Many technologies that improve the fuel efficiency of heavy trucks were announced at the recent Mid-America Trucking Show (MATS) in Louisville, KY, one such innovation being a tandem axle concept developed by Dana engineers for Class 8 linehaul applications.
The new Spicer AdvanTEK Dual Range Disconnect concept is optimized for trucks that implement engine “downspeeding,” combining the traction offered by a 6x4 configuration with the reduced drivetrain losses of a 6x2. The technology employs a single gear mesh configuration from the engine to the wheels.
Overall powertrain system efficiency can be improved by 2-5% compared to conventional 40k tandem axles paired with overdrive transmissions, the company claims.
“This is big news. No one has seen anything like this before,” Steve Slesinski, Director - Global Product Planning, Commercial Vehicle Driveline Technologies, Dana Holding Corp., told SAE Magazines on the MATS show floor. “Today people use primarily 6x4 tandem axles in North America for on-highway linehaul. Some fleets want to try 6x2s for fuel efficiency, where you have one drive axle instead of two. What this tandem [concept] does is it combines the benefits of [both].”
Spicer AdvanTEK Dual Range Disconnect allows the tandem axle to operate as a 6x4 with a traditional starting ratio at startup, on grades, at low speeds, during backup maneuvering, and on slippery surfaces. At a pre-determined speed, electronic controls in the axle coordinate with engine and transmission ECUs to disconnect the inter-axle shaft from the power divider, initiating 6x2 mode. The forward axle shifts to a faster ratio that enables engine downspeeding to as low as 900 rpm for highway cruise operation.
“The vehicle starts off in 6x4 mode and a higher-numeric axle ratio, say a 3:1 ratio, for example,” Slesinski explained. “Once you get up to a certain speed, it’ll disconnect the rear drive axle and shift to a faster axle ratio, say a 2.26:1. It’s very efficient, it slows the engine rpm down, and improves the fuel efficiency of the vehicle.”
By using separate axle ratios for low- and high-speed operation, the technology enables better acceleration than a 6x4 or 6x2 tandem axle with a single, fast ratio, according to Slesinski.
Dana engineers can program the 6x4-to-6x2 threshold in a variety of ways, he said. “Our truck [available for drives at MATS] is programmed to a certain gear—after ninth gear the axle shifts. But we can program it by the transmission [speed], by a certain speed of the vehicle, torque demand, or a certain traction demand.”
Dana has collaborated with Cummins for years on the development of solutions that enable engine downspeeding. Close integration of the engine and axle system controls is key to executing the Spicer AdvanTEK Dual Range Disconnect concept.
The dual-range disconnect technology improves fuel economy by reducing drivetrain losses in the inter-axle power divider, inter-axle shaft, and rear drive axle gearing. It also enhances net engine efficiency by better complementing torque curves, and can allow the use of smaller engine mounts and frame rails.
Dana has been evaluating a prototype of the dual-range disconnect technology for the past two-and-a-half years on the Spicer AdvanTEK 40 tandem axle and other high-efficiency axle platforms. The company plans to integrate the axle concept into manufacturers’ chassis for field testing this year.
“We’ve worked the issues out on how to do it, [but] getting this into a productionized model involves more tooling details, getting some more weight out of the design, and so forth, so that will be ongoing,” Slesinski said. “A lot of the development work [involves] how you shift the axle. There’s lots of way you interact with the engine and the OEM to accommodate that. So there’s a lot of good opportunity there for us to work together with an OEM.”
The North American market is Dana’s primary focus for the technology, with applications in Western Europe as well, he said.