Exhaust gas recirculation system for internal combustion engine

摘要

An exhaust gas recirculation system for an internal combustion engine has an exhaust gas recirculation passage, a constant pressure chamber disposed in the exhaust gas recirculation passage, a pressure regulating valve operative in response to the exhaust gas pressure in the constant pressure chamber, a first flow-rate control valve adapted to be actuated by the vacuum regulated by the pressure regulating valve so as to open and close the exhaust gas recirculating passage and a second flow-rate control valve disposed at the upstream side of the constant pressure chamber and adapted to change the cross-sectional area of the exhaust gas recirculating passage in response to the vacuum generated by the internal combustion engine. The exhaust gas recirculation system further has an atmospheric-pressure introduction passage attached to the constant pressure chamber or disposed in a pressure transmitting passage through which the constant pressure chamber is communicated with the pressure regulating valve. The atmospheric-pressure introduction valve is adapted to open in response to an increase of the level of the vacuum in the constant pressure chamber or in the pressure transmitting passage, so as to selectively introduce the atmospheric pressure.