Force sensor

Abstract

A strain-generating body according to the present invention includes a first connection part and a second sensor body-side connection part. The second sensor body-side connection part includes: a pair of pedestals that are connected to a second sensor body and located at both sides of a second end section in a second direction; a second connection part extending in the second direction from the second end section to one of the pedestals when viewed in a third direction; and a third connection part extending in the second direction from the second end section to the other of the pedestals when viewed in the third direction. A displacement part extends from the second end section in a direction intersecting the second direction when viewed in a first direction. A detection element detects, according to the displacement of the leading end section of the displacement part, a change in capacitance value.

Description

Force sensor

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

[0002] Force sensors are known that output electrical signals representing forces acting in a specific axial direction and moments (torques) acting around a specific rotation axis. Force sensors are widely used for force control in a variety of robots, including industrial robots, collaborative robots, life support robots, medical robots, and service robots.

[0003] A force sensor is placed between the robot arm and the end effector (gripper, etc.) to detect the force acting on the workpiece. The detected force is used to control the robot. For example, if the robot arm comes into contact with a person, the force sensor detects the contact. This allows the robot arm's operation to be stopped immediately.

[0004] Such force sensors are required to have improved detection sensitivity.

[0005] JP 2021-135103 A

[0006] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a force sensor that can improve detection sensitivity.

[0007] [1] The present disclosure provides a sensor device comprising: a first sensor body that is subjected to the action of a force or moment to be detected; a second sensor body that is disposed at a position different from the first sensor body in a first direction; a strain generating body that connects the first sensor body and the second sensor body and that elastically deforms due to the action of the force or moment received by the first sensor body; a detection element that detects displacement caused by the elastic deformation of the strain generating body; and a detection circuit that outputs an electrical signal that indicates the force or moment that has acted on the first sensor body based on the detection result of the detection element, wherein a direction perpendicular to the first direction is defined as a second direction, and a direction perpendicular to the first direction and perpendicular to the second direction is defined as a third direction, and the strain generating body includes a first connection portion that extends in the first direction from a first end connected to the first sensor body to a second end located on the opposite side to the first end, and a second sensor body side connection portion that connects the second end of the first connection portion to the second sensor body, The second sensor body side connection portion may include a pair of pedestals connected to the second sensor body, the pair of pedestals being located on both sides of the second end in the second direction, a second connection portion extending in the second direction from the second end to one of the pedestals when viewed in the third direction, a third connection portion extending in the second direction from the second end to the other pedestal when viewed in the third direction, and a displacement portion extending from the second end in a direction intersecting the second direction when viewed in the first direction, and the detection element may be a force sensor that detects a change in capacitance value due to displacement of the tip of the displacement portion.

[0008] [2] The present disclosure may also be a force sensor as described in [1], wherein the strain element includes a first sensor body side connection portion that connects the first end of the first connection portion to the first sensor body, and the first sensor body side connection portion is a thin-walled portion formed along the second direction and the third direction, and includes a thin-walled portion connected to the first end of the first connection portion.

[0009] [3] The present disclosure may be a force sensor according to [1] or [2], wherein the detection element includes a fixed electrode substrate provided on the second sensor body and a displacement electrode substrate provided at the tip of the displacement portion and facing the fixed electrode substrate.

[0010] [4] The present disclosure may be a force sensor as described in [3], wherein the fixed electrode substrate includes a first fixed electrode substrate located on one side of the base with respect to the central axis of the flexure body, and a second fixed electrode substrate located on the other side of the base with respect to the central axis of the flexure body.

[0011] [5] The present disclosure may be a force sensor as described in [3] or [4], wherein the displacement electrode substrate includes a first displacement electrode substrate located on one side of the base with respect to the central axis of the strain generating body, and a second displacement electrode substrate located on the other side of the base with respect to the central axis of the strain generating body.

[0012] [6] The present disclosure may be a force sensor according to any one of [1] to [5], wherein the displacement portion extends from the second end of the first connection portion in the third direction.

[0013] [7] The present disclosure may be a force sensor according to any one of [1] to [6], wherein, when viewed in the first direction, the second sensor body side connection portion is formed linearly along the second direction.

[0014] [8] The present disclosure may also be a force sensor described in any of [1] to [7], wherein, when viewed in the first direction, the first sensor body and the second sensor body are formed in a circular shape, and when viewed in the first direction, the second sensor body side connection portion is formed in an arc shape so as to follow at least one of the periphery of the first sensor body and the periphery of the second sensor body.

[0015] [9] The present disclosure may be a force sensor according to any one of [1] to [8], wherein the first sensor body and the second sensor body are connected by four flexure bodies, and the four flexure bodies include a first flexure body, a second flexure body, a third flexure body, and a fourth flexure body, the first direction is defined as a Z-axis direction in an XYZ three-dimensional coordinate system, the first flexure body is arranged on the positive side of the Y-axis direction with respect to the center of the first sensor body, the second flexure body is arranged on the negative side of the X-axis direction with respect to the center of the first sensor body, the third flexure body is arranged on the negative side of the Y-axis direction with respect to the center of the first sensor body, and the fourth flexure body is arranged on the positive side of the X-axis direction with respect to the center of the first sensor body.

[0016]

[10] The present disclosure may be a force sensor according to [9], wherein the displacement portion extends from the second end of the corresponding first connection portion toward the center of the first sensor body.

[0017] According to the present invention, it is possible to improve detection sensitivity.

[0018] FIG. 1 is a perspective view showing an example of a robot to which a force sensor according to a first embodiment is applied. FIG. 2 is a cross-sectional view showing the force sensor according to the first embodiment, corresponding to the cross section taken along line A-A in FIG. 3 described later. FIG. 3 is a plan view showing the force sensor of FIG. 2 with the force receiving body omitted. FIG. 4 is a front view showing the first flexure body of FIG. 2. FIG. 5 is a plan view showing the first flexure body of FIG. 4. FIG. 6 is a side view showing the first flexure body of FIG. 4. FIG. 7 is a planar development of the flexure body of the force sensor shown in FIG. 3. FIG. 8 is a front view schematically showing a deformation state of the first flexure body of FIG. 4 when it is subjected to a force in the positive X-axis direction. FIG. 9A is a side view schematically showing a deformation state of the first flexure body of FIG. 4 when it is subjected to a force in the positive Y-axis direction. FIG. 9B is a side view schematically showing a deformation state of the first flexure body of FIG. 4 when it is subjected to a force in the negative Y-axis direction. FIG. 10A is a front view schematically showing a deformed state of the first flexure body of FIG. 4 when it is subjected to a force in the positive direction of the Z axis. FIG. 10B is a front view schematically showing a deformed state of the first flexure body of FIG. 4 when it is subjected to a force in the negative direction of the Z axis. FIG. 11 is a table showing changes in the capacitance value of each capacitance element in the flexure body of FIG. 4. FIG. 12 is a table showing changes in the capacitance value of each capacitance element in the force sensor of FIG. 7. FIG. 13 is a front view of a first flexure body showing a modified example of the detection element of FIG. 4. FIG. 14 is a plan view showing a force sensor according to the second embodiment with the force receiving body omitted. FIG. 15 is a front view of the first flexure body shown in FIG. 14. FIG. 16 is a plan view showing the first flexure body of FIG. 15. FIG. 17 is a side view showing the first flexure body of FIG. 15. FIG. 18 is a plan view of a first flexure body showing a modified example of the detection element of FIG. 15.

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios of the actual objects have been appropriately changed and exaggerated for the sake of convenience in illustration and understanding.

[0020] As used herein, geometric conditions, physical characteristics, terms specifying the extent of a geometric condition or physical characteristic, and numerical values ​​indicating a geometric condition or physical characteristic may be interpreted without being bound by strict meaning. These geometric conditions, physical characteristics, terms, and numerical values ​​may also be interpreted to include the range of extent to which similar functions can be expected. Examples of terms specifying geometric conditions include "length," "angle," "shape," "parallel," "orthogonal," and "identical."

[0021] First Embodiment A force sensor according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 13. FIG.

[0022] First, a robot 1 according to the present embodiment will be described with reference to Fig. 1. Fig. 1 is a perspective view showing an example of a robot 1 according to the present embodiment. A force sensor 10 according to the present embodiment is attached to the robot 1. Examples of the robot 1 include various robots such as industrial robots, collaborative robots, life support robots, medical robots, and service robots. For convenience, the following description will be given taking an industrial robot to which the force sensor 10 is attached as an example.

[0023] 1, the industrial robot 1 includes 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-joint arm structure.

[0024] 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 electric 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).

[0025] The controller 5 controls the force of the robot 1 based on the electrical signal output from the force sensor 10. In this way, the operations of the robot body 2 and the tool 3 are controlled.

[0026] A force sensor 10 according to an embodiment of the present invention will now be described with reference to FIGS. 2 to 5. FIG. 2 is a cross-sectional view showing the force sensor according to this embodiment, corresponding to the cross section taken along line A-A in FIG. 3. FIG. 3 is a plan view showing the force sensor of FIG. 2 with the force receiving body omitted. FIG. 4 is a front view showing the first flexure element of FIG. 2. FIG. 5 is a plan view showing the first flexure element of FIG. 4, and FIG. 6 is a side view showing the first flexure element of FIG. 4. FIG. 7 is a planar development of each flexure element of the force sensor shown in FIG. 3.

[0027] In the following explanation, an XYZ three-dimensional coordinate system is defined, the Z-axis direction (first direction) is the up-down direction, and the force sensor 10 is arranged so that the force receiving body 20 is arranged on the upper side and the fixed body 25 is arranged on the lower side. Therefore, the force sensor 10 according to this embodiment is not limited to being used in a position in which the Z-axis direction is the up-down direction. Furthermore, it is optional whether the force receiving body 20 or the fixed body 25 is arranged on the upper side or the lower side.

[0028] The force sensor 10 has a function of outputting a force acting in a predetermined axial direction and a moment acting around a predetermined rotation axis as an electrical signal, but is not limited to this, and may be configured to output only one of the force and the moment as an electrical signal, or may be configured to output at least one axial component of the force or the moment as an electrical signal.

[0029] As shown in Figures 2 and 3, the force sensor 10 includes a force receiving body 20, a fixed body 25, strain generating bodies 30A to 30D, a detection element 70, a detection circuit 75, and an exterior body 80. Each component will be described in more detail below. Note that Figure 2 is a cross-sectional view taken along line A-A in Figure 3, but for convenience, the second strain generating body 30B and the fourth strain generating body 30D are shown in outline.

[0030] Force receiving body 20 is an example of a first sensor body. Force receiving body 20 is acted upon by the force or moment to be detected. This act causes force receiving body 20 to move relative to fixed body 25. In the example of FIG. 1 described above, force receiving body 20 is fixed to tool 3 with a bolt or the like, and receives a force or moment from tool 3. Strain generating bodies 30A to 30D are connected to force receiving body 20.

[0031] 3, in this embodiment, the planar shape of force receiving member 20 is circular. However, the planar shape of force receiving member 20 is not limited to circular and may be rectangular or any other shape. Force receiving member 20 may also be formed in a flat plate shape.

[0032] As shown in Fig. 2, fixed body 25 is an example of a second sensor body. Fixed body 25 supports force receiving body 20. Fixed body 25 is disposed at a different position from force receiving body 20 in the Z-axis direction. More specifically, fixed body 25 is disposed on the negative side of force receiving body 20 in the Z-axis direction. Force receiving body 20 and fixed body 25 are disposed at different positions from each other in the Z-axis direction, and fixed body 25 is spaced apart from force receiving body 20. In the example of Fig. 1, fixed body 25 is fixed to the tip of robot arm 4 with a bolt or the like and is supported by robot main body 2. Strain generating bodies 30A to 30D are connected to fixed body 25.

[0033] As shown in FIG. 3 , in this embodiment, the planar shape of fixed body 25 is circular, similar to force receiving body 20. When viewed in the Z-axis direction, fixed body 25 overlaps force receiving body 20. However, the planar shape of fixed body 25 is not limited to circular and may be rectangular or any other shape. Fixed body 25 may also be formed in a flat plate shape. Note that at least one of the planar shapes of force receiving body 20 and fixed body 25 may be circular. In this case, one of the planar shapes of force receiving body 20 and fixed body 25 may be circular, and the other may be a shape other than circular.

[0034] 2 and 3, flexure bodies 30A to 30D connect force receiving body 20 and fixed body 25. More specifically, flexure bodies 30A to 30D are disposed between force receiving body 20 and fixed body 25, and flexure bodies 30A to 30D are connected to force receiving body 20 and fixed body 25. Force receiving body 20 is supported by fixed body 25 via these flexure bodies 30A to 30D.

[0035] In the present embodiment, the force receiving body 20 and the fixed body 25 may be connected by four flexure bodies 30A to 30D. The four flexure bodies 30A to 30D may include a first flexure body 30A, a second flexure body 30B, a third flexure body 30C, and a fourth flexure body 30D.

[0036] 3, when viewed in the Z-axis direction, the first flexure body 30A may be disposed on the positive side of the Y-axis direction with respect to the center O of the force receiving body 20. Similarly, when viewed in the Z-axis direction, the second flexure body 30B may be disposed on the negative side of the X-axis direction with respect to the center O of the force receiving body 20. The third flexure body 30C may be disposed on the negative side of the Y-axis direction with respect to the center O of the force receiving body 20. The fourth flexure body 30D may be disposed on the positive side of the X-axis direction with respect to the center O of the force receiving body 20. In this case, the center O of the force receiving body 20 is disposed between the first flexure body 30A and the third flexure body 30C, and the center O of the force receiving body 20 is disposed between the second flexure body 30B and the fourth flexure body 30D.

[0037] The number of strain bodies connecting force receiving body 20 and fixed body 25 is not limited to four, but may be two, three, five or more, or any other number. Force receiving body 20 and fixed body 25 may be connected by only one strain body. In this case, if detection element 70 is configured with two capacitance elements as shown in Figure 4, it will be possible to detect two-axis components of force, as will be described later. Detection element 70 may also be configured with only one capacitance element to detect one-axis component of force.

[0038] As shown in FIG. 3 , the four flexure bodies 30A to 30D according to this embodiment are arranged in an annular shape. That is, as described above, the force receiving body 20 and the fixed body 25 are formed in a circular shape when viewed in the Z-axis direction, and the four flexure bodies 30A to 30D are arranged to form a rectangular annular shape. When viewed in the Z-axis direction, each of the flexure bodies 30A to 30D is formed linearly along the second direction. That is, the second direction of the first flexure body 30A and the second direction of the third flexure body 30C correspond to the X-axis direction. The first flexure body 30A and the third flexure body 30C are formed linearly along the X-axis direction. The second direction of the second flexure body 30B and the second direction of the fourth flexure body 30D correspond to the Y-axis direction. The second flexure body 30B and the fourth flexure body 30D are formed linearly along the Y-axis direction. The second direction of each of the flexure bodies 30A to 30D is not limited to the example shown in FIG. 3 and may be any direction. Furthermore, the second direction of each of the flexure bodies 30A to 30D does not have to be along either the X-axis direction or the Y-axis direction. For example, the arrangement of the four flexure bodies 30A to 30D is not limited to an annular arrangement, and each of them may be arranged irregularly at any position.

[0039] Next, the strain generating bodies 30A to 30D according to this embodiment will be described in more detail.

[0040] The flexure bodies 30A to 30D according to this embodiment are configured to elastically deform, generating strain and displacement due to the action of a force or moment received by the force receiving body 20. Here, of the four flexure bodies 30A to 30D described above, the first flexure body 30A, whose second direction is the X-axis direction, will be described as an example. The Y-axis direction corresponds to the third direction. The third direction is a direction that is perpendicular to the first direction and perpendicular to the second direction. The second flexure body 30B, the third flexure body 30C, and the fourth flexure body 30D have similar configurations, and therefore detailed description of the common configurations will be omitted.

[0041] As shown in FIGS. 2 and 4, the first strain generating element 30A may include a first connecting portion 31 and a fixed body side connecting portion 32.

[0042] The first connecting portion 31 includes a first end 31a connected to the force receiving body 20 and a second end 31b located opposite the first end 31a. The first connecting portion 31 extends in the Z-axis direction from the first end 31a to the second end 31b. The first end 31a is connected to a surface (the lower surface in FIG. 4 ) of the thin-walled portion 40 (described later) that faces the fixed body 25. The second end 31b is connected to a displacement portion 36 (described later) and is located between the second connecting portion 34 and the third connecting portion 35. The first connecting portion 31 may be formed linearly along both the Y-axis and the Z-axis directions. As shown in FIG. 4 , the first connecting portion 31 may be formed along the central axis CL of the first flexure body 30A. The central axis CL of the first flexure body 30A is a line along the Z-axis direction that passes through the center of the first flexure body 30A in the X-axis direction. First end 31a is connected to force receiving member 20 via force receiving member side connection portion 38, which will be described later. First connection portion 31 may be elastically deformable by the action of forces in the X-axis direction and the Y-axis direction.

[0043] The fixed body side connection portion 32 is an example of a second sensor body side connection portion. The fixed body side connection portion 32 connects the second end portion 31b of the first connection portion 31 to the fixed body 25. The fixed body side connection portion 32 includes a pair of fixed body side bases 33, a second connection portion 34, a third connection portion 35, and a displacement portion 36.

[0044] Fixed body side pedestal 33 according to the present embodiment may be connected to fixed body 25. Fixed body side pedestal 33 extends in the Z-axis direction from fixed body 25 toward force receiving body 20. Fixed body side pedestal 33 is located on both sides of second end 31b of first connecting portion 31 in the X-axis direction, and on both sides of central axis CL. One fixed body side pedestal 33 is located on the positive side of second end 31b in the X-axis direction. The other fixed body side pedestal 33 is located on the negative side of second end 31b in the X-axis direction.

[0045] The fixed body side base 33 abuts against the fixed body 25 and is attached to the fixed body 25 using bolts or the like (not shown). A screw hole (not shown) may be formed in the surface of the fixed body side base 33 on the side of the fixed body 25 (the lower surface in FIG. 4 ). The fixed body side base 33 may have one screw hole or multiple screw holes formed therein.

[0046] The second connection portion 34 extends in the X-axis direction. The second connection portion 34 may be formed in a flat plate shape along the X-axis direction and the Y-axis direction. When viewed in the Y-axis direction, the second connection portion 34 extends linearly from the second end 31b of the first connection portion 31 to one of the fixed body side pedestals 33. In the example shown in FIG. 4 , the second connection portion 34 is connected to and supported by the fixed body side pedestal 33 located on the positive side of the X-axis direction relative to the second end 31b. The second connection portion 34 may be elastically deformable by the action of forces in the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0047] The third connection portion 35 extends in the X-axis direction. The third connection portion 35 may be formed in a flat plate shape along the X-axis direction and the Y-axis direction. When viewed in the Y-axis direction, the third connection portion 35 extends linearly from the second end 31b of the first connection portion 31 to the other fixed body side base 33. In the example shown in FIG. 4 , the third connection portion 35 is connected to and supported by the fixed body side base 33 located on the negative side of the X-axis direction relative to the second end 31b. The third connection portion 35 may be elastically deformable by the action of forces in the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0048] As shown in FIGS. 4 to 6 , the displacement portion 36 extends from the second end 31b of the first connection portion 31 in a direction intersecting the X-axis direction when viewed in the Z-axis direction. The displacement portion 36 may extend from the second end 31b in the Y-axis direction, or may be formed linearly along the Y-axis direction. As shown in FIGS. 4 and 6 , the displacement portion 36 extends from the surface of the second end 31b facing the fixed body 25. The surface of the second end 31b facing the fixed body 25 is the surface of the second end 31b facing the negative side in the Z-axis direction, which corresponds to the bottom surface shown in FIG. 4 . However, the displacement portion 36 may also extend from the surface of the second end 31b facing the negative side in the Y-axis direction (the front surface shown in FIG. 4 ).

[0049] 3, the displacement portion 36 of the first flexure body 30A extends from the second end 31b of the first connection portion 31 of the first flexure body 30A toward the center O of the force receiving body 20 when viewed in the Z-axis direction. The displacement portion 36 of the first flexure body 30A extends from the second end 31b to the negative side in the Y-axis direction. The displacement portion 36 of the first flexure body 30A may be located at the center of the first flexure body 30A in the X-axis direction, or may overlap with the central axis CL (see FIGS. 4 and 7) of the first flexure body 30A when viewed in the Y-axis direction.

[0050] 3, the displacement portion 36 of the second flexure body 30B extends from the second end 31b of the first connection portion 31 of the second flexure body 30B toward the center O of the force receiving body 20 when viewed in the Z-axis direction. The displacement portion 36 of the second flexure body 30B extends from the second end 31b to the positive side in the X-axis direction. The displacement portion 36 of the second flexure body 30B may be located at the center of the second flexure body 30B in the Y-axis direction, or may overlap with the central axis CL (see FIGS. 4 and 7) of the second flexure body 30B when viewed in the X-axis direction.

[0051] 3, the displacement portion 36 of the third flexure body 30C extends from the second end 31b of the first connection portion 31 of the third flexure body 30C toward the center O of the force receiving body 20 when viewed in the Z-axis direction. The displacement portion 36 of the third flexure body 30C extends from the second end 31b to the positive side in the Y-axis direction. The displacement portion 36 of the third flexure body 30C may be located at the center of the third flexure body 30C in the X-axis direction, or may overlap with the central axis CL (see FIGS. 4 and 7) of the third flexure body 30C when viewed in the Y-axis direction.

[0052] 3, the displacement portion 36 of the fourth flexure body 30D extends from the second end 31b of the first connection portion 31 of the fourth flexure body 30D toward the center O of the force receiving body 20 when viewed in the Z-axis direction. The displacement portion 36 of the fourth flexure body 30D extends from the second end 31b to the negative side in the X-axis direction. The displacement portion 36 of the fourth flexure body 30D may be located at the center of the fourth flexure body 30D in the Y-axis direction, or may overlap with the central axis CL (see FIGS. 4 and 7) of the fourth flexure body 30D when viewed in the X-axis direction.

[0053] As shown in Figures 4 to 6, first strain element 30A may further include a force receiving element side connecting portion 38. Force receiving element side connecting portion 38 is an example of a first sensor element side connecting portion. Force receiving element side connecting portion 38 connects first end portion 31a of first connecting portion 31 to force receiving element 20. Force receiving element side connecting portion 38 is interposed between first end portion 31a of first connecting portion 31 and force receiving element 20. Force receiving element side connecting portion 38 may include a pair of force receiving element side pedestals 39 and a thin-walled portion 40.

[0054] The force receiving body side pedestal 39 may be connected to the force receiving body 20. The force receiving body side pedestal 39 extends in the Z-axis direction from the force receiving body 20 toward the fixed body 25. The force receiving body side pedestals 39 are located on both sides of the first end 31a of the first connection portion 31 in the X-axis direction, and on both sides of the central axis CL. One force receiving body side pedestal 39 is located on the positive side of the X-axis direction relative to the first end 31a. The other force receiving body side pedestal 39 is located on the negative side of the X-axis direction relative to the first end 31a.

[0055] Force receiving member side pedestal 39 abuts against force receiving member 20 and is attached to force receiving member 20 using bolts or the like (not shown). As shown in Figures 3 and 5, screw holes 41 may be formed in the surface of force receiving member side pedestal 39 facing force receiving member 20 (the upper surface in Figure 4). Each force receiving member side pedestal 39 may have one screw hole 41 formed therein, or may have multiple screw holes 41 formed therein.

[0056] The thin-walled portion 40 is located between a pair of force receiving member side pedestals 39 and is connected to each of the force receiving member side pedestals 39. The thin-walled portion 40 connects the force receiving member side pedestals 39 and the first connecting portion 31. A first end 31a of the first connecting portion 31 is connected to the surface of the thin-walled portion 40 facing the fixed body 25 (the lower surface in FIG. 4 ). The thin-walled portion 40 extends in the X-axis direction. The thin-walled portion 40 may be formed in a flat plate shape along the X-axis direction and the Y-axis direction. As shown in FIG. 4 , the thickness t1 (Z-axis dimension) of the thin-walled portion 40 is thinner than the thickness t2 (Z-axis dimension) of the force receiving member side pedestal 39. The thin-walled portion 40 may be elastically deformable by the action of forces in the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0057] The thin-walled portion 40 is connected to a portion of the force receiving member-side base 39 on the fixed body 25 side. This forms a first recess 42 on the force receiving member 20 side of the thin-walled portion 40. As shown in FIG. 4 , the first recess 42 may be formed in a rectangular shape when viewed in the Y-axis direction. If the thin-walled portion 40 and the first connecting portion 31 are formed separately, the head of a bolt (not shown) for fastening the thin-walled portion 40 and the first connecting portion 31 can be disposed in the first recess 42. This prevents the bolt head from protruding from the force receiving member-side connecting portion 38, allowing the height of the force sensor 10 to be reduced.

[0058] 4 and 5, the above-described fixed body side connection portion 32 may be formed linearly along the X-axis direction when viewed in the Z-axis direction. The above-described force receiving member side connection portion 38 may also be formed linearly along the X-axis direction. When viewed in the Z-axis direction, as shown in FIG. 5, force receiving member side connection portion 38 may overlap with fixed body side connection portion 32.

[0059] The first flexure element 30A configured as described above may be integrally formed from a continuous material. The first flexure element 30A may be produced by machining (e.g., cutting) a single block of material, or by casting. The first flexure element 30A may be produced from a metal material such as an aluminum alloy or an iron alloy.

[0060] The detection element 70 is configured to detect a displacement caused by the elastic deformation of the first strain element 30A. The detection element 70 according to this embodiment is configured as an element that detects a change in capacitance value due to the displacement of the tip end 36a of the displacement portion 36.

[0061] 4 and 5, the detection element 70 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 displacement of the tip portion 36a of the displacement portion 36 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 FIG.

[0062] 4 and 5 , the first capacitance element C1 includes a first fixed electrode substrate Ef1 provided on the fixed body 25 and a first displacement electrode substrate Ed1 provided on the tip 36a of the displacement portion 36. The second capacitance element C2 includes a second fixed electrode substrate Ef2 provided on the fixed body 25 and a second displacement electrode substrate Ed2 provided on the tip 36a of the displacement portion 36. The first capacitance element C1 is disposed on the positive side of the X-axis direction with respect to the central axis CL of the first flexure body 30A. The second capacitance element C2 is disposed on the negative side of the X-axis direction with respect to the central axis CL of the first flexure body 30A.

[0063] As shown in Fig. 4, the first fixed electrode substrate Ef1 is located on one of the fixed body-side pedestals 33 with respect to the central axis CL of the first flexure body 30A. More specifically, the first fixed electrode substrate Ef1 is located on the positive side of the X-axis direction with respect to the central axis CL of the first flexure body 30A. The second fixed electrode substrate Ef2 is located on the other fixed body-side pedestal 33 with respect to the central axis CL of the first flexure body 30A. The second fixed electrode substrate Ef2 is located on the negative side of the X-axis direction with respect to the central axis CL of the first flexure body 30A.

[0064] As shown in FIGS. 4 to 6 , the first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2 may be integrated. More specifically, the first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2 each include a fixed electrode Ef (see FIG. 13 ) and an insulator. The insulator is interposed between the fixed electrode Ef and the fixed body 25. The fixed electrode Ef of the first fixed electrode substrate Ef1 and the fixed electrode Ef of the second fixed electrode substrate Ef2 are integrated to form a common fixed electrode Efc. The insulator of the first fixed electrode substrate Ef1 and the insulator of the second fixed electrode substrate Ef2 are integrated to form a common insulator IBfc. The common insulator IBfc may be joined to the fixed body 25 with an adhesive or the like, or may be fixed with bolts or the like. The entire common insulator IBfc may be joined to the fixed body 25.

[0065] 4 and 5, the first displacement electrode substrate Ed1 is located on one of the fixed body-side pedestals 33 with respect to the central axis CL of the first flexure body 30A. More specifically, the first displacement electrode substrate Ed1 is located on the positive side of the X-axis direction with respect to the central axis CL of the first flexure body 30A, and faces the above-mentioned first fixed electrode substrate Ef1. The second displacement electrode substrate Ed2 is located on the other fixed body-side pedestal 33. More specifically, the second displacement electrode substrate Ed2 is located on the negative side of the X-axis direction with respect to the central axis CL of the first flexure body 30A, and faces the above-mentioned second fixed electrode substrate Ef2.

[0066] The first displacement electrode substrate Ed1 and the second displacement electrode substrate Ed2 each include a displacement electrode Ed and an insulator. 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 displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 may be formed separately and spaced apart from each other. An insulator is interposed between the displacement electrodes Ed and the displacement portion 36. The insulators of the first displacement electrode substrate Ed1 and the second displacement electrode substrate Ed2 may be integrated to form a common insulator IBdc. The common insulator IBdc may be bonded to the displacement portion 36 with an adhesive or the like, or may be fixed with bolts or the like. A portion of the common insulator IBdc may be bonded to the displacement portion 36.

[0067] The first capacitance element C1 and the second capacitance element C2 are arranged at the same position in the Y-axis direction. That is, as shown in Figures 3, 5, and 6, the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 are arranged at the same position in the Y-axis direction. The first capacitance element C1 and the second capacitance element C2 are arranged on the negative side of the first connection portion 31 in the Y-axis direction.

[0068] In this embodiment, the planar shape of the common fixed electrode Efc, which is formed by integrating the fixed electrodes Ef of the fixed electrode substrates Ef1 and Ef2, is rectangular. The planar shapes of the displacement electrodes Ed of the displacement electrode substrates Ed1 and Ed2 are also rectangular. However, the planar shapes of the common fixed electrode Efc and the displacement electrodes Ed are not limited to rectangular, and may be other shapes such as circular, polygonal, or elliptical.

[0069] When viewed in the Z-axis direction, the planar shape of the displacement electrodes Ed of the first displacement electrode substrate Ed1 may be smaller than the planar shape of the common fixed electrode Efc. Furthermore, the sizes of the displacement electrodes Ed and the common fixed electrode Efc may be set so that, even when the force receiving member 20 receives a force or moment and the first displacement electrode substrate Ed1 is displaced, the displacement electrodes Ed of the first displacement electrode substrate Ed1 as a whole overlap the common fixed electrode Efc when viewed in the Z-axis direction. This prevents changes in the opposing area between the displacement electrodes Ed and the common fixed electrode Efc, preventing changes in the opposing area from affecting changes in the capacitance value. Therefore, the capacitance value can be changed according to changes in the distance between the displacement electrodes Ed and the common fixed electrode Efc. Here, the opposing area refers to the area where the displacement electrodes Ed and the common fixed electrode Efc overlap when viewed in the Z-axis direction. When the displacement portion 36 is tilted, the displacement electrode Ed, which is smaller than the common fixed electrode Efc, may tilt and the opposing area may change, but 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 common fixed electrode Efc becomes dominant in the change in capacitance value. For this reason, in this specification, the change in the opposing area due to the tilt of the displacement electrode Ed is not taken into consideration, and the change in capacitance value is considered to be caused by the change in the distance between the displacement electrode Ed and the common fixed electrode Efc. Note that in Figure 8 and other figures described below, the tilt of the displacement portion 36 is exaggerated for clarity of the drawing.

[0070] Similarly, when viewed in the Z-axis direction, the planar shape of the displacement electrodes Ed of the second displacement electrode substrate Ed2 may be smaller than that of the common fixed electrode Efc, and the planar shape of the displacement electrodes Ed of the second displacement electrode substrate Ed2 may be the same as the planar shape of the displacement electrodes Ed of the first displacement electrode substrate Ed1.

[0071] The planar shape of the common fixed electrode Efc of the first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2 may be the same size as the planar shape of the common insulator IBfc of the first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2. However, the planar shape of the common fixed electrode Efc may be smaller than the planar shape of the common insulator IBfc. The planar shapes of the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 may each be smaller than the planar shape of the common insulator IBdc of the first displacement electrode substrate Ed1 and the second displacement electrode substrate Ed2.

[0072] The insulator 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 board (flexible printed circuit board). The FPC board is a thin, flexible printed board formed as a film. The FPC board has a thin metal film formed on the upper surface of a polyimide film, which forms electrodes and wiring. Portions of the FPC board corresponding to the fixed electrode substrates Ef1 and Ef2 may be fixed to the fixed body 25. The FPC board may include wiring connecting the fixed electrodes Ef to the detection circuit 75. When the insulator is made of an FPC board, portions corresponding to the displacement electrode substrates Ed1 and Ed2 may be fixed to the displacement portion 36. The FPC board may include wiring connecting the displacement electrodes Ed to the detection circuit 75.

[0073] The configuration of the first flexure body 30A and the corresponding detection element 70 can be similarly applied to the second flexure body 30B, the third flexure body 30C, and the fourth flexure body 30D.

[0074] 3, the detection element 70 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 portion 36a of the displacement portion 36 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.

[0075] 7, the third capacitance element C3 includes a third fixed electrode substrate Ef3 provided on the fixed body 25 and a third displacement electrode substrate Ed3 provided on the tip 36a of the displacement portion 36. The fourth capacitance element C4 includes a fourth fixed electrode substrate Ef4 provided on the fixed body 25 and a fourth displacement electrode substrate Ed4 provided on the tip 36a of the displacement portion 36.

[0076] The third fixed electrode substrate Ef3 is located on the positive side of the Y axis direction with respect to the central axis CL of the second flexure body 30B. The fourth fixed electrode substrate Ef4 is located on the negative side of the Y axis direction with respect to the central axis CL of the second flexure body 30B. In this embodiment, the third fixed electrode substrate Ef3 and the fourth fixed electrode substrate Ef4 are integrated and configured in the same manner as the fixed electrode substrates Ef1 and Ef2 described above.

[0077] The third displacement electrode substrate Ed3 is located on the positive side of the Y-axis direction with respect to the central axis CL of the second flexure body 30B. The third displacement electrode substrate Ed3 faces the third fixed electrode substrate Ef3 described above. The fourth displacement electrode substrate Ed4 is located on the negative side of the Y-axis direction with respect to the central axis CL of the second flexure body 30B. The fourth displacement electrode substrate Ed4 faces the fourth fixed electrode substrate Ef4 described above. The displacement electrode substrates Ed3 and Ed4 are configured in the same manner as the displacement electrode substrates Ed1 and Ed2 described above.

[0078] The third capacitance element C3 and the fourth capacitance element C4 are arranged at the same position in the X-axis direction. That is, as shown in FIG. 3 , the displacement electrodes Ed of the third displacement electrode substrate Ed3 and the displacement electrodes Ed of the fourth displacement electrode substrate Ed4 are arranged at the same position in the X-axis direction. The third capacitance element C3 and the fourth capacitance element C4 are arranged on the positive side in the X-axis direction with respect to the first connection portion 31.

[0079] 3, the detection element 70 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 portion 36a of the displacement portion 36 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.

[0080] 7, the fifth capacitance element C5 includes a fifth fixed electrode substrate Ef5 provided on the fixed body 25 and a fifth displacement electrode substrate Ed5 provided on the tip 36a of the displacement portion 36. The sixth capacitance element C6 includes a sixth fixed electrode substrate Ef6 provided on the fixed body 25 and a sixth displacement electrode substrate Ed6 provided on the tip 36a of the displacement portion 36.

[0081] The fifth fixed electrode substrate Ef5 is located on the negative side of the X-axis direction with respect to the central axis CL of the third flexure body 30C. The sixth fixed electrode substrate Ef6 is located on the positive side of the X-axis direction with respect to the central axis CL of the third flexure body 30C. In this embodiment, the fifth fixed electrode substrate Ef5 and the sixth fixed electrode substrate Ef6 are integrated and configured similarly to the fixed electrode substrates Ef1 and Ef2 described above.

[0082] The fifth displacement electrode substrate Ed5 is located on the negative side of the X-axis direction with respect to the central axis CL of the third flexure body 30C. The fifth displacement electrode substrate Ed5 faces the fifth fixed electrode substrate Ef5 described above. The sixth displacement electrode substrate Ed6 is located on the positive side of the X-axis direction with respect to the central axis CL of the third flexure body 30C. The sixth displacement electrode substrate Ed6 faces the sixth fixed electrode substrate Ef6 described above. The displacement electrode substrates Ed5 and Ed6 are configured in the same manner as the displacement electrode substrates Ed1 and Ed2 described above.

[0083] The fifth capacitance element C5 and the sixth capacitance element C6 are arranged at the same position in the Y-axis direction. That is, as shown in Fig. 3, the displacement electrodes Ed of the fifth displacement electrode substrate Ed5 and the displacement electrodes Ed of the sixth displacement electrode substrate Ed6 are arranged at the same position in the Y-axis direction. The fifth capacitance element C5 and the sixth capacitance element C6 are arranged on the positive side in the Y-axis direction with respect to the first connection portion 31.

[0084] 3, the detection element 70 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 displacement of the tip portion 36a of the displacement portion 36 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.

[0085] 7, the seventh capacitance element C7 includes a seventh fixed electrode substrate Ef7 provided on the fixed body 25 and a seventh displacement electrode substrate Ed7 provided on the tip 36a of the displacement portion 36. The eighth capacitance element C8 includes an eighth fixed electrode substrate Ef8 provided on the fixed body 25 and an eighth displacement electrode substrate Ed8 provided on the tip 36a of the displacement portion 36.

[0086] The seventh fixed electrode substrate Ef7 is located on the negative side of the Y axis direction with respect to the central axis CL of the fourth flexure body 30D. The eighth fixed electrode substrate Ef8 is located on the positive side of the Y axis direction with respect to the central axis CL of the fourth flexure body 30D. In this embodiment, the seventh fixed electrode substrate Ef7 and the eighth fixed electrode substrate Ef8 are integrated and configured similarly to the fixed electrode substrates Ef1 and Ef2 described above.

[0087] The seventh displacement electrode substrate Ed7 is located on the negative side of the Y-axis direction with respect to the central axis CL of the fourth flexure body 30D. The seventh displacement electrode substrate Ed7 faces the seventh fixed electrode substrate Ef7 described above. The eighth displacement electrode substrate Ed8 is located on the positive side of the Y-axis direction with respect to the central axis CL of the fourth flexure body 30D. The eighth displacement electrode substrate Ed8 faces the eighth fixed electrode substrate Ef8 described above. The displacement electrode substrates Ed7 and Ed8 are configured in the same manner as the displacement electrode substrates Ed1 and Ed2 described above.

[0088] The seventh capacitance element C7 and the eighth capacitance element C8 are arranged at the same position in the X-axis direction. That is, as shown in FIG. 3 , the displacement electrodes Ed of the seventh displacement electrode substrate Ed7 and the displacement electrodes Ed of the eighth displacement electrode substrate Ed8 are arranged at the same position in the X-axis direction. The seventh capacitance element C7 and the eighth capacitance element C8 are arranged on the negative side in the X-axis direction with respect to the first connection portion 31.

[0089] 2, the detection circuit 75 outputs an electrical signal indicating the force or moment acting on the strain bodies 30A-30D based on the detection results of the detection elements 70. This detection circuit 75 may have a calculation function implemented by, for example, a microprocessor. The detection circuit 75 may also have an A / D conversion function for converting analog signals received from the detection elements 70 into digital signals, and a signal amplification function. The detection circuit 75 may include a terminal for outputting an electrical signal, and the electrical signal is transmitted from this terminal to the controller 5 via an electrical cable (not shown).

[0090] 2 and 3, the exterior body 80 is configured to cover the four strain bodies 30A to 30D from the outside when viewed in the Z-axis direction. The exterior body 80 is a cylindrical housing that constitutes the force sensor 10. The strain bodies 30A to 30D are housed in the exterior body 80. In this embodiment, the cross-sectional shape of the exterior body 80 in plan view (the shape in a cross section along the XY plane) is a circular frame shape. A buffer member 81 may be interposed in the gap between the force receiving body 20 and the exterior body 80. The buffer member 81 may be formed of an elastically deformable flexible material such as rubber or sponge, for example.

[0091] Next, a method for detecting a force or moment acting on the force sensor 10 according to the present embodiment configured as described above will be described with reference to FIGS. 8 to 10B. FIG. 8 is a front view schematically illustrating the deformation of the first flexure body 30A when the first flexure body of FIG. 4 is subjected to a force Fx in the positive X-axis direction. FIG. 9A is a side view schematically illustrating the deformation of the first flexure body 30A when the first flexure body of FIG. 4 is subjected to a force Fy in the positive Y-axis direction. FIG. 9B is a side view schematically illustrating the deformation of the first flexure body 30A when the first flexure body of FIG. 4 is subjected to a force Fy in the negative Y-axis direction. FIG. 10A is a front view schematically illustrating the deformation of the first flexure body 30A when the first flexure body of FIG. 4 is subjected to a force Fz in the positive Z-axis direction. FIG. 10B is a front view schematically showing a deformation state of the first flexure element 30A in FIG. 4 when the first flexure element 30A is subjected to a force on the negative side in the Z axis direction.

[0092] When a force or moment is applied to the force receiving body 20, the force or moment is transmitted to the first flexure body 30A through the fourth flexure body 30D. More specifically, the force or moment is transmitted to the thin-walled portion 40, the first connecting portion 31, the second connecting portion 34, and the third connecting portion 35, causing elastic deformation in the thin-walled portion 40 and the connecting portions 31, 34, and 35. This causes displacement in the displacement portion 36. As a result, the distance between each of the fixed electrode substrates Ef1 through Ef8 of the detection element 70 and the corresponding displacement electrode substrates Ed1 through Ed8 changes, causing a change in the capacitance value of each of the capacitance elements C1 through C8. This change in capacitance value is detected by the detection element 70 as a displacement occurring in the flexure bodies 30A through 30D. In this case, the change in capacitance value of each of the capacitance elements C1 through C8 may differ. Therefore, the detection circuit 75 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 value of each capacitance element C1 to C8 detected by the detection element 70.

[0093] Here, first, using the first strain body 30A as an example, we will 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.

[0094] (When +Fx Acts) When a force Fx acts on the first flexure element 30A in the positive X-axis direction, as shown in FIG. 8 , the thin-walled portion 40, the first connection portion 31, the second connection portion 34, and the third connection portion 35 of the first flexure element 30A elastically deform, and the first end 31 a of the first connection portion 31 is displaced in the positive X-axis direction. This causes the first connection portion 31 to tilt so as to fall in the positive X-axis direction. In other words, the first connection portion 31 rotates clockwise when viewed toward the positive Y-axis direction (when viewed into the plane of the paper in FIG. 8 ). In conjunction with the first connection portion 31, the displacement portion 36 rotates clockwise and tilts.

[0095] The first displacement electrode substrate Ed1 moves closer to the first fixed electrode substrate Ef1, and the inter-electrode distance (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 capacitance element C1 increases. Meanwhile, the second displacement electrode substrate Ed2 moves farther away from the second fixed electrode substrate Ef2, and the inter-electrode distance (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 capacitance element C2 decreases.

[0096] (When a force -Fx acts) When a force Fx acts on the first strain body 30A in the negative X-axis direction, a phenomenon occurs that is opposite to the case shown in Fig. 8, although this 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.

[0097] (When +Fy Acts) When a force Fy acts on the first strain body 30A in the Y-axis direction positive direction, as shown in FIG. 9A , the thin-walled portion 40, the first connection portion 31, the second connection portion 34, and the third connection portion 35 elastically deform, and the first end 31 a of the first connection portion 31 is displaced in the Y-axis direction positive direction. This causes the first connection portion 31 to tilt so as to fall in the Y-axis direction positive direction. In other words, the first connection portion 31 rotates counterclockwise when viewed toward the X-axis direction positive side (when viewed toward the paper surface of FIG. 9A ). In conjunction with the first connection portion 31, the displacement portion 36 rotates counterclockwise and tilts. In this case, the tip 36 a of the displacement portion 36 is displaced in a direction away from the fixed body 25.

[0098] The first displacement electrode substrate Ed1 moves away from the first fixed electrode substrate Ef1, and the inter-electrode distance (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 capacitance element C1 decreases. Similarly, the second displacement electrode substrate Ed2 moves away from the second fixed electrode substrate Ef2, and the inter-electrode distance (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 capacitance element C2 decreases.

[0099] (When −Fy is Acted on) When a force Fy is acted on the first strain element 30A in the negative Y-axis direction, the opposite phenomenon to that shown in FIG. 9A occurs, as shown in FIG. 9B.

[0100] When a force Fy acts on the first strain element 30A in the negative Y-axis direction, as shown in FIG. 9B , the thin-walled portion 40, the first connection portion 31, the second connection portion 34, and the third connection portion 35 elastically deform, and the first end 31 a of the first connection portion 31 is displaced in the negative Y-axis direction. This causes the first connection portion 31 to tilt toward the negative Y-axis direction. In other words, the first connection portion 31 rotates clockwise when viewed toward the positive X-axis direction (when viewed toward the plane of the paper in FIG. 9B ). In conjunction with the first connection portion 31, the displacement portion 36 rotates clockwise and tilts. In this case, the tip 36 a of the displacement portion 36 is displaced in a direction toward the fixed body 25.

[0101] The first displacement electrode substrate Ed1 approaches the first fixed electrode substrate Ef1, and the inter-electrode distance (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 capacitance element C1 increases. Similarly, the second displacement electrode substrate Ed2 approaches the second fixed electrode substrate Ef2, and the inter-electrode distance (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 capacitance element C2 increases.

[0102] 10A , when a force Fz acts on the first strain body 30A in the positive Z-axis direction, the first connection portion 31 is displaced in the positive Z-axis direction while the thin-walled portion 40, the second connection portion 34, and the third connection portion 35 are elastically deformed. In conjunction with the first connection portion 31, the displacement portion 36 is displaced in the positive Z-axis direction.

[0103] The first displacement electrode substrate Ed1 moves away from the first fixed electrode substrate Ef1, and the inter-electrode distance (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 capacitance element C1 decreases. Similarly, the second displacement electrode substrate Ed2 moves away from the second fixed electrode substrate Ef2, and the inter-electrode distance (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 capacitance element C2 decreases.

[0104] (When −Fz is Acted on) When a force Fz is acted on the first strain element 30A in the negative Z-axis direction, as shown in FIG. 10B, the opposite phenomenon to that shown in FIG. 10A occurs.

[0105] 10B , when a force Fz is applied to the first strain element 30A in the negative Z-axis direction, the first connection portion 31 is displaced in the negative Z-axis direction while the thin-walled portion 40, the second connection portion 34, and the third connection portion 35 are elastically deformed. In conjunction with the first connection portion 31, the displacement portion 36 is displaced in the negative Z-axis direction.

[0106] The first displacement electrode substrate Ed1 approaches the first fixed electrode substrate Ef1, and the inter-electrode distance (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 capacitance element C1 increases. Similarly, the second displacement electrode substrate Ed2 approaches the second fixed electrode substrate Ef2, and the inter-electrode distance (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 capacitance element C2 increases.

[0107] Here, changes in the capacitance values ​​of the capacitance elements C1 and C2 provided in the first strain body 30A shown in Fig. 4 are shown in Fig. 11. Fig. 11 is a table showing changes in the capacitance values ​​of the capacitance elements C1 and C2 in the first strain body 30A shown in Fig. 4.

[0108] FIG. 11 shows the change in capacitance value of capacitance elements C1 and C2 with respect to 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. A decrease in capacitance value is indicated by a "- (minus)" and an increase in capacitance value is indicated by a "+ (plus)." For example, a "+" is shown next to C1 in the Fx row in the table shown in FIG. 11, which indicates that, as described above, when a force of +Fx is applied, the capacitance value of the first capacitance element C1 increases. On the other hand, a "-" is shown next to C2 in the Fx row in the table shown in FIG. 11, which indicates that, as described above, when a force of +Fx is applied, the capacitance value of the second capacitance element C2 decreases. As described above, when a force Fz is applied, the amount of change in capacitance value of the first capacitance element C1 differs from the amount of change in capacitance value of the second capacitance element C2. However, for simplicity, in FIG. 11, the change in capacitance value is simply represented by a symbol.

[0109] 11 , in a force sensor 10 in which the force receiving body 20 and the fixed body 25 are connected only by the first strain body 30A, the forces Fx, Fy, and Fz acting on the force receiving body 20 can be calculated using the following equations. For convenience, in the following equations, the force or moment and the change in capacitance value are connected with an equal sign (=). However, because the force or moment and the capacitance value are different physical quantities, the force is actually calculated by converting the change in capacitance value. In the following equations, C1 and C2 represent the change in capacitance value of each capacitance element.

[0110] 11 , in a force sensor 10 in which the force receiving body 20 and the fixed body 25 are connected only by the first strain body 30A, the force Fx in the X-axis direction can be detected by the difference between the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2. That is, as shown in the above-described equation (1), the output value of the force Fx can be calculated by the difference between the amount of change in the capacitance value of the first capacitance element C1 and the amount of 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 external disturbances such as noise or ambient temperature, the effect can be canceled out by the difference calculated in the above-described equation (1). This prevents the output value of the force Fx from being affected by external disturbances, thereby improving the performance of the force sensor 10.

[0111] As shown in the above-mentioned formulas (2) and (3), the same formula is used for Fy and Fz, making it difficult to distinguish whether the detected force is Fy or Fz. For this reason, a force sensor 10 using only one first strain element 30A can be used when either force Fy or force Fz, and force Fx, act. In this case, the force sensor 10 is a force sensor capable of detecting two-axis components.

[0112] The displacement portion 36 of the first strain generating element 30A shown in FIG. 4 extends from the second end 31b of the first connecting portion 31 to the negative side in the Y-axis direction. The first displacement electrode substrate Ed1 and the second displacement electrode substrate Ed2 are located at the tip end 36a of the displacement portion 36. This allows for a large displacement of the tip end 36a of the displacement portion 36 when a force Fy is applied, thereby increasing the change in capacitance value. This increases the detection sensitivity of the force Fy. For example, the detection sensitivity of the force Fy can be adjusted by adjusting the length of the displacement portion 36. The detection sensitivity of the force Fy may be higher than the detection sensitivity of the force Fx and the detection sensitivity of the force Fz.

[0113] For example, the center positions in the Y-axis direction (PY shown in FIGS. 5 and 6 ) of the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the second displacement electrode substrate Ed2 may be located on the negative side of the Y-axis direction relative to the second connection portion 34 and the third connection portion 35. This allows the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2 to change when a force Fy is applied. In this case, when viewed in the Z-axis direction, a portion of the first displacement electrode substrate Ed1 may overlap the second connection portion 34, and a portion of the second displacement electrode substrate Ed2 may overlap the third connection portion 35.

[0114] For example, the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 may be spaced apart in the Y-axis direction from the second connection portion 34 and the third connection portion 35. This allows the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2 to change even more when a force Fy is applied.

[0115] On the other hand, the length of the displacement portion 36 of the displacement electrode substrates Ed1 and Ed2 may be set so as not to interfere with the other displacement electrode substrates Ed3 to Ed8.

[0116] Next, changes in the capacitance value of each of the capacitance elements 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 about the X-axis, a moment My about the Y-axis, and a moment Mz about the Z-axis are applied to the force sensor 10 shown in Fig. 7 will be described with reference to Fig. 12. Fig. 12 is a table showing changes in the capacitance value of each capacitance element in the force sensor of Fig. 7.

[0117] (When +Fx Acts) First, a case where force Fx acts on force receiving member 20 shown in FIG. 7 in the positive X-axis direction will be described.

[0118] In this case, the first strain generating body 30A is elastically deformed in the same manner as the first strain generating body 30A shown in FIG. 8, and the capacitance value of the first capacitance element C1 increases while the capacitance value of the second capacitance element C2 decreases.

[0119] The second flexure body 30B elastically deforms in the same manner as the first flexure body 30A shown in FIG. 9B , and the capacitance value of the third capacitance element C3 increases, as well as the capacitance value of the fourth capacitance element C4. As described above, because the displacement portion 36 of the second flexure body 30B extends from the second end 31 b of the first connection portion 31 to the positive side in the X-axis direction, the increase in the capacitance value of the third capacitance element C3 is relatively large. For this reason, C3 in the Fx row in the table shown in FIG. 12 is marked "++." The increase in the capacitance value of the fourth capacitance element C4 is also relatively large, so C4 in the Fx row in the table shown in FIG. 12 is marked "++."

[0120] The third strain body 30C elastically deforms in the opposite direction to the first strain body 30A shown in FIG. 8, the capacitance value of the fifth capacitance element C5 decreases, and the capacitance value of the sixth capacitance element C6 increases.

[0121] The fourth flexure body 30D elastically deforms in the same manner as the first flexure body 30A shown in FIG. 9A, and the capacitance value of the seventh capacitance element C7 decreases, as well as the capacitance value of the eighth capacitance element C8. As described above, because the displacement portion 36 of the fourth flexure body 30D extends from the second end 31b of the first connection portion 31 to the negative side in the X-axis direction, the increase in the capacitance value of the seventh capacitance element C7 is relatively large. For this reason, C7 in the Fx row in the table shown in FIG. 12 is marked with "--". The decrease in the capacitance value of the eighth capacitance element C8 is also relatively large, so C8 in the Fx row in the table shown in FIG. 12 is marked with "--".

[0122] (When +Fy is Acted) Next, a case where force Fy is acted on force receiving member 20 in the positive Y-axis direction will be described. In the following explanation, the symbols in the table of FIG. 12 are determined according to the change in capacitance value, as described above.

[0123] The first flexure body 30A elastically deforms in the same manner as the first flexure body 30A shown in FIG. 9A, and the capacitance value of the first capacitance element C1 decreases, and the capacitance value of the second capacitance element C2 decreases. Because the displacement portion 36 of the first flexure body 30A extends from the second end 31b of the first connection portion 31 to the negative side in the Y-axis direction, the increase in the capacitance value of the first capacitance element C1 is relatively large. For this reason, C1 in the row Fy in the table shown in FIG. 12 is marked with "--". Because the increase in the capacitance value of the second capacitance element C2 is also relatively large, C2 in the row Fy in the table shown in FIG. 12 is marked with "--".

[0124] The second strain body 30B elastically deforms in the same manner as the first strain body 30A shown in FIG. 8, and the capacitance value of the third capacitance element C3 increases while the capacitance value of the fourth capacitance element C4 decreases.

[0125] The third flexure body 30C elastically deforms in the same manner as the first flexure body 30A shown in FIG. 9B , and the capacitance value of the fifth capacitance element C5 increases, as well as the capacitance value of the sixth capacitance element C6. Because the displacement portion 36 of the third flexure body 30C extends from the second end 31 b of the first connection portion 31 to the positive side in the Y-axis direction, the increase in the capacitance value of the fifth capacitance element C5 is relatively large. Therefore, C5 in the row Fy in the table shown in FIG. 12 is marked "++." The increase in the capacitance value of the sixth capacitance element C6 is also relatively large, so C6 in the row Fy in the table shown in FIG. 12 is marked "++."

[0126] The fourth flexure body 30D elastically deforms in the opposite direction to the first flexure body 30A shown in FIG. 8, the capacitance value of the seventh capacitance element C7 decreases, and the capacitance value of the eighth capacitance element C8 increases.

[0127] (When +Fz Acts) Next, a case where force Fz acts on force receiving member 20 in the positive Z-axis direction will be described. In the following explanation, the symbols in the table of FIG. 12 are determined according to the change in capacitance value, as described above.

[0128] 10A, the first strain body 30A is elastically deformed, and the capacitance value of the first capacitance element C1 decreases, and the capacitance value of the second capacitance element C2 decreases. Similarly, the capacitance values ​​of the third capacitance element C3 to the eighth capacitance element C8 also decrease.

[0129] (When +Mx is Acted) Next, a case will be described where a moment Mx (see FIG. 7) is acted on force receiving member 20 around the X-axis, i.e., clockwise toward the positive side in the X-axis direction. In the following explanation, the symbols in the table of FIG. 12 will be determined in the same manner as described above, depending on the change in capacitance value.

[0130] In this case, the first strain body 30A elastically deforms in the same manner as the first strain body 30A to which a force Fz directed toward the positive side in the Z-axis direction is applied as shown in FIG. 10A, and the capacitance value of the first capacitance element C1 decreases and the capacitance value of the second capacitance element C2 decreases.

[0131] In the second flexure body 30B, the central axis CL is located at the center O of the force receiving body 20 in the Y-axis direction, so the elastic deformation of the second flexure body 30B is smaller than that of the first flexure body 30A and the third flexure body 30C. Here, for simplicity of explanation, it is assumed that the second flexure body 30B does not elastically deform. Therefore, the capacitance value of the third capacitance element C3 does not change, and the capacitance value of the fourth capacitance element C4 does not change either. C3 and C4 in the Mx row in the table shown in FIG. 12 are set to "0 (zero)."

[0132] As shown in FIG. 10B, the third strain body 30C elastically deforms in the same manner as the first strain body 30A when a force Fz directed toward the negative side in the Z-axis direction acts on it, and the capacitance value of the fifth capacitance element C5 increases, and the capacitance value of the sixth capacitance element C6 also increases.

[0133] In the fourth flexure body 30D, the central axis CL is located at the center O of the force receiving body 20 in the Y-axis direction, and therefore the elastic deformation of the fourth flexure body 30D is smaller than that of the first flexure body 30A and the third flexure body 30C. Here, for simplicity of explanation, it is assumed that the fourth flexure body 30D does not elastically deform. Therefore, the capacitance value of the seventh capacitance element C7 does not change, and the capacitance value of the eighth capacitance element C8 does not change either. C7 and C8 in the Mx row in the table shown in FIG. 12 are set to "0 (zero)."

[0134] (When +My Is Acted) Next, a case will be described where a moment My (see FIG. 7) is acting on force receiving member 20 around the Y-axis, i.e., clockwise toward the positive side in the Y-axis direction. In the following explanation, the symbols in the table of FIG. 12 will be determined in the same manner as described above, depending on the change in capacitance value.

[0135] In this case, the central axis CL of the first flexure body 30A is located at the center O of the force receiving body 20 in the X-axis direction, so the elastic deformation of the first flexure body 30A is smaller than that of the second flexure body 30B and the fourth flexure body 30D. Here, for simplicity of explanation, it is assumed that the first flexure body 30A does not elastically deform. Therefore, the capacitance value of the first capacitance element C1 does not change, and the capacitance value of the second capacitance element C2 does not change either. C1 and C2 in the My row in the table shown in FIG. 12 are set to "0 (zero)."

[0136] As shown in FIG. 10A, the second strain body 30B elastically deforms in the same manner as the first strain body 30A when a force Fz directed toward the positive side of the Z-axis direction acts on it, and the capacitance value of the third capacitance element C3 decreases, and the capacitance value of the fourth capacitance element C4 decreases.

[0137] In the third flexure body 30C, the central axis CL is located at the center O of the force receiving body 20 in the X-axis direction, and therefore the elastic deformation of the third flexure body 30C is smaller than those of the second flexure body 30B and the fourth flexure body 30D. Here, for simplicity of explanation, it is assumed that the third flexure body 30C does not elastically deform. Therefore, the capacitance value of the fifth capacitance element C5 does not change, and the capacitance value of the sixth capacitance element C6 does not change either. C5 and C6 in the My row in the table shown in FIG. 12 are set to "0 (zero)."

[0138] As shown in FIG. 10B, the fourth strain body 30D elastically deforms in the same manner as the first strain body 30A when a force Fz directed toward the negative side in the Z-axis direction acts on it, and the capacitance value of the seventh capacitance element C7 and the capacitance value of the eighth capacitance element C8 increase.

[0139] (When +Mz is Acted) Next, a case will be described where a moment Mz (see FIG. 7) is acted on force receiving member 20 in the clockwise direction around the Z axis, i.e., toward the positive side in the Z axis direction. In the following explanation, the symbols in the table of FIG. 12 will be determined as described above in accordance with the change in capacitance value.

[0140] In this case, the first strain body 30A elastically deforms in the opposite direction to the first strain body 30A shown in FIG. 8, the capacitance value of the first capacitance element C1 decreases, and the capacitance value of the second capacitance element C2 increases.

[0141] The second strain body 30B elastically deforms in the opposite direction to the first strain body 30A shown in FIG. 8, and the capacitance value of the third capacitance element C3 decreases and the capacitance value of the fourth capacitance element C4 increases.

[0142] The third strain body 30C elastically deforms in the opposite direction to the first strain body 30A shown in FIG. 8, the capacitance value of the fifth capacitance element C5 decreases, and the capacitance value of the sixth capacitance element C6 increases.

[0143] The fourth flexure body 30D elastically deforms in the opposite direction to the first flexure body 30A shown in FIG. 8, the capacitance value of the seventh capacitance element C7 decreases, and the capacitance value of the eighth capacitance element C8 increases.

[0144] In this way, when a change in the capacitance value of each of capacitance elements C1 to C8 is detected, the direction and magnitude of the force or moment acting on force receiving member 20 are detected. Then, as shown in FIG. 12, the capacitance value of each of capacitance elements C1 to C8 changes.

[0145] From the table shown in FIG. 12, forces Fx, Fy, Fz and moments Mx, My, Mz acting on force receiving member 20 can be calculated using the following equations. This makes it possible to detect six-axis components of force. Note that in the following equations, for convenience, the force or moment and the amount of change in capacitance value are connected with an "=". However, because force or moment and capacitance value are different physical quantities, in reality, the force or moment is calculated by converting the amount of change in capacitance value. C1 to C8 in the following equations represent the amount of change in capacitance value for each capacitance element.

[0146] As described above, the force sensor 10 shown in FIG. 7 can detect forces Fx, Fy, and Fz and moments Mx, My, and Mz as shown in the above-described equations (4) to (9), and is therefore capable of detecting six-axis components of force. However, the number of axial components of force that the force sensor 10 can detect is not limited to six; any axial components can be detected depending on the number, structure, and shape of the strain-generating bodies. The coefficients a1 to a32 included in the above-described equations (4) to (9) are coefficients that indicate a relatively small amount of change (increase or decrease) in the capacitance value. The coefficients a1 to a32 may be different from one another.

[0147] The inclusion of coefficients a1 to a32 in the above-described equations (4) to (9) causes cross-axis sensitivity in each axis component. However, even when cross-axis sensitivity occurs, a correction calculation can be performed by finding the inverse matrix of the cross-axis sensitivity matrix and multiplying this inverse matrix by the output (characteristic matrix) of the force sensor. As a result, the cross-axis sensitivity can be reduced to a level where the occurrence of cross-axis sensitivity can be ignored.

[0148] As described above, the displacement portion 36 of each of the strain bodies 30A-30D extends in the X-axis or Y-axis direction from the second end 31b of the corresponding first connection portion 31. Each of the displacement electrode substrates Ed1-Ed8 is located at the tip 36a of the corresponding displacement portion 36. This allows for a large displacement of the tip 36a of the displacement portion 36 in the Z-axis direction when a force or moment acts on the force receiving body 20. This increases the change in capacitance value, thereby improving detection sensitivity. In particular, as shown in FIG. 12 , when a force Fx acts on the force receiving body 20, the changes in the capacitance values ​​of the third capacitive element C3, the fourth capacitive element C4, the seventh capacitive element C7, and the eighth capacitive element C8 are increased, thereby improving detection sensitivity for the force Fx. Similarly, when a force Fy acts on the force receiving body 20, the changes in the capacitance values ​​of the first capacitive element C1, the second capacitive element C2, the fifth capacitive element C5, and the sixth capacitive element C6 are increased, thereby improving detection sensitivity for the force Fy.

[0149] As described above, according to this embodiment, the displacement portion 36 of the first strain element 30A extends from the second end 31b of the first connection portion 31 in a direction intersecting the X-axis direction when viewed in the Z-axis direction. The detection element 70 detects a change in capacitance value based on the displacement of the tip end 36a of the displacement portion 36. This makes it possible to increase the displacement of the tip end 36a of the displacement portion 36 in the Z-axis direction when a force Fy is applied. This therefore increases the change in capacitance value, thereby improving the detection sensitivity of the force sensor 10.

[0150] Furthermore, according to the present embodiment, first strain element 30A includes force receiving element-side connecting portion 38 that connects first end 31a of first connecting portion 31 to force receiving element 20, and force receiving element-side connecting portion 38 includes thin-walled portion 40. Thin-walled portion 40 is formed along the X-axis direction and the Y-axis direction and is connected to first connecting portion 31. This allows thin-walled portion 40 to elastically deform when a force or moment acts on force receiving element 20, thereby further increasing the displacement of tip end 36a of displacement portion 36 in the Z-axis direction. This further improves the detection sensitivity of force sensor 10.

[0151] Furthermore, according to this embodiment, the detection element 70 includes fixed electrode substrates Ef1 and Ef2 provided on the fixed body 25, and displacement electrode substrates Ed1 and Ed2 provided on the tip 36a of the displacement portion 36 and facing the fixed electrode substrates Ef1 and Ef2. This allows the detection element 70 to detect changes in capacitance value due to displacement of the tip 36a of the displacement portion 36. This makes it possible to obtain a force sensor 10 with improved detection sensitivity.

[0152] Furthermore, according to this embodiment, the fixed electrode substrates Ef1 and Ef2 include a first fixed electrode substrate Ef1 located on one side of the fixed body-side pedestal 33 with respect to the central axis CL of the first flexure body 30A, and a second fixed electrode substrate Ef2 located on the other side of the fixed body-side pedestal 33 with respect to the central axis CL of the first flexure body 30A. As a result, when a force Fx in the X-axis direction is applied, it is possible to increase one of the capacitance values ​​of the first capacitance element C1 and the second capacitance element C2 and decrease the other. Therefore, the output value when the force Fx is applied can be calculated from the difference between the amount of change in the capacitance value of the first capacitance element C1 and the amount of change in the capacitance value of the second capacitance element C2. In this case, the influence of the above-mentioned disturbance can be canceled out. This prevents the output value of the force Fx from being affected by the disturbance, thereby improving the performance of the force sensor 10. Furthermore, when the force receiving body 20 and the fixed body 25 are connected by four strain bodies 30A to 30D as shown in FIG. 7, the number of detectable axial components can be increased, making it possible to detect six axial components.

[0153] Furthermore, according to this embodiment, the displacement electrode substrates Ed1 and Ed2 include the first displacement electrode substrate Ed1 located on one side of the fixed body-side pedestal 33 with respect to the central axis CL of the first flexure body 30A, and the second displacement electrode substrate Ed2 located on the other side of the fixed body-side pedestal 33 with respect to the central axis CL of the first flexure body 30A. As a result, when a force Fx in the X-axis direction is applied, either the capacitance value of the first capacitance element C1 or the capacitance value of the second capacitance element C2 can be increased and the other can be decreased. Therefore, the output value when the force Fx is applied can be calculated from the difference between the amount of change in the capacitance value of the first capacitance element C1 and the amount of change in the capacitance value of the second capacitance element C2. In this case, the influence of the above-mentioned disturbance can be canceled out. This prevents the output value of the force Fx from being affected by the disturbance, thereby improving the performance of the force sensor 10. Furthermore, when the force receiving body 20 and the fixed body 25 are connected by four strain bodies 30A to 30D as shown in FIG. 7, the number of detectable axial components can be increased, making it possible to detect six axial components.

[0154] Furthermore, according to this embodiment, the displacement portion 36 of the first strain generating body 30A extends in the Y-axis direction from the second end 31b of the first connection portion 31 of the first strain generating body 30A. This makes it possible to further increase the displacement in the Z-axis direction of the tip end 36a of the displacement portion 36 when a force Fy in the Y-axis direction acts on the force receiving body 20. This further improves the detection sensitivity of the force Fy, thereby further improving the detection sensitivity of the force sensor 10.

[0155] Furthermore, according to this embodiment, when viewed in the Z-axis direction, the second connecting portion 34 and the third connecting portion 35 are formed linearly along the X-axis direction. This facilitates the manufacture of the first flexure body 30A and reduces the cost of the force sensor 10. For example, when the first flexure body 30A is manufactured by machining a single block of material, the first flexure body 30A can be manufactured efficiently, which can effectively contribute to reducing the cost of the force sensor 10.

[0156] Furthermore, according to this embodiment, the first flexure body 30A is arranged on the positive side of the Y axis direction relative to the center O of the force receiving body 20, the second flexure body 30B is arranged on the negative side of the X axis direction, the third flexure body 30C is arranged on the negative side of the Y axis direction, and the fourth flexure body 30D is arranged on the positive side of the X axis direction. This allows the first flexure body 30A to the fourth flexure body 30D to be arranged in a ring shape around the center O of the force receiving body 20 when viewed in the Z axis direction. This makes it possible to improve the detection accuracy of a force or moment in any direction and to prevent the detection accuracy of a force or moment from decreasing depending on the direction of the force or moment.

[0157] Furthermore, according to this embodiment, the displacement portion 36 of each of the strain bodies 30A to 30D extends from the second end 31b of the corresponding first connection portion 31 toward the center of the force receiving body 20. This improves the space efficiency of each of the strain bodies 30A to 30D, and enables the force sensor 10 to be made smaller.

[0158] (Variation 1) In the above-described embodiment, the displacement portion 36 of the first flexure element 30A extends in the Y-axis direction from the second end 31b of the first connection portion 31 of the first flexure element 30A. However, this embodiment is not limited to this. For example, the displacement portion 36 may extend in a direction other than the Y-axis direction orthogonal to the X-axis direction, as long as the direction intersects the X-axis direction. For example, the displacement portion 36 may extend in a direction inclined to the X-axis direction when viewed in the Z-axis direction. Even in this case, when force Fy is applied, the displacement of the tip end 36a of the displacement portion 36 in the Z-axis direction can be increased.

[0159] (Variation 2) In the above-described embodiment, the fixed electrodes Ef of the first fixed electrode substrate Ef1 and the fixed electrodes Ef of the second fixed electrode substrate Ef2 are integrated to form the common fixed electrode Efc. However, this embodiment is not limited to this. For example, as shown in FIG. 13 , the fixed electrodes Ef of the first fixed electrode substrate Ef1 and the fixed electrodes Ef of the second fixed electrode substrate Ef2 may be formed separately and spaced apart from each other. In this case, the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 may be integrated to form the common displacement electrode Edc. The planar shape of the fixed electrodes Ef of the fixed electrode substrates Ef1 and Ef2 may be smaller than the planar shape of the common displacement electrode Edc. The same applies to the third fixed electrode substrate Ef3 to the eighth fixed electrode substrate Ef8 and the third displacement electrode substrates Ed3 to the eighth displacement electrode substrates Ed8. FIG. 13 is a front view of a first strain generating element 30A showing a modification of the detection element of FIG.

[0160] 13, the insulators of the first fixed electrode substrate Ef1 and the second fixed electrode substrate Ef2 may be integrated to form a common insulator IBfc. However, the insulators of the first fixed electrode substrate Ef1 and the insulators of the second fixed electrode substrate Ef2 may be formed separately and spaced apart from each other. The same applies to the third fixed electrode substrate Ef3 to the eighth fixed electrode substrate Ef8.

[0161] Second Embodiment Next, a force sensor according to a second embodiment of the present invention will be described with reference to FIGS.

[0162] The second embodiment shown in FIGS. 14 to 18 differs primarily in that the fixed body side connecting portion is formed in an arc shape when viewed in the Z-axis direction. Other configurations are substantially the same as those of the first embodiment shown in FIGS. 1 to 13. Note that in FIGS. 14 to 18, the same components as those of the first embodiment shown in FIGS. 1 to 13 are designated by the same reference numerals, and detailed descriptions thereof will be omitted. FIG. 14 is a plan view showing a force sensor according to the second embodiment, with the force receiving body omitted. FIG. 15 is a front view showing the first flexure body shown in FIG. 14. FIG. 16 is a plan view showing the first flexure body of FIG. 15. FIG. 17 is a side view showing the first flexure body of FIG. 15. FIG. 18 is a plan view of a first flexure body showing a modified example of the detection element of FIG. 15.

[0163] 14, the first strain element 30A according to this embodiment is formed in an arc shape when viewed in the Z-axis direction. As shown in FIGS. 14 to 17, the displacement portion 36 extends from the second end 31b of the first connection portion 31 to the inside of the second connection portion 34 and the third connection portion 35, i.e., radially inward.

[0164] Like the force receiving body 20 shown in Fig. 3 , the planar shape of the force receiving body 20 shown in Fig. 14 is also circular. Similarly, the planar shape of the fixed body 25 is also circular. The fixed body side connecting portion 32 of the first strain body 30A may be formed in an arc shape so as to follow at least one of the periphery of the force receiving body 20 and the periphery of the fixed body 25 when viewed in the Z-axis direction. In this embodiment, the fixed body side pedestal 33, the second connecting portion 34, and the third connecting portion 35 are formed in an arc shape so as to follow both the periphery of the force receiving body 20 and the periphery of the fixed body 25. The fixed body side connecting portion 32 of the first strain body 30A is formed concentrically with the outer edge of the force receiving body 20.

[0165] 14 and 16 , force receiving body side connecting portion 38 of first strain body 30A is also formed in an arc shape when viewed in the Z-axis direction. Force receiving body side connecting portion 38 may overlap second connecting portion 34 and third connecting portion 35 when viewed in the Z-axis direction. Force receiving body side base 39 and thin-walled portion 40 may also be formed in an arc shape so as to follow at least one of the periphery of force receiving body 20 and the periphery of fixed body 25.

[0166] 15 , the force receiving body side seat 39 of the force receiving body side connection portion 38 of the first strain generating body 30A may be located closer to the central axis line CL than the fixed body side seat 33. More specifically, as shown in FIG. 15 , the force receiving body side seat 39 located on the positive side in the X axis direction is located on the negative side in the X axis direction relative to the fixed body side seat 33 located on the positive side in the X axis direction. The force receiving body side seat 39 located on the negative side in the X axis direction is located on the positive side in the X axis direction relative to the fixed body side seat 33 located on the negative side in the X axis direction.

[0167] 15 , a second recess 43 may be formed in thin-walled portion 40 of force receiving member-side connecting portion 38. Second recess 43 may be formed on the surface of thin-walled portion 40 facing fixed body 25. Second recess 43 may be formed in an arc shape when viewed in the Y-axis direction. In this case, thin-walled portion 40 can be more elastically deformed when a force or moment is applied to force receiving member 20. This allows for even greater displacement of tip end 36a of displacement portion 36 in the Z-axis direction.

[0168] The fixed body side connecting portions 32 of the second to fourth flexure bodies 30B to 30D are also formed in the same manner as the first flexure body 30A. The force receiving body side connecting portions 38 of the second to fourth flexure bodies 30B to 30D are also formed in the same manner as the force receiving body side connecting portion 38 of the first flexure body 30A.

[0169] In this embodiment, as shown in FIG. 16 , the insulator of the first displacement electrode substrate Ed1 and the insulator of the second displacement electrode substrate Ed2 are integrated to form a common insulator IBdc. The planar shape of the common insulator IBdc is circular. The displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 are formed separately and spaced apart from each other. The planar shapes of the displacement electrodes Ed may each be formed in a substantially semicircular shape. When viewed in the Z-axis direction, the arc-shaped outer edge of the displacement electrode Ed may be formed concentrically with the outer edge of the common insulator IBdc. However, the planar shapes of the common insulator IBdc and the displacement electrodes Ed are arbitrary.

[0170] The planar shape of the common insulator IBfc (see FIG. 17) formed by integrating the insulators of the fixed electrode substrates Ef1, Ef2 may be circular, similar to the planar shape of the common insulator IBdc of the displacement electrode substrates Ed1, Ed2. The planar shape of the common fixed electrode Efc (see FIG. 17) formed by integrating the fixed electrodes Ef of the fixed electrode substrates Ef1, Ef2 may also be circular. However, the planar shapes of the common insulator IBfc and the common fixed electrode Efc are arbitrary.

[0171] In force sensor 10 according to this embodiment, when a force or moment acts on force receiving body 20, the change in the capacitance value of each of capacitance elements C1 to C8 is similar to the change shown in Fig. 12. Therefore, a detailed description thereof will be omitted.

[0172] As described above, according to this embodiment, the displacement portion 36 of the first strain element 30A extends from the second end 31b of the first connection portion 31 in a direction intersecting the X-axis direction when viewed in the Z-axis direction. This makes it possible to increase the displacement of the tip end 36a of the displacement portion 36 in the Z-axis direction when the force Fy is applied, even if the second connection portion 34 and the third connection portion 35 are formed in an arc shape when viewed in the Z-axis direction. This increases the change in capacitance value, thereby improving the detection sensitivity of the force sensor 10.

[0173] Furthermore, according to this embodiment, the first end 31 a of the first connection portion 31 is connected to the force receiving body 20 via the thin-walled portion 40. This allows the thin-walled portion 40 to elastically deform even when the second connection portion 34 and the third connection portion 35 are formed in an arc shape when viewed in the Z-axis direction. This allows the tip portion 36 a of the displacement portion 36 to be displaced even more in the Z-axis direction, thereby further improving the detection sensitivity of the force sensor 10.

[0174] Furthermore, according to this embodiment, when viewed in the Z-axis direction, force receiving body 20 and fixed body 25 are formed in a circular shape, and second connecting portion 34 and third connecting portion 35 are formed in an arc shape so as to follow at least one of the periphery of force receiving body 20 and the periphery of fixed body 25. This improves the space efficiency of each of strain bodies 30A to 30D and enables the miniaturization of force sensor 10. It also improves the load resistance of force sensor 10 and improves the reliability of force sensor 10.

[0175] Furthermore, according to this embodiment, the displacement portion 36 of each of the strain bodies 30A to 30D extends from the second end 31b of the corresponding first connection portion 31 toward the center of the force receiving body 20. This improves the space efficiency of each of the strain bodies 30A to 30D, and enables the force sensor 10 to be made smaller.

[0176] (Variation 3) In the above-described embodiment, the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 are formed separately and spaced apart. However, this embodiment is not limited to this. For example, as shown in FIG. 18 , the displacement electrodes Ed of the first displacement electrode substrate Ed1 and the displacement electrodes Ed of the second displacement electrode substrate Ed2 may be integrated to form a common displacement electrode Edc. In this case, the planar shape of the common displacement electrode Edc may be circular. The fixed electrodes Ef of the fixed electrode substrates Ef1 and Ef2 may be formed separately. In this case, the fixed electrodes may have a planar shape similar to the displacement electrode Ed shown in FIG. 16 . The same applies to the third displacement electrode substrate Ed3 to the eighth displacement electrode substrate Ed8 and the third fixed electrode substrates Ef3 to the eighth fixed electrode substrates Ef8. FIG. 18 is a plan view of a first strain element 30A illustrating a variation of the detection element 70 of FIG. 15 .

[0177] The present invention is not limited to the above-described embodiments and modifications, and can be embodied by modifying the components within the scope of the gist of the present invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments and modifications. Some components may be omitted from all the components shown in the embodiments and modifications. Furthermore, components from different embodiments and modifications may be appropriately combined.

Claims

a first sensor body that is subjected to the action of a force or moment to be detected; a second sensor body that is disposed at a position different from the first sensor body in a first direction; a straining body that connects the first sensor body and the second sensor body and elastically deforms due to the action of the force or moment received by the first sensor body; a detection element that detects a displacement caused by the elastic deformation of the straining body; and a detection circuit that outputs an electrical signal indicating the force or moment acting on the first sensor body based on the detection result of the detection element; wherein a direction perpendicular to the first direction is defined as a second direction, and a direction perpendicular to the first direction and perpendicular to the second direction is defined as a third direction, and the straining body includes a first connection portion that extends in the first direction from a first end connected to the first sensor body to a second end located on the opposite side to the first end, and a second sensor body side connection portion that connects the second end of the first connection portion to the second sensor body, A force sensor, wherein the second sensor body side connection portion is a pair of pedestals connected to the second sensor body, the pair of pedestals being located on either side of the second end in the second direction, a second connection portion extending in the second direction from the second end to one of the pedestals when viewed in the third direction, a third connection portion extending in the second direction from the second end to the other pedestal when viewed in the third direction, and a displacement portion extending from the second end in a direction intersecting the second direction when viewed in the first direction, and the detection element detects a change in capacitance value due to displacement of the tip of the displacement portion.

2. A force sensor as described in claim 1, wherein the strain body includes a first sensor body side connection portion that connects the first end of the first connection portion to the first sensor body, and the first sensor body side connection portion is a thin-walled portion formed along the second direction and the third direction and includes a thin-walled portion connected to the first end of the first connection portion.

3. A force sensor as described in claim 1, wherein the detection element includes a fixed electrode substrate provided on the second sensor body, and a displacement electrode substrate provided at the tip of the displacement portion and facing the fixed electrode substrate.

4. A force sensor as described in claim 3, wherein the fixed electrode substrate includes a first fixed electrode substrate located on one side of the pedestal with respect to the central axis of the flexure body, and a second fixed electrode substrate located on the other side of the pedestal with respect to the central axis of the flexure body.

5. A force sensor as described in claim 3, wherein the displacement electrode substrate includes a first displacement electrode substrate located on one side of the pedestal with respect to the central axis of the strain body, and a second displacement electrode substrate located on the other side of the pedestal with respect to the central axis of the strain body.

6. The force sensor according to claim 1, wherein the displacement portion extends in the third direction from the second end of the first connection portion.

7. The force sensor according to claim 1, wherein when viewed in the first direction, the second sensor body side connection portion is formed in a straight line along the second direction.

8. A force sensor as described in claim 1, wherein when viewed in the first direction, the first sensor body and the second sensor body are formed in a circular shape, and when viewed in the first direction, the second sensor body side connection portion is formed in an arc shape so as to follow at least one of the periphery of the first sensor body and the periphery of the second sensor body.

9. The force sensor of claim 1, wherein the first sensor body and the second sensor body are connected by four of the flexure bodies, the four flexure bodies including a first flexure body, a second flexure body, a third flexure body and a fourth flexure body, the first direction is the Z-axis direction in an XYZ three-dimensional coordinate system, the first flexure body is arranged on the positive side of the Y-axis direction with respect to the center of the first sensor body, the second flexure body is arranged on the negative side of the X-axis direction with respect to the center of the first sensor body, the third flexure body is arranged on the negative side of the Y-axis direction with respect to the center of the first sensor body, and the fourth flexure body is arranged on the positive side of the X-axis direction with respect to the center of the first sensor body.

10. The force sensor according to claim 9, wherein the displacement portion extends from the second end of the corresponding first connection portion toward the center of the first sensor body.

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