Camshaft unit

Abstract

A camshaft unit (1), having a first camshaft (2) which is phase-adjustable with respect to a crankshaft, having a second camshaft (3) which is arranged concentrically with respect to the first camshaft (2), and having a camshaft adjuster (5) by which both camshafts (2, 3) are phase-adjusted with respect to the crankshaft.

Claims

1. A camshaft unit, comprising: a first camshaft, a second camshaft that is arranged concentric to the first camshaft, a camshaft adjuster with which the first and second camshafts are phase-adjustable, the camshaft adjuster has a connecting element that moves in an axial direction of the camshafts and comprises a first toothed section and a second toothed section, the first toothed section meshes with a first counter toothed section on the first camshaft and the second toothed section meshes with a second counter toothed section on the second camshaft, and the first toothed section and the second toothed section of the connecting element are constructed as helical toothed sections, wherein the camshaft unit has an adjustment drive with a ball screw drive including a spindle that drives a threaded nut directly mounted on the connecting element, the connecting element is formed as a sleeve, and the threaded nut is arranged in a sleeve interior of the sleeve and secured in the axial direction.

2. The camshaft unit according to claim 1, wherein the first and second camshafts are coupled to the camshaft adjuster and the camshaft adjuster drives an opposite-phase adjustment of the first and second camshafts.

3. The camshaft unit according to claim 1, wherein the sleeve has a radial shoulder and the first and second toothed sections are formed on tubular wall sections with different diameters.

4. The camshaft unit according to claim 3, wherein the sleeve has an end-side ring groove having an outer wall that has the first toothed section and having an inner wall that has the second toothed section.

5. The camshaft unit according to claim 1, wherein the sleeve has an outer casing on which the first toothed section is formed and having an inner casing on which the second toothed section is formed.

6. The camshaft unit according to claim 1, wherein both of the first counter toothed section and the second counter toothed section are constructed as helical toothed sections.

7. A camshaft unit, comprising: a first camshaft, a second camshaft that is arranged concentric to the first camshaft, a camshaft adjuster with which the first and second camshafts are phase-adjustable, the camshaft adjuster has a connecting element that moves in an axial direction of the camshafts and comprises a first toothed section and a second toothed section, the first toothed section meshes with a first counter toothed section on the first camshaft and the second toothed section meshes with a second counter toothed section on the second camshaft, and the first toothed section and the second toothed section of the connecting element are constructed as helical toothed sections, wherein the camshaft unit has an adjustment drive with a ball screw drive including a spindle that drives a threaded nut directly mounted on the connecting element, and one of the first and second camshafts is supported by ball bearings on the spindle.

8. The camshaft unit according to claim 7, wherein the first and second camshafts are coupled to the camshaft adjuster and the camshaft adjuster drives an opposite-phase adjustment of the first and second camshafts.

9. The camshaft unit according to claim 7, wherein the sleeve has a radial shoulder and the first and second toothed sections are formed on tubular wall sections with different diameters.

10. The camshaft unit according to claim 9, wherein the sleeve has an end-side ring groove having an outer wall that has the first toothed section and having an inner wall that has the second toothed section.

11. The camshaft unit according to claim 7, wherein the sleeve has an outer casing on which the first toothed section is formed and has an inner casing on which the second toothed section is formed.

12. The camshaft unit according to claim 7, wherein both of the first counter toothed section and the second counter toothed section are constructed as helical toothed sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail below with reference to embodiments shown in the drawing. Shown are:

(2) FIG. 1 a first camshaft unit in longitudinal section with a displacement element that has two inner toothed sections,

(3) FIG. 2 a second camshaft unit in longitudinal section with a displacement element that has two outer toothed sections,

(4) FIG. 3 a third camshaft unit in longitudinal section with a displacement element that has an end-side ring groove,

(5) FIG. 4 a fourth camshaft unit in longitudinal section with a displacement element that has an inner and an outer toothed section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) FIG. 1 shows a first camshaft unit 1 with a first camshaft 2, a second camshaft 3 arranged concentric to the first camshaft 2, and a connecting element 4. The connecting element 4 connects to the first camshaft 2 via a first toothed section 16 and to the second camshaft via a second toothed section 17. For this purpose, the connecting element 4 is formed as a stepped sleeve that has two different inner radii and surrounds two camshafts 2, 3 on the outside in the radial direction. The inner radius difference corresponds to the ring diameter of the outer camshaft that is presently formed by the first camshaft 2. The two camshafts 2, 3 extend by different amounts in the axial direction into the inner hollow space 14 of the connecting element 4. The toothed sections 16, 17 of the connecting element 4 mesh with counter toothed sections 6, 7 of the camshafts 2, 3. All three components, the two camshafts 2, 3 and the connecting element 4, can rotate about the common rotational axis 10.

(7) The connecting element 4 can move in the axial direction. The axial advance is introduced by a camshaft adjuster 5 that is shown only schematically and has an adjustment drive 9 that can be operated by means of an electric motor. The adjustment drive 9 is formed by a shaft in the form of a spindle 8 on which a threaded nut 18 is arranged. With the threaded nut 18, the spindle 8 forms a ball screw-type drive. In the present case, the threaded nut 18 is produced separately from the connecting element 4 and is connected rigidly to the connecting element 4. On one side it contacts a radial shoulder 11 of the connecting element 4 and is held by a securing ring 12 on its other axial end.

(8) The shaft has, on its shaft end, a ball bearing 19 by means of which the inner camshaft is supported.

(9) The toothed sections 16, 17 and their contour toothed sections 6, 7 are constructed as helical toothed sections. Rotation of the spindle 8 initially causes an axial advance of the connecting element 4 connected to the threaded nut 18. The torque introduced by the toothed sections 16, 17 on the camshafts 2, 3 causes their rotation due to their fixed positioning in the axial direction.

(10) FIG. 2 shows a construction of a camshaft unit 1 that differs from that according to FIG. 1 essentially in that the connecting element 4 is formed as a sleeve whose wall thickness is approximately constant. Furthermore, the camshafts 2, 3 do not have meshing teeth with this on the inner periphery of the sleeve, but instead on the outer casing 13. The sleeve-shaped connecting element 4 can therefore have an essentially constant wall thickness and can be lighter in weight. This connecting element 4 also has a radial shoulder 11 on which the threaded nut 18 contacts. With the radial shoulder 11, the diameter of the sleeve is simultaneously expanded to the inner periphery of the outer camshaft 3. This sleeve therefore has only two steps, while the sleeve according to FIG. 1 has three different inner diameter regions (for the two camshafts 2, 3 and the threaded nut 18).

(11) FIG. 3 shows a construction of a camshaft unit 1 that differs from that according to FIG. 1 essentially in that the connecting element 4 is constructed as a sleeve with a ring groove 15 formed axially on the end side. The ring groove 15 runs concentric to the rotational axis 10 and has a groove base that is bounded by an outer wall with the first toothed section 16 and an inner wall with the second toothed section 17. The two toothed sections 6, 7 are in turn constructed as helical toothed sections. Because the two camshafts 2, 3 mesh on different walls, an axial offset of the camshaft is not required. The ring groove 15 can thus be relatively flat, so that the inner hollow space 14 still present here could also be completely omitted.

(12) On the end 20 of the connecting element 4 facing away from the ring groove 15 there is, on the radial inner side, a recess for the threaded nut 18.

(13) FIG. 4 shows a construction of a camshaft unit 1 that differs from that according to FIG. 1 in that the connecting element 4 is formed as a sleeve with an essentially constant diameter. Such a sleeve can be produced economically. As in the embodiment according to FIG. 3, the counter toothed sections 6, 7 of the camshafts 2, 3 engage in the toothed sections 16, 17 of the connecting element 4 from different radial directions. For this purpose, the camshafts 2, 3 adjacent to each other actually in the radial direction each form a ring-shaped recess and together form a ring gap 21. The counter toothed sections 6, 7 are arranged on the walls of the ring-shaped recess. The connecting element 4 extends with its toothed sections 16, 17 into the ring gap 21. The connecting element 4 is connected via the threaded nut 18 to the spindle 8 on its end 20 turned away from the ring gap 21.