Exhaust gas recirculation apparatus for engine
An EGR apparatus includes an EGR passage to allow part of exhaust gas discharged from a combustion chamber to flow in an intake passage and recirculate back to the combustion chamber and an EGR valve to regulate EGR gas in the EGR passage. The EGR valve includes a valve seat, a valve element, and a step motor. An ECU calculates a target correction value corresponding to an operating condition of an engine, cuts off energization to the step motor in order to hold the EGR valve at a predetermined opening degree during operation thereof, and then restarts energization to the step motor, calculates an energization cutoff correction value corresponding to an elapsed time from energization cutoff, and corrects the target correction value by the calculated energization cutoff correction value in order to control the EGR valve to the target opening degree.
1. An exhaust gas recirculation apparatus for an engine, the apparatus including:
an exhaust gas recirculation passage to allow part of exhaust gas discharged from a combustion chamber of an engine to an exhaust passage to flow as exhaust recirculation gas into an intake passage and recirculate back to the combustion chamber;
a motor-driven exhaust gas recirculation valve provided in the exhaust gas recirculation passage to regulate a flow rate of the exhaust recirculation gas in the exhaust gas recirculation passage,
the exhaust gas recirculation valve including a valve seat, a valve element provided to be seatable on the valve seat, a motor to drive the valve element, and a constituent component related to the valve seat, the valve element, and the motor; and
a control unit configured to control the exhaust gas recirculation valve according to an operating condition of the engine,
wherein the control unit is configured to:
calculate a target correction value corresponding to the operating condition of the engine;
cut off energization to the motor when the exhaust gas recirculation valve is to be held at a fully closing degree during operation of the exhaust gas recirculation valve; and then
restart energization to the motor, calculate an energization cutoff correction value corresponding to an elapsed time since energization to the motor is cut off in order to correct displacement of the valve element with respect to the valve seat in association with thermal contraction of the constituent component caused by reduction in temperature, and correct the target correction value by the calculated energization cutoff correction value when the exhaust gas recirculation valve is to be controlled to a target opening degree.
2. The exhaust gas recirculation apparatus for an engine according to claim 1 , wherein
the control unit is configured to further calculate an energization start correction value corresponding to an elapsed time since energization to the motor is restarted and further correct the target correction value by the calculated energization start correction value.
3. The exhaust gas recirculation apparatus for an engine according to claim 1 , wherein
the control unit is configured to limit calculation of the energization cutoff correction value in a range of a predetermined upper limit to a predetermined lower limit.
4. The exhaust gas recirculation apparatus for an engine according to claim 2 , wherein
the control unit is configured to limit calculation of the energization cutoff correction value in a range of a predetermined upper limit to a predetermined lower limit.
5. The exhaust gas recirculation apparatus for an engine according to claim 2 , wherein
the control unit is configured to limit calculation of the energization start correction value in a range of a predetermined upper limit to a predetermined lower limit.
6. The exhaust gas recirculation apparatus for an engine according to claim 4 , wherein
the control unit is configured to limit calculation of the energization start correction value in a range of a predetermined upper limit to a predetermined lower limit.