Temperature compensating device for torque measuring apparatus

• US 5,307,690 A
• Filed: 07/27/1992
• Issued: 05/03/1994
• Est. Priority Date: 07/29/1991
• Status: Expired due to Term

• Current Assignee: Kubota Corporation
• Original Assignee: Kubota Corporation
• Inventors: Hanazawa, Akiyoshi
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): BIEGEL, RONALD L
• Application Number:
  US07/919,953
• Time in Patent Office: 645 Days
• Field of Search: 73/862.333, 73/862.334, 73/862.335, 73/862.336
• 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

Abstract

A temperature compensating device for a torque measuring apparatus of the magneto-strictive type. A torque transmission shaft has a magnetically anisotropic portion formed on the periphery of the shaft. A sensing coil is disposed around the torque transmission shaft in corresponding relation to the magnetically anisotropic portion. A DC voltage from a constant voltage generator is supplied to the sensing coil. A torque detection signal is derived from the AC component of the voltage developed across the sensing coil, and the DC resistance of the sensing coil is detected from the DC component of the voltage, whereby the temperature of the sensing coil is detected. The torque detection characteristics of the apparatus is temperature-compensated on the basis of the temperature detection signal.

Claims

1. A temperature compensating device for a torque measuring apparatus of the magneto-strictive type including a magnetically anisotropic portion formed on the periphery of a torque transmission shaft, and sensing coil means provided in corresponding relation to the magnetically anisotropic portion for outputting an alternating current signal corresponding to the magnitude of a torque applied to the torque transmission shaft from the sensing coil means for measurement of the magnitude of the torque, said temperature compensating device comprising:

means for detecting the direct current resistance of said sensing coil means thereby to detect the temperature of said sensing coil means,

means for temperature-compensating the detecting characteristics of said torque measuring apparatus on the basis of a detection signal from said detecting means,

voltage division resistor means for applying a DC voltage to the sensing coil means

means for detecting the direct current component only of the terminal voltage of the sensing coil means thereby to find the DC resistance of the sensing coil means, and

means for deriving an alternating current component only out of an output signal from the sensing coil means thereby to provide a torque detection signal.

2. A temperature compensating device for a torque measuring apparatus as set forth in claim 1, wherein the torque transmission shaft has a pair of magnetically anisotropic portions formed on the periphery thereof, with a pair of sensing coils arranged in corresponding relation to the magnetically anisotropic portions, the sensing coils being disposed with their outputs in reversed polarity.

3. A temperature compensating device for a torque measuring apparatus as set forth in claim 2, further comprising exciting coils for excitation of the sensing coils, and means for supplying an AC voltage to the exciting coils.

4. A temperature compensating device for a torque measuring apparatus as set forth in claim 2, wherein a bridge circuit comprises said pair of sensing coils and a pair of resistors connected to the sensing coils, said temperature compensating means further comprising means for supplying an AC voltage to said bridge circuit, and means for deriving an AC signal only from said bridge circuit.

5. A temperature compensating device for a torque measuring apparatus as set forth in claim 2, further comprising means for detecting the temperature gradient of the locations at which the sensing coils are disposed from the difference between the DC resistance of one of said sensing coils and the DC resistance of the other sensing coil, and means for temperature-compensating the detection characteristics of said torque measuring apparatus.

6. A temperature compensating device for a torque measuring apparatus as set forth in claim 1, wherein the torque transmission shaft has a single magnetically anisotropic portion formed on the periphery thereof, with a single sensing coil disposed in corresponding relation to the magnetically anisotropic portion.

7. A temperature compensating device for a torque measuring apparatus of the magneto-strictive type including a magnetically anisotropic portion formed on the periphery of a torque transmission shaft, sensing coil means provided in corresponding relation to the magnetically anisotropic portion, and exciting coil means for excitation of the sensing coil means, so that an alternating current signal corresponding to the magnitude of a torque applied to the torque transmission shaft is output from the sensing coil means for measurement of the magnitude of the torque, said temperature compensating device comprising:

means for detecting the direct current resistance of said exciting coil means thereby to detect the temperature of said exciting coil means,

means for temperature-compensating the detecting characteristics of said torque measuring apparatus on the basis of a detection signal from said detecting means

means for supplying an AC voltage to the exciting coil means,

means for applying a DC voltage to the exciting coil means through a voltage division resistor, and

means for detecting the direct current component only of the terminal voltage of the exciting coil means thereby to find the DC resistance of the exciting coil means.

8. A temperature compensating device for a torque measuring apparatus as set forth in claim 7, wherein the torque transmission shaft has a pair of magnetically anisotropic portions formed on the periphery thereof, with a pair of exciting coils arranged in corresponding relation to the magnetically anisotropic portions.

9. A temperature compensating device for a torque measuring apparatus as set forth in claim 8, wherein the pair of exciting coils are disposed with their outputs in reversed polarity relative to each other, with separate AC exciting power supplies connected to the respective exciting coils, said AC exciting power supplies being shifted 180 degrees in phase relative to each other.

10. A temperature compensating device for a torque measuring apparatus of the magneto-strictive type including magnetically anisotropic means formed on the periphery of a torque transmission shaft, and sensing coil means provided in corresponding relation to the magnetically anisotropic means, so that an alternating current signal corresponding to the magnitude of a torque applied to the torque transmission shaft is output from the sensing coil means for measurement of the magnitude of the torque, comprising:

the AC exciting current for exciting said sensing coil means being a resultant current consisting of a high-frequency current for torque detection signaling and a low-frequency current for equipment-temperature detection signaling;

said temperature compensating means further comprising;

means for detecting the temperature of equipment on the basis of a temperature detection low-frequency signal from said sensing coil means, and

means for temperature-compensating a torque detection signal on the basis of a detection signal from said detecting means.

11. A temperature compensating device for a torque measuring apparatus as set forth in claim 10, wherein:

the torque transmission shaft has a pair of magnetically anisotropic portions formed on the periphery thereof,

with a pair of sensing coils arranged in corresponding relation to the magnetically anisotropic portions,

the sensing coils being disposed with their outputs in reversed polarity, and

said temperature compensating means further comprising;

means for calculating the difference between torque detection signals from the sensing coils to provide a torque detection signal, and

means for calculating the sum of temperature detection signals from the sensing coils to provide a temperature detection signal.