TOYOTA PRIUS 2001 Service Repair Manual

CHASSIS ± P111 HYBRID TRANSAXLE
CHASSIS
182CH01
MG (Motor Generator) 2Power Splitting Device
MG (Motor Generator) 1
Transaxle Damper
Differential Oil Pump79
P111 HYBRID TRANSAXLE
DESCRIPTION
The P111 hybrid transaxle has been newly developed for the hybrid system application.
Containing a MG (Motor Generator) 2 for driving the vehicle and a MG (Motor Generator) 1 for generating
electrical power, the P111 hybrid transaxle uses a continuously variable transmission mechanism with power
splitting device that achieve smooth and quiet operation.

Specifications 
Pl t
The No. of Ring Gear Teeth78
Planetary
GearThe No. of Pinion Gear Teeth23Gear
The No. of Sun Gear Teeth30
Gear Ratio3.905
Number of Links74
ChainDrive Sprocket39
Driven Sprocket36
Counter GearDrive Gear30Counter GearDriven Gear44
Final GearDrive Gear26Final GearDriven Gear75
Fluid Capacity Liters (US qts, Imp.qts)4.6 (4.9, 4.0)
Fluid TypeATF Type T-IV or equivalent

CHASSIS ± P111 HYBRID TRANSAXLE
182CH02
Power Splitting Device
Transaxle
Damper
MG2
Sun Gear
Carrier
Ring GearMG1
Oil Pump
Silent ChainEngine
Counter Gears
Final Gears
182CH03
Coil Spring
Drive force
from the
engine 80
TRANSAXLE UNIT
1. General
The transaxle unit consists primarily of a transaxle damper, MG (Motor Generator) 1, MG2, power splitting
device and a reduction unit (containing a silent chain, counter gears, and final gears).
2. Transaxle Damper

A coil-spring type damper with low-twist char-
acteristics has been adopted as the mechanism
to transmit the drive force from the engine.

A torque fluctuation absorbing mechanism that
uses a dry-type single-plate friction material
has been adopted.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH05
Stator
Rotor
Stator
Rotor
182CH04
81
3. MG (Motor Generator) 1
The MG1 recharges the HV (Hybrid Vehicle) bat-
tery and supplies electrical power to drive the
MG2. In addition, by regulating the amount of
electrical power generated, thus varying the
MG2's speed, the MG1 effectively controls the
continuously variable transmission function of the
transaxle. Connected to the sun gear of the plane-
tary gear unit, MG1 also functions as a starter for
starting the engine.
4. MG (Motor Generator) 2
Serving as the source of supplemental motive
force that provides power assist to the output of the
engine as needed, the electric motor helps the ve-
hicle achieve an excellent dynamic performance
that includes smooth start-offs and acceleration.
Connected to the ring gear in the planetary gear
unit, MG2 is an electric motor that converts the ve-
hicle's kinetic energy that is generated through the
activation of the regenerative brake into electrical
energy, which is then stored in the HV batteries.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH77 182CH06
Planetary
Gear UnitRing Gear
Carrier
Sun Gear
MG2
Oil PumpMG1
Transaxle
Damper
Engine
Chain
Counter Gear
Final Gear
MG2
Engine Output Shaft
MG1
182CH08
182CH07
HV Battery
Inverter
MG2 MG1
Engine : Flow of
: motive force
: Flow of
: electrical force
Discharge
Reactive
Control: Torque
: MG2
: Torque
Sun GearCarrier Ring Gear
rpm
MG1 Engine MG2
Nomographic Chart of Planetary
Gear Unit
82
5. Power Splitting Device
General
Planetary gear unit is used for a power splitting device.
As part of the planetary gear unit, the sun gear is connected to MG1, the ring gear is connected to MG2,
and the carrier is connected to the engine output shaft. The motive force is transmitted via the chain to the
counter drive gear.
Item
Connection
Sun GearMG1
Ring GearMG2
CarrierEngine Output Shaft
Operation
1) Starting the Engine
Both while the vehicle is stopped and is in motion, the starting of the engine is performed by MG1. Be-
cause the motive force is transmitted at this time to the ring gear in the planetary gear unit, an electrical
current is applied to MG2 to cancel out the motive force (reactive control).
The nomographic chart below gives a visual representation of the planetary gear's rotational direction,
rotational speed, and power balance. In the nomographic chart, the rpm of the 3 gears maintain a relation-
ship in which they are invariably joined by a direct line.

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.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH22
Oil Pump Drive
Shaft
Oil Pump Drive
Rotor
Oil Pump
Driven
Rotor
182CH23
182CH24
Parking Gear
Parking
Lock
Pawl
Link 1
Link 2
ªAº View Link 2
Parking Rod
Parking
Lock
Pawl ªAº View87

LUBRICATION SYSTEM
A force-feed lubrication system using a trocoid
pump has been adopted for lubrication of the plan-
etary gear unit and the bearings on the main shaft.
The oil pump is directly driven by the engine.
The same type of oil is used for both the reduction
unit portion and the differential portion.

PARKING LOCK MECHANISM
A mechanical parking lock mechanism has been
provided in the counter driven gear.
The engagement of the parking lock pawl with the
parking gear that is integrated with the counter
driven gear locks the movement of the vehicle.
The direction of the parking lock pawl changes via
the two link mechanisms that are connected to the
outer lever through the shift cable. The longitudi-
nal movement of the parking rod causes a vertical
movement of the parking lock pawl that meshes
with the parking gear.

CHASSIS ± P111 HYBRID TRANSAXLE
182CH25
182CH26Shift Position
Sensor
Shift
Position
SensorMain
Sub
HV
ECU
Serial Data
LinkEngine
ECUCombination
Meter
Voltage
: Defined
: Region
Voltage
Signal
Stroke B
D
N
R
P
PRNDBSwitch
Signal
Service Tip
Because it is extremely difficult to precisely assemble the shift position sensors, do not disassemble the
shift lever. 88

SHIFT CONTROL
1. Shift Lever
A column-type shift lever with 5 positions has been adopted. The shift lever is operated by moving it in the
vehicle's longitudinal direction to ensure excellent ease of use. The shift lever is integrated with the shift posi-
tion sensor.
2. Shift Control
For shift control, a shift-by-wire system has been
adopted. This system uses electrical signals that
are output by the shift position sensor to determine
the shift position. For operating the parking lock
pawl in the transaxle, however, a shift cable is used
for attaining P position.
The shift position sensor outputs two systems of
signals: the main switch signals, and the sub
switch signals containing high and low voltages.
When these signals match, the HV ECU deter-
mines the respective shift position.