Eighteen years ago, the world was a very different place indeed. In 1997, Toyota released the world’s first hybrid production vehicle in the form of the Prius. However, back then it merely represented a lone model by a lone manufacturer of a lone variation of hybrid technology. Things are very different in today’s automobile market. As the demand for more efficient and sustainable vehicles has grown over the past eighteen years, an industry-wide hybrid development spree has been sparked, bringing about a wealth of hybrid and electric powertrains and vehicles. Read on to learn a bit more about the various types of hybrid technology and the many innovative vehicles in which they are applied.
Series hybrid drive systems utilize the sole power of an electric motor to propel the vehicle. Energy for the system is sourced from the on-board battery pack, which can typically be charged from an outlet or fast-charging station. The series hybrid configuration comes into play only if the battery pack depletes while out on the road. These systems incorporate an ICE tuned to run as an electric generator only once the battery pack goes flat and not for providing direct propulsion. Thus, there is no mechanical connection between the engine and the wheels, as the battery pack and motor acts as a buffer between them. Series hybrid vehicles are less common in today’s automotive market. Two examples of this technology in action are in the Fisker Karma and BMW i3, which are also commonly termed extended range electric vehicles (EREV) or Plug-in Hybrid Electric Vehicles (PHEV).
Parallel hybrid drive systems involve the coupling of an internal combustion engine (ICE) and an electric motor in such a manner that they are able to power the vehicle either individually or while combined. In order to allow for this flexibility, a series of electrically-controlled clutches are typically included so that both the ICE and electric motor can operate independently of one another when desired. In some cases, both the ICE and motor are mounted along the same driveshaft, with the motor adding extra torque to the system only when necessary. Parallel hybrid systems are one of the more commonly manufactured variations of hybrid vehicle technology. On the road, the Chevrolet Malibu, Hyundai Sonata, and Infiniti Q70 hybrids are categorized as parallel hybrids, as are Honda’s Insight, Civic, and Accord hybrid models.
Power-split (a.k.a. Series-parallel) Hybrid
Power-split hybrid drive systems are a variation of the parallel hybrid drive systems described above. Most power-split systems contain an ICE plus two independent electric motors. Power from all three sources can be shared to propel the wheels via a power splitter, which usually takes the form of a planetary gear box. The gear ratios in the splitter can be changed from 0-100% for the ICE, 0-100% for the motor(s), but also any intermediate combination that provides the car with the best trade-off in torque demanded from the driver and vehicle efficiency. Newer power-split systems incorporate a second motor on the output shaft (to the wheels) which combines with the primary motor and power-splitter to provide a continuously-variable transmission, or CVT. Power-split systems are available in the Chevrolet Volt (a plug-in model), Cadillac ELR, Toyota’s Prius lineup, Ford Escape and Fusion hybrids, and numerous Lexus h models.
Categories: Under the Hood