Hydraulic pressure supply system of automatic transmission

1. A hydraulic pressure supply system of an automatic transmission for a vehicle, comprising:

a low-pressure hydraulic pump receiving oil from an oil pan through an input line, generating a low hydraulic pressure to the oil and supplying the oil of the low hydraulic pressure to a first low-pressure line;

a low-pressure regulator valve connected to the first low-pressure line, recirculating through a first recirculation line a portion of the oil of the low hydraulic pressure supplied through the first low-pressure line directly to the input line to regulate the low hydraulic pressure of the first low-pressure line, and supplying the regulated low hydraulic pressure to a low pressure portion through a second low-pressure line;

a high-pressure hydraulic pump connected to the first low-pressure line, receiving a portion of the oil of the low hydraulic pressure in the first low-pressure line, increasing the low hydraulic pressure to a high hydraulic pressure, and supplying the oil of the increased hydraulic pressure to a high pressure portion through a high-pressure line; and

a high-pressure regulator valve connected to the high-pressure line, recirculating a portion of the oil of the high hydraulic pressure supplied through the high-pressure line directly to the first low-pressure line through a second recirculation line, selectively recirculating a portion of the oil of the high hydraulic pressure supplied through the high-pressure line to the second recirculation line through a third recirculation line, and supplying the oil of the high hydraulic pressure regulated through the high-pressure regulator valve to the high pressure portion,

wherein the third recirculation line is selectively connected to the second recirculation line according to a strength of the high hydraulic pressure of the oil in the high-pressure line.

2. The hydraulic pressure supply system of claim 1 , wherein the low-pressure hydraulic pump is driven by a low-pressure motor and the high-pressure hydraulic pump is driven by a high-pressure motor.

3. The hydraulic pressure supply system of claim 1 , wherein the high-pressure regulator valve recirculates the oil of the high hydraulic pressure through the second recirculation line if the high hydraulic pressure of the high-pressure line is lower than a predetermined value, and recirculates the oil of the high hydraulic pressure through the second and third recirculation lines if the high hydraulic pressure of the high-pressure line is higher than or equal to the predetermined value.

4. The hydraulic pressure supply system of claim 3 , wherein the second recirculation line is provided with an orifice and a pressure sensor is mounted between the orifice and the high-pressure regulator valve.

5. The hydraulic pressure supply system of claim 1 , wherein the high-pressure regulator valve comprises:

a valve body having a first port receiving the high hydraulic pressure of the high-pressure line, a second port receiving the high hydraulic pressure of the high-pressure line as a control pressure, a third port selectively supplying a portion of the oil of the high hydraulic pressure supplied to the first port to the second recirculation line, a fourth port selectively supplying a portion of the oil of the high hydraulic pressure supplied to the first port to the third recirculation line, and a fifth port disposed at an opposite side to the second port and receiving a control pressure of a solenoid valve; and

a valve spool having a first land operated by the high hydraulic pressure supplied to the second port and controlling an opening area of the third port, a second land dividing the first port to supply the high hydraulic pressure supplied to the first port to the third port and the fourth port, and a third land selectively opening or closing the fourth port.

6. The hydraulic pressure supply system of claim 5 , wherein the high-pressure regulator valve further comprises an elastic member disposed between the third land and the valve body.