When choosing a gerotor motor, you need to consider multiple factors, including performance, quality, reliability, and cost. Choosing the wrong model can lead to a series of problems later on. Therefore, before finalizing a specific motor, it’s important to understand the basics of gerotor motors.
1. Orbital Motor: From Its Origin to Decades of Iteration
A standard orbital motor has a “star wheel” with six teeth and an outer ring with seven flanges. The spaces between the teeth and flanges form pressure chambers. When the pumped fluid enters these chambers, high pressure is generated on one side and low pressure on the other. This force imbalance drives the star wheel’s rotation (or “orbital motion”).
As shown in the figure below, the star wheel typically orbits six to eight times for each full rotation within the outer ring (the exact number depends on the geometric design of the star wheel and outer ring).
While the roller-type orbital motor uses the same cycloid principle, it replaces the flanges with rollers. This design reduces friction and wear, improves low-speed performance, and thus extends the motor’s life.
2. Performance and Application: Power Density is a Core Advantage
Gerotor and roller-type gerotor motors offer torques ranging from 1 to 5,600 Nm and speeds up to 2,000 rpm. Their simple structure and compact size make them suitable for both mobile and industrial applications. However, their extremely high power density makes them particularly well-suited for mobile applications, particularly in agricultural machinery, material handling equipment, and construction machinery.
3. How to Determine Motor Size? Start with Speed and Torque
The application’s speed and torque requirements will determine the motor size, which in turn will dictate the required displacement (the amount of fluid required to complete one rotation).
4. The Importance of Performance
Request mechanical and volumetric efficiency data, and ensure that these test data are from long-term operation. Some manufacturers may calibrate for peak performance during initial operation, but this performance will rapidly decline thereafter. This “short-lived” performance may not meet the actual needs of the equipment. Compare like with like: There is no standardized performance data for hydraulic motors, so be wary of ratings and test data that do not include comprehensive performance testing parameters.
5. Quality Determines Stability
Star wheel grinding processes are not one-size-fits-all: Grinding star wheel profiles beyond the capabilities of the profile grinder will result in inconsistent results. Pay attention to material quality to ensure the manufacturer is not using inferior materials (including heat treatment, profile grinding, and other process steps).
