JP2001066195A - Physical quantity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute detection of a physical quantity on a separated position. SOLUTION: Driving energy obtained by converting, into a direct current, an electric energy transferred by executing electromagnetic coupling of an induction coil 13 with a coil 12 generating a magnetic field based on an oscillation output from an external oscillator, is generated by an energy generation part 2. An internal oscillation part 3 is operated by the generated driving energy. An inductance of a coil 23 is changed at a physical quantity detection part 4 based on a detected physical quantity, and a resonant frequency of a circuit comprising a capacitor 22 and the coil 23 is transmitted from among pulse oscillation outputs of the internal oscillation part 3. The resonant frequency is measured by a frequency discrimination circuit 25 composing a reception part 5 installed externally and equipped with a coil 24 coupled electromagnetically with the coil 23. Hereby, measurement of the physical quantity is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a physical quantity sensor for converting a physical quantity such as temperature, pressure, acceleration and the like into a frequency and detecting the frequency at a remote position.

[0002]

2. Description of the Related Art In the case of a conventional physical quantity sensor, for example, a temperature sensor, a thermometer as a temperature sensor is brought into contact with the measured object to measure the temperature of the measured object. However, when the object to be measured is at a remote position and cannot directly contact the temperature sensor, temperature detection becomes difficult.

[0003]

In such a case, the temperature is detected using an infrared sensor or the like. However, this method has a problem that only the surface temperature of the measured object can be detected. For example, there is a problem that it is extremely difficult to detect the temperature of a deep part of a living body or the like. The same applies to pressure, acceleration, and the like, not limited to temperature.

When measuring a physical quantity at a remote location,
Due to the transmission of the detected physical quantity, there has been a problem that the physical quantity sensor becomes large and it is difficult to detect the temperature in the deep part of the living body.

It is an object of the present invention to provide a physical quantity sensor which can detect a physical quantity at a remote position.

[0006]

According to a first aspect of the present invention, there is provided a physical quantity sensor comprising: an energy generating means for generating driving energy based on a magnetic field generated by receiving an oscillation output from an external oscillator; A physical quantity detection means driven by the generated drive energy to detect a physical quantity and generate a frequency output based on the detected physical quantity, and a frequency determination in an externally installed receiving means provided with a coupling circuit for electromagnetically coupling with the physical quantity detection means The frequency output from the physical quantity detecting means is detected by a circuit.

According to the physical quantity sensor of the present invention, the driving energy is generated by the energy generating means based on the magnetic field generated by receiving the oscillation output from the external oscillator, and the generated driving energy is received. Then, the physical quantity detecting means is driven, the physical quantity is detected by the physical quantity detecting means, and a frequency output based on the detected physical quantity is generated.

Therefore, it is not necessary to provide a power supply device as an energy source for operating the physical quantity detecting means inside the physical quantity sensor.

The output based on the frequency based on the physical quantity detected by the physical quantity detecting means is electromagnetically coupled by the coupling circuit of the receiving means, and the frequency based on the physical quantity is determined by the frequency determining circuit, and the physical quantity is determined based on the determined frequency. Is detected.

However, the external oscillator and the receiving means are externally installed, the external oscillator and the energy generating means need only be electromagnetically coupled to detect the physical quantity from the device under test, and the physical quantity detecting means and the receiving means are electromagnetically connected. Because it only needs to be joined,
The volume of the physical quantity sensor can be reduced, and for example, it is possible to detect a physical quantity in a deep part of a living body.

In the physical quantity sensor according to the first aspect of the present invention, when the energy generating means generates energy based on a magnetic field generated by receiving an output from the external oscillator, the energy generating means includes an induction coil and an induction coil. By generating a magnetic field of a specific frequency determined from a circuit connected to the coil, it is possible to increase energy transmission efficiency.

A physical quantity sensor according to a second aspect of the present invention is the physical quantity sensor according to the first aspect, wherein the physical quantity detecting means is driven by the driving energy generated by the energy generating means to perform pulse oscillation. ,
A physical quantity detection unit that receives an oscillation output of the internal oscillation unit as an input, detects a physical quantity, and sends out an output of a frequency based on the detected physical quantity.

According to the physical quantity sensor of the second aspect of the present invention, the driving energy is generated by the energy generating means based on the magnetic field generated by receiving the oscillation output from the external oscillator, and the internal driving energy is generated by the generated driving energy. The oscillating section is driven to perform pulse oscillation, and an output of a frequency based on the detected physical quantity detected by the physical quantity detecting means is transmitted from the output of the internal oscillating section.

Therefore, the physical quantity detected by the physical quantity detecting means is converted into a frequency and transmitted, and a power supply device as an energy source for operating the physical quantity detecting means becomes unnecessary inside the physical quantity sensor.

The physical quantity sensor according to a third aspect of the present invention is the physical quantity sensor according to the first aspect, wherein the energy generating means includes an induction coil coupled to a magnetic field generated by receiving an output of the external oscillator, and an output of the induction coil. And rectifying means for rectifying the pressure.

According to the physical quantity sensor of the third aspect of the present invention, the energy generating means is coupled with the magnetic field generated by receiving the output of the external oscillator and the induction coil, and the output of the induction coil is rectified by the rectification means. Energy is generated by the output, and the configuration is simple.

A physical quantity sensor according to a fourth aspect of the present invention is the physical quantity sensor according to the first or second aspect, wherein the physical quantity detecting means includes a physical quantity detecting means for converting the detected physical quantity into one of an inductance and a capacitance. And converting the detected physical quantity into a frequency.

According to the physical quantity sensor according to claim 4 of the present invention, the physical quantity detection means is configured to include the physical quantity detection means for converting the detected physical quantity into either an inductance or a capacitance, and the detected physical quantity is detected. The frequency is converted into a frequency based on the physical quantity, and the physical quantity can be detected based on the converted frequency.

A physical quantity sensor according to claim 5 of the present invention is the physical quantity sensor according to claim 1 or 2, wherein the physical quantity detection means is wound around a magnetic material having a temperature-sensitive characteristic and a magnetic material having a temperature-sensitive characteristic. And a coil.

According to the physical quantity sensor according to claim 5 of the present invention, the physical quantity detecting means includes a magnetic material having a temperature-sensitive characteristic and a coil wound around the magnetic material having the temperature-sensitive characteristic. The temperature characteristic of the body changes according to the temperature, the temperature is converted into a frequency, and the temperature can be detected based on the converted frequency.

According to a physical quantity sensor according to claim 6 of the present invention, in the physical quantity sensor according to claim 1 or 2, the physical quantity detecting means is wound around a magnetic material having temperature-sensitive characteristics and a magnetic material having temperature-sensitive characteristics. In addition to the coil, the coil in the energy generating means is wound around a magnetic material having a temperature-sensitive characteristic.

According to the physical quantity sensor according to claim 6 of the present invention, the physical quantity detecting means includes the magnetic material having the temperature-sensitive characteristic and the coil wound around the magnetic material having the temperature-sensitive characteristic, and further includes the temperature-sensitive characteristic. Since the coil of the energy generating means is wound around the magnetic material, the coil of the energy generating unit and the coil of the physical quantity detecting means are both wound on the magnetic material, so that the required volume is small.

A physical quantity sensor according to claim 7 of the present invention is the physical quantity sensor according to claim 1 or 2, wherein the physical quantity detection means includes a capacitor having a temperature characteristic, and converts a temperature change into a capacitance change of the capacitor. It is characterized by.

According to the physical quantity sensor according to claim 7 of the present invention, the physical quantity detecting means uses a capacitor having a temperature characteristic, whereby a temperature change is converted into a capacitance change of the capacitor, and a temperature is converted into a frequency. Temperature can be detected by frequency.

According to a physical quantity sensor according to claim 8 of the present invention, in the physical quantity sensor according to claim 1 or 2, the physical quantity detecting means includes a magnetostrictive thin film for changing an inductance based on an external force applied when an external force is applied. It is characterized by having.

According to the physical quantity sensor according to claim 8 of the present invention, the inductance of the magnetostrictive thin film changes based on the applied external force, the external force is converted into a frequency, and the external force applied by the frequency can be detected. Therefore, it is possible to detect physical quantities such as pressure, stress, and acceleration.

A physical quantity sensor according to a ninth aspect of the present invention is the physical quantity sensor according to the first or second aspect, wherein the physical quantity detecting means includes an element whose capacitance changes based on the external force applied when an external force is applied. It is characterized by the following.

According to the physical quantity sensor according to the ninth aspect of the present invention, the capacitance changes based on the applied external force, the external force is converted into a frequency, and the external force can be detected based on the converted frequency. Therefore, it is possible to detect physical quantities such as pressure, stress, and acceleration.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a physical quantity sensor according to the present invention will be described.

FIG. 1 is a block diagram showing a configuration of a physical quantity sensor according to an embodiment of the present invention, and illustrates a case where temperature is measured as a measured physical quantity.

Reference numeral 1 denotes an energy supply circuit, which comprises an external oscillator 10, an amplifier 11, and a coil 12,
The output of the external oscillator 10 is applied to the coil 12 after being amplified by the amplifier 11, and the coil 12 generates a magnetic field.

Reference numeral 2 denotes an energy generating unit, which is an induction coil 13 which generates electromotive force by interlinking with a magnetic flux generated by the coil 12, and a capacitor 1 connected in parallel to the induction coil 13.
4 and a rectifier circuit 15 for rectifying the output voltage of the capacitor 14. Energy generated by electromagnetic induction in the induction coil 13 is stored in the capacitor 14. Here, the energy generating section 2 corresponds to an energy generating means.

In order to maximize the energy stored in the capacitor 14, the frequency of the output signal of the external oscillator 10 is
The resonance frequency of the circuit constituted by the induction coil 13 and the capacitor 14 is matched. A voltage based on the electric charge stored in the capacitor 14 is converted into a DC voltage by the rectifier circuit 15.

Therefore, the electromotive force induced in the induction coil 13 is converted into a direct current and output from the energy generating unit 2.

Reference numeral 3 denotes an internal oscillating unit. The internal oscillating unit 16 performs pulse oscillation using the energy supplied from the energy generating unit 2, and outputs an oscillation output of the internal oscillator 16 from a capacitor 19, a resistor 20 and a transistor 21. And an amplifier that amplifies the oscillation output of the internal oscillator 16 and supplies the amplified output to the physical quantity detector 4 described later. Here, the internal oscillation section 3 and the physical quantity detection section 4 correspond to a physical quantity detection means.

The internal oscillator 16 uses an integrated circuit MC14011 composed of, for example, four NOR circuits, connects each input terminal of the NOR circuits in common, and cascade-connects the four NOR circuits to form a first stage NOR circuit. Is fed back to the input of the first-stage NOR circuit via a resistor 17, and the output of the second-stage NOR circuit is fed back to the input of the first-stage NOR circuit via a capacitor 18, so that the resistance value of the resistor 17 is obtained. Then, pulse oscillation of a frequency based on the capacitance of the capacitor 18 is performed.

The physical quantity detecting section 4 includes a capacitor 22 and a coil 23 connected in parallel to the capacitor 22, and receives an oscillation output from the internal oscillating section 3. Here, since temperature is measured as a physical quantity to be measured, temperature measurement using a magnetic material having temperature-sensitive characteristics is exemplified, and the coil 23 is wound around a magnetic body having temperature-sensitive characteristics. Further, here, the coil 23 included in the physical quantity detection unit 4 and the coil for electromagnetically coupling with the reception unit 5 described later are shared.

The inductance of the coil 23 wound around the magnetic material having temperature-sensitive characteristics changes based on the temperature. If the capacitance of the capacitor 22 is C and the inductance of the coil 23 is L, the resonance frequency due to the capacitance C and the inductance L f changes based on the following equation (1).

F = 1 / {2π · (LC) ^1/2 } (1) Therefore, the signal of the frequency component f in the oscillation output output from the internal oscillation section 3 is amplified, and this frequency f is detected. As a result, the temperature can be detected.

The receiving section 5 includes a coil 24 forming a coupling circuit for electromagnetically coupling with the coil 23 and a frequency discriminating circuit 25, and detects the frequency f output from the physical quantity detecting section 4. The temperature detected by the physical quantity sensor can be measured based on the detected frequency f.

According to the physical quantity sensor according to the embodiment of the present invention configured as described above, it is possible to measure the local temperature at a remote position and in real time.

Next, each element used will be specifically described.

The coil 12 has a diameter of 200 mm, for example.
An air-core coil having a diameter of 27 μH and a length of 16 mm and a length of 10 turns wound by an insulated conductor was used. Induction coil 1
For example, a ferrite core having a square cross section of 28 mm ² and a length of 50 mm and having a winding of 50 turns of an insulated conductor is used for the capacitor 3.
Was used. The resonance frequency of the induction coil 13 and the capacitor 14 was about 90 kHz, and the output frequency of the external oscillator 10 was tuned to 90 kHz. At this time, the output voltage of the energy generation unit 2 was DC 10V.

The internal oscillator 3 includes, for example, an integrated circuit MC14.
By using a pulse oscillation circuit using 011, a resistor of 39 kΩ is used for the resistor 17 and a 15 n
When the capacitor of F was used, a pulse wave oscillation output having a period of 1 ms was obtained.

A temperature-sensitive ferrite was used as a magnetic material having a temperature characteristic for forming the coil 23. Curie temperature 55
Nine disc-shaped temperature-sensitive ferrites having a temperature of 4 ° C., a diameter of 4 mm, and a thickness of 1.6 mm were stacked, and 588 turns of an insulated conductor were wound therearound to form a coil 23. At this time, the inductance of the coil 23 changed between 817 μH and 2.4 mH at a temperature of 55 ° C. to 80 ° C. As the capacitor 22, a 0.5 nF capacitor was used. By using these elements, the resonance frequency f of the capacitor 22 and the coil 23 depends on the temperature and ranges from 140 kHz to 2 kHz.
It varied between 40 kHz.

The coil 24 was formed by winding a 200-turn winding of an insulated conductor on a ferrite cut core having a cross-sectional area of 22.5 mm ² , and the inductance was 2.9 mH. The frequency discrimination circuit 25 simulates an auto-tuning mechanism of a radio receiver, and measures the frequency of a signal received by the coil 24 by changing the capacitance of an internal capacitor.

The distance between the coil 12 and the induction coil 13 is 200 mm, and the distance between the coil 23 and the coil 24 is also 20 mm.
The measurement result of the temperature remote sensing ability under the condition of 0 mm was as follows.

When the temperature around the physical quantity detector 4 is changed, the frequency of the magnetic field generated in the coil 23 changes according to the temperature, and as shown in FIG. 2, the resonance frequency f increases monotonically with the temperature rise. . Since the voltage input to the frequency determination circuit 25 connected to the coil 24 has a frequency spectrum as schematically shown in FIG. 3, the temperature is measured by extracting the largest frequency component in this spectrum. can do.

From the above results, it has been clarified that in this case, the temperature measurement at a remote position can be performed in a temperature range of 55 ° C. to 80 ° C. at a remote position and in real time.

As described above, in the physical quantity sensor according to the embodiment of the present invention, since the temperature is converted into the frequency and measured, the position of the physical quantity sensor fluctuates during the measurement, and the signal transmitted and received by electromagnetic induction is transmitted. Even if the intensity changes, there is an effect that the measurement is not hindered at all.

Further, when two or more physical quantity sensors according to the embodiment of the present invention are arranged, the resonance frequency of the resonance circuit formed by the induction coil 13 and the capacitor 14 of each of the plurality of physical quantity sensors is changed. By doing
By changing the oscillation frequency of the external oscillator 10, it becomes possible to select a physical quantity sensor that receives energy supply, that is, an operating physical quantity sensor.

The induction coil 13 may be wound together with the coil 23 on the temperature-sensitive ferrite of the coil 23. By doing so, the physical quantity sensor according to one embodiment of the present invention can be downsized.

The induction coil 13 can be used in common with the coil 23, so that the physical quantity sensor can be downsized. In this case, the oscillation frequency of the external oscillator 10 is set outside the frequency range output from the physical quantity sensor, or energy is supplied as the induction coil 13 for a predetermined period of time in a time-division manner. During the other periods of the period, the induction coil 13 and the coil 23 are shared by a method such as acting as the coil 23 for sending out the output from the physical quantity detection unit 4.

The method of measuring the temperature may be a method using the temperature change of the capacitance of the capacitor 22 instead of the change of the inductance L, in addition to the method based on the change of the inductance of the coil 23 as described above.

When a magnetic material having a temperature-sensitive characteristic is used for the physical quantity detecting unit 4, a specific magnetic material is, for example, a soft magnetic material whose magnetic permeability changes with temperature, or a temperature-sensitive ferrite used for a temperature switch. Materials and the like can be applied.

FIG. 4 shows the temperature change of the dielectric constant of a dielectric such as barium titanate. By forming the capacitor 22 using this dielectric, the capacitor 2
2 changes with temperature, and the resonance frequency f of the capacitor 22 and the coil of the physical quantity detection unit 4 changes. Therefore, the frequency of the magnetic field output from the coil of the physical quantity detection unit 4 changes, and the temperature can be measured by measuring the frequency with the frequency determination circuit 25.

As shown in FIG. 5, in the acceleration detector 40 having a cantilever structure, a material whose inductance when directly energized changes due to strain, for example, cobalt.
By providing the magnetostrictive thin-film coil 42 in which the iron / silicon / boron thin film is formed in a coil structure at the base of the cantilever 41, the distortion of the base of the cantilever 41 based on the received acceleration can be converted into a change in inductance.
Therefore, by using the magnetostrictive thin-film coil 42 formed in the above-mentioned coil structure instead of the coil 23, remote sensing of acceleration becomes possible.

Further, as shown in FIG. 6, instead of the capacitor 22, the pressure and stress are measured by using a pressure sensor in which the distance between opposing electrode plates changes due to the received pressure and the capacitance changes. Can also. FIG. 6 shows a case where a single crystal Si substrate is doped with polycrystalline Si and n ⁺ doped layers as electrodes.
The capacitance changes based on the pressure applied to the polycrystalline Si and n ⁺ .

In the above, temperature measurement, acceleration measurement,
Although the case of pressure and stress measurement has been illustrated, a physical quantity detection unit that can convert a measured physical quantity into a change in inductance or a change in capacitance can be applied to this physical quantity sensor even if the physical quantity is other than this.

[0060]

As described above, according to the physical quantity sensor according to the present invention, a physical quantity is converted into a frequency and detected, and can be detected regardless of the position where the physical quantity sensor is placed. Is possible,
It becomes possible to detect a physical quantity at a position where measurement was impossible. Further, since the operation energy of the physical quantity sensor is magnetically applied from the outside, it is not necessary to provide an energy source inside the physical quantity sensor, and the physical quantity can be detected at a remote position.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a physical quantity sensor according to one embodiment of the present invention.

FIG. 2 is a temperature versus resonance frequency characteristic diagram for explaining the operation of the physical quantity sensor according to one embodiment of the present invention.

FIG. 3 is a reception voltage versus frequency characteristic diagram using temperature as a parameter for explaining the operation of the physical quantity sensor according to one embodiment of the present invention.

FIG. 4 is a temperature characteristic diagram of a dielectric constant of a dielectric used in the physical quantity sensor according to the embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating an example of an acceleration detector used in the physical quantity sensor according to one embodiment of the present invention.

FIG. 6 is a schematic diagram showing an example of a pressure sensor used for a physical quantity sensor according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Energy supply circuit 2 ... Energy generation part 3 ... Internal oscillation part 4 ... Physical quantity detection part 5 ... Reception part 10 ... External oscillator 11 ... Amplifier 12 ... Coil 13 ... Induction coil 14 ... Capacitor 15 ... Rectification circuit 16 ... Internal oscillator 22 ... Capacitor 23 ... Coil 24 ... Coil 25 ... Frequency discrimination circuit 40 ... Acceleration detector 41 ... Cantilever 42 ... Magnetostrictive thin film coil

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01L 9/12 G01L 9/12 G01P 15/11 G01P 15/11 15/125 15/125 H01L 29/84 H01L 29/84 A (72) Inventor Mitsuteru Inoue 20-8, Jizogairi, Iga-cho, Okazaki-shi, Aichi Pref. Hall A301 (72) Inventor Etsuo Otsuki 6-7-1, Koriyama, Taishiro-ku, Sendai-shi, Miyagi Prefecture Tokin Co., Ltd. F term (reference) 2F055 AA40 BB20 CC02 DD05 EE21 EE25 2F056 CL08 SA08 SA10 4M112 AA01 BA07 CA02 CA12 EA03 EA04

Claims (9)

[Claims] An energy generating means for generating driving energy based on a magnetic field generated by receiving an oscillation output from an external oscillator; a physical quantity detected by being driven by the driving energy generated by the energy generating means; Physical quantity detection means for generating an output of a frequency based on the physical quantity detection means, wherein the frequency output from the physical quantity detection means is detected by a frequency discrimination circuit in an externally installed receiving means provided with a coupling circuit for electromagnetically coupling with the physical quantity detection means. Physical quantity sensor. 2. The physical quantity sensor according to claim 1, wherein the physical quantity detecting means is driven by the drive energy generated by the energy generating means to perform pulse oscillation, and receives an oscillation output of the internal oscillation section as an input. A physical quantity detection unit for detecting a physical quantity and transmitting an output of a frequency based on the detected physical quantity. 3. The physical quantity sensor according to claim 1, wherein the energy generating means includes an induction coil coupled to a magnetic field generated by receiving an output of the external oscillator, and a rectifying means rectifying the output of the induction coil. A physical quantity sensor characterized by the above-mentioned. 4. The physical quantity sensor according to claim 1, wherein the physical quantity detecting means includes physical quantity detecting means for converting the detected physical quantity into one of inductance and capacitance, and converting the detected physical quantity into a frequency. Characteristic physical quantity sensor. 5. The physical quantity sensor according to claim 1, wherein the physical quantity detection means includes a magnetic material having temperature-sensitive characteristics and a coil wound around the magnetic material having temperature-sensitive characteristics. Sensor. 6. The physical quantity sensor according to claim 1, wherein the physical quantity detecting means has temperature-sensitive characteristics in addition to the magnetic material having temperature-sensitive characteristics and the coil wound around the magnetic material having temperature-sensitive characteristics. A physical quantity sensor, wherein a coil in an energy generating section is wound around a magnetic body. 7. The physical quantity sensor according to claim 1, wherein the physical quantity detecting means includes a capacitor having a temperature characteristic, and converts a temperature change into a capacitance change of the capacitor. 8. The physical quantity sensor according to claim 1, wherein the physical quantity detecting means includes a magnetostrictive thin film that changes an inductance based on the external force applied when the external force is applied. 9. The physical quantity sensor according to claim 1, wherein the physical quantity detection means includes an element whose capacitance changes based on the external force applied when the external force is applied.