Investigation of the Influences of Thrust Loads Resulted by Helix Angle Directions of Planetary Gear Sets on Bearing Power Losses in Automotive Planetary Gear Trains

Hyun Sik Kwon

doi:10.3390/app11198827

Abstract

In the recent automotive industries, automotive technologies for improving fuel efficiency have focused on the developments of reducing power losses in a transmission. As a well-developed and conventional power transmitting system, an automatic transmission is still widely used in many automotive vehicles. The automatic transmission is co-axially designed with several planetary gear sets and other mechanical parts. The co-axial arrangements and gear helix angles make the transmission necessarily include bearings for supporting loads and allowing relative rotations. In this study, the influences of thrust loads yielded by helix angle directions of planetary gear sets on bearing power losses are presented by performing the structural and power loss analysis. Bearing power losses consist of mechanical and spin power losses. For calculating thrust loads and bearing rotations, a complete transmission model is constructed by using an example structure, and structural analysis is performed for the combinations of helix angle directions of the gear sets. Finally, bearing power losses are computed by using the bearing power loss model, and the results of the entire combinations of helix angle directions are discussed.

Highlights

In order to analyze the influences of thrust loads resulting from helix angle directions of the gear sets on bearing power losses, the structural analysis on the model is carried out to predict the amounts of loads acting to bearings in the axial direction
The influences of thrust loads produced by the helix angle directions of planetary sets on bearing power losses are investigated in this study
Bearing power losses consist of gear sets on bearing power losses are investigated in this study

Summary

Introduction

The transmission delivers multiple speeds by disengaging or engaging friction devices to connect central members of planetary gear sets. A planetary gear set has powerful and spatial advantages which are its high power density and compact design coming from co-axial arrangements. This spatial advantage of co-axial installations mechanically requires connection parts, such as transmission hubs and drums, for linking central members, and rolling element bearings for allowing them to relatively rotate under diverse load conditions. Multiple speeds are provided from an automatic transmission, a limited power efficiency is achieved with structural complexities and many mechanical parts. As dealing with many parameters in designing an automatic transmission, there are still possibilities to improve power efficiency by systematically investigating parameters and resultant operation performances

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