Rotational angle sensor

Abstract

A rotational angle sensor device includes a casing, a movable body rotatably supported on the casing, a permanent magnet secured to the movable body, a magnetically soft member adjacent to the permanent magnet, and an electrical coil wound on the magnetically soft member. The movable body is responsive to a rotational angle or angular displacement caused by an external object, in response to which the permanent magnet moves in relation to the magnetically soft member, causing variations in the external flux. Those variations in external flux cause corresponding variations in the time interval from the instant at which a voltage is applied to the electrical coil to the instant at which the coil current reaches a certain level. The variations in the time interval are detected to determine the rotational angle caused by the external object. The magnetically soft member is preferably formed from an amorphous magnetically soft material. Various embodiments of the rotational angle sensor device are disclosed.

Dependencies are inferred from the claim text.