Pumps, Controls Could Boost Off-Highway Efficiency

Sauer-Danfoss' H1 hydrostatic pumps use proportional solenoid control to improve 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 in 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 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 1.5A signal and it's ready to go."