Force detector

Abstract

To provide a force detector that can detect mutually distinguishedly external force of six axes even with a single sensor unit.SOLUTION: A force detector 1 according to the present disclosure comprises: a layer structure 10 that has a first layer 11 on which external force F of a detection object acts, and a second layer 12 having the first layer 11 laminated and made of material different in Young's modulus from the first layer 11; at least one stress generation unit 20 that is formed inside of the layer structure 10, and, when the external force F acts on the first layer 11, forms a stress distribution around itself when viewed from a normal line direction of the first layer 11; and a plurality of sensors 30 that are arranged distributedly around the stress generation unit 20. The plurality of sensors 30 to be associated with the one stress generation unit 20 are configured to, as one sensor unit, detect mutually distinguishedly the external force F of six axes including force in a three-axis direction, and force in a rotation direction relative to each axis.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a force detector. [Background technology]

[0002] Conventionally, there are known techniques relating to force detectors used as, for example, tactile sensor modules that detect external forces. For example, Patent Document 1 discloses a force detector that is highly reliable and easier to bend, without the need to include an internal pressure transmission member with an extremely large Young's modulus. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-100447 Summary of the Invention [Problem to be solved by the invention]

[0004] The force detector described in Patent Document 1 has a structure that forms a stress distribution around itself when an external force to be detected acts on the detection surface, and a sensor unit including four sensors. The sensors include, for example, strain sensors and pressure sensors. This force detector detects forces in three axial directions with one sensor unit while distinguishing between them. However, it has been difficult for this force detector to detect external forces in six axes, including forces in the three axial directions and forces in the rotational directions about each axis, with one sensor unit while distinguishing between them.

[0005] An object of the present disclosure is to provide a force detector that can detect external forces on six axes while distinguishing them from one another using a single sensor unit. [Means for solving the problem]

[0006] In some embodiments, a force detector includes a layer structure having a first layer on which an external force to be detected acts, and a second layer on which the first layer is stacked and formed of a material having a Young's modulus different from that of the first layer; at least one stress generating unit formed inside the layer structure and which generates a stress distribution around itself when viewed from the normal direction of the first layer when the external force acts on the first layer; and a plurality of sensors distributed around the stress generating unit, wherein the plurality of sensors associated with one of the stress generating units function as a single sensor unit to detect the external forces in six axes, including forces in three axial directions and forces in rotational directions about each axis, while distinguishing between them.

[0007] This allows a single sensor unit to detect external forces along six axes, i.e., forces in the three axes and rotational forces relative to each axis, while distinguishing between them. The force detector can measure external forces along six axes, including torsional moments, while distinguishing between them, using a single sensor unit. Therefore, compared to conventional technologies that require the use of multiple sensor units to measure rotational forces, the spatial resolution when measuring external forces along six axes is improved.

[0008] In one embodiment, the force detector may include at least six sensors. This allows the force detector to detect six-axis external forces with a single sensor unit, even if each sensor is a single-axis sensor. Therefore, it is possible to calculate the six-axis components of any external force and measure the magnitude and direction of the external force.

[0009] In one embodiment, the force detector may have a sensor arrangement in which at least three sensors are arranged at positions where the stress distribution is formed for each of the forces included in the six-axis external force, thereby enabling the force detector to more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0010] In one embodiment, the force detector may include a plurality of first sensors located within a first distance from the center of the stress generating portion, and a plurality of second sensors located within a range between the first distance and a second distance from the center that is longer than the first distance. This allows the force detector to be configured with a sensor arrangement in which at least three sensors are arranged at positions where stress distributions based on six-axis external forces are formed. Therefore, the force detector can more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0011] In one embodiment of the force detector, the first sensor may be disposed at a position different from the position on the line connecting the center and the center of the second sensor. This allows the sensor to be more reliably disposed at a position where a strain distribution is formed, as shown in Figures 6 and 7, described later, even when an external force in a rotational direction about the Y axis acts on the detection surface. The force detector can more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0012] In one embodiment, the plurality of first sensors may be arranged at positions offset from each other in the same rotational direction and at the same angle relative to the straight line when viewed from the normal direction, thereby achieving the same effect as above and enabling the force detector to more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0013] In one embodiment, the stress generating portion may have an n-gonal shape when viewed from the normal direction, and the second sensors may have n-fold rotational symmetry about the center of the stress generating portion when viewed from the normal direction, thereby improving the symmetry of the second sensors with respect to the stress generating portion having an n-gonal shape when viewed from the normal direction of the detection surface.

[0014] In one embodiment, the sensor unit may include n first sensors and n second sensors, thereby allowing the sensor unit to have an appropriate number of sensors for a stress generating portion having an n-sided polygonal shape when viewed from the normal direction of the detection surface.

[0015] In one embodiment, in the force detector, each of the n second sensors may be arranged to face the corresponding side of the n-gon that forms the shape of the stress generating portion such that a line connecting the center of the stress generating portion and the center of the second sensor passes through the center of the corresponding side of the n-gon that forms the shape of the stress generating portion, thereby further improving the symmetry of the multiple second sensors with respect to the stress generating portion that has an n-gon shape when viewed from the normal direction of the detection surface.

[0016] In one embodiment of the force detector, the n-gon may be a regular polygon, which further improves the symmetry of the unit including one stress generating portion and one sensor unit. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a force detector that can detect external forces along six axes while distinguishing them from one another using a single sensor unit. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating a schematic configuration of a force detector according to an embodiment of the present disclosure when viewed from a normal direction of a detection surface. [Figure 2] FIG. 2 is a cross-sectional view taken along the line AA in FIG. [Figure 3] 3 is a schematic diagram corresponding to FIG. 1, showing a first example of a strain distribution formed inside the layer structure of FIG. 2. FIG. [Figure 4] 3 is a schematic diagram corresponding to FIG. 1, showing a second example of the strain distribution formed inside the layer structure of FIG. 2. FIG. [Figure 5] 1. FIG. 4 is a schematic diagram corresponding to FIG. 1, showing a third example of the strain distribution formed inside the layer structure of FIG. [Figure 6]1. FIG. 4 is a schematic diagram corresponding to FIG. 1, showing a fourth example of the strain distribution formed inside the layer structure of FIG. [Figure 7] 1. FIG. 4 is a schematic diagram corresponding to FIG. 1, showing a fifth example of the strain distribution formed inside the layer structure of FIG. [Figure 8] 1. FIG. 4 is a schematic diagram corresponding to FIG. 1, showing a sixth example of the strain distribution formed inside the layer structure of FIG. [Figure 9] 1. FIG. 5 is a schematic diagram corresponding to FIG. 1, showing a seventh example of the strain distribution formed inside the layer structure of FIG. [Figure 10] FIG. 2 is a schematic diagram corresponding to FIG. 1 and showing a schematic configuration of a force detector according to a modified example. [Figure 11] FIG. 10 is a schematic diagram showing a first example of a strain distribution formed inside a conventional force detector. [Figure 12] FIG. 10 is a schematic diagram showing a second example of a strain distribution formed inside a conventional force detector. DETAILED DESCRIPTION OF THE INVENTION

[0019] The background and problems of the prior art will now be described in more detail.

[0020] Conventional force detectors have a layer structure formed using two or more types of flexible resin with different hardness, such as silicone resin. The resin may include acrylic resin, urethane resin, etc., as long as it is flexible. The layer structure has a first layer having a detection surface and a second layer formed from a resin material with a larger Young's modulus than the first layer.

[0021] The force detector has an array of protrusion structures inside a layer structure, which form a strain distribution around themselves when an external force to be detected acts on a detection surface. The strain distribution is associated with a stress distribution. The protrusion structures have, for example, a quadrangular pyramid shape. One sensor unit is arranged around one protrusion structure. The multiple sensor units are arranged inside a first layer having a smaller Young's modulus.

[0022] Fig. 11 is a schematic diagram showing a first example of a strain distribution formed inside a conventional force detector. Fig. 12 is a schematic diagram showing a second example of a strain distribution formed inside a conventional force detector. Figs. 11 and 12 are schematic diagrams showing a cross section in the XZ plane showing the inside of the layer structure of the force detector. Figs. 11 and 12 show the state when viewed from the normal direction of the detection surface of the first layer. For ease of visualization, in Figs. 11 and 12, the sensor S arranged inside the layer structure is shown by a solid line.

[0023] In a conventional force detector, four sensors S are arranged in the XZ plane as shown in Figures 11 and 12. One sensor unit including four sensors S is arranged around one protrusion structure P. For example, when a force in the X-axis direction is applied to the force detector, a strain distribution like that shown in Figure 11 is formed. The darker the color, the greater the tensile strain in the X-axis direction. The lighter the color, the greater the compressive strain in the X-axis direction. The strain applied to each sensor S varies depending on the magnitude and direction of the force. The magnitude and direction of the force can be calculated by processing the signals output from each sensor S.

[0024] On the other hand, when a force in the rotational direction about the Y axis, i.e., a torsional moment, is applied to the force detector, a strain distribution like that shown in Figure 12 is formed. However, with the sensor arrangement shown in Figure 12, no strain is applied to sensor S. Therefore, the force in the rotational direction about the Y axis cannot be detected by a single sensor unit. As a result, to measure the force in the rotational direction, calculations must be made based on the distribution of forces in the three axial directions applied to multiple sensor units, which reduces spatial resolution.

[0025] In order to solve the above problems, the present disclosure aims to provide a force detector that can detect external forces in six axes, including forces in three axial directions and rotational forces relative to each axis, while distinguishing them from one another using a single sensor unit.

[0026] Hereinafter, one embodiment of the present disclosure will be mainly described with reference to the accompanying drawings.

[0027] Fig. 1 is a schematic diagram of a general configuration of a force detector 1 according to an embodiment of the present disclosure, viewed from the normal direction of the detection surface. Fig. 2 is a cross-sectional view taken along the arrow AA in Fig. 1. For ease of visualization, a sensor 30 covered with a first layer 11, which will be described later, is shown by a solid line in Fig. 1. First, the general configuration of the force detector 1 according to an embodiment will be mainly described.

[0028] The force detector 1 is a sensor module that converts an external force acting on a detection surface M into an electrical signal and outputs the signal. The force detector 1 is used, for example, as a tactile sensor module. In this disclosure, "external force" includes, for example, forces in three axial directions and forces in rotational directions about each axis. The force detector 1 detects six-axial external forces, including forces in the three axial directions and forces in rotational directions about each axis, while distinguishing between them. The force detector 1 includes a layer structure 10, a stress generating unit 20, and a plurality of sensors 30.

[0029] As shown in FIG. 2, the layer structure 10 has a first layer 11 on which an external force to be detected acts. The first layer 11 has a detection surface M. In the present disclosure, "detection surface M" refers to the surface of the first layer 11. The layer structure 10 has a second layer 12 provided on the surface of the first layer 11 opposite to the detection surface M and formed of a material with a Young's modulus different from that of the first layer 11. The layer structure 10 has a structure in which the first layer 11 as a detection layer and the second layer 12 as a support layer are stacked.

[0030] In the following description, for convenience of explanation, the stacking direction of the first layer 11 and the second layer 12 is defined as the Y direction as shown in FIGS. 1 and 2. The Y direction corresponds to the normal direction of the detection surface M. The direction perpendicular to the Y direction is defined as the X direction. The direction perpendicular to the X and Y directions is defined as the Z direction. The installation orientation of the force detector 1 according to one embodiment is not particularly limited with respect to the direction of gravity.

[0031] As shown in FIG. 2, the first layer 11 is laminated on the second layer 12, and the surface opposite to the second layer 12 is a detection surface M. For example, the first layer 11 is formed of a material having a smaller Young's modulus than the second layer 12. For example, the first layer 11 is formed of a silicone resin having a smaller Young's modulus than the material forming the second layer 12. However, the first layer 11 is not limited to this, and it is sufficient that the first layer 11 is formed of a material having a smaller Young's modulus than the second layer 12, and the first layer 11 may be formed of other resin materials including, for example, acrylic resin and urethane resin.

[0032] The detection surface M is a surface on which an external force of the detection target acts, and is, for example, a flat surface. The detection surface M is a surface parallel to the XZ plane. However, the detection surface M is not limited to this, and may be a curved surface. When an external object directly contacts the detection surface M, the force received from the object becomes the external force of the detection target. The force detector 1 can detect both force components acting in the tangential direction of the detection surface M, i.e., the X-axis and Z-axis directions, and force components pressing against the detection surface M along the normal direction of the detection surface M, i.e., the Y direction. In addition to forces in these three axes, the force detector 1 can also detect forces in the rotational direction about each axis, distinguishing between them.

[0033] The second layer 12 is fixed to the surface of the first layer 11 opposite to the detection surface M, and supports the first layer 11. As described above, the first layer 11 is formed of a material having a smaller Young's modulus than the second layer 12. That is, the second layer 12 is formed of a material having a larger Young's modulus than the first layer 11. For example, the second layer 12 is formed of a silicone resin having a larger Young's modulus than the material from which the first layer 11 is formed. However, the second layer 12 may be formed of any material having a larger Young's modulus than the first layer 11, and may be formed of other resin materials including, for example, acrylic resin and urethane resin.

[0034] The stress generating section 20 is formed inside the layer structure 10. When an external force acts on the first layer 11, for example, the detection surface M, the stress generating section 20 generates a stress distribution around itself when viewed from the normal direction of the detection surface M. The stress distribution and the strain distribution correspond to each other. The stress generating section 20 is formed by one of the first layer 11 and the second layer 12 protruding toward the other. The stress generating section 20 includes, for example, a protrusion 21 formed by the second layer 12 protruding toward the first layer 11. The stress generating section 20 is formed as a protrusion 21 protruding from the second layer 12 side, which has a relatively large Young's modulus, toward the first layer 11 side, which has a relatively small Young's modulus. The protrusion 21 is formed by a part of the second layer 12 and is made of a material having a larger Young's modulus than the first layer 11. The protrusion 21 as a protruding structure has, for example, a quadrangular pyramid shape.

[0035] The multiple sensors 30 are dispersedly arranged around the stress generating portion 20. The multiple sensors 30 are embedded inside the first layer 11, which has a smaller Young's modulus and is more flexible. The sensors 30 may include a strain sensor that detects strain, or a pressure sensor that detects stress generated in the first layer 11. Each of the multiple sensors 30 is arranged closer to the detection surface M than the top of the protrusion 21 serving as the stress generating portion 20. The strain becomes larger on the detection surface M side than on the top of the protrusion 21 serving as the stress generating portion 20.

[0036] As shown in FIG. 1 , multiple sensors 30 are associated with one stress generating portion 20. This means that the multiple sensors 30 are distributed around one stress generating portion 20. The multiple sensors 30 associated with one stress generating portion 20 constitute one sensor unit. The sensor unit has at least six sensors 30. As an example, the sensor unit has eight sensors 30. That is, eight sensors 30 are provided for one protrusion 21. The eight sensors 30 are provided to surround the top of the protrusion 21.

[0037] The stress generating section 20 has an n-sided polygon when viewed from the normal direction of the detection surface M. The n-sided polygon may be a regular polygon or a polygon other than a regular polygon. In this case, the sensor unit has n first sensors 31 and n second sensors 32 as the multiple sensors 30. For example, if the stress generating section 20 includes a protrusion 21 having a quadrangular pyramid shape, the stress generating section 20 has a quadrangular shape, such as a square, when viewed from the normal direction of the detection surface M. In this case, the sensor unit has four first sensors 31 and four second sensors 32.

[0038] The four first sensors 31 include first sensors 31a, 31b, 31c, and 31d. The first sensor 31a is located at a position displaced in the -X direction and the -Z direction from the center P0 of the stress generating portion 20, i.e., the top of the protrusion 21. In the present disclosure, the "center P0" refers to, for example, the geometric center of the shape of the stress generating portion 20 when viewed from the normal direction of the detection surface M. The first sensor 31b is located at a position displaced in the +X direction and the -Z direction from the center P0 of the stress generating portion 20. The first sensor 31c is located at a position displaced in the +X direction and the +Z direction from the center P0 of the stress generating portion 20. The first sensor 31d is located at a position displaced in the -X direction and the +Z direction from the center P0 of the stress generating portion 20.

[0039] The four second sensors 32 include second sensors 32a, 32b, 32c, and 32d. The second sensor 32a is located at a position displaced in the -Z direction from the center P0 of the stress generation portion 20, i.e., the apex of the protrusion 21. The second sensor 32b is located at a position displaced in the +X direction from the center P0 of the stress generation portion 20. The second sensor 32c is located at a position displaced in the +Z direction from the center P0 of the stress generation portion 20. The second sensor 32d is located at a position displaced in the -X direction from the center P0 of the stress generation portion 20.

[0040] The multiple first sensors 31 in the sensor unit are located within a range of a first distance L1 from the center P0 of the stress generating unit 20. For example, the center P1 of each first sensor 31 and the center P0 of the stress generating unit 20 are separated by the same first distance L1. In the present disclosure, the "center P1" refers to, for example, the geometric center of the shape of the first sensor 31 when viewed from the normal direction of the detection surface M. The multiple second sensors 32 in the sensor unit are located within a range between the first distance L1 and a second distance L2, which is longer than the first distance L1, from the center P0 of the stress generating unit 20. For example, the center P2 of each second sensor 32 and the center P0 of the stress generating unit 20 are separated by the same second distance L2. In the present disclosure, the "center P2" refers to, for example, the geometric center of the shape of the second sensor 32 when viewed from the normal direction of the detection surface M.

[0041] Because the first distance L1 is shorter than the second distance L2, the multiple first sensors 31 are arranged closer to the stress generating portion 20 than the multiple second sensors 32. The multiple first sensors 31 are located closer to the center P0 of the stress generating portion 20. The multiple second sensors 32 are located farther from the center P0 of the stress generating portion 20. The multiple first sensors 31 are included in a region located between the stress generating portion 20 and the multiple second sensors 32.

[0042] The multiple first sensors 31 are arranged symmetrically around the stress generation unit 20. For example, when viewed from the normal direction of the detection surface M, the multiple first sensors 31 have n-fold rotational symmetry with respect to the center P0 of the stress generation unit 20. When viewed from the normal direction of the detection surface M, if the stress generation unit 20 has a quadrangular shape, the multiple first sensors 31 have 4-fold rotational symmetry with respect to the center P0 of the stress generation unit 20.

[0043] The first sensor 31 is disposed at a position different from the position on the line connecting the center P0 of the stress generating part 20 and the center P2 of the second sensor 32. More specifically, when viewed from the normal direction of the detection surface M, each of the multiple first sensors 31 is disposed at a position shifted from the line by the same rotational direction and the same angle relative to the line.

[0044] When viewed from the normal direction of the detection surface M, the first sensor 31a is positioned at a position offset by a predetermined angle counterclockwise from the line connecting the center P0 of the stress generating portion 20 and the center P2 of the second sensor 32a.

[0045] When viewed from the normal direction of the detection surface M, the first sensor 31b is positioned at a position offset by a predetermined angle counterclockwise from the line connecting the center P0 of the stress generating portion 20 and the center P2 of the second sensor 32b.

[0046] When viewed from the normal direction of the detection surface M, the first sensor 31c is positioned at a position offset by a predetermined angle counterclockwise from the line connecting the center P0 of the stress generating portion 20 and the center P2 of the second sensor 32c.

[0047] When viewed from the normal direction of the detection surface M, the first sensor 31d is positioned at a position offset by a predetermined angle counterclockwise from the line connecting the center P0 of the stress generating portion 20 and the center P2 of the second sensor 32d.

[0048] The multiple second sensors 32 are arranged symmetrically around the stress generation unit 20. For example, when viewed from the normal direction of the detection surface M, the multiple second sensors 32 have n-fold rotational symmetry with respect to the center P0 of the stress generation unit 20. When viewed from the normal direction of the detection surface M, if the stress generation unit 20 has a quadrangular shape, the multiple second sensors 32 have four-fold rotational symmetry with respect to the center P0 of the stress generation unit 20.

[0049] Each of the n second sensors 32 faces an n-gon that is the shape of the stress generation unit 20 so that a line connecting the center P0 of the stress generation unit 20 and the center P2 of the second sensor 32 passes through the center C of the corresponding side of the n-gon that is the shape of the stress generation unit 20. When viewed from the normal direction of the detection surface M, the multiple second sensors 32 have line symmetry in addition to the above-mentioned n-fold rotational symmetry.

[0050] More specifically, the second sensors 32a and 32c are arranged at positions that are symmetrical with respect to a line that passes through the center P0 of the stress generating portion 20 and is parallel to the X-axis direction. The second sensors 32b and 32d are arranged at positions that are symmetrical with respect to a line that passes through the center P0 of the stress generating portion 20 and is parallel to the Z-axis direction.

[0051] The wiring that transmits electrical signals between the sensor 30 and the sensor body is fabricated using, for example, printing technology, and is embedded inside the first layer 11, which is made of a flexible material with a smaller Young's modulus.

[0052] 1 and 2, the force detector 1 may be provided with a plurality of units arranged in an array, each unit including one stress generating section 20 and one sensor unit. The plurality of protrusions 21 may be arranged at equal intervals or at unequal intervals in the X and Z directions. The arrangement intervals of the plurality of protrusions 21 can be changed.

[0053] Next, the function of the force detector 1 according to one embodiment will be mainly described.

[0054] Fig. 3 is a schematic diagram corresponding to Fig. 1, showing a first example of a strain distribution formed inside the layer structure 10 of Fig. 2. Fig. 4 is a schematic diagram corresponding to Fig. 1, showing a second example of a strain distribution formed inside the layer structure 10 of Fig. 2. The stress distribution is formed corresponding to the strain distribution shown in each of Fig. 3 and Fig. 4. The same applies to the other figures below relating to strain distribution.

[0055] 3 and 4 show simulation results of the strain distribution formed inside the first layer 11 when an external force F is applied to the detection surface M of the first layer 11 in a tangential direction of the detection surface M, for example, in the X direction. Fig. 3 relates to the strain distribution when the external force F is applied in the negative direction of the X axis. Fig. 4 relates to the strain distribution when the external force F is applied in the positive direction of the X axis.

[0056] In Figures 3 and 4, the magnitude of tensile strain and compressive strain are indicated by the depth of the color. The darker the color, the greater the tensile strain. The lighter the color, the greater the compressive strain. This is also true for the other figures below that relate to strain distribution.

[0057] 3, when an external force acts on detection surface M in the -X direction, the entire first layer 11 attempts to move in the -X direction. At this time, because the Young's modulus of protrusion 21 is greater than that of first layer 11, the portion of first layer 11 located on the +X direction side of protrusion 21 is pressed against protrusion 21. On the other hand, the portion of first layer 11 located on the -X direction side of protrusion 21 is located behind protrusion 21 with respect to the acting direction of external force F, and is pulled by protrusion 21, which is less deformed. As a result, stress generating portion 20 generates a strain distribution, i.e., a stress distribution, around itself.

[0058] For example, in a portion of the first layer 11 closer to the detection surface M than the tops of the protrusions 21, compressive strain occurs on the +X direction side of the tops of the protrusions 21. The compressive strain is largest in a portion adjacent to the stress generating portion 20 in the +X direction, and decreases with increasing distance from the stress generating portion 20 along the +X direction. In a portion of the first layer 11 closer to the detection surface M than the tops of the protrusions 21, tensile strain occurs on the -X direction side of the tops of the protrusions 21. The tensile strain is largest in a portion adjacent to the stress generating portion 20 in the -X direction, and decreases with increasing distance from the stress generating portion 20 along the -X direction.

[0059] 4, when an external force acts on detection surface M in the +X direction, the entire first layer 11 attempts to move in the +X direction. At this time, because the Young's modulus of protrusion 21 is greater than that of first layer 11, the portion of first layer 11 located on the -X direction side of protrusion 21 is pressed against protrusion 21. On the other hand, the portion of first layer 11 located on the +X direction side of protrusion 21 is located behind protrusion 21 with respect to the acting direction of external force F, and is pulled by protrusion 21, which is less deformed. As a result, stress generating portion 20 generates a strain distribution, i.e., a stress distribution, around itself.

[0060] For example, in a portion of the first layer 11 closer to the detection surface M than the top of the protrusion 21, compressive strain occurs on the -X direction side of the top of the protrusion 21. The compressive strain is largest in a portion adjacent to the stress generating portion 20 in the -X direction, and decreases with increasing distance from the stress generating portion 20 along the -X direction. In a portion of the first layer 11 closer to the detection surface M than the top of the protrusion 21, tensile strain occurs on the +X direction side of the top of the protrusion 21. The tensile strain is largest in a portion adjacent to the stress generating portion 20 in the +X direction, and decreases with increasing distance from the stress generating portion 20 along the +X direction.

[0061] 3 and 4, when an external force F acts in the tangential direction of the detection surface M, the magnitude and type of strain differs between the upstream and downstream sides of the protrusion 21 relative to the external force F. This means that the protrusion 21 receives the external force F acting in the tangential direction of the detection surface M, generating an asymmetric strain distribution around the protrusion 21 when viewed from the normal direction of the detection surface M. The strain distribution corresponds to a stress distribution. Therefore, the protrusion 21 as the stress generating portion 20 receives the external force F acting in the tangential direction of the detection surface M, and generates an asymmetric stress distribution around the protrusion 21 when viewed from the normal direction of the detection surface M.

[0062] 3 and 4, when the direction of the external force F acting in the tangential direction of the detection surface M is reversed, the strain distribution, i.e., the stress distribution, is also reversed. Therefore, by detecting these stress distributions with the sensor 30, it is possible to measure the direction of the external force F acting in the tangential direction of the detection surface M.

[0063] As described above, in the force detector 1, the protrusions 21 are provided, so that the magnitude and direction of the stress applied around the protrusions 21 change depending on the direction of the external force F acting on the detection surface M. Different strains are applied to at least some of the eight sensors 30 included in the sensor unit depending on the magnitude and direction of the stress. Opposite strains are applied with respect to the X-axis in the +X direction and the -X direction. Therefore, the magnitude and direction of the external force F in the X-axis direction can be calculated by computing the outputs of the eight sensors 30.

[0064] More specifically, the sensors 30 output signals with intensities corresponding to the strain, i.e., stress, occurring in the first layer 11. Based on the values ​​indicated by the output signals of the eight sensors 30 provided for one protrusion 21, i.e., the detection values, it is possible to calculate what kind of external force F is acting on the detection surface M at a position on the −Y direction side of the protrusion 21.

[0065] The sensor 30 is, for example, of a type that produces a negative output when compressive strain is applied and a positive output when tensile strain is applied. For example, a piezo-resistive strain gauge can be used as this type of sensor 30. However, the sensor is not limited to this, and it is also possible to use a sensor that produces a positive output when compressive strain is applied and a negative output when tensile strain is applied as the sensor 30.

[0066] For example, if the detection values ​​of the first sensors 31b, 31c, and second sensor 32b are negative and indicate compressive strain, and the detection values ​​of the first sensors 31a, 31d, and second sensor 32d are positive and indicate tensile strain, it can be seen that an external force F is acting in the −X direction with respect to the detection surface M, as shown in Fig. 3. In addition, the magnitude of the external force F acting in the −X direction can be measured from the difference between the detection values ​​of the first sensors 31b, 31c, and second sensor 32b and the detection values ​​of the first sensors 31a, 31d, and second sensor 32d.

[0067] For example, if the detection values ​​of the first sensors 31b, 31c, and second sensor 32b are positive and indicate tensile strain, and the detection values ​​of the first sensors 31a, 31d, and second sensor 32d are negative and indicate compressive strain, it can be seen that an external force F is acting in the +X direction with respect to the detection surface M, as shown in Fig. 4. In addition, the magnitude of the external force F acting in the +X direction can be measured from the difference between the detection values ​​of the first sensors 31b, 31c, and second sensor 32b and the detection values ​​of the first sensors 31a, 31d, and second sensor 32d.

[0068] The above explanation also applies to an external force acting on the detection surface M in the Z-axis direction.

[0069] For example, if the detection values ​​of the first sensors 31c, 31d, and second sensor 32c are negative and indicate compressive strain, and the detection values ​​of the first sensors 31a, 31b, and second sensor 32a are positive and indicate tensile strain, it is understood that an external force F is acting in the -Z direction with respect to the detection surface M. In addition, the magnitude of the external force F acting in the -Z direction can be measured from the difference between the detection values ​​of the first sensors 31c, 31d, and second sensor 32c and the detection values ​​of the first sensors 31a, 31b, and second sensor 32a.

[0070] For example, if the detection values ​​of the first sensors 31c, 31d, and second sensor 32c are positive and indicate tensile strain, and the detection values ​​of the first sensors 31a, 31b, and second sensor 32a are negative and indicate compressive strain, it is understood that an external force F is acting in the +Z direction on the detection surface M. In addition, the magnitude of the external force F acting in the +Z direction can be measured from the difference between the detection values ​​of the first sensors 31c, 31d, and second sensor 32c and the detection values ​​of the first sensors 31a, 31b, and second sensor 32a.

[0071] Fig. 5 is a schematic diagram corresponding to Fig. 1, showing a third example of the strain distribution formed inside the layer structure 10 of Fig. 2. Fig. 5 shows the simulation results of the strain distribution formed inside the first layer 11 when an external force F is applied to the detection surface M of the first layer 11 in the normal direction of the detection surface M, i.e., in the Y direction. That is, Fig. 5 shows the simulation results of the strain distribution formed inside the first layer 11 when the detection surface M is pressed from the normal direction.

[0072] At this time, strain, i.e., stress, of approximately equal magnitude occurs on both sides in the X direction and on both sides in the Z direction, centered around the top of the protrusion 21. Therefore, by detecting the stressed portion of the first layer 11 around the protrusion 21 with the sensor unit, it is possible to measure the direction of the external force F acting on the detection surface M. At this time, tensile strain is applied to all eight sensors 30 included in the sensor unit.

[0073] For example, if the detection values ​​of the first sensors 31a, 31b, 31c, and 31d and the second sensors 32a, 32b, 32c, and 32d are all positive and indicate tensile strain, it can be determined that an external force F is acting in the +Y direction on the detection surface M. At this time, detection values ​​are output from the eight sensors 30, and these detection values ​​will be the same or approximately the same in magnitude. From the magnitude of these detection values ​​or the sum of the detection values, the magnitude of the external force F pressing in the normal direction on the detection surface M can be measured.

[0074] As described above, the sensor unit detects forces in the three axial directions while distinguishing between them. In addition, the sensor unit also detects forces in the rotational directions about each axis while distinguishing between them. The multiple sensors 30 associated with one stress generating section 20, as one sensor unit, detect external forces in six axes, including forces in the three axial directions and forces in the rotational directions about each axis, while distinguishing between them.

[0075] Fig. 6 is a schematic diagram corresponding to Fig. 1, showing a fourth example of the strain distribution formed inside the layer structure 10 of Fig. 2. Fig. 7 is a schematic diagram corresponding to Fig. 1, showing a fifth example of the strain distribution formed inside the layer structure 10 of Fig. 2.

[0076] 6 and 7 show simulation results of the strain distribution formed inside the first layer 11 when an external force F in a rotational direction about the Y axis is applied to the detection surface M. Fig. 6 relates to the strain distribution when an external force F rotating counterclockwise about the Y axis is applied. Fig. 7 relates to the strain distribution when an external force F rotating clockwise about the Y axis is applied.

[0077] 6, in the first layer 11, in a portion closer to the detection surface M than the tops of the protrusions 21, compressive strain occurs in two regions on the +X and -Z sides and on the -X and +Z sides of the tops of the protrusions 21. In the first layer 11, in a portion closer to the detection surface M than the tops of the protrusions 21, tensile strain occurs in two regions on the +X and +Z sides and on the -X and -Z sides of the tops of the protrusions 21.

[0078] 7, in the first layer 11, in a portion closer to the detection surface M than the tops of the protrusions 21, compressive strain occurs in two regions on the +X and +Z direction sides and on the −X and −Z direction sides of the tops of the protrusions 21. In the first layer 11, in a portion closer to the detection surface M than the tops of the protrusions 21, tensile strain occurs in two regions on the +X and −Z direction sides and on the −X and +Z direction sides of the tops of the protrusions 21.

[0079] 6 and 7, when the rotation direction of the external force F acting on the detection surface M with respect to the Y axis is reversed, the strain distribution, i.e., the stress distribution, is also reversed. Therefore, by detecting these stress distributions with the sensor 30, it is possible to measure the rotation direction of the external force F acting on the detection surface M with respect to the Y axis.

[0080] As described above, in the force detector 1, by providing the protrusions 21, the magnitude and direction of the stress applied around the protrusions 21 change depending on the rotational direction of the external force F acting on the detection surface M. Different strains are applied to at least some of the eight sensors 30 included in the sensor unit depending on the magnitude and direction of the stress. Opposite strains are applied between one set of sensors 30 and another set of sensors 30. Therefore, the magnitude and direction of the external force F in the rotational direction relative to the Y axis can be calculated by computing the outputs of the eight sensors 30.

[0081] For example, if the detection value of one set of sensors 30 including the first sensors 31b and 31d is negative and indicates compressive strain, and the detection value of the other set of sensors 30 including the first sensors 31a and 31c is positive and indicates tensile strain, it can be seen that an external force F rotating counterclockwise about the Y axis is acting on the detection surface M, as shown in Fig. 6. In addition, the magnitude of the external force F rotating counterclockwise about the Y axis can be measured based on the detection values ​​of the one set of sensors 30 and the detection values ​​of the other set of sensors 30.

[0082] For example, if the detection value of one set of sensors 30 including the first sensors 31b and 31d is positive and indicates tensile strain, and the detection value of the other set of sensors 30 including the first sensors 31a and 31c is negative and indicates compressive strain, it can be seen that an external force F rotating clockwise about the Y axis is acting on the detection surface M, as shown in Fig. 7. In addition, the magnitude of the external force F rotating clockwise about the Y axis can be measured based on the detection values ​​of the one set of sensors 30 and the detection values ​​of the other set of sensors 30.

[0083] Fig. 8 is a schematic diagram corresponding to Fig. 1, showing a sixth example of the strain distribution formed inside the layer structure 10 of Fig. 2. Fig. 9 is a schematic diagram corresponding to Fig. 1, showing a seventh example of the strain distribution formed inside the layer structure 10 of Fig. 2.

[0084] 8 and 9 show simulation results of the strain distribution formed inside the first layer 11 when an external force F in a rotational direction about the Z axis is applied to the detection surface M. Fig. 8 relates to the strain distribution when an external force F that rotates clockwise about the Z axis is applied. Fig. 9 relates to the strain distribution when an external force F that rotates counterclockwise about the Z axis is applied.

[0085] As shown in FIG. 8 , in a portion of the first layer 11 closer to the detection surface M than the top of the protrusion 21, tensile strain occurs on the +X direction side of the top of the protrusion 21. The tensile strain increases with increasing distance from the stress generating section 20 along the +X direction within the region of the first layer 11 where one sensor unit is arranged. Compressive strain occurs in a portion of the first layer 11 closer to the detection surface M than the top of the protrusion 21, on the -X direction side of the top of the protrusion 21. The compressive strain increases with increasing distance from the stress generating section 20 along the -X direction within the region of the first layer 11 where one sensor unit is arranged.

[0086] As shown in FIG. 9 , in a portion of the first layer 11 closer to the detection surface M than the top of the protrusion 21, tensile strain occurs on the −X direction side of the top of the protrusion 21. The tensile strain increases with increasing distance from the stress generating section 20 along the −X direction within the region of the first layer 11 where one sensor unit is arranged. Compressive strain occurs in a portion of the first layer 11 closer to the detection surface M than the top of the protrusion 21, on the +X direction side of the top of the protrusion 21. The compressive strain increases with increasing distance from the stress generating section 20 along the +X direction within the region of the first layer 11 where one sensor unit is arranged.

[0087] 8 and 9, when the rotation direction of the external force F acting on the detection surface M with respect to the Z axis is reversed, the strain distribution, i.e., the stress distribution, is also reversed. Therefore, by detecting these stress distributions with the sensor 30, it is possible to measure the rotation direction of the external force F acting on the detection surface M with respect to the Z axis.

[0088] As described above, in the force detector 1, the protrusions 21 are provided, so that the magnitude and direction of the stress applied around the protrusions 21 change depending on the rotational direction of the external force F acting on the detection surface M. Depending on the magnitude and direction of the stress, different strains are applied to at least some of the eight sensors 30 included in the sensor unit. Opposite strains are applied in the +X direction and the -X direction. Therefore, the magnitude and direction of the external force F in the rotational direction relative to the Z axis can be calculated by computing the outputs of the eight sensors 30.

[0089] For example, if the detection values ​​of the first sensor 31d and the second sensor 32d are negative and indicate compressive strain, and the detection value of the second sensor 32b is positive and indicates tensile strain, it can be seen that an external force F rotating clockwise about the Z axis is acting on the detection surface M, as shown in Fig. 8. In addition, the magnitude of the external force F rotating clockwise about the Z axis can be measured from the difference between the detection values ​​of the first sensor 31d and the second sensor 32d and the detection value of the second sensor 32b.

[0090] For example, if the detection values ​​of the first sensor 31b and the second sensor 32b are negative and indicate compressive strain, and the detection values ​​of the first sensor 31d and the second sensor 32d are positive and indicate tensile strain, it can be seen that an external force F rotating counterclockwise about the Z axis is acting on the detection surface M, as shown in Fig. 9. In addition, the magnitude of the external force F rotating counterclockwise about the Z axis can be measured from the difference between the detection values ​​of the first sensor 31b and the second sensor 32b and the detection values ​​of the first sensor 31d and the second sensor 32d.

[0091] The above explanation also applies when an external force F acts on the detection surface M in the rotational direction about the X axis.

[0092] As shown in FIGS. 3 to 9, the sensor unit has a sensor arrangement in which at least three sensors 30 are arranged at positions where strain distributions are formed for each of the forces included in the external force F of six axes.

[0093] 3 and 4, when an external force F is applied in the X direction to the detection surface M of the first layer 11, strain distributions are formed at the positions where the first sensors 31b, 31c and the second sensor 32b, as well as the first sensors 31a, 31d and the second sensor 32d are arranged. On the other hand, no strain distributions are formed at the positions where the second sensors 32a, 32c are arranged.

[0094] For example, as shown in FIG. 5, when an external force F is applied to the detection surface M of the first layer 11 in the Y direction, a strain distribution is formed at all of the arrangement positions of the eight sensors 30 included in the sensor unit.

[0095] 6 and 7, when an external force F in the rotational direction about the Y axis is applied to the detection surface M, strain distributions are formed at the positions of the first sensors 31b, 31d and the first sensors 31a, 31c. On the other hand, no strain distributions are formed at the positions of the second sensors 32a, 32b, 32c, 32d.

[0096] 8, when an external force F rotating clockwise about the Z axis is applied to the detection surface M, a strain distribution is formed at the positions where the first sensor 31d, the second sensor 32d, and the second sensor 32b are arranged. On the other hand, no strain distribution is formed at the positions where the first sensors 31a, 31b, and 31c and the second sensors 32a and 32c are arranged.

[0097] 9, when an external force F rotating counterclockwise about the Z axis is applied to the detection surface M, strain distributions are formed at the positions where the first sensor 31b and the second sensor 32b, and the first sensor 31d and the second sensor 32d are arranged. On the other hand, no strain distributions are formed at the positions where the first sensors 31a and 31c and the second sensors 32a and 32c are arranged.

[0098] The following mainly describes a calculation method for measuring an external force F of any magnitude and direction using a force detector 1. In a force detector 1 according to one embodiment, one sensor unit has eight sensors 30, but in the following description of the calculation method, the number of sensors 30 is generalized to consider a case where n sensors 30 are used. The following describes a calculation method for measuring a six-axis external force F, including forces in the three axial directions (X-axis, Y-axis, and Z-axis) and forces in the rotational directions about each axis, using n sensors 30.

[0099] An external force F having an arbitrary magnitude and direction is expressed as a linear combination of six reference axial forces F1, F2, F3, F4, F5, and F6.

number

[0100] The output of each sensor 30 when forces F1, F2, F3, F4, F5, and F6 are individually applied to the detection surface M is expressed by the following matrix.

number

[0101] When an arbitrary external force F is applied to the detection surface M, the output from each sensor 30 is expressed by the following vector.

number

[0102] From the above, the following relational expression is obtained:

number

[0103] According to the force detector 1 of the embodiment described above, a single sensor unit can detect external forces along six axes, i.e., forces in the three axial directions and rotational forces relative to each axis, while distinguishing between them. The force detector 1 can measure external forces along six axes, including torsional moments, while distinguishing between them, using a single sensor unit. Therefore, compared to conventional techniques that require the use of multiple sensor units to measure rotational forces, the spatial resolution when measuring external forces along six axes is improved.

[0104] By having at least six sensors 30 in the sensor unit, even if each sensor 30 is a uniaxial type, the force detector 1 can detect external forces on six axes in a single sensor unit while distinguishing them from one another. This makes it possible to calculate the six-axis components of any external force F and measure the magnitude and direction of the external force F.

[0105] By having a sensor arrangement in which at least three sensors 30 are arranged at positions where a stress distribution is formed for each of the forces contained in the six-axis external force F, the force detector 1 can more reliably detect each of the forces in the three axial directions and the rotational forces relative to each axis.

[0106] The sensor unit has a plurality of first sensors 31 located within a range of a first distance L1 from the center P0 of the stress generating unit 20, and a plurality of second sensors 32 located within a range between the first distance L1 and a second distance L2, which is longer than the first distance L1, from the center P0. This allows the force detector 1 to configure the sensor unit with a sensor arrangement such that at least three sensors 30 are arranged at positions where a stress distribution is formed for each of the forces included in the six-axis external force F. Therefore, the force detector 1 can more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0107] The first sensor 31 is disposed at a position different from the position on the line connecting the center P0 and the center P2 of the second sensor 32. This makes it possible to more reliably dispose the sensor 30 at a position where a strain distribution is formed, as shown in Figures 6 and 7, even when an external force F in a rotational direction about the Y axis acts on the detection surface M. The force detector 1 can more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0108] Each of the multiple first sensors 31 is disposed at a position shifted from the above-mentioned straight line by the same rotational direction and the same angle when viewed from the normal direction of the detection surface M. This provides the same effect as above, and the force detector 1 can more reliably detect forces in the three axial directions and forces in the rotational directions about each axis.

[0109] The second sensors 32 have n-fold rotational symmetry with respect to the center P0 of the stress generating unit 20 when viewed from the normal direction of the detection surface M. This improves the symmetry of the second sensors 32 with respect to the stress generating unit 20, which has an n-gonal shape when viewed from the normal direction of the detection surface M.

[0110] The sensor unit has n first sensors 31 and n second sensors 32. This allows the sensor unit to have an appropriate number of sensors 30 for the stress generating section 20, which has an n-sided polygonal shape when viewed from the normal direction of the detection surface M.

[0111] Each of the n second sensors 32 faces a side such that a line connecting the center P0 of the stress generation unit 20 and the center P2 of the second sensor 32 passes through the center C of the corresponding side of the n-gon that is the shape of the stress generation unit 20. This further improves the symmetry of the multiple second sensors 32 with respect to the stress generation unit 20 that has an n-gon shape when viewed from the normal direction of the detection surface M.

[0112] When the n-gon is a regular polygon, the symmetry of the unit including one stress generating portion 20 and one sensor unit is further improved.

[0113] It will be apparent to those skilled in the art that the present disclosure may be embodied in other specific forms other than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the foregoing description is illustrative and not limiting. The scope of the disclosure is defined not by the foregoing description but by the appended claims. All modifications within the range of equivalents of any modifications are intended to be embraced therein.

[0114] For example, the shape, size, arrangement, orientation, and number of each of the above-mentioned components are not limited to those shown in the above description and drawings. The shape, size, arrangement, orientation, and number of each component may be configured arbitrarily as long as the function can be realized. The components of the illustrated force detector 1 are functional concepts, and the specific form of each component is not limited to those shown.

[0115] FIG. 10 is a schematic diagram corresponding to FIG. 1, showing a general configuration of a force detector 1 according to a modified example. In the above embodiment, the sensor unit has been described as having eight sensors 30, but this is not limited to this. The sensor unit may have at least six sensors 30, for example, six sensors 30. The details described in the above embodiment also apply to the force detector 1 according to the modified example shown in FIG. 10. The following mainly describes the differences from the above embodiment.

[0116] The stress generating section 20 may have an equilateral triangular shape when viewed from the normal direction of the detection surface M. In this case, the sensor unit may have three first sensors 31 and three second sensors 32. The multiple first sensors 31 may have three-fold rotational symmetry about the center of the stress generating section 20 when viewed from the normal direction of the detection surface M. The multiple second sensors 32 may have three-fold rotational symmetry about the center of the stress generating section 20 when viewed from the normal direction of the detection surface M.

[0117] In the above embodiment and modified example, the sensor unit has been described as having at least six sensors 30. However, the present invention is not limited to this. The sensor unit may have five or fewer sensors 30, for example, as long as the sensors 30 are not uniaxial but are capable of supporting multiple axes.

[0118] In the above embodiment and modified example, the sensor unit has been described as having a sensor arrangement in which at least three sensors 30 are arranged at positions where a stress distribution is formed for each of the forces included in the six-axis external force F, but this is not limited to this. The sensor unit may have any other sensor arrangement as long as it can distinguish and detect the six-axis external force F, including forces in the three axial directions and forces in the rotational directions about each axis.

[0119] In the above embodiment and modified example, the sensor unit has been described as including a plurality of first sensors 31 positioned at a first distance L1 from the center P0 of the stress generator 20 and a plurality of second sensors 32 positioned at a second distance L2 from the center P0 that is longer than the first distance L1. However, this is not limited to this. The second distance L2 may be equal to or less than the first distance L1. That is, the sensor unit may include a plurality of first sensors 31 positioned at the first distance L1 from the center P0 and a plurality of second sensors 32 positioned at a second distance L2 that is equal to or less than the first distance L1 from the center P0.

[0120] In the above embodiment and modified example, all of the first sensors 31 are located at the same first distance L1 from the center P0, but this is not limiting. At least some of the first sensors 31 may be located at different distances from the center P0.

[0121] In the above embodiment and modified example, all of the second sensors 32 are located at the same second distance L2 from the center P0, but this is not limiting. At least some of the second sensors 32 may be located at different distances from the center P0.

[0122] In the above embodiment and modified example, the first sensor 31 is described as being disposed at a position different from the position on the line connecting the center P0 and the center P2 of the second sensor 32, but this is not limiting. The first sensor 31 may be disposed at a position on the line connecting the center P0 and the center P2 as long as it can distinguish and detect six-axial external forces F including forces in the three axial directions and forces in the rotational directions about each axis.

[0123] In the above embodiment and modified example, the multiple first sensors 31 are described as being arranged at positions shifted from each other in the same rotational direction and at the same angle with respect to the straight line when viewed from the normal direction of the detection surface M, but this is not limiting. At least some of the multiple first sensors 31 may be arranged at positions shifted from each other in at least one of different rotational directions and different angles with respect to the straight line when viewed from the normal direction of the detection surface M.

[0124] In the above embodiment and modified example, the stress generating unit 20 has been described as having an n-sided polygonal shape when viewed from the normal direction of the detection surface M, but this is not limiting. The stress generating unit 20 may have any shape as long as it can form a stress distribution around itself when viewed from the normal direction of the detection surface M when an external force F acts on the detection surface M. The stress generating unit 20 may have any other shape when viewed from the normal direction of the detection surface M, including a shape corresponding to any other figure with some of its sides recessed or protruding, a circular shape, an elliptical shape, and the like.

[0125] For example, the shape of the protrusion 21 of the stress generating unit 20 is not limited to a quadrangular pyramid, and may be any shape in which the magnitude and direction of the stress applied to the periphery of the protrusion 21 changes depending on the direction of the external force F acting on the detection surface M. For example, the protrusion 21 may have any other shape, including a polygonal prism, a cylinder, a hemisphere, a cone, and a polygonal pyramid shape other than a quadrangle.

[0126] In the above embodiment and modified example, the stress generating portion 20 has been described as having a protruding structure such as the protrusion 21, but is not limited to this. The stress generating portion 20 may have a recessed structure formed in the surface of the second layer 12 instead of a protruding structure protruding from the second layer 12. The stress generating portion 20 does not have to be formed in the second layer 12, and may be, for example, a void formed in the first layer 11 made of a more flexible material.

[0127] In the above embodiment and modified example, the multiple first sensors 31 have been described as having n-fold rotational symmetry about the center P0 of the stress generation unit 20 when viewed from the normal direction of the detection surface M, but this is not limited to this. The multiple first sensors 31 may have t-fold (t≠n)-fold rotational symmetry about the center P0 of the stress generation unit 20 when viewed from the normal direction of the detection surface M, which does not correspond to the n-gonal shape of the stress generation unit 20. The multiple first sensors 31 do not necessarily have rotational symmetry about the center P0 of the stress generation unit 20 when viewed from the normal direction of the detection surface M.

[0128] In the above embodiment and modified example, the multiple second sensors 32 have been described as having n-fold rotational symmetry about the center P0 of the stress generation unit 20 when viewed from the normal direction of the detection surface M, but this is not limited to this. The multiple second sensors 32 may have t-fold (t≠n) rotational symmetry about the center P0 of the stress generation unit 20 when viewed from the normal direction of the detection surface M, which does not correspond to the n-gonal shape of the stress generation unit 20. The multiple second sensors 32 do not necessarily have rotational symmetry about the center P0 of the stress generation unit 20 when viewed from the normal direction of the detection surface M.

[0129] In the above embodiment and modified example, the sensor unit has been described as having n first sensors 31 and n second sensors 32, but this is not limited thereto. The sensor unit may have t (t≠n) first sensors 31 that do not correspond to the n-gonal shape of the stress generation section 20. The sensor unit may have t (t≠n) second sensors 32 that do not correspond to the n-gonal shape of the stress generation section 20. The sensor unit may have a mutually different number of first sensors 31 and second sensors 32.

[0130] In the above embodiment and modified example, each of the n second sensors 32 faces a side so that the straight line connecting the center P0 of the stress generation unit 20 and the center P2 of the second sensor 32 passes through the center C of the corresponding side of the n-gon that is the shape of the stress generation unit 20. However, this is not limited to this. At least some of the n second sensors 32 may face a side so that the straight line connecting the center P0 and the center P2 does not pass through the center C of the side. At least some of the n second sensors 32 may not face a side at all.

[0131] In the above embodiment and modified example, the n-gon is described as a regular polygon, but is not limited to this. The n-gon does not have to be a regular polygon. For example, when viewed from the normal direction of the detection surface M, the stress generating unit 20 may have any other shape, such as a rectangle, a parallelogram, or a rhombus, instead of a square. For example, when viewed from the normal direction of the detection surface M, the stress generating unit 20 may have any other shape, such as an isosceles triangle or a right triangle, instead of an equilateral triangle.

[0132] As described above, the force detector 1 may include a plurality of units, each including one stress generating section 20 and one sensor unit, arranged in an array. In this case, the protrusions 21 included in each unit may have the same shape or different shapes. The units may be on the same plane or on different planes. By including a plurality of units arranged in an array, the force detector 1 can detect external forces along six axes in each unit while distinguishing them from one another.

[0133] In the above embodiment and modified example, the Young's modulus of the material forming the first layer 11 is smaller than the Young's modulus of the material forming the second layer 12, but this is not limited to this. The Young's modulus of the material forming the first layer 11 may be larger than the Young's modulus of the material forming the second layer 12. When the Young's modulus of the material forming the first layer 11 is larger than the Young's modulus of the material forming the second layer 12, the sensor 30 may be embedded in the second layer 12.

[0134] Some embodiments of the present disclosure will be described below as examples, however, it should be noted that the embodiments of the present disclosure are not limited to these examples. [Appendix 1] a layer structure including a first layer on which an external force to be detected acts, and a second layer on which the first layer is stacked and which is formed of a material having a Young's modulus different from that of the first layer; at least one stress generating portion that is formed inside the layer structure and that generates a stress distribution around itself when viewed from a normal direction of the first layer when the external force acts on the first layer; a plurality of sensors distributed around the stress generating portion; Equipped with the plurality of sensors associated with one of the stress generating portions detects, as one sensor unit, six external forces including forces in three axial directions and forces in rotational directions about each axis, while distinguishing between each other; Force detector. [Appendix 2] 10. The force detector of claim 1, The sensor unit has at least six of the sensors. Force detector. [Appendix 3] 3. The force detector of claim 1 or 2, the sensor unit has a sensor arrangement in which at least three sensors are arranged at positions where the stress distribution is formed for each of the forces included in the six-axis external force; Force detector. [Appendix 4] 4. The force detector of claim 3, The sensor unit includes a plurality of first sensors positioned within a range of a first distance from a center of the stress generating portion, and a plurality of second sensors positioned within a range between the first distance and a second distance from the center that is longer than the first distance. Force detector. [Appendix 5] 5. The force detector of claim 4, the first sensor is disposed at a position different from a position on a line connecting the center and the center of the second sensor; Force detector. [Appendix 6] 6. The force detector of claim 5, each of the plurality of first sensors is disposed at a position shifted from the straight line by the same rotational direction and the same angle relative to the straight line when viewed from the normal direction; Force detector. [Appendix 7] 7. A force detector according to any one of claims 4 to 6, comprising: the stress generating portion has an n-sided polygonal shape when viewed from the normal direction, the plurality of second sensors have n-fold rotational symmetry with respect to the center of the stress generation portion when viewed from the normal direction; Force detector. [Appendix 8] 8. The force detector of claim 7, The sensor unit includes n first sensors and n second sensors. Force detector. [Appendix 9] 9. The force detector of claim 8, each of the n second sensors faces a corresponding side of the n-gon that is the shape of the stress generation portion such that a straight line connecting the center of the stress generation portion and the center of the second sensor passes through the center of the corresponding side of the n-gon that is the shape of the stress generation portion; Force detector. [Appendix 10] 10. The force detector of any one of claims 7 to 9, The n-gon is a regular polygon. Force detector. [Explanation of symbols]

[0135] 1 Force detector 10 layer structure 11 1st layer 12 2nd layer 20 Stress generating part 21 protrusion 30 sensors 31 First sensor 31a First sensor 31b First sensor 31c First sensor 31d First sensor 32 Second sensor 32a Second sensor 32b Second sensor 32c Second sensor 32d Second sensor C center F external force L1 1st distance L2 2nd distance M detection surface P0 center P1 center P2 center

Claims

1. a layer structure including a first layer on which an external force to be detected acts, and a second layer on which the first layer is stacked and which is made of a material having a Young's modulus different from that of the first layer; at least one stress generating portion formed inside the layer structure, the stress generating portion generating a stress distribution around itself when viewed from a normal direction of the first layer when the external force acts on the first layer; a plurality of sensors dispersedly arranged around the stress generating portion; Equipped with the plurality of sensors associated with one of the stress generating portions detects, as one sensor unit, six external forces including forces in three axial directions and forces in rotational directions about the respective axes, while distinguishing between each other; Force detector.

2. 2. A force detector according to claim 1, The sensor unit has at least six of the sensors. Force detector.

3. 3. A force detector according to claim 1 or 2, the sensor unit has a sensor arrangement in which at least three sensors are arranged at positions where the stress distribution is formed for each of the forces included in the six-axis external force; Force detector.

4. 4. A force detector according to claim 3, The sensor unit includes a plurality of first sensors positioned within a range of a first distance from a center of the stress generating portion, and a plurality of second sensors positioned within a range between the first distance and a second distance from the center that is longer than the first distance. Force detector.

5. 5. A force detector according to claim 4, the first sensor is disposed at a position different from a position on a straight line connecting the center and the center of the second sensor; Force detector.

6. 6. A force detector according to claim 5, the plurality of first sensors are disposed at positions shifted from each other in the same rotational direction and at the same angle with respect to the straight line when viewed from the normal direction; Force detector.

7. 5. A force detector according to claim 4, the stress generating portion has an n-sided polygonal shape when viewed from the normal direction, the second sensors have n-fold rotational symmetry with respect to the center of the stress generation portion when viewed from the normal direction; Force detector.

8. 8. A force detector according to claim 7, The sensor unit includes n first sensors and n second sensors. Force detector.

9. 9. A force detector according to claim 8, each of the n second sensors faces a corresponding side of the n-gon that is the shape of the stress generation portion such that a straight line connecting the center of the stress generation portion and the center of the second sensor passes through a center of the corresponding side of the n-gon that is the shape of the stress generation portion; Force detector.

10. 8. A force detector according to claim 7, The n-gon is a regular polygon. Force detector.

Images