engine INFINITI QX4 2001 Factory User Guide

ª11º Position=NBAT0012S0406
Forward clutch
Forward one-way clutch
Overrun clutch
Low and reverse brakeAs overrun clutch engages, rear internal gear is locked by the operation of low and
reverse brake.
This is different from that of D
1and 21.
Engine brake Overrun clutch always engages, therefore engine brake can be obtained when decelerat-
ing.
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OVERALL SYSTEM
Shift Mechanism (Cont'd)
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ªD1º and ª21º Positions=NBAT0012S0402
Forward one-way clutch
Forward clutch
Low one-way clutchRear internal gear is locked to rotate counterclockwise because of the functioning of
these three clutches. (Start-up at D
1)
Overrun clutch
engagement conditions
(Engine brake)D
1: Overdrive control switch in ªOFFº
Throttle opening less than 3/16
2
1: Throttle opening less than 3/16
At D
1and 21positions, engine brake is not activated due to free turning of low one-way
clutch.
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OVERALL SYSTEM
Shift Mechanism (Cont'd)
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ªD4º (OD) Position=NBAT0012S0405
High clutch
Brake band
Forward clutch
(Does not affect power transmission)Input power is transmitted to front carrier through high clutch.
This front planetary carrier turns around the sun gear which is fixed by brake band and
makes front internal gear (output) turn faster.
Engine brake At D
4position, there is no one-way clutch in the power transmission line and engine
brake can be obtained when decelerating.
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Shift Mechanism (Cont'd)
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ªRº Position=NBAT0012S0407
Reverse clutch
Low and reverse brakeFront planetary carrier is stationary because of the operation of low and reverse brake.
Input power is transmitted to front sun gear through reverse clutch, which drives front
internal gear in the opposite direction.
Engine brake As there is no one-way clutch in the power transmission line, engine brake can be
obtained when decelerating.
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OVERALL SYSTEM
Shift Mechanism (Cont'd)
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Control System=NBAT0013OUTLINENBAT0013S01The automatic transmission senses vehicle operating conditions through various sensors. It always controls
the optimum shift position and reduces shifting and lock-up shocks.
SENSORS
ETCM
EACTUATORS
PNP switch
Throttle position sensor
Closed throttle position switch
Wide open throttle position switch
Engine speed signal
A/T fluid temperature sensor
Revolution sensor
Vehicle speed sensor
Overdrive control switch
ASCD control unit
Stop lamp switch
Turbine revolution sensorShift control
Line pressure control
Lock-up control
Overrun clutch control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-II communication
line
Duet-EU controlShift solenoid valve A
Shift solenoid valve B
Overrun clutch solenoid valve
Torque converter clutch sole-
noid valve
Line pressure solenoid valve
O/D OFF indicator lamp
T/F control unit
CONTROL SYSTEMNBAT0013S02
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Control System
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TCM FUNCTION=NBAT0013S03The function of the TCM is to:
IReceive input signals sent from various switches and sensors.
IDetermine required line pressure, shifting point, lock-up operation, and engine brake operation.
ISend required output signals to the respective solenoids.
INPUT/OUTPUT SIGNAL OF TCMNBAT0013S04
Sensors and solenoid valves Function
InputPNP switch Detects select lever position and sends a signal to TCM.
Throttle position sensor Detects throttle valve position and sends a signal to TCM.
Closed throttle position switch Detects throttle valve's fully-closed position and sends a signal to TCM.
Wide open throttle position switchDetects a throttle valve position of greater than 1/2 of full throttle and sends
a signal to TCM.
Engine speed signal From ECM.
A/T fluid temperature sensor Detects transmission fluid temperature and sends a signal to TCM.
Revolution sensor Detects output shaft rpm and sends a signal to TCM.
Vehicle speed sensorUsed as an auxiliary vehicle speed sensor. Sends a signal when revolution
sensor (installed on transmission) malfunctions.
Overdrive control switchSends a signal, which prohibits a shift to ªD
4º (overdrive) position, to the
TCM.
ASCD control unitSends the cruise signal and ªD
4º (overdrive) cancellation signal from ASCD
control unit to TCM.
Turbine revolution sensor Sends an input shaft revolution signal.
Stop lamp switch Sends the lock-up release signal to the TCM at time of D
4(lock-up).
OutputShift solenoid valve A/BSelects shifting point suited to driving conditions in relation to a signal sent
from TCM.
Line pressure solenoid valveRegulates (or decreases) line pressure suited to driving conditions in rela-
tion to a signal sent from TCM.
Torque converter clutch solenoid
valveRegulates (or decreases) lock-up pressure suited to driving conditions in
relation to a signal sent from TCM.
Overrun clutch solenoid valveControls an ªengine brakeº effect suited to driving conditions in relation to a
signal sent from TCM.
O/D OFF indicator lamp Shows TCM faults, when A/T control components malfunction.
Control MechanismNBAT0180LINE PRESSURE CONTROLNBAT0180S01TCM has the various line pressure control characteristics to meet
the driving conditions.
An ON-OFF duty signal is sent to the line pressure solenoid valve
based on TCM characteristics.
Hydraulic pressure on the clutch and brake is electronically con-
trolled through the line pressure solenoid valve to accommodate
engine torque. This results in smooth shift operation.
OVERALL SYSTEM
Control System (Cont'd)
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Normal ControlNBAT0180S0101The line pressure to throttle opening characteristics is set for suit-
able clutch operation.
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Back-up Control (Engine brake)NBAT0180S0102If the selector lever is shifted to ª2º position while driving in D4(OD)
or D
3, great driving force is applied to the clutch inside the trans-
mission. Clutch operating pressure (line pressure) must be
increased to deal with this driving force.
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During Shift ChangeNBAT0180S0103The line pressure is temporarily reduced corresponding to a
change in engine torque when shifting gears (that is, when the shift
solenoid valve is switched for clutch operation) to reduce shifting
shock.
At Low Fluid TemperatureNBAT0180S0104IFluid viscosity and frictional characteristics of the clutch facing
change with fluid temperature. Clutch engaging or band-con-
tacting pressure is compensated for, according to fluid
temperature, to stabilize shifting quality.
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IThe line pressure is reduced below 60ÉC (140ÉF) to prevent
shifting shock due to low viscosity of automatic transmission
fluid when temperature is low.
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OVERALL SYSTEM
Control Mechanism (Cont'd)
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ILine pressure is increased to a maximum irrespective of the
throttle opening when fluid temperature drops to þ10ÉC (14ÉF).
This pressure rise is adopted to prevent a delay in clutch and
brake operation due to extreme drop of fluid viscosity at low
temperature.
SHIFT CONTROLNBAT0180S02The shift is regulated entirely by electronic control to accommodate
vehicle speed and varying engine operations. This is accomplished
by electrical signals transmitted by the revolution sensor and
throttle position sensor. This results in improved acceleration per-
formance and fuel economy.
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Control of Shift Solenoid Valves A and BNBAT0180S0201The TCM activates shift solenoid valves A and B according to sig-
nals from the throttle position sensor and revolution sensor to
select the optimum gear position on the basis of the shift schedule
memorized in the TCM.
The shift solenoid valve performs simple ON-OFF operation. When
set to ªONº, the drain circuit closes and pilot pressure is applied to
the shift valve.
[Relation between shift solenoid valves A and B and gear positions]
Shift solenoid valveGear position
D
1,21,11D2,22,12D3D4(OD) N-P
A ON (Closed) OFF (Open) OFF (Open) ON (Closed) ON (Closed)
B ON (Closed) ON (Closed) OFF (Open) OFF (Open) ON (Closed)
Control of Shift Valves A and BNBAT0180S0202
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OVERALL SYSTEM
Control Mechanism (Cont'd)
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Torque Converter Clutch Control Valve OperationNBAT0180S0303
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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 pres-
sure 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)
NBAT0180S04Forward one-way clutch is used to reduce shifting shocks in down-
shifting 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.
Overrun Clutch Operating ConditionsNBAT0180S0401
Gear position Throttle opening
ªDº position D
1,D2,D3gear position
Less than 3/16
ª2º position 2
1,22gear position
ª1º position 1
1,12gear position At any position
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OVERALL SYSTEM
Control Mechanism (Cont'd)
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Overrun Clutch Solenoid Valve ControlNBAT0180S0402The 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 ªONº, the pilot pressure drain port
closes. When it is ªOFFº, the drain port opens.
During the solenoid valve ªONº pilot pressure is applied to the end
face of the overrun clutch control valve.
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Overrun Clutch Control Valve OperationNBAT0180S0403When the solenoid valve is ªONº, pilot pressure A is applied to the
overrun clutch control valve. This pushes up the overrun clutch
control valve. The line pressure is then shut off so that the clutch
does not engage.
When the solenoid valve is ªOFFº, 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 ª1º position, the overrun clutch control valve remains pushed
down so that the overrun clutch is engaged at all times.
Control ValveNBAT0181FUNCTION OF CONTROL VALVENBAT0181S01
Valve name Function
IPressure regulator valve
IPressure regulator plug
IPressure regulator sleeve plugRegulate 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 conditions.
Modifier accumulator piston Smooths hydraulic pressure regulated by the pressure modifier valve to prevent pul-
sations.
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 sleeveRegulate 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.
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Control Mechanism (Cont'd)
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