JP5667723B1 - Force sensor - Google Patents

Abstract

A balance between detection sensitivity of force and moment is adjusted while securing an internal space. A circular detection ring 210 made of a conductive elastic body is disposed so that the Z axis is a central axis, a disk-shaped support body 100 is disposed below, and a washer-shaped force receiving body 300 is disposed above. To do. The outer peripheral surface of the detection ring 210 is connected to the support 100 by connecting members 221 and 222 arranged on the X axis, and the outer peripheral surface of the detection ring 210 is received by connecting members 231 and 232 arranged on the Y axis. Connect to force body 300. When a force or moment is applied to the force receiving body 300 with the support 100 fixed, the detection ring 210 is distorted. Forces and moments are detected based on the capacitance values of the eight sets of capacitive elements formed by the eight sets of electrodes E1 to E8 provided on the support 100 and the opposing surfaces of the detection ring 210. A plurality of detection rings 210 can be stacked one above the other, and the balance of detection sensitivity is adjusted according to the number of detection rings 210. [Selection] Figure 12

Description

  The present invention relates to a force sensor, and more particularly to a sensor suitable for detecting a force in each coordinate axis direction and a moment around each coordinate axis in a three-dimensional orthogonal coordinate system.

  Various types of force sensors are used to control the operation of robots and industrial machines. A small force sensor is also incorporated as a man-machine interface of an input device of an electronic device. In order to reduce the size and reduce the cost, the force sensor used for such an application has a simple structure as much as possible, and can detect the force relating to each coordinate axis in a three-dimensional space independently. Is required.

  Currently, the multi-axis force sensor that is generally used is a type that detects a specific direction component of a force acting on a mechanical structure part as a displacement generated in a specific part and a specific part. It is classified as a type to detect as mechanical strain. A typical example of the former displacement detection type is a capacitive element type force sensor, in which a capacitive element is configured by a pair of electrodes, and the displacement generated in one electrode by the applied force is detected by the capacitive element. The detection is based on the capacitance value. For example, Patent Document 1 (corresponding US publication is Patent Document 2) and Patent Document 3 (corresponding United States Publication is Patent Document 4) below disclose this capacitance-type multi-axis force sensor.

  On the other hand, a representative of the latter type of mechanical strain detection is a strain gauge type force sensor that detects mechanical strain caused by the applied force as a change in electrical resistance such as a strain gauge. is there. For example, the following Patent Document 5 (corresponding US publication is Patent Document 6) discloses this strain gauge type multi-axis force sensor.

  Various proposals have also been made on the form of the mechanical structure in order to reduce the size and thickness. For example, Patent Document 7 discloses a ring-shaped load detection unit that is generated by the action of a moment by disposing a flexible ring-shaped load detection unit on the outside of a cylindrical rigid body unit. A sensor for detecting strain is disclosed. Further, in Patent Document 8, two sets of rings, an inner ring and an outer ring, are arranged concentrically and connected between them, and the force acting on one ring is transmitted to the other ring to be deformed. A sensor for detecting a deformation mode is disclosed.

JP 2004-325367 A US Pat. No. 7,219,561 JP 2004-354049 A US Pat. No. 6,915,709 JP-A-8-122178 US Pat. No. 5,490,427 Japanese Patent Application Laid-Open No. 6-094548 Japanese Patent No. 4963138

  In order to electrically detect the applied force and moment, wiring and signal processing circuits that extract electrical signals are required. However, in force sensors that require miniaturization, the space for wiring and circuits is limited. ing. For example, in the force sensors disclosed in the above-mentioned Patent Documents 7 and 8, since a structure in which an inner member and an outer member are concentrically arranged is employed as a mechanical structure portion, the overall thickness is reduced. It becomes possible to plan.

  However, because the inner structure and the outer member have a nested structure, the internal space for incorporating the wiring and circuit is limited, and there is a case where it is necessary to adopt a form in which a signal is taken out from a connector provided outside the apparatus. Many. When such a force sensor is attached to the robot arm, it is necessary to mount the wiring outside the robot arm and connect it to the robot controller's main body. Therefore, when the robot arm is driven, the wiring contacts an external object. Accidents such as disconnection are likely to occur.

  Moreover, in the case of a force sensor having a function for detecting both force and moment, it is preferable that a balance between force detection sensitivity and moment detection sensitivity is practically used. With a sensor having a mechanical structure, it is difficult to design with a balance between the two.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a small force sensor that facilitates a design in which the balance between force detection sensitivity and moment detection sensitivity is adjusted while securing an internal space.

(1) A first aspect of the present invention is a force sensor that detects a force or a moment related to at least one axis among a force in each coordinate axis direction and a moment around each coordinate axis in an XYZ three-dimensional orthogonal coordinate system.
A plurality of m (m ≧ 2) detection rings that are arranged on an arrangement plane parallel to the XY plane so that the Z axis is the central axis, and that are elastically deformed at least in part by the action of a force or moment to be detected. When,
A support disposed below the detection ring;
A force receiving body disposed above the detection ring;
A support connection member for fixing the detection ring to the support at the position of a predetermined fixing point;
A force receiving connection member for connecting the detection ring to the force receiving body at the position of the predetermined action point;
A detection element for electrically detecting elastic deformation of the detection ring;
A detection circuit that outputs a detection value of a force in a predetermined coordinate axis direction acting on the force receiving member or a moment around the predetermined coordinate axis in a state where the support is fixed based on a detection result of the detection element;
Provided,
The projection image of the fixed point on the XY plane and the projection image of the action point on the XY plane are formed at different positions ,
A plurality of m detection rings are arranged adjacent to each other in the Z axis direction at a predetermined interval, and each detection ring is an individual arrangement plane parallel to the XY plane so that the Z axis is the central axis. Is located on top
The support body is disposed further below the lowermost detection ring, and the force receiving body is disposed further above the uppermost detection ring.
The fixing points of the individual detection rings are fixed to the support body by the support connection member, and the action points of the individual detection rings are fixed to the reception body by the force receiving connection member.

(2) According to a second aspect of the present invention, in the force sensor according to the first aspect described above,
The projected images of the fixed points and the action points of the individual detection rings on the XY plane overlap each other,
The support connection member connects the vicinity of each fixed point of different detection rings, which form a projected image at the same position on the XY plane, and fixes the support connection member to the support.
The force receiving connection member is configured to connect the vicinity of each action point of different detection rings, which form a projection image at the same position on the XY plane, to each other and to be fixed to the force receiving body.

(3) A third aspect of the present invention is the force sensor according to the first or second aspect described above,
A plurality of n (n ≧ 2) fixed points and a plurality of n action points are alternately arranged on the annular path along the contour of the detection ring,
The detection element is configured to electrically detect elastic deformation of the detection ring in the vicinity of the measurement point defined at a position between the fixed point and the action point arranged adjacent to each other.

(4) According to a fourth aspect of the present invention, in the force sensor according to the third aspect described above,
Two fixed points and two action points are arranged in the order of the first fixed point, the first action point, the second fixed point, and the second action point on the annular path along the contour of the detection ring. Has been
A first measurement point disposed at a position between the first fixed point and the first action point in the annular path; a position between the first action point and the second fixed point in the ring path; A second measurement point disposed at a position, a third measurement point disposed at a position between the second fixed point and the second action point in the ring road, and a second action point in the ring path; When each of the fourth measurement points arranged at a position between the first fixed point and the first measurement point is defined, the detection element electrically detects the elastic deformation of the detection ring in the vicinity of the first to fourth measurement points. It is intended to be detected.

(5 ) A fifth aspect of the present invention is the force sensor according to the fourth aspect described above,
The projected image of the first fixed point on the XY plane is on the X-axis positive region, the projected image of the first working point on the XY plane is on the Y-axis positive region, and the second fixed point is projected on the XY plane. The projected image is located on the X axis negative region, and the projected image of the second action point on the XY plane is located on the Y axis negative region,
By the first support connection member arranged so that the projected image on the XY plane is positioned on the X-axis positive region, the vicinity of the first fixed point of the detection ring is connected to the support,
By the second support connection member arranged so that the projected image on the XY plane is positioned on the X-axis negative region, the vicinity of the second fixed point of the detection ring is connected to the support,
By the first force receiving connection member arranged so that the projected image on the XY plane is positioned on the Y-axis positive region, the vicinity of the first action point of the detection ring is connected to the force receiving body,
By the second force receiving connection member arranged so that the projected image on the XY plane is positioned on the Y-axis negative region, the vicinity of the second action point of the detection ring is connected to the force receiving body,
The detection element has a first measurement point, a second measurement point, and a third measurement in which the projected image on the XY plane is located in the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant of the XY coordinate system, respectively. The elastic deformation of the detection ring in the vicinity of the point and the fourth measurement point is electrically detected.

(6) A sixth aspect of the present invention is the force sensor according to the fifth aspect described above,
A V-axis that passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is located in the first quadrant of the XY plane, the negative region is located in the third quadrant of the XY plane, and forms 45 ° with respect to the X axis; Defines the W axis that passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is located in the second quadrant of the XY plane, the negative region is located in the fourth quadrant of the XY plane, and is orthogonal to the V axis. Then, the projection image of the first measurement point on the XY plane is in the V-axis positive region, the projection image of the second measurement point on the XY plane is in the W-axis positive region, and the XY plane of the third measurement point The projection image onto the XY plane is located in the V-axis negative region, and the projection image of the fourth measurement point on the XY plane is located in the W-axis negative region.

(7) A seventh aspect of the present invention is the force sensor according to the first to sixth aspects described above,
The support connection member and the force receiving connection member are constituted by members that protrude further outward from the outer peripheral surface of the detection ring,
The lower surface of the support connection member is positioned below the lower surface of the lowermost detection ring and is connected to the upper surface of the support, and between the lower surface of the lowermost detection ring and the upper surface of the support A predetermined gap is formed,
The upper surface of the force receiving connection member is located above the upper surface of the uppermost detection ring and is connected to the lower surface of the force receiving body, and the upper surface of the uppermost detection ring and the lower surface of the force receiving body A predetermined gap is formed between them.

(8) The eighth aspect of the present invention is the force sensor according to the seventh aspect described above,
The projection image of the support connection member and the force receiving connection member on the XY plane is included in the projection image of the support body on the XY plane, and is included in the projection image of the support body on the XY plane. It is what you have.

(9) According to a ninth aspect of the present invention, in the force sensor according to the first to sixth aspects described above,
A support connecting member is a member that connects the lower surface of the lowermost detection ring and the support, and a member that connects the lower surface of the upper detection ring and the upper surface of the lower detection ring for each pair of detection rings adjacent vertically And consists of
The force receiving connection member connects the upper surface of the uppermost detection ring and the force receiving member, and the lower detection ring upper surface and the lower detection ring upper surface for each pair of detection rings adjacent vertically. And a member to be configured.

(10) The tenth aspect of the present invention is the force sensor according to the first to ninth aspects described above,
The detection ring is constituted by a circular ring arranged on the arrangement plane so that the Z axis becomes the central axis.

(11) The eleventh aspect of the present invention is the force sensor according to the first to tenth aspects described above,
The support is configured by a plate-like member disposed below the detection ring and having a plate surface parallel to the XY plane,
The force receiving body is configured by a plate-like member that is disposed above the detection ring and has a plate surface parallel to the XY plane.

(12) According to a twelfth aspect of the present invention, in the force sensor according to the eleventh aspect described above,
One or both of the support body and the force receiving body is constituted by a disk-shaped member having an opening at the center.

(13) The thirteenth aspect of the present invention is the force sensor according to the first to twelfth aspects described above,
The support body and the power receiving body are configured by a rigid body that does not substantially deform as long as the applied force or moment is within a predetermined allowable range.

(14) The fourteenth aspect of the present invention is the force sensor according to the first to thirteenth aspects described above,
The detection element is configured to electrically detect the displacement of a predetermined measurement point of the detection ring.

(15) According to a fifteenth aspect of the present invention, in the force sensor according to the fourteenth aspect described above,
The detection element is configured to electrically detect the distance between the measurement target surface in the vicinity of the measurement point of the detection ring and the opposing reference surface fixed to the support body or the force receiving body and facing the measurement target surface. .

(16) According to a sixteenth aspect of the present invention, in the force sensor according to the fifteenth aspect described above,
Define the inner measurement target surface near the measurement point on the inner peripheral surface of the detection ring,
A fixed structure that has an inner facing reference surface facing the inner measurement target surface and is fixed to the upper surface of the support or the lower surface of the force receiving member;
The detection element is configured to electrically detect the distance between the inner measurement target surface and the inner facing reference surface.

(17) A seventeenth aspect of the present invention is the force sensor according to the fifteenth aspect described above,
Define the lower measurement target surface near the measurement point on the lower surface of the detection ring,
The detection element is configured to electrically detect the distance between the lower measurement target surface and the upper surface of the support.

(18) According to an eighteenth aspect of the present invention, in the force sensor according to the fifteenth to seventeenth aspects described above,
The detection element is constituted by a capacitive element having a displacement electrode provided on the measurement target surface and a fixed electrode provided on the opposing reference surface.

(19) The nineteenth aspect of the present invention is the force sensor according to the eighteenth aspect described above,
The detection ring is made of a conductive material having flexibility, and a capacitive element is formed by using the surface of the detection ring as a common displacement electrode.

(20) According to a twentieth aspect of the present invention, in the force sensor according to the sixth aspect described above,
The detection ring is a circular ring arranged on an arrangement plane above the support so that the Z-axis is the central axis;
The sensing element
The first displacement electrode disposed in the vicinity of the first measurement point on the inner peripheral surface of the detection ring and the first displacement electrode disposed on the inner side of the detection ring are disposed at positions facing the first displacement electrode and fixed to the upper surface of the support. A first capacitive element comprising: a first fixed electrode;
The second displacement electrode disposed in the vicinity of the second measurement point on the inner peripheral surface of the detection ring and the second displacement electrode disposed on the inner side of the detection ring are disposed at positions facing the second displacement electrode, and are fixed to the upper surface of the support. A second capacitive element constituted by a second fixed electrode;
A third displacement electrode disposed in the vicinity of the third measurement point on the inner peripheral surface of the detection ring and a position opposed to the third displacement electrode inside the detection ring are fixed to the upper surface of the support. A third capacitive element constituted by a third fixed electrode;
A fourth displacement electrode disposed in the vicinity of the fourth measurement point on the inner peripheral surface of the detection ring and a position facing the fourth displacement electrode on the inner side of the detection ring are fixed to the upper surface of the support. A fourth capacitive element constituted by a fourth fixed electrode;
The fifth displacement electrode is disposed at a position near the first measurement point on the lower surface of the detection ring, and the fifth fixed electrode is disposed at a position facing the fifth displacement electrode on the upper surface of the support. A fifth capacitive element;
A sixth displacement electrode disposed at a position near the second measurement point on the lower surface of the detection ring and a sixth fixed electrode disposed at a position facing the sixth displacement electrode on the upper surface of the support. A sixth capacitive element;
The seventh displacement electrode is disposed at a position near the third measurement point on the lower surface of the detection ring, and the seventh fixed electrode is disposed at a position facing the seventh displacement electrode on the upper surface of the support. A seventh capacitor element;
An eighth displacement electrode disposed in the vicinity of the fourth measurement point on the lower surface of the detection ring and an eighth fixed electrode disposed at a position facing the eighth displacement electrode on the upper surface of the support. An eighth capacitive element;
It is made to have.

(21) According to a twenty-first aspect of the present invention, in the force sensor according to the twentieth aspect described above,
An upper detection ring and a lower detection ring are arranged adjacent to each other in the Z-axis direction at a predetermined interval, and both of these two detection rings are parallel to the XY plane so that the Z-axis is the central axis. Placed on individual placement planes,
The projection image of the first fixed point of the upper detection ring on the XY plane and the projection image of the first fixed point of the lower detection ring on the XY plane overlap each other.
The projected image of the second fixed point of the upper detection ring on the XY plane and the projected image of the second fixed point of the lower detection ring on the XY plane overlap each other,
The projection image of the first action point of the upper detection ring on the XY plane and the projection image of the first action point of the lower detection ring on the XY plane overlap each other,
The projection image of the second action point of the upper detection ring on the XY plane and the projection image of the second action point of the lower detection ring on the XY plane overlap each other.
The first support connection member connects the vicinity of the first detection point of the upper detection ring and the vicinity of the first detection point of the lower detection ring to each other and is also connected to the support body.
By the second support connection member, the vicinity of the second fixed point of the upper detection ring and the vicinity of the second fixed point of the lower detection ring are connected to each other and also connected to the support,
The first force receiving connection member connects the vicinity of the first action point of the upper detection ring and the vicinity of the first action point of the lower detection ring to each other and is also connected to the force receiving body,
By the second force receiving connection member, the vicinity of the second action point of the upper detection ring and the vicinity of the second action point of the lower detection ring are connected to each other and also connected to the force receiving body,
The first displacement electrodes are distributed and arranged in two locations: a position near the first measurement point on the inner peripheral surface of the upper detection ring and a position near the first measurement point on the inner peripheral surface of the lower detection ring. The first fixed electrode is opposed to both of the displacement electrodes that are dispersedly disposed at the two locations.
The second displacement electrodes are distributed and arranged at two locations, a position near the second measurement point on the inner peripheral surface of the upper detection ring and a position near the second measurement point on the inner peripheral surface of the lower detection ring. The second fixed electrode is opposed to both of the displacement electrodes distributed in the two locations,
The third displacement electrodes are distributed and arranged in two locations: a position near the third measurement point on the inner peripheral surface of the upper detection ring and a position near the third measurement point on the inner peripheral surface of the lower detection ring. The third fixed electrode is opposed to both of the displacement electrodes arranged in a dispersed manner at the two locations,
The fourth displacement electrodes are distributed and arranged in two locations: a position near the fourth measurement point on the inner peripheral surface of the upper detection ring and a position near the fourth measurement point on the inner peripheral surface of the lower detection ring. The fourth fixed electrode is opposed to both of the displacement electrodes arranged in a dispersed manner at the two locations.
The fifth displacement electrode is disposed at a position near the first measurement point on the lower surface of the lower detection ring, and the sixth displacement electrode is disposed at a position near the second measurement point on the lower surface of the lower detection ring. The displacement electrode is arranged in the vicinity of the third measurement point on the lower surface of the lower detection ring, and the eighth displacement electrode is arranged in the vicinity of the fourth measurement point on the lower surface of the lower detection ring. Is.

(22) According to a twenty-second aspect of the present invention, in the force sensor according to the twentieth or twenty-first aspect described above,
The detection ring is made of a conductive material having flexibility, and each capacitive element is formed by using the surface of the detection ring as a common displacement electrode.

(23) According to a twenty-third aspect of the present invention, in the force sensor according to the twentieth to twenty-second aspects described above,
The detection circuit sets the capacitance value of the first capacitance element to C1, the capacitance value of the second capacitance element to C2, the capacitance value of the third capacitance element to C3, and the capacitance value of the fourth capacitance element. The capacitance value is C4, the capacitance value of the fifth capacitance element is C5, the capacitance value of the sixth capacitance element is C6, the capacitance value of the seventh capacitance element is C7, and the eighth capacitance element. When the capacitance value of C8 is C8,
Fx = −C1 + C2 + C3-C4
Fy = + C1 + C2-C3-C4
Fz = -C5-C6-C7-C8
Mx = -C5-C6 + C7 + C8
My = + C5-C6-C7 + C8
Mz = + C1-C2 + C3-C4
Based on the following formula, the detection of the force Fx in the X-axis direction, the force Fy in the Y-axis direction, the force Fz in the Z-axis direction, the moment Mx around the X-axis, the moment My around the Y-axis, and the moment Mz around the Z-axis A value is output.

  In the force sensor according to the present invention, a structure in which a fixed point of a detection ring that generates elastic deformation is connected to a lower support body, an action point is connected to an upper power receiving body, and three components are stacked one above the other. Therefore, a sufficient space can be secured inside the detection ring. Also, if such a laminated structure is adopted, a plurality of detection rings can be stacked one above the other, so the balance between the force detection sensitivity and the moment detection sensitivity can be easily adjusted by the number of detection rings used. It becomes possible.

  As described above, according to the present invention, it is possible to provide a small force sensor that facilitates a design in which the balance between the force detection sensitivity and the moment detection sensitivity is adjusted while securing the internal space.

It is a disassembled perspective view of the basic structure part of the force sensor which concerns on fundamental embodiment of this invention. It is a perspective view which shows the state which assembles | assembles the basic structure part shown in FIG. 1, and uses for the joint part of a robot arm. FIG. 2 is a top view (FIG. (A)) and a side view (FIG. (B)) of the basic structure shown in FIG. FIG. 4 is a cross-sectional view (FIG. (A)) showing a state in which the basic structure shown in FIG. 3 is cut along the XZ plane and a cross-sectional view (FIG. (B)) showing a state cut along the YZ plane. 2 is a top view (FIG. (A)) of the intermediate body 200 shown in FIG. 1 and a top view (FIG. (B)) in which only the detection ring 210 is extracted. 1 is a plan view showing a deformation mode of the detection ring 210 when a force + Fx in the X-axis positive direction is applied to the force receiving portion 300 in a state where the support portion 100 is fixed in the basic structure portion shown in FIG. Shows previous state). 1 is a plan view showing a deformation mode of the detection ring 210 when a force + Fy in the Y-axis positive direction is applied to the force receiving portion 300 in a state where the support portion 100 is fixed in the basic structure portion shown in FIG. Shows previous state). FIG. 3 is a side view showing a deformation mode of the detection ring 210 when a force + Fz in the positive Z-axis direction is applied to the force receiving portion 300 in a state where the support portion 100 is fixed in the basic structure portion shown in FIG. 1. 2 is a side view showing a deformation mode of the detection ring 210 when a moment + Mx about the positive X-axis is applied to the force receiving portion 300 in a state where the support portion 100 is fixed in the basic structure portion shown in FIG. FIG. 6 is a side view showing a deformation mode of the detection ring 210 when a moment + My about the positive Y-axis is applied to the force receiving portion 300 in a state where the support portion 100 is fixed in the basic structure portion shown in FIG. 1. 1 is a plan view showing a deformation mode of the detection ring 210 when a moment + Mz about the positive Z-axis is applied to the force receiving portion 300 in a state where the support portion 100 is fixed in the basic structure portion shown in FIG. Shows previous state). It is a disassembled perspective view of a state where a fixed electrode is added to the basic structure of the force sensor according to the basic embodiment of the present invention. FIG. 13 is a top view of the support body 100 shown in FIG. 12 (for reference, the position of the detection ring 200 is indicated by a broken line). FIG. 13 is a plan view showing eight sets of capacitive elements used as detection elements in the force sensor according to the basic embodiment shown in FIG. 12. It is a perspective view which shows the size relationship of the counter electrode of each capacitive element used with the force sensor which concerns on fundamental embodiment shown in FIG. 13 is a table showing changes in capacitance values of capacitive elements C1 to C8 when a force in each coordinate axis direction and a moment around each coordinate axis are applied to the force sensor according to the basic embodiment shown in FIG. . It is a figure which shows the computing equation which calculates | requires the force of each coordinate axis direction which acts on the force sensor which concerns on basic embodiment shown in FIG. 12, and the moment around each coordinate axis. It is a circuit diagram which shows the detection circuit used for the force sensor which concerns on fundamental embodiment shown in FIG. It is a perspective view which shows the modification 200A of the intermediate body 200 utilized for basic embodiment shown in FIG. FIG. 20 is a side view of a basic structure configured using an intermediate body 200A according to a modified example shown in FIG. 19 instead of the intermediate body 200 in the basic embodiment shown in FIG. 1. It is sectional drawing which shows the state which cut | disconnected the basic structure part shown in FIG. 20 by XZ plane. It is a perspective view which shows another modification 200B of the intermediate body 200 utilized for basic embodiment shown in FIG. It is a side view of the basic structure part comprised using the intermediate body 200B which concerns on the modification shown in FIG. 22 instead of the intermediate body 200 in basic embodiment shown in FIG. It is sectional drawing which shows the state which cut | disconnected the basic structure part shown in FIG. 23 by XZ plane. It is a table | surface which shows the number of detection rings, and the dimension of each part about the various samples of the intermediate body used for the force sensor which concerns on this invention. It is a table | surface which shows the balance of the detection sensitivity of the force and moment in the force sensor using eight types of samples shown in FIG. It is sectional drawing which shows the state which cut | disconnected the modification using the support body 100C in the XZ plane instead of the support body 100 in the basic structure part shown in FIG. It is sectional drawing which shows the state cut | disconnected by the XZ plane using the power receiving body 300D instead of the power receiving body 300 in the double ring type basic structure part shown in FIG. It is a top view which shows the structural variation of the support connection member and force receiving connection member in this invention. It is sectional drawing which shows the state which cut | disconnected the example which applied the modification shown in FIG.29 (b) about the single-ring-type basic structure part by XZ plane. It is sectional drawing which shows the state which cut | disconnected the example which applied the modification shown in FIG.29 (b) about a double ring type basic structure part by XZ plane.

<<< §1. Basic structure of force sensor according to basic embodiment >>
First, the basic structure of a force sensor according to a basic embodiment of the present invention will be described. The force sensor according to the present invention has a function of detecting a force or a moment related to at least one axis among a force in each coordinate axis direction and a moment around each coordinate axis in an XYZ three-dimensional orthogonal coordinate system. Therefore, the configuration of the basic structure of the force sensor will be described below in a state where it is arranged in an XYZ three-dimensional orthogonal coordinate system.

  FIG. 1 is an exploded perspective view of a basic structure of a force sensor according to a basic embodiment of the present invention. As will be described later, the force sensor according to the present invention is configured by further adding a detection element and a detection circuit to the basic structure portion. As shown in the figure, this basic structure is formed by arranging a support body 100, an intermediate body 200, and a force receiving body 300 side by side in the vertical direction and joining them together.

  Here, for convenience of explanation, an XYZ three-dimensional orthogonal coordinate system is defined by taking the X-axis, Y-axis, and Z-axis as indicated by a dashed line arrow in the figure. The support body 100, the intermediate body 200, and the force receiving body 300 are all arranged such that the Z axis is the central axis.

  The intermediate body 200 is a component that plays the most important role in detecting force and moment, and includes a detection ring 210, support connection members 221 and 222, and force receiving connection members 231 and 232. In the case of the example shown here, the intermediate body 200 is configured as an integrally formed body, and the detection ring 210, the support connection members 221, 222, and the force receiving connection members 231, 232 are formed by individual parts of the integrally formed body. Will be composed. Of course, the intermediate body 200 does not necessarily have to be configured as an integrally molded body, and may be a structure obtained by joining individual portions.

  The detection ring 210 is a cylindrical (washer-like) annular structure disposed on the XY plane so that the Z axis is the central axis, and both the outer peripheral surface and the inner peripheral surface form a cylindrical surface. The detection ring 210 is made of a material that is elastically deformed by the action of a force or moment to be detected. The support connection members 221 and 222 are members for fixing the intersection position of the detection ring 210 and the X axis to the lower support body 100, and the lower surfaces thereof are joined to the upper surface of the support body 100. On the other hand, the force receiving connection members 231 and 232 are members for fixing the intersection position of the detection ring 210 and the Y axis to the upper force receiving member 300, and the upper surface thereof is joined to the lower surface of the force receiving member 300. The

  The support body 100 is disposed below the detection ring 210 and plays a role of supporting and fixing the detection ring 210 via the support connection members 221 and 222. On the other hand, the force receiving body 300 is disposed above the detection ring 210 and plays a role of transmitting an applied force or moment (detection target) to the detection ring 210 via the force receiving connection members 231 and 232. In the case of the illustrated example, the support body 100 is a disk-like member having plate surfaces whose upper and lower surfaces are parallel to the XY plane, and is arranged so that the Z axis is the central axis. The force receiving body 300 is also a disk-like member having plate surfaces whose upper and lower surfaces are parallel to the XY plane, and is arranged so that the Z axis is the central axis. The force receiving member 300 is provided with a circular opening H at the center, which is convenient for wiring inside as will be described later.

  By using such a basic structure portion, it is possible to detect a force in a predetermined coordinate axis direction or a moment around a predetermined coordinate axis applied to the force receiving body 300 in a state where the support body 100 is fixed. FIG. 2 is a perspective view showing a state in which the basic structure shown in FIG. 1 is assembled and used for the joint portion of the robot arm. A first arm part 400 of the robot is arranged below the figure, and a second arm part 500 of the robot is arranged above the figure.

  If the lower surface of the support body 100 of the basic structure part is connected to the first arm part 400 and the upper surface of the force receiving body 300 is connected to the second arm part 500, the basic structure part can be used as a joint of the robot arm. In addition, in a state where the first arm unit 400 is fixed, it can function as a force sensor that detects a force or moment acting on the second arm unit 500. Actually, a hole for inserting a bolt is formed in the disk-shaped support body 100 and the disk-shaped force receiving body 300, and each hole is used to reach the first arm section 400. It is preferable to be able to fix to the second arm portion 500.

  However, according to the law of action and reaction, when the first arm unit 400 is fixed, the force or moment applied to the second arm unit 500 acts on the first arm unit 400 in the state where the second arm unit 500 is fixed. The force and moment are equivalent, although the direction is reversed.

  Therefore, the force sensor according to the present invention can be said to be a sensor that detects a force in a predetermined coordinate axis direction or a moment around a predetermined coordinate axis applied to the force receiving body 300 in a state where the support body 100 is fixed. On the contrary, in a state where the force receiving body 300 is fixed (in this case, the member 300 is to be called a support), the member 100 acts on the support 100 (in this case, the member 100 is to be called a power receiving body). It can be said that the sensor detects a force in a predetermined coordinate axis direction or a moment around the predetermined coordinate axis.

  In this manner, in the illustrated basic structure, the force and moment acting on the member 300 when the member 100 is fixed and the force and moment acting on the member 100 when the member 300 is fixed are detected. That is physically equivalent. However, in this specification, for convenience of explanation, the member 100 is referred to as the support body 100, the member 300 is referred to as the force receiving body 300, and an example in which the force or moment acting on the latter is detected in a state where the former is fixed. The following explanation will be given.

  In this specification, for convenience of explanation, an example in which the support body 100 is disposed below the detection ring 200 and the force receiving body 300 is disposed above the detection ring 200 will be described. "/ Down" indicates a position for convenience in explanation with reference to the drawings. Therefore, when the force sensor according to the present invention is mounted, the support body 100 is disposed above the detection ring 200 and the power receiving body 300 is disposed below the detection ring 200 with the top and bottom reversed. There is no problem even if you use it.

  Subsequently, the structure of the basic structure will be described in more detail. FIG. 3A is a top view of the basic structure shown in FIG. Here, for convenience, the position of the intermediate 200 is indicated by a broken line. The force receiving body 300 is a washer-like member having a circular opening H at the center. In the example shown here, the diameter of the opening H coincides with the inner diameter of the detection ring 200. Therefore, in the top view of FIG. 3 (a), the upper surface of the disk-shaped support body 100 is viewed from behind the opening H.

  Further, in the case of the embodiment shown here, the outer diameter of the support body 100 and the outer diameter of the force receiving body 300 are equal to each other. On the other hand, the outer diameter of the detection ring 210 is set to be smaller than the outer diameters of the support body 100 and the force receiving body 300. As will be described later, even if the detection ring 210 is deformed, the support body 100 and the force receiving force are set. It does not protrude outside the outer contour line of the body 300.

  As shown in FIG. 1, the support connection members 221 and 222 and the force receiving connection members 231 and 232 are configured by members that protrude further outward from the outer peripheral surface of the detection ring 210. Moreover, the upper surfaces of the support connection members 221 and 222 are aligned with the upper surface of the detection ring 210, but the lower surface protrudes downward from the lower surface of the detection ring 210 by a predetermined dimension d 1. For this reason, when the lower surfaces of the support connection members 221 and 222 are joined to the upper surface of the support body 100, a gap having a dimension d1 is secured between the detection ring 210 and the support body 100. On the other hand, the lower surfaces of the force receiving connection members 231 and 232 are aligned with the lower surface of the detection ring 210, but the upper surface protrudes upward by a predetermined dimension d 2 from the upper surface of the detection ring 210. For this reason, when the upper surfaces of the force receiving connection members 231 and 232 are joined to the lower surface of the force receiving member 300, a gap of the dimension d2 is secured between the detection ring 210 and the force receiving member 300. In the embodiment shown here, d1 = d2 is set.

  FIG. 3B is a side view of the basic structure shown in FIG. Here, as shown in the figure, the origin O is defined as the center point of the circular detection ring 210 (intermediate position between the upper surface of the support body 100 and the lower surface of the force receiving body 300), and the right direction in the figure is the positive X-axis direction, An XYZ three-dimensional coordinate system is defined with the upward direction as the Z-axis positive direction and the vertical direction in the drawing as the Y-axis positive direction. As shown in the drawing, both ends (left and right ends in the figure) of the detection ring 210 in the direction along the X axis are joined to the upper surface of the support body 100 by support connection members 221 and 222, and along the Y axis of the detection ring 210. Both ends in the above direction are joined to the lower surface of the force receiving body 300 by force receiving connecting members 231 and 232 (the member 231 is located at the back, and does not appear in FIG. 3B).

  As a result, a gap dimension d1 is secured between the detection ring 210 and the lower support body 100, and a gap dimension d2 is secured between the detection ring 210 and the upper force receiving body 300. Each part can be deformed up and down within the range of these gap dimensions d1 and d2.

  4A is a cross-sectional view showing a state in which the basic structure shown in FIG. 3 is cut along the XZ plane, and FIG. 4B is a cross-sectional view showing a state in which the basic structure is cut along the YZ plane. In the cross-sectional view of FIG. 4A, the detection ring 210 is joined to the upper surface of the support body 100 via the support connection members 221 and 222 at both ends in the direction along the X axis, and along the Y axis. A state in which the back end portion is joined to the lower surface of the force receiving body 300 via the force receiving connecting member 231 is shown. Similarly, in the cross-sectional view of FIG. 4B, the detection ring 210 is joined to the lower surface of the force receiving body 300 via the force receiving connecting members 231 and 232 at both ends in the direction along the Y axis. A state in which the back end portion along the X axis is joined to the upper surface of the support body 100 via the force receiving connection member 222 is shown.

  With reference to the perspective views of FIGS. 1 and 2, the top view of FIG. 3 (a), the side view of FIG. 3 (b), and the side cross-sectional views of FIGS. 4 (a) and 4 (b), The specific structure of the basic structure composed of the body 200 and the force receiving body 300 can be easily understood.

  The detection ring 210 needs to be elastically deformed at least partially due to the action of a force or moment to be detected. This is because the force sensor according to the present invention detects the applied force or moment based on the elastic deformation generated in the detection ring 210. Therefore, at least a part of the detection ring 210 needs to be made of a flexible material.

  On the other hand, the support body 100 is a component that plays a role of supporting and fixing the detection ring 210, and the force receiving body 300 is a component that plays a role of applying a force and a moment to the detection ring 210. Alternatively, it may be composed of an elastic body that causes elastic deformation, or may be composed of a rigid body that does not cause elastic deformation. However, in practice, the support body 100 and the force receiving body 300 are preferably formed of a rigid body that does not substantially deform as long as the applied force or moment is within a predetermined allowable range. This is to transmit the acting force or moment to the detection ring 210 as efficiently as possible. For the same reason, it is preferable that the support connection members 221 and 222 and the force receiving connection members 231 and 232 are also constituted by rigid bodies that do not substantially deform as long as the applied force or moment is within a predetermined allowable range.

  In principle, each part of the basic structure can be composed of any material, but considering commercial use, general industrial materials such as metals (eg, aluminum alloys, ferrous metals) and plastics It is preferable to configure using A member made of such a general industrial material usually becomes an elastic body or a rigid body depending on its form. For example, in the case of metal, if it is a block-shaped metal lump, it will behave as a rigid body, but if it is made thin, it will behave as an elastic body. Therefore, even if the support body 100, the intermediate body 200, and the force receiving body 300 are made of the same material, they can perform their respective roles by changing their forms.

  For example, even if the support body 100, the intermediate body 200, and the force receiving body 300 are all made of the same aluminum alloy, the detection ring 210 has a radial width or a Z-axis direction as shown in the perspective view of FIG. By making the thickness of the film small to some extent, it can function as an elastic body that substantially undergoes elastic deformation. On the other hand, the force receiving body 300 can function as a rigid body that does not substantially undergo elastic deformation by increasing the radial width to some extent.

  Of course, when a force or moment is applied to the force receiving body 300, strictly speaking, a slight elastic deformation occurs in the force receiving body 300 itself, but it is slightly less elastic than the elastic deformation generated in the detection ring 210. If it is a deformation, it can be ignored and there is no problem in considering it as a rigid body. Therefore, in the embodiment shown here, the description will be made on the assumption that the support body 100 and the force receiving body 300 are rigid bodies, and elastic deformation due to a force or a moment occurs exclusively in the detection ring 210.

<<< §2. Detection principle of force sensor according to basic embodiment >>
The force sensor according to the present invention has a function of detecting a force or a moment related to at least one axis among a force in each coordinate axis direction and a moment around each coordinate axis in an XYZ three-dimensional orthogonal coordinate system. Therefore, the principle of detection of force and moment by the force sensor having the basic structure described in §1 will be described below.

  First, with reference to FIG. 5, a unique connection position of the detection ring 210 with respect to the support body 100 and the force receiving body 300 will be described. FIG. 5A is a top view of the intermediate body 200 shown in FIG. For reference, the position of the support body 100 (the same applies to the position of the force receiving body 300) is indicated by a broken line. As described above, the support connection members 221 and 222 disposed on the X axis serve to connect the detection ring 210 to the lower support body 100, and the force receiving connection members 231 and 232 disposed on the Y axis are The detection ring 210 is connected to the upper force receiving member 300.

  Therefore, for convenience of explanation, intersections P1 and P2 between the circular path S (annular center line of the detection ring 210) shown in FIG. 5 (a) and the X axis are called fixed points, Intersection points Q1 and Q2 will be referred to as action points. The first fixed point P1 is a point on the X-axis positive region, the second fixed point P2 is a point on the X-axis negative region, the first action point Q1 is a point on the Y-axis positive region, and the second action point Q2 is a point on the Y-axis negative region.

  As described above, when the operation of detecting the force or moment applied to the force receiving body 300 in the state where the support body 100 is fixed, the fixing points P1 and P2 in the detection ring 210 are fixed on the support body 100. The action points Q1 and Q2 in the detection ring 210 function as literally “action points” to which the external force applied to the force receiving body 300 acts. Therefore, the support connection members 221 and 222 function to fix the detection ring 210 to the support body 100 at the positions of the fixing points P1 and P2, and the force receiving connection members 231 and 232 support the detection ring 210 at the operation points Q1 and Q2. In this position, the function of connecting to the force receiving body 300 is achieved.

  FIG. 5 (b) is a top view showing only the detection ring 210 extracted from the intermediate body 200 shown in FIG. 5 (a). As described above, the fixed points P1 and P2 are points on the X axis, and the action points Q1 and Q2 are points on the Y axis. Here, the V axis and the W axis as shown in the figure are further defined, and the intersections R1 to R4 between these axes V and W and the circular path S (annular center line of the detection ring 210) indicated by a two-dot chain line are measured. Let's call it a point.

  Here, the V axis passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is located in the first quadrant of the XY plane, the negative region is located in the third quadrant of the XY plane, and is 45 with respect to the X axis. The W axis passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is located in the second quadrant of the XY plane, the negative region is located in the fourth quadrant of the XY plane, and the V axis Is an axis orthogonal to. Therefore, the first measurement point R1 is a point located in the V-axis positive region, the second measurement point R2 is a point located in the W-axis positive region, and the third measurement point R3 is located in the V-axis negative region. The fourth measurement point R4 is a point located in the W-axis negative region.

  Subsequently, in the state where the support body 100 of the basic structure section described in § 1 is fixed, any external force is applied to the detection ring 210 when a force and a moment in each coordinate axis direction are applied to the force receiving body 300. Let's consider what kind of elastic deformation occurs. In the detection ring 210 shown in FIG. 5 (b), the fixing points P1 and P2 are fixed on the support body 100, and the force or moment applied to the force receiving body 300 acts as an external force on the action points Q1 and Q2. Therefore, the detection ring 210 is elastically deformed according to the direction of the external force acting on the action points Q1 and Q2.

  FIG. 6 is a plan view showing a deformation mode of the detection ring 210 when a force + Fx in the X-axis positive direction is applied to the force receiving body 300 in a state where the support body 100 is fixed. Here, the broken line indicates the state before the deformation (the state in FIG. 5B), and the solid line indicates the state after the deformation. Since the fixed points P1 and P2 are fixed, the fixed positions are maintained, but the action points Q1 and Q2 move to the right in the figure under the action of the force + Fx in the X-axis positive direction. As a result, the portion between the two points P1 and Q1 and the portion between the two points P1 and Q2 of the detection ring 210 are elastically deformed in the direction away from the origin O, and the portion between the two points P2 and Q1 and the two points P2 and P2. The portion between Q2 is elastically deformed in a direction approaching the origin O. If attention is paid to the positions of the measurement points R1 to R4, the measurement points R1 and R4 are displaced outward, and the measurement points R2 and R3 are displaced inward. At this time, no displacement in the Z-axis direction occurs.

  FIG. 7 is a plan view showing a deformation mode of the detection ring 210 when a force + Fy in the Y-axis positive direction is applied to the force receiving body 300 in a state where the support body 100 is fixed. Here, the broken line indicates the state before the deformation (the state in FIG. 5B), and the solid line indicates the state after the deformation. Since the fixed points P1 and P2 are fixed, the fixed positions are maintained, but the action points Q1 and Q2 are moved upward in the figure under the action of the force + Fy in the Y-axis positive direction. As a result, the portion between the two points P1 and Q1 and the portion between the two points P2 and Q1 of the detection ring 210 are elastically deformed in a direction approaching the origin O, and the portion between the two points P1 and Q2 and the two points P2 and P2. The portion between Q2 undergoes elastic deformation in the direction away from the origin O. If attention is paid to the positions of the measurement points R1 to R4, the measurement points R1 and R2 are displaced inward, and the measurement points R3 and R4 are displaced outward. At this time, no displacement in the Z-axis direction occurs.

  FIG. 8 is a side view showing a deformation mode of the detection ring 210 when the force + Fz in the Z-axis positive direction is applied to the force receiving body 300 in a state where the support body 100 is fixed (the right is the X-axis positive direction). Since the fixed points P1 and P2 are fixed, the fixed positions are maintained, but the action points Q1 and Q2 move upward in the figure under the action of the force + Fz in the Z-axis positive direction. As a result, the portion between the two points P1 and Q1 of the detection ring 210, the portion between the two points P2 and Q1, the portion between the two points P1 and Q2, and the portion between the two points P2 and Q2 are pulled upward in the figure. Thus, elastic deformation occurs. If attention is paid to the positions of the measurement points R1 to R4, the measurement points R1 to R4 are all displaced in the positive direction of the Z axis (upward in the figure). At this time, no displacement occurs in the X-axis direction and the Y-axis direction.

  FIG. 9 is a side view showing a deformation mode of the detection ring 210 when a moment + Mx about the positive X-axis is applied to the force receiving member 300 in a state where the support 100 is fixed (the right is the Y-axis positive direction). In the present application, the sign of the moment acting around the predetermined coordinate axis is positive in the direction of rotation of the right screw for advancing the right screw in the positive direction of the coordinate axis. Therefore, the rotational direction of the moment + Mx shown in FIG. 9 is the rotational direction for advancing the right screw in the positive X-axis direction (frontward in the figure).

  Also in this case, since the fixed points P1 and P2 are fixed, the fixed positions are maintained. However, the action point Q1 moves upward and the action point Q2 moves downward in the figure by the action of the moment + Mx. . As a result, the portion between the two points P1 and Q1 and the portion between the two points P2 and Q1 of the detection ring 210 are elastically deformed so as to be pulled upward in the figure, and the portion between the two points P1 and Q2 and the two points The portion between P2 and Q2 undergoes elastic deformation so as to be pulled downward in the figure. If attention is paid to the positions of the respective measurement points R1 to R4, the measurement points R1 and R2 are displaced in the Z-axis positive direction (upward in the figure), and the measurement points R3 and R4 are displaced in the Z-axis negative direction (lower in the figure). . At this time, no displacement occurs in the X-axis direction and the Y-axis direction.

  FIG. 10 is a side view showing a deformation mode of the detection ring 210 when the moment + My about the positive Y-axis is applied to the force receiving member 300 in a state where the support 100 is fixed (the right is the positive X-axis direction). Also in this case, since the fixed points P1 and P2 are fixed, the fixed positions are maintained, but due to the action of the moment + My, an external force that rotates in the clockwise direction in the drawing acts on the action points Q1 and Q2. As a result, the portion between the two points P1 and Q1 and the portion between the two points P1 and Q2 of the detection ring 210 are elastically deformed so as to be pulled downward in the figure, and the portion between the two points P2 and Q1 and the two points The portion between P2 and Q2 undergoes elastic deformation so as to be pulled upward in the figure. If attention is paid to the positions of the measurement points R1 to R4, the measurement points R1 and R4 are displaced in the Z-axis negative direction (downward in the figure), and the measurement points R2 and R3 are displaced in the Z-axis positive direction (upward in the figure). . At this time, no displacement occurs in the X-axis direction and the Y-axis direction.

  FIG. 11 is a plan view showing a deformation mode of the detection ring 210 when a moment + Mz around the positive Z-axis is applied to the force receiving body 300 in a state where the support body 100 is fixed. Here, the broken line indicates the state before the deformation (the state in FIG. 5B), and the solid line indicates the state after the deformation. Since the fixed points P1 and P2 are fixed, the fixed positions are maintained. However, the operating points Q1 and Q2 are affected by a moment + Mz around the positive Z axis and move in the counterclockwise direction in the figure. As a result, the portion between the two points P1 and Q1 and the portion between the two points P2 and Q2 of the detection ring 210 are elastically deformed in the direction approaching the origin O, and the portion between the two points P1 and Q2 and the two points P2 and P2. The portion between Q1 undergoes elastic deformation in the direction away from the origin O. If attention is paid to the positions of the measurement points R1 to R4, the measurement points R1 and R3 are displaced inward, and the measurement points R2 and R4 are displaced outward. At this time, no displacement in the Z-axis direction occurs.

  As described above, with reference to FIGS. 6 to 11, the detection ring when the six-axis components of force + Fx, + Fy, + Fz, moment + Mx, + My, + Mz are applied to the force receiving body 300 with the support body 100 fixed. The elastic deformation mode 210 has been described. From these explanations, it can be seen that each of the detection rings 210 undergoes inherent elastic deformation when the six-axis component is applied. The force sensor according to the present invention detects the above six-axis components separately by electrically detecting the inherent elastic deformation generated in the detection ring 210. The specific method will be described in detail in the next §3.

<<< §3. Detection element and detection circuit of force sensor according to basic embodiment >>
The force sensor according to the present invention is configured by adding a detection element and a detection circuit to the basic structure described in §1. The detection element plays a role of electrically detecting elastic deformation of the detection ring 210, and the detection circuit is based on a detection result of the detection element, and a predetermined force that has acted on the force receiving body 300 in a state where the support body 100 is fixed. It serves to output a detected value of a force in the direction of the coordinate axis or a moment around a predetermined coordinate axis. Here, a specific embodiment of the detection element and the detection circuit will be described.

  The detection element may be any element as long as it can electrically detect elastic deformation of the detection ring 210 as shown in FIGS. However, in practice, it is preferable to use a detection element that can electrically detect the displacement of the measurement points R1 to R4 of the detection ring. More specifically, the distance between the measurement target surface in the vicinity of the measurement points R1 to R4 of the detection ring 210 and the opposing reference surface that is opposed to the measurement target surface and is fixed to the support body 100 or the force receiving body 300 is determined. It is preferable to use an electrically detecting element. Here, an embodiment using a capacitive element as such a detection element will be described.

  FIG. 12 is an exploded perspective view of the basic structure of the force sensor according to the basic embodiment shown in FIG. 1 with a fixed electrode for constituting a capacitive element added thereto. Specifically, in this embodiment, eight fixed electrodes E <b> 1 to E <b> 8 are added to the upper surface of the disk-shaped support body 100. Here, as shown in the drawing, the X axis, Y axis, V axis, and W axis (see FIG. 5B) defined on the XY plane are projected as projection axes obtained by orthogonal projection onto the upper surface of the support 100. The X ′ axis, the Y ′ axis, the V ′ axis, and the W ′ axis are defined respectively. In FIG. 12, these projection axes defined on the upper surface of the support 100 are indicated by a one-dot chain line. Further, in order to clarify the positions of the eight fixed electrodes E1 to E8, an orthogonal projection image of the detection ring 210 is indicated by a broken line on the upper surface of the support 100.

  As shown, the first fixed electrode E1 is disposed in the V′-axis positive region, the second fixed electrode E2 is disposed in the W′-axis positive region, and the third fixed electrode E3 is disposed in the V′-axis negative region. The fourth fixed electrode E4 is arranged in the W′-axis negative region. Here, if a cylinder whose outer diameter is slightly smaller than the inner diameter of the detection ring 210 is arranged on the upper surface of the support body 100 so that its central axis coincides with the Z axis, the four fixed electrodes E1 to E4 are: Both are constituted by a curved conductive member forming a part of the cylinder. Therefore, when the intermediate body 200 is joined to the upper surface of the support body 100, the four fixed electrodes E1 to E4 are all in a state of facing the inner peripheral surface of the detection ring 210.

  On the other hand, as shown in the figure, the fifth fixed electrode E5 is disposed outside the first fixed electrode E1 in the V′-axis positive region, and the sixth fixed electrode E6 is the second fixed electrode E2 in the W′-axis positive region. The seventh fixed electrode E7 is disposed outside the third fixed electrode E3 in the V′-axis negative region, and the eighth fixed electrode E8 is the fourth fixed electrode E4 in the W′-axis negative region. It is arranged outside. Here, the washer-like structure whose outer diameter is slightly smaller than the outer diameter of the detection ring 210 and whose inner diameter is slightly larger than the inner diameter of the detection ring 210 is an upper surface of the support body 100 so that the center axis thereof coincides with the Z axis. If it arrange | positions, all four fixed electrodes E5-E8 are comprised by the circular-arc-shaped electroconductive member which makes a part of the said washer-like structure. Therefore, when the intermediate body 200 is joined to the upper surface of the support body 100, the four fixed electrodes E5 to E8 are all opposed to the lower surface of the detection ring 210.

  FIG. 13 is a top view of the support body 100 shown in FIG. For reference, the position of the detection ring 210 (orthographic projection image of the detection ring 210 on the upper surface of the support 100) is indicated by a broken line. In the top view of FIG. 13, the eight fixed electrodes E1 to E8 are all drawn as arcuate electrodes arranged around the projection point O ′ of the origin O, but the fixed electrodes E1 to E4 and The fixed electrodes E5 to E8 are electrodes having different forms.

  That is, as described above, the fixed electrodes E1 to E4 are configured by a part of a cylinder having an outer diameter slightly smaller than the inner diameter of the detection ring 210 (a part near the intersection between the projection axes V ′ and W ′ and the cylinder). It is a structure like a wall that rises from the upper surface of the support 100 in the direction along the Z axis. On the other hand, the fixed electrodes E <b> 5 to E <b> 8 are arc-shaped thin layers formed on the upper surface of the support 100.

  As described above, the fixed electrodes E1 to E4 and the fixed electrodes E5 to E8 are greatly different in form, but these eight fixed electrodes are all fixed to the upper surface of the support body 100, and are part of the surface of the detection ring 210. It has the common feature that it is arrange | positioned in the position which opposes. And each capacitive element is comprised by each fixed electrode E1-E8 and the opposing part of the surface of the detection ring 210, respectively. When an insulating material such as a resin is used as the support 100, the fixed electrodes E1 to E8 can be directly formed on the upper surface of the support 100. However, when a conductive material such as a metal is used as the support 100, Needs to form an insulating layer between the upper surface of the support 100 and the fixed electrodes E1 to E8 so that the fixed electrodes E1 to E8 do not short-circuit each other.

  FIG. 14 is a plan view showing eight sets of capacitive elements C1 to C8 used as detection elements in the force sensor according to the basic embodiment shown in FIG. FIG. 14 is a plan view showing only the detection ring 210 and eight sets of fixed electrodes E1 to E8 extracted from the force sensor. In the embodiment shown here, the detection ring 210 is made of a conductive material such as a metal, and the surface thereof functions as a common electrode E0. While the eight sets of fixed electrodes E1 to E8 are electrodes fixed on the support body 100, the detection ring 210 is elastically deformed by the action of force or moment. Will be displaced. Therefore, here, an electrode formed on the surface of the detection ring 210 is referred to as a displacement electrode E0.

  When the entire detection ring 210 is made of a conductive material such as metal, the whole functions as one electrode. Here, in order to consider the function as a capacitive element, eight sets of fixed electrodes E1 to E8 are provided. It is assumed that the individual portions facing each other are grasped as separate displacement electrodes, and a total of eight sets of displacement electrodes exist. Eventually, eight sets of capacitive elements C1 to C8 are formed by the eight sets of fixed electrodes E1 to E8 and the eight sets of displacement electrodes E0 opposed thereto.

  Specifically, as shown by bold lines in the figure, the fixed electrodes E1 to E4 become displacement electrodes in which a part of the inner peripheral surface of the detection ring 210 is opposed, and the capacitive elements C1 to C4 are formed by both. On the other hand, with respect to the fixed electrodes E5 to E8 (because they are located below the detection ring 210, they are indicated by broken lines in FIG. 14), the opposing region on the lower surface of the detection ring 210 (in the plan view of FIG. 14, the fixed electrode E5). ˜E8 and the same shape region) are opposed displacement electrodes, and the capacitive elements C5 to C8 are formed by both.

  In general, a capacitive element including a pair of electrodes functions as a detection element that electrically detects a distance between the electrodes. This is because the capacitance value of the capacitive element has a property that is inversely proportional to the distance between the electrodes. Therefore, if the electrostatic capacitance values of the eight capacitive elements C1 to C8 are measured, the distance between the electrodes of the capacitive elements C1 to C8 can be obtained. Here, since one electrode of each of the capacitive elements C1 to C8 is a fixed electrode E1 to E8 that does not cause a displacement, the variation in the capacitance value of the eight capacitive elements C1 to C8 varies with each fixed electrode E1 to E8. The displacement electrode facing E8, that is, the displacement of a specific portion of the detection ring 210 is indicated.

  As shown in FIG. 14, the capacitive elements C1 and C5 are detection elements arranged in the vicinity of the first measurement point R1, and play a role of detecting the displacement of the first measurement point R1. More specifically, the first capacitive element C1 detects the displacement of the first measurement point R1 in the V-axis direction, and the fifth capacitive element C5 detects the displacement of the first measurement point R1 in the Z-axis direction. Detection will be performed. Similarly, the capacitive elements C2 and C6 are detection elements arranged in the vicinity of the second measurement point R2, and play a role of detecting the displacement of the second measurement point R2. More specifically, the second capacitive element C2 detects the displacement of the second measurement point R2 in the W-axis direction, and the sixth capacitive element C6 detects the displacement of the second measurement point R2 in the Z-axis direction. Detection will be performed.

  Capacitance elements C3 and C7 are detection elements arranged in the vicinity of the third measurement point R3, and play a role of detecting the displacement of the third measurement point R3. More specifically, the third capacitive element C3 detects the displacement of the third measurement point R3 in the V-axis direction, and the seventh capacitive element C7 detects the displacement of the third measurement point R3 in the Z-axis direction. Detection will be performed. Similarly, the capacitive elements C4 and C8 are detection elements disposed in the vicinity of the fourth measurement point R4, and play a role of detecting the displacement of the fourth measurement point R4. More specifically, the fourth capacitive element C4 detects the displacement of the fourth measurement point R4 in the W-axis direction, and the eighth capacitive element C8 detects the displacement of the fourth measurement point R4 in the Z-axis direction. Detection will be performed.

  As described above, the capacitive elements C1 to C4 have a function of detecting the displacement in the radial direction of the measurement points R1 to R4 in the detection ring 210. The detection result is the vertical direction of the measurement points R1 to R4. It is not affected by the displacement in the (Z-axis direction). Similarly, the capacitive elements C5 to C8 have a function of detecting displacement in the vertical direction (Z-axis direction) of the measurement points R5 to R8 in the detection ring 210. The detection results are obtained from the measurement points R5 to R8. It is not affected by the radial displacement of R8. The reason is as follows.

  Now, let us consider the capacitance value of a capacitive element composed of a pair of counter electrodes Ea and Eb as shown in FIG. In this example, both the electrodes Ea and Eb are rectangular plate electrodes, but the vertical and horizontal sizes of the electrode Ea are larger than the vertical and horizontal sizes of the electrode Eb. In addition, since both the electrodes Ea and Eb are arranged at positions where their respective center points face each other, a projection image A (orthographic projection image) obtained by projecting the electrode Eb onto the formation surface of the electrode Ea is formed inside the electrode Ea. Is included. In short, the electrode Ea is slightly larger than the electrode Eb.

  In the example shown in FIG. 15, the area inside the projected image A indicated by the broken line is the effective opposing area of this capacitive element, but both electrodes Ea and Eb are displaced in the direction parallel to the electrode surface. However, as long as the projection image A is included in the electrode Ea, the effective opposing area is constant, so that the capacitance value does not change. Therefore, for example, when the electrode Eb is displaced in the direction perpendicular to the electrode surface, the distance between the electrodes changes and the capacitance value changes, but the electrode Eb is displaced in the direction parallel to the electrode surface. In this case, the distance between the electrodes does not change, and as long as the projection image A is included in the electrode Ea, the effective facing area does not change, so the capacitance value does not change.

  Therefore, the capacitive element shown in FIG. 15 has a function of performing displacement detection in the direction perpendicular to the electrode surface of both electrodes Ea and Eb, but the detection result is the electrode surface of both electrodes Ea and Eb. Is not affected by the displacement in the direction parallel to.

  Capacitance elements C5 to C8 in the force sensor shown in FIG. 14 have the same characteristics. That is, since the size of the displacement electrode E0 (the lower surface of the detection ring 210) is larger than the size of the fixed electrodes E5 to E8, the measurement points R1 to R4 are displaced in the radial direction (direction parallel to the XY plane). Even if it occurs, the capacitance value does not change as long as the displacement is within a predetermined allowable range (a range in which the effective facing area is kept constant).

  As described above, the projection image obtained by projecting the fixed electrodes E5 to E8 constituting the capacitive elements C5 to C8 onto the formation surface of the opposing displacement electrode E0 (the lower surface of the detection ring 210) is included in the displacement electrode E0. It has become a relationship. For this reason, although the capacitive elements C5 to C8 have a function of detecting displacement in the vertical direction (Z-axis direction) of the measurement points R1 to R4, the measurement points R1 to R4 are displaced in the radial direction. However, as long as the displacement is within a predetermined allowable range, the displacement in the radial direction is not detected by the capacitive elements C5 to C8. In other words, changes in the capacitance values of the capacitive elements C5 to C8 can be handled exclusively as information indicating the vertical displacement (Z-axis direction) of the measurement points R1 to R4.

  Next, consider the capacitive elements C1 to C4. As shown in the plan view of FIG. 14, the capacitive elements C1 to C4 include fixed electrodes E1 to E4 and a displacement electrode E0 including opposing portions (indicated by bold lines) of the inner peripheral surface of the detection ring 210. , Is an element constituted by. Here, the fixed electrodes E1 to E4 are electrodes extending upward from the upper surface of the support body 100 as shown in the perspective view of FIG. Actually, the height of the fixed electrodes E <b> 1 to E <b> 4 is set so that the upper end protrudes further above the upper surface of the detection ring 210. Therefore, when the intermediate body 200 is joined to the upper surface of the support body 100, the upper ends of the fixed electrodes E1 to E4 protrude beyond the upper surface of the detection ring 210 by a predetermined amount δ.

  With such a configuration, even if the measurement points R1 to R4 of the detection ring 210 are displaced in the vertical direction (Z-axis direction), as long as the displacement amount is within the predetermined amount δ, the fixed electrodes E1 to E1 are used. There is no change in the effective facing area between E4 and the facing electrode E0 (the facing surface of the inner peripheral portion of the detection ring 210).

  After all, if the four portions (part of the inner peripheral surface of the detection ring 210) indicated by bold lines in FIG. 14 are grasped as displacement electrodes facing the fixed electrodes E1 to E4, these displacement electrodes are fixed to face each other. The projection images projected on the electrodes E1 to E4 are in a relationship included in the fixed electrodes E1 to E4, respectively (the fixed electrodes E1 to E4 spread upward and downward). For this reason, the capacitive elements C1 to C4 have a function of detecting displacement in the radial direction of the measurement points R1 to R4, but the measurement points R1 to R4 are displaced in the vertical direction (Z-axis direction). However, as long as the displacement is within a predetermined allowable range, the displacement in the vertical direction is not detected by the capacitive elements C1 to C4. In other words, changes in the capacitance values of the capacitive elements C1 to C4 can be handled exclusively as information indicating the radial displacement of the measurement points R1 to R4.

  FIG. 16 shows the capacity when force in the direction of each coordinate axis and moment about each coordinate axis are applied to the force receiving body 300 with the support 100 of the force sensor shown in FIG. It is a table which shows the change of the electrostatic capacitance value of element C1-C8. In this table, “+” indicates that the capacitance value increases (the distance between both electrodes decreases), and “−” indicates that the capacitance value decreases (the distance between both electrodes increases). “0” indicates that the capacitance value does not vary.

  In addition, the parenthesis written in the “C1 to C8” column of the table indicates a pair of counter electrodes constituting each capacitor element. For example, (E1 & E0) in the C1 column indicates that the capacitive element C1 includes a pair of counter electrodes E1 and E0. Here, the electrode E1 is a fixed electrode, and the electrode E0 (a part of the inner peripheral surface of the detection ring 210 or a part of the lower surface) is a displacement electrode.

  As described above, the change in capacitance value of the capacitive elements C1 to C4 exclusively indicates the radial displacement of the measurement points R1 to R4, and the change in capacitance value of the capacitive elements C5 to C8 is exclusively The displacement in the vertical direction (Z-axis direction) of the measurement points R1 to R4 is indicated. And the aspect of elastic deformation of the detection ring 210 when the six-axis components of force + Fx, + Fy, + Fz, moment + Mx, + My, + Mz are applied to the force receiving body 300 is shown in FIGS. It is as follows. Based on these facts, it can be easily understood that the results shown in the table of FIG. 16 are obtained.

  For example, when the force + Fx is applied, the detection ring 210 is elastically deformed as shown by the solid line in FIG. 6, and the measurement points R1 and R4 are moved away from the origin O along the radial direction. Approaches the origin O along the radial direction. For this reason, the capacitance values of the capacitive elements C1 and C4 decrease, and the capacitance values of the capacitive elements C2 and C3 increase. At this time, since the measurement points R1 to R4 are not displaced in the Z-axis direction, the capacitance values of the capacitive elements C5 to C8 do not change. The result in the column “+ Fx” in the table of FIG. 16 is a result obtained based on such a phenomenon.

  When the force + Fy is applied, the detection ring 210 is elastically deformed as shown by the solid line in FIG. 7, and the measurement points R1, R2 approach the origin O along the radial direction, and the measurement points R3, R4. Moves away from the origin O along the radial direction. For this reason, the capacitance values of the capacitive elements C1 and C2 increase, and the capacitance values of the capacitive elements C3 and C4 decrease. At this time, since the measurement points R1 to R4 are not displaced in the Z-axis direction, the capacitance values of the capacitive elements C5 to C8 do not change. The result in the column “+ Fy” in the table of FIG. 16 is a result obtained based on such a phenomenon.

  When force + Fz is applied, the detection ring 210 is elastically deformed as shown in FIG. 8, and the measurement points R1 to R4 are all displaced upward (Z-axis positive direction). For this reason, the capacitance values of the capacitive elements C5 to C8 decrease. At this time, since the measurement points R1 to R4 are not displaced in the radial direction, the capacitance values of the capacitive elements C1 to C4 do not change. The result in the column “+ Fz” in the table of FIG. 16 is a result obtained based on such a phenomenon.

  On the other hand, when the moment + Mx acts, the detection ring 210 is elastically deformed as shown in FIG. 9, and the measurement points R1 and R2 are displaced upward (Z-axis positive direction), and the measurement points R3 and R4. Is displaced downward (Z-axis negative direction). For this reason, the capacitance values of the capacitive elements C5 and C6 decrease, and the capacitance values of the capacitive elements C7 and C8 increase. At this time, since the measurement points R1 to R4 are not displaced in the radial direction, the capacitance values of the capacitive elements C1 to C4 do not change. The result in the column “+ Mx” in the table of FIG. 16 is a result obtained based on such a phenomenon.

  When the moment + My is applied, the detection ring 210 is elastically deformed as shown in FIG. 10, the measurement points R1, R4 are displaced downward (Z-axis negative direction), and the measurement points R2, R3. Is displaced upward (Z-axis positive direction). For this reason, the capacitance values of the capacitive elements C5 and C8 increase, and the capacitance values of the capacitive elements C6 and C7 decrease. At this time, since the measurement points R1 to R4 are not displaced in the radial direction, the capacitance values of the capacitive elements C1 to C4 do not change. The result in the column “+ My” in the table of FIG. 16 is a result obtained based on such a phenomenon.

  Finally, when the moment + Mz is applied, the detection ring 210 is elastically deformed as shown by the solid line in FIG. 11, and the measurement points R1 and R3 approach the origin O along the radial direction. R4 moves away from the origin O along the radial direction. For this reason, the capacitance values of the capacitive elements C1 and C3 increase, and the capacitance values of the capacitive elements C2 and C4 decrease. At this time, since the measurement points R1 to R4 are not displaced in the Z-axis direction, the capacitance values of the capacitive elements C5 to C8 do not change. The result in the column “+ Mz” in the table of FIG. 16 is a result obtained based on such a phenomenon.

  As shown in the table of FIG. 16, the six-axis component acts on the change pattern of the capacitance values of the eight capacitive elements C1 to C8 (here, for convenience, the capacitance values are also indicated by the same symbols C1 to C8). The amount of variation in the capacitance value increases as the applied force or moment increases. Therefore, if the detection circuit performs a predetermined calculation based on the measured values of the capacitance values C1 to C8, the detection values of the six-axis components can be output independently.

  FIG. 17 is a diagram showing specific arithmetic expressions for obtaining the forces Fx, Fy, Fz in the coordinate axis directions and the moments Mx, My, Mz around the coordinate axes acting on the force sensor shown in FIG. The reason why each detection value can be obtained by such an arithmetic expression can be understood by referring to the table shown in FIG. For example, referring to the + Fx row in the table of FIG. 16, + Fx is detected by the difference between the sum of C2 and C3 marked with “+” and the sum of C1 and C4 marked with “−”. It can be seen that the value is obtained. The same applies to other detection values.

  Further, when negative forces -Fx, -Fy, -Fz and negative moments -Mx, -My, -Mz are applied, "+" and "-" in the table of FIG. 16 are reversed. If the arithmetic expression shown in FIG. 17 is used as it is, each detected value can be obtained as a negative value. The arithmetic expression for the six-axis component shown in FIG. 17 does not receive interference from the other-axis component, so that each detection value for the six-axis component can be obtained independently. For example, when + Fy acts, C1 and C2 increase and C3 and C4 decrease. However, in the calculation formulas for Fx and Mz, these increase and decrease components are canceled with each other. The detected value does not include the Fy component. Similarly, interference does not occur for the other axial components.

  As shown in FIG. 17, the arithmetic expressions other than the force Fz have a format for obtaining a difference with respect to the sum of two sets of capacitance values. In such a difference detection, even if an error occurs in which the basic structure expands or contracts due to a change in the temperature environment and the distance between the counter electrodes fluctuates, the generated error can be canceled mutually. It is preferable for obtaining an accurate detection result that does not contain any. In addition, when it is desired to detect the difference with respect to Fz, a fixed electrode is also added to the lower surface of the force receiving body 300 (for example, in FIG. 12, the XY plane is symmetrical with respect to the fixed electrodes E5 to E8 with respect to the XY plane). An electrode may be formed), and a capacitive element having a displacement electrode on the opposing portion of the upper surface of the detection ring 210 may be formed. Since the capacitive element plays a role of measuring the distance between the measurement points R1 to R4 and the lower surface of the force receiving body 300, the difference between the capacitance values of these capacitive elements and the capacitive values of the capacitive elements C5 to C8 is obtained. Just take it.

  18 is a circuit diagram showing a detection circuit used in the force sensor shown in FIG. This detection circuit is a circuit that outputs detected values of the forces Fx, Fy, Fz and moments Mx, My, Mz as voltage values based on the arithmetic expression shown in FIG. First, the capacitance values C1 to C8 of the eight sets of capacitive elements C1 to C8 are converted into voltage values V1 to V8 by the C / V converters 11 to 18, respectively. Subsequently, addition / subtraction is performed by the addition / subtraction circuits 21 to 26 based on the calculation expressions shown in FIG. 17, and the calculation results are output as detection values of Fx, Fy, Mz, Mx, My, and Fz, respectively.

  Of course, the detection circuit shown in FIG. 18 shows an example, and any circuit may be used as long as the detection result based on the arithmetic expression of FIG. 17 can be output in principle. For example, if a pair of capacitive elements are connected in parallel, the capacitance value of the capacitive element pair after connection is the sum of the capacitance values of the individual capacitive elements. Therefore, in the circuit diagram shown in FIG. If the capacitive elements C2 and C3 are connected in parallel, the capacitance value of the capacitive element pair after the connection is “C2 + C3”, so that the calculation of “V2 + V3” in the adder / subtractor circuit 21 can be omitted.

  FIG. 18 shows a detection circuit using an analog computing unit, but the computation shown in FIG. 17 can of course be performed by digital computation. For example, if an A / D converter is connected to the subsequent stage of the C / V converters 11 to 18, the capacitance values C1 to C8 can be captured as digital values, respectively. The detection value can be output as a digital value by performing the calculation shown in FIG.

  Finally, the characteristics of the detection elements and detection circuits used in the force sensor shown in FIG. 12 can be summarized as follows.

  First, in the force sensor shown in FIG. 12, the detection elements mounted as the capacitive elements C1 to C4 are arranged on the inner measurement target surface (in FIG. 14) in the vicinity of the measurement points R1 to R4 on the inner peripheral surface of the detection ring 210. A thick line portion) is defined, and a fixed structure having an inner facing reference surface facing the inner measurement target surface and fixed to the upper surface of the support 100 is provided. It can be said that the element fulfills the function of electrically detecting the distance. In the case of the example shown in FIG. 12, the fixed electrodes E1 to E4 are fixed structures, and the inner side surfaces are inner facing reference surfaces. Capacitance elements C1 to C4 have a function of detecting the distance between the inner measurement target surface (the thick line portion in FIG. 14) and the inner facing reference surface (the inner surface of the fixed electrodes E1 to E4) as capacitance values C1 to C4. Fulfill.

  In the case of the embodiment shown in FIG. 12, the fixed electrodes E <b> 1 to E <b> 4 that are fixed structures are fixed to the upper surface of the support body 100, but a structure fixed to the lower surface of the force receiving body 300 may be adopted. Absent. In this case, the fixed electrodes E <b> 1 to E <b> 4 have a structure in which upper ends thereof are joined to the lower surface of the force receiving body 300 and extend downward from the lower surface of the force receiving body 300. In this case, the fixed electrodes E <b> 1 to E <b> 4 are displaced with respect to the support body 100, but are fixed to the force receiving body 300 in consideration of relative displacement between the detection ring 210 and the force receiving body 300. It can function as a fixed electrode and can play the same role as the embodiments described so far.

  On the other hand, in the force sensor shown in FIG. 12, when the detection elements mounted as the capacitive elements C5 to C8 define the lower measurement target surface in the vicinity of the measurement points R1 to R4 on the lower surface of the detection ring 210, It can be said that the element has a function of electrically detecting the distance between the lower measurement target surface and the upper surface of the support 100. The capacitive elements C5 to C8 are fixed at a predetermined position on the lower measurement target surface defined as a partial region in the vicinity of the measurement points R1 to R4 on the lower surface of the detection ring 210 and the upper surface of the support body 100 facing the lower measurement target surface. It functions to detect distances from the electrodes E5 to E8 as capacitance values C5 to C8.

  Of course, instead of providing the fixed electrodes E <b> 5 to E <b> 8 on the upper surface of the support body 100, the fixed electrodes E <b> 5 to E <b> 8 may be provided on the lower surface of the force receiving body 300 (symmetrical position when the XY plane is a symmetric plane). In this case, the capacitive elements C5 to C8 are fixed electrodes E5 to E8 provided on the lower surface of the force receiving member 300, and upper measurement target surfaces defined as partial regions in the vicinity of the measurement points R1 to R4 on the upper surface of the detection ring 210. That is, it is a capacitive element constituted by. When the fixed electrodes E5 to E8 are provided on the lower surface of the force receiving body 300, the fixed electrodes E5 to E8 are displaced with respect to the support body 100. However, the relative displacement between the detection ring 210 and the force receiving body 300 is also performed. , It can function as a fixed electrode fixed to the force receiving body 300, and can play a role equivalent to the embodiments described so far.

  In short, when a capacitive element is used as a detection element for detecting the displacement of each of the measurement points R1 to R4, the displacement electrode provided on the measurement target surface on the detection ring 210 side and the support 100 side or the receiving surface facing the displacement electrode. A capacitive element may be configured by the fixed electrode provided on the opposing reference surface on the force body 300 side.

  In particular, in the case of the embodiments described so far, since the detection ring 210 is made of a conductive material having flexibility, the surface of the detection ring 210 can be used as the common displacement electrode E0, thereby simplifying the structure. be able to. For example, in the embodiment shown in FIG. 12, it is necessary to provide eight sets of independent fixed electrodes E1 to E8 on the upper surface side of the support body 100. There is no need to provide a displacement electrode. This is because the surface of the detection ring 210 serves as a common electrode layer, and the opposing portions of the fixed electrodes E1 to E8 on the surface of the detection ring 210 function as individual displacement electrodes of the capacitive elements C1 to C8. It is.

  Of course, when the detection ring 210 is made of an insulating material such as a resin, an individual displacement electrode may be provided on the surface of the detection ring 210 facing each of the fixed electrodes E1 to E8. In this case, as described with reference to FIG. 15, the projection image obtained by projecting one electrode constituting each of the capacitive elements C1 to C8 onto the formation surface of the other electrode is included in the other electrode. Is maintained, the change in the capacitance value of the capacitive elements C1 to C4 exclusively indicates the displacement in the radial direction of the measurement points R1 to R4, and the capacitance value of the capacitive elements C5 to C8. The change exclusively indicates the displacement in the vertical direction (Z-axis direction) of the measurement points R1 to R4, so that more accurate detection can be performed.

After all, in the embodiment shown in FIG. 12, the detection ring 210 is a circular ring arranged on a predetermined arrangement plane (in this example, the XY plane) above the support 100 so that the Z axis becomes the central axis. As shown in FIG. 14, the following eight sets of capacitive elements are provided as detection elements.
(1) First displacement electrode (region near the intersection with the V-axis positive region on the inner peripheral surface of the detection ring 210: thick line in the figure) disposed near the first measurement point R1 on the inner peripheral surface of the detection ring 210 Portion) and a first fixed electrode E1 disposed at a position facing the first displacement electrode inside the detection ring 210 and fixed to the upper surface of the support 100. C1.
(2) Second displacement electrode disposed in the vicinity of the second measurement point R2 on the inner peripheral surface of the detection ring 210 (region near the intersection with the W-axis positive region on the inner peripheral surface of the detection ring 210: bold line in the figure) Portion) and a second fixed electrode E2 disposed at a position facing the second displacement electrode inside the detection ring 210 and fixed to the upper surface of the support 100. C2.
(3) Third displacement electrode (region near the intersection with the V-axis negative region on the inner peripheral surface of the detection ring 210: thick line in the figure) disposed at a position near the third measurement point R3 on the inner peripheral surface of the detection ring 210 Portion) and a third fixed electrode E3 disposed at a position facing the third displacement electrode inside the detection ring 210 and fixed to the upper surface of the support 100. C3.
(4) Fourth displacement electrode (region near the intersection with the W-axis negative region on the inner peripheral surface of the detection ring 210: thick line in the figure) disposed in the vicinity of the fourth measurement point R4 on the inner peripheral surface of the detection ring 210 Portion) and a fourth fixed element E4 arranged at a position facing the fourth displacement electrode inside the detection ring 210 and fixed to the upper surface of the support 100. C4.
(5) a fifth displacement electrode (a region located below the measurement point R1 on the lower surface of the detection ring 210) disposed on the lower surface of the detection ring 210 in the vicinity of the first measurement point R1; A fifth capacitive element C5 constituted by a fifth fixed electrode E5 disposed at a position facing the fifth displacement electrode.
(6) A sixth displacement electrode (a region located below the measurement point R2 on the lower surface of the detection ring 210) disposed in the vicinity of the second measurement point R2 on the lower surface of the detection ring 210, and the upper surface of the support body 100 A sixth capacitive element C6 constituted by a sixth fixed electrode E6 disposed at a position facing the sixth displacement electrode.
(7) a seventh displacement electrode (a region located below the measurement point R3 on the lower surface of the detection ring 210) disposed on the lower surface of the detection ring 210 in the vicinity of the third measurement point R3; A seventh capacitive element C7 including a seventh fixed electrode E7 disposed at a position facing the seventh displacement electrode.
(8) An eighth displacement electrode (a region located below the measurement point R4 on the lower surface of the detection ring 210) disposed on the lower surface of the detection ring 210 in the vicinity of the fourth measurement point R4, and the upper surface of the support body 100. An eighth capacitive element C8 constituted by the eighth fixed electrode E8 disposed at a position facing the eighth displacement electrode.

  Here, the projection image obtained by projecting one electrode constituting each of the capacitive elements C1 to C8 onto the formation surface of the other electrode is included in the other electrode, and the displacement of the detection ring 210 is reduced. As long as it is within a predetermined allowable range, the effective facing area of each capacitive element is kept constant. For this reason, as described above, the change in the capacitance value of the capacitive elements C1 to C4 exclusively indicates the radial displacement of the measurement points R1 to R4, and the change in the capacitance value of the capacitive elements C5 to C8 is Only the displacement of the measurement points R1 to R4 in the vertical direction (Z-axis direction) is indicated, and accurate detection becomes possible. In practice, since the detection ring 210 is made of a conductive material having flexibility, the surface of the detection ring 210 functions as a common electrode, and displacements that constitute the capacitive elements C1 to C8. Each of the electrodes is constituted by a partial region on the surface of the detection ring 210.

On the other hand, the detection circuit of this force sensor has a capacitance value of the first capacitive element C1, a capacitance value of the second capacitive element C2, a capacitance value of the third capacitive element C3, The capacitance value of the fourth capacitive element is C4, the capacitance value of the fifth capacitive element is C5, the capacitance value of the sixth capacitive element is C6, and the capacitance value of the seventh capacitive element is When the capacitance value of C7 and the eighth capacitive element is C8, as shown in FIG.
Fx = −C1 + C2 + C3-C4
Fy = + C1 + C2-C3-C4
Fz = -C5-C6-C7-C8
Mx = -C5-C6 + C7 + C8
My = + C5-C6-C7 + C8
Mz = + C1-C2 + C3-C4
Based on the following formula, the detection of the force Fx in the X-axis direction, the force Fy in the Y-axis direction, the force Fz in the Z-axis direction, the moment Mx around the X-axis, the moment My around the Y-axis, and the moment Mz around the Z-axis Serves to output values. A specific example of the detection circuit is as shown in the circuit diagram of FIG.

  As shown in the circuit diagram of FIG. 18, it is necessary to provide wiring between the eight capacitive elements C1 to C8 and the detection circuit. In the case of the force sensor according to the present invention, as shown in FIG. 12, a sufficient space can be secured inside the detection ring 210. Therefore, the wiring for the electrodes constituting each capacitive element is made using this internal space. Is possible. In particular, in the case of the embodiment shown in FIG. 12, since the opening H is formed in the force receiving body 300, the wiring can be led out of the force sensor through the opening H. Of course, if necessary, the detection circuit shown in FIG. 18 can be configured as a semiconductor integrated circuit and accommodated in the internal space of the detection ring 210.

<<< §4. Modification of the present invention >>
As described above, in §1 to §3, the structure and operation of the force sensor according to the basic embodiment of the present invention have been described. Here, some modifications to the basic embodiment will be described.

<4-1. Modified example of intermediate>
First, the modification regarding the intermediate body 200 is described. FIG. 19 is a perspective view showing a modification of the intermediate body 200 used in the basic embodiment shown in FIG. The intermediate body 200A according to this modification includes a detection ring 210A, support connection members 221A and 222A, and force receiving connection members 231A and 232A. The basic form and function of each of these components are substantially the same as the detection ring 210, the support connection members 221, 222, and the force receiving connection members 231, 232 of the intermediate body 200 according to the basic embodiment described so far. .

  However, as can be seen by comparing the intermediate body 200 shown in FIG. 1 with the intermediate body 200A shown in FIG. 19, the latter detection ring 210A has a thickness in the height direction (thickness in the Z-axis direction) compared to the former detection ring 210. Is set smaller, and the latter detection ring 210 </ b> A is more easily bent than the former detection ring 210 even when the same material is used. Therefore, the detection sensitivity of the force sensor using the detection ring 210A is higher than that of the force sensor using the detection ring 210.

  In short, when a force sensor with higher accuracy is required, a detection ring 200A having a small thickness in the height direction as shown in the modification of FIG. 19 is used, and a force sensor with a larger rated load is required. For this purpose, a detection ring 200 having a large thickness in the height direction as shown in the basic embodiment of FIG. 1 may be used.

  Regarding the basic principle of detection, there is no difference between a force sensor using the intermediate body 200 shown in FIG. 1 and a force sensor using the intermediate body 200A shown in FIG. That is, in the intermediate body 200A shown in FIG. 19, the lower surfaces of the support connection members 221A and 222A arranged on the X axis protrude downward from the lower surfaces of the force receiving connection members 231A and 232A arranged on the Y axis. Therefore, a predetermined gap is secured between the lower surfaces of the force receiving connection members 231A and 232A and the upper surface of the support body 100. Similarly, since the upper surfaces of the force receiving connection members 231A and 232A arranged on the Y axis protrude above the upper surfaces of the support connection members 221A and 222A arranged on the X axis, the support connection members 221A and 222A. A predetermined gap is secured between the upper surface of the power receiving member 300 and the lower surface of the force receiving member 300.

  20 is a side view of a basic structure configured using an intermediate body 200A according to a modified example shown in FIG. 19 instead of the intermediate body 200 in the basic embodiment shown in FIG. It is sectional drawing which shows the state which cut | disconnected the said basic structure part by XZ plane. As can be seen by comparing FIGS. 20 and 21 with FIGS. 3B and 4, the only difference is the thickness of the detection ring in the Z-axis direction, and there is no fundamental difference in the operating principle. Since the detection ring 210 </ b> A has a small thickness in the Z-axis direction, the detection ring 210 </ b> A is likely to be bent, and the detection sensitivity can be increased. In addition, since the distance between the lower surface of the detection ring 210A and the upper surface of the support body 100 and the distance between the upper surface of the detection ring 210A and the lower surface of the force receiving body 300 can be ensured, the amount of displacement at the measurement points R1 to R4 is increased. In this respect, the effect of increasing the detection sensitivity can be obtained.

  On the other hand, FIG. 22 is a perspective view showing another modified example of the intermediate body 200 used in the basic embodiment shown in FIG. A feature of the intermediate body 200B according to this modification is that it has a structure in which two detection rings, an upper detection ring 211B and a lower detection ring 212B, are arranged in two upper and lower stages. That is, the intermediate body 200B according to this modified example includes the upper detection ring 211B, the lower detection ring 212B, the support connection members 221B and 222B, and the force receiving connection members 231B and 232B.

  Here, the support connection members 221B and 222B serve to support both the upper detection ring 211B and the lower detection ring 212B at the X axis positive direction end and the X axis negative direction end and connect to the upper surface of the support body 100, The force receiving connection members 231 </ b> B and 232 </ b> B support both the upper detection ring 211 </ b> B and the lower detection ring 212 </ b> B at the Y axis positive direction end and the Y axis negative direction end, and serve to connect to the lower surface of the force receiving body 200.

  Also in the intermediate body 200B shown in FIG. 22, the lower surfaces of the support connection members 221B and 222B arranged on the X axis protrude downward from the lower surfaces of the force receiving connection members 231B and 232B arranged on the Y axis. Therefore, a predetermined gap is secured between the lower surfaces of the force receiving connection members 231B and 232B and the lower detection ring 212B and the upper surface of the support body 100. Similarly, the upper surfaces of the force receiving connection members 231B and 232B arranged on the Y axis protrude upward from the upper surfaces of the support connection members 221B and 222B arranged on the X axis, and thus the support connection members 221B and 222B. A predetermined gap is secured between the upper surface of the upper detection ring 211B and the lower surface of the force receiving member 300.

  FIG. 23 is a side view of a basic structure configured using an intermediate body 200B according to a modified example shown in FIG. 22 instead of the intermediate body 200 in the basic embodiment shown in FIG. It is sectional drawing which shows the state which cut | disconnected the said basic structure part by XZ plane. For comparison with the above-described modification using the intermediate 200A, when comparing the structure shown in FIGS. 20 and 21 with the structure shown in FIGS. 23 and 24, only the single detection ring 210A is used in the former. On the other hand, in the latter, it can be seen that a major difference is that two sets of detection rings, that is, an upper detection ring 211B and a lower detection ring 212B are used.

  In the case of the structure shown in FIGS. 20 and 21, the detection ring 210A is arranged on the XY plane. However, in the case of the structure shown in FIGS. 23 and 24, the arrangement positions of the two detection rings are both XY plane. Not above. That is, the upper detection ring 211B is arranged at a position slightly shifted from the XY plane, and the lower detection ring 212B is arranged at a position slightly shifted from the XY plane. In the present invention, even if the arrangement positions of the detection rings 211B and 212B are deviated from the XY plane in this way, the basic detection principle is not affected.

  The detection ring used in the present invention is arranged on a predetermined arrangement plane (which may be the XY plane) parallel to the XY plane so that the Z axis is the central axis, and the action of the force or moment to be detected It is sufficient if at least a part causes elastic deformation. In the case of the structure shown in FIGS. 23 and 24, the upper detection ring 211B is located above the XY plane and is arranged on an arrangement plane parallel to the XY plane, and the lower detection ring 212B is below the XY plane. It is located and arranged on an arrangement plane parallel to the XY plane. Accordingly, both the upper detection ring 211B and the lower detection ring 212B can perform the same function as the detection ring 210 according to the basic embodiment described so far.

  Here, measurement points R1 to R4 are defined for each of the two detection rings 211B and 212B. Specifically, for the upper detection ring 211B, measurement points R1 to R4 are defined at positions corresponding to the measurement points R1 to R4 on the detection ring 210 shown in FIG. Similarly, measurement points R1 to R4 are defined at positions corresponding to the measurement points R1 to R4 on the detection ring 210 shown in FIG.

  Since the connection form of the upper detection ring 211B and the lower detection ring 212B by the support connection members 221B and 222B and the force reception connection members 231B and 232B is exactly the same, the force + Fx, + Fy is applied to the force reception body 300 in a state where the support body 100 is fixed. , + Fz, moments + Mx, + My, and + Mz, the form of elastic deformation that occurs in the upper detection ring 211B is exactly the same as the form of elastic deformation that occurs in the lower detection ring 212B. Therefore, the displacement mode of the four measurement points R1 to R4 defined in the upper detection ring 211B is completely equivalent to the displacement mode of the four measurement points R1 to R4 defined in the lower detection ring 212B. The deformation | transformation operation | movement of the detection rings 211B and 212B becomes what was synchronized.

  Also in the modification using the intermediate body 200B shown in FIG. 22 as the intermediate body 200, the configuration of the fixed electrodes E1 to E8 for configuring the detection element is the same as the configuration of the basic embodiment shown in FIG. It doesn't matter. In the configuration shown in FIG. 12, when the intermediate body 200 is replaced with the intermediate body 200B shown in FIG. 22, the four fixed electrodes E1 to E4 are connected to the inner peripheral surface of the upper detection ring 211B and the inner peripheral surface of the lower detection ring 212B. However, there is no change in that the four capacitive elements C1 to C4 are formed by the electrodes facing each other.

  That is, a capacitive element constituted by a region in the vicinity of the V-axis positive region on the inner peripheral surface of the upper detection ring 211B and the opposing region of the fixed electrode E1 facing this is referred to as a first upper capacitive element C1 (upper). A capacitive element defined by a region near the V-axis positive region on the inner peripheral surface of the lower detection ring 212B and the opposing region of the fixed electrode E1 facing this is defined as a first lower capacitive element C1 (lower) In this case, the first capacitive element C1 is a capacitive element in which a first upper capacitive element C1 (upper) and a first lower capacitive element C1 (lower) are connected in parallel. The value indicates the radial displacement of each measurement point R1.

  Further, a capacitive element constituted by a region near the W-axis positive region on the inner peripheral surface of the upper detection ring 211B and a facing region of the fixed electrode E2 facing this is referred to as a second upper capacitive element C2 (upper). A capacitive element defined by a region near the W-axis positive region on the inner peripheral surface of the lower detection ring 212B and a region facing the fixed electrode E2 facing the second lower capacitive element C2 (lower) In this case, the second capacitive element C2 is a capacitive element in which a second upper capacitive element C2 (upper) and a second lower capacitive element C2 (lower) are connected in parallel. The value indicates the radial displacement of each measurement point R2.

  A capacitive element constituted by a region in the vicinity of the V-axis negative region on the inner peripheral surface of the upper detection ring 211B and a facing region of the fixed electrode E3 facing this is referred to as a third upper capacitive element C3 (upper). A capacitive element defined by a region near the V-axis negative region on the inner peripheral surface of the lower detection ring 212B and the opposing region of the fixed electrode E3 facing the third negative capacitive element C3 (lower) The third capacitive element C3 is a capacitive element in which a third upper capacitive element C3 (upper) and a third lower capacitive element C3 (lower) are connected in parallel. The value indicates the radial displacement of each measurement point R3.

  Finally, a capacitive element constituted by a region near the W-axis negative region on the inner circumferential surface of the upper detection ring 211B and a region facing the fixed electrode E4 facing the fourth upper capacitive device C4 (upper) And a capacitive element constituted by a region near the W-axis negative region on the inner peripheral surface of the lower detection ring 212B and a region facing the fixed electrode E4 facing the fourth lower capacitive element C4 (lower ) Is defined as a capacitive element in which a fourth upper capacitive element C4 (upper) and a fourth lower capacitive element C4 (lower) are connected in parallel. The capacitance value indicates the radial displacement of each measurement point R4.

  On the other hand, in the configuration shown in FIG. 12, when the intermediate body 200 is replaced with the intermediate body 200B shown in FIG. 22, the four fixed electrodes E5 to E8 face the lower surface of the lower detection ring 212B. The four capacitive elements C5 to C8 are formed by the opposing electrodes, and the capacitance value indicates the displacement in the Z-axis direction of the measurement points R1 to R4 on the lower detection ring 212B side. Become. In this case, the displacement in the Z-axis direction of the measurement points R1 to R4 on the upper detection ring 211B side is not detected, but there is no problem in detecting the six-axis components of force + Fx, + Fy, + Fz, moment + Mx, + My, + Mz. Does not occur.

  Of course, the displacement in the Z-axis direction of the measurement points R1 to R4 on the upper detection ring 211B side is also detected, and the displacement in the Z-axis direction of the measurement points R1 to R4 on the lower detection ring 212B side and the measurement on the upper detection ring 211B side are detected. If both the displacements in the Z-axis direction of the points R1 to R4 (for example, using the average value of both) are used to detect the force and moment to be detected, the detection accuracy is further improved. It is possible. In that case, four electrodes are provided on the lower surface of the force receiving body 300 at positions corresponding to the fixed electrodes E5 to E8 (symmetric positions when the XY plane is a symmetric plane), and these electrodes and the upper detection are provided. Four sets of capacitive elements are formed by the opposing surfaces of the ring 211B, and displacements in the Z-axis direction of the measurement points R1 to R4 on the upper detection ring 211B side are detected based on the capacitance values of the four sets of capacitive elements. You just have to do it.

<4-2. Features of Modification Using Multiple Detection Rings>
In §4-1, as shown in FIG. 22, the modification using the intermediate body 200B having a structure in which two detection rings of the upper detection ring 211B and the lower detection ring 212B are arranged in two upper and lower stages is described. It is also possible to use an intermediate having a structure in which three or more sets of detection rings are arranged vertically.

  In general, the structure of the modified example using a plurality of detection rings includes a plurality of m (m ≧ 2) detection rings arranged adjacent to each other in the Z-axis direction at a predetermined interval. Each detection ring is arranged on an individual arrangement plane parallel to the XY plane so that the Z axis is the central axis, and the support 100 is arranged further below the lowest detection ring. The force receiving body 300 can be said to be a structure arranged further above the detection ring located at the uppermost position. As in the embodiment shown in FIG. 22, the fixed points P <b> 1 and P <b> 2 of the individual detection rings (upper detection ring 211 </ b> B and lower detection ring 212 </ b> B because m = 2 in the embodiment of FIG. 22) are It is fixed to the support body 100 by the support connection members 221B and 222B, and the action points Q1 and Q2 of the individual detection rings are fixed to the force reception body 300 by the force reception connection members 231B and 232B.

  In practice, each of the plurality of m detection rings is a circular ring of the same shape and the same size arranged on each arrangement plane so that the Z axis is the central axis, and the fixing point P1 of each detection ring , P2 (in the case of FIG. 22, the positions supported by the support connection members 221B, 222B) and the positions of the action points Q1, Q2 (in the case of the example in FIG. 22, supported by the force receiving connection members 231B, 232B) It is preferable that the positions are set to the same position in a plane. In other words, the projected images of the fixed points P1 and P2 and the action points Q1 and Q2 of the individual detection rings on the XY plane may overlap each other. For example, FIG. 22 illustrates a fixed point P1 of the upper detection ring 211B and a fixed point P1 of the lower detection ring 212B. The projection images of the pair of fixed points P1 on the XY plane overlap each other.

  If such a structure is adopted, the support connecting member connects the vicinity of each fixing point of different detection rings, which form a projected image at the same position on the XY plane, and is fixed to the support 100. Since the force receiving connection member can connect the vicinity of each action point of different detection rings, which form a projected image at the same position on the XY plane, to each other and be fixed to the force receiving body 300, The structure of the support connection member and the force receiving connection member can be simplified.

  For example, in the case of the example shown in FIG. 22, the support connection member 221B is configured such that the fixed point P1 of the upper detection ring 211B and the fixed point P1 of the lower detection ring 212B (both projected images on the XY plane are on the X-axis positive region. The points near the same position) are connected to each other and fixed to the support 100, and the support connecting member 222B is fixed to the fixed point P2 of the upper detection ring 211B and the fixed point P2 of the lower detection ring 212B ( Although not shown in FIG. 22, in both cases, the vicinity of the point at which the projected image on the XY plane is at the same position on the X-axis negative region is connected to each other and fixed to the support 100. Yes.

  Similarly, in the case of the example shown in FIG. 22, the force receiving connection member 231 </ b> B includes the action point Q <b> 1 of the upper detection ring 211 </ b> B and the action point Q <b> 1 of the lower detection ring 212 </ b> B. The projection image onto the plane plays a role of connecting to each other and fixing to the force receiving body 300 in the vicinity of the point where the projected image on the Y-axis positive region is at the same position, and the force receiving connection member 232B is an upper detection ring 211B. Near the action point Q2 and the action point Q2 of the lower detection ring 212B (although not shown in FIG. 22, the projection image on the XY plane is at the same position on the Y-axis negative region) It plays a role of connecting to each other and fixing to the force receiving body 300. For this reason, the structure of the support connection members 221B and 222B and the force receiving connection members 231B and 232B in the embodiment shown in FIG. 22 is the same as that of the support connection members 221A and 222A and the force receiving connection members 231A and 232A in the embodiment shown in FIG. Like the structure, it becomes very simple.

  In short, even in a modification using a plurality of m detection rings, the positions of the fixed points P1 and P2 and the action points Q1 and Q2 may be determined in the same manner as in the basic embodiment using one detection ring. . Specifically, the fixed points P1 and P2 and the action points Q1 and Q2 may be set at the positions shown in FIG.

  Similarly to the basic embodiment using one detection ring, the positions of the measurement points R1 to R4 are four sets of measurement points R1 at the positions shown in FIG. 5 (b) for each detection ring. ~ R4 may be set. That is, even in the modification using a plurality of m detection rings, the positive region passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is the first quadrant of the XY plane, and the negative region is the third quadrant of the XY plane. Passing through the V axis that is 45 ° to the X axis and the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive area is the second quadrant of the XY plane, and the negative area is the fourth quadrant of the XY plane And a W-axis orthogonal to the V-axis. For each of the individual detection rings, a first measurement point R1 is defined as a point where the projection image on the XY plane is located on the V-axis positive region. , The second measurement point R2 is set as a point where the projection image on the XY plane is located on the W-axis positive region, and the third measurement point is set as a point where the projection image on the XY plane is located on the V-axis negative region. The fourth measurement point R3 is set, and the fourth projected point on the XY plane is located on the W-axis negative region. The measurement point R4 may be set.

  In particular, a force sensor according to a modified example in which m = 2 is adopted, that is, a modified example employing the intermediate 200B shown in FIG. 22 instead of the intermediate 200 in the basic embodiment shown in FIG. It has the following structural features.

  First, the detection ring is provided with an upper detection ring 211B and a lower detection ring 212B that are arranged adjacent to each other in the Z-axis direction at a predetermined interval, and the two detection rings 211B and 212B are either Also, it is a circular ring of the same shape and the same size arranged on each arrangement plane parallel to the XY plane so that the Z axis becomes the central axis.

  Moreover, as described above, the projection image of the first fixed point P1 of the upper detection ring 211B on the XY plane and the projection image of the first fixed point P1 of the lower detection ring 212B on the XY plane overlap each other. The projection image of the second fixed point P2 of the upper detection ring 211B on the XY plane and the projection image of the second fixed point P2 of the lower detection ring 212B on the XY plane overlap each other, and the first detection point of the upper detection ring 211B. The projected image of the first operating point Q1 on the XY plane and the projected image of the first operating point Q1 of the lower detection ring 212B on the XY plane overlap each other, and the second operating point Q2 of the upper detection ring 211B The projection image on the XY plane and the projection image on the XY plane of the second action point Q2 of the lower detection ring 212B overlap each other.

  In addition, the first support connection member 221B connects the vicinity of the first fixed point P1 of the upper detection ring 211B and the vicinity of the first fixed point P1 of the lower detection ring 212B to each other, and also supports the support body 100. The second support connection member 222B connects the vicinity of the second fixed point P2 of the upper detection ring 211B and the vicinity of the second fixed point P2 of the lower detection ring 212B to each other, Also connected to the support 100, the first force receiving connection member 231B connects the vicinity of the first action point Q1 of the upper detection ring 211B and the vicinity of the first action point Q1 of the lower detection ring 212B to each other. At the same time, it is also connected to the force receiving body 300, and the second force receiving connection member 232B allows the vicinity of the second action point Q2 of the upper detection ring 211B and the first of the lower detection ring 212B. With the vicinity they are mutually connected in the point Q2, and is also connected to the force receiving member 300.

  On the other hand, the fixed electrodes E1 to E8 used as detection elements in the force sensor according to this modification are fixed electrodes E1 to E8 used in the basic embodiment shown in FIG. 12 as described in §4-1. Can be used as is. In this case, the displacement electrodes corresponding to the fixed electrodes E1 to E8 are electrodes configured at the following positions. However, if the upper detection ring 211B and the lower detection ring 212B are made of a conductive material, each displacement electrode is actually constituted by a region of a part of the surface of the upper detection ring 211B or the lower detection ring 212B. become.

  The first displacement electrode has two positions: a position near the first measurement point R1 on the inner peripheral surface of the upper detection ring 211B and a position near the first measurement point R1 on the inner peripheral surface of the lower detection ring 212B. The first fixed electrode E1 is an electrode opposed to both of the displacement electrodes arranged in the two locations. The second displacement electrode has two positions: a position near the second measurement point R2 on the inner peripheral surface of the upper detection ring 211B and a position near the second measurement point R2 on the inner peripheral surface of the lower detection ring 212B. The second fixed electrode E2 is an electrode that faces both of the displacement electrodes that are dispersed and arranged at the two locations. The third displacement electrode has two positions: a position near the third measurement point R3 on the inner peripheral surface of the upper detection ring 211B and a position near the third measurement point R3 on the inner peripheral surface of the lower detection ring 212B. The third fixed electrode E3 is an electrode that faces both of the displacement electrodes that are dispersed and arranged at the two locations. The fourth displacement electrode has two positions: a position near the fourth measurement point R4 on the inner peripheral surface of the upper detection ring 211B and a position near the fourth measurement point R4 on the inner peripheral surface of the lower detection ring 212B. The fourth fixed electrode E4 is disposed in a distributed manner at the positions, and is an electrode facing both of the displacement electrodes disposed at the two positions.

  The fifth displacement electrode is disposed in the vicinity of the first measurement point R1 on the lower surface of the lower detection ring 212B, and the fifth fixed electrode E5 is an electrode facing the fifth displacement electrode. The sixth displacement electrode is disposed in the vicinity of the second measurement point R2 on the lower surface of the lower detection ring 212B, and the sixth fixed electrode E6 is an electrode facing the sixth displacement electrode. The seventh displacement electrode is arranged in the vicinity of the third measurement point R3 on the lower surface of the lower detection ring 212B, and the seventh fixed electrode E7 is an electrode facing the seventh displacement electrode. The eighth displacement electrode is arranged in the vicinity of the fourth measurement point R4 on the lower surface of the lower detection ring 212B, and the eighth fixed electrode E8 is an electrode opposed to the eighth displacement electrode.

<4-3. Advantages of Modification Using Multiple Detection Rings>
Here, the merit of configuring a force sensor using a plurality of detection rings will be described. Up to now, as the form of the intermediate body, an intermediate body 200 using one thick detection ring 210 as shown in FIG. 1 and an intermediate body 200A using one thin detection ring 210A as shown in FIG. An intermediate 200B using two thin detection rings 210B as shown in FIG. 22 is illustrated. In general, when the thickness in the height direction and the thickness in the radial direction of the detection ring are changed, the ease of elastic deformation changes even with the same material, so the detection sensitivity as a force sensor changes.

  Therefore, as described in §4-1, when a highly accurate force sensor is required, a detection ring 200A having a small thickness as in the example shown in FIG. 19 is used, and a force sensor having a large rated load is required. In such a case, a detection ring 200 having a large thickness may be used as in the example shown in FIG. Similarly, the number of detection rings is a factor that affects detection sensitivity as a force sensor. Therefore, the designer can adjust the precision and load rating of the force sensor to be designed by changing the number of detection rings.

  However, in the case of a force sensor having a function of detecting both force and moment, the inventor of the present application determines the number of detection rings to adjust the balance between force detection sensitivity and moment detection sensitivity. I found out that it would be an important factor.

  Generally, when the thickness of each part of the detection ring is changed, the ease of elastic deformation as a whole changes. For example, when the thickness is reduced and the elastic deformation is facilitated, the detection sensitivity of both force and moment increases, and when the thickness is increased and the elastic deformation is difficult, the detection sensitivity of both force and moment decreases. In addition, if the number of detection rings of the same size is increased, the intermediate body as a whole becomes less likely to elastically deform (because external forces are distributed to the individual detection rings), so the detection sensitivity of both force and moment is both Decrease.

  However, according to an experiment conducted by the inventor of the present application, it was found that the degree of decrease in detection sensitivity when the number of detection rings is increased is different between force and moment. Based on this experimental result, it can be seen that the number of detection rings is very effective as a factor for adjusting the balance between the force detection sensitivity and the moment detection sensitivity. Therefore, the modification using a plurality of detection rings has a unique merit of facilitating the design in which the balance between the force detection sensitivity and the moment detection sensitivity is adjusted.

  In the case of the force sensor according to the basic embodiment described in §3, six-axis components of force + Fx, + Fy, + Fz, moment + Mx, + My, + Mz can be detected. Here, the detection sensitivities of the forces + Fx, + Fy, and + Fz are almost the same, but there is a considerable difference between the detection sensitivities for these forces and the detection sensitivities of the moments + Mx, + My, and + Mz. In practice, some correction is preferably performed.

  However, since force and moment are different physical quantities in the first place, the values of both cannot be directly compared. That is, the force is a physical quantity expressed in the unit “N (Newton)”, whereas the moment is a physical quantity (torque) expressed in the unit “N · m”. It is defined as the product of “distance L between the force line of action and the center of rotation”. However, practically, a specific numerical value can be assumed as the distance L in the usage environment where the force sensor is planned to be mounted. Therefore, when designing a force sensor for a specific application, it is a standard. It is preferable to adjust the balance between the detection sensitivity of the force and the detection sensitivity of the moment after setting a simple distance L.

Therefore, the present inventor designed a structure having the following specific dimensions as a structure similar to the intermediate body 200A shown in FIG. 19 (the dimensional ratio of each part is the intermediate body shown in FIG. 19). 200A, when the support body 100 is fixed, the force receiving body 300 is subjected to 6-axis components of force + Fx, + Fy, + Fz, moment + Mx, + My, + Mz. The simulation which calculates | requires the numerical value which shows the specific deformation | transformation aspect of was performed. Hereinafter, the intermediate having such specific dimensions is referred to as “sample S1” for convenience.
Outer diameter of detection ring 210A: 27.5 mm
Inner diameter of detection ring 210A: 24.5 mm
Radial thickness (width) of detection ring 210A: 1.5 mm
Thickness (width) of detection ring 210A in the height direction: 5.5 mm
Radial dimension of each connecting member 221A, 222A, 232A, 232A: 10mm
(Dimensions from the inner peripheral position of the detection ring 210A to the outer peripheral position of each connecting member)

Specifically, the detection ring 210 </ b> A is generated when a force + Fx, + Fy, + Fz of 200 N is applied to the force receiving body 300 and when a moment + Mx, + My, + Mz of 10 N · m is applied, respectively. A numerical value indicating a specific deformation mode is determined. Here, as a numerical value indicating a specific modification, a capacitive element (a capacitive element in which a significant change is made in the inter-electrode distance) in which “+” or “−” is shown in the corresponding column of the table of FIG. An average value of the absolute values of the generated displacement amounts (hereinafter referred to as an average displacement amount Δ) is used. As a result, the following average displacement amount was obtained for the sample S1 (unit: mm).
When force + Fx is applied: average displacement Δ = 0.12
When force + Fy is applied: average displacement Δ = 0.12
When force + Fz is applied: average displacement Δ = 0.14
When moment + Mx is applied: average displacement Δ = 0.30
When moment + My is applied: average displacement Δ = 0.30
When moment + Mz is applied: average displacement Δ = 0.063

  Here, values of 200N are used for the forces + Fx, + Fy, and + Fz, and values of 10 N · m are used for the moments + Mx, + My, and + Mz, and this is a general value using the sample S1 having the above-described dimension values. This is because, in the use of the force sensor, L = 50 mm (assumed distance that seems to be appropriate in the usage environment where the force sensor is expected to be mounted) is set as the “distance L between the force action line and the rotation center”. . That is, when a force of 200 N acts in a direction perpendicular to the predetermined axis at a point 50 mm away from the rotation center along the predetermined axis, a moment of 200 N × 0.05 m = 10 N · m acts on the rotation center. Therefore, in evaluating the balance between the force detection sensitivity and the moment detection sensitivity in the use environment, the values are appropriate force and moment values. That is, the average displacement amount Δ is based on the assumption that an external force of 200 N acts on the force receiving body 300.

  Based on the above results, the balance between the force detection sensitivity and the moment detection sensitivity is not necessarily good in at least the setting environment of L = 50 mm. Therefore, the inventor of the present application creates several variations for the intermediate by changing the size of each part or the number of detection rings for the sample S1, and for these variations, In the same setting environment, a simulation for obtaining the average displacement amount Δ was performed.

  FIG. 25 is a table showing the number of detection rings and the dimensions of each part for various samples of these intermediates. Of the eight samples listed in this table, samples S1 to S3 are samples using one detection ring (single ring) (corresponding to the intermediate 200A shown in FIG. 19), and samples W1 to W4 are 2 samples. Sample using two detection rings (double ring) (corresponding to the intermediate 200B shown in FIG. 22), and sample T1 is a sample using three detection rings (triple ring) (not shown) 22 in which an intermediate detection ring of the same size is added between the upper detection ring 211B and the lower detection ring 212B. The “ring interval” in the table of FIG. 25 indicates the distance between the lower surface of the uppermost detection ring and the upper surface of the lowermost detection ring.

  Of the eight types of samples shown in the table of FIG. 25, the sample S1 is a basic sample having the above-described dimension values, and the sample S2 has a thickness of 2 in the height direction of the detection ring. Sample S3 is a sample in which the thickness of the detection ring in the radial direction is changed to 3 mm, which is twice as large. On the other hand, the sample W1 is a sample in which the number of detection rings of the same size as the sample S1 is increased to two, and the samples W2 to W4 are samples in which the interval between the two detection rings in the sample W1 is narrowed or widened. . Sample T1 is a sample in which the number of detection rings of the same size as sample S1 is increased to three.

  FIG. 26 is a table showing the balance between the detection sensitivity of the force and the moment in the force sensor using the eight types of samples shown in FIG. Specifically, FIG. 26 (a) is a table showing an average displacement amount Δ when 200N forces Fx and Fz are applied and an average displacement amount Δ when 10N · m moments My and Mz are applied. FIG. 26 (b) is a table showing the results of normalizing the results shown in FIG. 26 (a) based on the average displacement amount Δ for Fz. Since the result when the force Fy is applied is equal to the result when the force Fx is applied, and the result when the moment Mx is applied is equal to the result when the moment My is applied, FIG. The result display for Mx is omitted.

  As described above, the average displacement amount Δ indicates the average displacement amount of the inter-electrode distance for the capacitive element, and is a parameter that substantially indicates the detection sensitivity. In the table of FIG. 26 (b), normalization is performed based on the average displacement amount Δ for Fz, so all the Fz columns are 1.00. Here, in order to realize a force sensor balanced in detection sensitivity, it is ideal that the average displacement amount Δ in all the columns is Δ = 1.00. However, since it is very difficult to design such that all of the 6-axis components are Δ = 1.00, in practice, Fz is standardized so that Δ = 1.00. Therefore, the design is made so that the average displacement amount Δ of the other-axis component is as close to 1.00 as possible.

  From this point of view, the table in FIG. 26 (b) shows that the double ring samples W1 to W4 or the triple ring T1 are generally closer to the ideal than the single ring samples S1 to S3. You can see that Of course, considering that the ideal average displacement Δ is Δ = 1.00, the results obtained for the double ring and triple ring samples are by no means sufficient, but compared to the single ring samples. For example, it can be seen that the balance of detection sensitivity for the entire six-axis component is improved.

  In short, as long as the single ring structure is adopted, changing the thickness of the detection ring as in samples S2 and S3 shows little effect of improving the balance of detection sensitivity, but double or triple rings. In a modified example employing this structure (modified example using a plurality of detection rings), an effect of improving the balance of detection sensitivity can be seen. In other words, if a laminated structure in which a plurality of detection rings are stacked one above the other is adopted, the balance between the force detection sensitivity and the moment detection sensitivity can be easily adjusted according to the number of detection rings used. Therefore, it is possible to provide a small force sensor that facilitates a design in which the balance between force detection sensitivity and moment detection sensitivity is adjusted while securing the internal space.

  The difference in structure between the four samples W1 to W4 adopting the double ring structure is only the distance between the upper detection ring 211B and the lower detection ring 212B, as shown in the table of FIG. From the results shown in FIG. 26 (b), it cannot be determined in general whether the interval should be narrower or wider, but at least the ring interval is a parameter that affects the balance improvement effect. Therefore, in practice, various intervals may be set by trial and error, and the interval at which the most improvement effect can be expected is determined.

  Further, as shown in FIG. 26 (b), no significant difference was found between the results of the triple ring sample T1 and the results of the double rings W1 to W4. The inventor of the present application believes that even if the number of detection rings is increased to 3 or more, a great balance improvement effect cannot be expected. Therefore, it can be said that it is sufficient to use two detection rings from the viewpoint of obtaining a balance improvement effect.

<4-4. Modified examples of support and power receiving body>
Here, the modification regarding a support body and a power receiving body is described. In the embodiment described so far, for example, as shown in the perspective view of FIG. 1, as the support body 100 and the force receiving body 300, both use a disk-shaped member. The form of the body 100 and the force receiving body 300 is not necessarily a disk, and may be configured using a plate-shaped member having an arbitrary shape, and is not necessarily a plate-shaped member. In the force sensor according to the present invention, the support body 100 and the force receiving body 300 need only be able to apply a force to the other in a state where one is fixed, so that the shape is not particularly limited to a specific shape. Absent.

  However, as illustrated in FIG. 2, when considering a case where the robot is mounted by being interposed between the first arm unit 400 and the second arm unit 500 of the robot, the support body 100 and the force receiving body 300 are plate-shaped. The installation work becomes easier when it is made of members. In addition, since it is preferable to use a circular ring as the detection ring 210 used for the intermediate body 200, in practice, the support body 100 and the force receiving body 300 are also formed of disk-shaped members. It is consistent and efficient. Therefore, in practice, as in the embodiments described so far, it is preferable that the support body 100 and the force receiving body 300 are constituted by disk-shaped members arranged so that the upper and lower surfaces are parallel to the XY plane. .

  In the case of the embodiment described so far, as shown in the perspective view of FIG. 1, a simple disk-shaped member is used as the support body 100, and a disk-shaped member is used as the force receiving body 300. A washer-like member provided with a circular opening H at the center of is used. The opening H is convenient for passing wiring inside. For example, FIG. 12 shows an example in which eight fixed electrodes E1 to E8 are provided on the upper surface of the support body 100 as detection elements, and the wiring for each of these electrodes is led out to the outside of the basic structure portion. When the detection circuit is provided outside, the wiring can be taken out through the opening H provided in the force receiving body 300.

  Alternatively, even when a detection circuit is arranged in the internal space of the detection ring 210, a signal for outputting a detection signal from the detection circuit (outputs Fx, Fy, Fz, Mx, My, Mz in the detection circuit shown in FIG. 18). When the line is led out, the signal line can be taken out from the internal space of the detection ring 210 through the opening H provided in the force receiving member 300.

  Of course, the opening H is not necessarily provided on the force receiving member 300 side, and may be provided on the support member 100 side, or may be provided on both. In short, if one or both of the support body 100 and the force receiving body 300 is configured by a plate-like member having an opening H at the center, the wiring from the detection element and the detection circuit through the opening H are provided. The signal line can be taken out to the outside.

  FIG. 27 is a cross-sectional view showing a state in which a modification using the support 100C is cut along the XZ plane in place of the support 100 in the basic structure shown in FIG. The support 100 </ b> C is obtained by providing a circular opening h at the center of the disc-shaped support 100. In the case of the modification shown in FIG. 27, since the disk-shaped force receiving member 300 is also provided with a circular opening H, the wiring and the signal line can be led out through the opening H in the figure. It is also possible to lead out downward in the figure through the opening h. In addition, since it is necessary to provide the eight fixed electrodes E1 to E8 on the upper surface of the support 100C, the diameter of the opening h is slightly smaller than the diameter of the opening H.

  Of course, it is not always necessary to provide an opening in the support or power receiving body. For example, when adopting a configuration in which wiring for each of the fixed electrodes E1 to E8 and a signal line from a detection circuit provided in the internal space of the detection ring are led out from the side of the intermediate body, the support and power receiving body It is not necessary to form an opening in.

  FIG. 28 is a cross-sectional view showing a modification in which a force receiving body 300D is cut in the XZ plane instead of the force receiving body 300 in the double ring basic structure shown in FIG. The force receiving member 300 is provided with a circular opening H, but the force receiving member 300D shown in FIG. 28 is a simple disk-shaped member. For this reason, in the case of the basic structure shown in FIG. 28, neither the support body 100 nor the force receiving body 300D has an opening. However, in the case of this modification, for example, it is possible to insert / remove wirings and signal lines to / from the internal space of the detection ring from the side by using the gap between the upper detection ring 211B and the lower detection ring 212B. Even if there are no openings above and below, there will be no trouble.

<4-5. Modified example of connection member>
Here, the modification regarding a support connection member and a force receiving connection member is described. FIG. 29 (a) shows the detection ring 210 according to the basic embodiment described so far, and the support connection members 221, 222 and the force receiving connection members 231, 232 (shown by thick broken lines in the figure). It is a top view which shows a positional relationship. As described above, when the XY coordinate system is defined as illustrated, the fixed points P1 and P2 defined as points on the X axis in the detection ring 210 are placed on the upper surface of the support body 100 by the support connection members 221 and 222. The action points Q1 and Q2 defined as points on the Y axis in the detection ring 210 are fixed to the lower surface of the force receiving body 300 by the force receiving connecting members 231 and 232.

  Thus, in the embodiments described so far (including various modifications), the support connection members 221 and 222 and the force receiving connection members 231 and 232 protrude further outward from the outer peripheral surface of the detection ring 210. It is comprised by the member. The lower surfaces of the support connecting members 221 and 222 are located below the lower surface of the detection ring 210 (in the case of a modification having a plurality of detection rings, the lowest detection ring), and A predetermined gap is formed between the lower surface of the detection ring 210 (in the case of a modification having a plurality of detection rings, the detection ring positioned at the lowermost position) connected to the upper surface and the upper surface of the support body 100. . Further, the upper surfaces of the force receiving connection members 231 and 232 are located above the upper surface of the detection ring 210 (the uppermost detection ring in the case of a modification having a plurality of detection rings). A predetermined gap is connected between the upper surface of the detection ring 210 (the uppermost detection ring in the case of a modification having a plurality of detection rings) and the lower surface of the force receiving body 300. Is formed.

  Moreover, the projection images of the support connecting members 221 and 222 and the force receiving connection members 231 and 232 on the XY plane are included in the projection image of the support 100 on the XY plane, and the XY plane of the force receiving body 300 is included. It is included in the projection image. In other words, as shown in the perspective view of FIG. 2, the intermediate body 200 is completely accommodated in a cylindrical space sandwiched between the support body 100 and the force receiving body 300. It has become.

  As described above, when the connection members are arranged on the outer peripheral portion of the detection ring 210 and connected to the support body 100 or the force receiving body 300, the area of the connection surface with respect to the support body 100 or the force receiving body 300 is compared. It is preferable for ensuring sufficient connection strength. Further, as shown in the perspective view of FIG. 2, the intermediate body 200 is completely accommodated in a cylindrical space sandwiched between the support body 100 and the force receiving body 300. Therefore, even if elastic deformation occurs in the detection ring, the swelled deformation part of the detection ring does not protrude outside the cylindrical space, and a detection result is obtained when a part of the detection ring contacts an external object. There will be no situation that adversely affects

  However, it is preferable to make the diameter of the detection ring as large as possible from the viewpoint of securing space in order to incorporate wiring and circuits inside the detection ring. FIG. 29 (b) is a plan view showing a modified example based on such a viewpoint. The detection ring 210E, the support connection members 221E and 222E, and the force receiving connection members 231E and 232E (shown by thick broken lines in the figure). It shows the positional relationship.

  The detection ring 210E shown in FIG. 29 (b) has a larger diameter than the detection ring 210 shown in FIG. 29 (a). Instead, the support connection members 221E and 222E and the force receiving connection members 231E and 232E are arranged not on the outer periphery of the detection ring 210E but on the upper surface or the lower surface.

  That is, as shown in FIG. 29 (b), when the connection method from the upper and lower sides is adopted for the single ring type basic structure using only the single detection ring 210E, the support connection members 221E and 222E are The force receiving connection members 231E and 232E are constituted by members that connect the upper surface of the detection ring 210E and the force receiving body 300.

  FIG. 30 is a cross-sectional view showing a state in which an example in which the modification shown in FIG. 29B is applied to the single-ring basic structure is cut along the XZ plane. As shown in the drawing, support connection members 221E and 222E are arranged at the positions of the fixing points P1 and P2 on the lower surface of the detection ring 210E (left and right end positions in the drawing), and the connection to the upper surface of the support body 100 is performed. Also, force receiving connection members 231E and 232E are arranged at the positions of the operation points Q1 and Q2 on the upper surface of the detection ring 210E (center position in the figure) (only the force receiving connection member 231E located in the back is shown in the figure). The connection to the lower surface of the force receiving body 300 is made.

  On the other hand, as in the example shown in FIG. 22, when the connection method from the upper and lower sides as shown in FIG. 29 (b) is adopted for the multi-ring basic structure in which a plurality of detection rings are stacked, the support connection Members 221E and 222E for connecting the detection ring located at the lowest position and the support, and members for connecting the lower surface of the upper detection ring and the upper surface of the lower detection ring for each pair of detection rings adjacent vertically It may be configured by. Similarly, the force receiving connecting members 231E and 232E are connected to the uppermost detection ring and the force receiving member, and the upper detection ring lower surface and the lower detection ring of each of the upper and lower adjacent detection ring pairs. What is necessary is just to comprise by the member which connects an upper surface.

  FIG. 31 is a cross-sectional view showing a state in which an example in which the double-ring basic structure shown in FIG. 22 is modified by connecting the upper and lower surfaces as shown in FIG. 29B is cut along the XZ plane. is there.

  As shown in the figure, force receiving connection members 231F1 and 232F1 are disposed at the positions of the action points Q1 and Q2 on the upper surface of the upper detection ring 211F (center position in the figure) (in the figure, the force receiving connection members located in the back). Only 231F1 appears), the connection to the lower surface of the force receiving body 300 is made. Further, between the positions of the action points Q1, Q2 on the lower surface of the upper detection ring 211F (center position in the figure) and the positions of the action points Q1, Q2 on the upper surface of the lower detection ring 212F (center position in the figure). Are provided with force receiving connection members 231F2 and 232F2 (only the force receiving connection member 231F2 located at the back appears in the figure).

  On the other hand, support connection members 221F2 and 222F2 are arranged at positions (fixed left and right positions in the figure) of the fixing points P1 and P2 on the lower surface of the lower detection ring 212F, and are connected to the upper surface of the support body 100. Further, the positions of the fixing points P1, P2 on the lower surface of the upper detection ring 211F (the left and right end positions in the drawing), the positions of the fixing points P1, P2 on the upper surface of the lower detection ring 212F (the left and right both ends positions in the drawing), Between them, support connection members 221F1 and 222F1 are arranged.

  After all, in the modification shown in FIG. 31, the support connection members 221F1 and 221F2 function as support connection members for fixing the fixing points P1 of the upper and lower detection rings to the support body 100, and the support connection member 222F1. , 222F2 functions as a support connection member for fixing the fixing point P2 of the upper and lower detection rings to the support body 100. Similarly, the force receiving connection members 231F1 and 231F2 serve as force receiving connection members for fixing the action point Q1 of the upper and lower detection rings to the force receiving body 300, and the force receiving connection members 232F1 and 232F2 (FIG. 31). However, it functions as a force receiving connection member for fixing the action point Q2 of the upper and lower detection rings to the force receiving body 300.

  If the connection member is connected to the upper surface or the lower surface of the detection ring as in the modification shown in FIGS. 30 and 31, the area of the connection surface with respect to the support body 100 or the force receiving body 300 cannot be made too large. In addition, when elastic deformation occurs in the detection ring, the swelled deformation portion of the detection ring may protrude to the outside and come into contact with an external object, but the diameter of the detection ring can be increased. Therefore, there is a merit that a sufficient space can be secured for incorporating wiring and circuits.

  The embodiments described so far are examples in which two sets of fixed points P1 and P2 and two sets of action points Q1 and Q2 are set on the detection ring. The support connection members 221 and 222 and the two pairs of force receiving connection members 231 and 232 are provided. However, in carrying out the present invention, the fixed point P and the action point Q are not necessarily limited to two sets. Absent. The fixed point P in the present invention means one point on the detection ring and connected to the support, and the action point Q in the present invention is one point on the detection ring and is a force receiving body. Means a point connected to.

  Accordingly, in principle, at least one fixed point P and at least one action point Q are defined, and a projection image of the fixed point P onto the XY plane and a projection image of the action point Q onto the XY plane. It is sufficient that the definition is formed at different positions (if the projected image of the fixed point P on the XY plane and the projected image of the action point Q on the XY plane are formed at the same position. Since the elastic deformation does not occur in the detection ring due to the action of external force, the detection cannot be performed).

  However, in practice, it is preferable to provide two or more fixed points P and two or more action points Q. Specifically, a plurality of n (n ≧ 2) fixed points P and a plurality of n action points Q are defined alternately on the annular path along the contour of the detection ring, Thus, the elastic deformation of the detection ring in the vicinity of the measurement point R defined at the position between the fixed point P and the action point Q arranged adjacent to each other may be electrically detected.

  Each of the embodiments described so far is an example in which n = 2 is set, and as shown in FIG. 5 (b), an annular path S (indicated by a two-dot chain line in the figure) along the contour of the detection ring 210. Are arranged in the order of the first fixed point P1, the first action point Q1, the second fixed point P2, and the second action point Q2. The first measurement point R1 arranged at a position between the first fixed point P1 and the first action point Q1 in the annular path S, the first action point Q1 and the second action point in the annular path S, The second measurement point R2 disposed at a position between the second fixed point P2 and the third measurement point disposed at a position between the second fixed point P2 and the second action point Q2 in the circular path S. A measurement point R3 and a fourth measurement point R4 arranged at a position between the second action point Q2 and the first fixed point P1 in the circular path S are respectively provided. When defined, the detection element functions to electrically detect elastic deformation of the detection ring 210 in the vicinity of the first to fourth measurement points R1 to R4.

  In particular, in the embodiments described so far, two sets of fixed points P1 and P2 and two sets of action points Q1 and Q2 are defined to be points on a coordinate system orthogonal to each other. By performing such a definition, it becomes possible to efficiently detect the six-axis components in the three-dimensional orthogonal coordinate system of force + Fx, + Fy, + Fz, moment + Mx, + My, + Mz.

  In the example shown in FIG. 5B, the fixed points P1 and P2 and the action points Q1 and Q2 are all points on the XY plane, but as shown in FIG. 22, two sets of detection rings 211B and 212B are used. In the case of the modification using, fixed points P1 and P2 and action points Q1 and Q2 are defined for each ring, and these points are not necessarily points on the XY plane. However, the arrangement of the two sets of fixed points P1 and P2 and the two sets of action points Q1 and Q2 and the structure of the intermediate body including the modification using such a plurality of rings can be said as follows. .

  First, the projection image of the first fixed point P1 on the XY plane is on the X-axis positive region, the projection image of the first action point Q1 on the XY plane is on the Y-axis positive region, and the second fixed point P2. The projected image on the XY plane is positioned on the X-axis negative region, and the projected image of the second action point Q2 on the XY plane is positioned on the Y-axis negative region.

  The vicinity of the first fixed point P1 of the detection ring is connected to the support by the first support connection member arranged so that the projected image on the XY plane is positioned on the X-axis positive region, and is moved to the XY plane. A second support connection member arranged so that the projected image of the detection ring is positioned on the X-axis negative region, the vicinity of the second fixed point P2 of the detection ring is connected to the support. Similarly, the vicinity of the first action point Q1 of the detection ring is connected to the force receiving body by the first force receiving connecting member arranged so that the projected image on the XY plane is positioned on the Y-axis positive region, The vicinity of the second action point Q2 of the detection ring is connected to the force receiving body by the second force receiving connection member arranged so that the projected image on the XY plane is positioned on the Y-axis negative region.

  Further, the detection element includes a first measurement point R1, a second measurement point R2, and a projection image onto the XY plane, which are respectively located in the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant of the XY coordinate system. It plays a role of electrically detecting the elastic deformation of the detection ring in the vicinity of the third measurement point R3 and the fourth measurement point R4.

<4-6. Modified example regarding detection element>
Finally, a modification regarding the detection element will be described. Each of the embodiments described so far is an example in which a capacitive element is used as the detection element. However, the detection element used in the present invention is an element that can electrically detect elastic deformation of the detection ring. Any element may be used.

  For example, if a strain gauge is used as a detection element, elastic deformation of the detection ring can be electrically detected as mechanical strain of each part. Specifically, if a strain gauge is attached in the vicinity of the measurement point R of the detection ring and a Wheatstone bridge circuit is prepared as a detection circuit using these strain gauges as a detection element, the bridge voltage It is possible to detect the force and moment acting as.

  Further, the embodiments described so far are examples in which a capacitive element is used as a detection element, and the displacement of the measurement point R on the detection ring is detected as a change in the capacitance value of the capacitive element. The detection element that can electrically detect the displacement of the electrode is not necessarily limited to the capacitive element, and in general, any detection element that can detect the distance may be used. Absent.

  For example, if at least the vicinity of the measurement point R of the detection ring is made of a conductive material, an eddy current displacement meter fixed to the support in the vicinity thereof can be used as the detection element. The eddy current displacement meter has a function of generating an eddy current in the vicinity of the measurement point R by a high-frequency magnetic field and a function of detecting an impedance change generated in the coil. Based on the impedance change, the eddy current displacement meter Can be measured. Therefore, the function similar to that of the capacitive element described so far can be achieved.

  Further, if at least the vicinity of the measurement point R of the detection ring is constituted by a magnet, the Hall element fixed to the support in the vicinity thereof can be used as the detection element. Since the strength of the magnetic field acting on the Hall element changes due to the displacement of the magnet in the vicinity of the measurement point R, the detected value of the magnetic field by the Hall element can be used as the distance measurement value.

  In addition, a distance measuring device using a light beam can also be used as a detection element. For example, a light beam irradiator that irradiates a light beam obliquely with respect to the vicinity of the measurement point R of the detection ring and a light beam receiver that receives a light beam reflected from the irradiation surface are fixed to the support side. A measurement circuit that outputs a distance measurement value based on the light beam receiving position of the light beam receiver may be prepared. When the vicinity of the measurement point R of the detection ring 200 is displaced, the irradiation position of the light beam and the emission direction of the reflected beam change, so that the light beam receiving position by the light beam receiver also changes. Therefore, the measurement circuit can output a distance measurement value based on the light receiving position.

11 to 18: C / V conversion circuits 21 to 26: addition / subtraction circuit 100: support 100C: support 200: intermediate 200A: intermediate 200B: intermediate 210: detection ring 210A: detection ring 210E: detection rings 211B, 211F : Upper detection rings 212B and 212F: Lower detection rings 221 and 222: Support connection members 221A and 222A: Support connection members 221B and 222B: Support connection members 221E and 222E: Support connection members 221F1, 221F2, 222F1, and 222F2: Support connection members 231 and 232: force receiving connection members 231A and 232A: force receiving connection members 231B and 232B: force receiving connection members 231E and 232E: force receiving connection members 231F1, 231F2, 232F1 and 232F2: force receiving connection member 300: force receiving body 300D : Power receiving body 400: Robot First arm portion 500: second arm of the robot A: opposing area (projected image of the electrode Eb)
C1 to C8: Capacitance elements d1, d2: Gap size E0: Common displacement electrode (surface of detection ring 210)
E1 to E8: Fixed electrode Ea, Eb: Electrode Fx: Force in the X axis direction Fy: Force in the Y axis direction Fz: Force in the Z axis direction H, h: Opening Mx: Moment about the X axis My: Around the Y axis Moment Mz: moment about Z axis O: origin O ′ of XYZ three-dimensional orthogonal coordinate system: projection point P1 of origin O: first fixed point P2: second fixed point Q1: first action point Q2: Second action point R1: First measurement point R2: Second measurement point R3: Third measurement point R4: Fourth measurement point S: Circular paths S1 to S3 along the contour of the detection ring 210: Single Ring sample T1: Triple ring sample V: Coordinate axis inclined at 45 ° with respect to the X axis and the Y axis V ′: Projection axes V1 to V8 of the V axis on the upper surface of the support 100: Voltage signal W: X axis and Y Coordinate axis W ′ inclined at 45 ° with respect to the axis: W-axis support 100 upper surface Projection axes W1 to W4: Sample of double ring X: Coordinate axis X ′ of XYZ three-dimensional orthogonal coordinate system X: Projection axis Y of X axis on upper surface of support 100 Y: Coordinate axis Y ′ of XYZ three-dimensional orthogonal coordinate system Y: Y Projection axis Z on the upper surface of the support 100: coordinate axis of XYZ three-dimensional orthogonal coordinate system

Claims (23)

A force sensor for detecting a force or a moment related to at least one of a force in each coordinate axis direction and a moment around each coordinate axis in an XYZ three-dimensional orthogonal coordinate system,
A plurality of m (m ≧ 2) detection rings that are arranged on an arrangement plane parallel to the XY plane so that the Z axis is the central axis, and that are elastically deformed at least in part by the action of a force or moment to be detected. When,
A support disposed below the detection ring;
A force receiving body disposed above the detection ring;
A support connection member for fixing the detection ring to the support at a position of a predetermined fixing point;
A force receiving connection member for connecting the detection ring to the force receiving body at a position of a predetermined action point;
A detection element for electrically detecting elastic deformation of the detection ring;
A detection circuit that outputs a detection value of a force in a predetermined coordinate axis direction acting on the force receiving body or a moment around a predetermined coordinate axis in a state where the support is fixed based on a detection result of the detection element;
With
The projected image of the fixed point on the XY plane and the projected image of the working point on the XY plane are formed at different positions ,
The plurality of m detection rings are arranged adjacent to each other in the Z-axis direction at a predetermined interval, and each detection ring is individually arranged parallel to the XY plane so that the Z-axis is a central axis. Arranged on a plane,
The support body is disposed further below the lowermost detection ring, and the force receiving body is disposed further above the uppermost detection ring.
The fixing points of the individual detection rings are fixed to the support body by the support connection member, and the action points of the individual detection rings are fixed to the power reception body by the force receiving connection member. Force sensor. The force sensor according to claim 1 ,
The projected images of the fixed points and the action points of the individual detection rings on the XY plane overlap each other,
The support connection member connects the vicinity of each fixed point of different detection rings, which form a projected image at the same position on the XY plane, and fixes the support connection member to the support.
A force sensor is characterized in that the force receiving connection member forms a projected image at the same position on the XY plane, connects the vicinity of each action point of different detection rings to each other and fixes it to the force receiving body. The force sensor according to claim 1 or 2 ,
A plurality of n (n ≧ 2) fixed points and a plurality of n action points are alternately arranged on the annular path along the contour of the detection ring,
A force sensor, wherein the detection element electrically detects elastic deformation of a detection ring in the vicinity of a measurement point defined at a position between a fixed point and an action point arranged adjacent to each other. The force sensor according to claim 3 , wherein
Two fixed points and two action points are arranged in the order of the first fixed point, the first action point, the second fixed point, and the second action point on the annular path along the contour of the detection ring. Has been
A first measurement point arranged at a position between the first fixed point and the first action point in the annular path; the first action point and the second fixed point in the annular path; A second measurement point arranged at a position between the second measurement point, a third measurement point arranged at a position between the second fixed point and the second action point in the annular path, in the annular path When each of the fourth measurement points arranged at a position between the second action point and the first fixed point is defined, the detection element is in the vicinity of the first to fourth measurement points. A force sensor that electrically detects elastic deformation of a detection ring. The force sensor according to claim 4 ,
The projected image of the first fixed point on the XY plane is on the X-axis positive region, the projected image of the first working point on the XY plane is on the Y-axis positive region, and the second fixed point is projected on the XY plane. The projected image is located on the X axis negative region, and the projected image of the second action point on the XY plane is located on the Y axis negative region,
By the first support connection member arranged so that the projected image on the XY plane is positioned on the X-axis positive region, the vicinity of the first fixed point of the detection ring is connected to the support,
By the second support connection member arranged so that the projected image on the XY plane is positioned on the X-axis negative region, the vicinity of the second fixed point of the detection ring is connected to the support,
By the first force receiving connection member arranged so that the projected image on the XY plane is positioned on the Y-axis positive region, the vicinity of the first action point of the detection ring is connected to the force receiving body,
By the second force receiving connection member arranged so that the projected image on the XY plane is positioned on the Y-axis negative region, the vicinity of the second action point of the detection ring is connected to the force receiving body,
The detection element has a first measurement point, a second measurement point, and a third measurement in which the projected image on the XY plane is located in the first quadrant, the second quadrant, the third quadrant, and the fourth quadrant of the XY coordinate system, respectively. A force sensor characterized by electrically detecting elastic deformation of the detection ring in the vicinity of the point and the fourth measurement point. The force sensor according to claim 5 , wherein
A V-axis that passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is located in the first quadrant of the XY plane, the negative region is located in the third quadrant of the XY plane, and forms 45 ° with respect to the X axis; Defines the W axis that passes through the origin O in the XYZ three-dimensional orthogonal coordinate system, the positive region is located in the second quadrant of the XY plane, the negative region is located in the fourth quadrant of the XY plane, and is orthogonal to the V axis. Then, the projection image of the first measurement point on the XY plane is in the V-axis positive region, the projection image of the second measurement point on the XY plane is in the W-axis positive region, and the XY plane of the third measurement point The force sensor is characterized in that the projected image on the XY plane is located in the V-axis negative region and the projected image of the fourth measurement point on the XY plane is located in the W-axis negative region. In the force sensor in any one of Claims 1-6 ,
The support connection member and the force receiving connection member are constituted by members that protrude further outward from the outer peripheral surface of the detection ring,
The lower surface of the support connection member is positioned below the lower surface of the lowermost detection ring , connected to the upper surface of the support, and between the lower surface of the lowermost detection ring and the upper surface of the support A predetermined gap is formed,
The upper surface of the force receiving connection member is located above the upper surface of the uppermost detection ring and connected to the lower surface of the force receiving body, and the upper surface of the uppermost detection ring and the lower surface of the force receiving body A force sensor characterized in that a predetermined gap is formed between the two. The force sensor according to claim 7 , wherein
The projection image of the support connection member and the force receiving connection member on the XY plane is included in the projection image of the support body on the XY plane, and is included in the projection image of the support body on the XY plane. A force sensor. In the force sensor in any one of Claims 1-6 ,
A support connecting member is a member that connects the lower surface of the lowermost detection ring and the support, and a member that connects the lower surface of the upper detection ring and the upper surface of the lower detection ring for each pair of detection rings adjacent vertically And consists of
The force receiving connection member connects the upper surface of the uppermost detection ring and the force receiving member, and the lower detection ring upper surface and the lower detection ring upper surface for each pair of detection rings adjacent vertically. And a force sensor. The force sensor according to any one of claims 1 to 9 ,
A force sensor, wherein the detection ring is a circular ring arranged on an arrangement plane so that the Z axis is a central axis. The force sensor according to any one of claims 1 to 10 ,
The support is a disk-shaped member disposed below the detection ring and having a plate surface parallel to the XY plane,
A force sensor, wherein the force receiving body is a disk-shaped member disposed above the detection ring and having a plate surface parallel to the XY plane. The force sensor according to claim 11 , wherein
One or both of a support body and a power receiving body are disk-shaped members which have an opening part in center part, The force sensor characterized by the above-mentioned. The force sensor according to any one of claims 1 to 12 ,
A force sensor, wherein the support body and the power receiving body are constituted by a rigid body that does not substantially deform as long as an applied force or moment is within a predetermined allowable range. The force sensor according to any one of claims 1 to 13 ,
A force sensor, wherein the detection element electrically detects a displacement of a predetermined measurement point of the detection ring. The force sensor according to claim 14 , wherein
The detection element is configured to electrically detect a distance between a measurement target surface in the vicinity of a measurement point of the detection ring and an opposing reference surface that is fixed to a support body or a force receiving member and faces the measurement target surface. Force sensor. The force sensor according to claim 15 ,
Define the inner measurement target surface near the measurement point on the inner peripheral surface of the detection ring,
A fixed structure that has an inner facing reference surface facing the inner measurement target surface and is fixed to the upper surface of the support or the lower surface of the force receiving member;
A force sensor, wherein the detection element electrically detects a distance between the inner measurement target surface and the inner facing reference surface. The force sensor according to claim 15 ,
Define the lower measurement target surface near the measurement point on the lower surface of the detection ring,
A force sensor, wherein the detection element electrically detects a distance between the lower measurement target surface and the upper surface of the support. The force sensor according to any one of claims 15 to 17 ,
A force sensor, wherein the detection element is constituted by a capacitive element having a displacement electrode provided on a measurement target surface and a fixed electrode provided on a counter reference surface. The force sensor according to claim 18 ,
A force sensor characterized in that the detection ring is made of a conductive material having flexibility, and a capacitive element is formed by using the surface of the detection ring as a common displacement electrode. The force sensor according to claim 6 , wherein
The detection ring is a circular ring arranged on an arrangement plane above the support so that the Z-axis is the central axis;
The sensing element
A first displacement electrode disposed in the vicinity of the first measurement point on the inner peripheral surface of the detection ring, and a position opposed to the first displacement electrode inside the detection ring, the upper surface of the support body A first capacitive element fixed to the first capacitive element, and
A second displacement electrode disposed in the vicinity of the second measurement point on the inner circumferential surface of the detection ring, and a position opposed to the second displacement electrode inside the detection ring; A second capacitive element constituted by a second fixed electrode fixed to
A third displacement electrode disposed in the vicinity of the third measurement point on the inner circumferential surface of the detection ring, and a position opposed to the third displacement electrode inside the detection ring; A third capacitive element constituted by a third fixed electrode fixed to
A fourth displacement electrode disposed in the vicinity of the fourth measurement point on the inner circumferential surface of the detection ring, and a position opposed to the fourth displacement electrode on the inner side of the detection ring; A fourth capacitive element constituted by a fourth fixed electrode fixed to
A fifth displacement electrode disposed at a position near the first measurement point on the lower surface of the detection ring; and a fifth fixed electrode disposed at a position facing the fifth displacement electrode on the upper surface of the support. A fifth capacitive element configured by:
A sixth displacement electrode disposed at a position near the second measurement point on the lower surface of the detection ring; a sixth fixed electrode disposed at a position facing the sixth displacement electrode on the upper surface of the support; A sixth capacitive element configured by:
A seventh displacement electrode disposed at a position near the third measurement point on the lower surface of the detection ring; and a seventh fixed electrode disposed at a position facing the seventh displacement electrode on the upper surface of the support. A seventh capacitive element configured by:
An eighth displacement electrode disposed at a position near the fourth measurement point on the lower surface of the detection ring; and an eighth fixed electrode disposed at a position facing the eighth displacement electrode on the upper surface of the support. An eighth capacitive element configured by:
A force sensor characterized by comprising: The force sensor according to claim 20 ,
An upper detection ring and a lower detection ring are arranged adjacent to each other in the Z-axis direction at a predetermined interval, and both of these two detection rings are parallel to the XY plane so that the Z-axis is the central axis. Placed on individual placement planes,
The projection image of the first fixed point of the upper detection ring on the XY plane and the projection image of the first fixed point of the lower detection ring on the XY plane overlap each other.
The projected image of the second fixed point of the upper detection ring on the XY plane and the projected image of the second fixed point of the lower detection ring on the XY plane overlap each other,
The projection image of the first action point of the upper detection ring on the XY plane and the projection image of the first action point of the lower detection ring on the XY plane overlap each other,
The projection image of the second action point of the upper detection ring on the XY plane and the projection image of the second action point of the lower detection ring on the XY plane overlap each other.
The first support connection member connects the vicinity of the first detection point of the upper detection ring and the vicinity of the first detection point of the lower detection ring to each other and is also connected to the support body.
By the second support connection member, the vicinity of the second fixed point of the upper detection ring and the vicinity of the second fixed point of the lower detection ring are connected to each other and also connected to the support,
The first force receiving connection member connects the vicinity of the first action point of the upper detection ring and the vicinity of the first action point of the lower detection ring to each other and is also connected to the force receiving body,
By the second force receiving connection member, the vicinity of the second action point of the upper detection ring and the vicinity of the second action point of the lower detection ring are connected to each other and also connected to the force receiving body,
The first displacement electrodes are distributed and arranged in two locations: a position near the first measurement point on the inner peripheral surface of the upper detection ring and a position near the first measurement point on the inner peripheral surface of the lower detection ring. The first fixed electrode is opposed to both of the displacement electrodes that are dispersedly disposed at the two locations.
The second displacement electrodes are distributed and arranged at two locations, a position near the second measurement point on the inner peripheral surface of the upper detection ring and a position near the second measurement point on the inner peripheral surface of the lower detection ring. The second fixed electrode is opposed to both of the displacement electrodes distributed in the two locations,
The third displacement electrodes are distributed and arranged in two locations: a position near the third measurement point on the inner peripheral surface of the upper detection ring and a position near the third measurement point on the inner peripheral surface of the lower detection ring. The third fixed electrode is opposed to both of the displacement electrodes arranged in a dispersed manner at the two locations,
The fourth displacement electrodes are distributed and arranged in two locations: a position near the fourth measurement point on the inner peripheral surface of the upper detection ring and a position near the fourth measurement point on the inner peripheral surface of the lower detection ring. The fourth fixed electrode is opposed to both of the displacement electrodes arranged in a dispersed manner at the two locations.
The fifth displacement electrode is disposed at a position near the first measurement point on the lower surface of the lower detection ring, and the sixth displacement electrode is disposed at a position near the second measurement point on the lower surface of the lower detection ring. The displacement electrode is arranged near the third measurement point on the lower surface of the lower detection ring, and the eighth displacement electrode is arranged near the fourth measurement point on the lower surface of the lower detection ring. Force sensor. The force sensor according to claim 20 or 21 ,
A force sensor characterized in that the detection ring is made of a conductive material having flexibility, and each capacitive element is formed by using the surface of the detection ring as a common displacement electrode. The force sensor according to any one of claims 20 to 22 ,
The detection circuit sets the capacitance value of the first capacitance element to C1, the capacitance value of the second capacitance element to C2, the capacitance value of the third capacitance element to C3, and the capacitance value of the fourth capacitance element. The capacitance value is C4, the capacitance value of the fifth capacitance element is C5, the capacitance value of the sixth capacitance element is C6, the capacitance value of the seventh capacitance element is C7, and the eighth capacitance element. When the capacitance value of C8 is C8,
Fx = −C1 + C2 + C3-C4
Fy = + C1 + C2-C3-C4
Fz = -C5-C6-C7-C8
Mx = -C5-C6 + C7 + C8
My = + C5-C6-C7 + C8
Mz = + C1-C2 + C3-C4
Based on the following formula, the detection of the force Fx in the X-axis direction, the force Fy in the Y-axis direction, the force Fz in the Z-axis direction, the moment Mx around the X-axis, the moment My around the Y-axis, and the moment Mz around the Z-axis A force sensor that outputs a value.

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