Patent ID: 9036234
Filing Date: 2015-05-19
Classification: G02B

Abstract:
1. A head-up display device for a vehicle comprising: a display unit for displaying a light-emitted image; an optical system including a reflection mirror, which is provided rotatably to reflect the light-emitted image and project a reflected image toward a projection target so that a virtual image of vehicle related information is displayed; a stepper motor for driving, when powered by a drive signal, the reflection mirror to rotate for adjusting a display position of the virtual image, the stepper motor having plural electric stabilization points, at which a motor operation is electrically stabilized by a holding torque generated when powered, and plural mechanical stabilization points, at which the motor operation is stabilized by a detent torque generated when not powered; and a control system for controlling the drive signal for the stepper motor in response to an adjustment instruction inputted from an external side, wherein the stepper motor has stators of plural phases, between which pole teeth are shifted in position in a motor rotation direction, and a rotor, which is rotated to a position in correspondence to magnetic attraction force generated relative to the pole teeth, wherein the pole teeth of a specified phase of the plural phases are set as stabilization pole teeth, the magnetic attraction force of which generated when not powered provides the detent torque greater than that of another phase of the plural phases, wherein the control system is configured to continue to apply the drive signal even after the adjustment instruction is stopped until an electric angle of the stepper motor reaches a target stabilization point, which is set to one of the electric stabilization points where the magnetic attraction force for providing the holding torque when powered is generated between the stabilization pole teeth and the rotor, and wherein the stators includes a first stator for a first phase and a second stator for a second phase, and the first stator has less air gaps than the second stator.