The invention relates to a main shaft for a sliding cam valve train, said main shaft being provided, at least in the axial region of cam followers located thereunder, with axial toothing which is uniform over the length thereof, on which shaft there is placed, for each cam follower which is to be switched, a sliding cam piece and, for each cam follower which is not to be switched, an axially non-displaceable cam piece, each cam piece having inner toothing, respectively, which is complementary to the axial toothing of the main shaft.
Such a main shaft can be found in the supplement “Technik Profi” in the magazine “Auto Motor und Sport,” issue 24/2011, p. 1, on the right. There, a sliding cam valve train is disclosed, by means of which, in a V8 engines, only a portion of the cylinders can be switched off. The cam followers, here, rocker arms, are each loaded in the lifting sense by a cam piece that is fixed on the main shaft in the axial direction and run by means of an inner toothing on the axial toothing of the main shaft. Bearing points, indicated here as longitudinal sections of the main shaft without toothing, have no teeth and are used for supporting said main shaft relative to a cylinder head.
Axial toothing of the main shaft that is also continuous in the area of the axially non-displaceable cam pieces contributes to economical manufacturability in large-scale series production. Thus it is clear that the axially non-displaceable cam pieces must be connected by suitable measures to the main shaft, wherein it can be seen that these cam pieces here contact a ring collar of the main shaft on one side.
In general, for locking the non-displaceable cam pieces, those skilled in the art think of fastening these cam pieces by a threaded connection or bolt connection that disadvantageously intersects the base circle of these pieces. Press-fit or shrink-fit connections or internal high-pressure forming (injection molding) are also conceivable. Depending on the structure, the cam pieces also might not be able to be pushed over the entire length of the main shaft from one of their ends, so that it is absolutely necessary to think of an assembled shape for the main shaft.
The objective is therefore to provide a main shaft as mentioned above on which the axially non-displaceable cam pieces are held very simply and securely, which provides cost benefits to the entire main shaft structure.
According to the invention, this objective is achieved in that, to fix the cam piece in the section of the inner toothing thereof meshing with the axial toothing of the main shaft, at least one axial locking ring is provided. Here it is especially preferred to provide a ring groove in the cam piece and in the main shaft, wherein a snap ring with, e.g., radially outward biasing sits in each of these ring grooves, bridging a ring surface between both components.
In this way, a main shaft of a sliding cam valve train is provided with non-displaceable cam pieces that are fixed in a very simple and secure manner.
According to a preferred improvement of the invention, the main shaft is formed integrally, that is, not assembled. This reduces its costs. It is clear that such a main shaft, if its cam pieces are to be pushed on from one end, must be provided without ring collars and with continuous, constant axial toothing, because at the other end there is, e.g., a flange for a camshaft adjustment device or a cam or the like for a fuel injection pump.
The main shaft can also be provided with completely continuous axial toothing, which is especially preferable with respect to production. In this case, tooth regions for bearing points can be either, e.g., wrapped with sleeves or ground at a later time.
A standard mass-produced article can be used as the snap ring. In particular, a polygon-shaped or round wire ring is conceivable. Ruptured (slotted) discs are also conceivable.
In the drawings:
A section of an integrally formed main shaft 1 for a sliding cam valve train is shown. This main shaft 1 has uniform axial toothing 2 in a schematically shown bearing region 7 and an end piece 8, wherein, e.g., a camshaft adjustment device can be flanged onto said end piece 8. In the axial region of a not-shown, switchable cam follower lying underneath, a sliding cam piece 3 is shown that is displaceable in the axial direction on the axial toothing 2 of the main shaft 1 by means of its inner toothing 4.
In the section of a cam follower not to be switched, an axially non-displaceable cam piece 11 shown on the right is illustrated in an exploded view. This has inner toothing 5 that is also complementary to the axial toothing 2 of the main shaft 1. In the region of the inner toothing 5 of the cam piece 11 there is a ring groove 9 that lies radially opposite a ring groove 10 in the axial toothing 2 of the main shaft 1. In these ring grooves 9, 10 there is an axial locking ring 6, shown here as a polygon ring, with radially outward biasing (see also
Number | Date | Country | Kind |
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102012209310.9 | Jun 2012 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2013/058467 | 4/24/2013 | WO | 00 |