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AUTOMATED MANUAL TRANSMISSIONIN NEW GENERATION VEHICLES

GUIDED BY-U PRAKASH

PRESENTED BY-

ALBERT AUGUSTY 105 U7

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Introduction

Transmission play an important role in the improvement in vehicle performance and fuel economy.

Two basic main function of transmission are-

Disconnect the engine from the drive while the car has stopped, thus allowing the engine to keep idling while the wheels aren’t.

Provide a range of gear ratios that allow quick acceleration from a stop.

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Automatic transmission control is one of the key elements for the improvement of vehicle safety, comfort and performance together with the reduction of fuel consumption and emission in modern vehicles.

Different approaches such as automatic,continuosly variable and automated manual transmission have been pursued.The AMT represents an important solution for the automobile industry.

Manual transmission has an overall efficiency of 96.2 % which is highest in all types. Belt driven CVT have overall efficiency of 84.6%. Automatic transmission has efficiency of 86% whereas automated manual transmission has efficiency par with manual transmission.

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AMT has the advantage of lower weight and higher efficiency compared with other automatic transmissions.

AMT is directly derived from manual transmission with the integration of servo-actuators into existing devices, thus the development and production costs are generally lower compared to other transmission technique.

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What is AMT(Working principle)AMT consists of a multi speed gearbox and a clutch both

equipped with electro hydraulic actuators controlled by an Electronic Control Unit(ECU).

The AMT can work in two different ways:

1)Semiautomatic-Where the gear shifting is requested by the driver by means of proper levers.

2)Fully automatic-Here the ECU attends to the selection of gears depending on various engine and driving conditions.

In both these situations, clutch and gearbox actuators must

be properly controlled in order to perform the gear shift.

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Automated manual transmission

Main components-

Clutch actuation system

Transmission actuation system

Electronic and transmission control unit

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Clutch actuation system

Automated manual transmission can be divided on the basic of the clutch used.

They are divided as single clutch and dual clutch automated manual transnission.

Single clutches were used in the earlier models, modern day vehicles make use of dual clutch automated manual transmission.

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Electro-hydraulically operated single clutch

When no external force is applied, clutch disks are pressed together by preload springs, in this way clutch is locked and engine torque can be transmitted.

Force applied to the piston is provided by an electro-hydraulic actuator.

To disengage the clutch, the hydraulic piston pushes the release bearing

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The figure shows electronically operated clutch actuator.

It makes use of the rotary movement of the electric motor which is transformed via a toothed gear segment into a linear movement.

This helps to open the clutch with the help of the release levers and release bearing.

This is an older, lurch prone and generally unpleasent, only smart forkwo and exotic cars use them.

Electronically operated clutch actuator

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Dual clutch automated manual transmission

Dual clutch transmission has two separate manual gearboxes contained within one housing and working as one unit.

Sophisticated electronics and hydraulics control the clutches. One clutch would control the odd gears while the other control the even gears

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Transmission actuation systemThe actuator system can be divided into three main subsystems-

Pressure control valves

Pipelines

Hydraulic actuators

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Pressure control valvesThe servo valves used for gear engagement are single stage pressure control valve

Consists of a valve , diaphragm and a sensing unit which monitors the required pressure as required.

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Pipelines

Pipelines are long flexible pipes of about 0.7m length.

Pipelines are provided for connection between pressure control valve and hydraulic actuator.

Pipelines are used because the above connections may not be easy to make due to vehicle layout constraints

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Hydraulic actuators

The selection of the necessary gear ratios is performed by locking a set of gears to the shafts by means of electro-hydraulic actuator.

The actuator used comprises of a piston joined with a fork on which opposite axial forces can be applied by means of two distinct hydraulic circuit.

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The left and right movement corresponds to engaged odd and even gears respectively, while middle position corresponds to neutral.

Oil pressures on actuator chambers are controlled by means of two single stage pressure control valves connected to the actuator with two flexible pipelines.

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Electronic and transmission control unit

In this portion the automated manual transmission consists of a transmission control unit(TCU) and a elecronic control unit(ECU).

The transmission control unit receives input signals from various sensors like gear position sensor, clutch position sensor, brake position sensor, transmission output speed.

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It also collects vehicle related signals like torque requirement, engine speed and throttle position from ECU(Electronic control unit).

The TCU has a control strategy, which on receiving the input signals, generate the necessary output signal for the clutch actuator and gear shifting actuator.

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Recent developments

Zero shift automated manual transmission allows a manual transmission to shift gears in zero seconds.

It is easy to manufacture and is cost effective compared to alternative automatic transmission.

Compared to existing AMT, zero shift provides uninterrupted torque path from the engine to the vehicle which allows a seamless gearshift

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Recent developments (cont’d)

Shift control algorithm without clutch operation in automated manual transmission in hybrid electric vehicles.

Shift control without clutch operation is possible because both engine and motor can control the speed of input shaft.

The shift control algorithm is said to increase the shift quality of vehicle and prolongs the life of the clutch.

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Conclusion

An optimum control strategy is the key to successful working of AMT.

AMT allows to provide driving comfort and gear shift quality.

AMT has the advantage of lower weight and higher efficiency with respect to other automatic transmission.

Production cost is generally lower compared to other transmission techniques.

AMT has proved to provide 10% decrease in fuel consumption and also decrease in CO2 emissions.

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ReferenceLucente, Marcello Montanare, Carlo Rossi, G. Lucente, ‘Modeling of an

automated manual transmission system’,Mecatronics,volume17(2007),pp.73-91.

R.P.G Heath and A.J. Child, ‘Zeroshift Automated Manual Transmission(AMT)’ ,SAE Paper No. 2007-26-061,(2007),pp.693-696,2007.

Liao Chenglin, Zhang Junzhi, Zhu Haitao, ‘ A Study of Shift Control Algorithm without Clutch Operation for Automated Manual Transmission in the Parallel Hybrid Electric Vehicle’ ,SAE of China, Fiesta , World Automobile Congress, Barcelona, February 13. 2004.

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