We think so, because OEMs can reduce the cost of harvesting machines used in agriculture by using Parker's Overcenter Intelligent Flow Control (IFC) architecture.
Closed loop hydraulic systems are commonly utilized for rotary functions. They provide a simple solution without additional valving but can be very expensive when compared to open loop hydraulics. In certain applications, closed loop systems are used, but may be over specified for the application. In these applications, a partial overcenter solution may be worth considering.
In looking at agricultural harvester machines there is an opportunity for OEMs to reduce the costs of harvesting machines using the Parker's Overcenter IFC architecture. There are many potential harvester machines that could benefit from this type of system including;
To see why these machines are an attractive application, think about the typical harvesting duty cycles. Reversing applications are rare and typically do not require full flow. Reversing is also a low duty cycle, sometimes less than 5 percent of the overall duty cycle. Typical operating pressures in normal conditions tend to be low. In some applications, only reaching a continuous pressure rating of the designed components under rare conditions.
When we design a hydraulic system we typically ask ourselves questions about the functionality of the machine. In terms of pumps, we investigate how pumps can be better utilized. For example, in the event of a function reversal, cleaning functions are typically turned off or idle. Can the flow from these functions be re-directed?
We also investigate what happens when clearing a blockage. We found that the heat rejection requirements are reduced, as the machine comes to a stop to address the blockage. The question then becomes, can flow be diverted from a cooling system momentarily to provide the reversal?
Parker's Overcenter IFC architecture uses our uniquely designed overcenter open loop pump in conjunction with a reversing valve and one additional flow source. This unique design works well in systems that tend to operate in a primary direction most of the time and only need to reverse direction for small isolated duty cycles.
The diagrams below compare a traditional system to Parker's Overcenter IFC system. First, we explore the harvesting duty cycle, a traditional system may consist of a closed loop crop conveyance function and an open loop cleaning function. During a reversal the cleaning function is turned off, while the closed loop changes direction to clear a blockage.
Traditional System Overcenter IFC System
Using the Overcenter IFC system, flow from the cleaning function is diverted to the blocked motor, the flow then returns to tank by driving the crop conveyance pump overcenter.
Because proportional control is provided by the pump, valves are needed simply to provide direction change, assuming directional control is needed. When designing these systems, pressure drop through a directional valve must be considered. High pressure drop can lead to excess heat and may reduce system performance.
Parker has designed custom low pressure drop manifolds which can be integrated into existing manifolds or mounted as a standalone component. These directional cartridges and manifolds are designed for high flow while maintaining pressure drop. Our target is to be no more parasitic than a charge system.
The R08E3 cartridge provides simple reliable directional flow control at 300 LPM while maintaining pressure drop at or below 3 bar. The R08E3 is also pressure rated to 420 Bar for high pressure systems.
There are three main reasons why the Overcenter IFC is superior. The first is cost: the closed loop systems tend to be more expensive than open loop systems. The second is that the system reduces complexity. There is no longer a need for a charge filter and there is no need for a flushing valve in the system. And, finally the system may provide superior efficiency, it eliminates charge losses, although valve pressure drop should be considered and minimized.
In many applications, we see cost and system simplification advantages to utilizing either the Parker Overcenter IFC concept. While not all systems are applicable, it is probably time to consider the Parker Overcenter IFC system during your next machine architecture redesign.
The Parker Global Mobile Systems engineering team and Hydraulic Pump and Power Systems Division's application engineering experts are available to assist our customers in designing and implementing new systems to meet your application needs.
This article was contributed by David Schulte, P.E., senior systems engineer, Parker Hannifin Corporation.