Axial piston machine

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Axial piston machine is a collective term for a device used in hydraulics (axial piston pump, axial piston motor). An axial piston pump converts mechanical energy (torque, speed) into hydraulic energy (volume flow, pressure). An axial piston motor is very similar in structure to an axial piston pump, but converts hydraulic energy (volume flow, pressure) into mechanical energy (torque, speed).

A major advantage of axial piston machines over other types is their great stability and good internal sealing, which enables high pressures. The power spectrum as standard axial piston machines ranges from 1.2 to 1,000 kW at speeds up to 12,000 rpm -1 .

Axial piston machines normally have odd numbers of cylinders to prevent vibrations (e.g. 6 cylinders would result in 6 pressure peaks per revolution, 7 cylinders result in 14 pressure peaks per revolution). Usual cylinder numbers are 7 or 9 cylinders. There are basically three types of axial piston machines:

  • Bent axis machine ; Depending on the swivel angle of the drive and pump axis, the pistons arranged in a rotating cylinder perform a stroke movement.
  • Swash plate machine ; Depending on the swivel angle of a sliding disk, the pistons arranged in a rotating cylinder perform a stroke movement.
  • Swashplate machine; Reversal of the principle of the swash plate machine. A rotating disc that is inclined to the axis forces the non-rotating pistons to make stroke movements. Swash plate machines are usually fixed displacement pumps because the swivel angle of the swash plate cannot be adjusted.

The main reason for using the swash plate is the possible mechanical through drive, which allows several pumps on one axis. Bent axis motors usually have a higher efficiency than swash plate motors. A difference in bent axis motors is the pivotability. So-called large-angle units allow a wide ratio spread in the hydrostatic drive. Motors in standard design, in turn, allow additional functions due to their zero pivoting capability.

Today, constant machines and variable motors are mostly used in bent axis design; However, variable displacement pumps are mostly used as swash plate machines.