The agricultural market continues to demand mobile equipment that is both more powerful and more efficient. In response to this trend, a manufacturer of sugarcane harvesters began redesigning much of their equipment. Hydraulic systems for these machines typically use gear pumps for powering hydraulic systems. Although gear pumps are low cost, compact, and reliable, they are not as efficient as other types of pumps.
This presented an opportunity to increase machine efficiency and productivity—a combination that can substantially reduce fuel consumption. The goal was at least 10% to make their product more attractive to end-users. The OEM consulted with Parker’s Global Mobile Systems (GMS) team to create a new hydraulic system that would meet its new performance goals.
Parker’s P1 series variable-displacement, axial-piston pumps for open-circuit mobile applications offer compact, quiet and efficient, performance and can deliver a continuous operating pressure to 280 bar (4,060 psi).
Redesign Reduces System Complexity
GMS completely restructured the hydraulic system by switching to a variable-displacement open-circuit solution, using P1 Series pumps with Electronic Displacement Control (EDC) and F12 Series bent-axis piston motors. Parker’s P1 variable-displacement pumps have maximum displacement of 140 cc/rev (8.5 in.3/rev) and maximum flow of 278 lpm (73 gpm) at a max speed of 2,000 rpm. Maximum operating pressure is 280 bar (4,000 psi).
The F12 bent-axis, fixed-displacement motor features a proprietary spherical piston design that which provides high efficiency, speed, and acceleration capabilities. The result is high power density with reduced heat generation. The F12 motor is used on the fan blower to not only direct air through the machine’s radiator, but also to convey leaves and stripped chaff out the rear of the machine. The F12 motors accommodate pressures to 480 bar (6,960 psi) and produce output speeds to 7,300 rpm. Gear synchronization and double-tapered roller bearings provide robust and reliable operation in demanding applications for both open- and closed-loop systems.
This compact electronic solution reduced system complexity and increased efficiency, which reduces operational costs over the machine’s lifetime. Open-circuit EDC was chosen because a closed-circuit system would have required a charge pump and the losses associated with it as well as extra components needed for load sensing. The EDC hydraulic system also reduces the number of potential leakage points while providing better pump response and onboard diagnostics. Multiple P1 Series pumps were incorporated into the hydraulic circuit for different functions, including the primary extractor, base cutter, and fan drive.
The F12 series bent-axis hydraulic motor deliver operating pressures to 480 bar (7,000 psi) and speeds up to 7,300 rpm. Typical of bent-axis motors, the F12 motor has robust construction and can be used in both open- and closed-loop circuits. They are available in displacements from 30-250 cc/rev.
The P1 Series was chosen because of its high efficiency and power density. This combination provides high-efficiency power management by limiting torque to only that required by the load. Higher flow output at at different pressures and speeds allows the engine to use less fuel and produce less heat. This P1 pump was also equipped with a displacement sensor to monitor swashplate angle in real time. This allows users to achieve a more accurate flow output by closing the electronic loop via the sensor feedback, thereby allowing them to regulate overall vehicle power consumption more effectively.
The P1-045 pump used for the hydraulic fan drive system also features ripple chamber technology, which reduces noise and pressure pulsations. In conventional piston pumps, pumping chambers undergo wide changes in pressure with every revolution as they rotate through suction and discharge phases. These pressures create high reaction forces that, left unchecked, can cause cyclical deformation of pump case. Ripple chamber technology precompresses hydraulic fluid through each rotation of every pumping chamber to reduce the pressure pulsations, and, therefore, noise.
Measuring Equipment Performance
The results of the system lowered fuel consumption by more than 10%, exceeding the original goal. In addition, the system saves costs by simplifying the hydraulic system and reducing the number of components. It also provides better pump flow response and expands control versatility and stability that contribute to improved machine productivity.
Keith McDonald is product manager at Parker Hannifin’s Hydraulic Pump and Power Systems Div., Marysville, Ohio. For more information, visit www.parker.com/hps.
This article is based on an entry in Parker Hannifin’s Motion & Control Technology blogs. Click here to view the original material.