Hydraulic control system for working machine

A hydraulic control system for a working machine, comprising:

• a hydraulic actuator;
• a hydraulic pump for supplying working oil to said hydraulic actuator through a control valve;
• a relief mechanism disposed on the discharge side of said hydraulic pump, said relief mechanism is set to an open state in such a manner that said relief mechanism allows a passage of said working oil from said hydraulic pump when a pump discharge pressure of said hydraulic pump which varies according to a pump flow rate in said hydraulic pump exceeds a predetermined pressure and is set to a closed state in such a manner that said relief mechanism does not allow the passage when said pump discharge pressure becomes the predetermined pressure or lower;
• an ordinary control means for controlling said pump flow rate in accordance with working information;
• a pressure feedback control means for controlling said pump flow rate in accordance with said pump discharge pressure;
• and selecting means for selecting a pump flow rate based on a smaller one of the pump flow rates controlled by said ordinary control means and said pressure feedback control means, wherein controlling performed by said ordinary control means comprises plural types of controls,
• a mode select switch for switching between first and second modes of said selecting means, wherein one of said ordinary control means and said pressure feedback control means may be selected by said selecting means when switching is made to said first mode by said mode select switch, and wherein said pressure feedback control means may not be selected by said selecting means and said ordinary control means may be selected when switching is made to said second mode by said mode select switch.

A hydraulic control system for a working machine, comprising:

• a hydraulic actuator;
• a hydraulic pump for supplying working oil to said hydraulic actuator through a control valve;
• a relief mechanism disposed on the discharge side of said hydraulic pump, said relief mechanism is set to an open state in such a manner that said relief mechanism allows a passage of said working oil from said hydraulic pump when a pump discharge pressure of said hydraulic pump which varies according to a pump flow rate in said hydraulic pump exceeds a predetermined pressure and is set to a closed state in such a manner that said relief mechanism does not allow the passage when said pump discharge pressure becomes the predetermined pressure or lower;
• an ordinary control means for controlling said pump flow rate in accordance with working information;
• a pressure feedback control means for controlling said pump flow rate in accordance with said pump discharge pressure;
• and selecting means for selecting a pump flow rate based on a smaller one of the pump flow rates controlled by said ordinary control means and said pressure feedback control means, wherein controlling performed by said ordinary control means comprises plural types of controls and wherein said selecting means may turn off selection of said pressure feedback control means,
• an angle detecting means for detecting an inclination angle of a main body of the machine, and wherein said pressure feedback control means is turned on when an inclination angle detected by said angle detecting means is not larger than a preset value and is turned off when said inclination angle exceeds the preset value.