HYBRID CONTROL SYSTEM


  1. OUTLINE


    1. The hybrid system of this hybrid vehicle employs the LEXUS Hybrid Drive under the "Hybrid Synergy Drive" concept*.

    2. Hybrid vehicles use a combination of 2 kinds of power sources, such as an engine and HV battery, so as to take advantage of the benefits provided by each power source while compensating for each other's shortcomings. As a result, efficient operation is achieved.

    3. Hybrid vehicles do not need their batteries to be charged externally unlike existing electric-only vehicles. Therefore, special infrastructure is not required to use hybrid vehicles.

    4. Technical development of power units (such as an engine or fuel cell) is advancing in various fields. The hybrid system is a flexible system that uses a high-efficiency power unit and electric motors.

    5. Hybrid vehicles have high-voltage electrical circuits. Hybrid vehicles have been developed with consideration given to the protection of drivers and technicians against electrocution.

      Tech Tips

      *: The "Hybrid Synergy Drive" concept consists of 4 key benefits: Fuel efficiency, low emissions, seamless acceleration, and silent performance.

  2. MAJOR DIFFERENCE


    1. The new models have been modified from the previous models as shown below.


      1. Power management control ECU has been changed to hybrid vehicle control ECU assembly.

  3. SPECIFICATION


    1. Motor Generator

      Item Specification
      MG1 MG2
      Type Permanent Magnet Motor Permanent Magnet Motor
      Function Generate Electricity, Engine Starter Generate Electricity, Drive Wheels
      Maximum System Voltage V DC 650 DC 650
      Maximum Output kW - 105
      Maximum Torque N*m - 270
      Cooling System Water-cooled Water-cooled

    2. Inverter with Converter Assembly

      Item Specification
      Boost Converter Rated Voltage (Inverter Side) V DC 650
      Rated Voltage (HV Battery Side) V DC 244.8
      DC-DC Converter Rated Output Voltage V DC 13.5 to 15.0
      Maximum Output Current A 120

    3. HV Battery

      Item Specification
      Type Nickel Metal Hydride (Ni-MH) Battery
      Cell Quantity 204 Cells (6 Cells x 34 Modules)
      Nominal Voltage V 244.8
      Battery Capacity (3HR) Ah 6.5

    4. Cooling System (for Inverter with Converter Assembly and Hybrid Vehicle Transaxle Assembly)

      Item Specification
      Inverter Water Pump Assembly Motor Type Brushless
      Discharge Volume Liter (US qts, Imp. qts) 12 (12.7, 10.6) /min. or greater
      Coolant Type Toyota Genuine Super Long Life Coolant (SLLC)
      Color Pink
      Capacity Liter (US qts, Imp. qts) 3.2 (3.4, 2.8)
      Maintenance Intervals First Time km (miles) 240000 (150000)
      Subsequent km (miles) Every 80000 (50000)

    5. Cooling System (for HV Battery)

      Item Specification
      Battery Cooling Blower Assembly Motor Type Brushless
      Fan Type Sirocco Fan
      Air Flow Volume

      m3/h

      		 138

  4. MAIN FEATURES


    1. The LEXUS Hybrid Drive control has the following features.

      Item Outline
      Idle Stop Idling of the engine is automatically stopped (idle stop) to reduce energy loss.

      EV Drive

      (Efficient Drive Control)

      		 This allows the vehicle to be driven using only the electric motor when engine efficiency is low. In addition, electricity is generated when engine efficiency is high. Control is performed to maximize the total efficiency of the vehicle.
      EV Drive Mode If the driver operates the switch and the operating conditions are being met, the vehicle can run on only the electric motor.
      Motor Assist The electric motor supplements the engine power when accelerating.

      Regenerative Braking

      (Energy Regeneration)

      		 During deceleration and while depressing the brake pedal, part of the energy that was lost as heat is collected as electrical energy to be reused, such as for motor power.

    2. The mechanism of the LEXUS Hybrid Drive is as follows.


      1. The LEXUS Hybrid Drive consists of mainly the engine, hybrid vehicle transaxle assembly, inverter with converter assembly and HV battery, and employs the series/parallel-type hybrid system.

        A0002VAE04
        Text in Illustration
        *1 Engine *2 Hybrid Vehicle Transaxle Assembly
        *3 Motor Generator No. 1 (MG1) *4 Motor Generator No. 2 (MG2)
        *5 Power Split Planetary Gear Unit (Compound Gear Unit) *6 Motor Speed Reduction Planetary Gear Unit (Compound Gear Unit)
        *7 Inverter with Converter Assembly *8 HV Battery
        A000356 Electrical Power Path (DC) A0002KP Electrical Power Path (AC)
        A0002Y6 Mechanical Power Path - -

        Tech Tips

        Generally, there are 3 types of hybrid systems: A series-type hybrid system, a parallel-type hybrid system and a series/parallel-type hybrid system.


        • In a series-type hybrid system, the motor rotates the wheels, and the engine, using a generator, acts as an electric power source for the motor.

          A00035LE01
          Text in Illustration
          *1 Engine *2 Generator
          *3 Inverter *4 HV Battery
          *5 Motor - -
          A000356 Electrical Power Path (DC) A0002KP Electrical Power Path (AC)
          A0002Y6 Mechanical Power Path - -

        • In a parallel-type hybrid system, both the engine and the motor generator directly rotate the wheels. In addition to supplementing the power of the engine, the motor generator can also serve as a generator to charge the HV battery while the vehicle is in motion. Driving the vehicle only with the motor generator is also possible.

          A00038UE01
          Text in Illustration
          *1 Engine *2 Transmission
          *3 HV Battery *4 Inverter
          *5 Motor Generator - -
          A000356 Electrical Power Path (DC) A0002KP Electrical Power Path (AC)
          A0002Y6 Mechanical Power Path - -

        • In a series/parallel-type hybrid system, aspects of both a series-type hybrid system and a parallel-type hybrid system are combined. The system has 2 motor generators. Electricity can be generated by motor generator No. 1 using engine power. The generated electricity is used to charge the HV battery and also to power motor generator No. 2.

          A0002GBE04
          Text in Illustration
          *1 Engine *2 Power Split Planetary Gear Unit
          *3 HV Battery *4 Inverter
          *5 Motor Generator No. 1 *6 Motor Generator No. 2
          A000356 Electrical Power Path (DC) A0002KP Electrical Power Path (AC)
          A0002Y6 Mechanical Power Path - -

      2. This system optimally performs cooperative control of the 2AR-FXE engine, and Motor Generator No. 1 (MG1) and Motor Generator No. 2 (MG2) in the P314 hybrid vehicle transaxle assembly that provides excellent transmission performance.

      3. The system has 2 batteries that are used in different purposes. One is the HV battery (nominal voltage of DC 244.8 V) that stores electrical power to drive the vehicle, and the other is the auxiliary battery (nominal voltage of DC 12 V) that supplies electrical power to the electrical components.

      4. Furthermore, it uses a variable-voltage system consisting of a high-output HV battery with a nominal voltage of DC 244.8 V, a boost converter that boosts the operating voltage of MG1 and MG2 to a maximum voltage of DC 650 V, and an inverter that converts direct current and alternating current.

      5. Since hybrid vehicles are not equipped with a conventional alternator, the high-voltage from the HV battery is dropped to approximately DC 14 V using a DC-DC converter in order to charge the auxiliary battery. Also, the HV battery regularly charges and discharges within the constant State of Charge (SOC) range while the vehicle is running, thus, recharging from external power sources is not necessary.

        A0002L1E03
        Text in Illustration
        *1 2AR-FXE Engine *2

        P314 Hybrid Vehicle Transaxle Assembly

        - Motor Generator No. 1 (MG1)

        - Motor Generator No. 2 (MG2)
        *3

        Inverter with Converter Assembly

        - Inverter

        - Boost Converter

        - DC-DC Converter

        		 *4 HV Battery Assembly
        *5 Auxiliary Battery - -

      6. A cooling system that is independent from the engine cooling system is provided to cool the inverter with converter assembly, MG1 and MG2.

        A00032OE02
        Text in Illustration
        *1 Inverter Water Pump Assembly *2 Radiator Assembly
        *3 Inverter Reserve Tank Assembly - -
        A0002J8 HV Coolant Flow - -

      7. To ensure the proper performance of the HV battery while it generates heat during the repetitive charge and discharge cycles, a dedicated cooling system is used for the HV battery cooling.

        A0002SYE03
        Text in Illustration
        *1 Intake Air Duct *2 Battery Cooling Blower Assembly
        *3 HV Battery Assembly - -
        A0002J8 Cooling Air Flow - -

  5. PRECAUTION


    1. Hybrid Vehicle High-voltage Safety Measures


      1. High-voltage safety is comprised of 2 points: "Insulation of High-voltage Circuits" and "Cut-off of High-voltage Circuits". The hybrid system also detects whether or not a decrease in insulation resistance has occurred between the high-voltage system and body ground.

    2. Insulation of High-voltage Circuits


      1. High-voltage circuits are used between the HV battery, inverter with converter assembly, hybrid vehicle transaxle assembly and compressor with motor assembly. Each of these items is connected by the power cables (frame wire) and is electrically insulated using cases and covers.

      2. Cables (frame wire) are also shielded using a mesh conductor built into the electrical insulation of the wires. The shielding is grounded to the chassis of the vehicle and the main purpose is to prevent electromagnetic interference.

        A0002LUE04
        Text in Illustration
        *1 Compressor with Motor Assembly *2 Power Cable (Frame Wire)
        *3 Inverter with Converter Assembly *4 Hybrid Vehicle Transaxle Assembly
        *5 HV Battery Assembly - -

    3. Cut-off of High-voltage Circuits


      1. When any of the conditions below occurs, the System Main Relays (SMRs) are automatically shut off by the hybrid vehicle control ECU assembly.


        • Power switch is off.

        • Any airbag is deployed.

        • Inverter terminal cover is removed (interlock circuit is opened).

        • Power cable connector is disconnected (interlock circuit is opened).

        • Service plug grip handle is being unlocked (interlock circuit is opened).

        • A specified malfunction occurs.

        A00030YE02

      2. By removing the service plug grip before performing any inspection or service, the high-voltage circuit is shut off at the intermediate position of the HV battery, thus ensuring safety during service.

        A00034VE02
        Text in Illustration
        *1 Insulated Gloves *2 Service Plug Grip

        CAUTION:

        A charge remains in the high-voltage capacitor in the inverter with converter assembly after the high-voltage circuits are shut down. When servicing a hybrid vehicle, after the service plug grip is removed, wait at least 10 minutes to allow the capacitor to discharge before beginning work.

        Note


        • The service plug grip should never be removed when the system is in the READY-on state.

        • After removing the service plug grip, turning the power switch on (READY) may cause a malfunction. Do not turn the power switch on (READY) unless instructed by the Repair Manual.

    4. HV Battery Handling Precautions


      1. HV battery electrolyte is a highly alkaline potassium hydroxide solution (odorless, transparent, and colorless). Careless handling of the HV battery is very dangerous. Handle the HV battery properly according to the procedure below.

        Item Procedure
        When there is liquid leakage present in the area of the HV battery

        • Neutralize it with a saturated mixture of boric acid and water.

        • After litmus paper has been used to determine that the mixture is neutral, wipe it up with rags or waste cloth.
        When battery electrolyte gets on skin, eyes etc.*

        • Flush it with a diluted solution of boric acid and water, or with a large amount of water.

        • Remove contaminated clothes at once.
        When a vehicle is scrapped Remove the HV battery from the vehicle for collection via the specified route.
        When the HV battery is stored The HV battery should not be left in a damp or humid location.
        Prevention of the HV battery discharge or damage when a vehicle is stored for a long time

        • Disconnect the auxiliary battery negative terminal.

        • When in storage, the HV battery should be charged every 2 months. Using the following procedure, charge the HV battery with the vehicle.


          1. Connect the negative terminal of the auxiliary battery.

          2. Turn the power switch on (IG) for 3 minutes, do not apply any electrical loads. (This operation is needed to allow the hybrid vehicle control ECU assembly to detect the correct SOC.)

          3. Enter the READY-on state. After the engine starts, leave it running for 30 minutes to charge the HV battery. If the engine does not start or intermittently stops within 30 minutes, stop the operation at that time. (The HV battery does not need to be charged.)

        CAUTION:

        *: If you get electrolyte in your eyes, shout loudly for help, do not rub your eyes, rinse your eyes with large amount of water and seek medical attention immediately.