Vital sensor

Abstract

To provide a vital sensor subjected to antifouling measures and waterproof measures.SOLUTION: The vital sensor comprises: a strain-inducing body comprising one face on a subject side in use and the other face positioned on the opposite side from the one face; a gel adhesive to coat the one face therewith; and a strain gage provided on the other face.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vital sensor. [Background technology]

[0002] As an example of a vital sensor, a pulse wave sensor that detects pulse waves generated when the heart pumps blood is known. One example is a pulse wave sensor that is provided with a pressure-receiving plate that is a strain-generating body supported so as to be flexible under the action of an external force, and a piezoelectric conversion means that converts the bending of the pressure-receiving plate into an electrical signal. In this pulse wave sensor, the flexible area of ​​the pressure-receiving plate is formed in a dome shape that is a convex curved surface facing outward, and a pressure detection element is provided on the inner surface of the top of the pressure-receiving plate as the piezoelectric conversion means (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-78689 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a vital sensor such as a pulse wave sensor, it is preferable that dirt and moisture do not get into the inside of the sensor.

[0005] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a vital sensor that is anti-fouling and waterproof. [Means for solving the problem]

[0006] A vital sensor according to one embodiment of the present disclosure has a strain gauge having one surface facing a subject when in use and another surface positioned opposite the one surface, a gel-like adhesive covering the one surface, and a strain gauge provided on the other surface. Effect of the Invention

[0007] According to the disclosed technology, it is possible to provide a vital sensor that is anti-fouling and waterproof. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view illustrating a vital sensor according to a first embodiment; [Diagram 2] FIG. 2 is a plan view illustrating the vital sensor according to the first embodiment. [Diagram 3] 1 is a cross-sectional view illustrating a vital sensor according to a first embodiment. [Figure 4] FIG. 2 is a plan view illustrating the strain gauge according to the first embodiment. [Diagram 5] 1 is a cross-sectional view (part 1) illustrating a strain gauge according to a first embodiment. FIG. [Figure 6] 4 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. FIG. [Figure 7] 11 is a cross-sectional view illustrating a vital sensor according to a second embodiment. FIG. [Figure 8] 11 is a cross-sectional view illustrating a vital sensor according to a third embodiment. FIG. [Figure 9] 13 is a cross-sectional view illustrating a vital sensor according to a fourth embodiment. FIG. [Figure 10] 13 is a cross-sectional view illustrating a vital sensor according to a fifth embodiment. FIG. [Figure 11] 13A and 13B are a plan view and a cross-sectional view showing an example of a detection element included in a strain gauge according to a sixth embodiment. [Figure 12] 13A to 13C are a perspective view, a plan view, and a cross-sectional view showing an example of a detection element included in a strain gauge according to a seventh embodiment. [Figure 13] 13A to 13C are a perspective view, a plan view, and a cross-sectional view showing another example of a detection element included in a strain gauge according to the seventh embodiment. [Figure 14] 13A to 13C are a perspective view, a plan view, and a cross-sectional view showing still another example of a detection element included in a strain gauge according to the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated explanations may be omitted.

[0010] First embodiment Fig. 1 is a perspective view illustrating a vital sensor according to a first embodiment. Fig. 2 is a plan view illustrating the vital sensor according to the first embodiment. Fig. 3 is a cross-sectional view illustrating the vital sensor according to the first embodiment, showing a cross section along line AA in Fig. 2.

[0011] 1 to 3, the vital sensor 1 has a housing 10, a strain element 20, a wire 30, a gel adhesive 50, and a strain gauge 100. Note that although the gel adhesive 50 is not shown in Fig. 2, the gel adhesive 50 is present in Fig. 2 at the same position as shown in Fig. 1.

[0012] The flexure body 20 has a base portion 21, a beam portion 22, a load portion 23, and an extension portion 24. The flexure body 20 is flat. The flexure body 20 has, for example, a four-fold symmetric shape in a plan view. The material of the flexure body 20 may be, for example, a metal, a ceramic, a glass, or the like. The metal used as the material of the flexure body 20 may be, for example, SUS (stainless steel), copper, aluminum, or the like. The flexure body 20 may be integrally formed, for example, by a press processing method or the like. The thickness t of the flexure body 20 excluding the load portion 23 is constant. The thickness t of the flexure body 20 excluding the load portion 23 may be, for example, 0.03 mm or more and 0.3 mm or less.

[0013] In this embodiment, for convenience, the side of the vital sensor 1 on which the load portion 23 of the flexure body 20 is provided is referred to as the "upper side", and the side on which the load portion 23 of the flexure body 20 is not provided is referred to as the "lower side". The surface located on the upper side of each part is referred to as the "upper surface", and the surface located on the lower side of each part is referred to as the "lower surface". However, the vital sensor 1 can also be used upside down. The vital sensor 1 can also be disposed at any angle. The planar view refers to viewing the object in the normal direction from the top to the bottom of the upper surface of the flexure body 20. The planar shape refers to the shape of the object when viewed in the normal direction.

[0014] In the vital sensor 1, the housing 10 is a portion that holds the strain body 20. The housing 10 is a hollow cylinder with a closed bottom and an open top. The housing 10 can be made of, for example, metal or resin. The substantially disk-shaped strain body 20 is fixed with an adhesive or the like so as to close the opening on the top side of the housing 10.

[0015] In the flexure body 20, the base 21 is a circular frame-shaped (ring-shaped) region outside the circular dashed line shown in Figs. 1 and 2. The region inside the circular dashed line may be referred to as a circular opening. In other words, the base 21 of the flexure body 20 has a circular opening. The width w1 of the base 21 is, for example, 1 mm or more and 5 mm or less. The inner diameter d of the base 21 (i.e., the diameter of the circular opening) is, for example, 5 mm or more and 35 mm or less.

[0016] The beam portion 22 is provided so as to bridge the inside of the base portion 21. The beam portion 22 has, for example, two beams that cross in a cross shape in a plan view, and the crossing region of the two beams includes the center of the circular opening. In the example of FIG. 2, one beam constituting the cross has the X direction as its longitudinal direction, and the other beam constituting the cross has the Y direction as its longitudinal direction, and they are perpendicular to each other. Each of the two perpendicular beams is preferably located inside the inner diameter d (diameter of the circular opening) of the base portion 21 and is as long as possible. In other words, it is preferable that the length of each beam is approximately equal to the diameter of the circular opening. In each beam constituting the beam portion 22, the width w2 other than the crossing region is constant, and is, for example, 1 mm or more and 5 mm or less. It is not essential that the width w2 is constant, but it is preferable that the width w2 is constant in that the strain can be detected linearly.

[0017] The load portion 23 is provided on the beam portion 22. The load portion 23 is provided, for example, in a region where two beams constituting the beam portion 22 intersect. The load portion 23 protrudes from the upper surface of the beam portion 22. The amount of protrusion of the load portion 23 based on the upper surface of the beam portion 22 is, for example, about 0.1 mm. The beam portion 22 is flexible, and elastically deforms when a load is applied to the load portion 23.

[0018] The four extensions 24 are fan-shaped portions extending from the inside of the base 21 toward the beam 22 in a plan view. A gap of about 1 mm is provided between each extension 24 and the beam 22. The extensions 24 do not contribute to the sensing of the vital sensor 1, and therefore may not be provided.

[0019] The wire 30 is a cable that inputs and outputs electrical signals between the vital sensor 1 and the outside. The wire 30 may be a shielded cable, a flexible board, or the like. The wire 30 is not an essential component of the vital sensor 1. The vital sensor 1 may be in a form that communicates with the outside by a method such as wireless communication without using the wire 30.

[0020] The gel-like adhesive 50 covers one surface of the flexure body 20. Specifically, the flexure body 20 has an upper surface 20m that faces the subject when in use, and a lower surface 20n that is located opposite the upper surface 20m, and the gel-like adhesive 50 covers the upper surface 20m of the flexure body 20. The gel-like adhesive 50 may cover a portion of the upper surface 20m of the flexure body 20, but it is preferable that the gel-like adhesive 50 covers the entire upper surface 20m.

[0021] In this way, in the vital sensor 1, the upper surface 20m of the flexure body 20 is covered with the gel-like adhesive 50, so that the flexure body 20 does not directly touch the skin of the subject. Therefore, moisture from the subject's sweat, etc. is unlikely to be transmitted to the strain gauge 100 located on the lower surface 20n side of the flexure body 20. In other words, the gel-like adhesive 50 has a waterproof function.

[0022] Furthermore, since the flexure body 20 does not come into direct contact with the skin of the subject, if the flexure body 20 is made of metal, inflammation of the skin of the subject or the onset of metal allergies due to the metal can be avoided.

[0023] Furthermore, the gel-like adhesive 50 is less irritating to the human body and can provide a good feeling to the subject when it touches the human body. Furthermore, since the gel-like adhesive 50 covers the upper surface 20m of the flexure body 20, it can prevent the upper surface 20m of the flexure body 20 from becoming dirty. In other words, the gel-like adhesive 50 has an anti-fouling function.

[0024] In addition, since the gel adhesive 50 is softer than resin and the like and does not easily impede the elastic deformation of the beam portion 22, the presence of the gel adhesive 50 is unlikely to be a factor in reducing the detection sensitivity of the vital sensor 1.

[0025] The gel-like adhesive 50 is also formed on the gap between the beam portion 22 and the extension portion 24. Therefore, the gap between the beam portion 22 and the extension portion 24 is not exposed to the outside of the vital sensor 1. The gel-like adhesive 50 may enter the gap between the beam portion 22 and the extension portion 24 and fill in a part or all of the gap between the beam portion 22 and the extension portion 24.

[0026] If the gap between beam portion 22 and extension portion 24 were open to the outside of vital sensor 1, dust, foreign matter, etc. might get caught in the gap, preventing beam portion 22 from elastically deforming. However, in vital sensor 1, gel-like adhesive 50 is formed also on the gap between beam portion 22 and extension portion 24, and the gap between beam portion 22 and extension portion 24 is not exposed to the outside of vital sensor 1. As a result, dust, foreign matter, etc. will not get caught in the gap between beam portion 22 and extension portion 24, and therefore vital sensor 1 can measure pulse waves more reliably and stably.

[0027] The gel adhesive 50 is a viscoelastic material in which a colloidal solution has lost fluidity and solidified into a jelly-like form. The gel adhesive 50 is, for example, a film-like member, and can be easily attached to the strain generating body 20 by the adhesive force of the gel adhesive 50 itself. The gel adhesive 50 can also be used repeatedly.

[0028] The thickness of the gel-like adhesive 50 can be, for example, 3 μm or more and 100 μm or less. If the gel-like adhesive 50 has such a thickness, the signal to be detected (pulse wave, etc.) is more easily transmitted to the strain generating body 20. The thickness of the gel-like adhesive 50 may be 3 μm or more and 10 μm or less. If the gel-like adhesive 50 has such a thickness, the signal to be detected (pulse wave, etc.) is even more easily transmitted to the strain generating body 20.

[0029] Examples of materials for the gel-like adhesive 50 include silicone gel, urethane gel, and (meth)acrylic gel. For example, an ultra-thin film "Yuhada (registered trademark) Permiroll (registered trademark)" manufactured by Nitto Denko Corporation may be used as the gel-like adhesive 50. Furthermore, a gel derived from natural sources may be used as the material for the gel-like adhesive 50. Examples of gel derived from natural sources include jelly, tofu, konjac, silica gel, gel composed of napalm-gasoline and a surfactant, cement gel, fish paste products, and the like.

[0030] Since the gel-like adhesive 50 is formed along the upper surface 20m of the strain generating body 20, a load portion 53 that covers the load portion 23 is formed in the gel-like adhesive 50. The load portion 53 protrudes from the upper surface of the gel-like adhesive 50. The amount of protrusion of the load portion 53 based on the upper surface of the gel-like adhesive 50 is, for example, about 0.1 mm.

[0031] In addition, since the gel adhesive 50 absorbs the unevenness of the upper surface 20m of the flexure body 20 to some extent, the upper surface of the gel adhesive 50 may be nearly flat depending on the thickness of the gel adhesive 50. In other words, the projection amount of the load portion 53 based on the upper surface of the gel adhesive 50 may be smaller than the projection amount of the load portion 23 based on the upper surface 20m of the flexure body 20.

[0032] In the present disclosure, the strain gauge 100 is an example of a detection unit that detects pulse waves and the like. The strain gauge 100 is provided on the lower surface 20n of the strain generating body 20. In this embodiment, the other surface is the lower surface 20n. The strain gauge 100 can be provided, for example, on the lower surface side of the beam portion 22. Since the beam portion 22 is flat, the strain gauge can be easily attached. One or more strain gauges 100 may be provided, but in this embodiment, four strain gauges 100 are provided. By providing four strain gauges 100, strain can be detected by a full bridge.

[0033] Two of the four strain gauges 100 are arranged on the side closer to the load section 23 of the beam whose longitudinal direction is the X direction (the center side of the circular opening) so as to face each other across the load section 23 in a plan view. The other two of the four strain gauges 100 are arranged on the side closer to the base section 21 of the beam whose longitudinal direction is the Y direction so as to face each other across the load section 23 in a plan view. With this arrangement, compressive and tensile forces can be effectively detected and a large output can be obtained by the full bridge.

[0034] The vital sensor 1 is used by being fixed to the arm of a subject so that the load section 53 covering the load section 23 abuts against the radial artery of the subject. When a load is applied to the load section 23 via the load section 53 in response to the pulse wave of the subject, causing the beam section 22 to elastically deform, the resistance value of the resistor of the strain gauge 100 changes. The vital sensor 1 can detect the pulse wave based on the change in the resistance value of the resistor of the strain gauge 100 that accompanies the deformation of the beam section 22. The pulse wave is output, for example, as a periodic change in voltage from a measurement circuit connected to the electrodes of the strain gauge 100.

[0035] [Strain gauge 100] Fig. 4 is a plan view illustrating the strain gauge according to the first embodiment. Fig. 5 is a cross-sectional view (part 1) illustrating the strain gauge according to the first embodiment, showing a cross section along line BB in Fig. 4.

[0036] 4 and 5, the strain gauge 100 has a substrate 110, a resistor 130, wiring 140, electrodes 150, and a cover layer 160. That is, the strain gauge 100 has the resistor 130 as a detection element. The cover layer 160 can be provided as necessary. For convenience, only the outer edge of the cover layer 160 is shown by a dashed line in FIGS. 4 and 5. First, each part constituting the strain gauge 100 will be described in detail.

[0037] In the explanation of the strain gauge using Figs. 4 to 6, the definition of the upper surface and the lower surface is different from that in the other figures. Specifically, in Figs. 4 to 6, for convenience, in the strain gauge 100, the side of the substrate 110 on which the resistor 130 is provided is referred to as the "upper side", and the side on which the resistor 130 is not provided is referred to as the "lower side". Also, the surface located on the upper side of each part is referred to as the "upper surface", and the surface located on the lower side of each part is referred to as the "lower surface". However, the strain gauge 100 can also be used upside down. Also, the strain gauge 100 can be arranged at any angle. Also, the planar view refers to viewing the object in the normal direction from the upper side to the lower side with respect to the upper surface 110a of the substrate 110. And, the planar shape refers to the shape of the object when the object is viewed in the normal direction. The strain gauge 100 is attached to the lower surface 20n of the flexure body 20 such that the base material 110 faces the lower surface 20n of the flexure body 20.

[0038] The substrate 110 is a member that serves as a base layer for forming the resistor 130 and the like. The substrate 110 is flexible. There is no particular limitation on the thickness of the substrate 110, and it may be appropriately determined depending on the intended use of the strain gauge 100, etc. For example, the thickness of the substrate 110 may be about 5 μm to 500 μm. From the viewpoint of the transferability of strain from the lower surface 20n of the strain generating body 20 to the sensing part and the dimensional stability against environmental changes, the thickness of the substrate 110 is preferably within the range of 5 μm to 200 μm. From the viewpoint of insulation, the thickness of the substrate 110 is preferably 10 μm or more.

[0039] The substrate 110 is formed from an insulating resin film such as, for example, PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, LCP (liquid crystal polymer) resin, polyolefin resin, etc. The film refers to a member having a thickness of about 500 μm or less and having flexibility.

[0040] When the base material 110 is formed from an insulating resin film, the insulating resin film may contain a filler, impurities, etc. For example, the base material 110 may be formed from an insulating resin film containing a filler such as silica or alumina.

[0041] Examples of materials other than resin for the base material 110 include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, and perovskite ceramics (CaTiO3, BaTiO3). In addition to the above-mentioned crystalline materials, amorphous glass or the like may be used as the material for the base material 110. Metals such as aluminum, aluminum alloy (duralumin), and titanium may also be used as the material for the base material 110. When a metal base material 110 is used, an insulating film is provided so as to cover the upper surface 110a.

[0042] The resistor 130 is a thin film formed in a predetermined pattern on the upper side of the substrate 110. In the strain gauge 100, the resistor 130 is a sensing part that receives strain and generates a resistance change. The resistor 130 may be formed directly on the upper surface 110a of the substrate 110, or may be formed on the upper surface 110a of the substrate 110 via another layer. For convenience, the resistor 130 is shown in FIG. 4 as having a dense matte pattern.

[0043] The resistor 130 has a structure in which multiple elongated parts are arranged at regular intervals with their longitudinal direction in the same direction (the direction of the line BB in the example of FIG. 4), and the ends of adjacent elongated parts are alternately connected, folding back in a zigzag pattern as a whole. The longitudinal direction of the multiple elongated parts is the grid direction, and the direction perpendicular to the grid direction is the grid width direction (the direction perpendicular to the line BB in the example of FIG. 4).

[0044] One end in the longitudinal direction of the two elongated portions located at the outermost sides in the grid width direction is bent in the grid width direction to form terminal ends 130e1 and 130e2 of the resistor 130 in the grid width direction. The terminal ends 130e1 and 130e2 of the resistor 130 in the grid width direction are electrically connected to the electrode 150 via the wiring 140. In other words, the wiring 140 electrically connects the terminal ends 130e1 and 130e2 of the resistor 130 in the grid width direction to the electrodes 150.

[0045] The resistor 130 can be formed, for example, from a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 130 can be formed from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr mixed phase film. An example of a material containing Ni is Cu-Ni (copper nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0046] Here, the Cr mixed phase film is a film in which Cr, CrN, Cr2N, etc. are mixed. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0047] The thickness of the resistor 130 is not particularly limited and may be appropriately determined depending on the intended use of the strain gauge 100. For example, the thickness of the resistor 130 may be about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 130 is 0.1 μm or more, the crystallinity of the crystals constituting the resistor 130 (for example, the crystallinity of α-Cr) is improved. Furthermore, when the thickness of the resistor 130 is 1 μm or less, (i) cracks in the film and (ii) warping of the film from the substrate 110 caused by the internal stress of the film constituting the resistor 130 are reduced.

[0048] Considering the need to prevent lateral sensitivity and to prevent disconnection, the width of resistor 130 is preferably 10 μm to 100 μm. More specifically, the width of resistor 130 is preferably 10 μm to 70 μm, and more preferably 10 μm to 50 μm.

[0049] For example, when the resistor 130 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by making α-Cr (alpha chromium) which is a stable crystal phase the main component. For example, when the resistor 130 is a Cr mixed-phase film, the resistor 130 can make α-Cr the main component, so that the gauge factor of the strain gauge 100 is 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C. Here, the "main component" means a component that occupies 50% by weight or more of the total material constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 130 preferably contains 80% by weight or more of α-Cr. Furthermore, from the same viewpoint, the resistor 130 more preferably contains 90% by weight or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0050] In addition, when the resistor 130 is a Cr mixed-phase film, the Cr mixed-phase film preferably contains 20% by weight or less of CrN and Cr2N. By containing 20% ​​by weight or less of CrN and Cr2N in the Cr mixed-phase film, a decrease in the gauge factor of the strain gauge 100 can be suppressed.

[0051] In addition, the ratio of CrN and Cr2N in the Cr mixed phase film is preferably such that the ratio of Cr2N is 80% by weight or more and less than 90% by weight with respect to the total weight of CrN and Cr2N. More specifically, the ratio is more preferably such that the ratio of Cr2N is 90% by weight or more and less than 95% by weight with respect to the total weight of CrN and Cr2N. Cr2N has semiconductor properties. Therefore, by setting the ratio of Cr2N to 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more significant. Furthermore, by setting the ratio of Cr2N to 90% by weight or more and less than 95% by weight, the resistor 130 is less likely to become ceramic, and the resistor 130 is less likely to be brittle fractured.

[0052] On the other hand, CrN has the advantage of being chemically stable. By including more CrN in the Cr mixed-phase film, the possibility of unstable N being generated can be reduced, resulting in a stable strain gauge. Here, "unstable N" refers to trace amounts of N2 or atomic N that may be present in the Cr mixed-phase film. This unstable N may escape to the outside of the film depending on the external environment (e.g., high-temperature environment). When unstable N escapes to the outside of the film, the film stress of the Cr mixed-phase film may change.

[0053] In the strain gauge 100, when a Cr mixed-phase film is used as the material of the resistor 130, it is possible to realize high sensitivity and miniaturization. For example, while the output of a conventional strain gauge was about 0.04 mV / 2 V, when a Cr mixed-phase film is used as the material of the resistor 130, an output of 0.3 mV / 2 V or more can be obtained. In addition, while the size (gauge length x gauge width) of a conventional strain gauge was about 3 mm x 3 mm, when a Cr mixed-phase film is used as the material of the resistor 130, the size (gauge length x gauge width) can be miniaturized to about 0.3 mm x 0.3 mm.

[0054] The wiring 140 is provided on the substrate 110. The wiring 140 is electrically connected to the resistor 130 and the electrode 150. The wiring 140 is not limited to being linear, and may be in any pattern. The wiring 140 may have any width and any length. For convenience, the wiring 140 is shown in FIG. 4 as having a matte pattern with a lower density than the resistor 130.

[0055] The electrodes 150 are provided on the substrate 110. The electrodes 150 are electrically connected to the resistor 130 via the wiring 140. The electrodes 150 are formed in a substantially rectangular shape wider than the wiring 140 in a plan view. The electrodes 150 are a pair of electrodes for outputting a change in the resistance value of the resistor 130 caused by distortion to the outside. For example, a lead wire for external connection is joined to the electrodes 150. A metal layer having low resistance such as copper or a metal layer having good solderability such as gold may be laminated on the upper surface of the electrode 150. Although the resistor 130, the wiring 140, and the electrode 150 are denoted by different reference numerals for convenience, they can be integrally formed from the same material in the same process. In FIG. 4, the electrodes 150 are shown with a matte pattern having the same density as the wiring 140 for convenience.

[0056] The cover layer 160 (protective layer) is provided on the upper surface 110a of the base material 110 as necessary so as to cover the resistor 130 and the wiring 140 and expose the electrodes 150. Examples of materials for the cover layer 160 include insulating resins such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, and composite resins (e.g., silicone resin, polyolefin resin). The cover layer 160 may contain a filler or a pigment. The thickness of the cover layer 160 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness of the cover layer 160 can be about 2 μm to 30 μm. By providing the cover layer 160, it is possible to suppress mechanical damage and the like from occurring in the resistor 130. In addition, by providing the cover layer 160, it is possible to protect the resistor 130 from moisture and the like.

[0057] [Manufacturing method of strain gauge 100] In the strain gauge 100 according to this embodiment, a resistor 130, wiring 140, electrodes 150, and a cover layer 160 are formed on a substrate 110. Note that another layer (such as a functional layer described below) may be formed between the substrate 110 and the layers of these members.

[0058] A method for manufacturing the strain gauge 100 will be described below. To manufacture the strain gauge 100, first, a base material 110 is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on an upper surface 110a of the base material 110. The metal layer A is a layer that is finally patterned to become the resistor 130, the wiring 140, and the electrodes 150. Therefore, the material and thickness of the metal layer A are the same as the material and thickness of the resistor 130, the wiring 140, and the electrodes 150 described above.

[0059] The metal layer A can be formed by, for example, magnetron sputtering using a target made of a raw material capable of forming the metal layer A. Instead of magnetron sputtering, the metal layer A may be formed by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like. After the metal layer A is formed on the upper surface 110a of the base material 110, the metal layer A is patterned by a well-known photolithography method into a planar shape similar to that of the resistor 130, the wiring 140, and the electrode 150 in FIG. 4.

[0060] Alternatively, a base layer may be formed on the upper surface 110a of the base material 110, and then the metal layer A may be formed. For example, a functional layer of a predetermined thickness may be vacuum-formed by conventional sputtering on the upper surface 110a of the base material 110. By providing a base layer in this manner, the gauge characteristics of the strain gauge 100 can be stabilized.

[0061] In the present application, the functional layer refers to a layer having a function of promoting the crystal growth of at least the upper layer, metal layer A (resistor 130). The functional layer preferably further has a function of preventing oxidation of metal layer A due to oxygen or moisture contained in base material 110, and / or a function of improving adhesion between base material 110 and metal layer A. The functional layer may further have other functions.

[0062] The insulating resin film constituting the base material 110 may contain oxygen or moisture, and Cr may form a self-oxidized film. Therefore, particularly when the metal layer A contains Cr, it is preferable to form a functional layer having a function of preventing the oxidation of the metal layer A.

[0063] In this way, by providing a functional layer below the metal layer A, it is possible to promote crystal growth of the metal layer A, and to fabricate a metal layer A consisting of a stable crystal phase. As a result, the stability of the gauge characteristics of the strain gauge 100 is improved. In addition, the material constituting the functional layer diffuses into the metal layer A, thereby improving the gauge characteristics of the strain gauge 100.

[0064] Examples of materials for the functional layer include one or more metals selected from the group consisting of Cr (chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn (zinc), Cu (copper), Bi (bismuth), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), and Al (aluminum), an alloy of any of the metals in this group, or a compound of any of the metals in this group.

[0065] 6 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. FIG. 6 shows the cross-sectional shape of the strain gauge 100 when a functional layer 120 is provided as an underlayer for the resistor 130, the wiring 140, and the electrodes 150.

[0066] The planar shape of the functional layer 120 may be patterned to be substantially the same as the planar shapes of the resistor 130, the wiring 140, and the electrode 150, for example. However, the planar shapes of the functional layer 120, the resistor 130, the wiring 140, and the electrode 150 may not be substantially the same. For example, when the functional layer 120 is formed from an insulating material, the functional layer 120 may be patterned to be different from the planar shapes of the resistor 130, the wiring 140, and the electrode 150. In this case, the functional layer 120 may be formed in a solid shape in the region where the resistor 130, the wiring 140, and the electrode 150 are formed, for example. Alternatively, the functional layer 120 may be formed in a solid shape on the entire upper surface of the substrate 110.

[0067] After forming the resistor 130, the wiring 140, and the electrodes 150, a cover layer 160 is formed on the upper surface 110a of the base material 110 as necessary. The cover layer 160 covers the resistor 130 and the wiring 140, but the electrodes 150 may be exposed from the cover layer 160. For example, the cover layer 160 can be formed by laminating a semi-cured thermosetting insulating resin film on the upper surface 110a of the base material 110 so as to cover the resistor 130 and the wiring 140 and expose the electrodes 150, and then heating and curing the insulating resin film. Through the above steps, the strain gauge 100 is completed.

[0068] Second Embodiment In the second embodiment, an example of a vital sensor in which a gel-like adhesive is provided on the lower surface side of a strain generating body is shown. Note that in the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0069] 7 is a cross-sectional view illustrating a vital sensor according to the second embodiment. Referring to FIG. 7, the vital sensor 2 has a gel-like adhesive 50A on the lower surface 20n side of the flexure body 20, and does not have a gel-like adhesive on the upper surface 20m side of the flexure body 20. The gel-like adhesive 50A is provided on the lower surface 20n of the flexure body 20, and covers the strain gauge 100. The material and thickness of the gel-like adhesive 50A may be the same as those of the gel-like adhesive 50.

[0070] In the vital sensor 2, the lower surface 20n of the strain gauge 20 is covered with the gel-like adhesive 50A, so that moisture from the subject's sweat or the like is less likely to be transmitted to the strain gauge 100. That is, the gel-like adhesive 50A has a waterproof function. In the vital sensor 2, the gel-like adhesive 50A directly covers the strain gauge 100, so a greater waterproof effect can be obtained than in the case of the vital sensor 1. Furthermore, if the strain gauge 100 has a cover layer 160, the moisture-proof effect of the cover layer 160 can be obtained in addition to the waterproof effect of the gel-like adhesive 50A.

[0071] Furthermore, since the gel adhesive 50A easily absorbs unevenness and is less likely to cause undulations due to air entrapment when applied, the variation in detection sensitivity of the strain gauge 100 can be reduced.

[0072] Moreover, the gel adhesive 50A covers the lower surface 20n of the flexure body 20, and therefore can prevent the lower surface 20n of the flexure body 20 from becoming dirty. That is, the gel adhesive 50A has an anti-fouling function.

[0073] Furthermore, in vital sensor 2, it is preferable that gel-like adhesive 50A penetrates into and fills the gap between beam portion 22 and extension portion 24. This prevents dust, foreign matter, etc. from becoming caught in the gap between beam portion 22 and extension portion 24, making it possible for vital sensor 2 to measure pulse waves more reliably and stably.

[0074] In addition, since gel adhesive 50A is softer than resin and the like and does not easily impede elastic deformation of beam portion 22, the presence of gel adhesive 50A is unlikely to be a factor in reducing the detection sensitivity of vital sensor 2.

[0075] In the vital sensor 2, the material of the flexure body 20 can be metal, ceramic, glass, or the like, similar to that of the vital sensor 1. However, in the vital sensor 2, since the upper surface 20m of the flexure body 20 is exposed to the subject side, from the viewpoint of suppressing metal allergies, it is preferable that the flexure body 20 is made of a non-metallic material such as ceramic or glass.

[0076] Third embodiment In the third embodiment, an example of a vital sensor in which a protective member is provided on the lower surface side of the strain body will be described. Note that in the third embodiment, the description of the same components as those in the embodiments already described may be omitted.

[0077] Fig. 8 is a cross-sectional view illustrating a vital sensor according to a third embodiment. Referring to Fig. 8, the vital sensor 3 has a gel-like adhesive 50 on the upper surface 20m side of the flexure body 20, and further has a protective member 60 on the lower surface 20n side of the flexure body 20. The protective member 60 is provided on the lower surface 20n of the flexure body 20, and covers the strain gauge 100.

[0078] The protective member 60 is, for example, a resin film. As the resin film, for example, a polyimide film or the like can be used. The protective member 60 may be a gel adhesive. When the protective member 60 is a gel adhesive, the lower surface 20n of the flexure body 20 is covered with the gel adhesive, so that the same effect as in the second embodiment can be obtained. In addition, since both the upper surface 20m and the lower surface 20n of the flexure body 20 are covered with the gel adhesive, the moisture-proof effect can be further improved compared to the first and second embodiments.

[0079] Fourth embodiment In the fourth embodiment, an example of a vital sensor in which a coating layer is provided on the upper surface side of a strain generating body will be described. Note that in the fourth embodiment, the description of the same components as those in the embodiments already described may be omitted.

[0080] 9 is a cross-sectional view illustrating a vital sensor according to a fourth embodiment. Referring to Fig. 9, vital sensor 4 differs from vital sensor 1 in that a coating layer 70 is provided on one surface side of gel-like adhesive 50.

[0081] The coating layer 70 is, for example, a fluorine-based or silicone-based layer. The thickness of the coating layer 70 can be made thinner than that of the gel-like adhesive 50. The thickness of the coating layer 70 may be, for example, a thickness of about several molecular layers. The coating layer 70 may cover a part of the upper surface of the gel-like adhesive 50, but it is preferable that the coating layer 70 covers the entire upper surface.

[0082] In this way, in the vital sensor 4, the upper surface 20m of the strain body 20 is covered with the gel adhesive 50, and the gel adhesive 50 is covered with the covering layer 70, so that the strain body 20 and the gel adhesive 50 do not directly touch the skin of the subject. Therefore, there is an effect of non-stickiness.

[0083] Fifth embodiment In the fifth embodiment, an example of a vital sensor in which an inorganic layer or the like is provided on the lower surface side of a strain generating body will be described. Note that in the fifth embodiment, the description of the same components as those in the embodiments already described may be omitted.

[0084] Fig. 10 is a cross-sectional view illustrating a vital sensor according to the fifth embodiment. Referring to Fig. 10, vital sensor 5 differs from vital sensor 2 in that it has an inorganic layer 80 and a gel adhesive 50B on the other surface side of gel adhesive 50A.

[0085] The inorganic layer 80 is laminated on the other surface side of the gel-like adhesive 50A. Examples of materials for the inorganic layer 80 include metals and ceramics. The gel-like adhesive 50B is laminated on the other surface side of the inorganic layer 80. The material, thickness, elastic modulus, and adhesion rate of the gel-like adhesive 50B may be similar to those of the gel-like adhesive 50 and the gel-like adhesive 50A.

[0086] In this way, in the vital sensor 5, the lower surface of the waterproof gel-like adhesive 50A is covered with the moisture-proof inorganic layer 80, so that the sensor has not only a waterproof effect but also a moisture-proof effect. Also, in the vital sensor 5, the lower surface 20n of the strain body 20 is covered in turn with the gel-like adhesive 50A, the inorganic layer 80, and the gel-like adhesive 50B, which has the effect of preventing the inorganic layer 80 from peeling off.

[0087] Sixth embodiment In each of the above-described embodiments, an example has been described in which the detection unit according to the present disclosure is a strain gauge using a resistor. That is, in each of the above-described embodiments, a case has been described in which the detection unit according to the present disclosure is an electrical resistance type metal strain gauge. However, the detection unit according to the present disclosure is not limited to a metal strain gauge. For example, the detection unit according to the present disclosure may be a strain gauge that detects magnetic changes caused by strain of a strain body (or a structure equivalent to a strain body) by a detection element included in the strain gauge.

[0088] Specifically, the detection unit according to the present disclosure may be a strain gauge including a detection element that utilizes the Villari phenomenon (described later). Also, the detection unit according to the present disclosure may be a strain gauge including a detection element having a magnetic tunnel junction (described later) structure. In the sixth embodiment, a strain gauge including a detection element that utilizes the Villari phenomenon will be described below. In the seventh embodiment, a strain gauge including a detection element having a magnetic tunnel junction structure will be described.

[0089] In each embodiment of this specification, members having similar functions are given similar names and numbers, and descriptions will not be repeated. In addition, the directions of the x-axis, y-axis, and z-axis in each drawing (drawings from FIG. 11 onward) relating to each embodiment below are the same as the directions of the x-axis, y-axis, and z-axis shown in FIG. 2, FIG. 3, etc. In addition, in the following description, the positive direction of the z-axis is referred to as "upper", and the negative direction of the z-axis is referred to as "lower". That is, in the following description, "upper side" refers to the positive side of the z-axis, and "upper surface" refers to the surface on the positive side of the z-axis. In addition, "lower side" refers to the negative side of the z-axis, and "lower surface" refers to the surface on the negative side of the z-axis.

[0090] FIG. 11 is a diagram showing an example of a detection element 600 included in a strain gauge according to the sixth embodiment. FIG. 11(a) is a plan view of the detection element 600 when viewed from the negative direction to the positive direction of the z axis (i.e., from the bottom to the top). Meanwhile, FIG. 11(b) shows a cross-sectional view of the detection element 600 shown in FIG. 11(a) along the line α-α'. Note that, in FIG. 11(a) and (b), wiring extending from the detection element 600 is not shown. However, the detection element 600 may be connected to wiring connecting a drive coil 620 and a power source, which will be described later, and wiring for transmitting a current detected by a sensing coil 680.

[0091] As shown in FIG. 11(a), the detection element 600 includes a driving coil 620, a sensing coil 680, and a base layer 610. The base layer 610 is a layer that serves as a core material for the driving coil 620 and the sensing coil 680. The sensing coil 680 is a coil for detecting the intensity of magnetization of the base layer 610 (more precisely, a base metal 670 described later). The driving coil 620 is a coil for generating a magnetic field. The detection element 600 has a double structure in which the sensing coil 680 is wound on the inside and the driving coil 620 is wound on the outside, with the base layer 610 as the core material. The materials for the driving coil 620 and the sensing coil 680 are preferably conductive metals such as Cu, Ag, Al, and Au, and alloys of these metals. The number of turns and the size of the cross-sectional area of ​​the driving coil 620 and the sensing coil 680 may be appropriately designed according to the strain detection sensitivity required for the detection element 600.

[0092] As will be described in detail later, when stress is applied to the base layer 610, the strength of magnetization of a base metal 670 (described later) included in the base layer 610 changes. The detection element 600 can determine the strength of the stress applied to the base layer 610 (i.e., the degree of strain) by detecting this change in the strength of magnetization with the sensing coil 680.

[0093] The configuration of the detection element 600 will be further described with reference to the cross-sectional view of (b) of Fig. 11. In Fig. 11(b), the driving coil 620, the sensing coil 680, and the three insulating layers 640, 650, and 660 are each formed to surround the base metal 670, which is the core material. That is, the layers with the same component number in (b) of Fig. 11 are connected to surround the base metal 670.

[0094] The base metal 670 is a member that serves as a core material for various coils and insulating layers. The base metal 670 may be, for example, a substantially flat metal plate. The base metal 670 is covered so as to be surrounded by an insulating layer 660. The base metal 670 is preferably made of a soft magnetic material, for example, an Fe-Si-Al alloy such as sendust, or an Ni-Fe alloy such as permalloy. The aforementioned base layer 610 is made of the base metal 670 and the insulating layer 660, as shown in FIG. 11(b).

[0095] An insulating layer 650 is formed on the outside of the insulating layer 660 so as to surround the insulating layer 660. An insulating layer 640 is further formed on the outside of the insulating layer 650. The insulating layer 650 is a layer including the sensing coil 680, and is a layer in which the gaps in the sensing coil 680 are filled with an insulating material. The insulating layer 640 is a layer including the driving coil 620, and is a layer in which the gaps in the driving coil 620 are filled with an insulating material. The insulating layers 640, 650, and 660 are desirably made of a dry film that does not affect the magnetic field or a resist cured material such as photosensitive polyimide.

[0096] One surface of the detection element 600 may be attached to the substrate 110 as shown in FIG. 11(b). The substrate 110 is a member for fixing the detection element 600. For example, the substrate 110 may be a flexible substrate made of a plastic film or the like. The detection element 600 is attached to the flexure body 20 via the substrate 110. The detection element 600 may be a flat or thin-film detection element as a whole. When the detection element 600 is flat or thin-film, the detection element 600 can be attached to the substrate 110 more easily. The substrate 110 is not an essential component of the detection element 600. For example, the detection element 600 may be used by directly attaching the upper surface of the detection element 600 to the flexure body 20 without providing the substrate 110.

[0097] The flexure body 20 according to this embodiment may basically have the same configuration and material as the flexure body 20 according to the first embodiment. However, it is more preferable that the flexure body 20 be made of a non-magnetic material. The flexure body 20 according to this embodiment can be made of, for example, non-magnetic stainless steel.

[0098] Next, the principle of detecting strain using the detection element 600 will be outlined. The detection element 600 includes a base metal 670, which is a magnetic body. When an alternating current is supplied from a power source to the drive coil 620, the drive coil 620 generates an alternating magnetic field around it. This generates a magnetic field, and the base metal 670 is magnetized. When the flexure body 20 deforms in this state, strain occurs. The strain is transmitted through the substrate 110, and stress is applied to the base metal 670. Note that when the detection element 600 is attached to the flexure body 20 without the substrate 110, the stress is transmitted directly from the flexure body 20 to the base metal 670 (and the insulating layers 640 to 660 covering it).

[0099] When stress is applied to the base metal 670, the magnetic permeability of the base metal 670 changes according to the stress. Therefore, the strength of magnetization (degree of magnetization) of the base metal 670 changes. The phenomenon in which the magnetic permeability and strength of magnetization of a magnetic body change when stress is applied to the magnetic body is called the "Villari phenomenon". According to the configuration of the detection element 600, an AC voltage corresponding to the strength of magnetization of the base metal 670 is induced in the sensing coil 680, which is a pickup coil. Therefore, based on the principle of the Villari phenomenon, the stress applied to the base metal 670 can be calculated from the value of this AC voltage. Then, the degree of strain of the strain body 20 can be specified from the calculated stress. Note that when the detection element 600 has the shape shown in (a) and (b) of FIG. 11, the grid direction of the detection element 600 is equal to the α-α' direction in (a) of FIG. 11. Based on the principle described above, the detection element 600 can detect the strain of the strain body 20. That is, the sensing element 600 functions as a sensing element of a strain gauge.

[0100] It is desirable that the driving coil 620 is wound as uniformly as possible around the outside of the sensing coil 680 and over the entire area in which the sensing coil 680 exists. This allows an alternating magnetic field to be applied more uniformly to the entire area of ​​the base metal 670 in which the sensing coil 680 exists. This allows the change in the strength of magnetization of the base metal 670 due to the Villari phenomenon to be detected more precisely. This improves the performance of the detection element 600.

[0101] Furthermore, the insulating layer 660 may be formed on only a part of the base metal 670 rather than on the entirety of the base metal 670. For example, the region of the base metal 670 around which the sensing coil 680 and the driving coil 620 are wound may be covered with the insulating layer 660, the insulating layer 660 may be covered with the insulating layer 650 including the sensing coil 680, and the insulating layer 650 may be covered with the insulating layer 640 including the driving coil 620.

[0102] In addition, when the base metal 670 is substantially flat, the insulating layer 660 may be formed to surround only the base metal 670 in the winding direction of the coil. That is, in (b) of FIG. 11, both ends of the base metal 670 in the y direction do not need to be covered with the insulating layer 660.

[0103] In the vital sign sensor according to this embodiment, when the strain body 20 is deformed (i.e., strain occurs in the strain body), the substrate 110 of the strain gauge (or the detection element 600 itself) is strained. The detection element 600 can detect the magnetic change caused by this strain based on the principle of the Villari phenomenon described above.

[0104] The strain gauge including the detection element 600 according to this embodiment can be arranged on the strain body 20 in any arrangement pattern shown in the first to fifth embodiments. That is, the detection element 600 according to this embodiment can be used to detect the strain of the strain body 20 in the same manner as when an electrical resistance type strain gauge is used. Therefore, the strain gauge according to this embodiment has the same effects as the strain gauge 100 according to the first to fifth embodiments.

[0105] Seventh embodiment FIG. 12 is a diagram showing a detection element 700, which is an example of a detection element included in the strain gauge according to the seventh embodiment. FIG. 13 is a diagram showing a detection element 800, which is another example of the detection element according to the seventh embodiment. FIG. 14 is a diagram showing a detection element 900, which is yet another example of the detection element according to the seventh embodiment. (a) of FIG. 12 to 14 is a perspective view of the detection elements 700, 800, and 900, respectively. (b) of FIG. 12 to 14 is a plan view of the detection elements 700, 800, and 900, respectively, when viewed from the negative direction to the positive direction of the z axis. (c) of FIG. 12 to 14 is a cross-sectional view of the detection elements 700, 800, and 900 on a surface parallel to the zy plane. Note that wiring extending from the detection elements is not shown in any of FIG. 12 to 14. However, these detection elements 700, 800, and 900 may be connected to a wiring that connects an upstream electrode 710 to a power source, and a wiring that connects a downstream electrode 720 to a power source, which will be described later.

[0106] As shown in (a) of Figures 12 to 14, the detection elements 700, 800, and 900 include an upstream electrode 710, a downstream electrode 720, a magnetic film 730, and an insulating film 740. As shown in the figures, the insulating film 740 is sandwiched between the magnetic films 730. A magnetic tunnel junction is formed by the magnetic film 730 and the insulating film 740. In other words, the detection elements 700, 800, and 900 have a structure in which electrodes are connected to a magnetic tunnel junction structure.

[0107] The upper surfaces of the detection elements 700, 800, and 900 may be attached to a substrate similar to the substrate 110 according to the first embodiment. The detection element 700 may be attached to the flexure body 20 via the substrate. The detection elements 700, 800, and 900 may be flat or thin-film detection elements as a whole. When the detection elements 700, 800, and 900 are flat or thin-film, the detection elements 700, 800, and 900 can be attached to the substrate or the flexure body 20 more easily. For example, the upper surfaces of the detection elements 700, 800, and 900 may be directly attached to the flexure body 20 for use.

[0108] The magnetic film 730 is a magnetic nano-thin film. The insulating film 740 is a nano-thin film of an insulator. As long as a magnetic tunnel junction structure can be formed, the materials of the magnetic film 730 and the insulating film 740 are not particularly limited. For example, the magnetic film 730 can be made of cobalt iron boron, or a 3d transition metal ferromagnetic material such as Fe, Co, or Ni, or an alloy containing these. The insulating film 740 can be made of silicon oxide, silicon nitride, aluminum oxide, magnesium oxide, or the like.

[0109] The upstream electrode 710 and the downstream electrode 720 are electrodes for applying a voltage to the magnetic tunnel junction structure. In the examples of FIGS. 12 to 14, a current flows from the upstream electrode 710 to the downstream electrode 720. For example, in the case of FIG. 12(c), when a voltage is applied between the upstream electrode 710 and the downstream electrode 720, electrons flow from the lower (negative z-axis direction) magnetic film 730 to the upper (positive z-axis direction) magnetic film 730 over the insulating film 740. This is a phenomenon called the "tunnel effect", and the electrical resistance when electrons pass through the insulating film 740 is called the "tunnel resistance". In the examples of FIGS. 12 to 14, the junctions of the electrodes are structured such that the ends are processed so that no current flows that short-circuits the magnetic tunnel junction structure.

[0110] When strain is applied to the detection element 700 through the substrate 110 or the like, a magnetic change occurs in the tunnel junction structure. More specifically, the magnetization directions of the upper and lower magnetic films 730 are shifted. When the magnetization directions of the upper and lower magnetic films 730 are shifted in this way, the tunnel resistance becomes larger than when the magnetization directions are parallel (tunnel magnetoresistance effect). Therefore, in the detection element 700 having the above-mentioned configuration, the current flowing between the electrodes becomes smaller according to the magnitude of the strain of the detection element 700 (more precisely, the magnetic tunnel junction portion). That is, as the strain increases, the electric resistance increases. In this way, the detection element 700 can detect strain based on the current value for the applied voltage. Therefore, by attaching the detection element 700 to the strain body 20, the strain applied to the strain body 20 can be measured.

[0111] The detection element having the magnetic tunnel junction structure is not limited to the example shown in FIG. 12. For example, detection elements 800 and 900 shown in FIG. 13 and FIG. 14 can be adopted. The detection element 800 shown in FIG. 13 and the detection element 900 shown in FIG. 14 are both configured with an upstream electrode 710, a downstream electrode 720, a magnetic film 730, and an insulating film 740, and the principle of detecting strain by these configurations is the same as that of the detection element 700. The basic operation of the detection elements 800 and 900 is also the same as that of the detection element 700. The grid directions of the detection elements 700, 800, and 900 correspond to the y-axis direction (the positive direction of the y-axis and the negative direction of the y-axis) in FIG. 12 to FIG. 14, respectively. As shown in the figure, the detection element 800 shown in FIG. 13 has a structure in which the upper magnetic film 730 and the lower magnetic film 730 are partially connected. That is, a magnetic tunnel junction structure is formed only in a partial region of the magnetic film 730, and a tunnel magnetoresistance effect occurs in this structure. Meanwhile, the detection element 900 shown in Fig. 14 is attached to the base material 110 via a substrate 910. As shown in Figs. 12 to 14, the design of the detection element may be appropriately changed according to the required size, durability, magnitude of the stress to be detected, and the like, as long as it does not exceed the above-mentioned principle.

[0112] The flexure body 20 according to this embodiment may basically have the same configuration and material as the flexure body 20 according to the first embodiment. However, in this embodiment, it is more preferable that the flexure body 20 is made of a non-magnetic material. The flexure body 20 according to this embodiment may be made of, for example, non-magnetic stainless steel. The detection elements 700, 800, and 900 may have a substantially flat plate shape such as a film type as an entire element. This allows the detection element 700 to be easily attached to the flexure body 20. The detection elements 700, 800, and 900 may have a structure for applying a weak magnetic field to the structural part of the magnetic tunnel junction, such as a drive coil. By applying a magnetic field to the structural part of the magnetic tunnel junction, the tunnel magnetoresistance effect described above can be measured more stably, and therefore the strain can be detected stably.

[0113] In addition, the "upstream electrode" and the "downstream electrode" in the detection elements 700, 800, and 900 are names for convenience, and the direction of current flow may be reversed. That is, the detection elements 700, 800, and 900 shown in Figs. 12 to 14 may be designed so that the current flows from the downstream electrode 720 to the upstream electrode 710.

[0114] In the vital sign sensor according to this embodiment, when the strain body 20 is deformed (i.e., strain occurs in the strain body), the substrate of the strain gauge (or the detection element 700, 800, or 900 itself) is strained. The detection element 700, 800, or 900 can detect the magnetic change caused by this strain based on the principle of the tunnel magnetoresistance effect described above.

[0115] The strain gauge including the detection elements 700, 800, and 900 according to this embodiment can be arranged on the strain body 20 in any of the arrangement positions shown in the first to fifth embodiments. That is, the detection elements 700, 800, and 900 according to this embodiment can be used to detect the strain of the strain body 20 in the same manner as when an electrical resistance type strain gauge is used. Therefore, the strain gauge according to this embodiment has the same effects as the strain gauge 100 according to the first to fifth embodiments.

[0116] Eighth embodiment The detection unit according to the present disclosure may be a semiconductor strain gauge, a capacitance pressure sensor, or an optical fiber strain gauge. The detection unit according to the present disclosure may also be a mechanical pressure sensor, a vibration pressure sensor, or a piezoelectric pressure sensor. The principles of various strain gauges and pressure sensors are described below.

[0117] (Semiconductor type strain gauge) A semiconductor strain gauge is a strain gauge that detects strain by utilizing the piezo-resistance effect of a semiconductor, that is, a semiconductor is used as a strain detection element.

[0118] It is known that when stress is applied to a semiconductor, strain is generated in the crystal lattice of the semiconductor, causing changes in the number and mobility of carriers in the semiconductor, resulting in a change in electrical resistance. Similar to electrical resistance type metal strain gauges, semiconductor type strain gauges can be used by being directly attached to the strain body 20. In this case, when the strain body 20 expands and contracts, the strain electrical resistance of the attached semiconductor (more specifically, the crystal lattice of the semiconductor) changes. Therefore, the amount of strain in the strain body 20 can be identified by measuring this electrical resistance.

[0119] The semiconductor strain gauge can also be configured as a strain sensor with a diaphragm structure. In this case, the strain sensor has, for example, a nonmetallic diaphragm (or a metal diaphragm with an electrically insulating layer formed thereon) and a semiconductor (for example, a silicon thin film semiconductor) formed on the diaphragm. In such a structure including a diaphragm, when the diaphragm is distorted by a normal stress applied to the diaphragm, the electrical resistance of the semiconductor changes. Therefore, the amount of strain of the diaphragm (and thus the amount of strain of the strain body 20) can be determined by measuring the electrical resistance.

[0120] (Capacitive pressure sensor) A capacitance type pressure sensor is a pressure sensor that measures the pressure applied to a diaphragm as a change in the capacitance of a pair of electrodes. That is, a capacitance type pressure sensor is a pressure sensor that uses a pair of electrodes as a detection element. A capacitance type pressure sensor includes, for example, a diaphragm as a movable electrode and one or more fixed electrodes. The diaphragm is formed of, for example, silicon containing impurities (i.e., silicon that functions as a conductor).

[0121] When pressure is applied to the diaphragm, the diaphragm is displaced, and the distance between the fixed electrode and the movable electrode changes. It is known that the capacitance between the electrodes is determined according to the distance between the electrodes, provided that the dielectric constant of the interelectrode medium and the area of ​​the electrodes are constant. Therefore, the amount of displacement of the diaphragm (i.e., the magnitude of the pressure) can be determined by measuring the capacitance.

[0122] (Optical fiber strain gauge) An optical fiber strain gauge is a strain gauge that detects strain using an optical fiber on which a fiber Bragg grating (FBG) is formed. In other words, an optical fiber strain gauge is a strain gauge that uses an optical fiber as a strain detection element. An FBG is a diffraction grating that reflects light differently from other parts of the optical fiber, and each grating is formed at a fixed interval. When an optical fiber is distorted and stretched, the lattice interval of the FBG widens, and the wavelength of the reflected light of light (e.g., laser light) that is incident on the optical fiber changes. When an optical fiber is distorted and contracted, the lattice interval of the FBG narrows, and the wavelength of the reflected light of light (e.g., laser light) that is incident on the fiber changes.

[0123] By attaching an optical fiber having such characteristics to the strain body 20 and measuring the wavelength spectrum of the reflected light of the optical fiber, it is possible to identify the amount of strain in the optical fiber (i.e., the amount of strain in the strain body 20). Note that the optical fiber type strain gauge may be a strain gauge that identifies the amount of strain in the optical fiber from the change in frequency of the Brillouin scattered light generated in the optical fiber.

[0124] (Mechanical pressure sensor) A mechanical pressure sensor is a sensor that measures the amount of displacement of a mechanical structure to determine the pressure applied to the structure. A mechanical pressure sensor includes, for example, a spring or a bent tube, and measures the amount of expansion and contraction of the spring or the amount of expansion and contraction of the bent tube. These amounts of expansion and contraction (i.e., the amount of displacement) change depending on the magnitude of pressure applied to the spring or bent tube. Therefore, by measuring the amount of expansion and contraction, it is possible to determine the pressure applied to the spring or bent tube. The shape and size of the spring or bent tube may be determined appropriately depending on the size and shape of the object to which the mechanical pressure sensor is attached.

[0125] (Vibration pressure sensor) The vibration pressure sensor is a sensor that detects pressure by utilizing the phenomenon that the natural frequency of an elastic beam changes depending on the pressure (i.e., axial force) generated along the axis of the elastic beam. The vibration pressure sensor can be directly attached to the strain generating body 20 for use, similar to an electrical resistance type metal strain gauge. For example, the vibration pressure sensor may be a pressure sensor composed of a diaphragm formed on a substrate and a beam-shaped vibrator formed on the surface of the diaphragm.

[0126] In either case, when the strain body 20 is distorted, the pressure is transmitted directly or indirectly to the vibrator, generating an axial force in the vibrator. The natural frequency of the vibrator changes according to the axial force. Therefore, by measuring the natural frequency of the vibrator, the magnitude of the pressure on the strain body 20 can be determined.

[0127] (Piezoelectric pressure sensor) A piezoelectric pressure sensor is a sensor that contains a piezoelectric element (also called a piezo element) and detects pressure using the characteristics of this piezoelectric element. When a force is applied to a piezoelectric element and it deforms (strains), it generates an electromotive force according to that force. In addition, when a voltage is applied to a piezoelectric element, it expands and contracts, generating a force according to that voltage.

[0128] A piezoelectric pressure sensor can determine the force applied to a piezoelectric element (i.e., the amount of strain of the piezoelectric element) by measuring the electromotive force of the piezoelectric element. Therefore, by attaching a piezoelectric pressure sensor to the strain body 20, the amount of strain of the strain body 20 can be determined.

[0129] As described above, the same effects as those of the strain gauge 100 of the first to fifth embodiments can be obtained even when a semiconductor strain gauge, a capacitance pressure sensor, an optical fiber strain gauge, a mechanical pressure sensor, a vibration pressure sensor, and a piezoelectric pressure sensor are used.

[0130] The preferred embodiments and the like have been described above in detail. However, the vital sensor according to the present disclosure is not limited to the above-described embodiments and modifications. For example, various modifications and substitutions can be made to the vital sensor according to the above-described embodiments and the like without departing from the scope of the claims.

[0131] For example, moisture penetrates into the lower surface 20n of the flexure body 20 through the gap between the extension 24 and the beam 22, but also through other small gaps. Therefore, even in a vital sensor using a slitless flexure body with no gaps, a moisture-proof effect can be obtained by providing the gel adhesive 50 and / or the gel adhesive 50A. In other words, the present invention is applicable not only to a vital sensor equipped with a flexure body having slits, but also to a vital sensor using a slitless flexure body.

[0132] In the above embodiment, an example was shown in which the vital sensor 1 detects a pulse wave, but the detection target of the vital sensor 1 is not limited to a pulse wave. The vital sensor 1 can detect, for example, blood pressure, pulse, oxygen level, etc. [Explanation of symbols]

[0133] 1,2,3 vital sensor, 10 housing, 20 strain body, 20m upper surface, 20n lower surface, 21 base, 22 beam portion, 23 load portion, 24 extension portion, 30 wire, 50, 50A, 50B gel adhesive, 60 protective member, 70 coating layer, 80 inorganic layer, 100 strain gauge, 110 substrate, 110a upper surface, 130 resistor, 140 wiring, 150 electrode, 160 cover layer, 130e1, 130e2 termination, 600, 700, 800, 900 detection element, 610 base layer, 620 drive coil, 640, 650, 660 insulating layer, 670 base metal, 680 sensing coil, 710 upstream electrode, 720 downstream electrode, 730 Magnetic film, 740 insulating film, 910 substrate

Claims

1. a strain-generating body having one surface that faces a subject when in use and another surface that is located on the opposite side to the one surface; a gel-like adhesive coating the one surface; and a strain gauge provided on the other surface.

2. a strain-generating body having one surface that faces a subject when in use and another surface that is located on the opposite side to the one surface; a strain gauge provided on the other surface; a gel adhesive provided on the other surface and covering the strain gauge.

3. 2. The vital sensor according to claim 1, further comprising a protective member provided on the other surface and covering the strain gauge.

4. The vital sensor according to claim 3 , wherein the protective member is a gel adhesive.

5. 5. The vital sensor according to claim 1, wherein the strain element is made of metal.

6. The strain body is A base and A beam portion bridging the inside of the base portion; a load portion provided on the beam portion, The vital sensor according to claim 1 , wherein the strain gauge is provided on the beam portion.

7. The beam portion has two beams that intersect in a cross shape in a plan view, The vital sensor according to claim 6 , wherein the load portion is provided in an area where the beams intersect.

8. The strain gauge is provided in four pieces, Two of the four strain gauges are arranged on a side of the beam having a longitudinal direction in the first direction that is closer to the load portion so as to face each other across the load portion in a plan view, 8. The vital sensor of claim 7, wherein the other two of the four strain gauges are arranged on a side closer to the base of the beam, whose longitudinal direction is a second direction perpendicular to the first direction, so as to face each other across the load portion in a planar view.

9. 5. The vital sensor according to claim 1, wherein the strain gauge has a resistor formed of a Cr mixed phase film as a detection element.

10. a strain-generating body having one surface that faces a subject when in use and another surface that is located on the opposite side to the one surface; a gel-like adhesive coating the one surface; a detection unit provided on the other surface, The detection unit detects deformation of the flexure body and / or pressure applied to the flexure body.

11. a strain-generating body having one surface that faces a subject when in use and another surface that is located on the opposite side to the one surface; a detection unit provided on the other surface; a gel-like adhesive provided on the other surface and covering the detection unit.

12. The vital sensor according to claim 10 , further comprising a protective member provided on the other surface and covering the detection unit.

13. The vital sensor according to claim 12 , wherein the protective member is a gel adhesive.

14. The vital sensor according to claim 10, 12, or 13, wherein the strain element is made of metal.

15. The strain body is A base and A beam portion bridging the inside of the base portion; a load portion provided on the beam portion, The vital sensor according to claim 10 , wherein the detection portion is provided on the beam portion.

16. The beam portion has two beams that intersect in a cross shape in a plan view, The vital sensor according to claim 15 , wherein the load portion is provided in an area where the beams intersect.

17. The detector includes four detectors, Two of the four detection units are arranged on a side of the beam having a longitudinal direction in the first direction that is closer to the load portion so as to face each other across the load portion in a plan view, The vital sensor of claim 16, wherein the other two of the four detection units are arranged on the side closer to the base of the beam, whose longitudinal direction is a second direction perpendicular to the first direction, so as to face each other across the load unit in a planar view.

18. The vital sensor according to claim 10 , wherein the detection unit has a detection element that detects a magnetic change caused by deformation of the strain-generating body.

19. the detection element includes a magnetic material, 19. The vital sensor according to claim 18, wherein the detection element detects a change in intensity of magnetization of the magnetic body when pressure is applied to the magnetic body due to deformation of the strain body.

20. the detection element includes a magnetic tunnel junction structure in which an insulating film is sandwiched between magnetic films, The vital sensor according to claim 18, wherein the detection element detects a magnetic change generated in the structure due to deformation of the strain body.

21. The vital sensor according to claim 10 , wherein the detection unit is a semiconductor strain gauge.

22. The vital sensor according to claim 10 , wherein the detection unit is a capacitance type pressure sensor.

23. The vital sensor according to claim 10 , wherein the detection unit is an optical fiber strain gauge.

Images