Innovative Bevel Gear-Based Rotary Steering-Torque Transmission System

The steering mechanism determines the maneuverability of four-wheelers. In this paper a novel steering system (NSS) to accomplish steering according to the Ackermann geometry is proposed. The NSS advantageously utilizes the bevel gear technology to accomplish two main tasks (a) changing the direction of the steering torque and (b) steering the wheels in close approximation to Ackermann condition. For the second task, conjugate pairs of elliptic gears play a critically important role due to the variable transmission ratio property. This NSS is analyzed to derive the formula of the inner wheel steer angle and outer wheel steer angle achieved by a special assembly and configuration of circular and noncircular bevel gears. This formula is used to devise a plausible algorithm to obtain the required specification of bevel gears according to the dimension of vehicles. A comparative analysis of the steering performance of the NSS with two of the most popular steering systems, Ackermann four-bar linkage steering system and six-bar linkage steering system, is provided. Such an analysis is important for manufacturers in making a decision about switching from the current popular steering system to the NSS. A new insightful formula of the inner wheel and outer wheel steer angles provided by the Ackermann four-bar linkage and six-bar linkage steering systems are is derived to find the deviations of steering of these two popular steering systems from the Ackermann geometry in the form of anti-Ackermann steering condition and divergent-Ackermann steering condition. Deviation from the Ackermann geometry can cause faulty traction of the wheels which, in turn, may cause uncontrolled skidding of the vehicles leading to fatal accidents. Additionally, an analysis to explain limitations imposed by space constraints of vehicles on the steering performance of the abovementioned popular steering system, like the maximum allowable steering angle, is presented in this paper. In the NSS, the rotation motion of the steering handle on the central shaft is transmitted as a rotation motion to the left and right wheel steering shaft via the rotation action of the steer torque transmission arms. Such steer torque transmission, achieved using bevel gear technology, circumvents the need for complex planar movements of bars accomplished by the current prevalent steering systems in vehicles. The feasibility to accommodate the NSS in regular vehicles has been established. A prototype model built in the form of an electric four-wheeler to demonstrate the steer torque transmission mechanism of the NSS is also explained.