Exhaust gas recirculation and idle speed control device

Abstract

An exhaust gas recirculation and idle speed control device including an exhaust gas recirculation control valve responsive to negative pressure for controlling amounts of exhaust gas recirculation, an idle speed control valve responsive to negative pressure for controlling intake air flow rate when idling, a solenoid valve for regulating intake negative pressure, a change-over valve adapted to be changed to supply the negative pressure regulated by the solenoid valve to any one of the exhaust gas recirculation and idle speed control valves and a control circuit for generating signals depending upon engine operating parameters for controlling the solenoid valve and for changing the change-over valve to the idle speed control valve side when a throttle valve is closed and changing the change-over valve to the exhaust gas recirculation control valve side at the time other than when the throttle valve is closed according to the invention comprises a timer circuit in the control circuit to provide a constant delay time determined by the timer circuit in changing the change-over valve, during which the exhaust gas recirculation control valve is completely closed and thereafter the change-over valve is changed to the idle speed control valve side, thereby controlling exhaust gas recirculation and idle speed by means of only one solenoid valve and preventing malfunctions in changing the exhaust gas recirculation and idle speed controls.

Dependencies are inferred from the claim text.