Predicting the Behavior of Slipper Pads in Swashplate-Type Axial Piston Pumps

1996 ◽  
Vol 118 (1) ◽  
pp. 41-47 ◽  
Author(s):  
R. M. Harris ◽  
K. A. Edge ◽  
D. G. Tilley
Keyword(s):  
Dynamic Model ◽  
Dynamic Stability ◽  
High Speed ◽  
Axial Piston Pumps ◽  
High Speeds ◽  
Axial Piston ◽  
Plate Type ◽  
Simulation Package

This paper describes a dynamic model for slipper-pads that allows lift and tilt behavior to be predicted, including the effects of possible contact with the swashplate or slipper retaining plate. This model has been incorporated in the Bathfp simulation package and used to examine the dynamic stability of slipper-pads over the pumping cycle, and to compare the behavior over a range of pump speeds. The centripetal tilting moments acting on the slipper-pad increase with speed and as a consequence can lead to contact between the slipper and the swashplate at high speed. This is particularly likely to occur as the piston makes the transition between suction and delivery, where the pressure forces acting on the piston-slipper assembly change abruptly. The predicted nature of the swashplate contacts at high speeds correspond closely with witness marks on a dismantled pump. The model presented may also be used for predicting slipper behavior in other types of pump, for example, wobble-plate type pumps, or in piston motors.

The Suction Dynamics of Positive Displacement Axial Piston Pumps

1994 ◽  
Vol 116 (2) ◽  
pp. 281-287 ◽  
Author(s):  
R. M. Harris ◽  
K. A. Edge ◽  
D. G. Tilley
Keyword(s):  
High Speed ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Axial Piston Pumps ◽  
Positive Displacement ◽  
High Speeds ◽  
Suction Line ◽  
Pump Inlet ◽  
Suction Performance ◽  
Axial Piston

The suction dynamics of axial piston pumps become more critical if the pump is to be used at high speeds. In order to prevent air-release and cavitation from occurring within the pump it is necessary to pressurise the pump inlet. As the speed of a pump is increased, higher boost pressures are required, due to the extra losses incurred through the suction line and portplate at the higher flowrates. However, the lack of data regarding axial piston pump behavior at high speeds creates problems for the system designer in selecting suitable boost conditions and for the pump designer in selecting the portplate configuration that is required to reduce fluid-borne-noise levels. This paper discusses the suction performance of piston pumps, and presents experimental and simulation results exploring the behavior of a high-speed axial-piston pump. Different air-release and cavitation models that are suitable for simulation studies are investigated.

A New Yaw Dynamic Model for Improved High Speed Control of a Farm Tractor

2002 ◽  
Vol 124 (4) ◽  
pp. 659-667 ◽  
Author(s):  
David M. Bevly ◽  
J. Christian Gerdes ◽  
Bradford W. Parkinson
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Kinematic Model ◽  
Second Order ◽  
Lateral Control ◽  
Relaxation Length ◽  
High Speeds ◽  
Farm Tractor ◽  
Bicycle Model ◽  
Higher Order Models

This paper presents the system identification of a new model for the farm tractor’s yaw dynamics in order to improve automatic control at higher speeds and understand controller limitations from neglecting these dynamics. As speed increases, higher order models are required to maintain accurate lateral control of the vehicle. Neglecting these dynamics can cause the controller to become unstable at the bandwidths required for accurate control at higher speeds. The yaw dynamic model, which is found to be dominated by a second order response, is identified for multiple speeds to determine the effect of velocity on the model. The second order yaw dynamics cannot be represented by the traditional bicycle model. An analytical derivation shows that the model characteristics can, however, be captured by a model consisting of a significant (non-negligible) relaxation length in the front tire. Experimental results are presented showing that the new yaw dynamic model can provide lateral control of the tractor to within 4 cm (1σ) at speeds up to 8 m/s. These results are shown to be an improvement, at high speeds, over controllers based on models (such as a kinematic model) previously used for control of farm equipment.

Numerical Simulation of a Slipper Model for Swash Plate Type Axial Piston Pumps and Motors: Effects of Concave and Convex Surface Geometry

2012 ◽  
Vol 6 (4) ◽  
pp. 434-439 ◽  
Author(s):  
Toshiharu Kazama ◽  
◽  
Yukihito Narita
Keyword(s):  
Convex Surface ◽  
Sliding Surface ◽  
Surface Geometry ◽  
Axial Piston Pumps ◽  
Swash Plate ◽  
Convex Geometries ◽  
Thrust Pad ◽  
Axial Piston ◽  
Plate Type ◽  
Load Conditions

In this study, the slipper of swash plate axial piston pumps and motors is modeled as a hybrid (hydrostatic and hydrodynamic) thrust pad bearing. The effects of the slightly concave and convex geometries of the slipper sliding surface are examined. The motion of the slipper model is numerically simulated, and its tribological characteristics are examined under eccentric and dynamic load conditions. The calculations under these conditions indicate that, for the concave slipper, the fluctuation of the bearing pad azimuth increases, and the attitude of the slipper becomes unstable. In contrast, for the convex slipper, the attitude becomes stable, but the clearance increases.

Friction Forces Within the Cylinder Bores of Swash-Plate Type Axial-Piston Pumps and Motors

1999 ◽  
Vol 121 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Noah D. Manring
Keyword(s):  
Mathematical Model ◽  
High Speed ◽  
Hydrodynamic Lubrication ◽  
Stribeck Curve ◽  
Friction Forces ◽  
Swash Plate ◽  
Axial Piston Machine ◽  
Cylinder Bore ◽  
Axial Piston ◽  
Plate Type

In this research, the friction within the cylinder bore of a swash-plate type axial-piston machine is examined. Unlike previous research, this work develops a mathematical model for the friction based upon lubricating conditions which are described by the well-known Stribeck curve. Furthermore, a test device is built for measuring the frictional characteristics during low pressure and low speed operation and these results are compared with the mathematical model. For high pressure and high speed considerations, a numerical investigation based upon the model is conducted and it is shown that the friction associated with a pumping piston is greater than the friction associated with a motoring piston. It is also shown that increased piston speeds usually reduce the friction within the cylinder bore; however, a “cross-over” condition may exist where the increased speed will actually increase the friction as a result of increased fluid shear. Furthermore, it is shown that speed changes have a more significant impact on motoring pistons as opposed to pumping pistons due to a difference in the location of hydrodynamic lubrication within the cylinder bore. It is noted that this difference exits due to the bore geometry and the direction of piston travel.

scholarly journals A Study on Design of Notches in Valve Plate of Swash Plate Type Axial Piston Pumps Operated Bi-directionally

2016 ◽  
Vol 13 (3) ◽  
pp. 39-46
Author(s):  
Sae Ryung Choi ◽  
Ill Yeong Lee ◽  
Sung Min Han ◽  
Jung Woo Shin
Keyword(s):  
Valve Plate ◽  
Axial Piston Pumps ◽  
Swash Plate ◽  
Axial Piston ◽  
Plate Type

Centrifugal effects on cavitation in the cylinder chambers for high-speed axial piston pumps

Meccanica ◽  
2019 ◽  
Vol 54 (6) ◽  
pp. 815-829 ◽  
Author(s):  
Qun Chao ◽  
Junhui Zhang ◽  
Bing Xu ◽  
Hsinpu Huang ◽  
Jiang Zhai
Keyword(s):  
High Speed ◽  
Axial Piston Pumps ◽  
Axial Piston

scholarly journals An Empirical Model for the Churning Losses Prediction of Fluid Flow Analysis in Axial Piston Pumps

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 398
Author(s):  
Ying Li ◽  
Xing Chen ◽  
Hao Luo ◽  
Jin Zhang
Keyword(s):  
Power Density ◽  
High Speed ◽  
Flow Analysis ◽  
Piston Pump ◽  
Cylinder Block ◽  
Axial Piston Pump ◽  
Axial Piston Pumps ◽  
Wide Range ◽  
Fluid Flow Analysis ◽  
Axial Piston

The manufacturing development of axial piston pumps usually takes the trend of high speed and miniaturization, and increases power density. Axial piston pumps are usually characterized as high speed to improve the power density; thus, high-speed churning losses caused by the internal rotating components stirring the oil can increase significantly. In order to improve the efficiency, more attention should be given to the churning losses in axial piston pumps, especially in high-speed conditions. Using the method of least-squares curve fitting, this paper establishes a series of formulas based on the churning losses test rig over a wide range of speeds, which enable accurate predictions of churning losses on the cylinder block and pistons. The reduction coefficient of flow resistance of multi-pistons as calculated. The new churning losses formula devoted to the cylinder block and rotating pistons was validated by comparison with experimental evidence in different geometries of axial piston pumps. According to the prediction model of churning losses, some valuable guidance methods are proposed to reduce the energy losses of the axial piston pump, which are the theoretical support for the miniaturization of axial piston pump manufacturing.

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