JPS60129634A - Torque sensor - Google Patents

Abstract

PURPOSE:To enable the enhancement of S/N and the stable detection of torque, by fixing one or plural thin magnetic metal strip having magnetostriction to a part of a torque transmission shaft in the peripheral direction thereof and arranging a detection magnetic core to the outer periphery of the rotary surface thereof. CONSTITUTION:A pair of thin magnetic metal strip 321, 322 are partially fixed to a torque transmission shaft 31 comprising a ferromagnetic body at two places in the axial direction thereof so as to apply induction magnetic anisotropies to directions respectively inclined at angles of theta, -theta to the peripheral direction of the transmission shaft 31. Further, a pair of U-shaped detection magnetic cores 331, 332 respectively provided with excitation winding 341, 342 and detection windings 351, 352 are arranged to the outer peripheries of the thin metal strips 321, 322 in a concentric circular form. In this case, the relation of the length (l) of a metal strip 21 and the length (l') of the effective magnetic path of a detection magnetic core 22 is brought to a range of l'<=l<=2l'. By this mechanism, S/N is enhanced and the stable detection of torque can be 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 and its problems]

Torque is one of the basic ingredients 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 torque sensor as described above that uses a thin strip of amorphous magnetic alloy has been proposed (IEE of Japan Magnetics Study Group Materials MAG
-81-72).

The general structure of this druxe is as shown in Figure 1.
It is. 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 the entire circumference of the torque transmission shaft 1 and fixed thereto. This annular magnetic core 2 has an induced magnetic anisotropy Ku' in advance at an angle θ with respect to the circumferential direction 3.
4 is given. Note that, for example, a detection coil (not shown) is disposed close to the annular magnetic core 2, and this detection coil is further 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>O. Now, when torque 5 is applied to the torque transmission shaft 1, 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 tension σ in the +45° direction and -45° direction. Compressive stress -〇 occurs respectively. Along with this, the annular magnetic core 2 has an induced magnetic anisotropy Ku" (6) in the +45° direction due to the magnetostrictive effect.
('Ku''' = 3λ8・σ). As a result, as a combination of Ku' and Ku'', the induced magnetic anisotropy is Ku
Changes to (7).

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 annular magnetic core 2
The change in magnetic permeability due to the change in the direction of the induced magnetic anisotropy of
For example, the change in voltage can be measured by a detection coil and a detection circuit connected to it, and from that value, the torque transmission shaft 1
Torque 5 applied to can be detected.

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-At-81 alloy x Fe'-8i alloy can be used.

The mechanism for detecting the change in magnetic permeability described above is shown in Figure '2 (,
) and (b) are known.

In FIG. 2(,), an annular magnetic core 12 made of a magnetic metal ribbon is fixed to a hollow torque transmission shaft 11, and a solenoid coil 13 is used to excite the annular magnetic core 12 in the circumferential direction.
The output is detected by winding the wire. Also, the same figure (b)
An annular magnetic core 12 made of a magnetic thin ribbon is fixed to a torque transmission shaft '11, and a solenoid coil 13' wound around the outer periphery is used to excite the annular magnetic core 12 in the width direction. The output is detected by winding a detection winding 14' around the output.

In other words, in both of the detection mechanisms shown in Figures 2 (,) and (b), a change in magnetic permeability is treated 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. It is.

[Problems with background technology]

As mentioned above, in order to achieve a practical level of torque detection output during rotation with the torque detection mechanism, it is necessary to give a large induced magnetic anisotropy to the annular magnetic core that is wound and fixed around the torque transmission shaft. Large induced magnetic anisotropy in the core ±45
It is extremely difficult to apply it in the ° direction - Also, since the magnetic permeability is detected continuously over the entire circumference of the torque transmission shaft, it is necessary to set the magnetic permeability to a constant value at any position. ,
When a ferromagnetic material such as Fe-based material is used for 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 decrease in the SA ratio.

5- [Object of the invention] The present invention has been made in order to eliminate the above-mentioned drawbacks.
), S, and A ratios to provide a torque sensor that can perform stable torque detection.

[Summary of the invention]

The torque sensor of the present invention has one or more magnetic metal ribbons fixed to a part of the circumferential direction of a torque transmission shaft, and a detection magnetic core arranged on the outer periphery of the rotating surface of the magnetic metal ribbon. It is characterized by: - According to the above-mentioned torque sensor, since the magnetic metal ribbon is fixed only on a part of the torque transmission shaft, the length is shorter than when the magnetic metal ribbon is wound around the entire circumference, so there is a large induced magnetism in advance. It is easy to impart anisotropy. In addition, since torque is detected only in a part of the circumferential direction of the torque transmission shaft, there is little chance of being affected by non-uniformity of the material of the torque transmission shaft, and there is almost no output fluctuation per revolution. Since torque 6 can be detected under conditions equivalent to a stationary state, the SA ratio is high and stable torque detection can be performed.

In addition, in the torque sensor of the present invention, the length t of the magnetic metal ribbon (or each magnetic metal ribbon when a plurality of magnetic metal ribbons are fixed) is t', where t' is the effective magnetic path length of the detection magnetic core. ≦
It is desirable that t≦21'. The reason for this will be explained with reference to FIGS. 3 and 4. FIG. 3 is an explanatory diagram showing the relationship between the length t of the magnetic metal ribbon 21 fixed to a part of the torque transmission shaft and the effective magnetic path length t' of the detection magnetic core 22;
FIG. 4 is a characteristic diagram of the inductance obtained by the detection magnetic core when the torque transmission shaft is rotated. In FIG. 3, the effective magnetic path length t' means the magnetic path length that allows the detection magnetic core 22 to effectively obtain changes in magnetic flux. Therefore, if t is less than t', the magnetic flux change of the magnetic metal ribbon 21 cannot be effectively obtained, and the inductance P shown in FIG. 4 is significantly reduced. On the other hand, when t exceeds 21', W in FIG. 4 widens and the inductance P fluctuates within the range of W, resulting in a significant drop in the S/N ratio. Therefore, t is t
It is desirable that the range is '≦t≦21'. Furthermore, when considering the structure of the magnetic core for obtaining the effective magnetic path t', it is substantially effective that t'<TL, where L is the entire circumference of the torque transmission shaft.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 5 to 7.

In Fig. 5, 31 is a ferromagnetic torque transmission shaft with a diameter of 55 m, and a pair of magnetic metal thin strips 321° 32□ are attached at two locations in the axial direction of the torque transmission shaft 31. It is fixed with adhesive to a part of the circumference. These magnetic metal thin strips 321 and 322 were made by a single roll and had a width of 5m+a and a thickness of 30μm (Fe0.65"0.3C
r0.05) A ribbon of 75S111B, 4 amorphous magnetic alloy was cut into a length of t=10ml.

In addition, induced magnetic anisotropy is imparted to these magnetic metal thin strips 324, 82□ in directions of inclination at an angle θ and an angle −0 with respect to the circumferential direction of the torque transmission shaft 31, respectively. Further, on the outer periphery of the rotating surface of the magnetic metal ribbon 321.32°, the ends of a pair of υ-shaped detection magnetic cores 331, 33° are arranged concentrically with the torque transmission shaft 31 with a gap of 1 cm apart. has been done.

These detection magnetic cores 33. , 332 have excitation windings 34., 332, respectively. .

342 and detection windings 351,352 are provided.

Further, the detection winding 35. and the detection winding 352 are differentially connected. Note that the detection magnetic core 33. .

Assuming that the effective magnetic path length t' of 332 is both 10 mm,
・″・One way 1fil″1″7 ffl!M, there is the way 01.

When the motion and torque of the torque transmission shaft 31 at a rotational speed of 1,500 rpm was detected using the above torque sensor, it was possible to obtain detection characteristics with a high SA ratio, stability, and excellent linearity, as shown in A in Fig. 6. did it.

In addition, in the above torque sensor, as shown in Fig. 4 mentioned above, a peak of the inductance P can be obtained per rotation (multiple magnetic metal ribbons if multiple magnetic metal ribbons are fixed in the circumferential direction). Therefore, the rotational speed of the torque transmission shaft can also be obtained by introducing this output signal into a counter such as a counter.

In the above embodiment, the length t of the magnetic metal ribbon and the effective magnetic path length t' of the detection magnetic core were made equal, but even when t = 2t', as shown in B in FIG. Good results similar to those in the examples were obtained.

On the other hand, the case of t = 1/2 t' is shown in C in Fig. 7, and t
=3t' is shown in FIG.

As is clear from No. 7-6, when 1 = 1/2 t', the torque detection rate is significantly reduced.

Furthermore, when t=3t', the output becomes unstable due to a decrease in the 87N ratio. Therefore, t is t′≦t≦2
It can be seen that it is desirable that the value be in the range of 1'.

It has been confirmed that the same effect as in the above embodiment can be obtained when other magnetic materials such as permalloy, sendust, and Fe-81 alloy are used as the magnetic metal ribbon.

In addition, in order to improve the linearity of the torque detection characteristics associated with normal rotation and reversal of torque, it is desirable to use a pair of detection magnetic cores as in the above embodiment and further connect the detection windings differentially. .

〔Effect of the invention〕

As detailed above, according to the present invention, the S/N ratio is improved,
It is possible to provide a torque sensor that can perform stable torque detection.

[Brief explanation of drawings]

Figure 1 shows the principle of a non-contact torque sensor, Figure 2 (
, ) and (b) are block diagrams of conventional torque sensors, respectively, and FIG. 3 shows the relationship between the length t of the magnetic metal ribbon and the effective magnetic path length t' of the detection magnetic core in the torque sensor of the present invention. FIG. 4 is an explanatory diagram showing the relationship, FIG. 4 is a characteristic diagram of inductance obtained by the torque sensor, FIG. 5 is a configuration diagram of a torque sensor in an embodiment of the present invention, and FIG. Fig. 7 is a torque detection characteristic diagram when = t' and t = 2t'.
Torque detection characteristics when 1/2 t' and t=3t'
It is a diagram. 31...Torque transmission shaft, 32.322...Magnetic metal ribbon, 331,332...Detection magnetic core, 341.342
...Excitation winding, 351,352...Detection winding. Applicant's agent Patent attorney Takehiko Suzue Figure 6 Figure 7

Claims (2)

[Claims] (1) Non-contact detection of torque by fixing a magnetostrictive magnetic metal ribbon to 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. In a torque sensor that performs 1. One or more magnetic metal ribbons are fixed to a part of the upper transmission shaft in the circumferential direction, and a detection magnetic core is arranged on the outer periphery of the rotating surface of the magnetic metal ribbon. Torque sensor. (2) The cloudiness t of the magnetic metal thin strip fixed in the circumferential direction of the torque transmission shaft is: If the effective magnetic hoop length of the detection magnetic core is t', then
The torque sensor according to claim 1, characterized in that , 8 is in the range -≦l≦21'.