Variable valve opening property internal combustion engine

Abstract

In a variable valve opening property internal combustion engine, a control shaft ( 20 ) is supported by a control link ( 21 ) which is in turn is pivotally supported by a cylinder head ( 1 ), and a roller link ( 22 ) is pivotally supported by the control shaft. The roller link is provided with a cam roller ( 31 ) that engages a cam ( 3 ) of a camshaft ( 4 ) and a roller shaft ( 32 ) that engages a slipper surface ( 33 ) of a rocker arm ( 6 ). The arcuate movement of the cam roller centered around the control shaft varies the swing of the rocker arm and hence the valve lift in dependence on the position of the control shaft. A compression coil spring ( 41 ) is interposed between a part of the cylinder head and a side of the cam roller facing away from the cam. The coil spring is oriented such that a direction of a spring force (Fspg) substantially coincides with a direction of a guided movement of the cam roller, preferably in a low valve lift condition.

1 . A variable valve opening property internal combustion engine, comprising:
 an engine valve provided in a combustion chamber at least partly defined by a cylinder head of the engine and biased in a valve closing direction by a valve spring;   a rocker arm pivotally supported by the cylinder head and having an end acting upon a valve stem of the engine valve for opening the engine valve;   a camshaft rotatably supported by the cylinder head and carrying a cam;   a roller link including a cam engaging part configured to engage the cam and a rocker arm engaging part engaging a slipper surface of the rocker arm, and adjustably supported by the cylinder head for a guided motion of the cam engaging part;   a control link for adjusting a trajectory of the guided motion of the cam engaging part;   an actuator for actuating the control link; and   a spring member mounted on the cylinder head to apply a biasing force to a spring engaging part of the roller link to urge the cam engaging part against the cam;   wherein the spring member is oriented such that a direction of a spring force of the spring member substantially coincides with a direction of a guided movement of the spring engaging part caused by the guided motion of the cam engaging part at least in a prescribed adjusted state of the control link.   
   
   
       2 . The variable valve opening property internal combustion engine according to  claim 1 , wherein the cam engaging part comprises a cam roller. 
   
   
       3 . The variable valve opening property internal combustion engine according to  claim 2 , wherein the rocker arm engaging part of the roller link comprises a roller shaft disposed coaxially with the cam roller. 
   
   
       4 . The variable valve opening property internal combustion engine according to  claim 1 , wherein the cam roller also serves as the spring engaging part. 
   
   
       5 . The variable valve opening property internal combustion engine according to  claim 1 , wherein the prescribed adjusted state of the control link corresponds to a minimum valve lift condition. 
   
   
       6 . The variable valve opening property internal combustion engine according to  claim 5 , wherein a direction of a spring force of the valve spring substantially coincides with a direction of the movement of the spring engaging part in a maximum valve lift condition 
   
   
       7 . The variable valve opening property internal combustion engine according to  claim 1 , wherein the prescribed adjusted state of the control link corresponds to a maximum valve lift condition. 
   
   
       8 . The variable valve opening property internal combustion engine according to  claim 1 , wherein the control link is pivotally supported by a control link pivot shaft extending in parallel with the camshaft and supporting a control shaft located at a prescribed distance from the control ink pivot shaft and extending in parallel with the camshaft, and the roller link is pivotally supported by the control shaft so that the guided motion of the cam engaging part may be defined by an arcuate path centered around the control shaft. 
   
   
       9 . The variable valve opening property internal combustion engine according to  claim 8 , wherein the actuator comprises a rotary actuator fixedly mounted on the cylinder head, and the control link comprises a sector gear in a gearing connection with a gear mounted on an output shaft of the actuator.