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Almost everyone probably remembers the first independent attempt to move off the car with a manual gearbox. The left leg is angry at the right, she answers the same. The motor stalls or jerks you forward. It’s really fun to get started. It is just as fun to learn to ride at a very low speed: you just want to press down the clutch pedal, not paying attention to the instructor's discontent and the smell of burning pads. And what a thrill after all this seems to be the opening: the pedals in the car may not be three, but only two … And the motor will not stall, no matter how inept your right foot is.
How is an engine that rotates relentlessly connected to wheels motionless if the car is in front of a traffic light? Why doesn’t it stall and burn nothing? An automatic transmission is a rather complicated device, but a simple experiment will help clarify something.
We formulate the problem scientifically: it is required to transfer the moment from a rotating shaft to a fixed one without mechanically connecting them! The solution is in the photo. We put two fans against each other: the first depicts the crankshaft of the engine, the second - the gearbox shaft. The first one is plugged in: the blades are spinning, they create a pressure of air - and now the second impeller has set in motion! And her energy can already be used. If you brake the blades (take care of your fingers!) Of the slave device, the lead fan will not react to this in any way and will continue to rotate. That, in fact, is all.
A real automatic transmission is much more complicated, but the moment from the engine is transmitted to it in a similar way. The impeller on the crankshaft acts as a pump creating a stream of special oil, the blades of the driven “fan” work like a turbine. The oil is driven in a circle, returning part of the energy back to the pump. The whole structure took the shape of a donut - it is installed between the engine and the gearbox itself with planetary gear rows. The energy is transferred by the flow of the working fluid, which is discarded from the pump blades to the turbine blades.
In practice, the bagel has been improved (and complicated!) So much that it has turned from a fluid coupling (such as stood at ZIM, for example) into a torque converter. Here, between the pump and turbine wheels, there is another - the so-called reactor, connected to the pump wheel through an overrunning clutch. With a large difference in the speed of the pump and the turbine, the reactor is blocked - then more liquid enters the pump wheel, the torque increases approximately threefold under heavy load.
