Infiniti Q45 (FY33). Manual - part 8

Control System

OUTLINE

The automatic transmission senses vehicle operating conditions through various sensors. It always controls
the optimum shift position and reduces shifting and lock-up shocks.

SENSORS

TCM

ACTUATORS

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
Turbine revolution sensor
Overdrive control switch
ASCD control unit
TCS/ABS control unit

Shift control
Line pressure control
Lock-up control
Overrun clutch control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-II communication line
control
Duet-EA control

Shift solenoid valve A
Shift solenoid valve B
Overrun clutch solenoid valve
Torque converter clutch

solenoid valve

Line pressure solenoid valve
O/D OFF indicator lamp

CONTROL SYSTEM

SAT741J

IDX

OVERALL SYSTEM

AT-29

TCM FUNCTION

The function of the TCM is to:

Receive input signals sent from various switches and sensors.

Determine required line pressure, shifting point, lock-up operation, and engine brake operation.

Send required output signals to the respective solenoids.

INPUT/OUTPUT SIGNAL OF TCM

Sensors and solenoid valves

Function

Input

PNP 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 switch

Detects 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.

Turbine revolution sensor

Sends an input shaft revolution signal.

Vehicle speed sensor

Used as an auxiliary vehicle speed sensor. Sends a signal when revolution sen-
sor (installed on transmission) malfunctions.

Overdrive control switch

Sends a signal, which prohibits a shift to “D

” (overdrive) position, to the TCM.

ASCD control unit

Sends a cruise signal or “D

” (overdrive) cancel signal to TCM.

Output

Shift solenoid valve A/B

Selects shifting point suited to driving conditions in relation to a signal sent from
TCM.

Line pressure solenoid valve

Regulates (or decreases) line pressure suited to driving conditions in relation to
a signal sent from TCM.

Torque converter clutch solenoid valve

Regulates (or decreases) lock-up pressure suited to driving conditions in relation
to a signal sent from TCM.

Overrun clutch solenoid valve

Controls an “engine brake” effect suited to driving conditions in relation to a sig-
nal sent from TCM.

O/D OFF indicator lamp

Shows TCM faults, when A/T control components malfunction.

OVERALL SYSTEM

Control System (Cont’d)

AT-30

Control Mechanism

LINE PRESSURE CONTROL

TCM 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.

SAT003J

Normal control

The line pressure to throttle opening characteristics is set for suit-
able clutch operation.

SAT004J

Back-up control (Engine brake)

If the selector lever is shifted to “2” position while driving in D

(OD)

or D

, 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.

SAT005J

During shift change

The 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 temperature

Fluid 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.

IDX

OVERALL SYSTEM

AT-31

SAT006J

The line pressure is reduced below 60°C (140°F) to prevent
shifting shock due to low viscosity of automatic transmission
fluid when temperature is low.

SAT007J

Line pressure is increased to a maximum irrespective of the
throttle opening when fluid temperature drops to −10°C (14°F).
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 CONTROL

The 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.

SAT008J

Control of shift solenoid valves A and B

The 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 “ON”, the drain circuit closes and pilot pressure is applied to
the shift valve.

Relation between shift solenoid valves A and B and gear positions

Gear position

Shift solenoid valve

, 2

, 1

, 2

, 1

(OD)

N-P

ON (Closed)

OFF (Open)

ON (Closed)

OFF (Open)

ON (Closed)

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-32

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