Continuously Variable Transmission (CVT)

Continuously Variable Transmission (CVT)

Abstract

CVT makes for optimal tuning between epicycle gear and discharge rate reducing oil pump, and the direct control torque converter by which an efficient engine output transfer and a smooth ride are realized. Based on accelerator travel information from actual drivers under actual driving conditions, the optimal efficiency point between the engine and the CVT was obtained and a supple and smooth driving feel is obtained under numerous conditions while also achieving low fuel consumption.

Introduction

The more gear ratios we have, the more choices we have in setting the engine spin rate for any given speed. This allows us to call for power when we need it by revving high but to cruise economically by lowering the engine spin rate and reducing losses associated with the fast-moving internal engine parts. A conventional CVT has an infinite (or a very large number) of gear ratios. It selects a ratio that can deliver to the wheels the power being demanded by the driver, but keeps the engine spin rate low within this constraint to improve economy and engine life. You can imagine that as the car picks up speed, the transmission continually shifts into a slightly higher gear. The result is that the pitch of the engine tone stays fairly constant and the acceleration falls off smoothly, instead of in steps, as the higher gear ratios have a smaller multiplying effect on the engine torque.

The advantages of a CVT (selection of the best gear ratio at all times to balance performance and economy) are considerably offset by efficiency and reliability problems.

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