Force Sensor

Abstract

To provide a force sensor that can achieve improvement in detection sensitivity to strain by alleviating an impact of noise.SOLUTION: A force sensor comprises: a strain-inducing body (10) that has elasticity; an outer-side protrusion part (12) that extends over an entire circumference along a circumferential edge part of the strain-inducing body (10), and protrudes from a lower plane (102) of the strain-inducing body (10); an inner-side protrusion part (14) that protrudes from the lower plane (102); and strain sensitive members (21 to 24) that have an isotropic gauge factor in a principal plane direction of the strain-inducing body (10). The strain sensitive members (21 to 24) are arranged in designation latitude ranges (R1 and R2) of the principal plane (101) of the strain-inducing body (10). The strain sensitive members (21 to 24) are divided at one portion, and are composed of a pair of annular strain sensitive parts extending in an annular shape surrounding a pole (O) and a connection part connecting one end part of the pair of annular strain sensitive parts.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a force sensor using a strain-sensitive member. [Background technology]

[0002] The present inventor has proposed a force sensor that increases the amount of change in electrical resistance between the end points of a strain-sensitive member, thereby improving the measurement accuracy of the normal component of a force acting on a strain-generating body (see, for example, Patent Document 1). According to this force sensor, on the main surface of a strain-generating body whose entire periphery is supported continuously or discretely by a support portion, the strain-sensitive member is arranged so as to extend in a circular shape divided at one point within a designated latitudinal range that extends in a circular shape in the circumferential direction (latitude direction) to surround a pole. The "designated latitudinal range" is a latitudinal range within which the sum of the magnitudes of a first strain amount in the meridian direction of the strain-generating body and a second strain amount in the latitude direction of the strain-generating body is equal to or greater than a reference value.

[0003] When a force acts on the flexure element, the polarity of the normal component of the strain of the flexure element at each of a pair of locations on opposite sides of the pole in the latitudinal range will be the same, while the polarity of the principal-plane component of the strain will be opposite. Therefore, at the pair of locations of the strain-sensitive member extending in an annular shape and divided at a single location surrounding the pole, changes in electrical resistance corresponding to the normal component of the strain of the flexure element will be superimposed, while changes in electrical resistance corresponding to the principal-plane component of the strain of the flexure element will be offset. Therefore, based on the amount of change in electrical resistance between the end points of the strain-sensitive member, the principal-plane component of the force acting on the flexure element can be at least partially eliminated, and the normal component of the force can be measured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-153791 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the force sensor having the above configuration is susceptible to the influence of noise, which may reduce the sensitivity to detect minute strains in the strain generating body.

[0006] An object of the present invention is to provide a force sensor that can improve the detection sensitivity for strain by reducing the influence of noise. [Means for solving the problem]

[0007] The force sensor of the invention comprises: a plate-shaped strain generating body having a pair of opposing main surfaces; an outer protrusion extending continuously or discretely along the entire periphery of the flexure body and protruding from a main surface of the flexure body; a strain-sensitive member disposed on a main surface of the strain generating body and having an isotropic gauge factor in the direction of the main surface; an inner protrusion protruding from the main surface of the flexure body at a position more inward than the outer protrusion of the flexure body, When a vibration having a component in the direction perpendicular to the main surface acts on the flexure body, and when a force having a component in the direction perpendicular to the main surface acts on the flexure body, the magnitude of the sum of a first strain amount in the meridian direction of the flexure body and a second strain amount in the latitude direction of the flexure body with the pole as the reference is equal to or greater than a reference value, the flexure bodies extend in a ring shape surrounding the pole divided at one point and are separated from each other in the meridian direction within a commonly specified latitude range. Consists of an inner annular strain-sensitive portion and an outer annular strain-sensitive portion a pair of annular strain-sensitive portions; The inner annular distortion part and the outer annular distortion part and a connecting portion connecting one end of each of the strain-sensitive member. 、 The other end of the inner annular strain-sensitive portion is connected to a terminal via a conducting wire member, The other end of the outer annular strain-sensitive portion is connected to another terminal via a conductive wire member, The strain-sensitive member and the area surrounded by a line connecting the other ends of the inner annular strain-sensitive portion and the outer annular strain-sensitive portion extend in a circular ring shape surrounding the polar point divided at one point. are.

[0008] In this force sensor, strain-sensitive members are arranged in a designated latitudinal range extending annularly so as to surround the pole on the main surface of the strain-generating body, the entire periphery of which is continuously supported by the outer protrusion. Each strain-sensitive member is composed of a pair of annular strain-sensitive portions separated at one point in the common designated latitudinal range and extending annularly so as to surround the pole, and a connecting portion connecting one end of each of the pair of annular strain-sensitive portions (see Figure 1).

[0009] When a force acts on the flexure element 10, the polarity of the strain generated when a force in the vertical direction (z direction) acts on the flexure element 10 at each of a pair of locations on opposite sides of the pole O in each of the specified latitude ranges will be the same (see FIG. 5A). On the other hand, in this case, the polarity of the strain generated when a force in the principal surface direction (x, y directions) acts on the flexure element 10 at each of the pair of locations will be opposite (see FIGS. 5B and 5C). In FIGS. 5A to 5C, the strain-sensitive members are designated by the reference numeral "20."

[0010] Therefore, at each of the pair of locations of the strain-sensitive member, which is composed of a pair of annular strain-sensitive portions separated at one location, changes in electrical resistance value corresponding to the normal component of the force (inertial force) acting on the strain-generating body are superimposed, while changes in electrical resistance value corresponding to the main-plane component of the force (inertial force) can be offset. Therefore, based on the amount of change in electrical resistance value between each end point of the strain-sensitive member, the main-plane component of the force acting on the strain-generating body can be removed, and the normal component of the force can be measured.

[0011] Furthermore, the inward protrusion of the flexure body increases the inertial force acting on the flexure body. Furthermore, each of the specified latitude ranges is a latitude range in which the magnitude of the absolute value of the sum of the first strain amount in the meridian direction of the flexure body and the second strain amount in the latitude direction is equal to or greater than a reference value (see Figure 3). This increases the amount of change in electrical resistance between the end points of the strain-sensitive member, and ultimately improves the measurement accuracy of the normal component of the vibration (acceleration) acting on the flexure body.

[0012] The area surrounded by the pair of annular strain-sensitive portions constituting each strain-sensitive member, i.e., the area of ​​the surrounding area extending in a substantially annular (circular) shape divided at one point, is narrower than the area of ​​the surrounding area surrounded by the single annular strain-sensitive portion when each strain-sensitive member is composed of a single annular strain-sensitive portion of substantially the same diameter divided at one point. As a result, the large area of ​​the surrounding area reduces noise resulting from each strain-sensitive member functioning as an antenna.

[0013] In the force sensor having the above configuration, It is preferable that the pair of annular strain-sensitive portions are arranged on the main surface of the strain generating body so that the azimuth angle ranges of the respective dividing points of the pair of annular strain-sensitive portions relative to the pole point at least partially overlap.

[0014] According to the force sensor having this configuration, the conductive members (connecting portions, lead members, and / or resistive members) formed on the main surfaces of the strain generating body to configure the strain detection circuit and connected to at least one end of each of the pair of annular strain-sensitive portions can be shortened and / or the area at least partially surrounded by the conductive members can be narrowed, thereby reducing noise resulting from the conductive members functioning as part of the antenna.

[0015] In the force sensor having the above configuration, A plurality of the strain-sensitive members are arranged, The plurality of strain-sensitive members include On the main surface of the strain generating body, the azimuth angle ranges of the dividing points of the pair of annular strain sensitive portions of each of the plurality of strain sensitive members formed in the common specified latitude range with the pole as the reference are at least partially overlapped. , distribution It is preferable that the

[0016] According to the force sensor having this configuration, the conductive members (connecting portions, lead members, and / or resistive members) connected to at least one end of a pair of annular strain-sensitive portions constituting each of the plurality of strain-sensitive members, which are formed in a common specified latitude range on the main surface of the strain generating body to constitute the strain detection circuit, can be shortened and / or the area at least partially surrounded by the conductive members can be narrowed, thereby reducing noise resulting from the conductive members functioning as part of the antenna.

[0017] In the force sensor having the above configuration, A plurality of the strain-sensitive members are arranged, The plurality of strain-sensitive members include On the main surface of the strain generating body, the azimuth angle ranges of the dividing points of the pair of annular strain sensitive portions of the strain sensitive members formed in each of the plurality of specified latitude ranges with the pole as the reference are at least partially overlapped. , distribution It is preferable that the

[0018] According to the force sensor having this configuration, the conductive members (connecting portions, lead members, and / or resistive members) connected to at least one end of each of a pair of annular strain-sensitive portions constituting each of the strain-sensitive members formed in each of the plurality of specified latitude ranges on the main surface of the strain generating body to form the strain detection circuit can be shortened and / or the area at least partially surrounded by the conductive members can be narrowed, thereby reducing noise resulting from the conductive members functioning as part of the antenna. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is an explanatory diagram relating to the configuration of a force sensor according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the force sensor taken along line II-II in FIG. [Figure 3] FIG. 4 is an explanatory diagram illustrating one strain state of a strain element. [Figure 4] FIG. 2 is a diagram illustrating a strain detection circuit according to the first embodiment. [Figure 5A]FIG. 4 is an explanatory diagram relating to the function of the force sensor according to the first force application mode. [Figure 5B] FIG. 10 is an explanatory diagram relating to the function of the force sensor according to the second force application mode. [Figure 5C] FIG. 10 is an explanatory diagram relating to the function of the force sensor according to the third force application mode. [Figure 6] FIG. 6 is an explanatory diagram relating to the configuration of a force sensor according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a diagram illustrating a strain detection circuit according to a second embodiment. [Figure 8] FIG. 10 is an explanatory diagram relating to the configuration of a force sensor according to a third embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating a strain detection circuit according to a third embodiment. [Figure 10] FIG. 10 is an explanatory diagram relating to the configuration of a force sensor according to a fourth embodiment of the present invention. [Figure 11] FIG. 10 is a diagram illustrating a strain detection circuit according to a fourth embodiment. [Figure 12] FIG. 10 is an explanatory diagram relating to the configuration of a force sensor according to a fifth embodiment of the present invention. [Figure 13] FIG. 11 is a diagram illustrating a strain detection circuit according to a fifth embodiment. [Figure 14] 10 shows the applied load versus the measurement elapsed time in the load application test of the example. [Figure 15] 10 shows the results of a load application test on the force sensor of the embodiment. [Figure 16] 10A and 10B are enlarged views of the results of a load application test on the force sensor of the embodiment. [Figure 17] 10 shows the applied load versus the measurement elapsed time in the load application test of the comparative example. [Figure 18] 10 shows the results of a load application test on the force sensor of the comparative example. [Figure 19] FIG. 10 is an enlarged view of the results of a load application test on the force sensor of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0020] (First embodiment) (composition) 1 and 2, the force sensor according to the first embodiment of the present invention includes a strain-generating body 10 (strain-generating body), an outer protrusion 12, an inner protrusion 14, four strain-sensitive members 21 to 24, and eight conductor members L11, L12, L21, L24, L32, L33, L41, and L44. To explain the positions and orientations of the components of the force sensor, a three-dimensional Cartesian coordinate system (X, Y, Z) is used, with the center point of the top surface 101 of the strain-generating body 10 as the origin.

[0021] The flexure element 10 has a thickness direction in the Z direction and is formed in a generally circular plate shape having an upper surface 101 and a lower surface 102 as a pair of principal surfaces that are generally parallel to the XY plane. The thickness of the flexure element 10 may be uniform, or may be non-uniform, such as when there are locally thin regions. The shape of the flexure element 10 has rotational symmetry with respect to an axis (Z axis) that is parallel to the normal to the upper surface 101 and passes through the pole point O, or mirror symmetry with respect to a plane (for example, the XZ plane) that is perpendicular to the upper surface 101 and passes through the pole point O.

[0022] The flexure element 10 is supported by the outer protrusion 12 around the entire outer periphery. The outer protrusion 12 is formed in a substantially cylindrical shape. The outer protrusion 12 may have a flange-like protrusion that partially protrudes radially outward. The outer protrusion 12 may have a substantially cylindrical shape with an outer shape that is substantially uniform in the axial direction (z direction). The height position of the upper surface 101 of the flexure element 10 and the height position of the upper end surface of the outer protrusion 12 are the same. The flexure element 10 and the outer protrusion 12 are integrally molded structures formed by cutting and / or casting. The flexure element 10 and the outer protrusion 12 may be fixed by a mechanical fixing method such as bolts and nuts, or by a fixing method such as adhesive or welding. Furthermore, the continuous support pattern of the outer protrusion 12 at the outer periphery of the flexure element 10 has rotational symmetry with respect to the axis (which may be different from the rotational symmetry) or mirror symmetry with respect to the plane.

[0023] As described above, since the flexure element 10 is supported by the outer protrusions 12 along the entire periphery of the outer periphery, strain occurs in the flexure element 10 when a force is applied to the flexure element 10 .

[0024] The strain element 10 has a substantially cylindrical inner protrusion 14 that protrudes downward from the lower surface 102. The height position (Z coordinate value) of the lower end of the inner protrusion 14 is the same as the height position of the lower end of the outer protrusion 12. The inner protrusion 14 may have various shapes, such as a cylindrical shape, a prism shape, a truncated cone shape, a cone shape, or a pyramid shape, in addition to a cylindrical shape. The height position of the lower end of the inner protrusion 14 may be higher or lower than the height position of the outer protrusion 12.

[0025] FIG. 3 shows the calculation results of the strain characteristics of the flexure element 10 when an upward force (positive Z direction) is applied to the inner protrusion 14 of the flexure element 10. The change in the "first strain amount," which is the strain amount of the flexure element 10 in the meridian direction or radial direction from the pole O to the periphery of the flexure element 10, is shown by a solid line (ε r ), and the change in the "second strain amount" which is the strain amount of the strain element 10 in the latitude direction or the circumferential direction is indicated by a two-dot chain line (ε θ ), and the sum of the first strain and the second strain is indicated by the dashed line (ε r +ε θ ) The "negative" strain amount represents the amount of contraction of the flexure element 10 (more precisely, the upper surface 101 (the surface on the stress-applied side)), while the "positive" strain amount represents the amount of extension of the flexure element 10 (same as above).

[0026] 3, with the length D of the meridian as the reference, a range S1 of 0 to 0.25D from the pole point O corresponds to the region where the inward protrusion 14 exists on the lower surface 102 of the flexure element 10. A range S3 of 0.75D to 1.0D from the pole point O corresponds to the region where the outward protrusion 12 exists on the lower surface 102 of the flexure element 10. A range S2 of 0.25D to 0.75D from the pole point O corresponds to the intermediate region sandwiched between the outward protrusion 12 and the inward protrusion 14 on the lower surface 102 of the flexure element 10.

[0027] Here, the flexure element 10, outer protrusion 12, and inner protrusion 14 were integrally molded from SUS316L (Young's modulus: 193 GPa, Poisson's ratio: 0.28). The flexure element 10 was composed of a disk with a thickness of 0.05 mm and a diameter of 4.0 mm (=φ). The outer protrusion 12 was composed of a ring with a substantially cylindrical cross section, an inner diameter of 3.0 mm (=0.75φ), an outer diameter of 4.0 mm (=1.0φ), a protrusion (height) of 0.55 mm from the lower surface 102 of the flexure element 10, and a side wall thickness of 0.60 mm. The inner protrusion 14 was composed of a cylinder with a diameter of 1.0 mm (=0.25φ) and a protrusion (height) of 0.85 mm from the lower surface 102 of the flexure element 10.

[0028] The flexure element 10 is fixed to a support member (not shown) via the entire outer surface of the outer protrusion 12. When a force of 100 N acts uniformly in the Z direction on the end face of the inner protrusion 14 as an externally applied force, the strain in each of the meshes at 0.1 mm intervals defined in a cylindrical polar coordinate system (r, θ, z) with the center of the flexure element 10 as the reference was calculated using the finite element method.

[0029] When 80% of the maximum value of the sum (positive value) of the first strain amount and the second strain amount is set as the reference value, the magnitude of the sum (positive value) of the strain amounts is equal to or greater than the reference value in a first designated circular latitude range R1 located within a distance range of 0.254D to 0.321D from the pole O, based on the meridian length D. When 95% of the maximum value of the sum (positive value) of the first strain amount and the second strain amount is set as the reference value, the magnitude of the sum (positive value) of the strain amounts is equal to or greater than the reference value in a first designated circular latitude range R1 located within a distance range of 0.260D to 0.292D from the pole O, based on the meridian length D.

[0030] When 80% of the maximum absolute value of the sum (negative value) of the first strain amount and the second strain amount is set as the reference value, the magnitude of the absolute value of the sum (negative value) of the strain amounts is equal to or greater than the reference value in a second designated circular latitude range R2 located within a distance of 0.685D to 0.761D from the pole O, based on the meridian length D. When 95% of the maximum absolute value of the sum (negative value) of the first strain amount and the second strain amount is set as the reference value, the magnitude of the absolute value of the sum (positive value) of the strain amounts is equal to or greater than the reference value in a second designated circular latitude range R2 located within a distance of 0.718D to 0.755D from the pole O, based on the meridian length D.

[0031] In general, the first designated latitudinal range R1 and the second designated latitudinal range R2 change depending on the shape and size of the flexure body 10 and also on the force (inertial force) acting on the flexure body 10 due to vibration. Therefore, the first designated latitudinal range R1 and the second designated latitudinal range R2 can be adaptively set based on the expected acting force on the flexure body 10.

[0032] The flexure element 10 is made of, for example, an elastic metal or synthetic resin, or a combination of these. When the flexure element 10 is made of a conductive material such as metal, its upper surface 101 is covered with an insulating thin film at least in the areas where the strain-sensitive members 21-24 and the resistance members 41-42 are formed. This electrically insulates the flexure element 10 from the strain-sensitive members 21-24 and the resistance members 41-42.

[0033] A first strain-sensitive member 21 and a third strain-sensitive member 23 are arranged in a first designated latitudinal range R1 on the upper surface 101 of the flexure body 10. A second strain-sensitive member 22 and a fourth strain-sensitive member 24 are arranged in a second designated latitudinal range R2 on the upper surface 101 of the flexure body 10.

[0034] 1, the first strain-sensitive member 21 is composed of a pair of annular strain-sensitive portions, i.e., a first inner annular strain-sensitive portion 211 and a first outer annular strain-sensitive portion 212, which are spaced apart in the meridian direction and extend in an annular (substantially circular) shape surrounding a polar point O separated at one point in a first specified latitude range R1, and a first connecting portion 210 connecting one end of each of the pair of annular strain-sensitive portions 211 and 212. The pair of annular strain-sensitive portions 211 and 212 are arranged so that the azimuthal ranges of the separating points of the first inner annular strain-sensitive portion 211 and the first outer annular strain-sensitive portion 212 as seen from the polar point O are approximately the same.

[0035] 1, the third strain-sensitive member 23 is composed of a pair of annular strain-sensitive portions, i.e., a third inner annular strain-sensitive portion 231 and a third outer annular strain-sensitive portion 232, which are spaced apart in the meridian direction and extend in an annular (substantially circular) shape surrounding a polar point O separated at one point in the first specified latitude range R1, and a third connecting portion 230 connecting one end of each of the pair of annular strain-sensitive portions 231 and 232. The pair of annular strain-sensitive portions 231 and 232 are arranged so that the azimuthal ranges of the separating points of the third inner annular strain-sensitive portion 231 and the third outer annular strain-sensitive portion 232 as seen from the polar point O are approximately the same.

[0036] 1, in the first designated latitude range R1, four substantially annular strain-sensitive portions 231, 211, 212, and 232 are arranged in order from the inside to the outside, spaced apart from one another in the radial direction (meridian direction). It is preferable that the distance between adjacent strain-sensitive portions among the annular strain-sensitive portions 231, 211, 212, and 232 is not more than twice the width of at least one of the adjacent strain-sensitive portions.

[0037] 1, the second strain-sensitive member 22 is composed of a pair of annular strain-sensitive portions, i.e., a second inner annular strain-sensitive portion 221 and a second outer annular strain-sensitive portion 222, which are spaced apart in the meridian direction and extend in an annular (substantially circular) shape surrounding a polar point O separated at one point in the second specified latitude range R2, and a second connecting portion 220 connecting one end of each of the pair of annular strain-sensitive portions 221 and 222. The pair of annular strain-sensitive portions 221 and 222 are arranged so that the azimuthal ranges of the separating points of the second inner annular strain-sensitive portion 221 and the second outer annular strain-sensitive portion 222 as seen from the polar point O are approximately the same.

[0038] 1, the fourth strain-sensitive member 24 is composed of a pair of annular strain-sensitive portions, i.e., a fourth inner annular strain-sensitive portion 241 and a fourth outer annular strain-sensitive portion 242, which are spaced apart in the meridian direction and extend in an annular (substantially circular) shape surrounding the polar point O separated at one point in the second specified latitude range R2, and a fourth connecting portion 240 connecting one end of each of the pair of annular strain-sensitive portions 241 and 242. The pair of annular strain-sensitive portions 241 and 242 are arranged so that the azimuthal ranges of the separating points of the fourth inner annular strain-sensitive portion 241 and the fourth outer annular strain-sensitive portion 242 as seen from the polar point O are approximately the same.

[0039] 1, in the second designated latitude range R2, four substantially annular strain-sensitive portions 221, 241, 242, and 222 are arranged in order from the inside to the outside, spaced apart from one another in the radial direction (meridian direction). It is preferable that the distance between adjacent strain-sensitive portions among the annular strain-sensitive portions 221, 241, 242, and 222 is not more than twice the width of at least one of the adjacent strain-sensitive portions.

[0040] On the upper surface 101 of the strain generating body 10, the four strain-sensitive members 21 to 24 are arranged so that the azimuth angle ranges of the respective dividing points of the first inner annular strain-sensitive portion 211 and the first outer annular strain-sensitive portion 212, the azimuth angle ranges of the respective dividing points of the second inner annular strain-sensitive portion 221 and the second outer annular strain-sensitive portion 222, the azimuth angle ranges of the respective dividing points of the third inner annular strain-sensitive portion 231 and the third outer annular strain-sensitive portion 232, and the azimuth angle ranges of the respective dividing points of the fourth inner annular strain-sensitive portion 241 and the fourth outer annular strain-sensitive portion 242 at least partially overlap when viewed from the pole point O.

[0041] The orientation of the dividing point of at least one member may be different from the orientation of the dividing points of the other members. For example, the azimuth angle ranges of the dividing points of the first inner annular strain-sensitive portion 211 and the first outer annular strain-sensitive portion 212 and the third inner annular strain-sensitive portion 231 and the third outer annular strain-sensitive portion 232, which at least partially overlap when viewed from the pole point O in the first specified latitudinal range R1, may not overlap with the azimuth angle ranges of the dividing points of the second inner annular strain-sensitive portion 221 and the second outer annular strain-sensitive portion 222 and the fourth inner annular strain-sensitive portion 241 and the fourth outer annular strain-sensitive portion 242, which at least partially overlap when viewed from the pole point O in the second specified latitudinal range R2.

[0042] In the first specified latitude range R1, the azimuth angle ranges of the dividing points of the first inner annular strain-sensitive portion 211 and the first outer annular strain-sensitive portion 212 and the azimuth angle ranges of the dividing points of the third inner annular strain-sensitive portion 231 and the third outer annular strain-sensitive portion 232 may not overlap when viewed from the pole point O. In the second specified latitude range R2, the azimuth angle ranges of the dividing points of the second inner annular strain-sensitive portion 221 and the second outer annular strain-sensitive portion 222 and / or the azimuth angle ranges of the dividing points of the fourth inner annular strain-sensitive portion 241 and the fourth outer annular strain-sensitive portion 242 may not overlap when viewed from the pole point O.

[0043] Each of the strain-sensitive members 21 to 24 is formed on the upper surface 101 of the strain generating element 10. Each of the strain-sensitive members 21 to 24 has isotropy with respect to the gauge factor (the gauge factor is 3 or more), and is made of, for example, a Cr thin film made of Cr and unavoidable impurities, or a Cr-N thin film made of Cr, N and unavoidable impurities, as described in Patent Document 1. The Cr-N thin film is, for example, a thin film of the general formula Cr 100-x N x where the composition ratio x is 0.0001≦x≦30 in atomic percent.

[0044] Each of the strain-sensitive members 21 to 24 is made of a material having the general formula Cr 100-x Mn x (x is atomic %, and 0.1≦x≦34) or the general formula Cr 100-x Al x Each of the strain-sensitive members 21 to 24 may be made of a Cr-based thin film represented by the general formula Cr (where x is atomic %, and 4≦x≦25) (see Patent Document 2). 100-x-y Al x N y (x and y are atomic percentages, and 4≦x≦25, 0.1≦y≦20) (see Patent Document 3). The thin film is formed on the upper surface 101 of the flexure element 10 by a sputtering method or the like. The Cr—N thin film has an extremely small temperature coefficient of resistance (TCR) (<±50 ppm / °C), and is therefore stable against temperature changes.

[0045] The large gauge factor and transverse sensitivity of approximately 3 or greater across the entire temperature range from near room temperature to near 500°C are inherent properties of Cr thin films. This property is not only observed in Cr-N, Cr-Mn, Cr-Al, and Cr-Al-N thin films, but also in films containing one or more other elements, even if the Cr content is high. Therefore, these films are also included in the Cr-based thin films that make up the strain-sensitive members 21-24. Furthermore, thin films containing Cr-SiO2, Cr-Al2O3, Cr-SiC, Cr-Cr oxide, and Cr-Cr nitride—those in which other compounds are dispersed and precipitated within a Cr matrix—also exhibit the above property when the Cr content is high. Therefore, these films are also included in the Cr-based thin films that make up the strain-sensitive members 21-24. Furthermore, thin films containing a mixture of Cr and one or more of a Cr nitride phase, a Cr oxide phase, and a Cr carbide phase also retain the above Cr properties when the Cr content is high. Conversely, all thin films containing Cr as a main component and having the above properties are Cr-based thin films that make up the strain-sensitive members 21-24.

[0046] The four strain-sensitive members 21 to 24 form a bridge circuit of the four active gauge method as shown in Fig. 4. As shown in Fig. 1, terminals T1 to T4 of the bridge circuit are formed inside a first designated latitudinal range R1 on the top surface 101 of the flexure element 10. At least some of the terminals T1 to T4 of the bridge circuit may be formed on the top surface 101 of the flexure element 10 in an intermediate latitude range between the first designated latitudinal range R1 and the second designated latitudinal range R2 and / or outside the second designated latitudinal range R2.

[0047] The first strain-sensitive member 21 is connected to the first terminal T1 at the other end of the first inner annular strain-sensitive portion 211 via a conductor L11, and to the second terminal T2 at the other end of the first outer annular strain-sensitive portion 212 via a conductor L12. The second strain-sensitive member 22 is connected to the fourth terminal T4 at the other end of the second inner annular strain-sensitive portion 221 via a conductor L24, and to the second terminal T2 at the other end of the second outer annular strain-sensitive portion 222 via a conductor L22. The third strain-sensitive member 23 is connected to the first terminal T1 at the other end of the third inner annular strain-sensitive portion 231 via a conductor L31, and to the third terminal T3 at the other end of the third outer annular strain-sensitive portion 232 via a conductor L33. The fourth strain-sensitive member 24 is connected to the fourth terminal T4 at the other end of the fourth inner annular strain-sensitive portion 241 via a conductor member L44, and is connected to the third terminal T3 at the other end of the fourth outer annular strain-sensitive portion 242 via a conductor member L43.

[0048] The thickness, width, length, and electrical properties such as electrical conductivity of each of the strain-sensitive members 21-24 are appropriately designed so that their resistance values ​​are all approximately the same from the perspective of configuring a bridge circuit (strain detection circuit). The thickness, width, length, and material (which determines the electrical conductivity) of each of the conductor members L11, L12, L22, L24, L31, L33, L43, and L44 are appropriately designed so that their resistance values ​​are all approximately the same from the perspective of configuring the bridge circuit, just like each of the strain-sensitive members 21-24.

[0049] To ensure the continuity of the thin film and prevent breakage, it is preferable to integrally mold the sensor thin film that constitutes the strain-sensitive element, including the conductor and terminal portions, and then overlay a film of Ni and / or Au, which has a low resistivity and gauge factor, on the conductor, terminal, and electrode portions to form the conductor, terminal, and electrode. This makes it less likely for the thin-film element to break, and also makes it possible to minimize the output (noise) and resistance from unrelated locations other than the detection target, such as the conductor and terminal portions, to a negligible level. Furthermore, the electrode portions must be made of a material suitable for connecting lead wires to extract signals externally.

[0050] (function) According to the force sensor of the first embodiment of the present invention, as shown in FIG. 1, strain-sensitive members 21 to 24 are arranged in a specified latitudinal range extending in an annular shape so as to surround a pole point O on a main surface 101 of a strain-generating body 10 whose entire periphery is continuously supported by an outer protrusion 12.

[0051] As shown in Figure 1, each strain-sensitive member 21, 22, 23, 24 is composed of a pair of annular strain-sensitive portions that are separated at one point within a common specified latitude range and extend in a ring shape to surround pole point O, and a connecting portion that connects one end of each of the pair of annular strain-sensitive portions.

[0052] When force F acts on the flexure body 10, the polarity of the strain generated when a force in the vertical direction (z direction) acts on each of a pair of locations on opposite sides of the pole O in each of the specified latitude ranges R1 and R2 will be the same (see FIG. 5A). On the other hand, in this case, the polarity of the strain generated when a force in the principal surface direction (x, y directions) acts on the flexure body 10 at each of the pair of locations will be opposite (see FIGS. 5B and 5C).

[0053] Therefore, at each pair of locations of the strain-sensitive members 21-24, which are made up of a pair of annular strain-sensitive portions separated at one location, changes in electrical resistance value corresponding to the normal component of the force (inertial force) acting on the strain body 10 are superimposed, while changes in electrical resistance value corresponding to the main surface component of the force (inertial force) can be canceled out. Therefore, based on the amount of change in electrical resistance value between the end points of the strain-sensitive members 21-24, the main surface component of the force acting on the strain body 10 can be removed, and the normal component of the force can be measured.

[0054] Furthermore, the inward protrusion 14 of the flexure body 10 increases the inertial force acting on the flexure body 10. Furthermore, each of the specified latitude ranges R1 and R2 is a latitude range in which the magnitude of the absolute value of the sum of the first strain amount in the meridian direction of the flexure body 10 and the second strain amount in the latitude direction is equal to or greater than a reference value (see FIG. 3). This increases the amount of change in the electrical resistance between the end points of the strain-sensitive members 21-24, and ultimately improves the measurement accuracy of the perpendicular component of the vibration (acceleration) acting on the flexure body 10.

[0055] Each of the strain-sensitive members 21 to 24 is made of one of the following Cr-based thin films: (1) a Cr-based thin film made of Cr and inevitable impurities, or a Cr-based thin film made of Cr, N, and inevitable impurities; (2) a Cr-based thin film made of Cr and Mn, or a Cr-based thin film made of Cr and Al; (3) a Cr-based thin film made of Cr, Al, and N; a Cr-based thin film containing one or more or many additive elements other than those listed in (1), (2), and (3) and having a high Cr content; Cr-SiO2, Cr-Al2O3, Cr-SiC, Cr-Cr oxide, Cr-Cr nitride, etc., i.e., a Cr-based thin film with a high Cr content and a thin film in which other compounds are dispersed and precipitated in a Cr matrix; a Cr-based thin film with a high Cr content and having a mixture of one or more of Cr and Cr nitride phases, Cr oxide phases, and Cr carbide phases, etc., that is, ... high Cr content. For this reason, the electrical resistance of the strain-sensitive members 21, 22 changes more significantly due to the contribution to changes in the lattice structure of the strain-sensitive members, and ultimately the band energy structure of carriers (electrons), than due to the contribution to changes in shape caused by longitudinal strain and lateral strain, thereby further improving the measurement accuracy of the vibration (acceleration) acting on the strain-generating body 10.

[0056] The area of ​​the region surrounded by a pair of annular strain-sensitive portions constituting each of the strain-sensitive members 21, 22, 23, and 24, i.e., the surrounding region extending in a substantially annular (circular) shape divided at one point, is narrower than the area of ​​the surrounding region surrounded by the single annular strain-sensitive portion when each of the strain-sensitive members is composed of a single annular strain-sensitive portion of substantially the same diameter divided at one point. As a result, the large area of ​​the surrounding region reduces noise resulting from each of the strain-sensitive members 21, 22, 23, and 24 functioning as an antenna.

[0057] (Second embodiment) (composition) 6, the force sensor according to the second embodiment of the present invention has a first strain-sensitive member 21 and a second strain-sensitive member 22 formed in a second designated latitudinal range R2 on the upper surface 101 of the strain generating body 10. The first strain-sensitive member 21 and / or the second strain-sensitive member 22 may be formed in the first designated latitudinal range R1 instead of the second designated latitudinal range R2.

[0058] As shown in Fig. 6, the first strain-sensitive member 21 is composed of a pair of annular strain-sensitive portions, i.e., a first inner annular strain-sensitive portion 211 and a first outer annular strain-sensitive portion 212, spaced apart from each other in the meridian direction and extending in an annular (substantially circular) shape surrounding the polar point O, which is separated at one point, in the second specified latitudinal range R2, and a first connecting portion 210 connecting one end of each of the pair of annular strain-sensitive portions 211 and 212. Also as shown in Fig. 6, the second strain-sensitive member 23 is composed of a pair of annular strain-sensitive portions, i.e., a second inner annular strain-sensitive portion 221 and a second outer annular strain-sensitive portion 222, spaced apart from each other in the meridian direction and extending in an annular (substantially circular) shape surrounding the polar point O, which is separated at one point, in the second specified latitudinal range R2.

[0059] 6, in the second designated latitude range R2, four substantially annular strain-sensitive portions 221, 211, 212, and 222 are arranged in order from the inside to the outside, spaced apart from one another in the radial direction (meridian direction). It is preferable that the distance between adjacent strain-sensitive portions among the annular strain-sensitive portions 221, 211, 212, and 222 is not more than twice the width of at least one of the adjacent strain-sensitive portions.

[0060] On the upper surface 101 of the flexure body 10, the two strain-sensitive members 21-22 are arranged so that the azimuth angle range of the dividing points of the first inner annular strain-sensitive portion 211 and the first outer annular strain-sensitive portion 212 as viewed from the pole point O at least partially overlaps with the azimuth angle range of the dividing points of the second inner annular strain-sensitive portion 221 and the second outer annular strain-sensitive portion 222. The orientation of the dividing point of at least one member (portion) may differ from the orientation of the dividing point of the other member.

[0061] As shown in Fig. 6, in the mid-latitude range between the first designated latitude range R1 and the second designated latitude range R2 on the top surface 101 of the flexure body 10, a first resistance member 41 and a second resistance member 42, each having a substantially arc shape, are formed in this order from the inside to the inside and spaced apart from each other in the radial direction. The two strain-sensitive members 21-22, together with the two resistance members 41-42, form a bridge circuit of the two-active gauge method as shown in Fig. 7. As shown in Fig. 6, terminals T1-T4 of the bridge circuit are formed in the mid-latitude range between the first designated latitude range R1 and the second designated latitude range R2 on the top surface 101 of the flexure body 10. At least some of the terminals T1-T4 of the bridge circuit may be formed inside the first designated latitude range R1 and / or outside the second designated latitude range R2 on the top surface 101 of the flexure body 10.

[0062] The first strain-sensitive member 21 is connected at the other end of the first inner annular strain-sensitive portion 211 to the second terminal T2 via a conductor L12, and at the other end of the first outer annular strain-sensitive portion 212 to the first terminal T1 via a conductor L11. The second strain-sensitive member 22 is connected at the other end of the second inner annular strain-sensitive portion 221 to the second terminal T2 via a conductor L22, and at the other end of the second outer annular strain-sensitive portion 222 to the third terminal T3 via a conductor L23. The first resistance member 41 is connected at one end to the first terminal T1 and at the other end to the fourth terminal T4. The second resistance member 42 is connected at one end to the third terminal T3 and at the other end to the fourth terminal T4.

[0063] The thickness, width, length, and electrical properties such as electrical conductivity of each of the strain-sensitive members 21-22 and the resistance members 41-42 are appropriately designed from the perspective of configuring a bridge circuit (strain detection circuit). The thickness, width, length, and material (which determines electrical conductivity) of the conductor members L11, L12, L22, and L23 are also appropriately designed from the perspective of configuring the bridge circuit, similar to each of the strain-sensitive members 21-22 and the resistance members 41-42.

[0064] Other than these points, the force sensor according to the second embodiment of the present invention has a configuration that is almost the same as that of the force sensor according to the first embodiment of the present invention (see Figures 1 and 2). Therefore, the same reference numerals are used for the common components and their explanations are omitted.

[0065] (Third embodiment) (composition) 8, the force sensor according to the second embodiment of the present invention has a first strain-sensitive member 21 and a second strain-sensitive member 22 formed in a second designated latitudinal range R2 on the upper surface 101 of the strain generating element 10. The first strain-sensitive member 21 and / or the second strain-sensitive member 22 may be formed in the first designated latitudinal range R1 instead of the second designated latitudinal range R2.

[0066] As shown in Fig. 8, the first strain-sensitive member 21 is composed of a pair of annular strain-sensitive portions, i.e., a first inner annular strain-sensitive portion 211 and a first outer annular strain-sensitive portion 212, spaced apart from each other in the meridian direction and extending in an annular (substantially circular) shape surrounding the polar point O, which is separated at one point, in the second specified latitudinal range R2, and a first connecting portion 210 connecting one end of each of the pair of annular strain-sensitive portions 211 and 212. Also as shown in Fig. 8, the second strain-sensitive member 22 is composed of a pair of annular strain-sensitive portions, i.e., a second inner annular strain-sensitive portion 221 and a second outer annular strain-sensitive portion 222, spaced apart from each other in the meridian direction and extending in an annular (substantially circular) shape surrounding the polar point O, which is separated at one point, in the second specified latitudinal range R2, and a second connecting portion 220 connecting one end of each of the pair of annular strain-sensitive portions 221 and 222.

[0067] 8, in the second specified latitude range R2, four substantially annular strain-sensitive portions 221, 211, 212, and 222 are arranged in order from the inside to the outside, spaced apart from one another in the radial direction (meridian direction). It is preferable that the distance between adjacent strain-sensitive portions among the annular strain-sensitive portions 221, 211, 212, and 222 is not more than twice the width of at least one of the adjacent strain-sensitive portions.

[0068] As shown in Fig. 8, in the mid-latitude range between the first designated latitude range R1 and the second designated latitude range R2 on the upper surface 101 of the flexure body 10, a first resistance member 41 and a second resistance member 42 each having a substantially arc shape are formed in order from the inside to be spaced apart from each other in the radial direction. The two strain-sensitive members 21-22, together with three resistance members 41-43, form a bridge circuit of the one active gauge method (series type) as shown in Fig. 9. As shown in Fig. 8, terminals T1-T4 of the bridge circuit are formed in the mid-latitude range between the first designated latitude range R1 and the second designated latitude range R2 on the upper surface 101 of the flexure body 10. At least some of the terminals T1-T4 of the bridge circuit may be formed inside the first designated latitude range R1 and / or outside the second designated latitude range R2 on the upper surface 101 of the flexure body 10.

[0069] The first strain-sensitive member 21 is connected at the other end of the first inner annular strain-sensitive portion 211 to the other end of the second inner annular strain-sensitive portion 221, and at the other end of the first outer annular strain-sensitive portion 212 to the first terminal T1 via a conductor member L11. The second strain-sensitive member 22 is connected at the other end of the second outer annular strain-sensitive portion 222 to the second terminal T2 via a conductor member L22. The first resistance member 41 is connected at one end to the first terminal T1 and at the other end to the fourth terminal T4. The second resistance member 42 is connected at one end to the second terminal T2 and at the other end to the third terminal T3. The third resistance member 43 is connected at one end to the third terminal T3 and at the other end to the fourth terminal T4.

[0070] The thickness, width, length, and electrical properties such as electrical conductivity of each of the strain-sensitive members 21-22 and the resistance members 41-43 are appropriately designed from the perspective of configuring a bridge circuit (strain detection circuit). The thickness, width, length, and material (which determines the electrical conductivity) of the conductor members L11 and L22 are also appropriately designed from the perspective of configuring the bridge circuit, similar to each of the strain-sensitive members 21-22 and the resistance members 41-43.

[0071] Other than these points, the force sensor according to the third embodiment of the present invention has a configuration that is almost the same as that of the force sensor according to the second embodiment of the present invention (see FIGS. 6 and 7). Therefore, the same reference numerals are used for the common components and their explanations are omitted.

[0072] (Fourth embodiment) (composition) 10, a force sensor according to a fourth embodiment of the present invention has a first strain-sensitive member 21 formed in a first designated latitudinal range R1 on the upper surface 101 of the strain generating body 10, and a second strain-sensitive member 22 formed in a second designated latitudinal range R2. Both the first strain-sensitive member 21 and the second strain-sensitive member 22 may be formed in the first designated latitudinal range R1 or the second designated latitudinal range R2.

[0073] 10, the first strain-sensitive member 21 is comprised of a pair of annular strain-sensitive portions, i.e., a first inner annular strain-sensitive portion 211 and a first outer annular strain-sensitive portion 212, spaced apart from each other in the meridian direction and extending in an annular (substantially circular) shape surrounding the polar point O separated at one point in the first specified latitudinal range R1, and a first connecting portion 210 connecting one end of each of the pair of annular strain-sensitive portions 211 and 212. Also shown in Fig. 10, the second strain-sensitive member 22 is comprised of a pair of annular strain-sensitive portions, i.e., a second inner annular strain-sensitive portion 221 and a second outer annular strain-sensitive portion 222, spaced apart from each other in the meridian direction and extending in an annular (substantially circular) shape surrounding the polar point O separated at one point in the second specified latitudinal range R2, and a second connecting portion 220 connecting one end of each of the pair of annular strain-sensitive portions 221 and 222.

[0074] The distance between adjacent annular strain-sensitive portions 211 and 212 is preferably not more than twice the width of at least one of the adjacent annular strain-sensitive portions. The distance between adjacent annular strain-sensitive portions 221 and 222 is preferably not more than twice the width of at least one of the adjacent annular strain-sensitive portions.

[0075] As shown in Fig. 10, a first resistance member 41 extending in a ring shape (substantially annular) surrounding a polar point O divided at one point is formed inside or near the inside of a first specified latitudinal range R1 on the upper surface 101 of the strain generating element 10, and a second resistance member 42 extending in a ring shape (substantially annular) surrounding the polar point O divided at one point is formed outside or near the outside of a second specified latitudinal range R2. The two strain-sensitive members 21-22, together with the two resistance members 41-42, constitute a bridge circuit of the two-side active gauge method (two-wire system) as shown in Fig. 11. The resistance members 41-42, together with the first strain-sensitive member 21 and the second strain-sensitive member 22, may also constitute a bridge circuit of the two-side active gauge method (three-wire system).

[0076] 10, terminals T1 and T4 of the bridge circuit are formed near the inside of the first designated latitudinal range R1 on the upper surface 101 of the flexure body 10, and terminals T2 and T3 of the bridge circuit are formed near the outside of the second designated latitudinal range R2. At least some of the terminals T1 to T4 of the bridge circuit may be formed in an intermediate latitude range between the first designated latitudinal range R1 and the second designated latitudinal range R2 on the upper surface 101 of the flexure body 10.

[0077] On the upper surface 101 of the flexure body 10, the two strain-sensitive members 21-22 and the two resistance members 41-42 are arranged so that the azimuth angle ranges of the dividing points of the first inner annular strain-sensitive portion 211 and the first outer annular strain-sensitive portion 212, the azimuth angle ranges of the dividing points of the second inner annular strain-sensitive portion 221 and the second outer annular strain-sensitive portion 222, the azimuth angle ranges of the dividing points of the first resistance member 41, and the azimuth angle ranges of the dividing points of the second resistance member 42 at least partially overlap when viewed from the pole point O. The orientation of the dividing points of at least one member (portion) may differ from the orientation of the dividing points of the other members (portions).

[0078] The first strain-sensitive member 21 is connected to the first terminal T1 at the other end of the first inner annular strain-sensitive portion 211 and to the second terminal T2 at the other end of the first outer annular strain-sensitive portion 212 via a conductor member L12. The second strain-sensitive member 22 is connected to the fourth terminal T4 at the other end of the second inner annular strain-sensitive portion 221 via a conductor member L24 and to the third terminal T3 at the other end of the second outer annular strain-sensitive portion 222. The first resistance member 41 is connected to the first terminal T1 at one end and to the fourth terminal T4 at the other end. The second resistance member 42 is connected to the second terminal T2 at one end and to the third terminal T3 at the other end.

[0079] The thickness, width, length, and electrical properties such as electrical conductivity of each of the strain-sensitive members 21-22 and the resistance members 41-42 are appropriately designed from the perspective of configuring a bridge circuit (strain detection circuit). The thickness, width, length, and material (which determines the electrical conductivity) of the conductor members L12 and L24 are also appropriately designed from the perspective of configuring the bridge circuit, similar to each of the strain-sensitive members 21-22 and the resistance members 41-42.

[0080] Other than these points, the force sensor according to the fourth embodiment of the present invention has a configuration that is almost the same as that of the force sensor according to the third embodiment of the present invention (see FIGS. 8 and 9). Therefore, the same reference numerals are used for the common components and their explanations are omitted.

[0081] (Fifth embodiment) (composition) In the force sensor according to the fifth embodiment of the present invention shown in Fig. 12, the strain-sensitive member 20 is formed in the second designated latitudinal range R2 on the upper surface 101 of the strain-generating body 10. The strain-sensitive member 20 may also be formed in the first designated latitudinal range R1.

[0082] As shown in Figure 12, the strain-sensitive member 20 is composed of a pair of annular strain-sensitive portions, i.e., an inner annular strain-sensitive portion 201 and an outer annular strain-sensitive portion 202, which are spaced apart from each other in the meridian direction and extend in an annular (approximately circular) shape surrounding a polar point O separated at one point in the second specified latitude range R2, and a connecting portion 200 which connects one end of each of the pair of annular strain-sensitive portions 201 and 202.

[0083] The distance between adjacent annular strain-sensitive portions of the annular strain-sensitive portions 201 and 202 is preferably equal to or less than twice the width of at least one of the adjacent annular strain-sensitive portions.

[0084] As shown in Fig. 12, a first resistance member 41 and a second resistance member 42 each having a substantially arc shape are formed in this order from the inside to be spaced apart from each other in the radial direction in the mid-latitude range between the first designated latitude range R1 and the second designated latitude range R2 on the upper surface 101 of the strain-generating body 10. The two strain-sensitive members 21-22, together with the three resistance members 41-43, form a bridge circuit of one active gauge method (two-wire or three-wire type) as shown in Fig. 13.

[0085] 12, terminals T1 to T4 of the bridge circuit are formed in a mid-latitude range between the first designated latitudinal range R1 and the second designated latitudinal range R2 on the upper surface 101 of the flexure body 10. At least some of the terminals T1 to T4 of the bridge circuit may be formed inside the first designated latitudinal range R1 and / or outside the second designated latitudinal range R2 on the upper surface 101 of the flexure body 10.

[0086] The strain-sensitive member 20 is connected at the other end of the inner annular strain-sensitive portion 201 to the first terminal T1 via a conductor member L01, and at the other end of the first outer annular strain-sensitive portion 212 to the second terminal T2 via a conductor member L02. The first resistance member 41 is connected at one end to the first terminal T1 and at the other end to the fourth terminal T4. The second resistance member 42 is connected at one end to the second terminal T2 and at the other end to the third terminal T3. The third resistance member 43 is connected at one end to the third terminal T3 and at the other end to the fourth terminal T4.

[0087] The thickness, width, length, and electrical properties such as electrical conductivity of each of the strain-sensitive member 20 and the resistance members 41 to 43 are appropriately designed from the perspective of configuring a bridge circuit (strain detection circuit). The thickness, width, length, and material (which determines the electrical conductivity) of the conductor members L01 and L02 are also appropriately designed from the perspective of configuring the bridge circuit, similar to each of the strain-sensitive member 20 and the resistance members 41 to 43.

[0088] Other than these points, the force sensor according to the fifth embodiment of the present invention has a configuration that is almost the same as that of the force sensor according to the fourth embodiment of the present invention (see FIGS. 10 and 11). Therefore, the same reference numerals are used for the common components and their explanations are omitted.

[0089] (Example) An example force sensor was fabricated in which strain-sensitive members were formed for a bridge circuit of the four active gauge method according to the first embodiment. Specifically, an insulating thin film made of SiO2 was formed on one main surface 101 of a substantially circular plate-shaped strain element 10 made of SUS316L with a diameter of 4 mm and a thickness of 0.4 mm. Strain-sensitive members 21-24 made of a substantially annular Cr-N thin film, divided at one location, were then formed on the insulating thin film. The positions are, for example, as the strain-sensitive member 21, the first inner annular strain-sensitive portion 211 has an inner radius of 0.8 mm and an outer radius of 0.82 mm, the first outer annular strain-sensitive portion 212 has an inner radius of 0.84 mm and an outer radius of 0.86 mm, as the strain-sensitive member 22, the second inner annular strain-sensitive portion 221 has an inner radius of 1.408 mm and an outer radius of 1.443 mm, as the strain-sensitive member 22, the second outer annular strain-sensitive portion 222 has an inner radius of 1.463 mm and an outer radius of 1.500 mm, as the strain-sensitive member 23, the third inner annular strain-sensitive portion 231 has an inner radius of 0.88 mm and an outer radius The third outer annular strain-sensitive portion 232 had an inner radius of 0.922 mm and an outer radius of 0.944 mm, and the fourth inner annular strain-sensitive portion 241 of the strain-sensitive member 24 had an inner radius of 1.353 mm and an outer radius of 1.388 mm, and the fourth outer annular strain-sensitive portion 242 had an inner radius of 1.520 mm and an outer radius of 1.557 mm. The circumferential lengths of the dividing points of the strain-sensitive members 21, 22, 23, and 24 were approximately 0.21 mm, 0.07 mm, 0.16 mm, and 0.14 mm, respectively. Note that these positions and lengths may be changed within a range that does not cause problems due to convenience in element fabrication, etc.

[0090] A high-frequency magnetron sputtering system was used to prepare the Cr-N thin film, and a reactive sputtering method was also used, in which a small amount of nitrogen gas was introduced along with Ar to form the film. A 3-inch diameter Cr disk with a nominal purity of 99.9% was used as the target. The vacuum level before film formation (background vacuum level), target-substrate distance (TS distance), sputtering gas pressure, total sputtering gas flow rate, nitrogen gas flow rate ratio, input power, and substrate water cooling temperature were each set to 2 × 10 -5The film was deposited under conditions of 43 mm, 0.67 Pa, 5 SCCM, 0.06%, 10 W, and 20°C. The thin film pattern was formed using photolithography and etching techniques as described above, and heat treatment was performed by holding the thin film in air at 200°C for 1 hour. Au / Ni / Cr thin films were layered at predetermined positions, including the lead wire parts of the thin film, to form electrodes for resistance measurement. The four sensing elements can form a full bridge, and strain generated in the diaphragm when a load is applied is converted into an electrical signal for output.

[0091] The flexure element 10 of the force sensor of the embodiment was integrally formed with the outer protrusion 12 and the inner protrusion 14 by molding and fixed to the outer protrusion 12. The flexure element 10 (the fabricated diaphragm-type force sensor element) was then held with the inner protrusion 14 protruding upward and outward by external fixing jigs that sandwiched the outer protrusion 12 from above and below. Each external fixing jig had a central through-hole approximately the same diameter as the outer protrusion 12. This held the flexure element 10 (the fabricated diaphragm-type force sensor element) with the inner protrusion 14 protruding upward and outward. This caused the upper surface 101 of the flexure element 10, on which the strain-sensitive member was formed, to face downward. The strain-sensitive member thus fit like a ceiling in the upper part of the space defined by the through-hole inside the lower external fixing jig. Furthermore, a flexible cable substrate was connected to the electrodes within this space using an anisotropic conductive film. At this time, the flexure element 10 was held floating above its bottom surface within the through-hole by the sleeve of the lower external fixing jig, creating a movable space that functioned as a diaphragm. A load was applied to the upper end of the inner protrusion 14 using a mechanical testing machine. The signal lines of the flexible cable board were routed externally through a notch formed in a portion of the sleeve and connected to a power supply and measuring equipment to extract signals. The measuring equipment then digitized the signals and recorded them on a recording device (e.g., a computer). The metal external fixture jig had a rectangular outer shape with sufficient thickness, and had holes for passing bolts at the four corners outside a central through-hole. A metal member with the same thickness as the outer protrusion 12 of the flexure element 10 had a central through-hole that fit the flexure element 10 perfectly, and further holes at the four corners outside the through-hole for passing bolts common to the external fixture jig. The metal member was used as a spacer to fill the outside of the flexure element. The flexure element 10 was placed in the through-hole of the spacer, and the external fixture jig and the flexure element 10 were then sandwiched from above and below. Bolts were inserted into the four corner holes from above and below to secure the flexure element 10 (the fabricated diaphragm-type force sensor element) in place.

[0092] To evaluate the performance of the force sensor of the embodiment, a force in the z direction was applied intermittently to the strain body 10 via the inner protrusion 14, increasing in 1N increments from 1 N to 7 N, as shown in Fig. 14. At this time, in a common specified latitude range R1 where the magnitude of the sum of the first strain amount in the meridian direction of the strain body and the second strain amount in the latitude direction of the strain body with respect to the pole becomes equal to or greater than a reference value, output (resistance change) measurements were performed by a four-terminal method via electrodes T1 and T2 to examine the signal from the strain-sensitive member 21, which is composed of a pair of annular strain-sensitive portions 211 that extend in an annular shape surrounding the pole separated at one point and are spaced apart from each other in the meridian direction, and a connection portion 210 that connects one end of each of the pair of annular strain-sensitive portions 212.

[0093] FIG. 15 shows the output of the strain-sensitive member 21 versus the elapsed measurement time. It can be seen that the shape of the output waveform is nearly identical to the applied load in FIG. 14. FIG. 16 also shows an enlarged view of the change in resistance of 0.4 Ω on the vertical axis from 40 seconds to 60 seconds on the horizontal axis in FIG. 15. It can be seen that a resistance change of about 0.025 Ω is observed in the baseline excluding the signal line, but no noise is generated that would make it impossible to detect a 1 N signal. Therefore, by using a strain-sensitive member 21 having a connection portion 210, it is possible to provide a force sensor that can improve the detection sensitivity for strain.

[0094] (Comparative Example) Force sensors with conventional configurations are susceptible to noise, which can reduce the sensitivity of detecting minute strains in the strain-generating body. A force sensor with this conventional configuration was fabricated and its performance evaluated. A force sensor was fabricated according to the first embodiment, in which strain-sensitive members were formed for a bridge circuit using the four-active gauge method. Specifically, an insulating thin film made of SiO2 was formed on one main surface 101 of a substantially circular plate-shaped strain-generating body 10 made of SUS316L with a diameter of 4 mm and a thickness of 0.4 mm. On top of this, strain-sensitive members 21-24 made of a substantially annular Cr-N thin film, divided at one location, were formed on the insulating thin film. The positions were, for example, approximately an inner radius of 0.82 mm and an outer radius of 0.84 mm for strain-sensitive member 21, an inner radius of 1.435 mm and an outer radius of 1.471 mm for strain-sensitive member 22, an inner radius of 0.901 mm and an outer radius of 0.923 mm for strain-sensitive member 23, and an inner radius of 1.436 mm and an outer radius of 1.472 mm for strain-sensitive member 24. The circumferential lengths of the dividing points of each strain-sensitive member 21, 22, 23, and 24 were designed to be approximately 0.11 mm, 0.04 mm, 0.08 mm, and 0.07 mm, respectively. The Cr-N thin films and electrodes constituting the strain-sensitive members were fabricated using the same methods as in the previous examples.

[0095] The strain-generating element 10 of the force sensor of the comparative example was integrally formed with the outer protrusion 12 and the inner protrusion 14 by molding and fixed to the outer protrusion 12. The strain-generating element 10 (the fabricated diaphragm-type force sensor element) was then held in a direction such that the inner protrusion 14 protruded upward and outward using a roughly cylindrical external fixture jig with a central through-hole approximately the same diameter as the outer protrusion 12, which fixedly supported the outer protrusion 12 from below and from its outer peripheral side. This held the inner protrusion 14 in a direction such that the upper surface 101 of the strain-sensitive element 10, on which the strain-sensitive member was formed, faced downward. This placed the strain-sensitive member within the upper (ceiling) portion of the through-hole in the lower external fixture jig. Furthermore, a flexible cable substrate was connected to the electrodes within this space using an anisotropic conductive film. At this time, the strain-generating element 10 was held floating above its bottom surface by the sleeve of the lower external fixture, creating a movable space that functioned as a diaphragm. A load was applied to the upper end of the inner protrusion 14 using a mechanical testing machine. The signal line of the flexible cable board was led out from a notch formed in a part of the sleeve, and connected to a power source and measuring equipment to extract signals. The signals were converted into numerical values ​​by the measuring equipment and recorded in a recording device (such as a computer).

[0096] To evaluate the performance of the force sensor of the comparative example, a z-direction force was applied intermittently to the strain body 10 via the inner protrusion 14, increasing in increments of 0.5 N from 0.5 N to 3.5 N, as shown in Fig. 17. At this time, in a common specified latitude range R1 where the magnitude of the sum of the first strain amount in the meridian direction of the strain body and the second strain amount in the latitude direction of the strain body with the pole as the reference point is equal to or greater than a reference value, output (resistance change) measurements were performed using the four-terminal method via the electrode parts T1 and an electrode formed at the other end of the annular strain-sensitive part 211 to examine the signal from the strain-sensitive member 21, which extends in a ring shape surrounding the polar point separated at one point and is composed only of a pair of annular strain-sensitive parts 211 without any connecting part 210.

[0097] Figure 18 shows the output of the strain-sensitive member 21 versus the elapsed measurement time. The shape of the output waveform, with the thin signal line during load application, is roughly consistent with the applied load in Figure 17, but a rounded noise of approximately 0.1 Ω appears along the baseline between them. Figure 19 shows a magnified view of the horizontal axis from 700 seconds to 900 seconds in Figure 18, showing a change of 0.4 Ω on the vertical axis. Compared to the example in Figure 16, the presence of a large rounded noise can be seen along the same vertical axis of 0.4 Ω. Furthermore, Figure 18 shows that the output signal for 0.5 N is completely obscured by the noise, and the signal for 1 N is also approximately half obscured by the noise. Therefore, it is clear that a force sensor with improved strain detection sensitivity cannot be provided if a strain-sensitive member 21 having a conventional configuration without the annular strain-sensitive portion 212 and the connecting portion 210 is used. This invention is a new technology that solves the problems associated with the technique of annularly arranging strain-sensitive members with isotropic sensitivity, which is effective in realizing miniaturization and high load-bearing capacity of force sensors, by using a new configuration for the strain-sensitive members, thereby enabling improved detection sensitivity.

[0098] (Another embodiment of the present invention) In the above embodiment, all of the strain-sensitive members are formed on the upper surface 101 of the flexure element 10, but in another embodiment, some of the strain-sensitive members may be formed on the upper surface 101 while the remaining strain-sensitive members are formed on the lower surface 102. In this case, care must be taken because the positive and negative signs may differ between the upper surface 101 and the lower surface 102 depending on the position of the strain-sensitive members and the type of load. A through hole may be provided in the flexure element 10 to arrange a conductor member for configuring a strain detection circuit, or a conductor member having a via structure may be embedded in the flexure element 10.

[0099] In the above embodiment, the flexure body 10 is a substantially circular plate, but in other embodiments, the flexure body 10 may have various shapes, such as a substantially elliptical plate, a substantially triangular plate, a substantially rectangular plate, a substantially parallelogram plate, a substantially trapezoidal plate, or a substantially regular polygonal plate (such as a square, a regular dodecagonal plate, or a regular icosagonal plate). The flexure body 10 may have a shape that has rotational symmetry about an axis (e.g., the Z axis) that passes through the pole O and is perpendicular to the upper surface 101, or may have a shape that does not have rotational symmetry. The pole O of the flexure body 10 may be offset from the center point of the flexure body 10.

[0100] In the above embodiment, the strain element 10 is fixed to the support member over the entire circumference via the outer surfaces of the outer protrusions 12, but the strain element 10 may also be fixed to the support member discretely in the circumferential direction via the outer surfaces of the outer protrusions 12.

[0101] In the above embodiment, the device is provided with an inner protrusion that protrudes from the main surface of the flexure body more inward than the outer protrusion of the flexure body, and when vibration (acceleration) having a component perpendicular to the main surface acts on the flexure body, the inner protrusion 14 increases the inertial force acting on the flexure body 10, thereby making it possible to detect the magnitude of the vibration (acceleration) from the strain that occurs in the flexure body 10, and also when a force having a component perpendicular to the main surface acts on the end face of the inner protrusion 14 on the flexure body, the magnitude of the force can be detected from the strain that occurs in the flexure body 10. The strain generating element 10 does not have to have an inward protrusion, in which case the magnitude of the uniform force (e.g., pressure of a fluid, etc.) can be detected from the strain generated in the strain generating element 10 when a force having a component in the direction perpendicular to the main surface acts uniformly on the entire surface of the strain generating element 10.

[0102] In the above embodiment, the strain-sensitive member is composed of a pair of annular strain-sensitive portions that are spaced apart from each other in the meridian direction and extend in a ring shape surrounding the polar point that is separated at one point within a common specified latitude range on the strain-generating body, and a connecting portion that connects one end of each of the pair of annular strain-sensitive portions.However, either one of the pair of annular strain-sensitive portions may be a conductive wire member.

[0103] In the above embodiment, when a vibration having a component in the direction perpendicular to the main surface acts on the flexure body, the magnitude of the sum of a first strain amount in the meridian direction of the flexure body with a pole as the reference and a second strain amount in the latitude direction of the flexure body with a pole as the reference is equal to or greater than a reference value, and the force sensor is configured by a pair of annular strain-sensitive portions that are spaced apart from each other in the meridian direction and a connecting portion that connects one end of each of the pair of annular strain-sensitive portions, for a strain-sensitive member that extends in an annular shape surrounding the pole that is divided at one point, in a common specified latitude range in which, when a force acts on the flexure body, the magnitude of the sum of a first strain amount in the meridian direction of the flexure body with a pole as the reference and a second strain amount in the latitude direction of the flexure body is equal to or greater than a reference value. The support member supports at least a portion of the peripheral edge of the strain element so that strain is generated in the strain element in each of a plurality of spaced apart azimuth angle ranges, and the force sensor may also be configured along a specified line segment such that when a force acts on the strain element in at least one of the plurality of azimuth angle ranges, the sum of a first strain amount of the strain element along an azimuth line based on the reference point and a second strain amount of the strain element along a line segment perpendicular to or intersecting the azimuth line is greater than or equal to a reference value.The force sensor may also be configured from a pair of arc-shaped strain-sensitive portions spaced apart from each other in the meridian direction and a connecting portion connecting one end of each of the pair of arc-shaped strain-sensitive portions.

[0104] In the above embodiment, in order to reduce noise resulting from the large area of ​​the surrounding area and the functioning of each strain-sensitive member as an antenna, the area of ​​the area surrounded by a pair of annular strain-sensitive portions constituting each strain-sensitive member, i.e., the area of ​​the elongated surrounding area extending in an approximately annular (circular) shape divided at one point, is made narrower than the area of ​​the approximately circular surrounding area surrounded by the single annular strain-sensitive portion when each strain-sensitive member is composed of a single annular strain-sensitive portion of approximately the same diameter divided at one point, but it is even more preferable to make the narrowing also include the surrounding area formed by the wire member.

[0105] In the above embodiment, the strain element 10 is fixed to the support member via the entire outer surface of the outer protrusion 12, but it may also be fixed to the support member via the entire upper surface, lower surface, or both the upper and lower surfaces of the outer protrusion 12. [Explanation of symbols]

[0106] 10: Strain generating body, 12: Outer protrusion, 14: Inner protrusion, 20: Strain sensitive member, 21: First strain sensitive member, 22: Second strain sensitive member, 23: Third strain sensitive member, 24: Fourth strain sensitive member, 41, 42, 43, 44: Resistance members, 101: Upper surface (main surface) of strain generating body, 102: Lower surface (main surface) of strain generating body, 200: Connection portion, 201: Inner annular strain sensitive portion, 202: Outer annular strain sensitive portion, 210: First connection portion, 211: First inner Annular feeling distortion part, 212...First outer annular feeling distortion part, 220...Second connection part, 221...Second inner annular feeling distortion part, 222...Second outer annular feeling distortion part, 230...Third connection part, 231...Third inner annular feeling distortion part Minutes, 232...Third outer annular distortion part, 240...Fourth connecting part, 241...Fourth inner annular distortion part, 242...Fourth outer annular distortion part, O...Pole, R1...First designated latitude range, R2...Second designated latitude range.

Claims

1. a plate-shaped strain generating body having a pair of opposing main surfaces; an outer protrusion extending continuously or discretely along the entire periphery of the flexure body and protruding from a main surface of the flexure body; a strain-sensitive member disposed on a main surface of the strain generating body and having an isotropic gauge factor in the direction of the main surface; an inner protrusion protruding from the main surface of the flexure body at a position more inward than the outer protrusion of the flexure body, the strain-sensitive member is configured by a pair of annular strain-sensitive portions, each consisting of an inner annular strain-sensitive portion and an outer annular strain-sensitive portion, spaced apart from each other in the meridian direction and extending in an annular shape surrounding the polar point separated at one point, in a common specified latitude range in which, when a vibration having a component in the normal direction to the principal surface acts on the strain-generating body, a sum of a first strain amount in the meridian direction of the strain-generating body and a second strain amount in the latitude direction of the strain-generating body with respect to the polar point acting thereon becomes equal to or greater than a reference value when a force having a component in the normal direction to the principal surface acts on the strain-generating body, The other end of the inner annular strain-sensitive portion is connected to a terminal via a conducting wire member, The other end of the outer annular strain-sensitive portion is connected to another terminal via a conductive wire member, The area surrounded by a line connecting the other end of the strain-sensitive member and the other end of the inner annular strain-sensitive portion and the other end of the outer annular strain-sensitive portion extends in an annular shape surrounding the polar point divided at one point. Force sensor.

2. 2. The force sensor according to claim 1, The pair of annular strain-sensitive portions are arranged on the main surface of the strain generating body so that the azimuth angle ranges of the respective dividing points of the pair of annular strain-sensitive portions with respect to the pole point as a reference at least partially overlap each other. Force sensor.

3. 3. The force sensor according to claim 2, A plurality of the strain-sensitive members are arranged, The plurality of strain-sensitive members are arranged on the main surface of the strain generating body so that the azimuth angle ranges of the dividing points of the pair of annular strain-sensitive portions of the plurality of strain-sensitive members formed in the common specified latitude range, with the pole as the reference, at least partially overlap. Force sensor.

4. 3. The force sensor according to claim 2, A plurality of the strain-sensitive members are arranged, The plurality of strain-sensitive members are arranged on the main surface of the strain generating body such that the azimuth angle ranges of the dividing points of the pair of annular strain-sensitive portions of the strain-sensitive members formed in each of the plurality of specified latitude ranges, with the pole as the reference, at least partially overlap. Force sensor.

5. The force sensor according to any one of claims 1 to 4, The pair of annular strain-sensitive portions constituting at least one of the strain-sensitive members are arranged on the main surface of the strain generating body so as to be adjacent to each other at least partially in the latitude direction and at an interval not greater than twice the width W of at least one of the pair of annular strain-sensitive portions in the longitude direction. Force sensor.

6. The force sensor according to any one of claims 1 to 5, the shape of the strain generating body has rotational symmetry with respect to an axis parallel to a normal to the principal surface passing through the pole point or mirror symmetry with respect to a plane perpendicular to the principal surface passing through the pole point, the arrangement of the outer protrusions has rotational symmetry with respect to the axis or mirror symmetry with respect to the plane, At least one of the pair of annular strain-sensitive portions constituting the strain-sensitive member is disposed on the main surface of the strain generating body so as to have rotational symmetry with respect to the axis or mirror symmetry with respect to the plane, and The arrangement of the inner protrusions has rotational symmetry with respect to the axis or mirror symmetry with respect to the plane. Force sensor.

7. The force sensor according to any one of claims 1 to 6, The strain sensor further includes a resistance member that is installed on the strain generating body and that constitutes a strain detection circuit together with the strain-sensing member. Force sensor.

8. The force sensor according to any one of claims 1 to 7, The strain-sensitive member is made of a Cr-based thin film. Force sensor.

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