Force sensor

Abstract

In the present invention, a first optical function unit performs one of light emission and light reception. A plurality of optical waveguides are disposed along a first plane and are optically coupled to the first optical function unit at a first end, which is one end. Each of a plurality of second optical function units is optically coupled to a respective end face of a second end, which is the other end of a respective one of the plurality of optical waveguides, and constitutes a light receiving / emitting pair together with the first optical functional part. A support structure is provided to support a displacement member so that the displacement member is displaced when a force having a component parallel to the first plane or a force that acts to incline the displacement member with respect to the first plane is applied to the displacement member. The displacement member changes the degree of optical coupling between the end face of the second end of each of the optical waveguides and the second optical function unit according to the amount of displacement.

Description

Force sensor

[0001] This invention relates to a force sensor.

[0002] With the advancement of robot hands and controllers, the functionality and performance of sensors are also improving. A pressure sensor is known that applies loss fluctuations in an optical transmission path in response to an applied external force, and converts these loss fluctuations into pressure fluctuation values ​​(Patent Document 1).

[0003] Japanese Utility Model Publication No. 1-140146

[0004] For applications such as center of gravity detection, slip detection, and object texture detection, it is desirable to detect not only pressure (axial force) but also shear force and moment. The objective of the present invention is to provide a force sensor capable of measuring shear force and moment.

[0005] According to one aspect of the present invention, a force sensor is provided which includes: a first optical functional unit that emits light and / or receives light; a plurality of optical waveguides arranged along a first plane and optically coupled with the first optical functional unit at a first end, which is one end of each of the plurality of optical waveguides; a plurality of second optical functional units that optically coupled with each of the end faces of the second ends, which are the other ends of each of the plurality of optical waveguides, and which together with the first optical functional unit constitute an optical emission / receiving pair; a displacement member; and a support structure that supports the displacement member such that the displacement member is displaced when a force having a component parallel to the first plane or a force that tilts the displacement member with respect to the first plane is applied to the displacement member, wherein the displacement member is a force sensor that changes the degree of optical coupling between the end faces of the second ends of each of the optical waveguides and the second optical functional unit according to the amount of displacement.

[0006] When a force having a component parallel to the first plane, or a tilting force, is applied to the displacement member, the light-receiving level of the light-receiving pair changes according to the amount of displacement of the displacement member. Therefore, the amount of displacement of the displacement member can be calculated from the change in the light-receiving level. From the amount of displacement of the displacement member, the component of the force applied to the displacement member parallel to the first plane (shear force) or the force that tilts the displacement member (moment) can be calculated.

[0007] Figure 1 is an exploded perspective view of the force sensor according to the first embodiment. Figure 2 is a cross-sectional view of the force sensor according to the first embodiment. Figure 3 is a schematic diagram showing the coordinate system defined for the force sensor according to the first embodiment and the coordinates of each part. Figure 4A shows the i-th measurement point G ｉ Figure 4B is a schematic diagram showing the position of the displacement member 40, and Figure 5 is an exploded perspective view of the force sensor according to the second embodiment. Figure 6 is a cross-sectional view of the force sensor according to the second embodiment. Figure 7 is an exploded perspective view of the force sensor according to the third embodiment. Figure 8 is an exploded perspective view of the force sensor according to the fourth embodiment. Figure 9 is a cross-sectional view of the force sensor according to the fourth embodiment. Figure 10 is an exploded perspective view of the force sensor according to a modified example of the fourth embodiment. Figure 11 is an exploded perspective view of the force sensor according to the fifth embodiment.

[0008] [First Embodiment] A force sensor according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is an exploded perspective view of the force sensor according to the first embodiment. Multiple optical components are mounted on one surface of a circular support plate 50. The surface on which the optical components are mounted will be called the first plane 51. An xyz Cartesian coordinate system is defined with the first plane 51 as the xy plane and the normal direction of the first plane 51 as the z-axis direction. Hereinafter, the direction parallel to the xy plane will be called the transverse direction, and the z direction will be called the vertical direction. The support plate 50 includes a ring-shaped rising portion 53 that rises vertically from the first plane 51 along its outer circumference. A light-emitting portion 10 that emits light is surface-mounted on the first plane 51. For example, a light-emitting diode (LED) can be used as the light-emitting portion 10.

[0009] Four optical waveguides 20 are arranged along the first plane 51. A portion of the light emitted from the light-emitting unit 10 propagates through each of the optical waveguides 20 and is output from the output terminal. The four optical waveguides 20 are arranged radially from the light-emitting unit 10. For example, the propagation direction of light in two adjacent optical waveguides 20 in the circumferential direction forms a 90° angle. The directions parallel to the longitudinal direction of the optical waveguides 20 are defined as the x-axis direction and the y-axis direction.

[0010] The input ends of the four optical waveguides 20 are continuous with a transparent optical member covering the light-emitting unit 10. The four optical waveguides 20 and the transparent optical member covering the light-emitting unit 10 are integrally formed from the same material. A conical recess 21 is provided on the upper surface of the transparent optical member. Light emitted mainly laterally from the light-emitting unit 10 is directly incident on the optical waveguides 20. Light emitted mainly vertically is reflected by the conical surface of the recess 21 and then incident on the optical waveguides 20.

[0011] By providing the recess 21, the light emitted from the light-emitting unit 10 can be efficiently directed into the optical waveguide 20. However, since light emitted laterally from the light-emitting unit 10 is directly directed into the optical waveguide 20, it is not necessarily required to provide the recess 21. The lengths of the four optical waveguides 20 are equal. That is, the output ends of the four optical waveguides 20 are located on a common circumference centered on the light-emitting unit 10.

[0012] Multiple light-receiving units 30 are arranged at positions where light emitted from each output end of the four optical waveguides 20 enters. The light-receiving units 30 are spaced apart radially from the output ends of the optical waveguides 20, centered on the light-emitting unit 10. For example, each light-receiving unit 30 includes a light-receiving element 30A surface-mounted on the first plane 51 and an optical waveguide 30B covering the light-receiving element 30A. As the light-receiving element 30A, for example, a photodiode (PD), a phototransistor, etc., can be used.

[0013] The input end of the optical waveguide 30B faces the output end of the optical waveguide 20 at a distance, and the region near the output end of the optical waveguide 30B covers the photodetector 30A. A slope is provided on the upper surface near the output end of the optical waveguide 30B so that light emitted from the output end of the optical waveguide 20, incident on the input end of the optical waveguide 30B, and propagated to the output end of the optical waveguide 30B is efficiently incident on the photodetector 30A.

[0014] Light introduced into optical waveguides 20 and 30B is reflected by the walls of the waveguides 20 and 30B, confined within the waveguides, and propagates. Optical waveguides 20 and 30B are formed of a transparent material with a refractive index higher than that of the surrounding air. The walls of optical waveguides 20 and 30B may be covered with a material with a refractive index lower than that of the waveguide material 20 and 30B. Alternatively, the walls of optical waveguides 20 and 30B, excluding the input and output ends, may be formed of a metal film, and a light guide may be used in which light propagates through the space surrounded by the metal film while being reflected.

[0015] In a plan view of the first plane 51 (hereinafter sometimes simply referred to as "in a plan view"), a circular displacement member 40 encompassing the support plate 50 is displaceably supported on the support plate 50 by four elastic members 52. For example, coil springs are used as the elastic members 52. The four elastic members 52 are arranged on a common circumference centered on the light-emitting part 10. The elastic members 52 are also arranged on the angle bisector of the angle formed by two adjacent optical waveguides 20 that form a 90° angle.

[0016] The displacement member 40 includes a pressing plate 41, a light-shielding portion 42, and a downward-facing portion 43. The pressing plate 41 has a circular, flat shape, and an external force is applied to the pressing plate 41. The light-shielding portion 42 protrudes from the surface of the pressing plate 41 facing the support plate 50 and has a ring shape in plan view that follows the circumference centered on the light-emitting portion 10. The downward-facing portion 43 slopes downward from the outer circumference of the pressing plate 41 toward the support plate 50. With the displacement member 40 displaceably supported on the support plate 50, the inner circumferential surface of the downward-facing portion 43 is in substantially contact with the outer circumferential surface of the rising portion 53, or faces it with a small gap between them.

[0017] The calculation unit 80 controls the emission of light from the light-emitting unit 10 and receives the light-receiving results from the light-receiving unit 30. The calculation unit 80 calculates the displacement amount of the displacement member 40 based on the light-receiving level of each light-receiving unit 30, in other words, the light-receiving level of each of the multiple light-receiving pairs consisting of the light-emitting unit 10 and each of the multiple light-receiving units 30, and calculates the force applied to the displacement member 40 from the calculation results.

[0018] Figure 2 is a cross-sectional view of a force sensor according to the first embodiment. The light-emitting unit 10, optical waveguide 20, light-receiving unit 30, and elastic member 52 are mounted on the first plane 51 of the support plate 50. The light-receiving unit 30 is positioned at a distance from the output end of the optical waveguide 20. The displacement member 40 is supported by the elastic member 52 in a position facing the first plane 51. The light-shielding unit 42 is positioned between the output end of the optical waveguide 20 and the light-receiving unit 30. The light-shielding unit 42 intersects with a part of the cross-section of the light propagation path from the output end of the optical waveguide 20 to the light-receiving unit 30.

[0019] The inner circumferential surface 44 of the downward portion 43 of the displacement member 40 is in near contact with the outer circumferential surface 54 of the upward portion 53 of the support plate 50, or faces it with a small gap between them. The support structure, including the elastic member 52, the outer circumferential surface 54 of the upward portion 53 of the support plate 50, and the inner circumferential surface 44 of the downward portion 43 of the displacement member 40, restricts the lateral movement of the displacement member 40 and allows vertical displacement of the displacement member 40, as well as inclined displacement with respect to the first plane 51.

[0020] When the displacement member 40 is displaced vertically or in an inclined direction, the area of ​​the light propagation path blocked by the light-shielding portion 42 changes. That is, the range blocked by the light-shielding portion 42 changes depending on the amount of vertical displacement of the displacement member 40 and the inclination angle with respect to the first plane 51. As a result, the power of the light incident on the light-receiving portion 30 changes, and the light reception level of the light-receiving portion 30 changes.

[0021] The calculation unit 80 (Figure 1) calculates the displacement of each light-shielding section 42 based on the light-receiving levels of the multiple light-receiving sections 30, and calculates the displacement of the displacement member 40 from the displacement of each light-shielding section 42. Furthermore, from the calculation results, it determines the force that displaces the displacement member 40 in the vertical direction and the moment applied to the displacement member 40. Next, the calculation process of the calculation unit 80 will be explained with reference to Figure 3.

[0022] Figure 3 is a schematic diagram showing the coordinate system and the coordinates of each part defined in the force sensor according to the first embodiment. The point where the four optical waveguides 20 (Figure 1) intersect is defined as the origin O of the xyz Cartesian coordinate system. The points between the four optical waveguides 20 and the four light receiving units 30 (hereinafter referred to as measurement points) are each defined as G １ G ２ G３ , G ４ is marked as. The distance from the origin O to each measurement point G １ , G ２ , G ３ , G ４ to is marked as L.

[0023] The force applied to the displacement member 40 is received at the locations where the four elastic members 52 are arranged. The locations where the four elastic members 52 are arranged are respectively defined as the force receiving points R １ , R ２ , R ３ , R ４ . The xy coordinates of the force receiving points R １ , R ２ , R ３ , R ４ are respectively marked as (S ｘ , S ｙ ), (S ｘ , -S ｙ ), (-S ｘ , S ｙ ), (-S ｘ , -S ｙ ). The spring constant of each of the four elastic members 52 is marked as k.

[0024] The displacement amounts of the displacement member 40 at the positions of the force receiving points R １ , R ２ , R ３ , R ４ are respectively marked as Δx １ , Δx ２ , Δx ３ , Δx ４ . When the displacement member 40 (Fig. 1) is displaced, the displacement amounts of the light shielding portion 42 (Fig. 1) at the measurement points G １ , G ２ , G ３ , G ４ are respectively marked as H １ , H ２ , H ３ , H ４ . The displacement amount of the displacement member 40 at the origin O is marked as H ｚ . Here, the displacement in the direction in which the light shielding portion 42 approaches the first plane 51 (the direction in which the displacement member 40 is pushed in) is defined as positive.

[0025] The displacement amount H ｚIt is expressed by the following formula: H ｚ = (H １ +H ２ +H ３ +H ４ ) / 4 = (Δx １ +Δx ２ +Δx ３ +Δx ４ ) / 4...(1)

[0026] Force receiving point R １ , R ２ , R ３ , R ４ The force F applied to the elastic member 52 at each position １ F ２ F ３ F ４ It is expressed by the following formula: F １ = kΔx １ F ２ = kΔx ２ F ３ = kΔx ３ F ４ = kΔx ４ ... (2)

[0027] The compressive force F applied to the displacement member 40 ｚ It is expressed by the following formula: F ｚ = F １ +F ２ +F ３ +F ４ = k(Δx) １ +Δx ２ +Δx ３ +Δx ４ ) = k(H １ +H ２ +H ３ +H ４ ) ... (3) Displacement amount H １ H ２ H ３ H ４ This can be calculated from the light reception level of each of the four light receiving units 30. Therefore, from equation (3), the pressing force F applied to the displacement member 40 can be calculated. ｚ It is possible to calculate this.

[0028] Next, an example of a method for calculating the displacement amount from the light reception levels of the light receiving unit 30 will be described.

[0029] The relationship between each of the light reception levels of the light receiving unit 30 and the displacement amount of the light shielding unit 42 is measured in advance, and the result is stored in the arithmetic unit 80 (FIG. 1) in a table format. The arithmetic unit 80 can calculate the displacement amount of the light shielding unit 42 based on the light reception level of the light receiving unit 30 and this table.

[0030] In addition, the relationship between each of the light reception levels of the light receiving unit 30 and the displacement amount of the light shielding unit 42 may be stored as a function. Let the respective light reception levels of the light receiving unit 30 when no force is applied to the displacement member 40 be Ir ０ and mark the light reception level when the displacement amount of the light shielding unit 42 is h as Ir(h). Then, Ir(h) is expressed by the following formula using the function f(h). Ir(h) = Ir ０ ×f(h) ··· (4)

[0031] The relationship between the displacement amount h of the light shielding unit 42 and the change in the light transmission amount does not depend on the light amount of the light emitting unit 10 or the sensitivity of the light receiving unit 30. Therefore, even if the light amount of the light emitting unit 10 is different or the light reception sensitivity of the light receiving unit 30 is different, the shape of the function f(h) does not change. For this reason, there is no problem even if the light amounts of the light incident on the four optical waveguides 20 are non-uniform.

[0032] Next, the moment applied to the displacement member 40 when the displacement member 40 is inclined in the x-axis direction (rotates around the y-axis) will be described. Let the displacement amount at the position where the x-coordinate on the x-axis is S ｘ be marked as Δx, and the pushing force be F ｘ and marked as, then the following formula holds. F ｘ = 2kΔx ··· (5)

[0033] At the three points of the origin O, the coordinates (S ｘ ), 0), (L, 0), the following relational expression holds. (H ｚ - H １ ) / Δx = L / S ｘ ··· (6) From formulas (5) and (6), the following formula is derived. F ｘ = 2kS ｘ (H ｚ - H １ ) / L ··· (7)

[0034] Pushing force F ｘ is coordinate (S ｘ Since it acts on (0), the moment (moment around the y-axis) M causes the displacement member 40 to tilt in the x-axis direction. ｙ It is expressed by the following formula: M ｙ = S ｘ F ｘ = 2ks ｘ ２ (H ｚ -H １ ) / L...(8)

[0035] Similarly, the moment M that tilts the displacement member 40 in the y-axis direction (moment around the x-axis) ｘ It is expressed by the following formula: M ｘ = 2ks ｙ ２ (H ｚ -H ２ ) / L...(9) Displacement amount H from the light receiving level of the light receiving unit 30 １ H ２ H ３ H ４ Once this is determined, from equations (1), (8), and (9), the moment M ｙ M ｘ It is possible to calculate this.

[0036] Next, the excellent effects of the first embodiment will be described. In the first embodiment, the vertical force applied to the displacement member 40, the moment around the x-axis, and the moment around the y-axis can be calculated. For this reason, it can be used, for example, to measure the frictional force of an object in contact with the displacement member 40. When the force sensor according to the first embodiment is attached to the tip of a robot hand, it becomes possible to perceive the slippage and weight of the contacting object. By attaching a bar or stick to the displacement member 40, it can be used as a multi-function button for game controllers, virtual reality (VR) goggles, etc. When the displacement member 40 is attached to a joystick and operated, the z-direction component of the force applied to the displacement member 40 may be omitted from the calculation.

[0037] Next, a force sensor according to a modification of the first embodiment will be described with reference to Figures 4A and 4B. In the first embodiment (Figure 1), four optical waveguides 20 and four light receiving units 30 are arranged. That is, there are four measurement points. In contrast, in this modification, three or more optical waveguides 20 and light receiving units 30 are arranged corresponding to the optical waveguides 20. That is, there are three or more measurement points. Multiple measurement points are assigned sequential numbers starting from 1.

[0038] Figure 4A shows the i-th measurement point G. ｉ This is a schematic diagram showing the position of [point G]. The positive x-axis is used as the reference for the azimuth angle θ, and the azimuth angle in the direction of counterclockwise rotation is defined as positive. Measurement point G ｉ The azimuth angle is θ ｉ This is indicated as, and the measurement point G is measured from the origin O. ｉ The distance to r ｉ This is indicated as follows: Measurement point G ｉ The displacement amount of the light-shielding portion 42 in H ｉ This is indicated as follows: When the displacement member 40 is displaced in the vertical direction, the displacement amount H is determined for all i. ｉ They become identical.

[0039] Figure 4B is a schematic diagram showing the zx cross-section of the displacement member 40. Using the positive x-axis as the reference, the rotation angle (inclination angle) of the displacement member 40 around the y-axis in the direction in which the positive x-axis portion is compressed is φ ｙ This is indicated as follows: The amount of vertical displacement of the displacement member 40 is H ｚ This is how it is indicated. At this time, measurement point G ｉ Displacement amount H ｉ It is expressed by the following formula: H i ( ｘ ､φ ｙ ) = H z +r i ×tanφ ｙ ×cosθ ｉ +r i ×tanφ ｘ ×sinθ ｉ ... (10)

[0040] The unknown in equation (10) is H ｚ , φ ｘ , φ ｙ These are the three. Displacement amount H ｉIf we have three measurements of a variable, we can obtain a system of three linear equations. If the system of three equations is not dependent on each other, we can find the solution.

[0041] For example, three measurement points G １ G ２ G ３ θ １ = 0°, θ ２ = 90°, θ ３ When positioned at 180°, the values ​​of the sine and cosine functions in the above equation become 0 or 1, so H can be calculated using an extremely simple formula. ｚ , φ ｘ , φ ｙ It is possible to calculate this.

[0042] Next, a force sensor according to another modification of the first embodiment will be described. In the first embodiment (Figure 1), the light-shielding portion 42 is ring-shaped, but it may have other shapes. The light-shielding portion 42 only needs to be positioned between the output end of the optical waveguide 20 and the light-receiving portion 30. For example, separate plate-shaped light-shielding portions may be positioned between the output end of the optical waveguide 20 and the light-receiving portion 30.

[0043] In the first embodiment (Figure 1), the lateral displacement of the displacement member 40 is limited by a rising portion 53 arranged along the outer circumference of the support plate 50 and a falling portion 43 arranged along the outer circumference of the displacement member 40. However, the lateral displacement of the displacement member 40 may be limited by other structures. For example, one or more columns may be provided protruding from the first plane 51 of the support plate 50, and recesses or grooves may be provided at opposing locations on the displacement member 40. The lateral displacement of the displacement member 40 is limited by the fitting of the columns with the recesses or grooves.

[0044] Next, a force sensor based on yet another modification of the first embodiment will be described. In the first embodiment, multiple light-receiving units 30 are arranged for one light-emitting unit 10, but it is also possible to arrange the light-receiving units at the position of the light-emitting unit 10 and the light-emitting units at the positions of each of the multiple light-receiving units 30. In this case, by staggering the timing of the multiple light-emitting units, the displacement of the light-shielding portion 42 between each of the multiple light-emitting units and the optical waveguide 20 can be measured.

[0045] A modified version of the first embodiment in which the light-emitting unit 10 and the light-receiving unit 30 have their light-receiving and light-emitting functions reversed, and the first embodiment can be described together as follows: A first optical function unit that performs either light emission or light reception is arranged in place of the light-emitting unit 10. At the first end, which is one end of the plurality of optical waveguides 20, the optical waveguide 20 is optically coupled with the first optical function unit. A second optical function unit is arranged in place of each of the plurality of light-receiving units 30, and each of the second optical function units forms a light-receiving and light-emitting pair together with the first optical function unit. The second optical function unit is optically coupled with each of the end faces of the second ends, which are the ends of each of the plurality of optical waveguides 20 opposite to the first ends. The displacement member 40 changes the degree of optical coupling between the end faces of each of the second ends of the optical waveguides 20 and the second optical function unit according to the amount of displacement.

[0046] [Second Embodiment] Next, a force sensor according to the second embodiment will be described with reference to Figures 5 and 6. Hereinafter, the configuration common to the force sensor according to the first embodiment, described with reference to Figures 1 to 4B, will be omitted from the explanation.

[0047] Figures 5 and 6 are exploded perspective and cross-sectional views, respectively, of a force sensor according to the second embodiment. In the second embodiment, a metal dome (Peko plate) 55 is positioned between the first plane 51 and the displacement member 40 so as to cover the vicinity of the ends of the four optical waveguides 20 on the light-emitting portion 10 side.

[0048] The metal dome 55 functions as a support structure that supports the displacement member 40, together with the elastic member 52, the outer circumferential surface 54 of the rising portion 53 of the support plate 50, and the inner circumferential surface 44 of the falling portion 43 of the displacement member 40. The metal dome 55 has the function of providing a clicking sensation by deforming when the displacement member 40 is pushed toward the first plane 51. Similar to the first embodiment, the displacement member 40 is restricted from moving laterally, but is allowed to move inclined relative to the first plane 51.

[0049] Next, the superior effects of the second embodiment will be described. In the second embodiment, as in the first embodiment, the moment around the x-axis and the moment around the y-axis applied to the displacement member 40 can be calculated. Furthermore, in the second embodiment, it is possible to detect whether or not a force in the pushing direction has been applied to the displacement member 40. At this time, a click sensation can be given to the operator, so the operator can easily feel whether or not the pushing operation has been detected, thereby improving the feel of operation. In addition, at the moment of the click, that is, the moment when the metal dome deforms, the displacement amount Hz changes discontinuously and significantly. For this reason, by measuring the displacement amount Hz, the moment of the click can be easily detected.

[0050] Next, a modified example of the second embodiment will be described. In the second embodiment, a metal dome 55 is placed between the first plane 51 and the displacement member 40, but the displacement of the displacement member 40 in a direction perpendicular to the first plane 51 may be constrained at the location where the light-emitting part 10 is placed. Even in this case, the displacement member 40 is allowed to be inclined with respect to the first plane 51.

[0051] In this modified example, in equation (10), H ｚ Since this equals 0, the unknown in equation (10) is φ ｘ and φ ｙ Therefore, there are two options. For this reason, measurement point G ｉ The number of (Figure 3) can be reduced to two. For example, one measurement point can be placed on the x-axis and the other on the y-axis. In other words, two optical waveguides 20 and two light receiving units 30 can be placed.

[0052] [Third Embodiment] Next, a force sensor according to the third embodiment will be described with reference to Figure 7. The following description will omit the explanation of components common to the force sensor according to the first embodiment, which was described with reference to Figures 1 to 4B.

[0053] Figure 7 is an exploded perspective view of a force sensor according to the third embodiment. In the third embodiment, a reflecting portion 45 is provided instead of the light-shielding portion 42 (Figure 1) of the displacement member 40. With the displacement member 40 supported on the support plate 50, each output end of the optical waveguide 20 faces the inner surface of the reflecting portion 45. The reflecting portion 45 reflects the light output from each output end of the optical waveguide 20 toward the light-receiving portion 30. As a result, the light output from the output end of the optical waveguide 20 is reflected by the reflecting portion 45 and incident on the light-receiving portion 30. When the position and orientation of the reflecting portion 45 change according to the vertical displacement and tilt angle of the displacement member 40, the power of the light reflected by the reflecting portion 45 and incident on the light-receiving portion 30 changes. That is, the degree of optical coupling between the end face of the output end of the optical waveguide 20 and the light-receiving portion 30 changes.

[0054] Next, the superior effects of the third embodiment will be described. In the third embodiment, as in the first embodiment, the power of the light incident on the light receiving unit 30 changes according to the displacement of the displacement member 40. Therefore, the vertical force applied to the displacement member 40, the moment around the x-axis, and the moment around the y-axis can be calculated. In order to stabilize the relationship between the amount of displacement of the displacement member 40 and the light reception level of the light receiving unit 30, it is preferable to use a reflective part 45 that diffusely reflects light.

[0055] Furthermore, in the third embodiment, the light-emitting unit 10, the optical waveguide 20, and the light-receiving unit 30 are all arranged inside the reflecting unit 45. This allows for a compact arrangement of the optical components. As a result, it becomes possible to miniaturize and reduce the cost of the force sensor, and an excellent effect of making it easier to block external light is obtained.

[0056] Next, a force sensor according to a modification of the third embodiment will be described. In the third embodiment, as in the first embodiment, a first optical function unit having a light-receiving function may be placed at the position of the light-emitting unit 10, and a second optical function unit having a light-emitting function may be placed at each of the multiple light-receiving units 30.

[0057] [Fourth Embodiment] Next, a force sensor according to the fourth embodiment will be described with reference to Figures 8 and 9. Hereinafter, the configuration common to the force sensor according to the first embodiment, described with reference to Figures 1 to 4B, will be omitted from the explanation.

[0058] Figures 8 and 9 are exploded perspective and cross-sectional views of the force sensor according to the fourth embodiment, respectively. In the first embodiment (Figures 1 and 2), the displacement member 40 is allowed to be inclined with respect to the first plane 51 and to be vertically displaced. In contrast, in the fourth embodiment, the upper surface of the rising portion 53 that rises from the outer circumference of the support plate 50 comes into contact with the surface of the displacement member 40 that faces the first plane 51, thereby limiting the displacement of the displacement member 40 to be inclined with respect to the first plane 51 and to be vertically displaced.

[0059] In the first embodiment, the lateral displacement of the displacement member 40 is restricted. In contrast, in the fourth embodiment, a gap (tolerance) is secured between the outer circumferential surface 54 of the rising portion 53 and the inner circumferential surface 44 of the falling portion 43, allowing the lateral displacement of the displacement member 40. Multiple elastic members 56 are arranged in this gap, each connecting the outer circumferential surface 54 of the rising portion 53 and the inner circumferential surface 44 of the falling portion 43.

[0060] Multiple elastic members 56 are arranged at equal intervals in the circumferential direction. For example, elastic members 56 are arranged on the extensions of each of the four optical waveguides 20. When a force is applied to the displacement member 40 in a direction parallel to the first plane 51, the displacement member 40 is displaced laterally, and the elastic members 56 undergo elastic deformation. As the elastic members 56, for example, coil springs, highly elastic foam, etc., can be used.

[0061] The rising portion 53, the surface of the displacement member 40 facing the first plane 51, and the plurality of elastic members 56 function as a support mechanism that supports the displacement member 40 with respect to the support plate 50. The support mechanism of the force sensor according to the fourth embodiment supports the displacement member 40 so that it can be displaced laterally, and limits vertical displacement and inclined displacement.

[0062] The displacement member 40 includes a diffusion section 46 positioned perpendicular to the light propagation path from each output end of the optical waveguide 20 to the light receiving section 30. Light output from each output end of the optical waveguide 20 is incident on the diffusion section 46. The diffusion section 46 transmits the incident light and also diffuses it. For example, frosted glass or an optical diffuser designed for directionality can be used as the diffusion section 46.

[0063] When the diffusing portion 46 is displaced in a direction parallel to the first plane 51, the power of the light incident on the light-receiving portion 30 changes. That is, the degree of optical coupling between the end face of the output end of the optical waveguide 20 and the light-receiving portion 30 changes. For example, when the diffusing portion 46 moves closer to the output end of the optical waveguide 20 and further away from the light-receiving portion 30, the degree of light scattering at the position of the light-receiving portion 30 increases, so the power of the light incident on the light-receiving portion 30 decreases (the degree of optical coupling decreases). Conversely, when the diffusing portion 46 moves further away from the output end of the optical waveguide 20 and closer to the light-receiving portion 30, the power of the light incident on the light-receiving portion 30 increases (the degree of optical coupling increases).

[0064] Thus, the light-receiving level of the light-receiving unit 30 changes according to the amount of displacement of the diffusion unit 46 in a direction parallel to the first plane 51. Therefore, the amount of lateral displacement of the diffusion unit 46 and the displacement member 40 can be determined from the light-receiving level of the light-receiving unit 30.

[0065] The diffuser 46, positioned perpendicular to the x-axis, does not affect the light reception level even if it is displaced in the y-direction. Furthermore, the diffuser 46, positioned perpendicular to the y-axis, does not affect the light reception level even if it is displaced in the x-direction. Therefore, the amount of displacement in the x-direction and the amount of displacement in the y-direction can be detected independently.

[0066] Next, the excellent effects of the fourth embodiment will be described. In the fourth embodiment, the shear force applied to the displacement member 40 can be calculated from the amount of lateral displacement of the displacement member 40 and the elastic modulus of the elastic member 56.

[0067] Next, a modified example of the fourth embodiment will be described with reference to Figure 10. Figure 10 is an exploded perspective view of a force sensor according to a modified example of the fourth embodiment.

[0068] In the fourth embodiment, an elastic member 56 that applies a restoring force when the displacement member 40 is displaced laterally is positioned between the rising portion 53 and the falling portion 43. In the modified example shown in Figure 10, a plurality of elastic members 57 are positioned between the first plane 51 and the displacement member 40. A highly elastic foam having an upper surface and a lower surface parallel to each other is used as the elastic member 57. The lower surface of the elastic member 57 is fixed to the first plane 51, and the upper surface is fixed to the displacement member 40. When the displacement member 40 is displaced laterally, shear deformation occurs in the elastic member 57. The shear restoring force of the elastic member 57 causes a lateral restoring force to act on the displacement member 40.

[0069] In this way, the elastic member 57 may be placed between the first plane 51 and the displacement member 40, so that shear deformation occurs in the elastic member 57 due to the lateral displacement of the displacement member 40.

[0070] Next, various other modifications of the fourth embodiment will be described. In the fourth embodiment, the diffusion section 46 is positioned perpendicular to the light propagation path (x-axis or y-axis), but it is not necessarily required to be perpendicular. If the light propagation path and the diffusion section 46 are not perpendicular, the amount of displacement of the displacement member 40 in the x-direction and y-direction can be calculated by combining the changes in the light reception levels of the multiple light receiving sections 30.

[0071] In the fourth embodiment (Figure 9), the vertical displacement of the displacement member 40 is limited by bringing the upper surface of the rising portion 53 of the support plate 50 into contact with the surface of the displacement member 40 facing the first plane 51. Alternatively, a spacer may be placed between the first plane 51 and the displacement member 40 to limit the vertical displacement of the displacement member 40.

[0072] In the fourth embodiment, the four light propagation paths between the optical waveguide 20 and the light receiving unit 30 (hereinafter sometimes referred to as displacement measurement points) are arranged on the x-axis and y-axis, respectively. However, the three displacement measurement points may be arranged so as not to be aligned in a straight line. In this case, the lateral displacement of the displacement member 40 can be calculated from the positions of the three displacement measurement points and the change in the light receiving level.

[0073] In the fourth embodiment, as in the first embodiment, a first optical function unit having a light-receiving function may be placed at the position of the light-emitting unit 10, and a second optical function unit having a light-emitting function may be placed at each of the multiple light-receiving units 30.

[0074] When the light-emitting unit 10 and one displacement measurement point are arranged, the displacement can be calculated in a direction parallel to the straight line passing through the light-emitting unit 10 and the displacement measurement point. Furthermore, by placing one displacement measurement point on the x-axis and one displacement measurement point on the y-axis, the displacement can be calculated in the x-axis direction and the y-axis direction, respectively.

[0075] [Fifth Embodiment] Next, a force sensor according to the fifth embodiment will be described with reference to Figure 11. Hereinafter, the configuration common to the force sensor according to the fourth embodiment, described with reference to Figures 8 and 9, will be omitted from the explanation.

[0076] Figure 11 is an exploded perspective view of a force sensor according to the fifth embodiment. In the fifth embodiment, a reflecting section 47 is provided instead of the diffusion section 46 (Figures 8 and 9) of the force sensor according to the fourth embodiment. Light output from each output end of the optical waveguide 20 is reflected by the reflecting section 47. A light receiving section 30 is positioned where a portion of the light reflected by the reflecting section 47 enters.

[0077] The power of the light incident on the light-receiving unit 30, that is, the degree of optical coupling between the end face of the output end of the optical waveguide 20 and the light-receiving unit 30, depends on the distance from the output end of the optical waveguide 20 to the reflecting unit 47. The light-receiving level of the light-receiving unit 30 is maximized when the distance from the output end of the optical waveguide 20 to the reflecting unit 47 is a specific distance. As the reflecting unit 47 moves beyond a specific distance from the output end of the optical waveguide 20, the light-receiving level of the light-receiving unit 30 decreases monotonically. The movable range of the displacement member 40 is set so that when the displacement member 40 is displaced laterally, the reflecting unit 47 moves within a range in which the light-receiving level changes monotonically.

[0078] The displacement of the reflecting part 47 can be calculated from the light-receiving level of the light-receiving part 30. That is, the lateral displacement of the displacement member 40 can be calculated. In order to stabilize the relationship between the light-receiving level and the displacement of the reflecting part 47, it is preferable to use a reflecting part 47 that generates diffuse reflection.

[0079] Next, the excellent effects of the fifth embodiment will be described. In the fifth embodiment, as in the fourth embodiment, the shear force applied to the displacement member 40 can be calculated from the amount of lateral displacement of the displacement member 40 and the elastic modulus of the elastic member 56. Furthermore, since it is not necessary to place the light receiving unit 30 on the outer circumference side of the reflecting unit 47, it is possible to miniaturize the force sensor.

[0080] Next, a force sensor according to a modification of the fifth embodiment will be described. In the fifth embodiment, as in the first embodiment, a first optical function unit having a light-receiving function may be placed at the position of the light-emitting unit 10, and a second optical function unit having a light-emitting function may be placed at each of the multiple light-receiving units 30.

[0081] The embodiments described above are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects and benefits from similar configurations in multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the embodiments described above. For example, it will be obvious to those skilled in the art that various modifications, improvements, and combinations are possible.

[0082] 10 Light-emitting section 20 Optical waveguide 21 Recess 30 Light-receiving section 30A Light-receiving element 30B Optical waveguide 40 Displacement member 41 Pressing plate 42 Light-shielding section 43 Downward section 44 Inner surface of downward section 45 Reflecting section 46 Diffusing section 47 Reflecting section 50 Support plate 51 First plane 52 Elastic member 53 Upward section 54 Outer surface of upward section 55 Metal dome (Peko plate) 56, 57 Elastic member 80 Calculation section

Claims

1. A force sensor comprising: a first optical functional unit that emits light and / or receives light; a plurality of optical waveguides arranged along a first plane and optically coupled with the first optical functional unit at one end, which is a first end; a plurality of second optical functional units that optically coupled with each of the end faces of the second ends, which are the other ends of each of the plurality of optical waveguides, and that together with the first optical functional unit form an optical emission / receiving pair; a displacement member; and a support structure that supports the displacement member such that the displacement member is displaced when a force having a component parallel to the first plane or a force that tilts the displacement member with respect to the first plane is applied to the displacement member, wherein the displacement member is a force sensor that changes the degree of optical coupling between the end face of each of the second ends of the optical waveguides and the second optical functional unit according to the amount of displacement.

2. The force sensor according to claim 1, wherein the support structure restricts the movement of the displacement member in a direction parallel to the first plane and allows the displacement of the displacement member to be inclined with respect to the first plane.

3. The force sensor according to claim 2, wherein the support structure further includes a metal dome disposed between the first plane and the displacement member.

4. The force sensor according to claim 2 or 3, wherein the displacement member includes a light-shielding portion that shields a portion of the cross-section of the light propagation path between the end faces of each of the second ends of the optical waveguide and the second optical functional portion, and the range of light shielding changes according to the amount of displacement of the displacement member.

5. The force sensor according to claim 2 or 3, wherein the displacement member includes a reflecting portion that reflects light output from one of the end faces of the second ends of the optical waveguide and the second optical functional portion toward the other, and the position and orientation of the reflecting portion change according to the inclination angle of the displacement member, thereby changing the degree of optical coupling between the end face of the second end of the optical waveguide and the second optical functional portion.

6. The force sensor according to claim 1, wherein the support structure supports the displacement member so as to be displaceable in a direction parallel to the first plane.

7. The force sensor according to claim 6, wherein the displacement member is arranged to intersect the light propagation path between the end faces of each of the second ends of the optical waveguide and the second optical functional part, and includes a diffusing part that scatters and transmits incident light, and the degree of optical coupling between the end faces of the second ends of the optical waveguide and the second optical functional part changes as the diffusing part is displaced in a direction parallel to the first plane.

8. The force sensor according to claim 6, wherein the displacement member includes a reflecting portion that reflects light output from one of the end faces of the second ends of the optical waveguide and the second optical functional portion toward the other, and the degree of optical coupling between the end faces of the second ends of the optical waveguide and the second optical functional portion changes as the reflecting portion is displaced in a direction parallel to the first plane.

9. The force sensor according to any one of claims 1 to 8, further comprising a calculation unit that calculates the amount of displacement of the displacement member based on the light reception level of each of the light receiving and light emission pairs consisting of the first light function unit and a plurality of the second light function units, and determines the component of the force applied to the displacement member in a direction parallel to the first plane from the calculation result.

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