Force sensor

Abstract

In the present invention, a second sensor body faces a first sensor body in a first direction. A strain generating body includes: a connection body; a first thin-walled section that connects the connection body and the first sensor body and extends in a second direction orthogonal to the first direction; a base that connects the connection body and the second sensor body; a second thin-walled section that connects the base and the second sensor body and extends in the second direction; and displacement bodies. The base includes base protruding sections protruding from the connection body on both sides of the connection body in the second direction. The displacement bodies extend in the second direction from the base protruding sections.

Description

Force sensor

[0001] The present invention relates to a force sensor.

[0002] A force sensor that outputs a force acting in a predetermined axial direction and a moment (torque) acting around a predetermined rotation axis as an electric signal is known. Force sensors are widely used for force control of various robots such as industrial robots, collaborative robots, life support robots, medical robots, and service robots. The force sensor is required to be highly accurate, highly sensitive, and thin.

[0003] The force sensor is attached to the tip of the robot arm. The outer shape of the tip of the robot arm is relatively large, and the force sensor only needs to fit within this outer shape size. On the other hand, the height of the force sensor affects the distance from the tip of the robot arm to the workpiece. From the point of view of robot control, it is advantageous for this distance to be short. Therefore, there is a need to reduce the height of the force sensor, and a low-profile force sensor is required.

[0004] Japanese Patent Application Laid-Open No. 2021-135284

[0005] The present invention has been made in consideration of such points, and an object thereof is to provide a force sensor capable of achieving low profile.

[0006] [1] The present disclosure comprises: a first sensor body that is subjected to the action of a force or moment to be detected; a second sensor body facing the first sensor body in a first direction; a strain body connecting the first sensor body and the second sensor body, which is elastically deformed by the force or moment received by the first sensor body; a detection element that detects a change in capacitance value due to the displacement caused by the elastic deformation of the strain body; and a detection circuit that outputs an electrical signal indicating the force or moment acted on the first sensor body based on the detection result of the detection element, wherein the strain body includes: a connecting body portion extending in the first direction; a first thin-walled portion connecting the connecting body portion and the first sensor body, which is a first thin-walled portion extending in a second direction perpendicular to the first direction; a base connecting the connecting body portion and the second sensor body; a second thin-walled portion connecting the base and the second sensor body, which is a second thin-walled portion extending in the second direction; and a displacement body. The detection element may be a force sensor comprising a fixed electrode substrate attached to the second sensor body and a displacement electrode substrate attached to the displacement body and facing the fixed electrode substrate, wherein the base includes base protrusions that protrude from the connecting body on both sides of the connecting body in the second direction, and the displacement body extends from the base protrusions in the second direction.

[0007] [2] The present disclosure may be the force sensor described in [1], wherein the base is interposed between the second thin-walled portion and the connecting body portion in the first direction.

[0008] [3] The present disclosure may also be the force sensor described in [1] or [2], wherein the displacement body is formed separately from the base and bolted to the base projection, or joined by welding or adhesive.

[0009] [4] The present disclosure may also describe a force sensor according to any one of [1] to [3], wherein the first sensor body includes a first opening adjacent to the first thin-walled portion.

[0010] [5] The present disclosure may be the force sensor described in [4], wherein the first opening is formed on both sides of the first thin-walled portion in a third direction perpendicular to the first and second directions.

[0011] [6] The present disclosure may also be the force sensor described in [4] or [5], wherein the first opening is formed on one side of the first thin-walled portion in a third direction perpendicular to the first and second directions, and when viewed in the first direction, the portion of the first sensor body opposite to the first opening relative to the first thin-walled portion is cut out.

[0012] [7] The present disclosure may also be the force sensor described in [6], wherein the first sensor body includes a plurality of first protrusions projecting toward the second sensor body, and the strain generating body is positioned between two adjacent first protrusions.

[0013] [8] The present disclosure may also describe the force sensor described in any of [1] to [7], wherein the second sensor body includes a second opening adjacent to the second thin-walled portion.

[0014] [9] The present disclosure may be the force sensor described in [8], wherein the second opening is formed on both sides of the second thin-walled portion in a third direction perpendicular to the first and second directions.

[0015]

[10] The present disclosure may also be the force sensor described in [8], wherein the second opening is formed on one side of the second thin-walled portion in a third direction perpendicular to the first and second directions, and when viewed in the first direction, the portion of the second sensor body opposite to the second opening relative to the second thin-walled portion is cut out.

[0016]

[11] The present disclosure may also be the force sensor described in

[10] , wherein the second sensor body includes a plurality of second protrusions projecting toward the first sensor body, and the strain-generating body is positioned between two adjacent second protrusions.

[0017]

[12] The present disclosure may also be a force sensor according to any one of [1] to

[11] , wherein the strain generating body includes a first strain generating portion formed integrally with the first sensor body and including at least a part of the connecting body portion, and a second strain generating portion formed integrally with the second sensor body and including the base.

[0018]

[13] The present disclosure may also be the force sensor described in

[12] , wherein the strain-generating body further includes a strain-generating body fastening portion that fastens the first strain-generating portion and the second strain-generating portion.

[0019]

[14] The present disclosure may also be the force sensor described in

[12] , wherein the first strain-generating portion includes a part of the connecting body portion, and the second strain-generating portion includes another part of the connecting body portion.

[0020]

[15] The present disclosure may be a force sensor according to any one of [1] to

[13] , wherein the displacement body includes a first displacement portion extending from the base in the second direction and a second displacement portion extending from the first displacement portion in a third direction perpendicular to the first and second directions toward the inside of the force sensor as viewed in the first direction, and the displacement electrode substrate is attached to the second displacement portion.

[0021]

[16] The present disclosure may also be a force sensor according to any one of [1] to

[15] , wherein the first sensor body and the second sensor body are connected by four strain bodies, the four strain bodies include a first strain body, a second strain body, a third strain body, and a fourth strain body, the first direction being the Z-axis direction in an XYZ three-dimensional coordinate system, the first strain body being positioned on the positive Y-axis side with respect to the center of the first sensor body, the second strain body being positioned on the negative X-axis side with respect to the center of the first sensor body, the third strain body being positioned on the negative Y-axis side with respect to the center of the first sensor body, and the fourth strain body being positioned on the positive X-axis side with respect to the center of the first sensor body.

[0022] According to the present invention, it is possible to reduce the height.

[0023] Figure 1 is a perspective view showing an example of a robot to which the force sensor according to this embodiment is applied. Figure 2 is a cross-sectional view showing the force sensor according to this embodiment. Figure 3 is a plan view showing the force sensor of Figure 2 with the force-receiving body side cover omitted. Figure 4 is a plan cross-sectional view taken along line A-A in Figure 2. Figure 5 is a plan cross-sectional view taken along line B-B in Figure 2. Figure 6 is a view taken along arrow P in Figure 3 with the outer casing omitted. Figure 7 is a front cross-sectional view showing the first strain-generating body of Figure 2. Figure 8 is a side cross-sectional view showing the first strain-generating body of Figure 7 when viewed towards the positive X-axis direction. Figure 9 is a schematic front view showing the deformation state of the first strain-generating body of Figure 7 when subjected to a force in the positive X-axis direction. Figure 10 is a schematic front view showing the deformation state of the first strain-generating body of Figure 7 when subjected to a force in the positive Z-axis direction. Figure 11 is a schematic front view showing the deformation state of the first strain-generating body of Figure 7 when subjected to a force in the negative Z-axis direction. Figure 12 is a table showing the change in capacitance value of each capacitive element in the first strain body of Figure 7. Figure 13 is a table showing the change in capacitance value of each capacitive element in the force sensors shown in Figures 3 to 5. Figure 14 is a table showing the principal axis sensitivity and other axis sensitivity based on the change in capacitance value shown in Figure 13. Figure 15 is a front view showing a modified example of the first strain body of Figure 7. Figure 16 is a plan cross-sectional view showing a modified example of the force sensor of Figure 4. Figure 17 is a plan view showing another modified example of the force sensor of Figure 3. Figure 18 is a plan cross-sectional view corresponding to Figure 4, showing the force sensor of Figure 17. Figure 19 is a plan cross-sectional view corresponding to Figure 5, showing the force sensor of Figure 17. Figure 20 is a view taken along arrow Q in Figure 17, with the casing omitted. Figure 21 is a cross-sectional view showing a modified example of the force sensor of Figure 2. Figure 22 is a plan view of the strain body shown in Figure 21.

[0024] Embodiments of the present invention will be described below with reference to the drawings. Note that, for the sake of illustration and ease of understanding, the scale and aspect ratios of the drawings accompanying this specification have been appropriately altered and exaggerated from those of the actual objects.

[0025] In this specification, geometric conditions, physical properties, terms that specify the degree of geometric conditions or physical properties, and numerical values ​​that indicate geometric conditions or physical properties may be interpreted without being bound by strict meaning. Furthermore, these geometric conditions, physical properties, terms, and numerical values ​​may be interpreted to include a range that can be expected to perform similar functions. Examples of terms that specify geometric conditions include "length," "angle," "shape," "parallel," "orthogonal," and "identical."

[0026] An embodiment of the force sensor according to the present invention will be described using Figures 1 to 22.

[0027] First, the robot 1 according to this embodiment will be described with reference to Figure 1. Figure 1 is a perspective view showing an example of the robot 1 according to this embodiment. The robot 1 is fitted with a force sensor 10 according to this embodiment. Examples of robots 1 include industrial robots, collaborative robots, life support robots, medical robots, and service robots. For convenience, the following description will use an industrial robot fitted with a force sensor 10 as an example.

[0028] As shown in Figure 1, the industrial robot 1 comprises a robot body 2, a tool 3, a force sensor 10, and a controller 5. The robot body 2 includes a robot arm 4. The robot arm 4 has a multi-jointed arm structure.

[0029] A force sensor 10 is attached to the tip of the robot arm 4. More specifically, the force sensor 10 is attached between the robot arm 4 and the tool 3. The force sensor 10 is electrically connected to the controller 5 via an electrical cable (not shown). Examples of the tool 3 include an end effector (such as a gripper) and a tool changer (neither of which are shown).

[0030] The controller 5 controls the force of the robot 1 based on the electrical signals output from the force sensor 10. This controls the movement of the robot body 2 and the tool 3.

[0031] The force sensor 10 according to an embodiment of the present invention will be described below with reference to Figures 2 to 7. Figure 2 is a cross-sectional view showing the force sensor according to this embodiment. Figure 3 is a plan view showing the force sensor of Figure 2 with the force-receiving body side cover omitted. Figure 4 is a cross-sectional view taken along line A-A in Figure 2, and Figure 5 is a cross-sectional view taken along line B-B in Figure 2. Figure 6 is a view taken along arrow P in Figure 3 with the outer casing omitted, and Figure 7 is a front cross-sectional view showing the first strain-generating body of Figure 2. Figure 8 is a side cross-sectional view showing the first strain-generating body of Figure 7 when viewed towards the positive side in the X-axis direction.

[0032] In the following description, we define an XYZ three-dimensional coordinate system, with the Z-axis direction (first direction) being the vertical direction, and the force sensor 10 is positioned such that the force-receiving body 20 is on the upper side and the fixed body 25 is on the lower side. Therefore, the force sensor 10 according to this embodiment is not limited to being used in a position where the Z-axis direction is the vertical direction. Furthermore, it is arbitrary whether the force-receiving body 20 or the fixed body 25 is positioned on the upper or lower side.

[0033] The force sensor 10 has the function of outputting as an electrical signal the force acting in a predetermined axial direction and the moment acting around a predetermined rotation axis. However, it is not limited to this, and it may be configured to output only one of the force or moment as an electrical signal, or furthermore, it may be configured to output as an electrical signal the axial component of at least one of the force or moment.

[0034] As shown in Figures 2 and 3, the force sensor 10 comprises a force receiving body 20, a fixed body 25, strain generating bodies 30A to 30D, a detection element 50, a detection circuit 60, and an outer casing 70. Each component will be described in more detail below. Figure 2 is a cross-sectional view of the first strain generating body 30A shown in Figure 3, viewed from below in the plane of Figure 3.

[0035] [Force Receiving Body] The force receiving body 20 is an example of the first sensor body. The force receiving body 20 is subjected to the force or moment to be detected. As a result of this action, the force receiving body 20 moves relative to the fixed body 25.

[0036] As shown in Figure 3, in this embodiment, the planar shape of the force-receiving body 20 is circular. However, the planar shape of the force-receiving body 20 is not limited to a circle; it may be rectangular or any other shape.

[0037] As shown in Figure 2, the force-receiving body 20 may include a force-receiving body main body 20a, a force-receiving body projection 20b, and a stopper projection 20c. The force-receiving body main body 20a is the part that contacts the tool 3 and is generally formed to align with the X-axis and Y-axis directions. The force-receiving body main body 20a includes a plurality of screw holes 21 into which bolts (not shown) for fixing to the tool 3 are screwed, and is fixed to the tool 3. In this way, the force-receiving body 20 receives force or moment from the tool 3. The screw holes 21 do not have to penetrate the force-receiving body main body 20a. Strain generating bodies 30A to 30D are connected to the force-receiving body main body 20a. Strictly speaking, the stopper projection 20c, which is arranged as shown in Figure 3, does not appear in the cross-section shown in Figure 2, but for convenience, the stopper projection 20c is shown in Figure 2 to show the configuration of the force-receiving body 20 including the stopper projection 20c.

[0038] As shown in Figure 2, the force-receiving body projection 20b protrudes from the force-receiving body 20a toward the fixed body 25. The force-receiving body projection 20b is an example of the first projection.

[0039] As shown in Figures 3 and 4, when viewed in the Z-axis direction, the force-receiving body projection 20b may be formed on the outer circumference of the force-receiving body 20, or it may be positioned outside the strain-generating bodies 30A to 30D. The force-receiving body projection 20b may be formed around the entire circumference of the force-receiving body 20. In this case, the force-receiving body projection 20b may surround each of the strain-generating bodies 30A to 30D, which will be described later, from the outer circumference. In this case, as shown in Figure 6, when viewed from the outer circumference, the strain-generating bodies 30A to 30D may be covered by the force-receiving body projection 20b and the fixed body projection 25b (described later), and may not be exposed to the outer circumference. That is, the force-receiving body 20 and the fixed body 25 may not be cut out when viewed in the Z-axis direction, and may be formed in a circular shape overall.

[0040] As shown in Figures 2 and 6, the stopper protrusions 20c are formed on the surface of the force-receiving body projection 20b that faces the fixed body 25. The stopper protrusions 20c may be configured to be inserted into the stopper recess 25c (described later) of the fixed body 25. Multiple stopper protrusions 20c may be formed on the force-receiving body projection 20b. For example, the number of stopper protrusions 20c may be three or more, or four. As shown in Figure 3, the stopper protrusions 20c may be spaced apart in the circumferential direction of the force-receiving body 20 when viewed in the Z-axis direction.

[0041] As shown in Figure 3, the force-receiving body 20 may include a force-receiving body opening 22 formed in the force-receiving body main body 20a. The force-receiving body opening 22 is an example of a first opening. The force-receiving body 20 may include a plurality of force-receiving body openings 22. The force-receiving body openings 22 may be adjacent to the force-receiving body side thin-walled portion 32 of the strain-generating body 30A to 30D, which will be described later, and may also be formed on both sides of the force-receiving body side thin-walled portion 32. As shown in Figure 8, the force-receiving body opening 22 penetrates the force-receiving body main body 20a. The force-receiving body opening 22 may be formed to separate the force-receiving body side thin-walled portion 32 from the portions of the force-receiving body main body 20a on both sides of the force-receiving body side thin-walled portion 32. As shown in Figure 3, the force-receiving body opening 22 may extend beyond the force-receiving body side thin-walled portion 32 on both sides of the force-receiving body side thin-walled portion 32.

[0042] More specifically, for the first strain body 30A, force-receiving openings 22 may be formed on both sides of the force-receiving body side thin-walled portion 32 in the Y-axis direction. The force-receiving openings 22 adjacent to the force-receiving body side thin-walled portion 32 of the first strain body 30A are spaced apart from the force-receiving body side thin-walled portion 32 and the portions of the force-receiving body body 20a on both sides of the force-receiving body side thin-walled portion 32 in the Y-axis direction. The force-receiving openings 22 may extend further in the X-axis direction than the force-receiving body side thin-walled portion 32 on both sides of the force-receiving body side thin-walled portion 32 in the X-axis direction.

[0043] Regarding the second warped body 30B, in the X-axis direction, the force-receiving body openings 22 may be formed on both sides of the force-receiving body thin-walled portion 32. The force-receiving body openings 22 adjacent to the force-receiving body thin-walled portion 32 of the second warped body 30B separate the force-receiving body thin-walled portion 32 from the portions on both sides of the force-receiving body thin-walled portion 32 in the X-axis direction of the force-receiving body main body 20a. The force-receiving body openings 22 may extend in the Y-axis direction beyond the force-receiving body thin-walled portion 32 on both sides of the force-receiving body thin-walled portion 32 in the Y-axis direction.

[0044] Regarding the third warped body 30C, in the Y-axis direction, the force-receiving body openings 22 may be formed on both sides of the force-receiving body thin-walled portion 32. The force-receiving body openings 22 adjacent to the force-receiving body thin-walled portion 32 of the third warped body 30C separate the force-receiving body thin-walled portion 32 from the portions on both sides of the force-receiving body thin-walled portion 32 in the Y-axis direction of the force-receiving body main body 20a. The force-receiving body openings 22 may extend in the X-axis direction beyond the force-receiving body thin-walled portion 32 on both sides of the force-receiving body thin-walled portion 32 in the X-axis direction.

[0045] Regarding the fourth warped body 30D, in the X-axis direction, the force-receiving body openings 22 may be formed on both sides of the force-receiving body thin-walled portion 32. The force-receiving body openings 22 adjacent to the force-receiving body thin-walled portion 32 of the fourth warped body 30D separate the force-receiving body thin-walled portion 32 from the portions on both sides of the force-receiving body thin-walled portion 32 in the X-axis direction of the force-receiving body main body 20a. The force-receiving body openings 22 may extend in the Y-axis direction beyond the force-receiving body thin-walled portion 32 on both sides of the force-receiving body thin-walled portion 32 in the Y-axis direction.

[0046] [Fixing body] As shown in FIG. 2, the fixing body 25 is an example of the second sensor body. The fixing body 25 supports the force-receiving body 20. The fixing body 25 is arranged at a position different from the force-receiving body 20 in the Z-axis direction and faces the force-receiving body 20. More specifically, the fixing body 25 is arranged on the negative side of the force-receiving body 20 in the Z-axis direction.

[0047] As shown in FIG. 3, in the present embodiment, the planar shape of the fixed body 25 is circular, similar to the force-receiving body 20. When viewed in the Z-axis direction, the fixed body 25 overlaps the force-receiving body 20. However, the planar shape of the fixed body 25 is not limited to a circle and may be rectangular or arbitrary. At least one of the planar shapes of the force-receiving body 20 and the fixed body 25 may be circular. In this case, one of the planar shapes of the force-receiving body 20 and the fixed body 25 may be circular and the other may be a shape other than a circle.

[0048] As shown in FIG. 2, the fixed body 25 may include a fixed body main body 25a, a fixed body protruding portion 25b, and a stopper recess 25c. The fixed body main body 25a is a portion that abuts against the tip of the robot arm 4 and is generally formed along the X-axis direction and the Y-axis direction. The fixed body main body 25a includes a plurality of screw holes 26 into which bolts (not shown) for fixing to the tip of the robot arm 4 are screwed and is fixed to the robot arm 4. As a result, the fixed body 25 is supported by the robot body 2. The screw holes 26 do not have to penetrate the fixed body main body 25a. The strain generating bodies 30A to 30D are connected to the fixed body main body 25a. Strictly speaking, the stopper recess 25c arranged as shown in FIG. 3 does not appear in the cross section shown in FIG. 2, but for the sake of convenience, the stopper recess 25c is shown in FIG. 2 to show the configuration of the fixed body 25 including the stopper recess 25c.

[0049] As shown in FIG. 2, the fixed body protruding portion 25b protrudes from the fixed body main body 25a toward the force-receiving body protruding portion 20b described above. The fixed body protruding portion 25b is an example of the second protruding portion. The surface of the fixed body protruding portion 25b on the side of the force-receiving body 20 does not abut against the surface of the force-receiving body protruding portion 20b on the side of the fixed body 25 and may be opposed. A gap for enabling relative displacement between the force-receiving body 20 and the fixed body 25 is formed between the force-receiving body protruding portion 20b and the fixed body protruding portion 25b.

[0050] As shown in Figure 5, when viewed in the Z-axis direction, the fixed body projection 25b may be formed on the outer circumference of the fixed body 25, or it may be positioned outside the strain generating bodies 30A to 30D. The fixed body projection 25b may be formed around the entire circumference of the fixed body 25. In this case, the fixed body projection 25b may surround each of the strain generating bodies 30A to 30D, which will be described later, from the outer circumference. In this case, as shown in Figure 6, when viewed from the outer circumference, the strain generating bodies 30A to 30D may be covered by the force receiving projection 20b and the fixed body projection 25b, and may not be exposed to the outer circumference.

[0051] As shown in Figures 2 and 6, the stopper recess 25c is formed on the surface of the fixed body projection 25b that faces the force receiving body 20. The stopper projection 20c of the force receiving body 20 is inserted into the stopper recess 25c. Multiple stopper recesses 25c may be formed on the fixed body projection 25b. The number of stopper recesses 25c may be the same as the number of stopper projections 20c described above. As shown in Figure 3, the stopper recesses 25c may be spaced apart in the circumferential direction of the fixed body 25 when viewed in the Z-axis direction.

[0052] The stopper projection 20c of the force-receiving body 20 is inserted into the stopper recess 25c of the fixed body 25, thereby forming a stopper that restricts the relative displacement of the force-receiving body 20 and the fixed body 25 of the force sensor 10. In addition, to restrict the relative displacement of the force-receiving body 20 and the fixed body 25, the force-receiving body 20 may include other stopper projections (not shown), and the fixed body 25 may include other stopper recesses (not shown). This allows for the restriction of displacement in directions different from those restricted by the stopper projection 20c and stopper recess 25c described above. Note that the stopper projection 20c may be formed on the fixed body 25, and the stopper recess 25c may be formed on the force-receiving body 20.

[0053] As shown in Figure 5, the fixing body 25 may include a fixing body opening 27 formed in the fixing body body 25a. The fixing body opening 27 is an example of a second opening. The fixing body 25 may include a plurality of fixing body openings 27. The fixing body openings 27 may be adjacent to the fixing body side thin-walled portions 34 of the strain generating bodies 30A to 30D, which will be described later, and may also be formed on both sides of the fixing body side thin-walled portions 34. As shown in Figure 8, the fixing body openings 27 penetrate the fixing body body 25a. The fixing body openings 27 may be formed to separate the fixing body side thin-walled portions 34 from the portions of the fixing body body 25a on both sides of the fixing body side thin-walled portions 34. As shown in Figure 5, the fixing body openings 27 may extend beyond the fixing body side thin-walled portions 34 on both sides of the fixing body side thin-walled portions 34. Note that in Figure 4, the fixing body openings 27 are omitted for clarity.

[0054] More specifically, for the first strain-generating body 30A, a fixed body opening 27 may be formed on both sides of the fixed body-side thin-walled portion 34 in the Y-axis direction. The fixed body opening 27 adjacent to the fixed body-side thin-walled portion 34 of the first strain-generating body 30A separates the fixed body-side thin-walled portion 34 from the portions of the fixed body body 25a on both sides of the fixed body-side thin-walled portion 34 in the Y-axis direction. The fixed body opening 27 may extend further in the X-axis direction than the fixed body-side thin-walled portion 34 on both sides of the fixed body-side thin-walled portion 34 in the X-axis direction.

[0055] With respect to the second strain-generating body 30B, fixing body openings 27 may be formed on both sides of the thin-walled portion 34 on the fixing body side in the X-axis direction. The fixing body openings 27 adjacent to the thin-walled portion 34 on the fixing body side of the second strain-generating body 30B are spaced apart from the thin-walled portion 34 on the fixing body side and the portions of the fixing body body 25a on both sides of the thin-walled portion 34 on the fixing body side in the X-axis direction. The fixing body openings 27 may extend in the Y-axis direction beyond the thin-walled portion 34 on both sides of the thin-walled portion 34 on the fixing body side in the Y-axis direction.

[0056] For the third strain-generating body 30C, a fixed body opening 27 may be formed on both sides of the fixed body-side thin-walled portion 34 in the Y-axis direction. The fixed body opening 27 adjacent to the fixed body-side thin-walled portion 34 of the third strain-generating body 30C separates the fixed body-side thin-walled portion 34 from the portions of the fixed body body 25a on both sides of the fixed body-side thin-walled portion 34 in the Y-axis direction. The fixed body opening 27 may extend in the X-axis direction beyond the fixed body-side thin-walled portion 34 on both sides of the fixed body-side thin-walled portion 34 in the X-axis direction.

[0057] For the fourth strain-generating body 30D, a fixed body opening 27 may be formed on both sides of the fixed body-side thin-walled portion 34 in the X-axis direction. The fixed body opening 27 adjacent to the fixed body-side thin-walled portion 34 of the fourth strain-generating body 30D separates the fixed body-side thin-walled portion 34 from the portions of the fixed body body 25a on both sides of the fixed body-side thin-walled portion 34 in the X-axis direction. The fixed body opening 27 may extend in the Y-axis direction beyond the fixed body-side thin-walled portion 34 on both sides of the fixed body-side thin-walled portion 34 in the Y-axis direction.

[0058] [Strain-generating bodies] As shown in Figures 2 to 5, the strain-generating bodies 30A to 30D connect the force-receiving body 20 and the fixed body 25. The force-receiving body 20 is supported by the fixed body 25 via the strain-generating bodies 30A to 30D.

[0059] In this embodiment, the force-receiving body 20 and the fixed body 25 may be connected by four strain-generating bodies 30A to 30D. The four strain-generating bodies 30A to 30D may include a first strain-generating body 30A, a second strain-generating body 30B, a third strain-generating body 30C, and a fourth strain-generating body 30D.

[0060] As shown in Figures 3 to 5, when viewed in the Z-axis direction, the first strain element 30A may be positioned on the positive Y-axis side with respect to the center O of the force-bearing body 20. Similarly, when viewed in the Z-axis direction, the second strain element 30B may be positioned on the negative X-axis side with respect to the center O of the force-bearing body 20. The third strain element 30C may be positioned on the negative Y-axis side with respect to the center O of the force-bearing body 20. The fourth strain element 30D may be positioned on the positive X-axis side with respect to the center O of the force-bearing body 20. In this case, the center O of the force-bearing body 20 is positioned between the first strain element 30A and the third strain element 30C, and the center O of the force-bearing body 20 is positioned between the second strain element 30B and the fourth strain element 30D.

[0061] The number of strain-generating bodies connecting the force-receiving body 20 and the stationary body 25 is not limited to four; it may be two, three, five or more, or any number. For example, when the force-receiving body 20 and the stationary body 25 are connected by three strain-generating bodies, if the three strain-generating bodies are arranged at equal intervals (120-degree pitch) in the circumferential direction, the six-axis components of the force can be detected. Alternatively, the force-receiving body 20 and the stationary body 25 may be connected by only one strain-generating body. In this case, if the detection element 50 is configured with two capacitive elements as shown in Figure 6, the two-axis components of the force can be detected, as will be described later. The detection element 50 may also be configured with only one capacitive element to detect the one-axis component of the force.

[0062] As shown in Figures 3 to 5, the four strain-generating bodies 30A to 30D in this embodiment are arranged in an annular shape. That is, as described above, the force-receiving body 20 and the stationary body 25 are formed in a circular shape when viewed in the Z-axis direction, and the four strain-generating bodies 30A to 30D are arranged to form a rectangular annular shape. The thin-walled portion 32 on the force-receiving body side and the thin-walled portion 34 on the stationary body side of each strain-generating body 30A to 30D, described later, are formed linearly along the second direction when viewed in the Z-axis direction. That is, the second direction of the first strain-generating body 30A and the second direction of the third strain-generating body 30C correspond to the X-axis direction. For the first strain-generating body 30A and the third strain-generating body 30C, the thin-walled portion 32 on the force-receiving body side and the thin-walled portion 34 on the stationary body side are formed linearly along the X-axis direction. The second direction of the second strain-generating body 30B and the second direction of the fourth strain-generating body 30D correspond to the Y-axis direction. For the second strain body 30B and the fourth strain body 30D, the thin-walled portion 32 on the force-receiving body side and the thin-walled portion 34 on the fixed body side are formed in a straight line along the Y-axis direction. Note that the second direction of each strain body 30A to 30D is not limited to the example shown in Figure 3 and can be arbitrary. Also, the thin-walled portion 32 on the force-receiving body side and the thin-walled portion 34 on the fixed body side of each strain body 30A to 30D do not have to be aligned along the X-axis direction or the Y-axis direction. For example, the arrangement of the four strain bodies 30A to 30D is not limited to an annular arrangement, and they may be arranged irregularly at any position.

[0063] Next, the strain-generating bodies 30A to 30D according to this embodiment will be described in more detail.

[0064] The strain generating bodies 30A to 30D in this embodiment are configured to undergo elastic deformation and generate strain due to the action of a force or moment received by the force receiving body 20, thereby causing displacement. Here, we will explain using the first strain generating body 30A, which has the X-axis direction as the second direction, as an example from among the four strain generating bodies 30A to 30D described above. The Y-axis direction corresponds to the third direction. The third direction is perpendicular to both the first and second directions. The second strain generating body 30B, the third strain generating body 30C, and the fourth strain generating body 30D have the same configuration as the first strain generating body 30A. Therefore, below, we will mainly describe the first strain generating body 30A in detail, and add descriptions of the second strain generating body 30B, the third strain generating body 30C, and the fourth strain generating body 30D as appropriate.

[0065] As shown in Figure 7, the first strain-generating body 30A may include a connecting body portion 31, a force-receiving body side thin-walled portion 32, a base 33, a fixed body side thin-walled portion 34, and a displacement body 35.

[0066] The connecting body portion 31 may extend in the Z-axis direction. The connecting body portion 31 extends from the force-receiving body side thin-walled portion 32 to the base 33. The connecting body portion 31 is connected to the force-receiving body 20a of the force-receiving body 20 via the force-receiving body side thin-walled portion 32, and is also connected to the fixed body 25a of the fixed body 25 via the base 33 and the fixed body side thin-walled portion 34. The connecting body portion 31 may be formed along the central axis CL of the first strain-generating body 30A. The central axis CL of the first strain-generating body 30A is a line along the Z-axis direction that passes through the center of the first strain-generating body 30A in the X-axis direction.

[0067] The force-receiving body side thin-walled portion 32 is an example of the first thin-walled portion. The force-receiving body side thin-walled portion 32 connects the connecting body portion 31 and the force-receiving body 20a. As shown in Figures 3 and 7, the force-receiving body side thin-walled portion 32 of the first strain-generating body 30A extends in the X-axis direction. The force-receiving body side thin-walled portion 32 protrudes in the X-axis direction from the connecting body portion 31 on both sides of the connecting body portion 31 in the X-axis direction. In other words, the connecting body portion 31 is positioned in the center of the force-receiving body side thin-walled portion 32 in the X-axis direction.

[0068] The force-receiving body side thin-walled portion 32 may be formed in a rectangular shape such that, when viewed in the Z-axis direction, it has a longitudinal direction along the X-axis direction. As shown in Figure 7, the thickness t1 of the force-receiving body side thin-walled portion 32 is thinner than the thickness t2 of the force-receiving body 20a. The force-receiving body side thin-walled portion 32 is configured to be elastically deformable when the force-receiving body 20 is subjected to the action of a force or moment. The force-receiving body side thin-walled portion 32 may be formed so as to extend from the surface of the force-receiving body 20a facing the fixed body 25a in a direction along that surface. In this case, the force-receiving body side recess 36 may be formed on the surface of the force-receiving body 20a opposite to the fixed body 25a.

[0069] The base 33 is connected to the connecting body portion 31 and also to the fixed body body 25a of the fixed body 25 via the fixed body side thin-walled portion 34. The base 33 is formed on the fixed body side thin-walled portion 34. The base 33 protrudes from the connecting body portion 31 on both sides of the connecting body portion 31 in the X-axis direction. The base 33 includes a pair of base protrusions 33a that protrude from the connecting body portion 31. As shown in Figure 7, the dimension w1 in the X-axis direction of the base 33 of the first strain-generating body 30A is larger than the dimension w2 in the X-axis direction of the connecting body portion 31. Dimension w1 is the dimension including the base protrusions 33a described above.

[0070] The thin-walled portion 34 on the fixed body side is an example of the second thin-walled portion. The thin-walled portion 34 on the fixed body side connects the base 33 and the fixed body body 25a of the fixed body 25. As shown in Figures 5 and 7, the thin-walled portion 34 on the fixed body side of the first strain-generating body 30A extends in the X-axis direction. The thin-walled portion 34 on the fixed body side protrudes in the X-axis direction from the base 33 on both sides of the base 33 in the X-axis direction. In other words, the base 33 is positioned in the center of the thin-walled portion 34 on the fixed body side in the X-axis direction.

[0071] The thin-walled portion 34 on the fixed body side may be formed in a rectangular shape such that, when viewed in the Z-axis direction, it has a longitudinal direction along the X-axis direction. As shown in Figure 7, the thickness t3 of the thin-walled portion 34 on the fixed body side is thinner than the thickness t4 of the fixed body main body 25a. The thin-walled portion 34 on the fixed body side is configured to be elastically deformable when the force-receiving body 20 is subjected to force or moment. The thin-walled portion 34 on the fixed body side may be formed extending from the surface of the fixed body main body 25a facing the force-receiving body main body 20a in a direction along that surface. In this case, the recess 37 on the fixed body side may be formed on the surface of the fixed body main body 25a opposite to the force-receiving body main body 20a.

[0072] As shown in Figures 4 and 7, the displacement body 35 extends from the base 33 in the X-axis direction. The displacement body 35 may also extend from the base projection 33a of the base 33 in the X-axis direction. When viewed in the Z-axis direction, the displacement body 35 may be formed in a straight line along the X-axis direction, or it may be formed in a rectangular shape having a longitudinal direction along the X-axis direction. The tip of the displacement body 35 faces the fixed body 25a. In this embodiment, the displacement body 35 is formed separately from the base 33 and bolted to the base projection 33a. More specifically, the displacement body 35 is fastened to the base projection 33a by displacement bolts 38. The displacement body 35 does not have to be fastened to the base projection 33a by displacement bolts 38. For example, the displacement body 35 may be joined to the base projection 33a by welding or by adhesive.

[0073] In this embodiment, two displacement bodies 35 extend from the base 33. Each displacement body 35 may extend in the X-axis direction from a corresponding base projection 33a. One displacement body 35 of the first strain body 30A extends in the negative X-axis direction from a base projection 33a located on the negative X-axis side. The other displacement body 35 extends in the positive X-axis direction from a base projection 33a located on the positive X-axis side.

[0074] As shown in Figure 7, the first strain generating body 30A may be divided into two parts in the Z-axis direction. The first strain generating body 30A according to this embodiment may include a force-receiving body side strain generating portion 40, a fixed body side strain generating portion 41, and a strain generating body bolt 42.

[0075] The force-receiving body side strain portion 40 is an example of the first strain portion. The force-receiving body side strain portion 40 is formed integrally and continuously with the force-receiving body 20. The force-receiving body side strain portion 40 includes at least a part of the connecting body portion 31. In this embodiment, the force-receiving body side strain portion 40 includes a force-receiving body side body portion 31a and a force-receiving body side thin-walled portion 32 of the connecting body portion 31. The force-receiving body side body portion 31a is the portion of the connecting body portion 31 located on the force-receiving body 20 side.

[0076] The force-receiving body side strain-generating portion 40 and the force-receiving body 20 configured as described above may be integrally formed from a continuous material. The force-receiving body side strain-generating portion 40 and the force-receiving body 20 may be manufactured from a single block material by machining (e.g., cutting) or by casting. The force-receiving body side strain-generating portion 40 and the force-receiving body 20 may be made from a metallic material such as an aluminum alloy or an iron alloy.

[0077] The fixed body side strain portion 41 is an example of a second strain portion. The fixed body side strain portion 41 is formed integrally and continuously with the fixed body 25. The fixed body side strain portion 41 includes a base 33. The fixed body side strain portion 41 according to this embodiment includes another part of the connecting body portion 31. More specifically, the fixed body side strain portion 41 includes the fixed body side body portion 31b of the connecting body portion 31, the base 33, and the fixed body side thin-walled portion 34. The fixed body side body portion 31b is the portion of the connecting body portion 31 located on the fixed body 25 side.

[0078] The fixed body side strain portion 41 and the fixed body 25 configured as described above may be integrally formed from a continuous material. The fixed body side strain portion 41 and the fixed body 25 may be manufactured from a single block material by machining (e.g., cutting) or by casting. The fixed body side strain portion 41 and the fixed body 25 may be made from a metallic material such as an aluminum alloy or an iron alloy.

[0079] As shown in Figure 7, the boundary between the force-receiving body side strain-generating portion 40 and the fixed body side strain-generating portion 41 is formed in the connecting body portion 31. This boundary exists between the force-receiving body side body portion 31a that constitutes the force-receiving body side strain-generating portion 40 and the fixed body side body portion 31b that constitutes the fixed body side strain-generating portion 41. However, the boundary between the force-receiving body side strain-generating portion 40 and the fixed body side strain-generating portion 41 is not particularly limited and can be arbitrary. For example, the boundary between the force-receiving body side strain-generating portion 40 and the fixed body side strain-generating portion 41 may be located at the boundary between the connecting body portion 31 and the base 33. In this case, the force-receiving body side strain-generating portion 40 is configured to include the entire connecting body portion 31 in addition to the force-receiving body side thin-walled portion 32. The fixed body side strain-generating portion 41 is configured to include the base 33 and the fixed body side thin-walled portion 34, but does not include the connecting body portion 31. Furthermore, the boundary between the force-receiving body side strain portion 40 and the fixed body side strain portion 41 may be located on the same plane as the boundary between the force-receiving body protrusion 20b and the fixed body protrusion 25b described above, but it does not have to be located on the same plane.

[0080] The strain-generating bolt 42 is an example of a strain-generating fastening part. The strain-generating bolt 42 fastens the load-bearing side strain-generating part 40 and the fixed body side strain-generating part 41. In this embodiment, there is one strain-generating bolt 42, but it is not limited to this and there may be multiple. The strain-generating bolt 42 includes a head 42a that abuts against the load-bearing side thin-walled part 32. The strain-generating bolt 42 extends through a through hole 40a formed in the load-bearing side strain-generating part 40 to the fixed body side strain-generating part 41 and is screwed into a threaded hole 41a formed in the fixed body side strain-generating part 41. Note that the load-bearing side strain-generating part 40 and the fixed body side strain-generating part 41 do not necessarily have to be fastened with the strain-generating bolt 42. For example, the load-bearing side strain-generating part 40 and the fixed body side strain-generating part 41 may be joined by welding or by adhesive.

[0081] As shown in Figures 3 to 5, the load-bearing side thin-walled portion 32 and the fixed body side thin-walled portion 34 of the second strain-generating body 30B extend in the Y-axis direction. As shown in Figure 3, the load-bearing side thin-walled portion 32 extends in the Y-axis direction beyond the connecting body portion 31 on both sides of the connecting body portion 31 in the Y-axis direction. As shown in Figure 4, the base 33 protrudes in the Y-axis direction beyond the connecting body portion 31 on both sides of the connecting body portion 31 in the Y-axis direction. As shown in Figure 5, the fixed body side thin-walled portion 34 extends in the Y-axis direction beyond the base 33 on both sides of the base 33 in the Y-axis direction. As shown in Figure 4, the displacement body 35 extends from the base 33 in the Y-axis direction. The displacement body 35 may also extend from the base projection 33a in the Y-axis direction. One of the displacement bodies 35 of the second strain-generating body 30B extends in the negative Y-axis direction from the base projection 33a located on the negative Y-axis side. The other displacement body 35 extends in the positive direction in the Y-axis direction from the base projection 33a located on the positive side in the Y-axis direction.

[0082] The load-bearing side thin-walled portion 32 and the fixed side thin-walled portion 34 of the third strain-generating body 30C extend in the X-axis direction. As shown in Figure 3, the load-bearing side thin-walled portion 32 extends in the X-axis direction beyond the connecting body portion 31 on both sides of the connecting body portion 31 in the X-axis direction. As shown in Figure 4, the base 33 protrudes in the X-axis direction beyond the connecting body portion 31 on both sides of the connecting body portion 31 in the X-axis direction. As shown in Figure 5, the fixed side thin-walled portion 34 extends in the X-axis direction beyond the base 33 on both sides of the base 33 in the X-axis direction. As shown in Figure 4, the displacement body 35 extends from the base 33 in the X-axis direction. The displacement body 35 may also extend from the base projection 33a in the X-axis direction. One of the displacement bodies 35 of the third strain-generating body 30C extends in the negative X-axis direction from the base projection 33a located on the negative X-axis side. The other displacement body 35 extends in the positive direction in the X-axis direction from the base projection 33a located on the positive side in the X-axis direction.

[0083] The load-bearing side thin-walled portion 32 and the fixed side thin-walled portion 34 of the fourth strain-generating body 30D extend in the Y-axis direction. As shown in Figure 3, the load-bearing side thin-walled portion 32 extends in the Y-axis direction beyond the connecting body portion 31 on both sides of the connecting body portion 31 in the Y-axis direction. As shown in Figure 4, the base 33 protrudes in the Y-axis direction beyond the connecting body portion 31 on both sides of the connecting body portion 31 in the Y-axis direction. As shown in Figure 5, the fixed side thin-walled portion 34 extends in the Y-axis direction beyond the base 33 on both sides of the base 33 in the Y-axis direction. As shown in Figure 4, the displacement body 35 extends from the base 33 in the Y-axis direction. The displacement body 35 may also extend from the base projection 33a in the Y-axis direction. One of the displacement bodies 35 of the fourth strain-generating body 30D extends in the negative Y-axis direction from the base projection 33a located on the negative Y-axis side. The other displacement body 35 extends in the positive direction in the Y-axis direction from the base projection 33a located on the positive side in the Y-axis direction.

[0084] [Detection Element] The detection element 50 is configured to detect the displacement caused by the elastic deformation of the strain bodies 30A to 30D described above. The detection element 50 according to this embodiment is configured to detect a change in capacitance value due to the displacement of the displacement body 35 of each of the strain bodies 30A to 30D.

[0085] As shown in Figure 7, the detection element 50 includes a first capacitance element C1 and a second capacitance element C2. The first capacitance element C1 and the second capacitance element C2 each detect a change in capacitance value due to the displacement of the tip of the displacement body 35 of the first strain body 30A. The first capacitance element C1 and the second capacitance element C2 are capacitance elements for the first strain body 30A shown in Figure 7.

[0086] In the example shown in Figure 7, the first capacitive element C1 includes a first fixed electrode substrate Ef1 attached to the fixed body 25 and a first displacement electrode substrate Ed1 attached to the tip of the displacement body 35. The first fixed electrode substrate Ef1 is attached to the surface of the fixed body 25a facing the displacement body 35. The first displacement electrode substrate Ed1 is attached to the surface of the displacement body 35 facing the fixed body 25a.

[0087] The second capacitance element C2 includes a second fixed electrode substrate Ef2 attached to the fixed body 25 and a second displacement electrode substrate Ed2 attached to the tip of the displacement body 35. The second fixed electrode substrate Ef2 is attached to the surface of the fixed body 25a facing the displacement body 35. The second displacement electrode substrate Ed2 is attached to the surface of the displacement body 35 facing the fixed body 25a.

[0088] The first capacitance element C1 is positioned on the positive side in the X-axis direction with respect to the central axis CL of the first strain body 30A. The second capacitance element C2 is positioned on the negative side in the X-axis direction with respect to the central axis CL of the first strain body 30A.

[0089] As shown in Figure 7, the first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2 each include a fixed electrode Ef and an insulator IBf. The insulator IBf is interposed between the fixed electrode Ef and the fixed body 25a. The insulator IBf may be joined to the fixed body 25a with adhesive or the like, or fixed with bolts or the like. The fixed electrode Ef may be joined to the insulator IBf with adhesive or the like, or fixed with bolts or the like.

[0090] The first displacement electrode substrate Ed1 and the second displacement electrode substrate Ed2 each include a displacement electrode Ed and an insulator IBd. The displacement electrode Ed of the first displacement electrode substrate Ed1 faces the fixed electrode Ef of the first fixed electrode substrate Ef1, and the displacement electrode Ed of the second displacement electrode substrate Ed2 faces the fixed electrode Ef of the second fixed electrode substrate Ef2. The insulator IBd is interposed between the displacement electrode Ed and the displacement body 35. The insulator IBd may be joined to the displacement body 35 with adhesive or the like, or fixed with bolts or the like. The displacement electrode Ed may be joined to the insulator IBd with adhesive or the like, or fixed with bolts or the like.

[0091] As shown in Figures 3 to 5, the first capacitance element C1 and the second capacitance element C2 are positioned at the same location in the Y-axis direction. That is, the displacement electrode Ed of the first displacement electrode substrate Ed1 and the displacement electrode Ed of the second displacement electrode substrate Ed2 are positioned at the same location in the Y-axis direction and are positioned on both sides of the base 33 in the X-axis direction. The same applies to the fixed electrode Ef of the first fixed electrode substrate Ef1 and the fixed electrode Ef of the second fixed electrode substrate Ef2.

[0092] When viewed in the Z-axis direction, the planar shape of the displacement electrode Ed of the first displacement electrode substrate Ed1 may be smaller than the planar shape of the fixed electrode Ef of the first fixed electrode substrate Ef1. Furthermore, even when the force receiving body 20 receives a force or moment and the first displacement electrode substrate Ed1 is displaced, the sizes of the displacement electrode Ed and the fixed electrode Ef may be set so that, when viewed in the Z-axis direction, the displacement electrode Ed of the first displacement electrode substrate Ed1 overlaps the fixed electrode Ef of the first fixed electrode substrate Ef1 as a whole. This prevents a change in the opposing area between the displacement electrode Ed and the fixed electrode Ef, and prevents the change in the opposing area from affecting the change in the capacitance value. Therefore, the capacitance value can be changed in accordance with the change in the distance between the displacement electrode Ed and the fixed electrode Ef. Here, the opposing area refers to the area where the displacement electrode Ed and the fixed electrode Ef overlap when viewed in the Z-axis direction. When the displacement body 35 is tilted, the displacement electrode Ed, which is smaller than the fixed electrode Ef, may tilt, causing a change in the opposing area. However, in this case, the tilt angle of the displacement electrode Ed is small. As a result, the distance between the displacement electrode Ed and the fixed electrode Ef is dominant in determining the change in capacitance value. Therefore, in this specification, the change in the opposing area due to the tilt of the displacement electrode Ed is not considered, and the change in capacitance value is considered to be due to the change in the distance between the displacement electrode Ed and the fixed electrode Ef. Note that in Figure 9 and other figures described later, the tilt of the displacement body 35 is exaggerated for clarity.

[0093] Similarly, when viewed in the Z-axis direction, the planar shape of the displacement electrode Ed of the second displacement electrode substrate Ed2 may be smaller than the planar shape of the fixed electrode Ef of the second fixed electrode substrate Ef2. The planar shape of the displacement electrode Ed of the second displacement electrode substrate Ed2 may be the same as the planar shape of the displacement electrode Ed of the first displacement electrode substrate Ed1.

[0094] The planar shape of the fixed electrode Ef on the first fixed electrode substrate Ef1 may be the same size as the planar shape of the insulator IBf on the first fixed electrode substrate Ef1. However, the planar shape of the fixed electrode Ef may be smaller than the planar shape of the insulator IBf. The same applies to the second fixed electrode substrate Ef2, the first displacement electrode substrate Ed1, and the second displacement electrode substrate Ed2.

[0095] The insulators IBd and IBf may be made of an insulating material such as glass epoxy resin or ceramic. Alternatively, the fixed electrode substrates Ef1 and Ef2 may be made of an FPC substrate (flexible printed circuit board). An FPC substrate is a printed circuit board that is formed in the form of a thin film and is flexible. On the upper surface of the polyimide film of the FPC substrate, a thin metal film constituting electrodes and wiring is formed. The portion of the FPC substrate corresponding to the fixed electrode substrates Ef1 and Ef2 may be fixed to the fixed body 25a. The FPC substrate may include wiring that connects the fixed electrode Ef to the detection circuit 60. If the insulators IBd and IBf are made of an FPC substrate, the portion of the FPC substrate corresponding to the displacement electrode substrates Ed1 and Ed2 may be fixed to the displacement body 35. The FPC substrate may include wiring that connects the displacement electrode Ed to the detection circuit 60. When ceramics are used for the insulators IBd and IBf, the electrodes Ed and Ef may be formed on the insulators IBd and IBf using techniques such as vapor deposition, printing, or sputtering.

[0096] The configuration of the first strain-generating body 30A and the corresponding detection element 50 described above can also be applied similarly to the second strain-generating body 30B, the third strain-generating body 30C, and the fourth strain-generating body 30D.

[0097] In other words, as shown in Figures 3 to 5, the detection element 50 further includes a third capacitance element C3 and a fourth capacitance element C4. The third capacitance element C3 and the fourth capacitance element C4 each detect a change in capacitance value due to the displacement of the tip of the displacement body 35 of the second strain body 30B. The third capacitance element C3 and the fourth capacitance element C4 are capacitance elements for the second strain body 30B.

[0098] As shown in Figures 3 to 5, the third capacitance element C3 includes a third fixed electrode substrate Ef3 attached to the fixed body 25 and a third displacement electrode substrate Ed3 attached to the tip of the displacement body 35. The fourth capacitance element C4 includes a fourth fixed electrode substrate Ef4 attached to the fixed body 25 and a fourth displacement electrode substrate Ed4 attached to the tip of the displacement body 35.

[0099] The third capacitance element C3 is located on the positive side of the Y-axis with respect to the central axis CL of the second strain body 30B. The third displacement electrode substrate Ed3 faces the third fixed electrode substrate Ef3. The fourth capacitance element C4 is located on the negative side of the Y-axis with respect to the central axis CL of the second strain body 30B. The fourth displacement electrode substrate Ed4 faces the fourth fixed electrode substrate Ef4. The displacement electrode substrates Ed3 and Ed4 are configured in the same way as the displacement electrode substrates Ed1 and Ed2 described above.

[0100] The third capacitance element C3 and the fourth capacitance element C4 are positioned at the same location in the X-axis direction. That is, the displacement electrode Ed of the third displacement electrode substrate Ed3 and the displacement electrode Ed of the fourth displacement electrode substrate Ed4 are positioned at the same location in the X-axis direction. The same applies to the fixed electrode Ef of the third fixed electrode substrate Ef3 and the fixed electrode Ef of the fourth fixed electrode substrate Ef4.

[0101] Furthermore, as shown in Figures 3 to 5, the detection element 50 further includes a fifth capacitance element C5 and a sixth capacitance element C6. The fifth capacitance element C5 and the sixth capacitance element C6 each detect a change in capacitance value due to the displacement of the tip of the displacement body 35 of the third strain body 30C. The fifth capacitance element C5 and the sixth capacitance element C6 are capacitance elements for the third strain body 30C.

[0102] As shown in Figures 3 to 5, the fifth capacitance element C5 includes a fifth fixed electrode substrate Ef5 attached to the fixed body 25 and a fifth displacement electrode substrate Ed5 attached to the tip of the displacement body 35. The sixth capacitance element C6 includes a sixth fixed electrode substrate Ef6 attached to the fixed body 25 and a sixth displacement electrode substrate Ed6 attached to the tip of the displacement body 35.

[0103] The fifth capacitance element C5 is located on the negative side of the X-axis with respect to the central axis CL of the third strain body 30C. The fifth displacement electrode substrate Ed5 faces the fifth fixed electrode substrate Ef5. The sixth capacitance element C6 is located on the positive side of the X-axis with respect to the central axis CL of the third strain body 30C. The sixth displacement electrode substrate Ed6 faces the sixth fixed electrode substrate Ef6. The displacement electrode substrates Ed5 and Ed6 are configured in the same way as the displacement electrode substrates Ed1 and Ed2 described above.

[0104] The fifth capacitance element C5 and the sixth capacitance element C6 are positioned at the same location in the Y-axis direction. That is, the displacement electrode Ed of the fifth displacement electrode substrate Ed5 and the displacement electrode Ed of the sixth displacement electrode substrate Ed6 are positioned at the same location in the Y-axis direction. The same applies to the fixed electrode Ef of the fifth fixed electrode substrate Ef5 and the fixed electrode Ef of the sixth fixed electrode substrate Ef6.

[0105] Furthermore, as shown in Figures 3 to 5, the detection element 50 further includes a seventh capacitance element C7 and an eighth capacitance element C8. The seventh capacitance element C7 and the eighth capacitance element C8 each detect a change in capacitance value due to the displacement of the tip of the displacement body 35 of the fourth strain body 30D. The seventh capacitance element C7 and the eighth capacitance element C8 are capacitance elements for the fourth strain body 30D.

[0106] As shown in Figures 3 to 5, the seventh capacitance element C7 includes a seventh fixed electrode substrate Ef7 attached to the fixed body 25 and a seventh displacement electrode substrate Ed7 attached to the tip of the displacement body 35. The eighth capacitance element C8 includes an eighth fixed electrode substrate Ef8 attached to the fixed body 25 and an eighth displacement electrode substrate Ed8 attached to the tip of the displacement body 35.

[0107] The seventh capacitance element C7 is located on the negative side of the Y-axis with respect to the central axis CL of the fourth strain body 30D. The seventh displacement electrode substrate Ed7 faces the seventh fixed electrode substrate Ef7. The eighth capacitance element C8 is located on the positive side of the Y-axis with respect to the central axis CL of the fourth strain body 30D. The eighth displacement electrode substrate Ed8 faces the eighth fixed electrode substrate Ef8. The displacement electrode substrates Ed7 and Ed8 are configured in the same way as the displacement electrode substrates Ed1 and Ed2 described above.

[0108] The seventh capacitance element C7 and the eighth capacitance element C8 are positioned at the same location in the X-axis direction. That is, the displacement electrode Ed of the seventh displacement electrode substrate Ed7 and the displacement electrode Ed of the eighth displacement electrode substrate Ed8 are positioned at the same location in the X-axis direction. The same applies to the fixed electrode Ef of the seventh fixed electrode substrate Ef7 and the fixed electrode Ef of the eighth fixed electrode substrate Ef8.

[0109] [Detection Circuit] As shown in Figures 3 and 4, the detection circuit 60 outputs an electrical signal indicating the force or moment acting on the force-receiving body 20 based on the detection result of the detection element 50. This detection circuit 60 may have a calculation function configured by, for example, a microprocessor. The detection circuit 60 may also have an A / D conversion function that converts the analog signal received from the above-mentioned detection element 50 into a digital signal, and a signal amplification function. The detection circuit 60 may include a terminal for outputting an electrical signal, and the electrical signal is transmitted from this terminal to the above-mentioned controller 5 via an electrical cable (not shown). The detection circuit 60 may be located in the center of the force sensor 10 when viewed in the Z-axis direction. The detection circuit 60 is fixed to the force-receiving body 20 or the fixed body 25, but for example, it may be fixed to the fixed body 25.

[0110] [Outer Body] As shown in Figures 2 and 3, the outer body 70 is configured to house the force receiving body 20, the fixed body 25, and the strain generating bodies 30A to 30D. The outer body 70 may also include a force receiving body side cover 71, a fixed body side cover 72, a force receiving body side cylindrical body 73a, and a fixed body side cylindrical body 73b.

[0111] As shown in Figure 2, the force-receiving body side cover 71 is positioned on the opposite side of the force-receiving body 20 from the fixing body 25. The force-receiving body side cover 71 covers the force-receiving body 20 from above. The force-receiving body side cover 71 may be fixed to the force-receiving body 20 with bolts (not shown). The force-receiving body side cover 71 may include a force-receiving body side through hole 75 through which bolts (not shown) for attaching the force-receiving body 20 to the tool 3 pass. The force-receiving body side cover 71 may be formed in a flat plate shape.

[0112] The fixed body side cover 72 is positioned on the opposite side of the fixed body 25 from the force receiving body 20. The fixed body side cover 72 covers the fixed body 25 from below. The fixed body side cover 72 may be fixed to the fixed body body 25a with bolts (not shown). The fixed body side cover 72 may include a fixed body side through hole 76 through which bolts (not shown) for attaching the fixed body 25 to the tip of the robot arm 4 pass. The fixed body side cover 72 may be formed in a flat plate shape.

[0113] The force-receiving cylindrical body 73a is configured to surround and house the four strain-generating bodies 30A to 30D from the outer periphery when viewed in the Z-axis direction. The force-receiving cylindrical body 73a is in contact with the force-receiving cover 71 and may primarily surround and house the force-receiving body 20 from the outer periphery. The force-receiving cylindrical body 73a is a cylindrical housing that constitutes the force sensor 10. In this embodiment, the force-receiving cylindrical body 73a is formed in a cylindrical shape. A gap is formed between the force-receiving cylindrical body 73a and the force-receiving body 20 (more specifically, the force-receiving body main body 20a and the force-receiving body projection 20b) to allow relative displacement between the force-receiving body 20 and the fixed body 25.

[0114] The fixed body side cylindrical body 73b is configured to surround and house the four strain-generating bodies 30A to 30D from the outer periphery when viewed in the Z-axis direction. The fixed body side cylindrical body 73b is in contact with the fixed body side cover 72 and may primarily surround and house the fixed body 25 from the outer periphery. The fixed body side cylindrical body 73b is a cylindrical housing that constitutes the force sensor 10. In this embodiment, the fixed body side cylindrical body 73b is formed in a cylindrical shape. A gap is formed between the fixed body side cylindrical body 73b and the fixed body 25 (more specifically, the fixed body main body 25a and the fixed body projection 25b) to allow relative displacement between the force-receiving body 20 and the fixed body 25.

[0115] A cushioning member 74 may be interposed in the gap between the force-receiving cylindrical body 73a and the fixed cylindrical body 73b. The cushioning member 74 may be made of an elastically deformable flexible material such as rubber or sponge. As shown in Figure 2, the force-receiving cover 71 and the force-receiving cylindrical body 73a may be manufactured separately, but are not limited to this, and may be manufactured integrally by machining, casting, or forging. Similarly, the fixed cover 72 and the fixed cylindrical body 73b may be manufactured separately, but may also be manufactured integrally by machining, casting, or forging.

[0116] Next, a method for detecting a force or moment when it acts on the force sensor 10 according to this embodiment, which has the configuration described above, will be explained with reference to Figures 9 to 11. Figure 9 is a schematic front view showing the deformation state of the first strain body 30A when the first strain body 30A in Figure 7 is subjected to a force Fx on the positive side in the X-axis direction, and Figure 10 is a schematic front view showing the deformation state of the first strain body 30A when the first strain body 30A in Figure 7 is subjected to a force Fz on the positive side in the Z-axis direction. Figure 11 is a schematic front view showing the deformation state of the first strain body 30A when the first strain body 30A in Figure 7 is subjected to a force Fz on the negative side in the Z-axis direction.

[0117] When the force-receiving body 20 is subjected to a force or moment, that force or moment is transmitted to the first strain-generating body 30A to the fourth strain-generating body 30D. More specifically, that force or moment is transmitted to the force-receiving body side thin-walled portion 32, the connecting body portion 31, the base 33, and the fixed body side thin-walled portion 34, causing elastic deformation in the force-receiving body side thin-walled portion 32 and the fixed body side thin-walled portion 34. This causes displacement in the displacement body 35. As a result, the distance between each fixed electrode substrate Ef1 to Ef8 of the detection element 50 and the corresponding displacement electrode substrate Ed1 to Ed8 changes, and the capacitance values ​​of each capacitive element C1 to C8 change. This change in capacitance value is detected by the detection element 50 as displacement generated in the strain-generating bodies 30A to 30D. In this case, the change in capacitance value of each capacitive element C1 to C8 may differ. Therefore, the detection circuit 60 can detect the direction and magnitude of the force or moment acting on the force-receiving body 20 based on the change in the capacitance values ​​of each capacitive element C1 to C8 detected by the detection element 50.

[0118] Here, we will first explain the changes in the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2 when a force Fx in the X-axis direction, a force Fy in the Y-axis direction, and a force Fz in the Z-axis direction are applied, using the first strain-generating body 30A as an example.

[0119] (When +Fx is applied) When a force Fx is applied to the first strain body 30A in the positive X-axis direction, as shown in Figure 9, the load-receiving body 20 is displaced in the positive X-axis direction while the load-receiving body 20 is displaced in the positive X-axis direction, as

[0120] As the first displacement electrode substrate Ed1 moves closer to the first fixed electrode substrate Ef1, the distance between the electrodes (distance in the Z-axis direction) between the first displacement electrode substrate Ed1 and the first fixed electrode substrate Ef1 decreases. As a result, the capacitance value of the first capacitive element C1 increases. On the other hand, as the second displacement electrode substrate Ed2 moves further away from the second fixed electrode substrate Ef2, the distance between the electrodes (distance in the Z-axis direction) between the second displacement electrode substrate Ed2 and the second fixed electrode substrate Ef2 increases. As a result, the capacitance value of the second capacitive element C2 decreases.

[0121] (When -Fx is applied) When a force Fx is applied to the first strain body 30A on the negative side in the X-axis direction, the opposite phenomenon to that shown in Figure 9 occurs, although it is not shown in the figure. That is, the capacitance value of the first capacitance element C1 decreases, and the capacitance value of the second capacitance element C2 increases.

[0122] (When +Fy is applied) When a force Fy is applied to the first strain body 30A in the positive direction of the Y-axis, it can be assumed that there is no change in the capacitance values ​​of each capacitive element C1 and C2. That is, in this case, when viewed in the X-axis direction (when viewed toward the plane of the paper in Figure 8), the connecting body 31 rotates, so the capacitance value increases in a part of the first capacitive element C1 and decreases in another part of the first capacitive element C1. As a result, the changes in the capacitance value of the first capacitive element C1 cancel each other out. Similarly, the capacitance value increases in a part of the second capacitive element C2 and decreases in another part of the second capacitive element C2. As a result, the changes in the capacitance value of the second capacitive element C2 cancel each other out. For this reason, the changes in the capacitance values ​​of the first capacitive element C1 and the second capacitive element C2 become small and can be assumed to be no change at all.

[0123] (When -Fy is applied) Similarly, when a force Fy is applied to the first strain body 30A on the negative side in the Y-axis direction, it can be assumed that there is no change in the capacitance values ​​of each capacitive element C1 and C2.

[0124] (When +Fz is applied) When a force Fz is applied to the first strain body 30A in the positive Z-axis direction, as shown in Figure 10, the thin-walled portion 32 on the force-receiving body side and the thin-walled portion 34 on the fixed body side undergo elastic deformation, while the connecting body portion 31 and the base 33 are displaced in the positive Z-axis direction. In conjunction with the connecting body portion 31 and the base 33, the displacement body 35 is displaced in the positive Z-axis direction.

[0125] As the first displacement electrode substrate Ed1 moves away from the first fixed electrode substrate Ef1, the distance between the electrodes (distance in the Z-axis direction) between the first displacement electrode substrate Ed1 and the first fixed electrode substrate Ef1 increases. As a result, the capacitance value of the first capacitive element C1 decreases. Similarly, as the second displacement electrode substrate Ed2 moves away from the second fixed electrode substrate Ef2, the distance between the electrodes (distance in the Z-axis direction) between the second displacement electrode substrate Ed2 and the second fixed electrode substrate Ef2 increases. As a result, the capacitance value of the second capacitive element C2 decreases.

[0126] (When -Fz is applied) When a force Fz is applied to the first strain body 30A on the negative side in the Z-axis direction, the opposite phenomenon to that shown in Figure 10 occurs, as shown in Figure 11.

[0127] When a force Fz acts on the first strain body 30A in the negative Z-axis direction, as shown in Figure 11, the thin-walled portion 32 on the force-receiving body side and the thin-walled portion 34 on the fixed body side undergo elastic deformation, while the connecting body portion 31 and the base 33 are displaced in the negative Z-axis direction. In conjunction with the connecting body portion 31 and the base 33, the displacement body 35 is displaced in the negative Z-axis direction.

[0128] As the first displacement electrode substrate Ed1 approaches the first fixed electrode substrate Ef1, the distance between the electrodes (distance in the Z-axis direction) between the first displacement electrode substrate Ed1 and the first fixed electrode substrate Ef1 decreases. As a result, the capacitance value of the first capacitive element C1 increases. Similarly, as the second displacement electrode substrate Ed2 approaches the second fixed electrode substrate Ef2, the distance between the electrodes (distance in the Z-axis direction) between the second displacement electrode substrate Ed2 and the second fixed electrode substrate Ef2 decreases. As a result, the capacitance value of the second capacitive element C2 increases.

[0129] Here, Figure 12 shows the change in capacitance values ​​of each capacitive element C1 and C2 provided on the first strain body 30A shown in Figure 7. Figure 12 is a table showing the change in capacitance values ​​of each capacitive element C1 and C2 in the first strain body 30A shown in Figure 7.

[0130] Figure 12 shows the changes in capacitance values ​​of capacitive elements C1 and C2 for forces Fx in the X-axis direction, Fy in the Y-axis direction, and Fz in the Z-axis direction. A decrease in capacitance value is indicated by "-" (minus), and an increase in capacitance value is indicated by "+" (plus). For example, in the table shown in Figure 12, a "+" is shown for C1 in the row for Fx, which indicates that, as described above, the capacitance value of the first capacitive element C1 increases when a force of +Fx is applied. On the other hand, in the table shown in Figure 12, a "-" is shown for C2 in the row for Fx, which indicates that, as described above, the capacitance value of the second capacitive element C2 decreases when a force of +Fx is applied. In the table shown in Figure 12, "0" (zero) for C1 and C2 in the row for Fy indicates that, as described above, when a force of +Fy is applied, it can be considered that there is no change in the capacitance values ​​of each capacitive element C1 and C2.

[0131] As shown in the table in Figure 12, in a force sensor 10 in which the force receiving body 20 and the fixed body 25 are connected only by the first strain generating body 30A, the forces Fx, Fy, and Fz acting on the force receiving body 20 can be calculated using the following formulas. For convenience, in the following formulas, force or moment and the change in capacitance value are connected by "=". However, since force or moment and capacitance value are different physical quantities, in reality, force is calculated by converting the change in capacitance value. In the following formulas, C1 and C2 represent the change in capacitance value in each capacitive element.

[0132] As shown in Figure 12, in a force sensor 10 in which the force receiving body 20 and the fixed body 25 are connected only by the first strain generating body 30A, the force Fx in the X-axis direction can be detected by the difference between the capacitance value of the first capacitance element C1 and the capacitance value of the second capacitance element C2. That is, as shown in equation (1) above, the output value of force Fx can be calculated by the difference between the change in the capacitance value of the first capacitance element C1 and the change in the capacitance value of the second capacitance element C2. Even if the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2 are affected by disturbances such as noise or ambient temperature, these effects can be canceled out by the difference in equation (1) above. Therefore, the output value of force Fx can be prevented from being affected by disturbances, and the performance of the force sensor 10 can be improved.

[0133] Similarly, the force Fz in the Z-axis direction can be detected by the sum of the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2. That is, as shown in equation (2) above, the output value of force Fz can be calculated by summing the change in capacitance value of the first capacitance element C1 and the change in capacitance value of the second capacitance element C2.

[0134] Therefore, a force sensor 10 using only one first strain element 30A can be used when both force Fx and force Fz are acting. In this case, the force sensor 10 is a force sensor capable of detecting two-axis components.

[0135] Next, with reference to Figure 13, we will explain the changes in the capacitance values ​​of each capacitive element C1 to C8 when a force Fx in the X-axis direction, a force Fy in the Y-axis direction, a force Fz in the Z-axis direction, a moment Mx around the X-axis, a moment My around the Y-axis, and a moment Mz around the Z-axis are applied to the force sensor 10 shown in Figures 3 to 5. Figure 13 is a table showing the changes in the capacitance values ​​of each capacitive element in the force sensor 10 shown in Figures 3 to 5.

[0136] (When +Fx is applied) First, we will explain the case when a force Fx is applied to the force-receiving body 20 in the positive direction of the X-axis.

[0137] In this case, the first strain-generating body 30A undergoes elastic deformation similar to the first strain-generating body 30A shown in Figure 9, causing the capacitance value of the first capacitance element C1 to increase and the capacitance value of the second capacitance element C2 to decrease.

[0138] The second strain body 30B undergoes elastic deformation in the same way as when a force Fy is applied to the first strain body 30A in the Y-axis direction, as shown in Figure 7. Therefore, it can be assumed that there is no change in the capacitance values ​​of each capacitive element C3 and C4. In the table shown in Figure 13, C3 and C4 in the row for Fx are set to "0 (zero)".

[0139] When the third strain element 30C is viewed from the center O of the force-receiving body 20, it elastically deforms in the opposite direction to the first strain element 30A shown in Figure 9, causing the capacitance value of the fifth capacitor element C5 to decrease and the capacitance value of the sixth capacitor element C6 to increase.

[0140] The fourth strain element 30D undergoes elastic deformation in the same manner as when a force Fy is applied to the first strain element 30A in the Y-axis direction, as shown in Figure 7. Therefore, it can be assumed that there is no change in the capacitance values ​​of each capacitive element C7 and C8.

[0141] (When +Fy is applied) Next, we will explain the case when a force Fy is applied to the force-receiving body 20 in the positive direction of the Y-axis. In the following explanation as well, the symbols in the table in Figure 13 are determined according to the change in capacitance value, as described above.

[0142] The first strain body 30A undergoes elastic deformation in the same manner as when a force Fy is applied to the first strain body 30A in the Y-axis direction, as shown in Figure 7. Therefore, it can be assumed that there is no change in the capacitance values ​​of each capacitive element C1 and C2.

[0143] When the second strain element 30B is viewed from the center O of the force-receiving body 20, it undergoes elastic deformation similar to that of the first strain element 30A shown in Figure 9, causing the capacitance value of the third capacitance element C3 to increase and the capacitance value of the fourth capacitance element C4 to decrease.

[0144] The third strain element 30C undergoes elastic deformation in the same manner as when a force Fy is applied to the first strain element 30A in the Y-axis direction, as shown in Figure 7. Therefore, it can be assumed that there is no change in the capacitance values ​​of each capacitive element C5 and C6.

[0145] When the fourth strain element 30D is viewed from the center O of the force-receiving body 20, it elastically deforms in the opposite direction to the first strain element 30A shown in Figure 9, causing the capacitance value of the seventh capacitance element C7 to decrease and the capacitance value of the eighth capacitance element C8 to increase.

[0146] (When +Fz is applied) Next, we will explain the case when a force Fz is applied to the force-receiving body 20 in the positive direction of the Z axis. In the following explanation as well, the symbols in the table in Figure 13 are determined according to the change in capacitance value, as described above.

[0147] In this case, the first strain-generating body 30A undergoes elastic deformation similar to that shown in Figure 10, causing the capacitance value of the first capacitor element C1 to decrease, as well as the capacitance value of the second capacitor element C2. Similarly, the capacitance values ​​of the third capacitor element C3 to the eighth capacitor element C8 also decrease.

[0148] (When +Mx is applied) Next, we will explain the case when a moment Mx acts on the force-receiving body 20 around the X-axis, that is, clockwise toward the positive side of the X-axis direction. In the following explanation as well, the symbols in the table in Figure 13 are determined according to the change in capacitance value, as described above.

[0149] In this case, the first strain body 30A undergoes elastic deformation similar to that of the first strain body 30A when a force Fz directed in the positive direction of the Z-axis direction is applied, as shown in Figure 10. As a result, the capacitance value of the first capacitor element C1 decreases, and the capacitance value of the second capacitor element C2 also decreases.

[0150] In the second strain body 30B, the central axis CL is located at the center O of the force-receiving body 20 in the Y-axis direction. Therefore, the elastic deformation of the second strain body 30B is smaller than that of the first strain body 30A and the third strain body 30C. For convenience, it is assumed that the capacitance value of the third capacitance element C3 does not change, and the capacitance value of the fourth capacitance element C4 also does not change.

[0151] As shown in Figure 11, the third strain element 30C undergoes elastic deformation similar to that of the first strain element 30A when a force Fz directed in the negative direction of the Z-axis is applied, causing the capacitance value of the fifth capacitor element C5 to increase and the capacitance value of the sixth capacitor element C6 to increase.

[0152] In the fourth strain body 30D, the central axis CL is located at the center O of the force-receiving body 20 in the Y-axis direction. Therefore, the elastic deformation of the fourth strain body 30D is smaller than that of the first strain body 30A and the third strain body 30C. For convenience, we assume that the capacitance value of the seventh capacitance element C7 does not change, and the capacitance value of the eighth capacitance element C8 also does not change.

[0153] (When +My acts) Next, we will explain the case when a moment My acts on the force-receiving body 20 around the Y axis, that is, clockwise toward the positive side of the Y axis. In the following explanation as well, the symbols in the table in Figure 13 are determined according to the change in capacitance value, as described above.

[0154] In this case, since the central axis CL of the first strain body 30A is located at the center O of the force-receiving body 20 in the X-axis direction, the elastic deformation of the first strain body 30A is smaller than that of the second strain body 30B and the fourth strain body 30D. For convenience, we assume that the capacitance value of the first capacitance element C1 does not change, and the capacitance value of the second capacitance element C2 also does not change.

[0155] As shown in Figure 10, the second strain body 30B undergoes elastic deformation similar to that of the first strain body 30A when a force Fz directed in the positive Z-axis direction is applied, causing the capacitance value of the third capacitor element C3 to decrease, as well as the capacitance value of the fourth capacitor element C4 to decrease.

[0156] In the third strain body 30C, the central axis CL is located at the center O of the force-receiving body 20 in the X-axis direction. Therefore, the elastic deformation of the third strain body 30C is smaller than that of the second strain body 30B and the fourth strain body 30D. For convenience, it is assumed that the capacitance value of the fifth capacitance element C5 does not change, and the capacitance value of the sixth capacitance element C6 also does not change.

[0157] As shown in Figure 11, the fourth strain element 30D undergoes elastic deformation similar to that of the first strain element 30A when a force Fz directed in the negative direction of the Z-axis is applied, causing the capacitance value of the seventh capacitor element C7 to increase and the capacitance value of the eighth capacitor element C8 to increase.

[0158] (When +Mz acts) Next, we will explain the case when a moment Mz acts on the force-receiving body 20 around the Z axis, that is, clockwise toward the positive side of the Z axis direction. In the following explanation as well, the symbols in the table in Figure 13 are determined according to the change in capacitance value, as described above.

[0159] In this case, the first strain-generating body 30A elastically deforms in the opposite direction to the first strain-generating body 30A shown in Figure 9, causing the capacitance value of the first capacitance element C1 to decrease and the capacitance value of the second capacitance element C2 to increase.

[0160] When the second strain element 30B is viewed from the center O of the force-receiving body 20, it elastically deforms in the opposite direction to the first strain element 30A shown in Figure 9, causing the capacitance value of the third capacitance element C3 to decrease and the capacitance value of the fourth capacitance element C4 to increase.

[0161] When the third strain element 30C is viewed from the center O of the force-receiving body 20, it elastically deforms in the opposite direction to the first strain element 30A shown in Figure 9, causing the capacitance value of the fifth capacitor element C5 to decrease and the capacitance value of the sixth capacitor element C6 to increase.

[0162] When the fourth strain element 30D is viewed from the center O of the force-receiving body 20, it elastically deforms in the opposite direction to the first strain element 30A shown in Figure 9, causing the capacitance value of the seventh capacitance element C7 to decrease and the capacitance value of the eighth capacitance element C8 to increase.

[0163] In this way, when a change in the capacitance value of each capacitive element C1 to C8 is detected, the direction and magnitude of the force or moment acting on the force-receiving body 20 are detected. Then, as shown in Figure 13, the capacitance value of each capacitive element C1 to C8 changes.

[0164] From the table shown in Figure 13, the forces Fx, Fy, Fz, and moments Mx, My, Mz acting on the force-receiving body 20 can be calculated using the following equations (3) to (8). This allows for the detection of the six-axis components of the force. For convenience, in the following equations, the force or moment and the change in capacitance value are connected by "=". However, since force or moment and capacitance value are different physical quantities, in reality, the force or moment is calculated by converting the change in capacitance value. In the following equations, C1 to C8 represent the change in capacitance value in each capacitive element.

[0165] As described above, the force sensor 10 according to this embodiment can detect forces Fx, Fy, Fz, and moments Mx, My, Mz, as shown in equations (3) to (8) above, and is therefore capable of detecting six axial components of force. However, the number of axial components of force that the force sensor 10 can detect is not limited to six, and the number of detectable axial components can be arbitrary depending on the number, structure, and shape of the strain-generating body.

[0166] Applying the changes in capacitance values ​​of each capacitive element C1 to C8 shown in Figure 13 to equations (3) to (8) above yields the table showing the principal axis sensitivity and other axis sensitivity shown in Figure 14. Figure 14 is a table showing the principal axis sensitivity and other axis sensitivity based on the changes in capacitance values ​​shown in Figure 13. In Figure 14, VFx is the output when a force Fx in the X-axis direction is applied, VFy is the output when a force Fy in the Y-axis direction is applied, and VFz is the output when a force Fz in the Z-axis direction is applied. Also, VMx is the output when a moment Mx around the X-axis is applied, VMy is the output when a moment My around the Y-axis is applied, and VMz is the output when a moment Mz around the Z-axis is applied.

[0167] The values ​​shown in the table in Figure 14 are obtained by substituting the values ​​of each force Fx, Fy, Fz and each moment Mx, My, Mz listed in the table in Figure 13, with capacitive elements with a "+" sign set to "+1" and capacitive elements with a "-" sign set to "-1", into the right-hand side of the above-mentioned equations (3) to (8). For example, the value "4" written in the cell where the column for Fx and the row for VFx intersect is obtained by substituting "+1" into C1 and C6 and "-1" into C2 and C5 in equation (3) representing Fx, based on the row for Fx in Figure 13. Similarly, the value "0" written in the cell where the column for Fx and the row for VFy intersect is obtained by substituting 0 into C1, C2, C5, and C6 in equation (3) representing Fx, based on the row for Fy in Figure 13.

[0168] As shown in Figure 14, for force Fx, VFx is valued at "4", but VFy, VFz, VMx, VMy, and VMz are valued at "0". From this, it can be seen that for force Fx, there is no interaxial sensitivity, and only principal axis sensitivity can be detected. Similarly, for forces Fy and Fz, and moments Mx, My, and Mz, there is no interaxial sensitivity, and only principal axis sensitivity can be detected. In other words, a force sensor 10 can be obtained that can suppress the occurrence of interaxial sensitivity.

[0169] Furthermore, cross-axis sensitivity may occur. For example, when a force Fz acts on the force sensor 10 in the positive Z-axis direction, the change in capacitance value of the first capacitance element C1 and the change in capacitance value of the second capacitance element C2 may differ. In this case, cross-axis sensitivity may occur with respect to force Fz. Also, when force Fz, moment Mx, and My act on the force receiving body 20, the force sensor 10 is displaced in the Z-axis direction, so even if the same sign is assigned to the Fz, Mx, and My rows in the table shown in Figure 13, the change in capacitance value may differ. In this case, cross-axis sensitivity may occur with respect to force Fz, moment Mx, and My. Similarly, cross-axis sensitivity may occur with respect to force Fx, Fy, and moment Mz. For example, when a moment Mx acts on the force-receiving body 20, as shown in Figure 13, the capacitance values ​​of the third capacitance element C3, the fourth capacitance element C4, the seventh capacitance element C7, and the eighth capacitance element C8 do not change, and therefore the value "0" is indicated. However, the capacitance values ​​may change, causing cross-axis sensitivity. The same applies to moments My and Mz. Furthermore, even for capacitance elements in the rows for forces Fx and Fy where the value "0" is indicated, the capacitance values ​​may change, causing cross-axis sensitivity.

[0170] However, even if interaxial sensitivity occurs, a correction calculation can be performed by finding the inverse matrix of the interaxial sensitivity matrix (a 6x6 matrix corresponding to the table shown in Figure 14, also called the characteristic matrix) and multiplying this inverse matrix by the output of the force sensor (characteristic matrix). As a result, interaxial sensitivity can be reduced, and the occurrence of interaxial sensitivity can be suppressed.

[0171] As described above, according to this embodiment, the connecting body portion 31 of the first strain-receiving body 30A, which connects the force-receiving body 20 and the fixed body 25, is connected to the force-receiving body body 20a of the force-receiving body 20 via the force-receiving body side thin-walled portion 32. The connecting body portion 31 is connected to the fixed body body 25a of the fixed body 25 via the base 33. The base 33 is connected to the fixed body body 25a via the fixed body side thin-walled portion 34. The force-receiving body side thin-walled portion 32 and the fixed body side thin-walled portion 34 of the first strain-receiving body 30A extend in the X-axis direction. This makes it possible to reduce the distance between the force-receiving body 20 and the fixed body 25. As a result, the height of the force sensor 10 can be reduced, and a low profile can be achieved.

[0172] Furthermore, according to this embodiment, the base 33 of the first strain body 30A includes base protrusions 33a that protrude from the connecting body 31 on both sides of the connecting body 31 in the X-axis direction. The displacement body 35 extends in the X-axis direction from the base protrusions 33a. This allows the displacement body 35 to be stably supported. As a result, detection accuracy can be improved.

[0173] Furthermore, according to this embodiment, the base 33 is interposed between the thin-walled portion 34 on the fixed body side and the connecting body portion 31 in the Z-axis direction. This also reduces the distance between the force receiving body 20 and the fixed body 25. As a result, the height of the force sensor 10 can be reduced, further miniaturizing the device.

[0174] Furthermore, according to this embodiment, the displacement body 35 may be formed separately from the base 33 and fastened to the base projection 33a with bolts, or joined by welding or adhesive. This allows the parts of the strain generating bodies 30A to 30D other than the displacement body 35 to be manufactured separately from the displacement body 35. This makes it easier to manufacture the strain generating bodies 30A to 30D and reduces the manufacturing cost of the force sensor 10.

[0175] Furthermore, according to this embodiment, the force-receiving body 20 includes a force-receiving body opening 22 adjacent to the force-receiving body side thin-walled portion 32. This allows the force-receiving body side thin-walled portion 32 and the portion of the force-receiving body 20a near the force-receiving body side thin-walled portion 32 to be separated, thereby suppressing the inhibition of elastic deformation of the force-receiving body side thin-walled portion 32 by the force-receiving body 20a and the force-receiving body protrusion 20b. As a result, when the force-receiving body 20 is subjected to force or moment, the force-receiving body side thin-walled portion 32 can be made more elastically deformable, and the displacement of the displacement body 35 can be increased. As a result, the change in capacitance value can be increased, and the detection sensitivity of the force sensor 10 can be improved.

[0176] Furthermore, according to this embodiment, the force-receiving body opening 22 adjacent to the force-receiving body side thin-walled portion 32 of the first strain-generating body 30A is formed on both sides of the force-receiving body side thin-walled portion 32 in the Y-axis direction. This allows the force-receiving body side thin-walled portion 32 to be separated from the portions of the force-receiving body 20a on both sides of the force-receiving body side thin-walled portion 32, thereby suppressing the inhibition of elastic deformation of the force-receiving body side thin-walled portion 32 by the force-receiving body 20a and the force-receiving body protrusion 20b. As a result, when the force-receiving body 20 is subjected to force or moment, the force-receiving body side thin-walled portion 32 can be made to deform more elastically, and the displacement of the displacement body 35 can be made even larger. As a result, the change in capacitance value can be made even larger, and the detection sensitivity of the force sensor 10 can be further improved.

[0177] Furthermore, according to this embodiment, the fixed body 25 includes a fixed body opening 27 adjacent to the fixed body side thin-walled portion 34. This allows the fixed body side thin-walled portion 34 and the portion of the fixed body body 25a near the fixed body side thin-walled portion 34 to be separated, thereby suppressing the inhibition of elastic deformation of the fixed body side thin-walled portion 34 by the fixed body body 25a and the fixed body protrusion 25b. As a result, when the force receiving body 20 is subjected to force or moment, the fixed body side thin-walled portion 34 can be made more elastically deformable, and the displacement of the displacement body 35 can be increased. As a result, the change in capacitance value can be increased, and the detection sensitivity of the force sensor 10 can be improved.

[0178] Furthermore, according to this embodiment, the fixed body opening 27 adjacent to the fixed body side thin-walled portion 34 of the first strain-generating body 30A is formed on both sides of the fixed body side thin-walled portion 34 in the Y-axis direction. This allows the fixed body side thin-walled portion 34 to be separated from the portions of the fixed body body 25a on both sides of the fixed body side thin-walled portion 34, thereby suppressing the inhibition of elastic deformation of the fixed body side thin-walled portion 34 by the fixed body body 25a and the fixed body protrusion 25b. As a result, when the fixed body 25 is subjected to force or moment, the fixed body side thin-walled portion 34 can be made to deform more elastically, and the displacement of the displacement body 35 can be made even larger. As a result, the change in capacitance value can be made even larger, and the detection sensitivity of the force sensor 10 can be further improved.

[0179] Furthermore, according to this embodiment, each strain-generating body 30A to 30D includes a force-receiving body side strain-generating portion 40, which is integrally formed with the force-receiving body 20 and includes at least a part of the connecting body portion 31, and a fixed body side strain-generating portion 41, which is integrally formed with the fixed body 25 and includes a base 33. As a result, the force-receiving body side strain-generating portion 40 and the force-receiving body 20 can be manufactured as a single unit, for example by machining or casting. Similarly, the fixed body side strain-generating portion 41 and the fixed body 25 can be manufactured as a single unit, for example by machining or casting. Therefore, the force-receiving body side strain-generating portion 40 and the fixed body side strain-generating portion 41 of the strain-generating bodies 30A to 30D can be manufactured separately, making the manufacturing of the strain-generating bodies 30A to 30D easier. As a result, the manufacturing cost of the force sensor 10 can be reduced.

[0180] Furthermore, according to this embodiment, the load-bearing body-side strain-generating portion 40 and the fixed body-side strain-generating portion 41 are fastened together with strain-generating bolts 42. This allows the load-bearing body-side strain-generating portion 40 and the fixed body-side strain-generating portion 41 to be easily connected, and the load-bearing body-side strain-generating portion 40 and the fixed body-side strain-generating portion 41 to function as strain-generating bodies 30A to 30D.

[0181] Furthermore, according to this embodiment, the force-receiving body side strain portion 40 includes a part of the connecting body portion 31, and the fixed body side strain portion 41 includes another part of the connecting body portion 31. This allows the boundary between the force-receiving body side strain portion 40 and the fixed body side strain portion 41 to be formed in the connecting body portion 31.

[0182] Furthermore, according to this embodiment, the first strain element 30A is positioned on the positive Y-axis side with respect to the center O of the force-receiving body 20, the second strain element 30B is positioned on the negative X-axis side, the third strain element 30C is positioned on the negative Y-axis side, and the fourth strain element 30D is positioned on the positive X-axis side. As a result, when viewed in the Z-axis direction, the first strain elements 30A to the fourth strain elements 30D can be arranged in a ring with respect to the center O of the force-receiving body 20, and the six-axis components of force and moment can be detected. Therefore, the detection accuracy of force or moment in any direction can be improved, and the decrease in detection accuracy of force or moment depending on the direction of the force or moment can be suppressed.

[0183] (Modification 1) In the embodiment described above, the strain generating bodies 30A to 30D were described in an example that included a force-receiving body side strain generating portion 40, a fixed body side strain generating portion 41, and a strain generating body bolt 42. However, this embodiment is not limited to this. For example, as shown in Figure 15, the strain generating bodies 30A to 30D may each be formed integrally and not be separable into a force-receiving body side strain generating portion 40 and a fixed body side strain generating portion 41. In the example shown in Figure 15, the connecting body portion 31 is formed integrally from the force-receiving body side thin-walled portion 32 to the base 33. In this case, the number of parts of the force sensor 10 can be reduced. For example, the force-receiving body 20, the force-receiving body side strain generating portion 40, the fixed body side strain generating portion 41, and the fixed body 25 may be formed integrally from a continuous material. In this case, the force-receiving body 20, the force-receiving body side strain-generating portion 40, the fixed body side strain-generating portion 41, and the fixed body 25 may be manufactured from a single block material by machining (e.g., cutting) or by casting. Figure 15 is a front view showing a modified example of the first strain-generating body 30A shown in Figure 7. The second strain-generating bodies 30B to the fourth strain-generating bodies 30D may also be formed in the same manner as the first strain-generating body 30A shown in Figure 15.

[0184] (Modification 2) In the above-described embodiment, an example was described in which the displacement bodies 35 of the strain bodies 30A to 30D are each formed in a rectangular shape such that when viewed in the Z-axis direction, they have a longitudinal direction along the X-axis or Y-axis direction. However, this embodiment is not limited to this. For example, as shown in Figure 16, the displacement body 35 may be formed in an L-shape. In this case, the displacement body 35 may include a first displacement portion 35a and a second displacement portion 35b. The first displacement portion 35a of the first strain body 30A extends from the base 33 in the X-axis direction, and the second displacement portion 35b extends from the tip of the first displacement portion 35a in the Y-axis direction. When viewed in the Z-axis direction, the second displacement portion 35b extends toward the inside of the force sensor 10. Figure 16 is a plan cross-sectional view showing a modified example of the force sensor shown in Figure 4. The second strain-generating bodies 30B to the fourth strain-generating bodies 30D may also be formed in the same manner as the first strain-generating body 30A shown in Figure 15. Note that in Figure 16, the fixed body opening 27 is omitted for clarity.

[0185] The displacement electrode substrates Ed1 and Ed2 may be attached to the second displacement section 35b. Although not shown in Figure 16, the fixed electrode substrates Ef1 and Ef2 are attached to the fixed body 25 so as to face the displacement electrode substrates Ed1 and Ed2. The mounting positions of the displacement electrode substrates Ed1 and Ed2 are not particularly limited and are arbitrary. The displacement electrode substrates Ed1 and Ed2 may be attached from the tip of the first displacement section 35a to the second displacement section 35b. In this case, the facing area between the displacement electrode and the fixed electrode can be increased, and the detection sensitivity can be improved. The displacement electrode substrates Ed3 to Ed8 and the fixed electrode substrates Ef3 to Ef8 may also be formed in the same manner as the displacement electrode substrates Ed1 and Ed2 and the fixed electrode substrates Ef1 and Ef2.

[0186] In the force sensor 10 shown in Figure 16, when a force Fy acts on the force receiving body 20 in the positive direction of the Y-axis, the first strain generating body 30A elastically deforms so as to rotate counterclockwise toward the positive direction of the X-axis. As a result, the distance between the electrodes of the first displacement electrode substrate Ed1 and the first fixed electrode substrate Ef1 increases, and the distance between the electrodes of the second displacement electrode substrate Ed2 and the second fixed electrode substrate Ef2 also increases. Consequently, the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2 decrease. However, if the length of the second displacement portion 35b is significantly shorter than the length of the first displacement portion 35a, the change in the capacitance value of the first capacitance element C1 and the second capacitance element C2 is negligibly small compared to the change in the capacitance values ​​of the third capacitance element C3, the fourth capacitance element C4, the seventh capacitance element C7, and the eighth capacitance element C8. Therefore, in the force sensor 10 shown in Figure 16, the changes in capacitance of each capacitive element C1 to C8 are the same as those shown in the table in Figure 13. If the change in capacitance value of the first capacitive element C1 and the change in capacitance value of the second capacitive element C2 are not negligible compared to the changes in capacitance values ​​of the third capacitive element C3, the fourth capacitive element C4, the seventh capacitive element C7, and the eighth capacitive element C8, then cross-axis sensitivity may occur. However, even in this case, as described above, by performing a correction calculation using the inverse matrix of the cross-axis sensitivity matrix, the cross-axis sensitivity can be reduced and its occurrence can be suppressed. The same applies when a force Fy acts on the force-receiving body 20 on the negative side in the Y-axis direction.

[0187] As shown in the example in Figure 16, the displacement body 35 includes a first displacement section 35a and a second displacement section 35b, and the displacement electrode substrate is attached to the second displacement section 35b, which allows for effective use of the internal space of the force sensor 10. In this case, the opposing area between the displacement electrode Ed and the fixed electrode Ef can be increased. As a result, the change in capacitance value can be increased, and the detection sensitivity of the force sensor 10 can be improved.

[0188] (Modification 3) In the above-described embodiment, an example was described in which the force-receiving body opening 22 is formed on both sides of the force-receiving body side thin-walled portion 32, and the fixed body opening 27 is formed on both sides of the fixed body side thin-walled portion 34. However, this embodiment is not limited to this. For example, as shown in Figures 17 to 20, the force-receiving body opening 22 may be formed on one side of the force-receiving body side thin-walled portion 32, and the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 relative to the force-receiving body side thin-walled portion 32 may be cut out along the force-receiving body side thin-walled portion 32. In this case, the fixed body opening 27 is formed on one side of the fixed body side thin-walled portion 34, and the portion of the fixed body 25 opposite to the fixed body opening 27 relative to the fixed body side thin-walled portion 34 may be cut out along the fixed body side thin-walled portion 34. Figure 17 is a plan view showing a modified example of the force sensor shown in Figure 3. Figure 18 is a plan cross-sectional view corresponding to Figure 4, showing the force sensor shown in Figure 17. Figure 19 is a plan cross-sectional view corresponding to Figure 5, showing the force sensor shown in Figure 17. Figure 20 is a view taken from arrow Q in Figure 17, with the outer casing omitted. Note that in Figure 18, the fixing opening 27 is omitted for clarity.

[0189] As shown in Figure 17, the planar shape of the force-bearing body 20 may be approximately circular, or a part of the outer edge of the force-bearing body 20 may be cut out. The outer edge of the force-bearing body 20 may be cut out so as to follow the strain-generating bodies 30A to 30D when viewed in the Z-axis direction. The planar shape of the fixed body 25 is similar.

[0190] As shown in Figure 18, in this embodiment, each of the strain bodies 30A to 30D, the displacement body 35, may include a first displacement portion 35a and a second displacement portion 35b, similar to the example shown in Figure 16.

[0191] As shown in Figures 17 and 18, the force-receiving body 20 may include a plurality of force-receiving body protrusions 20b. One or more stopper protrusions 20c may be formed on each force-receiving body protrusion 20b.

[0192] Multiple force-receiving projections 20b may be arranged at intervals in the circumferential direction. The force-receiving projections 20b may be arranged alternately with strain-generating bodies 30A to 30D in the circumferential direction. The strain-generating bodies 30A to 30D may be arranged between two adjacent force-receiving projections 20b and exposed to the outer periphery from the force-receiving body 20. In other words, the strain-generating bodies 30A to 30D do not have to be surrounded from the outer periphery by the force-receiving projections 20b. The strain-generating bodies 30A to 30D may be surrounded by the force-receiving side cylindrical body 73a and the fixed body side cylindrical body 73b of the outer casing 70.

[0193] The force-receiving body opening 22 may be adjacent to the force-receiving body side thin-walled portion 32 of the strain-generating body 30A to 30D and may also be formed on one side of the force-receiving body side thin-walled portion 32. When viewed in the Z-axis direction, the force-receiving body opening 22 may be on the inside of the force-receiving body 20 relative to the force-receiving body side thin-walled portion 32 and adjacent to the force-receiving body side thin-walled portion 32. When viewed in the Z-axis direction, the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 relative to the force-receiving body side thin-walled portion 32 may be cut out along the force-receiving body side thin-walled portion 32. In this case, the force-receiving body main body 20a and the force-receiving body projection 20b are cut out. The strain-generating body 30A to 30D may be exposed to the outer circumference from the force-receiving body projection 20b of the force-receiving body 20.

[0194] More specifically, as shown in Figure 17, for the first strain-generating body 30A, a force-receiving body opening 22 may be formed on one side of the force-receiving body side thin-walled portion 32 and inside the force-receiving body 20 in the Y-axis direction. When viewed in the Z-axis direction, the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 relative to the force-receiving body side thin-walled portion 32 may be cut out along the force-receiving body side thin-walled portion 32. In this case, the first strain-generating body 30A may be exposed to the outer circumference from the force-receiving body protrusion 20b, as shown in Figure 20.

[0195] As shown in Figure 17, for the second strain-generating body 30B, a force-receiving body opening 22 may be formed on one side of the force-receiving body side thin-walled portion 32 and inside the force-receiving body 20 in the X-axis direction. When viewed in the Z-axis direction, the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 relative to the force-receiving body side thin-walled portion 32 may be cut out along the force-receiving body side thin-walled portion 32. In this case, the second strain-generating body 30B may be exposed to the outer circumference from the force-receiving body protrusion 20b.

[0196] With respect to the third strain-generating body 30C, in the Y-axis direction, a force-receiving body opening 22 may be formed on one side of the force-receiving body side thin-walled portion 32, on the inside of the force-receiving body 20. When viewed in the Z-axis direction, the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 with respect to the force-receiving body side thin-walled portion 32 may be cut out along the force-receiving body side thin-walled portion 32. In this case, the third strain-generating body 30C may be exposed to the outer circumference from the force-receiving body protrusion 20b.

[0197] With respect to the fourth strain-generating body 30D, in the X-axis direction, a force-receiving body opening 22 may be formed on one side of the force-receiving body side thin-walled portion 32, on the inside of the force-receiving body 20. When viewed in the Z-axis direction, the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 with respect to the force-receiving body side thin-walled portion 32 may be cut out along the force-receiving body side thin-walled portion 32. In this case, the fourth strain-generating body 30D may be exposed to the outer circumference from the force-receiving body protrusion 20b.

[0198] As shown in Figure 19, the fixed body 25 may include a plurality of fixed body protrusions 25b. Each fixed body protrusion 25b faces a corresponding force-receiving body protrusion 20b, and a gap may be formed between each fixed body protrusion 25b and the corresponding force-receiving body protrusion 20b to allow relative displacement between the force-receiving body 20 and the fixed body 25. One or more stopper recesses 25c may be formed in each fixed body protrusion 25b.

[0199] Multiple fixed body protrusions 25b may be arranged at intervals in the circumferential direction. The fixed body protrusions 25b may be arranged alternately with the strain generating bodies 30A to 30D in the circumferential direction. The strain generating bodies 30A to 30D may be arranged between two adjacent fixed body protrusions 25b and exposed to the outer circumferential side from the fixed body 25. In other words, the strain generating bodies 30A to 30D do not have to be surrounded from the outer circumferential side by the fixed body protrusions 25b. The strain generating bodies 30A to 30D may be surrounded by the force receiving side cylindrical body 73a and the fixed body side cylindrical body 73b of the outer casing 70.

[0200] The fixing body opening 27 may be adjacent to the fixing body side thin-walled portion 34 of the strain generating body 30A to 30D and may also be formed on one side of the fixing body side thin-walled portion 34. When viewed in the Z-axis direction, the fixing body opening 27 may be on the inside of the fixing body 25 relative to the fixing body side thin-walled portion 34 and adjacent to the fixing body side thin-walled portion 34. When viewed in the Z-axis direction, the portion of the fixing body 25 opposite to the fixing body opening 27 relative to the fixing body side thin-walled portion 34 may be cut out along the fixing body side thin-walled portion 34. In this case, the fixing body body 25a and the fixing body projection 25b are cut out. The strain generating body 30A to 30D may be exposed to the outer circumference from the fixing body projection 25b of the fixing body 25.

[0201] More specifically, as shown in Figure 19, for the first strain-generating body 30A, a fixing body opening 27 may be formed on one side of the thin-walled portion 34 on the fixing body side, on the inside of the fixing body 25, in the Y-axis direction. When viewed in the Z-axis direction, the portion of the fixing body 25 opposite to the fixing body opening 27 relative to the thin-walled portion 34 on the fixing body side may be cut out along the thin-walled portion 34 on the fixing body side. In this case, the first strain-generating body 30A may be exposed to the outer circumference from the fixing body projection 25b, as shown in Figure 20.

[0202] As shown in Figure 19, with respect to the second strain-generating body 30B, a fixing body opening 27 may be formed on one side of the thin-walled portion 34 on the fixing body side, on the inside of the fixing body 25, in the X-axis direction. When viewed in the Z-axis direction, the portion of the fixing body 25 opposite to the fixing body opening 27 relative to the thin-walled portion 34 on the fixing body side may be cut out along the thin-walled portion 34 on the fixing body side. In this case, the second strain-generating body 30B may be exposed to the outer circumference from the fixing body projection 25b.

[0203] With respect to the third strain-generating body 30C, in the Y-axis direction, a fixing body opening 27 may be formed on one side of the fixing body side thin-walled portion 34, on the inside of the fixing body 25. When viewed in the Z-axis direction, the portion of the fixing body 25 opposite to the fixing body opening 27 with respect to the fixing body side thin-walled portion 34 may be cut out along the fixing body side thin-walled portion 34. In this case, the third strain-generating body 30C may be exposed to the outer circumference from the fixing body projection 25b.

[0204] With respect to the fourth strain-generating body 30D, a fixing body opening 27 may be formed on one side of the thin-walled portion 34 on the fixing body side, on the inside of the fixing body 25, in the X-axis direction. When viewed in the Z-axis direction, the portion of the fixing body 25 opposite to the fixing body opening 27 with respect to the thin-walled portion 34 on the fixing body side may be cut out along the thin-walled portion 34 on the fixing body side. In this case, the fourth strain-generating body 30D may be exposed to the outer circumference from the fixing body projection 25b.

[0205] As shown in the example in Figure 17, in the Z-axis direction, a force-receiving body opening 22 is formed on one side of the force-receiving body thin-walled portion 32 of the first strain-generating body 30A. This allows the force-receiving body thin-walled portion 32 and the portion of the force-receiving body 20a on the force-receiving body opening 22 side to be separated. Also, when viewed in the Z-axis direction, the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 relative to the force-receiving body thin-walled portion 32 is cut out along the force-receiving body thin-walled portion 32. This prevents the force-receiving body thin-walled portion 32 from being inhibited from elastically deforming by the force-receiving body 20a and the force-receiving body protrusion 20b. Therefore, when the force-receiving body 20 is subjected to force or moment, the force-receiving body thin-walled portion 32 can be made to elastically deform more easily, and the displacement of the displacement body 35 can be made even larger. As a result, the change in capacitance value can be made even larger, and the detection sensitivity of the force sensor 10 can be further improved.

[0206] Furthermore, as shown in the example in Figure 17, by cutting out the portion of the force-receiving body 20 opposite to the force-receiving body opening 22 relative to the force-receiving body side thin-walled portion 32, it becomes unnecessary to form the force-receiving body opening 22 on the outside of the force-receiving body side thin-walled portion 32. Since the cutout can be formed by machining (e.g., cutting) at a lower cost than forming the force-receiving body opening 22, the manufacturing cost of the force-receiving body 20 can be reduced. In addition, by cutting out a portion of the outer edge of the force-receiving body 20, the external size of the force-receiving body 20 can be reduced, and the force sensor 10 can be miniaturized.

[0207] Furthermore, in the example shown in Figure 17, the first strain-generating body 30A is positioned between two adjacent force-receiving body protrusions 20b. This allows for effective use of the internal space of the force sensor 10. As a result, the external size of the force-receiving body 20 can be reduced, and the force sensor 10 can be miniaturized.

[0208] Furthermore, in the example shown in Figure 17, a fixed body opening 27 is formed on one side of the fixed body-side thin-walled portion 34 of the first strain-generating body 30A in the Z-axis direction. This allows the fixed body-side thin-walled portion 34 and the portion of the fixed body body 25a on the fixed body opening 27 side to be separated. Also, when viewed in the Z-axis direction, the portion of the fixed body 25 opposite to the fixed body opening 27 relative to the fixed body-side thin-walled portion 34 is cut out along the fixed body-side thin-walled portion 34. This prevents the elastic deformation of the fixed body-side thin-walled portion 34 from being inhibited by the fixed body body 25a and the fixed body protrusion 25b. As a result, when the force-receiving body 20 is subjected to force or moment, the fixed body-side thin-walled portion 34 can be made to deform more elastically, and the displacement of the displacement body 35 can be made even larger. As a result, the change in capacitance value can be made even larger, and the detection sensitivity of the force sensor 10 can be further improved.

[0209] Furthermore, as shown in the example in Figure 17, by cutting out a portion of the outer periphery of the fixed body 25 along the thin-walled portion 34 on the fixed body side, it becomes unnecessary to form a fixed body opening 27 on the outside of the thin-walled portion 34 on the fixed body side. Since the cutout can be formed by machining (e.g., cutting) at a lower cost than forming a fixed body opening 27, the manufacturing cost of the fixed body 25 can be reduced. In addition, by cutting out a portion of the outer periphery of the fixed body 25, the external size of the fixed body 25 can be reduced, and the force sensor 10 can be miniaturized.

[0210] Furthermore, as shown in Figure 17, the first strain-generating body 30A is positioned between two adjacent fixed body protrusions 25b. This allows for effective use of the internal space of the force sensor 10. As a result, the external size of the fixed body 25 can be reduced, and the force sensor 10 can be miniaturized.

[0211] (Modification 4) In the above-described embodiment, an example was described in which the strain generating bodies 30A to 30D include a strain generating portion 40 on the force receiving body 20 and a strain generating portion 41 on the fixed body 25. However, this embodiment is not limited to this. For example, as shown in Figure 21, the strain generating bodies 30A to 30D may be formed separately from the force receiving body 20 and also separately from the fixed body 25. Figure 21 shows the first strain generating body 30A as a representative example, but the second strain generating bodies 30B to the fourth strain generating bodies 30D can be configured in the same way.

[0212] As shown in Figure 21, the first strain-generating body 30A may include a force-receiving body side portion 81 that connects the force-receiving body side thin-walled portion 32 to the force-receiving body main body 20a, and a stationary body side portion 82 that connects the stationary body side thin-walled portion 34 to the stationary body main body 25a. The force-receiving body side portion 81 is an example of the first sensor body side portion, and the stationary body side portion 82 is an example of the second sensor body side portion.

[0213] The force-receiving body portion 81 and the force-receiving body thin-walled portion 32 are positioned at different locations from the force-receiving body 20a in the Z-axis direction. The force-receiving body portion 81 and the force-receiving body thin-walled portion 32 are positioned on the negative side in the Z-axis direction relative to the force-receiving body 20a. The force-receiving body portion 81 is in contact with the surface of the force-receiving body 20a that faces the fixed body 25a. The force-receiving body portion 81 may be fixed to the force-receiving body 20 with bolts (not shown) or other means, or it may be joined with adhesive.

[0214] The force-receiving body side portion 81 of the first strain body 30A is arranged on both sides in the X-axis direction of the force-receiving body side thin-walled portion 32. As shown in Figure 22, since the force-receiving body side portion 81 is not formed on both sides in the Y-axis direction of the force-receiving body side thin-walled portion 32, it is unnecessary to form the force-receiving body opening 22. The force-receiving body side thin-walled portion 32 shown in Figure 21 can suppress the inhibition of elastic deformation by the force-receiving body side portion 81 and the force-receiving body body 20a. The force-receiving body side portion 81 of the third strain body 30C may be formed in the same way as the force-receiving body side portion 81 of the first strain body 30A. The force-receiving body side portions 81 of the second strain body 30B and the fourth strain body 30D may also be formed in the same way as the force-receiving body side portion 81 of the first strain body 30A, although there is a difference in the X-axis direction and the Y-axis direction.

[0215] As shown in Figure 21, the thickness t1 of the thin-walled portion 32 on the force-receiving body side (see Figure 7) may be thinner than the thickness t2 of the force-receiving body main body 20a. The thickness t1 of the thin-walled portion 32 on the force-receiving body side may be thinner than the thickness t5 of the force-receiving body portion 81. A recess 36 on the force-receiving body side may be formed on the surface of the first strain-generating body 30A facing the force-receiving body main body 20a. The thin-walled portion 32 on the force-receiving body side may overlap with the force-receiving body main body 20a when viewed in the Z-axis direction.

[0216] The fixed body side portion 82 and the fixed body side thin-walled portion 34 are positioned at different locations from the fixed body main body 25a in the Z-axis direction. In the Z-axis direction, the fixed body side portion 82 and the fixed body side thin-walled portion 34 are positioned on the positive side of the fixed body main body 25a. The fixed body side portion 82 is in contact with the surface of the fixed body main body 25a that faces the force-receiving body 20a. The fixed body side portion 82 may be fixed to the fixed body 25 with bolts (not shown) or joined with adhesive.

[0217] The fixed body side portion 82 of the first strain body 30A is arranged on both sides in the X-axis direction of the fixed body side thin-walled portion 34. Similar to the force-receiving body side thin-walled portion 32, the fixed body side portion 82 is not formed on both sides in the Y-axis direction of the fixed body side thin-walled portion 34, thus eliminating the need to form the fixed body opening 27. The fixed body side thin-walled portion 34 shown in Figure 21 can suppress the inhibition of elastic deformation by the fixed body side portion 82 and the fixed body body 25a. The fixed body side portion 82 of the third strain body 30C may be formed in the same way as the fixed body side portion 82 of the first strain body 30A. The fixed body side portions 82 of the second strain body 30B and the fourth strain body 30D may also be formed in the same way as the fixed body side portion 82 of the first strain body 30A, although there is a difference in the X-axis direction and the Y-axis direction.

[0218] As shown in Figure 21, the thickness t3 of the thin-walled portion 34 on the fixed body side (see Figure 7) may be thinner than the thickness t4 of the fixed body main body 25a. The thickness t3 of the thin-walled portion 34 on the fixed body side may also be thinner than the thickness t6 of the fixed body side portion 82. A recess 37 on the fixed body side may be formed on the surface of the first strain-generating body 30A facing the fixed body main body 25a. The thin-walled portion 34 on the fixed body side may overlap with the fixed body main body 25a when viewed in the Z-axis direction.

[0219] As shown in Figure 21, the fixed body portion 82 is positioned between the displacement body 35 and the fixed body main body 25a in the Z-axis direction. The tip of each displacement body 35 faces the corresponding fixed body portion 82. The first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2 of the first capacitive element C1 are attached to the corresponding fixed body portion 82, more specifically, to the surface of the fixed body portion 82 facing the displacement body 35. The same applies to the third fixed electrode substrate Ef3 to the eighth fixed electrode substrate Ef3.

[0220] In the example shown in Figure 21, the outer casing 70 includes a force-receiving side cylindrical body 73a, a fixed body side cylindrical body 73b, and a cushioning member 74. The outer casing 70 does not necessarily include a force-receiving side cover 71 and a fixed body side cover 72. In this case, the force-receiving side cylindrical body 73a may be fixed to the force-receiving body 20a with bolts (not shown). The fixed body side cylindrical body 73b may be fixed to the fixed body 25a with bolts (not shown).

[0221] As shown in the example in Figure 21, the strain-generating bodies 30A to 30D are formed separately from the force-receiving body 20 and also separately from the fixed body 25. This allows the force-receiving body 20, the fixed body 25, and the strain-generating bodies 30A to 30D to be formed inexpensively by machining (for example, cutting). Therefore, the manufacturing cost of the force sensor 10 can be reduced.

[0222] The present invention is not limited to the above embodiments and modifications, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriate combinations of the multiple components disclosed in the above embodiments and modifications. Some components may be deleted from all the components shown in the embodiments and modifications. Moreover, components from different embodiments and modifications may be combined as appropriate.

[0223] 10 force sensor 20 force receiving body 20a force receiving body main body 20b force receiving body protrusion 20c stopper convex portion 21 screw hole 22 force receiving body opening 25 fixed body 25a fixed body main body 25b fixed body protrusion 25c stopper recess 26 screw hole 27 fixed body opening 30A first strain body 30B Second flexure element 30C Third flexure element 30D Fourth flexure element 31 Connection main body part 32 Thin part on force receiving body side 33 Pedestal 33a Pedestal protrusion part 34 Thin part on fixed body side 35 Displacement body 35a First displacement part 35b Second displacement part 36 Recessed part on force receiving body side 37 Recessed part on fixed body side 38 Displacement bolt 40 Force receiving body side strain generating part 41 Fixed body side strain generating part 42 Strain-generating bolt 50 Detection element 60 Detection circuit 70 Outer casing 71 Force-receiving body side cover 72 Fixed body side cover 73 Cylindrical body 74 Cushioning member 75 Force-receiving body side through hole 76 Fixed body side through hole 81 Force-receiving body side portion 82 Fixed body side portion

Claims

1. A first sensor body that is subjected to the action of a force or moment to be detected; a second sensor body facing the first sensor body in a first direction; a strain-generating body connecting the first sensor body and the second sensor body, which is elastically deformed by the force or moment received by the first sensor body; a detection element that detects a change in capacitance value due to the displacement caused by the elastic deformation of the strain-generating body; and a detection circuit that outputs an electrical signal indicating the force or moment acted on the first sensor body based on the detection result of the detection element, wherein the strain-generating body includes a connecting body portion extending in the first direction; a first thin-walled portion connecting the connecting body portion and the first sensor body, which is a first thin-walled portion extending in a second direction perpendicular to the first direction; a base connecting the connecting body portion and the second sensor body; a second thin-walled portion connecting the base and the second sensor body, which is a second thin-walled portion extending in the second direction; and a displacement body. The detection element includes a fixed electrode substrate attached to the second sensor body and a displacement electrode substrate attached to the displacement body and facing the fixed electrode substrate, the base includes base protrusions that protrude from the connecting body on both sides of the connecting body in the second direction, and the displacement body extends from the base protrusions in the second direction, a force sensor.

2. The force sensor according to claim 1, wherein the base is interposed between the second thin-walled portion and the connecting body portion in the first direction.

3. The force sensor according to claim 1 or 2, wherein the displacement body is formed separately from the base and fastened to the base projection by bolts, or joined by welding or adhesive.

4. The force sensor according to claim 1 or 2, wherein the first sensor body includes a first opening adjacent to the first thin-walled portion.

5. The force sensor according to claim 4, wherein the first opening is formed on both sides of the first thin-walled portion in a third direction perpendicular to the first and second directions.

6. The force sensor according to claim 4, wherein in a third direction perpendicular to the first and second directions, the first opening is formed on one side of the first thin-walled portion, and when viewed in the first direction, the portion of the first sensor body opposite to the first opening relative to the first thin-walled portion is cut out.

7. The force sensor according to claim 6, wherein the first sensor body includes a plurality of first protrusions projecting toward the second sensor body, and the strain generating body is positioned between two adjacent first protrusions.

8. The force sensor according to claim 1 or 2, wherein the second sensor body includes a second opening adjacent to the second thin-walled portion.

9. The force sensor according to claim 8, wherein the second opening is formed on both sides of the second thin-walled portion in a third direction perpendicular to the first and second directions.

10. The force sensor according to claim 8, wherein in a third direction perpendicular to the first and second directions, the second opening is formed on one side of the second thin-walled portion, and when viewed in the first direction, the portion of the second sensor body opposite to the second opening relative to the second thin-walled portion is cut out.

11. The force sensor according to claim 10, wherein the second sensor body includes a plurality of second protrusions projecting toward the first sensor body, and the strain generating body is positioned between two adjacent second protrusions.

12. The force sensor according to claim 1 or 2, wherein the strain generating body includes a first strain generating portion formed integrally with the first sensor body and including at least a part of the connecting body portion, and a second strain generating portion formed integrally with the second sensor body and including the base.

13. The force sensor according to claim 12, wherein the strain generating body further includes a strain generating body fastening portion that fastens the first strain generating portion and the second strain generating portion.

14. The force sensor according to claim 12, wherein the first strain-generating portion includes a part of the connecting body portion, and the second strain-generating portion includes another part of the connecting body portion.

15. The displacement body includes a first displacement portion extending from the base in the second direction, and a second displacement portion extending from the first displacement portion in a third direction perpendicular to the first and second directions, toward the inside of the force sensor as viewed in the first direction, wherein the displacement electrode substrate is attached to the second displacement portion, the force sensor according to claim 1 or 2.

16. The force sensor according to claim 1 or 2, wherein the first sensor body and the second sensor body are connected by four strain-generating bodies, the four strain-generating bodies include a first strain-generating body, a second strain-generating body, a third strain-generating body, and a fourth strain-generating body, wherein the first direction is the Z-axis direction in an XYZ three-dimensional coordinate system, the first strain-generating body is positioned on the positive Y-axis side with respect to the center of the first sensor body, the second strain-generating body is positioned on the negative X-axis side with respect to the center of the first sensor body, the third strain-generating body is positioned on the negative Y-axis side with respect to the center of the first sensor body, and the fourth strain-generating body is positioned on the positive X-axis side with respect to the center of the first sensor body.

Images