Patent ID: 7986151

Claim:
A head rest device for a vehicle comprising: a head rest rear portion supported to a seat back; a head rest front portion movable forward and backward between a full-close position which is close to the head rest rear portion, and a full-open position which is away from the head rest rear portion; a drive means moving the head rest front portion; an electrostatic capacitance sensor provided in the head rest front portion and structured such that an electrostatic capacitance is changed in accordance with a fluctuation of the distance with respect to the occupant head portion when the head rest front portion is moved relative to the head rest rear portion along a fore-and-aft direction of the vehicle; and a control means controlling the drive means and determining an approach between the head rest front portion and the occupant head portion on the basis of a detection result of the electrostatic capacitance sensor so as to stop the head rest front portion at a time of moving the head rest front portion in the full-open position direction, wherein the control means sets an electrostatic capacitance value of the electrostatic capacitance sensor at a predetermined timing to a reference electrostatic capacitance value which is changeable in correspondence to the timing, and determines that the head rest front portion comes close to the occupant head portion in the fore-and-aft direction of the vehicle on the basis of an absolute capacitance change with respect to the reference electrostatic capacitance value and a change amount of the electrostatic capacitance value per unit time.