ARTICLE
Mobile Machines : Options for driving hydraulic pumps
Electronically controlled hydrostatic fan drive systems reliably keep combustion engines at their optimum operating temperature , even under the most difficult of application conditions , enabling mobile vehicles to comply with strict emissions regulations for exhaust gas and noise .
Many of today ’ s on- and off-highway applications utilize hydraulics as a way to provide working energy that is more compact and precise than traditional mechanical methods . There are many components that comprise these systems such as valves , cylinders , motors , and of course a hydraulic power source , the pump .
The prime purpose of the pump is to convert the input of mechanical , rotational power into hydraulic power , meaning flow for the required functions on the machine . Hydraulics are used for many different mobile machine functions such as systems for transit drives , swing functions , boom operation , conveyor drives , etc . In all of these functions , there must be a pump located somewhere in the system that provides the flow to accomplish the intended work . Where that pump is placed in the system is dependent upon the availability of a mechanical rotational power source to drive the input shaft of the pump .
There are two separate base type applications , on and off-highway , that provide opportunities and distinct ways for pump mounting locations and drive inputs . Although there are a variety of options , keep in mind there is not one input that is preferred
Key considerations
• Typically , on-highway mobile machines mount hydraulic pumps on the side of the vehicle ’ s gearbox integrated power take-off units
• Dynamic performance and space requirements determine both the pump and mounting that works best
• Select motor size and drive based on pressure-flow-time cycle ( p / Q profile ) for the application
• Off-Highway equipment typically does not follow a pre-existing drive chassis and is designed for a specific machine purpose or activity .
• Options that are typically used in these applications are : engine flywheel case coupling , engine crankshaft , belt / pulley , single or multipad PTO ’ s , and pumps with built-in through drives
• Tier IV final engines show a more demanding torque / load ripple effect due to the higher injection pressures
• Make sure to consider the amount of angular acceleration ( rad / s2 ) fluctuation of the driven pump input in these designs
24 Global MDA Journal may 2018