1. When the Kobelco excavator bucket recovery operation is carried out, the bucket spool is converted to the second pressure of the bucket.
2. The change in the negative pressure control pressure caused by the switching of the bucket spool is input to the negative control sensor on the PI side. 26 and back pressure sensor SE-28
3. The output voltage of the PI side negative pressure control sensor and the back pressure sensor is input to the electromechanical integrated controller, and the negative pressure control signal is processed internally, and then output to the PI pump proportional valve (PSV-PI)
4. The PI pump proportional valve outputs the secondary pressure of the proportional valve corresponding to the command current of the electromechanical controller to control the pump discharge.
5. The spool of the bucket is switched by the pure hydraulic command (pilot 2 times pressure), and the discharge volume of the PI pump is controlled by the negative pressure.
