Valve drive of an internal combustion engine

Abstract

A valve drive (1, 1′) of an internal combustion engine with stroke-variable gas-exchange valve activation is provided. The valve drive includes a camshaft (2, 2′) with a carrier shaft (3) and a cam piece (4, 4′) that is arranged in a rotationally locked way on the carrier shaft and that can move between axial positions and that has a cam group of directly adjacent cams (14a-c, 15a-c) with different lobes and a groove-shaped axial link (16, 16′) and an activation element (18, 19) that can be coupled in the axial link for shifting the cam piece on the carrier shaft. The cam piece is provided with a bearing journal (12, 13, or 12′) on which the camshaft is supported in the radial direction at a camshaft bearing point (9, 10, or 9′) of the internal combustion engine. Here, the axial link is constructed overlapping with the camshaft bearing point on the bearing journal in the axial direction, and the activation element runs in the camshaft bearing point.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of German Patent Application No. 10 2009 016 463.4, filed Apr. 4, 2009, which is incorporated herein by reference as if fully set forth.[0002]1. Field of the Invention[0003]The invention relates to a valve drive of an internal combustion engine with stroke-variable gas-exchange valve activation. The valve drive comprises a camshaft with a carrier shaft and a cam piece that is arranged in a rotationally locked manner on the carrier shaft and that can move between axial positions and that has a cam group of directly adjacent cams with different lobes and a groove-shaped axial link extending on the outer periphery and an activation element that can be coupled in the axial link for shifting the cam piece on the carrier shaft. The cam piece is provided with a bearing journal on which the camshaft is supported in the radial direction at a camshaft bearing point of the internal combustion engine.[0004]2. Backg...

AI Technical Summary

Benefits of technology

[0007]Therefore, the present invention is based on the objective of refining a valve drive of the type named above so that the cam piece is constructed with the most compact possible structure in the axial direction, so that the valve drive not only can be used widely also in small-volume internal combustion engines, but there is also a high potential for stroke variability with more than two stages, in particular, three stages.

[0008]The objective is met with the arrangement according to the invention, while advantageous refinements and constructions of the invention are also provided. Accordingly, the axial link should be constructed overlapping with the camshaft bearing point on the bearing journal in the axial direction, wherein the activation element runs in the camshaft bearing point. In other words, the idea forming the basis of the invention provides that the spatial separation of the bearing journal and axial link is to be eliminated and these are to be “fused” with each other in the axial direction, in order to be able to reduce the axial structural space of the cam piece accordingly and / or in order to be able to provide the cam group with an additional cam.

[0013]In addition, it is provided that the cam piece has exactly one axial link that has a bidirectional construction with two connecting paths running in the opposite sense in the axial direction. One construction of such an axial link is already known from DE 101 48 177 A1 cited above: here the two connecting paths are arranged one next to the other in the peripheral direction of the bearing journal and cross in their middle. The essential advantage relative to the spatially separated, unidirectional connecting paths consists, on one hand, in the comparatively small, axial structural space requirements for the axial link and, on the other hand, in that a single activation element is sufficient for both directions of movement.

[0015]In addition, the two constructions named above allow a comparatively easily performed expansion of the stroke variability from two to three stages in that two activation elements are coupled selectively in the bidirectional axial links. This is disclosed in detail in DE 10 2007 051 739 A1 of the applicant, which is also not a prior publication, for the construction with crossing connecting paths. The entire contents of that publication are also incorporated herein by reference as if fully set forth.

Problems solved by technology

Under consideration of various structural parameters of the internal combustion engine, in particular, the cylinder and gas-exchange valve spacing, the number and width of the cams, and also the middle or end camshaft bearing position with respect to a cylinder, however, the required length of the cam piece quickly conflicts with the installation space available for this piece.

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