Unloading valve and loader variable speed hydraulic system

The invention relates to a loader variable speed hydraulic system, aims to solve the overflow loss, shifting impact and shifting delay problems of the loader variable speed hydraulic system, and provides the loader variable speed hydraulic system. The loader variable speed hydraulic system is characterized in that an oil inlet of a variable speed pump is connected with a gearbox oil body shell; an oil outlet is connected with an EF oil port of an unloading valve; a PW oil port of the unloading valve is connected with an oil inlet of a variable speed operating valve; an energy accumulator is connected onto a connecting oil line between the PW oil port of the unloading valve and the oil inlet of the variable speed operating valve; and a T oil port of the unloading valve is connected with the gearbox oil body shell through a torque converter and a counterbalance valve. In the technical scheme, the working pressure of the variable speed pump is approximately 0.2 to 0.5 MPa and is lower than the overflow pressure