CAMSHAFT HAVING AN AXIALLY GUIDED SLIDING ELEMENT

Abstract

A camshaft may include a shaft as well as a sliding element that is disposed on the shaft such that the sliding element is axially displaceable along a shaft axis. The shaft may comprise an external tooth for transmitting torque between the shaft and the sliding element. The external tooth may engage a mating tooth geometry formed in a passage of the sliding element. The sliding element on its axial end faces may comprise bearing collars that with the shaft form radial supporting bearings of the sliding element on the shaft. Further, the shaft may comprise cylindrical bearing portions for forming the radial supporting bearings, wherein the bearing portions can be configured with a diameter that is smaller than a diameter circumscribed by tips of the mating tooth geometry that protrude into the passage of the sliding element.

Claims

1.-10. (canceled)

11. A camshaft comprising: a sliding element with axial end faces, wherein the sliding element comprises on each of the axial end faces a bearing collar; and a shaft that receives the sliding element such that the sliding element is axially displaceable along a shaft axis, the shaft comprising an external tooth for transmitting torque between the shaft and the sliding element, wherein the external tooth engages a mating tooth geometry formed in a passage of the sliding element, wherein the bearing collars with the shaft form radial supporting bearings of the sliding element on the shaft, the shaft further comprising cylindrical bearing portions that form the radial supporting bearings, wherein a diameter of the cylindrical bearing portions is smaller than a diameter circumscribed by tips of the mating tooth geometry that protrude into the passage.

12. The camshaft of claim 11 wherein the mating tooth geometry comprises a hollow cylindrical portion with a tooth notch, wherein the external tooth of the shaft engages the tooth notch of the hollow cylindrical portion.

13. The camshaft of claim 12 wherein the bearing collars of the sliding element comprise a bearing internal diameter that is smaller than an internal diameter of the hollow cylindrical portion.

14. The camshaft of claim 12 wherein the cylindrical bearing portions of the shaft have an external diameter that is smaller than an internal diameter of the hollow cylindrical portion in the sliding element.

15. The camshaft of claim 11 wherein at least one of the bearing collars comprises a mounting notch, wherein the external tooth of the shaft is guided through the mounting notch as the sliding element is guided onto the shaft.

16. The camshaft of claim 15 wherein the mating tooth geometry comprises a hollow cylindrical portion with a tooth notch, wherein the external tooth of the shaft engages the tooth notch of the hollow cylindrical portion, wherein the tooth notch and the mounting notch are at mutually identical circumferential positions in the sliding element and are aligned with one another in a direction of the shaft axis.

17. The camshaft of claim 11 wherein a length of the external tooth as measured along the shaft axis is less than a distance between the bearing collars of the sliding element.

18. The camshaft of claim 11 further comprising at least two latch grooves disposed in the passage of the sliding element between one of the bearing collars and the mating tooth geometry, wherein a latching element that is received on the shaft is configured to latch into the at least two latch grooves.

19. The camshaft of claim 11 wherein an external diameter of a portion of the shaft where the external teeth are disposed is equivalent to an external diameter of the bearing portions.

20. The camshaft of claim 11 wherein the sliding element comprises a carrier tube, wherein the bearing collars are formed on the axial end faces of the carrier tube.

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 part of a camshaft, with a radial supporting bearing configured according to the invention,

[0019] FIG. 2 shows a further embodiment of a camshaft having the features of the present invention,

[0020] FIG. 2a shows a sectional view along the section line I-I in FIG. 2,

[0021] FIG. 2b shows a sectional view along the section line II-II in FIG. 2, and

[0022] FIG. 3 shows a cross-sectional view of the camshaft according to FIG. 2, in a section plane rotated about the shaft axis.

[0023] FIG. 1 shows a cross-sectional view of a camshaft 1 with a basic shaft 10 which extends along a shaft axis 12, wherein a sliding element 11, which is shown only schematically and in a simplified manner, is mounted on the basic shaft 10. The sliding element 11 comprises cam tracks, via which lift information can be transmitted to a valve of an internal combustion engine. To control the valve with different cam tracks, the sliding element 11 can be displaced on the basic shaft 10 in the direction of the shaft axis and, in order to generate discrete axial positions of the sliding element 11 on the basic shaft 10, a latching element 22 is used which is pretensioned with a compression spring 24 and is configured, for example, as a latching ball that can latch into latch grooves 21 formed in a passage in the sliding element 11.

[0024] For the transmission of torque between the basic shaft 10 and the sliding element 11, the basic shaft 10 comprises external teeth 13 shown by way of example, and the basic shaft 10 comprises, according to the embodiment shown, eight external teeth 13 which are mounted in pairs at 90° positions on the circumference of the basic shaft 10. In a modification of the illustrated distribution of the external teeth 13 on the basic shaft 10, these can also be arranged twice individually or twice in pairs at positions lying 180° opposite each other on the basic shaft 10, in which case, for example, a triple arrangement with a division of 120° distributed uniformly about the circumference is also advantageously possible.

[0025] The external teeth 13 engage in a mating tooth geometry 14 formed in the sliding element 11, such that a force can be transmitted via the flanks of the external teeth 13 and of the mating tooth geometry 14 in the circumferential direction. In this way, a torque can be transmitted between the basic shaft 10 and the sliding element 11, such that the sliding element 11 is not rotatable on the basic shaft 10, but the sliding element 11 is guided axially on the basic shaft 10 in the direction of the shaft axis.

[0026] The guiding is effected via bearing collars 15 which, viewed axially, are formed adjacent to the outsides within the sliding element 11. The bearing collars 15 run against bearing portions 17, which are formed by corresponding cylindrical portions of the basic shaft 10.

[0027] The bearing portions 17 are configured with a diameter that is smaller than the smallest diameter of the mating tooth geometry 14 in the sliding element 11. By virtue of the supporting bearing 16 configured according to the invention, the advantage is afforded that the sliding element 11 can be pushed onto the basic shaft 10 in the direction of the shaft axis, and the supporting bearing 16 with the bearing collars 15, which are substantially cylindrical and run against cylindrical bearing portions 17, can provide a plain bearing with minimal play and minimal wear for radially guiding the sliding element 11 on the basic shaft 10.

[0028] Corresponding to the positions of the external teeth 13 on the basic shaft 10, the bearing collars 15 can be configured with mounting notches 20 which extend axially parallel in the axial direction and correspond to the circumferential position of the external teeth 13. When the sliding element 11 is pushed onto the basic shaft 10, the external teeth 13 can be made to overlap the mounting notches 20 in the bearing collars 15, such that the sliding element 11 can be mounted on the basic shaft 10 despite the greater external diameter of the external teeth 13 in relation to the diameter of the bearing collars 15. The bearing collars 15, configured substantially as hollow cylinders with the mounting notches 20 as small interruptions, are not impeded by the mounting notches 20 in their guiding function for radially guiding the sliding element 11 on the basic shaft 10 over the bearing portions 17.

[0029] FIG. 2 shows a cross section through a camshaft 1 with a basic shaft 10 and a sliding element 11, and the sliding element 11 is axially movable on the basic shaft 10 in the direction of the shaft axis. The cross-sectional view of the basic shaft 10 shows a transition of the bearing portions 17 into the area of the basic shaft 10 in which the external teeth 13 are formed, which extend into the mating tooth geometry 14 in the sliding element 11. The mating tooth geometry 14 in this case comprises tooth notches 19 which are formed in a hollow cylindrical portion which is not depicted by reason of the section plane, and reference is made to FIG. 3 in which the hollow cylindrical portion 18 is shown.

[0030] The bearing collars 15 of the sliding element 11 run against the bearing portions 17, and the sectional view shows mounting notches 20 which are formed in the bearing collars and which correspond to the circumferential position of the external teeth 13, such that the sliding element 11 can be pushed onto the basic shaft 10.

[0031] FIG. 2a shows a cross-sectional view along the section line I-I, as shown in FIG. 2. The view shows the basic shaft 10 in the area of the bearing portion 17, and it also shows four mounting notches 20, distributed uniformly on the circumference, in the bearing collar 15 of the sliding element 11. Despite the mounting notches 20, a supporting bearing 16 between the sliding element 11 and the basic shaft 10 is created substantially in the manner of a plain bearing which allows the sliding element 11 to be guided on the basic shaft 10 with minimal play and with load-bearing capacity, without the sliding element 11 having to be guided via the meshing between the external teeth 13 and the mating tooth geometry 14, which serves only for the transmission of torque. In this way, particularly good run-out accuracy of the sliding element 11 on the basic shaft 10 is achieved.

[0032] FIG. 2b shows a cross-sectional view along the section line II-II, as shown in FIG. 2. The basic shaft 10 is shown sectioned in the area in which the basic shaft 10 comprises the external teeth 13, and the external teeth 13 extend into the tooth notches 19 formed in the hollow cylindrical portion 18 of the sliding element 11. The mating tooth geometry 14 is formed with the hollow cylindrical portion 18 and the tooth notches 19, and four tooth notches 19 are provided in uniform distribution on the circumference and correspond to likewise four external teeth 13. The circumferential positions of the tooth notches 19 match the circumferential positions of the mounting notches 20 in the bearing collars 15, as is shown in FIG. 2a.

[0033] FIG. 3 shows a cross-sectional view of the camshaft 1 according to FIG. 2, in a section plane rotated about the shaft axis 12. This plane shows the hollow cylindrical portion 18 in the passage of the sliding element 11, which transitions laterally into the bearing collar 15 and into the latch grooves 21 which, in their axial continuation, transition into the wider bearing collar 15.

[0034] The sliding element 11 comprises a carrier tube 23 on which cam elements 25 and an adjustment member 26 for axially adjusting the sliding element 11 are formed. The bearing collars 15 for forming the supporting bearing 16 are introduced internally in the carrier tube 23, and the cam elements 25 and the adjustment member 26 can be pressed individually or together onto the outside of the carrier tube 23.

[0035] The cross-sectional views of FIGS. 2 and 3 show that the cylindrical bearing portions 17 of the basic shaft 10 are configured with a diameter that is smaller than the smallest diameter of the mating tooth geometry 14 in the sliding element 11. This allows the sliding element 11 to be mounted on the basic shaft 10, while at the same time the bearing portions 17 for radially guiding the sliding element 11 can have a cylindrical configuration, while only the bearing collar 15 comprises individual mounting notches 20 through which the external teeth 13 can run when the sliding element 11 is mounted on the basic shaft 10. By means of external teeth 13 provided only individually on the circumference, and associated tooth notches 19, the sliding element 11 can be supported radially on the basic shaft 10 with minimal wear and with load-bearing capacity, without the bearing having to take place on the tooth tips of the outer tooth geometry of the basic shaft 10.

[0036] 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

[0037] 1 camshaft [0038] 10 basic shaft [0039] 11 sliding element [0040] 12 shaft axis [0041] 13 external tooth [0042] 14 mating tooth geometry [0043] 15 bearing collar [0044] 16 supporting bearing [0045] 17 bearing portion [0046] 18 hollow cylindrical portion [0047] 19 tooth notch [0048] 20 mounting notch [0049] 21 latch groove [0050] 22 latching element [0051] 23 carrier tube [0052] 24 compression spring [0053] 25 cam element [0054] 26 adjustment member