
THS II (TOYOTA HYBRID SYSTEM II)
TH-9
FUNCTION OF MAIN COMPONENTS
Item
Outline
MG1
MG1, which is driven by the engine, generates high-voltage
electricity in order to operate MG2 or charge the HV
battery. Also, it functions as a starter to start the engine.
MG1 operates so that the gear ratio of the power split
planetary gear unit will optimally suit the driving
conditions of the vehicle.
Hybrid
Transaxle
MG2
Driven by electrical power from MG1 or HV battery, and
generates motive force for the front wheels.
During braking, or when the accelerator pedal is not
depressed, it generates electricity to recharge the HV
battery (Regenerative brake control).
Transaxle
Compound
Power
Split
Planetary
Gear
Distributes the engine’s drive force as appropriate to directly
drive the vehicle as well as the generator.
Compound
Gear Unit
Motor
Speed
Reduction
Planetary
Gear
Located between MG2 and the power split planetary gear, the
motor speed reduction planetary gear reduces the rotational
speed of MG2 in accordance with the characteristics of the
planetary gear, in order to increase torque.
HV Battery
Supplies electrical power to the MG1 and MG2 in
accordance with the driving conditions of the vehicle.
Is recharged by the MG1 and MG2 in accordance with the
SOC and the driving conditions of the vehicle.
HV Battery
Unit
DC / DC Converter
Drops the maximum voltage of DC 244.8 V into DC12 V in
order to supply electricity to body electrical components, as
well as to recharge the auxiliary battery (DC 12 V).
Battery Smart Unit
Monitors the conditions of the HV battery and transmits them
to the THS ECU.
Service Plug
Shuts off the high-voltage circuit of the HV battery when this
plug is removed for vehicle inspection or maintenance.
Inverter Assembly
A device that converts the high-voltage DC (HV battery) into
AC (MG1 and MG2) and vice versa (Converts AC into DC).
Boost Converter
Boosts the maximum voltage of the HV battery from DC 244.8
V to DC 650 V and vice versa (drops DC 650 V to DC 244.8
V).
MG ECU
Controls the inverter and boost converter in accordance with
the signals received from the THS ECU, thus driving MG1 or
MG2 or causing them to generate electricity.
THS ECU
Effects comprehensive control of the THS II.
Information from each sensor as well as from the ECU
(battery smart unit, skid control ECU, and EPS ECU) is
received, and based on this the required torque and output
power is calculated. The THS ECU sends the calculated
result to the inverter assembly and skid control ECU.
Activates the ETCS-i (Electronic Throttle Control
System-intelligent) in accordance with the target engine
speed and required engine motive force.
Monitors the charging condition of the HV battery.
Controls the cooling fan of the HV battery and cooling fan
of the DC / DC converter.
Controls the DC / DC converter.
(Continued)