Considerably lighter differentials for JTEKT Torsen

Sirris is helping JTEKT Torsen to optimise its products through better materials management and layout.

JTEKT Torsen based in the Belgian province of Hainaut specialises in the manufacture of differentials for cars of various makes. Its products are made of steel and cast iron. Taking into account the rules regarding CO2 emissions that have become ever stricter for the automotive sector, the company tries to lower the weight of its products without incurring additional costs.

Since the form and compactness of the differentials have already been optimised in the past, JTEKT requested Sirris to provide assistance to find options for the materials (steel and cast iron). The objectives are ambitious: a weight reduction of 50% without reducing the technical performance, and a reduction of production costs by at least 25%.

Sirris first modelled the differential and performed various digital simulations on the basis of forces that are exercised on the product when operational as determined by JTEKT while taking into account the feasibility of making the components. 

It soon became apparent that injection-moulded polymers would not be able to handle the mechanical load and that thermoplastic composites would have to deal with unacceptable delaminations.

Sirris demonstrated that the metal housing could be lighter while retaining its properties. Optimising the geometry and modifying the design resulted in a weight reduction of 25%.

Cast iron is no longer the best solution, but, when replaced by cast steel, the mechanical resistance is assured with a sufficiently high safety coefficient and the weight can be further reduced.

Sand moulds are being produced in Germany using 3D printing to cast a small series of items. The housing is to be tested on the JTEKT testing workbenches.

Calculation of the fabrication costs has indicated that the gain can be considerable.

Sirris will next attempt to make other components such as crown gears and sprockets lighter, although not much weight gain is expected there.
The cover (lid) of the differential, however, can be improved. This issue is currently being studied. A welded assembly will probably be lighter. Moreover, it will take up less space, which should provide space to a revised geometry and thus reduce the required material.

Within the framework of this CWality project funded by the Walloon Region, JTEKT has found experts at Sirris who looked with new eyes at the already optimised products and who are well-versed in using advanced calculation tools. The company has obtained insight into what is taking place in its differentials and, in particular, in the plasticity of the materials that had not been taken into account up to now.

JTEKT hopes to be able to provide a solution with added value to car manufacturers, attract new customers and to increase its market share, once the project is completed.

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You will find this success story and many others in the Sirris annual report of 2017.