Variable valve operating apparatus for internal combustion engine

Abstract

A variable valve operating apparatus including a drive cam, a rocker cam swingably moveable about the swing axis so as to move an engine valve to open and closing positions, a motion transmission mechanism operative to convert a rotational motion of the drive cam to a swing motion of the rocker cam, and a control shaft operative to control an attitude of the motion transmission mechanism to vary a valve lift of the engine valve. A roller or a follower portion are disposed on one end portion of the motion transmission mechanism on a side of the drive cam and contacted with the drive cam. A biasing member is arranged to bias the roller onto the drive cam through a roller shaft or biases the follower portion onto the drive cam through a support for the biasing member.

1 . A variable valve operating apparatus for variably operating an engine valve of an internal combustion engine, the variable valve operating apparatus comprising:
 a drive cam which is rotationally driven by a crankshaft of the engine;   a rocker cam having a swing axis and swingably moveable about the swing axis so as to move the engine valve to an open position and a closing position;   a motion transmission mechanism operative to convert a rotational motion of the drive cam to a swing motion of the rocker cam, the motion transmission mechanism including a roller shaft which is disposed on one end portion of the motion transmission mechanism on a side of the drive cam, and a roller which is rotatably supported on the roller shaft and contacted with the drive cam;   a control shaft rotatable depending on an operating condition of the engine, the control shaft being operative to control an attitude of the motion transmission mechanism to vary a valve lift of the engine valve; and   a biasing member which biases the roller onto the drive cam through the roller shaft.   
   
   
       2 . The variable valve operating apparatus as claimed in  claim 1 , wherein the roller shaft, the motion transmission mechanism and the rocker cam are in a positive motion connection without separation therebetween during the swing motion of the rocker cam. 
   
   
       3 . The variable valve operating apparatus as claimed in  claim 1 , wherein the control shaft has a control cam on an outer circumferential surface thereof, the motion transmission mechanism comprises a rocker arm swingably supported on an outer circumferential surface of the control cam, and the roller shaft and the roller are disposed on one end portion of the rocker arm on a side of the drive cam. 
   
   
       4 . The variable valve operating apparatus as claimed in  claim 3 , wherein the rocker arm comprises at least a pair of support walls which are disposed on the one end portion of the rocker arm, and the roller shaft is supported between the support walls of the rocker arm. 
   
   
       5 . The variable valve operating apparatus as claimed in  claim 4 , wherein the biasing member is contacted with an end portion of the roller shaft which outward projects from the at least one of the support walls of the rocker arm, and the biasing member applies a biasing force to the end portion of the roller shaft. 
   
   
       6 . The variable valve operating apparatus as claimed in  claim 4 , wherein the biasing member is contacted with a portion of the roller shaft which is disposed between the at least a pair of support walls and a side face of the roller, and the biasing member applies a biasing force to said portion of the roller shaft. 
   
   
       7 . The variable valve operating apparatus as claimed in  claim 1 , further comprising an annular sleeve which is mounted to the roller shaft, the biasing member applying a biasing force to the roller shaft through the annular sleeve. 
   
   
       8 . The variable valve operating apparatus as claimed in  claim 7 , wherein the annular sleeve is formed on an outer peripheral surface thereof with an engaging groove in which the biasing member is engaged. 
   
   
       9 . The variable valve operating apparatus as claimed in  claim 1 , wherein the biasing member comprises a spring. 
   
   
       10 . The variable valve operating apparatus as claimed in  claim 1 , wherein the drive cam is rotatably supported by a rolling bearing. 
   
   
       11 . A variable valve operating apparatus for variably operating an engine valve of an internal combustion engine, the variable valve operating apparatus comprising:
 a drive cam which is rotationally driven by a crankshaft of the engine;   a rocker cam having a swing axis and swingably moveable about the swing axis so as to move the engine valve to an open position and a closing position;   a motion transmission mechanism operative to convert a rotational motion of the drive cam to a swing motion of the rocker cam, the motion transmission mechanism including a follower portion which is disposed on one end portion of the motion transmission mechanism on a side of the drive cam, the follower portion being contacted with the drive cam and having a generally arcuate cross-section;   a control shaft rotatable depending on an operating condition of the engine, the control shaft being operative to control an attitude of the motion transmission mechanism to vary a valve lift of the engine valve;   a biasing member support disposed on the one end portion of the motion transmission mechanism on the side of the drive cam; and   a biasing member which biases the follower portion onto the drive cam through the biasing member support,   wherein the biasing member support is disposed on or near a line that extends across an axis of the drive cam and a center of curvature of the follower portion.   
   
   
       12 . The variable valve operating apparatus as claimed in  claim 11 , wherein the control shaft has a control cam on an outer circumferential surface thereof, the motion transmission mechanism comprises a rocker arm swingably supported on an outer circumferential surface of the control cam, and the biasing member support comprises a support pin press-fitted into a pin mount hole which is formed in a boss on the one end portion of the rocker arm. 
   
   
       13 . The variable valve operating apparatus as claimed in  claim 11 , wherein the biasing member comprises a spring. 
   
   
       14 . The variable valve operating apparatus as claimed in  claim 11 , wherein the drive cam is rotatably supported by a rolling bearing. 
   
   
       15 . A variable valve operating apparatus for variably operating an engine valve of an internal combustion engine, the variable valve operating apparatus comprising:
 a drive cam which is rotationally driven by a crankshaft of the engine;   a rocker cam having a swing axis and swingably moveable about the swing axis so as to move the engine valve to an open position and a closing position;   a motion transmission mechanism operative to convert a rotational motion of the drive cam to a swing motion of the rocker cam, the motion transmission mechanism including one end portion which is contacted with the drive cam;   a control shaft rotatable depending on an operating condition of the engine, the control shaft being operative to control an attitude of the motion transmission mechanism to vary a valve lift of the engine valve;   biasing means for biasing the one end portion of the motion transmission mechanism onto the drive cam; and   support means for supporting the biasing member thereon;   wherein the biasing means and the support means are arranged such that a biasing force of the biasing means is applied to the one end portion of the motion transmission mechanism through the support means substantially along a line that extends across the support means and an axis of the drive cam.