1. When the Kobelco excavator bucket recovery operation is performed, the spool of the bucket is piloted twice to switch the pressure, and at the same time, it is input to the low pressure pressure sensor (SE-I.SE-2).
2. The output voltage of the low-pressure pressure sensor is input to the electromechanical controller, and the pilot signal processing is performed internally, and the command current corresponding to the input flashing is output to the P2 cut-off proportional valve (PSV-B) and straight-line proportional valve (PSV-C)
3. P2 cut-off ratio (PSV-B) and straight travel proportional valve law S№0, output the proportional valve secondary pressure corresponding to the command current of the electromechanical controller, switch P2 cut-off spool and straight travel spool,
4. Due to the switching of the bucket spool and the P2 cut-off spool, the negative pressure control pressure changes, and this pressure is input to the negative pressure sensors (SE-26, SE-27) and back pressure sensors (SE.28) of PI and P2. )
5. The output voltages of the negative pressure sensors and back pressure sensors on the PI and P2 sides are input to the electromechanical controller, and the negative pressure control signal processing is performed internally, and the output voltage is output to the PI pump proportional valve (PSV-PI) and the P2 pump proportional valve (PSV- P2).
6. The PI pump proportional valve and the P2 pump proportional valve output the secondary pressure of the proportional valve corresponding to the command current of the electromechanical controller, which changes the discharge volume of the PI pump and the P2 pump.
7. Through the pure hydraulic command (pilot 2 times pressure) to switch the core digging, plus the overcurrent hydraulic command (the proportional valve 2 times pressure) to switch the straight spool and the P2 cut-off spool. In this way, the discharge of the P2 pump is merged into the discharge oil of the PI pump when the bucket is recovered or raised.
