A bearing assembly is formed by coupling at least two units together in an axially abutting manner. Each unit has two connection portions on two opposite ends and a mounting portion on a largest outer periphery. The connection portions between two adjacent units form at least one set of interfaces, each set having complementary shapes contact with each other. The mounting portion is securely encased in an inner periphery of a jutting chamber located at each end of a motor housing. At least one groove and notches are formed on at least one of two abutting connection portions between the two adjacent units. The notches communicate with the groove and an axle hole. In the assembly, the groove forms at least one storage chamber to store lubricating media, and the notches form at least one set of passages communicating with the storage chamber and an axial hole.