HYBRID CONTROL SYSTEM DETAILS

Operating Condition of During Collision

1. If the vehicle encounters one of the situations described below, the power management control ECU (HV CPU) will shut down the power supply by turning the System Main Relays (SMRs) off, for safety.

2. The power management control ECU (HV CPU) receives an airbag deployment signal from the center airbag sensor assembly during a frontal collision.

   

Cooling Fan Control

1. The power management control ECU (HV CPU) detects increases in battery temperature via the 6 temperature sensors in the HV battery. Then, the power management control ECU (HV CPU) steplessly actuates the battery cooling blower assemblies using duty cycle control, in order to maintain the temperature of the HV battery within the specified range.

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

   

ECM Control

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

2. The ECM transmits the operating condition of the engine to the power management control ECU (HV CPU).

3. Upon receiving an engine stop signal from the power management control ECU (HV CPU) in accordance with basic LEXUS Hybrid Drive control, the ECM will stop the engine.

4. When a malfunction occurs in the system, the ECM activates the Malfunction Indicator Lamp (MIL) via the directions from the power management control ECU (HV CPU).

   

MG1, MG2 and MGR Main Control

1. MG1, which is driven by the engine, generates high voltage (alternating current) in order to power MG2 and charge the HV battery. Also, MG1 functions as a starter to start the engine.

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

3. MGR is driven by electrical power from the HV battery and MG1, and it generates motive force for the rear wheels.

4. MG2 and MGR generate electricity to charge the HV battery (regenerative brake control) during braking, or when the accelerator pedal is not being depressed.

5. The Motor Generator ECU (MG ECU), which follows the commands of the power management control ECU (HV CPU), controls MG1, MG2, and MGR via the Power Modules (PMs), for driving the vehicle. 6 Insulated Gate Bipolar Transistors (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 when a motor generator functions as a motor.

   
   

   1. The IGBTs switch on and off to supply three-phase alternating current to the motor.

   2. In order to create the motive force required of the motor generator as calculated by the power management control ECU (HV CPU), the Motor Generator ECU (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 a motor generator functions as a generator.

   
   

   1. The current that is generated sequentially by the three phases of the motor, which is driven by the wheels, is utilized to charge the HV battery or drive another motor generator.

      

Inverter with Converter Assembly Control

1. The inverter converts the direct current from the HV battery into alternating current for MG1, MG2, and MGR, or vice versa, in accordance with the signals provided by the power management control ECU (HV CPU) via the Motor Generator ECU (MG ECU). In addition, the inverter takes power generated by MG1 and supplies it to MG2 or MGR. However, the electricity generated by MG1 is converted into DC inside the inverter before being converted back into AC by the inverter for use by MG2 or MGR. This is necessary because the frequency of the AC output by MG1 is not appropriate for control of MG2.

2. The Motor Generator ECU (MG ECU) transmits signals to the power transistors in the inverter for switching the U, V, and W phases of stator coils of MG1, MG2, and MGR based on the rotor position information sent by the MG1, MG2, and MGR resolvers.

3. When the shift lever is in the N position, or the power management control ECU (HV CPU) has received an over-heating, over-current, or fault voltage signal from the inverter, the power management control ECU (HV CPU) transmits a shut down control signal to the inverter, in order to turn off the power transistors to electrically disconnect MG1, MG2, and MGR.

   

Boost Converter Control

1. The boost converter boosts the HV battery voltage of DC 288 V (nominal) up to a maximum voltage of DC 650 V, in accordance with the signals provided by the power management control ECU (HV CPU) via the Motor Generator ECU (MG ECU).

2. The inverter converts the alternating current generated by MG1, MG2 or MGR into direct current. The boost converter drops the voltage of DC 650 V (maximum) to DC 288 V (nominal) for the HV battery in accordance with the signals provided by the power management control ECU (HV CPU) via the Motor Generator ECU (MG ECU).

   

3. The boost converter consists of a boost Power Module (PM) with built-in IGBTs that perform switching control, and a reactor.

4. The reactor is an electronic component that has characteristics that resist changes in current flow. If a circuit containing a reactor is switched on and then off, the reactor will attempt to maintain current flow after being switched off. At the time of voltage reduction, these characteristics also assist in smoothing the output from the voltage drop IGBT (1). The reactor can be charged quickly by turning on the boost IGBT (2).

   

5. The boost converter boosts the HV battery voltage from DC 288 V (nominal) to a voltage of up to DC 650 V as described in the following 2 steps.

   Step	Outline
   1	The IGBT (2) turns on, causing the electrical power of the HV battery (nominal voltage of DC 288 V) to charge the reactor. As a result, the reactor stores power.
   2	The IGBT (2) 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 of DC 650 V.

   

6. The alternating current which is generated by MG1, MG2 or MGR for the purpose of charging the HV battery is converted into direct current (maximum voltage approximately 650 V) by the inverter. Then, the boost converter is used to drop the voltage to approximately DC 288 V. This is accomplished by IGBT (1) being switched on and off using duty cycle control, intermittently interrupting the electrical power provided to the reactor by the inverter.

   

E-Four System Control

1. E-Four system control calculates an optimum front to rear torque distribution ratio based on the signals from various sensors and the power management control ECU (HV CPU).

   

2. E-Four system control is performed as follows according to each driving condition, achieving optimum start-off performance, driving stability and the effective use of energy.

   Driving Condition	Control
   Starting-off	The skid control ECU calculates the total torque to be distributed to the front and rear wheels based on signals such as acceleration request drive torque or shift position signal sent from the power management control ECU (HV CPU). Based on the calculated total torque, the weight balance of the front and rear wheels and the best torque distribution in accordance with road conditions, signals are sent to the power management control ECU (HV CPU).
   Normal Driving	Based on signals sent from the power management control ECU (HV CPU) such as acceleration request drive torque, shift position signal, speed sensors or steering angle sensor, the skid control ECU sends a signal indicating the optimum torque distribution for the front and rear wheels to the power management control ECU (HV CPU).
   Deceleration	The skid control ECU evaluates signal inputs such as the acceleration drive torque or shift position signal, and then determines the amount of vehicle deceleration based on speed sensor readings sent from the power management control ECU (HV CPU). Based on this evaluation, the skid control ECU sends a regenerative braking request signal to the power management control ECU (HV CPU).

Skid Control ECU Control

1. The skid control ECU calculates the total braking force needed based on the master cylinder pressure in the brake actuator and brake pedal stroke sensor signal generated when the driver depresses the brake pedal.

2. After calculating the total brake force required, the skid control ECU sends a request to the power management control ECU (HV CPU). The power management control ECU (HV CPU) replies with the amount of regenerative brake force that is possible.

3. The power management control ECU (HV CPU) uses MG2 and MGR to create minus 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 total required braking force.

5. The skid control ECU outputs a request to the power management control ECU (HV CPU) to limit motive force while the VSC is operating to control wheel spin. The power management control ECU (HV CPU) controls the engine, MG1, MG2 and MGR in accordance with the present driving conditions in order to suppress the motive force.

   

Battery Voltage Sensor Control

1. The battery voltage sensor converts the HV battery related signals (voltage, current, and temperature) into digital signals, and transmits them to the power management control ECU (HV CPU) via serial communication. These signals are needed to determine the charge or discharge values that are calculated by the power management control ECU (HV CPU).

2. A leakage detection circuit is provided in the battery voltage sensor in order to detect any electrical leakage from the HV battery or high voltage circuit. Also, the battery voltage sensor detects the feedback voltage from the battery cooling blower assemblies, which is needed by the power management control ECU (HV CPU) to perform cooling fan control. The battery voltage sensor converts these signals into digital signals and transmits them to the power management control ECU (HV CPU) via serial communication.

   

Hybrid SNOW Mode Control

1. When hybrid SNOW mode control is activated, the drive force that changes in accordance with the accelerator pedal operation is controlled to be smaller than normal around the accelerator pedal angle which causes the wheels to slip easily, achieving enhanced accelerator pedal controllability.

2. If the front wheels slip, assistance using MGR will be optimized to enhance start-off stability.

   

Resolver

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 motor rotor is indispensable for ensuring efficient control of MG1, MG2 and MGR. MG1, MG2 and MGR 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 alternating current into excitation coil A results in the creation of a constant frequency magnetic field. Using this constant frequency magnetic field, coil S and coil C will output values that correspond to the position of the rotor. Therefore, the Motor Generator ECU (MG ECU) detects the absolute position based on the difference between the coil S and coil C output values. Furthermore, the Motor Generator ECU (MG ECU) calculates the rotational speed based on the amount of change in the position within a given length of time.

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

6. The detection coils have an electrical orientation as shown below.

   

   Text in Illustration

   *1	Resolver	*2	Image of Resolver Internal Construction
   *3	Detection Coil	*4	Rotor
   *5	Excitation Coil (Coil A)	*6	+S
   *7	+C	*8	-S
   *9	-C	*10	Electrical Orientation of Resolver Coils
   *11	Coil S	*12	Coil C

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

8. The Motor Generator ECU (MG ECU) constantly monitors these peak values, and connects them to form a virtual waveform. The Motor Generator ECU (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 Motor Generator ECU (MG ECU) calculates the rotational speed based on the amount of change in the rotor position within a given length of time.

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

   

Temperature Sensor

1. Temperature sensors are used to detect the temperature of the motor stators.

2. The temperature sensor thermistor resistance changes according to the change of motor temperature. The resistance of the thermistor is high when the temperature of the motor is low. Conversely, when the motor temperature is high, the thermistor resistance will be low.

3. When the temperature of a motor rises, motor output is limited.

   

Inverter with Converter Assembly

1. The inverter with converter assembly has a multi-layer structure which consists of the Motor Generator ECU (MG ECU), inverter, boost converter, condenser and DC-DC converter, achieving a lightweight and compact design.

   

   Text in Illustration

   *1	Control Circuit Portion - Motor Generator ECU (MG ECU) - Inverter - Boost Converter	*2	IGBT
   *3	Condenser	*4	DC-DC Converter Portion

2. The inverter with converter assembly is cooled by the dedicated radiator of a cooling system that is separate from that of the engine cooling system.

3. This inverter has a cooling system with a structure that makes it possible to cool the IGBTs of the boost converter and inverter from both sides, contributing to a compact design.

   

   Text in Illustration

   *1	Coolant Inlet	*2	Coolant Outlet
   	Coolant Flow	-	-

4. In consideration of safety, interlock switches are provided for the inverter with converter assembly. The interlock switches turn off the System Main Relays (SMRs) when the inverter terminal cover is removed or the connector of the HV battery power cable is disconnected.

5. An atmospheric pressure sensor is provided on the Motor Generator ECU (MG ECU) board. The sensor detects atmospheric pressure and transmits a signal to the Motor Generator ECU (MG ECU) to allow corrections that correspond to the usage environment.

   

   Text in Illustration

   *1	Inverter Terminal Cover	*2	Interlock Switch (For Inverter Terminal Cover)
   *3	Atmospheric Pressure Sensor	*4	Interlock Switch (For Power Cable)

   

Inverter

1. The inverter converts the boosted high-voltage direct current of the HV battery into three-phase alternating current to drive MG1, MG2 and MGR.

2. The activation of the power transistors is controlled by the Motor Generator ECU (MG ECU). In addition, the inverter transmits information that is needed for current control, such as the output amperage or voltage, to the power management control ECU (HV CPU) via the Motor Generator ECU (MG ECU).

3. The power transistors used in the inverter are Insulated Gate Bipolar Transistors (IGBTs).

4. Each of the bridge circuits for MG1, MG2, and MGR contains 6 IGBTs, mounted on the high voltage, high current module portion of a Power Module (PM). In addition, a signal processor/protective function processor has been integrated into control portion of the PM. The PM is used to operate the power transistors based on signals from the Motor Generator ECU (MG ECU).

   

Boost Converter

1. The boost converter boosts the nominal voltage of DC 288 V that is output by the HV battery to a maximum voltage of DC 650 V. The boost converter consists of the boost Power Module (PM) with a pair of built-in IGBTs which perform switching control, and a reactor which acts as an inductor. By using these components, the converter boosts the voltage.

2. When MG1, MG2 or MGR acts as a generator, the inverter converts the alternating current (maximum voltage of 650 V) into DC, and then the boost converter reduces the voltage to a nominal voltage of DC 288 V, thus the HV battery is charged.

   

DC-DC Converter

1. The power source for auxiliary equipment of the vehicle such as the lights, audio system, and the air conditioning system (except the cooler compressor with motor assembly), as well as the ECUs, is based on a DC 14 V system. Because the LEXUS Hybrid Drive generates output with a nominal voltage of DC 288 V, the DC-DC converter is used to transform the voltage from DC 288 V to approximately DC 14 V in order to recharge the auxiliary battery.

   

Current Sensor for Motor Generator

1. For the 3-phase AC used to drive MG1, MG2 and MGR, there are current sensors for the V and W phases. The actual current value is measured, and used as feedback by the Motor Generator ECU (MG ECU).

2. If the current value of 2 phases (V and W phases) is measured, the current of the U phase can be determined, even though it is not equipped with a current sensor. (U phase current + V phase current + W phase current = 0)

   

HV Battery Assembly

1. The HV battery assembly consists of the upper cover, 3 HV battery module groups, 3 battery cooling blower assemblies, junction connector, battery voltage sensor and service plug grip.

2. The cooling fan operation of the HV battery assembly is controlled to ensure the proper performance by the power management control ECU (HV CPU). The cooling fan control is required because the HV battery assembly creates heat while it is being charged and discharged. One cooling fan is provided for each of the 3 groups of the HV battery assembly. The cooling system uses air from the cabin.

3. A service plug grip is provided to shut off the internal circuit of the battery.

   

   Text in Illustration

   *1	Front	*2	Upper Battery Case
   *3	HV Battery Module Group (LH)	*4	HV Battery Module Group (Center)
   *5	HV Battery Module Group (RH)	*6	Battery Voltage Sensor
   *7	Service Plug Grip	*8	Battery Cooling Blower Assembly
   *9	Hybrid Junction Block Assembly	*10	Lower Battery Case

HV Battery Module Group

1. The HV battery module groups are split into 3 separate groups inside the battery case.

2. Metal is used for the material of the module cases to realize enhanced cooling performance and compact construction.

   

   Text in Illustration

   *1	HV Battery Module Group (LH)	*2	HV Battery Module Group (Center)
   *3	HV Battery Module Group (RH)	-	-

3. Each HV battery module group consists of 10 modules that are connected in series by a bus bar module. Furthermore, the connection between cells is made at 2 locations in order to reduce internal resistance and improve efficiency.

4. 1 module consists of 8 cells. 1 cell is 1.2 V.

   

Hybrid Junction Block Assembly

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

2. The SMRs consist of the SMRB (+), SMRG (-) and SMRP (precharge).

3. A large amount of current is generated due to the connection of the power cables. As a result, SMRP and SMRB (+) are turned on first to let the current enter the circuit in a controlled manner through the precharge resistor to protect the circuit. After that, the SMRG is turned on and SMRP is turned off.

   

   Text in Illustration

   *1	Hybrid Junction Block Assembly	*2	SMRB (+)
   *3	SMRG (-)	*4	SMRP (Precharge)
   *5	HV Battery Current Sensor	-	-

HV Battery Current Sensor

1. The HV battery current sensor is installed on the high-voltage cable inside the HV battery assembly, to detect current flow. It sends a voltage signal to the battery voltage sensor. This signal changes between 0.5 and 4.5 V in proportion to changes in the current flowing to or from the HV battery assembly. Less than 2.5 V means the HV battery assembly is being discharged, and more than 2.5 V means the HV battery assembly is being charged.

   

Service Plug Grip

1. By removing the service plug grip before performing any inspection or service, the high-voltage circuit is opened in the middle of the HV battery assembly, for safety during service.

2. The main fuse for the high-voltage circuit and the interlock switch are provided inside of the service plug grip.

3. For further details on how to handle the service plug grip and for other safety cautions, refer to the Repair Manual.

   

   Text in Illustration

   *1

   Service Plug Grip

   *2

   Insulated Glove

4. The main fuse is connected between module No. 10 and module No. 11 in the HV battery. When the service plug grip is removed, it interrupts the circuit for the HV battery. Before servicing any portion of the high-voltage circuit, make sure to turn the power switch off before removing the service plug grip.

   

Battery Temperature Sensor

1. The battery temperature sensor resistance changes along with the temperature change of the HV battery assembly.

2. The battery voltage sensor transmits the detection results of the battery temperature sensors to the power management control ECU (HV CPU) which then controls the battery cooling blower assemblies.

   

   Text in Illustration

   *1	Battery Temperature Sensor

Power Cable

1. The power cable is a set of high-voltage, high-amperage cables that connect the HV battery with the inverter with converter assembly, the HV battery with the power steering converter assembly (EPS DC-DC converter), the inverter with converter assembly with MG1, MG2 and MGR and the inverter with converter assembly with the cooler compressor with motor assembly.

2. The power cable 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	Power Cable	*2	Cooler Compressor with Motor Assembly
   *3	Inverter with Converter Assembly	*4	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly) - MG1 - MG2
   *5	Power Steering Converter Assembly (EPS DC-DC Converter)	*6	HV Battery
   *7	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly) - MGR	-	-

   

Acceleration Pedal Position Sensor

1. The non-contact type accelerator pedal position sensor uses a Hall IC which is mounted on the accelerator pedal arm.

   

   Text in Illustration

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

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 (HV CPU).

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 (HV CPU).

   

Auxiliary Battery Temperature Sensor

1. The battery characteristic (battery internal resistance) of taking in current for charging varies according to battery electrolyte temperature. If the battery electrolyte temperature is too low or too high, the battery will degrade more quickly, resulting in premature failure.

2. To prevent this, the auxiliary battery temperature sensor resistance changes as shown below to allow the power management control ECU (HV CPU) to detect the auxiliary battery temperature.

   

Starting Off

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

   

   Text in Illustration

   *1	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)	*2	Engine (Stopped)
   *3	Compound Gear Unit	*4	MG1 (Rotates Freely)
   *5	MG2 (Drive)	*6	Inverter
   *7	HV Battery	*8	MGR (Drive)
   *9	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)	*10	Front Wheels
   *11	Rear Wheels		Electrical Path
   	Mechanical Power Path		Power Transmission

2. When the vehicle starts off under normal conditions, it runs using the motive force of MG2 and MGR. While running under this condition, the rotational speed of the carrier 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. However, the sun gear rotates freely in the (-) direction balancing the rotating ring gear (Output).

   

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 and MGR.

   

   Text in Illustration

   *1	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)	*2	Engine (Drive)
   *3	Compound Gear Unit	*4	MG1 (Driven - Generates Electricity)
   *5	MG2 (Drive)	*6	Inverter
   *7	HV Battery	*8	MGR (Drive)
   *9	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)	*10	Front Wheels
   *11	Rear Wheels		Electrical Path
   	Mechanical Power Path		Power Transmission

   

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 motive force from the engine is split into two in the power split planetary gear 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.

4. MGR is not used to output motive force in the constant speed cruising mode, in order to make fuel economy a priority.

   

   Text in Illustration

   *1	SOC of the HV battery is sufficient:	*2	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)
   *3	Engine (Drive)	*4	Compound Gear Unit
   *5	MG1 (Driven - Generates Electricity)	*6	MG2 (Drive)
   *7	Inverter	*8	HV Battery
   *9	MGR	*10	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)
   *11	Front Wheels	*12	Rear Wheels
   	Electrical Path		Mechanical Power Path
   	Power Transmission	-	-

   

5. 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.

   

   Text in Illustration

   *1	SOC of the HV battery is low:	*2	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)
   *3	Engine (Drive)	*4	Compound Gear Unit
   *5	MG1 (Driven - Generates Electricity)	*6	MG2 (Drive)
   *7	Inverter	*8	HV Battery (Charged by MG1)
   *9	MGR	*10	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)
   *11	Front Wheels	*12	Rear Wheels
   	Electrical Path		Mechanical Power Path
   	Power Transmission	-	-

   

During Full Throttle Acceleration

1. 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.

2. MGR operates during full throttle acceleration and drives the rear wheels in order to make acceleration performance a priority.

   

   Text in Illustration

   *1	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)	*2	Engine (Drive)
   *3	Compound Gear Unit	*4	MG1 (Driven - Generates Electricity)
   *5	MG2 (Drive)	*6	Inverter
   *7	HV Battery	*8	MGR (Drive)
   *9	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)	*10	Front Wheels
   *11	Rear Wheels		Electrical Path
   	Mechanical Power Path		Power Transmission

3. When more engine power is required, in order to increase the engine speed, the rotation speeds of the related gears change as follows. The sun gear, carrier and ring gear rotate in the (+) direction. The engine rotates the carrier in the (+) direction, and the sun gear applies (-) torque to resist the motive force of the engine. MG1 generates electricity by creating the (-) torque that acts on the sun gear. The electricity created by MG1 is used to drive MG2 and MGR.

   

During Deceleration

1. While the vehicle is being driven with the shift lever in the D position 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 and MGR, causing MG2 and MGR to operate as generators and charge the HV battery. While MG2 and MGR are 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.

   

   Text in Illustration

   *1	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)	*2	Engine (Stopped)
   *3	Compound Gear Unit	*4	MG1 (Rotates Freely)
   *5	MG2 (Driven - Generates Electricity)	*6	Inverter
   *7	HV Battery	*8	MGR (Driven - Generates Electricity)
   *9	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)	*10	Front Wheels
   *11	Rear Wheels		Electrical Path
   	Mechanical Power Path		Power Transmission

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

   

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. In addition, when more drive force is needed, power is also provided to MGR.

3. While driving in reverse, when any of the conditions monitored by the power management control ECU (HV CPU) such as SOC, 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.

   

   Text in Illustration

   *1	P313 Hybrid Transaxle (Hybrid Vehicle Transaxle Assembly)	*2	Engine (Stopped)
   *3	Compound Gear Unit	*4	MG1 (Rotates Freely)
   *5	MG2 (Drive)	*6	Inverter
   *7	HV Battery	*8	MGR (Drive)
   *9	Q211 Rear Drive Unit (Rear Traction Motor with Transaxle Assembly)	*10	Front Wheels
   *11	Rear Wheels		Electrical Path
   	Mechanical Power Path		Power Transmission

4. 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 is 0 rpm but the sun gear (MG1) rotates freely in the (+) direction to balance the rotation of the ring gear (Output).

   

System Main Relay Control

1. The System Main Relays (SMRs) are relays that connect and disconnect the power source of the high-voltage circuit upon receiving a command from the power management control ECU (HV CPU). 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.

   

2. The power management control ECU (HV CPU) turns the SMRB on. After that, it turns the SMRP on. After the power management control ECU (HV CPU) has turned the SMRG on, it turns the SMRP off. As the controlled current is initially allowed to pass though a resistor in this manner, the contact point in the circuit is protected from damage that could be cause by a rush current.

   

3. First, the power management control ECU (HV CPU) turns the SMRG off. After is has determined whether the contact points of the SMRG are stuck, it turns the SMRB off. Subsequently, the power management control ECU (HV CPU) turns the SMRP on in order to determine whether the contact points of the SMRB are stuck. Then, it turns the SMRP off.

   

4. If the power management control ECU (HV CPU) detects that the contact points are stuck, it illuminates the master warning light and indicates "CHECK HYBRID SYSTEM" on the multi-information display, and stores a Diagnostic Trouble Code (DTC) in memory.