Dual Mode Clutch Hydraulic Control System In The Full Hybrid Electric CVT Vehicle

With the increasing depletion of oil resources, and the challenges of the transportsector’s energy crisis and environmental pollution, the development of new energyvehicles has become a new consensus on the global automotive industry. In response tothe global energy and environmental issues, the world’s major countries and regionsactively pursue transportation energy transformation strategy, enact the relevant laws,take the special action program to encourage the development of all kinds of newvehicle energy technologies, perform a variety of encouraging actions at the same time，such as all types of preferential policies，making it useful to accelerate marketpromotion of new energy vehicles.From the current development situation, the main new energy vehicles in the futurewill center on the pure electric vehicles, hybrid vehicles and fuel cell vehicles. Althoughthe pure electric vehicle is the development objective in the future, but the keytechnology of large-capacity battery which is the key component of pure electricvehicles is difficult to achieve substantial progress in a short period. The high cost of thebattery, the weak point in driving range because of the small amount of electricity thebattery contains，the inadequacy of supporting facilities have become the constraintsof volume-producing for pure electric vehicle’s industrialization. So hybrid electricvehicles will take advantage of its unique advantage for quite a long time and lead thedevelopment of new energy vehicles.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’s smooth start and the impact on transmissionsystem during the startup process, therefore, a precise pressure controlling of limitedtorque clutch’s hydraulic system is to ensure the key of the vehicle dynamics and ridecomfort in mode switching process of severe hybrid electric vehicles.Making the ISG severe hybrid electric vehicles as an application object, accordingto requirements of limited torque clutch in the process of mode switching which meetstorque and smooth performance, the two sets hydraulic system of limited torque clutchare designed, and the theoretical and experimental research on the performancecharacteristics of the hydraulic system are carried out. The main aspects as follows. ①By analyzing the wet clutch’s characteristics, principles and pressure-controlledmethod, we design a pilot-operated reducing valves controlled type and a ratio pressurereducing controlled type hydraulic systems, and formulate corresponding controlstrategies. The main components of two designed hydraulic system are selectedaccording to target-pressure and target-flow, and the hydraulic pump, the accumulatorstructure and the valve-controlled hydraulic systems integration manifolds are alsodesigned.②According to the designed hydraulic system and its main components’operating principles, the mathematical dynamic models of hydraulic reducing valve,solenoid valve, bladder accumulator and other valves in valve-controlled hydraulicsystem were established;③The reducing valve hydraulic system simulation model and the other valves’simulation models established based on the AMESim platform. And the hydraulicpressure characteristics of hydraulic reducing valve, accumulator, valve-controlledhydraulic system were simulated and optimization analysis according to the selectionparameters of valves.④The pilot-operated reducing valve-controlled hydraulic system test deviceswere built, the pressure control experiment and characteristics test were carried out,which verifies the right and suitability of the hydraulic pressure control.⑤ISG severe hybrid electric vehicle driving system test-bench was built, and thepilot-operated reducing valve-controlled hydraulic system was used in test-bench; Thepressure controlling test along with the engine starting in moving were carried on, andtest result show that the rationality, feasibility and effectiveness of the design of thehydraulic system.