AUTOMOBILE GEAR BOX

A automobile gear box transmits power from the engine to the wheels, adjusting torque and speed. Specifically an automobile gear box adjust the engine torque and speed to suit driving conditions, enables reverse motion and disconnects the engine from the wheels.

There are several types of automobile gear box and they are; manual transmission (MT), conventional automatic transmission (AT/torque converter), continuously variable transmission (CVT), dual clutch transmission (DCT/DSG) and automated manual transmission (AMT/electro-hydraulic MT) gear box.

Manual transmission (MT) uses a clutch pedal and a gear level to manually select gear ratios via synchromesh gears and a lay shaft arrangement. Example of manual transmission gear box automobiles includes; Honda civic Si (6-speed MT), Mazda MX-5 Miata, Porsche 911GT3 etc.

Conventional automatic transmission (AT/torque converter) uses a hydraulic torque converter instead of a clutch with planetary gear sets and electronically controlled clutch packs to shift automatically through typically 6-10 speeds. Example of conventional automatic transmission automobiles include; ZF8HP (BMW, Audi, RAM), GM10L80, Toyota A960 etc.

Continuously variable transmission (CVT) uses two variable diameter pulleys connected by a steel belt or chain. There are no discrete gear steps, the ratio changes seamlessly across an infinite range. Example of continuously variable transmission automobile vehicles includes; Nissan xtronic CVT, Honda earth dreams CVT, Subaru Lineartronic etc.

Dual-clutch transmission (DCT/DSG) uses two separate clutches, one for odd gears, one for even gears.

The next gear is pre-selected while the current gear is engaged, enabling extremely fast shifts (often under 100 milliseconds). Examples of dual-clutch transmission gear box automobile vehicles include; Volkswagen DSG, Porsche PDK, Ford power shift, BMW M DCT etc.

Automated manual transmission (AMT/electro-hydraulic MT) is a conventional manual gear box with an electronic/hydraulic actuator replacing the manual clutch and gear lever. Shifts are automated but the mechanical basis is manual. Examples of automated manual transmission gear box automobile vehicles include; Maruti Suzuki AMT (India), Fiat Dualogic, early Ferrari F1 paddle shift etc.

The advantages of automobile gear box are; allows the engine to operate within its optimal power band across varying speeds. Multiples engine torque for better acceleration and load handling and also significantly improve fuel economy. It enables smooth power delivery at both low and high speeds. It acts as a buffer between the engine and the drive train reducing shock loads thereby extending the life of the engine.

The disadvantages of automobile gear box are; it is complex, requiring precise manufacturing tolerances and are expensive to produce and maintain. It has multiple potential failure points such as gear bearings, seals, clutches, solenoids etc. its repair and replacement cost is very high and specialized knowledge is required for servicing. All gear boxes introduces some power loss through friction and fluid drag. It adds additional weight to overall vehicle mass and fuel consumption. It requires frequent servicing, especially as regards transmission fluid periodic replacement.

Automobile gear box find application in the following; passenger cars, sports and performance cars, heavy commercial trucks, buses and public transport vehicles, agricultural machinery vehicles, racing and motor sport vehicles, marine vessels, electric and hybrid vehicles etc.

The future of automobile gear box depends on the advances and development of the following technologies; wider adoption of 8-10 speed automatics and DCTs for better efficiency. AI-powered predictive shifting using GPS and traffic data. Implementation of 48V mild hybrid integration into conventional gear boxes. Shift by wire replacing all mechanical linkages. Fully integrated motor gear box units (e-axles) becoming mainstream. Intelligent power management system replacing the mechanical concept of gearing and the gear box function absorbed into broader vehicle energy management software.

 

SOURCES:

• Manual gear box design by Alec Stokes.
• Automotive transmissions: fundamentals, selection, design and applications by Harald Naunheimer Bernd Bertsche, Joachim Pyborz and Wolfgang Novak.
• Gear handbook: the design, manufacture and application of gears by Darle W. Dudley.
• Automobile mechanical and electrical systems by Tom Denton.
• Automotive engineering fundamentals by Richard Stone and Jeffrey K. Ball.