JPH01210485A - Element for detecting mechanical quantity - Google Patents

Abstract

PURPOSE:To cause the coefficient of thermal expansion of an element for detecting a mechanical quantity to approach to that of an adhesive layer, by fixing a ferromagnetic material thin belt element for detecting a mechanical quantity on the surface of an object to be measured for a mechanical quantity with an adhesive containing an inorganic fiber. CONSTITUTION:A ferromagnetic material thin belt element for detecting a mechanical quantity for utilizing the stress/magnetism effect of a ferromagnetic material having positive magnetostriction, made of, for example, an amorphous magnetic alloy is fixed on the surface of an object to be measured for a mechanical quantity (e.g., austenitic stainless steel) through a 100-200mum-thick layer of an adhesive containing an inorganic fiber (e.g., carbon fiber).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mechanical quantity detection element that is fixed to the surface of a mechanical quantity measurement object and utilizes the stress-magnetic effect of a ferromagnetic material.

In mechanical quantity sensors that measure LIL force, torque, etc., sensors that utilize the stress-magnetic effect of ferromagnetic materials (especially amorphous magnetic alloys) have been attracting attention in recent years.According to this mechanical quantity sensor, ■ Non-contact detection of force is possible; ■ Force can be directly converted into electrical quantity; ■ The structure of the device as a sensor is simple and miniaturization can be achieved. .

As an example, a thin ribbon 01 of a ferromagnetic material having positive magnetostriction that is sensitive to stress-magnetic effects is wound around a rotating shaft 02,
"Torsional strain" generated on the rotating shaft 02 by the torque T is introduced into the ribbon 01, and the ribbon 01 due to the stress-magnetic effect is
A torque sensor is known that detects a change in the magnetic properties of a magnet, thereby detecting a torque T (see FIG. 11). In a ferromagnetic material with positive magnetostriction, when tensile stress is applied, the magnetoelastic energy in the tensile direction decreases, and magnetization becomes easier in that direction. This phenomenon is called the stress-magnetic effect. In the torque sensor, by utilizing the stress-magnetic effect, a -like easy axis of magnetization (-axis magnetic anisotropy) is created on the entire surface of the ribbon 01 in the direction of an inclination angle α (α>45°) with respect to the circumferential direction 03. gender) is given a U. However, the rotation axis 02
When torque T is applied to the rotating shaft 02 as shown in FIG.
A maximum stress σ expressed as d is the outer diameter of the rotating shaft 02 is generated in the axial direction on the surface of U' is given to the resulting synthesized easy axis of magnetization.

Generally, the magnetic permeability of a magnetic material changes depending on the direction of the axis of easy magnetization with respect to the direction of the magnetic field, so the change in the axis of easy magnetization (Ku → ul) is regarded as a change in magnetic permeability, and the magnitude of torque T is detected. be able to. So, for example, an excitation coil (-order coil).

When a change in magnetic permeability (or magnetic flux density) is detected as a voltage change using a detection coil (secondary coil), a torque-output curve as shown in FIG. 3 is obtained.

By the way, the coefficient of thermal expansion of the adhesive used to bond the ribbon 01 to the surface of the rotating shaft 02 (e.g., the coefficient of thermal expansion of epoxy resin adhesive -40 to 50X 10-8/''C) is that of amorphous magnetism. Coefficient of thermal expansion of alloy (←IOX 10″s/℃),
Or that of a metal rotating shaft (e.g. JIS 5US30
The coefficient of thermal expansion of the 4 materials = 17X 10' / "C') is very large, and the difference in thermal expansion between the adhesive and the ribbon 01 due to temperature changes causes tensile or compressive stress in the ribbon 01. occurs, and the apparent characteristics of the ribbon 01 change depending on the environmental temperature.

To explain this with reference to FIG. 4, the ribbon 0 on the rotating shaft 02
Even if 1 has the characteristics as shown in curve A at room temperature, if the environmental temperature rises and the adhesive thermally expands to a greater extent than ribbon 01, tensile stress will occur in ribbon 01 and the characteristics will change to curve B. (
For example, when the temperature is 80°C), if the ring i temperature decreases and the resin adhesive thermally shrinks more than ribbon 01, compressive stress will occur in ribbon 01 and the characteristics will change [IC (
For example, when the temperature is -40°C). This makes it impossible to accurately measure the torque acting on the rotating shaft 02 when the humidity and temperature of the ring tM change.

Therefore, the present invention was devised against such a technical background, and is fixed to the surface of a mechanical quantity measurement object via an adhesive, and is made of a ferromagnetic material having positive magnetostriction. In a ribbon-shaped mechanical sensing element made of a ferromagnetic material that utilizes magnetic effects, the coefficient of thermal expansion of the adhesive layer interposed between the object to be measured and the mechanical sensing element is close to that of the mechanical sensing element. The purpose is to make the country a country.

The purpose of this process can be achieved by ■ mixing inorganic fibers in the adhesive, or by using a woven fabric made of warp and weft of inorganic fibers impregnated with adhesive as the bonding medium. be done.

The basic principle of the present invention is to use inorganic fibers with a small coefficient of thermal expansion as fillers for adhesives. The coefficient of thermal expansion of inorganic fibers is sufficiently smaller than that of commonly used adhesives, such as carbon I! The coefficient of thermal expansion is polyacrylonitrile (PAN)...3~5x104/'
C. Pitch system...1. 'S ~ 1.7X104/''C, and by using inorganic fibers as a filler, it is possible to reduce the coefficient of thermal expansion of the adhesive layer that fixes the mechanical detection element to the object to be measured. The coefficient of thermal expansion is adjusted by adjusting the amount of inorganic fiber mixed (mixing speed). Figure 5 shows the relationship between fiber volume fraction (Vf) and thermal expansion coefficient when carbon fibers are mixed in an epoxy resin adhesive.According to this graph, the mechanical quantity measurement target is In the case of JIS 303304 material (austenitic stainless steel), in order to bring the thermal expansion coefficient of the adhesive layer close to that of the mechanical quantity detection element (amorphous magnetic alloy) and the mechanical quantity measurement object, m male volume is required. It is preferable to set the coefficient (Vf) to 45 to 85%, and more preferably to 11%, aiming for an intermediate value between the coefficient of thermal expansion of the mechanical quantity detection element and that of the object to be measured.
It is preferable to set the fiber volume fraction (Vf) to 59 to 72%. What should be noted here is that if the fiber volume fraction (Vf) is set too high, the necessary bonding force from the adhesive cannot be obtained, and the mechanical quantity detection element is likely to peel off.

Further, as the inorganic fiber, any of long fibers, short fibers, and whiskers may be used, but short fibers are used.

In the case of whiskers, if the thread diameter is extremely fine, the thickness of the adhesive layer can be made sufficiently small;
It is difficult to handle when blending and control the adhesive layer thickness. Long fibers can be used as woven fabrics, and they can be easily handled by impregnating them with adhesive. The layer thickness of the adhesive layer including the woven fabric (herein, woven fabric is also considered to be a filler) is defined by the thickness of the woven fabric,
The thickness of the adhesive layer can be uniformly and precisely controlled over the entire adhesive surface.

The thickness of the adhesive layer is determined so that the strain generated on the surface of the mechanical measurement object due to the action of external force is correctly transmitted to the mechanical quantity detection element, which is a band of ferromagnetic material (thickness: 30 μm). It is best to make it as thin as possible within a range that ensures bonding strength, and a layer thickness of about 100 to 200 μm is preferred. As the woven fabric for the filler, which allows the thickness of the adhesive layer to be easily controlled, for example, a fabric made of carbon fiber is recommended. Commercially available carbon fiber woven fabrics are provided by twisting 1,000 to 6,000 Il miscellaneous fibers with a wire diameter of 5 to 8 μm into a thread, and weaving this thread as warp and weft threads.In the present invention, Ichihara 100 ~4
It is appropriate to use one with a diameter of 00 μm. Ichihara 100
μm is the lower limit of commercially available products, and the reason why the weight is limited to 400 μm or less is to ensure a sufficient thickness of the adhesive layer. Examples of commercially available carbon fiber woven fabrics that can be used include Toshiku Co., Ltd. Ill e6151B (trade name) and Kanebo (trade name).
Examples include CF1101B (trade name) manufactured by Co., Ltd.

Support JLfL Yu ■The warp yarn is made by twisting 1000 carbon fibers with a wire diameter of 7 μm.3. A woven fabric 2 having an Ichihara thickness of 140 μm as a weft thread 4 was prepared (FIG. 6).

■The medium is a woven fabric 2 impregnated with epoxy resin adhesive to give a fiber volume fraction (Vf) of 65%, and is made of an amorphous magnetic alloy in the same way as the ribbon 01 shown in Figures 1 and 2. The thin ribbon 1 was wound around the outer periphery of a steel shaft 5 and joined.

At that time, the warp thread 3. The weft 4 is in the maximum stress direction (the maximum stress direction that occurs when torque T is applied to the shaft 5...Fig. 2 +
(see Fig. 6). Warp 3. If the weft yarns 4 are oriented in this manner, the Young's modulus of the adhesive layer will be that of the warp yarns 3. The deformation behavior increases in the direction of the weft thread 4 and exhibits the same deformation behavior as the strain produced on the outer periphery of the shaft 5 by the torque T, and the strain on the shaft 5 is accurately transmitted to the ribbon 1.

Support 1 JL Yu■ Prepare a thin strip 1^ that differs from the thin strip 1 used in Example 1 only in that a plurality of mutually parallel inclined slits 1a (angle of inclination θ = 45°) are formed. (Figure 7).

■The inclined slit 1a of the thin strip 1A and the warp thread 3 of the woven fabric 2. As in Example 1, the ribbon 1A was wound around the outer periphery of the shaft 5 and fixed so that the weft thread 4 coincided with the direction of the maximum stress generated on the outer periphery of the shaft 5 under torque.

(2) Figures 8 and 9 show how the torque T acting on the shaft 5 is measured. Excitation coil 8. The magnetic cores 6, 7, and 7 around which the detection coils 9, 9 are wound are arranged close to each other at right angles to the 8 sides of the ribbon 1, and a high frequency current is supplied to the exciting coil 8, and the terminal wire 10 of the detection coils 9, 9 is (Figure 9 conceptually shows the arrangement of the excitation coil 8 and detection coil 9).

As mentioned above, this induced voltage (V) is caused by the change in magnetic permeability of the ribbon 1A made of an amorphous magnetic alloy, that is, by the tensile strain introduced into the ribbon 1A by the torque T applied to the shaft 5. It changes depending on the magnitude, and if the relationship between magnetic permeability and torque T is investigated in advance, the magnitude of torque T can be determined by measuring the induced voltage (V).

(2) The torque-output curve obtained in this case is shown in Fig. 4. Curve A' matches the previous curve A, and curve B' (when the temperature is 80°C)2 curve C' (when the temperature is -40°C) is different from the previous curve A (or A). ).

As is clear from the above description, according to the present invention, the following effects can be obtained.

■Since inorganic fibers with a small coefficient of thermal expansion are mixed in the adhesive that fixes the thin strip-shaped mechanical quantity detection element made of ferromagnetic material to the surface of the object to be measured, the coefficient of thermal expansion is smaller than that of the adhesive alone. The coefficient of thermal expansion of the adhesive layer is small, and it is possible to make the coefficient of thermal expansion of the adhesive layer sufficiently small by appropriately selecting the amount of inorganic fiber blended. It is best to adjust the thermal expansion coefficient of the adhesive layer to a value between the thermal expansion coefficient of the mechanical quantity measurement object and that of the mechanical quantity detection element, and by reducing the thermal expansion coefficient of the adhesive layer. It is possible to effectively prevent peeling of the mechanical quantity detecting element due to differences in thermal expansion and thermal contraction between the adhesive layer and the adhesive layer.

(2) In an example in which a woven fabric consisting of warp and weft yarns is used as the inorganic fiber, the thickness of the adhesive layer can be accurately controlled and the layer thickness can be easily made uniform over the entire joint surface. Furthermore, by using a woven fabric, the Young's modulus of the adhesive layer can be improved, and the strain generated on the surface of the mechanical quantity measurement object due to the action of external force can be accurately transmitted to the mechanical quantity detection element.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams explaining the principle of detecting the torque applied to the shaft by joining a piece made of ferromagnetic material around the shaft, and Figure 3 is a diagram showing the detection of mechanical quantities made of ferromagnetic material. FIG. 4 is a graph showing a torque-output curve as an example of shaft torque measurement by a torque sensor using an element, and shows how the torque-output curve changes depending on temperature due to the large coefficient of thermal expansion of the adhesive. The graphs shown (conventional characteristic curves A, B,
C and characteristic curves A I, B l as examples of the invention
. C'), Figure 5 is a graph showing the effect of the volume fraction (vr) of inorganic fibers on the thermal expansion coefficient of the adhesive layer, and Figure 6 is a graph showing the influence of the volume fraction (vr) of inorganic fibers on the thermal expansion coefficient of the adhesive layer. A partially cutaway diagram showing a state in which the element is wrapped and fixed, Figure 7 is a diagram showing a mechanical quantity detection element with multiple slits formed, and Figure 8 is a diagram showing an adhesive-impregnated woven fabric around the shaft. Figure 9 is a perspective view showing the state in which the mechanical quantity detecting element is wound and fixed through the wire and the device for detecting changes in magnetic permeability of the mechanical quantity detecting element.
FIG. 3 is a diagram conceptually illustrating the wiring of the detection device using a different display method. 1... Thin strip, 2... Woven fabric, 3... Warp, 4...
Weft, 5... Axis, 6.7... Magnetic core, 8... Excitation coil, 9... Detection coil, 10... Terminal wire.

Claims (2)

[Claims] (1) In a thin strip-shaped mechanical quantity sensing element made of a ferromagnetic material that is fixed to the surface of a mechanical quantity measurement object via an adhesive and that utilizes the stress-magnetic effect of a ferromagnetic material that has positive magnetostriction. , A mechanical quantity detection element characterized in that inorganic fibers are mixed in the adhesive. (2) In a thin strip-shaped mechanical quantity sensing element made of a ferromagnetic material that is fixed to the surface of a mechanical quantity measurement object via an adhesive and that utilizes the stress-magnetic effect of a ferromagnetic material that has positive magnetostriction. . A mechanical quantity detecting element, wherein the adhesive is an adhesive impregnated into a woven fabric made of warp and weft of inorganic fibers.