HYBRID TRANSAXLE SYSTEM


  1. CONSTRUCTION


    1. The compound gear unit consists of the power split planetary gear unit and the motor speed reduction planetary gear unit. Each planetary ring gear is integrated with the compound gear. Furthermore, this compound gear is integrated with a counter drive gear and parking lock gear.

    2. The power split planetary gear unit splits the motive force of the engine into 2 passages. One passage provides motive force to drive the wheels, and the other provides force to drive MG1, so that the MG1 can function as a generator.

    3. The motor speed reduction planetary gear reduces the speed of MG2 and amplifies its torque.

      A01RXQTC05
      *1 Motor Generator No. 1 (MG1) *2 Input Shaft
      *3 Ring Gear (Compound Gear) *4 Final Drive Gear
      *5 Final Driven Gear *6 Counter Driven Gear
      *7 Counter Drive Gear (Compound Gear) *8 Oil Pump
      *9 Motor Generator No.2 (MG2) *10 Carrier
      *11 Sun Gear *12 Pinion Gear
      *13 Motor Speed Reduction Planetary Gear Unit *14 Power Split Planetary Gear Unit

    4. The connection of the sun gear, ring gear and carrier of each planetary gear unit is as shown below:

      Planetary Gear Connection
      Power Split Planetary Gear Unit Sun Gear MG1
      Carrier Input Shaft (Engine)
      Ring Gear Compound Gear (Output)
      Motor Speed Reduction Planetary Gear Unit Sun Gear MG2
      Carrier Fixed
      Ring Gear Compound Gear (Output)

  2. OPERATION


    1. Motive Force Transmission Path


      1. The motive force created by the engine and MG2 is transmitted by the counter drive gear of the compound gear unit, the counter driven gear, the final drive gear, and then the differential gear unit, in order to drive the front wheels.

    2. How to Read Nomographic Charts


      1. The nomographic chart below gives a visual representation of the planetary gear rotation direction, rotational speed and torque balance.

      2. In the nomographic chart, a straight line is used to represent the relationship between the rotation directions and rotational speeds of the 3 gears in the planetary gear. The rotational speed of each gear is indicated by the distance from the 0 rpm point. Due to the structure of the planetary gear, the relationship between the rotational speeds of the 3 gears is always expressed by a straight line.

      3. The nomographic charts and the illustrations of the geartrain operation for each vehicle driving condition shown on the following descriptions are examples only. The examples shown are 'snapshots', whereas normal system operation is a constantly changing blend of conditions and system reactions to suit those conditions.

        A01RXO4E04

    3. Torque and Rotation Relationship


      1. For the hybrid system, motor generators have different roles depending on the situation. Understanding the relationship between the rotation direction and torque can help to make the role of a motor generator easier to understand.

      2. The table below shows the relationship of drive and electric generation for different combinations of plus or minus torque and forward or reverse rotation.

        Rotation Direction Torque Condition Role of Component
        Forward (+) Rotation Plus Torque Drive
        Minus Torque Electric Generation
        Reverse (-) Rotation Plus Torque Electric Generation
        Minus Torque Drive

      3. As an example, if a motor generator is rotating in the forward (+) direction and it applies minus torque, it will generate electricity (producing electrical power).

      4. Alternately, if the motor generator is rotating in the reverse (-) direction and it applies minus torque, it will act as a drive source (consuming electrical power).

    4. READY-ON State


      1. The engine will only start if conditions such as engine coolant temperature, HV battery State Of Charge (SOC), HV battery temperature and electrical load require an engine start.

      2. The motive force of MG1 is transmitted via the sun gear and is output to the carrier. Thus, motive force is transmitted in order to start the engine.

        Figure 1. READY-ON State when Starting Engine

        A01RXN2C01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Drive *b Stopped
        B00208D Rotation Direction B00209S From MG1
        A01RXVK To Engine - -

        Figure 2. Nomographic Charts

        A01RXN0E02

      3. If the SOC of the HV battery is low, it is charged by MG1 which is driven by the engine.

      4. The engine motive force, which is input by the carrier, is output to the sun gear. Thus, motive force is transmitted in order to operate MG1 as a generator.

        Figure 3. Charging when Stopped

        A01RXZ7C01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Driven - Generates Electricity *b Stopped
        B00208D Rotation Direction B00209S From Engine
        A01RXVK To MG1 - -

        Figure 4. Nomographic Charts

        A01RXIGE02

    5. Starting Off and Low Load Cruising


      1. When the vehicle starts off under normal conditions, it runs using the motive force of MG2 or MGR*.


        • *: 4WD/AWD models

      2. The motive force of MG2 is transmitted via the sun gear and is output to the ring gear, in order to drive the front wheels. The carrier of the motor speed reduction planetary gear in the compound gear unit is fixed. As a result, the motor speed reduction planetary gear unit reduces the speed of MG2, increasing torque, in accordance with a set reduction ratio. The motor reduction planetary gear unit changes the direction of rotation of MG2.

        Figure 5. Starting Off and Low Load Cruising

        A01RXVUC01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Rotates Freely *b Drive
        B00208D Rotation Direction B00209S From MG2
        A01RXVK To Front Wheels - -

        Figure 6. Nomographic Charts

        A01RY35E02

      3. If the SOC of the HV battery is low, it is charged by MG1 which is driven by the engine. This power is also used to power MG2 or MGR*.


        • *: 4WD/AWD models

      4. The engine motive force, which is input by the carrier, is output to the ring gear. The motive force of MG2 is output to the ring gear via the motor speed reduction planetary gear unit. The sum of these 2 motive forces is transmitted by the compound gear in order to drive the front wheels.

        Figure 7. Starting Off and Low Load Cruising when SOC Low

        A01RXHCC01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Driven - Generates Electricity *b Drive
        B00208D Rotation Direction B00209S From Engine
        A01RXVK From MG2 A01RXV4 To Front Wheels

        Figure 8. Nomographic Charts

        A01RXUBE02

    6. Constant-speed Cruising


      1. When the vehicle is running under low load and constant-speed cruising conditions, the engine will be operated in its most efficient range to power the vehicle.

      2. The engine motive force, which is input by the carrier, is output to the ring gear. The motive force of MG2 is output to the ring gear via the motor speed reduction planetary gear unit. The sum of these 2 motive forces is transmitted by the compound gear in order to drive the front wheels.

        Figure 9. Constant-speed Cruising

        A01RXHCC01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Driven - Amount of Electricity Generated is Low *b Drive
        B00208D Rotation Direction B00209S From Engine
        A01RXVK From MG2 A01RXV4 To Front Wheels

        Figure 10. Nomographic Charts

        A01RXSRE02

      3. If the SOC of the HV battery is low, more engine power is provided to increase the generation of electricity via MG1. This charges the HV battery.

        Figure 11. Constant-speed Cruising when SOC Low

        A01RXHCC01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Driven - When SOC is Low, a Greater Amount of Electricity is Generated. *b Drive
        B00208D Rotation Direction B00209S From Engine
        A01RXVK From MG2 A01RXV4 To Front Wheels

        Figure 12. Nomographic Charts

        A01RXUBE02

    7. During Full Throttle Acceleration


      1. When the vehicle driving condition changes from constant-speed cruising to full-throttle acceleration, this system supplements the motive force of MG2 or MGR* with electrical power from the HV battery.


        • *: 4WD/AWD models

      2. The engine motive force, which is input by the carrier, is output to the ring gear. The motive force of MG2 is output to the ring gear via the motor speed reduction planetary gear unit. The sum of these 2 motive forces is transmitted by the compound gear in order to drive the front wheels.

        Figure 13. During Full Throttle Acceleration

        A01RXHCC01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Driven - Generates Electricity *b Drive
        B00208D Rotation Direction B00209S From Engine
        A01RXVK From MG2 A01RXV4 To Front Wheels

        Figure 14. Nomographic Charts

        A01RXUBE02

    8. During Deceleration


      1. While the vehicle is being driven with the shift lever in D and it decelerates, the engine turns off and the engine motive force output to the front wheels will be zero. At this time, the wheels drive MG2, causing MG2 to operate as a generator and charge the HV battery. While MG2 is operating as a generator, it creates a resistance to the rotation at the front wheels, producing a braking effect.

      2. The motive force of front wheels is transmitted via ring gear and is output to the sun gear, in order to drive MG2. The carrier of the motor speed reduction planetary gear in the compound gear unit is fixed. As a result, the motor speed reduction planetary gear unit increase rotational speed of MG2, in accordance with a set reduction ratio.

        Figure 15. During Deceleration

        A01RXP0C01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Rotates Freely *b Driven - Generates Electricity
        B00208D Rotation Direction B00209S To MG2
        A01RXVK From Front Wheels - -

        Figure 16. Nomographic Charts

        A01RXHPE02

    9. Driving in Reverse


      1. While the vehicle is being driven in reverse, its power is delivered by MG2. At this time, MG2 spins in the opposite (-) direction of forward travel, the engine can remain stopped, and MG1 spins in the (+) direction without generating electricity.

      2. The motive force of MG2 is transmitted via the sun gear and is output to the ring gear, in order to drive the front wheels. The carrier of the motor speed reduction planetary gear in the compound gear unit is fixed. As a result, the motor speed reduction planetary gear unit reduces the speed of MG2, increasing torque, in accordance with a set reduction ratio. The motor reduction planetary gear unit changes the direction of rotation of MG2.

        Figure 17. Driving in Reverse

        A01RY0PC01
        *1 Motor Generator No. 1 (MG1) *2 Motor Generator No. 2 (MG2)
        *3 Motor Speed Reduction Planetary Gear Unit *4 Power Split Planetary Gear Unit
        *a Rotates Freely *b Drive
        B00208D Rotation Direction B00209S From MG2
        A01RXVK To Front Wheels - -

        Figure 18. Nomographic Charts

        A01RXLAE02