Hybrid vehicle drivetrain
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Hybrid vehicle
Hybrid vehicle drivetrain
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Hybrid vehicle drivetrains transmit power for hybrid vehicles. A hybrid vehicle has multiple forms of motive power.
Hybrids come in many configurations. For example, a hybrid may receive its energy by burning petroleum, but switch between an electric motor and a combustion engine.
Electrical vehicles have a long history combining internal combustion and electrical transmission –as in a diesel-electric powertrain–, although they have mostly been used for rail locomotives. A diesel-electric powertrain fails the definition of hybrid because the electrical drive transmission directly replaces the mechanical transmission rather than being a supplementary source of motive power. One of the earliest forms of hybrid land vehicle is the 'trackless' trolleybus of the 1930s, which normally used traction current delivered by wire. The trolleybus was commonly fitted with an internal combustion engine (ICE) either to directly power the bus or to independently generate electricity. This enabled the vehicle to manoeuvre around obstacles and broken overhead transmission wires.
The powertrain includes all of the components used to transform stored potential energy. Powertrains may either use chemical, solar, nuclear or kinetic and make them useful for propulsion. The oldest example is the galley that used sails and oars. A common modern example is the electric bicycle. Hybrid electric vehicles combine a battery supplemented by an ICE that can recharge the batteries or power the vehicle.
Among the different types of hybrid vehicles, only the electric/ICE type was commercially available as of 2016. One variety operated in parallel to simultaneously provide power from both motors. Another operated in series with one source exclusively providing the power and the second providing electricity. Either source may provide the primary motive force, with the other augmenting the primary.
Other combinations offer efficiency gains from superior energy management and regeneration that are offset by expense, complexity and the battery limitations. Combustion-electric (CE) hybrids have battery packs with far larger capacity than a combustion-only vehicle. A combustion-electric hybrid has batteries that are light that offer higher energy density that are far more costly. ICEs require only a battery large enough to operate the electrical system and ignite the engine.
- 1 Types by design
- 2 Types by degree of hybridization
- 3 Types by power source
- 4 Hybrid vehicle operation modes
- 5 Aftermarket options
- 6 See also
- 7 References
- 8 External links
Types by design
Parallel hybrid systems have both an internal combustion engine and an electric motor that can both individually drive the car or both coupled up jointly giving drive. This is the most common hybrid system as of 2016.
If they are joined at an axis (in parallel), the speeds at this axis must be identical and the supplied torques add together. (Most electric bicycles are of this type.) When only one of the two sources is in use, the other must either also rotate (idle), be connected by a one-way clutch or freewheel.
With cars the two sources may be applied to the same shaft (for example with the electric motor connected between the engine and transmission), turning at equal speeds and the torques adding up with the electric motor adding or subtracting torque to the system as necessary. (The Honda Insight uses this system.)
Parallel hybrids can be further categorized by the balance between the different motors are at providing motive power: the ICE may be dominant (engaging the electric motor only in specific circumstances) or vice versa; while in others can run on the electric system alone but because current parallel hybrids are unable to provide electric-only or internal combustion-only modes they are often categorized as mild hybrids (see below).
Parallel hybrids rely more on regenerative braking and the ICE can also act as a generator for supplemental recharging. This makes them more efficient in urban'stop-and-go' conditions. They use a smaller battery pack than other hybrids. Honda's Insight, Civic, and Accord hybrids are examples of production parallel hybrids. General Motors Parallel Hybrid Truck (PHT) and BAS Hybrids such as the Saturn VUE and Aura Greenline and Chevrolet Malibu hybrids also employ a parallel hybrid architecture.
Through The Road (TTR) Hybrid
An alternative parallel hybrid is the 'through the road' type. In this system a conventional drivetrain powers one axle, with an electric motor or motors driving another. This arrangement was used by the earliest 'off track' trolleybuses. It in effect provides a complete backup power train. In modern motors batteries can be recharged through regenerative braking or by loading the electrically driven wheels during cruise. This allows a simpler approach to power-management. This layout also has the advantage of providing four-wheel-drive in some conditions. (An example of this principle is a bicycle fitted with a front hub motor, which assists the cyclist's pedal power at the rear wheel.) Vehicles of this type include the Audi 100 Duo II, Subaru VIZIV and Peugeot 307 Hybrid HDi concept cars, the PSA Group vehicles Peugeot 3008, Peugeot 508, 508 RXH, Citroen DS5 all using the HYbrid4 system, the Volvo V60 plug-in hybrid, the BMW 2-series Active Tourer, BMW i8, and the second generation Honda NSX.
Series hybrids are also referred to as extended-range electric vehicles (EREV) or range-extended electric vehicles (REEV). (Series hybrids with particular characteristics are classified as range-extended battery-electric vehicle (BEVx) by the California Air Resources Board.)
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