Centrifugal fan

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.