Design and Analysis Improvement of Bidirectional Liquid Inlet Non-circular Gear Hydraulic Motor

In electromechanical actuation systems, non-circular gear hydraulic motors suffer from degraded lubrication between the commutation plate and gear end faces when using natural water as the working fluid. This wear increases axial clearance, reducing volumetric efficiency. To address this, we designed a bidirectional liquid inlet non-circular gear hydraulic motor, featuring an optimized commutation plate and inlet valve plate. Experimental testing revealed severe damage on the disassembled bidirectional commutation plate and rotor. Finite element analysis (FEA) showed that during forward rotation, the central deformation of the bidirectional commutation plate (19.2 μm) exceeded the axial clearance, causing surface damage. Structural modifications were implemented to constrain central deformation, reducing the maximum displacement to 3.8 μm—an 80.2% decrease. This enables the axial clearance to be controlled within 3.8 μm, eliminating surface damage while reducing leakage to 0.7% of the pre-improvement value. This work demonstrates the viability of bidirectional liquid inlet non-circular gear hydraulic motors and provides a critical reference for future designs.