259D Skid Steer Loaders Machine Systems – Piston Pump – High Flow (If Equipped)

General Information

Illustration 1g02853057

Location of Piston Pump (work tool)

(1) Piston Pump (work tool)

(2) Front section of the hydrostatic pump

(3) Outlet

(4) Inlet

Machines that are equipped with either the high flow hydraulic system use a two position piston pump for the work tool hydraulic system.

Hydraulic oil for the work tool control valve is supplied by the piston pump (work tool) (1). The piston pump (work tool) (1) is mounted on the front section of the hydrostatic pump (2).

Illustration 2g03401015

Typical of Piston pump (work tool)

(5) Head

(6) Actuator piston

(7) Bias spring

(8) Piston

(9) Slipper

(10) Housing

(11) Input shaft

(12) Swashplate

(13) Slipper retainer

(14) Cylinder barrel

(16) Valve plate

The piston pump (work tool) (1) is a two position axial piston pump. The displacement of the pump is determined by the angle of the swashplate (12) which is shifted by the actuator piston (6) which is driven by oil pressure from behind. The oil to drive the actuator piston (6) is controlled by the high flow solenoid which receives an electrical signal from the ECM when the conditions for high flow are met.

The machine will provide high flow capabilities when the following conditions are meet:

  • A high flow work tool has been detected at the work tool harness.

  • The auxiliary command (right-hand thumb wheel) is above 80%.

When the engine is in operation and drive shaft (11) is rotating, the components that rotate are cylinder barrel (14), pistons (8), slipper pads (9), and the slipper retainer (13). There are nine piston assemblies in the barrel assembly. The components of the pump that remain are fastened to pump housing (10) .

Oil from the hydraulic tank flows into pump head (5) at inlet passage (4). The oil then flows from inlet passage (4) through inlet passages in valve plate (16). When drive shaft (11) turns, the openings of cylinder barrel (14) move toward the inlet passages of valve plate (16) .

Each piston (8) inside cylinder barrel (14) is held against swashplate (12) by the slipper retainer (10). Swashplate (12) can be at either the standard flow angle (30cc displacement) or the high flow angle (45cc displacement).

As pistons (8) follow the angle of swashplate (12), the pistons move in and out of cylinder barrel (14). When pistons (8) move out of cylinder barrel (14), oil is pulled into cylinder barrel (14) .

The angle of swashplate (12) determines the amount of oil that is drawn into cylinder barrel (14). As cylinder barrel (14) rotates, the swashplate angle pushes pistons (8) back into cylinder barrel (14). Pistons (8) will then push oil out of cylinder barrel (14). The oil then flows through the outlet passages of valve plate (16) .

The discharge of oil is greater when the angle of swashplate (12) is greater. Oil is discharged through valve plate (16) to outlet passage (3)

Illustration 3g03401018

Typical of a Piston Pump (work tool)

(3) Outlet

(4) Inlet

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