Automotive evolution - Appunti

Sommario

Chapter 6 – Economic figures ............................................................................................................................ 1

Chapter 7 - Regulations ..................................................................................................................................... 3

Chapter 2 – Body and car architecture .............................................................................................................. 4

Chapter 8 - Body ................................................................................................................................................ 6

Chapter 3 – Chassis ............................................................................................................................................ 9

Chapter 4 – Powertrain ................................................................................................................................... 17

Chapter 5 – The technologies of Automobiles ................................................................................................ 27

Chapter 10 – Engine ........................................................................................................................................ 31

Chapter 9 – Chassis .......................................................................................................................................... 56

Chapter 11 – Transmission .............................................................................................................................. 73

Chapter 14 – Energy and environmental issues .............................................................................................. 80

Chapter 6 – Economic figures

Revolution in motor car production

1. From the first decade of the twentieth century, a few manufacturers in US promoted and organised

the first mass-production methods and introduced several technological innovations.

2. In 1950s, European manufacturers were able to apply mass-production while engineering a wide

product differentiation and reducing fuel consumption by widening the available engine choices to

improve overall fleet efficiency.

3. In 1950, in Japan, a lot of innovation were introduced to improve quality and at same time to lower

costs. In the same period were introduced environment and safety regulations.

4. In 2000s, Far-east countries, mainly North Korea and China, are capable of further boosting mass

production, both locally and for export.

During mass production, Ford, General motors and Chrysler creates the group called Big Three. This

determined the first move toward concentrating more manufacturers under the control of the strongest one.

When one brand is no longer profitable, its facilities can be sold or discontinued (e.g. Volvo Car Division). In

some cases, a famous manufacturer’s name, whose production had been discontinued in the past, was

resumed, as a brand, to rev-up selling in a specific car segment (e.g. Bugatti).

Some manufacturers, like Toyota, Nissan and Honda, launch a new premium brand (respectively Lexus,

Infinity and Acura).

Different car types must be distributed in the different geographical areas to meet several requirements such

as: i. Income: high-income countries are willing to pay for more sophisticated vehicles

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ii. Standards and regulations: different regulations on matters as safety, emissions and recycling are

stated in different countries

iii. Driving conditions: the vehicles must be adapted to local conditions, particularly with regard to

strengthening the body, suspension, steering and fuel system materials

iv. Consumer preferences: these arise in response to the characteristic of particular societies. In small

vehicle segment it is usual the preference for 2-volume solution in high-income countries while the

3-volume is preferred in Brazil, China and India. Another item is the preference for manual or

automatic gearbox

v. Taxation: tax policies, not only concerned about cars, can have a significant impact on vehicle

demand

The passenger car segmentation is quite different in the various countries:

USA and Canada use a scale based on interior volume index

  Minicompact (under 2.407 L)

 Subcompact (range 2.407 L – 2.831 L)

 Compact (range 2.832 L – 3.114 L)

 Midsize (range 3.115 L – 3.397 L)

 Large (over 3.397 L)

Europe

  Segment A: mini cars

 Segment B: small cars

 Segment C: medium cars

 Segment D: large cars

 Segment E: executive cars

 Segment F: luxury cars

 Segment S: sports cars

 Segment M: multi-purpose cars

 Segment J: Sport-Utility Vehicles (SUVs) and off-road vehicles

Asia use the length

  Segment A1: up to 3.400 mm

 Segment A2 (compact): from 3.401 to 4.000 mm

 Segment A3 (midsize): from 4.001 to 4.500 mm

 Segment A4 (executive): from 4.501 to 4.700 mm

 Segment A5 (premium): from 4.701 to 5.000 mm

 Segment A6 (luxury): above 5.000 mm

 Segment B1: small vans

 Segment B2: Multi-Utility Vehicles (MUVs) and Multi-Purpose Vehicles (MPVs)

 Segment SUV: Sport Utility Vehicles To survive, a company must follow at least one rule: to

reach the Break-Even Point (BEP). The total economic

burden consists of two types of fundamentally different

costs:

 Fixed costs (e.g. development costs, facilities, etc)

 Variable costs (costs proportional to production

volumes, e.g. raw materials, components, salaries…)

The launch of new and better products ensures survival

and development of all companies. New product are the

results of major decisions and aim at well-defined

commercial, technological and financial targets.

The need for renewal of restyling comes from

the concept of lifecycle. After the development

phase and product launch, the car lifecycle is a

consequence of the following main steps:

i. Introduction, characterized by the

commercial launch of a new model

ii. Growth, characterized by a rapid

expansion of its demand

iii. Maturity, in which the model reaches

the saturation of the interested

market

iv. Decline, during which the decrease of interest of the customers takes place

When approaching the decline step, strategies like restyling or face-lifting are almost always chosen to re-

launch or maintain sales volumes at a profitable level

Chapter 7 - Regulations

Motor vehicles must comply with the Technical Regulations applicable in the country they are offered for

sale. Almost worldwide, the relevant authorities are the Ministry of Transportations and the Ministry of the

Environment of the Country where the car is intended to be sold.

The main goals of the technical regulations are to:

1. Guarantee engine and vehicle performances and in particular the fuel consumption declare by the

manufacturer

2. Set limitations on the emission of pollutants and greenhouse gases through the exhaust

3. Set limitations to the external noise

4. Verify the efficiency of the systems needed to provide the safe driving (e.g. brakes, steering, etc)

5. Protect electronic devices against external radiofrequencies

6. Verify the efficiency of some key components, usually delivered by the supplier’s network

7. Provide for recycling the car body and related materials at the end of the vehicle’s life

The technical regulations cover also the administrative control and inspection procedures

For regulated pollutants is intended the pollutants considered in emission regulations: Carbon Monoxide

(CO), HydroCarbons (HC), Oxides of Nitrogen (NOX) and Particulate Matter (PM).

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Chapter 2 – Body and car architecture

The structure of early cars consisted in chassis and a body.

The chassis was the main structural frame on which all mechanical components such as engine, transmission,

suspensions and steering system, were mounted. It was stressed by relevant reaction forces due to all these

concentrated loads. Chassis manufacturers applied mainly metallic materials and were equipped with

machines for metal casting, stamping and machining.

The body was the container defining space for passengers and luggage. In early car it was mounted on the

chassis like the other mechanical components while, in modern cars it is integrated with the chassis. At the

dawn of the motor era car, body technology was not considered to be fundamental and was directly taken

from horse driven carriages and coaches, without significant modifications. Body manufacturers applied

wooden structures or composite structures of steel and wood and were equipped with machinery for

working wood or wrought iron components, with tools suitable for single specimens, often copying model

without the help of drawings. Many of the first car chassis were based on the existing technology

developed for bicycles. The 1899 Renault is an example of this

solution, with pieces of seamless steel tubes that were cut and

bent to their final shape. A second solution was applied in 1907 by

Sizaire and Naudin. This car is characterized by a chassis made with

solid wooden beams, with iron reinforcements. A third solution,

used by Panhard & Levassor firm in its first cars, applied wooden

beams covered and reinforced by a thin steel sheet layer.

As soon as the first four-cylinder engines were applied, the so-called grillage structures were developed.

During 1930s were developed different configuration from the grillage schemes, in particular the X cross

beams, which introduced a significant improvement in the stiffness performance. A further improvement to

this architecture was given by a chassis with only one central longitudinal beam.

The integration of the body and chassis in a single unit was considered as the best chance to improve the

structural performance, with reductions in weight and cost. Probably the first attempt to develop such an

architecture was done with the 1922 Lancia Lambda. A further step was made with the 1934 Citroën 11 CV,

where the chassis did not exist anymore as a physical element, nor it could be separated from the body,

without destroying the welds. The first car to exceed a speed of 100 km/h was the Alfa

Romeo 40-60 HP, a torpedo shaped car with a continuous

profile between hood cover, the cowl and the body sides. In

1934, with the FIAT Balilla Sport Berlinetta, the body was

developed according to systematic studies of the

aerodynamic behaviour, performed partly in an aeronautical

wind tunnel, partly on the road directly. The windshield

inclination, for example, was optimized on the road and each

corner is rounded. The leader of the revolution of the

streamlined design was the famous 1934 Chrysler Air Flow,

that bring the aerodynamic drag coefficient below 0.6.

Vehicle architecture may be defined as the layout of the main components, such as engine, gearbox,

transmission, axles, etc. By considering only the main features and neglecting the shape of the body, the

vehicle architecture can be identified as follows:

 The number of the wheels

 The position of the driving axle

 The position of the engine

 The kind of mechanical linkage between engine and wheels

 The position of the passengers

The first motorcar, the Benz Patentwagen was a tricycle, with the single wheel placed at the front axle. Later,

the 1894 Bernardi, placed the single wheel as a rear driving axle avoiding in this way the differential.

The low roll-over stability of a 3-wheels car causes a lot of accidents, so people prefer to buy a 4-wheels car.

Increasing roll-over stability, the cars were having problems to keep the wheels attached to the ground, so

were introduced the suspension.

Restricting to two axles vehicles with a single driving axle, it is possible to identify the following architectures,

in chronological order:

Early front-wheel drive vehicles with front engine

 Early rear-wheel drive vehicles with rear engine

 Early rear-wheel drive vehicles with front engine

 Evolved rear-wheel drive vehicles with front engine

 Evolved rear-wheel drive vehicles with rear engine

 Evolved front-wheel drive vehicles with front engine



Because horses were hitched in front of the carriage, it looked natural to many inventors to install the engine

in the front part of the vehicle. The first motor vehicle, the 1769 Cugnot’s Fardier (truck) had a front driving

wheel with the steam engine and the boiler rigidly mounted on the front steering wheel. Later, thanking to

the better visibility and comfort on bumps, the engine was placed in rear, connecting it with the driving axle

with a transmission, made of two chains.

Thanks to the developments of Panhard & Levassor, a more rational solution was identified in 1894. It

consists in a front-mounted engine that operates, through a clutch and a gearbox, an auxiliary shaft with the

differential, followed by a chain transmission to the rear wheels.

The solution that proved more expedient where the internal space is concerned, particularly for the luggage

compartment, was obviously front wheel drive with front engine. This architecture was attempted several

times without success, and found its conditions of economic feasibility only when some specific components

were developed, namely:

The constant speed ball joints (Ford 1936)

 The Mc Pherson front suspensions (Ford 1948)

 The powertrain with engine and gearbox aligned (Autobianchi 1964)

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Chapter 8 - Body

The car body is the external shell of the vehicle designed to accommodate and protect the people on board

and their luggage from external environment and the dangers motion may involve. In particular the car body

must:

 Withstand the external loads, mainly due to road surface discontinuities and air resistance, and the

internal loads due to mechanical components attached to the body

 Withstand the external loads with structural deformations remaining within the elastic range

 Protect the occupants in case of crash

The components and subsystems of the vehicle body can be classified:

Body structure: is the structural part of the body, mainly made of steel box-type sections and pillars,

 capable of contributing to the final mechanical strength and stiffness

Body shell: is the structural panel-work, mainly steel panels, capable of contributing to the final

 mechanical strength and stiffness

Body frame: is the structural lower part of the body (underbody) to which the main components are

 attached

Movable parts: they are steel components which can be removed without destroying welded joints

 (doors, engine hood, etc)

Aesthetic parts: they are mostly minor components now usually made of plastic materials

 Accessories: devices capable of providing specific functions such as door lock, lateral window

 mechanism…

Road surfaces induce random and asymmetrical loads

on the body. Each wheel follows a road profile with

irregularities characterized by different distributions

and geometry at different times and this determines

a specific load acting on the body as a result of

suspension spring flexibility. Due to unavoidable

obstacle asymmetry these loads cause torsional

stressing of the body.

To define the loads acting on the vehicle body, the

payload must be specified. Once the payload mass

and position are known, since the vehicle’s unloaded

mass is also known, the load applied to each axle can

be computed. In addition, the most frequently used accessories must be considered. During the vehicle type

approval, the following weights must be declared:

 Maximum load weight (or Gross Vehicle Weight GVW)

 Maximum weight on each axis

 Weight in running order

 Curb weight in running order (with all fluids filled up)

 Number of seats

The bending stiffness is defined as the ratio between the load applied to the centre of mass and the vertical

deformation measured at the same point.

The torsional stiffness is defined as the ratio between the torque and the rotation angle of the section in

which the load is applied with respect to the constrained section.

The modern road vehicles are built following

two different structural types: the bearing

chassis and the unitized body, shortly unibody.

If the body is joined to the bearing chassis

without rigid mounts, the final torsional

stiffness of the vehicle is usually poor, unless

the chassis is provided with heavy stiffening

elements, which creates severe difficulties in

obtaining the prescribed crash safety. For this

reason, the bearing chassis was later

abandoned in favour of the unibody approach,

which guarantee low weight, high stiffness, low production costs and good crash performances. For unitized

body structure the definition body frame is used to identify a semi-finished assembly that includes the floors,

with related cross-members, the front rear longitudinal members and the struts.

The unibody us a shell of steel box-type of sections and pillars welded together that constitute a reticular

structure to which the steel panels.

The main components of the unibody are:

 Elements 1, 12, 6 are the windscreen pillar or A pillar, the central pillar or B pillar and the rear pillar

or C pillar, respectively

 Element 15 is the front bumper cross-member and elements 4 and 9 are the cross-members for

central and rear parts of the floor

 Element 13 is the lateral side member and element 3 is the roof small-section longitudinal member.

The subassembly 3, 13, 14, 12, 11, 6 is often called the door ring.

 Elements 18, 10 and 7 are the cross-member below the windscreen, the cross-member below the

rear window and the cross-member of the rear bumper

 Element 16 is the front strut

The complete body frame is obtained by assembling the following subassemblies: front frame, floor, right/left

side members, rear panel and headlight crossbar. On a separate line, is assembled the side panels, which is

obtained by welding together outer skin, upper strut insert, rear light bottom, rear side lower insert, fuel

filler, bottom, windscreen pillar reinforcement, central pillar reinforcement, interior side frame, front pillar

reinforcement. 7

In case of impact, the kinetic energy must be dissipated by the car with no injury to the occupants. This

protective action is assured by building the body in two conceptually distinct parts: the front part that can be

sacrificed and the central part that constitu