SYSTEM / Hydraulic System Boom Raise / Arm Roll-In (Arm Regenerative Circuit) 1. Pressure oil from pump 1 is routed to the boom 1 spool and arm 2 spool through the 4-spool paral- lel circuit. 2. Pressure oil from pump 2 is routed to the boom 2 spool through the arm 1 spool and 5-spool paral- lel circuit. 3. During combined operation of boom raise and arm roll-in, arm roll-in pilot pressure shifts the arm flow rate control valve control spool in signal control valve. 4. Boom raise pilot pressure flows to the arm flow rate control valve control spool and acts on the switch valve in arm flow rate control valve. 5.
When the switch valve is shifted, the poppet valve in arm flow rate control valve moves to the direction to restrict the passage in arm 2 in re- sponse to the boom raise control pressure. 6. Consequently, more pressure oil from pump1 flows to the boom 1 side and boom operating speed is kept. 7. As return oil from the arm cylinder rod side is routed to the arm cylinder bottom side due to the regenerative circuit in arm 1 spool, arm roll-in speed increases. Operation in Arm Regenerative Circuit: 1. When arm is rolled in with the arm rolled-out po- sition, arm speed becomes faster comparing with pressure oil amount from pump 2 due to arm own weight. 2.
Therefore, pressure between pump 2 and arm cylinder bottom decreases. 3. When pressure in the cylinder bottom side is lower than that in rod side, the check valve is opened. 4. Therefore, return oil from the cylinder rod side is routed to the bottom side, is combined with oil from pump 2, and combined oil is routed to the cylinder bottom side. 5. Consequently, the regenerative operation is op- erated and cylinder speed increases. NOTE: Refer to the Flow Rate Control Valve in Control Valve group / COMPONENT OP- ERATION.
Arm Regenerative Circuit Arm Regenerative Valve (Switch Valve) Pump 2 Pressure Oil from Pilot Pump Arm Cylinder Arm 2 Arm 1 From Arm Flow Rate Control Valve Control Spool in Signal Con- trol Valve Arm Regenerative Valve (Check Valve) Arm Flow Rate Control Valve (Poppet Valve) Arm Flow Rate Control Valve (Switch Valve) T1J1-02-04-012 Pump 1 T2-4-22