Coupling structure for an electrode pad

Abstract

A coupling structure is provided for an electrode pad that is capable of suppressing tearing or detachment of a strain gauge tab and improving the coupling reliability between the strain gauge and a measuring lead. A coupling structure for an electrode pad is designed for electrically coupling the electrode pad, to which a measuring lead is attached, with a tab of a strain gauge mounted on an elastic body, which includes a measuring grid and the tab. The coupling structure has an insert structure into which one of the tab and the electrode pad is partially or completely inserted into the other.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a coupling structure for an electrode pad of a strain gauge. STATE OF THE ART

[0002] A load cell, also known as a force transducer or load cell, which uses a strain gauge whose resistance changes due to strain caused by a load, is commonly used. For example, a load cell is known in which a strain gauge is integrated into a bridge circuit. This bridge circuit is a conversion circuit that converts the change in the strain gauge's resistance due to a load into an electrical signal, and the change in resistance is output as the electrical signal. In such a load cell, the strain gauge, mounted on an elastic body, is integrated into the bridge circuit by forming an electrode pad as an extraction electrode on a tab or loop of the strain gauge and by soldering a measuring lead to the electrode pad.

[0003] Traditionally, a metal or alloy foil strain gauge with a measurement factor of approximately 2 has been used in many cases. However, it is desirable to increase the measurement factor of the strain gauge in a load cell with a large output, such as a force detection sensor mounted on an automotive axle that detects a load applied to a wheel, or a load cell that detects component forces and exhibits a large difference in sensitivity to each component force. As examples of strain gauges with a large measurement factor, PTLs 1 and 2 each disclose a strain gauge containing chromium nitride (Cr-N) as a primary material. CITATION LIST PATENT LITERATURE PTL 1: Japanese unexamined published patent application no. 2019-074454 PTL 2: Japanese unexamined published patent application no. 2019-090722 SUMMARY OF THE INVENTIONAL PROBLEM

[0004] In a case where a strain gauge made of nitrogen and chromium is used as the main materials, a phenomenon can occur where the strain gauge partially ceramicizes as its temperature increases. In contrast, a metallic material is generally used for the electrode pad. Therefore, when high-temperature heat is applied to the electrode pad and the strain gauge tab—for example, when a measuring lead is soldered to the strain gauge—the coefficients of thermal expansion of the electrode pad material and the strain gauge material differ significantly. Consequently, a tensile or compressive stress is applied to the tab in accordance with the expansion of the electrode pad.As a result, the tab may tear or detach from the elastic body, and the electrical circuit may be partially damaged or disconnected.

[0005] The present disclosure is made with regard to the problem described above, and one objective of the present disclosure is to provide a coupling structure for an electrode pad that is capable of suppressing tearing or detachment of a tab of a strain gauge and improving the coupling reliability between the strain gauge and a measuring lead. SOLUTION TO THE PROBLEM

[0006] In order to address the problem described above, according to one aspect of the present revelation, A coupling structure is set up for an electrode pad for electrically coupling the electrode pad, to which a measuring lead is coupled, with a tab of a strain gauge which is arranged on an elastic body and includes a measuring grid and the tab, and The coupling structure has an insertion structure into which one of the tabs and the electrode pad is partially or completely inserted into another of the tabs and the electrode pad. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0007] As described above, according to the present disclosure, tearing or detachment of the strain gauge tab can be suppressed and the coupling reliability between the tab and the electrode pad can be improved. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. Figure 1 is a sectional view showing a load cell (six-component force detector) of the present disclosure. [ Fig. 2] Fig. Figure 2 is a schematic view showing an arrangement of strain gauges in the load cell of the present disclosure. [ Fig. 3] Fig. Figure 3 is an explanatory diagram that represents a configuration of a bridge circuit of the load cell of the present disclosure. [ Fig. 4] Fig. Figure 4 is an explanatory view showing a coupling structure for an electrode pad according to a first embodiment of the present disclosure. [ Fig. 5] Fig. Figure 5 is a sectional view along line II in Fig. 4. [ Fig. 6] Fig. 6 is a sectional view along line II-II in Fig. 4. [ Fig. 7] Fig. Figure 7 is an explanatory view showing a coupling structure for an electrode pad according to a second embodiment of the present disclosure. [ Fig. 8] Fig. Figure 8 is an explanatory view showing a configuration example of a tab according to the embodiment. [ Fig. 9] Fig. Figure 9 is a sectional view along line III-III in Fig. 7. [ Fig. 10] Fig. 10 is a sectional view along line IV-IV in Fig. 7. [ Fig. 11] Fig. Figure 11 is a schematic view showing an arrangement of strain gauges in a six-component force detector of a modification. [ Fig. 12] Fig. Figure 12 is an explanatory view showing a measurement strip pattern of a biaxial shear strain gauge. DESCRIPTION OF EXECUTION FORMS

[0008] In the following, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. In the description and the drawings, components that have essentially the same functions and configurations are designated by the same reference numerals, and redundant descriptions are omitted. <<1. Overview of an embodiment of the present disclosure>><1-1. Details of the background of the present disclosure>

[0009] First, a background is described against which the technique of the present disclosure is created. The background described below represents only one aspect of a load cell configuration to which the technique of the present disclosure can be applied. The load cell to which the present disclosure can be applied is not limited to the load cell with the configuration illustrated below.

[0010] A six-component force detector is known that detects loads applied to a wheel of a vehicle, such as an automobile, loads (Fx, Fy, Fz) in a forward-backward direction (hereinafter also referred to as the "x-axis direction"), a vehicle width direction (hereinafter also referred to as the "y-axis direction"), and a vehicle height direction (hereinafter also referred to as the "z-axis direction"), as well as moments (Mx, My, Mz) about the x-axis, y-axis, and z-axis. Such a six-component force detector has a cylindrical elastic body attached to a shaft, wheel axle, or axle. However, with respect to resistance to an applied load, it is difficult to obtain an output equivalent to that of a load cell detecting a load in a uniaxial direction using a general foil strain gauge with a measurement factor of approximately 2.

[0011] In contrast, it is considered that a desirable output can be obtained by using a thin-film strain gauge, such as a Cr-N gauge with a high elemental resistivity and a high measurement factor (for example, a measurement factor of 10 to 12 in the case of the Cr-N gauge). However, if high-temperature heat is applied to the Cr-N gauge, a phenomenon can occur in which the Cr-N gauge partially ceramicizes, leading to brittle fracture. A metallic material is generally used for the electrode pad to which the solder is bonded, due to the fact that little alloying occurs between the metal and the solder, and the wettability between the solder and the electrode pad material is high.

[0012] When a measuring lead is soldered to the electrode pad, high-temperature heat is transferred to the electrode pad and to a tab of the strain gauge. In this case, the coefficient of thermal expansion of the electrode pad material differs significantly from that of the strain gauge material. Therefore, as the electrode pad, made of a metal material, expands, a tensile or compressive stress acts on the tab, which can cause the tab to tear or detach from the elastic body. For example, in the six-component force detector that detects the load applied to the wheel, the strain gauge is located on the cylindrical elastic body, and therefore the tearing or detachment of the tab described above is likely to occur.In the case of the six-component force detector, many coupling sections are provided between the tabs and the electrode pads, and if a coupling failure occurs in just one section, the six-component force detector becomes an abnormal, irregular, or deviant product. It is therefore desirable to increase the reliability of each coupling section.

[0013] In light of such a background, the technique of the present disclosure, in a case where a strain gauge with a measurement factor greater than that of a conventional foil strain gauge is used and is likely to be brittle-fractured, provides a coupling structure for an electrode pad capable of suppressing tab tearing or tab detachment from an elastic body, which can occur when high-temperature heat is transferred to the electrode pad and tab in the case of soldering or the like, and improving the coupling reliability between the strain gauge and a measuring lead. <1-2. Features of an embodiment of the present disclosure>

[0014] (1-2-1) An embodiment of the present disclosure provides a coupling structure for an electrode pad, which is configured to electrically couple the electrode pad, to which a measuring lead is / will be coupled, with a tab of a strain gauge which is / will be arranged on an elastic body and includes a measuring grid and the tab, and the coupling structure has an insert structure into which one of the tab and the electrode pad is partially or completely inserted into the other.

[0015] This configuration increases the connection strength between the tab and the electrode pad. Even if the strain gauge is made from a material prone to brittle fracture, and even if high-temperature heat is applied in a case where the measuring lead is soldered to the electrode pad, which is electrically coupled to the tab, or similar situations, tab tearing or detachment from the elastic body can be suppressed. Therefore, the coupling reliability between the strain gauge and the measuring lead can be improved.

[0016] The "insert structure in which one of the tabs and electrode pads is partially or completely inserted into the other" specifies a state in which the other link is partially or completely positioned on both sides of the first link by the tab or electrode pad in a predetermined direction. However, such an insert structure does not include, for example, a configuration in which the other link is positioned on both sides in an extension direction of a plane of a link, such as a configuration in which the other link, with a width exceeding that of a link, is positioned over the first link with a layered shape, and the first link is covered by the other link.

[0017] (1-2-2) Furthermore, in the embodiment of the present disclosure, the electrode pad, having a U-shaped area, can be arranged on the elastic body such that an opening of the U-shape is located on a lateral side, and The tab can be inserted into the electrode pad, which has a U-shape.

[0018] With this configuration, the upper and lower sides of the tab are inserted into the electrode pad, and the tab and electrode pad are firmly connected. Therefore, even if thermal stress is generated in the tab, the connection between the tab and the electrode pad is maintained, and the coupling reliability between the strain gauge and the measuring lead can be increased.

[0019] (1-2-3) Furthermore, in the embodiment of the present disclosure, the measuring grid can each include straight sections extending in a predetermined first direction, and both legs of the electrode pad having the U-shape can extend in the first direction, and the tab can enter the electrode pad having the U-shape in the first direction.

[0020] With this configuration, even if the straight sections of the measuring grid expand or contract due to the strain of the elastic body, the influence on the resistance change due to the strain of the tab can be reduced. Therefore, the reliability of a measurement from the load cell can be increased.

[0021] (1-2-4) Furthermore, in the embodiment of the present disclosure, the tab may have elongated holes, each having a longitudinal direction extending in a predetermined second direction and penetrating the tab in a thickness direction of the tab, or grooves which are recessed in the thickness direction of the tab, and The electrode pad can have a comb-like cross-sectional shape, and comb teeth of the electrode pad can enter the elongated holes or grooves.

[0022] With this configuration, one of the tabs and the electrode pad are inserted into the other, ensuring a firm connection between them. Even if thermal stress is generated in the tab, the connection between the tab and the electrode pad is maintained, thus increasing the coupling reliability between the strain gauge and the measuring lead.

[0023] (1-2-5) Furthermore, in the embodiment of the present disclosure, in the coupling structure for the electrode pad according to claim 4, The measuring grid includes straight sections extending in a predetermined first direction, and The second direction extends in the same direction as the first direction.

[0024] With this configuration, even if the straight sections of the measuring grid expand or contract due to the strain of the elastic body, the influence on the resistance change due to the strain of the tab can be reduced. Therefore, the reliability of a measurement from the load cell can be increased.

[0025] (1-2-6) Furthermore, in the embodiment of the present disclosure, The strain gauge can be arranged on the elastic body with an insulating layer or insulating layer in between, and The electrode pad can be formed in contact with the tab and the insulating layer.

[0026] With this configuration, the electrode pad is formed on the tab, and in an area that includes the insulating layer, the connection strength between the electrode pad and the insulating layer is increased, and therefore the connection strength between the electrode pad and the tab can be further increased.

[0027] (1-2-7) Furthermore, in the embodiment of the present disclosure, the strain gauge can be made of Cr-N and the electrode pad can be made of Au.

[0028] This configuration allows for a high output from the load cell by using a strain gauge with a large measurement factor. Furthermore, alloy formation between the solder and the electrode pad is suppressed, the wettability between the solder and the electrode pad is excellent, and thus the stability of the solder joint is improved. Additionally, the linear coefficient of thermal expansion is brought close to that of the solder, thereby reducing the thermal stress generated in the strain gauge. <<2. Details of embodiments of the present disclosure>>

[0029] The following describes a configuration example of a load cell to which a coupling structure for an electrode pad of each embodiment (described later) is applied, and then each embodiment is described. <2-1. Configuration example of a load cell (six-component force detector)>

[0030] Next, a configuration example of a load cell according to an embodiment of the present disclosure will be described.

[0031] In the present embodiment, an example in which the technology of the present disclosure is applied to a six-component force detector capable of detecting six component forces (Fx, Fy, Fz, Mx, My, and Mz) applied to a wheel of a vehicle is described as an aspect of a load cell. The load cell according to the present embodiment is a six-component force detector that detects six component forces applied to a wheel and is integrated into a hub-bearing unit that is attached to a suspension device or spring assembly and rotatably supports a wheel of a vehicle, such as an automobile.

[0032] Fig. Figure 1 is a sectional view of a hub-bearing unit incorporating a six-component force detector, along a plane that includes an axis. Fig. 1 indicates a right side, an outside in the direction of the vehicle's width, and a left side indicates an inside in the direction of the vehicle's width. The in Fig. The hub bearing unit configuration shown in Figure 1 is merely an example, and the hub bearing unit configuration is not limited to those shown in Figure 1. Fig. The configuration shown is limited to 1.

[0033] A hub-bearing unit 100 comprises a hub 110, an outer tube 120, an inner tube 130, a rolling element 140, a base link 150, and a six-component force detector 1. The hub 110 is a link to which a rim disc of a wheel (not shown), comprising a rim and a tire, is attached. The hub 110 includes a tubular section 111, a flange 112, and a collar 113, which are formed as a single unit.

[0034] The tubular section 111 has a cylindrical shape that is concentric with a rotational axis (shaft) of the wheel. The tubular section 111 is radially inwardly inserted by the inner tube 130, a sensitive body 10, and the base member 150. A keyed hole 111a, into which a splined shaft of a drive shaft (not shown) is fitted, is formed on the outside of an inner circumferential surface section of the tubular section 111 in the vehicle width direction. The flange 112 is a disc-shaped section that extends radially outward from an end section of the tubular section 111 on the outside in the vehicle width direction with a flat edge.A surface section of the flange 112 on the outside, in the vehicle width direction, serves as a base element to which the rim disc is / will be attached. The flange 112 has, for example, five openings 112a into which hub bolts are / will be inserted at equal intervals in the circumferential direction on a predetermined pitch circle. The collar 113 is a cylindrical section that projects from a surface section of the flange 112 on the outside, in the vehicle width direction, and is concentric with the axle. The collar 113 is fitted into a central bore, which is a circular opening formed in a central section of the rim disc, thereby improving the mounting accuracy of the wheel.

[0035] The outer tube 120, the inner tube 130, and the rolling element 140 define a rolling bearing (hub bearing) that rotatably supports the wheel. The outer tube 120 comprises a tubular section 121 and a flange 122, which are formed as a single unit. The tubular section 121 is a cylindrical section concentric with the shaft. A guide surface for guiding the rolling element 140 is formed on an inner circumferential surface of the tubular section 121. An end section of the tubular section 121 extends along the inside in the vehicle width direction towards an end section of a tubular section 131 of the inner tube 130, also on the inside in the vehicle width direction.

[0036] The flange 122 extends radially outward from an end section of the tubular section 121 on the outside, in the vehicle width direction, with a flat edge. The flange 122 is a section to which the flange 112 of the hub 110 is attached and fixed. A surface section of the flange 122 on the outside, in the vehicle width direction, is in contact with a surface section of the flange 112 of the hub 110 on the inside, also in the vehicle width direction. The flange 122 has a bolt hole 122a, which is concentric with the opening 112a of the hub 110. A hub bolt (not shown), used to fasten the wheel, is / will be attached to the bolt hole 122a.

[0037] The inner tube 130 comprises the tubular section 131 and a flange 132, which are formed as a single unit. The tubular section 131 is a cylindrical element concentric to the shaft and is inserted radially inward by the tubular section 121 of the outer tube 120. A predetermined gap is provided between an outer circumferential surface of the tubular section 131 and the inner circumferential surface of the tubular section 121 of the outer tube 120. A guide surface, which guides the rolling element 140, is formed on the outer circumferential surface of the tubular section 131. The flange 132 extends radially inward from an end section of the tubular section 131 on the outside in the vehicle width direction. The flange 132 holds an end section of a first flange 12 of the sensitive body 10 on the outside in the vehicle width direction.The rolling element 140 is a bearing integrated between the guide surfaces of the outer tube 120 and the inner tube 130. The rolling element 140 is integrated between the outer tube 120 and the inner tube 130 together with a holder 141 and a holder 142, which position the rolling element 140 between the outer tube 120 and the inner tube 130.

[0038] The base member 150 is a section that attaches and secures the hub-bearing unit 100 to a stator (hub journal) (not shown) of a suspension device. The base member 150 comprises a tubular section 151, a flange 152, a recess 153, and a projection 154, which are formed as a single unit. The tubular section 151 is a cylindrical member that is concentric with the shaft. An end section of the tubular section 111 of the hub 110, on its inner side in the vehicle width direction, is inserted into the tubular section 151. An outer circumferential surface of the tubular section 111 of the hub 110 is arranged to face an inner circumferential surface of the tubular section 151 with a predetermined radial gap between them.

[0039] The flange 152 extends radially outward from an end section of the tubular section 151 on the outside in the vehicle width direction in a flat edge shape. The flange 152 is a mounting surface section that attaches the base member 150 to the stand (not shown). The flange 152 has openings 152a into which bolts used for attachment to the stand are inserted, distributed circumferentially. The flange 152 has a through-hole 152b in which a wire, cable, or the like, coupled to the strain gauge, passes from the inside of a space in which an outer circumferential surface of a cylindrical section 11 of the sensitive body 10 is located to an outer circumferential edge section of the flange 152.

[0040] The recess 153 is a section of an inner circumferential surface of the base member 150. The recess 153 is formed in a stepped manner by increasing the inner diameter of a region corresponding to the flange 152 in the axial direction. The recess 153 is a section that holds a second flange 13 of the sensitive body 10. The projection 154 is a cylindrical section that projects on the outside in the vehicle width direction from a radially interposed section of the flange 152. An outer circumferential surface of the projection 154 is arranged to face an inner circumferential surface of the end section of the tubular section 121 of the outer tube 120 on the inside in the vehicle width direction, with a radially interposed gap.

[0041] The six-component force detector 1 is a load cell capable of detecting loads acting on the wheel in three orthogonal axes and moments about these three axes. The six-component force detector 1 includes the essentially cylindrical sensitive body 10, strain gauges provided on the sensitive body 10, and a bridge circuit incorporating the strain gauges.

[0042] The sensitive body (sensor core) 10 comprises the cylindrical section 11, the first flange 12, and the second flange 13. The cylindrical section 11 is a section with a cylindrical shape, whose inner and outer diameters are essentially constant over a predetermined length in the axial direction, and is a section to which strain gauges (described later) are attached (glued). The first flange 12 is provided on an end section of the cylindrical section 11 on the outside in the vehicle width direction and is a section that extends radially outward and inward with respect to the cylindrical section 11.The first flange 12 is attached to the inner tube 30 in a state in which an outer circumferential surface of the first flange 12 abuts or rests against an inner circumferential surface of the tubular section 131 of the inner tube 30 near the end section of the tubular section 131 on the outside in the vehicle width direction, and an end surface of the first flange 12 abuts a surface section of the flange 132 on the inside in the vehicle width direction.

[0043] The second flange 13 is a section provided on an end section of the cylindrical section 11 on the inside in the vehicle width direction and extends radially outwards and inwards with respect to the cylindrical section 11. The second flange 13 is attached to the base member 150 in such a way that an outer circumferential surface and an end surface of the second flange 13 are fitted into the recess 153 of the base member 150. With this configuration, essentially all forces acting on the wheel are transmitted via the sensitive body 10 to the base member 150.

[0044] The six-component force detector 1 includes an Fx detection system, an Fy detection system, an Fz detection system, an Mx detection system, a My detection system, and an Mz detection system, each comprising a bridge circuit containing a strain gauge provided on the cylindrical section 11 of the sensitive body 10 described above. The Fx detection system detects a force Fx in the radial direction (x-axis direction) acting on the cylindrical section 11 of the sensitive body 10. The Fy detection system detects a force Fy in the axial direction (y-axis direction) acting on the cylindrical section 11 of the sensitive body 10. The Fz detection system detects a force Fz in the radial direction (z-axis direction) orthogonal to the x-axis direction acting on the cylindrical section 11 of the sensitive body 10.The Mx detection system detects a moment Mx about the x-axis acting on the cylindrical section 11 of the sensitive body 10. The My detection system detects a moment My about the y-axis acting on the cylindrical section 11 of the sensitive body 10. The Mz detection system detects a moment Mz about the z-axis acting on the cylindrical section 11 of the sensitive body 10.

[0045] Each of the Fx detection system, Fy detection system, Fz detection system, Mx detection system, My detection system and Mz detection system described above includes a bridge circuit containing four strain gauges. Fig. Figure 2 is a schematic view showing an arrangement of the strain gauges in the six-component force detector 1. Fig. Figure 3 is a diagram that shows an arrangement of strain gauges and a configuration of the bridge circuit of the Fx detection system in the six-component force detector 1, and represents a representative example of the arrangement of strain gauges and the configuration of the bridge circuit of each force detection system (Fx detection system, Fy detection system, Fz detection system) and each moment detection system (Mx detection system, My detection system, Mz detection system).

[0046] As in Fig. 2 and Fig. As shown in Figure 3, the Fx detection system includes strain gauges 21 to 24. The strain gauges 21 to 24 are uniaxial and are attached to an outer circumferential surface of the cylindrical section 11 such that their detection directions are parallel to the central axis of the cylindrical section 11. Strain gauge 21 is located in a region of the outer circumferential surface of the cylindrical section 11 on the side of the first flange 12 (a region close to an intermediate section 14). Strain gauge 22 is arranged on a straight line passing through strain gauge 21 and parallel to the axial direction of the cylindrical section 11, and is located in a region of the outer circumferential surface of the cylindrical section 11 on the side of the second flange 13 (a region close to an intermediate section 15).Strain gauge 23 is positioned 180 degrees around the central axis of the cylindrical section 11 relative to strain gauge 22 (a position symmetrical to strain gauge 22 with respect to the central axis of the cylindrical section 11). Strain gauge 24 is positioned 180 degrees around the central axis of the cylindrical section 11 relative to strain gauge 21 (a position symmetrical to strain gauge 21 with respect to the central axis of the cylindrical section 11).

[0047] As in Fig. As shown in Figure 3, the bridge circuit of the Fx detection system is configured as a Wheatstone bridge circuit. Strain gauges 21 to 24 are sequentially coupled in a loop, and a positive and a negative electrode of a power supply are connected between strain gauge 22 and strain gauge 23, and between strain gauge 21 and strain gauge 24, respectively. The bridge circuit extracts a potential difference between a terminal between strain gauge 21 and strain gauge 22 and a terminal between strain gauge 23 and strain gauge 24 as an output. The configuration of the bridge circuit is described in detail later.

[0048] The Fy detection system includes strain gauges 41 to 44. Strain gauges 41 to 44 are uniaxial and are attached to the outer circumferential surface of the cylindrical section 11 so that their detection directions are parallel to the central axis of the cylindrical section 11. Strain gauge 41 is positioned between strain gauges 21 and 22 of the Fx detection system. Strain gauges 42, 43, and 44 are positioned at locations where their phases are shifted by 90 degrees, 180 degrees, and 270 degrees, respectively, around the central axis of the cylindrical section 11 with respect to the phase of strain gauge 41. The bridge circuit of the Fy detection system has the same configuration, except that the strain gauges 21 to 24 of the in Fig. The Fx detection system shown in Figure 3 is replaced by strain gauges 41 to 44.

[0049] The Fz detection system includes strain gauges 31 to 34. Strain gauges 31 to 34 are uniaxial and are attached to the outer circumferential surface of the cylindrical section 11 such that their detection directions are parallel to the central axis of the cylindrical section 11. Strain gauge 31 is positioned so that it is offset by 90 degrees around the central axis of the cylindrical section 11 with respect to strain gauge 21 of the Fx detection system. Strain gauge 32 is positioned so that it is offset by 90 degrees around the central axis of the cylindrical section 11 with respect to strain gauge 22 of the Fx detection system. The strain gauge 31 and the strain gauge 32 are arranged on the same straight line parallel to the axial direction of the cylindrical section 11.Strain gauge 33 is positioned 180 degrees around the central axis of the cylindrical section 11, relative to strain gauge 32 (a position symmetrical to strain gauge 32 with respect to the central axis of the cylindrical section 11). Strain gauge 34 is positioned 180 degrees around the central axis of the cylindrical section 11, relative to strain gauge 31 (a position symmetrical to strain gauge 31 with respect to the central axis of the cylindrical section 11). The bridge circuit of the Fz detection system has the same configuration, except that strain gauges 21 to 24 are located in the same position. Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 31 to 34.

[0050] The Mx detection system includes strain gauges 51 to 54. Strain gauges 51 to 54 are uniaxial and are attached to the outer circumferential surface of the cylindrical section 11 so that their detection directions are parallel to the central axis of the cylindrical section 11. Strain gauge 51 is located adjacent to strain gauge 31 of the Fz detection system in the central axis direction of the cylindrical section 11. Strain gauge 52 is located adjacent to strain gauge 32 of the Fz detection system in the central axis direction of the cylindrical section 11. Strain gauges 51 and 52 are arranged on the same straight line parallel to the axial direction of the cylindrical section 11.Strain gauge 53 is positioned 180 degrees around the central axis of the cylindrical section 11, relative to strain gauge 52 (a position symmetrical to strain gauge 52 with respect to the central axis of the cylindrical section 11). Strain gauge 54 is positioned 180 degrees around the central axis of the cylindrical section 11, relative to strain gauge 51 (a position symmetrical to strain gauge 51 with respect to the central axis of the cylindrical section 11). The bridge circuit of the Mx detection system has the same configuration, except that strain gauges 21 to 24 are located in the same position. Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 51 to 54.

[0051] The My detection system includes strain gauges 71 to 74. Strain gauges 71 to 74 are shear strain gauges and shear strain gauges, respectively, and are attached to the outer circumferential surface of the cylindrical section 11 so that their detection directions are the circumferential direction of the cylindrical section 11. Strain gauge 71 is positioned between strain gauges 41 and 42 of the Fy detection system. Strain gauge 72 is positioned between strain gauges 42 and 44 of the Fy detection system. Strain gauges 73 and 74 are positioned symmetrically to strain gauges 72 and 71, respectively, with respect to the central axis of the cylindrical section 11. The bridge circuit of the My detection system has the same configuration, except that the strain gauges 21 to 24 of the in Fig. The Fx detection system shown in Figure 3 is replaced by strain gauges 61 to 64.

[0052] The Mz detection system comprises strain gauges 61 to 64. Strain gauges 61 to 64 are uniaxial and are attached to the outer circumferential surface of the cylindrical section 11 so that their detection directions are parallel to the central axis of the cylindrical section 11. Strain gauge 61 is located adjacent to strain gauge 21 of the Fx detection system in the central axis direction of the cylindrical section 11. Strain gauge 62 is located adjacent to strain gauge 22 of the Fx detection system in the central axis direction of the cylindrical section 11. Strain gauges 61 and 62 are arranged on the same straight line parallel to the axial direction of the cylindrical section 11.Strain gauge 63 is positioned 180 degrees around the central axis of the cylindrical section 11 relative to strain gauge 62 (a position symmetrical to strain gauge 62 with respect to the central axis of the cylindrical section 11). Strain gauge 64 is positioned 180 degrees around the central axis of the cylindrical section 11 relative to strain gauge 61 (a position symmetrical to strain gauge 61 with respect to the central axis of the cylindrical section 11). The bridge circuit of the Mz detection system has the same configuration, except that strain gauges 21 to 24 are located in the... Fig. The Fx detection system shown in section 3 is replaced by the strain gauges 61 to 64. <2-2. Bridge circuit>

[0053] Next, a configuration example of a bridge circuit for each force detection system and each torque detection system will be presented with reference to Fig. 3 briefly described.

[0054] A bridge circuit 80 of the in Fig. The Fx detection system shown in Figure 3 has four terminals, comprising a first terminal 81, a second terminal 82, a third terminal 83, and a fourth terminal 84, and four strain gauges 21, 22, 23, and 24. Strain gauge 21 is located between the first terminal 81 and the second terminal 82, strain gauge 22 is located between the second terminal 82 and the fourth terminal 84, strain gauge 24 is located between the first terminal 81 and the third terminal 83, and strain gauge 23 is located between the third terminal 83 and the fourth terminal 84. A current path passing through the first terminal 81, the strain gauge 21, the second terminal 82, the strain gauge 22 and the fourth terminal 84 defines a first path 86.A current path passing through the first terminal 81, the strain gauge 24, the third terminal 83, the strain gauge 23 and the fourth terminal 84 defines a second path 87.

[0055] The strain gauges 21, 22, 23, and 24 are resistive elements whose resistance values ​​change in accordance with the amount of strain. In the present embodiment, the strain gauge is made of a material with a strain gauge factor of 4 or greater. For example, the strain gauge can be formed from a Cr-N thin film. If the strain gauge factor is 4 or greater, a desirable output such as the six-component force detector 1, which detects the load applied to the wheel, can be obtained. However, the strain gauge is not limited to the Cr-N thin film strain gauge.

[0056] In the bridge circuit 80, one or more of the sides on which the strain gauges 21, 22, 23, 24 are arranged can be coupled to a resistance element for setting an initial equilibrium of resistance values ​​or a resistance element for compensating for temperature properties where the output of the bridge circuit 80 changes with a temperature change.

[0057] In the bridge circuit 80, when a load is applied to an elastic body, strain occurs in each of the strain gauges 21, 22, 23, and 24, and the resistance value of each of the strain gauges 21, 22, 23, and 24 changes in accordance with the magnitude of the strain. The bridge circuit 80 outputs an electrical signal corresponding to a potential difference between the second terminal 82 of the first path 86 and the third terminal 83 of the second path 87. <2-3. Design of the coupling structure for an electrode pad>

[0058] Next, each embodiment of the coupling structure for the electrode pad of the present disclosure will be described as an example. (2-3-1. First embodiment)

[0059] Fig. 4 to Fig. Figure 6 are explanatory views that illustrate a coupling structure for an electrode pad according to a first embodiment of the present disclosure. Fig. Figure 4 is a top view showing a strain gauge mounted on an elastic body. Fig. Figure 5 is a sectional view along line II in Fig. 4 and Fig. 6 is a sectional view along line II-II in Fig. 4.

[0060] A strain gauge 201 is mounted on an elastic body 213 with an insulating layer 215 positioned between them. The elastic body 213 is made of a material with a predetermined stiffness, such as iron or another metal, and corresponds to the cylindrical section 11 in the six-component force detector 1 described above. The insulating layer 215 is made of an electrically insulating material and electrically isolates the strain gauge 201, which consists of a Cr-N thin film or the like, from the elastic body 213. If the elastic body 213 has a cylindrical shape or the like, the material of the insulating layer 215 is preferably a substance that can conform to a profile other than a completely flat surface, such as a curved surface.For example, the insulating layer 215 can be a thin film formed using a resin or plastic layer based on polyester, a resin or plastic layer based on polyimide or the like.

[0061] The strain gauge 201 comprises a measuring grid 203 and a tab 205. The measuring grid 203 includes straight sections 204 extending in a predetermined first direction (X-direction in the drawing). The straight sections 204 are arranged in an array or field orthogonal to the first direction in one direction (Y-direction in the drawing) and are electrically coupled in series. The tab 205 comprises a first tab 205a and a second tab 205b, which are provided at both ends of the measuring grid 203 (hereinafter collectively referred to as tab 205, unless otherwise specified). The tab 205 is located on the side of the first direction (X-direction) with respect to the measuring grid 203.

[0062] The first tab 205a and the second tab 205b are electrically coupled to a first electrode pad 207a and a second electrode pad 207b, respectively (hereinafter collectively referred to as electrode pad 207, unless otherwise specified). Measuring leads 211a and 211b are electrically coupled to the first electrode pad 207a and the second electrode pad 207b, respectively, using solders 209a and 209b.

[0063] A coupling structure between the second tab 205b and the second electrode pad 207b is described as an example. In the present embodiment, the second tab 205b has an insert structure in which the second tab 205b is inserted into the second electrode pad 207b. For example, the second electrode pad 207b has a U-shaped region along a plane extending in the first direction (X-direction) and is arranged on the elastic body 213 such that the opening of the U-shape on a lateral side is located on the side of the measuring grid 203. That is, both legs (upper leg 207bu and lower leg 207bd) of the second electrode pad 207b, which has the U-shape, extend in the first direction (X-direction). The second tab 205b is formed in a state in which the second tab 205b enters the second electrode pad 207b, which has the U-shape, in the first direction.

[0064] As in Fig. As shown in Figure 6, the second electrode pad 207b in the present embodiment has a rectangular parallelepiped shape with a recess that is open towards the side of the measuring grid 203 and is formed in a state in which the second tab 205b enters the recess.

[0065] Accordingly, the contact area where the second tab 205b and the second electrode pad 207b are in contact is increased compared to a case where an electrode pad is simply stacked on a tab. This strengthens the coupling between the second tab 205b and the second electrode pad 207b and reduces the possibility of separation due to insufficient adhesion or detachment. Furthermore, since the coupling between the second tab 205b and the second electrode pad 207b is strengthened even when the temperature of the load cell changes, a decrease in the electrical conductivity of the coupling section between the second tab 205b and the second electrode pad 207b is prevented.

[0066] Since the second tab 205b also enters the second electrode pad 207b in the first direction (X-direction) in which the straight sections 204 of the measuring grid 203 extend (the influence on the strain of the second tab 205b is reduced), the detection accuracy for the amount of strain by the strain gauge 201 can be increased.

[0067] The second electrode pad 207b is also in contact with the second tab 205b and the insulating layer 215. Accordingly, the area formed by the second electrode pad 207b is extended compared to a case where one electrode pad is stacked on a tab, and the possibility of the solder 209b protruding from the second electrode pad 207b and coming into contact with the strain gauge material 201 is reduced. This prevents the properties of the strain gauge material 201 from changing when high-temperature heat is applied.

[0068] The material forming the second electrode pad 207b is preferably a material that is less likely to alloy with the solder when high-temperature heat is applied during soldering or similar processes. This is because, when an alloy is formed, the electrical resistance changes, making it difficult to establish the bridge equilibrium. Furthermore, the material forming the second electrode pad 207b is preferably a material that exhibits good wettability with respect to the solder and results in a smaller contact angle of the solder 209b bonded to the upper leg 207bu. This is because the smaller the contact angle of the solder 209b, the greater the stability of the bond.

[0069] Furthermore, the material forming the second electrode pad 207b is preferably selected with respect to the linear coefficient of thermal expansion of the solder 209b. This is because if the linear coefficient of thermal expansion of the second electrode pad 207b is significantly larger than the linear coefficient of thermal expansion of the solder 209b, the thermal stress generated by the transfer of high-temperature heat to the second electrode pad 207b during soldering will be increased, and the thermal stress applied to the second tab 205b may be increased by the thermal expansion of the second electrode pad 207b. The linear coefficient of thermal expansion of the general solder 209b is 20 × 10 -6 / K to 22 × 10 -6 / K, and therefore the linear coefficient of thermal expansion of the material of the second electrode pad 207b is desirablely within a range of 30 × 10 -6 / K.

[0070] For example, the material of the second electrode pad can be 207b Ag (linear coefficient of thermal expansion: 19 × 10 -6 / K), Cu (linear coefficient of thermal expansion: 17 × 10 -6 / K) or Au (linear coefficient of thermal expansion: 14 × 10 -6 / K). For example, the tensile or compressive stress generated in the second electrode pad 207b at the time of soldering is smaller the smaller the linear coefficient of thermal expansion of the material of the second electrode pad 207b, and the smaller the tensile or compressive stress applied to the second tab 205b. Therefore, the material of the second electrode pad 207b is preferably Au.

[0071] In the present embodiment, any one of the insulating layer 215, the strain gauge 201, and the electrode pad 207 (the first electrode pad 207a and the second electrode pad 207b), which define the coupling structure for the electrode pad, is formed using a thin film. That is, any one of the insulating layer 215, the strain gauge 201, and the electrode pad 207 is formed using a thin film formed by a stacking step of stacking a material to form a thin film, a development step of stacking a resist layer onto the formed thin film, and then of forming a desired pattern by photolithography, and a structuring step of etching the thin film in an area not masked by the resist layer to form a thin film with a desired pattern.

[0072] For example, in the present embodiment, after the lower leg (207bd) of the electrode pad 207, which has the U-shape area, is formed, the strain gauge 201, which includes the tab 205, is formed, and then the upper leg (207bu) of the electrode pad 207 is formed so that the insert structure in which the tab 205 is / will be inserted into the electrode pad 207 can be formed.

[0073] In the Fig. In the coupling structure for the electrode pad shown in Figure 4, the tab 205 is fully inserted into the electrode pad 207, but the tab 205 can also be partially inserted into the electrode pad 207. Even after the insulating layer 215, the strain gauge 201, and the electrode pad 207 are formed on the elastic body 213, and the measuring lead 211 is coupled to the electrode pad 207 using the solder 209, the resultant is covered with an electrically insulating protective film, but this protective film is not shown.

[0074] As described above, the coupling structure for the electrode pad according to the present embodiment features an insert structure in which the tab of the strain gauge is partially or completely inserted into the electrode pad. Accordingly, the coupling between the tab and the electrode pad is strengthened, and the occurrence of separation or conduction failure between the strain gauge and the electrode pad can be prevented. Furthermore, in the coupling structure for the electrode pad according to the present embodiment, the possibility of the solder coming into contact with the strain gauge during soldering is reduced, and the occurrence of separation or conduction failure due to a change in the properties of the strain gauge can be prevented.

[0075] Furthermore, with the coupling structure for the electrode pad according to the present embodiment, the coupling reliability between the strain gauge and the measuring lead is improved, and it is possible to increase the yield or output at the time of manufacture of the six-component force detector in which ten or more strain gauges are arranged on the elastic body and to increase the reliability of the measurement result. (2-3-2. Second embodiment)

[0076] Fig. 7 to Fig. Figure 10 are explanatory views that illustrate a coupling structure for an electrode pad according to a second embodiment of the present disclosure. Fig. Figure 7 is a top view showing a strain gauge mounted on an elastic body, and Fig. Figure 8 is a top view showing a planar shape of a tab. Fig. Figure 9 is a sectional view along line III-III in Fig. 7, and Fig. 10 is a sectional view along line IV-IV in Fig. 7.

[0077] Similar to the strain gauge 201 of the first embodiment, a strain gauge 221 is arranged on an elastic body 233 with an insulating layer 235 positioned between them. The strain gauge 221 includes a measuring grid 223 and a tab 225. A first tab 225a and a second tab 225b are electrically coupled to a first electrode pad 227a and a second electrode pad 227b, respectively (hereinafter collectively referred to as electrode pad 227, unless otherwise specified). Measuring leads 231a and 231b are electrically coupled to the first electrode pad 227a and the second electrode pad 227b, respectively, using solders or soldering materials 229a and 229b.

[0078] A coupling structure between the second tab 225b and the second electrode pad 227b is described as an example. In the present embodiment, an insert structure is provided in which each of the second tab 225b and the second electrode pad 227b is partially inserted into the other.

[0079] As in Fig. As shown in Figure 8, the second tab 225b has elongated holes 226, each of which extends in a predetermined second direction (X-direction in the example in Fig. 8) have an extending longitudinal direction and penetrate the second tab 225b in a thickness direction thereof. As in Fig. As shown in Figure 10, the second electrode pad 227b also has a comb-like cross-sectional shape and is configured in such a way that the comb teeth engage in the elongated holes 226 of the second tab 205b. That is, each of the comb teeth is configured so that its longitudinal direction is oriented in the predetermined second direction (X-direction in the example shown in Figure 10). Fig. 8) extends.

[0080] Accordingly, the contact area where the second tab 225b and the second electrode pad 227b are in contact with each other is increased compared to a case where an electrode pad is simply stacked on a tab. Thus, the coupling between the second tab 225b and the second electrode pad 227b is strengthened, and the possibility of separation due to insufficient adhesion or detachment is reduced. Furthermore, since the coupling between the second tab 225b and the second electrode pad 227b is strengthened even when the temperature of the load cell changes, a decrease in the electrical conductivity of the coupling section between the second tab 225b and the second electrode pad 227b can be prevented.

[0081] The second direction in which the elongated holes 226 of the second tab 225b and the comb teeth of the second electrode pad 227b extend can differ from the first direction (X-direction). However, if the second direction extends in the same direction as the first (reducing the influence on the strain of the second tab 225b), the detection accuracy for the amount of strain by the strain gauge 221 can be increased. The number of elongated holes 226 and the number of comb teeth are not limited to the example shown and can be any number.

[0082] The material of the second electrode pad 227b can be selected in a similar manner to the material of the second electrode pad 227b of the first embodiment. Even in the present embodiment, any of the insulating layer 235, the strain gauge 221, and the electrode pad 227 (the first electrode pad 227a and the second electrode pad 227b), which define the coupling structure for the electrode pad, is formed using a thin film.That is, any one of the insulating layer 235, the strain gauge 221 and the electrode pad 227 is formed using a thin film formed by a stacking step of stacking a material to form a thin film, a development step of stacking a resist layer onto the formed thin film and then forming a desirable pattern by photolithography and a structuring step of etching the thin film in an area not masked by the resist layer to form a thin film with a desirable pattern.

[0083] The coupling structure for the electrode pad according to the present embodiment, described above, can also provide similar effects to those of the coupling structure for the electrode pad according to the first embodiment. Instead of providing the elongated holes in the tab, the tab can be formed in a grid shape, and the electrode pad can be partially inserted into the grid's gaps to form an insert structure. Even with such an insert structure, the contact area between the tab and the electrode pad is increased, and the coupling between the tab and the electrode pad can be strengthened.

[0084] Although the desirable embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited to such examples. It will be obvious to the person skilled in the art in the field to which the present disclosure relates that various modifications and variations can be conceived without departing from the technical idea of ​​the disclosure as defined by the accompanying claims. These modifications and variations obviously relate to the technical scope of the present disclosure.

[0085] For example, in the embodiment described above, the technique of the present disclosure is applied to the six-component force detector, which detects the load applied to the wheel, as the load cell. However, the target to which the technique of the present disclosure is applied is not limited to the six-component force detector. The technique of the present disclosure can be applied to various force detection sensors using a strain gauge.

[0086] The embodiment described above also included the example of a load cell using a uniaxial strain gauge, but the load cell to which the technique of the present disclosure can be applied is not limited to such an example. For example, the technique of the present disclosure can also be applied to a load cell using a biaxial shear strain gauge, which is described in Fig. 11 and Fig. 12 is shown.

[0087] For example, Fig. 11 a schematic view showing an arrangement of strain gauges in a six-component force detector of a modification, and Fig. Figure 12 is an explanatory view showing a measurement strip pattern of a biaxial shear strain gauge. The in Fig. The six-component force detector shown in Figure 11 is provided with shear strain gauges 271 and 272 of the Fx detection system and shear strain gauges 275 and 277 of the Fz detection system, which are described below, instead of the strain gauges 21 to 24 of the Fx detection system and the strain gauges 31 to 34 of the Fz detection system described above. Fig. Figure 12 presents the shear strain gauge 271 as an example, but the shear strain gauges 272, 275 and 277 also have an essentially identical measuring strip pattern.

[0088] The shear strain gauge 271 has a so-called arrow-shaped biaxial (bipolar) structure. In the shear strain gauge 271, a first detector 271a and a second detector 271b, consisting of a Cr-N thin film or the like, are formed on a common insulating layer 271c, which is a thin film of an insulating body. Each of the first detector 271a and the second detector 271b is formed by sequentially coupling straight sections arranged in series in parallel along their respective detection directions. The first detector 271a and the second detector 271b are adjusted such that their electrical resistances are likely to change in accordance with the strain in a direction (detection direction) in which straight sections expand or contract.The detection directions of the first detector 271a and the second detector 271b are adjusted so that they are substantially orthogonal to each other. The shear strain gauge 271 is attached to an outer circumferential surface of a cylindrical section 250 such that the detection directions of the first detector 271a and the second detector 271b are inclined in opposite directions by 45 degrees with respect to the central axis of the cylindrical section 250. The shear strain gauges 272, 275, and 277 are similarly attached to the outer circumferential surface of the cylindrical section 250.

[0089] As in Fig. As shown in Figure 11, shear strain gauges 271, 272, 275, and 277 are attached to the outer circumferential surface of a central section of the cylindrical section 250 in the direction of the central axis. Shear strain gauge 271 of the Fx detection system is located between strain gauges 251 and 252 of the Mx detection system. Shear strain gauge 272 of the Fx detection system is located between strain gauges 253 and 254 of the Mx detection system (at a position symmetrical to shear strain gauge 271 with respect to the central axis). Shear strain gauge 275 of the Fz detection system is located between strain gauges 261 and 262 of the Mz detection system. The shear strain gauge 277 of the Fz detection system is arranged between strain gauges 263 and 264 of the Mz detection system (at a position that is symmetrical to the shear strain gauge 275 with respect to the central axis).

[0090] Furthermore, strain gauges 281 to 284 of the Fy detection system and strain gauges 291 to 294 of the My detection system are arranged at positions offset around the central axis to avoid interference with strain gauges 271 and 272 of the Fx detection system and strain gauges 275 and 277 of the Fz detection system. For example, as shown in Fig. Figure 11 shows that the shear strain gauge 271, the strain gauge 282, the strain gauge 292, the shear strain gauge 277, the strain gauge 284, the strain gauge 294, the shear strain gauge 272, the strain gauge 283, the strain gauge 293, the shear strain gauge 275, the strain gauge 281 and the strain gauge 291 are arranged sequentially at positions that are displaced at intervals of 30 degrees around the central axis in the circumferential direction of the cylindrical section 250.

[0091] A first detector and a second detector, each incorporated in the shear strain gauges 271 and 272 of the Fx detection system, define a bridge circuit that corresponds to the one described in Fig. The bridge circuit is similar to the one shown in Figure 3. The bridge circuit generates an output corresponding to an Fx directional component force input into the sensitive body 250. Likewise, a first detector and a second detector, each included in the shear strain gauges 275 and 277 of the Fx detection system, define a bridge circuit similar to the one shown in Figure 3. Fig. The bridge circuit shown in Figure 3 is similar. The bridge circuit generates an output that corresponds to an Fz-direction component force input into the sensitive body 250.

[0092] The technique of the present disclosure can also be applied to the load cell using the biaxial shear strain gauge set up as described above, and the effects obtained by the embodiment described above can be achieved. REFERENCE MARK LIST

[0093] 21, 22, 23, 24: strain gauge, 80: bridge circuit, 201, 221: strain gauge, 203, 223: measuring grid, 204, 224: straight section, 205, 225: tab, 205a, 225a: first tab, 205b, 225b: second tab, 207, 227: electrode pad, 207a, 227a: first electrode pad, 207b, 227b: second electrode pad, 207bd, 207bu: leg, 209, 209a, 209b, 229, 229a, 229b: perpendicular, 211, 211a, 211b, 231, 231a ·231b: measuring lead, 213, 233: elastic body, 215, 235: insulating layer QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2019-074454

[0003] JP 2019-090722

[0003]

Claims

[1] Coupling structure for an electrode pad, arranged for electrically coupling the electrode pad, to which a measuring line is coupled, with a tab of a strain gauge arranged on an elastic body and comprising a measuring grid and the tab, wherein the coupling structure has an insert structure into which one of the tab and the electrode pad is partially or completely inserted into another of the tab and the electrode pad. [2] Coupling structure for the electrode pad according to claim 1, in which the electrode pad, having a U-shaped portion, is arranged on the elastic body so that an opening of the U-shaped portion is located on a lateral side, and wherein the tab is inserted into the electrode pad, which has the U-shape. [3] Coupling structure for the electrode pad according to claim 2, in which the measuring grid comprises rectilinear sections each extending in a predetermined first direction, and wherein both legs of the electrode pad having the U-shape extend in the first direction, and the tab enters the electrode pad having the U-shape in the first direction. [4] Coupling structure for the electrode pad according to claim 1, in which the tab has elongated holes each having a longitudinal direction extending in a predetermined second direction and penetrating the tab in a thickness direction of the tab, or grooves recessed in the thickness direction of the tab, and wherein the electrode pad has a comb-like cross-sectional shape, and comb teeth of the electrode pad enter the elongated holes or the grooves. [5] Coupling structure for the electrode pad according to claim 4, in which the measuring grid comprises rectilinear sections each extending in a predetermined first direction, and wherein the second direction extends in a same direction as the first direction. [6] Coupling structure for the electrode pad according to claim 1, in which the strain gauge is arranged on the elastic body with an insulating layer arranged therebetween, and wherein the electrode pad is formed in contact with the tab and the insulating layer. [7] The coupling structure for the electrode pad according to claim 1, wherein the strain gauge is made of Cr-N and the electrode pad is made of Au.

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