I just asked the web if
@RonD is right.
Guess What?
He is
Copied from
http://www.winnipegsynthetics.ca/articles/cvt-and-ecvt.html
How Transmissions Are Changing
CVTs take a different approach to managing rpm. Instead of gears, the most common CVTs use a metal belt or chain running between two pulleys. These pulleys are designed to spread open or squeeze closed under hydraulic pressure, forcing the belt or chain to ride higher or lower in them. The advantage of this system is the vehicle’s computer can quickly and continuously adjust the pulleys to whatever ratio is required for peak efficiency because it isn’t physically limited by gears.
When driving a CVT-equipped vehicle the driver pushes on the gas pedal and the CVT adjusts to keep the engine at its most efficient rpm through the entire acceleration process. There are no bumps or rpm increases felt by the driver. This is even true when climbing a grade. The engine stays at its most efficient rpm and the CVT adjusts to allow the car to get over the hill.
The eCVT found on the Toyota Prius and other hybrids differs from CVTs found in other vehicles, such as the 2013 Nissan Altima or 2012 Scion iQ, because it does not use a belt or chain connected to a pair of variable pulleys.
Instead, an eCVT uses electric motor/ generators to control the speeds of planetary gearset components. This allows the eCVT to continuously change the gear ratio, keeping the engine’s rpm in the sweet spot. Just like when driving other CVT-equipped vehicles, drivers of vehicles with eCVTs don’t feel the step change common to traditional automatic transmissions, yet the mechanisms (planetary gears) to achieve acceleration are largely the same.