Switchable lever for a valve drive of an internal combustion engine

Abstract

A switchable lever for a valve drive of an internal combustion engine which has two side walls with ends connected by a crossbar. There is a gas-exchange valve system in the crossbar at one end and a bearing for the pivotable support of the crossbar at the other end. An axle is held nondisplaceably in the side walls, between the ends, with two cam rollers running on the axle. The cam rollers are displaceable axially on the axle toward each other into a first position such that the cam rollers run up to each other on a longitudinal center plane of the lever and away from each other into a second position. One of the positions serves for a high-lift cam contact and the other position serves for a low-lift or zero-lift cam contact.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is claims the priority of DE 10 2010 019 065.9 filed May 3, 2010, which is incorporated by reference herein.FIELD OF THE INVENTION[0002]The invention relates to a switchable lever for a valve drive of an internal combustion engine.BACKGROUND OF THE INVENTION[0003]The lever revealed in subsequently published DE 102010011828.1 is considered to be the closest prior art. It is noticeable that the axle has to be acted upon in a complicated manner via external means in order to be displaced. In association therewith, the abovementioned lever requires a relatively large amount of construction space laterally, and, at least in the switching state shown in FIG. 5, an asymmetrical introduction of force occurs during the cam lift. It is also ascertained that the central region of the lever has a relatively large bulge because of the displaceable cam rollers positioned next to one another on the axle.[0004]It is therefore the object o...

AI Technical Summary

Benefits of technology

[0007]A lever is therefore present without the disadvantages referred to at the beginning. A particularly outstanding feature of the invention is the ultimately telescopic nesting of the cam rollers together with the support rollers, thus making it possible to save on construction space laterally. At the same time, forces are introduced into the lever symmetrically during the cam lift such that the lever has only an insignificant tilting tendency, if any at all. The cam rollers can be physically broad such that the loading on the components by the surface pressure is minimized. In addition, simple internal actuating means are proposed for the cam rollers for the displacement thereof (hydraulic medium / compression spring), and separate pressure spaces for the hydraulic medium can be omitted owing to said pressure spaces being formed axially between the support and cam rollers. It is obvious that this simultaneously provides excellent lubrication of the sealing rotary tapping between the inner annular casing of the particular cam roller and an outer casing of the support roller.

[0010]At least one co-rotating helical compression spring clamped between the cam rollers is proposed as the spring means for producing the second position. Said helical compression spring expediently sits in annular pockets of the inner faces of the cam rollers. It is advantageous here to place said annular pockets radially higher than the support rollers, thus providing sufficient construction depth for the latter.

[0012]According to another expedient physical embodiment of the invention, a center stop for the cam rollers runs on the axle. Said center stop can be designed as a simple snap ring or the like sitting in an annular groove. As an alternative, an annular collar on the axle is also possible.

[0015]Owing to the optionally provided support surfaces, for example on upper sides of the side walls, the lever can be supported as it passes through the cam base circle such that the respective cam base circles are free from contact with the cam rollers, which minimizes the effort expended on displacing the latter. Possible mating support surfaces include, for example, support cams on the earn shaft or elements which protrude from the cylinder head and project beyond the side walls.

Problems solved by technology

It is noticeable that the axle has to be acted upon in a complicated manner via external means in order to be displaced.

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