Infiniti I30 (A33). Manual — part 8
TCM FUNCTION
=NHAT0014S03
The function of the TCM is to:
I
Receive input signals sent from various switches and sensors.
I
Determine required line pressure, shifting point, lock-up operation, and engine brake operation.
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Send required output signals to the respective solenoids.
INPUT/OUTPUT SIGNAL OF TCM
NHAT0014S04
Sensors and solenoid valves
Function
Input
Park/neutral position (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.
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.
ASCD control unit
Sends the cruise signal and D
4
(overdrive) cancellation signal from ASCD
control unit to TCM.
Stop lamp switch
Send the lock-up release signal to the TCM at time of D
4
(lock-up).
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 rela-
tion 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
signal sent from TCM.
O/D OFF indicator lamp
Shows TCM faults, when A/T control components malfunction.
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OVERALL SYSTEM
Control System (Cont’d)
AT-29
Control Mechanism
=NHAT0015
LINE PRESSURE CONTROL
NHAT0015S01
TCM has 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
NHAT0015S0101
The line pressure to throttle opening characteristics is set for suit-
able clutch operation.
SAT004J
Back-up Control (Engine brake)
NHAT0015S0102
If the selector lever is shifted to 2 position while driving in D
4
(O/D)
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.
SAT005J
During Shift Change
NHAT0015S0103
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
NHAT0015S0104
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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.
OVERALL SYSTEM
Control Mechanism
AT-30
SAT006J
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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
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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
NHAT0015S02
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
NHAT0015S0201
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
Shift solenoid valve
Gear position
D
1
, 2
1
, 1
1
D
2
, 2
2
, 1
2
D
3
D
4
(O/D)
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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OVERALL SYSTEM
Control Mechanism (Cont’d)
AT-31
Control of Shift Valves A and B
NHAT0015S0202
SAT009J
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 upward.
LOCK-UP CONTROL
NHAT0015S03
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 pres-
sure signal which controls the lock-up piston.
Conditions for Lock-up Operation
NHAT0015S0301
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.
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)
SAT010J
Torque Converter Clutch Solenoid Valve Control
NHAT0015S0302
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.
OVERALL SYSTEM
Control Mechanism (Cont’d)
AT-32
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