Strain gauge and multi-axial force sensor

Abstract

The purpose of the present invention is to suppress measurement errors caused by changes in ambient temperature in a strain gauge for a multi-axis force sensor. A substrate (121) has a sensing region (121s) attached to a strain region in which a strain member receives a load and generates strain, and non-sensing regions (121n1, 121n2) disposed outside the strain region, and a first Wheatstone bridge circuit (BC11) that detects a load acting on the strain member in a first direction is configured from first direction strain sensing elements (X11, X12) and first direction fixed resistance elements (RX11, RX12). A second Wheatstone bridge circuit (BC12) that detects a load acting in a second direction orthogonal to the first direction of the strain member is configured from second direction strain sensing elements (Y11, Y12) and second direction fixed resistance elements (RY11, RY12), and the first direction strain sensing elements and the second direction strain sensing elements are formed in the sensing region. The first-direction fixed resistance element or the second-direction fixed resistance element is formed of the same material as the strain sensing element in the non-sensing region.

Description

[0001] This application is a divisional application of the parent application with the applicant being "Minebea Mitsumi Inc.", the invention title being "Strain Gauge and Multi-Axis Force Sensor", the application date being "July 5, 2018", and the application number being "201880037802.6". Technical Field

[0002] The present invention relates to a strain gauge and a multi-axis force sensor including the strain gauge. Background Art

[0003] Multi-axis force sensors including strain gauges are widely used in robots, game devices, various measuring devices, and other devices. An example of a multi-axis force sensor including a strain gauge is disclosed in Patent Documents 1 and 2.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-164495

[0005] Patent Document 2: Japanese Patent No. 5008188

[0006] In multi-axis force sensors including strain gauges, the existence of measurement errors caused by changes in the ambient temperature is recognized, and it is desired to suppress such measurement errors. Summary of the Invention

[0007] Accordingly, an object of the present invention is to provide a strain gauge that suppresses the occurrence of measurement errors caused by changes in the ambient temperature, and a multi-axis force sensor including the strain gauge.

[0008] According to the first aspect of the present invention, a strain gauge is provided, which is mounted on a strain component that generates strain under a load, and is used for detecting a load in a first direction acting on the strain component based on a first Wheatstone bridge circuit, and detecting a load in a second direction orthogonal to the first direction acting on the strain component based on a second Wheatstone bridge circuit. The strain gauge includes a substrate and a circuit pattern formed on the substrate. The substrate has a sensing region mounted on a strain region of the strain component that generates strain under a load, and a non-sensing region disposed outside the strain region. The circuit pattern includes two first-direction strain sensing elements constituting the first Wheatstone bridge circuit, two second-direction strain sensing elements constituting the second Wheatstone bridge circuit, and at least one of a first-direction fixed resistance element constituting the first Wheatstone bridge circuit and a second-direction fixed resistance element constituting the second Wheatstone bridge circuit. The two first-direction strain sensing elements, the two second-direction strain sensing 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 region, and at least one of the first-direction fixed resistance element and the second-direction fixed resistance element is formed in the non-sensing region.

[0009] According to a second aspect of the present invention, a strain gauge is provided which is mounted on a strain member that generates strain under a load and is used to detect a load in a first direction acting on the strain member based on a first Wheatstone bridge circuit and a load in a second direction orthogonal to the first direction acting on the strain member based on a second Wheatstone bridge circuit. The strain gauge includes a flexible substrate and a circuit pattern formed on the substrate. The substrate has a sensing region mounted on a strain region of the strain member that generates strain under a load, a non-sensing region disposed outside the strain region, and a connecting region connecting the sensing region and the non-sensing region. A dimension of the connecting region in an orthogonal direction orthogonal to a direction connecting the sensing region and the non-sensing region is smaller than dimensions of the sensing region and the non-sensing region in the orthogonal direction. The circuit pattern includes two first-direction strain sensing elements constituting the first Wheatstone bridge circuit, two second-direction strain sensing elements constituting the second Wheatstone bridge circuit, and at least one of a first-direction fixed resistance element constituting the first Wheatstone bridge circuit and a second-direction fixed resistance element constituting the second Wheatstone bridge circuit. The two first-direction strain sensing elements, the two second-direction strain sensing 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 region. At least one of the first-direction fixed resistance element and the second-direction fixed resistance element is formed in the non-sensing region.

[0010] It may also be configured that, based on the strain gauges of the first and second aspects, the circuit pattern includes two first-direction fixed resistance elements constituting the first Wheatstone bridge circuit and two second-direction fixed resistance elements constituting the second Wheatstone bridge circuit. The two first-direction strain sensing elements, the two second-direction strain sensing elements, the two first-direction fixed resistance elements, and the two second-direction fixed resistance elements are formed of the same material. The two first-direction fixed resistance elements and the two second-direction fixed resistance elements are formed in the non-sensing region.

[0011] It may also be configured that, based on the strain gauges of the first and second aspects, the circuit pattern further includes at least one terminal. The at least one terminal is formed in the non-sensing region.

[0012] It may also be configured that, for the strain gauges of the first and second aspects, in the non-sensing region, the at least one terminal is disposed on a side opposite to the sensing region of at least one of the first-direction fixed resistance element and the second-direction fixed resistance element.

[0013] It can also be configured as follows: based on the strain gauges in the first and second forms, a pair of the above non-sensing regions are provided on both sides of the above sensing region.

[0014] It can also be configured as follows: based on the strain gauges in the first and second forms, the above circuit pattern further includes two third-direction strain sensing elements or two third-direction fixed resistance elements, and the two third-direction strain sensing elements or the two third-direction fixed resistance elements connect the first Wheatstone bridge circuit and the second Wheatstone bridge circuit to form a third Wheatstone bridge circuit.

[0015] It can also be configured as follows: based on the strain gauge in the first form, the above substrate has flexibility, and the above substrate further has a connection region connecting the above sensing region and the above non-sensing region, and the dimension of the connection region in the orthogonal direction perpendicular to the direction connecting the above sensing region and the above non-sensing region is smaller than the dimensions of the above sensing region and the above non-sensing region in the orthogonal direction.

[0016] It can also be configured as follows: the strain gauge in the first form is also used to detect the load in the third direction perpendicular to the first and second directions acting on the above strain component based on the third Wheatstone bridge circuit. In addition, based on the strain gauge in the first form, the above substrate has flexibility, the above non-sensing region of the above substrate is a pair of regions, the above substrate further has a connection region connecting the above sensing region and the above non-sensing region, and the dimension of the connection region in the orthogonal direction perpendicular to the direction connecting the above sensing region and the above non-sensing region is smaller than the dimensions of the above sensing region and the above non-sensing region in the orthogonal direction. The above circuit pattern includes two third-direction strain sensing elements formed in the above sensing region and constituting the third Wheatstone bridge circuit, two first-direction fixed resistance elements formed in the above non-sensing region and constituting the first Wheatstone bridge circuit, and two second-direction fixed resistance elements formed in the above non-sensing region and constituting the second Wheatstone bridge circuit. The two first-direction strain sensing elements, the two second-direction strain sensing elements, the two third-direction strain sensing elements, the two first-direction fixed resistance elements, and the two second-direction fixed resistance elements are formed of the same material, and the two third-direction strain sensing elements connect the first Wheatstone bridge circuit and the second Wheatstone bridge circuit to form a third Wheatstone bridge circuit.

[0017] According to the third form of the present invention, a multi-axis force sensor is provided, and the multi-axis force sensor includes a strain plate, a load acting portion connected to the strain plate, and a strain gauge in the first or second form mounted on the strain plate.

[0018] It can also be configured as follows: on the basis of the multi-axis force sensor in the third form, the non-sensing area of the base material of the strain gauge is adhered to the side surface of the strain plate.

[0019] According to the fourth form of the present invention, there is provided a strain gauge which is mounted on a strain component that generates strain under a load and is used for detecting a load in a first direction acting on the strain component based on a first Wheatstone bridge circuit, detecting a load in a second direction orthogonal to the first direction acting on the strain component based on a second Wheatstone bridge circuit, and detecting a load in a third direction orthogonal to the first and second directions acting on the strain component based on a third Wheatstone bridge circuit. The strain gauge includes a flexible base material and a circuit pattern formed on the base material. The base material has a sensing area mounted on the strain area of the strain component that generates strain under a load, a pair of non-sensing areas disposed outside the strain area, and a connecting area connecting the sensing area and the non-sensing area. The dimension of the connecting area in the orthogonal direction orthogonal to the direction connecting the sensing area and the non-sensing area is smaller than the dimensions of the sensing area and the non-sensing area in the orthogonal direction. The circuit pattern includes two first-direction strain sensing elements constituting the first Wheatstone bridge circuit, two second-direction strain sensing elements constituting the second Wheatstone bridge circuit, two third-direction strain sensing elements constituting the third Wheatstone bridge circuit, two first-direction fixed resistance elements constituting the first Wheatstone bridge circuit, and two second-direction fixed resistance elements constituting the second Wheatstone bridge circuit. The first-direction strain sensing elements, the second-direction strain sensing elements, the third-direction strain sensing elements, the first-direction fixed resistance elements, and the second-direction fixed resistance elements are formed of the same material. The first-direction strain sensing elements, the second-direction strain sensing elements, and the third-direction strain sensing elements are formed in the sensing area. The first-direction fixed resistance elements and the second-direction fixed resistance elements are formed in the non-sensing area. The third-direction strain sensing elements connect the first Wheatstone bridge circuit and the second Wheatstone bridge circuit to constitute the third Wheatstone bridge circuit.

[0020] According to the fifth form of the present invention, there is provided a triaxial force sensor, which includes the strain gauge in the fourth form, a plate-shaped strain component, and a load acting portion connected to the strain component.

[0021] It can also be configured as follows: the triaxial force sensor in the fifth form further includes a peripheral wall which stands upright in the third direction from the peripheral portion of the surface of the strain component on the side opposite to the surface connected to the load acting portion, and the non-sensing area is adhered to the inner peripheral surface of the peripheral wall.

[0022] In the strain gauge of the present invention and the multi-axis force sensor equipped with the strain gauge, the generation of measurement errors caused by changes in the ambient temperature is suppressed. Description of the Drawings

[0023] Figure 1 Shows the wiring pattern of the strain gauge according to the first embodiment of the present invention.

[0024] Figure 2 is corresponding to Figure 1 the circuit diagram of the wiring pattern of the strain gauge.

[0025] Figure 3 (a) of Figure 3 (b) of shows an explanatory diagram of the measurement in the triaxial force sensor according to each embodiment of the present invention.

[0026] Figure 4 Shows a modified example of the wiring pattern of the strain gauge according to the first embodiment of the present invention.

[0027] Figure 5 Is a perspective view of the triaxial force sensor according to the second embodiment of the present invention.

[0028] Figure 6 is a cross-sectional view taken along the YZ plane including the axis A2 to cut the Figure 5 shown triaxial force sensor.

[0029] Figure 7 Shows the wiring pattern of the strain gauge according to the second embodiment of the present invention.

[0030] Figure 8 is corresponding to Figure 7 the circuit diagram of the wiring pattern of the strain gauge.

[0031] Figure 9 Shows another example of the wiring pattern of the strain gauge according to the second embodiment of the present invention.

[0032] Figure 10 Is a cross-sectional view of an electronic pen applying the triaxial force sensor according to the third embodiment of the present invention.

[0033] Figure 11 Is a perspective view of the triaxial force sensor according to the third embodiment of the present invention.

[0034] Figure 12 is a cross-sectional view taken along the yz plane including the axis A3 to cut the Figure 11 shown triaxial force sensor.

[0035] Figure 13This is a diagram showing the wiring pattern of the strain gauge according to the third embodiment of the present invention.

[0036] Figure 14 It is related to Figure 13 The circuit diagram corresponding to the wiring pattern of the strain gauge shown. Detailed implementation mode

[0037] <First Embodiment>

[0038] Taking the strain gauge 120 and the three-axis force sensor 1000 that applies the strain gauge 120 as an example, the first embodiment of the strain gauge and the multi-axis force sensor of the present invention will be described with reference to Figures 1 to 4 This is a description of the first embodiment of the strain gauge and the multi-axis force sensor of the present invention.

[0039] In Figure 1 It shows the state before the strain gauge 120 is installed on the strain plate 111 of the three-axis force sensor 1000 (refer to Figure 3 (a) of Figure 3 (b) of Figure 1 As shown, the strain gauge 120 includes a rectangular base material 121 and a circuit pattern CP1 printed on the surface of the base material 121. The base material 121 has an induction area 121s and non-induction areas 121n1, 121n2 sandwiching the induction area 121s. The circuit pattern CP1 includes six strain sensing elements X 11 、X 12 、Y 11 、Y 12 、Z 11 、Z 12 、four fixed resistance elements RX 11 、RX 12 、RY 11 、RY 12 、eight terminals T 11 ~T 18 、and the wiring W1 connecting these. In addition, in the description of the first embodiment, in the strain gauge 120 and the three-axis force sensor 1000 including the strain gauge 120, the direction in which the non-induction areas 121n1, 121n2 sandwich the induction area 121s is defined as the y-direction (the second direction), the direction orthogonal to the y-direction on the surface of the base material 121 is defined as the x-direction (the first direction). In addition, the direction of the axis orthogonal to the x-direction and the y-direction is defined as the z-direction (the third direction).

[0040] Here, in Figure 3 (a) of Figure 3In the triaxial force sensor 1000 shown in FIG. (b), the strain plate 111 is a disc-shaped member that bears an external load applied to the triaxial force sensor 1000 via the load application portion 112 and generates strain. The strain in the strain plate 111 is generated on the front and back surfaces (the upper and lower surfaces orthogonal to the z-direction) of the strain plate 111, and no strain or negligible strain is generated on the side surface (the circumferential surface parallel to the z-direction) of the strain plate 111. In this specification, a region in the strain plate 111 that bears an external load and generates strain, such as the front and back surfaces of the strain plate 111 in this embodiment, is referred to as a "strain region". The diameter and thickness of the strain plate 111 are arbitrary.

[0041] The load application portion 112 stands upright from the center of the front surface of the strain plate 111 in the direction of the rotation axis A1 (Z-direction) of the strain plate 111. The load application portion 112 is a part that bears an external load and moves, thereby causing the strain plate 111 to generate strain. For example, it is a prism with a square cross-sectional shape. The load application portion 112 is disposed on the front surface of the strain plate 111 in a coaxial manner with the strain plate 111, that is, with the central axis of the prism coinciding with the rotation axis A1 of the strain plate 111. The strain plate 111 and the load application portion 112 are integrally formed of a synthetic resin material, for example.

[0042] Return to Figure 1 The base material 121 is a flexible resin film, for example, and has a central circular induction region 121s and a pair of non-induction regions 121n1 and 121n2 sandwiching the induction region 121s. As the resin film, polyester, polyimide, etc. can be used. In addition, although the induction region 121s and the non-induction regions 121n1 and 121n2 can be formed of different materials respectively, it is preferable to form these regions of the same material so that the temperature characteristics (such as the resistance temperature coefficient) of the entire region are equal. In this case, it is preferable to integrally cut out the induction region 121s, the non-induction regions 121n1 and 121n2 from nearby parts within an integrally formed material (such as a sheet of polyester, polyimide, etc.) to form the base material 121. Thereby, the temperature characteristics of each region can be made more uniform.

[0043] The induction region 121s is a region pasted on the back surface of the strain plate 111, and thus has the same diameter as or smaller than the back surface of the strain plate 111. On one surface of the induction region 121s, strain sensing elements (first direction strain sensing elements) X 11 and X 12 are formed sandwiching the center c in the x-direction, and strain sensing elements (second direction strain sensing elements) Y 11 and Y 12 are formed sandwiching the center c in the y-direction, and strain sensing elements (third direction strain sensing elements) Z 11 and Z 12。

[0044] Strain sensing element X 11 、X 12 are formed parallel to each other with the y-direction as the width direction of the grid, respectively. Strain sensing element X 11 and strain sensing element X 12 are respectively formed at positions equidistant from the center c. The distance in the x-direction between strain sensing element X 11 and strain sensing element X 12 is greater than the width of the load application portion 112 in the x-direction.

[0045] Strain sensing element Y 11 、Y 12 are formed parallel to each other with the x-direction as the width direction of the grid, respectively. Strain sensing element Y 11 and strain sensing element Y 12 are respectively formed at positions equidistant from the center c. The distance in the y-direction between strain sensing element Y 11 and strain sensing element Y 12 is greater than the width of the load application portion 112 in the y-direction.

[0046] Strain sensing element Z 11 、Z 12 are respectively arc-shaped and are formed opposite to each other in the x-direction with the circumferential direction of the sensing region 121s as the width direction of the grid. Strain sensing element Z 11 、Z 12 are arranged on the side (outer side) opposite to the center c of strain sensing element X 11 、X 12 、Y 11 、Y 12 .

[0047] A pair of non-sensing regions 121n1 and 121n2 are shaped to sandwich the sensing region 121s in the y-direction.

[0048] On the part of the surface of the non-sensing region 121n1 that is far from the sensing region 121s, fixed resistance elements (first-direction fixed resistance elements) RX 11 、RX 12 are arranged in the x-direction and extend in the x-direction respectively. Four terminals T 11 、T 12 、T 13 、T 14 are formed in the part close to the sensing region 121s and arranged in the x-direction. That is, in the non-sensing region 121n1, the fixed resistance elements RX 11 、RX 12 are arranged between terminals T 11 ~T 14On the side opposite to the sensing region 121s.

[0049] Similarly, on the surface of the non-sensing region 121n2, in a portion farther from the sensing region 121s, fixed resistance elements (second-direction fixed resistance elements) RY that extend in the x direction are arranged in the x direction. 11 , RY 12 , and in a portion closer to the sensing region 121s, four terminals T are arranged in the x direction. 15 , T 16 , T 17 , T 18 . That is, in the non-sensing region 121n2, the fixed resistance elements RY 11 , RY 12 are arranged on the side opposite to the sensing region 121s with respect to the terminals T 15 to T 18 .

[0050] As Figure 1 and Figure 2 shown, the wiring W1 connects the strain sensing elements X 11 , X 12 , the fixed resistance elements RX 11 , RX 12 to form the first bridge circuit (first Wheatstone bridge circuit) BC11. Additionally, a terminal T 11 is connected between the strain sensing element X 11 and the fixed resistance element RX 11 , a terminal T 11 is connected between the strain sensing elements X 12 , X 12 , a terminal T 11 is connected between the fixed resistance elements RX 12 , RX 13 , and a terminal T 12 is connected between the strain sensing element X 12 and the fixed resistance element RX 14 .

[0051] Similarly, the wiring W1 connects the strain sensing elements Y 11 , Y 12 , the fixed resistance elements RY 11 , RY 12 to form the second bridge circuit (second Wheatstone bridge circuit) BC12. A terminal T 11 is connected between the strain sensing element Y 11 and the fixed resistance element RY 18 , and a terminal T 11 is connected between the strain sensing elements Y 12 , Y 16, between the fixed resistance element RY 11 , RY 12 , a terminal T is connected 17 , between the strain sensing element Y 12 and the fixed resistance element RY 12 , a terminal T is connected 15 .

[0052] One end of the strain sensing element Z 11 is connected to the first bridge circuit BC11 between the strain sensing element X 11 and the fixed resistance element RX 11 , and the other end is connected to the second bridge circuit BC12 between the strain sensing element Y 11 and the fixed resistance element RY 11 . Similarly, one end of the strain sensing element Z 12 is connected to the first bridge circuit BC11 between the strain sensing element X 12 and the fixed resistance element RX 12 , and the other end is connected to the second bridge circuit BC12 between the strain sensing element Y 12 and the fixed resistance element RY 12 . Thus, a third bridge circuit (third Wheatstone bridge circuit) BC13 is formed that has the first bridge circuit BC11 and the second bridge circuit BC12 on a pair of opposite sides, respectively, and has the strain sensing elements Z 11 , Z 12 on the other pair of opposite sides, respectively.

[0053] The strain sensing elements X 11 , X 12 , Y 11 , Y 12 , Z 11 , Z 12 , the fixed resistance elements RX 11 , RX 12 , RY 11 , RY 12 , and the wiring W1 are formed of the same material as each other, and more preferably are formed of parts in the vicinity within one material. As an example, the material is copper, copper alloy such as copper / nickel, etc. The printing of the circuit pattern CP1 onto the base material 121 can be performed by photolithography, printing, vapor deposition, sputtering, etc.

[0054] The strain gauge 120 is adhered to the strain plate 111 in such a manner that the surface of the base material 121 opposite to the surface on which the circuit pattern CP1 is formed is in contact with the strain plate 111.

[0055] Specifically, the sensing area 121s of the base material 121 is adhered to the back surface of the strain plate 111 in such a manner that the center c coincides with the rotation axis A1 of the strain plate 111. In addition, as described above, the strain sensing element X 11 , X 12 The distance in the x-direction between them is greater than the size of the load application portion 112 in the x-direction, and the strain sensing element Y 11 , Y 12 The distance in the y-direction between them is greater than the size of the load application portion 112 in the y-direction. Therefore, in the state where the sensing area 121s of the base material 121 is adhered to the strain plate 111, the strain sensing element X 11 , X 12 and the strain sensing element Y 11 , Y 12 Are respectively arranged in the areas where strain is generated more greatly outside the load application portion 112 in the x-direction and the y-direction. In addition, in Figure 1 and Figure 4 , the outline of the load application portion 112 in the state where the base material 121 is adhered to the strain plate 111 is indicated by a dotted line, and the positional relationship between the load application portion 112 and the strain sensing element X 11 , X 12 , Y 11 , Y 12 Is shown.

[0056] On the base material 121 adhered to the triaxial force sensor 1000, the terminals T 11 , T 12 , T 13 , T 14 formed in the non-sensing area 121n1, and the terminals T 15 , T 16 , T 17 , T 18 formed in the non-sensing area 121n2 are exposed to the radially outer side of the strain plate 111 (i.e., the outer side of the strain area).

[0057] Next, the usage method and operation of the strain gauge 120 and the triaxial force sensor 1000 of the present embodiment will be described.

[0058] When the triaxial force sensor 1000 is used as, for example, a tactile sensor of a robot hand, first, the triaxial force sensor 1000 is fixed to the fingertip of the robot hand. Then, the wires L 11 ~L 18 ( Figure 2 ) are used to connect the terminals T 11 ~T 18 to a signal processing unit (not shown). The terminals T 11 ~T 18 are connected to the wires L 11 ~L18 The joining can be performed by any method, for example, it can be performed using soldering or an anisotropic conductive film (ACF).

[0059] Terminal T 11 and T 15 are respectively connected to the power supply (not shown) of the signal processing unit through wires L 11 and L 15 . Terminal T 12 and T 13 , terminal T 16 and T 17 , terminal T 14 and T 18 are respectively connected to the operation unit (not shown) in the signal processing unit through wires L 12 and L 13 , wire L 16 and L 17 , wire L 14 and L 18 via an amplifier (not shown) in the signal processing unit.

[0060] When the triaxial force sensor 1000 operates, an input voltage Ei is applied between terminal T 11 and terminal T 15 by the power supply. The resistance values of the strain sensing elements and the resistance values of the fixed resistance elements constituting the first bridge circuit BC11, the second bridge circuit BC12, and the third bridge circuit BC13 are adjusted such that when there is no flexure in the sensing area 121s of the base material 121, the voltages between terminal T 12 and T 13 are equal, the voltages between terminal T 16 and T 17 are equal, and the voltages between terminal T 14 and T 18 are equal. Therefore, in a state where no strain is generated in the strain plate 111 and there is no flexure in the sensing area 121s ( Figure 3 in (a)), there is no potential difference between terminal T 12 and T 13 , between terminal T 16 and T 17 , and between terminal T 14 and T 18 , and the operation unit does not calculate the strain.

[0061] Next, if a load in the x direction is applied to the load application part 112, the load application part 112 receives the load and moves, thereby causing the strain plate 111 to generate strain ( Figure 3(b)). At this time, the sensing region 121s of the base material 121 of the strain gauge 120 adhered to the strain plate 111 also flexes integrally with the strain plate 111, so that compressive strain is generated in the strain sensing element X 11 and tensile strain is generated in the strain sensing element X 12 . As a result, the resistance values of the strain sensing elements X 11 and X 12 change respectively, and a potential difference is generated between the terminals T 11 and T 12 of the first bridge circuit BC11 including the strain sensing elements X 12 and X 13 . The arithmetic unit calculates the amount of strain generated in the strain plate 111 based on this potential difference, and calculates the magnitude of the load in the x direction acting on the load application part 112. At this time, no strain is generated in the non-sensing regions 121n1 and 121n2 outside the strain region, and the resistance values of the fixed resistance elements RX 11 and RX 12 are constant. When a load in the y direction is applied to the load application part 112, the magnitude of the load in the y direction acting is calculated in the same manner.

[0062] When a load in the Z direction is applied to the load application part 112, the strain plate 111 and the sensing region 121s of the base material 121 bend in a manner that the center protrudes. Therefore, tensile strain is generated in all of the strain sensing elements X 11 and X 12 , Y 11 and Y 12 , Z 11 and Z 12 . As a result, the combined resistance of the first bridge circuit BC11, the combined resistance of the second bridge circuit BC12, and the resistance values of the strain sensing elements Z 11 and Z 12 change respectively, and a potential difference is generated between the terminals T 14 and T 18 of the third bridge circuit BC13. The arithmetic unit calculates the amount of strain generated in the strain plate 111 based on this potential difference, and calculates the magnitude of the load in the Z direction acting on the load application part 112.

[0063] Here, the fixed resistance elements RX 11 and RX 12 of the first bridge circuit BC11, the fixed resistance elements RY 11 and RY 12 of the second bridge circuit BC12 are printed on the base material 121 and are composed of the strain sensing elements X 11 and X 12 , Y 11 and Y 12Explain the meaning of forming with the same material.

[0064] (1-1) By forming the fixed resistance element RX in this way 11 、RX 12 、RY 11 、RY 12 The fixed resistance element RX 11 、RX 12 、RY 11 、RY 12 is made of the same material as the strain sensing elements X 11 、X 12 、Y 11 、Y 12 、Z 11 、Z 12 and is formed at a position close to them. Here, the resistance temperature coefficient, which represents the ratio of the change in resistance value to the change in temperature, depends on the physical property values of the material. Therefore, in this embodiment, the resistance temperature coefficients of all the strain sensing elements and all the fixed resistance elements are equal. In addition, the fixed resistance element RX 11 、RX 12 、RY 11 、RY 12 is formed on the base material 121 and is formed near the strain sensing elements X 11 、X 12 、Y 11 、Y 12 、Z 11 、Z 12 So, the change in the ambient temperature that affects all the strain sensing elements and all the fixed resistance elements is substantially the same. Therefore, when there is a change in the ambient temperature, the resistance values of all the strain sensing elements and all the fixed resistance elements change in the same proportion.

[0065] When the balance of the resistance values changes between the resistance elements (strain sensing elements and fixed resistance elements) included in the first bridge circuit BC11, the second bridge circuit BC12, and the third bridge circuit BC13 respectively, between the terminals T 12 、T 13 between, between the terminals T 16 、T 17 between, between the terminals T 14 、T 18A potential difference is generated therebetween, and strain is detected based on the potential difference. Therefore, in a case where 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, measurement errors may occur due to the change in the balance. However, in the present embodiment, when the ambient temperature changes, the resistance values of all the strain sensing elements and the resistance values of all the fixed resistance elements change at the same ratio. Therefore, even when the ambient temperature changes, the balance of the resistance values between the elements does not change, thereby suppressing the occurrence of measurement errors. Further, when forming the circuit pattern CP1, by forming the strain sensing element or the like in a portion near a material (copper, copper alloy, etc.) prepared as an integral block, the strain sensing element X 11 、X 12 、Y 11 、Y 12 、Z 11 、Z 12 、the fixed resistance element RX 11 、RX 12 、RY 11 、RY 12 、and the wiring W1 have a more uniform temperature coefficient of resistance, and the occurrence of measurement errors can be suppressed more favorably.

[0066] (1-2) As in the present embodiment, the fixed resistance elements RX 11 、RX 12 of the first bridge circuit BC11 and the fixed resistance elements RY 11 、RY 12 of the second bridge circuit BC12 are formed in the non-sensing regions 121n1, 121n2 of the base material 121. Therefore, the fixed resistance elements RX 11 、RX 12 、RY 11 、RY 12 can function as temperature compensation balance strain gauges in a portion where no strain is generated (outside the strain region). Therefore, even when expansion or contraction occurs in the main body of the triaxial force sensor 1000 including the strain plate 111 due to a change in the ambient temperature, the change in the resistance values of the strain sensing elements X 11 、X 12 、Y 11 、Y 12 caused by the expansion or contraction can be compensated, thereby suppressing the occurrence of measurement errors.

[0067] (1-3) By arranging the fixed resistance elements RX 11 、RX 12 、RY 11 、RY 12It is formed by printing on the substrate 121, so that the first bridge circuit BC11, the second bridge circuit BC12, and the third bridge circuit BC13 can be respectively formed as closed circuits completed on the substrate 121.

[0068] When the strain sensing elements constituting the bridge circuit are printed on the substrate and the fixed resistance elements constituting the bridge circuit are provided outside the substrate, for example, in the signal processing unit, in order to make the bridge circuit a closed circuit, it is necessary to connect the strain sensing elements on the substrate and the fixed resistance elements of the signal processing unit through wires or the like. In this case, the wires are joined to the electrodes provided on the substrate to connect the wiring on the substrate and the wires. However, if a joint resistance is generated at the joint between the electrode and the wire, this joint resistance becomes a resistance within the bridge circuit and becomes a cause of a large strain detection error. Therefore, the joining method is limited to soldering with a substantially negligible joint resistance.

[0069] However, in order to perform soldering well, it is necessary to provide relatively large electrodes on the substrate and ensure the spacing between multiple electrodes, which results in an increase in the size of the substrate. In addition, in order to perform soldering well, it is necessary to stack solder with a certain thickness, which also hinders the miniaturization of the triaxial force sensor.

[0070] In contrast, in the present embodiment, the first bridge circuit BC11, the second bridge circuit BC12, and the third bridge circuit BC13 are respectively formed as closed circuits completed on the substrate 121. The connection between the substrate 121 via the terminals T 11 ~T 18 and the signal processing unit is only a joining for connecting the first bridge circuit BC11, the second bridge circuit BC12, and the third bridge circuit BC13 to the power supply and the arithmetic unit. Therefore, in the present embodiment, at the joints between the terminals T 11 ~T 18 and the wires L 11 ~L 18 the generation of joint resistance is allowed, so that any joining method other than soldering can be adopted, for example, joining using an anisotropic conductive film can be adopted. In addition, by using the anisotropic conductive film, the size of the electrodes, the spacing between the electrodes, and the thickness of the joint can be suppressed to about one-tenth of that in the case of soldering. Therefore, when miniaturization of the triaxial force sensor 1000 is desired, the joining based on the anisotropic conductive film is advantageous.

[0071] The effects of the strain gauge 120 and the triaxial force sensor 1000 of the present embodiment are as follows.

[0072] The strain gauge 120 of the present embodiment has the fixed resistance elements RX 11 、RX 12, the fixed resistance element RY of the second bridge circuit BC12 11 , RY 12 is formed on the base material 121, so it can achieve the effects of the above (1-2) and (1-3), and is composed of the same material as the strain sensing element X 11 , X 12 , Y 11 , Y 12 to form the fixed resistance element RX 11 , RX 12 , RY 11 , RY 12 , thus it can achieve the effect of the above (1-1).

[0073] In the strain gauge 120 of this embodiment, only the strain sensing elements X 11 , X 12 , Y 11 , Y 12 , Z 11 , Z 12 are formed in the sensing area 121s, and the terminals T 11 to T 18 and the fixed resistance elements RX 11 , RX 12 , RY 11 , RY 12 are formed in the non-sensing areas 121n1 and 121n2. Therefore, the diameter (size) of the sensing area 121s can be reduced, and further the strain plate 111 of the triaxial force sensor 1000 can be reduced. The miniaturization of the strain plate 111 leads to the miniaturization of the triaxial force sensor 1000, which is thus preferred.

[0074] In the strain gauge 120 of this embodiment, the electrodes T 11 to T 18 are arranged in the non-sensing areas 121n1 and 121n2. Therefore, as needed, without increasing the diameter of the sensing area 121s, by increasing the size of the electrodes T 11 to T 18 the bonding operation with wires and the like can be made easier.

[0075] The triaxial force sensor 1000 of this embodiment includes the strain gauge 120, so it can achieve the same effects as those of the strain gauge 120.

[0076] In the above first embodiment, the following modification forms can also be adopted.

[0077] It can also be configured that in the strain gauge 120, the strain sensing element Z 11 , Z 12Formed in the non-inductive region 121n1 and / or the non-inductive region 121n2. In this case, no flexure occurs in the non-inductive regions 121n1, 121n2, so the strain sensing elements Z 11 , Z 12 function substantially as fixed resistance elements (third-direction fixed resistance elements).

[0078] When the strain sensing elements Z 11 , Z 12 function as fixed resistance elements, it is also possible to detect the x-direction load using the first bridge circuit BC11 and the y-direction load using the second bridge circuit BC12 in the same manner as in the above-described first embodiment. In addition, it is also possible to detect the Z-direction load. This is because if a Z-direction load acts on the load application portion 112 and the resistance values of the strain detection elements X 11 , X 12 , Y 11 , Y 12 change, the combined resistance of the first bridge circuit BC11 and the combined resistance of the second bridge circuit BC12 change respectively. Even if the resistance values of the strain sensing elements Z 11 , Z 12 are constant, the balance of the resistance values between the elements of the third bridge circuit BC13 also changes.

[0079] It may also be configured such that the strain gauge 120 does not have the strain sensing elements Z 11 , Z 12 . In this case, for example, the first bridge circuit BC11 and the second bridge circuit BC12 are connected by two arc-shaped wiring lines W1 instead of the strain sensing elements Z 11 , Z 12 .

[0080] In the absence of the strain sensing elements Z 11 , Z 12 , it is also possible to detect the x-direction load using the first bridge circuit BC11 and the y-direction load using the second bridge circuit BC12 in the same manner as in the above-described first embodiment. The strain gauge 120 of such a deformed form can be used in a biaxial force sensor. Alternatively, it is also possible to connect the first Wheatstone bridge and the second Wheatstone bridge of the strain gauge of such a deformed form by a fixed resistance element formed in the signal processing unit to form a third Wheatstone bridge and use it in a triaxial force sensor.

[0081] It may also be configured such that in the strain gauge 120, for the fixed resistance elements RX 11 , RX 12 , RY 11 , RY12 For this, at least one of these is left on the base material 121, and the rest are arranged outside the base material 121, such as in the signal processing section. Even in such a configuration, by using the fixed resistance elements RX 11 , RX 12 constituting the first bridge circuit BC11 11 , RY 12 and the fixed resistance elements RY

[0082] constituting the second bridge circuit BC12, at least one of them is arranged in the non-inductive regions 121n1 and / or 121n2 on the base material 121, so that the effect of suppressing the temperature error in the strain gauge 120 and the triaxial force sensor 1000 can be achieved. 11 , RX 12 and the terminals T 11 ~T 14 are arranged in a row along the x-direction (the first direction) orthogonal to the y-direction (the second direction) in the non-inductive region 121n1 on one side of the y-direction (the second direction) of the inductive region 121s. It can also be configured that in the non-inductive region 121n2 on the other side of the y-direction (the second direction) of the inductive region 121s, the fixed resistance elements RY 11 , RY 12 and the terminals T 15 ~T 18 are arranged in a row along the x-direction (the first direction) orthogonal to the y-direction (the second direction).

[0083] As Figure 4 shown, it can also be configured that the fixed resistance elements RX 11 , RX 12 are formed in the part of the non-inductive region 121n1 closer to the inductive region 121s, and the terminals T 11 ~T 14 are formed in the part farther from the inductive region 121s. That is, it can also be configured that in the non-inductive region 121n1, the terminals T 11 ~T 14 are arranged on the side of the fixed resistance elements RX 11 , RX 12 opposite to the inductive region 121s. The configuration of the fixed resistance elements RY 11 , RY 12 and the terminals T 15 ~T 18 in the non-inductive region 121n2 is the same. By arranging the terminals T 11 ~T 18 outside like this, the joining of wires and the like to the terminals T 11 ~T 18 becomes easier.

[0084] It can also be configured as: terminal T 11 ~T 18 Any one or more of them are formed in the sensing region 121s. In this case, it is preferably pasted below the load acting portion 112 and disposed near the center c where strain is hardly generated.

[0085] It can also be configured as: in the sensing region 121s, the strain sensing element Z 11 , Z 12 is arranged on the strain sensing element X 11 , X 12 , Y 11 , Y 12 on the center c side (inner side). In addition, it can also be configured as: the strain sensing element X 11 , X 12 , Y 11 , Y 12 are each formed in an arc shape such that the width direction of their grids is the circumferential direction of the sensing region 121s. Such a strain gauge 120 can be pasted on the strain plate 111 connected to the cylindrical load acting portion 112 centered on the rotation axis A1 and used well.

[0086] The shape of the base material 121 of the strain gauge 120 is arbitrary. For example, it can be an elliptical shape, or it can have only either one of the non-sensing regions 121n1 and 121n2. In the base material 121 having only either one of the non-sensing regions 121n1 and 121n2, fixed resistance elements RX 11 , RX 12 , RY 11 , RY 12 , terminal T 11 ~T 18 can all be formed. In addition, the base material 121 can have any shape with a sensing region for pasting on the strain plate of the multi-axis force sensor and a non-sensing region disposed outside this region.

[0087] The strain gauge 120 of the above-described first embodiment can also be used for the strain component of any sensor other than the multi-axis force sensor.

[0088] <Second Embodiment>

[0089] Taking the three-axis force sensor 2000 used as a tactile sensor of a robot hand and the strain gauge 220 included in the three-axis force sensor 2000 as an example, mainly referring to Figures 5 to 9 the second embodiment of the multi-axis force sensor and the strain gauge of the present invention will be described.

[0090] As shown in Figure 5 andFigure 6 As shown, the triaxial force sensor 2000 of this embodiment has a main body 210 that is rotationally symmetrical about the axis A2, and a strain gauge 220 attached to the main body 210. The main body 210 includes a disc-shaped strain plate (strain component) 211 with the axis A2 as the rotation axis, a load application portion 212 that stands axially from the center of the surface 211a of the strain plate 211, a pair of retaining plates 213 that stand axially from the peripheral edge of the surface 211a of the strain plate 211, a peripheral wall 214 that stands axially from the peripheral edge of the back side 211b of the strain plate 211, and four legs 215 mounted on the peripheral wall 214. The main body 210 is integrally molded from, for example, a synthetic resin material.

[0091] In the description of the second embodiment, Figure 5 As shown, the two orthogonal radial directions of the strain plate 211 are defined as the X direction (first direction) and the Y direction (second direction) of the three-axis force sensor 2000 and the main body 210. In addition, the direction of the axis A2 orthogonal to the X direction and the Y direction is defined as the Z direction (third direction) of the three-axis force sensor 2000 and the main body 210.

[0092] The strain plate 211 is a circular plate that generates strain by receiving a load from the outside applied to the main body 210 of the triaxial force sensor 2000 via the load application portion 212. The strain in the strain plate 211 is generated on the surface 211a and the back surface 211b (in Figure 5 The upper and lower surfaces are perpendicular to the axis A2) and are generated on the side 211c of the strain plate 211 (in Figure 5 In the present specification, the area where the strain plate 211 is subjected to an external load and generates strain, such as the surface 211a and the back surface 211b of the strain plate 211 in the present embodiment, is referred to as a "strain area". The diameter and thickness of the strain plate 211 are arbitrary.

[0093] The load application part 212 is a part that moves under the load from the outside, thereby causing the strain plate 211 to generate strain, and is, for example, a prism with a square cross-sectional shape. The load application part 212 is provided on the surface 211a of the strain plate 211 in a coaxial manner with the strain plate 211 so that the central axis of the prism coincides with the rotation axis (axis A2) of the strain plate 211.

[0094] The pair of holding plates 213 is a base material 221 ( Figure 7 The retaining plates 213 are opposed to each other in a manner of sandwiching the load application portion 212 in the Y direction, stand upright from the surface 211a of the strain plate 211, and each has a curved surface along the outer periphery of the strain plate 211.

[0095] The peripheral wall 214 stands upright from the outer periphery of the back surface 211b of the strain plate 211 along the back surface 211b and surrounds the back surface 211b. In addition, a pair of cutout portions 214n are provided in the peripheral wall 214 so as to sandwich the load application portion 212 in the Y direction. That is, the pair of cutout portions 214n are provided at positions overlapping the pair of holding plates 213 in the circumferential direction of the strain plate 211. The peripheral wall 214 is used as a guide when attaching the strain gauge 220 to the strain plate 211, and the details thereof will be described later.

[0096] The leg portions 215 are pedestals for mounting the triaxial force sensor 2000 on the robot hand, and four of them are provided at equal intervals and separated from each other on the peripheral wall 214.

[0097] In Figure 7 shows the state (development view) before attaching the Figure 5 shown strain gauge 220 to the strain plate 211. As Figure 7 shown, the strain gauge 220 includes a base material 221 and a circuit pattern CP2 printed on the surface of the base material 221. The base material 221 has a sensing region 221s and non-sensing regions 221n1, 221n2 sandwiching the sensing region 221s. The circuit pattern CP2 includes six strain sensing elements X 21 、X 22 、Y 21 、Y 22 、Z 21 、Z 22 、four fixed resistance elements RX 21 、RX 22 、RY 21 、RY 22 、eight terminals T 21 ~T 28 、and a wiring W2 connecting these. In addition, in the following description, the direction in which the non-sensing regions 221n1, 221n2 sandwich the sensing region 221s is defined as the y-direction (second direction), and the direction orthogonal to the y-direction on the surface of the base material 221 is defined as the x-direction (first direction).

[0098] The base material 221 is a flexible resin film, which has a central circular induction area 221s, a pair of non-induction areas 221n1 and 221n2 sandwiching the induction area 221s, and a pair of connection areas 221c1 and 221c2 connecting the induction area 221s with the pair of non-induction areas 221n1 and 221n2 respectively. The resin film preferably uses a soft and highly flexible material that can be easily bent. As a specific example, it can be polyester, polyimide, etc. In addition, the induction area 221s, the non-induction areas 221n1 and 221n2, and the connection areas 221c1 and 221c2 can be formed of different materials respectively, but it is preferred that these areas are formed of the same material so that the temperature characteristics (such as the resistance temperature coefficient) of the entire area are equal. In addition, in this case, it is preferred to integrally cut out the induction area 221s, the non-induction areas 221n1 and 221n2, and the connection areas 221c1 and 221c2 from the nearby parts within an integrally formed material (such as a sheet of polyester, polyimide, etc.) to form the base material 221. Thereby, the temperature characteristics of each area can be made more uniform.

[0099] The induction area 221s is the area pasted on the back surface 211b of the strain plate 211 of the main body part 210, so it has the same diameter as or smaller than the back surface 211b of the strain plate 211. On one surface of the induction area 221s, strain sensing elements (first direction strain sensing elements) X 21 、X 22 are formed while sandwiching the center c in the x direction, and strain sensing elements (second direction strain sensing elements) Y 21 、Y 22 are formed while sandwiching the center c in the y direction, and strain sensing elements (third direction strain sensing elements) Z 21 、Z 22 are formed along the outer periphery.

[0100] The strain sensing elements X 21 、X 22 are formed in parallel with each other with the y direction as the grid width direction respectively. The strain sensing elements X 21 and the strain sensing elements X 22 are respectively formed at positions equidistant from the center c, and the x-direction distance between the strain sensing elements X 21 and the strain sensing elements X 22 is greater than the X-direction width of the load acting part 212 of the main body part 210.

[0101] The strain sensing elements Y 21 、Y 22 are formed in parallel with each other with the x direction as the grid width direction respectively. The strain sensing elements Y 21 and the strain sensing elements Y 22Strain sensing elements Y are respectively formed at positions equidistant from the center c. 21 The y-direction distance between the strain sensing element Y 22 and the load acting portion 212 of the main body portion 210 in the Y-direction is greater than the Y-direction width of the load acting portion 212 of the main body portion 210.

[0102] Strain sensing elements Z 21 and Z 22 are respectively arc-shaped and are formed opposite to each other in the x-direction with the circumferential direction of the sensing region 221s as the width direction of the grid. Strain sensing elements Z 21 and Z 22 are arranged on the side opposite to the center c (outer side) of the strain sensing elements X 21 and X 22 and Y 21 and Y 22 .

[0103] A pair of non-sensing regions 221n1 and 221n2 sandwich the sensing region 221s in the y-direction and are respectively rectangular with the x-direction as the long side direction and the y-direction as the short side direction.

[0104] On the portion of the surface of the non-sensing region 221n1 that is farther from the sensing region 221s, fixed resistance elements (first-direction fixed resistance elements) RX 21 and RX 22 are arranged in the x-direction and extend in the x-direction respectively. Four terminals T 21 and T 22 and T 23 and T 24 are formed in the x-direction in the portion closer to the sensing region 221s. That is, in the non-sensing region 221n1, the fixed resistance elements RX 21 and RX 22 are arranged on the side opposite to the sensing region 221s of the terminals T 21 to T 24 .

[0105] Similarly, on the portion of the surface of the non-sensing region 221n2 that is farther from the sensing region 221s, fixed resistance elements (second-direction fixed resistance elements) RY 21 and RY 22 are arranged in the x-direction and extend in the x-direction respectively. Four terminals T 25 and T 26 and T 27 and T 28 are formed in the x-direction in the portion closer to the sensing region 221s. That is, in the non-sensing region 221n2, the fixed resistance elements RY 21 and RY 22 are arranged on the side opposite to the sensing region 221s of the terminals T 25 to T28 On the side opposite to the sensing region 221s.

[0106] For the connection regions 221c1 and 221c2 that connect the sensing region 221s to the non-sensing regions 221n1 and 221n2, the dimensions (widths) in the x-direction orthogonal to the y-direction connecting the sensing region 221s to the non-sensing regions 221n1 and 221n2 are respectively smaller than the dimensions (widths) in the x-direction of the sensing region 221s, the non-sensing regions 221n1, and 221n2. Therefore, the substrate 221 has a reduced-diameter shape in the connection regions 221c1 and 221c2.

[0107] As Figure 7 and Figure 8 shown, the wiring W2 connects the strain sensing elements X 21 , X 22 , the fixed resistance elements RX 21 , RX 22 to form the first bridge circuit (the first Wheatstone bridge circuit) BC21. Additionally, a terminal T 21 is connected between the strain sensing element X 21 and the fixed resistance element RX 21 , a terminal T 21 is connected between the strain sensing elements X 22 , X 22 , a terminal T 21 is connected between the fixed resistance elements RX 22 , RX 23 , and a terminal T 22 is connected between the strain sensing element X 22 and the fixed resistance element RX 24 .

[0108] Similarly, the wiring W2 connects the strain sensing elements Y 21 , Y 22 , the fixed resistance elements RY 21 , RY 22 to form the second bridge circuit (the second Wheatstone bridge circuit) BC22. A terminal T 21 is connected between the strain sensing element Y 21 and the fixed resistance element RY 28 , a terminal T 21 is connected between the strain sensing elements Y 22 , Y 26 , a terminal T 21 is connected between the fixed resistance elements RY 22 , RY 27 , and a terminal T 22 is connected between the strain sensing element Y 22 and the fixed resistance element RY25 。

[0109] Strain sensing element Z 21 has one end connected to the first bridge circuit BC21 between the strain sensing element X 21 and the fixed resistance element RX 21 and the other end connected to the second bridge circuit BC22 between the strain sensing element Y 21 and the fixed resistance element RY 21 Similarly, one end of the strain sensing element Z 22 is connected to the first bridge circuit BC21 between the strain sensing element X 22 and the fixed resistance element RX 22 and the other end is connected to the second bridge circuit BC22 between the strain sensing element Y 22 and the fixed resistance element RY 22 Thus, a third bridge circuit (third Wheatstone bridge circuit) BC23 is formed which has the first bridge circuit BC21 and the second bridge circuit BC22 on a pair of opposite sides respectively, and has the strain sensing elements Z 21 、Z 22 on the other pair of opposite sides respectively.

[0110] The strain sensing elements X 21 、X 22 、Y 21 、Y 22 、Z 21 、Z 22 、the fixed resistance elements RX 21 、RX 22 、RY 21 、RY 22 、and the wiring W2 included in the circuit pattern CP2 are formed of the same material as each other, and more preferably are formed of parts in the vicinity within one material. As an example, the material is copper, copper alloys such as copper / nickel, etc. The printing of the circuit pattern CP2 on the substrate 221 can be performed by photolithography, printing, evaporation, sputtering, etc.

[0111] As Figure 5 、 Figure 6 shown, the strain gauge 220 is adhered to the main body portion 210 such that the surface of the substrate 221 opposite to the surface on which the circuit pattern CP2 is formed contacts the main body portion 210.

[0112] Specifically, the sensing area 221s of the substrate 221 is adhered to the back surface 211b of the strain plate 211 such that the x-direction and the y-direction thereof coincide with the X-direction and the Y-direction of the main body portion 210 respectively and the center c coincides with the axis A2. In addition, as described above, the strain sensing elements X 21 、X 22The distance in the X direction between them is greater than the size of the load acting portion 212 in the X direction, and the strain sensing elements Y 21 、Y 22 The distance in the Y direction between them is greater than the size of the load acting portion 212 in the Y direction. Therefore, in the state where the sensing region 221s of the base material 221 is adhered to the strain plate 211, the strain sensing elements X 21 、X 22 and the strain sensing elements Y 21 、Y 22 are respectively arranged in the regions where strain is generated more greatly outside the load acting portion 212 in the X direction and the Y direction. In addition, in Figure 7 and Figure 9 , the outline of the load acting portion 212 in the state where the base material 221 is adhered to the strain plate 211 is indicated by a dotted line, and the positional relationship between the load acting portion 212 and the strain sensing elements X 21 、X 22 、Y 21 、Y 22 is shown.

[0113] A pair of non-sensing regions 221n1, 221n2 of the base material 221 are respectively bent and adhered to the side surface 211c of the strain plate 211 and the outer surface of the holding plate 213 extending upward therefrom. Therefore, the terminals T 21 、T 22 、T 23 、T 24 formed in the non-sensing region 221n1, the terminals T 25 、T 26 、T 27 、T 28 project outward in the radial direction of the strain plate 211.

[0114] A pair of connection regions 221c1, 221c2 are respectively buckled at the connection portion between the back surface 211b and the side surface 211c of the strain plate 211 through the cutout portions 214n of the peripheral wall 214.

[0115] When the strain gauge 220 is adhered to the base material 221, the peripheral edge portion of the sensing region 221s of the base material 221 is brought into contact with the inner peripheral surface of the peripheral wall 214, and the pair of connection regions 221c1, 221c2 of the base material 221 are respectively arranged in the pair of cutout portions 214n of the peripheral wall 214, whereby the positioning of the strain gauge 220 with respect to the main body portion 210 and the strain plate 211 can be easily performed.

[0116] Specifically, by bringing the peripheral portion of the sensing region 221s of the base material 221 into contact with the inner peripheral surface of the peripheral wall 214, alignment is performed such that the center c of the sensing region 221s coincides with the axis A2 of the main body portion 210, and movement of the sensing region 221s in the X direction and the Y direction is restricted. Next, by disposing a pair of connection regions 221c1, 221c2 of the strain gauge 220 in a pair of cutout portions 214n of the peripheral wall 214, the strain gauge 220 is aligned with respect to the main body portion 210 and the strain plate 211 also in the circumferential direction centered on the axis A2.

[0117] Next, the usage method and operation of the three-axis force sensor 2000 and the strain gauge 220 of the present embodiment will be described.

[0118] When the three-axis force sensor 2000 is used as a tactile sensor of a robot hand, first, the three-axis force sensor 2000 is fixed to the fingertip of the robot hand via the leg portion 215. Then, wires L 21 ~L 28 ( Figure 8 ) are used to connect the terminals T 21 ~T 28 to a signal processing unit (not shown). The connection of the terminals T 21 ~T 28 to the wires L 21 ~L 28 can be performed by any method, for example, using soldering or an anisotropic conductive film (ACF).

[0119] The terminals T 21 、T 25 are respectively connected to the power supply (not shown) of the signal processing unit through the wires L 21 、L 25 . The terminals T 22 、T 23 、the terminals T 26 、T 27 、the terminals T 24 、T 28 are respectively connected to the arithmetic unit (not shown) in the signal processing unit through the amplifiers (not shown) in the signal processing unit via the wires L 22 、L 23 、the wires L 26 、L 27 、the wires L 24 、L 28 .

[0120] During the operation of the three-axis force sensor 2000, power is supplied to the terminal T 21 and the terminal T 25The resistance values ​​of the strain sensing elements and the fixed resistance elements constituting the first bridge circuit BC21, the second bridge circuit BC22, and the third bridge circuit BC23 are adjusted such that when the sensing region 221s of the substrate 221 is not bent, the resistance value of the strain sensing elements and the fixed resistance elements at the terminal T 22 , T 23 The voltage between them is equal, at terminal T 26 , T 27 The voltage between them is equal, at terminal T 24 , T 28 Therefore, in the state where the strain plate 211 does not generate strain and the sensing area 221s does not bend ( Figure 3 (a)) at terminal T 22 , T 23 Between terminals T 26 , T 27 Between terminals T 24 , T 28 There is no potential difference between them, so the calculation unit does not calculate the strain.

[0121] Next, if a load in the X direction is applied to the load application portion 212, the load application portion 212 receives the load and moves, causing the strain plate 211 to generate strain ( Figure 3 At this time, the sensing area 221s of the base material 221 of the strain gauge 220 attached to the strain plate 211 also bends integrally with the strain plate 211, thereby 21 Generate compressive strain in the strain sensing element X 22 Produce tensile strain. Therefore, the strain sensing element X 21 , X 22 The resistance values ​​of the strain sensing elements X 21 , X 22 The terminal T of the first bridge circuit BC21 22 , T 23 A potential difference is generated between the two. Based on the potential difference, the calculation unit calculates the amount of strain generated in the strain plate 211 and calculates the magnitude of the X-direction load acting on the load application portion 212. In addition, at this time, no strain is generated on the side 211c of the strain plate 211 and the retaining plate 213, and the fixed resistance element RX 21 RX 22 The resistance value is constant. When a load in the Y direction is applied to the load applying portion 212, the magnitude of the applied load in the Y direction is also obtained in the same manner.

[0122] When a load in the Z direction is applied to the load acting portion 212, the strain plate 211 and the sensing region 221s of the substrate 221 are bent in a centrally protruding manner, so that the strain sensing element X 21 , X22 , Y 21 , Y 22 , Z 21 , Z 22 All generate extensional strain. Thus, the combined resistance of the first bridge circuit BC21, the combined resistance of the second bridge circuit BC22, and the resistance values of the strain sensing elements Z 21 , Z 22 change respectively, and a potential difference is generated between the terminals T 24 , T 28 of the third bridge circuit BC23. Based on this potential difference, the arithmetic unit calculates the amount of strain generated in the strain plate 211 and calculates the magnitude of the load in the Z direction acting on the load application portion 212.

[0123] Here, the significance of printing the fixed resistance elements RX 21 , RX 22 of the first bridge circuit BC21, the fixed resistance elements RY 21 , RY 22 on the base material 221 and forming them from the same material as the strain sensing elements X 21 , X 22 , Y 21 , Y 22 will be described.

[0124] (2-1) By forming the fixed resistance elements RX 21 , RX 22 , RY 21 , RY 22 in this way, the fixed resistance elements RX 21 , RX 22 , RY 21 , RY 22 are made of the same material as the strain sensing elements X 21 , X 22 , Y 21 , Y 22 , Z 21 , Z 22 and are formed in positions close to them. Here, the resistance temperature coefficient, which represents the ratio of the change in resistance value to the change in temperature, is a physical property value depending on the material. Therefore, in this embodiment, the resistance temperature coefficients of all the strain sensing elements and all the fixed resistance elements are equal. In addition, the fixed resistance elements RX 21 , RX 22 , RY 21 , RY 22 are formed on the base material 221 and are formed in positions close to the strain sensing elements X 21 , X 22 , Y 21 , Y 22 , Z21 , Z 22 Near 22 , so the change in the ambient temperature affecting all strain sensing elements and all fixed resistance elements is substantially the same. Therefore, when there is a change in the ambient temperature, the resistance values of all strain sensing elements and the resistance values of all fixed resistance elements change in the same proportion.

[0125] In the first bridge circuit BC21, the second bridge circuit BC22, and the third bridge circuit BC23, when the balance of the resistance values among the respective included resistance elements (strain sensing elements and fixed resistance elements) changes, between the terminals T 22 , T 23 , between the terminals T 26 , T 27 , between the terminals T 24 , T 28 , a potential difference is generated, and strain is detected based on this potential difference. 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 this change in balance. However, in the present embodiment, when there is a change in the ambient temperature, the resistance values of all strain sensing elements and the resistance values of all fixed resistance elements change in the same proportion. Therefore, even when the ambient temperature changes, the balance of the resistance values between the elements does not change, thereby suppressing the occurrence of measurement errors. In addition, when forming the circuit pattern CP2, by using the parts near the materials (copper, copper alloy, etc.) prepared as an integrated block to form the strain sensing elements, etc., the strain sensing elements X 21 , X 22 , Y 21 , Y 22 , Z 21 , Z 22 , the fixed resistance elements RX 21 , RX 22 , RY 21 , RY 22 , and the resistance temperature coefficient of the wiring W2 are more uniform, and the occurrence of measurement errors can be suppressed better.

[0126] (2 - 2) As in the present embodiment, when the fixed resistance elements RX 21 , RX 22 of the first bridge circuit BC21 and the fixed resistance elements RY 21 , RY 22When formed in the non-inductive regions 221n1 and 221n2 of the base material 221 and the non-inductive regions 221n1 and 221n2 are pasted onto a portion (outside the strain region) that does not generate strain in the main body portion 210, the fixed resistance elements RX 21 、RX 22 、RY 21 、RY 22 can function as balance strain gauges for temperature compensation. Therefore, even when expansion and contraction occur in the main body portion 210 including the strain plate 211 due to changes in the ambient temperature, it is possible to compensate for the strain sensors X 21 、X 22 、Y 21 、Y 22 caused by such expansion and contraction, thereby suppressing the occurrence of measurement errors.

[0127] (2-3) By printing the fixed resistance elements RX 21 、RX 22 、RY 21 、RY 22 on the base material 221, the first bridge circuit BC21, the second bridge circuit BC22, and the third bridge circuit BC23 can be respectively formed as closed circuits completed on the base material 221.

[0128] When the strain sensors constituting the bridge circuit are printed on the base material and the fixed resistance elements constituting the bridge circuit are provided outside the base material, for example, in the signal processing unit, in order to make the bridge circuit a closed circuit, it is necessary to connect the strain sensors on the base material and the fixed resistance elements in the signal processing unit through wires or the like. In this case, the wires are joined to the electrodes provided on the base material to connect the wiring on the base material and the wires. However, if a joint resistance is generated at the joint between the electrode and the wire, this joint resistance becomes a resistance within the bridge circuit and becomes a cause of a large strain detection error. Therefore, the joining method is limited to soldering with a substantially negligible joint resistance.

[0129] However, in order to perform soldering well, it is necessary to provide relatively large electrodes on the base material and ensure the spacing between multiple electrodes, which results in an increase in the size of the base material. In addition, in order to perform soldering well, it is necessary to stack solder with a certain thickness, which also hinders the miniaturization of the triaxial force sensor.

[0130] In contrast, in the present embodiment, the first bridge circuit BC21, the second bridge circuit BC22, and the third bridge circuit BC23 are respectively formed as closed circuits completed on the base material 221, and via the terminals T 21 ~T 28The connection between the base material 221 and the signal processing unit is merely a joint for connecting the first bridge circuit BC21, the second bridge circuit BC22, and the third bridge circuit BC23 to the power supply and the arithmetic unit. Therefore, in the present embodiment, at the terminal T 21 ~T 28 and the wire L 21 ~L 28 The joint of allows the generation of joint resistance, so that any joint method other than soldering can be adopted, for example, a joint using an anisotropic conductive film can be adopted. In addition, by using an anisotropic conductive film, the size of the electrode, the pitch between electrodes, and the thickness of the joint can all be suppressed to about one-tenth of that in the case of soldering. Therefore, when miniaturization of the three-axis force sensor 2000 is desired, the joint based on the anisotropic conductive film is advantageous.

[0131] The effects of the three-axis force sensor 2000 and the strain gauge 220 of the present embodiment are as follows.

[0132] The strain gauge 220 of the present embodiment forms the fixed resistance elements RX 21 、RX 22 of the first bridge circuit BC21, the fixed resistance elements RY 21 、RY 22 of the second bridge circuit BC22 on the base material 221. Therefore, the effects of (2-2) and (2-3) above can be achieved, and the fixed resistance elements RX 21 、X 22 、Y 21 、Y 22 are formed of the same material as the strain sensing elements X 21 、RX 22 、RY 21 、RY 22 , so the effect of (2-1) above can be achieved.

[0133] In the strain gauge 220 of the present embodiment, only the strain sensing elements X 21 、X 22 、Y 21 、Y 22 、Z 21 、Z 22 are formed in the sensing area 221s, and the terminals T 21 ~T 28 and the fixed resistance elements RX 21 、RX 22 、RY 21 、RY 22It is formed in the non-inductive regions 221n1 and 221n2. Therefore, the diameter (size) of the inductive region 221s can be reduced, and thus the strain plate 211 of the triaxial force sensor 2000 can be shrunk. The miniaturization of the strain plate 211 leads to the miniaturization of the triaxial force sensor 2000, which is thus preferable.

[0134] In the strain gauge 220 of the present embodiment, the electrodes T 21 ~T 28 are provided in the non-inductive regions 221n1 and 221n2. Therefore, if necessary, without increasing the diameter of the inductive region 221s, the size of the electrodes T 21 ~T 28 can be increased to facilitate the joining operation with a wire or the like.

[0135] The base material 221 of the strain gauge 220 of the present embodiment has the connecting regions 221c1 and 221c2 that are narrower than the widths of the inductive region 221s and the non-inductive regions 221n1 and 221n2 between the inductive region 221s and the non-inductive regions 221n1 and 221n2. Therefore, the inductive region 221s and the non-inductive regions 221n1 and 221n2 can be arranged in various forms without being restricted by the connection portions with the connecting regions 221c1 and 221c2.

[0136] The triaxial force sensor 2000 of the present embodiment includes the strain gauge 220, and thus can achieve the same effects as those of the strain gauge 220.

[0137] In the above-described second embodiment, the following modified forms can also be adopted.

[0138] It may also be configured such that in the strain gauge 220, the strain sensing elements Z 21 、Z 22 are formed in the non-inductive region 221n1 and / or the non-inductive region 221n2. In this case, no flexure occurs in the non-inductive regions 221n1 and 221n2, and thus the strain sensing elements Z 21 、Z 22 substantially function as fixed resistance elements (third-direction fixed resistance elements).

[0139] When the strain sensing elements Z 21 、Z 22 function as fixed resistance elements, the detection of the X-direction load using the first bridge circuit BC21 and the detection of the Y-direction load using the second bridge circuit BC22 can be performed in the same manner as in the above-described second embodiment. In addition, the detection of the Z-direction load can also be performed. This is because if a Z-direction load acts on the load application portion 212 and in the strain detection elements X 21 、X 22 、Y 21, Y 22 When the resistance value changes, the combined resistance of the first bridge circuit BC21 and the combined resistance of the second bridge circuit BC22 change respectively. Even if the resistance values of the strain sensing elements Z 21 , Z 22 are constant, the balance of the resistance values between the elements of the third bridge circuit BC23 also changes.

[0140] It can also be configured that the strain gauge 220 does not have the strain sensing elements Z 21 , Z 22 . In this case, for example, the first bridge circuit BC21 and the second bridge circuit BC22 are connected by two arc-shaped wirings W2 instead of the strain sensing elements Z 21 , Z 22 .

[0141] In the absence of the strain sensing elements Z 21 , Z 22 , it is also possible to detect the X-direction load using the first bridge circuit BC21 and detect the Y-direction load using the second bridge circuit BC22 in the same manner as in the above-described embodiment. The strain gauge 220 in such a deformed form can be used in a two-axis force sensor. Alternatively, it is also possible to connect the first Wheatstone bridge and the second Wheatstone bridge of the strain gauge in such a deformed form through a fixed resistance element formed in the signal processing unit to form a third Wheatstone bridge and use it in a three-axis force sensor.

[0142] It can also be configured that in the strain gauge 220, for the fixed resistance elements RX 21 , RX 22 , RY 21 , RY 22 formed in the non-sensing regions 221n1 and 221n2 of the base material 221, at least one of these is left on the base material 221, and the rest are provided outside the base material 221, for example, in the signal processing unit. Even in such a form, by disposing at least one of the fixed resistance elements RX 21 , RX 22 constituting the first bridge circuit BC21 and the fixed resistance elements RY 21 , RY 22 constituting the second bridge circuit BC22 in the non-sensing regions 221n1 and / or 221n2 of the base material 221, it is possible to achieve the effect of suppressing the temperature error in the strain gauge 220 and the three-axis force sensor 2000.

[0143] It can also be configured that in the non-sensing region 221n1 on one side in the y-direction (second direction) of the sensing region 221s, the fixed resistance elements RX 21 , RX 22 and the terminal T21 ~T 24 They are arranged in a row along the x-direction (the first direction) orthogonal to the y-direction (the second direction). It can also be configured that in the non-sensing region 221n2 on the other side of the y-direction (the second direction) of the sensing region 221s, the fixed resistance elements RY 21 , RY 22 and the terminal T 25 ~T 28 are arranged in a row along the x-direction (the first direction) orthogonal to the y-direction (the second direction). Thus, the non-sensing regions 221n1 and 221n2 can be pasted on a longer and thinner part. For example, the holding plate 213 of the main body 210 can be omitted, and the non-sensing regions 221n1 and 221n2 can be pasted only on the side surface of the strain plate 211.

[0144] As Figure 9 shown, it can also be configured that the fixed resistance element RX 21 , RX 22 is formed in the part of the non-sensing region 221n1 closer to the sensing region 221s, and the terminal T 21 ~T 24 is formed in the part farther from the sensing region 221s. That is, it can also be configured that in the non-sensing region 221n1, the terminal T 21 ~T 24 is arranged on the side opposite to the sensing region 221s of the fixed resistance element RX 21 , RX 22 . The configuration of the fixed resistance element RY 21 , RY 22 and the terminal T 25 ~T 28 in the non-sensing region 221n2 is the same. By arranging the terminal T 21 ~T 28 on the outside like this, the connection of wires and the like to the terminal T 21 ~T 28 becomes easier.

[0145] It can also be configured that any one or more of the terminals T 21 ~T 28 are formed in the sensing region 221s. In this case, it is preferably pasted below the load application part 212 and arranged near the center c where strain is less likely to occur.

[0146] It can also be configured that in the sensing region 221s, the strain sensing elements Z 21 , Z 22 are arranged with the strain sensing elements X 21 , X 22 , Y 21 , Y 22On the center c side (inner side). Alternatively, it can also be configured such that the strain sensing element X 21 、X 22 、Y 21 、Y 22 are each formed in an arc shape such that the width direction of their grids is the circumferential direction of the sensing region 221s. Such a strain gauge 220 can be adhered to the main body portion 210 where the load application portion 212 is cylindrical with the axis A2 as the center and can be used well.

[0147] The shape of the base material 221 of the strain gauge 220 is arbitrary. It can be a rectangular shape or an elliptical shape without the connection regions 221c1 and 221c2, or it can have only one of the non-sensing regions 221n1 and 221n2. In the base material 221 having only one of the non-sensing regions 221n1 and 221n2, a fixed resistance element RX 21 、RX 22 、RY 21 、RY 22 、terminal T 21 ~T 28 can all be formed. In addition, the base material 221 can have any shape with a sensing region for adhering to the strain plate of the multi-axis force sensor and a non-sensing region disposed outside this region.

[0148] The holding plate 213 of the main body portion 210 can also be a flat plate extending parallel to the strain plate 211 from the outer periphery of the strain plate 211. In this case, the base material 221 of the strain gauge 220 can be adhered to the strain plate 211 and the holding plate 213 without being bent. In addition, the main body portion 210 can also not have the holding plate 213. In this case, all regions of the non-sensing regions 221n1 and 221n2 can be adhered to the side surface 211c of the strain plate 211. In addition, the non-sensing regions 221n1 and 221n2 can be not adhered to the side surface 211c of the strain plate 211, or can be not adhered to the main body portion 210. The arrangement of the non-sensing regions 221n1 and 221n2 in the state where the sensing region 221s is adhered to the back surface 211b of the strain plate 211 can be appropriately determined according to the shape of the main body portion of the multi-axis sensor and the use of the multi-axis sensor.

[0149] The strain gauge 220 of the above-described second embodiment can be used as a strain component for any sensor other than the multi-axis force sensor.

[0150] <Third Embodiment>

[0151] For the third embodiment of the strain gauge and the triaxial force sensor according to the present invention, taking the case where they are applied to an electronic pen as an example, it will be mainly described with reference to Figures 10 to 14 as follows.

[0152] like Figure 10 As shown, the electronic pen 4000 includes tips 431 and 432 , a three-axis force sensor 3000 , a bracket 433 , a pen body 434 , and a front cover 435 .

[0153] The tip 431 is formed of plastic, for example, and functions as a pen tip. The tip 432 is formed of SUS, for example, and one end thereof is connected to the tip 431, and the other end is connected to the triaxial force sensor 3000. Thus, the triaxial force sensor 3000 measures the external load applied via the pen tip.

[0154] The bracket 433 holds the signal processing circuit and power supply required for the operation of the three-axis force sensor 3000, and also holds the PCBA (Printed Circuit Board Assembly) on which various circuits are installed. The pen body 434 covers a portion of the three-axis force sensor 3000 and the bracket 433, and the front cover 435 covers the remaining portion of the three-axis force sensor 3000 and the tip 432.

[0155] Next, if Figure 11 and Figure 12 As shown, the three-axis force sensor 3000 of this embodiment has a main body 310 that is rotationally symmetrical about the axis A3. The main body 310 includes a disc-shaped strain plate (plate-shaped strain component) 311 with the axis A3 as the rotation axis, a load application portion 312 that stands axially upright from the center of the surface 311a of the strain plate 311, and a peripheral wall 313 that stands axially upright from the peripheral edge of the back side 311b of the strain plate 311. In addition, the load application portion 312 and the Figure 10 The tip 432 is shown to be engaged. The main body 310 is integrally formed of, for example, a synthetic resin material.

[0156] In the description of the third embodiment, Figure 11 As shown, the two orthogonal radial directions of the strain plate 311 are defined as the x-direction (first direction) and the y-direction (second direction) of the three-axis force sensor 3000 and the main body 310. In addition, the direction of the axis A3 orthogonal to the x-direction and the y-direction is defined as the Z-direction (third direction) of the three-axis force sensor 3000 and the main body 310.

[0157] The strain plate 311 is a circular plate that is subjected to an external load applied via the load application portion 312 and generates strain. The strain in the strain plate 311 is generated on the surface 311a and the back surface 311b (in Figure 11 The upper and lower surfaces perpendicular to the axis A3 are generated on the peripheral wall 313 (in Figure 11The circumferential surface (parallel to the axis A3) does not generate strain or the strain is so small as to be negligible. As described above, in this specification, a region that bears an external load and generates strain, such as the front surface 311a and the back surface 311b of the strain plate 311 in this embodiment, is referred to as a "strain region". The diameter and thickness of the strain plate 311 are arbitrary.

[0158] The load application portion 312 moves under an external load and causes the strain plate 311 to generate strain. The load application portion 312 is disposed on the front surface 311a of the strain plate 311 coaxially with the strain plate 311, that is, with its central axis coinciding with the rotation axis (axis A3) of the strain plate 311.

[0159] The peripheral wall 313 stands upright from the back surface 311b along the outer periphery of the back surface 311b of the strain plate 311 and surrounds the back surface 311b. In addition, Figure 11 In, the case where the outer peripheral surface of the peripheral wall 313 is cylindrical is illustrated, but the peripheral wall 313 can be changed as follows. That is, it can also be configured such that on one side or both sides of the peripheral wall 313 in the x-axis direction, a planar portion intersecting (orthogonal) with the x-axis is formed on the outer peripheral surface of the peripheral wall 313. Alternatively, it can also be configured such that on one side or both sides of the peripheral wall 313 in the y-axis direction, a planar portion intersecting (orthogonal) with the y-axis is formed on the outer peripheral surface of the peripheral wall 313.

[0160] In particular, when a planar portion is provided only on one side of the peripheral wall 313 in the x-axis direction, for the y-axis direction, a planar portion can also be provided only on one side of the peripheral wall 313. In this case, two planar portions are provided on the outer peripheral surface of the peripheral wall 313. In addition, when planar portions are provided on both sides of the peripheral wall 313 in the x-axis direction, for the y-axis direction, planar portions can also be provided on both sides of the peripheral wall 313. In this case, four planar portions are provided on the outer peripheral surface of the peripheral wall 313.

[0161] By providing a planar portion on the outer peripheral surface of the peripheral wall 313 in this way, the positioning of the main body portion 310 (i.e., the three-axis force sensor 3000) of the electronic pen 4000 relative to the bracket 433 can be easily and reliably performed using this planar portion. In addition, by providing alignment marks on the peripheral wall 313 having Figure 11 such a cylindrical outer peripheral surface, the positioning of the main body portion 310 relative to the bracket 433 can also be performed.

[0162] For the strain gauge 320 of this embodiment, a part (inductive region 321s) of its base material 321 (refer to Figure 13 ) is pasted on the back surface 311b of the strain plate 311, and the remaining parts (non-inductive regions 321n1, 321n2) are bent and pasted on the inner peripheral surface of the peripheral wall 313.

[0163] Before Figure 13 shows the state (development view) before the strain gauge 320 is installed on the strain plate 311. As Figure 13 shown, the strain gauge 320 includes a base material 321 and a circuit pattern CP3 printed on the surface of the base material 321. The base material 321 has an induction area 321s and non-induction areas 321n1, 321n2 sandwiching the induction area 321s. The circuit pattern CP3 includes six strain sensing elements X 31 、X 32 、Y 31 、Y 32 、Z 31 、Z 32 、four fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 、eight terminals T 31 ~T 38 、and wiring W3 connecting these. In addition, in the following description, the direction in which the non-induction areas 321n1, 321n2 sandwich the induction area 321s is taken as the y direction (second direction), and the direction orthogonal to the y direction on the surface of the base material 321 is taken as the x direction (first direction).

[0164] The base material 321 is a flexible resin film, having a central circular induction area 321s, a pair of non-induction areas 321n1, 321n2 sandwiching the induction area 321s, and a pair of connection areas 321c1, 321c2 connecting the induction area 321s to the pair of non-induction areas 321n1, 321n2 respectively. Preferably, the resin film uses a soft and highly flexible material that can be easily bent. As a specific example, polyester, polyimide, etc. can be used. In addition, the induction area 321s, non-induction areas 321n1, 321n2, connection areas 321c1, 321c2 can be formed of different materials respectively, but it is preferable to form these areas of the same material to make the temperature characteristics (such as the resistance temperature coefficient) of the entire area equal. In this case, it is preferable to integrally cut out the induction area 321s, non-induction areas 321n1, 321n2, connection areas 321c1, 321c2 from nearby parts within an integrally formed material (such as a sheet of polyester, polyimide, etc.) to form the base material 321. Thereby, the temperature characteristics of each area can be made more uniform.

[0165] The induction area 321s is the area pasted on the back surface 311b of the strain plate 311 of the main body 310, and thus has the same diameter as or smaller than the back surface 311b of the strain plate 311. On one surface of the induction area 321s, strain sensing elements (first direction strain sensing elements) X are formed sandwiching the center c in the x direction 31, X 32 , a strain sensing element (second direction strain sensing element) Y is formed while clamping the center c in the y direction 31 , Y 32 , a strain sensing element (third direction strain sensing element) Z is formed along the outer periphery 31 , Z 32 .

[0166] The strain sensing element X 31 , X 32 are respectively arc-shaped, and are formed to face each other in the x direction with the circumferential direction along the contour of the load application part 312 indicated by the dashed line in Figure 13 as the grid width direction. In addition, the strain sensing element X 31 and the strain sensing element X 32 are respectively formed at positions equidistant from the center c.

[0167] The strain sensing element Y 31 , Y 32 are respectively arc-shaped, and are formed to face each other in the y direction with the circumferential direction along the contour of the load application part 312 as the grid width direction. In addition, the strain sensing element Y 31 and the strain sensing element Y 32 are respectively formed at positions equidistant from the center c.

[0168] The strain sensing element Z 31 , Z 32 are respectively arc-shaped, and are formed to face each other in the x direction with the circumferential direction of the sensing area 321s as the grid width direction. Moreover, the strain sensing element Z 31 , Z 32 is arranged on the side (outer side) opposite to the center c of the strain sensing element X 31 , X 32 , Y 31 , Y 32 .

[0169] A pair of non-sensing areas 321n1, 321n2 sandwich the sensing area 321s in the y direction, and are respectively rectangular with the x direction as the long side direction and the y direction as the short side direction.

[0170] On the part of the surface of the non-sensing area 321n1 that is farther from the sensing area 321s, fixed resistance elements (first direction fixed resistance elements) RX 31 , RX 32 are formed to be arranged in the x direction and extend in the x direction. On the part closer to the sensing area 321s, four terminals T 31 , T 32 , T 33 , T 34. That is, in the non-inductive region 321n1, the fixed resistance elements RX 31 and RX 32 are arranged on the side of the terminals T 31 to T 34 opposite to the inductive region 321s.

[0171] Similarly, in a portion of the surface of the non-inductive region 321n2 that is farther from the inductive region 321s, fixed resistance elements (second-direction fixed resistance elements) RY 31 and RY 32 that extend in the x direction are arranged in the x direction. In a portion closer to the inductive region 321s, four terminals T 35 and T 36 and T 37 and T 38 are formed and arranged in the x direction. That is, in the non-inductive region 321n2, the fixed resistance elements RY 31 and RY 32 are arranged on the side of the terminals T 35 to T 38 opposite to the inductive region 321s.

[0172] For the connection regions 321c1 and 321c2 that connect the inductive region 321s to the non-inductive regions 321n1 and 321n2, the dimensions (widths) in the x direction (orthogonal direction) orthogonal to the y direction connecting the inductive region 321s to the non-inductive regions 321n1 and 321n2 are respectively smaller than the dimensions (widths) in the x direction of the inductive region 321s, the non-inductive regions 321n1, and 321n2. Therefore, the base material 321 has a reduced-diameter shape in the connection regions 321c1 and 321c2.

[0173] As Figure 13 and Figure 14 show, the wiring W3 connects the strain sensing elements X 31 and X 32 , the fixed resistance elements RX 31 and RX 32 to form the first bridge circuit (first Wheatstone bridge circuit) BC31. In addition, a terminal T 31 is connected between the strain sensing element X 31 and the fixed resistance element RX 31 . A terminal T 31 is connected between the strain sensing elements X 32 , and a terminal T 32 is connected between the fixed resistance elements RX 31 and RX 32 . A terminal T 33 is connected between the strain sensing element X 32 and the fixed resistance element RX32 is connected to a terminal T 34 .

[0174] Similarly, the wiring W3 connects the strain sensing elements Y 31 , Y 32 , the fixed resistance element RY 31 , RY 32 to form a second bridge circuit (second Wheatstone bridge circuit) BC32. A terminal T 31 is connected between the strain sensing element Y 31 and the fixed resistance element RY 38 . A terminal T 31 is connected between the strain sensing elements Y 32 , Y 36 . A terminal T 31 is connected between the fixed resistance elements RY 32 , RY 37 . A terminal T 32 is connected between the strain sensing element Y 32 and the fixed resistance element RY 35 .

[0175] One end of the strain sensing element Z 31 is connected to the first bridge circuit BC31 between the strain sensing element X 31 and the fixed resistance element RX 31 . The other end is connected to the second bridge circuit BC32 between the strain sensing element Y 31 and the fixed resistance element RY 31 . Similarly, one end of the strain sensing element Z 32 is connected to the first bridge circuit BC31 between the strain sensing element X 32 and the fixed resistance element RX 32 . The other end is connected to the second bridge circuit BC32 between the strain sensing element Y 32 and the fixed resistance element RY 32 . Thus, a third bridge circuit (third Wheatstone bridge circuit) BC33 is formed which has the first bridge circuit BC31 and the second bridge circuit BC32 on a pair of opposite sides respectively, and the strain sensing elements Z 31 , Z 32 on the other pair of opposite sides respectively.

[0176] The strain sensing elements X 31 , X 32 , Y 31 , Y 32 , Z 31 , Z 32 , the fixed resistance elements RX 31 , RX 32, RY 31 , RY 32 , The wiring W3 is formed of the same material throughout, and more preferably is formed of adjacent portions within a single material. As an example, the material is copper, a copper alloy such as copper / nickel, or the like. Printing of the circuit pattern CP3 onto the base material 321 can be performed by photolithography, printing, vapor deposition, sputtering, or the like.

[0177] As Figure 12 shown, the strain gauge 320 is adhered to the main body portion 310 such that the surface of the base material 321 opposite to the surface on which the circuit pattern CP3 is formed contacts the back surface 311b of the strain plate 311.

[0178] Specifically, the sensing region 321s of the base material 321 is adhered to the back surface 311b of the strain plate 311 such that its x-direction and y-direction coincide with the x-direction and y-direction of the main body portion 310, respectively, and the center c coincides with the axis A3. That is, the sensing region 321s is installed in the strain region that receives the load of the strain plate 311 and generates strain. Therefore, in a state where the sensing region 321s of the base material 321 is adhered to the strain plate 311, the strain sensing element X 31 , X 32 and the strain sensing element Y 31 , Y 32 are respectively arranged in regions that are outside the load application portion 312 and where strain is generated relatively largely in the x-direction and y-direction.

[0179] A pair of non-sensing regions 321n1, 321n2 of the base material 321 are respectively bent and adhered to the inner peripheral surface of the peripheral wall 313. That is, the non-sensing regions 321n1, 321n2 are arranged outside the strain region. Therefore, the terminals T 31 , T 32 , T 33 , T 34 , formed in the non-sensing region 321n1, and the terminals T 35 , T 36 , T 37 , T 38 formed in the non-sensing region 321n2 are exposed toward the radially inner side of the peripheral wall 313.

[0180] Next, the usage method and operation of the three-axis force sensor 3000 and the strain gauge 320 of the present embodiment will be described.

[0181] When the three-axis force sensor 3000 is used for the electronic pen 4000, first, the load application portion 312 is fitted with the pen tip (i.e., the tip 432). Then, using wires L 31 ~L 38 the terminals T 31 ~T 38are respectively connected to a signal processing circuit (not shown). Terminals T 31 ~T 38 and the wires L 31 ~L 38 can be joined by any method, for example, by using soldering or anisotropic conductive film (ACF).

[0182] Terminals T 31 、T 35 are respectively connected to a power supply (not shown) through the wires L 31 、L 35 Terminals T 32 、T 33 、terminals T 36 、T 37 、terminals T 34 、T 38 are respectively connected to the operation unit (not shown) in the signal processing circuit via an amplifier (not shown) in the signal processing circuit through the wires L 32 、L 33 、wires L 36 、L 37 、wires L 34 、L 38 When the triaxial force sensor 3000 operates, an input voltage Ei is applied between the terminal T

[0183] and the terminal T 31 by the power supply. The resistance values of the strain sensing elements and the resistance values of the fixed resistance elements constituting the first bridge circuit BC31, the second bridge circuit BC32, and the third bridge circuit BC33 are adjusted such that when there is no flexure in the sensing region 321s of the base material 321, the voltages between the terminals T 35 and T 32 are equal, the voltages between the terminals T 33 and T 36 are equal, and the voltages between the terminals T 37 and T 34 are equal.

[0184] Therefore, as shown in (a) of Figure 3 , when there is no strain in the strain plate 311 and no flexure in the sensing region 321s, there is no potential difference between the terminals T 38 and T 32 , between the terminals T 33 and T 36 , and between the terminals T 37 and T 34 , and the operation unit does not calculate the strain. 38 Next, as shown in

[0185] Next, as shown in Figure 3As shown in (b), when a load in the x direction is applied to the load application portion 312, the load application portion 312 receives the load and moves, causing the strain plate 311 to generate strain. At this time, the sensing region 321s of the base material 321 of the strain gauge 320 attached to the strain plate 311 also flexes integrally with the strain plate 311, so that compressive strain is generated in the strain sensing element X 31 and tensile strain is generated in the strain sensing element X 32 .

[0186] As a result, the resistance values of the strain sensing elements X 31 and X 32 change respectively, and a potential difference is generated between the terminals T 31 and T 32 of the first bridge circuit BC31 including the strain sensing elements X 32 and X 33 . The arithmetic unit calculates the amount of strain generated in the strain plate 311 based on this potential difference, and calculates the magnitude of the load in the c direction applied to the load application portion 312. At this time, no strain is generated in the peripheral wall 313, and the resistance values of the fixed resistance elements RX 31 and RX 32 are constant.

[0187] Similarly, when a load in the y direction is applied to the load application portion 312, the magnitude of the applied load in the y direction is calculated.

[0188] When a load in the Z direction is applied to the load application portion 312, the strain plate 311 and the sensing region 321s of the base material 321 bend in a manner that protrudes from the center. Therefore, extension strain is generated in all of the strain sensing elements X 31 , X 32 , Y 31 , Y 32 , Z 31 and Z 32 . As a result, the combined resistance of the first bridge circuit BC31, the combined resistance of the second bridge circuit BC32, and the resistance values of the strain sensing elements Z 31 and Z 32 change respectively, and a potential difference is generated between the terminals T 34 and T 38 of the third bridge circuit BC33. The arithmetic unit calculates the amount of strain generated in the strain plate 311 based on this potential difference, and calculates the magnitude of the load in the z direction applied to the load application portion 312.

[0189] Here, the fixed resistance elements RX 31 and RX 32 of the first bridge circuit BC31, the fixed resistance elements RY 31 and RY 32Printed on the base material 321 and made of the same material as the strain sensing elements X 31 、X 32 、Y 31 、Y 32 、Z 31 、Z 32 is described.

[0190] (3-1) By forming the fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 , the fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 are made of the same material as the strain sensing elements X 31 、X 32 、Y 31 、Y 32 、Z 31 、Z 32 and are formed in positions close to them. Here, the resistance temperature coefficient, which represents the ratio of the change in resistance value to the change in temperature, depends on the physical property values of the material. Therefore, in this embodiment, the resistance temperature coefficients of all the strain sensing elements and all the fixed resistance elements are equal. In addition, the fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 are formed on the base material 321 and are formed near the strain sensing elements X 31 、X 32 、Y 31 、Y 32 、Z 31 、Z 32 . Therefore, the change in the ambient temperature that affects all the strain sensing elements and all the fixed resistance elements is substantially the same. Therefore, when the ambient temperature changes, the resistance values of all the strain sensing elements and all the fixed resistance elements change in the same proportion.

[0191] In the first bridge circuit BC31, the second bridge circuit BC32, and the third bridge circuit BC33, when the balance of the resistance values between the respective included resistance elements (strain sensing elements and fixed resistance elements) changes, between the terminals T 32 、T 33 、between the terminals T 36 、T 37 、between the terminals T 34 、T 38A potential difference is generated therebetween, and strain is detected based on this potential difference. Therefore, in a case where 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 be generated due to this change in balance. However, in the present embodiment, when a change occurs in the ambient temperature, the resistance values of all the strain sensing elements and the resistance values of all the fixed resistance elements change at the same ratio. Therefore, even when the ambient temperature changes, the balance between the resistance values of the respective elements does not change, thereby suppressing the generation of measurement errors. Further, when forming the circuit pattern CP3, by forming the strain sensing element and the like using a portion near a material (copper, copper alloy, etc.) prepared as an integral block, the strain sensing elements X 31 、X 32 、Y 31 、Y 32 、Z 31 、Z 32 、the fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 、and the wiring W3 have a more uniform temperature coefficient of resistance, and the generation of measurement errors can be suppressed more favorably.

[0192] (3-2) As in the present embodiment, when the fixed resistance elements RX 31 、RX 32 of the first bridge circuit BC31 and the fixed resistance elements RY 31 、RY 32 of the second bridge circuit BC32 are formed in the non-inductive regions 321n1, 321n2 of the base material 321 and the non-inductive regions 321n1, 321n2 are adhered to a portion (outside the strain region) where no strain is generated in the main body portion 310, the fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 can function as temperature compensation balance strain gauges. Therefore, even when expansion or contraction occurs in the main body portion 310 including the strain plate 311 due to a change in the ambient temperature, the change in the resistance values of the strain sensing elements X 31 、X 32 、Y 31 、Y 32 caused by this expansion or contraction can be compensated, thereby suppressing the generation of measurement errors.

[0193] (3-3) By using the fixed resistance elements RX 31 、RX 32 、RY 31, RY 32 It is formed by printing on the base material 321, so that the first bridge circuit BC31, the second bridge circuit BC32, and the third bridge circuit BC33 can be respectively formed as closed circuits completed on the base material 321.

[0194] When the strain sensing elements constituting the bridge circuit are printed on the base material and the fixed resistance elements constituting the bridge circuit are provided outside the base material, such as in a signal processing circuit, in order to make the bridge circuit a closed circuit, it is necessary to connect the strain sensing elements on the base material and the fixed resistance elements of the signal processing unit through wires or the like. In this case, the wire is joined to the electrode provided on the base material to connect the wiring on the base material and the wire. However, if a joint resistance is generated at the joint between the electrode and the wire, this joint resistance becomes a resistance within the bridge circuit and becomes a cause of a large strain detection error. Therefore, the joining method is limited to soldering with a substantially negligible joint resistance.

[0195] However, in order to perform soldering well, it is necessary to provide relatively large electrodes on the base material and ensure the spacing between multiple electrodes, which results in an increase in the size of the base material. In addition, in order to perform soldering well, it is necessary to stack solder with a certain thickness, which also hinders the miniaturization of the triaxial force sensor.

[0196] In contrast, in the present embodiment, the first bridge circuit BC31, the second bridge circuit BC32, and the third bridge circuit BC33 are respectively formed as closed circuits completed on the base material 321, and the connection between the base material 321 via the terminals T 31 ~T 38 and the signal processing unit is only a joining for connecting the first bridge circuit BC31, the second bridge circuit BC32, and the third bridge circuit BC33 to the power supply and the arithmetic unit. Therefore, in the present embodiment, at the joints between the terminals T 31 ~T 38 and the wires L 31 ~L 38 the generation of joint resistance is allowed, so that any joining method other than soldering can be adopted, for example, joining using an anisotropic conductive film. In addition, by using an anisotropic conductive film, the size of the electrode, the spacing between electrodes, and the thickness of the joint can be suppressed to about one-tenth of that in the case of soldering. Therefore, when miniaturization of the triaxial force sensor 3000 is desired, the joining based on the anisotropic conductive film is advantageous.

[0197] The effects of the strain gauge 320 and the triaxial force sensor 3000 of the present embodiment are as follows.

[0198] The strain gauge 320 has the fixed resistance elements RX 31 , RX32 、The fixed resistance element RY of the second bridge circuit BC32 31 、RY 32 is formed on the base material 321, so it can achieve the effects of the above (3-2) and (3-3), and is made of the same material as the strain sensing elements X 31 、X 32 、Y 31 、Y 32 to form the fixed resistance element RX 31 、RX 32 、RY 31 、RY 32 , so it can achieve the effect of the above (3-1).

[0199] In the strain gauge 320, only the strain sensing elements X 31 、X 32 、Y 31 、Y 32 、Z 31 、Z 32 are formed in the sensing area 321s, and the terminals T 31 ~T 38 and the fixed resistance elements RX 31 、RX 32 、RY 31 、RY 32 are formed in the non-sensing areas 321n1 and 321n2. Therefore, the diameter (size) of the sensing area 321s can be reduced, and thus the strain plate 311 of the triaxial force sensor 3000 can be reduced. The miniaturization of the strain plate 311 preferentially leads to the miniaturization of the triaxial force sensor 3000.

[0200] In the strain gauge 320, the terminals T 31 ~T 38 are arranged in the non-sensing areas 321n1 and 321n2. Therefore, if necessary, without increasing the diameter of the sensing area 321s, increasing the size of the terminals T 31 ~T 38 can make the connection operation with wires and the like easier.

[0201] The base material 321 of the strain gauge 320 has connection areas 321c1 and 321c2 that are narrower than the widths of the sensing area 321s and the non-sensing areas 321n1 and 321n2 between the sensing area 321s and the non-sensing areas 321n1 and 321n2. Therefore, the sensing area 321s and the non-sensing areas 321n1 and 321n2 can be arranged in various forms without being restricted by the connection parts of the connection areas 321c1 and 321c2.

[0202] The triaxial force sensor 3000 and the electronic pen 4000 of the present embodiment are provided with a strain gauge 320, and thus can achieve the same effect as that of the strain gauge 320.

[0203] As long as the features of the present invention are maintained, the present invention is not limited to the above embodiments, and other forms that can be conceived within the technical idea of the present invention are also included in the scope of the present invention.

[0204] Industrial Applicability

[0205] The strain gauge and the multi-axial force sensor of the present invention can suppress the influence of temperature change in load detection, thereby contributing to the improvement of stability and reliability in robots, game devices, various measuring devices, and other devices.

[0206] Description of Reference Numerals

[0207] 111, 211, 311... strain plates (strain components); 112, 212, 312... load application parts; 120, 220, 320... strain gauges; 121, 221, 321... base materials; 121s, 221s, 321s... sensing regions; 121n1, 121n2, 221n1, 221n2, 321n1, 321n2... non-sensing regions; BC11, BC21, BC31... first bridge circuits (first Wheatstone bridge circuits); BC12, BC22, BC32... second bridge circuits (second Wheatstone bridge circuits); BC13, BC23, BC33... third bridge circuits (third Wheatstone bridge circuits); RX 11 、RX 12 、RX 21 、RX 22 、RX 31 、RX 32 … fixed resistor elements (first-direction fixed resistor elements); RY 11 、RY 12 、RY 21 、RY 22 、RY 31 、RY 32 … fixed resistor elements (second-direction fixed resistor elements); T 11 ~T 18 、T 21 ~T 28 、T 31 ~T 38 … terminals; X 11 、X 12 、X 21 、X 22 、X 31 、X 32 … strain sensing elements (first-direction strain sensing elements); Y11 , Y 12 , Y 21 , Y 22 , Y 31 , Y 32 … strain sensing element (second direction strain sensing element); Z 11 , Z 12 , Z 21 , Z 22 , Z 31 , Z 32 … strain sensing element (third direction strain sensing element).

Claims

1. A strain body for detecting a load acting in a first direction based on a first Wheatstone bridge circuit and detecting a load acting in a second direction orthogonal to the first direction based on a second Wheatstone bridge circuit, wherein, the strain body includes: a strain component; and a circuit pattern provided on the strain component, the strain component has a strain region that generates strain under the load to be detected and a region different from the strain region, the circuit pattern includes two first-direction strain sensing elements constituting the first Wheatstone bridge circuit, two second-direction strain sensing elements constituting the second Wheatstone bridge circuit, and at least one of a first-direction fixed resistance element constituting the first Wheatstone bridge circuit and a second-direction fixed resistance element constituting the second Wheatstone bridge circuit, the two first-direction strain sensing elements, the two second-direction strain sensing 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 provided in the strain region, and at least one of the first-direction fixed resistance element and the second-direction fixed resistance element is provided in a region different from the strain region, the circuit pattern further includes at least one terminal, the at least one terminal is provided in a region different from the strain region, in a region different from the strain region, the at least one terminal is provided on the side opposite to the strain region of at least one of the first-direction fixed resistance element and the second-direction fixed resistance element.

2. The strain body according to claim 1, wherein, the circuit pattern includes two first-direction fixed resistance elements constituting the first Wheatstone bridge circuit and two second-direction fixed resistance elements constituting the second Wheatstone bridge circuit, the two first-direction strain sensing elements, the two second-direction strain sensing elements, the two first-direction fixed resistance elements, and the two second-direction fixed resistance elements are formed of the same material, the two first-direction fixed resistance elements and the two second-direction fixed resistance elements are provided in a region different from the strain region.

3. The strain body according to claim 1 or 2, wherein, a pair of regions different from the strain region are provided on both sides of the strain region.

4. The strain body according to any one of claims 1 to 3, wherein, the circuit pattern further includes two third-direction strain sensing elements or two third-direction fixed resistance elements, the two third-direction strain sensing elements or the two third-direction fixed resistance elements connect the first Wheatstone bridge circuit and the second Wheatstone bridge circuit to form a third Wheatstone bridge circuit.

5. A sensor, wherein, the sensor includes: the strain body according to any one of claims 1 to 4; and a load acting part connected to the strain component.

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