| The oil charging and discharging hydraulic control system plays a critical role in the performance of hydrodynamic retarders. This paper focuses on the characteristics of a hydraulic control system applying large capacity cartridge valves to achieve switch control of charging flowrate and continuous adjustment of discharging flowrate. The features of critical components—charging and discharging cartridge valves, are investigated. Based on the results, the AMEsim simulation model is constructed in order to represent steady and dynamic response of the control valves. After that, proper control strategy is developed to control the action of control valves in the simulation. And simulation result shows that this control system can meet the requirements of regulating oil filling ratio of retarder chamber by adjusting the flowrate through valves, so it can realize typical functions such as constant torque braking and constant velocity down-hill driving.Hydraulic control system of high-power hydrodynamic retarders are required to charge and discharge oil rapidly, adjust oil filling ratio by demand and maintain a large circulating flow. So, cartridge valves are implemented as flow control valve in the hydraulic control system. Due to unique structural properties of cartridge valves, there is a lack of accurate components in commonly used commercial simulation platform to represent its characteristics. So, the proprieties of cartridge valves are studies at first. The accuracy of CFD flowfield simulation was proved by the comparison of CFD and experimental results. Then critical coefficients such as throttle area, flowrate number and flow force are determined by theoretical derivation and CFD simulation. On this basis, reasonable AMEsim simulation model was established as the foundation of hydraulic control system modeling.On the basis of the research and modeling of cartridge valves, the model of hydraulic control system was established to realize the function of calculating oil filling ratio of retarder chamber. The simulating model representing the working effect on vehicle level was established by combining the model of hydraulic control system, retarder characteristics, and vehicle dynamics. Calculating method of control pressure signal under due working condition was derived through the comparison of desired and current filling ratio, forming the control strategy of hydraulic system. Then simulation of retarder braking process was conducted under vary slope conditions. Simulation results showed that with proper control strategy, the hydraulic control system can actively control the oil filling ratio according to the change of road slope, and achieve typical functions such as constant brake torque and constant velocity down-hill driving. |
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