Fluid machine having a foil bearing arrangement

1. A fluid machine, comprising:

a rotary shaft;

an operation body configured to discharge fluid by rotation of the rotary shaft;

a housing accommodating the rotary shaft and the operation body; and

a foil bearing disposed in the housing and rotatably supporting the rotary shaft, the foil bearing including:

a bearing housing having a cylindrical shape and including an inner peripheral surface, wherein the inner peripheral surface forms an inner peripheral circle of the bearing housing;

a top foil disposed between the inner peripheral surface of the bearing housing and the rotary shaft; and

a bump foil disposed between the inner peripheral surface of the bearing housing and the top foil and elastically supporting the top foil, wherein

the bearing housing has a protrusion that protrudes inwardly in a radial direction of the bearing housing from the inner peripheral surface of the bearing housing,

the protrusion includes an abutment surface configured to restrict deformation of the bump foil to an elastic range so as not to reach a plastic range by abutting against an outer surface of the top foil or an outer surface of the bump foil when the top foil is displaced outwardly in the radial direction of the bearing housing, and

the protrusion protrudes more inwardly in the radial direction of the bearing housing than the inner peripheral circle of the bearing housing.

2. The fluid machine according to claim 1 , wherein

the top foil has a non-overlapped portion that extends longer in an axial direction of the bearing housing than the bump foil and that is not overlapped with the bump foil in the radial direction of the bearing housing, and

the protrusion is disposed adjacent to the bump foil in the axial direction and between an outer surface of the non-overlapped portion and the inner peripheral surface of the bearing housing.

3. The fluid machine according to claim 1 , wherein

the protrusion is disposed at an opening of the bearing housing, and

a portion of the protrusion overlaps with a part of the top foil and a part of the bump foil in the axial direction of the bearing housing.

4. The fluid machine according to claim 1 , wherein

the bearing housing has a holding groove in the inner peripheral surface of the bearing housing,

the part of the top foil and the part of the bump foil are inserted into the holding groove, and

the fluid machine further includes a rotation stopper that is formed integrally with the protrusion and inserted into the holding groove to interpose the part of the top foil and the part of the bump foil cooperatively with a side surface of the holding groove.

5. The fluid machine according to claim 1 , wherein

the fluid machine includes an electric motor configured to rotate the rotary shaft, and

the protrusion protrudes from a portion of the inner peripheral surface of the bearing housing located on a side opposite to the electric motor.

6. The fluid machine according to claim 5 , wherein

the foil bearing includes a first foil bearing and a second foil bearing between which the electric motor is interposed in an axial direction of the rotary shaft, and

the protrusion of each of the first foil bearing and the second foil bearing protrudes from the portion of the inner peripheral surface of the bearing housing located on the side opposite to the electric motor.

7. The fluid machine according to claim 1 , wherein the bump foil has a cylindrical shape, the bump foil includes:

a bottom portion that is in contact with the inner peripheral surface of the bearing housing; and

a raised portion that is in contact with an outer peripheral surface of the top foil and is elastically deformable along with outward displacement of the top foil in the radial direction of the bearing housing, and

the protrusion is disposed in the inner peripheral surface of the bearing housing at a circumferential position corresponding to the raised portion.

8. The fluid machine according to claim 7 , wherein

the bump foil includes:

a fixed end portion that is one end portion of the bump foil in a circumferential direction of the bump foil; and

a free end portion that is the other end portion of the bump foil in the circumferential direction of the bump foil,

a plurality of the bottom portions and a plurality of the raised portions are alternately arranged in a circumferential direction of the bearing housing from the fixed end portion toward the free end portion of the bump foil, and

the protrusion is disposed at a position corresponding to the raised portion located on a side close to the free end portion of the bump foil in the inner peripheral surface of the bearing housing.

9. The fluid machine according to claim 1 , wherein

the protrusion has a ring shape, and

the protrusion extends over an entire circumference of the inner peripheral surface of the bearing housing.

10. The fluid machine according to claim 7 , wherein

the bottom portion is one of a plurality of bottom portions and the raised portion is one of a plurality of raised portions, each respective bottom portion being alternately arranged with each respective raised portion in a circumferential direction of the bearing housing,

the protrusion is one of a plurality of protrusions, each respective protrusion protruding from a respective portion of the inner peripheral surface of the bearing housing at spaced intervals in a circumferential direction of the bearing housing, and

a width of each protrusion in the circumferential direction of the bearing housing is greater than a width of each raised portion in the circumferential direction of the bearing housing.