Variable valve timing apparatus

Abstract

An intake VVT mechanism includes: link mechanisms and connected to an intake camshaft and operated to change a phase of an intake valve; and a control pin sliding on a guide plate along a guide groove to allow the link mechanism to operate; a control pin sliding on the guide plate along a guide groove to allow the link mechanism to operate. The control pin is detached from an end of the guide groove when the control pins and are moved in a direction allowing the phase to be retarded until the control pin abuts against an end of the guide groove.

1 . A variable valve timing apparatus changing when at least one of an intake valve and an exhaust valve should be opened/closed, comprising a first operation unit provided to change when said at least one of said intake and exhaust valves should be opened/closed by an amount of variation depending on an amount of operation thereof;
 a second operation unit provided to change when a valve identical to said at least one of said intake and exhaust valves controlled by said first operation unit should be opened/closed by an amount of variation depending on an amount of operation thereof; and   a limiter unit limiting said first operation unit in operation such that said first operation unit is operable only within a range smaller than said second operation unit is operable,   wherein said first operation unit is smaller in strength than said second operation unit.   
   
   
       2 . (canceled) 
   
   
       3 . The variable valve timing apparatus according to  claim 1 , wherein:
 said valve is driven by a camshaft;   said operation unit is a link mechanism connected to said camshaft to rotate said camshaft and actuated by an actuator; and   when said at least one of said intake and exhaust valves should be opened/closed is changed as said camshaft is rotated by said actuator via said link mechanism.   
   
   
       4 . A variable valve timing apparatus changing when at least one of an intake valve and an exhaust valve should be opened/closed, comprising a first operation unit provided to change when said at least one of said intake and exhaust valves should be opened/closed by an amount of variation depending on an amount of operation thereof;
 a second operation unit provided to change when a valve identical to said at least one of said intake and exhaust valves controlled by said first operation unit should be opened/closed by an amount of variation depending on an amount of operation thereof; and   a first limiter unit limiting said first operation unit in operation such that said first operation unit is operable only within a range smaller than said second operation unit is operable for a direction retarding when said at least one of said intake and exhaust valves should be opened/closed;   a second limiter unit limiting said second operation unit in operation such that said second operation unit is operable only within a range smaller than said first operation unit is operable for a direction advancing when said at least one of said intake and exhaust valves should be opened/closed.   
   
   
       5 . The variable valve timing apparatus according to  claim 4 , wherein:
 said valve is driven by a camshaft;   said operation unit is a link mechanism connected to said camshaft to rotate said camshaft and actuated by an actuator; and   when said at least one of said intake and exhaust valves should be opened/closed is changed as said camshaft is rotated by said actuator via said link mechanism.