JPH0678952B2 - Torque detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a torque detector for detecting a torsion torque of a shaft to be measured by utilizing a so-called inverse Wiedmann effect.

<< Prior Art and its Problems >> In this type of torque detector disclosed in Japanese Patent Laid-Open No. 53-77572, when the axis to be measured is magnetized by the exciting coil, the magnetization waveform thereof is distorted. Therefore, the detection signal extracted from the detection coil contains the distortion, and it becomes necessary to remove the distortion by the filter.

However, if a detection signal having a frequency other than the frequency of the alternating current supplied to the exciting coil is removed by a filter, the relationship between the torsion torque applied to the shaft to be measured and the detection signal at the detection coil becomes non-linear. .

Therefore, there is a problem that a linearization circuit is required to make the linearization, and the detector becomes complicated.

<Object of the Invention> The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a torque detector of this type that does not require a linearization circuit.

<Structure of the Invention> In order to achieve the above object, the present invention is for exciting a measured shaft wound around an exciting core whose magnetic pole surface faces the circumferential surface of the measured shaft along the axial direction of the measured shaft. Of the exciting coil and the exciting core, and the magnetic pole surface is wound around the detection core facing the peripheral surface of the shaft to be measured to generate an electromotive force according to the torsion torque of the shaft to be measured. A detection coil, an alternating current power supply for energizing the exciting coil, and a bias alternating current power supply for generating a bias alternating current superimposed on the alternating current.

<< Description of Embodiments >> Preferred embodiments of a torque detector according to the present invention will be described below with reference to the drawings.

In FIG. 1, the torque detector 1 has a substantially U-shaped exciting core 3 and a substantially U-shaped detecting core 5 which is orthogonal to the exciting core 3. Excitation coil 7
And the detection coil 9 is wound.

Then, the exciting coil 7 is applied to the exciting coil 7 by the exciting oscillator 11.
An exciting alternating current (frequency ₁ ) for exciting is excited, and a bias exciting alternating current (frequency ₂ ) is applied by the bias exciting oscillator 13 while being superposed on the exciting alternating current.

The detection signal of the detection coil 9 is the bias signal filter 15
Is input to the amplifier 17 via the, and the output of the amplifier 17 is input to a torque value calculation circuit (not shown) as a voltage proportional to the torque value.

When the bias exciting alternating current is superposed, the bias signal filter 15 has a non-linear excitation characteristic of the shaft to be measured 19 as shown in FIG. It is provided for the purpose of removing the distorted wave of the bias excitation alternating current from the detection signal of 9.

Therefore, when the distorted wave of the bias excitation alternating current can be ignored in terms of torque detection accuracy, or when the magnetization characteristic of the measured shaft 19 has the characteristic shown in a of FIG. 2, the bias signal filter 15 is not necessary. The torque detector 1 can be simplified.

The exciting core 3 extends along the axial direction of the measured shaft 19 and its magnetic pole surface faces the circumferential surface of the measured shaft 19, while the detection core 5 extends along the circumferential direction of the measured shaft 19 and the measured core 5. It faces the peripheral surface of the shaft 19.

At least the peripheral surface of the measured shaft 19 is formed of a ferromagnetic material, and when the exciting core 3 is excited, the exciting core 3 and the measured shaft 19 form a magnetic circuit.

With the above configuration, when a torsion torque is applied to the shaft to be measured 19 while the exciting core 3 is excited, so-called reverse Wiedmann
Due to the effect, a magnetic flux change occurs along the circumferential direction of the measured shaft 19, and the magnetic flux change causes an induced electromotive force in the detection coil 9.

The induced electromotive force is proportional to the torsional torque applied to the shaft to be measured 19, and therefore the torsional torque can be measured by detecting the induced electromotive force.

Here, the magnetization characteristics of the shaft to be measured 19 are shown in FIG. 2, and as can be understood from the drawing, the exciting alternating current and the bias exciting alternating current are superposed on the exciting coil 7 and are energized. Therefore, the hysteresis characteristic of the measured shaft 19 is corrected in the horizontal portion (ab portion in FIG. 2) and magnetized with the characteristic indicated by the alternate long and short dash line in the figure.

As a result, the waveform showing the strength of magnetization of the measured shaft 19 becomes a waveform close to a sine wave with little distortion.

The detection signal generated in the detection coil 9 is proportional to the change in the magnetization intensity of the shaft to be measured 19 (flux density change; dΦ / dt) and the torsion torque (T), and its phase is the excitation oscillator. It is offset by 90 degrees with respect to the alternating alternating current supplied from 11 (see Fig. 2).

As described above, in this embodiment, the exciting coil 11 is connected to the exciting oscillator 11.
While energizing the excitation alternating current from, the bias excitation alternating current is supplied from the bias excitation oscillator 13 by superimposing it on the excitation alternating current, so the magnetization characteristic of the measured shaft 19 is corrected by the superimposed bias excitation alternating current, A detection signal having a waveform close to a sine wave is generated in the detection coil 9.

Therefore, the torsional torque applied to the shaft to be measured 19 and the detection signal obtained by the detection coil 9 are in a proportional relationship, and thus a circuit for linearizing the detection signal as in the conventional art is unnecessary,
The detector 1 can be simplified.

FIG. 3 shows a second embodiment of the torque detector according to the present invention.

The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

A set of exciting coils 7a (self-inductance L ₁ ) and 7b (self-inductance L ₂ ) are wound around the exciting core 3, and the exciting coils 7a and 7b are connected in series.

A capacitor 21 (capacitance c) is connected in parallel with the exciting coils 7a and 7b.

Therefore, the resonance circuit of the bias exciting alternating current (frequency ₂ ) is formed by the exciting coils 7a and 7b and the capacitor 21, and therefore even if the driving power is the same as the exciting alternating current (frequency ₁ ), the bias exciting alternating current is generated. The bias excitation by is relatively strong.

That is, the magnetization characteristic (hysteresis characteristic) of the measured shaft 19
In order to reduce the distortion caused by, the strength and frequency of the bias excitation alternating current must be made relatively larger than the excitation alternating current.

Therefore, in this embodiment, by forming a parallel resonance circuit with the exciting coils 7a, 7b and the capacitor 21 as described above, the strength and frequency of the bias exciting alternating current are made relatively large with respect to the exciting alternating current. .

As described above, in the present embodiment, a parallel resonance circuit is formed by the exciting coils 7a and 7b and the capacitor 21, and the strength and frequency of the bias exciting alternating current are thereby made relatively larger than the exciting alternating current. Even if the driving power is the same as the current, there is a special effect that the excitation by the bias excitation alternating current becomes relatively strong.

<< Effects of the Invention >> As is apparent from the above description, the torque detector according to the present invention superimposes the bias alternating current on the normal alternating current supplied to the exciting coil that excites the measured shaft. The detected detection signal has a waveform with almost no distortion and is close to a sine wave.

For this reason, the torsional torque applied to the shaft to be measured and the detection signal are in a proportional relationship, and thus the conventional linearization circuit becomes unnecessary.

As a result, the structure of the torque detector can be simplified and the cost thereof can be reduced.

[Brief description of drawings]

1 is an overall schematic view of a torque detector according to the present invention, FIG.
FIG. 3 is a characteristic diagram showing the magnetization characteristic of the shaft to be measured, the waveform of the detection signal of the detection coil, etc., and FIG. 3 is an overall schematic diagram showing another embodiment of the torque detector according to the present invention. 1 ... Torque detector 3 ... Excitation core 5 ... Detection core 7,7a, 7b ... Excitation coil 9 ... Detection coil 11 ... Excitation oscillator 13 ... Bias excitation oscillator 15 ... Bias signal filter 17 ... Amplifier 19 ... Measured axis 21 ... Capacitor

Claims (1)

[Claims] 1. An exciting coil for exciting a measured shaft, the magnetic pole surface of which is wound around an exciting core facing the circumferential surface of the measured shaft along the axial direction of the measured shaft, and an interlinking with the exciting core. The magnetic pole surface is wound around the detection core facing the circumferential surface of the shaft to be measured, and a detection coil that generates an electromotive force according to the torsion torque of the shaft to be measured is energized to the exciting coil. A torque detector, comprising: an alternating current power source for performing; and a bias alternating current power source for generating a bias alternating current superimposed on the alternating current.