JP4051797B2 - Pressure detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure detection device using a cable-shaped pressure sensor.
[0002]
[Prior art]
Conventionally, this type of cable-shaped pressure sensor has been as follows.
[0003]
In Japanese Patent Application Laid-Open No. 62-230071, as shown in FIG. 6, a flexible piezoelectric body 4 is arranged around a core electrode 3 composed of a linear conductive material 1 and a conductive rubber 2, and a flexible piezoelectric body 4 is arranged around the core electrode 3. A cable-shaped pressure sensor is disclosed in which a flexible outer electrode 5 is disposed and a sheath 6 made of a heat-shrinkable tube is covered around the flexible outer electrode 5. As the flexible piezoelectric body 4, a piezoelectric material such as a composite in which ceramic piezoelectric powder such as lead titanate is added to synthetic rubber or synthetic resin, or a vinylidene fluoride (VDF) / trifluoroethylene (TrFE) copolymer system, etc. Functional polymer is used. Moreover, as the flexible outer electrode 5, a silver-based conductive coating film by an aluminum foil or a coating method is used. 6 is an outer skin, and 7 is a vibration voltage detecting means.
[0004]
A similar cable-shaped pressure sensor is also disclosed in JP-A-3-259575. This publication discloses a composite in which a ceramic piezoelectric powder such as lead titanate is added to a resin such as polyethylene, polypropylene, or vinyl chloride as the flexible piezoelectric body 4. As the flexible outer electrode 5, a nickel film or a copper film by an electroless plating method, and an aluminum film or a silver film by a vapor deposition method are disclosed.
[0005]
When a temporally changing pressure is applied to a part or the entire surface of the cable-shaped pressure sensor, an oscillating voltage corresponding to the acceleration generated in the pressure sensor in that part is induced between the core electrode 3 and the outer electrode 5. By detecting this oscillating voltage by the oscillating voltage detecting means 7, a pressure changing with time is detected.
[0006]
[Problems to be solved by the invention]
However, the conventional cable-type pressure sensor has a problem that it can detect the pressure changing with time but cannot detect the temperature. Whether the composite described above is used as the flexible piezoelectric body 4 or a piezoelectric polymer is used, the maximum use temperature is about (80 to 120) ° C. When the flexible piezoelectric body 4 is exposed to a temperature higher than the maximum use temperature, the piezoelectric performance is deteriorated. Accordingly, sufficient temperature control is required when using the flexible piezoelectric body 4, but the conventional cable-shaped pressure sensor has a temperature sensor separately prepared, so that (1) the configuration becomes complicated. (2) There is a problem that the temperature detected by the temperature sensor does not necessarily match the temperature of the flexible piezoelectric body 4.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention includes a core electrode, a flexible piezoelectric member disposed around the core electrode, and a flexible outer electrode disposed on the surface of the flexible piezoelectric member. A pressure sensor including a cable-shaped pressure sensor, resistance detecting means connected to both ends of the core electrode, and vibration voltage detecting means connected to the core electrode and the flexible outer electrode.
[0008]
The temperature of the core electrode is approximately equal to the temperature of the surrounding flexible piezoelectric body. According to the invention, since the resistance of the core electrode can be detected by the resistance detection means, the average temperature of the flexible piezoelectric body around the core electrode can be detected based on the temperature dependence of the resistance, and the pressure can also be detected by the vibration voltage detection means. It can be detected. Therefore, since it is not necessary to prepare a temperature sensor specially, both can be detected with a simple configuration.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The pressure detection device according to claim 1 of the present invention includes a core electrode, a flexible piezoelectric member disposed around the core electrode, and a flexible outer electrode disposed on a surface of the flexible piezoelectric member. Including a cable-like pressure sensor, resistance detection means connected to both ends of the core electrode, and vibration voltage detection means connected to the core electrode and the flexible outer electrode.
[0010]
Since the resistance of the core electrode can be detected by the resistance detection means, the average temperature of the flexible piezoelectric body around the core electrode can be detected based on the temperature dependence of the resistance. The pressure can also be detected by the vibration voltage detecting means. Therefore, since it is not necessary to prepare a temperature sensor specially, both can be detected with a simple configuration.
[0011]
According to a second aspect of the present invention, there is provided a pressure detecting device in which temperature detecting means for converting resistance to temperature based on resistance temperature characteristics is connected to the resistance detecting means.
[0012]
Since the resistance detected by the resistance detection means is converted into temperature by the temperature calculation means, the temperature can be read directly.
[0013]
According to a third aspect of the present invention, there is provided a pressure detecting device comprising a coiled metal in which a core electrode is held on an insulating support.
[0014]
Since the resistance detected by the resistance detection means is a resistance of a coiled metal, the resistance is larger than that of a straight metal. Therefore, the resistance can be easily detected.
[0015]
According to a fourth aspect of the present invention, the pressure detection device has a configuration in which the insulating support is made of a polyester fiber bundle.
[0016]
The polyester fiber bundle is electrically insulative and has high flexibility and high mechanical strength, so that the coiled metal can be supported without impairing the flexibility of the entire cable-shaped pressure sensor.
[0017]
The pressure detection device according to claim 5 of the present invention has a configuration in which the coiled metal has a flat plate shape.
[0018]
In order to obtain the piezoelectricity of the cable-shaped pressure sensor, it is necessary to polarize the flexible piezoelectric body by applying a high DC voltage between the core electrode and the flexible outer electrode in advance. At this time, since the coiled metal is flat, a uniform high electric field is more easily applied between the core electrode and the flexible outer electrode than in the cylindrical shape.
[0019]
In the pressure detecting device according to claim 6 of the present invention, the coiled metal is made of copper or a copper alloy.
[0020]
Copper or a copper alloy is rich in flexibility and widely used industrially, so that it can be mass-produced without impairing the flexibility of the entire cable-shaped pressure sensor.
[0021]
The pressure detection device according to claim 7 of the present invention is configured such that the resistance detection means detects a DC resistance.
[0022]
Although the AC resistance has frequency dependency, the DC resistance does not have frequency dependency. Therefore, the resistance of the coil metal can be detected without being affected by the inductance or stray capacitance of the coil metal.
[0023]
The pressure detection device according to claim 8 of the present invention has a configuration in which the vibration voltage detection means is connected to the core electrode and the flexible outer electrode via a capacitor.
[0024]
When detecting the DC resistance, a DC potential is applied to both ends of the core electrode. On the other hand, the oscillating voltage is an AC signal. When the vibration voltage is detected by the vibration voltage detection means, the direct current component is removed by the capacitor, so that the vibration voltage can be detected without being affected by the direct current component.
[0025]
According to a ninth aspect of the present invention, there is provided a pressure detecting device having a flexible outer electrode as a ground potential and taking out a vibration voltage signal from the core electrode.
[0026]
Since the core electrode is shielded from the external space by the flexible outer electrode having the ground potential, it is not affected by noise in the external space when detecting resistance or vibration voltage.
[0027]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0028]
Example 1
FIG. 1 is a configuration diagram of a pressure detection device according to a first embodiment of the present invention.
[0029]
After forming the flexible piezoelectric body 4 around the core electrode 3, a flexible outer electrode 5 was formed to constitute a cable-shaped pressure sensor. As the core electrode 3, a core electrode having the configuration shown in the conventional example, a core electrode composed only of a plurality of fine metal wires, or the like is used. As the flexible piezoelectric body 4, a composite in which ceramic piezoelectric powder such as lead titanate and lead zirconate titanate is added to rubber or resin, or vinylidene fluoride (VDF) / trifluoroethylene (TrFE) is used. ) Piezoelectric polymers such as copolymer systems are used. The flexible outer electrode 5 is made of an aluminum foil, a silver-based conductive coating by a coating method, or a conductive film in which an aluminum layer is formed on a polyethylene terephthalate film. After the cable-shaped pressure sensor is formed as described above, the vibration voltage detection means 7 and the resistance detection means 8 are connected between the core electrode 3 and the flexible outer electrode 5 to constitute the pressure detection device of the present invention. The
[0030]
The resistance of the core electrode 3 is detected by the resistance detection means 8 between both ends thereof. The core electrode 3 is made of the conductive material as described above. Since these conductive materials exhibit specific resistance-temperature characteristics, the temperature can be obtained from the detected resistance. On the other hand, when a temporally changing pressure is applied to a part or the entire surface of the cable-shaped pressure sensor, an oscillating voltage corresponding to the acceleration generated in the pressure sensor in that part is induced between the core electrode 3 and the outer electrode 5. . This oscillating voltage is detected by the oscillating voltage detecting means 7. Using this oscillating voltage, a temporally changing pressure is detected. Thus, the structure of Example 1 shown in FIG. 1 can detect temperature and pressure simultaneously.
[0031]
In order to obtain the temperature from the detected resistance, it is necessary to refer to the resistance temperature characteristic. However, since it is troublesome to refer to each time, it is desirable to connect a temperature calculation means for converting the resistance into temperature based on the resistance temperature characteristic as shown in FIG. . This is because the temperature can be read directly.
[0032]
(Example 2)
FIG. 3 is a configuration diagram of the pressure detection device according to the second embodiment of the present invention.
[0033]
The core electrode 3 is composed of a coiled metal 11 wound around an insulating support 10. In the configuration of the conventional example shown in FIG. 6, a core electrode 3 composed of a linear conductive material 1 and a conductive rubber 2 is disclosed. However, in this case, since a plurality of fine metal wires are usually used as the linear conductive material 1, the resistance between both ends of the core electrode 3 is determined by the fine metal wires. Therefore, the resistance is often as low as 0.1 Ω / m or less at room temperature, making it difficult to detect the resistance. In the configuration of Example 2 shown in FIG. 3, since the core electrode 3 is composed of the coiled metal 11 wound around the insulating support 10, the resistance between both ends of the core electrode 3 is the both ends of the coiled metal 11. It is determined by the resistance between. Since the effective length of the coiled metal 11 is much longer than the length of the cable-shaped pressure sensor, the resistance between both ends is 1 Ω / m or more. Therefore, the resistance can be easily detected. For example, in the case of an alloy wire of copper and silver (0.3 mm ^W × 0.05 mm ^t ), it is 2.7 Ω / m or more at room temperature.
[0034]
The insulating support 10 is preferably composed of a polyester fiber bundle. Since the polyester fiber has high mechanical strength and flexibility, the coiled metal can be supported without impairing the flexibility of the entire cable-shaped pressure sensor. Moreover, since the heat resistance is also 120 ° C. or higher, sufficient stability is exhibited even at the maximum use temperature of the flexible piezoelectric body 4 [about (80 to 120) ° C.].
[0035]
Moreover, it is preferable that the coil-shaped metal 11 is flat form. After the cable-shaped pressure sensor is formed in the configuration shown in FIGS. 1 and 3, a DC high voltage (5 to 10) kV / mm is applied between the core electrode 3 and the flexible outer electrode 5, Piezoelectricity is imparted by the step of polarizing the flexible piezoelectric body 4. In this polarization step, it is necessary to apply a uniform high electric field between the core electrode 3 and the flexible outer electrode 5. A uniform high electric field can be obtained in the case of a flat plate shape as compared with the case where the coiled metal 11 has a cylindrical shape or a similar shape. Moreover, copper or a copper alloy is excellent as a coil-shaped metal material. Since these materials are rich in flexibility, they can be easily wound into a coil shape by being wound around an insulating support, and the flexibility of the entire cable-shaped pressure sensor is not impaired. In addition, since it is widely used industrially, it is excellent in mass productivity.
[0036]
In addition, since the coiled metal 11 has an inductance or stray capacitance based on its shape, the AC resistance has frequency dependency. However, since the DC resistance has no frequency dependence, the DC resistance is excellent in that the resistance of the coiled metal can be detected without being affected by the inductance of the coiled metal or stray capacitance. DC resistance between both ends of the core electrode 3 of the cable-shaped pressure sensor (length: about 7 m) formed using the above-described copper-silver alloy wire (0.3 mm ^W × 0.05 mm ^t ), that is, a coil-shaped alloy FIG. 4 shows the resistance temperature characteristics of the DC resistance between both ends of the wire. As can be seen from the figure, a high resistance value of about 18Ω (about 2.5Ω / m) is exhibited even at 0 ° C., and a high resistance temperature coefficient of about 3800 ppm / ° C. is exhibited. Therefore, it is easy to detect the resistance and to calculate the temperature of the flexible piezoelectric body 4 around the core electrode 3 based on the resistance temperature characteristic.
[0037]
In addition, since the measurement shown in FIG. 4 was performed by arranging the cable-shaped pressure sensor in the thermostat, the temperature of the cable-shaped pressure sensor is uniform. However, in a practical state, the temperature is not necessarily uniform as a whole. In such a case, since the resistance shows an average value, the average temperature is also detected. By grasping the temperature distribution in a practical state, for example, if it is a cable-shaped pressure sensor having a heat resistance of 120 ° C., means such as issuing an alarm when the average temperature reaches 80 ° C. can be used. Detection is also effective in practical use.
[0038]
As apparent from the configuration of FIG. 3, the configuration also includes the oscillating voltage detection means 7, so that it is possible to detect not only the DC resistance but also the oscillating voltage based on time-varying pressure. When detecting the DC resistance, a DC potential is applied to both ends of the core electrode 3. On the other hand, the oscillating voltage is an AC signal. When the vibration voltage is detected by the vibration voltage detection means 7, as shown in FIG. 5, a structure in which the vibration voltage detection means 7 is connected to the core electrode 3 and the flexible outer electrode 5 through a capacitor is desirable. This is because since the DC component is removed by the capacitor, the oscillating voltage can be detected without being affected by the DC component.
[0039]
When the resistance detection means 8 and the vibration voltage detection means 7 are connected between the core electrode 3 and the flexible outer electrode 5, it is desirable to take the voltage signal from the core electrode 3 by setting the flexible outer electrode 5 to the ground potential. This is because the core electrode 3 is shielded from the external space by the flexible outer electrode 5 having a ground potential, so that the voltage signal is blocked from noise. When a signal is taken out from the flexible outer electrode 5, since the flexible outer electrode 5 is not shielded from the external space, the voltage signal is greatly affected by noise from the external space.
[0040]
In the above embodiment, the conventional outer skin 6 shown in FIG. 6 is not particularly mentioned, but it is obvious that it may be used as necessary for protection. Further, as the outer skin 6, vinyl chloride or urethane resin may be used in addition to the heat shrinkable tube.
[0041]
【The invention's effect】
As described above, in the pressure detection device according to the first aspect of the present invention, the resistance of the core electrode can be detected by the resistance detection means. Therefore, the average temperature of the flexible piezoelectric body around the core electrode is determined based on the temperature dependence of the resistance. The pressure can also be detected by the vibration voltage detecting means. Therefore, since it is not necessary to prepare a temperature sensor specially, both can be detected with a simple configuration.
[0042]
In the pressure detection device according to claim 2 of the present invention, the resistance detected by the resistance detection means is converted into a temperature by the temperature calculation means, so that the temperature can be read directly.
[0043]
In the pressure detecting device according to claim 3 of the present invention, the resistance detected by the resistance detecting means is a resistance of a coiled metal, and therefore shows a larger resistance than a straight metal wire. Therefore, the resistance can be easily detected.
[0044]
In the pressure detection device according to claim 4 of the present invention, the insulating support made of the polyester fiber bundle is electrically insulative and flexible, and has high mechanical strength. The coiled metal can be supported without impairing the flexibility of the entire sensor.
[0045]
In the pressure detection device according to claim 5 of the present invention, the coiled metal has a flat plate shape. In order to obtain the piezoelectricity of the cable-shaped pressure sensor, it is necessary to polarize the flexible piezoelectric body by applying a high DC voltage between the core electrode and the flexible outer electrode in advance. At this time, since the coiled metal is flat, a uniform high electric field is more easily applied between the core electrode and the flexible outer electrode than in the cylindrical shape.
[0046]
In the pressure detection device according to claim 6 of the present invention, since copper or copper alloy is rich in flexibility and used in many industrial fields, the flexibility of the entire cable-shaped pressure sensor is not impaired. Can be mass-produced.
[0047]
The pressure detection device according to claim 7 of the present invention is configured such that the resistance detection means detects a DC resistance. Although the AC resistance has frequency dependency, the DC resistance does not have frequency dependency. Therefore, the resistance of the coil metal can be detected without being affected by the inductance or stray capacitance of the coil metal.
[0048]
The pressure detection device according to claim 8 of the present invention has a configuration in which the vibration voltage detection means is connected to the core electrode and the flexible outer electrode via a capacitor. When detecting the DC resistance, a DC potential is applied to both ends of the core electrode. On the other hand, the oscillating voltage is an AC signal. When the vibration voltage is detected by the vibration voltage detection means, the direct current component is removed by the capacitor, so that the vibration voltage can be detected without being affected by the direct current component.
[0049]
According to a ninth aspect of the present invention, there is provided a pressure detecting device having a flexible outer electrode as a ground potential and taking out a vibration voltage signal from the core electrode. Since the core electrode is shielded from the external space by the flexible outer electrode having the ground potential, it is not affected by noise in the external space when the vibration voltage is detected.
[Brief description of the drawings]
1 is a configuration diagram of a pressure detection device according to a first embodiment of the present invention. FIG. 2 is another configuration diagram of a pressure detection device according to a first embodiment of the present invention. FIG. 3 is a pressure detection device according to a second embodiment of the present invention. FIG. 4 is a characteristic diagram showing an example of temperature characteristics of DC resistance of the cable-shaped pressure sensor of the pressure detection device. FIG. 5 is another configuration diagram of the pressure detection device according to the second embodiment of the present invention. ] Configuration diagram of pressure detection device using conventional cable pressure sensor 【Explanation of symbols】
3 Core electrode 4 Flexible piezoelectric body 5 Flexible outer electrode 7 Vibration voltage detecting means 8 Resistance detecting means 9 Temperature calculating means 10 Insulating support 11 Coiled metal 12 Capacitor

Claims (9)

A cable-like pressure sensor including a core electrode, a flexible piezoelectric body disposed around the core electrode, a flexible outer electrode disposed on a surface of the flexible piezoelectric body, and both ends of the core electrode A pressure detection device comprising: resistance detection means connected to the electrode; and vibration voltage detection means connected to the core electrode and the flexible outer electrode. The pressure detection device according to claim 1, wherein temperature detection means for converting resistance to temperature based on resistance temperature characteristics is connected to the resistance detection means. 2. The pressure detecting device according to claim 1, wherein the core electrode is made of a coiled metal held on an insulating support. 4. The pressure detection device according to claim 3, wherein the insulating support is made of a polyester fiber bundle. The pressure detection device according to claim 3, wherein the coiled metal has a flat plate shape. 6. The pressure detecting device according to claim 5, wherein the coiled metal is made of copper or a copper alloy. 2. The pressure detection device according to claim 1, wherein the resistance detection means detects a direct current resistance. 2. The pressure detecting device according to claim 1, wherein the vibration voltage detecting means is connected to the core electrode and the flexible outer electrode via a capacitor. The pressure detection device according to claim 1, wherein the flexible outer electrode is set to a ground potential and the vibration voltage signal is taken out from the core electrode.

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