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Bearings and engine components maker Schaeffler Group has developed a slim design of spur gear differential for passenger cars, which it claims is 30% lighter than its predecessors, while creating up to 70% free axial space in the gearbox.
The slim shape of the differential enables the use of new bearing concepts with optimised friction characteristics, which Schaeffler says will in turn have a positive effect on fuel economy and CO2 emissions. Ultimately, the lightweight differential will save space that can be used for larger dual clutches or transfer gearboxes, as well as making room for electrical components on hybrid electric vehicles.
Thorsten Biermann, project manager of advance development automotive transmissions at Schaeffler Group said: “Our spur gear differential offers enormous advantages. Compared with the original bevel spur gear differential, it saves up to 30 per cent in weight and creates up to 70 per cent free axial space because of its slim design. In absolute terms, this means up to three kilogrammes mass reduction for each differential and up to 90mm of extra space in the gearbox.”
In the 1950s, a mid-sized car weighed in at around 900kg. 50 years later, this figure had increased to around 1,600kg. This steep rise was due to a host of new safety and comfort features. Numerous electronic aids were also responsible for the additional vehicle weight, which actually runs counter to the manufacturer’s demand for lower fuel consumption and emissions.
Every kilogramme that can be saved from the overall weight of a vehicle is therefore critical, putting increasing pressure on vehicle manufacturers and their suppliers to minimise the size and weight of powertrain systems and engine components.
The design of the new lightweight differential was inspired by another project at Schaeffler. The company came up with the new idea after working on a planetary stage design for an automatic transmission manufactured for a metal forming process application. This inspired the team to come up with a differential in a planetary design for a typical mid-size passenger car.
Tests are currently being carried out on the differential, including some on gearbox test rigs. These will be followed by a design optimisation stage, after which Schaeffler will decide whether to move into series production of the lightweight differential.