Prius offers an elegant, eco-friendly solution
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The Toyota Prius design team has responded to the challenge
of producing an advanced eco-friendly vehicle that embraces
futuristic technologies and fully meets contemporary motoring
expectations for a vehicle in this size class with a large scale
reduction in fuel usage.
As an ultra fuel efficient vehicle the a fundamental requirement
of the Prius design is an efficient aerodynamic form. The
success achieved in this regard can be measured by the low 0,26
drag co-efficient. This is achieved by the aero-efficient
tear-drop body shape of the Prius and the improvements in air
flow offered by aerodynamic aids placed in front of the wheels
and a full underfloor cover to clean up the air flow under the
car and reduce drag. A rear spoiler adds a finishing touch to
clean up the air at the rear of the car.
Aside from the drivetrain, the other significant contributor to
fuel usage is weight and here Toyota engineers have followed an
aggressive weight saving regimen to reduce mass in any area
possible without compromising the integrity or comfort of the
vehicle. To this end a number of major body panels and some cast
components are made from aluminium.
The advanced drivetrain with its Atkinson cycle engine, high
speed electric motor/generator, planetary gear final drive and
regenerative braking system provide the third element of the
fuel savings exhibited by the Prius. This Toyota Hybrid Synergy
Drive system has the unique ability to route energy to and from
the various components in virtually any combination to ensure
optimised performance at all times.
The interior of the Prius and its features list match the design
requirement of providing a vehicle that meets advanced fuel
saving and emissions requirements but matches contemporary
expectations. The first impression that the driver will have on
entering the Prius is one of relative simplicity.
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There is no floor mounted gear shift, no hand brake lever on the
floor and no apparent instrumentation other than a dark void
immediately under the windscreen. An electronic key is provided
to bring the vehicle to life and disengage the electronic
steering lock.
Press the brake pedal and then the "Power" button, and
the Prius immediately comes to life as the virtual image display
instruments light up. A brief systems check is followed by the
illumination of a "READY" light. At this time the
dashboard mounted shift lever is used to select the desired
direction of travel and pressing the accelerator will set the
vehicle in motion.
The electronic shift lever provides for the selection of the
desired range through a shift-by-wire system with a
spring-loaded momentary action that returns it to a central
position once the selection has been made. Shift options are:
Neutral; Drive; Reverse, and "B", an alternative
driving range that offers a more aggressive regenerative power
function. If an inappropriate selection is made the system will
reject the selection and sound a warning.
Not too different from a run-of-the-mill automatic you might
think, with one exception - there is no engine running at this
time. Even when the accelerator is depressed this action is met
with a mute response if in drive mode. In reverse a beeper will
sound to alert the driver that reverse is selected.
The Prius uses stored electrical energy for initial acceleration
up to 45 km/h at which point the hybrid drive system will
seamlessly add the petrol engine element to the drive. No sign
of engine cranking, not a hesitation or a stutter of any kind.
From this point on the Prius will perform like any other vehicle
in the compact sedan class as the vehicle's computer controls
distribute and collect energy in the most efficient manner
possible but without impeding performance.
If the EMV (Electro Multi Vision) display is set to the
corresponding page a fascinating graphic indication of the flow
of power between the various drive elements will be available.
This touch screen system with button pre-selects for main
function selection provides control for the audio system,
climate control, and vehicle information system.
An interrupt screen is also provided to alert the driver of any
system malfunction. If an abnormal condition is detected this
screen will override the selected screen with a flashing warning
to identify the area in which the abnormality has been detected.
Systems covered by this screen are: Electric Power Steering; HV
(Hybrid Vehicle) battery warning - warning of a voltage drop in
the hybrid battery; THS (Toyota Hybrid System) abnormality
alert; HV immobiliser system abnormality warning - when the
shift lever is in "P" range, and a Shift-by-wire
system warning.
This vehicle information element provides a mine of information
via its page options. The energy monitor screen is perhaps the
most fascinating with its continual display of the flow of
energy between the Hybrid Synergy Drive system components. The
current drive method (engine, motor, or both) is displayed, as
is the power generation status of the engine and the
regenerative braking system. The fuel consumption screen
indicates the average fuel consumption, the recovered energy
accumulated, and the current fuel consumption. The average fuel
consumption is calculated over a "last 5-minute" usage
history. The recovered energy indicator reflects the energy
recovered over a five-minute period.
The overall interior appointment level is in line with Toyota's
Camry GLi specification with some detail enhancements,
particularly with regard to the air conditioning system fitted
to the Prius. This system features a world first for mass
production passenger vehicles with an electric inverter
compressor system utilised. The system employs an electric motor
to exclusively power the compressor. This enables a stable
air-conditioned environment to be achieved without using engine
power. It is also independent of engine speed in its efficient
delivery of cooled air. The air conditioner is able to
continually control air temperature and humidity even when the
engine is stopped, as is often the case in an urban environment
where the Prius is at its best.
Toyota engineers have focused on producing a high efficiency,
low weight system that uses advanced controls to limit energy
usage. The Prius team also had to consider the unique heating
requirements of a hybrid vehicle where heated water from the
engine cooling system would not always be in circulation if the
system relied on the engine water pump. To counter this an
electric pump is fitted to ensure the continual supply of warmth
to the cabin even when the engine is stopped.
A full auto setting automatically adjusts the air outlet
temperature, blower speed, and vent direction in accordance with
the selected interior temperature. The interior temperature
sensor is able to detect humidity as well and assists in
controlling this aspect of the Prius interior to ensure that a
reasonable level of humidity is retained in to prevent
discomfort associated with extremely dry air. The air
conditioner can be operated by the touch screen controls of the
EMV display or via a set of steering wheel mounted satellite
controls.
The Prius standard features list includes: Audio system with
radio and 6-CD changer (activated by satellite controls on
steering wheel or touch screen on EMV display); nine-speaker
sound; power windows on all four doors with auto up and down on
the driver's window; electric power steering; cruise control;
height adjustment for the driver's seat; remote central locking
controlled by electronic smart key; anti- theft alarm system
with intrusion detection and electronic transponder type key
matching and courtesy light fade-in, fade-out; powered side
mirrors; plush velour upholstery; foot operated parking brake;
and 60/40 split folding rear seat configuration. Aluminium rims
(16 inch) with wheel covers are fitted. Tyres are special low
resistance type with the designation P195/55 R16.
Ample storage space is provided with three closed storage
facilities in the dashboard area, an overhead spectacle storage
area, and a centre console that features two main storage areas.
The front door side pockets include a recess designed to
accommodate a 500ml water or soft drink bottle. Two cup holders
are provided for the front and rear within the central console.
An auxiliary 12 volt power point is also provided in the central
console. A tonneau cover is provided to secure the luggage
compartment and an underfloor storage compartment in the boot
provides a secure stowage area.
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As a completely new platform within the Toyota vehicle range,
the Prius was targeted to provide the highest levels of passive
safety. To this end the body structure is based on an efficient
crash impact absorbing structure. Materials of different
thickness are employed in the front side members to assist in
absorbing and channelling impact energy away from the passenger
cell. Strategically placed reinforcing elements are also
designed to protect occupants by dispersing impact energy
through the body structure.
Cowl and door "belt-line" reinforcements add
further strength to the cabin in vulnerable areas and assist in
reducing cabin deformation in a crash. A tibia pad is provided
to minimise injury to the lower body area of the driver and
front seat passenger. An energy absorbing structure is fitted
behind the interior garnish at head and shoulder level on side
structural members. When impacted this element collapses and
acts as a cushion to limit injury. Air bag protection includes
frontal and side protection SRS airbags for front seat occupants
as well as full length curtain side airbags.
The Prius engineering team went further than protecting just the
occupants of the Prius from injury by incorporating a number of
design features that will assist in minimising injuries to
pedestrians. A larger than normal clearance between the bonnet
and the engine and drive components provides an effective energy
absorber to lessen head injuries in the event of a pedestrian
accident. The inner shape of the bonnet is also designed to
limit this type of injury. An impact absorber is fitted to the
front bumper to help minimise leg injuries in a pedestrian
accident. The placement of the windscreen wipers has also been
optimised to limit injuries to the head and face areas in the
event of a severe pedestrian accident.
This extensive list of safety features and their performance in
European NCAP tests has resulted in the Prius achieving NCAP
5-star status.
Toyota has specified its ECB2 (Electronically Controlled Brakes)
system for the Prius. This system features regenerative braking,
VSC (Vehicle Stability Control) and EBD (Electronic Brake force
Distribution).
The ECB2 system controls the four-wheel independent action of
the hydraulic brakes, VSC, brake assist and ABS with EBD in
accordance with the vehicle's operating conditions. Hydraulic
brakes and the regenerative brake, which uses the HV system
motor for its braking force, are applied in response to the
driver's brake inputs. The ECB2 system controls the blending of
the regenerative and hydraulic elements to use the regenerative
brake efficiently and optimise fuel economy.
A power backup unit is included as a supplemental power source
to ensure an uninterrupted supply of power to the braking system
in emergency situations. This system uses a capacitor to feed
power to the braking system in the event that the vehicle power
supply goes down. The capacitor draws its charge from the
vehicle power system and discharges when the ignition switch is
turned off.
Toyota's Prius brings the future to reality in an elegant
eco-friendly solution that provides an exceptional balance
between energy efficiency, performance, interior space,
features, and safety.
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