Honda Automobiles / Accord
2014 Honda Accord Hybrid: Chassis
With features like electric power-assisted rack-and-pinion steering (EPS), Amplitude Reactive Dampers and the world's first electric servo automobile brake system, the Accord Hybrid's chassis dynamics fully match the sophisticated operation of its Earth Dreams Technology™ powertrain. The benefits extend to every driving situation, including a smooth ride experience, minimal road noise, vibration and harshness (NVH), accurate steering response with a light steering feel, and minimal body roll during cornering. It all results in a fun-to-drive, best-in-class feel among midsize hybrid sedans.
(For more detail on the Accord Hybrid's common chassis features, please see the 2013 Accord Press Kit.)
Accord Hybrid Chassis Key Features:
- MacPherson strut front suspension
- Independent multi-link rear suspension
- Amplitude Reactive Dampers
- Electric power-assisted rack-and-pinion steering (EPS)
- 17-inch aluminum alloy wheels
- P225/50R17 all-season tires
- Electric servo brake system
- 4-wheel disc brakes with ABS
- Electronic Brake Distribution (EBD) and Brake Assist
- Vehicle Stability Assist™ (VSA®) with Traction Control
- Tire Pressure Monitoring System (TPMS)
- Hill start assist
- Active Noise Control (ANC)
Electric Power-Assisted Rack-and-Pinion Steering (EPS)
Electric power-assisted rack-and-pinion steering (EPS) allows the Accord Hybrid to operate in electric-drive mode with the same responsiveness, feel and precision as in gasoline-engine drive mode. The system uses a rack-and-pinion steering assembly with an electrically assisted steering rack. This energy-efficient system reduces steering effort while also contributing to the Accord Hybrid's increased fuel efficiency. Other EPS benefits include a more sophisticated, linear, solid and accurate steering feel, more nimble handling and improved highway stability.
Amplitude Reactive Dampers
Using two separate damping systems, Amplitude Reactive Dampers provide superior ride comfort and handling in all driving conditions. One damping system is tuned to provide maximum efficiency on smoother roads with small inputs, and the other is tuned to handle large inputs such as rough roads, potholes, and sudden steering and braking action. The result is that the Accord Hybrid remains composed and comfortable in a wide range of driving conditions.
The Amplitude Reactive Dampers are a purely mechanical system that does not require electronic controls. Their core technology includes two separate damping pistons - a main piston and a secondary piston. To improve overall ride comfort, when smaller inputs occur during normal driving conditions, such as minor road irregularities, only the main piston works to provide the ideal damping characteristics. To improve ride and handling during more severe conditions, a second piston also operates to provide additional damping force. In short, one damping system is for low-speed, low-amplitude suspension response and one is for high-speed, high-amplitude response.
The Accord Hybrid features wider diameter anti-roll bars than on the Accord Sedan, helping to trim body roll to a preferred level during all types of cornering and handling maneuvers. The Accord Hybrid has 19-mm front and 16-mm rear stabilizer bars.
Electric Servo Brake System
The Accord Hybrid's electric servo brake system maximizes regenerative braking capability for improved fuel efficiency. The braking system is fully hydraulic from the master cylinder all the way to the 4-wheel disc brakes, just like a traditional braking system. The key difference is that the braking function is electronically controlled rather than a purely mechanical activation, allowing regenerative braking from the electric drive motor to slow the vehicle, rather than the hydraulic friction brakes under most circumstances. Besides its payoff in efficiency, the system offers excellent feel and feedback for the driver through the brake pedal.
When the driver applies the brake pedal, a signal is sent to the vehicle's Electronic Control Unit (ECU), which determines the appropriate amount of braking force to assign to regenerative braking through the electric drive motor and to the hydraulic friction braking system. In many cases, friction braking is not needed until the vehicle speed drops below 5 mph, as the vehicle slows to a final stop. When the ECU determines that friction braking is needed, the dual hydraulic master cylinder pumps brake fluid through the system. Midway between the master cylinder and the calipers is a separate motorized electronic actuator. This actuator receives an electronic signal, generated in the master cylinder module that precisely defines how the driver has applied the brakes - soft or hard, slow or fast. The actuator then directly apportions hydraulic pressure to the brake calipers at each wheel.
While the gasoline Accord uses a 10-inch vacuum booster to assist the driver in applying needed brake pressure, the Accord Hybrid uses an electric servo brake actuator. The vented front brake rotors are 11.5 inches in diameter, while the rear discs are 11.1 inches - the same as the Accord Sedan. The front calipers have two pistons each and the rear calipers have one piston each.
The new electric servo brake system yields a 8-percent improvement in regenerative braking effect compared to Honda's Integrated Motor Assist (IMA) hybrid system, along with improved brake control - particularly when the brakes are first applied and also as the vehicle comes to a stop.
Regenerative braking begins as soon as the driver releases the throttle pedal, with a strong regenerative braking effect beginning when the brake pedal is depressed and continuing until the point that the vehicle speed drops below 1 mph, when the friction brakes fully engage. The result is to maximize battery recharging during normal driving - while still maintaining top levels of braking precision and driving enjoyment.