Gerotor Gear Pumps
Gerotors are positive displacement pumps that are used in a variety of applications. The name Gerotor is derived from the words “Generated Motor,” and refers to an internal-external gear pump, where an external gear fits inside a rotor that consists of an internal gear, and the pair are in constant sliding contact. The outer rotor has one more tooth than the inner rotor, and the latter is located off-center to the outer rotor – this design allows the gears to mesh neatly at the top during rotation, while simultaneously partitioning the chamber volume between the rotors into constantly changing volumes, each first increasing and decreasing. At each increase, a vacuum is created, which sucks the fluid into the gear cavity; then as the volume decreases with the turning inner rotor, the fluid is compressed and forced out of the pump.
Gerotors are low cost hydraulic motors that do not use much power – hence, they may be found in multiple applications, ranging from simple to complex. Specifically, they are most suitable for clean, low pressure applications such as lubrication systems or hot oil filtration systems. A useful advantage is that the design ensures little to no pressure fluctuations at the intake port, making these pumps suitable for crankshaft triggered ignition engines. They are also the pump of choice in high speed engines, since the opening and closing mechanisms of the intake and output ports reduces the likelihood of turbulence and cavitation at high engine speeds. Gerotors are a good alternative to electric motors in outdoor applications, where dust and dirt could damage the windings of the electric motor. They are also the obvious choice for underwater operations, as they do not require bulky and expensive sealing.
