Centrifugal fan

1 . A centrifugal fan comprising:

a first portion provided in a rotor that rotates integrally with a shaft; and

a second portion provided in a fan unit having a plurality of blades and fixed to the rotor and having a greater linear coefficient of expansion than that of the first portion, wherein

the first portion includes

a first top portion extending from a first hole through which the shaft is inserted toward a radially outside of the shaft and having a first flat surface facing a first axial direction in an axial direction of the shaft, and

a first tubular portion having a tubular shape and extending from a radially outside end portion of the first top portion in a second axial direction opposite to the first axial direction,

the second portion includes

a second top portion located in the first axial direction with respect to the first top portion, extending to the radially outside from a second hole through which the shaft is inserted, and having a second flat surface facing the first flat surface,

and

a second tubular portion having a tubular shape, extending in the second axial direction from a radially outside end portion of the second top portion, and having an inner tube surface facing an outer tube surface of the first tubular portion with a first clearance therebetween,

the second top portion is provided with a protrusion protruding from the second flat surface in the second axial direction beyond the second flat surface and abutting on the first flat surface,

the second top portion has a main portion extending to the radially outside and a second axial direction side from the second hole,

the second top portion further includes a rib portion protruding from the main portion in the second axial direction to reinforce the main portion, an end surface of the rib portion on the second axial direction side forming the second flat surface,

the rib portion includes a circular ring-shaped rib portion protruding from the main portion in the second axial direction and having a circular ring shape as viewed from the second axial direction side, and an auxiliary rib portion protruding from the main portion in the second axial direction and extending to the radially outside from the circular ring-shaped rib portion,

the protrusion protrudes from an end surface of the auxiliary rib portion on the second axial direction side,

and

the first flat surface and the second flat surface are bonded and fixed to each other with an adhesive provided in a second clearance formed by the protrusion.

2 . The centrifugal fan according to claim 1 , wherein a protruding amount of the protrusion from the second flat surface is set to an optimum film thickness of the adhesive.

3 . The centrifugal fan according to claim 1 , wherein the circular ring-shaped rib portion and the auxiliary rib portion are provided at a position apart from the second tubular portion in a radial direction.

4 . The centrifugal fan according to claim 1 , wherein the circular ring-shaped rib portion and the auxiliary rib portion are provided at a position apart from the second hole in the radial direction.

5 . The centrifugal fan according to claim 1 , wherein

the first portion is made of metal,

the second portion is made of resin, and

the protrusion is provided on the second top portion.

6 . A centrifugal fan comprising:

a first portion provided in a rotor that rotates integrally with a shaft; and

a second portion provided in a fan unit having a plurality of blades and fixed to the rotor and having a greater linear coefficient of expansion than that of the first portion, wherein

the first portion includes

a first top portion extending from a first hole through which the shaft is inserted toward a radially outside of the shaft and having a first flat surface facing a first axial direction in an axial direction of the shaft, and

a first tubular portion having a tubular shape and extending from a radially outside end portion of the first top portion in a second axial direction opposite to the first axial direction,

the second portion includes

a second top portion located in the first axial direction with respect to the first top portion, extending to the radially outside from a second hole through which the shaft is inserted, and having a second flat surface facing the first flat surface, and

a second tubular portion having a tubular shape, extending in the second axial direction from a radially outside end portion of the second top portion, and having an inner tube surface facing an outer tube surface of the first tubular portion with a first clearance therebetween,

the first top portion is provided with a protrusion protruding in the first axial direction beyond the first flat surface and abutting on the second flat surface, or the second top portion is provided with a protrusion protruding in the second axial direction beyond the second flat surface and abutting on the first flat surface,

the protrusion of the first top portion or the second top portion includes at least three protrusions,

the at least three protrusions are provided apart from each other at an equal interval in a circumferential direction of the shaft, and

the first flat surface and the second flat surface are bonded and fixed to each other with an adhesive provided in a second clearance formed by the protrusion.

7 . The centrifugal fan according to claim 6 , wherein a protruding amount of the protrusion from the first flat surface or the second flat surface is set to an optimum film thickness of the adhesive.

8 . The centrifugal fan according to claim 6 , wherein the second top portion has a main portion extending to the radially outside and a second axial direction side from the second hole.

9 . The centrifugal fan according to claim 8 , wherein

the second top portion further includes a rib portion protruding from the main portion in the second axial direction to reinforce the main portion, and

an end surface of the rib portion on the second axial direction side forms the second flat surface.

10 . The centrifugal fan according to claim 9 , wherein the protrusion protrudes from the second flat surface of the second top portion.

11 . The centrifugal fan according to claim 10 , wherein

the rib portion includes

a circular ring-shaped rib portion protruding from the main portion in the second axial direction and having a circular ring shape as viewed from the second axial direction side, and

an auxiliary rib portion protruding from the main portion in the second axial direction and extending to the radially outside from the circular ring-shaped rib portion, and

the protrusion protrudes from an end surface of the auxiliary rib portion on the second axial direction side.

12 . The centrifugal fan according to claim 9 , wherein the rib portion is provided at a position apart from the second tubular portion in a radial direction.

13 . The centrifugal fan according to claim 12 , wherein the rib portion is provided at a position apart from the second hole in the radial direction.

14 . The centrifugal fan according to claim 6 , wherein

the first portion is made of metal,

the second portion is made of resin, and

the protrusion is provided on the second top portion.