Air intake side secondary air supply system for an internal combustion engine using a linear-type solenoid valve

An air intake side secondary air supply system for an internal combustion engine having an intake air passage with a carburetor and a throttle valve and an exhaust gas passage, comprising:

• an air intake side secondary air supply passage leading to said intake air passage downstream from the throttle valve;
• a solenoid valve disposed in said air intake side secondary air supply passage, the opening degree of said solenoid valve being varied continuously in response to the magnitude of a drive current supplied to a solenoid thereof so that a flow area of said air intake side secondary air supply passage is varied continuously;
• first sensor means disposed in said exhaust gas passage for sensing the concentration of an exhaust gas component of the engine and producing a sensor output signal indicative of said concentration;
• further sensor means for monitoring a plurality of parameters indicative of the operating state of said engine and operative to produce output signals indicative of the magnitude of said parameters;
• and
• control means connected to each of said sensor means for effecting feedback control of the air-fuel ratio of the mixture to be supplied to said engine, said control means including means responsive to selected ones of said plurality of parameters representing the load on said engine for setting a base value, other than zero, of said drive current to be used in effecting such feedback control, and means responsive to said sensor output signal from said first sensor means for modifying the set base value of said drive current to determine a supply current value to be used in effecting such feedback control;
• said control means also including current supply means connected to said solenoid of said solenoid valve for supplying said solenoid with drive current having the supply current value determined by said control means.