Advanced electro-hydraulics makes off-road equipment cleaner, safer, and more productive. Interfacing engine controls with other subsystems can lead to cleaner-running off-highway equipment. M4 load-sensing control blocks from Bosch Rexroth offer a CAN-Bus interface. The sandwich-plate design features up to 10 elements, and can distribute flow to several functions that can operate simultaneously. Flow rating is to 180 lpm and pressure to 420 bar. Clean air and oil hydraulics would seem to have little in common. But new emissions requirements for off-road equipment are, surprisingly, driving the need for advanced and innovative mobile-hydraulic controls. Machine builders are turning to the latest electrohydraulic systems to improve vehicle efficiency and fuel economy, as well as make them safer and more productive. In the process they are meeting user demands for enhanced control, longer service life, easier diagnostics as machines become more complex and, of course, lower operating costs. A growing trend in mobile equipment is communication between the engine, transmission, and other vehicle subsystems, according to John Treharn, systems engineering manager at Parker Hannifin's Mobile Systems Div. ). The goal, he says, is to optimize performance, cut waste, improve vehicle safety, and provide status feedback to the operators. Key drivers are new EPA emissions guidelines for mobile equipment, and the new engines that the machines will require. "The Tier 2 and Tier 3 engine-emissions regulations are driving a lot of the need to have implements, cooling systems, and various other subsystems on the machine communicate with the engine," says Treharn. In these engines, an onboard computer monitors operating information such as speed, boost pressure, and crank position, compares it with ideal conditions, and sends out commands that control fuel-injection quantity, pressure, and timing. Thus, managing engine performance depends on knowing the demands from vehicle propulsion, steering, and other hydraulically powered systems. "We're taking information
