JP4122265B2 - Bed pad and bed using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bed pad, and more particularly to a bed pad that can detect heartbeat and breathing movements from a human body with a pressure-sensitive sensor laid on the lower surface of a cushion layer.
[0002]
[Prior art]
An arrangement in which a sensor is disposed under a urethane portion of a car seat is known from an earlier application related to the present applicant (see, for example, Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-282358
FIG. 7 shows a configuration diagram of a seat described in Patent Document 1.
In the figure, 70 is a seat, 71 is vibration detecting means, 72 is a front cloth, 73 is urethane foam, 74 is a seat spring, and 75 is a seat frame. The vibration detecting means 71 is fixed on a seat spring 74 constituting the seat 70 which is separated from the contact surface of the seat 70 with the human body via the front cloth 72 and the urethane foam 73 by a predetermined distance r or more. Here, r is a distance at which the human body seated on the seat 70 cannot feel the presence of the vibration detecting means 71, and the longer the outer shell hardness of the vibration detecting means 71 is, the longer the urethane foam 73 is softer.
In this way, the vibration detection means is fixed to a part away from the surface of the urethane seat by a certain distance, the output of the vibration detection means is processed, and the presence or absence of a human body on the seat is determined by the output. Since the vibration detecting means is installed away from the contact surface with the human body, the influence on the seating feeling can be reduced even if the vibration detecting means is made of a rigid body.
[0005]
However, the invention described in the above cited document 1 relates to a car seat. In the case of a car seat, the weight of the entire upper body is concentrated from the buttocks to the narrow buttocks, so that even if vibration detecting means is provided on the lower surface of the urethane seat, it is detected. However, when this technical idea was applied to the bed as it was, it was found that there were the following problems.
FIG. 2 shows various experimental examples in which the vibration detecting means (piezoelectric sensor) is used for the bed. (A) is Experimental Example 1, (b) is Experimental Example 2, and (c) is Experimental Example 3.
In FIG. 2B, 22 is a bed made of a urethane layer, 23 is a piezoelectric sensor laid under the urethane layer bed 22, and a cord-like piezoelectric sensor (described later) is used here. P is a human body lying on the bed.
When the cord-shaped piezoelectric sensor 23 is lying on the urethane layer bed 22 laid underneath, a signal (a heartbeat emitted from the human heart) obtained by the cord-shaped piezoelectric sensor 23 is detected and viewed. The detection value detected by the cord-like piezoelectric sensor 23 was only a slight value.
[0006]
The reason for this is that when lying on the urethane layer bed, the convex portions on the back side of the human body P, that is, the head P1, scapula P2, heel P3, and heel P4 are particularly strong against the bed pad. Since it sinks deeply and other parts do not sink so much, only the heartbeat vibration from these four points becomes the vibration source and is transmitted downward, and as a result, even the cord-like piezoelectric sensor 23 is detected as a sufficient signal. The applicant thought that it was not possible.
Therefore, when the degree of amplification was greatly increased, on the contrary, it picked up a lot of other noises (vibrations caused by cars passing outside, vibrations of people passing near the bed, etc.) It was found to be impractical for bed 2 (b).
[0007]
FIG. 2C is an experimental example considered by the present applicant to cover the drawback of FIG. 2B, in which a cord-shaped piezoelectric sensor 23 is laid on the urethane bed 22. When lying on such a bed, the sensor is not only the heartbeat vibration from the head P1, scapula P2, heel P3 and heel P4, but also other parts of the neck, waist, thigh, Heartbeat vibrations from the shin part etc. could be detected reliably.
However, it lays on a sensor cable having a diameter of several millimeters that is bent many times, which makes it uncomfortable to sleep, and this also has a problem in practical use.
[0008]
[Problems to be solved by the invention]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a bed bud that can reliably detect heartbeat vibration and has good sleeping comfort.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention of a bed pad capable of detecting a heartbeat according to claim 1 of the present invention comprises a low resilience urethane layer and a pressure sensitive sensor laid on the lower surface of the low resilience urethane layer. It is characterized by comprising.
By configuring in this way, a bed bud that can reliably detect heartbeat vibration and the like and has good sleeping comfort can be obtained.
The invention of the bed pad capable of detecting a heartbeat according to claim 2 comprises a low-rebound urethane layer, a normal urethane cushion layer laid on the lower surface of the low-repulsion urethane layer, and a lower surface of the cushion layer. It is characterized by comprising a pressure sensor.
With this configuration, it is possible to reliably detect heartbeat vibration and the like, and to obtain a bed bud that is comfortable to sleep at low cost.
According to a third aspect of the present invention, in the bed pad according to the first or second aspect, the pressure-sensitive sensor comprises a cord-shaped piezoelectric sensor having flexibility.
By doing so, heartbeat vibration and the like can be detected more reliably.
The invention of a bed element according to claim 4 comprises the rigid plate having irregularities formed on the surface thereof, and the bed pad according to any one of claims 1 to 3 placed on the rigid plate. Features.
With this configuration, heartbeat vibration and the like can be detected more reliably.
The bed invention according to claim 5 comprises a bed frame, a movable plate attached to the bed frame so as to be tiltable, and a bed element according to claim 4 placed on the movable plate. It is characterized by that.
By configuring in this way, it is possible to reliably detect heartbeat vibrations and to provide a nursing bed with good sleeping comfort.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a bed and the like capable of detecting a heartbeat according to the present invention will be described in detail with reference to the drawings.
First, the cord-shaped piezoelectric sensor used here will be briefly described.
The cord-shaped piezoelectric sensor is a cable-shaped sensor using a piezo element material that has been practically developed by the present applicant, and its configuration is shown in FIG.
In the figure, reference numeral 60 denotes a cord-shaped piezoelectric sensor, which has a core wire (center electrode) 61 at the center in the axial direction, a piezo element material 62 covered around the center electrode 61, and an outer electrode around the piezo element material 62. 63 is disposed, and the outermost periphery is covered with PVC (vinyl chloride resin) 64.
[0011]
The cord-shaped piezoelectric sensor 60 uses a heat-resistant resin-based material originally developed by the applicant, which can be used at a temperature of up to 120 ° C., as a piezo element material 62. Polyvinylidene fluoride) and piezo element materials (piezo element materials of chloroprene and piezoelectric ceramic powder) can be used in a temperature range higher than 90 ° C. (120 ° C. or less). The piezo element material 62 is composed of a flexible resin and piezoelectric ceramic, and is composed of a flexible electrode composed of a coiled metal center electrode and a film-shaped outer electrode, which is equivalent to a normal vinyl cord. Has flexibility.
[0012]
Further, the cord-shaped piezoelectric sensor 60 is as sensitive as a polymer piezo element material, and has a sensitivity as high as that of a polymer piezo element material in a low-frequency region (10 Hz or less) in which pinching of a human body is detected. Yes. This is because the relative dielectric constant (about 55) of the piezo element material 62 is larger than that of the polymer piezo element material (about 10), so that the decrease in sensitivity is small even in the low frequency region (10 Hz or less).
[0013]
The piezo element material 62 is composed of a composite of a resin material and a piezoelectric ceramic powder of 10 μm or less, and vibration detection characteristics are realized by ceramic, and flexibility is realized by resin. This piezo element material 62 uses chlorinated polyethylene as a resin material, realizes high heat resistance (120 ° C.) and flexibility that can be easily formed, and enables a simple manufacturing process that does not require crosslinking. .
[0014]
The cord-shaped piezoelectric sensor 60 obtained in this way does not have piezoelectric performance when the piezoelectric element material 62 is molded, so that by applying a DC high voltage of several kV / mm to the piezoelectric element material 62, the piezoelectric element material 62 is not piezoelectric. It is necessary to perform a process for imparting piezoelectric performance to the element material 62 (polarization process). This polarization process is performed by forming a center electrode 61 and an outer electrode 63 on the piezo element material 62 and then applying a DC high voltage to both electrodes. When a minute defect such as a crack is inherent in the piezo element material 62, it becomes easy to cause a short circuit between the two electrodes by discharging at the defect, so that a sufficient polarization voltage cannot be applied. By establishing a unique polarization process using an auxiliary electrode that can be brought into close contact with the piezo element material 62, it is possible to detect and avoid defects and stabilize the polarization, thereby enabling a length of several tens of meters or more.
[0015]
In the cord-shaped piezoelectric sensor, a coil-shaped metal center electrode is used for the center electrode 61, and a film-shaped electrode (aluminum-polyethylene terephthalate-aluminum three-layer laminate film) is used for the outer electrode 63. In addition to ensuring the adhesion of the electrodes, the external lead wires can be easily connected, and a flexible cable-like mounting configuration is possible.
The center electrode 61 is a copper-silver alloy coil, the outer electrode 63 is a three-layer laminate film made of aluminum-polyethylene terephthalate-aluminum, the piezo element material 62 is a polyethylene-based resin + piezoelectric ceramic powder, the outer shell is a thermoplastic, The relative dielectric constant is 55, the charge generation amount is 10-13 C (coulomb) / gf, and the maximum use temperature is 120 ° C.
[0016]
FIG. 5 is a diagram showing a load applied to the cord-shaped piezoelectric sensor 60 and sensor output characteristics. As a result of the experiment conducted by the applicant on the relationship between the load of the cord-shaped piezoelectric sensor 60 and the sensor output, when a bending load such as (a) is applied to the cord-shaped piezoelectric sensor 60, the sensor output becomes a phenomenon as shown in (b). Become.
(1) That is, when no load is applied to the cord-shaped piezoelectric sensor 60 at time t0, the sensor output indicates 2 (V).
(2) When a bending load is applied to the cord-shaped piezoelectric sensor 60 in a certain direction at time t1, the sensor output increases to 4 (V) from the moment it is applied and then reverses to 0 (V), and then 2 again. Return to (V).
(3) After that, the sensor output still shows 2 (V) even if it is kept bent.
(4) When the cord-shaped piezoelectric sensor 60 is returned to the original state at time t3, the sensor output decreases to 0.8 (V) from that moment, and then immediately reverses to 2.2 (V). Return to 2 (V) again.
Thus, since this cord-shaped piezoelectric sensor generates an output in response to acceleration, a signal is output only at the moment when force is applied, and thereafter there is no acceleration as long as there is no fluctuation even if force is continuously applied. And no longer output. Similarly, when the force is removed, the output is output only at that moment. Therefore, even if the cord-shaped piezoelectric sensor is bent and laid in a wave shape at the bottom of the bed, the output is not output after the laying is completed, although it is turned on at the moment of bending. After that, an output is output only when a force is applied to some part of the cord-shaped piezoelectric sensor.
[0017]
FIG. 2 (a) is an experimental example further considered by the present applicant as covering the drawbacks of the conventional devices of (b) and (c).
In the figure, 21 is a bed made of a low-resilience urethane layer, 23 is a cord-like piezoelectric sensor laid below, and P is a person lying on the bed.
According to this, even though the cord-like piezoelectric sensor 23 is far away from the person P lying on the bed, the heartbeat vibration can be reliably detected.
The reason is that because the low resilience urethane layer 21 is used, the back side of the human body sinks uniformly from the head to neck, shoulders, back, hips, buttocks, thighs, calves, and heels. It is judged that the heartbeat vibration is transmitted from the whole to the cord-like piezoelectric sensor.
[0018]
FIG. 1 is an exploded perspective view of a bed according to the present invention, which has been considered based on the experimental results of FIG.
In the figure, reference numeral 10 denotes a bed pad according to the present invention, which comprises a low resilience urethane layer 11 and a normal urethane layer 12 therebelow. The thickness of the low resilience urethane layer 11 is ½ or less of the total thickness of the bed pad 10.
Reference numeral 20 denotes a cord-like piezoelectric sensor laying sheet, which is composed of a cloth-like sheet 21 such as a cloth and a cord-like piezoelectric sensor 22 arranged meandering in a wavy shape on the sheet.
Numeral 30 is an uneven plastic plate, and unevenness is formed by providing a large number of depressions 321 on the surface of the plastic plate 32. The effect of this will be described later.
Reference numeral 40 denotes a cover bag in which a large sheet 41 is folded in two so that three sides can be opened and closed with a fastener 42. The fastener 42 is opened, and the bed pad 10, the cord-shaped piezoelectric sensor laying sheet 20, and the concavo-convex plastic plate 30 are stacked in this order from the top and stored in the cover bag 40. Is completed.
Reference numeral 50 denotes a bed frame, and support plates 52 and 53 are attached to the frame frame 51. The support plate 52 is inclined as shown in the figure by the operation of the motor 54. By placing the cover bag 40 on the support plates 52 and 53, the bed is completed.
[0019]
Here, “low resilience urethane” and “ordinary urethane” constituting the bed pad 10 will be described.
“Low resilience urethane” is a composition of urethane foam, that is, the type of polyisocyanate, the number of functional groups and the hydroxyl value of polyol, etc., and the glass transition occurs at the temperature (usually room temperature) at which the urethane foam is used. It is formulated so as to occur, and low resilience is imparted by this glass transition phenomenon.
On the other hand, “ordinary urethane” is formulated so that glass transition does not occur at the temperature (room temperature) at which the urethane foam is used, and is therefore highly repulsive.
[0020]
The physical property values of both are as follows.
Normal urethane foam is divided into three types according to the hardness. Soft type, medium type and hard type.
1) Soft type urethane foam has a density of 20 ± 2 kg / m3, hardness of 6 ± 1.5, tear strength of 0.2 kg / cm2 or more, tensile strength of 0.6 kg / cm2 or more, elongation of 150% or more, and resilience of 35 % Or more and residual strain of 6% or less.
2) Medium type urethane foam has a density of 20 ± 2kg / m3, hardness of 11 ± 1.5, tear strength of 0.2kg / cm2 or more, tensile strength of 0.7kg / cm2 or more, elongation of 120% or more, and resilience of 35 % Or more and residual strain of 6% or less.
3) Hard type urethane foam has a density of 21 ± 2 kg / m3, a hardness of 15 ± 2.0, a tear strength of 0.2 kg / cm2 or more, a tensile strength of 0.7 kg / cm2 or more, an elongation of 120% or more, and a resilience of 35 % Or more and residual strain of 6% or less.
[0021]
The low resilience urethane foam has a density of 65 ± 10 kg / m 3, a hardness of 5.5 ± 2.0, a tear strength of 0.2 kg / cm 2 or more, a tensile strength of 0.5 kg / cm 2 or more, an elongation of 150% or more, The impact resilience is 5% or less and the residual strain is 3% or less.
The above density and hardness were measured according to JIS-K6401, tear strength, tensile strength and elongation were measured according to JIS-K6301, and rebound resilience and residual strain were measured according to JIS-K6401.
[0022]
In addition, the bed pad may be configured with only a low resilience urethane layer, but the bed pad 10 having a low resilience urethane layer 11 and a normal urethane layer 12 as shown in FIG. This is because if a predetermined thickness is constituted only by the repulsive urethane layer, it becomes expensive and is too bad to sink.
In this case, a little less than half of the predetermined thickness is composed of a low-resilience urethane layer, and a urethane layer that is a normal cushion material is attached to the remaining thickness under the low-resilience urethane layer. It turned out to be good to use.
[0023]
3A and 3B are conceptual perspective views in which (a) is a concavo-convex plate and (b) is a flat plate and a cord-like piezoelectric sensor laying sheet 20 is laid on a flat plate in order to increase the detection sensitivity of the cord-like piezoelectric sensor laying sheet 20. Yes.
In the case where the cord-like piezoelectric sensor 31 is provided on the flat plate 33 as shown in FIG. 4B, when the hatched portion H of the cord-like piezoelectric sensor 31 is pressed from above, the enlarged view is shown in a balloon diagram. Thus, since the pressed cord-shaped piezoelectric sensor portion is pressed downward from the state before being pressed (dotted line), only the change appears as a signal.
[0024]
On the other hand, when the cord-like piezoelectric sensor 31 is provided on the concavo-convex plate 32 provided with the depression 321 as shown in FIG. When pressed, as shown in an enlarged view in the balloon diagram, the vertical change from before the pressed cord-shaped piezoelectric sensor portion appears as a signal, and in addition to being pressed above the depression 321 In the cord-shaped piezoelectric sensor portion, since a large bending deformation occurs at the edge of the recess 321, a signal due to the bending deformation is also generated. Then, a signal that is generated by bending deformation rather than a signal that is generated by the vertical change can be obtained.
Therefore, it is preferable to provide an uneven plate under the cord-shaped piezoelectric sensor.
[0025]
In addition, as a bed pad, it is good also as a structure which lays a piezoelectric sensor on the lower surface of the sandwich-type bed pad by which the normal urethane cushion layer was laid on the upper and lower sides of the low-resilience urethane layer.
[0026]
Based on the output signal of the cord-like pressure sensor of this embodiment, known signal processing can be performed to detect the heartbeat and breathing of a person on the bed pad. FIG. 6 illustrates the principle of pulsing from the block diagram (a) of the detection unit 100 for detecting heartbeats and respiration, and the detection signals of the cord-like pressure sensor due to body movements such as heartbeat, respiration, and rollover. FIG.
In FIG. 6A, reference numeral 100 denotes a detection unit for heartbeat, respiration, rollover, etc. 101 denotes a code-like pressure sensor (code-like piezoelectric sensor), 102 denotes a filter circuit, 103 denotes an amplification circuit, 104 denotes a counting circuit, and 105 denotes It is a display unit.
As shown in FIG. 6A, when the cord-like pressure sensor (cord-like piezoelectric sensor) 101 is deformed by body movements such as heartbeat, breathing, and turning over the human body on the bedding, the cord-like pressure sensor 101. Thus, a voltage due to the piezoelectric effect is generated in a waveform as shown in FIG. That is, the amplitude of the detection voltage is large in the case of entering the bed, turning over, and getting out of bed, and the respiration and the heartbeat are much smaller than that, but they are periodic and the frequencies of the two are different. Focusing on this, the filter circuit 102 passes only a predetermined frequency component corresponding to at least one of body movements such as heartbeat activity, respiratory activity, and roll-over among the generated voltage output, and the amplification circuit 103 amplifies it. . Further, the counting circuit 104 counts the number of times that the output signal of the amplifier circuit is equal to or greater than a predetermined threshold value, so that the heart rate is as shown in (1) of the figure and the respiration rate is as shown in (2) of the figure. Then, body movements such as turning over are pulsed as shown in (3) of the figure, the number of times is calculated, and the count value is displayed on the display unit 105.
[0027]
Here, when counting the heart rate, the band setting of the filter circuit 102 is set to about 0.7 to about 2 Hz, and when counting the respiratory rate, about 0.1 to about 0.5 Hz, and body movement such as turning over is counted. In this case, the frequency is about 1 to about 10 Hz. If body motion occurs when counting heart rate, the output signal level is higher than body beat, so the output signal may be disturbed and lead to malfunction, but when counting heart rate, A lower limit value is provided, and the number of times that a predetermined threshold value corresponding to the heart rate is exceeded may be counted when the output signal is within the range. The same procedure is used when counting the respiratory rate and the number of body movements.
[0028]
In the above description, the heart rate and the respiration rate are counted by counting the number of times exceeding a predetermined threshold. However, other known methods, for example, the output signal of the code-like pressure sensor 101 is AD converted by a microcomputer. Then, digital data may be used, and a method of calculating a heart rate and a respiration rate by calculating an autocorrelation coefficient from time series data of the digital data may be used.
Moreover, although the cord-like piezoelectric sensor is used as the cord-like pressure sensor, other sensors capable of detecting vibration such as a coaxial capacitance sensor or a cable-like pressure-sensitive resistance sensor may be used. Further, as long as it is laid on the lower surface of the bed pad and can detect vibration due to heartbeat or respiration of a human body, not only a cable shape but also a belt-like or sheet-like pressure sensor may be used.
[0029]
【The invention's effect】
As described above, the bed pad is composed of a low resilience urethane layer and a piezoelectric sensor laid on the bottom surface of the low resilience urethane layer, or a low resilience urethane layer and a bottom surface thereof. Since it is composed of a normal urethane cushion layer and a piezoelectric sensor laid on the lower surface of the cushion layer, a bed bud that can reliably detect heartbeat vibration and is comfortable to sleep is obtained.
Furthermore, the addition of a rigid plate with irregularities on the surface makes it possible to more reliably detect heartbeat vibration.
When a bed was made using such a bed pad, a nursing bed with good sleeping comfort was obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a bed according to the present invention.
FIG. 2 shows various experimental examples in which a piezoelectric sensor is used for a bed.
FIG. 3 is a conceptual perspective view of a cord-shaped piezoelectric sensor, in which (a) is laid on an uneven plate and (b) is laid on a flat plate.
FIG. 4 is a configuration diagram of a cord-shaped piezoelectric sensor.
FIG. 5 is a diagram showing a load applied to a cord-shaped piezoelectric sensor and sensor output characteristics.
FIG. 6 is a block diagram (a) of a detection unit 100 for detecting heartbeats and respirations, and explains the respective pulsing principles from detection signals of a cord-like pressure sensor due to body movements such as heartbeats, respirations and rollovers. FIG.
7 is a configuration diagram of a seat described in Patent Document 1. FIG.
[Explanation of symbols]
10 Bed pad according to the present invention 11 Low resilience urethane layer 12 Normal urethane layer 20 Cord-like piezoelectric sensor laying sheet 21 Fabric sheet 22 Cord-like piezoelectric sensor 30 Uneven plastic plate 31 Cord-like piezoelectric sensor 32 Plastic plate 321 Recess 40 Cover bag 41 Sheet 42 Fastener 50 Bed frame 51 Frame-shaped frame 52 Support plate 53 Movable plate 54 Motor 100 Detection unit 101 for heartbeat and respiration Code pressure sensor (code piezoelectric sensor)
102 Filter circuit 103 Amplifying circuit 104 Counting circuit 105 Display unit

Claims (5)

A bed pad comprising a low resilience urethane layer and a pressure-sensitive sensor laid on the lower surface of the low resilience urethane layer. A bed pad comprising: a low resilience urethane layer; a normal urethane cushion layer laid on the lower surface of the low resilience urethane layer; and a pressure-sensitive sensor laid on the lower surface of the cushion layer. The bed pad according to claim 1 or 2, wherein the pressure-sensitive sensor comprises a flexible cord-shaped piezoelectric sensor. A bed element comprising: a rigid plate having irregularities formed on a surface thereof; and the bed pad according to any one of claims 1 to 3 placed on the rigid plate. A bed comprising: a bed frame; a movable plate mounted on the bed frame so as to be tiltable; and a bed element mounted on the movable plate.

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