JP5815369B2 - Capacitive sensor - Google Patents

Description

  The present invention relates to a capacitance type sensor capable of detecting a surface pressure distribution from a change in capacitance.

  For example, as disclosed in Patent Documents 1 and 2, a capacitive sensor can be configured by sandwiching an elastomeric dielectric layer between a pair of front and back sheets. A front electrode and a front wiring are formed on the back surface of the front sheet. A back electrode and a back wiring are formed on the surface of the back sheet. The front electrode contacts the surface of the dielectric layer. The back side electrode contacts the back side of the dielectric layer. When a load is applied to the capacitive sensor, the thickness of the dielectric layer corresponding to that portion is reduced. Thereby, the electrostatic capacitance between a front side electrode and a back side electrode becomes large. The capacitance type sensor detects the surface pressure distribution based on the change in the capacitance.

  As the front side sheet and the back side sheet, a rubber film having elasticity is used so that elastic deformation of the dielectric layer is hardly restricted. Further, the front side electrode and the back side electrode (hereinafter referred to as “electrode” as appropriate) are each formed of a conductive paint containing a polymer for elastomer and carbon black. Front-side wiring and back-side wiring (hereinafter referred to as “wiring” as appropriate) are each formed from a conductive paint containing a polymer for elastomer and silver powder in order to make the electric resistance smaller than that of the electrode. Therefore, the electrode and the wiring can also be expanded and contracted according to the applied load.

JP 2010-43880 A JP 2010-43881 A JP 2011-75322 A

  The rubber film is soft and excellent in elasticity. Therefore, when the capacitance type sensor using rubber films on the front side sheet and the back side sheet is used as, for example, a body pressure distribution sensor for a bed, a sleeping person does not feel uncomfortable. However, when the rubber film expands and contracts, the electrodes and wirings formed there also expand and contract. As a result, the electrical resistance of the electrode and wiring changes, and depending on the use conditions, there is a possibility that the change in capacitance with respect to the load cannot be output accurately.

  For example, when the capacitance is calculated from the detected impedance, the impedance includes resistance components of the electrode and the wiring. In this case, the change in capacitance cannot be distinguished from the change due to the change in the thickness of the dielectric layer and the change due to the change in resistance of the electrode or the wiring itself. For this reason, if the electrical resistance of the electrode or wiring changes due to expansion, the capacitance may be output as a value different from the original value. Further, when the electrode is expanded by the load and the electrode area in the detection unit is increased, the capacitance is increased. In this case as well, the change in capacitance cannot be distinguished from the change due to the change in the thickness of the dielectric layer and the change due to the change in the electrode area. Thus, when a highly stretchable rubber film is used, the feeling of use is good, but the pressure applied to the detection unit may not be detected accurately. That is, in the capacitive sensor, the measurement accuracy of the surface pressure distribution may be reduced.

  In addition, the way in which the electrodes and wirings are stretched is not constant, and varies depending on the position of the sensor, how the load is applied, and the like. For example, sleepers of various physiques go to bed in various postures on beds in hospitals and care facilities. For this reason, when the capacitance type sensor is arranged on the bed, a portion where the elongation of the rubber film is large and a portion where the elongation is not so tend to occur. As a result, the influence on the output due to the extension of the electrodes and wiring may be increased.

  In particular, an electrode including carbon black as a conductive material has a higher electric resistance than a wiring including silver powder. Therefore, when an electrode is formed using carbon black, the resistance change due to expansion increases, and the influence on the output increases.

  On the other hand, in place of the rubber film, a resin film having poor stretchability such as a polyethylene terephthalate (PET) film may be used. However, the PET film is hard and stiff. For this reason, when a sleeping person lies on the capacitive sensor, the user feels uncomfortable. Therefore, it is difficult to apply to sensors that are placed in contact with the body, such as bed mattresses and car seats.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a capacitive sensor that is soft, has a little uncomfortable feeling during use, and has high measurement accuracy of surface pressure distribution.

  (1) In order to solve the above-described problem, a capacitive sensor of the present invention includes a polymer dielectric layer, a pair of front and back sheets disposed with the dielectric layer interposed therebetween, and the front sheet. Formed between the front electrode formed on the back surface in contact with the dielectric layer, the back electrode formed on the surface in contact with the dielectric layer of the back sheet, and the front electrode and the back electrode facing in the front-back direction A capacitance type sensor capable of detecting pressure applied to the detection unit from a change in capacitance of the detection unit, wherein at least a load is applied to the front side sheet and the back side sheet. The sheet on the side to which is input has a fabric layer and a polymer layer, and is composed of a laminate having a stress of 0.2 N / mm or more and 15.0 N / mm or less when stretched 5% in one direction, In the laminate, the polymer layer is disposed on the dielectric layer side. And wherein the Rukoto.

  In the capacitance type sensor of the present invention, at least the load input sheet has a stress when stretched 5% in one direction (hereinafter referred to as “5% stretch stress” as appropriate) of 0.2 N / It consists of a laminated body of mm or more and 15.0 N / mm or less. As the stress at 5% elongation of the laminate, a value measured in a tensile test according to JIS K7127 (1999) is adopted. The tensile test is performed using test piece type 2 having a width of 10 mm, a length of 150 mm, and a distance between marked lines of 50 mm, an initial distance between chucks of 100 mm, and a test speed of 500 mm / min. Then, the load when the test piece is extended by 5% is measured, and the value obtained by dividing the measured load by the width of the test piece is taken as the stress at the time of 5% extension.

  The laminate is poor in stretchability compared to a rubber film. For this reason, the electrode formed in the laminate is difficult to stretch. Therefore, the change in electrical resistance due to the extension of the electrode is small. Also, the change in the electrode area is small. Therefore, the influence on the output due to the extension of the electrode is small. For this reason, in the electrostatic capacitance type sensor of this invention, the pressure added to a detection part can be detected correctly. Therefore, the measurement accuracy of the surface pressure distribution is high.

  Moreover, a laminated body has a cloth layer. For this reason, the sheet | seat which consists of the said laminated body has a soft touch. Therefore, according to the capacitance type sensor of the present invention, it is possible to realize a soft touch similar to that when a rubber film is used as a sheet material. That is, at least the sheet on the load input side is made of the laminate. Therefore, for example, when the capacitive sensor of the present invention is used as a body pressure distribution sensor for a bed, the laminate is disposed on the uppermost surface. For this reason, it is difficult for a sleeping person to feel uncomfortable feelings such as hardness and stiffness. Therefore, the capacitive sensor of the present invention is suitable for a body pressure distribution sensor disposed on a bed mattress, a seating sensor disposed on a vehicle seat, and the like.

  Furthermore, a polymer layer is laminated on the fabric layer. For this reason, even if the cloth layer has stretchability, it is possible to regulate stretching as a laminate by laminating a polymer layer having poor stretchability. The polymer layer is disposed on the dielectric layer side. Therefore, for example, when the front sheet is made of a laminate, the front electrode is formed on the back surface of the front sheet, that is, the back surface of the polymer layer. Compared to the fabric layer, the surface roughness of the polymer layer is small. For this reason, when forming an electrode using a conductive paint, it is easy to form an electrode. Further, since the unevenness is small, the contact state between the formed electrode and the dielectric layer is also good.

  (2) Preferably, in the configuration of (1), the cloth layer is formed of one or more fibers selected from polyester fibers, polyamide fibers, acrylic fibers, polyolefin fibers, polyurethane fibers, and polyimide fibers. Better.

  As long as the 5% elongation stress of the laminate is 0.2 N / mm or more and 15.0 N / mm or less, any of woven fabric, knitted fabric, and nonwoven fabric may be used as the fabric layer. According to this structure, the laminated body with low hygroscopicity and excellent durability can be comprised. Moreover, adhesion with the polymer layer is easy.

(3) Preferably, in the configuration of (1) or (2), the fabric layer has a basis weight of 15 g / m ² or more and 300 g / m ² or less.

When the fabric weight is less than 15 g / m ² , the thickness of the fabric layer is too small, so that the softness of the laminate is difficult to develop. Further, the durability is lowered. A more suitable basis weight is 50 g / m ² or more. On the other hand, if the basis weight exceeds 300 g / m ² , the thickness of the fabric layer becomes too large, the laminate becomes heavy, and the soft feel of the laminate is impaired. Further, as the thickness of the laminate increases, the thickness variation increases. For this reason, when the electrode is formed by a printing method, the coating thickness is not uniform, and the electric resistance value may vary. A suitable basis weight is 200 g / m ² or less.

  (4) Preferably, in any one of the configurations (1) to (3), the front electrode and the back electrode can be formed on the polymer layer from a conductive paint containing an elastomer and a conductive material. It is better to have a configuration.

  Of the front side sheet and the back side sheet, in the sheet made of a laminate, the electrode is formed on the polymer layer. According to this structure, the thin film-like front side electrode and back side electrode can be easily formed by apply | coating and drying the electrically conductive coating material containing an elastomer and a electrically conductive material.

  The conductive coating material may contain additives such as a dispersant, a reinforcing agent, a plasticizer, an anti-aging agent, and a colorant as required in addition to the elastomer and the conductive material. The conductive coating material may be prepared by dispersing a conductive material in a solution obtained by dissolving a polymer of an elastomer component (a polymer before crosslinking when the elastomer is a crosslinked rubber) together with a predetermined additive in a solvent. As the conductive material, conductive carbon powder or metal powder such as silver or copper may be used.

  As a method for applying the conductive paint, various known methods can be employed. For example, in addition to printing methods such as screen printing, inkjet printing, flexographic printing, gravure printing, pad printing, and lithography, dipping, spraying, bar coating, and the like can be given. For example, when a printing method is employed, it is possible to easily separate the applied part and the non-applied part. Also, printing of large areas, thin lines, and complicated shapes is easy. Among the printing methods, a screen printing method is preferable because a highly viscous paint can be used and the coating thickness can be easily adjusted.

  (5) Preferably, in any one of the constitutions (1) to (4), the front electrode and the back electrode include an elastomer and conductive carbon powder.

  The front side electrode and the back side electrode have an elastomer as a base material. A conductive path made of conductive carbon powder is formed in the elastomer. For this reason, a front side electrode and a back side electrode are flexible and have high electroconductivity. Moreover, even if it expands and contracts or bends, cracks hardly occur and the change in conductivity is small. Conductive carbon powder has good conductivity and is relatively inexpensive. For this reason, if conductive carbon powder is used, the manufacturing cost of a capacitive sensor can be reduced. In this configuration, the front side electrode and the back side electrode contain conductive carbon powder. However, when it is formed in a laminated body, the influence on the output due to the extension of the electrode is small.

  (6) Preferably, in any one of the constitutions (1) to (5), the polymer layer is made of a polyurethane film, and the polyurethane film and the fabric layer are bonded with an adhesive. Is good.

  The strength of the polyurethane film is large. In addition, the polyurethane film has good adhesion to the conductive paint. For this reason, an electrode can be easily formed in a polyurethane film from a conductive paint. According to this structure, the laminated body which the cloth and the polyurethane film laminated | stacked using the adhesive agent can be manufactured easily.

  The manufacturing method of a laminated body is not specifically limited. For example, as in this configuration, a cloth and a polymer film may be bonded with an adhesive, or heated and fused (lamination method). Alternatively, the polymer solution may be brushed or sprayed on the cloth (coating method), or the cloth may be immersed in the polymer solution (dipping method). Especially, according to the coating method or dipping method, a part of the polymer penetrates between the fibers of the cloth. Thereby, the stretchability of cloth can be reduced remarkably.

  (7) Preferably, in any configuration of the above (1) to (6), a front side wiring connected to the front side electrode is formed on the back surface of the front side sheet, and on the surface of the back side sheet, It is better to have a configuration in which a backside wiring connected to the backside electrode is formed.

  For example, when the front side sheet is made of a laminate, the front side wiring is formed on the back surface of the laminate. For this reason, extension of the front side wiring is suppressed. Therefore, the change in electrical resistance due to the extension of the front wiring is reduced. That is, according to this configuration, in addition to the front side electrode, the influence on the output due to the extension of the front side wiring can be reduced. Thereby, the measurement accuracy of the surface pressure distribution can be further improved.

  It is desirable that the front side wiring and the back side wiring include an elastomer and a conductive material. As the conductive material, conductive carbon powder or metal powder such as silver or copper may be used.

  (8) Preferably, in any one of the constitutions (1) to (7), the front side sheet and the back side sheet are both composed of the laminate.

  In this configuration, both the front and back sheets are made of a laminate. For this reason, expansion of both the front side electrode and the back side electrode is suppressed. Therefore, in both the front and back electrodes, the change in electrical resistance due to expansion becomes small. Further, the change in the electrode area is also reduced. Therefore, the influence on the output due to the extension of the electrode can be further reduced. Therefore, according to this configuration, the measurement accuracy of the surface pressure distribution can be further improved. In addition, sheets made of a soft laminate are disposed not only on the load input side but also on both sides of the dielectric layer. For this reason, usability is improved.

  According to the present invention, it is possible to provide a capacitance type sensor that is soft, has a little uncomfortable feeling during use, and has high surface pressure distribution measurement accuracy.

It is a perspective view of the bed in which the body pressure distribution sensor of the embodiment is arranged. It is II-II sectional drawing of FIG. It is a disassembled perspective view of the body pressure distribution sensor of embodiment. It is an upper surface transmission figure of a body pressure distribution sensor. It is VV sectional drawing of FIG.

  Hereinafter, embodiments of the capacitive sensor of the present invention will be described. In the embodiment described below, the capacitance type sensor of the present invention is embodied as a body pressure distribution sensor for a bed.

[Composition of bed]
First, the configuration of the bed in which the body pressure distribution sensor of this embodiment is arranged will be briefly described. FIG. 1 shows a perspective view of a bed on which the body pressure distribution sensor of the present embodiment is arranged. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. In FIG. 1, it is shown through the body pressure distribution sensor.

  As shown in FIGS. 1 and 2, a mattress 91 is disposed above the floor plate 90 of the bed 9. The body pressure distribution sensor 1 is disposed on the upper surface of the mattress 91. The body pressure distribution sensor 1 is disposed over substantially the entire upper surface of the mattress 91. The body pressure distribution sensor 1 and the mattress 91 are covered with a sheet 92.

[Configuration of body pressure distribution sensor]
Next, the configuration of the body pressure distribution sensor of this embodiment will be described. FIG. 3 is an exploded perspective view of the body pressure distribution sensor of the present embodiment. FIG. 4 shows a top view of the body pressure distribution sensor. FIG. 5 shows a VV cross-sectional view of FIG. In FIG. 3, the front connector 11, the back connector 12, and the control unit 4 are omitted. In FIG. 4, the fused portion 13 and the detection portions A0101 to A0808 are hatched.

  As shown in FIGS. 3 to 5, the body pressure distribution sensor 1 of the present embodiment includes a dielectric layer 10, a front sheet 2, a back sheet 3, front electrodes 01X to 08X, back electrodes 01Y to 08Y, Detection units A0101 to A0808, front side wirings 01x to 08x, back side wirings 01y to 08y, a front side connector 11, a back side connector 12, and a control unit 4 are provided. It should be noted that in the sign “AOOΔΔ” of the detection unit, the upper two digits “OO” correspond to the front electrodes 01X to 08X. The last two digits “ΔΔ” correspond to the back side electrodes 01Y to 08Y.

  The dielectric layer 10 is made of urethane foam and has a rectangular sheet shape. The thickness of the dielectric layer 10 is 300 μm. The dielectric layer 10 extends in the XY directions (left and right and front and rear directions). Urethane foam is included in the “polymer” of the present invention.

The front sheet 2 is disposed on the upper side of the dielectric layer 10. The front sheet 2 has a rectangular shape with a thickness of 138 μm. The area of the front sheet 2 is larger than the area of the dielectric layer 10. The stress at 5% elongation of the front sheet 2 is 0.23 N / mm. The front side sheet 2 includes a front side fabric layer 20 and a front side polymer layer 21. The front fabric layer 20 is made of a polyester fabric having a basis weight of 55 g / m ² . The front polymer layer 21 is made of a polyurethane film (“Esmer (registered trademark) URL” manufactured by Nippon Matai Co., Ltd.). The front fabric layer 20 and the front polymer layer 21 are laminated in the thickness direction (vertical direction). The front side polymer layer 21 is adhered to the lower surface of the front side fabric layer 20 with a polyurethane-based adhesive (“Crisbon (registered trademark) 4070FT” manufactured by DIC Corporation). The front polymer layer 21 is disposed on the dielectric layer 10 side. The upper surface of the front sheet 2, that is, the upper surface of the front fabric layer 20 is covered with a sheet 92. The front side sheet 2 is included in the “sheet on the side where the load is input” of the present invention. The front sheet 2 is included in the “laminate” of the present invention.

  A total of eight front side electrodes 01 </ b> X to 08 </ b> X are formed on the lower surface (back surface) of the front side sheet 2, that is, the lower surface of the front side polymer layer 21. The front side electrodes 01X to 08X each contain acrylic rubber and conductive carbon black. The front side electrodes 01X to 08X each have a strip shape. The front-side electrodes 01X to 08X each extend in the Y direction (front-rear direction). The front side electrodes 01X to 08X are arranged in the X direction (left and right direction) so as to be substantially parallel to each other with a predetermined interval. The front-side electrodes 01X to 08X are disposed so as to be in contact with the upper surface of the dielectric layer 10, respectively.

  A total of eight front side wirings 01x to 08x are formed on the lower surface of the front side sheet 2. The front-side wirings 01x to 08x each contain acrylic rubber and conductive carbon black. The front connector 11 is disposed at the left front corner of the front sheet 2. The control unit 4 is electrically connected to the front connector 11. The front side wirings 01x to 08x connect the front end portions of the front side electrodes 01X to 08X and the front side connector 11, respectively.

  The back sheet 3 is disposed below the dielectric layer 10. The size, shape, configuration, and stress at 5% elongation of the back sheet 3 are the same as those of the front sheet 2. That is, the back side sheet 3 includes a back side fabric layer 30 and a back side polymer layer 31. The back side fabric layer 30 is made of the same polyester fabric as the front side fabric layer 20. The back polymer layer 31 is made of a polyurethane film (same as above). The back side fabric layer 30 and the back side polymer layer 31 are laminated in the thickness direction (vertical direction). The back polymer layer 31 is bonded to the upper surface of the back fabric layer 30 with a polyurethane-based adhesive (same as above). The back polymer layer 31 is disposed on the dielectric layer 10 side. The back sheet 3 is included in the “laminate” of the present invention.

  A total of eight back-side electrodes 01Y to 08Y are formed on the upper surface (front surface) of the back-side sheet 3, that is, the upper surface of the back-side polymer layer 31. The back-side electrodes 01Y to 08Y each contain acrylic rubber and conductive carbon black. The back side electrodes 01Y to 08Y each have a strip shape. The back-side electrodes 01Y to 08Y each extend in the X direction (left-right direction). The back-side electrodes 01Y to 08Y are arranged in the Y direction (front-rear direction) so as to be substantially parallel to each other at a predetermined interval. The back-side electrodes 01Y to 08Y are disposed so as to be in contact with the lower surface of the dielectric layer 10, respectively.

  A total of eight back-side wirings 01y to 08y are formed on the upper surface of the back-side sheet 3. The back side wirings 01y to 08y each contain acrylic rubber and conductive carbon black. The back connector 12 is disposed at the left front corner of the back sheet 3. The control unit 4 is electrically connected to the back-side connector 12. The back side wirings 01y to 08y connect the left end portions of the back side electrodes 01Y to 08Y and the back side connector 12, respectively.

  The front sheet 2 and the back sheet 3 are opposed to each other with the dielectric layer 10 in between. As shown by hatching in FIG. 4, a plurality of fused portions 13 are arranged on the peripheral portions of the front side sheet 2 and the back side sheet 3. The plurality of fused portions 13 are arranged in a dotted line so as to surround the periphery of the dielectric layer 10. The front side sheet 2 and the back side sheet 3 are joined at the fusion part 13.

  As shown by hatching in FIG. 4, the detectors A0101 to A0808 are arranged at portions (overlapping portions) where the front-side electrodes 01X to 08X and the back-side electrodes 01Y to 08Y intersect when viewed in the vertical direction. Each of the detection units A0101 to A0808 includes a part of the front side electrodes 01X to 08X, a part of the back side electrodes 01Y to 08Y, and a part of the dielectric layer 10. A total of 64 (= 8 × 8) detectors A0101 to A0808 are arranged. The detectors A0101 to A0808 are arranged at substantially equal intervals over substantially the entire surface of the dielectric layer 10.

  The control unit 4 includes a power supply circuit 41, a CPU (Central Processing Unit) 42, a RAM (Random Access Memory) 43, an EEPROM-ROM (Electronically Erasable and Programmable Read Only Memory) 44, and a circuit. ing. The control unit 4 is electrically connected to the front side connector 11 and the back side connector 12.

  The power supply circuit 41 applies a sinusoidal AC voltage to the detection units A0101 to A0808. The AC voltage is sequentially applied to the detection units A0101 to A0808 in a scanning manner. In the EEP-ROM 44, a map indicating the correspondence between the capacitance and the load (body pressure) in the detection units A0101 to A0808 is stored in advance. The RAM 43 temporarily stores impedance, phase, and the like input from the front connector 11 and the back connector 12. The CPU 42 calculates the capacitance of the detection units A0101 to A0808 based on the impedance and phase stored in the RAM 43. Then, the body pressure distribution (surface pressure distribution) in the body pressure distribution sensor 1 is calculated from the capacitance. The drive circuit 45 drives a member (not shown) connected to the drive circuit 45 according to the body pressure distribution calculated by the CPU 42.

[Manufacturing method of body pressure distribution sensor]
Next, the manufacturing method of the body pressure distribution sensor 1 of this embodiment is demonstrated. The manufacturing method of the body pressure distribution sensor 1 of this embodiment has a sheet | seat preparation process, a printing process, a lamination process, and a sheet | seat melt | fusion process.

In the sheet preparation process, the front side sheet 2 and the back side sheet 3 are prepared. First, using a 40 mesh gravure roll, a polyurethane adhesive (same as above) is applied to a polyurethane film (same as above) in a mesh form with a coating amount of 6 g / m ² (in terms of solid content). Thereafter, the applied adhesive is dried at 100 ° C. Next, a polyester fabric is laminated on the adhesive surface of the polyurethane film. Then, using a nip roll having a hardness of 80 degrees, the polyester fabric and the polyurethane film are pressure-bonded at a linear pressure of 100 kg / cm. In this way, a laminate having a fabric layer made of a polyester fabric and a polymer layer made of a polyurethane film is obtained. The obtained laminated body is cut into a predetermined size to produce the front side sheet 2 and the back side sheet 3.

  In the printing process, the front side electrodes 01X to 08X and the front side wirings 01x to 08x are formed on the produced front side sheet 2. Similarly, the back side electrodes 01Y to 08Y and the back side wirings 01y to 08y are formed on the back side sheet 3.

  First, a conductive paint is prepared by the following procedure. A roll kneader containing 100 parts by mass of an acrylic rubber polymer, 1 part by mass of stearic acid as a vulcanization aid, 2.5 parts by mass of zinc dimethyldithiocarbamate as a vulcanization accelerator, and 0.5 parts by mass of ferric dimethyldithiocarbamate. To prepare an elastomer composition. The prepared elastomer composition is dissolved in 1500 parts by mass of methyl ethyl ketone (MEK). To this solution, 22.86 parts by mass of conductive carbon black (Ketjen Black, “EC600JD” manufactured by Lion Corporation) was added and kneaded with a roll, and MEK having a solid content concentration of about 7.8% by mass. Obtain a solution. To the obtained MEK solution, 686.7 parts by mass of diethylene glycol monobutyl ether acetate as a printing solvent is added. Then, the MEK solution to which the printing solvent has been added is placed in a wide-mouthed container that easily comes into contact with the atmosphere, and is allowed to stand at room temperature for one day while stirring occasionally. In this way, low boiling point MEK is evaporated. In this way, a conductive paint is prepared. The boiling point of the printing solvent is 200 ° C. or higher. For this reason, the volatilization of the printing solvent is negligible.

  Next, the prepared conductive paint is printed on the lower surface of the front polymer layer 21 of the front sheet 2 (the lower surface in FIG. 3, which is arranged upward during printing) using a screen printer. Then, while drying a coating film by heating, an acrylic rubber polymer is bridge | crosslinked and the front side electrodes 01X-08X and the front side wiring 01x-08x are formed. Similarly, a conductive paint is printed on the upper surface of the back polymer layer 31 of the back sheet 3 to form the back electrodes 01Y to 08Y and the back wirings 01y to 08y.

  In the laminating step, as shown in FIG. 3, the back side sheet 3, the dielectric layer 10, and the front side sheet 2 are laminated in order from the bottom. That is, the back side sheet 3, the dielectric layer 10, so that the dielectric layer 10 is interposed between the back side electrodes 01 Y to 08 Y formed on the back side sheet 3 and the front side electrodes 01 X to 08 X formed on the front side sheet 2. And the front side sheet | seat 2 is laminated | stacked.

  In the sheet fusion process, the peripheral portions of the laminated front sheet 2 and back sheet 3 are spot fused at a predetermined interval. In this way, the body pressure distribution sensor 1 of the present embodiment is manufactured.

[Motion of body pressure distribution sensor]
Next, the movement of the body pressure distribution sensor 1 of this embodiment will be described. First, before the sleeping person M lies on the mattress 91 (initial state), the capacitance C is calculated for each of the detection units A0101 to A0808. That is, the capacitance C is calculated as if it were scanned from the detection unit A0101 to the detection unit A0808. The calculated capacitance C is stored in the RAM 43 for each of the detection units A0101 to A0808. Next, after the sleeping person M sleeps on the mattress 91 on the back, the electrostatic capacity C is calculated for each of the detection units A0101 to A0808. The calculated capacitance C is stored in the RAM 43 for each of the detection units A0101 to A0808. In the detection part where the weight of the sleeping person M is added, the distance between the front electrode and the back electrode is reduced. Thereby, the electrostatic capacitance C of the said detection part becomes large. The CPU 42 calculates body pressure for each of the detection units A0101 to A0808 from the change amount ΔC of the capacitance. In this way, the body pressure distribution on the mattress 91 is measured.

[Function and effect]
Next, the effect of the body pressure distribution sensor 1 of this embodiment will be described. According to the body pressure distribution sensor 1 of the present embodiment, both the front side sheet 2 and the back side sheet 3 are made of a laminate having poor stretchability with a 5% elongation stress of 0.23 N / mm. For this reason, the front-side electrodes 01X to 08X and the front-side wirings 01x to 08x formed on the front-side sheet 2, the back-side electrodes 01Y to 08Y and the back-side wirings 01y to 08y formed on the back-side sheet 3 (hereinafter referred to as “electrode and wiring” ")" Is difficult to grow even if the weight of the sleeping person M is added. Therefore, the change in electrical resistance in the electrode and wiring is small. Further, in the detection units A0101 to A0808, the change in the electrode area is small. Therefore, the influence on the output due to the extension of the electrode and the wiring is small. For this reason, in the body pressure distribution sensor 1, the pressure applied to the detection units A0101 to A0808 can be accurately detected. That is, in the body pressure distribution sensor 1, the measurement accuracy of the body pressure distribution (surface pressure distribution) is high.

The front side sheet 2 has a front side fabric layer 20. Similarly, the back side sheet 3 has a back side fabric layer 30. The basis weight of the polyester fabric constituting the front side fabric layer 20 and the back side fabric layer 30 is 55 g / m ² . For this reason, the front side sheet 2 and the back side sheet 3 are soft. That is, the body pressure distribution sensor 1 has a soft touch similar to that when a rubber film is used as a sheet material. Therefore, it is difficult for the sleeping person M to feel a sense of incongruity such as hardness and stiffness. Further, in the body pressure distribution sensor 1, not only the front sheet 2 on the load input side but also the back sheet 3 is made of a laminate. Therefore, a better feeling of use can be obtained. Moreover, the front side fabric layer 20 and the back side fabric layer 30 consist of a polyester fabric. For this reason, the front side sheet 2 and the back side sheet 3 are hard to absorb moisture and are excellent in durability.

  A front polymer layer 21 made of a polyurethane film is disposed on the dielectric layer 10 side of the front sheet 2. Similarly, a back polymer layer 31 made of a polyurethane film is disposed on the dielectric layer 10 side of the back sheet 3. The strength of the polyurethane film is large. In addition, the polyurethane film has good adhesion to the conductive paint. For this reason, an electrode and wiring can be easily formed from the conductive paint on the back surface of the front sheet 2 and the top surface of the back sheet 3. Further, the surface roughness of the front polymer layer 21 and the back polymer layer 31 is smaller than that of the front fabric layer 20 and the back fabric layer 30. Therefore, the contact state between the front side electrodes 01X to 08X formed on the front side polymer layer 21 and the back side electrodes 01Y to 08Y formed on the back side polymer layer 31 and the dielectric layer 10 is good.

  The laminate constituting the front sheet 2 and the back sheet 3 is manufactured by bonding a polyurethane film and a polyester fabric. For this reason, the front side sheet | seat 2 and the back side sheet | seat 3 can be manufactured easily.

  In the body pressure distribution sensor 1, the electrode and the wiring are formed including acrylic rubber and conductive carbon black. For this reason, an electrode and wiring are flexible and have high electroconductivity. In addition, cracks are less likely to occur even when stretched or bent, and the change in conductivity is small. The electrodes and wiring are formed by screen printing. For this reason, it is easy to form a thin film-like electrode and wiring in various shapes.

  The front side sheet 2 and the back side sheet 3 are joined by spot fusion of the peripheral edge portion. For this reason, the movement of air is possible between the inside and the outside where the dielectric layer 10 is interposed through the unfused portion. Therefore, even when a foamed material such as urethane foam is used as the dielectric layer 10, the air inflow and outflow associated with cell compression and recovery are not hindered.

  The strip-shaped front-side electrodes 01X to 08X are disposed at substantially equal intervals in the X direction and the Y direction over the entire surface of the dielectric layer 10. Similarly, the back-side electrodes 01Y to 08Y are disposed at substantially equal intervals in the X direction and the Y direction over the entire surface of the dielectric layer 10. The detectors A0101 to A0808 are arranged using the intersections of the front electrodes 01X to 08X and the back electrodes 01Y to 08Y. For this reason, the detection units A0101 to A0808 can be easily dispersed on the entire surface of the dielectric layer 10. Further, even when the surface pressure distribution in a wide area is measured, it is not necessary to arrange an electrode for each part where a load is desired to be detected.

<Others>
The embodiment of the capacitive sensor of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  For example, the material of the fabric layer and polymer layer constituting the laminate is not particularly limited as long as a laminate having a stress at 5% elongation of 0.2 N / mm or more and 15.0 N / mm or less can be constituted. Examples of the cloth layer include polyester fibers such as polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate, polyamide fibers such as nylon (registered trademark) 6 and nylon 6,6, polyolefin fibers such as acrylic fiber, polypropylene, and polyethylene, and polyurethane. It can form from 1 or more types of fibers chosen from a fiber and a polyimide fiber. The polymer layer may be formed from a resin or a thermoplastic elastomer. For example, polyurethane, acrylic, silicone, polyvinyl alcohol, polyamide, polyester, polycarbonate, fluorine, polyolefin, polyvinyl chloride, acrylonitrile-butadiene-styrene, melamine resin, etc. One or more selected from plastic elastomers may be used.

  The laminated body may have a two-layer structure of a cloth layer and a polymer layer as in the above embodiment, but may have a three-layer structure in which the cloth layer is sandwiched between polymer layers. Furthermore, a structure of four or more layers may be formed by overlapping fabric layers or polymer layers.

The laminated body needs to be soft and at the same time difficult to stretch with respect to a predetermined range of load. Table 1 shows the evaluation results of 5% elongation stress and flexibility in the laminate of the above embodiment (Example 1) and other film members (Comparative Example 1, Reference Example 1-5). In Table 1, “Trinty (registered trademark)” manufactured by Toray Industries, Inc. was used as the stretchable fabric of Comparative Example 1. Moreover, it shows that it is hard to extend, so that the stress at the time of 5% elongation is large. Further, the flexibility is judged by the touch when touched by a hand, and a circle that indicates a soft feel is indicated by a circle, and a soft feel that is indicated by a cross.

  The film member of Comparative Example 1 has a two-layer structure of a cloth layer and a polymer layer, similarly to the laminated body of Example 1 (laminated body in the present invention). However, the stress at 5% elongation is less than 0.2 N / mm, and the stretchability is high. For this reason, it is not suitable for the sheet of the capacitive sensor of the present invention. Moreover, when the film member of the single layer structure was evaluated for reference, in the film member of Reference Example 2, the stress at 5% elongation was less than 0.2 N / mm, and the stretchability was high. On the other hand, in the film members of Reference Examples 1 and 3-5, the stress at 5% elongation was 0.2 N / mm or more and 15.0 N / mm or less, but all were poor in flexibility.

  In the said embodiment, the laminated body was manufactured by the laminating method which adhere | attaches a polyester fabric and a polyurethane film. However, the manufacturing method of a laminated body is not limited to the said embodiment. For example, you may manufacture by the coating method which apply | coats a polymer solution to cloth, and the dipping method which immerses cloth in a polymer solution. In addition, the adhesive agent which adhere | attaches a cloth layer and a polymer layer is not specifically limited, either. For example, in addition to the polyurethane adhesive, a polyamide adhesive, a polyester adhesive, and the like can be given.

  In the said embodiment, the laminated body was used for both the front side sheet | seat and the back side sheet | seat. However, the laminate may be used only for the front side sheet (the sheet on the side where the load is input). In this case, a PET film or the like can be used as the back side sheet. When a transparent film such as a PET film is used, alignment is facilitated when the front side sheet, the dielectric layer, and the back side sheet are laminated and integrated.

  The type of polymer for the dielectric layer is not particularly limited. What is necessary is just to select suitably from resin and an elastomer (crosslinked rubber and thermoplastic elastomer). From the viewpoint of durability against repeated expansion and contraction and an increase in capacitance, an elastomer having a large elongation, strength, and relative dielectric constant is preferred. Examples thereof include silicone rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, natural rubber, isoprene rubber, and foams thereof. The dielectric layer may be a cloth made of polymer fibers in addition to a polymer sheet. By adjusting the Young's modulus of the dielectric layer, the detection sensitivity and detection range can be adjusted according to the application. For example, when a foam having a small Young's modulus such as urethane foam is employed, a small load is easily detected.

  The front side electrode, the back side electrode, the front side wiring, and the back side wiring include an elastomer and a conductive material, as in the above embodiment, from the viewpoint that cracks are less likely to occur even when stretched or bent, and the change in conductivity is small. Configuration is desirable. Elastomers include silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber. Etc. As the conductive material, conductive carbon powder such as carbon black or graphite powder, or metal powder such as silver or copper can be used. In addition to screen printing, the electrodes and wiring may be formed by inkjet printing, flexographic printing, gravure printing, pad printing, lithography, or the like. Or you may form by the dip method, the spray method, the bar coat method, etc.

  The shape of the front side electrode and the back side electrode, the number of arrangement, the interval between the electrodes, etc. are not particularly limited. For example, you may change the width | variety of a front side electrode and a back side electrode in the extending direction (front-back direction or the left-right direction). Further, the front electrode and the back electrode may not be formed at equal intervals, but may be formed at different intervals depending on the location. Further, the front side electrode and the back side electrode may be linear or curved.

  You may comprise the electrostatic capacitance type sensor of this invention further provided with another member. For example, a cover sheet may be arranged on the upper surface of the front sheet (the sheet on the load input side). Or you may accommodate the whole sensor (a control part is also OK) in a cover bag. Thereby, the designability is improved, and contamination of the capacitive sensor can be prevented.

  The capacitive sensor of the present invention includes a seat sensor for car seats and wheelchairs, a surface pressure distribution sensor for beds and carpets, a soft surface pressure sensor such as artificial skin, a motion capture for detecting human movement, and a keyboard. It can be used for various applications such as information input devices such as vehicle collision detection sensors.

1: body pressure distribution sensor (capacitance type sensor), 2: front side sheet, 3: back side sheet, 4: control unit, 9: bed, 10: dielectric layer, 11: front side connector, 12: back side connector, 13: Fusion part, 20: Front side fabric layer, 21: Front side polymer layer, 30: Back side fabric layer, 31: Back side polymer layer, 41: Power supply circuit, 42: CPU, 43: RAM, 44: EEP-ROM, 45: Drive Circuit: 90: Floor board, 91: Mattress, 92: Sheet, 01X to 08X: Front side electrode, 01Y to 08Y: Back side electrode, 01x to 08x: Front side wiring, 01y to 08y: Back side wiring, A0101 to A0808: Detection unit, M : Sleeper.

Claims (7)

A polymer dielectric layer;
A pair of front and back sheets disposed across the dielectric layer; and
A front electrode formed on the back surface of the front sheet that contacts the dielectric layer;
A backside electrode formed on a surface of the backside sheet that contacts the dielectric layer;
A detection portion formed between the front electrode and the back electrode facing in the front-back direction;
A capacitance type sensor capable of detecting pressure applied to the detection unit from a change in capacitance of the detection unit,
Of the front side sheet and the back side sheet, at least a sheet on which a load is input has a fabric layer and a polymer layer, and the stress when stretched 5% in one direction is 0.2 N / mm or more and 15. It consists of a laminate that is 0 N / mm or less,
The fabric layer is formed of one or more kinds of fibers selected from polyester fibers, polyamide fibers, acrylic fibers, polyolefin fibers, polyurethane fibers, polyimide fibers,
The polymer layer is made of a polyurethane film,
The electrostatic capacity sensor, wherein the polymer layer is disposed on the dielectric layer side in the laminate. The capacitance type sensor according to claim 1, wherein the fabric weight is 15 g / m ² or more and 300 g / m ² or less. The capacitive sensor according to claim 1 or 2 , wherein the front electrode and the back electrode can be formed on the polymer layer from a conductive paint containing an elastomer and a conductive material. The capacitive sensor according to any one of claims 1 to 3 , wherein the front side electrode and the back side electrode include an elastomer and a conductive carbon powder. The capacitive sensor according to any one of claims 1 to 4 , wherein the polyurethane film and the fabric layer are bonded to each other by an adhesive in the laminate. A front side wiring connected to the front side electrode is formed on the back surface of the front side sheet,
The capacitive sensor according to any one of claims 1 to 5 , wherein a back side wiring connected to the back side electrode is formed on a surface of the back side sheet. The capacitive sensor according to any one of claims 1 to 6 , wherein the front side sheet and the back side sheet are both made of the laminate.

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