JP2522995B2 - Magnetic fluid seal 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 because they have high airtightness with a simple structure and can support high-speed rotation, they are used for many rotary shafts instead of mechanical seals. Is becoming.

In this type of conventional magnetic fluid seal, a plurality of thick-walled cylindrical pole pieces are placed in the 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 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 projection group around the magnetic shaft or use a block ring with fine irregularities on the inner surface as the pole piece. Met.

However, the magnetic fluid seal as described above is uneconomical in the process of highly accurately forming the ring-shaped projections around the shaft and the fine irregularities on the inner surface of the block ring, and the magnetic flux is structurally contained in a narrow axial gap. There is a problem that it is not possible to form a large number of magnetic fluid traps with high density.

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 sealing 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. As a result of earnest studies, the inventor of the present application has found that one of the reasons is that the magnetic fluid in the minute gap is not sufficiently magnetized, and the magnetic fluid can be reliably captured between the magnetic disk having the smaller inner diameter and the magnetic shaft. Clarified that there are cases where there is no such case. In such a state, the differential pressure resistance characteristic between the primary side and the secondary side of the magnetic fluid device deteriorates, and the purpose of the seal device cannot be sufficiently achieved.

The present invention has been made in view of the above circumstances,
Without reducing the differential pressure resistance between the primary side and the secondary side,
An object of the present invention is to provide a magnetic fluid seal device that can surely capture a magnetic fluid in a minute gap and exhibit an excellent sealing function.

[Means for Solving the Problems] In order to achieve the above object, the magnetic fluid sealing device according to the present invention has two or more poles in which first and second magnetic disks having different inner diameters are alternately superposed and adhered. The piece
A permanent magnet is sandwiched between the pole pieces around the magnetic rotating body, and a minute magnetic disc between the first magnetic disk having the smaller inner diameter of the magnetic disks forming each pole piece and the magnetic rotating body is formed. In a magnetic fluid seal device in which a magnetic fluid is magnetically captured in a gap, a saturation magnetization of the magnetic fluid is M, a contact area between the pole piece and a permanent magnet is A, and a contact surface between the pole piece and the permanent magnet is A. Where B is the magnetic flux density, μ is the magnetic permeability of the first magnetic disk, s is the inner peripheral area of the first magnetic disk, and n is the number of the first magnetic disks, then n <(A · B / s · M · μ) and the thickness of the first magnetic disk is set in the range of 0.02 to 1.0 mm.

[Operation] According to the magnetic fluid sealing device of the present invention configured as described above, the strength of the magnetic field in the minute gap between the magnetic rotating body and the first magnetic disk is made larger than the saturation magnetization M of the magnetic fluid. Therefore, it becomes possible to capture the magnetic fluid in the minute gap with the upper limit of the magnetic amount, and the differential pressure resistance between the primary side and the secondary side of the magnetic fluid device can be made as high as possible to obtain an excellent seal. It can exert its function.

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, and a shaft hole 3 through which a magnetic shaft 2 penetrating the atmosphere side A and the vacuum section B is inserted is provided at the center of the housing cover 1b. 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 sleeve portion 2b at the center, and the non-magnetic housing 1 is arranged around the large diameter sleeve portion 2b.

Bearings 51, 52 provided between the non-magnetic housing 1 and the magnetic shaft 2 and a seal mechanism 6 arranged between these are housed in the storage chamber 4.

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 adhered to the outer surfaces of the pole pieces 71, 72, respectively. It consists of O-rings 101 and 102 mounted in the grooves formed in the spacers 91 and 92, and the magnetic fluid 14.

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 a predetermined number of the second magnetic disks 72b and the second magnetic disks 72b are alternately stacked and adhered. The first magnetic disks 71a, 72a and the second magnetic disks 71b, 72b are made of a material having corrosion resistance such as SUS403,
As shown in the figure, they are all formed to have the same thickness t. The thickness t is set to 0.02 mm or more so as not to be restricted by the processing accuracy or the assembly accuracy, and for the first magnetic disks 71a and 72a, the magnetic flux density is increased and the second magnetic disk It is set to 1.0 mm or less for the disks 71b and 72b in order not to reduce the magnetic flux density. Then, within this range of 0.02 to 1.0 mm, a numerical value satisfying the conditions described later is determined.

The first magnetic disks 71a, 72a have an inner diameter slightly larger than the outer diameter of the large-diameter sleeve 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, a minute gap h is formed between the first magnetic disks 71a, 72a and the outer peripheral surface of the large diameter sleeve 2b. 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. Then, these first magnetic disks 71a,
72a and the second magnetic disks 71b, 72b are alternately superposed 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 sleeve portion 2b is preferably set to be equal to or less than the thickness t of the second magnetic disks 71b, 72b.

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 sleeve portion 2b,
A space 113 is formed between the pole pieces 71 and 72. The permanent magnet 8 is axially magnetized 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 these spacers 91, 92 are close to the outer peripheral surface of the large diameter sleeve 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.
In b, the male screw 1ba is screwed into a female screw provided on the inner diameter of the housing body 1a to be screwed in, and the bearing 52 holding the seal mechanism 6 is pressed to push the non-magnetic housing 1 and the magnetic shaft 2 in the axial direction. The positioning is performed, and the atmosphere side A and the opening end of the storage chamber 4 are closed.
In addition, 1bb is a screw hole for screwing a set screw (not shown), and the set screw screwed in here is
It functions not only as a handle for screwing in the housing cover 1b but also as a rotation stopper after the screwing is completed.

The magnetic fluid 14 has a magnetic force of the permanent magnet 8 in and around a minute gap h formed between the inner diameter of the first magnetic disks 71a, 72a and the outer peripheral surface of the large diameter sleeve portion 2b of the magnetic shaft 2. Have been captured by. That is, since a magnetic circuit is formed by the permanent magnet 8, the pole pieces 71, 72 and the magnetic shaft 2, the magnetic flux concentrates in the minute gap h and the magnetic fluid 14 injected therein is captured.

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 16 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.

By the way, the magnetic field strength M ′ of the minute gap h is, for example, on the pole piece 71 side, the magnetic flux density at the contact surface 21 of the permanent magnet 8 with the pole piece 71 due to the residual magnetic flux of the permanent magnet 8 is B, When the contact area of the contact surface 21 is A, the area of the inner peripheral surface 71aa of the first magnetic disk 71a of the pole piece 71 is s, the number of the first magnetic disks 71a is n, and the magnetic permeability is μ, Becomes

The strength M'of this magnetic field is made larger than the saturation magnetization M of the magnetic fluid 14. That is, Is. Here, the inner peripheral area s of the first magnetic disk 71a
It has an inner diameter of D _S of the first magnetic disk 71a, when the thickness to t, because it is _{s = π · D S · t} ... ( d), wherein (c) expression It is expressed as That is, in order to make the strength M ′ of the magnetic field larger than the saturation magnetization M, it is necessary to determine the thickness t and the number n of the first magnetic disks 71a so as to satisfy the above equation (e). In the above embodiment, if the outer diameter of the permanent magnet 8 is D _O and the inner diameter is D _I , the entire annular portion defined by these contacts the pole piece 71. The contact area A is Becomes

Further, the thickness t of the first magnetic disk 71a satisfies the expression (e) as described above, and at the same time, as described above, is 0.
It is set in the range of 02 to 1.0 mm. On the other hand, it is desirable that the number n of the first magnetic disks 71a in the pole piece 71 be set between 2 and 10. When the number of the first magnetic disks 71a exceeds 10, the influence of the magnetic field on the first magnetic disks 71a far from the permanent magnet 8 becomes small, and there is a high possibility that there is no point in increasing the number.

It is needless to say that the pole piece 72 is also constructed in the same manner, and therefore its explanation is omitted here.

The magnetic fluid seal device configured as described above is provided with the first magnetic disks 71a, 72a and the large-diameter sleeve portion 2 of the magnetic shaft 2.
A magnetic fluid trapped magnetically between b seals between the atmosphere side A and the vacuum side B. When viscous heat generation increases due to an increase in the rotation speed of the magnetic shaft 2 and the like, the jacket 15 can be attached to circulate the cooling water in the cooling chamber 16 to cool the pole pieces 71, 72. .
Further, in the magnetic fluid seal device, the housing 51 is assembled by sequentially incorporating the bearing 51, the adhesive body of the spacer 91 and the pole piece 71, the permanent magnet 8, the adhesive body of the pole piece 72 and the spacer 92, and the bearing 52 in the storage chamber 4. It can be assembled simply by attaching the to 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 sets of pole pieces constitute a magnetic circuit. As shown in the figure, three permanent magnets 8A, 8B,
The magnetic circuit may be configured by using 8C and four sets of 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 it becomes difficult to set the minute gap accurately. Therefore, it is preferable to set the number of steps to 10 or less. Also, the magnetic fluid seal is 10
If the number of steps is exceeded, the starting torque of the magnetic rotating body may become excessively large. Even when the pole pieces are multi-tiered in this way, the size of the first magnetic disk of each pole piece can be determined in exactly the same manner as the first magnetic disks 71a, 72a of the above-mentioned embodiment. 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, according to the present invention, when the diameter of the device is large, a plurality of cylindrical permanent magnets 8a may be arranged annularly instead of the annular permanent magnet 8 in the above embodiment, as shown in FIG. You may

As described above, according to the magnetic fluid sealing device of the present invention, the contact area between the pole piece and the permanent magnet, the magnetic flux density at the contact surface, and the magnetic permeability of the first magnetic disk forming the pole piece. , The inner peripheral area and the number of sheets are set so that the above relational expressions with these factors as a factor are established, the strength of the magnetic field in the minute gap between the magnetic rotating body and the first magnetic disk is determined by the saturation magnetization of the magnetic fluid. Since the magnetic fluid can be reliably captured in the minute gap with the upper limit of the magnetic amount, the differential pressure resistance between the primary side and the secondary side of the magnetic fluid device should be set to the highest possible level. This has the effect of exhibiting an excellent sealing function.
Further, since the thickness of the first magnetic disk is 0.02 to 1.0 mm, it is not restricted by the processing accuracy and the assembly accuracy to prevent the realization thereof, and the magnetic flux density of the first magnetic disk is increased. With respect to the two-magnetic disk, the decrease in magnetic flux density can be suppressed.

[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. FIG. 5 is a longitudinal cross-sectional explanatory view showing a main part of another embodiment, and FIG. 5 is an explanatory view showing a modified example of the magnet 2 ... Magnetic shaft (magnetic rotating body) 71, 72 ..... Pole piece 71a, 72a .. 1st magnetic disk 71b, 72b ...... 2nd magnetic disk 8 ...... permanent magnet 14 ...... magnetic fluid 2A ...... magnetic shaft (magnetic rotating body) 71A ~ 74A ...... pole piece 8A ~ 8C ...... permanent magnet h ...... Small gap

Claims (1)

(57) [Claims] 1. A pole piece comprising two or more magnetic discs having different inner diameters which are alternately superposed and adhered to each other.
A permanent magnet is sandwiched between the pole pieces around the magnetic rotating body, and a minute magnetic disc between the first magnetic disk having the smaller inner diameter of the magnetic disks forming each pole piece and the magnetic rotating body is formed. In a magnetic fluid seal device in which a magnetic fluid is magnetically trapped in a gap, a saturation magnetization of the magnetic fluid is M, a contact area between the pole piece and a permanent magnet is A, and a contact surface between the pole piece and the permanent magnet is A. Where B is the magnetic flux density, μ is the magnetic permeability of the first magnetic disk, s is the inner peripheral area of the first magnetic disk, and
When the number of magnetic disks is n, the relational expression n <(A · B / s · M · μ) holds, and the thickness of the first magnetic disk is set in the range of 0.02 to 1.0 mm. A magnetic fluid sealing device characterized by the above.