Page 665 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CHAP TER 2 0. 1 Vehicle refinement: Purpose and targets

quality and cost. Although there was scatter in the results
Vehicle refinement
obtained, there was evidence of clustering with certain
Ride Driveability
classes of customer showing predictable tastes with
vehicle-refinement issues helping to define that taste.
NVH
Noise suppression Throughout the 1990s Rover Group in the UK (sub-
Noise design sequently they traded under the MG badge) defined
Vibration suppression
Squeaks, rattles and ‘Refinement’ as the invisible feature of their vehicles
tizzes 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
Fig. 20.1-1 The scope of the term ‘Vehicle Refinement’.
(witness the advertisements by manufacturers that stress
how quiet their cars are). Reasons for this include:
undertaken affects the driving experience directly.
Therefore, the reader is encouragedto think of refinement Legislation Since the adoption by Member States of
as being inextricably linked to the business of selling Council Directive 70/157/EEC (1970) limiting the
passenger cars (and increasingly this is being extended to permissible levels of noise emitted by accelerating
vans, light trucks, trucks, buses, coaches and other road vehicles, the sale of new non-conforming vehicles is
vehicles). prohibited in the European Community. Similar
Some further definitions are offered for the sake of legislation has been adopted in many non-EU coun-
clarity. In this section the terms: tries, and certainly in all the main automotive terri-
torial markets.
Noise shall be used to describe audible sound,
with particular attention paid to fre- Marketing to new customers Refinement is a feature
quencies in the range of 30–4000 Hz. that may be used to distinguish a vehicle from its
otherwise similar competitors, thus attracting cus-
Vibration shall be used to describe tactile vibra- tomers not necessarily loyal to that particular brand.
tion, with particular attention paid to
frequencies in the range of 30–200 Hz. Customer expectation Customers have come to
expect continuous improvement in the new vehi-
Other terms that will be encountered include:
cles that they buy. They expect their new purchase to
Primary ride taken to be the rigid body motion be better equipped, more comfortable, and perform
of the passenger compartment better than the vehicle they just traded in (which
relative to the road. Typical fre- may only be a few years old). The new vehicle may be
quency range – 0–6 Hz. better in all respects than the old one on paper, but if
Secondary ride taken to be the relatively large it lacks refinement then it will not feel better and the
amplitude motion of sub-elements customer will not be fully satisfied. They may choose
of the vehicle such as individual to take their loyalty to another vehicle manufacturer
wheels, axles or elements of the next time.
powertrain. Typical frequency Marketing to existing customers ‘Trade your old
range – 6–30 Hz. model in for this year’s model: it is loaded with fea-
Structure- tures, more comfortable and more refined.’ The
radiated noise being airborne noise radiated by modern car industry needs turnover to survive.
a structural surface that is vibrating. People need to be encouraged to trade in regularly.
Also known as ‘structure borne The increase in vehicle leasing schemes for retail
noise’. customers encourages this turnover.
The importance of vehicle refinement can be tested using
20.1.3 The purpose of vehicle the following group exercise where team members put
refinement a monetary price on refinement. This is an absolute test
on the value that they place on refinement.
Refinement helps manufacturers sell their vehicles. Brandl
et al. (2000) published the results of a formal investigation 20.1.4 How refinement can be
of customer attitudes to vehicle refinement. Customers
were asked to complete a questionnaire relating to their achieved in the automotive industry
own vehicle. They were asked questions relating to their
attitudes on vehicle prestige (brand by another name), The traditional vehicle manufacturer is organised
performance, convenience, family friendliness, noise according to functional divisions being typically: Design,

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