JP6552026B2 - 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 as an electrical signal a force acting along a predetermined axial direction and a moment acting about a predetermined rotation axis is described, for example, in Patent Document 1, and the force of an industrial robot is Widely used for control. In recent years, it has also been adopted for life support robots. As the market for force sensors expands, price reduction and higher performance of force sensors are increasingly required.

  By the way, as a force sensor, an electrostatic capacitance type force sensor that detects a force or a moment based on the amount of fluctuation of the capacitance value of the capacitive element, or a force based on the amount of fluctuation of the electrical resistance value of the strain gauge Strain gauge type force sensors that detect moments are also used. Among them, a strain gauge type force sensor has a complicated structure of a strain generating body (elastic body), and a process of attaching a strain gauge to the strain generating body in its manufacturing process is required. As described above, the strain gauge type force sensor is difficult to reduce in cost because it is expensive to manufacture.

  On the other hand, a capacitive force sensor can measure the force or moment exerted by a pair of parallel plates (capacitive elements), thus simplifying the structure of the strain generating body including the capacitive elements. be able to. In other words, the capacitance type force sensor has a merit that it is easy to reduce the price because it does not require a relatively high manufacturing cost. Therefore, if the structure of the strain generating body including the capacitive element is further simplified, it is possible to further reduce the price of the capacitive force sensor.

Citation List Patent Literature Patent Literature 1: JP 2004-354049 A Summary of the Invention The present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a capacitance type force sensor that is less expensive than the conventional one by simplifying the structure of the strain generating body including the capacitive element.

The 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 deformed body that is arranged so as to surround the origin O when viewed from the Z-axis direction, and generates elastic deformation by the action of a force or moment;
A detection circuit that outputs an electric signal indicating an applied force or moment based on elastic deformation generated in the deformable body;
The deformation body includes two fixed portions fixed with respect to the XYZ three-dimensional coordinate system, and two force receiving members alternately positioned with the fixed portions in the circumferential direction of the deformation body and receiving an action of a force or a moment And four deformation portions positioned between the fixing portion and the force receiving portion adjacent in the circumferential direction of the deformation body,
Each deformation portion has a curved portion bulging in the Z-axis direction,
The detection circuit outputs the electrical signal based on elastic deformation generated in the bending portion.

  According to the present invention, a simple deformation body having a curved portion bulging in the Z-axis direction can cause a displacement corresponding to an applied force or moment in the Z-axis direction at a detection site. For this reason, since the pair of electrodes constituting the capacitive element can be arranged in parallel with the XY plane, it is easy to construct the capacitive element. That is, in the conventional capacitance-type force sensor, since the displacement corresponding to the applied force or moment occurs in the direction orthogonal to the Z axis, the support extending in the Z axis direction is formed on the upper surface of the fixed body. Once installed, the other electrode (fixed electrode) had to be installed on this support, and the structure was somewhat complicated. The advantages of the present invention may be better understood in view of such conventional electrode arrangements. 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 the conventional one. In particular, in a force sensor having a plurality of capacitive elements, the fixed electrode (the electrode opposed to the displacement electrode disposed 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,
And a force receiver 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 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 of installation of the force sensor can be further enhanced.

The two fixed portions are arranged symmetrically with respect to the Y axis in 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 in a portion where the deformable body overlaps with the Y axis when viewed from the Z axis direction.

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

  The deformed body may have an annular shape centered on the origin O as viewed in the Z-axis direction.

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

  In these cases, since the deformation bodies are arranged symmetrically with respect to the X axis and the Y axis, the deformation bodies deform symmetrically due to the applied force or moment. For this reason, it is easy to measure the force or moment acting based on the deformation.

Each curved portion of the deformable body bulges in the Z-axis negative direction,
The detection circuit includes a total of four displacement electrodes disposed one by one in each curved portion, and a fixed electrode disposed opposite to the displacement electrodes and fixed to the fixing portion,
Each displacement electrode and the fixed electrode constitute four sets of capacitive elements,
The detection circuit may be configured to output an electric signal indicating an applied force or moment based on a variation amount of capacitance values of the four sets of capacitive elements.

  In this case, by focusing on the combination of variations in capacitance value of individual capacitive elements, a plurality of components among a total of six components of force in each axial direction and moment around each axis in the XYZ three-dimensional coordinate system Can be detected.

  When the V axis and the W axis are defined at 45 ° with respect to the X axis and the Y axis through the origin O on the XY plane, the four capacitive elements have the deformable body viewed from the Z axis direction. One each may be arranged at four portions 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, the symmetry of each capacitive element can be obtained with high symmetry, particularly when acting on a variant having a symmetrical shape with respect to the X axis and the Y axis. The capacitance value fluctuates. For this reason, it is possible to measure the applied force or moment extremely easily based on the variation of the capacitance value.

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

  If the displacement electrode is directly attached to the curved portion, warpage will occur in the displacement electrode due to the influence of the deformation of the curved portion, but if the configuration as described above is adopted, the displacement electrode is Since no warpage occurs, elastic deformation occurring in the curved portion can be efficiently converted into fluctuation of the capacitance value of the capacitive element.

In the above force sensor, each curved portion of the deformable body has a detection part defined at a part located on the most negative side of the Z axis,
The deformable body-side support is a beam disposed so as to overlap the detection portion of the curved portion to which the deformable body-side support is connected when viewed from the Z-axis direction, and one end of the beam is the detection portion And a connector connected to the curved portion at a position different from
Each of the displacement electrodes may be configured to be supported by the beam of the corresponding deformable body side support.

  In this case, since the beam is connected to the curved portion at a position different from the detection site, the displacement generated in the displacement electrode supported by the beam is amplified. That is, when a force or moment of a certain magnitude is applied, the displacement produced in the displacement electrode in such a force sensor corresponds to the displacement electrode supported by the displacement electrode at the detection portion of the bending portion. Larger than the displacement that occurs. For this reason, the sensitivity to the applied force or moment is high, and more accurate measurement can be performed.

Or the force sensor which can perform a failure diagnosis with a single force sensor by the following structures can be provided. That is, each curved portion of the deformable body bulges in the negative direction of the Z axis,
The detection circuit includes a total of eight displacement electrodes disposed two by two in each curved portion, and a fixed electrode disposed opposite to the displacement electrodes and fixed to the fixing portion,
The displacement electrode and the fixed electrode constitute eight sets of capacitive elements,
The detection circuit includes:
A first electricity indicating an applied force or moment based on a variation of capacitance values of a total of four capacitive elements, one of which is selected from capacitive elements arranged two by two at each curved portion of the deformable body. Outputting a signal, and outputting a second electrical signal indicating a force or a moment applied, based on the amount of fluctuation of the capacitance value of a total of four capacitive elements selecting each 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 a difference between the first electric signal and the second electric signal. It is good. In this case, it is possible to provide a force sensor which can detect an applied force or moment and can perform failure diagnosis.

Alternatively, each curved portion bulges in the negative direction of the Z-axis, and the first curved portion having a first spring constant and the second curved portion having a second spring constant different from the first spring constant are the deformations. It is constructed by being connected in the circumferential direction of the body,
The detection circuit includes a total of eight displacement electrodes disposed one each in the first curved portion and the second curved portion, and a fixed electrode disposed opposite to the displacement electrodes and fixed to the fixed portion, Have
Each displacement electrode and the fixed electrode constitute eight sets of capacitive elements,
The detection circuit includes:
A first electric signal indicating an applied force or moment based on a variation of capacitance values of four capacitive elements disposed in the first curved portion, and disposed in the second curved portion; A second electric signal indicating the applied force or moment is output based on the fluctuation amount of the capacitance values of the four capacitive elements;
Based on a change in the ratio between the first electric signal and the second electric signal, it may be determined whether or not the force sensor is functioning normally.

Specifically, the detection circuit
The ratio of 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 of the first electrical signal and the second electrical signal and the reference ratio.

  In this case, it is possible to provide a force sensor capable of detecting the applied force or moment and diagnosing a failure due to metal fatigue developed in the deformable body. The principle of more detailed 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 arranged symmetrically with respect to each axis of X, Y, V, W, the variation of the capacitance value generated in each capacitive element by the applied force or moment also becomes 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 around 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 deformed body that surrounds the fixed body and is connected to the fixed body and generates elastic deformation by the action of force or moment;
An annular force receiving body that surrounds the deformation body and is connected to the deformation body and moves relative to the fixed body by the action of a force or a moment;
A detection circuit that outputs an electric signal indicating a force or a moment acting on the force receiving member based on elastic deformation generated in the deforming member;
The fixed body, the deformation body and the force receiving body are arranged to be concentric with each other,
The Z coordinate value of the end surface on the positive side of the Z axis of the force receiving body is larger than the Z coordinate value of the end surface on the positive side of the Z axis of the deformable body,
The Z coordinate value of the end surface on the negative side of the Z axis of the fixed body is smaller than the Z coordinate value of the end surface on the negative side of the Z axis of the deformable body,
The deformable body is adjacent to two fixed portions connected to the fixed body, and 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 deforming portions positioned between the fixing portion and the force receiving portion.

  According to the force sensor of the present invention, by simplifying the structure of the strain-generating body including the capacitive element, it is possible to provide a capacitive force sensor that is cheaper than the conventional one. Furthermore, such a force sensor does not interfere with other members when the force sensor is attached to a joint part of a robot.

Each deformation portion has a curved portion bulging in the Z-axis direction,
The detection circuit may be configured to output the electrical signal based on elastic deformation generated in 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 configuration, the arrangement of the pair of electrodes constituting the capacitive element is easy.

Alternatively, each deformation portion has a curved portion bulging in the radial direction of the deformation body,
The detection circuit may output the electrical signal based on elastic deformation generated in the bending portion.

  In this case, even if a conventional deformable body is used, a force sensor that does not interfere with other members when mounted on a joint portion of the robot can be provided.

The two fixed portions are arranged symmetrically with respect to the Y axis in 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 in a portion where the deformable body overlaps with the Y axis when viewed from 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 cross-sectional view taken along line [3]-[3] in FIG. 2. It is a schematic plan view for demonstrating the elastic deformation which arises in each curved part when the moment + Mx of the X-axis positive | positive rotation acts with respect to the basic structure of FIG. It is a schematic sectional drawing of FIG. 5A is a cross-sectional view taken along line [5a]-[5a] in FIG. 4, and FIG. 5B is a cross-sectional view taken along 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 around Y-axis acts on the basic structure of FIG. It is a schematic sectional drawing of FIG. 7A is a cross-sectional view taken along line [7a]-[7a] in FIG. 6, and FIG. 7B is a cross-sectional view taken along line [7b]-[7b] in FIG. It is a schematic plan view for demonstrating the elastic deformation which arises in each curved part, when the moment + Mz around Z-axis positive acts with respect to the basic structure of FIG. It is a schematic sectional drawing of FIG. 9A is a cross-sectional view taken along line [9a]-[9a] in FIG. 8, and FIG. 9B is a cross-sectional view taken along 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 a Z-axis positive direction acts with respect to the basic structure of FIG. It is a schematic sectional drawing of FIG. 11A is a cross-sectional view taken along a line [11a]-[11a] in FIG. 10, and FIG. 11B is a cross-sectional view taken along a line [11b]-[11b] in FIG. It is a schematic plan view which shows the force sensor using the basic structure of FIG. It is the [13]-[13] sectional view taken on the line of FIG. 13 is a chart showing a variation in capacitance value that occurs in each capacitive element when a force or moment is applied to the force sensor of FIG. 12. It is a schematic plan view of a force sensor according to a second embodiment of the present invention. It is the [16]-[16] sectional view taken on the line of FIG. FIG. 16 is a sectional view taken along line [17]-[17] in FIG. FIG. 16 is a schematic cross-sectional view showing a first capacitive element C1 when a force in the negative X-axis 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 the first capacitive element C1 when a force in the X-axis positive direction is applied to 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 positive Z-axis direction is applied to 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 Z-axis direction is applied to the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the negative X-axis direction is applied to the first force receiving portion of the force sensor shown in FIG. FIG. 16 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the X-axis positive direction is applied to 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 Z-axis direction is applied to the first force receiving portion of the force sensor shown in FIG. 15. FIG. 16 is a partial schematic cross-sectional view showing the second capacitive element C2 when a force in the negative Z-axis direction is applied to the first force receiving portion of the force sensor shown in FIG. 15. It is a schematic plan view of a force sensor according to a third embodiment of the present invention. FIG. 27 is a sectional view taken along line [27]-[27] in FIG. FIG. 27 is a sectional view taken along line [28]-[28] in FIG. It is a graph which shows the fluctuation | variation of the electrostatic capacitance value which arises in each capacitive element when force or moment acts with respect to the force sensor of FIG. It is a schematic plan view of a force sensor according to a fourth embodiment of the present invention. FIG. 31 is a cross-sectional view taken along line [31]-[31] in FIG. FIG. 31 is a cross-sectional view taken along line [32]-[32] in FIG. FIG. 31 is a chart showing variations in capacitance values that occur in each capacitive element when a force or moment is applied to the force sensor of FIG. 30. FIG. In a state (initial state) in which metal fatigue does not occur in the force sensor shown in FIG. 30, the magnitude of the moment Mx around the X axis acting on the force sensor, and the electric signal output from the force sensor Is a graph showing the relationship of 30 is a graph showing the relationship between the magnitude of the moment Mx around the X axis acting on the force sensor and the electrical signal output from the force sensor in a state where metal fatigue is occurring in the force sensor of FIG. 30. is there. It is a schematic plan view which shows the basic structure of the force sensor by the 5th Embodiment of this invention. FIG. 37 is a sectional view taken along line [37]-[37] in FIG. FIG. 37 is a schematic plan view showing a modification of the basic structure of FIG. 36. It is the [39]-[39] line sectional drawing of FIG. It is a schematic plan view which shows an example of the force sensor using the basic structure of FIG. It is a schematic plan view which shows a rectangular deformation body. FIG. 42 is a schematic cross-sectional view of FIG. 42A is a cross-sectional view taken along line [42a]-[42a] in FIG. 41, and FIG. 42B is a cross-sectional view taken along line [42b]-[42b] in FIG.

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

<1-1. Basic structure>
FIG. 1 is a schematic 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 cross-sectional view taken along line [3]-[3] of FIG. In FIG. 2, the X axis is defined in the left-right direction, the Y axis is defined in the up-down direction, and the Z axis is defined in the depth direction. In this specification, the positive Z-axis direction is referred to as the upward direction, and the negative Z-axis direction is referred to as the downward direction. Further, in the present specification, the X-axis positive rotation means a rotation direction in which the right-hand screw is rotated to advance the right-hand screw in the X-axis positive direction, and the X-axis negative rotation is the reverse rotation direction thereof. Means. The method of defining the rotational direction is the same for the Y axis and the Z axis.

As shown in FIGS. 1 to 3, the basic structure 1 is a disk-like fixed body 10 having an upper surface parallel to the XY plane, and a disk relatively moved with respect to the fixed body 10 under the action of force or moment. And a ring-shaped deformable body 40 that is connected to the fixed body 10 and the force-receiving body 20 and generates elastic deformation by 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 disposed at a predetermined position of a gap formed between the deformable body 40 and the fixed body 10, and a predetermined detection circuit 50 (see FIG. 12) is provided to the capacitive element. By connecting, it functions as a force sensor. The detection circuit 50 is for measuring the applied force or moment based on the fluctuation amount of the capacitance value of the capacitive element. The specific arrangement of the capacitive element and the specific method for measuring the applied force or moment will be described later.

As shown in FIG. 1 and FIG. 2, the deformable body 40 as a whole has a shape of an annular ring disposed in parallel with the XY plane, with the origin O of the XYZ three-dimensional coordinate system as a center. 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 deformation body 40 of the present embodiment has a square cross-sectional shape.
As a material of the deformable body 40, for example, a metal may be employed. As shown in FIG. 2, the deformable body 40 is positioned on the positive X axis, the first fixed portion 41 positioned on the positive X axis, the second fixed portion 42 positioned on the negative X axis, and 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 and 42 and each of the force receiving portions 43 and 44 are regions to which the fixed body 10 and the force receiving body 20 are connected in the deformable body 40. It is not a site having characteristics different 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 the other regions of the deformable body 40. However, for convenience of explanation, in the drawings, the color is different from that of 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 positioned between the first fixing portion 41 and the first force receiving portion 43 (first quadrant of the XY plane), A 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), between the second fixed portion 42 and the second force receiving portion 44 (XY A third deformation portion 47 located in the third quadrant of the plane, and a fourth deformation portion 48 located between the second force receiving portion 44 and the first fixed portion 41 (the fourth quadrant in the XY plane); Have. Both ends of the deformable portions 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 and 44 is reliably transmitted to each of the deforming portions 45 to 48, whereby the elastic deformation corresponding to the acting force or moment is performed on each deforming portion 45. It is supposed to occur at ~ 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. And the third connecting member 33 and the fourth connecting member 34. The first connection member 31 connects the lower surface (the lower surface in FIG. 3) of the first fixed portion 41 and the upper surface of the fixed body 10 to each other, and the second connection member 32 fixes the lower surface of the second fixed portion 42 to the lower surface. The upper surface of the body 10 is connected to each other. The third connecting member 33 connects the upper surface (the 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 is connected to 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 connecting member 31 to 34 has a rigidity that can be regarded as substantially a rigid body. For this reason, the force or moment acting on the force receiving body 20 effectively causes elastic deformation in each of the deformation portions 45 to 48.

  Further, as shown in FIGS. 1 and 3, the deformable portions 45 to 48 of the deformable body 40 have curved portions 45 c to 48 c that are curved so as to bulge in the Z-axis negative direction. In the illustrated example, the respective deformation portions 45 to 48 form the curved portions 45 c to 48 c as a whole. For this reason, in FIG. 1 thru | or FIG. 3, the code | symbol 45-48 of a deformation | transformation part and the code | symbol 45c-48c of a bending part are written together. The same applies to the other embodiments described later. In the deformable body 40 according to the present embodiment, as shown in FIG. 3, the portion of the first curved portion 45 c that is located at the lowest position (the negative Z-axis direction) extends from the first fixing portion 41 to the circumferential direction of the deformable body 40. Along the counterclockwise direction 45 °. The shape of the first curved portion 45c from the first fixed portion 41 to the lowermost portion is the shape from the first force receiving portion 43 to the lowermost portion. It is the same. In other words, the first bending portion 45 c has a symmetrical shape with respect to the lowermost portion in the circumferential direction of the deformable body 40.

  The same applies to the remaining three curved portions 46c, 47c and 48c. That is, the second bending portion 46c is located at the lowermost portion of the first force receiving portion 43 in the circumferential direction of the deformable body 40 by 45 ° in the counterclockwise direction, and The deformation body 40 has a symmetrical shape with respect to the lowermost position in the circumferential direction. The third curved portion 47 c is located at the lowermost portion of the second fixed portion 42 in the circumferential direction of the deformable body 40 by 45 ° in the counterclockwise direction. It has a symmetrical shape with respect to the lowest position in the circumferential direction. The fourth curved portion 48 c is located at the lowermost portion of the second force receiving portion 44 in the circumferential direction of the deformable body 40 by 45 ° in the counterclockwise direction. It has a symmetrical shape with respect to the lowest position in the circumferential direction.

  After all, as shown in FIG. 2, when defining the V axis and the W axis which pass through the origin O and make 45 ° with the X axis and the Y axis on the XY plane, the first curved portion 45c is a positive V axis The second curved portion 46c is symmetric about the positive W axis, the third curved portion 47c is symmetric about the negative V axis, and the fourth curved portion 48c is negative W It is symmetrical about an axis.

  As shown in FIGS. 2 and 3, in the basic structure 1, the bending portions 45 c to 48 c have v-axis and w-axis in the lowermost portion of the bending portions 45 c to 48 c, that is, viewed from the Z-axis direction. In the overlapping portions, detection portions A1 to A4 for detecting elastic deformation generated in the respective curved portions 45c to 48c are defined. In FIG. 2, the detection sites A1 to A4 are illustrated as being provided on the upper surface (surface on the near side) of the deformable body 40, but in fact, on the lower surface (surface on the far side) 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 moment Mx around X axis acts on basic structure 1)
FIG. 4 is a schematic plan view for explaining elastic deformation that occurs in each of the curved portions 45c to 48c when a moment + Mx around the X-axis normal acts on the basic structure 1 of FIG. FIG. 5 is a schematic cross-sectional view of FIG. 5A is a cross-sectional view taken along line [5a]-[5a] in FIG. 4, and FIG. 5B is a cross-sectional view taken along line [5b]-[5b] in FIG. In FIG. 4 and FIG. 5, thick solid arrows indicate the acting force or moment, and solid thick arrows indicate the direction of displacement of the detection portions A1 to A4. The same applies to the other figures.

  As shown in FIG. 4, when moment + Mx around the X-axis positive acts on the basic structure 1 through the force receiving body 20 (see FIGS. 1 and 3), the first force receiving portion 43 of the deformable body 40 is 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, the circled symbol of the black point attached to the first force receiving portion 43 indicates that a force acts from the negative Z-axis direction to the positive Z-axis direction, and the second receiving The symbol that is attached to the force portion 44 and circles the X mark indicates that a force acts from the Z-axis positive direction toward the Z-axis negative direction. The meanings of these symbols are the same in FIG. 6, FIG. 8, and FIG.

  At this time, as shown in FIGS. 5A and 5B, the following elastic deformation occurs in the first to fourth curved portions 45c to 48c. That is, since the first force receiving portion 43 is moved upward by the force in the positive Z-axis direction 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. Thereby, as shown to Fig.5 (a), the 1st curved part 45c and the 2nd curved part 46c are generally upward except the end connected with the 1st and 2nd fixed parts 41 and 42. Move to That is, both the first detection site A1 and the second detection site A2 move upward. On the other hand, since the second force receiving portion 44 is moved downward by the force in the negative Z-axis direction 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 curved portion 47c and the fourth curved portion 48c are entirely downward except the end portions connected to the first and second fixed portions 41 and 42. Move to That is, both the third detection site A3 and the fourth detection site A4 move downward.

  Such movement is represented in FIG. 4 by adding a circled “+” or “−” symbol to the position of each detection site A1 to A4. That is, the detection site marked with a circled sign “+” is displaced in the positive direction of the Z-axis by the elastic deformation of the bending portion, and the detection site marked with a circle mark “−” is It is displaced in the negative Z-axis direction by elastic deformation of the bending portion. The same applies to FIGS. 6, 8 and 10 as well.

  After all, when moment + Mx around X-axis positive acts on the receiving body 20 of the basic structure 1, the separation distance between the first and second detection parts A1 and A2 and the upper surface of the fixed body 10 (see FIG. 3) is Both increase, and the separation 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 moment -Mx around the negative X-axis 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 those described above. That is, the distance between the first and second detection sites A1 and A2 and the upper surface of the fixed body 10 (see FIG. 2) decreases together by the action of the moment -Mx around the X axis negative, and the third and fourth Both the separation distances between the detection portions A3 and A4 and the upper surface of the fixed body 10 increase.

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

  As shown in FIGS. 6 and 7, when a moment + My about the positive Y-axis acts on the basic structure 1 via the force receiving body 20 (see FIGS. 1 and 3), the first and second of the deformable body 40 2 Force in the positive Z-axis direction acts on the area on the X-axis negative side of the force receiving portions 43 and 44, and the area on the X-axis positive side of the first and second force receiving portions 43 and 44 in the negative Z-axis direction The power of

  At this time, as shown in FIGS. 7A and 7B, the first to fourth bending portions 45c to 48c undergo the following elastic deformation. That is, since the region on the positive side of the X axis moves downward due to the force in the negative direction of the Z axis acting on the positive side of the X axis of the first force receiving portion 43 (the right side in FIG. 7A), the first bending portion Of 45c, the end connected to the first force receiving portion 43 is moved downward. Thereby, as shown to Fig.7 (a), the 1st curved part 45c moves below generally, except the edge part connected with the 1st fixing | fixed part 41. As shown in FIG. That is, the first detection site A1 moves downward. On the other hand, the region on the negative side of the X axis is moved upward by the force in the positive direction of the Z axis that acts on the negative side of the X axis of the first force receiving portion 43 (left side in FIG. 7A), 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 connected to the second fixed portion 42. That is, the second detection site A2 moves upward.

  Further, as shown in FIG. 7 (b), the area on the X-axis negative side by the force in the positive direction of the Z-axis acting on the X-axis negative side (right side in FIG. 7 (b)) of the second force receiving portion 44 is In order to move 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 curved portion 47c moves upward as a whole, except for the end connected to the second fixed portion 42. That is, the third detection site A3 moves upward.

  On the other hand, as shown in FIG. 7B, the area on the X-axis positive side is affected by the force in the negative Z-axis direction acting on the X-axis positive side (left side in FIG. 7B) of the second force receiving portion 44. To move downward, the end of the fourth bending portion 48c 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 connected to the first fixed portion 41. That is, the fourth detection site A4 moves downward.

  After all, when moment + My around the Y axis 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) is , Both decrease, and the separation distance between the second and third detection sites A2, A3 and the upper surface of the fixed body 10 increases.

  Although not shown, when the moment -My around the Y axis acts on the force receiving body 20 of the basic structure 1, the moving directions of the detection portions A1 to A4 are opposite to the above-described directions. That is, due to the action of the moment -My around the Y axis, the separation distance between the first and fourth detection portions A1 and A4 and the upper surface of the fixed body 10 (see FIG. 3) increases together, and the second and third Both the separation distances between the detection portions A2 and A3 and the upper surface of the fixed body 10 decrease.

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

  As shown in FIG. 8, when a moment + Mz around the positive Z-axis acts on 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 (left direction in FIG. 8) acts, and a force in the X-axis positive direction (right direction 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 curved portions 45c to 48c. That is, since the first force receiving portion 43 moves in the X axis negative direction by the force in the X axis negative direction acting on the first force receiving portion 43, the first bending portion 45c has a tensile force along the X axis direction. Force works. As a result, the first curved portion 45 c is elastically deformed so as to increase the radius of curvature while maintaining the Z coordinate values of the both end portions. That is, the first detection site A1 moves upward. On the other hand, when the first force receiving portion 43 moves in the X-axis negative direction, a compressive force along the X-axis direction acts on the second bending portion 46c. As a result, the second bending portion 46 c elastically deforms so that the radius of curvature becomes smaller while maintaining the Z coordinate values of the both end portions. That is, the second detection site 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 is elastically deformed so that the radius of curvature becomes large while maintaining the Z coordinate values of both end portions thereof. That is, the third detection site 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 curved portion 48 c elastically deforms so that the radius of curvature becomes smaller while maintaining the Z coordinate values of the both end portions. That is, the fourth detection site A4 moves downward.

  After all, when the moment + Mz around the Z axis acts on the force receiving member 20 of the basic structure 1, the separation distance between the first and third detection portions A1 and A3 and the upper surface of the fixed body 10 both increases, The separation distance between the second and fourth detection sites A2 and A4 and the top surface of the fixed body 10 (see FIG. 2) both decreases.

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

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

  As shown in FIGS. 10 and 11, when a force + Fz in the positive direction of the Z-axis acts on the basic structure 1 through the force receiving body 20 (see FIGS. 1 and 3), the first and 2 Forces in the positive Z-axis direction act on the force receiving portions 43 and 44.

  At this time, as shown in FIGS. 11A and 11B, the first to fourth curved portions 45c to 48c undergo the following elastic deformation. That is, since the force receiving portions 43 and 44 are moved upward by the force in the Z-axis positive direction acting on the first and second force receiving portions 43 and 44, the first and second of the curved portions 45c to 48c. 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 sites A1 to A4 move upward.

  After all, when a 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) is , All increase.

  Although not shown, when the force -Fz in the negative direction of the Z-axis acts on the force receiving body 20 of the basic structure 1, the moving direction of each of the detection portions A1 to A4 is opposite to the direction described above. 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 Z-axis negative direction.

<1-3. Capacitive element type force sensor>
(1-3-1. Configuration of force sensor)
§1-1. And §1-2. The basic structure 1 described in detail in the above can be suitably used as a 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 using the basic structure 1 of FIG. 1, and FIG. 13 is a cross-sectional view taken along line [13]-[13] of FIG. In FIG. 13, in order to clearly show the deformable body 40, the force receiving body 20 is not shown.

  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 parts A1 to A4 of the basic structure 1 of FIG. Specifically, as shown in FIG. 13, the force sensor 1 c is disposed opposite to the first displacement electrode Em1 disposed at the first detection site A1 and the first displacement electrode Em1, and the force sensor 1 c is disposed on the fixed body 10. The first fixed electrode Ef1 does not move relative to the first fixed electrode Ef1. These electrodes Em1, Ef1 constitute a first capacitive element C1. Furthermore, as shown in FIG. 13, the force sensor 1 c is disposed opposite to the second displacement electrode Em 2 disposed at the second detection site A 2 and the second displacement electrode Em 2, and is relative to the fixed body 10. A second fixed electrode Ef2 that does not move. These electrodes Em2 and Ef2 constitute a second capacitive element C2.

  Although not shown, the force sensor 1c is disposed opposite to the third displacement electrode Em3 disposed at the third detection site A3 and the third displacement electrode Em3 and does not move relative to the fixed body 10. A third fixed electrode Ef3, a fourth displacement electrode Em4 disposed at the fourth detection site A4, and a fourth fixed electrode Ef4 disposed opposite to the fourth displacement electrode Em4 and not moved relative to the fixed body 10; have. The electrode Em3 and the electrode Ef3 constitute a third capacitive element C3, and the electrode Em4 and the electrode Ef4 constitute a fourth capacitive element C4.

  As understood from FIG. 13, each of the displacement electrodes Em1 to Em4 is disposed on the lower surface 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. Furthermore, the fixed electrodes Ef1 to Ef4 are supported on the upper surfaces of the fixed body side supports 71 to 74 fixed on 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 all have the same area. However, as a device for maintaining the effective opposing areas of the capacitive elements C1 to C4 at a constant value by the action of force or moment, the electrode areas of the displacement electrodes Em1 to Em4 are the electrodes of the fixed electrodes Ef1 to Ef4. It is configured to be larger than the area. This will be described in detail later. In the initial state, the effective facing area and the separation distance of each pair of electrodes constituting capacitive elements C1 to C4 are all the same.

  Furthermore, as shown in FIG. 12 and FIG. 13, the force sensor 1 c is an electrical signal indicating the force or moment acting on the force receiving body 20 based on the elastic deformation occurring in each of the curved portions 45 c to 48 c of the deformable body 40. Is detected. In FIG. 12 and FIG. 13, wirings that electrically connect the capacitive elements C1 to C4 and the detection circuit 50 are not shown.

  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 fixing are provided so that the electrodes do not short. The substrates If1 to If4 need to be made of insulators.

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

  First, when a moment + Mx around the X axis normal acts on the force sensor 1c according to the present embodiment, as understood from the behavior of each of the detection sites A1 to A4 described in 1−21-2-1. The separation distance between the electrodes constituting the first capacitive element C1 and the second capacitive element C2 both increases. Therefore, the electrostatic capacitance values of the first capacitive element C1 and the second capacitive element C2 both decrease. On the other hand, the separation distance between the electrodes constituting the third capacitive element C3 and the fourth capacitive element C4 both decreases. For this reason, the electrostatic capacitance values of the third capacitive element C3 and the fourth capacitive element C4 both increase. The fluctuation of the capacitance value of each of the capacitive elements C1 to C4 is collectively shown in the "Mx" column of FIG. In this chart, "+" indicates that the capacitance value increases, and "-" indicates that the capacitance value decreases. When the moment −Mx around the X axis acts on the force sensor 1c, the fluctuation of the capacitance value of each of the capacitive elements C1 to C4 is opposite to the fluctuation described above (see the column of Mx in FIG. 14). The signs shown are all reversed).

(1-3-3. Regarding variation in capacitance value of each capacitive element when moment My around 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 is understood from the behavior of each of the detection sites A1 to A4 described in 1−21-2-2. In addition, the separation distance between the electrodes constituting the first capacitor element C1 and the fourth capacitor element C4 is decreased. Therefore, the capacitance values of the first capacitive element C1 and the fourth capacitive element C4 both increase. On the other hand, the separation distance between the electrodes constituting the second capacitor element C2 and the third capacitor element C3 increases. Therefore, the electrostatic capacitance values of the second capacitive element C2 and the third capacitive element C3 both decrease. Variations in the capacitance values of the capacitive elements C1 to C4 are collectively shown in the column “My” in FIG. When the moment -My around the Y axis acts on the force sensor 1c, the fluctuation of the capacitance value of each of the capacitive elements C1 to C4 is opposite to the fluctuation described above (see the column of My in FIG. 14). The signs shown are all reversed).

(1-3-4. Variation of Capacitance Value of Capacitance Elements When Moment Mz around Z-axis Acts on Force Sensor 1c)
Next, it is understood from the behavior of each of the detection sites A1 to A4 described in 1−21-2-3 when the moment + Mz around the Z axis normal acts on the force sensor 1c according to the present embodiment. In addition, the distance between the electrodes constituting the first capacitor element C1 and the third capacitor element C3 increases. Therefore, the capacitance values of the first capacitive element C1 and the third capacitive element C3 both decrease. On the other hand, the separation distance between the electrodes constituting the second capacitor element C2 and the fourth capacitor element C4 decreases. For this reason, the electrostatic capacitance values of the second capacitive element C2 and the fourth capacitive element C4 both increase. Variations in the capacitance values of the capacitive elements C1 to C4 are collectively shown in the column “Mz” in FIG. When the moment −Mz around the Z axis negative acts on the force sensor 1c, the fluctuation of the capacitance value of each of the capacitive elements C1 to C4 is opposite to the fluctuation described above (see the column of Mz in FIG. 14). The signs shown are all reversed).

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

(1-3-6. Method of calculating the acting force or moment)
In view of the fluctuation of the capacitance value of the capacitive elements C1 to C4 as described above, the detection circuit 50 uses the following [Equation 1] to apply the moments Mx, My, Mz and the force Fz to the force sensor 1c. calculate. In [Formula 1], C1 to C4 indicate the fluctuation amount of the capacitance values of the first to fourth capacitive elements C1 to C4.
[Equation 1]
Mx = −C1-C2 + C3 + C4
My = C1-C2-C3 + C4
Mz = -C1 + C2-C3 + C4
Fz =-(C1 + C2 + C3 + C4)
If the force or moment acting on the force sensor 1c is in the negative direction, Mx, My, Mz and -Fz may be substituted for 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 that acts on the detection portions A1 to A4 by the simple deformable body 40 having the curved portions 45c to 48c that bulge in the Z-axis direction. Can be generated in the Z-axis direction. Therefore, one of the pair of electrodes constituting the capacitive elements C1 to C4 may be disposed at the detection site A1 to A4, and the other may be disposed on the upper surface of the fixed body 10, for example. It is easy. Therefore, according to the present embodiment, by adopting such a simple structure, it is possible to provide an electrostatic capacitance type force sensor 1c which is cheaper than the conventional one.

  In the force sensor 1c, when the V axis and the W axis that pass through the origin O on the XY plane and form 45 ° with respect to the X axis and the Y axis are defined, the four capacitive elements C1 to C4 are arranged in the Z axis direction. One is arranged at each of four portions overlapping the V-axis and the W-axis. Therefore, since the capacitive elements C1 to C4 are arranged symmetrically with respect to the X axis and the Y axis, the capacitance value of each of the capacitive elements C1 to C4 fluctuates with high symmetry. For this reason, it is possible to very easily measure the applied force or moment based on the variation 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 configured to be common to four capacitive elements. With such a configuration as well, the force or the moment can be measured in the same manner as the force sensor 1c described above. Note that these configurations are also applicable to the embodiments described later.

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

  Alternatively, the sensitivity of the force sensor 1c with respect to the acting force or moment also changes when the radius of curvature (the degree of bending) of the bending portions 45c to 48c is changed. Specifically, when the curvature radii of the bending portions 45c to 48c are reduced (the degree of bending is increased), the sensitivity to the acting force or moment is increased. On the other hand, when the curvature radii of the bending portions 45c to 48c are increased (when the degree of bending is decreased), the sensitivity to the acting force or moment decreases.

  The sensitivity of the force sensor 1c is optimized in the environment to be used by considering the relationship between the cross-sectional shape of the deformable body 40 and the radius of curvature of the curved portions 45c to 48c and the sensitivity to force or moment. can do. Of course, the above description is similarly applied to each embodiment described later.

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

  FIG. 15 is a schematic plan view of a force sensor 201c according to the second embodiment. 16 is a cross-sectional view taken along line [16]-[16] of FIG. 15, and FIG. 17 is a cross-sectional view taken along line [17]-[17] of FIG. However, in FIG. 15, the drawing of the force receiving body 20 is omitted for the sake of clarity of the drawing.

  As shown in FIGS. 15 to 17, the force sensor 201 c is different from the force sensor 1 c according to the first embodiment in the following point. That is, in force sensor 201c according to the present embodiment, deformable bodies-side supports 261 to 264 supporting displacement electrodes Em1 to Em4 are curved at portions different from detection portions A1 to A4 of respective curved portions 45c to 48c. It is connected to the parts 45c to 48c. Specifically, as shown in FIG. 15 and FIG. 16, the first deformable body side support body 261 connected to the first bending portion 45 c is a first detection of the first bending portion 45 c when viewed from the Z-axis direction. A first connecting member for connecting a first beam 261b arranged to overlap with the portion A1 and an end of the first beam 261b on the first fixed portion 41 side (right side in FIG. 16) to the first bending portion 45c 261s, and a cantilever structure. Since the first connection body 261s extends in parallel with 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 than the first detection portion A1. It 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.

  In addition, the second deformable body side support 262 connected to the second curved portion 46c is also configured as a cantilever structure. That is, as shown in FIGS. 15 and 16, the second deformable body side support 262 is disposed 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 the end of the second beam 262b on the second fixing portion 42 side (left side in FIG. 16) to the second bending portion 46c. There is. Since the second connection body 262s extends in parallel with the Z axis, the connection position between the second connection body 262s and the second bending portion 46c is closer to the second fixed portion 42 than the second detection site A2. It is. The second displacement electrode Em2 is supported on the lower surface of the second beam 262b of the cantilever structure via a displacement substrate.

  Further, the third deformation body side support body 263 and the fourth deformation 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 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. There is. Since the third connector 263 s extends in parallel with the Z axis, the connection position between the third connector 263 and the third curved portion 47 c is closer to the second fixed portion 42 than the third detection site A 3. is there. The third displacement electrode Em3 is supported on the lower surface of the third beam 263b via a displacement substrate.

  The fourth deformable body side support 264 includes a fourth beam 264b disposed 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. And a fourth connecting body 264s that connects the end of the first fixing portion 41 (the left side in FIG. 17) to the fourth curved portion 48c. Since the fourth connector 264s extends in parallel with the Z axis, the connection position between the fourth connector 264s and the fourth curved portion 48c is closer to the first fixing portion 41 than the fourth detection site 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 connecting bodies 261s to 264s is connected to the curved portions 45c to 48c at a site different from the detection sites A1 to A4, but is viewed from the Z-axis direction. It arrange | positions so that Em1-Em4 may overlap with corresponding detection part A1-A4.

  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 another embodiment (not shown) ) May be configured as a doubly supported beam structure in which the ends of the beams 261b to 264b 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, for example, in the vicinity of a portion where the Z-axis and the upper surface of the fixed body 10 intersect. According to such a configuration, it is possible to stabilize the inclination behavior of the beams 261b to 264b generated by the action of the force or moment acting on the force sensor 201c from the external vibration.

<2-2. Action>
(2-2-1. Fluctuation of the capacitance value of the first capacitive element C1)
Consideration will be given to fluctuations in capacitance values generated in the capacitive elements C1 to C4 when a force or moment is applied to the force sensor 201c according to the present embodiment. Here, first, fluctuations in the capacitance value of the first capacitive element C1 will be described with reference to FIGS.

  FIG. 18 is a schematic cross-sectional view showing the first capacitive element C1 when a force in the negative direction of the X-axis is applied to the first force receiving portion 43 of the force sensor shown in FIG. 15 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the X-axis positive direction is applied to 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 positive Z-axis direction is applied to the first force receiving portion 43 of the force sensor 201c shown in FIG. FIG. 21 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the negative Z-axis direction is applied to 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 X-axis direction (left direction in FIG. 18) acts on the first force receiving portion 43, the first force receiving portion 43 moves in that direction. Accordingly, since the first bending portion 45c receives a tensile force along the X-axis direction, the first bending portion 45c is elastically deformed so that its radius of curvature is increased. In FIG. 18, the first curved portion 45c in the initial state is shown by a broken line, and the first curved portion 45c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 18, by 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 state of lying more horizontally. 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 a horizontal state to a left-up state by an amount corresponding to the change in inclination. As a result, the separation distance between the electrodes constituting the first capacitive element C1 increases. The degree of the 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, since the first deformable support 61 and the first bending portion 45c are connected at the first detection portion A1, the first detection portion A1 is The separation distance between the electrodes was uniformly changed by the same amount as the displacement amount along the Z-axis direction. However, in the example shown in FIG. 18, since the first beam 261b is inclined upward to the left, particularly in the left region of the first beam 261b, the first detection site A1 exceeds the amount displaced upward, and the distance between the electrodes Separation distance is increased. In other words, the first deformation body side support body 261 is a cantilever structure, and the first deformation body side support body 261 is connected to the first bending portion 45c at a position different from the first detection site A1. The displacement in the Z-axis direction that occurs at the first detection site A1 is amplified.

  With such a configuration, when a force in the negative X-axis 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. However, the degree of the 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 curved portion 45 c is elastically deformed so as to reduce its radius of curvature because it receives a compressive force along the X-axis direction. In FIG. 19, the first curved portion 45c in the initial state is shown by a broken line, and the first curved portion 45c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 19, due to this elastic deformation, the tangent L1 of the portion of the first curved portion 45c to which the first connection body 261s is connected changes to a more upright state. In FIG. 19, the tangent line after the change is indicated by L1 (X +). Then, the first beam 261b of the first deformable support 261 changes from the horizontal state to the left-down state by an amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the first capacitor 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 is inclined downward to the left, particularly in the left region of the first beam 261b, the distance between the electrodes exceeds the amount of the first detection portion A1 displaced downward. The distance is reduced. In other words, the displacement in the Z-axis direction that occurs at the first detection site A1 is amplified by the cantilever structure as described above.

  With such a configuration, when a force in the positive direction of the X-axis is applied to 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 the 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 45 c is elastically deformed so as to move upward as a whole since the region on the X axis negative side connected to the first force receiving portion 43 is moved upward. However, since the end on the X axis positive side is fixed to the first fixing portion 41, it does not move. In FIG. 20, the first curved portion 45c in the initial state is shown by a broken line, and the first curved portion 45c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 20, due to this elastic deformation, the tangent L1 of the portion of the first curved portion 45c to which the first connection body 261s is connected changes to lie more horizontally. 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 a horizontal state to a left-up state by an amount corresponding to the change in inclination. As a result, the separation distance between the electrodes constituting the first capacitive element C1 increases. The degree of the 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 is inclined upward to the left, particularly in the left region of the first beam 261b, the distance between the electrodes exceeds the amount by which the first detection site A1 is displaced upward. The distance increases. In other words, the displacement in the Z-axis direction generated at the first detection site A1 is amplified by the cantilever beam 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 the 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 direction 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 45 c is elastically deformed so as to move downward as a whole since the region on the X axis negative side connected to the first force receiving portion 43 is moved downward. However, since the end on the X axis positive side is fixed to the first fixing portion 41, it does not move. In FIG. 21, the first curved portion 45c in the initial state is shown by a broken line, and the first curved portion 45c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 21, due to this elastic deformation, the tangent L1 of the portion of the first curved portion 45c to which the first connection body 261s is connected changes to a more upright state. In FIG. 21, the tangent line after the change is indicated by L1 (Z−). As understood from such a change in the inclination of the tangent L1, the first beam 261b of the first deformable support 261 changes from the horizontal state to the left downward state by an amount corresponding to the change in the inclination. Do. As a result, the separation distance between the electrodes constituting the first capacitor 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. 21) (the separation distance gradually decreases).

  In the example shown in FIG. 21, since the first beam 261b inclines downward to the left, the separation 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. Decreases. In other words, the displacement in the Z-axis direction generated at the first detection site A1 is amplified by the cantilever beam structure as described above.

  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 first capacitive element C1 of the force sensor 201c according to the present embodiment increases. The degree of the increase is larger than that of the first capacitive element C1 of the force sensor 1c according to the first embodiment.

2-2-2. Fluctuation of the capacitance value of the second capacitive element C2
Next, fluctuations in the capacitance value of the second capacitive element C2 will be described with reference to FIGS.

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

  As shown in FIG. 22, when a force in the negative X-axis 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 curved portion 46c receives a compressive force along the X-axis direction, so it elastically deforms so that its radius of curvature becomes smaller. In FIG. 22, the second curved portion 46c in the initial state is shown by a broken line, and the second curved portion 46c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 22, due to this elastic deformation, the tangent L2 of the portion of the second curved portion 46c to which the second connection body 262s is connected changes to a more upright state. In FIG. 22, the tangent after the change is indicated by L2 (X-). Then, the second beam 262b of the second deformable support 262 changes from the horizontal state to the downward sloping state by an amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the second capacitive element C2 is reduced. The degree of the decrease gradually increases from the X-axis negative side to the X-axis positive side (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 site A2 of the second bending portion 46c. (2) The separation distance between the electrodes is uniformly changed by the same amount as the amount of displacement of the detection portion A2 along the Z-axis direction. However, in the example shown in FIG. 22, since the second beam 262b is inclined downward to the right, particularly in the right region of the second beam 262b, the amount of the second detection site A2 exceeds the amount displaced downward, and between the electrodes. 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 site A2. The displacement in the Z-axis direction generated at the second detection site A2 is amplified.

  With such a configuration, when a force in the negative X-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. The degree of the 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, since the second curved portion 46c receives a tensile force along the X-axis direction, the second curved portion 46c elastically deforms so that the radius of curvature thereof becomes large. In FIG. 23, the second curved portion 46c in the initial state is shown by a broken line, and the second curved portion 46c in the elastically deformed state is shown by a solid line. As shown in FIG. 23, due to this elastic deformation, the tangent L2 of the portion of the second curved portion 46c to which the second connection body 262s is connected changes to lie more horizontally. The tangent after the change is indicated by L2 (X +). Then, the second beam 262b of the second deformable support 262 changes from the horizontal state to the upward state by an amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the second capacitive element C2 is increased. The degree of increase gradually increases from the X-axis negative side to the X-axis positive side (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 to the right, particularly 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 displacement in the Z-axis direction generated at the second detection site A2 is amplified by the cantilever structure as described above.

  With such a configuration, when a force in the positive X-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 decreases. However, the degree of the 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, since the end on the X axis positive side connected to the first force receiving portion 43 is moved upward, the second bending portion 46c is elastically deformed so as to move upward as a whole. However, since the end on the X axis negative side is fixed to the second fixing portion 42, it does not move. In FIG. 24, the second curved portion 46c in the initial state is shown by a broken line, and the second curved portion 46c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 24, due to this elastic deformation, the tangent L2 of the portion of the second curved portion 46c to which the second connection body 262s is connected changes to a more horizontal lying state. The tangent after the change is indicated by L2 (Z +). Then, the second beam 262b of the second deformable body side support 262 changes from a horizontal state to a right-up state by an amount corresponding to the change in inclination. As a result, the separation distance between the electrodes constituting the second capacitive element C2 is increased. The degree of increase gradually increases from the X-axis negative side to the X-axis positive side (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 to the right, particularly 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 displacement in the Z-axis direction generated at the second detection site A2 is amplified by the cantilever structure as described above.

  With such a configuration, when a force in the positive 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 decreases. However, the degree of the 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 direction 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 to move downward as a whole. However, since the end on the X axis negative side 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 a broken line, and the second curved portion 46c in a state of being elastically deformed is shown by a solid line. As shown in FIG. 25, due to this elastic deformation, the tangent L2 of the portion of the second curved portion 46c to which the second connection body 262s is connected changes to a more upright state. The tangent after the change is indicated by L2 (Z-). Then, the second beam 262b of the second deformable support 262 changes from the horizontal state to the downward sloping state by an amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the second capacitive element C2 is reduced. The degree of the decrease gradually increases from the X-axis negative side to the X-axis positive side (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, particularly 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 is reduced. In other words, the displacement in the Z-axis direction generated at the second detection site A2 is amplified by the cantilever beam structure as described above.

  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 the 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 electrostatic 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 with a portion where the Y coordinate is positive (see FIG. 16) and a portion where the Y coordinate is negative (see FIG. 17). For this reason, about the fluctuation | variation of the electrostatic capacitance value of 3rd capacitive element C3 and 4th capacitive element C4, based on description of §2-2-1 and §2-2-2, it analogizes as follows. 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 the second force receiving force of the third bending portion 47c and the fourth bending portion 48c. When the end connected to the portion 44 is moved in the Z-axis negative 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 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 positive direction of the Z-axis, the capacitance values of the capacitive elements C3 and C4 decrease.

  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 inclined as described above, so that the third capacitor element C3 and the fourth capacitor element are provided. 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 fluctuation of the capacitance value generated in each of the capacitive elements C1 to C4 by the force or the moment acting on the force receiving body 20 is as shown in FIG. As understood from the above description, the amount of fluctuation is larger than the amount of fluctuation in the force sensor 1c according to the first embodiment. In other words, the force sensor 201c according to the present embodiment is more sensitive 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 portions A1 to A4, they are supported by the beams 261b to 264b. The displacement generated in the displacement electrodes Em1 to Em4 is amplified. That is, when a certain amount of force or moment is applied, the displacement generated in the displacement electrodes Em1 to Em4 is the first in which the displacement electrodes Em1 to Em4 are supported at the detection portions A1 to A4 of the curved portions 45c to 48c. In the force sensor 1c according to the embodiment, the displacement is larger than the displacement generated in the displacement electrodes Em1 to Em4. For this reason, the sensitivity to the applied force or moment is high, and more accurate measurement can be performed.

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

  FIG. 26 is a schematic plan view of a force sensor 301 c according to the third embodiment. 27 is a cross-sectional view taken along line [27]-[27] of FIG. 26, and FIG. 28 is a cross-sectional view taken along line [28]-[28] of FIG. However, in FIG. 26, the illustration of the force receiving body 20 is omitted for easy viewing of the drawing.

As shown in FIGS. 26 to 28, the force sensor 301c includes force sensors 1c according to the first and second embodiments, in that each of the bending portions 45c to 48c is provided with two capacitive elements. Different from 201c. Specifically, as shown in FIGS. 26 and 27, on the lower surface of the first curved portion 45c, two capacitive elements C11 and C12 are provided along the circumferential direction of the deformable body 40 with the first detection portion A1 interposed therebetween. Is arranged. Similarly, on the lower surface of the second curved portion 46c, two capacitive elements C21 and C22 are disposed along the circumferential direction of the deformable body 40 with the second detection site A2 interposed therebetween.
Further, as shown in FIGS. 26 and 28, on the lower surface of the third curved portion 47c, two capacitive elements C31 and C32 are disposed along the circumferential direction of the deformable body 40 with the third detection site A3 interposed therebetween. Two capacitive elements C41 and C42 are disposed on the lower surface of the fourth curved portion 48c along the circumferential direction of the deformable body 40 with the fourth detection site 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, and the 3-2. The capacitive element C32, the 4-1 capacitive element C41, and the 4-2 capacitive element C42 are counterclockwise (counterclockwise) along the circumferential direction of the deformable body 40 when viewed from the positive direction of the Z axis (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 sites A1 to A4.

  The configurations of the capacitive elements C11 to C42 are the same as 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 a position facing the 1-1st displacement electrode Em11 supported by the first curved portion 45c and the 1-1th displacement electrode Em11. And the fixed first electrode Ef11. The first-first displacement electrode Em11 is supported on the lower surface of the first-first deformable body support 361a connected to the first curved portion 45c via the first-first displacement substrate Im11. The first fixed electrode Ef11 is supported on the first fixed body side support 371 fixed to the upper surface of the fixed body 10 via the first fixed substrate If1.

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

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

  As shown in FIG. 27, the 2-2 capacitance element C22 is arranged at a position facing the 2-2 displacement electrode Em22 supported by the second bending portion 46c and the 2-2 displacement electrode Em22. And the second fixed electrode Ef22. The 2-2 displacement electrode Em22 is supported on the lower surface of the 2-2 deformation side support 362b connected to the second bending portion 46c via the 2-2 displacement substrate Im22. Similarly to the 2-1st fixed electrode Ef21, the 2nd-2 fixed electrode Ef22 is supported on the second fixed body side support 372 fixed to the upper surface of the fixed body 10 via the second fixed substrate If2 There is. That is, the second fixed body side support 372 and the second fixed substrate If2 are components common to the 2-1 capacitance element C21 and the 2-2 capacitance element C22.

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

  As shown in FIG. 28, the third-second capacitive element C32 is disposed at a position facing the third-second displacement electrode Em32 supported by the third bending portion 47c and the third-second displacement electrode Em32. And the third and second fixed electrode Ef 32. The 3-2 displacement electrode Em32 is supported on the lower surface of the 3-2 deformable body side support 363b connected to the 3rd bending portion 47c via the 3-2 displacement substrate Im32. Similarly to the 3-1st fixed electrode Ef31, the 3rd-2 fixed electrode Ef32 is supported on the third fixed body side support 373 fixed to the upper surface of the fixed body 10 via the third fixed substrate If3 There is. That is, the third fixed body side support 373 and the third fixed substrate If3 are components common to the 3-1 capacitance element C31 and the 3-2 capacitance element C32.

  Further, as shown in FIG. 28, the fourth-first capacitor element C41 is arranged at a position facing the fourth-first displacement electrode Em41 supported by the fourth bending portion 48c and the fourth-first displacement electrode Em41. And the (4-1) th fixed electrode Ef41. The fourth-first displacement electrode Em41 is supported on the lower surface of the fourth-first deformable body side support body 364a connected to the fourth bending portion 48c via the fourth-first displacement substrate Im41. The 4-1st fixed electrode Ef 41 is supported on the third fixed body side support 373 fixed to the upper surface of the fixed body 10 via the fourth fixed substrate If 4.

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

  The first to second to fourth capacitive elements C11 to C24 have the same effective opposing areas of the displacement electrodes Em11 to Em24 and the fixed electrodes Ef11 to Ef24 that constitute each of the capacitive elements C11 to C24. The separation distances of are all equal.

<3-2. Action>
Next, FIG. 29 is a table showing fluctuations in capacitance values generated in the capacitive elements C11 to C24 when a force or moment is applied to the force sensor 301c of FIG. In this chart, “+” indicates that the capacitance value of the capacitive element increases, and “−” indicates that the capacitance value of the capacitive element decreases.

  When a force or moment is applied to the force sensor 301c according to the present embodiment, the bending portions 45c to 48c are elastically deformed as described with reference to FIGS. 3 to 9 according to the applied force or moment. Will occur. Due to this elastic deformation, the capacitance values of the capacitive elements C11 to C42 vary 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). Also, the 2-1st capacitive element C21 and the 2-2nd capacitive element C22 exhibit the same behavior as the second capacitive element C2 of the force sensor 1c according to the first embodiment (see the column of C2 in FIG. 14). The 3-1 capacitive element C31 and the 3-2 capacitive element C32 exhibit the same behavior as the third capacitive element C3 of the force sensor 1c according to the first embodiment (column C3 in FIG. 14). ), The 4-1th capacitive element C41 and the 4-2th 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 view of the chart shown in FIG. 29, the detection circuit 250 calculates the moments Mx, My, Mz and the force Fz applied to the force sensor 301c based on the following [Equation 2]. In each formula described in this specification, the symbols C11 to C24 indicate the fluctuation amounts of the capacitance values of the first to second to fourth capacitance elements C11 to C24, respectively. Also, the sign of the end of Mx, My, Mz and Fz distinguishes the force or moment measured using [Equation 2] and the force or moment measured using [Equation 3] described later Is to do.
[Formula 2]
Mx1 = −C11−C21 + C31 + C41
My1 = C11−C21−C31 + C41
Mz1 = -C11 + C21-C31 + C41
Fz1 =-(C11 + C21 + C31 + C41)
[Equation 2] proceeds in the clockwise direction of the deformable body 40 as viewed from the positive direction of the Z-axis (as viewed from above) of the two capacitive elements disposed in the respective curved portions 45c to 48c. This is an equation for measuring the applied force or moment using the capacitive element on the side.

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

<3-3. Fault diagnosis>
The force sensor 301c according to the present embodiment can perform failure diagnosis by using a 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 and separation distance between the electrodes. Furthermore, four capacitive elements C11, C21, C31, C41 used in [Formula 2] and four capacitive elements C12, C22, C32, C42 used in [Formula 3] have first to fourth curved portions. It arrange | positions symmetrically with respect to detection site | part A1-A4 prescribed | regulated to 45c-48c. From these facts, in the force sensor 301c functioning normally, the force or moment measured based on [Equation 2] matches the force or moment measured based on [Equation 3] become. That is, in the force sensor 301c functioning normally, the following relationship of [Expression 4] is established.
[Formula 4]
Mx1 = Mx2
My1 = My2
Mz1 = Mz2
Fz1 = Fz2

From this, failure diagnosis of the force sensor 301 c can be performed as follows. That is, the detection circuit 250 measures the force or the moment acting on the force sensor 301 c based on both of [Expression 2] and [Expression 3], and the value (Mx1, My1) measured based on [Expression 2]. , Mz1, Fz1) and the values (Mx2, My2, Mz2, Fz2) measured based on [Equation 3] are all the absolute values of the difference between the predetermined threshold (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 [Expression 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 C1, the detection circuit 250 determines that the force sensor 301c is not functioning normally (fails).
That is, when the following [Expression 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 according to the present embodiment as described above, one (four in total) of the capacitive elements arranged two by one in the first to fourth curved portions 45c to 48c is used. Based on the difference between the value of the measured force or moment and the value of the force or moment measured using each of the remaining ones (four in total), the single force sensor 301c causes the failure. It can be diagnosed. This improves the safety and reliability of the force sensor 301c.

  In the above description, in order to perform a fault 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] However, the present invention 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 [Equation 2] or “Equation 3”. Failure diagnosis may be performed by comparing the specific force or moment (for example, Mx1 or Mx2). The specific diagnostic method is the same as that described above. That is, when performing failure diagnosis by paying attention to the moment Mx around the X axis, if a specific force or moment obtained based on Mx1 + Mx2 which is the sum of [Expression 2] and “Expression 3” is M12, It is evaluated whether Mx12-Mx1 | or | Mx12-Mx2 | exceeds a predetermined threshold value. This is also true when performing fault diagnosis based on other forces or moments.

  Furthermore, in the above description, in order to measure force or moment, one of [Expression 2] and “Expression 3” is used. However, the sum of [Expression 2] and “Expression 3” (example) Mx1 + Mx2) may be used.

<<< §4. Force sensor according to the fourth embodiment of the present invention >>>
<4-1. Configuration>
Next, a force sensor 401c according to a fourth embodiment of the present invention will be described.

  FIG. 30 is a schematic plan view of a force sensor 401c according to a fourth embodiment of the present invention, FIG. 31 is a cross-sectional view taken along line [31]-[31] of FIG. It is a 30 [32]-[32] line sectional view. However, in FIG. 30, the illustration of the force receiving body 20 is omitted for easy viewing of the drawing.

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

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

  As shown in FIGS. 31 and 32, each of the low elasticity portions 445L to 448L is configured to have a smaller thickness in the Z-axis direction (vertical direction) than each of the high elasticity portions 445H to 448H. Of course, the present invention is not limited to such an embodiment. In other embodiments, the low elastic portions 445L to 448L are configured to have a smaller radial width than the high elastic 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 bending portions 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 portions A1 to A4 interposed therebetween. Specifically, the 1-1 capacitive element C11 is disposed on the lower surface of the first low elasticity portion 445L, and the 1-2 capacitive element C12 is disposed on the lower surface of the first high elasticity portion 445H. . The 2-1st capacitance element C21 is disposed on the lower surface of the second low elasticity portion 446L, and the 2-2nd capacitance element C22 is disposed on the lower surface of the second high elasticity portion 446H. The 3-1st capacitance element C31 is disposed on the lower surface of the third low elasticity portion 447L, and the 3-2nd capacitance element C32 is disposed on the lower surface of the third high elasticity portion 447H. The 4-1st capacitive element C41 is disposed on the lower surface of the fourth low elasticity portion 448L, and the 4-2nd capacitive element C42 is disposed on the lower surface of the fourth high elasticity portion 448H. Since the other configuration is the same as that of the third embodiment, the corresponding components in the drawings are denoted by the same reference numerals and the detailed description thereof will be omitted.

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

  When force or moment is applied to 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 applied force or moment. Elastic deformation occurs. Accordingly, the capacitance values of the capacitive elements C11 to C42 vary due to this elastic deformation. This variation is substantially the same as the capacitance values 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 each of 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. For this reason, as shown in FIG. 33, the capacitance elements C11, C21, C31, and C41 arranged in the low elasticity portions 444L to 448L have relatively large capacitance value fluctuations, and the high elasticity portions 444H to 448H A relatively small variation in capacitance value occurs in the disposed capacitive elements C12, C22, C32, and C42.

Moments Mx, My, Mz and force Fz acting on the force sensor 401c are calculated using the following [Expression 7] based on the chart shown in FIG. The sign of the end of Mx, My, Mz and Fz is to distinguish the force or moment calculated using [Equation 7] from the force or moment calculated using [Equation 8] described later belongs to.
[Formula 7]
Mx1 = -C11-C21 + C31 + C41
My1 = C11−C21−C31 + C41
Mz1 = −C11 + C21−C31 + C41
Fz1 =-(C11 + C21 + C31 + C41)
[Equation 7] shows four capacitive elements C11 and C21 of the two capacitive elements disposed in the first to fourth curved portions 445c to 448c, which are disposed in the low elasticity portions 445L to 448L. , C31 and C41 are equations for measuring the applied force or moment.

Alternatively, the moments Mx, My, Mz and force Fz acting on the force sensor 401c are also calculated using the following [Equation 8].
[Formula 8]
Mx2 = -C12-C22 + C32 + C42
My2 = C12−C22−C32 + C42
Mz2 = −C12 + C22−C32 + C42
Fz2 =-(C12 + C22 + C32 + C42)
[Equation 8] shows 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 elasticity portions 445H to 448H. , C32 and C42 are equations for measuring the applied 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 in the capacitance values of the four capacitive elements C11, C21, C31, and C41 arranged in the low elasticity portions 445L to 448L. Measure the applied force or moment using [Equation 7]. This enables highly sensitive measurement with excellent S / N. Of course, you may measure the force or moment which acted using [Formula 8].

<4-3. Fault diagnosis>
The force sensor 401c according to the present embodiment can perform a more advanced fault diagnosis than the force sensor 301c according to the third embodiment in the following points. That is, the force sensor 301 c according to the third embodiment can detect a failure when the electrode is broken or when foreign matter is mixed between the electrodes. On the other hand, when the force sensor 301c does not function normally due to metal fatigue occurring in the deformable body 40, the force or moment (Mx1, My1, Mz1, Fz1) measured based on [Expression 2] ) And the force or moment (Mx2, My2, Mz2, Fz2) measured based on [Equation 3] may not occur. In this case, the force sensor 301c cannot perform failure diagnosis properly. When metal fatigue occurs in the deformable body 40, a crack or the like occurs in the elastic body constituting the deformable body 40, and the deformable body 40 may be eventually broken. For this reason, if a force sensor capable of detecting a failure due to metal fatigue can be provided, the 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, even when the force sensor 401c does not function properly due to metal fatigue in the deformable body 40, failure diagnosis can be properly performed. Hereinafter, 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 repetitive load acts on the deformable body 40 of the force sensor 401c, metal fatigue occurs in the deformable body 40. When the metal fatigue is accumulated, the strength of the deformable body 40 is reduced, and eventually the deformable body 40 is broken. In general, when metal fatigue accumulates in a metal material, the metal material softens. For this reason, the spring constants of the first to fourth curved portions 445c to 448c decrease. In other words, the deformation body 40 has an increased sensitivity to acting force or moment as compared with the initial state due to 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 in a state (initial state) where no metal fatigue occurs in the force sensor 401c shown in FIG. FIG. 35 is a graph showing the relationship between the electrical signal indicating the moment Mx that is output, and FIG. 35 shows the X-axis acting on the force sensor 401c in a state where metal fatigue occurs in the force sensor 401c of FIG. It is a graph which shows the relationship between the magnitude | size of the surrounding moment Mx, and the electrical signal which shows the moment Mx output from the said force sensor 401c. In FIG. 34 and FIG. 35, a symbol “T1” indicates a first electrical signal which is an electrical signal based on the variation of the capacitance value of the four capacitive elements arranged in the low elasticity portions 445L to 448L. "T2" has shown the 2nd electric signal which is an electric signal based on the variation of the electrostatic capacitance value of four capacity elements arranged in high elasticity parts 445H-448H. Further, the suffixes of “T1” and “T2” are an electrical signal in the initial state (added with a) and an electrical signal in the state where metal fatigue is accumulated (added b at the end). It is for distinction.

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) indicating the first electrical signal T1a in the initial state is 2.0, and the slope (straight line) of the graph (straight line) indicating the second electrical 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 electric signal T1b in a state where the metal fatigue is accumulated is 3.0, and the state where the metal fatigue is accumulated. The slope (sensitivity) of the graph (straight line) indicating the second electric signal T2b is 0.6.

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

  It should be noted here that the four capacitive elements C11, C21, C31, C41 arranged in the low elasticity portions 445L to 448L and the four capacitance elements C12, C22, C32, C42 arranged in the high elasticity portions 445H to 448H. And the change in sensitivity is different. Such a difference is that the distortion generated in the low elasticity portions 445L to 448L is larger than the distortion generated in the high elasticity portions 445H to 448H, and therefore, relatively much metal fatigue is accumulated in the low elasticity portions 445L to 448L. It is due. It is as follows when such change of sensitivity is quantitatively evaluated paying attention to the ratio of the 1st electric signal T1 and the 2nd electric signal T2. That is, in the initial state, the ratio (T1a / T2a) between the first electric signal T1a and the second electric signal T2a is 4.0. However, when the metal fatigue accumulates, the first electric signal T1b and the second electric signal T2a. The ratio to the signal T2b (T1b / T2b) rose to 5.0.

Based on the mechanism by which metal fatigue occurs, this ratio T1 / T2 gradually increases from 4.0 to 5.0 as repetitive load (force or moment) acts.
The force sensor 401c according to the present embodiment not only measures the applied force or moment, but also performs failure diagnosis of the force sensor 1c by focusing on the change of the ratio T1 / T2. In the failure diagnosis, the detection circuit 450 calculates the ratio (T1 / T2) of the first electric signal T1 to the second electric signal T2 at the measurement time point, and the ratio of the first electric signal T1a to the second electric signal T2a in the initial state. This is performed by evaluating whether the difference between (T1a / T2a) and (T1 / T2) − (T1a / T2a) exceeds a predetermined value (threshold C). That is, when the following [Equation 10] is established, the detection circuit 450 determines that the force sensor 401c is functioning normally. In the present embodiment, the ratio (T1a / T2a) of the first electric signal T1a to the second electric signal T2a in the initial state and the threshold C are stored in advance in the detection circuit 450.
[Formula 10]
(T1 / T2) − (T1a / T2a) ≦ C (C: threshold)

On the other hand, when the following [Formula 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 around the X axis is applied to the force sensor 401c has been described as an example. However, when other moments My, Mz or force Fz are applied, the same applies. Failure diagnosis can be performed. Specifically, for the force or moment of interest, let the equation described in [Equation 7] be the first electrical signal T1, and the equation described in [Equation 8] be the second electrical 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 the same as the graph shown in FIG. 34 in the initial state, and metal fatigue accumulates in the deformable body 40. It is similar to the graph shown in FIG. However, when the force Fz in the Z-axis direction is applied, the “moment” on the horizontal axis is read as “force”. Therefore, regardless of which force or moment acts, the failure diagnosis of the force sensor 401c is properly 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. 5. Force sensor according to the fifth embodiment of the present invention >>>
Next, a force sensor 501c according to a fifth embodiment of the present invention will be described.

  FIG. 36 is a schematic plan view showing a basic structure 501 of a force sensor 501c according to the fifth embodiment of the present invention, and FIG. 37 is a cross-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 structure 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. And, as shown in FIGS. 36 and 37, when viewed in the Z-axis direction, the fixed body 510 is disposed inside the deformable body 40, and the force receiving body 520 is disposed outside the deformable body 40. .
The fixed body 510, the force receiving body 520, and the deformable body 40 are all concentric with each other because their central axes overlap the Z axis. 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 portions 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.

  With 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 connection members 531 to 534 is also different from the force sensor 1c according to the first embodiment. ing. That is, as shown in FIGS. 36 and 37, on the positive X axis, the first connection member 531 is the outer surface (the side surface facing the X axis positive direction) of the fixed body 510 and the inner surface of the deformable body 40. (The side facing the negative direction of the X axis) is connected. On the other hand, on the negative X axis, the second connection member 532 is the outer surface of the fixed body 510 (the side surface facing the X axis negative direction) and the inner surface of the deformable body 40 (the side surface facing the X axis positive direction) And connected. Furthermore, as shown in FIG. 36, on the positive Y axis, the inner side surface of the force receiving body 520 (side surface facing in the negative direction of the Y axis) and the outer surface of the deformable body 40 (side surface facing in the positive direction of the Y axis) Are connected by the third connection member 533, and on the negative Y axis, the inner side surface of the force receiving body 520 (side surface facing in the positive Y axis direction) and the outer side surface of the deformable body 40 (in the negative Y axis direction). A fourth connecting member 534 is connected to the facing side). Other configurations are the same as those of the basic structure 1 of the force sensor 1c according to the first embodiment. For this reason, in the drawings, corresponding components are denoted by the same reference numerals, and detailed description thereof is omitted.

  Although not shown, the force sensor 501c is configured by arranging 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. In FIG. 37, a member for arranging the fixed electrode is not shown. However, the fixed electrode may be appropriately arranged at a portion where the force sensor 501c is attached, or an additional member is added to the fixed body 510. The member may be fixed and the fixed electrode may be disposed 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 member 510 is connected to the first member and the force receiving member 520 is connected to the second member, the force sensor 501c is disposed in a limited space in a manner that does not interfere with other members. be able to.

  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, and thus the detailed description thereof is omitted here.

  As a modification of the basic structure 501 as described above, the following basic structure 502 is also conceivable.

  FIG. 38 is a schematic plan view showing a modification of the basic structure 501 of FIG. 36, and FIG. 39 is a cross-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 deformation portion 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. The other configuration is the same as that of the basic structure 501 described above, so in the drawings, the corresponding components are denoted by the same reference numerals, and the detailed description thereof is 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 the displacement in the radial direction generated on the inner side surface (side surface facing the origin O) by the elastic deformation of the deformable body 40 caused by the applied force or moment, and uses the force or moment. It is supposed to measure. In this case, as shown in FIG. 40, displacement electrodes Em1 to Em4 are provided at four portions overlapping the V axis and the W axis among the inner side surfaces of the deformable body 540, and each of the outer side surfaces of the fixed body 510 is provided. What is necessary is just to provide the fixed electrodes Ef1 to Ef4 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 this modification detects a force or a moment acting based on the four capacitive elements C1 to C4.

  The specific principle for measuring the force or moment applied using the force sensor 502c as described above is described in, for example, Japanese Patent No. 4948630 in the name of the present applicant. 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 connection members 531 to 534, and the fixed body 510 are concentrically arranged along the XY plane. For this reason, each component of the basic structures 501 and 502 can be integrally formed by cutting. Such processing can provide force sensors 501c and 502c without hysteresis.

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

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

  The deformable body 640 according to the present variation has a rectangular shape as a whole. Here, as shown in FIG. 41, a square deformation body 640 will be described as an example. The deformable body 640 includes a first fixing portion 641 positioned on the positive X axis, a second fixing portion 642 positioned on the negative X axis, and a first force receiving portion 643 positioned on the positive Y axis. And a second force receiving portion 644 positioned on the negative Y axis. Each of the fixed portions 641 and 642 and each of the force receiving portions 643 and 644 is an area where the fixed body 10 and the force receiving body 20 are connected in the deformable body 640, and has different characteristics from other areas of the deformable body 640. It is 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 other regions of the deformable body 640. However, for convenience of explanation, in the drawing, the other regions of the deformable body 640 are shown in different colors.

  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 receiving portion. The second deforming portion 646 located between the force portion 643 and the second fixing portion 642 (second quadrant of the XY plane), and between the second fixing portion 642 and the second force receiving portion 644 (first 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 (fourth quadrant in the XY plane). There is. Both ends of each of the deformation 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 and 44 is reliably transmitted to the respective deformation portions 645 to 648, and thereby elastic deformation according to the applied force or moment is caused to each deformation portion 645. It is supposed to occur at ~ 648.

  As shown in FIG. 41, the first to fourth deformable portions 645 to 648 are all configured in a straight line when viewed from the Z-axis direction. Further, since the distances from the origin O to the fixed portions 641 and 642 and the force receiving portions 643 and 644 are all equal, the deformable portions 645 to 648 are arranged so as to constitute one side of the square.

  Furthermore, as shown in FIGS. 42A and 42B, each of the deformable portions 645 to 648 of the deformable body 640 includes curved portions 645c to 648c that are curved so as to bulge in the negative Z-axis direction. ing. In the illustrated example, each of the deforming portions 645 to 648 forms curved portions 645c to 648c as a whole. For this reason, in FIG. 42 (a) and FIG.42 (b), the code | symbol of a deformation | transformation part and the code | symbol of a bending part are written together. As illustrated, the lowermost portion (in the negative direction of the Z-axis) of the first curved portion 645c is present on the positive V-axis. The shape of the first bending portion 645c from the first fixing portion 641 to the lowermost portion is the shape from the first force receiving portion 643 to the lowermost portion. It is the same. In other words, the first curved portion 645 c has a symmetrical shape with respect to the positive V axis in the longitudinal direction of the deformable body 640.

  The same applies to the remaining three curved portions 646c, 647c, 648c. That is, the lowermost portion of the second curved portion 646c is present on the positive W axis, and has a symmetrical shape with respect to the positive W axis. The third bending portion 647c has a lowermost portion on the negative V-axis and has a symmetrical shape with respect to the negative V-axis. The fourth bending portion 648c has a lowermost 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), the deformable body 640 has curved portions at the lowest positions of the first to fourth curved portions 645c to 648c, that is, as viewed from the Z-axis direction. Detection portions A1 to A4 for detecting elastic deformation generated in the curved portions 645c to 648c are defined at lower portions of portions where the portions 645c to 648c overlap with the V axis and the W axis. In FIG. 41, detection portions A1 to A4 are illustrated as being provided on the upper surface (surface on the near side) of deformable body 640, but in fact on the lower surface (surface on the far side) of deformable body 640. Provided (see FIG. 42).

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

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

Claims (2)

A force sensor for a robot that detects at least one of a force in each axial direction and a moment around each axis in an XYZ three-dimensional coordinate system,
A first annular member disposed in an XYZ three-dimensional coordinate system;
A second annular member surrounding the first annular member and moving relative to the first annular member by the action of a force or moment;
Detecting means for detecting a relative displacement between the first annular member and the second annular member, and the detecting means comprises:
A deformable body that is disposed between the first annular member and the second annular member, and generates elastic deformation by the action of a force or a moment;
A capacitive element for detecting the elastic deformation of the deformable body;
A detection circuit that outputs an electric signal based on a variation amount of capacitance of the capacitive element;
The first annular member and the second annular member are arranged concentrically with each other so that their central axes overlap the Z-axis,
An end surface on the Z-axis positive side of the second annular member extends in the Z-axis positive direction from an end surface on the Z-axis positive side of the first annular member, and the Z-axis negative side of the first annular member. The end surface of the second annular member extends to the Z-axis negative side from the end surface on the Z-axis negative side of the second annular member ,
The end surface on the Z-axis negative side of the second annular member is located on the same plane as the end surface on the Z-axis negative side of the deformable body, and the end surface on the Z-axis positive side of the first annular member is , Located on the same plane as the end surface on the positive side of the Z-axis of the deformable body,
Force sensor characterized by The relative displacement between the first annular member and the second annular member is:
2. The force sensor according to claim 1, wherein the force sensor is a relative displacement around a Z-axis between the first annular member and the second annular member.

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