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