JPH02154129A - Strain detector - Google Patents

Abstract

PURPOSE:To facilitate a handling, to increase sensitivity, and to prevent a noise sound from being generated by providing magnetostrictive element piece groups fixed on a driven shaft made of PE 'permalloy(R)' and yokes on the outer periphery of a detection coil. CONSTITUTION:When torque is applied to the driven shaft 1, stress is generated and the magnetostrictive element piece groups 7 and 8 made of PE 'permalloy(R)' vary in magnetic permeability owing to the strain. Detection coils 12 and 13 detect the magnetic permeability variation as variation in magnetic impedance and a detecting circuit 18 generates an output V corresponding to the applied torque. The magnetostrictive element piece groups 7 and 8, yokes 14 and 15, and a shield 17 are made of 'permalloy(R)' and easy to handle. Further, the magnetostrictive element piece groups 7 and 8 are high in magnetic permeability and have large magneto-strictive constants, and the detection sensitivity is improved. Then the yokes 14 and 15 pass pieces of magnetic flux produced by the detection coils 12 and 13 concentrically to prevent the leak of magnetic flux and increase the sensitivity several times, and a resonance phenomenon due to magnetic strain in not caused to prevent a noise sound from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a strain detector that detects distortion caused by shaft torque of a passive shaft such as a rotating shaft.

(Prior art) Fig. 2 shows a conventional strain detector shown in, for example, Japanese Unexamined Patent Publication No. 57-211030, where l is a passive shaft that receives torque, and 2 and 3 are fixed to the passive shaft 1 in a chevron shape. It is a group of magnetostrictive elements whose magnetic permeability changes according to the amount of strain generated by the torque applied to the passive shaft l, and each has an angle of +45°.
, -45'. 4.5 is magnetostrictive piece group 2.
This is a detection coil that is wound around 3 and detects the change in magnetic permeability of each.

Next, the operation will be explained. When torque is applied to the passive shaft 1 from the outside, a principal stress is generated whose main axis is the long axis direction of the magnetostrictive element groups 2 and 3, and this principal stress is applied as a tensile force to one of the magnetostrictive element groups 2 and 3. and acts as a compressive force on the other. In general, when stress is applied to a magnetic material, its magnetic properties change, resulting in a change in magnetic permeability. This phenomenon is used in magnetostrictive transducers to convert mechanical energy into electrical energy, and when the magnetic material is deformed, This corresponds to the Villari effect in which magnetic permeability changes depending on the amount of deformation. Additionally, when the magnetostriction constant, which quantitatively represents the magnitude of magnetostriction, is positive, the magnetic permeability increases due to tensile force and decreases due to compressive force, and the opposite result occurs when the magnetostrictive constant is negative. It is also known that Therefore, the magnetic permeability of the magnetostrictive element group 2.3 changes due to deformation according to the amount of torque applied from the outside, and the detection coil 4.5 detects this change in magnetic permeability as a change in magnetic impedance.

Further, JP-A-59-180338 discloses a torque sensor in which a magnetic core made of an amorphous alloy is fixed around a passive shaft, and JP-A-60-260821 discloses a torque sensor in which a magnetic core made of an amorphous alloy is fixed around a passive shaft. Go-N to prevent magnetic flux leakage
A torque sensor is shown in which a yoke made of an i-based amorphous 1 magnetic alloy is disposed.

[Problem to be solved by the invention]

However, the magnetic properties of amorphous magnetic alloys are not stable over time due to their low Curie temperatures, and due to the manufacturing process, they have anisotropy in the longitudinal direction. When used, anisotropy perpendicular to the magnetic flux is forced,
Even if it could be improved by heat treatment in a magnetic field, it was brittle and difficult to handle, and sufficient adhesiveness could not be obtained. Also, amorphous '1
The magnetic alloy does not have a sufficiently large magnetostriction constant, making it difficult to obtain sufficient sensitivity, and when used as a yoke, there is a problem in that it generates noise due to the resonance phenomenon caused by magnetostriction.

This invention was made to solve the above-mentioned problems, and aims to provide a distortion detector that is easy to handle, increases sensitivity, and prevents the generation of noise. .

[Means for Solving the Problems] A strain detector according to the present invention includes a group of magnetostrictive elements formed of l'E permalloy and fixed on a passive shaft, and a P
It is made of C permalloy and includes a yoke provided around the outer periphery of the detection coil.

[For production]

The magnetostrictive element group in this invention is formed from PE permalloy, and is magnetically stable, and has a large magnetic permeability and magnetostriction constant.The yoke in this invention is formed from PC permalloy, and is magnetically stable and has zero magnetic flux. No resonance phenomenon occurs.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows the configuration of the strain detector according to this embodiment, where 6 is the central axis of the passive shaft 1, 7.8 is a magnetostrictive element group formed in the same manner as the conventional magnetostrictive element group 2.3, and Only the material is different,
It is made of PE permalloy. 9.10 corresponds to the bearing of the passive shaft 1, 11 a cylindrical coil bobbin supported by the bearings 9 and 10 and arranged around the passive shaft, 12.13 corresponds to the coil bobbin 11 and the magnetostrictive element group 7.8. 14.15 is a yoke made of PC permalloy of approximately 80% Ni, which is provided at intervals around the detection coil 12. A first shield is provided and is formed from a high conductivity metal material such as Cu or AI. 17 is a second shield provided on the outer periphery of the first shield 16, and P
Made from C permalloy. 18 is detection coil 1
This is a detection circuit connected to the output side of 2.13.

In the above configuration, when torque is applied to the passive shaft 1, stress is generated, and the magnetic permeability of the magnetostrictive element group 7.8 changes due to the strain. The detection coils 12, 13 detect this change in magnetic permeability as a change in magnetic impedance, and the detection circuit 18 generates an output (2) according to the applied torque.

In the above embodiment, (n strain element groups 7, 8, yoke 14
．． 15 and the shield 17 are made of permalloy, which is magnetically stable and easy to handle. Furthermore, the magnetostrictive element group 7.8 is made of PE permalloy, and has high magnetic permeability and a large magnetostriction constant, improving detection sensitivity and providing a large dynamic range. In addition, the yoke 1415 has a movement that concentrates the magnetic flux generated from the detection coils 12 and 13, prevents magnetic flux leakage, and increases sensitivity several times, but at the same time, since it is formed of PC permalloy with zero magnetic flux, it does not have magnetostriction. Therefore, the resonance phenomenon caused by the noise does not occur, and the generation of noise can be prevented. The first shield 16 is also provided to prevent magnetic flux leakage and protect the output from disturbance magnetic fields, but it is made of a highly conductive metal material such as Cu or A4, and is made of a metal material with high conductivity such as Cu or A4. The depth is as shown in Figure 3, and the detection coil 12.13
When the power frequency applied to the magnetic flux is 5Hz or more, the magnetic flux is completely cut off. The second shield 17 is made of PC permalloy, and also provides magnetic shielding.
By applying an insulating coating such as -go to form a multilayer structure, the shielding effect at high frequencies can be enhanced.

〔Effect of the invention〕

As described above, according to the present invention, permalloy is used for the magnetostrictive element group and the yoke, making it magnetically stable and easy to handle. In addition, P with a large magnetostriction constant is used as the magnetostrictive element group.
E-permalloy is used to obtain a large change in magnetic permeability, improving sensitivity and expanding the stress measurement range. moreover,
The yoke is made of PC permalloy with zero magnetostriction, which can prevent the generation of noise due to magnetostriction and is resistant to external disturbances such as thermal stress.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a strain detector according to the present invention, FIG. 2 is a sectional view of a conventional strain detector, and FIG. 3 is a characteristic diagram of the skin depth of each material. 1... Passive shaft, 7.8... Magnetostrictive element group, 1213.
...Detection coil, 14.15...Yoke. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] A passive shaft to which stress is applied, a group of magnetostrictive elements made of PE permalloy and fixed on the passive shaft and whose magnetic permeability changes according to strain, and a group of magnetostrictive elements wound around the group of magnetostrictive elements, a detection coil that detects a change in magnetic permeability of a group of elementary pieces;
A strain detector characterized in that it is made of PC permalloy and includes a yoke provided around the outer periphery of a detection coil.