Infiniti Q45 (FY33). Manual - part 9

Control of shift valves A and B

SAT047J

Pilot pressure generated by the operation of shift solenoid valves A and B is applied to the end face of shift
valves A and B.
The drawing above shows the operation of shift valve B. When the shift solenoid valve is “ON”, pilot pressure
applied to the end face of the shift valve overcomes spring force, moving the valve upward.

LOCK-UP CONTROL

The torque converter clutch piston in the torque converter is locked to eliminate torque converter slip to
increase power transmission efficiency. The solenoid valve is controlled by an ON-OFF duty signal sent from
the TCM. The signal is converted to oil pressure signal which controls the torque converter clutch piston.

Conditions for lock-up operation

When vehicle is driven in 4th gear position, vehicle speed and throttle opening are detected. If the detected
values fall within the lock-up zone memorized in the TCM, lock-up is performed.

Overdrive control switch

OFF

Selector lever

“D” position

Gear position

Vehicle speed sensor

More than set value

Throttle position sensor

Less than set opening

Closed throttle position switch

OFF

A/T fluid temperature sensor

More than 40°C (104°F)

SAT010J

Torque converter clutch solenoid valve control

The torque converter clutch solenoid valve is controlled by the
TCM. The plunger closes the drain circuit during the “OFF” period,
and opens the circuit during the “ON” period. If the percentage of
OFF-time increases in one cycle, the pilot pressure drain time is
reduced and pilot pressure remains high.
The torque converter clutch piston is designed to slip to adjust the
ratio of ON-OFF, thereby reducing lock-up shock.

IDX

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-33

SAT011J

OFF-time
INCREASING

Amount of drain
DECREASING

Pilot pressure
HIGH

Lock-up
RELEASING

Torque converter clutch control valve operation

SAT048J

Lock-up released
The OFF-duration of the torque converter clutch solenoid valve is long, and pilot pressure is high. The pilot
pressure pushes the end face of the torque converter clutch control valve in combination with spring force to
move the valve to the left. As a result, converter pressure is applied to chamber A (torque converter clutch
piston release side). Accordingly, the torque converter clutch piston remains unlocked.
Lock-up applied
When the OFF-duration of the torque converter clutch solenoid valve is short, pilot pressure drains and
becomes low. Accordingly, the control valve moves to the right by the pilot pressure of the other circuit and
converter pressure. As a result, converter pressure is applied to chamber B, keeping the torque converter
clutch piston applied.
Also smooth lock-up is provided by transient application and release of the lock-up.

OVERRUN CLUTCH CONTROL (ENGINE BRAKE CONTROL)

Forward one-way clutch is used to reduce shifting shocks in downshifting operations. This clutch transmits
engine torque to the wheels. However, drive force from the wheels is not transmitted to the engine because
the one-way clutch rotates idle. This means the engine brake is not effective.
The overrun clutch operates when the engine brake is needed.

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-34

Overrun clutch operating conditions

Gear position

Throttle opening

“D” position

, D

gear position

Less than 3/16

“2” position

, 2

gear position

“1” position

, 1

gear position

At any position

SAT014J

SAT015J

Overrun clutch solenoid valve control

The overrun clutch solenoid valve is operated by an ON-OFF sig-
nal transmitted by the TCM to provide overrun clutch control
(engine brake control).
When this solenoid valve is “ON”, the pilot pressure drain port
closes. When it is “OFF”, the drain port opens.
During the solenoid valve “ON” pilot pressure is applied to the end
face of the overrun clutch control valve.

SAT049J

Overrun clutch control valve operation

When the solenoid valve is “ON”, pilot pressure A is applied to the
overrun clutch control valve through shuttle shift valve S. This
pushes up the overrun clutch control valve. The line pressure,
which is routed by the overrun clutch reducing valve, is then shut
off so that the clutch does not engage.
When the solenoid valve is “OFF”, pilot pressure A is not gener-
ated. At this point, the overrun clutch control valve moves down-
ward by spring force. As a result, overrun clutch operation pressure
is provided by the overrun clutch reducing valve. This causes the
overrun clutch to engage.
In the “1” position, the overrun clutch control valve remains pushed
down so that the overrun clutch is engaged at all times.

IDX

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-35

Control Valve

FUNCTION OF CONTROL VALVES

Valve name

Function

Pressure regulator valve
Pressure regulator plug
Pressure regulator sleeve plug

Regulate oil discharged from the oil pump to provide optimum line pressure for all driving
conditions.

Pressure modifier valve

Used as a signal supplementary valve to the pressure regulator valve. Regulates pressure-
modifier pressure (signal pressure) which controls optimum line pressure for all driving con-
ditions.

Modifier accumulator piston

Smooths hydraulic pressure regulated by the pressure modifier valve to prevent pulsations.

Pilot valve

Regulates line pressure to maintain a constant pilot pressure level which controls lock-up
mechanism, overrun clutch, 3-2 timing required for shifting.

Accumulator control valve
Accumulator control sleeve

Regulate accumulator back-pressure to pressure suited to driving conditions.

Manual valve

Directs line pressure to oil circuits corresponding to select positions.

Hydraulic pressure drains when the shift lever is in Neutral.

Shift valve A

Simultaneously switches three oil circuits using output pressure of shift solenoid valve A to
meet driving conditions (vehicle speed, throttle opening, etc.).
Provides automatic downshifting and up-shifting (1st

2nd

3rd

4th gears/4th

3rd

2nd

1st gears) in combination with shift valve B.

Shift valve B

Simultaneously switches three oil circuits using output pressure of shift solenoid valve B in
relation to driving conditions (vehicle speed, throttle opening, etc.).
Provides automatic downshifting and up-shifting (1st

2nd

3rd

4th gears/4th

3rd

2nd

1st gears) in combination with shift valve A.

Shuttle shift valve S

Switches hydraulic circuits to provide 3-2 timing control and overrun clutch control in relation
to the throttle opening.
Inactivates the overrun clutch to prevent interlocking in “D” (D

) position when the throttle is

wide open.

Overrun clutch control valve

Switches hydraulic circuits to prevent engagement of the overrun clutch simultaneously with
application of the brake band in “D” position. (Interlocking occurs if the overrun clutch
engages during D

operation.)

4-2 relay valve

Memorizes that the transmission is in “D” (D

) position. Prevents the transmission from

downshifting from “D” (D

) to “2” position in combination with 4-2 sequence valve and shift

valves A and B when downshifting from “D” (D

) to “2” position.

4-2 sequence valve

Prevents band servo pressure from draining before high clutch operating pressure and band
servo releasing pressure drain (from the same circuit) during downshifting from “D” (D

) to

“2” position.

Servo charger valve

An accumulator and a one-way orifice are used in the “2” position band servo oil circuit to
dampen shifting shock when shifting from “1” to “2” position.
To maintain adequate flow rate when downshifting from “D” position to “2” position, the servo
charger valve directs “2” position band servo hydraulic pressure to the circuit without going
through the one-way orifice when downshifting from “D” position.

Position

Circuit

OVERALL SYSTEM

AT-36

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