Torque converter is used to transfer power from the engine to the transmission input shaft. It acts as an automatic clutch to engage and disengage the engine and the transmission. It allows the engine to run idle when the vehicle is standing still.The torque converter is mounted on the transmission input shaft and connected with the flywheel of the engine.
Functions of torque converter
It converts and transmits the engine torque.
It facilitates smooth, comfortable starting.
It damps the engine torsional vibrations.
A simple planetary gear set consists of
Sun gear
Planet gears
Ring gear
Planet carrier
The planet gears are supported with their axis in the planet carrier. The planet gears circulate on the internal teeth of the ring gear and the outer teeth of the sun gear. All gears are constantly meshed. The sun gear, planet carrier and ring gear are driven and braked. Output is effect1ive through the ring gear or the planet carrier. Different gear ratios are achieved by this planetary gear set.
Three different forward gear ratios and one reverse gear radio are possible in this type. The drive of the planetary gears is set through the multi plate clutch. Different gear ratios and directional change are obtained by braking anyone of the component.
A Continuously Variable Transmission is a type of automatic transmission that provides more useable power, better fuel economy and smoother driving experience than a traditional automatic transmission.
Conventional automatic transmissions use a set of gears that provided a given number of ratios (or speeds).The transmission shifts gears to provide the most appropriate ratio for a given situation: Lowest gears for starting out, middle gears for acceleration and passing, and higher gears for fuel efficient cruising.
The CVT replaces the gears with two variable – diameter pulleys , each shaped like a pair of opposing cones, with a metal belt or chain running between them. One pulley is connected to the engine (input shaft), the other to the drivewheels (output shaft). The halves of each pulley are moveable; as the pulley, effectively making the pulley's diameter larger.
Changing the diameter of the pulleys varies the transmission’s ratio (the number of times the output shaft spins for each revolution of the engine), in the same way that a 10-speed bike routes the chain over larger or smaller gears to change the ratio. Making the input pulley smaller and the output pulley larger gives a low ratio (a large number of engine revolutions producing a small number of output revolutions) for better low- speed acceleration. As the car accelerates , the pulleys vary their diameter to lower the engine speed as car speed rises. This is the same thing a conventional transmission does, but instead of changing the ratio in stages by shifting gears, the CVT continuously varies the ratio – hence its name.