Air compressor for vehicle

1. An air compressor for a vehicle, comprising:

a first compression unit including a front housing having a front inlet into which air to be compressed is introduced and a front outlet from which compressed air is discharged, and a front impeller positioned in the front housing;

a second compression unit including a rear housing having a rear inlet which is connected to the front outlet of the first compression unit through a connection pipe, and into which air passing through the first compression unit is introduced and a rear outlet from which compressed air is discharged, and a rear impeller positioned in the rear housing;

a driving unit having the front housing and the rear housing respectively positioned on the front and rear thereof, and including a motor housing having a cooling water flowing part in which cooling water flows, a stator coupled to an inner peripheral surface of the motor housing, a rotor rotated in the stator and a rotor disk integrally formed with the rotor to drive the front impeller and the rear impeller; and

a cooling unit into which a portion of compressed air compressed by the first compression unit and flowing through the connection pipe is introduced, exchanges heat with the cooling water to cool the driving unit.

2. The air compressor for a vehicle of claim 1 , wherein the air compressor for a vehicle is a rear runner type in which the rotor disk is positioned at the rear, and

the cooling unit is positioned long in a length direction of the motor housing and includes a first flow path exchanging heat with the cooling water flowing part.

3. The air compressor for a vehicle of claim 2 , wherein the first flow path includes

a 1-1-th flow path for conveying compressed air from the outer peripheral surface to inner center of the motor housing, and

a 1-2-th flow path for conveying compressed air from the 1-1-th flow path to the rear thereof.

4. The air compressor for a vehicle of claim 3 , further comprising a rear cover and a diffuser, positioned between the motor housing and the rear housing to support the rotor disk,

wherein the rear cover includes a second flow path for receiving compressed air conveyed from the first flow path and conveying the same to the rotor disk.

5. The air compressor for a vehicle of claim 4 , wherein the second flow path includes

a 2-1-th flow path open for communicating with the 1-2-th flow path, and

a 2-2-th flow path for conveying compressed air from the 2-1-th flow path to the inner center.

6. The air compressor for a vehicle of claim 5 , wherein the rear cover includes

a seating portion formed to be concave forward in a predetermined central region of its rear surface for the rotor disk to be seated therein, and

a second through hole having an open predetermined region adjacent to an outer periphery of the seating portion for a portion of compressed air conveyed through the second flow path to bypass the rotor disk.

7. The air compressor for a vehicle of claim 5 , wherein the 2-2-th flow path is inclined in a direction in which the rotor is rotated for the 2-1-th flow path to communicate with the seating portion.

8. The air compressor for a vehicle of claim 6 , further comprising a first thrust bearing and a second thrust bearing respectively supporting the front and rear of the rotor disk.

9. The air compressor for a vehicle of claim 8 , further comprising a front journal bearing and a rear journal bearing respectively supporting the front and rear of the rotor.

10. The air compressor for a vehicle of claim 9 , further comprising a front cover,

wherein the cooling unit includes a first cooling unit where compressed air, passing through the first flow path and the second flow path, cools the rotor disk, the first thrust bearing and the second thrust bearing, and performs the cooling while moving to the front from the rear of the rotor through a region between the rear cover, the front cover and the rotor.

11. The air compressor for a vehicle of claim 10 , further comprising a first through hole passing from the rear to front of the front impeller,

wherein the cooling unit includes a second cooling unit where compressed air cools the front impeller while passing through the first through hole.

12. The air compressor for a vehicle of claim 11 , wherein the first through hole is inclined from the outer rear to the central front.

13. The air compressor for a vehicle of claim 12 , further comprising a third through hole and a fourth through hole respectively open in the motor housing and the front cover for compressed air cooling the inside of the motor housing through the second through hole to move to the second cooling unit,

wherein the cooling unit includes a third cooling unit where compressed air cools the inside of the motor housing while passing through at least one of the second through hole, the third through hole and the fourth through hole.

14. The air compressor for a vehicle of claim 13 , wherein in the cooling unit, the connection pipe and the first flow path are connected with each other through a cooling pipe, and

the rear cover has a sum of cross-sectional areas of the first cooling unit and the second through hole larger than a cross-sectional area of the cooling pipe.

15. The air compressor for a vehicle of claim 13 , wherein the rotor includes an open shaft unit open in an axial direction to cool the rotor by receiving a portion of compressed air from the rear inlet.