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| Illustration 1 | g01179781 |
Main pump (1) Outlet port (right pump) (2) Outlet port (left pump) (3) Outlet port (swing pump) (4) Outlet port (pilot pump) (5) Housing (6) Inlet port (7) Swing pump (8) Right pump (9) Left pump | |
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| Illustration 2 | g01179712 |
Typical example of a piston pump's rotating group (10) Valve plate (11) Barrel (12) Swashplate (13) Shaft (14) Pistons (15) Retainer (16) Slippers (17) Guide | |
The main pump is constructed as a single body and functions as two pumps. The pump has barrel (11) in housing (5) . There are pistons (14) in the barrel. The pistons push oil into the outlet ports of valve plate (10) . Half of the pistons make up left pump (9) , and half of the pistons make up right pump (8) .
Oil from the hydraulic tank enters the pump through inlet port (6) . Then, the oil flows through the inlet passage into swing pump (7) and the pilot pump. Swing pump (7) and the pilot pump are directly connected to the main pump's inlet port.
Shaft (13) is directly connected to the engine. Barrel (11) is splined to the shaft. When the shaft rotates, the barrel (17) rotates. As a result, pistons (14) , slippers (16) , and retainers (15) rotate.
The slippers are connected to the pistons. When the shaft rotates, retainer (15) holds the slippers against swashplate (12) . At the same time, pistons (14) rotate on the inclined plane of the swashplate. As the slippers ride up on the inclined plane, oil is pushed out of the barrel. At the end of this stroke, the slippers follow the inclined plane of the swashplate. This action creates a space, which fills with oil from the tank.
Oil from the hydraulic tank enters the pump through inlet port (6) , and the oil flows into the barrel through the inlet passages in valve plate (10) . Oil that is pushed out by pistons (14) is divided into passages in the valve plate. Right pump oil flows out of outlet port (1) , and left pump oil flows out of outlet port (2) . The oil is directed to the right and left valves of the main control valve.
The pump changes the angle of the swashplate according to the pressure that is required for a machine operation. As the angle of the inclined surface of the swashplate changes, the stroke of pistons (14) changes, and the pump output increases or decreases.
ReferenceFor additional information on the pump regulator, see Systems Operation, "Pump Control (Main Hydraulic)".