HYBRID CONTROL SYSTEM DETAILS

Detection of Insulation Resistance Decrease

1. The leak detection circuit is built in the battery smart unit. The leak detection circuit constantly monitors that the insulation resistance between high-voltage circuits and body ground is maintained.

2. The power management control ECU determines decreases in the insulation resistance based on the information from the battery smart unit.

3. The leak detection circuit has an AC source and causes a small amount of AC to flow to the high-voltage circuit (positive and negative).

4. The more vehicle insulation resistance decreases, the more voltage drops at the detection resistor and the lower the waves of AC. The insulation resistance value is detected based on the amplitude of AC waves.

   

Cut-off of High-Voltage Circuits during Collision

1. If the vehicle encounters one of the situations described below, the power management control ECU will shut down the power supply by turning all SMR off, for safety.

2. The power management control ECU receives the airbag deployment signal from the airbag ECU assembly during a frontal collision, side collision or side rear collision.

   

SOC Control

1. The power management control ECU calculates the SOC of the HV battery based on the charge/discharge amperages detected by the HV battery current sensor. The power management control ECU constantly performs charge/discharge control based on the calculated SOC in order to maintain the SOC within its target range.

2. While the vehicle is in motion, the HV battery undergoes repetitive charge/discharge cycles, as it becomes discharged by MG2 during acceleration and charged by regenerative braking during deceleration.

3. When the SOC is below the lower level, the power management control ECU increases the power output of the engine to operate MG1, which charges the HV battery.

4. The battery smart unit converts the HV battery related signals (voltage, current and temperature) into digital signals, and transmits them to the power management control ECU via serial communication. These signals are needed to determine the SOC that is calculated by the power management control ECU.

   

Engine Control

1. The ECM receives the target engine speed and required engine motive force, which were sent from the power management control ECU, and controls the ETCS-i, fuel injection volume, ignition timing, VVT-i and EGR.

2. The ECM transmits the operating condition of the engine to the power management control ECU.

3. Upon receiving the engine stop signal from the power management control ECU in accordance with the basic hybrid vehicle control, the ECM will stop the engine.

   

MG1 and MG2 Main Control

1. MG1, which is driven by the engine, generates high-voltage electricity in order to operate MG2 and charge the HV battery. Also, it functions as a starter to start the engine.

2. MG2, which is driven by electrical power from MG1 and the HV battery, generates motive force for the drive wheels.

3. MG2 generates high-voltage electricity to charge the HV battery during braking (regenerative brake cooperative control), or when the accelerator pedal is not being depressed (energy regeneration).

4. MG1 and MG2 are basically shut down when the shift position is in N. In order to stop providing motive force, it is necessary to stop driving MG1 and MG2, because MG1 and MG2 are mechanically joined to the drive wheels.

5. The MG ECU controls the Insulated Gate Bipolar Transistors (IGBTs) in the Intelligent Power Module (IPM) for switching the U, V and W phases of motor generator in accordance with the signals received from the power management control ECU. The 6 IGBTs switch on and off to control each individual motor generator in accordance with operation as either a motor or as a generator.

6. The illustration below describes the basic control used when the motor generator functions as a motor. The IGBTs in the IPM switch on and off to supply three-phase alternating current to the motor generator. In order to create the motive force required of the motor generator as calculated by the power management control ECU, the MG ECU switches the IGBTs on and off and controls the speed, in order to control the speed of the motor generator.

   

7. The illustration below describes the basic control used when the motor generator functions as a generator. The current that is generated sequentially by the 3 phases of the motor generator, which is driven by the wheels, is utilized to charge the HV battery or drive another motor generator.

   

Inverter Control

1. The inverter converts the direct current from the HV battery into alternating current for MG1 and MG2, or vice versa. In addition, the inverter takes power generated by MG1 and supplies it to MG2. However, the electricity generated by MG1 is converted into the direct current inside the inverter before being converted back into the alternating current by the inverter for use by MG2. This is necessary because the frequency of the alternating current output by MG1 is not appropriate for control of MG2.

2. The MG ECU controls the IPMs for switching the three-phase alternating current of MG1 and MG2 in accordance with the signals received from the power management control ECU.

3. When the power management control ECU has received an overheating, overcurrent, or fault voltage signal from the MG ECU, the power management control ECU transmits a shut down control signal to the MG ECU, in order to turn off the IPMs.

   

Boost Converter Control

1. The boost converter boosts the HV battery nominal voltage of DC 207.2 V up to a maximum voltage of DC 650 V, in accordance with the signals provided by the power management control ECU via the MG ECU.

2. The inverter converts the alternating current generated by MG1 or MG2 into direct current. The boost converter steps down the generated voltage of DC 650 V (maximum voltage) to approximately DC 207.2 V, in accordance with the signals provided by the power management control ECU via the MG ECU.

3. The boost converter consists of the boost IPM with built-in IGBTs that perform switching control, the reactor that stores the electrical power and generates the electromotive force, and the capacitor that charges and discharges the boosted high-voltage electricity.

   

4. The flow of the boost converter boosting is as described below.

   Step	Outline
   1	The IGBT2 turns on, causing the voltage of the HV battery (nominal voltage of DC 207.2 V) to charge the reactor. As a result, the reactor stores the electrical power.
   2	The IGBT2 turns off, causing the reactor to produce an electromotive force (the current continues to flow from the reactor). This electromotive force causes the voltage to rise to a maximum voltage of DC 650 V. Induced by the electromotive force that is created by the reactor, the current that is flowing from the reactor flows into the inverter and the capacitor at the boosted voltage.
   3	The IGBT2 turns on again to cause the voltage of the HV battery to be charged into the reactor. For the duration, by discharging the electrical power (maximum voltage of DC 650 V) stored in the capacitor, the electrical power will be supplied to the inverter.

   

5. The alternating current which is generated by MG1 or MG2 for the purpose of charging the HV battery is converted into direct current (maximum voltage of DC 650 V) by the inverter. Then, the boost converter is used to step down the voltage to approximately DC 207.2 V. This is accomplished by IGBT1 being switched on and off using duty cycle control, intermittently interrupting the electrical power provided to the reactor by the inverter.

   

DC-DC Converter Control

1. The DC-DC converter steps down the HV battery nominal voltage of DC 207.2 V to approximately DC 14 V in order to supply electricity to the electrical components, as well as to recharge the auxiliary battery.

2. In order to regulate the output voltage from the DC-DC converter, the power management control ECU transmits an output voltage request signal to the DC-DC converter in response to auxiliary battery temperature sensor signals.

   

System Main Relay (SMR) Control

1. The power management control ECU controls the system main relays to connect and disconnect the high-voltage circuit from the HV battery. The power management control ECU also uses the timing of the operation of the system main relays to monitor the operation of the relay contacts.

2. A total of 3 relays, 1 for the positive side (SMRB), and 2 for the negative side (SMRP, SMRG), are provided to ensure proper operation.

   

3. When the hybrid system changes to the READY-on state, the power management control ECU turns on SMRB and SMRP in sequence, and applies the current through the precharge resistor. After that, it turns SMRG on, and applies the current by bypassing the precharge resistor. Then it turns SMRP off. As the controlled current is initially allowed to pass through the precharge resistor in this manner, the contact point in the circuit is protected from damage that could be caused by an inrush current.

   

4. When the hybrid system changes to a state other than the READY-on state, the power management control ECU turns SMRG off first. Next, it turns SMRB off after determining whether or not SMRG is operating properly. After that, it turns on SMRP and then off after determining whether or not SMRB is operating properly. As a result, the power management control ECU verifies that the respective relays have been properly turned off.

   

Cooling System Control for Inverter with Converter Assembly and MG1

1. The power management control ECU receives the signals from the temperature sensor (for inverter with converter assembly), temperature sensor (for MG1) and temperature sensor (for MG2). Then, the power management control ECU actuates the HV water pump with motor over 3 levels using duty cycle control, in order to cool the inverter with converter assembly and MG1.

2. When the HV coolant temperature rises above a certain level, the power management control ECU transmits a radiator fan drive request signal to the ECM. In response to that reception signal, the ECM actuates the radiator fan to restrain the HV coolant temperature increases, ensuring the cooling of the inverter with converter assembly and MG1.

3. The MG ECU converts the temperature sensor signals into digital signals, and transmits them to the power management control ECU via serial communication.

   

Cooling System Control for HV Battery

1. The power management control ECU receives the signals from the HV battery temperature sensors and HV battery intake air temperature sensor. Then, the power management control ECU steplessly actuates the battery cooling blower assembly using duty cycle control, in order to maintain the HV battery temperature within the specified range.

2. While the air conditioning system is operating and cooling down the cabin, if there is any leeway in the HV battery temperature, the power management control ECU turns the battery cooling blower assembly off or sets it to a low speed. The purpose of this control is to give priority to cooling down the cabin. If this control is not performed, air taken from the cabin for battery cooling assembly would slow the cooling of the cabin by the air conditioning system.

3. The battery smart unit converts the HV battery related signals (voltage, current and temperature) into digital signals, and transmits them to the power management control ECU via serial communication. Also, the battery smart unit detects and transmits the blower speed feedback voltage, which is necessary to perform the cooling system control, to the power management control ECU.

   

Regenerative Brake Cooperative Control

1. The skid control ECU calculates the total braking force needed based on the brake regulator pressure and brake pedal stroke when the driver depresses the brake pedal.

2. After calculating the required total braking force, the skid control ECU sends the regenerative braking force request to the power management control ECU. The power management control ECU replies with the amount of regenerative braking force that is possible.

3. The power management control ECU uses MG2 to create the negative torque (deceleration force), thus carrying out the regenerative braking.

4. The skid control ECU controls the brake actuator solenoid valves and generates wheel cylinder pressure. The pressure that is generated is what remains after the actual regenerative brake control value has been subtracted from the required total braking force.

   

Hybrid System Indicator

1. Hybrid System Indicator, which is displayed on the multi-information display, has 2 display modes, an HV mode and an EV/EV CITY mode. The EV driving range is displayed on the EV/EV CITY mode display.

   

   Text in Illustration

   *A	HV Mode	*B	EV/EV CITY Mode
   *a	EV Driving Indicator Light	*b	Eco Driving Indicator Light
   *c	EV Driving Range	-	-

EV Driving Ratio

1. The EV Driving Ratio displays EV and HV mode driving distance ratios for the actual traveling distance in values and a bar graph.

   

   Text in Illustration

   *a

   EV Driving Ratio

   *b

   Actual Traveling Distance

Resolver for MG1/MG2

1. A resolver is an extremely reliable and compact sensor that precisely detects the magnetic pole position. Knowing the precise position of the magnetic poles of the rotor (MG1 and MG2) is indispensable for ensuring efficient control of MG1 and MG2. MG1 and MG2 each have their own resolver.

2. The stator of the resolver contains 3 types of coils: excitation coil A, detection coil S and detection coil C.

3. The rotor of the resolver is oval, the distance of the gap between the stator and the rotor varies with the rotation of the rotor.

4. The flow of an alternating current into the excitation coil A results in the creation of a constant frequency magnetic field. Using this constant frequency magnetic field, the coil S and coil C will output values that correspond to the position of the rotor. Therefore, the MG ECU detects the absolute position based on the difference between the coil S and coil C output values.

5. The +S and -S pairs of the detection coil S are staggered by 90 degrees. The +C and -C pairs of the detection coil C are also staggered in the same way. The S and C pairs of coils are located 45 degrees from each other.

   

   Text in Illustration

   *1	+S (Detection Coil S)	*2	+C (Detection Coil C)
   *3	-S (Detection Coil S)	*4	-C (Detection Coil C)
   *5	Excitation Coil A	*6	Rotor
   *a	Image of Resolver Internal Construction	*b	Electrical Orientation of Resolver Coils
   *c	Circuit of Detection Coil S	*d	Circuit of Detection Coil C

6. Because excitation coil A is provided with an alternating current at a constant frequency, a constant frequency magnetic field is output to the coils S and C, regardless of the rotor speed. The magnetic field of the excitation coil A is carried to the coils S and C by the rotor. The rotor is oval, and the gap between the stator and the rotor varies with the rotation of the rotor. Due to the variation of the gap, the peak values of the waveforms output by the coils S and C vary in accordance with the position of the rotor.

7. The MG ECU constantly monitors these peak values, and connects them to form a virtual waveform. The MG ECU calculates the absolute position of the rotor from the difference between the values of the coils S and C. It determines the rotor direction based on the difference between the phases of the virtual waveform of the coil S and the virtual waveform of the coil C. Furthermore, the MG ECU calculates the rotational speed based on the amount of change in the rotor position within a given length of time.

8. The diagrams below illustrate the waveforms that are output at coils A, S and C when the rotor makes a positive rotation of 180° from a certain position.

   

Temperature Sensor for MG1/MG2

1. The temperature sensors are used to detect the temperature of the MG1 and MG2 stators.

2. The power management control ECU optimally controls MG1 and MG2 according to the signals from each temperature sensor.

   

Inverter with Converter Assembly

1. A compact, lightweight inverter with converter assembly, in which the MG ECU, inverter, boost converter, and DC-DC converter are integrated, is used. The inverter and boost converter primarily consist of Intelligent Power Modules (IPMs), a reactor, and capacitor. The IPM is an integrated power module consisting of a signal processor, protective function processor, and Insulated Gate Bipolar Transistors (IGBTs).

2. The inverter with converter assembly ensures heat dissipation through use of a water-cooled cooling system that is isolated from the engine cooling system.

3. As a safety measure due to the use of high-voltage electricity, interlock switches are provided, which shut off the system main relays via the power management control ECU when the inverter terminal cover is removed, or the HV battery power cable connector is disconnected.

   

   Text in Illustration

   *1	Capacitor	*2	MG ECU
   *3	Intelligent Power Modules (IPMs)	*4	Reactor
   *5	DC-DC Converter	*6	Interlock Switch (for Power Cable Connector)
   *7	Interlock Switch (for Inverter Terminal Cover)	-	-
   	HV Coolant Inlet		HV Coolant Outlet

4. The inverter employs an IPM that performs switching control. Each IPM of the MG1 and MG2 have a bridge circuit that consists of 6 IGBTs.

5. The boost converter consists of a boost IPM that performs switching control, a reactor that acts as an inductor, and a capacitor that accumulates and stores electricity. The boost IPM uses IGBT2 for boosting voltage, and IGBT1 for reducing voltage.

   

Inverter Current Sensors

1. The inverter current sensors detect the amperage of the three-phase alternating current that actuate MG1 and MG2. This actual amperage is used as feedback by the MG ECU.

2. Current sensors are used for the current sent to the three-phase windings of MG1 and MG2. They are located in the inverter with converter assembly for the V and W phases of each motor generator. Current that flows through the U phase winding flows through the V phase or W phase winding, thus the U phase amperage can be measured even if a current sensor is not set in the U phase winding.

   

HV Battery Assembly

1. The HV battery assembly mainly consists of 4 hybrid battery stacks, a hybrid vehicle junction block assembly, 2 battery cooling blower assemblies, a battery smart unit, an aluminum frame and a service plug grip.

   

   Text in Illustration

   *1	Hybrid Vehicle Junction Block Assembly	*2	Battery Smart Unit
   *3	No. 1 Hybrid Battery Stack	*4	No. 2 Hybrid Battery Stack
   *5	No. 3 Hybrid Battery Stack	*6	No. 4 Hybrid Battery Stack
   *7	Aluminum Frame	*8	Battery Cooling Blower
   *9	Service Plug Grip	-	-

2. Compact, lightweight 3.7 V lithium-ion battery cells are used in order to generate high power output.

   

   Text in Illustration

   *1

   Positive Terminal

   *2

   Negative Terminal

3. The 14 lithium-ion battery cells provided for each hybrid battery stack are connected in series in a bus bar module, ensuring 51.8 V per stack.

   

   Text in Illustration

   *1	No. 1 Hybrid Battery Stack	*2	No. 2 Hybrid Battery Stack
   *3	No. 3 Hybrid Battery Stack	*4	No. 4 Hybrid Battery Stack

4. The HV battery consists of 4 hybrid battery stacks. They are connected to each other in series through bus bar modules and wiring harness.

   

HV Battery Temperature Sensor and HV Battery Intake Air Temperature Sensor

1. 12 thermistor type battery temperature sensors are provided in the HV battery to detect the temperature of the HV battery.

2. 4 thermistor type intake air temperature sensor are provided to detect the temperature of the cooling air.

3. The power management control ECU optimally controls the cooling system so that the HV battery temperature and the cooling air temperature can be within a specified range according to the temperature information that is received via the battery smart unit.

   

   Text in Illustration

   *1

   HV Battery Temperature Sensor

   *2

   HV Battery Intake Air Temperature Sensor

Hybrid Battery Junction Block Assembly

1. The hybrid battery junction block assembly consists of the System Main Relays (SMRs), precharge resistor and battery current sensor.

2. The SMRs are relays that connect and disconnect the HV battery and power cable (frame wire) in accordance with the signal from the power management control ECU. 3 relays are provided; SMRB for the battery positive (+) side, SMRG for the battery negative (-) side, and SMRP for pre-charging.

   

   Text in Illustration

   *1	Hybrid Vehicle Junction Block Assembly	*2	Charging Relay (CHRG)
   *3	Charging Relay (CHRB)	*4	SMRB
   *5	SMRP	*6	SMRG

Battery Current Sensor

1. A battery current sensor, which is built into the hybrid vehicle junction block assembly, is used to detect the hybrid battery stack charging and discharging amperage.

2. The power management control ECU optimally controls the hybrid system so that the SOC of the hybrid battery stack can always be within a specified range according to the amperage information that is received via the battery smart unit.

   

Power Cable (Frame Wire)

1. The power cable (frame wire) is a set of high-voltage, high-amperage cables that connect the HV battery assembly with the inverter with converter assembly, the HV battery assembly with electric vehicle charger assembly, the inverter with converter assembly with MG1 and MG2, and the inverter with converter assembly with the compressor with motor assembly.

2. The power cable (frame wire) is made of shielded cables in order to reduce electromagnetic interference.

3. For identification purposes, the high-voltage wiring harness and connectors are color-coded orange to distinguish them from those of the ordinary low-voltage wiring.

   

   Text in Illustration

   *1	Compressor with Motor Assembly	*2	Inverter with Converter Assembly
   *3	Hybrid Vehicle Transaxle Assembly	*4	MG1
   *5	MG2	*6	Hybrid Battery Junction Block Assembly
   *7	Charging Relay	*8	Electric Vehicle Charger Assembly
   *9	HV battery	*10	Service Plug Grip
   *11	Charging Inlet (Electric Vehicle Charger Cable)	-	-
   	Power Cable (Frame Wire)		Electric Vehicle Charger Cable Wire

Inverter Water Pump Assembly

1. A compact and highly efficient electric type inverter water pump assembly is used.

2. A high output brushless type motor is used for the pump motor, furthermore, bearings that support the shaft at both ends are employed, thus suppressing noise and vibration.

3. The pump motor is controlled over 3 levels by the duty cycle signal from the power management control ECU.

   

   Text in Illustration

   *1	Impeller	*2	Bearing
   *3	Shaft	*4	Rotor
   *5	Stator	*6	Motor Controller
   	HV Coolant Inlet		HV Coolant Outlet

Accelerator Pedal Sensor Assembly

1. This non-contact type accelerator pedal sensor assembly uses a Hall IC.

2. A magnetic yoke is mounted at the base of the accelerator pedal arm. This yoke rotates around the Hall IC in accordance with the amount of effort that is applied to the accelerator pedal. The Hall IC converts the changes in the magnetic flux that occur into electrical signals, and outputs accelerator pedal position signals to the power management control ECU.

3. The Hall IC contains 2 circuits, one for the main signal, and one for the sub signal. It converts the accelerator pedal position (angle) into electric signals that have differing characteristics and outputs them to the power management control ECU.

   

   Text in Illustration

   *1	Hall IC	*2	Magnetic Yoke
   *3	Accelerator Pedal Arm	-	-

   

How to Read a Nomographic Chart

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', normal system operation is a constantly changing blend of conditions and system reactions to suit those conditions.

   

4. 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.

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

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

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

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

Driving Condition B*: Starting Off

1. When the vehicle is started off, the vehicle operates powered by MG2. If the required drive torque increases when running with MG2 only, MG1 is activated to start the engine.

   Tech Tips

   *: Refer to the preceding driving condition graph and table for more details.

   

   Text in Illustration

   *1	Engine (Stopped)	*2	Hybrid Vehicle Transaxle Assembly
   *3	MG1 (Rotates Freely)	*4	MG2 (Drive)
   *5	Power Split Planetary Gear Unit	*6	Motor Speed Reduction Planetary Gear Unit
   *7	Inverter with Converter Assembly	*8	HV Battery
   	Mechanical Power Path		Electrical Power Path
   	Power Transmission	-	-

2. While the vehicle is running with the motive force of MG2 only, the rotational speed of the carrier (engine) is 0 rpm due to the engine being stopped. In addition, since MG1 does not generate any torque, no torque acts on the sun gear (MG1). However, the sun gear rotates freely in the (-) direction balancing the rotating ring gear.

   

Driving Condition C*: Constant-speed Cruising in EV Mode / Driving Condition D*: Normal Acceleration in EV Mode

1. During constant-speed cruising in EV mode (Driving Condition C) and normal acceleration in EV mode (Driving Condition D), the vehicle runs with only the motive force of MG2, powered by the plug-in charged HV battery.

   Tech Tips

   *: Refer to the preceding driving condition graph and table for more details.

   

   Text in Illustration

   *1	Engine (Stopped)	*2	Hybrid Vehicle Transaxle Assembly
   *3	MG1 (Rotates Freely)	*4	MG2 (Drive)
   *5	Power Split Planetary Gear Unit	*6	Motor Speed Reduction Planetary Gear Unit
   *7	Inverter with Converter Assembly	*8	HV Battery
   	Mechanical Power Path		Electrical Power Path
   	Power Transmission	-	-

2. The geartrain and nomographic chart for the above conditions are the same as driving condition B (starting off).

Driving Condition E*: Constant-speed Cruising in HV Mode

1. When driving at high speed or with constant-speed cruising after EV mode driving finishes, the motive force of the engine is transmitted by the power split planetary gear unit. Some of this motive force is output directly, and the remaining motive force is used for generating electricity through MG1. Through the use of the electrical power path of the inverter with converter assembly, this electrical power is transmitted to MG2 to be output as the motive force of MG2. If the SOC level of the HV battery is low, it is charged by MG1 driven by the engine.

   Tech Tips

   *: Refer to the preceding driving condition graph and table for more details.

   

   Text in Illustration

   *1	Engine (Drive)	*2	Hybrid Vehicle Transaxle Assembly
   *3	MG1 (Generates Electricity)	*4	MG2 (Drive)
   *5	Power Split Planetary Gear Unit	*6	Motor Speed Reduction Planetary Gear Unit
   *7	Inverter with Converter Assembly	*8	HV Battery
   	Mechanical Power Path		Electrical Power Path
   	Power Transmission		Power Transmission at Low SOC Level

2. The torque from the engine acts on the carrier (engine) in the (+) direction, causing the sun gear (MG1) to turn in the (+) direction due to the reaction of negative torque. MG1 generates electricity by harnessing the negative torque that acts on the sun gear (MG1).

   

Driving Condition F*: During Full Throttle Acceleration with Engine Running

1. During EV mode, full throttle acceleration will cause the engine to start. The engine power will be transmitted to the wheels as motive force. Furthermore, MG1 will also be actuated to generate electrical power. In addition to the engine, the motive force of MG2, powered by the HV battery and MG1, accelerates the vehicle.

2. When the vehicle driving condition changes from low load cruising to full-throttle acceleration, the system supplements the motive force of MG2 with electrical power from the HV battery.

   Tech Tips

   *: Refer to the preceding driving condition graph and table for more details.

   

   Text in Illustration

   *1	Engine (Drive)	*2	Hybrid Vehicle Transaxle Assembly
   *3	MG1 (Generates Electricity)	*4	MG2 (Drive)
   *5	Power Split Planetary Gear Unit	*6	Motor Speed Reduction Planetary Gear Unit
   *7	Inverter with Converter Assembly	*8	HV Battery
   	Mechanical Power Path		Electrical Power Path
   	Power Transmission	-	-

3. When more engine power is required, in order to increase the engine speed, the rotational speeds of the related gears change as follows. The torque from the engine acts on the carrier (engine) in the (+) direction, causing the sun gear (MG1) to react with negative torque. MG1 generates electricity by harnessing the negative torque that acts on the sun gear (MG1).

   

Driving Condition G*: During Deceleration

1. While the vehicle decelerates with drive (D) selected, the engine is turned off and the motive force changes to zero. At this time, the wheels drive MG2, causing MG2 to operate as a generator, charging the HV battery. If the vehicle decelerates from a higher speed, the engine maintains a predetermined speed without stopping, in order to protect the planetary gears.

   Tech Tips

   *: Refer to the preceding driving condition graph and table for more details.

   

   Text in Illustration

   *1	Engine (Stopped)	*2	Hybrid Vehicle Transaxle Assembly
   *3	MG1 (Rotates Freely)	*4	MG2 (Generates Electricity)
   *5	Power Split Planetary Gear Unit	*6	Motor Speed Reduction Planetary Gear Unit
   *7	Inverter with Converter Assembly	*8	HV Battery
   	Mechanical Power Path		Electrical Power Path
   	Power Transmission	-	-

2. During deceleration, the ring gear is rotated by the wheels. Under this condition, due to the engine being stopped, the rotational speed of the carrier (engine) is 0 rpm. In addition, since MG1 does not generate any torque, no torque acts on the sun gear (MG1). However, the sun gear (MG1) rotates freely in the (-) direction, balancing the rotating ring gear.

   

Driving Condition H*: During Reverse

1. When the vehicle is being driven in reverse, the required power is supplied by MG2. At this time, MG2 rotates in the opposite direction, the engine remains stopped, and MG1 rotates in the normal direction without generating electricity.

   Tech Tips

   *: Refer to the preceding driving condition graph and table for more details.

   

   Text in Illustration

   *1	Engine (Stopped)	*2	Hybrid Vehicle Transaxle Assembly
   *3	MG1 (Rotates Freely)	*4	MG2 (Drive)
   *5	Power Split Planetary Gear Unit	*6	Motor Speed Reduction Planetary Gear Unit
   *7	Inverter with Converter Assembly	*8	HV Battery
   	Mechanical Power Path		Electrical Power Path
   	Power Transmission	-	-

2. The conditions of the planetary gear are opposite to those described in "Starting Off". Due to the engine being stopped, the rotational speed of the carrier (engine) is 0 rpm but the sun gear (MG1) rotates freely in the (+) direction, balancing the rotating ring gear.