Control system for engine exhaust gas recirculation according to engine operational condition

In an internal combustion engine provided with a throttle valve in the intake system and an exhaust gas recirculation system for recirculating a portion of the exhaust gas to the engine including a recirculation passage interconnecting the exhaust line to the intake system, a control system for controlling the quantity of the recirculated exhaust gas comprising:

• a flow control valve provided in the recirculation passage;
• at least two different sensor means for producing individually an electrical signal representing and corresponding to the magnitude of one of variables related to the operational condition of the engine;
• at least two function generators arranged to individually receive a respective one of the electrical signals produced by said at least two sensor means and individually produce an output signal corresponding to a desirable opening degree of said flow control valve based on the assigned electrical signal;
• an arithmetic operation circuit connected to said at least two function generators to modulate respectively in amplitude the outputs of the two function generators according to the respective and relative importance of said variables to the control of the opening degree of said flow control valve and means to produce from the two modulated outputs a control signal;
• valve-actuating means for varying the opening degree of said flow control valve in response to said control signal, said variables including the degree of opening of the throttle valve, a first one of said at least two function generators arranged to receive a first electrical signal representing the opening degree of the throttle valve having a differentiation circuit to differentiate the received electrical signal and an operational amplifier to provide an inversed addition of a constant to the output of said differentiation circuit such that the output signal of said first one function generator implies that the opening degree of said flow control valve is decreased and increased when the opening degree of the throttle valve is increasing and decreasing, respectively, a second one of said at least two function generators being connected for also receiving said first electrical signal and the output of said second function generator implies that the opening degree of said flow control valve is decreased when the opening degree of the throttle valve is either near the maximum or near the minimum but otherwise increased.

In an internal combustion engine provided with a throttle valve in the intake system and an exhaust gas recirculation system for recirculating a portion of the exhaust gas to the engine including a recirculation passage interconnecting the exhaust line to the intake system, a control system for controlling the quantity of the recirculated exhaust gas comprising:

• a flow control valve provided in the recirculation passage;
• at least two different sensor means for producing individually and electrical signal representing and corresponding to the magnitude of one of variables related to the operational condition of the engine, said variables including the degree of opening of the throttle valve;
• at least two function generators arranged to individually receive a respective one of the electrical signals produced by said at least two sensor means and individually produce an output signal corresponding to a desirable opening degree of said flow control valve based on the assigned electrical signal;
• at least two multipliers respectively connected to said at least two function generators and constructed to individually multiply the output signal produced by the assigned function generator by a constant and an adder for producing said control signal by adding up all the outputs of said at least two multipliers;
• and
• a valve-actuating means for varying the opening degree of said flow control valve in response to said control signal.