CAMSHAFT COMPRISING AN AXIALLY GUIDED SLIDING ELEMENT

Abstract

A camshaft may include a shaft on which at least one sliding element is received in such a way as to be axially displaceable along a shaft axis. The shaft may comprise an external longitudinal spline structure that meshes with an internal spline structure of a passage in the sliding element such that the sliding element is arranged in a rotationally fixed manner on the shaft. The sliding element, on its axial end faces, may comprise guiding portions by way of which the sliding element is guided on the shaft to minimize an axial offset of the sliding element. Further, guiding sleeves against which the guiding portions of the sliding element are supported may be received on the shaft.

Claims

1-10. (canceled)

11. A camshaft comprising: a sliding element that comprises a passage with an internal spline structure, wherein axial end faces of the sliding element comprise guiding portions; and a shaft that receives the sliding element such that the sliding element is axially displaceable along a shaft axis, wherein the shaft comprises an external longitudinal spline structure that meshes with the internal spline structure of the sliding element such that the sliding element is rotationally fixed on the shaft, wherein the sliding element is configured to be guided on the shaft by way of the guiding portions to minimize an axial offset of the sliding element with respect to the shaft, wherein the guiding portions of the sliding element are configured to be supported against guiding sleeves of the shaft.

12. The camshaft of claim 11 wherein the guiding sleeves are shrink-fitted or pressed onto the shaft.

13. The camshaft of claim 11 wherein the guiding sleeves, seen in a direction of the shaft axis, are disposed on the shaft laterally with respect to an area of engagement of the external longitudinal spline structure in the internal spline structure.

14. The camshaft of claim 11 wherein the guiding sleeves comprise an internal spline structure, wherein the external longitudinal spline structure is free of interruptions along the shaft axis such that the internal spline structure of the guiding sleeves can mesh with the external longitudinal spline structure independent of a position along the shaft axis.

15. The camshaft of claim 11 wherein the guiding sleeves comprise an internal spline structure.

16. The camshaft of claim 15 wherein the external longitudinal spline structure comprises cylindrical receiving portions, wherein the internal spline structure of the guiding sleeves sits on the cylindrical receiving portions via tooth tips formed on the internal spline structure of the guiding sleeves.

17. The camshaft of claim 11 wherein the shaft is disposed rotationally movably in a bearing bracket, wherein the guiding sleeves comprise a longitudinal portion that forms a bearing inner ring for mounting the shaft in the bearing bracket.

18. The camshaft of claim 17 wherein at least one of the guiding sleeves comprise a cylindrical outer circumferential surface against which the guiding portions of the sliding element are supported, or the external longitudinal spline structure of the shaft comprises interruption sections among the longitudinal portions of the guiding sleeves, wherein the interruption sections with the bearing bracket forms a plain bearing arrangement.

19. The camshaft of claim 17 wherein at least one of the guiding sleeves comprise a cylindrical outer circumferential surface against which the guiding portions of the sliding element and the bearing bracket are supported, or the external longitudinal spline structure of the shaft comprises interruption sections among the longitudinal portions of the guiding sleeves, wherein the interruption sections with the bearing bracket form a plain bearing arrangement.

20. The camshaft of claim 11 wherein the guiding portions of the sliding element are configured to axially overlap the guiding sleeves such that axial displacement of the sliding element is permitted while maintaining guiding of the guiding portions on the guiding sleeves.

21. The camshaft of claim 11 wherein the sliding element comprises a carrier tube on which functional elements of the sliding element are received, wherein the guiding portions are disposed on at least one of the functional elements.

Description

PREFERRED EMBODIMENT OF THE INVENTION

[0017] Further measures that improve the invention are set out in detail below, together with the description of a preferred embodiment of the invention, with reference to the figures in which:

[0018] FIG. 1 shows a cross-sectional view of a camshaft, with guiding sleeves which are mounted on receiving portions between an external longitudinal spline structure on the main shaft,

[0019] FIG. 2 shows a modified embodiment of a camshaft, with guiding sleeves which sit on a continuous external longitudinal spline structure of the main shaft,

[0020] FIG. 3 shows a further embodiment of a camshaft, with guiding sleeves which sit on the external longitudinal spline structure of the main shaft, wherein the external longitudinal spline structure comprises an interruption section.

[0021] FIG. 1 shows part of a camshaft 1 according to a first embodiment of the invention. The camshaft 1 comprises a main shaft 10, which extends along a shaft axis 12. A sliding element 11, which is axially displaceable along the shaft axis 12, is received on the main shaft 10. The camshaft 1 in principle comprises several sliding elements 11, which can each preferably be received in the same way on the main shaft 10. In order to mount the camshaft 1 in a cylinder head, for example, or in a module hood, bearing brackets 19 are provided, and the camshaft 1 is received, rotatably about the shaft axis 12, in two bearing brackets 19, for example.

[0022] The main shaft 10 comprises an external longitudinal spline structure 13, wherein the external longitudinal spline structure 13 is shown interrupted several times along the shaft axis 12.

[0023] The sliding element 11 comprises a carrier tube 21, and an internal spline structure 14 is formed in the internal passage of the carrier tube 21. The internal spline structure 14 meshes with the external longitudinal spline structure 13 of the main shaft 10, such that the sliding element 11 is received on the main shaft 10 in such a way as to be fixed in rotation but displaceable along the shaft axis 12. The tolerance or dimensioning of the external longitudinal spline structure 13 in relation to the internal spline structure 14 is provided such that only the torque transmission is ensured, and a radial guiding with a minimal axial offset of the sliding element 11 on the main shaft 10 is effected via the meshing between the external longitudinal spline structure 13 and the internal spline structure 14.

[0024] For the radial guiding of the sliding element 11, guiding portions 15 are formed on the latter, and the guiding portions 15 run against guiding sleeves 16 which are received on the main shaft 10. In this way, the guiding sleeves 16 support the sliding element 11 via the guiding portions 15.

[0025] The guiding portions 15 are formed on functional elements 22, which are received on the carrier tube 21. In this connection, the embodiment shows a sliding element 11 with two functional elements 22, which are designed as cam elements 23 with different cam tracks. Situated between the two illustrated cam elements 23 there is an adjustment member 24, via which the sliding element 11 can be displaced on the main shaft 10 in the direction of the shaft axis using a manipulator (not shown). The sliding element 11 is shown in a leftward position with respect to the drawing plane, such that the guiding portion 15 shown on the left has a greater overlap with the left-hand guiding sleeve 16 than the guiding portion 15 shown on the right has with the right-hand guiding sleeve 16. The two guiding sleeves 16 are arranged in the carrier tube 21 adjacent to the meshing of the external longitudinal spline structure 13 with the internal spline structure 14, wherein the distance between the two guiding sleeves 16 is such that the axial mobility of the sliding element 11 is still ensured.

[0026] The guiding sleeves 16 comprise an internal spline structure 17, wherein the internal spline structure 17 is designed such that it can be guided beyond the external longitudinal spline structure 13 of the main shaft 10 in the direction of the shaft axis. The embodiment shows the main shaft 10 with interruptions in the external longitudinal spline structure 13, such that seats for receiving the guiding sleeves 16 are formed by cylindrical receiving portions 25. The guiding sleeves 16 sit with their tooth tips 17a of the internal spline structure 17 on the cylindrical receiving portions 25, and the guiding sleeves 16 can be shrink-fitted or pressed onto the receiving portions 25. For example, the diameter of the receiving portions 25 can be dimensioned such that it is slightly greater than the root diameter of the external longitudinal spline structure 13 of the main shaft 10. In this way, the guiding sleeves 16 can be guided over the external longitudinal spline structure 13 to the seats which are formed by the receiving portions 25. When the guiding sleeves 16 reach the receiving portions 25, the pressing with the main shaft 10 is obtained by way of a longitudinal interference fit or a transverse interference fit.

[0027] The guiding sleeves 16 is of a length which is defined such that the guiding sleeves 16 extend with a longitudinal portion 16a to below or into the bearing brackets 19. In this way, the guiding sleeves 16 form, with their outer circumferential surface 20, a plain bearing arrangement with the bearing brackets 19, such that the camshaft 1 can be mounted rotatably about the shaft axis 12 via the guiding sleeves 16. The guiding sleeves 16 thus perform both a guiding function of the sliding element 11 via the guiding portions 15 formed on the sliding element 11 and also a bearing function for supporting the camshaft 1 in the bearing brackets 19. The outer circumferential surface 20 of the guiding sleeves 16 can be dimensioned and surface-finished such that the guiding sleeves 16 can serve as bearing inner rings for the plain bearing in the bearing brackets 19.

[0028] FIG. 2 shows a modified embodiment of the camshaft 1 with a main shaft 10 which is hollow, for purposes of weight reduction, and which extends along a shaft axis 12. A sliding element 11 is received on the main shaft 10, and the sliding element 11 comprises a carrier tube 21 which receives two cam elements 23 and an adjustment member 24. On the inside, the carrier tube 21 comprises an internal spline structure 14, which meshes with an external longitudinal spline structure 13 of the main shaft 10. As has already been described with reference to FIG. 1, the sliding element 11 is in this way received on the main shaft 10 in such a way as to be axially movable thereon but fixed in rotation.

[0029] The main shaft 10 is formed with an external longitudinal spline structure 13 which is continuous along the shaft axis 12, such that said external longitudinal spline structure 13 is free of interruptions and all the elements are received on the external longitudinal spline structure 13 itself. Laterally with respect to the arrangement of the sliding element 11, guiding sleeves 16, which have an internal spline structure 17 on the inside, are received on the external longitudinal spline structure 13 of the main shaft 10. This internal spline structure 17 meshes with the external longitudinal spline structure 13 of the main shaft 10, and the internal spline structure 17 is dimensioned such that it is pressed onto the external longitudinal spline structure 13 of the main shaft 10 by way of a transverse interference fit or longitudinal interference fit. In particular, tooth tips 17a of the internal spline structure 17 are shown via which the guiding sleeve 16 can be pressed onto the external longitudinal spline structure 13, for example by means of the tooth tip dimension of the internal spline structure 17 being greater (i.e. with smaller tip diameter) than the tooth root dimension of the external longitudinal spline structure 13.

[0030] The embodiment shows guiding sleeves 16 with a longitudinal portion 16a which extends into the bearing brackets 19, such that the guiding sleeves 16, with the bearing brackets 19, form a plain bearing arrangement of the camshaft 1.

[0031] Guiding portions 15 are formed internally in the cam elements 23 and are guided on the outer circumferential surface 20 of the guiding sleeves 16, thereby providing the radial guiding of the sliding element 11. The guide extent between the guiding portions 15 and the outer circumferential surface 20 of the guiding sleeves 16 can be defined such that a minimum axial offset of the sliding element 11 on the main shaft 10 is obtained.

[0032] FIG. 3, finally, shows another modified embodiment of the camshaft 1 with a main shaft 10 that comprises interruption sections 18. The guiding sleeves 16 are arranged on the main shaft 10 at positions along the shaft axis 12 where the interruption sections 18 are located. The interruption sections 18 here correspond to the bearing brackets 19 for rotatably receiving the camshaft 1 via the guiding sleeves 16, and the guiding sleeves 16, via their outer circumferential surface 20, serve to support the camshaft 1 in the bearing brackets 19.

[0033] The guiding sleeves 16 are longer than the width of the interruption sections 18 in the direction of the shaft axis, such that the guiding sleeves 16 on their outsides are mounted on the external longitudinal spline structure 13 of the main shaft 10, in particular pressed on. The section over which the bearing brackets 19 form a plain bearing with the outer circumferential surface 20 of the guiding sleeves 16 thus has no interference fit of the internal spline structure 17 of the guiding sleeves 16 with the external longitudinal spline structure 13 of the main shaft 10, such that the concentricity of the outer circumferential surface 20 is not adversely affected by the pressing action of the internal spline structure 17 in the external longitudinal spline structure 13 of the main shaft 10.

[0034] The sliding element 11 is guided on the guiding sleeves 16, in the manner described above, via the guiding portions 15 which are formed on cam elements 23 that are received on a carrier tube 21 of the sliding element 11. Between the two cam elements 23 there is an adjustment member 24 for axially adjusting the sliding element along the shaft axis 12 on the main shaft 10. For the torque transmission between the main shaft 10 and the sliding element 11, an internal spline structure 14 is used which is incorporated internally in the carrier tube 21 and which interacts with the external longitudinal spline structure 13.

[0035] The invention is not limited in terms of its design to the preferred embodiment described above. Rather, numerous variants are conceivable which make use of the presented solution even in fundamentally different embodiments. All of the features and/or advantages that emerge from the claims, from the description or from the drawings, including design details or spatial arrangements, may be essential to the invention both individually and in a wide variety of combinations.

LIST OF REFERENCE SIGNS

[0036] 1 camshaft [0037] 10 main shaft [0038] 11 sliding element [0039] 12 shaft axis [0040] 13 external longitudinal spline structure [0041] 14 internal spline structure [0042] 15 guiding portion [0043] 16 guiding sleeve [0044] 16a longitudinal portion [0045] 17 internal spline structure [0046] 17a tooth tip [0047] 18 interruption section [0048] 19 bearing bracket [0049] 20 outer circumferential surface [0050] 21 carrier tube [0051] 22 functional element [0052] 23 cam element [0053] 24 adjustment member [0054] 25 receiving portion