Variable valve actuation apparatus

Details Variable valve actuation apparatus Variable valve actuation apparatus

1998-10-27

2000-02-29

Lo, Weilun

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

123 9033, 123 9017, F01L 1300

Patent

active

060296186

ABSTRACT:
A variable valve actuation (VVA) apparatus is disclosed. The VVA apparatus can keep an engine cylinder valve closed. Rotating a camshaft in timed relation with a crankshaft of the engine causes an eccentric crank cam to move a link or crank arm, thereby causing one end of a rocker arm to reciprocate. This causes the other end of the rocker arm to reciprocate. The reciprocating motion of the other end of the rocker arm is transmitted via a link to a valve operating (VO) cam, thereby causing the VO cam to pivot to push a valve lifter for opening the associated cylinder valve. An eccentric circular cam, fixed to a control rod, supports the rocker arm for rotation relative thereto in such a manner that rotation of the control rod causes a pivot center of the rocker arm to move, thereby changing position of the VO cam relative to the valve lifter. The change in the position of the VO cam causes its valve lift diagram to change. The VO cam has a base circle portion that extends over a predetermined angle with respect to the center of pivot of the VO cam and the contiguous ramp portion. A predetermined valve clearance exists between the VO cam and the valve lifter when the base circle portion faces the valve lifter. When it is desired to keep the associated cylinder valve closed, the control rod is rotated to establish a state wherein the VO cam pivots to bring not only base circle but also the ramp portions into facing relation with the valve lifter. In this state, the maximum cam lift of a cam lift diagram is greater than zero and less than the valve clearance.

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patent: 5787849 (1998-08-01), Mitchell
patent: 5899180 (1999-05-01), Fischer

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