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"We’re seeing on the order of 40% reduction in parasitic losses. We quantify that as about a 1% improvement in label-type fuel economy to the vehicle," noted AAM CTO Phil Guys.  (Lindsay Brooke)

Engineering a Quantum leap in drive axle efficiency

OEMs are increasing their focus on the vehicle driveline, working with Tier 1s to wring out greater efficiencies, mass and NVH reduction and cost. Making drive axles as efficient, light and ‘intelligent’ as possible was the impetus behind the new Quantum technology now being demonstrated by American Axle & Manufacturing. Quantum is a family of drive axles that AAM claims deliver a 30 to 40% mass reduction and 20% greater power density as incumbent axles with the same torque capacity. Phil Guys, AAM’s Vice President and CTO, recently spoke with AE about Quantum developments.

Where did the Quantum concept come from?

From a brainstorming session with AAM’s advanced engineering team. We’d just been through an internal project aimed at seeking greater efficiencies—new bearings, lighter weight lubes, superfinished hypoid gears. A very iterative exercise, but we concluded that all of us in the Tier-1 axle space can do that. From a product-functional perspective there’s not a lot of differentiation.

We had a significant dialogue about how do we truly differentiate ourselves in the market, knowing that customers want less weight, more efficiency, quiet operation, reliability and durability, at reduced cost. So our advanced team benchmarked products outside the automotive space, including aerospace, medical—anything with a torque element to it that had to transfer energy.

Six months later—this was in 2014—they came up with a proposal. And the idea that came out of it, now called Quantum, was so radical that we thought no one would want to buy it. Quantum technology is all about a totally different approach to the axle’s gear-support structure. The concept encompasses beam-axle and IRS [independent rear suspension] versions for rear-drive applications, and an AWD derivative.

What makes it ‘radical’?

Well, it doesn’t look like a traditional axle so there was a bit of skepticism from some of our customers. It is a different-looking animal so we were right to gather a tremendous amount of validation, development, efficiency, NVH and durability data in support of the technology. We also built models to prove that it’s a quiet axle when installed in a vehicle.

We built a beam axle, the biggest product in AAM’s portfolio. It’s the first application of this technology; we felt the truck market would be looking for weight and efficiency improvements as a priority. And in our prototype we saw a 30-35% weight reduction. A benchmark beam axle for a 1500-series pickup weighs 82 kg [180 lb]; the Quantum is 57 kg [125 lb]; that’s a 30% mass reduction. A benchmark 2500-series axle is 144 kg [317 lb]; Quantum is 98 kg [180 lb], so we took 30-40 pounds out of that. We haven’t even tried to quantify the savings on the vehicle side that can come from the “cascade” benefits we bring; we’ll let the customers do that.

Each time we applied the technology in a different application we saw weight-reduction improvements. On the AWD version the weight savings is about 40% relative to current-market technology. And we’re seeing on the order of 40% reduction in parasitic losses. We quantify that as about a 1% improvement in label-type fuel economy to the vehicle. We went through one iteration and found more opportunities to make it even better. We did a second iteration, tweaked it a bit more and started taking that technology to our customers about 14 months ago.

What’s AAM’s ‘secret sauce’ for Quantum?

I’m not ready to show the insides just yet. The center section is heat-treated 356. I can tell you that while the new ball bearings we’re using for ring-and-pinion support are from aerospace applications, their cost isn’t! We use tapered roller bearings for the differential. All of our efficiencies are coming out of the ring-and-pinion support. Those bearings are not double-row and are not preloaded, so we don’t use shims [typically used in axles to set pinion bearing preload]. The design is radical in this regard.

Is the IP in the case design and bearing saddles?

Yes, they’re totally different. But the innovation is in how we apply these bearings in an axle in the most compact, efficient manner.

Automotive Engineering will have a feature article on AAM’s Quantum axle technology in the May 2017 issue.

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