JP2003106913A - Torque detector - Google Patents

Abstract

(57) Abstract: A pair of detection coils (5, 6) are provided corresponding to a pair of magnetically anisotropic parts provided on the outer peripheral surface of a torque transmission shaft. When an alternating current is applied to each detection coil from the oscillator 12, each detection coil generates an alternating current according to the impedance (Z1, R1, L1: Z2, R2, L2) in a circuit including the detection coil. Each AC is connected to a variable resistor R1, R2
When the torque is not applied to the torque transmission shaft by the trimmer capacitor Ca, the same adjustment is performed, and the output of the AC differential amplifier circuit 21 becomes zero. When a torque is applied to the torque transmission shaft, the impedance changes accordingly, so that a difference in amplitude occurs between the alternating currents generated in the respective detection coils.
The magnitude of the torque applied to the torque transmission shaft can be detected. [Effect] The magnitude of the torque applied to the torque transmission shaft can be detected from the difference between the AC amplitudes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque detecting device, and more particularly to a magnetostrictive torque detecting device.

[0002]

2. Description of the Related Art Conventionally, as a magnetostrictive torque detecting device,
A pair of magnetic anisotropic portions provided on the outer peripheral surface of the torque transmission shaft,
It is known that a pair of detection coils provided corresponding to the magnetic anisotropy portion is provided, and the magnitude of the torque applied to the torque transmission shaft is detected by the pair of detection coils. (JP-A-4-299226).
Further, in this type of torque detection device, when torque is applied to the torque transmission shaft, the magnetic permeability in the magnetic anisotropic portion provided on the torque transmission shaft changes. The magnitude of the torque applied to the shaft is detected.

[0003]

The conventional torque detecting device detects the difference in the magnitude of each direct current after converting the change in magnetic permeability into the direct current of the alternating current flowing in each detecting coil. The magnitude of the torque applied to the torque transmission shaft was detected from the magnitude of the difference. Further, in this type of torque detection device, it is necessary to provide three or more magnetic anisotropy portions when temperature compensation is performed, so that there is a drawback that the entire device becomes large. The present invention provides a torque detection device having a novel configuration capable of detecting the magnitude of torque based on the difference in the amplitude of the alternating current generated in each detection coil, not the difference in the magnitude of the direct current.

[0004]

That is, according to the invention of claim 1, a pair of magnetic anisotropic portions provided on the outer peripheral surface of the torque transmission shaft, and a pair of magnetic anisotropic portions provided corresponding to the magnetic anisotropic portions. In a torque detection device that includes a detection coil and detects the magnitude of the torque applied to the torque transmission shaft by the pair of detection coils, an oscillator that applies an alternating current to each of the detection coils, and each detection coil And a connected AC differential amplifier circuit, which detects the magnitude of the torque applied to the torque transmission shaft from the difference in the amplitude of the AC generated in each of the detection coils. It is characterized by. According to a fourth aspect of the invention, in the invention of the first aspect, between at least one of the two connecting portions connecting the AC differential amplifier circuit and each detection coil to the ground. It comprises a connected varicap and a phase detector that outputs a voltage according to the phase difference between the alternating currents applied to the alternating current differential circuit, and the output of the phase detector is applied to the varicap to reduce its capacitance. By adjusting, the phase difference between the alternating currents applied to the alternating current differential circuit is controlled to be zero.

According to the first aspect of the present invention, when an alternating current is applied to each detection coil by the oscillator, each detection coil generates an alternating current according to the impedance of the circuit including the detection coil. When the torque applied to the torque transmission shaft is zero, if the alternating current generated in each detection coil is the same, the output of the alternating current differential amplifier circuit to which the alternating current is applied can be zero. On the other hand, when torque is applied to the torque transmission shaft, the impedance changes accordingly, so that an amplitude difference occurs in the alternating current generated in each detection coil. The magnitude of the torque applied to the torque transmission shaft can be detected from the difference in the amplitude of the alternating current generated in the detection coil. Further, in the invention of the above-mentioned claim 1, even if the torque is not applied to the torque transmission shaft, if the temperature changes and a phase difference occurs between the alternating currents applied to the alternating current differential circuit, it causes the alternating current. Although the output is generated in the differential amplifier circuit, according to the invention of claim 4, the phase detector outputs the voltage according to the phase difference. The voltage of this phase detector is applied to the varicap so that its capacitance is adjusted, and the capacitance of this varicap is adjusted so that the phase difference between the alternating currents applied to the alternating current differential circuit becomes zero. Controlled. Therefore, this makes it possible to maintain the torque detection accuracy with high accuracy even if the temperature changes.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the embodiments shown in the drawings. In FIG. A pair of magnetic anisotropic portions 3 and 4 are formed on the surface. The one magnetic anisotropy portion 3 is configured by forming a large number of grooves inclined in the axial direction of the torque transmission shaft 1 by 45 degrees in the circumferential direction so as to be parallel to each other.
The other magnetic anisotropy part 4 is formed by forming a large number of grooves inclined in the opposite direction to the grooves of the one magnetic anisotropy part 3 in the circumferential direction so as to be parallel to each other by 45 degrees. I am doing it. Detection coils 5 and 6 surrounding the magnetic anisotropic portions 3 and 4 are provided so as to surround the magnetic anisotropic portions 3 and 4. The detection coils 5 and 6 are provided with resin yokes 7 and 8 on the inner peripheral surface of the housing 2. It is fixed to. A board 9 is fixed to the housing 2, and the circuit shown in FIG. 2 is provided on the board 9.

In FIG. 2, one end of each of the detection coils 5 and 6 is connected via a buffer amplifier 13 to an oscillator 12 that applies an alternating current (sine wave) to each of the detection coils 5 and 6, and each detection coil is detected. The other ends of the coils 5 and 6 are grounded via variable resistors R3 and R4 connected in series, respectively. The circuit including each of the detection coils 5 and 6 has impedance, and its inductance component is L1 and L.
2, the resistance component is R1, R2, the other components are Z1,
Each is represented by Z2. The terminals on the oscillator 12 side of each of the detection coils 5 and 6 are connected to the primary side of an AC differential amplifier 22 that constitutes an AC differential amplifier circuit 21, respectively. The detection coils 5 and 6 have the oscillator 12
When an alternating current is applied to each of the detecting coils 5 and 6, the alternating current differential amplifier 22 outputs zero when the alternating currents input from the detection coils 5 and 6 are the same. When there is a difference, it is possible to output an output according to the magnitude of the difference.

The circuit including the detection coils 5 and 6 includes, for example, variations in the internal resistance and reactance of the detection coils 5 and 6, so that no torque is applied to the torque transmission shaft 1. Each detection coil 5,
Generally, the AC waveforms input from the AC differential amplifier 22 to the AC differential amplifier 22 are not the same. Therefore, in the state where no torque is applied to the torque transmission shaft 1, the amplitude of the alternating current input from the detection coils 5 and 6 to the alternating current differential amplifier 22 is adjusted to be the same. The variable resistors R3 and R4 are provided. A trimmer capacitor Ca, a varicap Cv, and a capacitor Cb are provided in order to adjust the phases of the alternating currents input to the alternating-current differential amplifier 22 from the detection coils 5 and 6 to be the same. The trimmer capacitor Ca is provided between one input end of the AC differential amplifier 22 and the ground, and the other varicap Cv and the capacitor Cb are connected in series, and the other of the AC differential amplifier 22 is connected. It is provided between the input end and the ground. In order to adjust the output of the AC differential amplifier 22 to zero when no torque is applied to the torque transmission shaft 1, the respective detection coils 5 and 6 are precisely measured with a conventionally known LCR meter. The impedance of the circuit including it should be balanced. More specifically, by adjusting the variable resistors R3 and R4, it is possible to adjust the amplitudes of the alternating currents input to the alternating current differential amplifier 22 from the detection coils 5 and 6 to be the same, and the trimmer is also provided. By adjusting the capacitor Ca, it is possible to adjust the phases of the alternating currents input from the detection coils 5 and 6 to the alternating current differential amplifier 22 to be the same. Note that either one of the variable resistors R3 and R4 may be a fixed resistor, and the varicap Cv and the capacitor Cb connected in series are necessary for temperature compensation described later, and when temperature compensation is not required. Varicap Cv
Can be omitted. Further, if necessary, a coil may be used instead of the trimmer capacitor Ca in order to adjust the AC phases to be the same.

As described above, if the impedance of the circuit including the detection coils 5 and 6 is adjusted to be equal to each other, the output of the AC differential amplifier 22 will be zero when the torque is not applied to the torque transmission shaft 1. Can be On the other hand, in this state, when torque is applied to the torque transmission shaft 1 and the torque transmission shaft 1 is twisted in one direction, the magnetic anisotropy portions 3, 4 composed of a plurality of grooves inclined in opposite directions to each other. Since the compressive force acts on one of the two and the tensile force acts on the other, the magnetic permeability increases or decreases in each portion. As a result, the impedance of the circuit including the one detection coil 5 or 6 increases and the amplitude of the alternating current increases, while the impedance of the other decreases and the amplitude of the alternating current decreases. As a result, a difference according to the magnitude of the torque occurs in the amplitude of the alternating current input from the detection coils 5 and 6 to the alternating current differential amplifier 22, and the alternating current differential amplifier 22 responds to the difference. It will produce a large output. The output of the AC differential amplifier 22 is added to the DC amplifier 23 after the DC component is cut by the coupling capacitor C1 and then detected by the diode Di and the capacitor C2, and then the difference between the standard voltage V _REF and For example, the output DC signal is output as a + detection signal. When a torque in the opposite direction is applied to the torque transmission shaft 1, the increase / decrease in the magnetic permeability is opposite to that in the case described above, so the increase / decrease in the amplitude of the alternating current is also opposite. The signal is outputted as a _negative detection signal with respect to the standard voltage _VREF . As described above, the AC differential amplifier circuit 22 can output an output according to the magnitude and direction of the torque applied to the torque transmission shaft 1.

By the way, as described above, the trimmer condenser
AC input to the AC differential amplifier 22 by the sensor Ca
Can be adjusted to have the same phase. Adjustment
The latter phase is the same if the temperature at the time of adjustment is maintained.
Can be maintained in a state, but the ambient temperature changes
And it causes the phase to shift. AC differential above
If the phase of the alternating current input to the amplifier 22 shifts, the torque
Even if no torque is applied to the transmission shaft 1, the AC differential
Output is generated at the pump 22 due to the phase shift.
Therefore, the accuracy of torque detection is reduced. like this
In order to solve these problems, as shown in Fig. 2, temperature compensation
A compensation circuit is provided. This temperature compensating circuit is well known in the art.
The phase detector 32 is provided with the phase detector 32.
The phase difference Δφ between alternating currents applied to the alternating current differential amplifier 22
Detected, and as shown in FIG.
To be able to output the voltage according to the direction of deviation
It has become. At this time, the phase detector 32 is input.
Sinusoids have the same amplitude, the same frequency, and only the phase
If they are different, the output will be as shown in the formula below.
The DC component and the double sine wave are output. {Asin (ωt + θ₁)} × {Asin (ωt +
θ_Two)} = K₁sin (2ωt + θ) + K_Two In this equation, the DC component K_TwoIs the phase of the phase detector 32
It can be used as a detection output. Above phase detector
The output of 32 is amplified by DC amplifier 33,
Input to the filter LPF, where the frequency doubled
After suppressing the component to make only the DC component,
Will be injected into the Cv. This Varicap C
v has the characteristics shown in FIG. 4, and the applied voltage is
The higher the capacity, the smaller the capacity.

Therefore, for example, a of the phase detector 32
The signal on the detection coil 5 side input to the port is the other b
When the phase is advanced from the signal on the detection coil 6 side input to the port, a + voltage is generated from the c port of the phase detector 32, as shown in FIG. This + voltage is amplified by the DC amplifier 33 and injected into the varicap Cv. This voltage is the AC differential amplifier 22.
The larger the phase difference Δφ between the alternating currents applied to, the higher the potential in the + direction, and the smaller the capacitance of the varicap Cv. If the capacitance of the varicap Cv becomes smaller, the phase on the b port side of the phase detector 32 advances, so that the phase on the a port side and the phase on the b port side are kept the same. Be done. On the contrary, when the signal on the detection coil 5 side input to the a port of the phase detector 32 is delayed in phase from the signal on the detection coil 6 side input to the other b port, As shown in FIG. 3, a negative voltage is generated from the c port of the phase detector 32. As a result, the applied voltage applied to the varicap Cv decreases, and the capacitance of the varicap Cv increases. When the capacitance of the varicap Cv increases, the phase on the a port side of the phase detector 32 advances, so that the phase on the a port side and the phase on the b port side are kept the same. . As described above, the temperature compensation circuit 31 includes the phase detector 32 and the varicap C.
By combining with v, the phase error due to the ambient temperature change of the detection coils 5 and 6 is automatically corrected, and the AC differential amplifier 2
2 can be prevented from occurring.

[0012]

As described above, according to the present invention, the effect that the magnitude of the torque applied to the torque transmission shaft can be detected from the difference in the amplitude of the alternating current generated in each detection coil is obtained. To be

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a torque detection circuit of the present invention.

3 is a characteristic diagram of the phase detector 32 shown in FIG.

4 is a characteristic diagram of the varicap Cv shown in FIG.

[Explanation of symbols]

1 Torque transmission shaft 3, 4 Magnetic anisotropy part 5, 6 Detection coil 12 Oscillator 21 AC differential amplifier 22 AC differential amplifier 32 Phase Detector Ca Trimmer Capacitor R3, R4 variable resistance

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Chiaki Gohara             3-65 Midorigaoka, Toyota City, Aichi Prefecture             Business (72) Inventor Masayuki Hamasaki             3-65 Midorigaoka, Toyota City, Aichi Prefecture             Business

Claims (4)

[Claims] 1. A pair of magnetic anisotropy portions provided on the outer peripheral surface of the torque transmission shaft, and a pair of detection coils provided corresponding to the magnetic anisotropy portions. In a torque detection device configured to detect the magnitude of torque applied to the torque transmission shaft, an oscillator that applies an alternating current to each of the detection coils, and an alternating current differential amplifier circuit connected to each detection coil, The AC differential amplifier circuit detects the magnitude of the torque applied to the torque transmission shaft from the difference in the amplitude of the AC generated in each of the detection coils. 2. A variable resistor is connected in series to at least one of the detection coils, and when no torque is applied to the torque transmission shaft by the variable resistor,
The torque detection device according to claim 1, wherein the amplitude of the alternating current generated in each of the detection coils is adjusted to have the same magnitude. 3. A trimmer capacitor is provided between at least one of the two connecting portions connecting the AC differential amplifier circuit and each detection coil and the ground, and the trimmer capacitor is provided. The phase difference of the alternating current generated in each of the detection coils is adjusted to zero when no torque is applied to the torque transmission shaft. Torque detector. 4. A varicap connected between at least one of the two connecting portions connecting the AC differential amplifier circuit and each detection coil and the ground, and the AC differential circuit. And a phase detector that outputs a voltage according to the phase difference between the alternating current applied to the AC differential circuit by applying the output of the phase detector to the varicap to adjust its capacity. The torque detection device according to any one of claims 1 to 3, wherein control is performed so that the phase difference between the applied alternating currents becomes zero.