SUPPORT TUBE OF A CAMSHAFT WITH VARYING WALL THICKNESS

Abstract

A support tube for a camshaft may include at least one setting region for setting at least one component and a free region adjoining the setting region. The support tube may further include a tube wall that has a varying thickness. In the setting region, the tube wall may exhibit a wall thickness that is greater than the wall thickness of the tube wall in the free region. Furthermore, a method for producing such a support tube may involve forming a profiled strip material with varying wall thickness into the support tube. In some cases the tube wall of the support tube may be hydroformed.

Description

The present invention relates to a support tube for a camshaft having a varying tube wall thickness. Furthermore, the invention relates to a camshaft comprising a support tube with a varying tube wall thickness, and to a method for producing said support tube.

PRIOR ART

It is fundamentally known that camshafts, in particular assembled camshafts serve for the valve control of an internal combustion engine. Assembled camshafts are known for example from DE 3 717 190 C2 with sintered cams or from DE 4 121 951 C1 with forged cams. The cams can be mounted on the carrier shaft or support shaft of the camshaft in a wide variety of ways. Thus, it is possible for the carrier shaft itself to by slightly widened at those axial positions at which the cams are intended to be fastened, for example by being rolled, wherein subsequently, the cams are pushed over the tube or the carrier shaft as far as the intended axial position. As a result, it is possible to create a form fit and/or force fit between the carrier shaft and the cam. It is likewise known for the cams to be connected to the carrier shaft by welding. A defined configuration of cams can be found for example in EP 1 860 285 A1. Vehicle manufacturers, in particular OEMs, generally wish to provide assembled camshafts with a low weight and high strength. This is on account in particular of the increasingly stringent legal requirements in terms of emission levels of combustion engines. One possibility for saving weight is for example to produce cams which exhibit as small a volume as possible and an associated weight. It is furthermore conceivable to also produce the support tube itself with a reduced material mass, in order to achieve a desired weight reduction or weight optimization. However, in particular in the case of a support tube for a camshaft, it is necessary, on account of the mounting process, in which the individual cams are attached to the support tube, to maintain a particular minimum wall thickness, in particular a particular wall thickness ratio between the outside diameter and the inside diameter of the support tube.

SUMMARY OF THE INVENTION

Therefore, it is the object of the present invention to provide a support tube, in particular a camshaft, which is/are producible easily and cost-effectively, and afford sufficient weight-saving potential and, with regard to the connecting concepts in each case, allow reliable and economical mounting of individual components.

The above object is achieved by a support tube for a camshaft having the features of claim 1 and by a camshaft comprising a support tube having the features of claim 5 and by a method for producing the support tube having the features of claim 10. Further features and details of the invention can be gathered from the dependent claims, the description and the drawings. Here, features and details which are described in conjunction with the support tube according to the invention also apply, of course, in conjunction with the camshaft according to the invention and the method according to the invention, and vice versa in each case, and so reciprocal reference is or can always be made with regard to the disclosure relating to the individual aspects of the invention.

The support tube according to the invention for a camshaft comprises at least one setting region for setting at least one component and a free region adjoining the setting region, and a tube wall that has a varying thickness. According to the invention, in the setting region, the tube wall exhibits a wall thickness which is thicker than the wall thickness of the tube wall in the free region. Advantageously, the support tube is in the form of a hollow shaft and accordingly comprises a through-opening extending in an axial direction along the support tube. This serves particularly advantageously for the production of a lightweight camshaft, in particular of a lightweight support tube. The support tube for the camshaft is consequently a constituent part of an assembled camshaft, which, as described below, comprises, in addition to a support tube, components which are connected to the support tube in a form-fitting and/or force-fitting manner. Setting of the component on the setting region of the support tube is understood, in the scope of the invention, as meaning in particular that the at least one component is arranged or mounted, advantageously connected in a force-fitting and/or form-fitting manner to the support tube at least in the setting region. Advantageously, the thickened portion of the wall thickness of the tube wall of the support tube extends in the direction of the through-opening and consequently into the interior of the support tube. This means that the outer circumferential surface of the support tube itself is formed in such an unvarying manner that no transition or offset can be found between the setting region and the free region of the support tube.

In the scope of the invention, it is furthermore conceivable for the tube wall to exhibit, in the setting region, a wall thickness which corresponds to about 110% to 190% of the wall thickness of the tube wall in the free region. Advantageously, depending on the component to be set or on the setting method used, that is to say with or without the support tube being pretreated, the wall thickness of the setting region varies with respect to the wall thickness of the tube wall in the free region. Thus, it is possible for the support tube to comprise a plurality of setting regions, which each exhibit different wall thicknesses from one another. Consequently, it is possible for setting regions which are pretreated with a raised material formation, such as a rolled formation, to exhibit a greater or thicker wall thickness than for example a setting region of the support tube that has not be subjected to a pretreatment.

Furthermore, it is possible for the tube wall to exhibit, in the setting region, a wall thickness which is twice the wall thickness of the tube wall in the free region. Advantageously, it is conceivable here for, even when there are several setting regions, these each to exhibit twice the wall thickness compared to the free regions formed advantageously between the setting regions. As a result, easy and cost-effective production of the support tube is possible.

It is moreover conceivable for the support tube to have been produced by means of hydroforming. By virtue of the hydroforming, the formation of different wall thicknesses of setting regions and free regions is advantageously easily possible. However, it is also conceivable for the support tube to have been produced by means of some other process. Accordingly, it is possible for the support tube to have been produced by means of a cold upsetting process or even an upsetting process with application of heat. Advantageously, use is made of an upsetting press for this purpose. By means of the upsetting process, in particular defined different wall thicknesses of the support tube are created.

Also claimed is a camshaft which comprises a support tube of the abovementioned type and at least one component set in the setting region of the support tube. Advantageously, the camshaft comprises a plurality of set components. In this case, it is conceivable for the camshaft to comprise for example a setting region on which a plurality of components are set. It is also conceivable for the camshaft, in particular the support tube of the camshaft, to comprise a plurality of setting regions, wherein each of the setting regions comprises at least one, advantageously a plurality of components.

It is also possible for the component to be a cam, a cam segment comprising at least two cams with mutually different cam tracks, a bearing ring, a sliding element comprising at least one guide track, or a support sleeve for the arrangement of a cam, of a cam element or of a sliding element. Advantageously, the camshaft comprises a plurality of very different components. In this case, it is conceivable for components of very different configuration to each be set or arranged on a corresponding separate setting region or on one and the same setting region. Advantageously, a plurality of components are consequently arranged alongside one another in a manner spaced apart from one another in an axial direction via a free region or in a manner directly adjoining one another (in contact with one another) on a setting region or a plurality of setting regions.

In the scope of the invention, it is furthermore conceivable that, at least in the setting region, the material of the tube wall of the support tube comprises, on its outer circumferential surface, at least one raised formation or a protrusion or a toothing. The raised formation or raised material formation and the protrusion serve advantageously for positioning and particularly advantageously for holding or fixing the at least one component. In this case, it is possible for the component or at least one component to be arranged in a force-fitting manner on the support tube. The toothing serves advantageously for the form-fitting arrangement of the at least one component on the support tube, in particular the setting region of the support tube. It is conceivable for the camshaft to comprise a support tube which comprises a plurality of setting regions, wherein each of the setting regions comprises a mutually different outer surface. This means that, for example, one of the setting regions can comprise a raised material formation, while another of the setting regions has a toothing. Advantageously, the configuration of the outer surface of each particular setting region is dependent on the component to be set on the setting region.

It is furthermore possible for the toothing to be a longitudinal toothing. This has the advantageous result that the component arranged on the setting region provided with the longitudinal toothing can be moved at least to some extent in an axial direction.

It is furthermore likewise possible for the raised formation to be a rolled formation. A rolled formation is a raised material formation that is producible in a simple manner and serves for a force-fitting arrangement of a component on the support tube.

The camshaft according to the invention leads to all the advantages that have already been described for the support tube according to the first aspect of the invention.

Also claimed is a method for producing an abovementioned support tube of an abovementioned camshaft, wherein a profiled strip material comprising a varying wall thickness is formed into the support tube.

The method described leads to all the advantages that have already been described for the support tube according to the first aspect of the invention and for the camshaft according to the second aspect of the invention.

A camshaft according to the invention is explained in more detail in the following text with reference to a drawing, in which, schematically:

FIG. 1 shows a sectional illustration from the side of an embodiment of a camshaft according to the invention with an embodiment of a support tube according to the invention.

FIG. 1 schematically illustrates a sectional illustration from the side of an embodiment of a camshaft 10 according to the invention with an embodiment of a support tube 1 according to the invention. Consequently, the camshaft 10 comprises a support tube 1, which is in the form of a hollow shaft. A through-opening 5 extends in an axial direction through the support tube 1. The support tube 1 comprises a tube wall 2, which comprises at least one setting region 3.1 and 3.2, respectively, and at least one free region 4.1, 4.2 and 4.3, respectively. Advantageously, the support tube 1 comprises three free regions 4.1, 4.2 and 4.3 and two setting regions 3.1 and 3.2. In the region of the first setting region 3.1, a raised material formation 6 has advantageously been created on the outer surface 9 of the support tube 1. It is also conceivable for a toothing, in particular a longitudinal toothing, which serves as a raised material formation, to have been formed in the first setting region 3.1.

Furthermore, a cam segment 11 has been set on the support tube 1 in the first setting region 3.1. The shaft segment 11 comprises a first cam 11.1 and a second cam 11.2. The first cam 11.1 and the second cam 11.2 have different cam tracks from one another. In the second setting region 3.2 of the support tube 1, a support sleeve 12 has advantageously been placed on the support tube 1. Advantageously, no pretreatment of the outer surface 9 of the support tube 1 in the form of a raised material formation, in particular of a toothing or rolled formation or the like, is formed on the outer surface 9 of the support tube 1 in the second setting region 3.2, such that, for example, the support sleeve 12 has been merely slid onto the support tube 1, in particular onto the setting region 3.2. In this case, it is conceivable for the support sleeve 12 to be heated, for example, with the result that it undergoes a widening of its through-bore, such that, after being heated, the support sleeve 12 is slid onto the support tube 1 as far as its defined setting region 3.2. After the support sleeve 12 has been positioned on the support tube 1, the support sleeve 12 is cooled and reaches its starting temperature, with the result that in particular the through-opening of the support sleeve 12 contracts again and an interference fit between the support sleeve 12 and the support tube 1 arises. However, alternatively or additionally to the heating of the support sleeve 12, it would also be conceivable for the support tube 1 to be cooled, at least before the support sleeve 12 is slid onto the support tube 1. Advantageously, throughout the sliding-on process, at least the support sleeve 12 is heated or the support tube 1 is cooled. After the support sleeve 12 has been slid onto the support tube 1, at least the support sleeve 12 is then cooled or the support tube 1 is then heated. This (shaft/hub) connection is also referred to as a thermal shrink fit or thermal transverse interference fit. Advantageously, in this case, the support sleeve 12 only covers the support tube 1 in the setting region 3.2 of the support sleeve 12 on the support tube 1. Instead of the support sleeve 12, it also possible for other components, for example a cam or a cam segment, a sliding element, etc., to be attached to the support tube 1 by means of the abovementioned method.

However, it is also conceivable for a raised material formation for example in the form of a rolled formation to have been created on the outer surface 9 of the support tube 1 in the second setting region 3.2, such that when the support sleeve 12 is attached to the second setting region 3.2, a force-fitting connection is allowed on account of the material displacement between the support sleeve 12 and the support tube 1. The cam segment 11 and the support sleeve 12 are components 20 which are arranged or have been set on the respective setting regions 3.1 and 3.2 of the support tube 1 in order to form a camshaft 10.

As is apparent from FIG. 1, the thickened portions of the wall thicknesses, in particular the wall thickness 8 of the setting regions 3.1 and 3.2, extend in the direction of the through-opening 5 and thus into the interior of the support tube 1. The wall thickness 7 of the free region 4.1, 4.2, 4.3 is, as is apparent from FIG. 1, less or thinner than the wall thickness 8 of the setting regions 3.1 and 3.2.

LIST OF REFERENCE SIGNS

1 Support tube

2 Tube wall

3.1 (First) setting region

3.2 (Second) setting region

4.1 (First) free region

4.2 (Second) free region

4.3 (Third) free region

5 Through-opening

6 Raised (material) formation

7 Wall thickness of the free region

8 Wall thickness of the setting region

9 Outer surface of the support tube

10 Camshaft

11 Cam segment

11.1 First cam

11.2 Second cam

12 Support sleeve

20 Component

Claims

1-10. (canceled)

11. A support tube for a camshaft comprising: a first setting region for setting a first component;a second setting region for setting a second component, wherein the first and second setting regions have mutually different outer surfaces;a free region adjoining the first and second setting regions; anda tube wall that has a varying thickness, wherein thickened portions of the tube wall in the first and second setting regions have a greater thickness than a thickness of the tube wall in the free region, wherein the thickened portions of the tube wall in the first and second setting regions extend into an interior of the support tube such that an outer circumferential surface of the support tube is unvarying in that transitions or offsets between the free region and the setting regions are avoided.

12. The support tube of claim 11 wherein the thickened portions of the tube wall in the first and second setting regions are 110% to 190% as thick as the thickness of the tube wall in the free region.

13. The support tube of claim 11 wherein the thickened portions of the tube wall in the first and second setting regions are twice as thick as the thickness of the tube wall in the free region.

14. The support tube of claim 11 wherein the tube wall is hydroformed.

15. The support tube of claim 11 comprising the first component set on the first setting region, wherein the first component is at least one of a cam,a cam segment comprising at least two cams with mutually different cam tracks,a bearing ring,a sliding element having at least one guide track, ora support sleeve for receiving a cam of a cam segment or of a sliding element.

16. The support tube of claim 11 wherein at least in the first setting region a material of the tube wall has on the outer circumferential surface at least one of a raised formation, a protrusion, or a toothing.

17. The support tube of claim 16 wherein the toothing is a longitudinal toothing.

18. The support tube of claim 16 wherein the raised formation is a rolled formation.

19. A method for producing the support tube of claim 11, the method comprising forming a profiled strip material that has a varying wall thickness into the support tube of claim 11.

20. A support tube for a camshaft comprising: a first setting region for setting a first component;a second setting region for setting a second component;a free region adjoining the first setting region; anda tube wall, wherein thickened portions of the tube wall in the first and second setting regions have greater thicknesses than a thickness of the tube wall in the free region, wherein the thickened portion of the tube wall in the first setting region extends into an interior of the support tube such that an outer diameter of the tube wall in the first setting region is the same as an outer diameter of the tube wall in the free region.

21. The support tube of claim 20 wherein the first and second setting regions have mutually different outer surfaces.

22. The support tube of claim 20 wherein an outer circumferential surface of the support tube is free of any transition between the first setting region and the free region.

23. The support tube of claim 20 wherein an outer circumferential surface of the support tube is free of any offset between the first setting region and the free region.

24. The support tube of claim 20 wherein the thickened portion of the tube wall in the first setting region is 110% to 190% as thick as the thickness of the tube wall in the free region.

25. The support tube of claim 20 wherein the tube wall is hydroformed.

26. The support tube of claim 20 comprising the first component set on the first setting region, wherein the first component is at least one of a cam segment with at least two different cam tracks, ora sliding element having at least one guide track.

27. The support tube of claim 20 wherein at least in the first setting region a material of the tube wall has on the outer circumferential surface at least one of a rolled formation or a longitudinal toothing.