JP2615486B2 - Pressure detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure detector for measuring a pressure of a fluid.

Conventional technology Conventionally, as a pressure detector using magnetic fluid,
The thing as shown in Unexamined-Japanese-Patent No. 61-28032 was known. In this method, a pair of magnets are arranged at both ends of a magnetic fluid disposed in a tube to hold the magnetic fluid, a coil is provided at a neutral position of the magnetic fluid, and a change in the position of the magnetic fluid caused by a pressure difference is generated by the coil. It was detected as a change in inductance.

However, in this method, since the magnetic fluid is held by a pair of magnets, if these magnets are set apart, the magnetic fluid may be separated, and the magnets may be separated from each other. In the case of (1), there is a disadvantage that the displacement behavior of the magnetic fluid is complicated due to mutual interference of the magnets.

Means for Solving the Problems The present invention has been made to solve the above problems, and has a magnet disposed with a gap around a shaft of a magnetic body, and a magnet disposed on both sides of the magnet in the longitudinal direction of the shaft. And a magnetic circuit formed by the magnet, the pole piece, and the shaft holds a magnetic fluid disposed in a gap between the shaft and the pole piece, and displaces the magnetic fluid. Is provided as a change in inductance.

Operation With the configuration described above, the present invention regards the amount of displacement of the magnetic fluid caused by the pressure difference acting on both surfaces of the magnetic fluid as a change in the inductance of the coil, and thereby detects the pressure.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, 1 is a pressure detector, 2 is a magnetic circuit unit, 3 is a detection coil, and 4 and 5 are pipelines. The magnetic circuit section 2 forms a magnetic circuit by the annular permanent magnet 6, the pole pieces 7 and 8, and the shaft 9, and a magnetic fluid 10 is held between the pole piece 8 and the shaft 9. .
The shaft 9 is held by a support member 12 having an opening 11. The permanent magnet 6 is N in the axial direction of the pipeline as shown in the figure.
The pole and the S pole are magnetized. 13 is a chamber (a) connected to the pipe 4, and 14 is a chamber (b) connected to the pipe 5. The chamber (a) 13 and the chamber (b) 14 are partitioned by the magnetic fluid 10.

FIG. 3 shows the oscillation circuit 15. 16 is an inverter, 17 is a resistor, and 18 and 19 are capacitors.

 Next, the operation will be described.

Now, assuming that the pressures Pa and Pb of the chamber (a) 13 and the chamber (b) 14 are equal, the magnetic fluid 10 is held in the state shown in FIG. The circuit 15 shown in FIG. 3 oscillates based on the inductance of the coil 3 determined in this state. The output is taken out from terminal A. At this time, the frequency is f1.

Next, when the pressure in the chamber (a) 13 becomes larger than the pressure in the chamber (b) 14 (Pa> Pb), the magnetic fluid 10 is displaced toward the chamber (b) 14 as shown in FIG. Increase the inductance of the coil 3. As a result, the frequency f2 of the oscillation circuit 15 becomes f1
Lower frequency.

Thus, the displacement of the magnetic fluid 10 due to the pressure difference
Is changed, and this is detected as a change in the oscillation frequency, whereby the pressure can be detected.

As described above, in the present invention, since pressure detection is performed only by one permanent magnet and one detection coil, a small and compact pressure detector can be obtained.

 Next, a second embodiment will be described.

FIG. 5 shows that the permanent magnet 6 shown in FIG.
And an electromagnet configuration formed by the cylindrical yoke 21.

 Next, the operation will be described.

Now, assuming that the energizing current of the exciting coil is i1, the magnetic field generated by this causes the magnetic fluid 10 to be held. The detection operation when a pressure difference is applied is the same as in the first embodiment. Next, assuming that the energizing current is i2 (i1 <i2), the coercive force of the magnetic fluid 10 is increased, and a higher pressure difference can be detected.

As described above, the magnet holding the magnetic fluid is configured as an electromagnet, and by changing the energizing current, a pressure detector capable of coping with a wide pressure range can be formed with the same configuration. .

 Next, a third embodiment will be described.

FIG. 6 differs from FIG. 5 only in that the cylindrical yoke 21 is constituted by a holding permanent magnet 22.

 Next, the operation will be described.

As in the second embodiment, the coercive force of the magnetic fluid 10 changes when the energizing current changes, and a wide range of pressure differences can be detected. In this case, the energization is stopped. Even at this time, the magnetic fluid 10 is held by the holding permanent magnet 22.

As described above, by using the cylindrical yoke 21 of the excitation coil 20 as a permanent magnet, the magnetic fluid
Can be maintained, so that it is possible to support a wide pressure range with the same configuration by changing the energizing current, and it is possible to form a power saving type pressure detector that can stop energization when not in use. To play.

Effects of the Invention (1) In the present invention, since pressure detection is performed only by one permanent magnet and one detection coil, a small and compact pressure detector can be obtained.

(2) By forming the magnet holding the magnetic fluid in an electromagnet configuration and changing the current supplied thereto, it is possible to form a pressure detector capable of supporting a wide pressure range with the same configuration.

(3) By using a permanent magnet as the cylindrical yoke of the exciting coil, it is possible to hold the magnetic fluid without the need for normal energization. When not in use, there is an effect that a power saving type pressure detector that can stop energization can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pressure detector showing one embodiment of the present invention,
2 is a plan view of the shaft support member, FIG. 3 is an oscillation circuit diagram, FIG. 4 is a sectional view showing a different operation state of FIG. 1, and FIG. 5 is a pressure diagram showing a second embodiment of the present invention. Sectional view of detector, sixth
FIG. 7 is a sectional view of a pressure detector showing a third embodiment of the present invention. 1 ... pressure detector, 3 ... detection coil, 6 ... permanent magnet (magnet), 7, 8 ... pole piece, 9 ... axis, 10 ...
Magnetic fluid, 20 ... exciting coil, 21 ... cylindrical yoke (yoke), 22 ... permanent magnet for holding (permanent magnet).

Claims (3)

(57) [Claims] 1. A magnet provided with a gap around a shaft of a magnetic body, and pole pieces respectively disposed on both sides of the magnet in a longitudinal direction of the shaft, wherein the magnet, the pole piece, The magnetic circuit formed by the shaft holds the magnetic fluid disposed in the gap between the shaft and the pole piece, and provides pressure chambers on both sides of the magnetic fluid, and the pressure generated by the pressure applied to the pressure chamber. A pressure detector equipped with a detection coil that detects the displacement of a magnetic fluid as a change in inductance. 2. The pressure detector according to claim 1, wherein the magnet is constituted by an exciting coil and a yoke provided outside the exciting coil. 3. The pressure detector according to claim 2, wherein the yoke is constituted by a permanent magnet.