What Is an Axial Piston Pump?

An axial piston pump is a piece of equipment that moves several pistons up and down. The pump typically does this with the displacement motion of a swashplate, a circular piece of metal with a hole in the middle that slopes down and then up on one side. It can be used as simply a pump or as a part of other assemblies such as an automotive engines or hydraulic motors.

A typical axial piston pump consists of a swashplate, piston, piston shoe, cylinder block or barrel, and valve plate. The pistons are placed vertically and at an equal distance from each other on top of the swashplate. Each piston is fitted with a shoe piece. The pistons fit into holes in the cylinder block. Then the block is placed over the piston and swashplate so that it completely covers the assembly. A valve plate is then secured to the top of the cylinder block.

The swashplate is key to the displacement motion of the axial piston pump. It is also commonly know as the cam plate, tilting plate, or wobbling plate. When the pump is in motion, the swashplate revolves so that it alternates between having the thick and thin part of the plate under pistons. This forces the pistons to move in and out of the cylinder block. The length of the piston motion depends upon the depth of the swashplate.

All parts of an axial piston pump must be precisely measured in order for the piece to function properly. The pistons in particular must be engineered so that there is enough space for them to be able to move in and out of the cylinder block, but not so much that they cannot keep straight. Each piece has an effect on the speed of the pump and the depth of the piston movement.

Axial piston pumps that are a part of another piece of equipment are often built to accommodate the space available. This means they can be bent or straight — also known as in-line — depending on the necessary configuration. A bent pump will rely on a specially constructed cylinder block rather than a swashplate for the displacement motion. The pumps are powered by engine or electricity, depending on where and how the equipment will be used.

Responding to a specific cue, an axial piston pump can be configured so that it functions on demand. This can help to save energy, as the pump is not constantly running. The feature is an alternative to the constant flow of energy expended by fixed displacement pumps.