JPH04143601A - Method of measuring strain and strain sensor used therefor - Google Patents

Abstract

PURPOSE:To enable precise measurement of a minute strain by fixing the opposite ends of a plate-shaped or thin-film-shaped element to an object of measurement of the strain and by measuring magnetostriction of the element in a part not being fixed. CONSTITUTION:First, two rings of an outside diameter 26 mmphi, an inside diameter 20.02 mmphi and a width 10 mm are put on a round rod M1a of a diameter 20 mmphi and a length 180 mm so that the centers of the respective widths thereof are positioned at 70 mm from the opposite ends of the round rod M1a, and both of them are spot- welded to the round rod M1a at three spots on the side of the end of the round rod M1a respectively. Next, an amorphous substance of a width 50 mm, a length 81.68 mm and a thickness 30 mum is wound round on the circumference of the round rod M1a so that the opposite ends thereof are aligned with the opposite ends of the rings. Besides, two rings of an outside diameter 30 mm, an inside diameter 25.9 mm and a width 10 mm are prepared separately, and each of them is heated to about 600 deg.C and put on the amorphous leaf so that it overlaps the ring spot-welded to the round rod M1a. By a combination body of the round rod M1a obtained in this way and a strain sensor, S/N of the sensor can be improved and a minute strain can be measured precisely.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a strain measurement method and a strain sensor used therein, and in particular, the present invention relates to a strain measurement method and a strain sensor used therein. The material is mainly composed of metallic elements called molten metal, and is produced by rapidly cooling and solidifying from a molten state, so it does not have a crystal structure (hereinafter referred to as amorphous). It uses the magnetostrictive properties of the material to reduce the distortion caused by the torque applied to the rotating shaft. The present invention relates to a strain measurement method used for electromagnetically detecting strain (hereinafter referred to as strain) in a non-contact manner, and a strain sensor used for the measurement. Although the expression "detecting strain" is used here, if the strain on the rotating shaft or strength member is known, the applied stress can be estimated from the characteristics of the rotating shaft or the material of the member. is a stress sensor, or when detecting rotational torque, a strain sensor is the same as a torque sensor.

(Prior Art) Many attempts have been made to measure strain using the magnetostrictive properties of metals and amorphous materials. However, ordinary magnetic metals have a low magnetic output, and amorphous metals with a high magnetic output can be manufactured by various methods such as sputtering, vapor phase chemical methods, plating methods, etc. in addition to the rapid cooling method, but all of them have a diameter of several 100 μm. It could only be obtained as products in the form of thin sheets, thin wires, or powders, and could only be used for limited purposes.

Therefore, in the case of magnetic metals, the magnetic-electrical signal output in response to distortion is small in most cases, and in the case of three-step conversion from distortion to magnetism to electricity, distortion is caused by distortion noise caused by the vibration of the prime mover, etc., and magnetism is caused by the surrounding noise. Magnetic noise due to environmental conditions and electricity are similarly influenced by propagation noise from surrounding electronics and electrical equipment, and noise on circuits during electrical amplification. These noises have almost no relation to the magnitude of distortion or the magnitude of change in distortion, so if the change in distortion is small, the noise in response to a change in signal output is large, that is, the so-called S/N
The ratio is not good, making precise measurement difficult.

In addition, some magnetic metals have excellent magnetostrictive properties, but when considering applying stress to the metal and measuring strain, it is not practical due to problems in terms of strength, aging characteristics, and economy. On the other hand, in the case of amorphous, the shape is limited as mentioned above, so there are similar problems in using it as a strength member, and it is difficult to use it as a strength member.
As shown in No.-224623 "Torque sensor",
Attempts have been made to bond it to ordinary metals using an explosion, but many technical and economic problems have prevented it from being put to practical use.

(Problems to be Solved by the Invention) As explained in the previous section, even if an attempt is made to measure the strain of ordinary magnetic metals, such as steel, using the magnetostriction of the magnetic metal, the output is low, making it difficult to measure low distortion. It is difficult, and the S/N ratio against noise is low, making it extremely difficult to put it into practical use. On the other hand, when trying to electromagnetically measure the strain of a metal with excellent magnetic properties as a strength member, the magnetic properties change significantly over time, making it difficult to solve technically and economically. is also not appropriate. Since amorphous can only be obtained as foil, wire, or powder, it cannot be used as a strength member as it is; it will crystallize and cease to be amorphous at temperatures above 300°C to 400°C, depending on the composition. , it cannot be sintered or welded with heat, as it loses its excellent magnetic properties. Attempts have been made to use the explosion pressure of explosives to perform compression molding, or to use explosive pressure welding on ordinary metals, but these efforts require many complicated processes and are economically difficult to put into practical use. is difficult.

Of these, the most effective attempt is to explosively weld an amorphous foil several OuII+ thick to the surface of an ordinary metal, thereby imparting magnetic properties to the amorphous portion and imparting strength to the metal. Although it is considered to be close to practical use, it is technologically advanced and requires careful attention in the manufacturing process, resulting in an economic disadvantage.

The reason why amorphous is joined to normal metal by explosive welding is as follows.
This is because when welding or hot pressure welding is used, amorphous material crystallizes and loses its excellent magnetic properties. If possible, technical and economic difficulties can be avoided if similar effects can be obtained without using explosive welding. In addition, in the case of magnetic metals, although they have the same composition as amorphous metals, they are not amorphous but are finely crystallized by rapid cooling and exhibit excellent soft magnetism, and other previously known Regarding magnetic metals, it is appropriate to use a metal with excellent magnetic properties and soft magnetic properties for the receiver by means other than explosive welding, and use a material with excellent properties as a strength member for the stress-receiving part. It is believed that there is. However, like amorphous metals, the magnetic properties of most magnetic metals deteriorate when high temperatures are applied, so it has been difficult to join them to other metals using methods other than explosive welding.

(Means for Solving the Problems) The present invention was achieved as a result of repeated theoretical and experimental studies to eliminate the drawbacks of the conventional non-contact measurable strain sensors described in the previous section. We focused on the fact that when a thin plate, foil, or wire of a sensor element made of metal or amorphous is partially fixed to an object to be measured for distortion in two or more places, the relative positional fluctuations of the fixed parts also distort the sensor element. This method takes advantage of the fact that distortion is proportional to the distortion of the object to be measured.

FIG. 1 is a diagram for explaining the principle of a strain sensor according to the present invention. Figure 1a shows the cross section, ho is the radius R1
+1m round bar, sea is round bar 3. A cylindrical sensor element surrounding with an outer radius R11m at an interval d,
Baa is an annular spacer 811 for providing a distance d between the round bar Mlll, which is the object to be measured for strain, and the sensor element 511m, and C1m is an annular spacer 811 for connecting the sensor element S1m.
Round bar through? -11 is a welding part for metallurgically joining the sensor element S+m to the annular spacer B111 and the annular fixture C1m, and LIll is the annular spacer B1. of the sensor element S1M. And the part of the round bar that is not in contact with the annular fixture Cl1m? l
+a means the length along the longitudinal axis Al1m.

First, the round bar M1 shown in FIG. 1a. and sensor element 5i11
The principle when the round bar is subjected to torsional strain centered on the axis Al11 by other configurations will be explained. Such an example of measuring the torsion of a shaft is suitable for use as a so-called torque sensor, which estimates the loaded torque from the torsion of the shaft, for example, when the rotation of a prime mover is transmitted to a load by the shaft. Therefore, hereinafter, when a round bar is twisted by a load around the axis, the load around the axis will be referred to as torque, and will be expressed in units of N-m (kg-+yf/s") or kgf.-.

When a torque is applied to both ends of the round bar M+a, the round bar exhibits a twist with a twist angle ψ. The definition of the twist angle ψ means how much the straight line passing through the central axis of the cross section of the round bar is twisted with respect to that at the reference position 1. In this case, the torque T, the length of the rod, and the diameter D
, the following relationship holds true between the torsion angle ψ. However, in the case of the figure, D・2R,. 1, and G is the stiffness modulus of the material.

ψ= 32LT/πD'G -----(1) For example,
20 kg on a steel round bar with a length of 0.2 m and a diameter of 0.02 m.
When a torsional moment of 1.96 If the diameter is D, then τ= 16 T/πD' ------- From (2), r=16X1.96X102kg Hrrf/s2/
hr X(0,02m+)') =1.248XIO8
kg]/rrf-s2=124.8 MPa': 12
．． 7kgf/m" torsion angle ψ is: ψ=32X0.2mX1.96XlO"kg -rtr
/s2/ (πX (2X10-2m+)'X8.16
X10”kg-m/%・s2) = 3.06xlO
-2=1.75'' is obtained.

Sensor element S1. is sufficiently thinner than the round bar 3, and therefore has low strength, and does not provide resistance to the twisting of the round bar Mi1m, and the annular spacer B1m and the annular fixture C1m are also sufficiently small to resist the twisting of the round bar Mi11. If there is no effect, the twist angle per length of the round bar Mll will also not change. The definition of this twist angle ψ is that when one end of a round bar of a certain length is fixed and the other end is twisted, the twist angle is the twist angle. varies depending on location. Therefore, in order to know the torsion angle at any position of the round bar, it is convenient to introduce the torsion rate λ, which is the value obtained by dividing the torsion angle φ by the distance from the fixed end to that position. The torsion rate λ is given by λ=ψ/L (3) where L is the length from the fixed end to the torsion angle measurement position. Therefore, the torsion rate λ1 of the round bar M1m
．． If the twist angle is ψ11 and the length of the round bar is Ll, then ψ
+-/L+. Above length 0.2+++, diameter 0
．． 20kg f-o+-1, 96X1 on a round rod of 02 lin
The torsion rate λ1. when a torsion moment of 0" kg・i/SZ is applied is λ 1. = 1.75" 1
0.2m+・8.75°/-. Therefore,
The torsion rate λ11 of the round bar M is the same value no matter where it is taken, and the sensor element S1M is connected to the annular spacer B1.
As long as it is firmly fixed to the round bar MIm by the annular fixing member C1m and the annular fixing member C1m, it will be twisted at the same twist rate. That is, the sensor element 5l11 and the round bar 1 are twisted at the same angle at the same position in the ring. Therefore, sensor element S1m
reproduces the twist of the round bar Mu as it is. However, at this time, the shear strain on the surface of the sensor element 511m is
It must be noted that this is different from that of the m surface.

This is because the shear strain τ on the surface of a round bar or tube is expressed as τ=rψ=λr, where r is the radius, r is the length, and ψ is the twist angle.
---- (4) Therefore, from FIG. 1a, the radius R111 of the sensor element S0 is clearly the round bar M+
The radius R1° of m is larger, i.e. R++s > R
,. , is. Therefore, the shear strain on the surface of the sensor element 5111 is τ10, and the shear strain on the surface of the round bar M1m is τ. , then τzm > τ+o−−−−−−(5), and the formula (4
) from rl1m = λ + aRzm - Qi - (6) τl
On' λ1. R++1. -----(7). That is, in the sensor element SIm, the strain of the round bar Mu is mechanically amplified in shear strain.

Therefore, as shown in FIG. 1a, when measuring the torsion of the round bar, the shear strain can be mechanically amplified by placing the sensor element 5i11 away from the surface of the round bar M1□0.

The purpose of installing the sensor element 51m away from the surface of the round bar MILL in this way is to mechanically amplify shear strain, and also has the following effect.

First, the round bar M1m is made of magnetic metal, and the sensor element S+a
When installed in contact with the surface of the round bar Mll+, if you try to measure magnetostriction by exciting the sensor element 5l11 with an electromagnet, etc., the round bar M1m will also be excited at the same time, which may affect the magnetostriction measurement of the sensor element S1m. There is. Also,
Marubo A3. If the sensor element SIm is at a high temperature, the sensor element SIm will be affected by the heat and the measurement or material properties may be adversely affected. The configuration shown in FIG. 1a is also effective when preventing the influence of the round bar M1m from reaching the sensor element S1m.

The annular spacer B111 and the annular fixture C1m are round bars that can withstand twisting of the sensor element SIM? Must be securely fixed at l+m. One of the methods for this is shrink fitting. First, an annular spacer Blfi, which has an inner diameter slightly smaller than the outer diameter of the round bar M, is heated to several hundreds of degrees Celsius, so that the inner diameter becomes larger than the outer diameter of the round bar M due to thermal expansion, and in this state, the round bar When the annular spacer B+a tries to return to its original inner diameter at room temperature, the round bar M,
, the round bar MIm is strongly tightened, and the annular spacer B1. is firmly fixed mechanically. Annular fixture C1
Similarly, sensor elements 5lll are connected to annular spacer B.
The annular spacer B1m, the sensor element SIm and the annular fixing metal fitting C1 are wrapped around 1m and then shrink-fitted.
m is mechanically and firmly fixed to the round bar MIM. When fitting the annular fixture C11 onto the upper surface of the sensor element S1m, the sensor element 511
If there is a risk that the characteristics of the sensor element Sea may be deteriorated, the sensor element Sea may be thermally protected by water cooling or the like.

Also, if you want to completely avoid the thermal effects of shrink fitting,
It may also be cold fitted. This is the same in that an annular spacer B111 having an inner diameter slightly smaller than the outer diameter of the round bar M is prepared, but the round bar M11 is cooled with a low-temperature substance such as liquid nitrogen, and shrinks due to the low temperature. The outer diameter of the round bar M is made smaller than the inner diameter of the annular spacer B111, and when the temperature returns to room temperature, the round bar M is inserted into the annular spacer B111.
This is a method to tighten it to 1m. Furthermore, when fitting the annular fixture C1m onto the top surface of the sensor element 5l11,
Similarly, the round rod Ml11 and the annular spacer BJII may be cooled and then fitted together. Push-fitting is a method for fixing by mechanical tightening alone, without completely relying on high-temperature or low-temperature thermal methods. This is a round bar M+
When trying to fit the annular spacer B111 by inserting it into a part of the outer periphery of a from the end, the annular spacer B1M is tapered so that the outer diameter increases as it advances.
The inner circumference of the BIB is also tapered to match that, and as it is inserted, the annular spacer BIB becomes circular! This is a method of tightening M + -. By providing a similar mechanism on the outer periphery of the annular spacer Ill+m and the inner periphery of the annular fixture C4, the annular spacer B111 and the sensor element S1
m and the annular fixture C1m can be mechanically and firmly fixed to the round bar M111.

Regarding these mechanical fixing methods, how to set the inner circumference, outer circumference, or taper dimensions of each part can be determined by those with general machining knowledge, such as the coefficient of thermal expansion of the metal used, It can be easily determined according to values such as Young's modulus and elastic limit value.

In the above mechanical fixing method using only tightening, if twisting is repeated over a long period of time, there is a risk that displacement may occur and the fixed state may change, leading to erroneous measurements.

In such a case, it is conceivable to use a mechanical fixing means other than tightening, such as a key or a non-stop pin, or to use such mechanical means without tightening at all. However, when only tightening is used, there is an advantage that it does not introduce causes such as key grooves and dowel pin holes that reduce component strength due to a reduction in component cross-sectional area or stress concentration due to notches.

Welded part in Figure 1a 1. The annular spacer Bl! is formed by metallurgical means. , for integrally fixing the sensor element S1m and the annular fixture C0. In the figure, the round bar M1m is not welded, but if necessary, the round bar M11 may also be welded. In most cases, the magnetic material that is the sensor element is sensitive to high temperatures; a typical example of amorphous material is 300 to 40
It begins to crystallize at a temperature of 0″C, degrading its excellent magnetic properties.

The same applies to quenched metals, and when welding,
Care must be taken to ensure that the temperature of the sensor element does not deteriorate its magnetic properties.

However, the parts of the sensor element material that are not involved in strain measurement,
For example, this does not apply to the portion sandwiched between the annular spacer B0 and the annular fixture Cl1B.

During welding, the following measures can be considered to prevent the sensor element from overheating.

■ Minimize the welded area as much as possible by means such as spot welding. ■ Weld the sensor element while immersing it in water in a container or cooling it with running water.

■ If the round bar Mim, annular spacer BIB, and annular fixture C4 have sufficient heat capacity, it may not be necessary to cool the sensor element, but even in such a case, make sure that the magnetic properties of the sensor element do not deteriorate. Care should be taken to prevent overheating by taking measures such as welding while measuring the temperature rise of the sensor element.

Although only welding has been described above as a means of metallurgical joining, other means such as brazing or explosive welding may be employed. Measures to prevent overheating of the sensor element in the case of brazing are the same as those in the case of welding. In the case of explosive welding, there is no need to consider overheating, but it is necessary to take measures against distortion of components such as round bars due to explosive pressure. We are fully aware of the problems and countermeasures that need to be taken.

When metallurgically fixing the sensor element to a round bar by welding or brazing, if the round bar is a heat-treated metal, a change in the heat treatment condition is necessarily applied. If this is undesirable, fixing should be done in a way that does not affect heat, but the method to use depends on the type of material used, the conditions for measuring strain, and the stress transmitting member of the round bar being measured. As it is determined by the design specifications such as usage conditions as
-Cannot be explained generally. However, a person skilled in the art who is familiar with the design of machinery can easily select a fixing method from among the above fixing methods under various conditions.

Figure 1 shows a configuration that can be used when there is no mechanical amplification effect, and the round rod is made of a non-magnetic material, and there is no need to take into account the effect of the round rod on the sensor element, as in the case of Figure 1 a. The sensor element Slk is fixed in close contact with the round bar. However, the portion of the sensor element Slb that is not fixed by the annular fixture C0 only needs to be in mechanical contact with the round bar Mlb, and metallurgical bonding is not required. In addition, in the case of this figure, the welding part hub is a round bar Mo
, annular spacer fl+b, annular fixture C1b, and sensor element S1. However, depending on the situation as mentioned above, it may not be welded at all, it may not be welded to the round bar Mllll as shown in Figure 1a, or it may It is necessary to choose by brazing instead of relying on it.

In the case of Figure 1, the sensor element Slb is not fixed to the round bar Lb except for the fixed part, but it is in close contact with it, so
The shear strain of the sensor element Slk can be considered to be the same as the shear strain of the round bar M11+, if the thickness of the sensor element Slb is ignored.

FIG. 2 shows that in the strain sensor shown in FIGS. 1a and 1b, the sensor elements SIm and 51b surround the round bars M and Mlb, whereas the sensor elements SIm and 51b surround the round bars M and Mlb, whereas FIG. 3 is a plan view of a situation in which the sensor element S2 is attached to a part of the outer periphery of the round bar M2 in a direction along the axis, as seen from the side to which the sensor element S2 is attached. Since this is a plan view, the annular fixture C2
is visible, but the annular spacer is not visible, and it is possible to determine from this figure alone whether the sensor element is in close contact with the round bar, as shown in Figure 1 a and b, which are cross-sectional views, or whether it is installed at intervals on the round bar. I can't judge. In other words, it is not known whether there is an annular spacer or not. Whether or not to provide an annular spacer, that is, whether to separate the sensor element S2 from the round bar or to bring it into close contact with it, should be determined depending on the purpose of measurement. In this format, if the expansion/contraction or bending of a round bar is to be measured using the sensor element S2, the strain can always be measured by attaching a magnetostriction measurement mechanism to the position of the sensor element S2, but For example, when measuring the torque applied to a rotating shaft like a torque sensor, the sensor element S2 intermittently passes through the part where the magnetostriction measurement mechanism is attached as the round bar rotates, so the strain signal is generated as a pulse. It will be given as.

Further, when the round bar is stationary, the sensor element S2 does not always stop at the part where the magnetostriction measurement mechanism is attached, so the static torque cannot be measured. In this figure, there is a welded part -2 to metallurgically fix the annular fixture C2 and the round bar T, but as mentioned in the explanation for Fig. 1a, this was adopted due to the nature of the strain sensor. It's possible that you won't.

FIG. 3a is a cross-sectional view showing a case in which a flat plate is used as the object for strain measurement, whereas in the previous examples, the object to be strained is a round bar. What is characteristic in this case is that the fixing metal fitting C3i is provided with a recess, and the corresponding projection is provided on the specific target flat plate M3.
11, the sensor element 33m is bent and fixed therebetween.

Also, the fixing metal fitting C3 and the flat plate to be measured? In order to connect I1m, since they are both flat plates, methods such as shrink fitting or push fitting cannot be used, so both are tightened with bolts and Nando's cent I'1M.

Since the sensor element is bent and fixed in this way, if the bolts and nuts are not loosened,
A sufficiently large amount of friction can be obtained. However, when using this method, it must be noted that if amorphous is used for the sensor element 53m, the amorphous will break rapidly once it leaves the elastic deformation region and enters the plastic deformation region. It is necessary to design so that amorphous does not undergo plastic deformation due to bending, but those skilled in the art can easily know the elastic limit of amorphous and then design it so that the elastic limit is not exceeded. This is about as much as possible.

Figure 3 shows the flat plate strain sensor shown in Figure 3a.
This is a diagram seen from the direction of arrow A in figure a, and each symbol represents the third
This corresponds to the same symbol in the figure with the subscript a. In this figure, the bolt and nut set Fik does not pass through the sensor S3b, but a hole may be provided in the sensor element S3b so that the set Fik passes through the sensor element S3b. However, in order to prevent damage starting from the hole position due to the load or strain applied to the sensor element, it is necessary to pay sufficient attention to load stress design, hole construction, etc., and appropriate design is also required. This is something that a person skilled in the art can easily do.

Although metallurgical bonding is not used in the sensor elements shown in FIGS. If sufficient countermeasures are taken, there will be no problem (it can be considered a design problem determined by the application, etc.).

This type of sensor element is mainly suitable for measuring bending, compression, tension, torsional deformation, etc. of a flat plate-shaped strain measurement target. The shapes shown in Figures 3a and b are for illustrating the principle, and the width, length, mounting of the sensor element, and other shapes and dimensions should be shaped to suit the purpose. It is.

FIG. 4 is a sectional view showing a modification in the case of measuring the torsion around the axis of a round bar. In the cases shown in Figures 1a and b and Figure 2, it is assumed that the torsion of shafts with the same thickness is to be measured, but in this case, when a thick shaft and a thin shaft are connected. Alternatively, this is an effective form when a cylindrical shaft and a shaft with a smaller outer diameter are coupled in a transitional manner.

The cylindrical shaft M4° on the left side of the figure has its right end plugged at a right angle, and the bolted part of the left end of the thin shaft M4L passes through the hole provided in the center of the plugged surface. ing. The sensor element S4 is connected to the cylindrical shaft through a flat washer E4 between the surface that closes the right end of the cylindrical shaft M4° at right angles and the stage provided for cutting the bolt at the left end of the thin shaft M4L. It is located covering almost the entire surface perpendicular to the right side of the axis M4°. A hole is made in the center of the sensor element S4, as well as in the right-angled surface of the cylindrical axis M4°. Is sensor element S4 a thin shaft? The center portion is fixed by tightening the nut N4 fitted to the bolt at the left end of I4t. Furthermore, a thread is cut on the outside of the cylindrical shaft M4°, and the annular fixing metal fitting C4 is tightened by fitting the internal thread, and the peripheral part of the sensor element S4 is fixed by the annular protrusion 04' of the annular fixing metal fitting C4. Fixed. With this configuration, when a torsional stress is transmitted from the cylindrical axis M4° to the thin axle load 1 or vice versa, the sensor element S4 is connected to a surface perpendicular to the right end axis of the cylindrical axis M4°. Since they are subjected to approximately the same strain, the strain can be determined by measuring the magnetostriction of the sensor element S4, and the stress to which the system is subjected can be estimated.

In this configuration, the sensor element S4 has a cylindrical axle load,
. Although it is in close contact with the surface perpendicular to the right end axis of the cylindrical shaft M4, if necessary, the two can be separated by recessing the right end surface of the cylindrical shaft M4° or placing a spacer. be able to. In addition, in order to prevent the sensor element S from becoming unreliably fixed due to loosening of the annular fixing fitting C4 or Nara), known means for preventing loosening of the bolt donut, such as fixing with a cotter pin or wire, may be used. It is also possible to use the metallurgical means described in . Furthermore, if the applied load is sufficiently small and can be sufficiently supported only by the sensor element S4, the right end surface of the cylindrical axis M4° perpendicular to the axis is eliminated, and the cylindrical axle load is increased. The sensor element S may be the only thing that connects the thin axis L+. Such a design change can be easily made by a person skilled in the art based on the applied stress, the elastic limit of the sensor element S4, and knowledge of material mechanics.

FIGS. 5a and 5b are schematic views showing an example of a method for securely fixing the sensor element S without using metallurgical means.

Figure 5a shows only one side of the sensor element mounting section, which protrudes from the inner surface of the ring of the annular fixture C9, passes through the hole provided in the sensor element S5, and connects to the recess provided in the round bar H1. I'm hooked. For this reason, the sensor element S,
is securely fixed, and there is very little chance of it loosening even if a load is repeatedly applied over a long period of time. FIG. 5A is a sectional view of the mounting portion shown in FIG. 5A, taken in the direction of arrow B--B. In the figure, holes are provided at four locations for convenience, but the holes should be determined depending on conditions such as load and processing method, and can be easily set by a person skilled in the art.

In addition, the annular fixing metal fitting C of the hole provided in the sensor element S,
The side facing the inner surface of 1 has a chamfered edge, but if it has sharp corners, cracks may occur due to stress concentration and the sensor element S may be destroyed. Such consideration is especially necessary when using it as a sensor element. There are various methods for chamfering, such as cutting, grinding, chemical methods, electrochemical methods, and laser processing, but any method may be used depending on convenience. If you are familiar with it, you can easily perform it.

As shown in FIGS. 5a and 5b, a part of the annular fixing fitting passes through a hole drilled in the sensor element and enters a recess provided on the surface of the round bar to securely fix both ends of the sensor element. This can be carried out by a processing method called the plastic flow method. Figure 6 is a diagram showing an example of the plastic flow processing method, and the sensor element shown in Figure 5a is attached to one side of the part.
The state before plastic flow processing is shown. Annular fixing bracket C6
The inner surface is still cylindrical as it has not been processed yet.

D6 is a mold P that restrains the outside of the annular fixture C6.

is a punch for deforming the upper surface of the annular fixture C6 by applying a load thereto. ν, the annular fixture C8 is the punch P
, and when a load is applied in the direction of the arrow, the side and bottom surfaces are restrained by the mold D6, so the annular fixture C6 flows into the space due to plastic flow. In such a configuration, the punch P6 and the die D6 are made of a sufficiently strong material, such as cemented carbide, uniform speed steel, or steel, and the annular fixture C6 is made of a material that can sufficiently plastically flow, such as pure iron,
When made of mild steel, copper or a soft copper alloy, aluminum or a soft aluminum alloy, the annular fixture C6 is deformed and becomes shaped like the annular fixture C3 in FIG. 5a due to plastic flow, and the sensor element S6 is Can be fixed firmly enough. At that time, a person skilled in the art who is familiar with metal processing will be able to determine the load on the material of the annular fixture Cb, the number and dimensions of the holes to be drilled for the sensor element S, the dimensions and shape of the recess to be provided in the round bar H5, etc. It can be easily set based on the specifications determined by the purpose of the strain sensor by referring to textbooks on plastic working. Moreover, by making the mold D6 into a split mold, it can be easily assembled to the workpiece before machining, and can be removed from the workpiece after the machining is completed.

At this time, the jigs and the like for assembling the workpiece are well known to those skilled in the art, and therefore their explanation will be omitted here. Furthermore, in FIG. 5a, the annular fixture C1
For simplicity, the upper end of the sensor element 85 is illustrated as having a right angle, but when processed by the method shown in FIG. It is likely to be overturned at the top. However, the degree of this varies greatly depending on the material of the annular fixture C3. - For boat fishing, there is no problem as long as the sensor element S is not extremely deformed or damaged as a result, the fixation thereof is strengthened. Measures to prevent deformation or damage can be easily set by those familiar with ordinary metal processing. In addition, it is possible and equally effective to fix objects other than round bar shapes by the plastic flow processing method, but those skilled in the art can easily design and process them by referring to the above explanation. is possible.

FIG. 7 is an example of a strain sensor according to the present invention having a mechanism for converting the type of strain. The figure shows a state in which the sensor element S is attached to the round bar to which stress is applied via the fixing fittings C7a and Cab.
FIG. 3 is a plan view seen from the top side.

The sensor element S is attached to the fixing bracket C71 and the cab.Of course, the part shown in the diagram or the magnetic measurement is
Install it in a way that does not have any thermal effect on the 0 partoooo
oooooo must be. Arrow 0 marked St7 in the figure
00 means that a compressive load of value St is applied to a virtual round bar. Here, assuming that the Young's modulus of the round bar H is E7 and the cross-sectional area is A, the amount ΔL by which the round bar H1 is compressed by the compressive load Sh can be obtained as follows.

ΔL7=L?・sty / (A, ・E?)
...(8) Furthermore, the distortion ΔL between L and l,
l is ΔL,'=ΔL,・L7'/L7=L7'
・Sh/(AT・E,:...(9) Since this strain is directly transmitted to both ends of the sensor element S7, the sensor element S is subjected to the next pre-stage strain ε7.

ε? -L? ' ・stt / (AT・E?・L7′
)...0■ That is, by adopting such a configuration, compressive strain can be converted into pre-stage strain and measured. Furthermore, when Stt in the figure is set to a negative value, that is, when tensile stress is applied, a pre-stage strain in the opposite direction to that during compression is applied to the sensor element S7. At this time, when torsional stress is applied to the round bar A, that is, torque is applied, the sensor element S,
will be subjected to tensile or compressive stress.

Similarly, FIG. 8 is an example of a strain sensor according to the present invention having a mechanism for converting the type of strain. As is clear from the figure, when compressive stress Stg is applied to the round bar, the sensor element Sll shows a conversion mechanism in which tensile strain becomes compressive stress when tensile stress is applied. In the present invention, by making some changes to the structure of the sensor element, the strain (stress) applied to the sensor element can be measured in a strain (stress) form different from that of the material to which stress is applied. The stress (strain) applied to the material can be estimated.

(Function) As explained in detail so far, the function of the present invention is that when the strain applied to a material is measured using a magnetic material as a sensor element, the magnetic properties of the magnetic material are changed due to the thermal influence applied to the magnetic material. Provides a sensor structure that can prevent deterioration and impossibility of high-precision measurements, as well as obtain a large output or change in output even if the distortion or change in distortion is small, and convert it electrically. By increasing the electrical output or its change, a three-step conversion of distortion → magnetism → electricity is performed.For distortion, distortion noise is caused by the vibration of the prime mover, for magnetism, it is caused by magnetic noise due to the surrounding environmental conditions, and for electricity, it is Similarly, it relatively reduces the influence of propagation noise from surrounding electronics and electrical equipment, as well as noise on circuits during electrical amplification, improves the so-called S/N ratio, and reduces minute distortion or minute noise. This also makes it possible to accurately measure changes in strain. Furthermore, when the strain is mechanically amplified and the material to which the stress is applied is a magnetic material,
By isolating the sensor element, it is also possible to minimize the magnetic influence of the magnetic material and enable accurate measurements. Furthermore, by changing the form of stress applied to the material to a different form and applying it to the sensor, it is possible to obtain an optimal measurement method.

(Example) Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 Diameter: 20.0 mm, length: 180 mm. Owa's SS41 steel round bar, outer diameter 26.0amφ, inner diameter 20.02mmφ,
Width 10. Two rings made of Om 5541m were fitted so that the center of their width was 70m+ from both ends of the round bar, and both were spot welded to the round bar at three locations on the end side of the bar.

The spot welding was fillet welding so that the fillet part did not bulge out from the surface of the ring, and the raised part was ground down with a grinder so that it smoothly connected to the surface of the ring. Next, Fee+B+:+, amorphous with a composition of 5si3.5Cz (atomic ratio), width 50mm, length 81
．． A piece of 68 pieces with a thickness of 30 μm was wrapped around a round bar so that both ends coincided with both ends of the ring. As a result,
Amorphous foil is used around the central part of the round rod in the longitudinal direction.
It was surrounded with a gap of 3III11, and both ends around the axis were brought into contact with each other. Outside diameter 30.
0awm, inner diameter 25.9mm, width 10. Om's 5S41
Two steel rings were prepared, heated to about 600°C, and fitted over the ring spot-welded to the round bar from above the amorphous foil so as to overlap. At this time, to prevent the amorphous foil from overheating, place the round rod vertically in a container filled with water, submerge it in water except for the part where the ring of the amorphous foil will fit, and then insert one ring of the amorphous foil into the water. Then, the round bar was turned over and the same operation was carried out. The ring fitted on the outside of the amorphous foil was cooled by heat transfer and its diameter returned to its pre-heating dimension, and the amorphous foil was tightened and fixed.

Strain measurements were performed when stress was applied to the combination of the round bar and strain sensor (hereinafter referred to as combination) obtained above. Figure 9 shows a side view of the assembly from the end surface of the round bar and a block diagram of the measuring device, and is used to explain the measurement method. is an annular fixture, S is an amorphous foil sensor element, and d.

is a detection element, t is a temperature detection element, and F is a signal processing device. One end of the assembly was fixed in a vise attached to a sufficiently rigid and heavy workbench, torque was applied to the other end, and the output of the sensor element with respect to the twist of the round bar 7 was measured. When a GaAs Hall element is used as the detection element d, and the amplification factor of the signal processing device F is set to an amplification factor that is not affected by noise components, the distortion of the sensor element is estimated from its electrical output, as shown in Fig. 10. The values shown are obtained. In Figure 10, the horizontal axis shows the torque applied to the round bar and the torsional angle of the round bar gate estimated from it, and the vertical axis shows the torsional angle of the sensor element S estimated from the electrical output of the signal processing device F. .

In the figure, when a torque of 20 kgf-1 is applied, the torsion angle ψ
indicates approximately 1.3", which corresponds to the case where the length of the material is 150 m calculated from equation (2). The reason for this is that out of the length of the round bar gate of 180 m +, 30 This is thought to be because the cabinet is fixed in a vise or for torque load.Also, of the 50+ma width of the amorphous foil, 20m is fixed to the annular spacer B and the annular fixture C9, and as the round bar is twisted, The length of the twisted part along the axis of the round bar is 30 mm.Since the torsion angle ψ of the round bar is proportional to the distance from the measurement reference position from equation (3), the torsion corresponding to the length of 30 m is The angle ψ3° is 11 in the case of 150 cabinets.
5, which is approximately 0.26° (0,00454 rad). The shear strain on the surface of the round bar is calculated from equation (4) as follows: r=rψ/L=10 mX0.00454/30m++
+=O,0O151, and the shear strain τ1 of the amorphous group is τ=rψ/L=13.03 mmX0.0 because its surface is located 3.03 mm outside the round bar surface.
It increases to 0489/30mo+=O,0O197.

The value on the vertical axis of the figure is the estimated torsion angle ψ1 of the amorphous based on this knowledge, but up to a torsion angle of about 1'', the torsion of the sensor element (amorphous base) corresponds to the torsion of the round bar. shows the same angle, whereas in the parts where the torsion angle of the round bar is larger, the torsion of the sensor is lower.The reason for this is that the fixation of the sensor to the round bar is
This is thought to be due to the fact that only mechanical tightening is used, so when the load increases, the stress is not completely transmitted, causing misalignment. However, if the load or strain is small enough,
This means that it can be used without any problems.

Example 2 An assembly similar to that used in the experiment of Example 1 was prepared. However, as shown in FIG. 11, both ends of the amorphous-based sensor element Sl+ were fixed to the annular spacer Bl+ and the annular fixture CI+ by line welding-1. Welding was performed with the welded part facing upward and the lower part immersed in water in a container to cool it. Example 1
When the strain was measured in the same manner as in Figure 12, the distortion was measured in the same manner as in Figure 12.

Measured values were obtained in which the distortion of the sensor Sll and the distortion of the sensor Sll corresponded linearly over the entire measurement range. This is thought to be due to the fact that mechanical displacement could be prevented by welding.

Example 3 The same assembly as that made in Example 2 was made. However, welding was changed to silver brazing.

The silver material is BAg- of JIS Z 3261-1976.
1 equivalent was used. Brazing was carried out in the same manner as in Example 2 while cooling. When the strain was measured by the method of Example 1, the same measurement results as shown in FIG. 12 were obtained.

Example 4 An assembly similar to that used in the experiment of Example 1 was prepared. However, the length of the amorphous-based sensor element is 81.6
Pinch 1311II11 along the edge of 8- by chemical milling a hole with a diameter of 4m at a position 5wn from both ends.
A dish-shaped hole with a diameter of 3.5 m and a depth of 0.6 to 0.8 m was placed on the surface of the annular spacer where the hole would be located when the amorphous-based sensor element was wound. A depression was made. An annular spacer is attached to a round bar by spot welding, and an amorphous-based sensor is wrapped around the rod with the hole position aligned with the recess, and then an annular spacer with an outer diameter and width equal to that of Example 1 and an inner diameter of 26.15 mm is prepared. The fixing metal fitting is fitted, and the annular fixing metal is plastically deformed by the method shown in Fig. 6, and enters the recess of the annular spacer through the hole provided in the sensor element whose inner surface is an amorphous base, and the amorphous-based sensor element is firmly attached to the annular spacer. It was fixed to a round bar through the wire. When strain measurements were carried out in the same manner as in Example 1,
Similar to what is shown in FIG. 12, measurement values were obtained in which the distortion of the round bar Ml+ and the distortion of the sensor Sl linearly corresponded over the entire measurement range. This is thought to be because mechanical displacement was prevented by plastic deformation of the annular fixture, and linearity was maintained even in areas with high stress.

Example 5 An assembly having the shape shown in FIG. 4 was created. Cylindrical shaft M4
(l is diameter 40.0m, wall thickness 3.Owta, length 15
Attach a silver copper plate with a diameter of 40.0 mm and a thickness of 1.0 mm with a hole of 10.2 mm in the center to one end of the 0.0 mm steel pipe.
A male thread of M40F-+, s is provided over a length of 301 m on the side surface of the end where the copper plate is attached with silver, and a 5S4 thread of 13.0 mmφ and 100 mm long is installed on the thin shaft M41.
One end of the No. 1 steel was provided with a screw of MIO"'.5 over a length of 20 cm. Also, an amorphous base having the composition and thickness used in Example 1 was used as the sensor element S4, with a diameter of 40.0 mm. The circular fixing fitting C4 has an outer diameter of 47.0 mm, an inner diameter of 041 of 32 m, and a hole of 10.5 mm in the center. The width of the part that holds the sensor element is 2.5mm, the overall length is 35mm, and the part that fits into the H4° has a female thread of M40F-+, S over a length of 281m.Suitable for each of the above parts. The nuts and flat washers were attached and assembled into the shape shown in Fig. 4.At this time, after tightening the annular fixing metal fitting C4 to the cylindrical shaft M4° to fix the sensor element S4, to prevent the tightening from loosening. , A knock bottle was hammered into the annular fixing fitting C4 and the cylindrical shaft M4° to ensure fixation.

Fix the end of the cylindrical shaft M4° opposite to the side connected to the thin shaft M41 in a vise, apply torque to the end of the thin shaft L+, and apply the method shown in Fig. 9 to the rotating disk. The strain of the sensor element was measured using a method modified from . As a result, it was possible to obtain a strain output that linearly corresponds to the applied torque over the entire elastic region of the copper plate joined to the end of the cylindrical axis M4°.

Example 6 A metal foil with the same composition as the amorphous used in Example 1 but with microcrystals was used because the cooling rate was rather slow.
An assembly having the stress conversion mechanism shown in FIG. 7 was created.

The metal round bar is made of 545C steel by heat treatment. hardness H, C38, diameter 25 mm, length 1
Use a 20 m long annular fixture C? M and Cab were made of 5s41 steel with an outer diameter of 33.0 mgn, an inner diameter of 25.05 m, an annular portion width of 10III, and a length of 20 mm. Annular fixing bracket Chi and C
wb was fitted into the center of the metal round bar M7 in the longitudinal direction so that the opposing sides were spaced 30 mm apart, and the end faces of each were spot welded to the metal round bar M7 at six locations. On the other hand, the width is 10. Om+++, both ends of the metal foil cut to a length of 25 m are cooled with water in the center of the foil, and the annular fixing metal fitting C?
The techniques from a and cab were attached with silver to create the shape shown in Figure 7. At that time, L" was closed to 155w+.

This assembly was subjected to a compression test, and while stress was applied in the direction of Sty in Fig. 7, a sensor element made of metal foil with microcrystals formed was obtained using a method modified from the measurement method shown in Fig. 9 for use with a stationary object. The strain was measured. As a result, it was found that the shear strain applied to the sensor S7 and the compressive stress St applied to the metal round bar M7 corresponded with each other with good linearity.

Example 7 A round bar to which a strain sensor was attached was manufactured by explosive welding using the method shown in FIG. The annular spacer BI3 was attached to two axially symmetrical positions of the round bar gate 3 by spot welding -1, and the process of wrapping the amorphous foil S11 over it was the same as in Example 1, except that the annular fixing metal fitting was used. C1
The integral outer diameter is 30.0 m, the inner diameter is 26.2 m, and the width is 10.0 m. O
The ring was made of Kaku's 5S41 steel and was attached so as to cover the entire top surface of the amorphous foil. Separate explosion speed 6,30
0m/s plate-shaped explosive Fl with a plate thickness of 3cm! , outer diameter 36cm,
It is molded into a cylindrical shape with a length of 60 cm, and a plate with a thickness of 2 cm is placed at one end of the cylinder.
Glue the same type of disc-shaped explosive G1ff with a diameter of 36 mm,
From the top of the annular fixture C1ff, the length of the explosive is 81
11 overlapped with each other as shown in the cross-sectional view of FIG. 13. When the detonator PI3 was detonated to detonate the cylindrical explosive, the annular fixture COX was strongly compressed by the explosion pressure and its outer diameter was reduced, and the amorphous foil was fixed on the annular spacer B13 at that portion. When the same operation was performed on the other end, the amorphous foil was fixed on the annular spacer BI3 at both ends. Using the same measurement method as in Example 1, torque was applied to the round bar M+3, and the sensor s
When the output of ki was measured, the same measurement results as in Example 2 were obtained.

(Effects of the Invention) The strain sensor according to the present invention is characterized by a structure in which a high-performance magnetic material is attached to the material when the stress applied to the material is measured by a magnetic method, thereby minimizing the heat applied to the magnetic material. In addition to providing a structure in which the deterioration of the characteristics can be virtually ignored, it is also possible to provide a structure in which distortion can be mechanically amplified, thereby improving measurement accuracy. This is how it was done. Furthermore, the present invention provides a structure that minimizes the influence of stressed magnetic materials on the stress measurement by the sensor element. Furthermore, by making the strain (stress) applied to the sensor element different from the stress applied to the material, it is possible to use the most suitable measurement method.

[Brief explanation of the drawing]

FIGS. 1A and 1S are diagrams for explaining the principle of the strain sensor according to the present invention. Lm, Mlb: Round bar S+s with radius R1oa and R1°5, Slb:? t+a and Mtb O) Surrounding sensor element B1. : Annular spacer C1a, Cl1l 'Annular fixing metal fitting -+m, j'
l+b: Welded portion A11l, Alb'Round bar Mllll and Mlb longitudinal axis R11, Rzb'sensor elements sea and S
lb outer radius Llm, L+b: Effective length of sensor elements sea and Slb d: Difference between outer radius R311 of sensor element S1m and radius RIOII of round bar M1 Fig. 2 shows a string-like sensor element with a constant width. FIG. 3 is a plan view of a sensor element attached to a part of the outer periphery of a round bar in a direction along the axis, as seen from the side to which the sensor element is attached. B2: Sensor element A2: Round bar C2: Annular fixture-2: Welded portion FIG. 3a is a sectional view showing the case where a flat plate is the object. B3. :Sensor element Co :Fixing metal fitting gate1. :Flat plate F:Im :Set of bolts and nuts FIG. 3 is a view of the strain sensor for a flat plate shown in FIG. 3a, viewed from the direction of the arrow in FIG. 3a. 5311: Sensor element Crb: Fixing metal fitting A8. : Flat plate B3. : Set of bolts and nuts FIG. 4 is a sectional view showing a modification when measuring the torsion around the axis of a round bar. B4: Sensor element A4゜: Cylindrical shaft A41: Thin shaft N4: Nut B4: Flat washer C4: Annular fixing bracket Figure 5 a and b securely fix the sensor element S, without using metallurgical means. This is a diagram for showing an example of a method of
Figure a is a sectional view of the fixed part taken along the axis of the round bar, and Figure 5 is a sectional view perpendicular to the axis. S: Sensor element Ms: Round bar C1: Annular fixture FIG. 6 is a diagram showing an example of the plastic flow processing method, and shows the state before plastic flow processing. B6: Sensor element C1: Annular fixture Db: Mold for plastic flow machining B6: Punch for plastic flow machining vb: Space into which the annular fixture C6 flows by plastic flow FIG. This is an example of a device that has a mechanism for converting types. S7: Sensor element A7: Round bar C? ll+C'? b'Fixing metal fitting Stf: Compressive load Fig. 8 is another example of one having a mechanism for converting the type of strain. B8: Sensor element A8: Round bar C@m+ Cab: Fixing bracket Sts: Compressive load Figure 9 shows a side view of the assembly from the end surface of the round bar and a block diagram of the measuring device, and is used to explain the measuring method. It is something. A9: Round bar B, : Annular spacer C9: Annular fixture S, : Amorphous foil sensor element b9: Detection element t, : Temperature detection element F, : Signal processing device In Fig. 10, the horizontal axis is round bar -7. The loaded torque and the torsion angle of the round bar H1 estimated from it, the vertical axis is the signal processing device F,
The torsion angle of the sensor element S is estimated from the electrical output of the sensor element S. FIG. 11 shows an example in which both ends of an amorphous foil sensor element are fixed to an annular spacer and an annular fixture by line welding. S: Amorphous foil sensor element Bll: Annular spacer C1: Annular fixture Ll: Line welding Figure 12 shows a round bar when both ends of the amorphous foil sensor element are fixed to the annular spacer and annular fixture by line welding. The results of measuring the distortion of the sensor and the distortion of the sensor are shown. FIG. 13 shows a method of manufacturing a round bar with a strain sensor attached by explosive welding. Old: Round bar B1. : Annular spacer Spot-welded amorphous foil Annular fixing bracket Cylindrical plate explosive Disc-shaped explosive detonator element

Claims (1)

[Claims] 1. In a method of electrically or magnetically measuring strain using the magnetostrictive phenomenon, both ends of a plate-shaped or thin-film element are fixed to an object to be measured, and the unfixed portion is A strain measurement method characterized by determining the strain of an object by measuring the magnetostriction of an element. 2. A strain sensor consisting of a plate-shaped or thin-film element made of magnetic metal or amorphous, both ends of which are metallurgically or mechanically fixed to the object to be measured.