A gearbox is a transmission device which is used between engine’s output shaft and the final drive in order to transfer required torque and power to the wheels of the vehicle, a gearbox consists of the set of gears( i.e. spur, helical, bevel, worm and epicycle depending on the types of gearbox used )which are arranged in a special fashion in order to provide required gear or speed ratios to the final drive of the vehicle, a gearbox usually comes with the specification i.e.5-speed transmission with a reverse, and an automatic transmission.
Why do we need Gearbox?
When a car starts ,the torque provided by the engine output shaft is not enough to overcome the weight of the vehicle which make it difficult to move the car initially, so to solve this problem a gearbox is required which can provide high torque initially in order to move the vehicle.
When we go to the hill station it is essential that the vehicle should be equipped with device that can provide a wide range of high torque, to fulfill this need a gearbox is required so that a vehicle can go to the hills.
When a vehicle is going at high speed, torque is not at all effective so a gearbox is needed that can also provide a high speed low torque ratio so that vehicle can maintain the high speed.
In a race car continuous change of gears from high torque to high speed is there due to the curvy track so the race car should be equipped with a suitable gearbox so that shifting of gears is smooth and easy.
Main Parts of a Gearbox-
1. Main Shaft
It is the shaft used as an output shaft in a gearbox, this shaft is usually kept parallel to the lay shaft and in front of the clutch shaft or engine output shaft, the change of gear usually occur through this shaft as it is usually connected to gear lever.
2. Clutch Shaft
It is the shaft which carries the engine output to the gearbox, the engaging and disengaging of the engine output occurs with the help of clutch.
3. Lay Shaft or Counter Shaft
It is the shaft through which the output of the engine is transferred to the main shaft by the continuous meshing of a gear on the lay shaft to the gear on the clutch shaft.
4. Gears
They are the connecting circles with teeth that rotates and meshes with another gear on the different shaft in order to transmit the circular motion between 2 different shafts, they can be -spur gear, helical gear, bevel gear and worm gear.
5. Synchromesh Devices
They are the special devices used in modern gearbox (synchromesh gearbox) that makes the shifting of gears smooth by bringing the speed of main-shaft, lay-shaft and clutch-shaft at the same, they doesn’t have to slide over the shaft for the shifting of the gear.
6. Dog Clutches
They were used in old gear boxes like constant mesh gearbox, to avoid the sliding of gear over the shaft for meshing or shifting. As they slide over the shaft in order to shift a gear.
7. Gear lever
It is the lever operated by the driver to change or shift the gear, the movement of the lever is designed in a particular fashion.
Types of Gearbox-
1. Manual Transmission
A manual transmission is the types of gearbox used in most of the vehicle on the road due to its low cost. It is the type of gearbox in which there are limited gear or speed ratios i.e. maximum of 6- speed and 1- reverse is there, and the shifting of gears is a manual task performs by the driver by pushing or pulling the gear lever in predefined fashion. Manual transmission always requires the use of clutch.
Types of manual transmission used since the introduction of the gearbox are:
(i) Sliding Mesh Gearbox
(ii) Constant Mesh Gearbox
(iii) Synchromesh Gearbox
2. Automatic Transmission or Gearbox
It is used in high-end cars due to its high cost, in this types of gearbox infinite gear ratios can be obtained by just pressing the accelerator, the driver just need to select the mode of the drive i.e. forward or reverse, park, neutral, drive and sport, and the required gear ratios along with the timing of the meshing is obtained automatically. Automatic gearbox doesn’t require clutch pedal, so all the cars with automatic transmissions comes with only 2 pedals.
Types of automatic transmission used are-
(i) Epicyclic Gearbox
(ii) Hydraulic Torque Converter
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16 июл 2024
