Centrifugal fan and fixing method

A fixing method for fixing, to a first portion provided in a rotor of a motor unit having the rotor that rotates integrally with a shaft and a stator disposed so as to face the rotor, a second portion provided in a fan unit having a plurality of blades and having a greater linear coefficient of expansion than that of the first portion,

• the first portion being provided with a top portion extending to a radially outside from a first hole through which the shaft is inserted and having a flat surface facing a first axial direction, and a first tubular portion extending from a radially outside end portion of the top portion in a second axial direction opposite to the first axial direction, and
• the second portion being provided with a main portion extending to the radially outside from a second hole through which the shaft is inserted, an annular rib portion protruding from the main portion and having an annular end surface having an annular shape, a plurality of auxiliary rib portions protruding from the main portion in a direction identical to that of the annular rib portion, radially extending from the annular rib portion in a radial direction, and having end surfaces facing a direction identical to that of the annular end surface, and a second tubular portion extending from a radially outside end portion of the main portion in a direction identical to that of the annular rib portion,
• the fixing method comprising:
• a first step of applying an adhesive to the annular end surface or applying an adhesive to a portion facing the annular end surface when the main portion of the second portion is disposed on a first axial direction side with respect to the top portion of the first portion on the flat surface;
• a second step of disposing the main portion of the second portion on the first axial direction side with respect to the top portion of the first portion and making the annular end surface and the end surfaces face the flat surface;
• and
• a third step of making an inner tube surface of the second tubular portion face an outer tube surface of the first tubular portion with a clearance therebetween and expanding the adhesive between the annular end surface and the flat surface and between the end surfaces and the flat surface.