Shibaura SG280E, Workshop Manual

Page: 79 / 111

75
4. Operation
1) Operation principle
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Pump circuit
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The following figure shows the rotating area of a swash plate type axial piston pump. Nine pistons are built into
the cylinder block.
The shaft is linked to the engine, and the cylinder block rotates as the shaft rotates. (The swash plate does not
rotate.)
As shown in the figure, if the center of the shaft axis is perpendicular to the shaft plate, locations A and B in the
cylindrical spaces of the cylinder block will have the same capacity. Therefore, neither intake nor exhaust is
performed, and the pump does not operate.
If the center of the shaft axis and the swash plate are tilted, the capacity of spaces A and B will change as
shown in the figure.
If the shaft rotates under this condition, exhaust is performed in the 180 degrees as the piston moves from A to
B, and intake is performed in the 180 degrees that it moves from B to A.
Therefore, a single pump is formed by connecting intake and exhaust piping to a crescent moon shaped port
(valve plate) as shown in the figure.
Fig.5-3-4
Fig.5-3-5
Cylinder block
Valve plate
Discharge plate