Experimental investigation of the bearing of a radial piston pump focusing on the piston inertia force

In a radial piston pump where the pistons swing synchronously with the phase of the crankshaft, bearing condition measurements were conducted to improve the bearing design. Due to the swinging motion, the pistons are subjected to inertial forces that affect the bearing lubrication state and clearance distribution. In this study, these inertial forces were simulated by an externally applied pulling force, and the bearing conditions were measured under static conditions, excluding shaft eccentricity. The results indicated that, under most conditions, the bearing state temporarily changed in response to the inertial forces but subsequently recovered as the forces diminished. However, under certain conditions, the pistons were drawn toward the shaft during the application of inertial forces, leading to a non-recoverable bearing state. These findings suggest that, in specific cases, the wedge film effect continuously pulls the slipper toward the crankshaft, which may result in wear.