JPH0653822U - Magnetic fluid bearing - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a magnetic fluid bearing with high load capacity, high rotation accuracy, and long life even under high speed rotation. A porous body 6 is provided in a space 10 surrounded by an inner peripheral surface of a cylindrical magnetic force source 2 and an inner side surface of a pair of magnetic pole pieces 5 so as to face the shaft 1 with a minute gap 3 therebetween. The magnetic fluid 4 is interposed in the internal voids of the particulate body 6 and the minute gaps 3, and the portion of the outer peripheral surface of the shaft 1 facing the vicinity of both ends of the porous body 6 or the inner periphery of the porous body 6 It is characterized in that a spiral groove 7 for generating a dynamic pressure is provided on at least one of both ends of the surface.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a slide bearing type magnetic fluid bearing using magnetic fluid as a lubricant.

[0002]

[Prior art]

 Conventional magnetic fluid bearings of this type include those shown in FIGS. 13 and 14, for example. First, the first conventional magnetic fluid bearing shown in FIG. 13 supports a radial load, and is composed of a shaft 101 made of a non-magnetic material, and a cylindrical magnetic force arranged between the outer peripheral surface of the shaft 101 and a minute gap 103. It is composed of a cylindrical permanent magnet 102 as a source and a magnetic fluid 104 interposed in the minute gap 103.

Further, the second conventional magnetic fluid bearing shown in FIG. 14 supports a radial load similarly to the first conventional example, and includes a cylindrical permanent magnet 102 ′ serving as a cylindrical magnetic force source and a circular magnet. A pair of annular magnetic pole pieces 105 as a pair of magnetic pole pieces provided in contact with both end surfaces of the cylindrical permanent magnet 102 ', and a shaft 101 provided with an inner peripheral surface of the annular magnetic pole piece 105 and a minute gap 103. And a space 106 surrounded by the inner peripheral surface of the cylindrical permanent magnet 102 ′, the inner side surface of the annular magnetic pole piece 105, and the outer peripheral surface of the shaft 101, and a magnetic fluid 104 interposed in a minute gap 103. It is a thing.

[0004]

[Problems to be solved by the device]

 However, the magnetic fluid bearing according to the above-mentioned conventional technique has the following problems. That is, in the magnetic fluid bearing of the first conventional example, when the shaft 101 is rotated at a high speed, the temperature rise is large due to viscous heat generation of the magnetic fluid 104, deterioration of the magnetic fluid 104 and evaporation of the solvent occur, so the life of the bearing is increased. When the foreign matter is mixed in the magnetic fluid 104, the inner peripheral surface of the cylindrical permanent magnet 102 and the outer peripheral surface of the shaft 101 are damaged, which shortens the life of the bearing.

Next, in order to solve the problem of the first conventional example, the inner peripheral surface of the cylindrical permanent magnet 102 ′, the inner side surfaces of the pair of annular magnetic pole pieces 105 and the outer peripheral surface of the shaft 101 are surrounded. In the magnetic fluid bearing of the second conventional example in which the magnetic fluid 104 is interposed in the space 106 (internal space), the temperature rise of the magnetic fluid 104 during the high speed rotation of the shaft 101 is smaller than that in the first conventional example. Since the magnetic fluid 104 existing in the minute gap 103 and the magnetic fluid 104 existing in the internal space 106 are hard to be exchanged with each other, the magnetic fluid 104 existing in the minute gap 103 is apt to deteriorate and the life of the bearing is shortened. However, when foreign matter enters the minute gap 103, it is difficult to discharge the foreign matter to the internal space 106 side, which shortens the life of the bearing.

Furthermore, since the internal space 106 is provided, there is a problem that the area of the minute gap 103, that is, the bearing surface is reduced and the load capacity is reduced.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a magnetic fluid bearing having a high load capacity, a high rotation accuracy, and a long life even under high speed rotation. To provide.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, according to the present invention, a cylindrical magnetic force source, a pair of magnetic pole pieces provided in contact with both end surfaces of the cylindrical magnetic power source, and a small gap between the magnetic pole pieces are provided. A magnetic fluid bearing comprising a shaft provided and a magnetic fluid interposed in the minute gap, wherein the shaft is provided in a space surrounded by the inner peripheral surface of the cylindrical magnetic force source and the inner side surfaces of the pair of magnetic pole pieces. Porous bodies are provided so as to face each other with a minute gap, and the magnetic fluid is interposed in the inner voids of the porous body and the minute gaps, and both ends of the porous body on the outer peripheral surface of the shaft. Spiral grooves for generating dynamic pressure are provided in at least one of a portion facing the vicinity and both ends of the inner peripheral surface of the porous body.

Then, the cylindrical porous magnetic force source, a shaft provided with a minute gap between the inner peripheral surface of the cylindrical porous magnetic force source, and the porous magnetic force source on the outer peripheral surface of the shaft. A spiral groove for generating dynamic pressure, which is provided at least at a portion facing both end portions of the porous body or near both end portions of the inner peripheral surface of the porous body, and the minute gap and the cylindrical porous body. It may be composed of a magnetic fluid interposed in the inner space of the magnetic force source.

[0010]

[Action]

 In the magnetic fluid bearing configured as described above, when the shaft rotates, the porous body on the outer peripheral surface of the shaft or the cylindrical porous body faces the vicinity of both ends of the magnetic force source, or the porous body or the cylindrical body. Dynamic pressure is generated by the spiral groove provided in at least one of the both ends of the inner peripheral surface of the porous magnetic force source, and the magnetic fluid flows from the minute gap to the porous or cylindrical porous magnetic source. Since a circulating flow that flows into the internal voids and returns to the minute voids is generated again, the temperature rise of the magnetic fluid is suppressed even under high-speed rotation, and at the same time, the porous or cylindrical porous magnetic source serves as a filter. As a result, even if foreign matter is mixed in the magnetic fluid, it will not be confined in the internal space of the magnetic source of the porous body or cylindrical porous body, and will not remain in the minute gap, resulting in a long bearing life. Can be promoted.

Moreover, the load capacity and the rotational accuracy are improved by the dynamic pressure generated by the spiral groove.

[0012]

【Example】

 The present invention will be described below based on the illustrated embodiment. FIG. 1 shows a first embodiment of the present invention. This magnetic fluid bearing supports a radial load, and has a cylindrical permanent magnet 2 as a cylindrical magnetic force source and a pair of annular magnetic poles as a pair of magnetic pole pieces provided in contact with both end surfaces of the cylindrical permanent magnet 2. A piece 5, a shaft 1 of a non-magnetic material provided with an inner peripheral surface of the annular magnetic pole piece 5 and a minute gap 3, an inner peripheral surface of the cylindrical permanent magnet 2 and the pair of annular magnetic poles. A cylindrical porous body 6 as a porous body, which is provided so as to face a space 10 surrounded by the inner side surface of the piece 5 through a minute gap 3 which is a gap with the outer peripheral surface of the shaft 1, and the cylinder. Of the magnetic fluid 4 interposed in the internal voids of the porous body 6 and the minute gaps 3 and in the outer peripheral surface of the shaft 1 slightly inward from both ends of the inner peripheral surface of the cylindrical porous body 6. And a spiral groove 7 for generating dynamic pressure, which is provided in a portion opposed to.

In the magnetic fluid bearing of this embodiment having the above-described structure, when the shaft 1 rotates, the spiral groove 7 provided on the outer peripheral surface of the shaft 1 pumps the outer surface of the spiral groove 7 in the minute gap 3. The magnetic fluid 4 intervening in the axial direction is pushed toward the central portion side in the axial direction and the pressure of the magnetic fluid 4 located in the central portion in the axial direction of the minute gap 3 rises, and the axial direction of the inner peripheral surface of the cylindrical porous body 6 is increased. The magnetic fluid 4 is pushed into the internal void of the cylindrical porous body 6 from the central portion. The magnetic fluid 4 pushed in flows through the inner voids of the cylindrical porous body 6 toward the outer peripheral side in the radial direction, and is directed outward in the axial direction near the outer peripheral surface and toward the inner peripheral side in the radial direction near the end surface. The flow then returns to the outer portion of the spiral groove 7 of the minute gap 3. That is, a circulating flow of the magnetic fluid 4 as shown by an arrow in FIG. 1 is generated.

Therefore, even if the magnetic fluid 4 interposed in the minute gap 3 viscously generates heat, it is radiated and cooled in the inner void of the cylindrical porous body 6, so that even when the shaft 1 rotates at high speed. The temperature rise of the magnetic fluid 4 is suppressed. Moreover, even if foreign matter is mixed in the magnetic fluid 4, the foreign matter flows into the internal void of the cylindrical porous body 6 from the minute gap 3 together with the magnetic fluid 4, and only the foreign matter is trapped in the internal void, resulting in magnetic properties. Since the fluid 4 returns to the minute gap 3, the cylindrical porous body 6 serves as a filter, and foreign matter does not remain in the minute gap 3. Therefore, the life of the bearing can be extended.

Further, the dynamic pressure generated by the spiral groove 7 increases the load capacity and the rotation accuracy.

In this embodiment, two spiral grooves 7 are separately provided, but the spiral groove is extended and the grooves from both sides are joined at the center, that is, the herringbone groove. May be Further, in the present embodiment, the spiral groove 7 is provided on the outer peripheral surface side of the shaft 1, but it may be provided on the inner peripheral surface side of the cylindrical porous body 6, or may be provided on both sides in some cases.

Next, a second embodiment of the present invention is shown in FIG. This magnetic fluid bearing has a communication groove that extends radially inward and reaches the inner peripheral surface at the portion of the inner surface of the annular magnetic pole piece 51 as the magnetic pole piece that contacts the end surface of the cylindrical porous body 6. 8 are provided at four places on the circumference.

In the magnetic fluid bearing of the present embodiment configured as described above, since the communication groove 8 is provided, the circulation flow of the magnetic fluid 4 (in the direction of the arrow in FIG. 2) becomes easier to flow and the cooling efficiency is also high. And reliability is improved. Since other configurations and operations are similar to those of the first embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the example in which the communication groove 8 is provided at four places on the circumference has been shown, but it may be provided at least one place on the circumference, and the present invention is not limited to this.

Next, a third embodiment of the present invention is shown in FIG. This magnetic fluid bearing extends axially inward at a portion of the inner side surface of the annular magnetic pole piece 52 as a magnetic pole piece, which is in contact with the vicinity of the outer peripheral side of the end surface of the cylindrical porous body 6, and extends in the axial direction. Communication holes 9 that reach the vicinity of the central portion in the direction, extend radially inward toward the inner peripheral surface, and reach the inner peripheral surface side are provided at four locations on the circumference.

Since the magnetic fluid bearing of the present embodiment configured as described above is provided with the communication hole 9, the circulation flow of the magnetic fluid 4 (in the direction of the arrow in FIG. 3) is improved as in the second embodiment. As the flow becomes easier, the cooling efficiency becomes higher and the reliability is improved. Since other configurations and operations are the same as those in the above-described embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, similarly to the above embodiment, the spiral groove 7 is provided on the outer peripheral surface of the shaft 1 at a portion opposed to the inner peripheral surface of the cylindrical porous body 6 and slightly inward from both end portions of the inner peripheral surface. However, in the case of the present embodiment, the spiral groove 7 is provided in the outer peripheral surface of the shaft 1 in the inner peripheral surface of the annular magnetic pole piece 2 at a portion slightly inward of the opening of the communication hole 9. May be. With this structure, a circulating flow is generated in almost the entire area of the minute gap 3, so that the reliability is further improved.

In each of the above embodiments, the cylindrical permanent magnet 2 is used as the cylindrical magnetic force source, but the present invention is not limited to the cylindrical permanent magnet, and may be a cylindrical electromagnet or the like. good. Although the gap between the porous body and the shaft is the same as the minute gap between the pole piece and the shaft, the description has been given as an example, but the gap does not have to be the same.

FIG. 4 shows a fourth embodiment of the present invention. It should be noted that components having the same functions as those of the components described in each of the above-described embodiments will be described with the same reference numerals.

This magnetic fluid bearing supports a radial load and a thrust load in both directions, and has a cylindrical permanent magnet 2 as a cylindrical magnetic force source and a pair of cylindrical permanent magnets 2 provided in contact with both end faces of the cylindrical permanent magnet 2. And an annular magnetic pole piece 53 as a magnetic pole piece of the magnetic pole piece 53 and an inner peripheral surface of the annular magnetic pole piece 53 with a minute gap 3 therebetween, and an inner side surface of the annular magnetic pole piece 53 with a minute gap 3 therebetween. In the space 10A surrounded by the shaft 1A having the protruding portion 11, the inner peripheral surface of the cylindrical permanent magnet 2 and the inner side surfaces of the pair of annular magnetic pole pieces 53, the outer peripheral surface of the protruding portion 11 of the shaft 1A and the outer peripheral surface are minute. A cylindrical porous body 6 as a porous body provided so as to face each other with a gap 3 in between, and spiral grooves 7, 7 for dynamic pressure generation provided on the outer peripheral surface and the outer surface of the protruding portion 11 of the shaft 1A. 'And the pair of annular magnetic pole pieces 5 3 The inner surface of the cylindrical porous body 6 extends axially inward at a portion in contact with the vicinity of the outer peripheral side of the end surface of the cylindrical porous body 6, reaches the vicinity of the central portion in the axial direction of the annular magnetic pole piece 53, and from there, the radially inner peripheral side. Communicating holes 9 provided at four locations in the circumferential direction extending to the inner peripheral surface side, and a magnetic fluid 4 interposed in the communicating holes 9 and the internal voids of the cylindrical porous body 6 and the minute gaps 3. It is composed of

In the magnetic fluid bearing of the present embodiment configured as described above, when the shaft 1A rotates, the spiral groove 7, 7'provided on the outer peripheral surface and the outer surface of the protruding portion 11 of the shaft 1A causes the pumping action. The magnetic fluid 4 present on the thrust-side minute gap 3 and on the outer side of the radial-side minute gap 3 on the radial-side spiral groove 7 is pushed toward the central portion in the axial direction of the radial-side minute gap 3 and enters this portion. The pressure of the magnetic fluid 4 located increases, and the magnetic fluid 4 is pushed into the inner space of the cylindrical porous body 6 from the axial center of the inner peripheral surface of the cylindrical porous body 6. The pressed magnetic fluid 4 flows through the inner cavity of the cylindrical porous body 6 toward the outer peripheral side in the radial direction, passes through the communication hole 9, and again from the inner peripheral surface side of the annular magnetic pole piece 53 to the minute gap 3 again. Return to. That is, a circulating flow of the magnetic fluid 4 as shown by a thick arrow in FIG. 4 is generated.

Therefore, even if the magnetic fluid 4 interposed in the minute gap 3 viscously generates heat, heat is radiated and cooled in the internal void of the cylindrical porous body 6 and the communication hole 9 of the annular magnetic pole piece 53. The temperature rise of the magnetic fluid 4 is suppressed even when the shaft 1A rotates at high speed. Further, even if foreign matter is mixed in the magnetic fluid 4, the foreign matter flows into the internal void of the cylindrical porous body 6 together with the magnetic fluid 4 from the minute gap 3, and only the foreign matter is trapped in the internal void, so that the magnetic property is reduced. Since the fluid 4 returns to the minute gap 3, the cylindrical porous body 6 serves as a filter, and foreign matter does not remain in the minute gap 3. Therefore, the life of the bearing can be extended.

Further, the dynamic pressure generated by the spiral grooves 7, 7 ′ increases the load capacity and the rotation accuracy.

In the present embodiment, an example in which two spiral grooves 7 on the radial side are separated and provided is shown. However, the spiral groove is extended so that the grooves from both sides are joined at the center, that is, the herring. It may be a bone groove. Further, in this embodiment, both the spiral groove 7 on the radial side and the spiral groove 7'on the thrust side are provided, but at least one of them may be provided.

Further, in this embodiment, the spiral grooves 7 and 7 ′ are provided on the outer peripheral surface and the outer surface side of the protruding portion 11 of the shaft 1 A, but on the opposite side, that is, the inner peripheral surface of the cylindrical porous body 6. The spiral groove 7 on the radial side and the spiral groove 7'on the thrust side may be provided on the side and on the inner surface side of the annular magnetic pole piece 53, respectively, and may be provided on both sides of the facing surface in some cases. However, when the spiral groove 7 is provided on the inner peripheral surface side of the cylindrical porous body 6, it is not desirable to seal the pores on the surface of that portion.

Further, in the present embodiment, an example in which the communication holes 9 are provided at four places on the circumference is shown, but it is sufficient to provide the communication holes 9 at at least one place on the circumference, and the present invention is not limited to this.

Next, a fifth embodiment of the present invention is shown in FIG. In this magnetic fluid bearing, a Rayleigh step 12 is provided instead of the spiral groove 7 on the outer peripheral surface of the protruding portion 11 of the shaft 1A. Thus, providing the Rayleigh step 12 on the radial side further improves the rotational accuracy in the radial direction. Other configurations and operations are similar to those of the fourth embodiment, and therefore, the same components are designated by the same reference numerals and the description thereof will be omitted.

Next, a sixth embodiment of the present invention is shown in FIG. This magnetic fluid bearing is provided with a pair of Rayleigh steps 12 spaced apart from each other on the inner peripheral surface side of the cylindrical porous body 6, and the Rayleigh step 12 portion on the inner peripheral surface of the cylindrical porous body 6 and the shaft from the portion. The sealing portion 13 is provided on the outer side in the direction, and the oil repellent portion 14 is provided on the outer peripheral surface of the protruding portion 11 of the shaft 1A at a position facing the portion between the pair of Rayleigh steps 12. . The sealing portion 13 may be formed by cutting or polishing the pores on the surface of the porous body, or by applying or impregnating a sealing agent (adhesive, etc.), and other coatings (evaporation, plating). Etc.) or a sealing material (metal, resin, etc.) is attached (embedded). The oil-repellent portion 14 may be formed by applying or coating an oil-repellent agent (for example, a fluorine-based coating agent) that exhibits oil-repellency on the magnetic fluid 4, and an oil-repellent material (for example, a fluorine-based resin) is attached. It may be formed by attaching (embedding).

In the magnetic fluid bearing of the present embodiment thus configured, the sealing portion 13 is provided on the axially outer portion of the cylindrical porous body 6 excluding the vicinity of the central portion of the inner peripheral surface thereof. Since the magnetic fluid 4 flows into the internal voids only from the vicinity of the central portion of the inner peripheral surface of the cylindrical porous body 6, and flows to the outer peripheral side in the radial direction and the outer side in the axial direction, the magnetic fluid 4 remains inside the cylindrical porous body 6. The longer the distance passes through the gap, the higher the cooling efficiency. Further, since the oil repellent portion 14 is provided on the outer peripheral surface of the protrusion 1 1 of the shaft 1A at a position facing the portion between the pair of Rayleigh steps 12, the protrusion of the shaft 1A unrelated to the action of the Rayleigh step 12. At the central portion of the outer peripheral surface of the portion 11, slippage of the magnetic fluid 4 occurs on the surface of the oil repellent portion 14, viscous heat generation of the magnetic fluid 4 due to breaking is reduced, and loss torque can be reduced. Since other configurations and operations are the same as those in the fourth and fifth embodiments, the same components are designated by the same reference numerals and the description thereof will be omitted.

In the fourth to sixth embodiments, the cylindrical permanent magnet 2 is used as the cylindrical magnetic force source, but the cylindrical magnetic magnet is not limited to the cylindrical permanent magnet. And so on.

FIG. 7 shows a seventh embodiment of the present invention. It should be noted that components having the same functions as those of the components described in each of the above-described embodiments will be described with the same reference numerals.

This magnetic fluid bearing supports a radial load, and has a pair of cylindrical porous permanent magnets 22 serving as a magnetic force source of a cylindrical porous body, and a pair provided in contact with both end surfaces of the cylindrical porous permanent magnet 22. Of the magnetic pole piece 5, the sealing portion 13 provided on the outer peripheral surface of the cylindrical porous permanent magnet 22, the inner peripheral surface of the cylindrical porous permanent magnet 22, and the pair of annular rings. The shaft 1 that faces the inner peripheral surface of the pole piece 5 with a minute gap 3 and the shaft 1 that faces the outer peripheral surface of the shaft 1 slightly inward of both ends of the inner peripheral surface of the cylindrical porous permanent magnet 22. It is composed of a spiral groove 7 for dynamic pressure generation provided in a portion to be formed, and a magnetic fluid 4 interposed in the minute gap 3 and the internal void of the cylindrical porous permanent magnet 22.

The cylindrical porous permanent magnet 22 is a porous permanent magnet having an internal void. For example, by mixing a polymer with a magnet material and molding the polymer, only the polymer is removed by evaporation or combustion. can get. Further, the sealing portion 13 may be formed by cutting or polishing to fill the pores on the surface of the cylindrical porous permanent magnet 22 or by applying or impregnating a sealing agent (adhesive or the like). Alternatively, it may be formed by coating (evaporation, plating, etc.) or attaching a sealing material (metal, resin, etc.). When the sealing portion 13 is formed by using a magnetic material as the material, it has a magnetic shield effect, and the leakage magnetic field to the outside is reduced.

In the magnetic fluid bearing of the present embodiment having the above-described structure, when the shaft 1 rotates, the spiral groove 7 provided on the outer peripheral surface of the shaft 1 pumps, so that the outer portion of the spiral groove 7 of the minute gap 3 is separated. The magnetic fluid 4 intervening in the axial direction is pushed toward the central portion side in the axial direction, and the pressure of the magnetic fluid 4 located in the central portion in the axial direction of the minute gap 3 rises, and the shaft of the inner peripheral surface of the cylindrical multi-hole permanent magnet 22 is The magnetic fluid 4 is pushed into the inner space of the cylindrical porous permanent magnet 22 from the central portion in the direction. The magnetic fluid 4 pushed in passes through the inner void of the cylindrical porous permanent magnet 22 toward the outer peripheral side in the radial direction, faces the outer side in the axial direction near the outer peripheral surface, and faces the inner peripheral side in the radial direction near the end surface. Flow back to the outside of the spiral groove 7 of the minute gap 3. That is, a circulating flow of the magnetic fluid 4 as shown by an arrow in FIG. 7 is generated.

Therefore, even if the magnetic fluid 4 interposed in the minute gap 3 viscously generates heat, it is radiated and cooled in the internal void of the cylindrical porous permanent magnet 22, so that when the shaft 1 rotates at high speed. Also, the temperature rise of the magnetic fluid 4 is suppressed. Further, even if foreign matter is mixed in the magnetic fluid 4, the foreign matter flows into the internal void of the cylindrical porous permanent magnet 22 together with the magnetic fluid 4 from the minute gap 3 and only foreign matter is trapped in the internal void. Since the magnetic fluid 4 returns to the minute gap 3, the cylindrical porous permanent magnet 22 serves as a filter, and foreign matter does not remain in the minute gap 3. Therefore, the life of the bearing can be extended.

Further, the dynamic pressure generated by the spiral groove 7 increases the load capacity and the rotation accuracy.

Further, since the cylindrical porous permanent magnet 22 has the two functions of the permanent magnet and the porous body, the outer diameter is smaller and lighter than the case where the permanent magnet and the porous body are provided separately. Therefore, the cost can be reduced by reducing the number of parts.

In this embodiment, an example in which two spiral grooves 7 are separately provided is shown. However, the spiral groove is extended and the grooves from both sides are joined at the center, that is, the herringbone groove. May be Further, in this embodiment, the spiral groove 7 is provided on the outer peripheral surface side of the shaft 1, but it may be provided on the inner peripheral surface side of the cylindrical porous permanent magnet 22, or may be provided on both sides in some cases. However, when the spiral groove 7 is provided on the inner peripheral surface side of the cylindrical porous permanent magnet 22, it is desirable to seal the surface voids in that portion.

Next, an eighth embodiment of the present invention is shown in FIG. This magnetic fluid bearing has a communication groove 8 which extends radially inward and reaches the inner peripheral surface at the portion of the inner surface of the annular magnetic pole piece 51 in contact with the end surface of the cylindrical porous permanent magnet 22. It is provided in four places.

In the magnetic fluid bearing of the present embodiment thus configured, since the communication groove 8 is provided, the circulation flow of the magnetic fluid 4 becomes easier to flow, the cooling efficiency is also increased, and the reliability is improved. . Since other configurations and operations are the same as those of the seventh embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the communication groove 8 is provided at four places on the circumference, but it may be provided on at least one place on the circumference, and the present invention is not limited to this.

Next, a ninth embodiment of the present invention is shown in FIG. In this magnetic fluid bearing, instead of a pair of annular magnetic pole pieces 51, a magnetic pole piece 5'having a concave cross section having a protrusion 15 on the inner peripheral side that contacts both end surfaces and the outer peripheral surface of the cylindrical porous permanent magnet 22 is provided. At the same time, the inner surface of the protrusion 15 of the magnetic pole piece 5 ′ extends inward in the axial direction and reaches the vicinity of the central portion in the axial direction at a portion in contact with the outer peripheral side of the end surface of the cylindrical porous permanent magnet 22. Communication holes 9 extending radially inward from the inner peripheral side toward the inner peripheral surface side are provided at four locations on the circumference.

Since the magnetic fluid bearing of the present embodiment configured as described above is provided with the communication hole 9, the circulation flow of the magnetic fluid 4 becomes easier to flow and the cooling efficiency is the same as in the eighth embodiment. Also becomes higher, and reliability is improved. Further, since the magnetic pole pieces 5'are in contact with both end surfaces and the outer peripheral surface of the cylindrical porous permanent magnet 22, the magnetic shield effect is high and the leakage magnetic field to the outside is extremely small. Since other configurations and operations are the same as those of the seventh and eighth embodiments, the same components are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, as in the seventh and eighth embodiments, the spiral groove 7 is located on the outer peripheral surface of the shaft 1 in the vicinity of the inner peripheral surface of the cylindrical porous permanent magnet 22 slightly less than both ends. In the case of this embodiment, it is provided on the outer peripheral surface of the shaft 1 on the inner peripheral surface of the magnetic pole piece 5'a little inside the communication hole 9 opening. The spiral groove 7 may be provided in the portion to be covered. According to this structure, a circulating flow is generated in almost the entire area of the minute gap 3, so that the reliability is further improved.

Next, a tenth embodiment of the present invention is shown in FIG. This magnetic fluid bearing uses only the cylindrical porous permanent magnet 22 provided with the sealing portions 13 on the outer peripheral surface and both end surfaces without providing the pair of annular magnetic pole pieces 5 and the magnetic pole pieces 5 '. . As described above, when only the cylindrical porous permanent magnet 22 is used, the structure is extremely simple, so that the size and weight can be further reduced and the cost can be reduced. Although the leakage magnetic field to the outside is larger than that in the case where the pair of annular magnetic pole pieces 5 and the magnetic pole piece 5'is used, the leakage magnetic field is reduced by the magnetic shield effect when the magnetic material is used for the sealing portion 13. be able to. Since other configurations and operations are the same as those in the above-described respective embodiments, the same components are designated by the same reference numerals, and the description thereof will be omitted.

Next, an eleventh embodiment of the present invention is shown in FIG. This magnetic fluid bearing supports both radial load and thrust load, and comprises a cylindrical porous permanent magnet 22 and a pair of annular magnetic poles provided in contact with both end surfaces of the cylindrical porous permanent magnet 22. The piece 54, the sealing portion 13 provided on the outer peripheral surface of the cylindrical porous permanent magnet 22, and the inner peripheral surface of the pair of annular magnetic pole pieces 54 face each other through a minute gap 3 and the cylindrical porous Shaft 1A having a protrusion 11 that faces the inner peripheral surface of the permanent magnet 22 and the inner surface of the pair of annular magnetic pole pieces 54 with a minute gap 3, and the outer peripheral surface and the outer surface of the protrusion 11 of the shaft 1A. The spiral grooves 7 and 7 ′ for generating dynamic pressure provided on the side surfaces and the inner surface of the pair of annular magnetic pole pieces 54 are axially contacted with the outer peripheral side of the end surfaces of the cylindrical porous permanent magnets 22. It extends inward and reaches near the center, where Communication holes 9 provided at four circumferential positions extending radially inward toward the inner peripheral surface side, the communication holes 9 and the internal voids of the cylindrical porous permanent magnet 22 and the minute gaps. The magnetic fluid 4 is interposed between the magnetic fluid 4 and the magnetic fluid 4.

In the magnetic fluid bearing of the present embodiment configured as described above, when the shaft 1A rotates, the spiral groove 7, 7'provided on the outer peripheral surface and the outer surface of the protrusion 11 of the shaft 1A causes the pumping action. The magnetic fluid 4 present on the thrust-side minute gap 3 and on the outer side of the radial-side minute gap 3 of the radial-side spiral groove 7 is pushed toward the central portion in the axial direction of the radial-side minute gap 3 and enters this portion. The pressure of the magnetic fluid 4 located increases, and the magnetic fluid 4 is pushed into the internal void of the cylindrical porous permanent magnet 22 from the axial center portion of the inner peripheral surface of the cylindrical porous permanent magnet 22. The pressed magnetic fluid 4 flows through the inner space of the cylindrical porous permanent magnet 22 to the outer peripheral side in the radial direction, passes through the communication hole 9, and again from the inner peripheral surface side of the annular magnetic pole piece 5 to form a small gap again. Return to 3. That is, a circulating flow of the magnetic fluid 4 as shown by a thick arrow in FIG. 11 is generated. Since other configurations and operations are the same as those in the above-mentioned respective embodiments, the same components are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, both the spiral groove 7 on the radial side and the spiral groove 7'on the thrust side are provided, but at least one of them may be provided. Further, in this embodiment, the spiral grooves 7 and 7'are provided on the outer peripheral surface and the outer surface side of the projecting portion 11 of the shaft 1A, but on the opposite side, that is, the inner peripheral surface side of the cylindrical porous permanent magnet 22 and the circular surface. The radial side spiral groove 7 and the thrust side spiral groove 7'may be provided on the inner side surface side of the annular magnetic pole piece 54, respectively, and in some cases, may be provided on both sides of the facing surface. However, when the spiral groove 7 is provided on the inner peripheral surface side of the cylindrical porous permanent magnet 22, it is desirable to seal the pores on the surface of that portion. Further, in the present embodiment, the pair of annular magnetic pole pieces 54 are used, but instead of this, the rotating body having a concave cross section having the protrusions contacting both end surfaces and the outer peripheral surface of the cylindrical porous permanent magnet 22 on the inner peripheral side. You may use the magnetic pole piece of.

Next, FIG. 12 shows a twelfth embodiment of the present invention. This magnetic fluid bearing also supports both radial load and thrust load, and without providing a pair of annular magnetic pole pieces 54, a small gap 3 is formed between the outer peripheral surface and the outer surface of the protrusion 11 of the shaft 1A. Is provided with a porous permanent magnet 22 'having a concave cross section having an inwardly facing protruding portion 15 on the inner peripheral side, and the protruding portion of the porous permanent magnet 22' facing the outer peripheral surface of the protruding portion 11 of the shaft 1A. Sealing portions 13 are provided on the inner peripheral surface of the inner peripheral surface of 15 except the central portion, the inner surface of the protruding portion 15, the outer peripheral surface of the porous permanent magnet 22 ', and both end surfaces.

As described above, when only the porous permanent magnet 22 'having a concave rotating body is used, the number of parts is reduced, and the size and weight can be further reduced and the cost can be reduced. Since other configurations and operations are the same as those in the above-mentioned respective embodiments, the same components are designated by the same reference numerals and the description thereof will be omitted.

Although the seventh to twelfth embodiments have been described by taking the cylindrical porous permanent magnet 22 as the magnetic source of the cylindrical porous body as an example, the present invention is not limited to the cylindrical porous permanent magnet. Instead, it may be a cylindrical porous electromagnet or the like.

[0054]

[Effect of device]

 The present invention has the above-described structure and action, and is formed on the outer peripheral surface of the shaft by a porous body or a cylindrical porous body, a portion facing the vicinity of both ends of the magnetic source, or a porous body or a cylindrical body. Due to the dynamic pressure generated by the spiral groove provided on at least one of the both ends of the inner peripheral surface of the porous magnetic force source, the magnetic fluid flows from the minute gap to the internal void of the porous body or the cylindrical porous magnetic force source. Since a circulating flow that flows into the magnetic fluid and returns to the minute gap is generated again, the temperature rise of the magnetic fluid is suppressed even under high speed rotation, and the foreign matter mixed in the magnetic fluid is a porous body or a cylindrical porous body magnetic source. Since it does not stay in the minute gap due to the filter action of, the life of the bearing can be extended.

Further, the dynamic pressure generated by the spiral groove increases the load capacity and the rotation accuracy.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a magnetic fluid bearing according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a magnetic fluid bearing according to a second embodiment of the present invention.

FIG. 3 is a vertical sectional view of a magnetic fluid bearing according to a third embodiment of the present invention.

FIG. 4 is a vertical sectional view of a magnetic fluid bearing according to a fourth embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a magnetic fluid bearing according to a fifth embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of a magnetic fluid bearing according to a sixth embodiment of the present invention.

FIG. 7 is a longitudinal sectional view of a magnetic fluid bearing according to a seventh embodiment of the present invention.

FIG. 8 is a vertical sectional view of a magnetic fluid bearing according to an eighth embodiment of the present invention.

FIG. 9 is a vertical cross-sectional view of a magnetic fluid bearing according to a ninth embodiment of the present invention.

FIG. 10 is a longitudinal sectional view of a magnetic fluid bearing according to a tenth embodiment of the present invention.

FIG. 11 is a longitudinal sectional view of a magnetic fluid bearing according to an eleventh embodiment of the present invention.

FIG. 12 is a vertical cross-sectional view of a magnetic fluid bearing according to a twelfth embodiment of the present invention.

FIG. 13 is a vertical sectional view of a magnetic fluid bearing of a first conventional example.

FIG. 14 is a vertical sectional view of a magnetic fluid bearing of a second conventional example.

[Explanation of symbols]

 1,1A Axis 2 Cylindrical permanent magnet (cylindrical magnetic force source) 22 Cylindrical porous permanent magnet (cylindrical porous magnetic force source) 3 Micro gap 4 Magnetic fluid 5,51,52,53,54 Annular magnetic pole piece (Magnetic pole piece) 6 Cylindrical porous body (porous body) 7 Spiral groove 8 Communication groove 9 Communication hole 10 Space 11 Projection part 12 Rayleigh step 13 Sealing part 14 Oil repellent part 15 Projection part

Claims (2)

[Scope of utility model registration request] 1. A cylindrical magnetic force source, a pair of magnetic pole pieces provided in contact with both end faces of the cylindrical magnetic force source, a shaft provided with the magnetic pole pieces with a minute gap, and a shaft provided in the minute gap. In a magnetic fluid bearing composed of a magnetic fluid, a porous body is disposed so as to face a space surrounded by an inner peripheral surface of the cylindrical magnetic force source and inner side surfaces of the pair of magnetic pole pieces with the shaft with a minute gap therebetween. Is provided, and the magnetic fluid is interposed also in the internal voids and the minute gaps of the porous body, and the portion of the outer peripheral surface of the shaft that faces the vicinity of both ends of the porous body or the inside of the porous body. A magnetic fluid bearing characterized in that a spiral groove for generating a dynamic pressure is provided on at least one of both ends of the peripheral surface. 2. A cylindrical porous magnetic force source, a shaft provided with a minute gap from the inner peripheral surface of the cylindrical porous magnetic force source, and the porous magnetic force source on the outer peripheral surface of the shaft. A spiral groove for generating dynamic pressure, which is provided in at least one of a portion facing the vicinity of both ends or near both ends of the inner peripheral surface of the porous body, the minute gap and the cylindrical porous body magnetic source Magnetic fluid bearing consisting of a magnetic fluid interposed in the inner space of the.