JP6685568B2 - 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.

  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 is described in, for example, Patent Document 1, and a force of an industrial robot is used. Widely used for control. In recent years, it has also been adopted in life support robots. As the market for force sensors has expanded, there has been a further demand for lower price and higher performance of force sensors.

  By the way, as the force sensor, a capacitance type force sensor that detects a force or a moment based on a variation amount of a capacitance value of a capacitive element, or a force sensor based on a variation amount of an electric resistance value of a strain gauge is used. A strain gauge type force sensor that detects a moment is used. Among these, the strain gauge type force sensor has a complicated structure of a strain generating body (elastic body), and requires a step of attaching a strain gauge to the strain generating body in its manufacturing process. As described above, the strain gauge type force sensor requires a high manufacturing cost, and thus it is difficult to reduce the cost.

  On the other hand, the capacitance type force sensor can measure the force or the moment applied by a pair of parallel flat plates (capacitance elements), so that the structure of the strain generating body including the capacitance elements is simplified. be able to. That is, the capacitance type force sensor has an advantage that it is easy to reduce the cost because the manufacturing cost is relatively low. Therefore, by further simplifying the structure of the flexure element including the capacitive element, it is possible to further reduce the cost of the capacitance type force sensor.

JP, 2004-354049, A The present invention was devised in view of the above circumstances. That is, an object of the present invention is to provide an electrostatic capacitance type force sensor that is less expensive than conventional ones by simplifying the structure of the strain-generating body including the capacitive element.

A force sensor according to the present invention detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system,
An annular deformable body that is arranged so as to surround the origin O when viewed from the Z-axis direction and that elastically deforms by the action of a force or moment;
A detection circuit that outputs an electrical signal indicating an applied force or moment based on elastic deformation of the deformable body,
The deformable body is provided with two fixed portions fixed to the XYZ three-dimensional coordinate system, and two force receiving members that are alternately positioned with the fixed portions in the circumferential direction of the deformable body and that receive a force or a moment. A portion and four deforming portions positioned between the fixed portion and the force receiving portion that are adjacent to each other in the circumferential direction of the deformable body,
Each deformed portion has a curved portion that bulges in the Z-axis direction,
The detection circuit outputs the electric signal based on the elastic deformation of the bending portion.

  According to the present invention, the displacement corresponding to the applied force or moment can be generated in the Z-axis direction at the detection site by the simple deformable body having the curved portion that bulges in the Z-axis direction. Therefore, the pair of electrodes forming the capacitor can be arranged in parallel with the XY plane, so that the capacitor can be easily formed. That is, in the conventional capacitance type force sensor, the displacement corresponding to the applied force or moment is generated in the direction orthogonal to the Z axis, so that the support body extending in the Z axis direction is provided on the upper surface of the fixed body. The other electrode (fixed electrode) had to be installed on this support after being provided, and the structure was rather complicated. In view of such a conventional arrangement example of the electrodes, the effect of the present invention can be better understood. According to the present invention, by adopting the simple structure as described above, it is possible to provide a capacitance-type force sensor that is less expensive than conventional ones. In particular, in the force sensor having a plurality of capacitance elements, the fixed electrode (the electrode facing the displacement electrode arranged in the curved portion) of each pair of electrodes can be configured using a common substrate. Furthermore, the fixed electrode can be configured as a common electrode corresponding to a plurality of capacitive elements.

Such a force sensor includes a fixed body fixed with respect to an XYZ three-dimensional coordinate system,
A force receiving member that moves relative to the fixed portion by the action of a force or a moment,
The fixed portion of the deformable body is connected to the fixed body,
The force receiving portion of the deformable body may be configured to be connected to the force receiving body.

  In this case, it is easy to apply a force or moment to the deformable body.

  Through holes through which the Z axis is inserted may be formed in the fixed body and the force receiving body, respectively. In this case, the force sensor can be reduced in weight, and the degree of freedom in installing the force sensor can be increased.

The two fixing portions are arranged symmetrically with respect to the Y axis at a portion where the deformable body overlaps with the X axis when viewed from the Z axis direction,
The two force receiving portions may be arranged symmetrically with respect to the X axis at a portion where the deformable body overlaps with the Y axis when viewed in the Z axis direction.

  In this case, the acting force or moment can be effectively transmitted to the deformable body.

  The deformable body may have an annular shape centered on the origin O when viewed from the Z-axis direction.

  Alternatively, the deformable body may have a rectangular shape centered on the origin O when viewed from the Z-axis direction.

  In these cases, since the deformable body is arranged symmetrically with respect to the X axis and the Y axis, the deformable body is deformed symmetrically due to the applied force or moment. Therefore, it is easy to measure the force or moment acting on the basis of the deformation.

Each curved portion of the deformable body bulges in the negative direction of the Z axis,
The detection circuit has a total of four displacement electrodes, one disposed on each curved portion, and a fixed electrode that is disposed so as to face the displacement electrodes and is fixed to the fixed portion,
Each displacement electrode and the fixed electrode constitute four sets of capacitive elements,
The detection circuit may output an electric signal indicating an applied force or moment based on the amount of change in the capacitance value of the four sets of capacitive elements.

  In this case, by paying attention to the combination of variations in the capacitance value of each capacitive element, a plurality of components out of a total of six components of the force in each axial direction and the moment around each axis in the XYZ three-dimensional coordinate system can be obtained. Can be detected.

  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 four sets of capacitive elements are One may be arranged at each of four sites intersecting with the V axis and the W axis.

  In this case, since the capacitive elements are arranged symmetrically with respect to the X-axis and the Y-axis, when the deformed body having a symmetrical shape with respect to the X-axis and the Y-axis is applied, the static elements of the capacitive elements have high symmetry. The capacitance value fluctuates. Therefore, the applied force or moment can be very easily measured based on the variation amount of the capacitance value.

In such a force sensor, one deformation body side support body is connected to each bending portion of the deformation body,
Each of the four displacement electrodes may be supported by the corresponding deformable body side support.

  If the displacement electrode is directly attached to the curved portion, the displacement electrode will be warped due to the influence of the deformation of the curved portion. Since no warpage occurs, elastic deformation occurring in the curved portion can be efficiently converted into fluctuations in the capacitance value of the capacitive element.

In the force sensor described above, a detection portion is defined in each of the curved portions of the deformable body at a portion located closest to the Z-axis negative side,
Each of the deformable body side support bodies is arranged so as to overlap with the detection site of the curved portion to which the deformable body side support body is connected, and one end of the beam is located at the detection site. A connecting body connected to the bending portion at a position different from,
Each of the displacement electrodes may be configured to be supported by the corresponding beam of the corresponding deformable body side support.

  In this case, since the beam is connected to the bending portion at a position different from the detection site, the displacement generated in the displacement electrode supported by this beam is amplified. That is, when a certain amount of force or moment acts, the displacement generated in the displacement electrode in such a force sensor is applied to the displacement electrode in the force sensor in which the displacement electrode is supported at the detection site of the bending portion. Greater than the resulting displacement. Therefore, the sensitivity to the applied force or moment is high, and more accurate measurement can be performed.

Alternatively, with the following configuration, it is possible to provide a force sensor capable of performing failure diagnosis with a single force sensor. That is, each curved portion of the deformable body bulges in the Z-axis negative direction,
The detection circuit has a total of eight displacement electrodes, two of which are arranged in each curved portion, and a fixed electrode which is arranged to face these displacement electrodes and is fixed to the fixed portion,
The displacement electrode and the fixed electrode constitute eight sets of capacitive elements,
The detection circuit is
A first electrical device that indicates an applied force or moment based on the amount of change in the capacitance value of a total of four capacitive elements, one of which is selected from two capacitive elements arranged in each curved portion of the deformable body. A signal is output, and a second electric signal indicating an applied force or moment is output based on the amount of change in the capacitance value of the total of four capacitive elements selected from the remaining one.
Based on the first electric signal and the second electric signal, it is determined whether or not the force sensor is functioning normally.

  In such a force sensor, the detection circuit determines whether or not the force sensor is functioning normally based on the difference between the first electric signal and the second electric signal. You can stay. In this case, it is possible to provide a force sensor that can detect the applied force or moment and can perform failure diagnosis.

Alternatively, each bending portion bulges in the Z-axis negative direction, and the first bending portion having a first spring constant and the second bending portion having a second spring constant different from the first spring constant are deformed. It is constructed by connecting in the circumferential direction of the body,
The detection circuit includes a total of eight displacement electrodes arranged one each in the first curved portion and the second curved portion, and fixed electrodes fixed to the fixed portion, arranged in opposition to these displacement electrodes. Have
Each displacement electrode and the fixed electrode constitute eight sets of capacitive elements,
The detection circuit is
A first electric signal indicating the applied force or moment is output based on the amount of change in the capacitance value of the four capacitive elements arranged in the first bending portion, and the first electric signal is arranged in the second bending portion. Based on the amount of change in the capacitance value of the four capacitive elements, a second electric signal indicating the applied force or moment is output,
Whether the force sensor is functioning normally may be determined based on a change in the ratio of the first electric signal and the second electric signal.

Specifically, the detection circuit is
The ratio between the first electric signal and the second electric signal in a state where the force sensor is functioning normally is stored as a reference ratio,
Whether or not the force sensor is functioning normally may be determined based on a difference between the ratio between the first electric signal and the second electric signal and the reference ratio.

  In this case, it is possible to provide a force sensor that can detect the applied force or moment and can also diagnose a failure due to metal fatigue developed in the deformable body. A more detailed principle of failure diagnosis will be described later.

In the force sensor having the above eight capacitive elements, 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 two displacement electrodes arranged in the first quadrant of the XY plane are arranged symmetrically with respect to the positive V axis,
The two displacement electrodes arranged in the second quadrant of the XY plane are arranged symmetrically with respect to the positive W axis,
The two displacement electrodes arranged in the third quadrant of the XY plane are arranged symmetrically with respect to the negative V axis,
The two displacement electrodes arranged in the fourth quadrant of the XY plane may be arranged symmetrically with respect to the negative W axis.

  In this case, since the eight capacitive elements are symmetrically arranged with respect to the X, Y, V, and W axes, the variation amount of the electrostatic capacitance value generated in each capacitive element due to the acting force or moment is also symmetrical. . Therefore, it is easy to measure the applied force or moment.

Alternatively, the present invention is a force sensor that detects at least one of a force in each axial direction and a moment about each axis in an XYZ three-dimensional coordinate system,
A circular fixed body fixed with respect to the XYZ three-dimensional coordinate system,
An annular deformable body that surrounds the fixed body and is connected to the fixed body and elastically deforms by the action of a force or a moment,
An annular force receiving body that surrounds the deformable body and is connected to the deformable body and that moves relative to the fixed body by the action of a force or a moment;
A detection circuit for outputting an electric signal indicating a force or a moment acting on the force receiving body based on elastic deformation of the deformable body,
The fixed body, the deformable body and the force receiving body are arranged so as to be concentric with each other,
The Z coordinate value of the Z axis positive side end surface of the force receiving body is larger than the Z coordinate value of the Z axis positive side end surface of the deformable body,
The Z coordinate value of the end surface of the fixed body on the Z axis negative side is smaller than the Z coordinate value of the end surface of the deformable body on the Z axis negative side,
The deformable body is adjacent to two fixed portions connected to the fixed body, two force receiving portions connected to the force receiving body and alternately positioned with the fixed portion in the circumferential direction of the deformable body. And four deformation portions positioned between the fixed portion and the force receiving portion.

  According to the force sensor of the present invention, it is possible to provide an electrostatic capacitance type force sensor that is less expensive than conventional ones by simplifying the structure of the strain-generating body including the capacitive element. Furthermore, such a force sensor does not interfere with other members when it is attached to the joint portion of the robot.

Each deformed portion has a curved portion that bulges in the Z-axis direction,
The detection circuit may output the electric signal based on elastic deformation of the bending portion.

  In this case, since the elastic body can be displaced in the Z-axis direction by the applied force or moment with a simple structure, it is easy to dispose the pair of electrodes forming the capacitive element.

Alternatively, each deformable portion has a curved portion that bulges in the radial direction of the deformable body,
The detection circuit may output the electric signal based on elastic deformation occurring in the bending portion.

  In this case, even if the conventional deformable body is used, it is possible to provide a force sensor that does not interfere with other members when attached to the joint portion of the robot.

The two fixing portions are arranged symmetrically with respect to the Y axis at a portion where the deformable body overlaps with the X axis when viewed from the Z axis direction,
The two force receiving portions may be arranged symmetrically with respect to the X axis at a portion where the deformable body overlaps with the Y axis when viewed in the Z axis direction.

  In this case, the acting force or moment can be effectively transmitted to the deformable body.

It is a schematic perspective view which shows the basic structure of the force sensor by one embodiment of this invention. It is a schematic plan view which shows the basic structure of FIG. FIG. 3 is a sectional view taken along line [3]-[3] of FIG. 2. It is a schematic plan view for demonstrating the elastic deformation which arises in each curved part, when the moment + Mx about a positive X-axis acts on the basic structure of FIG. It is a schematic sectional drawing of FIG. 5A is a sectional view taken along the line [5a]-[5a] in FIG. 4, and FIG. 5B is a sectional view taken along the line [5b]-[5b] in FIG. It is a schematic plan view for demonstrating the elastic deformation which arises in each curved part, when the moment + My about the Y-axis positive rotation acts on the basic structure of FIG. It is a schematic sectional drawing of FIG. 7A is a sectional view taken along the line [7a]-[7a] in FIG. 6, and FIG. 7B is a sectional view taken along the line [7b]-[7b] in FIG. It is a schematic plan view for demonstrating the elastic deformation which arises in each bending part, when the moment + Mz about the Z-axis normal acts on the basic structure of FIG. It is a schematic sectional drawing of FIG. 9A is a sectional view taken along the line [9a]-[9a] in FIG. 8, and FIG. 9B is a sectional view taken along the line [9b]-[9b] in FIG. It is a schematic plan view for demonstrating the elastic deformation which arises in each curved part, when the force + Fz of the Z-axis positive direction acts on the basic structure of FIG. It is a schematic sectional drawing of FIG. 11A is a sectional view taken along the line [11a]-[11a] of FIG. 10, and FIG. 11B is a sectional view taken along the line [11b]-[11b] of FIG. It is a schematic plan view which shows the force sensor which utilized the basic structure of FIG. FIG. 13 is a sectional view taken along line [13]-[13] of FIG. 12. 13 is a chart showing variations in electrostatic capacitance value generated in each capacitance element when a force or moment acts on the force sensor of FIG. 12. It is a schematic plan view of the force sensor according to the second embodiment of the present invention. FIG. 16 is a sectional view taken along line [16]-[16] of FIG. 15. FIG. 16 is a sectional view taken along the line [17]-[17] of FIG. 15. FIG. 16 is a schematic cross-sectional view showing the first capacitive element C1 when a force in the negative direction of the X axis acts on the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the X-axis positive direction acts on the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the Z-axis positive direction acts on the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the negative direction of the Z-axis acts on the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the negative direction of the X axis acts on the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the positive direction of the X axis acts on a first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the Z-axis positive direction acts on a first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the Z-axis negative direction acts on the first force receiving portion of the force sensor shown in FIG. 15. It is a schematic plan view of the force sensor according to the third embodiment of the present invention. FIG. 27 is a sectional view taken along line [27]-[27] of FIG. 26. FIG. 27 is a cross-sectional view taken along the line [28]-[28] of FIG. 26. FIG. 27 is a table showing variations in electrostatic capacitance value generated in each capacitive element when a force or moment acts on the force sensor of FIG. 26. It is a schematic plan view of the force sensor according to the fourth embodiment of the present invention. It is the [31]-[31] sectional view taken on the line of FIG. It is the [32]-[32] sectional view taken on the line of FIG. FIG. 31 is a table showing variations in electrostatic capacitance value generated in each capacitance element when a force or moment acts on the force sensor of FIG. 30. In a state where metal fatigue does not occur in the force sensor shown in FIG. 30 (initial state), the magnitude of the moment Mx acting on the force sensor about the X axis and the electric signal output from the force sensor, It is a graph which shows the relationship of. 30 is a graph showing the relationship between the magnitude of the moment Mx about the X-axis acting on the force sensor and the electric signal output from the force sensor when the force sensor of FIG. is there. It is a schematic plan view which shows the basic structure of the force sensor by the 5th Embodiment of this invention. It is the [37]-[37] sectional view taken on the line of FIG. FIG. 37 is a schematic plan view showing a modified example of the basic structure of FIG. 36. It is the [39]-[39] sectional view taken on the line of FIG. FIG. 39 is a schematic plan view showing an example of a force sensor using the basic structure of FIG. 38. It is a schematic plan view which shows a rectangular deformable body. FIG. 42 is a schematic sectional view of FIG. 41. 42A is a sectional view taken along the line [42a]-[42a] in FIG. 41, and FIG. 42B is a sectional view taken along the line [42b]-[42b] in FIG. 41.

<<<< §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>
1 is a schematic perspective view showing a basic structure 1 of a force sensor according to a first embodiment of the present invention, FIG. 2 is a schematic plan view showing the basic structure 1 of FIG. 1, and FIG. FIG. 3 is a sectional view taken along line [3]-[3] of FIG. 2. In FIG. 2, 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. In this specification, the Z-axis positive direction is referred to as an upward direction, and the Z-axis negative direction is referred to as a downward direction. Further, in the present specification, the X-axis positive rotation means a rotation direction in which the right-hand screw is rotated in order to advance the right-hand screw in the X-axis positive direction, and the X-axis negative rotation is the reverse rotation direction. To mean. The method of defining the rotation direction is the same for the Y axis and the Z axis.

  As shown in FIGS. 1 to 3, the basic structure 1 includes a disk-shaped fixed body 10 having an upper surface parallel to the XY plane, and a disk that moves relative to the fixed body 10 when subjected to a force or moment. The force receiving body 20 and the fixed body 10 and the annular deformable body 40 connected to the force receiving body 20 and elastically deformed by the relative movement of the force receiving body 20 with respect to the fixed body 10. The fixed body 10, the force receiving body 20, and the deformable body 40 are concentric with each other and have the same outer diameter. In FIG. 2, the force receiving body 20 is not shown in order to clearly show the deformable body 40.

  In the basic structure 1 according to the present embodiment, a capacitive element is arranged at a predetermined position in the gap formed between the deformable body 40 and the fixed body 10, and a predetermined detection circuit 50 (see FIG. 12) is provided in this capacitive element. By connecting with, it will function as a force sensor. The detection circuit 50 is for measuring the applied force or moment based on the variation amount of the electrostatic capacitance value of the capacitive element. A specific arrangement mode of the capacitive element and a specific method for measuring the applied force or moment will be described later.

  As shown in FIGS. 1 and 2, the deformable body 40 as a whole has the shape of a ring centered on the origin O of the XYZ three-dimensional coordinate system and arranged parallel to the XY plane. Here, as shown in FIG. 3, it is assumed that the XY plane exists at a position half the thickness of the deformable body 40 in the Z-axis direction. As shown in FIG. 3, the deformable body 40 of the present embodiment has a square cross-sectional shape. The material of the deformable body 40 may be, for example, metal. As shown in FIG. 2, the deformable body 40 is positioned on the positive X-axis, is fixed on the positive X-axis, is fixed on the negative X-axis, and is positioned on the positive Y-axis. It has a first force receiving portion 43 and a second force receiving portion 44 located on the negative Y axis. As will be described later, each of the fixed portions 41, 42 and each of the force receiving portions 43, 44 is an area of the deformable body 40 to which the fixed body 10 and the force receiving body 20 are connected, and other of the deformable body 40. It is not a part that has different characteristics from the region. Therefore, the materials of the fixing portions 41 and 42 and the force receiving portions 43 and 44 are the same as those of the other regions of the deformable body 40. However, for convenience of description, in the drawings, the color is shown different from the other regions of the deformable body 40.

  As shown in FIGS. 1 to 3, the deformable body 40 further includes a first deformable portion 45 located between the first fixed portion 41 and the first force receiving portion 43 (first quadrant of the XY plane). The second deformable portion 46 located between the first force receiving portion 43 and the second fixed portion 42 (the second quadrant of the XY plane), and between the second fixed portion 42 and the second force receiving portion 44 (XY A third deforming portion 47 located in the third quadrant of the plane, and a fourth deforming portion 48 located between the second force receiving portion 44 and the first fixing portion 41 (fourth quadrant of the XY plane). Have Both ends of each deforming portion 45 to 48 are integrally connected to the adjacent fixing portions 41 and 42 and force receiving portions 43 and 44, respectively. With such a structure, the force or moment acting on the force receiving portions 43, 44 is surely transmitted to each of the deforming portions 45 to 48, whereby the elastic deformation corresponding to the applied force or moment is applied to each deforming portion 45. ~ 48.

  As shown in FIGS. 1 and 3, the basic structure 1 connects the first connecting member 31 and the second connecting member 32 that connect the fixed body 10 and the deformable body 40, and the force receiving body 20 and the deformable body 40. The third connecting member 33 and the fourth connecting member 34 are further provided. The first connecting member 31 connects the lower surface (the lower surface in FIG. 3) of the first fixing portion 41 and the upper surface of the fixing body 10 to each other, and the second connecting member 32 fixes the lower surface of the second fixing portion 42. The upper surface of the body 10 is connected to each other. The third connecting member 33 connects the upper surface (upper surface in FIG. 3) of the first force receiving portion 43 and the lower surface of the force receiving body 20 to each other, and the fourth connecting member 34 connects the second force receiving portion 44. The upper surface and the lower surface of the force receiving body 20 are connected to each other. Each of the connecting members 31 to 34 has a rigidity that can be regarded as a substantially rigid body. Therefore, the force or the moment acting on the force receiving body 20 effectively causes the deformation portions 45 to 48 to elastically deform.

  Further, as shown in FIGS. 1 and 3, each of the deformable portions 45 to 48 of the deformable body 40 has curved portions 45c to 48c that are curved so as to bulge in the Z axis negative direction. In the illustrated example, the respective deforming portions 45 to 48 form the curved portions 45c to 48c as a whole. Therefore, in FIGS. 1 to 3, reference numerals 45 to 48 of the deforming portion and reference numerals 45c to 48c of the bending portion are shown together. This also applies to other embodiments described later. In the deformable body 40 of the present embodiment, as shown in FIG. 3, a portion of the first bending portion 45c located at the lowermost position (Z-axis negative direction) extends from the first fixing portion 41 in the circumferential direction of the deformable body 40. It is located at a position that is rotated by 45 ° counterclockwise along. Further, the shape of the first bending portion 45c from the first fixing portion 41 to the portion at the lowest position is the shape from the first force receiving portion 43 to the portion at the lowest position. It is the same. In other words, the first bending portion 45c has a symmetrical shape with respect to the lowermost portion in the circumferential direction of the deformable body 40.

  This also applies to the remaining three curved portions 46c, 47c, 48c. That is, the second curved portion 46c is present at a position where the lowermost portion is rotated from the first force receiving portion 43 by 45 ° counterclockwise along the circumferential direction of the deformable body 40, and The deformable body 40 has a symmetrical shape with respect to the lowermost portion in the circumferential direction. The third curved portion 47c is located at a position where the lowermost portion is rotated from the second fixing portion 42 in the counterclockwise direction by 45 ° along the circumferential direction of the deformable body 40, and the deformable body 40c. It has a symmetrical shape with respect to the lowermost part in the circumferential direction. The fourth curved portion 48c is located at a position where the lowermost portion is rotated from the second force receiving portion 44 by 45 ° counterclockwise along the circumferential direction of the deformable body 40. It has a symmetrical shape with respect to the lowermost portion in the circumferential direction.

  After all, as shown in FIG. 2, if 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 bending portion 45c will have the positive V axis. Is symmetrical about the second curved portion 46c is symmetrical about the positive W axis, the third curved portion 47c is symmetrical about the negative V axis, and the fourth curved portion 48c is negative W. It is symmetrical about an axis.

  As shown in FIG. 2 and FIG. 3, in the basic structure 1, the bending portions 45c to 48c are located at the lowest position of the bending portions 45c to 48c, that is, the bending portions 45c to 48c are viewed from the Z-axis direction. Detection portions A1 to A4 for detecting elastic deformations occurring in the respective curved portions 45c to 48c are defined in the portions overlapping with. In addition, in FIG. 2, the detection parts A1 to A4 are illustrated as being provided on the upper surface (front side surface) of the deformable body 40, but actually, on the lower surface (back side surface) of the deformable body 40. It is provided (see FIG. 3).

<1-2. Action of basic structure ＞
Next, the operation of the basic structure 1 will be described.

(1-2-1. When the moment Mx about the X axis acts on the basic structure 1)
FIG. 4 is a schematic plan view for explaining elastic deformation that occurs in each of the bending portions 45c to 48c when a moment + Mx about the X-axis is applied to the basic structure 1 of FIG. 5 is a schematic sectional view of FIG. 5A is a sectional view taken along the line [5a]-[5a] in FIG. 4, and FIG. 5B is a sectional view taken along the line [5b]-[5b] in FIG. 4 and 5, the thick black arrow indicates the acting force or moment, and the thick white arrow indicates the direction of displacement of the detection parts A1 to A4. This also applies to the other figures.

  As shown in FIG. 4, when the moment + Mx about the positive X axis acts on the basic structure 1 via the force receiving body 20 (see FIGS. 1 and 3), the basic force 1 is applied to the first force receiving portion 43 of the deformable body 40. A force in the Z-axis positive direction (upward direction in FIG. 5A) acts, and a force in the Z-axis negative direction (downward direction in FIG. 5B) acts on the second force receiving portion 44. In FIG. 4, a symbol surrounded by a black dot attached to the first force receiving portion 43 indicates that a force acts from the Z axis negative direction to the Z axis positive direction, and the second force receiving portion 43 The symbol surrounded by a circle and attached to the force portion 44 indicates that the force acts from the Z-axis positive direction to the Z-axis negative direction. The meanings of these symbols are the same in FIGS. 6, 8 and 10.

  At this time, as shown in FIGS. 5A and 5B, the following elastic deformation occurs in the first to fourth bending portions 45c to 48c. That is, since the first force receiving portion 43 moves upward due to the Z-axis positive direction force acting on the first force receiving portion 43, the first force receiving portion of the first bending portion 45c and the second bending portion 46c. The end connected to 43 is moved upward. As a result, as shown in FIG. 5A, the first bending portion 45c and the second bending portion 46c are entirely upward except for the end portions connected to the first and second fixing portions 41 and 42. Move to. That is, both the first detection portion A1 and the second detection portion A2 move upward. On the other hand, since the second force receiving portion 44 moves downward due to the Z-axis negative direction force acting on the second force receiving portion 44, the second force receiving portion of the third bending portion 47c and the fourth bending portion 48c. The end connected to 44 is moved downward. As a result, as shown in FIG. 5B, the third bending portion 47c and the fourth bending portion 48c are entirely downward except for the end portions connected to the first and second fixing portions 41 and 42. Move to. That is, both the third detection portion A3 and the fourth detection portion A4 move downward.

  Such movement is shown in FIG. 4 by adding a circled symbol “+” or “−” to the positions of the detection sites A1 to A4. That is, the detection part surrounded by a circle and marked "+" is displaced in the Z-axis positive direction by the elastic deformation of the curved portion, and the detection part surrounded by a circle and marked "-" is It is displaced in the negative direction of the Z-axis due to the elastic deformation of the curved portion. This also applies to FIGS. 6, 8 and 10.

  After all, when the moment + Mx about the X-axis is applied to the force receiving body 20 of the basic structure 1, the distance between the first and second detection portions A1 and A2 and the upper surface of the fixed body 10 (see FIG. 3) is reduced. , Both increase, and the distance between the third and fourth detection portions A3, A4 and the upper surface of the fixed body 10 decreases.

  Although not shown, when the negative force X-axis moment −Mx acts on the force receiving body 20 of the basic structure 1, the moving directions of the respective detection portions A1 to A4 are opposite to the above-described directions. That is, the distance between the first and second detection portions A1 and A2 and the upper surface of the fixed body 10 (see FIG. 2) is reduced by the action of the negative moment about the X axis −Mx, and the third and fourth portions are reduced. The distances between the detection parts A3 and A4 and the upper surface of the fixed body 10 both increase.

(1-2-2. When the moment My about the Y axis acts on the basic structure 1)
FIG. 6 is a schematic plan view for explaining elastic deformation that occurs in each of the bending portions 45c to 48c when a moment + My about the Y axis is applied to the basic structure 1 of FIG. FIG. 7 is a schematic sectional view of FIG. 7A is a sectional view taken along the line [7a]-[7a] in FIG. 6, and FIG. 7B is a sectional view taken along the line [7b]-[7b] in FIG.

  As shown in FIGS. 6 and 7, when the moment + My about the Y axis in the normal direction acts on the basic structure 1 via the force receiving body 20 (see FIGS. 1 and 3), the first and The force in the Z-axis positive direction acts on the regions on the X-axis negative side of the second force receiving units 43 and 44, and the Z-axis negative direction on the regions on the X-axis positive side of the first and second force receiving units 43 and 44. Force of.

  At this time, as shown in FIGS. 7A and 7B, the following elastic deformation occurs in the first to fourth bending portions 45c to 48c. That is, the region in the X-axis positive side moves downward due to the force in the Z-axis negative direction that acts on the X-axis positive side (right side in FIG. 7A) of the first force receiving portion 43, and thus the first bending portion. Of 45c, the end connected to the first force receiving portion 43 is moved downward. As a result, as shown in FIG. 7A, the first bending portion 45c moves downward as a whole except for the end portion connected to the first fixing portion 41. That is, the first detection portion A1 moves downward. On the other hand, the area on the negative side of the X-axis moves upward due to the force in the positive direction of the Z-axis that acts on the negative side of the X-axis (the left side in FIG. 7A) of the first force receiving portion 43, so the second bending portion An end portion of 46c connected to the first force receiving portion 43 moves upward. As a result, as shown in FIG. 7A, the second bending portion 46c moves upward as a whole except for the end portion connected to the second fixing portion 42. That is, the second detection portion A2 moves upward.

  Further, as shown in FIG. 7B, the region on the X-axis negative side is caused by the force in the Z-axis positive direction acting on the X-axis negative side of the second force receiving portion 44 (right side in FIG. 7B). Since it moves upward, the end portion of the third bending portion 47c connected to the second force receiving portion 44 is moved upward. As a result, as shown in FIG. 7B, the third bending portion 47c moves upward as a whole except for the end portion connected to the second fixing portion 42. That is, the third detection portion A3 moves upward.

  On the other hand, as shown in FIG. 7B, the area on the X-axis positive side is caused by the Z-axis negative direction force acting on the X-axis positive side (left side in FIG. 7B) of the second force receiving portion 44. Since it moves downward, the end portion of the fourth bending portion 48c that is connected to the second force receiving portion 44 is moved downward. As a result, as shown in FIG. 7B, the fourth bending portion 48c moves downward as a whole except for the end portion connected to the first fixing portion 41. That is, the fourth detection portion A4 moves downward.

  After all, when the moment + My about the Y axis in the normal direction acts on the force receiving body 20 of the basic structure 1, the distance between the first and fourth detection portions A1 and A4 and the upper surface of the fixed body 10 (see FIG. 3) becomes smaller. , Both decrease, and the distance between the second and third detection portions A2, A3 and the upper surface of the fixed body 10 increases together.

  Although not shown, when the negative force Y about the Y axis acts on the force receiving body 20 of the basic structure 1, the moving directions of the respective detection portions A1 to A4 are opposite to the above-described directions. That is, the distance between the first and fourth detection portions A1 and A4 and the upper surface of the fixed body 10 (see FIG. 3) is increased by the action of the negative moment about the Y axis −My, and the second and third detection portions A1 and A4 increase. The distance between the detection parts A2 and A3 and the upper surface of the fixed body 10 is reduced.

(1-2-3. When the moment Mz about the Z axis acts on the basic structure 1)
FIG. 8 is a schematic plan view for explaining elastic deformation that occurs in each of the bending portions 45c to 48c when a moment + Mz about the Z-axis is applied to the basic structure 1 of FIG. 9 is a schematic sectional view of FIG. 9A is a sectional view taken along the line [9a]-[9a] in FIG. 8, and FIG. 9B is a sectional view taken along the line [9b]-[9b] in FIG.

  As shown in FIG. 8, when a moment + Mz about the Z-axis is applied to the basic structure 1 via the force receiving body 20 (see FIGS. 1 and 3), the first force receiving portion 43 of the deformable body 40 is affected. On the other hand, a force in the X-axis negative direction (leftward in FIG. 8) acts, and a force in the X-axis positive direction (rightward in FIG. 8) acts on the second force receiving portion 44.

  At this time, as shown in FIGS. 9A and 9B, the following elastic deformation occurs in the first to fourth bending portions 45c to 48c. That is, since the first force receiving portion 43 moves in the negative direction of the X axis by the force in the negative direction of the X axis acting on the first force receiving portion 43, the first bending portion 45c has a tensile force along the X axis direction. Power acts. As a result, the first bending portion 45c elastically deforms so that the radius of curvature becomes large while maintaining the Z coordinate values of both ends thereof. That is, the first detection portion A1 moves upward. On the other hand, when the first force receiving portion 43 moves in the negative direction of the X axis, a compressive force along the X axis direction acts on the second bending portion 46c. As a result, the second bending portion 46c elastically deforms so that the radius of curvature becomes smaller while maintaining the Z coordinate values of both ends thereof. That is, the second detection portion A2 moves downward.

  Further, since the second force receiving portion 44 moves in the X axis positive direction due to the force in the X axis positive direction acting on the second force receiving portion 44, the third bending portion 47c has a tensile force along the X axis direction. Works. As a result, the third bending portion 47c elastically deforms so that the radius of curvature becomes large while maintaining the Z coordinate values of both ends thereof. That is, the third detection portion A3 moves upward. On the other hand, when the second force receiving portion 44 moves in the positive direction of the X axis, a compressive force along the X axis direction acts on the fourth bending portion 48c. As a result, the fourth bending portion 48c elastically deforms so that the radius of curvature becomes smaller while maintaining the Z coordinate values at both ends thereof. That is, the fourth detection portion A4 moves downward.

  Eventually, when the moment + Mz about the Z-axis is applied to the force receiving body 20 of the basic structure 1, the distance between the first and third detection portions A1 and A3 and the upper surface of the fixed body 10 increases, The distance between the second and fourth detection parts A2 and A4 and the upper surface of the fixed body 10 (see FIG. 2) is both reduced.

  Although not shown, when the negative force about the Z-axis -Mz acts on the force receiving body 20 of the basic structure 1, the moving directions of the detection parts A1 to A4 are opposite to the above-described directions. That is, the distance between the first and third detection portions A1 and A3 and the upper surface of the fixed body 10 is reduced by the action of the negative moment about the Z-axis −Mz, and the second and fourth detection portions A2 and A4 are reduced. The distance between the upper surface of the fixed body 10 and the upper surface of the fixed body 10 (see FIG. 2) both increases.

(1-2-4. When the force Fz in the Z direction acts on the basic structure 1)
Next, FIG. 10 is a schematic plan view for explaining elastic deformation that occurs in each of the bending portions 45c to 48c when the force + Fz in the Z-axis positive direction acts on the basic structure 1 of FIG. Further, FIG. 11 is a schematic sectional view of FIG. 10. 11A is a sectional view taken along the line [11a]-[11a] of FIG. 10, and FIG. 11B is a sectional view taken along the line [11b]-[11b] of FIG.

  As shown in FIGS. 10 and 11, when the force + Fz in the Z-axis positive direction acts on the basic structure 1 via the force receiving body 20 (see FIGS. 1 and 3), the first and The force in the Z-axis positive direction acts on the two force receiving portions 43 and 44.

  At this time, as shown in FIGS. 11A and 11B, the following elastic deformation occurs in the first to fourth curved portions 45c to 48c. That is, since the force receiving portions 43 and 44 move upward due to the Z-axis positive direction force acting on the first and second force receiving portions 43 and 44, the first and second bending portions 45c to 48c are first and second. Each end connected to the force receiving portions 43 and 44 is moved upward. As a result, as shown in FIGS. 11A and 11B, the detection parts A1 to A4 move upward.

  After all, when the force + Fz in the Z-axis positive direction acts on the force receiving body 20 of the basic structure 1, the separation distance between the first to fourth detection portions A1 to A4 and the upper surface of the fixed body 10 (see FIG. 2) becomes smaller. , All increase.

  Although not shown, when a force −Fz in the negative Z-axis direction acts on the force receiving body 20 of the basic structure 1, the moving directions of the detection parts A1 to A4 are opposite to the above-described directions. That is, the distance between the first to fourth detection portions A1 to A4 and the upper surface of the fixed body 10 (see FIG. 2) is all reduced by the action of the force −Fz in the negative Z-axis direction.

<1-3. Capacitive element type force sensor ＞
(1-3-1. Structure of force sensor)
§1-1. And §1-2. The basic structure 1 described in detail above can be suitably used as the capacitive element type force sensor 1c. Here, such a force sensor 1c will be described in detail below.

  12 is a schematic plan view showing a force sensor 1c utilizing the basic structure 1 of FIG. 1, and FIG. 13 is a sectional view taken along the line [13]-[13] of FIG. In FIG. 13, the force receiving body 20 is not shown in order to clearly show the deformable body 40.

  As shown in FIGS. 12 and 13, the force sensor 1c is configured by disposing one capacitive element C1 to C4 at each of the detection sites A1 to A4 of the basic structure 1 of FIG. Specifically, as shown in FIG. 13, the force sensor 1c is disposed on the fixed body 10 so as to face the first displacement electrode Em1 disposed at the first detection site A1 and the first displacement electrode Em1. It has the 1st fixed electrode Ef1 which does not move relatively with respect to it. These electrodes Em1 and Ef1 form a first capacitive element C1. Further, as shown in FIG. 13, the force sensor 1c is arranged so as to face the second displacement electrode Em2 arranged at the second detection site A2 and the second displacement electrode Em2, and is relatively fixed to the fixed body 10. It has the 2nd fixed electrode Ef2 which does not move. These electrodes Em2 and Ef2 form a second capacitance element C2.

  Although not shown, the force sensor 1c is disposed so as to face the third displacement electrode Em3 and the third displacement electrode Em3 disposed at the third detection site A3, and does not move relative to the fixed body 10. 3 fixed electrode Ef3, 4th displacement electrode Em4 arrange | positioned at 4th detection site | part A4, 4th fixed electrode Ef4 arrange | positioned facing 4th displacement electrode Em4, and does not move relative to the fixed body 10, have. The electrode Em3 and the electrode Ef3 configure a third capacitive element C3, and the electrode Em4 and the electrode Ef4 configure a fourth capacitive element C4.

  As can be understood from FIG. 13, the displacement electrodes Em1 to Em4 have the first to fourth displacements on the lower surfaces of the first to fourth deformable body side supports 61 to 64 supported by the corresponding detection sites A1 to A4. It is supported via the substrates Im1 to Im4. Further, each of the fixed electrodes Ef1 to Ef4 is supported on the upper surfaces of the fixed body side support bodies 71 to 74 fixed to the upper surface of the fixed body 10 via the first to fourth fixed substrates If1 to If4. The displacement electrodes Em1 to Em4 all have the same area, and the fixed electrodes Ef1 to Ef4 also have the same area. However, the electrode area of the displacement electrodes Em1 to Em4 is the electrode area of the fixed electrodes Ef1 to Ef4 as a device for maintaining the effective facing area of each of the capacitive elements C1 to C4 at a constant value by the action of force or moment. It is configured to be larger than the area. This point will be described in detail later. In the initial state, the effective facing areas and the distances between the electrodes of each pair of the capacitors C1 to C4 are the same.

  Further, as shown in FIGS. 12 and 13, the force sensor 1c is an electrical signal indicating a force or moment acting on the force receiving body 20 based on the elastic deformation generated in each of the bending portions 45c to 48c of the deformable body 40. It has a detection circuit 50 for outputting In FIGS. 12 and 13, the wiring that electrically connects each of the capacitive elements C1 to C4 and the detection circuit 50 is omitted.

  When the fixed body 10, the force receiving body 20, and the deformable body 40 are made of a conductive material such as metal, the first to fourth displacement substrates Im1 to Im4 and the first to fourth fixed bodies are arranged so that the electrodes are not short-circuited. The substrates If1 to If4 need to be made of an insulator.

(1-3-2. Regarding fluctuation of electrostatic capacitance value of each capacitive element when moment Mx about X axis acts on force sensor 1c)
Next, FIG. 14 is a chart showing variations in the capacitance value generated in each of the capacitive elements C1 to C4 when a force or moment acts on the force sensor 1c of FIG.

  First, when the moment + Mx about the X-axis is applied to the force sensor 1c according to the present embodiment, as will be understood from the behavior of the detection parts A1 to A4 described in §1-2-1. , The distance between the electrodes forming the first capacitive element C1 and the second capacitive element C2 both increases. Therefore, the capacitance values of the first capacitive element C1 and the second capacitive element C2 both decrease. On the other hand, the distance between the electrodes forming the third capacitive element C3 and the fourth capacitive element C4 both decreases. Therefore, the capacitance values of the third capacitive element C3 and the fourth capacitive element C4 both increase. The variation of the capacitance value of each of the capacitive elements C1 to C4 is collectively shown in the column of “Mx” in FIG. In this chart, "+" indicates that the capacitance value increases, and "-" indicates that the capacitance value decreases. When the negative moment about the X-axis -Mx acts on the force sensor 1c, the variation of the capacitance value of each of the capacitive elements C1 to C4 is opposite to the variation described above (in the column of Mx in FIG. 14). All signs are reversed).

(1-3-3. Regarding Variation of Capacitance Value of Each Capacitance Element when Moment My about Y Axis Acts on Force Sensor 1c)
Next, when a moment + My around the Y axis acts on the force sensor 1c according to the present embodiment, it will be understood from the behavior of the detection parts A1 to A4 described in §1-2-2. In addition, the distance between the electrodes forming the first capacitive element C1 and the fourth capacitive element C4 both decreases. Therefore, the capacitance values of the first capacitive element C1 and the fourth capacitive element C4 both increase. On the other hand, the distance between the electrodes forming the second capacitive element C2 and the third capacitive element C3 both increases. Therefore, the capacitance values of the second capacitive element C2 and the third capacitive element C3 both decrease. The variation in the capacitance value of each of the capacitive elements C1 to C4 is collectively shown in the column “My” in FIG. When the negative moment about the Y-axis -My is applied to the force sensor 1c, the variation of the capacitance value of each of the capacitive elements C1 to C4 is opposite to the variation described above (in the column of My in FIG. 14). All signs are reversed).

(1-3-4. Regarding fluctuation of capacitance value of each capacitance element when moment Mz about Z axis acts on force sensor 1c)
Next, when the moment + Mz about the Z-axis is applied to the force sensor 1c according to the present embodiment, it can be understood from the behaviors of the detection parts A1 to A4 described in §1-2-3. In addition, the distance between the electrodes forming the first capacitive element C1 and the third capacitive element C3 both increases. Therefore, the capacitance values of the first capacitive element C1 and the third capacitive element C3 both decrease. On the other hand, the distance between the electrodes forming the second capacitive element C2 and the fourth capacitive element C4 both decreases. Therefore, the capacitance values of the second capacitive element C2 and the fourth capacitive element C4 both increase. The variation of the capacitance value of each of the capacitive elements C1 to C4 is collectively shown in the “Mz” column of FIG. When the negative force about the Z-axis -Mz acts on the force sensor 1c, the variation in the capacitance value of each of the capacitive elements C1 to C4 is opposite to the variation described above (in the column of Mz in FIG. 14). All signs are reversed).

(1-3-5. Regarding fluctuation of electrostatic capacitance value of each capacitive element when force Fz in the Z-axis direction acts on the force sensor 1c)
Next, when the force + Fz in the Z-axis positive direction acts on the force sensor 1c according to the present embodiment, it will be understood from the behavior of the detection parts A1 to A4 described in §1-2-4. In addition, the distances between the electrodes forming each of the capacitive elements C1 to C4 are all increased. Therefore, the capacitance values of the capacitive elements C1 to C4 are all reduced. The variation in the capacitance value of each of the capacitive elements C1 to C4 is collectively shown in the “Fz” column of FIG. When the force −Fz in the negative Z-axis direction acts on the force sensor 1c, the variation in the capacitance value of each of the capacitive elements C1 to C4 is opposite to the variation described above (see the Fz column in FIG. 14). All signs are reversed).

(1-3-6. Method of calculating applied force or moment)
In consideration of the fluctuations in the capacitance values of the capacitive elements C1 to C4 as described above, the detection circuit 50 calculates the moments Mx, My, Mz, and the force Fz acting on the force sensor 1c using the following [Equation 1]. calculate. In [Equation 1], C1 to C4 represent variations in the capacitance values of the first to fourth capacitive elements C1 to C4.
[Formula 1]
Mx = -C1-C2 + C3 + C4
My = C1-C2-C3 + C4
Mz = -C1 + C2-C3 + C4
Fz =-(C1 + C2 + C3 + C4)
When the force or moment acting on the force sensor 1c is in the negative direction, -Mx, -My, -Mz and -Fz may be used instead of Mx, My, Mz and Fz on the left side.

  According to the force sensor 1c according to the present embodiment as described above, the force or moment acting on the detection portions A1 to A4 is caused by the simple deformable body 40 having the curved portions 45c to 48c bulging in the Z-axis direction. It is possible to generate a displacement corresponding to the Z axis direction. Therefore, one of the pair of electrodes forming the capacitive elements C1 to C4 may be arranged at the detection sites A1 to A4, and the other may be arranged on, for example, the upper surface of the fixed body 10, so that the capacitive elements C1 to C4 are formed. It is easy to do. Therefore, according to the present embodiment, by adopting such a simple structure, it is possible to provide the electrostatic capacitance type force sensor 1c that is less expensive than the conventional one.

  In the force sensor 1c, 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 four sets of capacitive elements C1 to C4 are arranged in the Z axis direction. One is arranged at each of the four parts that overlap with the V axis and the W axis when viewed from above. Therefore, since the capacitive elements C1 to C4 are symmetrically arranged with respect to the X axis and the Y axis, the capacitance values of the capacitive elements C1 to C4 vary with high symmetry. Therefore, the applied force or moment can be very easily measured based on the variation amount of the capacitance value of the capacitive elements C1 to C4.

  In the above description, the four capacitive elements C1 to C4 have the individual fixed substrates If1 to If4 and the individual fixed electrodes Ef1 to Ef4. However, in another embodiment, the fixed substrate may be configured to be common to the four capacitive elements, and individual fixed electrodes may be provided on the fixed substrate. Alternatively, the fixed substrate and the fixed electrode may be shared by the four capacitive elements. With such a configuration, the force or moment can be measured in the same manner as the force sensor 1c described above. Note that these configurations are also applicable to each of the embodiments described later.

  Further, the force sensor 1c changes its sensitivity to the acting force or moment by changing the cross-sectional shape of the deformable body 40. Specifically, it is as follows. That is, in the present embodiment, the cross-sectional shape of the deformable body 40 is square (see FIG. 3), but if this cross-sectional shape is a vertically long rectangle long in the Z-axis direction, the moment Mx about the X and Y axes is obtained. , My and the force Fz in the Z-axis direction is relatively lower than the sensitivity to the moment Mz about the Z-axis. On the other hand, when the cross-sectional shape of the deformable body 40 is a horizontally long rectangle that is long in the radial direction of the deformable body 40, the moments Mx, My about the X and Y axes and the force in the Z axis direction are reversed, contrary to the above case. The sensitivity to Fz is relatively higher than the sensitivity to the moment Mz about the Z axis.

  Alternatively, in the force sensor 1c, the sensitivity to the acting force or moment changes also by changing the radii of curvature (the degree of bending) of the bending portions 45c to 48c. Specifically, if the radius of curvature of the curved portions 45c to 48c is reduced (the degree of bending is increased), the sensitivity to the acting force or moment increases. On the other hand, when the radius of curvature of the curved portions 45c to 48c is increased (the degree of bending is reduced), the sensitivity to the acting force or moment decreases.

  The sensitivity of the force sensor 1c is optimized in the environment in which it is used by considering the relationship between the cross-sectional shape of the deformable body 40 and the radii of curvature of the curved portions 45c to 48c and the sensitivity to a force or moment. can do. Of course, the above description also applies to each of the embodiments described later.

<<<< §2. Force sensor according to a second embodiment of the present invention >>>
<2-1. Composition>
Next, the force sensor 201c according to the second embodiment of the present invention will be described.

  FIG. 15 is a schematic plan view of the force sensor 201c according to the second embodiment. 16 is a sectional view taken along line [16]-[16] of FIG. 15, and FIG. 17 is a sectional view taken along line [17]-[17] of FIG. However, in FIG. 15, the force receiving body 20 is not shown for ease of viewing the drawing.

  As shown in FIGS. 15 to 17, the force sensor 201c differs from the force sensor 1c according to the first embodiment in the following points. That is, in the force sensor 201c according to the present embodiment, the deformable body side supports 261 to 264 that support the displacement electrodes Em1 to Em4 are bent at different portions from the detection portions A1 to A4 of the bending portions 45c to 48c. It is connected to the parts 45c to 48c. Specifically, as shown in FIGS. 15 and 16, the first deformable body side support body 261 connected to the first bending portion 45c has the first detection of the first bending portion 45c when viewed from the Z-axis direction. A first beam 261b arranged so as to overlap the portion A1, and a first connecting body that connects an end of the first beam 261b on the first fixing portion 41 side (right side in FIG. 16) to the first bending portion 45c. It is a cantilever structure having 261s. Since the first connection body 261s extends parallel to the Z axis, the connection position between the first connection body 261s and the first bending portion 45c is closer to the first fixing portion 41 side than the first detection portion A1. Is. The first displacement electrode Em1 is supported on the lower surface of the first beam 261b of the cantilever structure via a displacement substrate.

  Further, the second deformable body side support body 262 connected to the second bending portion 46c is also configured as a cantilever structure. That is, as shown in FIGS. 15 and 16, the second deformable body side support body 262 is arranged so as to overlap the second detection portion A2 of the second bending portion 46c when viewed from the Z-axis direction. And a second connecting body 262s that connects an end of the second beam 262b on the second fixing portion 42 side (left side in FIG. 16) to the second bending portion 46c, which is a cantilever structure. There is. Since the second connection body 262s extends parallel to the Z axis, the connection position between the second connection body 262s and the second bending portion 46c is closer to the second fixing portion 42 side than the second detection portion A2. Is. The second displacement electrode Em2 is supported on the lower surface of the second beam 262b of the cantilever structure via the displacement substrate.

  Furthermore, the third deformable body side support body 263 and the fourth deformable body side support body 264 are also configured as a similar cantilever structure. That is, as shown in FIGS. 15 and 17, the third deformable body side support body 263 is arranged so as to overlap the third detection portion A3 of the third bending portion 47c when viewed from the Z-axis direction. And a third connecting body 263s that connects the end of the third beam 263b on the second fixing portion 42 side (the right side in FIG. 17) to the third bending portion 47c, which is a cantilever structure. There is. Since the third connection body 263s extends parallel to the Z axis, the connection position between the third connection body 263 and the third bending portion 47c is closer to the second fixing portion 42 side than the third detection portion A3. is there. The third displacement electrode Em3 is supported on the lower surface of the third beam 263b via a displacement substrate.

  Further, the fourth deformable body side support body 264 is arranged so as to overlap the fourth detection portion A4 of the fourth bending portion 48c when viewed from the Z-axis direction, and the fourth beam 264b of the fourth beam 264b. It is a cantilever structure having a fourth connecting body 264s that connects the end portion on the 1st fixing portion 41 side (left side in FIG. 17) to the fourth bending portion 48c. Since the fourth connection body 264s extends parallel to the Z axis, the connection position between the fourth connection body 264s and the fourth bending portion 48c is closer to the first fixing portion 41 side than the fourth detection portion A4. is there. The fourth displacement electrode Em34 is supported on the lower surface of the fourth beam 264b via a displacement substrate.

  With the configuration as described above, each of the connection bodies 261s to 264s is connected to the bending portions 45c to 48c at a site different from the detection sites A1 to A4, but the first to fourth displacement electrodes are viewed from the Z-axis direction. Em1 to Em4 are arranged so as to overlap the corresponding detection parts A1 to A4.

  Note that, in the example shown in FIGS. 15 to 25, as described above, each of the deformable body side supports 261 to 264 is configured as a cantilever structure, but other embodiments (not shown). In (), the ends of the beams 261b to 264b may be configured as a doubly supported beam structure in which the tips are connected to the fixed body 10 by a flexible material. The flexible material may have a linear shape or a curved shape, and may be connected to the fixed body 10 in the vicinity of a portion where the Z axis and the upper surface of the fixed body 10 intersect, for example. With such a configuration, it is possible to stabilize the inclination behavior of the beams 261b to 264b caused by the action of the force or moment acting on the force sensor 201c from external vibration.

<2-2. Action>
(2-2-1. Variation in capacitance value of the first capacitive element C1)
The fluctuation of the electrostatic capacitance value generated in each of the capacitive elements C1 to C4 when a force or moment acts on the force sensor 201c according to the present embodiment will be examined. Here, first, fluctuations in the capacitance value of the first capacitive element C1 will be described with reference to FIGS. 18 to 21.

  18 is a schematic cross-sectional view showing the first capacitive element C1 when a force in the negative direction of the X-axis acts on the first force receiving portion 43 of the force sensor shown in FIG. 15, and FIG. 16 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the positive direction of the X axis acts on the first force receiving portion 43 of the force sensor 201c shown in FIG. 20 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the Z-axis positive direction acts on the first force receiving portion 43 of the force sensor 201c shown in FIG. 21 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the negative Z-axis direction acts on the first force receiving portion 43 of the force sensor 201c shown in FIG.

  As shown in FIG. 18, when a force in the negative direction of the X axis (leftward in FIG. 18) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the first bending portion 45c receives a tensile force along the X-axis direction, so that the first bending portion 45c elastically deforms so that the radius of curvature thereof increases. In FIG. 18, the first bending portion 45c in the initial state is shown by the broken line, and the first bending portion 45c in the elastically deformed state is shown by the solid line. As shown in FIG. 18, due to this elastic deformation, the tangent line L1 of the portion of the first bending portion 45c to which the first connecting body 261s is connected changes to a more horizontal state. In FIG. 18, the tangent line after the change is indicated by L1 (X−). Then, the first beam 261b of the first deformable body side support body 261 changes from the horizontal state to the leftward upward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the first capacitive element C1 increases. The degree of increase gradually increases from the X-axis positive side to the X-axis negative side (from the right side to the left side in FIG. 18) (the separation distance gradually increases).

  In the force sensor 1c according to the first embodiment described above, the first deformable body side support body 61 and the first bending portion 45c are connected at the first detection portion A1, so that the first detection portion A1 is The distance between the electrodes is changed uniformly by the same amount as the displacement along the Z-axis direction. However, in the example shown in FIG. 18, since the first beam 261b inclines upward to the left, the first detection part A1 exceeds the amount displaced upwards, especially in the left region of the first beam 261b. The separation distance is increased. In other words, the first deformable body side support body 261 is a cantilever structure, and the first deformable body side support body 261 is connected to the first bending portion 45c at a position different from the first detection portion A1. , The displacement in the Z-axis direction that occurs at the first detection portion A1 is amplified.

  With such a configuration, when a force in the negative direction of the X axis acts on the first force receiving portion 43, the capacitance value of the first capacitive element C1 of the force sensor 201c according to the present embodiment decreases. However, the degree of decrease is larger than that of the first capacitive element C1 of the force sensor 1c according to the first embodiment.

  Next, as shown in FIG. 19, when a force in the X-axis positive direction (right direction in FIG. 19) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the first bending portion 45c receives a compressive force along the X-axis direction, and thus elastically deforms so that the radius of curvature thereof becomes smaller. In FIG. 19, the first bending portion 45c in the initial state is shown by a broken line, and the first bending portion 45c in the elastically deformed state is shown by a solid line. As shown in FIG. 19, due to this elastic deformation, the tangent line L1 of the portion of the first bending portion 45c to which the first connecting body 261s is connected changes to a more vertical state. In FIG. 19, the tangent line after the change is indicated by L1 (X +). Then, the first beam 261b of the first deformable body side support body 261 changes from the horizontal state to the left downward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the first capacitive element C1 is reduced. The degree of the decrease gradually increases from the X-axis positive side to the X-axis negative side (from the right side to the left side in FIG. 19) (the separation distance gradually decreases).

  In the example shown in FIG. 19, since the first beam 261b inclines to the lower left, in particular in the left region of the first beam 261b, the distance between the electrodes exceeds the amount by which the first detection portion A1 is displaced downward. The distance decreases. In other words, the Z-axis displacement generated at the first detection portion A1 is amplified by the cantilever structure as described above.

  With such a configuration, when a force in the X-axis positive direction acts on the first force receiving portion 43, the capacitance value of the first capacitive element C1 of the force sensor 201c according to the present embodiment increases. However, the degree of increase is larger than that of the first capacitive element C1 of the force sensor 1c according to the first embodiment.

  Next, as shown in FIG. 20, when a force in the Z-axis positive direction (upward direction in FIG. 20) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the first bending portion 45c is elastically deformed so as to move upward as a whole because the region on the X-axis negative side connected to the first force receiving portion 43 is moved upward. However, the end on the X axis positive side does not move because it is fixed to the first fixing portion 41. In FIG. 20, the first bending portion 45c in the initial state is shown by the broken line, and the first bending portion 45c in the elastically deformed state is shown by the solid line. As shown in FIG. 20, due to this elastic deformation, the tangent line L1 of the portion of the first bending portion 45c to which the first connecting body 261s is connected changes to a more horizontal state. In FIG. 20, the tangent line after the change is indicated by L1 (Z +). Then, the first beam 261b of the first deformable body side support body 261 changes from the horizontal state to the leftward upward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the first capacitive element C1 increases. The degree of increase gradually increases from the X-axis positive side to the X-axis negative side (from the right side to the left side in FIG. 20) (the separation distance gradually increases).

  In the example shown in FIG. 20, since the first beam 261b inclines upward to the left, in particular, in the left region of the first beam 261b, the distance between the electrodes exceeds the amount by which the first detection portion A1 is displaced upward. The distance increases. In other words, the Z-axis displacement generated at the first detection portion A1 is amplified by the cantilever structure as described above.

  With such a configuration, when a force in the Z-axis positive direction acts on the first force receiving portion 43, the capacitance value of the first capacitive element C1 of the force sensor 201c according to the present embodiment decreases. The degree of decrease is larger than that of the first capacitive element C1 of the force sensor 1c according to the first embodiment.

  Next, as shown in FIG. 21, when a force in the negative Z-axis direction (downward in FIG. 21) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the first bending portion 45c is elastically deformed so as to move downward as a whole because the region on the X-axis negative side connected to the first force receiving portion 43 is moved downward. However, the end on the X axis positive side does not move because it is fixed to the first fixing portion 41. In FIG. 21, the first bending portion 45c in the initial state is shown by the broken line, and the first bending portion 45c in the elastically deformed state is shown by the solid line. As shown in FIG. 21, due to this elastic deformation, the tangent line L1 of the portion of the first bending portion 45c to which the first connecting body 261s is connected changes to a more vertical state. In FIG. 21, the tangent line after the change is indicated by L1 (Z−). As can be understood from the change in the inclination of the tangent line L1, the first beam 261b of the first deformable body side support 261 changes from the horizontal state to the left downward state by an amount corresponding to the change in the inclination. To do. As a result, the distance between the electrodes forming the first capacitive element C1 is reduced. The degree of decrease gradually increases from the X-axis positive side to the X-axis negative side (from the right side to the left side in FIG. 21) (the separation distance gradually decreases).

  In the example shown in FIG. 21, since the first beam 261b is inclined downward to the left, the distance between the electrodes exceeds the amount by which the first detection portion A1 is displaced downward, particularly in the left end region of the first beam 261b. Is reduced. In other words, the Z-axis displacement generated at the first detection portion A1 is amplified by the cantilever structure as described above.

  With such a configuration, when a force in the Z-axis negative direction acts on the first force receiving portion 43, the capacitance value of the first capacitive element C1 of the force sensor 201c according to the present embodiment increases. The degree of increase is larger than that of the first capacitive element C1 of the force sensor 1c according to the first embodiment.

(2-2-2. Variation of capacitance value of second capacitance element C2)
Next, changes in the capacitance value of the second capacitive element C2 will be described with reference to FIGS. 22 to 25.

  22 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the negative direction of the X-axis acts on the first force receiving portion 43 of the force sensor 201c shown in FIG. 23 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the X-axis positive direction acts on the first force receiving portion 43 of the force sensor 201c shown in FIG. 24 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the Z-axis positive direction acts on the first force receiving portion 43 of the force sensor 201c shown in FIG. 25 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the negative Z-axis direction acts on the first force receiving portion of the force sensor 201c shown in FIG.

  As shown in FIG. 22, when a force in the X-axis negative direction (left direction in FIG. 22) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the second bending portion 46c receives a compressive force along the X-axis direction, and thus elastically deforms so that its radius of curvature becomes smaller. In FIG. 22, the second bending portion 46c in the initial state is shown by the broken line, and the second bending portion 46c in the elastically deformed state is shown by the solid line. As shown in FIG. 22, due to this elastic deformation, the tangent line L2 of the portion of the second bending portion 46c to which the second connecting body 262s is connected changes to a more vertical state. In FIG. 22, the tangent line after the change is indicated by L2 (X−). Then, the second beam 262b of the second deformable body side support 262 changes from the horizontal state to the downward rightward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the second capacitive element C2 is reduced. The degree of the decrease gradually increases from the negative side of the X axis to the positive side of the X axis (from the left side to the right side in FIG. 22) (the separation distance gradually decreases).

  In the force sensor 1c according to the first embodiment described above, the second deformable body side support body 62 is connected to the second bending portion 46c at the second detection portion A2 of the second bending portion 46c. The separation distance between the electrodes was changed uniformly by the same amount as the amount of displacement of the two detection parts A2 along the Z-axis direction. However, in the example shown in FIG. 22, since the second beam 262b inclines to the lower right, the second detection part A2 exceeds the amount displaced downward, especially in the right side region of the second beam 262b. The separation distance is reduced. In other words, the second deformable body side support body 262 is a cantilever structure, and the second deformable body side support body 262 is connected to the second bending portion 46c at a position different from the second detection portion A2. , The displacement in the Z-axis direction generated at the second detection portion A2 is amplified.

  With such a configuration, when a force in the negative direction of the X axis acts on the first force receiving portion 43, the capacitance value of the second capacitive element C2 of the force sensor 201c according to the present embodiment increases. The degree of increase is larger than that of the second capacitive element C2 of the force sensor 1c according to the first embodiment.

  Next, as shown in FIG. 23, when a force in the X-axis positive direction (right direction in FIG. 23) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the second bending portion 46c receives a tensile force along the X-axis direction, so that the second bending portion 46c elastically deforms so that its radius of curvature increases. In FIG. 23, the second bending portion 46c in the initial state is shown by the broken line, and the second bending portion 46c in the elastically deformed state is shown by the solid line. As shown in FIG. 23, due to this elastic deformation, the tangent line L2 of the portion of the second bending portion 46c to which the second connecting body 262s is connected changes to a more horizontal state. The tangent line after the change is indicated by L2 (X +). Then, the second beam 262b of the second deformable body side support 262 changes from the horizontal state to the right upward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the second capacitive element C2 increases. The degree of increase gradually increases from the negative side of the X axis toward the positive side of the X axis (from the left side to the right side in FIG. 23) (the separation distance gradually increases).

  In the example shown in FIG. 23, since the second beam 262b is inclined upward to the right, in particular in the right region of the second beam 262b, the distance between the electrodes exceeds the amount by which the second detection portion A2 is displaced upward. The distance increases. In other words, the cantilever structure as described above amplifies the displacement in the Z-axis direction that occurs at the second detection portion A2.

  With such a configuration, when a force in the positive direction of the X axis acts on the first force receiving portion 43, the capacitance value of the second capacitive element C2 of the force sensor 201c according to the present embodiment decreases. However, the degree of decrease is larger than that of the second capacitive element C2 of the force sensor 1c according to the first embodiment.

  Next, as shown in FIG. 24, when a force in the Z-axis positive direction (upward direction in FIG. 24) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the X-axis positive side end connected to the first force receiving portion 43 is moved upward, so that the second bending portion 46c is elastically deformed so as to move upward as a whole. However, since the end on the negative side of the X axis is fixed to the second fixing portion 42, it does not move. In FIG. 24, the second bending portion 46c in the initial state is shown by a broken line, and the second bending portion 46c in the elastically deformed state is shown by a solid line. As shown in FIG. 24, due to this elastic deformation, the tangent line L2 of the portion of the second bending portion 46c to which the second connecting body 262s is connected changes to a more horizontal state. The tangent line after the change is indicated by L2 (Z +). Then, the second beam 262b of the second deformable body side support 262 changes from the horizontal state to the right upward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the second capacitive element C2 increases. The degree of the increase gradually increases from the negative side of the X axis toward the positive side of the X axis (from the left side to the right side in FIG. 24) (the separation distance gradually increases).

  In the example shown in FIG. 23, since the second beam 262b is inclined upward to the right, in particular in the right region of the second beam 262b, the distance between the electrodes exceeds the amount by which the second detection portion A2 is displaced upward. The distance increases. In other words, the cantilever structure as described above amplifies the displacement in the Z-axis direction that occurs at the second detection portion A2.

  With such a configuration, when a force in the Z-axis positive direction acts on the first force receiving portion 43, the capacitance value of the second capacitive element C2 of the force sensor 201c according to the present embodiment decreases. However, the degree of decrease is larger than that of the second capacitive element C2 of the force sensor 1c according to the first embodiment.

  Next, as shown in FIG. 25, when a force in the negative Z-axis direction (downward in FIG. 25) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Along with this, the X-axis positive side end connected to the first force receiving portion 43 is moved downward, so that the second bending portion 46c is elastically deformed so as to move downward as a whole. However, since the end on the negative side of the X axis is fixed to the second fixing portion 42, it does not move. In FIG. 25, the second curved portion 46c in the initial state is shown by the broken line, and the second curved portion 46c in the elastically deformed state is shown by the solid line. As shown in FIG. 25, this elastic deformation changes the tangent line L2 of the portion of the second bending portion 46c to which the second connecting body 262s is connected to a more vertical state. The tangent line after the change is indicated by L2 (Z-). Then, the second beam 262b of the second deformable body side support 262 changes from the horizontal state to the downward rightward state by an amount corresponding to the change in the inclination. As a result, the distance between the electrodes forming the second capacitive element C2 is reduced. The degree of the decrease gradually increases from the negative side of the X axis toward the positive side of the X axis (from the left side to the right side in FIG. 25) (the separation distance gradually decreases).

  In the example shown in FIG. 25, since the second beam 262b is inclined downward to the right, in particular, in the right region of the second beam 262b, the distance between the electrodes exceeds the amount by which the second detection portion A2 is displaced downward. The distance decreases. In other words, the cantilever structure as described above amplifies the displacement in the Z-axis direction that occurs at the second detection portion A2.

  With such a configuration, when a force in the negative Z-axis direction acts on the first force receiving portion 43, the capacitance value of the second capacitive element C2 of the force sensor 201c according to the present embodiment increases. However, the degree of increase is larger than that of the second capacitive element C2 of the force sensor 1c according to the first embodiment.

(2-2-3. Variation of capacitance value of third capacitive element C3 and fourth capacitive element C4)
The force sensor 201c according to the present embodiment has a symmetrical structure in which the Y coordinate is positive (see FIG. 16) and the Y coordinate is negative (see FIG. 17). Therefore, the variation of the electrostatic capacitance values of the third capacitive element C3 and the fourth capacitive element C4 can be analogized as follows based on the description in §2-2-1 and §2-2-2. Can be understood.

  That is, although not shown, when the third bending portion 47c and the fourth bending portion 48c are compressed along the X-axis direction, and when the third bending portion 47c and the fourth bending portion 48c receive the second force. When the end connected to the portion 44 is moved in the negative Z-axis direction, the capacitance value of each of the capacitive elements C3 and C4 increases. On the other hand, when the third bending portion 47c and the fourth bending portion 48c are pulled along the X-axis direction, and when connected to the second force receiving portion 44 of the third bending portion 47c and the fourth bending portion 48c. When the end portion is moved in the Z-axis positive direction, the capacitance value of each of the capacitive elements C3 and C4 decreases.

  When the third bending portion 47c and / or the fourth bending portion 48c is elastically deformed, the third and / or fourth beams 263b and 264b are tilted as described above, so that the third capacitive element C3 and the fourth capacitive element C3. The variation of the capacitance value of C4 is larger than that of the third capacitive element C3 and the fourth capacitive element C4 of the force sensor 1c according to the first embodiment.

  After all, in the force sensor 201c according to the present embodiment, the variation in the capacitance value generated in each of the capacitive elements C1 to C4 due to the force or moment acting on the force receiving body 20 is as shown in FIG. As will be understood from the description above, the variation amount is larger than the variation amount in the force sensor 1c according to the first embodiment. In other words, the force sensor 201c according to the present embodiment has higher sensitivity than the force sensor 1c according to the first embodiment.

  According to the present embodiment as described above, since the beams 261b to 264b are connected to the curved portions 45c to 48c at positions different from the corresponding detection sites A1 to A4, they are supported by the beams 261b to 264b. The displacements generated in the displacement electrodes Em1 to Em4 are amplified. That is, when a certain amount of force or moment acts, the displacements generated in the displacement electrodes Em1 to Em4 are the first displacement electrodes Em1 to Em4 supported at the detection portions A1 to A4 of the bending portions 45c to 48c. The displacement is larger than the displacement generated in the displacement electrodes Em1 to Em4 in the force sensor 1c according to the embodiment. Therefore, the sensitivity to the applied force or moment is high, and more accurate measurement can be performed.

<<<< §3. Force sensor according to the third embodiment of the present invention >>>
<3-1. Composition>
Next, the force sensor 301c according to the third embodiment of the present invention will be described.

  FIG. 26 is a schematic plan view of the force sensor 301c according to the third embodiment. 27 is a sectional view taken along the line [27]-[27] in FIG. 26, and FIG. 28 is a sectional view taken along the line [28]-[28] in FIG. However, in FIG. 26, the force receiving body 20 is not shown for ease of viewing the drawing.

  As shown in FIGS. 26 to 28, the force sensor 301c is provided with two capacitive elements in each of the bending portions 45c to 48c, and thus the force sensor 1c according to the first and second embodiments, Different from 201c. Specifically, as shown in FIGS. 26 and 27, two capacitive elements C11 and C12 are arranged on the lower surface of the first bending portion 45c along the circumferential direction of the deformable body 40 with the first detection portion A1 interposed therebetween. Are arranged. Similarly, on the lower surface of the second curved portion 46c, two capacitive elements C21 and C22 are arranged along the circumferential direction of the deformable body 40 with the second detection portion A2 interposed therebetween. Further, as shown in FIGS. 26 and 28, two capacitive elements C31 and C32 are arranged on the lower surface of the third curved portion 47c along the circumferential direction of the deformable body 40 with the third detection portion A3 interposed therebetween. On the lower surface of the fourth curved portion 48c, two capacitive elements C41 and C42 are arranged along the circumferential direction of the deformable body 40 with the fourth detection portion A4 interposed therebetween.

  In the illustrated example, the 1-1st capacitive element C11, the 1-2nd capacitive element C12, the 2-1st capacitive element C21, the 2-2nd capacitive element C22, the 3-1st capacitive element C31, the 3-2nd The capacitive element C32, the 4-1st capacitive element C41, and the 4-2nd capacitive element C42 are counterclockwise (counterclockwise) along the circumferential direction of the deformable body 40 when viewed from the Z-axis positive direction (as viewed from above). ) Are arranged in this order. Further, as shown in FIGS. 27 and 28, two capacitive elements C11 to C42 arranged in each of the curved portions 45c to 48c are arranged at equal intervals from the corresponding detection parts A1 to A4.

  The configurations of the respective capacitive elements C11 to C42 are similar to those of the capacitive elements C1 to C4 employed in the force sensor 1c according to the first embodiment. That is, as shown in FIG. 27, the 1-1st capacitive element C11 is disposed at the 1-1st displacement electrode Em11 supported by the first bending portion 45c and at a position facing the 1-1st displacement electrode Em11. And the 1-1st fixed electrode Ef11. The 1-1st displacement electrode Em11 is supported on the lower surface of the 1-1st deformable body side support body 361a connected to the first bending portion 45c via the 1-1st displacement substrate Im11. The 1-1st fixed electrode Ef11 is supported on the first fixed body side support body 371 fixed to the upper surface of the fixed body 10 via the first fixed substrate If1.

  Further, as shown in FIG. 27, the 1-2nd capacitive element C12 is arranged at a position opposite to the 1-2nd displacement electrode Em12 supported by the first bending portion 45c and the 1-2nd displacement electrode Em12. And the 1st-2 fixed electrode Ef12. The first-second displacement electrode Em12 is supported on the lower surface of the first-second deformable body side support body 361b connected to the first curved portion 45c via the first-second displacement substrate Im12. The 1-2 fixed electrode Ef12 is supported on the first fixed body side support body 371 fixed to the upper surface of the fixed body 10 via the first fixed substrate If1 similarly to the 1-1 fixed electrode Ef11. There is. That is, the first fixed body side support body 371 and the first fixed substrate If1 are components common to the 1-1st capacitive element C11 and the 1-2st capacitive element C12.

  As shown in FIG. 27, the 2-1st capacitive element C21 is arranged at the 2-1st displacement electrode Em21 supported by the second bending portion 46c and at a position facing the 2-1st displacement electrode Em21. The 2-1st fixed electrode Ef21. The 2-1st displacement electrode Em21 is supported on the lower surface of the 2-1st deformable body side support body 362a connected to the second bending portion 46c via the 2-1st displacement substrate Im21. The 2-1st fixed electrode Ef21 is supported on the second fixed body side support body 372 fixed to the upper surface of the fixed body 10 via the second fixed substrate If2.

  Further, as shown in FIG. 27, the 2-2nd capacitive element C22 is arranged at the 2-2nd displacement electrode Em22 supported by the second bending portion 46c and at a position facing the 2-2nd displacement electrode Em22. 2-2 fixed electrode Ef22 that has been formed. The 2-2nd displacement electrode Em22 is supported on the lower surface of the 2-2nd deformation body side support body 362b connected to the second bending portion 46c via the 2-2nd displacement substrate Im22. The 2-2nd fixed electrode Ef22 is supported on the 2nd fixed body side support body 372 fixed to the upper surface of the fixed body 10 via the 2nd fixed substrate If2 similarly to the 2-1 fixed electrode Ef21. There is. That is, the second fixed body side support body 372 and the second fixed substrate If2 are common constituent elements for the 2-1st capacitive element C21 and the 2-2nd capacitive element C22.

  As shown in FIG. 28, the 3-1st capacitive element C31 is arranged at the 3-1st displacement electrode Em31 supported by the third curved portion 47c and at a position facing the 3-1st displacement electrode Em31. And a 3-1st fixed electrode Ef31. The 3-1st displacement electrode Em31 is supported on the lower surface of the 3-1st deformable body side support body 363a connected to the third bending portion 47c via the 3-1st displacement substrate Im31. The 3-1st fixed electrode Ef31 is supported on the third fixed body side support body 373 fixed to the upper surface of the fixed body 10 through the third fixed substrate If3.

  Further, as shown in FIG. 28, the 3-2nd capacitive element C32 is arranged at a position facing the 3-2nd displacement electrode Em32 supported by the third curved portion 47c and the 3-2nd displacement electrode Em32. 3-2 fixed electrode Ef32. The 3-2nd displacement electrode Em32 is supported on the lower surface of the 3-2nd deformable body side support body 363b connected to the 3rd curved portion 47c via the 3-2nd displacement substrate Im32. The 3-2nd fixed electrode Ef32 is supported on the 3rd fixed body side support body 373 fixed to the upper surface of the fixed body 10 via the 3rd fixed substrate If3 similarly to the 3-1 fixed electrode Ef31. There is. That is, the third fixed body side support body 373 and the third fixed substrate If3 are common constituent elements for the 3-1st capacitive element C31 and the 3-2nd capacitive element C32.

  Further, as shown in FIG. 28, the 4-1st capacitive element C41 is arranged at a position facing the 4-1st displacement electrode Em41 supported by the fourth bending portion 48c and the 4-1st displacement electrode Em41. The 4-1st fixed electrode Ef41 that has been formed. The 4-1st displacement electrode Em41 is supported on the lower surface of the 4-1st deformable body side support body 364a connected to the fourth bending portion 48c via the 4-1st displacement substrate Im41. The 4-1st fixed electrode Ef41 is supported on the 3rd fixed body side support body 373 fixed to the upper surface of the fixed body 10 via the 4th fixed substrate If4.

  Further, as shown in FIG. 28, the 4-2nd capacitive element C42 is arranged at the 4-2nd displacement electrode Em42 supported by the fourth curved portion 48c and at a position facing the 4-2nd displacement electrode Em42. And the 4-2nd fixed electrode Ef42 that is formed. The 4-2nd displacement electrode Em42 is supported via the 4-2nd displacement substrate Im42 on the lower surface of the 4-2nd deformable body side support body 364b connected to the fourth bending portion 48c. The 4-2nd fixed electrode Ef42 is supported on the 4th fixed body side support body 374 fixed to the upper surface of the fixed body 10 via the 4th fixed substrate If4 similarly to the 4-1 fixed electrode Ef41. There is. That is, the fourth fixed body side support 374 and the fourth fixed substrate If4 are common constituent elements to the 4-1st capacitive element C41 and the 4-2nd capacitive element C42. Since other configurations are almost the same as those of the force sensor 1c according to the first embodiment, corresponding components are denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted.

  In the 1-1 to 2-4 capacitive elements C11 to C24, the displacement electrodes Em11 to Em24 and the fixed electrodes Ef11 to Ef24 forming the capacitive elements C11 to C24 have the same effective facing area, and The separation distances are also equal to each other.

<3-2. Action>
Next, FIG. 29 is a chart showing variations in the capacitance value generated in each of the capacitive elements C11 to C24 when a force or moment acts on the force sensor 301c of FIG. In this chart, "+" indicates that the capacitance value of the capacitance element increases, and "-" indicates that the capacitance value of the capacitance element decreases.

  When a force or moment acts on the force sensor 301c according to the present embodiment, the bending portions 45c to 48c are elastically deformed as described in FIGS. 3 to 9 according to the acting force or moment. Occurs. Due to this elastic deformation, the capacitance values of the capacitive elements C11 to C42 fluctuate as shown in FIG. That is, the 1-1st capacitive element C11 and the 1-2nd capacitive element C12 exhibit the same behavior as the first capacitive element C1 of the force sensor 1c according to the first embodiment (see the column of C1 in FIG. 14). reference). Further, the 2-1st capacitive element C21 and the 2-2nd capacitive element C22 behave similarly to the second capacitive element C2 of the force sensor 1c according to the first embodiment (see the column C2 in FIG. 14). ), The 3-1st capacitive element C31 and the 3-2nd capacitive element C32 behave similarly to the third capacitive element C3 of the force sensor 1c according to the first embodiment (column C3 in FIG. 14). ), The 4-1st capacitive element C41 and the 4-2nd capacitive element C42 exhibit the same behavior as the fourth capacitive element C4 of the force sensor 1c according to the first embodiment (of C4 in FIG. 14). See column).

In consideration of the chart shown in FIG. 29, the detection circuit 250 calculates the moments Mx, My, Mz and the force Fz acting on the force sensor 301c based on the following [Equation 2]. In each formula described in this specification, the symbols C11 to C24 indicate the amounts of variation in the capacitance values of the 1-1 to 2-4 capacitive elements C11 to C24, respectively. Further, the symbols at the end of Mx, My, Mz and Fz distinguish between the force or moment measured using [Equation 2] and the force or moment measured using [Equation 3] described later. It is for doing.
[Formula 2]
Mx1 = -C11-C21 + C31 + C41
My1 = C11-C21-C31 + C41
Mz1 = -C11 + C21-C31 + C41
Fz1 =-(C11 + C21 + C31 + C41)
This [Formula 2] advances in the clockwise direction of the deformable body 40 when viewed from the Z-axis positive direction (as viewed from above) among the two capacitive elements arranged in the respective curved portions 45c to 48c. This is an equation for measuring the acting force or moment by using the capacitive element of the one.

Alternatively, the moments Mx, My, Mz and the force Fz acting on the force sensor 301c can be calculated by using the following [Formula 3].
[Formula 3]
Mx2 = -C12-C22 + C32 + C42
My2 = C12-C22-C32 + C42
Mz2 = -C12 + C22-C32 + C42
Fz2 =-(C12 + C22 + C32 + C42)
This [Formula 3] advances in the counterclockwise direction of the deformable body 40 when viewed from the Z-axis positive direction (viewed from above) among the two capacitive elements arranged in each of the curved portions 45c to 48c. This is an equation for measuring an applied force or moment by using the capacitive element on the other side.

<3-3. Fault diagnosis ＞
The force sensor 301c according to the present embodiment can perform failure diagnosis with the single force sensor 301c. Here, the diagnosis method will be described.

As described above, the eight capacitive elements C11 to C24 arranged in the force sensor 301c have the same effective facing area between electrodes and the same distance. Furthermore, the four capacitive elements C11, C21, C31, C41 used in [Equation 2] and the four capacitive elements C12, C22, C32, C42 used in [Equation 3] are the first to fourth curved portions. They are arranged symmetrically with respect to the detection parts A1 to A4 defined by 45c to 48c. From these facts, in the force sensor 301c that is functioning normally, the force or moment measured based on [Equation 2] and the force or moment measured based on [Equation 3] match. become. That is, in the force sensor 301c that is functioning normally, the following [Equation 4] relationship holds.
[Formula 4]
Mx1 = Mx2
My1 = My2
Mz1 = Mz2
Fz1 = Fz2

From this, the failure diagnosis of the force sensor 301c can be performed as follows. That is, the detection circuit 250 measures the force or moment acting on the force sensor 301c based on both [Equation 2] and [Equation 3], and the values (Mx1, My1) measured based on [Equation 2]. , Mz1, Fz1) and the absolute values of the differences between the values (Mx2, My2, Mz2, Fz2) measured based on [Equation 3] are all predetermined thresholds (Cmx, Cmy in [Equation 5]). , Cmz, Cfz) or less, it is determined that the force sensor 301c is functioning normally. That is, when the following [Equation 5] is established, the detection circuit 250 determines that the force sensor 301c is functioning normally. In the present embodiment, the predetermined threshold values Cmx, Cmy, Cmz, and Cfz are stored in the detection circuit 250 in advance.
[Formula 5]
| Mx1-Mx2 | ≦ Cmx and | My1-My2 | ≦ Cmy and | Mz1-Mz2 | ≦ Cmz and | Fz1-Fz2 | ≦ Cfz

On the other hand, if at least one of the differences is larger than the predetermined threshold value C1, the detection circuit 250 determines that the force sensor 301c is not functioning normally (has failed). That is, when the following [Equation 6] is established, the detection circuit 250 determines that the force sensor 301c is not functioning normally.
[Formula 6]
| Mx1-Mx2 |> Cmx or | My1-My2 |> Cmy or | Mz1-Mz2 |> Cmz or | Fz1-Fz2 |> Cfz

  According to the force sensor 301c of the present embodiment as described above, one each (four in total) of the two capacitive elements arranged in each of the first to fourth bending portions 45c to 48c is used. The failure is detected by the single force sensor 301c based on the difference between the measured force or moment value and the remaining force or moment value (four in total). Can be diagnosed. This improves the safety and reliability of the force sensor 301c.

  In the above description, in order to perform the failure diagnosis of the force sensor 301c, the specific force or moment obtained based on [Equation 2] and the specific force or moment obtained based on [Equation 3] are used. However, the method is not limited to such a method. For example, a specific force or moment (eg Mx1 + Mx2) obtained based on the sum of [Equation 2] and "Equation 3" and either one of [Equation 2] or "Equation 3" The failure diagnosis may be performed by comparing the specific force or moment (eg, Mx1 or Mx2). The specific diagnosis method is the same as the method described above. That is, in the case of performing a failure diagnosis focusing on the moment Mx about the X axis, if M12 is a specific force or moment obtained based on Mx1 + Mx2, which is the sum of [Equation 2] and [Equation 3], then | It is evaluated whether or not Mx12-Mx1 | or | Mx12-Mx2 | exceeds a predetermined threshold value. This also applies to fault diagnosis based on other forces or moments.

  Further, in the above description, one of [Equation 2] and “Equation 3” is used to measure the force or moment, but the sum of [Equation 2] and “Equation 3” (example : Mx1 + Mx2) may be used.

<<<< §4. Force Sensor According to Fourth Embodiment of the Present Invention >>
<4-1. Composition>
Next, a force sensor 401c according to a fourth embodiment of the present invention will be described.

  30 is a schematic plan view of the force sensor 401c according to the fourth embodiment of the present invention, FIG. 31 is a sectional view taken along the line [31]-[31] of FIG. 30, and FIG. It is the [32]-[32] sectional view taken on the line of 30. However, in FIG. 30, the force receiving body 20 is not shown for ease of viewing the drawing.

  As shown in FIGS. 30 to 32, the force sensor 401c according to the present embodiment is characterized in that the first to fourth bending portions 445c to 448c are composed of portions having two spring constants different from each other. It is different from the force sensor 301c according to the third embodiment. Specifically, as shown in FIGS. 30 and 31, the first bending portion 445c is located in a region sandwiched by the positive X axis and the positive V axis and has a relatively small spring constant. It is composed of a low elastic portion 445L and a first high elastic portion 445H having a relatively large spring constant, which is located in a region sandwiched by the positive V axis and the positive Y axis. The first low-elasticity portion 445L and the first high-elasticity portion 445H are integrally connected at the first detection portion A1 (on the V axis). Similarly, the second bending portion 446c is located in a region sandwiched by the positive Y axis and the positive W axis, and has a second low elastic portion 446L having a relatively small spring constant and the positive W axis and the negative W axis. And a second high-elasticity portion 446H having a relatively large spring constant, which is located in a region sandwiched by the X axis. The second low-elasticity portion 446L and the second high-elasticity portion 446H are integrally connected at the second detection portion A2 (on the W axis).

  Further, as shown in FIGS. 30 and 32, the third bending portion 447c is located in a region sandwiched by the negative X axis and the negative V axis, and has a relatively low spring constant. 447L and a third high-elasticity portion 447H having a relatively large spring constant, which is located in a region sandwiched by the negative V axis and the negative Y axis. The third low-elasticity portion 447L and the third high-elasticity portion 447H are integrally connected at the third detection portion A3 (on the V axis). Similarly, the fourth bending portion 448c is located in a region sandwiched by the negative Y axis and the negative W axis, and has a fourth low elastic portion 448L having a relatively small spring constant, and the negative W axis and the positive W axis. And a fourth high elastic portion 448H having a relatively large spring constant, which is located in a region sandwiched by the X axis. The fourth low-elasticity portion 448L and the fourth high-elasticity portion 448H are integrally connected at the fourth detection portion A4 (on the W axis).

  As shown in FIGS. 31 and 32, the low-elasticity portions 445L to 448L are configured to have a smaller thickness in the Z-axis direction (vertical direction) than the high-elasticity portions 445H to 448H. Of course, the present invention is not limited to such an aspect, and in other embodiments, the low-elasticity portions 445L to 448L have a smaller radial width than the high-elasticity portions 445H to 448H. The spring constants may be different, or the spring constants may be different by being made of different materials.

  As shown in FIGS. 30 to 32, each of the two curved elements 445c to 448c is provided with two capacitive elements C11 to C42 similarly to the force sensor 301c according to the third embodiment. The two capacitive elements are arranged along the circumferential direction of the deformable body 40 with the corresponding detection parts A1 to A4 sandwiched therebetween. Specifically, the 1-1st capacitive element C11 is arranged on the lower surface of the first low elastic portion 445L, and the 1-2nd capacitive element C12 is arranged on the lower surface of the first high elastic portion 445H. . The 2-1st capacitive element C21 is arranged on the lower surface of the second low-elasticity portion 446L, and the 2-2nd capacitive element C22 is arranged on the lower surface of the second high-elasticity portion 446H. The 3-1st capacitive element C31 is arranged on the lower surface of the third low-elasticity portion 447L, and the 3-2nd capacitive element C32 is arranged on the lower surface of the third high-elasticity portion 447H. The 4-1st capacitive element C41 is arranged on the lower surface of the fourth low-elasticity portion 448L, and the 4-2nd capacitive element C42 is arranged on the lower surface of the fourth high-elasticity portion 448H. Since other configurations are similar to those of the third embodiment, corresponding components in the drawings are designated by the same reference numerals, and detailed description thereof will be omitted.

<4-2. Action>
Next, FIG. 33 is a chart showing variations in the capacitance value generated in each of the capacitive elements C11 to C24 when a force or moment acts on the force sensor 401c of FIG. In this chart, “+” indicates that the capacitance value increases, and “++” indicates that the capacitance value greatly increases. Further, “−” indicates that the electrostatic capacitance value decreases, and “−−” indicates that the electrostatic capacitance value greatly decreases.

  When a force or moment acts on the force sensor 401c according to the present embodiment, the bending portions 445c to 448c as a whole are described with reference to FIGS. 3 to 9 according to the acting force or moment. Elastic deformation occurs. Therefore, due to this elastic deformation, the capacitance values of the capacitive elements C11 to C42 vary. This variation is almost the same as the capacitance value of each of the capacitive elements C11 to C42 of the force sensor 301c according to the third embodiment. However, due to the difference in spring constant, in the curved portions 445c to 448c, relatively large elastic deformation occurs in the low elastic portions 444L to 448L, and relatively small elastic deformation occurs in the high elastic portions 444H to 448H. Therefore, as shown in FIG. 33, a relatively large capacitance value variation occurs in the capacitive elements C11, C21, C31, C41 arranged in the low elastic portions 444L to 448L, and the high elastic portions 444H to 448H. A relatively small capacitance value variation occurs in the arranged capacitance elements C12, C22, C32, C42.

The moments Mx, My, Mz and the force Fz acting on the force sensor 401c are calculated using the following [Equation 7] based on the chart shown in FIG. The symbols at the end of Mx, My, Mz, and Fz are for distinguishing the force or moment calculated using [Equation 7] from the force or moment calculated using [Equation 8] described below. belongs to.
[Formula 7]
Mx1 = -C11-C21 + C31 + C41
My1 = C11-C21-C31 + C41
Mz1 = -C11 + C21-C31 + C41
Fz1 =-(C11 + C21 + C31 + C41)
This [Equation 7] is based on the four capacitive elements C11 and C21 that are arranged in the low-elasticity portions 445L to 448L among the two capacitive elements arranged in the first to fourth curved portions 445c to 448c. , C31, C41 are used to measure the acting force or moment.

Alternatively, the moments Mx, My, Mz and the force Fz acting on the force sensor 401c are also calculated using the following [Formula 8].
[Formula 8]
Mx2 = -C12-C22 + C32 + C42
My2 = C12-C22-C32 + C42
Mz2 = -C12 + C22-C32 + C42
Fz2 =-(C12 + C22 + C32 + C42)
This [Formula 8] is based on the four capacitive elements C12 and C22 of the two capacitive elements disposed in the first to fourth curved portions 445c to 448c, which are disposed in the high elastic portions 445H to 448H. , C32, C42 are used to measure the acting force or moment.

  In the present embodiment, in view of the chart shown in FIG. 33, the detection circuit 450 is based on the variation of the capacitance values of the four capacitive elements C11, C21, C31, C41 arranged in the low-elasticity portions 445L to 448L. The force or moment acting is measured using [Equation 7]. This enables highly sensitive measurement with excellent S / N. Of course, the force or moment acting may be measured using [Equation 8].

<4-3. Fault diagnosis ＞
The force sensor 401c according to the present embodiment can perform a higher failure diagnosis than the force sensor 301c according to the third embodiment in the following points. That is, the force sensor 301c according to the third embodiment can detect a failure when the electrodes are damaged or when a foreign substance is mixed between the electrodes. On the other hand, when the force sensor 301c does not function normally due to metal fatigue of the deformable body 40, the force or moment (Mx1, My1, Mz1, Fz1) measured based on [Equation 2] is obtained. ) And the force or moment (Mx2, My2, Mz2, Fz2) measured based on [Equation 3] may not be different. In this case, the force sensor 301c cannot properly perform the failure diagnosis. When metal fatigue occurs in the deformable body 40, the elastic body forming the deformable body 40 is cracked and the deformable body 40 may eventually break. Therefore, if a force sensor capable of detecting a failure due to metal fatigue can be provided, reliability and safety can be further enhanced.

  The force sensor 401c according to the present embodiment is for coping with such a problem. That is, the force sensor 401c can properly perform the failure diagnosis even when the deformable body 40 fails to function normally due to metal fatigue. Hereinafter, the failure diagnosis by the force sensor 401c according to the present embodiment will be described in detail.

  First, the principle of failure diagnosis will be described. When a repeated load acts on the deformable body 40 of the force sensor 401c, metal fatigue occurs in the deformable body 40. When this metal fatigue is accumulated, the strength of the deformable body 40 is reduced, and the deformable body 40 is eventually broken. Generally, when metal fatigue accumulates in a metal material, the metal material softens. Therefore, the spring constants of the first to fourth bending portions 445c to 448c decrease. In other words, the deformable body 40 has increased sensitivity to the acting force or moment as compared with the initial state due to the accumulation of metal fatigue.

  FIG. 34 shows the magnitude of the moment Mx about the X axis acting on the force sensor 401c and the force sensor 401c when the force sensor 401c shown in FIG. 30 has no metal fatigue (initial state). 35 is a graph showing a relationship between the output electric signal and the electric signal indicating the moment Mx, and FIG. 35 is an X-axis acting on the force sensor 401c in a state where metal fatigue occurs in the force sensor 401c of FIG. 6 is a graph showing the relationship between the magnitude of the surrounding moment Mx and the electrical signal indicating the moment Mx output from the force sensor 401c. Reference numeral “T1” in FIGS. 34 and 35 indicates the first electric signal that is an electric signal based on the amount of change in the capacitance value of the four capacitive elements arranged in the low-elasticity portions 445L to 448L. “T2” indicates a second electric signal that is an electric signal based on the amount of change in the capacitance value of the four capacitive elements arranged in the high-elasticity portions 445H to 448H. The symbols at the end of "T1" and "T2" indicate the electric signal in the initial state (adding a to the end) and the electric signal in the state where metal fatigue is accumulated (adding b to the end). It is for distinguishing.

When the first electric signal T1 and the second electric signal T2 are specifically written, the following [Equation 9] is obtained.
[Formula 7]
T1 (T1a, T1b) = − C11−C21 + C31 + C41
T2 (T2a, T2b) =-C12-C22 + C32 + C42

  Referring to FIG. 34, the slope (sensitivity) of the graph (straight line) showing the first electric signal T1a in the initial state is 2.0, and the slope (sensitivity) of the graph (straight line) showing the second electric signal T2a in the initial state ( The sensitivity) is 0.5. On the other hand, referring to FIG. 35, the slope (sensitivity) of the graph (straight line) showing the first electrical signal T1b in the state where metal fatigue is accumulated is 3.0, and the state where metal fatigue is accumulated The slope (sensitivity) of the graph (straight line) showing the second electric signal T2b of is 0.6.

  From these, it can be seen that the force sensor 401c has increased sensitivity to the acting moment Mx about the X axis due to the accumulation of metal fatigue in the deformable body. Particularly, the detection sensitivities of the four capacitive elements arranged in the low-elasticity portions 445L to 448L are increased by 50%. On the other hand, although the detection sensitivities of the four capacitive elements arranged in the high-elasticity portions 445H to 448H have also increased, the ratio remains at 20%.

  It should be noted here that four capacitive elements C11, C21, C31, C41 arranged in the low elastic portions 445L to 448L and four capacitive elements C12, C22, C32, C42 arranged in the high elastic portions 445H to 448H. That is, the change in sensitivity is different. The difference is that the strain generated in the low-elasticity portions 445L to 448L is larger than the strain generated in the high-elasticity portions 445H to 448H, so that a large amount of metal fatigue accumulates in the low-elasticity portions 445L to 448L. It is due. The change in sensitivity as described above is quantitatively evaluated by focusing on the ratio between the first electric signal T1 and the second electric signal T2. That is, in the initial state, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a was 4.0, but when metal fatigue accumulates, the first electric signal T1b and the second electric signal The ratio with the signal T2b (T1b / T2b) increased to 5.0.

Considering the mechanism of metal fatigue, this ratio T1 / T2 gradually increases from 4.0 to 5.0 with the repeated load (force or moment). The force sensor 401c according to the present embodiment also performs a failure diagnosis of the force sensor 1c by paying attention to the change in the ratio T1 / T2 in addition to measuring the applied force or moment. In the failure diagnosis, the detection circuit 450 uses the ratio (T1 / T2) of the first electric signal T1 and the second electric signal T2 at the time of measurement and the ratio of the first electric signal T1a and the second electric signal T2a in the initial state. It is performed by evaluating whether or not the difference between (T1a / T2a) and ((T1 / T2)-(T1a / T2a)) exceeds a predetermined value (threshold value C). That is, when the following [Formula 10] is established, the detection circuit 450 determines that the force sensor 401c is functioning normally. In the present embodiment, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a and the threshold value C in the initial state are stored in the detection circuit 450 in advance.
[Formula 10]
(T1 / T2)-(T1a / T2a) ≦ C (C: threshold)

On the other hand, when the following [Equation 11] is established, the detection circuit 450 determines that the force sensor 401c is not functioning normally (has a failure).
[Formula 11]
(T1 / T2)-(T1a / T2a)> C (C: threshold)

  In the above description, the case where the moment Mx about the X-axis acts on the force sensor 401c has been described as an example, but the same applies when the other moments My, Mz or the force Fz act. Fault diagnosis can be performed. Specifically, regarding the force or moment of interest, the formula described in [Formula 7] is the first electric signal T1, and the formula described in [Formula 8] is the second electric signal T2. At this time, the relationship between the force or moment acting on the force sensor 401c and the first and second electric signals T1 and T2 is similar to the graph shown in FIG. 34 in the initial state, and metal fatigue is accumulated in the deformable body 40. In the state where it is doing, it is similar to the graph shown in FIG. However, when the force Fz in the Z-axis direction acts, the “moment” on the horizontal axis is read as “force”. Therefore, no matter what force or moment acts, the failure diagnosis of the force sensor 401c is appropriately performed based on the above [Equation 10] and [Equation 11].

  According to the present embodiment as described above, it is possible to provide the force sensor 401c capable of detecting a failure due to metal fatigue that has occurred in the deformable body 40 while measuring a force or a moment. This further enhances the reliability and safety of the force sensor 401c.

<<<< §5. Force sensor according to a fifth embodiment of the present invention >>>
Next, a force sensor 501c according to a fifth embodiment of the present invention will be described.

  36 is a schematic plan view showing a basic structure 501 of a force sensor 501c according to a fifth embodiment of the present invention, and FIG. 37 is a sectional view taken along line [37]-[37] of FIG.

  As shown in FIGS. 36 and 37, the basic structure 501 is different from the basic structure 1 of the force sensor 1c according to the first embodiment in the structures of the fixed body 510 and the force receiving body 520. Specifically, both the fixed body 510 and the force receiving body 520 of the basic structure 501 have an annular (cylindrical) shape. Then, as shown in FIGS. 36 and 37, the fixed body 510 is arranged inside the deformable body 40, and the force receiving body 520 is arranged outside the deformable body 40 as viewed in the Z-axis direction. . The central axes of the fixed body 510, the force receiving body 520, and the deformable body 40 all overlap with the Z axis, and are concentric with each other. Further, as shown in FIG. 37, the fixed body 510 is arranged such that the Z coordinate value of the lower end thereof is smaller than the Z coordinate value of the lower end (detection sites A1 to A4) of the deformable body 40. Further, the force receiving body 520 is arranged such that the Z coordinate value of the upper end thereof is larger than the Z coordinate value of the upper end of the deformable body 40.

  Due to the arrangement of the fixed body 510, the force receiving body 520, and the deformable body 40 as described above, the arrangement of the first to fourth connecting members 531 to 534 is also different from that of the force sensor 1c according to the first embodiment. ing. That is, as shown in FIGS. 36 and 37, the first connecting member 531 has an outer surface (a side surface facing the positive direction of the X axis) of the fixed body 510 and an inner surface of the deformable body 40 on the positive X axis. (Side surface facing the negative direction of the X-axis). On the other hand, the second connecting member 532 has an outer surface (side surface facing the negative direction of the X axis) of the fixed body 510 and an inner side surface (side surface facing the positive direction of the X axis) of the fixed body 510 on the negative X axis. And are connected. Further, as shown in FIG. 36, on the positive Y axis, the inner side surface of the force receiving body 520 (side surface facing the negative direction of the Y axis) and the outer side surface of the deformable body 40 (side surface facing the positive direction of the Y axis). Are connected by a third connecting member 533, and on the negative Y-axis, the inner side surface of the force receiving body 520 (side surface facing the Y-axis positive direction) and the outer side surface of the deformable body 40 (in the Y-axis negative direction). The facing side surface) is connected by a fourth connecting member 534. Other configurations are the same as the basic structure 1 of the force sensor 1c according to the first embodiment. Therefore, in the drawings, corresponding components are designated by the same reference numerals, and detailed description thereof will be omitted.

  Although not shown, the force sensor 501c is configured by disposing four capacitive elements in the same arrangement as the force sensor 1c according to the first embodiment with respect to the basic structure 501 as described above. can do. Although a member for arranging the fixed electrode is not shown in FIG. 37, the fixed electrode may be appropriately arranged at a portion to which the force sensor 501c is attached, or an additional member may be added to the fixed body 510. A member may be fixed and a fixed electrode may be arranged on this member.

  The force sensor 501c as described above can be suitably installed in a mechanism unit including a first member and a second member that move relative to each other, such as a joint of a robot. That is, if the fixed body 510 is connected to the first member and the force receiving body 520 is connected to the second member, the force sensor 501c is arranged in a limited space in such a manner as not to interfere with other members. be able to.

  Since the method for measuring the force or moment acting on the force sensor 501c is the same as that of the force sensor 1c according to the first embodiment, the detailed description thereof is omitted here.

  As a modified example of the above basic structure 501, the following basic structure 502 can be considered.

  38 is a schematic plan view showing a modified example of the basic structure 501 of FIG. 36, and FIG. 39 is a sectional view taken along the line [39]-[39] of FIG.

  As shown in FIGS. 38 and 39, the basic structure 502 according to the present modification differs from the basic structure 501 shown in FIGS. 36 and 37 in that the deformable body 540 is not provided with a curved portion. Therefore, the deformable body 540 of the present modification has an annular (cylindrical) shape, and the upper and lower surfaces thereof are parallel to the XY plane. Since other configurations are similar to those of the basic structure 501 described above, in the drawings, corresponding components are designated by the same reference numerals, and detailed description thereof will be omitted.

  FIG. 40 is a schematic plan view showing an example of a force sensor 502c using the basic structure 502 of FIG. The force sensor 502c shown in FIG. 40 uses a radial displacement generated on the inner side surface (side surface facing the origin O) by elastic deformation of the deformable body 40 caused by the applied force or moment to detect the force or moment. It is designed to measure. In this case, as shown in FIG. 40, displacement electrodes Em <b> 1 to Em <b> 4 are provided at four portions of the inner surface of the deformable body 540 that overlap the V axis and the W axis, and each of the outer surfaces of the fixed body 510 is The fixed electrodes Ef1 to Ef4 may be provided at the portions facing the displacement electrodes Em1 to Em4. With such a configuration, four capacitive elements C1 to C4 are formed at four locations on the V axis and the W axis. The force sensor 502c using the basic structure 502 according to the present modification detects a force or moment acting on the basis of these four capacitive elements C1 to C4.

  The specific principle for measuring the force or moment acting using the force sensor 502c as described above is described in, for example, Japanese Patent No. 4948630 in the name of the applicant of the present application, and therefore the details thereof will be described here. Detailed description is omitted.

  In the basic structures 501 and 502 as described above, the force receiving body 520, the deformable bodies 40 and 540, the connecting members 531 to 534, and the fixed body 510 are arranged concentrically and along the XY plane. Therefore, each component of the basic structures 501 and 502 can be integrally formed by cutting. By such processing, it is possible to provide the force sensors 501c and 502c without hysteresis.

<<<< §6. Other variants >>>
Next, with reference to FIGS. 41 and 42, a modification of the deformable body 640 applicable to the force sensor or the basic structure according to each of the above-described embodiments will be described.

  FIG. 41 is a schematic plan view showing a rectangular deformable body 640. 42 is a schematic sectional view of FIG. 41, FIG. 42 (a) is a sectional view taken along the line [42a]-[42a] of FIG. 41, and FIG. 42 (b) is a sectional view of FIG. ]-[42b] line sectional view.

  The deformable body 640 according to the present modification has a rectangular shape as a whole. Here, as shown in FIG. 41, a square deformable body 640 will be described as an example. The deformable body 640 includes a first fixing portion 641 located on the positive X-axis, a second fixing portion 642 located on the negative X-axis, and a first force receiving portion 643 located on the positive Y-axis. , And a second force receiving portion 644 located on the negative Y axis. Each of the fixed portions 641 and 642 and each of the force receiving portions 643 and 644 is a region of the deformable body 640 to which the fixed body 10 and the force receiving body 20 are connected, and has different characteristics from other regions of the deformable body 640. Not a part. Therefore, the materials of the fixing portions 641 and 642 and the force receiving portions 643 and 644 are the same as those of the other regions of the deformable body 640. However, for convenience of description, in the drawing, the color is shown different from the other regions of the deformable body 640.

  As shown in FIG. 41, the deformable body 640 further includes a first deformable portion 645 positioned between the first fixed portion 641 and the first force receiving portion 643 (first quadrant of the XY plane), and a first deformable portion 645. The second deforming portion 646 located between the force portion 643 and the second fixing portion 642 (the second quadrant of the XY plane), and between the second fixing portion 642 and the second force receiving portion 644 (the first portion of the XY plane). A third deforming portion 647 located in the third quadrant, and a fourth deforming portion 648 located between the second force receiving portion 644 and the first fixing portion 641 (the fourth quadrant in the XY plane). There is. Both ends of each of the deforming portions 645 to 648 are integrally connected to the adjacent fixing portions 641 and 642 and the force receiving portions 643 and 644, respectively. With such a structure, the force or moment acting on the force receiving portions 43, 44 is surely transmitted to the respective deforming portions 645 to 648, whereby the elastic deformation corresponding to the acting force or moment is applied to each deforming portion 645. ~ 648.

  As shown in FIG. 41, the first to fourth deforming portions 645 to 648 are all linear when viewed in the Z-axis direction. Further, since the distances from the origin O to the fixing portions 641 and 642 and the force receiving portions 643 and 644 are all equal, the deforming portions 645 to 648 are arranged so as to form one side of the square.

  Further, as shown in FIGS. 42A and 42B, each of the deformable portions 645 to 648 of the deformable body 640 has curved portions 645c to 648c that are curved so as to bulge in the Z-axis negative direction. ing. In the illustrated example, the respective deforming portions 645 to 648 form the curved portions 645c to 648c as a whole. Therefore, in FIGS. 42 (a) and 42 (b), the reference numerals of the deformed portion and the curved portion are shown together. As shown in the figure, the portion of the first bending portion 645c that is located at the lowest position (Z axis negative direction) exists on the positive V axis. Further, the shape of the first bending portion 645c from the first fixing portion 641 to the portion at the lowest position is the shape from the first force receiving portion 643 to the portion at the lowest position. It is the same. In other words, the first bending portion 645c has a symmetrical shape with respect to the positive V axis in the length direction of the deformable body 640.

  This also applies to the remaining three curved portions 646c, 647c, 648c. That is, in the second curved portion 646c, the lowest portion is located on the positive W axis and has a symmetrical shape with respect to the positive W axis. The third curved portion 647c has a lowermost portion located on the negative V-axis, and has a symmetrical shape with respect to the negative V-axis. The fourth curved portion 648c has the lowest-positioned portion on the negative W axis, and has a symmetrical shape with respect to the negative V axis.

  As shown in FIGS. 42 (a) and 42 (b), in the deformable body 640, the first to fourth bending portions 645c to 648c are located at the lowest position, that is, each bending is seen from the Z-axis direction. Detection portions A1 to A4 for detecting elastic deformations occurring in the curved portions 645c to 648c are defined below the portions where the portions 645c to 648c overlap the V axis and the W axis. 41 shows that the detection parts A1 to A4 are provided on the upper surface (front surface) of the deformable body 640, in reality, on the lower surface (back surface) of the deformable body 640. It is provided (see FIG. 42).

<<<< §7. Device to keep the effective facing area between the plates constant ＞＞＞
In each of the force sensors described above, even if the relative position of the displacement electrode with respect to the fixed electrode changes as a result of the force in each axis direction or the moment around each axis acting, the effective opposing of the pair of electrodes forming the capacitive element It is conceivable to set the area of one of the fixed electrode and the displacement electrode forming each capacitance element to be larger than the area of the other so that the area does not change. This is when the contour of the electrode with the smaller area (for example, the displacement electrode) is projected on the surface of the electrode with the larger area (for example, the fixed electrode) in the normal direction of the electrode to form an orthogonal projection image. The projected image of the electrode having the smaller area is completely contained in the surface of the electrode having the larger area. If this state is maintained, the effective area of the capacitive element formed by both electrodes becomes equal to the area of the smaller electrode, and is always constant. That is, the force detection accuracy can be improved.

  In each of the embodiments and modifications described above, the area of the fixed electrode is larger than the area of the displacement electrode, as shown in the corresponding drawings.

Claims (3)

A force sensor for detecting at least one of a force in each axis direction and a moment about each axis in an XYZ three-dimensional coordinate system,
An annular fixed body fixed with respect to the XYZ three-dimensional coordinate system, and any one component of an annular force receiving body that moves relative to the fixed body by the action of force or moment,
A deformable body that surrounds the one component and is connected to the component, and includes a deformable portion that elastically deforms by the action of a force or a moment,
Surrounding the deformable body and connected to the deformable body, the other component of the fixed body and the force receiving body,
A detection circuit for outputting an electric signal indicating a force or a moment acting on the force receiving body based on elastic deformation of the deformable body,
The fixed body, the deformable body and the force receiving body are arranged so as to be concentric with each other,
The deformable body is adjacent to two fixed portions connected to the fixed body, two force receiving portions connected to the force receiving body and alternately positioned with the fixed portion in the circumferential direction of the deformable body. And four deformation portions positioned between the fixed portion and the force receiving portion,
The detection circuit, a displacement electrode including at least one electrode provided in the deformable portion,
The fixed body or the force receiving body, provided with a fixed electrode having at least one electrode facing the displacement electrode,
One of the displacement electrode and the fixed electrode has at least two electrodes. When the displacement electrode has at least two electrodes, one electrode of the displacement electrode and the electrode of the fixed electrode form a first capacitive element, and another electrode of the displacement electrode and the fixed electrode A second capacitive element is formed by the electrode,
When the fixed electrode has at least two electrodes, one electrode of the fixed electrode and the electrode of the displacement electrode constitute a first capacitive element, and the other electrode of the fixed electrode and the electrode of the displacement electrode. A second capacitive element is formed by the electrode,
The first capacitive element outputs a first electric signal and the second capacitive element outputs a second electric signal by a force or a moment acting on the force receiving body,
The force sensor according to claim 1, wherein whether or not the force sensor is functioning normally is determined based on a change in the first electric signal and the second electric signal. The deformable portion has a curved portion that is curved with respect to a straight line connecting the centers of the fixed portion and the force receiving portion arranged at both ends thereof,
The fixing portion, the force receiving portion, and the bending portion of the deformable body are integrally formed of the same material,
The force sensor according to claim 1 or 2, characterized in that.

Images