ABSTRACT

The duty of this design is to design a FR type manual transmission used

in the saloon,It’s the countershaft-type transmission gearbox.This

transmission has two prominent merits: Firstly,the transmission efficiency

of the direct drive keeps off high, the attrition and the noise are also

slightest;Secondly ,it’s allowed to obtain in the biger gear ratio of the

first gear when the center distance is smaller.

According to the contour,track，wheel base，the smallest ground

clearance,the smallest turning radium,the vehicles weight, the all-up

weight as well as the highest speed and so on, union the choosing engine

model we can obtain the important parameters of the max power,the max torque,

the displacement and so on. According to the basic parameters of the certain

saloon,choose the suitable final drive ratio.According to the above

parameters,combining the knowledge of automobile design, automobile theory,

machine design and so on, calculate the correlated parameters of the gearbox

and proof the rationality of the design.

Its function is:①Changing gear ratio,expanding the torque of the

driving wheel and the range of the rotational speed,to adapt the travel

condition which frequently changes, like start, acceleration, climbing and

so on, simultaneously causes the engine to work under the advantageous

operating mode;②Under the premise of the invariable rotation, enables the

automobile to travel back;③Using neutral, severances the power

transmission, to make the engine start, idle, and is advantageous for the

engine to shift gears or to carry on the dynamic output. This gearbox has

five (including over drive—fifth gear) and a reverse gear, and through the

inertial type of synchronizer to realize shift gears.

KEY WORDS：transmission, inertial type of synchronizer,gear ratio,

countershaft,second axis, gear

目 录