Exhaust-gas recirculation system for internal combustion engine

Claim 1

An exhaust-gas recirculation system for an internal combustion engine comprising: an exhaust-gas recirculation passage through which a portion of the exhaust gas from the internal combusion engine is sent back to an intake system, an exhaust-gas recirculation control valve disposed in said passage, valve actuating means for actuating said control valve in such a manner to continuously control the opening thereof, a valve opening sensor for generating an actual valve opening signal corresponding to the actual opening of said control valve, detecting means for detecting certain operating conditions of the internal combustion engine, and a main control device for supplying an output signal to said valve actuating means, said main control device having means for setting a desired opening amount of said control valve based on a signal sent from said detecting means, comparing means for detecting a difference between the desired opening amount and the actual valve opening detected by said valve opening sensor, sensing means for sensing, judging and setting a sudden change in the desired opening amount, means for setting a given length of quiescent time, and pulse actuating means for supplying actuating signals to said valve actuating means and operative to withhold the supply of the next actuating signal during the quiescent time preset by said quiescent time setting means after said pulse actuating means supplies an actuating signal the length of which corresponds to the difference detected by said comparing means and operative when the desired opening amount changes suddenly and in response to a signal from said sensing means to supply immediately a new actuating signal the length of which corresponds to a new difference.