In the mechanical field, interference fit technology is widely used in the assembly process of an outer part and an inner part passing through the outer part. Especially, at present, interference fit technology is widely used in the assembly process of motor power transmission system. For example, the interference fit process can be applied to assemble the stator of the motor and the cooling water jacket of the motor, or it can be applied to assemble the rotor hub of the motor and the rotor of the motor. An interference fit process known in the art is to cool the inner part to a very low temperature (e.g., minus 80 ° C or lower) to cause it to shrink, and then install the shrunk inner part into the outer part. After the temperature of the inner part is restored, a firm interference fit is formed between the inner part and the outer part.
For the water-cooled motor, the interference between the inner circumference of the cooling water jacket and the outer circumference of the stator can be about 0.25 mm when the interference fit process is used to assemble the stator and the cooling water jacket of the motor. After the interference fit process is completed, the cooling water jacket will expand greatly.