Air foil bearing

1. An air foil bearing comprising:

a bearing housing having a cylindrical shape that forms an accommodation space in a middle thereof for a rotating shaft, rotor, or journal;

a first foil including a plurality of bump foils, which are arranged along an inner wall surface of the accommodation space of the bearing housing; and

a second foil including a plurality of top foils, which are arranged in a circumferential direction along an inner circumference of the bearing housing to correspond to the plurality of bump foils and to support the rotating shaft, rotor, or journal,

wherein a portion of at least one of the plurality of top foils of the second foil is thicker than the other top foils of the plurality of top foils,

wherein the plurality of top foils are configured as leaf springs and each top foil of the plurality of top foils includes:

a coupling body, which is coupled to a respective key slot that is provided on the inner circumference of the bearing housing;

a first region, which is placed on a top surface of at least one of the plurality of bump foils, connected to the coupling body of the top foil; and

a second region, which is elastically bent from an end of the first region of the top foil and is exposed to be in contact with the rotating shaft, rotor, or journal, the second region of the top foil overlapped by the first region of a respective neighboring top foil of the plurality of top foils,

wherein the plurality of top foils include at least three top foils and the plurality of bump foils include at least three bump foils,

wherein at least two top foils of the plurality of top foils are adjacent to each other in a rotational direction of the rotating shaft, rotor, or journal, and each of the at least two top foils include the portion that is thicker than the other top foils of the plurality of top foils, and

wherein, for each of the at least two top foils, a thickness of the second region thereof is greater than a thickness of the coupling body thereof.

2. The air foil bearing of claim 1 , wherein, for each of the at least two top foils, a thickness of the first region and the thickness of the second region thereof is greater than the thickness of the coupling body thereof.

3. The air foil bearing of claim 2 , wherein the thickness of the first region and the second region of each of the at least two top foils is greater than a thickness of each of the coupling body, the first region, and the second region of the other top foils.

4. The air foil bearing of claim 1 , wherein, for each of the at least two top foils, a thickness of the top foil continuously increases from the coupling body thereof to an end of the second region thereof, furthest away from the coupling body.

5. The air foil bearing of claim 4 , wherein the end of the second region of each of the at least two top foils is thicker than each of the coupling body, the first region, and the second region of the other top foils.

6. The air foil bearing of claim 1 , wherein, for each of the at least two top foils, the thickness of the second region thereof is greater than a thickness of the first region thereof and the thickness of the coupling body thereof.

7. The air foil bearing of claim 6 , wherein the thickness of the second region of each of the at least two top foils is greater than a thickness of each of the coupling body, the first region, and the second region of the other top foils.

8. The air foil bearing of claim 1 , wherein, for each of the at least two top foils, a thickness of the top foil continuously increases from an end of the second region thereof to an opposite end of the second region thereof.

9. The air foil bearing of claim 8 , wherein, for each of the at least two top foils, the thickness of the coupling body and the first region thereof is the same.

10. The air foil bearing of claim 1 , wherein the coupling body, the first region, and the second region of each of the at least two top foils is thicker than each of the coupling body, the first region, and the second region of the other top foils.

11. The air foil bearing of claim 1 , wherein at least one bump foil of the plurality of bump foils, corresponding to the at least one of the plurality of top foils of the second foil that is thicker than the other top foils, is thicker than other bump foils of the plurality of bump foils.

12. The air foil bearing of claim 1 , wherein the plurality of bump foils include a plurality of overlapping foils.

13. The air foil bearing of claim 1 , wherein an entirety of the other top foils of the plurality of top foils has a constant thickness.

14. A set of foils for an air foil bearing that includes a bearing housing having a cylindrical shape that forms an accommodation space in a middle thereof for a rotating shaft, rotor, or journal, and that further includes a first foil including a plurality of bump foils, which are arranged along an inner wall surface of the accommodation space of the bearing housing, the set of foils comprising:

a plurality of top foils, which are configured to be arranged in a circumferential direction along an inner circumference of the bearing housing to correspond to the plurality of bump foils and to support the rotating shaft, rotor, or journal,

wherein a portion of at least one of the plurality of top foils of the set of foils is thicker than the other top foils of the plurality of top foils, and each of the at least one of the plurality of top foils has a continuously varying thickness.

15. An air foil bearing comprising:

the set of foils of claim 14 ;

the bearing housing; and

the first foil.