JP6923988B2 - 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 rotating axis as an electric signal.

For example, Patent Document 1 describes a force sensor having a function of outputting a force acting along a predetermined axial direction and a moment acting around a predetermined rotation axis as an electric signal, and is a force of an industrial robot. Widely used for control. In recent years, it has also been adopted for life support robots. As the market for force sensors has expanded, there has been a growing demand for lower prices and higher performance of force sensors.

By the way, as a force sensor, a capacitance type force sensor that detects a force or a moment based on a fluctuation amount of a capacitance value of a capacitance element, or a force based on a fluctuation amount of an electric resistance value of a strain gauge. Or a strain gauge type force sensor that detects moments is used. Of these, the strain gauge type force sensor has a complicated structure of the strain generating body (elastic body), and a step of attaching a strain gauge to the strain generating body is required in the manufacturing process thereof. As described above, it is difficult to reduce the price of the strain gauge type force sensor because the manufacturing cost is high.

On the other hand, the capacitance type force sensor can measure the force or moment acted by one set of parallel flat plates (capacitive elements), which simplifies the structure of the strain-causing body including the capacitive element. be able to. That is, the capacitance type force sensor has an advantage that the price can be easily reduced because the manufacturing cost is relatively low. Therefore, if the structure of the strain-causing body including the capacitive element is further simplified, the price of the capacitive type force sensor can be further reduced.

Japanese Unexamined Patent Publication No. 2004-354049

The present invention has been devised in view of the above circumstances. That is, an object of the present invention is to provide a capacitance type force sensor which is cheaper 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 the XYZ three-dimensional coordinate system.
An annular plasmodium that is arranged so as to surround the origin O when viewed from the Z-axis direction and that elastically deforms due to the action of a force or moment.
A detection circuit that outputs an electric signal indicating an acting force or moment based on the elastic deformation generated in the deformed body is provided.
The deformed body has two fixed portions fixed to the XYZ three-dimensional coordinate system and two receiving forces that are alternately positioned with the fixed portions in the circumferential direction of the deformed body and are subjected to the action of a force or a moment. It has a portion and four deformed portions positioned between the fixed portion and the receiving portion that are adjacent to each other in the circumferential direction of the deformed body.
Each deformed portion has a curved portion that bulges in the Z-axis direction.
The detection circuit outputs the electric signal based on the elastic deformation generated in the curved portion.

According to the present invention, a simple deformed body having a curved portion bulging in the Z-axis direction can cause a displacement corresponding to the applied force or moment in the Z-axis direction at the detection site. Therefore, 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, the displacement corresponding to the applied force or moment occurs in the direction orthogonal to the Z axis, so that the support extending in the Z axis direction is provided on the upper surface of the fixed body. After that, the other electrode (fixed electrode) had to be installed with respect to this support, and the structure was somewhat complicated. In view of such conventional electrode arrangement examples, the effects of the present invention can be better understood. According to the present invention, by adopting the simple structure as described above, it is possible to provide a capacitance type force sensor which is cheaper than the conventional one. In particular, in a force sensor having a plurality of capacitive elements, a fixed electrode (an electrode facing a displacement electrode arranged in a curved portion) of each pair of electrodes can be configured by using a common substrate. Further, the fixed electrode can be configured as a common electrode corresponding to a plurality of capacitive elements.

Such a force sensor is a fixed body fixed to the XYZ three-dimensional coordinate system and
Further provided with a receiving body that moves relative to the fixed portion by the action of a force or a moment.
The fixed portion of the deformed body is connected to the fixed body and is connected to the fixed body.
The receiving portion of the deformed body may be configured to be connected to the receiving body.

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

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

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

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

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

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

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

Each curved portion of the deformed body bulges in the negative direction of the Z axis.
The detection circuit has a total of four displacement electrodes arranged one by one in each curved portion, and fixed electrodes arranged opposite to these displacement electrodes and fixed to the fixed portion.
Each displacement electrode and the fixed electrode constitute four sets of capacitive elements.
The detection circuit may output an electric signal indicating an acting force or moment based on the amount of fluctuation in the capacitance value of the four sets of capacitive elements.

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

When the V-axis and the W-axis that pass through the origin O and form 45 ° with respect to the X-axis and the Y-axis are defined on the XY plane, the four sets of capacitive elements are such that the deformed body is viewed from the Z-axis direction. One may be arranged at each of the four parts intersecting 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 electrostatic elements of each capacitive element have high symmetry, especially when a deformed body having a symmetrical shape with respect to the X-axis and the Y-axis is applied. The capacitance value fluctuates. Therefore, the acting force or moment can be measured extremely easily based on the fluctuation amount of the capacitance value.

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

If the displacement electrode is directly attached to the curved portion, the displacement electrode will be warped due to the influence of the deformation of the curved portion. However, if the above configuration is adopted, the displacement electrode can be used. Since the warp is not generated, the elastic deformation generated in the curved portion can be efficiently converted into the fluctuation of the capacitance value of the capacitive element.

In the above force sensor, each curved portion of the deformed body has a detection portion defined at a portion located on the most negative side of the Z axis.
The deformed body-side support has a beam arranged 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. It has a connecting body that connects to the curved portion at a position different from that of the above.
Each of the displacement electrodes may be configured to be supported by the beam of the corresponding deformed body side support.

In this case, since the beam is connected to the curved portion at a position different from the detection portion, 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 generated in the displacement electrode in such a force sensor is applied to the displacement electrode in the force sensor in which the displacement electrode is supported at the detection site of the curved portion. Greater than the displacement that occurs. Therefore, the sensitivity to the applied force or moment is high, and more accurate measurement can be performed.

Alternatively, with the following configuration, it is possible to provide a force sensor capable of performing failure diagnosis with a single force sensor. That is, each curved portion of the deformed body bulges in the negative direction of the Z axis.
The detection circuit has a total of eight displacement electrodes arranged on each curved portion, and fixed electrodes arranged opposite to these displacement electrodes and fixed to the fixed portion.
The displacement electrode and the fixed electrode form eight sets of capacitive elements.
The detection circuit
First electricity indicating the acting force or moment based on the amount of fluctuation in the capacitance value of a total of four capacitive elements selected from two capacitive elements arranged on each curved portion of the deformed body. A signal is output, and a second electric signal indicating the acting force or moment is output based on the amount of fluctuation in the capacitance value of a total of four capacitive elements in which each of the remaining ones is selected.
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 has come to determine whether or not the force sensor is functioning normally based on the difference between the first electric signal and the second electric signal. It's okay to have it. In this case, it is possible to provide a force sensor capable of detecting the acting force or moment and performing failure diagnosis.

Alternatively, each curved portion bulges in the negative direction of the Z axis, and the first curved portion having the first spring constant and the second curved portion having a second spring constant different from the first spring constant are deformed. It is composed of being connected in the circumferential direction of the body.
The detection circuit includes a total of eight displacement electrodes arranged one by one in the first curved portion and one in the second curved portion, and fixed electrodes arranged opposite to these 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
Based on the amount of fluctuation in the capacitance value of the four capacitive elements arranged in the first curved portion, a first electric signal indicating the acting force or moment is output and arranged in the second curved portion. Based on the amount of fluctuation in the capacitance value of the four capacitive elements, a second electric signal indicating the acting force or moment is output.
Based on the change in the ratio of 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 the 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 the difference between the ratio of the first electric signal and the second electric signal and the reference ratio.

In this case, it is possible to provide a force sensor capable of detecting the acting force or moment and diagnosing a failure due to metal fatigue developed in the deformed body. A more detailed failure diagnosis principle will be described later.

In the force sensor having the above eight capacitive elements, when the V-axis and 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 capacitance elements are arranged symmetrically with respect to each axis of X, Y, V, and W, the amount of fluctuation of the capacitance value generated in each capacitance element due to the applied force or moment is also symmetrical. .. Therefore, it is easy to measure the acting 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 the XYZ three-dimensional coordinate system.
A circular fixed body fixed to the XYZ three-dimensional coordinate system,
An annular deformed body that surrounds the fixed body and is connected to the fixed body to cause elastic deformation by the action of a force or moment.
An annular receiving body that surrounds the deformed body, is connected to the deformed 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 moment acting on the receiving body based on the elastic deformation generated in the deformed body is provided.
The fixed body, the deformed body and the receiving body are arranged so as to be concentric with each other.
The Z coordinate value of the end face on the positive side of the Z axis of the receiving body is larger than the Z coordinate value of the end face on the positive side of the Z axis of the deformed body.
The Z coordinate value of the end face on the negative side of the Z axis of the fixed body is smaller than the Z coordinate value of the end face on the negative side of the Z axis of the deformed body.
The deformed body is adjacent to two fixed portions connected to the fixed body and two receiving portions connected to the receiving body and alternately positioned with the fixed portion in the circumferential direction of the deformed body. It has four deformed portions positioned between the fixed portion and the 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 capacitance type force sensor that is cheaper than the conventional one. Further, when such a force sensor is attached to a joint portion of the robot, the force sensor does not interfere with other members.

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

In this case, with a simple configuration, the elastic body can be displaced in the Z-axis direction by the acting force or moment, so that the pair of electrodes constituting the capacitive element can be easily arranged.

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

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

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

In this case, the acting force or moment can be effectively transmitted to the deformed 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. 2 is a cross-sectional view taken along the line [3]-[3] of FIG. It is a schematic plan view for demonstrating the elastic deformation which occurs in each curved part when the moment + Mx around the X-axis acts on the basic structure of FIG. It is a schematic cross-sectional view of FIG. 5 (a) is a cross-sectional view taken along the line [5a]-[5a] of FIG. 4, and FIG. 5 (b) is a cross-sectional view taken along the line [5b]-[5b] of FIG. It is a schematic plan view for demonstrating the elastic deformation which occurs in each curved part when the moment + My about the positive direction of the Y axis acts on the basic structure of FIG. FIG. 6 is a schematic cross-sectional view of FIG. 7 (a) is a cross-sectional view taken along the line [7a]-[7a] of FIG. 6, and FIG. 7 (b) is a cross-sectional view taken along the line [7b]-[7b] of FIG. It is a schematic plan view for demonstrating the elastic deformation which occurs in each curved part when the moment + Mz about the Z-axis forward acts on the basic structure of FIG. It is a schematic cross-sectional view of FIG. 9 (a) is a cross-sectional view taken along the line [9a]-[9a] of FIG. 8, and FIG. 9 (b) is a cross-sectional view taken along the line [9b]-[9b] of FIG. It is a schematic plan view for demonstrating the elastic deformation which occurs in each curved part when the force + Fz in the positive direction of the Z axis acts on the basic structure of FIG. It is a schematic cross-sectional view of FIG. 11 (a) is a cross-sectional view taken along the line [11a]-[11a] of FIG. 10, and FIG. 11 (b) is a cross-sectional view taken along the line [11b]-[11b] of FIG. It is a schematic plan view which shows the force sensor using the basic structure of FIG. 12 is a cross-sectional view taken along the line [13]-[13] of FIG. It is a figure which shows the fluctuation of the capacitance value which occurs in each capacitance element when a force or a moment acts on the force sensor of FIG. It is a schematic plan view of the force sensor according to the 2nd Embodiment of this invention. FIG. 15 is a cross-sectional view taken along the line [16]-[16] of FIG. FIG. 15 is a cross-sectional view taken along the line [17]-[17] of FIG. FIG. 5 is a schematic cross-sectional view showing a first capacitive element C1 when a force in the negative direction of the X-axis acts on the first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a first capacitive element C1 when a force in the positive direction of the X-axis acts on the first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a first capacitive element C1 when a force in the positive direction of the Z axis is applied to a first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a first capacitive element C1 when a force in the negative direction of the Z axis is applied to a first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the negative direction of the X-axis acts on the first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the positive direction of the X-axis acts on a first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the positive direction of the Z axis is applied to a first receiving portion of the force sensor shown in FIG. FIG. 15 is a partial schematic cross-sectional view showing a second capacitive element C2 when a force in the negative direction of the Z axis is applied to a first receiving portion of the force sensor shown in FIG. It is a schematic plan view of the force sensor according to the 3rd Embodiment of this invention. FIG. 6 is a cross-sectional view taken along the line [27]-[27] of FIG. 26. FIG. 26 is a cross-sectional view taken along the line [28]-[28] of FIG. It is a figure which shows the fluctuation of the capacitance value which occurs in each capacitance element when a force or a moment acts on the force sensor of FIG. 26. It is a schematic plan view of the force sensor according to the 4th Embodiment of this invention. FIG. 30 is a cross-sectional view taken along the line [31]-[31] of FIG. FIG. 30 is a cross-sectional view taken along the line [32]-[32] of FIG. It is a figure which shows the fluctuation of the capacitance value which occurs in each capacitance element when a force or a moment acts on the force sensor of FIG. In a state where metal fatigue does not occur in the force sensor shown in FIG. 30 (initial state), the magnitude of the moment Mx around the X axis acting on the force sensor, the electric signal output from the force sensor, and the electric signal. It is a graph which shows the relationship of. In the graph showing the relationship between the magnitude of the moment Mx around the X axis acting on the force sensor and the electric signal output from the force sensor in the state where the force sensor of FIG. 30 is metal fatigued. be. It is a schematic plan view which shows the basic structure of the force sensor according to the 5th Embodiment of this invention. FIG. 6 is a cross-sectional view taken along the line [37]-[37] of FIG. It is a schematic plan view which shows the modification of the basic structure of FIG. 36. FIG. 38 is a cross-sectional view taken along the line [39]-[39] of FIG. 38. It is a schematic plan view which shows an example of the force sense sensor using the basic structure of FIG. 38. It is a schematic plan view which shows the deformed body of a rectangle. FIG. 41 is a schematic cross-sectional view of FIG. 41. 42 (a) is a cross-sectional view taken along the line [42a]-[42a] of FIG. 41, and FIG. 42 (b) is a cross-sectional view taken along the line [42b]-[42b] of FIG. 41.

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

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

As shown in FIGS. 1 to 3, the basic structure 1 has a disk-shaped fixed body 10 having an upper surface parallel to the XY plane and a disk that moves relative to the fixed body 10 by the action of a force or a moment. It includes a shaped receiving body 20 and an annular deformed body 40 that is connected to the fixed body 10 and the receiving body 20 and elastically deforms due to the relative movement of the receiving body 20 with respect to the fixed body 10. The fixed body 10, the receiving body 20, and the deformed body 40 are concentric with each other and have the same outer diameter. In addition, in FIG. 2, in order to clearly show the deformed body 40, the drawing of the receiving body 20 is omitted.

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

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

As shown in FIGS. 1 to 3, the deformed body 40 further includes a first deformed portion 45 located between the first fixed portion 41 and the first receiving portion 43 (the first quadrant of the XY plane). A second deformed portion 46 located between the first receiving portion 43 and the second fixed portion 42 (the second quadrant of the XY plane), and between the second fixed portion 42 and the second receiving portion 44 (XY). A third deformed portion 47 located in the third quadrant of the plane) and a fourth deformed portion 48 located between the second receiving portion 44 and the first fixed portion 41 (fourth quadrant of the XY plane). Have. Both ends of the deformed portions 45 to 48 are integrally connected to the adjacent fixing portions 41 and 42 and the receiving portions 43 and 44, respectively. With such a structure, the force or moment acting on the receiving portions 43 and 44 is surely transmitted to each deforming portion 45 to 48, whereby the elastic deformation corresponding to the acting force or moment is transmitted to each deforming portion 45. It is supposed to occur in ~ 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 deformed body 40, and the receiving body 20 and the deformed body 40. It further has a third connecting member 33 and a fourth connecting member 34. The first connecting member 31 connects the lower surface of the first fixing portion 41 (lower surface in FIG. 3) and the upper surface of the fixed body 10 to each other, and the second connecting member 32 is fixed to the lower surface of the second fixing portion 42. The upper surface of the body 10 is connected to each other. The third connecting member 33 connects the upper surface of the first receiving portion 43 (upper surface in FIG. 3) and the lower surface of the receiving body 20 to each other, and the fourth connecting member 34 is the second receiving portion 44. The upper surface and the lower surface of the receiving body 20 are connected to each other. Each of the connecting members 31 to 34 has a rigidity that can be regarded as a substantially rigid body. Therefore, the force or moment acting on the receiving body 20 effectively causes elastic deformation in each of the deformed portions 45 to 48.

Further, as shown in FIGS. 1 and 3, each of the deformed portions 45 to 48 of the deformed body 40 has curved portions 45c to 48c curved so as to bulge in the negative direction of the Z axis. In the illustrated example, each of the deformed portions 45 to 48 forms a curved portion 45c to 48c as a whole. Therefore, in FIGS. 1 to 3, the reference numerals 45 to 48 of the deformed portion and the reference numerals 45c to 48c of the curved portion are shown together. This also applies to other embodiments described later. In the deformed body 40 of the present embodiment, as shown in FIG. 3, the portion located at the lowermost position (Z-axis negative direction) of the first curved portion 45c is the circumferential direction from the first fixed portion 41 to the deformed body 40. It exists at a position where it orbits counterclockwise by 45 ° along. The shape of the first curved portion 45c from the first fixed portion 41 to the lowermost portion is the same as the shape from the first receiving portion 43 to the lowermost portion. It is the same. In other words, the first curved portion 45c has a shape symmetrical with respect to the portion located at the lowermost position in the circumferential direction of the deformed body 40.

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

After all, as shown in FIG. 2, when the V-axis and the W-axis passing through the origin O and forming 45 ° with respect to the X-axis and the Y-axis are defined on the XY plane, the first curved portion 45c is a positive V-axis. The second curved portion 46c is symmetric with respect to the positive W axis, the third curved portion 47c is symmetric with respect to the negative V axis, and the fourth curved portion 48c is negative W. It is symmetric with respect to the axis.

As shown in FIGS. 2 and 3, in the basic structure 1, the curved portions 45c to 48c are located at the lowermost portion of the curved portions 45c to 48c, that is, the curved portions 45c to 48c are V-axis and W-axis when viewed from the Z-axis direction. Detection sites A1 to A4 for detecting elastic deformation occurring in each of the curved portions 45c to 48c are defined at the portions overlapping with the above. In FIG. 2, the detection sites A1 to A4 are shown to be provided on the upper surface (front surface) of the deformed body 40, but in reality, they are on the lower surface (back side surface) of the deformed body 40. It is provided (see FIG. 3).

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

(1-2-1. When the moment Mx around the X axis acts on the basic structure 1)
FIG. 4 is a schematic plan view for explaining the elastic deformation that occurs in each of the curved portions 45c to 48c when the moment + Mx around the X-axis is applied to the basic structure 1 of FIG. Further, FIG. 5 is a schematic cross-sectional view of FIG. 5 (a) is a cross-sectional view taken along the line [5a]-[5a] of FIG. 4, and FIG. 5 (b) is a cross-sectional view taken along the line [5b]-[5b] of FIG. In FIGS. 4 and 5, the thick black arrows indicate the acting force or moment, and the thick white arrows indicate the directions of displacement of the detection sites A1 to A4. This also applies to other figures.

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

At this time, as shown in FIGS. 5 (a) and 5 (b), the following elastic deformations occur in the first to fourth curved portions 45c to 48c. That is, since the first receiving portion 43 moves upward by the force acting on the first receiving portion 43 in the positive direction of the Z axis, the first receiving portion of the first curved portion 45c and the second curved portion 46c The end connected to 43 is moved upward. As a result, as shown in FIG. 5A, the first curved portion 45c and the second curved portion 46c are generally upward except for the ends connected to the first and second fixed portions 41 and 42. Move to. That is, the first detection site A1 and the second detection site A2 both move upward. On the other hand, since the second receiving portion 44 moves downward due to the force acting on the second receiving portion 44 in the negative direction of the Z axis, the second 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 generally downward except for the ends connected to the first and second fixed portions 41 and 42. Move to. That is, the third detection site A3 and the fourth detection site A4 both move downward.

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

After all, when the moment + Mx around the X-axis forward acts on the receiving body 20 of the basic structure 1, the separation distance between the first and second detection sites A1 and A2 and the upper surface of the fixed body 10 (see FIG. 3) is increased. , Both increase, and the distance between the third and fourth detection sites A3, A4 and the upper surface of the fixed body 10 decreases together.

Although not shown, when the moment-Mx around the negative axis of the X axis acts on the receiving body 20 of the basic structure 1, the moving direction of each of the detection sites A1 to A4 is opposite to the above-described direction. That is, due to the action of the moment −Mx around the negative axis of the X axis, the separation distance between the first and second detection sites A1 and A2 and the upper surface of the fixed body 10 (see FIG. 2) is reduced, and the third and fourth detection sites are reduced. The separation distance between the detection sites A3 and A4 and the upper surface of the fixed body 10 increases together.

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

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

At this time, as shown in FIGS. 7 (a) and 7 (b), the following elastic deformations occur in the first to fourth curved portions 45c to 48c. 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 (the right side in FIG. 7A) of the first receiving portion 43, the first curved portion. Of the 45c, the end connected to the first receiving portion 43 is moved downward. As a result, as shown in FIG. 7A, the first curved portion 45c moves downward as a whole except for the end portion connected to the first fixed portion 41. That is, the first detection site A1 moves downward. On the other hand, since the region on the negative side of the X-axis moves upward due to the force in the positive direction of the Z-axis acting on the negative side of the X-axis of the first receiving portion 43 (the left side in FIG. 7A), the second curved portion Of the 46c, the end connected to the first receiving portion 43 moves upward. As a result, as shown in FIG. 7A, the second curved portion 46c moves upward as a whole except for the end portion connected to the second fixed portion 42. That is, the second detection site A2 moves upward.

Further, as shown in FIG. 7B, the region on the negative side of the X-axis is caused by the force in the positive direction of the Z-axis acting on the negative side of the X-axis of the second receiving portion 44 (the right side in FIG. 7B). In order to move upward, the end portion of the third curved portion 47c connected to the second 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 portion 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 region on the positive side of the X-axis is caused by the force in the negative direction of the Z-axis acting on the positive side of the X-axis of the second receiving portion 44 (the left side in FIG. 7B). In order to move downward, the end portion of the fourth curved portion 48c connected to the second receiving portion 44 is moved downward. As a result, as shown in FIG. 7B, the fourth curved portion 48c moves downward as a whole except for the end portion connected to the first fixed portion 41. That is, the fourth detection site A4 moves downward.

After all, when the moment + My in the normal direction of the Y axis acts on the receiving body 20 of the basic structure 1, the separation distance between the first and fourth detection sites A1 and A4 and the upper surface of the fixed body 10 (see FIG. 3) is increased. , 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 together.

Although not shown, when the moment-My around the negative axis of the Y axis acts on the receiving body 20 of the basic structure 1, the moving direction of each of the detection sites A1 to A4 is opposite to the above-described direction. That is, the distance between the first and fourth detection sites A1 and A4 and the upper surface of the fixed body 10 (see FIG. 3) is increased by the action of the moment-My around the negative Y-axis, and the second and third detection sites A1 and A4 are separated from each other. The distance between the detection sites A2 and A3 and the upper surface of the fixed body 10 is reduced.

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

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

At this time, as shown in FIGS. 9 (a) and 9 (b), the following elastic deformations occur in the first to fourth curved portions 45c to 48c. That is, since the first receiving portion 43 moves in the negative direction of the X axis due to the force acting on the first receiving portion 43 in the negative direction of the X axis, the first curved portion 45c is pulled along the X axis direction. Force acts. As a result, the first curved portion 45c is elastically deformed so that the radius of curvature becomes large while maintaining the Z coordinate values of both ends thereof. That is, the first detection site A1 moves upward. On the other hand, as the first receiving portion 43 moves in the negative direction of the X-axis, a compressive force acts on the second curved portion 46c along the X-axis direction. As a result, the second curved portion 46c is elastically deformed so that the radius of curvature becomes smaller while maintaining the Z coordinate values of both ends thereof. That is, the second detection site A2 moves downward.

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

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

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

(1-2-4. When a force Fz in the Z direction acts on the basic structure 1)
Next, FIG. 10 is a schematic plan view for explaining the elastic deformation that occurs in each of the curved portions 45c to 48c when a force + Fz in the positive direction of the Z axis acts on the basic structure 1 of FIG. Further, FIG. 11 is a schematic cross-sectional view of FIG. 11 (a) is a cross-sectional view taken along the line [11a]-[11a] of FIG. 10, and FIG. 11 (b) is a cross-sectional view taken along the line [11b]-[11b] of 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 via the receiving body 20 (see FIGS. 1 and 3), the first and first deformed bodies 40 2 A force in the positive direction of the Z axis acts on the receiving portions 43 and 44.

At this time, as shown in FIGS. 11A and 11B, the following elastic deformations occur in the first to fourth curved portions 45c to 48c. That is, since each of the receiving portions 43 and 44 moves upward by the force acting on the first and second receiving portions 43 and 44 in the positive direction of the Z axis, the first and second of the curved portions 45c to 48c Each end connected to the receiving portions 43 and 44 is moved upward. As a result, as shown in FIGS. 11 (a) and 11 (b), the detection sites A1 to A4 move upward.

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

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

<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.

FIG. 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 the line [13]-[13] of FIG. In FIG. 13, in order to clearly show the deformed body 40, the drawing of the receiving body 20 is omitted.

As shown in FIGS. 12 and 13, the force sensor 1c is configured by arranging one capacitive element C1 to C4 at each of the detection sites A1 to A4 of the basic structure 1 of FIG. Specifically, as shown in FIG. 13, the force sensor 1c is arranged on the fixed body 10 so as to face the first displacement electrode Em1 arranged at the first detection portion A1 and the first displacement electrode Em1. It has a first fixed electrode Ef1 that does not move relative to each other. These electrodes Em1 and Ef1 constitute the first capacitive element C1. Further, as shown in FIG. 13, the force sensor 1c is arranged to face the second displacement electrode Em2 arranged at the second detection portion A2 and the second displacement electrode Em2, and is relative to the fixed body 10. It has a second fixed electrode Ef2 that does not move. These electrodes Em2 and Ef2 constitute a second capacitance element C2.

Although not shown, the force sensor 1c is arranged so as to face the third displacement electrode Em3 arranged at the third detection portion A3 and the third displacement electrode Em3, and does not move relative to the fixed body 10. 3 Fixed electrode Ef3, 4th displacement electrode Em4 arranged at the 4th detection site A4, 4th fixed electrode Ef4 arranged facing the 4th displacement electrode Em4 and not moving relative to the fixed body 10. have. The electrode Em3 and the electrode Ef3 constitute the third capacitance element C3, and the electrode Em4 and the electrode Ef4 constitute the fourth capacitance element C4.

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

Further, as shown in FIGS. 12 and 13, the force sensor 1c is an electric signal indicating a force or moment acting on the receiving body 20 based on the elastic deformation generated in each of the curved portions 45c to 48c of the deformed body 40. It has a detection circuit 50 that outputs. In FIGS. 12 and 13, the wiring for electrically connecting the capacitance elements C1 to C4 and the detection circuit 50 is not shown.

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

(1-3-2. Fluctuation of capacitance value of each capacitive element when moment Mx around the X axis acts on the force sensor 1c)
Next, FIG. 14 is a chart showing fluctuations in capacitance values that occur in the capacitance elements C1 to C4 when a force or moment acts on the force sensor 1c of FIG. 12.

First, when the moment + Mx around the X-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 §1-2-1. , The separation distance between the electrodes constituting the first capacitance element C1 and the second capacitance element C2 both increases. Therefore, the capacitance values of the first capacitance element C1 and the second capacitance element C2 both decrease. On the other hand, the separation distance between the electrodes constituting the third capacitance element C3 and the fourth capacitance element C4 both decreases. Therefore, the capacitance values of the third capacitance element C3 and the fourth capacitance element C4 both increase. The fluctuations in the capacitance values of the capacitance elements C1 to C4 are collectively shown in the column of "Mx" in FIG. In this chart, "+" indicates that the capacitance value increases, and "-" indicates that the capacitance value decreases. When the moment-Mx around the negative axis of the X axis acts on the force sensor 1c, the fluctuation of the capacitance value of each of the capacitance elements C1 to C4 is opposite to the above-mentioned fluctuation (in the column of Mx in FIG. 14). All the symbols shown are reversed).

(1-3-3. Fluctuation of capacitance value of each capacitive element when moment My around Y-axis acts on force sensor 1c)
Next, when the moment + My around the Y-axis positively 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 §1-2-2. In addition, the separation distance between the electrodes constituting the first capacitance element C1 and the fourth capacitance element C4 is both reduced. Therefore, the capacitance values of the first capacitance element C1 and the fourth capacitance element C4 both increase. On the other hand, the separation distance between the electrodes constituting the second capacitance element C2 and the third capacitance element C3 both increases. Therefore, the capacitance values of the second capacitance element C2 and the third capacitance element C3 both decrease. The fluctuations in the capacitance values of the capacitance elements C1 to C4 are collectively shown in the column of "My" in FIG. When the moment-My around the negative Y-axis acts on the force sensor 1c, the fluctuation of the capacitance value of each of the capacitance elements C1 to C4 is opposite to the above-mentioned fluctuation (in the column of My in FIG. 14). All the symbols shown are reversed).

(1-3-4. Fluctuation of capacitance value of each capacitive element when moment Mz around Z axis acts on force sensor 1c)
Next, when the moment + Mz around the Z-axis positively 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 §1-2-3. In addition, the separation distance between the electrodes constituting the first capacitance element C1 and the third capacitance element C3 both increases. Therefore, the capacitance values of the first capacitance element C1 and the third capacitance element C3 both decrease. On the other hand, the separation distance between the electrodes constituting the second capacitance element C2 and the fourth capacitance element C4 both decreases. Therefore, the capacitance values of the second capacitance element C2 and the fourth capacitance element C4 both increase. The fluctuations in the capacitance values of the capacitance elements C1 to C4 are collectively shown in the column of "Mz" in FIG. When a moment −Mz around the negative axis of the Z axis acts on the force sensor 1c, the fluctuation of the capacitance value of each of the capacitance elements C1 to C4 is opposite to the above-mentioned fluctuation (in the column of Mz in FIG. 14). All the symbols shown are reversed).

(1-3-5. Fluctuation of capacitance value of each capacitive element when force Fz in the Z-axis direction acts on the 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 is understood from the behavior of each of the detection sites A1 to A4 described in §1-2-4. In addition, the separation distances between the electrodes constituting the capacitive elements C1 to C4 are all increased. Therefore, the capacitance values of the capacitive elements C1 to C4 are all reduced. The fluctuations in the capacitance values of the capacitance elements C1 to C4 are collectively shown in the column of "Fz" in FIG. When a 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 capacitance elements C1 to C4 is opposite to the above-mentioned fluctuation (in the Fz column of FIG. 14). All the symbols shown are reversed).

(1-3-6. Calculation method of applied force or moment)
In view of the fluctuation of the capacitance value of the capacitance elements C1 to C4 as described above, the detection circuit 50 uses the following [Equation 1] to generate the moments Mx, My, Mz and the force Fz acting on the force sensor 1c. calculate. In [Equation 1], C1 to C4 indicate the amount of fluctuation in the capacitance value of the first to fourth capacitance 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)
When the force or moment acting on the force sensor 1c is in the negative direction, -Mx, -My, -Mz and -Fz may be used instead of Mx, My, Mz and Fz on the left side.

According to the force sensor 1c according to the present embodiment as described above, the force or moment acted on the detection sites A1 to A4 by the simple deformed body 40 having the curved portions 45c to 48c bulging in the Z-axis direction. The displacement corresponding to can be generated in the Z-axis direction. Therefore, one of the pair of electrodes constituting the capacitive elements C1 to C4 may be arranged on the detection sites A1 to A4, and the other may be arranged on, for example, the upper surface of the fixed body 10, so that the capacitive elements C1 to C4 are formed. Is easy. Therefore, according to the present embodiment, by adopting such a simple structure, it is possible to provide a 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 sets of capacitive elements C1 to C4 are in the Z-axis direction. One is arranged at each of four parts overlapping the V-axis and the W-axis when viewed from the viewpoint. Therefore, since the capacitance elements C1 to C4 are arranged symmetrically with respect to the X-axis and the Y-axis, the capacitance values of the capacitance elements C1 to C4 fluctuate with high symmetry. Therefore, the acting force or moment can be measured extremely easily based on the amount of fluctuation in the capacitance value of the capacitance elements C1 to C4.

In the above description, the four capacitive elements C1 to C4 have separate fixed substrates If1 to If4 and individual fixed electrodes Ef1 to Ef4. However, in other embodiments, 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 the four capacitive elements. With such a configuration, the force or moment can be measured in the same manner as the force sensor 1c described above. It should be noted that these configurations can also be applied to each embodiment described later.

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

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

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

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

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

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

Further, the second deformed 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 deformed body side support 262 is arranged so as to overlap the second detection portion A2 of the second curved portion 46c when viewed from the Z-axis direction. A cantilever structure having a second connecting body 262s for connecting the end portion of the second beam 262b on the second fixed portion 42 side (left side in FIG. 16) to the second curved portion 46c. There is. Since the second connecting body 262s extends parallel to the Z axis, the connection position between the second connecting body 262s and the second curved portion 46c is closer to the second fixed portion 42 than the second detection portion A2. Is. The second displacement electrode Em2 is supported on the lower surface of the second beam 262b of the cantilever structure via a displacement substrate.

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

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

With the above configuration, the connecting bodies 261s to 264s are connected to the curved portions 45c to 48c at a portion different from the detection portions A1 to A4, but the first to fourth displacement electrodes are viewed from the Z-axis direction. Em1 to Em4 are arranged so as to overlap the corresponding detection sites A1 to A4.

In the examples shown in FIGS. 15 to 25, as described above, each of the deformed body side supports 261 to 264 is configured as a cantilever structure, but other embodiments (not shown). ), The tips of the beams 261b to 264b may be configured as a double-sided beam structure in which the tips thereof are connected to the fixed body 10 by a flexible material. The flexible material may have a linear shape or a curved shape, and may be connected to the fixed body 10 in the vicinity of a portion where the Z-axis and the upper surface of the fixed body 10 intersect, for example. According to such a configuration, the tilting behavior of the beams 261b to 264b caused by the action of the force or moment acting on the force sensor 201c can be stabilized from the external vibration.

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

FIG. 18 is a schematic cross-sectional view showing a first capacitive element C1 when a force in the negative direction of the X axis acts on the first receiving portion 43 of the force sensor shown in FIG. 15, and FIG. 19 is a schematic cross-sectional view. 15 is a partial schematic cross-sectional view showing a first capacitive element C1 when a force in the positive direction of the X-axis acts on the first receiving portion 43 of the force sensor 201c shown in 15. Further, FIG. 20 is a partial schematic cross-sectional view showing the first capacitive element C1 when a force in the positive direction of the Z axis is applied to the first receiving portion 43 of the force sensor 201c shown in FIG. 21 is a partial schematic cross-sectional view showing a first capacitive element C1 when a force in the negative direction of the Z axis is applied to the first receiving portion 43 of the force sensor 201c shown in FIG.

As shown in FIG. 18, when a force in the negative direction of the X axis (leftward in FIG. 18) acts on the first receiving unit 43, the first receiving unit 43 moves in that direction. Along with this, the first curved portion 45c receives a tensile force along the X-axis direction, so that the first curved portion 45c is elastically deformed so that its radius of curvature becomes large. 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 the elastically deformed state is shown by a solid line. As shown in FIG. 18, due to this elastic deformation, the tangent line L1 of the portion of the first curved portion 45c to which the first connecting body 261s is connected changes to a more horizontal lying state. In FIG. 18, the tangent after the change is indicated by L1 (X−). Then, the first beam 261b of the first deformed body side support 261 changes from the horizontal state to the left rising state by the amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the first capacitance element C1 increases. The degree of the increase gradually increases from the positive side of the X-axis toward the negative side of the X-axis (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 deformed body side support 61 and the first curved portion 45c are connected at the first detection portion A1, the first detection portion A1 is connected. The separation distance between the electrodes changed uniformly by the same amount as the amount displaced along the Z-axis direction. However, in the example shown in FIG. 18, since the first beam 261b inclines upward to the left, the distance between the electrodes exceeds the amount in which the first detection portion A1 is displaced upward, especially in the left region of the first beam 261b. The separation distance of is increased. In other words, the first deformed body side support 261 is a cantilever structure, and the first deformed body side support 261 is connected to the first curved portion 45c at a position different from the first detection portion A1. , The displacement in the Z-axis direction generated at the first detection portion A1 will be amplified.

With such a configuration, when a force in the negative direction of the X axis acts on the first receiving unit 43, the capacitance value of the first capacitance 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 capacitance element C1 of the force sensor 1c according to the first embodiment.

Next, as shown in FIG. 19, when a force in the positive direction of the X axis (right direction in FIG. 19) acts on the first receiving unit 43, the first receiving unit 43 moves in that direction. Along with this, the first curved portion 45c receives a compressive force along the X-axis direction, so that the first curved portion 45c is elastically deformed so that its radius of curvature becomes smaller. 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 the elastically deformed state is shown by a solid line. As shown in FIG. 19, due to this elastic deformation, the tangent line L1 of the portion of the first curved portion 45c to which the first connecting body 261s is connected changes to a state in which it stands more vertically. In FIG. 19, the changed tangent is indicated by L1 (X +). Then, the first beam 261b of the first deformed body side support 261 changes from the horizontal state to the left downward state by the amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the first capacitance element C1 is reduced. The degree of decrease gradually increases from the positive side of the X-axis toward the negative side of the X-axis (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, the distance between the electrodes exceeds the amount by which the first detection portion A1 is displaced downward, especially in the left region of the first beam 261b. The distance is reduced. In other words, the cantilever structure as described above amplifies the displacement in the Z-axis direction that occurs in the first detection portion A1.

With such a configuration, when a force in the positive direction of the X-axis acts on the first receiving unit 43, the capacitance value of the first capacitance 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 capacitance 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 in FIG. 20) acts on the first receiving portion 43, the first receiving portion 43 moves in that direction. Along with this, the first curved portion 45c is elastically deformed so as to move upward as a whole because the region on the negative side of the X axis connected to the first receiving portion 43 is moved upward. However, since the end on the positive side of the X-axis 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 the elastically deformed state is shown by a solid line. As shown in FIG. 20, due to this elastic deformation, the tangent line L1 of the portion of the first curved portion 45c to which the first connecting body 261s is connected changes to a more horizontal lying state. In FIG. 20, the tangent line after the change is indicated by L1 (Z +). Then, the first beam 261b of the first deformed body side support 261 changes from the horizontal state to the left rising state by the amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the first capacitance element C1 increases. The degree of the increase gradually increases from the positive side of the X-axis toward the negative side of the X-axis (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, the distance between the electrodes exceeds the amount by which the first detection portion A1 is displaced upward, especially in the left region of the first beam 261b. The distance increases. In other words, the cantilever structure as described above amplifies the displacement in the Z-axis direction that occurs in the first detection portion A1.

With such a configuration, when a force in the Z-axis positive direction acts on the first receiving unit 43, the capacitance value of the first capacitance 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 capacitance element C1 of the force sensor 1c according to the first embodiment.

Next, as shown in FIG. 21, when a force in the negative direction of the Z axis (downward in FIG. 21) acts on the first receiving portion 43, the first receiving portion 43 moves in that direction. Along with this, the first curved portion 45c is elastically deformed so as to move downward as a whole because the region on the negative side of the X axis connected to the first receiving portion 43 is moved downward. However, since the end on the positive side of the X-axis 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 the elastically deformed state is shown by a solid line. As shown in FIG. 21, due to this elastic deformation, the tangent line L1 of the portion of the first curved portion 45c to which the first connecting body 261s is connected changes to a state in which it stands more vertically. In FIG. 21, the tangent line after the change is indicated by L1 (Z−). As can be understood from such a change in the inclination of the tangent line L1, the first beam 261b of the first deformed body side support 261 changes from the horizontal state to the downward-sloping state by the amount corresponding to the change in the inclination. do. As a result, the separation distance between the electrodes constituting the first capacitance element C1 is reduced. The degree of decrease gradually increases from the positive side of the X-axis toward the negative side of the X-axis (from the right side to the left side in FIG. 21) (the separation distance gradually decreases).

In the example shown in FIG. 21, since the first beam 261b is inclined downward to the left, the separation distance between the electrodes exceeds the amount by which the first detection portion A1 is displaced downward, especially in the left end region of the first beam 261b. Decreases. In other words, the cantilever structure as described above amplifies the displacement in the Z-axis direction that occurs in the first detection portion A1.

With such a configuration, when a force in the negative direction of the Z axis acts on the first receiving unit 43, the capacitance value of the first capacitance 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 capacitance element C1 of the force sensor 1c according to the first embodiment.

(2-2-2. Fluctuation of capacitance value of second capacitance element C2)
Next, the fluctuation of the capacitance value of the second capacitance element C2 will be described with reference to FIGS. 22 to 25.

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

As shown in FIG. 22, when a force in the negative direction of the X axis (leftward in FIG. 22) acts on the first receiving portion 43, the first 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 that the second curved portion 46c is elastically deformed 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 the elastically deformed state is shown by a solid line. As shown in FIG. 22, due to this elastic deformation, the tangent line L2 of the portion of the second curved portion 46c to which the second connecting body 262s is connected changes to a state in which it stands more vertically. In FIG. 22, the tangent line after the change is indicated by L2 (X−). Then, the second beam 262b of the second deformed body side support 262 changes from the horizontal state to the downward-sloping state by the amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the second capacitance element C2 is reduced. The degree of decrease gradually increases from the negative side of the X-axis toward the positive side of the X-axis (from the left side to the right side in FIG. 22) (the separation distance gradually decreases).

In the force sensor 1c according to the first embodiment described above, the second deformed body side support 62 is connected to the second curved portion 46c at the second detection portion A2 of the second curved portion 46c. 2 The separation distance between the electrodes changes uniformly by the same amount that the detection portion A2 is displaced along the Z-axis direction. However, in the example shown in FIG. 22, since the second beam 262b inclines downward to the right, the second detection portion A2 exceeds the amount displaced downward, especially in the right region of the second beam 262b, and is between the electrodes. The separation distance is reduced. In other words, the second deformed body side support 262 is a cantilever structure, and the second deformed body side support 262 is connected to the second curved portion 46c at a position different from the second detection portion A2. , The displacement in the Z-axis direction generated at the second detection portion A2 will be amplified.

With such a configuration, when a force in the negative direction of the X-axis acts on the first receiving unit 43, the capacitance value of the second capacitance 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 capacitance element C2 of the force sensor 1c according to the first embodiment.

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

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

With such a configuration, when a force in the positive direction of the X-axis acts on the first receiving unit 43, the capacitance value of the second capacitance 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 capacitance 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 in FIG. 24) acts on the first receiving portion 43, the first receiving portion 43 moves in that direction. Along with this, the second curved portion 46c is elastically deformed so as to move upward as a whole because the end portion on the positive side of the X axis connected to the first receiving portion 43 is moved upward. However, since the end on the negative side of the X-axis is fixed to the second fixing portion 42, it does not move. In FIG. 24, the second 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. 24, due to this elastic deformation, the tangent line L2 of the portion of the second curved portion 46c to which the second connecting 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 deformed body side support 262 changes from the horizontal state to the upward right state by the amount corresponding to the change in the inclination. As a result, the separation distance between the electrodes constituting the second capacitance element C2 increases. The degree of the increase gradually increases from the negative side of the X-axis toward the positive side of the X-axis (from the left side to the right side in FIG. 24) (the separation distance gradually increases).

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

With such a configuration, when a force in the Z-axis positive direction acts on the first receiving unit 43, the capacitance value of the second capacitance 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 capacitance element C2 of the force sensor 1c according to the first embodiment.

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

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

With such a configuration, when a force in the negative direction of the Z axis acts on the first receiving unit 43, the capacitance value of the second capacitance 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 capacitance element C2 of the force sensor 1c according to the first embodiment.

(2-2-3. Fluctuations in capacitance values of the third capacitance element C3 and the fourth capacitance element C4)
The force sensor 201c according to the present embodiment has a symmetrical structure between a portion where the Y coordinate is positive (see FIG. 16) and a portion where the Y coordinate is negative (see FIG. 17). Therefore, the fluctuations in the capacitance values of the third capacitance element C3 and the fourth capacitance element C4 are analogically as follows based on the explanations of §2-2-1 and §2-2-2. Can be understood.

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

When the third curved portion 47c and / or the fourth curved portion 48c is elastically deformed, the third and / or the fourth beams 263b and 264b are inclined as described above, so that the third capacitance element C3 and the fourth capacitance element The variation in the capacitance value of C4 is larger than that of the third capacitance element C3 and the fourth capacitance 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 capacitance elements C1 to C4 due to the force or moment acting on the receiving body 20 is as shown in FIG. As can be understood from the above description, the fluctuation amount is larger than the fluctuation amount in the force sensor 1c according to the first embodiment. In other words, the force sensor 201c according to the present embodiment has higher sensitivity than the force sensor 1c according to the first embodiment.

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

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

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

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

In the illustrated example, 1-1 capacitance element C11, 1-2 capacitance element C12, 2-1 capacitance element C21, 2-2 capacitance element C22, 3-1 capacitance element C31, 3-2. The capacitive element C32, the 4-1st capacitive element C41, and the 4-2nd capacitive element C42 are counterclockwise (counterclockwise) along the circumferential direction of the deformed body 40 when viewed from the Z-axis positive direction (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 portions A1 to A4.

The configurations of the capacitive elements C11 to C42 are the same as those of the capacitive elements C1 to C4 adopted in the force sensor 1c according to the first embodiment. That is, as shown in FIG. 27, the 1-1 capacitance element C11 is arranged at a position facing the 1-1 displacement electrode Em11 supported by the first curved portion 45c and the 1-1 displacement electrode Em11. It is composed of the first 1-1 fixed electrode Ef11 and the above. The 1-1 displacement electrode Em11 is supported on the lower surface of the 1-1 deformed body side support 361a connected to the first curved portion 45c via the 1-1 displacement substrate Im11. The 1-1 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 1-2 capacitance element C12 is arranged at a position facing the 1-2 displacement electrode Em12 supported by the first curved portion 45c and the 1-2 displacement electrode Em12. It is composed of the first and second fixed electrodes Ef12 and the above. The 1-2 displacement electrode Em12 is supported on the lower surface of the 1-2 deformed body side support 361b connected to the first curved portion 45c via the 1-2 displacement substrate Im12. Like the 1-1 fixed electrode Ef11, the 1-2 fixed electrode Ef12 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. There is. That is, the first fixed body side support 371 and the first fixed substrate If1 are components common to the 1-1 capacitance element C11 and the 1-2 capacitance element C12.

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

Further, as shown in FIG. 27, the 2nd-2nd capacitive element C22 is arranged at a position facing the 2nd-2nd displacement electrode Em22 supported by the 2nd curved portion 46c and the 2nd-2nd displacement electrode Em22. It is composed of the 2nd and 2nd fixed electrodes Ef22. The 2-2 displacement electrode Em22 is supported on the lower surface of the 2-2 deformed body side support 362b connected to the 2nd curved portion 46c via the 2-2 displacement substrate Im22. Like the 2-1 fixed electrode Ef21, the 2-2 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 capacitive element C21 and the 2-2 capacitive element C22.

As shown in FIG. 28, the 3-1 capacitance element C31 is arranged at a position facing the 3-1 displacement electrode Em31 supported by the third curved portion 47c and the 3-1 displacement electrode Em31. It is composed of a 3-1 fixed electrode Ef31. The 3-1 displacement electrode Em31 is supported on the lower surface of the 3-1 deformed body side support 363a connected to the third curved portion 47c via the 3-1 displacement substrate Im31. The 3-1 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.

Further, as shown in FIG. 28, the 3rd to 2nd capacitance element C32 is arranged at a position facing the 3rd-2nd displacement electrode Em32 supported by the 3rd curved portion 47c and the 3rd-2nd displacement electrode Em32. It is composed of the 3rd and 2nd fixed electrodes Ef32. The 3rd-2nd displacement electrode Em32 is supported on the lower surface of the 3rd-2nd deformed body side support 363b connected to the 3rd curved portion 47c via the 3rd-2nd displacement substrate Im32. Like the 3-1 fixed electrode Ef31, the 3-2 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 4-1 capacitive element C41 is arranged at a position facing the 4-1 displacement electrode Em41 supported by the fourth curved portion 48c and the 4-1 displacement electrode Em41. It is composed of the 4-1 fixed electrode Ef41 and the above. The 4-1 displacement electrode Em41 is supported on the lower surface of the 4-1 deformed body side support 364a connected to the fourth curved portion 48c via the 4-1 displacement substrate Im41. The 4-1 fixed electrode Ef41 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 If4.

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

In the 1st to 2nd-4th capacitive elements C11 to C24, the effective facing areas of the displacement electrodes Em11 to Em24 and the fixed electrodes Ef11 to Ef24 constituting the respective capacitive elements C11 to C24 are all the same, and the distance between the electrodes is the same. The separation distances of the above are all equal.

<3-2. Action ＞
Next, FIG. 29 is a chart showing fluctuations in capacitance values that occur in the capacitance elements C11 to C24 when a force or moment acts on the force sensor 301c of FIG. 26. 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 acts on the force sensor 301c according to the present embodiment, the curved portions 45c to 48c are elastically deformed as described with reference to FIGS. 3 to 9 according to the applied force or moment. Occurs. Due to this elastic deformation, the capacitance values of the capacitive elements C11 to C42 fluctuate as shown in FIG. 29. That is, the 1-1 capacitance element C11 and the 1-2 capacitance element C12 behave in the same manner as the first capacitance element C1 of the force sensor 1c according to the first embodiment (see the row of C1 in FIG. 14). reference). Further, the 2-1 capacitive element C21 and the 2-2 capacitive element C22 behave in the same manner as the second capacitive element C2 of the force sensor 1c according to the first embodiment (see the row of C2 in FIG. 14). (See), the 3-1 capacitance element C31 and the 3-2 capacitance element C32 show the same behavior as the third capacitance element C3 of the force sensor 1c according to the first embodiment (row of C3 in FIG. 14). The 4-1st capacitive element C41 and the 4-2nd capacitive element C42 behave in the same manner as the fourth capacitive element C4 of the force sensor 1c according to the first embodiment (see 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 acting on the force sensor 301c based on the following [Equation 2]. In each of the formulas described in the present specification, the symbols C11 to C24 indicate the amount of variation in the capacitance value of the first to second to fourth capacitive elements C11 to C24, respectively. Further, the sign at the end of Mx, My, Mz and Fz distinguishes between the force or moment measured using [Equation 2] and the force or moment measured using [Equation 3] described later. It is for doing.
[Equation 2]
Mx1 = -C11-C21 + C31 + C41
My1 = C11-C21-C31 + C41
Mz1 = -C11 + C21-C31 + C41
Fz1 =-(C11 + C21 + C31 + C41)
This [Equation 2] proceeds in the clockwise direction of the deformed body 40 when viewed from the Z-axis positive direction (viewed from above) among the two capacitive elements arranged in the curved portions 45c to 48c. This is an equation for measuring the acting force or moment using the capacitive element on the other side.

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

<3-3. Failure diagnosis ＞
The force sensor 301c according to the present embodiment can perform failure diagnosis by a single force sensor 301c. Here, the diagnostic 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. Further, the four capacitive elements C11, C21, C31 and C41 used in [Equation 2] and the four capacitive elements C12, C22, C32 and C42 used in [Equation 3] are the first to fourth curved portions. It is arranged symmetrically with respect to the detection sites A1 to A4 defined in 45c to 48c. From these facts, in the force sensor 301c that is functioning normally, the force or moment measured based on [Equation 2] and the force or moment measured based on [Equation 3] are the same. become. That is, in the force sensor 301c that is functioning normally, the following relationship [Equation 4] is established.
[Equation 4]
Mx1 = Mx2
My1 = My2
Mz1 = Mz2
Fz1 = Fz2

From this, the failure diagnosis of the force sensor 301c can be performed as follows. That is, the detection circuit 250 measures the force or moment acting on the force sensor 301c based on both [Equation 2] and [Equation 3], and the measured values (Mx1, My1) based on [Equation 2]. , Mz1, Fz1) and the values measured based on [Equation 3] (Mx2, My2, Mz2, Fz2). , Cmz, Cfz) or less, it is determined that the force sensor 301c is functioning normally. That is, when the following [Equation 5] is satisfied, 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.
[Equation 5]
| Mx1-Mx2 | ≤Cmx and | My1-My2 | ≤Cmy and | Mz1-Mz2 | ≤Cmz and | Fz1-Fz2 | ≤Cfz

On the other hand, if at least one of the differences is larger than the predetermined threshold value C1, the detection circuit 250 determines that the force sensor 301c is not functioning normally (failed). That is, when the following [Equation 6] is satisfied, the detection circuit 250 determines that the force sensor 301c is not functioning normally.
[Equation 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 of the two capacitive elements arranged in each of the first to fourth bending portions 45c to 48c (four in total) is used. Based on the difference between the measured force or moment value and the force or moment value measured using each of the remaining ones (four in total), the failure is detected by a single force sensor 301c. Can be diagnosed. This improves the safety and reliability of the force sensor 301c.

In the above description, in order to diagnose the failure 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, it is not limited to such a method. For example, it is obtained based on a specific force or moment (example: 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 with the specific force or moment (eg, Mx1 or Mx2). The specific method of diagnosis is the same as the method described above. That is, when performing a failure diagnosis focusing on the moment Mx around the X-axis, if the specific force or moment obtained based on Mx1 + Mx2, which is the sum of [Equation 2] and "Equation 3", is M12, then | Whether or not Mx12-Mx1 | or | Mx12-Mx2 | exceeds a predetermined threshold value is evaluated. This also applies when fault diagnosis is performed based on other forces or moments.

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

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

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

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

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

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

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

<4-2. Action ＞
Next, FIG. 33 is a chart showing the fluctuation of the capacitance value that occurs in each of the capacitance elements C11 to C24 when a force or a moment is applied to the force sensor 401c of FIG. 30. In this chart, "+" indicates that the capacitance value increases, and "++" indicates that the capacitance value increases significantly. Further, "-" indicates that the capacitance value decreases, and "-" indicates that the capacitance value decreases significantly.

When a force or moment acts on the force sensor 401c according to the present embodiment, the curved 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. Therefore, due to this elastic deformation, the capacitance values of the capacitive elements C11 to C42 fluctuate. This variation is substantially the same as the capacitance value of each of the capacitance 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. Therefore, as shown in FIG. 33, relatively large fluctuations in the capacitance value occur in the capacitance elements C11, C21, C31, and C41 arranged in the low elasticity portions 444L to 448L, and the high elasticity portions 444H to 448H. A relatively small variation in the capacitance value occurs in the arranged capacitance elements C12, C22, C32, and C42.

The moments Mx, My, Mz and the force Fz acting on the force sensor 401c are calculated using the following [Equation 7] based on the chart shown in FIG. 33. The sign at the end of Mx, My, Mz and Fz is used to distinguish between the force or moment calculated using [Equation 7] and the force or moment calculated using [Equation 8] described later. belongs to.
[Equation 7]
Mx1 = -C11-C21 + C31 + C41
My1 = C11-C21-C31 + C41
Mz1 = -C11 + C21-C31 + C41
Fz1 =-(C11 + C21 + C31 + C41)
In this [Equation 7], of the two capacitive elements arranged in the first to fourth curved portions 445c to 448c, the four capacitive elements C11 and C21 arranged in the low elasticity portions 445L to 448L are used. , C31, and C41 are used to measure the acting force or moment.

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

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

<4-3. Failure diagnosis ＞
The force sensor 401c according to the present embodiment can perform more advanced failure diagnosis than the force sensor 301c according to the third embodiment in the following points. That is, the force sensor 301c according to the third embodiment can detect a failure when the electrodes are damaged or when foreign matter is mixed between the electrodes. On the other hand, when the force sensor 301c does not function normally due to metal fatigue in the deformed body 40, the force or moment (Mx1, My1, Mz1, Fz1) measured based on [Equation 2] ) And the force or moment (Mx2, My2, Mz2, Fz2) measured based on [Equation 3], there is a possibility that there is no difference. In this case, the force sensor 301c cannot properly perform the failure diagnosis. When metal fatigue occurs in the deformed body 40, cracks or the like may occur in the elastic body constituting the deformed body 40, and the deformed body 40 may eventually break. Therefore, if a force sensor capable of detecting a failure due to metal fatigue can be provided, reliability and safety can be further improved.

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

First, the principle of failure diagnosis will be described. When a repeated load acts on the deformed body 40 of the force sensor 401c, metal fatigue occurs on the deformed body 40. When this metal fatigue accumulates, the strength of the deformed body 40 decreases, and finally the deformed body 40 breaks. Generally, when metal fatigue accumulates in a metal material, the metal material softens. Therefore, the spring constants of the first to fourth curved portions 445c to 448c decrease. In other words, due to the accumulation of metal fatigue, the deformed body 40 is more sensitive to the acting force or moment than in the initial state.

FIG. 34 shows the magnitude of the moment Mx around the X-axis acting on the force sensor 401c in a state where metal fatigue does not occur in the force sensor 401c shown in FIG. 30 (initial state), and from the force sensor 401c. It is a graph which shows the relationship with the electric signal which shows the moment Mx which is output, and FIG. It is a graph which shows the relationship between the magnitude of the surrounding moment Mx, and the electric signal which shows the moment Mx output from the force sensor 401c. Reference numeral "T1" in FIGS. 34 and 35 indicates a first electric signal which is an electric signal based on the fluctuation amount of the capacitance value of the four capacitance elements arranged in the low elasticity portions 445L to 448L. “T2” indicates a second electric signal which is an electric signal based on the fluctuation amount of the capacitance value of the four capacitance elements arranged in the high elasticity portions 445H to 448H. Further, the symbols at the end of "T1" and "T2" are an electric signal in the initial state (a is added at the end) and an electric signal in the state where metal fatigue is accumulated (b is added at the end). It is for distinguishing.

When the first electric signal T1 and the second electric signal T2 are specifically written down, it becomes as follows [Equation 9].
[Equation 7]
T1 (T1a, T1b) =-C11-C21 + C31 + C41
T2 (T2a, T2b) =-C12-C22 + C32 + C42

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

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

What should be noted here is the four capacitance 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. It means that the change in sensitivity is different. Such a difference is due to the fact that the strain generated in the low elasticity portions 445L to 448L is larger than the strain generated in the high elasticity portions 445H to 448H, so that a relatively large amount of metal fatigue accumulates in the low elasticity portions 445L to 448L. It is due. Quantitative evaluation of such a change in sensitivity by focusing on the ratio of the first electric signal T1 and the second electric signal T2 is as follows. That is, in the initial state, the ratio (T1a / T2a) of the first electric signal T1a and the second electric signal T2a was 4.0, but when metal fatigue accumulates, the first electric signal T1b and the second electric signal T1b and the second electric signal. The ratio to the signal T2b (T1b / T2b) increased to 5.0.

Based on the mechanism by which metal fatigue develops, this ratio T1 / T2 gradually increases from 4.0 to 5.0 with the action of repeated loads (forces or moments). In addition to measuring the applied force or moment, the force sensor 401c according to the present embodiment also diagnoses the failure of the force sensor 1c by paying attention to the change in the ratio T1 / T2. In the failure diagnosis, the detection circuit 450 determines the ratio of the first electric signal T1 and the second electric signal T2 (T1 / T2) at the time of measurement and the ratio of the first electric signal T1a and the second electric signal T2a in the initial state. It is performed by evaluating whether or not the difference between (T1a / T2a) and ((T1 / T2)-(T1a / T2a)) exceeds a predetermined value (threshold value C). That is, when the following [Equation 10] is satisfied, 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 and the second electric signal T2a and the threshold value C in the initial state are stored in advance in the detection circuit 450.
[Equation 10]
(T1 / T2)-(T1a / T2a) ≤ C (C: threshold)

On the other hand, when the following [Equation 11] is satisfied, the detection circuit 450 determines that the force sensor 401c is not functioning normally (it is out of order).
[Equation 11]
(T1 / T2)-(T1a / T2a)> C (C: threshold)

In the above description, the case where the moment Mx around the X axis acts on the force sensor 401c has been described as an example, but the same applies to the case where other moments My, Mz or force Fz act. Failure diagnosis can be performed. Specifically, regarding the force or moment of interest, the equation described in [Equation 7] is referred to as the first electric signal T1, and the equation described in [Equation 8] is referred to as the second electric signal T2. At this time, the relationship between the force or moment acting on the force sensor 401c and the first and second electric signals T1 and T2 is the same as the graph shown in FIG. 34 in the initial state, and metal fatigue accumulates in the deformed body 40. In this state, the graph is the same as that shown in FIG. 35. However, when a force Fz in the Z-axis direction acts, the "moment" on the horizontal axis is read as "force". Therefore, regardless of which force or moment is applied, the failure diagnosis of the force sensor 401c is properly performed based on the above-mentioned [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 developed in the deformed body 40 while measuring a force or a moment. As a result, the reliability and safety of the force sensor 401c are further enhanced.

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

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

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

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

Although not shown, the force sensor 501c is configured by 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. Although the member for arranging the fixed electrode is not shown in FIG. 37, the fixed electrode may be appropriately arranged at the portion where the force sensor 501c is attached, or is additionally attached to the fixed body 510. A member may be fixed and a fixed electrode may be placed on the member.

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

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

As a modification of the basic structure 501 as described above, the following basic structure 502 can also be considered.

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

As shown in FIGS. 38 and 39, the basic structure 502 according to this modification is different from the basic structure 501 shown in FIGS. 36 and 37 in that the deformed body 540 is not provided with a curved portion. Therefore, the modified body 540 of this modified example has a ring (cylindrical) shape, and its upper surface and lower surface are parallel to the XY plane. Since other configurations are the same as those of the basic structure 501 described above, the corresponding components are designated by the same reference numerals in the drawings, and detailed description thereof will be omitted.

FIG. 40 is a schematic plan view showing an example of the force sensor 502c using the basic structure 502 of FIG. 38. The force sensor 502c shown in FIG. 40 uses the radial displacement generated on the inner side surface (the side surface facing the origin O) due to the elastic deformation of the deformed body 40 caused by the applied force or moment to obtain the force or moment. It is designed to measure. In this case, as shown in FIG. 40, displacement electrodes Em1 to Em4 are provided at four portions of the inner surface of the deformed body 540 that overlap the V-axis and the W-axis, respectively, and each of the outer surfaces of the fixed body 510 is provided with displacement electrodes Em1 to Em4. Fixed electrodes Ef1 to Ef4 may be provided at locations facing the displacement electrodes Em1 to Em4. With such a configuration, four capacitive elements C1 to C4 are configured 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 the force or moment acting on the four capacitive elements C1 to C4.

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

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

<<< §6. Other variants >>>
Next, with reference to FIGS. 41 and 42, a modified example of the deformed 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 variant 640. 42 is a schematic cross-sectional view of FIG. 41, FIG. 42 (a) is a cross-sectional view taken along the line [42a]-[42a] of FIG. 41, and FIG. 42 (b) is [42b] of FIG. 41. ]-[42b] is a cross-sectional view taken along the line.

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

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

As shown in FIG. 41, the first to fourth deformed portions 645 to 648 are all formed 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 receiving portions 643 and 644 are all equal, each of the deformed portions 645 to 648 is arranged so as to form one side of the square.

Further, as shown in FIGS. 42 (a) and 42 (b), each of the deformed portions 645 to 648 of the deformed body 640 has curved portions 645c to 648c curved so as to bulge in the negative direction of the Z axis. ing. In the illustrated example, each deformed portion 645 to 648 forms a curved portion 645c to 648c as a whole. Therefore, in FIGS. 42 (a) and 42 (b), the reference numeral of the deformed portion and the reference numeral of the curved portion are shown together. As shown, the lowermost portion (Z-axis negative direction) of the first curved portion 645c exists on the positive V-axis. The shape of the first curved portion 645c from the first fixed portion 641 to the lowermost portion is the same as the shape from the first receiving portion 643 to the lowermost portion. It is the same. In other words, the first curved portion 645c has a shape symmetrical with respect to the positive V axis in the length direction of the deformed body 640.

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

As shown in FIGS. 42 (a) and 42 (b), the deformed body 640 has each curved portion in the lowermost portion of the first to fourth curved portions 645c to 648c, that is, when viewed from the Z-axis direction. Detection portions A1 to A4 for detecting elastic deformation occurring in each of the curved portions 645c to 648c are defined in the lower portion of the portion where the portions 645c to 648c overlap the V-axis and the W-axis. In FIG. 41, the detection sites A1 to A4 are shown to be provided on the upper surface (front surface) of the deformed body 640, but are actually on the lower surface (back side surface) of the deformed body 640. It is provided (see FIG. 42).

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

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

Claims (3)

A force sensor for a robot that detects at least one of a force in each axial direction and a moment around each axis in the XYZ three-dimensional coordinate system.
The first annular member arranged in the XYZ three-dimensional coordinate system,
A second annular member that surrounds the first annular member and moves relative to the first annular member by the action of a force or moment.
A detection means for detecting a relative displacement between the first annular member and the second annular member is provided.
The detection means
A deformed body arranged between the first annular member and the second annular member and elastically deformed by the action of a force or a moment.
A capacitive element that detects elastic deformation of the deformed body, and
It has a detection circuit that outputs an electric signal based on the fluctuation amount of the capacitance of the capacitance element.
The first annular member and the second annular member are arranged concentrically with each other so that their central axes overlap with the Z axis.
The end face of the first annular member on the negative side of the Z axis extends from the end surface of the second annular member on the negative side of the Z axis to the negative side of the Z axis.
The end face on the Z-axis positive side of the first annular member is located on the same plane as the end face on the Z-axis positive side of the deformed body.
A force sensor characterized by that. The end face on the negative side of the Z axis of the first annular member is the end face on the negative side of the Z axis of the deformed body, and the end face on the negative side of the Z axis of the connecting member connecting the first annular member and the deformed body. Extends from the end face to the negative side of the Z axis
The end face on the negative side of the Z axis of the deformed body is located on the same plane as the end face on the negative side of the Z axis of the connecting member, and the end face on the positive side of the Z axis of the deformed body is on the positive side of the Z axis of the connecting member. Located on the same plane as the end face of
The force sensor according to claim 1. The relative displacement between the first annular member and the second annular member is
The relative displacement of the first annular member and the second annular member around the Z axis.
The force sensor according to claim 1 or 2.

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