A shifting market

New challenges for transmissions and fluids as fast changing automotive industry looks for e-solutions

The number of automotive OEMs across the globe pledging to reach net-zero emissions by 2050 is growing. As they work to meet these commitments, these organisations are looking even deeper into their technology platforms for contributions. The resulting drive for improved efficiency is having a dramatic impact on the transmissions technology landscape. Insight takes a close look at the shifts in the market and assesses the potential impacts these changes may have on the requirements for future fluids.

Just 10 years ago the transmissions technology mix was dominated by manual and conventional stepped automatic transmission designs. At that time, continuously variable (CVT) and dual clutch transmission (DCT) systems, although forecast for strong growth, appeared as mere blips on the global transmission installation bar chart. But, as the drive for CO2 emissions reduction forced OEMs to capture efficiency from the entire vehicle system, so the transmission landscape changed. Smaller, lighter automatic transmission systems with increasing numbers of forward speeds gained popularity, and CVT and DCT installations saw significant growth.

The continued drive for efficiency means we are now entering another period of change.

This time, in support of OEMs’ net-zero emissions ambitions via vehicle electrification, we can expect dedicated hybrid transmissions and reduction gearboxes to experience substantial growth. While these segments represent just over 10% of global installations today, in just six years time they are expected to account for more than one third, with most growth in reduction gearboxes, used in battery electric and some full hybrid all-wheel-drive vehicles.

global transmission installations by type

Growing market for fluids

The global car parc is about to pass the 1.5 billion mark and is continuing to expand, which means the service fill transmission fluids market is also expected to grow, with North America and China accounting for the majority of the growth. Demand for CVT and DCT fluids is expected to outpace that of automatic transmission fluids, mainly owing to their shorter drain intervals. Although the current global hybrid and electric transmission fluid market is small, the rising interest in these electrified vehicles means it is projected to double in this timeframe and to continue growing.

Today, conventional transmission fluids are commonly used in both full hybrid and battery electric vehicles. However, as the number of e-installations, where the e-motor is in direct contact with the fluid, increases and the designs become more demanding, bespoke fluids for these complex applications are required.

E-fluid challenges

These new tailored e-fluids must continue to deliver the traditional transmission lubrication requirements including oxidation control, frictional properties, wear protection and viscometrics. But, at the same time, they must also meet the new e-specific requirements of heat transfer, materials compatibility and electrical properties.

Heat transfer: Cooling is important, since high temperatures in these new systems may lead to loss of motor performance and demagnetisation, and winding heads and rotors may experience localised hot spots at peak loads. E-fluids must cool the windings and here, although a separate jacketed cooling system with a dedicated fluid can be used, it makes the system larger and more complex and is not as efficient as direct contact cooling. Direct cooling via e-fluids can improve motor efficiency and enable OEMs to introduce smaller, higher power density e-motors. This means that the fluid must be able to withstand higher temperatures and have a higher oxidation resistance.

Electrical properties: Higher voltages in electric vehicles enable faster charging times but also mean utilisation of newer materials that can handle such high voltages. Thus, with regards to electrical properties, e-fluids must have a balanced formulation for electrical properties, ensuring there are no electrical shorts or current leakages but equally, they must not be so insulating that a static charge builds up. Good electrical properties can also enable higher e-motor voltages, allowing smaller motors to deliver equal power, thus reducing overall package size.

Materials compatibility: A further challenge for e-fluids is their compatibility with the materials that are being used in hybrid and electric vehicles. Plastics of the connectors can be vulnerable to chemical attacks, copper windings may be corroded and resin degradation can occur. All of these issues can generate electric current leakages or even a short circuit in the transmission - making materials compatibility critical for e-fluids.

Click here to read our article on overcoming the challenges of optimising fluids for increasingly electrified powertrains.

Ultra-low viscosity adds complexity

Meeting the requirements of transmissions used in electric and hybrid vehicles must be carefully balanced with the need to optimise transmission performance and protection. This is particularly the case as fluids trend to even lower viscosities to help improve vehicle fuel economy in hybrids and vehicle range in battery electric vehicles.

transmission fluid viscometricsOver the past 40 years transmission fluid viscosities have been trending lower

As OEMs look to overcome the barriers to consumer electric vehicles acceptance (e.g. vehicle range) e-fluids will be expected to offer reduced energy consumption to enable the vehicle to travel further in pure electric vehicle mode. But, at the same time, these fluids must deliver improved heat transfer to cool both the electronics and the battery. To meet these extreme requirements it may be necessary to move to ultra low viscosity e-fluids, something that can be enabled by the use of next generation anti-wear additives.

We are now charting a new formulation space to break away from current performance trade-offs, of for example extending pure electric range vs. gear protection and resistivity vs. conductivity. In our view these next generation e-fluids are step out technologies, which will enable the optimisation of smaller, more powerful e-motor integrated transmission designs.

ultra-low viscosity fluids for battery electric vehiclesUltra low viscosity battery electric vehicles require step out fluid technology

Infineum has been working to develop transmission fluids tailored to meet the latest OEM requirements – which includes ensuring their suitability for use in electric vehicles.

Click here to watch a video on our broad portfolio of dedicated e-mobility products, covering all of the major hybrid and full battery electric vehicle models and tailored for every type of electrified transmission application.

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