JPS6014228B2 - Magnetic fluid seal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a magnetic fluid replenishment device 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 minute protrusions 7 are formed on the outer peripheral surface of a magnetic cylinder 6 which is attached to the shaft 1 via an O-ring 5. Between opposing end surfaces of the annular pole block 2 are bridged magnets 8 on the same circumference at appropriate pitches, and both outer end surfaces that are not facing each other face bearings 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 reaches the inner peripheral surface of the fixed casing 4 and the magnetic cylinder 6.
After filling the space 11 surrounded by the outer circumferential surface of the pipe and the opposing sides of the annular pole block 2, the pipe passes through the pipe outlet 12 penetrating the fixed casing 4. Inner peripheral surface of fixed casing 4, outer peripheral surface of rotating shaft 1, annular pole block 2
A space 13 surrounded by the side surfaces of the magnetic cylinder 6, and the bearing 9 is filled with the atmosphere. Further, the magnetic fluid supply pipe 14 is provided to penetrate the fixed casing 4 and the annular pole block 2. In such a structure, the 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 magnetic 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 tube 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 magnetic flux density is highest, and this magnetic fluid 15 generates a pressure resistance that seals the gas, and the gas in the space 11 does not leak into the space 13, which is an example of the atmosphere. . In such a conventional magnetic fluid seal device, if a sudden pressure increase occurs in the gas for some reason, the magnetic fluid 15
Since the magnetic fluid 15 is scattered and the sealing performance is lost, it is necessary to immediately replenish the magnetic fluid 15 by injecting it from the magnetic fluid supply path 14. However, for example, in the case of a helium gas seal in a superconducting rotating machine that uses liquid helium, the gas pressure is high. Therefore, cold gas is ejected from the magnetic fluid supply pipe 14 to the outside, and even if the surrounding area is cooled and frosted, and the gas returns to a steady state pressure, the magnetic fluid cannot be injected and replenished from the magnetic fluid supply pipe 14. It had the disadvantage of not being able to do so. 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. Also, since the magnetic fluid evaporates and is consumed, it was necessary to replenish it once every few weeks. This invention eliminates the above-mentioned drawbacks and automatically and quickly replenishes magnetic fluid to restore sealing performance without having to stop the operation of the rotating machine or reduce the gas pressure. The purpose of the present invention is to provide a magnetic fluid sealing device capable of

Therefore, according to the present invention, the above object is achieved by providing a replenishment pump as an injection device in the magnetic fluid replenishment path, forcibly replenishing the magnetic fluid, and controlling the replenishment pump using, for example, a pressure detector, a pulse generator, etc. This can be achieved by using a structure that uses a spline shaft joint and a pulse motor. 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 that are the same as those in the conventional system (FIG. 1) are designated by the same reference numerals. In this embodiment, pressure detectors 22 and 23 are provided in the gas space 11 and the atmospheric space 13, respectively, and the outputs of these pressure detectors are applied to a matching circuit 21. When the matching circuit 21 detects that the difference between the outputs of the pressure detectors 22 and 23 has fallen below a predetermined value, it provides an output signal to the pulse generator 20. When this pulse generator receives the output signal from the matching circuit 21, it emits pulses for a predetermined period of time or a predetermined number of pulses, and the number of pulses can be set in advance. The output pulses of the pulse generator 20 are applied via an amplifier 19 to a pulse motor 18 , which drives the magnetic fluid injection device 16 via a spline shaft coupling 17 . This injection device 16 stores a large amount of magnetic fluid, and a pulse motor that rotates by the number of pulses set by the pulse transmitter 201 supplies the amount of magnetic fluid corresponding to the set number to the supply pipe 14. The structure is such that it can be sent to FIG. 3 is a longitudinal cross-sectional view of the magnetic fluid injection device 16 and the spline joint 17, where 17a is a spline portion and the shaft 17b is integrated with the shaft of the magnetic fluid injection device 16. Reference numeral 16a denotes a cylinder of the magnetic fluid injection device 16, which has a thread 16b cut on its inner surface, and a plunger 16c having a screw on the outer periphery for screwing the cylinder 16b is connected to a shaft 17b, and the plunger 16c rotates as the rod 17b rotates. The magnetic fluid 16d is pushed out and the cylinder 1
The magnetic fluid is injected into a magnetic fluid supply path 14 connected to the bottom surface of the magnetic fluid 6a.

In such a structure, for some reason the magnetic fluid 15
If the seal is broken, the high-pressure gas flows to the lower-pressure atmosphere side, and the pressures in space 11 and space 13 become equal, the plexus pressure in pressure detectors 22 and 23 disappears, and the pressure signals match. When the signal is transmitted to the circuit 21, an output signal is output from the coincidence circuit 21, and in response to this output signal, a pulse is transmitted from the pulse generator 20, and after being amplified by the amplifier 19, it enters the pulse motor 8, and the pulse motor 18 is rotated.

The rotation of the pulse motor 18 is transmitted to the magnetic fluid injection device 16 via the spline shaft 17, and as the magnetic fluid injection device 16 operates, the magnetic fluid 16d flows into the magnetic fluid supply path 1.
Injected from 4. At a pressure higher than this injection gas pressure, the magnetic fluid is forcibly injected through the magnetic fluid supply path 14 until the entire circumference of the annular microprotrusion 7 is sealed. As the injection of the magnetic fluid progresses and a seal is established, the high pressure gas is sealed by this seal, creating a pressure difference between spaces 11 and 13, which is transmitted to the matching circuit 20' and its output signal is stopped. . According to the present invention, since a predetermined amount of magnetic fluid is forcibly pushed in by detecting a pressure drop, the advantage is that the sealing performance can be automatically restored without the need for special control. has.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a conventional magnetic fluid sealing device, FIG. 2 is a vertical cross-sectional view of a magnetic fluid sealing device according to an embodiment of the present invention, and FIG. 3 is a vertical cross-sectional view of a magnetic fluid injection device spline shaft joint. It is a diagram. 1... Rotating shaft, 2... Annular pole block, 4... Fixed casing, 6... Magnetic cylinder, 7... Annular microprotrusion. , 8... Magnet, 9... Bearing, 14... Magnetic fluid supply path, 15... Magnetic fluid, 16... Magnetic fluid injection device , 17...Subline shaft joint, 2
2, 23...Seal breakage detection device. Figure 1 Figure 2 ^ * Figure 3

Claims (1)

[Claims] 1. An annular pole block surrounding a rotating shaft, a plurality of annular microprotrusions formed on either the inner circumferential surface of the annular pole block or the outer circumferential surface of the rotating shaft, and an annular microprotrusion injected into the annular microprotrusions. In a device comprising a magnetic fluid and a magnet having a magnetic circuit that concentrates the magnetic fluid at the tip of the annular microprotrusion, the magnetic fluid is supplied from the outside to the annular microprotrusion through the annular pole block. an injection device for pushing magnetic fluid when necessary through the supply channel, and a detection device for detecting when the magnetic fluid seal is broken, and the injection device A magnetic fluid sealing device characterized in that a fixed amount of magnetic fluid is replenished by operating the magnetic fluid sealing device.