Valve timing control apparatus for internal combustion engine and control method thereof

Abstract

A variable valve timing mechanism changes a relative rotation phase of a camshaft to a target phase based on hydraulic pressure supplied to an advance and a retard sides pressure chambers. A lock mechanism is placed in a locked state in which the relative rotation phase is locked at a maximum retard phase when the hydraulic pressure in the advance and the retard side pressure chambers is low, and that is placed in an unlocked state in which the locked state is released when the hydraulic pressure becomes high. Hydraulic pressure regulations in a first mode that changes the relative rotation phase to a side toward the maximum retard phase and in a second mode that changes the relative rotation phase to a side away from the maximum retard phase are executed in combination during a period from when an operating switch is turned off until a crankshaft stops rotating.

1 . A valve timing control apparatus for an internal combustion engine, comprising:
 a variable valve timing mechanism that changes a relative rotation phase of a camshaft with respect to a crankshaft to a target phase based on hydraulic pressure supplied to an advance side pressure chamber and a retard side pressure chamber;   a lock mechanism that is placed in a locked state in which the relative rotation phase is locked at a limit phase of a changing range of the relative rotation phase when the hydraulic pressure is low, and that is placed in an unlocked state in which the locked state is released when the hydraulic pressure becomes high; and   an executing apparatus that is configured to execute, in combination, regulation of the hydraulic pressure in a first mode that changes the relative rotation phase to a side toward the limit phase and regulation of the hydraulic pressure in a second mode that changes the relative rotation phase to a side away from the limit phase, during a period of time from when a stop operation to stop the internal combustion engine is started until the crankshaft stops rotating.   
     
     
         2 . The valve timing control apparatus according to  claim 1 , wherein the executing apparatus executes the hydraulic pressure regulation in the first mode until the relative rotation phase reaches the limit phase, and when the relative rotation phase reaches the limit phase, the executing apparatus executes the hydraulic pressure regulation in the second mode. 
     
     
         3 . The valve timing control apparatus according to  claim 1 , wherein the executing apparatus starts to execute the hydraulic pressure regulation in the second mode following the start of the stop operation, and when the relative rotation phase changes to a phase on the side away from the limit phase, the executing apparatus temporarily suspends the hydraulic pressure regulation in the second mode and executes the hydraulic pressure regulation in the first mode. 
     
     
         4 . The valve timing control apparatus according to  claim 3 , wherein when a state in which the relative rotation phase does not change to a phase on the side away from the limit phase when the hydraulic pressure regulation in the second mode is executed continues for a predetermined period of time, the executing apparatus then suspends the hydraulic pressure regulation in the second mode for a predetermined period of time and executes the hydraulic pressure regulation in the first mode. 
     
     
         5 . The valve timing control apparatus according to  claim 1 , wherein the limit phase is a limit phase on a retard side for the relative rotation phase, the first mode is a regulation mode in which hydraulic fluid is discharged from the advance side pressure chamber and hydraulic fluid is supplied to the retard side pressure chamber, and the second mode is a regulation mode in which hydraulic fluid is supplied to the advance side pressure chamber and hydraulic fluid is discharged from the retard side pressure chamber. 
     
     
         6 . The valve timing control apparatus according to  claim 1 , further comprising:
 a hydraulic pressure control valve that regulates an amount of hydraulic fluid supplied to the advance side pressure chamber or the retard side pressure chamber according to a duty ratio of a drive signal that is input, wherein the first mode is obtained by setting the duty ratio to 0% and the second mode is obtained by setting the duty ratio to 100%.   
     
     
         7 . The valve timing control apparatus according to  claim 1 , wherein the stop operation is a stop operation that is in response to an operating switch being operated to stop the operation of the internal combustion engine. 
     
     
         8 . A control method for a valve timing control apparatus for an internal combustion engine, the valve timing control apparatus including a variable valve timing mechanism that changes a relative rotation phase of a camshaft with respect to a crankshaft to a target phase based on hydraulic pressure supplied to an advance side pressure chamber and a retard side pressure chamber, and a lock mechanism that is placed in a locked state in which the relative rotation phase is locked at a limit phase of a changing range of the relative rotation phase when the hydraulic pressure is low, and that is placed in an unlocked state in which the locked state is released when the hydraulic pressure becomes high, the control method comprising:
 executing regulation of the hydraulic pressure in a first mode that changes the relative rotation phase to a side toward the limit phase and regulation of the hydraulic pressure in a second mode that changes the relative rotation phase to a side away from the limit phase in combination, during a period of time from when a stop operation to stop the internal combustion engine is started until the crankshaft stops rotating.