Radial foil bearing

1. A radial foil bearing comprising:

a bearing housing that has an insertion hole into which a shaft is to be inserted;

a base sheet that is disposed in the insertion hole;

a back foil that is supported by the base sheet and has unevenness in a radial direction of the insertion hole; and

a top foil that is supported by the back foil,

wherein the back foil has a notch in an end edge in an axial direction in which the insertion hole extends,

wherein the base sheet has a first branch deviated in the radial direction of the insertion hole, and

wherein a first extension portion extending from the first branch is inserted into the notch.

2. The radial foil bearing according to claim 1 ,

wherein the first extension portion passes through the notch to an inner peripheral side of the back foil and extends to one side in a circumferential direction of the insertion hole.

3. The radial foil bearing according to claim 2 , wherein

the base sheet includes

a first base sheet that has the first branch, the first extension portion, and a notch in an end edge in the axial direction, and

a second base sheet that supports the first base sheet, has a second branch deviated in the radial direction of the insertion hole, and has a second extension portion extending from the second branch inserted into the notches of the first base sheet and the back foil, and

on the inner peripheral side of the back foil, the second extension portion extends to the other side in the circumferential direction of the insertion hole.

4. The radial foil bearing according to claim 3 , wherein

a through-groove extending in the axial direction from an end surface of the bearing housing is formed in the insertion hole, and

a through-groove extension portion extending from a through-groove branch of the second base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first and second branches are deviated in is inserted into the through-groove.

5. The radial foil bearing according to claim 4 , further comprising:

a housing groove that is provided in the end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the second base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first and second branches are deviated in is inserted into the housing groove.

6. The radial foil bearing according to claim 3 , further comprising:

a housing groove that is provided in an end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the second base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first and second branches are deviated in is inserted into the housing groove.

7. The radial foil bearing according to claim 2 , wherein

a through-groove extending in the axial direction from an end surface of the bearing housing is formed in the insertion hole, and

a through-groove extension portion extending from a through-groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the through-groove.

8. The radial foil bearing according to claim 7 , further comprising:

a housing groove that is provided in the end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the housing groove.

9. The radial foil bearing according to claim 2 , further comprising:

a housing groove that is provided in an end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the housing groove.

10. The radial foil bearing according to claim 1 , wherein

a through-groove extending in the axial direction from an end surface of the bearing housing is formed in the insertion hole, and

a through-groove extension portion extending from a through-groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the through-groove.

11. The radial foil bearing according to claim 10 , wherein

an end portion of the top foil is inserted into the through-groove, and

the base sheet has an engaging protrusion portion that extends into the through-groove and engages with the end portion of the top foil in the radial direction.

12. The radial foil bearing according to claim 11 , wherein

the top foil comprises two end portions,

a first end and a second end are inserted as the end portions of the top foil into the through-groove,

the top foil has a part extending from the first end to one side in a circumferential direction of the insertion hole and a part extending from the second end to the other side in the circumferential direction, which intersect each other in the axial direction, and

the engaging protrusion portion extends into the through-groove and engages with both of the intersecting ends of the top foil in the radial direction.

13. The radial foil bearing according to claim 11 , further comprising:

a housing groove that is provided in the end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the housing groove.

14. The radial foil bearing according to claim 10 , further comprising:

a lid body that is attached to the end surface of the bearing housing in the axial direction and covers the through-groove extension portion.

15. The radial foil bearing according to claim 10 , further comprising:

a housing groove that is provided in the end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the housing groove.

16. The radial foil bearing according to claim 1 , further comprising:

a housing groove that is provided in an end surface of the bearing housing in the axial direction and extends toward an outer side in the radial direction from an inner peripheral edge of the insertion hole,

wherein a housing groove extension portion extending from a housing groove branch of the base sheet deviated in the radial direction of the insertion hole that is opposed from the radial direction that the first branch is deviated in is inserted into the housing groove.