JPS6050429A - Torque sensor - Google Patents

Abstract

PURPOSE:To perform stable torque detection, by detecting the phase difference caused by the change in magnetic characteristics of a magnetic metal thin belt, which is fixed to a rotary shaft, thereby obtaining a large output. CONSTITUTION:A sine wave from of an oscillator 26 is applied to an exciting coil 24, which is wound around a detecting magnetic core 23. When torque is applied to a torque transmitting shaft 21, the permeability of an annular core (magnetic metal thin belt) 22 is changed. The amount of change is converted into a sine wave voltage by a detecting coil 25, and a rectangular wave 28 is obtained by a Schmitt trigger circuit 27. Phase shift of + or -omegaDELTAL is generated in the sine wave voltage accompanied by the change in permeability. A reference rectangular wave 30 from a rectangular-wave oscillating circuit 29 and the rectangular wave 28 are overlapped in an EX-OR gate circuit 31, and a phase difference time (t) is generated. The time (t) is processed by a pulse modulation circuit 32 and a reference-time generator 33 and detected as a pulse number, which is proportional to the torque value, through a pulse counter 34. Thus the large output is obtained, and the stable detection of the torque is performed.

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 a non-contact method.In recent years, a non-contact method using a thin strip of amorphous magnetic alloy has been proposed as the above-mentioned non-contact method. (IEEJ Magnetics Study Group Material MAG-81-72).

A schematic configuration diagram of this torque sensor is shown in FIG. In the figure, reference numeral 1 denotes a rotating shaft on which torque is to be detected, 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 I. This annular magnetic core 2 has a circumferential direction 3 in advance.
induced magnetic anisotropy Ku' in the direction of inclination at an angle of 0 to
has been granted. 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, in order to simplify the explanation, it is assumed that θ>45° and the saturation magnetostriction constant J8>0. Now, torque 5 is applied to torque transmission shaft 1.
is applied to the torque transmission shaft 1 and the emitted magnetic core 2 is +45°
A tension force σ is generated in the direction of , and a compressive stress −σ is generated in the direction of −45°. Along with this, the annular magnetic core 2 has an induced magnetic anisotropy Ku″6 in the +45° direction due to the magnetostrictive effect.
(=3λS·σ) is induced. As a result, Ku' and K
The induced magnetic anisotropy changes to Ku 7 as a composite of u''. Generally, the magnetic permeability of a magnetic material changes depending on the direction of the induced magnetic anisotropy with respect to the excitation direction. Therefore, the induced magnetic anisotropy of the annular magnetic core 2 The change in magnetic permeability due to the change in direction can be measured as a change in voltage by a detection coil and a detection circuit connected to it in one row, and from that value the torque 5 applied to the torque transmission axis l can be detected. can do.

In addition, in the above description of the torque sensor, a case was described in which an amorphous magnetic alloy was used as the magnetic material constituting the annular magnetic core, but the present invention is not limited to this, and as long as it exhibits soft magnetism, for example, permalloy (Fe-Ni alloy), Sendust (
Other magnetic materials such as Fe-Al-8+ alloy) and Fe-8i alloy 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, the above-mentioned detection mechanism fixed the annular magnetic core 12 as shown in FIG. This is to detect. In addition, in the same figure (color), an annular magnetic core 12 made of a magnetic metal ribbon is fixed to a torque transmission shaft 11.
A solenoid coil 13' wound around the outer periphery of the annular magnetic core 12 is used to excite the annular magnetic core 12 in the inward direction, and a detection winding 14' is further wound around the outside of the annular magnetic core 12 to detect its exit.

That is, in both the detection mechanisms shown in Figures 2 (al and 2), a change in magnetic permeability is interpreted as a change in voltage due to mutual induction between the solenoid coil and the detection winding, and an output is obtained via an amplifier circuit. .

C. Problems with Background Art] In order to achieve a practical level of detection output with the detection mechanism described above, it is necessary to impart large induced magnetic anisotropy to the annular magnetic core that is wound and fixed around the torque transmission shaft in advance. Also,
Since the excitation solenoid coil requires an excitation current of 100 mA or more, there are disadvantages in terms of the magnetic circuit.

Furthermore, since changes in magnetic permeability are interpreted as changes in voltage, a high-magnification amplification circuit is required, making the electrical circuit complicated.

[Purpose of the invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks, and it is an object of the present invention to provide a torque sensor that can obtain a large output and perform stable torque detection.

[Summary of the invention]

The torque sensor of the present invention is characterized in that it is fixed to a rotating shaft and detects it as a phase difference.

If changes in the magnetic properties (magnetic permeability) of the annular magnetic core are detected as phase differences in this way, there is no need to detect changes in magnetic permeability as changes in voltage, so a high-magnification amplifier circuit can be omitted.
Furthermore, the excitation current can also be significantly reduced. As a result, the electric circuit can be simplified and no inconvenience occurs in the Vf1 air circuit.

[Embodiments of the invention]

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

Reference numeral 21 in FIG. 3 is a torque transmission shaft having a diameter of 55 mm, and an annular magnetic core 22 is fixed to this torque transmission shaft 21.

This annular magnetic core 22 has a width of 5 m manufactured by a single roll method.
, 3011 m thick (F'eo, 6! Nio, s C
ro, os) ts 8itt B14 A thin ribbon of amorphous magnetic alloy is wound around the torque transmission shaft 21 and fixed thereto. In this annular magnetic core 22, a U-shaped detection magnetic core 23 made of an oxide magnetic material is arranged in advance in the circumferential direction in a non-contact manner above the dielectric magnetic core 22 at an angle θ with respect to the circumferential direction. ing. This detection magnetic core 23 is provided with an excitation coil 24 and a detection coil 25.

FIG. 4 shows a circuit configuration for detecting a phase difference caused by a change in the magnetic properties of the annular magnetic core 22.

First, a sine wave obtained from the oscillator 26 is transmitted to the detection magnetic core 23.
It is added to the excitation coil 24 installed in the Now, when torque is applied to the torque transmission shaft 21, the annular magnetic core 2
The magnetic permeability of 2 also changes. The coil 25 for detecting this amount of change
Convert it to a sine wave voltage with Schmitt trigger circuit 27
A square wave 28 is obtained. Here, a phase shift of ±ωΔL occurs in the sinusoidal voltage due to a change in magnetic permeability.

On the other hand, in the rectangular wave oscillation circuit 29, the rectangular wave 3 having a quasi-phase
0, and the EX-OR gate circuit 31 generates the rectangular wave 2.
8 and the rectangular wave 30 to produce a phase difference time t.
let Next, this phase difference time t is determined by the pulse modulation circuit 32.
and a reference time generator 33, and can be detected as a pulse number proportional to the torque value via a pulse counter 34.

When the dynamic torque of the torque transmission shaft 21 was detected using the torque sensor, it was found that it had extremely excellent linearity as shown in FIG. Note that the output in FIG. 5 is the number of pulses converted into voltage by a DA converter.

In addition, while a conventional torque sensor that uses a solenoid coil to excite the annular magnetic core in the width direction requires an excitation current of about 100 mA, the above-mentioned torque sensor requires an excitation current of about 5 mA. No inconvenience will occur. Moreover, since the excitation current can be reduced, the influence of the torque transmission shaft made of ferromagnetic material can also be greatly reduced. Furthermore, unlike conventional torque sensors, a high-magnification amplifier circuit can be omitted, so the electric circuit can be simplified. Moreover, since digital processing is used, the output can be arbitrarily performed using a DA converter, making stable torque detection possible. Furthermore, since the pulse number can be directly introduced into the microcomputer, there is great added value.

The same effect as in the above embodiment can be obtained by using permalloy, Sendust, Fe-8i alloy as the annular magnetic core, and amorphous alloy, permalloy, Sendust), Fe-8i alloy as the detection core.
It was also obtained when -8i alloy was used.

In addition, in the torque sensor of the above embodiment, the linearity of the output deteriorates due to the positive/negative reversal of the torque.
With the structure shown in the figure, the linearity of the output can be improved even if the torque is reversed.

Reference numeral 41 in FIG. 6 denotes a torque transmission shaft. This torque transmission shaft 41 has a pair of annular magnetic cores 42 made of a ribbon of the same amorphous magnetic alloy as that used in the above embodiment. ．． 4
2. is wrapped and fixed. These annular magnetic cores (z
One of the annular magnetic cores 42 □ and 42 is provided with induced magnetic anisotropy in the direction of inclination at an angle -l with respect to the circumferential direction. Moreover, these annular magnetic cores 42. ．． 42. Above the U-shaped detection cores 4J, 43., each made of an oxide magnetic material.
are arranged circumferentially in a non-contact manner. These detection magnetic cores 431.4B.

are each provided with an excitation coil 44. ．． 44. and a detection coil "1e45R".

Said annular magnetic core 42m, 42. FIG. 7 shows a circuit configuration for detecting a phase difference caused by a change in the magnetic properties of the magnetic field.

First, the oscillator 46. Magnetic core 4 for detecting the sine wave obtained from
In addition to the excitation coil 441 installed at 3m, an oscillator 46.
The sine wave obtained by the detection magnetic core 43. Excitation coil 44 applied to! Add to. Now, when torque is applied to the torque transmission shaft 41, the annular magnetic cores 42m, 42. The magnetic permeability of each increases or decreases. This amount of change is detected by the detection coil 45. ．． 45. Convert to sinusoidal voltage with ±
A phase difference of ωΔL is generated. That is, when the torque is 0, the detection coil 45 and the detection coil 45. Although there is no phase difference between the detection coil 45. and the detection coil 45. has an advanced phase of +ωΔL, and the detection coil 45. has a delayed phase of −ωΔL. Therefore, the detection coil 4-5. A phase difference of 2ωΔL(71) occurs between the detection coil 452 and the detection coil 452. Next, the obtained sinusoidal voltage is applied to Schmitt trigger circuits 47, . 47
．． is converted into a rectangular wave 4B, , 48t. Then E
The X-OR circuit 49 generates a rectangular wave 48, and a rectangular wave 48. are superimposed to generate a phase difference time t. Further, this phase difference time t can be processed by a pulse modulation circuit 50 and a reference time generator 51, and detected as a pulse number proportional to the torque value via a pulse counter 52.

When the dynamic torque of the torque transmission shaft 4I was detected using the above torque sensor, as shown in Fig. 8, the number of pulses was DA
It was found that the output voltage and torque value converted by the converter had excellent linearity even when the torque was reversed.

Moreover, it goes without saying that the same effects as the torque sensor of the above embodiment can be obtained.

Although the torque sensor shown in FIG. 6 uses a pair of Ug magnetic cores, the present invention is not limited to this, and the magnetic core 61 shown in FIG.
The excitation coil 62 and the detection filter 63 are applied to the magnetic core 71 as shown in FIG. Similarly, highly accurate torque detection can be performed even with the one provided with the secondary coil 73.

〔Effect of the invention〕

As described in detail above, according to the present invention, the torque of a wide range of torque transmission shafts can be detected with high accuracy with a small excitation current without being affected by the material of the torque transmission shaft, and is extremely practical in industry. It is possible to provide a torque sensor.

[Brief explanation of drawings]

Figure 1 shows the principle of a non-contact torque sensor, Figure 2 (
al and (bl are respectively block diagrams of conventional torque sensors, Fig. 3 is a block diagram of a torque sensor according to an embodiment of the present invention, Fig. 4 is a circuit block diagram of the same torque sensor, and Fig. 5 is a block diagram of the same torque sensor. Torque detection characteristic diagram; FIG. 6 is a configuration diagram of a torque sensor according to another embodiment of the present invention; FIG. 7 is a circuit configuration diagram of the same torque sensor; FIG. 8 is a torque detection characteristic diagram of the same torque sensor; Figure ta) and Figure 10 (a) are respectively perspective views of the magnetic core used in still other embodiments of the present invention, Figure 9 (a) and Figure 10 are respectively Figure 9 (al) and Figure 10 (ca). 21.41... Torque transmission shaft, 22.42+. 42!... Annular magnetic core, 2 J p 4 j 1 e
” x #61.71...Magnetic core, 24,44.・4
4! p stone 2,72... excitation coil, 25,451
゜45t, 63.73...Detection coil, 26゜4
6,・46! ...oscillator, 27, 47. ．． 47!・・・
・Schmitt trigger circuit, 2B, 30° 4B,, 4
B, . . . rectangular wave, 29 . . . rectangular wave oscillation circuit, 31.
49...'EX-OR gate circuit, 32°50...
Pulse modulation circuit, 33, 57. ...Reference time occurrence Ma,
s4. tsz...Pulse counter. Applicant's agent Patent attorney Suzue Takehikojs9 (a) (a) (b) Figure (b)

Claims (1)

[Claims] A torque sensor that performs non-contact detection of torque by winding and fixing a magnetostrictive magnetic metal ribbon around a torque transmission shaft and utilizing the fact that the magnetic properties of the magnetic metal ribbon change due to the torque applied to the shaft. A torque sensor, characterized in that it detects a phase difference caused by a change in the magnetic properties of the magnetic metal ribbon.