Research Of Shaft Insertion Interference Fit In Commutator Used In Radiator Fan Motor

Commutator is one of the most important components used in DC-motor. The assembly quality between commutator and armature shaft is an important factor to ensure the transmission of torque and to resist relative slip on the fitting surface. Currently, the assembly method of the armature shaft to the commutator is press fit. The motor manufacturers now have a more critical demand for the press-on force during the assembly, and how to control the press-on force becomes an important issue. Under these circumstances, this paper take one kind of commutator used in an automobile cooling fan made by Ningbo Sunico Commutator Co., Ltd. as the study object, using the FEA software ABAQUS to simulate the press-on fit of the armature shaft to commutator, providing a new method to properly choose interference size and control of the press-on force of the assembly.According to the stress state during the assembly, the model of the commutator was simplified. Based on the classic thick-wall cylinder theory, the stress calculation formula of the fitting surface was applied to figure out the relationship between the press-on forces after the assembly, which provides theoretical basis for the simulation.The mechanical data of phenolic molding compound, silver-copper and brass were gained from tests. The material properties of the phenolic molding compound were analyzed emphatically and the deficiency of the tensile test was pointed out. By analyzing the relationship between the tensile strength and the flexure strength, the real tensile strength was gained from two different flexure tests with different thickness.The FEA model for the simulation of the press-on fit of the armature shaft to commutator was established, and the stress states of all the components of the commutator after the assembly were analyzed. Simulation results shows that the fitting surface of the bore is the most dangerous area, what’s more, the contact stress increases sharply on the edge of the bore. Then the commutator with bushing was simulated and analyzed with similar method.The changes of stresses and the max press-on force with interference size of the commutator with bushing and without bushing were analyzed and compared. Then the proper range of the interference size and the fit tolerance that can meet the requirement of the press-on fore were gained. Experimental results show that the press-on forces of the samples can meet the requirements of assembly.