FOUR WHEEL DRIVE CONTROL SYSTEM DETAILS


  1. OPERATING CONDITION


    1. The center differential can be switched between free and lock when the vehicle is running. However, the center differential should not be switched from free to lock when the vehicle is turning or the tires are spinning.

    2. On the models with manual transmission, the transfer gear ratio can be switched between high and low only when the vehicle is stationary and the clutch pedal is being depressed.

    3. On the models with automatic transmission, the transfer gear ratio can be switched between high and low only when the vehicle is stationary and the shift lever is in N.

  2. CONSTRUCTION


    1. Transfer Assembly


      1. A planetary gear unit is used in the reduction mechanism.

      2. A synchromesh mechanism is used for smooth engagement from low gear to high gear.*


        • *: Models with manual transmission

      3. The center differential uses a TORSEN* LSD. As a result, this LSD ensures the proper torque distribution during acceleration and high-speed driving.

        Tech Tips

        *: TORSEN is a registered trademark of JTEKT Corporation.

        A01J2KZE03
        Text in Illustration
        *A Models with Automatic Transmission or Brake Control System or Rear Differential Lock System *B Models with Automatic Transmission
        *1 Transfer Low Planetary Gear Assembly *2 Transfer Input Shaft
        *3 Transfer Front Output Shaft *4 Front Driven Sprocket
        *5 Transfer Front Drive Chain *6 Front Drive Sprocket
        *7 Transfer Rear Output Shaft *8 Transfer Clutch Hub
        *9 Transfer Front Drive Gear Piece *10 Front Drive Clutch Sleeve
        *11 Center Differential *12 Transfer Indicator Switch (L4 Position)
        *13 Transfer Indicator Switch (Neutral Position) *14 Transfer Indicator Switch (Center Differential Lock Position)
        *a Shift Pattern - -

    2. Transfer Low Planetary Gear Assembly


      1. A transfer low planetary gear assembly is used on the planetary gear unit to switch the transfer gear ratio between high and low.

      2. The transfer low planetary gear assembly consists of a planetary sun gear, 4 planetary pinion gears, planetary ring gear, and planetary carrier.

      3. The planetary sun gear is integrated with the transfer input shaft. A transfer clutch hub spline piece is fitted to the rear of the planetary sun gear.

      4. 4 planetary pinion gears are fitted to the planetary carrier. Each planetary pinion gear shaft is fixed to the planetary carrier. A transfer low planetary spline piece is fitted to the rear of the planetary carrier.

      5. The planetary ring gear is fixed to the front transfer case and its internal teeth mesh with the planetary pinion gears.

      6. In this planetary gear unit, the power transmission route is switched in accordance with the movement of the transfer high and low clutch sleeve. The input power from the transfer input shaft is transmitted to the center differential case via the transfer high and low clutch sleeve.

        A01J2MQE03
        Text in Illustration
        *1 Transfer Input Shaft *2 Planetary Pinion Gear
        *3 Center Differential Case *4 Transfer Clutch Hub Spline Piece
        *5 Transfer High and Low Clutch Sleeve *6 Transfer Low Planetary Spline Piece
        *7 Planetary Carrier *8 Planetary Ring Gear
        *9 Planetary Sun Gear - -

    3. Center Differential


      1. The center differential uses a TORSEN* LSD. Also, a mechanism is used to switch the center differential between free and lock.

      2. The TORSEN* LSD is a torque-sensing LSD. It generates a limited-differential torque in proportion to the drive torque, and instantly changes the front and rear torque distribution.

      3. The torque distribution during straightline driving is 40/60 (front/rear), which is helpful for an appropriate steering response during the initial stage of a turn. During the acceleration stage of a turn, the torque distribution increases in the rear wheels.

      4. This center differential consists of a center differential case, sun gear, ring gear, coupling, 8 pinion gears, clutch plates, and planetary carrier.

      5. The drive torque is input to the center differential case.

      6. The center differential case is connected with the planetary carrier.

      7. The sun gear is connected to the front drive sprocket (in the front wheel output side) through the transfer clutch hub and transfer front drive gear piece.

      8. The ring gear is connected to the transfer rear output shaft (in the rear wheel output side) through the coupling.

      9. The center differential is switched between free and lock in accordance with the movement of the front drive clutch sleeve.

        Tech Tips

        *: TORSEN is a registered trademark of JTEKT Corporation.

        A01J2MJE01
        Text in Illustration
        *1 No. 1 Clutch Plate *2 Coupling
        *3 Transfer Rear Output Shaft *4 Sun Gear
        *5 Center Differential Case *6 No. 3 Clutch Plate
        *7 No. 2 Clutch Plate *8 Transfer Clutch Hub
        *9 No. 4 Clutch Plate *10 Transfer Front Drive Gear Piece
        *11 Front Drive Sprocket *12 Planetary Carrier
        *13 Front Drive Clutch Sleeve *14 Pinion Gear
        *15 Ring Gear - -

  3. OPERATION


    1. High-low Switching of Transfer Gear Ratio


      1. High Position


        • In the high position, the internal gear teeth of the transfer high and low clutch sleeve mesh with the transfer clutch hub spline piece.

        • Also, the transfer high and low clutch sleeve is connected to the center differential case.

        • The rotation of the transfer input shaft is transmitted to the planetary sun gear, transfer clutch hub spline piece, transfer high and low clutch sleeve, and the center differential case.

        A01J2M2E02
        Text in Illustration
        *1 Planetary Sun Gear *2 Transfer Input Shaft
        *3 Transfer Clutch Hub Spline Piece *4 Center Differential Case
        *5 Transfer High and Low Clutch Sleeve *6 Planetary Carrier (Planetary Pinion Gear Shaft)
        *7 Planetary Ring Gear *8 Planetary Pinion Gear
        A01J2OA Drive Torque A01J2L7 Movement

      2. Low Position


        • In the low position, the external teeth of the transfer high and low clutch sleeve mesh with the transfer low planetary spline piece.

        • Also, the transfer high and low clutch sleeve is connected to the center differential case.

        • The rotation of the transfer input shaft is transmitted in a reduced form to the planetary sun gear, planetary pinion gears, planetary pinion gear shafts, planetary carrier, transfer low planetary spline piece, transfer high and low clutch sleeve, and center differential case.

        A01J2LNE02
        Text in Illustration
        *1 Planetary Sun Gear *2 Transfer Input Shaft
        *3 Center Differential Case *4 Transfer High and Low Clutch Sleeve
        *5 Transfer Low Planetary Spline Piece *6 Planetary Carrier (Planetary Pinion Gear Shaft)
        *7 Planetary Ring Gear *8 Planetary Pinion Gear
        A01J2OA Drive Torque A01J2L7 Movement

    2. Free-lock Switching of Center Differential


      1. Lock Position


        • In the lock position, the front drive clutch sleeve connects the center differential case and the transfer front drive gear piece to set the center differential to lock.

        A01J2M5E02
        Text in Illustration
        *1 Transfer Rear Output Shaft *2 Front Drive Sprocket
        *3 Transfer Front Drive Gear Piece *4 Front Drive Clutch Sleeve
        *5 Center Differential Case - -
        *a Rear Output Torque *b Front Output Torque
        *c Input Torque - -
        A01J2OA Drive Torque A01J2L7 Movement

    3. Operation of Center Differential


      1. Normal Driving Operation


        • During normal driving (front wheel speed = rear wheel speed), the drive torque that is input by the differential case is transmitted (front: 40/rear: 60) as shown below, without involving the LSD function.

        A01J2QME02
        Text in Illustration
        *1 Sun Gear *2 Transfer Rear Output Shaft
        *3 Front Drive Sprocket *4 Transfer Front Drive Gear Piece
        *5 Planetary Carrier *6 Ring Gear
        *7 Pinion Gear *8 Center Differential Case
        *a Rear Output Torque *b Front Output Torque
        *c Input Torque - -
        A01J2OA Drive Torque - -

      2. Front Wheel Skid Driving Operation


        • During front wheel skid driving (front wheel speed > rear wheel speed), when a rotational difference exists between the sun gear and the ring gear, the distribution of the drive torque that is input by the center differential case changes instantly before the torque is transmitted, as follows:


          • The sun gear transmits torque to the planetary carrier while pushing on the No. 4 clutch plate. The planetary carrier transmits this torque to the ring gear from the center differential case via the No. 1 clutch plate.

          • The ring gear outputs torque while pushing on the No. 1 clutch plate.

          • These LSD functions change the torque distribution.

        A01J2S2E02
        Text in Illustration
        *1 No. 1 Clutch Plate *2 Coupling
        *3 Sun Gear *4 No. 4 Clutch Plate
        *5 Transfer Clutch Hub *6 Transfer Rear Output Shaft
        *7 Front Drive Sprocket *8 Transfer Front Drive Gear Piece
        *9 Planetary Carrier *10 Ring Gear
        *11 Pinion Gear *12 Center Differential Case
        *a Pushing on No. 1 Clutch Plate *b Pushing on No. 4 Clutch Plate
        *c Rear Output Torque *d Front Output Torque
        *e Input Torque - -
        A01J2OA Drive Torque - -

      3. Rear Wheel Skid Driving Operation


        • During rear wheel skid driving (front wheel speed < rear wheel speed), when a rotational difference exists between the sun gear and the ring gear, the distribution of the drive torque that is input by the center differential case changes instantly before the torque is transmitted, as follows:


          • The ring gear transmits torque to the center differential case while pushing on the No. 1 clutch plate. The center differential case transmits this torque from the planetary carrier to the sun gear via the No. 4 clutch plate.

          • The sun gear outputs torque while pushing on the No. 4 clutch plate.

          • These LSD functions change the torque distribution.

        A01J2RWE03
        Text in Illustration
        *1 No. 1 Clutch Plate *2 Coupling
        *3 Sun Gear *4 No. 4 Clutch Plate
        *5 Transfer Clutch Hub *6 Transfer Rear Output Shaft
        *7 Front Drive Sprocket *8 Transfer Front Drive Gear Piece
        *9 Planetary Carrier *10 Ring Gear
        *11 Pinion Gear *12 Center Differential Case
        *a Pushing on No. 1 Clutch Plate *b Pushing on No. 4 Clutch Plate
        *c Rear Output Torque *d Front Output Torque
        *e Input Torque - -
        A01J2OA Drive Torque - -