Axial piston machine

Axial piston machines can convert mechanical energy into hydraulic energy (axial piston pump) or, conversely, hydraulic energy into mechanical energy (axial piston motor).

Axial piston pumps provide maximum pressure.

How the axial piston machine works

The axial piston machine operates with reciprocating pistons that are parallel to the drive shaft. By contrast, the pistons in a radial piston pump are perpendicular to the drive shaft.

This makes the axial piston machine significantly narrower than the radial piston pump, but also considerably longer. Which pump type is best suited to a given purpose depends primarily on the available installation space. In terms of flow rate and technical complexity, both pump designs are comparable.

An axial piston machine consists of the following components

• Pump housing
• Cylinders arranged in a ring
• Wobble plate
• Connecting rods
• Pistons
• Inlet port
• Outlet port
• Central shaft

Function

The hydraulic fluid flows through the inlet port into the pump housing. From there, it is initially drawn in by the pistons. During the intake process, the piston travels along a 180° arc. At this point, bottom dead centre is reached and the piston begins the discharge process again. After a further 180°, this is completed and the cycle starts anew. The wobble plate angle determines the pump’s displacement volume. The rotary motion is driven by the drive shaft, which is usually powered by an electric motor.

Applications of the axial piston machine

The axial piston machine is used wherever particularly high hydraulic pressures are required. For this reason, it is the standard component of its type in heavy construction vehicles. Thanks to its slim design and the almost arbitrary positioning options, it can be integrated particularly well in these machines’ tight engine compartments. Other application areas for axial piston machines include hydraulic presses, high-capacity lifting platforms (for example on aircraft carriers) or lock gates.

How axial piston machines are maintained

Axial piston machines are among the most complex hydraulic pumps. Nevertheless, their maintenance and servicing are manageable. The components of these high-performance machines are designed to be correspondingly robust. The only notable weak point of axial piston machines is the seals. These are designed as multiple rings arranged in series. They are easy to replace and are usually changed according to a fixed maintenance interval. As with all hydraulic pumps, continuous self-lubrication by the hydraulic oil contributes to a long service life. The prerequisite, however, is that this oil is filtered continuously and replaced regularly.