Pump device

1. A pump device for pumping a gas, comprising:

a motor portion including a rotor chamber and a rotor rotatably disposed in the rotor chamber, wherein the rotor includes a rotor shaft;

a pump portion including a pump chamber and an impeller rotatably disposed in the pump chamber, wherein the impeller is coupled to the rotor shaft and is configured to rotate with the rotor shaft;

a partition wall separating the rotor chamber from the pump chamber, wherein the partition wall has a first side that faces the pump chamber and a second side that faces the rotor chamber;

a shaft hole extending through the partition wall along a central axis, wherein the rotor shaft extends through the shaft hole; and

a bearing provided in the shaft hole, wherein the bearing rotatably supports the rotor shaft and is configured to be injected with grease,

wherein the partition wall includes a first breathing passage and a second breathing passage that each extend linearly through the partition wall separately from the shaft hole and that each provide fluid communication between the rotor chamber and the pump chamber,

wherein the first breathing passage has a first opening on positioned on the first side of the partition wall and a second opening on the second side of the partition wall, wherein the first opening is radially closer to the shaft opening than the second opening with respect to the central axis, and

wherein the second breathing passage has a third opening positioned on the first side of the partition wall and a fourth opening on the second side of the partition wall, wherein the third opening is radially closer to the shaft opening than the fourth opening with respect to the central axis.

2. The pump device of claim 1 , wherein the first opening of the first breathing passage is positioned adjacent to the third opening of the second breathing passage about the shaft hole.

3. The pump device of claim 1 , wherein:

a discharge opening of the pump chamber is positioned on a lower side of the pump chamber in a vertical direction of the pump chamber when the pump device is in a vehicle mounted state, and

a bottom surface of a downstream end of the discharge opening is positioned lower than a bottom surface of an upstream end of the discharge opening.

4. The pump device of claim 3 , wherein the first opening of the first breathing passage and the third opening of the second breathing passage are positioned above the rotor shaft along the vertical direction.

5. The pump device of claim 3 , wherein a guide recess is formed at the lower side of the pump chamber, wherein the guide recess is configured to guide a liquid on a rear surface of the impeller toward the discharge opening.

6. The pump device of claim 3 , wherein a liquid reservoir is formed at the lower side of the pump chamber, wherein the liquid reservoir has a bottom lower than a bottom surface of an upstream end of the discharge opening.

7. The pump device of claim 1 , wherein a distance between the first opening of the first breathing passage and the central axis is greater than a distance between the third opening of the second breathing passage and the central axis.

8. The pump device of claim 1 , wherein the first breathing passage is configured to be in fluid communication with the second breathing passage when the rotor shaft is rotating.

9. The pump device of claim 1 , wherein the first breathing passage and the second breathing passage are configured to circulate a circulation flow from the pump chamber to the rotor chamber via the first breathing passage, and then from the rotor chamber to the pump chamber via the second breathing passage.