ARTICLE
Energy efficient fan drives like the compact A1VO provides opportunity to switch to a variable fan drive system which uses hydraulic power on as it is needed.
Driving multiple pump stack( s) in a system can also be accomplished by utilizing pump through drives. Most axial piston pumps offer a through drive option to allow for mating an additional pump to the back. These through drives are available in various sizes to allow for different mounting flanges such as SAE, A, B, C, or other standards. Many combinations can be created by this method, but one must consider the available maximum torque levels each pump or thru-drive can provide to the additional mounted pump. As well, there are maximum limitations in regards to bending moments / weights / lengths of the pump stack( rear support of the stack( s) may be necessary) and a limitation of the torque available at each pad.
Other considerations
Even with the cases mentioned, there are still other elements of the machine design that should be considered for determining the input method to the hydraulic pump. The impact of Tier IV final emissions on machine design should be considered. The additional engine exhaust after treatment systems will take up more real estate on mobile equipment. This will present new challenges for hydraulic systems as more pumps with higher power density will be required due to space limitations. These power dense pumps may be operating at higher pressures that may alter how the pump should be driven within the system.
Additionally, it is now well known that the upcoming Tier IV final engines show a more demanding torque / load ripple effect due to the higher injection pressures. As pumps are used on direct engine drives as well as PTOs, it is important to consider the amount of angular acceleration( rad / s2) fluctuation of the driven pump input. Most pump manufacturers have published limits of angular acceleration that the input shaft can withstand.
In summary, manufacturers of both On- and off-Highway equipment must consider the desired functionality of the machine while evaluating the best approach to transfer the engine power to the desired function. The pump drive is a key decision in the layout of the machine and overall performance for the OEM. Depending on where the hydraulic work is performed, e. g. at the cylinders on a boom or the wheel drives of a loader, the freedom that hydraulics provide allow the designer to place his components in multiple locations on a machine which cannot be surpassed by any mechanical drive. Pumps can be placed with complete disregard to the point of power usage. This is one of the major reasons designers of mobile machinery will continue to use hydraulics for years to come.
Hydraulics are used for many different mobile machine functions, all of which require a pump that provides the flow to accomplish the intended work. There are many options for where that pump is located, dependent upon the availability of a mechanical rotational power source to drive the input shaft of the pump. www. boschrexroth. com
may 2018 Global MDA Journal 27