Abstract: An oil supply system of an automatic transmission includes a first oil pump pumping up oil from the oil reservoir and supplying the oil to the low-pressure part, a low-pressure regulating valve connected to a low-pressure part channel connecting the first oil pump with the low-pressure part, and controlling the pressure of the oil discharged from the first oil pump at pressure required by the low-pressure part, a second oil pump receiving the oil of which the pressure is controlled through the low-pressure regulating valve and supplying the oil to the high-pressure part, and a high-pressure regulating valve connected to a high-pressure part channel connecting the second oil pump with the high-pressure part and controlling the pressure of the oil discharged from the second oil pump at pressure required by the high-pressure part.

Abstract: An oil supply system of an automatic transmission may remarkably reduce the total consuming power of oil pumps by discharging the entire oil on the basis of a low-pressure part and controlling only some of the oil, which is required by a high-pressure part, at high pressure, and then supplying the oil to high-pressure part. The oil supply system may considerably improve power transmission efficiency of the transmission, and may improve fuel efficiency and durability of the oil pumps and reduce noise and pressure vibration.