Harrison Vehicle Refinement

Controlling Noise and Vibration in Road Vehicles
1. Auflage 2004
ISBN: 978-0-08-047475-5
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 360 Seiten

High standards of NVH (Noise, Vibration and Harshness) performance are expected by consumers of all modern cars. Refinement is one of the main engineering and design attributes to be addressed in the course of developing new vehicle models and vehicle components. Written for students and engineering practitioners, this is the first book to address automotive NVH. It will help readers to understand and develop quieter, more comfortable cars. With chapters on the fundamentals of acoustics and detailed coverage of practical engineering solutions for noise control issues it is suitable for students of automotive engineering and engineers who haven't been trained in acoustics, and will be an important reference for practicing engineers in the motor industry.
· The first book devoted to the refinement of noise and vibration in automobiles
· Combines a detailed explanation of the fundamentals of acoustics and the science behind vehicle noise and vibration with practical tips and know-how for noise and vibration control.
· Based on real world experience with a variety of automotive companies including Ford, BMW and Nissan

Zielgruppe

Academic/professional/technical: Undergraduate. Academic/professional/technical: Postgraduate. Academic/professional/technical: Research and professional

Autoren/Hrsg.

Harrison, Matthew

Inhaltsverzeichnis

1;Cover;1
2;Contents;8
3;Acknowledgements;10
4;Preface;11
5;About the author;13
6;Vehicle refinement: purpose and targets;14
6.1;Introduction and definitions;14
6.2;Scope of this book;15
6.3;The purpose of vehicle refinement;16
6.4;How refinement can be achieved in the automotive industry;18
6.5;The history of vehicle refinement: one representative 20-year example;19
6.6;Refinement targets;22
6.7;References;28
7;The measurement and behaviour of sound;30
7.1;How sound is created and how it propagates;30
7.2;Making basic noise measurements: the sound level meter, recording sound;46
7.3;Making basic noise measurements: the decibel scale, frequency and time weightings;56
7.4;Analysis and presentation of noise data;61
7.5;Sound power level, sound intensity level, sound pressure level;72
7.6;References;83
7.7;Introduction to logarithms;85
8;Exterior noise: assessment and control;87
8.1;Pass-by noise homologation;87
8.2;Noise source ranking;94
8.3;Air intake systems and exhaust systems: performance and noise effects;97
8.4;Tyre noise;149
8.5;References;153
8.6;Valve and port geometry;157
9;Interior noise: assessment and control;158
9.1;Subjective and objective methods of assessment;158
9.2;Noise path analysis;164
9.3;Measuring the sound power of IC engines and other vehicle noise sources;172
9.4;Engine noise;186
9.5;Road noise;192
9.6;A note on aerodynamic (wind) noise;194
9.7;A note on brake noise;195
9.8;A note on squeak, rattle and tizz noises;196
9.9;Control of sound through absorption within porous materials;197
9.10;Control of sound by minimising transmission through panels;207
9.11;References;224
9.12;Some background information on systems;228
9.13;The convolution integral;230
9.14;The covariance function, correlation and coherence;233
9.15;The frequency response function;238
9.16;Plane waves in a tube with a termination impedance;240
9.17;The derivation of the linearised mass conservation equation;244
9.18;The derivation of the non-linear (and linearised) inviscid Euler equation;246
10;The measurement and behaviour of vibration;247
10.1;Making basic vibration measurements;247
10.2;Laser-based vibration measurements;251
10.3;Analysis and presentation of vibration data: quantifying vibration;253
10.4;Modes of vibration and resonance;261
10.5;Modal analysis;277
10.6;References;281
11;Sources of vibration and their control;282
11.1;Introduction;282
11.2;Damping of vibrations;282
11.3;Vibration isolation and absorption;300
11.4;Engine and drivetrain vibrations;312
11.5;Vehicle and chassis vibrations: ride quality;347
11.6;References;351
12;Index;354

Leseproben

1 Vehicle refinement: purpose and targets
1.1 Introduction and definitions
The book opens with one man's thesis: “Styling and value sell cars – Quality keeps them sold”. Lee Iacocca, Iacocca: An Autobiography* To explain, it takes years and millions of US dollars to produce a new car. If the styling is attractive and the marketing is effective, and if the value for money is good then that car will probably sell moderately well for the first few months after launch. However, if the quality is bad then word will get round and sales will quickly drop off. It is vital that good sales are maintained for a significant period if the development costs for the car are going to be recouped. Lee Iacocca was writing from Ford's and Chrysler's perspective. Both of these already had their own strong brand image and so branding was not included in his thesis, but it should be when comparing cars from different manufacturers. To test this idea the following group activity can be tried. It has been found to work well with larger teams of people and needs a group of at least twenty to be effective: Group exercise – Four corners What is most important when deciding which new car to buy? • styling? • performance? • value? • brand? Stand in the comer of the room associated with your choice. If you favour two of the above, stand midway between the appropriate corners. Be prepared to explain your decision. At least ten minutes should be allocated to this exercise. A confident facilitator is required to interview team members as to the reasons for their choice. The four-corners exercise can be used to obtain different effects from different groups of people. With a group of managers from the same automotive organisation the exercise can quickly identify if there is consensus on a marketing strategy (also it is interesting to watch peer-pressure at work as individual choice is being exercised in a very public way during this exercise). With a group of engineers the exercise can be used to remind them that their own work affects the customer's buying decision. With a group of engineering students, the exercise teaches them that the customer's buying decision is a multi-criteria choice and probably a compromise at the end. It is useful to introduce some definitions at this point. The term Vehicle Refinement* covers: • noise, vibration and harshness** (NVH – a well-known umbrella term in the automotive industry); • ride quality; • driveability. A refined vehicle has certain attributes,*** they being: • high ride quality; • good driveability; • low wind noise; • low road noise; • low engine noise; • idle refinement (low noise and vibration); • cruising refinement (low noise and vibration, good ride quality); • low transmission noise; • low levels of shake and vibration; • low levels of squeaks, rattles and tizzes; • low level exterior noise of good quality; • noise which is welcome as a ‘feature’. The term ‘NVH’ is usually taken to cover: • noise suppression; • noise design (altering the character of noise but not necessarily its level); • vibration suppression; • suppression of squeaks, rattles and ‘tizzes’. 1.2 Scope of this book
The scope of this book is illustrated in Figure 1.1. Figure 1.1 The scope of the term ‘Vehicle Refinement’. It has been designed to cover the core science, engineering and technology required by the NVH engineer with added material on ride quality and driveability. Wherever possible, issues that affect the customer's buying decision have been emphasised. Refinement is a customer-facing subject as any refinement engineering undertaken affects the driving experience directly. Therefore, the reader is encouraged to think of refinement as being inextricably linked to the business of selling passenger cars (and increasingly this is being extended to vans, light trucks, trucks, buses, coaches and other road vehicles). Some further definitions are offered for the sake of clarity. In this book the terms: Noise shall be used to describe audible sound, with particular attention paid to frequencies in the range of 30–4000 Hz. Vibration shall be used to describe tactile vibration, with particular attention paid to frequencies in the range of 30–200 Hz. Other terms that will be encountered include: Primary ride taken to be the rigid body motion of the passenger compartment relative to the road. Typical frequency range – 0–6 Hz. Secondary ride taken to be the relatively large amplitude motion of sub-elements of the vehicle such as individual wheels, axles or elements of the powertrain. Typical frequency range – 6–30 Hz. Structure-radiated noise being airborne noise radiated by a structural surface that is vibrating. Also known as ‘structure borne noise’. 1.3 The purpose of vehicle refinement
Refinement helps manufacturers sell their vehicles. Brandl et al. (2000) published the results of a formal investigation of customer attitudes to vehicle refinement. Customers were asked to complete a questionnaire relating to their own vehicle. They were asked questions relating to their attitudes on vehicle prestige (brand by another name), performance, convenience, family friendliness, noise quality and cost. Although there was scatter in the results obtained, there was evidence of clustering with certain classes of customer showing predictable tastes with vehicle-refinement issues helping to define that taste. Throughout the 1990s Rover Group in the UK (subsequently they traded under the MG badge) defined ‘Refinement’ as the invisible feature of their vehicles suggesting a strong commitment to it. Refinement (or NVH) has always been a consideration for vehicle design and development. However, over the last 20–30 years it has assumed a greater importance (witness the advertisements by manufacturers that stress how quiet their cars are). Reasons for this include: • Legislation Since the adoption by Member States of Council Directive 70/157/EEC (1970) limiting the permissible levels of noise emitted by accelerating vehicles, the sale of new non-conforming vehicles is prohibited in the European Community. Similar legislation has been adopted in many non-EU countries, and certainly in all the main automotive territorial markets. • Marketing to new customers Refinement is a feature that may be used to distinguish a vehicle from its otherwise similar competitors, thus attracting customers not necessarily loyal to that particular brand. • Customer expectation Customers have come to expect continuous improvement in the new vehicles that they buy. They expect their new purchase to be better equipped, more comfortable, and perform better than the vehicle they just traded in (which may only be a few years old). The new vehicle may be better in all respects than the old one on paper, but if it lacks refinement then it will not feel better and the customer will not be fully satisfied. They may choose to take their loyalty to another vehicle manufacturer next time. • Marketing to existing customers ‘Trade your old model in for this year's model: it is loaded with features, more comfortable and more refined.’ The modern car industry needs turnover to survive. People need to be encouraged to trade in regularly. The increase in vehicle leasing schemes for retail customers encourages this turnover. The importance of vehicle refinement can be tested using the following group exercise where team members put a monetary price on refinement. This is an absolute test on the value that they place on refinement. Group exercise – Line up How much extra are you willing to pay for a B+ class vehicle (such as a small family sedan) that offers significant additional refinement compared to its rivals? Stand up and form a line – those willing to spend nothing extra at one end and those willing to pay a significant sum at the other. You should interview those standing next to you...