JP2023021715A - Pulse wave measuring device - Google Patents

Abstract

To provide a pulse wave measuring device capable of adjusting adhesion between a subject and a pulse wave sensor.SOLUTION: A pulse wave measuring device that can be mounted on a subject includes: a pulse wave sensor having a strain gauge; a sensor fixing part for fixing the pulse wave sensor; and a belt-like body, one end of which is swingably connected to one end side of the sensor fixing part by a first shaft, and the other end of which is swingably connected to the other end side of the sensor fixing part by a second shaft. The first shaft and the second shaft are positioned on a side opposite to the subject with respect to the surface that comes in contact with the subject of the pulse wave sensor.SELECTED DRAWING: Figure 4

Description

The present invention relates to a pulse wave measuring device.

2. Description of the Related Art A pulse wave sensor is known that detects a pulse wave generated as the heart pumps out blood. One example is a pulse wave sensor provided with a pressure-receiving plate serving as a strain-generating body supported flexibly by the action of an external force, and piezoelectric conversion means for converting the flexure 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 with a convex curved surface facing outward, and a pressure detecting element is provided on the inner surface of the top of the pressure receiving plate as piezoelectric conversion means (for example, , see Patent Document 1).

JP-A-2002-78689

Since a pulse wave sensor needs to detect minute signals, a pulse wave measuring device using a pulse wave sensor needs to bring the pulse wave sensor into close contact with the subject in order to improve measurement accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pulse wave measuring device capable of adjusting the adhesion between a subject and a pulse wave sensor.

This pulse wave measuring device is a pulse wave measuring device that can be worn on a subject, and includes a pulse wave sensor having a strain gauge, a sensor fixing portion that fixes the pulse wave sensor, and one end of which is one end side of the sensor fixing portion. a band-shaped body that is swingably connected to the sensor fixing portion by a first shaft and whose other end is swingably connected to the other end side of the sensor fixing portion by a second shaft; The two axes are located on the side opposite to the subject with respect to the surface of the pulse wave sensor that contacts the subject.

According to the disclosed technique, it is possible to provide a pulse wave measuring device capable of adjusting the close contact between the subject and the pulse wave sensor.

1 is a perspective view illustrating a pulse wave measuring device according to a first embodiment; FIG. 1 is a front side perspective view illustrating a pulse wave measuring device according to a first embodiment; FIG. FIG. 2 is a back side perspective view illustrating the pulse wave measuring device according to the first embodiment; 1 is a side view illustrating a pulse wave measuring device according to a first embodiment; FIG. 1 is an exploded perspective view of a pulse wave measuring device according to a first embodiment; FIG. 1 is a perspective view illustrating a pulse wave sensor according to a first embodiment; FIG. 1 is a plan view illustrating a pulse wave sensor according to a first embodiment; FIG. 1 is a cross-sectional view illustrating a pulse wave sensor according to a first embodiment; FIG. 1 is a plan view illustrating a strain gauge according to a first embodiment; FIG. 1 is a cross-sectional view illustrating a strain gauge according to a first embodiment; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<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 how the pulse wave measuring device is worn on the wrist of a subject. FIG. 2 is a front side perspective view illustrating the pulse wave measuring device according to the first embodiment. FIG. 3 is a back side perspective view illustrating the pulse wave measuring device according to the first embodiment. FIG. 4 is a side view illustrating the pulse wave measuring device according to the first embodiment; FIG. 5 is an exploded perspective view of the pulse wave measuring device according to the first embodiment. The arrow N in FIG. 4 indicates the normal direction of the detection surface (lower surface in FIG. 4) of the pulse wave sensor 10 .

With reference to FIGS. 1 to 5, the pulse wave measuring device 1 is a wristwatch-type wearable device that can be worn by a subject, and mainly includes a pulse wave sensor 10, a sensor fixing portion 20, and a belt 80. ing.

The pulse wave measuring device 1 is worn, for example, on the subject's wrist such that the pulse wave sensor 10 is placed near the subject's radial artery. A pulse wave is a waveform obtained by capturing a change in the volume of a blood vessel that occurs as the heart pumps out blood, and the pulse wave measurement device 1 can monitor the change in the volume of the blood vessel.

Pulse wave sensor 10 is fixed to one side (subject side) of sensor fixing portion 20 . Specifically, for example, a plurality of screw holes 10y are provided on the back side of the pulse wave sensor 10 . Further, for example, the sensor fixing portion 20 is provided with a plurality of insertion holes 20y into which screws are inserted so as to penetrate the sensor fixing portion 20 . For example, two screws 90 are inserted into each insertion hole 20y, and the distal end protrudes from each insertion hole 20y and is screwed into each screw hole 10y, so that the pulse wave sensor 10 is fixed to one side of the sensor fixing portion 20. be. A cylindrical positioning hole for positioning the pulse wave sensor 10 may be provided on one side of the sensor fixing portion 20 .

A side surface of the pulse wave sensor 10 may be provided with a through hole 10x through which a cable for extracting an electric signal from the inside of the pulse wave sensor 10 passes. By passing a cable through the through hole 10x, the signal detected by the pulse wave sensor 10 can be connected to an external circuit by wire. For example, a notch 20x is provided in the sensor fixing portion 20, and the through hole 10x is exposed in the notch 20x.

The belt 80 is a belt-like body for attaching the pulse wave sensor 10 and the sensor fixing portion 20 to the subject's wrist or the like, and is configured to be able to be wound around the subject's wrist or the like from the outside. The belt 80 is made of, for example, resin, rubber, cloth, or the like, and has flexibility.

One end of the belt 80 is uniaxially oscillatably connected to one end of the sensor fixing portion 20 , and the other end of the belt 80 is uniaxially oscillatably connected to the other end of the sensor fixing portion 20 . Specifically, one end of the belt 80 is inserted into a groove provided in the belt fixing portion 30 and fixed to the belt fixing portion 30 . Protrusions 30 a that protrude on both sides in the width direction of the belt 80 are provided at the end of the belt fixing portion 30 on the side of the sensor fixing portion 20 . The projecting portion 30 a is inserted into a through hole of the mounting portion 20 a provided in the sensor fixing portion 20 .

As a result, as shown in FIG. 4, the sensor fixing portion 20 and the belt fixing portion 30 to which one end of the belt 80 is fixed are connected so as to be uniaxially swingable in the direction of the arrow about UA1. The belt fixing portion 30 and the belt 80 move together. In other words, the axis UA1 becomes an axis when the one end side of the belt 80 swings.

The other end of the belt 80 is inserted into a through hole provided in the belt insertion portion 40 . Protrusions 40 a that protrude on both sides in the width direction of the belt 80 are provided at the end of the belt insertion portion 40 on the side of the sensor fixing portion 20 . The projecting portion 40 a is inserted into a through hole of the mounting portion 20 b provided in the sensor fixing portion 20 . In other words, the other end of the belt 80 is pivotably connected to the other end of the sensor fixing portion 20 via the belt insertion portion 40 via the shaft UA2.

As a result, the sensor fixing portion 20 and the belt insertion portion 40 into which the other end of the belt 80 is inserted are connected to each other so as to be uniaxially swingable about UA2 as an axis in the direction of the arrow. The belt insertion portion 40 and the belt 80 move together. In other words, the axis UA2 becomes the axis when the other end side of the belt 80 swings. The direction of the arrow in FIG. 4 is the direction in which the tightening strength of the belt 80 is strengthened or weakened.

The other end of the belt 80 inserted into the through-hole of the belt insertion portion 40 passes through the through-hole of the belt insertion portion 40 and reaches the outer peripheral surface of the portion of the belt 80 that is not inserted into the belt insertion portion 40, for example, a surface. It can be detachably connected by a fastener or the like. By changing the position where the other end of the belt 80 is connected in the longitudinal direction of the belt 80, the tightening strength when the pulse wave measuring device 1 is attached to the subject can be changed.

When the pulse wave measuring device 1 is worn by the subject, the sensor fixing portion 20 and the belt 80 swing about the axes UA1 and UA2, so the pulse wave measuring device 1 as a whole conforms to the shape of the subject's wrist or the like. can follow. At that time, by changing the tightening strength of the belt 80, the pulse wave sensor 10 can be pressed in the N direction, so that the close contact between the subject and the pulse wave sensor 10 can be adjusted. Thereby, the strain generating body 12 side of the pulse wave sensor 10 can be brought into close contact with the subject's radial artery.

4, the lower surface of pulse wave sensor 10 serves as a detection surface for detecting pulse waves, but axis UA1 and axis UA2 are above the detection surface of pulse wave sensor 10, that is, pulse wave sensor 10 It is located on the side opposite to the subject with respect to the detection surface. The detection surface of the pulse wave sensor 10 is the surface of the pulse wave sensor 10 that comes into contact with the subject, and more specifically, the surface of the strain body 12, which will be described later, on the subject side.

Since the axis UA1 and the axis UA2 are located on the opposite side of the detection surface of the pulse wave sensor 10 from the subject, by changing the tightening strength of the belt 80, the detection surface of the pulse wave sensor 10 can be adjusted to the subject. It becomes possible to easily press the wrist. In particular, it is preferable that the lower surface of the pulse wave sensor 10 protrude from the sensor fixing portion 20 toward the subject. Accordingly, by changing the strength with which the belt 80 is tightened, the detection surface of the pulse wave sensor 10 can be more easily pressed against the subject's wrist.

The axis UA1 and the axis UA2 preferably extend in a direction (depth direction in FIG. 4) perpendicular to the longitudinal direction of the belt 80 when the belt 80 is stretched in the horizontal direction in FIG.

Moreover, in FIG. 4 , that is, in a side view, a straight line connecting the center of axis UA1 and the center of axis UA2 is preferably parallel to the detection surface of pulse wave sensor 10 . In this case, the distance between the straight line connecting the center of axis UA1 and the center of axis UA2 and the detection surface of pulse wave sensor 10 is, for example, 2 mm or more and 8 mm or less. Note that "parallel" here includes the case where the angle formed by the two straight lines is within ±5 degrees. A straight line connecting the center of the axis UA1 and the center of the axis UA2 is parallel to the detection surface of the pulse wave sensor 10, so that when the belt 80 is tightened, the detection surface of the pulse wave sensor 10 is evenly pressed against the subject. be able to.

In addition, when the detection surface of the pulse wave sensor 10 is a curved surface that protrudes toward the subject, the tangent line of the tip closest to the subject on the detection surface of the pulse wave sensor 10 is the detection surface of the pulse wave sensor 10 described above. shall be read as

Further, in FIG. 4, that is, in a side view, a straight line connecting the center of the axis UA1 and the center of the axis UA2 and the middle point of the detection surface of the pulse wave sensor 10 is the center of the axis UA1 and the axis It is preferably perpendicular to the straight line connecting the centers of UA2. It should be noted that the vertical here includes the case where the angle formed by the two straight lines is within 90±5 degrees. The straight line connecting the midpoint of the straight line connecting the center of the axis UA1 and the center of the axis UA2 and the midpoint of the detection surface of the pulse wave sensor 10 is perpendicular to the straight line connecting the center of the axis UA1 and the center of the axis UA2. Therefore, when the belt 80 is tightened, the detection surface of the pulse wave sensor 10 can be evenly pressed against the subject.

An urging mechanism may be provided between the sensor fixing portion 20 and the pulse wave sensor 10 to urge the pulse wave sensor 10 toward the subject. For example, the urging mechanism may be composed only of a spring, may be configured to include a spring and an adjustment section for adjusting the urging force of the spring, or may be configured in some other manner. By having a biasing mechanism that biases the pulse wave sensor 10 toward the subject, the detection surface of the pulse wave sensor 10 can be stably pressed against the wrist of the subject.

[Pulse wave sensor 10]
FIG. 6 is a perspective view illustrating the pulse wave sensor according to the first embodiment; FIG. 7 is a plan view illustrating the pulse wave sensor according to the first embodiment; FIG. FIG. 8 is a cross-sectional view illustrating the pulse wave sensor according to the first embodiment, showing a cross section along line AA of FIG. 6 to 8 are viewed from a different direction from FIG. 5, and the lower surface (rear surface) of the pulse wave sensor 10 in FIG. 5 is the upper surface in FIGS.

6 to 8, the pulse wave sensor 10 has a housing 11, a strain body 12, and a strain gauge 100. FIG. The pulse wave sensor 10 is held by the sensor fixing portion 20 in a state in which the strain generating body 12 is exposed from the sensor fixing portion 20 toward the subject and can come into contact with the subject (see FIG. 3). The pulse wave sensor 10 may protrude from the sensor fixing portion 20 toward the subject.

The strain generating body 12 has a base portion 12a, a beam portion 12b, a load portion 12c, and an extending portion 12d. The strain-generating body 12 has, for example, a four-fold symmetrical shape in a plan view. As a material of the strain generating body 12, for example, SUS (stainless steel), copper, aluminum, or the like can be used. The strain-generating body 12 is, for example, a flat plate, and each constituent element is integrally formed by, for example, a press working method. The strain-generating body 12 may be flat, or may have a dome shape or the like projecting so that the subject side is convex. The thickness t of the strain body 12 excluding the load portion 12c is constant, for example. The thickness t is, for example, 0.01 mm or more and 0.25 mm or less.

In the description of the pulse wave sensor 10 in FIGS. 6 to 8, for convenience, the side where the load portion 12c of the strain body 12 is provided is the upper side or one side, and the side where the load portion 12c is not provided is the lower side. side or the other side. Also, the surface on the side where the load portion 12c of each part is provided is defined as one surface or upper surface, and the surface on the side where the load portion 12c is not provided is defined as the other surface or the lower surface. However, the pulse wave sensor 10 can be used upside down or placed at any angle. The term "planar view" refers to viewing the object from the direction normal to the upper surface of the strain body 12, and the term "planar shape" refers to the shape of the object viewed from the direction normal to the upper surface of the strain body 12. and

In pulse wave sensor 10 , housing 11 is a portion that holds strain body 12 . The housing 11 is cylindrical, closed on the bottom side and open on the top side. The housing 11 can be made of metal, resin, or the like, for example. A substantially disk-shaped strain-generating body 12 is fixed with an adhesive or the like so as to block the opening on the upper surface side of the housing 11 . The strain-generating body 12 is a portion where the strain gauge 100 is arranged and which detects a pulse wave.

In the strain generating body 12, the base portion 12a is a circular frame-shaped (ring-shaped) region outside the circular dashed line shown in FIGS. Note that the area inside the circular dashed line may be referred to as a circular opening. That is, the base portion 12a of the strain body 12 has a circular opening. The width _w1 of the base portion 12a is, for example, 1 mm or more and 5 mm or less. The inner diameter d of the base portion 12a (that is, the diameter of the circular opening) is, for example, 5 mm or more and 40 mm or less.

The beam portion 12b is provided so as to bridge the inside of the base portion 12a. The beam portion 12b has, for example, two beams crossing each other in a cross shape in plan view, and the crossing area of the two beams includes the center of the circular opening. In the example of FIG. 7, one beam forming the cross has its longitudinal direction in the X direction, and another beam forming the cross has its longitudinal direction in the Y direction, and they are orthogonal to each other. Each of the two orthogonal beams is preferably inside the inner diameter d (the diameter of the circular opening) of the base 12a and is as long as possible. That is, the length of each beam is preferably approximately equal to the diameter of the circular opening. The width _w2 of each beam constituting the beam portion 12b is constant except for the intersecting region, and is, for example, 1 mm or more and 5 mm or less. Although it is not essential that the width _w2 is constant, it is preferable in that the strain can be detected linearly by making the width _w2 constant.

The load portion 12c is provided on the beam portion 12b. The load portion 12c is provided, for example, in an area where two beams forming the beam portion 12b intersect. The load portion 12c protrudes from the upper surface of the beam portion 12b. The amount of projection of the load portion 12c based on the upper surface of the beam portion 12b is, for example, about 0.1 mm. The beam portion 12b is flexible, and elastically deforms when a load is applied to the load portion 12c.

The four extending portions 12d are fan-shaped portions extending from the inside of the base portion 12a toward the beam portion 12b in plan view. A gap of about 1 mm is provided between each extending portion 12d and beam portion 12b. Incidentally, if the gap is, for example, about 0.05 to 0.2 mm, it is possible to prevent contaminants from entering the housing 11 from the outside. The extending portion 12d does not contribute to the sensing of the pulse wave sensor 10, so it does not have to be provided. The pulse wave sensor 10 has a shielded cable, a flexible substrate, and the like (not shown) for inputting and outputting electric signals with the outside.

The strain gauge 100 is provided on the strain generating body 12 . The strain gauge 100 can be provided, for example, on the lower surface side of the beam portion 12b. Since the beam portion 12b has a flat plate shape, the strain gauge can be easily attached. One or more strain gauges 100 may be provided, but four strain gauges 100 are provided in this embodiment. By providing four strain gauges 100, strain can be detected by a full bridge.

Two of the four strain gauges 100 are arranged so as to face the load portion 12c in plan view on the side near the load portion 12c of the beam whose longitudinal direction is the X direction (center side of the circular opening). are placed. The other two of the four strain gauges 100 are arranged on the side close to the base portion 12a of the beam whose longitudinal direction is the Y direction so as to face each other across the load portion 12c in a plan view. Such an arrangement allows effective detection of compressive and tensile forces to provide greater power output from the full bridge.

The pulse wave sensor 10 is used by being fixed to the subject's arm so that the load portion 12c contacts the subject's radial artery. When a load is applied to the load portion 12c according to the subject's pulse wave and the beam portion 12b is elastically deformed, the resistance value of the resistor of the strain gauge 100 changes. The pulse wave sensor 10 can detect a pulse wave based on the change in the resistance value of the resistor of the strain gauge 100 accompanying deformation of the beam portion 12b. A pulse wave is output as a periodic change in voltage from a measurement circuit connected to the electrodes of the strain gauge 100, for example.

[Strain gauge 100]
FIG. 9 is a plan view illustrating the strain gauge according to the first embodiment; FIG. FIG. 10 is a cross-sectional view illustrating the strain gauge according to the first embodiment, showing a cross section along line BB in FIG. 9 and 10, the strain gauge 100 has a substrate 110, a resistor 130, wiring 140, electrodes 150, and a cover layer 160. FIG. In addition, in FIG. 9, only the outer edge of the cover layer 160 is shown with a dashed line for convenience. Note that the cover layer 160 may be provided as necessary.

9 and 10, for the sake of convenience, in the strain gauge 100, the side of the substrate 110 on which the resistor 130 is provided is the upper side or one side, and the resistor 130 is not provided. side is the bottom side or the other side. In addition, the surface on the side where the resistor 130 of each part is provided is defined as one surface or upper surface, and the surface on the side where the resistor 130 is not provided is defined as the other surface or the lower surface. However, the strain gauge 100 can be used upside down or placed at any angle. For example, in FIG. 8, the strain gauge 100 is affixed to the beam portion 12b in a state in which the top and bottom of FIG. 10 are reversed. That is, the base material 110 in FIG. 10 is attached to the lower surface of the beam portion 12b with an adhesive or the like. Further, the term “planar view” refers to viewing an object from the direction normal to the top surface 110a of the base material 110, and the term “planar shape” refers to the shape of the object viewed from the direction normal to the top surface 110a of the base material 110. and

The base material 110 is a member that serves as a base layer for forming the resistor 130 and the like, and has flexibility. The thickness of the base material 110 is not particularly limited, and can be appropriately selected according to the purpose. In particular, when the thickness of the base material 110 is 5 μm to 200 μm, the transmission of strain from the surface of the strain generating body bonded to the lower surface of the base material 110 via an adhesive layer or the like, and the dimensional stability against the environment. The thickness is preferably 10 μm or more, and more preferable from the viewpoint of insulation.

The substrate 110 is made of, for example, PI (polyimide) resin, epoxy resin, PEEK (polyetheretherketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, LCP (liquid crystal It can be formed from an insulating resin film such as polymer) resin, polyolefin resin, or the like. Note that the film refers to a flexible member having a thickness of about 500 μm or less.

Here, "formed from an insulating resin film" does not prevent the base material 110 from containing fillers, impurities, etc. in the insulating resin film. The base material 110 may be formed from an insulating resin film containing a filler such as silica or alumina, for example.

Materials other than the resin of the base material 110 include, for example, SiO ₂ , ZrO ₂ (including YSZ), Si, Si ₂ N ₃ , Al ₂ O ₃ (including sapphire), ZnO, perovskite ceramics (CaTiO ₃ , BaTiO ₃ ) and other crystalline materials, as well as amorphous glass and the like. As the material of the base material 110, a metal such as aluminum, an aluminum alloy (duralumin), or titanium may be used. In this case, for example, an insulating film is formed on the base material 110 made of metal.

The resistor 130 is a thin film formed in a predetermined pattern on the substrate 110, and is a sensing part that undergoes a change in resistance when subjected to strain. The resistor 130 may be formed directly on the upper surface 110a of the base material 110, or may be formed on the upper surface 110a of the base material 110 via another layer. In addition, in FIG. 9, the resistor 130 is shown with a dark pear-skin pattern for the sake of convenience.

The resistor 130 has a plurality of elongated portions arranged in the same longitudinal direction (the direction of line BB in FIG. 9) at predetermined intervals, and the ends of adjacent elongated portions are alternately connected. , is a zigzag folding structure as a whole. The longitudinal direction of the elongated portions is the grid direction, and the direction perpendicular to the grid direction is the grid width direction (perpendicular to line BB in FIG. 9).

One ends in the longitudinal direction of the two elongated portions located on the outermost side in the grid width direction are bent in the grid width direction to form respective ends 130e ₁ and 130e ₂ of the resistor 130 in the grid width direction. Each end 130 e ₁ and 130 e ₂ of the resistor 130 in the grid width direction is electrically connected to the electrode 150 via the wiring 140 . In other words, the wiring 140 electrically connects the ends 130e ₁ and 130e ₂ of the resistor 130 in the grid width direction and each electrode 150 .

The resistor 130 can be made of, for example, 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 made of a material containing at least one of Cr and Ni. Materials containing Cr include, for example, a Cr mixed phase film. Materials containing Ni include, for example, Cu—Ni (copper nickel). Materials containing both Cr and Ni include, for example, Ni—Cr (nickel chromium).

Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N, or the like is mixed. The Cr mixed phase film may contain unavoidable impurities such as chromium oxide.

The thickness of the resistor 130 is not particularly limited, and can be appropriately selected according to the purpose. In particular, when the thickness of the resistor 130 is 0.1 μm or more, the crystallinity of the crystal (for example, the crystallinity of α-Cr) forming the resistor 130 is preferably improved. In addition, it is more preferable that the thickness of the resistor 130 is 1 μm or less in that cracks in the film caused by internal stress of the film constituting the resistor 130 and warping from the base material 110 can be reduced. The width of the resistor 130 can be optimized with respect to the required specifications such as the resistance value and the lateral sensitivity, and can be set to, for example, about 10 μm to 100 μm in consideration of disconnection countermeasures.

For example, when the resistor 130 is a Cr mixed phase film, the stability of gauge characteristics can be improved by using α-Cr (alpha chromium), which is a stable crystal phase, as the main component. In addition, since the resistor 130 is mainly composed of α-Cr, the gauge factor of the strain gauge 100 is 10 or more, and the temperature coefficient of gauge factor TCS and the temperature coefficient of resistance TCR are in the range of -1000 ppm/°C to +1000 ppm/°C. can be Here, the term "main component" means that the target material accounts for 50% by weight or more of all the materials constituting the resistor. It preferably contains 90% by weight or more, more preferably 90% by weight or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

Further, when the resistor 130 is a Cr mixed phase film, it is preferable that CrN and Cr ₂ N contained in the Cr mixed phase film be 20% by weight or less. When CrN and Cr ₂ N contained in the Cr mixed phase film are 20% by weight or less, a decrease in gauge factor can be suppressed.

Also, the ratio of Cr ₂ N in CrN and Cr ₂ N is preferably 80% by weight or more and less than 90% by weight, more preferably 90% by weight or more and less than 95% by weight. When the ratio of Cr ₂ N in CrN and Cr ₂ N is 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more pronounced due to Cr ₂ N having semiconducting properties. . Furthermore, by reducing ceramicization, brittle fracture is reduced.

On the other hand, when a small amount of N ₂ or atomic N is mixed in the film and is present, the external environment (for example, high temperature environment) causes a change in the film stress by escaping from the film. By creating chemically stable CrN, a stable strain gauge can be obtained without generating unstable N.

The wiring 140 is formed on the base material 110 and electrically connected to the resistor 130 and the electrode 150 . The wiring 140 has a first metal layer 141 and a second metal layer 142 laminated on the upper surface of the first metal layer 141 . The wiring 140 is not limited to a straight line, and may have any pattern. Also, the wiring 140 can be of any width and any length. In addition, in FIG. 9, the wiring 140 and the electrode 150 are shown with a pear-skin pattern that is thinner than the resistor 130 for the sake of convenience.

The electrode 150 is formed on the base material 110 and electrically connected to the resistor 130 via the wiring 140. For example, the electrode 150 is wider than the wiring 140 and formed in a substantially rectangular shape. The electrodes 150 are a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 130 caused by strain, and are connected to, for example, lead wires for external connection.

The electrode 150 has a pair of first metal layers 151 and a second metal layer 152 laminated on the upper surface of each first metal layer 151 . The first metal layer 151 is electrically connected to the ends 130e ₁ and 130e ₂ of the resistor 130 via the first metal layer 141 of the wiring 140 . The first metal layer 151 is formed in a substantially rectangular shape in plan view. The first metal layer 151 may be formed to have the same width as the wiring 140 .

Although the resistor 130, the first metal layer 141, and the first metal layer 151 are denoted by different symbols for convenience, they can be integrally formed from the same material in the same process. Therefore, the resistor 130, the first metal layer 141, and the first metal layer 151 have substantially the same thickness. In addition, although the second metal layer 142 and the second metal layer 152 are given different symbols for the sake of convenience, they can be integrally formed from the same material in the same process. Therefore, the second metal layer 142 and the second metal layer 152 have substantially the same thickness.

The second metal layers 142 and 152 are made of a material with lower resistance than the resistor 130 (the first metal layers 141 and 151). The materials for the second metal layers 142 and 152 are not particularly limited as long as they have lower resistance than the resistor 130, and can be appropriately selected according to the purpose. For example, when the resistor 130 is a Cr mixed phase film, the material of the second metal layers 142 and 152 is Cu, Ni, Al, Ag, Au, Pt, etc., or an alloy of any of these metals, or any of these. or a laminated film obtained by appropriately laminating any of these metals, alloys, or compounds. The thickness of the second metal layers 142 and 152 is not particularly limited and can be appropriately selected according to the purpose, but can be, for example, about 3 μm to 5 μm.

The second metal layers 142 and 152 may be formed on part of the top surfaces of the first metal layers 141 and 151 or may be formed on the entire top surfaces of the first metal layers 141 and 151 . One or more other metal layers may be laminated on the upper surface of the second metal layer 152 . For example, a copper layer may be used as the second metal layer 152, and a gold layer may be laminated on the upper surface of the copper layer. Alternatively, a copper layer may be used as the second metal layer 152, and a palladium layer and a gold layer may be sequentially laminated on the upper surface of the copper layer. Solder wettability of the electrode 150 can be improved by using a gold layer as the top layer of the electrode 150 .

Thus, the wiring 140 has a structure in which the second metal layer 142 is laminated on the first metal layer 141 made of the same material as the resistor 130 . Therefore, since the wiring 140 has a lower resistance than the resistor 130, the wiring 140 can be prevented from functioning as a resistor. As a result, the accuracy of strain detection by the resistor 130 can be improved.

In other words, by providing the wiring 140 having a resistance lower than that of the resistor 130, it is possible to limit the substantial sensing portion of the strain gauge 100 to the local area where the resistor 130 is formed. Therefore, the strain detection accuracy by the resistor 130 can be improved.

In particular, in a highly sensitive strain gauge with a gauge factor of 10 or more using a Cr mixed phase film as the resistor 130, the wiring 140 has a lower resistance than the resistor 130, and the resistor 130 is formed as a substantial sensing part. Restricting to a local region exhibits a significant effect in improving strain detection accuracy. Further, making the wiring 140 lower in resistance than the resistor 130 also has the effect of reducing lateral sensitivity.

A cover layer 160 is formed on the substrate 110 to cover the resistor 130 and the wiring 140 and expose the electrode 150 . A portion of the wiring 140 may be exposed from the cover layer 160 . By providing the cover layer 160 that covers the resistor 130 and the wiring 140, mechanical damage or the like to the resistor 130 and the wiring 140 can be prevented. Also, by providing the cover layer 160, the resistor 130 and the wiring 140 can be protected from moisture and the like. Note that the cover layer 160 may be provided so as to cover the entire portion excluding the electrode 150 .

The cover layer 160 can be made of insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, composite resin (eg, silicone resin, polyolefin resin). The cover layer 160 may contain fillers and pigments. The thickness of the cover layer 160 is not particularly limited, and can be appropriately selected according to the purpose.

In order to manufacture the strain gauge 100 , first, the base material 110 is prepared, and a metal layer (referred to as metal layer A for convenience) is formed on the upper surface 110 a of the base material 110 . The metal layer A is a layer that is finally patterned to become the resistor 130 , the first metal layer 141 and the first metal layer 151 . Therefore, the material and thickness of the metal layer A are the same as those of the resistor 130, the first metal layer 141, and the first metal layer 151 described above.

The metal layer A can be formed, for example, by magnetron sputtering using a raw material capable of forming the metal layer A as a target. The metal layer A may be formed by using a reactive sputtering method, a vapor deposition method, an arc ion plating method, a pulse laser deposition method, or the like instead of the magnetron sputtering method.

From the viewpoint of stabilizing the gauge characteristics, before forming the metal layer A, a functional layer having a predetermined thickness is vacuum-formed on the upper surface 110a of the base material 110 as a base layer by conventional sputtering, for example. is preferred.

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

Since the insulating resin film that constitutes the base material 110 contains oxygen and moisture, especially when the metal layer A contains Cr, Cr forms a self-oxidizing film. Being prepared helps.

The material of the functional layer is not particularly limited as long as it has a function of promoting the crystal growth of at least the upper metal layer A (resistor 130), and can be appropriately selected according to the purpose. 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), Al (aluminum) 1 selected from the group consisting of Metal or metals, alloys of any of this group of metals, or compounds of any of this group of metals.

Examples of the above alloy include FeCr, TiAl, FeNi, NiCr, CrCu, and the like. Examples of _the above compounds include TiN, TaN _{, Si3N4} , _TiO2 , _Ta2O5 , _SiO2 and the like.

When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is preferably 1/20 or less of the thickness of the resistor. Within this range, it is possible to promote the crystal growth of α-Cr, and to prevent a part of the current flowing through the resistor from flowing through the functional layer, thereby preventing a decrease in strain detection sensitivity.

When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is preferably 1/50 or less of the thickness of the resistor. Within this range, it is possible to promote the crystal growth of α-Cr, and further prevent the deterioration of the strain detection sensitivity due to part of the current flowing through the resistor flowing through the functional layer.

When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is more preferably 1/100 or less of the thickness of the resistor. Within such a range, it is possible to further prevent a decrease in strain detection sensitivity due to part of the current flowing through the resistor flowing through the functional layer.

When the functional layer is made of an insulating material such as oxide or nitride, the thickness of the functional layer is preferably 1 nm to 1 μm. Within such a range, the crystal growth of α-Cr can be promoted, and the film can be easily formed without causing cracks in the functional layer.

When the functional layer is made of an insulating material such as oxide or nitride, the thickness of the functional layer is more preferably 1 nm to 0.8 μm. Within such a range, the crystal growth of α-Cr can be promoted, and the functional layer can be formed more easily without cracks.

When the functional layer is made of an insulating material such as oxide or nitride, the thickness of the functional layer is more preferably 1 nm to 0.5 μm. Within such a range, the crystal growth of α-Cr can be promoted, and the functional layer can be formed more easily without cracks.

The planar shape of the functional layer is patterned to be substantially the same as the planar shape of the resistor shown in FIG. 9, for example. However, the planar shape of the functional layer is not limited to being substantially the same as the planar shape of the resistor. If the functional layer is made of an insulating material, it may not be patterned in the same planar shape as the resistor. In this case, the functional layer may be solidly formed at least in the region where the resistor is formed. Alternatively, the functional layer may be formed all over the top surface of the substrate 110 .

Further, when the functional layer is formed of an insulating material, the thickness and surface area of the functional layer can be increased by forming the functional layer relatively thick such that the thickness is 50 nm or more and 1 μm or less and forming the functional layer in a solid manner. Since the resistance increases, the heat generated by the resistor can be dissipated to the base material 110 side. As a result, in the strain gauge 100, deterioration in measurement accuracy due to self-heating of the resistor can be suppressed.

The functional layer can be formed, for example, by conventional sputtering using a raw material capable of forming the functional layer as a target and introducing Ar (argon) gas into the chamber in a vacuum. By using the conventional sputtering method, the functional layer is formed while etching the upper surface 110a of the substrate 110 with Ar, so that the amount of film formation of the functional layer can be minimized and the effect of improving adhesion can be obtained.

However, this is an example of the method of forming the functional layer, and the functional layer may be formed by another method. For example, before forming the functional layer, the upper surface 110a of the substrate 110 is activated by a plasma treatment using Ar or the like to obtain an adhesion improvement effect, and then the functional layer is vacuum-formed by magnetron sputtering. You may use the method to do.

The combination of the material of the functional layer and the material of the metal layer A is not particularly limited and can be appropriately selected according to the purpose. It is possible to form a Cr mixed phase film as a main component.

In this case, for example, the metal layer A can be formed by magnetron sputtering using a raw material capable of forming a Cr mixed-phase film as a target and introducing Ar gas into the chamber. Alternatively, the metal layer A may be formed by reactive sputtering using pure Cr as a target, introducing an appropriate amount of nitrogen gas into the chamber together with Ar gas. At this time, by changing the introduction amount and pressure (nitrogen partial pressure) of nitrogen gas and adjusting the heating temperature by providing a heating process, the ratio of CrN and Cr ₂ N contained in the Cr mixed phase film, and the ratio of CrN and Cr The proportion of _Cr2N in _2N can be adjusted.

In these methods, the growth surface of the Cr mixed phase film is defined by the functional layer made of Ti, and a Cr mixed phase film containing α-Cr, which has a stable crystal structure, as a main component can be formed. In addition, the diffusion of Ti constituting the functional layer into the Cr mixed phase film improves the gauge characteristics. For example, the strain gauge 100 can have a gauge factor of 10 or more and a temperature coefficient of gauge factor TCS and a temperature coefficient of resistance TCR within the range of -1000 ppm/°C to +1000 ppm/°C. When the functional layer is made of Ti, the Cr mixed phase film may contain Ti or TiN (titanium nitride).

When the metal layer A is a Cr mixed phase film, the functional layer made of Ti has the function of promoting the crystal growth of the metal layer A and the function of preventing oxidation of the metal layer A due to oxygen and moisture contained in the base material 110. , and the function of improving the adhesion between the base material 110 and the metal layer A. The same is true when Ta, Si, Al, or Fe is used as the functional layer instead of Ti.

In this way, by providing the functional layer under the metal layer A, the crystal growth of the metal layer A can be promoted, and the metal layer A having a stable crystal phase can be produced. As a result, in the strain gauge 100, the stability of gauge characteristics can be improved. In addition, by diffusing the material forming the functional layer into the metal layer A, the gauge characteristics of the strain gauge 100 can be improved.

Next, the second metal layer 142 and the second metal layer 152 are formed on the upper surface of the metal layer A. As shown in FIG. The second metal layer 142 and the second metal layer 152 can be formed by photolithography, for example.

Specifically, first, a seed layer is formed so as to cover the upper surface of the metal layer A by, for example, sputtering or electroless plating. Next, a photosensitive resist is formed on the entire upper surface of the seed layer, exposed and developed to form openings exposing regions where the second metal layers 142 and 152 are to be formed. At this time, the pattern of the second metal layer 142 can be made into an arbitrary shape by adjusting the shape of the opening of the resist. As the resist, for example, a dry film resist or the like can be used.

Next, a second metal layer 142 and a second metal layer 152 are formed on the seed layer exposed in the opening by, for example, electroplating using the seed layer as a power supply path. The electroplating method is suitable in that the tact time is high and low-stress electroplating layers can be formed as the second metal layer 142 and the second metal layer 152 . The strain gauge 100 can be prevented from warping by reducing the stress of the thick electroplated layer. The second metal layer 142 and the second metal layer 152 may be formed by electroless plating.

Next, the resist is removed. The resist can be removed, for example, by immersing it in a solution capable of dissolving the material of the resist.

Next, a photosensitive resist is formed on the entire upper surface of the seed layer, exposed and developed, and patterned into a planar shape similar to the resistor 130, wiring 140, and electrode 150 in FIG. As the resist, for example, a dry film resist or the like can be used. Then, using the resist as an etching mask, the metal layer A and the seed layer exposed from the resist are removed to form the planar resistor 130, the wiring 140 and the electrode 150 shown in FIG.

For example, wet etching can remove unnecessary portions of the metal layer A and the seed layer. When a functional layer is formed under the metal layer A, the functional layer is patterned by etching into the planar shape shown in FIG. At this point, a seed layer is formed on the resistor 130, the first metal layer 141, and the first metal layer 151. Next, as shown in FIG.

Next, using the second metal layer 142 and the second metal layer 152 as an etching mask, unnecessary seed layers exposed from the second metal layer 142 and the second metal layer 152 are removed, thereby removing the second metal layer 142 and the second metal layer 152 . A two metal layer 152 is formed. Note that the seed layer immediately below the second metal layer 142 and the second metal layer 152 remains. For example, the unnecessary seed layer can be removed by wet etching using an etchant that etches the seed layer but does not etch the functional layer, resistor 130 , wiring 140 , and electrode 150 .

After that, the strain gauge 100 is completed by providing a cover layer 160 covering the resistor 130 and the wiring 140 and exposing the electrodes 150 on the upper surface 110a of the base material 110, if necessary. For the cover layer 160, for example, a semi-cured thermosetting insulating resin film is laminated 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 is cured by heating. can be produced by The cover layer 160 is formed by coating the upper surface 110a of the base material 110 with a liquid or paste thermosetting insulating resin so as to cover the resistor 130 and the wiring 140 and expose the electrodes 150, and heat and harden the resin. may be made.

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

1 pulse wave measuring device, 10 pulse wave sensor 10, 10x through hole, 10y screw hole, 11 housing, 12 straining body, 12a base, 12b beam, 12c load part, 12d extension part, 20 sensor fixing part, 20a , 20b mounting portion, 20x notch, 20y insertion hole, 30 belt fixing portion, 30a, 40a protrusion, 40 belt insertion portion, 80 belt, 90 screw, 100 strain gauge, 110 base material, 110a upper surface, 130 resistor, 130e ₁ , 130e ₂ termination, 140 wiring, 150 electrode, 160 cover layer

Claims (10)

A pulse wave measuring device attachable to a subject,
a pulse wave sensor having a strain gauge;
a sensor fixing portion for fixing the pulse wave sensor;
a belt-shaped body having one end swingably connected to one end side of the sensor fixing portion by a first shaft, and the other end being swingably connected to the other end side of the sensor fixing portion by a second shaft; death,
The pulse wave measuring device, wherein the first axis and the second axis are located on a side opposite to the subject with respect to a surface of the pulse wave sensor that contacts the subject. The pulse wave measuring device according to claim 1, wherein the pulse wave sensor protrudes from the sensor fixing portion toward the subject. 3. The pulse wave measurement according to claim 1, wherein the other end of said belt-like body is connected to the other end of said sensor fixing part through said belt-like body insertion part so as to be swingable about said second shaft. Device. 4. The other end of said strip can be detachably connected to the outer peripheral surface of a portion of said strip which is not inserted into said strip inserting portion by passing through a through hole of said strip inserting portion. The pulse wave measuring device according to . The pulse wave measuring device according to any one of claims 1 to 4, further comprising a biasing mechanism between the sensor fixing portion and the pulse wave sensor that biases the pulse wave sensor toward the subject. 6. The pulse wave sensor according to any one of claims 1 to 5, wherein the strain gauge is provided with a strain-generating body, and the strain-generating body is exposed from the sensor fixing portion and can come into contact with the subject. The pulse wave measuring device according to . The strain-generating body is
a base with a circular opening;
a beam that bridges the inside of the base;
and a load portion provided on the beam portion,
7. The pulse wave measuring device according to claim 6, wherein a pulse wave is detected based on a change in resistance value of said strain gauge accompanying deformation of said strain body. The beam portion has two beams that intersect in a cross shape in a plan view,
the area of intersection of the beams includes the center of the circular opening;
8. The pulse wave measuring device according to claim 7, wherein said load section is provided in an area where said beams intersect. Equipped with four strain gauges,
Two of the four strain gauges are arranged on a side of the beam having a first direction as a longitudinal direction and close to the load section so as to face each other across the load section in a plan view,
The other two of the four strain gauges are opposed to the side of the beam near the base portion whose longitudinal direction is the second direction orthogonal to the first direction, with the load portion interposed therebetween in a plan view. 9. The pulse wave measuring device according to claim 8, arranged to: 10. The pulse wave measuring device according to claim 1, wherein said strain gauge has a resistor made of a Cr mixed phase film.

Images