CONTROL GP-ENGINE ELECTRONIC 2131986 - Caterpillar

Illustration 1 g03317349
(1) Pilot Gear Pump
(2) Rear Pump
(3) Servo Pilot Hose
(4) Front Pump The main hydraulic pump is located on the right rear side of the machine.The main hydraulic pump is made of two piston-type variable displacement pumps constructed in tandem. The pump is driven by the engine from the flange plate. The pump uses pressure compensation, an electronically controlled solenoid, and a negative control system to manage pump output.As the load pressure increases during operating conditions, the tandem pumps increase the delivery pressure, and the pumps decrease the flow rate. As the engine load increases, the machine ECM reduces ESS shift pressure, and the pumps decrease the flow rate. In these two cases, the hydraulic horsepower remains constant even though the delivery pressure, and the flow rates change.When no operation is being performed, pump oil flows through the main control valve, through a control orifice, and into the hydraulic tank. The pressure upstream from the orifice becomes a negative flow control signal. The main control valve sends the negative flow control signal to each pump in order to destroke the pump to the minimum output flow.The front pump provides a maximum flow rate of 243 L/min (64 US gpm). This pump provides oil flow to the following functions: boom control, grapple rotate, stick one control. The rear pump provides a maximum flow rate of 243 L/min (64 US gpm). This pump provides flow to the following functions: swing control, grapple open and close, and stick two controls.
Illustration 2 g03693569
(5) Pressure Tap "a4"
(6) Port "A2"
(7) Pressure Tap "a2"
(8) Pilot Pump
(9) Servo Pilot Hose
(10) Port a3
(11) Pilot Pressure Tap Port "A3"
(12) Filter Screen
(13) Pilot Relief Valve
(14) Port "B3"
(15) Rear Pump
(16) Port "B1"
(17) Front Pump
(18) Port "Dr"
(19) Pressure Tap "a1"
(20) ESS Control Valve
(21) Port "A1"
(22) Port "Psv"
Illustration 3 g03269318
(20) ESS Control Valve
(23) Swashplate
(24) Pistons
(25) Cylinder Block
(26) Servo Piston The pilot pump draws oil from the hydraulic tank through port B3 (14). When the engine is operating, pilot oil flows out port A3 (11) to the pilot shutoff manifold. Pilot oil also flows out port a3 (10) to the ESS control valve (20) through the servo pilot hose (9) and into port "Psv" (22).The pilot relief valve (13) limits the maximum pressure in the pilot system.Port A1 (21) is the outlet port for the front pump (17). Port A2 (6) is the outlet port for the rear pump (15). Supply pressure from front pump can be measured at pressure tap a1 (19). Supply pressure from rear pump can be measured at the pressure tap a2 (7).The tandem pumps of the main hydraulic pump draw oil from the hydraulic tank through port B1 (16). Case drain oil is directed out port Dr (18).The ESS control valve (20) is located on the rear face of the implement hydraulic pump. Pilot oil is delivered to this valve through the servo pilot hose. The