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For simple systems with
a relatively low level of pressure (about 140 to 180
bar or 14 to 18 MPa) the
gearpump is the
most used type of pump. The gearpump is a very
simple, reliable, relatively cheap and less dirt
sensitive hydraulic pump. The pump in the picture is
driven in the indicated direction. As the gears
rotate and the teeth at the suction side come clear
of the meshing point, a vacuum is created and oil
flows into the spaces between the theeth. The oil in
the chambers is transported to the
pressure side
of the pump. There the teeth mesh and the oil is
forced out the spaces between the theeth into the
output port of the pump. The meshing of the teeth
prevents the oil flowing back from the pressure to
the suction side of the pump. So the oil is
transported from the
suction side to
the
pressure side
along the housing side of the gear wheels! The
pressure at the
pressure side
is determined by the resistance in the system. The
most important resistance is the load on the
hydraulic cilinder or hydraulic motor. In order to
prevent cavitation, the pressure at the suction side
of the pump should not exceed 0.1 to 0.2 bar (10 to
20 kPa) below atmospheric pressure (minimim absolute
pressure: 0.8 bar or 80 kPa). |
