ROTARY DEVICE

1 . A rotary device comprising:

a sleeve having an inner cylindrical surface, a first end portion at an outer position in an axial direction of the inner cylindrical surface, and a second end portion that is an end portion opposite to the first end portion;

a shaft that has at least a part thereof accommodated in the inner cylindrical surface and that is rotatable relative to the inner cylindrical surface;

a fluid present at least in a space between the shaft and the sleeve;

a first pump portion formed in a middle portion in the axial direction of the inner cylindrical surface and configured to generate a first flow of the fluid in a direction toward the first end portion by the relative rotation of the shaft and the sleeve;

a first radial narrow gap formed at a region of the inner cylindrical surface on a side of the first end portion with respect to the first pump portion; and

a first circulation path connected to the first end portion of the sleeve and communicated with the first pump portion.

2 . The rotary device according to claim 1 , wherein a region of an outer cylindrical surface of the shaft and a region of the inner cylindrical surface forming the first radial narrow gap are smoothed.

3 . The rotary device according to claim 1 , wherein a first thrust narrow gap is formed at a region outside of the inner cylindrical surface in a radial direction of the first end portion.

4 . The rotary device according to claim 1 , wherein the first pump portion includes first pumping grooves arranged in stripes and formed in at least one of an outer cylindrical surface of the shaft and the inner cylindrical surface.

5 . The rotary device according to claim 3 , further comprising a first thrust member extending outward in a radial direction of the shaft and substantially fixed to the shaft, wherein

the first thrust narrow gap is formed in a region where the first thrust member and the first end portion are opposed to each other along the axial direction.

6 . The rotary device according to claim 5 , wherein a region of the first end portion and a region of the first thrust member forming the first thrust narrow gap are smoothed.

7 . The rotary device according to claim 1 , further comprising a housing accommodating at least a part of the sleeve.

8 . The rotary device according to claim 7 , wherein at least a part of the first circulation path is formed between the sleeve and the housing.

9 . The rotary device according to claim 1 , further comprising:

a second pump portion formed in a middle portion in the axial direction of the inner cylindrical surface and configured to generate a second flow of the fluid in a direction toward the second end portion by the relative rotation of the shaft and the sleeve;

a second radial narrow gap formed at a region of the inner cylindrical surface on a side of the second end portion with respect to the second pump portion; and

a second circulation path connected to the second end portion of the sleeve and communicated with the second pump portion.

10 . The rotary device according to claim 7 , further comprising:

a second pump portion formed in a middle portion in the axial direction of the inner cylindrical surface and configured to generate a second flow of the fluid in a direction toward the second end portion by the relative rotation of the shaft and the sleeve;

a second radial narrow gap formed at a region of the inner cylindrical surface on a side of the second end portion with respect to the second pump portion; and

a second circulation path connected to the second end portion of the sleeve and communicated with the second pump portion, wherein

at least a part of the second circulation path is formed between the sleeve and the housing.

11 . The rotary device according to claim 9 , wherein a region of an outer cylindrical surface of the shaft and a region of the inner cylindrical surface forming the second radial narrow gap are smoothed.

12 . The rotary device according to claim 9 , wherein a second thrust narrow gap is formed at a region outside of the inner cylindrical surface in a radial direction of the second end portion.

13 . The rotary device according to claim 9 , wherein the second pump portion includes second pumping grooves arranged in stripes and formed in at least one of an outer cylindrical surface of the shaft and the inner cylindrical surface.

14 . The rotary device according to claim 10 , further comprising a second thrust member extending outward in a radial direction of the shaft and substantially fixed to the shaft, wherein

the second thrust narrow gap is formed in a region where the second thrust member and the second end portion are opposed to each other along the axial direction.

15 . The rotary device according to claim 14 , wherein a region of the second end portion and a region of the second thrust member forming the second thrust narrow gap are smoothed.

16 . The rotary device according to claim 14 , wherein a thrust accommodating region is formed between a bottom portion of the housing and the second end portion, and the second thrust member is arranged in the thrust accommodating region.

17 . The rotary device according to claim 9 , wherein a part of the first circulation path is connected to a part of the second circulation path.

18 . The rotary device according to claim 9 , wherein the fluid is a liquid, and

the rotary device further comprises a capillary seal portion connected to at least one of the first circulation path and the second circulation path and having an air-liquid interface between the fluid and air at a middle portion thereof.

19 . The rotary device according to claim 18 , wherein the capillary seal portion surrounds the sleeve and is formed at a position overlapping with the sleeve in the axial direction.

20 . The rotary device according to claim 1 , wherein the shaft and the sleeve are formed of materials having substantially equal coefficients of linear expansion.