Transfer Case: Description and Operation
Description
Part Time
Part Time is selective electric 4 wheel drive system.
The mode switch consists of the 3 modes ; 2High, 4High, 4Low.
When the vehicle speed is 0mi/h(standing) and the shift lever is in neutral position, it can switch 4High to 4Low.
When selects 4Low mode, it has better driving power (torque ratio-2.481:1) in case not exceeds 40kph(25mi/h).
Full Time
Full Time is electronic 4 wheel drive system.
The mode switch consists of the 3 modes ; Auto, 4High-Lock, 4Low.
In Auto mode TCCU receives load condition, driver's will, and ABS/ESP signal, etc and controls the front/rear driving power in the range of 0:100 to 50:50.
When the vehicle speed is 0mi/h(standing) and the shift lever is in neutral position, it can switch 4High-Lock to 4Low.
When selects 4Low mode, it has better driving power (torque ratio-2.481:1) in case not exceeds 40kph(25mi/h).
Operation
Part Time
1. TCCU receives the mode switch signal and activates the shift motor.
The shift cam linked to the shift motor moves the lock-up fork(2High<->4High) or reduction fork(4High<->4Low).
TCCU controls the motor by receiving MPS(Motor Position Sensor) signal inside the shift motor.
Driving chain delivers the power to the front propeller shaft.
2. TCCU receives the mode switch signal(2High->4High) and activates the shift motor.
The shift cam linked to the shift motor moves the lock-up fork(2High<->4High).
Before moving the fork TCCU magnetizes the EMC coil,
TCCU synchronizes the lock-up hub(Front) with EMC housing(Rear) for better shifting.
3. TCCU receives the mode switch signal(4High->4Low) and activates the shift motor.
The shift cam linked to the shift motor moves the reduction fork(4High->4Low).
The reduction hub connected to the reduction fork moves the planetary gear to change the torque ratio(2.481:1) for better driving force.
Full Time
In Auto mode TCCU activates the magnetic clutch by magnetizing the EMC coil and variates the ratio of front/rear driving power by 0:100 - 50:50 related to the EMC duty.
In 4High mode TCCU fix the ratio of 50:50.
In 4Low mode the torque ratio is 2.481:1.
Operating Elements
Part Time
1. Mode switch (2High<->4High<->4Low)
A. Drivers toggle the mode switch to select the 4WD mode(2High, 4High, 4Low)
B. It can switch 2High<->4High under the vehicle speed of 80kph(50mph) but mode switching of 2High<->4Low, 4High<->4Low is possible at standing and neutral position of shift lever.
2. Motor Position Sensor (MPS)
MPS is magnetic field sensor and places inside the shift motor.
The MPS and round magnetic in TCCU are as an assembly and the angle is calibrated so should not be disassembled in any case.
Because the angle never be calibrated once the shift motor and TCCU are disassembled.
3. Shift motor
The shift motor switches the 4WD mode(2High<->4High<->4Low) by receiving TCCU signal.
4. Electronic Magnet Clutch(EMC) coil
The EMC coil synchronizes the lock-up hub with the EMC housing for shifting 4High to 4Low while driving.
EMC is activated before the shift motor moves the lock-up fork and stops after completing shifting 4High.
EMC is activated about 6 seconds. TCCU sends 12V of duty 100%.
5. Indicator and Warning lamp
The indicator lamp for 4WD mode(4High,4Low) is in the cluster. But there is no indicator lamp for 2High.
When the 4WD system fails, the 4WD warning lamp(yellow) is on center in the cluster.
The cluster controls 4WD related lamps by receiving TCCU signal via CAN.
Full Time
1. Mode switch (Auto<->4High<->4Low)
A. Drivers toggle the mode switch to select the 4WD mode(Auto, 4High, 4Low)
B. It can switch Auto<->4High under the vehicle speed of 80kph(50mph) but mode switching of Auto<->4Low, 4High<->4Low is possible at standing and neutral position of shift lever.
2. Motor Position Sensor (MPS)
MPS is magnetic field sensor and places inside the shift motor.
The MPS and round magnetic in TCCU are as an assembly and the angle is calibrated so should not be disassembled in any case.
Because the angle never be calibrated once the shift motor and TCCU are disassembled.
3. Shift motor
The shift motor switches the 4WD mode(2High<->4High<->4Low) by receiving TCCU signal.
4. Electronic Magnet Clutch(EMC) coil
The driving force deviates by EMC duty.
TCCU controls EMC duty by receiving the related sensor signals via CAN.
EMC duty is normally 200Hz, 12V at duty 100%, and 0V at duty 0%.
* While ABS/ESP control is activated, EMC duty control is limited.
5. Indicator and Warning lamp
The indicator lamp for 4WD mode(4High-Lock,4Low) is in the cluster. But there is no indicator lamp for Auto.
When the 4WD system fails, the 4WD warning lamp(yellow) is on center in the cluster.
The cluster controls 4WD related lamps by receiving TCCU signal via CAN.