Valve operating mechanism

A valve operating mechanism for an internal combustion engine, the mechanism comprising:

• an engine valve for opening and closing a port of a cylinder of the engine;
• a control arm pivoting about a pivot axis and having a cam surface spaced apart from the pivot axis;
• a drive member which reciprocates with rotation of the engine and which acts on the control arm to rotate the control arm about the pivot axis thereof;
• a cam follower member engaging the cam surface of the control arm which relays camming action of the cam surface to the engine valve;
• wherein:
• the drive member engages the control arm at a contact point spaced apart from the pivot axis of the control arm;
• control means is provided to vary in position the contact point in order to vary a spacing between the contact point and the pivot axis of the control arm;
• varying the spacing of the contact point from the pivot axis varies amplitude of reciprocation of the cam surface of the control arm, whereby the control means can vary which part of the cam surface is engaged by the cam follower member during pivoting of the control arm to thereby vary the amount of lift and/or opening duration of the engine valve;
• and
• the drive member is a push rod actuated by a camshaft, the push rod engaging the control arm.

A valve operating mechanism for an internal combustion engine, the mechanism comprising:

• an engine valve for opening and closing a port of a cylinder of the engine;
• a control arm pivoting about a pivot axis and having a cam surface spaced apart from the pivot axis;
• a drive member which reciprocates with rotation of the engine and which acts on the control arm to rotate the control arm about the pivot axis thereof;
• a cam follower member engaging the cam surface of the control arm which relays camming action of the cam surface to the engine valve;
• wherein:
• the drive member engages the control arm at a contact point spaced apart from the pivot axis of the control arm;
• control means is provided to vary in position the contact point in order to vary a spacing between the contact point and the pivot axis of the control arm;
• varying the spacing of the contact point from the pivot axis varies amplitude of reciprocation of the cam surface of the control arm, whereby the control means can vary which part of the cam surface is engaged by the cam follower member during pivoting of the control arm to thereby vary the amount of lift and/or opening duration of the engine valve;
• the cam follower member is a rocker;
• the valve is an exhaust valve;
• and
• the cam surface is configured such that at part loads the rotation of the control arm causes the cam follower to move along a part of the cam surface which operates the exhaust valve to close prior to an end of an exhaust stroke to trap combusted gases in the cylinder, which trapped combusted gases are subsequently mixed with fresh charge air and fuel to create a mixture which ignites by homogeneous charge compression ignition.

A valve operating mechanism for an internal combustion engine, the mechanism comprising:

• an engine valve for opening and closing a port of a cylinder of the engine;
• a control arm pivoting about a pivot axis and having a cam surface spaced apart from the pivot axis;
• a drive member which reciprocates with rotation of the engine and which acts on the control arm to rotate the control arm about the pivot axis thereof;
• a cam follower member engaging the cam surface of the control arm which relays camming action of the cam surface to the engine valve;
• wherein:
• the drive member engages the control arm at a contact point spaced apart from the pivot axis of the control arm;
• control means is provided to vary in position the contact point in order to vary a spacing between the contact point and the pivot axis of the control arm;
• varying the spacing of the contact point from the pivot axis varies amplitude of reciprocation of the cam surface of the control arm, whereby the control means can vary which part of the cam surface is engaged by the cam follower member during pivoting of the control arm to thereby vary the amount of lift and/or opening duration of the engine valve;
• the valve is an exhaust valve;
• and
• the cam surface is configured such that at part loads the rotation of the control arm causes the cam follower to move along a part of the cam surface which operates the exhaust valve to close prior to an end of an exhaust stroke to trap combusted gases in the cylinder, which trapped combusted gases are subsequently mixed with fresh charge air and fuel to create a mixture which ignites by homogeneous charge compression ignition.