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Plug-in

powertrainETIhas gleaned early details on an innovative prototype vehicledue next year that will be powered by a state-of-the-artthree-cylinder IC engine with e-drive capabilityWORDS:DR FRIEDRICHWILHELM SPECKENS AND DR DEAN TOMAZIC

60January 2011Engine Technology International.com Engine Technology Internati

The mission hasnt changed, but thesize has. Making engines smaller,lighter, more efficient and morepowerful is what the globalautomotive industry strives for.

Todays engineers are continually faced with

these challenges, but instead of starting witha 5-liter V8 powerplant, todays entry pointinto this optimization process is an alreadyrelatively refined four- or six-cylinderpassenger car unit, making a tangibleoptimization step perhaps more challengingthan it has ever been. Over the next fewyears, the electrified drivetrain will gaina considerable share of the market. Inaddition to reducing climate-relevant CO

2

emissions, this development also contributesto improving local air quality, reducing traffic-related noise pollution, and increasing drivingand operating comfort.

As a result of these factors, in the foreseeablefuture plug-in hybrids will play an importantrole alongside pure electric vehicles. Theseplug-in hybrids can be operated in a pureelectric-drive mode, preferably from electricityproduced through regeneration. Conversely,

the hybrid drive can be fully used in dailyoperations, at higher vehicle speeds and alsounder difficult climatic conditions.

Project HiCEPS

FEV powertrain engineers faced this taskwithin the EU-funded Highly IntegratedCombustion Electric Powertrain System

(HiCEPS) project. The Tier 1 suppliefurther improvements had to come frsystems approach, rather than improindividual components. The result ofis a very attractive version of a new hcombustion electric-powertrain syste

developed by a team of FEV engineerof paper to demonstrate the improvemplug-in hybrid powertrain with an inan automatic transmission, electric mELDOR), actuation system and condesigning and developing this newresponsible for full simulation of tand designing all the componentsteam of FEV engineers performeddesign, including CAE work on thgearsets, clutches and shafts. FEVs

was also responsible for the completassociated with the IC engine.

The engine concept is a turbochargthree-cylinder SI engine with 698cm3

on the Smart Brabus engine. FEV engioriginal twin spark ignition with a sinthe exhaust side, combined with a higcoil. The position of the replaced sparside was then used as the location for

The arrangement of the injector and scombustion chamber is shown in Figu

The spray pattern layout was optimfuel injector layout tool chain. The injwere optimized to ensure the most favspray geometry and reduced wall wetengineering challenge with a 66.5mmThe general effect of different injector

Figure 2 (above): Thearrangement of the injectorand spark plug in thecombustion chamber

Figure 3 (right): Positions ofengine bore influence infavorable spray geometry

Figure 1: A highlyintegrated combustionelectric powertrain

CASE STUDY: FEV CAS

VITA L STATI STI CS

Engine:Torque 105Nm at 1,800rpmPower 60kW at 6,000rpm

Idle 600rpm

E-motorDiameter 300mm

Length 381/357mm (EH / EHactuation)

Torque 143/250Nm (continuous)Power 20/38kW (continuous)

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The cam-in-cam system enables the invalves to phase independently.

The phasing angle of the intake camon the exhaust side, enabling positivevalve overlap at full load and low engis a dramatic increase in low-end torqTypically with downsized engine concacceleration at speeds above 1,500rpm

With the HiCEPS, there is no decreasbe achieved only with a cam-in-cam wa DI injector. FEVs testing also resultea specific power of more than 100kW130Nm), achieved without changing

FEV has filed for patents related to of the hybrid system and the electromconcept, which is currently undergoin

development at the companys test facGermany. The thought leadership andintelligence in developing this concepcustomers expectations. Currently, a being developed, complete with the dall the mechanics of the parallel hybriMotorentechnik is leading this endeavscheduled for completion in 2011.

positions and engine bore influence is shown in Figure3. The resulting homogeneous combustion systemspecification includes a multihole injector with solenoidactuation, asymmetric spray pattern with five spray cones,single piston high-pressure fuel pump (200 bar), an HPpump driven by an additional cam-on-cam shaft, and acylinder head adaptation for different injector suppliers.

The main focus for injector layout in small DISI enginesis to prevent wall wetting, thus ensuring low f uel contentin the oil. At 66.5mm, the bore diameter of this downsizedengine is smaller than all competitor engines currently onthe market.

Seventh heaven

FEVs project goal was to develop a parallel hybridpowertrain that could deliver pure electric driving as wellas boost and recuperation modes. To make the conceptwork, engineers integrated FEVs newly developedplanetary gearset transmission. The seven-speed electricallyassisted hybrid automatic transmission has been designedfor transverse (FWD) applications. The transmission, ratedat 200Nm, is very compact and supports full hybridfunctionality (Figure 4).

The hybrid transmission is equipped with three planetarygearsets (PGS), three clutches, and two brakes (Figure 5).The first PGS is coupled to the engine and electric motor.Two additional PGS are coupled to a differential to achievethe desired seven-speed hybrid functionality. The e-motorand engine are controlled with three clutches and twobrakes. The existing gear ratios of the PGS can be multi pliedwith the clutches/brakes to generate additional ratios.

Vehicle launch can be performed either in pure electricmode or by using one of the clutches as a launch clutch.

To maximize fuel economy, FEVs designand engineering team developed a means ofactuating the clutch without hydraulics. Adirect mechanical actuation of the clutchesand brakes is possible. The electromechanicalclutch actuator for this application helps toachieve the fuel economy benefit by stayingin its open or closed position, even when it isnot being energized.

The transmission design also featuresa cam disc. Additional coupling of non-linear stiffness compensates for clutch wearand thermal strain. FEV engineers builtcomponent test rigs equipped with force,speed, current and position sensors to validatethe functionality of the electromechanicalactuators. Tests showed that, even in theworst-case scenario, the engagement timefor the transmission remains below 140ms.

The design of the electromechanical actuatoris still under mechanical development. Thecurrent version of the transmission still useselectrohydraulic actuation until the mechanicaldevelopment of the electromechanicalactuation system is complete.

The transmission, with electromechanicalactuators, can contribute to fuel consumptionreductions of up to 9% and a reduction in totaldriveline losses of approximately 60%.

Combined, the parallel hybrid powertrainsystem provides key benefits, such as stop/startfunction, two-speed pure electric driving,seven-speed IC engine drive, boosting andrecuperation, restart of the IC engine out ofe-drive, full powershift capability, no torquedrop while shifting, integration of the electricmotor with 20kW continuous and 38kW peakpower, three-shaft compact design with sevenforward gears realized through three clutches

and two brakes, and an electromechanical orelectrohydraulic actuation.

Three-cylinder heart

With funding by the EU, FEV created a smalldirect-injection turbocharged version of athree-cylinder gasoline engine equipped with aSOHC and two valves per cylinder (Figure 5).

Due to the small single cylinder displacementof 233cm and a cylinder bore diameter of66.5mm, the injector layout and its adaptationto the combustion chamber was a key factorduring the concept phase to avoid oil dilutioneffects. By using the existing and proven FEVtool chain (which considers injector spraycharacteristics, combustion chamber geometry,piston movement and in-cylinder chargemotion effects), a very low oil dilution levelwas realized. The level of oil dilution is in thelower range of the scatter band of all enginesin this class of series production direct-injection gasoline engines, despite itscomparatively very small bore diameter.

The overall fuel consumption advantageof using the small, boosted engine duringthe NEDC is 16% compared with a naturallyaspirated 1.4-liter engine with similar

driving performance. By introducing furtherpowertrain and vehicle-related CO

2reduction

measures, an overall fuel-consumptionimprovement of 29% is achieved. Combinedwith a mild hybridization strategy, a CO

2level

below 95g/km over the NEDC is possible.FEVs complete project involvement covered

the following areas: hybrid system simulationand the definition of components; hybridpowertrain concept, including layout anddesign; CAE for housing, planetary gearsets,clutches and shafts; downsizing of the ICengine (698cm3, 60kW, 105Nm); procurementof engine and transmission components;mechanical testing of engine and transmission;complete software structure for TCU, ECUand HCU; and hybrid powertrain testing ontransient test bench.

Encouraged by the results of the combustionengine downsizing, FEV has continued the

development of downsized engines on thebasis of the HiCEPS engine. To enable fullyindependent phasing of intake and exhaustcams on a SOHC valvetrain, FEV engineershave worked with Mahle to integrate itscam-in-cam camshaft into the cylinder-head concept. The actuation is realized by ahydraulic-ring dual-stacked vane-cam system.

62January 2011 Engine Technology International.com Engine Technology Internat

Figure 4: The transmissionis compact and supportsfull hybrid functionality

CASE STUDY: FEV CAS

Figure 5: A small direct-injection turbocharged

version of a three-cylindergasoline powertrainequipped with a SOHC,two valves per cylinder

The engine concept

is a turbocharged,

two-valve SOHC three

cylinder SI engine with

698cm3displacement

based on the Smart

Brabus engine