Seminar On Continuously Variable Transmission (CVT) Report

Seminar On Continuously Variable Transmission (CVT) Report


After more than a century of research and development, theinternal combustion (IC) engine is nearing both perfection andobsolescence: engineers continue to explore the outer limits of IC efficiency and performance, but advancements in fuel economy and emissions have effectively stalled. While many IC vehicles meet Low Emissions Vehicle standards, these will give way to new, stricter government regulations in the very near future. With limited room for improvement, automobile manufacturers have begun full-scale development of alternative power vehicles. Still, manufacturers are loath to scrap a century of development and billions or possibly even trillions of dollars in IC infrastructure, especially for technologies with no history of commercial success. Thus, the ideal interim solution is to further optimize the overall efficiency of IC vehicles.

One potential solution to this fuel economy dilemma is the continuously variable transmission (CVT), an old idea that has only recently become a bastion of hope to automakers. CVTs could potentially allow IC vehicles to meet the first wave of new fuel regulations while development of hybrid electric and fuel cell vehicles continues. Rather than selecting one of four or five gears, a CVT constantly changes its gear ratio to optimize engine efficiency with a perfectly smooth torque-speed curve. This improves both gas mileage and acceleration compared to traditional transmissions.

While IC development has slowed in recent years as automobile manufacturers devote more resources to hybrid electric vehicles (HEVs) and fuel cell vehicles (FEVs), CVT research and development is expanding quickly. Even U.S. automakers, who have lagged in CVT research until recently, are unveiling new designs: General Motors plans to implement metal-belt CVTs in some vehicles by 2002.


CVTs & Hybrid Electric Vehicles

While CVTs will help to prolong the viability of internal combustion engines, CVTs themselves will certainly not fade if and when IC does. Several companies are currently studying implementation of CVTs with HEVs. Nissan recently developed an HEV with ³fuel efficiency « more than double that of existing vehicles in the same class of driving performance´. The electric motor avoids the low speed/ high torque problems often associated with CVTs, through an innovative double-motor system. At low speeds: A low-power traction motor is used as a substitute mechanism to accomplish the functions of launch and forward/reverse shift. This has made it possible to discontinue use of a torque converter as the launch element and a planetary gear set and wet multi-plate clutches as the shift mechanism.

Thus use of a CVT in a HEV is optimal: the electric portion of the power system avoids the low-speed problems of CVTs, while still retaining the fuel efficiency and power transmission benefits at high speeds. Moreover, ³the use of a CVT capable of handling high engine torque allows the system to be applied to more powerful vehicles´. Obviously, automakers cannot develop individual transmissions for each car they sell; rather, a few robust, versatile CVTs must be able to handle a wide range of vehicles. Korean automaker Kia has proposed a rather novel approach to CVTs and their application to hybrids. Kia recently tested a system where ³the CVT allows the engine to run at constant speed and the motor allows the engine to run at constant torque independent of driving conditions´. Thus, both gasoline engine and electric motor
always run at their optimal speeds, and the CVT adjusts as needed to accelerate the vehicle. Kia also presented a control system for this unified HEV/CVT combination that optimizes fuel efficiency for the new configuration.



Tractors just as cars have the need for a flexible system to convey power from their engine to their wheels. The C.V.T. will provide just this and at high fuel savings with low atmospheric pollution.

Golf Carts stand to benefit from the C.V.T. as well in the way electric cars do. i.e.: Large range of speeds, longer driving range between charges, fewer batteries, lower maintenance cost, less weight.

Ride on Lawn Mowers like small tractors are gas powered and contribute to t he air pollution problem. The C.V.T. approach can prevent ride-ons to pollute the air to the extent they currently do.

Motorized Wheelchairs. Battery run, speed controlled by a rheostat. Going up a ramp slowly causes a drop in power (when it’s most needed). C.V.T. is a form of transmission, lower speed means MORE POWER.

Bicycles. Ever try to shift gears while pedaling uphill? Good news; the KINESIS C.V.T. will automatically select the appropriate for the situation “gear” ratio.

Power tools and household appliances, that vary from bench-top drills to wash machines and blenders need to depart from the centuries old belt and pulley configuration for smoother operation and more reliability.

Industrial Equipment and production machinery often use either gears or cumbersome belt and pulley configurations. C.V.T. can do away with all that and additionally give them infinite ratios.

Minimachines. Small devices that need to operate in a wide range of speeds, as the need arises. Our unique design allows the production of an inexpensive miniature C.V.T. to enable them do just that!.


Today, only a handful of cars worldwide make use of CVTs, but the applications and benefits of continuously variable transmissions can only increase based on today’s research and development. As automakers continue to develop CVTs, more and more vehicle lines will begin to use them. As development continues, fuel efficiency and performance benefits will inevitably increase; this will lead to increased sales of CVT-equipped vehicles. Increased sales will prompt further development and implementation, and the cycle will repeat ad infinitum. Moreover, increasing development will foster competition among manufacturers automakers from Japan, Europe, and the U.S. are already either using or developing CVTs which will in turn lower manufacturing costs. Any technology with inherent benefits will eventually reach fruition; the CVT has only just begun to blossom.


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Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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