GB2259468A

GB2259468A - Making cam ring

Info

Publication number: GB2259468A
Application number: GB9119689A
Authority: GB
Inventors: Brian James Tidmarsh; Robin Christopher Wall
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1991-09-14
Filing date: 1991-09-14
Publication date: 1993-03-17
Also published as: GB9119689D0

Abstract

A method of making an annular member comprises cutting a strip or strips (12) from a block (10) of material, bonding the strips to part circular form and then joining the presented end faces of the strips by friction welding. <IMAGE>

Description

CAM RING This invention relates to an annular member and a method of producing same, and more particularly to a cam ring being for use in a rotary distributor type fuel injection pump, the cam ring having cam lobes formed on its internal surface.

The cam lobes of a distributor type fuel pump are engaged in use, by rollers which are associated with the pumping plungers of the pump respectively and the material forming the cam lobes has to be a high grade steel in order to be able to withstand the stresses which occur when the pump is in use. The steel used in practice is tool steel.

A known way of producing the cam ring is to machine it from a solid block of material. This involves an expensive machining operation. In an effort to reduce the cost of producing the cam ring it has been proposed to form the outer portion of the cam ring from a low grade material and to locate against the inner surface of the outer portion, an inner portion which is formed from a strip of high grade material. In the arrangement shown in GB-A-2099948 the inner portion is cemented to the inner surface of the outer portion but it is also known to weld the portions together.

The object of the present invention is to provide a method of producing an annular member in a simple and convenient form.

According to the invention a method of making an annular member comprises cutting a strip or strips of material from a block, deforming the strip or strips to part circular form and joining the presented end faces of the strip or strips to produce an annular ring, by linear friction welding.

According to a further feature of the invention an annular member is formed from at least one strip of material which is bent to part circular form, the presented end faces of the strip or strips being welded together.

In the accompanying drawings: Figure 1 shows a perspective view of a billet of high grade material, and Figure 2 is a diagrammatic end view of an annular member in the form of a cam ring produced in accordance with the invention, before the final machining operation.

Referring to the drawings there is shown in Figure 1 a block 10 of high grade material from which it is required to form the cam ring. The block is of rectangular section and is formed so that the grain orientation extends lengthwise as shown by the arrow 11.

In order to produce the cam ring a strip 12 of material is cut from the block transversely thereof. Conveniently the block is of sufficient width to allow two strips 12 to be cut therefrom.

In the particular example the cam ring shown diagrammatically at 13, is formed from two strips of material and each strip is bent to semi-circular shape and then the end faces of the strips are machined to form mating surfaces 14. The two deformed rings are then inserted into a linear friction welding machine with the mating surfaces 14 in engagement with each other. A load is applied to the mating faces and at the same time the mating surfaces are oscillated relative to each other to produce a friction weld.

Once the two strips have been secured together the machining of the cam lobes can take place in the conventional manner. It will be noted that the grain orientation in the completed ring is substantially radial. Moreover, it is arranged that the welds occur at positions around the cam ring such that the cam lobes which are eventually machined do not occur at the weld points.

As described the cam ring is formed from two strips of material. It is however possible to form the cam ring from an increased number of strips of material.

It is also possible to form an annular member from a single strip of material so that the member produced will have only one weld. Since a cam ring for a distributor type fuel pump is formed from thick material it may not be possible to form a cam ring from a single strip of material since the partly formed ring may be too stiff to allow relative movement of the presented faces.

Moreover, whilst it is desirable in a cam ring that the grain orientation should be radial, again this is not an absolute necessity and in some instances it may be desirable for the grain orientation to be other than radial. This can be arranged by cutting the strips at an angle relative to the longitudinal axis of the block.

Additionally although as described the joints are radial, they again can be at an angle if so required.

For other applications the grain orientation may be in the circumferential direction. This can be achieved by cutting the initial strip from the block in a direction along the grain.

Claims

1. A method of making an annular member more particularly a cam ring for use in a fuel injector pump comprising cutting a strip or strips of material from a block, deforming the strip or strips to part circular form and joining the presented end faces of the strip or strips to produce the annular member, by linear friction welding.

2. A method according to Claim 1, in which the strip or strips of material are cut from the block so that in the finished annular member the grain orientation is radial.

3. A cam ring for use in a fuel injector pump when produced according to the methods of Claim 1 or Claim 2.