| Hydraulic retarder,as an excellent hydraulic auxiliary braking device,is widely used.Hydraulic retarder needs to adjust the braking moment according to the braking demand,transient output characteristics of the hydraulic control system will directly determine the dynamic output characteristics of the braking torque.Hydraulic system of Dual Torus Hydrodynamic Retarder is studied in this paper,ansysis the influence of cartridge electrohydraulic proportional valve on the transient output characteristics of hydraulic system,and the optimization design.Studied the output characteristics of the braking torque before and after optimization of cartridge electro-hydraulic proportional valve.Combined with the vehicle dynamics,the constant speed braking type,following braking type of braking torque varying with the opening of brake pedal and fully charged emergency braking type,simulation research is carried out.Study on transient characteristics of proportional solenoid valve which is cartridge electro-hydraulic proportional valve's pilot valve.Proportional solenoid valve model is established,and make experiments verify the accuracy of model.In this paper,the response time and pressure overshoot of proportional solenoid valve are chosen as optimization targets,select the spool diameter and other design parameters for DOE analysis,then optimize the design of proportional solenoid valve.Results show,the response time is slightly reduced,but the output pressure overshoot is greatly decreased,with a maximum decrease of 72%.In this paper,we derive the flow force expression of cartridge valve which is cartridge electro-hydraulic proportional valve's main valve,under transient conditions.Through the method of CFD transient simulation,the accuracy of the improved expression and the traditional expression is studied.The result show,the improved expression's accuracy is higher than traditional,and the solution error can be controlled below 20%.Build up model of cartridge valve based on improved flow force expression,and make experiments verify the accuracy of model.In this paper,the response time and oil pressure amplitude of cartridge electro-hydraulic proportional valve's inlet are chosen as optimization targets,select the cartridge valve's spool face chamfering and other design parameters for DOE analysis,then optimize the design of cartridge electro-hydraulic proportional valve.Results show,the response time remains basically unchanged,but the cartridge electro-hydraulic proportional valve ‘s inlet oil pressure amplitude is greatly decreased,with a maximum decrease of 49%.Design experiments verify the influence of the cartridge valve's spool face chamfering on the characteristics of the inlet oil pressure,and contrast experiments were carried out,and the experimental results achieved the desired results.The hydraulic retarder system model is established,and the accuracy of the model is verified by bench test.The results show that the fluctuation amplitude of the braking torque decreases after the cartridge electro-hydraulic proportional valve is optimized,and the minimum drop can reach 40%.Establish the whole vehicle braking model is,three braking types are designed,In the constant speed braking type,the fuzzy PI control compared with the PI control,the speed overshoot decreased by 57% and the response time decreased by 37%.Analyze the effection of the following brake type and the emergency braking type,the results show in the following brake type,the driver can adjust the braking torque by adjusting the opening of the brake pedal to realize the control of the braking process.. |
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