World Innovation AX

29.05.2019 | written by Gabi Olpp

Piston pumps and motors have been established on the market for many years and are undoubtedly one of the most important components in a hydraulic circuit. The technology behind a conventional piston pump is both simple and complex: Several pistons (usually seven or nine) convert mechanical torque into oil pressure. In a piston motor, this process is reversed. Everyone who works with high-performance industrial and mobile applications will be very familiar not only with the positive aspects but with the negative ones as well.

The problems of current hydraulic systems

Every project engineer has experienced the limitations of piston pumps or motors: pressure pulsation and sub-optimal mechanical and volumetric efficiency at all operating points. In addition, the growing demand for electrically powered construction and agricultural machinery means that noise and minimum speed limits at high pressure are becoming more significant.

Industrial applications with ever-faster work cycles and high working pressures, more responsive dynamics and precise pressure and flow control, as well as the demand to reduce power losses, are pushing current pump technology to its limits. In today's applications, these limitations are often counteracted by using accumulators and auxiliary valves, which is associated with high energy consumption and high costs.

Say goodbye to the disadvantages

For these reasons, we decided to work with a new and better pump concept that solves many of the problems of the earlier pump technology. This is not just a further evolution of existing concepts, but a real revolution in the market: it brings better efficiency, excellent dynamics, low noise, and low minimum speed at high torque. Our piston pump is based on a principle in which the internal forces are balanced by having two rotating piston groups facing each other, both equipped with twelve pistons. This results in a very high power density and at the same time limits the axial forces, for which only a light bearing is now required.

After several years of successful research and development work, Bucher Hydraulics is now launching the new AX piston pump and the new AX piston motor, with displacements of 18 to 76 cm³/rev. In the future, units up to 115 cm³/rev will be available.

Advantages in numerous applications

The particular disadvantages that the AX series eliminates are shown in the following application examples:

Electrically powered construction and agricultural machinery

The characteristics of the AX pump have been optimized with a special focus on machines with electric motors. The high volumetric and mechanical efficiency, low noise, low pressure pulsations and permissible minimum speed of just 2 to 3 rpm, together with the ability to change the direction of flow by simply reversing the pump rotation, make the AX pump the ideal solution for the electrical and hybrid machines of the future.

Winches

In the standard version, the AX pumps and motors can be operated at a working pressure of 450 bar. The pressure rating on its own is not the most important advantage, however. For hoist winches, the start-up efficiency under maximum load is very significant. The AX motor achieves 99% start-up efficiency. This eliminates any troublesome breakaway effects. In the same situation, conventional axial piston motors achieve a start-up efficiency of only 60 to 65%, with stick-slip effects. Thanks to the high start-up efficiency, very slow and precise assembly work can be carried out. These characteristics are also ideal for crane slewing gears.

Industry

The high performance level of the new AX hydraulic pumps and motors means that they can also help in increasing energy efficiency. In addition, the AX shows its most notable advantages when high pressures at low speeds are required.

Wheel motors

The high power density, high working pressure and low permissible minimum speed make the AX motor an ideal drive motor. The minimum speed of 2-3 rpm at high pressure opens up new possibilities for mobile machines: For example, travel drives can be designed with new and higher ratios. For straight travel in vehicles such as crawler excavators, the advantage delivered by the higher volumetric efficiency of around 96% is that a higher travel speed can be achieved with the same size of unit.