JPS6014229B2 - Magnetic fluid seal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a magnetic fluid replenishment mechanism in a magnetic fluid seal device applied to various gas seals.

Conventional magnetic fluid seal devices have sufficient sealing performance during steady operation, but if a sudden pressure rise occurs or the magnetic fluid evaporates and is consumed, the magnetic fluid scatters and loses its sealing performance. Therefore, magnetic fluid must be replenished.

As an example of the conventional structure of a magnetic fluid sealing device having this replenishing device, a vertical cross-sectional view is shown in FIG. In FIG. 1, two annular pole blocks 2 surrounding a rotating shaft 1 are supported on the inner peripheral surface of a fixed casing 4 via a ring 3, and rotated facing the inner peripheral surface of the two annular pole blocks 2. A plurality of annular microprotrusions 7 are formed on the outer peripheral surface of a magnetic cylinder 6 attached to the shaft 1 via an O-ring 5, respectively. Raised magnets 8 are bridged between opposing end surfaces of the annular ball block 2 at equal pitches on the same circumference, and both non-opposed outer end surfaces are opposed to a bearing 9 with a space between them. The gas passes through the pipe inlet 10, passes through the rotating shaft 1 and the magnetic cylinder 6, and enters the space 1 surrounded by the inner circumferential surface of the fixed casing 4, the competitive surface of the magnetic cylinder 6, and the opposing sides of the annular pole block 2.
1 and then passes through the pipe outlet 12 that penetrates the fixed casing 4. A space 13 surrounded by the inner circumferential surface of the fixed casing 4, the outer circumferential surface of the rotating shaft 1, the side surface of the annular pole block 2, the side surface of the magnetic cylinder 6, and the side surface of the bearing 9.
is filled with atmosphere. Further, the magnetic fluid supply pipe 14 includes a fixed casing 4 and an annular pole valve. It is provided through the rack 2. In such a structure, the twill magnet 8 → left annular pole block 2 → (gap) → the plurality of annular microprotrusions 7 on the left side → the magnetic cylinder 6 → the multiple annular microprotrusions 7 on the right side → (gap) → the right side A magnetic circuit is formed from the annular pole flock 2 to the birch magnet 8. When a viscous fluid containing magnetic particles, so-called magnetic fluid 15, is appropriately injected into each of the annular microprotrusions 7 from the magnetic fluid supply path 14, this magnetic fluid 15 is located in the magnetic circuit described above. Therefore, the magnetic flux density is concentrated at the tip of the annular microprotrusion 7 where the density is highest, and this magnetic fluid 15 generates a pressure resistance that seals the gas, so that the gas in the space 11 does not leak into the space 13 on the atmosphere side. do not have. In such a conventional magnetic fluid sealing device, if a sudden abnormal pressure rise occurs in the gas for some reason, the magnetic fluid 15 will scatter and the sealing performance will be lost, so the magnetic fluid supply path 14 will be immediately closed.
Although it is necessary to inject and replenish the magnetic fluid 15, for example, in the case of a superconductive rotating machine, the gas pressure of low-temperature helium gas is high, so cold gas is ejected to the outside from the magnetic fluid replenishment pipe 14, and the surrounding area is cooled. This has the disadvantage that, even if frost forms and the gas returns to a steady state pressure, the magnetic fluid cannot be injected and replenished from the magnetic fluid supply path 14.
That is, in order to replenish the magnetic fluid 15, it was necessary to stop the operation of the rotating machine and lower the gas pressure. This invention eliminates the above-mentioned drawbacks and makes it possible to automatically and quickly replenish magnetic fluid and restore sealing performance without having to stop the rotating machine and reduce gas pressure. The purpose of the present invention is to provide a magnetic fluid sealing device. Therefore, according to the present invention, the above object is to provide a replenishment device in a magnetic fluid replenishment path to forcibly replenish the magnetic fluid, and to control the replenishment device, for example, a pressure detector, a comparator circuit, a pulse generator, an amplifier, etc. This can be achieved by using a structure that uses a spline bag joint, a pressure sensor, and a differential circuit. Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a longitudinal section of a magnetic fluid seal device according to an embodiment of the present invention. In the figure, parts corresponding to those of the conventional device (FIG. 1) are given the same reference numerals. In this embodiment, a magnetic fluid replenishing device 16 that stores a large amount of magnetic fluid in advance and replenishes it little by little is connected to the magnetic fluid replenishing path 14, and a pulse motor 18 is connected to the magnetic fluid replenishing device 16 via a spline shaft joint 17. Directly connected. 20 is this pulse mode 18
A pulse oscillator that supplies pulses to
9 is interposed.

21 is a comparison circuit that outputs a pressure signal to the atmospheric side pressure sensor (often set to 2.3 billion) and a pressure sensor 22 that detects the pressure that drops from high pressure to atmospheric pressure when the seal is broken. compare.

Figure 3 shows the magnetic fluid supply device 16 and spline shaft joint 17.
In the vertical cross-sectional view of the part, 17a is a spline part, and the shaft 17b is integrated with the shaft of the magnetic fluid replenishing device 16. 16a
is a cylinder with a straight 16 magnetic fluid supply bag and a screw 16b on the inside.
A plunger 16c is connected to the shaft 17b, and the plunger 16c has a screw on the outer periphery to be screwed into the plunger 16c.As the shaft 17b rotates, the plunger 16c rotates and descends, pushing out the magnetic fluid 16d, and pushing out the plunger 16c. The structure is such that the magnetic fluid is injected into a magnetic fluid supply path 14 connected to the bottom surface of the magnetic fluid.

Further, the pressure detector 23 provided in the space 11 (gas side) and the pressure sensor 23 provided in the space 13 (atmospheric side) are both configured to give signals to the comparison circuit 21, and the magnetic fluid replenishing device 16, that is, the pressure of the magnetic fluid 16d, is configured to be fed back to the pulse generating circuit 20 via a pressure sensor 24 and a differential circuit 25. In this structure, if the seal of the magnetic fluid 15 is broken for some reason, the high pressure gas flows to the lower pressure atmosphere side, and the pressures in the spaces 11 and 13 become equal, and the pressure detectors 22 and 23 The comparator circuit 21 is informed that the differential pressure has disappeared, and the pulse generator 20 transmits a predetermined pulse based on the output signal from the comparator circuit 21. After this is amplified by the amplifier 19, it enters the pulse motor 18 and generates a pulse. The motor 8 is rotated. Pulse motor 1
8 is transmitted to the magnetic fluid replenishing device 16 via the aforementioned spline shaft 17, and as the magnetic fluid replenishing device 16 operates, the magnetic fluid 16d is injected from the magnetic fluid replenishing path 14. This injection is forcibly replenished over the entire circumference of the annular micro 4 and protrusion 7 via the magnetic fluid supply path 14 at a pressure higher than the gas pressure. At this time, the maximum withstand pressure of the magnetic fluid seal is determined by the number of annular microprotrusions 7 and the gap size between the annular microprotrusions 7 and the annular pole block 2, so even if more than a certain amount of magnetic fluid is replenished, Utilizing the property that the internal pressure of the device 16 does not rise above the maximum withstand pressure of the magnetic fluid seal, the magnetic fluid replenishing device 16 is operated while being monitored by the pressure detector 22, and the pressure detector 22 is operated while the magnetic fluid is being replenished. When the pressure stops increasing and reaches a certain value, the signal from the differential circuit 25 via the pressure sensor 24 becomes 0, and in this case, the pulse generator 20' is configured to generate an output, so the pulse generator 20' commands is sent and the pulse transmission ceases, so the pulse motor 18 is stopped, and the restoration of the sealing performance is completed by stopping the injection of the magnetic fluid. According to the above invention, it is possible to forcibly replenish magnetic fluid by detecting the difference between gas pressure and atmospheric pressure or temperature change and operating the magnetic fluid replenishing device.
A magnetic fluid sealing device capable of automatically restoring sealing performance can be provided.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a subordinate magnetic fluid seal device, Fig. 2 is a longitudinal sectional view of a magnetic fluid seal device according to an embodiment of the present invention, and Fig. 3 shows a magnetic fluid replenishment layer and a spline shaft coupling. FIG. 11... Rotating shaft, 2... Annular pole flock, 4... Fixed casing, 6...
・Magnetic cylinder, 7... Annular microprotrusion, 8...
・Magnet, 9...bearing, 14...magnetic fluid supply path, 15...magnetic fluid, 16...
Magnetic fluid supply bag hawk, 17...Spline shaft joint, 18...Pulse motor, 19...Amplifier, 2
0... Pulse transmitter, 21... Comparison circuit,
22, 23...Pressure detector, 24...Pressure sensor, 25...Differential circuit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A pole block surrounding a rotating shaft, a plurality of annular microprotrusions provided on either the inner peripheral surface of the pole block or the outer periphery of the rotating shaft, and a magnetic fluid injected into the annular microprotrusions; A magnet having a magnetic circuit for concentrating the magnetic fluid at the tip of the annular microprotrusion, and a magnetic fluid supply path passing through the pole block is provided, and the magnetic fluid is injected into this supply path when necessary. The magnetic fluid replenishing device is configured to be driven by a pulse motor, and the pulse motor is driven by a signal from a detection device that detects breakage of the seal, and the pulse motor is driven until the pressure stops increasing by the detection device that detects an increase in seal pressure. A magnetic fluid seal device characterized by driving a pulse motor.