How does a gerotor motor work?

A gerotor motor star has six teeth and seven lobes. The spaces among them are pressure chambers. Pump fluid flows into these pockets, creating high pressure in one chamber and low pressure in another. This creates an imbalance of forces, which causes the gerotor motor star to rotate, or orbit.

When selecting a gerotor or Geroler motor there are many items to consider. Performance. Quality. Reliability. Support. Cost. Sounds pretty basic, but with the influx of new entrants into the market, it is clear not all manufacturers are the same. Choosing the wrong one could lead you down the wrong path of costly recalls and frustration. Before selecting your motor, let`s discuss what sets a gerotor or Geroler motor apart from the others on the market.

The gerotor motor, or generated rotor motor, has been around for decades. In fact, the first gerotor motor in Eaton`s Geroler^® Portfolio was manufactured over 65 years ago. Soon after, Eaton invented the Geroler motor to meet the needs of the market and improve upon performance, reliability, quality and cost while still providing quality support.

Gerotor and Geroler motors use what is termed as the Orbit principle, which is what gives the motors their tremendous power density and compact size. A gerotor motor star has six teeth and seven lobes. The spaces among them are pressure chambers. Pump fluid flows into these pockets, creating high pressure in one chamber and low pressure in another. This creates an imbalance of forces, which causes the gerotor motor star to rotate, or orbit. A gerotor motor star orbits multiple times (image 1) – typically six to eight times depending on the specific star and ring geometry – for each complete single revolution within the outer ring. Eaton`s Geroler Portfolio uses the gerotor principle, but incorporate Eaton`s advanced Geroler technology (image 1). Geroler motors use rollers instead of lobes which reduce friction, wear, and improve low speed performance, extending the motors life.

Gerotor and Geroler motors deliver from 10 to 50,000 inch pounds of torque and can operate at speeds up to 2,000 RPM. Because of their simple design and compact size, they can be used in both mobile and industrial applications. However, they are ideal for mobile applications – especially agriculture, material handling and construction – because of their incredible power density.

Speed and torque requirements of the application will determine the size of a gerotor or Geroler motor. This will point users into what displacement (how much fluid is needed to turn one revolution) is needed. Speed and torque can be determined with the following basic motor equations. These are the starting points for finding the right sized motor.

Theoretical Torque (in-lbs) = CIR x Pressure differential/(2Pi)

Theoretical Speed (RPM) = GPM x 231 / CIR

So, when it comes to choosing which manufacturer`s gerotor or Geroler style motor to use in your machine, it`s just as simple as [Potato, pah-tato", right?

Not really!