Release time : 2015-06-11 08:45:18
By Bearing Manufacturer>Bearing News>Schaeffler Differential Holds Promise for OEMs
A new reduced-weight spur differential could dramatically increase the fuel economy of passenger cars.
In the 1950s, a mid-sized passenger car weighed around 900kg. Fifty years later, this figure had markedly increased to around 1,600kg. This steep rise was a result of a host of new safety and comfort features that were partly driven by consumer demand, yet ran counter to both the manufacturer's and the consumer's demand for lower fuel consumption and emissions.
But in today's energyand emissions-conscious world, every kilogramme that can be saved from the overall weight of a vehicle is critical, putting increasing pressure on both vehicle manufacturers and their OEM suppliers to minimise the weight of all the components in a car not in the least those in the vehicle drivetrain.
Recognising the importance of that fact, engineers at Schaeffler, a manufacturer of precision bearings and automotive engine parts based in Herzogenaurach, Germany, recently set about designing a differential for automotive applications that would address these concerns.
According to Thorsten Biermann, the engineer responsible for the development of differential systems at Schaeffler, the standard bevel gear differentials commonly found in vehicles have changed little over the years. Such differentials comprise a mechanical assembly of planetary and sun gears that enable each of the driven wheels of a vehicle to rotate at different speeds to prevent one or both of them from sliding when a car is making a turn.
Nevertheless, Bierman's design team saw an opportunity not only to reduce the weight of such differentials, but to create a design that would also sport a smaller, slimmer mechanical envelope. Better yet, they were determined to ensure that their new design would be less expensive to manufacture, have a higher reliability and be less noisy than existing products.
From a purely functional perspective, however, there is no difference between a traditional differential and the new Schaeffler design; they both perform exactly the same role, splitting the torque from an engine in two ways. The major dissimilarity is that, while traditional differentials use bevelled gears, the new Schaeffler differential makes use of spur gears for the inner gearing of its planetary gear set.
As far as weight is concerned, however, there is a big difference between earlier incarnations of such differentials and the Schaeffler design. While the new differential is claimed to be 30 per cent lighter than standard bevel gear differentials, it is still able to produce the same torque.
Indeed, if the Schaeffler differential were to be incorporated in a car with a manual transmission with an input torque of approximately 350Nm, it would come in at a mere 6kg, compared with earlier bevelled gear differential designs that would weigh nearly 9kg. According to Biermann, this weight reduction would not only have a dramatic effect on increasing fuel economy and reducing CO2 emissions in such a vehicle but, as an added benefit, reduce emissions during the manufacturing processes used to make the differential too.