PRODUCTS & SERVICES
Piston problem solver
78
FREE READER ENQUIRY SERVICE
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iVTInternational.com February 2020
MARCH 10-14, 2020
LAS VEGAS
South Hall 3 – S82119
FLUID POWER CONEXPO
BUCHER HYDRAULICS
NEW PISTON PUMPS AND MOTORS OVERCOME HYDRAULIC LIMITATIONS SUCH AS
HIGH-PRESSURE RIPPLE, AND LOW MECHANICAL AND VOLUMETRIC EFFICIENCY
RIGHT: The large, noncompensated
forces in
bent-axis motors need
to be absorbed by an
extra-large ball or roller
bearings
BELOW: AXFP fixed
displacement piston pump
is available in multiple
sizes with displacements
from 18 cc/rev up to 76
cc/rev
Piston pumps and motors have been established
in the market for many years, and they are two of
the main components, possibly the two most important,
in a hydraulic circuit.
The technology behind a conventional piston pump
is both simple and complex: pistons, usually seven or
nine in number, convert mechanical torque into oil
pressure. In a piston motor, the process is reversed. That
is the basis of piston-based hydraulic drive units, and
everyone who works with high-power industrial and
mobile applications will be familiar not only with their
positive aspects but with the negative ones as well.
Limitations
Every project engineer will have experienced
the limitations of piston pumps and motors: highpressure
ripple, less than desired mechanical and
volumetric efficiency.
In addition, the growing demand for electricallypowered
machines has exposed some inadequate
performance characteristics such as noise and minimal
shaft speeds when working at high pressure.
Industrial applications with increasing working cycles
and high working pressures, together with a need for
very responsive dynamics and accurate flow and
pressure control, have already identified the limitations
of current pump technology. These limitations are
normally compensated by using accumulators and
valves with associated high energy consumption and
additional costs.
New pump principle
For these reasons Bucher Hydraulics has introduced a
new pump concept that overcomes the limitations of
current piston technology, bringing to market not just a
further evolution of the existing concept but a
revolution that offers better efficiency, excellent
dynamics, low noise and low minimum speed at high
output torque.
The Bucher Hydraulics piston pump is based on a
new concept, which works on the principle of balancing
the internal forces by having two rotating barrel plates
facing each other and each possessing 12 pistons. This
achieves a very high-power density and limits axial
forces, which need only a light bearing to absorb them.
After several successful years of research and
development testing, Bucher Hydraulics is now proud to
introduce to the market the new AX piston pump and AXM
piston motor in displacements of 18-76cc/rev, with an
immediate target of extending the range up to 115cc/rev.
Electric machines
The characteristics of the Bucher Hydraulics AX pump
were studied with a particular focus on machines
powered by an electric motor. The high volumetric and
mechanical efficiency, low noise, low-pressure ripple and
minimum permissible speed of 2-3 RPM, together with
the possibility of enabling the pump to turn in both
directions, make the AX pump the perfect solution for
electrical and hybrid machines of the future.
Winches
In the standard version, the AX pumps and motors can
reach a working pressure of 450bar. This characteristic is
not the main advantage. In the low-speed range of just a
few RPMs, the AX motor has a start efficiency of 99%
against the 60-65% of a conventional axial-piston unit.
Thanks to this feature, the performance can be
significantly increased with the benefit of precise and
accurate crane movements. This characteristic benefits
crane slew drives too.
Industry
The performance of the new Bucher AX hydraulic pumps
and motors means higher energy efficiency. This high
performance is also evident when the unit must start
rotating and run very slowly under high load and
´high pressure.
Wheel motor
The high-power density, high-working pressure
and low permissible speed make the AXM motor the
perfect alternative to applying a gear motor. The
minimum speed of 2 RPM at high pressure brings
mobile machines into a new arena. New calculations are
now possible during the study phase, offering several
options in different and lower gear ratios. For straight
travel in vehicles such as crawler excavators, the
volumetric efficiency of approximately 96% will increase
ground speed. iVT
Author: Tiziano Cattani, product manager, Bucher Hydraulics
/pivt
/iVTInternational.com