JP7125767B2 - Bending detection sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curvature detection sensor capable of detecting the amount of change in the curvature of an object to be measured, the direction of change, and force.

Metal strain gauges and semiconductor strain gauges are conventionally known strain gauges (bending detection sensors). Among them, the metal strain gauge includes, for example, a metal wire (metal foil) as a resistor formed in a zigzag pattern on a thin insulating layer such as a resin film (see, for example, Patent Document 1). When the object to be measured is deformed by attaching such a metal strain gauge to the object to be measured, the metal wire also expands and contracts according to the deformation, and the electrical resistance value of the metal wire changes. The strain of the object to be measured can be measured by detecting such a change in electrical resistance.

In addition, the semiconductor strain gauge utilizes the piezoresistive effect in which the electrical resistivity of the semiconductor changes according to the stress applied. The deformation of the electron changes the kinetic potential of the electron. As a result, the mobility of carriers in the semiconductor changes and the electrical resistance changes, so the strain of the object to be measured can be measured by detecting the change in electrical resistance.

JP 2016-125977 A

However, the conventional strain gauge has a problem that it is difficult to measure the deformation of an object whose curvature changes greatly. For example, it is difficult for a conventional strain gauge to detect an object to be measured, such as the motion of a joint of a human body, which repeatedly deforms with a large curvature and an angle greater than a right angle. For example, since the resistive metal used in conventional metal strain gauges has a low elastic limit (maximum of about 0.7%), plastic deformation occurs when a large bending such as that of a human joint is applied. undergoes irreversible deformation.

On the other hand, since most of the semiconductor materials used in conventional semiconductor strain gauges are brittle materials, it is difficult for them to follow large bending such as the joints of the human body.
For this reason, there has been a demand for a curvature detection sensor that can accurately measure deformation of an object to be measured that repeatedly bends at a large curvature and at a large angle. Further, there has been a demand for a curvature detection sensor that can accurately measure the force (stress) applied to the object to be measured.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a curvature detection sensor capable of repeatedly and accurately measuring strain on an object to be measured having a large change in curvature.

The inventors have found that by applying a rolled alloy plate made of an alloy newly discovered in recent years whose elastic limit reaches 3% to a curvature detection sensor, it is possible to accurately measure the strain of an object to be measured in which large curvature changes occur repeatedly. Found it.
That is, the curvature detection sensor of the present invention has the following configuration.
A first metal plate and a second metal plate having an elastic limit of 1% or more and different Young's moduli are joined together.

Moreover, in the present invention, the Young's modulus of the first metal plate may be 40 GPa or less, and the Young's modulus of the second metal plate may be greater than 40 GPa.

Further, in the present invention, the second metal plate may have a Young's modulus of 50 GPa or more.

Further, in the present invention, the elastic limits of the first metal plate and the second metal plate may be 1.2% or more.

Moreover, in the present invention, the first metal plate and the second metal plate may be made of a Ti—Nb based alloy.

Further, in the present invention, the first metal plate and the second metal plate may be joined by a plurality of spot welds.

Further, in the present invention, the first metal plate and the second metal plate may be rolled alloy plates.

Another curvature detection sensor of the present invention has the following configuration.
A third metal plate and a fourth metal plate having an elastic limit of 1% or more, the same Young's modulus, and different specific resistances are joined together.

According to the curvature detection sensor of the present invention, it is possible to provide a curvature detection sensor capable of repeatedly and accurately measuring strain and force applied to an object to be measured having a large change in curvature.

1 is a cross-sectional view showing a bending detection sensor of the present invention; FIG. FIG. 4 is an explanatory diagram showing a strain measurement form using the curvature detection sensor of the present invention; It is a graph concerning the example of the present invention. It is a graph concerning the example of the present invention. It is a graph concerning the example of the present invention.

A curvature detection sensor according to an embodiment of the present invention will be described below with reference to the drawings. It should be noted that each embodiment shown below is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make it easier to understand the features of the present invention, there are cases where the main parts are enlarged for convenience, and the dimensional ratio of each component is the same as the actual one. not necessarily.

FIG. 1 is a cross-sectional view showing a curvature detection sensor according to one embodiment of the present invention.
The bending detection sensor 10 of the present invention directly connects a first rolled alloy plate (first metal plate) 11, which is a first metal plate, and a second rolled alloy plate (second metal plate) 12, which is a second metal plate. It is a joined leaf spring-like member.
The first rolled alloy plate 11 is made of, for example, a plate material obtained by rolling a Ti—Nb-based alloy having an elastic limit of 3% and a Young's modulus of 30 GPa. The second rolled alloy plate 12 is made of, for example, a plate material obtained by rolling a Ti—Nb-based alloy having an elastic limit of 1.5% and a Young's modulus of 70 GPa.
In this embodiment, a rolled alloy plate is used as the first metal plate and the second metal plate. nothing.

In this embodiment, the first rolled alloy plate 11 and the second rolled alloy plate 12 are each formed in a strip shape with a width of 3 mm, a length of 30 mm, and a thickness of 0.1 mm.

The first rolled alloy plate 11 and the second rolled alloy plate 12 are directly joined to each other by spot welding. In this embodiment, along the longitudinal direction of the first rolled alloy plate 11 and the second rolled alloy plate 12, two joints 13 (see FIG. 2) are formed by spot welding at intervals of 7.5 mm. .

For example, when two alloy plates are entirely welded or joined by brazing, the metal structure of the alloy is destroyed by the heat during joining, and there is a concern that the desired characteristics cannot be obtained. As such, by joining the first rolled alloy plate 11 and the second rolled alloy plate 12 by local spot welding, the Ti—Nb-based alloy constituting the first rolled alloy plate 11 and the second rolled alloy plate 12 can be joined with almost no destruction of the metal structure.

In addition, spot welding, which is an example of a joining method for joining the first rolled alloy plate 11 and the second rolled alloy plate 12, is made into various welding shapes such as spot welding, linear welding, and planar welding. The shape and arrangement of the spot welds are not limited.

As shown in FIG. 2, current terminals T1 and T2 are provided at both ends of the bending detection sensor 10 configured as described above to apply a current, and voltage terminals are connected to the two spot-welded joints 13, respectively. S1 and S2 are provided and the voltage between the voltage terminals S1 and S2 is measured.
Although FIG. 2 shows an example of measurement using a direct current, measurement can also be performed using an alternating current or a pulse current.
In this embodiment, the current terminals T1 and T2 are provided outside the voltage terminals S1 and S2 in the longitudinal direction, but the positions of the current terminals T1 and T2 are not limited. Current terminals T1 and T2 can also be provided between S1 and voltage terminal S2.

For example, when the bending detection sensor 10 is bent in the longitudinal direction, the first rolled alloy plate 11 with a Young's modulus of 30 GPa deforms more than the second rolled alloy plate 12 with a Young's modulus of 70 GPa. As described above, the first rolled alloy plate 11 and the second rolled alloy plate 12 deform asymmetrically, thereby changing the electric resistance value of the bending detection sensor 10 . By detecting the amount of change (ΔV) and the direction of change (positive or negative of ΔV) in the voltage value between the voltage terminal S1 and the voltage terminal S2 of the bending detection sensor 10 before and after bending, the bending detection sensor 10 can be detected. Curvature and bending direction can be detected.

According to the bending detection sensor 10 of the present invention, the first rolled alloy plate 11 and the second rolled alloy plate 12 have different mechanical properties, that is, Young's modulus, and have a high elastic limit of 1% or more, for example, 3%. By forming the curvature detection sensor 10 by spot welding, it is possible to detect not only the strain applied to the curvature detection sensor 10, for example, the curvature due to bending deformation, but also the bending direction.

In addition, according to the bending detection sensor 10 of the present invention, by using a rolled alloy plate with a high elastic limit of 1% or more, for example, 3%, metal with a conventional elastic limit of about 0.7% can be used. A strain gauge using a material can be applied to an object to be measured having a high curvature such that a metal resistance wire is permanently deformed by plastic deformation. In addition, since breakage of the first rolled alloy plate 11 and the second rolled alloy plate 12 is less likely to occur due to repeated bending, the present invention can be applied to objects to be measured that repeatedly bend repeatedly.

Also, since the bend detection sensor 10 of the present invention operates in the elastic range of the material, a linear relationship is established between deformation and stress. Therefore, the force acting on the bending detection sensor 10 can be measured. Thereby, the bending detection sensor 10 of the present invention can be used as a sensor for measuring bending stress.

Further, according to the bending detection sensor 10 of the present invention, a rolled alloy plate having a high elastic limit of 1% or more, for example, 3% is used. It can be used as a member that also has the function of , and if used as a mechanical part, the structure can be simplified. Furthermore, since the curvature detection sensor 10 of the present invention has no nonlinearity or hysteresis, it can also be used as a vibration detection sensor.

In addition, since the first rolled alloy plate 11 and the second rolled alloy plate 12 of the bending detection sensor 10 of the present invention are both made of metal and do not contain materials other than metal, they can be used in an environment such as an ultra-high vacuum. can also be used. In addition, since the bending detection sensor 10 is made of metal, it has an electrically low impedance, and strain can be measured even at a low voltage of 1 V or less. Since it is a low-impedance device, it can be operated even in water or organic solvents, which have low electrical conductivity.
Further, since the bending detection sensor 10 of the present invention is configured by joining two rolled alloy plates, it can be manufactured inexpensively and easily.

In addition, the curvature detection sensor of the present invention is not limited to the embodiment described above.
For example, the two rolled alloy plates to be joined to each other may use an alloy having at least an elastic limit of 1% or more, one having a Young's modulus of 40 GPa or less, and the other having a Young's modulus of 40 GPa or more. It is not limited to alloys.

Moreover, the shape of the curvature detection sensor 10 described above is an example, and it can be formed in any shape other than such a strip shape according to the object to be measured.
Further, in the above-described curvature detection sensor 10, spot welding is used as a method for joining the first rolled alloy plate 11 and the second rolled alloy plate 12, but the first rolled alloy plate 11 and the second rolled alloy plate 12 are Various joining methods can be employed as long as the method does not destroy the metal structure of the alloy constituting the joint, and the joining method is not limited. For example, as a bonding method, bonding with an adhesive or the like can be used.

In addition, the above-described bending detection sensor 10 is configured by joining two rolled alloy plates with different Young's moduli, but it may be configured by joining three or more rolled alloy plates with different Young's moduli. can also

The bending detection sensor of the present invention includes a third rolled alloy plate (third metal plate) and a fourth rolled alloy plate (fourth metal plate) having an elastic limit of 1% or more, the same Young's modulus, and different specific resistances. It can also be constructed by joining two plates together. Even if these bending detection sensors have the same Young's modulus and different specific resistances, as with the bending detection sensor 10 described above, the strain applied to the bending detection sensor, for example, the curvature due to bending deformation, is detected and the bending direction is detected. can also be detected. Moreover, it can be used as a bending detection sensor for measuring bending stress.

Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

Hereinafter, considerations and experimental examples relating to the invention of the curvature detection sensor of the present invention will be shown.
When tension or uniaxial pressure is applied to a metal sample, the electrical resistance changes due to changes in the length and cross-sectional area of the sample. If tension is applied, the resistance increases, and if compressive force is applied, the resistance decreases. If the sample is a normal metal, the maximum elastic limit is about 0.7%, so if stress is applied enough to change the electrical resistance by about 1%, plastic deformation will occur. Dont return.

Here, if a material with a very large elastic limit, for example, a recently discovered Ti—Nb-based alloy with an elastic limit reaching about 3% is used, the change in shape due to repeated stress can be continuously measured by measuring the electrical resistance value. A bend detection sensor can be made to detect. Since deformation below the elastic limit does not cause hysteresis, there is a linear relationship between stress and electrical resistance, so it is possible to measure not only shape change but also stress by electrical resistance.

In this case, since a metal with a specific resistance that is several orders of magnitude lower than that of semiconductor materials is used, the electrical resistance is low, and high voltage is not required for measurement. Since it detects changes in pure electrical resistance that does not include capacitance or inductance, it can measure both AC and DC. Since the electrical resistance changes according to the deformation of the sample, it has good followability and can detect mechanical vibrations. As in the bending detection sensor of the present invention, when two metal plates having significantly different Young's moduli, such as two rolled alloy plates (metal plates), are joined together, the amount of deformation between the inside and the outside when bent is inadequate. Because of the balance, the electrical resistance value of the entire joined rolled alloy plate changes.

Next, a trial calculation is made of the change in the resistance value. Let _RH be the resistance of the high Young's modulus rolled alloy plate, and _RL be the resistance of the low Young's modulus rolled alloy plate. Here, in order to facilitate the trial calculation, the high Young's modulus rolled alloy plate does not expand and contract when the sample is bent and stretched, and only the low Young's modulus rolled alloy plate changes in length a = (1 + δ) times, Assume that the cross-sectional area remains unchanged. The combined resistance R when two rolled alloy plates are connected in parallel with an insulating layer sandwiched between them is given by the following equation (1).

Also, the ratio to the resistance before deformation of the sample is given by equation (2).

Here, simplifying as R _H =R _L =R ₀ yields formula (3), and it can be seen that a resistance change that is half the length change rate δ can be obtained.

Here, when the relationship between δ and Δ is plotted with R _L =1.2R _H , the graph shown in FIG. 3 is obtained. According to this graph, it can be seen that a resistance change about half of δ can be obtained.

When a bending detection sensor is created with the structure described above, and only the two ends of the two rolled alloy plates are fixed to each other and subjected to a large bending deformation, the plate on the side where the compressive force acts buckles, so one of the rolled alloy plates is bent. The length of the plate did not shrink, and the expected resistance change was not obtained. Next, in order to prevent buckling, the insulating layer is divided into n equal parts, and the combined resistance when two rolled alloy plates are fixed at the cut is obtained. In this case, it is equivalent to a circuit in which n blocks in which resistors R _H /n and R _L /n are connected in parallel through gaps between insulating layers are connected in series. Therefore, the combined resistance is given by equation (4), which is completely the same as the original combined resistance.

As shown in equation (4), the combined resistance does not depend on the number n of divisions of the insulating layer, so as many fixing points as necessary to prevent buckling may be created. If necessary, the result is the same even if two rolled alloy plates are brought into close contact with each other without an insulating layer by setting n->∞. Therefore, an insulating layer is not required, and the bending detection sensor can be manufactured by directly bonding two rolled alloy plates to prevent buckling.

Two rolled alloy plates may be joined by an adhesive or brazing, but it is necessary to use a fixing method that does not cause separation when bent and does not damage the structure (mechanical properties) of the material due to heat. In this example, spot welding was used to join two rolled alloy plates. With spot welding, although the temperature rises locally, it has little effect on the material properties because it does not affect most of the other parts. In addition, unlike joining by bolting, etc., the shape does not become large due to joining, and it is compact, making it suitable for sensor fabrication.

Two flat rolled alloy plates may be overlapped and spot-welded, but if the two rolled alloy plates are welded in a bent state, the bent state is the base point of zero stress and zero deformation. can be done. If the length of the curvature detection sensor is insufficient, a plurality of curvature detection sensors can be spot-welded so as to be connected to form one curvature detection sensor, thereby realizing an arbitrary length of the curvature detection sensor.

When measuring the resistance of two joined rolled alloy plates, current terminals are provided at both ends of the rolled alloy plates, and voltage terminals are provided at the point where the two rolled alloy plates are spot-welded. By measuring the voltage between the terminals, it is possible to detect the electrical resistance between the voltage terminals, that is, the deformation (distortion) of the bending detection sensor. Further, by providing an arbitrary number of voltage terminals and detecting the potential difference between the respective voltage terminals, it is possible to detect a portion of the bending detection sensor that is partially deformed.

Since the sample resistivity is almost proportional to the temperature, it is preferable to perform temperature correction (~5%/100K) when the temperature of the usage environment changes greatly. Conversely, if the deformation of the bending detection sensor is constant, it also functions as a temperature sensor.

(Experimental example)
Titanium-based high elastic limit low Young's modulus alloy and high elastic limit high Young's modulus alloy were prepared. Both alloys have the same composition, and the Young's modulus of one alloy is set to 30 GPa, and the Young's modulus of the other alloy is set to 70 GPa by the difference in thermomechanical treatment.
At 26° C., the high elastic limit high Young's modulus alloy has a specific resistance of 128 μΩ·cm, and the high elastic limit low Young's modulus alloy has a specific resistance of 155 μΩ·cm. As the rolled sheets of these two alloys, two strip-shaped alloy rolled sheets having a width of 3 mm, a length of 30 mm, and a thickness of 0.12 mm were spot-welded at two points at intervals of 7.5 mm to the straight portions of the two alloy rolled sheets of the present invention. A curve detection sensor is used. Note that the bending detection sensor that was spot-welded at intervals of 15 mm caused buckling due to bending.

The electrical resistance value was measured by the DC four-terminal method. The measured current is 100 mA, and the distance between the voltage terminals is 29.3 mm. In order to measure the resistance change due to the deformation of the bending detection sensor, an insulator rod was pressed between the voltage terminals and the resistance value was plotted against the radius of the rod. The resistance value in the flat state before bending was 58.84 mΩ.

A graph plotting the resistance of the bend detection sensor against the radius of the round bar around which the sensor is wrapped is shown in FIG. The □ mark indicates the case where tension is applied to the high elastic limit, low Young's modulus rolled alloy plate, and the ◯ mark indicates the case where compressive force is applied to the high elastic limit, low Young's modulus rolled alloy plate. As expected, the resistance increased against tension and decreased against compression. It was found that there was a hyperbolic change with respect to the radius of curvature as a whole.

Assuming that the length of the high elastic limit high Young's modulus rolled alloy plate does not change when the bending detection sensor is bent, and that only the length of the high elastic limit low Young's modulus rolled alloy plate changes, the high elastic limit high Young's modulus rolled If l is the length of the alloy plate, r is the radius of curvature, and θ is the central angle of bending, then l=rθ and δr is the thickness of the plate. /l)=(δr/r).

Since the length of the high elastic limit high Young's modulus rolled alloy plate does not change when the bending detection sensor is bent, the electric resistance value does not change, and only the electric resistance value of the high elastic limit low Young's modulus rolled alloy plate changes. In this case, as described above, the rate of change in combined resistance is considered to be about half of the rate of change in length of the high elastic limit, low Young's modulus rolled alloy plate. FIG. 5 shows a graph plotted with the reciprocal of the curvature radius plotted on the horizontal axis.

According to the graph shown in FIG. 5, a linear relationship with the same inclination was obtained for both convex and concave deformed shapes of the curvature detection sensor. In the graph shown in FIG. 5, the dashed line is the resistance change (ΔR / R) = 0.5 × (δr / r) when it is assumed that the length of the high elastic limit high Young's modulus rolled alloy plate does not change. . It turned out that the measured value is about 1.55 times the simple calculation. This is considered to be due to the influence of the change in the cross-sectional area of the curvature detection sensor, which was not taken into consideration in the simple calculation. In addition, the x mark in FIG. 5 indicates the case where only the high elastic limit low Young's modulus rolled alloy single plate with a thickness of 0.1 mm is bent, and it can be seen that the electrical resistance value does not change as expected in advance.

The curvature detection sensor of the present invention can be used for the following applications.
(1) Measurement of bending and stretching parts of living organisms such as elbows and knees.
(2) Input devices such as data gloves and sensor gloves.
(3) Bending and stretching detection of robots and machines.
(4) Measurement of mechanical vibrations of engines and the like.
(5) Cantilevers.
(6) Bending in solution, stress measurement.
(7) Deformation detection of structures such as buildings.
(8) Measurement of stress and load.
(9) A large number of voltage terminals are provided to detect the position of deformation.
(10) Detection of door opening/closing and position (angle) of reclining seat.
(11) Measurement of displacement and stress in vacuum.
(12) A leaf spring with a built-in displacement/stress detection function that utilizes the characteristics of high elastic limit materials.
(13) Sensors for medical rehabilitation equipment, for example sensors for detecting and notifying joint bending angles

DESCRIPTION OF SYMBOLS 10... Bending detection sensor 11... 1st rolled alloy plate (1st metal plate)
12... Second rolled alloy plate (second metal plate)

Claims (8)

A curve detection sensor comprising a first metal plate and a second metal plate having an elastic limit of 1% or more and different Young's moduli from each other. 2. The curvature detection sensor according to claim 1, wherein the Young's modulus of the first metal plate is 40 GPa or less, and the Young's modulus of the second metal plate is greater than 40 GPa. 3. The curvature detection sensor according to claim 2, wherein said second metal plate has a Young's modulus of 50 GPa or more. 4. The curvature detection sensor according to claim 1, wherein the elastic limit of said first metal plate and said second metal plate is 1.2% or more. 5. The curvature detection sensor according to claim 1, wherein said first metal plate and said second metal plate are made of a Ti--Nb based alloy. 6. The curvature detection sensor according to claim 1, wherein the first metal plate and the second metal plate are joined by a plurality of spot welds. 7. The curvature detection sensor according to claim 1, wherein said first metal plate and said second metal plate are rolled alloy plates. A curve detection sensor comprising a third metal plate and a fourth metal plate having an elastic limit of 1% or more, the same Young's modulus, and different specific resistances.

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