JOINING DEVICE FOR JOINING COMPONENTS ON A SHAFT

Abstract

A joining device for joining components on a shaft, e.g., for joining camshaft components on a camshaft tube, is disclosed. The joining device includes a joining device body composed of a material with a heat expansion coefficient that is lower than 10.0 μm/m° C. The heat expansion coefficient of the joining device is smaller than that of the components and/or the shaft.

Claims

1. A joining device for joining components on a shaft, comprising a joining device body composed of a material with a heat expansion coefficient that is lower than 10.0 μm/m° C.

2. The joining device according to claim 1, wherein the material of the joining device body is a silicon nitride ceramic (Si.sub.3N.sub.4) having a heat expansion coefficient of 2.5 μm/m° C.

3. The joining device according to claim 1, wherein the material of the joining device body is an iron nickel alloy having a heat expansion coefficient of 1.7 μm/m° C.

4. The joining device according to claim 1, wherein the joining device body is structured for thermally joining the components on the shaft.

5. The joining device according to claim 1, wherein the joining device body is structured for press-fitting the components on the shaft.

6. The joining device according to claim 1, wherein the joining device body includes a plurality of openings for receiving the shaft, the plurality of openings being surrounded by the material with the heat expansion coefficient that is lower than 10.0 μm/m° C.

7. The joining device according to claim 1, wherein the joining device body includes transverse walls arranged axially spaced apart at a distance from one another relative to a shaft axis, and wherein transverse walls have a respective opening for receiving the shaft and are composed of the material with the heat expansion coefficient that is lower than 10.0 μm/m° C.

8. The joining device according to claim 7, wherein the transverse walls are composed of a silicon nitride ceramic (Si.sub.3N.sub.4) having a heat expansion coefficient 2.5 μm/m° C.

9. The joining device according to claim 7, wherein the transverse walls are composed of an iron nickel alloy having a heat expansion coefficient of 1.7 μm/m° C.

10. The joining device according to claim 1, wherein the heat expansion coefficient of the material of the joining device body is smaller than that of the components and the shaft.

11. A joining device for joining camshaft components on a camshaft tube, comprising: a joining device body composed of a material with a heat expansion coefficient that is lower than 10.0 μm/m° C.

12. The joining device according to claim 11, wherein the material of the joining device body is a silicon nitride ceramic (Si.sub.3N.sub.4) having a heat expansion coefficient 2.5 μm/m° C.

13. The joining device according to claim 11, wherein the material of the joining device body is an iron nickel alloy having a heat expansion coefficient of 1.7 μm/m° C.

14. The joining device according to claim 11, wherein the joining device body includes transverse walls arranged axially spaced apart at a distance from one another relative to a shaft axis, and wherein transverse walls have a respective opening for receiving the shaft and the transverse walls are composed of the material with the heat expansion coefficient that is lower than 10.0 μm/m° C.

15. The joining device according to claim 14, wherein the transverse walls have an axial extent of 30 mm.

16. The joining device according to claim 11, wherein the joining device body is structured for thermally joining the camshaft components on the camshaft tube.

17. The joining device according to claim 11, wherein the joining device body is structured for press-fitting the camshaft components on the camshaft tube.

18. The joining device according to claim 11, wherein the camshaft components include at least one of a drive element and a cam.

19. The joining device according to claim 11, the heat expansion coefficient of the material of the joining device body is smaller than that of the camshaft components and the camshaft tube.

20. The joining device according to claim 11, wherein the joining device body includes a plurality of openings for receiving the camshaft tube, the plurality of openings being surrounded by the material with the heat expansion coefficient that is lower than 10.0 μm/m° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] There it shows, in each case schematically

[0017] FIG. 1 a joining device according to the invention while joining multiple camshaft components on a camshaft tube,

[0018] FIG. 2 a detail representation from FIG. 1.

DETAILED DESCRIPTION

[0019] According to the FIGS. 1 and 2, a joining device 1 according to the invention for joining components 2 on a shaft 3, in particular for joining camshaft components 4 on a camshaft tube 5, comprises a material having a heat expansion coefficient α of <10.0 μm/m° C. Concretely, this means that the joining device 1 is formed out of such a material, wherein a heat expansion coefficient α of approximately 12.0 μm/m° C. corresponds to that of steel. This means that the joining device 1 is formed out of a material the heat expansion coefficient α of which is smaller than that of the components 2 or the shaft 3 to be joined. Particularly preferably, the joining device 1 is formed out of a silicon nitride ceramic (Si.sub.3N.sub.4) having a heat expansion coefficient α of 2.5 μm/m° C.

[0020] In a further advantageous and alternative embodiment of the joining device 1 according to the invention, the same is formed out of an iron nickel alloy having a heat expansion coefficient α of merely 1.7 μm/m° C. This means that such a joining device 1 merely has a ¼ or less than ⅕ of the heat expansion of steel, i.e. of the components 2 to be joined on the shaft 3, as a result of which temperature-induced fluctuations of the heat expansion of the joining device 1 can be minimised.

[0021] A material of the camshaft components 4 to be joined is generally specified, wherein for example a drive element 6, the camshaft tube 5 and for example cams 7 are generally made of steel. Other camshaft components 4, such as for example sensor wheels or output elements can be produced for example out of a sinter material. In order to minimise the influence of temperature fluctuations of the joining device 1, the same is now produced out of a material the heat expansion coefficient α of which is significantly lower than the heat expansion coefficient α of the component 2 and of the shaft 3 to be joined.

[0022] In addition it is true that the greater a distance dimension D between a reference surface 8 and the joining device 1 is, the greater is also the effect that can be achieved with the joining device 1 formed according to the invention. Upon a simultaneous joining in the joining device 1 of multiple, in particular even distinct camshaft components 4 out of a material which has a significantly lower heat expansion coefficient α, it is particularly advantageous since here the different heat input of the camshaft components 4, because of the component variance or process fluctuations of the heating, has almost no effect on the joining device 1 and thus also on the axial dimensions and therefore not only the dimensional variance of the reference surface 8 but also the dimensional variance between the individual camshaft components 4 can be reduced.

[0023] When for example the differential dimension D amounts to 70 mm between the joining device 1 and the reference surface 8 of the shaft 3, the expansion variance of the shaft 3, provided the same is formed out of steel and has a heat expansion coefficient α of 12 μm per m and ° C. at +/−10° C. temperature differential is 16.8 μm.

[0024] A further advantage also is that the joining device 1 and because of this also the camshaft components 4 to be joined to the same, almost uninfluenced by temperature fluctuations, remain better in terms of a coaxiality between tube axis and joining axis, which in turn results in an improved axial dimension precision. Because of this, rejects can also be reduced as a result of which a substantial cost reduction through the omission for example of an additional process that would be required for producing the precise axial dimension can be achieved.

[0025] All in all, a significantly improved axial positioning of components 2 to be joined on a shaft 3 by means of a thermal joining fit can be achieved with the joining device 1 according to the invention. The joining device 1 can also be formed for press-fitting the components 2 on the shaft 3, in particular with a longitudinal pressing method.

[0026] The temperature-induced expansion variance of the joining device 1 in a portion A (see FIG. 2), which extends 30 mm in the axial direction, is 7.2 μm at +/−10° C. in the case of steel. With a joining device formed out of a silicon nitride ceramic having a heat expansion coefficient α of 2.5 μm per m and ° C., the expansion variance of the portion A amounts to 1.5 μm at +/−10° C., while the same, with a joining device 1 formed out of an iron nickel alloy having a heat expansion coefficient α of 1.7 μm per m ° C. amounts to merely 1 μm at +/−10° C. temperature differential.

[0027] This produces a dimensional variance for +/−10° C. for a joining device 1 out of steel of +/−12 μm, for a joining device 1 out of a silicon nitride ceramic of +/−9.9 μm and for a joining device 1 out of an iron nickel alloy of +/−9.4 μm.

[0028] These values already show that with same assumed temperature variance of +/−10° C. of the camshaft tube 5 and of the joining device 1, a tolerance of +/−10 μm with a joining device 1 out of steel is not attainable even because of the heat expansion alone. However, this would be attainable with a joining device 1 formed out of a silicon nitride ceramic or iron nickel alloy.