CONSTRUCTION
AND
FUNCTION
Under
the
full-load
condit
ion
,
the
tension l
ever
behaves
as
if
it
were
ri
gid
and
the
control block
is
opposed by
the
adaptor spring. In other words,
th
e state
of
equilibrium
is
produced by the
adapto
r
spr
i
ng
and
the
con
tr
ol
bl
ock.
If
the
s
peed
faUs
due
[0
a
rise
in
load,
then
the
ad
aptor
spring
push
..
'he
block to
'h
e left, causing the co Dual
rack
to
move
inward
,
thus
increasing
the
de
li
very
of
fuel
to
the
engine
.
Co
nside
r
the
reverse
ca
se:
the
lo
ad
is
de
crease
d on
'he
engine running slow with
full
load. In this
case, the control block keeps
on
pUShing
the
adaptor spring to prevent the speed
fr
om rising
and
>
.after
comp
ress
in
g this
spr
in
g fully ,
tou
ch
es
the
tensi
on
le'Ver.
From
ltti
s p
oint
onward,
the
block pushes the lever
awa
y from the
fu
ll
·load
SLOp
per as the
load
keeps
decreasing.
(8) Adapting injection quantity to engine
34
The true funct
io
n
of
the
,daptor
spring can
be
appreciated
when
the
two
important
chara
c
ter-
is'ics of a diesel engine and also
of
a plunger.type
inje
erion
pump
a
re
recalled
.
The amount
of
fu.1 delivered per stroke by the
plunger
in
the pumping element
is
theoretically
constant
when
the
pl
unger
is
in
a
given
angular
position
(with
the
control
rack
held
in
one
posi
·
tion), regardless
of
its reciprocating speed (depend·
enl on engine speed). Aclually, this amount
decreases
as
the
speed
rises.
The
reason
is
that
the
leakage
of
fuel, though extremely small, through
the
sliding
clearance
around
the
plunger
decreases
as
the
speed
rises.
On
the other hand, the amount
of
intake air
drawn
into
each
cylinder
of a diesel
engine
is
theoretically
coo~ant
and equal to the "swept
volume"
of
the cylinder; actually, this amount
inc.reases
as
the
spet!d
of
tile
engine
rises.
The
reason
is
that
air
has
mass
and
takes
a
definite
time to flow.
As
long
as
the
amount
of
air
drawn
mlo
the
cylinder is sulficiently large for the amount
of
fuel
spray
ed into
il
,
there
is
practically
no
problem
:
th
e fuel
wiIJ
burn complerely and the ,x.b..u
Sl
smoke
will
be
c
lean
.
How
e
ver,
under
full·load
condillon a
nd,
consequently,
with
a
large
amount
of
pe
r
-stroke
fuel
inj
ected, a qu
es
ti
on
has
to
be
asked
:
is
there
a sufficient
amount
of
excess
air
in the drawn·
in
air?
To s
ummarize
,
where
the
control
rack
is
held
steady a
nd
the ,peed
is
increased, fuel injection
quantjty
increases
but
intake
air
decreases.
Under
full·lo.tI condition, the
"'moke
limit" would
be
..
exceeded to result in a dirty
ex.b.aust
smoke. To
avoid
this.
situation,
the
control
rack
must
be
pulled
out
ward
to d
ecrease
injection quantity I
mat is, the control block must
be
allowed to
move
toward
the
tension lever
instead
of being
'toppe
d
by
this lever. This requirement
is
mel
by
the
adaptor
sp{ing.
The
graph .hown here explains how the
adap'o!
spring adaplS
in
jection
quantit
y
to
'
h'
available
air
in
the
en
gin
e:
Per-cycle in
t"ake
ai
r f
or.8
c'J'
linder
of
t
h.e
s
ngi
lli!
. A I B
a
9'"
----
--
---
I, !
~1
:==:,:::
'c : ·
-9"
.-
it
co
0·-
i ' ....
___
__ -_ h b Injecti
on
qYatltitv
,
Lf
~
~
'""~
'
..
"'.-
r : WPleal .f.'Utngs o f
~
• cor.trol rack
N
1
N
l
Spted
~ i
l1jl!!:clfon
pump
Dr
E!~In,e-,
This graph assumes that the control rack
or
the
injection
pump
ls
se
t (or maximum injection
quantity.
Curve
a -
b'
repre-sents
one setting,
and
curve
a'
- b another.
With
curve
a -
b'l
injection
quantity
would
too
much
at
speed N
l
hut
JUSt
right
at
$pe:ed
N
1
•
With
curve
il'
- b,
the
quantity
would be just right .t speed
..
N'
bu,
'00
Iitt!o
at N
1
.
What
is
deslred
for
the
air
curve
A - B
is
the
modified curve a - b, which can be produced
by
causing the control tack
to
be
pulled out
by
a
small amount
as
the
'peed
rise, under rull·load
condition. The
ad.ptor
spring makes this possible.
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