What are Gerotor Motors?

Blog | March 7th, 2017

In order to understand how Gerotor Motors operate, we need to cut into one to see how its parts work. The teardown shows the discrete parts in motion. Unlike common motor geometries, there are two gyrating rotors inside this positive displacement mechanism. Primarily, the outer rim of the internal rotor is equipped with a number of teeth. They project outward, interact with the matching inserts that form the outer rotor, and produce a pressure differential effect. Let’s take a closer look at this hydraulic motor.

Gerotor Motors in a Nutshell

Generator motors or Gerotors are used in the hydraulics industry to create positive displacement. The pumping action is generated as a result of an internal gearing architecture. The virtual gearing configuration is incorporated onto the inner rotor as a sweeping series of curving teeth. Typically, a six-star rotor interacts with a seven lobe outer rotor/stator to generate pockets of fluid energy. The off-center shaft of the motor rolls in accordance with the generated pressure differential, with one outer fluid pocket compressing to create a high-pressure cavity while its neighbour exhibits a slightly lower pressure differential.

Powerful Fluid Drive Mechanisms

The star-configured geometry within a high-performance Gerotor Motor produces an orbiting action, a rotational movement reaction that’s built on the small pressure differences exhibited by each curved tooth as it closes down on each concave lobe. Capable of directly converting fluid energy into high-velocity radial motion, these hydraulic pumps excel as hydraulic-to-rotational power converters. Applications for Gerotor pumps include hydraulic power systems, so expect to see one or more of these units in the fluid-powered machines that employ drive shafts. Oil pumps and fuel pumps also rely on this geometrical profile.

Compressive Alternatives

Sliding contact and orbiting pressure differentials use the standard star profile, but there’s at least one other working outline that compresses fluid and generates positive displacement. Primarily, we’re referring to the roller vane model, a compression-based Gerotor form that replaces the plain lobe shape with a matching number of rollers. The orbiting principle is maintained within this latter machine, but the supplementary components do improve overall performance. The lobe-less design experiences less friction, it doesn’t wear as quickly, and it performs better when lower speeds are required.

Gerotor Motors (Generator Rotors) only use two moving parts to create substantial quantities of radial torque. The design easily converts fluid energy into rotating power so that heavy shaft-mounted loads can be driven by the compact motor housing that is the Gerotor positive displacement pump.

Mobile Hydraulic Specialties Pty Ltd

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