Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1997-12-31
1999-11-09
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 906, F01L 1356, F01L 1344
Patent
active
059793813
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a valve gear mechanism for an internal combustion engine and particularly to a valve gear mechanism for an internal combustion engine, wherein a rotating body, preferably a cam, is rotatable in a cyclical manner on a shaft, preferably a cam shaft, during rotation of such shaft in order to provide thereby a variable valve control.
A valve gear mechanism of such kind is for instance disclosed in the German patent application 195 02 836.0 which does not constitute a prior disclosure. A timing mechanism disclosed in this patent application is shown in FIG. 23 and includes a cam shaft 100 having an axis of rotation 500 on which a cam 200 is supported. Also supported on the cam shaft 100 is an inner eccentric element 300, that inner eccentric element 300 having an outer surface 320 being eccentric with respect to axis of rotation 500 on which an outer eccentric element 400 is supported. The outer eccentric element 300 and the inner eccentric element 400 are rotatable via an inner eccentric gear ring 340 and an outer eccentric gear ring 440, respectively, whereby an intermediate member 490 supported on an eccentric outer surface of the outer eccentric element 400 is displaceable with respect to the cam shaft 100 in a plane perpendicular to that axis of rotation 500. The intermediate member 490 is operationally linked with the cam 200 and the cam shaft 100. In order to accomplish this, an axial pin 800 rotatably supported in the cam shaft 100 as a first transmission element 800 is in engagement with a first groove 600 formed as a sliding guide in the intermediate member 490, the engagement being effected by a sliding block lug 810 integrally formed with that axial pin 800. A second groove 700 of intermediate member 490 located diametrically opposed first groove 600 is in engagement with a sliding block lug 910 integrally formed with a second axial pin 900 being rotatably supported in a bore 110 of cam 200.
The rotation of cam shaft 100 is transmitted via first axial pin 800 by lug 810 thereof and first groove 600 to intermediate member 490 and further via second groove 700 and lug 910 of second axial pin 900 to cam 200. If the intermediate member 490 is in a concentric position with respect to cam shaft 100, cam 200 rotates in synchronism with cam shaft 100. If, however, intermediate member 490 is displaced in a plane perpendicular to the axis of rotation 500, during each rotation of cam shaft 100 there is a cyclic increasing and subsequent decreasing of the speed of rotation of cam 200 with respect to cam shaft 100 which is used to affect the effective duration of opening of a gas inlet valve of an internal combustion engine not shown which is actuated by a tappet 205.
With the motion just described there are exerted not only rotational forces but also a tilting moment onto intermediate member 490 which tilting moment acts on the bearing of intermediate member 490 on outer eccentric element 400. Due to his, comparatively high forces act in this region which forces are particularly critical in this region since it constitutes a fast running bearing which is exposed to the difference in speed of rotation between the outer eccentric element 400 almost standing still and the intermediate member 490 rotating with almost the same speed of rotation as the cam shaft. Under unfavorable circumstances, the intermediate member 490 may tend to tilt and jam.
A further disadvantage of this known device is provided by the fact that such tilting moment of intermediate member 490 has the effect that parallelism to cam 200 cannot be ensured. This may have the effect that there is not always planar contact between sliding block lugs 810 and 910 of axial pins 800 and 900, respectively, and grooves 900 and 700, respectively, of intermediate member 490 but that there is only contact at the respective edges. This substantially increases the wear in this region.
It is an object of the present invention to further develop the prior art described above such that in a compact device occupying minimal space the frict
Bertsch Armin
Korostenski Erwin
Walter Reiner
Livingston, Esq. Edward M.
Lo Weilun
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