Choosing the right hydraulic pump

WHILE MANY industries are impacted by the search for smaller machinery, construction and agriculture are at the forefront. Skid loaders, wind rowers and other traditional equipment in these fields have been decreasing in size for years, driven primarily by a need for greater efficiency. Whether that efficiency is needed to meet regulatory standards or simply to improve operational or overall costs, it is a key factor all designers must consider.

Of course, as efficiency demands increase, so have productivity demands. An efficient machine at the cost of an efficient jobsite helps no one, meaning the machinery needs to maintain power and maneuverability in a smaller and smaller envelope.

A growing shortage of qualified machine operators is beginning to force design changes as well. End users need equipment that is easier to operate, allowing for shorter training cycles, which helps get new operators into the field more quickly. Productivity gains also come from smoother, more precise machine operations – more effectively placing concrete or moving equipment from A to B without tearing up the ground – and of course, a less bumpy machine is also easier to operate.

This circular challenge of efficiency feeding productivity and vice versa ends with the question of reliability. End users look for efficiency of investment as well as fuel consumption and operation. What does it take for a machine designer to build a machine that will need less maintenance and be easier and cheaper to maintain when required?

With best-in-class hysteresis and the smallest package size on the market, Eaton’s new X3 back-to-back pump and single pump solution helps machine designers meet all these demands. The compact package size makes it easier for designers to fit the pump into smaller machines, a key given the direction of the construction and agricultural equipment markets.

Hysteresis

Hysteresis refers to an error based on past input, a variation caused by friction and drag of various interfaces in the control loop. In hydraulics, these interfaces are found in the servo valve, control piston, swash plate and rotating pump, mechanical feedback link and the swash feedback valve. This common problem can greatly impede the precision and repeatability of a machine, making it more difficult to operate, particularly for less skilled drivers.

Measured as a percentage of error against the pump’s peak flow, hysteresis levels range from 4 to 11%, with 5% typically found in pumps today. Though 5% hysteresis sounds small, this means that a 100cc pump commanded to half displacement could produce 50 cc – or it could produce 55 cc – depending on the previously commanded position. This variance can alter the output flow and require the operator to compensate in the input command to achieve the desired flow.

The X3 single and back-to back pump features the lowest available hysteresis on the market today. For additional hysteresis reduction, the pump can be paired with Eaton’s HFX controller, part of Eaton’s Dynamic Machine Control offering. By providing current to the solenoid valves, the controller helps minimise the difference between the desired position and the existing position via a swash feedback sensor. The sensor bypasses the sources of mechanical friction and backlash and allows the controller to dynamically adjust the solenoid valve current based on current working conditions. This further improves the pump’s hysteresis performance, as well as enabling a host of other control options.

When paired with an X3 cartridge motor, the pump and controls create a compact propel solution with best-in-class control accuracy.

When it comes to reliability, the X3 closed loop hydrostatic pumps family features swash roller bearings instead of the standard journal bearings. Swash roller bearings provide an additional hysteresis reduction, as well as reducing wear and tear on the machine. This cuts down on the need for ongoing maintenance, allowing for longer uninterrupted machine use and the productivity benefits that naturally stem from more uptime and less downtime.

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