Patent ID: 8512008

Claim:
An oil supply system of an automatic transmission which supplies oil from an oil reservoir to a high-pressure part and a low-pressure part, the oil supply system comprising: 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 through a first valve channel, and controlling an oil pressure discharged from the first oil pump at a first pressure required by the low-pressure part wherein the low-pressure part channel connects the first oil pump with the low-pressure part; a sub-channel branching from the low pressure part channel to a high-pressure part channel connected to the high pressure part, wherein the first valve channel is disposed upstream of the sub-channel; a second oil pump disposed between the sub-channel and the high pressure part channel and receiving the oil of which the first pressure is controlled by the low-pressure regulating valve and supplying the oil to the high-pressure part; and a high-pressure regulating valve connected to the high-pressure part channel connecting the second oil pump with the high-pressure part and controlling an oil pressure discharged from the second oil pump at a second pressure required by the high-pressure part; a connection channel connecting the low-pressure part channel with the high-pressure part channel; and a one-way check valve disposed in the connection channel to allow for oil flow from the low-pressure part channel to the high-pressure part channel and prevent oil flow in the opposite direction; wherein one end of the connection channel is connected to the low-pressure part channel, and the other end of the connection channel is connected to the high-pressure part channel; wherein the one-way check valve is a valve opening the connection channel, only when the oil pressure of the high-pressure part channel is lower than the oil pressure of the low-pressure part channel, in a state of stopping the second oil pump.