Force sensor and robot comprising a force sensor

Abstract

A force sensor and a robot including the same are provided. A force sensor includes a strain body including a base, a displacement portion configured to be displaced relative to the base under an external force, and an elastic connection portion configured to elastically connect the base and the displacement portion; a plate including a detection unit configured to detect displacement of the displacement portion relative to the base in a first direction; and an insertion member inserted between the strain body and the plate, the insertion member including an extension portion extending in a second direction intersecting a surface of the plate and the first direction.

Description

TECHNICAL FIELD

[0001] The present application relates to a force sensor and a robot including the force sensor. BACKGROUND

[0002] A force sensor is used as a means for detecting a multi-axis external force component acting on each part of an industrial robot arm and a medical manipulator. Such a force sensor has a problem that an output (a detected value) varies with temperature change.

[0003] Japanese Patent Application Publication No. 2019-074421 discusses including a six-axis external force component and a two-axis thermal expansion component in output calculation so that an output (a detected value) is less likely to be affected by temperature change. Here, the six-axis external force component refers to an external force Fx in an X-axis direction, an external force Fy in a Y-axis direction, an external force Fz in a Z-axis direction, a moment Mx about the X-axis, a moment My about the Y-axis, and a moment Mz about the Z-axis. The two-axis thermal expansion component refers to a thermal expansion component Tx in the X-axis direction and a thermal expansion component Ty in the Y-axis direction.

[0004] The force sensor discussed in the aforementioned Japanese Patent Application Publication No. 2019-074421 reduces the influence of thermal expansion in a direction parallel to a mounting surface (an XY plane) of a sensor plate. However, it is not possible to reduce the influence of complex thermal stress (and resulting non-uniform deformation of the sensor plate) due to thermal expansion that occurs at a position where the sensor plate is fixed to a housing. Therefore, among changes in the output (the detected value) due to temperature change, it is still not possible to reduce changes in the output (the detected value) due to thermal stress. SUMMARY

[0005] According to one aspect of the present application, a force sensor includes a strain body including a base, a displacement portion configured to displace relative to the base under an external force, and an elastic connection portion configured to elastically connect the base and the displacement portion; a plate including a detection unit configured to detect displacement of the displacement portion relative to the base in a first direction; and an insertion member inserted between the strain body and the plate, the insertion member including an extension portion extending in a second direction intersecting a surface of the plate and the first direction.

[0006] Further features of the present application will become clear on the basis of the following description of embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a conceptual diagram illustrating a force sensor.

[0008] Figure 2A is a perspective view illustrating a schematic configuration of the force sensor viewed from above.Figure 2B is a layout diagram of a detection target and a displacement detector (detection unit). Figure 2C is a sectional view of a force sensor.

[0009] Figure 3 is a plan view showing a circuit board (board) included in the force sensor of Figures 2A to 2C .

[0010] Figure 4 is a diagram for describing a configuration of a displacement detector (detection unit) and a method of reading a detection target.

[0011] Figure 5A and Figure 5B are a perspective view and a sectional view, respectively, showing a schematic configuration of a force sensor according to a first embodiment, as viewed from above. Figure 5C is a perspective view of a strain body, as viewed from below.

[0012] Figure 6A is a perspective view showing a schematic configuration of a force sensor according to a second embodiment, as viewed from above. Figure 6B and Figure 6C are sectional views of a force sensor. Figure 6D is a perspective view of a strain body, as viewed from below.

[0013] Figure 7A and Figure 7B are a perspective view and a sectional view, respectively, showing a schematic configuration of a force sensor according to a third embodiment, as viewed from above. Figure 7C is a perspective view of a strain body, as viewed from below.

[0014] Figure 8A and Figure 8B are a perspective view and a sectional view, respectively, showing a schematic configuration of a force sensor according to a fourth embodiment, as viewed from above.

[0015] Figure 9 is a perspective view showing an intermediate member (insert member) according to the fourth embodiment.

[0016] Figure 10A and Figure 10B are a perspective view and a sectional view, respectively, showing a schematic configuration of a force sensor according to a fifth embodiment, as viewed from above.

[0017] Figure 11 is a perspective view showing an intermediate member (insert member) according to the fifth embodiment.

[0018] Figure 12 is a perspective view showing another mode of an intermediate member (insert member) according to the fifth embodiment.

[0019] Figure 13A is a perspective view showing another mode of the intermediate member (insert member) according to the fifth embodiment, viewed from above. Figure 13B and Figure 13C is a cross-sectional view of the intermediate member (insert member).

[0020] Figure 14A and Figure 14B are a perspective view and a cross-sectional view, respectively, showing the schematic configuration of the force sensor according to the sixth embodiment, viewed from above.

[0021] Figure 15 is a perspective view showing the intermediate member (insert member) according to the sixth embodiment.

[0022] Figure 16A and Figure 16B are a perspective view and a cross-sectional view, respectively, showing the schematic configuration of the force sensor according to the seventh embodiment, viewed from above.

[0023] Figure 17 is a perspective view showing the intermediate member (insert member) according to the seventh embodiment.

[0024] Figure 18 is a perspective view showing another mode of the intermediate member (insert member) according to the seventh embodiment.

[0025] Figure 19 is a side view showing the schematic configuration of the transmission device according to the eighth embodiment. DETAILED DESCRIPTION

[0026] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. Figure 1 is a conceptual diagram showing a force sensor 100. The force sensor 100 detects an input (applied) external force and outputs a signal corresponding to the external force. The force sensor 100 includes an outer ring portion 1 (base portion), an inner ring portion 2 (displacement portion), an elastic support portion 3 (hereinafter, referred to as "elastic connection portion"), a detection target 4, a displacement detector 10 (detection unit), and a circuit board 6 (board).

[0027] The elastic connection portion 3 is intended to elastically connect members. The shape and material of the elastic connection portion 3 are selected to allow elastic deformation due to an external force acting between the outer ring portion 1 (base portion) and the inner ring portion 2 (displacement portion). The elasticity of the elastic connection portion 3 is appropriately designed based on the range of the external force to be detected. More specifically, in order to detect a small external force, the elasticity is designed to be high (modulus of elasticity (modulus of elasticity) is low) so as to facilitate deformation. In order to detect a large external force or increase mechanical rigidity, the elasticity is designed to be low (modulus of elasticity is high).

[0028] Figure 2Ais a perspective view showing the schematic configuration of the force sensor 100A viewed from above. Figure 2B The detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H and the displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units) among the components of the force sensor 100A are shown. Figure 2C is a perspective view showing the schematic configuration of the force sensor 100A viewed from above. Figure 2A is a cross-sectional view showing the schematic configuration of the force sensor 100A taken along the line A-A shown in

[0029] The force sensor 100A includes a strain body 5, detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H, a circuit board 6 (board), and displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units).

[0030] The strain body 5 includes an outer ring portion 1 (base portion), an inner ring portion 2 (displacement portion), and elastic connection portions 3. The strain body 5 is a member that causes strain under an external force. Application of a force to the strain body 5 causes the strain body 5 to generate strain. The strain body 5 includes a detection target holding portion 7 that holds the detection targets 4A, 4B, 4C, and 4D.

[0031] For ease of description, the X-axis, Y-axis, and Z-axis, which intersect with each other or are ideally orthogonal to each other, will be defined as shown in Figures 2A to 2C and used as appropriate in the description.

[0032] The inner ring portion 2 (displacement portion) and the outer ring portion 1 (base portion) of the force sensor 100A are connected using four elastic connection portions 3 that are arranged radially at intervals of 90° when viewed from above. The circuit board 6 (board) is fixed to the inner ring portion 2 (displacement portion). The detection target holding portion 7 that holds the detection targets 4A, 4B, 4C, and 4D is located on the inner peripheral side of the outer ring portion 1 (base portion). The detection targets 4A, 4B, 4C, and 4D are fixed to the surface of the detection target holding portion 7 opposite the circuit board 6 (board). For example, the detection targets 4A, 4B, 4C, and 4D are chrome reflection films with a lattice pattern on a glass substrate.

[0033] In the force sensor 100A, the elastic connection portions 3 have a displacement direction conversion function. This displacement direction conversion function is used with U-shaped recesses 30. One detection target is fixed to the end surface (surface opposite the circuit board 6) of each of the four recesses 30, thereby providing the detection targets 4E, 4F, 4G, and 4H. The detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H are located at approximately the same height (i.e., in the same plane) in the Z-direction.

[0034] Figure 3is a plan view of a circuit board 6 (board) included in the force sensor 100A. Displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units) are mounted to the circuit board 6 (board) in the Z direction opposite the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H. The displacement detectors 10A and 10B (detection units) are each separated from each other by a predetermined distance in the X direction and the Y direction, and are positioned symmetrically about the center of the XY surface of the force sensor 100A. The displacement detection direction of the displacement detectors 10A and 10B (detection units) is the X direction. Similarly, the displacement detectors 10C and 10D (detection units) are each separated from each other by a predetermined distance in the X direction and the Y direction, and are positioned symmetrically about the center of the XY surface of the force sensor 100A. The displacement detection direction of the displacement detectors 10C and 10D (detection units) is the Y direction.

[0035] Assuming that the force sensor 100A (circuit board 6) is divided into four quadrants by two straight lines (one parallel to the X axis and the other parallel to the Y axis) passing through the center of the XY surface of the force sensor 100A. The displacement detectors 10A and 10C (detection units) are located in the same quadrant. The displacement detectors 10B and 10D (detection units) are located in the same quadrant.

[0036] The quadrants in which the displacement detectors 10A and 10C (detection units) are located and the quadrants in which the displacement detectors 10B and 10D (detection units) are located are in a position relationship symmetric about the center of the XY surface of the force sensor 100A. Electronic components such as the signal processing circuit 20 and the connector 21 for outputting a signal from the signal processing circuit 20 are mounted on the quadrants on which the displacement detectors 10A, 10B, 10C, and 10D (detection units) are not mounted.

[0037] Figure 4 is a diagram for describing the configuration of the displacement detector 10A (detection unit) and a method of reading the detection target 4A by the displacement detector 10A (detection unit).

[0038] The configuration of the displacement detectors 10B to 10H (detection units) and the method of reading the detection targets 4B to 4H by the displacement detectors 10B to 10H (detection units) are similar to the configuration of the displacement detector 10A (detection unit) and the method of reading the detection target 4A by the displacement detector 10A (detection unit). Therefore, a detailed description thereof will be omitted.

[0039] The displacement detector 10A (detection unit) is an integrated light emission-reception sensor unit including a light source 12 and a light-receiving integrated circuit (IC) 14 packaged together. The light-receiving IC 14 includes a light-receiving device array 16. A current-limited light-emitting diode (LED) or a semiconductor laser can be used as the light source 12. The light-receiving device array 16 includes a plurality of light-receiving devices (detection elements) for detecting a distribution of light from the pattern of the detection target 4A, the light-receiving devices of the light-receiving device array 16 being arranged in a movement direction (position measurement direction, first direction) of the detection target 4A.

[0040] The displacement detector 10A (detection unit) opposes the detection target 4A to detect an amount of relative displacement of the detection target 4A. More specifically, a diverging light beam emitted from the light source 12 is reflected by the lattice pattern on the detection target 4A, thereby forming a distribution of light amounts of a fringe pattern (interference fringes) on the light-receiving device array 16 due to diffraction and interference. The displacement of the detection target 4A relative to the displacement detector 10A (detection unit) is detected by detecting movement of the interference fringes. The displacement of the inner ring portion 2 (displacement portion) relative to the outer ring portion 1 (base portion) is thereby detected.

[0041] The displacement detection direction of the displacement detector 10E (detection unit) is the X direction. The displacement detector 10E (detection unit) is located at substantially the same position as the position of the displacement detector 10A (detection unit) in the X direction and is located at a predetermined distance from the displacement detector 10A (detection unit) in the Y direction. The displacement detection direction of the displacement detector 10F (detection unit) is the X direction. The displacement detector 10F (detection unit) is located at substantially the same position as the position of the displacement detector 10B (detection unit) in the X direction and is located at a predetermined distance from the displacement detector 10B (detection unit) in the Y direction. The displacement detectors 10E and 10F (detection units) are located on the same straight line parallel to the X axis.

[0042] The displacement detection direction of the displacement detector 10G (detection unit) is the Y direction. The displacement detector 10G (detection unit) is located at substantially the same position as the position of the displacement detector 10C (detection unit) in the Y direction and is located at a predetermined distance from the displacement detector 10C (detection unit) in the X direction. The displacement detection direction of the displacement detector 10H (detection unit) is the Y direction. The displacement detector 10H (detection unit) is located at substantially the same position as the position of the displacement detector 10D (detection unit) in the Y direction and is located at a predetermined distance from the displacement detector 10D (detection unit) in the X direction. The displacement detectors 10G and 10H (detection units) are located on the same straight line parallel to the Y axis.

[0043] As described above, the elastic connecting portion 3 has a displacement direction conversion function. More specifically, the bottom of the recess 30 of the elastic connecting portion 3 is a displacement portion that generates displacement in the X direction or the Y direction with respect to the outer ring portion 1 (base) as the inner ring portion 2 (displacement portion) is displaced in the Z direction.

[0044] Specifically, if an external force Fz in the Z direction is applied to the inner ring portion 2 (displacement portion), the detection targets 4E provided on the elastic connecting portion 3 are displaced in the -X direction, the detection targets 4F are displaced in the X direction, the detection targets 4G are displaced in the -Y direction, and the detection targets 4H are displaced in the Y direction. If a moment Mx is applied to the inner ring portion 2 (displacement portion), the detection targets 4G and 4H are displaced in the -Y direction. If a moment My is applied to the inner ring portion 2 (displacement portion), the detection targets 4E and 4F are displaced in the X direction.

[0045] If an external force Fx is applied to the inner ring portion 2 (displacement portion), the circuit board 6 (board) including the displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units) is displaced in the X direction together with the inner ring portion 2 (displacement portion). As a result, the displacement detectors 10A and 10B (detection units) respectively detect the relative displacement of the opposing detection targets 4A and 4B in the -X direction. If an external force Fy is applied to the inner ring portion 2 (displacement portion), the displacement detectors 10C and 10D (detection units) similarly respectively detect the relative displacement of the opposing detection targets 4C and 4D in the -Y direction. If a moment Mz is applied to the inner ring portion 2 (displacement portion), the displacement detectors 10A, 10B, 10C, and 10D (detection units) similarly respectively detect the relative displacement of the opposing detection targets 4A, 4B, 4C, and 4D in the -X, X, Y, and -Y directions. From such detection amounts, the external forces Fx, Fy, and Fz and the moments Mx, My, and Mz can be determined by calculation.

[0046] The detection target holding portion 7 can be integrated with the outer ring portion 1 (base) or can be a separate member.

[0047] As the temperature of the force sensor 100A changes, the members expand or contract based on the coefficient of thermal expansion of their respective materials. For example, assume that the strain body 5 is made of an aluminum alloy and the circuit board 6 (board) is made of a glass epoxy circuit board material. The coefficient of thermal expansion of the aluminum alloy is approximately 23. The coefficient of thermal expansion of the glass epoxy circuit board material in the horizontal direction of the mounting surface (the direction parallel to the XY plane in the figure) is approximately 15. If the temperature of the force sensor 100A increases, the thermal expansion of the strain body 5 is thus greater than the thermal expansion of the circuit board 6 (board). This causes thermal stress at the joint where the circuit board 6 (board) is fixed to the strain body 5.

[0048] To reduce thermal stress, one method is to form the strain body 5 of a material similar in thermal expansion coefficient to that of the circuit board 6 (board). However, this limits the material type of the strain body 5, resulting in difficulty in imparting the elasticity required of the elastic connection portion 3 and an increase in weight.

[0049] In the force sensor 100A, the circuit board 6 (board) is fixed to the inner ring portion 2 (displacement portion). Such a configuration reduces the amount of relative displacement at the joint due to thermal expansion compared to the case where the circuit board 6 (board) is fixed to the outer ring portion 1 (base portion). This reduces the thermal stress generated.

[0050] Accordingly, deformation of the circuit board 6 (board) other than simple thermal expansion can be reduced. Furthermore, this configuration provides a force sensor that is less susceptible to temperature changes.

[0051] The configurations of the force sensors that optically detect the displacement of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H using the displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units) have been described. However, the method of displacement detection is not limited to the optical method, and other displacement detection methods, such as a magnetic method or a capacitance method, can also be employed. For example, if a magnetic detection method is employed, the detection target can be a magnetic body (magnet) having a magnetic pole distribution similar to the shape of the reflective film of the detection targets 4A to 4H, and an array of magnetic field detection devices can be in close opposition to the detection target. Using such a configuration, by detecting changes in the magnetic field using the magnetic field detection devices, the displacement of the magnet can be detected.

[0052] If a capacitance detection method is employed, a conductive electrode pattern having a shape similar to that of the reflective film of the detection targets 4A to 4H can be formed on the detection target, and another array of electrode patterns can be in close opposition thereto. Using such a configuration, by detecting changes in the capacitance between the electrode patterns, the displacement of the detection target can be detected.

[0053] The detection target array and the detector array are not always used. The external force can be detected by at least one detection unit and one detection target pattern edge. In this case, the displacement detection direction is the normal line of the edge in the detection target plane.

[0054] Figure 5A is a perspective view showing a schematic configuration of the force sensor 100B according to the first embodiment of the present application as viewed from above. Figure 5B is a cross-sectional view of the schematic configuration of the force sensor 100B taken along the line A-A shown in Figure 5A Figure 5C ​is a perspective view of the strain body 5 of the force sensor 100B viewed from below. Like reference numerals refer to like components of the force sensor 100. Elaboration on these components will be omitted.

[0055] The force sensor 100B includes the strain body 5, the scales 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H (detection targets), the circuit board 6 (board), the detection target holding portion 7, and the displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units). The strain body 5 includes the outer ring portion 1 (base portion), the inner ring portion 2 (displacement portion), the elastic connection portion 3, and the cylindrical protrusion 8 (extension portion, insertion member). The extension portion has a flat spring structure with a higher elastic modulus in a first direction described below than in a second direction described below.

[0056] In the present embodiment, the protrusion 8 (extension portion, insertion member) is integrated with the inner ring portion 2 (displacement portion) and is included in the strain body 5. In other embodiments, the protrusion 8 (extension portion, insertion member) is a separate member from the inner ring portion 2 (displacement portion).

[0057] The protrusion 8 (extension portion, insertion member) is located below the inner ring portion 2 (displacement portion). The circuit board 6 (board) is located below the protrusion 8 (extension portion, insertion member) and is fixed to the protrusion 8 (extension portion, insertion member). Here, the protrusion 8 (extension portion, insertion member) extends in a direction (second direction) that intersects with the direction of movement of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H (position measurement direction, first direction).

[0058] Similar to the above-described force sensor, as the temperature of the force sensor 100B changes, thermal stress occurs at the junction between the circuit board 6 (board) and the protrusion 8 (extension portion, insertion member). However, the protrusion 8 (extension portion, insertion member) deforms under the thermal stress, thereby reducing the thermal stress that occurs at the junction between the protrusion 8 (extension portion, insertion member) and the circuit board 6 (board). This results in a reduction in the deformation of the circuit board 6 (board) that is different from simple thermal expansion. Furthermore, this configuration provides a force sensor that is less susceptible to temperature changes.

[0059] In order to facilitate deformation under thermal stress, it is appropriate for the height of the cylindrical protrusion 8 (extension portion, insertion member) in the Z direction to be greater than the diameter of its horizontal cross section.

[0060] In the present embodiment, the protrusion 8 (extension portion, insertion member) is described as having a cylindrical shape. However, in some embodiments, the protrusion 8 (extension portion, insertion member) has other shapes, such as a quadrangular prism shape. The protrusion 8 (extension portion, insertion member) can be formed in a shape in which the horizontal cross section changes with height.

[0061] Figure 6A is a perspective view showing a schematic configuration of the force sensor 100C according to the second embodiment as viewed from above. Figure 6B is a cross-sectional view of the schematic configuration of the force sensor 100C taken along the line A-A shown in Figure 6A Figure 6C is a cross-sectional view of the schematic configuration of the force sensor 100C taken along the line B-B shown in Figure 6A Figure 6D is a perspective view of the strain body 5 of the force sensor 100C as viewed from below.

[0062] Like reference numerals refer to like components of the force sensors 100A and 100B. Elaboration on these components will be omitted.

[0063] The force sensor 100C includes the strain body 5, the scales 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H (detection targets), the circuit board 6 (board), the detection target holding portion 7, and the displacement detectors 10A, 10B, 10C, 10D, 10E, 10F, 10G, and 10H (detection units). The strain body 5 includes the outer ring portion 1 (base portion), the inner ring portion 2 (displacement portion), the elastic connection portion 3, and the cylindrical protrusion 8 (extension portion, insertion member). The extension portion has a flat spring structure whose elastic modulus in the first direction described below is higher than that in the second direction described below.

[0064] In the present embodiment, the protrusion 8 (extension portion, insertion member) is integrated with the outer ring portion 1 (base portion) and is included in the strain body 5. In other embodiments, the protrusion 8 (extension portion, insertion member) is a member separate from the outer ring portion 1 (base portion).

[0065] The outer ring portion 1 (base portion) includes a protrusion holding portion 9 for providing the protrusion 8 (extension portion, insertion member). The protrusion 8 (extension portion, insertion member) is located below the protrusion holding portion 9. The circuit board 6 (board) is located below the protrusion 8 (extension portion, insertion member) and is fixed to the protrusion 8 (extension portion, insertion member). Here, the protrusion 8 (extension portion, insertion member) extends in a direction (second direction) intersecting the direction of movement (direction of position measurement, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0066] ​​In this embodiment (second embodiment), the detection target holding portion 7 is located at the outer periphery of the inner ring portion 2 (displacement portion) and holds the detection targets 4A, 4B, 4C, and 4D. If an external force Fx is applied to the inner ring portion 2 (displacement portion), the detection targets 4A and 4B are displaced in the X direction. Similarly, if an external force Fy is applied to the inner ring portion 2 (displacement portion), the detection targets 4C and 4D are displaced in the Y direction. Similarly, if a moment Mz is applied to the inner ring portion 2 (displacement portion), the detection targets 4A, 4B, 4C, and 4D are displaced in the X, -X, -Y, and Y directions, respectively. The displacement of the detection targets 4E, 4F, 4G, and 4H is similar to that of the detection targets in the example of Figures 1 to 4 .

[0067] From such detection amounts, the external forces Fx, Fy, and Fz and the moments Mx, My, and Mz can be determined by calculation.

[0068] The detection target holding portion 7 can be integrated with the inner ring portion 2 (displacement portion) or can be separate therefrom.

[0069] Similar to the first embodiment, as the temperature of the force sensor 100C changes, thermal stress occurs at the joint between the protrusion 8 (extension portion, insertion member) and the circuit board 6 (board). However, the protrusion 8 (extension portion, insertion member) deforms under the thermal stress, thereby reducing the thermal stress occurring at the joint between the protrusion 8 (extension portion, insertion member) and the circuit board 6 (board).

[0070] In the second embodiment, the amount of relative displacement due to thermal expansion is greater than that in the first embodiment in which the protrusion 8 (extension portion, insertion member) is located below the inner ring portion 2 (displacement portion). Therefore, the effect of reducing the thermal stress at the joint is lower than that in the first embodiment. However, compared to the case where the protrusion 8 (extension portion, insertion member) is not present and the circuit board 6 (board) is fixed to the outer ring portion 1 (base), the thermal stress at the joint can be reduced. As a result, the deformation of the circuit board 6 (board) that is different from simple thermal expansion can be reduced. Furthermore, this configuration provides a force sensor that is less susceptible to temperature changes.

[0071] Similar to the first embodiment, it is appropriate for the height of the cylindrical protrusion 8 (extension portion, insertion member) in the Z direction to be greater than the diameter of the horizontal cross section thereof in order to facilitate deformation under thermal stress.

[0072] In this embodiment, the protrusion 8 (extension portion, insertion member) is described as having a cylindrical shape. However, in some embodiments, the protrusion 8 (extension portion, insertion member) has other shapes, such as a quadrangular prism shape. The protrusion 8 (extension portion, insertion member) can be formed in a shape in which the horizontal cross section changes with height.

[0073] Figure 7A is a perspective view showing a schematic configuration of the force sensor 100D according to the third embodiment as viewed from above. Figure 7B is a cross-sectional view of the schematic configuration of the force sensor 100D taken along the line A-A shown in Figure 7A Figure 7C is a perspective view of the strain body 5 of the force sensor 100D as viewed from below. Like reference numerals refer to like components of the aforementioned force sensors 100A, 100B, and 100C. Elaboration on these components will be omitted.

[0074] The force sensor 100D includes the strain body 5, the scales 4A to 4H (detection targets), the circuit board 6 (board), the detection target holding portion 7, the displacement detectors 10A to 10H (detection units), and the intermediate member 11A (extension portion, insertion member). The intermediate member 11A (extension portion, insertion member) is itself an extension portion. The strain body 5 includes the outer ring portion 1 (base portion), the inner ring portion 2 (displacement portion), and the elastic connection portion 3.

[0075] The intermediate member 11A (extension portion, insertion member) is located below the inner ring portion 2 (displacement portion) and is fixed to the inner ring portion 2 (displacement portion). The circuit board 6 (board) is located below the intermediate member 11A (extension portion, insertion member) and is fixed to the intermediate member 11A (extension portion, intermediate member). Here, the intermediate member 11A (extension portion, insertion member) extends in a direction (second direction) intersecting the movement direction (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0076] The intermediate member 11A (extension portion, insertion member) is not limited to any particular material. In order to reduce the influence of temperature changes on the output, it is appropriate for the intermediate member to have a coefficient of thermal expansion that is less than the coefficient of thermal expansion of the displacement portion and greater than the coefficient of thermal expansion of the board. By using a material having a coefficient of thermal expansion that is closer to the coefficient of thermal expansion of the material of the circuit board 6 (board) than the coefficient of thermal expansion of the material of the strain body 5 (first member), it is possible to further reduce the influence of temperature changes on the output. In other words, it is appropriate for the intermediate member 11A (extension portion, insertion member) to be made of a material having a coefficient of thermal expansion that is closer to the coefficient of thermal expansion of the material of the circuit board 6 (board).

[0077] According to the present embodiment (third embodiment), as the temperature of the force sensor 100D changes, thermal stress that occurs at the junction between the intermediate member 11A (extension portion, insertion member) and the circuit board 6 (board) is less than the thermal stress that would occur if the circuit board 6 (board) were fixed directly to the strain body 5. This results in a reduction in the deformation of the circuit board 6 (board) that is different from simple thermal expansion. Furthermore, this configuration provides a force sensor that is less susceptible to the effects of temperature changes.​

[0078] Regarding the thermal stress generated at the junction between strain 5 and intermediate member 11A (extension, insertion member), the thermal stress has a small effect on circuit board 6 (board), resulting in a small effect of temperature change on output.

[0079] Figure 8A This is a perspective view showing a schematic configuration of the force sensor 100E according to the fourth embodiment, as seen from above. Figure 8B It is along Figure 8A The diagram shows a schematic cross-sectional view of the force sensor 100E taken by line AA. The force sensor 100E has a similar structure to the force sensor 100D, but includes an intermediate member 11B (insertion member) that is constructed differently from the intermediate member 11A (extension, insertion member).

[0080] Figure 9 This is a perspective view of the intermediate member 11B (insertion member). The intermediate member 11B (insertion member) is not limited to any particular material. To reduce the impact of temperature changes on the output, it is suitable that the coefficient of thermal expansion of the insertion member is less than that of the displacement portion and greater than that of the board. By using a material with a coefficient of thermal expansion that is closer to that of the material of the circuit board 6 (board) than that of the material of the strain gauge 5, the impact of temperature changes on the output can be further reduced. In other words, it is suitable that the intermediate member 11B (insertion member) is made of a material with a coefficient of thermal expansion that is closer to that of the material of the circuit board 6 (board).

[0081] The intermediate member 11B (insertion member) includes a bottom 111B and arms 112BA, 112BB, 112BC and 112BD (extensions). The extensions have a flat spring structure, the elastic modulus of which in a first direction, as described below, is higher than the elastic modulus in a second direction, as described below.

[0082] Arms 112BA, 112BB, 112BC, and 112BD (extensions) are fixed to one of the inner ring 2 (displacement portion) and the circuit board 6 (board). The second surface of the bottom 111B, described below, is fixed to the other of the inner ring 2 (displacement portion) and the circuit board 6 (board). Here, the circuit board 6 (board) is fixed to the second surface of the intermediate member 11B (insertion member), which is opposite to the first surface of the bottom 111B, from which the arms 112BA, 112BB, 112BC, and 112BD (extensions) extend.

[0083] The intermediate member 11B (insertion member) is fixed to the inner ring portion 2 (displacement portion) of the strain body 5 at the arm portions 112BA, 112BB, 112BC, and 112BD (extension portions). Here, the arm portions 112BA, 112BB, 112BC, and 112BD (extension portions) extend in a direction (second direction) that intersects with the moving direction (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0084] Each of the arm portions 112BA, 112BB, 112BC, and 112BD (extension portions) has a portion at which the thickness in the radial direction (first direction) is smaller (thin) than the thickness in the two directions orthogonal to the radial direction (Y and Z directions in the case where the X direction is the radial direction). Take the arm portion 112BA as an example. The arm portion 112BA has a portion at which the dimension (thickness) in the X direction in the drawing is smaller (thin) than the dimensions in the Y and Z directions (directions orthogonal to the X direction) in the drawing.

[0085] In the present embodiment, by the deformation of the arm portions 112BA, 112BB, 112BC, and 112BD (extension portions), thermal stress at the joint due to the difference between the thermal expansion coefficients of the intermediate member 11B (insertion member) and the strain body 5 is reduced. In addition to this effect, for the same reason as in the third embodiment, thermal stress at the joint between the intermediate member 11B (insertion member) and the circuit board 6 (board) is reduced. As a result, the influence of temperature changes on the output can be further reduced.

[0086] Figure 10A is a perspective view showing a schematic configuration of the force sensor 100F according to the fifth embodiment as viewed from above. Figure 10B is a cross-sectional view of the schematic configuration of the force sensor 100F taken along the line A-A shown in Figure 10A The force sensor 100F has a substantially similar configuration to that of the force sensors 100D and 100E. However, the intermediate member 11C (insertion member) is configured differently from the intermediate member 11A (extension portion, intermediate member) and the intermediate member 11B (insertion member). Figure 11 is a perspective view of the intermediate member 11C (insertion member).

[0087] The intermediate member 11C includes a bottom portion 111C and arm portions 112CA, 112CB, 112CC, and 112CD (extension portions). The extension portions have a flat spring structure whose elastic modulus in a first direction described below is higher than the elastic modulus in a second direction described below.

[0088] The arm portions 112CA, 112CB, 112CC, and 112CD (extension portions) are fixed to one of the inner ring portion 2 (displacement portion) and the circuit board 6 (board). The second surface of the bottom portion 111C described below is fixed to the other of the inner ring portion 2 (displacement portion) and the circuit board 6 (board). Here, the circuit board 6 (board) is fixed to the arm portions 112CA, 112CB, 112CC, and 112CD (extension portions) of the intermediate member 11C (insertion member). The intermediate member 11C (insertion member) is fixed to the inner ring portion 2 (displacement portion) of the strain body 5 at a second surface that is opposite the first surface of the bottom portion 111C from which the arm portions 112CA, 112CB, 112CC, 112CD (extension portions) extend. Here, the arm portions 112CA, 112CB, 112CC, and 112CD (extension portions) extend in a direction (second direction) that intersects the direction of movement (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0089] Each of the arm portions 112CA, 112CB, 112CC, and 112CD (extension portions) has a portion at which the thickness in the radial direction (first direction) is smaller (thinner) than the thickness in the two directions orthogonal to the radial direction (Y and Z directions in the case where the X direction is the radial direction). Take the arm portion 112CA as an example. The arm portion 112CA has a portion at which the dimension (thickness) in the X direction (first direction) in the figure is smaller than the dimensions in the Y and Z directions (directions orthogonal to the X direction) in the figure.

[0090] In the present embodiment, by the deformation of the arm portions 112CA to 112CD (extension portions), thermal stress at the joint due to the difference between the coefficients of thermal expansion of the intermediate member 11C (insertion member) and the circuit board 6 (board) is reduced. This results in a reduction in the influence of temperature changes on the output.

[0091] Figure 12 FIG. 17 is a perspective view that shows another mode of the intermediate member 11D (insertion member) as an intermediate member (insertion member) according to the present embodiment (fifth embodiment).

[0092] The intermediate member 11D (insertion member) includes a bottom portion 111D and arm portions 112DA, 112DB, 112DC, 112DD, 112DE, 112DF, 112DG, and 112DH (extension portions). The extension portions have a flat spring structure in which the elastic modulus in a first direction described below is higher than the elastic modulus in a second direction described below.

[0093] The arm portions 112DA to 112DD (extension portions) are fixed to one of the inner ring portion 2 (displacement portion) and the circuit board 6 (board). The arm portions 112DE to 112DH (extension portions) are fixed to the other of the inner ring portion 2 (displacement portion) and the circuit board 6 (board). Here, the circuit board 6 (board) is fixed to the arm portions 112DA, 112DB, 112DC, and 112DD (extension portions) of the intermediate member 11D (insertion member). The intermediate member 11D (insertion member) is fixed to the inner ring portion 2 (displacement portion) of the strain body 5 at the arm portions 112DE, 112DF, 112DG, and 112DH (extension portions). Here, the arm portions 112DA, 112DB, 112DC, 112DD, 112DE, 112DF, 112DG, and 112DH (extension portions) extend in a direction (second direction) that intersects with a moving direction (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0094] In addition to the foregoing effects, thermal stress at the joint between the strain body 5 and the intermediate member 11D (insertion member) is reduced by the deformation of the arm portions 112DE, 112DF, 112DG, and 112DH during a change in temperature. This results in a reduction in the deformation of the circuit board 6 (board) that is different from simple thermal expansion. Furthermore, this configuration further reduces the influence of a change in temperature on the output.

[0095] Figure 13A 、 Figure 13B and Figure 13C is a drawing that shows a further mode of the intermediate member 11E (insertion member) as an intermediate member (insertion member) according to the present embodiment. Figure 13A is a drawing of the intermediate member 11E (insertion member) viewed from above. Figure 13B is a cross-sectional view of the intermediate member 11E (insertion member) taken along the line A-A shown in Figure 13A . Figure 13C is a cross-sectional view of the intermediate member 11E (insertion member) taken along the line B-B shown in Figure 13A . The behavior of the intermediate member 11E (insertion member) and the respective portions (bottom portion 111E and arm portions 112EA to 112EH) of the intermediate member 11E (insertion member) is similar to the behavior of the intermediate member 11D (insertion member) and the respective portions (bottom portion 111D and arm portions 112DA to 112DH) of the intermediate member 11D (insertion member). A description thereof will therefore be omitted.

[0096] The intermediate member (insertion member) described in this embodiment (fifth embodiment) is not limited to any specific material. To reduce the impact of temperature changes on the output, it is suitable that the coefficient of thermal expansion of the insertion member is less than that of the displacement portion and greater than that of the board. By using a material with a coefficient of thermal expansion that is closer to that of the material of the circuit board 6 (board) than that of the material of the strain gauge 5, the impact of temperature changes on the output can be further reduced. In other words, it is suitable that the intermediate member (insertion member) described in this embodiment (fifth embodiment) be made of a material with a coefficient of thermal expansion closer to that of the material of the circuit board 6 (board).

[0097] Figure 14A This is a perspective view showing a schematic configuration of the force sensor 100G according to the sixth embodiment, as seen from above. Figure 14B It is along Figure 14A The diagram shows a schematic cross-sectional view of the force sensor 100G, taken from line BB. Figure 15 This is a perspective view of the intermediate component 11F (inserted component).

[0098] In the force sensor 100G, the intermediate member 11F (insertion member) is fixed to the outer ring 1 (base). The circuit board 6 (board) is located below the intermediate member 11F (insertion member) and is fixed to the arms 112FA, 112FB, 112FC and 112FD (extensions) of the intermediate member 11F (insertion member).

[0099] The intermediate component 11F (insertion component) is not limited to any specific material. To reduce the impact of temperature changes on the output, it is suitable that the coefficient of thermal expansion of the insertion component is less than that of the displacement portion and greater than that of the board. Further reduction of the impact of temperature changes on the output can be achieved by using a material with a coefficient of thermal expansion that is closer to that of the material of the circuit board 6 (board) than that of the material of the strain gauge 5. In other words, it is suitable that the intermediate component 11F (insertion component) is made of a material with a coefficient of thermal expansion closer to that of the material of the circuit board 6 (board).

[0100] The intermediate member 11F (insertion member) includes a bottom 111F and arms 112FA, 112FB, 112FC and 112FD (extensions). The extensions have a flat spring structure, the elastic modulus of which in a first direction, as described below, is higher than the elastic modulus in a second direction, as described below.

[0101] The arm portions 112FA, 112FB, 112FC, and 112FD (extension portions) are fixed to one of the outer ring portion 1 (base) and the circuit board 6 (board). The second surface of the bottom portion 111F described below is fixed to the other of the outer ring portion 1 (base) and the circuit board 6 (board). Here, the circuit board 6 (board) is fixed to a second surface of the intermediate member 11F (insert member) that opposes a first surface of the bottom portion 111F from which the arm portions 112FA, 112FB, 112FC, 112FD (extension portions) extend. The intermediate member 11F (insert member) is fixed to the outer ring portion 1 (base) of the strain body 5 (first member) at the arm portions 112FA, 112FB, 112FC, and 112FD (extension portions). Here, the arm portions 112FA, 112FB, 112FC, and 112FD (extension portions) extend in a direction (second direction) that crosses a direction of movement (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0102] Each of the arm portions 112FA, 112FB, 112FC, and 112FD (extension portions) has a portion at which the thickness in the radial direction (first direction) is smaller (thin) than the thickness in the two directions orthogonal to the radial direction (Y and Z directions in the case where the X direction is the radial direction). Take the arm portion 112FD as an example. The arm portion 112FD has a portion at which the dimension (thickness) in the X direction in the drawing is smaller (thin) than the dimensions in the Y and Z directions (directions orthogonal to the X direction) in the drawing.

[0103] According to the present embodiment (sixth embodiment), as the temperature of the force sensor 100G changes, thermal stress that occurs at the joint between the intermediate member 11F (insert member) and the circuit board 6 (board) is small compared to the case in which the circuit board 6 (board) is fixed directly to the strain body 5. Furthermore, thermal stress at the joint due to a difference between the coefficients of thermal expansion of the intermediate member 11B (insert member) and the strain body 5 is reduced by deformation of the arm portions 112FA, 112FB, 112FC, and 112FD (extension portions). This results in a reduction in deformation of the circuit board 6 (board) that is different from simple thermal expansion. Furthermore, this configuration provides a force sensor that is less affected by changes in temperature on the output.

[0104] Figure 16A is a perspective view that shows the schematic configuration of a force sensor 100H according to a seventh embodiment, viewed from above. Figure 16B is a view along Figure 16AA cross-sectional view of the schematic configuration of the force sensor 100H taken along the line B-B shown. The force sensor 100H has a substantially similar configuration to the force sensor 100G, but in which the intermediate member 11G (insert member) is configured differently from the intermediate member 11F (insert member).

[0105] Figure 17 A perspective view of the intermediate member 11G (insert member). The intermediate member 11G (insert member) can be made of any material, and there is no particular restriction on the coefficient of thermal expansion.

[0106] The intermediate member 11F (insert member) includes a bottom portion 111G and arm portions 112GA, 112GB, 112GC, and 112GD (extension portions). The extension portions have a flat spring structure in which the modulus of elasticity in a first direction described below is higher than the modulus of elasticity in a second direction described below.

[0107] The arm portions 112GA, 112GB, 112GC, and 112GD (extension portions) are fixed to one of the outer ring portion 1 (base) and the circuit board 6 (board). The second surface of the bottom portion 111G described below is fixed to the other of the outer ring portion 1 (base) and the circuit board 6 (board). Here, the circuit board 6 (board) is fixed to the arm portions 112GA, 112GB, 112GC, and 112GD (extension portions) of the intermediate member 11G (insert member). The intermediate member 11G (insert member) is fixed to the outer ring portion 1 (base) of the strain body 5 at a second surface opposite the first surface of the bottom portion 111G from which the arm portions 112GA, 112GB, 112GC, 112GD (extension portions) extend. Here, the arm portions 112GA, 112GB, 112GC, and 112GD (extension portions) extend in a direction (second direction) that intersects the direction of movement (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0108] Each of the arm portions 112GA, 112GB, 112GC, and 112GD (extension portions) has a portion at which the thickness in the radial direction (first direction) is smaller (thinner) than the thickness in the two directions orthogonal to the radial direction (Y and Z directions in the case where the X direction is the radial direction). Take the arm portion 112GD as an example. The arm portion 112GD has a portion at which the dimension (thickness) in the X direction in the figure is smaller (thinner) than the dimensions in the Y and Z directions (directions orthogonal to the X direction) in the figure.

[0109] In the present embodiment, by deformation of the arm portions 112GA, 112GB, 112GC, and 112GD (extension portions), thermal stress at the joint due to a difference between the coefficients of thermal expansion of the intermediate member 11G (interposed member) and the circuit board 6 (board) is reduced. This results in a reduction in the influence of temperature changes on the output.

[0110] Figure 18 is a view showing another mode of the intermediate member (interposed member) according to the present embodiment (seventh embodiment).

[0111] The intermediate member 11H (interposed member) includes a bottom portion 111H and arm portions 112HA, 112HB, 112HC, 112HD, 112HE, 112HF, 112HG, and 112HH (extension portions). The extension portions have a flat spring structure in which the modulus of elasticity in a first direction described below is higher than the modulus of elasticity in a second direction described below.

[0112] Each of the arm portions 112HA, 112HB, 112HC, 112HD, 112HE, 112HF, 112HG, and 112HH (extension portions) has a portion at which the thickness in the radial direction (first direction) is smaller than the thickness in two directions orthogonal to the radial direction (Y and Z directions in the case where the X direction is the radial direction).

[0113] The arm portions 112HA to 112HD (extension portions) are fixed to one of the outer ring portion 1 (base portion) and the circuit board 6 (board). The arm portions 112HE to 112HH (extension portions) are fixed to the other of the outer ring portion 1 (base portion) and the circuit board 6 (board). Here, the circuit board 6 (board) is fixed at the arm portions 112HA, 112HB, 112HC, and 112HD (extension portions) of the intermediate member 11H (interposed member). The intermediate member 11H (interposed member) is fixed at the arm portions 112HE, 112HF, 112HG, and 112HH (extension portions) to the outer ring portion 1 (base portion) of the strain body 5. Here, the arm portions 112HA, 112HB, 112HC, 112HD, 112HE, 112HF, 112HG, and 112HH (extension portions) extend in a direction (second direction) intersecting the moving direction (position measurement direction, first direction) of the detection targets 4A, 4B, 4C, 4D, 4E, 4F, 4G, and 4H.

[0114] In addition to the foregoing effects, thermal stress at the joint between the strain body 5 and the intermediate member 11H (insertion member) is reduced by deformation of the arm portions 112HE, 112HF, 112HG, and 112HH (extension portions) during temperature changes. This results in a greater reduction in deformation of the circuit board 6 (board) than simple thermal expansion. This configuration further reduces the effects of temperature changes on the output.

[0115] The intermediate member (insertion member) described in this embodiment (seventh embodiment) is not limited to any particular material. In order to reduce the effects of temperature changes on the output, it is appropriate for the coefficient of thermal expansion of the insertion member to be smaller than the coefficient of thermal expansion of the displacement portion and larger than the coefficient of thermal expansion of the board. By using a material having a coefficient of thermal expansion closer to the coefficient of thermal expansion of the material of the circuit board 6 (board) than the coefficient of thermal expansion of the material of the strain body 5 to make the intermediate member (insertion member), it is possible to further reduce the effects of temperature changes on the output.

[0116] An eighth embodiment will be described. A transfer device including the force sensor 100B described in the second embodiment will be described here. Alternatively, the transfer device can include the force sensor described in the other embodiments. Figure 19 is a side view showing a schematic configuration of a transfer device 400. The transfer device 400 includes a robot arm 200 (movable unit), the force sensor 100B, a gripping unit 201 (movable unit), and a control device 210 (control unit).

[0117] The robot arm 200 (movable unit) is coupled with another robot arm not shown. The robot arm 200 is one of the movable units that is movable between predetermined positions. The gripping unit 201 (movable unit) is one of the movable units that is capable of gripping a to-be-transferred object 205 in a closed operation and releasing the gripped to-be-transferred object 205 in an open operation. Here, the transfer device 400 operates so that the gripping unit 201 (movable unit) grips the to-be-transferred object 205 at a predetermined position and inserts the gripped to-be-transferred object 205 into a hole 206a formed in a base 206. This operation is controlled by the control device 210 (control unit).

[0118] The force sensor 100B located between the robot arm 200 (movable unit) and the gripping unit 201 (movable unit) detects upward external force F received by the gripping unit 201 (movable unit) from the base 206 via the to-be-transferred object 205. For example, if the to-be-transferred object 205 comes into contact with the upper surface of the base 206 other than the hole 206a, some external force acts on the force sensor 100B from the gripping unit 201 (movable unit). Thus, it is detected that the position of the to-be-transferred object 205 is different from the position of the hole 206a.

[0119] Then, the control device 210 (control unit) controls the operation of the robot arm 200 (movable unit) to move the object to be conveyed 205 along the upper surface of the base 206. When the object to be conveyed 205 is positioned above the hole 206a, the external force acting on the force sensor 100B via the gripping unit 201 (movable unit) disappears. Thus, it is detected that the position of the object to be conveyed 205 is now at the hole 206a. The control device 210 (control unit) controls the operation of the robot arm 200 (movable unit) to put the object to be conveyed 205 into the hole 206a, and then controls the gripping unit 201 (movable unit) to release the object to be conveyed 205.

[0120] In this way, the force sensor 100B allows the conveying device 400 to control the operation of the robot arm 200 (movable unit) with high precision.

[0121] The force sensor according to the foregoing embodiments of the present application can also be used for various other mechanical devices other than the conveying device 400, which use the detection result of the external force to control the operation.

[0122] Thus far, the embodiments of the present application have been described in detail. However, the present application is not limited to the specific embodiments described above, and the present application also covers various modes not departing from the gist of the present application. The foregoing embodiments are merely some of the embodiments of the present application, and these embodiments can be appropriately combined.

[0123] According to the embodiments of the present application, a force sensor is provided, which can reduce the variation in output (detection value) due to thermal stress.

[0124] While the present application has been described with reference to the embodiments, it is understood that the present application is not limited to the disclosed embodiments, but is defined by the scope of the appended claims.

Claims

1. A force sensor comprising: a strain body including a base, a displacement portion configured to displace with respect to the base under an external force, and an elastic connection portion configured to elastically connect the base and the displacement portion; a plate including a detection unit configured to detect displacement of the displacement portion with respect to the base in a first direction; and an interposed member interposed between the strain body and the plate, the interposed member including an extension portion extending in a second direction intersecting a surface of the plate and the first direction, wherein a coefficient of thermal expansion of the interposed member is smaller than a coefficient of thermal expansion of the displacement portion and larger than a coefficient of thermal expansion of the plate. The extension portion has a flat spring structure having a higher elastic modulus in the first direction than in the second direction.

2. The force sensor of claim 1, wherein, 3. The force sensor according to claim 1, the interposed member including the extension portion and a base portion having a first surface and a second surface opposite to the first surface, the extension portion extending from the first surface, wherein wherein the extension portion is fixed to one of the displacement portion and the plate, and wherein the second surface is fixed to the other of the displacement portion and the plate.

4. The force sensor according to claim 1, the interposed member including a base portion, a first extension portion serving as the extension portion, and a second extension portion extending in a third direction intersecting the surface of the plate and the first direction, the third direction being different from the second direction, the base portion having a first surface and a second surface, the first extension portion extending from the first surface, the second extension portion extending from the second surface, the second surface being opposite to the first surface, wherein wherein the first extension portion is fixed to one of the displacement portion and the plate, and wherein the second extension portion is fixed to the other of the displacement portion and the plate. The second extension portion has a flat spring structure having a higher elastic modulus in the first direction than in the second direction.

5. The force sensor of claim 4, wherein, The coefficient of thermal expansion of the interposed member is closer to the coefficient of thermal expansion of the plate than the coefficient of thermal expansion of the displacement portion.

6. The force sensor of claim 1, wherein, 7. The force sensor according to claim 1, the interposed member including the extension portion and a base portion having a first surface and a second surface opposite to the first surface, the extension portion extending from the first surface, wherein wherein the extension portion is fixed to one of the base portion and the plate, and wherein the second surface is fixed to the other of the base portion and the plate.

8. The force sensor according to claim 1, the interposed member including a base portion, a first extension portion serving as the extension portion, and a second extension portion extending in a third direction intersecting the surface of the plate and the first direction, the third direction being different from the second direction, the base portion having a first surface and a second surface, the first extension portion extending from the first surface, the second extension portion extending from the second surface, the second surface being opposite to the first surface, wherein wherein the first extension portion is fixed to one of the base portion and the plate, and wherein the second extension portion is fixed to the other of the base portion and the plate. ​ 9. The force sensor of claim 8, wherein, The second extension portion has a flat spring structure with a higher elastic modulus in the first direction than in the second direction.

10. The force sensor of claim 7, wherein, The coefficient of thermal expansion of the insert member is less than the coefficient of thermal expansion of the base and greater than the coefficient of thermal expansion of the plate.

11. The force sensor of claim 10, wherein, The coefficient of thermal expansion of the insert member is closer to the coefficient of thermal expansion of the plate than the coefficient of thermal expansion of the base.

12. The force sensor of claim 1, wherein, The thickness of the extension portion in the first direction is less than the thickness in a direction orthogonal to the first direction.

13. The force sensor of claim 7, wherein, The thickness of the extension portion in the first direction is less than the thickness in a direction orthogonal to the first direction.

14. The force sensor of claim 8, wherein, The thickness of the first extension portion in the first direction and the thickness of the second extension portion in the first direction are each less than the thickness in a direction orthogonal to the respective first direction.

15. A robot comprising: a movable unit; a force sensor according to any one of claims 1 to 13; and a control unit configured to control operation of the movable unit based on output from the force sensor.

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