1

MINOR PROJECT

ON

THE TOPIC

“TO STUDY THE DESIGN AND WORKING OF HYBRID VEHICLES”

UNDER THE GUIDANCE AND SUPERVISION OF

Prof. DALGOBIND MAHTO

SUBMITTED BY:

NAME COLLEGE (UNIV. ROLL NO.)

Ashish Sharma 3074008(22597)

Jayant Pathak 3074060(22649)

Asheesh Dev 3074073(22662)

Ankush Sharma 3074074(22663)

Ritesh Thakur 3074086(22675)

4th year (7th semester) Mechanical Engineering Department

GREEN HILLS ENGINEERING COLLEGE, KUMARHATTI,

SOLAN (H.P), INDIA

[2010]

2

3

4

MINOR PROJECT

ON

THE TOPIC

“TO STUDY THE DESIGN AND WORKING OF HYBRID VEHICLES”

UNDER THE GUIDANCE AND SUPERVISION OF

Prof. DALGOBIND MAHTO

SUBMITTED BY:

NAME COLLEGE (UNIV. ROLL NO.)

Ashish Sharma 3074008(22597)

Jayant Pathak 3074060(22649)

Asheesh Dev 3074073(22662)

Ankush Sharma 3074074(22663)

Ritesh Thakur 3074086(22675)

4th year (7th semester) Mechanical Engineering Department

GREEN HILLS ENGINEERING COLLEGE, KUMARHATTI,

SOLAN (H.P), INDIA

[2010]

5

STUDENT’S DECLARATION

I hereby, certify that the work, which is being presented in the Project Report, entitled “TO STUDY THE DESIGN AND WORKING OF HYBRID VEHICLES” in fulfillment of the requirement for the award of Degree of B. Tech in Mechanical Engineering , submitted in the Department of Mechanical Engineering of “Green Hills Engineering College, Kumarhatti, Solan”, Affiliated to Himachal Pradesh University, Shimla, India is an authentic record of my work under the supervision of Prof. Dalgobind Mahto and Mr. Amar Raj Singh Suri .The results embodied in this thesis have not been submitted by me or any body else to any other University or Institute for the award of any Degree or Diploma.

The Project Report contains my own work and it does not include any copyright material of any person or publication.

ASHISH SHARMA (22597) ANKUSH SHARMA(22663)

JAYANT PATHAK (22649) RITESH THAKUR(22675)

ASHEESH DEV SHARMA (22662)

CERTIFICATE

This is to certify that the above statement made by the student is correct to the best of

our knowledge

(GUIDES) (H.O.D.) Prof. D Mahto and Mr. A.R. S.Suri Prof.M.S.Sethi (G.H.E.C) (G.H.E.C)

(PRINCIPAL)

Dr.S.S.Sen

(G.H.E.C)

The Student has passed the viva-voce examination held on…… (Date)…… at Green Hills Engg.College ,Kumarhatti, Solan.

The Project Report is recommended for the award of B.Tech in Mechanical Engineering.

Internal Examiner External Examiner

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ACKNOWLEDGEMENT

The success of the work comprising professional intellect rests upon the

firm and steady shoulders of hard working men, who in their quest for

perfection strive untiringly to reach the pinnacle. We are greatly thankful

to such people involved directly or indirectly for their inspiration and

guidance.

We are thankful to Prof. Dalgobind Mahto and Mr. Amar Raj Singh

Suri of Mechanical Engineering Department of G.H.E.C, Solan for their

encouragement during this project and without whose guidance this

project would not have been completed.

Our sincere gratitude also goes to the Head of Mechanical Engineering

Department. Prof .M.S. Sethi for his valuable support throughout the

project work.

ASHISH SHARMA (22597)

JAYANT PATHAK (22649)

ASHEESH DEV SHARMA (22662)

ANKUSH SHARMA(22663)

RITESH THAKUR (22675)

7

Abstract:

A hybrid vehicle is the next technological innovation and step in the field of

Automobiles in the move to achieve greener emissions and better fuel consumption

albeit keeping the vehicles practical enough for consumer satisfaction.Using different

types of conventional and non-conventional power trains and drive trains, and

applying a combination of them to obtain a successful vehicle that can suitably behave

as a conventional vehicle summarizes the design and conceptualization of a hybrid

vehicle. Several varieties of conventional and non-conventional varieties of power

trains and drive trains have been discovered, experimented with and pros and cons

weighed upon to obtain optimum solutions. In our project, we have begun with

investigating the various alternatives for developing a hybrid vehicle. Each

component of such alternatives has been reviewed for various pros and cons. A case

study of the largest selling commercial hybrid vehicle the Toyota Prius has been done

for better understanding of practical hybrid technology design and implementation.

Once a suitable alternative was chosen, dynamics of the vehicle were estimated by

calculating and estimating the various requirements for an approximate vehicle. Based

on these calculations choices were made on the type of engine and transmissions

system to be used. A control system was also estimated based on these

approximations. Renderings were done on CATIA V5 and AutoCAD for chassis

estimation. Further work on the project shall include chassis design and design of

various other structural components. Also to be done would be the identification and

estimation of various accessories before we begin with our fabrication. Fabrication is

expected to be completed by the end of academic calendar 2010- 2011.

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Contents

Acknowledgement…………………………………………...……….………..6

Abstract……………………………………………………………….………..7

Chapter 1 – Introduction……………………………………………………….

………….10

1.1 Introduction

1.1.1Vehicles.................................................................................................10

1.1.2 Hybrid Vehicles....................................................................................10

1.1.3 Aims And Objectives...........................................................................12

1.1.4 Scope And Development......................................................................12

1.1.5 Salient Terms Associated with Hybrid Vehicles..................................13

1.1.6 Scope Of The Study.............................................................................14

1.1.7 Limitations Of The Study....................................................................14

Chapter 2 – LiteratureReview……………………………………..........……15

2.1 Electric Hybrids …………………………………………….............….15

2.1.1 Types Of Electric Hybrids..................................................................15 2.1.2 Pneumatic Hybrids..............................................................................19 2.1.3 Motors..................................................................................................27 2.1.4 Generators............................................................................................30 2.2. Case Study – Toyota Prius.....................................................................41

Chapter 3 –Discussion........................................................................................60

Chapter 4 – Conclusion......................................................................…………61

References………………………………………………............…...…………62

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List of figures

Fig.2.1-Series Hybrid Transmission.

Fig.2.2- Parallel Hybrid Transmission.

Fig.2.3- Power split Hybrid Transmission.

Fig.2.4- Air Motor Exploded View.

Fig.2.5-Working Mechanism of Air Motor.

Fig.2.6-Variation of torque Vs speed curve of air.

Fig.2.7- Modes of working of pneumatic engine.

Fig.2.8- Total pneumatic hybrid engine.

Fig.2.9- DC motors with shunt.

Fig.2.10- DC motors without shunt.

Fig.2.11- Brushless DC motor.

Fig.2.12- AC induction motor.

Fig.2.13- Exploded view of alternator.

Fig.2.14- Toyota hybrid transmission system.

Fig.2.15- Toyota hybrid theoretical model.

Fig.2.16- Toyota hybrid sattery pack.

Fig.2.17- Toyota hybrid transmission

Fig.2.18- Regenerative breaking.

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CHAPTER 1

INTRODUCTION

1.1 Introduction :

1.1.1 Vehicles:

A vehicle in a general manner means a mechanical system which has an

engine and is used to carry people or good from one destination to other. In modern

times vehicles play major role in accumulating various needs of human beings, which

results in violent consumption of energy resources causing the need of energy

efficient vehicles.

1.1.2 Hybrid Vehicles:

A hybrid vehicle is essentially aimed at negating the deficiencies of a

conventional vehicle and improving the mechanical efficiency of the vehicle through

the incorporation of several technologies. A conventional vehicle generally has a

specific range of characteristics both advantageous and disadvantageous. These

include a given range of torque output, speed variation, drivability, fuel efficiency,

emissions, and other factors gauging efficiency like the power-weight ratio, the power

to fuel/energy input ratio, mechanical efficiency, etc. In the current scenario of ever

growing demands expected out of an Automobile and the declining global resources

of fossil fuels, apart from the already alarming global warming, pollution and climate

change scenarios. It is expected out of an automobile to consume lesser fuel, emit

lesser, and produce more output while being more efficient and driveable. To achieve

this, which has been proved to be expensive or rather quite difficult and challenging

with a conventional vehicle, hybrid vehicles have been developed.

A hybrid vehicle, as the name suggests, utilizes a combination of one or more hybrid

power trains alongside a host of other technologies which eventually make it more

efficient while less fuel consuming and polluting in nature. A hybrid vehicle may use

a combination of power trains like gasoline-electric, gasoline-pneumatic, electric-

pneumatic, etc. The combination may be in a series or parallel or combined setup as is

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described below. The hybrid vehicles are essentially designed to tap and utilise all the

energy generated in the automobile and minimize wastage. The wastage of energy

during braking, idling and other conditions like coasting and during inefficient

running conditions of an automobile like low load and low torque conditions are all

tapped by a host of technologies like regenerative braking, start/stop technologies that

cut off fuel supply during idling/braking/non-throttle conditions, low drag body and

wheels, light weight composite construction, intelligent packing, solar roofs, etc.

The different types of hybrids as shall be illustrated further are described here under:

Series Hybrids –

A single power unit propels the vehicle. This power unit may obtain its

power through a major unit available separately and also through energy saved

up during braking/idling/coasting etc.

Parallel Hybrids –

A parallel hybrid has two or more propulsive units providing power to

the drivetrain separately at the same time so when one unit drives the wheels,

the other unit is generating energy constantly for storage and retrieval. Energy

saving measures are also adopted here.

Series Parallel Hybrids –

Both the power units may run the final drive train while in certain

specific driving conditions one of the power units may be entirely switched

off.

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1.1.3 Aims and Objectives:

Our aim with the project is to study, design, devise a hybrid vehicle by

researching at all the possible varieties and studying the pros and cons and arriving at

an appropriate solution with a hybrid vehicle that features a conventional powertrain

like an IC engine mated to a non-conventional power source like an electric

motor/pneumatic engine and achieve the above said efficiency factors and lesser

emissions and fuel consumption as compared to a conventional vehicle. We also aim

to fabricate a vehicle practical enough to be employed in places like Kumarhatti with

several scopes for modifications which could improve the vehicular factors mentioned

above.

Our idea is to primarily use an IC engine that allows us to keep the vehicle practical

for utility purposes while hybridising the final drive train using an electric motor or a

pneumatic motor.

All the features, available options and varieties are mentioned below in the literature

review and history. The available options are-

Gasoline Electric Hybrid – Series and Parallel

Gasoline Pneumatic Hybrid – Series and Parallel

Total Pneumatic Model

Apart from the above said options, we also aim at incorporating these technologies

which might be the general scopes for improvement in the vehicle that we initially

develop.

1.1.4 Scope for Development:

Regenerative Braking – Utilising the electric motor and reversing it when the

braking is done to act as a generator so that energy lost as heat during braking

could be tapped and resupplied as electrical energy to the motor.

Smooth flow Body Panels – Low Friction smooth flow body panels could be

obtained to cover the wheels, front and rear overhangs etc. These could be

made out of reinforced plastic to save weight.

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Start/Stop Functions – Electronic governing could be installed to use the

ECU to stop/start fuel control to the engine whenever necessary.

Solar Roof – The Roof of the passenger cabin could be made of a solar

photovoltaic panel to tap energy and store it in the reservoir for usage later.

Electronic Transmissions – An electronically handled transmission could be

installed with robots doing the gear changing operations saving time and fuel.

1.1.5 Salient terms associated with hybrid vehicles:

Following are the various terms associated with hybrid vehicles

HCV : Hybrid Electric Vehicles

ICE : Internal Combustion

IMA : Integrated Motor Assist

DC MOTORS : Direct Current Motors

BLDC : Brushless Direct Current Motors

AC : Alternating Current

DC : Direct Current

RPM : Revolution Per Minute

KM : Motor Constant

PCU : Power Control Unit

EGR : Exhaust Gasses Regulator

CD : Drag Co-efficient

EFI : Electronic Fuel Injection

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1.1.6 Scope of the study:

After studding the various aspects of hybrid vehicles and going through the

case study of Toyota Prius, we are now in a position for the following

Preparing the design.

Analyzing the various relations between the torque transmitted, power of

conventional engine and the electric system.

Developing a prototype of the electric hybrid vehicle using the above stated

design and analysis.

Performing various engine testing experiments on the prototype for checking

the affect of load variations on engine performance.

Checking the results obtained from the experiments, performed on the

prototype and their closeness with the theoretical study.

Hence checking the efficiency of hybrid vehicle by comparing it with non-

hybrid vehicles.

Checking for the failures obtained due to various factors such as toque

transmitted, power required and load variations under running conditions.

Finally making improvements on the prototype or modifying the prototype

from the results obtained above.

1.1.7 Limitations of the study:

In north India electric hybrid vehicles are not made, so we didn’t get any

practical knowledge of such vehicles.

Difficult to design the electric hybrid vehicle.

Complexity of drive trains.

Obtained data in active speech.

Difficult to get data for mathematical analysis.

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CHAPTER 2

LITERATURE REVIEW

Below is a brief insight into the three different powertrain possibilities and the models

currently being employed and their plausibility in terms of project realisation. The

respective pros/cons have also been studied.

2.1 Electric Hybrids:

A hybrid electric vehicle (HEV) combines a conventional internal combustion

engine (ICE) propulsion system with an electric propulsion system. The presence of

the electric powertrain is intended to achieve either better fuel economy than a

conventional vehicle, or better performance. A variety of types of HEV exist, and the

degree to which they function as EVs varies as well. The most common form of HEV

is the hybrid electric car, although hybrid electric trucks (pickups and tractors) also

exist. The better fuel efficiency and the better performance is the saving of the fuel

and less emissions from the car. Hybrid is a very bigger term and hybrid electric

vehicle is a part of development of the hybrid vehicles.

2.1.1 Types of electric hybrids:

Series Electric Hybrids.

Parallel Electric Hybrids.

Series Parallel Electric Hybrids.

2.1.1.1 Series Electric Hybrid:

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A series hybrid uses a gasoline or diesel ICE, coupled with a generator, to generate

electricity but not to drive the car. The engine can send the electric current directly to the

electric motor or charge a large battery that stores the electricity and delivers it to an

electric motor on-demand. The electric motor propels the vehicle, using its power to rotate a

driveshaft or a set of drive axles that turn the wheels Series-hybrid vehicles are driven only

by electric traction.

Fig. 2.1- Series Hybrid Transmission

Unlike internal combustion engines, electric motors are efficient with exceptionally

high power to weight ratios providing adequate torque over a wide speed range.

Unlike combustion engines electric motors matched to the vehicle and do not require

a transmission between the engine and wheels shifting torque ratios. Transmissions

add weight, bulk and sap power from the engine. Mechanical automatic shifting

transmissions can be very complex. The engine is typically smaller in a series

drivetrain because it only has to meet average driving power demands; the battery

pack is generally more powerful than the one in parallel hybrids in order to provide

remaining peak driving power needs. This larger battery and motor, along with the

generator, add to the cost, making series hybrids more expensive than parallel hybrids.

While the engine in a conventional vehicle is forced to operate inefficiently in order to

satisfy varying power demands of stop-and-go driving, series hybrids perform at their

best in such conditions. This means the engine is no longer subject to the widely

varying power demands experienced in stop-and-go driving and can instead operate in

a narrow power range at near optimum efficiency. This also eliminates the need for a

complicated multi-speed transmission and clutch.In short, in a series-hybrid electric

vehicle the vehicle is driven by electric motors with a generator set providing the

electric power.

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2.1.1.2 Parallel Electric Hybrid:

Parallel hybrid systems, which are most commonly produced at present, have

both an internal combustion engine (ICE) and an electric motor connected to a

mechanical transmission. Most designs combine a large electrical generator and a

motor into one unit, often located between the combustion engine and the

transmission, replacing both the conventional starter motor and the alternator. To store

power, a hybrid uses a large battery pack with a higher voltage than the normal

automotive 12 volts. Accessories such as power steering and air conditioning are

powered by electric motors instead of being attached to the combustion engine. This

allows efficiency gains as the accessories can run at a constant speed.

Parallel hybrids can be categorized by the way the two sources of power are

mechanically coupled. If they are joined at some axis truly in parallel, the speeds at

this axis must be identical and the supplied torques will be added together. Most

electric bicycles are of this type. When only one of the two sources is being used, the

other must either also rotate in an idling manner or be connected by a one-way clutch

or freewheel. With cars it is more usual to join the two sources through a differential

gear. Thus the torques supplied must be the same and the speeds add up, the exact

ratio depending on the differential characteristics.

Fig. 2.2 - Parallel Hybrid Transmission.

This is the technology in the Insight, Civic, and Accord hybrids from Honda. Honda

calls it their Integrated Motor Assist (IMA) technology. Parallel hybrids can use a

smaller battery pack and therefore rely mainly on regenerative braking to keep it

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recharged. However, when power demands are low, parallel hybrids also utilize the

drive motor as a generator for supplemental recharging, much like an alternator in

conventional cars.

Since, the engine is connected directly to the wheels in this setup, it eliminates the

inefficiency of converting mechanical power to electricity and back, which makes

these hybrids quite efficient on the highway. Yet the same direct connection between

the engine and the wheels that increases highway efficiency compared to a series

hybrid does reduce, but not eliminate, the city driving efficiency benefits (i.e. the

engine operates inefficiently in stop-and-go driving because it is forced to meet the

associated widely varying power demands).

Some up-and-coming hybrid models use a second electric motor to drive the rear

wheels, providing electronic all-wheel drive that can improve handling and driving in

bad weather conditions

2.1.1.3 Series Parallel Electric Hybrids:

The series parallel hybrid is a relatively newer concept and is introduced in

market recently in Toyota Prius. This drivetrain merges the advantages and

complications of the parallel and series drivetrains. By combining the two designs, the

engine can both drive the wheels directly (as in the parallel drivetrain) and be

effectively disconnected from the wheels so that only the electric motor powers the

wheels (as in the series drivetrain). As a result of this dual drivetrain, the engine

operates at near optimum efficiency. At lower speeds it operates more as a series

vehicle, while at high speeds, where the series drivetrain is less efficient, the engine

takes over and energy loss is minimized. This system incurs higher costs than a pure

parallel hybrid since it needs a generator, a larger battery pack, and more computing

power to control the dual system. However, the series/parallel drivetrain has the

potential to perform better than either of the systems alone.

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Fig.2.3 - Power split hybrid transmission

2.1.2 Pneumatic Hybrids:

One significant step towards hybridization of a vehicle could be the use of

pneumatic propulsion. Air motors or engines running on compressed air could be

extensively employed as propulsion devices. Essentially an air motor runs on the

simple principle of converting the energy stored as pressure in compressed air into

mechanical energy, specifically rotational energy. An air motor could be reciprocating

or rotary with the rotary type more efficient in terms of rotary speeds while the

reciprocating variety is more efficient in terms of extraction of energy from the

compressed air. An air motor is extensively employed for pumping air into deeply

hidden locations under the earth’s crust like mines and oil fields. This characteristic of

the pneumatic motor can be exploited by using it as a propellant in an automobile.

However, the efficiency of the pneumatic engine deems that the Automobile has to be

extremely light and mechanically efficient to extract any plausible power and torque

output from the air motor to the road wheels. However, this has not been achieved

quite practically as the automobile powered by a simple pneumatic motor had to

sacrifice body structure and strength for lightness which proved unsafe for mass

production and passenger transportation while the real world efficiency in terms of

driveability and speeds achievable as well as pulling power of the car in different

terrains has been quite unsatisfactory. Hence the pneumatic motor as a sole propellant

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of the Automobile has been deemed to be quite challenging for realisation and

implementation.

However, studies and researches on efforts to hybridize engines with pneumatic

motors in several fashions proved some very significant facts which highlight the

efficiency of Automobiles which have been integrated with a hybrid system that uses

an air motor as a secondary propellant alongside an IC engine for the final drivetrain

in either a series or a parallel configuration as we have reported earlier. Reports and

experimentation have also suggested the applicability of an IC engine hybridized to be

run as a compressed air pump and motor with a host of other hybrid mechanisms

aiding the car to be more efficient than a conventional vehicle in terms of fuel

efficiency and emissions control. Integratable mechanisms in the hybrid system could

include regenerative braking, start/stop functions/supercharging/downsizing etc which

cumulatively improve the efficiency of the Automobile.

Following here under is a brief insight into the basic characteristics and the successive

advancements in the air motors, pneumatic cars, employability of Air motors as

primary/secondary sources of propulsion in a vehicle/hybridization of IC engines to

run as semi-pneumatic motors and the conversion of IC engine to run as a permanent

pneumatic motor which might then be adopted as the secondary propulsion source.

2.1.2.1 Air Motors:

Some salient features of Air Motors.

Air Motors are very efficient in terms of power and torque output to the size

occupied and their weight . Tey are known to have about 1/4 th less weight and

1/6th less space compared to an electric motor of the same power output.

They can provide a constant torque output without much variation in the

output with the increase in load.

The speeds can be steplessly varied without the need for any drive train by the

variation in the input pressure.

They are not prone easily to overloading or sparks or overheating

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They are simple to install, maintain and run ruggedly.

Air Motors are of three primary varieties based on their working principles and

construction –

Vane Type

Reciprocating Type

Turbine Type

A Vane Type works on the simple principle of a roots type blower with a rotary

cylinder with vanes mobile and slotted onto the cylinder. This cylinder rotates inside a

chamber where in it is mounted with a little offset at the centre. The vanes move

outwards radially thus forming chambers for the compressed air entering in to be held

and thus, this air exerts pressure on the vanes thus rotating the cylinder. The volume

of this chamber successively increases while an inlet is provided for the entry of

compressed air which is also governed by the motion of the vanes. The vanes block

the inlet or allow the inlet to be open in cycles while the chambers formed by the

outward motion of the vanes expand in volume thus allowing the pressurized air to

exert a torque on the rotor.

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Fig.2.4 - Air Motor (Exploded view)

Fig.2.5 - Working Mechanism of Air Motor

A Reciprocating air motor on the other hand works on the basic principle of a piston

in a slider crank mechanism inside a cylinder. The intake and output of compressed

air with the compressor runs with the help of a suitable valve train. The piston intakes

air into the chamber during its down stroke and then compresses the air during the

upward stroke and then send the compressed air through the exhaust valve before the

down stroke is begun again. The valve cycle and the run of the piston in the cylinder

resemble closely the cycles of that of a 2 stroke IC engine with the only exception

being the utilization of a camshaft driven or similar valve train. The valve timings and

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the cycle nature quite closely resemble that of a 2 stroke IC engine. Hence

exploitations may begun to modify 2 stroke IC engines into air motors for propulsion

purposes in Automobiles.

A turbine type air motor utilizes the basic principle of a turbine run by an impeller.

When an impeller is enclosed inside a chamber into which compressed air is fed by a

controlled valve the compressed air impinges onto the vanes of the impeller causing

the impeller to rotate thus obtaining rotary motion.

Performance of an air motor:

Performance of an air motor is independent of the initial inlet pressure. At constant

inlet pressure, air motors exhibit linear output Torque/Speed characteristics. However

by simple pressure regulation or throttling, the output of air motor can be varied.

Air motors produce a characteristic power curve, with maximum power occurring at

around 50 % of the free speed. The torque produced at this point is often referred to as

“torque at the maximum output.”

Fig.6 - Variation of Torque V/s Speed Curve of Air Motor.

Performance of air motor can be modified according to application by two methods...

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1. Throttling - for speed variation application at constant torque.

2. Pressure Regulation - for torque varying applications at constant rpm.

Disadvantages of an air motor-

Major problem with air motor are noise produced during exhaust by air. Noise level

increases with speed and can go upto 80-120db and maximizes at no load speed.

2.1.2.2 Pneumatic Hybridisation – Methods:

Deriving from the limitations of utilizing purely pneumatic systems for

automobile propulsion, several different hybrid systems may be proposed which have

some inherent advantages and which essentially help in curbing the deficiencies of a

pure Air car.

2.1.2.3 Series Hybrid System:

Idea is to use an air motor alongside an IC engine on a vehicular chassis so that

there are two sources of propulsive power and a suitable switching mechanism or

coupling mechanism may be ensured between the two drivetrains for a series

connection or a parallel connection. In a series connection, an IC engine is used to run

a compressor to compress air which is then fed to an air motor which provides

propulsive power to the final drive wheels. This system is highly inefficient in terms

of the drivability and flexibility of the vehicle as only a fixed amount of torque and

speed is generated which may not be suitable for varying load conditions. Besides the

torque losses might be high due to low energy capacity of air.

2.1.2.4 Parallel Hybrid System:

IC engine and air motor might be attached together and separately to the final

drive wheels so that they might run the drive wheels individually or in a combined

fashion as is the requirement of the vehicle. The pneumatic motor may entirely run the

vehicle at low speed and low load conditions while the IC engine might take over at

high loads and speed conditions. The IC engine might generate the compressed air

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required to run the air motor during braking, idling and other such conditions like

coasting. They might also be tuned to run simultaneously to provide additional

propulsion boost to the vehicle as and when required.

For economic and feasibility reasons, one major variation in the above type of system

is proposed where in an easily available, and rugged 2 stroke engine might be used in

place of an air motor in view of the various limitations of an air motor that have been

stated earlier. The major advantage that leads us to this modification is that the

operation cycle of a 2 stroke engine matches that of a pneumatic reciprocating motor

to a great extent. The lighter weight, less noise, and to a great extent the reduced cost

in obtaining an IC engine which might be tuned to run as a pneumatic motor spurred

us to undertake this proposition.

However, this method has a crucial drawback which might prove the concept

impractical. The addition of an extra propulsion source in the form of a pneumatic

motor in addition to the IC engine adds up to the weight of the vehicle evidently. This

adds up to the difficulty for the pneumatic motor to propel the vehicle by itself and

deems it quite implausible. Only when the IC engine and the air motor run

simultaneously to give additional boost to the vehicle can this concept be considerably

fruitful which isn’t essentially contributing to improving the efficiency of the vehicle.

2.1.2.5 Total Pneumatic Hybrid Concept:

This concept involves integration of a pneumatic mechanism into an IC engine

to improve its efficiency which is claimed to be better than a normal electric hybrid

vehicle. The mechanism involves a compressed air routine run alongside a normal

gasoline/diesel cycle being run in an IC engine such that both the cycles are integrated

to be run on the same IC engine as per the requirements and driving conditions of the

vehicle.

Essentially, an IC engine is used for the propulsion of the vehicle. However, the IC

engine is linked to a tank to store compressed air. When the vehicle brakes or is idling

the fuel supply to the engine is cut off and the engine acts as a reciprocating air

compressor compressing air which is stored in the tank. Now when the vehicle is

moving at low load or low speed conditions, or when the vehicle is starting to move

from standstill where in the efficiency of the regular IC engine drivetrain is low, the

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IC engine is essentially run on compressed air which provides sufficient low range

torque with the help of a supercharger and an intercooler, if necessary. This requires a

manipulation in the engine in the form of revised valve timings. However, if the

camshafts are not variable, using fixed camshafts the same pneumatic hybridisation

might be achieved by using a third valve in the cylinder which is actuated with a

variable valve timing to convey compressed air to the storage tank. The compressed

air cycles maybe run on 2 stroke or 4 stroke as per the nature of the engine. The valve

actuation that is the only major modification that might be required on the IC engine

is shown in the following illustration as has been experimented by ETH – IDSC, a

university at Zurich. The concept can be further modified by integration of a

supercharger or a turbocharger which allows for additional boost of compressed air at

lower load conditions allowing for better propulsive torque output. The concept might

be schematically shown as illustrated below.

Fig. 2.7 - Modes of Working of Pneumatic Engine

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Fig. 2.8 - Total Pneumatic Hybrid Engine

Basically the integration of pneumatic technology helps in downsizing the IC engine.

Downsizing a gasoline engine can save up to 25 % fuel and emissions while 32 %

savings in fuel can be obtained by allowing for precision switching between

compressed air and gasoline using start/stop fuel control and proper actuation of the

compressed air valve by variable timing.

A disadvantage of this application is the difficulty in fabrication due to reasons to do

with modifications in the valve timing and application of cut off start/stop

technologies. One major disadvantage to do with pneumatic engines could be the use

of a very high pressure tank to store compressed air whose pressure might go up to

300 bars.

2.1.3 Motors Used in Hybrid Electric Vehicles:

Generally 3 types of motors are used in the electric hybrid vehicles:

DC Motors

Brushless DC Motors

AC Induction motors

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2.1.3.1 DC Motors:

There are four main types of DC motor, namely permanent magnet, series,

shunt and separately excited DC motor. Series, shunt & separately excited DC motors

uses field coils in the stator (the part which doesn't move) to generate a magnetic field

for the rotor to spin in. Their name simply refers to the way the field coils are wired

with respect to the rotor coils. All four types use a commutator to control by which

rotor coils are energized at any given time in order to maintain rotation. They are

relatively easy to control.

Currently series DC are the most economical and commonly used type of motor in

electric vehicles. DC motors are quite good – with efficiencies up to 90% and only

needing servicing every 100,000kms. However, using a commutator is restrictive and

a source of inefficiency. Also, with series DC motors regenerative braking is very

difficult to do.

.

Fig. 2.9 - DC Motors with shunt.

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Fig. 2.10 - DC Motors without shunt.

2.1.3.2 Brushless DC Motors:

In a brushless DC motor (BLDC), the rotor has permanent magnets and the stator has

an electronically-controlled rotating field, using sensors (rotary encoders or back-

EMF) to detect rotor position. As such they have no commutator, and tend to be more

efficient and more powerful than commutated motors. They require a more

complicated motor controller system and are popular for smaller motorsThe main

disadvantage for EV use is the cost of the large permanent magnet(s) required for the

rotor.

Fig. 2.11 - Brushless DC Motor.

30

2.1.3.3 AC Induction Motors:

AC Induction motors uses a rotating magnetic field in the stator to induce a

magnetic field in the rotor and hence a current to flow in the rotor's coils. The rotor

coils actually just loop around on themselves - they are not explicitly powered. The

induced field in the rotor tried to stay aligned with the rotating field of the stator, so it

turns to chase the stator's field. Due to loads on the motor, the rotor's field is forced to

rotate slightly slower than the stator's field (if it kept up exactly, there would be no

difference in the fields and hence no torque).

Three phase induction motors are very common and they are highly efficient and

reliable. The implementation of an AC induction motor in a Hybrid electric vehicle

is complicated as a variable-speed inverter is required to control the AC motor from a

DC power supply (the battery). They are relatively more expensive but are more

efficient.

Fig. 2.12 - AC Induction Motor.

2.1.4 GENERATORS:

The principle behind the dynamo or electric generator was discovered by

Michael Faraday and Joseph Henry but the process of its development into a practical

power generator consumed many years. Without a dynamo for the generation of

power, the development of the electric motor was at a standstill, and electricity could

not be widely used for transportation, manufacturing, or lighting, like it is used for

today.

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2.1.4.1 TERMINOLOGY:

The two main parts of a generator or motor can be described in either mechanical or

electrical terms:

Mechanical

Rotor : The rotating part of an electrical machine

Stator: The stationary part of an electrical machine

Electrical

Armature: The power-producing component of an electrical machine. In a

generator, alternator, or dynamo the armature windings generate the electrical

current. The armature can be on either the rotor or the stator.

Field: The magnetic field component of an electrical machine. The magnetic

field of the dynamo or alternator can be provided by either electromagnets or

permanent magnets mounted on either the rotor or the stator.

2.1.4.2 PRINCIPLE OF OPERATION:

Alternators generate electricity by the same principle as DC generators, namely,

when the magnetic field around a conductor changes, a current is induced in the

conductor. Typically, a rotating magnet called the rotor turns within a stationary set of

conductors wound in coils on an iron core, called the stator. The field cuts across the

conductors, generating an induced EMF, as the mechanical input causes the rotor to

turn.

The rotating magnetic field induces an AC voltage in the stator windings. Often there

are three sets of stator windings, physically offset so that the rotating magnetic field

produces three phase currents, displaced by one-third of a period with respect to each

other.

The rotor magnetic field may be produced by induction (in a "brushless" alternator),

by permanent magnets (in very small machines), or by a rotor winding energized with

direct current through slip rings and brushes. The rotor magnetic field may even be

provided by stationary field winding, with moving poles in the rotor. Automotive

32

alternators invariably use a rotor winding, which allows control of the alternator

generated voltage by varying the current in the rotor field winding. Permanent magnet

machines avoid the loss due to magnetizing current in the rotor, but are restricted in

size, owing to the cost of the magnet material. Since the permanent magnet field is

constant, the terminal voltage varies directly with the speed of the generator.

Brushless AC generators are usually larger machines than those used in automotive

applications.

Let θ be the angle between B and the normal to the coil, so the magnetic flux φ is

NAB.cos θ. Faraday's law gives:

emf = − dφ/dt = − (d/dt) (NBA cos θ)

= NBA sin θ (dθ/dt) = NBAω sin ωt.

2.1.4.3 VEHICLE MOUNTED GENERATORS:

Early motor vehicles until about the 1960s tended to use DC generators with

electromechanical regulators. These have now been replaced by alternators with built-

in rectifier circuits, which are less costly and lighter for equivalent output.

Automotive alternators power the electrical systems on the vehicle and recharge the

battery after starting. Rated output will typically be in the range 50-100 A at 12 V,

depending on the designed electrical load within the vehicle. Some cars now have

electrically-powered steering assistance and air conditioning, which places a high load

on the electrical system.

Large commercial vehicles are more likely to use 24 V to give sufficient power

at the starter motor to turn over a large diesel engine. Vehicle alternators do not use

permanent magnets and are typically only 50-60% efficient over a wide speed range.

Motorcycle alternators often use permanent magnet stators made with rare earth

magnets, since they can be made smaller and lighter than other types. These tend to be

0.5 ampere, permanent-magnet alternators supplying 3-6 W at 6 V or 12 V. Being

powered by the rider, efficiency is at a premium, so these may incorporate rare-earth

magnets and are designed and manufactured with great precision. Nevertheless, the

maximum efficiency is only around 80% for the best of these generators—60% is

33

more typical—due in part to the rolling friction at the tire-generator interface from

poor alignment, the small size of the generator, bearing losses and cheap design.

The use of permanent magnets means that efficiency falls even further at high

speeds because the magnetic field strength cannot be controlled in any way. Sailing

yachts may use water or wind powered generator to trickle-charge the batteries. A

small propeller, wind turbine or impeller is connected to a low-power alternator and

rectifier to supply currents of up to 12 A at typical cruising speeds.

2.1.4.4 AUTOMOTIVE ALTERNATORS:

Alternators are used in modern automobiles to charge the battery and to power a

car's electric system when its engine is running. Alternators have the great advantage

over direct-current generators of not using a commutator .Which makes them simpler,

lighter, less costly, more rugged than a DC generator, and the slip rings allow for

greatly extended brush life. The stronger construction of automotive alternators allows

them to use a smaller pulley so as to turn faster than the engine, improving output

when the engine is idling

The automotive alternator is usually belt driven at 2-3 times the engine crankshaft

speed. Automotive alternators are not restricted to a certain RPM because the

alternating current is rectified to direct current and need not be any constant

frequency. Modern automotive alternators have a voltage regulator built into them.

The voltage regulator operates by modulating the small field current in order to

produce a constant voltage at the stator output.

Efficiency of automotive alternators is limited by fan cooling loss, bearing loss, iron

loss, copper loss, and the voltage drop in the diode bridges; at part load, efficiency is

between 50-62% depending on the size of alternator, and varies with alternator speed.

Larger permanent magnet alternators can achieve much higher efficiency. By contrast,

the large AC generators used in power stations run at carefully controlled speeds and

have no constraints on size or weight. Consequently, they have much higher

efficiencies, on the order of 98% from shaft to AC output power.

34

Fig.2.13 - Exploded view of an Alternator

2.1.4.5 GENERATORS IN EHV’s:

Typical lead-acid batteries get about 60 watt-hours to the kilogram. The newer

nickel metal hydride batteries used to power hybrid cars get up to 120 watt-hours to

the kilogram. Still further advanced lithium-ion batteries are approaching 200 watt-

hours to the kilogram. This means that whatever range an electric car may have had

using lead-acid batteries can now be doubled, or even tripled.

35

Free-piston engines could be used to generate electricity as efficiently as, and less

expensively than, fuel cells. An unconventional engine design is attracting

attention as a potential alternative to hydrogen fuel cells or conventional engines

36

in some hybrid vehicles. Called the free-piston engine, it could be used to generate

electricity as efficiently as fuel cells yet cost less. Free-piston engines aren't new:

they were invented in the 1920s. But the increased recent focus on hybrid cars has

led a growing number of research groups and automakers to start research

programs to develop the technology. Unlike in conventional engines, there is no

mechanical connection between the piston and a crankshaft (hence the name free-

piston). Since the design allows for improved combustion and less friction, the

engines could be far more efficient in generating electricity than either

conventional generators or newer fuel-cell technology.

2.1.4.6 AC GENERATOR

A very simple AC generator consists to a permanent magnet that rotates

inside a coil in such a way that the N-pole and S-pole alternate as seen from the coil.

An analog voltmeter that has its zero at the middle of the scale is connected to the

ends of the coil. As the magnet is rotated the voltmeter moves first one way, then the

other way. The speed of rotation determines the number of "cycles per second” called

Hertz (Hz). A rotation speed of 3000 revolutions per minute (RPM) produces 50 Hz,

and 3600 RPM produce 60 Hz. The rotating permanent magnet can be replaced by

another coil that is fed by DC and acts as an electromagnet. Doubling the number of

coils will double the number of, what is called "the poles", and then only half the

rotation speed is required for a given output frequency.

2.1.4.7 DC GENERATOR:

DC generators are basically AC generators whose output voltage is switched

the other way round at the proper moment. Hence, the direction of the voltage is

always in a single direction. But the magnitude of the voltage keeps changing, just as

it does in an AC generator. The output of a DC generator is DC plus a "superimposed"

AC voltage, called "ripple". Connecting a capacitor across the output terminals

reduces that ripple.

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2.1.4.8 SPECIFICATIONS:

Frequently a dc motor or generator specification will include the value of the

motor constant KM, which is the torque sensitivity divided by the square root of the

winding resistance. Oftentimes even seasoned dc motor applications specialist will

view this intrinsic motor property as a somewhat esoteric figure of merit useful only

to the motor designer. The feeling is that motor constant KM has no real practical

value in selecting and dc motors and generators in the real world. Nothing could be

further from the truth! Utilizing this figure of merit properly will substantially reduce

the iterative process in selecting a dc motor or generator since it is generally winding

independent in a given case or frame size motor or generator from a given vendor.

Even in ironless dc motors, where the KM may vary somewhat depending on winding

due to variations in the copper fill factor, it remains a solid tool in the selection

process. Particularly if there is a listing with Motor Constant in ascending or

descending order, like there is in Appendix III at the end of this document. This

methodology limits the “winding hunt” where one winding satisfies the current

requirements but not the voltage requirements and vice versa. You “can’t get there

from here” if the motor does not have the intrinsic electromechanical ability to satisfy

the application requirements. This is NOT a thermal issue, but the intrinsic ability of

the motor to transform electrical power to mechanical power or the generator to

transform mechanical power to electrical power.

Since the KM of an electromechanical device does not address the losses in that

device in all circumstances the minimum KM must be larger than calculated to

address those losses. This method may not get you to exactly the correct “house” but

it will put you on the correct “street”.

This methodology is also a good “sanitycheck” since it forces the user to compute

both the input and output power. This was an omission the author made more than a

quarter century ago in attempting to address a requirement from a University PhD’s

need for a motorized prosthesis device that simply defied the Laws of Physics. It was

also the first and last time such an error was ever made The Motor Constant addresses

the fundamental electromechanical nature of a motor or generator. The selection of a

38

suitable winding is simple after an adequately powerful “case or frame size” is

determined.

The motor constant KM is defined as:

1. KM = KT/√R

In a dc motor application with limited power availability and a known torque needed

at the motor shaft the minimum KM will be set. A derivation is in Appendix II at the

end of this document.

For a given motor application the minimum KM will be:

2. KM = T / (PIN- POUT) 0.5

The power into the motor will be positive. For a generator application it would be

negative since you are taking power out. PIN is simply the product of the current and

voltage, assuming no phase shift between them.

3. PIN = V I

The power out of the motor will be positive, since it is supplying mechanical power.

For a generator application it would be negative since the generator is taking

mechanical power. It is simply the product of the rotational speed and torque.

4. POUT = W T

The finesse of performing these calculations in the metric system is that no

burdensome conversion factors are needed.

INSTANCE 1-Motor Application:

A battery-powered device needs 300 rad/sec and 5 mNm of torque (2865

rpm and 0.708 oz-in). Power available is 12 Volts and 0.16 Amps. This example

actually represents an efficiency of 78.125%.

Using equation 2,

KM = T / (PIN - POUT) 0.5

KM = 5 x 10-3 Nm / (12 Volts x 0.16 Amps – 300 rad/sec x 5 x 10-3 Nm) 0.5

KM = 5 x 10-3 Nm / (1.92 Watt – 1.5 Watt) 0.5

KM = 7.715 x 10-3 Nm/√Watt

Consulting the table in Appendix III we see that the first MicroMo Coreless Motor

that at nominal values has sufficient KM is the 2842 006C. It should be noted that the

tolerances of the Torque Constant and the Winding Resistance should be accounted

for. For example, if the Torque Constant and the Winding Resistance have ± 12%

tolerances KM worst case will be:

KMWC = 0.88 KT/√(R * 1.12) = 0.832 KM

39

Or almost 17% below nominal values with a cold winding. Taking worst case KMWC

we find that the first motor that might work is the 3540 024C. Heating of the winding

will further reduce KM since copper resistivity rises almost 0.4% per degree °C. Just

to exacerbate the problem the magnetic field will attenuate with rising temperatures.

Depending on the permanent magnet material utilized this could be as much as 20%

for a 100°C rise in temperature. The 20% attenuation for 100°C magnet temperature

rise would be for Ferrite Magnets. Neodymium-Boron-Iron has 11% or more, and

Samarium Cobalt about 4%.

INSTANCE 2-Generator Application:

A brushless dc generator must develop 500 Watt at 24 Volts dc. This must be

developed at a rotor speed of 30 rad/sec and 20.833 Nm of torque. To calculate the

mechanical power delivered

6. PIN = W T

PIN = - 30 rad/sec x 20.833 Nm = - 625 Watt

To determine the efficiency of the generator:

7. n = PIN / POUT= - 500 Watt /- 625 Watt = 80%

We can utilize equation 2 or

KM = T / (PIN- POUT) 0.5

KM = 20.833 Nm / (- 625 Watt + 500 Watt) 0.5

KM = 1.863 Nm / √Watt = 1,863 mNm / √Watt

Just like in a motor application, this minimum KM must be at the winding’s steady

state worst case operating temperature. Generators have heat losses just like motors

do. This approach for a minimum KM is only the first step in analysis. Tolerances in

torque constant (or back emf constant) and winding resistance must also be accounted

for, as well as any attenuation in the torque constant due to a rise in magnet

temperature. A suitable winding must then be selected and a thermal analysis must be

performed. Additionally, in the case of a generator it must be clear if the efficiency is

before or after losses in rectifying the ac voltage to a dc level. Interestingly, if for the

same mechanical input power if a target of 88% efficiency was desired then the

minimum KM would skyrocket from 1.863 Nm/√Watt to 2.406 Nm/√Watt. That is

equivalent to having the same Winding Resistance but needing the Torque Constant to

increase more than 29%. The higher the efficiency desired, the higher the KM

required. Graph 1 illustrates the sensitivity of KM as efficiency requirements.

40

Compute the lowest torque constant that is acceptable.

8. KT =T/I

The next step will then be to select a suitable winding and insure that all application

parameters and motor/generator limitations are acceptable, including consideration

due to winding tolerances.

Because of the manufacturing tolerances, thermal effects, and internal losses one

should ALWAYS choose a KM somewhat larger than what the application requires.

Indeed, a certain amount of latitude is needed since there are not an infinite number of

winding variations available from a practical point of view. The larger the KM, the

more forgiving it is in satisfying a given application’s requirements.

2.1.4.9 EXCITATION:

Separate excitation: For older and very large power generating equipment, it has been

traditionally necessary for a small separate exciter generator to be operated in

conjunction with the main power generator. This is a small permanent-magnet or

battery-excited generator which produces the initial current flow necessary for the

larger generator field to function.

Self excitation: Modern generators with field coils are self-excited, where some of the

power output from the rotor is used to power the field coils. The rotor iron retains a

residual magnetism when the generator is turned off. The generator is started with no

load connected; the initial weak field creates a weak voltage in the stator coils, which in

turn increases the field current, until the machine "builds up" to full voltage.

Starting: Self-excited generators must be started without any external load attached.

An external load will continuously drain off the buildup voltage and prevent the

generator from reaching its proper operating voltage

.Field flashing: If the machine does not have enough residual magnetism to build up

to full voltage, usually provision is made to inject current into the rotor from another

source. This may be a battery, a house unit providing direct current, or rectified

current from a source of alternating current power.

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2.2 CASE STUDY - TOYOTA PRIUS

2.2.1 Technology Overview

Full hybrid system is capable of operating in either gas or electric modes, as well as operating under both engine and electric mode. Major improvement with new HSD from 1997 Prius by designing more efficient drivetrain to increase duration of electric mode driving as well as the peak power delivered electrically.

42

Fuel Efficiency at its best:

HYBRID SYNERGY DRIVE makes intelligent selective use of its electric motors and gas/petrol engine to deliver fuel efficiency comparable to cars of one class smaller in engine displacement/body size, and at the same time the power comparable to cars one class larger.

HYBRID SYNERGY DRIVE delivers the highest level of fuel efficiency for cars of the same-size engine displacement.

It is mechanically simple and contains only one planetary gear set and two electric motors, without clutches. The input power from the engine comes immediately to a planetary gear set.

Fig.2.14 - Toyota Hybrid Transmission System.

Planetary gearing splits the power through the transmission between a mechanical path and an electrical path. A significant portion of the power flows mechanically through the transmission and is delivered directly to the final drive. The remaining power from the engine flows to the first electric motor. This first motor acts as a generator, changing part of the engine power into electric current. The electric current from this motor can either go into the battery for storage or on to the second electric motor. The second motor changes electric current from the first motor or from the battery back into mechanical power for the output.

The following set of illustrations show a brief insight into the mechanism and technology adopted by the Toyota Prius.

43

Fig. 2.15 - Toyota Hybrid Theoretical model.

44

45

MECHANISM

46

47

48

49

50

51

52

World's top level input/output to weight ratio - light weight:

In addition to being light-weight, the high power output nickel metal hydride (Ni-MH) battery used in the HYBRID SYNERGY DRIVE system provides a high input/output to weight ratio. (Power output in relation to weight).

Fig.2.16 - Toyota hybrid Battery pack.

The battery pack and its components have been redesigned for the new Prius. The cooling system for the battery cells including the cooling duct is optimized, while components such as the system main relay are designed for reduction in size and weight.

Furthermore, the system maintains the battery charge at a constant level at all times by monitoring and computing the cumulative amount of discharge under acceleration, and recharging by regenerative braking or with surplus power under normal running conditions.

The hybrid battery (traction battery) has a limited service life. The lifespan of the

hybrid battery (traction battery) can change in accordance with driving style and

driving conditions. 

53

Energy-efficient, high-output gas/petrol engine:

The gas/petrol engine used in HYBRID SYNERGY DRIVE is more energy-efficient,

producing higher output than conventional gas/petrol engines.

The new Prius’ 1.8L 2ZR-FXE high-expansion-ratio Atkinson cycle engine replaces

the former 1.5L 1NZ-FXE. The wealth of torque created by an increased displacement

decreases the engine rpm during high-speed cruising. Further improvements in fuel

efficiency have been achieved through the following new mechanisms.

Electric water pump:

The water pump is now driven by electricity from the battery. Elimination of the drive

belt decreases mechanical loss, and the flow of the coolant can be controlled even

more precisely according to the vehicle’s conditions.

Exhaust heat recirculation system:

This system utilizes exhaust heat – what used to go wasted – for the heater and to

warm up the engine, allowing quicker heater and engine warm-ups.

Cool-EGR system:

Flow volume of the exhaust gas is controlled carefully by the electric EGR valve and

is channeled into the intake manifold, alleviating negative pressure in the manifold

and decreasing pumping loss in the engine. Cooling the exhaust gas with the EGR

cooler actualizes large volume EGR.

Roller rocker arm:

The valve train system features roller rocker arms, decreasing friction loss in valve

movements.

Power Split Device:

54

The HYBRID SYNERGY DRIVE power splitting device distributes the power

produced by the gas/petrol engine to the drive train and to the generator. To divide the

power efficiently, it uses a planetary gear consisting of a ring gear, pinion gears, a sun

gear and a planetary carrier.

The rotating axle of the planetary carrier is directly connected to the gas/petrol engine

and rotates the perimeter ring gear and the sun gear inside via the pinion gears

The rotating axle of the ring gear is directly connected to the electric motors, and thus

transfers the driving power to the wheels. The axle of the sun gear is directly

connected to the generator and converts the power produced by the gas/petrol engine

into electric energy.

Fig. 2.17 - Toyota Hybrid Transmission.

55

Regenerative braking:

HYBRID SYNERGY DRIVE can reuse kinetic energy by using its electric motors to

regenerate electricity in what is called "regenerative braking".Normally, electric

motors are turned by passing an electric current through it. However, if some outside

force is used to turn the electric motors, it functions as a generator and produces

electricity. This makes it possible to employ the rotational force of the driving axle to

turn the electric motors, thus regenerating electric energy for storage in the battery

and simultaneously slowing the car with the regenerative resistance of the electric

motors.

The system coordinates regenerative braking and the braking operation of the

conventional hydraulic brakes so that kinetic energy, which is normally discarded as

friction heat when braking, can be collected for later reuse in normal driving mode.

Typically, driving in city traffic entails a cycle of acceleration followed by

deceleration. The energy recovery ratio under these driving conditions can therefore

be quite high.

To take advantage of this situation, the system proactively uses regenerative braking

when running the car in the low speed range. Taking Prius as an example, the system

can save the energy equivalent of 1ℓ of gas/petrol while running in city traffic for 100

km.

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Fig. 2.18 - Regenerative Braking.

Generator:

As with electric motors, HYBRID SYNERGY DRIVE uses a

synchronous AC generator capable of high speed axial rotation,

realizing substantial electrical power while the car is running in the

mid-speed range. 

Toyota has put together the ideal generator, high output electric motor

and gas/petrol engine combination to enhance low to mid-speed range

acceleration.

57

Reduction Gear:

HYBRID SYNERGY DRIVE incorporates the newly developed reduction gear. The

reduction gear is designed to reduce the high rpm of the front electric motors so that

the power produced can be transferred to the wheels, with the added benefit of torque

amplification, i.e. with greater power.This torque amplification effect, coupled with

higher revving capability of the front electric motors, combine to provide seamless

acceleration at will.

TOYOTA PRIUS TECHNICAL SPECIFICATIONS:

HYBRID SYNERGY DRIVE: Type Series/parallel, full hybrid System output (bhp) 134bhp

ENGINE: Engine type 2ZR-FXE (Atkinson cycle) No. of cylinders Four in-line Valve mechanism 16-valve DOHC with VVT-i Bore x stroke (mm) 80.5 x 88.3 Displacement (cc) 1,798 Compression ratio 13.0:1 Fuel system EFI Octane No. 95 or greater Max. power (bhp @ rpm) 98 @ 5,200 Max. torque (Nm @ rpm) 142 @ 4,000 Emissions level Euro 5

ELECTRIC MOTOR Motor type Permanent magnet, synchronous Max. voltage (CD V) 650 Max. power (bhp) 80 Max. torque (Nm) 207

HIGH-VOLTAGE BATTERY: Battery type Nickel-metal hydride Nominal voltage (SC V) 201.6 (168 x 1.2V cells) No. of battery modules 28 Battery capacity (Ah) 6.5 System voltage (V) 650

58

TRANSMISSION: Transmission type Electric CVT Gear ratios Forward 2.683 Reverse 2.683 Differential gear ratio 3.267

PERFORMANCE: Max. speed (mph) 112 Full system power (bhp) 134 0-62mph acceleration (sec) 10.4

FUEL CONSUMPTION: 15in wheel 17in wheel Combined 72.4 70.6 Extra urban (mpg) 76.4 74.3 Urban (mpg) 72.4 70.6 Fuel tank capacity (l) 45

SUSPENSION: Front MacPherson strut with anti-roll bar, coil springs and dampers Rear Torsion beam with coil springs and dampers

BRAKES: Front Ventilated discs, hydraulic with power

assist Rear Solid discs, hydraulic with power assist Disc size (diameter x width, mm) Front 255 x 25 Rear 259 x 9 Parking brake Pedal-type

STEERING: 15in wheel 17in wheel Steering type Electric power-assisted rack and pinion Steering ratio 14.6:1 Turns lock-to-lock 2.8 Turning radius Tyre 5.5 Body 5.9

TYRES: 15in wheel 17in wheel 195 65 R15 215 45 R17

EXTERIOR DIMENSIONS: 15in wheel 17in wheel

59

Overall length (mm) 4,460 Overall width (mm) 1,745 Overall height (mm) 1,490 (1,505 with Solar Pack) Wheelbase (mm) 2,700 Front track 1,525 1,515 Rear track 1,520 1,510 Front overhang (mm) 905 Rear overhang (mm) 855 Ground clearance (mm) 140 Drag coefficient (Cd) 0.25

WEIGHTS Curb weight (kg) 1,370 – 1,420

CHAPTER 3

DISCUSSION

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By studying hybrid vehicle, it’s a versatile project in the automobile field. Keeping in mind the immense expense of non renewable sources of energy such as: - petrol, diesel and L.P.G etc. Hybrid vehicles use electricity which is low in cost as compared to non hybrid vehicles (use petrol, diesel etc.) These vehicles do not cause environmental hazards e.g. global warming, pollution etc. Poisonous gases are not emitted by these vehicles as use of electric power is the major source of driving the drive train. This is more economic as the combustible fuel is only used when load is excessively high. This is most suitable for driving the vehicle in city areas where a large amount of traffic jam occurs and is more economic due to the use of electricity. As the speed of these vehicles is not too fast a greater amount of road safety can be expected. By employing these vehicles in the local transports such as taxis and buses comparably large amount of profit can be generated by the owner.

The hybrid vehicles too have limitations. These vehicles have high breakeven point i.e. the price of the hybrid vehicle pays for the less fuel consumptions. The battery of the system is large and expensive need excessive maintenance and has to be replaced after every one lakh mile. The electromagnetic waves from the battery can cause cancer due to its prolonged use these vehicles have poor acceleration and can be run to a very limited distance. If these vehicles are used in city they give the actual result and economy for which vehicles are known. But if used in highways the results of these vehicles are not fetched and give the same mileage as given by known hybrid vehicles. In some cases different energy meters are required in households for the charging of electric batteries used in the hybrid vehicles as there are mainly electric motors working on 240 volts. As if it not so done it may damage the house hold circuits.

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CHAPTER 4

CONCLUSION

Based on the study we conclude that hybrid vehicles are those vehicles which work on multifuel. These are of many types such as electric hybrids, pneumatic hybrids. As on the bases of study on electric hybrid vehicles, these are classified into three main drive trains .i.e. Series, parallel, series-parallel. These drives trains connected with the two power sources are capable of running individually as well as in a combined manner by switching the power sources.

Hybrid vehicles use electricity which is low in cost as compared to non hybrid vehicles (use petrol, diesel etc.) These vehicles do not cause environmental hazards e.g. global warming, pollution etc. Poisonous gases are not emitted by these vehicles as use of electric power is the major source of driving the drive train. This is more economic as the combustible fuel is only used when load is excessively high. This is most suitable for driving the vehicle in city areas where a large amount of traffic jam occurs and is more economic due to the use of electricity. As the speed of these vehicles is not too fast a greater amount of road safety can be expected. By employing these vehicles in the local transports such as taxis and buses comparably large amount of profit can be generated by the owner.

The hybrid vehicles too have limitations. These vehicles have high breakeven point i.e. the price of the hybrid vehicle pays for the less fuel consumptions. The battery of the system is large and expensive need excessive maintenance and has to be replaced after every one lakh mile. The electromagnetic waves from the battery can cause cancer due to its prolonged use these vehicles have poor acceleration and can be run to a very limited distance. If these vehicles are used in city they give the actual result and economy for which vehicles are known. But if used in highways the results of these vehicles are not fetched and give the same mileage as given by known hybrid vehicles. In some cases different energy meters are required in households for the charging of electric batteries used in the hybrid vehicles as there are mainly electric motors working on 240 volts. As if it not so done it may damage the house hold circuits.

Hence we conclude that the use of hybrid vehicles plays a prominent role the reduction of level of pollution and reduces the fuel cost i.e. cost of the fuel used per miles and as the fuel costs are rising day by day the use of hybrid vehicles is best for cities.

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