JP3002470U - pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a pressure sensor with excellent measurement accuracy. [Structure] The bellows 1 which closes the airtight body 14 with a bellows 13 or a diaphragm and moves in response to a measurement pressure.
In the pressure sensor 10 for detecting the amount of movement of the diaphragm 3 or the diaphragm by the reactance amount of the coil portion 16 of the LC oscillation circuit 17, a cylindrical permanent magnet 19 is fixed to the bellows 13 or the diaphragm, and the coil portion 1
6 is supported in a fixed state, and is wound around a drum 15 formed of a magnetic core fitted into the cylindrical permanent magnet 19 according to the movement of the bellows 13 or the diaphragm.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pressure sensor that detects the amount of movement of a bellows or diaphragm that moves in response to a measured pressure using an LC oscillation circuit.

[0002]

[Prior art]

 As shown in FIG. 4, a conventional pressure sensor 70 includes a pressure measuring port 71, a flat metal plate 72, an airtight body 74 that is closed by a bellows 73 that is fixed to the outside, and is supported in a fixed state. And an LC oscillation circuit 77 having a coil portion 76 wound inside an E-shaped pot core 75. Then, the movement amount of the bellows 73 that moves according to the measured pressure is converted into a change in the reactance of the coil portion 76 of the LC oscillation circuit 77, the oscillation frequency of the LC oscillation circuit 77 is changed, and the oscillation frequency is counted or The pressure was measured electrically by f / V conversion.

[0003]

[Problems to be solved by the device]

 However, in the pressure sensor 70, a flat non-magnetic material is used for the metal plate 72, and the effective reactance is changed by changing the internal eddy current by bringing it close to the pot core 75, so that the metal plate 72 is changed. Change of the effective reactance is small with respect to the moving amount, and thus the change of the frequency of the LC oscillation circuit 77 with respect to the moving amount is small. On the other hand, an electric component or a mechanical component causes an error due to a temperature change or an aging change. However, if the vibration frequency changes little with respect to the movement amount of the bellows 73 as described above, the error and a slight pressure change may occur. There is a problem that the accuracy of pressure measurement becomes poor because it is difficult to distinguish it from the detected amount. The present invention has been made in view of such circumstances, and an object thereof is to provide a pressure sensor having excellent measurement accuracy.

[0004]

According to a first aspect of the present invention, there is provided a pressure sensor according to claim 1, wherein an airtight body is closed with a bellows or a diaphragm, and a movement amount of the bellows or the diaphragm that moves in response to a measured pressure is an LC oscillation circuit. In the pressure sensor that detects by the reactance amount of the coil part of the above, a cylindrical permanent magnet is fixed to the bellows or the diaphragm, the coil part is supported in a fixed state, and the cylindrical part is fixed according to the movement of the bellows or the diaphragm. It is wound around a drum consisting of a magnetic core that fits into a cylindrical permanent magnet. The pressure sensor according to a second aspect is the pressure sensor according to the first aspect, wherein the magnetic core has flange portions on both sides and is composed of a ferrite core. The pressure sensor according to claim 3, wherein the airtight body is closed with a bellows or a diaphragm, and the movement amount of the bellows or the diaphragm that moves in response to the measured pressure is detected by the reactance amount of the coil portion of the LC oscillation circuit. A rod-shaped permanent magnet is fixed to the bellows or the diaphragm, the coil portion is supported in a fixed state, and the rod-shaped permanent magnet is wound from the inside so that the rod-shaped permanent magnet is fitted according to the movement of the bellows or the diaphragm. It is configured to be turned. The pressure sensor according to a fourth aspect is the pressure sensor according to the third aspect, wherein the pot core is formed of a ferrite core.

[0005]

[Action]

 In the pressure sensor according to claim 1 or 2, the airtight body is closed by a bellows or diaphragm to which a cylindrical permanent magnet is fixed, and when the bellows or diaphragm moves in response to pressure, the cylindrical shape is fixed to the bellows. The reactance of the coil portion is changed by changing the amount of insertion of the drum including the magnetic core, which is wound around the coil portion of the LC oscillator circuit and is supported in a fixed state, around the permanent magnet. In this case, the coil portion is wound around the magnetic core, and the magnetic core is fitted into the cylindrical permanent magnet. Therefore, the magnetic core is magnetized by the cylindrical permanent magnet and is biased, so that it is substantially transparent. The magnetic susceptibility changes, which greatly changes the reactance. Particularly, in the pressure sensor according to the second aspect, since the magnetic core has the flanges on both sides, the gap between the magnetic core and the cylindrical permanent magnet becomes small, which increases the magnetic susceptibility of the magnetic core and further increases the magnetic susceptibility. The frequency change rate can be obtained. In the pressure sensor according to claims 3 and 4, the airtight body is closed by a bellows or a diaphragm to which a rod-shaped permanent magnet is fixed, and when the bellows or the diaphragm moves in response to pressure, the rod-shaped permanent magnet is fixed to the bellows. However, the reactance of the coil portion of the LC oscillator circuit is changed by changing the amount of the coil portion wound into the pot core of the magnetic material supported in a fixed state. In this case, the coil portion is wound around the pot core made of a magnetic material, and the rod-shaped permanent magnet is fitted into the pot core. Therefore, the pot core is magnetized by the rod-shaped permanent magnet and is in a biased state. The magnetic permeability changes, and this greatly changes the reactance.

[0006]

【Example】

 Next, an embodiment of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. 1 is a front sectional view of the pressure sensor according to the first embodiment of the present invention, FIG. 2 is a graph showing the relationship between the moving distance of the bellows and the oscillation frequency, and FIG. 3 is the second embodiment of the present invention. FIG. 3 is a front sectional view of a pressure sensor according to an example. A pressure sensor 10 according to a first embodiment of the present invention shown in FIG. 1 is wound around an airtight body 14 closed by a bellows 13 and a drum 15 made of a ferrite core which is an example of a magnetic core. It has an LC oscillation circuit 17 having a coil section 16.

The airtight body 14 is provided with a pressure measuring port 18 at the upper part, and is closed by a bellows 13 to which a cylindrical permanent magnet 19 is fixed at the outer center thereof. The cylindrical permanent magnet 19 is adapted to move. The cylindrical permanent magnet 19 is made of a strong permanent magnet and has a fitting hole 20 in the center. The drum 15 has flanges 15a on both sides, and is fixedly supported at a position slightly inserted into the insertion hole 20 of the cylindrical permanent magnet 19, and the drum 15 has a coil portion of the LC oscillation circuit 17. 16 are wound. Then, when the cylindrical permanent magnet 19 fixed to the bellows 13 approaches the drum 15, the reactance of the coil portion 16 changes. Therefore, the movement amount of the bellows 13 that moves according to the pressure changes the reactance of the coil portion 16. The LC oscillation circuit 17 is detected by changing the oscillation frequency of the LC oscillation circuit 17.

The LC oscillating circuit 17 is a normal high frequency (about 200 KHz to 2 MHz) LC oscillating circuit, and the oscillating frequency is changed by changing the reactance of the coil section 16.

The operation of the pressure sensor 10 will be described. When the pressure measuring port 18 of the airtight body 14 is appropriately connected to the object to be measured with a hose, a metal fitting or the like, and the pressure in the airtight body 14 is set to the measurement pressure, The bellows 13 moves in response to the internal pressure, which changes the amount of the drum 15 fitted into the cylindrical permanent magnet 19, which changes the reactance and changes the oscillation frequency of the LC oscillation circuit 17. . The output pulse of the LC oscillating circuit 17 per predetermined time is counted by a digital counter, and the counted number is converted into a measured pressure to measure the pressure. It is also possible to convert the output of the LC oscillation circuit 17 into f / V to obtain the pressure number.

Here, the data comparing the performance of the pressure sensor 10 with the pressure sensor 70 according to the conventional example will be described. FIG. 2 shows the pressure sensor 10 according to the first embodiment of the present invention. As shown, when the bellows 13 moved by 0.6 mm, the oscillation frequency (Δf) changed by about 50%. On the other hand, when the movement amount of the bellows 73 of the conventional pressure sensor 70 having a different structure under substantially the same conditions is 0.6 mm, the change (Δf ′) in the oscillation frequency is about 7%. Therefore, the pressure sensor 10 of this embodiment has about 7 times the sensitivity, and the measurement accuracy can be improved.

Next, a pressure sensor 21 according to a second embodiment of the present invention shown in FIG. 3 will be described. The pressure sensor 21 of the present invention is a pot core 22 made of ferrite which is an example of a magnetic material in place of the drum 15 around which the coil portion 16 of the LC oscillator circuit 17 is wound in the pressure sensor 10 of the first embodiment. The rod-shaped permanent magnet 23 is fixed to the bellows 13 instead of the cylindrical permanent magnet 19. The pot core 22 has a fitting hole 24 formed in the center thereof, and the coil portion 16 is wound from the inside. The rod-shaped permanent magnet 23 fixed to the bellows 13 is fitted in the pot core 22. In this case as well, since it operates on the same principle as the pressure sensor 10 according to the first embodiment, a frequency change rate of a sufficient magnitude (about 7 times) is produced as compared with the conventional pressure sensor 70. Further, although the case of using the bellows has been described in the present embodiment, a pressure sensor with high accuracy can be obtained in the same manner in the case of using the diaphragm.

[0012]

[Effect of device]

 In the pressure sensor according to claim 1 or 2, a cylindrical permanent magnet is fixed to the bellows or the diaphragm, and the coil portion is supported in a fixed state and is fitted into the cylindrical permanent magnet according to the movement of the bellows or the diaphragm. Since the bellows or diaphragm moves in response to the pressure and the cylindrical permanent magnet approaches the drum, the reactance of the coil part increases depending on the amount of movement of the bellows. It changes, and the oscillation frequency also changes greatly according to the change of the reactance, and a large frequency change rate can be obtained. Therefore, the amount of change is large with respect to heat of parts or changes with time, and the accuracy of the pressure sensor can be improved. In addition, since the rate of change of the oscillation frequency is large, if a digital counter that counts output pulses (including sine curve output) within a specific measurement time is used to measure the output of the LC oscillator circuit, the measurement time Even if is shortened, it is possible to count the pulses having many rate of change with respect to the change in pressure. Therefore, if the accuracy is the same, it is possible to shorten the pulse measurement time of the conventional digital counter, which can reduce the operating time, which reduces the power consumption and is particularly convenient in the case of battery drive. Become. Particularly, in the pressure sensor according to the second aspect, since the magnetic core has the flanges on both sides and is composed of the ferrite core, the magnetic susceptibility by the cylindrical permanent magnet is improved, and a larger frequency change rate can be obtained. .

In the pressure sensor according to claims 3 and 4, a rod-shaped permanent magnet is fixed to the bellows or the diaphragm, the coil portion is supported in a fixed state, and the rod-shaped permanent magnet is fixed in accordance with the movement of the bellows or the diaphragm. Since it is wound from the inside on the pot core made of a magnetic material to be inserted, when the bellows or diaphragm moves in response to pressure and the rod-shaped permanent magnet approaches the pot core, the reactance of the coil part changes according to the amount of movement of the bellows. A large change is made, and the oscillation frequency is greatly changed in accordance with the change in the reactance, and a large frequency change rate can be obtained. Therefore, the pressure sensor has high accuracy. For the same reason as described in claims 1 and 2, the change rate of the oscillation frequency is large, so that the output pulse (including the sine curve output) within a specific measurement time is measured for the output of the LC oscillator circuit. When a digital counter that counts is used, this can reduce the operation time and further reduce its power consumption.

[Brief description of drawings]

FIG. 1 is a front sectional view of a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a moving distance of the bellows and an oscillation frequency.

FIG. 3 is a front sectional view of a pressure sensor according to a second embodiment of the present invention.

FIG. 4 is a front sectional view of a pressure sensor according to a conventional example.

[Explanation of symbols]

 10 Pressure Sensor 13 Bellows 14 Airtight Body 15 Drum 15a Collar 16 Coil 17 LC Oscillation Circuit 18 Pressure Measuring Port 19 Cylindrical Permanent Magnet 20 Fitting Hole 21 Pressure Sensor 22 Pot Core 23 Rod-like Permanent Magnet 24 Fitting Hole

Claims (4)

[Scope of utility model registration request] 1. A pressure sensor for closing an airtight body with a bellows or a diaphragm, and detecting a moving amount of the bellows or the diaphragm which moves in response to a measured pressure by a reactance amount of a coil portion of an LC oscillation circuit. A tubular permanent magnet is fixed to the coil, and the coil portion is supported in a fixed state and wound around a drum having a magnetic core that is fitted into the tubular permanent magnet in accordance with the movement of the bellows or the diaphragm. Pressure sensor. 2. The pressure sensor according to claim 1, wherein the magnetic core has flanges on both sides and is made of a ferrite core. 3. A pressure sensor for closing an airtight body with a bellows or a diaphragm, and detecting a moving amount of the bellows or the diaphragm which moves in response to a measured pressure by a reactance amount of a coil portion of an LC oscillation circuit. A rod-shaped permanent magnet is fixedly attached to the coil portion, the coil portion is supported in a fixed state, and is wound from the inside on a pot core made of a magnetic material into which the rod-shaped permanent magnet is fitted according to the movement of the bellows or the diaphragm. Pressure sensor. 4. The pressure sensor according to claim 3, wherein the pot core comprises a ferrite core.