03-08-2012, 03:01 PM
Hybrid Drive Systems
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Hybrid Vehicle History
In 1898, Ferdinand Porsche, the founder of Porsche
Motor Car Company, designed and built a car that used a
small internal combustion engine to spin an electrical generator.
The large electric generator was then used to power electric
motors at each drive wheel. No mechanical link, clutch,
transmission, or mechanical drive train was used. This hybrid
car had large wires between the engine and drive motors.
This same basic principle is used in locomotives. A
locomotive uses a diesel engine to spin an electrical generator.
The generator can then energize one or more electric
traction motors that turn the locomotive’s wheels.
In 1966, the Congress of the United States enacted a Bill
recommending the development of electric vehicles to reduce
air pollution and our dependence on foreign oil. By the 1990s,
automakers started perfecting hybrid drive systems to meet
these demands. These fi rst hybrids were heavy and sluggish
during acceleration due to the weight of their batteries.
Advances in electric motor and battery technology
have allowed automakers to build hybrid vehicles that
accelerate just as well as conventional gas-engine only
vehicles while reducing the amount of fuel burned in both
city and highway driving. Hybrid vehicles now have the
highest combined average fuel economy numbers of any
type of mass-produced passenger vehicle.
Major Hybrid Drive Assemblies
Figure 22-2 shows the six major assemblies of a hybrid
vehicle drive system. The six major assemblies are:
Hybrid battery pack—large number of voltaic cells
wired in series to produce a high-voltage, high-power
storage battery.
Hybrid motor-generator—armature and stator assembly
that acts as a high-power electric motor or a highpower
electrical generator.
Single Motor-Generator Hybrid
A single motor-generator hybrid uses only one large
motor-generator to assist the gas engine. This is a compact
design with the motor-generator assembly bolted to the rear of
the engine block in front of the transaxle or transmission. The
motor-generator armature is connected to an engine crankshaft
and to the transmission input shaft. The motor-generator is a
large-diameter, high-torque motor with minimum complexity.
As shown in Figure 22-14, the single motor-generator is
the least complex type of hybrid drive train. Note how the
motor-generator (shown in red) bolts between the cylinder
block of the engine and to the bellhousing of the transaxle.
Dual Motor-Generator Hybrid
A dual motor-generator hybrid uses two separate
motor-generators located at different locations in the drive
train. The two motor-generators are usually located inside
the transmission or transaxle. Look at Figure 22-15.
During regenerative braking, both motor-generators
act as generators to recharge the HV battery pack and help
drag the drive train to a stop. Under all-electric drive, both
motor-generators act as motors to help propel the vehicle.
In the all-electric mode, the larger rear motor-generator
is used to propel the vehicle, Figure 22-16A. The power control
module feeds battery pack power into the rear motorgenerator.
The motor-generator drives a planetary gearset.
The gearset transfers mechanical torque out of the transmission
and to the drive wheels through the drive train.
Triple Motor-Generator Hybrid
A triple motor-generator hybrid uses three motorgenerators
in one vehicle drive train, Figure 22-19. Two
motor-generators are located in the transmission or transaxle,
and one can be located in the rear drive axle assembly. A triple
motor-generator arrangement is often used in four-wheel drive
vehicles to help electrically drive all four wheels and tires.
Figure 22-20 shows a front hybrid transaxle and a rear
hybrid transaxle for a triple motor-generator hybrid drive
line. The rear transaxle allows the third motor-generator to
rotate the rear drive axles.
Hybrid Power Cables
Hybrid power cables transfer huge amounts of current
to the high-voltage components of the electric drive
system. The power cables are heavily insulated to prevent
these voltages from shorting to ground.
Two large HV battery pack power cables connect to the
power control module. Three large power cables connect the
power control module to the motor-generator. These three
cables are normally routed under the fl oor pan on the inside
of the rocker panel. The three high-voltage power cables have
orange insulation to warn technicians of their danger.