| 摘要 |
PURPOSE:To enable to enhance the exhaust-gas clarifying efficincy by a method wherein the warming-up of a catalyst is accelerated by closing an EGR valve when the vehicle speed is not higher than a predetermined value and the negative-pressure is not larger than a predetermined value, in an internal-combustion engine provided with an EGR device and a secondary-air supply device. CONSTITUTION:In the case where the indication of a vehicle-speed sensor 32 is on the lower side of a set point and the load is low, when a negative-pressure swtich 33 is not lower than a set point, a signal of this condition energizes the first solenoid valve 14 to cut off the negative-pressure fed from an EGR sensing port 16, and the EGR valve 12 is operated in the direction for closing. As a result, secondary air controlled by a signal from an O2 sensor is introduced into an EGR passage 11 on the exhaust manifold side, but it is supplied only to the exhaust manifold side since the EGR valve 12 is closed. Accordingly, the primary air-fuel ratio has a value of rich mixture and, at the same time, the exhaust system is supplied with a large amount of secondary air, so that the warming-up of the catalyst 5 is accelerated and the exhaust-gas clarifying performance is enhanced. |
