| 摘要 |
PURPOSE:To enable reduction of the quantity of EGR irrespective of the degree of a load in a low rotational region to improve the drivability by providing a negative pressure changeover valve in the intermediate of a passage leading a negative pressure to a diaphragm chamber of an EGR pressure valve from a second negative pressure port. CONSTITUTION:When a throttle valve 20 is opened up to a first port 19, a manifold negative pressure is applied to a diaphragm chamber 24 of the EGR valve 4, and a valve body 14 is opened and an EGR gas flows. Furthermore, when the throttle valve 20 is opened up to a second port 8, the negative pressure is applied similarly to the diaphragm chamber 7 of an EGR adjusting valve 6, and a valve body 15 rises up and the quantity of the EGR is increased. Here, in a case where the rotational speed of the engine is low even when the throttle valve 20 is opened up to the second port 8, a negative pressure is prevented by a switchover valve (VSV) 9 provided in a second negative pressure passage 27, and atmospheric air is bred from a VSV filter 25 to the above chamber 7 and the negative pressure of the above chamber 24 is reduced to lower the above valve body 14. |
