Pic. 12.0. iB5 gearbox in section: 1 - gearbox input shaft; 2 – a secondary shaft of a transmission; 3 - drive shaft; 4 - gearshift lever; 5 – draft of a gear change; 6 - hinge of equal angular velocities; 8 - shift fork; 9 - reverse drive gear; 10 - clutch housing
The transmission consists of a clutch, gearbox and final drive. The amount of force transmitted to the drive wheels depends on the engine model. It should be remembered that each engine operates in a certain range of crankshaft speeds. In order for the car to always develop sufficient traction when accelerating and climbing, it is equipped with a fully synchronized five-speed gearbox. Traction is changed by shifting into different gears. In combination with the Zetec 1.25i engine, Ford also offers a continuously variable automatic transmission (STX).
Torque transmission
The engine develops maximum torque only in a certain range of crankshaft speeds. The gearbox converts the torque transmitted from the engine in magnitude and direction. This is necessary to ensure optimal speed, good vehicle flotation, the most economical operation of the engine and reversing of the vehicle. In order to match the relatively high engine speed with the low wheel speed when starting the vehicle, the first gear with the maximum gear ratio is used. When turning on the fourth and fifth gears, the situation is just the opposite: in both gears, «overdrive», to keep the vehicle moving at maximum speed.
In addition, the gearbox separates the engine and transmission when the vehicle is stopped and parked, and when it coasts with the engine running.
Purpose of the clutch
The clutch is located between the engine and the gearbox and is designed to briefly disconnect and smoothly connect the crankshaft of the engine and the input shaft of the gearbox when starting the car from a stop and while driving during gear changes without noise and risk of damage to parts.
CTX stepless automatic transmissions are also installed on Fiesta cars. The role of the clutch is performed by the torque converter. It synchronizes timing differences in speed. In the Fiesta CTX, you do not need to manually change gears while driving - the automation will do it all for you.
Pic. 12.1. Fiesta car clutch: 1 - flywheel; 2 – a conducted disk of coupling; 3 - clutch pressure plate with diaphragm spring
On all Fiesta car models, a single-disk dry clutch is installed, which consists of a flywheel 1 (pic. 12.1), driven 2 and pressure 3 clutch discs, central diaphragm spring and casing.
Main gear functions
The main gear is the last transmission link between the engine and the drive wheels. Its task is to reduce the speed transmitted from the gearbox in order to increase torque and simultaneously distribute it between the drive wheels.
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