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14-8
FUEL SYSTEM
- Sen
sors
If
a vortex gen eration column is p laced in the path
of the air
flow, regular vortexes are
generated
clownstream alternately. This is called
the
Karman
vortex
~ne
and the number of vortexes gerlerated
is proportiona
l to
the air flow speed, in other
words,
the amount of air
flow.
If a vortex pressure
inlet
is made downstream of
the
vortex
generating col
umn
and the pressu re
detected,
this pressure va
ri
es each time the
vortex p<lsses the inlet and
w
hen the numbar of
vortexes inc rease
s,
t he num
ber
of pressure
variations also irICreoses in proportio
n
to t his. In
othe
r words,
the frequency
of
t he pressu re
varfotions is
proportional \0
the amount of
~
.i
r
f
low.
The pressu re detection
type AFS is different f rom
the corwentiorJal ultrasonic detection type
AFS,
and
it detects the pressu re variations due 10 the
Karman
vortex
us
ing
a semkonduclOr type
pressure
sensor.
The AFS charlQes the pressure
variations 10 a SQuare wave and iropuls il as
a
pulse
signal
proportional 10 Ihe amounl of in!a ke air flow
10 IhG erlQine
cont
rol unit
"-
"
~
- - - - ,
'" throttle
Ixxtv
~
~>
,
Pow&r ~""'*"
If
rom control
'
.
"y)
Amplifi,.-
Air_
MnOG<
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