Construction
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| Illustration 1 | g01238113 |
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Main pumps (1) Port (negative flow control pressure for drive pump) (2) Outlet port (pilot pressure) (3) Idler pump (4) Outlet port (idler pump) (5) Inlet port (supply oil from the hydraulic tank) (6) Proportional reducing valve (power shift pressure) (7) Port (negative flow control pressure for idler pump) (8) Drive pump (9) Outlet port (drive pump) (10) Housing (11) Pilot pump (14) Port (power shift pressure) (15) Case drain port |
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The main pump consists of drive pump (8) and idler pump (3). The drive pump and the idler pump are contained in an integral housing. Both pumps are variable displacement piston pumps. The drive pump and the idler pump are identical in construction and operation.
Supply oil from the hydraulic tank enters inlet port (5). The single inlet port is common to main pumps (8) and (3) as well as pilot pump (11). The drive pump delivers oil through outlet port (9). The idler pump delivers oil through outlet port (4). The pilot pump delivers oil through outlet port (2) .
Both the drive pump and the idler pump have a regulator as part of the pump control system. The flow control of the pumps is performed by the operation of the regulators. The control system is identical for both pumps.
Proportional reducing valve (6) for the power shift pressure is located on the head of the main pump. The proportional reducing valve is controlled by the machine ECM. The proportional reducing valve controls the signal from the power shift pressure for both the drive pump and the idler pump.
Negative flow control pressure from the main control valve enters the drive pump regulator at port (1). Negative flow control pressure from the main control valve enters the idler pump regulator at port (7) .
Case drain oil from the pump housing flows from port (15) to the case drain filter.
Operation
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| Illustration 2 | g01238115 |
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Main pumps (sectional view) (3) Idler pump (8) Drive pump (11) Pilot pump (16) Gear (17) Drive shaft (18) Drive shaft (19) Gear (20) Swashplate (21) Plate (22) Retainer (23) Piston slipper (24) Piston (25) Barrel (26) Port plate (27) Passage |
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Gear (19) of drive shaft (18) meshes with gear (16) of drive shaft (17). Gear (16) and gear (17) have the same number of teeth. Drive shaft (18) of drive pump (8) is connected to the engine by a coupling. When the engine is running, drive shaft (17) and drive shaft (18) rotate at the same speed. Therefore, drive pump (8) and idler pump (3) rotate at the same speed.
Pilot pump (11) is directly connected with drive shaft (17) .
Barrel (25) contains nine pistons (24). Piston slippers (23) are connected to pistons (24) by retainers (22). The piston slippers are pressed against plate (21). Plate (21) lies on swashplate (20). Barrel (25) is splined to drive shaft (18). As drive shaft (18) rotates, the barrel, the pistons and the piston slippers rotate around swashplate (20) .
The angle of swashplate (20) determines the length of stroke of piston (24). As the angle of the swashplate increases, the length of stroke of the pistons increases and the output flow of the pump increases. As piston slipper (23) rotates around the swashplate, the piston moves out of barrel (25). The piston draws oil from passage (27) of port plate (26) during this movement. As the piston slipper continues to rotate around the swashplate, the piston moves into the barrel. The piston delivers oil to outlet port (13) during this movement. The oil delivery from ports (4) and (9) flows to the main control valve.