PressClub Global · Article.
Drive technology featured in the new BMW 2 Series Active Tourer.
Thu Nov 27 10:00:00 CET 2014 Press Release
Light, powerful and efficient with BMW xDrive.
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Munich. Since the premiere of the first four-wheel drive BMW 325i in 1985, BMW has consistently expanded its four-wheel drive competence with new models and constant further development in the field of drive technology. One of the milestones is undoubtedly the intelligent four-wheel drive system BMW xDrive, which was first used in the BMW X3 and the X5 in 2004 and is now available for numerous models and series. Even at that time, engineers did not focus solely on improving traction and vehicle stability. In addition to a high degree of functionality and enhanced cornering dynamics, the minimisation of system-related losses and constant weight reduction are top priorities set to keep the fuel consumption and emission levels of four-wheel drive vehicles as low as possible. To this end, the intelligent four-wheel drive system BMW xDrive is always aligned to each vehicle concept (Sedan/Coupe, SAV, SAC) with the aim of implementing the optimum solution.
Premiere: BMW xDrive complements front-wheel drive concept.
The latest example of model-specific alignment of the four-wheel
drive system is provided by the BMW 2 Series Active Tourer. The
fundamental difference to previous variants is that, for the first
time, BMW xDrive is premised on a front-wheel drive concept with
transversally installed engines. The Active Tourer has already proven
that front-wheel drive technology fully meets the brand’s demands in
terms of driving dynamics. This is largely owed to the new range of
modularly constructed three- and four-cylinder engines which, thanks
to state-of-the-art TwinPower Turbo technology, excel to an equal
extent through high performance characteristics and outstanding
efficiency. With the BMW 225i xDrive Active Tourer (fuel consumption
combined: 6,5–6,4 l/100 km; CO2 emissions combined: 152-148 g/km)* and
the BMW 220d xDrive Active Tourer (fuel consumption combined: 4,8-4,6
l/100km; CO2 emissions combined: 127-122 g/km)*, the intelligent
four-wheel drive system is now available for top-of-the-range power
units to further improve traction, vehicle stability and cornering
dynamics, with the aim of enhancing safety and driving pleasure. Both
models feature BMW xDrive as standard in combination with the 8-speed
Steptronic transmission.
Slender, lightweight four-wheel
architecture.
The slender architecture featuring
compact, lightweight components and the resulting low amount of space
required by the new four-wheel drive system are excellently suited to
the concept of the BMW 2 Series Active Tourer. Thus the additional
weight of the entire four-wheel drive technology is only around 61 kg.
Furthermore, measures for reducing system-related losses and an
energy-efficient operating strategy ensure extremely favourable fuel
consumption and emission levels.
Power from the front drive to the rear axle is transferred by means of an angular gear (Power Take-Off) on the front differential and a two-part cardan shaft. The central component of the four-wheel drive system is an electro-hydraulically controlled multiple-disk clutch (Hang-On) inside the rear axle drive, which facilitates infinitely variable distribution of torque to the front and rear wheels. The corresponding commands are provided by an electronic control unit which, like the hydraulic pump, is located on the rear axle.
Power Take-Off: angular gear and two-part cardan shaft.
The angular gear is mounted behind the engine on the automatic
transmission and crankcase. The input shaft is a hollow shaft
construction and directly connected to the front axle differential. In
this way, part of the drive force is transferred from the differential
basket to the cardan shaft via the hollow shaft, the crown wheel and
the pinion shaft. The angular gear operates at a fixed gear ratio
(1:1.74) and is permanently engaged, meaning that the cardan shaft
always rotates when the vehicle is driven. Reversal of transmission
takes place in the rear axle drive so that the front and rear axle
drive shafts both rotate at exactly the same speed.
Hang-On: electro-hydraulically controlled multiple-disk
clutch.
The multiple-disk clutch located in the rear
axle drive (Hang-On) directs a proportion of torque to the rear wheels
according to each driving situation, thus ensuring variable power
distribution between the front and rear axle as required. In extreme
cases (e.g. the front wheels are standing on ice), the ratio can be
0:100. The required operating pressure (0 to 40 bar) is delivered by
an electro-hydraulic pump, the speed of which is defined by a
pulse-width-modulated signal from the electronic control unit.
Pressure is not measured by a sensor, but extremely accurately by
means of voltage and power alignment. In order to ensure maximum
positioning accuracy, run-in behaviour and temperature influences are
independently compensated, the system constantly adapting to ever
changing operating conditions.
Efficient valve helps reduce fuel
consumption.
Moreover, xDrive utilises an
energy-efficient operating strategy: When four-wheel drive is not
required – which is usually the case in day-to-day operation – the
pump is deactivated, rendering the system unpressurised. The BMW 2
Series Active Tourer is then driven only via the front wheels. In
order to make use of additional saving potentials, BMW has provided
the multiple-disk clutch with a spring-loaded Efficient valve, which
lowers the oil level in the clutch and significantly reduces friction
losses (oil splash losses). When required, the system takes only
fractions of a second to build up maximum operating pressure in the
Efficient mode and thus deliver maximum torque to the rear wheels.
This intervention goes unnoticed by the driver and passengers and
without any losses in traction.
Intelligent networking: fast, precise and proactive.
In order to guarantee efficient and constant power distribution
to the front and rear axle as required, the four-wheel drive system is
managed from the control unit of the Dynamic Stability Control feature
(DSC). In order to analyse each driving situation, DSC analyses a
large amount of data providing information on each respective running
condition and ensuring optimum distribution of drive torque. This
information includes vehicle speed, lateral and longitudinal
acceleration, steering angle, wheel speed, longitudinal inclination,
accelerator position and the setup via Driving Experience Control.
Furthermore, the DSC status, including Dynamic Traction Control (DTC),
Electronic Differential Lock Control (EDLC) and Performance Control is
taken into account. Adjustment of the four-wheel drive system to the
ever changing driving and road conditions is performed – in typical
BMW xDrive manner – within fractions of a second, thus guaranteeing
consistently neutral and safe handling even in difficult conditions.
Nevertheless, the variable distribution of power between the two axles
goes virtually unnoticed by the driver. Also, within the framework of
the efficient operating strategy, torque distribution is precisely
regulated as to avoid any loss of power due to wheel spin.
BMW xDrive: maximum traction, enhanced cornering
dynamics.
Thanks to DSC networking, any imminent wheel
slip for example can be detected at an early stage. Through precise
distribution of drive torque this situation can be anticipated and
avoided. If for instance the vehicle threatens to drift outwards over
the front wheels, increased tractive force is supplied to the rear
axle, allowing the vehicle to turn in more accurately. On the other
hand, xDrive directs excess force to the front wheels, should the rear
of the vehicle threaten to swerve outwards. As a result, maximum
four-wheel performance is available even before slippage occurs.
Therefore, xDrive featured in the BMW 2 Series Active Tourer not only
ensures best possible traction and safety in adverse road conditions,
but also enhances vehicle stability, cornering dynamics and ride
comfort. In driving situations where the interconnection of all four
wheels is disadvantageous – i.e. in an emergency stop – the system
opens the multiple-disk clutch completely within milliseconds.
Only if optimum power distribution to the front and rear axle is not sufficient to keep the Active Tourer on the desired course, DSC intervenes by reducing engine output and/or by decelerating individual wheels. Moreover, DSC assumes the function of a transverse differential lock: If a wheel spins without transferring power, it is automatically slowed down, whereby the axle differential directs more power to the wheel opposite.
* Fuel consumption figures were calculated on the basis of the ECE test cycle, depending on tyre format.
Further information on official fuel consumption figures, specific CO2 emission values and the electric power consumption of new passenger cars is included in the following guideline: “Leitfaden über Kraftstoffverbrauch, die CO2 emissions und den Stromverbrauch neuer Personenkraftwagen” (Guideline for fuel consumption, CO2 emissions and electric power consumption of new passenger cars), which can be obtained from all dealerships, from Deutsche Automobil Treuhand GmbH (DAT), Hellmuth-Hirth-Str. 1, 73760 Ostfildern-Scharnhausen and at http://www.dat.de/en/offers/publications/guideline-for-fuel-consumption.html. LeitfadenCO2 (GuidelineCO2) (PDF ‒ 2.7 MB)
Article Offline Attachments.
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Drive technology featured in the new BMW 2 Series Active Tourer. PDF, EN, 191.49 KB
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Technologie d’entraînement dédiée à la nouvelle BMW Série 2 Active Tourer. PDF, FR, 141.82 KB
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Tecnología de propulsión del nuevo BMW Serie 2 Active Tourer. PDF, ES, 94.88 KB
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La tecnologia della trazione integrale nella nuova BMW Serie 2 Active Tourer. PDF, IT, 109.48 KB