Drive for motor-vehicle accessory

Abstract

A drive for a motor-vehicle accessory has a drive motor, a controller that regulates the drive motor, and a sensor associated with the drive motor and that measures the motor speed of the drive motor and transmits to the controller a signal having a pulse rate corresponding to the motor speed. A pulse-rate modifier between the sensor of the drive motor and the controller serves to modify the pulse rate received from the drive motor in such a way that this rate is within a range of the pulse rate processable by the controller and to transmit a modified value of the pulse rate to the controller.

Claims

1. A drive for a motor-vehicle accessory comprising: a drive motor; a controller that regulates the drive motor; a sensor associated with the drive motor and that measures the motor speed of the drive motor and transmits to the controller a signal having a pulse rate corresponding to the motor speed; and a pulse-rate modifier between the sensor of the drive motor and the controller that modifies the pulse rate received from the drive motor in such a way that this rate is within a range of the pulse rate processable by the controller, and transmits a modified value of the pulse rate to the controller.

2. The drive according to claim 1, wherein the pulse-rate modifier is an electronic component.

3. The drive according to claim 1, wherein the pulse-rate modifier is a frequency divider.

4. The drive according to claim 1, wherein the pulse-rate modifier is an electronic controller.

5. A displacement device comprising a component for a motor-vehicle accessory and a support, wherein the component can be moved relative to the support by a drive according to claim 1.

6. A head restraint with a head part mounted by at least one support rod in at least one bearing on a seat back of a vehicle seat, the head part being displaceable relative to the seat back, wherein the head part and the seat back form a displacement device for moving the head part relative to the seat back, the head part is a component and the seat back is a support, and the head part can be moved relative to the seat back by a drive according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Further advantages are apparent with reference to an illustrated embodiment illustrated in the drawing whose sole FIGURE is a schematic representation of the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

(2) A drive as a whole is shown in the drawing at 10.

(3) In the present illustrated embodiment the drive 10 is provided for controlling a head restraint 11 displaceable in the directions z.sub.1 and z.sub.2 and mounted on the seat back 12 of a vehicle seat 13. The head restraint 11 has a head part 14 and support rods 15. The head part 14 is secured to the support rods 15. The support rods 15 in turn are mounted in bearings fixed to the seat back. The head part 14 is mounted so as to movable in the directions z.sub.1 and z.sub.2 relative to the seat back 12 by an electric motor 16. The head part 14 is mounted for example so as to be movable relative to the support rods 15 and the support rods 15 are for example mounted so as to be fixed in the seat back 12.

(4) According to an alternative embodiment, the drive motor can move the support rods 15 relative to the bearings fixed to the seat back, and the head part 14 is fixed on the support rods 15.

(5) The drive motor 16 is regulated by a seat controller 17. The drive motor 16 and seat controller 17 are connected by data lines shown at 19 and 20 such that data can be transferred. This can take place for example by cable, wireless communication, WLan etc. The seat controller 17 can control the drive motor 16 through the data lines 19 and 20. For control of the drive motor 16 the seat controller 17 requires the current value of the speed n.sub.Motor of the drive motor 16. The drive motor has a sensor that records the motor speed n.sub.Motor and converts it into a signal having a pulse rate P.sub.Motor corresponding to the motor speed. This may for example be a Hall effect sensor.

(6) The seat controller 17 that only processes pulses with a half-cycle duration greater than 3.6 ms can record a maximum pulse rate P.sub.S of 8333/min. If the motor emits 1 pulse/revolution to the seat controller, in the prior art this means that a maximum engine speed n.sub.MotorMax=8333/min could be processed. If the seat controller receives higher pulse rates P.sub.Motor>8333/min, a system failure would occur.

(7) In order to meet the requirements as to overall size, weight and displacement noise, a smaller drive motor 16 must be used whose maximum speed n.sub.MotorMax is for example greater than 8333/min, for example 12000/min. According to the invention it is possible for the pulse rate supplied by the sensor of the drive motor processable by the seat controller 17, because a pulse-rate modifier 18 is provided between the drive motor 16 and the seat controller 17. The pulse rate P.sub.Motor corresponding to the motor speed n.sub.Motor is transmitted by the sensor of the drive motor 16 via the line 20 to the pulse-rate modifier 18.

(8) If the pulse-rate modifier 18 operates for example with a ratio of 2:1, the pulse rate P.sub.Motor is divided for example in such a way that only every second pulse is transmitted to the seat controller 17, and thus the pulse rate P.sub.Motor of the sensor is halved. The reduced value of the pulse rate P.sub.Reduz must be below the maximum pulse rate of the seat controller P.sub.S to be processed. With a half-cycle duration of the seat controller greater than 3.6 ms, P.sub.S=8333/min. The reduced value of the pulse rate P.sub.Reduz is transmitted via the line 19 to the seat controller 17.

(9) In this illustrated embodiment the maximum pulse rate of the motor P.sub.MotorMax=12000/min. With a division ratio of the pulse-rate modifier of 2:1, the maximum pulse rate arriving at the seat controller P.sub.Reduz=6000/min. In this way, due to a pulse count P.sub.Motor>P.sub.S transmitted to the seat controller 17, system failure is prevented. At the same time, a reduced pulse rate P.sub.Reduz proportional to the motor speed n.sub.Motor is supplied to the seat controller 17.