HYBRID CONTROL SYSTEM GENERAL

OUTLINE
1. The hybrid system of this hybrid vehicle employs the LEXUS Hybrid Drive under the "Hybrid Synergy Drive" concept*.
  
  Tech Tips
  
  *: The "Hybrid Synergy Drive" concept consists of 4 key benefits: fuel efficiency, low emissions, seamless acceleration and silent performance.
2. Hybrid vehicles use a combination of 2 kinds of power sources, such as an engine and electric motor, 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.

SPECIFICATION

Motor Generator

Motor Generator	MG1	MG2
Type	Permanent Magnet Motor	Permanent Magnet Motor
Function	Generates Electricity Starts Engine	Drives Rear Wheels Generates Electricity
Maximum System Voltage	DC 650 V	DC 650 V
Maximum Output	-	147 kW (197 HP)
Maximum Torque	-	275 Nm (203 ft.lbf)
Cooling System	Water-cooled	Water-cooled

Inverter with Converter Assembly

Item		Specifications
Boost Converter	Rated Voltage (Inverter Side)	DC 650 V
Boost Converter	Rated Voltage (HV Battery Side)	DC 288 V
Hybrid Vehicle Converter Assembly	Rated Output Voltage	DC 13 V to 14.5 V (Normal Condition) DC 11.5 V (Activated at Low Temperatures)
Hybrid Vehicle Converter Assembly	Maximum Output Current	150 A

Cooling System for Inverter with Converter Assembly, MG1 and MG2

Item			Specifications
Inverter Water Pump with Motor Assembly	Motor Type		Brushless
	Discharge Volume	High	12 L/min (12.7 US qts, 10.6 Imp. qts) or Greater@65°C (149°F)
		Mid	9 L/min (9.5 US qts, 7.9 Imp. qts) or Greater@55°C (131°F)
		Low	7 L/min (7.4 US qts, 6.2 Imp. qts) or Greater@50°C (122°F)
Inverter Coolant	Type		Toyota Genuine Super Long Life Coolant (SLLC) or Equivalent
	Color		Pink
	Capacity		3.1 Liters (3.3 US qts, 2.7 Imp. qts)1 2.9 Liters (3.1 US qts, 2.6 Imp. qts)2
	Maintenance Intervals	First Time	240000 km (150000 miles) or 7 years
	Maintenance Intervals	Subsequent	Every 80000 km (50000 miles) or 4 years

*1: LHD models
*2: RHD models

HV Battery

Item	Specifications
Type	Sealed Nickel Metal Hydride (Ni-MH) Battery
Cell Quantity	240 Cells (6 Cells x 6 Modules + 6 Cells x 34 Modules)
Nominal Voltage	288 V (1.2 V x 240 Cells)
Battery Capacity (3HR)	6.5 Ah

Cooling System for HV Battery

Item			Specifications
Battery Cooling Blower Assembly	Motor Type		Brushless
	Fan Type		Sirocco Fan
	Air Flow Volume	Upper Side	93 m³/h
	Air Flow Volume	Lower Side	138 m³/h

MAIN FEATURES

Hybrid vehicles have the following features:

Features	Outline
Idle Stop (Reduction of Energy Loss)	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 met, the vehicle can run on only the electric motor.
Motor Assist	An 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, for example as motor power.

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.

Series-type Hybrid System

The motor rotates the wheels, and the engine acts as an electric power source for the motor using a generator.

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

Parallel-type Hybrid System

Both the engine and the motor directly rotate the wheels. In addition to supplementing the power of the gasoline engine, the electric motor can also serve as a generator to charge the high-voltage battery pack while the vehicle is in motion. Driving the vehicle with the motor only is also possible.

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

Series/Parallel Hybrid System

Features 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 1 (MG1) using engine power. The generated electricity is used to charge the HV battery and/or also to power Motor Generator 2 (MG2).

Text in Illustration
*1	Engine	*2	Power Split Planetary Gear
*3	HV Battery	*4	Inverter
*5	Motor Generator 1 (MG1)	*6	Motor Generator 2 (MG2)
	Mechanical Power Path		Electrical Power Path (DC)
	Electrical Power Path (AC)	-	-

The mechanism of the LEXUS Hybrid Drive is as follows:

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

Text in Illustration
*1	Engine	*2	Hybrid Transmission (Hybrid Vehicle Transmission Assembly)
*3	Power Split Planetary Gear	*4	2-stage Motor Speed Reduction Planetary Gear
*5	Motor Generator 1 (MG1)	*6	Motor Generator 2 (MG2)
*7	Inverter with Converter Assembly	*8	Differential
*9	HV Battery	-	-
	Mechanical Power Path		Electrical Power Path (DC)
	Electrical Power Path (AC)	-	-

This system optimally performs cooperative control of the high-output 2GR-FXE engine and the high-speed, high-output Motor Generator 1 (MG1) and Motor Generator 2 (MG2) in the L110 hybrid transmission (hybrid vehicle transmission assembly) that provides excellent transmission performance.
Hybrid vehicles have 2 batteries that are used in different purposes. One is the HV battery (nominal voltage of DC 288 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.
Furthermore, this vehicle uses a variable-voltage system consisting of a high-output HV battery with a nominal voltage of DC 288 V, a boost converter that boosts the operating voltage of the system to a maximum voltage of DC 650 V and an inverter that converts direct current and alternating current.
Since hybrid vehicles are not equipped with a conventional generator, the voltage from the HV battery is dropped to approximately DC 14 V using the hybrid vehicle converter assembly in order to charge the auxiliary battery.

The HV battery uses sealed Nickel Metal Hydride (Ni-MH) battery cells. This HV battery has a high power density, is lightweight, and it offers longevity to match the characteristics of the LEXUS Hybrid Drive. Because charge/discharge control is performed to maintain the HV battery within a constant State Of Charge (SOC) range while the vehicle is operating normally, it does not require external recharging.

Text in Illustration
*1	Inverter with Converter Assembly - Inverter - Boost Converter - Hybrid Vehicle Converter Assembly	*2	2GR-FXE Engine
*3	L110 Hybrid Transmission (Hybrid Vehicle Transmission Assembly) - Motor Generator 1 (MG1) - Motor Generator 2 (MG2)	*4	Auxiliary Battery (Nominal Voltage of DC 12 V)
*5	HV Battery (Nominal Voltage of DC 288 V)	-	-

Hybrid vehicles have 2 hybrid related cooling systems, one for cooling the inverter with converter assembly, MG1 and MG2 and one for cooling the HV battery.

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

This cooling system activates when the power switch is turned on (READY).

Text in Illustration
*1	Inverter Radiator	*2	Inverter Water Pump with Motor Assembly
*3	L110 Hybrid Transmission (Hybrid Vehicle Transmission Assembly) - Motor Generator 1 (MG1) - Motor Generator 2 (MG2)	*4	Inverter Reservoir Tank
*5	Inverter with Converter Assembly	-	-
	Inverter Coolant Flow	-	-

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.
One battery cooling blower assembly is provided for each of the upper and lower module groups of the HV battery. Because each of the 2 battery cooling blower assemblies has been made compact, the overall operating sound has been reduced. Furthermore, because the battery cooling blower assemblies are mounted using rubber dampers, this construction also contributes to noise reduction. In addition, a fiber material with noise absorption ability is provided to part of the intake air duct for the lower battery module group, thus ensuring a high level of quietness in the cabin.
The intake air ducts have been optimally shaped and located to allow a large amount of air to flow smoothly, thus directing cabin air which is taken in from the rear seat sides toward the battery modules. The cabin air flows across the battery modules, thus lowering the temperature of the battery modules. Low temperature cabin air, which is less affected by temperature increase caused by heat from the sun, is taken in, thus ensuring a high level of cooling efficiency.

The power management control ECU controls the operation of the battery cooling blower assemblies. The power management control ECU receives signals from the battery smart unit about the HV battery temperature sensors which are built into the HV battery assembly. Then, the power management control ECU controls the battery cooling blower assemblies in order to control the battery temperature to an appropriate level.

Text in Illustration
*1	Lower Battery Cooling Blower Assembly	*2	Lower HV Battery Module Group
*3	Upper Battery Cooling Blower Assembly	*4	Upper HV Battery Module Group
*a	From Cabin	-	-
	Cooling Air Flow	-	-

PRECAUTION

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.

Insulation of High-voltage Circuits

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

Cables 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.

Text in Illustration
*1	Inverter with Converter Assembly	*2	Compressor with Motor Assembly
*3	Power Cable	*4	HV Battery Assembly
*5	Service Plug Grip	*6	L110 Hybrid Transmission (Hybrid Vehicle Transmission Assembly)

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 power management control ECU:
  - Power switch is turned off.
  - Any airbag is deployed.
  - Inverter terminal cover is removed (interlock circuit is opened).
  - Connector cover assembly is removed (interlock circuit is opened).
  - Power cable from the HV battery is removed from the inverter with converter assembly (interlock circuit is opened).
  - Service plug grip handle is raised partway (interlock circuit is opened)*.
  - Specified malfunction occurs.
  Tech Tips
  
  *: The service plug grip should never be removed when the vehicle is in the READY-ON state.
2. The service plug grip is used to cut off the high-voltage circuit manually for when service is to be performed on the vehicle.
  
  Text in Illustration
  
  *1 Service Plug Grip *2 Insulated Glove
  
  CAUTION:
  
  Regarding discharge of the capacitor in the inverter with converter assembly: 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 in the inverter to discharge before beginning work.

Text in Illustration
*1	Service Plug Grip	*2	Insulated Glove

HV Battery Handling Precautions

HV battery electrolyte is a highly alkaline potassium hydroxide solution (odorless, transparent, colorless). Careless handling of the HV battery is very dangerous. Handle the HV battery properly in accordance with the procedures below:

Procedure	Precaution
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 saturated 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 stored.	The battery should not be left in a damp or wet location.
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 to prevent HV battery discharge or damage. Using the following procedure, charge the HV battery: Connect the negative terminal of the auxiliary battery. Turn the power switch on (IG) for 3 minutes, and do not apply any electrical loads. (This operation is needed to allow the power management control ECU to detect the correct SOC.) 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, call for help, do not rub your eyes. Rinse your eyes with a large amount of water and seek medical attention immediately.