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Schaeffler has been offering its vision of e-axles for some time: This 2-speed, parallel-layout e-axle was displayed at the Frankfurt motor show in 2017. (Schaeffler)

Top transmission engineers project big future for e-axles, advanced motors

Driveline electrification will transform everything from all-wheel-drive to Class 8 tractor-trailers, said expert panel in SAE Leadership Roundtable series.

A panel of high-ranking transmission and driveline engineers projected outsized adoption for electric-axle (e-axle) technology, as well as significant expansion of other driveline-electrification strategies now being adopted for new or near-future production vehicles. The engineering executives participated in a recent webinar in SAE’s Leadership Roundtable series, a virtual event replacing the in-person program planned for April’s SAE WCX 2020 conference that was cancelled because of the COVID-19 outbreak.

Most of the panel agreed that hybrid and other electrification strategies such as e-axles are the transition from internal combustion-based drivetrains to volume production and sales of battery electric vehicles (BEVs). “Long-term, BEV is going to be the better answer,” conceded Michael Solt, global head, transmission, driveline and axle at FCA USA LLC. But the EV solution – and when volume adoption happens – “depends on which market you’re in,” he added. But he said that COVID-related reductions in traffic volumes for many global population areas have palpably demonstrated the smog-reducing effect expected when EVs become mainstream.

On the path to EVs, the panel agreed, adding electric motors somewhere in the driveline in one of the so-called “P” positions (see graphic) can deliver a number of marked benefits, including the potential to use fewer gears in the transmission and adopt simpler yet potentially more-sophisticated all-wheel-drive (AWD) and 4-wheel-drive (4WD) systems. The latter is particularly attractive as the U.S. and other world markets gravitate to pickup trucks and SUVs purchased, at least in part, for their AWD capability.

For now, blending electric
Many said they believe driveline electrification for the U.S. market must prove itself in the large and heavy vehicles customers prefer. That’s why Ram Krishnaswami, Ford’s director, transmission & driveline engineering, promised his company soon will have a “no-excuses” hybrid-electric F-150 pickup in the market with an electric motor in the P2 position and a BEV variant of the F-150 in the near future. In the week following the Leadership Roundtable, Ford COO Jim Farley was even more direct, confirming the all-electric F-150 will launch within the next 24 months.

“The number-one-selling-car [in the U.S.] is the F-150,” added Patrick Lindemann, president of transmission systems & E-mobility at Schaeffler North America. “Nowhere else in the world do you see any other product like this. To completely electrify that is extremely difficult and extremely costly. For these bigger vehicles in the U.S., we have P1, P0, P2 hybrid strongly going in that direction.”

For FCA, first of the Detroit Three automakers to offer electrification in the fullsize-pickup segment with its eTorque starter-generator (P0 position) to boost the V6 and V8 engines of its Ram 1500, COVID-19 disruption put the company’s long-range plans only about three months in arrears, Solt said, adding that R&D planning is “on track.” He said electric machines in the driveline might lead to transmissions with fewer gears as one direct cost savings.

Gary Horvat, vice-president, eMobility at Navistar, agreed. “For commercial vehicles, you will see fewer gears,” he asserted, adding that heavy trucks and other commercial vehicles don’t require fast shifting times, which reduces pressure for passenger-vehicle levels of integration and refinement. He said Navistar is introducing electrification in commercial-vehicle segments first “where it makes sense in total cost of ownership.”

“We like dedicated hybrid transmissions; we call them DHTs,” Solt asserted. “Many times, DHTs (FCA currently uses one in the Chrysler Pacifica Hybrid) can be 20%-plus more efficient than add-on hybrids on conventional boxes. The beauty of a DHT is its efficiency. We don’t have a valve body and we have very few parts. We see DHTs as being really good for front-wheel drive (FWD).”

For RWD vehicles such as pickups and performance vehicles, Solt said FCA doesn’t view DHTs or hybrid transmissions as optimum. Instead, he said, “we prefer the add-on solution, the P2 solution, where you can have a base transmission with a P2 electric machine; P2s work out well for rear-wheel-drives.”

E-axle excitement, hotter motors
The driveline experts seemed most optimistic about e-axles in general, regardless of how many speeds their integral gearboxes might use. Typically at the rear axle, fitting an e-axle allows the elimination of the floorpan “tunnel” that typically houses the propshaft, not to mention discarding the numerous individual mechanical pieces of a propshaft and its related components.

Navistar’s Horvat said heavy trucks are on a fast progression to e-axles, as they offer the ability to operate the most amount of time in the highest possible efficiency – a fundamental equation for commercial-vehicle industry. And e-axles offer a higher potential for more-sophisticated driveline integration.

Solt said FCA soon will have an e-axle system in production for its Jeep brand, an icon with an image based on its rugged 4WD capability. At 2019’s Geneva motor show, Jeep unveiled Compass and Renegade plug-in hybrid models that both featured e-axle-enabled AWD. And Solt mentions a future Jeep BEV with 4WD/AWD completely via electric motors and possibly dubbed 4Xe. “E-axles are a beautiful thing,” he enthused.

The panelists said they also believe traction motors themselves have plenty of room for advance – higher-speed operation being a particular focus. Current drive motors generally have operating ceilings of around 30,000 rpm. Schaeffler’s Lindemann said, “The faster you can run an electric motor, the smaller you can make it.” But to exceed 30,000 rpm requires more-robust structures and cooling. However, “I’m convinced the industry will see motors that exceed 30,000 rpm,” he added.

How important is driveline electrification to near-term product plans? Solt said that by 2022, FCA will offer 30 nameplates with some type of electrification. And Ford’s Krishnaswami said for his company’s near-term lineup, “Pretty much every nameplate will have an electrified offering.”

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