The dream team: Powder metal and x-by-wire technology

Light, small, strong and efficient: these are the parameters automotive engineers have to meet when working on "by-wire" application solutions for modern hybrid and full-electric powertrains. 

The challenge, for engineers, is to create new, unique technical product solutions that lower emissions, but do so at a reasonable cost level, ensuring market acceptance.

What role does powder metal (PM) technology play in supporting solutions to these challenges and how can customer partnerships enhance the playing field? 

I interviewed Stefan Tiller, who leads the advanced PM technology group for vehicle electrification at GKN Powder Metallurgy to discuss PM's role in vehicle electrification.

Stefan, sometimes the PM industry is perceived as a heavy and slow process. How could this technology  be a perfect fit for solutions to vehicle electrification on a large scale? 

Unfortunately, there are still some that have a prejudice about powder metallurgy technology. But honestly, when we are working together with young or experienced and open-minded engineers, they are really excited about the intelligent product solutions our PM technology offers.

PM allows for endless material compositions that are not feasible to do in traditional wrought steels. In electrified applications, magnetically active materials with very specific physical requirements are needed for functionality reasons. This is where we can offer a wide range of customizations; designing the material characteristics the way customer and application needs them.

On your question if powder metallurgy is a competitive technology for large scale? Definitely, and there are so many proven application examples established in the market where powder metallurgy is the best choice! Small gears, sliding bearings and especially structural components are known for their unique functional and economical advantages.

SMC E-Pump Stefan Tiller

Could you provide more concrete examples for typical applications in hybrid electric vehicles (HEVs) and fully electric vehicles (EVs)? 

Well, you'll find powder metal components as technical solutions in electromagnetical applications like linear actuators, E-Drive traction motors or electric pumps. For these applications, specific magnetic material characteristics are key - hence our soft magnetic sintered and non-sintered iron types (SMCs) are the perfect fit.

Another important area of application in the electrification trend of vehicles are "by-wire" applications. Steer-by wire, shift-by-wire and brake-by-wire applications have included sintered components for years and even decades and provide cost effective solutions. I still remember in 2006, when we started to deliver the first pair of belt pulleys in powder metal for an electrically assisted EPS steering system. Since then, this steer-by-wire application has spread from luxury vehicle classes to mid and even small class cars. 

I would also like to mention the break-by-wire application, where sintered components play a key role. Think about when you are parking your car. For around a decade, this functionality is performed by electric parking brakes. And as an add-on functionality, the  'assisted hill-start' offers additional safety and comfort. In both cases, the driver just pushes a button and the brake is electrically activated or released. In recent cars, emergency braking is activated when collision objects are detected by several types of sensors or integrated radar systems. This is only feasible with the brake-by-wire technology.

What is the exact role of PM in a brake-by-wire system?

The key technology in transforming the electric signal into an actuation force at the brake discs is done by a very powerful and lightweight mechanical actuator. The heart of this actuator is a small planetary gearbox set with high strength gears and toothed carriers; all made out of powdered metal components. This technology is responsible for converting the rotational movement of an electric motor into a lower speed ratio and into an axial clamping force that secures or opens the rear wheel discs. 

The same happens when you are switching gears by the paddle shifters on the side of your car's steering wheel. In this case, the hardware job of shifting the transmission gear inside the hybrid transmission is done by a planetary gearbox actuator produced out of hardened and annealed powdered metal components. This technology is known as shift-by-wire.

Shift by wire PM actuator, Concept_800x600

You have mentioned that a specific PM material - SMCs - are used for electric motor applications. What is the magic behind SMCs?

SMC material is based on pure iron powder where each particle is covered with a very thin isolation layer. It is called a 3D isotropic material and is crucial for reducing the so called eddy current losses in electrical systems.

This material allows for specific stator designs of e-motors creating a unique 3D-magnetic flux. That offers enormous advantages for the e-motor size, design integration capabilities and enables highest torque and power densities.

E-motors of this class are called axial flux (AFM) or transverse flux (TFM) motor types, also called e-motor topologies.

Let's put in perspective how powerful and effective SMC e-motors can be. Recently it was announced that Ferrari's new plug-in-hybrid car model Stradale F90 uses the YASA e-motor. This high-performance AFM type motor uses a double disc rotor and stator technology, made with SMC poles.  

Quite astonishing! It's obvious that electric AFMs and TFMs are not widely known. Why would you recommend that electrical design engineers consider researching this? 

First of all, thanks for asking this and helping bring light to the use of SMC powered e-motors!

While electrical engineers are happy with the electric efficiency and account for enough space for standard radial flux motors, I don't see a need to promote the use of AFM or TFM e-motor topologies.

As most recent automotive or industrial applications require higher efficiency, smaller and lighter sizes.  SMC based e-motor types comply with the highest expectations for power or torque density and overall efficiency. The assembly process is easier due to a less complex winding of the copper coils. This could also help for reduced investments on winding equipment.

The AFM motor especially allows for space-saving, integrated designs and supports small assembly spaces for e-pumps.

We know that the latest design and simulation softwares for electric motor design are normally capable to consider AFM and TFM types. You can find electromagnetic values of our soft magnetic iron materials, sintered and non-sintered (SMC) on our website by following this link.

high specific strength graph-2

We are here to support engineers around related topics touched in the interview. Learn more on our electrification strategy for powder metal on the website here.

If you'd like talk and touch base with myself and my team members in person, visit us at booth #22 at the upcoming Dritev 2nd International VDI conference - E-Drive, integral development of powertrains in Bonn Germany, July 10-11.

Thank you.