TRANSMISSION IN AUTOMOBILE AND DIRECT SHIFT GEARBOX AND STEERING MECHANISM

TRANSMISSION IN AUTOMOBILE

What is transmission?

Transmission is mechanism through which the engine torque is delivered to the the driving wheel so that vehicle can move on the road. The reciprocating action of piston moves the crankshaft, rotating a flywheel with the help of connecting rod. The circular motion of crankshaft is now to be transmitted to rear wheel. This is done by number of mechanical components which are as fallows:-

• Clutch 
• Gearbox 
• Universal joint 
• Propeller shaft or drive shaft 
• Differentials 
• Axle 
• Wheel 

The application of engine power to driving wheel with the help of above mentioned components is called POWER TRANSMISSION.

 
PURPOSE OF TRANSMISSION

• It enables the engine to get disconnected from driving wheels. 
• Enables the running engine to get connected to the driving wheel smoothly without any shock. 
• It enables reduction in the speed of engine in the ratio 4:1 in case of passenger car and greater ratios in case of trucks and lorries. 
• It enables driving wheel to be driven at various speed. 
• It enables turning and driving through angle 90 degrees 

DIFFERENT TYPE OF TRANSMISSION USED ARE

• Manual transmission uses gear shift stick for engagement or disengagement of gear. 
• Automatic transmission uses sensors, hydraulic system, mechatronic system. 
• Semi automatic transmission uses computer system that does clutch engagement and disengagement. 
• Continuously variable transmission is the most efficient transmission system of world presently.

CONTINUOUS VARIABLE TRANSMISSION

When other transmission system offer limited gear ratio the continuously variable transmission system offers unlimited gear ration between maximum and minimum limit. It is employed when power is basic necessity than fuel or economy.


MANUAL TRANSMISSION

                         FIG:- manual transmission



In manual transmission offers manual operation in shifting gears.It offers basically 4 speed up to 6 speed transmission. The clutch pedal is applied and gear is shifted upward or downward as per speed requirement.


DIRECT SHIFT GEAR BOX

A direct shift gear box is an automated gearbox system without clutch pedal. Apart from smooth driving experience it also provides lightning fast gear shift and hence reduces the time required to shift gear. The gear shifts without reducing the tractive power of engine. A direct shift gearbox requires or contains:-

• Mechatronic system
• Hydraulic system

Today technology is so sound that we have employed it for various human comforts. One of such achievement is sensors in automobiles. Sensors are automatic detectors which uses computerized assembly that automatically senses the gear shifting timing in accordance with speed of vehicle. It consists of basically three elements. These are primary sensor, transducer and transmitter. The sensing element senses the incoming signal and transducer converts one form of signal to another and transmitter amplifies the the converted signal to desired or standard form. Rather sensors and actuators senses the gear shift timing automatically as speed varies. Presently the transmission system in the world are dominated by Europe in manual transmission and by USA in automatic gearboxes.

On one hand where manual transmission offers robust and sporty characteristics, high efficiency and cheap cost on the other hand automatic gearbox offers smooth gear shift operation, high comfort zone to the driver and no interruption in tractive power. The dual clutch transmission is also called twin clutch transmission and DIRECT SHIFT GEARBOX. This transmission can deliver more power than traditional automatic transmission and manual system. It has electronically controlled dual clutch multiple shaft manual gearbox.

EXPLANATION

Two separate manual gearbox and clutches are contained within one housing and work as one unit. By using independent clutches DSG can achieve faster shift time of gear. Hall effect sensor senses the direction of shift of gear based on speed of automobile. This input, together with a sensor in gear box which senses the current speed and gear selected,feeds into central processing unit. This unit then determines the torque required and timing for smooth clutch engagement. Based of inputs from these two sensors and some other parameter like engine rotation, air conditioner, instruments (electronic) etc, proper gear shifting is done. The CPU activates a hydro-mechanical unit to either engage or disengage the clutch. The hydro-mechanical unit contains servomotor coupled to a gear arrangement for linear actuator with the help of break fluid from braking system. The system provides precise signal supply which is enough to carry out gear shifting process. The need of sensor is not only to measure speed but also position of teeth engaged in transmission power line and also checks weather throttle opening and closing is harder or softer.

ADVANTAGE

• High speed in short time.
• Faster gear shift operation as no need of application of clutch pedal.
• DCT offers gear up shift to mere 8 millisecond,hence most dynamic acceleration. 
• Better fuel economy (up to 15%).
• No loss in torque transmission from engine to driving wheel.

DISADVANTAGE

• Cost increases as automated components are used
• Mechatronic parts are susceptible to damage, hence more error prone.

APPLICATION

• Buggati
• Audi A4, A6
• BMW X1

            
STEERING MECHANISM

                                   FIG:-STEERING

A car without steering is just like man without hand. It is very necessary to guide or roll the car in desired direction, this is accomplished by steering system. No automobile can exist without steering mechanism. Some automobile are provides left hand drive and some right hand drive yet their mechanism are same.

Different types of linkages are there in steering mechanism which makes steering possible and smooth

PURPOSE OF STEERING:-

The main purpose of steering mechanism is transform the rotary motion of steering wheel (in cockpit) to angular movement of wheels. To provide ease in driving or rolling the automobile. Less human effort to steer the automobile while running. For driving stability and reducing tyre wear.

OPERATION:-

The pit arm is present between steering box and link rod.
Link rod connects to the steering arm with the help of ball joint. Tie rod is connected with tie rod arm with ball joint. This tie rod is attached to the stub of wheels, on which wheels are attached. The steering gear provides mechanical advantage, reducing human effort to steer automobile.