Patent ID: 8024926

Claim:
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.