Destroking (2) 14 1 2 4 6 15 LS pressure 12 13 X 21 10 22 L B 16 LS pressure oil System pressure oil Return oil L1 S 10 4 17 18 23 13 19 20 12 75796WE34 1 Drive shaft 2 Swash plate 4 Counter piston 6 Counter spring 10 Control piston 12 Pressure compensator spool 13 Flow compensator spool 14 Case drain 15 Passage 16 Passage 17 Spring 18 Spring 19 LS line from the metering pump 20 Cavity 21 Passage 22 Passage 23 Cavity The decreased flow demand causes a LS pressure in line (19). The LS pressure in line (19) combines with the force of spring (18) in cavity (20). This combination of LS pressure and of spring force is less than the pump pressure in passage (21).
This causes flow compensator spool (13) to move left. Pump oil now flows through passage (15). The oil then flows past flow compensator spool (13), through passage (22), and then to control piston (10). The pump pressure behind control piston (10) is now greater than the combined force of counter piston(4) and of counter spring (6). The angle of swash plate (2) decreases. This decreases the pump output and the system pressure. When the lower flow requirements are met, flow compensator spool (13) moves right up to the balanced position. Swash plate (2) maintains an angle that is sufficient to provide the lower required pressure.
If the operator does not turn the steering wheel and does not move RCV, then the pump will return to low pressure standby. Control piston Changes pump displacement ; influenced by controller. Counter piston Helps to change pump displacement but no possible to control this piston. 6-15