Controller for internal combustion engine and method for variable valve timing control for the same

Abstract

A controller is provided to an engine including a variable valve timing unit for manipulating a valve timing of an intake valve of the engine. The controller includes an idle-continuation determining unit for determining whether an idling operation of the engine is in a continued state. The controller further includes a torque reserve control unit for executing a torque reserve control to advance the valve timing and increase an intake air quantity of the engine within a combustion limit of the engine when the idle-continuation determining unit determines that the idling operation is in the continued state. The controller further includes a torque correction unit for executing a torque correction control to retard the valve timing in the torque reserve control in at least one of conditions where: an auxiliary device exerts a load; the load is increased; and a vehicle starts moving.

1 . A controller for an engine of a vehicle, the engine including a variable valve timing unit for manipulating an intake valve timing including opening and closing timings of an intake valve of the engine, the controller comprising:
 an idle-continuation determining unit for determining whether an idling operation of the engine is in a continued state;   a torque reserve control unit for executing a torque reserve control for advancing the intake valve timing and increasing an intake air quantity of the engine within a combustion limit of the engine when the idle-continuation determining unit determines that the idling operation is in the continued state; and   a torque correction unit for executing a torque correction control to retard the intake valve timing in the torque reserve control in at least one of conditions where:   an auxiliary device of the vehicle exerts a load;   the load is increased; and   the vehicle starts moving.   
   
   
       2 . The controller according to  claim 1 , wherein the torque reserve control unit regulates an advance in the intake valve timing such that a pressure in an intake pipe of the engine is equal to or less than a predetermined pressure in the torque reserve control. 
   
   
       3 . The controller according to  claim 1 , wherein the torque reserve control unit sets an advance in the intake valve timing and an increase in the intake air quantity such that a variation in an actual speed of the engine is within a predetermined range relative to the target idling speed in the torque reserve control. 
   
   
       4 . The controller according to  claim 1 , wherein the torque reserve control unit determines the combustion limit on the basis of a fluctuation in a speed of the engine in the torque reserve control. 
   
   
       5 . The controller according to  claim 1 , wherein the torque reserve control unit determines the combustion limit on the basis of an air-fuel ratio of the engine in the torque reserve control. 
   
   
       6 . The controller according to  claim 1 , further comprising:
 a unit for gradually shifting a target throttle position to an accelerator demand throttle position, which is set on the basis of an accelerator position, after the torque correction unit retards the intake valve timing when the vehicle starts moving.   
   
   
       7 . The controller according to  claim 1 , further comprising:
 a unit for shifting a target throttle position to an accelerator demand throttle position, which is set on the basis of the accelerator position, since the accelerator demand throttle position becomes greater than a throttle position demanded by the torque reserve control unit, after the torque correction unit retards the intake valve timing when the vehicle starts moving.   
   
   
       8 . The controller according to  claim 1 , wherein the idle-continuation determining unit determines whether the idling operation is in the continued state on the basis of the accelerator position. 
   
   
       9 . The controller according to  claim 8 ,
 wherein the idle-continuation determining unit determines that the idling operation is in the continued state in a condition where:   the accelerator position is equal to or less than a predetermined threshold; and   a deviation between an actual speed of the engine and the target idling speed is equal to or less than a predetermined threshold.   
   
   
       10 . The controller according to  claim 1 , wherein the idle-continuation determining unit determines whether the idling operation is in the continued state on the basis of a deviation between a throttle position, which produces the target idling speed, and one of an actual throttle position and a target throttle position. 
   
   
       11 . The controller according to  claim 1 , wherein the variable valve timing unit includes:
 a housing;   a vane that partitions an interior of the housing into an advance chamber and a retard chamber respectively connected with hydraulic passages;   a pair of check valves respectively provided to the hydraulic passages for restriction of a counterflow of a working fluid from the advance chamber and the retard chamber, and   the hydraulic passages are respectively provided with drain passages being respectively in parallel with the hydraulic passages to respectively bypasses the check valves; and   a pair of drain change-over valves respectively provided to the hydraulic passages for communicating and blocking the hydraulic passages.   
   
   
       12 . A method for a variable valve timing control for an engine of a vehicle, the method comprising:
 determining whether an idling operation of the engine is in a continued state;   executing a torque reserve control for advancing an intake valve timing, which includes opening and closing timings of an intake valve of the engine, and increasing an intake air quantity of the engine within a combustion limit of the engine when the idling operation is in the continued state; and   executing a torque correction control to retard the intake valve timing in the torque reserve control in at least one of conditions where:   an auxiliary device of the vehicle exerts a load to the engine;   the load is increased; and   the vehicle starts moving.