JPH09184776A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an application of a simple method by an inexpensive device by detecting the change in deformation generating on the surface of a shaft due to torque transmitting to the shaft, as the change in self inductance of a coil, according to the change of permeability of a magnetosensing means and detecting the degree of torque on the basis of its difference. SOLUTION: An amorphous metallic body 3 is a flat plate wherein a plurality of slits are formed in directions of 45 deg. (left) and -45 deg. (right) respectively against the lengthwise direction of a shaft 1, and the body 3 which is not subjected to pre-heat-treatment is adhered by pressing, with an adhesive agent at almost a lower temperature than Curie point and in the air. A bobbin 4, which is arranged at a desired position opposite to the body 3 with an interval of distance. is provided with a coil 5 (5a and 5b) for energization and detection, and a magnetic yoke 6 made of permalloy is fitted to the outside of the coil 5. In such a configuration, when any torque is applied to a shaft 1, deformation is generated on the body 3 and the permeability on the right and left of the body 3 is changed, then the self inductance on the right and left of the coil 5 is changed accordingly. Therefore, the degree and direction of torque can be detected according to its difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor which can detect a torque transmitted to a shaft in a non-contact manner by applying a stress magnetic effect of a magnetic material.

[0002]

2. Description of the Related Art As a prior art of a torque detection method utilizing the stress-magnetic effect, an exciting coil in which an amorphous metal ribbon having a magnetostrictive effect is fixed around the shaft and a change in permeability due to applied torque is installed near the shaft. There has been proposed a method of detecting by a combination of a detector coil and a detection coil. In this torque detection method, when the amorphous metal ribbon is fixed to the shaft, for example, the proceedings of the National Conference of the Institute of Electrical Engineers of Japan (NO. 1277, Showa 57).
2), the two high-magnetostrictive amorphous magnetic alloy thin ribbons, which have been previously formed into a cylindrical shape and subjected to strain relief annealing, are bonded to each other in a state in which a twist is applied to the shafts. It is known that bias strain is applied to a high magnetostrictive amorphous magnetic alloy ribbon.

Further, as disclosed in Japanese Patent Application Laid-Open No. 62-182630, a high magnetostrictive amorphous ribbon is wound around a solid shaft and adhered at high temperature to compress it into a high magnetostrictive amorphous magnetic alloy ribbon. It is known that distortion is added.

[0004]

In the torque sensor disclosed in the above-mentioned proceedings of the National Conference of the Institute of Electrical Engineers of Japan (NO. 1277, 1982), the high magnetostrictive amorphous magnetic alloy ribbon is preliminarily formed into a cylindrical shape. Since strain relief annealing must be carried out, a high-precision jig that matches the shaft diameter must be used and high-temperature treatment must be performed in a special atmosphere. Therefore, not only the workability is remarkably reduced, but also a special device for extremely strictly controlling the temperature and time in order to prevent embrittlement due to crystallization occurring during high-temperature treatment is required. In addition, in order to impart bias strains in opposite directions to each other at the time of bonding to the high magnetostrictive amorphous magnetic alloy ribbon, it is necessary to twist each shaft, and a very large device is required for that purpose. Furthermore, since the amorphous magnetic alloy ribbon processed into a cylindrical shape according to the shaft diameter has to be adhered on the circumferential surface, there is a problem that a special process is required for applying the adhesive and adhering itself. .

Further, in the torque sensor disclosed in Japanese Patent Application Laid-Open No. 62-182630, since a difference in thermal expansion is used to impart a compressive strain when bonding at high temperature, each shaft as described above is provided. Although a construction method such as adding a twist is unnecessary, in order to give a stable compressive strain, it must be molded into a cylindrical shape and subjected to strain relief annealing in the same manner as described above, and bonding on the circumferential surface must be performed. I won't. Therefore, there is a common problem that the specialty of the device and a special process are required.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a high performance torque sensor having a structure to which an extremely inexpensive device and a simple construction method can be applied.

[0007]

In order to achieve this object, a torque sensor according to the present invention comprises a shaft having a plane parallel to the axial direction and rotatably supported, and the shaft provided on the plane of the shaft. A plurality of slits are formed in the directions of 45 ° and −45 ° with respect to the longitudinal direction of the magnetic field, and the magnetic field sensing means has a magnetostriction to which a compressive strain is applied, and the magnetic field sensing means at a position facing each of the magnetic field sensing means. An excitation / detection coil for exciting and detecting the magnetic field, a magnetic yoke provided outside the excitation / detection coil, and a change in strain generated on the shaft surface due to the torque transmitted to the shaft, through a change in magnetic permeability of the magnetically sensitive means. And an electric means for detecting the magnitude of torque from the self-inductance difference of the excitation / detection coil.

With this structure, since the magnetic sensing means can be attached to the plane of the shaft, an inexpensive and simple construction method can be applied as a device for the attachment, and a high-performance torque sensor can be realized. You can

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in the claims of the present invention
An axis having a plane parallel to the axial direction and rotatably supported,
45 degrees on the plane of the shaft with respect to the longitudinal direction of the shaft.
Magnetism-sensing means having a plurality of slits formed in the directions forming the angles of −45 ° and −45 ° and having a compressive strain, and an excitation for exciting and detecting the magnetism-sensing means at a position facing each of the magnetism-sensing means. And the detection coil, a magnetic yoke provided outside the excitation and detection coil, and a change in strain generated on the shaft surface due to the torque transmitted to the shaft through self-inductance of the coil through a change in magnetic permeability of the magnetic sensing means. A torque sensor having electrical means for detecting a change and detecting the magnitude of torque from the self-inductance difference of the excitation / detection coil, on the plane of the shaft at 45 ° and −45 with respect to the longitudinal direction of the shaft. Since it is possible to bond a magnetically sensitive means having a planar magnetostriction with a plurality of slits formed in the direction that makes an angle, it is possible to apply an adhesive as compared to conventional bonding on the circumferential surface. Easily and enables very stable. Therefore, since it is possible to obtain a very uniform application of compressive strain to the magnetic sensing means, it is easy to prevent characteristic variations from occurring. In addition, since the flat magnet can be used as it is, the high-accuracy jig and the special device have been used to adjust the shaft diameter to a very strict temperature and time under special atmosphere. There is no need to perform cylindrical forming and strain relief annealing. Therefore, it is possible to provide a high-performance torque sensor with a structure that can be applied to an extremely inexpensive device and a simple construction method.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a torque sensor body according to an embodiment of the present invention, and FIG. 2 is a perspective view of a shaft used in the sensor.

In FIGS. 1 and 2, 1 is a shaft made of carbon steel for machine structural use, and 2 is a plane formed on a part of the shaft 1 so that its cross-sectional shape is a D-cut shape. It is a parallel plane. Reference numeral 3 denotes an amorphous metal body having magnetostriction, which is adhered and fixed on the flat surface 2 and serves as a magnetic sensing means, and 4 is a gap at a desired position facing the amorphous metal body 3, which is adhered and fixed on the flat surface 2. Resin bobbins 5a,
5b is an excitation / detection coil wound around the bobbin 4 at a predetermined distance, and 6 is an excitation / detection coil 5 wound on the bobbin 4.
Magnetic yokes attached to the outside of a and 5b, 7 is bobbin 4
And a storage case in which the excitation / detection coils 5a and 5b and the magnetic yoke 6 are housed, and 8 is a bearing which holds the shaft 1 rotatably and is coupled to the storage case 7.

In the present embodiment, the shaft 1 has a diameter of 18.0.
mm, coefficient of thermal expansion is 12.7 × 10 ^-6(1 / ° C)
You. The amorphous metal body 3 is 45 ° with respect to the longitudinal direction of the shaft (
Below, write the "left part". ) And −45 ° (hereinafter “right”
Section ". ) Multiple slits were formed in the direction
Fe-Ni-Mo-B system (for example, # 28 manufactured by Allied Company)
26 MB) and a flat plate 25 mm long with a saturation magnetostriction constant of 12
× 10^-6, The thermal expansion coefficient is 11.7 × 10^-FiveAt (1 / ° C)
is there. Flat amorphous gold without any prior heat treatment
The genus 3 is a bismaleimide triazine-based BT2135
Use the adhesive of Mitsubishi Gas Chemical Co., Ltd.
250 ° C (2 hours), which is sufficiently low, pressurized under atmospheric conditions
To glue. Amorphous metal body 3 adhered and fixed on the flat surface 2
A resin-made boss provided at a desired position facing the
The bin 4 has 132 turns each for excitation and detection.
Output coils 5a and 5b are provided, and further outside thereof
Is permalloy (for example, (77-80%) Ni-Fe
The magnetic yoke 6 composed of the system} is attached. Coil 5
a and 5b are rotating magnets of the magnetization vector of the amorphous metal body 3.
Drive the excitation field by selecting a value that can utilize the
Apply from the road block. With this configuration, the shaft 1
Amorphous metal body adhered and fixed on the flat surface 2 when a force is applied
3 is also distorted, and 45 ° to the longitudinal direction of the shaft and
Amorphous with multiple slits formed at -45 °
As a result, the magnetic permeability of the left and right parts of the metal body 3 changes.
Change the self-inductance of the left and right parts of the coils 5a, 5b.
Become From the difference in self-inductance between the left and right parts,
It is possible to detect the size and direction of the black circle.

In order to attach the amorphous metal body 3 to the flat surface 2 of the shaft 1 in a state in which a compressive strain is applied, the amorphous metal having a thermal expansion coefficient smaller than that of the shaft 1 is used. The body 3 is overlaid with the adhesive, and the temperature is higher than the operating temperature range (for example,
It is possible to complete the heat-adhesion curing at 250 ° C.) and to cool it to the operating temperature range. By this process, a compression strain corresponding to the difference of thermal expansion coefficient × the difference of temperature is automatically applied to the amorphous metal body 3.

As described above, even though the shaft having the circular cross section which is the basis of the rotary shaft is used, since the flat surface portion is provided on the shaft, the method of applying the adhesive is also intaglio transfer, screen printing,
Various high-precision and inexpensive processes such as drawing can be applied.

In addition, since various high-precision and inexpensive processes can be applied to a series of processes from the application of the adhesive to the pressure-adhesive curing, the zero point temperature drift and the sensitivity variation which are the basic performance of the torque sensor are applicable. Etc. are significantly improved.

In addition to this, in order to attach the amorphous metal body 3 in a state in which a compressive strain is applied on the flat surface 2 of the shaft 1, the shaft temperature is exceeded beyond the operating temperature range of the amorphous metal body 3. 1. In the state where any one of the amorphous metal body 3 is heated, the other shaft 1 or the amorphous metal body 3 is bonded by an adhesive, and then the other shaft 1 or the amorphous metal body 3 in the heated state By cooling the body 3 to the above-mentioned operating temperature range, a compressive strain can be applied to the amorphous metal body 3 attached to the plane 2 of the shaft 1.

Further, in the embodiment, the plane having the D-cut cross section is used as the axis 1, but other axes having an oval plane or a square plane may be used. Good.

Further, in this embodiment, the magnetically sensitive means adhered and fixed to the shaft is an iron-based amorphous metal body # 2 manufactured by Allied Company.
826MB was used, but for example, # 2 manufactured by Allied Co., Ltd.
605Co, # 2605SC, # 2605S2, # 26
05S-3A, # 2605SM can also be used. In addition to this, a low Ni composition permalloy {for example, (45-4
8%) Ni-Fe system}, 2% V-Fe-Co alloy, Fe
-(10 to 13%) Al alloy, 3% Si-Fe may be used. Furthermore, although an example of using carbon steel for machine structure as the shaft material as it is has been described, since the cross section of the shaft to which the magnetic sensing means is attached is not rotationally symmetric with the D-cut shape, when magnetized by AC drive, the shaft surface is non-magnetic. A treatment of forming a layer or weakening the magnetization of the shaft surface as compared with the inside is more preferable. As a result, it is possible to expect a significant improvement in zero-point drift during rotation and sensitivity variations. Further, since the plane portion is formed by D-cutting with respect to the axis of the circular cross section, depending on the required specifications, non-heat treated high strength steel (for example, MI
It is also possible to use CA-75 (manufactured by Sumitomo Metal Industries, Ltd.) or the like. As a result, there is an advantage that the strength of the shaft is high, the uniformity is good, and the overall price is low, without requiring special heat treatment such as quenching. Further, Ti and non-magnetic stainless steel can also be used as a matter of course. Also, although Permalloy was used as an example of the magnetic yoke, low carbon steel, soft magnetic stainless steel, pure iron, 1% Si-Fe, Fe were also used.
-Al-Si alloy, Fe-Co alloy, ferrite, ultra-fine crystal soft magnetic alloy Finemet (manufactured by Hitachi Metals, Ltd.), amorphous metal or various materials such as composites with resin can be used Is. In order to achieve higher performance, ultra-fine crystalline soft alloy Finemet (Hitachi Metals Ltd.) with electromagnetic strain
Co) amorphous metal bodies having a small magnetostriction, for example, # 2705M and # 2714A manufactured by Allied Company are preferable.

[0019]

As described above, the torque sensor of the present invention is
An axis having a plane parallel to the axial direction and rotatably supported,
45 degrees on the plane of the shaft with respect to the longitudinal direction of the shaft.
Magnetism-sensing means having a plurality of slits formed in the directions of 90 ° and −45 ° and having a compressive strain, and an excitation for exciting and detecting the magnetism-sensing means at a position facing each of the magnetism-sensing means. And the detection coil, a magnetic yoke provided outside the excitation and detection coil, and a change in strain generated on the shaft surface due to the torque transmitted to the shaft through self-inductance of the coil through a change in magnetic permeability of the magnetic sensing means. It has an electric means for detecting the change and detecting the magnitude of the torque from the self-inductance difference of the excitation / detection coil. A high-performance torque sensor can be realized by making it possible to apply an inexpensive device, a simple and highly accurate construction method as compared with a wearable device.

[Brief description of the drawings]

FIG. 1 is a sectional view of a torque sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a shaft used for the sensor.

[Explanation of symbols]

 1 axis 2 plane 3 amorphous metal body 5a, 5b excitation and detection coil 6 magnetic yoke

Claims (4)

[Claims] 1. A shaft having a plane parallel to the axial direction and rotatably supported, and a plurality of slits provided on the plane of the shaft and forming directions of 45 ° and −45 ° with respect to the longitudinal direction of the shaft. Of the magnetosensitive means having a magnetostriction to which a compressive strain is applied, an exciting and detecting coil for exciting and detecting the magnetic sensitive means at a position facing each of the magnetic sensitive means, and the exciting and detecting coil. A magnetic yoke provided on the outside and a change in strain generated on the surface of the shaft due to the torque transmitted to the shaft are detected as a change in the self-inductance of the coil via a change in the magnetic permeability of the magnetic sensing means, and the excitation / detection coil A torque sensor having electrical means for detecting the magnitude of torque from the self-inductance difference. 2. The torque sensor according to claim 1, wherein the magnetic sensing means is an iron-based amorphous metal body or permalloy. 3. At least a portion of the surface of the shaft is non-magnetic or has a weaker magnetization than the inside.
The described torque sensor. 4. The magnetic yoke comprises low carbon steel, soft magnetic stainless steel, pure iron, 1% Si—Fe, Fe—Al—Si.
The torque sensor according to claim 1, which is made of an alloy, an Fe-Co alloy, a permalloy, a ferrite, an ultrafine crystal soft magnetic alloy, an amorphous metal body, or a composite of these and a resin.