Patent ID: 7926411

Claim:
A valve control unit comprising: a first pilot-operated control valve that controls a first fluid pressure actuator wherein the first fluid pressure actuator is a boom cylinder that pivots a boom of a hydraulic excavator in an up-and-down direction; a second pilot-operated control valve that controls a second fluid pressure actuator wherein the second fluid pressure actuator is a stick cylinder that pivots a stick pivotally supported on a front end of the boom in an in/out direction; a third pilot-operated control valve that controls the first fluid pressure actuator in conjunction with the first pilot-operated control valve; a first proportional solenoid valve that controls a pilot pressure that acts on one side of the first pilot-operated control valve relative to a manual operation amount; a second proportional solenoid valve that controls a pilot pressure that acts on one side of the third pilot-operated control valve relative to a manual operation amount; a third proportional solenoid valve that controls a pilot pressure that acts on a side, which is opposite to the side on which the pilot pressure generated by the second proportional solenoid valve acts, of the third pilot-operated control valve relative to a manual operation amount; and a fourth proportional solenoid valve that controls a pilot pressure that acts on a side of the second pilot-operated control valve relative to a manual operation amount, wherein the first and second proportional solenoid valves have common manual operation amount/pilot pressure characteristics and are inputted with a common manual operation amount, the first and second proportional solenoid valves have common lever operation amount/boom-up pilot pressure characteristics and are inputted with a common boom-up lever operation amount, the third proportional solenoid valve has manual operation amount/pilot pressure characteristics common to the first and second proportional solenoid valves and is inputted with a manual operation amount common to the fourth proportional solenoid valve, the third proportional solenoid valve has lever operation amount/boom-up pilot pressure characteristics common to the first and second proportional solenoid valves and is inputted with a stick-in lever operation amount common to the fourth proportional solenoid valve, the fourth proportional solenoid valve has manual operation amount/pilot pressure characteristics different from those of the first, second, and third proportional solenoid valves and is inputted with the manual operation amount common to the third proportional solenoid valve, and the fourth proportional solenoid valve has lever operation amount/stick-in pilot pressure characteristics different from those of the first, second, and third proportional solenoid valves and is inputted with the stick-in lever operation amount common to the third proportional solenoid valve.