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Belt-driven starter generator claw pole electric motors are used in hybrid automobiles to start the engine, charge the battery and to power the electrical system when its engine is running. Shaft and claw pole are important components in the claw pole electric motor. The claw pole is fitted onto the shaft through press-fit force. Press-fit is a widely used fastening process to join two different components by pushing a component inside or over another component with high press force which will create a strong bond between the components. Determining press-fit force required to assemble parts is very complex since it depends on a lot of factors such as mechanical material properties of components, interference fit condition whether it is in Min, mean and max condition, amount of contact pressure induced by contact surface, co-efficient of friction created in between components. The press-fit will help to prevent loosening components from its bond at high torque and speed.

SAE 8620 and 20CrMo materials were subjected to carburizing process to obtain the identical hardened layer of HRC 61-64. The carburized surface and core properties of the materials were examined and characterized through optical microstructure to measure the presence of cementite carbides and Retained Austenite (RA). From the results, it was found that the SAE 8620 and 20CrMo materials have 10 % and 14% of RA respectively. Whereas, the core and case structure were free from network carbides. The fatigue test was conducted to correlate the RA and fatigue strength of the materials. It was revealed that material with lower RA has higher fatigue strength than material with higher RA. Higher amount of retained austenite leads to reduction in amount of martensitic and compressive residual stress attributed to lower the contact fatigue strength.

In Micro hybrid, start-stop system automatically stop and start the engine to reduce the idling time of engine spend in traffic jams and signals, thereby reducing fuel consumption and emissions. Starter motors used in Micro hybrid (Start/Stop) application has 5~10 times more life cycles than compare to conventional starter because of need to starter in every idling time of engine. There are multiple components in starter motor have sliding contact (mechanical/electrical), rolling contact will inflict the life cycles of starter motor. Brush is one of the major sliding contact elements to inflict the life cycle of starter, brushes are commonly used to conduct current between the stationary and moving part of starter. Brushes are exposed both mechanical and electrical loading conditions. Brush wear is affected by the association of Mechanical wear and electrical wear.