The main power relays will also open to disconnect
the battery during air bag deployment. If the vehicle is in a
collision serious enough to trigger an impact sensor, the
vehicle ECUs will also cut power to the HV battery pack
contactors so power cannot enter the power control module
and other components in the high-voltage system.
Impact Sensors
Impact sensors, or inertia switches, open during a
severe impact to open the high-voltage hybrid circuits,
disable the electric fuel pumps for the gas engine, and
deploy the air bags. If the air bags have deployed, you
must follow manufacturer instructions to replace the air
bags and re-energize the electric drive system.
High-Voltage Fuse
A high-voltage fuse will open and disconnect the
battery pack power if current flow becomes too high due
to a short. If no power is reaching the electric drive
system, find out why the fuse burned open, correct the
problem, and install a new high-voltage fuse.
Motor-Generator Sensor
A motor-generator sensor is used by the hybrid drive
system to detect armature speed and position, Figure 38-18.
A rotor on the motor-generator’s armature spins inside
three sensing coils. The motor-generator sensor produces
ac signals, which are sent to the power control module.
Based on these signals, the power control module
changes the amount of current and the phase shift of the
3-phase ac for efficient motor-generator operation.
Hybrid Drive Cooling
The motor-generators, battery pack, and power con-
trol module carry tremendous amounts of electrical
energy and can become hot from the high current flowing
through them. There are three methods used to remove
heat from these components.
Hybrid water cooling circulates engine coolant
through the transaxle, the motor-generators, and power
control module, as shown in Figure 38-19. Coolant is
Chapter 38 Hybrid Drive System Operation and Repair 707
Figure 38-17. A power splitter can be used to change power flow
and rotating speeds inside a hybrid transaxle or transmission.
Gas engine
Motor-generator 1
Motor-generator 2
Sun gear
(generator)
Planetary
carrier
(engine)
Pinion
gear
Ring gear
(motor/output
axle)
Reduction
gear unit
connected
to the final
drive
Figure 38-18. The motor-generator speed sensor uses a small
rotor keyed to the armature shaft to induce current in three
pickup coils. As the armature spins, the sensor sends out an
armature speed signal. This signal allows the ECUs and the
power control module to monitor motor-generator speed.
Speed sensor
(resolver)
Excitation
Coil A
Detection
Coil S
Detection
Coil C