Nissan Almera Tino V10. Instruction — part 76
AT-28
OVERALL SYSTEM
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 solenoid valves.
INPUT/OUTPUT SIGNAL OF TCM
Control Mechanism
ECS0096R
LINE PRESSURE CONTROL
TCM has various line pressure control characteristics to match 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 controlled through the line pressure solenoid valve
to accommodate engine torque. This results in smooth shift operation.
Normal Control
The line pressure to throttle opening characteristics is set for suitable
clutch operation.
Sensors, switches and solenoid
valves
Function
Input
PNP switch
Detects select lever position and sends a signal to TCM.
Throttle position sensor (accelerator
pedal position (APP) sensor)
Detects throttle valve position 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 sensor
Used as an auxiliary vehicle speed sensor. Sends a signal when revolution
sensor (installed on transmission) malfunctions.
Overdrive control switch
Sends a signal, which prohibits a shift to “D
4
” (overdrive) position, to the
TCM.
Stop lamp switch
Releases lock-up system when depressing pedal in lock-up condition.
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 rela-
tion to a signal sent from TCM.
Overrun clutch solenoid valve
Controls an “engine brake” 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.
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OVERALL SYSTEM
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D
E
F
G
H
I
J
K
L
M
A
B
AT
Back-up Control (Engine Brake)
If the selector lever is shifted to “2” position while driving in D
4
(OD)
or D
3
, great driving force is applied to the clutch inside the transmis-
sion. Clutch operating pressure (line pressure) must be increased to
deal with this driving force.
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-contacting pressure is compensated for, according to fluid temperature, to stabilize
shifting quality.
●
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.
●
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.
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AT-30
OVERALL SYSTEM
SHIFT CONTROL
The shift is regulated entirely by electronic control to accommodate vehicle speed and varying engine opera-
tions. This is accomplished by electrical signals transmitted by the revolution sensor and throttle position sen-
sor. This results in improved acceleration performance and fuel economy.
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 memo-
rized 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
Control of Shift Valves A and B
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 to right side on illustration.
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 an 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.
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Shift solenoid valve
Gear position
D
1
, 2
1
, 1
1
D
2
, 2
2
, 1
2
D
3
D
4
(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)
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Overdrive control switch
ON
OFF
Selector lever
“D” position
Gear position
D
4
D
3
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)
OVERALL SYSTEM
AT-31
D
E
F
G
H
I
J
K
L
M
A
B
AT
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.
OFF-time INCREASING
↓
Amount of drain DECREASING
↓
Pilot pressure HIGH
↓
Lock-up RELEASING
Torque Converter Clutch Control Valve Operation
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 pis-
ton 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.
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MCIB9000E
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