A fundamental study on self-locking gear and its application in seat height adjuster

摘要

The self-locking gear has great potential application in controlling the position stability of gearbox, which is a critical requirement in some precision machineries and instruments. However, the design procedure, load capacity, and dynamic behaviours of self-locking gear has not been investigated and systemized, which is a great barrier for the potential users. This research focuses on addressing these issues by developing new mathematical models and finite element method. Moreover, in this PhD project, we attempt to investigate the design method of the self-locking gear in seat height adjuster, which may eliminate the back-driving thereby improving the occupant driving comfort, enhance the driving safety, and reduce the volume of gearbox. A comprehensive literature review of spur gear, helical gear and epicyclical gear is presented in chapter 2. Chapter 3 gives an introduction of the analytical models of gear geometry, gear load capacity, and dynamics. Chapter 4 elaborates the procedure of finite element analysis. Chapter 5 presents the effects of different parameters on self-locking gear pairs. The dynamic performance of self-locking gears are presented in the Chapter 6. Chapter 7 depicts the mathematical models of seat cushion structure and plastic gears used to design the self-locking gear in seat height adjusters. Chapter 8 draws the conclusions and recommends the potential further In summary, this thesis developed a new finite element method to investigate the static and dynamic characteristics of self-locking gear. The effects of torque, tip radius, centre to centre distance error and misalignment axes on self-locking gear pairs were quantified. The non-linear dynamic behaviour of self-locking gear system subjected to the variation ratio of contact length were clarified. The design method of self-locking gear system in seat height adjuster subject to the automotive seat structure and plastic gears were developed. The obtained results in this thesis provide significant knowledge for predicting the static and dynamic performance of self-locking gear pairs, optimizing their design parameters, and diagnosing possible design errors in self-locking gear pair design. The work detailed in this thesis resulted in five peer-reviewed journal publications.