CA1326768C

CA1326768C - Process for producing an assembled shaft

Info

Publication number: CA1326768C
Application number: CA000588273A
Authority: CA
Inventors: Helmut Swars; Wolfgang Maus
Original assignee: Emitec Gesellschaft fuer Emissionstechnologie mbH
Current assignee: Vitesco Technologies Lohmar Verwaltungs GmbH
Priority date: 1988-01-14
Filing date: 1989-01-13
Publication date: 1994-02-08
Anticipated expiration: 2011-02-08
Also published as: DE3800912C2; DE58900118D1; DE3800912A1; MX174534B; BR8900137A; ES2022724B3; JP2862884B2; EP0324499A1; IN170886B; KR920001674B1; KR890011672A; EP0324499B1; JPH01216113A

Abstract

ABSTRACT OF THE DISCLOSURE
A known process for attaching drive elements, e.g.
cams or end flanges, to a hollow shaft by expanding portions of the latter is improved in that additional supporting sleeves are arranged inside the hollow shaft opposite the drive elements and undergo plastic deformation. This method permits greater freedom in choosing the material for the hollow shaft which may then consist of, for example, two layers. Expansion is then effected in regions of a pressure probe which are limited by seals, with a pressurised fluid being supplied to the pressure probe via a channel.

Description

- l - 132~7~8 , ,, The present invention relates to an assembled shaft comprising a hollow shaft and elements having through-bores such as bearing bushes, cams or gear wheels attached to the hollow shaft by expansion of the hollow shaft in individual associated longitudinal portions; and to a process for producing an assembled shaft by fixing elements such as bearing bushes ? cams or gear wheels to a hollow shaft by expanding the latter in individual associated longitudinal portions.
EP-A-O 213 529 proposes a process for securing drive-elements, such as cams, gear wheels or bearin~
shells to a hollow shaft, wherein the latter is made of commercial tube onto which the elements are slid and to which they are secured by expanding sections of the tube ; 15 lying within the said ele~ents, the material of the tube itself being deformed plastically while the material of the drive-elements is deformed only elastically, so that the spring-back of the latter ensures a firm seat upon the shaft. Unpublished German Patent Applications P 36 33 435.9 and P 37 17 516.5 give dimensioning rules according to which, as a function of the properties of the materials of which the tube and the drive-elements are made, more particularly the modulus of elasticity and the yield point, the geometrical conditions, e.g. the inside and outside diameters of the tube, are to be determined, in order to obtain a non-positive joint, secure against rotation, between the parts. It has been found that when the invention is applied in particular to camshafts of motor vehicle engines, the component dimensions required by these dimensioning rules, for design and weight reasons~ cannot always be achieved.
It is an object of the present invention to provide a shaft of the said type such that a sufficiently safe attachment of the drive elements on the hollow shaft is achieved even in those cases where the possible dimensions ` of the shaft and drive elements do not permit the above-mentioned dimensioning rules to be observed.

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- 2 - i326768 The objective is achieved in that inside at least individual elements, supporting sleeves resting against the hollow shaft and plastically expanded in situ have been provided and that at least the individual elements are under elastic deformation in their through-bores. In contrast to the process described above, i-t is then no longer necessarily the material of the hollow shaft itself which is plastically deformed, but primarily the material of the supporting sleeve. As a result, the thickness of the material undergoing plastic expansion may be increased to the required dimension if the material of the hollow shaft i5 not sufficient for generating the required deformation in the drive element. It is then also possible to select for the hollow shaft a material which does not necessarily have the properties otherwise required for plastic expansion, but which has other advanta~es such as offering the possibility of saving weight~ e.g. aluminium.
In an advantageous embodiment of the invention it is possible to select for the supporting sleeve a material which has a higher modulus of elasticity or a higher yield point than that of the hollow shaft. As the former then undergoes plastic deformation at a lower rate of expansion, the amount of its elastic spring-back after completion of the expansion process,, by an amount which must be deducted from the elastic de~ormation of the outer parts during the expansion process and which reduces correspondingly the force producing the frictional connection between the parts, is reduced.
3Q It is desirable for the supporting slee~es to be longer axially than the drive-elementsl i.e. the sections on the inside of the hollow shaft project axially beyond those on the outside thereof constituted by the drive-elements. This prevents bulging of the tube and a ~otch-effect at the ends of the elements. If the drive-elements are arranged at only short distances apart, a common supporting sleeve ma~ be provided, since the excess -` 13~676~
lengths of the supporting sleeves beyond the elements would in any case touch.
According to another configuration of -the invention, use is made of supporting sleeves the ends of which have internal conical bevels. This ensures a gradual transition from expanded to non~expanded sections of the shaft. More particularly, it eliminates any notch effect at abrupt transitions between these areas.
An embodiment of the invention is illustrated in the drawing attached hereto showing a longitudinal axial section through a section of a camshaft. Cams ~ and an end flange 3 are secured to a hollow shaft 1 by plastic expansion of supporting sleeves 4 which cover, with a certain amount of excess length, those areas of hollow shaft 1 on which externally are mounted the drive elements (in this case cams 2 and end-flange 3). ~ams 2 and end-~lange 3 are defor~ed only in the elastic range so that, upon completion of the expansion process, they spring back and form a fixed non-positive union with hollow shaft 1.
This makes it possible to use a hollow shaft having material properties dif~ering from those which would be possible with direct plastic expansion. For exa~ple, for weight saving purposes, the hollow shaft 1 may consist of an outer layer 5 made of high-tensile steel and an inner layer 6 produced from J for example, aluminium. The strength and surface of the outer layer 5 may then be such that without any further machining it may be inserted into friction or roller bearings (not illustrated). Fixing the cams 2 and the end flange 3 is preferably effected in one operation by means of a hydraulic pressure probe 7 which is inserted into the hollo~ shaft and in the interior of which,via a channel ~ provided with branches, a pressure fluid may be supplied to regions 9 to be expanded which are axially li~ited by annular seals 10. The ends of the supporting sleeves 4 are shaped so as to be inwardly conical, so that in the course of expansion a gradual transition ~etween the elastically expanded and the _ 4 - ~32~

unexpanded part of the hollow shaft 1 is achieved. The process has certain advantages if, as in this case, for reasons of providing a superior result, because the camshaft is to be used in the engine of a motor vehicle, the outer diameter of the end flange 3 is so limited that the remaininB thickness of the component is not sufficient for allowing a sufficient amount of spring-back required for achieving the necessary pressure force against the hollow shaft 1. Furthermore, the introduction of torque via the end flange 3 of the camshaft to the hollow shaft is improved and the risk of slip between these two parts is reduced.

Claims

1. An assembled shaft comprising a hollow shaft and elements having through-bores such as bearing bushes, cams or gear wheels attached to the hollow shaft by expansion of the hollow shaft in individual associated longitudinal portions, wherein inside at least individual elements, supporting sleeves resting against the hollow shaft and plastically expanded in situ have been provided, and at least the individual elements are under elastic deformation in their through-bores.

2. An assembled shaft according to claim 1, wherein the material of the supporting sleeves has a higher modulus of elasticity or a higher yield point than the material of the hollow shaft.

3. An assembled shaft according to one of claims 1 and 2, wherein the supporting sleeves are axially longer than the associated elements.

4. An assembled shaft according to one of claims 1 and 2, wherein the supporting sleeves are internally provided with conical ends.

5. An assembled shaft according to one of claims 1 and 2, wherein the hollow shaft is of aluminum or a similar material.

6. An assembled shaft according to one of claims 1 and 2, wherein the hollow shaft is of two layers, with the outer layer consisting of a high-tensile bearing material.

7. A process for producing an assembled shaft by fixing elements such a bearing bushes, cams or gear wheels on a hollow shaft by expanding the hollow shaft in individual associated longitudinal portions, wherein supporting sleeves are inserted in an essentially clearance-free way into individual hollow shaft portions which are to be expanded elastically, and the supporting sleeves are expanded by exceeding the limit of elasticity of the material thereof.