Infiniti M35/M45 Y50. Manual - part 28

A/T CONTROL SYSTEM

AT-35

SHIFT CHANGE

The clutch is controlled with the optimum timing and oil pressure by the engine speed, engine torque informa-
tion, etc.

Shift Change System Diagram

*1: Full phase real-time feedback control monitors movement of gear ratio at gear change, and controls oil
pressure at real-time to achieve the best gear ratio.

BLIPPING CONTROL

This system makes transmission clutch engage readily by controlling (synchronizing) engine revolution
according to the (calculation of) engine revolution after shifting down.

●

“BLIPPING CONTROL” functions.

–

When downshifting by accelerator pedal depression at “D” position.

–

When downshifting under the manual mode.

●

TCM selects “BLIPPING CONTROL” or “NORMAL SHIFT CONTROL” according to the gear position, the
select lever position, the engine torque and the speed when accelerating by pedal depression.

●

Revolution control demand signal is transmitted from TCM to ECM under “BLIPPING CONTROL”.

●

TCM synchronizes engine revolution according to the revolution control demand signal.

PCIA0013E

AT-36

A/T CONTROL SYSTEM

Shift Change System Diagram

ASC (ADOPTIVE SHIFT CONTROL)

ASC automatically shifts or hold at the 3rd or 4th gear on certain roads (up/down slope and curve) and driving
condition.

When Driving on an Up/Down Slope

●

ASC judges up/down slope according to the angle of accelerator pedal and vehicle speed. Holding gear at
the 3rd or 4th on an up-slope prevents shift hunting and controls the vehicle to gain maximum driving
force. On a down-slope, automatic shift-down to the 3rd or 4th gear controls to gain maximum engine
brake.

When Driving on a Curve

●

TCM receives side G sensor signal from ABS actuator and electric unit (control unit). Holding gear at the
3rd or 4th based on the signal prevents shift-up and kick-down and controls to drive smoothly.

SCIA6483E

SCIA6469E

A/T CONTROL SYSTEM

AT-37

Lock-up Control

NCS001JU

The torque converter clutch piston in the torque converter is engaged to eliminate torque converter slip to
increase power transmission efficiency.
The torque converter clutch control valve operation is controlled by the torque converter clutch solenoid valve,
which is controlled by a signal from TCM, and the torque converter clutch control valve engages or releases
the torque converter clutch piston.

Lock-up operation condition table

TORQUE CONVERTER CLUTCH CONTROL VALVE CONTROL
Lock-up Control System Diagram

Lock-up Released

●

In the lock-up released state, the torque converter clutch control valve is set into the unlocked state by the
torque converter clutch solenoid and the lock-up apply pressure is drained.
In this way, the torque converter clutch piston is not coupled.

Lock-up Applied

●

In the lock-up applied state, the torque converter clutch control valve is set into the locked state by the
torque converter clutch solenoid and lock-up apply pressure is generated.
In this way, the torque converter clutch piston is pressed and coupled.

SMOOTH LOCK-UP CONTROL

When shifting from the lock-up released state to the lock-up applied state, the current output to the torque con-
verter clutch solenoid is controlled with the TCM. In this way, when shifting to the lock-up applied state, the
torque converter clutch is temporarily set to the half-clutched state to reduce the shock.

Half-clutched State

●

The current output from the TCM to the torque converter clutch solenoid is varied to steadily increase the
torque converter clutch solenoid pressure.
In this way, the lock-up apply pressure gradually rises and while the torque converter clutch piston is put
into half-clutched status, the torque converter clutch piston operating pressure is increased and the cou-
pling is completed smoothly.

Slip Lock-up Control

●

In the slip region, the torque converter clutch solenoid current is controlled with the TCM to put it into the
half-clutched state. This absorbs the engine torque fluctuation and lock-up operates from low speed.
This raises the fuel efficiency for 3rd, 4th and 5th gears at both low speed and when the accelerator has a
low degree of opening.

Selector lever

“D” position

“M” position

Gear position

Lock-up

–

Slip lock-up

–

PCIA0014E

AT-38

A/T CONTROL SYSTEM

Engine Brake Control

NCS001JV

●

The forward one-way clutch transmits the drive force from the engine to the rear wheels. But the reverse
drive from the rear wheels is not transmitted to the engine because the one-way clutch is idling.
Therefore, the low coast brake solenoid is operated to prevent the forward one-way clutch from idling and
the engine brake is operated in the same manner as conventionally.

●

The operation of the low coast brake solenoid switches the low coast brake switching valve and controls
the coupling and releasing of the low coast brake.
The low coast brake reducing valve controls the low coast brake coupling force.

Control Valve

NCS001JW

FUNCTION OF CONTROL VALVE

SCIA1520E

Name

Function

Torque converter regulator valve

In order to prevent the pressure supplied to the torque converter from being excessive,
the line pressure is adjusted to the optimum pressure (torque converter operating pres-
sure).

Pressure regulator valve
Pressure regulator plug
Pressure regulator sleeve

Adjusts the oil discharged from the oil pump to the optimum pressure (line pressure) for
the driving state.

Front brake control valve

When the front brake is coupled, adjusts the line pressure to the optimum pressure
(front brake pressure) and supplies it to the front brake. (In 1st, 2nd, 3rd, and 5th gears,
adjusts the clutch pressure.)

Accumulator control valve

Adjusts the pressure (accumulator control pressure) acting on the accumulator piston
and low coast reducing valve to the pressure appropriate to the driving state.

Pilot valve A

Adjusts the line pressure and produces the constant pressure (pilot pressure) required
for line pressure control, shift change control, and lock-up control.

Pilot valve B

Adjusts the line pressure and produces the constant pressure (pilot pressure) required
for shift change control.

Low coast brake switching valve

During engine braking, supplies the line pressure to the low coast brake reducing valve.

Low coast brake reducing valve

When the low coast brake is coupled, adjusts the line pressure to the optimum pressure
(low coast brake pressure) and supplies it to the low coast brake.

N-R accumulator

Produces the stabilizing pressure for when N-R is selected.

Direct clutch piston switching valve

Operates in 4th gear and switches the direct clutch coupling capacity.

High and low reverse clutch control valve

When the high and low reverse clutch is coupled, adjusts the line pressure to the opti-
mum pressure (high and low reverse clutch pressure) and supplies it to the high and low
reverse clutch. (In 1st, 3rd, 4th and 5th gears, adjusts the clutch pressure.)

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