JPH05113375A - Magnetostriction type torque detection device - Google Patents

Abstract

PURPOSE:To enable a torque to be detected accurately even if the temperature of a coil changes. CONSTITUTION:The amount of inductance change of coils is 9a and 9b is obtained from the coils 9a and 9b which allow a line of force using a magnetic anisotropy part which is provided on a surface of an axis to be measured as one part of a magnetic path to be generated by conduction and a coil output when AC is conducted in both of the coils 9a and 9b and a coil output when DC is conducted. Detection circuits 40 and 50 which detect a torque which is applied to the axis to be measured based on the amount of inductance change are also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque detecting device for detecting torque by utilizing a magnetostrictive phenomenon.

[0002]

2. Description of the Related Art As a conventional magnetostrictive torque detecting device,
For example, there is one as shown in FIG. 11 and FIG. 12 (similarly known examples include JP-A 1-213533).

A torque pickup unit 101 of the torque detection device shown in FIG. 11 has a shaft 103 to be measured, at least the surface of which is made of a magnetic material. The shaft 103 to be measured has a surface 103 to be measured. The concave portions 105a and 105b and the convex portion 107 that form a predetermined angle with respect to the axial direction of the
a, 107b are formed, and these concave portions 105a, 1a are formed.
05b and the convex portions 107a and 107b have a shape magnetic anisotropy.

In addition to the shaft 103 to be measured, the torque pickup portion 101 has one concave portion 105a and a convex portion 107a formed on the shaft 103 to be measured, and the other concave portion 105b and a convex portion 107b. It has a pair of coils 109a and 109b arranged opposite to each other, and a cylindrical yoke 113 made of a high magnetic permeability material is provided outside the coils 109a and 109b with a gap 111 between the coil 103a and 109b to be measured. It has a structure provided.

The torque pickup unit 1 having such a structure
To retrieve the value detected by 01, as shown in FIG. 12, the coils 109a and 109b and the resistor 115,
117 is combined to form a bridge circuit, a balancing variable resistor 119 is provided in this bridge circuit, and the excitation oscillator 1 is provided between the connection points A and C of the bridge circuit.
21 is connected to align the excitation directions of both coils 109a and 109b in the same direction, and the differential amplifier 1 is provided between the connection points B and D.
23 is connected, and its output 125 is connected to a detector 127 which is synchronized (synchronized by the excitation oscillator 121) with B,
After half-wave rectifying the differential output of D, the smoothing device 129 converts it into a direct current, and the output terminals 131 and 133 can extract the detection output.

Next, the operation when the torque pickup unit 101 shown in FIG. 11 is connected to the electric circuit shown in FIG. 12 will be described.

First, in operation, the excitation oscillator 12
By 1, the alternating current of constant amplitude (V) and frequency (f) is applied to the coils 109a and 109b. By this energization,
Measured shaft 103 → gap 111 → yoke 113 → gap 11
1 → The magnetic force line having the magnetic path of the shaft 103 to be measured is the coil 10
It occurs so as to surround 9a and 109b.

Now, considering the magnetic path on the shaft to be measured 103, the magnetic field lines concentrate near the surface as the frequency (f) of the alternating current that flows becomes higher due to the skin effect. Is along the longitudinal direction of the convex portion. Therefore, the concave portions 105a, 1
05b and the convex portions 107a and 107b exhibit the effect of shape magnetic anisotropy.

The concave portions 105a and 105b and the convex portion 10
The angles of the 7a and 107b with respect to the axial direction are generally the opposite directions of the concave portion 105a and the convex portion 107a on one side and the concave portion 105b and the convex portion 107b on the other side, and the same angle, Desirable shaft 103 to be measured
Direction of principal stress when torque is applied to
That is, the angle direction is 45 ° and the angle direction is 45 ° to the left.
The reason for this is that the lines of magnetic force mainly flow in the principal stress direction, and the convex portions 107a and 107b are the outermost surface portions of the shaft to be measured 103, so that the strain is the largest, and the change in magnetic permeability of the magnetic body due to this strain is This is because it can be extracted most effectively.

When torque is applied to the shaft 103 to be measured in the T direction shown in FIG.
Since 7a is formed in the right 45 ° direction, the maximum tensile stress + δ acts, and conversely, the other convex portion 107b is left 4
Since it is formed at 5 °, the maximum compressive stress −δ acts.

Here, if the shaft 103 to be measured has a positive magnetostrictive effect, the magnetic permeability of the one convex portion 107a increases as compared with that when the torque is zero, and conversely, the other convex portion 107a. 107b
The magnetic permeability of is smaller than that when the torque is zero.

Therefore, since the inductance of one coil 109a increases and the inductance of the other coil 109b decreases, the bridge circuit in FIG. 12 loses balance and an output corresponding to the torque is generated between the output terminals 131 and 133. ..

When the torque is applied in the opposite direction, the one coil 109
Since the inductance of “a” decreases and the inductance of the other coil 109b increases, the bridge circuit in FIG. 12 loses balance and an output corresponding to the torque is generated between the output terminals 131 and 133.

More specifically, the coil 109
The inductances of a and 109b are L ₁ [H],
L ₂ [H] and the direct current resistance of these coils is R
₁ Ω and R ₂ Ω, the resistance values of the bridge resistors 115 and 117 are R, and the voltage of the excitation oscillator 121 is V [V].
When the frequency is f [Hz], the bridge circuit AB-
Current flowing through C, A-D-C i ₁ [A], i ₂ [A]
Are respectively expressed by the following equations.

I ₁ = V / [(R + R ₁ + 2πfL ₁ cos θ ₁ ) ² + (2πfL ₁ sin θ ₁ ) ² ] ^1/2 (1) i ₂ = V / [(R + R ₂ + 2πfL ₂ cos θ ₂ ) ² + (2πfL ₂ sin θ ₂ ) ² ] ^1/2 (2) where θ ₁ and θ ₂ are the real axes of their inductances when the impedance Z ₁ of the coils 109a and 109b is expressed on a complex number. Is the angle to make.

At this time, the potentials V ₁ and V _{2 at the} points B and D are V _1
1 = i ₁ · R and V ₂ = i ₂ · R, and the difference between these two potentials is obtained by the differential amplifier 123. Further, a smoothing device 129 is passed through a synchronous detector 127 that determines the forward and reverse directions of the torque.
An output more proportional to torque is obtained. In addition, the synchronous detector 1
In No. 27, the drift of the output caused by the temperature change of the torque pickup unit 101 is different from the output phase proportional to the torque to be measured by the output phase of the drift caused by the temperature change, and the detection timing is determined by the torque. It also has the function of making it smaller by synchronizing with the output phase proportional to.

[0017]

In the conventional magnetostrictive torque detector, the output phase caused by the temperature change of the torque pickup unit is proportional to the torque to be measured by the output phase of the drift caused by the temperature change. It is designed to be smaller by synchronizing the detection timing with the output phase proportional to the torque by utilizing the difference of about 90 ° from the above. Therefore, when the phase of the output drift due to the temperature change slightly changes, the value of this drift However, there is a problem in that the torque detection accuracy is deteriorated.

Therefore, an object of the present invention is to provide a magnetostrictive torque detecting device capable of accurately detecting the torque even if the temperature of the coil changes.

[0019]

In order to solve the above problems, the present invention firstly provides a shaft to be measured and a surface of the shaft to be measured so as to form a predetermined angle with respect to the axial direction. A magnetic anisotropy part, a coil for generating magnetic lines of force by energizing the magnetic anisotropy part as a part of a magnetic path, and a coil output when an alternating current is applied to the coil and a direct current when a direct current is applied. The gist of the present invention is to have a detection circuit that obtains a change in inductance of the coil from the coil output and detects the torque applied to the shaft to be measured based on the change in inductance.

Secondly, the gist of the first configuration is that the detection circuit is configured to energize the coil to switch between alternating current and direct current in a time division manner.

Third, the shaft to be measured, the magnetic anisotropy portion provided on the surface of the shaft to be measured so as to form a predetermined angle with respect to the axial direction, and the magnetic anisotropy due to alternating current application. A detection coil for generating a magnetic force line whose part is a part of a magnetic path, a compensation coil installed near the detection coil for energizing direct current, and a coil output of the detection coil and a coil output of the compensation coil. The gist of the present invention is to have a detection circuit that obtains a change in inductance of the detection coil and detects the torque applied to the shaft to be measured based on the change in inductance.

[0022]

In the above structure, firstly, the DC resistance of the coil, which is the main factor of the output drift due to the temperature change, is obtained from the coil output when DC is applied to the coil, and the torque change is calculated from the inductance change obtained by subtracting this term. Is required. Thereby, the torque is accurately detected.

Secondly, more accurate torque detection can be performed by switching the direct current and alternating current to the coil in a time division manner.

Third, the detection coil is energized with an alternating current, and the compensation coil provided in the vicinity thereof is energized with a direct current to estimate the direct current resistance of the detection coil from the coil output. Then, the torque is obtained from the inductance change amount obtained by subtracting the DC resistance component from the coil output of the detection coil. Thereby, accurate torque detection is performed without switching the alternating current and direct current to the detection coil by time division or the like and energizing.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 6 are views showing a first embodiment of the present invention.

First, the structure of the magnetostrictive torque detecting device will be described with reference to FIGS.

The torque pickup unit 1 shown in FIG. 1 has a structure substantially similar to that shown in FIG. 11, and the surface of the shaft 3 to be measured has a concave portion that makes a predetermined angle with the axial direction thereof. 5a, 5b and convex portions 7a, 7b are formed,
A magnetic anisotropic portion is formed by the concave portions 5a and 5b and the convex portions 7a and 7b. 9a and 9b are a pair of coils, 13 is a yoke, and 11 is a gap between the shaft 3 to be measured and the yoke 13. As shown in FIG. 2, the coils 9a, 9b
And the resistors 15 and 17 form a bridge circuit. The circuit devices other than the coils 9a and 9b and the resistors 15 and 17 can be configured by an 8-, 16-, or 32-bit microcomputer, but in order to facilitate understanding, the circuits are configured by individual electric devices below. Explain in shape.

Reference numeral 21 is a sine wave oscillator, the oscillation frequency of which is determined by a main clock 41 which controls the time of the entire circuit (for example, 10 kHz). 42 is a constant voltage generator, 43 is an alternating-current switching device, 44 is a frequency divider for switching the switching device 43, and 45 is a frequency divider for obtaining a signal for controlling the data output of the bridge output. Four
6 is a peak hold device for detecting the inductance Z ₀₁ when the 9b side coil is energized with alternating current, 47 is a peak hold device for detecting the resistance value (R ₀₁ + R ₁ ) when the 9b side coil is energized with direct current, and 48 is 9b A phase detector for measuring the phase difference θ ₀₁ between the current phase on the coil side and the drive voltage phase, 49 is the above Z
_This is a calculator for calculating the inductance L _{1 of the} coil 9b from three values of ₀₁ , (R ₀₁ + R ₁ ), θ ₀₁ . Thus, the peak hold devices 46 and 47, the phase detector 48, and the calculator 49 constitute the inductance detection circuit 40 of the coil 9b. 50 is an inductance detection circuit for the coil 9a, and 56, 57, 58, 59 are
These are a peak hold device for detecting the impedance Z ₀₂ , a peak hold device for detecting the resistance value (R ₀₂ + R ₂ ), a phase detector, and a computing device corresponding to each of the above devices. Reference numeral 23 is a differential amplifier that detects a difference in inductance between the coils 9 a and 9 b, and 31 is an output terminal of the differential amplifier 23.

Next, the operation of the magnetostrictive torque detecting device configured as described above will be described with reference to FIGS. 3 and 4 are diagrams for explaining the principle, and FIGS. 5 and 6 show signal waveforms of respective parts in FIG.

When torque is applied to the shaft 3 to be measured, convex portions 7a, 7a formed on the surface of the shaft 3 in the direction of 45 ° with respect to the axial direction.
Tensile stress and compressive stress act on b, respectively. Then, due to the inverse magnetostriction effect, the magnetic permeability of the convex portion on the tensile side becomes high, the impedance of the coil through which the magnetic flux passes through this portion increases, and the opposite side becomes the opposite on the compression side. The voltage applied from the high voltage side of the coils 9a and 9b is connected to the ground from the low voltage side of the coils 9a and 9b through the resistors 15 and 17, respectively, and the terminal voltages Va and Vb of the resistors 15 and 17 are
It is proportional to the currents ia and ib passing through a and 9b. The detection circuit will process these voltages Va and Vb. Since the present embodiment is characterized in that only the pure inductance of the coil is taken out, this principle will be described first. FIG. 3 is a view in which the bridge portion on the coil 9b side is taken out. The coil impedance Z ₁ can be considered by being divided into an inductance component L ₁ and a DC resistance component R ₁ of the coil 9b itself. Further, considering the system on the side of the coil 9b including the resistance value R ₀₁ of the resistor 17, it can be shown as on the right side of FIG. 3 on the complex plane. Based on this principle, alternating current is applied to the bridge to obtain impedance and phase difference (Z ₀₁ , θ
₀₁ ), and then a direct current is applied to measure the resistance value (R ₀₁ + R ₁ ), and the inductance L ₁ is obtained from these two values. This action will be explained with a concrete circuit.

First, at a clock of 41, a fixed period (frequency f
(Hz) signal is output (FIG. 5A). Based on this, the sine wave oscillator 21 oscillates a sine wave (a triangular wave is possible at the expense of accuracy). This sinusoidal alternating current is supplied to the coils 9a and 9b through the AC / DC switch 43. Here, the description will proceed on the side of the coil 9b. On the other hand, a DC voltage having a constant value is supplied from the constant voltage source 42 to the coil 9b through the switch 43. The timing of this switching is fixed to 1/2 to 1/100 of the reference frequency of the clock 41 by the frequency divider 44 (FIG. 5 (c)). 1/2 when high responsiveness is required
Approximately 1/3.

FIG. 5 (d) shows the voltage at the outlet of the switching device 43 when the coil 9b is energized by alternating current and direct current in this manner. When this is applied to the bridge, the voltage on the high voltage side of the resistor 17 is as shown in FIG. At this time, in order to obtain a stable voltage during AC energization, the high-voltage side voltage of the resistor 17 (see FIG. 5C) after a certain time (about 1/2 to 2/3 of the switching cycle) from the AC / DC switching timing (FIG. 5C). 5 (e)) is held by the peak hold device. At this time, the signal during AC energization is held by the peak hold unit 46, and the signal during DC energization is held by the peak hold unit 47 by the frequency divider 45 as shown in FIGS. 6A and 6C, respectively. A sample command signal is issued. The peak hold device first resets the output when it receives the sample command signal, always shows the maximum value of the inputs while receiving the signal, and maintains the value at that time when the command signal disappears. With the above functions, the peak hold device 46 stores the voltage determined by the absolute value of the impedance | Z ₀₁ | during AC energization (FIG. 6B).

On the other hand, the peak hold device 47 has a resistor 1
The voltage determined by the sum of the resistance value of 7 and the DC resistance of the coil is stored (FIG. 6D). Further, the phase of the current when the alternating current is applied is obtained by the phase detector 48.

The calculator 49 performs the following calculation based on these values to obtain the inductance-equivalent voltage V _L1 of the coil 9b.

V _L1 = [| Z ₀₁ | ² + (R ₀₁ + R ₁ ) ² −2 · | Z ₀₁ | · cos θ ₀₁ · (R ₀₁ + R ₁ )] ^1/2 (3) Also on the coil 9 a side In the same manner as above, the inductance equivalent voltage V _L2 of the coil 9a is obtained.

V _L2 = [| Z ₀₂ | ² + (R ₀₂ + R ₂ ) ² −2 · | Z ₀₂ | · cos θ ₀₂ · (R ₀₂ + R ₂ )] ^1/2 (4) In this way The obtained inductance-equivalent voltages V _L1 and V _L2 of both coils 9a and 9b are input to the differential amplifier 23, and the difference therebetween is obtained. Since this value is proportional to the torque, the torque applied to the shaft 3 to be measured can be obtained based on the difference between the voltages V _L1 and V _L2 .

Next, FIG. 7 and FIG. 8 show the second embodiment of the present invention.
An example is shown. In this embodiment, two coils 9a and 9b are used.
The differential amplifier 223 for obtaining the inductance difference is placed immediately after the bridge circuit, and the coil inductance detection circuit is omitted by that much for that portion. 246 is a peak hold device for detecting impedance when AC current is applied to the coil, 247 is a peak hold device for detecting resistance value when DC current is applied to the coil, 2
Reference numeral 48 is a phase difference detector, and 249 is a calculator.

To explain the operation, FIG. 8 shows coils 9a, 9
The outputs at the output points B and D of b are represented on a complex plane. If the impedances of the coils 9a and 9b are the same, both outputs match the N point in FIG. When torque is applied to the shaft 3 to be measured, the coil corresponding to the pulling side will have ΔL ₁
The inductance increases, and the coil corresponding to the compression side decreases in inductance by ΔL ₂ . The torque detection device wants to measure the value of (ΔL ₁ + ΔL ₂ ). On the other hand, in the circuit of this embodiment, the output as shown by | δZ ₁₂ | in FIG. 8 is obtained from the differential amplifier 223. The phase of the current and the driving voltage at this time is θ ₁₂ as shown in the figure. In the same manner as in the case of FIG. 2, | δZ ₁₂ | and θ ₁₂ , δR ₁₂ are obtained from the output difference between the output terminal voltages of the coils 9a and 9b. Here &Dgr; R ₁₂ is mainly the difference in the DC resistance of the coil 9a, 9b upon applying a direct current to the bridge circuit. Here, from FIG. 8, the inductance change equivalent voltage V _L12 is represented by V _L12 = [| δZ ₁₂ | ² + δR ₁₂ ² −2 · | δZ ₁₂ | · δR ₁₂ · cos θ ₁₂ ] ^1/2 (5) Therefore, this calculation is performed by the calculator 249.
This value is an output proportional to the torque that is not affected by the change in the DC resistance component due to the change in the coil temperature. Therefore, the torque applied to the shaft 3 to be measured can be accurately obtained based on this inductance change equivalent voltage V _L12 .

9 and 10 show a third embodiment of the present invention. In this embodiment, the compensation coils 19a and 19b are installed in the immediate vicinity of the detection coils 9a and 9b, and a direct current is supplied to the compensation coils 19a and 19b, so that the DC resistance components of the detection coils 9a and 9b are removed. It is supposed to be estimated.

The compensation coils 19a and 19b may be installed outside the detection coils 9a and 9b, but inside the detection coils 9a and 9b, or both, and further, as shown in FIG.
It is also possible to wind both coils 9a and 19a on one bobbin at the same time as in (b). However, the method of FIG. 9B has a high compensation accuracy but a high cost.

The operation will be described with reference to the circuit diagram of FIG.
Unlike the previous embodiments, it is not necessary to alternately flow alternating current and direct current through the detection coils 9a and 9b, and the detection coils 9a and 9b
AC is energized to b, and DC is constantly energized to the compensation coils 19a and 19b. By doing so, δR ₁₂ described in FIG. 8 is obtained from the compensating coils 19a and 19b side. This may be slightly different from the DC resistance of the detection coils 9a and 9b, but since they are installed very close to each other, they can be sufficiently approximated in practical use. The value of the direct current flowing through the compensation coils 19a and 19b to obtain the direct current resistance is
Although it is set to the same level as the effective value of the alternating current flowing through the detection coils 9a and 9b, it may be possible to perform the compensation more accurately by making a slight difference depending on the position of the coil.

[0043]

As described above, according to the present invention,
Firstly, a magnetic anisotropy portion is formed on the surface of the shaft to be measured so as to form a predetermined angle with respect to the axial direction, and a magnetic force line is formed by energizing the magnetic anisotropy portion as part of the magnetic path A detection circuit for detecting the torque applied to the shaft to be measured based on the inductance change amount of the coil and the coil output when the AC current is applied to the coil and the coil output when the DC current is applied. Therefore, the DC resistance component of the coil, which is the main factor of the output drift due to temperature change, is obtained from the coil output when DC is applied to the coil, and the torque is obtained from the inductance change amount by subtracting this term. Even if the temperature changes, the torque can be accurately detected.

Secondly, since alternating current and direct current are switched and energized to the coil in a time division manner, more accurate torque detection can be performed in a short time.

Thirdly, an alternating current is supplied to the detection coil, a direct current is supplied to a compensation coil installed in the vicinity thereof, a DC resistance is obtained from the coil output, and a DC resistance component of the detection coil is obtained from the DC resistance. Since the inductance change amount of the detection coil is estimated and obtained, accurate torque detection can be performed without switching the alternating current and direct current to the detecting coil by time division or the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a torque pickup section in a first embodiment of a magnetostrictive torque detection device according to the present invention.

FIG. 2 is a circuit diagram of the first embodiment.

FIG. 3 is a diagram for explaining the principle of detecting the inductance component in the first embodiment.

FIG. 4 is a diagram for explaining a principle of detecting an inductance component in the first embodiment.

5 is a timing chart showing a signal waveform of each part in FIG.

FIG. 6 is a timing chart showing signal waveforms of respective parts in FIG.

FIG. 7 is a circuit diagram of a second embodiment of the present invention.

FIG. 8 is a diagram for explaining the detecting action of the inductance change amount in the second embodiment.

FIG. 9 is a diagram showing an example of installation of compensation coils in the third embodiment of the present invention.

FIG. 10 is a circuit diagram of the third embodiment.

FIG. 11 is a cross-sectional view showing a pickup section in a conventional magnetostrictive torque detection device.

FIG. 12 is a circuit diagram of a conventional example.

[Explanation of symbols]

3 Axis to be measured 5a, 5b Concave part 7a, 7b Convex part forming a magnetic anisotropic part together with the concave part 9a, 9b Coil 19a, 19b Compensating coil 21 Sine wave oscillator 40, 50 Inductance detecting circuit 42 DC constant voltage Generator 43 AC / DC switching device

Claims (3)

[Claims] 1. An axis to be measured, a magnetic anisotropy section provided on the surface of the axis to be measured so as to form a predetermined angle with respect to the axial direction, and a magnetic path between the magnetic anisotropy section by energization. And a coil for generating a magnetic field line as a part of the coil, and an inductance change amount of the coil is obtained from a coil output when an alternating current is applied to the coil and a coil output when a direct current is applied to the coil. A magnetostrictive torque detection device, comprising: a detection circuit that detects a torque applied to a measurement axis. 2. The magnetostrictive torque detection device according to claim 1, wherein the detection circuit is configured to switch and energize the coil between alternating current and direct current in a time division manner. 3. An axis to be measured, a magnetic anisotropy section provided on the surface of the axis to be measured so as to form a predetermined angle with respect to the axial direction, and the magnetic anisotropy section by energizing alternating current. A detection coil that generates a magnetic force line that is a part of a magnetic path, a compensation coil that is installed in the vicinity of the detection coil and that conducts a direct current, and a detection coil from the detection coil output and the compensation coil output. And a detection circuit for detecting the torque applied to the shaft to be measured based on the inductance change amount of the magnetostrictive torque detection device.