JPH08334124A - Gas bearing structure - Google Patents

Abstract

PURPOSE: To achieve an electrical purpose without using an electrical control part so as to improve explosion proof properties much better, by interposing compressed air in a bearing void, and actuating upon a part for receiving the load of a counter, magnetic action formed by a permanent magnet, preferably magnetic repulsive force. CONSTITUTION: A thin layered ring bearing void 4 is formed between a counter member 1 (rotary shaft) and a bearing main body 3 (bearing metal). Multiple air supply holes 5 are opened and arranged at equal intervals in the peripheral direction from the outer circumferential surface side of the bearing main body 3 toward the inner circumferential side of a magnet body 20. These air supply holes 5 are provided adjacently to a compressed air supply source 7 through a check valve 6 on the outer circumferential side of the bearing main body 3. The counter member 1 is formed in such a manner that a cylindrical permanent magnet 1B having the same magnetism as the ring magnet body 20 is included in a rotary shaft 1A so that magnetic repulsive force consisting of the repulsive magnetic fields of two magnets 1B, 20 by using the rotary shaft 1A formed of a magnetic material is generated in the bearing void 4 opposed to the ring magnetic body 20.

Description

Detailed Description of the Invention

[0001]

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 shaft which reciprocates, and more particularly to a gas bearing structure applied to a rotary machine.

[0002]

2. Description of the Related Art Generally, a gas bearing guides compressed gas that has passed through a throttle into a bearing gap formed between a mating member and a bearing surface, and obtains load capacity and bearing rigidity by its pressure distribution. It is widely used in precision equipment, taking advantage of its features such as low friction resistance, high precision and cleanliness.

Depending on the type of the throttle, the gas bearing is of a porous type in which a porous material is used for the throttle, a multi-hole type in which a few to several tens of small holes are opened in the bearing surface, and a bearing inner peripheral surface is formed. There are various types such as a surface drawing type in which a large number of shallow grooves are provided and the narrow grooves are communicated with the compressed air introduction hole, and they are used properly depending on the performance requirements.

For example, when the 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 size bearings, the multi-hole type is suitable, especially when the mating member is the rotating shaft and the rotating shaft expands due to centrifugal force, etc. It changes compared to the bearing air gap. In particular, it is difficult to adopt a porous type throttle mechanism for a bearing having a large diameter, and a multi-hole type is used.

Therefore, the multi-hole type is often used except for the field of small precision equipment, but the multi-hole type gas bearing is made of stainless steel or carbon steel for machine structure plated.
On the other hand, since a similar bearing member is used,
Even if compressed air is interposed, the burden on the load is large, and there is a problem that the bearing is often seized. Further, in the gas bearing, since the viscosity of air is small, the vibration damping characteristic is poor, and minute vibrations are easily generated by the flow of pressure air flowing out from the throttle. Further, at high speed rotation, the minute vibration is amplified and a so-called whirling phenomenon occurs, resulting in a problem that a bearing seizure accident occurs.

In order to eliminate such drawbacks, as shown in, for example, Japanese Patent Laid-Open No. 3-74628, a bearing body having an intake port for letting pressurized air flow around a rotary shaft has a natural vibration and a synchronous vibration during rotation. Natural vibration damping means for detecting unstable vibration such as whirling and adding a pressure wave in the damping direction corresponding to the signal, in other words, a first vibration communicating with the intake port.
The technique of providing a second compressed air source having a higher pressure than the compressed air source of the above is disclosed.

However, providing a plurality of pressure sources as described above leads to a complicated structure, and it is electrical to detect an unstable vibration and add a pressure wave in the damping direction corresponding to the signal. It also requires detection means and electrical control means therefor, which leads to complication of the configuration as described above,
In particular, it is difficult to use it in places with strong explosion-proof properties.

On the other hand, there is conventionally a magnetic bearing which utilizes the magnetic repulsive force of a magnet instead of the compressed air. FIG. 5 shows the structure of a radial magnet bearing according to such a conventional technique.
In the figure, 020 is a rotating shaft, 021 is a magnetic pole, 022 is a coil for supplying a bias current, 023 is a coil for supplying a control current, 024 is a position sensor, and 025 is a control device. By supplying the bias current I _R coil 022, a magnetic loop is formed by the adjacent electrodes 021 in the Y direction. The magnitude of this magnetic force determines the position of the rotary shaft 020 in the Y direction. 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 current I _C
The magnetic repulsive force set by the magnetic loop acts on the rotary shaft 020 by flowing the magnetic field, and a non-contact bearing becomes possible.

However, the above-mentioned device also requires a coil, a control device and the like, which leads to a complicated structure and is difficult to use particularly in a place having a strong explosion-proof property.

In view of the above-mentioned drawbacks of the prior art, the present invention can effectively hold a bearing that bears a heavy load weight in a non-contact manner, and effectively generates a microvibration due to the low viscosity of air (gas). An object is 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 capacity in the 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 a coil and a control device, which simplifies the structure and, in particular, makes it possible to enhance the explosion-proof property by several steps. To provide a bearing structure.

[0011]

In view of the above technical problems, the present invention allows compressed gas to be interposed in a bearing gap between a mating member and a bearing surface, and receives at least a load of the mating member in the bearing gap. A magnetic acting force, preferably a magnetic repulsive force, formed by a permanent magnet is applied to the portion. In this case, in order to generate the magnetic repulsive force, for example, it is easily achieved by disposing opposing permanent magnets of the same polarity on the mating member side such as the rotating shaft and the bearing surface side facing the mating member side. However, the present invention is not limited to this.

Further, the present invention is effective not only in the multi-hole type gas bearing structure but also in the porous type and surface drawing type gas bearings.

[0013]

According to such a technical means, the bearing force of the compressed air and the magnetic repulsion force are generated at least in the bearing gap of the compressed air where the load of the counterpart member is applied. The load capacity at the time of low speed rotation is improved, and the mating member can be effectively held in a non-contact manner even in a bearing that bears a heavy load weight. Further, since the magnetic repulsion force is composed of a permanent magnet, no electric control device such as a control device or an emergency safety device is required, which simplifies the structure and particularly increases the explosion-proof property. It is possible to obtain a gas bearing structure that can be stepped up.

Further, according to the present invention, since the viscosity of air (gas) is small, the load capacity is small and the magnetic repulsive force acts on the vibration due to the imbalance so as to prevent it, and the vibration is suppressed to a small level. It is possible to prevent an accident such as seizure due to excessive vibration.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, the dimensions, materials, shapes, relative positions, etc., of the components described in this embodiment are not intended to limit the scope of the present invention thereto, unless there is a specific description, and are merely illustrative examples. Nothing more than. 1A and 1B are schematic views showing a main part of a multi-hole type gas bearing structure according to an embodiment of the present invention. FIG. 1A is a cross sectional view taken along a line orthogonal to the axial direction, and FIG. . In the figure, 1 is a mating member (rotating shaft), 3 is a bearing main body (bearing metal), and a thin-layer ring-shaped bearing gap 4 is formed between them.

On the bearing surface side of the bearing body 3, the bearing body 3
A ring-shaped magnet body 20 having an inner diameter equal to that of the inner circumferential surface is fitted, and the bearing body 3 is circumferentially equidistant from the outer circumferential surface side toward the inner circumferential surface side of the magnet body 20. A large number of air supply holes 5 are arranged in a hole. As shown in FIG. 1 (B), the air supply hole 5 is connected to the compressed air supply source 7 through a check valve 6 on the base side (outer peripheral side of the bearing body 3), and the tip side is an orifice-shaped throttle 5a. The inner peripheral surface of the magnet body 20 is opened through. Further, the air passage communicating with the opening extends for a predetermined length in the axial direction so that a wedge-shaped air film is formed on the inner peripheral surface of the magnet body 20 and the inner peripheral surface of the bearing body 3 facing the outer periphery of the mating member 1. are doing.

On the other hand, the mating member 1 uses, for example, a rotating shaft 1A made of a magnetic material obtained by plating carbon steel for machine structure, and a rod-shaped permanent magnet 1B having the same polarity as the ring-shaped magnet body 20 is attached to the rotating shaft 1A. Two magnets 1B, 2 are included in the bearing gap 4 facing the ring-shaped magnet body 20.
A magnetic repulsive force composed of a repulsive magnetic field of 0 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 distributed all around the mating member 1. Bearing force is generated and a magnetic repulsive force composed of 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 structure bears a large load weight. Also in the above, it is possible to effectively hold the mating member 1 in a non-contact manner.

Although not shown in detail, since the mating member 1 is a rotary shaft 1A of a vertical rotary machine, it is not necessary to support the bearing load, and the permanent magnets 2 are incorporated around the entire circumference of the bearing to provide load capacity. Is increasing.

FIG. 2 shows a sleeve bearing structure applied to a horizontal type rotary machine. In the case of a horizontal type rotary machine, the bearing load acts downward, so that a magnetic field composed of repulsive magnetic fields of the two permanent magnets 1C and 21 is used. The repulsive force acts only on the lower peripheral surface of the bearing gap 4. Therefore, 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 in a vertical rotary machine, wherein 16 is a bearing pad and 17 is a pivot. Also in the present embodiment, the rotating shaft 1 made of a magnetic material plated with carbon steel for machine structure is used as a mating member.
A rod-shaped magnet 1B is included in A, while the tilting pad type substantially ring-shaped permanent magnet 20 is incorporated in the bearing main body 3 side. Can generate magnetic repulsion. still,
Although the sleeve bearing type and the tilting pad type bearing have been described above, the thrust bearing can also be a gas bearing incorporating a permanent magnet.

FIG. 4 shows a porous bearing structure in which a bearing member 11 made of a porous material is arranged on the inner surface of a housing 12, and the bearing surface has a bearing gap 4 in a rotating shaft which is a counterpart member 1.
Are facing 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 a cylindrical sintered body obtained by impregnating a resin into a porous body obtained by compacting carbon or graphite and then sintering, and cutting the inner peripheral surface side into a rectangular shape, The ring-shaped permanent magnet body 20 is fitted to the cut portion. An air supply cavity 15 is provided on the outer peripheral side and is connected to 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 obtained by plating carbon steel for machine structural use, and the rotating shaft 1A contains a rod-shaped magnet having the same polarity as that of the ring-shaped magnet body 20. A magnetic repulsive force composed of repulsive magnetic fields of the two magnets 1B and 20 is formed in the bearing gap 4 facing the ring-shaped magnet body 20.

According to such an 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 into the bearing gap 4 through a large number of minute communication holes formed in the sintered body, and a supporting force of the compressed air is generated over the entire circumference of the mating member 1, and the bearing member 11 A magnetic repulsive force composed of the repulsive magnetic fields of the two permanent magnets 1B and 20 is generated in the bearing gap 4 located substantially in the center, and the same effect as that of the above-described embodiment is produced.

[0024]

As described above, according to the present invention, the absolute load capacity of the gas bearing is small, but the repulsive force of the permanent magnet is relatively large as compared with the load capacity of the gas bearing, and the load capacity of the bearing is greatly increased. Can be improved. In particular, since the repulsive force of the permanent magnet is irrelevant to the rotation speed of the shaft, it is very effective in improving the load capacity of the gas bearing in the low speed rotation range. Further, according to the present invention, even a bearing that bears a heavy load can be effectively held in a non-contact manner, and it is possible to effectively prevent the occurrence of minute vibrations due to the low viscosity of air (gas).
Further, according to the present invention, the electric purpose can be achieved with a simple structure without using an electric control component such as a coil or a control device, whereby the structure can be simplified and particularly the explosion-proof property can be increased by several steps.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a multi-hole type gas bearing structure according to an embodiment of the present invention, in which (A) is a cross-sectional view taken along a line orthogonal to the axial direction, and (B) is a vertical cross-sectional view. Show.

FIG. 2 is a schematic view of a main part showing a gas bearing structure in which a permanent magnet according to another embodiment of the present invention is incorporated in the lower peripheral surface of the bearing, and is a cross-sectional view taken along a line orthogonal 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 bearing structure.

FIG. 5 is a configuration diagram of a conventional radial magnetic bearing.

[Explanation of symbols]

 1 Mating member 4 Bearing gap 3, 11, 12 Bearing body 5, 14 Air supply hole 20, 21, 1B Permanent magnet

Claims (1)

[Claims] 1. A magnetic force formed by a permanent magnet in a bearing space between a mating member and a bearing surface, and a compressed gas is interposed in the bearing space, and at least a portion of the bearing space receiving a load of the mating member, preferably a magnetic force. Is a gas bearing structure characterized by magnetic repulsion.