JP6771797B2 - 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 electric signal.

For example, Patent Document 1 describes a force sensor having a function of outputting a force acting along a predetermined axial direction and a moment acting around a predetermined rotation axis as an electric signal, and the force of an industrial robot. Widely used for control. In recent years, it has also been adopted for life support robots. Under these circumstances, the magnitude of the force or moment to be detected is wide-ranging, and the 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 fluctuation amount of a capacitance value of a capacitance element, or a force based on a fluctuation amount of an electric resistance value of a strain gauge. Or a strain gauge type force sensor that detects moments is used. Therefore, regardless of whether it is configured as a capacitance type or a strain gauge type, it is convenient if a force sensor capable of detecting a force or a moment with high accuracy and high sensitivity can be provided.

Japanese Unexamined Patent Publication No. 2004-354049

The present invention has been devised in view of the above circumstances. That is, an object of the present invention is to provide a force sensor capable of detecting a force or a 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 that detects a force in the uniaxial direction.
Fixed part and
A movable part that moves relative to the fixed part by the action of force,
A deformed body which is connected to the fixed portion and the movable portion and elastically deforms in a direction non-parallel to the uniaxial direction when the movable portion moves relative to the fixed portion.
A detection circuit that outputs an electric signal indicating a force acting on the movable portion based on the elastic deformation generated in the deformed body is provided.
The modified body includes a first detection site having a first spring constant and a second detection site having a second spring constant different from the first spring constant.
The detection circuit is a force sensor characterized in that it outputs an electric signal based on elastic deformation that occurs in at least one of the first detection portion and the second detection portion.

According to the present invention, by arranging the capacitive element at the detection site where the spring constant is relatively small, that is, the detection site where relatively large elastic deformation occurs, the force sensor capable of detecting the force with high accuracy and high sensitivity. A sensor can be provided. Furthermore, by arranging the strain gauge at the detection site where the spring constant is relatively large, that is, the detection site where the stress generated due to elastic deformation is relatively large, the force capable of detecting the force with high accuracy and high sensitivity. A sensory sensor can be provided. From the above, according to the present invention, it is possible to provide a force sensor capable of detecting 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 portion and the second detection portion may be arranged in parallel between the movable portion and the fixed portion. In this case, since the first detection portion and the second detection portion can be greatly deformed, the acting force can be detected with higher accuracy and higher sensitivity.

The first detection site 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 the first detection portion and the second detection portion can be displaced in the direction orthogonal to the applied force, the force can be easily measured.

The above force sensor can be configured as a capacitance type. That is, the force sensor includes displacement electrodes arranged at at least one of the first detection portion and the second detection portion.
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion is further provided.
The displacement electrode and the fixed electrode form a capacitive element, and the displacement electrode and the fixed electrode form a capacitive element.
The detection circuit may output an electric signal indicating a force acting on the movable portion based on the amount of fluctuation of the capacitance value of the capacitance 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 at at least one of the first detection portion and the second detection portion.
The detection circuit may output an electric signal indicating a force acting on the movable portion based on the amount of fluctuation of the electric resistance value of the strain gauge.

Further, the first detection portion has a first displacement portion and a pair of first deformation portions provided on both sides of the first displacement portion and connected to the fixed portion and the movable portion, respectively.
The second detection portion may have a second displacement portion and a pair of second deformation portions provided on both sides of the second displacement portion and connected to the fixed portion and the movable portion, respectively. ..

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

In the force sensor having such a first detection portion and a second detection portion, it is easy to provide a highly accurate and highly sensitive capacitance type force sensor. That is, the displacement electrodes arranged at 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 arranged to face the displacement electrode and does not move relative to the fixed portion is further provided.
The displacement electrode and the fixed electrode form a capacitive element, and the displacement electrode and the fixed electrode form a capacitive element.
The detection circuit may output an electric signal indicating the uniaxial force acting on the movable portion based on the amount of fluctuation of the capacitance value of the capacitance element.

Of course, it is also possible to configure a force sensor having such a first detection portion and a second detection portion 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 arranged on the surface thereof.
The detection circuit may output an electric signal indicating the uniaxial force acting on the movable portion based on the amount of fluctuation of the electric 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 the XYZ three-dimensional coordinate system.
A fixed part fixed to the XYZ three-dimensional coordinate system,
A movable part that moves relative to the fixed part by the action of a force or moment,
A deformed body that is connected to the fixed portion and the movable portion and that elastically deforms when the movable portion moves relative to the fixed portion.
A detection circuit that outputs an electric signal indicating a force or moment acting on the movable portion based on the elastic deformation generated in the deformed body is provided.
The variant is
An annular first deformed body made of a material that elastically deforms due to the action of a force or moment and has a first through opening.
It is made of a material that elastically deforms due to the action of a force or moment, has a second through opening, and has an annular second deformed body that surrounds the first deformed body.
The first deformed body and the second deformed body are connected by a connecting member, and are connected.
The first variant has at least one first detection site having a first spring constant.
The second variant has at least one second detection site having a second spring constant different from the first spring constant.
The detection circuit is a force sensor characterized in that it outputs an electric signal based on elastic deformation that occurs 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 arranging a capacitive element at a detection site where the spring constant is relatively small, that is, a detection site where a relatively large elastic deformation occurs. A force sensor can be provided. Furthermore, by arranging the strain gauge at the detection site where the spring constant is relatively large, that is, the detection site where the stress generated due to elastic deformation is relatively large, it is possible to detect the force or moment with high accuracy and high sensitivity. Can provide a force sensor. From the anomaly, according to the present invention, it is possible to provide a force sensor capable of detecting a force or a 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 variant and the second variant are both annular and may be concentric with each other. In this case, the force sensor can be configured with a simple configuration.

The above force sensor can be configured as a capacitance type. That is, the displacement electrodes arranged at at least one of the first detection portion of the first variant and the second detection portion of the second variant.
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion is further provided.
The displacement electrode and the fixed electrode form a capacitive element, and the displacement electrode and the fixed electrode form a capacitive element.
The detection circuit may output an electric signal indicating an acting force or moment based on the amount of fluctuation in the capacitance value of the capacitance 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 deformed body and the second deformed body.
The detection circuit may output an electric signal indicating the acting force or moment based on the amount of fluctuation of the electric resistance value of the strain gauge.

The connecting member includes a first connecting member whose positive X-axis connects two portions overlapping the first deformed body and the second deformed body when viewed from the Z-axis direction, and the positive Y-axis is the first deformed body. A second connecting member that connects the deformed body and two parts that overlap the second deformed body, and a third connecting member that connects two parts where a negative X overlaps the first deformed body and the second deformed body. , A fourth connecting member connecting two portions whose negative Y-axis overlaps the first deformed body and the second deformed body may be provided.

Further, when the V-axis and the W-axis that pass through the origin O and form 45 ° with respect to the X-axis and the Y-axis are defined on the XY plane,
The first variant has the first detection site at four sites that overlap the V-axis and the W-axis when viewed from the Z-axis direction.
The second deformed body may have the second detection portion at four portions overlapping the V-axis and the W-axis when viewed from the Z-axis direction.

In this case, the applied force or moment causes symmetrical elastic deformation in the first deformed body and the second deformed body, so that the force or moment can be easily detected.

In addition, the first variant has at least one first gap.
The first detection site is interposed in the first gap and
The first detection portion has a first displacement portion and a pair of first deformation portions provided on both sides of the first displacement portion and connected to both ends of the corresponding first gap.
The second variant has at least one second gap and
The second detection site is interposed in the second gap and
The second detection portion may have 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, in a relatively small space, displacement in the direction orthogonal to the applied force can be generated in the first detection portion and the second detection portion.

In the force sensor having such a first detection portion and a second detection portion, it is easy to provide a highly accurate and highly sensitive capacitance type force sensor. That is, the displacement electrodes arranged at at least one of the first displacement portion of the first detection portion and each second displacement portion of the second detection portion.
A fixed electrode that is arranged to face the displacement electrode and does not move relative to the fixed portion is further provided.
The displacement electrode and the fixed electrode form a capacitive element, and the displacement electrode and the fixed electrode form a capacitive element.
The detection circuit may output an electric signal indicating a force or moment acting on the movable portion based on the amount of fluctuation of the capacitance value of the capacitance element.

Of course, it is also possible to configure a force sensor having such a first detection portion and a second detection portion 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 arranged on the surface thereof.
The detection circuit may output an electric signal indicating the uniaxial force acting on the movable portion based on the amount of fluctuation of the electric resistance value of the strain gauge.

Further, in another example, each first detection site is thinner than the other region of the first variant.
Each second detection site may be thinner than the other regions of the second variant.

In this case, since the degree of elastic deformation occurring in the first detection portion and the second detection portion can be adjusted as desired, it is possible to provide a force sensor with higher accuracy and higher sensitivity.

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

Alternatively, according to the present invention, it is possible to perform a failure diagnosis of the force sensor by a single force sensor. That is, such a force sensor detects a force in the uniaxial direction.
Fixed part and
A movable part that moves relative to the fixed part by the action of force,
A deformed body which is connected to the fixed portion and the movable portion and elastically deforms in a direction non-parallel to the uniaxial direction when the movable portion moves relative to the fixed portion.
A detection circuit that outputs an electric signal indicating a force acting on the movable portion based on the elastic deformation generated in the deformed body is provided.
The modified body includes a first detection site having a first spring constant and a second detection site having a second spring constant different from the first spring constant.
The detection circuit
As the electric signal, a first electric signal provided based on the elastic deformation occurring in the first detection portion and a second electric signal provided based on the elastic deformation occurring in the second detection portion are output. ,
It is a force sensor that determines whether or not the force sensor is functioning normally based on the first electric signal and the second electric signal.

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

In these force sense sensors, the detection circuit has a storage unit that stores the ratio of the first electric signal and the second electric signal in the state where the force sense sensor is functioning normally as a reference ratio, and "the first By determining whether or not the "difference between the ratio of the 1 electric signal and the 2nd electric signal and the reference ratio" is within a predetermined range, it is determined whether or not the force sensor is functioning normally. You may be able to do it. In this case, the failure of the force sensor can be reliably determined. The principle of this determination will be described in detail later.

It is a schematic top view which shows the basic structure of the force sensor by 1st Embodiment of this invention. It is a figure which shows the displacement in the X-axis direction and the stress in the Y-axis direction which occur in each detection part when the movable part of the basic structure of FIG. 1 is displaced by 100 μm in the negative direction of the Z axis. It is a schematic top view which shows the 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. It is a schematic top view which shows the state which the force acted on the basic structure of FIG. FIG. 6A shows a state in which a compressive force f1 along the Y-axis direction acts on the basic structure, and FIG. 6B shows a state in which a tensile force f2 along the Y-axis direction acts on the basic structure. is there. A partial schematic top view of the first detection portion A of the strain gauge type force sensor in which the modification shown in FIG. 5 is adopted is shown. FIG. 7A is a schematic view showing an initial state of the first detection part A, and FIG. 7B is a schematic view showing the first detection part A when a compressive force acts on the basic structure. FIG. 7 (c) is a schematic view showing a first detection site A when a tensile force acts on 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. It is a schematic top view which shows the basic structure of FIG. 8 when the moment around the Z axis acts on a movable part. It is a schematic top view which shows the 2nd quadrant part of the basic structure of FIG. It is a schematic above view which shows the 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 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 occurs in the deformed body when the force + Fx in the positive direction of the X axis is applied to the movable part of the basic structure of FIG. It is a figure for demonstrating the elastic deformation which occurs in the deformed body when the force + Fy in the positive direction of the Y axis is applied to the movable part of the basic structure of FIG. It is a figure for demonstrating the stress generated in the detection part of the deformed body when the force in the positive direction of the X axis is applied to the movable part of the basic structure of FIG. It is a figure for demonstrating the stress generated in the detection part of a deformed body when the force + Fy in the positive direction of the Y axis is applied to the movable part of the basic structure of FIG. It is a schematic top view which shows the basic structure of FIG. 8 which adopted the structure shown in FIG. 5 as the detection part of a deformed body. It is a schematic side view which looked at the 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 generated in the detection part of the deformed body when the moment around the Z axis acts on the movable part of the basic structure of FIG. It is a figure for demonstrating the force acting on the detection part of the deformed body when the force in the positive direction of the X-axis is applied to the movable part of the basic structure of FIG. When metal fatigue does not occur 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 between. 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 metal fatigue does not occur 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 between. 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 deformation example of the detection part. FIG. 29 (a) is a schematic view showing the detection site when a compressive force in the Y-axis direction acts on the detection site shown in FIG. 28, and FIG. 29 (b) shows the detection site shown in FIG. 28 on the Y axis. It is a schematic diagram which shows the detection part when the tensile force in a direction is applied. FIG. 8 is a schematic top view showing an example of a deformed body having the detection site shown in FIG. 28. 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 sectional view taken along line bb of FIG. 31 (a). .. It is a schematic diagram which shows the detection part of FIG. 28 in which a capacitive element is arranged. It is the schematic which shows the detection site of FIG. 28 in which a strain gauge is arranged.

<<< §1. Force sensor according to the first embodiment of the present invention >>>
Hereinafter, the force sensor according to the 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 the first embodiment of the present invention. In this figure, it is assumed that the X-axis is defined in the horizontal direction, the Y-axis is defined in the vertical 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 a force, and the fixed portion 10 and the movable portion 20. It includes a deformed body 30 that is connected and causes elastic deformation when the movable portion 20 moves 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 predetermined intervals in the Y-axis direction. The movable portion 20 functions as a receiving body that receives a force.

The deformed body 30 connected to the fixed portion 10 and the movable portion 20 has a first deformed body 31 and a second deformed body 32 arranged in parallel in the X-axis direction. The first deformed body 31 is connected to the movable portion 20 and is arranged apart from the first fixed portion side connecting portion 31f in the Y-axis direction and the first fixed portion side connecting portion 31f connected to the fixed portion 10. It has one movable portion side connecting portion 31m, and an elastically deformable arc-shaped first elastic body 31e that connects the first fixed portion side connecting portion 31f and the first movable portion side connecting portion 31m. The second deformed body 32 is connected to the movable portion 20 and is arranged apart from the second fixed portion side connecting portion 32f in the Y-axis direction with the second fixed portion side connecting portion 32f connected to the fixed portion 10. It has two movable portion side connecting portions 32m, and an elastically deformable arc-shaped second elastic body 32e that connects the second fixed portion side connecting portion 32f and the second movable portion side connecting portion 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 be convex in the negative direction of the X axis (to the right in FIG. 1).

The first elastic body 31e and the second elastic body 32e are located on the most negative side of the X-axis (right side in FIG. 1), that is, on the negative side of the X-axis of the first elastic body 31e and the second elastic body 32e. A first detection site A and a second detection site B are defined as sites 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 portion A and the second detection portion B or the displacement in the X-axis direction. Force is being measured. As shown in FIG. 1, the first elastic body 31e and the second elastic body 32e have different radii of curvature. Specifically, the radius of curvature of the second elastic body 32e is larger than the radius of curvature 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 in the XZ plane. As a result, 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 are the magnitudes of the forces acting on the movable portion 20 in the Y-axis direction and the magnitudes of the displacements in the X-axis directions generated in the detection sites 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 in the detection sites A and B when the movable portion 20 of the basic structure 1 of FIG. 1 is displaced by 100 μm in the negative direction of the Z axis. Is.

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

<1-2. Capacitance type force sensor ＞
Next, the 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 1c is arranged so as to face the first displacement electrode Em1 arranged at the first detection portion A and the first displacement electrode Em1 and does not move relative to the fixed portion 10. The first fixed electrode Ef1, the second displacement electrode Em2 arranged at the second detection portion B, and the second fixed electrode Ef2 arranged facing 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 the first capacitance element C1, and the second displacement electrode Em2 and the second fixed electrode Ef2 constitute the second capacitance element C2. ing. In the present embodiment, the first displacement electrode Em1 and the second displacement electrode Em2 have the same area. Further, the first fixed electrode Ef1 and the second fixed electrode Ef2 have the same area. Further, the effective facing area of the first displacement electrode Em1 and the first fixed electrode Ef1 and the distance between the electrodes are equal to the effective facing area of the second displacement electrode Em2 and the second fixed electrode Ef2 and the distance between the electrodes. The electrodes Em1, Ef1, Em2, and Ef2 are all arranged so as to be parallel to the YZ plane.

Further, as shown in FIG. 3, the force sensor 1c transmits an electric signal indicating a force acting on the movable portion 20 in the Y-axis direction based on the elastic deformation generated in the first deformed body 31 and the second deformed body 32. It has a detection circuit 40 for output. The detection circuit 40 is adapted to output an electric signal indicating a force acting on the movable portion 20 based on the amount of fluctuation of the capacitance value of each of the capacitance elements C1 and C2. The wiring for electrically connecting the capacitance elements C1 and C2 and the detection circuit 40 is not shown.

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

Here, a case where a force in the negative direction of the Y-axis (downward in FIG. 3) acts on the movable portion 20 will be described as an example. When a force in the negative direction of the Y axis acts on the movable portion 20, the movable portion 20 moves relative to the fixed portion 10 in the negative direction of the Y axis. As a result, 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 such that the radius of curvature of both the first elastic body 31e and the second elastic body 32e is reduced. As a result, both the first detection site A and the second detection site B are displaced in the negative direction of the X-axis. Therefore, the capacitance values of the first capacitance element C1 and the second capacitance element C2 both increase as the distance between the 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 portion B in the negative direction of the X axis is larger. Is larger than the displacement of the first detection site A in the negative direction of the X axis. Therefore, the capacitance value of the second capacitance element C2 fluctuates more than that of the first capacitance element C1. That is, the second capacitance element C2 has higher sensitivity than the first capacitance element C1.

Then, the detection circuit 40 measures the force acting on the movable portion 20 based on the fluctuation amount of the capacitance value of one of the first capacitance element C1 and the second capacitance element C2. The capacitance type force sensor 1c is excellent in S / N by measuring the applied force based on the fluctuation amount of the capacitance value of the second capacitance element C2, which has 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 fluctuation amount of the capacitance value of the first capacitance element C1, and for example, the fluctuation 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 quantity and the force measured based on the fluctuation amount of the capacitance value of the second capacitance element C2 as the acting force.

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

<1-3. Strain gauge type force sensor ＞
Alternatively, the basic structure 1 as described above can also be used for the 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 1s has a first strain gauge R1 arranged in the first detection part A and a second strain gauge R2 arranged in the second detection part B. .. The first strain gauge R1 and the second strain gauge R2 have the same characteristics. Since the other configurations are the same as those of the force sensor 1c shown in FIG. 3 except that they do not have a capacitive element, detailed description thereof will be omitted.

As the strain gauges R1 and R2, for example, a metal foil strain gauge or a semiconductor strain gauge can be adopted. The metal foil strain gauge has a property that the resistance value decreases when a compressive stress acts, and conversely, the resistance value increases when a tensile stress acts. Further, the semiconductor strain gauge is a strain gauge utilizing the piezo resistance effect, and 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. The gauge has the characteristic that the resistance value decreases. On the other hand, when a compressive stress acts on the semiconductor strain gauge, the resistance value decreases in the p-type semiconductor strain gauge and increases in the n-type semiconductor strain gauge. Here, it is assumed that a metal foil strain gauge is adopted 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 direction of the Y axis acts on the movable portion 20, the movable portion 20 moves relative to the fixed portion 10 in the negative direction of the Y axis, and as described above, the first elastic body 31e and the second elastic body 32e move. , It elastically deforms so that its radius of curvature decreases together. As a result, tensile stress is generated in the regions including the detection sites A and B on the surfaces of the arc-shaped first elastic body 31e and the second elastic body 32e on the negative side of the X axis. 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 portion A is larger than the tensile stress generated in the second detection portion B. .. This is as described above with reference to FIG. Therefore, the electric resistance value of the first strain gauge R1 fluctuates (increases) more than that of the second strain gauge R2.

Then, the detection circuit 40 measures the applied force based on the fluctuation amount of the electric resistance value of one of the first strain gauge R1 and the second strain gauge R2. In the strain gauge type force sensor 1s, the force applied based on the fluctuation amount of the electric resistance value of the first strain gauge R1, which has a relatively high sensitivity, is measured, so that the measurement excellent in S / N can be performed. It will be possible. Of course, it is also possible to measure the force acting based on the fluctuation amount of the electric resistance value of the second strain gauge R2, and for example, it was measured based on the fluctuation 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 acting force.

In the above description, the case where the force in the negative direction of the Y axis acts on the movable portion 20 has been described as an example, but on the contrary, the force in the positive direction of the Y axis (upward in FIG. 4) is applied. The force can be measured even if it acts on the movable portion 20. In this case, as described above, the first elastic body 31e and the second elastic body 32e are elastically deformed so that their radius of curvature both increase. As a result, compressive stress is generated in the region including the detection sites A and B on the surfaces of the arc-shaped first elastic body 31e and the second elastic body 32e on the negative side of the X axis, and the electricity of the strain gauges R1 and R2 Both resistance values decrease. Also in this case, the electric resistance value of the first strain gauge R1 fluctuates more than that of the second strain gauge R2.

According to the force sensor 1c and 1s according to the present embodiment as described above, the second capacitance element is located in the second detection portion B having a relatively small spring constant, that is, the second detection portion B having a relatively large elastic deformation. By arranging C2, it is possible to provide a capacitance type force sensor 1c capable of detecting force with high accuracy and high sensitivity. Alternatively, by arranging 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 generated due to elastic deformation is relatively large, high accuracy and high accuracy are achieved. It is possible to provide a force sensor 1s capable of detecting force with sensitivity. From the above, according to the present embodiment, the force acting with high accuracy and high sensitivity is detected regardless of whether it is configured as a capacitance type or a strain gauge type while having a common basic structure 1. It is possible to provide force sensor 1c and 1s capable of the above.

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

As shown in FIG. 5, in this modified example, two corrugated elastic structures are adopted instead of the two arc-shaped elastic bodies shown in FIG. Here, the elastic structures having these waveforms will be referred to as a first detection site A and a second detection site B. As shown, the first detection portion A is provided on both sides of the first displacement portion 61d and the first displacement portion 61d, via connecting portions 61m and 61f arranged at intervals in the Y-axis direction. It has a pair of first deformed portions 61e1 and 61e2 connected to the fixed portion 10 and the movable portion 20, respectively, and the second detection portion B is provided on both sides of the second displacement portion 62d and the second displacement portion 62d. It has a pair of second deformable portions 62e1 and 62e2 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 deformed portions 62e1 and 62e2 are configured to stand up from the pair of first deformed portions 61e1 and 61e2 in the Y-axis direction.

In the case of the example shown here, the pair of first deformed portions 61e1 and 61e2 and the pair of second deformed portions 62e1 and 62e2 are composed of flexible plate-shaped pieces, and the first displacement portion 61d and the second displacement portion are formed. 62d is composed of a third plate-shaped piece. Each plate-shaped piece is made of the same material as each connection portion 61f, 61m, 62f, 62m, but is a plate-shaped member having a relatively thin wall thickness as shown in FIGS. 5 and 6. Therefore, it has flexibility.

In the case of the example shown here, the first displacement portion 61d and the second displacement portion 62d are also flexible because they are thin plate-shaped 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 examples shown in FIGS. 5 and 6, the left and right sides of the first displacement portion 61d and the second displacement portion 62d (third plate-shaped piece) are planes parallel to the YZ plane.

Next, with reference to FIGS. 6 (a) and 6 (b), when a force along the Y-axis direction acts on the movable portion 20 of the basic structure 1w, the detection sites A and B The action will be described. In FIGS. 6 (a) and 6 (b), the thick black arrows indicate the direction of the acting force, and the thick white arrows indicate the displacement directions of the displacement portions 61d and 62d, respectively. There is.

As shown in FIG. 6A, when a compressive force f1 along the Y-axis direction acts on the movable portion 20 of the basic structure 1w, compression along the Y-axis direction is applied to the detection sites A and B. Force acts. Therefore, the postures of the pair of first deformed portions 61e1 and 61e2 and the pair of second deformed portions 62e1 and 62e2 change to a more horizontal lying state. As a result, the displacement portions 61d and 62d are displaced in the negative X-axis direction (to the right in FIG. 6A) as indicated by the white arrows in the figure. On the other hand, as shown in FIG. 6B, when a tensile force f2 in the positive direction of the Y axis acts on the movable portion 20 of the basic structure 1w, the detection sites A and B are along the Y axis direction. Tensile force acts. Therefore, the postures of the pair of first deformed portions 61e1 and 61e2 and the pair of second deformed portions 62e1 and 62e2 change to a more vertical standing state. As a result, the displacement portions 61d and 62d are displaced in the positive direction of the X-axis (leftward in FIG. 6B) as shown by the white arrows in the figure.

As described above, the pair of first deformed portions 61e1 and 61e2 are configured to stand up in the Y-axis direction from the pair of second deformed portions 62e1 and 62e2 in the initial state (see FIG. 5). Therefore, as shown in FIGS. 6 (a) and 6 (b), 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 portion A and the second detection portion B mean a value 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 by utilizing such displacement. That is, the direction of the applied force is detected by the displacement direction of each of the displacement portions 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 capacitance element C2 is arranged at the second detection portion B where the spring constant is relatively small, that is, the second detection portion B where relatively large elastic deformation occurs. This makes it possible to provide a force sensor 1c capable of detecting force with high accuracy and high sensitivity.

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

FIG. 7 shows a partial schematic top view of the first detection portion A of the strain gauge type force sensor configured in this way. FIG. 7A is a schematic view showing an initial state of the first detection part A, and FIG. 7B is a schematic view showing the first detection part A when a compressive force acts on the basic structure 1w. FIG. 7 (c) is a schematic view showing a first detection site A when a tensile force acts on the basic structure 1w. In each figure, the thick black arrow indicates the direction of the acting force, and the thin arrow indicates the stress generated on the surface of each displacement portion 61d and 62d on the negative side of the X axis (“→ ←” is the compressive stress. “← →” indicates tensile stress).

As shown in FIG. 7A, the first displacement portion 61d of the first detection portion A in the initial state is parallel to the ZY plane. Then, as shown in FIG. 7B, when a compressive force acts on the basic structure 1w, the postures of the pair of first deformed portions 61e1 and 61e2 change to a more horizontal lying state as described above. As a result, as shown in FIG. 7 (b), the first displacement portion 61d of the first detection portion A bends and deforms so as to be convex in the negative direction of the X-axis (right direction in FIG. 7 (b)). .. That is, as shown in the figure, tensile stress is generated along the Y-axis direction on the surface on the negative side of the X-axis of the first displacement portion 61d in which the first strain gauge R1 is arranged. On the other hand, as shown in FIG. 7C, when a tensile force acts on the basic structure 1w, the postures of the pair of first deformed portions 61e1 and 61e2 change to a more vertical standing state as described above. As a result, as shown in FIG. 7 (c), the first displacement portion 61d of the first detection portion A bends and deforms so as to be convex in the positive direction of the X-axis (left direction in FIG. 7 (c)). .. That is, as shown in the figure, compressive stress is generated along the Y-axis direction on the X-axis negative side surface of the first displacement portion 61d in which the first strain gauge R1 is arranged. After all, the direction of the force acting on the first detection portion A1 (compression or tension) and the direction of the stress generated on the surface on the negative side of the X axis of the first displacement portion 61d (compression or tension) are opposite to each other. .. As can be understood from the aspect of the deflection deformation of FIGS. 7 (b) and 7 (c), the direction (compression or tension) of the stress generated on the surface of the first displacement portion 61d on the positive side of the X axis is determined. It is the same as the direction of the force acting on the first detection site A1 (compression or tension).

Although the second detection portion B is not shown in FIG. 7, the same bending deformation occurs in the second displacement portion 62d also in the second detection portion 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 stress generated. From this, it is possible to provide a force sensor 1s capable of detecting a force with high accuracy and high sensitivity by detecting a force Fy acting by using a first strain gauge arranged in the first displacement portion 61d. Can be done.

From the above, according to the present embodiment, the force sensor 1c, 1s capable of detecting force with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type is provided. 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. Can be generated, and the acting force can be detected with higher accuracy and sensitivity.

Further, the first detection portion 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 portion B has a radius different from the predetermined radius. It has a shape along a part of the arc. Therefore, the force can be easily measured because the first detection site A and the second detection site B can be displaced in the direction orthogonal to the applied force. The same applies to the basic structure 1w shown in FIG.

<<< §2. Force sensor according to the second embodiment of the present invention >>>
Next, the force sensor according to the 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 portion 120 as a receiving body. FIG. 10 is a schematic top view showing the basic structure 101 of FIG. 8 and FIG. 10 is a schematic top view showing a second quadrant portion 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 the XYZ three-dimensional coordinate system. As shown in FIGS. 8 to 10, the basic structure 101 includes a fixed portion 110 fixed to the XYZ three-dimensional coordinate system and a movable portion 120 that moves relative to the fixed portion 110 by the action of a force or a moment. The deformed body 140 is connected to the fixed portion 110 and the movable portion 120, and elastically deforms 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 the shape of a disk centered on the origin when viewed from the positive direction of the Z axis. The movable portion 120 has the shape of an annulus arranged concentrically with the fixed portion 110 on the XY plane when viewed from the positive direction of the Z axis. The fixing portion 110 may also have an annular shape.

Further, as shown in FIGS. 8 to 10, the deformed body 140 is arranged so as to surround the first deformed body 141 having an annular shape composed of the elastic body and the first deformed body 141, and is an elastic body. It has a second deformed body 142 having an annular shape composed of the above. The first deformed body 141 is arranged concentrically with the fixed portion 110 so as to surround the fixed portion 110 when viewed from the Z-axis positive direction, and the second deformed body 142 is formed by the first deformed body 141 and the movable portion 120. Arranged concentrically with them in between. After all, the fixed portion 110, the first deformed body 141, the second deformed body 142, and the movable portion 120 are arranged in this order concentrically with each other and outward in the radial direction when viewed from the Z-axis positive direction. There is.

Further, the first deformed body 141 and the second deformed body 142 of the basic structure 101 according to the present embodiment have the same cross-sectional shape. Therefore, due to the difference in diameter between the deformed bodies 141 and 142, the spring constants of the detected parts A1 to A4 of the first deformed body 141 are larger than the spring constants of the detected parts B1 to B4 of the second deformed body. Here, the spring constants of the detection sites A1 to A4 and B1 to B4 are the displacements of the force acting on the movable portion 20 in the detection sites 1 to A4 and B1 to B4 in the V-axis direction and the W-axis direction. It means the value divided.

As shown in FIGS. 8 to 10, the fixed portion 110 and the first deformed body 141 are a connecting body 133 arranged on the positive Y axis and a connecting body arranged on the negative Y axis in a gap between each other. They are connected to each other by 137. Further, the first deformed body 141 and the second deformed body 142 are connected to each other by the connecting body 134 arranged on the positive Y axis and the connecting body 138 arranged on the negative Y axis in the gap between them. Has been done. As a result, in the first deformed body 141 and the second deformed body 142, each of the two portions located on the Y-axis does not move relative to the fixed portion 110.

Further, as shown in FIGS. 8 to 10, the first deformed body 141 and the second deformed body 142 are arranged on the negative X-axis with the connecting body 131 arranged on the positive X-axis in the gap between them. They are connected to each other by the connected body 135. Further, the movable portion 120 and the second deformed body 142 are connected to each other by the connecting body 132 arranged on the positive X-axis and the connecting body 136 arranged on the negative X-axis in the gap between them. There is. As a result, in the first deformed body 141 and the second deformed body 142, each of the two portions located on the X-axis moves relative to the fixed portion 110 integrally with the movable portion 120. ..

Next, the action of the basic structure 101 when a moment −Mz around the Z axis acts on the movable portion 120 of the basic structure 101 will be described with reference to FIG. In FIG. 9, the thick black arrows indicate the direction of the acting force, and the thick white arrows indicate the displacement directions of the detection sites A1 to A4 and B1 to B4.

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

Since these displacements are maximum on the W axis and the V axis, pay attention to the displacement or stress of the portion of each of the deformed bodies 141 and 142 that intersects the W axis and the V axis when viewed from the positive Z axis direction. It is efficient to measure the acting force or moment. Therefore, here, as shown in FIG. 9, four parts of the first deformed body 141 that intersect the W-axis and the V-axis are identified in order from the first quadrant to the 1-1 detection part A1 and the 1-2 detection part. A2, 1-3 detection site A3 and 1-4 detection site A4, and 4 sites of the second deformed body 142 that intersect the W axis and V axis are the 2-1 detection site B1 in order from the first quadrant. The second 2nd detection site B2, the 3rd 3rd detection site B3, and the 2nd-4th 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, the portion of each of the deformed bodies 141 and 142 located on the positive Y axis is fixed with respect to the XYZ three-dimensional coordinate system, and each deformed body 141 , 142, which is located on the negative X-axis, moves integrally with the fixed portion 110 together with the movable portion 120. In such a structure, the portion of each of the deformed bodies 141 and 142 located on the positive Y-axis is regarded as the fixed portion 10 of the basic structure 1 according to the first embodiment, and the negative X of each of the deformed bodies 141 and 142 is taken. By regarding the portion 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 have substantially the same structure. It is understood that there is. The same is true for the first, third and fourth quadrants. Further, regarding the relationship between the spring constants of the deformed bodies 141 and 142, in the basic structure 1 in the first embodiment, the spring constant of the first detection portion A of the first deformed body 31 is the second of the second deformed body 32. It also corresponds to the fact that it is larger than the spring constant of the detection site 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. That is, as described in the first embodiment, the basic structure 101 according to the present embodiment has the second to first to fourth detection sites A1 to A4 in terms of displacement. The 2-4 detection sites B1 to B4 are more sensitive, and when looking at the stress, the 1-1 to 1-4 detection sites A1 to A4 are higher than the 2-1 to 2-4 detection sites B1 to B4. Has the characteristic that it has higher sensitivity.

<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 upper view showing a capacitance type force sensor 101c according to the basic structure 101 of FIG. As shown in FIG. 11, the force sensor 101c includes the first-to-first-fourth displacement electrodes Em11 to Em14 arranged on the outer surface of the first-to-first-fourth detection sites A1 to A4, respectively. First 1-1 to 1-4 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 2-1 to 2-4 detection sites B1 to The 2-1st to 2nd-4th displacement electrodes Em21 to Em24 arranged on the outer surface of B4 and the 2nd to 1st to 2nd to 1st, which are arranged facing each displacement electrode Em21 to Em24 and do not move relative to the fixed portion 110. It has 2-4 fixed electrodes Ef21 to Ef24.

As shown in FIG. 11, the 1-1 displacement electrode Em11 and the 1-1 fixed electrode Ef11 constitute the 1-1 capacitive element C11, and the 1-2 displacement electrode Em12 and the 1-2 fixed electrode Ef12. Consists of the 1-2 capacitance element C12, the 1-3 displacement electrode Em13 and the 1-3 fixed electrode Ef13 constitute the 1-3 capacitance element C13, and the 1-4 displacement electrodes Em14 and the first The 1-4 fixed electrode Ef14 constitutes the 1-4 capacitive element C14. Further, the 2-1 displacement electrode Em21 and the 2-1 fixed electrode Ef21 constitute the 2-1 capacitive element C21, and the 2-2 displacement electrode Em22 and the 2-2 fixed electrode Ef22 are the 2-th. The 2nd capacitance element C22 is formed, and the 2-3 displacement electrode Em23 and the 2-3 fixed electrode Ef23 constitute the 2-3 capacitance element C23, and the 2nd-4th displacement electrode Em24 and the 2-4 fixed electrode The Ef24 constitutes the 2nd-4th capacitive element C24. The fixed electrodes Ef11 to Ef24 are formed with the first and second deformed bodies 141 and 142 even if a force is applied to the movable portion 120 by, for example, a support (not shown) fixed on the XY plane and extending in the positive Z-axis direction. It is supported in a position that 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. Further, 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 facing area of each electrode constituting each of the capacitance elements C11 to C24 and the distance between the facing electrodes are all the same.

Further, as shown in FIG. 11, the force sensor 101c outputs an electric signal indicating the force or moment acting on the movable portion 120 based on the elastic deformation generated in the first deformed body 141 and the second deformed body 142. It has a detection circuit 150. The detection circuit 150 of the force sensor 101c shown in FIG. 11 outputs an electric signal indicating the force or moment acting on the movable portion 120 based on the fluctuation amount of the capacitance value of each of the capacitance elements C11 to C24. It has become. The wiring for electrically connecting the capacitance elements C11 to C24 and the detection circuit 150 is not shown.

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

Here, a case where a clockwise force (moment) when 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 deformed bodies 141 and 142, the first-2, 2-2, 1-4, and 2-4 detection sites A2, B2, and A4 located on the W axis, In B4, displacement occurs outward in the radial direction, and in the first, 2-1 and 1-3, and 2-3 detection sites A1, B1, A3, and B3 located on the V axis, , Radial inward displacement occurs. As a result, the capacitance values of the 1st-2nd, 2nd-2nd, 1st-4th, and 2nd-4th capacitive elements C12, C22, C14, and C24 increase because the distance between the electrodes decreases. On the other hand, in the first, second, first, third, and second and third capacitive elements C11, C21, C13, and C23, the capacitance value decreases because the distance between the electrodes increases. ..

In the present embodiment, as described above, since the spring constants of the detection sites 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, each capacitance Focusing on the absolute value of the fluctuation amount of the capacitance value, the fluctuation amount of the capacitance value of the second to second-4th capacitance elements C21 to C24 arranged on the second variant 142 is the first variant. It is larger than the fluctuation amount of the capacitance value of the first to first to fourth capacitance elements C11 to C14 arranged on 141.

Then, the detection circuit 150 measures the acted moment Mz around the Z axis using the following [Equation 1]. In [Equation 1], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformed body 141, and Mz2 is the moment around the Z axis measured based on the elastic deformation of the second deformed body 142. Moment of. In the following equation, C11 to C24 indicate the amount of fluctuation in the capacitance value of the first to second to fourth capacitance elements C11 to C24. This also applies to other formulas herein.
[Equation 1]
-Mz1 = -C11 + C12-C13 + C14
-Mz2 = -C21 + C22-C23 + C24

In the capacitance type force sensor 101c, based on the fluctuation amount of the capacitance value of the second to second to fourth capacitance elements C21 to C24, which have relatively high sensitivity, that is, [Equation 1]. By measuring the acting moment based on -Mz2, it is possible to measure the S / N excellently. Of course, the acting moment may be measured based on the amount of fluctuation of the capacitance value of the first to first to fourth capacitance elements C11 to C14. If only the moment Mz around the Z axis is to be measured, only one of the 1-1 to 1-4 capacitive elements C11 to C14 and the 2-1 to 2-4 capacitive elements C21 to C24 is provided. It is good if it is done.

<2-3. Strain gauge type force sensor ＞
The basic structure 101 as described above can also be used for the 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 101s has a 1-1 strain gauge R11 arranged at the 1-1 detection site A1 and a 1-2 detection site on the outer surface of the annular first deformed body 141. The 1-2 strain gauge R12 arranged in A2, the 1-3 strain gauge R13 arranged in the 1-3 detection part A3, and the 1-4 strain arranged in the 1-4 detection part A4. It has a gauge R14 and. Further, the force sensor 101s is arranged on the outer surface of the annular second deformed body 142 at the 2-1 strain gauge R21 arranged at the 2-1 detection part B1 and at the 2-2 detection part B2. The 2-2 strain gauge R22, the 2-3 strain gauge R23 arranged at the 2-3 detection site B3, and the 2-4 strain gauge R24 arranged at the 2-4 detection site B4 are Have. Each strain gauge R11 to R24 is a metal foil strain gauge and all have the same characteristics. Since the other configurations are the same as those of the force sensor 1c shown in FIG. 11 except that they do not have a capacitive element, detailed description thereof will be omitted.

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

Here, too, the case where a clockwise force (moment) when 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 deformed bodies 141 and 142, the first-2, 2-2, 1-4, and 2-4 detection sites A2, B2, and A4 located on the W axis, In B4, displacement occurs outward in the radial direction, and in the first, 2-1 and 1-3, and 2-3 detection sites A1, B1, A3, and B3 located on the V axis, , Radial inward displacement occurs. As a result, tensile stress is generated at the first-2, 2-2, 1-4, and 2-4 detection sites A2, B2, A4, and B4 located on the W axis, and the positions are located on the V axis. Compressive stress is generated in the first, second, first, third, and second detection sites A1, B1, A3, and B3. As described above, since the spring constants of the detection sites A1 to A4 of the first deformed body 141 are larger than the spring constants of the detected parts B11 to B14 of the second deformed body 142, each of the first deformed bodies 141 The absolute value of the stress generated in the detection sites A1 to A4 is larger than the absolute value of the stress generated in the detection sites B1 to B4 of the second deformed body 142. Therefore, the electric resistance values of the 1-1 to 1-4 strain gauges R11 to R14 fluctuate more than the electric resistance values of the 2-1 to 2-4 strain gauges R21 to R24.

Then, the detection circuit 150 uses the following [Equation 2], and for example, at least one of the 1st to 1st to 4th strain gauges R11 to R14 and the 2nd to 1st to 2nd to 4th strain gauges R21 to R24. The moment Mz around the acting Z-axis is measured based on the amount of fluctuation of the electric resistance value of. In [Equation 2], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformed body 141, and Mz2 is the moment around the Z axis measured based on the elastic deformation of the second deformed body 142. Moment of. Further, in the following equation, R11 to R24 indicate the amount of fluctuation of the electric resistance value of the first to second to second strain gauges R11 to R24. This also applies to other formulas herein.
[Equation 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 electric resistance value of the first to fourth strain gauges R11 to R14, which are relatively highly sensitive, that is,-in [Equation 2]. By measuring the acting moment based on Mz1, it is possible to measure the S / N excellently. Of course, the acting moment may be measured based on the fluctuation amount of the electric resistance value of the 2-1st to 2nd-4th strain gauges R21 to R24. Further, in the measurement, the Wheatstone bridge circuit (not shown) was configured by the first 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 the moment. If only the moment Mz around the Z axis is to be measured, only 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 is provided. It is good if it is done.

According to the force sensor according to the present embodiment as described above, the spring constant is relatively small, that is, the elastic deformation that occurs is relatively large, and the capacitance is applied to the second to second to second-4 detection sites B1 to B4. By arranging the elements C21 to C24, it is possible to provide a force sensor 101c capable of detecting a moment with high accuracy and high sensitivity. Further, by arranging the strain gauges R11 to R14 at the first to first to fourth detection sites A1 to A4 where the spring constant is relatively large, that is, the stress generated by the elastic deformation is relatively large. It is possible to provide a force sensor 101s capable of detecting a moment with high accuracy and high sensitivity. From the above, according to the present embodiment, the force sensor 101c, 101s capable of detecting force with high accuracy and high sensitivity regardless of whether it is configured as a capacitance type or a strain gauge type is provided. can do.

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

Further, the first deformed body 141 has the first 1-1 to 1-4 detection parts A1 to A4 at four parts overlapping the V-axis and the W-axis when viewed from the Z-axis direction, and the second deformed body 142 has. The 2-1st to 2nd-4th detection sites B1 to B4 are provided at four sites overlapping the V-axis and the W-axis when viewed from the Z-axis direction. Therefore, the acting moment causes symmetrical elastic deformation in the first deformed body 141 and the second deformed body 142, so that the force other than the acting moment is not affected.

<2-4. Deformation example of basic structure ＞
Next, a modified example of the above 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. 8. Is a schematic top view showing a third modification of the basic structure 101 of FIG.

First, the basic structure 101a according to the modified example shown in FIG. 13 will be described. This basic structure 101a is different from the above-mentioned basic structure 101 in that a thin portion having a thin wall thickness is provided on the annular second deformed body 142. Specifically, the second deformed body 142 has the second to second to second-4 thin-walled portions 142t1 to 142t4 in the region including the portions located on the V-axis and the W-axis. Therefore, the 2-1 to 2-4 detection sites B1 to B4 are provided in the 2-1 to 2-4 thin-walled portions 142t1 to 142t4, respectively. On the other hand, the first modified body 141 is the same as the first modified body 141 of the basic structure 101 shown in FIGS. 8 to 10.

In this modified example, as shown in FIG. 13, each thin-walled portion 142t1 to 142t4 is formed by forming a thin wall thickness in the radial direction of the second deformed body 142. Of course, in another modification, the second variant 142 may be formed by making the wall thickness thin 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 configurations are designated by the same reference numerals, and detailed description thereof will be omitted.

When a moment clockwise (same direction as in FIG. 9) is applied to the basic structure 101a having such a configuration when viewed from the positive direction of the Z axis, the deformed bodies 141 and 142 have the same elasticity as in FIG. Deformation occurs. However, the elastic deformation that occurs in the thin portions 142t1 to 142t4 of the second deformed body 142 is larger than that in the case of FIG.

According to the basic structure 101a having such a configuration, the presence of the thin-walled portions 142t1 to 142t4 relatively reduces the spring constants of the second to second-4th detection sites B1 to B4. Therefore, when the basic structure 101a is used as a capacitance type force sensor, it is provided at the second to second-4th detection sites B1 to B4 as compared with the above-mentioned basic structure 101. In the capacitive element, a particularly large fluctuation amount of the capacitance value is observed. That is, in the capacitance type force sensor, the force or moment acting based on the fluctuation amount of the capacitance value of the second to second to fourth capacitance elements C21 to C24, which have relatively high sensitivity. By measuring the above, it is possible to perform measurement with even better S / N. Of course, the acting force may be measured based on the fluctuation amount of the capacitance value of the first to first to fourth capacitance elements C11 to C14.

A further modification example of the basic structure provided with the deformed body having such thin-walled 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 variant 142b is divided into four by the X-axis and the Y-axis. That is, the second deformed body 142b is the 2-1 deformed body 142b1 arranged in the first quadrant of the XY plane, the 2-2 deformed body 142b2 arranged in the second quadrant of the XY plane, and the XY plane. It has a 2-3 variant 142b3 arranged in the 3rd quadrant and a 2-4 variant 142b4 arranged in the 4th quadrant of the XY plane. As shown in FIG. 14, the 2-1 variant 142b1 is connected to the first variant 141 by a connecting body 134a in which a portion near the positive Y-axis extends parallel to the Y-axis, and is near the positive X-axis. Is connected to the movable portion 120 by a connecting body 132b extending parallel to the X-axis. Further, in the 2-2 variant 142b2, the portion near the positive Y-axis is connected to the first variant 141 by the connecting body 134b extending parallel to the Y-axis, and the portion near the negative X-axis is the X-axis. It is connected to the movable portion 120 by a connecting body 136a extending in parallel with. In the 2-3 variant 142b3, the portion near the negative X-axis is connected to the first variant 141 by the connecting body 136b extending parallel to the X-axis, and the portion near the negative Y-axis is parallel to the Y-axis. It is connected to the movable portion 120 by a connecting body 138a extending to the movable portion 120. In the 2nd-4th deformed body 142b4, the part near the negative Y-axis is connected to the first deformed body 141 by the connecting body 138b extending parallel to the Y-axis, and the part near the positive X-axis is parallel to the X-axis. It is connected to the movable portion 120 by a connecting body 132a extending to.

Further, as shown in FIG. 14, the two connecting bodies 132a and 132b extending parallel to the X-axis are separated from each other in the Y-axis direction, and the two connecting bodies 132a and 132b are separated from each other in the Y-axis direction. A connecting body 131l connecting the deformed body 141 and the movable portion 120 extends along the X axis. Similarly, the two extending joints 136a and 136b extending parallel to the X-axis are separated from each other in the Y-axis direction, and the first variant is between the two connecting bodies 136a and 136b. A connecting body 135l connecting the 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 designated by the same reference numerals, and detailed description thereof will be omitted.

When a moment clockwise (same direction as in FIG. 9) is applied to the basic structure 101b having such a configuration when viewed from the positive direction of the Z axis, the deformed bodies 141 and 142 have the same elasticity as in FIG. Deformation occurs. However, the elastic deformation that occurs in the thin portions 142t1 to 142t4 of the second deformed body 142 is the same as the basic structure 101a according to the first deformation example 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-walled portions 142t1 to 142t4 will be described with reference to FIG. The basic structure 101b'according to the third modification is the second one shown in FIG. 14 in that the second to second-4th variants 142b1 to 142b4 are not directly connected to the movable portion 120. It is different from the basic structure 101b according to the modified example. That is, as shown in FIG. 15, in the basic structure 101b'according to the third modification, the regions of the 2-1 variant 142b1 and the second-4 variant 142b4 near the positive X-axis are the conjugates 132d and 132e. 2-2 deformed body 142b2 and 2-3 deformed body 142b3 near the negative X axis are connected to the first deformed body 141 by the connecting bodies 136c and 136d, respectively. It is connected. In this modification, none of the 2-1 to 2-4 variants 142b1 to 142b4 are connected to the movable portion 120, but instead, the connecting portion between the connector 131l and the first variant 141 is connected. The ends of the connecting bodies 132d and 132e are connected to the first deformed body 141 in the vicinity, and further, the ends of the connecting bodies 136c and 136d are connected in the vicinity of the connecting portion between the connecting body 135l and the first deformed body 141. The portion is connected to the first deformed body 141. Therefore, even in this modification, substantially the same operation as that of the basic structures 101a and 101b shown in FIGS. 13 and 14 is provided.

<2-5. Detection principle 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 sense sensors 101c and 101s has been described, but the force sense sensors 101c and 101s have the force Fx in the X-axis direction and the force Fy in the Y-axis direction. Can also be measured.

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

As shown in FIG. 16, when a force + Fx in the positive direction of the X axis acts on the movable portion 120 of the basic structure 101, the portion of the deformed body 140 on the X axis moves in the positive direction of the X axis together with the movable portion 120. On the other hand, the parts on the Y axis corresponding to the points P1 and P2 do not move. From this, in the deformed 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 inward in the radial direction of the deformed body 140, while the deformed body 140 has one. The detection sites B and C located in the second quadrant and the third quadrant are elastically deformed so as to be displaced outward in the radial direction of the deformed 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 portion 120 of the force sensor 101c shown in FIG. 11, the 1-1 capacitance element C11 and the 2-1 capacitance element C21 arranged in the first quadrant, and In the first to fourth capacitance elements C14 and the second to fourth capacitance elements C24 located in the fourth quadrant, the capacitance value decreases because the separation distance between the fixed electrode and the displacement electrode increases. On the other hand, the first and second capacitance elements C12 and the second and second capacitance elements C22 located in the second quadrant, and the first and third capacitance elements C13 and the second and third capacitance elements C23 located in the third quadrant are Since the separation distance between the fixed electrode and the displacement electrode is reduced, the capacitance value is increased.

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

Next, with reference to FIG. 17, the principle for measuring the force + Fy in the positive direction of the Y axis will be described. FIG. 17 is a diagram for explaining elastic deformation that occurs in the deformed body 140 when a force + Fy in the positive direction of the Y axis is applied to the movable portion 120 of the basic structure 101 of FIG. The elastic deformations that occur in the first deformed body 141 and the second deformed body 142 have the same tendency although the degree is different. Therefore, for the sake of simplicity, only a single deformed body 140 is shown in FIG. .. Further, for the sake of simplicity, the fixing portion 110 and the connecting body connecting the fixing portion 110 and the deformed body 140 are not shown, but the points P1 and P2 in FIG. 17 are relative to the origin O. Does not move. Further, in the deformed body 140, four detection parts A, B, C, and D are provided in this order counterclockwise from the first quadrant at the parts intersecting the V-axis and the W-axis when viewed from the Z-axis positive direction. Has been done. In FIG. 17, the thick black arrow indicates the direction of the acting force, and the thick white arrow indicates the direction of displacement of each of the detection sites A to D.

As shown in FIG. 17, when a force + Fy in the positive direction of the Y axis acts on the movable portion 120 of the basic structure 101, the portion of the deformed body 140 on the X axis moves in the positive direction of the Y axis together with the movable portion 120. On the other hand, the parts on the Y axis corresponding to the points P1 and P2 do not move. From this, in the deformed body 140, among the four detection parts A to D, the detection parts A and B located in the first quadrant and the second quadrant move outward in the radial direction of the deformed body 140, while one of them. The detection sites 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 deformed body 140.

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

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

As described above, in the capacitance type force sensor 101c, based on the fluctuation amount of the capacitance value of the second to second to fourth capacitance elements C21 to C24, which have relatively high sensitivity. That is, the acting force is measured based on Fx2 of [Equation 3] when calculating the force Fx in the X-axis direction, and based on Fy2 of [Equation 4] when calculating the force Fy in the Y-axis direction. This makes it possible to measure with excellent S / N. Of course, the acting force may be measured based on the amount of fluctuation in the capacitance value of the first to first to fourth capacitance elements C11 to C14.

Here, a force sensor 101c provided with a total of eight capacitive elements of the 1-1 to 1-4 capacitive elements C11 to C14 and the 2-1 to 2-4 capacitive elements C21 to C24 will be described as an example. Was done. However, if only the force Fx in the X-axis direction and / or the force Fy in the Y-axis direction is measured, the first to first to fourth capacitance elements C11 to C14 and the second to second to second to fourth capacitances are measured. Only one of the elements C21 to C24 needs to be provided.

When the direction of the acting force is the negative direction of the X-axis, the fluctuations of the capacitance values of the capacitance elements C11 to C24 are all reversed. Therefore, the signs of the forces Fx1 and Fx2 measured by [Equation 3] are opposite to each other. That is, the direction (sign) and magnitude of the applied force Fx are measured by [Equation 3]. This also applies when the force Fy in the Y-axis direction is measured using [Equation 4].

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

As shown in FIG. 18, when a force + Fx in the positive direction of the X axis acts on the movable portion 120 of the basic structure 101, the deformed body 140 elastically deforms as in FIG. At this time, paying attention to the change in the radius of curvature in each of the detection sites A to D, as shown in FIG. 18, the detection sites 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 sites B and C located in the second quadrant and the third quadrant bend so that the radius of curvature becomes smaller. Due to such deflection deformation, compressive stress is generated in the detection sites A and D located in the first and fourth quadrants, and in the detection sites B and C located in the second and third quadrants. , Tensile stress is generated.

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 portion 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 , The electrical resistance values of the 1st-4th strain gauge R14 and the 2nd-4th strain gauge R24 located in the 4th quadrant decrease due to the compressive stress. On the other hand, the first and second strain gauges R12 and the second and second strain gauges R22 arranged in the second quadrant, and the first and third strain gauges R13 and the second and third strain gauges R23 located in the third quadrant are , The tensile stress increases the electrical resistance value.

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

Next, with reference to FIG. 19, the principle for measuring the force + Fy in the positive direction of the Y axis will be described. FIG. 19 is a diagram for explaining the stress generated in the deformed body detection unit 140 when a force + Fy in the positive direction of the Y axis is applied to the movable portion of the basic structure 101 of FIG. Since the elastic deformations that occur in the first deformed body 141 and the second deformed body 142 have the same tendency although the degree is different, only a single deformed body 140 is shown in FIG. 19 for the sake of simplicity. .. Further, for the sake of simplicity, the fixed portion 110 and the connected body connecting the fixed portion 110 and the deformed body 140 are not shown, but the points P1 and P2 in FIG. 19 are relative to the origin O. Does not move. The arrangement of the detection sites 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, and the thin arrow indicates the stress generated in each of the detection sites A to D (“→ ←” is the compressive stress, “← →” is the tensile stress. ) Is shown.

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

From the above, the following can be understood. That is, when a force + Fy in the positive direction of the Y axis acts on the movable portion 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 The electric resistance values of the first and second strain gauges R12 and the second and second strain gauges R22 located in the second quadrant increase due to tensile stress. On the other hand, the 1-3 strain gauges R13 and 2-3 strain gauges R23 arranged in the 3rd quadrant, and the 1-4 strain gauges R14 and 2-4 strain gauges R24 located in the 4th quadrant are , The electric resistance value decreases due to the compressive stress.

Therefore, the detection circuit 150 measures the acting force Fy in the Y-axis direction using the following [Equation 6]. In [Equation 6], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformed body 141, and Fy2 is a force in the Y-axis direction measured based on the elastic deformation of the second deformed body 142. Is the power of.
[Equation 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 electric resistance value of the first to first to fourth strain gauges R11 to R14, which have relatively high sensitivity. As a result, it is possible to measure with excellent S / N. Of course, the acting force may be measured based on the fluctuation amount of the electric resistance value of the 2-1st to 2nd-4th strain gauges R21 to R24.

Here, a force sensor 101s provided with a total of eight strain gauges of the 1-1 to 1-4 strain gauges R11 to R14 and the 2-1 to 2-4 strain gauges R21 to R24 will be described as an example. Was done. However, if only the force Fx in the X-axis direction and / or the force Fy in the Y-axis direction is to be measured, the 1-1 to 1-4 strain gauges R11 to R14 and the 2-1 to 2-4 strains are strained. Only one of the gauges R21 to R24 needs to be provided.

When the direction of the acting force is the negative direction on the X-axis or the negative direction on the Y-axis, the fluctuation amounts of the electric resistance values of the strain gauges R11 to R24 are all reversed. Therefore, the signs of the forces Fx1 and Fx2 measured by [Equation 5] are opposite to each other. That is, the direction (sign) and magnitude of the applied force are measured by [Equation 5]. This also applies when measuring the force in the Y-axis direction using [Equation 6].

In the strain gauge type force sensor 101s described above, the strain gauges R11 to R24 may be arranged on the radial inner surfaces of the deformed bodies 141 and 142 on the V-axis and the W-axis. The electric resistance value of each strain gauge R11 to R24 in this case, and the electric resistance value due to the force acting on the movable portion 120 when each strain gauge R11 to R24 is arranged on the radial outer surface of the deformed bodies 141 and 142. The opposite of the fluctuation of. Therefore, by inverting the sign on the right side or the left side of [Equation 5] and [Equation 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 site>
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 deformed bodies 141 and 142. FIG. 21 is a schematic side view of the 1-1 detection portion A1 of the basic structure 101w shown in FIG. 21 as viewed from the positive direction of the V axis.

As shown in FIGS. 20 and 21, the detection sites A1 to A4 and B1 to B4 of the basic structure 101w are all detection sites having a downwardly convex waveform having the structure shown in FIG. The detection sites A1 to A4 of the first modified body 141 all have the same structure. Further, the detection sites B1 to B4 of the second modified body 142 all have the same structure. On the other hand, the detection sites B1 to B4 of the second deformed body 142 are relatively longer in the circumferential direction than the detection parts A1 to A4 of the first deformed body 141. Specifically, in the circumferential direction of each of the deformed bodies 141 and 142, the pair of second deformed portions 62e1 and 62e2 of the second to second to second-4 detection sites B1 to B4 are the first to first to first 1st. 4 The detection sites A1 to A4 are longer than the pair of first deformed portions 61e1 and 61e2, and are in a state of lying down on the XY plane. Further, in the circumferential direction of each of the deformed bodies 141 and 142, the second displacement portions 62d of the second to second to second-4 detection sites B1 to B4 are the second displacement portions 62d of the first to first to first-4 detection sites A1 to A4. It is longer than the first displacement portion 61d. With such a configuration, the displacement caused by the action of a 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 1-1 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 sites A1 to A4 and B1 to B4.

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

FIG. 22 shows the stress generated in the detection sites A1 to A4 and B1 to B4 of the deformed bodies 141 and 142 when the moment Mz around the Z axis acts clockwise on the movable portion 120 of the basic structure 101w of FIG. It is a figure for demonstrating. In FIG. 22, the 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 deformed body 141 and the second deformed body 142. The thick arrows indicate the directions of the forces acting on the detection sites A1 to A4 and 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 sites A3 and 2-3 detection located in the third quadrant. A tensile force is generated at the portion 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 have Compressive force is generated.

When the basic structure 101w is used as a capacitance type force sensor, each of the first 1-1 to 1-2 detection sites A1 to A4 and the 2-1 to 2-4 detection sites B1 to B4. Capacitive elements may be arranged in the displacement portions 61d and 62d. As a specific arrangement method, for example, in the 1-1 detection portion A1, as shown in FIG. 21, a displacement electrode Em11 is provided on the displacement portion 61d via the displacement substrate Im11 and faces the displacement electrodes Em11. As described above, the fixed electrode Ef11 may be arranged so as not to move relative to the fixed portion 110. The fixed electrode Ef11 is arranged on the fixed substrate 73 via the fixed substrate If11 (insulator). Such an arrangement is the same for the other displacement portions 61d and 62d. As can be understood from FIG. 21, the displacement electrode Em11 and the fixed electrode Ef11 adopted here both 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 pair of eight displacement electrodes and fixed electrodes facing each other.

Examining the fluctuation of the capacitance value of each capacitance element C11 to C24 when a clockwise moment -Mz is applied to such a capacitance type force sensor when viewed from the positive direction of the Z axis, it is as follows. It's a street. That is, the tensile force or compressive force as described above acts on the detection sites A1 to A4 and B1 to B4. Therefore, the 1-1 capacitance element C11 and the 2-1 capacitance element C21 arranged in the first quadrant, and the 1-3 capacitance element C13 and the 2-3 capacitance element C23 arranged in the third quadrant are arranged. In each case, the capacitance value decreases because the separation distance between the displacement electrode and the fixed electrode increases. On the other hand, the first and second capacitance elements C12 and the second and second capacitance elements C22 arranged in the second quadrant, and the first and fourth capacitance elements C14 and the second and fourth capacitance elements C24 arranged in the fourth quadrant are In both cases, the capacitance value increases because the separation distance between the displacement electrode and the fixed electrode decreases.

Therefore, the detection circuit 150 measures the acted moment Mz around the Z-axis using the following [Equation 7]. In [Equation 7], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformed body 141, and Mz2 is the moment around the Z axis measured based on the elastic deformation of the second deformed body 142. Moment of.
[Equation 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, fluctuations in the capacitance values of the second to second to fourth capacitance elements C21 to C24, which have relatively high sensitivity. By measuring the force acting on the basis of the amount, it is possible to measure the S / N excellently. Of course, the acting force may be measured based on the amount of fluctuation in the capacitance value of the first to first to fourth capacitance elements C11 to C14.

When the direction of the acting moment is opposite (counterclockwise when viewed from the Z-axis positive direction), the fluctuation amounts of the capacitance values of the capacitance elements C11 to C24 are all reversed. Therefore, the signs of the moments Mz1 and Mz2 measured by [Equation 7] are reversed. That is, the direction and magnitude of the acted moment Mz are measured by [Equation 7].

Alternatively, when the basic structure 101w is used as a strain gauge type force sensor, the first 1-1 to 1-2 detection sites A1 to A4 and the 2-1 to 2-4 detection sites B1 to B4 Instead of the capacitive elements C11 to C24 provided in the displacement portions 61d and 62d, specifically, the 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.

The fluctuations in the electrical resistance of each strain gauge R11 to R24 when a clockwise moment -Mz is applied to such a strain gauge type force sensor when viewed from the positive direction of the Z axis are as follows. is there. That is, the tensile force or compressive force as described above acts on 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 each case, the electric resistance value decreases due to the action of compressive stress (see FIG. 7C). On the other hand, the first and second strain gauges R12 and the second and second strain gauges R22 arranged in the second quadrant, and the first and fourth strain gauges R14 and the second and fourth strain gauges R24 arranged in the fourth quadrant are In both cases, the electric resistance value increases due to the action of tensile stress (see FIG. 7B).

Therefore, the detection circuit 150 measures the acting moment Mz around the Z-axis using the following [Equation 8]. In [Equation 8], Mz1 is a moment around the Z axis measured based on the elastic deformation of the first deformed body 141, and Mz2 is the moment around the Z axis measured based on the elastic deformation of the second deformed body 142. Moment of.
[Equation 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 electric resistance value of the first to first to fourth strain gauges R11 to R14, which have relatively high sensitivity, By measuring the force acting based on this, it is possible to measure the S / N excellently. Of course, the acting force may be measured based on the fluctuation amount of the electric resistance value of the 2-1st to 2nd-4th strain gauges R21 to R24. Further, in the measurement, the Wheatstone bridge circuit (not shown) was configured by the first 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 the moment.

<2-6. Measurement principle of force Fx in the X-axis direction and force Fy in the Y-axis direction by a basic structure having a waveform detection site>
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, but the force sensor has a force Fx in the X-axis direction and a force Fy in the Y-axis direction. It is also possible to measure. As an example, the principle for measuring the force + Fx in the positive direction of the X-axis will be described with reference to FIG.

FIG. 23 is a diagram for explaining the force acting on the detection sites A1 to A4 and B1 to B4 of the deformed body when a force in the positive direction of the X axis is applied to the movable portion 120 of the basic structure of FIG. In FIG. 23, the thick black arrow shown parallel to the X-axis indicates the acting force + Fx, and the thick black arrow shown in the gap between the first deformed body 141 and the second deformed body 142. The arrows indicate the directions of the forces acting on the detection sites A1 to A4 and B1 to 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, the 1-1 detection sites A1 and the first of the deformed bodies 141 and 142 located in the first quadrant. A tensile force acts on the 2-1 detection site B1 and the first-4 detection sites A4 and the second-4 detection sites B4 located in the fourth quadrant. On the other hand, among the deformed bodies 141 and 142, the first and second detection sites A2 and the second and second detection sites B2 located in the second quadrant, and the first and third detection sites A3 and third located in the third quadrant. 2-3 A compressive force acts on the detection site B3. This can be understood from the state of elastic deformation of the deformed body 140 shown in FIGS. 16 and 18. Therefore, 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 sites A4 and 2-th located in the fourth quadrant. 4 At the detection portion B4, the displacement portions 61d and 62d are displaced in the Z-axis positive direction (front direction in FIG. 23). On the other hand, in the 1-2 detection site A2 and the 2-2 detection site B2 located in the second quadrant, and the 1-3 detection site A3 and the 2-3 detection site B3 located in the third quadrant, The displacement portions 61d and 62d are displaced in the negative Z-axis direction (depth direction in FIG. 23).

In other words, when the basic structure 101w is used as a capacitance type force sensor, it is placed in the 1-1 capacitance element C11 and the 2-1 capacitance element C21 arranged in the first quadrant, and in the fourth quadrant. The capacitance value of each of the arranged 1-4 capacitance element C14 and the 2-4 capacitance element C24 is reduced. On the other hand, the first and second capacitance elements C12 and the second and second capacitance elements C22 arranged in the second quadrant, and the first and third capacitance elements C13 and the second and third capacitance elements C23 arranged in the third quadrant are In both cases, the capacitance value increases.

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

On the other hand, although not shown, when a force + Fy in the positive direction of the Y axis acts on the movable portion 120, the following static electricity is understood from the state of elastic deformation of the deformed body 140 shown in FIGS. 17 and 19. The capacitance value fluctuates. That is, the capacitance of the 1-1 capacitance element C11 and the 2-1 capacitance element C21 located in the first quadrant, and the 1-2 capacitance element C12 and the 2-2 capacitance element C22 located in the second quadrant. The capacitance value increases, and the 1-3 capacitance element C13 and 2-3 capacitance element C23 located in the 3rd quadrant, and the 1-4 capacitance element C14 and the 2-4 capacitance element located in the 4th quadrant. The capacitance value of C24 decreases.

Therefore, the detection circuit 150 measures the acting force Fy in the Y-axis direction using the following [Equation 10]. In [Equation 10], Fy1 is a force in the Y-axis direction measured based on the elastic deformation of the first deformed body 141, and Fy2 is a force in the Y-axis direction measured based on the elastic deformation of the second deformed body 142. Is the power of.
[Equation 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, fluctuations in the capacitance values of the second to second to fourth capacitance elements C21 to C24, which have relatively high sensitivity. By measuring the force acting on the basis of the amount, it is possible to measure the S / N excellently. Of course, the acting force may be measured based on the amount of fluctuation in the capacitance value of the first to first to fourth capacitance elements C11 to C14.

When the direction of the acting force is the negative direction on the X-axis or the negative direction on the Y-axis, the fluctuation amounts of the capacitance values of the capacitance elements C11 to C24 are all reversed. Therefore, the signs of the forces Fx1 and Fx2 measured by [Equation 9] are opposite to each other. That is, by examining the sign and magnitude of the force Fx obtained by [Equation 9], the direction and magnitude of the applied force can be measured. This also applies when measuring the force in the Y-axis direction using [Equation 10].

On the other hand, if strain gauges are arranged in the displacement portions 61d of the first to first to fourth detection sites 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 acts on the basic structure 101w is as described in 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. In R14 and the 2nd-4th strain gauge R24, the electric resistance value decreases due to the action of compressive stress (see FIG. 7C). On the other hand, the first and second strain gauges R12 and the second and second strain gauges R22 arranged in the second quadrant, and the first and third strain gauges R13 and the second and third strain gauges R23 arranged in the third quadrant are , The electric resistance value increases due to the action of tensile stress (see FIG. 7B).

Here, it is necessary to pay attention to the following points when observing. That is, in FIG. 7, when a compressive stress acts on the deformed body (see FIG. 7B), a tensile stress is generated on the surface of the displacement portion 61d on the negative side of the X-axis as shown by a thin arrow in the drawing. When a tensile force (see FIG. 7C) acts on the deformed body, a compressive stress is generated on the surface of the displacement portion 61d on the negative side of the X-axis. Therefore, the strain gauges R11 and R21 arranged in the first quadrant and the strain gauges R14 and R24 arranged in the fourth quadrant in FIG. 22 are arranged in the second quadrant because the electric resistance value decreases due to the action of compressive stress. The strain gauges R12 and R22 and the strain gauges R13 and R14 arranged in the third quadrant increase their electrical resistance values due to the action of tensile stress.

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

On the other hand, although not shown, when a force + Fy in the positive direction of the Y axis acts on the movable portion 120, as can be understood from the elastic deformation of the deformed body 140 shown in FIGS. 16 and 18, the following electricity is applied. The resistance value fluctuates. 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 tensioned. The action of stress (see FIG. 7 (c)) increases the electrical resistance value. On the other hand, the 1-3 strain gauge R13 and the 2-3 strain gauge R23 located in the 3rd quadrant, and the 1-4 strain gauge R14 and the 2-4 strain gauge R24 located in the 4th quadrant are The action of compressive stress (see FIG. 7B) reduces the electrical resistance value.

Therefore, the detection circuit 150 measures the acting 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 deformed body 141, and Fy2 is a force in the Y-axis direction measured based on the elastic deformation of the second deformed body 142. Is the power of.
[Equation 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 arranged at the first to first to fourth detection sites A11 to A14 where relatively large stress is generated. By measuring the acting force or moment based on the fluctuation amount of, it is possible to measure with high sensitivity excellent in S / N.

<<< §3. Principle of failure diagnosis of force sensor according to the present invention >>>
The force sensor using the basic structures 1, 101, 101w according to the present invention can perform failure diagnosis by a single force sensor. Since the deformed bodies 30, 141, and 142 of the basic structures 1, 101, and 101w have flexibility, metal fatigue occurs due to overload or repeated load. As a result, the elastic bodies constituting the deformed bodies 30, 141 and 142 may crack or eventually break. Therefore, if a force sensor capable of performing failure diagnosis can be provided, the reliability and safety of the force sensor can be improved. The principle of failure diagnosis is also described in, for example, the international application PCT / JP2016 / 75236 by the applicant.

<3-1. Failure diagnosis in capacitance type force sensor>
First, returning to FIGS. 1 to 4, the principle of failure diagnosis will be described by taking 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 deformed body 31 and the second deformed body 32. When this metal fatigue accumulates, the strength of the first deformed body 31 and the second deformed body 32 decreases, and finally the deformed bodies 31 and 32 are broken. Generally, when metal fatigue accumulates in a metal material, the metal material softens, so that the spring constants of the deformed bodies 31 and 32 decrease. In other words, the plasmodiums 31 and 32 are more sensitive to force-Fy than in the initial state due to the accumulation of metal fatigue. This is understood by comparing FIGS. 24 and 25. In the force sensor 1c, metal fatigue is remarkably exhibited in the first deformed body 31 in which a relatively large stress is generated. Therefore, the change (decrease) in the spring constant, that is, the increase in the sensitivity to the force −Fy is remarkable in the first deformed body 31.

FIG. 24 shows the magnitude of the force acting on the force sensor 1c and the first electrical signal output from the force sensor 1c when the force sensor 1c of FIG. 3 is not subject to metal fatigue (initial state). It is a graph showing the relationship between T1a and the second electric 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 force sensor 1c. The reference numerals at the end of T1 and T2 are for distinguishing between the electric signal in the initial state (adding a at the end) and the electric signal in the state where metal fatigue is accumulated (adding b at the end). is there. The first electric signals T1a and T1b are electric signals indicating the amount of fluctuation of the capacitance value of the first capacitance element C1, and the second electric signals T2a and T2b are the capacitance values of the second capacitance element C2. It is an electric signal indicating the amount of fluctuation of.

As can be understood from FIG. 24, focusing on the first electric signal T1 corresponding to the first capacitance element C1 provided in the first deformed body 31 in which the decrease in the spring constant (increase in sensitivity) is relatively large, the initial stage 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, the slope (sensitivity) of the straight line indicating the first electric signal T1b is 0.75 in the state where metal fatigue is accumulated. Therefore, the sensitivity is increased by 50%.

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

What should be noted here is that the degree of occurrence of metal fatigue differs between the first deformed body 31 and the second deformed body 32. That is, in the initial state, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a is 0.25, whereas in the state where metal fatigue is accumulated, the first is The ratio of the electric signal T1b to the second electric signal T2b (T1b / T2b) has risen to 0.3125. Since this ratio T1 / T2 gradually increases from 0.25 to 0.3125 as a repeated load acts, failure diagnosis of the force sensor 1c is performed by paying attention to the change in this ratio. It will be done.

Specifically, while measuring the force −Fy based on the fluctuation amount of the capacitance value of the second capacitance element C2 arranged in the second deformed body 32, the first electric signal T1 and the second electric signal T2 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 it is. Of course, the acting force −Fy may be measured based on the amount of fluctuation in the capacitance value of the first capacitance element C1.

<3-2. Failure diagnosis in strain gauge type force sensor>
In the strain gauge type force sensor 1s, a new failure diagnosis can be performed in the same manner. That is, although not shown, when a force −Fy in the negative direction of the Y axis acts on the force sensor 1s, the electrical resistance values of both the first strain gauge R1 and the second strain gauge R2 increase as described above. .. Therefore, if the electric resistance value is on the vertical axis and the acting force −Fy in the negative direction of the Y axis is on the horizontal axis and the relationship between them is represented in a graph, it becomes a straight line similar to that in FIGS. 24 and 25. However, also in this case, the deformed bodies 31 and 32 soften (the spring constant decreases) with the use of the force sensor 1s, that is, with the accumulation of metal fatigue in the deformed bodies 31 and 32. .. Due to this softening, the displacement generated in the detection sites A and B of the deformed bodies 31 and 32 increases, and the stress acting on the strain gauge increases accordingly. Even in the force sensor 1s, metal fatigue is remarkably exhibited in the first deformed body 31 in which a relatively large stress is generated. Therefore, the change (decrease) in the spring constant is remarkable in the first deformed body 31. In the strain gauge type force sensor 1s, the smaller the spring constant of the deformed body 30, the smaller the stress generated in the deformed body. Therefore, as the spring constant decreases, the sensitivity increases. That is, as the spring constant decreases, the sensitivity of each of the elastic bodies 31 and 32 to the force −Fy increases.

From the above, assuming that 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 2 The ratio (T1 / T2) to the electric signal T2 is different between the initial state and the accumulated metal fatigue. Utilizing this, the failure diagnosis of the force sensor 1s is performed.

Hereinafter, the principle for performing failure diagnosis in the force sensor 1s will be described with reference to FIGS. 26 and 27. FIG. 26 shows the magnitude of the Y-axis negative force −Fy acting on the force sensor 1s when metal fatigue does not occur in the force sensor 1s of FIG. 4 (initial state), and the force sense sensor 1s. It is a graph which shows the relationship between the output 1st electric signal T1a and the 2nd electric signal T2a, and FIG. 27 shows the force sensor 1s of FIG. 4 when metal fatigue occurs in the force sensor 1s of FIG. It is a graph which shows the relationship between the magnitude of the acting Y-axis negative direction force −Fy, and the 1st electric signal T1b and the 2nd electric signal T2b output from the force sensor 1s. The first electric signals T1a and T1b are electric signals indicating the amount of fluctuation 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. Here, too, the reference numerals at the end of T1 and T2 are used to distinguish between the electric signal in the initial state (a is added at the end) and the electric signal in the state where metal fatigue is accumulated (b is added at the end). belongs to.

As can be seen from FIG. 26, focusing on the first electric signal T1 corresponding to the first strain gauge R1 provided on the first deformed 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, the slope (sensitivity) of the straight line indicating the first electric signal T1b is 2.8 in the state where metal fatigue is accumulated. Therefore, the sensitivity is increased by 40%.

On the other hand, focusing on the second electric signal T2 corresponding to the second strain gauge R2 provided on the second deformed body 32 in which the decrease in spring constant (increase in sensitivity) is relatively small, as can be 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 can be understood from FIG. 27, in the state where 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%.

What should be noted here is that the degree of occurrence of metal fatigue differs between the first deformed body 31 and the second deformed body 32. That is, in the initial state, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a is 4.0, whereas in the state where metal fatigue is accumulated, the first is The ratio of the electric signal T1b to the second electric signal T2b (T1b / T2b) is increased to 4.667. Since this ratio T1 / T2 gradually increases from 4.0 to 4.667 with the action of repeated loads, failure diagnosis of the force sensor 1s is performed by paying attention to the change in this ratio. It will be done.

Specifically, while measuring the force −Fy based on the fluctuation amount of the electric resistance value of the first strain gauge R1 arranged in the first deformed body 31, the first electric signal T1 and the second electric signal T2 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. Whether or not it is determined. Of course, the acting force −Fy may be measured based on the amount of fluctuation in the electric resistance value of the second strain gauge R2.

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

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

Also in the force sensor 101c shown in FIG. 11, the ratio of the first electric signal T1 and the second electric signal T2 changes as metal fatigue accumulates in the first deformed body 141 and the second deformed body 142. This is used to diagnose the failure of the force sensor. Therefore, again, in the following description, the first and second electrical signals in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142 are T1a and T2a, respectively, and the first The first and second electrical signals in a state where metal fatigue is accumulated in the deformed body 141 and the second deformed body 142 are designated as T1b and T2b, respectively, to distinguish them from each other.

In the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed 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. The relationship between and is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformed body 141 and the second deformed body 142, the magnitude of the moment −Mz acting on the force sensor and the first and second electric signals T1a and T2a at this time. The relationship between and 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 as. That is, 3-1. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in [Equation 13], the principle and method of failure diagnosis of the force sensor 101c are understood. Therefore, a detailed description of the principle and method will be omitted here. Even if the reverse moment + Mz acts, the failure diagnosis can be performed in the same manner.

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

Again, in the following description, the first and second electrical signals in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142 are T1a and T2a, respectively, and the first deformed body The first and second electrical signals in a state where metal fatigue is accumulated in 141 and the second deformed body 142 are designated as T1b and T2b, respectively, to distinguish them from each other.

The magnitude of the force Fx acting on the force sensor 101c in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG. 24. Further, the magnitude of the force Fx acting on the force sensor 101c in a state where metal fatigue is accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and 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 as. That is, 3-1. By replacing the first electric signal T1 (T1a, T1b) and the second electric signal T2 (T2a, T2b) in the above with [Equation 14], the principle and method of failure diagnosis of the force sensor 101c are understood. Therefore, a detailed description of the principle and method will be omitted here.

Further, it is also possible to perform a failure diagnosis of the force sensor 101c by using the force Fy in the Y-axis direction acting on the receiving body 120. In this case, the electric signals corresponding to Fy1 and Fy2 in the above-mentioned [Equation 4] may be the first electric signal T1 and the second electric signal T2. The magnitude of the force Fy acting on the force sensor 101c in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG. 24. Further, the magnitude of the force Fy acting on the force sensor in a state where metal fatigue is accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG.

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

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

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

Also in the force sensor 101s shown in FIG. 12, the ratio of the first electric signal T1 and the second electric signal T2 changes as metal fatigue accumulates in the first deformed body 141 and the second deformed body 142. This is used to diagnose the failure of the force sensor. Therefore, again, in the following description, the first and second electrical signals in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142 are T1a and T2a, respectively, and the first The first and second electrical signals in a state where metal fatigue is accumulated in the deformed body 141 and the second deformed body 142 are designated as T1b and T2b, respectively, to distinguish them from each other.

In the initial state where metal fatigue is not accumulated in the first deformed body 141 and the second deformed 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. The relationship between and is the same as the graph shown in FIG. Further, in a state where metal fatigue is accumulated in the first deformed body 141 and the second deformed 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. 27.

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

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

Again, in the following description, the first and second electrical signals in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142 are T1a and T2a, respectively, and the first deformed body The first and second electrical signals in a state where metal fatigue is accumulated in 141 and the second deformed body 142 are designated as T1b and T2b, respectively, to distinguish them from each other.

The magnitude of the force Fx acting on the force sensor 101s in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG. Further, the magnitude of the force Fx acting on the force sensor 101s in a state where metal fatigue is accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG. 27.

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

Further, it is also possible to perform a failure diagnosis by using the force Fy in the Y-axis direction acting on the receiving body 120. In this case, the electric signals corresponding to Fy1 and Fy2 in the above-mentioned [Equation 6] may be the first electric signal T1 and the second electric signal T2. The magnitude of the force Fy acting on the force sensor 101s in the initial state in which metal fatigue is not accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG. Further, the magnitude of the force Fy acting on the force sensor 101s in a state where metal fatigue is accumulated in the first deformed body 141 and the second deformed body 142, and the first and second electric signals T1a and T2a at this time. The relationship between and is the same as the graph shown in FIG. 27.

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 will be omitted here.

(3-3-3. In the case of a force sensor using the basic structures 101a, 101b, 101b'shown in FIGS. 13 to 15)
Next, a failure diagnosis in the capacitance type force sensor using the basic structure 101a shown in FIG. 13 will be described. Although this force sensor is not shown, eight parts of the force sensor located on the V-axis and the W-axis (first to first to first-4 detection parts A1 to A4 and 2-1). It is assumed that the capacitive elements C11 to C24 are arranged in all of the 2-4 detection sites B1 to B4). It is assumed that the separation distances of the electrodes constituting the capacitance elements C11 to C24 are all the same, and the effective facing areas are also the same.

The principle and method of failure diagnosis in such a force sensor are described in 3-3-1. It is substantially the same as the case of the capacitance type force sensor 101c shown in FIG. However, the 2-1st to 2nd-4th capacitive elements C21 to C24 are arranged on the thin-walled portions 142t1 to 142t4 of the second deformed body 142. Therefore, a graph showing the relationship between the acting 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. 24. And the second electric signals T2a and T2b shown in FIG. 25 both have a larger inclination than the inclination. However, the ratio of their 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 in the state where metal fatigue is accumulated, the first electric signal T1b and the second electric signal T1b The ratio (T1b / T2b) to the two electric signals T2b is 0.3125.

Next, failure diagnosis in the 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 sites (first 1-1 to 1-4 detection sites A1 to A4 and second) located on the V axis and the W axis of each force sensor are not shown. It is assumed that the capacitive elements C11 to C24 are arranged in all of the -1 to 2-4 detection sites B1 to B4). Further, it is assumed that the separation distances of the electrodes constituting the capacitance elements C11 to C24 are all the same, and the effective facing areas are also the same.

As described above, these force sensors also have the second 2-1 to 2-4 capacitive elements C21 to C24 arranged in the same manner as the force sensors using the basic structure 101a shown in FIG. Since the thin-walled portions 142t1 to 142t4 are provided only on the deformed body 142, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a in the initial state and metal fatigue are accumulated. The ratio (T1b / T2b) of the first electric signal T1b and the second electric signal T2b in the state is the same value as in the case 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. are doing. Therefore, even in these force sensors, the principle and method of failure diagnosis are as follows: 3-3-1. It is substantially the same as the case of the force sensor 101c shown in FIG. 10 described with reference to.

Next, a 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, eight parts of the force sensor located on the V axis and the W axis (first to first to first-4 detection parts A1 to A4 and 2nd). It is assumed that strain gauges R11 to R24 are arranged in all of the 1st to 2nd-4th detection sites B1 to B4). Further, it is assumed that the strain gauges R11 to R24 all have the same characteristics.

The principle and method of failure diagnosis in such a force sensor are described in 3-3-2. It is substantially the same as the case of the force sensor 101s shown in FIG. 11 described with reference to. However, the 2-1st to 2nd-4th strain gauges R21 to R24 are arranged on the thin portion 142t1 to 142t4 of the second deformed body 142. Therefore, the 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. 26 and FIG. Both have a slope larger than the slopes of the second electric signals T2a and T2b shown in FIG. 27. However, the ratio of their inclinations is the same. That is, in the initial state, the ratio (T1a / T2a) of 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 in a state where metal fatigue is accumulated. The ratio to the signal T2b (T1b / T2b) is 4.667.

Next, a 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 sites (first 1-1 to 1-4 detection sites A1 to A4 and second) located on the V axis and the W axis of each force sensor are not shown. It is assumed that strain gauges R11 to R24 are arranged in all of the -1 to 2-4 detection sites B1 to B4). Further, it is assumed that the strain gauges R11 to R24 all have the same characteristics.

As described above, these force sensors also have the second strain gauges R11 to R24 in which the second to second to second-4 strain gauges R11 to R24 are arranged, similarly to the force sensors using the basic structure 101a shown in FIG. Since the thin-walled portions 142t1 to 142t4 are provided only on the deformed body 142, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a in the initial state and metal fatigue are accumulated. The ratio (T1b / T2b) of the first electric signal T1b and the second electric signal T2b in the state is the same value as in the case 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. There is. Therefore, even in these force sensors, the principle and method of failure diagnosis are described in 3-3-2. It is substantially the same as the case of the force sensor 101s shown in FIG. 11 described with reference to.

<<< §4. Further deformation example of the detection site >>>
Next, FIG. 28 is a schematic side view showing a modified example of the detection portion of the basic structure in each of the above embodiments. As shown in FIG. 28, the detection sites E according to this modification are of the first connection portion 71 and the second connection portion 72 arranged so as to be relatively movable in the uniaxial direction (Y-axis direction in FIG. 28). It is placed in between. The detection portion E is made of an elastic material (for example, metal) and has a uniform thickness, and has an arcuate shape that is smoothly curved so as to bulge in the negative direction of the X axis (right side in FIG. 29). ing. As shown in FIG. 29, the detection portion E corresponds to the detection portion E when viewed from the Z-axis direction when the virtual axis L parallel to the X-axis is taken into consideration so as to pass through the portion located on the most negative side (right side) of the X-axis. It is symmetric with respect to the virtual axis.

Next, the action of such a detection site E will be described with reference to FIG. 29. FIG. 29A is a schematic view showing the detection part E when a compressive force in the Y-axis direction acts on the detection part E shown in FIG. 28, and FIG. 29B is a schematic view showing the detection part E shown in FIG. 28. It is a schematic diagram which shows the detection part E when the tensile force in the Y-axis direction acts on the part E. As will be described later, the detection element (capacitive element or strain gauge) is arranged at the position R on the negative side of the X-axis in the portion where the detection portion 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. In the initial state, it is assumed that no stress is generated on the surface of the detection site E. Further, in FIG. 29, the thick black arrow indicates the direction of the force acting along the Y-axis direction, and the thick white arrow arranged parallel to the X-axis is the most of the detection sites E. The direction of displacement occurring at the position R on the negative side of the X-axis is indicated, and the thin arrow indicates the stress generated at the position R (“→ ←” is the compressive stress, “← →” is the tensile stress).

First, as shown in FIG. 29A, when the first connection portion 71 is relatively moved so as to approach the second connection portion 72 along the Y-axis direction, the detection portion E is moved in the Y-axis direction. It is compressed. As a result, the position R is displaced in the negative direction of the X-axis. Further, at this time, since the radius of curvature in the vicinity of 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 so as to be separated from the second connecting portion 72 along the Y-axis direction, the detection portion E is moved in the Y-axis direction. Stretched. As a result, the position R is displaced in the positive direction of the X-axis.

In addition, the stress generated at the position R when a force acts on the detection site E will be examined. As shown in FIG. 29 (a), when a compressive force acts between the first connection portion 71 and the second connection portion 72, the radius of curvature near the position R becomes smaller, so that the position R is located in the Y-axis direction. Tensile stress is generated along. On the other hand, as shown in FIG. 29B, when a tensile force acts between the first connecting portion 71 and the second connecting portion 72, the radius of curvature near the position R becomes large, so that the Y axis is located at the position R. Compressive stress is generated along the direction. After all, 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 stress (compression or tension) generated at the position R'on the positive side of the X-axis is the deformation of FIGS. 29 (a) and 29 (b). As understood from the aspect, it is the same as the direction (compression or tension) of the force acting on the detection site E.

When such a detection portion is adopted in the basic structure 1 shown in FIG. 1, the above-mentioned is described between the first movable portion side connecting portion 31m and the first fixed portion side connecting portion 31f instead of the first deformed body 31. The detected detection site E is arranged as the first detection site E1, and the above-mentioned detection site E is placed between the second movable portion side connection portion 32m and the second fixed portion side connection portion 32f instead of the second deformed body 32. 2 It may be arranged as the detection site E2. However, the second detection site E2 is configured to have a larger radius of curvature than the first detection site E1. As a result, the spring constant of the second detection portion E2 is set smaller than the spring constant of the first detection portion E1.

Alternatively, when such a detection site is adopted in the basic structure 101 having the annular deformed bodies 141 and 142 shown in FIG. 8, the first 1-1 to 1-4 detection sites A1 to A4 and 2-1 are used. ~ 2-4 The above-mentioned detection sites E may be arranged at positions corresponding to the detection sites B1 to B4, respectively. That is, gaps are provided along the circumferential direction at eight positions corresponding to the first 1-1 to 1-4 detection sites A1 to A4 and the 2-1 to 2-4 detection sites B1 to B4, and the gaps are within the gaps. The detection site E shown in FIG. 28 may be arranged so as to intervene in. 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 1st 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. As a result, the spring constant of the second detection portion E2 is set smaller than the spring constant of the first detection portion E1. The four detection sites E of the first detection site E1 may have the same configuration as each other, and the four detection sites E of the second detection site E2 may have the same configuration as each other.

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

In the first modified body 141 shown in FIG. 30, the region including the position overlapping the V-axis and the W-axis when viewed from the Z-axis direction is replaced with the detection portion E1 shown in FIG. 28. Here, each detection site E1 is formed in such a manner that the circle providing the arc of the detection site E1 exists parallel to the XY plane. Each detection site E1 is arranged so as to be convex outward in the radial direction.

When a force or moment acts on the first deformed 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 deformed body. Therefore, as described above, the portion of the detection portion E1 that overlaps the V-axis and the W-axis is displaced along the radial direction of the first deformed body 141 (along the V-axis direction or the W-axis direction). Further, compressive stress or tensile stress is generated at the site.

On the other hand, in the first deformed body 141 shown in FIG. 31A, a region including a position overlapping the V-axis and the W-axis when viewed from the Z-axis direction is shown in FIG. 28, similarly to the first deformed body 141 shown in FIG. Although it is replaced with the detection site E1 shown, its arrangement is different from that in FIG. That is, as shown in FIG. 31 (b), in the first variant 141 of FIG. 31 (a), the detection sites E1 arranged in the first and third quadrants provide the arcs of these detection sites E1. In the detection sites E1 arranged in the second quadrant and the fourth quadrant, the circles providing the arcs of the detection sites E1 are formed in such a manner that the circles to be formed are parallel to the WZ plane. It is formed in such a manner that it exists in parallel with.

When a force or moment acts on the first deformed 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 deformed body. Therefore, as described above, the portion of the detection portion E1 that overlaps 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 at the site.

FIG. 32 is a schematic view showing the detection portion E of FIG. 28 in which the capacitive element C is arranged. As an example, in the capacitive element C, as shown in FIG. 32, a displacement electrode Em is arranged at a position R via a displacement substrate Im (insulator), and a fixed substrate If (insulation) is arranged at a position facing the displacement electrode Em. It can be constructed by arranging a fixed electrode Ef that does not move in the XYZ three-dimensional coordinate system via the body). Of course, the detection portion E having the capacitive element C can be adopted in the force sensor using the basic structure 1 shown in FIG. 1 and in the force sensor using the annular basic structure 101 shown in FIG. The position R is a position among the detection sites E that is most displaced in the X-axis direction due to the force (compressive force and tensile force) acting on the detection site E. Therefore, if the capacitive element C is configured at the position R, the force or moment acting with the highest sensitivity can be measured.

When a compressive force acts on 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. 29 (a)). Therefore, the separation distance between the displacement electrode Em and the fixed electrode Ef decreases, and the capacitance value of the capacitance element C increases. On the other hand, when a tensile force acts on the detection portion E shown in FIG. 32, the position R moves in the positive direction of the X axis as described above (see FIG. 29 (b)). Therefore, the separation distance between the displacement electrode Em and the fixed electrode Ef increases, and the capacitance value of the capacitance element C decreases. Eventually, each detection site of the force sensor 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 is replaced with the detection site E shown in FIG. 28. Even if a new force sensor is configured, this new force sensor exhibits the same behavior (output characteristics) as when a force or moment acts on each force sensor before replacement. It will be.

As shown in FIG. 32, if the fixed substrate 73 is arranged on the same plane as the fixed portion 110, the fixed electrodes E (4) facing the four displacement electrodes Em of the first deformed body 141 and the second deformation It is advantageous because a total of eight fixed electrodes (four) facing the four displacement electrodes Em of the body can be formed by a single substrate (fixed substrate 73).

Further, FIG. 33 is a schematic view showing the detection portion E of FIG. 28 in which the strain gauge R is arranged. The strain gauge may be arranged at the position R as an example. Such a detection site E can be adopted in the basic structure 1 shown in FIG. 1 or in the annular basic structure 101 shown in FIG. The position R is the position where the largest stress acts due to the force (compressive force and tensile force) acting on the detection site E among the detection sites E. Therefore, 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 acts on the detection site E shown in FIG. 33, a tensile stress acts on the position R as described above (see FIG. 29 (a)). Therefore, the electric resistance value of the strain gauge R increases. On the other hand, when a tensile force acts on the detection portion E shown in FIG. 33, a compressive stress acts on the position R as described above. (See FIG. 29 (b)). Therefore, the electric resistance value of the strain gauge R decreases. Eventually, each detection site of the force sensor 1s and 101s shown in FIGS. 4 and 12 and the force sensor using the basic structures 1w and 101w shown in FIGS. 5 and 20 is replaced with the detection site E shown in FIG. 28. Even if a new force sensor is configured, this new force sensor exhibits the same behavior (output characteristics) as when a force or moment acts on each force sensor before replacement. It will be.

<<< §5. In the capacitance type force sensor, a device to keep the effective facing area between the plates constant >>>
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 action of a force in each axial direction or a moment around each axis, a pair constituting the capacitive element. It is also conceivable to set the area of one of the fixed electrode and the displacement electrode constituting each capacitance element to be larger than the area of the other so that the effective facing area of the electrodes of This is the case where the contour of the electrode having a smaller area (for example, a displacement electrode) is projected onto the surface of the electrode having a larger area (for example, a fixed electrode) in the normal direction of the electrode to form a normal projection image. , The projected 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 composed of 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.

1 Basic structure 1c Capacitive type force sensor 1s Strain gauge type force sensor 1w Basic structure 10 Fixed part 20 Movable part 30 Deformed body 31 First deformed body 31e First elastic body 31f First fixed part side connection part 31m 1st movable part side connection part 32 2nd deformed 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 first deformations Parts 61f, 61m Connection part 62d Second displacement part 62e1, 62e2 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 Moving part 131 Connecting body 131l Connecting body 132 Connecting body 132a, 132b, 132c, 132d Connecting body 133 Connecting body 134, 134a, 134b Connecting Body 135 Connecting body 135l Connecting body 136, 136a, 136b Connecting body 137 Connecting body 138, 138a, 138b Connecting body 140 Deformed body 141 First deformed body 142 Second deformed body 142t1, 142t2, 142t3, 142t4 Thin-walled parts 142b, 142b1, 142b2, 142b3, 142b4 Variant 150 detection circuit

Claims (5)

A force sensor that detects the moment around the Z axis in the XYZ three-dimensional coordinate system, and 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 when viewed from the Z-axis positive direction,
An elastic plasmodium whose one end is supported by the fixed body and the other end is supported by the receiving body.
A capacitive element having a displacement electrode arranged on the elastically deformed body and a fixed electrode facing the displacement electrode and not moving relative to the fixed body .
With
As the elastic deformed body,
With first and second elastic plasmodium arranged symmetrically with respect to the X axis,
The first elastic deformed body includes a first arc-shaped deformed body having one end and the other end, a first connecting body that connects the one end of the first arc-shaped deformed body to the fixed body, and the above-mentioned. It has a second connecting body that connects the other end of the first arc-shaped deformed body to the receiving body.
The second elastic deformed body includes a second arc-shaped deformed body having one end and the other end, and a third connected body that connects the one end of the second arc-shaped deformed body to the fixed body. It has a fourth connecting body that connects the other end of the second arc-shaped deformed body to the receiving body.
The first arc-shaped deformed body is thinner than the first and second connected bodies, and the second arc-shaped deformed body is thinner than the third and fourth connected bodies. ,
A connecting body connecting the fixed body and the receiving body is provided between the second connecting body and the fourth connecting body.
A force sensor characterized in that the first arc-shaped deformed body and the second arc-shaped deformed body are formed in an arc shape bulging outward in the radial direction. The force sensor according to claim 1, wherein the connecting body connecting the fixed body and the receiving body extends in parallel with the second connecting body and the fourth connecting body. The force sensor according to claim 1 or 2, wherein the first and second arcuate deformed bodies have the same curvature as the annular receiving body. One of claims 1 to 3, wherein the fixed body is formed in an annular shape, and the first and second arcuate deformed bodies have the same curvature as the annular fixed body. The force sensor described in. Further provided with a third elastic deformed body arranged symmetrically with respect to the first elastic deformed body with respect to the Y axis.
The third elastic deformed body includes a third arc-shaped deformed body having one end and the other end, a fifth connecting body that connects the one end of the third arc-shaped deformed body to the fixed body, and the above-mentioned It has a sixth connecting body that connects the other end of the third arc-shaped deformed body to the receiving body.
The force sensor according to any one of claims 1 to 4, wherein the third arc-shaped deformed body is formed in an arc shape bulging outward in the radial direction.

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