JPS5977326A - Magneto-striction type torque sensor - Google Patents

Abstract

PURPOSE:To detect both the magnitude and direction of torque simultaneously by a magneto-striction film having a single constitution, by providing a plurality of slits in the direction, which is inclined to the direction of torsional torque that is applied to a shaft, on the magneto-striction film that is provided on the surface of the shaft. CONSTITUTION:A magneto-striction film 23 having a rectangular shape as a whole, in which a plurality of slits 23a are provided in the slant direction, is bonded to the surface of a shaft 22 of a magneto-striction type torque sensor 21. An exciting coil 24 and a detecting coil 25 are arranged in the vicinity of the outer surface of the magnetostriction film 23. At the outside of the coils 24 and 25, a cylindrical yoke 27 comprising a high permeability material is provided with a gap 26 being provided between the shaft 22 and the yoke. In this constitution, both the magnitude and direction of the torque that is applied to the shaft 22 can be simultaneously detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetostrictive torque sensor that utilizes the magnetostrictive effect.

An example of a conventional structure of this type of magnetostrictive torque sensor is shown in FIG. This magnetostrictive torque sensor 1 has an excitation coil 6 and a detection coil 4 disposed on the surface of a shaft 2 made of a material having a magnetostriction effect. It has a structure in which a yoke 6 made of a high magnetic permeability material is provided with a gap 5 between the two.

When operating this magnetostrictive torque sensor 1, a magnetic circuit passing through the shaft 2, the gap 5, and the yoke 6 is formed by energizing the magnetic excitation coil 4. At this time, an induced electromotive force is generated in the detection coil 4.

In such a state, when torsional torque is applied to the shaft 2, the magnetic permeability of the shaft itself changes due to the magnetostrictive effect of the shaft 2, so the magnetic flux density passing through the magnetic circuit changes. The induced electromotive force generated in the detection coil 4 also changes, and by reading the change in the induced electromotive force, the pupil of the torsional torque can be determined.

In this case, even when torsional torque is applied to the shaft 2 in either the left or right direction, the change in magnetic permeability of the shaft itself is the same, so as shown in FIG. The starting force (output) E is the same. Furthermore, when the temperature (T) changes, the output also changes.

Therefore, the magnetostrictive torque sensor 1 having the above-described structure has the drawback that the direction of the torsional torque applied to the shaft 2 cannot be detected.

Unfortunately, it also had the drawback of not being able to compensate for changes in output values due to temperature.

On the other hand, as described in the Journal of the Japan Rubber Association, Vol. 55, No. 6, there is a magnetostrictive torque sensor with the structure shown in Figure 3 that can detect the direction of torsional torque applied to the shaft. . This magnetostrictive torque sensor 11 includes two magnetostrictive films 13a having a magnetostrictive effect on the outer circumference of a shaft 12, which is twisted at both ends of the shaft 12.
16b and by removing the twist after adhesion, twisting moments in opposite directions are applied to both magnetostrictive films 13a, 1' 3b, and further, an interval is created on the outer periphery of the magnetostrictive films 13a, 13b. The cylindrical member 14
are arranged, and on this cylindrical member 14, both the magnetostrictive films 13a,
The excitation coil 15 facing the magnetostrictive film 13b and each of the magnetostrictive films 13
It has a structure in which detection coils 16&, 16b are provided facing each other.a, 13b.

In the magnetostrictive torque sensor 11 having such a structure, the shaft 12
When a torsional torque is applied to the magnetostrictive film 13b, the torsional moment in one magnetostrictive film 13b becomes larger than the previously given twisting moment, and the threading moment in the other magnetostrictive film 13b becomes smaller than the previously given moment. Therefore, the magnetostrictive films 13a and 1
6b changes, and a corresponding induced electromotive force is generated from each detection coil 16a, 16b. By differentially coupling these outputs, the magnitude of the torsional torque applied to the shaft 12 and the corresponding induced electromotive force are generated. Its direction can be detected.

However, the magnetostrictive torque sensor 1 with such a structure
In No. 1, it is necessary to twist the shaft 12 when adhering the magnetostrictive film 13a13b during the manufacturing process, which does not make it easy to create a smooth structure and tends to cause variations in torque detection characteristics. Magnetostrictive films 13a, 16b
Is it a disadvantage that the direction of torque cannot be detected without using ? Yes] 7.

This system was developed by focusing on the various shortcomings of the conventional methods mentioned above.It is possible to know the direction of the torsional torque as well as the magnitude of the torsional torque applied to the shaft, and it has a simple structure and torque detection characteristics. It is an object of the present invention to provide a magnetostrictive torque sensor that has small variations in torque and can eliminate the influence of temperature.

In this invention, a magnetostrictive film having a magnetostrictive effect is provided on the surface of the shaft, and an excitation coil and a detection coil are arranged near the magnetostrictive film to form a magnetic circuit passing through the magnetostrictive film. In a magnetostrictive torque sensor configured to detect torque applied to the front axis by utilizing magnetostriction of the film, the magnetostrictive film is provided with a direction inclined with respect to the direction of the torsional torque applied to the axis. The feature is that a plurality of slits are provided in the slit.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

4 to 6 are views showing one embodiment of the present invention, and the magnetostrictive torque sensor 21 shown in the drawings has a plurality of slits in the oblique direction on the surface of the shaft 22, as shown in FIG. 23a
A magnetostrictive film 26 having an overall rectangular shape is provided by adhesion as shown in FIG. It has a structure in which a cylindrical yoke 27 made of a cylindrical magnetic permeability material is provided on the outside of the yoke 25 and with a gap 26 between it and the shaft 22.

In this structure, the magnetostrictive film 26 has a magnetostrictive effect, and is, for example, an amorphous film. For example, an Fe-based amorphous metal with a large magnetostrictive effect is used, and a plurality of sulins (23) are applied to the Fe-based amorphous metal ribbon as shown in FIG.
The magnetostrictive film 26 formed by forming a is bonded to the shaft 22 as shown in FIG.

Next, the operation of the magnetostrictive torque sensor 21 will be explained.

First, in operation, an alternating current with a constant amplitude and frequency is applied to the excitation coil 24. As a result of this application, lines of magnetic force are generated surrounding the excitation coil 24 and the detection coil 25, with the magnetic path being the magnetostrictive film 26→gap 26→yoke 27→gap 26→magnetostrictive film 26. Here, time t
Let the magnetic flux passing through the detection coil 25 be Φ(1), and the self-inductance of the detection coil 25 be Lp and L,
When the number of turns of the detection coil 25 is N, an induced electromotive force E expressed as follows is generated at the output end of the detection coil 25. At this time, the line of magnetic force m at time t
flows in the magnetostrictive film 26 in the same direction as each sulin 25a, as shown in FIG. 4(c).

Next, when a torsional torque is applied to the shaft 22, for example, in the direction of () shown in FIG. 4(b), the magnetostrictive film 26 is
) is subjected to tensile deformation in the direction of ■−■.

As a result, since the amorphous magnetostrictive film 26 used in this embodiment has the characteristic that its magnetic permeability increases due to the above-described tensile deformation, the magnetic flux Φ(1) passing through the inside of the detection coil 25 increases.

On the other hand, since the frequency does not change, d shown in equation (1) above
Φ(t)/dt increases, and the induced electromotive force E increases.

On the other hand, when the screw 9 torque is applied to the shaft 22 in the direction of ■ shown in FIG. 4(b), the magnetostrictive film 26 undergoes compressive deformation in the direction of ■-■ shown in FIG. Since the magnetic permeability of the membrane 26 decreases, the magnetic flux Φ(
1) decreases, dΦ(t)/dt shown in the above equation (1) decreases, and the induced electromotive force E decreases.

The range of change in magnetic permeability of the magnetostrictive film 26 due to the above-mentioned tension and compression increases as the applied torque to the shaft 22 increases, so as shown in FIG. 7, the induced electromotive force (output) The direction of the applied torque can be detected at the same time.

Note that the width of the ring 23a formed on the magnetostrictive film 26 is preferably set to such a level that leakage of magnetic flux can be ignored. Furthermore, although it is preferable to use a non-magnetic material for the shaft 22, this is not the case if the magnetic permeability of the magnetostrictive film 23 is greater than that of the shaft 22.

FIG. 8 is a diagram showing another embodiment of the present invention, showing another example in which a magnetostrictive film 26 is provided on the surface of the shaft 22. That is, in this case, as shown in FIG. 8(b), after masking 28 is applied to the surface of the shaft 22 other than the part where the magnetostrictive film is to be formed, electroplating, physical vapor deposition, etc. (PVD: vacuum evaporation, sputtering, ion blating, etc.), chemical vapor deposition (CVD), etc., as shown in FIG. 8 (Pt) 23
Magnetostriction 1t with a! 423 = shows what is provided on the surface of the r-axis 22.

In this way, the magnitude and direction of the torsional torque applied to the shaft 22 can be detected simultaneously, as in the previous ML embodiment.

By the way, the magnetostrictive torque sensor 21 shown in each of the above embodiments
As shown in Figure 9, the change in temperature (T) (T1
Since the induced electromotive force (output) Ep generated in the detection coil 25 differs depending on s T2 ), it is effective for use in places where temperature changes are small.

FIGS. 10 to 12 are diagrams showing still other embodiments of the present invention, and show embodiments in which the influence of temperature changes on the output in the case of embodiment III is eliminated.

That is, the magnetostrictive torque sensor 61 shown in FIGS. 10(a) and 10(b) each has two sets of magnetostrictive films 23, 23, excitation coils 24, 24, and a detection coil on one shaft 22. 25.25 and a yoke 27.27, and a gap 26 is provided between the shaft 22 and the yoke 27, and both magnetostrictive films 23, 23 have a slit 23a formed in each,
23a is provided so as to be inclined in a different direction with respect to the direction of the torsional torque applied to the shaft 22, with this direction being the center of symmetry.

In this case, the magnetostrictive torque sensor 6 is not shown in FIG. 10(a).
As shown in FIG. 11, the A and B strain films 23 and 21 of 1
A magnetic flux blocking slit 23b is located approximately in the center of one magnetostrictive ribbon.
f: A plurality of slits (25a, 23) formed and tilted in opposite directions with this slit 23b as the center of symmetry
This is provided by attaching a layer formed with the shape "a" to the shaft 22. Further, the magnetostrictive films 23 and 26 of the magnetostrictive torque sensor 61 shown in FIG. 10(b) are provided by bonding magnetostrictive thin ribbons having shapes as shown in FIG. 5, which are each manufactured separately, to the shaft 22. It is something. Of course, even in the case of V displacement, it is possible to form the magnetostrictive film 26 by plating, vapor deposition, etc., as explained based on FIG. 8, without using the magnetostrictive ribbon. In order to prevent magnetic interference of 26'', both magnetostrictive films 23,
It is better that each 2+ is independent.

In the magnetostrictive torque sensor 61 having such a structure, when torsional torque is applied to the shaft 22, each magnetostrictive film 23, 2
Different deformations of tension and compression are applied in the direction of the slits 3, and the induced electromotive force E,1 of one detection coil 25 increases, and the induced electromotive force E,2 of the other detection coil 25 decreases. Therefore, the torsional torque applied to the shaft 22 is Tq
, If the ratio 9N constant is K, then if the output when these outputs are subtracted by the differential circuit is E, then E = Ep, -Ep2 = 2 and -Tq...
- (3) As shown in FIG. 12, in this embodiment, the output change rate is doubled, and the direction of torque can also be detected at the same time.

Next, temperature compensation of the magnetostrictive torque sensor 61 shown in FIG. 10 will be explained. When the temperature changes,
Under a constant input, the magnetic permeability of the magnetostrictive film 26 changes and the coil 2
4.25 Due to changes in magnetic flux due to resistance changes, etc.
In the torque sensor 21 shown in the figure, its output value shifts to the decreasing side as shown in FIG. Therefore, this transition width is Δ
E, then in the torque sensor 61 shown in FIG.
The output Ep1 of one detection coil 25 is Ep1=■(・
Tq0Epo−ΔEp・−・−(4), and the output Ep2 of the other detection coil 25 is Ep2=−K−Tq
+ Epo−ΔEp (5).

Then, if the output when these outputs are subtracted by a differential circuit is ET, then ET = Epl - Ep2 = 2
．． K - Tq (6), the effect of temperature is removed and the output is doubled, and at the same time, torque can also be detected.

As described above, according to the present invention, in a magnetostrictive torque sensor in which a magnetostrictive film having a magnetostrictive effect is provided on the surface of a shaft, the magnetostrictive film is tilted with respect to the direction of torsional torque applied to the shaft. Since multiple slits are provided in the direction of
Both the magnitude of the torque applied to the shaft and the direction of the torque can be detected simultaneously, the structure is simple, and the variation in torque detection characteristics is small (1k) (an excellent strain type torque sensor can be obtained). When magnetostrictive films with multiple configurations are used, the effects of temperature can be completely eliminated, and torque can be measured with high accuracy even in areas where there are temperature changes. .

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory diagram showing an example of a conventional magnetostrictive torque sensor, Fig. 2 is a graph showing the output characteristics of the magnetostrictive torque sensor shown in Fig. 1, and Fig. 3 is another example of a conventional magnetostrictive torque sensor. 4 (a) (b) (e)
5 and 6 are respectively cross-sectional explanatory views of a magnetostrictive torque sensor according to an embodiment of the present invention, an explanatory view showing the direction of torque applied to the shaft, and an explanatory view showing the deformation direction of the magnetostrictive film. FIG. 7 is a graph showing the output characteristics of the magnetostrictive torque sensor of FIG. 4, and FIGS. 289 is a graph showing the influence of temperature on the output characteristics of the magnetostrictive torque sensor of FIG. 4; FIG.
Figures (a) and (b) are cross-sectional explanatory views of a magnetostrictive torque sensor according to still another embodiment of the present invention, and Figure 11 is a first
FIG. 12 is a graph showing the output characteristics of the magnetostrictive torque sensor shown in FIG. 10. 21.31... fIIi distortion torque sensor, 22...
・Axis, 26... (IB & membrane, 26a... slit,
24... Excitation coil, 25... Jjj coil, 2
6... Gap, 27... Yoke, 28... Masking. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Yutaka Koshio Figure 4 27 (b) ■ m Figure 5 Figure 6 3 23a 22 Figure 7 Figure 8 (a) (b) Figure 9 Revised No. Figure 10 (a) (b) j'r7'j111 figure

Claims (2)

[Claims] (1) A magnetostrictive film having a magnetostrictive effect is provided on the surface of the shaft, and an excitation coil and a detection coil are arranged near the magnetostrictive film to form a magnetic circuit passing through the magnetostrictive film. In a magnetostrictive torque sensor that detects the torque using magnetostriction caused by deformation of the magnetostrictive film due to a torsional torque applied to the shaft, the magnetostrictive film is tilted with respect to the direction of the torsional torque applied to the shaft. A magnetostrictive torque sensor characterized by having multiple slits in one direction. (2) The magnetostrictive type according to claim (1), wherein the plurality of slits are inclined in different directions with the direction of the torsion torque applied to the shaft as a center of symmetry. Torque sensor.