A car’s transmission is what moves power from the engine to the wheels, allowing the car to move. The gear, the ratio between the crankshaft and the driveshaft speeds, determines how much energy is transferred to the wheels. Each transmission system achieves this ratio differently.
In this article, we’ll discuss whether the continuously variable transmission (CVT) or an automatic transmission is better at selecting gears.
An automatic transmission uses hydraulic power to shift the teeth of the gears without a driver’s input. It converts energy into transmission fluids that spin the car’s central shaft via a torque converter.
Whereas a manual transmission lets the driver change gears by actively engaging/disengaging the clutch, the torque converter in an automatic transmission does this autonomously.
The CVT is a type of automatic transmission. Pioneered by Leonardo da Vinci some 500 years ago and realized by Subaru in 1989, CVTs drive through a spectrum of gear ratios using one of three methods.
The pulley-based CVT has three main parts:
Each pulley has two cones sliding along a connecting groove. The belt rides along this groove and connects the input to the output pulley. The pitch radius is the distance between the centre of the pulley and where the belt contacts the groove.
When the cones come closer, the belt rides higher in the groove at a larger pitch radius.
As one pitch radius increases, the other shrinks. The belt spins along a variable-length groove so there is an infinite combination of input-output radii. The result is a fluid ratio of gears at each speed.
Toroidal CVTs use two discs and rollers to transfer energy between the engine and wheels. Speed increases when the rollers touch the input disc near its rim. Deceleration happens when it contacts the input disc near the centre.
In a hydrostatic CVT, rotational energy from the engine reaches a hydrostatic pump on the input side. The pump converts this to a fluid flow that transmits to the output pump.
Here, it converts into a rotational flow to move the driveshaft at desired speeds.
Here are some examples of the best CVT cars you can buy:
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