Three basic types of transmission

The transmission (or gearbox) transfers power from the engine to the driveshaft. That causes axles to rotate and turn the wheels. The transmission usually is located just behind the engine, although some automobiles are designed with a gearbox mounted on the rear axle. There are three basic transmission types: manual, automatic, and continuously variable (CVT).

A manual transmission has a gearbox from which the driver selects specific gears depending on road speed and engine load. Higher gears permit the car to travel faster, while low gears provide more power for starting a car from a standstill and for climbing hills. Gears are selected with a shift lever located on the floor next to the driver or on the steering column. The driver presses on the clutch to disengage the transmission from the engine to permit a change of gears. The clutch disk attaches to the transmission’s input shaft. It presses against a circular plate attached to the engine’s flywheel. When the driver presses down on the clutch pedal to shift gears, a mechanical lever called a clutch fork and a device called a throwout bearing separate the two disks. Releasing the clutch pedal presses the two disks together, transferring torque from the engine to the transmission.

An automatic transmission is one of the key components of an automobile. It selects gears itself according to road conditions and the amount of load on the engine. Instead of a manual clutch, automatic transmissions use a hydraulic torque converter to transfer engine power to the transmission. Located just behind the engine, the transmission changes the speed and power ratios between the engine and the driving wheels of a vehicle.

Instead of making distinct changes from one gear to the next, a continuously variable transmission (CVT) uses belts and pulleys to smoothly slide the gear ratio up or down. Continuously variable transmissions appeared on machinery during the 19th century and on a few small-engine automobiles as early as 1900. The transmission keeps the engine running at its most efficient speed by more precisely matching the gear ratio to the situation. Commercial applications have been limited to small engines.

Thus, nowadays cars use only two types of the transmission: an automatic transmission and a manual one.

ANSWER THE QUESTIONS:

1. How many types of transmission do you know? 2. Which one is commonly abbreviated “AT”? 3. How does the manual transmission work? 4. How does the automatic transmission work? 5. Why do you think CVT are not so popular today?

Дата добавления: 2015-07-15