Hybrid Auto Technology

The exhaust gas emissions and fuel consumption of conventional automobiles are drastically reduced with hybrid auto technology.

Hybrid technology allows an automotive powertrain to use two distinct sources of power: a gasoline-powered internal combustion engine in combination with an electric motor. A computerized control system monitors dozens of inputs to select the best power balance to maximize performance and efficiency. Compared to conventional automobiles, this technology makes better use of energy and significantly reduces exhaust emissions. Hybrid automobiles rely on a special hybrid transaxle, an inverter assembly, a high-voltage, high-capacity battery and advanced electronic control components.

Hybrid Operation

Hybrid technology combines the power and performance advantages of the gasoline engine with the efficiency and environmental advantages of electric motors. Hybrid vehicles provide significant energy savings and reduced carbon emission.
When the automobile is starting or driving slowly (under 15 mph), the engine remains off and battery power propels the vehicle. Under steady driving conditions, energy from the engine continually recharges the battery while driving the wheels. During acceleration, the stored battery power supplements engine power to provide excellent performance.
When the vehicle is braking, the system recovers the energy that would otherwise be lost as heat in the brakes. This braking energy supplements the power in the battery generated by the engine.

Hybrid Engine

The gasoline engine in a hybrid vehicle is smaller and more efficient than a conventional engine, but the basic internal combustion operation is the same. Performance is not compromised because the technology compensates by boosting power through the electric motor as needed. Because the resource requirements are lower, other engine system components (fuel, ignition, cooling, emissions, etc.) are also smaller and more efficient than on conventional automobiles.
Another engine advance with hybrid technology is adjustable valve timing. Hybrid systems are able to hold open the intake valve well into the compression stroke. This forces cylinder volume back into the manifold, allowing the system to precisely control timing. This improves efficiency while still producing maximum power when needed.

Hybrid Transaxle

The transaxle assembly on hybrid automobiles is similar to conventional transaxles with a variable gear set, reduction unit and differential. But the hybrid technology also includes two electric motor/generators: one to drive the vehicle, and a second to charge the battery. Both are highly efficient A/C synchronous generators and electric motors. The generator that drives the wheels provides strong torque for dynamic performance; it is also driven by the energy from braking for reclamation. The other generator regulates engine power to charge the battery, and also serves as the starter.

Inverter/Converter Assembly

The inverter converts D/C voltage from the battery into A/C power for the transaxle. The assembly also includes a converter to boost power. The inverter assembly shares a cooling system with the two electric motor/generators.

High-Voltage Battery

Hybrid technology includes a high-voltage nickel-metal hydride (Ni-MH) battery capable of high power density and longevity. The technology manages charge and discharge rates to maintain a constant state of charge. Power cables to the electric motor/generators are high-voltage, high-amperage, shielded cables designed to reduce electromagnetic interference.

Hybrid Engine Control Components

Hybrid technology relies on all of the engine control components found in conventional automobiles, plus extra sensors and modules designed to optimize performance and efficiency. The Onboard Diagnostic (OBD) system includes several hybrid-specific diagnostic trouble codes, as well as the typical OBD-II codes.

References

• "Hybrid Vehicles;" James L. Benson; 2008
• "How Do Hybrid Cars Work?;" Richard Hantula; 2009
• "Modern Electric, Hybrid Electric and Fuel Cell Vehicles: Fundamentals, Theory, and Design;" Mehrdad Ehsani, Yimin Gao and Ali Emadi; 2009
• "Electric and Hybrid Cars;" Curtis D. Anderson and Judy Anderson; 2010

Resources

• Motor Trend: Hybrid Cars
• U.S. Department of Energy: Hybrid Vehicle Comparisons
• Hybrid Cars.com