Variable valve actuating apparatus

Abstract

A variable valve actuating apparatus for an internal combustion engine includes a drive cam, a control shaft, a control cam, a rocker arm, and a swing cam. The drive cam is rotated by the internal combustion engine. The control shaft is supported for rotation about a rotation axis. The control cam is coupled to the control shaft, and is eccentric with respect to the rotation axis of the control shaft. The rocker arm is linked with the drive cam, and arranged to swing about the control cam in response to rotary motion of the drive cam. The rocker arm includes a recess slidably engaged with an outer radial periphery of the control cam. The swing cam is linked with the rocker arm, and arranged to swing in response to swinging motion of the rocker arm for opening and closing an engine valve of the internal combustion engine.

1 . A variable valve actuating apparatus for an internal combustion engine, comprising:
 a drive cam adapted to be rotated by the internal combustion engine;   a control shaft supported for rotation about a rotation axis;   a control cam coupled to the control shaft, wherein the control cam is eccentric with respect to the rotation axis of the control shaft;   a rocker arm linked with the drive cam, and arranged to swing about the control cam in response to rotary motion of the drive cam, the rocker arm including a recess slidably engaged with an outer radial periphery of the control cam; and   a swing cam linked with the rocker arm, and arranged to swing in response to swinging motion of the rocker arm for opening and closing an engine valve of the internal combustion engine.   
   
   
       2 . The variable valve actuating apparatus as claimed in  claim 1 , further comprising a device for maintaining contact between the recess of the rocker arm and the outer radial periphery of the control cam. 
   
   
       3 . The variable valve actuating apparatus as claimed in  claim 2 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, wherein:
 the drive cam is fixedly mounted to an outer radial periphery of the drive shaft;   change of a rotational position of the control shaft causes a movement of the control cam with respect to the drive shaft, and causes at least a change in a lift of the engine valve; and   the rotational position of the control shaft is controlled according to an operating state of the internal combustion engine.   
   
   
       4 . The variable valve actuating apparatus as claimed in  claim 2 , wherein the device is a device for mechanically pressing the recess of the rocker arm on the outer radial periphery of the control cam. 
   
   
       5 . The variable valve actuating apparatus as claimed in  claim 2 , wherein:
 the recess of the rocker arm has an entrance that is narrower than a diameter of the recess;   the outer radial periphery of the control cam partly has a thickness in a radial direction of the control cam which is narrower than the entrance of the recess of the rocker arm; and   the control cam is engaged with the rocker arm in such a rotational position that the control cam is prevented from escaping through the entrance from the recess of the rocker arm.   
   
   
       6 . The variable valve actuating apparatus as claimed in  claim 2 , wherein the control shaft includes a flange supporting the control cam. 
   
   
       7 . The variable valve actuating apparatus as claimed in  claim 2 , wherein the recess of the rocker arm and the outer radial periphery of the control cam have shapes fit on each other. 
   
   
       8 . The variable valve actuating apparatus as claimed in  claim 2 , wherein the recess of the rocker arm has an entrance directed opposite to a direction in which a force of gravity acts. 
   
   
       9 . The variable valve actuating apparatus as claimed in  claim 2 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, and coupled to the drive cam, wherein the swing cam is swingably supported with respect to the drive shaft. 
   
   
       10 . The variable valve actuating apparatus as claimed in  claim 2 , wherein the rocker arm includes a first longitudinal end portion defining the recess, and a second longitudinal end portion opposite to the first longitudinal end portion in a longitudinal direction of the rocker arm, and wherein the second longitudinal end portion is linked with the swing cam for transmitting swinging motion of the rocker arm to the swing cam. 
   
   
       11 . The variable valve actuating apparatus as claimed in  claim 10 , further comprising a link rod linking the rocker arm with the swing cam. 
   
   
       12 . The variable valve actuating apparatus as claimed in  claim 2 , further comprising a roller rotatably supported with respect to the rocker arm, and arranged in rolling contact with the drive cam. 
   
   
       13 . The variable valve actuating apparatus as claimed in  claim 2 , wherein the drive cam has such an asymmetrical cam profile that at least at a maximum lift set point, the engine valve accelerates more rapidly when ascending to a peak of lift than when descending from the peak. 
   
   
       14 . The variable valve actuating apparatus as claimed in  claim 2 , further comprising an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein when the actuator applies no torque to the control shaft, the control cam is mechanically held at a position for an intermediate lift set point of the engine valve between a minimum lift set point and a maximum lift set point of the engine valve. 
   
   
       15 . The variable valve actuating apparatus as claimed in  claim 1 , further comprising an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein the recess of the rocker arm has an entrance directed opposite to a portion of the rocker arm which is linked with the swing cam. 
   
   
       16 . The variable valve actuating apparatus as claimed in  claim 15 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft. 
   
   
       17 . The variable valve actuating apparatus as claimed in  claim 15 , wherein the outer radial periphery of the control cam has an outer diameter which is larger than a width of an entrance of the recess of the rocker arm, and the outer radial periphery of the control cam partly has a thickness in a radial direction of the control cam which is smaller than the width of the entrance of the recess of the rocker arm. 
   
   
       18 . The variable valve actuating apparatus as claimed in  claim 15 , wherein the control shaft includes a flange supporting the control cam. 
   
   
       19 . The variable valve actuating apparatus as claimed in  claim 15 , wherein the recess of the rocker arm and the outer radial periphery of the control cam have shapes fit on each other. 
   
   
       20 . The variable valve actuating apparatus as claimed in  claim 15 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, and coupled to the drive cam, wherein the swing cam is swingably supported with respect to the drive shaft. 
   
   
       21 . The variable valve actuating apparatus as claimed in  claim 15 , wherein the rocker arm includes a first longitudinal end portion defining the recess, and a second longitudinal end portion opposite to the first longitudinal end portion in a longitudinal direction of the rocker arm, and wherein the second longitudinal end portion is linked with the swing cam for transmitting swinging motion of the rocker arm to the swing cam. 
   
   
       22 . The variable valve actuating apparatus as claimed in  claim 21 , further comprising a link rod linking the rocker arm with the swing cam. 
   
   
       23 . The variable valve actuating apparatus as claimed in  claim 15 , wherein the recess of the rocker arm has an entrance directed in a longitudinal direction of a longitudinal end portion of the rocker arm toward a longitudinal end of the rocker arm. 
   
   
       24 . The variable valve actuating apparatus as claimed in  claim 1 , further comprising an actuator for controlling a rotational position of the control shaft according to an operating state of the internal combustion engine, wherein when the engine valve is open, the recess of the rocker arm is pressed on the outer radial periphery of the control cam by an elastic force of a valve spring provided for the engine valve. 
   
   
       25 . The variable valve actuating apparatus as claimed in  claim 24 , further comprising a drive shaft adapted to be rotated by the internal combustion engine, wherein the drive cam is mounted for rotation therewith to an outer radial periphery of the drive shaft. 
   
   
       26 . The variable valve actuating apparatus as claimed in  claim 24 , further comprising a device for preventing the recess of the rocker arm from escaping from the control cam.