The Research Of A Tractor's Brake System Integrated Control On Pedal

With the rapid development of social economy,people's living standards are improving,so that higher safety and comfort are required.The brake system is an important guarantee for the vehicle safety performance.As a result,the technical innovation of vehicle main-braking system is ongoing,from the traditional mechanical control pneumatic valve to nowadays.Specifically,a large number of electronic technologies are applied in vehicle braking systems,which not only reduce the brake time,improve the control accuracy,enhance the drive safety,but also reduce the divers' burden of manipulation and improve the drive comfort.However,the basic principal of main-brake system is that the drivers input stop requirements by manipulating brake pedal,where pressed air(or liquid)is the transmission medium to transmit the driver's stop requirements to wheel-side,resulting in the conduct friction between friction plate of wheel-side brake and the wheel hubs to convert the kinetic energy into heat and slow down or stop the vehicle.The high temperature of wheel-side brake under frequent braking conditions has not been solved,which tends to fade or failure the braking system.This problem have led to the emerge of non-friction braking systems,i.e.auxiliary braking systems,such as exhaust brake butterfly valve,engine assisted braking,hydrodynamic retarder,eddy current retarder appear,which are now commonly applied in vehicle brake system.It has been proved that the auxiliary brake system can remit the operate pressure of main-brake system,and solve the problem of wheel-side brake high temperature.When a vehicle is matched brake butterfly valve,engine assisted braking and retarder in the same time,how to control and coordinate the work performances of these brake system to achieve a good braking effect and braking feeling has become a new problem.Heavy-duty tractor as a long highway transport vehicle,get high speed and heavy load.When driving in the long downgrade road,or driving in downtown and braking frequently,the wheel brake temperature rise sharply,braking efficiency decreased significantly.In order to solve the problem,the vehicle manufacture arranged the exhaust brake butterfly valve,engine brake and retarder on the heavy tractor.The auxiliary brake system is controlled by the handle switch,and the different positions of the handle correspond to the auxiliary brake to output the corresponding braking torque.The main brake system is actuated by the brake pedal.Under this independent control principal,the driver has to do a complex work to finish brake;and when each system can work independently,the brake system can not meet the braking requirements of variety road conditions.In order to ensure the safety of the vehicle and improve the handling performance,it is necessary to develop a new braking system control principal.In this paper,the development back ground,composition structure and work principal of main stream auxiliary brake systems are discussed in detail.Then a strategy of integration of main-brake system control,WEVB engine assisted brake control,hydrodynamic retarder control on main-brake pedal is proposed.The designation is accomplished by composing the control logic,designing the electronic control principal,developing the completely new main brake valve.Furthermore,the strategy is verified to be effective and workable after integrating the brake system control on a tractor and testing the brake system performance of this tractor.