JP3408664B2 - Gas bearing structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas bearing structure for supporting a rotating shaft or a reciprocating shaft, and more particularly to a gas bearing structure applied to a rotating machine. . 2. Description of the Related Art Generally, in a gas bearing, a compressed gas that has passed through a throttle is introduced into a bearing gap formed between a mating member and a bearing surface, and a load distribution and a bearing rigidity are obtained by the pressure distribution. It is widely used in precision equipment, etc., taking advantage of its features such as low frictional resistance and high accuracy and cleanness. [0003] Such a gas bearing has a porous type using a porous material for the throttle, a multi-hole type in which several to several tens of small holes are opened in the bearing surface, and a gas bearing having an inner peripheral surface. There are a variety of types such as a surface drawing type in which a large number of shallow narrow grooves are provided and the narrow grooves communicate with the compressed air introduction holes. For example, when a bearing gap is small and high precision and high rigidity are aimed at, a porous type and a surface drawing type are suitable. On the other hand, in terms of ease of processing and large bearings, a multi-hole type is suitable.Particularly, the mating member is a rotating shaft, centrifugal force causes expansion of the rotating shaft, etc., and the bearing gap during rotation is stationary. Of the bearing gap. In particular, for a bearing having a large diameter, it is difficult to employ a porous type drawing mechanism, and a multi-hole type is used. Therefore, except for the field of small precision equipment, a multi-hole type is often used, but a multi-hole type gas bearing is formed by plating stainless steel or carbon steel for machine structure.
On the other hand, since the same material is used for the mating bearing member,
Even if compressed air is interposed, there is a problem in that the load weight burden is large and bearings are frequently burned. Further, in the gas bearing, since the viscosity of the air is small, the vibration damping characteristics are poor, and the minute vibration is easily generated by the flow of the compressed air flowing out of the throttle. Further, when the rotation speed is increased, the minute vibration is amplified and a so-called whirling phenomenon occurs. As a result, there is a problem that a burning accident of the bearing occurs. In order to solve such a drawback, for example, as shown in Japanese Patent Application Laid-Open No. 3-74628, a bearing body having an intake port through which compressed air flows around a rotating shaft is provided with a natural vibration and a synchronous vibration during the rotation. Natural vibration damping means for detecting an unstable vibration such as whirling and adding a pressure wave in a damping direction in accordance with the signal, in other words, a first vibration communicating means connected to the intake port.
A technique is disclosed in which a second pressure air source having a higher pressure than the compressed air source is provided. However, providing a plurality of pressure sources as described above complicates the configuration. Further, detecting unstable vibration and adding a pressure wave in a damping direction in response to the signal is an electrical problem. Detecting means and electrical control means for it are also required, which leads to complicated configuration as described above,
In particular, it is difficult to use in places with strong explosion-proof properties. On the other hand, there has conventionally been a magnet bearing utilizing a magnetic repulsive force of a magnet instead of the compressed air. FIG. 5 shows the configuration of such a conventional radial magnet bearing.
In the figure, 020 is a rotation axis, 021 is a magnetic pole, 022 is a coil for flowing a bias current, 023 is a coil for flowing a control current, 024 is a position sensor, and 025 is a control device. To form a magnetic loop electrode 021 are next phase in the Y direction by flowing the bias current I _R coil 022. The position of the rotating shaft 020 in the Y direction is determined by the magnitude of the magnetic force. There is also a similar device in the X direction. According to such a bearing, the position reference position of the shaft is set, the setting position is compared with the signal position from the position sensor 024, and the control device 025 controls the control current I _{C in a} direction in which it becomes zero.
, The magnetic repulsion force set by the magnetic loop acts on the rotating shaft 020 to enable a non-contact bearing. However, the above-described device also requires a coil, a control device, and the like, which leads to a complicated configuration, and it is difficult to use the device in a location having a particularly strong explosion-proof property. In view of the above-mentioned drawbacks of the prior art, the present invention can effectively maintain a non-contact state even in a bearing having a large load weight, and effectively prevents the generation of minute vibrations due to the low viscosity of air (gas). It is an object of the present invention to provide a gas bearing structure that can be prevented. Another object of the present invention is to provide a gas bearing structure capable of effectively improving the load capability in a low speed rotation range. Another object of the present invention is to achieve an electric object with a simple structure without using electric control parts such as coils and control devices, thereby simplifying the structure and improving the explosion-proof property by several steps. It is to provide a bearing structure. SUMMARY OF THE INVENTION In view of the above technical problems, the present invention has a compressed gas interposed in a bearing gap between a mating member and a bearing surface, and has at least the mating member in the bearing gap. The invention is characterized in that a magnetic repulsive force formed by a permanent magnet is applied to a portion receiving a load, and the invention according to claim 1 is formed by a permanent magnet at least in a portion of the bearing gap that receives a load of a mating member. In a bearing structure in which a magnetic repulsion force is applied, a ring-shaped magnet body having an inner diameter equal to the inner diameter of the bearing body is fitted on the bearing surface of the bearing body. A large number of air supply holes are arranged in a circumferential direction from the outer peripheral surface side toward the inner peripheral surface side of the magnet, and compressed gas is interposed in a bearing gap between the mating member and the bearing surface, while the mating member is a machine. Structural carbon steel Using a rotating shaft consisting of, comprising a permanent magnet having the same polarity as the ring-shaped magnet body in the rotating shaft,
The bearing gap is configured to generate a repulsive magnetic field . Further, the present invention is effective not only for a multi-hole type gas bearing structure but also for a porous type and a surface drawing type gas bearing. [0013] According to the above technical means, since the bearing force of the compressed air and the magnetic repulsion force are generated at least in a portion of the bearing gap of the compressed air to which the load of the partner member is applied, the gas bearing is provided. The load capacity at the time of low-speed rotation, which is a drawback of the above, is improved, and the mating member can be effectively held in a non-contact manner even in a bearing having a large load weight load. In addition, since the magnetic repulsion is constituted by permanent magnets, no electrical control device such as a control device and an emergency safety device is required, thereby simplifying the configuration and increasing explosion-proof properties. It is possible to obtain a gas bearing structure that can be stepped up. Further, according to the present invention, the load of the air (gas) is small due to the low viscosity of the air (gas), and the magnetic repulsive force acts in a direction to prevent the vibration due to the imbalance, thereby suppressing the vibration. In addition, accidents such as burn-in caused by excessive vibration can be prevented. Embodiments of the present invention will be described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. It's just FIG. 1 is a schematic view of a main part showing a multi-hole type gas bearing structure according to an embodiment of the present invention, in which (A) is a cross-sectional view cut perpendicularly to the axial direction, and (B) is a longitudinal cross-sectional view. . In the figure, reference numeral 1 denotes a mating member (rotating shaft), and 3 denotes a bearing body (bearing metal), between which a thin ring-shaped bearing gap 4 is formed. On the bearing surface side of the bearing body 3, the bearing body 3
A ring-shaped magnet body 20 having the same inner diameter as the inner circumferential surface is fitted, and is arranged at equal intervals in the circumferential direction from the outer circumferential surface side of the bearing body 3 toward the inner circumferential surface side of the magnet body 20. A large number of air supply holes 5 are pierced and arranged. As shown in FIG. 1B, the air supply hole 5 is connected to a compressed air supply source 7 via a check valve 6 on the base side (outer peripheral side of the bearing body 3), and an orifice-shaped throttle 5a is formed at the tip end. The opening is formed on the inner peripheral surface of the magnet body 20 through the opening. An air passage communicating with the opening extends a predetermined length in the axial direction so that a wedge-shaped gas film is formed on the inner peripheral surface of the magnet body 20 facing the outer periphery of the counterpart member 1 and the inner peripheral surface of the bearing body 3. are doing. On the other hand, the mating member 1 uses, for example, a rotating shaft 1A made of a magnetic material plated with carbon steel for machine structure, and a rod-shaped permanent magnet 1B having the same polarity as that of the ring-shaped magnet body 20 on the rotating shaft 1A. The two magnets 1 </ b> B, 2 </ b> B
It is configured such that a magnetic repulsive force consisting of a zero repulsive magnetic field is generated. According to this embodiment, the compressed air is supplied from the compressed air supply source 7 to the bearing gap 4 through the check valve 6 and the air supply hole 5, so that the compressed air is supplied over the entire circumference of the mating member 1. And a magnetic repulsive force consisting of the repulsive magnetic fields of the two permanent magnets is generated in the bearing gap 4, so that the load capacity is improved even at low speed rotation and the load weight burden is large. Can effectively hold the mating member 1 in a non-contact manner. The mating member 1 is a rotating shaft 1A of a vertical rotary machine (not shown in detail), so that it is not necessary to support a bearing load. Is increasing. FIG. 2 shows a sleeve bearing structure applied to a horizontal rotating machine. In the case of a horizontal rotating machine, the bearing load acts downward, so that the magnetic field is formed by the repulsive magnetic fields of the two permanent magnets 1C and 21. The repulsive force acts only on the lower peripheral surface of the bearing gap 4. For this reason, the magnet body 21 incorporated in the bearing main body 3 has a semicircular ring shape, and the rod-shaped magnet 1C included in the mating member also has a semicircular shape. FIG. 3 shows a third embodiment of the present invention, which is a gas bearing incorporating a tilting pad type permanent magnet 2 used for a vertical rotary machine, 16 is a bearing pad, and 17 is a pivot. Also in this embodiment, the rotating shaft 1 made of a magnetic material obtained by plating a mating member with carbon steel for machine structural use.
A, in which a rod-shaped magnet 1B is included in A, is used. On the other hand, a tilting pad-shaped substantially ring-shaped permanent magnet 20 is incorporated in the bearing body 3 side, so that the entire circumference is the same as in the above embodiment. Magnetic repulsion can be generated. still,
Although the sleeve bearing type and the tilting pad type bearing have been described, the thrust bearing may be a gas bearing incorporating a permanent magnet. FIG. 4 shows a porous type bearing structure, in which a bearing member 11 made of a porous material is disposed on the inner surface of a housing 12, and the bearing surface of the bearing member 11 is formed on a rotating shaft which is a mating member 1.
Are opposed to each other. Bearing member 11 and housing 1
An annular air supply cavity 15 is provided between the two, and is connected to the compressed air source 7 through an air supply hole 14 formed in the housing 12. And the bearing member 1
1 is formed of a cylindrical sintered body in which resin is impregnated with a porous body obtained by compacting carbon or graphite and then sintering, and the inner peripheral surface side is cut into a rectangular shape. A ring-shaped permanent magnet body 20 is fitted to the cut portion. Further, an air supply cavity 15 is provided on the outer peripheral side so as to be continuous with the air supply hole 14. On the other hand, the mating member 1 uses, for example, a rotating shaft 1A made of a magnetic material plated with carbon steel for machine structure, and the rotating shaft 1A includes a rod-shaped magnet having the same polarity as the ring-shaped magnet body 20. It is configured such that a magnetic repulsive force consisting of the repulsive magnetic fields of the two magnets 1B, 20 is generated in the bearing gap 4 facing the ring-shaped magnet body 20. According to this embodiment, the compressed air supply source 7
By supplying compressed air to the bearing member 11 made of a sintered body through the air supply hole 14 and the air supply cavity 15,
Compressed air flows out toward the bearing gap 4 from a large number of minute communication holes formed in the sintered body, and a supporting force by the compressed air is generated over the entire circumference of the mating member 1. A magnetic repulsive force consisting of the repulsive magnetic fields of the two permanent magnets 1B and 20 is generated in the bearing gap 4 located substantially at the center, and the same effect as in the above embodiment is obtained. As described above, according to the present invention, the gas bearing has a small absolute load capacity, but the repulsive force of the permanent magnet is relatively large as compared with the load capacity of the gas bearing. Ability can be greatly improved. In particular, since the repulsive force of the permanent magnet is independent of the rotational speed of the shaft, it is very effective in improving the load capability of the gas bearing in the low-speed rotation range. Further, according to the present invention, it is possible to effectively hold the bearing in a non-contact manner even in a bearing having a large load weight burden, and it is possible to effectively prevent the generation of minute vibration due to the low viscosity of air (gas).
Further, according to the present invention, an electric object can be achieved with a simple configuration without using electric control parts such as a coil and a control device, so that the configuration can be simplified and the explosion-proof property can be particularly improved by several steps.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a main part showing a multi-hole type gas bearing structure according to an embodiment of the present invention, where (A) is a cross-sectional view cut perpendicularly to the axial direction, B) shows a longitudinal section. FIG. 2 is a schematic cross-sectional view of a main part of a gas bearing structure in which a permanent magnet according to another embodiment of the present invention is incorporated in a lower peripheral surface of a bearing, and is cut perpendicular to the axial direction. FIG. 3 is a sectional view of a tilting pad type gas bearing incorporating a permanent magnet according to a third embodiment of the present invention. FIG. 4 shows a porous type bearing structure. FIG. 5 is a configuration diagram of a conventional radial magnetic bearing. [Description of Signs] 1 Mating member 4 Bearing gap 3, 11, 12 Bearing body 5, 14 Air supply holes 20, 21, 1B Permanent magnet

Claims (1)

(57) [Claim 1] In a bearing structure in which a magnetic repulsive force formed by a permanent magnet is applied to at least a portion of a bearing gap that receives a load of a mating member, A ring-shaped magnet body having the same inner diameter as the inner circumferential surface of the bearing body is fitted, and a large number of circumferentially extending from the outer circumferential surface side of the bearing body toward the inner circumferential surface side of the magnet. The air supply holes are pierced and arranged, and compressed gas is interposed in the bearing gap between the mating member and the bearing surface. On the other hand, the mating member uses a rotating shaft made of carbon steel for machine structure, and the ring shaft is used as the rotating shaft. A gas bearing structure comprising a permanent magnet having the same polarity as that of a magnet body and configured to generate a repulsive magnetic field in the bearing gap.