JP2020024218A - Strain gauge and multiaxial force sensor - Google Patents

Abstract

To provide a strain gauge in which occurrence of measurement errors arising from a change in ambient temperature is suppressed.SOLUTION: A stain gauge 20 comprises a flexible base material 21 and a circuit pattern that is formed on the base material. The base material has: a sensitive region 21s that is attached in a strain region; non-sensitive regions 21n1 an 21n2 outside the strain region; joint regions 21c1 and 21c2 that joint the regions. The circuit pattern includes: first-direction strain sensitive elements X1 and X2 that constitute a first bridge circuit BC1; second-direction strain sensitive elements Y1 and Y2 that constitute a second bridge circuit BC2; and at least one of first-direction stationary resistance elements RX1 and RX2 constituting the first bridge circuit and second-direction stationary resistance elements RY1 and RY2 constituting the second bridge circuit. The strain sensitive elements X1, X2, Y1 and Y2 and stationary resistance elements RX1, RX2, RY1 and RY2 are formed of the same material. The strain sensitive element is formed in the sensitive region and the stationary resistance element is formed in the non-sensitive region.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a strain gauge and a multiaxial force sensor including the strain gauge.

  Multiaxial force sensors provided with strain gauges are widely used in robots, game machines, various measuring devices, and other devices. Patent Documents 1 and 2 disclose examples of a multiaxial force sensor including a strain gauge.

JP 2010-164495 A Japanese Patent No. 508188

  In a multiaxial force sensor including a strain gauge, the existence of a measurement error due to a change in ambient temperature is recognized, and suppression of the error is desired.

  Therefore, an object of the present invention is to provide a strain gauge in which generation of a measurement error due to a change in ambient temperature is suppressed, and a multiaxial force sensor including the same.

According to a first aspect of the present invention,
The first Wheatstone bridge circuit detects a load applied to the strain-generating member that is distorted under load and acts in the first direction of the strain-generating member, and in a second direction orthogonal to the first direction of the strain-generating member. A strain gauge used for detecting an applied load by a second Wheatstone bridge circuit,
A flexible substrate;
And a circuit pattern formed on the base material,
The base material is a sensitive region attached to a strain generating region where a strain is generated by receiving a load of the strain generating member, a dead region arranged outside the strain generating region, the sensitive region and the dead region. And a connection region for connecting
The dimension of the connection area in the orthogonal direction orthogonal to the direction in which the sensitive area and the insensitive area are connected is smaller than the dimension in the orthogonal direction of the sensitive area and the insensitive area,
The circuit pattern includes two first-directional strain-sensitive elements forming a first Wheatstone bridge circuit, two second-directional strain-sensitive elements forming a second Wheatstone bridge circuit, and a first Wheatstone bridge circuit. At least one of a first direction fixed resistance element and a second direction fixed resistance element forming a second Wheatstone bridge circuit.
The two first direction strain-sensitive elements, the two second direction strain-sensitive elements, and at least one of the first direction fixed resistance element and the second direction fixed resistance element are formed of the same material,
The two first direction strain sensing elements and the two second direction strain sensing elements are formed in the sensing area,
At least one of the first direction fixed resistance element and the second direction fixed resistance element is formed in the dead area.
A strain gauge is provided.

  In the strain gauge of the first aspect, the circuit pattern includes two first direction fixed resistance elements forming a first Wheatstone bridge circuit and two second direction fixed resistance elements forming a second Wheatstone bridge circuit. The two first direction strain-sensitive elements, the two second direction strain-sensitive elements, the two first direction fixed resistance elements, and the two second direction fixed resistance elements may be made of the same material. The two first direction fixed resistance elements and the two second direction fixed resistance elements may be formed in the dead area.

  In the strain gauge according to the first aspect, the circuit pattern may further include at least one terminal, and the at least one terminal may be formed in the dead area.

  In the strain gauge according to the first aspect, in the insensitive area, the at least one terminal is provided on a side of at least one of the first direction fixed resistance element and the second direction fixed resistance element opposite to the sensitive area. It may be.

  In the strain gauge according to the first aspect, a pair of the insensitive regions may be provided on both sides of the sensitive region.

  In the strain gauge according to the first aspect, the circuit pattern may further include two third-direction strain-sensitive elements or two third-direction fixed resistance elements, and the two third-direction strain-sensitive elements or 2 The three third direction fixed resistance elements may form a third Wheatstone bridge circuit by connecting the first Wheatstone bridge circuit and the second Wheatstone bridge circuit.

According to a second aspect of the present invention,
Strain plates,
A load acting portion connected to the strain plate,
A multiaxial force sensor including the strain gauge according to the first aspect attached to the strain plate.

  In the strain sensor according to the second aspect, an insensitive region of the base material of the strain gauge may be attached to a side surface of the strain plate.

  In the strain gauge of the present invention and the multiaxial force sensor including the strain gauge, the occurrence of a measurement error due to a change in the ambient temperature is suppressed.

FIG. 1 is a perspective view of a three-axis force sensor according to the embodiment of the present invention. FIG. 2 is a cross-sectional view of the three-axis force sensor shown in FIG. FIG. 3 shows a wiring pattern of the strain gauge. FIG. 4 is a circuit diagram corresponding to the wiring pattern of the strain gauge in FIG. FIG. 5A and FIG. 5B are explanatory diagrams illustrating a state of measurement by the three-axis force sensor. FIG. 6 shows another example of the wiring pattern of the strain gauge.

<Embodiment>
Embodiments of the multiaxial force sensor and the strain gauge of the present invention are described with reference to FIGS. 1 to 6 by taking a three-axis force sensor 100 used as a tactile sensor of a robot hand and a strain gauge 20 included in the three-axis force sensor 100 as examples. This will be described with reference to FIG.

  As shown in FIGS. 1 and 2, the three-axis force sensor 100 of the present embodiment has a main body 10 that is rotationally symmetric about the axis A, and a strain gauge 20 attached to the main body 10. The main body 10 includes a disk-shaped strain-generating plate (strain-generating member) 11 having the axis A as a rotation axis, a load acting portion 12 that stands upright in the axial direction from the center of the surface 11 a of the strain-generating plate 11, A pair of holding plates 13 erecting in the axial direction from the peripheral edge of the surface 11a of the plate 11, a peripheral wall 14 erecting in the axial direction from the peripheral edge of the back surface 11b of the strain-flexing plate 11, and four attached to the peripheral wall 14. Includes legs 15. The main body 10 is integrally formed of, for example, a synthetic resin material.

  In the following description, as shown in FIG. 1, two orthogonal radial directions of the strain plate 11 are defined as an X direction (first direction) and a Y direction (second direction) of the three-axis force sensor 100 and the main body 10. I do. The direction of the axis A orthogonal to the X direction and the Y direction is defined as the Z direction (third direction) of the three-axis force sensor 100 and the main body 10.

  The strain plate 11 is a disk that is distorted by receiving an external load applied to the main body 10 of the three-axis force sensor 100 via the load application section 12. The strain in the strain generating plate 11 occurs on the front surface 11a and the back surface 11b (upper and lower surfaces orthogonal to the axis A in FIG. 1) of the strain generating plate 11, and the side surface 11c of the strain generating plate 11 (in the circumferential direction parallel to the axis A in FIG. 1). Surface) does not occur or is negligibly small. In the present specification, a region of the strain plate 11 that is distorted by receiving an external load, such as the front surface 11a and the back surface 11b of the strain plate 11 in the present embodiment, is referred to as a “strain region”. The diameter and thickness of the strain plate 11 are arbitrary.

  The load acting portion 12 is a portion that moves by receiving a load from the outside and generates a strain in the strain generating plate 11, and is, for example, a prism having a square cross section. The load acting portion 12 is provided on the surface 11 a of the strain plate 11 such that the center axis of the prism coincides with the rotation axis (axis A) of the strain plate 11, that is, coaxially with the strain plate 11.

  The pair of holding plates 13 are portions to which a part of the base material 21 (FIG. 3) of the strain gauge 20 described later (insensitive regions 21n1 and 21n2) is attached. The holding plates 13 are opposed to each other so as to sandwich the load acting portion 12 in the Y direction, and stand upright from the surface 11a of the strain plate 11, each having a curved surface along the outer periphery of the strain plate 11.

  The peripheral wall 14 stands upright from the back surface 11b along the outer periphery of the back surface 11b of the strain plate 11, and surrounds the back surface 11b. The peripheral wall 14 is provided with a pair of cutouts 14 n so as to sandwich the load application part 12 in the Y direction. That is, the pair of notches 14 n are provided at positions overlapping the pair of holding plates 13 in the circumferential direction of the strain body 11. The peripheral wall 14 is used as a guide when attaching the strain gauge 20 to the strain plate 11, and details thereof will be described later.

  The legs 15 are pedestals for mounting the triaxial force sensor 100 to the robot hand, and are provided on the peripheral wall 14 at equal intervals.

FIG. 3 shows a state (developed view) before the strain gauge 20 shown in FIG. As shown in FIG. 3, the strain gauge 20 includes a substrate 21 and a circuit pattern CP printed on the surface of the substrate 21. Substrate 21 has a dead zone 21n1,21n2 sandwiching the sensitive regions 21s and this circuit pattern CP is sensitive elements _X 1 6 one _{strain, X 2, Y 1, Y} 2, Z 1, Z 2 And four fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ , eight terminals T _{1 to} T _8, and a wiring W connecting these terminals. In the following description, the direction in which the insensitive regions 21n1 and 21n2 sandwich the sensitive region 21s is defined as the y direction (second direction), and the direction orthogonal to the y direction on the surface of the base 21 is defined as the x direction (first direction). ).

  The base material 21 is a flexible resin film, and has a central circular sensing area 21s, a pair of sensing areas 21n1 and 21n2 sandwiching the sensing area 21s, and a sensing area 21s and a pair of sensing areas. It has a pair of connection regions 21c1 and 21c2 that respectively connect 21n1 and 21n2. It is desirable to use a flexible and highly flexible resin film that can be easily bent, and specific examples thereof include polyester and polyimide. The sensitive region 21s, the insensitive regions 21n1 and 21n2, and the connecting regions 21c1 and 21c2 can be formed of different materials, respectively. Etc.) are desirably equal. In this case, the sensitive region 21s, the insensitive regions 21n1 and 21n2, and the connection regions 21c1 and 21c2 are cut out from a nearby portion in a material (eg, a sheet of polyester, polyimide, or the like) formed integrally to form a substrate. More preferably, 21 is formed. Thereby, the temperature characteristics of each region can be made more uniform.

Since the sensing region 21s is a region that is attached to the back surface 11b of the strain plate 11 of the main body 10, it has a diameter equal to or smaller than the back surface 11b of the strain plate 11. On one surface of the sensing region 21s, strain sensing elements (first direction strain sensing elements) X ₁ and X ₂ sandwiching the center c in the x direction and strain sensing elements (second strain sensing element) in the y direction. direction strain sensitive elements) Y _1, Y ₂ are formed, sensitive elements) Z 1 strain sensitive elements (third direction strain along the _periphery, Z ₂ are formed.

The strain sensing elements X ₁ and X ₂ are formed in parallel with each other, with the y direction being the width direction of the grid. The sensitive elements X ₂ and strain sensitive elements X ₁ strain, are formed respectively from the center c equidistant, in the x direction between the sensitive elements X ₂ and strain sensitive elements X ₁ strain The distance is larger than the width in the X direction of the load acting portion 12 of the main body 10.

The strain sensing elements Y ₁ and Y ₂ are formed in parallel with each other, with the x direction as the width direction of the grid. Strain and the sensitive elements Y ₁ and the strain sensitive elements Y _2, are formed equidistant from the center c, respectively, in the y direction between the sensitive elements Y ₂ and strain sensitive elements Y ₁ strain The distance is greater than the width of the load acting portion 12 of the main body 10 in the Y direction.

Each of the strain sensing elements Z ₁ and Z ₂ has an arc shape, and is formed to face the x direction with the circumferential direction of the sensing area 21 s being the width direction of the grid. The strain sensing elements Z ₁ and Z ₂ are arranged on the opposite side (outside) of the center c of the strain sensing elements X ₁ , X ₂ , Y ₁ and Y ₂ .

  The pair of insensitive regions 21n1 and 21n2 sandwich the sensitive region 21s in the y direction, and have a rectangular shape with the x direction as a long side direction and the y direction as a short side direction.

Fixed resistance elements (first-direction fixed resistance elements) RX ₁ and RX ₂ extending in the x direction are formed side by side in the x direction on portions of the surface of the insensitive area 21n1 far from the sensing area 21s. Four terminals T ₁ , T ₂ , T ₃ , and T ₄ arranged in the x direction are formed in a portion near the sensing region 21s. That is, in the dead region 21N1, a fixed resistance element _RX 1, RX ₂ terminal _T 1 through T _4, are disposed on the opposite side of the sensitive region 21s.

Similarly, fixed resistance elements (second-direction fixed resistance elements) RY ₁ and RY ₂ extending in the x direction are formed side by side in the x direction on portions of the surface of the insensitive area 21n2 far from the sensing area 21s. The four terminals T ₅ , T ₆ , T ₇ , and T ₈ arranged in the x direction are formed in a portion near the sensing area 21s. That is, in the dead region 21N2, the fixed resistance element _RY 1, RY ₂ terminal _T 5 through T _8, it is arranged on the opposite side of the sensitive region 21s.

  The connection areas 21c1 and 21c2 that connect the sensitive area 21s and the insensitive areas 21n1 and 21n2 each have a dimension (width) in the x direction orthogonal to the y direction in which the sensitive area 21s and the insensitive areas 21n1 and 21n2 are connected. Is smaller than the dimension (width) in the x direction of the sensed area 21s and the insensitive areas 21n1 and 21n2. Therefore, the base material 21 has a constricted shape in the connection regions 21c1 and 21c2.

As shown in FIGS. 3 and 4, the wiring W connects the strain sensing elements X ₁ and X ₂ and the fixed resistance elements RX ₁ and RX ₂ to form a first bridge circuit (first Wheatstone bridge circuit) BC1. ing. Further, the terminal _{T 1} between the sensitive elements _{X 1} strain and the fixed resistance element RX ₁ is, the terminal _{T 2} between the strain sensitive elements _X 1, _{X 2} is, between the fixed resistance element _RX 1, RX ₂ to the terminal _{T 3,} the terminal _{T 4} is connected between the strain sensitive elements _{X 2} and the fixed resistance element RX _2.

Similarly, wiring W constitutes the strain sensitive elements _Y 1, _{Y 2,} second bridge circuit by connecting the fixed resistance element _RY 1, RY ₂ (second Wheatstone bridge circuit) BC2. Strain terminal _{T 8} between the sensitive elements _{Y 1} and the fixed resistance element RY ₁ is strained terminal _{T 6} between the sensitive elements _Y 1, _{Y 2} are, terminal T between the fixed resistance element _RY 1, RY _{2 7,} the terminal _{T 5} is connected between the strain sensitive elements _{Y 2} and the fixed resistance element RY _2.

Is connected to the first bridge circuit BC1 between the one end of the strain sensitive elements Z ₁ and sensitive elements X ₁ strain and the fixed resistance element RX _1, the other end the strain sensitive elements Y ₁ and the fixed resistance element RY ₁ is connected to the second bridge circuit BC2. Similarly, the strain is connected to the first bridge circuit BC1 between the one end of the sensitive elements Z ₂ are the sensitive elements X ₂ strain and the fixed resistance element RX _2, the other end to the sensitive elements Y ₂ strain fixed It is connected to the second bridge circuit BC2 between the resistive element RY _2. Thus, a third bridge circuit (third bridge circuit) having the first bridge circuit BC1 and the second bridge circuit BC2 in the pair of opposite sides, respectively, and having the strain sensing elements Z ₁ and Z ₂ in the other pair of opposite sides, respectively. Wheatstone bridge circuit) BC3.

The strain sensing elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ , fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ , and the wiring W included in the circuit pattern CP are made of the same material. , More preferably, by a nearby portion in one material. This material is, for example, copper or a copper alloy such as copper / nickel. The circuit pattern CP can be printed on the base material 21 by photoetching, printing, vapor deposition, sputtering, or the like.

  As shown in FIGS. 1 and 2, the strain gauge 20 is attached to the main body 10 such that the surface of the substrate 21 opposite to the surface on which the circuit pattern CP is formed is in contact with the main body 10. I have.

Specifically, the sensitive region 21 s of the base material 21 has a strain-flexing plate such that the x direction and the y direction match the X direction and the Y direction of the main body 10, respectively, and the center c matches the axis A. 11 is attached to the back surface 11b. As described above, the distance in the x direction between the strain sensing elements X ₁ and X ₂ is larger than the dimension in the X direction of the load acting portion 12, and the distance in the y direction between the strain sensing elements Y ₁ and Y ₂ is It is larger than the dimension of the load acting portion 12 in the Y direction. Therefore, in a state where the sensing part 21s of the base material 21 is attached to the strain plate 11, the strain sensing elements X ₁ and X ₂ and the strain sensing elements Y ₁ and Y ₂ are in the X direction and the Y direction, respectively. It is arranged outside the load acting portion 12 in the direction, in a region where a relatively large strain occurs. 3 and 6, the outline of the load acting portion 12 in a state where the base material 21 is attached to the strain generating plate 11 is indicated by a broken line, and the load acting portion 12 and the strain sensing elements X ₁ , X ₂ , The positional relationship between Y ₁ and Y ₂ is shown.

The pair of dead regions 21n1 and 21n2 of the base member 21 are respectively bent and attached to the side surface 11c of the strain plate 11 and the outer surface of the holding plate 13 extending upward. Therefore, the terminals T ₁ , T ₂ , T ₃ , T ₄ formed in the dead area 21n1 and the terminals T ₅ , T ₆ , T ₇ , T ₈ formed in the dead area 21n2 are in the radial direction of the strain plate 11. It is exposed facing outside.

  Each of the pair of connecting portions 21c1 and 21c2 is bent at a connecting portion between the back surface 11b and the side surface 11c of the strain plate 11 through the notch portion 14n of the peripheral wall 14.

  When the strain gauge 20 is attached to the substrate 21, the periphery of the sensing region 21 s of the substrate 21 is brought into contact with the inner peripheral surface of the peripheral wall 14, and the pair of connection regions 21 c 1 and 21 c 2 of the substrate 21 are By arranging the strain gauges 20 in the pair of cutouts 14n, respectively, the positioning of the strain gauge 20 with respect to the main body 10 and the strain plate 11 can be easily performed.

  Specifically, by making the peripheral edge of the sensing area 21 s of the base material 21 abut on the inner peripheral surface of the peripheral wall 14, the center c of the sensing area 21 s is aligned with the axis A of the main body 10. In addition, the movement of the sensing area 21s in the X and Y directions is restricted. Next, by disposing the pair of connecting portions 21c1 and 21c2 of the strain gauge 20 in the pair of cutouts 14n of the peripheral wall 14, the strain gauge 20 can maintain the body 10 and the strain plate 11 even in the circumferential direction around the axis A. Is aligned with

  Next, how to use and operate the three-axis force sensor 100 and the strain gauge 20 of the present embodiment will be described.

When using the three-axis force sensor 100 as a tactile sensor of the robot hand, first, the three-axis force sensor 100 is fixed to the fingertip of the robot hand via the leg 15. Next, the terminals T _{1 to} T ₈ and a signal processing unit (not shown) are connected using lead wires L _{1 to} L ₈ (FIG. 2), respectively. The terminals T _{1 to} T ₈ and the lead wires L _{1 to} L ₈ can be joined by any method, for example, by using solder or an anisotropic conductive film (ACF).

The terminals T ₁ and T ₅ are connected to a power supply (not shown) of the signal processing unit by lead wires L ₁ and L ₅ , respectively. Terminals T ₂ , T ₃ , terminals T ₆ , T ₇ , and terminals T ₄ , T ₈ are respectively signaled by leads L ₂ , L ₃ , L ₆ , L ₇ , L ₄ , L ₈ . It is connected to an arithmetic unit (not shown) in the signal processing unit via an amplifier (not shown) in the processing unit.

3 During operation of the force sensor 100, apply an input voltage Ei between the terminals T ₁ and the terminal T ₅ by the power source. The resistance value of each strain sensing element and the resistance value of each fixed resistance element forming the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 do not bend in the sensing area 21s of the base 21. In the state, the voltage is adjusted so that the voltage is equal between the terminals T ₂ and T ₃ , the voltage is equal between the terminals T ₆ and T ₇ , and the voltage is equal between the terminals T ₄ and T ₈ . Therefore, in a state in which no strain is generated in the strain plate 11 and there is no deflection in the sensing area 21s (FIG. 5A), between the terminals T ₂ and T _3, between the terminals T ₆ and T ₇ , There is no potential difference between T ₄ and T ₈ , and the calculation unit does not calculate distortion.

Next, when a load in the X direction is applied to the load application unit 12, the load application unit 12 receives the load and moves, causing the strain plate 11 to be distorted (FIG. 5B). At this time, the sensitive region 21s of the substrate 21 of the strain gauge 20 attached to Okoshiibitsuban 11 also strain-generating plate 11 and the flexure together, compressive strain in the strain sensitive elements X ₁ is, strain sensitive elements elongation strain is generated in the X _2. As a result, the resistance values of the strain sensing elements X ₁ and X ₂ change, and a potential difference occurs between the terminals T ₂ and T ₃ of the first bridge circuit BC1 including the strain sensing elements X ₁ and X ₂ . The calculation unit obtains the amount of strain generated in the strain plate 11 based on the potential difference, and obtains the magnitude of the load acting on the load application unit 12 in the X direction. At this time, no distortion occurs on the side surface 11c of the strain plate 11 and the holding plate 13, and the resistance values of the fixed resistance elements RX ₁ and RX ₂ are constant. In the case where a load in the Y direction is applied to the load application section 12, the magnitude of the applied load in the Y direction is obtained in the same manner.

When a load in the Z direction is applied to the load acting part 12, the sensitive region 21s of the strain-flexing plate 11 and the base material 21 is curved so that the center protrudes, so that the strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ cause elongation strain. As a result, the combined resistance of the first bridge circuit BC1, the combined resistance of the second bridge circuit BC2, and the resistance values of the strain sensing elements Z ₁ and Z ₂ change, and the terminals T ₄ and T _{8 of} the third bridge circuit BC3. A potential difference occurs between them. The calculation unit obtains the amount of strain generated in the strain plate 11 based on the potential difference, and obtains the magnitude of the load acting on the load application unit 12 in the Z direction.

Here, the fixed resistance elements RX ₁ , RX ₂ of the first bridge circuit BC ₁ and the fixed resistance elements RY ₁ , RY ₂ of the second bridge circuit BC ₂ are printed on the substrate 21, and the strain sensing elements X ₁ , X ₂ , it described the significance of forming the _Y 1, _{Y 2} same material as.

(1) By forming the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ in this way, the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ become strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ are formed of the same material and at a position close to them. Here, since the resistance temperature coefficient indicating the ratio of the change in the resistance value to the temperature change is a physical property value depending on the material, in the present embodiment, the resistance temperature coefficient of the total strain sensing element is equal to that of the fixed resistance element. Further, fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed on the substrate 21, and the vicinity of the strain sensing elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ . Therefore, the change in the ambient temperature affecting the total strain sensing element and the total fixed resistance element becomes substantially the same. Therefore, when a change occurs in the ambient temperature, the resistance value of the total strain sensing element and the resistance value of all the fixed resistance elements change at the same rate.

In the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3, when the balance of the resistance value among the resistance elements (strain sensing element and fixed resistance element) included in each of them changes, the terminals are changed. A potential difference is generated between T ₂ and T _3, between terminals T ₆ and T _{7, and} between terminals T ₄ and T ₈ , based on which a distortion is detected. Therefore, when the balance between the resistance value of the strain sensing element and the resistance value of the fixed resistance element changes due to a change in the ambient temperature, a measurement error may occur due to the change in the balance. However, in the present embodiment, when a change occurs in the ambient temperature, the resistance value of the total strain sensing element and the resistance value of all the fixed resistance elements change at the same rate, so that the ambient temperature changes. Even in this case, the balance of the resistance values between the elements does not change, and the occurrence of measurement errors is suppressed. Note that, when the circuit pattern CP is formed, the strain-sensitive element or the like is formed by using a portion near a material (copper, copper alloy, or the like) prepared as an integral lump, so that the strain-sensitive element X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ , the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ , and the temperature coefficient of resistance of the wiring W can be made more uniform, and the occurrence of measurement errors can be made more favorable. Can be suppressed.

(2) As in the present embodiment, the fixed resistance elements RX ₁ , RX ₂ of the first bridge circuit BC ₁ and the fixed resistance elements RY ₁ , RY ₂ of the second bridge circuit BC ₂ are replaced by the insensitive regions 21 n ₁ , 21 n ₂ of the base 21. When the insensitive regions 21n1 and 21n2 are attached to portions of the main body 10 where no distortion occurs (outside the strain generating region), the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are attached. It can function as a dummy gauge for temperature compensation. Therefore, even when the main body 10 including the strain plate 11 expands or contracts due to a change in the ambient temperature, the resistance values of the strain sensing elements X ₁ , X ₂ , Y ₁ , and Y ₂ due to the expansion and contraction. , The occurrence of measurement errors can be suppressed.

(3) The first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 are formed by printing the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ on the base material 21 and forming them. Each can be formed as a complete closed circuit on the substrate 21.

  When the strain sensing element constituting the bridge circuit is printed on the base material and the fixed resistance element constituting the bridge circuit is provided outside the base material, for example, in a signal processing unit, in order to make the bridge circuit a closed circuit. In addition, it is necessary to connect the strain sensing element on the base material and the fixed resistance element of the signal processing unit with a lead wire or the like. In this case, the connection between the wiring on the base material and the lead wire is performed by bonding the lead wire to the electrode provided on the base material. Joining methods are limited to solder joints whose joining resistance is so small as to be substantially negligible, since the resistance becomes a resistance in the circuit and causes a large strain detection error.

  However, in order to perform a good solder joint, it is necessary to provide a relatively large electrode on the base material and secure a pitch between the plurality of electrodes, so that the base material becomes large. In addition, in order to perform the solder joint satisfactorily, it is necessary to lay the solder with a certain thickness, which hinders miniaturization of the three-axis force sensor.

On the other hand, in the present embodiment, the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 are each formed as a complete closed circuit on the base material 21, and the terminals T _{1 to} T ₁ The connection between the base material 21 and the signal processing unit via ₈ is merely a connection for connecting the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 to a power supply and a calculation unit. Therefore, in the present embodiment, the occurrence of joining resistance is allowed at the joining portion between the terminals T _{1 to} T ₈ and the lead wires L _{1 to} L _8, and any joining method other than solder joining, for example, an anisotropic conductive film Can be employed. In addition, by using an anisotropic conductive film, the size of the electrodes, the pitch between the electrodes, and the thickness of the joint can all be suppressed to about one tenth of that in the case of the solder joint, so that the triaxial force is used. When miniaturization of the sensor 100 is desired, joining with an anisotropic conductive film is advantageous.

  The effects of the three-axis force sensor 100 and the strain gauge 20 of the present embodiment are as follows.

In the strain gauge 20 of the present embodiment, the fixed resistance elements RX ₁ , RX ₂ of the first bridge circuit BC ₁ and the fixed resistance elements RY ₁ , RY ₂ of the second bridge circuit BC ₂ are formed on the base material 21. The effects of (2) and (3) can be obtained, and the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are the same as the strain-sensitive elements X ₁ , X ₂ , Y ₁ , and Y ₂ . Since it is made of a material, the effect (1) can be obtained.

In the strain gauge 20 of the present embodiment, the sensitive area 21s, the strain sensitive elements _{X 1, X 2, Y 1} , Y 2, Z 1, only the _{Z 2} are formed, the terminal _T 1 through T ₈ and the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , RY ₂ are formed in the insensitive regions 21n1, 21n2. Therefore, the diameter (dimension) of the sensing area 21s can be reduced, and the strain plate 11 of the triaxial force sensor 100 can be reduced. The downsizing of the strain plate 11 leads to the downsizing of the three-axis force sensor 100, which is preferable.

In the strain gauge 20 of the present embodiment, since the electrode _T 1 through T ₈ is provided in the dead region 21N1,21n2, if necessary, without increasing the diameter of the sensitive area 21s, electrodes _T 1 ~ increasing the size of the T _8, it is possible to facilitate the bonding operation of the lead wire or the like.

  Since the base material 21 of the strain gauge 20 of the present embodiment has the connecting portions 21c1 and 21c2 between the sensitive region 21s and the insensitive regions 21n1 and 21n2, the connecting portions 21c1 and 21c2 are narrower than the sensitive region 21s and the insensitive regions 21n1 and 21n2. The sensible area 21s and the insensitive areas 21n1 and 21n2 can be arranged in various modes without being restricted by the connecting portions with the connecting portions 21c1 and 21c2.

  Since the three-axis force sensor 100 of the present embodiment includes the strain gauge 20, the same effect as that of the strain gauge 20 can be obtained.

  In the above embodiment, the following modified modes can be adopted.

In the strain gauge 20, sensitive elements _Z 1, _{Z 2} strain, may be formed in the dead regions 21n1 and / or dead regions 21N2. In this case, since the deflection in the dead zones 21n1,21n2 does not occur, sensitive elements _Z 1, _{Z 2} strain acts as a substantially fixed resistance element (third direction fixed resistance element).

Even when the strain sensing elements Z ₁ and Z ₂ act as fixed resistance elements, the detection of the X-direction load using the first bridge circuit BC1 and the detection of the Y-direction load using the second bridge circuit BC2 are performed as described above. It can be performed in the same manner as in the embodiment. In addition, detection of a Z-direction load can be performed. When a load in the Z direction is applied to the load application unit 12 and the resistance value of the strain detecting elements X ₁ , X ₂ , Y ₁ , and Y ₂ changes, the combined resistance of the first bridge circuit BC 1 and the resistance of the second bridge circuit BC 2 This is because even when the combined resistance changes and the resistance values of the strain sensing elements Z ₁ and Z ₂ are constant, the balance of the resistance values between the elements of the third bridge circuit BC3 changes.

The strain gauge 20 need not have the strain sensing elements Z ₁ and Z ₂ . In this case, for example, the first bridge circuit BC1, second bridge circuit BC2 is, instead of the strain sensitive elements _Z 1, _{Z 2,} are connected by two arcuate lines W.

Even when the strain sensing elements Z ₁ and Z ₂ are not present, the detection of the load in the X direction using the first bridge circuit BC1 and the detection of the load in the Y direction using the second bridge circuit BC2 are the same as in the above embodiment. It can be carried out. The strain gauge 20 having such a modification can be used in a biaxial force sensor. Alternatively, the first Wheatstone bridge and the second Wheatstone bridge included in the strain gauge of such a modified embodiment are connected by a fixed resistance element formed in the signal processing unit to form a third Wheatstone bridge, and a three-axis force sensor is used. It can also be used.

In the strain gauge 20, at least one of the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ formed in the insensitive regions 21 n 1 and 21 n ₂ of the base material 21 leaves at least one of them on the base material 21, It may be provided outside the material 21, for example, in a signal processing unit. Even in such an embodiment, at least one of the fixed resistance elements RX ₁ and RX ₂ forming the first bridge circuit BC ₁ and the fixed resistance elements RY ₁ and RY ₂ forming the second bridge circuit BC ₂ Providing the upper insensitive region 21n1 and / or 21n2 can provide an effect of suppressing a temperature error in the strain gauge 20 and the three-axis force sensor 100.

In dead zones 21n1 provided on one side in the y direction sensitive region 21s (second direction), perpendicular to the fixed resistance element _RX 1, RX ₂ and the terminal _T 1 through T ₄ in the y direction (second direction) The fixed resistance elements RY ₁ , RY may be arranged in a line along the x direction (first direction) in the insensitive area 21n2 provided on the other side of the sensitive area 21s in the y direction (second direction). it may be disposed in a line in the ₂ and the terminal T ₅ through T ₈ and the y-direction x-direction perpendicular to the (second direction) (the first direction). Thereby, the insensitive regions 21n1 and 21n2 can be attached to a more elongated portion. For example, the holding plate 13 of the main body 10 can be omitted, and the insensitive regions 21n1 and 21n2 can be attached only to the side surfaces of the strain generating plate 11. .

As shown in FIG. 6, the fixed resistance element _RX 1 to a portion close to the sensitive region 21s of the dead region 21n1, RX ₂ may also be the terminal _T 1 through T ₄ to portion distant from the sensitive region 21s are formed. That is, in the dead region 21N1, may be provided on the side opposite to the terminal _T 1 through T ₄ is fixed resistor _RX 1, RX ₂ sensitive region 21s. Placement of fixed resistor _RY 1, RY ₂ and the terminal _T 5 through T ₈ in the dead region 21n2 versa. By arranging the terminals T ₁ through T ₈ outside, bonding of the lead wire or the like to the terminal T ₁ through T ₈ it becomes easier.

Any one or more of the terminals _T 1 through T ₈ may be formed in the sensitive region 21s. In this case, it is desirable to provide it in the vicinity of the center c, which is stuck below the load acting portion 12 and hardly causes distortion.

In sensitive areas 21s, sensitive elements _Z 1, _{Z 2} strain, may be disposed on the strain sensitive elements _{X 1, X 2, Y 1} , Y 2 of the center c side (inside). Further, each of the strain sensing elements X ₁ , X ₂ , Y ₁ , and Y ₂ may be formed in an arc shape such that the width direction of the grid is the circumferential direction of the sensing area 21 s. Such a strain gauge 20 can be favorably used by attaching the load acting portion 12 to the cylindrical main body 10 having the axis A as a center.

The shape of the substrate 21 of the strain gauge 20 is arbitrary, and may be a rectangular shape or an elliptical shape having no connecting portions 21c1 and 21c2, or may have only one of the insensitive regions 21n1 and 21n2. In the substrate 21 having only one of the dead zone 21N1,21n2, the fixed resistor insensitive area element _{RX 1, RX 2, RY 1} , RY 2, all the terminals _T 1 through T ₈ can be formed. In addition, the base material 21 can have any shape including a sensitive region attached to the strain plate of the multiaxial force sensor and a dead region arranged outside the region.

  The holding plate 13 of the main body 10 may be a flat plate extending from the outer periphery of the strain plate 11 in parallel with the strain plate 11. In this case, the substrate 21 of the strain gauge 20 is attached to the strain plate 11 and the holding plate 13 without bending. Further, the main body 10 may not have the holding plate 13. In this case, the entirety of the dead regions 21n1 and 21n2 can be attached to the side surface 11c of the strain plate 11. In addition, the dead regions 21n1 and 21n2 do not have to be attached to the side surface 11c of the strain plate 11 and need not be attached to the main body 10. The arrangement of the insensitive regions 21n1 and 21n2 in a state where the sensitive region 21s is attached to the back surface 11b of the strain plate 11 can be appropriately determined according to the shape of the main body of the multiaxial sensor and the application of the multiaxial sensor. it can.

  The strain gauge 20 of the above embodiment can be used as a strain generating member of any sensor other than the multiaxial force sensor.

  As long as the features of the present invention are maintained, the present invention is not limited to the above-described embodiment, and other forms that can be considered within the technical idea of the present invention are also included in the scope of the present invention. .

  INDUSTRIAL APPLICABILITY The strain gauge and the multiaxial force sensor of the present invention can suppress the influence of a temperature change in load detection, and can contribute to improvement in stability and reliability of robots, game devices, various measuring devices, and other devices.

10 body part 11 strain-generating plate (strain-generating member)
DESCRIPTION OF SYMBOLS 12 Load acting part 13 Holding plate 14 Perimeter wall 15 Leg 20 Strain gauge 21 Base material 21s Sensitive area 21c1, 21c2 Connecting area 21n1, 21n2 Dead area BC1 First bridge circuit (first Wheatstone bridge circuit)
BC2 2nd bridge circuit (2nd Wheatstone bridge circuit)
BC3 3rd bridge circuit (3rd Wheatstone bridge circuit)
RX ₁ , RX ₂ fixed resistance element (first direction fixed resistance element)
RY ₁ , RY ₂ fixed resistance element (second direction fixed resistance element)
T _{1 to} T ₈ terminals X ₁ , X ₂ strain sensing element (first direction strain sensing element)
Y ₁ , Y ₂ strain sensing element (second direction strain sensing element)
Z _{1, Z 2} strain sensitive elements (third direction strain sensitive elements)

Claims (8)

The first Wheatstone bridge circuit detects a load applied to the strain-generating member that is distorted under load and acts in the first direction of the strain-generating member, and in a second direction orthogonal to the first direction of the strain-generating member. A strain gauge used for detecting an applied load by a second Wheatstone bridge circuit,
A flexible substrate;
And a circuit pattern formed on the base material,
The base material is a sensitive region attached to a strain generating region in which a strain is generated by receiving a load of the strain generating member, a dead region arranged outside the strain generating region, the sensitive region, and the dead region. And a connection region for connecting
The dimension of the connection area in the orthogonal direction orthogonal to the direction in which the sensitive area and the insensitive area are connected is smaller than the dimension in the orthogonal direction of the sensitive area and the insensitive area,
The circuit pattern comprises two first directional strain sensitive elements constituting a first Wheatstone bridge circuit, two second directional strain sensitive elements constituting a second Wheatstone bridge circuit, and a first Wheatstone bridge circuit. At least one of a first direction fixed resistance element and a second direction fixed resistance element forming a second Wheatstone bridge circuit.
The two first direction strain-sensitive elements, the two second direction strain-sensitive elements, and at least one of the first direction fixed resistance element and the second direction fixed resistance element are formed of the same material,
The two first direction strain sensing elements and the two second direction strain sensing elements are formed in the sensing area,
At least one of the first direction fixed resistance element and the second direction fixed resistance element is formed in the dead area.
Strain gauge. The circuit pattern includes two first direction fixed resistance elements forming a first Wheatstone bridge circuit and two second direction fixed resistance elements forming a second Wheatstone bridge circuit,
The two first direction strain sensitive elements, the two second direction strain sensitive elements, the two first direction fixed resistance elements, and the two second direction fixed resistance elements are formed of the same material. Yes,
The strain gauge according to claim 1, wherein the two first direction fixed resistance elements and the two second direction fixed resistance elements are formed in the dead area. The circuit pattern further includes at least one terminal,
The strain gauge according to claim 1, wherein the at least one terminal is formed in the dead area.   4. The at least one terminal in the insensitive region, wherein the at least one terminal is provided on a side of at least one of the first direction fixed resistance element and the second direction fixed resistance element opposite to the sensing region. Strain gauge.   The strain gauge according to any one of claims 1 to 4, wherein a pair of the insensitive regions is provided on both sides of the sensitive region. The circuit pattern further includes two third direction strain sensing elements or two third direction fixed resistance elements,
The said 1st Wheatstone bridge circuit and a 2nd Wheatstone bridge circuit connect the said 2nd 3rd direction strain sensing element or 2nd 3rd direction fixed resistance elements, and comprise a 3rd Wheatstone bridge circuit. 6. The strain gauge according to any one of items 5 to 5. Strain plates,
A load acting portion connected to the strain plate,
The strain gauge according to any one of claims 1 to 6, attached to the strain plate,
Multi-axial force sensor comprising: The multiaxial force sensor according to claim 7, wherein a dead area of the base material of the strain gauge is affixed to a side surface of the strain plate.

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