JPS6315129A - Torque detector - Google Patents

Abstract

PURPOSE:To allow distortion torque to be proportional to a detection signal by converting the detection signal to a sinusoidal wave free from strain, by superposing a bias AC to the usual AC supplied to the coil wound around an exciting core arranged along the axial direction of a shaft to be measured. CONSTITUTION:The exciting core 3 opposed to the peripheral surface of a shaft 19 to be measured is arranged along the axial direction of the shaft 19 and a C-shaped detection core 5 is provided so as to cross the core 3 at a right angle. An exciting AC is supplied to the exciting coil 7 wound around the core 3 by an exciting oscillator 11 and a bias exciting AC is superposed to the exciting AC to be supplied by a bias exciting oscillator 13. The detection signal of the detection coil 9 wound around the core 5 is inputted to an amplifier 17 through a bias signal filter 15 and voltage proportional to torque value is calculated from the output of the amplifier 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a torque detector that detects torsional torque of a shaft to be measured by utilizing the so-called inverse Wiedma curve effect.

(Prior art and its problems) In this type of torque detector disclosed in Japanese Patent Application Laid-Open No. 53-77572, etc., when a shaft to be measured is magnetized by an excitation coil, distortion occurs in the magnetization waveform. Therefore, the detection signal taken out from the detection coil contains that distortion,
It becomes necessary to remove the distortion using a filter.

However, if a detection signal with a frequency other than the frequency of the alternating current applied to the excitation coil is removed by a filter, the relationship between the torsional torque applied to the measured shaft and the detection signal at the detection coil will not be linear. .

Therefore, in order to achieve linearization, a linearization circuit is required, resulting in a problem that the detector becomes complicated.

(Objective of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and its object 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 provides a device for excitation of a shaft to be measured whose magnetic pole surface is wound around an excitation core facing the peripheral surface of the shaft to be measured along the axial direction of the shaft to be measured. The excitation coil is wound around a detection core which is interlinked with the excitation core and whose magnetic pole surface faces the circumferential surface of the shaft to be measured, thereby generating an electromotive force according to the torsional torque of the shaft to be measured. An alternating current power supply that energizes the excitation coil; and a bias alternating current power supply that generates a bias alternating current that is superimposed on the alternating current.

(Description of Embodiments) Hereinafter, preferred embodiments of the torque detector according to the present invention will be described based on the drawings.

In FIG. 1, the torque detector 1 has a substantially square-shaped excitation core 3 and a substantially square-shaped detection core 5 that is orthogonal to the excitation core 3. An excitation coil 7 and a detection coil 9 are wound.

The excitation coil 7 is supplied with an excitation alternating current (frequency f+) that excites the excitation core 3 by an excitation oscillator 11, and a bias excitation alternating current (frequency fz) is superimposed on the excitation alternating current to be applied to the bias excitation oscillator 11. 13
is energized by.

Also, the detection signal of the detection coil 9 is transmitted to the bias signal filter 1.
5 to the amplifier 17, and this amplifier 1
The output of 7 is input to a torque value calculation circuit (not shown) as a voltage proportional to the torque value.

Note that when the bias excitation alternating current is superimposed on the bias signal filter 15, the excitation characteristic of the measured shaft 19 becomes non-linear as indicated by a'' as shown in FIG. This is provided for the purpose of removing distorted waves of the bias excitation alternating current from the detection signal of No. 9.

Therefore, if the distorted wave of the bias excitation alternating current can be ignored in terms of torque detection accuracy, or if the magnetization characteristic of the shaft 19 to be measured has the characteristic shown by a in FIG. 2, the bias signal filter 15 is unnecessary. The torque detector 1 can be simplified.

The excitation core 3 is along the axial direction of the shaft to be measured 19 and its magnetic pole face is opposed to the circumferential surface of the shaft to be measured 19, and the force detection core 5 is along the circumferential direction of the shaft to be measured 19 and is It faces the circumferential surface of the measurement shaft 19.

Incidentally, at least the peripheral surface of the shaft to be measured 19 is formed of a ferromagnetic material, and when the excitation core 3 is excited, a magnetic circuit is formed by the excitation core 3 and the shaft to be measured 19.

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

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

Here, FIG. 2 shows the magnetization characteristics of the shaft 19 to be measured, and as can be understood from the figure, the excitation coil 7 is energized with a bias excitation alternating current superimposed on the excitation alternating current. Therefore, the hysteresis characteristic of the measured axis 19 is corrected in the horizontal section (section a-b in Fig. 2).
It is magnetized with the characteristics shown by the dashed line in the figure.

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

Note that the detection signal generated in the detection coil 9 is a change in the magnetization strength of one axis to be measured (magnetic flux density change; dΦ/'d t ).
and the torsional torque (T>), and its phase is shifted by 90 degrees with respect to the excitation alternating current supplied from the excitation oscillator 11 (see FIG. 2).

As described above, in this embodiment, the excitation coil 7 is connected to the excitation oscillator 1.
1, and a bias excitation alternating current is applied from the bias excitation oscillator 13 superimposed on the excitation alternating current, so that the magnetization characteristics of the shaft 19 to be measured are corrected by the superimposed bias excitation alternating current. , a detection signal having a waveform substantially close to a sine wave is generated in the detection coil 9.

Therefore, there is a proportional relationship between the torsional torque applied to the shaft 19 to be measured and the detection signal obtained by the detection coil 9. Therefore, there is no need for a conventional circuit to linearize the detection signal, and the detector 1 simplification is possible.

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

Note that the same parts as in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

In addition, the excitation core 3 includes a set of excitation coils 7a (self-inductance L+) and 7b (self-inductance L2).
The excitation coils 7a and 7b are connected in series.

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

Therefore, the excitation coils 7a, 7b and the capacitor 21 form a resonant circuit of the bias excitation alternating current (frequency f2), and therefore the excitation alternating current (frequency f+
), the bias excitation by the bias excitation alternating current becomes relatively strong.

That is, in order to reduce the distortion caused by the magnetization characteristic (hysteresis characteristic) of one axis to be measured, it is necessary to make the intensity and frequency of the bias excitation alternating current relatively larger than the excitation alternating current.

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

As described above, in this embodiment, a parallel resonant circuit is formed by the excitation coils 7a, 7b and the capacitor 21, thereby making the intensity and frequency of the bias excitation alternating current relatively larger than the excitation alternating current. Even if the drive amount force is the same as the current, the excitation by the bias excitation alternating current becomes relatively strong, which is a special effect.

(Effects of the Invention) As is clear from the above explanation, the torque detector according to the present invention superimposes the bias alternating current on the normal alternating current that is supplied to the excitation coil that excites the shaft to be measured, so that The detected signal has a waveform almost like a sine wave with little distortion.

Therefore, the torsional torque applied to the shaft to be measured and the detection signal are in a proportional relationship, and therefore a conventional linearization circuit is not required.

As a result, the configuration of the torque detector can be simplified and its cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic diagram of a torque detector according to the present invention, and FIG.
The figure is a characteristic diagram showing the magnetization characteristics 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 cores 7.7a, 7b... Excitation coil 9... Detection coil 11... Excitation excavator 13... Bias excitation oscillator 15 ... Bias signal filter 17 ... Amplifier 19 ... Axis to be measured 21 ... Capacitor

Claims (1)

[Claims] (1) An excitation coil for excitation of the measured shaft, the magnetic pole surface of which is wound around an excitation core facing the circumferential surface of the measured shaft along the axial direction of the measured shaft, intersects with the excitation core. a detection coil whose magnetic pole surface is wound around a detection core facing the circumferential surface of the shaft to be measured and generates an electromotive force according to the torsional torque of the shaft to be measured; and an alternating box that energizes the excitation coil. A torque detector comprising: a current power source; and a bias alternating current power source that generates a bias alternating current to be superimposed on the alternating current.