DIRECT SHIFT GEARBOX (DSG)

VII SEMESTER SEMINAR REPORT

ME 1780 – SEMINAR

by

ABHAY GUPTA (159106001)

Under the guidance of

Mr. SUMIT TANEJA & Dr. ASHISH GOYAL

DEPARTMENT OF MECHANICAL
ENGINEERING (SAMM)
MANIPAL UNIVERSITY JAIPUR
DEHMI KALAN, JAIPUR – 303007.

2019-20

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 CERTIFICATE

This is to certify that the seminar entitled “DIGITAL SHIFTGEAR BOX (DSG)” is a bona
fide record of the major project done by ABHAY GUPTA (159106001), under my
supervision and guidance, in partial fulfillment of the requirements to complete the course
ME1780/Seminar of Mechanical Engineering from Manipal University Jaipur for the year
2019-20.

Mr. SUMIT TANEJA

(Guide)

Dept. of Mechanical Engineering

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 ACKNOWLEDGEMENT

I would like to express my Gratitude towards my guide, Mr. Sumit Taneja and Dr. Ashish
Goyal, without whose support, this project would have been a complete failure.
I would also like to thank other concerned faculties that supported me throughout the
project and helped me achieve this goal.

ABHAY GUPTA

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 ABSTRACT

The Direct Shift Gear Transmission (DSG) also known as Dual Clutch Transmission
(DCT) or twin-clutch transmission, is an automated transmission that can change gears
faster than any other geared transmission. Dual clutch transmissions deliver more power
and better control than a traditional automatic transmission and faster performance than a
manual transmission. Modern DSG automatic gearboxes use a pair of clutches in place of
a single unit to help you change gear faster than a traditional manual or automatic
alternative. Cars with DSG gearboxes don’t feature a clutch pedal and are controlled in
exactly the same way as a conventional automatic. Direct Shift Gear transmission (DSG)
also called as Dual Clutch Transmissions (DCTs) are providing the full shift comfort of
traditional step automatics but offer significantly improved full efficiency and
performance. Fuel efficiency increased by 15% compared to planetary-ATs, the DCTs are
the first automatics to provide better values than manual transmissions. Higher top speed
and, more important in everyday driving, better acceleration compared to planetary-ATs
and CVTs are additional benefits.

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 CONTENTS
TITLE PAGE NO.

1. INTRODUCTION
1.1. Introduction 6

2. CVT THEORY AND DESIGN

2.1 Push Belt 7
2.2 Toroidal Traction-Drive 8
2.3 Variable Diameter Elastomer Belt 8
2.4 Other CVT Varieties 9

3. RESEARCH AND DEVELOPMENT

5.1 New CVT Research 10
5.2 Future Prospects for CVTs 12
5.3 CVTs & Hybrid Electric Vehicles 14

4. OTHER APPLICATIONS 15
5. ADVANTAGES 16
6. DISADVANTAGES 17
7. CONCLUSION 18

REFERENCES 19

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 1. INTRODUCTION

Most people know that cars come with two basic transmission types: manuals, which
require that the driver change gears by depressing a clutch pedal and using a stick shift,
and automatics, which do all of the shifting work for drivers using clutches, a torque
converter and sets of planetary gears. But there's also something in between that offers
the best of both worlds -- the dual clutch transmission, also called the semi-automatic
transmission, the automated manual transmission. Despite the incredible development
and investment costs required to launch a new automatic transmission, it is the unit in the
power train that has gone through the most design innovations in recent years. An
important aim was to significantly reduce fuel consumption in automatic vehicles.

Fig-1: DSG Transmission

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 2. CVT THEORY & DESIGN

Today’s automobiles almost exclusively use either a conventional manual or automatic

transmission with “multiple planetary gears sets that use integral clutches and bands to
achieve discrete gear ratios”. A typical automatic use four or five such Years, while a
manual normally employs five or six. The continuously variable transmission replaces
discrete gear ratios with infinitely adjustable gearing through one of several basic CVT
designs.

Push Belt

This most common type of CVT uses segmented steel blocks stacked on a steel ribbon, as
shown in Figure (1). This belt transmits power between two conical pulleys, or sheaves,
one fixed and one movable. With a belt drive:

In essence, a sensor reads the engine output and then electronically increases or decreases
the distance between pulleys, and thus the tension of the drive belt. The continuously
changing distance between the pulleys—their ratio to one another—is analogous to
shifting gears. Push-belt CVTs were first developed decades ago, but new advances in
belt design have recently drawn the attention of automakers worldwide.

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Toroidal Traction-Drive

These transmissions use the high shear strength of viscous fluids to transmit torque
between an input torus and an output torus. As the movable torus slides linearly, the
angle of a roller changes relative to shaft position, as seen in Figure (2). This results in a
change in gear ratio.

Variable Diameter Elastomer Belt

This type of CVT, as represented in Figure (2), uses a flat, flexible belt mounted on
movable supports. These supports can change radius and thus gear ratio. However, the
supports separate at high gear ratios to form a discontinuous gear path, as seen in Figure
(3). This can lead to the problems with creep and slip that have plagued CVTs for years.

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This inherent flaw has directed research and development toward push belt CVTs.

Other CVT Varieties

Several other types of CVTs have been developed over the course of automotive history,
but these have become less prominent than push belt and toroidal CVTs. A nutating
traction drive uses a pivoting, conical shaft to change “gears” in a CVT. As the cones
change angle, the inlet radius decreases while the outlet radius increases, or vice versa,
resulting in an infinitely variable gear ratio. A variable geometry CVT uses adjustable
planetary gear-sets to change gear ratios, but this is more akin to a flexible traditional
transmission than a conventional CVT.

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 3. RESEARCH & DEVELOPMENT

While IC development has slowed in recent years as automobile manufacturers devote

more resources to hybrid electric vehicles (HEVs) and fuel cell vehicles (FEVs), CVT
research and development is expanding quickly. Even U.S. automakers, who have lagged
in CVT research until recently, are unveiling new designs:

General Motors plans to implement metal-belt CVTs in some vehicles by 2002.

The Japanese and Germans continue to lead the way in CVT development. Nissan has
taken a dramatic step with its “Extroid” CVT, offered in the home-market Cedric and
Gloria luxury sedans. This toroidal CVT costs more than a conventional belt driven CVT,
but Nissan expects the extra cost to be absorbed by the luxury cars’ prices. The Extroid
uses a high viscosity fluid to transmit power between the disks and rollers, rather than
metal-to-metal contact. Coupled with a torque converter, this yield “exceptionally fast
ratio changes”. Most importantly, though, the Extroid is available with a turbocharged

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version of Nissan’s 3.0 litre V6 producing 285 lb-ft of torque; this is a new record for
CVT torque capacity.

Audi’s new CVT offers both better fuel mileage than a conventional automatic and better
acceleration than even a manual transmission. Moreover, Audi claims it can offer the
CVT at only a slight price increase. This so-called “multitronic” CVT uses an all-steel
link plate chain instead of a V-belt in order to handle up to 280 lb-ft of torque. In
addition, “Audi claims that the multitronic A6 accelerates from 0-100 km/h (0-62 mph)
1.3 s quicker than a geared automatic transmission and is 0.1 s quicker over the same
speed than an equivalent model with “optimum” use of a five-speed manual gearbox”. If
costs were sufficiently reduced, a transmission such as this could be used in almost any
automobile in the world.

Many small cars have used CVTs in recent years, and many more will use them in the
near future. Nissan, Honda, and Subaru currently use belt-drive CVTs developed with
Dutch company Van Doorne Transmissie (VDT) in some of their smaller cars. Suzuki

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and Daihatsu are jointly developing CVTs with Japanese company Aichi Machine, using
an aluminium/plastic composite belt reinforced with Aramid fibres. Their CVT uses an
auxiliary transmission for starts to avoid low-speed slip. After about 6 mph, the CVT
engages and operates as it normally would. “The auxiliary gear train’s direct coupling
ensures sufficiently brisk take off and initial acceleration”. However, Aichi’s CVT can
only handle 52 lb-ft of torque. This alone effectively negates its potential for the U.S.
market. Still, there are far more CVTs in production for 2000 than for 1999, and each
major automobile show brings more announcements for new CVTs.

New CVT Research

As recently as 1997, CVT research focused on the basic issues of drive belt design and
power transmission. Now, as belts by VDT and other companies become sufficiently
efficient, research focuses primarily on control and implementation of CVTs.

Nissan Motor Co. has been a leader in CVT research since the 1970s. A recent study
analysing the slip characteristics of a metal belt CVT resulted in a simulation method for
slip limits and torque capabilities of CVTs. This has led to a dramatic improvement in
drive belt technology, since CVTs can now be modelled and analysed with computer
simulations, resulting in faster development and more 8 efficient design. Nissan’s
research on the torque limits of belt-drive CVTs has also led to the use of torque
converters, which several companies have since implemented. The torque converter is
designed to allow “creep,” the slow speed at which automatic transmission cars drive
without driver-induced acceleration. The torque converter adds “improved creep
capability during idling for improved driveability at very low speeds and easy launch on
uphill grades”. Nissan’s Extroid uses such a torque converter for “smooth starting,
vibration suppression, and creep characteristics”.
CVT control has recently come to the forefront of research; even a mechanically perfect
CVT is worthless without an intelligent active control algorithm. Optimal CVT
performance demands integrated control, such as the system developed by Nissan to
“obtain the demanded drive torque with optimum fuel economy”. The control system

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determines the necessary CVT ratio based on a target torque, vehicle speed, and desired
fuel economy. Honda has also developed an integrated control algorithm for its CVTs,
considering not only the engine’s thermal efficiency but also work loss from drivetrain
accessories and the transmission itself. Testing of Honda’s algorithm with a prototype
vehicle resulted in a one percent fuel economy increase compared to a conventional
algorithm. While not a dramatic increase, Honda claims that its algorithm is
fundamentally sound, and thus will it become “one of the basic technologies for the next
generation’s powerplant control

Although CVTs are currently in production, many control issues still amount to a
“tremendous number of trials and errors”. One study focusing on numerical
representation of power transmission showed that “both block tilting and pulley
deformation meaningfully effected the pulley thrust ratio between the driving and the
driven pulleys”. Thus, the resultant model of CVT performance can be used in future
applications for transmission optimization. As more studies are conducted, fundamental
research such as this will become the legacy of CVT design, and research can become
more specialized as CVTs become more refined.
As CVTs move from research and development to assembly line, manufacturing research
becomes more important. CVTs require several crucial, high-tolerance components in
order to function efficiently; Honda studied one of these, the pulley piston, in 1998.
Honda found that prototype pistons “experienced a drastic thickness reduction (32% at
maximum) due to the conventional stretch forming method”. A four-step forming process
was developed to ensure “a greater and more uniform thickness increase” and thus
greater efficiency and performance. Moreover, work-hardening during the forming
process further increased the pulley piston’s strength.
Size and weight of CVTs has long been a concern, since conventional automatics weigh
far more than manual transmissions and CVTs outweigh automatics. Most cars equipped
with automatic transmissions have a curb weight between 50 and 150 pounds heavier
than the same cars with manual transmissions. To solve this problem, Audi is currently
developing magnesium gearbox housings, a first for cars in its class. This results in nearly
a 16-pound weight reduction over conventional automatics.

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Future Prospects for CVTs

Much of the existing literature is quick to admit that the automotive industry lacks a
broad knowledge base regarding CVTs. Whereas conventional transmissions have been
continuously refined and improved since the very start of the 20th century, CVT
development is only just beginning. As infrastructure is built up along with said
knowledge base, CVTs will become ever-more prominent in the automotive landscape.
Even today’s CVTs, which represent first-generation designs at best, outperform
conventional transmissions. Automakers who fail to develop CVTs now, while the field
is still in its infancy, risk being left behind as CVT development and implementation
continues its exponential growth.
Moreover, CVTs are do not fall exclusively in the realm of IC engines.

CVTs & Hybrid Electric Vehicles

While CVTs will help to prolong the viability of internal combustion engines, CVTs
themselves will certainly not fade if and when IC does. Several companies are currently
studying implementation of CVTs with HEVs. Nissan recently developed an HEV with
“fuel efficiency … more than double that of existing vehicles in the same class of driving
performance”. The electric motor avoids the low speed/ high torque problems often
associated with CVTs, through an innovative double-motor system. At low speeds:
A low-power traction motor is used as a substitute mechanism to accomplish the
functions of launch and forward/reverse shift. This has made it possible to discontinue
use of a torque converter as the launch element and a planetary gearset and wet multiplate
clutches as the shift mechanism.

Thus, use of a CVT in a HEV is optimal: the electric portion of the power system avoids
the low-speed problems of CVTs, while still retaining the fuel efficiency and power
transmission benefits at high speeds. Moreover, “the use of a CVT capable of handling
high engine torque allows the system to be applied to more powerful vehicles”.

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Obviously, automakers cannot develop individual transmissions for each car they sell;
rather, a few robust, versatile CVTs must be able to handle a wide range of vehicles.
Korean automaker Kia has proposed a rather novel approach to CVTs and their
application to hybrids. Kia recently tested a system where “the CVT allows the engine to
run at constant speed and the motor allows the engine to run at constant torque
independent of driving conditions”. Thus, both gasoline engine and electric motor always
run at their optimal speeds, and the CVT adjusts as needed to accelerate the vehicle. Kia
also presented a control system for this unified HEV/CVT combination that optimizes
fuel efficiency for the new configuration.

4. OTHER APPLICATIONS

 Tractors just as cars have the need for a flexible system to convey power from
their engine to their wheels. The C.V.T. will provide just this and at high fuel
savings with low atmospheric pollution.

 Golf Carts stand to benefit from the C.V.T. as well in the way electric cars do.
that is: Large range of speeds, longer driving range between charges, Fewer
batteries, lower maintenance cost, less weight.

 Ride on Lawn Mowers like small tractors are gas powered and contribute to the
air pollution problem. The C.V.T. approach can prevent ride-on to pollute the air
to the extend they currently do.

 Motorized Wheelchairs. Battery run, speed controlled by a rheostat. Going up a

ramp slowly, causes a drop-in power (when it's most needed). C.V.T. is a form of
transmission, lower speed means MORE POWER.

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  Bicycles. Ever try to shift gears while pedalling uphill? Good news; the KINESIS
C.V.T. will automatically select the appropriate for the situation "gear" ratio. No
hassle, no trouble. End of story.

 Power tools and household appliances, that vary from benchtop drills to wash
machines and blenders need to depart from the centuries old belt and pulley
configuration for smoother operation and more reliability.

 Industrial Equipment and production machinery often use either gears or

cumbersome belt and pulley configurations. C.V.T. can do away with all that and
additionally give them infinite ratios.

 Minimachines. Small devices that need to operate in a wide range of speeds, as

the need arises. Our unique design allows the production of an inexpensive
miniature C.V.T. to enable them does just that!

5. ADVANTAGES

 Better fuel consumption than a regular

automatic transmission as the CVT is able
to keep the car in its optimum power
range regardless of speed.

 There is improved acceleration due to the

lower power loss experienced.

 Stepless transmission.

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  It has the ability to allow the engine to rev almost immediately which delivers maximum
torque.

6. DISADVANTAGES

 Higher cost.

 Belt-driven CVTs (VDP system) have a limited amount of torque; however,

the technology is constantly being improved.

 Transmitting motion by friction causes greater wear

 Require special oil and other materials.

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 7. CONCLUSION

Today, only a handful of cars worldwide make use of CVTs, but the applications and
benefits of continuously variable transmissions can only increase based on today’s
research and development. As automakers continue to develop CVTs, more and more
vehicle lines will begin to use them. As development continues, fuel efficiency and
performance benefits will inevitably increase; this will lead to increased sales of CVT-
equipped vehicles. Increased sales will prompt further development and implementation,
and the cycle will repeat ad infinitum. Moreover, increasing development will foster
competition among manufacturers—automakers from Japan, Europe, and the U.S. are
already either using or developing CVTs—which will in turn lower manufacturing costs.
Any technology with inherent benefits will eventually reach fruition; the CVT has only
just begun to blossom.

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8. REFERENCES

 www.google.co.in
 www.wikipedia.org
 www.carflux.com
 https://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/cvt.html

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