Force sensor module

Abstract

To provide a force sensor module that is not damaged even when a load greater than the load expected at the time of design is applied.SOLUTION: A force sensor module (50) according to one aspect of the present invention includes: a force sensor (10) that detects an external force according to the amount of deflection of a strain element that deflects in response to the external force; a housing (2) that accommodates the force sensor (10); and a force transmission portion (3) that transmits the external force to the strain element, the force transmission portion accommodated in the housing in a state where the force transmission portion (3) is in contact with the strain element, and having a part including a tip of the force transmission portion (3) and protruding outside the housing from a surface of the housing. The amount of protrusion of the part of the force transmission portion (3) from the surface of the housing (2) is set such that the force sensor is not damaged, even in a case where the tip is positioned in the same plane as the surface of the housing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a force sensor module. [Background technology]

[0002] A force sensor module is known that comprises a metasurface pattern provided on a first substrate made of glass, a reflective layer provided on a second substrate facing the metasurface pattern, and a spacer that defines the distance between the first and second substrates (for example, Patent Document 1). In such a force sensor module, light is incident on the metasurface pattern, and information regarding the distance between the metasurface pattern and the reflective layer is obtained using the light that passes through the metasurface pattern and is reflected by the reflective layer. Since this distance is determined according to the magnitude of the force acting in the direction normal to the main surface of the second substrate, the force sensor module can detect the magnitude of the force acting on the second substrate along a uniaxial direction using an optical method. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-94973 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the force sensor module shown in Figure 29 of Patent Document 1, the gap d (air gap d) between the reflective layer and the metasurface pattern narrows in accordance with the load applied to the second substrate. When using this force sensor module, the load corresponding to the measured gap d can be detected by measuring the gap d using an optical method.

[0005] Incidentally, if such a force sensor module is subjected to a load greater than that assumed during the design phase, at least one of the second substrate or the metasurface pattern may be damaged.

[0006] A force sensor module according to one aspect of the present invention has been made in view of the above-mentioned problems, and its purpose is to provide a force sensor module that does not break even when a load greater than the load assumed at the time of design is applied. [Means for solving the problem]

[0007] To solve the above problems, a force sensor module according to one aspect of the present invention comprises a force sensor, a housing, and a force transmission unit. The force sensor includes a strain-generating body that bends in response to an external force, and detects the external force according to the amount of bending of the strain-generating body. The housing houses the force sensor. The force transmission unit transmits the external force to the strain-generating body. The force transmission unit is housed in the housing in contact with the strain-generating body, and a portion of the force transmission unit, including its tip, protrudes from the surface of the housing to the outside of the housing. The amount of protrusion of the portion of the force transmission unit from the surface of the housing is set so that the force sensor is not damaged even when the tip is located on the same plane as the surface of the housing. [Effects of the Invention]

[0008] According to one aspect of the present invention, a force sensor module can be provided that does not break even when a load greater than the load assumed during the design phase is applied. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of the main part of a force sensor module according to Embodiment 1 of the present invention. [Figure 2] The figure shows the configuration of the main part of a force sensor module according to Embodiment 2 of the present invention, where (a) is an external view of the main part, (b) is a perspective view of the preload adjustment mechanism provided in the main part, and (c) is a cross-sectional view taken along the cutting line AA' in (a). [Figure 3] FIG. 1 is a diagram showing an embodiment of a force sensor module according to Embodiment 1 of the present invention, with the main part shown in a cross-sectional view. [Figure 4] Each of (a) to (c) in the figure is a plan view of a first substrate, a second substrate, and a spacer that constitute a force sensor provided in the main part shown in FIG. 1 and the like. [Figure 5] FIG. 2 is a diagram showing another embodiment of the force sensor module according to Embodiment 1 of the present invention, with the main part shown in a cross-sectional view. [Figure 6] FIG. 3 is a schematic perspective view of a robot hand which is an example of an acquisition device according to one aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment 1] Hereinafter, an embodiment of a force sensor module according to the present invention will be described in detail. First, the configuration of the main part of the force sensor module will be described.

[0011] <Main Part of Force Sensor Module> FIG. 1 is a cross-sectional view of the main part of the force sensor module according to the present embodiment. The main part 1 of the force sensor module 50 includes a housing 2, a force transmission part 3, and a force sensor 10.

[0012] <​​​​​​​​​​​​The housing 2 houses the force sensor 10. If the space in the housing 2 that houses the force sensor 10 is called the housing space S, then the force sensor 10 is located at the bottom of the housing space S.

[0014] The housing 2 has an opening 21 at the top, opposite the bottom. A force transmission unit 3 is located in the opening 21, and the opening 21 is sealed by the force transmission unit 3, so the housing space S is generally sealed.

[0015] The enclosure 2 can be made of a rigid material such as flame-retardant resin. The length (height) from the bottom to the opening 21 in the containment space S is constant.

[0016] While the force transmission unit 3 and force sensor 10 can be installed in the housing space S of the housing 2 through the opening 21, they may also be installed through another opening, such as the bottom of the housing 2.

[0017] (Force transmission section 3) The force transmission unit 3 is located in the opening 21 of the housing 2 and is subjected to a point load F applied from outside the opening side of the housing 2. E To allow it to receive force, a portion of the force transmission unit 3, including its tip, protrudes from the surface of the housing 2 to the outside of the housing 2. The force transmission unit 3 is housed in the housing 2 in contact with the surface (hard coat layer 17) on the opening 21 side of the force sensor 10.

[0018] The force transmission section 3 includes a fluid spring 31 made of an elastic body 311 containing a fluid 312 inside, and a protruding portion 32.

[0019] The fluid spring 31 comprises an elastic body 311 with a hollow portion and a fluid 312 filled in the hollow portion. A portion of the elastic body 311 protrudes outside the housing 2 as part of the force transmission section 3. The fluid spring 31 is a so-called diaphragm, and has a direction of expansion and contraction as a spring, and a point load F E It is positioned in the opening 21 of the housing 2 so as to substantially coincide with the direction of the load.

[0020] The elastic body 311 is preferably made of a metal material such as stainless steel, but is not limited to this.

[0021] The fluid 312 is preferably oil or air, but is not limited to these.

[0022] The protruding portion 32 is interposed between the elastic body 311 and the surface (hard coat layer 17) on the opening 21 side of the force sensor 10, and protrudes from the elastic body 311. In this example, the protruding portion 32 is composed of a substantially hemispherical structure that protrudes from the elastic body 311 toward the force sensor 10, and the tip region of the substantially hemispherical surface is in contact with the surface on the opening 21 side of the force sensor 10.

[0023] The protruding portion 32 has a structure that protrudes most at a position along the central axis of the fluid spring 31 (the point where the spring expands and contracts the most).

[0024] The protrusion 32 can be made of a material that is less deformable than the elastic body 311, and can be made of a resin material such as silicone, but is not limited to this. The protrusion 32 can be joined to the elastic body 311 by an appropriate method.

[0025] The force transmission unit 3 described above applies a point load F to the surface (hard coat layer 17) on the opening 21 side of the force sensor 10. E External forces can be transmitted. This is achieved by a portion of the tip of the fluid spring 31 protruding outside the housing 2 from the surface of the portion of the housing 2 where the opening 21 is provided. Furthermore, as will be described later, the force transmission unit 3 is positioned in the opening 21 such that the amount of protrusion of the portion that protrudes outside the housing 2 is appropriate.

[0026] (Force sensor 10) The force sensor 10 includes a strain-generating body that flexes in response to an external force. In the example shown in Figure 1, the strain-generating body that flexes in response to an external force is shown as a second substrate 12. The second substrate 12 has a hard coat layer 17 with an anti-slip structure in at least the region facing the protrusion 32 of the force transmission unit 3. Since the protrusion 32 of the force transmission unit 3 is a spherical body, the point load F E Depending on the direction in which the external force acts, the protrusion 32 may have an inclination with respect to the normal direction of the main surface of the second substrate 12. In this case, the anti-slip structure provided on the hard coat layer 17 can prevent the protrusion 32 from sliding sideways. The anti-slip structure can be realized by forming irregularities on the surface of the hard coat layer 17. Alternatively, the anti-slip structure may be realized by applying an anti-glare coating to the hard coat layer 17.

[0027] The force sensor 10 can be any force sensor that includes a strain-generating body and detects the external force according to the amount of deflection of the strain-generating body. For example, a metamaterial sensor, as described later, can be used as the force sensor 10. The second substrate 12 and the hard coat layer 17 will be described later.

[0028] <Point load (external force) acting on the force transmission section 3> The amount of protrusion of a portion of the force transmission section 3 from the surface of the housing 2 is set so that the force sensor is not damaged even when the tip of the force transmission section 3 (the tip of the fluid spring 31) is located on the same plane as the surface of the housing 2. The amount of protrusion corresponds to the length P shown in Figure 1.

[0029] In short, in the example shown in Figure 1, a point load F acts on the force transmission unit 3 from outside the housing 2. EThe load-bearing object Ob, which applies an external force, pushes the fluid spring 31 toward the second substrate 12, which is the strain-generating body, for a short period after contact begins with the tip of the force transmission unit 3 (the tip of the fluid spring 31). At this time, the force sensor 10 detects a point load (external force) due to the second substrate 12 bending under the pressure. When the fluid spring 31 is pushed further, the load-bearing object Ob is prevented from moving further in the direction of the load by the surface of the housing 2 once the tip of the force transmission unit 3 (the tip of the fluid spring 31) is in the same plane as the surface of the housing 2. As a result, the tip of the force transmission unit 3 (the tip of the fluid spring 31) cannot move any further toward the second substrate 12 than the position in the same plane as the surface of the housing 2. This prevention of further movement prevents excessive point load on the second substrate 12. Therefore, the force sensor 10 is not damaged by excessive point load.

[0030] In order to determine the length P shown in Figure 1 as described above, it is necessary to appropriately set the relative positions of the housing 2, the force transmission unit 3, and the force sensor 10. The installation of the force transmission unit 3 in the opening 21 of the housing 2 may be provided with a positioning mechanism, and the configuration may allow for fine adjustment of the position.

[0031] Furthermore, if the main part 1 of the force sensor module 50 shown in Figure 1 is configured to detect external forces on its own, then the force sensor module can be constructed using only the main part 1. On the other hand, as in Embodiment 3 described later, if the force sensor module detects external forces based on the input and output of light to a metamaterial sensor, then there are other configurations that can be included in the force sensor module besides the main part 1.

[0032] In this embodiment, even when a load greater than the load assumed during design is applied to the force transmission part, the tip of the force transmission part is not pushed inward beyond the plane of the housing surface. Therefore, this embodiment can provide a force sensor module that does not break even when a load greater than the load assumed during design is applied. Furthermore, because the force transmission part is a fluid spring made of an elastic body containing fluid, it is possible to reduce the loss of external force that may occur when the direction of the external force acting on the force transmission part is inclined with respect to the normal direction of the main surface of the second substrate. Therefore, the force sensor module of this embodiment can improve the accuracy when detecting external forces. In addition, by providing the protrusion 32, an external force can be applied to a predetermined position on the force sensor 10 (second substrate 12), which is a strain-generating body. Furthermore, in this embodiment, since an anti-slip structure is provided on the second substrate 12 at least in the area facing the protrusion 32 of the force transmission part 3, slippage of the protrusion 32 can be reduced, and as a result, the loss of external force can be reduced. Therefore, this force sensor module can improve the accuracy when detecting external forces.

[0033] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0034] Figure 2 shows the configuration of the main part of the force sensor module according to this embodiment. (a) in the figure is an external view of the main part, (b) is a perspective view of the preload adjustment mechanism provided in the main part, and (c) is a cross-sectional view taken by cutting the main part in (a) along the XZ plane including the cutting line AA', viewed from the negative side to the positive side of the Y axis.

[0035] As shown in Figure 2(a), the main part 1 of the force sensor module is covered by a cover part 5, and the protruding part of the force transmission part 3 is covered by the cover part 5 and protrudes from the sensor surface in the center of the sensor surface. A part of the preload adjustment mechanism 4, which is shown in its entirety in Figure 2(b), is exposed on the side of the main part.

[0036] As shown in the cross-sectional view (c) in Figure 2, the main part 1 of the force sensor module is covered by a cover part 5, and the housing 2 is arranged inside it. The force sensor 10, including a strain generating element (second substrate 12), is arranged in the housing space S of the housing 2.

[0037] On the side of the second substrate 12 in the force sensor 10, a force transmission unit 3 is provided to transmit external force to the second substrate 12.

[0038] (Force transmission section 3) The power transmission unit 3 is, for example, a perfectly round spherical body, and is fitted into the opening 21 of the housing 2.

[0039] The spherical force transmission section 3 has an end facing the housing space S of the housing 2 that is in contact with the force sensor 10. On the other hand, the end of the spherical force transmission section 3 that faces outward from the opening 21 of the housing 2 protrudes from the surface of the housing 2.

[0040] (Enclosure 2) The opening 21 of the housing 2 has an inner diameter D2 equal to the diameter of the spherical force transmission part 3, but in the region closer to the outside, the inner diameter narrows outward, and the inner diameter D1 is smaller than the diameter of the spherical force transmission part 3. This prevents the spherical force transmission part 3 from moving undesirably outward from the opening 21.

[0041] On the opposite side of the housing 2 from the opening 21, i.e., at the bottom of the housing 2, there is also an opening region 29 on the bottom side. Through this opening region 29, a configuration (such as an optical fiber, which will be described later) connected to the force sensor 10 can be brought out to the outside of the main part 1. Furthermore, this opening region 29 can be used as a passage when arranging the force transmission unit 3, the force sensor 10, and the preload adjustment mechanism 4 in the housing space S, but other openings may be provided in the housing 2 and used as passages.

[0042] (Cover part 5) The cover portion 5 is, for example, realized by a boot that covers the opening 21 of the housing 2 and its surrounding area. By being covered by the cover portion 5, it is possible to prevent dust from entering the storage space S through the opening 21. The cover portion 5 can be made of resin, for example.

[0043] (Preload adjustment mechanism 4) The preload adjustment mechanism 4 adjusts the preload applied to the strain generating body by adjusting the position of the force sensor 10 within the housing space S, specifically the position of the force sensor 10 in the direction normal to the main surface of the force sensor 10. Here, preload is the force that the force transmission unit applies to the strain generating body when no external force is applied to the force transmission unit.

[0044] The preload adjustment mechanism 4 includes an elastic tube 42 containing fluid 41, with a portion of the elastic tube 42 forming an annular section and the other portion forming a straight section. The annular section is positioned adjacent to the side of the force sensor 10 opposite to the strain-generating body (second substrate 12). The elastic tube 42 can contain fluid, and its diameter can be adjusted according to the amount of fluid contained. By positioning this preload adjustment mechanism 4 on the side of the force sensor 10 opposite to the strain-generating body (second substrate 12), the position of the force sensor 10 within the housing space S, specifically its position in the direction normal to the main surface of the force sensor 10, is adjusted.

[0045] The straight part is exposed to the outside from the side surface of the housing 2. In the figure, the exposed straight pipe is configured to be open at the pipe end, but this shows the state of being open for adjusting the amount of fluid as described above in the manufacturing process of the force sensing module, and the pipe end is closed by an appropriate method when the force sensing module is shipped.

[0046] The elastic tube 42 can be made of a material having abrasion resistance, and as an example, it can be made of polyacetal resin (POM). The fluid 41 can employ, for example, oil, but is not limited thereto.

[0047] As in this embodiment, the optical force sensing sensor using the metasurface pattern and the reflective layer exhibits a non-linear light response characteristic with respect to the change in the distance between the metasurface pattern and the reflective layer. Therefore, for example, the preload can be adjusted using a preload adjustment mechanism before shipment, so that the variations in the achievable response characteristics can be expanded.

[0048] <Point load (external force) acting on the force transmission part 3> Similar to the above-described Embodiment 1, in this embodiment as well, the protruding amount of a part of the force transmission part 3 from the surface of the housing 2 is set so that the force sensing sensor does not break even when the tip of the force transmission part 3 (the tip of the fluid spring 31) is located on the same plane as the surface of the housing 2. The protruding amount corresponds to the length P shown in (c) in FIG. 2.

[0049] In short, also in the example shown in (c) in FIG. 2 similar to the example shown in FIG. 1, the point load F acting on the force transmission part 3 from outside the housing 2 EThe load-bearing object that applies the external force pushes the force-bearing object 3 toward the strain-generating body, the second substrate 12, for a while after contact (contact via the cover portion 5) begins with the tip of the force-bearing object 3. At this time, the force sensor 10 detects a point load (external force) due to the second substrate 12 bending under pressure. When the force-bearing object 3 is pushed further, once the tip of the force-bearing object is positioned on the same plane as the surface of the housing 2, the surface of the housing 2 prevents it from moving any further in the direction of the load. As a result, the tip of the force-bearing object cannot move any further toward the second substrate 12 than the position on the same plane as the surface of the housing 2. This prevention of further movement avoids excessive point load on the second substrate 12. Therefore, the force sensor 10 is not damaged by excessive point load.

[0050] [Embodiment 3] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0051] One embodiment of the force sensor 10 and the force sensor module equipped therewith according to the above-described embodiments will be explained with reference to Figures 3 and 4.

[0052] Figure 3 is a diagram showing the configuration of a force sensor system 60 including a force sensor module 50, and is a cross-sectional view showing the configuration of the force sensor 10, which is part of the main part 1 of the force sensor module 50. For the sake of explanation, the housing 2, force transmission unit 3, and cover unit 5 described in the above embodiment are omitted from the illustration in Figure 3. Figures 4(a) to (c) are plan views of the first substrate 11, the second substrate 12, and the spacer 13, which constitute the force sensor 10, respectively.

[0053] (Configuration of force sensor 10) The force sensor 10 is a metamaterial sensor. Specifically, the force sensor 10 comprises a first substrate 11, a second substrate 12 (strain-generating body), a spacer 13, a metasurface pattern 14, a protective layer 15, a reflective layer 16, and a hard coat layer 17 (strain-generating body). In the force sensor 10, a point load F is applied to the second substrate 12 side of the first substrate 11 side and the second substrate 12 side. E In the state in which the point load F is applied, E Detects.

[0054] <First substrate 11> The first substrate 11 is a translucent plate-like member. In this embodiment, alkali-free glass is used as the material constituting the first substrate 11. Because alkali-free glass does not contain alkaline components, its surface is less susceptible to corrosion by chemicals and water, and it has excellent electrical insulation properties. However, the material constituting the first substrate 11 can be any solid material that is translucent in the wavelength band of light L1, as described later, and can be appropriately selected from materials available on the market. Other examples of materials constituting the first substrate 11 include quartz and polycarbonate resin. As will be described later, in this embodiment, the wavelength band of light L1 is set to 1400 nm or more and 1600 nm or less.

[0055] In this embodiment, the shape of the first substrate 11 when viewed from above (see Figure 4(a)) is a square with sides of 4 cm. Also in this embodiment, the thickness of the first substrate 11 is 500 μm. The shape and thickness of the first substrate 11 are not limited to the above example and can be determined as appropriate. A preferred thickness of the first substrate 11 is 500 μm or more and 2000 μm or less.

[0056] The first substrate 11 includes a pair of opposing main surfaces, namely main surface 111 and main surface 112. In the state shown in Figure 1, the first substrate 11 is arranged such that main surface 111 is on the upper side and main surface 112 is on the lower side. Main surface 111 is an example of a first main surface.

[0057] Furthermore, as described above, the force sensor 10 applies a point load F to the second substrate 12.E The force sensor 10 then applies a point load F. E The point load F is applied by utilizing the deflection of the second substrate 12 caused by this. E The first substrate 11 detects the point load F. E It is preferable that the material is configured such that it does not bend when the material is applied to the second substrate 12, or bends only to an extent that is negligible compared to the amount of bending of the second substrate 12.

[0058] The metasurface pattern 14 is provided on the main surface 111 of the first substrate 11, as shown in Figures 3 and 4(a). In Figure 4(a), the metasurface pattern 14 is covered by the protective layer 15 and is therefore shown with a dashed line.

[0059] The metasurface pattern 14 consists of multiple (25 in Figure 4(a)) periodically arranged subpatterns 141. In this embodiment, the subpatterns 141 are arranged in a 5x5 matrix. However, Figure 4(a) is a schematic diagram to illustrate the subpatterns 141 clearly. The actual metasurface pattern 14 is composed of many more (for example, 10,000 in the case of a 100x100 arrangement) subpatterns 141.

[0060] In this embodiment, each sub-pattern 141 (i.e., metasurface pattern 14) is made of a metal (aluminum in this embodiment). A metasurface pattern 14, as shown in Figure 4(a), can be obtained, for example, by forming a solid film of aluminum on the main surface 111 and then using lithography techniques. Aluminum has good corrosion resistance and is cheaper than gold. However, the metasurface pattern 14 is not limited to aluminum and may be made of other metals (e.g., gold, silver, copper). Gold is easy to process and corrosion resistant, but it is expensive. In this embodiment, the aluminum used to form the sub-pattern 141 is pure aluminum, not an alloy. Even pure aluminum with high purity contains small amounts of impurities. Here, the performance of the metasurface pattern 14 differs depending on the purity of the aluminum. This is because the optical constants (refractive index, extinction coefficient) change depending on the purity of the aluminum, and therefore the purity of the aluminum affects the optical properties.

[0061] Each sub-pattern 141 is a square with sides of 300 nm. The thickness of each sub-pattern 141 (i.e., the thickness of the metasurface pattern 14) is 30 nm. The preferred thickness of each sub-pattern 141 is between 20 nm and 60 nm. The performance of the metasurface pattern 14 changes depending on the thickness of each sub-pattern 141. The lower limit of the thickness of each sub-pattern 141 is the skin depth. Skin depth is the depth of the surface determined by the skin effect, and is the depth of the region where the electromagnetic field density is high when electromagnetic waves of a certain frequency are irradiated onto a metal. As the thickness of each sub-pattern 141 approaches the skin depth, the optical properties deteriorate due to insufficient light reflection, etc. On the other hand, if the thickness of each sub-pattern 141 is too thick, a different resonance mode may occur or the resonance wavelength may shift. Furthermore, the difficulty of fabrication increases with the thickness of each sub-pattern 141.

[0062] However, the periodic arrangement in the metasurface pattern 14, the material constituting the metasurface pattern 14, the shape of each sub-pattern 141, the size of each sub-pattern 141, and the thickness of each sub-pattern 141 are not limited to those described above and can be determined as appropriate by referring to existing technologies.

[0063] Furthermore, the force sensor 10 is equipped with a protective layer 15, described later, for the purpose of reducing or preventing oxidation of the metasurface pattern 14 during cleaning. In order to suppress oxidation of the metasurface pattern 14 without using the protective layer 15, it is conceivable to use materials that are resistant to oxidation, such as gold and platinum, as the material constituting the metasurface pattern 14. However, since gold and platinum are expensive, this is undesirable from the standpoint of reducing the manufacturing cost of the force sensor 10.

[0064] As shown in Figure 4(a), the protective layer 15 is provided so as to completely cover each sub-pattern 141 that constitutes the metasurface pattern 14 on the main surface 111 of the first substrate 11. The protective layer 15, like the first substrate 11, is translucent.

[0065] In this embodiment, the protective layer 15 is a solid film made of quartz glass (SiO2). In this embodiment, the thickness of the protective layer 15 is 35 nm. The thickness of the protective layer 15 is not limited to the example described above and can be determined as appropriate. The preferred thickness of the protective layer 15 is 35 nm or more and 60 nm or less.

[0066] The protective layer 15 is provided to reduce or prevent oxidation of the metasurface pattern 14 (particularly oxidation on its surface) that may occur when the first substrate 11 on which the metasurface pattern 14 is provided is directly exposed to a cleaning solution (for example, pure water) during the cleaning process. Therefore, it is preferable that the protective layer 15 is not only translucent but also composed of a dense film that does not allow the cleaning solution to pass through.

[0067] The protective layer 15 only needs to be capable of reducing or preventing oxidation of the metasurface pattern 14 described above. The materials that make up the protective layer 15, its deposition method, and its thickness can be determined as appropriate.

[0068] <Second board 12> The second substrate 12 is subjected to a point load F E It is a plate-shaped member (strain-generating body) configured to bend when a point load F is applied. As shown in Figure 3, the second substrate 12 is provided facing the first substrate 11. In this embodiment, polycarbonate resin is used as the material constituting the second substrate 12. However, the material constituting the second substrate 12 is a point load F E Any solid material that bends when subjected to a force can be used, and can be appropriately selected from materials available on the market. Other examples of materials constituting the second substrate 12 include resin materials such as acrylic resin, polystyrene resin, AS resin, and silicone resin, and metal materials such as aluminum, copper, and stainless steel.

[0069] In this embodiment, the shape of the second substrate 12 when viewed from above (see Figure 4(b)) is a square with sides of 4 cm, the same as the first substrate 11. Also in this embodiment, the thickness of the second substrate 12 is 300 μm. The shape and thickness of the second substrate 12 are determined by a point load F E It is sufficient that the substrate is configured to bend by an appropriate amount when the force is applied, and it is not limited to the examples described above. The preferred thickness of the second substrate 12 is 300 μm or more and 400 μm or less.

[0070] The second substrate 12 includes a pair of opposing main surfaces, main surface 121 and main surface 122. Main surface 121, an example of a second main surface, faces the main surface 111 of the first substrate 11. Main surface 122, which faces main surface 121, is an example of a third main surface. In the state shown in Figure 3, the second substrate 12 is arranged such that main surface 121 is on the lower side and main surface 122 is on the upper side.

[0071] The reflective layer 16 is provided on the main surface 121 of the second substrate 12, as shown in Figures 3 and 4(b). The reflective layer 16 is a metal film that generates reflected light L2 by reflecting light L1. In this embodiment, aluminum is used as the material constituting the reflective layer 16. However, the material constituting the reflective layer 16 can be any solid material that reflects light L1, and can be appropriately selected from metals available on the market. Other examples of materials constituting the reflective layer 16 include gold and silver. Here, it is advantageous in terms of process simplification and cost if the material of the reflective layer 16 is the same as the metal of the metasurface. Furthermore, the second substrate 12 does not simply need to be a metal with high reflectivity. In the force sensor module 50, the second substrate 12 and the metasurface pattern 14 are integrated via surface plasmon polaritons to form an optical resonator. Therefore, it is thought that changing the metal of the second substrate 12 will affect the optical properties.

[0072] In this embodiment, the thickness of the reflective layer 16 is 50 nm. The thickness of the reflective layer 16 is not limited to the example described above and can be determined as appropriate. A preferred thickness of the reflective layer 16 is 50 nm or more and 100 nm or less.

[0073] However, the materials that make up the reflective layer 16, the method of forming the film, and its thickness can be determined as appropriate.

[0074] As shown in Figure 3, the hard coat layer 17 is provided on the main surface 122. In this embodiment, the hard coat layer 17 is provided so as to cover the entire second substrate 12. The hard coat layer 17 may also be provided so as to further cover the side surfaces of the second substrate 12.

[0075] The hard coat layer 17 is a coating layer configured similarly to the coating layers provided on the surface of smartphones and display panels. In this embodiment, silicone resin is used as the material constituting the hard coat layer 17. However, the material constituting the hard coat layer 17 is not limited to this. Other examples of materials constituting the hard coat layer 17 include acrylic resin and fluororesin.

[0076] The hard coat layer 17 is harder than the material constituting the second substrate 12 (polycarbonate in this embodiment), making it less susceptible to scratches. Furthermore, the hard coat layer 17 has the property of being less permeable to gases.

[0077] The hard coat layer 17 is preferably on the surface of the second substrate 12 and covers as wide an area as possible, including the contact area of ​​the force transmission section 3.

[0078] Furthermore, if the second substrate 12 is made of resin, the main surface 121 of the second substrate 12, which is the surface facing the first substrate 11, may also be provided with the same coating layer as the hard coat layer 17. If the second substrate 12 is made of resin, the amount of gas that may leak out from the resin can be suppressed by the hard coat layer.

[0079] <Spacer 13> As shown in Figure 3, the spacer 13 is a component that defines the distance (distance under no load) between the first substrate 11 and the second substrate 12. In this embodiment, the spacer 13 is sandwiched between the first substrate 11 and the second substrate 12. The first substrate 11 and the spacer 13 are joined to each other, and the second substrate 12 and the spacer 13 are joined to each other. In this embodiment, a photocurable resin is used as a bonding member for joining the spacer 13 to the first substrate 11 and the second substrate 12, respectively. However, the bonding member is not limited to this, and can be appropriately selected from bonding members available on the market.

[0080] In this embodiment, the thickness of the spacer 13 is determined so that the gap G between the protective layer 15 and the reflective layer 16 is 190 nm. Also, a point load F is applied near the center of the second substrate 12. E The amount of deflection of the second substrate 12 when the point load F is applied is denoted as the deflection amount ΔG. E When this is applied, the second substrate 12 bends by an amount of deflection ΔG, so the gap G becomes narrower by the amount of deflection ΔG than the gap G in the unloaded case.

[0081] In this way, the spacing between the first substrate 11 and the second substrate 12 is fixed by interposing the spacer 13 between them. Specifically, as shown in Figure 4(c), an annular frame with both its outer and inner edges being square is used as the spacer 13. In this embodiment, the spacer 13 has an outer edge with a side length of 4 cm and the contour shape is the same as that of the first substrate 11 and the second substrate 12. However, the shape of the outer edge of the spacer 13 is not limited to this and can be determined as appropriate. Also, the spacer 13 is not limited to a closed frame and may have a part of it cut out. Furthermore, the spacer 13 may be composed of one member or of multiple members. In the latter case, each of the multiple members may be a columnar member or a cylindrical member that functions as a column.

[0082] The thickness of the spacer 13 is constant. Therefore, the first substrate 11 and the second substrate 12 can be fixed so that the main surfaces 111 and 121 that sandwich the spacer 13 are parallel to each other.

[0083] <Internal space 10S> As shown in Figure 3, the force sensor 10 is obtained by stacking a first substrate 11, which is provided with a metasurface pattern 14 and a protective layer 15, a spacer 13, and a second substrate 12, which is provided with a reflective layer 16 and a hard coat layer 17, in that order, and then joining them together. Therefore, the metasurface pattern 14, the protective layer 15, and the reflective layer 16 are housed in an internal space 10S surrounded by the first substrate 11, the second substrate 12, and the spacer 13.

[0084] In the force sensor 10 shown in Figure 3, the internal space 10S is sealed. However, in one embodiment of the present invention, the internal space 10S does not have to be sealed. If the internal space 10S is not sealed, a ventilation hole can be provided in at least one of the first substrate 11, the second substrate 12, or the spacer 13 to connect the internal space 10S with the external space of the force sensor 10 (the housing space S in Figure 1, etc.).

[0085] In the force sensor 10 of this embodiment, the metasurface pattern 14 provided on the first substrate 11 is protected by a protective layer. Therefore, even when the first substrate 11 including the metasurface pattern 14 is cleaned in a process after the metasurface pattern 14 is formed on the main surface 111, it is possible to prevent the metasurface pattern 14 from being directly exposed to the cleaning solution. If the metasurface pattern is directly exposed to the cleaning solution, the surface of the metasurface pattern may oxidize. The force sensor 10 can suppress adverse effects such as oxidation that may occur on the metasurface pattern 14, even when the first substrate 11 including the metasurface pattern 14 is cleaned in the manufacturing process. Therefore, the force sensor 10 can obtain the desired response characteristics defined at the time of design.

[0086] In the force sensor 10, the second substrate 12 is preferably made of metal or resin. With the above configuration, unlike when the second substrate 12 is made of glass, the possibility of the second substrate 12 breaking can be reduced even if a force exceeding expectations is applied to the second substrate 12. Therefore, such a force sensor 10 can enhance safety when a force exceeding expectations is applied.

[0087] Furthermore, when a second substrate 12 made of metal or resin is used, the range of Young's modulus and Poisson's ratio of the materials constituting the second substrate 12 can be expanded compared to when a second substrate made of glass is used. The response characteristics of the force sensor 10 (for example, the range of detectable force and the resolution of detectable force) are as follows: EThe deflection amount ΔG when the force is applied depends on the Young's modulus and Poisson's ratio of the material constituting the second substrate 12. Therefore, the force sensor 10 can expand the variations in achievable response characteristics by selecting the material constituting the second substrate 12 from metal and resin instead of glass. In other words, the force sensor 10 can expand the variations in its product lineup.

[0088] Furthermore, the force sensor 10 is equipped with a hard coat layer 17. If resin is used as the material constituting the second substrate 12, there is a possibility that gas will continue to be generated from the second substrate 12 even after the force sensor 10 has been manufactured. With the above configuration, the main surface 122 of the second substrate 12 is covered with the hard coat layer 17. The material constituting the hard coat layer 17 has high hardness and can suppress gas permeation. Therefore, the force sensor 10 can suppress the amount of gas that may be generated from the second substrate 12. Also, as shown in the above embodiment, an anti-slip structure is provided on the upper surface of the hard coat layer 17.

[0089] Furthermore, in the force sensor 10, it is preferable that the internal space 10S is sealed. With the above configuration, it is possible to suppress the intrusion of foreign matter (for example, dust in the air) into the internal space 10S. Therefore, the force sensor 10 can easily maintain the response characteristics assumed during the design phase.

[0090] Furthermore, in the force sensor 10, a configuration in which the internal space 10S and the external space of the force sensor 10 are in communication can also be adopted. With the above configuration, since the internal space 10S is not sealed, even if the pressure in the external space changes, the gap G between the first substrate 11 and the second substrate 12 under no load can be maintained at a predetermined distance. Therefore, one modified version of the force sensor 10 can exhibit the response characteristics assumed at the time of design, regardless of the pressure in the external space.

[0091] The force sensor 10 configured as described above is housed in the storage space S of the housing 2 shown in Figures 1 and 2, thereby forming the main part 1 of the force sensor module of each embodiment described above. The configuration of the force sensor module other than the main part 1 will be explained using Figure 3.

[0092] (Other configurations of the force sensor module 50) In addition to the main part 1, the force sensor module 50 includes an optical circulator 23, an optical fiber 24, and a collimating lens 25.

[0093] The optical circulator 23 is an optical element provided at the other end of the optical fiber 24. The optical circulator 23 is an optical element having three ports P1, P2, and P3. The optical circulator 23 is configured to emit light incident on port P1 from port P2, emit light incident on port P2 from port P3, and emit light incident on port P3 from port P1. An optical combiner may be provided instead of the optical circulator 23.

[0094] The optical fiber 24 has one end connected to a port P located on the main surface 111 side of the first substrate 11. IO It is connected to the collimating lens 25. Therefore, the optical fiber 24 emits light L1 from port P2 of the optical circulator 23 to the collimating lens 25, and also emits light L2 that enters from the collimating lens 25 into port P2.

[0095] The collimating lens 25 converts light L1 emitted from one end of the optical fiber 24 into collimated light. The collimated light L1 is then reflected by the reflective layer 16 and converted into light L2, which propagates in the reverse direction along the same path. Light L2 enters the other end of the optical fiber 24 via the collimating lens 25. Here, the collimating lens 25 efficiently couples L1, which is collimated light just like light L1, to the other end of the optical fiber 24.

[0096] [Configuration of the force sensor system 60] As shown in Figure 3, the force sensor system 60 includes, in addition to the force sensor module 50 described above, a light source 20, an optical fiber 22, an optical fiber 26, and a light detection unit 27.

[0097] The light source 20 is configured to emit light L1 with a wavelength range of 1400 nm to 1600 nm. In this embodiment, a light-emitting diode (LED) that emits near-infrared light is used as the light source 20. However, the light source 20 is not limited to an LED and can be appropriately selected from light sources available on the market. Furthermore, the light source 20 is a filter provided downstream of the LED, which limits the wavelength range of light L1 to 1400 nm to 1600 nm.

[0098] One end of the optical fiber 22 is connected to the light source 20, and the other end is connected to port P1 of the optical circulator 23. Therefore, the optical fiber 22 receives the light L1 emitted from the light source 20 into port P1 of the optical circulator 23.

[0099] One end of the optical fiber 26 is connected to the photodetector 27, and the other end is connected to port P3 of the optical circulator 23. Therefore, the optical fiber 26 emits the light L2 emitted from port P3 of the optical circulator 23 to the photodetector 27.

[0100] The photodetector 27 is configured to measure the spectrum of light L2 (in this embodiment, the reflectance spectrum). In this embodiment, the photodetector 27 includes a spectrometer that spectrally analyzes light L2, and a photodiode that converts the spectrally analyzed light L2 into electrical signals.

[0101] The inset in Figure 3 is a schematic graph showing the spectra of light L1, which is the input light of the force sensor 10, and light L2, which is the output light of the force sensor 10. In the inset, the spectrum of light L1 is shown with a solid line, and the spectrum of light L2 is shown with a dashed line.

[0102] As can be seen from the inset, the spectrum of light L2 is shifted to longer wavelengths by a shift amount Δλ when comparing the spectrum of light L1 and light L1 at their central wavelengths. The shift amount Δλ is a quantity determined by the spacing G shown in Figure 3. Furthermore, the spacing G is determined by the point load F E This is a quantity determined by the amount of deflection ΔG of the second substrate 12 when the force is applied near the center of the second substrate 12. Therefore, in the force sensor 10, the shift amount Δλ is determined by the point load F E It is a quantity determined by the magnitude of the force sensor module 50. The point load F at the force sensor 10 is determined by the force sensor module 50. E By obtaining or calculating the correlation between the point load F and the shift amount Δλ in advance, E It can detect this.

[0103] [Variation] The configuration shown in Figure 3 is one in which both the incidence and emission of light are realized through a single port. However, the configuration is not limited to this, and may also be one in which the incidence port and emission port are separate. This configuration will be explained using Figure 5.

[0104] Figure 5 is a configuration diagram showing a modified example of a force sensor system 60 including a force sensor module 50. The configuration of the force sensor 10, which is part of the main part 1 of the force sensor module 50, is shown as a cross-sectional view and is identical to the cross-sectional view of the force sensor 10 shown in Figure 3.

[0105] In the embodiment shown in Figure 5, the first substrate 11 has an incident port P on the main surface 112 side for injecting light toward the internal space 10S. I Then, the emission port P emits light from the internal space 10S. O And, is provided.

[0106] Injection port P I The first optical fiber 22A, with one end connected, is connected to it. (Ingress port P) I A diffusion lens 25A is provided.

[0107] The first optical fiber 22A is positioned so that the optical axis at one end is aligned with the normal direction of the first substrate 11. The other end of the first optical fiber 22A is connected to the light source 20 shown in Figure 3.

[0108] Light L1, which is diffused by the diffusion lens 25A and incident on the internal space 10S, is reflected by the reflection layer 16 to become reflected light L2, which passes through the first substrate 11 and enters the output port P0.

[0109] A focusing lens 28A is provided at the output port P0. Additionally, one end of the second optical fiber 26A is connected to the output port P0.

[0110] The second optical fiber 26A is positioned so that its optical axis aligns with the normal direction of the first substrate 11. The other end of the second optical fiber 26A is connected to the photodetector 27 shown in Figure 3, and the light L2 focused by the condensing lens 28A of the output port P0 enters the photodetector 27 via the second optical fiber 26A.

[0111] [Embodiment 4] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0112] The main part 1 of the force sensor module 50 in each of the embodiments described above can be attached to the finger portion of a robot hand (acquisition device) that grasps and acquires an object to be acquired (load-bearing object Ob). Figure 6 is a schematic perspective view showing an example of a robot hand. The robot hand 70 is provided with finger portions 71, and the finger portions 71 have a region that contacts the object to be acquired. The main part 1 of the force sensor module 50 in each of the embodiments described above is disposed on the finger portions 71. By distributing the main part 1 on the finger portions 71 in this way, the force sensor 10 can detect, via the force transmission unit 3, that the finger portions 71 have grasped the object to be acquired.

[0113] The main part 1 of the force sensor module 50 is not limited to robot hands. For example, if the main part 1 is attached to an acquisition device (instrument) that acquires an object, it can be used to detect when the object has been acquired. Also, for example, if the main part 1 is attached to a medical (surgical) forceps (acquisition device), it can be used to detect when an object (e.g., tissue) has been grasped by the forceps.

[0114] In this embodiment, external forces are accurately transmitted to the force sensor 10 via the force transmission unit 3, allowing detection even small forces of around mN. Therefore, in the aforementioned applications of robot hands and forceps, excessive force is not applied when grasping or pinching the object being acquired, thus preventing damage to the object due to such force.

[0115] [Additional Notes] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of Symbols]

[0116] 50 Force Sensor Modules 1. Main part of the force sensor module 2 cabinets 3. Force transmission section 31 Fluid spring 311 Elastic body 312 Fluid 32 Protrusion 10 force sensors 11. First circuit board 12 Second board 13 Spacers 14 Metasurface Patterns 15 Protective layer 16 Reflective layer 17. Hard court layer 20 light source 22A First Optical Fiber 23 Light Circulator 24 optical fibers 25 Collimating Lenses 26 Optical Fiber 26A Second Optical Fiber 27 Light detection unit 29 Optical Fiber 60 Force Sensor System 70. Robot Hand (Acquisition Device) 71 Finger part (area that contacts the object to be acquired) P O Ejection port P I Injection port P IO port

Claims

1. A force sensor includes a strain-generating body that bends in response to an external force, and detects the external force according to the amount of bending of the strain-generating body, A housing for the force sensor, A force transmission unit for transmitting the external force to the strain generating body, the force transmission unit being housed in the housing in contact with the strain generating body, and a portion of the force transmission unit, including its tip, protruding from the surface of the housing to the outside of the housing, The amount of protrusion of the part of the force transmission section from the surface of the housing is set so that the force sensor is not damaged even when the tip is located on the same plane as the surface of the housing. The force sensor is A first substrate having light-transmitting properties, A metasurface pattern provided on the first main surface of the first substrate, A second substrate provided so as to face the first substrate, the second substrate including a second main surface facing the first main surface, A reflective layer provided on the second main surface, It includes a spacer that defines the distance between the first substrate and the second substrate, The second substrate is the strain-generating body, A force sensor module characterized by the following features.

2. The aforementioned force transmission section includes an elastic body containing fluid inside as a fluid spring. A portion of the force transmission section is such that a portion of the elastic body protrudes from the housing. The force sensor module according to feature 1.

3. The force transmission section further includes a protruding portion interposed between the elastic body and the strain generating body and protruding from the elastic body. The aforementioned protrusion is made of a material that is less prone to deformation than the elastic body. The force sensor module according to feature 2.

4. A non-slip structure is provided on the surface of the strain-generating body in the region facing the protruding portion. The force sensor module according to feature 3.

5. The second substrate is made of resin, The second substrate further comprises a hard coat layer covering a third main surface that is opposite to the second main surface among a pair of main surfaces of the second substrate. A force sensor module according to any one of claims 1 to 4.

6. The first substrate, the second substrate, and the spacer constitute an internal space that accommodates the metasurface pattern and the reflective layer. The first substrate is provided with an input port for injecting light into the internal space and an output port for emitting light from the internal space. A first optical fiber, whose end is connected to the input port such that the optical axis at the end is aligned with the normal direction of the first substrate, The system further comprises a second optical fiber, the end of which is connected to the output port such that the optical axis at the end is aligned with the normal direction of the first substrate, A force sensor module according to any one of claims 1 to 5.

7. The first substrate, the second substrate, and the spacer constitute an internal space that accommodates the metasurface pattern and the reflective layer. The first substrate is provided with a port that allows light to be incident toward the internal space and to be emitted from the internal space. An optical fiber, with one end connected to the port such that the optical axis at one end is aligned with the normal direction of the first substrate, The optical fiber further comprises an optical combiner or optical circulator provided at the other end of the optical fiber. A force sensor module according to any one of claims 1 to 5.

8. The space in the housing that houses the force sensor is used as the housing space. The system further includes a preload adjustment mechanism that adjusts the preload applied to the strain generating body by adjusting the position of the force sensor within the housing space, in the direction normal to the first main surface, The preload is the force that the force transmission unit applies to the strain generating body when no external force is applied to the force transmission unit. A force sensor module according to any one of claims 1 to 7.

9. The preload adjustment mechanism includes an elastic body containing fluid inside. The force sensor module according to feature 8.

10. The force sensor module according to claim 7, A light source connected to the optical combiner or optical circulator via an optical fiber, The optical combiner or optical circulator is equipped with an optical detection unit connected via an optical fiber. A force sensor system characterized by the following features.

11. An acquisition device for acquiring an object to be acquired, A force sensor module according to any one of claims 1 to 9 is disposed in the region that contacts the object to be acquired. An acquisition device characterized by the following features.

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