Method and apparatus for controlling a variable valve system

Abstract

A variable valve timing apparatus for an internal combustion engine, includes an actuator ( 15 ) that operates a first variable valve timing mechanism; a detecting portion ( 35 ) that detects a driving position of the actuator ( 15 ); and a control portion ( 21 ) that executes an initialization process only when a preset execution condition is satisfied. In the initialization process, the control portion drives the actuator ( 15 ) to one end of a driving range and sets the driving position detected in this state as an initial value, and then drives the actuator ( 15 ) to an opposite end of the driving range and reflects an offset amount of the driving position detected in that state with respect to an optimum value in the driving position to compensate for the offset amount. The execution condition includes a condition that an increase amount in acceleration required of the internal combustion engine ( 1 ) be equal to or greater than a preset first determining value.

1 . A variable valve timing apparatus for an internal combustion engine, comprising:
 an actuator that operates a first variable valve timing mechanism that changes a valve characteristic of an engine valve;   a detecting portion that detects a driving position of the actuator; and   a control portion that drivingly controls the actuator within a driving range of the actuator based on the detected driving position, and executes an initialization process that matches the driving position of the actuator detected by the detecting portion with an actual driving position of the actuator only when a preset execution condition is satisfied, wherein   in the initialization process, the control portion drives the actuator to one end of the driving range and sets the driving position detected by the detecting portion in this state as an initial value, and then drives the actuator to an opposite end of the driving range that is opposite the one end of the driving range and reflects an offset amount, that is an amount that the driving position detected by the detecting portion when the actuator is driven to the opposite end is offset from an optimum value, in the driving position to compensate for the offset amount; and   the execution condition includes a condition that an amount of increase in acceleration required of the internal combustion engine be equal to or greater than a preset first determining value.   
     
     
         2 . The variable valve timing apparatus according to  claim 1 , wherein
 the first variable valve timing mechanism includes a variable valve lift mechanism that is operated by the actuator and changes a maximum lift amount and an operation angle of an intake valve; and   in the initialization process, the control portion drives the actuator to an end where the maximum lift amount and the operation angle of the intake valve are smallest, as the one end of the driving range, and then drives the actuator to an end where the maximum lift amount and the operation angle of the intake valve are largest, as the opposite end of the driving range that is opposite the one end of the driving range.   
     
     
         3 . The variable valve timing apparatus according to  claim 2 , wherein the variable valve lift mechanism changes the maximum lift amount and the operation angle of the intake valve in synchronization with each other by displacing a control shaft of the variable valve lift mechanism in an axial direction of the control shaft. 
     
     
         4 . The variable valve timing apparatus according to  claim 3 , wherein the actuator includes an electric motor that displaces the control shaft in the axial direction. 
     
     
         5 . The variable valve timing apparatus according to  claim 2 , further comprising
 a second variable valve timing mechanism that changes a valve characteristic of an engine valve and that is operated by a driving source other than the actuator, wherein   the second variable valve timing mechanism includes a variable intake valve timing mechanism that changes a valve timing of the intake valve and a variable exhaust valve timing mechanism that changes a valve timing of an exhaust valve; and   the execution condition further includes a condition that an engine speed be equal to or greater than a preset second determining value and an engine load be equal to or greater than a preset third determining value, and a condition that an advance amount from a maximum retard angle of the valve timing of the intake valve be equal to or less than a preset fourth determining value, and a retard amount from a maximum advance angle of the valve timing of the exhaust valve be equal to or less than a preset fifth determining value.   
     
     
         6 . The variable valve timing apparatus according to  claim 5 , wherein the control portion adjusts the valve timing of the intake valve to the maximum retard angle and adjusts the valve timing of the exhaust valve to the maximum advance angle, before executing the initialization process. 
     
     
         7 . The variable valve timing apparatus according to  claim 1 , wherein the execution condition further includes a condition that a change-allowing condition to allow the valve characteristic of the engine valve to be changed be satisfied. 
     
     
         8 . The variable valve timing apparatus according  claim 1 , wherein when the driving position detected by the detecting portion is a position closer to the opposite end than a sixth determining value when the execution condition is satisfied, the control portion executes the initialization process by setting a current driving position detected by the detecting portion as the initial value of the driving position, and then driving the actuator to the opposite end of the driving range and reflecting the offset amount, that is the amount that the driving position detected by the detecting portion when the actuator is driven to the opposite end is offset from the optimum value, in the driving position to compensate for the offset amount. 
     
     
         9 . The variable valve timing apparatus according to  claim 8 , wherein the sixth determining value corresponds to a center of the driving range. 
     
     
         10 . A control method of a variable valve timing apparatus for an internal combustion engine, comprising:
 determining whether an amount of increase in acceleration required of an internal combustion engine is equal to or greater than a preset first determining value; and   executing an initialization process that matches a driving position, detected by a detecting portion, of an actuator that operates a variable valve timing mechanism that changes a valve characteristic of an engine valve, with an actual driving position of the actuator only when the amount of increase in the acceleration required of the internal combustion engine is equal to or greater than the first determining value, wherein   the initialization process includes drivingly controlling the actuator to drive the actuator to one end of a driving range of the actuator; detecting the driving position at the one end of the driving range by the detecting portion when the actuator has been driven to the one end of the driving range; setting the driving position at the one end of the driving range detected by the detecting portion as an initial valueposition; drivingly controlling the actuator to drive the actuator to an opposite end of the driving range that is opposite the one end of the driving range, after setting the initial value; detecting the driving position at the opposite end of the driving range by the detecting portion when the actuator has been driven to the opposite end of the driving range; identifying an offset amount that is an amount that the driving position at the opposite end detected by the detecting portion is offset from an optimum value; and reflecting the offset amount in the driving position at the opposite end detected by the detecting portion to compensate for the offset amount.