PURPOSE: To provide a valve means which improves orifice opening resolution without adding a decelerating gear or the like, in a valve opening which controls orifice opening with a stepping motor, and provide a control type rotational difference sensitive joint with transmission torque control accuracy improved in a small range of orifice opening.

CONSTITUTION: A valve means where a control unit 40 (stepping motor control means) which conducts duty control within an stepping interval between the first stepping position including a target position and the second stepping position, and control type rotational difference sensitive joints 7L, 7R where the valve means is applied to an orifice opening control part are mounted to control the driving of stepping motors 30L, 30R.