Method for producing a built shaft

Abstract

The invention relates to a method for producing a built shaft, whereby at least one part (2), particularly a cam, is mounted on the shaft (1), particularly a camshaft, whereby the shaft (1) is inserted into an opening (3) of the part (2). Before mounting the part (2), the shaft (1) is stretched by means of a stretching and tightening device (7′, 7″) in such a manner that an original diameter (D1) in the area of at least one fastening location (4) is reduced to a diameter (D4). Afterwards, the part (2) is slid onto the shaft (1) and up to the fastening location (4) on the shaft (1). The stretching and tightening device (7′, 7″) is then loosened once again thereby enabling the diameter of the shaft (1) to enlarge once more towards its original diameter (D1). The part (2) is firmly fastened at the fastening location (4) by interference fit in both an axial as well as rotationally fixed manner.

Description

[0001] This invention relates to a method of producing a worked shaft according to the preamble of Patent claim 1. In particular, this invention relates to a method of producing worked camshafts.

[0002] To attach cams or other components to a camshaft, which is hollow in a manner that has long-term stability, it is known that prefabricated cams or components may be pushed onto the camshaft and to widen them hydraulically in some locations so that the cams and/or components are secured in a torsionally fixed manner. The locally limited widening of the camshaft is relatively complex because special provisions are required (special probes, seals, etc.).

[0003] U.S. Pat. No. 5,299,881 describes a worked camshaft in which the individual cams and the corresponding camshaft are first manufactured completely in separate manufacturing steps and then the cams are pushed onto the camshaft using a special joining technique so that there is a fit without play between the shaft and the cams. The prefabricated cams each have an inside bore and at least two annular zones spaced a distance apart axially, separated by at least one free space which is in the inside bore of the cams. The space and the zones are arranged symmetrically with the center plane of the cams. To manufacture the worked camshaft, the individual cams are pushed onto the camshaft in such a way that a fit is obtained between said zones and the circumference of the shaft. There is a problem inasmuch as it is relatively difficult and problematic to attach said shafts, in particular when the shafts are pushed onto or over the regions to which they are to be secured. Furthermore, the cams have a relatively complex design and therefore may be manufactured only at a comparatively high cost.

[0004] The object of the present invention is to create a method of manufacturing a worked shaft in which the mounting of cams and/or other components on the shaft can be accomplished relatively easily and inexpensively.

[0005] This object is achieved by a method of manufacturing a worked shaft having the features of Patent claim 1.

[0006] The essential advantage of the present invention is that complex hydraulic widening operations on a hollow shaft, in particular a camshaft such as those required in the related art need not be performed because the diameter of the shaft is reduced elastically by stretching before pushing the cams and/or other components onto the shaft, so that it is readily possible to push said cams and/or components onto the shaft. Advantageously, no complex changes need be made on the cams and/or components themselves in the implementation of the method according to this invention.

[0007] The invention and the embodiments thereof are explained below in conjunction with the figures, which show:

[0008] FIG. 1 a camshaft and a cam to be mounted on it in a schematic diagram;

[0009] FIG. 2 a method step in which the diameter of the camshaft is elastically reduced by stretching;

[0010] FIG. 3 a cam mounted on the camshaft; and

[0011] FIG. 4 a refinement of this invention.

[0012] FIG. 1 shows a shaft, preferably designed as a hollow shaft, in particular a camshaft 1. A component to be mounted on the camshaft 1 may be, for example, a cam 2. The cam 2 has an inner opening 3 into which the camshaft 1 is inserted in the manner described below for mounting the cam 2 on the camshaft 1. The camshaft 1 has an outside diameter D1 at least at the mounting site 4 where the cam 2 is to be mounted. The inside diameter of the inner opening 3 of the cam 2 is labeled as D2.

[0013] A so-called threading area 6 having an outside diameter D3 preferably smaller than the diameter D2 and also smaller than the diameter D1 is provided on an end area of the camshaft 1 so that the cam 2 or other cams and/or components may be pushed onto the shaft there with some play and/or they may already be threaded onto the shaft.

[0014] In a method step, the end areas of the camshaft 1 are preferably mounted in a stretching and chucking device 7′, 7″. This stretching and chucking device 7′, 7″ is preferably created according to FIG. 1 so that it acts with a chucking element 7′ on the outside circumference of the camshaft 1 and exerts a chucking force P1 on the camshaft 1. With its other chucking element 7″, the stretching and chucking device 7′, 7″ acts on the inside circumference of the hollow camshaft 1, preferably exerting a chucking force P2 on the camshaft 1 acting in the radial direction. Before attaching the chucking element 7″, the cams 2 and/or other components to be mounted on the camshaft 1 are pushed onto the threading area 6.

[0015] The camshaft 1 especially preferably has an inside thread on its side facing the chucking element 7″ onto which an outside thread of the chucking element 7″ can be screwed.

[0016] It is pointed out that the chucking element 7′ may also be designed according to the chucking element 7″.

[0017] The stretching and chucking device 7′, 7″ is subsequently operated so that a tension is exerted on the chucked camshaft 1 so that the diameter D1 of the camshaft 1 is reduced to a diameter D4. It holds that D1>D4>D3, as also shown in FIG. 2. The chucking elements 7′ and 7″ exert the stretching forces P3 and P4 thereby.

[0018] To permit the aforementioned reduction in the diameter D1 to the diameter D4 by operation of the stretching and chucking device 7′, 7″ and in stretching of the camshaft 1, the camshaft 1 is made of a material, preferably a special steel alloy, which permits an elastic axial elongation of the camshaft 1 due to the stretching and chucking device 7′, 7″ for said reduction in diameter. In addition to the elastic deformation, plastic deformation of the camshaft in stretching is also possible.

[0019] According to FIG. 2, the camshaft 2 is then pushed from the threading area 6 onto the stretched camshaft 1 having the diameter D4 and pushed in direction A to the mounting site. This is readily possible because the diameter D4 is smaller than the diameter D2. The cam 2 is secured at the fastening site 4 by retaining devices, which are not shown in greater detail here, with respect to displacement in the axial direction and in the circumferential direction.

[0020] It is also conceivable for the diameter D4 to be larger than the diameter D2 as long as it is certain that the cam 2 can then be shifted by use of force to the mounting site 4 after the stretching operation.

[0021] When the stretching and chucking device 7′, 7″ according to FIG. 3 is released, the camshaft 1 returns in the direction of its original position shown in FIG. 1 due to the release and its elasticity, so that its outside diameter D4 increases again in the direction of the outside diameter D1. In doing so, the cam 2 is permanently secured in the mounting site 4 both axially and in a torsionally fixed manner by a press fit. The stretching and chucking device can then be removed.

[0022] According to FIG. 4, it is also conceivable to provide a threading area 6″ on a chucking element 7″ which acts on the inside circumference of the camshaft 1, instead of the threading area being located on the camshaft 1 (FIGS. 1 through 3) or to provide a threading area on two such chucking elements. In this case, the components and/or cams 2 to be mounted on the camshaft 1 are arranged on the threading area 6″, the diameter of which is preferably smaller than the inside diameter of the inside opening 3 of the components and/or cams 2, before positioning the chucking element 7″. After the stretching, then the components and/or cams 2 are pushed onto the camshaft 1 and brought into the predetermined position.

[0023] To permit the threading area 6″ to be pushed onto the camshaft 1, it preferably has an approach ramp 8 which forms a transition from the diameter D3″ of the threading area 6″ to the diameter D4 of the stretched camshaft 1.

[0024] It is also pointed out that it is conceivable to use a shaft 1 having the original diameter D1, which is subsequently reduced in drawing to the diameter D4, only in the area of the mounting site(s) 4. The other shaft areas then have a diameter smaller than D1. These shaft areas are also reduced in drawing.

Claims

1. A method of manufacturing a worked shaft, whereby at least one component (2) is placed on the shaft (1), in particular a cam being placed on a camshaft, whereby the shaft (1) is introduced into an opening (3) in the component (1), whereby, before mounting the component (2), the shaft (1) is stretched with the help of a stretching and chucking device (7′, 7″) such that an original diameter (D1) in the area of at least one mounting site (4) is reduced to a diameter (D4); then the component (2) is pushed onto the shaft (1) and is shifted to the mounting site (4) on the shaft (1) and next the stretching and chucking device (7′, 7″) is released again, whereupon the diameter of the shaft (1) enlarges again in the direction of the original diameter (D1), characterized in that the shaft (1) is reduced by the stretching and chucking device (7′, 7″) to a diameter (D4) which is slightly larger than the inside diameter (D2) of the opening (3) of the component (2), and the component (2) is displaced to the mounting site (4) with a force acting on the shaft (1).

2. Method according to claim 1, characterized in that the shaft (1) has in an edge area a threading area (6) in which at least one component (2) is situated, and after stretching the shaft (1) by the stretching and chucking device (7′, 7″), the component (2) is pushed out of the threading area (6) and onto the stretched shaft (1) and then is shifted to the mounting site (4) on the stretched shaft (1).

3. Method according to claim 1 or 2, characterized in that the stretching and chucking device (7′, 7″)

4. Method according to claim 3, characterized in that the chucking element (7″) which acts on the inside circumference of the shaft (1) has a threading area (6″) on which is arranged at least one component (2), and the component (2) is pushed out of the threading area (6″) of the chucking element (7″) and onto the shaft (1) after the stretching of the shaft (1) and then is shifted on the shaft (1) to the mounting site (4).

5. Method according to one of claims 1 through 4, characterized in that a stretching and chucking device (7′, 7″) is used, having a chucking element (7′) which acts on the outside circumference of the shaft (1) and a chucking element (7″) which acts on the inside circumference of a shaft (1) that is designed to be at least partially hollow.

6. Method according to one of claims 1 through 5, characterized in that a stretching and chucking device (7′, 7″) which has two chucking elements (7″) acting on the inside circumference of a shaft (1) which is designed to be at least partially hollow is used.

7. Method according to one of claims 1 through 6, characterized in that the chucking element (7″) of the stretching and chucking device (7′, 7″) acting on the inside circumference of the shaft (1) has an area with an outside thread which is screwed onto an inside thread situated in the inside circumference of a shaft (1) which is designed to be at least partially hollow.

8. Method according to one of claims 1 through 7, characterized in that the area of the shaft (1) facing the threading area (6″)

9. Method according to one of claims 1 through 8, characterized in that the shaft (1) is a solid shaft.

10. Method according to one of claims 1 through 9, characterized in that the shaft (1) is a hollow shaft.

11. Method according to one of claims 1 through 10, characterized in that a lubricant is supplied for shifting the component (2) on the shaft (1) into the area between the component (2) and the shaft (1).

12. Method according to one of claims 1 through 11, characterized in that a shaft having the original diameter (D1) essentially along its total length is used.

13. Method according to one of claims 1 through 11, characterized in that a shaft having the original diameter (D1) essentially only in the area of its at least one mounting site (4) and having a diameter smaller than the original diameter (D1) in the other areas of the shaft is used.