| Method for manufacturing a constructed camshaft -> Monitor Keywords |
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Method for manufacturing a constructed camshaftRelated Patent Categories: Metal Working, Crankshaft Making ApparatusMethod for manufacturing a constructed camshaft description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060064860, Method for manufacturing a constructed camshaft. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of international patent application PCT/EP2004/002236 filed Mar. 3, 2004 and designating the U.S., which was not published under PCT Article 21(2) in English, and claims priority of German patent application DE 103 13 812.9, filed Mar. 21, 2003, which is incorporated herein by reference. FIELD OF THE INVENTION [0002] The invention relates to a method for manufacturing a constructed camshaft starting from a tube into which a plurality of noncircumferential depressions, which are oriented parallel to the longitudinal axis and are transverse with respect to the longitudinal axis, are pressed, and separated prefabricated cams are attached to the tube. BACKGROUND OF THE INVENTION [0003] Camshafts are used for controlling valves in internal combustion engines of motor vehicles. As technical progress has continued these internal combustion engines have been constructed with increasingly compact designs. The fabrication of engines, specifically the assembly, takes place in a highly automated fashion so that in this context use is increasingly being made of easy-to-assemble modules which are pre-assembled by the system suppliers. For reasons of space, the camshafts are often positioned in pairs so close to one another that direct access to the cylinder head bolts is no longer possible. As a result of these requirements, there is a need for specially shaped camshafts which allow, for example, automatic screwdriver devices to access the cylinder head bolts. [0004] In relation to constructed camshafts composed of a tube and prefabricated cams attached thereto, DE 20116112 UI specifies a solution with which access to the cylinder head bolts is made possible in the installed state of the camshaft via depressions formed in the tube. [0005] When such a camshaft is manufactured, the desired depressions are produced on the initial tube by pressing a plurality of shaping dies, which are arranged in holding tools, into the wall of the tube in a separate fabrication step before the cams are pushed on and attached. [0006] The tool which is used for producing the depressions in the transverse direction with respect to the axis of the camshaft must be shaped in such a way that the deformation produced in the region of the wall of the tube during the pressing-in process does not result in the original external diameter of the tube being made larger in the adjacent region of the wall of the tube. This is absolutely necessary so as to permit the prefabricated cams, provided with a bore corresponding to the external diameter of the tube, to be pushed over the tube, provided with the depressions, to their position in the subsequent fabrication step. [0007] The camshaft which is manufactured according to this method has the disadvantage that an additional, costly fabrication step for producing the depressions in the camshaft tube is necessary and that the external diameter of the tube must not be changed. OBJECTS OF THE INVENTION [0008] The object of the invention is therefore to specify a method for manufacturing constructed camshafts and a device for carrying out this method with which depressions can be produced on the camshaft in an easy and cost-effective way. SUMMARY OF THE INVENTION [0009] According to the invention, a method for manufacturing a constructed camshaft is provided, wherein a plurality of non-circumferential depressions, which are oriented parallel to the longitudinal axis and are transverse with respect to the longitudinal axis, are pressed into a tube, wherein separately prefabricated cams are attached to the tube, and wherein the pressing-in of the depressions and the attachment of the cams to the tube take place in one working step. [0010] The cams are attached to the tube by hydroforming, with the pressing-in of the depressions taking place before the start of the increase in pressure or during the increase in pressure in the tube to a predefined final pressure. [0011] In the device according to the invention for carrying out the method, a hydroforming tool composed of an upper tool and a lower tool with axially moveable sealing dies is used, in which hydroforming tool shaping dies, which can be moved radially with respect to the axis of the tube and as far as into the cavity formed by the closed tool, are arranged in the upper and/or lower tools. [0012] As a result of this method, on the one hand, an additional, costly fabrication step is avoided and, on the other hand, the shaping dies can easily be integrated into the existing hydroforming tool, allowing additional tool costs to be kept very low. [0013] According to one advantageous refinement of the invention, in a first step, before the pressing-in of the depressions, a predefined supporting pressure is applied to the tube, in which case, after this supporting pressure has been reached, the depressions are pressed in completely and the internal pressure is then increased to the final pressure to be attained. [0014] This procedure has the advantage that it requires substantially lower die forces than if the shaping dies have to be moved counter to the maximum final pressure. [0015] On the other hand, it is advantageous if the shaping dies are not already moved into their final position before the supporting pressure is applied so that the axial widening of the resulting deformation is reduced. Furthermore, when the depressions are pressed in without a supporting pressure in the tube, undesired deformations or buckling points may be formed, these can even be equalized by the maximum final pressure. [0016] By optimizing the supporting pressure which is to be reached before the shaping die penetrates the tube, it is thus possible to reduce the axial widening of the depression which is formed and to avoid undesired deformations or buckling points in the tube. [0017] Since further functional elements or additional elements such as, for example, bearing rings or gear wheels are also simultaneously joined to the tube by means of the hydroforming process, it is possible also to advantageously minimize the overall length of the camshaft by minimizing the necessary distance between the depression and the functional parts. [0018] The maximum supporting pressures in the case of the shaping die which is drawn back in the tool should advantageously be selected such that the tube is prevented from widening into the die guide, as a result of which otherwise notches, which constitute weak points in the camshaft, may be formed. [0019] When the depressions are pressed in, in addition to the axial movement of the sealing dies which is necessary to maintain the seal, it is advantageously possible for the tube to be pushed axially beyond this. The change in the wall thickness caused by the material flow in the region of the depression can thus be utilized to even out the thickness of the wall in particular at the depressions which are respectively closest to the end of the tube. Continue reading about Method for manufacturing a constructed camshaft... Full patent description for Method for manufacturing a constructed camshaft Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method for manufacturing a constructed camshaft patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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