| 摘要 |
PURPOSE:To make highly accurate EGR control with no secular change performable, by controlling an exhaust gas recirculating quantity according to each output of an oxygen sensor detecting oxygen content in suction air mixed with exhaust gas and a pressure sensor detecting atmospheric pressure of this oxygen sensor. CONSTITUTION:During engine running, at an EGR control circuit 14, first a desired EGR rate is read out of a memory device on the basis of each output signal out of an engine speed detector 8 and a suction pressure detector 10, and the desired oxygen content conformed to this desired EGR rate is calculated. On the other hand, oxygen content in the suction air mixed with EGR gas is calculated by output of an oxygen sensor 18, and the calculated value of this oxygen content is compensated by output of a pressure sensor 19. And, the oxygen content after compensation is compared with the desired oxygen content, and on the basis of the compared deviation, output negative pressure of a control negative pressure generator 16 is regulated with each pressure of a suction negative pressure intake passage 9 and an atmospheric pressure intake passage 15, and opening of an exhaust gas recirculation control valve 12 is controlled by the output negative pressure after being regulated.
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