In brief
An axial piston pump is a positive displacement pump in which pistons arranged parallel to the drive shaft deliver hydraulic oil at high pressure.
Contents
What is Axial piston pump?
Several pistons are arranged in a circle around the shaft in a rotating cylinder block. A tilted plate or an angled axis makes them move back and forth with each revolution, drawing in oil and pushing it into the pressure line. Axial piston pumps achieve high pressures and efficiencies and are widely used in high-performance systems such as presses, rolling mills and injection moulding machines.
A distinction is made between swashplate and bent-axis designs. Changing the swivel angle changes the displacement; such variable displacement pumps can be adapted to demand via controllers, for example pressure, flow, load-sensing or power controllers. Fixed displacement pumps have a fixed angle. Key parameters are maximum displacement, rated and peak pressure, speed, direction of rotation, controller version, shaft end and mounting flange.
Typical damage is caused by contaminated oil, cavitation, inadequate case pressure relief via the case drain line and overheating. Wear on slippers, valve plate and pistons increases the leakage flow. Given the high replacement values, it is often weighed up whether a repair with new rotating group parts or a replacement is more economical. Oil cleanliness after the repair is decisive for the remaining service life.
In practice: maintenance and procurement
For a replacement, the complete type designation is crucial because it encodes displacement, controller, direction of rotation, shaft and ports. Before commissioning, the housing must be filled with oil via the case drain port.
Synonyms and abbreviations: variable displacement pump · swashplate pump · bent-axis pump · piston pump
Frequently asked questions
What is the difference between swashplate and bent-axis designs?
In the swashplate design, the cylinder block is coaxial with the shaft and the pistons are supported via slippers on an inclined plate. In the bent-axis design, the entire cylinder block is angled relative to the shaft. Swashplate pumps are compact and well suited as variable displacement pumps, while bent-axis units achieve larger swivel angles.
What does a load-sensing controller do?
A load-sensing controller adapts the pump’s pressure and displacement to the actual demand of the consumer. It measures the load pressure and maintains a constant pressure differential across the control valve. As a result, the pump delivers only as much oil and pressure as necessary, which significantly reduces energy losses and heat generation compared with fixed displacement systems.
What information is needed to replace an axial piston pump?
Required are the complete type designation from the nameplate, displacement, rated pressure, speed, direction of rotation, controller type with settings, shaft end, mounting flange, port sizes and, where applicable, a through-drive for a second pump. The serial number helps to identify special versions. Controller settings should be documented before removal.
Why is the case drain line important for axial piston pumps?
The case drain line returns oil from the pump housing to the tank without pressure. If it is too small, kinked or blocked, the case pressure rises and can destroy the shaft seal or cause the slippers to lift. The drain oil also carries heat away. The line must therefore be free and adequately sized.