Analysis of Common Failures in Cycloidal Hydraulic Motors: How Many Have You Encountered? Stalling, Overheating, Oil Leaks

As one of the three main types of hydraulic motors, cycloidal motors are no stranger to those in the hydraulic industry. Cycloidal hydraulic motors typically feature compact sizes, lighter weights compared to other motor types, and a speed range suitable for most machinery. Most importantly, they are more affordable than gear motors and piston motors.

Working Principle

The internal structure of a cycloidal motor involves the coordination of a stator and rotating vanes. Two independent oil chambers, connected via a drive shaft, drive the vanes to oscillate within the structure. When one chamber receives oil, the other discharges it, causing the vanes to swing back and forth. The rotor and stator form a cycloidal pin gear engagement pair. When pressurized oil acts on the rotor, hydraulic torque creates planetary motion (rotation and reverse revolution) around the stator center via an eccentric distance. As the intake and discharge chambers alternate, the volume expands and contracts, pushing oil out through the distribution mechanism.

Cycloidal Motor Oil Leakage

Oil leakage refers to abnormal hydraulic fluid escape from the motor’s seals.

• Primary Cause: In 80% of cases, leaks stem from seal issues—aging seals, poor-quality seals, or mismatched seals. Replacing the seals usually resolves the problem.

• Other Causes: Excessive internal pressure due to a blocked or missing drain port, which deforms seals. Rare cases include improper installation damaging seals or excessive back pressure in the return line.

Cycloidal Motor Overheating

Overheating occurs when the motor’s temperature rises abnormally during operation, often manifesting as a hot exterior or even affecting system stability.

• Key Factors:

1. Mechanical friction: Prolonged overload operation increases flow, raising housing temperature.

2. High back pressure: Causes both leaks and overheating.

3. Internal wear: Component wear leads to internal leakage, bypassing oil chambers and reducing efficiency.

As taught in middle school physics: energy cannot disappear but transfers. Excessive heat indicates energy conversion in unintended areas.

Cycloidal Motor Stalling

Stalling refers to the motor failing to rotate after the hydraulic system starts, even with proper oil supply. Note: Stalling ≠ motor failure.

• Common Causes:

1. Insufficient drive force: Low system pressure (e.g., pump output below startup torque) or relief valve setting too low.

2. Internal blockage: Foreign objects or severe wear jamming components.

3. Oil flow issues: Insufficient flow, clogged lines, or reversed inlet/outlet ports.