JPH0356838A - Magnetostrictive sensor built into tires - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetostrictive sensor that measures stress acting on a material using a magnetostrictive sensor, and in particular to a magnetostrictive sensor that maintains a constant slip-off to accurately measure stress. This article relates to a magnetostrictive sensor that can be built into tires. [Conventional technology] A method of measuring stress acting on a material using a magnetostrictive sensor is to measure stress acting on large structures such as bridges or long structures such as piping continuously while moving from place to place. It has the advantage of being able to measure stress, and it is expected that it will be increasingly applied to continuous measurement of stress in the future. The principle of stress measurement using the magnetostrictive sensor described above is as follows. In other words, when stress is generally applied to a ferromagnetic material, the magnetic permeability in the direction in which the stress acts due to the magnetostrictive effect becomes slightly larger than the magnetic permeability in the direction orthogonal to the direction in which the stress acts. Then, the magnetostrictive sensor 2
The cores 22 and 23, which are orthogonally combined and make up the material 24, are made to face each other in such a way that each core presents a direction inclined at 45 degrees from the direction of the stress acting on the material 24. Then, when a current is passed through the coil (excitation coil) 25 wound around the core 22 as shown in FIG. However, as shown by the arrow in FIG. 3, a portion flows from the foot 26 of the core 22 in the direction of stress in the material 24, reaches the foot 28 of the core 23, flows through the core 23, and flows into the core 23. From the other leg 29, the material 24 flows again in the direction in which the stress is acting, reaches the leg 27 of the core 22, flows through the core 22, and reaches the leg 26 of the core 22. Part of the magnetic flux follows such a path because the magnetic permeability of the material 23 in the direction in which the stress acts is greater than the magnetic permeability in the direction perpendicular to the direction in which the stress acts. Considering the above magnetic circuit in terms of alternating current magnetic flux, a voltage is generated in the coil (anisotropy detection coil) 30 wound around the core 23. This voltage V is (1)
It is expressed by the formula. V=M・K・(μ8−μy) ・・・・・・・・・〈1
〉However, M: A constant (magnetostriction sensitivity) determined by the magnetic properties of the material and the distance (lift-off) between the sensor and the material K: A constant determined by the excitation conditions and coil conditions μX = Magnetic permeability of the material in the direction of stress action 11y The magnetic permeability of the two materials in the direction perpendicular to the direction of stress action, that is, the output voltage V of the magnetostrictive sensor, is proportional to the difference in magnetic permeability (μ, 1μ,) of the materials, which is also in the direction of stress action of the materials. Since it is proportional to the difference between stress 6X and stress 6y in the direction perpendicular to the direction of stress action on the material (5X - 15y>), the stress acting on the material can be determined from this voltage. [Invention] In the method of measuring stress acting on a material using the magnetostrictive sensor described above, the constant M in equation (1) changes depending on the lift-off of the magnetostrictive sensor, so the lift-off is not constant. Even if the same stress is applied, the output voltage (2) of the magnetostrictive sensor differs depending on the location, and there is a problem in that it is difficult to understand the stress from this V.
Furthermore, there has never been a magnetostrictive sensor built into a tire that maintains a constant lift-off even when the measurement location is continuously moved. This invention solves the above-mentioned problems of the prior art,
The purpose of this invention is to provide a magnetostrictive sensor built into a tire that can accurately and continuously measure the stress acting on a material because the lift-off can be kept constant. (Means for solving the three problems) A magnetostrictive sensor built into a tire according to the present invention uses a magnetostrictive sensor to detect magnetic anisotropy and measure stress acting on a material. This is a magnetostrictive sensor built into a tire, consisting of a tire-shaped case that rotates around a fixed shaft via a bearing, and a magnetostrictive sensor that is suspended from the fixed shaft inside the tire-shaped case.
Effect j The magnetostrictive sensor built into a tire according to the present invention is a magnetostrictive sensor that uses a magnetostrictive sensor to detect magnetic anisotropy and measure stress acting on a material. It consists of a tire-shaped case that rotates, and a magnetostrictive sensor that is suspended from the fixed shaft inside the tire-shaped case. Therefore, with the fixed axis parallel to the measurement surface, the tire-shaped case is brought into contact with the object whose stress is to be measured, and the magnetic anisotropy is continuously detected while rotating the tire-shaped case. Then, the lift-off between the magnetostrictive sensor inside the tire-shaped case and the target object is kept constant, making it possible to measure the stress acting on the material continuously and with high precision over a long period of time. [Example] An in-tire magnetostrictive sensor according to an example of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1 is a side view of a magnetostrictive sensor built into a tire according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a magnetostrictive sensor built into a tire according to an embodiment of the present invention.

Although this magnetostrictive sensor built into the tire is not shown, it is fixed to the frame of the truck! ! l, a tire-shaped case 3 that rotates around a fixed shaft 1 via a bearing 2,
The inside of the tire-shaped case 3 is oval shaped from a magnetostrictive sensor 5 suspended from a fixed shaft 1 by a hanging fitting 4. Furthermore, the tire-shaped case 3 is composed of a side plate 6 and a wheel portion 7 made of hard resin and in contact with the surface of the object to be measured. Since the magnetostrictive sensor built into a tire according to one embodiment of the present invention is configured as described above, the magnetostrictive sensor built into a tire can be moved in a state where the wheel portion 7 is in close contact with the object to be measured. Since the distance wL (lift-off) between the magnetostrictive sensor 5 and the object to be measured is constant at any location on the object to be measured, the magnetic difference is proportional to the magnitude of the stress acting on the object to be measured. The orientation can be detected. Therefore, the stress distribution of the stress acting on the object to be measured can be accurately grasped. [Effects of the Invention] With this invention, the lift-off of the magnetostrictive sensor can be kept constant. It is possible to accurately grasp the distribution of stress acting on the 11I structure.

[Brief explanation of drawings]

FIG. 1 is a side view of a magnetostrictive sensor built into a tire according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a magnetostrictive sensor built into a tire according to an embodiment of the present invention, and FIG. A perspective view showing a state in which stress is being measured. FIG. 4 is a perspective view showing a magnetostrictive sensor.

Claims (1)

[Claims] In a magnetostrictive sensor that uses a magnetostrictive sensor to detect magnetic anisotropy and measure stress acting on a material, there is a fixed shaft, a tire-shaped case that rotates around the fixed shaft via a bearing, and an interior of the tire-shaped case. and a magnetostrictive sensor suspended from the fixed shaft.