Subaru SVX 1992 Manual page 397

3- 2 [rv13B1]
AUTOMATIC TRANSMISSION AND DIFFERENTIAL
~
B: FUNCTION
Lock-up piston
Lock-up control valve
Lock-up apply circuit
C i
L_
~ Pilot
pressure
;
I E:1
cooler
Lock-up release circuit-/
Torque converter
REG . pressure
~'-
Lock-up duty pressure
(B) (A) or pilot pressure
Vehicle speed Drain
Throttle opening
t ~- Pilot pressure
Engine speed
ATF temperature - - r
sensor signal
Range signal
A/T control unit
Filter
'-- Plunger
I Duty solenoid B (lock-up)
C3-003
Fig . 5
The lock-up control valve is pushed downward by
torque converter REG pressure and pilot pressure. It is
pushed upward by lock-up duty pressure and spring
force.
1 . LOCK-UP OPERATION
Oil pressure at the lock-up control duty solenoid valve is
drained (duty ratio 95%) by a signal from the automatic
transmission control unit so that no lock-up duty pres-
sure is developed and the lock-up control valve remains
in condition (A). As a result, hydraulic oil flows into the
lock-up apply circuit . On the other hand, the lock-up
release circuit drains . This causes a pressure differential
across the lock-up piston . The piston is then forced
against the impeller cover and turned as an integral unit
with the cover. Thus, power from the engine is directly
transmitted to the transmission input shaft. That is, the
transmission is directly coupled to the engine .
2. NON-LOCK-UP OPERATION
In this mode, the lock-up control duty solenoid is driven
at a 5% duty ratio . This causes the lock-up duty pres-
sure (pilot pressure) to be generated. With this pres-
sure, the lock-up control valve is set to condition (B),
and hydraulic oil flows into the lock-up release circuit.
On the other hand, the lock-up apply circuit is con-
nected to the oil cooler in the radiator . Accordingly, the
relationship between "lock-up release pressure lock-up
apply pressure" is established. As a result, the lock-up
piston is forced to separate from the impeller cover, and
power is transmitted from impeller to turbine to input
shaft, as with an ordinary torque converter coupling .
3 . SMOOTH CONTROL
When the lock-up clutch activates, the clutch partially
engages. Lock-up apply pressure increases smoothly to
engage the lock-up clutch .
4. NON-LOCK-UP OPERATION DURING "1ST
SPEED", "N", "R" AND "P" POSITION
In this mode of operation, pilot pressure is generated,
and the lock-up control valve is set to condition (B)
where lock-up is inoperative.
6