29-475: Haldex Traction is a manufacturer of intelligent all-wheel drive (AWD) systems, founded in Sweden . Since the invention of Gen I in 1998, the company produced several generations of products licensed to and customized for some major automotive brands, that in turn have marketed Haldex Traction AWD under different names. On 17 December 2010, American-based BorgWarner announced that it had signed an agreement to acquire
58-536: A differential between the front and rear drive shafts, and active management of torque transfer, especially following the advent of the anti-lock braking system (ABS). However, the designations AWD and all-wheel drive long predated the trend, with Associated Equipment Company (AEC) producing AWD trucks in 1929 in conjunction with the British subsidiary of the pioneering American firm Four Wheel Drive Auto Company . Additionally, General Motors began manufacturing
87-568: A ring gear is driven by a pinion gear connected to the transmission. The functions of this design are to change the axis of rotation by 90 degrees (from the propshaft to the half-shafts) and provide a reduction in the gear ratio . The components of the ring-and-pinion differential shown in the schematic diagram on the right are: 1. Output shafts ( axles ) 2. Drive gear 3. Output gears 4. Planetary gears 5. Carrier 6. Input gear 7. Input shaft ( driveshaft ) An epicyclic differential uses epicyclic gearing to send certain proportions of torque to
116-401: A common shaft. This forces both wheels to turn in unison, regardless of the traction (or lack thereof) available to either wheel individually. When this function is not required, the differential can be "unlocked" to function as a regular open differential. Locking differentials are mostly used on off-road vehicles, to overcome low-grip and variable grip surfaces. An undesirable side-effect of
145-418: A differential, which allows the two wheels to rotate at different speeds. The purpose of a differential is to transfer the engine's power to the wheels while still allowing the wheels to rotate at different speeds when required. An illustration of the operating principle for a ring-and-pinion differential is shown below. A relatively simple design of differential is used in rear-wheel drive vehicles, whereby
174-400: A gear ratio between the input and output shafts (called the "axle ratio" or "diff ratio"). For example, many differentials in motor vehicles provide a gearing reduction by having fewer teeth on the pinion than the ring gear . Milestones in the design or use of differentials include: During cornering, the outer wheels of a vehicle must travel further than the inner wheels (since they are on
203-405: A larger radius). This is easily accommodated when the wheels are not connected , however it becomes more difficult for the drive wheels , since both wheels are connected to the engine (usually via a transmission). Some vehicles (for example go-karts and trams ) use axles without a differential, thus relying on wheel slip when cornering. However, for improved cornering abilities, many vehicles use
232-687: A line as "all-wheel drive" as early as the late 1930s. This distinction in terminology is not generally used outside North America. In the context of hybrid and electric vehicles , the North American designation of 'all-wheel-drive' may differ. In some hybrid vehicles, the combustion engine is only mechanically connected to the front wheels, while the rear wheels are powered independently by an electric motor; this may be marketed as eAWD . Furthermore, many electric vehicles have individual, unconnected motors powering each axle, or even each individual wheel, also without any center differential. When tire grip
261-412: A pointer which constantly pointed to the south, no matter how the chariot turned as it travelled. It could therefore be used as a type of compass . It is widely thought that a differential mechanism responded to any difference between the speeds of rotation of the two wheels of the chariot, and turned the pointer appropriately. However, the mechanism was not precise enough, and, after a few miles of travel,
290-494: A regular ("open") differential is that it can send most of the power to the wheel with the lesser traction (grip). In situation when one wheel has reduced grip (e.g. due to cornering forces or a low-grip surface under one wheel), an open differential can cause wheelspin in the tyre with less grip, while the tyre with more grip receives very little power to propel the vehicle forward. In order to avoid this situation, various designs of limited-slip differentials are used to limit
319-454: A type of mechanical analogue computer, were used from approximately 1900 to 1950. These devices used differential gear trains to perform addition and subtraction. The Mars rovers Spirit and Opportunity (both launched in 2004) used differential gears in their rocker-bogie suspensions to keep the rover body balanced as the wheels on the left and right move up and down over uneven terrain. The Curiosity and Perseverance rovers used
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#1732859129524348-407: Is good during road driving, a differential is used between the axles to avoid driveline windup . This is not required off-road, as the limited grip allows the tires to slip. All-wheel drive vehicles designed for extensive off-road use may not have such a differential, and so they suffer from wind-up when used on-road. Selectable 4WD also avoids this problem and requires only a simple dog clutch in
377-484: Is one with a powertrain capable of providing power to all its wheels, whether full-time or on-demand. The most common forms of all-wheel drive are: Vehicles may be either part-time all-wheel drive or full-time: Particularly in North America for several decades, the designation AWD has been used and marketed – distinctly from 4×4 and 4WD – to apply to vehicles with drive train systems that have permanent drive,
406-410: The transfer case , rather than a differential. For this reason, most early off-road vehicles used that system; e.g., Jeep , Land Rover . As vehicles became more sophisticated and tires gave better winter performance in the 1960s, there was an interest in giving the benefits of all-wheel drive to conventional cars: not for off-road use but for winter use in snow or on wet roads. Exotic vehicles such as
435-449: The "correct" time, so an ordinary clock would frequently have to be readjusted, even if it worked perfectly, because of seasonal variations in the equation of time. Williamson's and other equation clocks showed sundial time without needing readjustment. Nowadays, we consider clocks to be "correct" and sundials usually incorrect, so many sundials carry instructions about how to use their readings to obtain clock time. Differential analysers ,
464-614: The Sun and Moon position pointers. The ball was painted black and white in hemispheres, and graphically showed the phase of the Moon at a particular point in time. An equation clock that used a differential for addition was made in 1720. In the 20th century, large assemblies of many differentials were used as analogue computers , calculating, for example, the direction in which a gun should be aimed. Chinese south-pointing chariots may also have been very early applications of differentials. The chariot had
493-600: The Traction Systems division of Haldex AB . BorgWarner completed the acquisition of the Traction Systems division on 1 February 2011. Haldex Traction Systems was incorporated in BorgWarner TorqTransfer Systems. The Haldex Coupling made its first appearance in the Audi TT , Audi S3 8L and VW Golf with an electronically controlled hydraulic-mechanical all-wheel drive concept. This system attempts to engage
522-539: The carrier is rotated (by the input torque), the relationship between the speeds of the input (i.e. the carrier) and that of the output shafts is the same as other types of open differentials. Uses of spur-gear differentials include the Oldsmobile Toronado American front-wheel drive car. Locking differentials have the ability to overcome the chief limitation of a standard open differential by essentially "locking" both wheels on an axle together as if on
551-408: The dial could be pointing in the wrong direction. The earliest verified use of a differential was in a clock made by Joseph Williamson in 1720. It employed a differential to add the equation of time to local mean time , as determined by the clock mechanism, to produce solar time , which would have been the same as the reading of a sundial . During the 18th century, sundials were considered to show
580-480: The difference in power sent to each of the wheels. Torque vectoring is a technology employed in automobile differentials that has the ability to vary the torque to each half-shaft with an electronic system; or in rail vehicles which achieve the same using individually motored wheels. In the case of automobiles, it is used to augment the stability or cornering ability of the vehicle. Non-automotive uses of differentials include performing analogue arithmetic . Two of
609-474: The differential's three shafts are made to rotate through angles that represent (are proportional to) two numbers, and the angle of the third shaft's rotation represents the sum or difference of the two input numbers. The earliest known use of a differential gear is in the Antikythera mechanism, c. 80 BCE, which used a differential gear to control a small sphere representing the Moon from the difference between
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#1732859129524638-468: The drivetrain. A new electro-hydraulic clutch actuator uses a centrifugal overflow valve design aimed at accurately distributing power between the front and rear axles, and eliminating the need for an accumulator, solenoid valve and filter. It also employs an integrated electronic control unit. The Haldex all-wheel drive system is currently used in the following vehicle models: 4motion All-wheel drive An all-wheel drive vehicle ( AWD vehicle )
667-401: The front axle and the rear axle in an all-wheel drive vehicle. An advantage of the epicyclic design is that it is relatively compact width (when viewed along the axis of its input shaft). A spur-gear differential has an equal-sized spur gears at each end, each of which is connected to an output shaft. The input torque (i.e. from the engine or transmission) is applied to the differential via
696-565: The high-powered Jensen FF followed by the AMC Eagle , Subaru Leone and Audi Quattro series were the first to offer all-wheel drive in a high-speed road-based car. These, particularly the Quattro, would extensively develop this drivetrain with the use of viscous couplings and differentials to provide a safe and drivable car. The first off-road / on-road hybrids such as the Range Rover also chose
725-537: The newly re-designed Land Rover Freelander 2 (LR2 in the United States). With enhanced capabilities, it is aimed at providing a more immediate off-road response. This generation of Haldex coupling is later shared with Volvo's complete lineup (Manufactured 2005–2008, depending on model) and is called "Instant Traction" in documentation by Volvo. Saab introduced a combination of Haldex Couplings on its 9-3 Turbo-X in late 2007, called XWD (Cross-Wheel Drive). This
754-512: The permanent all-wheel-drive system rather than manual selection. Differential (mechanical device) A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles , to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analogue computers . Differentials can also provide
783-470: The rear wheels when the front wheels start to slip. The second generation of Haldex coupling is an electronically controlled permanent 4x4 system with a Haldex differential calculating how much drive should be directed to the rear wheels. The Haldex system automatically distributes power between the front and rear wheels depending on slippage, but normally sends 95% of the power to the front wheels. The third generation of Haldex coupling made its appearance on
812-418: The rotating carrier. Pinion pairs are located within the carrier and rotate freely on pins supported by the carrier. The pinion pairs only mesh for the part of their length between the two spur gears, and rotate in opposite directions. The remaining length of a given pinion meshes with the nearer spur gear on its axle. Each pinion connects the associated spur gear to the other spur gear (via the other pinion). As
841-431: Was later introduced to the rest of Saab's lineup including the 9-3 , 9-3X, 9-5 and 9-4X . On 16 April 2009 Haldex announced a deal worth SEK4.5B (approx US$ 530M) to provide Volkswagen with a new AWD system for the company's new modular platform due in 2012. The GenV AWD coupling, now distributed by BorgWarner TorqTransfer Systems, features a new design aimed at reducing vehicle complexity and simplifying integration into
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