Lubrication Technology Innovation and Solution for Electric Vehicles: A New Scuffing Test Method
With the rapid development of new energy vehicles, especially electric vehicles（EVs), there is a strong demand for a lubrication technology upgrade for EVs. To achieve energy savings, more stringent requirements of transmission efficiency are put forward on EVs. One electric drive system will become the mainstream of EV power systems. New energy vehicle lubricants require much lower viscosity (3-5 mm2/s) to achieve high transmission efficiency, in addition to meeting the lubrication requirement of high speed (up to 20,000 rpm) gear and bearing, excellent extreme pressure load carrying capacity and anti-wear performance. Furthermore, in order to achieve higher speed, the electric motor needs to be cooled with the oil directly.
Based on the technical requirements of new energy vehicles, a new generation of power transmission oils was developed to meet the integrated lubrication requirements of oil-cooled motors and transmission of new energy vehicles. It has a lower viscosity, high transmission efficiency and high load carrying capacity. Its viscosity is between 3-5 mm2/s, it has a FZG(A10/16.6R/90) load carrying capacity above 7 stage, and is based on special additive technology.
PetroChina Lubricant Company developed a new test procedure to determine the scuffing temperature limit of lubricating oils. The new test method also uses the SRV test machine to measure the temperature limit for operating a lubricant under prescribed conditions. It is a temperature step increase test. Scuffing is indicated by a sudden increase in the coefficient of friction at a given temperature. The method has been determined to be highly repeatable. The ASTM D02 research report reveals a repeatability r of 12.9 Kelvin (K) and a reproducibility R of 17.3 K, which means scuffing occurs within 1-2 temperature steps of 10 K. The method determines the ability of non-extreme pressure lubricating oils to resist scuffing. Furthermore, the friction coefficient of the oils can be monitored to assess their tribological performance and retention over a range of temperatures. PetroChina has found the test method useful as a screening test for engine oils, gear lubricants and turbine oils—where temperatures may reach up to 300°C.
