Research On Transmission Characteristic And Comprehensive Control Technology Of Metal V-belt Type CVT

Based on the projects of one company,'Research on key technology of electrichydraulic system of CVT for passengers car' and 'Building of CVT mass productioncapacity200,000sets per year', research in this paper is focusing on the key technology formass production and the software improvement, the research object is one local producedCVT and its target local produced car. Based on the analysis of test data recorded during testrig experiment and road experiment, the applicable solutions for the occurred problem werefound. The main content is showed as follows.1Starting from the friction force between element and pulley surface, the slipmechanism is analyzed. The force distribution outline within the whole running circle is gotby analyzing the relative movement between element and ring. Then the detailed forcecalculation is carried out, by which the push force in between elements and the tension forcein the ring are got, also the torque capacity and the balance between primary clamping forceand secondary clamping force, which provides one theoretical basis for control strategy.2Aiming at the belt breakage caused by the mis-setted AS value of belt misalignment,by combining the misalignment sensitivity and comprehensive working condition of car, thefirst time comprehensive sensitivity factor is brought forwarded. Then by this method, theAS value is optimized and it is proved to be one feasible solution, and the belt breakagecaused by the same reason never reoccurs after this solution.3Based on the need of application control software (ASW) developing, the HIL (hardware in loop) testing rig is setted up. With the test data of clamping force balance and thedidt factor, the first time didt simulation model is established. Then with the combination ofmodel identification, mathematic analysis and test calibration methods, the CVT dynamicmodel, hydraulic model and the vehicle dynamic model are founded, which are consistentwith testing results after comparing.4With the feedback regarding drivability of CVT car from market, road test is carriedout, the main factors that affect drivability is analyzed. Out from the great influence by thedrive power increment, the optimized target engine speed control strategy is broughtforwarded, after compare with another two methods, it is proved can greatly improve thedrivability and the response speed, also it can reduce the manipulation times and thevariation of engine speed and CVT ratio to make the vehicle more stable. The obviousadvantage of this method is, it eliminates the non-linear response of engine within in the whole operating area, enhanced the cooperation between engine and CVT, which conqueredthe disadvantage of soley CVT control. Besides that, it provided the theoretical basis forthe CVT control and also the joint calibration of power system.5To prevent the over clamping caused by the traditional safety clamping control, thetracing characteristic of speed ratio towards sine harmonic pressure input is tested. The testresult shows that the tracing characteristic can be divided into two sections, phase180°difference is between them. According to such characteristic, the clamping force controller isdesigned, which is proved to be an effective method for reducing the clamping force andincreasing the efficiency.The disadvantages of traditional ratio error PID controller are explained, to get rid ofsuch disadvantages, one new controller is introduced in, which is one comprehensiveconsidering result of hydraulic flow and didt calculation. Then implemented it into car fortesting, the effect is evaluated well.All the analyzing and research are aiming at the problems occurred during massproduction and testing, try to find applicable solutions for such problems. Someunmentioned or neglected factors before are stated, such as the comprehensive misalignmentfactors, the didt model and its affect parameters, drivability factors, some applicable methodwere introduced in, such as slip clamping force control, improved ratio controller andreserved drive power based control method. All the above mentioned methods have beenevaluated to be feasible and effective.