Research On Hydraulic System Of Limited Torque Clutch In The Severe Hybrid Electric Vehicle

Energy-saving and environmental protection have became a future developmenttrend of the automotive market under the double pressures of the energy crisis andenvironmental pollution. Although pure electric vehicles is the development objectivesin the future, but the key technology of large-capacity battery which is the keycomponent of pure electric vehicles is difficult to achieve substantial progress in a shortperiod. So hybrid electric vehicles will be to play its unique advantage for quite a longtime.Idling start-stop and starting the engine in walking mode are the importantoperation modes of ISG severe hybrid electric vehicles, and they were finished bycontrolling the limited torque clutch. However the limited torque clutch’s engagementpressure is directly related to the engine is a smooth start and the impact of transmissionsystem during the startup process, therefore, a precise pressure controlling of limitedtorque clutch’s hydraulic system is to ensure that the key of the vehicle dynamics andride comfort in mode switching process of severe hybrid electric vehicles.Using the severe hybrid electric vehicles as an application object, according torequirements of limited torque clutch in the process of mode switching which meetstorque and smooth performance, the hydraulic system of limited torque clutch isdesigned, and the theoretical and experimental research on the performancecharacteristics of the hydraulic system are carried out. Mainly the following aspects:①Though the wet clutch’s characteristics, principles and pressure-controlledmethod analysis, design a static-pressure type and a valve-controlled type hydraulicsystems, and formulate corresponding control strategies. The main components of twodesigned hydraulic system are selected according to target-pressure and target-flow, anda static-pressure hydraulic pump, a spring-loaded accumulator structure and avalve-controlled hydraulic systems integration manifolds are also designed.②According to the designed hydraulic system and its main components’operating principles, the mathematical dynamic models of hydraulic pump,spring-loaded accumulator and the piston of ring hydraulic cylinder were established;The mathematical dynamic models of hydraulic reducing valve, solenoid valve, bladderaccumulator and other valves in valve-controlled hydraulic system were established;The hydrostatic system simulation model, the valve-controlled hydraulic system simulation model and the other valves’ simulation models were established based on theAMESim platform; And the hydraulic pressure characteristics of hydraulic reducingvalve, accumulator, hydrostatic hydraulic system and valve-controlled hydraulic systemwere simulated and optimization analysis according to the selection parameters ofvalves.③The hydro-static and the valve-controlled hydraulic system test devices werebuilt, the pressure control experiment and the pressure-output tension characteristics testwere carried out, which verifies the right and suitability of the hydraulic pressurecontrol.④ISG severe hybrid electric vehicle driving system test-bench was built, andvalve-controlled hydraulic system was used in test-bench;The pressure calibration testof valve-controlled hydraulic system and the pressure controlling test along with theengine starting in moving were carried on, and test result show that the rationality,feasibility and effectiveness of the design of the hydraulic system.