4.
TRAVEL SPEED CONTROL SYSTEM ARM CYLINDER BUCKET CYLINDER BOOM CYLINDER SWING MOTOR ps1 T3 T4 ps2 T1 T2 pa11 DR1 pc1 pa10 TRAVEL MOTOR pb9 A5 B5 pb5 B9 A9 pa5 ARM1 ARM2 pb9 pc1 (34,2) PO A4 B4 B8 A8 pa5 pa9 (34,1) P2 B A A1 B1 DR7 OPTION BUCKET DR2 pa11 pb8 pa8 pc7 A3 B3 pc2 A7 B7 pc2 A2 B2 pa3 pb3 BOOM2 BOOM1 pb3 pb7 pa3 pa7 pc7 B6 TURNING JOINT DR3 pc6 pa2 pb2 SWING pc6 TRAVEL-RH pb6 A6 A1 B1 pb1 TRAVEL-LH pa6 pa1 pr1 TRAVEL STRAIGHT RCV PEDAL P T TRAVEL PT PS P1 P2 PH PA PP PS SH P3 (4) (1) (2) (3) pa6 pb6 pb1 pa1 A1 A2 SWING ARM BUCKET BOOM P T P T Dr#, dr# FRONT PUMP REAR PUMP PILOT PUMP TRAVEL SPEED SOLENOID VALVE Pk (T/Joint) PH (MCV) (4) (1) (2) (3) (4) (1) (2) (3) A5 A1 A2 A3 h2 pb5 pa2 pb2 pa9 a b d e f g h j c d1 h1 PS PS PS P3 P2 P4 PP(MCV) PG (S/Motor) HYDRAULIC TANK pb8 pa8 pa7 pb7 T(dr1) P1 LINE FILTER RELIEF VALVE 900L3HC05 When the travel speed switch is pushed, the travel speed solenoid valve is actuated and the discharged oil from the pilot pump flows to the Pi port of pilot valve in the travel motors.
As a result, the control piston is pushed by the main oil flow, thus the displacement is minimized. When the travel speed switch is pushed once more, the travel speed solenoid valve is return to original position by the force of spring, the hydraulic oil of Pi port returns to the hydraulic tank. As a result, the control piston is returned by the main oil flow, thus the displacement is maximized. 3-9