| 摘要 |
PURPOSE: To reduce the fluctuation range of the valve opening amount of an EGR gas control valve when a target valve opening amount is small by reducing the correction operation by a feed forward correction means in comparison with a larger target valve opening amount when it is small. CONSTITUTION: In a negative pressure room 9, when a duty ratio is 0%, only the atmosphere is introduced and the displace amount of a diaphragm 8 becomes zero and an EGR gas control valve is closed. When the duty ratio is increased and the negative pressure of a vacuum pump B is introduced in the negative pressure room 9, the diaphragm 8 is displaced upward and the EGR gas control valve is opened. In this case, as the negative pressure is getting bigger, the displace amount of the diaphragm 8 is also getting bigger and the EGR gas control valve is fully opened when the duty ratio is 0%. When the target valve opening amount to supply the most suitable EGR gas amount to an engine is small, the worsening of the exhaust performance improvement operation of EGR gas is prevented by preventing the feed forward correction control by which the shifted amount rate from an actual valve opening amount becomes large. |
