| 摘要 |
PURPOSE:To heighten the set degree of freedom of the EGR factor, and enable fine EGR control conforming to the demand from the engine. CONSTITUTION:The degree of opening of an EGR control valve 5 is feedback controlled by a pressure adjusting valve 6 so that the pressure P2 in an EGR passage 4 downstream of the EGR control valve 5 is held at a specified value, while a valve 10 is installed in the suction passage 3 to control the section area of the suction passage 3 in accordance with the engine operating conditions. According to this constitution, the EGR factor R is made variable according to the suction amount and the degree of opening of the valve 10 based upon the formula R=(A2/A1)[(gammaa/gammae)[1-{(P1-P2)/(P1-P0)}]<1/2>, where P1 is pressure upstream of valve 10, P2 is pressure in EGR passage dowstream of EGR control valve. A1 is section area of suction passage, A2 is section area of EGR passage, (g) is gravitational acceleration, and gammaa and gammae are respective specific gravities of suction air and EGR gas. This enlarges the set degree of freedom of the EGR factor and enables fine EGR control conforming to the operating conditions. |
