Changan CS35 2012 - Vibration Process Engineering

1.1.5-2
CS35 2013.04
1.1.5-2Noise, Vibration and Harshness
Noise T
r
ansmitted Through V
e
hicle
Example:
•
The
noise comes from engine.
• directly through air.
• It is transmitted from engine to vehicle
body with vibration and spread to the cab
by the way of sound
wa
ve.
Vibration Process Engineering
• Vibration waves with a frequency lower
than 20 Hz (low frequency) or higher than
20,
000 Hz (20 kHz,
h
i
gh freq
uency) can
not
be he
ard by human ears.
•
The
en
gine with fle
x
ib
le inst
a
llat
i
on will
vibrate up and down when running on
rou
gh road
.
•
W
he
n fle
x
ib
le inst
allation of
engine is in
trouble, vibration will be transmitted from
enigne to vehicle body and even cab.
Applicable for the following:
•
V
ehicle process en
gine
ering
does no
t
only concern audible low frequency
vibration but also
th
e
high freque
ncy
vibration tha
t ca
n not b
e
heard
.
• Generally, the low frequency vibration is
visible.
•
The
h
i
gh-fr
equency vibration is p
a
lp
able
thro
ugh th
e floo
r and the st
eering
wheel.
R
eson
a
nce
•
E
very o
bject ha
s it
s in
herent
vibratio
n
frequency.
• If a certain system vibrates the object
with
it
s in
heeren
t vibratio
n freque
ncy
, it
will cause
reso
nance.
•
W
h
en engin
e
re
ache
s reso
nance
fre
quency
,
th
e e
ngin
e
will
operat
e
un
st
ably (eng
ine critical spe
ed).
•
O
nce
the
en
gine
sp
eed
exceeds th
e
critical
point, it becomes t
o
ope
rate st
ably
at once.
Damping
• The vibration can be reduced if a damper
is connected wit
h
spr
i
ng in p
a
rallel.
• The vehicle shock absorber is made
based on this principle.
•
D
amping
influences
the resonan
ce o
f
object and system.
• The vibration can be weaken with shock
absorber in order to eliminate the
vibrat
ion o
f veh
i
cle bod
y
.
•
I
n
fact
, veh
i
cle shock absorber
is
a
damper and the vibration on vehicle body
is weakened by the way of damping.
Item Component Description
1-
The noise transmitted
through air
2-
T
h
e no
ise
tr
an
sm
itt
e
d
through vehicle body
1 2
A1105002
Item
Compone
nt
Description
1 - Non-damping vibration
2 - Damping vibration
21
A1105003