Pumps, Controls Could Boost Off-Highway Efficiency

New diesel emission requirements could mean less engine horsepower for off-highway equipment, but they needn’t mean less power for hydraulic implements, say engineers from Sauer-Danfoss, Inc.

Sauer-Danfoss, a maker of hydraulic pumps, motors, and valves for the mobile equipment market, recently rolled out a series of efficient fluid power products that could help compensate for the forthcoming power reductions in next generation off-road diesels. The products, introduced at the recent International Fluid Power Exhibition (IFPE 2005) in Las Vegas -- include hydrostatic pumps and electronic controls. Both are aimed at helping OEM engineers make best use of the available power.

“The 100-HP engines of a few years ago have become 93 HP today,” notes Randy Rodgers product portfolio manager for hydrostatics at Sauer-Danfoss. “If we can give some of that lost horsepower back to the end users, then we can make them more productive.”

Indeed, engineers may need that extra power, especially in light of new Environmental Protection Agency (EPA) regulations for off-road engines. EPA regulations for off-highway vehicles stipulate a complex grid of four tiers of requirements, to be phased during a nine-year period starting in 2005. All of the requirements would cut nitrogen oxides and hydrocarbon emissions and, by extension, engine horsepower. As a result, hydraulic systems that depend on engine power would be affected.

To help users of off-highway equipment deal with those regulations, Sauer-Danfoss engineers rolled out a series of high-efficiency products, with the most prominent power savings coming from its new H1 family of servo-controlled hydrostatic pumps. The H1 pumps, which will initially offer between 147 cc/rev and 165 cc/rev, employ proportional solenoid control. By doing so, the new pumps eliminate the need for a small torque motor, which was used to feed about three-quarters of a gallon of charge oil to a pilot stage on previous hydrostatic pump designs, and thus used more power. In contrast, the new pump’s proportional solenoid uses little or no charge oil.

“It’s a force-balanced solenoid that requires no hydraulic supply pressure or flow,” Rodgers says. “All the pump needs is a pulse-width modulated 1.5-Amp signal and it’s ready to go.

Rodgers notes that conventional charge pumps typically draw about 3 HP, but do no work. Therefore, by eliminating the charge pump, as well as by improving the pump’s rotating parts, the H1 uses power more efficiently.

Users of the pump and Sauer-Danfoss’ other products also gain hydraulic power through the company’s Plus 1 electronic control network, which employs digital signal processing (DSP) and CAN-based communications. The company says that Plus 1 enables OEM engineers to address hydraulic power issues by employing software-based schemes to gain greater control of work and propel functions. The system includes a DSP-based microcontroller, input/output modules, joysticks, and graphics terminals. The company’s engineers say that engineers can use the Plus 1 to add features to their hydraulic systems without having to write the software code themselves.

“Whether it’s anti-stall of the engine, load-limiting, or speed control, the idea is that the sub-routines are already pre-packaged,” Rodgers says. “The OEM engineer just drags and drops the software modules into his vehicle management system.”

Taken together, Rodgers says, the controller, proportional solenoid, and new rotating group in the pump enable engineers to regain the hydraulic power that might otherwise have been lost as a result of the new EPA regulations.

“Anything we can do to give that power back is going to be important,” Rodgers says. “It’s a good deal for the vehicle designer and for the equipment operator.”