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Analysis of Axial Piston Pump Lubrication & Dynamics. David Richardson Research Assistant. Outline. Motivation & Objectives Background Pressure Profiles & Cavitation Adams Kinematic Model Aux Cam Forces Contact Forces Component Interference. Motivation and Objectives.
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Analysis of Axial Piston Pump Lubrication & Dynamics David Richardson Research Assistant
Outline • Motivation & Objectives • Background • Pressure Profiles & Cavitation • Adams Kinematic Model • Aux Cam Forces • Contact Forces • Component Interference
Motivation and Objectives • Components within an Axial Piston Pump have shown signs of abnormal contact and wear causing damage and sharp temperature rises • Abnormal wear occur on the port plate of the pump as well as between the cam plate and the shoes • The objective of this research is to investigate and model the dynamics of the axial piston pump port plate and cam plate • Cavitation is the major cause of wear on the port plate • The geometric tolerances of the cam plate affect the performance and forces that act on it
Axial Piston Pump-Background • The cam plate at the bottom of the piston was modeled using Adams • Previous work has modeled the port plate using fluent showing cavitation in the transition regions from low to high pressure 1 2 7 Cavitation 6 3 Shoe Shoe Pocket 6 5 4 Cam Plate Port Plate Shoe Cam Plate [1] www.hydraulic-pump.info
Pressure Profiles &Cavitation • Pressure profiles were created for a step and inclined slider bearing • The model was used as the basis to include cavitation • Cavitation was then applied to a bearing with circular pockets • The model could possibly be applied to the geometry of a port plate
Adams Kinematic Cam Plate Model • Adams was used to create a rigid body dynamic model and the forces were measured at the contact between the shoe and cam plate • 3 different cam plate geometries (A,B,C) and 3 different angles (19.0o, 9.5o,0.1o) were tested on the pump • For the different geometries, A was a perfectly dimensioned cam plate, B and C had mismatched dimensions • The model was setup with a steady rotational velocity of the block • 50 rpm was used for numerical stability – higher speeds cause the solution to diverge
Contact Forces Assembly A – 0.1º Assembly A - 19.0º -Shoe Path-Cam Plate Hanger Angle Effects • At high angles the shoes contact the cam plate for only a short period of time • Clear, discrete spikes occur once per revolution • A handoff occurs between consecutive pistons with some overlap • At low angles the shoes remain in contact for a longer period of time • The handoff between shoes is smoother due to the lower elliptic path of the shoes 19.0º 0.1º
Component Interference Assembly A – 19.0º Assembly C - 19.0º • Assembly A – Perfect Machine Tolerances • At high angles the shoes contact the cam plate for only a short period of time • Clear, discrete spikes occur once per revolution and only one shoe is in contact at a time • Assembly C – Mismatched Shoe/Block/Cam Plate Dimensions • With mismatched dimensions, two shoes will contact the cam plate simultaneously causing “kicking” to occur • Contact occurs with pistons on opposite sides of the plate