TIMING WHEEL ASSEMBLY FOR A CONCENTRIC CAMSHAFT

Abstract

A camshaft assembly is disclosed that comprises an inner shaft, an outer tube surrounding and rotatable relative to the inner shaft, and two groups of cam lobes mounted on the outer tube. The first group of cam lobes is fast in rotation with the outer tube and the second group is rotatably mounted on the outer surface of the outer tube and is connected for rotation with the inner shaft. A timing wheel is connected for rotation with the inner shaft to provide position information to a sensor, the timing wheel being formed as a separate part that is assembled to one of the cam lobes in the second group.

Claims

1. A camshaft assembly comprising: an inner shaft, an outer tube surrounding and rotatable relative to the inner shaft, two groups of cam lobes mounted on the outer tube, the first group of cam lobes being fast in rotation with the outer tube, the second group being rotatably mounted on the outer surface of the outer tube and connected for rotation with the inner shaft, and a timing wheel connected for rotation with the inner shaft to provide position information to a sensor, wherein the timing wheel is formed as a separate part that is assembled to one of the cam lobes in the second group.

2. A camshaft as claimed in claim 1, wherein the cam lobe to which the timing wheel is assembled is identical to at least one other cam lobe in the second group.

3. A camshaft as claimed in claim 1, wherein the timing wheel is a stamped sheet metal part.

4. A camshaft as claimed in claim 1, wherein the timing wheel is a sintered part.

5. A camshaft as claimed in claim 3, wherein the timing wheel is joined to the cam lobe by a welding process.

6. A camshaft as claimed in claim 3, wherein the timing wheel is a press fit on to a cylindrical feature of the cam lobe.

7. A camshaft as claimed in claim 3, wherein timing wheel is located concentrically on the cam lobe and its angular position relative to the cam lobe is defined by a connecting pin that connects the cam lobe (10) for rotation with the inner drive shaft.

8. A camshaft as claimed in claim 3, wherein the timing wheel is assembled to the cam lobe and then deformed in order to retain it in the correct position relative to the cam lobe.

9. A camshaft as claimed in claim 2, wherein the timing wheel is a stamped sheet metal part.

10. A camshaft as claimed in claim 2, wherein the timing wheel is a sintered part.

11. A camshaft as claimed in claim 9, wherein the timing wheel is joined to the cam lobe by a welding process.

12. A camshaft as claimed in claim 4, wherein the timing wheel is joined to the cam lobe by a welding process.

13. A camshaft as claimed in claim 10, wherein the timing wheel is joined to the cam lobe by a welding process.

14. A camshaft as claimed in claim 9, wherein the timing wheel is a press fit on to a cylindrical feature of the cam lobe.

15. A camshaft as claimed in claim 4, wherein the timing wheel is a press fit on to a cylindrical feature of the cam lobe.

16. A camshaft as claimed in claim 10, wherein the timing wheel is a press fit on to a cylindrical feature of the cam lobe.

17. A camshaft as claimed in claim 9, wherein the timing wheel is located concentrically on the cam lobe and its angular position relative to the cam lobe is defined by a connecting pin that connects the cam lobe for rotation with the inner drive shaft.

18. A camshaft as claimed in claim 4, wherein the timing wheel is located concentrically on the cam lobe and its angular position relative to the cam lobe is defined by a connecting pin that connects the cam lobe for rotation with the inner drive shaft.

19. A camshaft as claimed in claim 10, wherein the timing wheel is located concentrically on the cam lobe and its angular position relative to the cam lobe is defined by a connecting pin that connects the cam lobe for rotation with the inner drive shaft.

20. A camshaft as claimed in claim 9, wherein the timing wheel is assembled to the cam lobe and then deformed in order to retain it in the correct position relative to the cam lobe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The invention will now be described further, by way of example with reference to the accompanying drawings, in which:

[0029] FIGS. 1 and 2 are sectional and perspective views, respectively, of part of a camshaft assembly of a first embodiment of the invention,

[0030] FIG. 3 is a view similar to FIG. 1 of part of a camshaft assembly of a second embodiment of the invention,

[0031] FIG. 4 is a perspective view of the timing wheel of the embodiment shown in FIG. 4,

[0032] FIGS. 5 and 6 are views similar to FIGS. 1 and 2 of part of a camshaft assembly of a third embodiment of the invention, and

[0033] FIGS. 7 and 8 are views similar to FIGS. 1 and 2 of part of a camshaft assembly of a fourth embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

First Embodiment

[0034] A “concentric camshaft” is an assembly that comprises an inner shaft, an outer tube surrounding and rotatable relative to the inner shaft, and two groups of cam lobes mounted on the outer tube. The first group of cam lobes is fast in rotation with the outer tube, while the second group, herein termed sliding cam lobes, are rotatably mounted on the outer surface of the tube and are connected for rotation with the inner shaft.

[0035] In FIGS. 1 and 2, there is shown one of the sliding cam lobes 10 rotatably supports on the outer tube 12 of the concentric camshaft and connected for rotation with the inner shaft 14 of the concentric camshaft by a pin 16 that passes through a tangentially elongated slot (not shown) formed in the outer tube 12. A timing wheel 18 formed as a stamped sheet metal component separate from the cam lobe has a number of small features 20 to allow projection welding onto the end of the cam lobe.

Second Embodiment

[0036] The second embodiment shown in FIGS. 3 and 4 is similar to the first and like parts have been allocated like reference numerals. The essential difference from the first embodiment is that the timing wheel 28 is sintered and is formed with small protrusions 30 to allow it to be projection welded in place on the cam lobe 10.

Third Embodiment

[0037] The third embodiment, shown in FIGS. 5 and 6, has a timing wheel 38 that is engaged on the cylindrical collar 10a of the cam lobe 10 and its correct angular position is preferably guaranteed by arranging for the connecting pin 16 to pass through both the cam lobe collar 10a and the timing wheel 38. It would also be possible just to rely on an interference fit to maintain the angle of the timing wheel and provide a clearance hole through which the connecting pin could be fitted.

Fourth Embodiment

[0038] The fourth embodiment, shown in FIGS. 7 and 8, is similar to the third in that it has a timing wheel 48 that is engaged on the cylindrical collar 10a of the cam lobe 10. However, instead of using the connecting pin 16 to fix the timing wheel 48 in position, a staking operation shown at 50 in FIGS. 7 and 8 is used. In the staking operation, after the timing wheel 48 has been fitted to the collar 10a, it is deformed to engage with one or more slot or hole features in the cam lobe, in order to lock its position. The timing wheel 48 can either have clearance holes for the cam lobe connecting pin 16 to pass through or it can be staked to the cam lobe 10 after the connecting pin 16 has been fitted through the cam lobe 10 and the inner shaft 14.