| 摘要 |
PURPOSE: To widely select the maximum, minimum or middle valve lift or opening suitable for an EGR control valve of a vehicular engine. CONSTITUTION: An actuator 20 for controlling the lift or the opening of a valve member 16 into three stages is constituted of a first piston 26 slidably fitted in a first cylinder 24 in a housing 12, a second piston 30 slidably fitted into a second cylinder 28 integrated with it, and a third piston 46 for regulating the stroke of the first piston 26. The first piston 26 is displaced in the valve opening direction by the operating medium from a first supply and discharge port 36, and the second piston 30 is displaced in the valve opening direction by the operating medium from a second supply and discharge port 52. When the operating medium from the second supply and discharge port 52 acts on the third piston 46, the stroke of the first piston 26 is set smaller, and when the operating medium does not act on the third piston 46, the stroke of the first piston 26 is set larger. As an output member, the second piston 30 directly opens and closes the valve member 16 or opens and closes the valve member 16 through a link device. |
