JP2021173680A - Sensor circuit - Google Patents

Abstract

To provide a sensor circuit which is hardly affected by external noise.SOLUTION: Provided is a sensor circuit 20 comprising a sensor wire 10 and a differential amplifier 150. The sensor wire 10 includes a first internal conductor 101 covered with a piezoelectric material, a second internal conductor 102 provided on the outside of the piezoelectric material, and an external shield conductor 103 enclosing the first and second internal conductors 101, 102, with insulators arranged between the first and second internal conductors 101, 102 and the external shield conductor 103. The first and second internal conductors 101, 102 are connected to respectively different input terminals of the differential amplifier 150, with a potential difference between these input terminals outputted after being amplified. The impedance between the external shield conductor 103 and the ground is lower than the impedance between the second internal conductor 102 and the ground.SELECTED DRAWING: Figure 3

Description

The present invention relates to a sensor circuit using a piezoelectric material.

Conventionally, a sensor electric wire using a piezoelectric material is known (see, for example, Patent Document 1 and the like). When the sensor wire is deformed by a force, a voltage is induced between the inner conductor and the outer conductor. This characteristic can be used for a tactile sensor, a vibration sensor, or the like.

Japanese Unexamined Patent Publication No. 2008-151638

Since the sensor electric wire of Patent Document 1 is easily affected by external noise, the reliability of the sensor may decrease.

In view of the above circumstances, an object of the present invention is to provide a sensor circuit that is not easily affected by external noise.

The sensor circuit according to the first aspect of the present invention that solves the above object is
With sensor wires
A sensor circuit with a first differential amplifier.
The sensor wire is
With the first inner conductor covered with piezoelectric material,
A second inner conductor provided on the outside of the piezoelectric material,
It has the first inner conductor and the outer shield conductor surrounding the second inner conductor.
An insulator is arranged between the first inner conductor, the second inner conductor, and the outer shield conductor.
The first differential amplifier
The first inner conductor and the second inner conductor are connected to different input ends, and the potential difference between these input ends is amplified and output.
The impedance between the outer shield conductor and the ground is lower than the impedance between the second inner conductor and the ground.
It is characterized by that.

According to this sensor circuit, the external shield conductor prevents noise from entering inside, and the differential amplifier amplifies the potential difference between the first internal conductor and the second internal conductor and outputs it, thereby affecting the effect of external noise. It can be used as a sensor that outputs a voltage according to an external force while suppressing the noise.

In addition, the sensor circuit described above is
It may have a switching circuit which switches to a state where either one of the input ends of the first differential amplifier is connected to the external shield conductor.

According to this sensor circuit, the sensor circuit may be effectively utilized in a state where no external force is applied to the sensor electric wire.

In addition, the sensor circuit described above is
With a second differential amplifier in which either one of the first inner conductor and the second inner conductor and the outer shield conductor are connected to different input ends, and the potential difference between these input ends is amplified and output. , May be provided.

According to this sensor circuit, the degree of influence of external noise can be determined by the output of the second differential amplifier, and it can be determined whether the signal from the first differential amplifier corresponds to an external force. ..

In addition, the sensor circuit described above is
The second inner conductor may cover the outer periphery of the piezoelectric material.

In addition, there may be a gap in the second inner conductor covering the piezoelectric material, for example, when the second inner conductor has a mesh shape. That is, the term "covering" as used herein is not limited to completely covering the outer peripheral surface of the piezoelectric material, and there may be a gap within the range.

In addition, the sensor circuit described above is
The second inner conductor constitutes a core different from that of the first inner conductor.
The first inner conductor and the second inner conductor may be in a twisted state.

According to this sensor circuit, it is possible to suppress the fluctuation of the potentials of the first inner conductor and the second inner conductor caused by the external noise, and to suppress the influence of the external noise when detecting the induced voltage due to the external force.

In addition, the sensor circuit described above is
With a plurality of the first internal conductors
One of the first internal conductors may have a different piezoelectric material from the other, or may have a different thickness of the piezoelectric material.

According to this sensor circuit, the induced voltage due to an external force can be made larger and the dynamic range can be made larger.

In addition, the sensor circuit described above is
The sensor wire is provided with a sheath that covers the outer circumference.
At one end of the sensor wire, the outside of the end of the first inner conductor and the second inner conductor is surrounded by the outer shield conductor or a conductor having the same potential as the outer shield conductor. It has become
Further, one end of the sheath may be covered with a cover member up to the end of the sheath.

According to this sensor circuit, it is possible to make it less susceptible to noise at the end portion on the side that is not used for connection with the outside.

The sensor circuit of the second aspect of the present invention that solves the above object is
With sensor wires
The non-piezoelectric wire connected to the sensor wire and
A sensor circuit with a first differential amplifier.
The sensor wire is
With the first inner conductor covered with piezoelectric material,
A second inner conductor provided on the outside of the piezoelectric material,
It has a first inner conductor and a first outer shield conductor that surrounds the second inner conductor.
An insulator is arranged between the first inner conductor, the second inner conductor, and the first outer shield conductor.
The non-piezoelectric wire is
With the third inner conductor,
A fourth inner conductor provided outside the insulator covering the third inner conductor,
It has a third inner conductor and a second outer shield conductor that surrounds the fourth inner conductor.
An insulator is arranged between the third inner conductor, the fourth inner conductor, and the second outer shield conductor.
The first inner conductor is connected to the third inner conductor,
The second inner conductor is connected to the fourth inner conductor,
The first outer shield conductor is connected to the second outer shield conductor.
The first differential amplifier
The third inner conductor and the fourth inner conductor are connected to different input ends, and the potential difference between these input ends is amplified and output.
It is characterized by that.

In addition, the sensor circuit described above is
In the connection portion between the sensor electric wire and the non-piezoelectric electric wire, the first connection portion which is the connection portion between the first inner conductor and the third inner conductor, the second inner conductor and the first A state in which the second connection portion, which is the connection portion with the four inner conductors, and the third connection portion, which is the connection portion between the first outer shield conductor and the second outer shield conductor, are insulated from each other. ,
It is characterized by that.

In addition, the sensor circuit described above is
The third connecting portion surrounds the first connecting portion and the second connecting portion.
It is characterized by that.

According to the present invention, it is possible to provide a sensor circuit that is not easily affected by external noise.

(A) is a cross-sectional view showing the structure of the sensor electric wire 10 of the first embodiment of the present invention, and (B) is a cross-sectional view showing the structure of the first internal conductor 101 of the sensor electric wire 10. It is a figure which shows an example of the winding method of the 1st insulation coating 104. It is a figure which shows the sensor circuit 20 using the sensor electric wire 10 shown in FIG. It is a figure which shows an example which provided the insulating member and the conductor member with respect to the end | end of the sensor electric wire 10 which is not connected to a circuit. It is sectional drawing which shows the structure of the sensor electric wire 11 provided with two first inner conductors 101 covered with the first insulation coating 104. It is a figure which shows an example of the sensor circuit using the sensor electric wire 11 shown in FIG. It is a figure which shows an example of the sensor circuit using the sensor electric wire 11 shown in FIG. It is sectional drawing which shows the structure of the sensor electric wire 12 which provided two combinations of the 1st insulation coating 104 which covers the 1st inner conductor 101, and 2nd inner conductor 102 which further covers the outer side thereof. It is a figure which shows an example of the sensor circuit using the sensor electric wire 12 shown in FIG. (A) is a cross-sectional view showing the structure of the sensor electric wire 13 of the second embodiment of the present invention, and (B) is the first inner conductor 201 and the second inner conductor 201 covered with the first insulating coating 204. It is a figure which shows the state which twisted the inner conductor 202. It is a figure which shows the sensor circuit 24 using the sensor electric wire 13 shown in FIG. It is a figure which shows an example which provided the insulating member and the conductor member with respect to the end | end of the sensor electric wire 13 which is not connected to a circuit. It is sectional drawing which shows the modification of the 2nd Embodiment. It is a figure which shows the sensor circuit 25 using the sensor electric wire 14 shown in FIG. It is sectional drawing which shows the modification of the 2nd Embodiment. It is a figure which shows an example of the sensor circuit using the sensor electric wire 15 shown in FIG. It is sectional drawing which shows the modification of the 2nd Embodiment. It is a figure which shows an example of the sensor circuit using the sensor electric wire 16 shown in FIG. It is a figure which shows an example of the sensor circuit using the sensor electric wire 16 shown in FIG. It is sectional drawing which shows the modification of the 2nd Embodiment. It is a figure which shows the sensor circuit 29 using the sensor electric wire 17 shown in FIG. It is a figure which shows the sensor circuit 30 which added the switch 301 to a part of the sensor circuit 20 shown in FIG. It is a figure which shows the sensor circuit 31 which added the switch 301 to a part of the sensor circuit 24 shown in FIG. FIG. 3 is a diagram showing a sensor circuit 32 in which a differential amplifier 151 that amplifies and outputs a potential difference between the outer shield conductor 103 and the second inner conductor 102 is added to the sensor circuit 20 shown in FIG. FIG. 11 is a diagram showing a sensor circuit 33 in which a differential amplifier 251 that amplifies and outputs a potential difference between the outer shield conductor 203 and the second inner conductor 202 is added to the sensor circuit 24 shown in FIG.

The sensor electric wire of the present invention is a sensor in the shape of an electric wire. Hereinafter, embodiments of this sensor electric wire will be described.

[Sensor wire of the first embodiment]
FIG. 1A is a cross-sectional view showing the structure of the sensor electric wire 10 according to the first embodiment of the present invention. The sensor electric wire 10 has a first inner conductor 101 provided in the center, a second inner conductor 102 provided on the outside thereof, and an outer shield conductor 103 provided on the outer side thereof. Of these, a first insulating coating 104 is provided between the first inner conductor 101 and the second inner conductor 102. That is, the first inner conductor 101 is covered with the first insulating coating 104, which is insulated from the second inner conductor 102 and the outer shield conductor 103. Further, a second insulating coating 105 is provided between the second inner conductor 102 and the outer shield conductor 103. That is, the second inner conductor 102 is covered with the second insulating coating 105, which is insulated from the outer shield conductor 103. Further, a sheath 130 is provided on the outside of the outer shield conductor 103.

In FIG. 1A, the first inner conductor 101 is shown by hatching by diagonal lines orthogonal to each other, and the second inner conductor 102 and the outer shield conductor 103 are shown by hatching by horizontal lines. Further, the first insulating coating 104 is indicated by hatching by a downward-sloping line, and the second insulating coating 105 is indicated by hatching by a downward-sloping line.

The first inner conductor 101 is made by twisting seven conductor wires 1000 as shown in FIG. 1 (B). Although not shown, the conductor wire 1000 shown in FIG. 1B is also composed of seven thinner conductor wires (thickness 10 μm in the present embodiment) twisted together. That is, the first inner conductor 101 is formed by twisting 49 conductor wires in two stages.

The configuration of the first internal conductor 101 is not limited to the configuration of the present embodiment, and the number of stages to be twisted may be different, the number of conductor wires to be twisted may be different, and the conductor to be twisted may be different. The line thickness may be different. When twisting, conductor wires twisted in different directions may be combined, or the twisting direction may be different depending on the twisting step. Further, one conductor wire may form the first inner conductor 101. Further, in the present embodiment, these conductor wires are made of copper, but the material is not particularly limited, and for example, stainless steel, tungsten, titanium, magnesium, or an alloy thereof may be used, and a plurality of different materials may be used. You may combine different types of conductor wires.

The second inner conductor 102 and the outer shield conductor 103 are both made of a combination of an aluminum film and a copper mesh, but these conductors are not limited to this structure. Therefore, for example, a metal film, a metal mesh, a metal wire wound spirally, or a combination thereof may be used. Further, the configurations and materials of the second inner conductor 102 and the outer shield conductor 103 do not have to be the same, but may be different. Further, for example, the outer shield conductor 103 may have a plurality of layers, such as a two-layer structure of a metal mesh layer and a PET film layer to which a metal foil is attached.

The first insulating coating 104 is formed by using a PVDF (polyvinylidene fluoride) film which is a piezoelectric material, and is spirally wound around the first inner conductor 101 as shown in FIG. be. The first insulating coating 104 has piezoelectricity due to the polarization treatment.

Note that FIG. 2 shows an example in which the first insulating coating 104 is composed of two piezoelectric films, but the number of cases where the piezoelectric film is used is not limited to this, and for example, one. It may be a sheet or a plurality. When the piezoelectric film is wound around the first inner conductor 101, it is preferable that no gap is formed so that the influence of noise on the first inner conductor 101 is less likely to occur. Therefore, in the first insulating coating 104 of the present embodiment, as shown in FIG. 2, by winding the two strip-shaped piezoelectric films in the same direction while shifting them by 180 degrees, the first inner conductor 101 is centered. The tension of the piezoelectric film is made even, and gaps are prevented from being generated due to the bias of the film. Further, as shown in FIG. 1A, when the first inner conductor 101 is configured by twisting the conductor wires 1000, the piezoelectric film is wound in the same direction as the twisting direction of the first inner conductor 101. It may be wound in the opposite direction. Depending on this direction, the flexibility of the sensor wire 10 may be changed.

Although PVDF is used in this embodiment, the first insulating coating 104 may be made of a material having piezoelectricity. For example, trifluoroethylene (TrEF) or a mixed crystal material of PVDF and TrEF. Alternatively, a polymer material having a dipole moment such as polylactic acid, polyuric acid, and polyamino acid may be used. Further, the first insulating coating 104 is not limited to a configuration in which a film of a piezoelectric material such as a PVDF film is used, and may be a configuration in which a piezoelectric material is applied. As such a method, it may be a dipping (ditching) coating, a spray coating by a spray or the like, an impregnation coating, a brush coating, or a coater or the like. It may be coated by a coating device.

The second insulating coating 105 is a coating of an insulator resin (for example, vinyl chloride, polyethylene, etc.), and unlike the first insulating coating 104, it does not have piezoelectricity.

Next, a usage example of the sensor electric wire 10 described above will be described with reference to FIG. FIG. 3 is a diagram showing a sensor circuit 20 using the sensor electric wire 10 shown in FIG. In the sensor circuit 20, the first inner conductor 101 and the second inner conductor 102 are connected to the differential amplifier 150, and the outer shield conductor 103 is connected to the ground. The differential amplifier 150 amplifies and outputs the potential difference between the first inner conductor 101 and the second inner conductor 102.

When an external force is applied to the sensor wire 10 in the sensor circuit 20, the first insulating coating 104 having piezoelectricity is deformed, and the piezoelectric effect causes the first inner conductor 101 and the second inner conductor 102 to be deformed. The potential difference fluctuates. This potential difference is amplified by the differential amplifier 150 and output. That is, the sensor circuit 20 has a function as a sensor that outputs a signal based on an external force applied to the sensor electric wire 10. The sensor wire 10 can be installed in various ways, such as attaching it to the measurement target area, fixing it with a fixing member, or fixing it in a floating state so that a part of it easily vibrates. The method is not particularly limited.

Further, the sensor circuit 20 is configured to suppress the influence of external noise on a signal based on an external force. First, the first inner conductor 101 and the second inner conductor 102 are surrounded by an outer shield conductor 103 connected to the ground, and are configured so that the potential is less likely to fluctuate due to external noise. Further, even if the external noise passes through the external shield conductor 103, both the first inner conductor 101 and the second inner conductor 102 inside are affected by this noise, and these inner conductors are similarly affected by the noise. The potential of is fluctuated. The sensor circuit 20 is configured to cancel the potential fluctuation due to the influence of external noise by amplifying the potential difference between the first inner conductor 101 and the second inner conductor 102.

As described above, in the sensor circuit 20, when an external force is applied to the sensor electric wire 10, a potential difference between the first inner conductor 101 and the second inner conductor 102 is generated, while the first due to the influence of external noise. The potential difference between the inner conductor 101 and the second inner conductor 102 can be suppressed. With this configuration, it is possible to obtain a signal based on an external force while suppressing the influence of external noise.

Although the ground potential may fluctuate depending on the grounding condition, the sensor circuit 20 described above uses the potential difference between the first inner conductor 101 and the second inner conductor 102 instead of the potential difference with the ground. Therefore, the influence of fluctuations in the ground potential can be suppressed.

In the sensor electric wire 10, the outer shield conductor 103 and the second inner conductor 102 are insulated by the second insulating coating 105, and this configuration can be regarded as a capacitor. Further, in FIG. 3, an example in which the external shield conductor 103 is connected to the ground is shown, but in an actual circuit, there is an impedance due to the wiring between the external shield conductor 103 and the ground. Depending on the capacity of these deemed capacitors, the magnitude of impedance, and the frequency of external noise, if the potential fluctuation occurs in the external shield conductor 103 due to external noise, it cannot be completely absorbed by the ground, and the second internal conductor 102 side. It may be affected by external noise. Therefore, it is preferable to make the impedance between the external shield conductor 103 and the ground as low as possible, for example, by providing a bypass capacitor between the external shield conductor 103 and the ground. Although omitted in FIG. 3, the second inner conductor 102 is connected to the ground via the differential amplifier 150, and the impedance between the outer shield conductor 103 and the ground is the same as that of the second inner conductor 102. It is preferably lower than the impedance between the grounds. Further, a variable capacitor may be used for the above bypass capacitor. In this case, the impedance can be adjusted lower according to the frequency to be detected by the sensor electric wire 10.

When installing the sensor electric wire 10, there may be a region not to be measured between the measurement target region and the output side circuit. In this case, it is possible to install one sensor electric wire 10 from the measurement target region to the output side circuit (for example, the differential amplifier 150 in FIG. 3) via the measurement target region. When installed in this way, one sensor electric wire 10 can be used as a sensor in the measurement target area and as a mere signal wiring in the non-measurement target area.

However, if there is vibration of the ground or vibration due to the operation of the machine in the region not to be measured, the noise signal due to these will be superimposed on the signal in the region to be measured. In order to eliminate the influence of such a noise signal, an electric wire having no piezoelectricity (non-piezoelectric electric wire) may be used without installing the sensor electric wire 10 in the region not to be measured. In this case, the non-piezoelectric wire may be configured so that the conductor portion of the sensor wire 10 can be extended while maintaining mutual insulation, and the extension portion of the external shield conductor surrounds the other conductor portion. It should be. Further, also in the connection portion between the sensor electric wire 10 and the non-piezoelectric electric wire, the connection portion of each conductor portion should be maintained in a mutually insulated state, and the connection portion with the external shield conductor should surround the other connection portion. Just do it. As an example of such an electric wire, an electric wire having a multilayer structure similar to that of the sensor electric wire 10 and using an insulating coating having no piezoelectricity may be used. Further, when using the sensor electric wire 10 or the non-piezoelectric electric wire, it is not necessary to properly use the electric wire used at the boundary between the measurement target area and the non-measurement target area. For example, the non-piezoelectric wire in the non-measurement target area is measured. The non-piezoelectric wire may be installed not only in the non-measurement target area but also in the measurement target area, such as entering the target area. In this case, the connection portion between the sensor electric wire 10 and the non-piezoelectric electric wire is provided in the measurement target area. In this configuration, since the installation location of the sensor electric wire 10 is moved away from the noise source in the region not to be measured, it is possible to make it less susceptible to noise.

Hereinafter, an example of a configuration in which the non-piezoelectric wire has a multilayer structure similar to that of the sensor wire 10 and uses an insulating coating having no piezoelectricity will be described. Like the sensor wire 10, this non-piezoelectric wire has a multi-layer structure of a conductor and an insulator. Specifically, the first layer and the first insulation corresponding to the first inner conductor 101 are sequentially arranged from the inside. A second layer corresponding to the coating 104, a third layer corresponding to the second inner conductor 102, a fourth layer corresponding to the second insulating coating 105, and a fifth layer corresponding to the outer shield conductor 103 are provided. There is. Although each of these layers can adopt the same configuration as the sensor electric wire 10, it differs from the sensor electric wire 10 in that the second layer does not have piezoelectricity. As for the second layer, the same configuration as that of the second insulating coating 105 can be adopted.

Among the non-piezoelectric wires having a multi-layer structure, the first layer, the third layer, and the fifth layer are conductors. Of these, the thickness of the first layer is preferably greater than or equal to the thickness of the first inner conductor 101. Further, the thickness of the third layer is preferably equal to or greater than the thickness of the second inner conductor 102, and the thickness of the fifth layer is preferably equal to or greater than the thickness of the outer shield conductor 103. For example, the thickness (or thickness) of the corresponding portion of the sensor wire 10 to be connected is preferably in the range of 1 to 5 times, and 1.2 times to 3.5 times. Is more preferable. If these conductors are too thin (thin), the resistance value will be high, which is not preferable for high-precision and high-speed measurement, and if the non-piezoelectric wire is thick, it will be difficult to bend (hard), so the measurement target area. It is preferably within the above range because the degree of freedom in wiring up to is reduced. In particular, the thickness of the first layer is preferably 1.5 to 2.5 times, and that of the third and fifth layers is preferably 2 to 3 times.

Among the non-piezoelectric wires having a multi-layer structure, the second layer and the fourth layer are insulators. Of these, the second layer is preferably thicker than the thickness of the first insulating coating 104, and the fourth layer is preferably thicker than the thickness of the second insulating coating 105. .. For example, the thickness of the corresponding portion of the sensor electric wire 10 to be connected is preferably in the range of 1 to 5 times, more preferably 1.2 times to 3 times. If these insulators are too thin, the parasitic capacitance will be high, which is not preferable for high-precision and high-speed measurement, and if the non-piezoelectric wire is made too thick, it will be difficult to bend (hard), so the measurement target area. It is preferably within the above range because the degree of freedom in wiring up to is reduced. In particular, each of the second layer and the fourth layer is preferably 1.5 to 2.5 times thicker.

When connecting the sensor wire 10 and the non-piezoelectric wire having a structure corresponding to the sensor wire 10, the layer of the corresponding non-piezoelectric wire is maintained so that the conduction state and the insulation state of each layer of the sensor wire 10 are maintained. At this time, it is preferable to connect the electric wires in a structure corresponding to each layer and using the same material as each layer. However, as the insulating film, a resin having an insulating property such as a silicon resin, a polyimide resin, a capton resin, a fluororesin, an acrylic resin, a polyolefin resin, a urethane resin, an epoxy resin, or a styrene resin may be used. Further, as the conductor, a metal compound such as solder (leaded solder, unleaded solder) such as copper, silver, gold, aluminum, nickel, and titanium may be used.
As for the structure for connecting the electric wires, it is convenient in manufacturing to gradually wind the upper layer (outside) while sequentially winding the tape-shaped one from the lower layer (inside). Alternatively, it may be applied like a bond, plated, vapor-deposited, or crushed and connected like a crimp terminal. Most preferably, the conductor is soldered, silver brazed, a thermal connection method by an arc method, or the like because of low resistance and high reliability of the connection portion. In addition, the insulating film has a simple method of wrapping an insulating tape (the material of the tape part is the above-mentioned polymer resin) having a paste-like adhesive portion on one or both sides, and has high insulating properties, so that corrosive liquids such as moisture can enter after processing. Since it can be prevented, reliability is also good. When connecting the external shield conductor 103 of the sensor electric wire 10 and the fifth layer of the non-piezoelectric electric wire, these connecting portions cover the other connecting portions, and the entire connection structure is shielded. Is preferably maintained.

When the sensor electric wire 10 is used, if the first inner conductor 101, the second inner conductor 102, and the outer shield conductor 103 are exposed at the end on the side not connected to the circuit, these are exposed. In some cases, they come into contact with each other and a signal based on an external force cannot be obtained accurately. Therefore, it is preferable to ensure the insulation of the first inner conductor 101, the second inner conductor 102, and the outer shield conductor 103 at the end portion on the side not connected to the circuit. Further, if there is a portion where the first inner conductor 101 and the second inner conductor 102 are not covered by the outer shield conductor 103 at the end on the side not connected to the circuit, the external noise may affect the portion. There is. Therefore, it is preferable to securely shield the first inner conductor 101 and the second inner conductor 102 at the end portion on the side not connected to the circuit.

FIG. 4 is a diagram showing an example in which an insulating member and a conductor member are applied to the end of the sensor wire 10 on the side not connected to the circuit. In this figure, insulating members 171 and 173, conductor members 172, 174, and cover member 175 are applied to the ends, but FIGS. 4 (A) to 4 (F) are shown so that each stage can be easily understood. It is shown in stages.

FIG. 4A shows the exposed ends of the first inner conductor 101, the second inner conductor 102, and the outer shield conductor 103. FIG. 4B shows a state in which the first inner conductor 101 and the first insulating coating 104 shown in FIG. 4A are covered with the insulating member 171. In this example, the insulating member 171 is covered up to the first insulating coating 104, and the first internal conductor 101 can be reliably insulated from other conductors without being exposed.

FIG. 4C shows a state in which the insulating member 171 and the second inner conductor 102 are covered with the conductor member 172 from the state shown in FIG. 4B. In this example, the potentials of the second inner conductor 102 and the conductor member 172 are the same. With this conductor member 172, the first internal conductor 101 can be made less susceptible to external noise.

FIG. 4D shows a state in which the conductor member 172 and the second insulating coating 105 are covered with the insulating member 173 from the state shown in FIG. 4C. In this example, the insulating member 173 is covered up to the second insulating coating 105, and the second inner conductor 102 can be surely insulated from other conductors without being exposed.

FIG. 4 (E) shows a state in which the insulating member 173 and the outer shield conductor 103 are covered with the conductor member 174 from the state shown in FIG. 4 (D). In this example, the potentials of the outer shield conductor 103 and the conductor member 174 are the same. The conductor member 174 shields the first inner conductor 101 and the second inner conductor 102 so that they are less susceptible to external noise.

FIG. 4 (F) shows a state in which the conductor member 174 and the sheath 130 are covered with the cover member 175 (the same material as the sheath 130) from the state shown in FIG. 4 (E). In this example, the ends provided with the insulating members 171 and 173 and the conductor members 172 and 174 can be protected. The cover member 175 may be made of a material that heat-shrinks (or heat-seals), and may be brought into close contact with the cover member by heating while covering the end portion.

The insulating members 171 and 173 described in the above example may be made of an insulating material (for example, vinyl chloride, polyethylene, etc.). Further, the conductor members 172 and 174 may be made of a conductive material (for example, aluminum, copper, tin, or an alloy made of a plurality of materials). Further, as for the shape of the conductor members 172 and 174, a cylindrical rod terminal may be used in addition to a film shape or a mesh shape, and the shape is not limited.

It should be noted that the insulating members 171 and 173, the conductor members 172, 174, and the cover member 175 described in the above example do not have to be all applied, such as using only the cover member 175 or excluding the conductor member 172. good. Further, not limited to the above example, for example, when the end portion excluding the sheath 130 is flat, the end portion excluding the sheath 130 is covered with an insulating member, and a conductor is provided so as to be in contact with the outer shield conductor 103. It may be configured such that it is covered with a member and a cover member is further provided. Further, the first inner conductor 101, the first insulating coating 104, the second inner conductor 102, and the second insulating coating 105 are cut shorter than the outer shield conductor 103, and these are insulated and then the outer shield is used. It may be configured such that it is wrapped with a conductor 103 and a cover member is further provided. That is, any configuration is sufficient as long as the insulation and shielding between the conductors are more reliable, and the configuration is not limited.

[Modification 1 of the first embodiment]
The sensor electric wire 10 described with reference to FIG. 1 has a configuration in which the first inner conductor 101 covered with the first insulating coating 104 is one, but the first inner conductor covered with the first insulating coating 104 is formed. A plurality of 101 may be provided. FIG. 5 is a cross-sectional view showing the structure of the sensor electric wire 11 provided with two first internal conductors 101 covered with the first insulating coating 104. In the sensor electric wire 11, a plurality of (here, two) cores are formed by the first internal conductors 101A and 101B, and a signal based on an external force is output from each of these cores. In this cross-sectional view, there is a gap between the first insulating coatings 104A and 104B and the second inner conductor 102, and the gap is filled with inclusions. When a plurality of first internal conductors 101 covered with the first insulating coating 104 are provided, they may be twisted together in order to suppress the influence of external noise. Further, for example, the thicknesses of the first insulating coatings 104A and 104B are made different, or the materials are made different, so that the fluctuation of the potential (sensor sensitivity) with respect to the external force is different for each of the first inner conductors 101. You may. Further, the second inner conductor 102 may have the same configuration as the sensor electric wire 10 of FIG. 1, or may have a configuration using inclusions made of a conductive material.

6 and 7 are diagrams showing an example of a sensor circuit using the sensor electric wire 11 shown in FIG. The sensor circuit 21 shown in FIG. 6 employs a configuration in which the outputs of the plurality of first internal conductors 101A and 101B are combined and amplified, so that the sensitivity to an external force can be increased. On the other hand, the sensor circuit 22 shown in FIG. 7 has a configuration in which the potential difference between the plurality of first inner conductors 101A and 101B and the second inner conductor 102 is amplified and a plurality of signals are output. When the configuration of the sensor circuit 22 of FIG. 7 is adopted when the fluctuation of the potential with respect to the external force (sensor sensitivity) is different for each of the first internal conductors 101A and 101B, an appropriate signal can be used according to the external force. The dynamic range can be increased.

[Modification 2 of the first embodiment]
The sensor electric wire 11 described with reference to FIG. 5 is provided with a plurality of first inner conductors 101 covered with a first insulating coating 104, and these are covered together with one second inner conductor 102. However, the second inner conductor 102 may be provided for each of the first inner conductors 101 covered with the first insulating coating 104. FIG. 8 is a cross-sectional view showing the structure of a sensor electric wire 12 provided with two combinations of a first insulating coating 104 covering the first inner conductor 101 and a second inner conductor 102 further covering the outside thereof. In the sensor electric wire 12, a plurality of cores are formed by the first internal conductors 101A and 101B, and a signal based on an external force is output from each of these cores. When a plurality of first internal conductors 101 covered with the first insulating coating 104 are provided, they may be twisted together in order to suppress the influence of external noise. For example, the first insulating coating 104A, It is the same as the sensor electric wire 11 of FIG. 5 in that the thickness of 104B is made different or the material is made different. Further, when constructing a sensor circuit using the sensor electric wire 12, the outputs of the plurality of first internal conductors 101A and 101B are combined as shown in the sensor circuit 21 of FIG. 6, and the second internal conductor 102 ( It may be configured to amplify the potential difference with either or both of 102A and 102B), or as shown in the sensor circuit 22 of FIG. A configuration may be configured in which a potential difference with the conductor 102 (either or both of 102A and 102B) is amplified to output a plurality of signals.

FIG. 9 is a diagram showing an example of a sensor circuit using the sensor electric wire 12 shown in FIG. In the sensor electric wire 12, the first inner conductor 101A and the second inner conductor 102A belong to one core, and the first inner conductor 101B and the second inner conductor 102B belong to the other core. .. Here, the thicknesses of the first insulating coatings 104A and 104B provided on these cores may vary during manufacturing, and as a result, the amount of change in potential according to the external force varies depending on the site. May differ compared to. Therefore, the sensor circuit 23 shown in FIG. 9 employs a configuration that amplifies the potential difference between the internal conductors belonging to different cores, not the potential difference between the internal conductors belonging to the same core. Specifically, the potential difference between the first inner conductor 101A and the second inner conductor 102B and the potential difference between the first inner conductor 101B and the second inner conductor 102A are amplified, and the potential difference between these outputs is further amplified. The configuration to amplify is adopted. In this configuration, the output can be averaged and stabilized even if the amount of change in the potential according to the external force varies.

[Sensor wire of the second embodiment]
FIG. 10A is a cross-sectional view showing the structure of the sensor electric wire 13 according to the second embodiment of the present invention.

The sensor electric wire 13 has a first inner conductor 201 and a second inner conductor 202 covered with a first insulating coating 204, a second insulating coating 205 covering these, and further provided on the outer side thereof. It has an outer shield conductor 203. The first inner conductor 201, the second inner conductor 202, and the outer shield conductor 203 are insulated from each other. Further, a sheath 230 is provided on the outside of the outer shield conductor 203. In this cross-sectional view, there is a gap between the first insulating coating 204, the second inner conductor 202, and the second insulating coating 205, and the gap is filled with inclusions. In the first embodiment described above, the second inner conductor 102 does not form a core different from that of the first inner conductor 101, whereas in the second embodiment, the second inner conductor 202 is used to form a core different from that of the first inner conductor 101. The difference is that a core different from that of one inner conductor 201 is formed. Further, as shown in FIG. 10B, the first inner conductor 201 and the second inner conductor 202 covered with the first insulating coating 204 are twisted together in order to suppress the influence of external noise. It has become.

In FIG. 10, the first inner conductor 201 and the second inner conductor 202 are shown by hatching by orthogonal diagonal lines, and the outer shield conductor 203 is shown by hatching by horizontal lines. Further, the first insulating coating 204 is indicated by hatching by a downward-sloping line, and the second insulating coating 205 is indicated by hatching by a downward-sloping line.

The first inner conductor 201 and the second inner conductor 202 have the same configuration as the first inner conductor 101 in the first embodiment, and the materials are the same as the first inner conductor 101 in the first embodiment. Similar ones can be adopted. The configurations and materials of the first inner conductor 201 and the second inner conductor 202 do not have to be the same, but may be different.

The outer shield conductor 203 is composed of a combination of an aluminum film and a copper mesh, but is not limited to this configuration. Therefore, for example, a metal film, a metal mesh, a metal wire wound spirally, or a combination thereof may be used. Further, for example, the outer shield conductor 203 may have a plurality of layers, such as a two-layer structure of a metal mesh layer and a PET film layer to which a metal foil is attached.

The first insulating coating 204 is constructed by using a PVDF (polyvinylidene fluoride) film which is a piezoelectric material like the first insulating coating 104 in the first embodiment, and is the first embodiment shown in FIG. Similar to the first insulating coating 104 of the form, it is spirally wound around the first inner conductor 201. The first insulating coating 204 has piezoelectricity due to the polarization treatment. As for the material and composition of the first insulating coating 204, the same materials and configurations as those of the first insulating coating 104 in the first embodiment can be adopted.

The second insulating coating 205 is a coating of an insulator resin (for example, vinyl chloride, polyethylene, etc.), and unlike the first insulating coating 204, it does not have piezoelectricity.

Next, a usage example of the sensor electric wire 13 shown in FIG. 10 will be described with reference to FIG. FIG. 11 is a diagram showing a sensor circuit 24 using the sensor electric wire 13 shown in FIG. In the sensor circuit 24, the first inner conductor 201 and the second inner conductor 202 are connected to the differential amplifier 250, and the outer shield conductor 203 is connected to the ground. The differential amplifier 250 amplifies and outputs the potential difference between the first inner conductor 201 and the second inner conductor 202.

When an external force is applied to the sensor electric wire 13 in the sensor circuit 24, the first insulating coating 204 having piezoelectricity is deformed, and the piezoelectric effect causes the first inner conductor 201 and the second inner conductor 202 to be deformed. The potential between them fluctuates. This potential difference is amplified by the differential amplifier 250 and output. That is, the sensor circuit 24 has a function as a sensor that outputs a signal based on an external force applied to the sensor electric wire 13. The sensor wire 13 can be installed in various ways, such as attaching it to the measurement target area, fixing it with a fixing member, or fixing it in a floating state so that a part of it easily vibrates. The method is not particularly limited.

Further, the sensor circuit 24 is configured to suppress the influence of external noise on a signal based on an external force. First, the first inner conductor 201 and the second inner conductor 202 are surrounded by an outer shield conductor 203 connected to the ground, and are configured so that the potential is less likely to fluctuate due to external noise. Further, even if the external noise passes through the external shield conductor 203, both the first inner conductor 201 and the second inner conductor 202 inside are affected by this noise, and these inner conductors are similarly affected by the noise. The potential of is fluctuated. The sensor circuit 24 is configured to cancel the potential fluctuation due to the influence of external noise by amplifying the potential difference between the first inner conductor 201 and the second inner conductor 202.

As described above, in the sensor circuit 24, when an external force is applied to the sensor electric wire 13, a potential difference between the first inner conductor 201 and the second inner conductor 202 is generated, while the first due to the influence of external noise. The potential difference between the inner conductor 201 and the second inner conductor 202 can be suppressed. With this configuration, it is possible to obtain a signal based on an external force while suppressing the influence of external noise.

Although the ground potential may fluctuate depending on the grounding condition, the sensor circuit 24 described above uses the potential difference between the first inner conductor 201 and the second inner conductor 202 instead of the potential difference with the ground. Therefore, the influence of fluctuations in the ground potential can be suppressed.

In the sensor electric wire 13, the outer shield conductor 203 and the second inner conductor 202 are insulated by the second insulation coating 205, and this configuration can be regarded as a capacitor. Further, in FIG. 3, an example in which the external shield conductor 203 is connected to the ground is shown, but in an actual circuit, there is an impedance due to the wiring between the external shield conductor 203 and the ground. Depending on the capacity of these deemed capacitors, the magnitude of impedance, and the frequency of external noise, if the potential fluctuation occurs in the external shield conductor 203 due to external noise, it cannot be completely absorbed by the ground, and the second internal conductor 202 side. It may be affected by external noise. Therefore, it is preferable to make the impedance between the external shield conductor 203 and the ground as low as possible, for example, by providing a bypass capacitor between the external shield conductor 203 and the ground. Although omitted in FIG. 11, the second inner conductor 202 is connected to the ground via the differential amplifier 250, and the impedance between the outer shield conductor 203 and the ground is the same as that of the second inner conductor 202. It is preferably lower than the impedance between the grounds. Further, a variable capacitor may be used for the above bypass capacitor. In this case, the impedance can be adjusted lower according to the frequency to be detected by the sensor electric wire 13.

When the above sensor electric wire 13 is installed, there may be a region not to be measured between the measurement target region and the output side circuit. In this case, it is possible to install one sensor electric wire 13 from the measurement target region to the output side circuit (for example, the differential amplifier 250 in FIG. 11) via the measurement target region. When installed in this way, one sensor electric wire 13 can be used as a sensor in the measurement target area and as a mere signal wiring in the non-measurement target area.

However, if there is vibration of the ground or vibration due to the operation of the machine in the region not to be measured, the noise signal due to these will be superimposed on the signal in the region to be measured. In order to eliminate the influence of such a noise signal, an electric wire having no piezoelectricity (non-piezoelectric electric wire) may be used without installing the sensor electric wire 13 in the region not to be measured. In this case, the non-piezoelectric wire may be configured so that the conductor portion of the sensor wire 13 can be extended while maintaining mutual insulation, and the extension portion of the external shield conductor surrounds the other conductor portion. It should be. Further, also in the connection portion between the sensor electric wire 13 and the non-piezoelectric electric wire, the connection portion of each conductor portion should be maintained in a mutually insulated state, and the connection portion with the external shield conductor should surround the other connection portion. Just do it. As an example of such an electric wire, an electric wire having a multi-layer structure similar to that of the sensor electric wire 13 and using an insulating coating having no piezoelectricity may be used. Further, when using the sensor electric wire 13 or the non-piezoelectric electric wire, it is not necessary to properly use the electric wire used at the boundary between the measurement target area and the non-measurement target area. For example, the non-piezoelectric wire in the non-measurement target area is measured. The non-piezoelectric wire may be installed not only in the non-measurement target area but also in the measurement target area, such as entering the target area. In this case, the connection portion between the sensor electric wire 13 and the non-piezoelectric electric wire is provided in the measurement target area. In this configuration, since the installation location of the sensor electric wire 13 is moved away from the noise source in the region not to be measured, it is possible to make it less susceptible to noise.

Hereinafter, an example of a configuration in which the non-piezoelectric wire has a multilayer structure similar to that of the sensor wire 13 and uses an insulating coating having no piezoelectricity will be described. Like the sensor electric wire 13, this non-piezoelectric electric wire has a multi-layer structure of a conductor and an insulator. Specifically, in order from the inside, the first layer and the first insulation corresponding to the first inner conductor 201. The second layer corresponding to the coating 204, the third layer corresponding to the second inner conductor 202 (separate core twisted with the core up to the second layer), the fourth layer corresponding to the second insulating coating 205, and the outside. A fifth layer, which corresponds to the shield conductor 203, is provided. Although each of these layers can adopt the same configuration as the sensor electric wire 13, it differs from the sensor electric wire 13 in that the second layer does not have piezoelectricity. As for the second layer, the same configuration as that of the second insulating coating 205 can be adopted.

Among the non-piezoelectric wires having a multi-layer structure, the first layer, the third layer, and the fifth layer are conductors. Of these, the thickness of the first layer is preferably greater than or equal to the thickness of the first inner conductor 201. The third layer is preferably thicker than the thickness of the second inner conductor 202, and the fifth layer is preferably thicker than the thickness of the outer shield conductor 203. For example, the thickness (or thickness) of the corresponding portion of the sensor wire 13 to be connected is preferably in the range of 1 to 5 times, and 1.2 times to 3.5 times. Is more preferable. If these conductors are too thin (thin), the resistance value will be high, which is not preferable for high-precision and high-speed measurement, and if the non-piezoelectric wire is thick, it will be difficult to bend (hard), so the measurement target area. It is preferably within the above range because the degree of freedom in wiring up to is reduced. In particular, it is preferable that the first layer and the third layer are 1.5 to 2.5 times thicker, and the fifth layer is 2 to 3 times thicker.

Among the non-piezoelectric wires having a multi-layer structure, the second layer and the fourth layer are insulators. Of these, the second layer preferably has a thickness equal to or greater than the thickness of the first insulating coating 204, and the fourth layer preferably has a thickness equal to or greater than the thickness of the second insulating coating 205. .. For example, the thickness of the corresponding portion of the sensor wire 13 to be connected is preferably in the range of 1 to 5 times, more preferably 1.2 times to 3 times. If these insulators are too thin, the parasitic capacitance will be high, which is not preferable for high-precision and high-speed measurement, and if the non-piezoelectric wire is made too thick, it will be difficult to bend (hard), so the measurement target area. It is preferably within the above range because the degree of freedom in wiring up to is reduced. In particular, each of the second layer and the fourth layer is preferably 1.5 to 2.5 times thicker.

When connecting the sensor wire 13 and the non-piezoelectric wire having a structure corresponding to the sensor wire 13, the layer of the corresponding non-piezoelectric wire is maintained so that the conduction state and the insulation state of each layer of the sensor wire 13 are maintained. However, at this time, it is preferable to connect the electric wires in a structure corresponding to each layer and using the same material as each layer. However, as the insulating film, a resin having an insulating property such as a silicon resin, a polyimide resin, a capton resin, a fluororesin, an acrylic resin, a polyolefin resin, a urethane resin, an epoxy resin, or a styrene resin may be used. Further, as the conductor, a metal compound such as solder (leaded solder, unleaded solder) such as copper, silver, gold, aluminum, nickel, and titanium may be used.
As for the structure for connecting the electric wires, it is convenient in manufacturing to gradually wind the upper layer (outside) while sequentially winding the tape-shaped one from the lower layer (inside). Alternatively, it may be applied like a bond, plated, vapor-deposited, or crushed and connected like a crimp terminal. Most preferably, the conductor is soldered, silver brazed, a thermal connection method by an arc method, or the like because of low resistance and high reliability of the connection portion. In addition, the insulating film has a simple method of wrapping an insulating tape (the material of the tape part is the above-mentioned polymer resin) having a paste-like adhesive portion on one or both sides, and has high insulating properties, and prevents corrosive liquids such as moisture from entering after processing. Since it can be prevented, reliability is also good. When connecting the external shield conductor 203 of the sensor electric wire 13 and the fifth layer of the non-piezoelectric electric wire, these connecting portions cover the other connecting portions, and the entire connection structure is shielded. Is preferably maintained. When the sensor electric wire 13 is used, if the first inner conductor 201, the second inner conductor 202, and the outer shield conductor 203 are exposed at the end on the side not connected to the circuit, these are May come into contact with each other and the signal based on the external force may not be obtained accurately. Therefore, it is preferable to ensure the insulation of the first inner conductor 201, the second inner conductor 202, and the outer shield conductor 203 at the end portion on the side not connected to the circuit. Further, if there is a portion where the first inner conductor 201 and the second inner conductor 202 are not covered by the outer shield conductor 203 at the end on the side not connected to the circuit, the external noise may affect the portion. There is. Therefore, it is preferable to securely shield the first inner conductor 201 and the second inner conductor 202 at the end portion on the side not connected to the circuit.

FIG. 12 is a diagram showing an example in which an insulating member and a conductor member are applied to the end of the sensor wire 10 on the side not connected to the circuit. In this figure, the insulating members 271 and 273, the conductor member 274, and the cover member 275 are applied to the ends, but FIGS. 12A to 12E are stepwise so that each step can be easily understood. It is shown in.

FIG. 12A shows the exposed ends of the first inner conductor 201, the second inner conductor 202, and the outer shield conductor 203. FIG. 12B shows a state in which the first inner conductor 201 and the first insulating coating 204 shown in FIG. 12A are covered with the insulating member 271. In this example, the insulating member 271 is covered up to the first insulating coating 204, and the first internal conductor 201 can be reliably insulated from other conductors without being exposed.

FIG. 12C shows a state in which the insulating member 271 and the second inner conductor 202 and the second insulating coating 205 are covered with the insulating member 273 from the state shown in FIG. 12B. .. In this example, the insulating member 273 is covered up to the second insulating coating 205, and the second inner conductor 202 can be surely insulated from other conductors without being exposed.

FIG. 12 (D) shows a state in which the insulating member 273 and the outer shield conductor 203 are covered with the conductor member 274 from the state shown in FIG. 12 (C). In this example, the potentials of the outer shield conductor 203 and the conductor member 274 are the same. The conductor member 274 shields the first inner conductor 201 and the second inner conductor 202 so that they are less susceptible to external noise.

FIG. 12 (E) shows a state in which the conductor member 274 and the sheath 230 are covered with the cover member 275 (the same material as the sheath 230) from the state shown in FIG. 12 (D). In this example, the ends provided with the insulating members 271, 273 and the conductor member 274 can be protected. The cover member 275 may be made of a material that heat-shrinks (or heat-seals), and may be brought into close contact by heating while covering the end portion.

The insulating members 271 and 273 described in the above example may be made of an insulating material (for example, vinyl chloride, polyethylene, etc.). Further, the conductor member 274 may be made of a conductive material (for example, aluminum, copper, tin, or an alloy made of a plurality of materials). Further, as for the shape of the conductor member 274, a cylindrical rod terminal may be used in addition to a film shape or a mesh shape, and the shape is not limited.

The insulating members 271, 273, the conductor member 274, and the cover member 275 described in the above example may use only the cover member 275 or an insulating member that insulates only the conductor member 272 from other conductors. As such, it does not have to have the same configuration. Further, not limited to the above example, for example, when the end portion excluding the sheath 230 is flat, the end portion excluding the sheath 230 is covered with an insulating member so that the end portion excluding the sheath 230 is in contact with the external shield conductor 203. The configuration may be such that it is covered with a conductor member and a cover member is further provided. Further, the first inner conductor 201, the first insulating coating 204, the second inner conductor 202, and the second insulating coating 205 are cut shorter than the outer shield conductor 203, and these are insulated and then the outer shield is used. The configuration may be such that the conductor 203 is wrapped and a cover member is further provided. That is, any configuration is sufficient as long as the insulation and shielding between the conductors are more reliable, and the configuration is not limited.

[Modification 1 of the second embodiment]
The sensor electric wire 13 described with reference to FIG. 10 adopts a configuration in which the first inner conductor 201 and the second inner conductor 202 covered with the first insulating coating 204 are covered with the second insulating coating 205. , Not limited to this configuration, for example, each of the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205 is provided, and these are further provided. The outside of the wire may be covered with the outer shield conductor 203. FIG. 13 is a cross-sectional view showing the structure of the sensor electric wire 14 adopting this configuration. The sensor wire 14 has a first inner conductor 201 covered with a first insulating coating 204 and a second inner conductor 202 covered with a second insulating coating 205, and is further provided outside these. It has an external shield conductor 203. The first inner conductor 201, the second inner conductor 202, and the outer shield conductor 203 are insulated from each other. Further, a sheath 230 is provided on the outside of the outer shield conductor 203. The position where the second insulating coating 205 is provided is different from that of the sensor electric wire 13 in FIG. In this cross-sectional view, there is a gap between the first insulating coating 204, the second insulating coating 205, and the outer shield conductor 203, and the gap is filled with inclusions. In the sensor electric wire 13 of FIG. 10, the first inner conductor 201 and the second inner conductor 202 covered with the first insulating coating 204 are twisted together in order to suppress the influence of external noise. The electric wire 14 has a configuration in which the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205 are twisted together.

Further, the second insulating coating 205 adopts a coating having the same material and composition as the first insulating coating 204 and does not have piezoelectricity. That is, the second insulating coating 205 is different from the first insulating coating 204 in the presence or absence of piezoelectricity. The material is not limited to the same material as the first insulating coating 204, and a material different from the first insulating coating 204 such as an insulator resin (for example, vinyl chloride, polyethylene, etc.) may be used.

FIG. 14 is a diagram showing a sensor circuit 25 using the sensor electric wire 14 shown in FIG. The sensor circuit 25 has the same configuration as the sensor circuit 24 shown in FIG. 11 except for the position of the second insulating coating 205. When an external force is applied to the sensor electric wire 14 in the sensor circuit 25, the first insulating coating 204 having piezoelectricity is deformed, and the potential of the first inner conductor 201 fluctuates due to the piezoelectric effect. On the other hand, since the second insulating coating 205 does not have piezoelectricity, the potential of the second inner conductor 202 does not fluctuate according to the external force. As a result, when an external force is applied to the sensor electric wire 14, the potential difference between the first inner conductor 201 and the second inner conductor 202 fluctuates, and this potential difference is amplified and output by the differential amplifier 250. That is, the sensor circuit 25 has a function as a sensor that outputs a signal based on an external force applied to the sensor electric wire 14.

Further, the sensor circuit 25 is configured to suppress the influence of external noise on a signal based on an external force. First, the first inner conductor 201 and the second inner conductor 202 are surrounded by an outer shield conductor 203 connected to the ground, and are configured so that the potential is less likely to fluctuate due to external noise. Further, even if the external noise passes through the external shield conductor 203, both the first inner conductor 201 and the second inner conductor 202 inside are affected by this noise, and these inner conductors are similarly affected by the noise. The potential of is fluctuated. The sensor circuit 25 is configured to cancel the potential fluctuation due to the influence of external noise by amplifying the potential difference between the first inner conductor 201 and the second inner conductor 202. In order to more effectively offset the fluctuation of the potential due to the influence of external noise, the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 201 covered with the second insulating coating 205 are used. It is preferable that the electrical and physical conditions such as the length and thickness of the inner conductor 202, the capacitance (dielectric constant and thickness of the insulating coating), the impedance, and the degree of shielding are met.

As described above, in the sensor circuit 25, when an external force is applied to the sensor electric wire 14, a potential difference between the first inner conductor 201 and the second inner conductor 202 is generated, while the first due to the influence of external noise. The potential difference between the inner conductor 201 and the second inner conductor 202 can be suppressed. With this configuration, it is possible to obtain a signal based on an external force while suppressing the influence of external noise.

The ground potential may fluctuate depending on the grounding condition of the outer shield conductor 203, but in the sensor circuit 25 described above, the first inner conductor 201 and the second inner conductor 202 are used instead of the potential difference from the ground. Since the potential difference is used, the influence of fluctuations in the ground potential can be suppressed.

[Modification 2 of the second embodiment]
In the sensor wire 14 described with reference to FIG. 13, both the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205 are externally shielded. It is configured to be housed in one space partitioned by the conductor 203. However, the configuration of the sensor electric wire is not limited to this, and the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205 are included. , Each may be housed in a separate space partitioned by the outer shield conductor 203. The sensor wire 15 shown in FIG. 15 is an example of such a configuration, and the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor covered with the second insulating coating 205. 202 is configured to be covered with different external shield conductors 203A and 203B, respectively. The outer shield conductor 203A and the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the outer shield conductor 203B and the second insulating coating 205 are external. In order to suppress the influence of noise, these may be twisted together.

FIG. 16 is a diagram showing an example of a sensor circuit using the sensor electric wire 15 shown in FIG. The sensor circuit 26 of FIG. 16 has the same configuration as the sensor circuit 25 shown in FIG. 14 except that the two external shield conductors 203A and 203B are connected to the ground, respectively, and is the same as the sensor circuit 25 shown in FIG. It works. In the sensor electric wire 15 shown in FIG. 15, since the two external shield conductors 203A and 203B are in contact with each other, one of the two external shield conductors 203A and 203B may be connected to the ground. Further, the two external shield conductors 203A and 203B may be insulated, and in this case, as shown in FIG. 16, any of the external shield conductors 203 may be connected to the ground.

[Modification 3 of the second embodiment]
The sensor electric wire 13 described with reference to FIG. 10 and the sensor electric wire 14 described with reference to FIG. 13 have a configuration in which the first internal conductor 201 covered with the first insulating coating 204 is one, but the first insulating coating 204 A plurality of first inner conductors 201 covered with may be provided. FIG. 17 is an example of such a configuration, and is a cross-sectional view showing the structure of a sensor electric wire 16 provided with two first internal conductors 201 covered with a first insulating coating 204. In the sensor electric wire 16, signals based on external forces are output from the first internal conductors 201A and 201B, respectively. In this cross-sectional view, there is a gap between the first insulating coatings 204A and 204B, the second insulating coating 205, and the outer shield conductor 203, and the gaps are filled with inclusions. When a plurality of first internal conductors 201 covered with the first insulating coating 204 are provided, they may be twisted together in order to suppress the influence of external noise, and covered with the second insulating coating 205. It may be configured by twisting with the second inner conductor 202. Further, for example, the thicknesses of the first insulating coatings 204A and 204B are made different, or the materials are made different, so that the fluctuation of the potential (sensor sensitivity) with respect to the external force is different for each of the first inner conductors 201. You may. Further, in the sensor electric wire 16 shown in FIG. 17, the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205 are all external shield conductors. The configuration is contained in one space partitioned by 203, but as described in the example of FIG. 15, the configuration is divided into different spaces partitioned by the external shield conductor 203. You may.

18 and 19 are diagrams showing an example of a sensor circuit using the sensor electric wire 16 shown in FIG. The sensor circuit 27 shown in FIG. 18 employs a configuration in which the outputs of the plurality of first internal conductors 201A and 201B are combined and amplified, so that the sensitivity to an external force can be increased. On the other hand, the sensor circuit 28 shown in FIG. 19 has a configuration in which the potential difference between the plurality of first inner conductors 201A and 201B and the second inner conductor 102 is amplified and a plurality of signals are output. When the configuration of the sensor circuit 28 of FIG. 19 is adopted when the fluctuation of the potential with respect to the external force (sensor sensitivity) is different for each of the first internal conductors 201A and 201B, an appropriate signal can be used according to the external force. The dynamic range can be increased.

[Modification 4 of the second embodiment]
In the description of the sensor electric wire 14 of FIG. 13, the length, thickness, and static of the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205. I mentioned that it is preferable that the electrical and physical conditions such as capacitance, impedance, and degree of shielding are met. However, when adopting a set that meets such electrical and physical conditions, The number is not limited to one, and a plurality of them may be provided. In this case, the fluctuation (sensor sensitivity) of the potential of the first internal conductor 201 generated with respect to the external force may be the same or different in each set.

The sensor electric wire 17 shown in FIG. 20 is a cross-sectional view showing an example in which two sets of a first inner conductor 201 and a second inner conductor 202 are provided. In FIG. 20, the first inner conductor 201 covered with the first insulating coating 204 is arranged on the left side and the upper side, respectively, and the second inner conductor covered with the second insulating coating 205 is arranged on the right side and the lower side, respectively. 202 is arranged. The two first inner conductors 201 have different thicknesses of the first insulating coating 204 covering them. Specifically, the first insulating coating 204B located on the upper side is thicker than the first insulating coating 204A located on the left side of FIG. 20. As a result, the first inner conductor 201B located on the upper side has a higher potential fluctuation (sensor sensitivity) with respect to the external force than the first inner conductor 201A located on the left side. There is. In this cross-sectional view, there is a gap between the first insulating coatings 204A and 204B, the second insulating coatings 205A and 205B, and the outer shield conductor 203, and the gaps are filled with inclusions.

When a plurality of first inner conductors 201 covered with the first insulating coating 204 and a plurality of second inner conductors 202 covered with the second insulating coating 205 are provided, these are used in order to suppress the influence of external noise. May be twisted together. At this time, for example, the first set and the second set, which will be described later, may be twisted and then twisted, and the twisting method may be limited. No. Further, in the sensor electric wire 17 shown in FIG. 20, the first inner conductor 201 covered with the first insulating coating 204 and the second inner conductor 202 covered with the second insulating coating 205 are all external shield conductors. The configuration is contained in one space partitioned by 203, but as described in the example of FIG. 15, the configuration is divided into different spaces partitioned by the external shield conductor 203. You may.

Of the two second inner conductors 202, the second inner conductor 202A on the right side is provided to cancel the influence of external noise on the first inner conductor 201A on the left side. The first inner conductor 201A and the second inner conductor 202A have the same configuration. Further, in the first insulating coating 204A and the second insulating coating 205A, the first insulating coating 204A has piezoelectricity (polarization treatment is applied), whereas the second insulating coating 205A is provided. Is different in that it does not have piezoelectricity (it is not polarized), but its material and thickness are the same. That is, the first inner conductor 201A covered with the first insulating coating 204A and the second inner conductor 202A covered with the second insulating coating 205A are electrically and physically, except for the presence or absence of piezoelectricity. It is a set of various conditions. In the following description, the set of the first inner conductor 201A covered with the first insulating coating 204A and the second inner conductor 202A covered with the second insulating coating 205A is referred to as the first set. Refer to.

Of the two second inner conductors 202, the second inner conductor 202B on the lower side is provided to cancel the influence of external noise on the first inner conductor 201B on the upper side. The first inner conductor 201B and the second inner conductor 202B have the same configuration. Further, in the first insulating coating 204B and the second insulating coating 205B, the first insulating coating 204B has piezoelectricity (polarization treatment is applied), whereas the second insulating coating 205B is provided. Is different in that it does not have piezoelectricity (it is not polarized), but its material and thickness are the same. That is, the first inner conductor 201B covered with the first insulating coating 204B and the second inner conductor 202B covered with the second insulating coating 205B are electrically and physically, except for the presence or absence of piezoelectricity. It is a set of various conditions. In the following description, the set of the first inner conductor 201B covered with the first insulating coating 204B and the second inner conductor 202B covered with the second insulating coating 205B is referred to as the second set. Refer to.

FIG. 21 is a diagram showing a sensor circuit 29 using the sensor electric wire 17 shown in FIG. 20. In this sensor circuit 29, the first set of first inner conductors 201A and the second inner conductor 202A are connected to the differential amplifier 250, and the second set of first inner conductors 201B and second inner conductors 201B and second inner conductors. 202B is connected to the differential amplifier 250 and the external shield conductor 203 is connected to ground. The differential amplifier 250 amplifies and outputs the potential difference between the first inner conductor 201 and the second inner conductor 202 in each of the first set and the second set. In this sensor circuit 29, an appropriate signal can be used according to an external force, and a large dynamic range can be obtained.

[Configuration 1 as a noise sensor]
The first embodiment and the second embodiment described above, and the sensor circuits 20 to 29 of these modified examples cannot be effectively utilized in a state where an external force is not applied to the sensor electric wire. For example, when considering applications such as applying these sensor circuits to a bed or pillow to monitor the condition of a sleeping patient, external force is not applied to the sensor wire while the patient is away from the bed. It cannot be used effectively. Therefore, by switching the connection to the differential amplifier in the above sensor circuit so that it can be used as a noise sensor, the chances of its use can be increased. In the above example, since external noise is detected when the patient approaches the bed, it can be used as data of movement around the bed. This configuration will be described below.

In the first embodiment and the second embodiment described above, and the sensor circuits 20 to 29 of these modifications, the first internal conductors 101 and 201 and the second internal conductors 102 and 202 are differential amplifiers 150. , 250, and the outer shield conductors 103, 203 are connected to the ground (FIGS. 3, 5, 6, 8, 10, 12, 14, 16, 17, 19). The outer shield conductors 103 and 203 surround the first inner conductors 101 and 201 and the second inner conductors 102 and 202, and are most affected by external noise among these conductors. Therefore, in these sensor circuits 20 to 29, by switching one of the inputs to the differential amplifiers 150 and 250 to the external shield conductors 103 and 203, the external noise is reflected in the outputs of the differential amplifiers 150 and 250. It can be used as a noise sensor. At this time, the other input to the differential amplifiers 150 and 250 may be left as it is or may be connected to the ground.

The sensor circuit 30 shown in FIG. 22 is an example of the configuration described above, and is obtained by adding a switch 301 to a part of the sensor circuit 20 shown in FIG. When the switch 301 is in the initial state (the state shown in FIG. 22), it has the same configuration as the sensor circuit 20 shown in FIG. 3, but when the switch 301 is switched, it replaces the first internal conductor 101. The external shield conductor 103 is connected to the differential amplifier 150 and can be used as a noise sensor.

Further, the sensor circuit 31 shown in FIG. 23 is an example of the configuration described above, and the switch 301 is added to a part of the sensor circuit 24 shown in FIG. When the switch 301 is in the initial state (the state shown in FIG. 23), it has the same configuration as the sensor circuit 24 shown in FIG. 11, but when the switch 301 is switched, it replaces the first internal conductor 201. The external shield conductor 203 is connected to the differential amplifier 250 and can be used as a noise sensor.

Regarding the switch 301 of FIGS. 22 and 21, the sensor function may be switched by switching the state of the switch 301 using, for example, a timer. Further, the switch 301 may be switched according to a desired condition by using a microcomputer or the like.

[Configuration 2 as a noise sensor]
In the sensor circuit 30 of FIG. 22 and the sensor circuit 31 of FIG. 23, the switch 301 is used to perform a function as a sensor that outputs a signal based on an external force applied to the sensor electric wire and a function as a sensor that outputs a signal caused by noise. The switching configuration was explained. Of these, the former function can be realized by amplifying the potential difference between the first inner conductors 101 and 201 and the second inner conductors 102 and 202 by the differential amplifiers 150 and 250. Regarding the latter function, the potential difference between the first inner conductors 101, 201 and the second inner conductors 102, 202 and the outer shield conductors 103, 203 is amplified by the differential amplifiers 150, 250. It can be realized by. Here, it may be configured to have both functions without switching these functions.

The sensor circuit 32 shown in FIG. 24 is an example of the configuration described above, and is a differential amplifier that amplifies and outputs the potential difference between the outer shield conductor 103 and the second inner conductor 102 with respect to the sensor circuit 20 shown in FIG. 151 is added. In this sensor circuit 32, both a signal corresponding to an external force and a signal corresponding to noise can be used at the same time.

Further, the sensor circuit 33 shown in FIG. 25 is an example of the configuration described above, and is a difference in which the potential difference between the outer shield conductor 203 and the second inner conductor 202 is amplified and output with respect to the sensor circuit 24 shown in FIG. The dynamic amplifier 251 is added. In this sensor circuit 33, both a signal corresponding to an external force and a signal corresponding to noise can be used at the same time.

For example, in the sensor circuit 20 shown in FIG. 3 and the sensor circuit 24 shown in FIG. 11, when a signal corresponding to an external force is affected by external noise, is the signal due to external force or is due to external noise? It may not be possible to judge. In the sensor circuit 32 shown in FIG. 24 and the sensor circuit 33 shown in FIG. 25, the degree of influence of external noise can be determined by the outputs of the differential amplifiers 151 and 251 added separately, and whether the signal corresponds to the external force can be determined. You can judge.

[others]
The configurations of the sensor electric wire and the sensor circuit described above are examples, and the processing contents may be the same, and the configuration is not limited. For example, in the above-described embodiment of the sensor electric wire, twisting of the internal conductors has been described, but when there are three or more objects to be twisted, they may be twisted by braiding, for example, as in a braid. Further, when the conductor of the sensor electric wire is formed in a mesh shape, there is a problem that noise easily enters inside depending on the size of the hole. In this case, by configuring the hole size to be half or less of the wavelength of the noise in question, it is possible to prevent noise from entering. Further, in the embodiment of the sensor circuit described above, one differential amplifier may be shared without using a plurality of differential amplifiers, or a notch filter or the like may be appropriately provided. Further, in the above-described embodiment of the sensor circuit, the configuration in which the differential amplifier is connected to one side of the end of the sensor wire has been described, but both ends of the sensor wire may be connected to the same differential amplifier.

Further, the non-piezoelectric electric wire and its connection structure adopting the same structure as the sensor electric wire described in each embodiment can be applied to each modified example, and have the same configuration as the sensor electric wire of the modified example. Non-piezoelectric wires can be used.

10, 11, 12, 13, 14, 15, 16, 17 Sensor wire 101, 201 First inner conductor 102, 202 Second inner conductor 103, 203 External shield conductor 104, 204 First insulation coating 105, 205 Second Insulation Coating 130, 230 Sheath 171, 173, 271, 273 Insulation Member 172, 174, 274 Conductive Member 175, 275 Cover Member 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 Sensors Circuit 30, 31, 32, 33 Sensor circuit 150, 151, 250, 251 Differential amplifier

Claims (7)

With sensor wires
A sensor circuit with a first differential amplifier.
The sensor wire is
With the first inner conductor covered with piezoelectric material,
A second inner conductor provided on the outside of the piezoelectric material,
It has the first inner conductor and the outer shield conductor surrounding the second inner conductor.
An insulator is arranged between the first inner conductor, the second inner conductor, and the outer shield conductor.
The first differential amplifier
The first inner conductor and the second inner conductor are connected to different input ends, and the potential difference between these input ends is amplified and output.
The impedance between the outer shield conductor and the ground is lower than the impedance between the second inner conductor and the ground.
A sensor circuit characterized by that. The sensor circuit according to claim 1.
It has a switching circuit that switches to a state in which one of the input ends of the first differential amplifier is connected to the external shield conductor.
A sensor circuit characterized by that. The sensor circuit according to claim 1.
With a second differential amplifier in which either one of the first inner conductor and the second inner conductor and the outer shield conductor are connected to different input ends, and the potential difference between these input ends is amplified and output. ,
A sensor circuit characterized by being equipped with. The sensor circuit according to any one of claims 1 to 3.
The second inner conductor covers the outer circumference of the piezoelectric material.
A sensor circuit characterized by that. The sensor circuit according to any one of claims 1 to 3.
The second inner conductor constitutes a core different from that of the first inner conductor.
The first inner conductor and the second inner conductor are twisted together.
A sensor circuit characterized by that. The sensor circuit according to any one of claims 1 to 5.
With a plurality of the first internal conductors
One of the first internal conductors has a different piezoelectric material from the other, or has a different thickness of the piezoelectric material.
A sensor circuit characterized by that. The sensor circuit according to any one of claims 1 to 6.
The sensor electric wire is provided with a sheath that covers the outer circumference.
At one end of the sensor wire, the outside of the end of the first inner conductor and the second inner conductor is surrounded by the outer shield conductor or a conductor having the same potential as the outer shield conductor. It has become
Further, one end of the sheath is covered with a cover member up to the end of the sheath.
A sensor circuit characterized by that.

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