Claims:We Claim

1. A high pressure fuel pump (10), said high pressure fuel pump (10) comprising:
a cam shaft (12);
a bearing plate (14) secured to said cam shaft (12) and adapted to rotate about the axis of said cam shaft (12);
a bush (16) inserted within a gap defined between said cam shaft (12) and said bearing plate (14), said bush (16) adapted to prevent fuel from escaping past the interface of the bearing plate (14) and the cam shaft (12); characterized in that
a shim (18) integrated with said bush (16) to form a unitary assembly, said shim (18) positioned between said bearing plate (14) and said cam shaft (12).

2. The high pressure fuel pump (10) in accordance with Claim 1 wherein said shim (18) is integrated with said bush by means of plasma welding
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a high pressure fuel pump, and more specifically to a shim that is integrated with a bush and secured to a cam shaft of a high pressure fuel pump.

Background of the invention
[0002] JP 9177637 A describes a bearing device of a fuel injection pump. To improve the assembling property, and to reduce the vibration and noise by fitting a center bearing to a lower opening part of a pump housing in an in-line fuel injection pump through a shim of the prescribed thickness to a pump housing. When a center bearing having a face to support a lower half of a cam shaft is fitted to an opening part open inside of a lower part of a pump housing in an in-line fuel injection pump, and a flange part is fixed by bolts, a shim of the prescribed thickness is interposed between the pump housing and the center bearing. The thickness of the shim is the dimension of the distance between the pump housing and the center bearing when the center bearing is pressed relative to the cam shaft with the preset clearance C added thereto. The prescribed clearance can be secured between the cam shaft and the center bearing.

Brief description of the accompanying drawing
[0003] Figure 1 illustrates a schematic diagram of a shim that is integrated with a bush and secured to a high pressure fuel pump in one embodiment of the invention.

Detailed description of the embodiments
[0004] Figure 1 illustrates a schematic diagram of a shim 18 that is integrated with a bush 16 and secured to a high pressure fuel pump 10 in one embodiment of the invention. The high pressure fuel pump 10 comprises a cam shaft 12, and a bearing plate 14 that is secured to the cam shaft 12 and is adapted to rotate about the axis of the cam shaft 12. A bush 16 is inserted within a space that is defined between the cam shaft 12 and the bearing plate 14, the bush 16 adapted to prevent fuel from escaping past the interface of the bearing plate 14 and the cam shaft 12. A shim 18 is integrated with the bush 16 to form a unitary assembly, the shim 18 positioned between the bearing plate 14 and the cam shaft 12 to facilitate sealing the gap between the bearing plate 14 and the cam shaft 12.

[0005] The high pressure fuel pump 10 comprises a cam shaft 12. A crank shaft of an engine is secured to the cam shaft 12 of the high pressure fuel pump 10 and is adapted to rotate the cam shaft 12. The rotation of the cam shaft 12 causes fuel to be delivered from the high pressure fuel pump 10 to an engine. In the exemplary embodiment, a bearing plate 14 is secured to the cam shaft 12 and is adapted to rotate about the axis of the cam shaft 12. A gap is defined between the bearing plate 14 and the cam shaft 12. A bush 16 is inserted within the gap that is defined between the cam shaft 12 and the bearing plate 14 and facilitates preventing fuel from flowing past the interface of the bearing plate 14 and the cam shaft 12 and escaping out of the high pressure fuel pump 10. In an alternate exemplary embodiment, the gap that is defined between the cam shaft 12 and the bearing plate 14 may be closed by means of any other filler material that is known in the art that facilitates sealing the gap that is defined between the cam shaft 12 and the bearing plate 14 and prevents fuel from flowing past the interface of the bearing plate 14 and the cam shaft 12, thereby escaping out of the high pressure fuel pump 10.

[0006] A shim 18 is integrated with the bush 16 to form a unitary assembly. In an exemplary embodiment, the shim 18 is secured to the bush 16 by means of plasma welding. In an alternate exemplary embodiment, the shim 18 is secured to the bush 16 by any fastening means that is known in the art. In yet another alternate exemplary embodiment, the shim 18 is secured to the bush 16 during the casting process of the bush 16. The shim 18 that is positioned between the bearing plate 14 and the cam shaft 12 facilitates sealing the gap between the bearing plate 14 and the cam shaft 12. More specifically, when the cam shaft 12 is assembled onto the bearing plate 14, the shim 18 acts as a cushioning member to reduce the degree of wear between the rotating cam shaft 12 and the bearing plate 14. In the absence of the shim 18, the cam shaft 12 would rotate against the bearing plate 14, thereby leading to a surface of the cam shaft 12 as well as the bearing plate 14 from being worn out. In an exemplary embodiment, the bush 16 is manufactured by means of polyether ether ketone (PEEK) material. Moreover, the shim 18 is manufactured from a low carbon steel material that is both malleable and ductile in nature.

[0007] The choice of material that is selected for manufacturing the shim 18 is such that it should deform moderately when the cam shaft 12 is pressed against the bearing plate 14, thereby acting as a shock absorbing material. Moreover, when the cam shaft 12 is pressed against the bearing plate 14, the rotation of the cam shaft 12 causes the shim 18 to wear out gradually, thereby preventing wear on the surface of the bearing plate 14. Therefore, as can be seen from Figure 1, the integration of the shim 18 with the bearing plate 14 prevents the shim 18 from being manufactured independently and assembled as a separate sub-assembly. The integration of the shim 18 and the bush 16 to constitute a unitary assembly saves manufacturing time, and the deployment of the shim 18 as a separate component against the bearing plate 14. As the shim 18 is pressed against the surface of the bearing plate 14, the low carbon steel material of the shim 18 deforms marginally to form a compact sealing arrangement between the cam shaft 12 and the shim 18, thereby preventing the surface of the bearing plate 14 from being deformed or worn out over a period of time.

[0008] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to dimensions of various components are envisaged and form a part of this invention. The scope of the invention is only limited by the scope of the claims.