Construction
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| Illustration 1 | g02176646 |
The illustrations and schematic show the front pump to the left side. (1) Minimum angle adjustment (front pump) (2) Case drain (front pump) (3) Outlet port (front pump) (4) Outlet port (rear pump) (5) Maximum angle adjustment (for both pumps) (6) Case drain (rear pump) (7) Power shift port (rear pump) (8) Load sensing regulator (front pump) (9) Power shift port (front pump) (10) Constant power regulator (front pump) (11) Center manifold (12) Constant power regulator (rear pump) (13) Load sensing regulator (rear pump) (14) Minimum angle adjustment (rear pump) (15) Rear pump (16) Inlet port (17) Front pump (18) Load signal port (front pump) (19) Load signal port (rear pump) (20) Pilot pressure port (front pump) (21) Pilot pressure port (rear pump) (22) Servo piston (front pump) (23) Servo piston (rear pump) (36) Charge pump | |
The main pumps consist of a front pump (17) and a rear pump (15) . The pumps are connected in series by a center manifold (11) . Both pumps are variable displacement piston pumps. The displacement is controlled by the regulators (8) and (10) for the front pump and (12) and (13) for the rear pump. The front pump and the rear pump are identical in construction and operation. The front pump and the rear pump are equipped with a common charge pump (36) .
Charge pump (36) is a fixed displacement pump that consists of an impeller. Charge pump (36) draws oil from inlet port (16) in the center manifold. The charge pump delivers oil to the front pump and the rear pump. The front pump delivers oil through outlet port (3) , and the rear pump delivers oil through outlet port (4) .
Both pumps have regulators which are used for pump control. The control system is identical for both pumps. The front pump consists of a load sensing regulator (8) and constant power regulator (10) and the rear pump regulators (12) and (13) consist of a load sensing regulator and a constant power regulator. The regulators are mounted on top of each pump housing.
The pressure inputs to the regulators control the output of the pump. Two pressure inputs, power shift pressure (7) and duplicate load signal or true load signal (front pump (18) , rear pump (19) ) are input to the regulators.
The power shift pressure flows through port (7) of the rear pump to the regulator. The power shift port (9) for the front pump is blocked on the pump housing. Power shift pressure is provided to the front pump regulator through an internal passage. The duplicate load signal or true load signal pressure flows to the regulator through front pump port (18) and rear pump port (19) . In addition, oil from the pilot pump is delivered to the front pump and the rear pump through front pump port (20) and rear pump port (21) .
Operation
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| Illustration 2 | g03263604 |
Pump swashplates in the upstroked position. (1) Minimum angle adjustment (Front pump) (3) Passage (4) Passage (5) Maximum angle adjustment (For both pumps) (11) Center manifold (14) Minimum angle adjustment (Rear pump) (15) Rear pump (16) Inlet port (17) Front pump (22) Servo piston (Front pump) (23) Servo piston (Rear pump) (26) Pin linkage (Both pumps) (27) Barrel (Front pump) (28) Barrel (Rear pump) (29) Swashplate (Front pump) (30) Guide (31) Slipper (32) Piston (33) Spring (34) Rear pump shaft (35) Passage (36) Charge pump (37) Coupling (38) Port plate (39) Front pump shaft (40) Plate (41) Swashplate (Rear pump) | |
The engine crankshaft drives the hydraulic pumps. The engine is connected to shaft (39) through the coupling in the flywheel housing. Shaft (39) is connected to shaft (34) by coupling (37) . Barrel (27) is splined to shaft (39) . Barrel (28) is splined to shaft (34) . The impeller in the charge pump (36) is splined to shaft (39) . Barrel (27) and barrel (28) contain sets of pistons. Pistons (32) rotate with the barrels. Pistons (32) rotate about swashplate (29) and swashplate (41) . As the angle of swashplate (29) and swashplate (41) increases, pistons (32) will extend and retract within the barrels. The extending and retracting of pistons (32) will cause oil to flow from the inlet port (16) to the outlet ports (3) and (4) . The pump shafts, barrels, pistons, and impeller all rotate together within the pump housing.
Each piston (32) is attached to a slipper (31) . All of the slippers are contained in plate (40) . Guide (30) contacts plate (40) and forces the slippers (31) against the swashplate with springs (33) . Pistons (32) rotate around swashplate (29) and (41) with slippers (31) .
Note: The operation of the front pump is described below. The rear pump operates in the same manner as the front pump.
When shaft (39) rotates, the impeller in charge pump (36) , barrel (27) , and pistons (32) rotate. Rotation of the impeller draws oil from inlet port (16) to inlet passage (35) and then through port plate (38) . The oil fills in the voids of barrel (27) .
The angle of swashplate (29) causes pistons (32) to be retracted from barrel (27) at passage (35) . When pistons (32) align with passage (3) , the swashplate causes pistons (32) to be extended into barrel (27) . As barrel (27) rotates, passage (35) is closed off from the voids in barrel (27) . Swashplate (29) forces pistons (32) to be extended into barrel (27) . Pistons (32) pressurize the oil inside barrel (27) . As barrel (27) continues to rotate, the oil pressure in barrel (27) is able to flow into passage (3) of port plate (38) . Oil flow is provided to the main hydraulic system.
The angle of swashplate (29) determines the stroke length of pistons (32) . The angle of swashplate (29) is controlled by regulators (8) and (10) .
When the pump output is low, the signal pressure is not high enough to reduce the pump output. Servo piston (22) is shifted to the right because of pin linkage (26) . Swashplate (22) rotates in a clockwise direction. This rotation increases the angle of the swashplate. The output flow of the pump is increased.
When the pump output is too high, signal pressure is used to reduce the output flow of the pump. Signal oil pressure is delivered to the left end of the servo piston (22) through regulators (8) and (10) . When servo piston (22) moves to the left, swashplate (29) rotates in a counterclockwise direction. The rotation reduces the angle