KR101968658B1 - Bi-directional foil bearing - Google Patents

Abstract

Bi-directional foil bearings with excellent damping performance and high stability are introduced. The rotor is supported by a sleeve provided with a top plate. The top foil includes a column extending in the thickness direction from one end of the inner circumferential surface of the sleeve; A route extending on both sides in the circumferential direction from one end of the column; And a leaf extending in the circumferential direction from the other end of the column so as to elastically support the rotor.

Description

Bidirectional foil bearings {BI-DIRECTIONAL FOIL BEARING}

The present invention relates to a foil bearing, also referred to as an air bearing, and more particularly to a foil bearing capable of supporting a bi-directionally rotating rotor.

Foil bearing is a hydrodynamic gas bearing which uses gas as a lubricant. It forms a gas film between a rotor and a bearing rotating around the gas, so that the rotor is floated. Used in high-speed rotating machines.

The first foil bearings were used in the 1970's aircraft air conditioning cooling turbines and air circulation systems and gradually improved the load bearing capacity of the foil bearings. As a result, turbo pumps, motor blowers, heat pumps, turbo compressors, micro gas turbines, turbochargers And so on.

The foil bearings can significantly improve load bearing capability or damping, and the rigidity is also easily adjustable, thereby greatly improving dynamic stability. It is also easy to use because it is adaptable to mechanical deformation such as thermal deformation, misalignment, and mechanical machining error.

The foil bearings can not avoid solid friction in the low speed region, friction between the rotor and the bearing. Therefore, in order to reduce the coefficient of friction between the rotor and the bearing at low speed, and to improve the reliability and durability of the bearing, the bearing surface may be coated with a solid friction material such as MoS ₂ .

An example of a conventional journal foil bearing is shown in Fig.

1, the foil bearing is disposed in a gap between the rotating rotor 1 and the housing 2 and includes a top foil 3 directly supporting the rotor 1 and a bump foil 4 having substantial damping performance . Although the arcuate bump foil 4 is shown in Fig. 1, it may be of a cantilever type or the like.

One end of the top foil 3 is fixed to the inner circumferential surface of the housing 2, and the other end is a free end. Such a foil bearing can support only a rotor rotating in one direction. When the rotor 1 shown in Fig. 1 rotates counterclockwise and then rotates clockwise, the top plate 3 is curled by the rotor 1 from the free end side, and the load supporting ability of the foil bearing is lost.

When the turbo blower is stopped while supplying air by increasing the pressure, the blower may slightly rotate reversely due to the residual or leaking pressurized air. Even a few millimeters of movement will cause a large friction between the heavy rotor and the top of the gun, and if this occurs repeatedly, the coating on the top gun will peel off and, in severe cases, the top gun work can be permanently deformed or fatigued.

The problem of the rotational direction of the foil bearing as described above can be solved by fixing both ends of the top foil to the housing and eliminating the free ends. For example, the free end of the top foil may be inserted into a groove provided in the housing or fixed using a fixing member separately provided in the housing. However, such a foil bearing needs to be improved in terms of stable support of the rotor and damping performance.

SUMMARY OF THE INVENTION The present invention is based on the recognition of the prior art as described above, and aims to provide a bi-directional foil bearing capable of stably supporting the rotor regardless of the rotational direction.

The present invention also provides a foil bearing excellent in damping performance.

The present invention also provides a foil bearing capable of adjusting the stiffness and damping performance of a bearing supporting the rotor according to requirements.

Further, the present invention aims to provide a foil bearing with less whirring of the rotor and excellent high-speed stability.

The present invention also provides a foil bearing which is easy to repair and replace.

Also, the present invention provides a foil bearing with less fear of assembly tolerance or misalignment that can occur during manufacture.

The problems to be solved by the present invention are not necessarily limited to those described above, and other tasks not mentioned in the present invention may be understood by the following.

In order to accomplish the above object, a bi-directional foil bearing according to the present invention is configured such that a rotor is rotatably supported in a hollow sleeve provided with a top foil. The top foil includes a column extending in the thickness direction from one end of the inner circumferential surface of the sleeve; A route extending on both sides in the circumferential direction from one end of the column; And a leaf extending in the circumferential direction from the other end of the column so as to elastically support the rotor.

A slit may be provided between the main topsheet and the sleeve so that each of the leaf, the column and the root may be elastically deformed. The main topsheet may be provided with two or more gaps in the circumferential direction of the sleeve. A bump foil may be provided on the back surface of the leaf to elastically support the leaf. The bump foil is a kind of spring, and its shape can vary.

According to the present invention, the sleeve may further comprise at least one sub topfoil so that at least two leaves may be spaced apart in the radial direction. The sub top foil is provided on both sides in the circumferential direction on the basis of the column of the main top foil, and can extend parallel to the main top foil spaced apart from each other.

The leaves, the columns and the roots of the main topoil and the sub topoil may all be elastically deformed, and the bump foil may be interposed between the leaves, between the inner circumferential surface of the sleeve and the opposite leaf.

According to the present invention, the bi-directional foil bearing may further include a housing surrounding the sleeve, and the sleeve may be detachable from the housing. The bump foil can be assembled into a sleeve having a top foil and formed into a single module, and the module can be mounted on and detached from the housing, thereby facilitating replacement maintenance.

According to the present invention, a bump foil may be interposed between the sleeve and the housing. This bump foil adds additional stiffness and damping to the foil bearing.

According to the bi-directional foil bearing of the present invention as described above, the leaf, which has elasticity to the column and the root as well as the leaf, and the leaf directly supporting the rotor are formed on both sides in the circumferential direction from the column, Lt; / RTI >

Further, according to the bi-directional foil bearing according to the present invention, the rotor rotating in the gap between the main top foils disposed adjacent to each other in the circumferential direction of the sleeve can be stably positioned, so that occurrence of whirling is reduced and stable rotor support at high speed is possible.

Further, the bi-directional foil bearing according to the present invention can arrange the leaf supporting the rotor in several layers in the radial direction, and can also elastically deform the column or the root, so that the damping performance is excellent.

Further, the bi-directional foil bearing according to the present invention may have a different shape or stiffness of the bump foil according to the layer in the radial direction, or the bump foil of the specific layer may have different shape, stiffness and the like from those of other layers. The stability and damping performance of the bearing supporting the rotor can be precisely controlled and improved by suitably combining the stiffness coefficients of the bump foil according to use or requirements.

Further, the bi-directional foil bearing according to the present invention can modularize the sleeve, so that it is easy to replace and repair the foil bearing.

The top foil of the bi-directional foil bearing according to the present invention can also be manufactured by wire-cutting electric discharge machining. Wire cutting electric discharge machining is a machining method in which a spark generated by a discharge between a running electrode and a workpiece is used as a saw blade to cut a workpiece. Wire cutting discharge machining can be finely performed using computer numerical control (CNC), so there is less concern about assembly tolerances and misalignment that can occur in the process of manually varying the skill of the operator or mechanically fixing the parts.

1 is a schematic view of a conventional foil bearing,
2 is a schematic view of a foil bearing according to an embodiment of the present invention,
FIG. 3 is a schematic view showing a bump foil assembled to the foil bearing of FIG. 2;
Figure 4 is a partial enlarged view of the foil bearing of Figure 3,
5 is a schematic axial cross-sectional view of a foil bearing according to an embodiment of the invention,
6 is a schematic view of a foil bearing according to another embodiment of the present invention,
7 is a schematic view of a foil bearing according to another embodiment of the present invention,
8 is a schematic view of a foil bearing according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same or equivalent elements or parts may be represented by the same reference numerals as much as possible for convenience of description, and the drawings are exaggerated and schematically shown in the drawings for the sake of clarity and explanation of the features of the present invention. .

In the description of the present invention, unless the second element is disposed on the first element or the two elements are connected to each other, the two elements are in direct contact with each other, But need to be understood to mean that a third element is interposed between the elements of the two elements. It is also to be understood that the directional expressions such as forward, backward, leftward and rightward, and up and down are for explanation convenience.

Fig. 2 is a schematic view of a foil bearing according to one embodiment, showing a cross section in the direction perpendicular to the axial direction.

Referring to FIG. 2, the foil bearing is configured to rotatably support the rotor 10 within the hollow sleeve 20. As shown in FIG. On the inner circumferential surface of the sleeve 20, a top foil 31, 32, 33: 30 for elastically supporting the rotor 10 is formed. The sleeve 20 extends along the axial direction of the rotor 10 and may be a bearing housing itself or may be a separate module from the bearing housing.

The top foil 30 has a column 30b extending in the thickness direction from one end inside the inner circumference of the sleeve, a root 30c provided at one end of the column 30b and a leaf 30a provided at the other end of the column 30b Respectively. The top foil 30, that is, the leaf 30a, the column 30b, and the root have the form of a foil spreading in the circumferential direction and the axial direction of the rotor 10, and the shape may vary.

The leaf 30a extends from the other end of the column 30b in the circumferential direction so as to be spaced apart from the inner circumferential surface of the sleeve 20 so as to support the rotor 10. The root 30c extends in the circumferential direction from one end of the column 30b. The column 30b can be elastically deformed against the load of the rotor 10 transferred from the leaf 30a and the root 30c elastically supports the column 30b.

The topsheet 30 may be arranged in two or more parallel to each other with gaps or slits S1, S2, S3: S interposed therebetween. Each top sheet 30 has a leaf 30a, a column 30b and a root 30c and is elastically deformable.

According to an embodiment, the topfoil 30 may comprise a main topfoil 31 and a sub topfoil 32,33. The main topfoil 31 has a leaf arranged to support the rotor 10 in direct contact with the rotor 10 and the sub topfoils 32 and 33 are connected to the leaves of the main topfoil 31, (20). According to this embodiment, two or more leaves 30a are arranged in the radial direction.

The leaf 30a of the main topfoil 30 extends in the circumferential direction from the other end of the column 30b so as to elastically support the rotor 10 regardless of the rotating direction of the rotor 10. [ Referring to FIG. 2, the leaf 30a of the main top plate 30 extends clockwise and counterclockwise from the other end of the column 30b, respectively.

The root 30c of the main top foil 30 extends on both sides in the circumferential direction from one end of the column 30b. Referring to FIG. 2, the root 30c of the main topfoil 30 extends clockwise and counterclockwise, respectively. The root 30c may have a symmetrical form with the leaf 30a. The root 30c is for elastically supporting the column 30b, and the circumferential length need not necessarily be the same as the leaf 30a, but may be smaller than the leaf 30a.

The leaves 30a and the root 30c of the main topfoil 30 do not have to be symmetrical to each other with respect to the column 30b. The left and right leaves 30a may have different loads from each other with respect to the column 30b. In this case, the left and right leaves 30a may have different lengths and thicknesses It can be formed asymmetrically.

The sub top spreaders 32 and 33 may include a first sub top spreader 32 and a second sub top spreader 33. The first and second sub top spreaders 32 and 33 may be disposed in the circumferential direction Respectively.

Referring to FIG. 2, the first sub-topsheet 32 disposed on the left side in the circumferential direction is disposed in parallel with the main topsheet 31 by the slits S1 formed continuously. The leaf 30a of the first sub-top foil 32 extends circumferentially to the left from the other end of the column 30b and likewise the root 30c extends circumferentially to the left from one end of the column 30b. The first sub-top foil 32 is also provided symmetrically in the circumferential direction.

The second sub topsheet 33 disposed on the left side in the circumferential direction is disposed in parallel with the first sub topsheet 32 with the slit S2 formed therebetween in between. The leaf 30a of the second sub-top 33 extends circumferentially to the left from the other end of the column 30b and likewise the root 30c extends circumferentially to the left from one end of the column 30b. A second sub-top 33 is also provided symmetrically to the right in the circumferential direction.

A continuous slit S3 is also provided between the second sub topsheet 33 and the sleeve 20. This slit S3 enables the second sub top 33 to elastically support the load transmitted from the rotor 10. [ A rear slit Sx is provided along the route 30c so that the root 30c can elastically support the column 30b between the root 30c of the main top plate 31 and the sleeve 20. [

The set of the topoil 30, i.e., the main topoil 31 and the sub-topoil 32, 33 arranged in the radial direction are provided in two or more with a gap G between them in the circumferential direction of the sleeve 20 . The free ends of the leaves 30a can be spaced apart from each other with the gap G interposed therebetween. A bump foil (not shown) for resiliently supporting the leaf above the leaves 30a is interposed.

3 shows that the bump foils 41, 42, and 43 are disposed on the back surface of the leaf 30a of the topfoil 30 described above.

The bump foil 40 is inserted between the leaves S1 and S2 and between the leaves of the second sub top spreader 33 and the inner circumferential surface S3 of the sleeve 20 as shown in FIG. The bump foil 40 may be inserted axially at one end in the longitudinal direction of the sleeve 20.

3, the bump foils 30 are arranged in three layers in the radial direction. The bump foil 30 of at least one of these three layers may differ in shape or thickness, i.e., stiffness coefficient, from the bump foils 30 of the other layers. The bump foils 41 and 42 disposed between the leaves 30a and the bump foil 43 disposed on the rear surface of the leaf 30a of the second sub top 33 may have a shape Or the thickness may be different. By adjusting the stiffness coefficient of the bump foils 30, the support performance of the rotor 10 can be improved, and optimum damping performance can be ensured according to the conditions of use of the foil bearing.

4, the load applied to the leaves 30a by the rotor 10 is elastically supported by the bump foils 41, 42 and 43 for supporting the leaves 30a, (32) to the routes (33). The columns 32 elastically supported by the roots 33 can be deformed or tilted with respect to the load, so that the damping performance against the rotor 10 is excellent.

A gap G is provided between the top foils 30 adjacent to each other in the circumferential direction. This gap G enables the rotor 10 to rotate stably without generating whirling. It is preferable in terms of stability that the rotor 10 in the sleeve 20 does not move in a direction perpendicular to the axis but rotates to a constant position. The concave gap G provided between the top foil pieces 30 allows the rotor 10 to stably stay in the position.

The load applied to the leaves 30a by the rotor 10 at the position of the gap G is the deformation of the leaves 30a due to the load and the bump foils 41, 42 and 43, respectively. The gap (G) portion between the adjacent leaves 30a provides a concave space where the rotating rotor 10 can stably remain.

The end portions of the leaves 30a adjacent to each other with the gap G interposed therebetween are easily resiliently restored immediately after being struck and there is no problem of permanent deformation or fatigue failure even if the rotor 10 rotating at this position is repeatedly placed . Since the ends of the leaves 30a are elastically concave by the rotor 10 by the rotor 10, the leaf 30a is damaged by the rotor 10 even if the rotor 10 rotates in any direction Or problems such as drying are not caused.

It is sufficient that the bump foils 40 are simply inserted into the slits S1, S2, S3. The bump foil 40 can move in the circumferential direction by the rotating rotor 10 but the degree of the bump foil 40 is small and the gap G is small so that the damping performance of the foil bearing does not occur . As another example, it is possible to bend one end portion in the circumferential direction of the bump foil 40 and fix the bending portion by inserting the slit S in parallel with the column 30a, but the elastic deformation of the column 30b by the bending portion Lt; / RTI >

5 is a sectional view schematically showing an axial section of the foil bearing according to the embodiment.

5, the bump foil 40 may be inserted axially at one end in the longitudinal direction of the sleeve 20 and may be inserted into both ends of the sleeve 20 in the longitudinal direction of the sleeve 20 to prevent axial disengagement of the bump foil 40. [ A stopper 50 is provided.

FIG. 6 shows a bi-directional foil bearing according to another embodiment. This foil bearing can be configured so that two leaves 30a in the radial direction are spaced apart. The top foil 30 'is spaced circumferentially of the sleeve 20 with a gap G, and the components according to the embodiment described above can be applied to this embodiment as well.

7 shows a bi-directional foil bearing according to yet another embodiment. This foil bearing can be configured so that one leaf 30a in the radial direction supports the rotor 10. The top foil 30 " is spaced apart circumferentially of the sleeve 20 with a gap G, and the components according to the previously described embodiment are applicable to this embodiment as well.
Referring to FIG. 7, bump foils 40 are provided at both ends with bending portions 40a and 40b directed toward the center of the sleeve, and bump foils 40 Are arranged so that the bent portions 40a and 40b face each other and the bent portions 40a and 40b can be disposed between the adjacent top foils 30 ".

Referring to FIG. 8, the sleeve 20 may be a module assembled to the bearing housing 60. Between the rotor 10 and the sleeve 20 the top foil 30 and the bump foil 40 of the previously described embodiments are disposed and the bump foil is inserted between the sleeve 20 and the housing 60, And elasticity.

On the other hand, between the columns 30b in which the bump foil 40 is not interposed, between the passages 33c, and between the bumps 30b and 30c and the sleeve 20, an elastic body for adjusting rigidity or damping performance is interposed . As an example, a resin such as an elastic resin having viscoelasticity, such as urethane, may be interposed in these gaps. A viscoelastic resin coating can be applied to the gaps by wetting a foil bearing with a liquid urethane resin and drawing air with vacuum pressure.

While the invention has been shown and described with respect to the specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention as set forth in the following claims.

1, 10: rotor 2, 60: housing
20: Sleeve 3,30: Topo
30a: Leaf 30b: Column
30c: root 4, 40: bump foil

Claims (5)

A rotor is rotatably supported within a hollow sleeve, the sleeve having a topfoil formed by machining a sleeve,
The topfoil includes a main topfoil directly supporting the rotor; And a sub topfoil arranged between the main topfoil and the inner circumferential surface of the sleeve so as to be spaced apart from the main topfoil,
The main top foil and sub top foil,
A column extending in the thickness direction from one end of the inner circumferential surface of the sleeve;
A root extending circumferentially from one end of the column and having its tip integrally connected to the sleeve; And
And a leaf extending in a circumferential direction from the other end of the column so as to support the rotor, the leaf having a free end,
The root and leaf of the main topfoil extend in both circumferential directions from the column,
The sub topsheet is provided with at least one each on either side in the circumferential direction with respect to the column of the main topsheet so that two or more leaves can be spaced apart in the radial direction and the root and leaves of the sub topsheet extend in one circumferential direction from the column ,
The top foil is provided at least two in the circumferential direction with a gap therebetween,
A continuous slit is provided between the main top plate, the sub top plate and the sleeve so that each of the leaf, the column and the root can be elastically deformed,
And a bump foil is interposed on the back face of the leaf so as to elastically support the leaf. The bumper foil of claim 1, wherein the bump foils are provided with bends at both ends toward the center of the sleeve, the bump foils disposed in the top foils adjacent to each other in the circumferential direction are arranged such that the bending portions face each other, Lt; RTI ID = 0.0 > 1, < / RTI > The bi-directional foil bearing as claimed in claim 1, wherein a viscoelastic resin is coated between the columns and between the roots for adjusting the damping performance. The apparatus of any one of claims 1 to 3, further comprising a housing surrounding the sleeve,
Wherein the sleeve is detachable from the housing. 5. The bi-directional foil bearing of claim 4, further comprising a bump foil interposed between the sleeve and the housing.

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