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Transmission Fluids for Limited Slip Differentials in Arctic Conditions
At the Division of Machine Elements at Luelå University of Technology a research project called ¿Wet Clutch Tribology¿ are carried out in cooperation with Statoil Lubricants R&D and Haldex Traction Systems AB.
Haldex Traction is a supplier of all-wheel drive systems featuring an electronically controlled limited slip wet clutch differential working as centre differential, connecting the propeller shaft to the rear axle of the vehicle. The system is used in cars by companies such as Audi, Bugatti, Ford, Seat, Volvo and Volkswagen. In order to achieve desired properties of the system it is important to have transmission fluids that give the ¿right¿ frictional properties in order to transmit torque and suppress vibrations.
The all-wheel drive system have to operate at low temperatures, but the knowledge about the performance of different transmission fluids under arctic conditions, i.e. at temperatures ranging typically between 0 and -40ºC (+32 to -40ºF) are very limited today.
The aim of this thesis work is to investigate how several different specially developed transmission fluids perform at low temperatures, and based on this knowledge formulate new fluids in cooperation with Statoil Lubricants. This new fluid will give superior performance and an enhanced driving experience in arctic conditions compared to other fluids on the market.
The work will be divided into the following steps:
1. A literature survey will be conducted in order to understand which type of transmission fluids that are used for wet clutches, and which demands the fluid have to meet with respect to friction characteristics, pour point and so on.
2. Modify the cooling system of the clutch test rig that will be used for the measurements. Current cooling system gives a temperature of -25ºC, for this work we want to reach at least -50ºC.
3. Run a series of tests on different fluids consisting of different base fluids with a complete additive package. All tests will be carried out in a clutch test equipment using sintered bronze friction material from the commercial coupling.
4. Analyse the results, i.e. friction characteristics of each fluid, using Matlab software. Describe and classify the influence on friction from each base fluid in order to find the most suitable base fluid for further investigations.
5. Run a series of tests on different fluids with variations in the additive package, in order to find the most suitable additives for the final formulation.
6. Formulate a new fluid combination based on the results, and test this fluid.
7. Compare the new formulation with the commercial formulation and make suggestions for further optimization of the product.
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