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Optimizing hybrid design With the proliferation in hybrid transmission designs as the industry shifts toward e-mobility, lubricant design plays a critical role in solving performance challenges Legislation to reduce emissions means that every gram of CO2 that can be saved is hugely valuable. And as the automotive industry turns to hybridization and e-mobility to help meet stringent emissions targets, the transmission is at the heart of these changes. Transmission fluid should be viewed as a crucial engineering tool; after all, it touches more parts of the transmission than any other component. With the right additives, fluid performance can be customized and tuned to a fine degree – and yet many design engineers still regard fluid as a limiting factor. On the contrary; when hybrid engineers and lubricant providers work closely together, the resulting fluids can enable new hardware approaches. Afton Chemical works closely with OEM partners and hardware engineers, and a recent survey showed that hybridization has replaced the number of transmission speeds as the dominant OEM concern. With hybrid vehicle production volumes still low, the general trend is to adapt existing designs to create hybrid transmissions rather than developing units from scratch. As manufacturing plants prefer to
Lubricants can unlock efficiency directly or by enabling new engineering avenues
use just one transmission fluid for their whole range, hybrid requirements are now effectively dictating the lubricant needs for all cars. “Lubricant formulation requires a fine balance of components. Introducing new or enhanced requirements for hybrids, even in just one area, can impact all aspects of fluid performance,” warns Susie Hurley, senior adviser in automatic transmission fluid R&D at Afton. “For example, compatibility with copper is a basic ATF need that is even more critical for hybrid control system components like sensors and e-motors. However,
most of the anti-wear chemistries needed to protect gears and pumps are inherently aggressive toward yellow metals, so a major challenge is to create lubricant solutions that simultaneously protect the gears and the copper parts.” The price of getting this wrong can be rapid component failure. Electrical and hybrid lubricants must maintain low conductivity throughout their life to ensure safety as well as function. Even with a suitably resistive formulation, if gear wear occurs and the amount of metal in solution rises, conductivity will increase. The same can happen if the lubricant
Graphical representation of the varying effects fluids can have on copper parts within a vehicle’s powertrain
oxidizes at high temperatures. As e-motor speeds increase and energy recovery is routed through the transmission, fluids will need to provide cooling and remain thermally stable. “A further example is the drive to use lower viscosity fluids that provide much-needed reductions in energy losses; these can also make it harder to deliver traditional lubricant qualities such as wear protection,” adds Hurley. “Expert lubricant advice is invaluable during hybrid transmission development.” Afton is continuously problem solving with manufacturers that are leading the way in electric drives and hybridization. “OEMs need to be confident that the final lubricant solution will enable the transmission to function consistently and reliably throughout its lifetime. Testing to ensure robustness is essential, although designing meaningful tests that mimic real life on a shortened time-scale is no simple task,” says Harald Maelger, senior OEM relationship manager and hybrid expert at Afton. “Overcoming multiple challenges will require OEMs, oil marketers and additive companies to work collaboratively with trusted partners from early in the design process. That partnership is what I believe will offer the greatest potential for e-mobility advancements.” Being in control of fluid development can pave the way for the unlocking of new hardware designs. Furthermore, customized lubricants and tests can be created that will assure robust performance for the lifetime of these exciting new transmission styles. FREE READER INQUIRY SERVICE To learn about Afton Chemical, visit: www.ukimediaevents.com/info/tr
INQUIRY NO. 518
94 // September 2017 // Transmission Technology International