Research On The Parameters Design Of Hydraulic Retarder And Simulation For Vehicle Auxiliary Braking Performance

In recent years, the transportation and vehicle technology in our country are improving rapidly, so the average vehicle speed is also increasing. Therefore, vehicle's braking performance is demanded higher, especially for the heavy trucks and coaches, which load heavily and often drive on complicated roads. And for the vehicles driving on the mountain and hill areas, braking performance is much more important. Owing to the traditional service braking system cannot meet the braking requirements, so all kinds of auxiliary braking systems are applied on the vehicles, and hydraulic auxiliary braking system is one of the most important auxiliary braking systems.This paper mainly studies the parameters design and vehicle braking performance simulation technology, and the following items are included.1) In this paper, three main types of vehicle auxiliary braking systems are described, which are namely hydraulic auxiliary braking system, eddy-current auxiliary braking system, engine exhaust auxiliary braking system. The paper mainly introduces the structure and working principle of hydraulic retarder, and the research conditions of this field both in domestic and overseas are also analyzed.2) The paper mainly analyzes the basic theories for the hydraulic retarder, including hydraulic theory and braking theory. In hydraulic theory part, it mainly discusses the process of solving auxiliary braking torque by using hydraulic calculation method, and the similarity calculation theory is also discussed, which is commonly used in hydraulic parts design. Meanwhile, it also discusses the auxiliary braking torque when hydraulic retarder is in different fluid ratios and when the auxiliary braking torque is effected. In braking theory part, the stresses acting on the braking tires are analyzed, all the same, the stresses acting on the vehicle are discussed when vehicle is executing braking on lasting downhill. The evaluation indexes for braking efficiency when vehicles execute braking are introduced lastly.3) Based on the similarity design for hydraulic retarder, the similarity design for the parameters of hydraulic retarder is conducted.4) The paper establishes the hydraulic retarder auxiliary braking simulation model with hydraulic calculation method, moreover, the engine braking simulation model, service braking simulation model and driving resistance driving resistance are established by using the matlab/simulink software tool.5) The vehicle's braking performance is simulated by using the parameters of hydraulic retarder and FAW Jie Fang Jun Wei J5K truck. Firstly, the vehicle's braking performance is simulated, and the simulation results are analyzed detailedly. The simulation mainly includes hydraulic retarder auxiliary braking only and the association of hydraulic retarder auxiliary braking and engine braking when vehicle is executing braking on horizontal road and lasting downhill road. Supposed the vehicle is carrying out braking on horizontal road without using service braking system, it can be concluded from the braking speed curve, braking deceleration curve and braking distance curve that the vehicle's braking performance is satisfied by using hydraulic retarder auxiliary braking only. And the braking performance is better when using hydraulic retarder auxiliary braking and engine braking together. When the vehicle is executing braking on lasting downhill road, the vehicle speed will come to a low value ultimately when adopting hydraulic retarder auxiliary braking only and the association of hydraulic retarder auxiliary braking and engine braking. Therefore, the vehicle braking safety is enhanced dramatically. Secondly, the auxiliary braking torque simulation is conducted when the hydraulic retarder is in different fluid ratios. And the simulation results indicate that the auxiliary braking torque is larger and the vehicle's braking performance is better when the fluid ration is higher. Finally, the vehicle's engine braking torque and driving resistance are simulated. It can be seen from the simulation results that the engine braking performance is better when the gearbox is in lower gears with the same other conditions. Meanwhile, the vehicle driving resistance is becoming lower when the vehicle speed descends.The contents of the paper will have referential value and practical significance for parameters optimization of hydraulic retarder, auxiliary braking performance optimization of vehicle and development of hydraulic retarder.