Compact Torque Vectoring Technology
opens up new Possibilities

Knowledge LibraryKnowledge LibraryCompact Torque Vectoring Technology
opens up new Possibilities
BorgWarner’s new drivetrain solution offers numerous benefits forOEMs and drivers.
By John Barlage, Director of Product Strategy, BorgWarner PowerDrive Systems

Introduction

The use of differential gears has been oneof the fundamentals of vehicle handling almost since the birth of the automobile because they allow driven wheels to adjust
their relative speeds during cornering. As asupplier of numerous drivetrain solutions,BorgWarner has always been at the forefront of developments with advanced technologies such as all-wheel drive (AWD)systems, electronic limited-slip differentials,
hybrid electric drivelines and torque vectoring systems. Compact torque vectoring(CTV), the company’s latest product, which
can be seen in Figure 1 , builds on its proven expertise in on-demand AWD applications and offers the next step forward inefficient drivetrain solutions. Due to theever-increasing demand for AWD solutions
across all vehicle segments, BorgWarnerhas developed a number of innovative technologies such as the highly successful AWD
coupling, which automatically distributes
torque from the primary driven axle to thesecond axle when required. BorgWarner’s
CTV technology takes this know-how to awhole new level. Offering a more progressive
approach to tracking stability and safety ascompared with systems like the electronicstability control (ESC), CTV induces a yaw
moment into a cornering vehicle. Unlike
other advanced driving assistance systems
BorgWarner Knowledge Library 201 6

such as ESC, which applies the brakes
when it detects loss of steering control, CTVchanges the torque distribution between theleft- and right-hand wheels to pre-emptively
improve handling and safety. Considerably
faster cornering as compared to brakebased systems such as ESC is the resultof using BorgWarner’s CTV technology.

Changes of differential drive torquefor enhanced stability

Used to improve the consistency of steering wheel input versus yaw rate, controlledchanges to the torque distribution between
the wheels on the left- and right-hand sideenhance the vehicle dynamics and the response. While the total drive torque remains
the same, the vehicle dynamics software

Figure 1 . BorgWarner’s compact torquevectoring (CTV) technology facilitates improved
handling, stability and vehicle dynamics.
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Figure 2. The CTV unit is considerably lighter
than existing series solutions and features a net
weight of just 1 3 kg, a length of 1 83 mm to thedrive shaft, a height of 207 mm and a width of1 98 mm.

determines the amount of differential drive
torque using input from different sensors foryaw rate, lateral acceleration, wheel speed
and steering angle.
BorgWarner’s demonstration vehicle features a standard front-to-rear AWD coupling and a modified rear differential with theCTV unit mounted on the left-hand side ofthe differential. The CTV unit consists of
two sun gears and twelve planet gears.
Transmitting torque between the differential
case and the left drive shaft, pairs of 1 9-toothand 21 -tooth planet gears operate on six concentric shafts surrounding the two 76-tooth
sun gears. When triggered by a reversible
centrifugal electro-hydraulic (CEH) actuator
based on the proven AWD coupling technology, torque can be transferred between the1 9-tooth wheel and the 21 -tooth wheel byapplying clamping force to a small wet
clutch located at the end of each planet
shaft. The CTV is inactive and the rear drive
unit works in the traditional manner if noclamping force is applied. The clutch clamping force is obtained via annular hydraulicpistons located on each clutch. By controllBorgWarner Knowledge Library 201 6ing the hydraulic pressure, it is possible toobtain the required torque vectoring effect.
An additional drive torque is transferred tothe left-hand rear wheel to increase its speed
by simultaneously applying force to theclutches of three of the shafts. Correspondingly, the speed and torque at the righthand rear wheel are reduced, and the resulting yaw moment causes the vehicle toveer right. Alternatively, by pressurising theother three clutches that slow down the left
hand side wheel, its torque and speed decrease, the differential automatically increases the torque and the wheel speed
on the right-hand side, and the resulting
yaw moment causes the vehicle to veer
left. While the vehicle is running straightahead, no hydraulic pressure is applied,so there is no clutch activity.

Increased vehicle dynamics, safety
and versatile production

OEMs benefit especially from the CTV’s
compact size, its low weight and versatility.
With a net weight of just 1 3 kg, a length of
1 83 mm to the driveshaft, a height of 207
mm and a width of 1 98 mm, the CTV unit,
as displayed in Figure 2, is considerably
lighter than existing series solutions. Additionally, its location at the side of the differential unit and its compact dimensions
help with vehicle packaging. Carryover axle
components can be used for reduced system cost since the torque vectoring components are packaged on one side of theaxle differential. The modular design, as
shown in Figure 3, allows low-impact platform integration, and this facilitates the useof the units in applications across different
vehicle platforms. Another advantage isthat the CTV components can equally beapplied to AWD systems based on rearwheel and front-wheel drive. As a simple2

“bolt-on” unit on the rear differential, CTV
can allow the same base vehicle or platform to be offered with or without optional
torque vectoring.

Moreover, direct actuation using the provenreversible CEH actuator is less sensitive tocontamination and more robust than systems comprising control valves. The flow is
directed in two directions, thus eliminating
the need for an additional valve. While allowing easy pressure sensing and detection by the pressure sensor, hydraulic actuation also provides excellent torque accuracy and low hysteresis.
BorgWarner’s new technology also offers
numerous benefits for the driver. Compact
torque vectoring helps to improve handling,stability and vehicle dynamics across allvehicle sectors. Enhancing vehicle dynamics and safety significantly by distributing
additional torque in fractions of a second,
the system features a torque vectoring capacity of up to 1 000 Nm. This technology
controls the torque distribution in critical
driving situations such as accelerating andsteering into a corner and provides smoothersteering responses as well as considerably
less steering input compared to similar cars
without torque vectoring. As a result, it offers superior vehicle handling, particularlyon slippery road surfaces.

Figure 3. Low-impact platform integration isenabled due to the system’s modular design,
facilitating the use of the units in applications
across different vehicle platforms and models.
BorgWarner Knowledge Library 201 6Contact

Email: technology@borgwarner.com
For more information please visit
borgwarner.com
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