ROTATIONAL POSITION SENSOR, COMPOUND ROTATIONAL POSITION SENSOR AND MOTOR OPERATED POWER STEERING DEVICE

Abstract

It is an object to provide a new rotational position sensor, compound rotational position sensor and motor operated power steering device capable of detecting the rotational position of a rotation detection shaft of which a steering shaft is representative. According to a compound rotational position sensor of the present invention, the number of times a steering shaft has rotated from a reference position is identified by a rotational position sensor and the angle of rotation for one turn of the steering shaft is identified by an encoder. Furthermore, the current angle of rotation of the steering shaft may be specified as an absolute angle of rotation from the reference position based on these two pieces of rotational position information. Furthermore, since a magnetic circuit that is closed by the steering shaft and the base part is formed, the efficiency of the electromagnetic induction is improved, and the electric power consumed can be controlled.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram of a vehicle according to one embodiment of the present invention;

FIG. 2 is a conceptual diagram of the combined rotational position sensor;

FIG. 3 is a cross-sectional diagram of the steering shaft in a state where the variable winding coil is wound;

FIG. 4 is a conceptual diagram showing the changes in the number of windings for the variable winding coil;

FIG. 5 is a graph showing the relationship between the number of turns for the variable winding coil and the induced voltage arising in the fixed coil;

FIG. 6 is a conceptual diagram of the compound position sensor in another embodiment; and

FIG. 7( a) is a perspective view of the variable winding coil according to one of embodiments.

FIG. 7( b) is a side view of the variable winding coil according to one of embodiments.

Claims

1. A rotational position sensor that detects the rotational position of a rotation detection shaft attached rotatably to a base part, comprising: a variable winding coil constituted by a wire, one end of which is affixed to and wound around the rotation detection shaft and the other end of which is held by the base part, a number of coils of the wire being configured to vary according to the rotational position of the rotation detection shaft; anda fixed coil capable of electromagnetic induction with the variable winding coil.

2. The rotational position sensor according to claim 1, further comprising: an alternating current power supply that causes a reference voltage established in advance to pass through either one of the fixed coil and the variable winding coil; anda data processing part that calculates the rotational position of the rotation detection shaft based on the induced voltage arising in the other coil and the reference voltage.

3. The rotational position sensor according to claim 1, wherein the rotation detection shaft, along with being constituted of a magnetic substance, is fitted within the fixed coil so as to allow play between them.

4. The rotational position sensor according to claim 1, wherein the base part, along with being constituted of a magnetic substance, has one pair of magnetic path forming opposed walls through which both ends of the rotation detection shaft pass, and a magnetic path forming wall that joins the magnetic path forming opposed walls.

5. The rotational position sensor according to claim 1, wherein the variable winding coil is a flat cable and that flat cable is wound around the rotation detection shaft in a coiled shape.

6. The rotational position sensor according to claim 1, wherein the wire of the variable winding coil is wound around the rotation detection shaft in a spiral shape.

7. The rotational position sensor according to claim 1, further comprising a cable reel capable of winding up the wire of the variable winding coil by a reactive force of a spring between the other end of the variable winding coil and the base part.

8. The rotational position sensor according to claim 1, wherein the rotation detection shaft is a steering shaft connected to a steering wheel provided in a vehicle.

9. The rotation position sensor according to claim 8, wherein the variable winding coil is conductively connected to the steering shaft.

10. A compound rotational position sensor comprising: the rotational position sensor according to claim 1;an encoder capable of detecting the rotational position in one rotation of the rotation detection shaft; anda composite computation part that receives both detection results from the rotational position sensor and the encoder, and along with identifying how many rotations the rotation detection shaft has undergone from a reference position by means of the rotational position sensor, identifies the rotational position in one rotation of the rotation detection shaft by means of the encoder and computes the absolute rotational position of the rotation detection shaft from the reference position.

11. A compound rotational position sensor comprising: the rotational position sensor according to claim 1;a resolver capable of detecting the rotational position in one rotation of the rotation detection shaft; anda composite computation part that receives both detection results from the rotational position sensor and the resolver, and along with identifying how many rotations the rotation detection shaft has undergone from a reference position by means of the rotational position sensor, identifies the rotational position in one rotation of the rotation detection shaft by means of the resolver and computes the absolute rotational position of the rotation detection shaft from the reference position.

12. A motor operated power steering device comprising the compound rotational position sensor according to claim 10.

13. A motor operated power steering device comprising the compound rotational position sensor according to claim 11.