ベルトCVTの効率向上と制御性能を両立するハイドロメカニカル変速制御機構の研究

概要

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A new-generation belt type Continuously Variable Transmission ranging up to 3.5 liter class engine is on the market. This CVT contributes to improvement in both efficiency and performance. This article describes a ‘control method’ newly developed for this CVT pulley ratio control. In the former control system, pulley ratio was controlled only by step-motor. Extra margin of line pressure was indispensable compared to primary pressure to accomplish target-ratio. If line pressure was not sufficient for primary pressure, pulley ratio couldnt be controlled accurately, and would be lower. On the other hand, in this new control, characteristics of hydro-mechanical shift system are utilized positively, and pulley ratio can be controlled by not only step-motor but also linear solenoid for line pressure. At this time, the most suitable line pressure is searched for by confirming the relation between command of step-motor and pulley ratio. In the result, line pressure can also be reduced a little less than primary pressure without causing unpleasant pulley ratio hunting.