Design and Fatigue Analysis of an E-Drive Transmission System of Single-Speed Gear for Electric Vehicle

Design an e-drive transmission gear, it is very crucial, to understand the failure modes since gears should be sized correctly to withstand loads that will expect to act on the gear teeth and make sure that still be within reasonable load-carrying capacity, compact and lightweight. Fatigue failure can happen on gears under cyclic loading due to higher stresses on tooth root and surface in contact. To prevent such failure, utilizing proper design, material development and fatigue analysis is very vital. In this study, Materials used were two developed alloy steels of Cr-Mo and Cr-Mo-Ni. The methods of design and analysis employed in this paper were by iteration through KISSsoft gear simulation software and American Gear Manufacturers Association (AGMA) standard approaches. Investigations have been done by altering helix angle, face-width, and input torque to get fitting safety factors, fatigue stresses, lightweight, compactness, and quiet operation of the gear pair. From the obtained results, it was found out that by increasing face width and helix angle both safety factors were increased uniformly regardless of the input torque. Through increasing input torque from 50 Nm to 75 Nm by keeping other parameters constant fatigue safety factor decreases. Similarly, results showed that by increasing the helix angle and face width it brings to reduce the contact and bending stresses on transmission gear. Regarding smooth and quietness operation of the system as contact ratio increases vibration of the system decreases. By comparing the results, the KISSsoft software values are a little higher than the AGMA standard values as depicted in all figures of fatigue safety factors. For better design approach, the transmission gears geometric parameters were selected based on the safety factors, downsizing and weight saving. As a result it was chosen as the face width is 24.5 mm and the helix angle is 25 degrees.