Design and simulation of a steering gearbox with variable transmission ratio

Abstract

This article presents the geometric and functional characteristics of a steering gearbox with variable transmission ratio, which contains a translating wheel (circular curved rack) in gearing with an eccentric sector (segment). The solution requires no special technology because it uses conventional involute gears, being obtained/derived from a classic gearbox with constant ratio by changing the gearing characteristics. The precision of the steering system and the reversibility of the gearing are not affected by these modifications, the driver having a good/safe control of the vehicle. This gearbox can be used for the steering systems of some low-power vehicles, assuring an increased actuating torque (less effort); in this way, the assistance (hydraulic power steering or electric power steering) can be avoided. The study is focused on the following objectives: formulating the theoretical bases, establishing the geometrical parameters, and simulating the functionality of the gearbox, based on the specific requirements of the vehicles’ steering system. Important conclusions have been drawn on the influence of some specific parameters in terms of insuring good gearing conditions, such as the variation of the distances between axes and the variation of the clearance between teeth.