JPH0720468U - Magnetic fluid sealing device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the outflow of fluid in the groove to the low pressure side when the burst phenomenon occurs. [Structure] Either one member 2 and the other member 1 with a minute gap 9 between the rotating member 2 and the fixed members 1A and 1B.
The low-pressure side S1 of the grooves 7A to 7K between the plurality of protrusions 8A to 8J facing the A and having a predetermined interval in the axial direction.
The volume of at least one of the groove portions 7A to 7C is smaller than the volume of the other groove portions 7D to 7K.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention seals a minute gap between a fixed member and a rotating member with a magnetic fluid, thereby preventing a fluid such as gas from leaking from a high pressure side to a low pressure side through the minute gap. Regarding the device.

[0002]

[Prior art]

 As a conventional magnetic fluid sealing device of this type, for example, there is a magnetic fluid sealing device 100 as shown in FIG. A rod-shaped rotating member 102 made of a magnetic material is arranged so as to penetrate through openings of a pair of annular fixing members 101A and 101B made of a magnetic material. The rotating member 102 is rotatably supported by a bearing (not shown). An annular permanent magnet 103 is arranged as a magnetic force source between the pair of fixing members 101A and 101B. A plurality of fixed members 101A, 101B and a plurality of fixed members 101A, 101B are provided on the outer circumferential surface of the rotating member 102 between the pair of fixed members 101A, 101B and the rotating member 102 at predetermined intervals in the axial direction via a minute gap 104. Projections 106, ... Are formed. The volumes of the plurality of groove portions 105, ... Between the protruding portions 106, ... Are all substantially the same.

Then, the magnetic fluid 106 is held in the minute gap 104 formed by generating an appropriate magnetic field distribution in the magnetic circuit constituted by the permanent magnet 103, the pair of fixed members 101A and 101B, and the rotating member 102. By this, the pressure resistance of the atmospheric pressure A 1 on the high pressure side is obtained, and the vacuum V on the low pressure side is sealed.

As another conventional technique, a sleeve fitted to a rotating member is provided with a plurality of protrusions at predetermined intervals in the axial direction (see Japanese Utility Model Laid-Open No. 58-97970), a fixing member. In which a plurality of protrusions are provided on the rotating member side at predetermined intervals in the axial direction (see Japanese Patent Publication No. 61-266873), and a pole piece as a fixing member is a first disk-shaped magnetic member having a different inner diameter. There is one (Japanese Utility Model Laid-Open No. 63-89463) in which a body and a second disk-shaped magnetic body are provided and a plurality of protrusions are provided on the rotating member side at predetermined intervals in the axial direction.

[0005]

[Problems to be solved by the device]

 By the way, in an ideal case where the center of rotation of the rotating member 102 does not change at all, even if the rotating member 102 rotates, the state of the magnetic circuit does not change, and there is no problem in sealing performance. However, in reality, the magnetic field state fluctuates due to the processing accuracy of each component, the rotational accuracy of the bearing that holds the rotating member 102, and the like. Therefore, the sealing performance is slightly disturbed, and the degree of vacuum of the vacuum V is temporarily lowered.

Further, when the magnetic fluid 104 in that portion breaks due to center runout during rotation and a fluid phenomenon such as residual gas in the adjacent groove portion 105 flows to the vacuum V side, each groove portion is generated. Since the volume of 105 is almost the same as the volume of the other groove portions 105, the fluid such as the gas remaining in the groove portions 105 flows out to the vacuum V side as it is, which greatly reduces the degree of vacuum.

There is a problem that the above-mentioned decrease in the degree of vacuum directly affects the device performance in a vacuum device requiring a high vacuum.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to reduce the outflow of the fluid in the groove portion to the low pressure side when the burst phenomenon occurs. It is to provide a magnetic fluid seal device.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, in the present invention, a fixing member made of a magnetic material, a rotating member rotatably supported by the fixing member and made of a magnetic material, the rotating member and the fixing member are provided. A plurality of protrusions provided on either one of the members facing the other member with a predetermined gap in the axial direction with a minute gap between the members, and a groove portion between these protrusions, In a magnetic fluid seal device comprising a magnetic fluid interposed in the minute gap and a magnetic force source for forming a magnetic circuit between the fixed member and the rotating member, at least one groove portion on the low pressure side is It is characterized in that it is smaller than the volume of the groove part.

[0010]

[Action]

 In the magnetic fluid seal device having the above configuration, the volume of at least one groove on the low pressure side is smaller than the volume of the other groove. As a result, the amount of fluid remaining in the groove on the low pressure side is smaller than that in the other grooves, so the amount of fluid flowing out to the low pressure side in the burst phenomenon can be reduced. Therefore, when the low-pressure side is a vacuum, the degree of reduction in vacuum due to the burst phenomenon can be reduced.

[0011]

【Example】

 The present invention will be described below based on the illustrated embodiment. FIG. 1 shows a magnetic fluid sealing device according to an embodiment of the present invention. A shaft (magnetic material) 2 as a rod-shaped rotating member made of a magnetic material is arranged so as to penetrate through openings of rings (magnetic material) 1A and 1B as an annular fixing member made of a magnetic material. The shaft 2 is rotatably supported by bearings (not shown). An annular permanent magnet 3 is disposed as a magnetic force source between the pair of rings 1A and 1B. The pair of rings 1A and 1B and the permanent magnet 3 are arranged in a cylindrical housing 4 made of a non-magnetic material. Spacers 5A and 5B made of a non-magnetic material are arranged on the left side of the ring 1A and the right side of the ring 1B, respectively, to prevent the pair of rings 1A and 1B from moving left and right in the housing 4. .

An outline of a magnetic circuit formed by the permanent magnet 3 is as shown by arrows 6A and 6B in FIG. This is because only the pair of rings 1A and 1B and the shaft 2 are made of a magnetic material. The space on the left side of the ring 1A is a low pressure space S1 as a low pressure side, the space on the right side of the ring 1B is a high pressure space S2 as a high pressure side, and the space S3 between the ring 1A and the ring 1B is a low pressure space S1. And an intermediate pressure in the high-pressure space S2.

FIG. 2 is an enlarged view near the inner surface of the ring 1A in FIG. A plurality of projections 8A to 8J are provided on the outer peripheral surface of the shaft 2 at predetermined intervals in the axial direction, and grooves 7A to 7K are provided between the projections 8A to 8J. The three grooves 7A to 7C close to the low-pressure space S1 (at least one on the low-pressure space S1 side) may be filled with the fillers 12A to 12C made of a non-magnetic material, and the grooves 7A to 7C may be filled. The volume is smaller than the volume of the other groove portions 7E to 7K.

The tips of the protrusions 8A to 8J face the ring 1A via the minute gap 9, and the magnetic fluids 10A to 10I are present in the minute gap 9. On the outer peripheral surface of the shaft 2, the magnetic flux is retained between the tips of the protrusions 8A to 8J and the ring 1A. Arrows 11A to 11J in FIG. 2 indicate magnetic fluxes passing through the protrusions 8A to 8J, respectively.

With such a configuration, there are many spaces from the low pressure space S1 to the intermediate pressure space S3, that is, the grooves 7A to 7K, and the pressure in the grooves 7A to 7K is the intermediate pressure. It gradually increases as it approaches the space S3. Therefore, the magnetic fluids 10A to 10J will seal the pressure difference between the spaces on both sides of the corresponding protrusions 8A to 8J. For example, the magnetic fluid 10B seals the pressure difference between the spaces on both sides of the corresponding protrusion 8B, that is, between the grooves 7A and 7B. In this way, by providing a large number of spaces, that is, the groove portions 7A to 7K, and the similar protrusions and groove portions formed in the ring 1B portion, it is possible to obtain a withstand pressure corresponding to the atmospheric pressure, and to obtain a high pressure. It is also possible to seal when the space S2 is at atmospheric pressure and the low-pressure space S1 is at vacuum.

In the magnetic fluid seal device having the above-described configuration, the three groove portions 7A to 7C near the low pressure space S1 are filled with the fillers 12A to 12C, so that the volume of the groove portions 7A to 7C is It is smaller than the volume of the other groove portions 7D to 7K. As a result, the amount of gas or the like remaining in the groove portions 7A to 7C becomes smaller than that in the other groove portions 7D to 7K, so that one of the magnetic fluids 10A to 10J breaks due to core runout during rotation, etc. It is possible to reduce the outflow of gas or the like flowing out from the groove portion near the intermediate pressure space S3 to the low pressure space S1 through the broken portion, and to reduce the degree of vacuum reduction when the low pressure space S1 is a vacuum. You can

For example, when the diameter of the shaft 2 is 40 mm and the low pressure space S1 is in a vacuum, the degree of vacuum reduction in the low pressure space S1 due to the burst phenomenon is 1.0 × 10 ^{− on} average in the conventional case shown in FIG. It was ⁸ torr. On the other hand, in the case of the present embodiment of FIG. 1 in which the low pressure space S1, that is, the four grooves 7A to 7D close to the vacuum side are shallow, the average is 0.5 × 10 ⁻⁸ torr, and the decrease in the vacuum degree is halved. I was able to do it.

When the shaft 2 as a rotating member is processed, rather than being filled with the fillers 12A to 12D, the depth of at least one groove portion closer to the low pressure space S1 is set to be smaller than the depths of the other groove portions. By making the depth shallower, the volume of the groove near the low pressure space S1 can be reduced. Further, although the projections 8A to 8J, the grooves 7A to 7K, and the fillers 12A to 12D are provided on the rotating member side, they may be provided on the fixed member side. Furthermore, although the permanent magnet 3 is used as the magnetic force source, an electromagnet may be used, or a permanent magnet and an electromagnet may be used in combination.

[0019]

[Effect of device]

 The present invention has the above-described configuration and operation, and the volume of at least one groove portion on the low pressure side is smaller than the volume of the other groove portions. As a result, the amount of fluid such as gas remaining in the groove on the low pressure side is smaller than that in the other grooves, so the amount of fluid flowing out to the low pressure side in the burst phenomenon can be reduced. Therefore, from the viewpoint of sealing performance, when the low-pressure side is a vacuum, the degree of vacuum reduction due to the burst phenomenon can be reduced.

[Brief description of drawings]

FIG. 1 (a) is an overall vertical cross-sectional view of a magnetic fluid sealing device according to an embodiment of the present invention, and FIG. 1 (b) is an enlarged view of a main part on the low pressure space side of FIG. 1 (a). is there.

FIG. 2 is a vertical cross-sectional view of a conventional magnetic fluid seal device, and FIG. 2 (b) is an enlarged view of portion B of FIG. 2 (a).

[Explanation of symbols]

 1A, 1B Ring (fixing member) 2 Shaft (rotating member) 3 Permanent magnet (magnetic force source) 4 Housing 5A, 5B Spacer 6A, 6B Magnetic circuit 7A to 7K Groove 8A to 8J Projection 9 Small gap 10A to 10I Magnetic fluid 11A ~ 11J magnetic flux

Claims (1)

[Scope of utility model registration request] 1. A fixed member made of a magnetic material, a rotary member rotatably supported by the fixed member, and made of a magnetic material, and a rotary member and the fixed member with a small gap therebetween. A plurality of protrusions provided on one of the members so as to face the other member at predetermined intervals in the axial direction, a groove between the protrusions, a magnetic fluid interposed in the minute gap, and the fixing member. And a magnetic fluid seal device including a magnetic force source for forming a magnetic circuit between the rotating members, wherein the volume of at least one of the groove portions on the low pressure side is smaller than the volume of the other groove portion. Fluid sealing device.