JP2010051586A - Displacement measuring sensor and displacement measuring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement measuring sensor and a displacement measuring system for highly sensitively measuring the displacement. <P>SOLUTION: A piezoelectric film structure 10, composed of projection-shaped parts 101 and recessed parts 102 formed by inverting the same shape, is formed by processing a piezoelectric film made of a flat material. Long sides of the respective projection-shaped part 101 and recessed part 102 are cyclically connected with each other via flat strip-shaped parts respectively. Further, the projection-shaped part 101 and the recessed part 102 are connected with each other in such a way that slopes of the same inclination face each other by the strip-shaped part with displacement of half a cycle. In this way, the displacement is measured by measuring the signal voltage output from the piezoelectric film structure 10 tucked in such a way as to generate a negative Poisson's ratio. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a displacement measuring sensor and a displacement measuring system for measuring displacement with high sensitivity. In particular, the present invention relates to a sensor and system for detecting physical information of a bedridden person such as a newborn or an elderly person.

  In general, a method of attaching an electrocardiogram electrode, a pulse oximeter, a thermistor temperature sensor, a strain gauge band, or the like to a predetermined part of the body is used for monitoring biological information such as heart rate and respiration rate. However, since such a measurement restrains the patient, it gives a sense of incongruity and may result in a heart rate and respiratory rate different from normal. In particular, in patients with weak skin such as newborns, symptoms such as rash are likely to occur due to electrodes and sensors attached to the skin. Furthermore, there is a possibility that the patient moves during measurement and the sensor comes off. In order to solve these problems, research on non-restrained (non-contact) heart rate / respiration monitoring system and development of devices are underway.

  For this reason, a heartbeat / respiration monitoring system for quantitatively monitoring the heartbeat and breathing state of newborns, particularly premature babies, has been studied (for example, see Patent Document 1). In the technique described in this document, a plurality of detection pieces 2 made of a polymer piezoelectric film are laid in parallel on a core made of soft silicone rubber, and this is placed between two towels 1. A sandwich detection mat is formed by sandwiching the two in a sandwich shape. Each detection piece is connected to a computer via an amplifier and an A / D converter to perform various information analysis processes, and the results are input to a display and displayed visually and quantitatively.

  In addition, a displacement enlarging device for realizing an increase in the amount of displacement in a micro displacement device based on the displacement of the micro displacement actuator with a necessary and sufficient displacement magnification rate while responding to the demand for space saving has been studied ( For example, see Patent Document 2.) In the technique described in this document, the displacement magnifying device is composed of a long plate-like plate body having substantially the same length direction dimension and width direction dimension as the laminated piezoelectric element. A fulcrum portion supported by the fixed end of the multilayer piezoelectric element is provided on one end side of the plate body, and a force point portion supported by the free end of the multilayer piezoelectric element is provided on the other end side of the plate body. . And an action point part is provided in each center part of the upper side of a board, and a lower side. Therefore, when the multilayer piezoelectric element expands due to voltage application, the action point is large in the direction perpendicular to the length direction of the multilayer piezoelectric element due to the action of the link mechanism having a honeycomb-like periodic structure formed in the plate body. Displace with displacement magnification.

In such a displacement enlarging device, a negative Poisson's ratio is used. This Poisson's ratio is, for example, the ratio between the elongation (strain%) in the load direction and the shrinkage (strain%) in the direction perpendicular to the load when tension is applied. Then, it has been studied to provide a method for producing a composite material having a desired Poisson's ratio, particularly a negative Poisson's ratio (see, for example, Patent Document 3). In the technique described in this document, in a manufacturing method in which a composite material composed of a first material and a second material is made into a material having a desired Poisson's ratio, the first material forms a linear element, and the second material The material forms a medium for linear elements. Furthermore, the linear elements have a first width and intersect with each other in a direction different from the first linear elements and the first linear elements arranged in a direction intersecting each other. It consists of the 2nd linear element arrange | positioned in the direction to do. Then, the ratio between the first width and the second width or / and the ratio between the elastic moduli of the first material and the second material are changed.
JP 2006-247329 A (first page, FIG. 1) Japanese Patent Laying-Open No. 2005-94920 (first page, FIG. 1) JP-A-10-134102 (first page, FIG. 3)

  As described above, since the body is partially displaced by heartbeat and respiration, it can be measured by the pressure generated by such displacement. However, since the newborn has a smaller body (height / weight) than adults, the body signals generated by heartbeat and breathing are also weak. It is therefore desirable to be able to sense body signals with as much sensitivity as possible. Further, a member using a negative Poisson's ratio as in Patent Document 2 and a configuration that generates a negative Poisson's ratio as in Patent Document 3 have been studied, but there was no idea of using these for sensors.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a displacement measurement sensor and a displacement measurement system for measuring displacement with high sensitivity.

  In order to solve the above-mentioned problems, the invention described in claim 1 is a sensor for measuring displacement using a planar material that outputs a signal by pressure, and the height direction is obtained by folding the planar material. The gist is that a change was made.

The gist of the invention described in claim 2 is that, in the displacement measuring sensor according to claim 1, the planar material is further folded so as to have a cell structure.
The gist of the invention described in claim 3 is the displacement measuring sensor according to claim 1 or 2, wherein the planar material is a piezoelectric film.

  According to a fourth aspect of the present invention, in the displacement measurement sensor according to any one of the first to third aspects, a first surface having a shape for maintaining a change in a height direction in the planar material. The gist is that the cell structure is configured by being sandwiched between a mold member and a second mold member having a surface having a shape corresponding to the first mold member.

  The invention according to claim 5 is a displacement measuring system comprising a sensor made of a planar material that outputs a signal by pressure, and an analysis means for acquiring a signal from the sensor, wherein the sensor uses the planar material. It is composed of a piezoelectric film which is folded and provided with a change in the height direction, and the gist is that the analyzing means analyzes and outputs a signal output from the sensor.

  The gist of the invention described in claim 6 is that, in the displacement measuring system according to claim 5, monitoring of breathing or heartbeat is performed by lying down on the sensor.

(Function)
According to invention of Claim 1 or 5, the sensor is comprised so that a flat raw material may be folded and a change may be provided in a height direction. Here, the force applied to the high region is transmitted to other adjacent regions and deformed. Since the amount of deformation is added, it is amplified more than usual and the sensor sensitivity is improved. Furthermore, since the planar material is folded and configured, high sensitivity can be obtained with a simple structure.

  According to the second aspect of the present invention, the planar material is further folded so as to have a cell structure. As a result, the force applied to the cell structure is also transmitted to the cells adjacent in all directions and amplified, thereby improving the sensor sensitivity.

According to invention of Claim 3, an electrical signal can be output by a piezoelectric film.
According to the invention described in claim 4, the first mold member having a surface having a shape for maintaining the change in the height direction in the planar material, and the surface having a shape corresponding to the first mold member are provided. The cell structure is configured by being sandwiched between the provided second mold members. Thereby, if a 1st, 2nd type | mold member is prepared, a plane member can be processed easily.

  According to invention of Claim 5, the signal output from the piezoelectric film which folded the plane | planar raw material and provided the change in the height direction is analyzed and output. Thereby, noise etc. can be removed and displacement can be evaluated.

  According to the sixth aspect of the present invention, respiration or heartbeat monitoring can be performed. For example, even when it is difficult to directly attach the sensor to the skin, such as a newborn baby, respiration or heart rate can be measured easily and efficiently.

  According to the present invention, it is possible to provide a displacement measuring sensor and a displacement measuring system for measuring displacement with high sensitivity.

  Hereinafter, the displacement measuring sensor and the displacement measuring system of the present invention will be described. In the present embodiment, it is used when measuring the change in the ribcage portion of the respiratory motion and the displacement of the body due to the heartbeat in the recumbent state. Due to such displacement, the pressing force against the floor such as a bed periodically changes minutely. In the present embodiment, a heartbeat or respiration monitoring system that measures this minute change by converting it into a voltage using a piezoelectric sensor will be described with reference to FIGS.

(Sensor shape)
In this monitoring system, as shown in FIG. 1, a piezoelectric film structure 10 in which a flat material is folded to provide a change in the height direction is used. FIG. 1A is a perspective view of a part of the piezoelectric film structure 10. As shown in FIG. 1, in this embodiment, it consists of a structure folded in order to improve the sensitivity of a sensor. Specifically, the cell structure is folded so as to produce a negative Poisson's ratio when viewed in the plane direction.

  FIG. 1B shows three views (a top view 10A, a side view 10B, and a front view 10C) of a part of the piezoelectric film structure 10. In this piezoelectric film structure 10, as represented by a bold line, two trapezoidal slopes, a convex shape part 101 made of a rectangle connecting the upper ends of these trapezoids, and a concave shape part 102 obtained by inverting the same shape, It is comprised including. Each long side part of each convex-shaped part 101 and the concave-shaped part 102 is periodically connected via a flat strip-shaped part. Furthermore, the convex shape portion 101 and the concave shape portion 102 are connected to each other so that the slope portions having the same inclination are opposed to each other by the belt-like portion, with a half cycle shift.

  Such a piezoelectric film structure 10 is formed by folding a planar material piezoelectric film sheet 10D as shown in FIG. In the piezoelectric film sheet 10D, the shape of the piezoelectric film structure 10 is created by bending a mountain fold line (solid line) and a valley fold line (broken line) at a predetermined angle.

(Configuration of measurement unit)
Next, the structure of the measurement unit used in the monitoring system will be described with reference to FIG.

For the piezoelectric film structure 10, a piezoelectric film sheet made of polyvinylidene fluoride (PVDF) to which an electrode made of nickel (Ni) / copper (Cu) is added is used. This PVDF film functions as a planar material that outputs a signal by pressure. PVDF film does not respond to static pressure, but responds to changes in pressure over time. Therefore, it is possible to obtain a voltage signal about body displacement due to heartbeat, respiration, etc. regardless of the patient's weight. In the present embodiment, “200 mm × 280 mm × 28 μm” is used as the size. And the piezoelectric film structure 10 is inserted | pinched with the sheet | seat materials 21, such as rubber | gum, for moisture prevention etc.

  In the measurement unit, the piezoelectric film structure 10 is held between a pair of soft members (22A, 22B) in order to maintain a folded state. In this embodiment, a soft urethane resin sheet (hapla pudding gel) is used as the soft member (22A, 22B).

  Specifically, each surface of the soft member 22A as the first mold member and the soft member 22B as the second mold member has a coupling as a shape for maintaining a change in the height direction in the planar material. An uneven shape with a common size is formed so that it can be made. And the shape which produces a negative Poisson's ratio is formed by the space | gap pinched | interposed into the surface. And the piezoelectric film structure 10 coated with the sheet material 21 is sandwiched between the soft members (22A, 22B). Thereby, the piezoelectric film structure 10 is deformed into a structure having a negative Poisson's ratio.

And as shown in FIG. 3, a soft member (22A, 22B) is wound in with the towel 23, and it installs on the cushion 24 (for example, cushion) on the mat 25. FIG.
(Measuring method)
Next, a measurement method using such a piezoelectric film structure 10 will be described with reference to FIGS.

  When measuring heart rate and respiration, as shown in FIG. 4, lying on the back so that the subject's thorax hits the cushion 24 on the mat 25. In this case, the piezoelectric film structure 10 is disposed immediately below the rib cage.

Before the subject lies down (before weighting), the piezoelectric film structure 10 having the three-dimensional structure 10E shown in FIG. 5A becomes a three-dimensional structure 10F shown in FIG.
In the monitoring system, the signal voltage output from the electrode of the piezoelectric film structure 10 is taken into the computer terminal 33 by the signal processing unit (analyzing means) shown in FIG. In this case, the signal passes through the AD converter 32 via the low-pass filter 31. The low-pass filter 31 removes noise in the signal voltage, and the AD converter 32 converts the analog signal into a digital signal. After the signal stabilized, measurement was started. The sampling frequency and the frequency of the low-pass filter were set to 100 Hz and 1.5 Hz, respectively.

According to this embodiment, the following effects can be obtained.
In the present embodiment, in the piezoelectric film structure 10, a structure that is folded so as to produce a negative Poisson's ratio is used as a cell structure in which a planar material is folded. When a fold as shown in FIG. 1 is inserted into the piezoelectric film, it is deformed not only in the height direction but also in the horizontal direction by the pressing force. At this time, if one unevenness is regarded as one cell, the force applied by the cell is transmitted to other adjacent cells and deformed. It is considered that the folded piezoelectric film is amplified more than usual because these deformations are added, and the sensor sensitivity is improved.

Here, the characteristics of the sensor output from the computer terminal 33 will be described. Here, for comparison, a signal voltage was measured under the same conditions using a piezoelectric film alone and a piezoelectric film sandwiched between flat haplin pudding gel sheets as sensors. FIG. 7A shows a signal voltage from a piezoelectric film alone, and FIG. 7B shows a signal voltage from a piezoelectric film sandwiched between flat haplin pudding gel sheets. And the signal voltage from the piezoelectric film structure 10 of this invention is shown in FIG.7 (c). In either case, a voltage output including typical respiratory / heartbeat signals is obtained. And as for the piezoelectric film structure 10 of this invention, the amplitude of an output voltage is expanded compared with the case where a piezoelectric film is pinched | interposed with a piezoelectric film single-piece | unit or a flat sheet. Specifically, the sensitivity is improved about 1.2 to 1.5 times that of a single piezoelectric film, and about twice that when sandwiched between flat sheets.

  In the present embodiment, the planar film piezoelectric film sheet 10D is folded and created. Specifically, a shape that generates negative Poisson's ratio of the same size is formed on each surface of the soft member 22A and the soft member 22B, and the piezoelectric material coated with the sheet material 21 between the soft members (22A, 22B). The film structure 10 is sandwiched. Thereby, a structure having a negative Poisson's ratio can be easily formed.

Moreover, you may change the said embodiment as follows.
In the embodiment described above, in the piezoelectric film structure 10, a structure that is folded so as to produce a negative Poisson's ratio is used as a cell structure in which a planar material is folded to provide a change in the height direction. The folding shape of the piezoelectric film is not limited to this, as long as the pressing force can be propagated to the surrounding cells.

  In the above embodiment, it is assumed that the system is used as a heartbeat or respiration monitoring system that converts a voltage into a voltage by a piezoelectric sensor. The application of the present invention is not limited to this, and can be applied to a sensor or system for measuring a pressure generated by displacement.

  In the above embodiment, a piezoelectric film sheet made of polyvinylidene fluoride (PVDF) to which an electrode made of nickel (Ni) / copper (Cu) is added is used for the piezoelectric film structure 10. Further, a sheet material 21 such as rubber is used for moisture prevention or the like. Furthermore, a soft urethane resin sheet (hapla purine gel) is used as the soft member (22A, 22B). These members are not limited to these materials.

  In the above embodiment, the piezoelectric film structure 10 includes two trapezoidal slopes, a convex shape portion 101 that is a rectangle that connects the upper ends of these trapezoids, and a concave shape portion 102 that is the same shape inverted. Consists of. That is, a structure having a flat portion at the top or the bottom is used. Instead of this, it is also possible to use a structure having no flat portion at the top or the bottom. In this case, the piezoelectric film structure 11 shown in FIG. 8 is used. FIG. 8A is a perspective view of a part of the piezoelectric film structure 11. Even in such a structure, a negative Poisson's ratio is produced.

  FIG. 8B shows three views (a top view 11A, a side view 11B, and a front view 11C) of a part of the piezoelectric film structure 11. The piezoelectric film structure 11 is configured to include a convex shape portion 111 in which the upper end portions of two trapezoidal slopes are directly connected and a concave shape portion 112 in which the same shape is inverted, as represented by a bold line. The Each convex-shaped part 111 and the concave-shaped part 112 are periodically connected at the lower end. Furthermore, the convex shape portion 111 and the concave shape portion 112 are connected to each other so that the slope portions having the same inclination are opposed to each other by the belt-like portions while being shifted by a half cycle.

Such a piezoelectric film structure 11 is formed by folding a planar material piezoelectric film sheet 11D as shown in FIG. In the piezoelectric film sheet 11D, the shape of the piezoelectric film structure 11 can be created by bending a mountain fold line (solid line) and a valley fold line (broken line) at a predetermined angle. Even with such a shape, a structure having a negative Poisson's ratio can be formed.

  In the above-described embodiment, in the piezoelectric film structure 10, the two trapezoidal slopes, the convex shape portion 101 made of a rectangle connecting the upper end portions of these trapezoids, and the concave shape portion 102 obtained by inverting the same shape Consists of including. That is, a structure in which the fold line is a straight line is used. Alternatively, a negative Poisson's ratio can be realized by a structure using a curve. In this case, the piezoelectric film structure 12 shown in FIG. 10 is used. FIG. 10A is a perspective view of a part of the piezoelectric film structure 12. Even in such a structure, a negative Poisson's ratio is produced.

  FIG. 10B shows three views (a top view 12A, a side view 12B, and a front view 12C) of a part of the piezoelectric film structure 12. In this piezoelectric film structure 12, as represented by a bold line, the same shape is inverted with the convex shape portion 121 of FIG. 8B and the convex shape portion 121 having curved sides constituting the concave shape portion 112. And a concave shape portion 122. Each convex-shaped part 121 and the concave-shaped part 122 are periodically connected at the other end. Further, the convex shape portion 121 and the concave shape portion 122 are connected to each other so that the slope portions having the same inclination are opposed to each other by the belt-like portions while being shifted by a half cycle.

  Such a piezoelectric film structure 12 is formed by folding a planar material piezoelectric film sheet 12D as shown in FIG. In the piezoelectric film sheet 12D, the shape of the piezoelectric film structure 12 can be created by bending a mountain fold line (solid line) and a valley fold line (broken line) at a predetermined angle. Even with such a shape, a structure having a negative Poisson's ratio can be formed.

It is explanatory drawing of the piezoelectric film sensor of one Embodiment of this invention, Comprising: (a) is a perspective view, (b) is a trihedral view. The expanded view for folding the piezoelectric film sensor of one Embodiment of this invention. Explanatory drawing of a structure of the sensor part of one Embodiment of this invention. Explanatory drawing of the measuring method using the sensor part of one Embodiment of this invention. It is explanatory drawing of the shape of the structure used for the piezoelectric film sensor of one Embodiment of this invention, Comprising: (a) is the shape before weighting, (b) is explanatory drawing of the shape at the time of weighting from the upper surface. Explanatory drawing of the signal processing part of one Embodiment of this invention. It is explanatory drawing of a measurement result, (a) is the signal voltage from a piezoelectric film single-piece | unit, (b) is the signal voltage from the piezoelectric film pinched | interposed with the flat hapla pudding gel sheet, (c) is the piezoelectric film sensor of this invention. Explanatory drawing of the signal voltage from. It is explanatory drawing of the piezoelectric film sensor of other embodiment of this invention, Comprising: (a) is a perspective view, (b) is a trihedral view. The expanded view for folding the piezoelectric film sensor of other embodiment of this invention. It is explanatory drawing of the piezoelectric film sensor of other embodiment of this invention, Comprising: (a) is a perspective view, (b) is a trihedral view. The expanded view for folding the piezoelectric film sensor of other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 11, 12 ... Piezoelectric film structure, 101, 111, 121 ... Convex shape part, 102, 112, 122 ... Concave shape part, 21 ... Sheet material, 22A, 22B ... Soft member, 31 ... Low pass filter, 32 ... AD converter, 33... Computer terminal.

Claims (6)

A sensor for measuring displacement using a flat material that outputs a signal by pressure,
A displacement measuring sensor, wherein the flat material is folded to provide a change in the height direction.   The displacement measuring sensor according to claim 1, wherein the planar material is further folded so as to have a cell structure.   The displacement measuring sensor according to claim 1, wherein the planar material is a piezoelectric film.   Sandwiched between a first mold member having a surface having a shape for maintaining a change in the height direction of the planar material and a second mold member having a surface having a shape corresponding to the first mold member. The displacement measuring sensor according to any one of claims 1 to 3, wherein a cell structure is configured. A sensor made of flat material that outputs a signal by pressure,
A displacement measurement system comprising an analysis means for acquiring a signal from the sensor,
The sensor is composed of a piezoelectric film in which the flat material is folded to provide a change in the height direction,
The displacement measuring system characterized in that the analyzing means analyzes and outputs a signal output from the sensor.   6. The displacement measuring system according to claim 5, wherein respiration or heartbeat monitoring is performed by lying down on the sensor.

Images