Excavators are asked to perform a variety of tasks—from digging foundations, to laying pipe, to crushing concrete—and the quicker they can accomplish these tasks, the better the bottom line for contractors. That is why heavy equipment manufacturers such as Komatsu America International Co. have made electronics, hydraulics, and computer systems an integral part of their machines.
Boosting the productivity of Komatsu's Avance line of Dash-6 excavators is the company's patented HydrauMind System. Featuring almost 200 Komatsu patents, the system's load-sensing (LS) and pressure-compensated valves automatically adjust to operating conditions based on the pressure and lever stroke detected. Electronic controls maximize engine operation so that full power is always available. Five working modes match engine speed and pump pressure to the application.
The load-sensing (LS) valves are the "brains" behind Komatsu's HydrauMind system.
|
Many excavator operations are made easier by HydrauMind. Even without operating the lever to the maximum position, maximum digging power can be obtained during reverse scraping operations because the arm can be moved slowly under full power. Digging through soft rock or pulling up boulders is easier because the system precisely controls boom raise, preventing the cutting edge from slipping. Fine-control lifting is possible because the system keeps lever control steady regardless of load size. Bucket loading is maximized during simultaneous operations because the equipment moves slowly at maximum power, without being influenced by the other actuators.
In a conventional open-center hydraulic system, as the load is increased, oil escapes via the neutral circuit, causing a decrease in actuator speed. When load on the actuator changes, work equipment speed changes even if the lever is kept in the same position. HydrauMind's closed-center hydraulic system does not allow load to determine actuator speed. Instead, lever stroke determines the amount of oil that the pump delivers (thus actuator speed) regardless of load. There is no neutral circuit, so the full amount of oil required from the pump flows to the actuator.
HydrauMind also ensures smooth operation when working in a compound operation. When moving the boom, arm, and bucket at the same time, all equipment works at the best combination of speed and power. When two or more actuators are operated at the same time, the oil is divided and sent to each actuator corresponding to the lever stroke, regardless of the size load. Excess oil does not flow to the circuit at light load, and operations can be carried out simply in accordance with the operating feel.
Four "Komatsu-exclusive" valves are what set the system apart from its competitors, according to the company:
LS EPC valve—Enhances fuel efficiency by reducing LS differential pressure to make swing speed proportional to engine rpm.
Pump merge/divide valve—Improves cycle time and fuel efficiency by automatically merging or separating the two pump outputs, depending on the application. The valve merges most of the time and divides for travel, fine control, or boom up plus swing.
LS select valve—Reduces travel shock while traveling and activating swing operations by canceling swing LS pressure. In addition, the boom accelerates faster for superior swing performance with 90° loading. And in swing priority, LS swing pressure is activated to make 180° loading easier.
LS bypass valve—Improves stability during operations by reducing hydraulic surge pressure of the LS line.
SAE Off-Highway Engineering April 2000
