HYBRID CONTROL SYSTEM GENERAL

OUTLINE
1. The hybrid system of this hybrid vehicle employs the Toyota Hybrid System-II (THS-II) 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.

SPECIFICATION

Motor Generator

Item	Specification
Item	MG1	MG2
Type	Permanent Magnet Motor	Permanent Magnet Motor
Function	Generate, Engine Starter	Generate, Drive Wheels
Maximum System Voltage	DC 650 V	DC 650 V
Maximum Output	-	60 kW (80 HP)
Maximum Torque	-	207 Nm (153 ft.lbf)
Cooling System	Water-cooled	Air-cooled

Inverter with Converter Assembly

Item		Specification
Boost Converter	Rated Voltage (Inverter Side)	DC 650 V
Boost Converter	Rated Voltage (HV Battery Side)	DC 201.6 V
DC-DC Converter	Rated Output Voltage	DC 13.5 V to 15.0 V (normal condition) DC 11.5 V (activated at low temperatures)
DC-DC Converter	Maximum Output Current	120 A

HV Battery

Item	Specification
Type	Nickel Metal Hydride (Ni-MH) Battery
Cell Quantity	168 Cells (6 Cells x 28 Modules)
Nominal Voltage	201.6 V
Battery Capacity (3HR)	6.5 Ah

Cooling System (for Inverter with Converter Assembly and MG1)

Item			Specification
Inverter Water Pump Assembly	Motor Type		Brushless
Inverter Water Pump Assembly	Discharge Volume		10 Liter (10.6 US qts, 8.8 Imp. qts) /min. or greater
Coolant	Type		Toyota Genuine Super Long Life Coolant (SLLC)
	Color		Pink
	Capacity		2.1 Liters (2.2 US qts, 1.8 Imp. qts)
	Maintenance Intervals	First Time	240000 km (150000 miles)
	Maintenance Intervals	Subsequent	Every 80000 km (50000 miles)

Cooling System (for HV Battery)

Item		Specification
HV Battery Cooling Blower	Motor Type	Brushless
	Fan Type	Sirocco Fan
	Air Flow Volume	138 m³/h

MAIN FEATURES

The THS-II 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.

The mechanism of the THS-II is as follows.

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

Text in Illustration
*1	Engine	*2	Hybrid Vehicle Transaxle Assembly
*3	Motor Generator 1 (MG1)	*4	Motor Generator 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
	Electrical Power Path (DC)		Electrical Power Path (AC)
	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.

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

Text in Illustration
*1	Engine	*2	Transmission
*3	HV Battery	*4	Inverter
*5	Motor Generator	-	-
	Electrical Power Path (DC)		Electrical Power Path (AC)
	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 the motor generator 1 using engine power. The generated electricity is used to charge the HV battery and also to power the motor generator 2.

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

This system optimally performs cooperative control of the 2ZR-FXE engine, and Motor Generator 1 (MG1) and Motor Generator 2 (MG2) in the P410 hybrid vehicle transaxle assembly that provides excellent transmission performance.
The system has 2 batteries that are used in different purposes. One is the HV battery (nominal voltage of DC 201.6 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, it uses a variable-voltage system consisting of a high-output HV battery with a nominal voltage of DC 201.6 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 alternates direct current and alternating current.

Since hybrid vehicles are not equipped with a conventional generator, 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 SOC (state of charge) range while the vehicle is running, thus, recharging from external power sources is not necessary.

Text in Illustration
*1	2ZR-FXE Engine	*2	P410 Hybrid Vehicle Transaxle Assembly Motor Generator 1 (MG1) Motor Generator 2 (MG2)
*3	Inverter with Converter Assembly Inverter Boost Converter DC-DC Converter	*4	HV Battery
*5	Auxiliary Battery	-	-

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

Text in Illustration
*1	Inverter Water Pump Assembly	*2	HV Radiator
*3	HV Radiator Reserve Tank	-	-
	HV 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.

Text in Illustration
*1	Intake Air Duct	*2	HV Battery
*3	HV Battery Cooling Blower	*4	Exhaust Air Duct
	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 vehicle transaxle assembly and cooler compressor with motor assembly. Each of these items is connected by the power cables 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	Cooler Compressor with Motor Assembly	*2	Power Cable
*3	Inverter with Converter Assembly	*4	Hybrid Vehicle Transaxle Assembly
*5	HV Battery	-	-

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 (HV CPU).
  - 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.
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.
  
  Text in Illustration
  
  *1 Service Plug Grip *2 Insulated Gloves
  
  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.

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

HV Battery Handling Precautions

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. Connect the negative terminal of the auxiliary battery. Turn the power switch on (IG) for 3 minutes, do not apply any electrical loads. (This operation is needed to allow the power management control ECU (HV CPU) 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, shout loudly for help, do not rub your eyes, rinse your eyes with large amount of water and seek medical attention immediately.