Magnetostrictive torque sensor (magnetic erasing)

• US 7,584,673 B2
• Filed: 10/09/2007
• Issued: 09/08/2009
• Est. Priority Date: 10/10/2006
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Shimizu, Yasuo
• Primary Examiner(s): NOORI, MASOUD H
• Application Number:
  US11/907,042
• Publication Number:
  US 20080134803A1
• Time in Patent Office: 700 Days
• Field of Search: 73862331-862333
• US Class Current: 73/862.333
• CPC Class Codes: G01L 3/102 involving magnetostrictive means magnetostrictive sensors H10N35/101
• CPC Class Codes: G01L 3/105 involving inductive means G01L3/102, G01L3/104 take precedence
• CPC Class Codes: G01L 5/221 to steering wheels, e.g. for power assisted steering

Abstract

A magnetostrictive torque sensor includes a magnetostrictive portion provided on a shaft. At least one torque detection coil is disposed opposite the shaft. The at least one torque detection coil detects a torque applied to the shaft. A demagnetization circuit (C) demagnetizes the shaft via the detecting coil.

Claims

1. A magnetostrictive torque sensor comprising:

a magnetostrictive portion provided on a shaft;

first and second torque detection coils disposed opposite the shaft,

wherein at least one first and second torque detection coil detects a torque applied to the shaft,

a demagnetization circuit (C) demagnetizes the shaft via said at least one first and second torque detection coil, and the demagnetization circuit (C) provides an excitation function to said at least one first and second torque detection coil; and

torque calculating means for calculating the detected torque, wherein the detected torque is calculated by an equation;

VT3=k(VT1−

VT2)+Vb

wherein VT1 is a first voltage signal detected by the first torque detection coil facing a first magnetostrictive portion, and when the steering torque increases, the first voltage signal increases, and

wherein VT2 is a second voltage signal detected by the second torque detection coil facing a second magnetostrictive portion, and when the steering torque increases, the first voltage signal decreases, and Vb is a bias voltage.

2. The magnetostrictive torque sensor according to claim 1, wherein the demagnetization circuit (C) generates and transmits a decreasing signal to said at least one first and second torque detection coil.

3. The magnetostrictive torque sensor according to claim 1, wherein the demagnetization circuit (C) comprises an alternate current generator which includes a plurality of switching elements and a plurality of resistor elements.

4. The magnetostrictive torque sensor according to claim 1, wherein the demagnetization circuit (C) is provided with an electric current by at least one charge maintaining device.

5. The magnetostrictive torque sensor according to claim 1, wherein the demagnetization circuit (C) stops demagnetizing the shaft while the torque is being detected.

6. The magnetostrictive torque sensor according to claim 1, wherein the shaft is a steering shaft of a vehicle.

7. The magnetostrictive torque sensor according to claim 6, wherein the demagnetization circuit (C) supplies a demagnetizing signal to the steering shaft when a velocity of the vehicle is substantially zero.

8. The magnetostrictive torque sensor according to claim 6, wherein the demagnetization circuit (C) supplies a demagnetizing signal to the steering shaft while a steering torque is substantially zero.

9. The magnetostrictive torque sensor according to claim 4, wherein the at least one charge maintaining device is a condenser.

10. The magnetostrictive torque sensor according to claim 1, wherein the demagnetization circuit (C) comprises a bridge circuit having a plurality of transistors.

11. A magnetostrictive torque sensor comprising:

a magnetostrictive portion provided on a shaft;

first and second torque detection coils disposed opposite the shaft,

wherein at least one first and second torque detection coil detects a torque applied to the shaft,

a demagnetization circuit (C) demagnetizes the shaft via said at least one first and second torque detection coil, and a magnetization of one of the magnetostrictive portion and the shaft is detected based on a torque detecting signal; and

torque signal calculating means for calculating the detected torque, wherein the detected torque is calculated by an equation;

VT3=k(VT1−

VT2)+Vb

wherein VT1 is a first voltage signal detected by the first torque detection coil facing a first magnetostrictive portion, and when the steering torque increases, the first voltage signal increases, and

wherein VT2 is a second voltage signal detected by the second torque detection coil facing a second magnetostrictive portion, and when the steering torque increases, the first voltage signal decreases, and Vb is a bias voltage.

12. The magnetostrictive torque sensor according to claim 11, wherein the demagnetization circuit (C) comprises a bridge circuit having a plurality of transistors.

13. A magnetostrictive torque sensor according to claim 11, wherein the demagnetization is detected when a velocity of a vehicle in which the sensor is mounted is substantially zero.

14. A magnetostrictive torque sensor according to claim 11, wherein the demagnetization is detected while a steering torque is substantially zero.