2001 TOYOTA PRIUS Service Repair Manual

CHASSIS ± P111 HYBRID TRANSAXLE
182CH10
182CH09
: Flow of
: motive force
: Flow of
: electrical force
RechargingInverterHV Battery
Reactive
Control
MG2MG1Generate
EngineSun Gear Carrier Ring Gear
rpm
MG1 Engine MG2
: Torque
: MG2
: Torque
Nomographic Chart of Planetary
Gear Unit
Discharge
182CH12
182CH11
Inverter
HV Battery
Discharge
Drive
MG2
MG1
Engine : Flow of
: motive force
: Flow of
: electrical force
Sun Gear Carrier Ring Gear
rpm
MG1Engine
MG2
Nomographic Chart of Planetary
Gear Unit
: Driving
: Load
: MG2
: Torque
83
2) Generation During Shift Position P
When the shift lever is in the P position, if the SOC (State Of Charge) of the HV batteries exceeds the
specified value, the engine remains stopped. However, if the SOC is below the specified value, the engine
operates to generate electricity through MG1 in order to recharge the HV batteries. At this time, reactive
control is effected to allow the electric current to flow from the HV batteries to MG2, thus receiving the
reactive force of MG2.
3) Starting and Light-Load Driving
When the vehicle is started off or is being driven under light-load conditions, and the SOC of the HV
batteries exceeds the specified value, the vehicle operates powered only by MG2. At this time, the engine
remains stopped, and MG1 is spinning in the opposite direction without generating electricity. If the SOC
is below the specified value, the engine operates to generate electricity through MG1 in order to recharge
the HV batteries.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH14
182CH13
HV Battery
Inverter
Drive
MG2 MG1
Discharge
Recharging
Electrical Path
Generation
Engine : Flow of
: motive force
: Flow of
: electrical force
Sun Gear Carrier Ring Gear
rpm
MG1 Engine MG2: Torque
: Driving Load
: MG2 Torque
Nomographic Chart of Planetary
Gear Unit
182CH18
182CH17
Inverter
HV Battery
MG2MG1
Speed
Control
Engine
Recharging
Electrical Path
Generation: Flow of
: electrical force
Sun Gear Carrier Ring Gear
MG1 Engine MG2: Driving
: Load
: MG2
: Torque
Nomographic Chart of Planetary
Gear Unitrpm Speed
Control : Flow of
: motive force 84
4) Normal Traveling
When the vehicle is being driven under normal traveling condition, the motive force of the engine is divided
by the planetary gears. A portion of this motive force is output directly, and the remaining motive force
is used for generating electricity through MG1. Through the use of an electrical path of an inverter, this
electrical force is sent to MG2 to be output as the motive force of MG2. Under further high-load conditions,
the electrical force from the HV batteries is also used as a motive force of MG2.
5) Deceleration Driving
If the SOC of the HV batteries is within the specified value during deceleration, electricity is generated
by MG2 to recharge the HV batteries. If the SOC is excessive, the apportionment of energy to the hydrau-
lic brakes is increased. However, if the shift lever is in position B, the engine is started by MG1 in order
to apply the engine brake.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH20
182CH19
Inverter
HV Battery
MG2MG1
Engine
Discharge
Electrical Path
Recharging
GenerationDrive: Flow of
: motive force
: Flow of
: electrical force
Sun Gear Corrier Ring Gear
rpm
MG1 Engine MG2: Driving Load
: MG2 Torque
Nomographic Chart of Planetary
Gear Unit
NOTICE
Because it is not possible for this transaxle to separate the MG2 output force from the drive wheels when
the shift lever is in position N, the generation of electricity is disabled. In this condition, the generation
of electricity could cause the motive force to be transmitted, which creates a hazardous situation. There-
fore, beware that the HV batteries could become discharged in this state.85
6) Reverse Driving
The vehicle drives in reverse powered only by MG2. If the SOC of the HV batteries exceeds the specified
value, the vehicle drives powered only by MG2. If the SOC is below the specified value, the engine starts,
and the electrical force generated by MG1 passes through the electrical path function of the inverter in
order to be used as the motive force of MG2.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH21
Silent Chain
Final Gears
Differential ShaftCounter Gears Engine's Center Shaft 86
6. Reduction Unit
The reduction unit consists of the silent chain, counter gears and final gears.
A silent chain with a small pitch width has been adopted to ensure quiet operation, and the overall length has
been reduced in contrast to the gear-driven mechanism.
The counter gears and final gears teeth have been processed through high-precision housing and their tooth
flanks have been optimized to ensure extremely quiet operation.
The final gears have been optimally allocated to reduce the distance between the engine's center shaft and
the differential shaft, thus resulting in a transmission with a compact package.

DIFFERENTIAL UNIT
For the differential unit, a 2-pinion type that is similar to the differential unit of the conventional transaxle
has been adopted.