Pulse wave measurement device

Abstract

To provide a pulse wave measurement device capable of adjusting the angle and pressing force of a detection surface of a pulse wave sensor against the artery of a subject.SOLUTION: A pulse wave measurement device comprises: a body part; a pulse wave sensor which has a strain-inducing body and is fixed to the body part such that the strain-inducing body is exposed from the first surface side of the body part; and a pair of pressing parts which is arranged so as to sandwich the pulse wave sensor when viewed from a first direction perpendicular to the first surface, and provided on the body part such that the protrusion amounts from the first surface can be independently changed.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a pulse wave measuring device. [Background technology]

[0002] There is known a pulse wave measuring device equipped with a pulse wave sensor that detects a pulse wave generated when the heart pumps blood. Such a pulse wave measuring device is configured to be worn on the wrist of a subject, for example. Some devices also have an adjustment means that makes it possible to adjust the pressure of the pulse wave sensor against an artery (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-160621 A Summary of the Invention [Problem to be solved by the invention]

[0004] Since a pulse wave measuring device using a pulse wave sensor needs to detect minute signals, in order to improve measurement accuracy, in addition to adjusting the pressing force of the pulse wave sensor against the artery, it is preferable to position the detection surface of the pulse wave sensor approximately parallel to the artery.

[0005] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a pulse wave measuring device that makes it possible to adjust the angle and pressing force of the detection surface of the pulse wave sensor relative to the subject's artery. [Means for solving the problem]

[0006] A pulse wave measuring device according to one embodiment of the present disclosure includes a main body, a pulse wave sensor having a flexure body and fixed to the main body such that the flexure body is exposed from a first surface side of the main body, and a pair of pressing parts provided on the main body arranged to sandwich the pulse wave sensor when viewed from a first direction perpendicular to the first surface and capable of independently varying the amount of protrusion from the first surface. Effect of the Invention

[0007] According to the disclosed technique, it is possible to provide a pulse wave measuring device that is capable of adjusting the angle and pressure of the detection surface of the pulse wave sensor relative to the subject's artery. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view illustrating a pulse wave measuring device according to a first embodiment. [Diagram 2] 1 is a side view illustrating a pulse wave measuring device according to a first embodiment. [Diagram 3] 1 is a rear perspective view illustrating a pulse wave measuring device according to a first embodiment; [Figure 4] 2 is a back view illustrating the vicinity of the main body of the pulse wave measuring device according to the first embodiment. FIG. [Diagram 5] 2 is a cross-sectional view illustrating the vicinity of a pressing unit and an adjustment unit of the pulse wave measuring device according to the first embodiment. FIG. [Figure 6] FIG. 13 is a diagram (part 1) for explaining the positional relationship between the protrusion of the pressing part and the radial artery. [Figure 7] FIG. 2 is a diagram (part 2) for explaining the positional relationship between the protrusion of the pressing part and the radial artery. [Figure 8] 1 is a plan view illustrating a pulse wave sensor according to a first embodiment. [Figure 9] 1 is a cross-sectional view illustrating a pulse wave sensor according to a first embodiment. [Figure 10] This is an example of a bridge circuit. [Figure 11] FIG. 2 is a plan view illustrating the strain gauge according to the first embodiment. [Figure 12]1 is a cross-sectional view (part 1) illustrating a strain gauge according to a first embodiment. FIG. [Figure 13] 4 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. FIG. 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 designated by the same reference numerals, and duplicated explanations may be omitted.

[0010] First embodiment [Pulse wave measuring device 1] FIG. 1 is a perspective view illustrating the pulse wave measuring device according to the first embodiment, showing a state in which the pulse wave measuring device is attached to the wrist of a subject. FIG. 2 is a side view illustrating the pulse wave measuring device according to the first embodiment. FIG. 3 is a rear perspective view illustrating the pulse wave measuring device according to the first embodiment. FIG. 4 is a rear view illustrating the vicinity of the main body of the pulse wave measuring device according to the first embodiment. FIG. 5 is a cross-sectional view illustrating the vicinity of the pressing unit and the adjustment unit of the pulse wave measuring device according to the first embodiment. In addition, in FIGS. 2 to 5, the arrow N indicates a direction perpendicular to the first surface 10a of the main body 10. Hereinafter, the direction perpendicular to the first surface 10a of the main body 10 may be referred to as the first direction N.

[0011] 1 to 5, pulse wave measuring device 1 is a wristwatch-type wearable device that can be worn by a subject, and includes a main body 10, a pulse wave sensor 20, and a pair of pressing parts 30. Pulse wave measuring device 1 may further include a pair of adjustment parts 40, and a belt 80.

[0012] Pulse wave measuring device 1 is worn on the wrist of a subject, for example, so that pulse wave sensor 20 is located near the subject's radial artery. A pulse wave is a waveform that represents changes in the volume of blood vessels that occur as the heart pumps blood, and pulse wave measuring device 1 can monitor these changes in the volume of blood vessels.

[0013] The main body 10 has a first member 11 and a second member 12. The first member 11 and the second member 12 are screwed together by a screw 13. The first member 11 and the second member 12 can be made of, for example, resin.

[0014] The first member 11 is provided with a sensor fixing portion 11a, a belt fixing portion 11b, and a pair of pressing portion holding portions 11c. The sensor fixing portion 11a, the belt fixing portion 11b, and the pressing portion holding portions 11c protrude from the first surface 10a to the side opposite to the second member 12.

[0015] The pulse wave sensor 20 includes a flexure body 22 and is fixed to the main body 10 so that the flexure body 22 is exposed from the first surface 10a side of the main body 10. The pulse wave sensor 20 is fixed, for example, to the inside of a sensor fixing part 11a of the main body 10. Specifically, the sensor fixing part 11a is, for example, hollow and cylindrical, and the pulse wave sensor 20 is fixed to the inside of the sensor fixing part 11a so that the flexure body 22 is exposed from one axial end side (the subject side) of the sensor fixing part 11a.

[0016] The pair of pressing parts 30 are held, for example, inside the pressing part holding parts 11c of the main body part 10. Specifically, the pressing part holding part 11c is, for example, a hollow rectangle with rounded corners when viewed from the first direction N. The rounded rectangle is a shape consisting of two parallel lines of equal length and two semicircles. The pair of pressing parts 30 are held, for example, inside the pressing part holding parts 11c, so as to be movable in the first direction N or the direction opposite to the first direction N.

[0017] The pair of pressing portions 30 are disposed to sandwich the pulse wave sensor 20 when viewed from the first direction N, and are provided on the main body 10 so that the amount of protrusion from the first surface 10a can be independently changed. In Fig. 4, V1 indicated by a two-dot chain line indicates a first imaginary line passing through the center of the pulse wave sensor 20 when viewed from the first direction N. Each pressing portion 30 can be disposed so as to intersect with the first imaginary line V1 when viewed from the first direction N. When viewed from the first direction N, the longitudinal direction of each pressing portion 30 is, for example, perpendicular to the first imaginary line V1.

[0018] Each pressing portion 30 includes, for example, a base portion 31 and a pair of protrusions 32 protruding from the base portion 31. In each pressing portion 30, the pair of protrusions 32 can be arranged, for example, in the directions of second virtual straight lines V2 and V3 perpendicular to the first virtual straight line V1 when viewed from the first direction N, so as to sandwich the first virtual straight line V1.

[0019] Each of the protrusions 32 is, for example, cylindrical. The tip of each of the protrusions 32 may be flat or not flat. If the tip of each of the protrusions 32 is not flat, it may be, for example, a part of a spherical surface or a part of an aspherical surface. The tip of each of the protrusions 32 may be a rigid body such as a metal, or an elastic body such as rubber. It is preferable to use a material that is less likely to cause allergies, such as titanium, as the metal.

[0020] Each of the protrusions 32 may be formed integrally with the base 31, or may be formed by joining separate pieces. In each pressing portion 30, the two protrusions 32 protrude from the base 31 by substantially the same amount. The protrusion amount of each of the protrusions 32 from the base 31 is, for example, about several mm.

[0021] Each adjustment unit 40 is configured to be movable relative to the first surface 10a in the first direction N or in the direction opposite to the first direction N. Each adjustment unit 40 operates in conjunction with each pressing unit 30. By driving each adjustment unit 40, the amount of protrusion of the pressing unit 30 from the first surface 10a can be independently varied.

[0022] Each adjustment portion 40 includes, for example, a knob portion 41 and a screw portion 42. The knob portion 41 is provided on one end side of the screw portion 42. The knob portion 41 has a larger diameter than the screw portion 42, and the two are joined concentrically. The knob portion 41 and the screw portion 42 may be formed integrally. The other end side of the screw portion 42 is fixed to the base portion 31 of the pressing portion 30 by the screw portion 43.

[0023] For example, a male thread is provided on the outer periphery of the screw portion 42. A through hole 12x is provided in the second member 12, and a female thread is provided on the inner wall of the through hole 12x. The screw portion 42 is screwed into the through hole 12x. As the knob portion 41 and the screw portion 42 rotate, the amount of protrusion of the pressing portion 30 from the first surface 10a changes.

[0024] The belt 80 is a band-shaped body for attaching the main body 10 and the pulse wave sensor 20 to the wrist or the like of the subject, and is configured so as to be able to be wrapped around the wrist or the like from the outside of the subject. The belt 80 is made of, for example, resin, rubber, cloth, or the like, and is flexible.

[0025] One end of the belt 80 is inserted into the belt insertion section 81 and fixed to the belt insertion section 81. The belt insertion section 81 is connected to one end side of the belt fixing section 11b so as to be able to swing freely around an axis 81x as one axis. The vicinity of the other end of the belt 80 is inserted into the belt insertion section 82 and fixed to the belt insertion section 82. The belt insertion section 82 is connected to the other end side of the belt fixing section 11b so as to be able to swing freely around an axis 82x as one axis. By changing the insertion length of the vicinity of the other end of the belt 80 into the belt insertion section 82, it is possible to adjust the tightness of the belt 80 when it is attached to the wrist or the like of the subject.

[0026] In this manner, in the pulse wave measuring device 1, a pair of pressing parts 30, the amount of protrusion of which from the first surface 10a of the main body 10 can be independently varied, are provided on the main body 10 so as to sandwich the pulse wave sensor 20. As a result, as shown in Fig. 6 and Fig. 7, the pair of pressing parts 30 are arranged along the direction of the radial artery 310 extending into the skin 300 of the subject, and the amount of protrusion of each pressing part 30 from the first surface 10a can be independently varied, thereby enabling fine angle adjustment in the direction of the arrow in Fig. 7. That is, since the orientation of the strain body 22 of the pulse wave sensor 20 is influenced by elastic bodies such as muscles and fats near the radial artery 310, the strain body 22 is not necessarily arranged parallel to the radial artery 310. However, in pulse wave measuring device 1, by adjusting the angle of the detection surface of pulse wave sensor 20 (the surface exposed to the outside of strain body 22) with respect to the subject's radial artery 310 in the direction of the arrow in Figure 7, the detection surface of pulse wave sensor 20 can be positioned approximately parallel to radial artery 310.

[0027] Furthermore, in the pulse wave measuring device 1, the amount of protrusion of each pressing portion 30 from the first surface 10a can be independently varied, making it possible to finely adjust the pressing force of the pulse wave sensor 20 against the radial artery 310 beneath the skin 300 of the subject.

[0028] As shown in FIG. 4, the pair of protrusions 32 of each pressing portion 30 are arranged on either side of the first imaginary line V1 in a direction perpendicular to the first imaginary line V1 when viewed from the first direction. The first imaginary line V1 is assumed to be the direction in which the radial artery 310 extends. In this way, by providing each pressing portion 30 with a bifurcated protrusion 32, as shown in FIG. 6, the protrusions 32 can be arranged on both sides of the radial artery 310 so as not to directly press the skin on the radial artery 310. As a result, only the strain body 22 of the pulse wave sensor 20 presses the skin on the radial artery 310, making it possible to accurately measure the pulse wave while applying an appropriate pressing force to the radial artery 310.

[0029] [Pulse wave sensor] Here, as an example of the pulse wave sensor 20, a pulse wave sensor having a plurality of strain gauges is shown.

[0030] Fig. 8 is a plan view illustrating the pulse wave sensor according to the first embodiment. Fig. 9 is a cross-sectional view illustrating the pulse wave sensor according to the first embodiment, taken along line AA in Fig. 8.

[0031] 8 and 9, pulse wave sensor 20 has housing 21, strain body 22, and a plurality of strain gauges (strain gauges 1001, 1002, 1003, 1004). Note that, unless there is a particular need to distinguish between them, strain gauges 1001, 1002, 1003, 1004 may be collectively referred to as strain gauge 100.

[0032] The flexure body 22 has a base portion 22a, a beam portion 22b, a load portion 22c, and an extension portion 22d. The flexure body 22 is in the shape of a flat plate. The flexure body 22 has a first main surface 22m and a second main surface 22n located on the opposite side to the first main surface 22m.

[0033] The material of the flexure body 22 may be, for example, metal, ceramic, glass, etc. Examples of metals used as the material of the flexure body 22 include SUS (stainless steel), copper, aluminum, etc. The flexure body 22 may be integrally formed, for example, by a press processing method or the like. The thickness t of the flexure body 22 excluding the load portion 22c is constant. The thickness t may be, for example, 0.03 mm or more and 0.3 mm or less.

[0034] In the explanation of Figs. 8 and 9, for convenience, the side of the pulse wave sensor 20 where the load portion 22c of the flexure body 22 is provided is referred to as the "upper side", and the side where the load portion 22c of the flexure body 22 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 pulse wave sensor 20 can also be used upside down. The pulse wave sensor 20 can also be disposed at any angle. The planar view refers to viewing the object in the normal direction from the upper side to the lower side of the first main surface 22m of the flexure body 22. The planar shape refers to the shape of the object when viewed in the normal direction.

[0035] In the pulse wave sensor 20, the housing 21 is a portion that holds the strain body 22. The housing 21 is a hollow cylinder with a closed bottom and an open top. The housing 21 can be made of, for example, metal or resin. The substantially disk-shaped strain body 22 is fixed with an adhesive or the like so as to close the opening on the top side of the housing 21.

[0036] In the flexure body 22, the base 22a is a circular frame-shaped (ring-shaped) region outside the circular dashed line shown in FIG. 8. The region inside the circular dashed line may be referred to as a circular opening. In other words, the base 22a of the flexure body 22 has a circular opening. The width w1 of the base 22a is, for example, 1 mm or more and 5 mm or less. The inner diameter d of the base 22a (i.e., the diameter of the circular opening) is, for example, 10 mm or more and 15 mm or less.

[0037] The beam portion 22b is provided so as to bridge the inside of the base portion 22a. The beam portion 22b 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. 8, 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 22a 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 22b, 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.

[0038] The load portion 22c is provided on the beam portion 22b. The load portion 22c is provided, for example, in a region where two beams constituting the beam portion 22b intersect. The load portion 22c protrudes from the upper surface of the beam portion 22b. The amount of protrusion of the load portion 22c based on the upper surface of the beam portion 22b is, for example, about 0.1 mm. The beam portion 22b is flexible, and elastically deforms when a load is applied to the load portion 22c. The upper surface of the beam portion 22b is a part of the first main surface 22m of the strain body 22.

[0039] The four extensions 22d are sector-shaped portions extending from the inside of the base 22a toward the beams 22b in a plan view. A gap of about 1 mm is provided between each extension 22d and the beams 22b. The extensions 22d do not contribute to the sensing of the pulse wave sensor 20, and therefore may not be provided.

[0040] The pulse wave sensor 20 may have a cable, a shielded cable, a flexible board, or the like for inputting and outputting electrical signals to and from the outside. The pulse wave sensor 20 may be configured to communicate with the outside wirelessly or the like without using a cable or the like.

[0041] The output signal of the pulse wave sensor 20 is generated based on the outputs of a plurality of strain gauges. In the illustrated example, the pulse wave sensor 20 has a pair of strain gauges 1001 and 1002 arranged on a beam extending in the Y direction on the second main surface 22n of the strain body 22, facing each other in a plan view with the load portion 22c therebetween. In addition, the pulse wave sensor 20 has another pair of strain gauges 1003 and 1004 arranged on a beam extending in the X direction intersecting the beam on which the pair of strain gauges 1001 and 1002 are arranged, facing each other in a plan view with the load portion 22c therebetween.

[0042] The strain gauges 1001 and 1002 detect the compressive strain of the strain body 22 that occurs in the beam extending in the Y direction when the load section 22c is pressed. The strain gauges 1003 and 1004 detect the tensile strain of the strain body 22 that occurs in the beam extending in the X direction when the load section 22c is pressed. The distance between the strain gauges 1001 and 1002 that detect the compressive strain is wider than the distance between the strain gauges 1003 and 1004 that detect the tensile strain. By arranging the strain gauges 100 in this manner, it is possible to effectively detect the compressive strain and the tensile strain and obtain a large output from the bridge circuit that constitutes a full bridge.

[0043] The strain gauges 1001 to 1004 are connected to form each side of a bridge circuit, and the output signal of the pulse wave sensor 20 can be generated by the bridge circuit. FIG. 10 is an example of a bridge circuit. In the bridge circuit shown in FIG. 10, the strain gauge 1001 forms the upper left side. The strain gauge 1002 forms the lower right side. The strain gauge 1003 forms the upper right side. The strain gauge 1004 forms the lower left side.

[0044] 10, a DC voltage E is supplied between the connection between the upper left side and the lower left side and the connection between the upper right side and the lower right side. This allows an analog voltage output signal S1 to be obtained between the connection between the upper left side and the upper right side and the connection between the lower left side and the lower right side. The bridge circuit can be provided, for example, on a wiring board attached to the inside surface of the housing 21.

[0045] In pulse wave sensor 20, when load portion 22c comes into contact with the radial artery of the subject, a load is applied to load portion 22c in accordance with the subject's pulse wave, causing beam portion 22b to elastically deform, and changing the resistance value of the resistor in strain gauge 100. Pulse wave sensor 20 can detect the pulse wave based on the change in the resistance value of the resistor in strain gauge 100 that accompanies the deformation of beam portion 22b. The pulse wave is detected as a periodic voltage change from the bridge circuit as output signal S1.

[0046] In the above, an example has been shown in which the pulse wave sensor 20 has four strain gauges and generates the output signal S1 by connecting the four strain gauges in a full bridge configuration. However, the pulse wave sensor 20 may have two strain gauges and generate the output signal S1 by connecting the two strain gauges in a half bridge configuration.

[0047] [Strain gauge 100] Fig. 11 is a plan view illustrating the strain gauge according to the first embodiment. Fig. 12 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. 11.

[0048] 11 and 12, 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. 11 and 12. First, each part constituting the strain gauge 100 will be described in detail.

[0049] In the explanation of the strain gauge using Figs. 11 to 13, the definition of the upper surface and the lower surface is different from that in the other figures. Specifically, in Figs. 11 to 13, 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 second main surface 22n of the flexure body 22 such that the base material 110 faces the second main surface 22n of the flexure body 22.

[0050] 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. The thickness of the substrate 110 is not particularly limited and may be appropriately determined depending on the intended use of the strain gauge 100 and the like. 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 second main surface 22n of the strain generating body 22 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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. 11 as having a dense matte pattern.

[0055] 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 line BB in the example of FIG. 11), and the ends of adjacent elongated parts are alternately connected to form a zigzag fold 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 line BB in the example of FIG. 11).

[0056] 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.

[0057] 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).

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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. 11 as having a matte pattern with a lower density than the resistor 130.

[0067] 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. 11, the electrodes 150 are shown with a matte pattern having the same density as the wiring 140 for convenience.

[0068] 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.

[0069] [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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 13 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. FIG 13 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.

[0078] 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.

[0079] 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.

[0080] Although preferred embodiments have been described above in detail, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0081] 1 Pulse wave measuring device, 10 main body, 10a first surface, 11 first member, 11a sensor fixing portion, 11b belt fixing portion, 11c pressing portion holding portion, 12 second member, 12x through hole, 13 screw, 20 pulse wave sensor, 21 housing, 22 strain body, 22a base portion, 22b beam portion, 22c load portion, 22d extension portion, 22m first main surface, 22n second main surface, 30 pressing portion, 31 base portion, 32 convex portion, 40 adjustment portion, 41 knob portion, 42 screw portion, 80 belt, 81, 82 belt insertion portion, 81x, 82x shaft, 1001, 1002, 1003, 1004 strain gauge, 110 base material, 110a upper surface, 130 resistor, 130e1, 130e2 termination, 140 wiring, 150 electrode, 160 cover layer, 300 skin, 310 radial artery

Claims

1. The main body and A pulse wave sensor comprising a strain generating element, the strain generating element being fixed to the main body such that it is exposed from the first surface side of the main body, A pulse wave measuring device comprising: a pair of pressing parts provided on the main body so as to sandwich the pulse wave sensor when viewed from a first direction perpendicular to the first surface, and such that the amount of protrusion from the first surface can be independently varied.

2. The pulse wave measuring device according to claim 1, wherein each of the pressing portions is arranged to intersect a first virtual straight line passing through the center of the pulse wave sensor when viewed from the first direction.

3. Each of the pressing portions includes a base and a pair of protrusions projecting from the base, The pulse wave measuring device according to claim 2, wherein in each of the pressing portions, the pair of protrusions are arranged so as to sandwich the first virtual line in a direction perpendicular to the first virtual line when viewed from the first direction.

4. Furthermore, it has a pair of adjustment parts, The pulse wave measuring device according to any one of claims 1 to 3, wherein the amount of protrusion of the pressing portion from the first surface can be independently varied by driving each of the adjustment portions.

5. Each of the aforementioned adjustment parts includes a knob and a screw part, The pulse wave measuring device according to claim 4, wherein the amount of protrusion of the pressing portion from the first surface changes with the rotation of the knob portion and the screw portion.

6. The strain generating body has a plurality of strain gauges, The pulse wave measuring device according to claim 1, wherein the pulse wave sensor detects a pulse wave based on the change in the resistance value of the resistors of a plurality of strain gauges.

7. The plurality of strain gauges include a pair of strain gauges for detecting the compressive strain of the strain-generating body and another pair of strain gauges for detecting the tensile strain of the strain-generating body, The pair of strain gauges and the other pair of strain gauges are connected to form each side of a bridge circuit. The pulse wave measuring device according to claim 6, wherein the signal indicating the pulse wave is generated by the bridge circuit.

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