Fabrication and Analysis Of A Continuously Variable Planetary Transmission System

Abstract:

A continuously variable transmission (CVT), in theory, has an unlimited number of gear ratios between the highest and lowest settings. But most CVTs are complex, expensive, have poor efficiencies, and aren’t scalable. A new type of CVT, CONTINUOSLY VARIABLE PLANETARY TRANSMISSION(CVPT),combines toroidaltraction CVT with the versatility of the planetary gear arrangement to create a low-cost, highly efficient drive for human-powered and motorized vehicles.While the CVPT uses rolling traction to distribute torque like toroidal CVTs, it distributes the transmitted torque over several spheres in an inherently stable configuration. The rotating balls between the input and output section of the CVT tilt to vary transmission speed. As the balls tilt, they change their contact diameters to vary the speed ratio. This lowers contact pressures and improves durability, stability, and torque density. And since it uses a planetary arrangement, torque can be summed or divided.In the present work, a CVPT has been mounted to a bicycle for conducting the experiments. Normally tilting of spheres for changing gear ratios is done manually, however in our case, this has been obtained automatically. For automated shifting, a shift actuator, a controller and a battery to power this circuit is used.Also, results have been obtained with speed variations of a bicycle with and without CVPT. Graphs are plotted using the obtained results and analysed.

INTRODUCTION
A continuously variable transmission (CVT) is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios. The flexibility of a CVT allows the driving shaft to maintain a constant angular velocity over a range of output velocities. This can provide better fuel economy than other transmissions by enabling the engine to run at its most efficient revolutions per minute (RPM) for a range of vehicle speeds. Alternatively it can be used to maximize the performance of a vehicle by allowing the engine to turn at the RPM at which it produces peak power. This is typically higher than the RPM that achieves peak efficiency. Finally, a CVT does not strictly require the presence of a clutch, allowing the dismissal thereof. In some vehicles though (i.e. motorcycles), a centrifugal clutch is nevertheless added however this is only to provide a “neutral” stance on a motorcycle.

CONTINUOUSLY VARIABLE PLANETARY TRANSMISSION (CVPT)
A continuously variable transmission (CVT) is a type of automatic transmission that can change the “gear ratio” (gears are not generally involved) to any arbitrary setting within the limits. The CVT is not constrained to a small number of gear ratios, such as the 4 to 6 forward ratios in typical automotive transmissions. CVT control computers often emulate the traditional abrupt gear changes, especially at low speeds, because most drivers expect the sudden jerks and will reject a perfectly smooth transmission as lacking in apparent power. The CVPT is continuously variable and infinitely applicable to almost any product using mechanical power transmission. Planetary transmission technology combines the advantages of a toroidal traction CVT with the time-proven versatility of the planetary gear arrangement. It uses rolling traction to transfer torque, just as do toroidal transmissions. However, unlike toroidal CVTs, it distributes the transmitted torque over several spheres in an inherently stable configuration, thus lowering total clamping force required and significantly improving durability, control stability, and torque density. This arrangement makes the CVPT the only practical CVT to combine the smooth, continuous power transfer of a CVT with the utility of a conventional planetary gear drive. Torque inputs can be summed or divided, just as in a conventional planetary. Ratio control is stable, and can be actuated down the center line of the transmission, which again is similar to the proven planetary transmission. Part shapes are simple and relatively easy to manufacture, and in most applications, there is no need for power-robbing, high-pressure hydraulics. The CVPT reduces energy consumption, such as fuel, through its seamless speed changing characteristics, allowing the power input such as a gasoline engine to operate in its most efficient speed range. Overall, the CVPT’s mechanical and manufacturing characteristics improve performance and reliability while reducing costs over traditional CVTs and stepped transmissions.

WORKING MECHANISM
CVP transmission uses a set of rotating and tilting balls positioned between the input and output components of a transmission that tilt to vary the speed of the transmission. Tilting the balls changes their contact diameters and varies the speed ratio. As a result, the CVPT offers seamless and continuous transition to any ratio within its range, thus maximizing overall power train efficiency, with no jarring or shocks from the shifting process, and improving acceleration, performance and overall vehicle efficiency over conventional transmissions. When compared to traditional continuously variable transmissions (CVTs), the CVPT is less complex, has considerably fewer parts, offers more stable control and scalability across product lines, is better packaged, and is less expensive to manufacture and assemble.

Fabrication and Analysis Of A Continuously Variable Planetary Transmission System

DIFFERENT PARTS OF CVPT
The tilting of balls can be done manually and automatically.We are making it automatic for this we have the following parts.
• Hub.
• Automatic shift actuator.
• Controller.
• A battery to run controller and shift actuator.
• Hall effect sensor.

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Fabrication and Analysis Of A Continuously Variable Planetary Transmission System