WO2020202821A1 - Force sensor - Google Patents

Abstract

The present invention makes it possible to obtain a highly sensitive force sensor having a small size.　In this force sensor, a strain-sensing material is arranged on at least one surface section of a plate-shaped member, strain occurring in the plate-shaped member in response to force being applied to the surface section of the plate-shaped member is sensed by the strain-sensing material, and the force applied to the plate-shaped member is thereby sensed. The strain-sensing material is formed from a strip-shaped conductive material. The strain-sensing material is arranged on the surface section of the plate-shaped member so as to correspond to each of a first ring-shaped area serving as the center of a force application section in which force is applied to the surface section of the plate-shaped member and a second ring-shaped area at a different distance from the force application section than the first ring-shaped area.

Description

Force sensor

The present invention relates to a force sensor that detects the received force based on detecting a displacement such as strain generated according to the received force.

As a force sensor, a strain gauge using a strain gauge that utilizes a phenomenon in which the electrical resistance of a strain-sensitive material changes due to the strain of the strain-sensitive material (including not only elastic strain but also plastic strain) is known. The strain gauge uses the piezoresistive effect, in which the electrical resistivity of the strain-sensitive material changes due to stress, and the piezoelectric effect, in which polarization (surface charge) proportional to the applied force appears. Is.

As a force sensor using a strain gauge, a so-called three-axis force sensor that detects force components in the three-axis directions (X-axis direction, Y-axis direction, Z-axis direction) orthogonal to each other of the applied force has also been proposed. (See Patent Document 1). When a 3-axis force detecting member using this strain gauge is used for an electronic pen, not only the pressure (writing pressure) in the axial direction of the electronic pen, but also the tilt angle of the electronic pen and the frictional force of the pen tip of the electronic pen It is convenient to be able to detect such things as well.

FIG. 7 shows an example of the triaxial force detecting member of Patent Document 1 described above. The force detecting member of this example includes a strain generating portion 101, a force receiving portion 102 integrally coupled to the strain generating portion 101, and a force sensor 103 attached to the strain generating portion 101. In this example, the direction orthogonal to the plane of the strain generating portion 101 is the Z-axis direction, the direction parallel to the plane of the strain generating portion 101, and the directions orthogonal to each other are the X-axis direction and the Y-axis direction.

FIG. 7A is a view of the force detecting member of this example from the lateral direction (X-axis direction or Y-axis direction), and FIG. 7B is a perspective view of the force detecting member of this example. .. 7 (C) to 7 (E) are vertical cross-sectional views (cross-sectional views in the direction including the Z-axis direction) of the force detecting member of this example, and FIG. 7 (C) shows the force receiving unit 102. 7 (D) shows a state in which the force receiving unit 102 receives a force in the Z-axis direction, and FIG. 7 (E) shows a state in which the force receiving unit 102 receives a force in the X-axis direction or the Y-axis direction. The state of receiving is shown respectively. In FIGS. 7B to 7E, for convenience, the force receiving unit 102 shows only the vicinity of the strain generating unit 101.

The force receiving unit 102 has a function of receiving a force applied to the tip portion on the side opposite to the coupling side with the strain generating portion 101 and transmitting the force to the strain generating portion 101. In this example, the force receiving portion 102 is a rod-shaped member. Will be done.

As shown in FIGS. 7B and 7C, the strain-causing portion 101 has a structure in which a thin disk-shaped diaphragm 101a is provided on one opening side of the cylindrical diaphragm holding portion 101b. I have. The strain generating portion 101 is coupled to the rod-shaped force receiving portion 102 at the central portion of the disc-shaped diaphragm 101a.

A force sensor 103 is attached to the surface of the diaphragm 101a on the side opposite to the connection side with the force receiving portion 102. FIG. 8A shows an example of the conventional configuration of the force sensor 103.

As shown in FIG. 8A, the force sensor 103 of this example is a strain-sensitive material that changes its resistance value according to the strain displacement received on a flexible substrate 103a made of, for example, a disk-shaped insulating film sheet. 104 is composed of a plurality of arranged ones. As shown in FIG. 8A, in this example, as the strain-sensitive material 104, six strain-sensitive materials 104X1, 104X2, 104Y1, 104Y2, 104Z1, 104Z2, 104Z3, 104Z4 are arranged on the flexible substrate. It is installed. In this example, the resistance values of the strain-sensitive materials 104X1, 104X2, 104Y1, 104Y2, 104Z1, 104Z2, 104Z3, 104Z4 are set to be equal to each other when no strain is applied. In the following description, when it is not necessary to distinguish each of the plurality of strain-sensitive materials 104, the strain-sensitive material 104 will be described.

The strain-sensitive materials 104X1 and 104X2 are for detecting strain in the X-axis direction, which is a direction orthogonal to the axial direction of the force receiving portion 102, and are the center positions 103ac (force application position) of the flexible substrate 103a. On a straight line in the X-axis direction passing through the above, both sides of the center position 103ac are provided at equal distances from the center position 103ac.

The strain-sensitive materials 104Y1 and 104Y2 are for detecting strain in the Y-axis direction, which is orthogonal to the axial direction of the force receiving unit 102 and orthogonal to the X-axis direction, and Y passes through the center position 103ac. On a straight line in the axial direction, they are provided at positions equal to each other from the center position 103ac on both sides of the center position 103ac.

The strain-sensitive materials 104Z1, 104Z2, 104Z3, 104Z4 are for detecting strain in the Z-axis direction, which is the axial direction of the force receiving unit 102. In the example of FIG. 8A, the center position 103ac is sandwiched on a straight line that passes through the center position 103ac and is inclined at a predetermined angle so as not to overlap with other strain-sensitive materials 104X1, 104X2, 104Y1, 104Y2. Two strain-sensitive materials 104Z1 and 104Z3 and two strain-sensitive materials 104Z2 and 104Z4 are provided at point-symmetrical positions on both sides.

In the force detecting member of this example, when a force in the Z-axis direction is applied to the strain generating portion 101 via the force receiving portion 102, the diaphragm 101a of the strain generating portion 101 receives tensile / compressive stress, and the figure. As shown in 7 (D), the force receiving portion 102 is curved so as to be convex downward according to the displacement in the Z-axis direction. Then, the force sensor 103 is also displaced according to the curvature of the diaphragm 101a. In this case, as shown in FIG. 7 (D), in the diaphragm 101a, that is, in the force sensor 103, an extension displacement occurs in the vicinity of the center position 103ac, and the diaphragm holding portion 101b away from the center position 103ac causes an extension displacement. Causes contraction displacement.

Therefore, in the strain-sensitive materials 104Z1 and 104Z3, one changes the resistance in the increasing direction and the other changes the resistance in the decreasing direction. Therefore, the resistance values of the strain-sensitive material 104Z1 and the strain-sensitive material 104Z3 By detecting the difference between the two, the force component in the Z-axis direction can be detected. The same applies to the strain-sensitive material 104Z2 and the strain-sensitive material 104Z4. Therefore, the output of the difference in resistance between the strain-sensitive material 104Z1 and the strain-sensitive material 104Z3 and the output of the difference in resistance between the strain-sensitive material 104Z2 and the strain-sensitive material 104Z4 are added to form the Z-axis. It can be the detection output of the force component in the direction.

That is, by forming a bridge circuit as shown in FIG. 9A with the four strain-sensitive materials 104Z1, 104Z2, 104Z3, 104Z4, the force detecting member can make the applied force a force in the Z-axis direction. The detection output of the component can be obtained. In FIG. 9A, a power supply voltage is applied to the terminal E, the terminal G is grounded, and a detected output voltage of the force component in the Z-axis direction is obtained between the terminals Za and Zb.

Further, in the force detecting member, the force component in the X-axis direction or the force component in the Y-axis direction of the applied force acts as a bending moment according to the length of the force receiving portion 102, and the diaphragm of the strain generating portion 101 Bending stress and shear stress are applied to 101a. As a result, as shown in FIG. 7 (E), in the direction of applying the force in the X-axis direction or the Y-axis direction, on one side of both sides of the coupling portion (center position 101ac of the diaphragm 101a) with the force receiving portion 102. , The diaphragm 101a is displaced so as to contract, and on the other side, the diaphragm 101a is displaced so as to extend.

The strain-sensitive materials 104X1 and 104X2 or the strain-sensitive materials 104Y1 and 104Y2 arranged on the force sensor 103 change their resistance in an increasing direction and decrease in the other depending on the generated displacement. The resistance changes. Therefore, by detecting the difference in resistance between the strain-sensitive material 104X1 and the strain-sensitive material 104X2, the force component in the X-axis direction can be detected, and the resistance value between the strain-sensitive materials 104Y1 and 104Y2 can be detected. By detecting the difference, the force component in the Y-axis direction can be detected.

FIG. 9B shows a configuration example of a bridge circuit that obtains a detected output voltage of a force in the Y-axis direction, and FIG. 9C shows a configuration example of a bridge circuit that obtains a detected output voltage of a force in the X-axis direction. .. In addition, in FIG. 9B and FIG. 9C, the resistance value of RY1, RY2 and RX1, RX2 is the same as that when strain is not applied to the strain-sensitive material 104X1, X2, Y1, Y2. It is a fixed resistance (reference resistance) indicating a value, and these are provided outside the force sensor 103 of this example.

Conventionally, for example, Cu—Ni alloy as a material constituting the strain sensitive material 104 has a small gauge ratio for determining strain sensitivity (for example, the gauge ratio is 2), but the temperature constant is linear and stable, so that the bridge It is often used in a circuit because it is stable against temperature changes because the resistance values of strain-sensitive materials can cancel each other's temperature conversions. As the strain-sensitive material 104, semiconductor carbon, silicon, germanium, etc. are also known, but these have a relatively large gauge coefficient (gauge coefficient is 10 to 170), but the strain-sensitive direction is different. Its use is limited because it has a high property, a high temperature coefficient, and is anisotropy, so that it fluctuates greatly with respect to temperature changes and lacks stability.

When the strain-sensitive material 104 is made of, for example, a Cu—Ni alloy, its longitudinal direction is the radial direction (strain generation direction) as shown in the enlarged view of FIG. 8B. ), It is configured to be bent in a zigzag shape and arranged in a direction orthogonal to the radial direction (circumferential direction). FIG. 8B shows an example of the strain-sensitive material 104Y1, but the same applies to the other strain-sensitive materials 104X1, 104X2, 104Y1, 104Z1, 104Z2, 104Z3, 104Z4.

In this way, the strip-shaped strain-sensitive material 104 made of fine metal wire or metal foil is arranged along the radial direction and is bent in a zigzag shape and arranged in the circumferential direction as follows. For some reason. That is, in the conventional strain-sensitive material, the strain-sensitive sensitivity in the longitudinal direction is high, but the strain-sensitive sensitivity in the width direction (direction orthogonal to the longitudinal direction) is very low, so that the strip-shaped conductivity The strain-sensitive material made of the material needs to be arranged in the longitudinal direction along the radial direction of the diaphragm 101a, which is the direction in which the strain generated in the diaphragm 101a is generated according to the applied force.

However, in the conventional strain-sensitive material 104, the resistance value is too small if only one strip-shaped conductive member is arranged in the radial direction. Therefore, the total length of the thin metal wire or the metal foil is lengthened to obtain a desired resistance. It was necessary to secure a value to obtain an appropriate detection output voltage.

Therefore, as shown in FIG. 8B, each of the strain-sensitive materials 104X1, 104X2, 104Y1, 104Y2, 104Z1, 104Z2, 104Z3, 104Z4 has a strain-sensitive length L of the diaphragm 102 in the radial direction. Although it is long, a relatively large area is required because a large resistance value is secured by bending it in a zigzag shape in the circumferential direction.

Note that the diaphragm 101a undergoes strain deformation not only in the radial direction but also in the circumferential direction. Then, as described above, the strain-sensitive material 104 is in a state of being arranged in the circumferential direction of the diaphragm 101a, but as described above, the conventional strain-sensitive material 104 has a strip shape. Since the strain-sensitive sensitivity is very small (almost not detected) in the width direction of the conductive material, the conventional strain-sensitive material 104 hardly detects strain deformation in the circumferential direction.

Even when the strain-sensitive material 104 is made of a semiconductor material such as carbon, silicon, or germanium, the crystal orientations of the semiconductor materials having a high gauge ratio are arranged in the longitudinal direction according to the above, and the longitudinal direction thereof is It is provided along the radial direction (strain generation direction).

JP-A-2010-164495 Japanese Patent No. 6084393

By the way, recently, there has been an increasing demand for further miniaturization of this type of force sensor. However, the force sensor 103 described with reference to FIGS. 7 and 8 has a problem that further miniaturization becomes difficult.

That is, the main reason is that the above-mentioned conventional strain-sensitive material 104 (104X1, 104X2, 104Y1, 104Y2, 104Z1, 104Z2, 104Z3, 104Z4) receives strain only in the longitudinal direction thereof, as described above. Since the effective part that senses strain is the length part in the radial direction (strain generation direction) of the force sensor 103, the applied force is detected with a predetermined strain sensitivity. This means that it is difficult to reduce the diameter of the force sensor 103.

Further, as described above, in order to detect the applied force, a bridge circuit for each axial direction is required, and the conductor pattern for forming the bridge circuit is the flexible substrate 103a of the force sensor 103. Often formed on top. However, as described above, since the conventional strain-sensitive material 104 occupies a large occupied area in the radial direction and the circumferential direction of the force sensor 103, there is also a problem that it is difficult to take a space for forming the bridge circuit. Further, in the above-mentioned example of the conventional force sensor 103, a reference resistor is required as the bridge circuit for the X-axis direction and the Y-axis direction, and this reference resistor needs to be provided outside the force sensor 103. There is also.

An object of the present invention is to provide a force sensor capable of solving the above problems.

To solve the above problems
A strain-sensitive material is arranged on at least one surface of the plate-shaped member, and the strain-sensitive material senses the strain generated in the plate-shaped member in response to the force applied to the surface of the plate-shaped member. By doing so, it is a force sensor that senses the force applied to the surface portion.
The strain-sensitive material is made of a strip-shaped conductive material, and has a first surface portion of the plate-shaped member centered on a force applied portion applied to the surface portion of the plate-shaped member. Provided is a force sensor characterized in that the ring-shaped region of the above and the first ring-shaped region are arranged corresponding to each of the second ring-shaped regions having different distances from the force application portion. To do.

In the force sensor having the above configuration, the strain sensitizer is arranged in the first ring-shaped region and the second ring-shaped region centered on the force applied portion applied to the surface portion of the plate-shaped member. Therefore, it is possible to detect the extension strain on one side of the strain-sensitive material in the first ring-shaped region and the strain-sensitive material in the second ring-shaped region, and the contraction strain on the other side.

As the strain-sensitive material, for example, by using a Cr thin film composed of Cr and unavoidable impurities, or a strip-shaped conductive material composed of a Cr—N thin film composed of Cr, N and unavoidable impurities, a compact and highly sensitive material is used. A force sensor can be obtained.

It is a figure for demonstrating the structural example of the force detecting member provided with the embodiment of the force sensor by this invention. It is a figure for demonstrating the structural example of the embodiment of the force sensor by this invention. It is a figure for demonstrating the structural example of the embodiment of the force sensor by this invention. It is a circuit diagram which shows the example of the circuit applied to the embodiment of the force sensor by this invention. It is a figure for demonstrating the example of the simulation result of the embodiment of the force sensor by this invention, and the comparative example. It is a figure for demonstrating the structure of the other embodiment of the force sensor by this invention. It is a figure for demonstrating the example of the force detecting member provided with the conventional force sensor. It is a figure for demonstrating an example of the conventional force sensor. It is a circuit diagram for demonstrating an example of a conventional force sensor.

Hereinafter, embodiments of the force sensor according to the present invention will be described with reference to the drawings.

FIG. 1 shows a force detecting member 2 using the force sensor 1 of this embodiment. The force detecting member 2 of this example is composed of a pedestal portion 21, a force receiving portion 22, and a force sensor 1. FIG. 1A is a side view of the force detecting member 2 of this example viewed from a direction parallel to the surface portion 10a of the plate-shaped member 10 of the force sensor 1, and FIG. 1B is one of the plate-shaped members 10. FIG. 1 (C) is a perspective view of the surface portion 10b on the side opposite to the surface portion 10a of the plate-shaped member 10 viewed from an oblique direction, and FIG. 1 (C) is a perspective view of one surface portion 10a side of the plate-shaped member 10 viewed from an oblique direction. Is a bottom view of the surface portion 10a of the plate-shaped member 10 as viewed from a direction orthogonal to the surface portion 10a. FIG. 1 (E) is a vertical cross-sectional view of the force detecting member 2 on the pedestal portion 21 side.

2 and 3 are diagrams for explaining a configuration example of the force sensor 1 according to the embodiment of the present invention. The force sensor 1 of this example is formed by disposing a plurality of strain-sensitive materials 11 on one surface portion 10a of a plate-shaped member 10 made of an elastic insulating member. FIG. 2 shows the arrangement positions of the plurality of strain-sensitive members 11 arranged on one surface portion 10a of the plate-shaped member 10 of the force sensor 1 of this embodiment, and the plate-shaped member 10 according to the applied force. The relationship with the strain generated in is shown. As shown in FIG. 3A, one surface portion 10a of the plate-shaped member 10 is formed with a plurality of strain-sensitive materials 11 and a conductive pattern 12 for electrically connecting them. In 2 (A), the conductive pattern 12 is omitted.

2 (A) and 3 (A) show a view of the force sensor 1 in a direction orthogonal to one surface portion 10a of the plate-shaped member 10 and viewed from the one surface portion 10a side. ing. Further, FIG. 3B is a side view of the force sensor 1 as viewed from a direction parallel to the surface portion of the plate-shaped member 10. As shown in FIG. 3B, in this example, the plate-shaped member 10 is formed of a disc shape having a constant thickness d.

In the force sensor 1 of this embodiment, the plate-shaped member 10 is composed of a plate made of an elastic material, for example, a metal plate, and in this example, a SUS. In this example, an insulating layer (not shown) is provided on one surface 10a side of the plate-shaped member 10 to form an insulating member. Then, as will be described later, the strain-sensitive material 11 and the conductive pattern 12 are formed by forming a film on the insulating layer on one surface 10a side of the plate-shaped member 10, so that the force sensor 1 is formed. .. In the force sensor 1 of this embodiment, a strain-sensitive material is arranged on a flexible substrate as in the conventional case, and the strain-sensitive material is not adhered to the strain-generating body constituting the diaphragm by an adhesive. It is possible to avoid problems such as variations in strain-sensitive characteristics due to the influence of the material.

As shown in FIGS. 1A to 1C, the pedestal portion 21 of the force detecting member 2 is composed of a tubular member having the same outer diameter as the disc-shaped plate-shaped member 10 of the force sensor 1. .. The pedestal portion 21 is made of SUS in this example. For example, the peripheral edge portion 10E (see FIGS. 2 and 3) of the surface portion 10a of the plate-shaped member 10 of the force sensor 1 is joined to the end surface having a thickness determined by the outer diameter and the inner diameter of the pedestal portion 21. As a result, the force sensor 1 is fixed to the pedestal portion 21.

Note that the joining method in this case may be welding or a method of joining with an adhesive. Further, the method of connecting the pedestal portion 21 and the force sensor 1 is not limited to the joining as in this example, and the pedestal portion 21 and the plate-shaped member 10 may be integrally formed, or the pedestal portion 21 may be integrally formed. The plate-shaped member 10 may be sandwiched and fixed by a tubular body having the same outer diameter and inner diameter.

The force receiving unit 22 has a function of receiving the applied force and transmitting it to the plate-shaped member 10 of the force sensor 1, and in this example, it is a rod-shaped member made of, for example, SUS. One end of the force receiving portion 22 in the axial direction is coupled to the plate-shaped member 10 at the central portion of the plate-shaped member 10 of the force sensor 1. In this example, as shown in the cross-sectional view of FIG. 1 (E), the screw 23 is screwed into the axial end of the force receiving portion 22 via the plate-shaped member 10, so that the force receiving portion 22 is screwed. Is bonded to the plate-shaped body portion 10. As shown in FIG. 1 (DE), a through hole 10c into which the screw 23 is inserted is formed in the central portion of the plate-shaped member 10 of the force sensor 1. In this example, the plate-shaped member 10 is sandwiched between the columnar head 23a of the screw 23 and the axial end of the force receiving portion 22 at the center thereof, so that the force receiving portion 22 is a force sensor. Combined with respect to 1.

Needless to say, the method of connecting the force receiving unit 22 and the force sensor 1 is not limited to screwing as in this example. For example, one end of the force receiving portion 22 in the axial direction may be joined to the central portion on the opposite side of the surface portion 10a of the plate-shaped member 10 by welding or the like, or may be joined by an adhesive material. May be good. Further, the force receiving unit 22 and the plate-shaped member 10 may be integrally formed.

In this example, one end of the force receiving portion 22 in the axial direction is connected at the center of the surface portion opposite to the one surface portion 10a of the force sensor 1, but the plate-shaped member 10 Of course, the coupling may be performed on the surface portion 10a side.

In this example, as described above, in the plate-shaped member 10 of the force sensor 1, the peripheral portion 10E thereof is fixed to the pedestal portion 21, and the force receiving portion 22 is screwed at the central portion thereof by, for example, a screw 23. Since they are combined, as shown in FIG. 1D, a ring-shaped region RG having a width W between the position of the peripheral edge of the cylindrical head 23a of the screw 23 and the position of the inner diameter of the tubular pedestal portion 21. Is a region where elastic strain can be generated according to the force applied to the force receiving unit 22.

That is, assuming that the radius of the cylindrical head 23a of the screw 23 is ri and the inner diameter of the pedestal portion 21 is ro, as shown in FIGS. 1 (D) and 2 (A), the plate-shaped member 10 of the force sensor 1 The ring-shaped region RG whose radius centered on the center position Occ is in the range of ri ≦ r ≦ ro is a region where elastic strain is generated corresponding to the force transmitted from the force receiving unit 22.

As shown in FIGS. 1 (D), 2 (A) and 3 (A), in the force sensor 1 of this embodiment, the ring-shaped region RG having a width W of one surface portion 10a of the plate-shaped member 10 Is provided with a plurality of strain-sensitive materials 11.

By the way, in the force detecting member 2 of this example, the plate-shaped member 10 of the force sensor 1 has a disk shape having a constant thickness d, is fixed by the peripheral edge portion 10E thereof, and has its center position Occ. (See FIG. 2A), a force is applied through the force receiving unit 22.

Here, the radius of the center position in the width direction of the ring-shaped region RG having the width W of the plate-shaped member 10 is set to rc (rc = (ri + ro) / 2), and the ring-shaped region RG is set to the radius ri to the radius. It is divided into a first ring-shaped region RG1 located inside the range of rc and a second ring-shaped region RG2 located outside the range of radius rc to radius ro. Then, when a force is applied to the force receiving portion 22, strains in opposite directions occur in the first ring-shaped region RG1 inside the ring-shaped region RG and the second ring-shaped region RG2 outside.

That is, when the plate-shaped member 10 of the force sensor 1 receives a force (force in the Z-axis direction) in the direction orthogonal to the surface portion 10a via the force receiving portion 22, the plate-shaped member 10 is shown in FIG. 2 (B). As shown, it elastically deforms so that it protrudes downward. In this case, when the force other than the force in the Z-axis direction is zero, the plate-shaped member 10 causes the same strain over the entire circumference at the same radial position in the radial direction from the center Occ. Then, the strain becomes according to the magnitude of the applied force, and as shown in FIG. 2 (B), becomes an extension strain in the first ring-shaped region RG1, and also becomes a second ring. In the shape region RG2, shrinkage strain occurs, and strains in opposite directions occur.

Therefore, strain-sensitive materials 11 are provided in the first ring-shaped region RG1 and the second ring-shaped region RG2, respectively, and the elongation strain in the first ring-shaped region RG1 and the second ring-shaped region RG2 are provided. By detecting each of the contraction strains in the above, the force in the Z-axis direction can be detected. That is, the resistance values of the strain-sensitive material 11 provided in the first ring-shaped region RG1 and the strain-sensitive material provided in the second ring-shaped region RG2 change in opposite directions (increase direction and decrease direction). Therefore, the force applied to the force sensor 1 in the Z-axis direction can be detected based on the change in the resistance value.

Further, when a force (force in the X-axis direction or Y-axis direction) in the direction parallel to the surface portion 10a of the plate-shaped member 10 of the force sensor 1 is received via the force receiving portion 22, the plate-shaped member 10 is shown in FIG. As shown in C), strain deformation is performed so as to asymmetrically undulate around the center position Occ of the plate-shaped member 10. The degree of strain deformation depends on the magnitude of the applied force, and as shown in FIG. 2C, the plate-shaped member 10 has strains in opposite directions with the center Occ as the center. Occurs.

That is, as shown in FIG. 2C, contraction strain occurs in the first ring-shaped region RG1 on the front side of the center position Occ when viewed from the direction of the force applied to the force receiving unit 22. Further, elongation strain occurs in the second ring-shaped region RG2. Further, when viewed from the direction of the force applied to the force receiving unit 22, extension strain occurs in the first ring-shaped region RG1 behind the center position Occ, and the outer second ring-shaped region Shrinkage strain occurs in RG2. In the case of this example, as shown in FIG. 2C, in the first ring-shaped region RG1, the strain in the innermost peripheral portion thereof becomes large, and in the second ring-shaped region RG2, the strain becomes large. Since the strain on the outermost peripheral side becomes large, the strain-sensitive material 11 is arranged corresponding to the portion where the strain becomes large.

Therefore, the change in resistance value according to the strain of the strain-sensitive material 11 arranged in the first ring-shaped region RG1 and the strain of the strain-sensitive material 11 arranged in the second ring-shaped region RG2 The force component in the X-axis direction or the Y-axis direction can be detected from the corresponding change in the resistance value. Then, in this case, the first ring-shaped region RG1 and the second ring-shaped region RG2 on the front side of the center position Occ, and the first ring-shaped region RG1 and the second ring-shaped region RG2 on the rear side are Then, since the mode of the generated strain is opposite, the difference between the strain detection outputs detected by the strain sensitive material 11 on each of the front side and the back side of the center position Occ is taken in the X-axis direction. Alternatively, as the detection output of the force component in the Y-axis direction, a detection output having a synergistic magnitude can be obtained.

Based on the fact that the plate-shaped member 10 of the force sensor 1 of the force detecting member 2 of this embodiment has the above-mentioned strain generation mode, the force detecting member 2 of the embodiment has the plate-shaped member of the force sensor 1. By disposing the strain-sensitive material 11 on the 10 as described below, a 3-axis force sensor is configured.

In the force detecting member 2 of this embodiment, a force applied in the axial direction of the force receiving unit 22 orthogonal to the surface portion 10a of the plate-shaped member 10 of the force sensor 1 is received as a force in the Z-axis direction. Detect the size. Further, in the force detecting member 2 of this embodiment, the forces applied in the direction orthogonal to the axial direction of the force receiving unit 22 parallel to the surface portion 10a of the plate-shaped member 10 of the force sensor 1 and are mutually exclusive. The force in the orthogonal direction is received as the force in the X-axis direction and the Y-axis direction, and the magnitude thereof is detected.

Therefore, in the force sensor 1 of this embodiment, in order to form a triaxial force sensor, a plate-shaped member 10 made of a disk is shown as shown by being divided by a dotted line in FIGS. 2 (A) and 3 (A). One surface portion 10a is divided into four in the circumferential direction, and each is divided into four fan-shaped regions SX1, SY1, SX2, and SY2 in a 90 degree angle range. In this case, as shown in FIG. 2A, in this example, the fan-shaped regions SX1 and SX2 face each other in the X-axis direction with the center position Occ as the center, and the fan-shaped regions SY1 and SY2 have the center position Occ. It is configured to face the Y-axis direction as a center.

Then, in this embodiment, in each of the fan-shaped regions SX1, SY1, SX2, and SY2, the first ring-shaped region RG1 and the second ring-shaped region RG1 and the second ring-shaped region RG1 and the second ring-shaped region RG1 and the second ring-shaped region RG1 and the second The strain-sensitive material 11 is arranged so as to detect strains (extension strain and contraction strain) that occur in opposite directions in the ring-shaped region RG2.

That is, in this embodiment, the first ring-shaped region RG1 and the second ring-shaped region RG2 of the ring-shaped region RG in each fan-shaped region SX1, SY1, SX2, SY2 of one surface portion 10a of the plate-shaped member 10 A strain-sensitive material 11 is provided for each of the above.

Then, in this embodiment, in each of the fan-shaped regions SX1, SY1, SX2, and SY2, the first ring-shaped region RG1 and the second ring can be configured so that the bridge circuit constituting the strain detection circuit can be configured. Two strain-sensitive materials 11 are provided in each circumferential direction with the shape region RG2.

In FIGS. 2A and 3A, the strain-sensitive material 11 provided in each of the fan-shaped regions SX1, SY1, SX2, and SY2 of one surface portion 10a of the plate-shaped member 10 can be distinguished. , A parenthesis is attached to the reference code 11, and another reference code is attached in the parentheses. In the following description, when it is not necessary to distinguish the strain-sensitive material 11, it is described as the strain-sensitive material 11 by using the reference code as it is, and when it is necessary to distinguish it, the reference code in parentheses is used. I decided to.

That is, as shown in FIGS. 2 (A) and 3 (A), in the fan-shaped region SX1, the first ring-shaped region RG1 has two strain-sensitive materials X1 and X2 along the circumferential direction thereof. However, the second ring-shaped region RG2 is provided with two strain-sensitive materials X3 and X4, respectively, along the circumferential direction thereof. Further, in the fan-shaped region SX2, the first ring-shaped region RG1 has two strain-sensitive materials X5 and X6 along the circumferential direction thereof, and the second ring-shaped region RG2 has two strain-sensitive materials X5 and X6 in the circumferential direction. Two strain-sensitive materials X7 and X8 are provided along the line, respectively.

Further, in the fan-shaped region SY1, the first ring-shaped region RG1 has two strain-sensitive materials Y1 and Y2 along its circumferential direction, and the second ring-shaped region RG2 has two strain-sensitive materials Y1 and Y2 in its circumferential direction. Two strain-sensitive materials Y3 and Y4 are provided along the line. Further, in the fan-shaped region SY2, the first ring-shaped region RG1 has two strain-sensitive materials Y5 and Y6 along the circumferential direction thereof, and the second ring-shaped region RG2 has two strain-sensitive materials Y5 and Y6 in the circumferential direction. Two strain-sensitive materials Y7 and Y8 are provided along the line.

Here, as the strain-sensitive material 11, in this embodiment, a conductive material whose resistance value changes according to strain deformation, and a strip-shaped conductor (strip-shaped conductor) having a predetermined width k is used. In the example, a strip-shaped conductive material of a strain-sensitive material having excellent characteristics as described below is used.

As described above, a strip-shaped conductor (strip-shaped conductor) using a strain-sensitive material such as a Cu—Ni alloy, which is generally used in the past, has a strain-sensitive sensitivity only in the longitudinal direction thereof. Not done. Therefore, as shown in FIG. 8B, the strain-sensitive material made of strip-shaped conductors has its longitudinal direction in the radial direction (radiation direction seen from the point where the force is applied), which is the direction in which the strain is generated. In addition to arranging them together, since the resistance value of the material is low, it is necessary to form a zigzag pattern in which a plurality of folds are made in the circumferential direction to increase the resistance value.

For this reason, when a conventional strain-sensitive material is used, the pattern area thereof becomes large, and in particular, it is necessary to set the length of the plate-shaped member 10 of the strain-sensitive material pattern in the radial direction to a predetermined length. If this is arranged in the first ring-shaped region RG1 and the second ring-shaped region RG2, the size (diameter) of the plate-shaped member 10 (diaphragm) cannot be reduced. , It is difficult to miniaturize the force sensor 1.

In this embodiment, a strain-sensitive material having improved such defects is used. That is, in this example, the strip-shaped conductive material used as the strain-sensitive material is composed of a Cr thin film composed of Cr and unavoidable impurities, or a Cr—N thin film composed of Cr, N and unavoidable impurities (Patent No. 6084393). See Publication No. 2 (described in the column of Prior Art Documents as Patent Document 2). In the embodiment described below, a Cr—N thin film is used as the strain sensitive material 11.

The strip-shaped conductive material composed of this Cr—N thin film has no directional sensitivity to strain (isotropic), and has sensitivity not only in the longitudinal direction but also in the width direction (lateral direction). Moreover, the gauge rate that regulates the magnitude of the sensitivity is also high. Further, as described in Patent Document 2, the Cr—N thin film not only has a high gauge ratio, but also has a temperature coefficient of resistance (TCR) that can be controlled to about zero (<± 50 ppm / ° C.). It is stable against temperature changes, has a high resistance (several tens of kΩ), and has a feature that the pattern area of the strain sensitive material 11 may be small.

In the force sensor 1 of this embodiment, the strain-sensitive material 11 is arranged on one surface portion 10a of the plate-shaped member 10 as described below by utilizing the above-mentioned characteristics of the strain-sensitive material 11. The strain-sensitive material 11 having a high resistivity provides a high resistance value in a small area, and the strain generated by this can be detected pinpointly, so that high sensitivity can be achieved, and further, the high resistance makes it small. The strain-sensitive material 11 having an area may be sufficient, and the force sensor 1 can be miniaturized.

That is, in this embodiment, the strain-sensitive material 11 made of a strip-shaped conductive material has a plate-like longitudinal direction as shown by hatching in FIGS. 2 (A) and 3 (A). The radial direction seen from the point where the force is applied to the member 10 (the center position of the plate-shaped member 10) is not aligned in the longitudinal direction, but is arranged along the circumferential direction. That is, in this embodiment, each of the plurality of strain-sensitive materials 11 has an arc shape, and is arranged on the surface portion 10a of the plate-shaped member 10 along the circumferential direction. In this case, in this embodiment, the strip-shaped conductive materials constituting the strain-sensitive material 11 are the first ring-shaped region RG1 and the second ring according to the force applied to the plate-shaped member 10. The width direction is aligned with the pinpoint at the site where the strain generated in each of the shape regions RG2 is generated.

By disposing the strain-sensitive material 11 in this way, the force sensor 1 can detect the strain with sufficient sensitivity and while maintaining the magnitude of the detected output voltage. That is, when the longitudinal direction of the strain-sensitive material 11 made of a strip-shaped conductive material having a width k is arranged along the circumferential direction, the width direction portion of the width k of the strain-sensitive material 11 Strain is detected in, and strain detection in the width direction portion of the width k is performed over the length of the strain sensitizing material 11 in the longitudinal direction.

Further, since the plate-shaped member 10 is elastically deformed according to the applied force, strain is generated not only in the radial direction centered on the center position Occ of the plate-shaped member 10 but also in the circumferential direction, but the strain is received. The sensitive material 11 is also displaced according to the strain in the circumferential direction, and by changing its resistance value, the strain in the circumferential direction is also detected. Further, the resistance value of the conductive material constituting the strain-sensitive material 11 of this embodiment is high, and the strain-sensitive material having a small area can be provided according to the local strain while maintaining low power consumption. .. Therefore, in the force sensor 1 of this embodiment, the strain corresponding to the applied force can be sufficiently detected in each of the strain-sensitive materials 11.

Then, in this embodiment, the strain-sensitive materials X1, X2, X5, X6 and the strain-sensitive materials Y1, Y2, which are arranged in the first ring-shaped region RG1 on one surface portion 10a of the plate-shaped member 10. Y5 and Y6 are positions where a large strain is generated in response to the force applied in the first ring-shaped region RG1, in this example, in the width direction (radial direction) of the first ring-shaped region RG1. It is arranged at or near the innermost peripheral position separated by a radius ri from the central position Occ. That is, the width direction of the strip-shaped conductive material constituting each of the strain-sensitive materials X1, X2, X5, X6 and the strain-sensitive materials Y1, Y2, Y5, Y6 is set in the first ring-shaped region RG1. In the width direction (radial direction) where the generated strain is large, pinpoint the position on the innermost peripheral side or its vicinity, which is separated from the center position Oct by a radius of ri, and the longitudinal direction of the strip-shaped conductive material. It is arranged according to the circumferential direction in which strain is generated.

As described above, the strain-sensitive materials X1, X2, X5, X6 and the strain-sensitive materials Y1, Y2, Y5, Y6 are located at the same radial position from the center position Occ on one surface portion 10a of the plate-shaped member 10. Is arranged along the circumferential direction according to the strain generation position.

Similarly, the strain-sensitive materials X3, X4, X7, X8 and the strain-sensitive materials Y3, Y4, Y7, Y8 arranged in the second ring-shaped region RG2 are applied in the second ring-shaped region RG2. A position where a large amount of strain is generated according to the applied force, in this example, the outermost peripheral side position in the width direction (radial direction) of the second ring-shaped region RG2, which is separated by a radius r0 from the center position Occ, or its vicinity. Is arranged in. Therefore, the strain-sensitive materials X3, X4, X7, X8 and the strain-sensitive materials Y3, Y4, Y7, Y8 are located in the second ring-shaped region RG2 of one surface portion 10a of the plate-shaped member 10 from the center position Occ. At the same radial position, they are arranged along the circumferential direction according to the strain generation position.

In FIG. 3, for convenience of explanation, the strain sensitive material 11 is arranged at the center of the first ring-shaped region RG1 and the second ring-shaped region RG2 in the radial direction, but in practice. Of course, as shown in FIG. 2, the strain is arranged at the position where the magnitude of the strain is maximized.

Then, the strain-sensitive materials X1, X2, X5, X6 and the strain-sensitive materials Y1, Y2, Y5, Y6 arranged in the first ring-shaped region RG1 and the strain-sensitive materials Y1, Y2, Y5, Y6 are arranged in the second ring-shaped region RG2. The strain-sensitive materials X3, X4, X7, X8 and the strain-sensitive materials Y3, Y4, Y7, Y8 are the center positions of the plate-shaped member 10 as shown in FIGS. 2 (A) and 3 (A). It is arranged so as to be aligned in the radial direction centered on Occ, that is, in the strain generation direction.

Further, in this embodiment, the strain-sensitive materials X1, X2, X5, X6 and the strain-sensitive materials Y1, Y2, Y5, Y6 arranged in the first ring-shaped region RG1 and the second ring-shaped material. Of the strain-sensitive materials X3, X4, X7, X8 and the strain-sensitive materials Y3, Y4, Y7, Y8 arranged in the region RG2, at least two of them are arranged in the radial direction (radial direction) from the center position Occ. The strain-sensitive material 11 is configured so that the resistance values when no strain is generated are equal.

In this embodiment, the plate-shaped member 10 is arranged in the circumferential direction in the first ring-shaped region RG1 so that the strain sensitivity is equal in all the radial directions set to the central position Occ. The strain-sensitive materials X1, X2, X5, X6 and the strain-sensitive materials Y1, Y2, Y5, and Y6 all have the same resistance value when no strain is generated. Therefore, in this example, all of the strain-sensitive materials X1 to X8 and the strain-sensitive materials Y1 to Y8 are formed so that the resistance values when no strain is generated are equal.

In this case, the resistance value of the strain-sensitive material 11 is determined by the width of the strip-shaped conductive material, the length in the longitudinal direction, the thickness, and the material of the conductive material. In this example, since Cr—N is used as the material for all the strip-shaped conductive materials of the strain-sensitive materials X1 to X8 and the strain-sensitive materials Y1 to Y8, the width and length of the conductive material. By making the length in the direction equal to the thickness, the resistance value when no strain is generated is made equal. However, when strain is not generated by adjusting the width, length, and thickness of the strip-shaped conductive materials of the strain-sensitive materials X1 to X8 and the strain-sensitive materials Y to Y8, respectively. The resistance values of may be equal.

As disclosed in Patent Document 2, the strip-shaped conductive material made of Cr—N used in the strain-sensitive material 11 of the force sensor 1 of this embodiment is formed on a flexible substrate as in a conventional example. Instead, it can be formed directly on the plate-shaped member 10 itself, which is a strain-causing body, as a thin film.

Therefore, in the force sensor 1 of this embodiment, each of the strain-sensitive materials 11 is formed into a thin film in advance on one surface portion 10a of the plate-shaped member 10, and the conductor pattern 12 is the same. It is formed by forming a film. Therefore, the production of the force sensor 1 of this embodiment does not require a step of adhering the flexible substrate in which the strain-sensitive material is patterned and arranged by the adhesive, so that mass production is easy. Then, the force sensor 1 of this embodiment is connected to the pedestal portion 21 at the peripheral edge portion 10E of the plate-shaped member 10, and the force receiving portion 22 is connected by, for example, screwing at the central portion of the plate-shaped member 10. Since the force detecting member 2 can be generated, the force detecting member 2 is also characterized by being easy to manufacture.

In the force sensor 1 of this embodiment, as described above, the four strain-sensitive materials arranged in each of the fan-shaped regions SX1, SY1, SX2, and SY2 of the one surface portion 10a of the plate-shaped member 10 are used. , The bridge circuit that constitutes the strain detection circuit is configured. By arranging the conductive pattern 12 as shown in FIG. 3A, a bridge circuit is formed in each of the fan-shaped regions SX1, SY1, SX2, and SY2. In FIG. 3A, the conductive pattern 12 is shown as a white line pattern in order to distinguish it from the strain-sensitive material 11 shown with hatching.

The bridge circuit composed of the four strain-sensitive materials 11 arranged in each of the fan-shaped regions SX1, SY1, SX2, and SY2 has the same configuration. FIG. 4 is a diagram showing a configuration of a bridge circuit formed by electrically connecting four strain-sensitive materials X1 to X4 by a conductive pattern 12 in a fan-shaped region SX1 as a typical example.

That is, as shown in FIG. 4, between the terminal tV to which the power supply voltage Vcc is supplied and the grounded terminal tG, a series circuit of the strain sensitizer X1 and the strain sensitizer X3 and the strain sensation A series circuit of the material X2 and the strain-sensitive material X4 is connected in parallel. Then, the first output terminal tO (-) from the connection point between the strain-sensitive material X1 and the strain-sensitive material X3, and the second from the connection point between the strain-sensitive material X2 and the strain-sensitive material X4. The output terminals tO (+) are derived respectively. The terminals tV, tG, tO (−), and tO (+) are formed on the surface portion 10a of the plate-shaped member 10 as shown in FIG. 3A.

In the circuit of FIG. 4, when no strain is generated, the resistance values of the strain-sensitive materials X1 to X4 are all equal, so that the output voltages of the output terminal tO (−) and the output terminal tO (+) are equal. The output voltage of the difference is zero.

Then, when a force is applied to the force sensor 1, the force is applied to the first ring-shaped region RG1 in which the strain-sensitive material X1 exists and the second ring-shaped region RG2 in which the strain-sensitive material X3 exists. Since strains are received in opposite directions according to the force applied, the resistance values of the strain-sensitive material X1 and the strain-sensitive material X3 change in opposite directions. Then, a voltage corresponding to the difference between the resistance value of the strain-sensitive material X1 and the resistance value of the strain-sensitive material X3 is obtained at the output terminal tO (−), and the output terminal tO (+) is strained. A voltage in the direction opposite to that of the output terminal tO (−) is obtained according to the difference between the resistance value of the sensitive material X2 and the resistance value of the strain sensitive material X4. Therefore, the difference voltage between the voltage obtained at the output terminal tO (−) and the output voltage obtained at the output terminal tO (+) corresponds to the force component of the force applied to the force sensor 1 in the X-axis direction. The output voltage EX1 is obtained.

As described above, in the other fan-shaped regions SX2, SY1, and SY2, a bridge circuit is formed in the same manner, and an output voltage corresponding to the force applied to the force sensor 1 can be obtained. That is, in the case of the fan-shaped region SX2, as shown in parentheses in FIG. 4, the strain-sensitive material X5 replaces the strain-sensitive material X1 in the fan-shaped region SX1, and the strain-sensitive material X5 replaces the strain-sensitive material X2. The sensitive material X6 is obtained at the output terminal tO (-) by connecting the strain sensitive material X7 instead of the strain sensitive material X3 and the strain sensitive material X8 instead of the strain sensitive material X4. As the difference voltage between the voltage and the output voltage obtained at the output terminal tO (+), the output voltage EX2 corresponding to the force component of the force applied to the force sensor 1 in the X-axis direction is obtained.

Further, in the case of the fan-shaped region SY1, the strain-sensitive material Y1 replaces the strain-sensitive material X1 and the strain-sensitive material Y2 replaces the strain-sensitive material X2 in FIG. By connecting the strain-sensitive material Y3 instead of the strain-sensitive material X4 and the strain-sensitive material Y4 instead of the strain-sensitive material X4, the voltage obtained at the output terminal tO (-) and the voltage obtained at the output terminal tO (+) are obtained. As a voltage difference from the output voltage to be obtained, an output voltage EY1 corresponding to the force component of the force applied to the force sensor 1 in the Y-axis direction is obtained.

Further, in the case of the fan-shaped region SY2, the strain-sensitive material Y5 replaces the strain-sensitive material X1 and the strain-sensitive material Y6 replaces the strain-sensitive material X2 in FIG. By connecting the strain-sensitive material Y7 instead of the strain-sensitive material X4 and the strain-sensitive material Y8 instead of the strain-sensitive material X4, the voltage obtained at the output terminal tO (-) and the voltage obtained at the output terminal tO (+) are obtained. As a voltage difference from the output voltage to be obtained, an output voltage EY2 corresponding to the force component of the force applied to the force sensor 1 in the Y-axis direction is obtained.

Then, as described above, by using the output voltages EX1, EX2, EY1 and EY2 of the four bridge circuits formed in the fan-shaped regions SX1, SX2, SY1 and SY2, the force of the force detecting member 2 is used. The output voltage EZ for the Z-axis direction force component of the force applied to the receiving unit 22, the output voltage EX for the X-axis direction force component, and the output voltage EY for the Y-axis direction force component are as follows. Obtained from the arithmetic formula.

That is, as for the force component in the Z-axis direction, as shown in FIG. 2 (B), the same strain deformation occurs in the radial direction centered on the center position Occ of the plate-shaped member 10, so that the force detecting member 2 The detected output voltage EZ is
EZ = EX1 + EX2 + EY1 + EY2
Is calculated as.

As for the force component in the X-axis direction, as shown in FIG. 2C, reverse strain occurs on the front side and the rear side of the center position Occ of the plate-shaped member 10, so that the force is detected. The detected output voltage EX of member 2 is
EX = EX1-EX2
Is calculated as.

Similarly, with respect to the force component in the Y-axis direction, as shown in FIG. 2C, reverse strain occurs on the front side and the rear side of the center position Occ of the plate-shaped member 10. , The detection output voltage EY of the force detection member 2 is
EY = EY1-EY2
Is calculated as.

[Effect of Embodiment]
As described above, according to the force sensor 1 of the above-described embodiment, the first ring-shaped region RG1 which is a region different from the center position of the disc-shaped plate-shaped member 10 in the radial direction (radial direction). By arranging the strain-sensitive material 11 in each of the second ring-shaped region RG2 and the second ring-shaped region RG2, the force applied to the force sensor 1 can be detected.

In this case, the strain-sensitive material 11 sets the width direction position of the strip-shaped conductive material to the radial position of each of the ring-shaped regions RG1 and RG2 in accordance with the strain generation position, and also sets the strip-shaped conductive material. Since the longitudinal direction of the material is arranged along the circumferential direction that matches the strain generation position, the area of the strain-sensitive material 11 that occupies the radial direction of the disc-shaped plate-shaped member 10 can be reduced. The radius of the plate-shaped member 10 can be reduced, and the force sensor 1 can be miniaturized.

Then, in the force sensor 1 of this embodiment, a thin film of the strain-sensitive material 11 is directly formed on the plate-shaped member 10, and the strain-sensitive materials 11 for forming a bridge circuit are electrically connected to each other. Since the conductive pattern for this purpose is also formed on the plate-shaped member 10, a strain-sensitive material is formed on the flexible substrate and the flexible substrate is used as a strain-causing body as in the conventional force sensor described at the beginning. It is not necessary to adhere to the plate-shaped member of the above with an adhesive. Therefore, the force sensor 1 can be easily manufactured, and there is an advantage that the strain sensitivity is not lowered or varied due to the presence of the adhesive as in the conventional case, and the stress-strain characteristic is not changed. Further, since the temperature characteristics of the flexible substrate (polyimide, etc.) are different from those of the diaphragm and the plate-shaped member, the temperature characteristics of the force sensor are affected, but there is an advantage that it is not necessary to consider this.

Further, in the force sensor 1 of this embodiment, since the strain sensitive material 11 is composed of a Cr—N thin film composed of Cr, N and unavoidable impurities, the strain sensitive sensitivity does not depend on the directionality and is high. It also has the effect of realizing a sensitive force sensor. As described above, the strain sensitive material 11 may be a Cr thin film composed of Cr and unavoidable impurities.

Then, in the force sensor 1 of this embodiment, as described above, in each of the fan-shaped regions obtained by dividing the disc-shaped plate-shaped member 10 in the circumferential direction, the strain generated in the fan-shaped region according to the applied force. A bridge circuit can be configured to detect, and the outputs of the plurality of bridge circuits can be used to detect the X-axis direction component, Y-axis direction component, and Z-axis direction component of the applied force with high sensitivity. Can be detected.

In order to confirm the effect of the force sensor 1 of the above-described embodiment, the applicant created a force sensor using a conventional strain-sensitive material as a comparative example, and simulated the strain detection of both. This comparative example and the simulation result will be described with reference to FIG.

Using a Cu—Ni alloy as an example of a strain-sensitive material that is generally used in the past, a force sensor 1 ′ having the same configuration as the force sensor 1 of this embodiment is created. FIG. The configuration is as follows. For ease of comparison, FIG. 5B shows the force sensor 1 of this embodiment.

As can be seen from FIGS. 5A and 5B, in the force sensor 1'of the comparative example, the shape of the strain-sensitive material arranged in each fan-shaped region SX1, SX2, SY1, SY2 is this. It is different from the strain-sensitive material 11 of the force sensor 1 of the embodiment. That is, the strain-sensitive material of the force sensor 1'in the comparative example has a zigzag pattern as shown in the figure. For the sake of simplicity, in FIGS. 5A and 5B, reference numerals are arranged on behalf of the fan-shaped region SX1, and in the force sensor 1'of the comparative example, the fan-shaped region SX1 is zigzag. The strain-sensitive materials X1'to X4' of the shape pattern are arranged.

As described above, the strain-sensitive materials generally used in the past are not limited to Cu—Ni alloys, but have a large anisotropy in the strain-sensitive direction, and the sensitivity of the strip-shaped strain-sensitive material in the width direction. Therefore, it was necessary to arrange the pattern so that the length of the plate-shaped member 10 changes in the radial direction. Since the resistance value of the strain-sensitive material is low, the strain-sensitive materials X1'to X4' are formed into a zigzag pattern in which a plurality of times are folded back, as shown in FIG. 5A, from the viewpoint of heat generation and current consumption. The resistance value is increased.

The force sensor 1'of the comparative example of FIG. 5 (A) and the force sensor 1 of this embodiment of FIG. 5 (B) having the above configuration are coupled to the center position of the plate-shaped member 10. The simulation result when the same force in the Z-axis direction (direction orthogonal to the plate-shaped member 10) is applied through the rod-shaped force receiving unit 22 (not shown in FIG. 5) is shown in FIG. 5 (FIG. 5). It will be as shown in the table of C). The detected strain amount shown at the right end of FIG. 5C is the total strain amount detected in the fan-shaped region SX1 by the strain-sensitive materials X1'to X4' in the force sensor 1'.

In this simulation, the outer diameter of the plate-shaped member 10 of the force sensor 1 and the force sensor 1'is 6 mm, the thickness of the plate-shaped member 10 is 0.5 mm, the diameter of the force receiving portion 22 is 2 mm, and the plate-shaped member. The width of the peripheral edge portion 10E to which the 10 is fixed is set to 0.7 mm.

As shown in the table of FIG. 5 (C), in the force sensor 1'of the conventional pattern of the comparative example of FIG. 5 (A), the strain-sensitive materials X1'to X4' have the diameters of the plate-shaped members 10. It can be seen that only the strain change in the direction is detected, and the strain change in the circumferential direction of the plate-shaped member 10 cannot be detected.

In the force sensor 1'of the comparative example, the strain-sensitive materials X1'to X4' have a zigzag pattern in order to increase the resistance value, so that the detection area becomes large and the maximum strain concentrated on the pinpoint. Is difficult to detect. Then, in the force sensor 1'of the comparative example, it is not possible to obtain a practical resistance value, considering that the strain-sensitive materials X1'to X4' are formed as a pattern with a full bridge configuration and the like with high accuracy (plate). When the diameter of the shape member 10 is 6 mm, it is 100 Ω or less), and the detection output detected when the bridge circuit as shown in FIG. 4 is configured can be obtained, for example, only a value of 0.1 mV / V or less.

On the other hand, in the strain-sensitive materials X1 to X4 of the force sensor 1 of this embodiment, not only the strain change in the radial direction of the plate-shaped member 10 but also the strain change in the circumferential direction of the plate-shaped member 10 can be detected. I understand. Then, as shown at the right end of FIG. 5C, the total amount of strain detected in the fan-shaped region SX1 of the force sensor 1 of this embodiment is detected in the sector region SX1 of the force sensor 1 ′ of the comparative example. It can be seen that the amount of distortion is more than twice the total amount.

Since the strain-sensitive materials X1 to X4 of the force sensor 1 of this embodiment are composed of Cr—N thin films capable of forming a thin film into a pattern by a fine process, a high resistance (a thin pattern of 50 μm or less is formed by the fine process). It can be formed, the surface resistance is high because the film is thin, and the kΩ order is possible). Further, according to the strain-sensitive materials X1 to X4 of the force sensor 1 of this embodiment, it is possible to form the strip-shaped pattern by the width direction (lateral sensitivity) of the strip-shaped pattern. It saves space and enables pinpoint strain detection. Further, since the Cr—N thin film itself has a high gauge ratio, a high output can be obtained even with the same strain value. An output of several mV / V can be obtained as an output when the bridge circuit as shown in FIG. 4 is configured, and a high-output compact force sensor can be realized.

[Modification example of force sensor]
<Other examples of strain-sensitive material patterns>
In the above-described embodiment, since the strain-sensitive material 11 is arranged along the longitudinal direction of the strip-shaped conductive material along the circumferential direction of the plate-shaped member 10, the plate-shaped member 10 is divided in the circumferential direction. When arranged in each of the fan-shaped regions, the length in the longitudinal direction is shorter than the angle of the fan-shaped region, the length in the longitudinal direction of the strip-shaped conductive material is limited, and the resistance value. Will also be restricted.

FIG. 6 shows an example force sensor 1A that improves this problem. In the force sensor 1A of the example of FIG. 6, the same reference numerals are given to the same parts as the force sensor 1 of the above-described embodiment, and detailed description thereof will be omitted.

As shown in FIG. 6, in the force sensor 1A of this example, in the force sensor 1 described above, in each of the four fan-shaped regions SX1, SY1, SX2, and SY2, the first ring-shaped region RG1 and Two strain-sensitive materials 11A are provided in each of the second ring-shaped region RG2 in the circumferential direction, and the pattern shape of the strain-sensitive material 11A in the force sensor 1A of this example is the above-described embodiment. It is different from the strain sensitive material 11 of the force sensor 1. Other configurations are the same as the force sensor 1A of this example and the force sensor 1 of the example of the above-described embodiment. In FIG. 6, the portion of the strain-sensitive material 11A is shown with hatching, and the conductive pattern 12A that electrically connects the strain-sensitive material 11A is shown as a white line pattern.

In FIG. 6, for convenience of explanation, the strain-sensitive material 11A is arranged at the center of the first ring-shaped region RG1 and the second ring-shaped region RG2 in the radial direction, but in practice. Of course, as shown in FIG. 2, the strain is arranged at the position where the magnitude of the strain is maximized.

Similar to the force sensor 1 of the above-described embodiment, in FIG. 6, the strain sensation provided in each fan-shaped region SX1, SY1, SX2, SY2 of one surface portion 10a of the plate-shaped member 10 of the force sensor 1A of this example. A parenthesis is attached to the reference numeral 11A so that the material 11A can be distinguished, and another reference numeral is attached within the parenthesis. In the following description, when it is not necessary to distinguish the strain-sensitive material 11A, it will be described as it is as the strain-sensitive material 11A, and when it is necessary to distinguish it, it will be described using the reference reference numerals in parentheses.

That is, as shown in FIG. 6, in the fan-shaped region SX1 of the plate-shaped member 10, two strain-sensitive materials X1A and X2A are provided in the first ring-shaped region RG1 and two strain-sensitive materials X1A and X2A are provided in the second ring-shaped region RG2. The strain-sensitive materials X3A and X4A are provided in their circumferential directions, respectively. Further, in the fan-shaped region SX2, two strain-sensitive materials X5A and X6A are provided in the first ring-shaped region RG1, and two strain-sensitive materials X7A and X8A are provided in the second ring-shaped region RG2. It is provided in each of the circumferential directions.

Further, in the fan-shaped region SY1, two strain-sensitive materials Y1A and Y2A are provided in the first ring-shaped region RG1, and two strain-sensitive materials Y3A and Y4A are provided in the second ring-shaped region RG2. It is provided in each direction. Further, in the fan-shaped region SY2, two strain-sensitive materials Y5A and Y6A are provided in the first ring-shaped region RG1, and two strain-sensitive materials Y7A and Y8A are provided in the second ring-shaped region RG2. It is provided in each direction.

Here, the strain-sensitive material 11A is composed of a Cr thin film composed of Cr and unavoidable impurities, or a Cr—N thin film composed of Cr, N and unavoidable impurities, similarly to the strain-sensitive material 11 of the above-described embodiment. A strip-shaped conductive material having a predetermined width is used. Also in the example of FIG. 6, a Cr—N thin film is used as the strip-shaped conductive material of the strain-sensitive material 11A.

Then, in the force sensor 1A of this example, as shown in FIG. 6, the strain-sensitive material 11A has the longitudinal direction of the strip-shaped conductive material as the direction along the circumferential direction of the plate-shaped member 10. At the same time, by folding back in a zigzag shape in the radial direction, the total length of the strip-shaped conductive material in the longitudinal direction is made longer than the strain-sensitive material 11 of the force sensor 1 of the above-described embodiment.

That is, in the strain-sensitive material 11A of this example, a plurality of strip-shaped conductive materials in the circumferential direction centered on the center position Occ of the plate-shaped member 10 are centered on the center position Occ of the plate-shaped member 10. It is arranged in the radial direction, and the longitudinal ends of the plurality of strip-shaped conductive materials are sequentially connected to each other to form one strip-shaped conductive material.

Also in the case of this example, all of the strain-sensitive materials X1A to X8A and the strain-sensitive materials Y1A to Y8A are formed so that the resistance values when no strain is generated are equal. In this example, strain is generated by making the width and thickness of all the strip-shaped conductive materials of the strain-sensitive materials X1A to X8A and the strain-sensitive materials Y1A to Y8A equal to the total length in the longitudinal direction. The resistance values when not set are equal.

In this case, in the force sensor 1 of the above-described embodiment, since the strain-sensitive material 11 is composed of one strip-shaped conductive material without folding back, it is arranged in the first ring-shaped region RG1. Strain sensitive materials X1, X2, X5, X6 and Y1, Y2, Y5, Y6 to be installed, and strain sensitive materials X3, X4, X7, X8 and Y3, Y4 arranged in the second ring-shaped region RG2. As shown in FIGS. 2 (A) and 3 (A), the lengths (longitudinal direction) of the strip-shaped conductive material in the circumferential direction are made equal to those of Y7 and Y8.

However, in the example of FIG. 6, since the strain-sensitive material 11A is configured to be folded back in the radial direction of the plate-shaped member 10, the total length of the strip-shaped conductive material of the strain-sensitive material 11A in the longitudinal direction is , Can be the length including the folded part. Therefore, as shown in FIG. 6, the strain-sensitive materials X1, X2, X5, X6 and Y1, Y2, Y5, Y6 arranged in the first ring-shaped region RG1 and the second ring-shaped region RG2 The strain-sensitive materials X3, X4, X7, X8 and Y3, Y4, Y7, Y8 to be arranged can have different lengths in the circumferential direction. In this case, in order to equalize the total length of the strip-shaped conductive material of the strain-sensitive material 11A in the longitudinal direction and make the resistance value at the time of no strain equal, as shown in FIG. 6, the first ring-shaped region Strain sensitive materials X1, X2, X5, X6 and Y1, Y2, Y5, Y6 arranged in RG1 and strain sensitive materials X3, X4, X7, X8 and Y3 arranged in the second ring-shaped region RG2. , Y4, Y7, Y8 differ in the number of wrappings and the like.

Also in the example of FIG. 6, the four strain-sensitive materials 11A arranged in each of the fan-shaped regions SX1, SY1, SX2, and SY2 of the plate-shaped member 10 of the force sensor 1A are shown by the conductor pattern 12A. As shown in 6, the bridge circuit is formed by being connected. For example, in the fan-shaped region SX1, in FIG. 4, the strain-sensitive material X1 is changed to X1A, the strain-sensitive material X2 is changed to X2A, the strain-sensitive material X3 is changed to X3A, and the strain-sensitive material X4 is changed to X4A. A bridge circuit is generated.

Therefore, also in the force sensor 1A of the example of FIG. 6, the voltage obtained as the difference between the voltage obtained at the output terminal tO (−) and the output voltage obtained at the output terminal tO (+) corresponds to the applied force. The output voltage EX1A is obtained. Then, in the other fan-shaped regions SX2, SY1, SY2, a bridge circuit is formed in the same manner, and output voltages EX2A, EY1A, and EY2A corresponding to the force applied to the force sensor 1 can be obtained.

Then, the detected output voltage EZA for the force component in the Z-axis direction of the force applied to the force sensor 1A, the detected output voltage EXA for the force component in the X-axis direction, and the detected output voltage EYA for the force component in the Y-axis direction are ,
EZA = EX1A + EX2A + EY1A + EY2A
EXA = EX1A-EX2A
EYA = EY1A-EY2A
Is calculated as.

According to the force sensor 1A of the example of FIG. 6, the total length of the strain-sensitive material 11A in the longitudinal direction can be made longer than the length of the fan-shaped region in which the strain-sensitive material 11A is arranged in the circumferential direction. The resistance value of the strain-sensitive material 11A can be increased, and the power consumption can be reduced by increasing the resistance value while suppressing the decrease in sensitivity as much as possible.

<Other variants>
In the above-described embodiment, the example in which the strain-sensitive material 11 is arranged on one surface portion 10a of the plate-shaped member 10 has been described, but the strain-sensitive material 11 is provided on the surface portion 10b opposite to the surface portion 10a. It may be arranged and formed. In that case, the strain that occurs shows the same sensation state, only the sign is opposite to that of the surface portion 10a.

Further, in the above-described embodiment, each of the ring-shaped region RG, the first ring-shaped region RG1 and the second ring-shaped region RG2 is taken up as a region where elastic strain occurs, but a region where elastic strain occurs. Is not limited to these areas. For example, when the outer peripheral portion of 1A of the force sensor 1 is fixed, elastic strain is also generated in the outer peripheral portion region, and the outer peripheral portion 10E is located on one surface portion 10b of the plate-shaped member 10. It is also possible to detect the elastic strain that occurs.

In the above-described embodiment, the strain detection output corresponding to the force component in the Z-axis direction, the force component in the X-axis direction, and the force component in the Y-axis direction of the force applied to the force sensors 1 and 1A in the three-axis directions. Therefore, one surface portion 10a of the plate-shaped member 10 is divided into four fan-shaped regions SX1, SX2, SY1, SY2, and strain- sensitive materials 11 and 11A are provided in each region. However, it is not limited to such a configuration.

For example, strain detection output corresponding to the force component in the Z-axis direction of the force applied to the force sensors 1 and 1A, and one of the force component in the X-axis direction and the force component in the Y-axis direction in the biaxial direction. In each of the two semicircular regions formed by dividing one surface portion 10a of the plate-shaped member 10 into two in the X-axis direction or two in the Y-axis direction. Two strain- sensitive materials 11 or 11A may be arranged in the ring-shaped region RG1 of 1, and two strain- sensitive materials 11 or 11A may be arranged in the second ring-shaped region RG1, respectively.

However, when the strain detection output corresponding to the biaxial force component of the force component in the X-axis direction and the force component in the Y-axis direction of the force applied to the force sensors 1 and 1A is to be obtained, the above-mentioned It is necessary to make the same as the force sensor 1.

Further, in the case of detecting only the force component of the force applied to the force sensors 1 and 1A in the Z-axis direction, when the bridge circuit is formed on one surface portion 10a of the plate-shaped member 10, the above-mentioned two axes are used. As in the case of detecting the direction, in each of the two semicircular regions, the first ring-shaped region RG1 has two strain- sensitive materials 11 or 11A, and the second ring-shaped region RG2 has two strain- sensitive materials 11 or 11A. The strain sensitive material 11 or 11A may be arranged respectively.

In the case of detecting only the force component of the force applied to the force sensors 1 and 1A in the Z-axis direction, one ring-shaped strain- sensitive material 11 or 11A is arranged in the first ring-shaped region RG1. In addition, one ring-shaped strain- sensitive material 11 or 11A may be arranged in the second ring-shaped region RG2, respectively. In that case, the resistance values of the two ring-shaped strain- sensitive materials 11 or 11A are formed to be equal to each other, and a reference resistor having the same resistance value is provided outside, thereby bridging. By configuring the circuit, it is possible to detect the force component of the force applied to the force sensors 1 and 1A in the Z-axis direction.

When detecting only the force component of the force applied to the force sensors 1 and 1A in the X-axis direction, one surface portion 10a of the plate-shaped member 10 is divided into two semicircles in the X-axis direction. In each of the regions, the strain- sensitive material 11 or 11A may be arranged in the first ring-shaped region RG1 and the strain- sensitive material 11 or 11A may be arranged in the second ring-shaped region RG2, respectively.

Similarly, when detecting only the force component of the force applied to the force sensors 1 and 1A in the Y-axis direction, one surface portion 10a of the plate-shaped member 10 is divided into two semicircles in the Y-axis direction. In each of the circular regions, the strain- sensitive material 11 or 11A may be arranged in the first ring-shaped region RG1 and the strain- sensitive material 11 or 11A may be arranged in the second ring-shaped region RG2, respectively. ..

In the above-described embodiment, the strain- sensitive materials 11 and 11A are formed in an arc shape along the circumferential direction of the plate-shaped member 10, but may be formed in a straight line.

Further, the longitudinal direction of the strain sensitizing materials 11 and 11A does not need to be arranged exactly along the circumferential direction in the first and second ring-shaped regions RG1 and RG2 of the plate-shaped member 10, and is a circle. It may be arranged in a direction intersecting with the circumferential direction.

In other words, the longitudinal direction of the strain- sensitive materials 11, 11A does not have to be along the direction orthogonal to the radiation direction centered on the center position Occ, which is the force application portion of the force sensors 1, 1A. With respect to the direction of strain generated in the radial direction about the application portion of, for example, when the clockwise direction is the + direction, the strain may be displaced to the + direction side or the-direction side to an angle of 90 degrees.

In the above-described embodiment, the plate-shaped member 10 of the force sensors 1 and 1A is made of SUS, but it goes without saying that the plate-shaped member 10 is not limited to SUS and other elastic materials can be used.

Further, the conductive material constituting the strain- sensitive materials 11 and 11A is not limited to a Cr thin film composed of Cr and unavoidable impurities, or a Cr—N thin film composed of Cr, N and unavoidable impurities, and is strip-shaped conductive. As the material, any material may be used as long as it has strain sensitivity in the width direction.

Further, the circuit formed on one surface portion 10a of the plate-shaped member 10 of the force sensor together with the strain-sensitive material may be a part of the bridge circuit, not the whole. Further, the circuit formed together with the strain-sensitive material is not limited to a bridge circuit, and any circuit can be used as long as it is a circuit for sensing strain according to the applied force using the strain-sensitive material. May be good. Further, each of the strain-sensitive materials constituting the bridge circuit may have a different resistance value, and each resistance value of the strain-sensitive material may be set so as to satisfy the equilibrium condition of the bridge circuit.

Further, the plate-shaped member 10 of the force sensor may have a polygonal shape instead of a disk, and the ring-shaped region in that case may also have a polygonal shape.

Further, although the plate-shaped member 10 of the force sensor has a constant thickness, the thickness may change in the radial direction centered on the force application portion. For example, in the case of the force sensors 1 and 1A of the above-described embodiment, in the first ring-shaped region RG1 and the second ring-shaped region RG2, strain deformation is likely to occur in the vicinity of the portion where the strain-sensitive material is arranged. The thickness may be made thinner than other parts as described above.

1,1A ... force sensor, 2 ... force detection member, 10 ... plate-shaped member, 11,11A ... strain-sensitive material, 12,12A ... conductor pattern, 21 ... pedestal part, 22 ... force receiving part, RG ... ring-shaped Region, RG1 ... first ring-shaped region, RG2 ... second ring-shaped region, SX1, SX2, SY1, SY2 ... fan-shaped region

Claims (14)

1. A strain-sensitive material is arranged on at least one surface of the plate-shaped member, and the strain-sensitive material senses the strain generated in the plate-shaped member in response to the force applied to the surface of the plate-shaped member. By doing so, it is a force sensor that senses the force applied to the surface portion.
   The strain-sensitive material is made of a strip-shaped conductive material, and has a first surface portion of the plate-shaped member centered on a force applied portion applied to the surface portion of the plate-shaped member. The force sensor is characterized in that the ring-shaped region of the above and the first ring-shaped region are arranged corresponding to each of the second ring-shaped regions having different distances from the force applying portion.
2. The strain-sensitive material has a direction in which the longitudinal direction of the strip-shaped conductive material intersects the radial direction centered on the force applied portion applied to the surface portion of the plate-shaped member. The force sensor according to claim 1, wherein the force sensor is arranged on the plate-shaped member as described above.
3. The force sensor according to claim 1, wherein the strip-shaped conductive material has an arc shape.
4. The force sensor according to claim 1, wherein the strip-shaped conductive material has a linear shape.
5. The longitudinal direction of the strip-shaped conductive material is displaced by a predetermined angle with respect to the direction in which the strain generated in the radial direction is centered on the portion where the force applied to the surface portion of the plate-shaped member is applied. The force sensor according to claim 1.
6. The first ring-shaped region and the second ring-shaped region are characterized in that an elongation strain is generated in one ring-shaped region and a contraction strain is generated in the other ring-shaped region. The force sensor according to claim 1.
7. A plurality of strip-shaped conductive materials are arranged in a direction intersecting the radial direction centered on the force application portion, corresponding to the first ring-shaped region or the second ring-shaped region. The force sensor according to claim 1, wherein the plurality of strip-shaped conductive materials are sequentially connected to each other.
8. Two strip-shaped conductive materials are arranged corresponding to the first ring-shaped region, and two strip-shaped conductive materials are arranged corresponding to the second ring-shaped region. The force sensor according to claim 1, wherein a bridge circuit is formed of the conductive material of the above.
9. The strip-shaped conductive material is formed by dividing the circumferential direction around the application portion of the force applied to the surface portion of the plate-shaped member into n (integer of n ≧ 2). The force sensor according to claim 8, wherein the force sensor is arranged in one sector.
10. The strip-shaped conductive material is characterized in that it is composed of a conductive material capable of detecting strain generated in a radial direction around at least the applied portion of the force applied to the surface portion of the plate-shaped member. The force sensor according to claim 1.
11. The force sensor according to claim 10, wherein the strip-shaped conductive material is composed of a Cr thin film composed of Cr and unavoidable impurities, or a Cr—N thin film composed of Cr, N and unavoidable impurities.
12. The force sensor according to claim 1, wherein the plate-shaped member is made of an insulating substrate.
13. The force sensor according to claim 12, wherein the insulating substrate is formed by disposing an insulating material on a metal substrate.
14. The force sensor according to claim 13, wherein the strain-sensitive material is formed on an insulating layer formed of the insulating material.

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