Valve timing adjustment apparatus

Abstract

A main locking mechanism locks a phase at a main locking phase, at which an intake valve is closed at timing later than a bottom dead center, by inserting a main locking member into a main locking hole. A sub locking mechanism locks a phase at a sub locking phase advanced more than the main locking phase by inserting a sub locking member into a sub locking hole. A movable body disposed in the main locking hole reciprocates between an open position and a blocking position of the main locking hole. During a warm start of an engine, a driving source maintains the movable body at the open position at which the inserting of the main locking member into the main locking hole is maintained. In contrast, during a cold start of the engine, the driving source drives the movable body to the blocking position at which the main locking member is removed from the main locking hole.

What is claimed is: 
     
         1 . A valve timing adjustment apparatus that adjusts valve timing of an intake valve, which opens and closes a cylinder of an internal combustion engine, by a pressure of a working fluid, the valve timing adjustment apparatus comprising:
 a housing rotor that rotates in connection with a crank shaft of the internal combustion engine;   a vane rotor that rotates in connection with a cam shaft of the internal combustion engine, a rotational phase of the vane rotor relative to the housing rotor being changed by receiving the pressure of the working fluid in the housing rotor;   a main locking portion that has a main locking member and a main locking hole, the main locking portion locking the rotational phase to a main locking phase, at which the intake valve is closed at timing later than when a piston in the cylinder reaches a bottom dead center of the cylinder, by inserting the main locking member into the main locking hole when the rotational phase is the main locking phase during the starting of the internal combustion engine;   a sub locking portion that has a sub locking member and a sub locking hole, the sub locking portion locking the rotational phase to a sub locking phase, which is advanced more than the main locking phase, by inserting the sub locking member into the sub locking hole when the rotational phase is changed from the main locking phase to the sub locking phase during the starting of the internal combustion engine;   a movable body that is disposed in the main locking hole to reciprocate between an open position at which the movable body opens the main locking hole and a blocking position at which the movable body blocks the main locking hole;   a determination portion that determines a warm start when a temperature of the internal combustion engine is equal to or higher than a specific temperature and a cold start when a temperature of the internal combustion engine is lower than the specific temperature; and   a driving source that maintains the movable body at the open position, at which the main locking member is inserted into the main locking hole, when the determination portion determines the warm start, and drives the movable body to the blocking position, at which the main locking member is removed from the main locking hole, when the determination portion determines the cold start.   
     
     
         2 . The valve timing adjustment apparatus according to  claim 1 , wherein
 the movable body has a protruding end portion that protrudes to an outside of the housing rotor from the main locking hole when the movable body is at the open position, and   the driving source has a drive shaft disposed outside the housing rotor that presses the protruding end portion at the open position toward the blocking position during the cold start.   
     
     
         3 . The valve timing adjustment apparatus according to  claim 2 , wherein
 the housing rotor and the vane rotor rotate around an axis,   the movable body reciprocates in a direction parallel to the axis of the housing rotor and the vane rotor,   the protruding end portion has a tapered outer circumferential surface having a diameter that decreases toward a distal end of the protruding end portion,   the drive shaft is supported by a stationary component of the internal combustion engine, and   the driving source withdraws the drive shaft from a rotation region of the protruding end portion during the warm start and advances the drive shaft into the rotation region during the cold start.   
     
     
         4 . The valve timing adjustment apparatus according to  claim 3 , wherein
 the housing rotor integrally has a sliding contact surface which is an inclined surface angled relative to a radial direction of the housing rotor and the vane rotor, and   the drive shaft is brought into sliding contact with the sliding contact surface and driven from an advance position inside of the rotation region to a retreat position outside of the rotation region as the housing rotor rotates.   
     
     
         5 . The valve timing adjustment apparatus according to  claim 1 , wherein
 the housing rotor and the vane rotor rotate around an axis, and   the movable body reciprocates in a direction parallel to the axis of the housing rotor and the vane rotor.   
     
     
         6 . The valve timing adjustment apparatus according to  claim 1 , further comprising:
 an advance angle elastic member that biases the vane rotor in an advance direction relative to the housing rotor when the rotational phase of the vane rotor is between the main locking phase and the sub locking phase.