Pressure Modifier Valve; Vacuum Throttle Valve - Datsun 620 Series 1977 Service Manual

3
Jit
f
ng valve
24
1
3
L
l
r
I
Js
I i
ilr
t
pressure
6 when
shif
ing from 3rd
to
2nd
at
D range Thus the
throttle of line
pressure
6
reduces
the
shock generated
fro
shifting
A
plug
in
the
SSV
left
end
readjust
the throttle
piessu
e
I
6
which
varies
depending
on
the engine
throttle
con
dition
to
a
throttle
pressure
19
suiled
to
the
sp
ed
change
control
Moreover
the
plug is
a
valve which
applies
line
P
esspre
13
in lieu
of the
throttle
pressure
to the
SSV and the
FSV when
kickdowri
is
performed
When the
throttle
pressure
16 is
applied
to
the
left side of this
plug
and the plug
is epressed
toward the
right
a
slight
space
is
formed from
the
throttle
pressure
6
10
19
A throt
tIepressu
19
w 1 i F h
is lower by
the
pressure loss
equivalent to
this
space is
rH
1
Pressure Odifier valve PMV
I
Compared to
the operating
pressure
required
in
starting th vehicle the
ppwer
trimsinitting
capacity
of the
clutch
that
is
required
operating
pres
sure
may be
lower when the vehicle
is
once
started When the line pressure is
retained
at
a
high
level
up
to a
high
vehicle
speed
shock
gerieraled
from
the
shirring
increases
arid
the oil
pump loss also
jncrdases
In
order
to
prevent
his the
t
l r ot t le
pressure
must
be
l
hanged
over
with
the
operation
of
the
governor
pressure
15
to
reduce
Ihe line pressure The
PMV
is
used for
this
purposc
Automatic Transmission
generated the
piessure
loss is added
to
the
spring
force
and
the plug
is lhus
forced back from
the
right
to the
left
When this pressure 19
increases
ex
cessively the plug
is
further depressed
toward the left
space from
the
lhrot
tle pressure 19
to
the drain circuit
13
increases
and the throttle
press
ure
19
decreases Thus the
plug is
balanced imd the throttle
pressure
19
is reduced
to
Ii
certain
value
against the throttle pressure
6
Wheri
performing
kickdowri
the
SDV
moves a
high
line
pressure
is led
to
the
circuit
19 from the line
pressure
circuit
13
which had been
drained
the plug
is
forced toward the
left and
circuit 19
becomes equal
to
the line
pressure
13
I
W
15
I
A
TOgS
Fig
iT 13
2nd 3rd shift vallJe
I
When the
governor
pressuie IS
which is
applied to
the
right
side of
the PMV
is
low
the
valve
is
forced
toward the
right by
the throttle
ines
sure 16
applied
to the
area differ
ence
of the value
and
the
spring
foice
and
t he
circuit
from circuit 16 to
circuit
18 is
closed However when
vehicle
speed
increases
andl
the
gaver
nor
pressure
15
exceeds a certain
level the
governor pressure
toward the
left which is
applied
to
the
right
side
exceeds the
spring
force and the throt
tle
pressure
16 toward thc
right
the
valve
is
depressed loward the
lefi
and
the throttle pressure is
led from
circuit
AT 9
16
to
circuit 18 This throttle
pressure
18 is applied to
the
top of
the PRV
and the force
of the
line
pressure source
7
is reduced Contra
rily
when
the vehicle
speed
decreases
arid
the
governor ipressure
15
de
creases the force toward
the
fight
exceeds ithe governor
pressure the
valve
is
forced back
toward
the
right
and
the
throttle
pressure
18
is
drained
to
the
spring unit
This valve is
sWitched
when the
throttle pressure and the
governor
pressure
are
high
or
when
tIiey
are
both
Tow i
i
I
11
18
16
n
r
I
I
15
AT099
Fig
AT 14 Pre
ure
modifier
valve
Vacuum thro le valve VTV
The
vacuum
t
rottle valve
is
a
regula tor
valve
whiCh
uses
the
line
pressure
7
for the
pressure
source
and
regulates
the throttle pressure 16
I
which
is
proportioned
t
the
force of
the
vacuum
diaphragm
The
vacuum
dia
phragm
yories
depending
on
the
engine
throt le condition
negative
pressure
in
the
inta
e
line
When the
line
pressure
7
is ap
plied
to
the
bottom
through
the valve
hole and
the
v a ve
is
forced
upward
space
from the line pressure
7
to
the
throttle
pressure
16
is
dosed and
the space from the Ihrottle
pressure
16
to
the
drain circuit
17 is about
to
open
In
this operation
the
throttle
pressure
16
becomes
lower than
the
linep
s
ureY
btthe
p
e sur
9
iv
alenl
of
the
loss of
space
and Ihe
force depressing
tlie rod
if the vaeuum
diaphragm
is balanced wit Ii thethrot
tie
pressure 16
a
pplied upward
tOlthe
bottom
When the
erigine torque is high
Ihe
negative pressure
in
the intake
iirie
rises
tending
ioward atmospheric
pressure
and the force of the rod
to
depress
the valve increases
As
a
result
the valve
is
depressed
downward the