Silent running

The Schaeffler has unveiled its latest innovation in electric technology - the ACTIVeDRIVE. The group's growing portfolio of battery electric, ICE-powered and hybrid electric vehicles utilises some of the most innovative, energy-efficient engine and powertrain components available today.

Although the internal combustion engine (ICE) is likely to dominate the automotive landscape for the next decade, the increasing mismatch between energy consumption and available resources, together with tighter legal restrictions on engine emissions, is increasing demands for improvements to existing automotive technologies and the development of 'greener' alternatives.

The latest in The Schaeffler Group's growing portfolio of energy-efficient electric vehicles has now arrived. The ACTIVeDRIVE is a four-wheel drive, battery-electric demonstration vehicle (BEV) based on a Skoda Octavia Scout.

The vehicle, to be showcased at the Frankfurt Motor Show in September 2011, complements two other equally innovative Schaeffler vehicles, the Schaeffler Hybrid and the CO2ncept-10%. Together, this trio of vehicles represents Schaeffler's future strategy for a greener automotive industry.

As Prof. Dr.-Ing Peter Gutzmer, president technical development at Schaeffler, puts it: "These three cars are full of ideas and function as platforms for the testing of various components and systems under realistic conditions."

Innovative Design
The innovation behind the ACTIVeDRIVE is its active electric differential (eDifferential), which is installed on both the front and rear axles. This component combines the electric drive with the option of wheel-selectable drive power control. This enables torque vectoring (torque distribution between the right and left wheels), which enhances the driving experience, car safety and comfort.

"The eDifferential enables active intervention in driving dynamics via well-directed power supply – rather than braking intervention and therefore power reduction, as is the case with ESP (Electronic Stability Programme). The active electric differential significantly improves power transmission when driving on surfaces with different friction coefficients. Furthermore, it assists steering and has a clearly positive effect on driving dynamics, safety and comfort. In addition, the use of two eDifferentials enables the longitudinal distribution of drive torques," explains Gutzmer. The possibility of active longitudinal and lateral distribution of drive torque makes the eDifferential an ideal platform for innovative vehicle dynamics control systems.

Actively controlled torque vectoring means the vehicle can be controlled without the use of steering and braking, by using a wheel-selective flow of forces.

"This means that the potential fields of application for the eDifferential range from sports cars with extremely high driving dynamics, to conventional passenger cars and agricultural vehicles," explains Dr. Tomas Smetana, senior manager advance development power transmission systems at Schaeffler Automotive.

The eDifferential system integrates two water-cooled permanent magnet synchronous motors (PMSM) of different dimensions, a planetary gear, a gearbox for active torque distribution and a central element: Schaeffler's lightweight differential. The electric motors were developed by Schaeffler's IDAM (INA Drives & Mechatronics) division.

The larger PMSM, which delivers up to 105kW and 170Nm, is the primary drive. The second PMSM controls torque distribution and is only required to deliver a 5kW output, in order to generate up to 2,000Nm of torque difference to the axle.

Other novel features of the ACTIVeDRIVE include an integrated electromechanical parking lock; a new forced lubrication system for the gearbox that requires no oil pump; sheet metal planetary carriers; and various high speed, friction-optimised bearings. The electronic controls for the ACTIVeDRIVE are supplied by AFT (Atlas Fahrzeugtechnik GmbH), Schaeffler's automotive drivetrain mechatronics and vehicle testing division.

Due to the use of two active electric differentials, the four-wheel drive ACTIVeDRIVE has an overall output of up to 210kW. Fitted in the cardan shaft tunnel, in front of the rear axle, are Lithium-ion batteries, which have a capacity of 18kWh. These function as energy storage devices for the vehicle.

Due to its performance and traction capacity, the 1,900kg test platform accelerates from 0 to 100km/h in just 8.5 seconds. The vehicle has an electronic maximum speed regulation of 150km/h. In this configuration, the vehicle's cruise range is up to 100km.

The CO2ncept-10%
Based on a Porsche Cayenne, Schaeffler's CO2ncept-10% vehicle demonstrates improvements that can be achieved through consistent, detailed work on ICE vehicles. In the CO2ncept-10%, these optimisation measures utilise solutions already available on the market, or close to series production, without changing the basic configuration of the vehicle. Also, the optimisation of the classic drivetrain includes the use of electrical components, rather than hydraulically actuated elements.

CO2ncept-10% is the result of a power train friction reduction development project between The Schaeffler Group and Porsche. Schaeffler was responsible for the design and testing of components, while Porsche managed system coordination and validation for the entire vehicle.

The project involved the use of novel, optimised engine components which, when combined, achieve an overall 10% reduction in fuel consumption and CO2 emissions.

CO2ncept-10% is a CO2 demonstration vehicle based on a Porsche Cayenne with a V8 engine. In addition to tried and tested, optimised engine components, the vehicle is also equipped with several new powertrain and chassis components manufactured by Schaeffler. These components help to significantly reduce the car's fuel consumption, compared to existing production models.

The reductions in fuel consumption and CO2 emissions have been verified theoretically through complex simulation calculations at Schaeffler and practically via extensive bench testing at Porsche. The calculation standard used was the Standardised New European Driving Cycle (NEDC).

The engine accounts for 5.8% of the optimised fuel consumption and associated CO2 emissions. Most of this (4.1%) comes from modification of the VarioCam Plus valve control system, by replacing hydraulic cam timers with electromechanical equivalents, as well as the use of optimised switching tappets on the intake side. An extra 1.7% reduction can be achieved through minimising frictional losses, by cross-system optimisation of valve train, belt drive and chain drive components.

Schaeffler's double-row angular contact ball bearings, which are installed in the front and rear axle differentials, generated a further 1.1% in fuel savings. These 'Twin Tandem' bearings, which replaced the existing tapered roller bearings, reduce frictional resistance significantly when compared to conventional transmission systems. This reduction amounts to 35% in the front axle transmission and 42% in the rear axle transmission.

Schaeffler Hybrid
Based on a Vauxhall Corsa, this fully operational hybrid vehicle is part of an advanced development project at Schaeffler that enables practical comparisons to be made of a number of different vehicle configurations and driving conditions.

As well as using a conventional volume-manufactured combustion engine, the Schaeffler Hybrid also incorporates a central electric motor and two wheel hub motors. The vehicle incorporates every Schaeffler brand, including INA, FAG, LuK, IDAM and AFT.

Each of the concepts of a conventional, electric or hybrid vehicle can be demonstrated, tested and compared. Each of the elements can be switched on or off to simulate a wide range of different driving conditions. These options range from classic operation using a combustion engine, through to parallel hybrid or serial hybrid operation, or on an electric motor-only basis.

The combustion engine can power the vehicle and be coupled for use as a range extender. An automated manual transmission increases the options available. The transmission incorporates Schaeffler's LuK clutch products, which are specifically matched to the requirements of hybrid vehicles. The energy store, which is a 16 kWh lithium-ion battery (400 V, 400 A), is charged using energy recovery methods, via a range extender and an external power supply (plug-in hybrid).

The vehicle's central unit is connected to the automated manual transmission using a toothed chain that drives the front wheels. This unit comprises a liquid-cooled, 50kW, 95Nm electric motor, which was designed and manufactured by IDAM.

Author
Matthew Valentine

Related Companies
Porsche
Schaeffler (UK) Ltd
Skoda Brand - Volkswagen Group UK Ltd
Vauxhall Motors

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