JP6600824B2 - Force sensor - Google Patents

Description

  The present invention relates to a force sensor, and more particularly to a sensor having a function of outputting a force acting in a predetermined axial direction and a moment (torque) acting around a predetermined rotation axis as an electrical signal.

  A force sensor having a function of outputting, as an electrical signal, a force acting along a predetermined axial direction and a moment acting around a predetermined rotation axis is described in, for example, Patent Document 1, and the force of an industrial robot Widely used for control. In recent years, it has been adopted for life support robots. Under such circumstances, the magnitude of the force or moment to be detected is in a wide range, and development of a force sensor capable of measuring such a wide range of force or moment with high accuracy and high sensitivity is underway. .

  By the way, as a force sensor, a capacitance type force sensor that detects a force or a moment based on a variation amount of a capacitance value of a capacitive element, or a force based on a variation amount of an electric resistance value of a strain gauge. Strain gauge type force sensors that detect moments are also used. Therefore, it is convenient if a force sensor capable of detecting force or moment with high accuracy and high sensitivity can be provided regardless of whether it is configured as a capacitance type or a strain gauge type.

JP 2004-354049 A

  The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a force sensor capable of detecting force or moment with high accuracy and high sensitivity, regardless of whether it is configured as a capacitance type or a strain gauge type. .

The present invention is a force sensor for detecting a uniaxial force,
A fixed part;
A movable part that moves relative to the fixed part by the action of force;
A deformable body connected to the fixed portion and the movable portion, and causing elastic deformation in a direction non-parallel to the uniaxial direction as the movable portion moves relative to the fixed portion;
A detection circuit that outputs an electric signal indicating a force acting on the movable part based on elastic deformation generated in the deformable body;
The deformable body includes a first detection part having a first spring constant and a second detection part having a second spring constant different from the first spring constant,
The detection circuit is a force sensor that outputs the electrical signal based on elastic deformation generated in at least one of the first detection portion and the second detection portion.

  According to the present invention, the capacitive element is arranged at a detection portion having a relatively small spring constant, that is, a detection portion where relatively large elastic deformation occurs, thereby enabling a force sense that can detect force with high accuracy and high sensitivity. A sensor can be provided. In addition, a strain gauge is placed at a detection site with a relatively large spring constant, that is, a detection site with a relatively large stress due to elastic deformation, so that the force can be detected with high accuracy and high sensitivity. A sense sensor can be provided. As described above, according to the present invention, it is possible to provide a force sensor capable of detecting a force with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type.

  The first detection part and the second detection part may be arranged in parallel between the movable part and the fixed part. In this case, since the first detection site and the second detection site can be greatly deformed, the applied force can be detected with higher accuracy and higher sensitivity.

The first detection portion has a shape along a part of an arc having a predetermined radius,
The second detection portion may have a shape along a part of an arc having a radius different from the predetermined radius. In this case, since it is possible to cause displacement in the first detection site and the second detection site in a direction orthogonal to the applied force, the force can be easily measured.

The force sensor described above can be configured as a capacitance type. That is, the force sensor includes a displacement electrode disposed on at least one of the first detection portion and the second detection portion;
A fixed electrode that is disposed opposite to the displacement electrode and does not move relative to the fixed portion;
The displacement electrode and the fixed electrode constitute a capacitive element,
The detection circuit may be configured to output an electrical signal indicating a force acting on the movable portion based on a variation amount of the capacitance value of the capacitive element.

Alternatively, the above force sensor can be configured as a strain gauge type. That is, the force sensor is provided with a strain gauge in at least one of the first detection site and the second detection site,
The detection circuit may be configured to output an electric signal indicating a force acting on the movable part based on a variation amount of the electric resistance value of the strain gauge.

The first detection part includes a first displacement part and a pair of first deformation parts provided on both sides of the first displacement part and connected to the fixed part and the movable part, respectively.
The second detection portion may include a second displacement portion and a pair of second deformation portions provided on both sides of the second displacement portion and respectively connected to the fixed portion and the movable portion. .

  In this case, the displacement in the direction orthogonal to the applied force can be generated in the first detection site and the second detection site in a relatively small space.

In the force sensor having such a first detection part and a second detection part, it is easy to provide a highly accurate and sensitive electrostatic force type force sensor. That is, a displacement electrode disposed on at least one of the first displacement portion of the first detection portion and the second displacement portion of the second detection portion;
A fixed electrode that is disposed opposite to the displacement electrode and does not move relative to the fixed portion;
The displacement electrode and the fixed electrode constitute a capacitive element,
The detection circuit may be configured to output an electric signal indicating the uniaxial force acting on the movable portion based on a variation amount of the capacitance value of the capacitive element.

Of course, a force sensor having such a first detection site and a second detection site can be configured as a strain gauge type. That is, at least one of the first displacement portion and the second displacement portion is made of an elastic material, and a strain gauge is disposed on the surface thereof.
The detection circuit may be configured to output an electrical signal indicating the uniaxial force acting on the movable portion based on a variation amount of the electrical resistance value of the strain gauge.

Alternatively, the present invention is a force sensor that detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system,
A fixed part fixed with respect to the XYZ three-dimensional coordinate system;
A movable part that moves relative to the fixed part by the action of force or moment;
A deformable body that is connected to the fixed portion and the movable portion, and generates elastic deformation when the movable portion moves relative to the fixed portion;
A detection circuit that outputs an electric signal indicating a force or a moment acting on the movable part based on elastic deformation generated in the deformable body;
The deformation body is
An annular first deformable body made of a material that is elastically deformed by the action of a force or moment and having a first through opening;
Made of a material that undergoes elastic deformation by the action of force or moment, has a second through opening, and has an annular second deformable body surrounding the first deformable body,
The first deformable body and the second deformable body are connected by a connecting member,
The first deformation body has at least one first detection portion having a first spring constant,
The second deformable body has at least one second detection portion having a second spring constant different from the first spring constant,
The detection circuit is a force sensor that outputs the electrical signal based on elastic deformation generated in at least one of the first detection portion and the second detection portion.

  According to the present invention, it is possible to detect a force or a moment with high accuracy and high sensitivity by disposing a capacitive element in a detection portion where the spring constant is relatively small, that is, a detection portion where relatively large elastic deformation occurs. A force sensor can be provided. In addition, it is possible to detect force or moment with high accuracy and high sensitivity by placing strain gauges at detection sites with relatively large spring constants, that is, detection sites with relatively large stresses that occur due to elastic deformation. Can provide a simple force sensor. According to the present invention, it is possible to provide a force sensor capable of detecting force or moment with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type. it can.

  The first deformable body and the second deformable body are both annular and may be concentric with each other. In this case, the force sensor can be configured with a simple configuration.

The force sensor described above can be configured as a capacitance type. That is, a displacement electrode disposed on at least one of the first detection portion of the first deformable body and the second detection portion of the second deformable body,
A fixed electrode that is disposed opposite to the displacement electrode and does not move relative to the fixed portion;
The displacement electrode and the fixed electrode constitute a capacitive element,
The detection circuit may be configured to output an electric signal indicating an applied force or moment based on a variation amount of the capacitance value of the capacitive element.

Alternatively, the above force sensor can be configured as a strain gauge type. That is, a strain gauge is provided on at least one of the first deformation body and the second deformation body,
The detection circuit may be configured to output an electric signal indicating an applied force or moment based on a fluctuation amount of the electric resistance value of the strain gauge.

  The connecting member includes a first connecting member that connects two portions where the positive X-axis overlaps the first deformable body and the second deformable body as viewed from the Z-axis direction; A second connecting member that connects the two parts that overlap the deformable body and the second deformable body, and a third connecting member that connects the two parts that the negative X overlaps the first and second deformable bodies; And a fourth connecting member that connects two portions where the negative Y axis overlaps the first deformable body and the second deformable body.

Furthermore, on the XY plane, when the V axis and the W axis that define 45 ° with respect to the X axis and the Y axis through the origin O are defined,
The first deformation body has the first detection part in four parts overlapping the V axis and the W axis when viewed from the Z-axis direction,
The second deformable body may have the second detection part at four parts overlapping the V axis and the W axis when viewed from the Z-axis direction.

  In this case, since the symmetrical deformation is generated in the first deformable body and the second deformable body due to the applied force or moment, the force or moment can be easily detected.

The first deformation body has at least one first gap,
The first detection site is interposed in the first gap,
The first detection portion includes a first displacement portion and a pair of first deformation portions provided on both sides of the first displacement portion and connected to the corresponding first gap both ends,
The second deformable body has at least one second gap;
The second detection site is interposed in the second gap,
The second detection portion may include a second displacement portion and a pair of second deformation portions provided on both sides of the second displacement portion and connected to both ends of the corresponding second gap.

  In this case, the displacement in the direction orthogonal to the applied force can be generated in the first detection site and the second detection site in a relatively small space.

In the force sensor having such a first detection part and a second detection part, it is easy to provide a highly accurate and sensitive electrostatic force type force sensor. That is, a displacement electrode disposed on at least one of each first displacement portion of the first detection site and each second displacement portion of the second detection site;
A fixed electrode that is disposed opposite to the displacement electrode and does not move relative to the fixed portion;
The displacement electrode and the fixed electrode constitute a capacitive element,
The detection circuit may be configured to output an electric signal indicating a force or a moment acting on the movable part based on a fluctuation amount of a capacitance value of the capacitive element.

Of course, a force sensor having such a first detection site and a second detection site can be configured as a strain gauge type. That is, at least one of each first displacement portion and each second displacement portion is made of an elastic material, and a strain gauge is disposed on the surface thereof.
The detection circuit may be configured to output an electrical signal indicating the uniaxial force acting on the movable portion based on a variation amount of the electrical resistance value of the strain gauge.

In another example, each first detection site is thinner than other regions of the first deformation body,
Each second detection site may be thinner than other regions of the second deformable body.

  In this case, since the degree of elastic deformation occurring in the first detection site and the second detection site can be adjusted as desired, a force sensor with higher accuracy and sensitivity can be provided.

  In the force sensor as described above, the first detection site and the second detection site may have an arc shape. Also in this case, the displacement in the direction orthogonal to the applied force can be generated in the first detection site and the second detection site in a relatively small space.

Alternatively, according to the present invention, failure diagnosis of the force sensor can be performed with a single force sensor. That is, such a force sensor detects a uniaxial force,
A fixed part;
A movable part that moves relative to the fixed part by the action of force;
A deformable body connected to the fixed portion and the movable portion, and causing elastic deformation in a direction non-parallel to the uniaxial direction as the movable portion moves relative to the fixed portion;
A detection circuit that outputs an electric signal indicating a force acting on the movable part based on elastic deformation generated in the deformable body;
The deformable body includes a first detection part having a first spring constant and a second detection part having a second spring constant different from the first spring constant,
The detection circuit includes:
As the electrical signal, a first electrical signal provided based on elastic deformation occurring in the first detection site and a second electrical signal provided based on elastic deformation occurring in the second detection site are output. ,
The force sensor is configured to determine whether or not the force sensor is functioning normally based on the first electric signal and the second electric signal.

Alternatively, the force sensor capable of fault diagnosis detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system,
A fixed part fixed with respect to the XYZ three-dimensional coordinate system;
A movable part that moves relative to the fixed part by the action of force or moment;
A deformable body that is connected to the fixed portion and the movable portion, and generates elastic deformation when the movable portion moves relative to the fixed portion;
A detection circuit that outputs an electric signal indicating a force or a moment acting on the movable part based on elastic deformation generated in the deformable body;
The deformation body is
An annular first deformable body made of a material that is elastically deformed by the action of a force or moment and having a first through opening;
Made of a material that undergoes elastic deformation by the action of force or moment, has a second through opening, and has an annular second deformable body surrounding the first deformable body,
The first deformable body and the second deformable body are connected by a connecting member,
The first deformation body has at least one first detection portion having a first spring constant,
The second deformable body has at least one second detection portion having a second spring constant different from the first spring constant,
The detection circuit includes:
As the electrical signal, a first electrical signal provided based on elastic deformation occurring in the first detection site, and a second electrical signal provided based on elastic deformation occurring in at least one of the second detection sites, Output
The force sensor is configured to determine whether or not the force sensor is functioning normally based on the first electric signal and the second electric signal.

  In these force sensors, the detection circuit includes a storage unit that stores a ratio of the first electric signal and the second electric signal in a state where the force sensor is functioning normally as a reference ratio. It is determined whether or not the force sensor is functioning normally by determining whether or not the “difference between the ratio between the first electric signal and the second electric signal and the reference ratio” is within a predetermined range. You may be supposed to. In this case, the failure of the force sensor can be reliably determined. The principle of this determination will be described later in detail.

It is a schematic top view which shows the basic structure of the force sensor by the 1st Embodiment of this invention. 3 is a chart showing displacement in the X-axis direction and stress in the Y-axis direction that occur at each detection site when the movable portion of the basic structure in FIG. 1 is displaced by 100 μm in the negative Z-axis direction. It is a schematic top view which shows the electrostatic capacitance type force sensor by the basic structure of FIG. It is a schematic top view which shows the strain gauge type force sensor by the basic structure of FIG. It is a schematic top view which shows the modification of the basic structure of FIG. FIG. 6 is a schematic top view showing a state in which a force is applied to the basic structure of FIG. 5. 6A shows a state in which a compressive force f1 along the Y-axis direction is applied to the basic structure, and FIG. 6B shows a state in which a tensile force f2 along the Y-axis direction is applied to the basic structure. is there. FIG. 6 is a partial schematic top view of a first detection site A of a strain gauge type force sensor employing the modification shown in FIG. 5. FIG. 7A is a schematic diagram showing an initial state of the first detection site A, and FIG. 7B is a schematic diagram showing the first detection site A when a compressive force is applied to the basic structure. FIG. 7C is a schematic diagram showing the first detection site A when a tensile force is applied to the basic structure. It is a schematic top view which shows the basic structure of the force sensor by the 2nd Embodiment of this invention. FIG. 9 is a schematic top view showing the basic structure of FIG. 8 when a moment around the Z-axis acts on the movable part. It is a schematic top view which shows the 2nd quadrant part of the basic structure of FIG. FIG. 9 is a schematic top view showing a capacitance type force sensor according to the basic structure of FIG. 8. It is a schematic top view which shows the strain gauge type force sensor by the basic structure of FIG. It is a schematic top view which shows the 1st modification of the basic structure of FIG. It is a schematic top view which shows the 2nd modification of the basic structure of FIG. It is a schematic top view which shows the 3rd modification of the basic structure of FIG. It is a figure for demonstrating the elastic deformation which arises in a deformation body when force + Fx of the X-axis positive direction acts on the movable part of the basic structure of FIG. It is a figure for demonstrating the elastic deformation which arises in a deformation body when force + Fy of the Y-axis positive direction acts on the movable part of the basic structure of FIG. It is a figure for demonstrating the stress which arises in the detection part of a deformation body when the force of the X-axis positive direction acts on the movable part of the basic structure of FIG. It is a figure for demonstrating the stress which arises in the detection part of a deformation | transformation body when force + Fy of the Y-axis positive direction acts on the movable part of the basic structure of FIG. It is a schematic top view which shows the basic structure of FIG. 8 by which the structure shown in FIG. 5 was employ | adopted as the detection site | part of a deformation body. It is the schematic side view which looked at 1-1 detection part A1 of the basic structure shown in FIG. 20 from the V-axis positive direction. It is a figure for demonstrating the stress which arises in the detection part of a deformation body when the moment of the surroundings of a Z-axis acts with respect to the movable part of the basic structure of FIG. It is a figure for demonstrating the force which acts on the detection part of a deformation | transformation body when the force of the X-axis positive direction acts on the movable part of the basic structure of FIG. When no metal fatigue occurs in the force sensor of FIG. 3 (initial state), the magnitude of the force acting on the force sensor, and the first electric signal T1a and the second electric signal T2a output from the force sensor. It is a graph which shows the relationship. When metal fatigue occurs in the force sensor of FIG. 3, the relationship between the magnitude of the force acting on the force sensor and the first electric signal T1b and the second electric signal T2b output from the force sensor. It is a graph which shows. When no metal fatigue occurs in the force sensor of FIG. 4 (initial state), the magnitude of the force acting on the force sensor, and the first electric signal T1a and the second electric signal T2a output from the force sensor. It is a graph which shows the relationship. When metal fatigue occurs in the force sensor of FIG. 4, the relationship between the magnitude of the force acting on the force sensor and the first electric signal T1b and the second electric signal T2b output from the force sensor. It is a graph which shows. It is the schematic which shows the modification of a detection site | part. FIG. 29A is a schematic diagram showing the detection site when a compressive force in the Y-axis direction is applied to the detection site shown in FIG. 28, and FIG. 29B is a schematic diagram showing the detection site shown in FIG. It is the schematic which shows the said detection part when the tensile force of a direction acts. It is a schematic top view which shows an example of the deformation body which has a detection site | part shown in FIG. FIG. 31A is a schematic top view showing another example of the deformable body having the detection site shown in FIG. 28, and FIG. 31B is a cross-sectional view taken along the line bb in FIG. . It is the schematic which shows the detection site | part of FIG. 28 with which the capacitive element is arrange | positioned. It is the schematic which shows the detection site | part of FIG. 28 in which the strain gauge is arrange | positioned.

<<< §1. Force sensor according to the first embodiment of the present invention >>>
Hereinafter, a force sensor according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<1-1. Basic structure>
FIG. 1 is a schematic top view showing a basic structure 1 of a force sensor according to a first embodiment of the present invention. In this figure, it is assumed that the X-axis is defined in the left-right direction, the Y-axis is defined in the up-down direction, and the Z-axis is defined in the depth direction. As shown in FIG. 1, the basic structure 1 includes a fixed portion 10, a movable portion 20 that moves relative to the fixed portion 10 along the Y-axis direction by the action of force, and a fixed portion 10 and a movable portion 20. And a deformable body 30 that is elastically deformed when the movable portion 20 is moved relative to the fixed portion 10.

  The basic structure 1 according to the present embodiment is used for a force sensor capable of detecting a force in the Y-axis direction. As shown in FIG. 1, the fixed portion 10 and the movable portion 20 are arranged at a predetermined interval in the Y-axis direction. The movable part 20 functions as a power receiving body that receives a force.

  The deformable body 30 connected to the fixed portion 10 and the movable portion 20 includes a first deformable body 31 and a second deformable body 32 that are arranged in parallel in the X-axis direction. The first deformable body 31 includes a first fixed portion side connection portion 31f connected to the fixed portion 10 and a first fixed portion side connection portion 31f that is connected to the movable portion 20 and spaced apart from the first fixed portion side connection portion 31f in the Y-axis direction. The first movable portion side connection portion 31m, and an elastically deformable arc-shaped first elastic body 31e that connects the first fixed portion side connection portion 31f and the first movable portion side connection portion 31m are provided. The second deformable body 32 includes a second fixed portion side connection portion 32f connected to the fixed portion 10 and a second fixed portion side connection portion 32f that is connected to the movable portion 20 and spaced apart from the second fixed portion side connection portion 32f in the Y-axis direction. 2 has a movable part side connection part 32m, and an elastically deformable arc-shaped second elastic body 32e that connects the second fixed part side connection part 32f and the second movable part side connection part 32m. In the present embodiment, as shown in FIG. 1, both the first elastic body 31e and the second elastic body 32e are arranged so as to protrude in the negative X-axis direction (the right direction in FIG. 1).

  The first elastic body 31e and the second elastic body 32e are located closest to the X axis negative direction side (right side in FIG. 1), that is, on the X axis negative side of the first elastic body 31e and the second elastic body 32e. The first detection part A and the second detection part B are respectively defined in parts that give a tangent line parallel to the Y axis when viewed from the Z-axis direction. When the basic structure 1 shown in FIG. 1 is used as a force sensor, it acts on the movable portion 20 based on the stress generated in the first detection site A and the second detection site B or the displacement in the X-axis direction. Force is to be measured. As shown in FIG. 1, the first elastic body 31e and the second elastic body 32e have different radii of curvature. Specifically, the curvature radius of the second elastic body 32e is larger than the curvature radius of the first elastic body 31e. On the other hand, although not shown, the first elastic body 31e and the second elastic body 32e have the same cross-sectional shape cut along the XZ plane. Thus, the spring constant of the second elastic body 32e is smaller than the spring constant of the first elastic body 31e. Here, the spring constants of the first elastic body 31e and the second elastic body 32e refer to the magnitude of the force in the Y-axis direction that has acted on the movable portion 20 and the magnitude of the displacement in the X-axis direction that occurs in the detection portions A and B. It means the value divided by.

  FIG. 2 is a chart showing the displacement in the X-axis direction and the stress in the Y-axis direction that occur at each detection site A and B when the movable part 20 of the basic structure 1 in FIG. 1 is displaced by 100 μm in the negative Z-axis direction. It is.

  As shown in FIG. 2, when the movable part 20 is displaced (relatively moved) in the negative Y-axis direction (downward in FIG. 1) with respect to the fixed part 10 by the action of force, it occurs at each detection site A, B. The displacement in the X-axis direction is different from the stress in the Y-axis direction. Specifically, when the movable unit 20 moves relative to the fixed unit 10 by 100 μm in the negative Y-axis direction, the magnitude of the displacement that occurs in the X-axis direction is greater than the first detection site A than the second detection site B. Is larger, and the stress is larger in the first detection region A than in the second detection unit B. From this, the basic structure 1 shown in FIG. 1 is more sensitive to the second detection site B than the first detection site A when viewed in terms of displacement, and is more sensitive than the second detection site B when viewed from the stress. The detection site A has a characteristic that it has higher sensitivity.

<1-2. Capacitance type force sensor>
Next, a capacitance type force sensor 1c using the basic structure 1 as described above will be described.

  FIG. 3 is a schematic top view showing a capacitance type force sensor 1c according to the basic structure 1 of FIG. As shown in FIG. 3, the force sensor 1 c is disposed so as to face the first displacement electrode Em <b> 1 disposed at the first detection site A and the first displacement electrode Em <b> 1, and does not move relative to the fixed portion 10. A first fixed electrode Ef1, a second displacement electrode Em2 disposed at the second detection site B, a second fixed electrode Ef2 disposed opposite to the second displacement electrode Em2, and not moving relative to the fixed portion 10. ,have. As shown in FIG. 1, the first displacement electrode Em1 and the first fixed electrode Ef1 constitute a first capacitive element C1, and the second displacement electrode Em2 and the second fixed electrode Ef2 constitute a second capacitive element C2. ing. In the present embodiment, the first displacement electrode Em1 and the second displacement electrode Em2 have the same area. Furthermore, the first fixed electrode Ef1 and the second fixed electrode Ef2 have the same area. The effective opposing area of the first displacement electrode Em1 and the first fixed electrode Ef1 and the distance between the electrodes are equal to the effective opposing area of the second displacement electrode Em2 and the second fixed electrode Ef2 and the distance between the electrodes. All the electrodes Em1, Ef1, Em2, and Ef2 are arranged so as to be parallel to the YZ plane.

  Further, as shown in FIG. 3, the force sensor 1 c generates an electric signal indicating a force in the Y-axis direction that has acted on the movable portion 20 based on the elastic deformation generated in the first deformable body 31 and the second deformable body 32. A detection circuit 40 for outputting is provided. The detection circuit 40 is configured to output an electric signal indicating the force acting on the movable portion 20 based on the variation amount of the capacitance values of the capacitive elements C1 and C2. Note that wirings that electrically connect the capacitive elements C1 and C2 and the detection circuit 40 are not shown.

  Next, the operation of the force sensor 1c will be described.

  Here, a case where a force in the negative Y-axis direction (downward in FIG. 3) acts on the movable portion 20 will be described as an example. When a force in the negative Y-axis direction acts on the movable part 20, the movable part 20 moves relative to the fixed part 10 in the negative Y-axis direction. Thereby, the arc-shaped first elastic body 31e and the second elastic body 32e are elastically deformed by the action of the compressive force. This elastic deformation is a deformation in which the radii of curvature of the first elastic body 31e and the second elastic body 32e are both reduced. Thereby, both the 1st detection part A and the 2nd detection part B are displaced to the X-axis negative direction. For this reason, both the capacitance values of the first capacitive element C1 and the second capacitive element C2 increase as the distance between the electrode plates decreases. In the present embodiment, as described above, since the spring constant of the second elastic body 32e is smaller than the spring constant of the first elastic body 31e, the displacement of the second detection site B in the negative direction of the X-axis Is larger than the displacement of the first detection site A in the negative X-axis direction. For this reason, the capacitance value of the second capacitive element C2 varies more greatly than that of the first capacitive element C1. That is, the second capacitive element C2 is more sensitive than the first capacitive element C1.

  And the detection circuit 40 measures the force which acted on the movable part 20 based on the variation | change_quantity of one electrostatic capacitance value of the 1st capacitive element C1 and the 2nd capacitive element C2. The electrostatic force type force sensor 1c is excellent in S / N by measuring the acting force based on the fluctuation amount of the capacitance value of the second capacitive element C2 having relatively high sensitivity. Measurement is possible. Of course, it is also possible to measure the force acting on the movable portion 20 based on the variation amount of the capacitance value of the first capacitance element C1, and for example, the variation of the capacitance value of the first capacitance element C1. It is also possible to treat the average value of the force measured based on the amount and the force measured based on the variation amount of the capacitance value of the second capacitive element C2 as the applied force.

  In the above description, the case where a force in the negative Y-axis direction acts on the movable part 20 has been described as an example. On the contrary, the force in the positive Y-axis direction (upward in FIG. 3) is applied. Even if it acts on the movable part 20, the force can be measured. In this case, the first elastic body 31e and the second elastic body 32e are elastically deformed so that their radii of curvature both increase. As a result, both the first detection site A and the second detection site B are displaced in the positive X-axis direction (left direction in FIG. 3), and the capacitance values of the first capacitive element C1 and the second capacitive element C2 are Both decrease. In this case as well, the capacitance value of the second capacitive element C2 varies more greatly than the first capacitive element C1.

<1-3. Strain gauge type force sensor>
Alternatively, the basic structure 1 as described above can also be used for a strain gauge type force sensor 1s.

  FIG. 4 is a schematic top view showing a strain gauge type force sensor 1s according to the basic structure 1 of FIG. As shown in FIG. 4, the force sensor 1 s includes a first strain gauge R1 disposed at the first detection site A and a second strain gauge R2 disposed at the second detection site B. . The first strain gauge R1 and the second strain gauge R2 have the same characteristics. Since the other configuration is the same as that of the force sensor 1c shown in FIG. 3 except that the capacitive element is not included, detailed description thereof is omitted.

  As the strain gauges R1 and R2, for example, a metal foil strain gauge or a semiconductor strain gauge can be adopted. Metal foil strain gauges have the property that the resistance value decreases when compressive stress acts, and conversely the resistance value increases when tensile stress acts. The semiconductor strain gauge is a strain gauge using the piezoresistive effect. When a tensile stress acts on the semiconductor strain gauge, the resistance value increases in the p-type semiconductor strain gauge, and the n-type semiconductor strain gauge. The gauge has a characteristic that the resistance value decreases. On the other hand, when compressive stress acts on the semiconductor strain gauge, the resistance value decreases in the p-type semiconductor strain gauge, and the resistance value increases in the n-type semiconductor strain gauge. Here, it is assumed that metal foil strain gauges are employed as the first strain gauge R1 and the second strain gauge R2.

  Next, the operation of the force sensor 1s will be described.

  When a force in the negative Y-axis direction acts on the movable part 20, the movable part 20 moves relative to the fixed part 10 in the negative Y-axis direction. As described above, the first elastic body 31e and the second elastic body 32e are , It is elastically deformed so that its radius of curvature decreases. Thereby, tensile stress is generated in a region including the detection portions A and B on the surfaces on the X axis negative side of the arc-shaped first elastic body 31e and the second elastic body 32e. As described above, since the spring constant of the first elastic body 31e is larger than the spring constant of the second elastic body 32e, the tensile stress generated in the first detection site A is larger than the tensile stress generated in the second detection site B. . This is as described above with reference to FIG. For this reason, the electric resistance value of the first strain gauge R1 fluctuates (increases) to a greater extent than the second strain gauge R2.

  And the detection circuit 40 measures the force which acted based on the variation | change_quantity of one electrical resistance value of 1st strain gauge R1 and 2nd strain gauge R2. In the strain gauge type force sensor 1s, by measuring the force acting on the basis of the fluctuation amount of the electric resistance value of the first strain gauge R1 having relatively high sensitivity, measurement with excellent S / N can be performed. It becomes possible. Of course, it is also possible to measure the force applied based on the variation amount of the electric resistance value of the second strain gauge R2, and for example, the force was measured based on the variation amount of the electric resistance value of the first strain gauge R1. It is also possible to treat the average value of the force and the force measured based on the fluctuation amount of the electric resistance value of the second strain gauge R2 as the applied force.

  In the above description, the case where a force in the negative Y-axis direction is applied to the movable part 20 has been described as an example. On the contrary, the force in the positive Y-axis direction (upward in FIG. 4) is applied. Even if it acts on the movable part 20, the force can be measured. In this case, as described above, the first elastic body 31e and the second elastic body 32e are elastically deformed so that their curvature radii increase together. Thereby, compressive stress is generated in the region including the detection portions A and B on the surfaces on the X axis negative side of the arc-shaped first elastic body 31e and the second elastic body 32e, and the electric power of the strain gauges R1 and R2 is generated. Both resistance values decrease. Also in this case, the electric resistance value of the first strain gauge R1 varies more greatly than that of the second strain gauge R2.

  According to the force sensors 1c and 1s according to the present embodiment as described above, the second capacitive element is added to the second detection part B having a relatively small spring constant, that is, the second detection part B having a relatively large elastic deformation. By disposing C2, it is possible to provide a capacitance type force sensor 1c capable of detecting force with high accuracy and high sensitivity. Alternatively, by disposing the first strain gauge R1 in the first detection site A having a relatively large spring constant, that is, the first detection site A in which the stress expressed with elastic deformation is relatively large, high accuracy and high A force sensor 1 s capable of detecting force with sensitivity can be provided. As described above, according to the present embodiment, the force detected with high accuracy and high sensitivity can be detected regardless of whether it is configured as a capacitance type or a strain gauge type while having the common basic structure 1. Can be provided.

<1-4. Basic structure with waveform detection section>
Next, FIG. 5 is a schematic top view showing a modification of the basic structure 1 of FIG. FIG. 6 is a schematic top view showing a state in which a force in the Y-axis direction is applied to the basic structure 1w of FIG. FIG. 6A shows a state where a compressive force f1 along the Y-axis direction is acting on the basic structure 1w, and FIG. 6B shows a state where a tensile force f2 along the Y-axis direction is applied to the basic structure 1w. It is in a working state.

  As shown in FIG. 5, in this modification, two corrugated elastic structures are employed instead of the two arc-shaped elastic bodies of FIG. Here, the elastic structures having these waveforms are referred to as a first detection site A and a second detection site B. As shown in the drawing, the first detection site A is provided on the first displacement portion 61d and the connection portions 61m and 61f provided on both sides of the first displacement portion 61d and spaced from each other in the Y-axis direction. A pair of first deformation portions 61e1 and 61e2 connected to the fixed portion 10 and the movable portion 20, respectively, and the second detection site B is provided on both sides of the second displacement portion 62d and the second displacement portion 62d. And a pair of second deforming portions 62e1 and 62e2 respectively connected to the fixed portion 10 and the movable portion 20 via connecting portions 62m and 62f arranged at intervals in the Y-axis direction. As shown in FIG. 5, the pair of second deformable portions 62e1 and 62e2 are configured to rise in the Y-axis direction from the pair of first deformable portions 61e1 and 61e2.

  In the case of the example shown here, the pair of first deforming portions 61e1 and 61e2 and the pair of second deforming portions 62e1 and 62e2 are configured by flexible plate-like pieces, and the first displacement portion 61d and the second displacement portion. 62d is comprised by the 3rd plate-shaped piece. Each plate-like piece is made of the same material as each connection portion 61f, 61m, 62f, 62m, but is a relatively thin plate-like member as shown in FIGS. Therefore, it has flexibility.

  In the case of the example shown here, the first displacement part 61d and the second displacement part 62d are also flexible because they are thin plate members, but the basic structure 1w is a capacitance type. When used as a force sensor, the first displacement portion 61d and the second displacement portion 62d do not necessarily have to be flexible members. On the other hand, when the basic structure 1w is used as a strain gauge type force sensor, the first displacement portion 61d and the second displacement portion 62d need to be flexible members. In the example shown in FIGS. 5 and 6, the first displacement portion 61d and the second displacement portion 62d (third plate-like piece) have both left and right surfaces parallel to the YZ plane.

  Next, with reference to FIG. 6A and FIG. 6B, each of the detection sites A and B when a force along the Y-axis direction acts on the movable portion 20 of the basic structure 1w. The operation will be described. In FIG. 6A and FIG. 6B, the thick black arrow indicates the direction of the acting force, and the white thick arrow indicates the direction of displacement of each of the displacement portions 61d and 62d. Yes.

  As shown in FIG. 6A, when the compressive force f1 along the Y-axis direction acts on the movable portion 20 of the basic structure 1w, the detection sites A and B are compressed along the Y-axis direction. Force acts. For this reason, the postures of the pair of first deforming portions 61e1 and 61e2 and the pair of second deforming portions 62e1 and 62e2 change to a state of lying more horizontally. As a result, each of the displacement portions 61d and 62d is displaced in the negative X-axis direction (the right direction in FIG. 6A) as indicated by the white arrow in the figure. On the other hand, as shown in FIG. 6B, when a tensile force f2 in the positive Y-axis direction acts on the movable portion 20 of the basic structure 1w, each detection site A, B is along the Y-axis direction. A tensile force acts. For this reason, the postures of the pair of first deforming portions 61e1 and 61e2 and the pair of second deforming portions 62e1 and 62e2 change to a more vertically standing state. As a result, each of the displacement portions 61d and 62d is displaced in the positive X-axis direction (left direction in FIG. 6B) as indicated by a white arrow in the figure.

  As described above, the pair of first deformable portions 61e1 and 61e2 are configured to rise in the Y-axis direction from the pair of second deformable portions 62e1 and 62e2 in the initial state (see FIG. 5). For this reason, as shown in FIGS. 6A and 6B, the displacement caused by the action of the force is relatively larger in the second displacement portion 62d than in the first displacement portion 61d. In other words, the spring constant of the second detection site B is relatively smaller than the spring constant of the first detection site A. Here, the spring constants of the first detection site A and the second detection site B mean values obtained by dividing the force acting on the movable portion 20 by the displacement in the X-axis direction generated in the displacement portions 61d and 62d. .

  In the force sensor using the basic structure 1w, the direction and magnitude of the applied force are detected using such displacement. That is, the direction of the applied force is detected by the displacement direction of each of the displacement parts 61d and 62d, and the magnitude of the applied force is detected by the magnitude of the displacement.

  According to the force sensor according to the present embodiment as described above, the capacitive element C2 is arranged in the second detection portion B having a relatively small spring constant, that is, the second detection portion B in which relatively large elastic deformation occurs. Thereby, the force sensor 1c which can detect force with high accuracy and high sensitivity can be provided.

  Alternatively, the basic structure 1w as described above can be used for a strain gauge type force sensor. In order to construct a strain gauge type force sensor, in place of the capacitive elements arranged at the displacement portions 61d and 62d of the capacitance type force sensor, more specifically, instead of the displacement electrodes, the strain gauge R1 and R2 may be arranged.

  FIG. 7 is a partial schematic top view of the first detection portion A of the strain gauge type force sensor configured as described above. FIG. 7A is a schematic diagram illustrating an initial state of the first detection site A, and FIG. 7B is a schematic diagram illustrating the first detection site A when a compressive force is applied to the basic structure 1w. FIG. 7C is a schematic diagram showing the first detection site A when a tensile force is applied to the basic structure 1w. In each drawing, the thick black arrow indicates the direction of the acting force, and the thin arrow indicates the stress (“→ ←” is a compressive stress, which is generated on the surface on the negative side of the X axis of each displacement portion 61d, 62d. “← →” indicates tensile stress).

  As shown in FIG. 7A, the first displacement portion 61d of the first detection site A in the initial state is parallel to the ZY plane. And as shown in FIG.7 (b), when compressive force acts on the basic structure 1w, as above-mentioned, the attitude | position of a pair of 1st deformation | transformation part 61e1, 61e2 will change to the state which lay down more horizontally. As a result, as shown in FIG. 7B, the first displacement portion 61d of the first detection site A is bent and deformed so as to be convex in the X-axis negative direction (right direction in FIG. 7B). . That is, as shown in the drawing, tensile stress is generated along the Y-axis direction on the X-axis negative side surface of the first displacement portion 61d on which the first strain gauge R1 is disposed. On the other hand, as shown in FIG. 7C, when a tensile force acts on the basic structure 1w, as described above, the postures of the pair of first deformable portions 61e1 and 61e2 change to a more vertical state. As a result, as shown in FIG. 7C, the first displacement portion 61d of the first detection site A is bent and deformed so as to be convex in the X-axis positive direction (left direction in FIG. 7C). . That is, as shown in the drawing, compressive stress is generated along the Y-axis direction on the surface on the X-axis negative side of the first displacement portion 61d where the first strain gauge R1 is disposed. Eventually, the direction of the force acting on the first detection site A1 (compression or tension) and the direction of the stress (compression or tension) generated on the X-axis negative side surface of the first displacement portion 61d are opposite to each other. . As can be understood from the bending deformation modes of FIGS. 7B and 7C, the direction of the stress (compression or tension) generated on the X-axis positive side surface of the first displacement portion 61d is: This is the same as the direction of force (compression or tension) acting on the first detection site A1.

  Although the second detection site B is not shown in FIG. 7, the same bending deformation occurs in the second displacement portion 62d also in the second detection site B. However, as described above, since the second detection portion has a relatively smaller spring constant than the first detection portion A, the stress generated in the first displacement portion 61d is applied to the second displacement portion 62d. Greater than the resulting stress. From this, it is possible to provide a force sensor 1 s capable of detecting force with high accuracy and high sensitivity by detecting the force Fy applied using the first strain gauge arranged in the first displacement portion 61 d. Can do.

  As described above, according to the present embodiment, there are provided force sensors 1c and 1s capable of detecting force with high accuracy and high sensitivity regardless of whether they are configured as a capacitance type or a strain gauge type. can do.

  Further, since the first detection part A and the second detection part B are arranged in parallel between the movable part 20 and the fixed part 10, the first detection part A and the second detection part B are greatly deformed or displaced. The applied force can be detected with higher accuracy and higher sensitivity.

  Further, the first detection site A of the basic structure 1 shown in FIG. 1 has a shape along a part of an arc having a predetermined radius, and the second detection site B has a radius different from the predetermined radius. It has a shape along a part of the arc. For this reason, since it is possible to cause the first detection site A and the second detection site B to be displaced in a direction orthogonal to the applied force, the force can be easily measured. The same applies to the basic structure 1w shown in FIG.

<<< §2. Force sensor according to the second embodiment of the present invention >>
Next, a force sensor according to a second embodiment of the present invention will be described in detail.

<2-1. Basic structure>
FIG. 8 is a schematic top view showing the basic structure 101 of the force sensor according to the second embodiment of the present invention, and FIG. 9 shows a moment around the Z-axis acting on the movable part 120 as a force receiving body. FIG. 10 is a schematic top view showing the basic structure 101 of FIG. 8 at the time, and FIG. 10 is a schematic top view showing a second quadrant of the basic structure 101 of FIG.

  The force sensor according to the present embodiment is for detecting at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system. As shown in FIGS. 8 to 10, the basic structure 101 includes a fixed part 110 fixed with respect to the XYZ three-dimensional coordinate system, and a movable part 120 that moves relative to the fixed part 110 by the action of a force or a moment. And a deformable body 140 that is connected to the fixed portion 110 and the movable portion 120 and generates elastic deformation when the movable portion 120 moves relative to the fixed portion 110.

  As shown in FIGS. 8 to 10, the fixing portion 110 is fixed on the XY plane and has a disk shape centered on the origin when viewed from the positive direction of the Z axis. The movable part 120 has an annular shape arranged concentrically with the fixed part 110 on the XY plane when viewed from the positive direction of the Z axis. Note that the fixing portion 110 may also have an annular shape.

  Also, as shown in FIGS. 8 to 10, the deformable body 140 is arranged so as to surround the first deformable body 141 in the shape of a ring made of an elastic body and the first deformable body 141. And a second deformable body 142 having an annular shape constituted by When viewed from the positive direction of the Z axis, the first deformable body 141 is disposed concentrically with the fixed portion 110 so as to surround the fixed portion 110, and the second deformable body 142 is formed between the first deformable body 141 and the movable portion 120. They are placed concentrically with them. After all, the fixed portion 110, the first deformable body 141, the second deformable body 142, and the movable portion 120 are arranged in this order concentrically with each other and radially outward as viewed from the positive Z-axis direction. Yes.

  Moreover, the 1st deformation body 141 and the 2nd deformation body 142 of the basic structure 101 by this Embodiment have the same cross-sectional shape. For this reason, due to the difference in diameter between the deformable bodies 141 and 142, the spring constants of the detection portions A1 to A4 of the first deformable body 141 are larger than the spring constants of the detection portions B1 to B4 of the second deformable body. Here, the spring constants of the detection parts A1 to A4 and B1 to B4 are the displacements in the V-axis direction and the W-axis direction generated by the forces acting on the movable part 20 in the detection parts 1 to A4 and B1 to B4. It means the value divided.

  As shown in FIGS. 8 to 10, the fixing portion 110 and the first deformable body 141 are a connecting body 133 disposed on the positive Y axis and a connecting body disposed on the negative Y axis in a gap between each other. 137 to each other. Further, the first deformable body 141 and the second deformable body 142 are connected to each other by the connecting body 134 disposed on the positive Y axis and the connecting body 138 disposed on the negative Y axis in the gap between each other. Has been. As a result, the first deformable body 141 and the second deformable body 142 are configured such that the two portions located on the Y axis do not move relative to the fixed portion 110.

  Further, as shown in FIGS. 8 to 10, the first deformable body 141 and the second deformable body 142 are disposed on the negative X axis and the connecting body 131 disposed on the positive X axis in the gap between each other. The connected body 135 is connected to each other. Furthermore, the movable part 120 and the second deformable body 142 are coupled to each other by a coupling body 132 disposed on the positive X axis and a coupling body 136 disposed on the negative X axis in a gap between each other. Yes. As a result, the first deformable body 141 and the second deformable body 142 are configured such that the two portions located on the X axis move relative to the fixed portion 110 integrally with the movable portion 120. .

  Next, the action of the basic structure 101 when the moment -Mz around the Z-axis acts on the movable part 120 of the basic structure 101 will be described with reference to FIG. In FIG. 9, the thick black arrow indicates the direction of the acting force, and the thick thick arrow indicates the direction of displacement of each of the detection sites A1 to A4 and B1 to B4.

  As shown in FIG. 9, when the movable portion 120 is rotated relative to the fixed portion 110 clockwise by the action of the moment −Mz, the first and second deformable bodies 141 and 142 Among these, the portion on the positive X-axis connected by the connecting bodies 131 and 132 is the Y-axis negative direction (downward in FIG. 9), and the portion on the negative X-axis connected by the connecting bodies 135 and 136 is Each moves in the Y-axis positive direction (upward in FIG. 9). On the other hand, of the first and second deformable bodies 141 and 142, the portions on the Y axis that are connected by the connecting bodies 133, 134, 137, and 138 do not move. As a result, the following elastic deformation occurs in each of the deformable bodies 141 and 142. That is, when the V axis and the W axis that pass through the origin O and form an angle of 45 ° with respect to the X axis and the Y axis are defined on the XY plane, the part located on the W axis among the deformable bodies 141 and 142 In, a radially outward displacement occurs, and a radially inward displacement occurs in a portion located on the V-axis. On the other hand, although not shown, when a force in the opposite direction acts on the movable part 120 and the movable part 120 is rotated counterclockwise with respect to the fixed part 110, in a portion located on the W axis, A radially inward displacement occurs, and a radially outward displacement occurs at a portion located on the V axis.

  Since these displacements are maximum on the W-axis and the V-axis, pay attention to the displacements or stresses of the portions of the deformable bodies 141 and 142 that intersect the W-axis and the V-axis when viewed from the positive Z-axis direction. It is efficient to measure the force or moment that is applied. Therefore, here, as shown in FIG. 9, four portions intersecting the W-axis and the V-axis in the first deformable body 141 are sequentially arranged from the first quadrant to the 1-1 detection portion A1 and the 1-2 detection portion. A2, 1st-3 detection part A3 and 1-4 detection part A4, and the 4th part which intersects with the W axis and V axis among the 2nd modification 142 is the 2nd-1 detection part B1, in order from the 1st quadrant, Let it be the 2-2 detection site B2, the 3-3 detection site B3, and the 2-4 detection site B4.

  Here, the relationship between the basic structure 101 according to the present embodiment and the basic structure 1 according to the first embodiment will be described with reference to FIG.

  As described above, in the basic structure 101 according to the present embodiment, a portion of the deformable bodies 141 and 142 located on the positive Y axis is fixed with respect to the XYZ three-dimensional coordinate system, and the deformable bodies 141 are arranged. , 142 are located on the negative X-axis and move relative to the fixed portion 110 together with the movable portion 120. In such a structure, a portion located on the positive Y axis of each of the deformable bodies 141 and 142 is regarded as the fixing portion 10 of the basic structure 1 according to the first embodiment, and the negative X of each of the deformable bodies 141 and 142 is taken. By grasping the part located on the axis as the movable part 20 of the basic structure 1 according to the first embodiment, the structure shown in FIG. 10 and the basic structure 1 according to the first embodiment are substantially the same structure. It is understood that there is. The same is true for the first, third and fourth quadrants. Furthermore, the relationship between the spring constants of the deformable bodies 141 and 142 is that the spring constant of the first detection portion A of the first deformable body 31 is the second constant of the second deformable body 32 in the basic structure 1 in the first embodiment. It corresponds also to being larger than the spring constant of the detection part B.

  After all, it can be said that the basic structure 101 shown in FIGS. 8 and 9 is a combination of four basic structures 1 according to the first embodiment. In other words, as described in the first embodiment, the basic structure 101 according to the present embodiment is 2-1st to 1st to 1st-4th detection sites A1 to A4 in terms of displacement. 2-4 detection site | parts B1-B4 are more sensitive, and when it sees about stress, it will be 1-1 to 1-4 detection site | parts A1-A4 rather than the 2-1st-2nd detection site | part B1-B4. It has the characteristic that is more sensitive.

<2-2. Capacitance type force sensor>
Next, a capacitance type force sensor 101c using the basic structure 101 as described above will be described.

  FIG. 11 is a schematic top view showing an electrostatic force type force sensor 101c according to the basic structure 101 of FIG. As shown in FIG. 11, the force sensor 101c includes first to first to fourth displacement electrodes Em11 to Em14 disposed on the outer surfaces of the first to first to first to fourth detection portions A1 to A4. The first to first to fourth fixed electrodes Ef11 to Ef14, which are arranged to face the displacement electrodes Em11 to Em14 and do not move relative to the fixed portion 110, and the first to second to fourth detection sites B1 to B1. The 2-1 to 2-4 displacement electrodes Em21 to Em24 disposed on the outer surface of B4, and the 2-1 to 2-1 that are disposed to face the displacement electrodes Em21 to Em24 and do not move relative to the fixed portion 110. Second to fourth fixed electrodes Ef21 to Ef24.

  As shown in FIG. 11, the 1-1 displacement electrode Em11 and the 1-1 fixed electrode Ef11 constitute a 1-1 capacitive element C11, and the 1-2 displacement electrode Em12 and the 1-2 fixed electrode Ef12. Constitutes the first-second capacitance element C12, the first-third displacement electrode Em13 and the first-third fixed electrode Ef13 constitute the first-third capacitance element C13, and the first-fourth displacement electrode Em14 and the first The 1-4 fixed electrode Ef14 constitutes a 1-4 capacitive element C14. Furthermore, the 2-1 displacement electrode Em21 and the 2-1 fixed electrode Ef21 constitute a 2-1 capacitive element C21, and the 2-2 displacement electrode Em22 and the 2-2 fixed electrode Ef22 are the second 2- The second-capacitance element C22 constitutes the second-third displacement electrode Em23 and the second-third fixed electrode Ef23, and the second-third capacitance element C23 constitutes the second-fourth displacement electrode Em24 and the second-fourth fixed electrode. Ef24 constitutes the second-fourth capacitive element C24. Each of the fixed electrodes Ef11 to Ef24 is fixed to the XY plane and extends in the positive Z-axis direction, for example, even if a force acts on the movable portion 120, the first and second deformable bodies 141 and 142 It is supported at a position where it does not interfere.

  In the present embodiment, the 1-1 to 1-4 displacement electrodes Em11 to Em14 and the 2-1 to 2-4 displacement electrodes Em21 to Em24 all have the same area. Furthermore, the 1-1 to 1-4 fixed electrodes Ef11 to Ef14 and the 2-1 to 2-4 fixed electrodes Ef21 to Ef24 all have the same area. Further, the effective opposing area of each electrode constituting each of the capacitive elements C11 to C24 and the distance between the opposing electrodes are all the same.

  Further, as shown in FIG. 11, the force sensor 101 c outputs an electrical signal indicating a force or a moment acting on the movable portion 120 based on the elastic deformation generated in the first deformable body 141 and the second deformable body 142. A detection circuit 150 is included. The detection circuit 150 of the force sensor 101c shown in FIG. 11 outputs an electrical signal indicating the force or moment acting on the movable part 120 based on the variation amount of the capacitance value of each of the capacitive elements C11 to C24. It has become. Note that wirings that electrically connect the capacitive elements C11 to C24 and the detection circuit 150 are not shown.

  Next, the operation of the force sensor 101c will be described.

  Here, the case where a clockwise force (moment) as viewed from the positive direction of the Z-axis acts on the movable portion 120 will be described as an example (see FIG. 9). In this case, as described above, among the deformable bodies 141 and 142, the first, second, second, first, and second-4 detection sites A2, B2, A4, which are located on the W axis, In B4, a radially outward displacement occurs, and in the 1-1, 2-1, 1-3, 2-3 detection sites A1, B1, A3, B3 located on the V-axis A displacement inward in the radial direction occurs. As a result, the capacitance values of the 1-2, 2-2, 1-4, and 2-4 capacitive elements C12, C22, C14, and C24 increase because the distance between the electrodes decreases. In contrast, the capacitance values of the 1-1, 2-1, 1-3, and 2-3 capacitor elements C11, C21, C13, and C23 decrease because the inter-electrode distance increases. .

  In the present embodiment, as described above, the spring constants of the detection parts B1 to B4 of the second deformable body 142 are smaller than the spring constants of the detection parts A1 to A4 of the first deformable body 141. Focusing on the absolute value of the variation amount of the capacitance value, the variation amount of the capacitance value of the 2-1 to 2-4 capacitance elements C21 to C24 arranged on the second deformation body 142 is the first deformation body. 141 is larger than the fluctuation amount of the capacitance values of the first to first to fourth capacitance elements C11 to C14 disposed on the substrate 141.

Then, the detection circuit 150 measures the moment Mz around the applied Z-axis using [Equation 1] below. In [Expression 1], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is around the Z axis measured based on the elastic deformation of the second deformable body 142. Moment. In the following equations, C11 to C24 indicate the amount of change in the capacitance value of the first to second to fourth capacitance elements C11 to C24. The same applies to other formulas in this specification.
[Formula 1]
-Mz1 = -C11 + C12-C13 + C14
-Mz2 = -C21 + C22-C23 + C24

  In the capacitance type force sensor 101c, the capacitance value of the 2-1st to 2nd-4th capacitive elements C21 to C24 having relatively high sensitivity is based on the variation amount, that is, [Equation 1]. By measuring the applied moment based on -Mz2, the measurement with excellent S / N becomes possible. Of course, the acting moment may be measured based on the variation amount of the capacitance values of the first to first to fourth capacitance elements C11 to C14. If only the moment Mz around the Z axis is measured, only one of the first to first to fourth capacitive elements C11 to C14 and the 2-1 to second to fourth capacitive elements C21 to C24 is provided. It only has to be done.

<2-3. Strain gauge type force sensor>
The basic structure 101 as described above can also be used for a strain gauge type force sensor 101s.

  FIG. 12 is a schematic top view showing a strain gauge type force sensor 101s according to the basic structure 101 of FIG. As shown in FIG. 12, the force sensor 101 s includes a first strain gauge R <b> 11 arranged at the first-first detection site A <b> 1 and a first-second detection site on the outer surface of the annular first deformation body 141. The 1-2 strain gauge R12 disposed at A2, the 1-3 strain gauge R13 disposed at the 1-3 detection site A3, and the 1-4 strain disposed at the 1-4 detection site A4. And a gauge R14. Furthermore, the force sensor 101s is disposed on the outer surface of the annular second deformable body 142 at the 2-1 strain gauge R21 disposed at the 2-1 detection site B1 and at the 2-2 detection site B2. A 2-2 strain gauge R22, a 2-3 strain gauge R23 disposed at the 2-3 detection site B3, and a 2-4 strain gauge R24 disposed at the 2-4 detection site B4. Have. Each of the strain gauges R11 to R24 is a metal foil strain gauge, and all have the same characteristics. Since the other configuration is the same as that of the force sensor 1c shown in FIG. 11 except that the capacitive element is not provided, detailed description thereof is omitted.

  Next, the operation of the force sensor 101s will be described.

  Here, the case where a clockwise force (moment) as viewed from the positive direction of the Z-axis acts on the movable part 120 will be described as an example (see FIG. 9). In this case, as described above, among the deformable bodies 141 and 142, the first, second, second, first, and second-4 detection sites A2, B2, A4, which are located on the W axis, In B4, a radially outward displacement occurs, and in the 1-1, 2-1, 1-3, 2-3 detection sites A1, B1, A3, B3 located on the V-axis A displacement inward in the radial direction occurs. As a result, tensile stress is generated in the first, second, second, first, fourth, and second-4 detection sites A2, B2, A4, and B4 located on the W axis, and the positions on the V axis. Compressive stress is generated in the 1-1, 2-1, 1-3, 2-3 detection sites A1, B1, A3, B3. As described above, the spring constants of the detection parts A1 to A4 of the first deformation body 141 are larger than the spring constants of the detection parts B11 to B14 of the second deformation body 142. The absolute value of the stress generated in the detection parts A1 to A4 is larger than the absolute value of the stress generated in the detection parts B1 to B4 of the second deformable body 142. For this reason, the electrical resistance values of the first to first to fourth strain gauges R11 to R14 vary more greatly than the electrical resistance values of the 2-1 to second to fourth strain gauges R21 to R24.

And the detection circuit 150 uses the following [Formula 2], for example, at least one of the 1-1 to 1-4 strain gauges R11 to R14 and the 2-1 to 2-4 strain gauges R21 to R24. On the basis of the fluctuation amount of the electrical resistance value, the applied moment Mz around the Z axis is measured. In [Expression 2], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is around the Z axis measured based on the elastic deformation of the second deformable body 142. Moment. Moreover, in the following formula | equation, R11-R24 has shown the variation | change_quantity of the electrical resistance value of the 1-1st-2nd-4 strain gauge R11-R24. The same applies to other formulas in this specification.
[Formula 2]
-Mz1 = -R11 + R12-R13 + R14
-Mz2 = -R21 + R22-R23 + R24

  In the strain gauge type force sensor 101c, based on the fluctuation amount of the electrical resistance values of the first to first to fourth strain gauges R11 to R14 having relatively high sensitivity, that is, − in [Expression 2]. By measuring the applied moment based on Mz1, measurement with excellent S / N becomes possible. Of course, you may measure the moment which acted based on the variation | change_quantity of the electrical resistance value of the 2-1st-2nd-4 strain gauge R21-R24. In measurement, the Wheatstone bridge circuit (not shown) was constituted by the 1-1 to 1-4 strain gauges R11 to R14 or the 2-1 to 2-4 strain gauges R21 to R24. It is also possible to measure moments. If only the moment Mz around the Z-axis is measured, only one of the first to first to fourth strain gauges R11 to R14 and the second to first to second strain gauges R21 to R24 is provided. It only has to be done.

  According to the force sensor according to the present embodiment as described above, the spring constant is relatively small, that is, the generated elastic deformation is relatively large, and the capacities are provided in the first to second to fourth detection portions B1 to B4. By arranging the elements C21 to C24, it is possible to provide the force sensor 101c capable of detecting the moment with high accuracy and high sensitivity. Furthermore, by arranging the strain gauges R11 to R14 in the first to first to fourth detection portions A1 to A4, in which the spring constant is relatively large, that is, the stress that is expressed with elastic deformation is relatively large. Thus, it is possible to provide the force sensor 101s capable of detecting the moment with high accuracy and high sensitivity. As described above, according to the present embodiment, force sensors 101c and 101s that can detect force with high accuracy and high sensitivity, whether configured as a capacitance type or a strain gauge type, are provided. can do.

  In the force sensors 101c and 101s described above, the first deformable body 141 and the second deformable body 142 are both annular and are concentric with each other. Therefore, the force sensors 101c and 101s can be configured with a simple configuration.

  Further, the first deformable body 141 has first to first to fourth detection portions A1 to A4 at four portions overlapping the V axis and the W axis as viewed from the Z-axis direction, and the second deformable body 142 is The four parts overlapping the V-axis and the W-axis when viewed from the Z-axis direction have first to second-4th detection parts B1 to B4. For this reason, symmetrical elastic deformation occurs in the first deformable body 141 and the second deformable body 142 due to the applied moment, and therefore, there is no influence of force other than the applied moment.

<2-4. Modification of basic structure>
Next, a modified example of the basic structure 101 will be described. 13 is a schematic top view showing a first modification of the basic structure 101 of FIG. 8, and FIG. 14 is a schematic top view showing a second modification of the basic structure 101 of FIG. FIG. 10 is a schematic top view showing a third modification of the basic structure 101 in FIG. 8.

  First, the basic structure 101a according to the modification shown in FIG. 13 will be described. This basic structure 101a is different from the basic structure 101 described above in that a thin portion having a small thickness is provided on the annular second deformable body 142. Specifically, the second deformable body 142 has first to second to fourth thin portions 142t1 to 142t4 in a region including portions located on the V axis and the W axis. For this reason, the 2-1 to 2-4 detection sites B1 to B4 are provided in the 2-1 to 2-4 thin wall portions 142t1 to 142t4, respectively. On the other hand, the first deformable body 141 is the same as the first deformable body 141 of the basic structure 101 shown in FIGS.

  In the present modification, as shown in FIG. 13, the thin portions 142t1 to 142t4 are formed by reducing the radial thickness of the second deformable body 142. Of course, in other modified examples, the second deformable body 142 may be formed by reducing the thickness in the Z-axis direction. Since other configurations are the same as those of the basic structure 101 shown in FIGS. 8 to 10, the corresponding components are denoted by the same reference numerals, and detailed description thereof is omitted.

  For example, when a clockwise moment (same direction as in FIG. 9) acts on the basic structure 101a having such a configuration when viewed from the positive direction of the Z-axis, each of the deformable bodies 141 and 142 has the same elasticity as in FIG. Deformation occurs. However, the elastic deformation generated in the thin portions 142t1 to 142t4 of the second deformable body 142 is larger than that in the case of FIG.

  According to the basic structure 101a having such a configuration, the spring constants of the first to second to fourth detection portions B1 to B4 relatively decrease due to the presence of the thin portions 142t1 to 142t4. Therefore, when the basic structure 101a is used as a capacitance type force sensor, it is provided in the 2-1 to 2-4 detection parts B1 to B4 as compared with the basic structure 101 described above. In the capacitive element, a particularly large variation in capacitance value is observed. That is, in the capacitance type force sensor, the force or moment acting based on the variation amount of the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively sensitive. By measuring this, it becomes possible to perform measurement with even better S / N. Of course, you may measure the force which acted based on the variation | change_quantity of the electrostatic capacitance value of the 1-1st-1-4th capacitive elements C11-C14.

  A further modified example of the basic structure provided with the deformed body having such thin portions 142t1 to 142t4 will be described with reference to FIG.

  The basic structure 101b shown in FIG. 14 is different from the basic structure 101a according to the first modification in that the second deformable body 142b is divided into four parts by the X axis and the Y axis. That is, the second deformation body 142b includes a 2-1 deformation body 142b1 disposed in the first quadrant of the XY plane, a 2-2 deformation body 142b2 disposed in the second quadrant of the XY plane, It has the 2nd-3 deformation body 142b3 arrange | positioned in the 3rd quadrant, and the 2nd-4 deformation body 142b4 arrange | positioned in the 4th quadrant of XY plane. As shown in FIG. 14, the second-first deformable body 142b1 is connected to the first deformable body 141 by a connecting body 134a extending in parallel with the Y-axis in the vicinity of the positive Y-axis, and near the positive X-axis. Is connected to the movable portion 120 by a connecting body 132b extending in parallel with the X axis. Further, the second-second deformable body 142b2 is connected to the first deformable body 141 by a coupling body 134b extending in parallel with the Y-axis at a portion near the positive Y-axis, and a portion near the negative X-axis is connected to the X-axis. Is connected to the movable portion 120 by a coupling body 136a extending in parallel with the movable portion 120a. The second to third deformable body 142b3 is connected to the first deformable body 141 by a connecting body 136b in which a portion near the negative X axis extends in parallel with the X axis, and a portion near the negative Y axis is parallel to the Y axis. It is connected to the movable part 120 by a connecting body 138a extending in the direction. The second to fourth deformable body 142b4 is connected to the first deformable body 141 by a connecting body 138b in which a portion near the negative Y axis extends in parallel to the Y axis, and a portion near the positive X axis is parallel to the X axis. It is connected to the movable part 120 by a connecting body 132a extending to the center.

  Furthermore, as shown in FIG. 14, the two coupling bodies 132a and 132b extending in parallel with the X axis are separated from each other in the Y axis direction, and between the two coupling bodies 132a and 132b, A connecting body 131l that connects the first deformable body 141 and the movable portion 120 extends along the X axis. Similarly, the two connecting members 136a and 136b extending in parallel with the X axis are separated from each other in the Y axis direction, and the first deformable member is interposed between the two connecting members 136a and 136b. A connecting body 135l that connects 141 and the movable portion 120 extends along the X-axis. Since other configurations are the same as those of the first modification shown in FIG. 14, the same components are denoted by the same reference numerals, and detailed description thereof is omitted.

  When, for example, a clockwise moment (same direction as in FIG. 9) acts on the basic structure 101b having such a configuration as viewed from the positive direction of the Z-axis, each of the deformable bodies 141 and 142 has the same elasticity as in FIG. Deformation occurs. However, the elastic deformation generated in the thin portions 142t1 to 142t4 of the second deformable body 142 is the same as that of the basic structure 101a according to the first modification shown in FIG. 13, and is larger than the case of FIG.

  Next, a third modified example of the basic structure provided with the deformed body having the thin portions 142t1 to 142t4 will be described with reference to FIG. The basic structure 101b ′ according to the third modification is the second structure shown in FIG. 14 in that the 2-1 to 2-4 deformation bodies 142b1 to 142b4 are not directly connected to the movable part 120. This is different from the basic structure 101b according to the modification. That is, as shown in FIG. 15, in the basic structure 101b ′ according to the third modification, the regions near the positive X axis of the 2-1 deformation body 142b1 and the 2-4 deformation body 142b4 are connected bodies 132d and 132e. Are connected to the first deformable body 141, and regions near the negative X-axis of the 2-2 deformable body 142b2 and the 2-3 deformable body 142b3 are connected to the first deformable body 141 by the connected bodies 136c and 136d, respectively. It is connected. In this modification, none of the 2-1 to 2-4 deformation bodies 142b1 to 142b4 is connected to the movable part 120, but instead of the connection part between the connection body 131l and the first deformation body 141. The ends of the connecting bodies 132d and 132e are connected to the first deformable body 141 in the vicinity, and the ends of the connecting bodies 136c and 136d are close to the connecting portion between the connecting body 135l and the first deformable body 141. The part is connected to the first deformable body 141. For this reason, also in this modification, substantially the same operation as the basic structures 101a and 101b shown in FIGS. 13 and 14 is provided.

<2-5. Principle of detection of force Fx in the X-axis direction and force Fy in the Y-axis direction>
In the above description, the method of measuring the moment Mz around the Z-axis by the force sensors 101c and 101s has been described. However, the force sensors 101c and 101s use the force Fx in the X-axis direction and the force Fy in the Y-axis direction. Can also be measured.

  First, the principle for measuring the force + Fx in the X-axis positive direction will be described with reference to FIG. FIG. 16 is a diagram for explaining elastic deformation that occurs in the deformable body 140 when a force + Fx in the X-axis positive direction is applied to the movable portion 120 of the basic structure 101 in FIG. Since the elastic deformations generated in the first deformation body 141 and the second deformation body 142 are different in degree but have the same tendency, only a single deformation body 140 is shown in FIG. 16 for simplicity. . Further, for the sake of simplicity, illustration of the fixed portion 110 and the connecting body that connects the fixed portion 110 and the deformable body 140 is omitted, but the points P1 and P2 in FIG. Do not move. In the deformed body 140, four detection parts A, B, C, and D are arranged in this order in the counterclockwise direction from the first quadrant on the outer surface of the part that intersects the V axis and the W axis when viewed from the positive direction of the Z axis. Is provided. In FIG. 16, the thick black arrow indicates the direction of the acting force, and the white thick arrow indicates the direction of displacement of each of the detection portions A to D.

  As shown in FIG. 16, when a force + Fx in the X-axis positive direction acts on the movable portion 120 of the basic structure 101, the portion of the deformable body 140 on the X-axis moves in the X-axis positive direction together with the movable portion 120. On the other hand, the part on the Y axis corresponding to the points P1 and P2 does not move. From this, in the deformable body 140, among the four detection parts A to D, the detection parts A and D located in the first quadrant and the fourth quadrant are displaced radially inward of the deformable body 140, The detection parts B and C located in the second quadrant and the third quadrant are elastically deformed so as to be displaced radially outward of the deformable body 140.

  From the above, the following can be understood. That is, when a force + Fx in the positive direction of the X-axis acts on the movable part 120 of the force sensor 101c shown in FIG. 11, the first and second capacitive elements C11 and C21 arranged in the first quadrant, and In the first to fourth capacitive elements C14 and the second to fourth capacitive elements C24 located in the fourth quadrant, since the separation distance between the fixed electrode and the displacement electrode increases, the capacitance value decreases. On the other hand, the first and second capacitive elements C12 and C22 located in the second quadrant, and the first and third capacitive elements C13 and C23 located in the third quadrant, Since the separation distance between the fixed electrode and the displacement electrode decreases, the capacitance value increases.

Therefore, the detection circuit 150 measures the applied force Fx in the X-axis direction using [Equation 3] below. In [Expression 3], Fx1 is a force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is an X-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 3]
Fx1 = −C11 + C12 + C13−C14
Fx2 = −C21 + C22 + C23−C24

  Next, the principle for measuring the force + Fy in the Y-axis positive direction will be described with reference to FIG. FIG. 17 is a diagram for explaining elastic deformation that occurs in the deformable body 140 when a force + Fy in the Y-axis positive direction is applied to the movable portion 120 of the basic structure 101 in FIG. Since the elastic deformations generated in the first deformation body 141 and the second deformation body 142 are different in degree but have the same tendency, FIG. 17 also shows only a single deformation body 140 for the sake of simplicity. . Further, for the sake of simplicity, illustration of the fixed portion 110 and the connecting body that connects the fixed portion 110 and the deformable body 140 is omitted, but the points P1 and P2 in FIG. Do not move. In addition, in the deformable body 140, four detection portions A, B, C, and D are provided in this order counterclockwise from the first quadrant at a portion that intersects the V axis and the W axis when viewed from the positive direction of the Z axis. It has been. In FIG. 17, the thick black arrow indicates the direction of the acting force, and the thick thick arrow indicates the direction of displacement of each of the detection portions A to D.

  As shown in FIG. 17, when a force + Fy in the Y-axis positive direction acts on the movable portion 120 of the basic structure 101, the portion on the X-axis of the deformable body 140 moves in the Y-axis positive direction together with the movable portion 120. On the other hand, the part on the Y axis corresponding to the points P1 and P2 does not move. From this, in the deformable body 140, the detection portions A and B located in the first quadrant and the second quadrant among the four detection portions A to D move radially outward of the deformable body 140, The detection parts C and D located in the third quadrant and the fourth quadrant are elastically deformed so as to move inward in the radial direction of the deformable body 140.

  From the above, the following can be understood. That is, when a force + Fy in the Y-axis positive direction acts on the movable part 120 of the force sensor 101c shown in FIG. 11, the 1-1st capacitive element C11 and the 2-1th capacitive element C21 located in the first quadrant, and Since the distance between the fixed electrode and the displacement electrode of the first and second capacitive elements C12 and C22 located in the second quadrant decreases, the capacitance value increases. On the other hand, the first to third capacitive elements C13 and the second to third capacitive elements C23 located in the third quadrant, and the first to fourth capacitive elements C14 and the second to fourth capacitive elements C24 located in the fourth quadrant, Since the separation distance between the fixed electrode and the displacement electrode increases, the capacitance value decreases.

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using [Equation 4] below. In [Expression 4], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 4]
Fy1 = C11 + C12-C13-C14
Fy2 = C21 + C22-C23-C24

  As described above, in the capacitance type force sensor 101c, based on the variation amount of the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24, which are relatively highly sensitive, That is, when the force Fx in the X-axis direction is obtained, the applied force is measured based on Fx2 in [Expression 3], and when the force Fy in the Y-axis direction is obtained, based on Fy2 in [Expression 4]. Thus, measurement with excellent S / N becomes possible. Of course, you may measure the force which acted based on the variation | change_quantity of the electrostatic capacitance value of the 1-1st-1-4th capacitive elements C11-C14.

  Here, the force sensor 101c provided with a total of eight capacitive elements including the first to first to fourth capacitive elements C11 to C14 and the 2-1 to second to fourth capacitive elements C21 to C24 will be described as an example. Went. However, if only the force Fx in the X-axis direction and / or the force Fy in the Y-axis direction are measured, the first to first to fourth capacitance elements C11 to C14 and the 2-1 to second to fourth capacitances are used. Only one of the elements C21 to C24 may be provided.

  Note that when the direction of the acting force is the negative direction of the X-axis, all the variations in the capacitance values of the capacitive elements C11 to C24 are reversed. For this reason, the signs of the forces Fx1 and Fx2 measured by [Equation 3] are reversed. That is, the direction (sign) and magnitude of the applied force Fx are measured by [Equation 3]. The same applies to the case where the force Fy in the Y-axis direction is measured using [Equation 4].

  Next, a method for measuring the force in the X-axis direction by the strain gauge type force sensor 101s will be described with reference to FIG.

  FIG. 18 is a diagram for explaining the stress generated in the detection portions A to D of the deformable body 140 when a force in the X-axis positive direction is applied to the movable portion 120 of the basic structure 101 in FIG. Since the elastic deformations generated in the first deformation body 141 and the second deformation body 142 are different in degree but have the same tendency, only a single deformation body 140 is shown in FIG. 18 for simplicity. . The arrangement of the detection portions A to D is the same as in FIGS. 16 and 17. In FIG. 18, a thick black arrow indicates the direction of the acting force, and a thin arrow indicates a stress generated in each of the detection sites A to D (“→ ←” is a compressive stress, “← →” is a tensile stress). ).

  As shown in FIG. 18, when a force + Fx in the X-axis positive direction acts on the movable portion 120 of the basic structure 101, the deformable body 140 is elastically deformed in the same manner as in FIG. At this time, focusing on the change in the radius of curvature in each of the detection portions A to D, as shown in FIG. 18, the detection portions A and D located in the first quadrant and the fourth quadrant are bent so that the radius of curvature becomes large. On the other hand, the detection parts B and C located in the second quadrant and the third quadrant bend so that the radius of curvature becomes small. Due to such bending deformation, compressive stress is generated in the detection parts A and D located in the first quadrant and the fourth quadrant, and in the detection parts B and C located in the second quadrant and the third quadrant. Tensile stress is generated.

  From the above, the following can be understood. That is, when a force + Fx in the X-axis positive direction acts on the movable part 120 of the force sensor 101s shown in FIG. 12, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and In the first to fourth strain gauges R14 and the second to fourth strain gauges R24 located in the fourth quadrant, the electric resistance value decreases due to the compressive stress. On the other hand, the 1-2 strain gauge R12 and the 2-2 strain gauge R22 arranged in the second quadrant, and the 1-3 strain gauge R13 and the 2-3 strain gauge R23 located in the third quadrant, The electrical resistance value increases due to the tensile stress.

Therefore, the detection circuit 150 measures the applied force Fx in the X-axis direction using [Equation 5] below. In [Expression 5], Fx1 is a force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is an X-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 5]
Fx1 = −R11 + R12 + R13−R14
Fx2 = −R21 + R22 + R23−R24

  Next, the principle for measuring the force + Fy in the Y-axis positive direction will be described with reference to FIG. FIG. 19 is a view for explaining the stress generated in the detection unit 140 of the deformed body when a positive force + Fy in the Y-axis direction acts on the movable portion of the basic structure 101 in FIG. The elastic deformation generated in the first deformable body 141 and the second deformable body 142 is different in degree but has the same tendency. Therefore, only the single deformable body 140 is shown in FIG. 19 for simplicity. . Further, for the sake of simplicity, illustration of the fixed portion 110 and the connecting body that connects the fixed portion 110 and the deformable body 140 is omitted, but the points P1 and P2 in FIG. Do not move. The arrangement of the detection portions A to D is the same as in FIGS. 16 and 17. In FIG. 19, the thick black arrow indicates the direction of the acting force, the thin arrow indicates the stress generated in each detection part A to D (“→ ←” indicates compressive stress, “← →” indicates tensile stress). ).

  As shown in FIG. 19, when a force + Fy in the Y-axis positive direction acts on the movable portion 120 of the basic structure 101, the deformable body 140 is elastically deformed in the same manner as in FIG. At this time, paying attention to the change in the radius of curvature in each of the detection parts A to D, as shown in FIG. 19, the detection parts A and B located in the first quadrant and the second quadrant are bent so that the curvature radius becomes small. On the other hand, the detection parts C and D located in the third quadrant and the fourth quadrant bend so that the radius of curvature becomes large. Due to such bending deformation, tensile stress is generated in the detection parts A and B located in the first quadrant and the second quadrant, and in the detection parts C and D located in the third and fourth quadrants. , Compressive stress occurs.

  From the above, the following can be understood. That is, when a force + Fy in the Y-axis positive direction acts on the movable part 120 of the force sensor 101s shown in FIG. 12, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and In the first-second strain gauge R12 and the second-second strain gauge R22 located in the second quadrant, the electrical resistance value increases due to the tensile stress. On the other hand, the first-3 strain gauge R13 and the second-3 strain gauge R23 arranged in the third quadrant, and the first-4 strain gauge R14 and the second-4 strain gauge R24 located in the fourth quadrant, The electrical resistance value decreases due to the compressive stress.

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using [Equation 6] below. In [Expression 6], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 6]
Fy1 = R11 + R12-R13-R14
Fy2 = R21 + R22-R23-R24

  In the strain gauge type force sensor 101s, the applied force is measured based on the fluctuation amount of the electrical resistance values of the first to first to fourth strain gauges R11 to R14 which are relatively highly sensitive. Therefore, measurement with excellent S / N becomes possible. Of course, the applied force may be measured based on the variation amount of the electrical resistance value of the 2-1st to 2nd-4th strain gauges R21 to R24.

  Here, the force sensor 101s provided with a total of eight strain gauges including the first to first to fourth strain gauges R11 to R14 and the second to second to second strain gauges R21 to R24 will be described as an example. Went. However, if only the force Fx in the X-axis direction and / or the force Fy in the Y-axis direction are measured, the first to first to fourth strain gauges R11 to R14 and the second to first to second to fourth strains are used. Only one of the gauges R21 to R24 may be provided.

  In addition, when the direction of the acting force is the X-axis negative direction or the Y-axis negative direction, the variation amounts of the electric resistance values of the strain gauges R11 to R24 are all reversed. For this reason, the signs of the forces Fx1 and Fx2 measured by [Equation 5] are reversed. That is, the direction (sign) and magnitude of the applied force are measured by [Equation 5]. The same applies to the case where the force in the Y-axis direction is measured using [Equation 6].

  In the strain gauge type force sensor 101s described above, the strain gauges R11 to R24 may be arranged on the radially inner surface of the deformable bodies 141 and 142 on the V axis and the W axis. In this case, the electrical resistance values of the strain gauges R11 to R24, and the electrical resistance values due to the force acting on the movable portion 120 when the strain gauges R11 to R24 are arranged on the radially outer surfaces of the deformable bodies 141 and 142, respectively. The fluctuation opposite to the fluctuation occurs. Accordingly, by reversing the sign of the right side or the left side of [Expression 5] and [Expression 6] described above, it is possible to measure the direction (sign) and magnitude of the acting force or moment even in this case. .

<2-5. Basic structure with waveform detection section>
Next, FIG. 20 is a schematic top view showing an annular basic structure 101w in which the structure shown in FIG. 5 is adopted for each of the detection sites A1 to A4 and B1 to B4 of the deformable bodies 141 and 142, and FIG. It is the schematic side view which looked at 1-1st detection site | part A1 of the basic structure 101w shown in FIG. 21 from the V-axis positive direction.

  As shown in FIGS. 20 and 21, the detection portions A1 to A4 and B1 to B4 of the basic structure 101w are all detection portions having a downwardly convex waveform having the structure shown in FIG. The detection portions A1 to A4 of the first deformable body 141 all have the same structure. Further, the detection portions B1 to B4 of the second deformable body 142 all have the same structure. On the other hand, the detection parts B1 to B4 of the second deformation body 142 are relatively longer in the circumferential direction than the detection parts A1 to A4 of the first deformation body 141. Specifically, in the circumferential direction of each of the deformable bodies 141 and 142, the pair of second deformable portions 62e1 and 62e2 of the 2-1 to 2-4 detection sites B1 to B4 are the first to the first 1st It is longer than the pair of first deforming portions 61e1 and 61e2 of the four detection parts A1 to A4, and is in a state of lying on the XY plane. Further, in the circumferential direction of each of the deformable bodies 141 and 142, the second displacement portions 62d of the first to second to fourth detection sites B1 to B4 are connected to the first to first to fourth detection sites A1 to A4. It is longer than the first displacement part 61d. With such a configuration, the displacement caused by the action of force or moment is relatively larger in the second displacement portion 62d than in the first displacement portion 61d. In other words, the spring constant of the second detection site B is relatively smaller than the spring constant of the first to 1-4 detection sites A1 to A4. Here, the spring constant means a value obtained by dividing the force acting on the movable portion 20 by the displacement in the Z-axis direction generated in each of the detection portions A1 to A4 and B1 to B4.

  Next, the operation of the basic structure 101w will be described with reference to FIG.

  FIG. 22 shows stresses generated in the detection portions A1 to A4 and B1 to B4 of the deformable bodies 141 and 142 when the moment Mz around the Z axis acts clockwise on the movable part 120 of the basic structure 101w of FIG. It is a figure for demonstrating. In FIG. 22, a thick black arrow shown on the movable portion 120 indicates the acting moment -Mz, and the black painted arrow shown in the gap between the first deformable body 141 and the second deformable body 142. The thick arrows indicate the direction of the force acting on each detection site A1 to A4, B1 to B4.

  As shown in FIG. 22, the 1-1 detection site A1 and the 2-1 detection site B1 located in the first quadrant, and the 1-3 detection site A3 and the 2-3 detection located in the third quadrant. A tensile force is generated at the site B3. On the other hand, the 1-2 detection site A2 and the 2-2 detection site B2 located in the second quadrant, and the 1-4 detection site A4 and the 2-4 detection site B4 located in the 4th quadrant, A compressive force is generated.

  When the basic structure 101w is used as an electrostatic force type force sensor, each of the first to first to first to second detection sites A1 to A4 and the second to first to second to fourth detection sites B1 to B4. What is necessary is just to arrange | position a capacitive element in the displacement parts 61d and 62d. As a specific arrangement method, for example, in the 1-1 detection site A1, as shown in FIG. 21, a displacement electrode Em11 is provided on the displacement portion 61d via a displacement substrate Im11, and faces the displacement electrodes Em11. Thus, the fixed electrode Ef11 may be arranged so as not to move relative to the fixed portion 110. The fixed electrode Ef11 is disposed on the fixed substrate 73 via a fixed substrate If11 (insulator). Such an arrangement is the same in the other displacement portions 61d and 62d. As understood from FIG. 21, the displacement electrode Em11 and the fixed electrode Ef11 employed here each have a plane parallel to the XY plane, and are separated by a predetermined distance in the Z-axis direction. In this way, a total of eight capacitive elements C11 to C14 and C21 to C24 are configured by the set of eight opposing displacement electrodes and fixed electrodes.

  Examining the variation of the capacitance values of the capacitive elements C11 to C24 when a clockwise moment -Mz as viewed from the positive direction of the Z-axis acts on such a capacitive force sensor, Street. That is, the tensile force or the compressive force as described above acts on each of the detection sites A1 to A4 and B1 to B4. Therefore, the first and second capacitive elements C11 and C21 arranged in the first quadrant, and the first and third capacitive elements C13 and C23 arranged in the third quadrant. In any case, since the distance between the displacement electrode and the fixed electrode increases, the capacitance value decreases. On the other hand, the first and second capacitive elements C12 and C22 arranged in the second quadrant, and the first and fourth capacitive elements C14 and C24 arranged in the fourth quadrant, In either case, the distance between the displacement electrode and the fixed electrode decreases, so that the capacitance value increases.

Therefore, the detection circuit 150 measures the moment Mz around the applied Z axis using [Equation 7] below. In [Expression 7], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is around the Z axis measured based on the elastic deformation of the second deformable body 142. Moment.
[Formula 7]
-Mz1 = -C11 + C12-C13 + C14
-Mz2 = -C21 + C22-C23 + C24

  As described above, in the capacitance type force sensor using the basic structure 101w, the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24 having relatively high sensitivity vary. By measuring the force acting on the basis of the quantity, measurement with excellent S / N becomes possible. Of course, you may measure the force which acted based on the variation | change_quantity of the electrostatic capacitance value of the 1-1st-1-4th capacitive elements C11-C14.

  When the direction of the acting moment is reverse (counterclockwise when viewed from the positive direction of the Z axis), the variation amounts of the capacitance values of the capacitive elements C11 to C24 are all reversed. For this reason, the signs of the moments Mz1 and Mz2 measured by [Expression 7] are reversed. That is, the direction and magnitude of the applied moment Mz are measured by [Equation 7].

  Alternatively, when the basic structure 101w is used as a strain gauge type force sensor, the first to 1-2 detection parts A1 to A4 and the 2-1 to 2-4 detection parts B1 to B4 are used. Instead of the capacitive elements C11 to C24 provided in the displacement portions 61d and 62d, specifically, strain gauges R11 to R24 may be arranged instead of the displacement electrodes. In this case, the displacement portions 61d and 62d need to be made of an elastic body.

  Examining fluctuations in the electrical resistance values of the strain gauges R11 to R24 when a clockwise moment -Mz as viewed from the positive direction of the Z-axis acts on such a strain gauge type force sensor is as follows. is there. That is, the tensile force or the compressive force as described above acts on each of the detection sites A1 to A4 and B1 to B4. Therefore, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and the 1-3 strain gauge R13 and the 2-3 strain gauge R23 arranged in the third quadrant. In either case, the electric resistance value is reduced by the action of compressive stress (see FIG. 7C). On the other hand, the 1-2 strain gauge R12 and the 2-2 strain gauge R22 arranged in the second quadrant, and the 1-4 strain gauge R14 and the second-4 strain gauge R24 arranged in the fourth quadrant, In either case, the electrical resistance value is increased by the action of the tensile stress (see FIG. 7B).

Therefore, the detection circuit 150 measures the moment Mz around the applied Z axis using [Equation 8] below. In [Expression 8], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformable body 141, and Mz2 is around the Z axis measured based on the elastic deformation of the second deformable body 142. Moment.
[Formula 8]
-Mz1 = -R11 + R12-R13 + R14
-Mz2 = -R21 + R22-R23 + R24

  As described above, in the strain gauge type force sensor using the basic structure 101w, the fluctuation amount of the electrical resistance value of the first to first to fourth strain gauges R11 to R14 which is relatively high sensitivity is used. By measuring the force acting on the basis, measurement with excellent S / N becomes possible. Of course, the applied force may be measured based on the variation amount of the electrical resistance value of the 2-1st to 2nd-4th strain gauges R21 to R24. In measurement, the Wheatstone bridge circuit (not shown) was constituted by the 1-1 to 1-4 strain gauges R11 to R14 or the 2-1 to 2-4 strain gauges R21 to R24. It is also possible to measure moments.

<2-6. Principle of measurement of force Fx in the X-axis direction and force Fy in the Y-axis direction by a basic structure having a waveform detection portion>
In the above description, the method of measuring the moment Mz around the Z-axis using the basic structure 101w shown in FIG. 20 has been described. However, the force sensor uses the force Fx in the X-axis direction and the force Fy in the Y-axis direction. Can also be measured. As an example, the principle for measuring the force + Fx in the X-axis positive direction will be described with reference to FIG.

  FIG. 23 is a diagram for explaining the forces acting on the detection parts A1 to A4 and B1 to B4 of the deformed body when a force in the X-axis positive direction is applied to the movable portion 120 having the basic structure in FIG. In FIG. 23, a thick black arrow shown parallel to the X axis indicates an acting force + Fx, and a thick black arrow shown in the gap between the first deformable body 141 and the second deformable body 142. The arrow has shown the direction of the force which acts on each detection site | part A1-A4 and B1-B4.

  As shown in FIG. 23, when a force + Fx in the positive direction of the X-axis acts on the movable portion 120 of the basic structure 101w, among the deformable bodies 141 and 142, the first and first detection portions A1 and A1 located in the first quadrant Tensile force acts on the 2-1 detection site B1 and the 1-4 detection site A4 and the 2-4 detection site B4 located in the fourth quadrant. On the other hand, among the deformable bodies 141 and 142, the first and second detection parts A2 and B2 located in the second quadrant, and the first and third detection parts A3 and A3 located in the third quadrant. A compressive force acts on the 2-3 detection part B3. This can be understood from the state of elastic deformation of the deformable body 140 shown in FIGS. For this reason, in the basic structure 101w, the 1-1 detection site A1 and the 2-1 detection site B1 located in the first quadrant, and the 1-4 detection site A4 and the second 2-position located in the fourth quadrant. In 4 detection site | part B4, the displacement parts 61d and 62d displace to the Z-axis positive direction (front side in FIG. 23). On the other hand, in the 1-2 detection part A2 and the 2-2 detection part B2 located in the second quadrant, and the 1-3 detection part A3 and the 2-3 detection part B3 located in the third quadrant, Displacement parts 61d and 62d are displaced in the Z-axis negative direction (the depth direction in FIG. 23).

  In other words, when the basic structure 101w is used as a capacitance-type force sensor, the first-first capacitive element C11 and the second-first capacitive element C21 arranged in the first quadrant, and the fourth quadrant. The first to fourth capacitive elements C14 and the second to fourth capacitive elements C24 that are arranged have a reduced capacitance value. On the other hand, the first and second capacitive elements C12 and C22 arranged in the second quadrant, and the first and third capacitive elements C13 and C23 arranged in the third quadrant, In either case, the capacitance value increases.

Therefore, the detection circuit 150 measures the applied force Fx in the X-axis direction using [Equation 9] below. In [Expression 10], Fx1 is a force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is an X-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 9]
Fx1 = −C11 + C12 + C13−C14
Fx2 = −C21 + C22 + C23−C24

  On the other hand, although not shown, when a force + Fy in the Y-axis positive direction acts on the movable part 120, as will be understood from the state of elastic deformation of the deformable body 140 shown in FIGS. The capacitance value fluctuates. That is, the electrostatic capacitances of the first and second capacitive elements C11 and C21 located in the first quadrant, and the first and second capacitive elements C12 and C22 located in the second quadrant. The first to third capacitive elements C13 and the second to third capacitive elements C23 located in the third quadrant and the first to fourth capacitive elements C14 and the second to fourth capacitive elements located in the fourth quadrant are increased. The capacitance value of C24 decreases.

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using [Equation 10] below. In [Expression 10], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 10]
Fy1 = C11 + C12-C13-C14
Fy2 = C21 + C22-C23-C24

  As described above, in the capacitance type force sensor using the basic structure 101w, the capacitance values of the 2-1 to 2-4 capacitance elements C21 to C24 having relatively high sensitivity vary. By measuring the force acting on the basis of the quantity, measurement with excellent S / N becomes possible. Of course, you may measure the force which acted based on the variation | change_quantity of the electrostatic capacitance value of the 1-1st-1-4th capacitive elements C11-C14.

  Note that when the direction of the acting force is the X-axis negative direction or the Y-axis negative direction, the variation amounts of the capacitance values of the capacitive elements C11 to C24 are all reversed. For this reason, the signs of the forces Fx1 and Fx2 measured by [Equation 9] are reversed. That is, by examining the sign and magnitude of the force Fx obtained by [Equation 9], the direction and magnitude of the applied force are measured. The same applies to the case where the force in the Y-axis direction is measured using [Equation 10].

  On the other hand, if a strain gauge is disposed in each of the displacement portions 61d of the first to first to fourth detection portions A1 to A4, the basic structure 101w can be used as a strain gauge type force sensor. The stress generated in each displacement portion 61d when a force is applied to the basic structure 101w has already been described with reference to FIG. Therefore, according to the force Fx shown in FIG. 23, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 arranged in the first quadrant, and the 1-4 strain gauge arranged in the fourth quadrant. The electrical resistance value of R14 and the 2-4th strain gauge R24 decreases due to the action of compressive stress (see FIG. 7C). On the other hand, the 1-2 strain gauge R12 and the 2-2 strain gauge R22 arranged in the second quadrant, and the 1-3 strain gauge R13 and the 2-3 strain gauge R23 arranged in the third quadrant, The electrical resistance value is increased by the action of the tensile stress (see FIG. 7B).

  Here, the following points need to be observed carefully. That is, in FIG. 7, when compressive stress acts on the deformed body (see FIG. 7B), tensile stress is generated on the surface on the negative side of the X-axis of the displacement portion 61d, as indicated by a thin arrow in the drawing, When a tensile force (see FIG. 7C) acts on the deformable body, a compressive stress is generated on the surface on the X axis negative side of the displacement portion 61d. Therefore, the strain gauges R11 and R21 arranged in the first quadrant of FIG. 22 and the strain gauges R14 and R24 arranged in the fourth quadrant have electric resistance values reduced by the action of compressive stress, and are arranged in the second quadrant. The strain gauges R12 and R22 and the strain gauges R13 and R14 arranged in the third quadrant increase the electric resistance value by the action of the tensile stress.

From this, the detection circuit 150 measures the applied force X in the X-axis direction using the following [Equation 11]. In [Expression 11], Fx1 is a force in the X-axis direction measured based on the elastic deformation of the first deformable body 141, and Fx2 is an X-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 11]
Fx1 = −R11 + R12 + R13−R14
Fx2 = −R21 + R22 + R23−R24

  On the other hand, although not shown, when a positive force + Fy in the Y-axis acts on the movable part 120, as will be understood from the state of elastic deformation of the deformable body 140 shown in FIGS. The resistance value varies. That is, the 1-1 strain gauge R11 and the 2-1 strain gauge R21 located in the first quadrant, and the 1-2 strain gauge R12 and the 2-2 strain gauge R22 located in the second quadrant are tensile. The electrical resistance value is increased by the action of stress (see FIG. 7C). On the other hand, the first-3 strain gauge R13 and the second-3 strain gauge R23 located in the third quadrant, and the first-4 strain gauge R14 and the second-4 strain gauge R24 located in the fourth quadrant, The electric resistance value is reduced by the action of the compressive stress (see FIG. 7B).

Therefore, the detection circuit 150 measures the applied force Fy in the Y-axis direction using the following [Equation 12]. In [Equation 12], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformable body 141, and Fy2 is a Y-axis direction measured based on the elastic deformation of the second deformable body 142. Is the power of
[Formula 12]
Fy1 = R11 + R12-R13-R14
Fy2 = R21 + R22-R23-R24

  In the case of the strain gauge type force sensor as described above, the electrical resistance values of the strain gauges R11 to R14 disposed in the first to first to fourth detection portions A11 to A14 where a relatively large stress is generated. By measuring the force or moment acting on the basis of the fluctuation amount, it is possible to perform highly sensitive measurement excellent in S / N.

<<< §3. Principle of force sensor failure diagnosis according to the present invention >>>
The force sensor using the basic structure 1, 101, 101w according to the present invention can perform failure diagnosis with a single force sensor. Since the deformable bodies 30, 141, 142 of the basic structures 1, 101, 101w have flexibility, metal fatigue occurs due to overload or repeated load. As a result, cracks or the like may occur in the elastic bodies constituting the deformable bodies 30, 141, and 142, and there is a possibility that they will eventually break. For this reason, if the force sensor which can perform a failure diagnosis can be provided, the reliability and safety | security of a force sensor can be improved. The principle of failure diagnosis is also described in, for example, the international application PCT / JP2016 / 75236 by the present applicant.

<3-1. Fault Diagnosis in Capacitive Type Force Sensor>
First, referring back to FIGS. 1 to 4, the principle of failure diagnosis will be described using the basic structure 1 as an example.

  When a repeated load (force -Fy) acts on the basic structure 1 shown in FIGS. 1 to 4, metal fatigue occurs in the first deformable body 31 and the second deformable body 32. When this metal fatigue is accumulated, the strength of the first deformable body 31 and the second deformable body 32 is reduced, and eventually, the deformable bodies 31 and 32 are broken. In general, when metal fatigue accumulates in a metal material, the metal material softens, so that the springs 31 and 32 have a reduced spring constant. In other words, each of the deformable bodies 31 and 32 has increased sensitivity to the force -Fy as compared with the initial state due to accumulation of metal fatigue. This can be understood by comparing FIG. 24 with FIG. In the force sensor 1c, metal fatigue is noticeably manifested in the first deformable body 31 where a relatively large stress is generated. For this reason, the change (decrease) in the spring constant, that is, the increase in sensitivity to the force -Fy is significant in the first deformable body 31.

  FIG. 24 shows the magnitude of the force acting on the force sensor 1c and the first electric signal output from the force sensor 1c when no metal fatigue occurs in the force sensor 1c of FIG. 3 (initial state). FIG. 25 is a graph showing the relationship between T1a and the second electrical signal T2a, and FIG. 25 shows the magnitude of the force acting on the force sensor 1c when metal fatigue occurs in the force sensor 1c of FIG. It is a graph which shows the relationship between the 1st electric signal T1b and the 2nd electric signal T2b output from the said force sensor 1c. The sign at the end of T1 and T2 is for distinguishing between an electric signal in the initial state (added a at the end) and an electric signal in a state where metal fatigue is accumulated (added b at the end). is there. The first electric signals T1a and T1b are electric signals indicating the amount of change in the capacitance value of the first capacitance element C1, and the second electric signals T2a and T2b are capacitance values of the second capacitance element C2. This is an electric signal indicating the amount of fluctuation.

  As understood from FIG. 24, when attention is paid to the first electric signal T1 corresponding to the first capacitor element C1 provided in the first deformable body 31 in which the decrease in spring constant (increase in sensitivity) is relatively large, In the state, the slope (sensitivity) of the straight line of the first electric signal T1a is 0.5. On the other hand, referring to FIG. 25, in a state where metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the first electric signal T1b is 0.75. Therefore, the sensitivity is increased by 50%.

  On the other hand, when attention is paid to the second electric signal T2 corresponding to the second capacitive element C2 provided in the second deformable body 32 in which the decrease in spring constant (increase in sensitivity) is relatively small, as understood from FIG. In the initial state, the slope (sensitivity) of the straight line indicating the second electric signal T2a corresponding to the second capacitive element C2 arranged in the second deformable body 32 is 2.0. On the other hand, as understood from FIG. 25, in the state where the metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the second electric signal T2b corresponding to the second capacitive element C2 is 2.4. Therefore, the increase in sensitivity is only 20%.

  It should be noted here that the first deformation body 31 and the second deformation body 32 are different in the degree of occurrence of metal fatigue. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 0.25, whereas in the state where metal fatigue is accumulated, This means that the ratio (T1b / T2b) between the electric signal T1b and the second electric signal T2b has increased to 0.3125. The ratio T1 / T2 gradually increases from 0.25 to 0.3125 as the repeated load is applied. Therefore, the failure diagnosis of the force sensor 1c is performed by paying attention to the change in the ratio. It is.

  Specifically, the first electric signal T1 and the second electric signal T2 are measured while measuring the force -Fy based on the variation amount of the capacitance value of the second capacitance element C2 arranged in the second deformable body 32. The force sensor 1c functions normally by evaluating whether or not the difference between the ratio of the first electric signal T1a and the ratio of the second electric signal T2a in the initial state is within a predetermined range. It is determined whether or not. Of course, the applied force -Fy may be measured based on the variation amount of the capacitance value of the first capacitive element C1.

<3-2. Fault diagnosis of strain gauge type force sensor>
In the strain gauge type force sensor 1s as well, a new fault diagnosis can be performed in the same manner. That is, although not shown, when a force -Fy in the Y-axis negative direction acts on the force sensor 1s, as described above, both the first strain gauge R1 and the second strain gauge R2 increase in electrical resistance value. . Accordingly, when the electrical resistance value is taken on the vertical axis, the applied Y-axis negative force -Fy is taken on the horizontal axis, and these relations are represented in a graph, a straight line similar to FIGS. 24 and 25 is obtained. However, also in this case, as the force sensor 1s is used, that is, as the metal fatigue accumulates in the deformable bodies 31 and 32, the deformable bodies 31 and 32 soften (spring constant decreases). . Due to this softening, the displacement generated in the detection portions A and B of the deformable bodies 31 and 32 increases, and the stress acting on the strain gauge increases accordingly. Also in the force sensor 1s, the metal fatigue is remarkably exhibited in the first deformable body 31 where a relatively large stress is generated. For this reason, the change (decrease) in the spring constant is significant in the first deformable body 31. In the strain gauge type force sensor 1s, the smaller the spring constant of the deformable body 30, the smaller the stress generated in the deformable body. Therefore, when the spring constant decreases, the sensitivity increases. That is, as the spring constant decreases, each of the elastic bodies 31 and 32 increases in sensitivity to the force -Fy.

  From the above, when the electric signal representing the fluctuation amount of the electric resistance value of the first strain gauge is T1, and the electric signal representing the fluctuation amount of the electric resistance value of the second strain gauge R2 is T2, the first electric signal T1 and the first electric signal The ratio (T1 / T2) to the two electrical signals T2 differs between the initial state and the case where metal fatigue has accumulated. Using this fact, failure diagnosis of the force sensor 1s is performed.

  Hereinafter, the principle for performing failure diagnosis in the force sensor 1 s will be described with reference to FIGS. 26 and 27. FIG. 26 shows the magnitude of the force -Fy in the negative Y-axis direction acting on the force sensor 1s and the force sensor 1s when no metal fatigue occurs in the force sensor 1s of FIG. 4 (initial state). FIG. 27 is a graph showing the relationship between the first electric signal T1a and the second electric signal T2a to be output. FIG. 27 shows the force sensor 1s when metal fatigue occurs in the force sensor 1s of FIG. It is a graph which shows the relationship between the magnitude | size of the force -Fy of the Y-axis negative direction which acts, and the 1st electric signal T1b and the 2nd electric signal T2b output from the said force sensor 1s. The first electric signals T1a and T1b are electric signals indicating the fluctuation amount of the electric resistance value of the first strain gauge R1, and the second electric signals T2a and T2b are fluctuations of the electric resistance value of the second strain gauge R2. It is an electrical signal indicating the quantity. Again, the sign at the end of T1 and T2 is for distinguishing between the electrical signal in the initial state (added a at the end) and the electrical signal in the state where metal fatigue is accumulated (added b at the end). belongs to.

  As can be understood from FIG. 26, when attention is paid to the first electric signal T1 corresponding to the first strain gauge R1 provided in the first deformable body in which the decrease in spring constant (increase in sensitivity) is relatively large, the initial state , The slope (sensitivity) of the straight line of the first electric signal T1a is 2.0. On the other hand, referring to FIG. 27, in a state where metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the first electric signal T1b is 2.8. Therefore, the sensitivity is increased by 40%.

  On the other hand, when attention is paid to the second electric signal T2 corresponding to the second strain gauge R2 provided in the second deformable body 32 in which the decrease in spring constant (increase in sensitivity) is relatively small, as understood from FIG. In the initial state, the slope (sensitivity) of the straight line indicating the second electric signal T2a is 0.5. On the other hand, as understood from FIG. 27, in the state where the metal fatigue is accumulated, the slope (sensitivity) of the straight line indicating the second electric signal T2b corresponding to the second strain gauge R2 is 0.6. Therefore, the increase in sensitivity is only 20%.

  It should be noted here that the first deformation body 31 and the second deformation body 32 are different in the degree of occurrence of metal fatigue. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 4.0, but in the state where metal fatigue is accumulated, That is, the ratio (T1b / T2b) between the electric signal T1b and the second electric signal T2b is increased to 4.667. The ratio T1 / T2 gradually increases from 4.0 to 4.667 as a repeated load is applied. Therefore, the failure diagnosis of the force sensor 1s is performed by paying attention to the change in the ratio. It is.

  Specifically, the force -Fy is measured based on the fluctuation amount of the electric resistance value of the first strain gauge R1 disposed in the first deformable body 31, and the first electric signal T1 and the second electric signal T2 are measured. By evaluating whether or not the difference between the ratio and the ratio between the first electric signal T1a and the second electric signal T2a in the initial state is within a predetermined range, the force sensor 1s functions normally. It is determined whether or not there is. Of course, the applied force -Fy may be measured based on the amount of change in the electrical resistance value of the second strain gauge R2.

<3-3. Fault diagnosis of other force sensors>
(3-3-1. In the case of the force sensor 101c shown in FIG. 11)
The failure diagnosis as described above can also be employed in failure diagnosis in the capacitance type force sensor 101c of FIG.

As an example, a description will be given of a method for performing failure diagnosis using a clockwise moment -Mz (the same moment as in FIG. 9) acting on the force receiving body 120 of the force sensor 101c. First, the electrical signals corresponding to -Mz1 and -Mz2 in [Expression 1] described above are set as a first electrical signal T1 and a second electrical signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written, the following [Equation 13] is obtained.
[Formula 13]
T1 = −C11 + C12−C13 + C14
T2 = −C21 + C22−C23 + C24

  Also in the force sensor 101c shown in FIG. 11, the ratio between the first electric signal T1 and the second electric signal T2 changes as the metal fatigue accumulates in the first deformation body 141 and the second deformation body 142. The fault diagnosis of the force sensor is performed using this fact. Therefore, here again, in the following description, the first and second electrical signals in the initial state in which metal fatigue has not accumulated in the first deformable body 141 and the second deformable body 142 are denoted as T1a and T2a, respectively. The first and second electrical signals in a state where metal fatigue is accumulated in the deformable body 141 and the second deformable body 142 are distinguished from each other as T1b and T2b, respectively.

  In an initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor 101c and the first and second electric signals T1a and T2a at this time Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor and the first and second electric signals T1a, T2a at this time Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101c is functioning normally are described in 3-1. Is the same. That is, 3-1. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 13] with [Equation 13], the principle and method of failure diagnosis of the force sensor 101c can be understood. For this reason, detailed description of the principle and method is omitted here. Even if the reverse moment + Mz acts, failure diagnosis can be performed in the same manner.

It is also possible to perform failure diagnosis using the force Fx in the X-axis direction acting on the force receiving body 120. In this case, the electrical signals corresponding to Fx1 and Fx2 in [Expression 3] described above may be the first electrical signal T1 and the second electrical signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written, the following [Equation 14] is obtained.
[Formula 14]
T1 = −C11 + C12 + C13−C14
T2 = −C21 + C22 + C23−C24

  Here again, in the following description, the first and second electric signals in the initial state in which metal fatigue has not accumulated in the first deformable body 141 and the second deformable body 142 are denoted as T1a and T2a, respectively. The first and second electric signals in a state where metal fatigue is accumulated in 141 and the second deformable body 142 are distinguished from each other as T1b and T2b, respectively.

  In the initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101c and the first and second electric signals T1a and T2a at this time Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101c and the first and second electric signals T1a, T2a at this time Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101c is functioning normally are described in 3-1. Is the same. That is, 3-1. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 14], the principle and method of failure diagnosis of the force sensor 101c can be understood. For this reason, detailed description of the principle and method is omitted here.

  Further, failure diagnosis of the force sensor 101c can be performed using the force Fy in the Y-axis direction acting on the force receiving body 120. In this case, the electrical signals corresponding to Fy1 and Fy2 in [Expression 4] described above may be the first electrical signal T1 and the second electrical signal T2. In the initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor 101c and the first and second electric signals T1a, T2a at this time Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor and the first and second electric signals T1a and T2a at this time Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101c is functioning normally are the same as in the case of diagnosing a failure based on the force Fx, and therefore a detailed description thereof is omitted here.

(3-3-2. In the case of the force sensor 101s shown in FIG. 12)
Next, the failure diagnosis as described above can also be employed in failure diagnosis in the strain gauge type force sensor 101s shown in FIG.

As an example, a description will be given of a method for performing failure diagnosis using a clockwise moment -Mz (the same moment as in FIG. 9) acting on the force receiving body 120 of the force sensor 101s. First, the electrical signals corresponding to -Mz1 and -Mz2 in [Expression 2] described above are set as a first electrical signal T1 and a second electrical signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written, the following [Equation 15] is obtained.
[Formula 15]
T1 = −R11 + R12−R13 + R14
T2 = −R21 + R22−R23 + R24

  Also in the force sensor 101s shown in FIG. 12, the ratio between the first electric signal T1 and the second electric signal T2 changes as the metal fatigue accumulates in the first deformation body 141 and the second deformation body 142. The fault diagnosis of the force sensor is performed using this fact. Therefore, here again, in the following description, the first and second electrical signals in the initial state in which metal fatigue has not accumulated in the first deformable body 141 and the second deformable body 142 are denoted as T1a and T2a, respectively. The first and second electrical signals in a state where metal fatigue is accumulated in the deformable body 141 and the second deformable body 142 are distinguished from each other as T1b and T2b, respectively.

  In an initial state in which no metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor 101s and the first and second electric signals T1a and T2a at this time Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the moment -Mz acting on the force sensor 101s and the first and second electric signals T1a at this time, The relationship with T2a is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101s is functioning normally are described in 3-2. Is the same. That is, 3-2. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 15], the principle and method of failure diagnosis of the force sensor 101s can be understood. For this reason, detailed description of the principle and method is omitted here. Of course, even if the reverse moment + Mz is applied, failure diagnosis can be performed in the same manner.

It is also possible to perform failure diagnosis using the force Fx in the X-axis direction acting on the force receiving body 120. In this case, the electrical signals corresponding to Fx1 and Fx2 in [Expression 5] described above may be the first electrical signal T1 and the second electrical signal T2. That is, when the first electric signal T1 and the second electric signal T2 are newly written, the following [Equation 16] is obtained.
[Formula 16]
T1 = −R11 + R12 + R13−R14
T2 = −R21 + R22 + R23−R24

  Here again, in the following description, the first and second electric signals in the initial state in which metal fatigue has not accumulated in the first deformable body 141 and the second deformable body 142 are denoted as T1a and T2a, respectively. The first and second electric signals in a state where metal fatigue is accumulated in 141 and the second deformable body 142 are distinguished from each other as T1b and T2b, respectively.

  In the initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101s and the first and second electric signals T1a and T2a at this time Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fx acting on the force sensor 101s and the first and second electric signals T1a, T2a at this time Is the same as the graph shown in FIG.

  The principle and method for determining whether or not the force sensor 101s is functioning normally are described in 3-2. Is the same. That is, 3-2. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 16] with [Equation 16], the principle and method of failure diagnosis of the force sensor according to the present embodiment can be understood. The For this reason, detailed description of the principle and method is omitted here.

  Further, failure diagnosis can be performed using the force Fy in the Y-axis direction acting on the force receiving member 120. In this case, the electrical signals corresponding to Fy1 and Fy2 in [Expression 6] described above may be the first electrical signal T1 and the second electrical signal T2. In the initial state where metal fatigue is not accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor 101s and the first and second electric signals T1a and T2a at this time Is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformable body 141 and the second deformable body 142, the magnitude of the force Fy acting on the force sensor 101s and the first and second electric signals T1a, T2a at this time Is the same as the graph shown in FIG.

  Since the principle and method for determining whether or not the force sensor 101s is functioning normally are the same as in the case of performing a failure diagnosis based on the force Fx, detailed description thereof is omitted here.

(3-3-3. Force Sensor Using Basic Structures 101a, 101b, and 101b ′ shown in FIGS. 13 to 15)
Next, failure diagnosis in a capacitance type force sensor using the basic structure 101a shown in FIG. 13 will be described. Although this force sensor is not shown in the drawing, eight parts (first to first to fourth detection parts A1 to A4 and second to 2-1) located on the V-axis and the W-axis of the force sensor. In addition, it is assumed that capacitive elements C11 to C24 are arranged in all of the second to fourth detection sites B1 to B4). It is assumed that the separation distances of the electrodes constituting the capacitive elements C11 to C24 are all the same, and the effective opposing areas are all the same.

  The principle and method of failure diagnosis in such a force sensor are described in 3-3-1. This is substantially the same as the case of the capacitance type force sensor 101c shown in FIG. However, the 2-1 to 2-4 capacitive elements C21 to C24 are disposed on the thin portions 142t1 to 142t4 of the second deformable body 142. Therefore, a graph showing the relationship between the applied force (Fx, Fy) or moment (Mz) and the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) is shown in FIG. And both of the slopes of the second electric signals T2a and T2b shown in FIG. However, the ratio of the slopes is the same.

  From this, in the initial state, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a is 0.25, and the first electric signal T1b and the second electric signal T1a in the state where metal fatigue is accumulated. The ratio (T1b / T2b) to 2 electrical signals T2b is 0.3125.

  Next, failure diagnosis in a capacitance type force sensor using the basic structures 101b and 101b 'shown in FIGS. 14 and 15 will be described. Also in these force sensors, although not shown, eight parts (first to 1-4 detection parts A1 to A4 and second parts) located on the V axis and the W axis among the force sensors. It is assumed that the capacitive elements C11 to C24 are arranged in all of the (-1 to 2-4th detection sites B1 to B4). Furthermore, it is assumed that the separation distances of the electrodes constituting the capacitive elements C11 to C24 are all the same, and the effective opposing areas are all the same.

  As described above, these force sensors are the same as the force sensor using the basic structure 101a shown in FIG. 13, and the second to second to fourth capacitive elements C21 to C24 are arranged in the second. Since the thin portions 142t1 to 142t4 are provided only on the deformable body 142, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a in the initial state and metal fatigue are accumulated. The ratio (T1b / T2b) between the first electric signal T1b and the second electric signal T2b in the state is the same value as that of the force sensor using the basic structure 101a shown in FIG. In other words, the capacitance type force sensor using the basic structures 101b and 101b ′ shown in FIGS. 14 and 15 has the same characteristics as the capacitance type force sensor using the basic structure 101a. is doing. Therefore, even in these force sensors, the principle and method of failure diagnosis are described in 3-3-1. This is substantially the same as the case of the force sensor 101c shown in FIG.

  Next, failure diagnosis in a strain gauge type force sensor using the basic structure 101a shown in FIG. 13 will be described. In this force sensor, although not shown in the drawing, eight parts (first to 1-4 detection parts A1 to A4 and second to second parts) located on the V-axis and the W-axis of the force sensor. It is assumed that strain gauges R11 to R24 are arranged in all of the first to second to fourth detection sites B1 to B4). Furthermore, all the strain gauges R11 to R24 have the same characteristics.

  The principle and method of failure diagnosis in such a force sensor are described in 3-3-2. This is substantially the same as the case of the force sensor 101s shown in FIG. However, the 2-1 to 2-4 strain gauges R21 to R24 are disposed on the thin portions 142t1 to 142t4 of the second deformable body 142. Therefore, a graph showing the relationship between the applied force (Fx, Fy) or moment (Mz) and the first electric signal (T1a, T1b) and the second electric signal T2 (T2a, T2b) is shown in FIG. Both the slopes of the second electric signals T2a and T2b shown in FIG. 27 are larger. However, the ratio of the slopes is the same. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 4.0, and the first electric signal T1b and the second electric signal are accumulated in a state where metal fatigue is accumulated. The ratio (T1b / T2b) to the signal T2b is 4.667.

  Next, failure diagnosis in a strain gauge type force sensor using the basic structures 101b and 101b 'shown in FIGS. 14 and 15 will be described. Also in these force sensors, although not shown, eight parts (first to 1-4 detection parts A1 to A4 and second parts) located on the V axis and the W axis among the force sensors. The strain gauges R11 to R24 are arranged in all of the -1 to the second to fourth detection sites B1 to B4). Further, all the strain gauges R11 to R24 have the same characteristics.

  As described above, these force sensors also have second to second strain gauges R11 to R24 arranged in the same manner as the force sensor using the basic structure 101a shown in FIG. Since the thin portions 142t1 to 142t4 are provided only on the deformable body 142, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a in the initial state and metal fatigue are accumulated. The ratio (T1b / T2b) between the first electric signal T1b and the second electric signal T2b in the state is the same value as that of the force sensor using the basic structure 101a shown in FIG. In other words, the strain gauge type force sensor using the basic structures 101b and 101b ′ shown in FIGS. 14 and 15 has the same characteristics as the strain gauge type force sensor using the basic structure 101a. Yes. Accordingly, even in these force sensors, the principle and method of failure diagnosis are described in 3-3-2. This is substantially the same as the case of the force sensor 101s shown in FIG.

<<< §4. Further modification of detection part >>>
Next, FIG. 28 is a schematic side view showing a modification of the detection site of the basic structure in each of the above embodiments. As shown in FIG. 28, the detection part E according to the present modification example has a first connection part 71 and a second connection part 72 arranged so as to be relatively movable in one axis direction (Y-axis direction in FIG. 28). Arranged between. The detection portion E is made of an elastic material (for example, metal) with a uniform thickness and has an arcuate shape that is smoothly curved so as to swell in the negative X-axis direction (right side in FIG. 29). ing. As shown in FIG. 29, when the detection part E considers a virtual axis L parallel to the X axis so as to pass through the part located on the most negative side (right side) of the X axis, Symmetric with respect to the virtual axis.

  Next, the operation of such a detection site E will be described with reference to FIG. FIG. 29A is a schematic diagram illustrating the detection site E when a compressive force in the Y-axis direction is applied to the detection site E illustrated in FIG. 28, and FIG. 29B is a detection illustrated in FIG. It is the schematic which shows the said detection part E when the tensile force of the Y-axis direction acts on the part E. FIG. As will be described later, a detection element (capacitance element or strain gauge) is disposed at a position R on the negative side of the X axis in a region where the detection region E intersects the virtual axis L. Therefore, here, the displacement of the position R or the stress generated at the position R will be described in detail. It is assumed that no stress is generated on the surface of the detection site E in the initial state. In FIG. 29, the thick black arrow indicates the direction of the force acting along the Y-axis direction, and the white thick arrow arranged in parallel with the X-axis is the largest of the detection sites E. The direction of displacement generated at the position R on the X-axis negative side is shown, and the thin arrow indicates the stress generated at the position R (“→ ←” is compressive stress, “← →” is tensile stress).

  First, as shown in FIG. 29 (a), when the first connecting portion 71 is relatively moved along the Y-axis direction so as to approach the second connecting portion 72, the detection site E is moved in the Y-axis direction. Compressed. Thereby, the position R is displaced in the negative direction of the X axis. Further, at this time, since the radius of curvature near the position R becomes small, a tensile stress is generated at the position R along the Y-axis direction. On the other hand, as shown in FIG. 29B, when the first connecting portion 71 is relatively moved along the Y-axis direction so as to be separated from the second connecting portion 72, the detection site E is moved in the Y-axis direction. Stretched. Thereby, the position R is displaced in the positive direction of the X axis.

  Further, the stress generated at the position R when a force is applied to the detection site E will be examined. As shown in FIG. 29 (a), when a compressive force is applied between the first connecting portion 71 and the second connecting portion 72, the radius of curvature near the position R decreases, so that the position R has a Y-axis direction. A tensile stress is generated along. On the other hand, as shown in FIG. 29 (b), when a tensile force acts between the first connection portion 71 and the second connection portion 72, the radius of curvature near the position R increases. A compressive stress is generated along the direction. Eventually, the direction of the force acting on the detection site E (compression or tension) and the direction of the stress generated at the position R (compression or tension) are opposite to each other. Of the parts where the detection part E intersects the virtual axis L, the direction of the stress (compression or tension) generated at the position R ′ on the positive side of the X axis is the deformation of FIG. 29 (a) and FIG. 29 (b). As understood from the embodiment, the direction of the force acting on the detection site E (compression or tension) is the same.

  When such a detection site is employed in the basic structure 1 shown in FIG. 1, the first deformable body 31 is replaced with the first movable portion side connection portion 31m and the first fixed portion side connection portion 31f described above. The detected part E is disposed as the first detection part E1, and the detection part E described above is provided between the second movable part side connection part 32m and the second fixed part side connection part 32f instead of the second deformable body 32. What is necessary is just to arrange | position as 2 detection site | part E2. However, the second detection site E2 is configured to have a larger radius of curvature than the first detection site E1. Thus, the spring constant of the second detection site E2 is set smaller than the spring constant of the first detection site E1.

  Alternatively, when such a detection site is employed in the basic structure 101 having the annular deformable bodies 141 and 142 shown in FIG. 8, the first to first to fourth detection sites A1 to A4 and the second to 2-1 The detection site E described above may be arranged at positions corresponding to the second to fourth detection sites B1 to B4. That is, gaps are provided along the circumferential direction at eight positions corresponding to the first to first to fourth detection sites A1 to A4 and the second to second to second detection sites B1 to B4. The detection site E shown in FIG. However, the second detection site E2, which is the four detection sites E arranged in the 2-1 to 2-4 detection sites B1 to B4, is arranged in the first to 1-4 detection sites A1 to A4. It is configured to have a larger radius of curvature than the first detection site E1, which is the four detection sites E. Thus, the spring constant of the second detection site E2 is set smaller than the spring constant of the first detection site E1. The four detection sites E of the first detection site E1 may have the same configuration, and the four detection sites E of the second detection site E2 may have the same configuration.

  A specific arrangement example will be described with reference to FIGS. 30 and 31. FIG. FIG. 30 is a schematic top view showing an example of a deformed body having the detection site shown in FIG. FIG. 31 (a) is a schematic top view showing another example of the deformed body having the detection site shown in FIG. 28, and FIG. 31 (b) is a cross-sectional view taken along the line bb of FIG. 31 (a). It is. Since the detection site may be provided in a form common to the first deformable body 141 and the second deformable body 142, the first deformable body 141 is representative of the two deformable bodies 141 and 142 in FIGS. 30 and 31. Only shown.

  In the first deformable body 141 shown in FIG. 30, a region including a position overlapping with the V axis and the W axis when viewed from the Z-axis direction is replaced with a detection site E1 shown in FIG. Here, each detection site | part E1 is formed in the aspect in which the circle | round | yen which provides the circular arc of the said detection site | part E1 exists in parallel with XY plane. Each detection part E1 is arrange | positioned so that it may protrude on the radial direction outer side.

  When force or moment is applied to the first deformable body 141 having such a detection site E1, the detection site E1 receives a compressive force or a tensile force in the circumferential direction of the first deformable body. For this reason, as described above, a portion of the detection portion E1 that overlaps the V-axis and the W-axis is displaced along the radial direction of the first deformable body 141 (along the V-axis direction or the W-axis direction). Further, compressive stress or tensile stress is generated in the portion.

  On the other hand, the first deformable body 141 shown in FIG. 31A is similar to the first deformable body 141 shown in FIG. 30 in that the region including the position overlapping the V axis and the W axis when viewed from the Z axis direction is shown in FIG. Although it is substituted with the detection site E1 shown, the arrangement is different from that in FIG. That is, as shown in FIG. 31B, in the first deformable body 141 in FIG. 31A, the detection sites E1 arranged in the first quadrant and the third quadrant provide arcs of these detection sites E1. The detection part E1 arranged in the second quadrant and the fourth quadrant has a circle that provides an arc of the detection part E1 in the VZ plane. Are formed in such a manner that they exist in parallel with each other.

  When force or moment is applied to the first deformable body 141 having such a detection site E1, the detection site E1 receives a compressive force or a tensile force in the circumferential direction of the first deformable body. For this reason, as described above, a portion of the detection portion E1 that overlaps with the V-axis and the W-axis is displaced along the Z-axis direction (along the V-axis direction or the W-axis direction). Further, compressive stress or tensile stress is generated in the portion.

  32 is a schematic diagram showing the detection site E of FIG. 28 in which the capacitive element C is arranged. As an example, as shown in FIG. 32, the capacitive element C has a displacement electrode Em disposed at a position R via a displacement substrate Im (insulator), and a fixed substrate If (insulation) at a position facing the displacement electrode Em. The fixed electrode Ef that does not move in the XYZ three-dimensional coordinate system can be arranged via the body). Of course, the detection site E having the capacitive element C can be employed in both the force sensor using the basic structure 1 shown in FIG. 1 and the force sensor using the annular basic structure 101 shown in FIG. Note that the position R is a position that is displaced most in the X-axis direction by the force (compression force and tensile force) acting on the detection site E among the detection sites E. For this reason, if the capacitive element C is comprised in the position R, the force or moment which acted with the highest sensitivity can be measured.

  When a compressive force is applied to the detection site E shown in FIG. 32, the position R moves in the negative direction of the X axis as described above (see FIG. 29A). For this reason, the distance between the displacement electrode Em and the fixed electrode Ef decreases, and the capacitance value of the capacitive element C increases. On the other hand, when a tensile force acts on the detection site E shown in FIG. 32, the position R moves in the positive direction of the X axis as described above (see FIG. 29B). For this reason, the separation distance between the displacement electrode Em and the fixed electrode Ef increases, and the capacitance value of the capacitive element C decreases. After all, the detection parts of the force sensors 1c and 101c shown in FIGS. 3 and 11 and the force sensor using the basic structures 1w and 101w shown in FIGS. 5 and 20 are replaced with the detection parts E shown in FIG. Even if a new force sensor is configured, the new force sensor exhibits the same behavior (output characteristics) as when a force or moment is applied to each force sensor before replacement. It will be.

  As shown in FIG. 32, if the fixed substrate 73 is disposed on the same plane as the fixed portion 110, the fixed electrodes E (four) facing the four displacement electrodes Em of the first deformable body 141 and the second deformation This is advantageous because a total of eight fixed electrodes, including the fixed electrodes (four) opposed to the four displacement electrodes Em of the body, can be constituted by a single substrate (fixed substrate 73).

  FIG. 33 is a schematic diagram showing the detection site E of FIG. 28 in which the strain gauge R is arranged. The strain gauge may be disposed at the position R as an example. Such a detection site E can be employed in the basic structure 1 shown in FIG. 1 or in the annular basic structure 101 shown in FIG. The position R is a position where the greatest stress is applied by the force (compression force and tensile force) acting on the detection part E among the detection parts E. For this reason, if the strain gauge R is arranged at the position R, the force or moment acting with the highest sensitivity can be measured.

  When a compressive force is applied to the detection site E shown in FIG. 33, as described above, a tensile stress is applied to the position R (see FIG. 29A). For this reason, the electrical resistance value of the strain gauge R increases. On the other hand, when a tensile force acts on the detection site E shown in FIG. 33, a compressive stress acts on the position R as described above. (See FIG. 29 (b)). For this reason, the electrical resistance value of the strain gauge R decreases. After all, the detection parts of the force sensor using the force sensors 1s and 101s shown in FIGS. 4 and 12 and the basic structure 1w and 101w shown in FIGS. 5 and 20 are replaced with the detection parts E shown in FIG. Even if a new force sensor is configured, the new force sensor exhibits the same behavior (output characteristics) as when a force or moment is applied to each force sensor before replacement. It will be.

<<< §5. A device to keep the effective facing area between electrode plates constant in a capacitance-type force sensor >>>
In the capacitance type force sensor, even when the relative position of the displacement electrode with respect to the fixed electrode changes as a result of the force in each axial direction or the moment around each axis acting, the pair constituting the capacitive element It is also conceivable that one area of the fixed electrode and the displacement electrode constituting each capacitive element is set to be larger than the other area so that the effective opposing area of each electrode does not change. This is a case where an orthographic projection image is formed by projecting the contour of an electrode having a smaller area (for example, a displacement electrode) onto the surface of the electrode having a larger area (for example, a fixed electrode) in the normal direction of the electrode. The projection image of the electrode having the smaller area is completely included in the surface of the electrode having the larger area. If this state is maintained, the effective area of the capacitive element constituted by both electrodes becomes equal to the area of the smaller electrode and is always constant. That is, the force detection accuracy can be improved.

  Among the embodiments described so far, the force sensor 1c shown in FIG. 3, the force sensor 101s shown in FIG. 11, and the structure shown in FIG. 19 are fixed as shown in the respective drawings. The area of the electrode is larger than the area of the displacement electrode.

DESCRIPTION OF SYMBOLS 1 Basic structure 1c Capacitance type force sensor 1s Strain gauge type force sensor 1w Basic structure 10 Fixed part 20 Movable part 30 Deformed body 31 Deformed body 31e First elastic body 31f First fixed part side connection part 31m 1st movable part side connection part 32 2nd deformation body 32e 2nd elastic body 32f 2nd fixed part side connection part 32m 2nd movable part side connection part 40 Detection circuit 61d 1st displacement part 61e1, 61e2 A pair of 1st deformation | transformation Part 61f, 61m Connection part 62d Second displacement part 62e1, 62e2 A pair of second deformation parts 62f, 62m Connection part 71 First connection part 72 Second connection part 73 Fixed substrate 101 Basic structure 101a Basic structure 101b Basic structure 101c Electrostatic Capacitive type force sensor 101s Strain gauge type force sensor 101w Basic structure 110 Fixed part 120 Movable part 131 Linked body 131l Linked body 1 2 connector 132a, 132b, 132c, 132d connector 133 connector 134, 134a, 134b connector 135 connector 135l connector 136, 136a, 136b connector 137 connector 138, 138a, 138b connector 140 variant 141 first 1 deformation body 142 2nd deformation body 142t1, 142t2, 142t3, 142t4 thin part 142b, 142b1, 142b2, 142b3, 142b4 deformation body 150 detection circuit

Claims (7)

A force sensor for detecting a moment about the Z axis in an XYZ three-dimensional coordinate system, which is fixed on the XY plane and has a fixed body centered on the origin when viewed from the positive direction of the Z axis;
An annular force receiving body arranged concentrically with the fixed body as viewed from the positive direction of the Z axis and moving relative to the fixed body by the action of a moment around the Z axis;
An elastic deformation body having one end supported by the fixed body and the other end supported by the force receiving body;
A capacitive element having a displacement electrode disposed on the elastic deformation body and a fixed electrode facing the displacement electrode;
A detection circuit that outputs an electrical signal indicating a moment around the Z-axis acting on the force receiving member based on a change in capacitance value of the capacitive element;
With
The elastic deformable body includes an arc-shaped deformable body having one end and the other end, a first connecting body that connects the one end of the arc-shaped deformable body to the fixed body, and the other end of the arc-shaped deformable body. A second coupling body coupled to the force receiving body,
The arcuate deformable body, the thin wall thickness than the first connecting member, and the thick than the second coupling body is rather thin,
As the elastic deformation body,
A first elastic deformation body arranged in the first quadrant of the XY plane as viewed from the Z-axis direction;
A second elastic deformation body arranged in the second quadrant of the XY plane as viewed from the Z-axis direction;
A third elastic deformation body arranged in the third quadrant of the XY plane as viewed from the Z-axis direction;
A fourth elastic deformation body disposed in the fourth quadrant of the XY plane as viewed from the Z-axis direction;
With
The first elastic deformation body and the second elastic deformation body are arranged symmetrically with respect to the Y axis,
The third elastic deformation body and the fourth elastic deformation body are arranged symmetrically with respect to the Y axis,
The first elastic deformation body and the fourth elastic deformation body are arranged symmetrically with respect to the X axis,
The second elastic deformation body and the third elastic deformation body are arranged symmetrically with respect to the X axis,
The first connection body of the first elastic deformation body, the first connection body of the second elastic deformation body, the first connection body of the third elastic deformation body, and the fourth connection body. The first connecting body of the elastically deformable body extends parallel to the Y axis; and
The second coupling body of the first elastic deformation body, the second coupling body of the second elastic deformation body, the second coupling body of the third elastic deformation body, and the fourth The force sensor according to claim 2, wherein the second connecting body of the elastically deformable body extends in parallel with the X axis . The fixed body and the force receiving body extend along the X axis between the second coupling body of the first elastic deformation body and the second coupling body of the fourth elastic deformation body. A connecting body for connecting,
The fixed body and the force receiving body extend along the X axis between the second coupling body of the second elastic deformation body and the second coupling body of the third elastic deformation body. A connecting body for connecting,
The force sensor according to claim 1 , further comprising: A force sensor for detecting a moment around the Z axis in an XYZ three-dimensional coordinate system, A fixed body fixed on the XY plane and centered on the origin when viewed from the positive direction of the Z axis;
An annular force receiving body arranged concentrically with the fixed body as viewed from the positive direction of the Z axis and moving relative to the fixed body by the action of a moment around the Z axis;
An elastic deformation body having one end supported by the fixed body and the other end supported by the force receiving body;
A capacitive element having a displacement electrode disposed on the elastic deformation body and a fixed electrode facing the displacement electrode;
A detection circuit that outputs an electrical signal indicating a moment around the Z-axis acting on the force receiving member based on a change in capacitance value of the capacitive element;
With
The elastic deformable body includes an arc-shaped deformable body having one end and the other end, a first connecting body that connects the one end of the arc-shaped deformable body to the fixed body, and the other end of the arc-shaped deformable body. A second coupling body coupled to the force receiving body,
The arcuate deformed body is thinner than the first connected body and thinner than the second connected body,
As the elastic deformation body,
A first elastic deformation body arranged in the first quadrant of the XY plane as viewed from the Z-axis direction;
A second elastic deformation body arranged in the second quadrant of the XY plane as viewed from the Z-axis direction;
A third elastic deformation body arranged in the third quadrant of the XY plane as viewed from the Z-axis direction;
A fourth elastic deformation body arranged in the fourth quadrant of the XY plane as viewed from the Z-axis direction;
With
The first elastic deformation body and the second elastic deformation body are arranged symmetrically with respect to the Y axis,
The third elastic deformation body and the fourth elastic deformation body are arranged symmetrically with respect to the Y axis,
The first elastic deformation body and the fourth elastic deformation body are arranged symmetrically with respect to the X axis,
The second elastic deformation body and the third elastic deformation body are arranged symmetrically with respect to the X axis,
The fixed body and the force receiving body extend along the X axis between the second coupling body of the first elastic deformation body and the second coupling body of the fourth elastic deformation body. A connecting body for connecting,
The fixed body and the force receiving body extend along the X axis between the second coupling body of the second elastic deformation body and the second coupling body of the third elastic deformation body. A connecting body for connecting,
A force sensor further comprising: The first connection body of the first elastic deformation body, the first connection body of the second elastic deformation body, the first connection body of the third elastic deformation body, and the fourth connection body. The first connecting body of the elastically deformable body extends parallel to the Y axis; and
The second coupling body of the first elastic deformation body, the second coupling body of the second elastic deformation body, the second coupling body of the third elastic deformation body, and the fourth The force sensor according to claim 3, wherein the second connecting body of the elastically deformable body extends in parallel with the X axis.   The force sensor according to any one of claims 1 to 4, further comprising an electrical wiring extending from the force receiving body and connected to the detection circuit.   The force sensor according to claim 5, wherein the electrical wiring extends from an outer peripheral surface of the force receiving body.   The fixed body includes a fixed portion centered on the origin of an XYZ three-dimensional coordinate system, an annular deformable body arranged so as to surround the fixed portion, and a connecting body that connects the fixed portion and the annular deformable body. The force sensor according to claim 1, wherein the force sensor is provided.

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