in-line swash-plate type axial piston pump

IN-LINE SWASH-PLATE TYPE AXIAL PISTON PUMP

1. Introduction

In the axial piston pump, rotary shaft motion is converted to axial reciprocating motion which drives the piston. Most axial-piston pumps are multi-piston designs and utilize check valves or port plates to direct liquid flow from inlet to discharge. Output can be controlled by manual, mechanical, or pressure compensated controls.

2. Fixed-Displacement In-Line Axial Piston Pump

An axial piston pump, in which the pistons are in line with the axis of the drive shaft, is illustrated in Fig.4.15.

As shown in Fig.4.15, the rotary drive motion is converted to reciprocating, axial piston motion by means of the swash plate (also known as thrust cam ōr wobble plate), mounted on the drive shaft. Thus the rotation of the swash plate produces in-and-out motion of the pistons in their cylinders and hence the fluid is discharged.

The axial pump illustrated in Fig.4.15 is a constant-displacement piston pump. That means constant volume of oil is discharged for a set rotor speed. In these, pistons are stroked by a fixed angle plate.

3. Variable-Displacement In-Line Axial Pump (Swash Plate Design)

This type of pump can also be designed to have variable displacement capability. This can be achieved by altering the angle of the swash plate. Because in the swash plate axial pump, the angle of tilt of the swash plate determines the piston stroke and hence the pump displacement. This is schematically illustrated in Fig.4.16.

As could be seen from Fig.4.16, the increase in the swash plate angle (0) will increase the piston stroke and hence the fluid displacement. When the swash plate is vertical (i.e., angle is zero), then the displacement will be zero. Even one can reverse the flow direction by changing the angle of swash plate. However, the maximum swash plate angle is generally limited to 171⁄2°, due to various design considerations.