PRODUCTS & SERVICES
Shifting priorities As hybrid solutions rise in popularity, learnings from dedicated BEV lubricant additives are proving valuable in creating new DHT additives While the automotive world is on a charge towards allelectric drive, there are still limited battery capabilities and charging infrastructure, which is why hybrid solutions are rising again in popularity, bringing with it greater investment in dedicated hybrid transmissions (DHTs). Behind this rapid DHT development is the desire to achieve maximum driving range with minimal environmental impact and cost. Eschewing heavy torque convertors and launch clutches, as well as reducing the number of gear steps enables OEMs to create smaller, lighter, less expensive hybrid transmissions with better fuel efficiency. However well-designed, no transmission can work without one essential component: transmission fluid, explains Chris Cleveland, leader of Afton Chemical’s ATF formulation team. “It interacts with the hardware in numerous ways, protecting and enabling, as well as influencing efficiency.” As DHTs become increasingly electrified, the thermal and electrical properties of the lubricant and its compatibility with electrical materials are critically required just as much as the traditional core performance priorities of wear protection and friction control. Without the torque converters and launch clutches, DHTs experience higher power transfer across the gears and bearings. This makes stop-start, climbing and towing extra challenging. Synchros and clutches require sufficient friction to be able to function properly, while planetary gears need minimal friction to improve fuel efficiency. “Gears and bearings in DHTs are at greater risk of wear than in a traditional transmission,” says Cleveland. “Consistent friction
The development of dedicated electrified transmission fl uid (ETF) has led to highly-efficient DHTs
control that optimizes power transfer efficiency must be balanced carefully with wear protection.” OEMs are also seeking everlonger oil drain intervals of up to 250,000 miles. Transmission fluid stability and long-term performance are crucial, and it’s not enough just to pass industry tests. “OEM transmission designs have diverged in the race for efficiency, with no consolidation of parts,” says Cleveland. “This diversity makes industry tests less valuable predictors of fluid performance. We believe DHT lubricants should be developed in parallel with the preprototype hardware, using bespoke testing and rigs.” Uniting engineers and chemists early on produces more valuable fluid screening tests, helping to mitigate the risk of issues appearing later in development, and unlocking the full potential of new hardware. DHT fluid formulation is also being made more challenging by the speed of electrification.
130 // July 2021 // www.electrichybridvehicletechnology.com
“Today’s lubricant technology can be superseded in just 12-36 months, instead of the six to seven year lifespan one might expect with traditional hardware development cycles,” Cleveland explains. “Creating new additive molecules takes a long time, so it’s vital that OEMs think about future-proofing their solutions. Molecules we’re working on today are targeting the needs of hardware in three to four years’ time,” he continues. “One of our first concerns when we started developing lubricants for pioneer BEV OEMs years ago was how to maintain effective wear protection while using chemistries that are electronics-compatible.” Zinc-, sulfur- and phosphorusbased additives are effective. They are popular antiwear and extreme pressure (EP) agents, but specific forms of each can be aggressive towards the sensitive materials used in electronics systems, such as copper, silver, tin and plastics. Therefore, it is important to choose
the versions of each that provide the balance between antiwear and EP protection, as well as a compatibility with materials. As Cleveland describes: “Applying molecules more creatively in developing dedicated electrified transmission fluid (ETF) has highlighted how different types of friction modifiers, detergents and dispersants affect relevant fluid properties differently. This has shaped our choice of chemistries for high-efficiency DHT solutions.” By applying the extensive learnings from electronicscompatible BEV additive chemistries that do not compromise on wear protection or friction characteristics, it can help unlock the full potential of diverse new DHT designs, complete with sufficient performance reserve to remain relevant as the industry races ahead. FREE READER INQUIRY SERVICE To learn more about Afton Chemical, visit: www.magupdate.co.uk/PEHV