JPH0522858B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a torque sensor that detects torque without contact.

[Technical background of the invention]

Torque is one of the basic quantities when controlling a rotational drive system. In order to accurately detect torque, the detection mechanism must be of a non-contact type.

In recent years, a non-contact type torque sensor as described above using a ribbon of amorphous magnetic alloy has been proposed (IEE of Japan Magnetics Study Group Material MAG-81-72).

The general structure of this torque sensor is as shown in FIG. In the figure, reference numeral 1 denotes a rotating shaft for producing torque, that is, a torque transmission shaft, and an annular magnetic core 2 made of an amorphous magnetic alloy is wound around and fixed to this torque transmission shaft 1. This annular magnetic core 2 has an angle θ with respect to its circumferential direction 3 in advance.
An induced magnetic anisotropy Ku′4 is given in the direction of inclination of . Note that, for example, a detection coil (not shown) is disposed close to the annular magnetic core 2,
Furthermore, this detection coil is connected to a detection circuit (not shown).

The principle of the torque sensor described above will be schematically explained.
Here, to simplify the explanation, it is assumed that θ>45° and the saturation magnetostriction constant λs>0. Now, torque transmission shaft 1
When torque 5 is applied to , the strain stress generated on the torque transmission shaft 1 is transmitted to the annular magnetic core 2, and the annular magnetic core 2 receives a tension force σ in the +45° direction and a compressive stress −σ in the −45° direction. Occur. Along with this, an induced magnetic anisotropy Ku″6 (=3λs・σ) is induced in the +45° direction in the annular magnetic core 2 due to the magnetostriction effect.As a result, the induced magnetic anisotropy Ku″6 (=3λs・σ) is The orientation changes to Ku7. Generally, the magnetic permeability of a magnetic material changes depending on the direction of induced magnetic anisotropy with respect to the excitation direction. Therefore, the change in magnetic permeability due to the change in the direction of induced magnetic anisotropy of the annular magnetic core 2 is expressed as
For example, it can be measured as a change in voltage using a detection coil and a detection circuit connected thereto, and the torque 5 applied to the torque transmission shaft 1 can be detected from that value.

In the above description of the torque sensor, we have described the case where an amorphous magnetic alloy is used as the magnetic material constituting the annular magnetic core.
-Ni alloy), Sendust (Fe-Al-Si alloy), Fe
Other magnetic materials such as -Si alloys can be used.

By the way, as mentioned above, torque can be detected by arranging a detection coil close to the annular magnetic core made of a thin magnetic metal strip, but the detection mechanism is an important factor that affects the performance of the torque sensor. .

Conventionally, as the above-mentioned detection mechanism, the one shown in FIGS. 2a and 2b is known.

In Fig. 2a, an annular magnetic core 12 made of a thin magnetic metal strip is fixed to a hollow torque transmission shaft 11, the annular magnetic core 12 is excited in the circumferential direction using a solenoid coil 13, and a detection winding 14 is further wound to output an output. It is something to detect. In addition, in the same figure b, an annular magnetic core 12 made of a magnetic metal ribbon is fixed to a torque transmission shaft 11, and a solenoid coil 13' wound around the outer circumference of the annular magnetic core 12 is fixed.
The sensor is excited in the width direction of the sensor 2, and a detection winding 14' is further wound around the outer side of the sensor to detect the output.

That is, in both of the detection mechanisms shown in FIGS. 2a and 2b, a change in magnetic permeability is interpreted as a change in voltage due to mutual induction between a solenoid coil and a detection winding, and an output is obtained through an amplifier circuit.

[Problems with background technology]

However, devices that excite the annular magnetic core in the width direction as shown in Figure 2b are difficult to miniaturize and cannot be stored in a narrow space, and the excitation solenoid coil requires an excitation current of 100 mA or more. In order to
Inconveniences arise in the magnetic circuit.

Further, in the case where the annular magnetic core is excited in the circumferential direction as shown in FIG. 2a, the magnetic permeability of the entire circumference of the annular magnetic core is continuously detected, so the magnetic permeability for one circumference must be kept at a constant value. However, when a ferromagnetic material such as Fe-based material is used as the torque transmission shaft, magnetic permeability changes within one revolution due to non-uniformity of the material. Therefore, the output fluctuation caused by this change in magnetic permeability is superimposed on the torque detection output, resulting in a significant deterioration of the S/N ratio.

[Purpose of the invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks, and aims to provide a torque sensor that is small in size, requires a small excitation current, and can improve the S/N ratio to perform stable torque detection. It is something.

[Summary of the invention]

In the torque sensor of the present invention, a magnetic metal ribbon having magnetostriction and diagonal induced magnetic anisotropy is fixed to a torque transmission shaft, and a torque applied to the torque transmission shaft causes the magnetic metal ribbon to In a torque sensor that performs non-contact detection of torque by utilizing changes in the magnetic properties of one or a pair of magnetic cores corresponding to the pair of magnetic metal ribbons and arranged along the circumferential direction without contacting the torque transmission shaft so as to excite the magnetic metal ribbons in the circumferential direction; ,
Torque is detected by means for generating a gate pulse signal synchronized with the rotation of the torque transmission shaft, and by obtaining a change in magnetic properties of a specific part of the circumferential direction of the magnetic metal ribbon obtained by the magnetic core as a detection signal. The invention is characterized by comprising means.

According to such a torque sensor, since a gate pulse signal having a pulse period and a pulse width synchronized with the rotation speed is used, changes in the magnetic properties of a specific part of a rotating magnetic metal thin strip can be equivalently detected at a standstill. Can be detected under conditions. Therefore, even if the magnetic permeability of the magnetic metal ribbon is not always constant on the circumference of the torque transmission shaft, torque can be accurately detected. Furthermore, even if a ferromagnetic material such as Fe-based material is used as the torque transmission shaft, output fluctuations due to changes in its magnetic permeability are eliminated, and stable torque detection can be performed with a high S/N ratio.

Further, according to such a torque sensor, a low excitation current is required to obtain the same output, and even when excited in the circumferential direction, an output with a good S/N ratio can be obtained. That is, when a magnetic metal ribbon is wound around a torque transmission shaft, excitation in the width direction requires a considerably larger excitation current than in the circumferential direction due to the demagnetizing field coefficient. On the other hand, in the case of excitation in the circumferential direction, a low excitation current is required, but when considering maintaining the uniformity of magnetic permeability of the magnetic metal ribbon, some problems remain compared to the case of excitation in the width direction. However, according to the present invention, this uniformity can be sufficiently covered and is very effective. Further, the magnetic metal ribbon may not be completely wound but may be provided partially.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 3 to 5.

In FIG. 3, an annular magnetic core 22 ₁ , 22 ₂ is attached to the outer periphery of a torque transmission shaft 21 made of a ferromagnetic material with a diameter of 55 mm and rotated by a drive source such as a motor (not shown).
is fixed. These annular magnetic cores 22 ₁ , 22 ₂
is 5mm wide and 30μ thick made by single roll method.
A thin ribbon of (Fe _0.65 Ni _0.3 Cr _0.05 ) ₇₅ Si ₁₁ B ₁₄ amorphous magnetic alloy of m is wound around the torque transmission shaft 21 and fixed. These annular magnetic cores 22 ₁ ,
22 ₂ is previously provided with induced magnetic anisotropy in the inclination directions of angle +θ and angle −θ with respect to its circumferential direction, respectively.

Above these annular magnetic cores 22 ₁ and 22 ₂ are U-shaped detection magnetic cores 23 made of oxide magnetic material.
₁ and 23 ₂ are arranged in the circumferential direction without contact. These detection magnetic cores 23 ₁ and 23 ₂ include excitation coils 24 ₁ and 24 ₂ and detection coils 25 ₁ and 2, respectively.
5 ₂ has been applied.

Using a gate pulse signal synchronized with the rotation speed of the torque transmission shaft 21, the annular magnetic cores 22 ₁ , 22 ₂
FIG. 4 shows a circuit configuration for detecting torque by using the output voltage obtained from a specific portion of the motor as one detection signal per rotation.

First, the excitation coils 24 ₁ , 24 ₂ applied to the detection magnetic cores 23 ₁ , 23 ₂ are summatively coupled, and the detection coils 25 ₁ , 25 ₂ are differentially coupled, and the sine waves obtained from the oscillator 26 are excited. In addition to the coils 24 ₁ and 24 ₂ , the annular magnetic cores 22 ₁ and 22 ₂ are excited in the circumferential direction of the torque transmission shaft 21 . Now, when torque is applied to the torque transmission shaft 21, the magnetic permeability of the annular magnetic cores 22 ₁ and 22 ₂ increases or decreases depending on the direction of the induced magnetic anisotropy given in advance. This amount of change is converted into a sine wave voltage by the detection coils 25 ₁ and 25 ₂ ,
In addition to the detection circuit 27, an integration circuit 28 and an A/
Sample and hold circuit 3 via D converter 29
0.

On the other hand, a rotation speed sensor 31 is disposed at another position on the torque transmission shaft 21, and a rotation speed signal obtained by this rotation speed sensor 31 is sent to a gate pulse generation circuit 32, which is further synchronized with the rotation speed. A gate pulse signal having a pulse period and a pulse width is introduced into the sample and hold circuit 30.

Therefore, in the sample and hold circuit 30, the output voltage due to the change in the magnetic properties of a specific part on the circumference of the annular magnetic cores 22 ₁ and 22 ₂ fixed to the torque transmission shaft 21 is adjusted to 1 per rotation by the gate pulse signal. can be obtained as two digital output values. Further, by converting this digital output value into a DC analog output voltage by the D/A converter 33, stable torque detection with a high S/N ratio can be performed.

According to the torque sensor of the present invention, the circumferential direction of the annular magnetic cores 22 ₁ and 22 ₂ can be determined by using a gate pulse signal having a pulse period and a pulse width synchronized with the rotation speed of the torque transmission shaft 21. It is possible to equivalently detect changes in the magnetic properties of a portion of the magnetic field under a stationary state. Therefore, the magnetic metal ribbon 22 ₁ fixed on the circumference of the torque transmission shaft 21,
Even if the magnetic permeability of 22 ₂ is not always a constant value on the circumference, torque can be detected accurately. Further, even if a ferromagnetic material such as Fe-based material is used as the torque transmission shaft 21, output fluctuations due to changes in its magnetic permeability are eliminated, and stable torque detection with a high S/N can be performed. Furthermore, the entire device can be downsized and can be housed in a narrow space.

In fact, when the dynamic torque of the torque transmission shaft 21 at N=2000 rpm was detected using the torque sensor, it was found that it had extremely excellent linearity as shown in FIG.

Note that the output in Figure 5 is a digital output value that is D/A.
Although it is converted into a voltage by the converter 33, the output can be made variable by any D/A converter. Further, since the digital output value can be directly introduced into the microcomputer, there is great added value.

Further, although digital signal processing was performed in the above embodiment, the same result could be obtained even if the A/D converter 29 and the D/A converter 33 were omitted and the sample and hold circuit 30 processed the analog signal.

Note that the same effect as in the above example can be obtained when permalloy, sendust, or Fe-Si alloy is used as the magnetic metal ribbon, and when an amorphous alloy, permalloy, sendust, or Fe-Si alloy is used as the detection core. Obtained.

In addition, in the torque sensor of the above embodiment, the annular magnetic core is fixed around the entire circumference of the torque transmission shaft, but even if a magnetic metal ribbon is fixed only in a part of the circumferential direction of the torque transmission shaft and dynamic torque is detected, the same method can be used. high S/N
It is possible to obtain an output voltage with a stable ratio.

Furthermore, in the above embodiment, two detection magnetic cores are used,
Although the excitation coil is summatively coupled and the detection coil is differentially coupled, if it is not necessary to know whether the torque is positive or negative, only one detection core may be used. Also,
Even when two detection magnetic cores are used, the detection coil may be a summative coupling. However, in order to detect positive and negative torques with good linearity and high output, it is desirable to have a configuration like the above embodiment.

Further, in the above embodiment, a case has been described in which one detection signal is obtained per rotation, but the present invention is not limited to this, and by generating a plurality of gate pulse signals per rotation, a plurality of detection signals can be obtained per rotation. It's okay.

〔Effect of the invention〕

As detailed above, according to the present invention, the torque of the torque transmission shaft made of a wide range of materials can be transmitted with a high S/N ratio without being affected by the material of the torque transmission shaft or the change in magnetic permeability within the magnetic metal ribbon. It is possible to provide a torque sensor that is industrially extremely practical and can perform stable detection.

[Brief explanation of drawings]

Figure 1 is a diagram of the principle of a non-contact torque sensor.
Figures 2a and b are block diagrams of conventional torque sensors, Figure 3 is a block diagram of a torque sensor according to an embodiment of the present invention, Figure 4 is a circuit diagram of the same torque sensor, and Figure 5 is a diagram of the same torque sensor. FIG. 3 is a characteristic diagram of dynamic torque detection by a sensor. 21...Torque transmission shaft, ₂₂₁ , ₂₂₂ ...Annular magnetic _core , _231,232 ...Detection magnetic core, _241,2
4 ₂ ... Excitation coil, 25 ₁ , 25 ₂ ... Detection coil, 26 ... Oscillator, 27 ... Detection circuit, 2
8...Integrator circuit, 29...A/D converter, 3
0...Sample hold circuit, 31...Circuit number sensor, 32...Gate pulse generation circuit, 33...
D/A converter.

Claims (1)

[Claims] 1. A magnetic metal ribbon with magnetostriction and diagonal induced magnetic anisotropy is fixed to a torque transmission shaft, and the magnetic properties of the magnetic metal ribbon are changed by the torque applied to the torque transmission shaft. In a torque sensor that performs non-contact detection of torque by utilizing the one or a pair of magnetic cores disposed along the circumferential direction without contacting the torque transmission shaft so as to circumferentially excite the magnetic metal ribbon in correspondence with the torque transmission shaft; A means for generating a gate pulse signal synchronized with rotation, and a means for detecting torque by obtaining a change in magnetic properties of a specific part of the circumferential direction of the magnetic metal ribbon obtained by the magnetic core as a detection signal. A torque sensor characterized by: