BOOM AR 2873977 - Caterpillar

Construction
Illustration 1 g03784839
Main hydraulic pump
(1) Load sense spool
(2) Horsepower control solenoid
(3) Horsepower control spool
(4) Main pump
(5) Mechanical horsepower control setting
(6) Differential (margin) pressure setting
(7) Regulator
(A) Pump outlet port
(M) Pressure test point
(S) Pump inlet port
(T2) Case drain port
(X) Load sense signal pressure port The main hydraulic system has one main hydraulic pump. The hydraulic pump is mechanically driven by the engine. The main pump is a variable displacement piston pump. The displacement is controlled by regulator (7).Main pump (4) draws oil from the tank through inlet port (S). Main pump (4) delivers oil through outlet port (A) to the main control valve.Pump regulator (7) is mounted on the side of the pump. The main pump has a regulator as part of the pump control system.The input to the regulator controls the output of the pump. Load signal pressure and an electrical signal to horsepower control solenoid (2) are inputs to the regulators.Pump regulator (7) consists of horsepower control spool (3) and load sense spool (1). The duplicate load signal pressure or the true load signal pressure flows to load sense spool (1) through port (X).Operation
Illustration 2 g03784834
Hydraulic schematic of main pump
(1) Load sense spool
(2) Horsepower control solenoid
(3) Horsepower control spool
(4) Main pump
(7) Regulator
(8) Control piston
(9) Swashplate
(10) Counter piston
(A) Pump outlet port
(S) Supply port
(T2) Case drain port
(X) Load sense signal pressure port The engine crankshaft drives the hydraulic pump. Main pump (4) contains a set of pistons. The pistons rotate with the main shaft. The pistons rotate about swashplate (9). As the angle of swashplate (9) increases, the pistons will extend and retract within the barrels. The extending and retracting of the pistons will cause oil to flow from inlet port (S) to outlet port (A). The following components rotate together within the pump housing: pump shafts, barrels, pistons and impeller.The angle of swashplate (9) causes the pistons to be retracted from the barrels at the inlet passage. When the pistons align with the passage, the swashplate causes pistons to be extended into the barrels. As the barrel rotates, the inlet passage is closed off from the voids in the barrel. Swashplate (9) forces the pistons into the barrels. As the barrel continues to rotate, the oil pressure in the barrel is able to flow into the outlet passage of the port plate. Oil flows from the outlet passage to outlet port (A). Oil flow is provided to the main hydraulic system.The angle of swashplate (9) determines the stroke length of the pistons. The angle of swashplate (9) is controlled by regulator (7).Load sense spool (1) will control pump flow when horsepower control solenoid (2) does not receive an electrical signal from the ECM. Load sense signal and spring force act against pump flow pressure to control the signal oil that is delivered to the right end of the control piston (8). When the piston and rod in control piston (8) moves to the left, the angle of swashplate (9) is reduced. The output flow of the pump is reduced.Reference: For more