JP4051043B2 - Pressure sensor - Google Patents

Description

The present invention relates to a pressure sensor. More specifically, the present invention relates to a pressure sensor that has a simple configuration and can easily adjust sensitivity.

Conventionally, a sensor used as a tactile sensor includes a solid member such as silicone rubber, a sensor element embedded in the solid member, and a power transmission coil and a signal reception coil attached to the solid member. . The sensor element is configured as a Colpitts LC oscillation circuit by attaching a signal transmission coil and a power receiving coil to a sensor circuit chip including a capacitor. The sensor element is supplied with power from the power transmission coil via the power reception coil and oscillates at a constant frequency via the signal transmission coil by the LC transmission circuit so that the transmitted signal is received by the signal reception coil. (For example, refer to Patent Document 1). When the object comes into contact with the surface of the solid member, the sensor element is pressed through the solid member. For this reason, the frequency of the signal oscillated by the sensor element changes, and the contact of the object is detected based on the change in the frequency.
JP-A-11-245190 (pages 2 to 4)

  However, the sensor element constituting this conventional sensor has a problem that its configuration is complicated because the signal transmission coil and the power receiving coil are attached to the sensor circuit chip. Further, in order to adjust the sensitivity of the sensor, it is necessary to change the type of capacitor constituting the LC transmission circuit, and there is a problem that adjustment of the sensitivity of the sensor is complicated.

The present invention has been made paying attention to the problems existing in the prior art as described above. An object of the present invention is to provide a pressure sensor that has a simple configuration and can easily adjust sensitivity.

In order to achieve the above object, a pressure sensor according to a first aspect of the present invention includes a medium, and a plurality of sensor elements that are configured by a coiled carbon fiber having conductivity and provided in the medium. And a pair of electrodes electrically connected to the medium, wherein the medium is formed of a dielectric material and has a capacitance (C) component, and the coiled carbon fiber has a coil diameter of 1 nm. The sensor element has an inductance (L) component based on the helical structure of the coil, a capacitance (C) component, and a resistance (R) component, and an LCR of ˜50 μm and a coil length of 10 nm to 10 mm. to act as a resonant circuit, the three components of deformation of the coil-like carbon fiber length or medium when the pressure applied to the medium By converting the focus variation, and detects the change in pressure.

A pressure sensor according to a second aspect of the present invention is the pressure sensor according to the first aspect, wherein the coiled carbon fiber has a crystallized graphite layer .

A pressure sensor according to a third aspect of the present invention is the pressure sensor according to the first or second aspect, wherein the sensor elements are dispersed in the medium while being oriented in the same direction .
A pressure sensor according to a fourth aspect of the present invention is the pressure sensor according to any one of the first to third aspects, wherein the sensor elements are each composed of coiled carbon fibers having different inherent frequencies. It is what.
A pressure sensor according to a fifth aspect of the present invention is the pressure sensor according to any one of the first to fourth aspects, wherein the piezoelectric powder is dispersed in the medium.
A pressure sensor according to a sixth aspect of the present invention is the pressure sensor according to any one of the first to fifth aspects, wherein the coiled carbon fiber is amorphous in order to improve the detection accuracy of the sensor element. The carbon grains forming the carbon fibers in the graphite layer crystallized by subjecting the carbon fibers to heat treatment at 1500 to 3000 ° C. are regularly arranged.

The present invention has the following effects.
According to the pressure sensor of the first aspect of the invention, the configuration is simple and the sensitivity can be easily adjusted. In addition, the pressure sensor can be reduced in size.

According to the pressure sensor of the invention according to claim 2-4, it is possible to improve the sensitivity.

According to the pressure sensor of the fifth aspect of the invention, the output of the sensor element acting as the LCR resonance circuit can be stabilized by dispersing the piezoelectric powder in the medium.
According to the pressure sensor of the invention described in claim 6, the coiled carbon fiber has an electric resistance generated when the carbon particles forming the carbon fiber are regularly arranged in the graphite layer and exposed to a variable magnetic field or the like. Since the fluctuation becomes remarkable, the resonance characteristic becomes remarkable. Furthermore, when the sensor element acts as an LCR resonance circuit, fluctuations in the R component and the like in the LCR resonance circuit become significant. For this reason, the sensitivity of the pressure sensor can be improved by improving the detection accuracy of the sensor element.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the sensor 11 according to the first embodiment includes a medium 12, a plurality of sensor elements 13 dispersed in the medium 12, and a pair of electrodes 14 electrically connected to the medium 12. It is composed of For example, the sensor 11 disperses 3 to 5% by mass of the sensor element 13 in the heated melt of acrylic resin as the medium 12 with respect to the total amount of the heated melt and the sensor element 13, and then cools the heated melt The pair of electrodes 14 is attached to the solidified acrylic resin. A measuring instrument such as a power source and a voltmeter (not shown) is attached to the pair of electrodes 14 via a conductive wire 15, and a current is passed from the power source to the medium 12 via the electrode 14. Fluctuations and the like are detected.

  The medium 12 mechanically connects the sensor elements 13 distributed to each other, and electrically connects the sensor elements 13 to each other, the electrodes 14, and the sensor elements 13. The medium 12 is not particularly limited as long as it has lower conductivity than the coil 13a constituting the sensor element 13, and may be any of solid, liquid, gas, or vacuum. Specific examples of solids include synthetic resin materials such as acrylic resins, non-conductive magnetic materials such as ferrite, ceramic materials such as silica (silicon dioxide), natural rubber, etc., and liquids include oils and gases. For example, air is used. These may form the medium 12 alone, or two or more may be combined to form the medium 12.

  Here, the medium 12 existing between the sensor elements 13 dispersed in the medium 12 has a mass and acts as a mass point in the spring mass point system. For this reason, the sensor elements 13 are mechanically connected to each other as shown in FIG. 4A, FIG. 5A and FIG. The sensor elements 13 are connected to each other via a medium 12 which exists between them and acts as a mass point 17. On the other hand, when the sensor elements 13 are electrically connected to each other and the electrodes 14 and the sensor elements 13 are electrically connected to each other through the medium 12 existing between the sensor elements 13. In other words, the sensor elements 13, the electrodes 14, and the sensor elements 13 are connected to each other so as to flow through the sensor elements 13.

  The medium 12 is preferably formed of a dielectric and having a capacitance (C) component when the sensor element 13 functions as an LCR resonance circuit. Specific examples of the medium 12 formed of a dielectric and having a C component include a synthetic resin material mixed with ferrite. In this case, the medium 12 existing between the sensor elements 13 acts as a capacitor together with the coil 13a constituting the sensor element 13 and having a function as a C component, so that the electrostatic capacitance of the capacitor in the LCR resonance circuit is obtained. The capacity can be increased. For this reason, the adjustment range of the capacitance of the LCR resonance circuit can be increased. Here, the C component is a capacitance and shows a dielectric characteristic with respect to an electric field.

  Furthermore, when the sensor 11 is used as a pressure sensor, a tactile sensor, a displacement sensor, or the like, it is more preferable that the medium 12 is solid because the strength of the sensor 11 can be improved. On the other hand, when the sensor 11 is used as an acceleration sensor, an odor sensor, a taste sensor, a gas sensor, or the like, the medium 12 is more preferably a liquid or a gas in order to facilitate the fluctuation of the sensor element 13 acting as a minute spring. . In addition, when the sensor 11 is used as an optical sensor, an electromagnetic wave sensor, a magnetic sensor, or the like, the medium 12 is generally a solid, liquid, or gas.

  The sensor element 13 includes a coil 13a formed of a conductive material, and specific examples of the conductive material include a metal material such as copper, a polymer material such as polyacetylene, and a carbon material. The sensor element 13 is preferably composed of a coil 13a formed of a carbon material among the coils 13a formed of the above material, that is, a coiled carbon fiber. In this case, the sensitivity of the sensor 11 can be improved by high conductivity and improved detection accuracy.

  The coiled carbon fiber has either a single helical structure in which a single carbon fiber forms a helical structure, or a multiple helical structure in which two or more carbon fibers each form a helical structure in the same winding direction. is doing. In addition, the winding direction of the carbon fiber includes a clockwise direction (right-handed) and a counterclockwise direction (left-handed) around the axis of the coil. Each has a left-handed form.

  This coiled carbon fiber has electrical conductivity, thermal conductivity, adsorptivity, surface activity, and biological activity, and acts as a microspring by expanding and contracting itself. Furthermore, the coiled carbon fiber has a resonance characteristic in which an induced electromotive force is generated according to Faraday's law when exposed to a varying magnetic field or the like.

  The coiled carbon fiber may be composed of amorphous carbon fiber, but preferably has a graphite layer crystallized by subjecting the amorphous carbon fiber to heat treatment. In this case, the coiled carbon fiber resonates because the variation in electric resistance that occurs when the carbon particles forming the carbon fiber in the graphite layer are regularly arranged is exposed to a varying magnetic field. The characteristic becomes remarkable. Further, when the sensor element 13 acts as an LCR resonance circuit, the fluctuation of the R component or the like in the LCR resonance circuit becomes significant. For this reason, the sensitivity of the sensor 11 can be improved by improving the detection accuracy of the sensor element 13. Here, the heat treatment temperature is preferably 1500 to 3000 ° C. When the heat treatment temperature is less than 1500 ° C., the crystallization of the carbon fiber becomes insufficient, and even when it exceeds 3000 ° C., it cannot be further crystallized.

  The coiled carbon fiber may be manufactured by any manufacturing method, but a coiled carbon fiber manufactured by a vapor phase growth method such as a catalyst activated CVD (chemical vapor deposition) method is used. This is preferable because the coil diameter and coil length can be easily set within a predetermined range. In this vapor phase growth method, a hydrocarbon such as acetylene or carbon monoxide as a carbon material is heated to 600 to 3000 ° C. in the presence of a metal catalyst, and the hydrocarbon or carbon monoxide is decomposed in the gas phase. is there. Most of the coiled carbon fibers obtained by this vapor deposition method are formed in a state where fine carbon particles are packed up to the center of the carbon fibers, and some of them are also observed to be hollow. Is done.

  The coil 13a constituting the sensor element 13 acts as a micro spring and has resonance characteristics, like the coiled carbon fiber. Here, the coil 13a has a specific frequency, and when the coil 13a receives an electromagnetic wave having the same frequency as this frequency, the amplitude is amplified by tuning these frequencies, and the coil 13a has a different frequency from the specific frequency. A higher induced electromotive force is generated than when receiving electromagnetic waves of a frequency.

  Therefore, the sensor elements 13 each having a unique frequency may be dispersed in the medium 12, or each sensor element having a unique frequency constituted by the same coil 13 a. 13 may be dispersed. When the sensor elements 13 each composed of coils 13a having different intrinsic frequencies are dispersed in the medium 12, the sensor element 13 can generate a high induced electromotive force with respect to electromagnetic waves having different frequencies. On the other hand, when each sensor element 13 configured by the coils 13a having the same specific frequency is dispersed in the medium 12, the sensor element 13 generates a higher induced electromotive force with respect to the electromagnetic wave having a specific frequency. Can do.

  As shown in FIGS. 2A and 2B, the sensor element has an inductance (L) component 18 based on the helical structure of the coil 13a, a C component 19 and a resistance (R) component 20, and the sensor element. Those that themselves act as the LCR resonance circuit 21 are preferable. In this case, when the coil length or the like of the sensor element varies due to expansion / contraction of the coil 13a, the magnitudes of the L component 18, the C component 19 and the R component 20 of the sensor element are varied due to the variation of the coil length or the like. Each varies.

  For this reason, the sensor element 13 converts the fluctuations of the coil length and the like due to the expansion and contraction into electromagnetic fluctuations by converting the fluctuations of the L component 18, the C component 19 and the R component 20 of the LCR resonance circuit 21. Can be converted to Here, the L component 18 is a self-induction coefficient or a mutual induction coefficient, and indicates electromagnetic induction characteristics. On the other hand, the R component 20 is an electrical resistance and exhibits conductive characteristics.

  The coil diameter of the coil 13a constituting the sensor element 13 is preferably 1 nm to 50 μm, and the coil length is preferably 10 nm to 10 mm. If the coil diameter is less than 1 nm, it is difficult to manufacture the coil 13a. Further, when the coil length is less than 10 nm, the coil length is short, so that the function as the L component cannot be sufficiently exhibited when the sensor element 13 acts as the LCR resonance circuit 21. On the other hand, when the coil diameter exceeds 50 μm or the coil length exceeds 10 mm, the sensor element 13 becomes large, so that it is difficult to reduce the size of the sensor 11. Further, the fiber diameter of the coil 13a, that is, the diameter of the coil-shaped fiber is preferably 1 nm to 10 μm. If the fiber diameter is less than 1 nm, it is difficult to manufacture the coil 13a. Further, if the fiber diameter exceeds 10 μm, it is difficult to make the coil diameter within the above range. Here, the concept of the fiber diameter is not limited to the diameter of the fiber formed in a circular cross section, but the length of the long side (long diameter) of the fiber formed in an elliptical cross section, or the fiber formed in a square cross section Including long side length.

  As shown in FIG. 1, the sensor element 13 may be randomly dispersed in the medium 12 by, for example, mixing the sensor element 13 with the liquid medium 12 and then stirring and solidifying the medium 12. Further, as shown in FIG. 3A, for example, by applying a magnetic field in which magnetic lines of force extend in one direction after a plurality of sensor elements 13 are dispersed in a liquid medium 12, the entire sensor element 13 is made parallel to the magnetic lines of force. Each is oriented as desired. Then, by solidifying the medium 12, the sensor elements 13 may be dispersed in the medium 12 in a state of being oriented in the same direction.

  In addition, as shown in FIG. 3B, for example, a liquid medium 12 is first filled in a mold (not shown) to about one third of the volume of the mold, and then the sensor element 13 is dispersed in the medium 12. In the same manner as described above, the medium 12 is solidified with the sensor elements 13 oriented in the same direction. Next, by repeating the same operation as described above, the sensor elements 13 may be dispersed in the medium 12 so as to form a lattice shape.

  When the sensor elements 13 are randomly distributed, as shown in FIG. 4A, each sensor element 13 is in a randomly distributed state, and the medium 12 existing between the sensor elements 13 is pointed as a mass. 17 are connected to each other through the respective mass points 17 and configured as a mechanical mechanical equivalent circuit 22 of a composite spring mass point system. Further, as shown in FIG. 4B, when the coil 13a constituting the sensor element 13 acts as an LCR resonance circuit 21 and the medium 12 is formed of a dielectric and has a C component 19, the mutual connection between the sensor elements 13 The medium 12 present in the acts as a capacitor. The sensor elements 13 are connected to each other via a medium 12 existing between the sensor elements 13 in a randomly distributed state, and are configured as an electrical equivalent circuit 23 that is a composite resonance circuit. . Here, FIGS. 4A and 4B respectively show the equivalent circuits in FIG.

  On the other hand, when all of the sensor elements 13 are dispersed in a state of being oriented in the same direction, or when the sensor elements 13 are dispersed so as to form a lattice shape, as shown in FIGS. 5 (a) to 6 (b). Each sensor element 13 is configured as a mechanical mechanical equivalent circuit 22 and an electrical equivalent circuit 23 having a lattice shape in the same manner as described above. For this reason, as shown in FIG. 7, the sensor elements dispersed in the medium 12 can function as one LCR resonance circuit 21 by collecting all the sensor elements in an electrical equivalent circuit. 5A and 5B show the equivalent circuit in FIG. 3A, respectively, and FIGS. 6A and 6B show the equivalent circuit in FIG. 3B, respectively.

  The sensor 11 of the first embodiment includes an acceleration sensor, a pressure sensor, a strain sensor, a temperature sensor, a humidity sensor, an electromagnetic wave sensor, a radio wave sensor, an optical sensor, a gas sensor, an electric field sensor, a magnetic field sensor, an odor sensor, a tactile sensor, and a fine vibration sensor. , Position sensor, taste sensor, micro-earthquake / crustal movement sensor, infrared sensor, fluctuation sensor, destruction detection sensor, angular velocity sensor, polarization sensor, ultrasonic sensor, flow sensor, highly directional electromagnetic wave sensor, thermal energy sensor, weak Used as an electromagnetic sensor or the like.

  For example, when using the sensor 11 in which the sensor element 13 acting as the LCR resonance circuit 21 is randomly dispersed in the medium 12 as an electromagnetic wave sensor, first, a power source and a voltmeter are attached to the electrode 14 via the conductor 15. The sensor 11 is disposed in the air. Here, the medium 12 is formed of a synthetic resin material in which ferrite is mixed. Subsequently, a constant alternating current is always supplied to the medium 12 by the power source. The frequency of the alternating current is, for example, 10 kHz to 1 MHz, and the waveform is not particularly limited, and may be a sine wave or a rectangular wave.

  At this time, a magnetic field is generated in each sensor element 13 when a current is applied. When a part of the sensor 11 receives an electromagnetic wave, the strength of the magnetic field of the sensor element 13 at the location where the electromagnetic wave is received in the sensor element 13 dispersed in the medium 12 varies due to the influence of the electromagnetic wave. Since a constant current flows through the sensor element 13, the voltage and electric resistance in the sensor element 13 vary due to the variation in the strength of the magnetic field, and the voltage variation can be detected by a voltmeter. For this reason, electromagnetic waves can be detected by the sensor 11.

  On the other hand, when this sensor 11 is used as, for example, a pressure sensor, first, a power source and an oscilloscope are attached to the electrode 14 via the lead wire 15 and then the medium 12 is energized in the same manner as described above. Here, the sensor elements 13 dispersed in the medium 12 are configured as shown in the equivalent circuits of FIGS. 4 (a) and 4 (b). When the pressure applied to the sensor 11 in a part of the sensor 11 changes, or when pressure is applied, in the mechanical mechanical equivalent circuit 22 of the composite spring mass point system, at the location where the pressure is changed or the location where the pressure is applied. The length of the microspring 16 varies due to a change in pressure or the like. Alternatively, the mass point 17 at the place where the pressure is changed or the place where the pressure is applied fluctuates due to a decrease in the volume of the medium 12 existing between the sensor elements 13 due to a change in pressure or the like.

  At this time, since the sensor element 13 also functions as the LCR resonance circuit 21, the variation of the length of the microspring 16 and the variation of the mass point 17 are converted into a comprehensive variation of the L component 18, the C component 19 and the R component 20. It can be converted to electromagnetic fluctuations. For this reason, the voltage of the LCR resonance circuit 21 fluctuates, and the fluctuation of the voltage or the like can be detected by the oscilloscope. Therefore, a change in pressure can be detected by the sensor 11. Furthermore, by changing the coil length of the coil 13 a constituting the sensor element 13, the length of the microspring 16 in the mechanical mechanical equivalent circuit 22 can be easily changed, and in the LCR resonance circuit 21. The size of the L component 18 and the like can be easily changed. For this reason, the sensitivity of the sensor element 13 can be easily adjusted only by changing the coil length of the coil 13a constituting the sensor element 13.

According to the embodiment described in detail above, the following effects are exhibited.
-The sensor element 13 which comprises the sensor 11 of 1st Embodiment is comprised by the coil 13a formed of the material which has electroconductivity. For this reason, the structure of the sensor 11 can be simplified by simplifying the structure of the sensor element 13 as compared with the conventional sensor. Furthermore, the sensor 11 can easily change the length of the microspring 16 in the mechanical mechanical equivalent circuit 22 by changing the coil length of the coil 13 a constituting the sensor element 13. Can be easily adjusted. For this reason, the sensitivity of the sensor 11 can be easily adjusted compared with the conventional sensor.

  The sensor element 13 preferably has an L component 18, a C component 19, and an R component 20, and functions as an LCR resonance circuit 21. In this case, the sensor element 13 can convert the length of the micro spring 16 and the variation of the mass point 17 in the mechanical mechanical equivalent circuit 22 into a total variation of the L component 18, the C component 19, and the R component 20. . For this reason, the sensitivity of the sensor 11 can be improved compared with the case where the fluctuation | variation of L component 18, C component 19, or R component 20 is each detected.

  When the sensor element 13 acts as the LCR resonance circuit 21, the medium 12 is preferably formed of a dielectric and has a C component 19. In this case, the medium 12 existing between the sensor elements 13 acts as a capacitor together with the coil 13 a constituting the sensor element 13, thereby increasing the adjustment range of the capacitance of the LCR resonance circuit 21. be able to. For this reason, the sensitivity of the sensor 11 can be adjusted more easily.

  -Carbon material is preferable as the conductive material. In this case, the sensitivity of the sensor 11 can be improved by improving the detection accuracy by configuring the sensor element 13 with the coiled carbon fiber.

  The coil diameter of the coil 13a constituting the sensor element 13 is preferably 1 nm to 50 μm, and the coil length is preferably 10 nm to 10 mm. In this case, since the sensor element 13 is small, the size of the sensor 11 can be reduced.

  -The coiled carbon fiber preferably has a graphite layer. In this case, the resonance characteristics of the coiled carbon fiber and the fluctuation of each component in the LCR resonance circuit 21 can be made remarkable, so that the sensitivity of the sensor 11 can be further improved.

  It is preferable to disperse the sensor elements 13 each composed of coils 13 a having different natural frequencies in the medium 12. In this case, for example, when the sensor 11 is used as an electromagnetic wave sensor, a high induced electromotive force can be generated for electromagnetic waves having different frequencies, and the sensitivity of the sensor 11 can be further improved.

(Second Embodiment)
Hereinafter, the second embodiment of the present invention will be described in detail. Note that the second embodiment will be described with a focus on differences from the first embodiment.

  The sensor 11 according to the second embodiment includes a medium 12, a plurality of sensor elements 13 dispersed in the medium 12, and the electrode 14 electrically connected to the medium 12. The medium 12 is not particularly limited as long as it has a conductivity lower than that of the conductive fiber constituting the sensor element 13, and may be any of solid, liquid, gas, and vacuum. Examples of the solid medium 12 include elastic resins such as silicone resins and urethane resins. Specific examples of liquid and gas are the same as those in the first embodiment. These may constitute the medium 12 alone, or two or more may be combined to form the medium 12.

  The sensor element 13 is made of a conductive fiber. This conductive fiber is formed of a conductive material. Specific examples of the conductive material include metal materials such as copper and silver, alloy materials such as titanium carbide (TiC), titanium nitride (TiN), and zinc oxide (ZnO), carbon Examples thereof include polymer materials such as materials and polyacetylene. Examples of the fiber shape of the conductive fiber include a linear shape, a coil shape, and a cylindrical shape.

  The manufacturing method of this conductive fiber is not specifically limited, The said vapor phase growth method etc. are mentioned. Specific examples of the conductive fiber include the coiled carbon fiber, carbon nanotube, VGCF (vapor-grown carbon fiber), carbon fiber such as PAN-based carbon fiber and pitch-based carbon fiber, and conductive whisker. These may constitute the sensor element 13 alone, or two or more types may be combined to constitute the sensor element 13.

  The conductive fiber has an L component 18, a C component 19, and an R component 20, and acts as an LCR resonance circuit and has elasticity. That is, the conductive fiber bends easily, for example, when stress is applied from the outside, and the bending causes distortion inside to change the R component 20 and also the positional relationship with the medium 12 as compared to before bending. The reactance components (L component 18 and C component 19) change due to the difference.

  The conductive fiber preferably has a fiber diameter of 1 nm to 10 μm, a fiber diameter of preferably 1 nm to 50 μm, and a fiber length of preferably 10 nm to 10 mm. Here, the fiber diameter indicates the diameter of the conductive fiber when the fiber shape is linear, indicates the diameter of the fiber forming the coil shape when the conductive fiber is in a coil shape, and indicates the thickness of the peripheral wall when it is cylindrical. Further, the fiber diameter indicates the diameter when the fiber shape is linear, indicates the coil diameter when the fiber shape is coiled, and indicates the diameter of the outer periphery in the cross section when the fiber shape is cylindrical. In addition, the concept of the diameter of the fiber is not limited to the diameter of the fiber formed in a circular cross section, the length of the long side (long diameter) of the fiber formed in an elliptical cross section, or the fiber formed in a square cross section Including the length of the long side. The fiber length indicates the coil length when the fiber shape is coiled.

  If the fiber diameter or the fiber diameter is less than 1 nm, the change in the R component when the conductive fiber is bent may be small. Moreover, if the fiber length is less than 10 nm, the conductive fiber cannot be bent sufficiently. On the other hand, when the fiber diameter exceeds 10 μm, the fiber diameter exceeds 50 μm, or the fiber length exceeds 10 mm, it takes time to manufacture the conductive fiber, which may reduce the manufacturing efficiency. Furthermore, since the sensor element 13 made of conductive fibers is large, it is difficult to reduce the size of the sensor 11.

  The conductive fiber preferably has an aspect ratio obtained by dividing the fiber length by the fiber diameter from 2 to 10,000, more preferably from 100 to 1,000, and most preferably from 200 to 800. If the aspect ratio is less than 2, the conductive fibers cannot be bent sufficiently. Conversely, if the aspect ratio exceeds 10,000, the conductive fibers become excessively long and the production efficiency is lowered, and the sensor 11 is difficult to downsize. .

  Therefore, also in the sensor 11 of the second embodiment, since the sensor element 13 is composed of conductive fibers, the configuration of the sensor element 13 can be simplified and the configuration of the sensor 11 can be simplified compared to the conventional sensor. can do. Furthermore, the sensitivity of the sensor 11 can be easily adjusted by changing the fiber length of the conductive fibers constituting the sensor element 13.

In addition, the said embodiment can also be changed and comprised as follows.
In each of the embodiments, the sensor 11 may be used as an energy conversion element, a remote power feeding element, a micro antenna, or the like.

  In the first embodiment, when the sensor element 13 in which the sensor element 13 is made of a coiled carbon fiber is used as a humidity sensor or a gas sensor, the surface of the coiled carbon fiber has moisture absorption / release properties such as silica gel or gas absorption. A substance having a releasing property may be coated. At this time, the medium 12 is preferably a gas such as air. Alternatively, a conductive material such as copper, an insulating material such as silica or titania (titanium oxide), a magnetic material such as ferrite, or the like may be coated.

  When the surface of the coiled carbon fiber is coated with a material having moisture absorption / release properties such as silica gel, the mechanical mechanics accompanies the moisture absorption / desorption or gas absorption / release of the silica gel coated on the surface of the coiled carbon fiber. The length of the microspring 16 in the static equivalent circuit 22 can be varied. Furthermore, the electrical resistance in the LCR resonance circuit 21, that is, the magnitude of the R component 20 varies with the absorption / release of silica gel or the like, and the magnitudes of the L component 18 and the C component 19 also vary. For this reason, the displacement of the length of the minute spring 16 can be converted into an electromagnetic fluctuation, and the L component 18, the C component 19 and the R component 20 in the LCR resonance circuit 21 can fluctuate comprehensively. Therefore, changes in humidity and gas concentration can be detected by the sensor 11. Similarly, in the second embodiment, the surface of conductive fibers constituting the sensor element 13 may be coated with the substance.

In each of the above embodiments, only one sensor element 13 may be provided in the medium 12.
In each of the above embodiments, the sensor element 13 may be oriented by applying an electric field after the sensor element 13 is buried in the liquid medium 12.

In each of the above embodiments, the piezoelectric powder may be dispersed in the medium 12. Specific examples of the piezoelectric powder include ferrite, titanium oxide (TiO ₂ ), lead zirconate (PbZrO ₃ ), lead titanate (PbTiO ₃ ), lead zirconate titanate (PbZrTiO ₃ ), and barium titanate (BaTiO ₃ ). Etc. At this time, the output of the sensor element 13 acting as an LCR resonance circuit can be stabilized by dispersing the piezoelectric powder in the medium 12.

Sectional drawing which shows the sensor of 1st Embodiment. (A) And (b) is a circuit diagram which shows an LCR resonance circuit. (A) And (b) is sectional drawing which shows the sensor element disperse | distributed in the medium. (A) is a circuit diagram which shows a mechanical mechanical equivalent circuit, (b) is a circuit diagram which shows an electrical equivalent circuit. (A) is sectional drawing which shows a mechanical mechanical equivalent circuit, (b) is sectional drawing which shows an electrical equivalent circuit. (A) is sectional drawing which shows a mechanical mechanical equivalent circuit, (b) is sectional drawing which shows an electrical equivalent circuit. Sectional drawing which shows a LCR resonance circuit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Sensor, 12 ... Medium, 13 ... Sensor element, 13a ... Coil, 14 ... Electrode, 18 ... Inductance (L) component, 19 ... Capacitance (C) component, 20 ... Resistance (R) component, 21 ... LCR resonance circuit .

Claims (6)

In a pressure sensor comprising a medium, a plurality of sensor elements that are configured by a coiled carbon fiber having conductivity and provided in the medium, and a pair of electrodes that are electrically connected to the medium ,
The medium is formed of a dielectric and has a capacitance (C) component;
The coiled carbon fiber has a coil diameter of 1 nm to 50 μm and a coil length of 10 nm to 10 mm,
The sensor element has an inductance (L) component based on a helical structure of a coil, a capacitance (C) component, and a resistance (R) component, and acts as an LCR resonance circuit. Therefore, when pressure is applied to the medium A pressure sensor for detecting a change in pressure by converting the length of the coiled carbon fiber and the deformation of the medium into a comprehensive variation of the three components . The pressure sensor according to claim 1, wherein the coiled carbon fiber has a crystallized graphite layer. The pressure sensor according to claim 1, wherein the sensor elements are dispersed in the medium in a state of being oriented in the same direction. The pressure sensor according to any one of claims 1 to 3, wherein each of the sensor elements is formed of coiled carbon fibers having different intrinsic frequencies. The pressure sensor according to any one of claims 1 to 4, wherein piezoelectric powder is dispersed in the medium. In order to improve the detection accuracy of the sensor element, the coiled carbon fiber has carbon grains forming carbon fibers in a graphite layer crystallized by subjecting amorphous carbon fiber to heat treatment at 1500 to 3000 ° C. The pressure sensor according to any one of claims 1 to 5, wherein the pressure sensors are regularly arranged.

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