JP2002372468A - Torque measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque measuring apparatus in which a zero-point fluctuation and a sensitivity fluctuation can be corrected precisely even when a temperature difference is generated in a detection part used to detect a torque. SOLUTION: The torque T to be detected is applied to a detection shaft 1, magnetostrictive material parts 2, 3 are formed on its outer circumference, and detection coils 4, 5 are installed respectively so as to be adjacent to the parts 2, 3. A resistance 15 is connected to the detection coil 4, a resistance 16 is connected to the detection coil 5, and a bridge circuit 18 is constituted of them. An AC signal generator 17 applies an AC signal to the input end of the bridge circuit. Temperature detection circuits 6, 7 are arranged near the detection coils 4, 5. A zero-point correction circuit 21 corrects the zero point of a torque detection output on the basis of the output of the circuit 6. A sensitivity correction circuit 50 corrects the sensitivity of the torque detection output on the basis of the output of the circuit 6. A zero-point correction circuit 22 and a sensitivity correction circuit 51 function in the same manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque measuring device for non-contactly measuring a torque applied to a rotating shaft.

[0002]

2. Description of the Related Art A conventional torque measuring device includes a magnetostrictive material portion provided on an outer peripheral surface of a detection shaft, and a detection coil disposed around the magnetostriction material portion, and detects a torque applied to the detection shaft. 2. Description of the Related Art There is known a device that detects an AC signal according to a magnitude from a detection coil and converts torque into an electric signal. However, in this torque measuring device, when a temperature change occurs in the magnetostrictive material portion, the magnetic characteristics change, thereby changing the impedance of the detection coil and causing a change in the measurement output.

In the apparatus disclosed in Japanese Patent Application No. 11-150728, a change in impedance of a detection coil due to a change in temperature is corrected by a thermistor circuit connected in series to the detection coil, and a zero point fluctuation of a measurement output is obtained. Was being held down. However, this device has a problem that it can correct the zero point fluctuation, but cannot correct the sensitivity fluctuation due to the temperature change.

[0004]

On the other hand, JP-A-6-26
Japanese Unexamined Patent Publication No. 950 discloses a method of obtaining a sum of respective temperature signals of two detection coils provided in a torque detection unit, which are detected from a change in resistance value due to a temperature. In addition, the sensitivity fluctuation is corrected. However, this device corrects the zero point fluctuation and the sensitivity fluctuation assuming that the two detection coils have a uniform temperature, and thus corrects the zero point fluctuation and the sensitivity fluctuation when a temperature difference occurs between the two detection coils. There was a problem that was difficult. Furthermore, this device has a disadvantage that it is difficult to accurately detect the temperature because the amount of change in the resistance value of the detection coil due to the temperature change is small.

The present invention has been made in view of such circumstances, and has as its object to accurately correct zero point fluctuations and sensitivity fluctuations even when a temperature difference occurs in a detecting unit for detecting torque. It is another object of the present invention to provide a torque measuring device that can perform the correction with higher accuracy than before.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the invention according to claim 1 has the following features.
First and second magnetostrictive material portions formed on the outer periphery of a detection shaft to which a torque to be detected is applied, and first and second magnetostrictive material portions provided near the first and second magnetostrictive material portions, respectively. A detection coil, a detection circuit for detecting a change in impedance of the first and second detection coils, and first and second temperature detection means disposed near the first and second detection coils; A correction circuit that corrects the output of the detection circuit based on the outputs of the first and second temperature detection means.

[0007] According to a second aspect of the present invention, there is provided a motor control apparatus comprising:
A second magnetostrictive material portion, first and second detection coils provided close to the first and second magnetostrictive material portions, respectively;
A bridge circuit including the first and second detection coils, a resistor connected in series to the first detection coil, and a resistor connected in series to the second detection coil; and an AC signal to an input terminal of the bridge circuit. And an AC source for applying
A first and a second temperature detecting means arranged near the detecting coil of the first circuit, and a first correction for correcting a signal at a first output point of the bridge circuit based on an output of the first temperature detecting means. Means, a second correction means for correcting a signal at a second output point of the bridge circuit based on an output of the second temperature detection means, and a difference signal between outputs of the first and second correction means. And a difference signal output means for outputting the difference signal.

[0008] Further, the invention described in claim 3 is based on claim 2.
Wherein the first correction means corrects a zero point of the torque detection output based on the output of the first temperature detection means, and an output of the first temperature detection means. And a sensitivity correction means for correcting a sensitivity variation of the torque detection output based on the second temperature detection means. The second correction means corrects a zero point of the torque detection output based on the output of the second temperature detection means. Means, and sensitivity correction means for correcting sensitivity fluctuation of the torque detection output based on the output of the second temperature detection means.

According to a fourth aspect of the present invention, there is provided a motor vehicle comprising: a first shaft formed on an outer periphery of a detection shaft to which a torque to be detected is applied;
A second magnetostrictive material portion, first and second detection coils provided close to the first and second magnetostrictive material portions, respectively;
A bridge circuit including the first and second detection coils, a resistor connected in series to the first detection coil, and a resistor connected in series to the second detection coil; and an AC signal to an input terminal of the bridge circuit. An AC source, a first and a second AC / DC converter for converting signals at the first and second output terminals of the bridge circuit into a DC signal, and an AC / DC converter for the first and second detection coils. First and second temperature detecting means disposed in the vicinity,
An analog / digital converter for converting the outputs of the first and second AC / DC converters and the outputs of the first and second temperature detectors into digital data, respectively, and the first and second AC / DC converters; The digital data based on the output of the direct conversion means is corrected by digital data based on the outputs of the first and second temperature detecting means to perform a zero point correction and a sensitivity correction of the torque detection output, and the difference between the corrected data is calculated. And a calculation circuit for performing a calculation.

The invention described in claim 5 is the same as the invention in claim 4.
3. The torque measuring device according to claim 1, further comprising a digital / analog conversion circuit that converts an output of the arithmetic circuit into an analog signal. According to a sixth aspect of the present invention, in the torque measuring device according to the first to fifth aspects, the temperature detecting means is a temperature detecting circuit including a thermistor and a resistor.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a torque measuring device according to the embodiment. In this drawing, reference numeral 1 denotes a detection shaft to which a torque T to be detected is applied, and magnetostrictive material portions 2 and 3 are formed on an outer peripheral portion thereof. These magnetostrictive material parts 2 and 3 are, for example, F
It is made of an alloy of e: Ni: Mo: B, and its magnetic permeability changes according to the strain caused by the acting force, and also changes according to the temperature. In the magnetostrictive material portion 2, a plurality of strip-shaped films having the same shape are formed with respect to the axis direction of the detection shaft 1.
They are arranged at the same interval on the outer periphery of the detection shaft 1 at an angle of 45 °. In addition, the magnetostrictive material portion 3 is formed by a plurality of film bodies having the same shape in the shape of a strip, which are +45 with respect to the direction orthogonal to the film body of the magnetostrictive material portion 2, that is, the axis direction of the detection axis 1.
It is arranged at the same interval on the outer circumference of the detection shaft 1 at an angle of °.

Reference numeral 4 denotes a detection coil arranged around the magnetostrictive material portion 2 with a small gap, and 5 denotes a detection coil arranged around the magnetostrictive material portion 3 with a small gap.
Reference numeral 6 denotes a temperature detection circuit arranged close to the detection coil 4, which is composed of a thermistor for temperature detection and a resistor.
Since the resistance value changes in accordance with the temperature of the detection coil 4 and the magnetostrictive material portion 2, the detection coil 4 and the magnetostrictive material portion 2
And outputs a DC voltage corresponding to the temperature. Similarly, 7 is a temperature detection circuit arranged close to the detection coil 5,
It comprises a thermistor for temperature detection and a resistor, and since the resistance value changes in accordance with the temperature of the detection coil 5 and the magnetostrictive material 3, a DC voltage corresponding to the temperature of the detection coil 5 and the magnetostrictive material portion 3 is output. I do. 8 is a temperature detection circuit 6, 7
This is a constant voltage generator that supplies a constant DC voltage.

11 to 14 are amplifiers, 15 and 16 are resistors,
17 is an AC signal generator. The above-described detection coil 4,
5 and resistors 15 and 16 constitute a bridge circuit 18. An AC signal generator 17 supplies an AC signal to two input terminals of the bridge circuit 18 and an output terminal 1 of the bridge circuit 18.
The signals 8a and 18b are supplied to zero point correction circuits 21 and 22 via amplifiers 12 and 13 and AC / DC conversion circuits 19 and 20 for converting AC to DC, respectively. When a torque T is applied to the detection shaft 1, the magnetic characteristics of the magnetostrictive material portions 2 and 3 change in the opposite direction, so that the impedances of the detection coils 4 and 5 change in the opposite directions. Therefore, by taking the difference between the output terminals 18a and 18b of the bridge circuit 18,
The value of the torque T applied to the detection shaft 1 can be detected.

The zero point correction circuits 21 and 22 are circuits for correcting the fluctuation of the zero point of the torque detection output due to the temperature, and details thereof are shown in FIG. In this figure, 24 is a resistor 26 to
28, an operational amplifier 29, and a variable resistor 25 for offset adjustment.
The temperature signal output from (or 14) is amplified and output to the multiplier 31. 33 is a variable resistor 34 and a resistor 35 to
The amplifier circuit includes an operational amplifier 37 and an operational amplifier 38. The amplifier circuit amplifies the output voltage of the variable resistor 34 and outputs the amplified voltage to the multiplier 31. The multiplier 31 multiplies each output of the amplifier circuits 24 and 33 and outputs the result. Reference numeral 40 denotes an amplifier circuit including resistors 41 to 43 and an operational amplifier 44, which amplifies and outputs a torque signal output from the AC / DC converter circuit 19 (or 20).

In such a configuration, the output of the multiplier 31 becomes a signal proportional to the temperature signal, and the output of the amplifier circuit 40 amplifies the torque signal and outputs the amplified output to the output of the multiplier 31. Becomes a signal whose level has been shifted according to. Therefore, by appropriately adjusting the variable resistor 34, the fluctuation of the torque signal due to the temperature can be corrected.

Next, in FIG. 1, reference numerals 50 and 51 denote sensitivity correction circuits. Although the impedances of the detection coils 4 and 5 change according to the temperature change (zero point fluctuation), the amount of change in impedance when a constant torque is applied (the amount of change from no load) also changes with temperature (sensitivity fluctuation). ). FIG.
Is a graph showing a change in impedance of the detection coils 4 and 5 that changes according to temperature. As shown in this figure,
As the temperature of the detection coil 4 increases, the impedance at the rated load becomes higher (see the straight line L1). In other words, when the temperature increases, the positive impedance change of the detection unit composed of the detection coil 4 and the magnetostrictive material unit 2 increases. On the other hand, the detection coil 5 has a larger negative impedance change (see the straight line L2). The sensitivity correction circuits 50 and 51 are circuits for correcting the sensitivity fluctuation as shown by a broken line in FIG. 4, and the details thereof are shown in FIG.

In FIG. 3, reference numeral 55 denotes a variable resistor 56 for offset adjustment, resistors 57 to 59, and an operational amplifier 60.
And amplifies the torque signal (the output of the zero point correction circuit 21 or 22). 62 is a variable resistor 63 for offset adjustment, resistors 64-66,
This is an amplification circuit including the operational amplifier 67 and amplifies a temperature signal (output of the amplifier 11 or 14). 69
Is a multiplier for multiplying the outputs of the amplifier circuits 55 and 62. 70 is a resistor 71, a variable resistor 72 and an operational amplifier 73
, And amplifies the output of the multiplier 69. Reference numeral 75 denotes an amplifier circuit including resistors 76 to 78 and an operational amplifier 79. The amplifier circuit 75 amplifies the output of the amplifier circuit 55, and performs level shifting in accordance with the output of the amplifier circuit 73 to output.

In such a configuration, the output of the multiplier 69 is a signal obtained by multiplying the amplified value of the temperature signal by a value corresponding to the torque signal. Therefore, the multiplier 69
Is a value obtained by correcting the temperature signal according to the value of the torque signal. The amplification circuit 70 amplifies the output of the multiplier 69 and outputs it to the amplification circuit 75. The amplifier circuit 75 amplifies the output of the amplifier circuit 55 that amplifies the torque signal, and outputs the amplified output after level-shifting the amplified output according to the temperature signal corrected by the torque signal. Thereby, the temperature of the sensitivity of the torque detection output can be corrected.

Next, in FIG. 1, reference numeral 81 denotes a differential amplifier, which obtains a detection signal proportional to the torque T by amplifying the difference between the outputs of the sensitivity correction circuits 50 and 51. An offset adjustment circuit 82 adjusts the offset level of the output of the differential amplifier 81. 83 is a gain control circuit that further amplifies the output of the offset adjustment circuit 82,
Output as a torque detection signal.

As described above, in the above embodiment, the change in the impedance of the detection coils 4 and 5 is converted into signals at the output terminals 18a and 18b of the bridge circuit 18, and these output terminals 18a and 18b are converted.
The signals a and b are individually subjected to zero point correction and sensitivity correction based on the temperature detection circuits 6 and 7, and then subtracted to obtain a torque detection signal corresponding to the torque T.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing the configuration of the torque detection device according to the embodiment. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this figure, reference numerals 90 and 91 denote AC / DC conversion circuits for converting AC into DC, respectively, and convert the respective outputs of the amplifiers 12 and 13 into DC and output them to an A / D (analog / digital) conversion circuit 92. . The A / D conversion circuit 92 converts the outputs of the amplifiers 11 and 14 and the outputs of the AC / DC conversion circuits 90 and 91 into digital data and outputs the digital data to the arithmetic circuit 93. The arithmetic circuit 93 uses the constants preset in the internal memory to perform the above-described zero point correction operation (see FIG. 2) and sensitivity correction operation (see FIG. 3) on the outputs of the AC / DC conversion circuits 90 and 91. ), Subtract the result (see differential amplifier 81), and output the result to D / A (digital / analog) conversion circuit 94. The D / A conversion circuit 94 includes the arithmetic circuit 9
3 is converted into an analog signal and output as a torque detection signal. As described above, in the second embodiment, the above-described first embodiment is configured by a digital circuit, and the same effects as in the first embodiment can be obtained.

[0022]

As described above, according to the present invention, each of the first and second detecting coils is provided with the temperature detecting means, and the temperature is corrected based on the output of each temperature detecting means. Therefore, even when a temperature difference occurs in the detecting unit for detecting the torque, the zero point fluctuation and the sensitivity fluctuation can be accurately corrected. Further, according to the invention described in claim 6, since the temperature is detected by the thermistor, it is possible to perform the correction with higher accuracy than before.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating zero-point correction circuits 21 and 22 according to the first embodiment;
FIG. 3 is a circuit diagram showing the configuration of FIG.

FIG. 3 is a diagram illustrating sensitivity correction circuits 50 and 51 according to the first embodiment.
FIG. 3 is a circuit diagram showing the configuration of FIG.

FIG. 4 is a graph showing impedance change characteristics of the detection coils 4 and 5 with respect to temperature in the embodiment.

FIG. 5 is a block diagram showing a configuration of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Detection shaft 2,3 ... Magnetostrictive material part 4,5 ... Detection coil 6,7 ... Temperature detection circuit 17 ... AC signal generator 18 ... Bridge circuit 18a, 18b ... Output terminal 21,22 ... Zero point correction circuit 50,51 … Sensitivity correction circuit 81… Differential amplifier

Claims (6)

[Claims] A first and a second magnetostrictive material formed on an outer periphery of a detection shaft to which a torque to be detected is applied; and a first and a second magnetostrictive material provided adjacent to the first and the second magnetostrictive material, respectively. First and second detection coils, a detection circuit for detecting a change in impedance of the first and second detection coils, and first and second detection coils arranged near the first and second detection coils.
A torque measuring device comprising: a second temperature detecting unit; and a correction circuit that corrects an output of the detecting circuit based on outputs of the first and second temperature detecting units. 2. A first and a second magnetostrictive material portion formed on the outer periphery of a detection shaft to which a torque to be detected is applied, and provided near the first and second magnetostrictive material portions, respectively. A bridge circuit including first and second detection coils, the first and second detection coils, a resistor connected in series to the first detection coil, and a resistor connected in series to the second detection coil; An AC source for applying an AC signal to an input end of the bridge circuit; a first AC source disposed near the first and second detection coils;
Second temperature detecting means, first correcting means for correcting a signal at a first output point of the bridge circuit based on an output of the first temperature detecting means, and an output of the second temperature detecting means And a difference signal output means for outputting a difference signal between the outputs of the first and second correction means. A torque measuring device, characterized in that: 3. The first correction means includes: a zero point correction means for correcting a zero point of a torque detection output based on an output of the first temperature detection means; and a first correction means based on an output of the first temperature detection means. A sensitivity correction unit configured to correct a sensitivity variation of the torque detection output, wherein the second correction unit corrects a zero point of the torque detection output based on an output of the second temperature detection unit; 3. The torque measuring device according to claim 2, further comprising a sensitivity correction unit configured to correct a sensitivity variation of the torque detection output based on an output of the second temperature detection unit. 4. A first and second magnetostrictive material portion formed on an outer periphery of a detection shaft to which a torque to be detected is applied, and provided near the first and second magnetostrictive material portions, respectively. A bridge circuit including first and second detection coils, the first and second detection coils, a resistor connected in series to the first detection coil, and a resistor connected in series to the second detection coil; An AC source for applying an AC signal to an input terminal of the bridge circuit; first and second AC / DC converters for converting signals at first and second output terminals of the bridge circuit into DC signals; First and second detection coils arranged near the first and second detection coils
Second temperature detecting means; analog / digital converting means for converting the outputs of the first and second AC / DC converting means and the outputs of the first and second temperature detecting means into digital data, respectively; The digital data based on the outputs of the first and second AC / DC converters are corrected by digital data based on the outputs of the first and second temperature detectors to perform zero point correction and sensitivity correction of the torque detection output. And a calculation circuit for calculating a difference between the corrected data, and a torque measurement device. 5. The torque measuring device according to claim 4, further comprising a digital / analog conversion circuit for converting an output of said arithmetic circuit into an analog signal. 6. The torque measuring device according to claim 1, wherein said temperature detecting means is a temperature detecting circuit comprising a thermistor and a resistor.