JP6836641B2 - Strain gauge and 3-axis force sensor - Google Patents

Description

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

Three-axis force sensors equipped with strain gauges are widely used in robots, game machines, various measuring devices, and other devices. For example, Patent Documents 1 and 2 disclose an example of a triaxial force sensor including a strain gauge.

JP-A-2010-164495 Japanese Patent No. 508188

In the 3-axis force sensor provided with the strain gauge, the existence of measurement error due to the change in ambient temperature is recognized, and its suppression is desired.

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

The strain gauge according to the present invention is attached to a strain-causing member that is distorted by receiving a load, detects a load acting in the first direction of the strain-causing member by a first Wheatstone bridge circuit, and is orthogonal to the first direction of the strain-causing member. Strain used for detecting the load acting in the second direction by the second Wheatston bridge circuit and detecting the load acting in the third direction orthogonal to the first and second directions of the strain generating member by the third Wheatston bridge circuit. It is a gauge and includes a flexible base material and a circuit pattern formed on the base material, and the base material is attached to a strain-causing region where strain is generated under the load of a strain-causing member. It has a region, a pair of dead regions arranged outside the strain-causing region, and a connecting region that connects the sensitive region and the dead region, and the sensitive region and the dead region of the connected region are connected. The dimensions in the orthogonal direction perpendicular to the direction are smaller than the dimensions in the orthogonal direction of the sensitive region and the dead region, and the circuit pattern consists of the two first-direction strain-sensitive elements constituting the first Wheatston bridge circuit and the first strain-sensitive element. Two second-direction strain-sensitive elements constituting the two-Wheatstone bridge circuit, two third-direction strain-sensitive elements constituting the third Wheatstone bridge circuit, and two first directions constituting the first Wheatstone bridge circuit. A first-direction strain-sensitive element, a second-direction strain-sensitive element, and a third-direction strain-sensitive element, which include a fixed resistance element and two second-direction fixed resistance elements constituting the second Wheatstone bridge circuit. The first-direction fixed resistance element and the second-direction fixed resistance element are made of the same material, and the first-direction strain-sensitive element, the second-direction strain-sensitive element, and the third-direction strain-sensitive element are sensitive. The first-direction fixed resistance element and the second-direction fixed resistance element are formed in the region, and the third-direction strain-sensitive element is the first Wheatstone bridge circuit and the second Wheatstone bridge circuit. Is connected to form a third Wheatston bridge circuit.

The triaxial force sensor according to the present invention includes the above-mentioned strain gauge, a plate-shaped strain-causing member, and a load acting portion connected to the strain-causing member.

The triaxial force sensor according to the present invention is further provided with a peripheral wall that stands upright in the third direction from the peripheral edge of the surface opposite to the surface to which the load acting portion of the strain generating member is connected, and the dead region is formed. It may be attached to the inner peripheral surface of the peripheral wall.

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

It is sectional drawing of the electronic pen to which the triaxial force sensor which concerns on embodiment of this invention is applied. It is a perspective view of the triaxial force sensor which concerns on embodiment of this invention. FIG. 5 is a cross-sectional view of the triaxial force sensor shown in FIG. 2 cut along the yz plane including the axis A. It is a figure which shows the wiring pattern of the strain gauge which concerns on embodiment of this invention. It is a circuit diagram corresponding to the wiring pattern of the strain gauge shown in FIG. It is explanatory drawing which shows the state of the measurement in 3 axis force sensor.

<Embodiment>
The strain gauge and the embodiment of the triaxial force sensor according to the present invention will be described with reference to FIGS. 1 to 6 as an example of applying these to an electronic pen.

As shown in FIG. 1, the electronic pen 200 includes tips 31 and 32, a three-axis force sensor 100, a holder 33, a body 34, and a front cap 35.

The tip 31 is made of, for example, plastic and functions as a pen tip. The tip 32 is formed of, for example, SUS, one end of which is connected to the tip 31 and the other end of which is connected to the triaxial force sensor 100. As a result, the external load applied through the pen tip is measured by the 3-axis force sensor 100.

The holder 33 holds a PCBA (Printed Circuit Board Assembly) on which various circuits are mounted, in addition to a signal processing circuit and a power supply necessary for the operation of the three-axis force sensor 100. The body 34 covers a part of the 3-axis force sensor 100 and the holder 33, and the front cap 35 covers the remaining part of the 3-axis force sensor 100 and the tip 32.

Next, as shown in FIGS. 2 and 3, the triaxial force sensor 100 of the present embodiment includes a main body portion 10 that is rotationally symmetric around the axis A. The main body 10 includes a disk-shaped strain-causing plate (plate-shaped strain-causing member) 11 having a shaft A as a rotation axis, and a load acting portion 12 that stands upright in the axial direction from the center of the surface 11a of the strain-causing plate 11. Includes a peripheral wall 13 that stands upright in the axial direction from the peripheral edge of the back surface 11b of the strain generating plate 11. Further, the load acting portion 12 is fitted to the tip 32 shown in FIG. The main body 10 is integrally molded with, for example, a synthetic resin material.

In the following description, as shown in FIG. 2, the two orthogonal radial directions of the strain generating plate 11 are defined as the x direction (first direction) and the y direction (second direction) of the triaxial force sensor 100 and the main body 10. To do. Further, 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 triaxial force sensor 100 and the main body 10.

The strain generating plate 11 is a disk that is distorted by receiving an external load applied via the load acting portion 12. The strain in the strain generating plate 11 occurs on the front surface 11a and the back surface 11b of the strain generating plate 11 (upper and lower surfaces orthogonal to the axis A in FIG. 2), and does not occur on the peripheral wall 13 (the peripheral surface parallel to the axis A in FIG. 2). Or small enough to be ignored. In the present specification, a region that is distorted by receiving an external load, such as the front surface 11a and the back surface 11b of the strain generating plate 11 in the present embodiment, is referred to as a “distortion region”. The diameter and thickness of the strain generating plate 11 are arbitrary.

The load acting unit 12 moves by receiving a load from the outside, and causes strain in the strain generating plate 11. The load acting portion 12 is provided on the surface 11a of the strain generating plate 11 so that its central axis coincides with the rotation axis (axis A) of the strain generating plate 11, that is, coaxially with the strain generating plate 11.

The peripheral wall 13 stands upright from the back surface 11b along the outer periphery of the back surface 11b of the strain generating plate 11 and surrounds the back surface 11b. Although FIG. 2 illustrates the case where the outer peripheral surface of the peripheral wall 13 is cylindrical, the peripheral wall 13 may be changed as follows. That is, on one side or both sides of the peripheral wall 13 in the x-axis direction, a plane portion intersecting (orthogonal) with the x-axis may be formed on the outer peripheral surface of the peripheral wall 13. Alternatively, on one side or both sides of the peripheral wall 13 in the y-axis direction, a flat surface portion intersecting (orthogonal) with the y-axis may be formed on the outer peripheral surface of the peripheral wall 13.

In particular, when the flat surface portion is provided only on one side of the peripheral wall 13 in the x-axis direction, the flat surface portion can be provided only on one side of the peripheral wall 13 in the y-axis direction as well. In this case, two flat surfaces are provided with respect to the outer peripheral surface of the peripheral wall 13. Further, when the flat surface portions are provided on both sides of the peripheral wall 13 in the x-axis direction, the flat surface portions can be provided on both sides of the peripheral wall 13 in the y-axis direction as well. In this case, four flat surfaces are provided with respect to the outer peripheral surface of the peripheral wall 13.

By providing the flat surface portion on the outer peripheral surface of the peripheral wall 13 in this way, the main body portion 10 (that is, the three-axis force sensor 100) can be easily and reliably positioned with respect to the holder 33 of the electronic pen 200 by using the flat surface portion. It will be possible to do. The main body 10 may be positioned with respect to the holder 33 by providing an alignment mark on the peripheral wall 13 having a cylindrical outer peripheral surface as shown in FIG.

In the strain gauge 20 of the present embodiment, a part (sensing region 21s) of the base material 21 (see FIG. 4) is attached to the back surface 11b of the strain generating plate 11, and the remaining portion (dead regions 21n1, 21n2) is a peripheral wall. It is bent and attached to the inner peripheral surface of 13.

FIG. 4 shows a state (developed view) before the strain gauge 20 is attached to the strain generating plate 11. As shown in FIG. 4, the strain gauge 20 includes a base material 21 and a circuit pattern CP printed on the surface of the base material 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 , 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. In the following description, the direction in which the insensitive regions 21n1 and 21n2 sandwich the sensitive region 21s is the y direction (second direction), and the direction orthogonal to the y direction on the surface of the base material 21 is the x direction (first direction). ).

The base material 21 is a flexible resin film, and has a central circular sensation region 21s, a pair of insensitive regions 21n1 and 21n2 sandwiching the sensation region 21s, and a pair of insensitivity regions 21s. It has a pair of connecting regions 21c1 and 21c2 that connect 21n1 and 21n2, respectively. It is desirable to use a resin film that is flexible and highly flexible so that it can be easily bent, and as a specific example, polyester, polyimide, or the like can be used. Further, although it is possible to form the sensitive region 21s, the dead region 21n1, 21n2, and the connecting regions 21c1 and 21c2 from different materials, these are formed from the same material and the temperature characteristics (resistance temperature coefficient) of the entire region are formed. Etc.) should be equal. Further, in this case, the sensitive region 21s, the insensitive regions 21n1, 21n2, and the connecting regions 21c1 and 21c2 are integrally cut out from a nearby portion in the integrally formed material (for example, a sheet of polyester, polyimide, etc.) to form a base material. It is more desirable to form 21. As a result, the temperature characteristics of each region can be made more uniform.

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

The strain-sensitive elements X ₁ and X ₂ are arcuate, respectively, and are formed so as to face the x direction with the circumferential direction along the contour of the load acting portion 12 shown by the broken line in FIG. 4 as the width direction of the grid. There is. Further, the strain-sensitive element X ₁ and the strain-sensitive element X ₂ are formed at positions equidistant from the center c, respectively.

The strain-sensitive elements Y ₁ and Y ₂ are arcuate, respectively, and are formed so as to face each other in the y direction with the circumferential direction along the contour of the load acting portion 12 as the width direction of the grid. Further, the strain-sensitive element Y ₁ and the strain-sensitive element Y ₂ are formed at positions equidistant from the center c, respectively.

The strain-sensitive elements Z ₁ and Z ₂ are arcuate, respectively, and are formed so as to face each other in the x direction with the circumferential direction of the sensitive region 21s as the width direction of the grid. The strain-sensitive elements Z ₁ and Z ₂ are arranged on the opposite side (outside) of the center c of the strain-sensitive elements X ₁ , X ₂ , Y ₁ , and Y _2.

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

_{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 in a portion of the surface of the dead region 21n1 far from the sensitive region 21s. _{Four terminals T 1} , T ₂ , T ₃ , and T ₄ arranged in the x direction are formed in a portion close to the sensitive 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 in a portion of the surface of the dead region 21n2 far from the sensitive region 21s. In the portion close to the sensitive region 21s, four terminals T ₅ , T ₆ , T ₇ and T ₈ arranged in the x direction are formed. That is, in the dead region 21N2, a fixed resistance element _RY 1, RY ₂ terminal _T 5 through T _8, are arranged on the opposite side of the sensitive region 21s.

The connecting regions 21c1 and 21c2 connecting the sensitive regions 21s and the insensitive regions 21n1 and 21n2 are in the x direction (orthogonal direction) orthogonal to the y direction in which the insensitive regions 21s and the insensitive regions 21n1 and 21n2 are connected, respectively. The dimension (width) is smaller than the dimension (width) in the x direction of the sensitive region 21s and the dead regions 21n1 and 21n2. Therefore, the base material 21 has a constricted shape in the connecting regions 21c1 and 21c2.

As shown in FIGS. 4 and 5, wire W may constitute the strain sensitive elements _X 1, _{X 2,} the first bridge circuit by connecting the fixed resistance element _RX 1, RX ₂ (first Wheatstone bridge circuit) BC1 doing. Further, the terminal T ₁ is between the strain-sensitive element X ₁ and the fixed resistance element RX _{1 , the terminal T 2} is between the strain-sensitive elements X ₁ and X ₂ , and the terminal T 2 is between the fixed resistance elements RX ₁ and RX ₂ . The terminal T ₃ is connected to the terminal T ₄ between the strain-sensitive element X ₂ and the fixed resistance element RX _2.

Similarly, the wiring W connects the strain-sensitive elements Y ₁ and Y ₂ and the fixed resistance elements RY ₁ and RY ₂ to form a second bridge circuit (second Wheatstone bridge circuit) BC2. The terminal T ₈ is between the strain-sensitive element Y ₁ and the fixed resistance element RY _{1 , the terminal T 6} is between the strain-sensitive elements Y ₁ and Y ₂ , and the terminal T is between the fixed resistance elements RY ₁ and RY _{2. No. 7} has a terminal T ₅ connected between the strain-sensitive element Y ₂ and the fixed resistance element RY _2.

One end of the strain-sensitive element Z ₁ is connected to the first bridge circuit BC1 between the strain-sensitive element X ₁ and the fixed resistance element RX ₁ , and the other end is connected to the strain-sensitive element Y ₁ and the fixed resistance element RY. It is connected to the second bridge circuit BC2 with _1. Similarly, one end of the strain-sensitive element Z ₂ is connected to the first bridge circuit BC1 between the strain-sensitive element X ₂ and the fixed resistance element RX ₂ , and the other end is fixed to the _{strain-sensitive element Y 2.} It is connected to the second bridge circuit BC2 with the resistance element RY _2. Thus, a first bridge circuit BC1 to a pair of opposite sides portion of the second bridge circuit BC2 respectively sensitive elements Z ₁ strain to another pair of opposite side _portions, a third bridge circuit having Z _2, respectively (Third Wheatstone bridge circuit) BC3.

The strain-sensitive 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 wiring W included in the circuit pattern CP are made of the same material. , More preferably formed by nearby sites within one material. This material is, for example, a copper alloy such as copper or copper / nickel. The circuit pattern CP can be printed on the base material 21 by photoetching, printing, thin film deposition, sputtering or the like.

As shown in FIG. 3, the strain gauge 20 is attached to the main body 10 so that the surface of the base material 21 opposite to the surface on which the circuit pattern CP is formed is in contact with the back surface 11b of the strain generating plate 11. Has been done.

Specifically, the sensitive region 21s of the base material 21 is a strain-causing plate so that its x-direction and y-direction coincide with the x-direction and y-direction of the main body 10, respectively, and the center c coincides with the axis A. It is attached to the back surface 11b of 11. That is, the sensitive region 21s is attached to the straining region where strain is generated by receiving the load of the strain generating plate 11. Therefore, in the state where the sensitive region 21s of the base material 21 is attached to the strain generating plate 11, the strain sensitive elements X ₁ and X ₂ and the strain sensitive elements Y ₁ and Y ₂ , respectively, are in the x direction and y. It is arranged in a region outside the load acting portion 12 in the direction in which a relatively large strain is generated.

The pair of insensitive regions 21n1 and 21n2 of the base material 21 are bent and attached to the inner peripheral surface of the peripheral wall 13, respectively. That is, the dead regions 21n1 and 21n2 are arranged outside the strain-causing region. Therefore, the terminals T ₁ , T ₂ , T ₃ , T ₄ formed in the dead region 21n1 and the terminals T ₅ , T ₆ , T ₇ , and T ₈ formed in the dead region 21n 2 are radially inside the peripheral wall 13. It is facing and exposed.

Next, the usage and operation of the three-axis force sensor 100 and the strain gauge 20 of the present embodiment will be described.

When the 3-axis force sensor 100 is used for the electronic pen 200, first, the load acting portion 12 is fitted to the pen tip (that is, the tip 32). Then, the terminal _T 1 through T ₈ and the signal processing circuit (not shown), respectively, connected with the lead wire _L 1 ~L _8. The terminals T _{1 to} T ₈ and the lead wires L _{1 to} L ₈ can be joined by any method, for example, using solder or an anisotropic conductive film (ACF).

Terminals T ₁ and T ₅ are connected to a power source (not shown) by lead wires L ₁ and L _{5, respectively.} Terminals _T 2, _{T 3,} the terminal _T 6, _{T 7,} the terminal _T 4, _{T 8,} respectively, the leads _L 2, _{L 3,} the leads _L 6, _{L 7,} the lead wire _L 4, _{L 8,} signal It is connected to a calculation unit (not shown) in the signal processing circuit via an amplifier (not shown) in the processing circuit.

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-sensitive element and the resistance value of each fixed resistance element constituting the first bridge circuit BC1, the second bridge circuit BC2, and the third bridge circuit BC3 have no deflection in the sensitive region 21s of the base material 21. in the state, a voltage equal between terminals _T 2, _{T 3,} the voltage equal between the terminal _T 6, _{T 7,} is adjusted so that the voltage becomes equal between the terminal _T 4, _{T 8.}

Therefore, no distortion occurs in the strain-generating plate 11 as shown in FIG. 6 (a), in the absence of deflection sensitive region 21s, between the terminals _T 2, _{T 3,} between the terminals _T 6, _{T 7,} no potential difference between the terminals T _4, T _8, the arithmetic unit does not calculate the strain.

Next, when a load in the x direction is applied to the load acting portion 12 as shown in FIG. 6B, the load acting portion 12 receives the load and moves, causing strain on the strain generating plate 11. 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 occurs in X _2.

Accordingly, the strain sensitive elements _X 1, the resistance value of _{X 2} is changed respectively, a potential difference occurs between the terminals _T 2, _{T 3} of the first bridge circuit BC1 including sensitive elements _X 1, _{X 2} strain. Based on this potential difference, the calculation unit obtains the amount of strain generated in the strain generating plate 11, and obtains the magnitude of the load acting on the load acting unit 12 in the c direction. At this time, no strain is generated on the peripheral wall 13, and the resistance values of _{the fixed resistance elements RX 1} and RX _{2 are constant.}

When a load in the y direction is applied to the load acting portion 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 portion 12, the sensation region 21s of the strain generating plate 11 and the base material 21 is curved so that the center protrudes, so that the strain sensitizing elements X ₁ and X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ all have extended 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-sensitive elements Z 1} and Z ₂ , respectively, change, and the terminals T ₄ and T _{8 of the third bridge circuit BC 3 change.} There is a potential difference between them. Based on this potential difference, the calculation unit obtains the amount of strain generated in the strain generating plate 11, and obtains the magnitude of the load acting on the load acting unit 12 in the z direction.

Here, the fixed resistance elements RX ₁ and RX _{2 of} the first bridge circuit BC1 and the fixed resistance elements RY ₁ and RY ₂ of the second bridge circuit BC 2 are printed on the base material 21, and the strain sensitive elements X ₁ and X _{2 are printed.} , Y ₁ , Y ₂ , Z ₁ , Z ₂ and the significance of forming with the same material will be described.

(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 are strain-sensitive elements X ₁ , X. It will be formed of the same material as ₂ , Y ₁ , Y ₂ , Z ₁ , and Z _{2, and at a position close to these.} Here, since the resistance temperature coefficient indicating the rate of change of the resistance value with respect to the temperature change is a physical property value depending on the material, the resistance temperature coefficients of the total strain-sensitive element and the total fixed resistance element are equal in the present embodiment. Further, the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed on the base material 21, and are in the vicinity of the _{strain-sensitive elements X 1} , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z _2. Since it is formed in, the change in ambient temperature that affects the total strain sensitive element and the total fixed resistance element is substantially the same. Therefore, when the ambient temperature changes, the resistance value of the total strain-sensitive element and the resistance value of the total fixed resistance element 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 resistance values changes between the resistance elements (distortion-sensitive element and fixed resistance element) included in each, the terminals between T _{2, T 3,} between the terminals _T 6, _{T 7,} the potential difference between the terminals _T 4, _{T 8} occurs, the strain on the basis of which is detected. Therefore, when the balance between the resistance value of the strain-sensitive 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 this change in the balance. However, in the present embodiment, when the ambient temperature changes, the resistance value of the total strain-sensitive element and the resistance value of the total fixed resistance element change at the same rate, so that the ambient temperature changes. Even in this case, the balance of resistance values between the elements does not change, and the occurrence of measurement error is suppressed. _{When the circuit pattern CP is formed, the strain-sensitive element X 1} is formed by forming a strain-sensitive element or the like using a portion near the material (copper, copper alloy, etc.) prepared as an integral mass. The resistance temperature coefficient of X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ , fixed resistance element RX ₁ , RX ₂ , RY ₁ , RY ₂ , and wiring W can be made more uniform, and the occurrence of measurement error is better. It can be suppressed.

(2) As in the present embodiment, the fixed resistance elements RX ₁ and RX _{2 of} the first bridge circuit BC1 and the fixed resistance elements RY ₁ and RY ₂ of the second bridge circuit BC 2 are arranged in the dead regions 21n1 and 21n2 of the base material 21. When the dead regions 21n1 and 21n2 are attached to the portion of the main body 10 where distortion does not occur (outside the strain-causing region), the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed. It can act as a dummy gauge for temperature compensation. Therefore, even when the main body 10 including the strain generating plate 11 expands or contracts due to a change in ambient temperature, the resistance values _{of the strain-sensitive elements X 1} , X ₂ , Y ₁ , and Y _{2 due to the expansion and contraction.} It is possible to compensate for the change in the above and suppress the occurrence of measurement error.

(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.} Each can be formed as a complete closed circuit on the substrate 21.

When the strain-sensitive 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 the signal processing circuit, the bridge circuit is closed. , It is necessary to connect the strain-sensitive 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 wiring on the base material and the lead wire are connected by joining the lead wire to the electrode provided on the base material, but when a joining resistance occurs at the joint portion between the electrode and the lead wire, this is a bridge. Since it becomes a resistance in the circuit and causes a large strain detection error, the joining method is limited to solder joining in which the joining resistance is substantially negligible.

However, in order to perform good solder bonding, 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. Further, in order to perform good solder bonding, it is necessary to pile up the solder with a certain thickness, which hinders the miniaturization of the triaxial force sensor.

In contrast, in the present embodiment, the first bridge circuit BC1, second bridge circuit BC2, the third bridge circuit BC3, respectively, is formed as a closed circuit was completed on the substrate 21, the terminal _T 1 through T _{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 the power supply and the arithmetic unit. Accordingly, in the present embodiment, generation of junction resistance at the junction between the terminal T ₁ through T ₈ and the lead wire L ₁ ~L ₈ is allowed, any bonding means other than solder bonding, for example, an anisotropic conductive film It is possible to adopt the joining using. 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 1/10 of that in the case of solder bonding, so that the triaxial force can be suppressed. When it is desired to reduce the size of the sensor 100, bonding with an anisotropic conductive film is advantageous.

The effects of the strain gauge 20 and the triaxial force sensor 100 of this embodiment are as follows.

_{Since the strain gauge 20 forms the fixed resistance elements RX 1} and RX _{2 of} the first bridge circuit BC1 and the fixed resistance elements RY ₁ and RY ₂ of the second bridge circuit BC 2 on the base material 21, the above (2) , (3) can be exhibited, and the fixed resistance elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed of the same material as the strain-sensitive elements X ₁ , X ₂ , Y ₁ , and Y _2. Therefore, the effect of (1) above can be achieved.

In the strain gauge 20, only the strain-sensitive elements X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ are formed in the strain-sensitive region 21s, and the terminals T _{1 to} T ₈ and the fixed resistance are formed. The elements RX ₁ , RX ₂ , RY ₁ , and RY ₂ are formed in the dead regions 21n1 and 21n2. Therefore, the diameter (dimension) of the sensitive region 21s can be reduced, and the strain generating plate 11 of the triaxial force sensor 100 can be reduced. The miniaturization of the strain generating plate 11 leads to the miniaturization of the 3-axis force sensor 100, which is preferable.

In the strain gauge 20, since the terminal _T 1 through T ₈ is provided in the dead region 21N1,21n2, if necessary, without increasing the diameter of the sensitive area 21s, the size of the terminal _T 1 through T ₈ Can be increased to facilitate the joining work with the lead wire or the like.

Since the base material 21 of the strain gauge 20 has the sensitive regions 21s and the connecting regions 21c1 and 21c2 narrower than the sensitive regions 21n1 and 21n2 between the sensitive regions 21s and the dead regions 21n1 and 21n2, the sensitive regions 21c1 and 21c2. The 21s and the dead regions 21n1 and 21n2 can be arranged in various ways without being restricted by the connection portion with the connecting regions 21c1 and 21c2.

Since the three-axis force sensor 100 and the electronic pen 200 of the present embodiment include the strain gauge 20, the same effect as that of the strain gauge 20 can be obtained.

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

10 Main body 11 Distortion plate (distortion member)
12 Load acting part 13 Peripheral wall 20 Strain gauge 21 Base material 21s Sensitive area 21c1, 21c2 Connecting area 21n1, 21n2 Insensitive area 31, 32 Tip 33 Holder 34 Body 35 Front cap 100 3-axis force sensor 200 Electronic pen BC1 First bridge circuit (1st 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-sensitive element (first-direction strain-sensitive element)
Y ₁ , Y ₂ strain-sensitive element (second-direction strain-sensitive element)
Z ₁ and Z ₂ strain-sensitive elements (third-direction strain-sensitive elements)

Claims (4)

It is a strain-causing body used for force detection.
A force acting position on which the force of the detection target acts, a straining region in which strain is generated by receiving the force acting on the force acting position, and a straining member having a region different from the straining region.
A pair of strain- sensitive elements provided in the strain-causing region of the strain-causing member, and
A first fixed resistance element provided in a region different from the strain-causing region of the strain-causing member is provided.
The pair of strain-sensitive elements and the first fixed resistance element are made of the same material and form a Wheatstone bridge for detecting a force.
The pair of strain- sensitive elements are provided at positions equidistant from the force acting position and symmetrical with respect to the force acting position .
A second fixed resistance element provided in a region different from the strain-causing region of the strain-causing member is further provided.
A strain-causing body in which the pair of strain-sensitive elements, a first fixed resistance element, and a second fixed resistance element form a Wheatstone bridge for detecting a force. It is a strain-causing body used for force detection.
A force acting position on which the force of the detection target acts, a straining region in which strain is generated by receiving the force acting on the force acting position, and a straining member having a region different from the straining region.
A pair of first strain-sensitive elements provided in the strain-causing region of the strain-causing member, and
A pair of second strain-sensitive elements provided in the strain-causing region of the strain-causing member, and
A first fixed resistance element provided in a region different from the strain-causing region of the strain-causing member, and
A first wiring provided on the strain-causing member and electrically connecting one of the pair of first strain-sensitive elements and one of the pair of second strain-sensitive elements.
A second wiring different from the first wiring, which is provided on the strain-causing member and electrically connects the other of the pair of first strain-sensitive elements and the other of the pair of second strain-sensitive elements. Equipped with a second wiring to connect to
The pair of first strain-sensitive elements and first fixed resistance elements are made of the same material and form a Wheatstone bridge for detecting force.
The pair of first strain-sensitive elements are provided at positions equidistant from the force acting position and symmetrical with respect to the force acting position.
A strain-causing body in which the pair of second strain-sensitive elements are equidistant from the force acting position and symmetrical with respect to the force acting position. A second fixed resistance element provided in a region different from the strain-causing region of the strain-causing member is further provided.
The strain-causing body according to claim 2 , wherein the pair of first strain-sensitive elements, a first fixed resistance element, and a second fixed resistance element constitute a Wheatstone bridge for detecting a force. The strain-causing body according to any one of claims 1 to 3,
A sensor including a force acting member connected to the strain generating member so as to apply a force to be detected to the force acting position.

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