Download Manual Drivetrains and Axles Fourth Edition

Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
OBJECTIVES:
After studying Chapter 2, the reader should be able to:
• Describe the different types of hybrid electric vehicles.
• Explain how a hybrid vehicle is able to achieve an improvement in fuel
•
•
•
economy compared to a conventional vehicle design.
Discuss the advantages and disadvantages of the various hybrid
designs.
Describe HEV components, including motors, energy sources, and
motor controllers.
Discuss the operation of a typical hybrid electric vehicle.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
KEY TERMS:
assist hybrid • BAS • BEV • EV
full-hybrid • HEV • HOV lane • hybrid • ICE • idle stop mode
medium-hybrid • micro-hybrid-drive • mild-hybrid • motoring
mode
parallel-hybrid • power assist mode
series-hybrid • series-parallel-hybrid • strong hybrid
ZEV
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
HYBRID VEHICLE
A hybrid vehicle, abbreviated HEV, is one that uses uses both an
internal combustion engine (ICE) and an electric motor to
propel the vehicle.
Most hybrids use a high-voltage battery pack and a combination
electric motor and generator to help or assist a gasoline engine.
The ICE used in a hybrid vehicle can be either gasoline or diesel,
although only gasoline-powered engines are currently used in
hybrid vehicles.
An electric motor is used to help propel the vehicle, and in some
designs, capable of propelling the vehicle alone without having to
start the internal combustion engine.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Background
In the early years of vehicle development, various propulsion
systems were used, including steam-, gasoline-, and electric-motorpowered.
Early electric vehicles (EVs), also called battery electric vehicles
(BEV) used lead-acid batteries, an electric traction motor, and a
mechanical controller.
A traction motor is an electric motor used to rotate drive wheels and
propel the vehicle, which moves as a result of traction between the
wheel and the road surface.
The controller allowed different voltages to be applied to the electric
motor, depending on the needs of the driver.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Assume that an early electric vehicle used six 6-volt batteries. If the
batteries are connected in series, the negative terminal of one battery
is connected to the positive terminal of the second battery.
Two 6-volt batteries in series result in 12 volts, but the same current
as one of the batteries. Two 6-volt 500-amp/hour batteries in series,
then, would output 12 volts and 500-amp/hours.
Batteries connected in parallel increase the current, but the voltage
remains the same. Two 6-volt 500-amp/hour batteries in parallel,
would be six volts and 1,000 amp/hours.
Old electric vehicle mechanical controllers were able to switch all
six batteries in combinations of series and parallel configurations
to achieve lower voltage for slow speeds and higher voltages for
higher speeds.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Electric vehicles did not have a long range and needed to have the
batteries charged regularly.
Electric vehicles were almost more popular than steam power in
1900, when steam had 40% and electric had 38% of the sales.
Gasoline-powered cars represented only 22% of the vehicles sold.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
In the late 1990s, several manufacturers produced electric vehicles,
using electronic controllers to meet the demands for zero emission
vehicles specified California law.
Electric vehicles were produced by Ford, Toyota, Nissan, and
General Motors.
Legislation was passed in California that included the zero
emissions vehicle (ZEV) mandate.
As a direct result of the California zero emissions vehicle (ZEV)
mandate originally calling for 10% ZEV, GM developed the Electric
Vehicle 1, known as EV1, leased to customers in California and
Arizona.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Figures 2–1 and 2-2Views of the components of the General Motors electric vehicle (EV-1). Many
of the features of this vehicle, such as regenerative braking and DC-to-DC converters currently
used on hybrid vehicles, were first put into production on this vehicle.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
DRIVING AND OWNING A HYBRID VEHICLE
Driving a hybrid electric vehicle is the same as driving any other
conventional vehicle. In fact, many drivers and passengers are
often not aware they are driving or riding in a hybrid electric
vehicle.
Some unique characteristics that the driver may or may not notice:
 After the internal combustion engine achieves normal operating
temperature and other conditions are met, the engine will stop
when the vehicle slows down and stops. This may concern some
drivers, who, thinking the engine has stalled, try to restart it.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
 The brake pedal may feel different, especially at slow speeds,
when slowing to a stop. At low speeds the brake system switches
from regenerative braking to applying brake force to the
mechanical brakes. A slight surge or pulsation may be felt.
 The power steering works even when the engine stops because
all hybrid electric vehicles use an electric power steering system.
 Some hybrid electric vehicles are able to propel the vehicle
using the electric motor alone, resulting in quiet, almost eerie
operation.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
 If a hybrid electric vehicle is being driven aggressively and at a
high rate of acceleration, there is often a feeling that the vehicle
is not going to slow down when the accelerator pedal is first
released. This is caused by two factors:
• The inertia of the rotor of the electric motor attached to the
crankshaft of the ICE results in the engine continuing to
rotate after the throttle has been closed.
• The slight delay that occurs when the system switches the
electric motor from powering the vehicle to generating
(regenerative braking).
While this delay would rarely be experienced, and is not
dangerous, for a fraction of a second it gives a feeling the
accelerator pedal did not react to a closed throttle.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
 Fuel economy will be higher compared to a similar-type vehicle.
In city-type driving conditions, engine stop and regenerative
braking really add to the efficiency of a hybrid electric vehicle.
Range of the hybrid version may be about the same as the
conventional version of the same vehicle because the hybrid
version usually has a smaller fuel tank capacity.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
 The hybrid version will cost and weigh more than the
conventional version.
The increased cost is due to batteries, electric motor(s), and
controllers used plus additional components needed to allow
operation of heating and air conditioning systems during idle
stop periods.
While the cost is offset in part by returning improved fuel, it
may take many years of operation before the extra cost is
offset by cost savings from the improved fuel economy.
Many owners purchase a hybrid electric vehicle for other
reasons, including a feeling that they are helping the
environment and love of the high technology involved
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
CLASSIFICATIONS OF HYBRID-ELECTRIC
VEHICLES
Types of hybrid-electric vehicles include series, parallel, and
series-parallel designs.
In a series-hybrid design, the
engine turns a generator, which
can charge batteries or power
an electric motor that drives the
transmission.
The internal combustion engine
never powers the vehicle
directly.
Figure 2–3
A drawing of the power flow in a typical series-hybrid vehicle.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
In a series-hybrid design, sole propulsion is by a battery-powered
electric motor. Energy for the batteries comes from another onboard energy source, such as an internal combustion engine.
Figure 2–4 This diagram shows the components included in a typical series-hybrid design. The
solid-line arrow indicates the transmission of torque to the drive wheels. The dotted-line
arrows indicate the transmission of electrical current.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
The engine is only operated to keep the batteries charged, thus the
vehicle could be moving with or without the internal combustion
engine running.
Series-hybrid vehicles also use regeneration braking to help keep
the batteries charged. An advantage of a series-hybrid design is
that no transmission, clutch, or torque converter is needed.
A disadvantage of a series-hybrid design is the added weight of the
internal combustion engine—actually a heavy, on-board battery
charger—to what is basically an electric vehicle.
The electric motor and battery capacity have to be large enough to
power the vehicle under all operating conditions.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
In a parallel-hybrid design, multiple propulsion sources can be
combined, or one energy source alone can drive the vehicle. The
battery and engine are both connected to the transmission.
The vehicle can be powered
by internal combustion alone,
by electric motor alone, (full
hybrids), or a combination.
In most cases, the electric
motor is used to assist the
internal combustion engine.
Figure 2–5 The power flow in a typical parallel-hybrid
vehicle.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Among the advantages of using a parallel-hybrid design is that by
using an electric motor or motors to assist the internal combustion
engine, the engine itself can be smaller than normally needed.
One disadvantage of a parallel-hybrid design is that complex
software is needed to seamlessly blend electric and ICE power.
Another concern about the parallel-hybrid design is that it had to
be engineered to provide proper heating and air-conditioning
system operation when the ICE stops at idle.
The Toyota and Ford hybrids are classified as series-parallelhybrids because they operate using electric motor power alone or
with the assist of the ICE.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Figure 2–6 Diagram showing the components involved in a typical parallel-hybrid vehicle. The
solid-line arrows indicate the transmission of torque to the drive wheels, and the dotted-line arrows
indicate the flow of electrical current.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Figure 2–7 A series-parallel-hybrid design allows the vehicle to operate in electric motor mode
only or in combination with the internal combustion engine.
The internal combustion engine may be operating even though the vehicle is
stopped if the electronic controller has detected that the batteries need to be
charged.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
BELT ALTERNATOR STARTER SYSTEMS
The belt system, called the belt alternator starter (BAS), is the
least expensive system that can still claim the vehicle is a hybrid.
For many buyers, cost is a major concern and the BAS system
allows certain hybrid features without an entire redesign of the
engine and power train. Consumers can upgrade to BAS hybrids
at a reasonable cost and will get a 2% to 5% increase in fuel
economy, mostly affecting city mileage.
BAS replaces the belt-driven alternator with an electric motor that
serves as a generator and motor. When the engine is running the
motor, acting as a generator will charge a separate 36-volt battery
(42-volt charging voltage).
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
When the engine needs to be started again after being in idle stop,
the BAS motor cranks the engine by taking power from the 36volt battery pack and applies its torque via the accessory belt
Figure 2–8
This chart shows what is occurring during various driving conditions in a BAS-type hybrid.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
The motor-generator is larger than a standard starter motor so more
torque can be generated in cranking mode, also referred to as the
motoring mode.
The fast rotation of the BAS allows for quicker starts of the engine,
and makes the start/stop operation possible. Having the engine shut
off when the vehicle is at a stop saves fuel.
On extremely small vehicles, the belt alternator starter might nudge
a vehicle into the mild hybrid category.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
The BAS system is used in the Saturn VUE hybrid SUV.
Figure 2–9
The components of a typical belt alternator-starter (BAS) system.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Micro-Hybrid Drive System A major fuel-saving feature of
hybrid electric vehicles is idle stop mode. The internal combustion
engine is stopped, instead of idling, while in traffic.
A system developed by Valeo, often
called a micro-hybrid-drive system,
uses a reversible starter/alternator.
It is used as a conventional alternator
when the engine is running, and as a
starter by transmitting power through
the drive belt system to start the
engine.
Figure 2–11 A reversible starter/alternator is used to provide idle stop function to conventional
vehicles. This very limited and low cost system is called a micro-hybrid-drive.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Common Features of Most Hybrids that improve fuel economy:
Idle stop Turns off engine when the vehicle is stopped. When
the brake is released, the engine immediately starts. This ensures
the vehicle is not using fuel, nor creating CO2 emissions, when
the engine is not required to propel the vehicle.
Regenerative braking When decelerating, the braking system
captures energy and stores it in the battery or other device for later
use, helping to keep batteries charged.
Power assist The electric motor provides extra power using
current drawn from the battery to assist ICE during acceleration.
This power-assist mode enables the vehicle to use a smaller,
more fuel-efficient engine without giving up performance.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Engine-off drive-electric vehicle mode The electric motor
propels the vehicle at lower speeds. The ICE is not being used
during acceleration, no fuel is being used and no emissions are
being released. When the hybrid is in this mode, it is essentially an
electric vehicle.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
LEVELS OF HYBRID VEHICLES
The term hybrid refers to a type of vehicle. However, there are
different levels of “hybridization” on the market. Different vehicle
manufacturers use various hybrid technologies.
Mild Hybrid Incorporates idle stop and regenerative braking,
but not capable of using the electric motor to propel the vehicle
without help from the internal combustion engine.
A mild hybrid costs less, but saves less fuel (8% to 15%) compared
to a full hybrid vehicle and usually uses a 42-volt electrical motor
and battery package (36-volt batteries, 42-volt charging).
Examples include the GM Silverado pickup truck and Saturn VUE.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Medium Hybrid Using voltages of about 144 to 158 volts, a
medium hybrid provides engine stop/start, regenerative braking,
and power assist.
Like a mild hybrid, it typically is not capable of propelling the
vehicle from a stop using battery power alone.
Fuel economy savings are about 20% to 25%.
Examples of a medium hybrid vehicle include the Honda Insight,
Civic, and Accord.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Full Hybrid Also called a strong hybrid, a full hybrid uses idle
stop, regenerative braking, and is able to propel the vehicle using
the electric motor(s) alone.
Fuel economy savings are about 30% to 50%.
Examples include the Ford Escape SUV, Toyota Highlander,
Lexus RX400h, Lexus GS450h, Toyota Prius, and Toyota Camry.
Each vehicle manufacturer has made its decision on which hybrid
type to implement based on assessments of the market niche for a
particular model.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
EFFICIENCIES OF ELECTRIC MOTORS AND
INTERNAL COMBUSTION ENGINES
Internal Combustion Engines
 An electric motor can have efficiency (including controller) of
over 90%, while a gasoline engine has efficiency of 35% or less.
 An ICE does not have the overload capability of an electric
motor, which is why the rated power of an internal combustion
engine is usually much higher than required for highway
cruising.
 Operating smoothly at idle speed produces a much lower
efficiency than operating at a higher speed.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
 Maximum torque of an internal combustion engine is reached
at intermediate speed and the torque declines as speed increases
further.
 There is a maximum fuel efficiency point in the speed range
for the ICE, and this speed is optimized by many hybrid vehicle
manufacturers by using a transmission that keeps the engine
speed within the most efficient range.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
Electric Motors Offer ideal characteristics for use in a vehicle
because of the following factors:
 Constant power over all speed ranges
 Constant torque at low speeds needed for acceleration and hill
climbing capability
 Constant torque below base speed
 Constant power above base speed
 Only single gear or fixed gear is needed in the electric motor
transmission
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
SUMMARY
1. Hybrids use two different power sources to propel the vehicle.
2. A mild hybrid with a lower voltage system (36–50 volts) is
capable of increasing fuel economy and reducing exhaust
emissions but is not capable of using the electric motor alone
to propel the vehicle.
3. A medium hybrid uses a higher voltage than a mild hybrid
(140 150 volts) and offers increased fuel economy over a mild
hybrid design but is not capable of operating using the electric
motor alone.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
4.
A full or strong hybrid uses a high-voltage system (250–650
volts) and is capable of operating using the electric motor(s)
alone and achieves the highest fuel economy improvement of
all types of hybrids.
5.
Early in vehicle history, electric vehicles were more popular
than either steam- or gasoline-powered vehicles.
6. Legislation passed in California in 1998, which mandated zero
emission vehicles (ZEVs), caused the vehicle manufacturers to
start producing electric vehicles. When the law was changed to
allow the substitution of other vehicles that produced lower
emissions, but not zero, it helped promote the introduction of
hybrid electric vehicles (HEVs).
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458
7.
A hybrid vehicle is defined as having two power sources to
propel the vehicle.
8. Electric motors are perfect for vehicle use because they
produce torque at lower speed, whereas internal combustion
engines need to have an increased speed before they produce
maximum power and torque.
Hybrid and Alternative Fuel Vehicles
By James D Halderman and Tony Martin
© 2009 Pearson Education, Inc.
Pearson Prentice Hall
Upper Saddle River, NJ 07458