Hydraulic circuit for heavy equipment

A hydraulic circuit for heavy equipment, comprising:

• first to third hydraulic pumps connected to an engine;
• a first control valve installed in a flow path of the first hydraulic pump, and controlling a hydraulic fluid to be supplied to an actuator that drives a working device when shifting;
• a second control valve installed in a flow path of the second hydraulic pump, and controlling hydraulic fluid to be supplied to an actuator that drives a working drive when shifting;
• a hydraulic motor connected to the third hydraulic pump;
• a cooling fan, connected to the hydraulic motor, for discharging cooling wind to an oil cooler which is installed in a return path of the first and second hydraulic pump to cool the hydraulic fluid to be returned to a hydraulic tank;
• a temperature sensor for detecting a temperature of the hydraulic fluid in the hydraulic tank;
• an electric relief valve, installed in a drain flow path of the third hydraulic pump, for controlling hydraulic pressure that drives the hydraulic motor to variably control a rotation velocity of the cooling fan;
• a controller for varying a set pressure of the electric relief valve in response to a detected signal from the temperature sensor to control the hydraulic pressure that drives the hydraulic motor;
• and
• a pilot pressure generator, installed in a pilot flow path branched and connected to a flow path of the third hydraulic pump, for supplying a pilot signal pressure to the first and second control valves when shifting.