) is produced by an injection molding method.

9. The pump as claimed in claim 1, characterized in that the bearing bush (46) is produced by a method of pressing.

10. The pump as claimed in claim 1, characterized in that the bearing bush (46) is produced as a portion of a bar material.

11. The pump as claimed in claim 1, wherein the pump is a high-pressure fuel pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] An exemplary embodiment of the invention is represented in the drawing and is explained in more detail in the following description.

[0006] FIG. 1 shows a simplified representation of a pump in a longitudinal section; and

[0007] FIG. 2 shows an enlarged representation of a detail of a roller tappet of the pump.

DETAILED DESCRIPTION

[0008] FIG. 1 represents a pump, which is in particular a high-pressure fuel pump for a fuel injection device of an internal combustion engine. The pump comprises at least one pump element 10, which comprises a pump piston 16, displaceably and tightly guided in a cylinder bore 12 of a housing part 14, which is referred to hereinafter as a cylinder head. With its end projecting into the cylinder bore 12 the pump piston 16 defines a pump working chamber 18. The end of the pump piston 16 projecting from the cylinder bore 12 is connected to a roller tappet 20. The roller tappet 20 is supported on a cam 22 of a drive shaft 24, which cam under the rotational movement of the drive shaft 24 produces a reciprocating movement of the pump piston 16 in the cylinder bore 12. The drive shaft 24 may be part of the pump or part of the internal combustion engine, for example its camshaft or another shaft.

[0009] The pump working chamber 18 can be connected via an inlet valve 26 to a low-pressure inlet 27 to the pump and via an outlet valve 28 to a high-pressure outlet, which leads, for example, to a high-pressure accumulator 30. The low-pressure inlet 27 may be fed, for example, by a feed pump, which draws in fuel from a storage tank.

[0010] The roller tappet 20 comprises a hollow cylindrical tappet body 40, into which the end of the pump piston 16 protruding from the cylinder bore 12 projects on the side thereof remote from the cam 22. On the side of the tappet body 40 facing the cam 22 a roller 42, which rolls on the cam 22, is rotatably supported in said tappet body. A bearing pin 44, on which the roller 42 is rotatably supported by a bearing bush 46, is fixed in the tappet body 40. The tappet body 40 has a bore 48, which runs at least approximately perpendicular to the longitudinal axis 17 of the pump piston 16, wherein the diameter of the bore 48 is enlarged in its middle area, viewed in the longitudinal direction, and the bore 48 in its middle area is open to the cam 22. The bearing pin 44 may be pressed into the bore 48 at its end areas or may be secured in the bore 48 by means of a sprung retaining clip 50, for example, so that it cannot be pushed out of the bore 48 in the direction of its longitudinal axis.

[0011] The bearing bush 46 is of hollow cylindrical design and is arranged with a slight radial play on the middle area of the bearing pin 44. The hollow cylindrical roller 42 is supported with a slight radial play on the bearing bush 46. Here the roller 42 is arranged with its larger diameter in the middle area of the bore 48 and protrudes out through the open side of the middle area of the bore 48 towards the cam 22. The bearing bush 46 is produced from a plastic material, preferably from polyether ether ketone (PEEK) or from polyphthalamide (PPA). In addition, polyimide, polyamide imide or polyphenylene sulfide (PPS) may also be used as plastic material.

[0012] Fillers, which serve in particular to improve the emergency running characteristics of the bearing bush 46 in the event of inadequate lubrication, may be added to the plastic material. Carbon fibers, for example, and/or glass fibers and/or potassium titanate and/or polyaramid may be used as fillers. In addition, fillers which improve the anti-frictional characteristics of the bearing bush may be added to the plastic material. Solid lubricant particles, which may contain graphite, may be used as fillers for this purpose. Titanium dioxide and/or zinc sulfide and/or polytetrafluoroethylene may also be used as additives.

[0013] The bearing bush 46 is preferably produced by an injection molding method, wherein no further production operation, or at least only a machining of the inside and/or outside diameter of the bearing bush 46, is necessary following the injection molding process. Alternatively, the bearing bush 46 may also be produced by a method of pressing. In addition, the bearing bush 46 may also be produced from a bar material, from which portions of the required width are cut off.