Patent ID: 8102139
Filing Date: 2012-01-24
Classification: G01D

Abstract:
1. An indicating instrument for a vehicle comprising: a step motor that includes a field winding and is rotated upon application of a drive signal to the field winding, wherein the drive signal is an alternating current that alternates in accordance with an electrical angle; a pointer that points to a vehicle state value, which is indicated with a zero value as a reference thereof, in accordance with a rotational position of the pointer, and that is rotated in a zero-reset direction to return to a zero position that indicates the zero value; a reduction gear mechanism that includes a plurality of gears in engagement with each other, and that reduces a speed of rotation of the step motor and transmits the rotation of the step motor to the pointer thereby rotating the pointer; a stopper means for stopping the pointer, which is rotating in the zero-reset direction, at a stopper position that is located within a predetermined range from the zero position in the zero-reset direction; a detecting means for detecting an induced voltage generated in the field winding at each of a plurality of detecting points, which are electrical angles and include a zero point corresponding to the stopper position; a control means for controlling the drive signal applied to the field winding, wherein: an updating means for updating the zero point based on the induced voltage detected by the detecting means during the zero-reset control that is performed by the control means.