JPS6215775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bearing, and more particularly to an improvement in a tailing pad type gas bearing that rotatably supports a shaft rotating at high speed in a suspended state with a gas film. Related.

Tailing pad type gas bearings have been known as one type of high-speed rotation bearings. Tailing pad type gas bearings generally have a wedge-shaped structure between a housing and the rotating shaft that is circumferentially spaced around and pivotally supported by the housing. It has a plurality of bearing pads that can define a space, and the rotating shaft floats above the bearing pads when the gas drawn into the wedge-shaped space due to viscosity is pressurized by the so-called wedge effect. It is designed to be supported in this state. Such tailing pad type gas bearings use gas such as air, which has a relatively low viscosity, as a lubricant, and therefore the rotating shaft supported by it can rotate at a very high speed, and there is no power loss due to friction. It has advantages such as small friction, small wear on the bearing engagement surface, and no need for lubricating oil supply or circulation.

However, when the rotational speed of the rotating shaft is low, such as when starting and stopping rotation, almost no increase in gas pressure occurs due to the so-called wedge effect, and therefore the rotating shaft and the bearing pad are in solid contact. Therefore, large sliding friction occurs between the rotating shaft and the bearing pad, and the engagement surfaces of the rotating shaft and the bearing pad wear out prematurely. Therefore, the tailing pad type gas bearing has disadvantages in that its durability is poorer than other bearings, and the starting torque at the time of starting rotation is large.

Conventionally, attempts have been made to overcome the above-mentioned drawbacks by coating the surfaces of rotating shafts and bearing pads with ceramic coatings containing chromium oxide as the main component. Since solid contact between the rotating shaft and the bearing pad cannot be avoided, the above-mentioned drawbacks have not yet been solved.

The object of the present invention is to utilize the above-mentioned advantages of the tailing pad type gas bearing while improving the above-mentioned drawbacks in the low-speed rotation range of the rotating shaft, especially when starting and stopping the rotation. An object of the present invention is to provide a tailing pad type bearing structure.

Such an object, according to the present invention, provides a wedge-shaped structure between a rotating shaft, a housing, and a wedge-shaped shaft spaced circumferentially around the rotating shaft and pivotally supported by the housing. a plurality of bearing pads capable of defining a space; a first magnet incorporated in the rotating shaft; and a second magnet supported by the housing and exerting a magnetic repulsion force on the first magnet. a magnet, the second magnet is fixedly attached to the bearing pad such that its magnetic axis of action passes through a position closer to the leading edge of the bearing pad than the pivot point of the bearing pad. This is achieved by a tailing pad type bearing structure characterized by the following.

In the tailing pad type bearing structure, in order to reduce the wear of the bearing surface etc. in the low rotational speed range of the rotating shaft and the starting torque of the rotating shaft, it is necessary to In addition to reducing surface pressure, it is desirable to form a gas film that is as effective as possible even in the low rotational speed range of the rotating shaft.Furthermore, these two functions are not achieved by separate magnets, but by a common magnet. This is preferably achieved by a magnet.

According to the present invention, the first and second magnets that cooperate with each other to generate a magnetic repulsion force not only function to separate the rotating shaft and the bearing pad from each other, but also serve to move the bearing pad away from each other. It also has the effect of actively forming a wedge-shaped space between the rotating shaft and the bearing pad by pivoting around the pivot point, and these two actions avoid wear of the rotating shaft and the bearing pad, and also prevent the rotating shaft from being worn out. The starting torque, etc. of
Also, compared to the case where the rotating shaft and the bearing pad are simply separated from each other by magnetic repulsion, the first and second magnets may be smaller and lighter, and the bearing structure It is possible to reduce the size of the rotary shaft, and furthermore, it is possible to reduce the weight of the rotary shaft and improve the responsiveness of the rotary shaft to rotational drive input.

According to one detailed feature of the invention, the single magnet is a permanent magnet and the second magnet is an electromagnet. In a tailing pad type bearing structure, as is well known, the smaller the rotational speed of the rotating shaft, the larger the opening angle of the wedge-shaped space within a predetermined range is. It is preferable that the opening angle of the wedge-shaped space formed between the pad and the pad is controlled in accordance with the rotational speed of the rotating shaft. According to the detailed features described above, by controlling the voltage value or current value of the current passed through the second magnet, the opening angle of the wedge-shaped space can be appropriately controlled according to the rotational speed of the rotating shaft. In addition, in the region where the rotational speed of the rotating shaft is above a predetermined value, that is, in the region where a gas film with sufficient pressure is formed, the power supply to the second magnet may be stopped, so that the electrical energy is It is not consumed in large quantities.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

1 and 2 are schematic cross-sectional views showing a first embodiment of the tailing pad type gas bearing structure according to the present invention, and are respectively shown along the lines shown in FIG.
, a cross-sectional view and a vertical cross-sectional view taken along the line - of FIG. 1; In these figures, 1 is a hollow rotating shaft, and annular permanent magnets 2, 2' are mounted on its inner wall.
is fixed. These permanent magnets are toroidal permanent magnets having substantially uniform radial magnetic domains in their radial direction. Around the rotating shaft 1, three bearing pads 3a, 3b, 3c having inner surfaces with a radius of curvature slightly larger than the rotating shaft are arranged at equal intervals from the rotating shaft. These bearing pads are respectively pivot members 4a, 4b, 4c.
It is pivotably supported about a pivot by a spherical portion of. The pivot members 4b, 4c are inserted into screw holes provided in the housing 5, and are fixed in predetermined positions by lock nuts 6. On the other hand, the pivot support member 4a that pivotally supports the bearing pad 3a located above the rotating shaft 1 is provided with a screw of the elastic member 7 so that the clearance a between the rotating shaft 1 and the bearing pad 3a can be adjusted to a preferable value during rotation. It is inserted through the resistor 7a and fixed by a lock nut 6. The elastic member 7 is attached to the housing 5 by a pressing plate 8 and bolts 9.
It is fastened and fixed.

Electromagnets 12, 12' formed by winding conductive wires around iron cores 10, 11 integrally fixed to the bearing pads 3b, 3c located substantially below the rotating shaft 1, respectively. and 1
3, 13' are provided. In this case, the respective polarities of the electromagnets 12, 12' and 13, 13' are the same as those of the permanent magnets 2, 2' fixed to the rotating shaft 1.
It is designed to generate a magnetic repulsion force against the magnetic field. That is, for example, if the polarity along the outer periphery of the permanent magnets 2, 2' is S pole and the polarity along the inner periphery is N pole, the radially inner magnetic pole of each electromagnet is S pole.
It is determined to be the ultimate. Furthermore, as is clear from FIG. 1, the electromagnets 12, 12' and 13,
13' has its magnetic action axis in the rotational direction A of the rotating shaft 1 with respect to the pivot axis of the bearing pads 3b and 3c, respectively.
It is arranged so as to pass through the position on the lagging side, that is, on the leading edge 3L side of the bearing pad.

3 and 4 are schematic cross-sectional views of a second embodiment of the tailing pad type gas bearing structure according to the present invention, and are cross-sectional views and cross-sectional views corresponding to FIGS. 1 and 2, respectively. FIG. In these figures, the same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals as those shown in FIGS. 1 and 2. In this second embodiment, in addition to the configuration of the first embodiment described above, the bearing pad 3a located above the rotating shaft 1 also has the same structure as the electromagnets 12, 12' and 13, 13'. Electromagnets 15, 15' are provided. These electromagnets 15, 15', like the electromagnets described above, have their magnetic poles determined so as to generate a magnetic repulsive force against the permanent magnet fixed to the rotating shaft 1, and their magnetic action axes coincide with the axis of the bearing pad 3a. On the other hand, it is configured to pass through a position on the lagging side as viewed in the rotational direction A of the rotating shaft 1, that is, a position on the leading edge 3L side of the bearing pad.

According to the tailing pad type gas bearing structure constructed as described above, rotation can be started by appropriately selecting the number of windings of each electromagnet and the magnitude of the energizing current in relation to the weight of the rotating shaft. Even when the rotary shaft is rotating at a relatively low speed, such as when the rotary shaft is stopped or stopped, the rotary shaft can be made to float above the bearing pad against gravity by magnetic action. Frictional contact between the rotating shaft and the bearing pad, such as in hard-type bearings, can be avoided. In addition, by energizing the electromagnet before the rotating shaft starts rotating, it is possible to start rotating the rotating shaft while the rotating shaft is floating above the bearing pad, so the starting torque can be significantly reduced. can.

Furthermore, as mentioned above, since the magnetic action axis of each electromagnet is biased toward its leading edge with respect to the pivot axis of its respective bearing pad, each electromagnet is energized and is connected to the permanent magnet fixed to the rotating shaft. When magnetic repulsion is generated between each electromagnet, each electromagnet not only causes the rotating shaft to levitate above each bearing pad, but also moves each bearing pad around its axis in a clockwise direction as seen in Figure 1. It can be pivoted to force a wedge-shaped space between the rotating shaft and the bearing pad. Therefore, even under operating conditions such as when starting and stopping rotation, where a wedge-shaped space is difficult to form only due to the viscosity of the gas, it is possible to forcibly form a wedge-shaped space by magnetic action. Also, the frictional contact between the rotating shaft and the bearing pad can be reduced.

Furthermore, especially in the second embodiment, since electromagnets are provided for all bearing pads, the levitation of the rotating shaft as described above can be achieved by appropriately selecting the winding of each electromagnet and the energizing current. In addition to the forced pivoting of the bearing pad, it is possible to reduce vibrations of the rotating shaft in a direction perpendicular to its axis, and furthermore to avoid frictional contact between the rotating shaft and the bearing pad due to such vibrations.

Furthermore, when the rotating shaft is in a steady, high-speed rotation state, by de-energizing the electromagnet, it is possible to achieve substantially the same operating state as a conventional tailing pad type gas bearing. During high-speed rotation, the original function of the tailing pad type gas bearing can be effectively utilized.

Although the present invention has been described above in detail with reference to specific embodiments thereof, the present invention is not limited to these embodiments, and various modifications and omissions can be made within the scope of the present invention. This will be obvious to those skilled in the art. For example, the tailing pad type bearing structure according to the present invention is not limited to three bearing pads as in the two illustrated embodiments, but may be constructed with more bearing pads. Further, the rotating shaft is not limited to a hollow shaft, but may be a solid shaft with an annular groove provided on the outer periphery and into which divided arcuate permanent magnets are fitted.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views showing a first embodiment of a tailing pad type bearing structure according to the present invention, and are taken along the line in FIG. 2 and the line in FIG. 1, respectively. 3 and 4 are cross-sectional views of a second embodiment of the tailing pad type bearing structure according to the present invention, and correspond to FIGS. 1 and 2, respectively. FIG. 1 ~ rotating shaft, 2, 2' ~ permanent magnet, 3a, 3
b, 3c - bearing pad, 4a, 4b, 4c - pivot member, 5 - housing, 6 - nut, 7 - elastic member, 8 - press plate, 9 - bolt, 10, 11 - iron core, 12, 12', 13, 13', 15, 15'~
electromagnet.

Claims (1)

[Claims] 1 a rotational shaft, a housing, and a plurality of units circumferentially spaced around the rotational shaft and pivotally supported by the housing to define a wedge-shaped space between the rotational shaft and the rotational shaft; a first magnet incorporated in the rotating shaft; a second magnet supported by the housing and exerting a magnetic repulsion force on the first magnet; A tailing pad characterized in that the second magnet is fixedly attached to the bearing pad so that its axis of magnetic action passes through a position closer to the leading edge of the bearing pad than the pivot point of the bearing pad. type bearing structure.