000000 073 1. SPECIFICATION Unit Description Specification PTU (Power Transfer Unit) Gear ratio 2.929 Numbers of helical gear 22/39 Numbers of hypoid gear 23/38 Weight 21.5 kg (with oil) Oil LW 80W90 Oil capacity 0.6 L (600 ml) Operating temperature 40 to 150 C Ecoupling Maximum torque 1,000 Nm Operating temperature 40 to 120 C Numbers of main clutch Outer: 11, Inner: 11 Numbers of pilot clutch Outer: 4, Inner: 3 Coil windings Weight Oil Oil capacity 240 turns 8 kg ECF107 (ATF based EMCD special oil) 0.145 L (145 ml)
074 000000 1. OVERVIEW The system in this vehicle is the electronic 4WD system and controls the traction to rear wheels according to the driving conditions. 1) Driving Mode (1) AUTO mode (Normal driving mode) Normally the vehicle is in 2WD mode. Automatically change to this mode when the vehicle needs higher traction. (2) LOCK mode (when pressing 4WD LOCK switch) This mode provides the highest traction. Use this mode when driving on unpaved, rugged, steep, sandy, wet or slippery roads. In 4WD LOCK mode, if the rear wheel speed exceeds 40 km/h, 4WD LOCK mode is canceled and 4WD AUTO mode is activated (Indicator OFF). If the speed is decreased below 35 km/h, 4WD LOCK mode is resumed (Indicator ON again). Mode table 4WD LOCK switch Vehicle speed Driving mode Not pressed (4WD AUTO) No conditions 4WD AUTO Pressed (4WD LOCK) over 40 km/h 4WD AUTO Pressed (4WD LOCK) below 35 km/h 4WD LOCK
000000 075 2. SYSTEM LAYOUT PTU assembly Ecoupling control unit (located on the floor under driver seat) Ecoupling 1) Components (1) PTU (Power Transfer Unit) The power transfer unit in the front wheel drive model changes the angle of engine torque to 90 and transfer it to Ecoupling to distribute the torque to rear wheels. (2) ECoupling (Electronic Coupling) ECoupling transfer the engine torque from PTU to rear axle and controls to distribute it between front wheels and rear wheels. (3) ECoupling Control Unit (ECU) ECoupling controls the current (clutch engagement force) of EMCD in ECoupling according to CAN signals (wheel speed, engine torque, pedal position, ABS/ESP signals). * EMCD: ElectroMagnetic Control Device
076 327001 The power transfer unit in the front wheel drive model changes the angle of engine torque to 90 by combination between helical gear and hypoid gear and transfer it to Ecoupling to distribute the torque to rear wheels. 1) Component 1. Input shaft 2. Helical gear 3. Dust seal 4. Helical gear 5. Hypoid gear 6. Hypoid gear 7. Output shaft 8. Companion flange
327001 077 2) Torque Flow and Gear Combination PTU Gear ratio: 2.929 22/39 (helical gear) x 23/38 (hypoid gear) = 0.341 PTU gear ratio = 1/0.341 = 2.929 3) Engagement of Input Shaft PTU is engaged with the ring gear on transaxle and always runs to rotate the propeller shaft.
078 328001 1) Component 1. Coupling assy Electric 2. Coupling Electric 3. BRG assy Race 4. Cover 5. Seal Dust 6. Flange assy Companion 7. Nut Drive pinion 8. Wiring assy Harness
328001 079 2) Sectional Diagram 1. Companion flange 2. Housing 3. Main clutch 4. Pressure plate 5. Ball 6. Cam 7. Magnet 8. Drive pinion (to rear differential) 9. Xring 10. Rotor clutch 11. Pilot clutch 12. Armature 13. Hub 14. Oil 15. Rubber coupling 16. Propeller shaft The housing is engaged with propeller shaft through companion flange and rubber coupling and turns with propeller shaft. The outer main clutch and the outer pilot clutch are connected to housing and the inner main clutch is connected to hub. The inner pilot clutch is connected to hub through cap, ball and pressure plate. ECoupling is filled with oil. The hub is connected to rear axle drive pinion by spline.
0710 328001 3) Operation (1) When ECoupling is not operating (2WD: No current to magnet) The torque from PTU is transferred to housing through propeller shaft, rubber coupling and companion flange. But, if the current is not supplied to the magnet, the pilot clutch is not engaged and the cam thrust cannot be generates. Thus, the main clutch is not engaged and the torque cannot be transferred to the companion flange.
328001 0711 (2) When ECoupling is operating (: supplying current to magnet) The torque from PTU is transferred to housing through propeller shaft, rubber coupling and companion flange. As soon as the current is supplied to magnet, the magnet flux is generated in rotor clutch, pilot clutch and armature according to the amount of current. The magnetic induction moves the armature and engage the pilot clutch. If there is a speed difference between front axle and rear axle, This also makes the speed difference between cam and pressure plate. This difference rotates and slides the ball on the ramp. According to this, the cam is separated from the pressure plate. Therefore, the pressure plate with cam thrust pushes the main clutch to engage between housing and hub. The driving force is transferred to the rear axle through housing, hub, drive pinion and rear differential in order.
0712 328017 1) System Layout ECoupling controls the clutch engagement force by the magnetic coil. ECoupling determines the clutch engagement force according to CAN signals (wheel speed, engine torque, pedal position, ABS/ESP signals). (1) Operating mode 4WD AUTO/LOCK mode Smart controlling according to steering angle and wheel speed In 4WD LOCK mode, if the rear wheel speed exceeds 40 km/h, 4WD LOCK mode is canceled and 4WD AUTO mode is activated (Indicator OFF). If the speed is decreased below 35 km/h, 4WD LOCK mode is resumed (Indicator ON again).
328017 0713 2) Circuit Diagram
0714 328017 3) Block Diagram of Input & Output
328017 0715 4) System Protection for 4WD (1) Abnormal tire detection function If an abnormal tire installed, ECoupling control unit reduces the torque to rear wheels. In this mode, ECoupling operates as if it is in 2WD mode. ECoupling control unit recognizes the abnormal tire by calculating the differences in CAN signals from wheel speed sensors. (2) ECoupling overheat protection function When ECoupling is overheated, ECoupling control unit reduces the torque to rear wheels. In this mode, ECoupling operates as if it is in 2WD mode. The oil temperature sensor for ECoupling is not applicable. ECoupling control unit recognizes the overheat condition by temperature characteristics of clutch and coil current. ECoupling control unit monitors the system for 30 minutes to precisely control the torque transferring. To check this period, ECoupling control unit monitors the engine coolant temperature and the intake air temperature.