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| Illustration 1 | g00759210 |
Hydraulic Pump (4) Charge pump (15) Drive shaft (16) Swashplate (17) Adjustment screw (servo piston) (18) Barrel assembly (19) Charge pump inlet (20) Piston (21) Spring (22) Valve plate (23) Main circuit ports | |
The hydraulic pump for the water spray system is a variable displacement piston pump. The pump output is electrically controlled through the electrical displacement control (EDC). The EDC maintains the position of the swashplate in proportion to the electrical input.
When the engine is running, shaft (15), barrel assembly (18) and charge pump (4) are rotating. There are nine pistons (20) in barrel assembly (18). Spring (21) keeps a force on barrel assembly (18) in order to make a high pressure seal between barrel assembly (18) and valve plate (22). When barrel assembly (18) is rotating, each piston (20) follows the angle of swashplate (16). If the angle of swashplate (16) is at zero, the pistons do not move in and out of barrel assembly (18). This would cause no flow of oil. Charge oil from charge pump (4) will maintain oil pressure in the hydraulic pump in order to keep barrel assembly (18) full of oil. Charge oil lubricates the pump components. This makes up for the normal, internal loss of oil, which is due to leakage. The position of swashplate (16) is controlled by the EDC and servo piston (17). The EDC receives an electrical signal from the flow control box. This causes movement of the servo valve inside the EDC. Servo piston (17) will activate and servo piston (17) will adjust due to charge oil that is routed from the servo valve. Servo piston (17) controls the direction and the amount of angle for swashplate (16) .
Oil flows from the pump to the drive motor and back to the pump. This oil flows through main circuit ports (23). The position of swashplate (16) determines the direction of flow.
EDC
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| Illustration 2 | g00759265 |
(9) Displacement control spool (10) Pressure control pilot (PCP) (11) Sensing pistons (12) Feedback linkage (13) Servo control piston (14) Electronic displacement control (EDC) (17) Neutral adjustment (servo piston) (24) Spring (25) neutral adjustment (EDC) (26) Control oil passages | |
Electric displacement control (14) is mounted on the hydraulic pump.
The pump control consists of EDC (14), displacement control spool (9), and servo control piston (13). EDC (14) is a two-stage electrohydraulic control. The EDC uses feedback linkage (12) and control oil (26) from the charge pump in order to set up a closed swashplate control circuit. EDC (14) receives an electrical input from the flow analyzer control dial at the pressure control pilot valve (10) .
EDC (14) uses an electrohydraulic pressure control pilot in order to control differential pilot pressure. PCP (10) converts an electrical input signal to a hydraulic input signal in order to operate spring (24) that is centered in the sensing piston (11). Sensing piston (11) is mechanically hooked up with the displacement control spool (9) through feedback linkage (12). As sensing piston (11) moves, the displacement control spool is moved. This opens a path for control oil (26) in order to move through servo control piston (13). Servo control piston (13) tilts the swashplate. This varies the pump displacement.
As sensing piston (11) moves to the left, displacement control spool (9) is moved to the right. This opens a path for control oil (26) to servo control piston (13). As servo control piston (13) tilts the swashplate, feedback linkage (12) moves sensing piston (11). This moves sensing piston (11) through spring (24). Then sensing piston (11) moves back toward the NEUTRAL position. This will maintain the swashplate angle that is set by PCP valve (10) .
EDC (14) maintains the position of the swashplate in proportion to the electrical input. Servo control piston (13) has feedback linkage (12), which moves the displacement control spool (9) in proper relation to the input signal and the position of the swashplate. Any swashplate position error is corrected if the error is sensed by the feedback linkage (12) and displacement control spool (9) .
Combination Valves
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| Illustration 3 | g00759356 |
Combination Valves (View A) Charge check valve (return side of the drive circuit) (View B) Crossover relief valve (the pressure side of the drive circuit). (5) Hydraulic pump (7) High pressure oil (8) Return oil from the motor. (27) Spring (28) Poppet stem (29) Plunger stem (30) Plunger (31) Spring (32) Seat (33) Charge oil passage (34) Poppet valve | |
Hydraulic pump (5) is equipped with two identical combination charge check (A) and high pressure relief valves (B).
Make Up Function
(View A) displays return oil (8) from the motor. Return oil (8) fills the chamber above plunger (30). Charge pressure (33) acts against the bottom face of plunger (30). If the pressure of return oil (8) becomes lower than charge pressure (33), plunger (30) becomes unseated. This allows charge oil (33) to fill return side (8) of the circuit. If this occurs, plunger (30) moves up against return oil pressure (8). This exerts the force by spring (27) at the top.
Main Relief Function (High Pressure)
High pressure oil (7) is shown in (View B) from the pump and plunger (30) that is seated against charge pressure. High pressure oil (7) will work against poppet valve (34) within plunger stem (29). Spring (31) acts to keep poppet (34) closed. If the relief pressure is reached, poppet (34) moves down. This allows high pressure oil (7) to dump to the charge circuit.
The combination valves will not adjust. The combination valves must be replaced if relief pressures are not correct.