The control block diagram of the boom-up confluence system is shown in Figure 3-4.
① When the Kobelco excavator performs the boom raising operation, the pilot switches the boom spool and the boom confluence spool twice, and is simultaneously input to the low pressure sensor (SE-3).
② The output voltage of the low-pressure pressure sensor is input to the electromechanical controller, and the pilot signal is processed internally. The command current corresponding to the input voltage is input to the P2 cut-off proportional valve (PSV-B), as shown in Figure 3-5.
③ The P2 cut-off proportional valve switches the P2 cut-off spool with the secondary pressure of the proportional valve corresponding to the command current from the electromechanical controller.
④ Due to the switching between the boom spool and the P2 shut-off spool, the negative pressure control pressure fluctuates, and the fluctuating pressure is input to the Pl and P2 negative pressure sensors (SE-26, SE-27) and back pressure sensor (SE-28) .
⑤ The output voltages of Pl and P2 negative pressure sensors and back pressure sensors are input to the electromechanical controller, and the negative pressure control signal processing is performed internally, and the command current corresponding to the input voltage is output to the Pl pump proportional valve (PSV-P1) and P2 Pump proportional valve (PSV-P2), as shown in Figure 3-6.
⑥ Pl pump proportional valve and P2 pump proportional valve change the discharge volume of P1 and P2 pumps with the secondary pressure of the proportional valve corresponding to the command current from the electromechanical controller.
⑦Switch the boom spool and boom confluence spool by the pure hydraulic command (pilot 2 times pressure), and switch the P2 cut-off spool by the current hydraulic command (proportional valve 2 times pressure). In this way, the discharge oil of the P2 pump is merged into the discharge oil of the P1 pump during the boom raising operation, and is supplied to the boom hydraulic cylinder.
