Re-evaluating hybrid fluid chemistries
February 2022
© 2022. Afton Chemical Corporation is a wholly owned subsidiary of NewMarket Corporation (NYSE:NEU). 02/22. The information in this bulletin is, to our best knowledge, sure and accurate, but all recommendations or suggestions are made without guarantee since the conditions of use are beyond our control. Afton Chemical Corporation and its affiliates disclaim any liability incurred in connection with the use of these data or suggestions. Furthermore, nothing contained herein shall be construed as a recommendation to use any product in conflict with existing patents covering any material or its use.
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Re-evaluating hybrid fluid chemistries As shifting Chinese legislation rekindles the focus on hybrid solutions, investment in dedicated hybrid transmissions (DHTs) is increasing again. DHTs require specialist transmission fluids for optimum performance and Afton is spearheading a fresh approach to formulation: rooted in tradition, yet shooting firmly for the future. Alongside legislated emissions reduction, consumers are demanding good fuel economy from their hybrid vehicles and this has added impetus to DHT development. Designing a DHT from the ground up is a perfect opportunity for OEMs to revisit first principles and optimise the entire system, which includes more than just hardware. ‘However well designed, no transmission can work without one essential component: transmission fluid,’ says 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’.
Shifting performance priorities As DHTs become increasingly electrified, it is critical that the lubricant has suitable thermal and electrical conductivity properties and that it is also compatible with the range of new materials used in electrical systems. However these needs must be balanced against the traditional core performance priorities of wear protection and friction control. Without the torque converters and launch clutches, DHTs experience higher power transfer across gears, bearings and shifting clutches – which makes stop-start, climbing and towing extra demanding. At the same time, DHT synchros and clutches require sufficient friction to be able to function properly, while the gears will need minimal friction if energy efficiency is to be improved. ‘What all this means is that the gears and bearings in DHTs are at greater risk of wear than they are in a traditional transmission,’ explains Cleveland. ‘Consistent friction control, to optimise power transfer efficiency, must be balanced carefully with the wear protection properties of the lubricant’.
New approach to fluid development To maintain the right balance of performance, hybrid fluid formulation needs to focus even more closely on the types of additives being used. Additives can impact the fluid’s electrical conductivity and its compatibility with DHT hardware. ‘One of our first concerns, when we started developing lubricants for the pioneer BEV OEMs years ago, was how to maintain effective wear protection while using chemistries that are electronics-compatible,’ explains Cleveland. ‘Zinc-, sulfur- and phosphorus-based additives make effective and popular antiwear and extreme pressure (EP) agents. However, specific forms of each element can be more aggressive towards the sensitive materials used in electronics systems, such as copper, silver, tin and plastics. It is vital to choose the versions of each additive in order to balance gear and bearing protection with compatibility’. Cleveland continues: ‘Applying molecules more creatively to develop dedicated electrified transmission fluid (ETF) has highlighted just how the different types of friction modifiers, detergents and dispersants can affect other fluid properties in different ways. This has shaped our choice of chemistries for high-efficiency DHT solutions’. Not only is Afton exploring brand new componentry for these three classes of additives, it is also revisiting traditional components and examining how these could be applied in new ways. This involves going right back to the additive’s molecular structure and how that will impact relevant lubricant properties, not just looking at its designated function inside the DHT. Take friction modifiers, for example. The head group of a friction modifier determines its potency – how aggressively it will coat a given surface – while the tail group determines how much control it will give over friction quality. These actions must be considered with the degree to which the molecule will impact electrical resistivity and balance with the EP and antiwear chemistry. All this means that today’s hybrid ETF is being built quite differently to traditional ATFs, with existing chemistries – where used – often playing new roles.
© 2022. Afton Chemical Corporation is a wholly owned subsidiary of NewMarket Corporation (NYSE:NEU). 02/22. The information in this bulletin is, to our best knowledge, sure and accurate, but all recommendations or suggestions are made without guarantee since the conditions of use are beyond our control. Afton Chemical Corporation and its affiliates disclaim any liability incurred in connection with the use of these data or suggestions. Furthermore, nothing contained herein shall be construed as a recommendation to use any product in conflict with existing patents covering any material or its use.
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Re-evaluating hybrid fluid chemistries Planning for every eventuality One of the most challenging aspects of DHT fluid formulation is the sheer pace of vehicle electrification. ‘Today’s lubricant technology could be superseded in as little as 12-36 months, instead of the six- to seven-year lifespan one might have expected 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. The molecules being worked on at Afton today are designed to account for the needs of hardware in three to four years’ time.
Effective testing for future fluids OEMs are also seeking ever-longer oil drain intervals of up to 250,000 miles. Transmission fluid stability and longterm performance therefore become even more crucial, to ensure that friction, antiwear and electrical properties can be maintained as the lubricant ages. This again requires the fluid to be built in a different way, with a multiple role for many chemistries. No longer is it enough just to pass existing industry lubricant tests. ‘OEM designs have diverged considerably in the race for efficiency, and there is no consolidation of DHT parts,’ says Cleveland. ‘This diversity means that industry tests are now less valuable predictors of lubricant performance. We believe DHT fluids should be developed in parallel with pre-prototype hardware, using bespoke testing and rigs, to get the most effective and reliable outcomes’. Bringing engineers and chemists together at an early stage enables more relevant fluid screening tests to be developed, which have greater predictive value. This helps to mitigate the risk of issues appearing later in development. Afton is uniquely positioned to apply learnings from electronics-compatible BEV additive chemistries alongside its considerable heritage in traditional ATF. With the expertise to balance wear protection and friction characteristics within an electrified environment, Afton can help to unlock the full potential of next generation DHT designs. All while ensuring that fluids have sufficient performance reserve to remain relevant as the industry races onwards.
© 2022. Afton Chemical Corporation is a wholly owned subsidiary of NewMarket Corporation (NYSE:NEU). 02/22. The information in this bulletin is, to our best knowledge, sure and accurate, but all recommendations or suggestions are made without guarantee since the conditions of use are beyond our control. Afton Chemical Corporation and its affiliates disclaim any liability incurred in connection with the use of these data or suggestions. Furthermore, nothing contained herein shall be construed as a recommendation to use any product in conflict with existing patents covering any material or its use.