Hybrid vehicle drivetrain 1

Hybrid vehicle drivetrainHybrid vehicles are vehicles with two or more power sources in the drivetrain. There are many different types ofhybrid vehicles, although only the gasoline-electric hybrid is currently commercially available.Hybrids are classified by the division of power between sources; both sources may operate in parallel tosimultaneously provide acceleration, or they may operate in series with one source exclusively providing theacceleration and the second being used to augment the first's power reserve. The sources can also be used in bothseries and parallel as needed, the vehicle being primarily driven by one source but the second capable of providingdirect additional acceleration if required.Current hybrids use both an internal combustion (IC) engine and a battery/electric drive system (usingultracapacitors) to improve fuel consumption, emission, and performance. Electrically assisted pedal bicycles are aform of hybrid drive. Other combinations of energy storage and conversion are possible, although not yet incommercial production.Combustion-electric hybrids have larger battery sets than what a normal combustion engine only vehicle wouldhave. Battery and supercapacitor technology is advancing.[1] A potential advantage is that when these battery setsrequire renewing in the future, the newer battery sets will be potentially superior having higher energy storage givinggreater range enhancing a vehicle.

Types by drive train structure

Parallel hybrid

Structure of a parallel hybrid electric vehicle. Thegray squares represent differential gears.

Parallel hybrid systems, which are most commonly produced atpresent, have both an internal combustion engine (ICE) and an electricmotor coupled. If they are joined at an axis in parallel, the speeds atthis axis must be identical and the supplied torques add together. Mostelectric bicycles are of this type. When only one of the two sources isbeing used, the other must either also rotate in an idling manner, beconnected by a one-way clutch, or freewheel. With cars, the twosources may be applied to the same shaft- for example with the electricmotor lying between the engine and transmission. The speeds are thusequal and the torques add up, with the electric motor adding or subtracting torque to the system as necessary. TheHonda Insight uses this system.

An alternative parallel hybrid layout is the 'through the road' type. Here a conventional drivetrain powers one axle,with an electric motor or motors driving the other. The batteries can be recharged through regenerative braking, orby loading the electrically driven wheels during cruise. Power is thus transferred from the engine to the batteriesthrough the road surface. This layout also has the advantage of providing four-wheel-drive in some conditions. Anexample of this principle is a bicycle fitted with a front hub motor, which assists the cyclist's pedal power at the rearwheel.Parallel hybrids can be further categorized depending upon how balanced the different portions are at providingmotive power. In some cases, the combustion engine is dominant (the electric motor turns on only when a boost isneeded) and vice versa. Others can run with just the electric system operating. But because current parallel hybridsare unable to provide all-electric (ICE=OFF) propulsion, they are often categorized as mild hybrids (see below).Because parallel hybrids can use a smaller battery pack as they rely more on regenerative braking and the internal combustion engine can also act as a generator for supplemental recharging, they are more efficient on highway driving compared to urban stop-and-go conditions or city driving.[2] Honda's Insight, Civic, and Accord hybrids are

Hybrid vehicle drivetrain 2

examples of production parallel hybrids.[2] General Motors Parallel Hybrid Truck (PHT) and BAS Hybrids such asthe Saturn VUE and Aura Greenline and Chevrolet Malibu hybrids are also considered as utilizing a parallelarchitecture.

Series hybrid

Structure of a series-hybrid vehicle. The greysquare represents a differential gear. An

alternative arrangement (not shown) is to haveelectric motors at two or four wheels.

Series hybrids have also been referred to as range-extended electricvehicles (REEV) where they are designed to be run mostly by thebattery, but have a petrol or diesel generator to recharge the batterywhen going on a long drive. However, range extension can beaccomplished with either series or parallel hybrid layouts.Alternatively, it can be viewed as an electric transmission, with thebattery storing reserve power until it is needed.

Series-hybrid vehicles are driven only by electric traction. Unlikepiston internal combustion engines, electric motors are efficient withexceptionally high power-to-weight ratios providing adequate torque over a wide speed range. Unlike combustionengines electric motors matched to the vehicle a multiple-speed transmission is not essential, and often only a simpleconstant-ratio gearbox is required. Transmissions add weight, bulk and sap power from the engine. Mechanicalautomatic shifting transmissions can be very complex. In a series-hybrid system, the combustion engine drives anelectric generator instead of directly driving the wheels. The generator provides power for the driving electricmotors. In short, a series-hybrid is simple, the vehicle is driven by electric motors with a generator set providing theelectric power.

This arrangement is common in diesel-electric locomotives and ships. Ferdinand Porsche used this setup in the early20th century in racing cars, effectively inventing the series-hybrid arrangement. Porsche named the system, SystemMixt. A wheel hub motor arrangement, with a motor in each of the two front wheels was used, setting speed records.This arrangement was sometimes referred to as an electric transmission, as the electric generator and driving motorreplaced a mechanical transmission. The vehicle could not move unless the internal combustion engine was running.The setup was difficult for production cars being unable to synchronize the electric driving motors with the generatorset power, resulting in higher fuel consumption. This is no longer an issue with modern computer enginemanagement systems optimizing when the generator runs to match the power needed. Electric motors have becomesubstantially smaller, lighter and efficient over the years. These advances have given the advantage to the electrictransmission in normal operating conditions, over a conventional internal combustion engine and mechanicalautomatic transmission. One of the advantages is the smoother progressive ride with no stepped gear ratio changes.The electric transmission is currently viable in replacing the mechanical transmission. However, the modernseries-hybrid vehicles takes the electric transmission to a higher plane adding greater value. There is a difference toan electric transmission. Modern series-hybrids contain:• Electric traction only - using only one or more electric motors to turn the wheels.• Combustion engine - that turns only a generator.• A generator - turned by the combustion engine to make up a generator set that also acts as an engine starter.• A battery bank - which acts as an energy buffer.• Regenerative braking - Driving motor becomes a generator and recovers potential and kinetic (inertial) energies

through its conversion to electrical energy, a process which in turn is able to slow the vehicle and thus preventingwasteful transfer of this energy as thermal losses within the friction brakes.

•• May be plugged into the electric mains system to recharge the battery bank.• May have supercapacitors to assist the battery bank and claw back most energy from braking - only fitted in

proven prototypes currently.

Hybrid vehicle drivetrain 3

The electric driving motor may run entirely fed by electricity from a large battery bank or via the generator turned bythe internal combustion engine, or both. The battery bank may be charged by mains electricity reducing runningcosts as the range running under the electric motors only is extended. The vehicle conceptually resembles aDiesel-electric locomotive with the addition of large battery bank that may power the vehicle without the internalcombustion engine running. The generator may simultaneously charge the battery bank and power the drivingelectric motor that moves the vehicle. The battery bank acts as an energy buffer. An advantage is that when thevehicle is stopped the combustion engine is switched off. When the vehicle moves it does so using the energy in thebatteries. This reduces kerbside emissions greatly in cities and towns. Vehicles at traffic lights, or in slow movingstop start traffic need not be polluting when stationary.In some arrangements when high levels of power are required, such as in vehicle acceleration, the electric drivingmotor draws electricity from both the batteries and the generator. With the Chevrolet Volt if the battery bank isdepleted the vehicle may run entirely with electricity provided only from the generator. Some prototype vehicledesigns such as the Volvo ReCharge and Ford F-Series pickup have electric motors in wheel hubs reducing the needfor a differential saving weight, space and power being sapped by the differential. Series-hybrids can be also fittedwith a supercapacitor or a flywheel to store regenerative braking energy, which can improve efficiency by clawingback energy that otherwise would be lost being dissipated via heat through the braking system.Because a series-hybrid omits a mechanical link between the combustion engine and the wheels, the engine can berun at a constant and efficient rate even as the vehicle changes speed. The vehicle speed and engine speed are notnecessarily in synchronization. The engine can thus maintain an efficiency closer to the theoretical limit of 37%,rather than the current average of 20%.[3] At low or mixed speeds this could result in ~50% increase in overallefficiency (19% vs 29%). The Lotus company has introduced an engine/generator set design that runs at two speeds,giving 15 kW of electrical power at 1,500 rpm and 35 kW at 3,500 rpm via the integrated electrical generator.[4]

As the requirements for the engine are not directly linked to vehicle speed, this gives greater scope for more efficientor alternative engine designs, such as a microturbine,[5] rotary Atkinson cycle engine or a linear combustionengine.[6]

General Motors in 1999 made the experimental EV1 series hybrid using a turbine generator set. The turbine weighed220 lb (99.8 kg), measured 20 inches (50.8 cm) in diameter by 22 inches (55.9 cm) long and ran between 100,000and 140,000 rpm. Fuel consumption was 60 mpg-US (3.9 L/100 km; 72 mpg-imp) to 100 mpg-US (2.4 L/100 km;120 mpg-imp) in hybrid mode. Depending on the driving conditions, a highway range of more than 390 miles(627.6 km) was achieved. The results were highly successful, and would have promised to be more successful if asmaller microturbine was used, yet the EV1 project was dropped.There are stages of operation: power from the combustion engine to the generator and then to the electric motor and,depending on the design, may also run through the generator and into the battery pack then to the electric motorfurther reducing efficiency (see illustration). Each transformation through each stage results in a loss of energy.However in normal vehicle operating conditions the energy buffer of the battery bank, which stores clawed backenergy from braking and the optimum running of the combustion engine may raise overall operating efficiency,despite each stage being an energy loss. The engine to a mechanical automatic shifting transmission efficiency isapproximately 70%-80%. A conventional mechanical clutch transmission, has an engine to transmission efficiencyof 98%. In a series-hybrid vehicle, during long-distance high speed highway driving, the combustion engine willneed to supply the majority of the energy, in which case a series-hybrid may be 20%-30% less efficient than aparallel hybrid.The use of a motor driving a wheel directly eliminates the conventional mechanical transmission elements: gearbox, transmission shafts and differential, and can sometimes eliminate flexible couplings. This offers great simplicity. If the motors are integrated into the wheels a disadvantage is that the unsprung mass increases and suspension responsiveness decreases which impacts ride performance and potentially safety. However the impact should be minimal if at all as electric motors in wheel hubs such as Hi-Pa Drive, may be very small and light having

Hybrid vehicle drivetrain 4

exceptionally high power-to-weight ratios. The braking mechanisms can be lighter as the wheel motors brake thevehicle. Light aluminum wheels may be used reducing the unsprung mass of the wheel assembly. Vehicle designsmay be optimized to lower the center of gravity having the heavy mechanics and battery banks at floor level. If themotors are attached to the vehicle body, flexible couplings are still required. Advantages of individual wheel motorsinclude simplified traction control and all wheel drive if required, allowing lower floors, which is useful for buses.Some 8x8 all-wheel drive military vehicles use individual wheel motors. Diesel-electric locomotives have used thisconcept (albeit with the individual motors driving axles connecting pairs of wheels) for 70 years.[7]

In a typical road vehicle the whole series-hybrid power-transmission setup may be smaller and lighter than theequivalent conventional mechanical power-transmission setup which liberates space. As the combustion generatorset only requires cables to the driving electric motors, there is greater flexibility in major component layout spreadacross the vehicle giving superior weight distribution and maximizing vehicle cabin space. This flexibility may leadto superior vehicle designs.In 1997 Toyota released the first series-hybrid bus sold in Japan.[8] Designline International of Ashburton, NewZealand produces city buses with a microturbine powered series-hybrid system. Supercapacitors combined with alithium ion battery bank have been used by AFS Trinity in a converted Saturn Vue SUV vehicle. Usingsupercapacitors they claim up to 150 mpg in a series-hybrid arrangement.[9]

Power-split or series-parallel hybrid

Structure of a combined hybrid electric vehicle

Power-split hybrid or series-parallel hybrid are parallel hybrids.They incorporate power-split devices allowing for power paths fromthe engine to the wheels that can be either mechanical or electrical. Themain principle behind this system is the decoupling of the powersupplied by the engine (or other primary source) from the powerdemanded by the driver.

A combustion engine's torque output is minimal at lower RPMs and, ina conventional vehicle, a larger engine is necessary for acceptable acceleration from standstill. The larger engine,however, has more power than needed for steady speed cruising. An electric motor, on the other hand, exhibitsmaximum torque at standstill and is well-suited to complement the engine's torque deficiency at low RPMs. In apower-split hybrid, a smaller, less flexible, and highly efficient engine can be used. The conventional Otto cycle(higher power density, more low-rpm torque, lower fuel efficiency) is often also modified to a Miller cycle orAtkinson cycle (lower power density, less low-rpm torque, higher fuel efficiency). The smaller engine, using a moreefficient cycle and often operating in the favorable region of the brake specific fuel consumption map, contributessignificantly to the higher overall efficiency of the vehicle.

Interesting variations of the simple design (pictured at right) found, for example, in the well-known Toyota Prius arethe:•• addition of a fixed gear second planetary gearset as used in the Lexus RX400h and Toyota Highlander Hybrid.

This allows for a motor with less torque but higher power (and higher maximum rotary speed), i.e. higher powerdensity

• addition of a Ravigneaux-[10]-type planetary gear (planetary gear with 4 shafts instead of 3) and two clutches asused in the Lexus GS450h. By switching the clutches, the gear ratio from MG2 (the "drive" motor) to the wheelshaft is switched, either for higher torque or higher speed (up to 250 km/h / 155 mph) while sustaining bettertransmission efficiency.

Hybrid vehicle drivetrain 5

Power-splitter series-hybrid Toyota Prius.

• addition of 2 additional planetary gear sets in combination with 4clutches to create a Two-Mode Hybrid configuration able to operatein all-electric, blended electric and ICE, or ICE alone with 4 fixedgears. Examples of Two-Mode Hybrids include the General MotorsTwo-Mode Hybrid full-size trucks and SUVs, the BMW X6ActiveHybrid[11] and the Mercedes ML 450 hybrid.[11]

The Toyota Hybrid System THS / Hybrid Synergy Drive has a singlepower-split device (incorporated as a single 3 shaft planetary gearset)and can be classified as an Input-Split, since the power of the engine issplit at the input to the transmission. This in turn makes this setup verysimple in mechanical terms, but does have some drawbacks of its own. For example, the maximum speed is mainlylimited by the speed of the smaller electric motor (usually functioning as a generator). Also, the efficiency of thetransmission is heavily dependent on the amount of power being transmitted over the electrical path, as multipleconversions, each with their own, less than perfect efficiency, lead to a low efficiency of that path (~0.7) comparedwith the purely mechanical path (~0.98). Especially in higher speed regimes (>120 km/h or 70 mph) the efficiency(of the transmission alone) therefore drops below that of a generic automatic transmission with hydrodynamiccoupler.

Hybrid Synergy Drive engine with electric motorand generator.

General Motors, BMW, and DaimlerChrysler have developed incollaboration a system named "Two-Mode Hybrid" as part of theGlobal Hybrid Cooperation. The technology was released in the fall of2007 on the Chevrolet Tahoe Hybrid. The system was also featured onthe GMC Graphite SUV concept vehicle at the 2005 North AmericanInternational Auto Show in Detroit.[12] BYD Auto's F3DM sedan is aseries-parallel plug-in hybrid automobile, which went on sale in Chinaon December 15, 2008.[13][14][15]

The Two-Mode Hybrid name is intended to emphasize the drive-train'sability to operate in all-electric (Mode 1, or Input-Split) as well ashybrid (Mode 2, or Compound-Split) modes. The design, however, allows for operation in more than two modes; twopower-split modes are available along with several fixed gear (essentially parallel hybrid) regimes. For this reason,the design can be referred to as a multi-regime design.[16] The Two-Mode Hybrid powertrain design can be classifiedas a compound-split design, since the addition of four clutches within the transmission allows for multipleconfigurations of engine power-splitting. In addition to the clutches, this transmission also has a second planetarygearset. The objective of the design is to vary the percentage of mechanically vs. electrically transmitted power tocope both with low-speed and high-speed operating conditions. This enables smaller motors to do the job of largermotors when compared to single-mode systems, because the derived electrical peak power is proportional to thewidth of the continuous variation range. The four fixed gears enable the Two-Mode Hybrid to function like aconventional parallel hybrid under high continuous power regions such as sustained high speed cruising or trailertowing. Full electric boost is available in fixed gear modes.[17]

Hybrid vehicle drivetrain 6

Types by degree of hybridization

Full Hybrids

Engine compartment of a 2006 Mercury MarinerHybrid.

A full hybrid, sometimes also called a strong hybrid, is a vehicle thatcan run on just the engine, just the batteries, or a combination of both.The Toyota Prius, Toyota Camry Hybrid, Ford Escape Hybrid/MercuryMariner Hybrid, Ford Fusion Hybrid/Mercury Milan Hybrid, KiaOptima Hybrid, as well as the General Motors 2-mode hybrid trucksand SUVs, are examples of this type of hybridization as they are ableto be propelled on battery power alone. A large, high-capacity batterypack is needed for battery-only operation. These vehicles have a splitpower path that allows more flexibility in the drivetrain byinter-converting mechanical and electrical power, at some cost incomplexity. To balance the forces from each portion, the vehicles use adifferential-style linkage between the engine and motor connected tothe head end of the transmission.

The Toyota brand name for this technology is Hybrid Synergy Drive, which is being used in the Prius, theHighlander Hybrid SUV, and the Camry Hybrid. A computer oversees operation of the entire system, determiningwhich half should be running, or if both should be in use. The operation of the Prius can be divided into six distinctregimes.

Electric vehicle mode: The engine is off, and the battery provides electrical energy to power the motor (or thereverse when regenerative braking is engaged). Used for idling as well when the battery State Of Charge(SOC) is high.Cruise mode: The vehicle is cruising (i.e. not accelerating), and the engine can meet the road load demand.The power from the engine is split between the mechanical path and the generator. The battery provideselectrical energy to power the motor, whose power is summed mechanically with the engine. If the batterystate-of-charge is low, part of the power from the generator is directed towards charging the battery.Overdrive mode: A portion of the rotational energy is siphoned off by the main electric motor, operating as agenerator, to produce electricity. This electrical energy is used to drive the sun gear in the direction oppositeits usual rotation. The end result has the ring gear rotating faster than the engine, albeit at lower torque.Battery charge mode: Also used for idling, except that in this case the battery state-of-charge is low andrequires charging, which is provided by the engine and generator.Power boost mode: Employed in situations where the engine cannot meet the road load demand. The batteryis then used to power the motor to provide a boost to the engine power.Negative split mode: The vehicle is cruising and the battery state-of-charge is high. The battery providespower to both the motor (to provide mechanical power) and to the generator. The generator converts this tomechanical energy that it directs towards the engine shaft, slowing it down (although not altering its torqueoutput). The purpose of this engine "lugging" is to increase the fuel economy of the vehicle.

The hybrid drivetrain of the Prius, in combination with aerodynamics and optimizations in the engine itself to reducedrag, results in 80%–100% gains in fuel economy compared to four-door conventional cars of similar weight andsize.

Hybrid vehicle drivetrain 7

Mild Hybrids

Engine compartment of a 2006 GMC SierraHybrid.

Mild hybrids are essentially conventional vehicles with some degreeof hybrid hardware, but with limited hybrid feature utilization.Typically they are a parallel system with start-stop only or possibly incombination with modest levels of engine assist or regenerativebraking features. Unlike full hybrids, Mild hybrids generally cannotprovide ICE-OFF all-electric (EV) propulsion.

Mild hybrids like the General Motors 2004-07 Parallel Hybrid Truck(PHT) and the Honda Eco-Assist hybrids are equipped with a 3-phaseelectric motor motor mounted within the bell-housing between theengine and transmission, allowing the engine to be turned off wheneverthe truck is coasting, braking, or stopped, yet restart quickly whenrequired. Accessories can continue to run on electrical power while the engine is off, and as in other hybrid designs,the motor is used for regenerative braking to recapture energy. The large electric motor is used to spin up the engineto operating rpm speeds before injecting any fuel.

The 2004-07 Chevrolet Silverado PHT, was a full-size pickup truck. Chevrolet was able to get a 10% improvementon the Silverado's fuel efficiency by shutting down and restarting the engine on demand and using regenerativebraking. However the electrical motor was not used to provide propulsion or assist, rather the electrical energy wasused to drive accessories like the A/C and power steering.The GM PHT used a 42 volt systems via a pack comprisedthree 12V vented lead acid batteries connected in series (36V total) to supply the power needed for the startup motor,as well as to compensate for the increasing number of electronic accessories on modern vehicles.General Motors followed the parallel hybrid truck with their BAS Hybrid system, another mild hybridimplementation officially released on the 2007 Saturn Vue Green Line. For its "start-stop" functionality, it operatessimilarly to the system in the Silverado, although via a belted connection to the motor/generator unit. However theGM BAS Hybridsystem has broader hybrid functionality as the electric motor can also provide modest assist underacceleration and during steady driving, and captures energy during regenerative (blended) braking. The BAS Hybridcan result in as much as a 27% improvement in combined fuel efficiency as noted by the EPA in testing of th 2009Saturn VUE.[18] The BAS Hybrid system can also be found on the 2008-09 Saturn Aura and the 2008-2010Chevrolet Malibu hybrids.Another way to provide for shutting off a car's engine when it is stopped, then immediately restarting it when it'stime to go, is by employing a static start engine. Such an engine requires no starter motor, but employs sensors todetermine the exact position of each piston, then precisely timing the injection and ignition of fuel to turn over theengine.[19]

Mild hybrids are sometimes called Power assist hybrids' as they use the engine for primary power, with atorque-boosting electric motor also connected to a largely conventional power train. The electric motor, mountedbetween the engine and transmission, is essentially a very large starter motor, which operates not only when theengine needs to be turned over, but also when the driver "steps on the gas" and requires extra power. The electricmotor may also be used to re-start the combustion engine, deriving the same benefits from shutting down the mainengine at idle, while the enhanced battery system is used to power accessories.GM is going to produce BuickLaCrosse and [Buick Regal] mild hybrids dubbed Eassist.Honda's hybrids including the Insight use this design, leveraging their reputation for design of small, efficientgasoline engines; their system is dubbed Integrated Motor Assist (IMA). Assist hybrids differ fundamentally fromfull hybrids in that propulsion cannot be accomplished on electric power alone. However, since the amount ofelectrical power needed is much smaller, the size of the system is reduced.

Hybrid vehicle drivetrain 8

A variation on this type of hybrid is the Saturn Vue Green Line BAS Hybrid system that uses a smaller electricmotor (mounted to the side of the engine), and battery pack than the Honda IMA, but functions similarly.Another variation on this type is Mazda's e-4WD system, offered on the Mazda Demio sold in Japan. Thisfront-wheel drive vehicle has an electric motor which can drive the rear wheels when extra traction is needed. Thesystem is entirely disengaged in all other driving conditions, so it does not directly enhance performance or economybut allows the use of a smaller and more economical engine relative to total performance.Ford has dubbed Honda's hybrids "mild" in their advertising for the Escape Hybrid, arguing that the Escape's fullhybrid design is more efficient.

Plug-in hybrid

The number of US survey respondents willing topay $4,000 more for a plug-in hybrid car

increased from 17% in 2005 to 26% in 2006.

Engine compartment of a BYD F3DM plug-inhybrid.

A plug-in hybrid electric vehicle (PHEV) has two definingcharacteristics: 1) it can be plugged in to an electrical outlet to becharged and (2) has some range that can be traveled on the energy itstored while plugged in. They are full hybrid, able to run inelectric-only mode, with larger batteries and the ability to rechargefrom the electric power grid. And can be parallel or series hybriddesigns. They are also called gas-optional, or griddable hybrids.Their main benefit is that they can be gasoline-independent for dailycommuting, but also have the extended range of a hybrid for long trips.They can also be multi-fuel, with the electric power supplemented bydiesel, biodiesel, or hydrogen. The Electric Power Research Institute'sresearch indicates a lower total cost of ownership for PHEVs due toreduced service costs and gradually improving batteries. The"well-to-wheel" efficiency and emissions of PHEVs compared togasoline hybrids depends on the energy sources of the grid (the USgrid is 50% coal; California's grid is primarily natural gas,hydroelectric power, and wind power). Particular interest in PHEVs isin California where a "million solar homes" initiative is under way, andglobal warming legislation has been enacted.

Prototypes of PHEVs, with larger battery packs that can be rechargedfrom the power grid, have been built in the U.S., notably at Prof. AndyFrank's Hybrid Center[20] at University of California, Davis and oneproduction PHEV, the Renault Kangoo, went on sale in France in2003. DaimlerChrysler is currently building PHEVs based on theMercedes-Benz Sprinter van. Light Trucks are also offered by Micro-Vett SPA[21] the so called Daily Bimodale.

The California Cars Initiative has converted the '04 and newer Toyota Prius to become a prototype of what it callsthe PRIUS+. With the addition of 140 kg (300 lb) of lead-acid batteries, the PRIUS+ achieves roughly double thegasoline mileage of a standard Prius and can make trips of up to 16 km (10 mi) miles using only electric power.[22]

Chinese battery manufacturer and automaker BYD Auto released the F3DM PHEV-62 (PHEV-100 km) compactsedan to the Chinese fleet market on December 15, 2008.[23][24] General Motors expects to launch the 2011Chevrolet Volt series plug-in (PHEV-40) by November 2010.[25][26]

Hybrid vehicle drivetrain 9

Types by nature of the power source

Electric-internal combustion engine hybridThere are many ways to create an electric-Internal Combustion Engine (ICE) hybrid. The variety of electric-ICEdesigns can be differentiated by how the electric and combustion portions of the powertrain connect, at what timeseach portion is in operation, and what percent of the power is provided by each hybrid component. Two majorcategories are series hybrids and parallel hybrids, though parallel designs are most common today.Most hybrids, no matter the specific type, use regenerative braking to recover energy when slowing down thevehicle. This simply involves driving a motor so it acts as a generator.Many designs also shut off the internal combustion engine when it is not needed in order to save energy. Thatconcept is not unique to hybrids; Subaru pioneered this feature in the early 1980s, and the Volkswagen Lupo 3L isone example of a conventional vehicle that shuts off its engine when at a stop. Some provision must be made,however, for accessories such as air conditioning which are normally driven by the engine. Furthermore, thelubrication systems of internal combustion engines are inherently least effective immediately after the engine starts;since it is upon startup that the majority of engine wear occurs, the frequent starting and stopping of such systemsreduce the lifespan of the engine considerably. Also, start and stop cycles may reduce the engine's ability to operateat its optimum temperature, thus reducing the engine's efficiency.

Structure of a fuel cell hybrid electric vehicle

Electric-fuel cell hybrid

Fuel cell vehicles are often fitted with a battery or supercapacitor todeliver peak acceleration power and to reduce the size and powerconstraints on the fuel cell (and thus its cost); this is effectively also aseries hybrid configuration.

Internal combustion engine-hydraulic hybrid

Chrysler are adapting a minvan to agasoline-hydraulic hybrid setup

A hydraulic hybrid vehicle uses hydraulic and mechanical componentsinstead of electrical. A variable displacement pump replaces theelectric motor/generator. A hydraulic accumulator, is a vessel whichstores energy. The vessel typically has a flexible bladder ofpre-charged pressurized nitrogen gas inside. Pumped hydraulic fluid iscompressed against the bladder storing the energy in the highlycompressed nitrogen gas. Some versions have a piston in a cylinderrather than pressurized bladder of nitrogen gas. The accumulatorreplaces the batteries on petro-electric hybrid. The hydraulicaccumulator is potentially cheaper and more durable than batteries.

Hydraulic hybrid technology was originally implemented in Germany in the 1930s. Volvo Flygmotor usedpetro-hydraulic hybrids experimentally in buses from the early 1980s and is still an active area.

Initial concept involved a giant flywheel (see Gyrobus) for storage connected to a hydrostatic transmission, howeverlater changed to a simpler system using a hydraulic accumulator connected to a hydraulic pump/motor. The system isalso being actively developed by Eaton and several other companies, primarily in heavy vehicles like buses, trucksand military vehicles. An example is the Ford F-350 Mighty Tonka concept truck shown in 2002. It features anEaton system that can accelerate the truck up to highway speeds.

Hybrid vehicle drivetrain 10

The system components were expensive which precluded installation in smaller trucks and cars. A drawback wasthat the power driving motors were not efficient enough at part load. Focus has now switched to smaller vehicles. ABritish company has made a breakthrough by introducing an electronically controlled hydraulic motor/pump, theDigital Displacement motor/pump, that is highly efficient at all ranges and loads making small applications ofpetro-hydraulic hybrids feasible.[27] The company converted a BMW car as a test bed to prove viability. The BMW530i, gave double the MPG in city driving compared to the standard car. This was test was using the standard3,000cc engine. Petro-hydraulic hybrids using well sized accumulators entails downsizing an engine to averagepower usage, not peak power usage. Peak power is provided by the energy stored in the accumulator.[28]

The kinetic braking energy recovery rate is higher and therefore the system is more efficient than current batterycharged hybrids, demonstrating a 60% to 70% increase in economy in EPA testing.[29] Under tests undertaken by theEPA, a hydraulic hybrid Ford Expedition returned 32 mpg-US (7.4 L/100 km) in urban driving, and 22 mpg-US(11 L/100 km) on the highway.[30] UPS currently has two trucks in service with this technology.[31] While thesystem has faster and more efficient charge/discharge cycling, the accumulator size and pressure dictates total energycapacity, and requires more space than a battery. However for the energy stored the accumulator is smaller inphysical size than a current battery pack.One research company's goal is to create a blank paper design new car, to maximize the packaging ofgasoline-hydraulic hybrid components in the vehicle. All bulky hydraulic components are integrated into the chassisof the car. One design has claimed to return 130mpg in tests by using a large hydraulic accumulator which is also thestructural chassis of the car. The small hydraulic driving motors are incorporated within the wheel hubs driving thewheels and reversing to claw-back kinetic braking energy. The aim is 170mpg in average driving conditions. Energycreated by shock absorbers and kinetic braking energy that normally would be wasted assists in charging theaccumulator. A small fossil fuelled piston engine sized for average power use charges the accumulator. Theaccumulator is sized at running the car for 15 minutes when fully charged. The aim is a fully charged accumulatorwith an energy storage potential of 670 HP, which will produce a 0-60 mph acceleration speed of under 5 secondsusing four wheel drive.[32][33][34]

In January 2011 industry giant Chrysler announced a partnership with the U.S. Environmental Protection Agency(EPA) to design and develop an experimental gasoline-hydraulic hybrid powertrain suitable for use in largepassenger cars. In 2012 an existing production minvan will be adapted to the new hydraulic powertrain.[35][36][37][38]

Internal combustion engine-pneumatic hybridCompressed air can also power a hybrid car with a gasoline compressor to provide the power. Motor DevelopmentInternational in France is developing such air-powered cars. A team led by Tsu-Chin Tsao, a UCLA mechanical andaerospace engineering professor, is collaborating with engineers from Ford to get Pneumatic hybrid technology upand running. The system is similar to that of a hybrid-electric vehicle in that braking energy is harnessed and storedto assist the engine as needed during acceleration.

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Human power and environmental power hybridsMany land and water vehicles use human power combined with a further power source. Common are parallelhybrids, e.g. a boat being rowed and also having a sail set, or motorized bicycles, or a human-electric hybrid vehiclesuch as the Twike. Also some series hybrids exist, see in hybrid vehicle. Such vehicles can be tribrid vehicles,combining at the same time three power sources e.g. from on-board solar cells, from grid-charged batteries, and frompedals.

Hybrid vehicle operation modesHybrid vehicles can be used in different modes. The figure shows some typical modes for a parallel hybridconfiguration.

Adding powertrains and aftermarket kitsOne can install conmarket or aftermarket powertrain to a vehicle to hybridise it.[39]

The conmarket solution is used when the user buys the glider (rolling chasis) and the hybrid (two engines) orall-electric (only an electric motor) powertrain kit to the automaker and receives it installed in the car.[40] Also an(electric or hybrid) powertrain can be added to a glider[41] by a third party aftermarket installer.A University of Central Florida senior design team, On the Green, is currently developing a bolt-on hybridconversion kit to transform an older model vehicle into a gas-electric hybrid.[42]

An example of a conversion using a 1966 Mustang was demonstrated by an engineer in California. The systemreplaces the alternator with a 12kW (30kW peak) brushless electric motor. Gas mileage and power wereimproved.[43]

Hybrid vehicle drivetrain 12

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hybrid-center-how-hybrid-cars-work-under-the-hood-2. html). Union of Concerned Scientists. . Retrieved 2010-03-18.[3] Improving IC Engine Efficiency (http:/ / courses. washington. edu/ me341/ oct22v2. htm)[4] Lotus vehicle generator set (http:/ / www. greencarcongress. com/ 2009/ 09/ lotus-range-extender. html#more)[5] Neuman, William (October 11, 2007). "The turbine on the bus goes purr purr purr" (http:/ / cityroom. blogs. nytimes. com/ 2007/ 10/ 11/

the-turbine-on-the-bus-goes-purr-purr-purr/ ). New York Times. .[6] Linear Combustion Engine Project (http:/ / www. lceproject. org/ en/ )[7][7] Churella, 28-30[8] "Toyota debuts power-hybrid bus | The Japan Times Online" (http:/ / search. japantimes. co. jp/ cgi-bin/ nn19970822a8. html).

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www. mathworks. com/ help/ toolbox/ physmod/ sdl/ ref/ ravigneauxgear. html). Mathworks.com. . Retrieved 2012-08-01.[11] " BMW, Daimler, GM hybrid alliance nears end (http:/ / www. autonews. com/ apps/ pbcs. dll/ article?AID=/ 20090714/ COPY02/

307149993& AssignSessionID=373348067472168)", Matthias Krust, Automotive News, July 14, 2009[12] "The GMC Graphyte — A hybrid SUV concept vehicle" (http:/ / web. archive. org/ web/ 20060116181503/ http:/ / www. gm. com/

company/ gmability/ edu_k-12/ 9-12/ fc_energy/ graphyte. html). GM - GMability Education 9-12: Fuel Cells & Energy. Archived from theoriginal (http:/ / www. gm. com/ company/ gmability/ edu_k-12/ 9-12/ fc_energy/ graphyte. html) on January 16, 2006. . Retrieved January20, 2006.

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pdf?arnumber=511737). IEEE. 1996. .[20] "Team Fate" (http:/ / www. team-fate. net/ ). UC-Davis Hybrid Electric Vehicles Group. . Retrieved January 11, 2006.[21] "Hybrid Daily: Technical Data" (http:/ / web. archive. org/ web/ 20060110114534/ http:/ / www. micro-vett. it/ english/ bimodaleing2.

html). Micro-Vett. Archived from the original (http:/ / www. micro-vett. it/ english/ bimodaleing2. html) on January 10, 2006. . RetrievedJanuary 11, 2006.

[22] "How We Green-Tuned an '04 Prius into a PRIUS+ Plug-In Hybrid!" (http:/ / www. priusplus. org). CalCars.com - The California CarsInitiative. . Retrieved January 11, 2006.

[23] Crippen, A. (December 15, 2008) "Warren Buffett's Electric Car Hits the Chinese Market, But Rollout Delayed For U.S. & Europe" (http:/ /www. cnbc. com/ id/ 28236421) CNBC. Retrieved December 2008.

[24] Balfour, F. (December 15, 2008) "China's First Plug-In Hybrid Car Rolls Out" (http:/ / www. businessweek. com/ globalbiz/ content/dec2008/ gb20081215_913780. htm)Business Week. Retrieved December 2008.

[25] Kim, Soyoung (2008-06-03). "GM says all-electric Volt approved for 2010 launch" (http:/ / www. reuters. com/ article/ pressReleasesMolt/idUSN037009220080603). Reuters. . Retrieved 2008-07-04.

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15/ capturing-the-power-of-hydraulics). Autobloggreen.com. . Retrieved 2009-10-17.[31] Nunez, Alex (2006-06-26). "EPA unveils hydraulic hybrid UPS delivery truck — Autoblog" (http:/ / www. autoblog. com/ 2006/ 06/ 26/

epa-unveils-hydraulic-hybrid-ups-delivery-truck/ ). Autoblog.com. . Retrieved 2009-10-17.[32] "Hybrid Hydraulic Drive Vehicle Promises 170 MPG | Inhabitat - Sustainable Design Innovation, Eco Architecture, Green Building" (http:/ /

inhabitat. com/ hybrid-hydraulic-drive-vehicle-promises-170-mpg/ ). Inhabitat. 2010-07-16. . Retrieved 2012-08-01.

Hybrid vehicle drivetrain 13

[33] "INGOCAR from Valentin Tech shatters the way we think about cars" (http:/ / www. torquenews. com/ 1080/ingocar-valentin-tech-shatters-way-we-think-about-cars). Torquenews.com. 2012-02-16. . Retrieved 2012-08-01.

[34] "Valentin Technologies, Inc. - The 170MPG Car" (http:/ / www. valentintechnologies. com/ default. asp). Valentintechnologies.com. .Retrieved 2012-08-01.

[35] "Chrysler announces development of hydraulic hybrid technology for cars" (http:/ / www. gizmag. com/chrysler-announces-development-of-hydraulic-hybrid-technology-for-cars/ 17686/ ?utm_source=PESWiki. com). Gizmag.com. . Retrieved2012-08-01.

[36] "01/19/2011: EPA and Chrysler to Take Latest Hybrid Technology from Lab to Street/Partnership to adapt fuel efficient technology" (http:/ /yosemite. epa. gov/ opa/ admpress. nsf/ 0/ 837c1d022dba18448525781d005995be?OpenDocument). Yosemite.epa.gov. 2011-01-19. .Retrieved 2012-08-01.

[37] "Hydraulic Hybrid Research| Clean Automotive Technology | Transportation and Air Quality| US EPA" (http:/ / epa. gov/ otaq/ technology/research/ research-hhvs. htm). Epa.gov. 2010-11-17. . Retrieved 2012-08-01.

[38] "Demonstration Vehicles | Clean Automotive Technology | Transportation and Air Quality| US EPA" (http:/ / epa. gov/ otaq/ technology/research/ demonstration-vehicles. htm). Epa.gov. . Retrieved 2012-08-01.

[39] California Motors hybrid drivetrains (http:/ / www. calmotors. com/ )[40] Two-stage vehicle (http:/ / www. mva. state. md. us/ AboutMVA/ INFO/ 27300-31T. htm#two_stage)[41] Energy Storage Fuel Cell Vehicle Analysis: Preprint (http:/ / www. nrel. gov/ docs/ fy05osti/ 37567. pdf)[42] On the Green (http:/ / ucfhybridcart. wordpress. com/ )[43] www.howtobuildahybrid.com (http:/ / www. howtobuildahybrid. com/ )

External links• Hybrid Cars Need Special Mechanics (http:/ / www. howstuffworks. com/

3290-hybrid-cars-need-special-mechanics-video. htm) at HowStuffWorks• The Rise of the REEV (http:/ / www. ecogeek. org/ content/ view/ 1298/ )• Serial Hybrids Are Here - Ecoworld.com (http:/ / www. ecoworld. com/ blog/ 2006/ 11/ 10/

serial-hybrids-are-here/ )• Air Car video (http:/ / science. discovery. com/ fansites/ discoveriesthisweek/ videogallery/ videogallery.

html?myClip=dtw_aircar)• Zeroshift hybrid and electric vehicle Transmission (EV transmission) Systems (http:/ / www. zeroshift. com/

transmission-technology/ Hybrid-Electric-Vehicle-Transmissions. html)

Article Sources and Contributors 14

Article Sources and ContributorsHybrid vehicle drivetrain  Source: http://en.wikipedia.org/w/index.php?oldid=516702067  Contributors: ANTIcarrot, Ageekgal, Andromon58, Ariedartin, Atarivideomusic, Aznshark4, Beland,Brianhe, Brucedp, By78, Caltas, Casey56, Chizu, Chris the speller, ClockwerkMao, D0li0, Daniel.Cardenas, DeFacto, Deicas, Derek R Bullamore, Dhirukapur, Dude1024, Fatsamsgrandslam,FlyHigh, Funandtrvl, Gerben1974, GoingBatty, Greasywheel, Gregalton, Grs1969, Hadlock, Honza.havlicek, IJB TA, IanOsgood, Igodard, Improbcat, JanCeuleers, Jeffwishart, Joeinwap,Jovianeye, Jzylstra, KJRehberg, Ken Gallager, LHOON, Leonard G., LilHelpa, Liverpool-8-boy, Lkruijsw, Lotje, Mac, Magioladitis, Mariordo, Mattbrundage, MaxDZ8, Mhrogers, Mulad,Mwarren us, NCWA1, Nbrewton, Newuser06081958, Ng.j, Numindast, Ospalh, Pepsi132, Pineapple fez, Plek, RJFJR, Rchandra, RedGreenInBlue, Rich Farmbrough, Rich Janis,RightCowLeftCoast, Rudimae, Sam8, Sfan00 IMG, Skierpage, Smenjas, Ssilvers, Stemonitis, StuffOfInterest, Theosch, Thumperward, Tomcha, Torotrak, Tri400, Typ932, Vegaswikian, Vsmith,Whgs09, Wingchi, Woohookitty, WopOnTour, Wtshymanski, Zero10one, Zilyuki, Zojj, 138 anonymous edits

Image Sources, Licenses and ContributorsFile:Hybridpar.png  Source: http://en.wikipedia.org/w/index.php?title=File:Hybridpar.png  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Conscious, LHOON, WylveFile:Hybridpeak.png  Source: http://en.wikipedia.org/w/index.php?title=File:Hybridpeak.png  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Honza.havlicek,Joey-das-WBF, LHOON, YOKOTA KuniteruFile:Hybridcombined.png  Source: http://en.wikipedia.org/w/index.php?title=File:Hybridcombined.png  License: Creative Commons Attribution-Sharealike 2.5  Contributors: LHOONFile:Toyota Prius III 20090710 front.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Toyota_Prius_III_20090710_front.JPG  License: Attribution  Contributors: S 400 HYBRIDFile:Toyota 1NZ-FXE Engine 01.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Toyota_1NZ-FXE_Engine_01.JPG  License: Public Domain  Contributors: Hatsukari715File:2006 Mercury Mariner Hybrid engine.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:2006_Mercury_Mariner_Hybrid_engine.jpg  License: Creative CommonsAttribution-ShareAlike 3.0 Unported  Contributors: SfoskettFile:2006 GMC Sierra Hybrid engine.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:2006_GMC_Sierra_Hybrid_engine.jpg  License: Creative Commons Attribution-ShareAlike3.0 Unported  Contributors: SfoskettFile:New Vehicle Purchase Preference.svg  Source: http://en.wikipedia.org/w/index.php?title=File:New_Vehicle_Purchase_Preference.svg  License: Public Domain  Contributors: US Dept. ofEnergy, converted to SVG by MaxDZ8.File:Byd duel mode engine.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Byd_duel_mode_engine.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors:TEDizen (Flickr User)File:Hybridfuelcell.png  Source: http://en.wikipedia.org/w/index.php?title=File:Hybridfuelcell.png  License: Creative Commons Attribution-Sharealike 2.5  Contributors: LHOON, YOKOTAKuniteruFile:2011 Chrysler Town & Country Touring - L -- 04-22-2011.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:2011_Chrysler_Town_&_Country_Touring_-_L_--_04-22-2011.jpg License: Public Domain  Contributors: IFCARFile:Hybrid modes.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Hybrid_modes.gif  License: GNU Free Documentation License  Contributors: MB-one, Pjbarraud, 2 anonymousedits

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