September 17, 2004
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Torrance, Calif.
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Overview
Based on the same class-leading chassis and suspension design that underpins
the Accord V-6 sedan, the Accord hybrid makes use of an Electric Power Steering
(EPS) system - similar to that in an S2000 and Acura NSX - as opposed
to the hydraulic-powered variable assist rack-and-pinion setup in its gasoline-powered
Accord siblings. The EPS system allows the Accord Hybrid to provide power steering
even when the vehicle is in idle stop mode.
Already recognized as one of the more nimble entrants in the mid-sized class,
all Accords employ a 4-wheel double wishbone suspension. This entirely independent
suspension allows the Accord consistent linear tracking under all conditions,
while minimizing body roll during hard cornering. When combined with the EPS
system, the Accord Hybrid is able to enhance steering response and minimize
torque steer associated with the increased horsepower to provide a very balanced
and stable ride.
4-wheel disc brakes with 3-channel anti-lock braking system (ABS)
Electronic Brake Distribution
Advanced Traction Control System with integrated Creep Aid System
16" alloy wheels with 215/60 R16 tires
Front double wishbone suspension
The Accord's double-wishbone front suspension is designed to maintain
a stable ride under all driving conditions, including hard acceleration, braking
and cornering. With a large lower arm connected directly to the front subframe
and a smaller upper arm positioned high, above the wheel and tire, this suspension
is able to isolate wheel movement and minimize the effects of bumpy roads intruding
into the passenger cabin.
Rear Five-link Suspension
Mounted entirely to the Accord's rear subframe, its rear five-link double
wishbone suspension is meant to keep the vehicle flat during hard cornering
and minimize the amount of roll steer associated with most independent rear
suspensions. By providing precise camber and toe control, this double wishbone
suspension helps to keep a flat tire contact patch between the Accord and the
road. Each of the five tubular steel links is designed to keep the rear wheels
upright through their full range of movement in all conditions, including cornering
at higher speeds.
With a compact design, the Accord's rear suspension was also developed
to minimize the space it takes up behind the rear wheels, and thus maximize
the cargo area in the Accord Hybrid's trunk. With the Intelligent Power
Unit (IPU) of the IMA system mounted behind the rear seats, Accord Hybrid continues
to have over 10 cubic feet of cargo area (11.2), down only 2.8 cu.-ft from a
traditional Accord V-6 Sedan.
Electric Power Steering (EPS)
To allow for power steering operation during idle stop mode and further reduce
fuel consumption while enhancing steering accuracy, the Accord Hybrid employs
a modified version of the Electric Power Steering (EPS) system used in the S2000.
This electric steering rack eliminates the need for power from the gasoline
engine to regulate hydraulic pressure as in a traditional rack-and-pinion setup.
Instead, a high-output motor replaces the oil pump. In addition, the high-mount
design allows for longer tie rods, which reduces the amount of unwanted steering
feedback during bumpy drives.
4-wheel disc brakes
With large, 11.1" ventilated front discs in front and solid disc brakes
in the rear wheels, the Accord Hybrid continues to have one of the most effective
braking arrangements in the mid-sized sedan segment, delivering smooth, linear
and stable braking performance across a broad range of conditions and braking
loads. The braking system is further enhanced by a standard anti-lock braking
system and electronic brake distribution.
ABS
The standard Anti-lock Braking System (ABS) from the Accord V-6 carries on
in the Accord Hybrid. This arrangement incorporates wheel sensors at each wheel
and three control channels to modulate braking pressure. With this type of system,
the ABS control unit is able to monitor wheel speed at each wheel and adjust
braking pressure to each of the front drive wheels or both rear wheels jointly.
As such, wheel lockup is avoided in virtually all driving conditions, including
situations where one side of the vehicle has significantly less traction than
the other. This is critical in the Accord Hybrid's ability to maintain
steering control during hard braking in normal and adverse road conditions.
Electronic Brake Distribution
The ABS system is further enhanced by Electronic Brake Distribution (EBD) which
adjusts braking pressure front-to-rear, based on the weight distribution of
passengers and/or cargo. Weight distribution is determined via the relative
difference in rotational speed of the front and rear wheels. Greater braking
pressure, and subsequently stopping power, is directed to the rear wheels when
cargo loads in the rear are heavier. This contributes to a more controlled stop,
and in conjunction with the front double wishbone suspension minimizes "brake
dive" during hard braking.
Traction Control System
An advanced Traction Control System (TCS) has been added to the Accord Hybrid
to help harness the increased horsepower. Similar to previous Honda TCS systems,
the Accord Hybrid's system uses wheel sensors to monitor the rotational
speed of each wheel.
When wheel-slippage is detected at any wheel (higher rotational speed), the
TCS pulses the brakes until traction is regained and all four wheels are again
traveling at the same speed. The Accord Hybrid's TCS system is most effective
at low speeds when the vehicle is accelerating on a split-traction surface.
Specific to the Accord Hybrid's traction control system is the additional
Creep Aid System, which prevents the vehicle from rolling backwards after a
restart during idle-stop. Without creep aid, the brake actuators are released
fully when a driver releases the brake pedal. Thus, slow foot movement from
the brake to the accelerator could allow the vehicle to roll backwards if stopped
on a hill. In the Accord Hybrid, however, the TCS system recognizes the idle-stop
status and upon pedal release slowly reduces brake pressure from each of the
wheels. In doing so, each brake caliper maintains a small amount of braking
pressure until the driver accelerates the car.
The Civic Hybrid and Insight, hybrid-powered cars without traction control,
controlled this rolling situation with a separate creep aid clutch attached
to the CVT transmission. By incorporating the Creep Aid System into the Accord
Hybrid's TCS, Honda was able to save weight and production costs.
Tires
Standard wheel size for the Accord Hybrid continues to be 16 inches, but wider
215/60 R16 tires surround each. The wider tires allows the Accord Hybrid, which
weighs approximately 120 pounds more than an Accord EX V-6 and has 15 more horsepower,
to maintain a larger contact patch for handling, steering and traction performance
on par with the regular gasoline-only powered Accord V-6 Sedan.