GB2305704A

GB2305704A - A cam constructed from a plurality of stamped-out sheets

Info

Publication number: GB2305704A
Application number: GB9619888A
Authority: GB
Inventors: Alfred Beier; Dietrich Distler; Conrad Kulus
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1995-09-28
Filing date: 1996-09-24
Publication date: 1997-04-16
Anticipated expiration: 2016-09-24
Also published as: DE19638329A1; FR2739429A1; GB2305704B; GB9619888D0; DE19638329B4; FR2739429B1

Abstract

A cam 1 is constructed from a plurality of stamped-out metal sheets 2, eg cold-rolled C75 sheet steel, which simplifies production, by eliminating subsequent fine surface treatment, and improves lubrication of face 4 by providing lubrication pockets in the form of depressions 15. The sheets 2 are stamped out in direction A which furnishes a cut portion 13, having the required surface finish, followed by a fractional portion 14 which, when the sheets 2 are assembled, engage via fractional burrs 16 in roundings 12 to form the depressions 15. The cut portion 13 has an axial extent S of between 80% and 95% of extent D while the fractional portions 14 have an axial extent B of between 20% and 5% of axial extent D. Parameters, eg cutting speed and choice of material, of the stamping process are selected so that the correct dimensions for the roundings 12 and the burrs 16 occur automatically.

Description

DESCRIPTION CAM The present invention relates to a cam.

Cams, such as are used, for example, for the control of inlet and exhaust valves of internal combustion engines, generally require complicated and cost-intensive production methods, since the cam profile face, after actual shaping, necessitates additional surface machining.

To solve this problem, DE-44 23 107 Al has already proposed manufacturing a cam from a plurality of axially successive stamped-out material plies.

Advantageously, it is particularly simple to manufacture a cam of this type, because the shaping of the individual material plies already occurs as a result of the stamping and all the material plies can be shaped by means of one and the same stamping machine. There is thus no need for subsequent fine surface treatment.

An aim of the present invention is to provide an improved cam which consists of a plurality of axially successive stamped-out material plies and which is optimized particularly with regard to the frictional and lubricating conditions prevailing on its cam profile bearing face.

According to the present invention there is provided a cam comprising a plurality of axially successive, stamped-out material plies, each with a cam profile face and, as a result of stamping process parameters, each with a predetermined axial extent, a cut portion running in a straight line and having an axial extent of between 80 and 95 percent of said predetermined axial extent, being arranged as seen in a stamping-out direction, on the cam profile face, the said cut portion being followed by a fractional portion having an axial extent of between 20 and 5 percent of said predetermined axial extent, a fractional burr of one material ply projecting beyond said predetermined axial extent in the stamping direction and engaging into a rounding of a directly adjacent material ply, the said rounding occurring as a result of the stamping-out process and being located at the front of the material ply in the stamping direction.

The solution according to the present invention is that, as a result of suitable stamping process parameters, on the one hand a cut portion sufficient for the loads occurring and running in a straight line and a fractional portion resulting necessarily from the stamping process, are established on the cam profile bearing face, and on the other hand an entirely planar assembly of the mutually confronting surfaces of adjacent material plies is guaranteed in that a fractional burr, adjoining the fractional portion and projecting beyond the material thickness of the individual material ply, can engage into a corresponding rounding of the respectively adjacent material ply.

In the present invention the axial extent of the cut portion amounts to approximately nine tenths of the entire axial extent of a material ply, the fractional portion consequently extending over approximately one tenth.

Advantageously, those fractional portions of the individual material plies which occur as depressions on the cam profile face of the cam as a whole, act as lubricating pockets, e.g. when such cams are used in a valve drive of an internal combustion engine. In this case, the supply of these lubricating pockets with lubricating oil can advantageously take place through the gaps which are of extremely small dimension and which occur between the individual material plies.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a plan view of one embodiment of a cam constructed according to the present invention, with the cam elevation vertically above the drawing plane; and Fig. 2 is an enlarged and highly diagrammatic partial view of the two adjacent material plies.

The cam 1 shown in Fig. 1 has a multiplicity of material plies 2 consisting of highly tempered, coldrolled C75 sheet steel. Such material has sufficient hardness, for example for using the cam 1 in the valve drive of an internal combustion engine, so that there is no need for any subsequent treatment.

In production terms, the material plies 2 are formed by being stamped out in such a way that their radially outer edges in the form of cam profile faces 3 constitute as a whole an overall profile face 4 of the cam 1. At the same time, by virtue of the material used, a peak-to-valley height sufficiently fine for the intended use is obtained on the face 4.

Simultaneously with the stamping-out of the individual material plies 2, recesses 5 serving for receiving a camshaft 6 are punched out of the plies.

The individual material plies 2 are fastened on the camshaft 6 in such a way that axial retention occurs in the region of the recess 5. A further axial connection is made by a pin 7 which is arranged in the region of the cam elevation and which clamps the material plies 2 together in an axis-parallel manner between its head 8 and a disc 10 fixed at 9 on the pin 7, by laser welding.

The cam 1 has an axial length L which is derived from the sum of the axial extents D of each material ply 2.

Each material ply 2 is stamped out in a stamping out direction A, a rounding 12 occurring as a result of the stamping-out process in the region of the cam profile face 3 at the edge 11 located at the front in the stamping direction A. Furthermore, a cut portion 13 running in a straight line occurs on the cam profile face 3 after the rounding 12 in the stamping direction A, the axial extent S of the said cut portion being between 80 and 95% of the extent D of the thickness of the material ply 2.

The cut portion 13 is followed in the stamping-out direction A by a fractional portion 14 having an axial extent B of between 20 and 5 percent of the extent D.

These fractional portions 14 result, together with the roundings 12, in depressions 15 in the overall profile face 4.

As a result of the stamping-out process, a fractional burr 16, which projects beyond the extent D of the individual material ply 2, occurs at the end of the extent B, as seen in the stamping-out direction A.

The stamping process parameters can be selected in such a way that, as a result of the cutting speed, the extent D and the choice of material, roundings 12 and fractional burrs 16 occur which are such that the burrs 16 can engage into the gap created by the rounding 12 of the adjacent material ply 2.

By weighing up stamping process parameters and the costs, for example for the raw material of the material plies 2, different extents D of the material plies 2 can be selected, as becomes clear from the following numerical example In the case of a desired overall extent L of a cam 1 of 15mm, with an extent D per ply 2 of 0.25 mm, altogether 60 plies are required. The fractional portion 14 which occurs extends in each case over approximately 0.03mm in the region B, so that a fractional portion of approximately 1.8mm is obtained in respect of the overall extent L of 15 mm.

If material plies having the extent D of 0.15 mm, that is to say 100 material plies 2, are used, a fractional portion of approximately 0.015 mm occurs for each ply, so that a fractional portion of approximately 1.5 mm is obtained on the overall extent L.

Cams 1 having extents D of between 0.1 and 0.5 mm yielded satisfactory results in tests, the latter varying between 30 and 100 material plies. At the same time, particularly in the case of extents D of between 0.15 and 0.35 mm and 100 to 40 material plies 2, good results were obtained in terms of the surface roughness of the profile face 3, 4 and the fractional portions 14 in respect of the overall extent L.

Finer sheets are generally to be aimed for, since, in stamping processes, better surfaces are obtained by the use of thinner sheets, for example in respect of the roughness of the cam profile face 3. Advantageously, the cam according to the present invention gives very high process reliability and process accuracy in comparison with conventional cams, since, as a result of the stamping process and the suitable choice of material, tolerance levels of the next higher tolerance class can be achieved without difficulty in comparison with conventional cams.

A further advantage is to be seen in that different cam shapes can be established simply by exchanging the stamping tool, without a new camshaft having to be manufactured in a complicated way.

Claims

CLAIMS 1. A cam comprising a plurality of axially successive, stamped-out material plies, each with a cam profile face and, as a result of stamping process parameters, each with a predetermined axial extent, a cut portion running in a straight line and having an axial extent of between 80 and 95 percent of said predetermined axial extent, being arranged as seen in a stamping-out direction, on the cam profile face, the said cut portion being followed by a fractional portion having an axial extent of between 20 and 5 percent of said predetermined axial extent, a fractional burr of one material ply projecting beyond said predetermined axial extent in the stamping direction and engaging into a rounding of a directly adjacent material ply, the said rounding occurring as a result of the stamping-out process and being located at the front of the material ply in the stamping direction. 2. A cam as claimed in claim 1, in which coldrolled, tempered sheet steel is used for the material plies. 3. A cam as claimed in claim 1 or 2, in which the said predetermined axial extent of each material ply is between 0.1 and 0.5 mm. 4. A cam as claimed in claim 1 or 2, in which said predetermined axial extent of each material ply is between 0.15 and 0.35 mm. 5. A cam as claimed in any one or more of the preceding claims, in which the cam is formed from 30 to 100 material plies. 6. A cam as claimed in any one or more of claims 1 to 4, in which the cam is formed from 60 to 100 material plies. 7. A cam constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. Amendments to the claims have been filed as follows

1. A cam comprising a plurality of axially successive, stamped-out material plies, each with a cam profile face and, as a result of stamping process parameters, each with a predetermined axial extent, a cut portion running in a straight line and having an axial extent of between 80 and 95 percent of said predetermined axial extent, being arranged as seen in a stamping-out direction, on the cam profile face, the said cut portion being followed by a fractional portion having an axial extent of between 20 and 5 percent of said predetermined axial extent, a fractional burr of one material ply projecting beyond said predetermined axial extent in the stamping direction and engaging into a rounding of a directly adjacent material ply, the said rounding occurring as a result of the stamping-out process and being located at the front of the material ply in the stamping direction.

2. A cam as claimed in claim 1, in which coldrolled, tempered sheet steel is used for the material plies.

3. A cam as claimed in claim 1 or 2, in which the said predetermined axial extent of each material ply is between 0.1 and 0.5 mm.

4. A cam as claimed in claim 1 or 2, in which said predetermined axial extent of each material ply is between 0.15 and 0.35 mm.

5. A cam as claimed in any one or more of the preceding claims, in which the cam is formed from 30 to 100 material plies.

6. A cam as claimed in any one or more of claims 1 to 4, in which the cam is formed from 60 to 100 material plies.

7. A cam as claimed in any one or more of claims 1 to 4, in which the cam is formed from 40 to 100 material plies.

8. A cam constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.