ACCUMULATOR GP-STEERING 2050226 - Caterpillar

Illustration 1 g00538694
Hydraulic schematic (S/N: 3MR4979-UP4MR716-UP) (1) Swing motor (2) Left travel motor (3) Right travel motor (4) Stick cylinder (5) Left travel brake valve (6) Right travel brake valve (7) Bucket cylinder (8) Boom cylinders (9) Stick drift reduction valve (10) Swivel (11) Main control valve (12) Pressure switch (implement or swing) (13) Pressure switch (travel) (14) Boom drift reduction valve (15) Main relief valve (16) Pressure switch (boom raise) (17) Pilot control valve (travel) (18) Pilot control valve (swing and stick) (19) Solenoid valve (fine control) (20) Solenoid valve (travel speed) (21) Solenoid valve (trenching) (22) Solenoid valve (proportional reducing) (23) Pilot control valve (boom and bucket) (24) Hydraulic activation control valve (25) Accumulator (26) Pilot relief valve (27) Shock reducing valve (28) Front pump (29) Rear pump (30) Automatic travel speed change valve (31) Pilot pump (32) Pilot oil manifold (33) Pilot filter (34) Drain filter (35) Slow return check valve (36) Oil cooler (37) Bypass check valve (38) Return filter (39) Hydraulic tankIntroduction
Illustration 2 g00630150
Pump compartment (28) Front pump (29) Rear pump (30) Pilot pumpThis machine is driven and controlled by the following systems.
The main hydraulic system supplies oil to the cylinders and motors of the machine.
The pilot hydraulic system supplies oil to the control circuits.
The electronic control system controls the output from the engine and the pump.Main Hydraulic System
The main hydraulic system oil is supplied by front pump (28) and rear pump (29). Pumps (28) and (29) are variable displacement piston pumps. Pumps (28) and (29) are identical in performance. Front pump (28) is directly connected to the engine by a flexible coupling. Pumps (28) and (29) are mechanically connected by a spline coupling.Gear type pilot pump (30) supplies oil to the pilot hydraulic system. Gear type pilot pump (30) is directly connected to rear pump (29) by a shaft. All engine output is used to drive these three pumps.When the load on the machine increases, the delivery pressure of pumps (28) and (29) increases. When the delivery pressure of pumps (28) and (29) increases the flow rate decreases. The hydraulic horsepower remains constant even though the oil pressure and the flow rates change. The hydraulic horsepower is approximately identical to the engine horsepower.
Illustration 3 g00466332
Main control valve compartment (15) Main relief valve (44) Right control valve body (45) Left control valve bodyThe oil from front pump (28) flows into right valve body (44). The oil from rear pump (29) flows into left valve body (45). Main control valve (11) is made up of right valve body (44) and left valve body (45) .When no work is being performed, pump oil flows through main control valve (11) and into hydraulic tank (39). This creates a negative flow control signal. The main control valve sends this negative flow control signal to each main pump in order to destroke the pump to the minimum output flow.If an operation is being performed, main control valve (11) directs pump oil to the respective cylinders (boom, bucket, and stick) and/or motors