KR20080088293A - A wear prevention device of gas foil bearing in high-speed revolution axis system - Google Patents

Abstract

A wear prevention device for a gas foil bearing in a high-speed revolution axis system is provided to prevent abrasion of foils such as a top foil and a bumper foil by widening plural blade parts circumferentially using the centrifugal force of a collet. A wear prevention device for a gas foil bearing in a high-speed revolution axis system comprises a rotating shaft(20) having plural blade parts(41) formed at its one end, a collet(40), a sleeve(50), and a bearing housing(31). The collet widens plural blade parts circumferentially by the centrifugal force resulting from high speed rotation. The sleeve limits the displacement of the collet. The bearing housing includes an outer wheel(71) of a rolling bearing, and an inner wheel(72) including a bushing(60). The rolling bearing supports the rotating shaft by mounting the collet on the bushing in a stop of rotation or low speed rotation.

Description

A wear prevention device of gas foil bearing in high-speed revolution axis system

1A is a cross-sectional view showing a state in which a rotating shaft is stopped in a high speed rotating shaft system supported by a gas foil bearing according to the present invention.

1B is a cross-sectional view showing a state in which a rotating shaft rotates at a high speed in a high speed rotating shaft system supported by a gas foil bearing according to the present invention.

Figure 2 is an exploded perspective view showing an example of the wear protection device provided in the high speed rotary shaft system supported by the gas foil bearing according to the present invention,

Figure 3a shows a state in which the rotating shaft is stopped in the longitudinal cross-sectional view of a state in which the conventional foil bearing is cut in the vertical direction of the rotating shaft,

3B illustrates a state in which a rotating shaft is lifted by the foil bearing during high speed rotation so that the center of the foil bearing is aligned with the center of the rotating shaft.

<Explanation of symbols for main parts of the drawings>

10: wear protection system 20: rotating shaft

30: foil bearing 31: bearing housing

40: collet 41: wing

42: groove 50: sleeve

60: bushing 70: rolling bearing

71: outer ring 72: inner ring

The present invention relates to a gas foil bearing wear prevention system in a high speed rotating shaft system, in which a bearing supporting a rotating shaft at high speed and low speed is mounted by mounting a collet formed with a wing portion that is formed according to a centrifugal force in a rotating shaft system having a foil bearing. Therefore, the present invention relates to a wear protection system for a gas foil bearing, which prevents a problem that the rotation shaft interferes with the top foil and causes plastic deformation even in the shape of the bump foil by reducing the load bearing capacity of the foil bearing at start or stop.

In the 1970s, it was applied to cooling air turbines for passenger cabin air conditioning, and has been expanded to rocket engine turbo pumps, cryogenic coolers, small gas turbines, turbochargers, heat pumps, and turbo compressors. Bearings widely used in high-speed rotary shaft systems are oil film bearings (eg, tilting pad bearings). These bearings have a high degree of reliability and many advantages, but they require hydraulic fluid, so supply, cooling, circulation and sealing are required. In addition, in the case of a high speed turbocompressor, a small amount of bearing hydraulic oil is discharged together with the compressor body, which is not suitable for applications requiring cleanliness. The gas foil bearing proposed as an alternative to this can solve the disadvantages of the oil film bearings, but it is still less reliable and shorter in life than oil film bearings. There is a lack of stiffness and damping ability.

In recent years, as a result of much research and development, the reliability, lifespan, load bearing capacity, rigidity and damping capacity of gas foil bearings are being improved day by day. In terms of reliability and lifespan, foil bearings have a fundamental problem of friction between the rotating shaft and the top foil due to a decrease in load bearing capacity at start and stop.

The top foil 120 of the conventional foil bearing 100 has one end fixed to the bearing housing 110 and the other end freely left to surround the shaft. In the state in which the rotating shaft 200 is stopped, as shown in FIG. 3A, the lower top foil and the bump foil 130 are pressed by the own weight of the rotating shaft. When the rotation starts in this state and reaches a predetermined rotation speed having a load supporting ability capable of floating the rotating shaft, as shown in FIG. 3B, the centers of the rotating shaft 200 and the foil bearing 100 are aligned and rotated. As described above, when the rotation shaft is stopped and the rotation shaft is suspended and the rotation shaft is decelerated and stopped while the rotation shaft is stopped, the rotation shaft 200 and the top foil 120 come into contact with each other due to insufficient load bearing ability of the foil bearing. Occurs. This friction further causes wear on the contact surfaces of the rotating shaft and the top foil, and the generated heat causes plastic deformation or breakage of the top foil and bump foil to degrade or dissipate the inherent performance of the foil bearing.

In order to alleviate this problem, temporary alternatives such as coating and heat treatment techniques are applied to increase the lubricity and wear resistance of the top foil and the rotating shaft, but fundamental structural problems are still inherent.

The present invention was invented to solve the above problems,

By using a centrifugal force that increases in proportion to the rotational speed, the collet having a radially widening wing portion is coupled to the rotational shaft, and the bushing mounted on the inner ring of the rolling bearing is located inside the collet. Rotation of the additional bushings to allow the rolling bearings to support the rotary shafts, and at high speeds, the wing of the collet is opened by the centrifugal force to short-circuit the bushings and to support the foil bearings. It is for the purpose of providing.

In order to achieve the above object, a wear protection system in a high speed rotation shaft system according to the present invention,

In the wear prevention system of the rotary shaft system supported by the foil bearing, a plurality of wings are formed at one end of the rotary shaft to collet the wings are circumferentially spread by the centrifugal force during high-speed rotation, and the sleeve to limit the displacement of the collet Is installed, the outer ring of the rolling bearing is inserted in the bearing housing of the foil bearing, the inner ring of the rolling bearing is provided with a bushing is installed on the inner ring of the rolling bearing when the collet is seated on the bushing and the rolling bearing combined with the bushing rotation shaft To support it.

In addition, the collet, the sleeve, and the bushing is made of a material of high strength and the surface facing each other so that the lubricant is supplied, the collet, the sleeve and the bushing is preferably made of a porous material impregnated with lubricating oil.

In addition, the collet is characterized in that the groove is formed along the outer periphery so as to thin the thickness of the start of the wing portion to be easily opened to the outside by centrifugal force.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily understand and reproduce the present invention.

Figure 1a is a cross-sectional view showing a state in which the rotating shaft of the high speed rotary shaft system with a foil bearing wear protection device in accordance with the present invention is stopped or at start-up, Figure 1b is a cross-sectional view showing a state of rotating at high speed. FIG. 2 is an exploded perspective view showing a rolling bearing, a collet-sleeve, a displacement limiting sleeve, and a bushing, which are components of a foil bearing wear protection device, together with a rotating shaft.

As shown, the gas foil bearing wear protection system 10 of the high speed rotary shaft system according to the present invention is located at the center of the foil bearing.

The outer ring 71 of the rolling bearing 70 is firmly inserted in the housing 31 of the foil bearing so that slip does not occur, and the bushing 60 is shrinkable and restrained in the inner ring 72 of the rolling control ring. Fitting, or in addition to assembling so that the slip does not occur in various ways so that the wing 41 of the collet 40 to be described later is seated. The rolling bearing 70 is installed to maintain the concentricity with the foil bearing 30 to prevent abrasion of the foil bearing, and serves to temporarily support the rotating shaft during low speed rotation of the rotating shaft (usually 5,000 rpm or less). To support the rotating shaft at low speed or stop to decrease the bearing capacity of.

On the other hand, the collet 40 is assembled to the rotating shaft 20, and the sleeve 50 to limit the displacement of the collet is also assembled to secure it so as not to move by a nut or other methods. The collet 40 has a groove portion 42 formed on the outer circumference thereof, and a plurality of cutting grooves are formed along one circumference of the collet 40 in one direction based on the groove portion. To be formed.

The wing portion 41 of the collet is to be opened to the outside by the centrifugal force as the rotational speed of the rotating shaft 20 increases, the groove portion 42 formed on the outer periphery of the collet is a wing portion in contact with the body of the collet ( 41) The thickness of the part is made thin so that the wing part 41 can be bent to the outside by centrifugal force. In addition, the inner surface of the wing portion 41 is formed in the inclined surface having a gradually smaller diameter in the direction of the body of the collet at the end so that it can be easily bent by centrifugal force.

The collet 40 according to the present invention increases the centrifugal force acting on the wing portion 41 of the collet as the rotational speed of the rotating shaft 20 increases, so that the wing portion 41 opens in the circumferential direction, and the speed of the rotating shaft If is less than a certain speed to be engaged with the bushing (60).

That is, in the stationary state and at the start-up and low-speed rotation at the time of stop, as shown in FIG. 1A, the wing portion 41 of the collet is engaged with the bushing 60 assembled to the inner ring 72 of the rolling bearing 70, thereby rolling the rolling bearing ( 70 supports the rotation shaft 20. In addition, when the rotational speed is increased and the wing portion 41 of the collet is opened by centrifugal force, as shown in FIG. 1B, the support of the rotating shaft 20 by the rolling bearing 70 is short-circuited and the load bearing capacity is ensured. The rotating shaft 20 is supported by this. On the contrary, even in the situation where the rotating shaft 20 is stopped at the high speed, the rotating shaft supporting system is switched and operated.

The design of the displacement of the wings 41 of the collet 40 in the circumferential direction by the centrifugal force primarily requires the rotational speed at which the load bearing capacity of the foil bearing is fully developed through the design, analysis, and experiment of the foil bearing. do. In addition, the displacement of the collet 40 may be determined through structural analysis of the shape, the material used, and the rotational speed as variables. Displacement limit sleeve 50, which is assembled to the rotating shaft together with the collet, is used for the purpose of preventing plastic deformation due to concentration of fatigue by limiting the unevenness of the collet wings 41 in the circumferential direction due to excessive centrifugal force. .

In addition, the material of the collet 40 and the bushing 60 is preferably a combination of dissimilar materials that are not compatible with each other, one of which uses a hard metal or hard coating, heat-treated metal, the other is self It is preferable to use a lubricating material or a sintered metal impregnated with the lubricating material, and it is preferable to use a porous material to increase the impregnation degree of the lubricating material.

That is, the foil bearing wear prevention system 10 according to the present invention is a collet 40 mounted on the rotating shaft 20 even in a stopped state, when starting and stopping when the foil bearing is not sufficiently exerted in the load supporting ability. And the rolling bearing supports the rotating shaft by the coupling force of the bushing 60 mounted on the rolling bearing 70, and during the high-speed rotation of the rotating shaft, the wing portion 41 of the collet is opened by centrifugal force and shorted with the bushing 60. The rotating shaft 20 is supported by the top foil and the bump foil of the foil bearing, so that the rotating shaft is biased to one side at the time of stopping, starting, and stopping when the bearing capacity of the foil bearing decreases, thereby intensively frictioning the top foil of the foil bearing. This is to avoid the occurrence.

As described in detail above, the foil bearing wear prevention system in the high speed rotary shaft system of the present invention,

Using a centrifugal force that increases in proportion to the rotational speed, the collet formed with a radially flared wing is coupled to the rotational shaft, and the bushing mounted on the inner ring of the rolling bearing is located inside the collet. Top bearing and bumper due to excessive contact due to the bias of rotation shaft by rotating the additional bushing so that the rolling bearing supports the rotating shaft. Foil wear and plastic deformation can be prevented and a useful system can be provided to permanently extend the life of the foil bearing.

In addition, the above-mentioned example is only an example to demonstrate this invention. Therefore, it is a matter of course that those skilled in the art to which the present invention pertains use the partial change with reference to this detailed description fall within the scope of the present invention.

Claims (4)

In the wear protection system of the rotating shaft system supported by the foil bearing (30), The rotating shaft 20 is provided with a collet 40 having a plurality of wings formed at one end thereof, the wings 41 being opened in the circumferential direction by centrifugal force during high-speed rotation, and a sleeve 50 for limiting the displacement of the collets. , The outer ring 71 of the rolling bearing 70 is inserted in the bearing housing 31 of the foil bearing, and the bushing 60 is installed in the inner ring 72 of the rolling bearing so that the collet 40 is stopped and rotated at low speed. Foil bearing wear prevention system in a high speed rotary shaft system, characterized in that seated on the bushing (60) to enable the rolling bearing coupled bushing to support the rotating shaft (20). The method of claim 1, The collet (40), the sleeve (50), the bushing (60) is made of a material of high strength and the foil bearing wear prevention system in the high-speed rotary shaft system, characterized in that the lubricant supplied to the surface facing each other. The method of claim 2, The collet (40), sleeve (50) and the bushing (60) is a foil bearing wear protection system in a high speed rotary shaft system, characterized in that made of a porous material impregnated with lubricating oil. The method of claim 1, The collet 40 is formed in the groove 42 along the outer periphery to thin the thickness of the start of the wing portion 41 to prevent the flare bearing wear in the high-speed rotary shaft system, characterized in that it is easily opened to the outside by centrifugal force system.

Images