2) WHEN THE RCV LEVER IS IN THE LOWER POSITION 14 13 4 Aux Bucket 5 Control unit EH18 EH17 EH20 EH19 6 4 1 6(4) 3(2) a3 b3 a1 b1 a2 b2 Steering valve (EHPS) EF port Steering valve (EHPS) LS port Return line Steering system 757F6WE04 В When the RCV lever (4, boom) is pushed forward, the boom spool is moved to lower position by pilot pressure from EH contril block (6). The oil from main pump (1) flows into main control valve (3) and then goes to small chamber of boom cylinder (13) by pushing the load check valve of the boom spool. The oil returned from large chamber of boom cylinder (13) returns to hydraulic tank (22) through the boom spool at the same time.
When the lowering speed of boom is faster, the return oil from the large chamber of boom cylinder combines with the oil from the pump through the regeneration check valve, and flows into the small chamber of the cylinder. This prevents cylinder cavitation by the negative pressure when the pump flow cannot match the boom down speed. В В В 6-6 LH RH 29 PS PS 29 40 a1 a2 a3 P A1 B1 A2 B2 A3 B3 3 Floating LS Boom Dump Bucket Boom Aux Joystick Down 4' Pst back Up Roll ick steering) T H22 EH21 T P 5(3) 2(1) ( ) :
2 Spool Regeneration check valve To MCV b1 b2 b3 A1 28 28 11 12 S1 X1 X2 P1 T X3 9PS1 X1 X2 23 Return line B1 B2 24 25 26 22 S1 L2 L1 S2 L4L3 Fan & brake pump LH 40 a1 a2 A1 B1 A2 LH RH 29 PS PS 29 a3 B2 A3 B3 Dump Bucket Floating Boom Aux Roll back Down Up Down Up