Electric and Hybrid Electric Vehicles Technology Chapter Seven
Electric and Hybrid Electric Vehicles Technology Chapter Seven
The Concept of vehicle Hybridization • The major challenge in the EV industry is the energy storage and recharging. • These vehicles can travel about 300 km, but they need an extended time to recharge the batteries (nearly 5~10 hours). • The deficiencies of thermal engine especially at the low speed range, characterized by low-performance and output, high fuel consumption and high emissions.
These reasons necessitate the production of a new transient generation of vehicles. Vehicles characterized by: • Longer range with the same amount of fuel (perhaps doubled), • Ultra-low ~ zero emissions and • Higher performance. Therefore, two powertrain systems are mounted on the vehicle. These are a combination of an • Internal combustion engine and a • motor/generator group or probably a fuel cell.
The Regenerative Braking System The concept During engine braking and braking using the brake pedal, the regenerative braking system is actuated. • It operates the electric motor as a generator, converting the vehicle’s kinetic energy into electric energy rather than heat, which is used to charge the batteries. • It controls, by the ECB, and coordinates between the hydraulic and the regenerative brake and preferentially uses the regenerative brake, thereby recovering energy even at lower vehicle speeds.
More energy is recovered by: • improving the battery input performance. • Reducing the energy lost in the drivetrain by elimination of the transmission. The two stages of braking: • begins with a slight regenerative braking applied automatically by the system. It is confined by the time elapsed between leaving the accelerator pedal and pushing the brake pedal.
• The regenerative braking action continuous when the driver applies low to moderate braking force on the brake pedal. • However, when a higher braking pressure is applied, the hydraulic brake system will come to action to assist the regenerative brake. • The second stage, starts as the driver fully depresses the brake pedal. The vehicle speed decreases dramatically under the synergistic action of the two systems. • Finally the regenerative braking effort fades out at low vehicle speeds and the vehicle will come to rest solely by the hydraulic brake.
Power Split Device The power split device uses a planetary gear. • The rotational shaft of the planetary carrier inside the gear mechanism is directly linked to the engine, and transmits the motive power to the outer ring gear and the inner sun gear via pinion gears. • The rotational shaft of the ring gear is directly linked to the motor and transmits the drive force to the wheels, while • The rotational shaft of the sun gear is directly linked to the generator.
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