Development Of The Electric-hydraulic System For Continuously Variable Transmission And Research On The Key Technology

Relying on the platform of combination of ‘production, studying andresearching’, based on International Cooperation Project’New-GenerationEnergy-saving CVT’, the subject is selected out from the need of CVT engineering,which focuses on the difficulties of the electric-hydraulic encountered during the CVTmass production realizing process. In this paper, the theory analysis is combined withthe author’s experience in the CVT mass production; some innovative, applicable andquantitative methods are raised up, which are fully evaluated by test. The maincontent is listed as follows.1Start from the customer request, design destination and scheme to realize it aredetermined and the independent circuit is chosen. By analysis and calculation of theCVT working conditions, based on the request of belt clamping force and ratiochanging, the max value of the line pressure, secondary pressure and the primarypressure are determined,also the time requirements on their dynamic response.2The dual-acting blade vane pump is chosen, then its displacement is calculatedby simulation method based pressure and flow needed on the emergent stop.3To reduce the power consuming, two new energy-saving proposals areimplemented into the system. One is the self-adaptive flow regulating, comparing tothe active flow regulating，it gets rid of the complicated structure and the difficulty tocalculated the flow needed. Also, it can reduce the pump energy consuming byregulating the flow precisely fitting the system need. Second is to take the clutchpressure as the pilot pressure of the auxiliary value, which is of higher level of clutch,this proposal makes the auxiliary pressure varying according to realistic need, then thelower pressure limitation applied on the line pressure by auxiliary pressure isremoved.4Regarding the designed hydraulic circuit, the characteristic of the componentsare analyzed, then the simulation model of this circuit is built up, also the cylindermodels and the ratio response model. Comparing between the simulation results andthe test results is carried out, result shows well alignment between model responseand test (both time domain and frequency domain). This model is proved can be usedfor open loop system analyzing and the non-real-time close-loop simulation. 5The diversity，uncertainty and time-varying bring the consistency problem intothe DNR control. Regarding the filling time and the slipping process, oneself-learning method is introduced into, which takes the smooth turbine accelerationas the target. The learning rule is derived from on the Lyapunov argument. Then bytest, this method is proved to be applicable and asymptotic stable.6Taken the benefit of the Phase transition point of ratio tracing the clampingforce variation, one new clamping control concept is introduced, which can beobviously decrease the pressure level and the increase the efficiency.7Comprehensively considered the rapidly ratio changing request, the pumpability and the flow needed, one updated proposal is raised up. Comparing with thetraditional PID, this method is testing proved not can only follow the target ratio fastand stable, but also more safe for the flow and clamping force.6. The test rig specific for the hydraulic valve body is built for testing theperformance of the hydraulic body, including the static characteristic, repeatabilityand the step response. Also on the vehicle level, kick down, emergency stop andcomprehensive working conditions are tested. By these test items, it is obviously thatthe rapidity, stability of ratio, pressure tracing and heat balance ability can fulfill thedesign purpose and customer request.