HYBRID CONTROL SYSTEM


  1. CONSTRUCTION


    1. The hybrid system uses motive force provided by the engine, MG2 and the system uses MG1 primarily as a generator. The system optimally combines these forces in accordance with various driving conditions.

    2. The hybrid vehicle control ECU assembly constantly monitors the State Of Charge (SOC) of the HV battery (HV supply battery assembly), the HV battery temperature, the engine coolant temperature and the electrical load condition. If any one of the monitoring items fails to meet requirements when the READY indicator light is on and the shift position is in P, R, D or M, or if the vehicle is driven in reverse, the hybrid vehicle control ECU assembly demands an engine start to drive MG1 in order to charge the HV battery (HV supply battery assembly).

    3. The hybrid system drives the vehicle by optimally combining the operation of the engine, MG1 and MG2 in accordance with the driving conditions listed in the table below

      A004CTQE02
      *1 Forward
      *2 Vehicle Speed
      *3 Time
      *4 Reverse
      Driving Condition
      A On (READY)
      B Starting Off
      C Low Load Cruising
      Constant-speed Cruising
      D During Full Throttle Acceleration
      E During Deceleration
      F Driving in Reverse

  2. OPERATION


    1. Driving Condition A: On (READY) State


      1. Even if the driver turns the power switch (push start switch) to on (READY), sometimes the engine will not start. If this happens, the engine, MG1 and MG2 remain stopped. The engine will only start if conditions such as engine coolant temperature, SOC of the HV battery (HV supply battery assembly), HV battery temperature and electrical load require an engine start.

      2. After driving, if the driver stops the vehicle and moves the shift position to P, the hybrid vehicle control ECU assembly will continue to operate the engine. The engine will continue to operate until SOC of the HV battery (HV supply battery assembly), engine coolant temperature, HV battery temperature and/or electrical load conditions reach a specified level.

      3. If any of the items monitored by the hybrid vehicle control ECU assembly indicates the need for an engine start when the READY indicator light is on and the shift position is in P, the hybrid vehicle control ECU assembly will activate MG1 to start the engine.

      4. While the engine is cranking, to prevent the reactive force of the sun gear of MG1 from rotating the ring gear and driving the drive wheels, current is also applied to MG2 in order to prevent MG2 from rotating. This function is called "reactive control".

        Figure 1. On (READY) State when Starting Engine

        A004C3NC01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

      5. If the SOC of the HV battery (HV supply battery assembly) is low, it is charged by MG1 which is driven by the engine.

        Tech Tips

        When the engine is cold and the SOC is good, the engine starts only to warm the engine.

        Figure 2. Charging when Stopped

        A004CL7C01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

    2. Driving Condition B: Starting Off


      1. When the vehicle is started off, the vehicle operates powered by MG2.

        Figure 3. Starting Off

        A004CJEC01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

      2. If the SOC of the HV battery (HV supply battery assembly) is low, it is charged by MG1 which is driven by the engine. This power is also used to power MG2.

        Tech Tips

        When the engine is cold and the SOC is good, the engine starts only to warm the engine.

    3. Driving Condition C: Low Load Cruising


      1. When the vehicle is running under low load cruising conditions, the vehicle operates powered by MG2.

        Figure 4. Low Load Cruising

        A004CJEC01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

      2. If the SOC of the HV battery (HV supply battery assembly) is low, it is charged by MG1 which is driven by the engine.

        Tech Tips

        When the engine is cold and the SOC is good, the engine starts only to warm the engine.

    4. Driving Condition C: Constant-speed Cruising


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

      2. The motive force from the engine is split into two in the power split device unit. One portion of the motive force is used to drive the wheels directly and the other is used to generate electricity using MG1.

      3. The electricity from MG1 is used to drive MG2. This supports the directly transmitted engine motive force, contributing to fuel efficiency.

        A004CHDC01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

    5. Driving Condition D: during Full Throttle Acceleration


      1. When the vehicle driving condition changes from low load cruising and constant-speed cruising to full throttle acceleration, the system supplements the motive force of MG2 with electrical power from the HV battery (HV supply battery assembly).

        Figure 5. During Full Throttle Acceleration

        A004CJ4C01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

    6. Driving Condition E: during Deceleration


      1. While the vehicle is being driven with the shift position in D and it decelerates, the engine turns off and the engine motive force output to the wheels will be zero. At this time, the wheels drive MG2, causing MG2 to operate as generators and charge the HV battery (HV supply battery assembly). While MG2 is operating as generators, they create a resistance to rotation at the wheels, producing a braking effect.

      2. If the vehicle decelerates at a higher speed, the engine (crankshaft) will not stop turning. The engine will maintain a predetermined speed in order to protect the planetary gear unit. This operation is not shown in the following diagrams.

        Figure 6. During Deceleration

        A004CNVC01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -

    7. Driving Condition F: Driving in Reverse


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

      2. While driving in reverse, when any of the conditions monitored by the hybrid vehicle control ECU assembly such as SOC of the HV battery (HV supply battery assembly), HV battery temperature, engine coolant temperature and electrical load condition reach a specified level, MG1 will be used to start the engine. The following illustration represents an example when the engine is not running:

        Figure 7. Driving in Reverse

        A004C0WC01
        *1 Engine *2 Hybrid Vehicle Transmission Assembly
        *3 Power Split Device *4 Shift Device
        *5 Inverter with Converter Assembly *6 MG1
        *7 MG2 *8 Differential
        *9 HV Battery (HV Supply Battery Assembly) - -
        *a Alternating Current *b Electrical Power Path (AC)
        *c Direct Current *d Electrical Power Path (DC)
        *e Power Transmission Mechanical Power Path *f Engine Stopped
        *g Engine Running - -