COMPONENT OPERTATION / Control Valve REGENERATIVE VALVE The regenerative valves are provided in the boom lower, arm roll-in and bucket roll-in circuits. The re- generative valve increases cylinder speeds in order to cylinder hesitation, and improve machine controllabil- ity. Operation of Boom Regenerative Valve 1. During boom lower operation, return oil from the cylinder bottom side enters hole on the spool and acts on the check valve. 2. During boom lower operation, the boom is low- ered faster as compared with amount of supply from the pump due to boom own weight. 3. Therefore, pressure in the circuit between pump and boom cylinder rod decreases. 4.
When pressure in the cylinder rod side becomes lower than that in the bottom side, the check valve opens. 5. Consequently, return oil from the cylinder bottom side flows to the rod side, is combined with pres- sure oil from pump 1, and is supplied to the cyl- inder rod side so that the regenerative operation is done. 6. Therefore, speed of the cylinder increases. 7. When the cylinder is moved full stroke or the load increases, pressure in the cylinder rod side circuit increases more than that in the bottom side. 8. Consequently, the check valve is closed and re- generative operation stops. Boom Cylinder Boom Lower Pilot Pressure Pressure Oil from Pump 1 T450-03-03-041 T3-3-32