JP4587317B2 - Proximity sensor and proximity / contact sensor - Google Patents

Description

  The present invention relates to an approach sensor and an approach / contact sensor that can detect that a part of an object such as a human body has approached.

  In recent years, there has been a demand for a technique that equips a surgical instrument or the like with a proximity sensor, detects that the surgical instrument has approached the human body, and prevents the surgical instrument from contacting the human body. As such a proximity sensor, for example, a proximity sensor having a detection plate made of a pair of electrodes and detecting the approach of a human body as a change in capacitance of the detection plate is known (see, for example, Patent Document 1). That is, the proximity sensor detects the phase difference between the oscillation circuit that generates the measurement signal of the predetermined frequency, the VSWR bridge circuit connected to the oscillation circuit, and the output signal of the bridge circuit and the measurement signal from the oscillation circuit. A phase comparison circuit and control means for determining whether or not a human body is approaching based on the output of the phase comparison circuit are provided.

As another proximity sensor, a sensor composed of a capacitive proximity sensor section and a conductor whose thickness and surface resistance are set in a predetermined range is known (for example, see Patent Document 2). In this proximity sensor, the detection range can be expanded without increasing the area of the sensor unit by setting the area ratio of the conductor and the capacitive proximity sensor unit to 2 or more.
JP 2001-203565 A (second page and third page) JP 2004-150869 A (pages 2 and 4)

  However, the conventional proximity sensors described in Patent Documents 1 and 2 have a capacitance (capacitance) generated between the detection object and the detection plate or the capacitive proximity sensor unit as the detection object approaches. ) Is detected by a detection plate or a capacitive proximity sensor. As described above, when detecting based only on the change in capacitance, there is a problem that the change in capacitance becomes minute and the detection sensitivity becomes low when the approach speed of the detection target is slow. . In addition, if the change in capacitance becomes small, it becomes difficult to detect the change in capacitance due to noise or the like, and it becomes impossible to detect in a stable state. Furthermore, the conventional proximity sensor cannot perform quantitative detection such as the approach speed, and has a problem that the type of the detection target cannot be distinguished.

  The present invention has been made paying attention to such problems existing in the prior art. The purpose is to detect the approach of the detection object with high detection sensitivity and in a stable state, as well as quantitative detection of the approach speed and the type of the detection object. It is an object of the present invention to provide a proximity sensor and a proximity / contact sensor that can distinguish between the two.

  In order to achieve the above object, the proximity sensor according to claim 1 has an inductance (L) component, a capacitance (C) component, and a resistance (R) component based on a coil shape, and serves as an LCR resonance circuit. A functional coiled carbon fiber is dispersed in a base material to form a sensor element, and a pair of electrodes electrically connected to the sensor element are provided, a high-frequency oscillation circuit is connected between both electrodes, and A detection circuit for detecting a signal that changes based on the LCR resonance circuit is connected.

  The proximity sensor according to a second aspect of the invention is characterized in that, in the first aspect of the invention, the content of the coiled carbon fiber in the base material is 1 to 20% by mass. .

  A proximity sensor according to a third aspect of the present invention is the proximity sensor according to the first or second aspect, wherein the frequency of the high-frequency signal by the high-frequency oscillation circuit is 100 to 800 kHz.

A proximity sensor according to a fourth aspect of the present invention is the proximity sensor according to any one of the first to third aspects, wherein the base material is an elastic polymer.
A proximity sensor according to a fifth aspect of the present invention is the proximity sensor according to any one of the first to fourth aspects, wherein the detection target is a living body and is used to detect the approach of the living body. It is a feature.

  According to a sixth aspect of the present invention, in the proximity / contact sensor according to any one of the first to fifth aspects, when the detection object contacts the sensor element of the proximity sensor, the detection circuit is coiled carbon. It is configured to detect a signal that changes based on the LCR resonance circuit of the fiber.

According to the present invention, the following effects can be exhibited.
In the proximity sensor according to the first aspect of the present invention, the sensor element is configured by dispersing the coiled carbon fiber in the base material. The coiled carbon fiber has an inductance (L) component, a capacitance (C) component, and a resistance (R) component based on the coil shape, and functions as an LCR resonance circuit. A pair of electrodes are electrically connected to the sensor element, a high-frequency oscillation circuit is connected between the electrodes, and a detection circuit that detects a signal that changes based on the LCR resonance circuit is connected. For this reason, when the detection object approaches the proximity sensor, the impedance changes based on changes in the inductance (L) component, capacitance (C) component, and resistance (R) component of the coiled carbon fiber, and the detection circuit Changes based on impedance can be detected. Therefore, compared with the case where it detects based only on the conventional capacitance, the detection sensitivity can be detected in a stable state with respect to the approach of the detection object.

  Furthermore, it is possible to quantitatively detect the approach speed by the continuous change of the output signal based on the continuous change of the impedance due to the approach of the detection target to the sensor element, and to distinguish the type of the detection target Can do.

  In the proximity sensor of the invention according to claim 2, since the content of the coiled carbon fiber in the base material is set to 1 to 20% by mass, the effect of the invention according to claim 1 is sufficiently exhibited. be able to.

  In the proximity sensor according to the third aspect of the invention, since the frequency of the high-frequency signal by the high-frequency oscillation circuit is 100 to 800 kHz, the effect of the invention according to the first or second aspect can be effectively exhibited.

  In the proximity sensor of the invention according to claim 4, since the base material is a polymer having elasticity, in addition to the effect of the invention according to any one of claims 1 to 3, the object to be detected is the proximity sensor. It functions as a contact sensor when it touches, and damage to the detection object or the proximity sensor can be suppressed.

  In the proximity sensor according to the fifth aspect of the invention, the detection target is a living body, and is used for detecting the approach of the living body. For this reason, in addition to the effect of the invention according to any one of claims 1 to 4, the detection sensitivity can be increased by the charge on the surface of the living body, and the approach of the living body can be accurately detected.

  In the proximity / contact sensor according to claim 6, when a detection target object contacts the sensor element of the proximity sensor, the detection circuit detects a signal that changes based on the LCR resonance circuit of the coiled carbon fiber. It is configured as follows. For this reason, the proximity / contact sensor can obtain an effect as a proximity sensor when the detection object approaches the sensor element, and can obtain an effect as a contact sensor when the detection object contacts the sensor element. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments that are considered to be the best of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the sensor element 11 constituting the proximity sensor 10 is formed by dispersing a coiled carbon fiber 12 in a base material 13 having a plate shape, and a pair of electrodes 14 is formed on the bottom surface of the sensor element 11. Are electrically connected. The pair of electrodes 14 is formed of a copper plate or the like, and a detection circuit 16 is connected between the electrodes 14 via a first connection line 15. A display device 18 such as an oscilloscope for displaying on the screen the waveform of the output signal detected by the detection circuit 16 is connected to the detection circuit 16 via the second connection line 17. The electrical connection means that a current passed from the electrode 14 to the base material 13 flows from the electrode 14 through the base material 13 to the coiled carbon fiber 12 or between the coiled carbon fibers 12. To do.

  An equivalent circuit of the sensor element 11 is shown in FIG. As shown in FIG. 2, the coiled carbon fiber 12 is based on its coil shape (spiral shape), and has an intrinsic inductance (L) component, capacitance (C) component, and resistance (R) component (hereinafter referred to as electromagnetic characteristics). , L component, C component, R component, or collectively referred to as LCR component). Furthermore, a number of coiled carbon fibers 12 are connected via a C component by the base material 13. For this reason, the coiled carbon fiber 12 forms an LCR resonance circuit based on the LCR component and forms a complex resonance circuit with the base material 13 including a large number of coiled carbon fibers 12.

  Next, the electrical circuit of the proximity sensor 10 will be described in detail with reference to FIG. As shown in FIG. 3, the detection circuit 16 includes a high-frequency oscillation circuit (AC circuit) 19 that applies a high-frequency signal to the sensor element 11, an amplification circuit 20 that amplifies an output signal from the sensor element 11, and an amplification circuit 20. And a detection circuit 22 and an output circuit 23 to which a signal from the high-frequency oscillation circuit 19 via the phase adjustment circuit 21 is input. The detection circuit 22 obtains an output signal by comparing the signal from the amplifier circuit 20 with the signal from the high-frequency oscillation circuit 19.

  The sensor element 11 has a specific impedance, and the detection object 24 also has a specific impedance. Since a high frequency signal having a predetermined frequency is applied to the sensor element 11 from the high frequency oscillation circuit 19, an alternating electric field is generated in the vicinity of the sensor element 11. Since the sensor element 11 has a capacitance (C) component between the sensor element 11 and the detection target object 24 in addition to the capacitance (C) component of the sensor element 11, the detection target object 24 has the sensor element 11. When both are close to each other, both the capacitance (C) components fluctuate as a whole. The overall impedance from the detection object 24 to the sensor element 11 changes due to such overall fluctuation. When the detection object 24 comes into contact with the sensor element 11, the entire resistance (R) component of the sensor element 11 and the detection object 24 changes, and the change reaches the sensor element 11 from the detection object 24. The overall impedance changes.

  Then, the amount of change in the overall impedance changes the voltage and phase of the high-frequency signal applied to the sensor element 11, and the amount of change is amplified by the amplifier circuit 20 and input to the detection circuit 22. By detecting together with the high-frequency signal input to the detection circuit 22 via the phase adjustment circuit 21, a continuous change in impedance due to the approach of the detection object 24 is detected. The obtained detection signal is sent to the output circuit 23 and is output from the output circuit 23 as, for example, a voltage. For example, as shown in FIG. 4, when the palm as the detection object 24 approaches the proximity sensor 10, the output voltage (V) increases as the distance (cm) between the palm and the proximity sensor 10 decreases, and the detection is performed. Sensitivity increases proportionally. Thus, the output signal shows a change inherent to the detection object 24.

  Therefore, by detecting in advance a unique change in the output signal for each detection object 24, it is possible to quantitatively detect the approach speed, distance, and the like of the detection object 24 with respect to the sensor element 11. Furthermore, by detecting in advance a unique change in the output signal for various detection objects 24, the types of detection objects 24 can be distinguished and recognized. For example, as the detection object 24, it is possible to distinguish between living things and inanimate objects, between metals and ceramics, and between metals and resins.

  Next, when the detection object 24 comes into contact with the sensor element 11 of the proximity sensor 10, the detection circuit 22 detects a signal that changes based on the LCR resonance circuit of the coiled carbon fiber 12 or the composite resonance circuit. The proximity sensor 10 functions as an proximity / contact sensor. In this case, a mechanical external force is applied to the sensor element 11, and the impedance based on the change in the LCR component of the coiled carbon fiber 12 or the change in the C component due to the change between the coiled carbon fibers 12 changes. The change amount is detected by the detection circuit 22.

  The base material 13 is a dispersion medium of the coiled carbon fiber 12 and has a capacitance (C) component as electromagnetic characteristics, and an elastic resin (an elastic polymer), a hard resin, or the like is used. Specifically, a silicone resin, a urethane resin, an epoxy resin, a copolymer resin of styrene and a thermoplastic elastomer, or the like is used as the base material 13. Examples of the silicone resin include trade names manufactured by Shin-Etsu Chemical Co., Ltd., KE103 (JIS A hardness 18), KE106 (JIS A hardness 50), KE1202 (JIS A hardness 65), and the like. Examples of the copolymer resin of styrene and thermoplastic elastomer include Kuraray's trade name, Septon resin # 4033 (JIS A hardness 76), # 8104 (JIS A hardness 98), and the like. As a urethane resin, trade name of Nippon Polyurethane Co., Ltd., Coronate 4387 and the like can be mentioned.

  The hardness of the base material 13 is also related to the sensitivity of the proximity sensor 10, but when a silicone resin or the like having excellent elasticity is used as the base material 13, the capacitance can be increased, and the sensor element 11 Sensitivity can be increased. On the other hand, when a hard silicone resin, urethane resin, septon resin, or the like is used, the capacitance is slightly reduced, so that the sensitivity of the sensor element 11 is lowered, but a wide detection range can be detected. Thus, since the base material 13 has a C component and functions as a capacitor, the capacitance of the capacitor can be increased together with the C component of the coiled carbon fiber 12. For this reason, the adjustment range of the capacitance in the LCR resonance circuit can be widened.

  Next, since the coiled carbon fiber 12 has a coil shape, a high-frequency signal flowing through the coiled carbon fiber 12 changes, and as described above, a resonant circuit using the L component, the C component, and the R component. Further, a large number of coiled carbon fibers 12 form a composite resonance circuit in the base material 13, and the impedance of the entire sensor element 11 changes. For this reason, the approach of the detection object 24 can be detected by the detection circuit 22 based on the amount of change in impedance. Here, the inductance (L) component is an induction coefficient, that is, a self-induction coefficient or a mutual induction coefficient, and is one of electromagnetic induction characteristics. The capacitance (C) component is a capacitance and represents a ratio of electric charge to electric potential (voltage) and is one of electromagnetic induction characteristics. The resistance (R) component is an electric resistance and is one of electromagnetic induction characteristics.

  As the coiled carbon fiber 12, a single coiled carbon fiber 12, a double coiled carbon fiber 12, a superelastic coil, or a mixture thereof is used. The single-winding coiled carbon fiber 12 is formed such that a coil made of a fiber having a constant wire diameter extends in a spiral manner with a single winding at a constant pitch (interval). The single-winding coiled carbon fiber 12 has, for example, a wire diameter of 0.1 to 1 μm, a coil diameter of 0.01 to 50 μm, a coil pitch of 0.01 to 10 μm, and a coil length of 0.1 to 0.1 μm. It is comprised so that it may be set to 10 mm. From the viewpoint of ease of manufacture and the like, the diameter of the coil is preferably 0.1 to 10 μm, and the pitch is preferably 0.1 to 10 μm.

  On the other hand, in the case of the double-wound coiled carbon fiber 12, the two coils extend in a spiral shape in close contact with each other, and thus have a substantially cylindrical shape as a whole, with a cavity formed at the center. . The double-winding coiled carbon fiber 12 is configured so that, for example, the wire diameter is 0.1 to 1 μm, the diameter is 0.01 to 50 μm, the pitch is approximately 0, and the length is 0.1 to 10 mm. .

  A superelastic coil is a coil having a large coil diameter and a small wire diameter, and having a higher elasticity. Specifically, the superelastic coil is configured such that the coil diameter is 5 to 50 μm, the coil pitch is 0.1 to 10 μm, and the coil length is 0.3 to 5 mm. The winding direction of the coiled carbon fiber 12 may be either clockwise (right-handed) or counterclockwise (left-handed) around the coil axis.

  The coiled carbon fiber 12 may be randomly oriented in the base material 13, but by aligning in a certain direction using an electric field or a magnetic field, the function of the LCR circuit can be highly expressed in that direction. The directivity which can be given can be given. The coiled carbon fiber 12 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 12 is resonated because the carbon particles forming the carbon fiber are regularly arranged in the graphite layer, so that the fluctuation of electric resistance that occurs when exposed to a fluctuating electromagnetic field becomes significant. The characteristic becomes remarkable. Therefore, the detection accuracy of the sensor element is improved and the sensitivity is improved.

  The content of the coiled carbon fiber 12 is preferably 1 to 20% by mass in the base material 13. When the content is less than 1% by mass, the ratio of the coiled carbon fiber 12 in the base material 13 is small, and the sensitivity of the proximity sensor 10 based on the coiled carbon fiber 12 is lowered. On the other hand, when the content exceeds 20% by mass, the ratio of the coiled carbon fiber 12 in the base material 13 becomes too large and becomes hard, the sensitivity of the sensor element 11 is lowered, and the moldability is also deteriorated. Show the trend.

As a method of dispersing the coiled carbon fiber 12 in the base material 13, the following method is employed.
(1) A method in which the coiled carbon fiber 12 is added to the base material 13 and stirred and dispersed uniformly, then defoamed, poured into a mold, and then press-molded. This method is suitable when a silicone resin is used as the base material 13.
(2) After adding a plasticizer to the pellets of the base material 13, the mixture is heated and melted, and the coiled carbon fiber 12 is added thereto, stirred and dispersed uniformly, then poured into a mold, pressurized, and cooled. How to solidify.
(3) A method in which the base material 13 is heated and melted, the coiled carbon fiber 12 is added thereto, and the mixture is stirred and dispersed uniformly, then poured into a mold, pressurized, cooled and solidified.

  The frequency of the high-frequency signal generated by the high-frequency oscillation circuit 19 can be used as long as it is in the range of 50 kHz to 1 MHz, but is preferably 100 to 800 kHz from the viewpoint of the sensitivity and stability of the sensor element 11. When this frequency is less than 50 kHz, the generation of noise increases and the detection stability is lacking. On the other hand, when the frequency exceeds 1 MHz, the output signal becomes weak and the sensitivity is lowered, which is not preferable.

  The detection object 24 of the proximity sensor 10 may be a living body such as the palm, or any metal, ceramics, resin, and the like. Among these, since the living body has a charge on its surface, the function of the LCR resonance circuit of the coiled carbon fiber 12 is enhanced when the living body approaches the sensor element 11, and the detection sensitivity of the proximity sensor 10 is increased. improves. Examples of the living body (or a part of the living body) include an arm, a face, and a leg in addition to the palm.

  Now, the operation of the present embodiment will be described. A high frequency signal is applied from the high frequency oscillation circuit 19 to the sensor element 11 of the proximity sensor 10, and in this state, the detection object 24 such as a part of the human body is detected by the sensor element 11. To approach. For this reason, the distance between the detection object 24 and the sensor element 11 each having a unique impedance becomes shorter as the detection object 24 approaches. At this time, each coiled carbon fiber 12 in the sensor element 11 has a unique L component, C component, and R component to form an LCR resonance circuit, and at the same time, many coiled carbon fibers 12 are in the base material 13. Since the composite resonance circuit is formed, the impedance of the entire sensor element 11 is changed by the resonance circuit.

  The impedance change of the sensor element 11 changes the high frequency signal (voltage, phase, etc.), the amount of change is amplified by the amplifier circuit 20, and the amplified signal is input to the detection circuit 22. Since the high-frequency signal input to the sensor element 11 is input to the detection circuit 22, the amplified signal is detected based on the high-frequency signal, and the obtained detection signal is sent to the output circuit. The output signal output from the output circuit 23 is displayed as a predetermined waveform on the screen of an oscilloscope as the display device 18 and can be visually recognized.

  Furthermore, when the approach speed and distance of the detection target 24 with respect to the sensor element 11 are changed by detecting in advance an output waveform (curve shape) due to a specific change of the output signal for the specific detection target 24 In addition, the approach speed and distance can be measured based on the output waveform. In addition, by detecting changes in the output waveform specific to various detection objects 24, for example, living things (palms) and inanimate objects (iron plates), either living things (palms) or inanimate objects (iron plates) can be detected. When approaching the sensor element 11, it is possible to distinguish and recognize which of the detection objects 24 is based on the unique output waveform.

The effects exhibited by the above embodiment will be described collectively below.
In the proximity sensor 10 of the embodiment, the sensor element 11 is configured by dispersing the coiled carbon fiber 12 in the base material 13. The coiled carbon fiber 12 has an L component, a C component, and an R component based on the coil shape and functions as an LCR resonance circuit and functions as a composite resonance circuit with the base material 13. A pair of electrodes 14 are electrically connected to the sensor element 11, and a high-frequency oscillation circuit 19 and a detection circuit 22 are connected between the electrodes 14.

  For this reason, when the detection object 24 approaches the sensor element 11 to which the high frequency signal is applied, the impedance of the sensor element 11 is changed by the action of the LCR resonance circuit and the composite resonance circuit, and the change of the high frequency signal due to the impedance change is changed. It can be detected by the detection circuit 22. Therefore, compared with the case where the detection is based only on the capacitance component as in the case of the conventional proximity sensor, the detection sensitivity of the approach of the detection object 24 is high and can be detected in a stable state.

  Furthermore, it is possible to perform quantitative detection such as the approach speed based on the continuous change in impedance due to the approach of the detection target 24 to the sensor element 11, and to distinguish the type of the detection target 24. Therefore, the proximity sensor 10 can be preferably used in fields such as medical devices such as surgical devices and robots.

-By setting the content of the coiled carbon fiber 12 in the base material 13 to 1 to 20% by mass, the effect of the proximity sensor 10 can be sufficiently exhibited.
The effect of the proximity sensor 10 can be effectively exhibited by setting the frequency of the high frequency signal by the high frequency oscillation circuit 19 in the range of 100 to 800 kHz.

  By using an elastic polymer such as an elastic silicone resin as the base material 13, the proximity sensor 10 can be used as the proximity / contact sensor when the detection object 24 comes into contact with the proximity sensor 10. At the same time, damage to the detection object 24 or the proximity sensor 10 can be suppressed.

When the detection object 24 is a living body, the detection sensitivity can be increased by the charge on the surface of the living body, and the approach of the living body can be detected with high accuracy.
In the proximity / contact sensor, when the detection object 24 contacts the sensor element 11 of the proximity sensor 10, the detection circuit 22 detects a signal that changes based on the LCR resonance circuit of the coiled carbon fiber 12. It is configured. For this reason, the proximity / contact sensor can obtain the effect as the proximity sensor 10 when the detection object 24 approaches the sensor element 11, and the effect as the contact sensor when the detection object 24 contacts the sensor element 11. Can be obtained.

Hereinafter, the embodiment will be described more specifically with reference to examples.
Example 1
A pair of electrodes 14 was attached to the bottom surface of the sensor element 11 having a flat plate shape of 95 mm in length, 95 mm in width, and 2 mm in thickness. As the elastic resin constituting the sensor element 11, a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., KE103, JIS A hardness is 18) was used. The coiled carbon fiber 12 was a double-wound one having a wire diameter of 0.5 to 1 μm, a coil diameter of 5 to 10 μm, a coil pitch of 0, and a coil length of 150 to 300 μm. Four types of sensor elements 11 were prepared so that the content of the coiled carbon fiber 12 in the sensor element 11 would be 1% by mass, 5% by mass, 10% by mass, and 20% by mass. In FIG. 5, the content of the coiled carbon fiber 12 is simply expressed as 1%, 5%, 10% and 20%, respectively.

  A copper electrode was used for the pair of electrodes 14. A detection circuit 16 having a high-frequency oscillation circuit 19 and a detection circuit 22 is connected to both electrodes 14 by a first connection line 15, and a digital oscilloscope is connected to the detection circuit 16 as a display device 18 by a second connection line 17. . A high frequency signal of 200 kHz was applied to the sensor element 11 from the high frequency oscillation circuit 19. In this way, the proximity sensor 10 was configured.

Then, a person's palm is placed as an object to be detected 24 cm above the sensor element 11, and the change in the output voltage when the palm is brought close to the sensor element 11 is the distance (cm) between the palm and the sensor element 11 surface. Was measured. The results are shown in FIG. As shown in FIG. 5, the output voltage (V) tended to increase as the content of the coiled carbon fiber 12 in the sensor element 11 increased, but the content of the coiled carbon fiber 12 was 10 mass. %, The output voltage was highest, that is, the sensitivity was highest. Furthermore, even after the palm touched the sensor element 11, it showed a predetermined voltage, and it became clear that it also functions as an approach / contact sensor.
(Example 2)
In Example 1, the content of the coiled carbon fiber 12 as the sensor element 11 was 20 mass%. And the frequency of the high frequency signal applied to the sensor element 11 from the high frequency oscillation circuit 19 was changed to 50 kHz, 100 kHz, 200 kHz, 400 kHz, 600 kHz and 800 kHz. Otherwise, the change in output voltage when the palm was brought close to the sensor element 11 was measured in the same manner as in Example 1 with respect to the distance between the palm and the surface of the sensor element 11. The results are shown in FIG. From the results shown in FIG. 6, when the frequency of the high-frequency signal is 800 kHz, the change in the output voltage when the palm is brought close to the sensor element 11 is small and the detection sensitivity is low, but the approach of the palm can be detected. I found out. Further, the lower the frequency, the larger the change in output voltage and the higher the detection sensitivity. However, when the frequency reached 50 kHz, the noise increased and the output waveform was disturbed. Therefore, it was found that the frequency is preferably 100 to 800 kHz.
(Example 3)
In Example 1, the content of the coiled carbon fiber 12 as the sensor element 11 was 5 mass%. The frequency of the high frequency signal applied from the high frequency oscillation circuit 19 to the sensor element 11 was set to 200 kHz. An acrylic resin was used as the base material 13 of the sensor element 11. Other than that, the change of the output voltage when the palm was brought close to the sensor element 11 in the same manner as in Example 1 was measured with respect to the distance between the palm and the surface of the sensor element 11. The results are shown in FIG. As shown in FIG. 7, in the case of the acrylic resin, the output voltage is slightly lower than that in the case of the silicone resin, but the approach of the detection object 24 can be sufficiently detected.
Example 4
In Example 1, the content of the coiled carbon fiber 12 as the sensor element 11 was 20 mass%, and the frequency of the high frequency signal applied from the high frequency oscillation circuit 19 to the sensor element 11 was 200 kHz. As the detection object 24, an acrylic resin plate, an aluminum plate, an iron plate, and a ceramic plate were used. Other than that, the change of the output voltage when the detection target 24 was brought close to the sensor element 11 was measured with respect to the distance between the detection target 24 and the surface of the sensor element 11 in the same manner as in Example 1. The results are shown in FIG. As shown in FIG. 8, the change of the output voltage was the largest in Example 1, followed by iron plate, aluminum plate, ceramic plate, and acrylic resin plate. From this result, it was found that the detection object 24 preferably has a charge on the surface or is a conductive material. In addition, it is estimated that the palm has the highest sensitivity because it has a charge on its surface.
(Example 5, measurement of approach speed)
In Example 4, the approach speed when the detection target 24 is a palm will be described with reference to FIG. When the distance between the palm and the surface of the sensor element 11 is set in advance to 9 cm (90 mm, output voltage 0 V) and the palm is brought close to the sensor element 11 at a speed of 10 mm / sec, the distance between the palm and the sensor element 11 is 8 seconds. Is 10 mm (output waveform 1 in FIG. 9). That is, the moving distance of the palm is 80 mm. At this time, the output voltage is 3V. When this condition is set, for example, when the palm approaches the sensor element 11 from a position where the distance between the palm and the sensor element 11 is 90 mm, the time for the output voltage to reach 3 V is 4 seconds (output waveform 2 in FIG. 9). ), The approach speed is 20 mm / sec (80/4 = 20). Thus, when the detection object 24 is brought close to the sensor element 11 from the position where the distance between the detection object 24 and the sensor element 11 is 90 mm, the approach speed can be detected from the time when the output voltage reaches 3V. it can.
(Example 6, distinction between living and inanimate)
In the case of Example 4, by using the point that the output voltage when the detection target 24 is brought close to the sensor element 11 to a distance of 1 cm is 2.5 V, a living thing (palm) and an inanimate object (iron plate, A distinction can be made between an aluminum plate, a ceramic plate and an acrylic resin plate. That is, when the distance between the detection object 24 and the sensor element 11 is 1 cm, if the output voltage is 2.5 V or more (position indicated by the two-dot chain line in FIG. 8), it is a living thing, and if it is less than 2.5 V, it is an inanimate object. Can be determined. However, the reference of the output voltage can be changed as appropriate by adjusting the setting condition of the proximity sensor 10 according to the detection object 24.

In addition, the said embodiment can also be changed and implemented as follows.
A metal thin film such as gold or copper can be formed on the surface of the coiled carbon fiber 12 in order to increase conductivity. In this case, the sensitivity and stability of the sensor element 11 can be improved.

  In the base material 13, in addition to the coiled carbon fiber 12, vapor grown fiber (VGCF), carbon nanofiber, carbon powder, metal powder, dielectric powder, piezoelectric powder and the like can be blended.

-As the base material 13, physical properties such as hardness can be prepared by mixing resins having different hardnesses.
As the coiled carbon fiber 12, a single coiled carbon fiber 12 and a double coiled carbon fiber 12 can be mixed and used.

The living body as the detection target 24 may be a non-human animal such as a dog or cat.
Further, the technical idea that can be grasped from the embodiment will be described below.

  The proximity sensor according to any one of claims 1 to 4, wherein the coiled carbon fiber is a single coiled carbon fiber or a double coiled carbon fiber. When comprised in this way, the effect of the invention which concerns on any one of Claims 1-4 can fully be exhibited.

Schematic explanatory drawing for demonstrating the structure and effect | action of an proximity sensor in embodiment. Explanatory drawing which shows the equivalent circuit of a sensor element. Explanatory drawing for demonstrating the electric circuit of a proximity sensor. The graph which shows the relationship between the distance and output voltage of a detection target object and a proximity sensor when a palm is made to approach a proximity sensor as a detection target object. The graph which shows the relationship between the distance of a detection target object and a proximity sensor, and output voltage when content of coiled carbon fiber is changed. The graph which shows the relationship between the distance of a detection target object and a proximity sensor, and output voltage when changing the frequency of a high frequency signal. The graph which shows the relationship between the distance of a detection target object and a proximity sensor, and an output voltage when changing the kind of base material. The graph which shows the relationship between the distance and output voltage of a detection target object and a proximity sensor when changing the kind of detection target object. The graph which shows the relationship between time and output voltage for demonstrating the measurement of the approach speed of a detection target object.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Proximity sensor, 11 ... Sensor element, 12 ... Coiled carbon fiber, 13 ... Base material, 14 ... Electrode, 19 ... High frequency oscillation circuit, 22 ... Detection circuit

Claims (6)

A sensor element is formed by dispersing coiled carbon fibers having an inductance (L) component, a capacitance (C) component and a resistance (R) component based on the coil shape and functioning as an LCR resonance circuit in a base material, A pair of electrodes electrically connected to the sensor element, a high-frequency oscillation circuit is connected between both electrodes, and a detection circuit that detects a signal that changes based on the LCR resonance circuit is connected. Proximity sensor. The proximity sensor according to claim 1, wherein the content of the coiled carbon fiber in the base material is 1 to 20% by mass. The proximity sensor according to claim 1 or 2, wherein the frequency of the high-frequency signal by the high-frequency oscillation circuit is 100 to 800 kHz. The proximity sensor according to any one of claims 1 to 3, wherein the base material is an elastic polymer. The proximity sensor according to any one of claims 1 to 4, wherein the detection target is a living body and is used to detect the approach of the living body. When a detection target object contacts the sensor element of the proximity sensor according to any one of claims 1 to 5, the detection circuit detects a signal that changes based on an LCR resonance circuit of a coiled carbon fiber. Proximity / contact sensor characterized by being configured to.

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