What is an automobile gearbox?
An automobile gearbox is an assemblage of gears and shafts, which is used to control the output speed and torque of a machine/vehicle.
Using the gearbox, the power from the engine can be converted into different speed and torque combinations to fulfil the running requirements of the vehicle.
Need of automobile gearbox:
The engine or motor provides a fixed speed for a certain amount of power. If it is directly coupled to the output shaft, then it will give the fixed velocity to the vehicle.
In the case of a vehicle running on a straight road with a higher speed, it doesn’t require a higher amount of torque because of the momentum of the vehicle. It can run with less amount of torque.
In Another case, when the vehicle is climbing the heel, it needs a higher amount of torque.
Therefore, the power transmission depends upon the running condition of the vehicle. Also, the vehicle requires neutral gear to keep the engine in idle state.
Therefore, gearbox is necessary to control output speed & torque. As per the need of the vehicle, we can achieve different speeds or torque with the help of a gearbox.
It is located between the clutch & propeller shaft. It has N number of speed steps & one reverse step.
The gearbox works on the following principle:
If the smaller input gear meshes with the larger output gear, speed reduction occurs. Low speed and high torque is obtained at output shaft.
If a larger input gear meshes with a smaller output gear, high speed and low torque will be obtained at the output shaft.
Types of automobile gearbox:
The automobile gearbox or transmission are classified as: manual transmission, automatic transmission.
A) Manual Transmission:
In manual transmission, the driver has to shift the gears manually by using the gear shifter. The below figure shows the basic structure of the manual transmission gearbox.
It consists of following components:
Engine Shaft: The engine shaft is connected to the engine through clutch. The gear on engine shaft transfers the power to the gear on lay shaft.
Lay Shaft: Lay shafts has fixed gears on it. The lay shaft gets power from the engine shaft and transmits power further to the output shaft.
Output shaft: The gears on the output shaft meshes with the gears on lay shaft to obtain different gear ratios.
In case of sliding mesh gearbox, the output shaft gears continuously rotate with the output shaft while in other gearbox, the output shaft gears are mounted with bearings hence these gears rotates separately.
Following are the different types of manual transmission gearbox:
B) Automatic Transmission:
In automatic transmission, the shifting of gears occurs automatically. Following are the different types of automatic transmission systems.
- Continuously variable transmission (CVT)
- Epicyclic gear transmission with torque converter
Significance of gearbox:
Following are some significance of gearbox in automobile:
- It helps to control output torque.
- The output speed can be controlled.
- It helps to achieve neutral position.
- It can obtain reverse gear transmission.