Secondary air regulating system

A secondary air regulating system for an exhaust purifying device of an internal combustion engine having an air intake passage and an exhaust passage in which said exhaust purifying device is disposed, which system in combination comprises:

• secondary air supply means connected to a portion upstream of said exhaust purifying device in said exhaust passage for supplying secondary air into said portion;
• a sensor disposed downstream of said exhaust purifying device in said exhaust passage for generating a first signal in response to a predetermined concentration of a predetermined component being sensed in exhaust gases discharged from said exhaust purifying device;
• a controller electrically connected to said sensor for producing a second signal in response to said first signal from said sensor;
• and
• regulating means electrically connected to said controller and connected to said secondary air supply means for controlling said secondary air supply means in response to said second signal, whereby said secondary air supply means supplies the optimal amount of secondary air into the portion upstream of said exhaust purifying device in said exhaust passage, said regulating means comprising,
• a three way solenoid valve electrically connectable and respondable to said controller and communicating with said air passage in response to said second signal from said controller, said three-way solenoid valve including a solenoid coil electrically connected with said controller and provided with a bore inside thereof, said coil being variably energizable by either polarity of said second signal and the energizing magnitude of said second signal, an atmospheric chamber adjacent to said bore and provided with an air inlet port communicating with the atmosphere, a vacuum chamber adjacent to said atmospheric chamber through a partition wall having an opening therethrough and provided with a vacuum inlet port communicating with said air intake passage and a vacuum outlet port communicating with said diaphragm assembly, an elongate permanent magnet plunger slidably disposed in said bore inside of said solenoid coil, said plunger being reversably movable therein in dependence on the polarity of solenoid coil and in response to the energizing signal magnitude of said solenoid coil, biasing means biasing said plunger at both ends thereof for holding it at neutral position, and a needle valve integrated with said plunger and being movably disposed in said opening of said partition wall so as to determine the opening area of said opening in accordance with the movement of said plunger,
• a diaphragm assembly communicating with said air intake passage through said three-way solenoid valve for actuation by the vacuum regulated by said solenoid valve, and
• a relief valve mechanically connected to said diaphragm assembly, said relief valve communicating with said air supply means for control of said air supply means in response to said second signal from said controller.