JP2508576Y2 - Multi-stage magnetic fluid seal device for vacuum - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION The multistage magnetic fluid sealing device for vacuum according to the present invention is used for keeping airtightness of a portion penetrating a wall surface of a container having a vacuum inside.

[0002]

2. Description of the Related Art When an object provided in a clean space in a casing is rotationally driven by a motor provided outside, a drive shaft of the motor is attached to a portion penetrating a wall surface of the casing.
It is necessary to provide a sealing device to prevent the passage of dust.

Conventionally, as a sealing device installed in such a portion to prevent passage of dust and the like, Japanese Patent Laid-Open No. 62-11 has been used.
No. 0080, No. 58-191423, No. 61-13025, No. 61-44067,
No. 61-79070, No. 62-195261, No. 61-204027, No. 63-8419, No. 63-139325, and No. 63-29.
The magnetic fluid seal devices described in Japanese Patent No. 944, US Pat. No. 4,628,384, US Pat. No. 4,692,826, etc. are generally used.

The structure of the magnetic fluid seal device described in each of the above prior art documents is different in detail, but basically, the structure as shown in FIGS. 12 (A) and 12 (B) is adopted. Have

In FIG. 12 (A), reference numeral 1 denotes a housing, at least the inner peripheral surface of which is made of a non-magnetic material such as aluminum or synthetic resin, and is fixed to, for example, the wall surface of the casing. Reference numeral 2 is a shaft made of a magnetic material such as iron.
A cylindrical space 6 between the inner peripheral surface 4 of the shaft and the outer peripheral surface 5 of the shaft 2.
It is installed in.

The magnetic fluid seal device body 3 has a pair of poles formed by a magnetic material in the form of a ring-shaped permanent magnet 7 magnetized in the axial direction (left and right direction in FIG. 12). By sandwiching the pieces 8 and 9 in a sandwich shape, and holding the magnetic fluids 10 and 10 between the inner peripheral edges of the pole pieces 8 and 9 and the outer peripheral surface 5 of the shaft 2 by the magnetic force of the permanent magnet 7, It is configured. The outer diameters of the pair of pole pieces 8 and 9 are substantially the same as the inner diameter of the housing 1, and the magnetic fluid seal device main body 3 constituted by the respective members 7, 8, 9 and 10 is attached to the inner peripheral surface of the housing 1. 4, internal fitting,
Alternatively, it is fixed by adhesion or the like.

The magnetic fluid seal device body 3 is constructed as described above, and is mounted between the inner peripheral surface 4 of the housing 1 and the outer peripheral surface 5 of the shaft 2 to construct the magnetic fluid seal device as described above. Rotation of the shaft 2 inside the housing 1 or the shaft 2
Despite the rotation of the housing 1 around the circumference of the housing 1, the magnetic fluid 10, 10 held between the outer peripheral surface 5 of the shaft 2 and the inner peripheral edge of each pole piece 8, 9 causes the inner peripheral surface 4 of the housing 1 to The sealability between the outer peripheral surface 5 of the shaft 2 and the outer peripheral surface 5 is maintained.

Further, as shown in FIG. 12B, the outer peripheral surface 5 of the shaft 2 is formed of a non-magnetic material, and the inner peripheral surface 4 of the housing 1 is formed of a magnetic material. Of the pole pieces 8 and 9 are externally fitted and fixed to the outer peripheral surface 5 side of the shaft 2, and the magnetic fluids 10 and 10 are provided between the outer peripheral edges of the pole pieces 8 and 9 and the inner peripheral surface 4 of the housing 1. Magnetic fluid sealing devices for holding are also known in the art.

By the way, in the magnetic fluid seal device constructed as described above, the magnetic fluids 10, 10 held by the magnetic force of the permanent magnet 7 block the spaces existing on both sides of each of the magnetic fluids 10, 10. Since there is a large pressure difference between the two spaces, the magnetic fluid 1
0 and 10 are smashed (burst) and cannot be sealed.

For this reason, as a magnetic fluid seal device provided in the rotating shaft penetrating portion of a high vacuum device such as a rotating anticathode X-ray tube, there have been conventionally known Japanese Patent Publications Nos. 51-9853 and 61-61.
As described in US Pat. No. 43,588, US Pat. No. 3,620,584, British Patent No. 783881, etc., magnetic fluids 10, 10 are provided in a plurality of stages in the axial direction. There is known a multi-stage magnetic fluid seal device for vacuum in which a pressure difference existing on both sides of the is suppressed.

FIG. 13 shows a first example of such a vacuum multi-stage magnetic fluid sealing device. In FIG. 13,
Reference numeral 13 denotes a cylindrical bearing housing, which is provided on the wall surface of the casing 11 whose inside (the left portion in FIG. 13) has a vacuum. Rolling bearings 12, 12 are provided at two positions on the inner peripheral surface of the bearing housing 13, respectively.
A shaft 2 made of a magnetic material is rotatably supported by 2 and 12.

A multistage vacuum magnetic fluid seal device 14 is provided between the inner peripheral surface of the bearing housing 13 and the outer peripheral surface 5 of the shaft 2. The vacuum multi-stage magnetic fluid seal device 14 includes a ring-shaped permanent magnet 7 and 7 magnetized in the axial direction, and a ring-shaped pole piece 15 and 16 made of a magnetic material.
Are alternately superposed, and the magnetic fluids 10 and 10 are provided between the inner peripheral edges of the pole pieces 15 and 16 and the outer peripheral surface 5 of the shaft 2,
The permanent magnets 7, 7 are constituted by being held by the magnetic force.

In the illustrated example, each pole piece 1
By forming a concave hole with a V-shaped cross section on the inner peripheral edge of 5, 16,
The inner peripheral edge of each pole piece 15, 16 is bifurcated, and the magnetic fluids 10, 10 are held in each pole piece 15, 16 in two axial stages. Therefore, FIG.
In the case of the vacuum multi-stage magnetic fluid seal device 14 shown in FIG. 10, the magnetic fluids 10, 10 are provided in 10 stages in the axial direction (the horizontal direction in FIG. 13).

Since the multistage magnetic fluid seal device 14 for vacuum is provided with the magnetic fluids 10 and 10 in multiple stages as described above, the pressure difference existing on both sides of the magnetic fluids 10 and 10 at each stage is eliminated. Multi-stage magnetic fluid sealing device for vacuum 1 while keeping it small
A large pressure difference can be generated on both sides of 4. or,
The O-rings 18, 18 are attached to the concave grooves 17, 17 formed on the outer peripheral edges of the pole pieces 16, 16 located at both ends,
The O-rings 18, 18 serve to maintain airtightness between the outer peripheral surface of the vacuum multistage magnetic fluid seal device 14 and the inner peripheral surface of the bearing housing 13.

Further, FIGS. 14 to 17 show second to fifth examples of conventionally known multi-stage magnetic fluid sealing devices for vacuum. In the case of the second example shown in FIG. 14, the permanent magnet 7
A plurality of ridges 20, 20 are formed on the inner peripheral surfaces of the pole pieces 19, 19 provided on both sides of the ridge, and the inner peripheral edges of the ridges 20, 20 and the outer peripheral surface of the shaft 2 are formed. The magnetic fluids 10 and 10 are held between them.

In the case of the third example shown in FIG. 15, the ridges 20, 20 (FIG. 1) are formed on the inner peripheral surfaces of the pole pieces 21, 21.
4) is not formed, but instead of the outer peripheral surface of the cylindrical member 22 made of a magnetic material that is externally fitted and fixed to the shaft 2, the pole pieces 21, 2,
1. The ridges 23, 23 are formed in the portion facing the inner peripheral surface of the first ridge 1, and the outer peripheral edges of the ridges 23, 23 and the pole pieces 2 are formed.
Magnetic fluids 10 and 10 are held between the inner peripheral surfaces of 1 and 21.

Further, in the case of the fourth example shown in FIG. 16, the O-rings 18, 18 are connected to the pole pieces 24, 2 located at both ends.
The bearing housing 13 and the vacuum multi-stage magnetic fluid seal device 14 are kept airtight by being brought into contact with the outer side surface of the No. 4.

Further, in the case of the fifth example shown in FIG. 17, the magnetic fluid seal device main bodies 3 and 3 as shown in FIG.
Are stacked on each other via spacers 25 made of non-magnetic material to form a vacuum multi-stage magnetic fluid seal device 14, and the vacuum multi-stage magnetic fluid seal device 14 is attached to a cylindrical holder 26. Holds inside. The airtightness between the inner peripheral surface of the holder 26 and the vacuum multi-stage magnetic fluid sealing device 14 is improved by the adhesive 27, 27 between the outer peripheral surface of the holder 26 and the inner peripheral surface of the bearing housing 13. It is held by O-rings 18 and 18, respectively.

[0019]

However, in the vacuum multi-stage magnetic fluid seal device configured and used as described above, the vacuum multi-stage magnetic fluid seal device 14 has the same structure as the vacuum multi-stage magnetic fluid seal device 14 in any structure. Since the airtightness between the bearing housing 13 and the bearing housing 13 is maintained by the O-ring 18 and the adhesive 27,
It was difficult to maintain airtightness, and it was not possible to create an ultrahigh vacuum inside.

For example, in the case of each of the above-mentioned conventional structures, the amount of gas leakage at the installation portion of the multistage magnetic fluid seal device for vacuum 14 can be suppressed to 10 ⁻⁹ torr · l / sec (He) or less. Absent. Therefore, when the pressure inside the device equipped with the multistage magnetic fluid sealing device for vacuum 14 is set to an ultrahigh vacuum of 10 ^-8 torr or less, a high-performance vacuum pump (having a large discharge capacity) is continuously connected. Since it is necessary to operate, the manufacturing cost and the operating cost of the device in which the multistage magnetic fluid sealing device for vacuum 14 is installed increase.

The multistage magnetic fluid seal device for vacuum according to the present invention eliminates the above-mentioned disadvantages.

[0022]

The multistage magnetic fluid sealing device for vacuum of the present invention is a first member made of a magnetic material having a cylindrical peripheral surface, like the conventional multistage magnetic fluid sealing device for vacuum described above. And a second member concentric with the first member and rotating relative to the first member, and a cylindrical shape between the peripheral surface of the second member and the peripheral surface of the first member. Is formed into a circular ring shape having a size that can be inserted into the space, and is formed into a circular ring shape having a size that can be inserted into the cylindrical space and a permanent magnet that is magnetized in the axial direction. , A pole piece fixed to the side surface of the permanent magnet, and held by the magnetic force of the permanent magnet at a plurality of axial positions between the first peripheral edge of the pole piece and the peripheral surface of the first member. It is used with the one side in the axial direction facing the vacuum space. It is.

Further, in the vacuum multi-stage magnetic fluid seal device of the present invention, the pole piece and the second member are welded over the entire circumference in the portion in contact with the vacuum space. Is characterized by.

[0024]

In the vacuum multi-stage magnetic fluid seal device of the present invention constructed as described above, the airtightness between the second member and the pole piece can be reliably maintained by welding over the entire circumference.

For this reason, the amount of gas leakage at the part where the multistage magnetic fluid sealing device for vacuum is installed is 10 ^-10 torr · l / sec (He) or less, which is extremely small. It is possible to increase the degree of vacuum inside the device in which the above-mentioned multistage magnetic fluid sealing device for vacuum is installed without using.

[0026]

1 and 2 show a first embodiment of the present invention. This first embodiment corresponds to the structure shown in FIG. 14 as a second example of the conventional structure. A plurality of ridges 20, 20 are formed on the inner peripheral surfaces of a pair of pole pieces 19a, 19b provided on both sides of the permanent magnet 7 over the entire circumference thereof, and each protrusion is a first peripheral edge. The magnetic fluids 10, 10 (see FIG. 14) can be held between the inner peripheral edges of the strips 20, 20 and the outer peripheral surface 5 of the shaft 2, which is the first member.

Of the pair of pole pieces 19a, 19b, a part of the pole piece 19b on the vacuum side (right side in FIG. 1), and the outer peripheral edge portion of the side surface which is in contact with the vacuum space is formed over the entire circumference. The eaves portion 28 is formed. The outer peripheral surface of the eaves portion 28 exists on an extension of the outer peripheral surface of the pole piece 19b. Then, the eaves portion 28 is welded 29 to the inner peripheral surface of the bearing housing 13 that is the second member over the entire circumference.

Therefore, in the case of the multistage magnetic fluid seal device for vacuum of the present invention, the bearing housing 13 and the pole piece 19 are used.
Airtightness with b is surely achieved by welding over the entire circumference.

As a result, the leakage amount of gas at the installation portion of the multistage magnetic fluid seal device for vacuum is 10 ⁻¹⁰ torr · l / sec (He).
The following can be suppressed to a very low level, and the degree of vacuum inside the apparatus equipped with the above-mentioned multistage magnetic fluid sealing apparatus for vacuum can be increased without using a high-performance vacuum pump.

The size of the eaves 28 is determined by design according to the size of the vacuum multi-stage magnetic fluid sealing device including the pole piece 19b, but the width w is preferably 0.3 to 5 mm. The thickness t is set to 0.5 to 1 mm, and the thickness t is set to 0.2 to 5 mm, preferably 0.5 to 1 mm. The eaves portion 28 and the bearing housing 13 may be welded before or after the pole piece 19b and the permanent magnet 7 are bonded.

Further, the method of welding the eaves portion 28 and the bearing housing 13 is determined by design depending on the material of the pole piece 19b and the bearing housing 13, but electron beam welding and laser beam welding occur during welding. Since it is difficult for the pole piece 19b to be distorted by the heat generated, it can be preferably used.

In this case, if electron beam welding is used, the thickness t of the eaves portion 28 is 0.2 to 1 mm, the rotational movement speed of the eaves portion 28 is 1 m / min, and the welding current is If it is 0.5 to 3 mA, good welding can be performed.
For laser beam welding, carbon dioxide laser, YA
G laser, etc. can be used, but for example, continuous output YA
If G laser is used, the laser output is 200-40
If 0 W, the defocusing distance is 0, and the rotational movement speed of the eaves portion 28 is 0.6 m / min, good welding can be performed.

Next, FIGS. 3 to 4 show a second embodiment of the present invention. In the first embodiment described above, diametrical welding 29 is applied between the overhang portion 28 formed on the pole piece 19b and the bearing housing 13, whereas in the case of this embodiment, the bearing is used. An inward flange-shaped flange portion 30 is formed on the inner peripheral surface of the housing 13, and welding 29 extending in the axial direction is applied between the flange portion 30 and the side surface of the pole piece 19b.

When performing the welding 29, the pole piece 1
9b is pressed against the collar portion 30 by the jig 31. Other configurations and operations are similar to those of the above-described first embodiment.

Next, FIGS. 5 to 6 show a third embodiment of the present invention. The first and second embodiments described above are the pole pieces 1.
9b or the bearing housing 13 and the eaves portion 28 or the collar portion 30 which are integrally formed with the bearing housing 13 or the pole piece 19b, the welding 29 is applied between the case of this embodiment. The welding ring 32, which is separate from the pole piece 19b and the bearing housing 13, is attached to the intersection of the side surface of the pole piece 19b and the inner peripheral surface of the bearing housing 13, and the welding ring 32 has the above-mentioned diagonally cross section. Welding 29 is applied toward the intersections on both sides.
Other configurations and operations are similar to those of the above-described first and second embodiments.

Next, FIG. 7 shows a fourth embodiment of the present invention. In the case of this embodiment, a pair of pole pieces 19a, 1
The magnetic fluid sealing device main body 3 is further attached to the vacuum side portion (right side portion of FIG. 7) of the magnetic fluid sealing device in which the permanent magnet 7 is sandwiched by 9b via the spacer 25 made of a non-magnetic material. There is. Then, the outer peripheral edge of the pole piece 9 constituting the magnetic fluid seal device main body 3 is welded to the inner peripheral surface of the bearing housing 13 by the same structure as in the first embodiment. Other configurations and operations are similar to those in the above-described first to third embodiments.

Next, FIG. 8 shows a fifth embodiment of the present invention. In the case of the present embodiment, the pole piece 8 which does not face the vacuum space is omitted from the magnetic fluid sealing device 3 of the fourth embodiment. Other configurations and operations are similar to those in the case of the fourth embodiment.

Next, FIGS. 9 to 10 show a sixth embodiment of the present invention. The present embodiment corresponds to the structure shown in FIG. 16 as the fourth example of the conventional structure. The inner peripheral edge of the lid 33 and the side surface of the pole piece 24, which are fixed to the opening of the bearing housing 13 on the vacuum space side (left side in FIG. 9) and hold the multistage magnetic fluid sealing device for vacuum 14 in the bearing housing 13. In the meantime, welding 29 is applied all around.

As described above, in order to perform the welding 29 over the entire circumference between the inner peripheral edge of the lid 33 and the side surface of the pole piece 24, as shown in FIG. A flange portion 30 is formed on the inner peripheral edge of the shaft, and welding 29 extending in the axial direction is performed between the flange portion 30 and the pole piece 24.
As shown in (B), an eaves portion 28 is formed on the side surface of the pole piece 24, and welding 29 in the diametrical direction is applied between the eaves portion 28 and the inner peripheral edge of the lid 33.

Also in the case of this embodiment, the airtightness between the bearing housing 13 and the pole piece 24 can be surely achieved by welding over the entire circumference.

Next, FIG. 11 shows a seventh embodiment of the present invention. The present embodiment is the same as the fifth example of the conventional structure shown in FIG.
This corresponds to the structure shown in FIG. In the case of the present embodiment, the vacuum side (left side in FIG. 11) of the magnetic fluid seal device including a plurality of permanent magnets 7, 7 and pole pieces 8, 9 and spacers 25, 25 inside the holder 26 is provided. Further, the magnetic fluid seal device main body 3 is attached. Then, the outer peripheral edge of the pole piece 9 constituting the magnetic fluid seal device main body 3 is welded to the inner peripheral surface of the bearing housing 13.

Also in the case of this embodiment, the airtightness between the bearing housing 13 and the pole piece 9 can be reliably maintained by welding over the entire circumference.

In each of the above-mentioned embodiments, the bearing housing 1
The multi-stage magnetic fluid sealing device for vacuum, which is fixed to the shaft 3 and mounted on the rotating part of the shaft 2, is shown, but the multi-stage magnetic fluid sealing device for vacuum of the present invention is not limited to such a part. As shown in FIG. 12 (B), the shaft 2 can be fixed and the housing 1 can be used in a rotating portion.

[0044]

The multistage magnetic fluid seal device for vacuum according to the present invention is constructed and operates as described above, but the amount of gas leakage can be suppressed to a minimum and the degree of vacuum inside can be increased.

[Brief description of drawings]

FIG. 1 is a half sectional view showing a first embodiment of the present invention.

FIG. 2 is a half sectional view showing only a pole piece.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a bearing housing.

FIG. 5 is a half sectional view showing the third embodiment before welding.

FIG. 6 is a half sectional view showing a state after welding similarly.

FIG. 7 is a half sectional view showing the fourth embodiment.

FIG. 8 is a half sectional view showing the fifth embodiment.

FIG. 9 is a half sectional view showing the sixth embodiment.

FIG. 10 is a view showing a cross-sectional shape of a lid body and a pole piece used in the sixth embodiment.

FIG. 11 is a half sectional view showing the seventh embodiment.

FIG. 12 is a cross-sectional view showing two examples of the basic structure of the magnetic fluid seal device.

FIG. 13 shows a first conventional multi-stage magnetic fluid sealing device for vacuum.
Sectional drawing which shows an example.

FIG. 14 is a half sectional view showing the second example.

FIG. 15 is a half sectional view showing the third example.

FIG. 16 is a half sectional view showing the fourth example.

FIG. 17 is a half sectional view showing the fifth example.

[Explanation of symbols]

 1 Housing 2 Shaft 3 Magnetic Fluid Sealing Device Main Body 4 Inner Surface 5 Outer Surface 6 Space 7 Permanent Magnet 8 Pole Piece 9 Pole Piece 10 Magnetic Fluid 11 Casing 12 Rolling Bearing 13 Bearing Housing 14 Vacuum Multi-Stage Magnetic Fluid Sealing Device 15 Pole Piece 16 Pole piece 17 Recessed groove 18 O-ring 19 Pole piece 19a Pole piece 19b Pole piece 20 Ridge 21 Pole piece 22 Cylindrical member 23 Ridge 24 Pole piece 25 Spacer 26 Holder 27 Adhesive 28 Far part 29 Weld 30 Collar part 31 jig 32 welding ring 33 lid

Claims (1)

(57) [Scope of utility model registration request] 1. A first member made of a magnetic material having a cylindrical peripheral surface, a second member concentric with the first member and rotating relative to the first member; A permanent magnet that is formed in a ring shape having a size that can be inserted into a cylindrical space between the peripheral surface of the two members and the peripheral surface of the first member, and is magnetized in the axial direction, A pole piece formed in a circular ring shape having a size that can be inserted into the cylindrical space and fixed to a side surface of the permanent magnet, a first peripheral edge of the pole piece, and a peripheral surface of the first member. A multi-stage magnetic fluid seal for vacuum which is composed of a magnetic fluid held by the magnetic force of the permanent magnet at a plurality of axial positions between the two, and is used with one axial side facing the vacuum space. In the device, the pole piece and the second member are in contact with the vacuum space. A multi-stage magnetic fluid sealing device for vacuum, which is characterized by being welded over the entire circumference in part.