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.

Study of optimal strategy and linkage-model for external non-circular helical gears shaping

“…b , and ! c are also very close in strategy (2), (4), (6), and (8). The characteristics of curves v x are similar in eight strategies.…”

A mechanical integral steering system for increasing the stability and handling of motor vehicles

“…transmission ratio of the speed reducer m n normal modulus r 0 radius of the cam reference circle r p polar radius of the cam S a/b motion amplitudes of the follower S r linear displacement of the front rack S s linear displacement of the follower S [1][2][3][4][5][6] linear displacements of the follower in the limit points z p number of teeth of the pinion from the front steering box z t number of teeth of the gear wheel from the front end of the longitudinal transmission shaft teeth inclination angle e/i steering angles of the wheel outside/ inside (external/internal) the turn f/r medium steering angles of the front/ rear wheels ' a/b phase angles of the cam profile ' c revolute angle of the cam ' t revolute angle of the longitudinal transmission shaft ' w revolute angle of the steering wheel È motion amplitude of the cam (' c max ) È 1/2 angle periods of the steering wheel motion…”

“…It should be mentioned that part of these tests were carried out by using the experimental facilities from the Transilvania University of Brasov, namely the MTS-HTC hydraulic testing equipment from the The front suspension subsystem ( Figure 8) contains two double-wishbone (SLA (Short Long Arms)) mechanisms, which are symmetrically disposed relative to the longitudinal axis of the vehicle. The specific MBS model contains 12 bodies (6 per left/right mechanism) as follows: lower suspension arms (1,2), upper suspension arms (3,4), wheel carriers (5, 6), tierods (7,8), dampers' cylinders (9,10), and pistons (11,12). The suspension arms are connected to the wheel carrier through spherical joints, while bushings (compliant joints) are used for the double-connections to the mount part from the car body subsystem.…”

“…Improving the dynamic behavior of the motor vehicles is a permanent concern and challenge. From the stability and maneuverability (handling) point of view, an important role belongs to the steering system, certain developments being directed toward reducing the driving effort by using variable transmission ratio steering gearboxes (such as the solution with translating wheel and eccentric sector presented in Alexandru et al 1 ), or the modern solution with electric power steering (EPS) system. 2 As the traditional two-wheel steering systems (usually acting on the level of the front wheels) have inherent limitations, the integral steering (also called four-wheel steering for two-axle vehicles) represents a good solution for increasing the vehicle stability and handling, the references pointed here sustaining the usefulness of the four-wheel steering solutions.…”

Investigation of a steering defect and its compensation using a steering-torque control strategy in an extreme driving situation

“…The equations of this model can be expressed as where m is the mass of the vehicle, u is the longitudinal velocity, v is the lateral velocity, F xij are the longitudinal forces at each wheel, F yij are the lateral forces at each wheel (where the subscript ij represents different wheels with fl representing the front left wheel, fr representing the front right wheel, rl representing the rear left wheel and rr representing the rear right wheel), r is the vehicle yaw rate, I z is the inertia moment about the vertical axis, B f is the track width of the front axle, B r is the track width of the rear axle, a is the distance from the front axle to the centre of gravity of the vehicle, b is the distance from the rear axle to the centre of gravity of the vehicle and d is the steered tyre angle, which is the average value for the two front wheels. In general, d can be expressed as u/i ts , where u is the steering-wheel angle and i ts is steering transmission ratio, which usually remains a constant value when the steering angle 35 is less than 300°(the details of a gear with a variable ratio can be found in the papers by Alexandru et al 36,37 but are not considered here).…”