November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) David Richardson Research Assistant Analysis of Axial Piston Pump Lubrication & Dynamics

2 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) Outline Motivation & Objectives Background Pressure Profiles & Cavitation Adams Kinematic Model Aux Cam Forces –Contact Forces –Component Interference

3 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) 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

4 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) 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 Cam Plate Shoe Shoe Pocket Cavitation Shoe Port Plate Cam Plate 6 [1]

5 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) 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

6 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) 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 (19.0 o, 9.5 o,0.1 o ) 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

7 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) Contact Forces 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 - Shoe Path -Cam Plate 19.0º0.1º Assembly A º Assembly A – 0.1º

8 November 14, 2013 Mechanical Engineering Tribology Laboratory (METL) Component Interference 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 Assembly C º Assembly A – 19.0º