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| Illustration 1 | g00869043 |
Main pump (1) Housing (2) Outlet port (left pump) (3) Swing pump (4) Outlet port (right pump) (5) Outlet port (swing pump) (6) Outlet port (pilot pump) (7) Right pump (8) Left pump (9) Inlet port | |
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| Illustration 2 | g00869075 |
Main pump (sectional view) (1) Housing (2) Outlet port (left pump) (3) Swing pump (4) Outlet port (right pump) (10) Pilot pump (11) Valve plate (12) Passage (13) Passage (14) Inlet passage (15) Inlet port (16) Inlet port (pilot pump) (17) Inlet port (swing pump) (19) Swashplate (20) Piston (21) Retainer (22) Shoe (23) Shaft (24) Guide (25) Creep plate (26) Barrel (27) Control piston | |
The main pump is constructed as a single body and functions as two pumps. The pump has barrel (26) in housing (1). There are ten pistons (20) in the barrel. The pistons direct oil into outlet ports (2) and (4) alternately. Five of the ten pistons make up left pump (8), and five of the pistons make up right pump (7) .
Oil from the hydraulic tank enters the pump through inlet port (15). Then, the oil is drawn through the inlet passage into swing pump (3) and pilot pump (10). Swing pump (3) and pilot pump (10) are directly connected to the main pump.
Shaft (23) is directly connected to the engine. Barrel (26) is splined to the shaft. When the shaft rotates, the barrel and guide (24) rotate. As a result, pistons (20), shoes (22), and retainers (21) rotate.
The shoes are connected to the pistons. When the shaft rotates, retainers (21) push the shoes against swashplate (19). At the same time, pistons (20) rotate on the inclined plane of the swashplate. As the shoes ride up on the inclined plane, oil is pushed out of the pistons. At the end of this stroke, the shoes follow the inclined plane of the swashplate. This action creates a suction, which draws oil into the pistons.
Oil from the hydraulic tank enters the pump through inlet port (15), and the oil is drawn through the inlet passages in valve plate (11). Oil that is pushed out of pistons (20) is divided into passages in the valve plate. Right pump oil flows out of outlet port (4), and left pump oil flows out of outlet port (2). The oil is directed to the right and left parts of the main control valve.
The pump regulator changes the angle of the swashplate according to the flow that is required for a machine operation. As the angle of the inclined surface of the swashplate changes, the stroke of pistons (20) changes, and the pump output increases or decreases.
Reference: For additional information on the pump regulator, see Systems Operation, "Pump Control (Main Hydraulic)".