Human body detection device, bed device and human body detection system

Abstract

To provide a human body detection device, a bed device, and a human body detection system which detect a human body with high sensitivity when detecting it by using a piezoelectric material.SOLUTION: A human body detection device 30 includes: a linear piezoelectric base material 100 whose axial direction is provided along a reference plane 33 intersecting with a direction of a pressure received from a human body and which detects a pressure applied in a radial direction; and a buffer 37 which is provide relative to the reference plane 33 in a manner to support the piezoelectric base material 100 and whose section viewed from the axial direction is formed in such a manner that its width on the side of the piezoelectric base material 100 is smaller than that on the side of the reference plane 33.SELECTED DRAWING: Figure 3B

Description

[Technical field]

[0001] The present disclosure relates to a human body detection device, a bed device, and a human body detection system. [Background technology]

[0002] In recent years, it has been considered to provide beds installed in hospitals and various nursing facilities with pressure sensors that detect the presence or absence of a care recipient and changes in physical condition of the person in bed. For example, Patent Document 1 discloses a bed device in which a piezoelectric cable is arranged in a wave shape and incorporated into a mattress, making it possible to detect the body of a person in bed using the piezoelectric cable. In addition, Patent Document 2 discloses a biological monitoring device in which a long tape-shaped piezoelectric sensor is arranged across the width of the top surface of the bed, and the piezoelectric sensor detects the body of the person in bed and determines the blood pressure value and degree of arteriosclerosis of the person in bed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-351781 A [Patent Document 2] Japanese Patent Application Publication No. 10-229973 Summary of the Invention [Problem to be solved by the invention]

[0004] When a piezoelectric cable as in Patent Document 1 or a piezoelectric line as in Patent Document 2 is used as a sensor, the sensor sensitivity is insufficient when a very light person lies on the bed, and the presence or absence may be falsely detected. Therefore, there is a demand for a highly sensitive device that can detect even a very light person.

[0005] The present invention has been made in consideration of the above-mentioned facts, and aims to provide a human body detection device, a bed device, and a human body detection system that are capable of detecting a human body with high sensitivity when detecting a human body using a piezoelectric material. [Means for solving the problem]

[0006] Specific means for achieving the above object are as follows.

[0007] <1> The present invention comprises: a linear piezoelectric substrate having an axial direction along a reference plane intersecting the direction of pressure received from a human body and adapted to detect pressure applied in a radial direction; and a buffer body provided with respect to the reference plane so as to support the piezoelectric substrate, and formed such that a cross section viewed from the axial direction is narrower on the piezoelectric substrate side than on the reference plane side, the buffer body comprising: an inclined surface that is inclined toward the reference surface as it moves toward the outside in the axial direction at an end portion on the axial side, and the piezoelectric substrate is attached along the inclined surface, A human body detection device in which the wide buffer portion on the reference surface side and the narrow buffer portion on the piezoelectric substrate side are both formed from the same material, and as the pressure received by the piezoelectric substrate increases, the range over which the material is distorted expands from the narrow buffer portion to the wide buffer portion. <2> a linear piezoelectric substrate having an axial direction aligned along a reference plane that intersects with the direction of pressure received from a human body and that detects pressure applied in a radial direction; a buffer provided with respect to the reference plane to support the piezoelectric substrate and formed so that a cross section viewed from the axial direction is narrower on the piezoelectric substrate side than on the reference plane side; a retaining plate that constitutes the reference plane and receives the pressure; a connection portion that connects the piezoelectric substrate and wiring that transmits an output signal generated by the piezoelectric substrate; and a metal tube fixed to the retaining plate and accommodating the connection portion, the metal tube having a fixing portion at one end that fixes the wiring and an insertion portion at the other end that allows the piezoelectric substrate to be inserted, the buffer having a wide buffer portion on the reference plane side and a narrow buffer portion on the piezoelectric substrate side that are both formed from the same material, and as the pressure received by the piezoelectric substrate increases, the range of distortion of the material expands from the narrow buffer portion to the wide buffer portion. <3> The piezoelectric substrate includes a long conductor and a long piezoelectric body wound in a spiral shape in one direction around the conductor, and detects pressure input to the piezoelectric body from a potential difference between the conductor and the piezoelectric body. <1> or <2> The human body detection device described in

[0008] <4> The piezoelectric body is made of an organic piezoelectric material. <3> The human body detection device described in <5> The piezoelectric material is a helical chiral polymer (A) having optical activity. <4> The human body detection device described in <6> The helical chiral polymer (A) is polylactic acid. <5> The human body detection device described in <7> The piezoelectric substrate is sandwiched between the buffer body and the piezoelectric substrate, and a covering member is attached to the surface of the buffer body. <1> ~ <6> 13. A human body detection device according to any one of the above.

[0009] <8> The buffer has a density of 0.05 to 0.5 kg / m 3 And the rubber hardness based on JIS K7312 (Asker C type method) is in the range of 5 to 60. <1> ~ <7> The human body detection device according to any one of the above. Place.

[0010] <9> <1>~<8> A bed apparatus comprising the human body detection device according to any one of the above. <10> <1> ~ <8> A human body detection system comprising a plurality of human body detection devices according to any one of the above, wherein the plurality of human body detection devices are respectively installed in a plurality of regions on the reference plane, and further comprising a detection unit capable of detecting an output signal of each of the piezoelectric substrates installed in each of the regions. Effect of the Invention

[0011] According to the present invention, when a human body is detected using a material having piezoelectricity, the human body can be detected with high sensitivity. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an exploded perspective view of a bed apparatus according to a first embodiment. [Diagram 2] 1 is a plan view of a human body detection device provided in a bed apparatus according to a first embodiment. [Figure 3A] 2 is a cross-sectional view taken along a piezoelectric substrate of the sensor unit of the human body detection device of the first embodiment. FIG. [Figure 3B] 3B is a cross-sectional view (cross-sectional view taken along line 3B-3B in FIG. 3A) of the sensor unit of the human body detection device according to the first embodiment. [Figure 4] 3 is a cross-sectional view of a connection portion between a piezoelectric substrate and a coaxial cable in the first embodiment. [Diagram 5] 1 is a block diagram showing a hardware configuration of a bed apparatus according to a first embodiment. [Figure 6] FIG. 2 is a block diagram showing an example of a functional configuration of a CPU in an analysis PC. [Figure 7]FIG. 2 is a side view showing one embodiment of a piezoelectric substrate. [Figure 8] 8 is a cross-sectional view (cross-sectional view taken along line XX' in FIG. 7) illustrating one embodiment of a piezoelectric substrate. [Figure 9] FIG. 4 is a side view showing another embodiment of the piezoelectric substrate. [Figure 10A] 10 is a cross-sectional view of a sensor unit of a human body detection device according to a first modified example of the first embodiment. FIG. [Figure 10B] 11 is a cross-sectional view of a sensor unit of a human body detection device according to a second modified example of the first embodiment. FIG. [Figure 11A] 11 is a cross-sectional view of a sensor unit of a human body detection device according to a second embodiment. FIG. [Figure 11B] 13 is a cross-sectional view of a sensor unit of a human body detection device according to a first modified example of the second embodiment. FIG. [Figure 11C] 13 is a cross-sectional view of a sensor unit of a human body detection device according to a second modification of the second embodiment. FIG. [Figure 12A] 13 is a cross-sectional view of a sensor unit of a human body detection device according to a third embodiment. FIG. [Figure 12B] FIG. 13 is a cross-sectional view of a sensor unit of a human body detection device according to a modified example of the third embodiment. [Figure 13A] FIG. 13 is a cross-sectional view of a sensor unit of a human body detection device according to a fourth embodiment. [Figure 13B] FIG. 13 is a cross-sectional view of a sensor unit of a human body detection device according to a modified example of the fourth embodiment. [Figure 14A] FIG. 13 is a cross-sectional view of a sensor unit of a human body detection device according to a fifth embodiment. [Figure 14B] FIG. 13 is a cross-sectional view of a sensor unit of a human body detection device according to a modified example of the fifth embodiment. [Figure 15] FIG. 13 is a cross-sectional view of a sensor unit of a human body detection device according to a sixth embodiment. [Figure 16] FIG. 13 is a cross-sectional view of a connection portion between a piezoelectric substrate and a coaxial cable in the seventh embodiment. [Figure 17] FIG. 13 is an exploded perspective view of a bed apparatus according to an eighth embodiment. [Figure 18A]FIG. 23 is a plan view of a case used in a bed apparatus according to an eighth embodiment. [Figure 18B] FIG. 23 is a rear view of a case used in the bed apparatus according to the eighth embodiment. [Figure 19] FIG. 11 is a cross-sectional view of a sensor unit of a human body detection device according to a second embodiment. [Figure 20] 11 is a cross-sectional view of a sensor unit of a human body detection device according to a comparative example. [Figure 21] FIG. 1 is a configuration diagram of a group of devices for measuring sensitivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present invention will be described. However, the present disclosure is not limited to the following embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In this specification, unless otherwise specified, the "surface" of a member means the "main surface" of the member. In this specification, the thickness, width, and length satisfy the relationship thickness<width<length as usually defined. In this specification, the angle between two line segments is expressed in the range of 0° to 90°. In this specification, the term "film" is a concept that encompasses not only what is generally called a "film" but also what is generally called a "sheet." In this specification, the term "MD direction" refers to the machine direction in which the film flows, that is, the stretching direction. When an embodiment is described with reference to the drawings in this specification, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0014] [First embodiment] As a first embodiment, a bed apparatus 10, which is a human body detection system, and a human body detection device 30 included in the bed apparatus 10 will be described with reference to Figs. 1 to 9.

[0015] (Configuration of bed device) 1, the bed apparatus 10 of this embodiment includes a bed 20 with legs and a human body detection device 30. The bed 20 includes a frame 22 that is placed on the floor, a floor plate 24 that covers the center of the frame 22, and a mattress 26 that is placed on the upper surface of the floor plate 24. The mattress 26 as the pressure applying section is a plate-shaped urethane foam covered with polyester fabric. The mattress 26 is placed on the floor board 24 and the sensor unit 32 described later, and a person in a supine position lies on the upper surface of the mattress 26. The mattress 26 of this embodiment is in contact with the piezoelectric substrate 100 covered with an insulating member 38 (see FIG. 3A) which is a covering member, and is pressurized by contact with the body of the person in bed.

[0016] In the present embodiment, the portion of mattress 26 that receives pressure is made of polyurethane (urethane foam), but it may be made of fiber or latex. The pressure part does not necessarily have to be mattress 26 provided in bed 20, but may be a sheet or a mat. Here, the thickness of mattress 26 is in the range of 0.005 to 50 mm, and the hardness of mattress 26 is in the range of 50 to 200 N, preferably 100 to 200 N, and more preferably 110 to 170 N, when measured in accordance with Method A specified in JIS K6400-2.

[0017] In accordance with Method A of JIS K6400-2, the hardness of mattress 26 of this embodiment is determined as follows: That is, the hardness of mattress 26 is determined as the load value in N (Newtons) when the foam inside mattress 26 is placed flat, a circular pressure plate with a diameter of 200 mm is placed on top, the pressure plate is pressed down to a distance of 75% of the original thickness of the foam, then returned to its original state, and pressed down again to a distance of 40% of the original thickness, and the plate is left to stand for 30 seconds. As described above, the bed device 10 of this embodiment functions as a bed 20 by means of the frame 22, floor board 24 and mattress 26, but by installing a sensor unit 32 between the floor board 24 and the mattress 26, it becomes possible to detect the position of the human body on the floor surface.

[0018] (Configuration of the human body detection device) The human body detection device 30 of this embodiment includes a mattress 26 as a pressure applying unit, seven sensor units 32, and an information processing unit 40. The sensor units 32 are installed between the floor board 24 and the mattress 26, and are capable of detecting pressure from the human body. As shown in FIG. 2, five sensor units 32 are installed on the floor board 24 on one side in the bed depth direction so that the bed depth direction is the longitudinal direction. That is, the five sensor units 32 are installed along the human body in a lying position. In addition, two sensor units 32 are installed on the floor board 24 on the other side in the bed depth direction so that the bed width direction is the longitudinal direction. That is, the two sensor units 32 are installed in a cross direction with respect to the human body in a lying position.

[0019] The sensor unit 32 is formed so as to be able to detect pressure (see arrow P) applied from a direction intersecting the reference surface 33, with the surface on which the sensor unit 32 is mounted on a support plate 36 described below being used as the reference surface 33 (see FIG. 3B). 3A and 3B, the sensor unit 32 includes a support plate 36 placed on the floor board 24, a buffer material 37 bonded to the support plate 36, a cable-shaped piezoelectric substrate 100 placed on the upper surface of the buffer material 37, and an insulating member 38 covering the piezoelectric substrate 100. The support plate 36 serving as a retaining plate is a plate-shaped member that supports the buffer material 37, and is made of, for example, hard polyvinyl chloride. As an example, the dimensions of the support plate 36 can be set to a length of 850 mm, a width of 20 mm, and a thickness of 3 mm.

[0020] The cushioning material 37 serving as a buffer is a sponge sheet provided to relieve tension applied to the piezoelectric substrate 100. The cushioning material 37 also has a lower cushioning section 37A provided on the upper part of the support plate 36, and an upper cushioning section 37B provided on the upper part of the lower cushioning section 37A. In the cushioning material 37 of this embodiment, the lower cushioning section 37A and the upper cushioning section 37B are made of the same material, and have a density of 0.05 to 0.5 kg / m 3 and has an Asker C type hardness in the range of 5 to 60 as specified in JIS K7312. Specific materials for the cushioning material 37 are preferably foamed rubber and foamed resin materials. Examples of foamed resin materials that can be used include soft polyurethane foam, hard polyurethane foam, polystyrene foam, polyethylene foam, polypropylene foam, EVA crosslinked foam, PET resin foam, phenol foam, silicone foam, polyvinyl chloride foam, urea foam, acrylic foam, polyimide foam, and EPDM foam.

[0021] The dimensions of the lower buffer section 37A are length 800 mm, width 20 mm, and thickness 5 mm, and the dimensions of the upper buffer section 37B are length 800 mm, width 5 mm, and thickness 5 mm. That is, the width of the upper buffer section 37B is set narrower than the width of the lower buffer section 37A, in other words, the buffer material 37 is formed so that the width on the piezoelectric substrate 100 side is narrower than the width on the support plate 36 (reference surface 33) side. The thicknesses of the lower buffer section 37A and the upper buffer section 37B do not necessarily have to be the same.

[0022] 3A, the buffer material 37 has an inclined surface SL formed such that the height of the end portion on the coaxial cable 110 side decreases toward the coaxial cable 110. In the lower buffer part 37A, the inclined surface SL is formed at the bottom of a groove GR formed in the widthwise center portion of the end portion on the coaxial cable 110 side. That is, the piezoelectric substrate 100 extending toward the coaxial cable 110 on the upper surface of the buffer material 37 descends along the inclined surface SL at the end portion of the buffer material 37 and reaches the upper portion of the support plate 36. The lower cushioning portion 37A is adhered to the support plate 36 with double-sided tape 34, and the upper cushioning portion 37B is adhered to the lower cushioning portion 37A with double-sided tape 34. The support plate 36 and the lower cushioning portion 37A may be adhered to each other with an adhesive instead of the double-sided tape 34. Similarly, the lower cushioning portion 37A and the upper cushioning portion 37B may be adhered to each other with an adhesive instead of the double-sided tape 34.

[0023] The piezoelectric substrate 100 is placed on the upper surface of the double-sided tape 34 attached to the upper surface of the cushioning material 37. The piezoelectric substrate 100 generates a voltage when subjected to pressure. The piezoelectric substrate 100 is electrically connected to the information processing unit 40 via a coaxial cable 110 serving as wiring. The detailed structure of the piezoelectric substrate 100 will be described later. The insulating member 38 covers the piezoelectric substrate 100 and is adhered to the cushioning material 37 via double-sided tape 34 .

[0024] Examples of the insulating member 38 include a commercially available adhesive tape, a flexible insulating film, an adhesive film, etc. As the insulating member 38 in this embodiment, for example, a biaxially oriented nylon film, a polyimide film, a polyethylene terephthalate film, a polyphenylene sulfide film, a polysulfene sulfide film, a polyester film, a polystyrene film, etc., each having a Young's modulus of 2.0 to 10 GPa and a thickness of 4 to 50 μm, can be used. As described above, in the sensor unit 32 of this embodiment, the mattress 26, the insulating member 38, the piezoelectric substrate 100, the cushioning material 37 and the support plate 36 are arranged in this order along the direction of pressure applied by the body of the person in bed (that is, the direction of arrow P).

[0025] 4 shows a cross section of the connection portion 105 between the piezoelectric substrate 100 and the coaxial cable 110. The resin R (see FIG. 3A) covering the outer periphery of the connection portion 105 is omitted. As shown in FIG. 4, the piezoelectric substrate 100 includes an internal conductor 12, a piezoelectric body 14, and an external conductor 16. The coaxial cable 110 includes an internal conductor 112, an insulating layer 114, an external conductor 116, and a protective layer 118. The internal conductor 12 of the piezoelectric substrate 100 and the internal conductor 112 of the coaxial cable 110 are connected by solder 125. The exposed portions of the internal conductor 12 and the internal conductor 112, including the solder 125, are covered by an insulating covering layer 120. The insulating coating layer 120 is a heat shrink tube, and after the internal conductor 12 and the internal conductor 112 are soldered, the internal conductor 12 and the internal conductor 112 are covered with the unshrunk heat shrink tube and heated to form the insulating coating layer 120 that adheres closely to the internal conductor 12 and the internal conductor 112. Furthermore, a metal layer 130 is provided on the outer periphery of the insulating coating layer 120. For example, copper foil is used as the metal layer 130. The metal layer 130 is wound around the outer periphery of the insulating coating layer 120 so as to bridge the outer conductor 16 of the piezoelectric substrate 100 and the outer conductor 116 of the coaxial cable 110. The metal layer 130 and the outer conductor 16 are connected by solder 135, and the metal layer 130 and the outer conductor 116 are connected by solder 136. Then, as shown in FIG. 3A, the outer periphery of the metal layer 130 is filled with resin R, thereby insulating the metal layer 130.

[0026] The information processing unit 40 detects an output signal from the sensor unit 32. As shown in Fig. 5, the information processing unit 40 includes an AD converter 42 that converts a voltage output, which is an analog signal output from the piezoelectric substrate 100, into a digital signal, and a processing PC 50 that detects the converted digital signal of each piezoelectric substrate 100. The AD converter 42 is provided with a plurality of input terminals for inputting analog signals, and the piezoelectric substrate 100 is electrically connected to each input terminal. The processing PC 50 includes a CPU (Central Processing Unit) 50A, a ROM (Read Only Memory) 50B, a RAM (Random Access Memory) 50C, a storage 50D, a communication I / F (Interface) 50E, and an input / output I / F 50F. The CPU 50A, the ROM 50B, the RAM 50C, the storage 50D, the communication I / F 50E, and the input / output I / F 50F are connected to each other via a bus 51 so as to be able to communicate with each other.

[0027] The CPU 50A is a central processing unit, and executes various programs and controls each part. That is, the CPU 50A reads out a program from the ROM 50B or the storage 50D, and executes the program using the RAM 50C as a working area. In this embodiment, the storage 50D stores an execution program for executing various processes. The CPU 50A executes the execution program to function as a detection unit 55, a determination unit 56, and a notification unit 57 shown in FIG. 6. The ROM 50B stores various programs and various data. The RAM 50C temporarily stores programs or data as a working area. The storage 50D as a memory unit is composed of an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs including an operating system and various data.

[0028] The communication I / F 50E is an interface for communicating with a mobile terminal such as a smartphone, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark). The input / output I / F 50F is an interface for communicating with each device constituting the information processing unit 40. To the processing PC 50 of this embodiment, an AD converter 42, a monitor 44, and a speaker 46 are connected via the input / output I / F 50F.

[0029] Fig. 6 is a block diagram showing an example of a functional configuration of the CPU 50A. As shown in Fig. 6, the CPU 50A has a detection unit 55, a determination unit 56, and a notification unit 57. Each functional configuration is realized by the CPU 50A reading and executing an execution program stored in the storage 50D. The detection unit 55 has a function of detecting digital signals related to each piezoelectric substrate 100 output from the AD converter 42 via the communication I / F 50E. This makes it possible to detect where the body of the person in bed is located on the bed 20. The detection unit 55 also digitizes the detected data. This makes it possible to know how much pressure is being applied to each part of the bed 20.

[0030] The determination unit 56 has a function of identifying the dynamic position of the body of the person in bed by comparing the output signals of adjacent piezoelectric substrates 100. For example, the determination unit 56 determines that the person has turned over in bed when the voltage output of one piezoelectric substrate 100 is reduced and the voltage output of the adjacent piezoelectric substrate 100 is increased. The determination unit 56 also determines that the person has gotten up from the bed apparatus 10 when the voltage outputs of all the piezoelectric substrates 100 are reduced. Furthermore, the determination unit 56 determines that the person is sleeping unevenly when the voltage outputs of the piezoelectric substrates 100 at both ends in the bed width direction are large. The notification unit 57 has a function of notifying the result of the determination made by the determination unit 56 regarding turning over, getting up, and deviation in sleeping position. For example, the notification unit 57 can transmit the determination result to the caregiver's mobile phone via the communication I / F 50E. Also, for example, the notification unit 57 can output text information related to the determination result to the monitor 44 via the communication I / F 50E, or output audio information related to the determination result to the speaker 46.

[0031] (Piezoelectric substrate) An overview of the piezoelectric substrate 100 used for pressure detection in the bed apparatus 10 of this embodiment will be described. For a detailed structure of the piezoelectric substrate 100, refer to publicly known documents such as Japanese Patent No. 6663085 and Japanese Patent Laid-Open No. 2019-067969 as appropriate. As described above, the piezoelectric substrate 100 of this embodiment is configured to include the internal conductor 12, the piezoelectric body 14, and the external conductor 16.

[0032] <Inner conductor> A signal line conductor is applied to the internal conductor 12, which is a conductor in this embodiment. The signal line conductor means a conductor for efficiently detecting an electric signal from the piezoelectric body 14. More specifically, when tension is applied to the piezoelectric substrate 100, the signal line conductor is a conductor for detecting a voltage signal (charge signal) corresponding to the applied tension. The internal conductor 12 may be a cord-like object having a core and a conductor covering the core. Such an internal conductor is also called a tinsel wire. Alternatively, the internal conductor 12 may be made of conductive fiber. There are no particular limitations on the thickness of the core material, and it can be selected according to the desired characteristics of the piezoelectric substrate 100. For example, the wire outer diameter is preferably within a range of 0.1 mm to 10 mm.

[0033] <Piezoelectric body> The piezoelectric body 14 of this embodiment can be made of an organic piezoelectric material, and the organic piezoelectric material can be any of low molecular weight materials and polymeric materials. For example, polyvinylidene fluoride, polyvinylidene fluoride copolymers, polyvinylidene cyanide, vinylidene cyanide copolymers, odd-numbered nylons such as nylon 9 and nylon 11, aromatic nylons, alicyclic nylons, helical chiral polymers such as polylactic acid, polyhydroxycarboxylic acids such as polyhydroxybutyrate, cellulose derivatives, polyurea, etc. can be mentioned. As the piezoelectric body 14, from the viewpoints of good piezoelectric characteristics, processability, availability, etc., it is preferable to use a polymeric organic piezoelectric material, in particular one containing a helical chiral polymer (A) having optical activity.

[0034] In the piezoelectric substrate 100 of this embodiment, it is preferable that the piezoelectric body 14 contains an optically active helical chiral polymer (A), the length direction of the piezoelectric body 14 and the main orientation direction of the helical chiral polymer (A) contained in the piezoelectric body 14 are approximately parallel to each other, and the orientation degree F of the piezoelectric body calculated by the following formula (a) is in the range of 0.5 or more and less than 1.0. Orientation degree F=(180°-α) / 180°··(a) (In formula (a), α represents the half-width of the peak derived from the orientation measured by X-ray diffraction.)

[0035] Here, the degree of orientation F of the piezoelectric body 14 is an index showing the degree of orientation of the helical chiral polymer (A) contained in the piezoelectric body 14, and is, for example, the degree of c-axis orientation measured by a wide-angle X-ray diffraction device (Rigaku Corporation, RINT2550, accessories: rotating sample stage, X-ray source: CuKα, output: 40 kV, 370 mA, detector: scintillation counter). More specifically, in the piezoelectric substrate 100 of this embodiment, the piezoelectric body 14 contains a helical chiral polymer (A), the main orientation direction of the helical chiral polymer (A) is along the longitudinal direction of the piezoelectric body 14, and the degree of orientation F of the piezoelectric body 14 is 0.5 or more and less than 1.0, so that the piezoelectricity is suitably expressed. As a result, when tension is applied to the piezoelectric substrate 100, the amount of generated charge increases.

[0036] In the piezoelectric substrate 100 of this embodiment, the piezoelectric body 14 is preferably long and spirally wound in one direction along the outer circumferential surface of the internal conductor 12 . Here, "one direction" refers to the direction in which the piezoelectric body 14 is wound from the front side to the back side of the internal conductor 12 when the piezoelectric substrate 100 of this embodiment is viewed from one end side in the axial direction of the internal conductor 12. Specifically, it refers to the right direction (right-handed, i.e., clockwise) or the left direction (left-handed, i.e., counterclockwise).

[0037] Furthermore, since the piezoelectric body 14 is long, the piezoelectric body 14 is easily arranged spirally in one direction with respect to the axial direction of the internal conductor 12 while maintaining a spiral angle β. Here, the "helical angle β" refers to the angle formed between the axial direction of the internal conductor 12 and the direction in which the piezoelectric body 14 is arranged relative to the axial direction of the internal conductor 12 (the length direction of the piezoelectric body 14). As a result, for example, when tension is applied in the longitudinal direction of the piezoelectric substrate 100, polarization of the helical chiral polymer (A) is likely to occur in the radial direction of the piezoelectric substrate 100. As a result, a voltage signal (charge signal) proportional to the tension is effectively detected, and piezoelectric sensitivity is likely to be improved.

[0038] In the piezoelectric substrate 100 of this embodiment, in order to improve piezoelectric sensitivity, the piezoelectric body 14 is preferably wound at an angle (i.e., helix angle β) of 15° to 75° (45°±30°) relative to the axial direction of the internal conductor 12, and more preferably at an angle of 35° to 55° (45°±10°). As a result, when tension (stress) is applied in the longitudinal direction of the piezoelectric substrate 100, a shear force is easily applied to the helical chiral polymer (A), and polarization of the helical chiral polymer (A) is easily generated in the radial direction of the piezoelectric substrate 100.

[0039] In addition, in the piezoelectric substrate 100 of this embodiment, the piezoelectric body 14 is arranged helically in one direction, and when tension (stress) is applied in the longitudinal direction of the piezoelectric substrate 100, a shear force is applied to the helical chiral polymer (A), and the helical chiral polymer (A) is polarized in the radial direction of the piezoelectric substrate 100. If the helically wound piezoelectric body 14 is regarded as an assembly of minute domains that can be regarded as a plane in the longitudinal direction, when a shear force caused by tension (stress) is applied to the helical chiral polymer on the plane of the constituent minute domains, the piezoelectric constant d 14 The direction of the electric field generated due to the above phenomenon is approximately the same as that of the electric field generated due to the above phenomenon. Specifically, for example, in the case of a homopolymer of L-lactic acid (PLLA) whose molecular structure is a left-handed helical structure, when tension (stress) is applied to a structure in which a piezoelectric body whose length is aligned with the main orientation direction of PLLA is wound in a left-handed helical shape around an internal conductor, an electric field (polarization) is generated from the center of the circle of the circular cross section perpendicular to the tension in a radial direction to the outside direction. Conversely, when tension (stress) is applied to a structure in which a piezoelectric body whose length is aligned with the main orientation direction of PLLA is wound in a right-handed helical shape around an internal conductor, an electric field (polarization) is generated from the outside of the circle of the circular cross section perpendicular to the tension in a radial direction to the center direction.

[0040] For example, in the case of homopolymer of D-lactic acid (PDLA) whose molecular structure is a right-handed helical structure, when tension (stress) is applied to a structure in which a piezoelectric body whose length is aligned with the main orientation direction of PDLA is wound in a left-handed helical shape around an internal conductor, an electric field (polarization) is generated along the radial direction from the outside to the center of the circle of the circular cross section perpendicular to the tension. Conversely, when tension (stress) is applied to a structure in which a piezoelectric body whose length is aligned with the main orientation direction of PDLA is wound in a right-handed helical shape around an internal conductor, an electric field (polarization) is generated parallel to the radial direction from the center of the circle of the circular cross section perpendicular to the tension to the outside. As a result, when tension is applied in the longitudinal direction of the piezoelectric substrate 100, a potential difference proportional to the tension is generated in phase at each part of the spirally arranged piezoelectric body 14, and it is believed that a voltage signal proportional to the tension can be effectively detected.

[0041] The piezoelectric substrate 100 of this embodiment has excellent piezoelectric sensitivity and excellent stability of piezoelectric output. In particular, by using a non-pyroelectric polylactic acid-based polymer as the helical chiral polymer (A), the stability of the piezoelectric sensitivity and the stability of the piezoelectric output (stability over time or against temperature changes) are further improved compared to a piezoelectric substrate 100 using pyroelectric PVDF.

[0042] The piezoelectric substrate 100 of this embodiment may include a structure in which the piezoelectric bodies 14 are wound in a right-handed spiral shape and some of the piezoelectric bodies 14 are wound in a left-handed spiral shape around the internal conductor 12. When some of the piezoelectric bodies 14 are wound in a left-handed spiral shape, the proportion of left-handed windings is preferably less than 50% of the total (the sum of right-handed and left-handed windings) in order to suppress a decrease in piezoelectric sensitivity. Furthermore, the piezoelectric substrate 100 of this embodiment may include a structure in which the piezoelectric bodies 14 are wound in a left-handed spiral shape and a portion of the piezoelectric bodies 14 are wound in a right-handed spiral shape around the internal conductor 12. When a portion of the piezoelectric bodies 14 is wound in a right-handed spiral shape, the proportion of right-handed windings is preferably less than 50% of the total (the sum of right-handed and left-handed windings) in order to suppress a decrease in piezoelectric sensitivity.

[0043] In order to improve the piezoelectric sensitivity, it is preferable that the piezoelectric body 14 has a long flat plate shape or a fiber shape. In particular, by using a long flat plate-like piezoelectric body as the piezoelectric body 14, the contact surface with the internal conductor 12 can be increased, and the charge generated by the piezoelectric effect can be efficiently detected as a voltage signal. There is no particular limitation on the method for producing the long, flat piezoelectric body, and it can be produced by a known method.

[0044] <Helical chiral polymer (A)> The piezoelectric body 14 in this embodiment preferably contains a helical chiral polymer (A) having optical activity. Here, the term "helical chiral polymer having optical activity" refers to a polymer having a helical molecular structure and having molecular optical activity.

[0045] Examples of the helical chiral polymer (A) include polypeptides, cellulose derivatives, polylactic acid polymers, polypropylene oxide, and poly(β-hydroxybutyric acid). Examples of the polypeptide include poly(γ-benzyl glutarate) and poly(γ-methyl glutarate). Examples of the cellulose derivatives include cellulose acetate and cyanoethyl cellulose.

[0046] From the viewpoint of improving the piezoelectricity of the piezoelectric body 14, the helical chiral polymer (A) preferably has an optical purity of 95.00% ee or more, more preferably 96.00% ee or more, even more preferably 99.00% ee or more, and even more preferably 99.99% ee or more. Desirably, it is 100.00% ee. By setting the optical purity of the helical chiral polymer (A) within the above range, it is believed that the packing of the polymer crystals that exhibit piezoelectricity is improved, resulting in high piezoelectricity. From the viewpoints of increasing the optical purity and improving the piezoelectricity, the helical chiral polymer (A) is preferably a polymer having a main chain containing a structural unit represented by the following formula (1).

[0047] [ka]

[0048] Examples of polymers having a structural unit represented by the above formula (1) as the main chain include polylactic acid-based polymers. Here, polylactic acid-based polymer refers to "polylactic acid (a polymer consisting only of structural units derived from monomers selected from L-lactic acid and D-lactic acid)", "a copolymer of L-lactic acid or D-lactic acid and a compound copolymerizable with said L-lactic acid or D-lactic acid", or a mixture of both. Among polylactic acid-based polymers, polylactic acid is preferred, and a homopolymer of L-lactic acid (PLLA, also simply referred to as "L-form") or a homopolymer of D-lactic acid (PDLA, also simply referred to as "D-form") is most preferred.

[0049] Polylactic acid is a polymer in which lactic acid is polymerized through ester bonds and linked together in long chains. It is known that polylactic acid can be produced by the lactide method via lactide, or by a direct polymerization method in which lactic acid is heated in a solvent under reduced pressure and polymerized while removing water. Examples of polylactic acid include homopolymers of L-lactic acid, homopolymers of D-lactic acid, block copolymers containing at least one polymer of L-lactic acid and D-lactic acid, and graft copolymers containing at least one polymer of L-lactic acid and D-lactic acid.

[0050] Examples of the above-mentioned "compound copolymerizable with L-lactic acid or D-lactic acid" include hydroxycarboxylic acids such as glycolic acid, dimethylglycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxycaproic acid, 3-hydroxycaproic acid, 4-hydroxycaproic acid, 5-hydroxycaproic acid, 6-hydroxycaproic acid, 6-hydroxymethylcaproic acid, and mandelic acid; cyclic esters such as glycolide, β-methyl-δ-valerolactone, γ-valerolactone, and ε-caprolactone; oxalic acid, malonic acid, succinic acid, and glutaric acid. Examples of suitable polycarboxylic acids include polycarboxylic acids such as adipic acid, pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, and terephthalic acid, and their anhydrides; polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, tetramethylene glycol, and 1,4-hexanedimethanol; polysaccharides such as cellulose; and aminocarboxylic acids such as α-amino acids.

[0051] The above-mentioned "copolymer of L-lactic acid or D-lactic acid and a compound copolymerizable with said L-lactic acid or D-lactic acid" includes a block copolymer or a graft copolymer having a polylactic acid sequence capable of forming a helical crystal. In addition, the concentration of the structure derived from the copolymer component in the helical chiral polymer (A) is preferably 20 mol % or less. For example, when the helical chiral polymer (A) is a polylactic acid-based polymer, it is preferable that the concentration of the structure derived from the copolymer component is 20 mol % or less relative to the total number of moles of the structure derived from lactic acid and the structure derived from a compound copolymerizable with lactic acid (copolymer component) in the polylactic acid-based polymer.

[0052] Furthermore, in order to make the polylactic acid-based polymer have an optical purity of 95.00% ee or more, for example, when polylactic acid is produced by a lactide method, it is preferable to polymerize lactide whose optical purity has been improved to 95.00% ee or more by a crystallization procedure. The weight average molecular weight (Mw) of the helical chiral polymer (A) is preferably from 50,000 to 1,000,000. When the Mw of the helical chiral polymer (A) is 50,000 or more, the mechanical strength of the piezoelectric body is improved. The Mw is preferably 100,000 or more, and more preferably 200,000 or more.

[0053] On the other hand, by making the Mw of the helical chiral polymer (A) 1,000,000 or less, the moldability is improved when obtaining a piezoelectric body by molding (e.g., extrusion molding, melt spinning). The Mw is preferably 800,000 or less, and more preferably 300,000 or less. From the viewpoint of the strength of the piezoelectric body, the molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) is preferably 1.1 to 5, more preferably 1.2 to 4, and further preferably 1.4 to 3. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) refer to values ​​measured using gel permeation chromatography (GPC), where Mn is the number average molecular weight of the helical chiral polymer (A). As the polylactic acid-based polymer, which is an example of the helical chiral polymer (A), commercially available polylactic acid can be used.

[0054] Commercially available products include, for example, PURASORB (PD, PL) manufactured by PURAC, LACEA (H-100, H-400) manufactured by Mitsui Chemicals, and Ingeo manufactured by NatureWorks LLC. TM biopolymers, etc. When using a polylactic acid-based polymer as the helical chiral polymer (A), in order to make the weight average molecular weight (Mw) of the polylactic acid-based polymer 50,000 or more, it is preferable to produce the polylactic acid-based polymer by the lactide method or the direct polymerization method. The piezoelectric body 14 in this embodiment may contain only one type of the above-mentioned helical chiral polymer (A), or may contain two or more types. The content of the helical chiral polymer (A) in the piezoelectric body in this embodiment (the total content when there are two or more types) is preferably 80 mass % or more with respect to the total amount of the piezoelectric body .

[0055] <Stabilizer> It is preferable that the piezoelectric body 14 further contains a stabilizer (B) having one or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule and a weight average molecular weight of 200 to 60000. This can further improve the moisture and heat resistance. As the stabilizer (B), the "stabilizer (B)" described in paragraphs 0039 to 0055 of WO 2013 / 054918 can be used. Specific examples of the stabilizer (B) (stabilizers B-1 to B-3) are shown below.

[0056] [ka]

[0057] The compound names, commercially available products, etc. of the above stabilizers B-1 to B-3 are shown below. Stabilizer B-1: The compound name is bis-2,6-diisopropylphenylcarbodiimide. The weight average molecular weight (in this example, simply equivalent to "molecular weight") is 363. Commercially available products include "Stabaxol I" manufactured by Rhein Chemie and "B2756" manufactured by Tokyo Chemical Industry Co., Ltd. Stabilizer B-2: The compound is poly(4,4'-dicyclohexylmethanecarbodiimide). Commercially available products with a weight average molecular weight of about 2000 include "Carbodilite LA-1" manufactured by Nisshinbo Chemical Co., Ltd. Stabilizer B-3: The compound is poly(1,3,5-triisopropylphenylene-2,4-carbodiimide). Commercially available products include "Stabaxol P" manufactured by Rhein Chemie, which has a weight-average molecular weight of about 3000. Also, "Stabaxol P400" manufactured by Rhein Chemie, which has a weight-average molecular weight of 20,000, is available.

[0058] When the piezoelectric body contains a stabilizer (B), the piezoelectric body may contain only one type of stabilizer, or may contain two or more types of stabilizers. When the piezoelectric body 14 contains a stabilizer (B), the content of the stabilizer (B) is preferably 0.01 parts by mass to 10 parts by mass, more preferably 0.01 parts by mass to 5 parts by mass, even more preferably 0.1 parts by mass to 3 parts by mass, and particularly preferably 0.5 parts by mass to 2 parts by mass, relative to 100 parts by mass of the helical chiral polymer (A). When the content is 0.01 part by mass or more, the moist heat resistance is further improved. When the content is 10 parts by mass or less, the decrease in transparency is further suppressed.

[0059] <Other ingredients> The piezoelectric body may contain other components as necessary. Examples of other components include known resins such as polyvinylidene fluoride, polyethylene resin, and polystyrene resin; known inorganic fillers such as silica, hydroxyapatite, and montmorillonite; known crystal nucleating agents such as phthalocyanine; and stabilizers other than stabilizer (B).

[0060] <Adhesive layer> The piezoelectric substrate 100 preferably has an adhesive layer between the internal conductor 12 and the piezoelectric body 14. By providing the piezoelectric body 14 with an adhesive layer, the relative positions of the internal conductor 12 and the piezoelectric body 14 are less likely to shift. This makes it easier for tension to be applied to the piezoelectric body 14, and makes it easier for shear stress to be applied to the helical chiral polymer contained in the piezoelectric body 14. This makes it possible to effectively detect a voltage output proportional to tension from the internal conductor 12 (preferably the signal line conductor). Furthermore, by providing an adhesive layer, the absolute value of the amount of generated charge per unit tensile force tends to increase. In the present disclosure, the term "adhesion" includes the concept of "sticking." Furthermore, the term "adhesive layer" includes the concept of "sticking layer."

[0061] <Outer conductor> In this embodiment, a ground conductor is applied to the outer conductor 16. The ground conductor refers to, for example, a conductor that is paired with the inner conductor 12 (preferably a signal line conductor) when detecting a signal. The ground conductor can be made of copper foil ribbon, aluminum foil ribbon, copper wire, aluminum wire, stainless steel wire, metal wire coated with an insulating film, carbon fiber, resin fiber integrated with carbon fiber, or tinsel wire made of fiber with copper foil wound in a spiral. The ground conductor may also be made of an organic conductive material coated with an insulating material, or may be made of conductive fibers.

[0062] The ground conductor is preferably disposed so as to enclose the internal conductor 12 and the piezoelectric body 14 so as not to short-circuit with the internal conductor 12 (preferably the signal line conductor). The cross-sectional shape of the external conductor 16 can be various shapes such as a circle, an ellipse, a rectangle, an irregular shape, etc. In particular, a rectangular cross section allows for a flat surface to come into close contact with the internal conductor (preferably the signal line conductor), the piezoelectric body, and, if necessary, an insulator, etc., making it possible to efficiently detect the charge generated by the piezoelectric effect as a voltage signal.

[0063] Fig. 7 shows a side view of the piezoelectric substrate 100 including the outer conductor 16. Fig. 8 shows a cross-sectional view taken along line XX' in Fig. 7. As shown in FIG. 7, in the piezoelectric substrate 100, the piezoelectric body 14 is spirally wound in one direction with no gaps from one end to the other end along the outer peripheral surface of the internal conductor 12 at a helical angle β1 so that the internal conductor 12 is not visible. "Spiral angle β1" refers to the angle between the axial direction G1 of the internal conductor 12 and the arrangement direction of the piezoelectric body 14 with respect to the axial direction of the internal conductor 12. Moreover, the piezoelectric body 14 in this embodiment is wound counterclockwise around the internal conductor 12. Specifically, when viewed from one end side of the axial direction of the internal conductor 12 (the right end side in the case of FIG. 7), the piezoelectric body 14 is wound counterclockwise from the front side to the back side of the internal conductor 12. 7, the main orientation direction of the helical chiral polymer (A) contained in the piezoelectric body 14 is indicated by a double-headed arrow E1. That is, the arrangement direction of the piezoelectric body 14 (the length direction of the piezoelectric body 14) is aligned with the main orientation direction of the helical chiral polymer (A).

[0064] In the piezoelectric substrate 100 according to this embodiment, the external conductor 16 is wound spirally in one direction around the outer periphery of the piezoelectric body 14. That is, the piezoelectric substrate 100 includes, from the inside, an elongated internal conductor 12, an elongated piezoelectric body 14, and an external conductor 16. The function of the piezoelectric substrate 100 according to this embodiment will be described below. For example, when tension is applied in the longitudinal direction of the piezoelectric substrate 100, a shear force is applied to the helical chiral polymer (A) contained in the piezoelectric body 14, causing the helical chiral polymer (A) to become polarized. The polarization of this helical chiral polymer (A) occurs in the radial direction of the piezoelectric substrate 100 (the radial direction of the piezoelectric body 14) as shown by the arrows in Fig. 8, and it is considered that the polarization directions occur in phase with each other. This allows a voltage signal that is proportional to the tension to be detected effectively.

[0065] The piezoelectric substrate 100 according to the present embodiment is not limited to the above embodiment. For example, in the piezoelectric substrate 100, an adhesive layer may be disposed between the internal conductor 12 and the piezoelectric body 14. This makes it difficult for the relative positions of the piezoelectric body 14 and the internal conductor 12 to shift even when tension is applied in the longitudinal direction of the piezoelectric substrate 100, so that tension can be more easily applied to the piezoelectric body 14. In addition, in the piezoelectric substrate 100, the external conductor 16 is arranged by being wound helically in one direction around the outer circumferential surface of the piezoelectric body 14, but the arrangement of the external conductor 16 is not limited to this. That is, it is sufficient that the external conductor 16 is arranged on at least a part of the outer periphery of the piezoelectric body 14. Furthermore, the winding direction of the external conductor 16 is not particularly limited.

[0066] Although the piezoelectric substrate 100 of the present embodiment includes one piezoelectric body 14, the present invention is not limited thereto and may include a plurality of piezoelectric bodies 14. For example, as shown in Fig. 9, the piezoelectric substrate 100A may include another long piezoelectric body 15 in addition to the long piezoelectric body 14, and the piezoelectric body 14 and the other piezoelectric body 15 may form a braided structure. 9, in the piezoelectric substrate 100A, the piezoelectric body 14 is wound in a counterclockwise spiral shape from one end to the other end at a helical angle β1 with respect to the axial direction G2 of the internal conductor 12. Another piezoelectric body 15 is wound in a clockwise spiral shape from one end to the other end at a helical angle β2, and the piezoelectric body 14 and the other piezoelectric bodies 15 cross each other alternately to form a braided structure.

[0067] By forming a braided structure of the piezoelectric body 14 and the other piezoelectric body 15 along the outer circumferential surface of the internal conductor 12, the piezoelectric substrate can bend and deform more flexibly when a force that would cause bending deformation is applied, compared to a case where the braided structure is not formed. This makes it easier to increase the amount of generated charge when a tensile force is applied to the piezoelectric substrate, for example. Therefore, the piezoelectric substrate 100A has excellent piezoelectric sensitivity. The outer conductor 16 of the piezoelectric substrate 100 of this embodiment may be coated with a resin. As the resin for the coating, a fluorine-based resin such as PTFE (polytetrafluoroethylene) is preferable.

[0068] (action) The bed apparatus 10 of this embodiment functions as follows. The bed apparatus 10 of this embodiment is configured to be capable of detecting a human body in a lying position by means of seven sensor units 32 placed on the floor board 24 of the bed 20. The sensor unit 32 includes a linear piezoelectric substrate 100 that is axially disposed along the reference surface 33 and detects pressure applied in the radial direction, and a buffer material 37 that is disposed relative to the reference surface 33 so as to support the piezoelectric substrate 100. The buffer material 37 of this embodiment is formed so that the cross section of the piezoelectric substrate 100 viewed from the axial direction is narrower on the piezoelectric substrate 100 side than on the reference surface 33 side. In more detail, the buffer material 37 is composed of a lower buffer section 37A and an upper buffer section 37B made of the same material, and is configured so that the width of the upper buffer section 37B is narrower than the width of the lower buffer section 37A.

[0069] As described above, the piezoelectric substrate 100 of this embodiment has excellent piezoelectric sensitivity. However, when the sensor unit 32 having the piezoelectric substrate 100 is arranged on the bed device 10, if a buffer material 37 having a rectangular cross section is simply used, the detection accuracy of the piezoelectric substrate 100 depends on the material of the buffer material 37. Therefore, if the elastic modulus, rubber hardness, and density of the material constituting the buffer material 37 are too low, the voids of the buffer material 37 are crushed by the distortion caused by a large compressive load, making it difficult for the piezoelectric substrate 100 to be distorted, making it difficult to perform high-sensitivity sensing. On the other hand, if the elastic modulus, rubber hardness, and density of the material constituting the buffer material 37 are too high, when a person with an extremely light weight lies on the bed 20, the piezoelectric substrate 100 does not distort, the voltage output is insufficient, and the presence or absence of a person may be erroneously detected.

[0070] In contrast, according to this embodiment, when the load applied to the sensor unit 32 is low, the load is absorbed mainly by the upper buffer section 37B, and when the load is high, the load is absorbed by the lower buffer section 37A in addition to the upper buffer section 37B. Therefore, according to this embodiment, accurate detection can be performed for a wide range of loads. In particular, the density of the cushioning material 37 is 0.05 to 0.5 kg / m 3 Furthermore, by setting the Asker C-type rubber hardness specified in JIS K7312 to the range of 5 to 60, it is possible to handle a wide range of loads.

[0071] Furthermore, in the sensor unit 32 of this embodiment, the buffer material 37 has an inclined surface SL that approaches the reference surface 33 as it moves axially outward at the end portion on the axial side of the piezoelectric substrate 100, and the piezoelectric substrate 100 is attached along the inclined surface SL. According to this embodiment, the piezoelectric substrate 100 can be disposed without floating from the upper surface of the raised buffer material 37 to the reference surface 33. This makes it possible to suppress erroneous detection when a load is applied to the floating portion of the piezoelectric substrate 100, rather than to the upper surface of the buffer material 37.

[0072] As shown in FIG. 2, in the bed apparatus 10 of this embodiment, seven sensor units 32 are installed on the bed plate 24. Therefore, when a person is lying on the mattress 26, pressure is applied from the body of the person to each sensor unit 32 in the radial direction of the piezoelectric substrate 100. As a result, a voltage corresponding to the pressure is output from each piezoelectric substrate 100. The AD converter 42 to which the voltage output from each piezoelectric substrate 100 is input converts the voltage output, which is an analog signal, into a digital signal and outputs it to the processing PC 50. Then, in the processing PC 50, the detection unit 55 detects the digital signal, thereby making it possible to detect whether or not a person is lying on the mattress 26 and in what position the person is lying. For example, when the voltage output V of a certain piezoelectric substrate 100 exceeds the threshold value Vt, it is possible to detect that the person is lying on a certain sensor unit 32 of the piezoelectric substrate 100.

[0073] In addition, the bed apparatus 10 of this embodiment can be a human body detection system capable of detecting the turning over of a person in bed by providing a determination unit 56 in the processing PC 50 of the human body detection device 30. In the bed apparatus 10 as a human body detection system, the sensor units 32 are arranged along the bed width direction of the bed 20. The determination unit 56 can determine the movement of the person in bed on the mattress 26 by comparing the voltage outputs of the piezoelectric substrates 100 adjacent to each other in the bed width direction. In practice, the detection unit 55 of the processing PC 50 records the moment when the voltage output V from each piezoelectric substrate 100 exceeds the threshold value Vt, and the determination unit 56 can determine that the person in bed has turned over and the direction of the turning over from the order of the piezoelectric substrates 100 that exceed the threshold value Vt.

[0074] As described above, according to this embodiment, it is possible to detect not only the presence or absence of a person sleeping, but also the position on the floor surface of the bed 20. Then, by using the processing PC 50 to monitor the deviation of the position of the person sleeping on the floor surface and notifying the person sleeping or a caregiver, it is possible to prevent the person from falling off the bed 20.

[0075] In the sensor unit 32 of this embodiment, the linear piezoelectric substrates 100 are arranged linearly, but this is not limited to the above. For example, by arranging them in a wave shape or a spiral shape along the reference surface 33, the direction and sensitivity of pressure detection can be changed. The piezoelectric substrate 100 is characterized by having a long piezoelectric body 14 wound in a spiral shape in one direction around the internal conductor 12, and detecting the pressure input to the piezoelectric body 14 from the potential difference between the internal conductor 12 and the external conductor 16. According to the bed device 10 of this embodiment, by using the piezoelectric substrate 100 as a sensor for detecting pressure, a power supply to the sensor is not required. As a result, compared to a load cell in which the sensor for detecting pressure is a strain gauge, for example, it does not consume power in a standby state. In other words, it is suitable for miniaturization because it can be driven by a simple circuit. Furthermore, polylactic acid used in the piezoelectric body is cheaper than a load cell, so the manufacturing cost of the sensor part is suppressed.

[0076] (remarks) The human body detection device 30 of this embodiment may be incorporated into an existing bed 20 to form the bed device 10, or may be installed and used on a carpet, flooring, tatami mat, etc. The human body detection device 30 installed on a carpet, flooring, tatami mat, etc. also achieves the same effects as the above-mentioned bed device 10. According to the human body detection device 30 of this embodiment, since it can be combined with existing bedding, it is possible to use existing bedding as it is and to prevent deterioration of sleeping comfort.

[0077] In the bed apparatus 10 of this embodiment, the greater the foaming ratio of the foamed rubber or resin that is the cushioning material 37, the greater the variation in density and rubber hardness, and the greater the variation in sensor sensitivity of the piezoelectric substrate 100. In addition, materials such as natural rubber have a large change in rubber hardness over time, and the variation in sensor sensitivity is large. EPDM foam, which changes little over time, is preferable. Furthermore, when the cushioning material 37 is used in the bed 20, flame retardancy is often required. In this case, the material for the cushioning material 37 is preferably a foamed plastic material mixed with various flame retardant additives to make it flame retardant, or a polyvinyl chloride foam or polyimide foam, etc., whose resin itself has flame retardancy.

[0078] In addition, in the bed apparatus 10 of each embodiment, the support plate 36 is not necessarily required, and a cushioning material 37 may be provided on the bed plate 24 . The insulating member 38, which is a covering member in this embodiment, is, but is not limited to, an adhesive tape, an adhesive film, etc. For example, the insulating member 38 may be in the form of a laminate, a heat shrink tube, or a covering made of an insulating material (for example, wrapping a PET or fluorine tape around the piezoelectric line), etc.

[0079] In the above embodiment, the processes related to the detection unit 55, the determination unit 56, and the notification unit 57, which are executed by the CPU 50A by reading the software (program), may be executed by various processors other than the CPU. In this case, examples of the processor include a PLD (Programmable Logic Device) such as an FPGA (Field-Programmable Gate Array) whose circuit configuration can be changed after manufacture, and a dedicated electric circuit such as an ASIC (Application Specific Integrated Circuit) which is a processor having a circuit configuration designed exclusively for executing a specific process. In addition, the various processes may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same or different types (for example, a plurality of FPGAs, and a combination of a CPU and an FPGA). In addition, the hardware structure of these various processors is, more specifically, an electric circuit that combines circuit elements such as semiconductor elements.

[0080] In the above embodiment, the execution programs are stored (installed) in advance in the storage 50D, but the present invention is not limited to this. Each program may be provided in a form recorded on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. The programs may also be downloaded from an external device via a network.

[0081] (Modification of the first embodiment) In the sensor unit 32 of the first embodiment, the piezoelectric substrate 100 is disposed on the upper surface of the buffer material 37. However, this is not limiting, and the piezoelectric substrate 100 may be embedded in the upper part of the buffer material 37. 10A, for example, in the center of the width direction of the upper buffer section 37B of the first modification, a slit S is formed from the upper surface downward along the longitudinal direction of the sensor unit 32. The depth of this slit S is, for example, about 2 to 3 times the diameter of the piezoelectric substrate 100. Then, after the piezoelectric substrate 100 is placed in the slit S, the upper part of the slit S is adhered, thereby forming the sensor unit 32.

[0082] 10B, for example, upper buffer section 37B of modification 2 has slit S as in modification 1, and sensor unit 32 of modification 2 has covering buffer member 39 made of the same material as buffer material 37 adhered to cover slit S. Supplementally, after piezoelectric substrate 100 is placed in slit S formed in the center of upper buffer section 37B in the width direction, sensor unit 32 can be formed by adhering covering buffer member 39 to the top surface of upper buffer section 37B with double-sided tape 34 without adhering slit S. Even when the piezoelectric substrate 100 is embedded in the buffer material 37 as in the first and second modifications of the first embodiment, the same effects as those of the first embodiment can be achieved.

[0083] Second Embodiment Next, a bed apparatus 10 according to a second embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first embodiment in the shape of the cushioning material 37 in the sensor unit 32. The cushioning material 37 of this embodiment shown in Fig. 11A has a trapezoidal cross section when viewed in the longitudinal direction. A slit S is formed in the center of the width of the cushioning material 37 from the upper surface downward along the longitudinal direction of the sensor unit 32. The slit S has a depth of, for example, about 2 to 3 times the diameter of the piezoelectric substrate 100. After the piezoelectric substrate 100 is placed in the slit S, the upper part of the slit S is adhered to form the sensor unit 32.

[0084] (Modification of the second embodiment) In the second embodiment, the piezoelectric substrate 100 is placed in a slit S formed in the buffer material 37, and then the upper part of the slit S is adhered. In contrast, as shown in Fig. 11B, in the sensor unit 32 of the first modification, insert molding is performed when the buffer material 37 is molded, and the piezoelectric substrate 100 and the buffer material 37 are molded integrally. In this case, the piezoelectric substrate 100 is placed at a depth of about 2 to 3 times the diameter of the piezoelectric substrate 100 from the upper surface of the buffer material 37.

[0085] 11C, for example, sensor unit 32 of Modification 2 is provided with cushioning material 37 having slits S as in the second embodiment. In addition, in sensor unit 32 of Modification 2, covering cushioning member 39 made of the same material as cushioning material 37 is adhered so as to cover slit S. To supplement this, sensor unit 32 can be formed by arranging piezoelectric substrate 100 in slit S formed in the center of cushioning material 37 in the width direction, and then adhering covering cushioning member 39 to the upper surface of cushioning material 37 with double-sided tape 34 without adhering slit S. Even when the piezoelectric substrate 100 is embedded in the buffer material 37 as in the second embodiment and the first and second modifications of the second embodiment, the same effects as those of the first embodiment can be achieved.

[0086] Third embodiment Next, a bed apparatus 10 according to a third embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first and second embodiments in the shape of the cushioning material 37 in the sensor unit 32. The cushioning material 37 of this embodiment shown in Fig. 12A has a triangular cross section as viewed in the longitudinal direction. A slit S is formed in the apex of the widthwise center of the cushioning material 37, extending downward from the apex along the longitudinal direction of the sensor unit 32. The slit S has a depth of, for example, about 2 to 3 times the diameter of the piezoelectric substrate 100. After the piezoelectric substrate 100 is placed in the slit S, the upper part of the slit S is adhered to form the sensor unit 32.

[0087] (Modification of the third embodiment) In the third embodiment, the piezoelectric substrate 100 is placed in a slit S formed in the buffer material 37, and then the upper part of the slit S is adhered. In contrast, as shown in Fig. 12B, in a sensor unit 32 of a modified example, the piezoelectric substrate 100 and the buffer material 37 are integrally formed by insert molding when the buffer material 37 is molded. In this case, the piezoelectric substrate 100 is placed at a depth of about 2 to 3 times the diameter of the piezoelectric substrate 100 from the upper surface of the buffer material 37. Even when the piezoelectric substrate 100 is embedded in the buffer material 37 as in the third embodiment and the modified example of the same embodiment, the same effects as those of the first embodiment can be achieved.

[0088] [Fourth embodiment] Next, a bed apparatus 10 according to a fourth embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first to third embodiments in the shape of the cushioning material 37 in the sensor unit 32. The cushioning material 37 of this embodiment shown in Fig. 13A is formed in a parabolic mountain shape in cross section as viewed in the longitudinal direction. In addition, at the apex of the cushioning material 37 in the center in the width direction, a slit S is formed from the apex downward along the longitudinal direction of the sensor unit 32. The depth of this slit S is, for example, about 2 to 3 times the diameter of the piezoelectric substrate 100. Then, after the piezoelectric substrate 100 is placed in the slit S, the upper part of the slit S is adhered to form the sensor unit 32.

[0089] (Modification of the fourth embodiment) In the fourth embodiment, the piezoelectric substrate 100 is placed in a slit S formed in the buffer material 37, and then the upper part of the slit S is adhered. In contrast, as shown in Fig. 13B, in a sensor unit 32 of a modified example, the piezoelectric substrate 100 and the buffer material 37 are integrally formed by insert molding when the buffer material 37 is molded. In this case, the piezoelectric substrate 100 is placed at a depth of about 2 to 3 times the diameter of the piezoelectric substrate 100 from the upper surface of the buffer material 37. Even when the piezoelectric substrate 100 is embedded in the buffer material 37 as in the fourth embodiment and the modified example of the fourth embodiment, the same effects as those of the first embodiment can be achieved.

[0090] Fifth embodiment Next, a bed apparatus 10 according to a fifth embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first to fourth embodiments in the shape of the cushioning material 37 in the sensor unit 32. The cushioning material 37 of this embodiment shown in Fig. 14A has a cross section in a longitudinal direction formed into a Gaussian curve type. A slit S is formed in the apex of the widthwise center of the cushioning material 37, extending downward from the apex along the longitudinal direction of the sensor unit 32. The slit S has a depth of, for example, about 2 to 3 times the diameter of the piezoelectric substrate 100. After the piezoelectric substrate 100 is placed in the slit S, the upper part of the slit S is adhered to form the sensor unit 32.

[0091] (Modification of the fifth embodiment) In the fifth embodiment, the piezoelectric substrate 100 is placed in a slit S formed in the buffer material 37, and then the upper part of the slit S is adhered. In contrast, as shown in Fig. 14B, in a sensor unit 32 of a modified example, insert molding is performed when the buffer material 37 is molded, and the piezoelectric substrate 100 and the buffer material 37 are molded integrally. In this case, the piezoelectric substrate 100 is placed at a depth of about 2 to 3 times the diameter of the piezoelectric substrate 100 from the upper surface of the buffer material 37. Even when the piezoelectric substrate 100 is embedded in the buffer material 37 as in the fifth embodiment and the modified example of the fifth embodiment, the same effects as those of the first embodiment can be achieved.

[0092] Sixth embodiment Next, a bed apparatus 10 according to a sixth embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first embodiment in the method of installing the piezoelectric substrate 100 in the sensor unit 32. As shown in Fig. 15, in the sensor unit 32 of this embodiment, the piezoelectric substrate 100 sandwiched between a pair of insulating members 38 is attached to the upper surface of the cushioning material 37 via double-sided tape 34. Note that in this embodiment, the insulating members 38 to which the double-sided tape 34 has been attached in advance are attached to each other to cover the piezoelectric substrate 100, but this is not the only possible method. For example, an adhesive may be used to attach the opposing insulating members 38 together so that the piezoelectric substrate 100 is sandwiched between them. Even when the piezoelectric substrate 100 is embedded in the buffer material 37 as in the sixth embodiment, the same effects as those of the first embodiment can be achieved.

[0093] Seventh embodiment Next, a bed apparatus 10 according to a seventh embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first embodiment in the structure of the connection portion 105 between the piezoelectric substrate 100 and the coaxial cable 110. FIG. 16 is a cross-sectional view of the connection portion 105 between the piezoelectric substrate 100 and the coaxial cable 110 corresponding to FIG. 4. The resin R (see FIG. 3A) covering the outer periphery of the connection portion 105 is omitted. In the first embodiment, the outer conductor 16 of the piezoelectric substrate 100 and the outer conductor 116 of the coaxial cable 110 are connected by the metal layer 130 which is copper foil. In contrast, in this embodiment, the outer conductor 16 of the piezoelectric substrate 100 and the outer conductor 116 of the coaxial cable 110 are connected by the metal tube 150 and the short-circuit wire 160. The metal tube 150 is fixed to the support plate 36 by adhesive or the like.

[0094] Specifically, on the coaxial cable 110 side, the outer conductor 116 is fitted into the fitting portion 150A of the metal tube 150, and the surface of the metal tube 150 and the outer conductor 116 are connected by solder 155. The fitting portion 150A is an example of a fixed portion. On the piezoelectric substrate 100 side, the piezoelectric substrate 100 is inserted into the insertion portion 150B of the metal tube 150, and the metal tube 150 and the outer conductor 16 of the piezoelectric substrate are electrically connected via a short-circuit wire 160. The insertion portion 150B is an example of an insertion portion. One end of the short-circuit wire 160 is connected to the metal tube 150 by solder 165, and the other end is connected to the outer conductor 16 by solder 166.

[0095] According to this embodiment, in addition to the effects of the first embodiment, the following effects are obtained at the connection portion 105 between the piezoelectric substrate 100 and the coaxial cable 110. That is, in this embodiment, in the metal tube 150 integrated with the support plate 36 by fixing, the coaxial cable 110 is fixed at the insertion portion 150A, and the piezoelectric substrate 100 is inserted without being fixed at the insertion portion 150B. Therefore, it is possible to prevent the tension applied to the coaxial cable 110 by a person's touch from spreading to the piezoelectric substrate 100, and to prevent the coaxial cable 110 from coming off the piezoelectric substrate 100. In addition, since the piezoelectric substrate 100 is fixed to the metal tube 150 so as to be slidable, even if the piezoelectric substrate 100 is displaced in the axial direction due to the deformation of the buffer material 37 when pressure is received, the tension at the connection portion 105 can be relaxed. By suppressing the tension caused by the displacement of the piezoelectric substrate 100, it is possible to suppress detection errors in the piezoelectric substrate 100. Furthermore, since the connection portion 105 is covered with the metal tube 150, it is possible to shield it from external noise.

[0096] Eighth embodiment Next, a bed apparatus 10 according to an eighth embodiment will be described. In the following description, the same components as those in the first embodiment are given the same reference numerals, and duplicated descriptions will be omitted. The bed apparatus 10 of this embodiment differs from the first embodiment in the arrangement of the sensor unit 32. Specifically, in the bed apparatus 10 of the first embodiment, seven sensor units 32 are installed on the floor board 24, but in the bed apparatus 10 of this embodiment, only one sensor unit 32 is installed as shown in Fig. 17. The sensor unit 32 of this embodiment is installed so that its longitudinal direction is the bed width direction and so as to be located near the chest of the human body in a lying position.

[0097] The sensor unit 32 of this embodiment is stored in a long bag-shaped case 60. As shown in FIG. 18A and FIG. 18B, the case 60 is configured to include an outer material 62, a lining 64, an enclosing portion 63, a strip portion 66, and a hook-and-loop fastener 68. The outer material 62 is a fabric that faces the mattress 26 and covers the surface that receives the load. The outer material 62 is preferably a thin and soft woven or knitted fabric. The lining 64 is a fabric that faces the floorboard 24 and is preferably made of a rubber sheet, a polyurethane sheet, or a woven or knitted fabric containing polyurethane fiber to provide anti-slip properties. The enclosing portion 63 is provided in the case 60 so as to surround the periphery except for one short side, and is sewn to the outer material 62 and the lining 64. The outer material 62, the lining 64, and the enclosing portion 63 form a bag-shaped storage portion 65 having an opening 65A.

[0098] The strip portions 66 are strips of fabric sewn to the lining 64 near the opening 65A. The strip portions 66 are provided in pairs in the width direction of the case 60, and extend outward in the longitudinal direction of the case 60. The hook and loop fastener 68 includes hook portions 68A that are raised in a hook shape, and loop portions 68B that are raised in a dense loop shape. The hook portions 68A are provided in pairs near the tip of the strip portions 66, and the loop portions 68B are provided on the outer fabric 62 near the opening 65A. The hook portions 68A and the loop portions 68B may be arranged in the opposite directions. The sensor unit 32 is inserted into the housing 65 from the opening 65A, and the strip portions 66 are folded back to bring the hook portion 68A and the loop portion 68B into surface contact and engage with each other, thereby closing the opening 65A. At this time, the coaxial cable 110 can be passed between the pair of strip portions 66.

[0099] According to this embodiment, the bed apparatus 10 can be easily configured by simply installing one sensor unit 32 to an existing bed 20. Although this embodiment cannot detect turning over in bed, it can determine the presence or absence of a person in the bed 20 and measure the heart rate and respiratory rate with high accuracy. Moreover, according to the case 60 of this embodiment, it is possible to suppress misalignment with respect to the bed 20, and it is possible to improve the pressure detection accuracy by the piezoelectric substrate 100. In particular, according to this embodiment, the sensor unit 32 does not slide off when the bed 20 is partially reclined. In the eighth embodiment, the case 60 is not an essential component. In other embodiments, the sensor unit 32 may be housed in the case 60. EXAMPLES

[0100] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0101] (1) Checking sensitivity based on the shape of the cushioning material First, the sensor sensitivity when the shape of the cushioning material 37 is changed will be confirmed. (Production of Examples 1, 2 and Comparative Example) <Production of piezoelectric substrate> Polylactic acid (product name: Ingeo) manufactured by NatureWorks LLC was used as the helical chiral polymer (A). TM To 100 parts by mass of 4032D biopolymer, 1.0 part by mass of a stabilizer [a mixture of Stabaxol P400 (10 parts by mass, weight average molecular weight 20,000) manufactured by Rhein Chemie, Stabaxol I (70 parts by mass, weight average molecular weight 363) manufactured by Rhein Chemie, and Carbodilite LA-1 (20 parts by mass, weight average molecular weight 2,000) manufactured by Nisshinbo Chemical Inc.] was added and dry blended to prepare a raw material.

[0102] The prepared raw material was placed in an extrusion molding machine hopper, extruded from a T-die while being heated to 210°C, and contacted with a cast roll at 50°C for 0.3 minutes to produce a pre-crystallized sheet with a thickness of 150 μm (pre-crystallization step). The obtained pre-crystallized sheet was heated to 70°C and stretched roll-to-roll at a stretching speed of 10 m / min, and uniaxially stretched in the MD direction up to 3.5 times (stretching step). Thereafter, the uniaxially stretched film was annealed by contacting it with a roll heated to 145° C. for 15 seconds in a roll-to-roll manner, and then rapidly cooled to produce a piezoelectric film (annealing process). Next, a slitting machine was used to slit the piezoelectric film so that the slitting direction was approximately parallel to the stretching direction of the piezoelectric film, thereby obtaining a piezoelectric body.

[0103] A tinsel wire with a radius of 0.135 mm and a length of 100 mm was prepared as the internal conductor. The slit ribbon (piezoelectric body) with a width of 0.6 mm and an average thickness of 50 μm obtained as described above was wound around the tinsel wire in a left-handed spiral manner at an angle (spiral angle) of 45° to the long axis direction of the tinsel wire, without any gaps so that the tinsel wire was not visible (exposed), and the tinsel wire was enclosed. In this way, a coaxial line structure consisting of the tinsel wire and the slit ribbon was obtained. The number of turns of the slit ribbon around the tinsel wire in this case was 17 times / cm. Next, a copper foil ribbon cut into a slit having a width of 0.6 mm and a thickness of 100 mm was prepared as an outer conductor. This copper foil ribbon was wrapped around the slit ribbon of the coaxial line structure by the same method as the slit ribbon, without any gaps, so that the slit ribbon was not visible. In this manner, the piezoelectric substrates 100 used in Examples 1 and 2 and the comparative example were obtained. When the average radius a of the tinsel wire and the average thickness T of the slit ribbons were measured by the above-mentioned method using the piezoelectric substrate 100, the average radius a was 0.000135 m and the average thickness T was 0.00005 m.

[0104] <Sensor unit manufacturing> Example 1 As shown in FIG. 3B, first, a foamed resin having a length of 800 mm, a width of 20 mm, and a thickness of 5 mm that becomes the lower buffer part 37A, with double-sided tape 34 attached to the upper surface of a support plate 36 made of vinyl chloride and having a length of 850 mm, a width of 20 mm, and a thickness of 3 mm, was attached. In addition, a foamed resin having a length of 800 mm, a width of 5 mm, and a thickness of 5 mm that becomes the upper buffer part 37B, with double-sided tape attached to both the upper and lower surfaces, was attached to the foamed resin as the lower buffer part 37A. In addition, a piezoelectric substrate 100 was attached to the center in the width direction of the upper surface of the foamed resin as the upper buffer part 37B. Furthermore, a polyimide tape having a thickness of 25 μm that becomes the insulating member 38 was attached to the upper part of the upper buffer part 37B including the piezoelectric substrate 100, and the piezoelectric substrate 100 was sandwiched between the buffer material 37 and the insulating member 38.

[0105] On the other hand, the piezoelectric substrate 100 and the 2 m coaxial cable 110 with a jack connector were electrically connected in the following manner. First, the internal conductor 12 of the piezoelectric substrate 100 and the internal conductor 112 of the coaxial cable 110 were placed opposite each other and connected by soldering. Next, the internal conductors 12 and 112 were covered with a heat shrink tube that became the insulating coating layer 120, and heated to make the periphery of the solder 125 tightly adhered. Furthermore, the periphery of the insulating coating layer 120 was covered with a copper foil tape that became the metal layer 130, and the metal layer 130 was connected to the external conductor 116 of the coaxial cable 110, and the metal layer 130 was connected to the external conductor 16 of the piezoelectric substrate 100 by soldering. Furthermore, hot melt resin R was filled so as to cover the entire connection portion 105 of the coaxial cable 110 and the piezoelectric substrate 100, and the sensor unit 32 was completed. As shown in FIGS. 2 and 5, the sensor unit 32 is connected to the information processing unit 40 via a coaxial cable 110 .

[0106] Example 2 19, the cushioning material 37 in the sensor unit 32 of Example 2 has a lower cushioning part 37A adhered to the support plate 36 and an upper cushioning part 37C adhered to the upper surface of the lower cushioning part 37A. The sensor unit 32 of Example 2 is configured similarly to Example 1, except that the foamed resin constituting the upper cushioning part 37C has a width of 10 mm. (Comparative Example) 20, the cushioning material 37 in the sensor unit 232 of the comparative example has a lower cushioning part 37A adhered to the support plate 36, and an upper cushioning part 37D adhered to the upper surface of the lower cushioning part 37A. The sensor unit 232 of the comparative example is configured in the same manner as in Example 1, except that the foamed resin constituting the upper cushioning part 37D has the same width as the lower cushioning part 37A, that is, 20 mm.

[0107] <Manufacturing of bed devices> The bed apparatus 10 of Examples 1 and 2 and Comparative Example includes a single-size bed 20 composed of a frame 22, a floor plate 24, and a mattress 26, as shown in Fig. 1. The bed apparatus 10 was manufactured by arranging the sensor units 32, 232 between the floor plate 24 and the mattress 26. The arrangement of the sensor unit 32 is as shown in Fig. 2. When arranging the sensor unit 32, the sensor unit 32 may be housed in a bag-shaped case 60 in order to provide the sensor unit 32 with antifouling, waterproof, anti-slip properties, etc. The material of the case 60 may be a PVC sheet, a cloth case, or the like, which is appropriately selected depending on the purpose. For example, in order not to inhibit distortion deformation of the sensor unit 32 when a load is applied, the outer material 62 covering the surface receiving the load is preferably a thin and soft woven or knitted fabric. In addition, the lining 64 in contact with the floorboard 24 is preferably made of a rubber sheet, a polyurethane sheet, or a woven or knitted fabric containing polyurethane fibers in order to provide anti-slip properties. The mattress 26 in Examples 1 and 2 and the Comparative Example is made of polyurethane, and has a width W of 970 mm, a length L of 2000 mm, and a thickness da of 40 mm. The hardness of the mattress 26 is 150 N according to JIS K 6400-2 (Soft foamed materials-Physical properties-Part 2: Determination of hardness and compressive stress-strain properties), 6.4 "Method A (method of determining the force after 30 seconds of constant compression at 40%)".

[0108] <Sensor sensitivity measurement> The sensitivity of the sensor unit 32 manufactured as described above was measured. As shown in FIG. 21, the sensitivity was measured using a tensile tester 410 (tensile tester Tensilon RTG1250 manufactured by A&D Co., Ltd.), an electrometer 450 (electrometer 6514 manufactured by Keithley Co., Ltd.), an AD converter 452, and an analysis PC 454. The tensile tester 410 further includes a crosshead 415 that moves up and down, a load cell 420 fixed to the crosshead 415, a metal rod 425 attached to the tip of the load cell 420, and a stand 440 on which a measurement object is placed. In addition, a pressing jig 430 is fixed to the tip of the metal rod 425. This pressing jig 430 is made of acrylic resin, has a thickness of 10 mm, a height of 55 mm, and a length of 700 mm, and the radius of curvature of the contact surface on the lower surface is set to 12.3 m.

[0109] Here, the charge generated in the piezoelectric substrate 100 is detected by the electrometer 450. Meanwhile, the charge detected by the electrometer 450 and the load detected by the load cell 420 are input to the AD converter 452. Then, the information digitized by the AD converter 452 is output to the analysis PC 454, where the sensor sensitivity is analyzed.

[0110] 21, the sensor unit 32 is set on a stand 440 of a tensile tester 410, and the sensor unit 32 is repeatedly pressed by a pressing jig 430 to measure the sensitivity. When the speed of the crosshead 415 is 100 mm / min and the load applied to the sensor unit 32 is repeatedly applied in the range of 1 N to 150 N, the applied load is measured by a load cell 420, and the amount of generated charge of the piezoelectric substrate 100 is measured by an electrometer 450. Next, in an analysis PC 454, the measurement data is plotted on a scatter diagram with the applied load on the horizontal axis and the amount of charge Q on the vertical axis, and the slope of the straight line approximated by the least squares method is obtained as the sensor sensitivity (pC / N). The sensor sensitivities of Examples 1 and 2 and the comparative example are shown in Table 1 below.

[0111] [Table 1]

[0112] As shown in Table 1, it can be seen that the sensor sensitivity increases as the width of the upper buffer portions 37B, 37C, and 37D relative to the lower buffer portion 37A decreases.

[0113] (2) Confirmation of sensitivity due to differences in cushioning materials Next, the sensor sensitivity when the material of the cushioning material 37 is changed will be confirmed. (Production of Examples 3 to 7) <Sensor unit manufacturing> For sensor unit 32 in Examples 3 to 7, first, a foamed resin that would become lower cushioning part 37A, measuring 570 mm in length, 20 mm in width and 5 mm in thickness and having double-sided tape 34 attached thereto, was attached to the top surface of support plate 36 made of hard polyvinyl chloride and measuring 640 mm in length, 30 mm in width and 5 mm in thickness. In addition, a foamed resin that would become upper cushioning part 37B, measuring 570 mm in length, 5 mm in width and 5 mm in thickness and having double-sided tape attached to both the top and bottom surfaces, was attached to the foamed resin as lower cushioning part 37A.

[0114] Here, the material of the cushioning material 37 is natural rubber in Example 3, chloroprene rubber in Examples 4 and 5, and EPDM rubber in Examples 6 and 7. The density of the cushioning material 37 according to each example and the rubber hardness measured with an Asker rubber hardness tester type C in accordance with JIS K7312 are as shown in Table 2. Then, the piezoelectric substrate 100 covered with a 25 μm-thick polyimide tape serving as the insulating member 38 was attached to the center in the width direction of the upper surface of the foamed resin serving as the upper buffer section 37B. Regarding the covering method, for the sensor units 32 of Examples 3, 5, and 7, the insulating members 38 were sandwiched from both sides of the piezoelectric substrate 100 and then attached to the upper buffer section 37B as shown in Fig. 15. For the sensor units 32 of Examples 4 and 6, the insulating member 38 was attached to the top of the upper buffer section 37B including the piezoelectric substrate 100 as shown in Fig. 3B. The remaining manufacturing steps are the same as those in the first and second embodiments described above.

[0115] <Sensor sensitivity measurement> As in Examples 1 and 2, the sensor sensitivity of Examples 3 to 7 was measured using the device shown in FIG. 21. The pressing tool 430 used in the measurements of Examples 3 to 7 was made of acrylic resin, had a thickness of 10 mm, a height of 50 mm, and a length of 600 mm, and the radius of curvature of the contact surface on the lower surface was set to 9 m. In addition, when the speed of the crosshead 415 was 10 mm / min and the load applied to the sensor unit 32 was repeatedly applied in the range of 10 N to 50 N, the applied load was measured by the load cell 420, and the amount of generated charge of the piezoelectric substrate 100 was measured by the electrometer 450. Next, in the analysis PC 454, the measurement data was plotted on a scatter diagram with the applied load on the horizontal axis and the amount of charge Q on the vertical axis, and the slope of the straight line approximated by the least squares method was obtained as the sensor sensitivity (pC / N). Furthermore, since the length of the piezoelectric substrate 100 and the amount of generated charge are proportional, the sensor sensitivity of the piezoelectric substrate 100 was normalized to the amount of output charge per 1 m of the length of the piezoelectric substrate 100. The sensor sensitivities of Examples 3 to 7 are shown in Table 2 below. The sensitivity ratios in Table 2 indicate the ratios to Example 3.

[0116] [Table 2]

[0117] As shown in Table 2, the sensitivity is improved when the material of the buffer material 37 is changed to a softer one. Also, the sensitivity is improved when the insulation member 38 covering the piezoelectric substrate 100 is changed from covering both sides to covering one side. [Explanation of symbols]

[0118] 10 Bed device (human body detection system) 12 Inner conductor (conductor) 14 Piezoelectric 30 Human body detection device 33 Reference plane 36 Support plate (retaining plate) 37 Cushioning material (buffer) 38 Insulating materials (coating materials) 55 Detection unit 100 Piezoelectric substrate 105 Connection 110 Coaxial cable (wiring) 150 metal tube 150A Inset part (fixed part) 150B Insertion part (insertion part) SL slope

Claims

1. A linear piezoelectric substrate having an axial direction along a reference plane intersecting the direction of pressure received from a human body and configured to detect pressure applied in a radial direction; a buffer body that is provided with respect to the reference surface so as to support the piezoelectric substrate, and that is formed so that a cross section viewed in the axial direction has a width on the piezoelectric substrate side that is narrower than a width on the reference surface side; the buffer body has an inclined surface at an end portion on the axial direction side, the inclined surface inclining toward the reference surface as it moves toward the outer side in the axial direction, The piezoelectric substrate is attached along the inclined surface, A human body detection device in which the wide buffer portion on the reference surface side and the narrow buffer portion on the piezoelectric substrate side are both formed from the same material, and as the pressure received by the piezoelectric substrate increases, the range over which the material is distorted expands from the narrow buffer portion to the wide buffer portion.

2. A linear piezoelectric substrate having an axial direction along a reference plane intersecting the direction of pressure received from a human body and detecting pressure applied in a radial direction; a buffer body that is provided with respect to the reference surface so as to support the piezoelectric substrate, and that is formed so that a cross section viewed in the axial direction has a width on the piezoelectric substrate side that is narrower than a width on the reference surface side; A holding plate that constitutes the reference surface and receives the pressure; a connection portion that connects the piezoelectric substrate and a wiring that transmits an output signal generated by the piezoelectric substrate; a metal tube fixed to the retaining plate and accommodating the connection portion; The metal tube is A fixing portion for fixing the wiring at one end and an insertion portion for allowing the piezoelectric substrate to be inserted at the other end, A human body detection device in which the buffer has a wide buffer portion on the reference surface side and a narrow buffer portion on the piezoelectric substrate side that are both formed from the same material, and as the pressure received by the piezoelectric substrate increases, the range of distortion of the material expands from the narrow buffer portion to the wide buffer portion.

3. The piezoelectric substrate is A long conductor; a long piezoelectric body wound in a spiral shape in one direction around the conductor, 3. The human body detection device according to claim 1, wherein a pressure input to the piezoelectric body is detected from a potential difference between the conductor and the piezoelectric body.

4. A human body detection device as described in claim 3, wherein an organic piezoelectric material is used for the piezoelectric body.

5. A human body detection device as described in Claim 4, wherein the piezoelectric material is a helical chiral polymer (A) having optical activity.

6. A human body detection device as described in Claim 5, wherein the helical chiral polymer (A) is polylactic acid.

7. A human body detection device as described in any one of claims 1 to 6, wherein the piezoelectric substrate is sandwiched between the buffer body and the human body, and a covering member is attached to the surface of the buffer body.

8. The human body detection device according to claim 1, wherein the buffer has a density of 0.05 to 0.5 kg / m 3 and an Asker C-type rubber hardness, as specified in JIS K7312, in the range of 5 to 60.

9. A bed apparatus equipped with a human body detection device described in any one of claims 1 to 8.

10. A human body detection device comprising a plurality of human body detection devices according to any one of claims 1 to 8, The plurality of human body detection devices are installed in a plurality of regions on the reference plane, The human body detection system further includes a detection unit capable of detecting an output signal of each of the piezoelectric substrates installed in each of the regions.

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