Improvement of Torque Density Using Output Reduction Method in Transmission

Abstract

Gears are one of the vital components to transmit torque efficiently. Helical gears are chosen as they transmit higher torque with lesser noise compared to spur gears of same size. All new age gearboxes require to transmit maximum torque with minimum packaging space available to improve torque density. Ways of reducing weight are using lesser density material, decreasing centre distance, and thereby reducing pitch circle diameter of all gears, etc. However, they will also affect torque carrying capacity of gearbox which can lead to gear failure in conventional transmission architecture gearboxes with input reduction method. In input reduction method, torque gets multiplied from input shaft to countershaft. Countershaft torque is multiplied to output shaft gears requiring higher torque capacity gears on output shaft. In this research, output shaft reduction architecture is proposed to avoid torque multiplication from input shaft to countershaft gears. It helps to reduce gear sizing on input shaft and countershaft gears. By using modular calculation methods, face width, centre distance and number of teeth are optimized to get higher torque density.

This paper presents a discussion on types of transmission layout configuration and compares input reduction method and output reduction configurations. Weight, size, deflection, and efficiency for same torque output is calculated between input reduction and output reduction. It is observed that output reduction configuration offers significant weight reduction for same torque capacity compared to input reduction with slight deterioration in efficiency.