418 Auto Electricity and Electronics
A hybrid vehicle (HV), also termed a hybrid gas-electric
vehicle (HGEV), uses two power sources to provide energy
for propulsion: an internal combustion engine and an electric
drive system. The two power sources are combined into one
vehicle power train. The internal combustion engine and
electric drive system work in unison under computer control
to propel the vehicle and operate its electrical accessory
systems. Refer to Figure 22-1.
Most major auto companies manufacture and sell hybrid
cars, SUVs, and trucks. Besides the gas-electric hybrid, auto-
makers are experimenting with fuel cell hybrids, hydraulic
hybrids, and pneumatic hybrids. However, none of these
experimental drive systems are presently mass-produced and
used in passenger vehicles.
This chapter covers the design, construction, and opera-
tion of gas-electric hybrid passenger vehicles. It will help you
prepare to fully understand Chapter 33 on the diagnosis, test-
ing, and repair of hybrids.
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 genera-
tor. The large electric generator was then used to power elec-
tric 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 gener-
ator. 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 assem-
bly that acts as a high-power electric motor or a high-
power electrical generator.
Figure 22-1. An internal combustion engine and motor-generator
are used to propel a hybrid vehicle. Note how the motor-generator
bolts to the back of the cylinder block. Engine crankshaft torque
and motor-generator torque can both be applied to the transaxle.
(Honda Motor Co.)
Motor-Generator
Internal
Combustion
Engine
Figure 22-2. These are the major parts of a typical hybrid drive train.
The electric drive train primarily operates at low vehicle speeds.
The internal combustion engine operates at higher engine speeds
or when the battery pack becomes discharged.
Internal
Combustion
Engine
Engine/Body
ECU
Hybrid Drive
ECU Fuel
Tank
Battery
Pack
Power
Cables
Power
Control
Module
Three-Phase
Power Cables
Motor-
Generator