Infiniti F50. Manual - part 37

 

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Infiniti F50. Manual - part 37

 

 

A/T CONTROL SYSTEM

AT-33

D

E

F

G

H

I

J

K

L

M

A

B

AT

Normal Control

Each clutch is adjusted to the necessary pressure to match the
engine drive force.

Back-up Control (Engine brake)

When the select operation is executed during driving and the trans-
mission is shifted down, the line pressure is set according to the
vehicle speed.

During Shift Change

The necessary and adequate line pressure for shift change is set.
For this reason, line pressure pattern setting corresponds to input
torque and gearshift selection. Also, line pressure characteristic is
according to engine speed, during engine brake operation.

PCIA0008E

PCIA0009E

PCIA0010E

AT-34

A/T CONTROL SYSTEM

At Low Fluid Temperature

When the A/T fluid temperature drops below the prescribed tempera-
ture, in order to speed up the action of each friction element, the line
pressure is set higher than the normal line pressure characteristic.

Shift Control

ECS0082U

The clutch pressure control solenoid is controlled by the signals from the switches and sensors. Thus, the
clutch pressure is adjusted to be appropriate to the engine load state and vehicle driving state. It becomes
possible to finely control the clutch hydraulic pressure with high precision and a smoother shift change charac-
teristic is attained.

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.

PCIA0011E

PCIA0012E

PCIA0013E

A/T CONTROL SYSTEM

AT-35

D

E

F

G

H

I

J

K

L

M

A

B

AT

Lock-Up Control

ECS0082V

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.

Select lever

D position, M5 position

M4 position

Gear  position

5

4

3

4

Lock-up

×

×

Slip lock-up

×

×

×

PCIA0014E

AT-36

A/T CONTROL SYSTEM

Engine Brake Control

ECS0082W

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

ECS0082X

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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