JPH081262B2 - Magnetic fluid sealing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact type shaft seal part for a rotary shaft part of a vacuum device such as an ion plating device or a dry etching device or a rotary device handling gas. The present invention relates to a magnetic fluid seal device used as.

[Prior Art] Magnetic fluid seals have no friction or noise, and have high airtightness with a simple structure and can support high-speed rotation of several thousand rpm or more. Therefore, many rotary shaft parts are used instead of mechanical seals. Is being used for.

In this type of conventional magnetic fluid seal, a plurality of thick-walled cylindrical pole pieces are placed in a housing around the magnetic shaft with a magnet sandwiched between them, thereby creating a narrow gap between each pole piece and the magnetic shaft. Basically, it is formed and the magnetic fluid is trapped magnetically in this gap.
In order to obtain a wide and narrow gap (labyrinth) between the pole piece and the magnetic shaft, it is common to form an annular protrusion around the magnetic shaft or use a block ring with fine irregularities on the inner surface as the pole piece. there were.

However, in the magnetic fluid seal as described above, there is an uneconomical process in forming irregularities around the shaft and fine irregularities on the inner surface of the block ring with high precision,
There is a problem that a large number of magnetic fluid traps having a high magnetic flux density cannot be formed structurally in the narrow gap in the axial direction.

As a magnetic fluid sealing device for solving such a problem, the applicant of the present application uses a disc pack in which magnetic discs having different inner diameters are alternately superposed and adhered as a pole piece, as disclosed in Japanese Utility Model Laid-Open No. 62-71473. I am proposing what I did.

[Problems to be Solved by the Invention] However, in the magnetic fluid seal device disclosed in Japanese Utility Model Laid-Open No. 62-71473, the magnetic fluid is reliably trapped between the magnetic disk having the smaller inner diameter and the magnetic shaft. However, there is a problem in that it may not be possible to obtain a sufficient sealing effect. The inventor of the present application has conducted extensive research and found that when the gap between the magnetic disk having a small inner diameter and the outer peripheral surface of the magnetic rotating body becomes larger than the thickness of the magnetic disk having a small inner diameter, the magnetic disk serving as the seal portion and the magnetic rotating body It was clarified that this is because the magnetic flux density between them was reduced. In such a state, the differential pressure resistance characteristic between the primary side and the secondary side of the magnetic fluid device deteriorates, and as described above, the purpose as the sealing device cannot be sufficiently achieved.

An object of the present invention is to provide a magnetic fluid seal device that is suitable for practical use without lowering the differential pressure resistance characteristic.

[Means for Solving the Problems] In order to achieve the above object, the magnetic fluid sealing device according to the present invention is such that the pole piece has at least two first magnetic disks, and The minute gap between the inner peripheral surface and the outer peripheral surface of the magnetic rotating body opposed to the inner peripheral surface is less than or equal to the thickness of the second magnetic disk having the larger inner diameter and 20 μm or more. I am trying.

[Operation] In the magnetic fluid seal device configured as described above, the gap between the magnetic rotating body and the magnetic disk having the smaller inner diameter is larger than the gap between the magnetic disks having the smaller inner diameter. The magnetic flux is concentrated between the magnetic disks on the smaller side. Further, since the gap between the magnetic rotating body and the magnetic disk having the smaller inner diameter is 20 μm or more, it is not affected by the processing error and the assembly error.

EXAMPLES Hereinafter, the present invention will be described in detail based on illustrated examples.

1 is a vertical cross-sectional explanatory view when a magnetic fluid sealing device according to the present invention is applied to a partition wall portion between the atmosphere side A and the vacuum side B, and FIG. 2 is a cross-sectional view perpendicular to the axis of FIG.

In the figure, reference numeral 1 is a non-magnetic housing, and the non-magnetic housing 1 includes a cylindrical housing body 1a fixed to a partition wall C between the atmosphere side A and the vacuum side B, and the atmosphere side of the housing body 1a. A housing cover 1b for closing an opening provided in A is provided with a shaft hole 3 through which a magnetic shaft 2 penetrating the atmosphere side A and the vacuum side B penetrates in a central portion thereof. That is, the non-magnetic housing 1 is arranged around the magnetic shaft 2, and an annular storage chamber 4 is formed between the non-magnetic housing 1 and the magnetic shaft 2. A flange 1aa is formed on the end of the housing body 1a on the vacuum side B, and the flange 1aa is fixed to the partition wall C.
The magnetic shaft 2 is composed of a small diameter portion 2a on the end side and a large diameter portion 2b at the center, and the non-magnetic housing 1 is arranged around the large diameter portion 2b.

In the storage chamber 4, bearings 51 and 52 provided between the non-magnetic housing 1 and the magnetic shaft 2 and a sealing mechanism 6 are provided.
Has been installed. That is, one bearing 51 is installed in the inner part of the storage chamber 4, and the seal mechanism 6 is installed between the bearing 51 and the other bearing 52.

The seal mechanism 6 includes two sets of pole pieces 71, 72, a permanent magnet 8 held between these pole pieces 71, 72, spacers 91, 92 closely attached to the outer surfaces of the pole pieces 71, 72, and these. It comprises O-rings 101, 102 mounted in grooves formed in the spacers 91, 92.

The pole pieces 71 and 72 are respectively the first magnetic disk 7
1a and second magnetic disk 71b or first magnetic disk 7
It is configured as a disk pack in which 2a and the second magnetic disk 72b are alternately superposed and adhered. The first magnetic disks 71a, 72a and the second magnetic disks 71b, 72b are made of, for example, SUS4.
It is made of a material having corrosion resistance such as 03 and is formed to have the same thickness t (see FIG. 3). This thickness t is the first
In order to increase the magnetic flux density for the magnetic disks 71a and 72a and to prevent the magnetic flux density from decreasing for the second magnetic disks 71b and 72b, it is desirable that the thickness be 1.0 mm or less.

The first magnetic disks 71a, 72a have an inner diameter slightly larger than the outer diameter of the large diameter portion 2b of the magnetic shaft 2 and an outer diameter substantially equal to the inner diameter of the storage chamber 4. That is, when the pole pieces 71, 72 are stored in the storage chamber 4,
Between the first magnetic disks 71a, 72a and the outer peripheral surface of the large-diameter portion 2b, as shown in FIG. 3, a magnetic fluid trapping portion 100 facing each other with a minute gap h is formed. On the other hand, the second magnetic disks 71b and 72b have an inner diameter larger than that of the first magnetic disks 71a and 72a and an outer diameter equal to that of the first magnetic disks 71a and 72a. The first magnetic disks 71a and 72a and the second magnetic disks 71b and 72b are alternately polymerized and adhered by using resin or silver solder.

The gap h between the first magnetic disks 71a, 72a and the outer peripheral surface of the large diameter portion 2b is set to be smaller than the distance between the adjacent first magnetic disks 71a, 72a or 72a, 72a.
The thickness is set to be equal to or less than the thickness t of the magnetic disks 71b, 72b.
At the same time, the gap h is set to 20 μm or more because if it is less than 20 μm, processing accuracy and assembly accuracy are restricted.

The permanent magnet 8 is formed in a ring shape having the same inner diameter and outer diameter as the second magnetic disks 71b, 72b. Therefore, the inner circumference of the permanent magnet 8 and the outer circumference of the large diameter portion 2b, and the pole piece. A space 113 is formed between 71 and 72. Also,
The permanent magnet 8 is magnetized in the axial direction as shown in FIG.

Spacers 91 and 92 are adhered to the outer surfaces of the pole pieces 71 and 72, respectively, using a resin adhesive such as epoxy resin. The minimum inner diameter portions of the spacers 91, 92 are close to the outer peripheral surface of the large diameter portion 2b of the magnetic shaft 2 with a minute gap.

The O-rings 101 and 102 are mounted in the grooves formed in the outer peripheral surfaces of the spacers 91 and 92, respectively, and ensure the sealing performance with the inner wall surface of the storage chamber 4.

13 is a bearing 52 arranged on the open end side of the storage chamber 4.
Is a snap ring for positioning.

A male screw 1ba is screwed on the outer peripheral surface of the housing cover 1b of the non-magnetic housing 1.
b is a bearing by screwing the male screw 1ba into a female screw threaded on the inner diameter of the housing body 1a and screwing it in.
52 is pressed to position the seal mechanism 6 in the axial direction of the non-magnetic housing 1 and the magnetic shaft 2 and closes the open end of the storage chamber 4 on the atmosphere side A. In addition, 1bb is a screw hole for screwing a set screw (not shown), and the set screw screwed therein functions as a handle for screwing the housing cover 1b and also as a rotation stopper after the screwing is completed. .

Reference numeral 14 is a magnetic fluid, and the first magnetic disks 71a, 72
The magnetic force of the permanent magnet 8 traps the trapping portion 100 formed between the inner diameter portion of a and the outer peripheral surface of the large diameter portion 2b of the magnetic shaft 2 and its periphery. That is, since the magnetic circuit is formed by the permanent magnet 8, the pole pieces 71, 72, and the magnetic shaft 2, the capturing portion 10 having the minute gap h is formed.
The magnetic flux concentrates at 0, and the injected magnetic fluid 14 is captured. At this time, the minute gap h is equal to the second magnetic disk 71b,
Since the thickness t is 72 b or less, the magnetic circuit passing between the adjacent first magnetic disks 71a and 72a or 72a and 72a is not formed, and the magnetic flux concentrates in the minute gap h.

Reference numeral 15 is a cylindrical jacket that is detachably provided on the outer periphery of the non-magnetic housing 1. This jacket 15
A cooling chamber 16 is formed between the housing body 1a and the outer peripheral surface of the housing body 1a, and the cooling chamber 16 is attached to the housing body 1a by a set screw (not shown) to be screwed into the screw hole 15a. 15b
Is an inflow passage formed in the peripheral wall of the jacket 15, and a cooling fluid is pumped from a cooler (not shown) into the cooling chamber 15 via the inflow passage 15b. Also, the second
Reference numeral 15c shown in the drawing is an outflow passage formed in the peripheral wall of the jacket 15 for discharging the cooling fluid from the cooling chamber 16, and the cooling fluid introduced into the cooling chamber 16 from the inflow passage 15b is an outflow passage. The cooling fluid is circulated between the cooler and the cooling chamber 16 by being discharged from 15c.

The magnetic fluid sealing device configured as described above seals between the atmosphere side A and the vacuum side B by the magnetic fluid magnetically captured between the first magnetic disks 71a, 72a and the large diameter portion 2b of the magnetic shaft 2. are doing. Also, when viscous heat generation increases due to the increase in the rotation speed of the magnetic shaft 2, the jacket
It is possible to cool the pole pieces 71, 72 by mounting the 15 and circulating circulating water in the cooling chamber 16. Further, in the magnetic fluid sealing device, the storage chamber 4 has the bearings 51,
The spacer 91 and the pole piece 71, the permanent magnet 8, the pole piece 72 and the spacer 92, and the bearing 52 are sequentially assembled, and the housing cover 1b is mounted on the housing body 1a.

Of course, the present invention is not limited to the above-mentioned embodiment, and for example, in the embodiment, one permanent magnet and two pole pieces constitute a magnetic circuit. As shown in, three permanent magnets 8A, 8B,
A magnetic circuit may be configured using 8C and the four pole pieces 71A, 72A, 73A, 74A, and in this case, the pressure resistance can be further improved. In this case, the magnetic fluid seal composed of one permanent magnet and two pole pieces has three stages. If the number of steps of this magnetic fluid seal exceeds 10, the axial length becomes too long, and bending may occur, making it difficult to set the minute gaps accurately. Therefore, it is preferable to set the number of steps to 10 or less. Further, if the magnetic fluid seal has more than 10 stages, the starting torque of the magnetic rotating body may become excessively large. In FIG. 4, parts other than the inside of the storage chamber 4A and the magnetic shaft 2A are omitted, and the same parts as those in FIG. 1 are denoted by the same reference numerals.

In addition, it is preferable that the number of the first magnetic disks on the side having the smaller inner diameter that configures each pole piece is 10 or less. When the number of the first magnetic disks exceeds 10, the influence of the magnetic field on the magnetic disks far from the permanent magnet becomes small, and there is a high possibility that there is no point in increasing the number.

[Effects of the Invention] As is clear from the above description, according to the magnetic fluid sealing device of the present invention, since the magnetic flux is concentrated between the magnetic disk and the magnetic rotating body, the primary side and the secondary side of the magnetic fluid sealing device are improved. The differential pressure resistance characteristic between the sides can be set to a high level by effectively utilizing the magnetic force of the permanent magnet. Further, since the gap between the magnetic rotating body and the magnetic disk is secured to be 20 μm or more, the processing accuracy and the assembly accuracy are not restricted and the realization is not hindered. The same can be said when the thickness of the magnetic disk is 20 μm or more.

[Brief description of drawings]

FIG. 1 is an explanatory longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view perpendicular to the axis of FIG. 1, FIG. 3 is an enlarged view of an essential part of FIG. 1, and FIG. It is a longitudinal section explanatory view showing the important section of other examples. 2 ... Magnetic shaft (magnetic rotating body) 71, 72 ... Pole piece 8 ... Permanent magnet (magnet) 14 ... Magnetic fluid 2A ... Magnetic shaft (magnetic rotating body) 71A to 74A ... Pole piece 8A to 8C ... Permanent magnet (magnet)

Claims (1)

[Claims] 1. Two or more pole pieces formed by alternately superposing and contacting first and second magnetic disks having different inner diameters are arranged around a magnetic rotating body with a magnet sandwiched between the pole pieces. A magnetic fluid seal device in which a magnetic fluid is magnetically trapped in a minute gap between a magnetic rotating body and a first magnetic disk having a smaller inner diameter of the magnetic disks forming each pole piece. The pole piece includes at least two of the first magnetic disks, and a minute gap between the inner peripheral surface of the first magnetic disk and the outer peripheral surface of the magnetic rotating body facing the inner peripheral surface has an inner diameter. The magnetic fluid sealing device is characterized in that the thickness is not more than 20 μm and not more than the thickness of the second magnetic disk on the larger side.