Drain pump

1. A drain pump for an indoor unit of an air-conditioner comprising:

a motor;

a rotary impeller connected to an output shaft of the motor; and

a housing that includes an inlet formed at a lower end portion thereof and an outlet formed at a side portion thereof, the rotary impeller being rotatably received in the housing,

wherein the rotary impeller includes a shaft portion connected to the output shaft of the motor, a plurality of plate-like large-diameter blades that extends from the shaft portion in a radial direction, a plurality of plate-like small-diameter blades connected to lower edge portions of the large-diameter blades and is received in the inlet, and a ring member connected to outer peripheral portions of the large-diameter blades,

each of the large-diameter blades is divided into an inner blade that extends outward from the shaft portion with a leading end thereof being separated from the ring member, and a corresponding outer blade that extends inward from the ring member with a leading end thereof being separated from the shaft portion, and

the inner and outer blades of the large-diameter blades are alternately disposed around the shaft portion,

the rotary impeller further includes plate-like auxiliary blades, which extend in the radial direction, between the large-diameter blades that are adjacent to each other in a circumferential direction of the shaft portion,

each of the auxiliary blades is divided into an inner auxiliary blade that extends in the radial direction between the shaft portion and the ring member, and an outer auxiliary blade that extends inward from the ring member, and

the inner blades and the inner auxiliary blades, and the outer blades and the outer auxiliary blades are alternately disposed around the shaft portion,

each auxiliary blade is disposed between two adjacent large-diameter blades, and

each outer blade of the large-diameter blade is arranged, with respect to the corresponding inner blade of the large-diameter blade, at a position displaced around the shaft portion by ½ of the angle between the inner blade of the large-diameter blade and the inner auxiliary blade adjacent thereto in the circumferential direction of the shaft portion.

2. The drain pump according to claim 1 ,

wherein a relationship between a distance R 1 between the center of the shaft portion and an outer end of the inner blade in the radial direction and a distance R 2 between the center of the shaft portion and an inner end of the outer blade in the radial direction satisfies R 1 ≦R 2 .

3. The drain pump according to claim 1 ,

wherein the inner and outer blades are divided from each other in the vicinity of a gas-liquid boundary.

4. The drain pump according to claim 1 ,

wherein the plurality of auxiliary blades is disposed around the shaft portion between the large-diameter blades, which are adjacent to each other, at regular intervals.

5. A drain pump for an indoor unit of an air-conditioner comprising: a motor; a rotary impeller connected to an output shaft of the motor; and a housing that includes an inlet formed at a lower end portion thereof and an outlet formed at a side portion thereof, the rotary impeller being rotatably received in the housing, wherein the rotary impeller includes a shaft portion connected to the output shaft of the motor, a plurality of plate-like large-diameter blades that extends from the shaft portion in a radial direction, a plurality of plate-like small-diameter blades connected to lower edge portions of the large-diameter blades and is received in the inlet, and a ring member connected to outer peripheral portions of the large-diameter blades,

each of the large-diameter blades is divided into an inner blade, an outer blade, and an intermediate blade,

the inner blades, the outer blades, and the intermediate blades are sequentially disposed in the circumferential direction of the shaft portion so as to be shifted relative to each other,

each of the auxiliary blades is divided into an inner auxiliary blade, an outer auxiliary blade, and an intermediate auxiliary blade,

the inner auxiliary blades, the outer auxiliary blades, and the intermediate auxiliary blades are sequentially disposed in the circumferential direction of the shaft portion so as to be shifted relative to each other,

the intermediate blades, the intermediate auxiliary blades, the outer blades, and the outer auxiliary blades are alternately disposed around the shaft portion,

the intermediate blades are disposed around the shaft portion so as to be shifted relative to the inner auxiliary blades and the outer auxiliary blades,

the intermediate auxiliary blades are disposed around the shaft portion so as to be shifted relative to the inner blades and the outer blades, each inner blade of the large-diameter blades extends outward from the shaft portion and terminates at an outer end, and each outer blade of the large-diameter blades extends inward from the ring member towards the shaft and terminates at an inner end, and wherein a relationship between a distance R 1 between the center of the shaft portion and the outer end of the outwardly extending inner blade in the radial direction and a distance R 2 between the center of the shaft portion and the inner end of the inwardly extending outer blade in the radial direction satisfies R 1 ≦R 2 .

6. A drain pump comprising:

a motor;

a rotary impeller connected to an output shaft of the motor; and

a housing that receives the rotary impeller, the housing including an inlet formed at a lower portion thereof and an outlet formed at a cylindrical side portion of a pump chamber,

wherein the rotary impeller includes a shaft portion connected to the output shaft of the motor, plate-like large-diameter blades that extend from the shaft portion in a radial direction, plate-like small-diameter blades that are connected to the large-diameter blades by connecting portions and are received in the inlet, a ring member provided at outer peripheral portions of the large-diameter blades, and an annular member that is connected to a lower end portion of the ring member and includes an opening at a central portion thereof, and

each of the large-diameter blades is divided into an inner blade that extends outward from the shaft portion and terminates at an outer end, and an outer blade that extends inward from the ring member towards the shaft and terminates at an inner end, and

the inner and outer blades are alternately disposed around the shaft portion and

wherein a relationship between a distance R 1 between the center of the shaft portion and the outer end of the outwardly extending inner blade in the radial direction and a distance R 2 between the center of the shaft portion and the inner end of the inwardly extending outer blade in the radial direction satisfies R 1 ≦R 2 , and

an outer portion of an upper edge portion of the-ring member is formed in a shape where the thickness of the ring member is decreased, so that an expanded space is formed between the pump chamber and the outer portion of the upper edge portion of the ring member.

7. The drain pump according to claim 6 ,

wherein the outer portion of the upper edge portion of the ring member is formed in a tapered shape.

8. The drain pump according to claim 6 ,

wherein the outer portion of the upper edge portion of the ring member is formed in an arc shape.

9. The drain pump according to claim 6 ,

wherein the outer portion of the upper edge portion of the ring member is formed in a stepped shape.