JPH0210233A - Strain detector - Google Patents

Abstract

PURPOSE:To improve the temperature characteristics of a strain detector by forming magnetostriction layers comprising Fe-Ni alloy incorporating 35-60wt.% Ni on the surface of a passive member, and providing detecting coils around the magnetostriction layers. CONSTITUTION:Magnetostriction layers 4 are formed with Fe-Ni alloy incorporating 35-60wt.% Ni. Said Fe-Ni alloy is heat-treated in an reducing atmosphere at 1,000 deg.C or more, and inner stress is removed. Thereafter, the Fe-Ni alloy is bonded to a passive member 1 with an epoxy based thermosetting bonding agent. Then, a mask is used, the Fe-Ni alloy undergoes photoetching and the magnetostricton layers 4 in a desired chevron pattern are formed. The two magnetostriction layers 4 and two detecting coils are provided. When the Ni content in the Fe-Ni alloy is 35-60wt.%, curie temperature becomes as high as 400-600 deg.C, temperature dependency of the magnetic characteristics of the magnetostriction layer 4 becomes less and the temperature characteristics of a strain detector can be improved.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a distortion detector.

[Conventional technology]

FIG. 2 shows a conventional strain detector disclosed in, for example, Japanese Patent Application Laid-Open No. 57-211030 or Japanese Patent Application Laid-Open No. 58-9034, where ■ is a shaft-shaped passive member that receives torque, and 2 is a passive member 1. A pair of magnetostrictive layers made of a high magnetic permeability soft magnetic material whose i3 magnetic properties change according to the amount of internal strain generated by the torque applied to the passive member 1, 3 is attached to the outer periphery of each magnetostrictive layer 2. A pair of detection coils are respectively provided and detect the amount of change in the iJ 1ff rate. Each magnetostrictive layer 2 is composed of a plurality of strip-shaped pieces, which are arranged symmetrically at an angle of ±45°.

Next, the operation will be explained. When a torque is applied to the passive member 1 from the outside, a principal stress is generated whose main axis is the long axis direction of the magnetostriction M2 made of a strip-shaped element. For example, if this principal stress is a tensile force for one group of magnetostrictive N2 fragments, it is a compressive force for the other fragment group of the strained layer 2. Generally, when stress is applied to a magnetic material whose magnetostriction constant is not zero, its magnetic properties change, resulting in a change in magnetic permeability. This phenomenon is used in so-called magnetostrictive converters that convert mechanical energy into electrical energy.
This corresponds to the lari effect. In addition, if the magnetostriction constant, which is a quantity that quantitatively represents the magnitude of magnetostriction, is positive, the magnetic permeability increases when a tensile force is applied, and decreases when a compressive force acts, and the magnetostrictive constant It is known that the opposite result occurs when is negative. Therefore, the deformation corresponding to the amount of torque applied from the outside is detected as a change in magnetic permeability of the magnetostrictive layer 2, and this i3 magnetic permeability change is detected by the detection coil 3 as a change in magnetic impedance. The amount of torque applied and the amount of distortion associated with it are detected.

(Problems to be Solved by the Invention) In the conventional strain detector described above, an amorphous magnetic material is used as the magnetostrictive layer 2, but since the Curie temperature of the amorphous magnetic material is as low as about 350°C, the magnetic properties of the amorphous magnetic material are low. It easily changes depending on the temperature and tends to cause strain detection errors.Also, amorphous magnetic materials tend to form an oxide film on their surfaces, and when bonded to the passive member 1 with epoxy adhesive, the peel strength is weak and the signal chain It was something that Koviolet lacked.

This invention was made to solve the above-mentioned problems, and it is possible to improve the temperature characteristics, increase the adhesive strength of the magnetostrictive layer to the passive member, and improve the detection sensitivity. The purpose is to obtain a distortion detector that can

[Means to solve the problem]

The strain detector according to the present invention has a magnetostrictive layer containing 35 to 60% Ni.
It is made of a Fe--Ni alloy containing a heavy weight of %.

[For production]

The magnetostrictive layer in this invention is formed of an Fe-old alloy containing 35 to 60% by weight of Ni, has a high Curie temperature, is chemically relatively stable, and has a large magnetostriction constant.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1st
In the figure, the magnetostrictive layer 4 contains 35 to 60 ffiffi of Ni.
% and some other components such as molybdenum (also called permalloy), and this Pe-Ni alloy has an I+ temperature of 1000°C or higher.

A heat treatment is performed in a reducing atmosphere such as the above to remove internal stress. Thereafter, the Fe--Ni alloy is bonded to the passive member 1 using an epoxy thermosetting adhesive 5, and the adhesive 5 is heated and hardened while being pressurized, and then slowly cooled.

Thereafter, the Fe--Ni alloy is photo-etched using a mask to form the magnetostrictive layer 4 in a desired chevron pattern. Two magnetostrictive layers 4 and two detection coils 3 are provided as in the conventional case.

In the above configuration, the operation as a distortion detector is the same as the conventional one. FIG. 3 shows the relationship between Ni content and Curie temperature. In the case of a Fe-Ni alloy with a Ni-containing wall of 40 to 60%, the Curie temperature is as high as 400 to 600°C, and the magnetic properties of the magnetostrictive layer 4 are Temperature dependence is reduced, and temperature characteristics as a strain detector are improved. Also, Ni is 35-60%
Although the contained Fe-Ni alloy has a somewhat low magnetic permeability, the influence of the anisotropic energy Kv is small and rapid cooling treatment is not necessary. In addition, as shown in Fig. 4, the saturation magnetic flux density Bs is large, and as shown in Fig. 5, the resistivity P is large and the eddy current loss is low when used at high frequencies, making it suitable for high frequency and large amplitude driving. ing. Furthermore, since there are few Ni-containing walls, the cost is low. Furthermore, as shown in Fig. 6, the magnetostriction of Fe-Ni alloy polycrystals has a peak at Ni content of 30 to 60% in the region where the magnetic field strength H is several Oe or less, and the magnetostriction constant increases when used in this vicinity. Larger than amorphous magnetic material,
Sensitivity is improved. Further, Fe--Ni alloys are chemically more stable than amorphous magnetic materials, and can provide higher adhesive strength.

Fig. 7 shows a comparison of sensor outputs when a 16φ 5pcc steel rod is used as the passive member l, and the magnetostrictive layer is formed of various materials. Case (c) is the case of Fe5@Ni5°, and it can be seen that case (c) has almost twice the sensitivity than case (a).

〔Effect of the invention〕

As described above, according to the present invention, the Curie temperature of the magnetostrictive layer is increased, so the temperature dependence is reduced, and the temperature characteristics of the strain detector can be improved. Moreover, since the Fe-Ni alloy is chemically more stable than an amorphous magnetic material, a large adhesive strength can be obtained when a magnetostrictive layer is adhered to a passive member. Furthermore, since the magnetostrictive layer has a large magnetostriction constant, detection sensitivity can be improved.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main parts of a strain detector according to the present invention, Figure 2 is a configuration diagram of a conventional strain detector, Figure 3 is a Curie temperature characteristic diagram of FeNi alloy, and Figure 4 is a diagram of Fe-Ni alloy. FIG. 5 is a saturation magnetic flux density characteristic diagram, FIG. 5 is a resistivity characteristic diagram of an Fe--Ni alloy, FIG. 6 is a magnetostriction characteristic diagram of a Pe--Ni alloy, and FIG. 7 is an output characteristic diagram of a strain detector. DESCRIPTION OF SYMBOLS 1... Passive member, 3... Detection coil, 4... Magnetostrictive layer. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa Diagram t m% 〃Ωcm wt%

Claims (1)

[Claims] a passive member that receives an external force; a magnetostrictive layer made of a Fe-Ni alloy containing 35 to 60% by weight of Ni formed on the surface of the passive member; A strain detector characterized in that it is equipped with a detection coil that detects changes in magnetic permeability due to strain.