THEORY OF OPERATION - CONTINUED
BRAKE AND HYDRAULIC FAN SYSTEM - CONTINUED
Pump is a variable displacement, axial piston type pump used to supply oil flow to control manifold. Movement of
piston assembly in pump draws oil from hydraulic tank. Oil is pressurized in pump. High pressure oil flows from
pump to control manifold to operate brakes and hydraulic fan.
When engine is in operation and drive shaft is driven by gears in engine, components that rotate are cylinder barrel,
piston assemblies, and slipper. There are nine piston assemblies in cylinder barrel.
Oil from hydraulic tank flows into pump head through pump inlet, then through inlet passages in valve plate.
When drive shaft rotates, cylinder barrel openings move toward valve plate inlet passages.
Each piston assembly inside cylinder barrel is held against swashplate by slipper. Swashplate angle determines
amount of oil pushed out of each cylinder barrel. Swashplate can be at any angle between maximum and neutral.
Neutral angle is perpendicular with drive shaft. When swashplate is at neutral angle, piston assemblies do not
move in and out of rotating cylinder barrel, therefore, no oil is drawn into or pushed out of pump. Pump has zero
displacement and zero flow.