JP2011017262A - Drain pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drain pump that maintains pump performance such as lifting amount and discharge amount, and reduces noise and vibration accompanying water scooping of a rotary impeller.SOLUTION: A large-diameter blade 101 is divided into an inner blade 102 extending outward from a shaft part 52 and an outer blade 103 extending inward from a cylindrical wall member 64. A radius of an impeller scooping up water, that is a sum of a radius length of the inner blade 102 and a radius length of the outer blade 103 is made substantially equal to a radius length of the large-diameter blade of a conventional one. Therefore, pump performance equal to the conventional one is secured. As an opening area and flow passage area of a suction port is made substantially equal to the conventional one, the discharge amount of the pump can be equal to the conventional one. The large-diameter blade 101 is divided at a position where an amount of generated air bubbles increases, and the inner blade 102 and outer blade 103 are alternately disposed. Accordingly, air bubbles are escaped to a downstream side in a rotational direction, so that intensity of collision with the blades and air bubbles is reduced, and noise caused by burst of air bubbles and vibration caused by a collision load of the flow of a gas-liquid mixture are reduced.

Description

  The present invention particularly relates to a drainage pump installed in an air conditioner.

  In the indoor unit of the air conditioner, moisture in the air condenses and adheres to the heat exchanger during cooling operation, and water droplets drip into a drain pan provided below the heat exchanger. In order to drain the drain water accumulated in the drain pan, a drain pump is installed in the indoor unit. As an example of this drainage pump, a rotary blade is rotatably provided in a housing having a suction port at the lower end and a discharge port at the side, and is rotated by a motor fixed to the upper opening of the housing through a cover. Some rotate the blades. When the motor is driven to rotate the rotating blade, the drain water stored in the drain pan is sucked from the lower end of the suction port, pumped up along the inner surface of the housing, and discharged from the discharge port of the housing to the outside.

  As a prior art example of this type of drainage pump, there is one disclosed in Patent Document 1. FIG. 15 is a partially broken front view showing the entire configuration of the drainage pump disclosed in Patent Document 1, and FIG. 16 is a top view and a side view of the rotary blade. The drainage pump indicated by reference numeral 1 as a whole has a motor 10 and a pump body 30 attached to the motor 10 below via a bracket 20. The bracket 20 is formed integrally with a cover 32 that covers an upper opening of the housing 40, and the cover 32 is connected to the housing 40 via a seal member 34. The housing 40 is made of plastic, and has a pipe-like suction port 42 that opens downward, a pump chamber 44 formed inside, and a discharge port 46 that opens toward the side. The suction end portion 43 of the suction port 42 is formed in a tapered surface whose inner diameter dimension is narrowed toward the opening end.

  In the housing 40, a rotary blade 50 that is rotated by the output of the motor 10 is installed in a state of being accommodated in the pump chamber 44. The rotary blade 50 is connected to the shaft portion 52, a plurality of plate-shaped large-diameter blades 60 extending in the radial direction from the outer periphery at the upper portion of the shaft portion 52, and the lower edge portion of each large-diameter blade 60 and a suction port And a plurality of flat plate-shaped small-diameter blades 54 accommodated in 42. The shaft portion 52 passes through a through hole 36 formed at the center of the cover 32 and protrudes toward the motor 10. The drive shaft 12 of the motor 10 is inserted into a hole 53 provided at the center of the upper end of the shaft portion 52. It is fixed. A draining disc 14 is attached to the upper surface of the shaft portion 52, and the draining disc 14 prevents the drain water ejected from the through hole 36 of the cover 32 from scattering toward the motor 10.

  The lower edge portion of the large-diameter blade 60 is formed in a tapered shape, and the lower edge portion is connected by a disk-shaped annular member 62 having an opening 63. The small-diameter blades 54 are formed integrally with the large-diameter blades 60 and the resin, and are disposed below the large-diameter blades 60. An auxiliary blade 68 is provided between the adjacent large-diameter blades 60, 60, and the pump head can be secured by the auxiliary blade 68 and the large-diameter blade 60.

  The outer peripheral ends of the large-diameter blade 60 and the auxiliary blade 68 are connected by a cylindrical wall member 64. The position of the upper edge portion of the cylindrical wall member 64 is set lower than the positions of the upper edge portions of the large-diameter blade 60 and the auxiliary blade 68. The flow of bubbles generated from the liquid by the rotation of the large-diameter blades 60 smoothly flows to the discharge port 46 by the cylindrical wall member 64, and the collision of the bubbles with the bottom surface 35 of the cover 32 is alleviated and noise is reduced. Further, when the drainage pump 1 is stopped, water returning from the discharge port 46 to the pump chamber 44 of the housing 40 hits the cylindrical wall member 64 and is gradually diffused by the buffering of the cylindrical wall member 64, and is caused by the return water. Noise is also reduced. In addition, the position of the upper edge part of the cylindrical wall member 64 is made higher than the position of the upper edge part of the large diameter blade | wing 60 and the auxiliary blade | wing 68 according to pump capability (the head to be used), or is made into the same position. Noise can be reduced.

  The lower end portion of the cylindrical wall member 64 is annularly connected to an annular member 62 that connects the lower edge portion of the large-diameter blade 60 and the auxiliary blade 68. The annular member 62 divides the level of the drain water rising from the suction port 42 substantially vertically, reducing the amount of water in contact with the large-diameter blade 60 and reducing the generation of bubbles. The annular member 62 has an opening 63 between the inner peripheral portion side and the shaft portion 52. The lower edge portion of the large-diameter blade 60 and the auxiliary blade 68 is formed in a shape inclined toward the small-diameter blade 64, and the annular member 62 is also formed in a dish shape in accordance with this inclination.

JP 09-68185 A

  In the drainage pump 1 as described above, when the air conditioning machine is turned on and the drainage pump 1 starts operation, drain water is applied to the small-diameter blade 54, suction is started by applying rotational force, and the water gradually flows into the pump chamber. 44. In the pump chamber 44, water and air are mixed, and the gas-liquid mixed fluid collides with the rotary blade 50. This collision leads to water scraping noise and vibration.

  In the rotary blade 50, a large amount of bubbles generated at the gas-liquid boundary directly collide with the front surface of the large-diameter blade 60 and burst, and bubbles are generated downstream of the large-diameter blade 60, so that cavitation noise and vibration increase. . Although the position of the upper edge of the cylindrical wall member 64 is formed lower than the position of the upper edge of the large-diameter blade 60, the noise can be reduced to some extent, but the noise is more effectively reduced. No special consideration was given to this.

  Accordingly, an object of the present invention is to provide a drainage pump capable of reducing noise and vibration associated with scrubbing of rotating blades while maintaining pump performance such as a head and discharge amount.

  In order to solve the above problems, the drainage pump according to the present invention includes a motor, a rotary blade connected to the output shaft of the motor, a suction port at the lower end, and a discharge port at the side. A housing that rotatably accommodates the rotating blade, and the rotating blade includes a shaft portion coupled to the output shaft of the motor, and a plurality of plate-shaped large-diameter blades extending radially from the shaft portion; Drainage having a plurality of plate-shaped small-diameter blades connected to the lower edge portion of the large-diameter blade and accommodated in the suction port, and a cylindrical wall member connecting the outer peripheral portion of the large-diameter blade. The large-diameter blade is divided into an inner blade that extends outward from the shaft portion and an outer blade that extends inward from the cylindrical wall member, and the inner blade and the outer blade are Alternatingly arranged around the shaft It is characterized.

  According to the drainage pump of the present invention, the large-diameter blade is divided into the inner blade and the outer blade, and the inner blade and the outer blade are alternately arranged around the shaft portion. , Between the inner blade and the cylindrical wall member, and between the outer blade and the shaft portion, the bubbles can escape to the downstream side in the rotation direction. Noise due to crushing can be reduced. Moreover, since the force opposite to the rotational direction acting on the large-diameter blade is reduced, the load is reduced and the vibration is reduced. By making the distance R1 from the center of the shaft part to the radially outer end of the inner blade and the distance R2 from the center of the shaft part to the radially inner end of the outer blade substantially the same, Since the radial length of the large-diameter blade to be lifted is substantially the same as the radial length of the conventional large-diameter blade, the pump performance equivalent to that of the conventional product can be ensured. Further, by making the opening area of the suction port and the flow path area substantially the same as those of the conventional product, it is possible to secure the same amount of pump discharge as that of the conventional product.

  According to the drainage pump of the present invention, air bubbles can escape from the inner blade and the outer blade, between the inner blade and the cylindrical wall member, and between the outer blade and the shaft portion to the downstream side in the rotation direction. Regardless of the shape of the cylindrical wall member and the position of its upper edge, the amount of bubbles that collide with the large-diameter blades can be reduced, and noise caused by the collapse of the bubbles can be reduced. Moreover, since the force opposite to the rotational direction acting on the large-diameter blade is reduced, the load is reduced and the vibration is reduced. Therefore, it can contribute to the calming of the air conditioner.

It is a partially broken front view which shows an example of the drainage pump by this invention. It is a figure which shows one Example of the rotary blade used for the drainage pump by this invention. It is a figure which shows the modification of the rotary blade | wing of FIG. It is explanatory drawing which shows the mode of the gas-liquid boundary at the time of the low head operation of the rotary blade shown in FIG. 2 compared with the case of the conventional rotary blade. It is explanatory drawing which shows the mode of the gas-liquid boundary at the time of the high head operation of the rotary blade shown in FIG. 2 compared with the case of the conventional rotary blade. It is a figure which shows another Example of the rotary blade used for the drainage pump by this invention. It is a figure which shows another Example of the rotary blade used for the drainage pump by this invention. It is a figure which shows another Example of the rotary blade used for the drainage pump by this invention. It is a fragmentary sectional view of the Example of the rotary blade used for the drainage pump by this invention. It is a bottom view of the modification of the small diameter blade | wing of a rotary blade used for the drainage pump by this invention. It is the graph which showed the relationship between the head of the drainage pump by this invention, and the magnitude | size of the vibration of the radial direction according to it along with the case of the conventional drainage pump. It is the graph which showed the relationship between the head of the drainage pump by this invention, and the magnitude | size of the vibration of the axial direction according to it along with the case of the conventional drainage pump. It is the table | surface which showed the head capacity of the drainage pump by this invention along with the case of the conventional drainage pump. It is a graph which shows the relationship between the rotation speed of an AC motor and a DC motor, and torque. It is a partially broken front view which shows an example of the conventional drainage pump. It is the upper side figure and side view of a rotary blade of the drainage pump shown in FIG.

  Embodiments of the drainage pump according to the present invention will be described below with reference to the drawings. FIG. 1 is a partially cutaway front view of an example of a drainage pump according to the present invention, and FIG. 2 shows an embodiment of a rotary blade used in the drainage pump shown in FIG. 2A is a top view of the rotary blade, FIG. 2B is a cross-sectional view taken along the line AA of the rotary blade shown in FIG. 2A, and FIG. 2C is a view of the rotary blade shown in FIG. It is a bottom view. The structure of the drainage pump in which the rotating blades are incorporated is not described again by using the same reference numerals for those equivalent to those shown in FIGS. 15 and 16. Also, with respect to the rotating blades, the same reference numerals are used for the structures other than the parts that characterize the present invention, and the same components as those shown in FIGS.

  In the rotary blade 100 shown in FIG. 2, the large-diameter blade 101 is divided into an inner blade 102 that extends radially outward from the shaft portion 52 and an outer blade 103 that extends radially inward from the cylindrical wall member 64. The inner blades 102 and the outer blades 103 are alternately arranged around the shaft portion 52.

  4 and 5, the state of the gas-liquid boundary in the low head operation (FIG. 4) and the high head operation (FIG. 5) of the drainage pump according to the present invention is compared with that of the conventional drainage pump. Has been shown. During the low head operation (FIG. 4), the vicinity of the position where the large-diameter blade 101 is divided into the inner blade 102 and the outer blade 103 (the position indicated by the one-dot chain line circle) is substantially the gas-liquid boundary. Become. The inside of the gas-liquid boundary is the air layer region, and the outside of the gas-liquid boundary is the water layer region. That is, the large-diameter blade 101 is divided into the inner blade 102 and the outer blade 103 at a position where the amount of generated bubbles increases. The division position of the large-diameter blade 101 is set according to the head for reducing noise. That is, it is effective to divide the large-diameter blade 101 into the inner blade 102 and the outer blade 103 in the vicinity of the gas-liquid boundary generated in the rotary blade 100 at the head for reducing noise.

  When the rotary blade 100 rotates in the direction of the arrow shown in the figure, the bubbles and water flow in the rotary blade 100 as indicated by the arrows, and the bubbles pass between them without colliding with the inner blade 102 and the outer blade 103. It is possible to suppress the amount of bubbles that pass through and downstream. As described above, the air bubbles are allowed to escape from between the inner blade 102 and the outer blade 103, between the inner blade 102 and the cylindrical wall portion 64, and between the outer blade 103 and the shaft portion 52. Since the amount of collision with the blades is reduced, cavitation due to bubble collapse is reduced, thereby reducing noise and vibration. In addition, when the air bubbles collide with the blades, a force in the direction opposite to the rotation direction acts on the blades, but by providing a water escape path, the reverse force acting on each blade is reduced. Is reduced.

  As the head rises, as shown in the high head operation (FIG. 5), the diameter of the gas-liquid boundary decreases, and the amount of water scraped by the inner blade 102 and the outer blade 103 increases. It hits only the blade 102. Since the load increases as the amount of water scraping increases, the rotational speed of the rotary blade 50 decreases compared to that at the time of activation. Since the diameter of the gas-liquid boundary is reduced and the rotational speed of the rotary blade 50 is reduced, the amount of bubbles colliding with the rotary blade 100 is reduced, so that the cavitation noise is reduced. Further, since water escapes downstream from the gap between the inner blade 102 and the cylindrical wall member 64 and between the inner blade 102 and the outer blade 103, the load per blade can be reduced. The vibration can be reduced as compared with the conventional case.

  The graph of FIG. 11 shows the relationship between the head of the drainage pump according to the present invention and the magnitude of vibration in the radial direction, and the graph of FIG. 12 shows the relationship between the head and the magnitude of vibration in the axial direction. It is shown side by side with the product. As shown in FIGS. 11 and 12, in the product of the present invention, the vibration in the radial direction is greatly improved particularly in the low head operation. In general, the vibration of the product of the present invention is lower than that of the conventional product at any head.

  The radial lengths of the inner blade 102 and the outer blade 103 can be determined according to the actual lift. That is, when the blade radius is r, there is a relationship of lift H = r ^ 2 × ω ^ 2 ÷ (2 × g). By making the sum of the radial lengths of the inner blade 102 and the outer blade 103 equal to the radial length of the conventional large blade, it is possible to keep the blade radius r that rakes water from changing, thereby The pump performance equivalent to that of the conventional product can be ensured.

  That is, in the example shown in FIG. 2, the distance R2 from the center of the shaft portion 52 to the radially inner end portion 103a of the outer blade 103 is the distance from the center of the shaft portion 52 to the radially outer end portion 102a of the inner blade 102. It is substantially the same as R1. By maintaining such a relationship between R1 and R2, the pump performance equivalent to that of the conventional product can be secured, and the radially inner end 103a of the outer blade 103 and the radially outer end of the inner blade 102 can be secured. A flow F of a mixture of air bubbles and water easily flows between the end portions 102a. That is, an escape path is secured for the bubbles, collision of the bubbles with the inner blades 102 and the outer blades 103 is reduced, and noise and vibration due to cavitation due to bubble collapse are reduced. R2 may be larger than R1. Conversely, if R2 is made sufficiently smaller than R1, the state of collision between the gas-liquid mixed flow and the rotary blade 100 becomes the same as in the prior art, and therefore the noise / vibration reducing action / effect is reduced.

  3 is a view showing a modification of the rotary blade of FIG. 2, FIG. 3 (a) is a top view, FIG. 3 (b) is a cross-sectional view taken along line A′-A ′ of FIG. 3 (a), and FIG. ) Is a bottom view of FIG. In FIG. 2, the cylindrical wall member 64 has a stepped shape. However, as shown in FIG. 3, the flow path in the rotary blade 100 ′ is widened by making the cylindrical wall member 64 a straight thin shape. Since the gas-liquid mixture flows more easily, the noise / vibration reduction effect is further enhanced.

  Moreover, in order to ensure the discharge amount, the opening area and the flow path area of the suction port 42 are not changed from the conventional product. As for ensuring the pump performance, as shown in FIG. 13, it has been confirmed that the same capacity as that of the conventional product can be ensured with respect to the discharge amount and the deadline lifting height.

  A rotary blade 100 shown in FIG. 2 includes a plate-like auxiliary blade 104 extending in the radial direction between large-diameter blades 101 and 101 adjacent to each other in the circumferential direction of the shaft portion 52. In order to make the drawing easy to see, the reference numeral 104 is attached to only one auxiliary blade. The auxiliary blade 104 is divided into an inner auxiliary blade 105 extending in the radial direction at a position spaced from the shaft portion 52 and the cylindrical wall member 64, and an outer auxiliary blade 106 extending inward in the radial direction from the cylindrical wall member 64. . The inner blade 102 of the large blade 101 and the inner blade 105 of the auxiliary blade 104, and the outer blade 103 of the large blade 101 and the outer blade 106 of the auxiliary blade 104 are alternately arranged around the shaft portion 52. . Thus, a large head can be secured by providing the auxiliary blade 104 in the middle between the large-diameter blades 101 on both sides.

  FIG. 6 shows another embodiment of the rotary blade used in the drainage pump according to the present invention. In the rotary blade 110, the position of the upper edge portion of the cylindrical wall member 164 is set lower than the positions of the upper edge portions of the large-diameter blade 101 and the auxiliary blade 104. An arc-shaped chamfered portion (not shown) can be formed inside the upper edge portion of the cylindrical wall member 164. By forming the cylindrical wall member 164 in this manner, the flow of bubbles generated from the liquid around the large-diameter blade 101 flows smoothly to the discharge port 46, and the bubbles collide with the bottom surface 35 of the cover 32. Alleviated and reduced noise.

  Further, when the drainage pump is stopped, the return water returning from the discharge port 46 to the pump chamber 44 in the casing hits the cylindrical wall member 164 and is gradually diffused by the buffering of the cylindrical wall member 164, resulting from the return water. Reducing noise. Moreover, the arc-shaped chamfered portion has, for example, a radius of curvature approximately equal to the plate thickness dimension of the cylindrical wall member 164, thereby providing a drain to which energy flowing in the radial direction is imparted by the rotation of the large-diameter blade 101 or the auxiliary blade 104. The water smoothly moves over the upper edge of the cylindrical wall member 164, that is, the flow of bubbles is smoothed toward the discharge port 46, and noise can be reduced.

  The lower end portion of the cylindrical wall member 164 is annularly connected to an annular member 62 that connects the lower edge portion of the large-diameter blade 101 and the auxiliary blade 104. In addition, although the figure shows the case where the cylindrical wall member 164 and the annular member 62 are integrally configured, it is needless to say that they may be configured separately. The liquid level of the drain water rising from the suction port 42 is substantially vertically divided by the annular member 62, the amount of water in contact with the large-diameter blade 101 is reduced, and the generation of bubbles is reduced. The inner peripheral side of the annular member 62 has an opening 63 between the center of the rotary blade 110. The lower edge portions of the large-diameter blade 101 and the auxiliary blade 105 are formed in a shape inclined toward the small-diameter blade 54, and the annular member 62 is also formed in a dish shape in accordance with this inclination.

  In FIG. 9, the fragmentary sectional view of the rotary blade of the drainage pump by this invention is shown. FIG. 9A is a partial cross-sectional view of FIG. 2, and other than that, it is a partial cross-sectional view of an embodiment having a shape different from that of FIG. As shown in these embodiments, the large-diameter blade 101 is divided into the inner blade 102 and the outer blade 103 regardless of the shape of the cylindrical wall member 64 and the position of the upper edge portion thereof. Cavitation is reduced and noise and vibration can be reduced.

  FIG. 10 shows a bottom view of a modified example of a small-diameter blade of a rotary blade used in the drainage pump according to the present invention. In the example shown in FIG. 2, in order to maintain the pump performance such as the head and the discharge amount equivalent to that of the conventional product, the opening area of the suction port and the flow path area are made equivalent to those of the conventional product. Accordingly, it is also possible to adjust the opening area and the flow path area of the suction port by making the small-diameter blade into a shape as shown in FIG. 10, for example.

  FIG. 7 shows still another embodiment of the rotary blade used in the drainage pump according to the present invention. In this rotary blade 120, a plurality of auxiliary blades 104, 104 are arranged between adjacent large-diameter blades 101, 101. In this example, the number of auxiliary blades 104 is two, but the number is not limited to this, and may be three or more. The plurality of auxiliary blades 104 and 104 are arranged at positions that divide the adjacent large-diameter blades 101 and 101 around the shaft portion 52 at equal intervals. That is, in this embodiment, the large-diameter blades 101 are arranged every 90 degrees around the shaft portion 52, and there are two auxiliary blades 104 between the adjacent large-diameter blades 101, 101. The inner auxiliary blades 105 are arranged around the shaft portion 52 with an interval of 30 degrees, and the outer blades 103 and the outer auxiliary blades 106 are also arranged around the shaft portion 52 with an interval of 30 degrees. When the outer and inner blades are combined, the blades are displaced by 15 degrees.

  FIG. 8 shows still another embodiment of the rotary blade used in the drainage pump according to the present invention. In the rotary blade 130, the large-diameter blade 101 and the auxiliary blade 104 are each divided into three in the radial direction of the shaft portion 52. That is, the large-diameter blade 101 is divided into an inner blade 102, an outer blade 103, and an intermediate blade 107, and the auxiliary blade 104 is divided into an inner auxiliary blade 105, an outer auxiliary blade 106, and an intermediate auxiliary blade 108. The inner blade 102 and the intermediate blade 107, and the inner auxiliary blade 105 and the intermediate auxiliary blade 108 are sequentially shifted around the shaft portion 52. The intermediate blades 107 and the intermediate auxiliary blades 108, the outer blades 103 and the outer auxiliary blades 106 are alternately arranged around the shaft portion 52, and the intermediate blades 107 are arranged between the inner auxiliary blade 105, the outer auxiliary blade 106 and the shaft portion 52. The intermediate auxiliary blades 108 are arranged to be shifted around the inner blade 102 and the outer blade 103 and the shaft portion 52, and between the end portions of each blade, as in the previous embodiment. Are not connected, providing a gas escape route near the gas-liquid boundary.

  In addition, as a motor of the drainage pump of the present invention, either an AC motor or a DC motor can be adopted. In the case of a low head, the lower the load and the higher the rotation, the wider the gas-liquid boundary surface, and the cavitation noise increases due to the collision of bubbles during water scraping, and the vibration tends to deteriorate, but due to the difference in motor characteristics, As shown in FIG. 14, the DC motor tends to have a higher rotational speed at a low load, and therefore, the effect of applying the present invention to the DC pump can be greater.

DESCRIPTION OF SYMBOLS 10 Motor 12 Output shaft 14 Drained disk 20 Bracket 30 Pump main body 32 Cover 34 Seal member 35 Bottom surface 40 Housing 42 Suction port 43 Suction end 44 Pump chamber 46 Ejection port 52 Shaft unit 54 Small diameter blade 62 Ring member 63 Opening unit 64, 164 Cylindrical wall member 100, 110, 120, 130 Rotary blade 101 Large diameter blade 102 Inner blade 102a Radial outer end 103 Outer blade 103a Radial inner end 104 Auxiliary blade 105 Inner auxiliary blade 106 Outer auxiliary blade 107 Intermediate blade 108 Intermediate auxiliary blade

Claims (7)

  A motor, a rotary blade connected to the output shaft of the motor, a suction port at the lower end and a discharge port at the side, and a housing for rotatably housing the rotary blade, The rotary blade is connected to a shaft portion connected to the output shaft of the motor, a plurality of plate-shaped large-diameter blades extending radially from the shaft portion, and a lower edge portion of the large-diameter blade, and A drainage pump having a plurality of plate-shaped small-diameter blades accommodated in a suction port and a cylindrical wall member that connects outer peripheral portions of the large-diameter blades, wherein the large-diameter blade includes the shaft portion. An inner blade extending outward from the outer wall and an outer blade extending inward from the cylindrical wall member, and the inner blade and the outer blade are alternately arranged around the shaft portion. Drainage pump characterized.   The relationship between the distance R1 from the center of the shaft portion to the radially outer end of the inner blade and the distance R2 from the center of the shaft portion to the radially inner end of the outer blade is R1 ≦ R2. The drainage pump according to claim 1.   The drainage pump according to claim 1 or 2, wherein the inner blade and the outer blade are divided in the vicinity of a gas-liquid boundary.   The rotary blade includes a plate-like auxiliary blade extending in a radial direction between the large-diameter blades adjacent in the circumferential direction of the shaft portion, and the auxiliary blade is between the shaft portion and the cylindrical wall member. Are divided into an inner auxiliary blade extending in the radial direction and an outer auxiliary blade extending inwardly from the cylindrical wall member, and the inner blade and the inner auxiliary blade, and the outer blade and the outer auxiliary blade. The drainage pump according to any one of claims 1 to 3, wherein the drainage pump is alternately arranged around the shaft portion.   The drainage pump according to claim 4, wherein a plurality of the auxiliary blades are disposed between the adjacent large-diameter blades.   6. The drainage pump according to claim 4, wherein the auxiliary blade is disposed at a position that divides the adjacent large-diameter blades at equal intervals around the shaft portion.   The large-diameter blade is divided into the inner blade, the outer blade, and the intermediate blade, which are sequentially shifted in the circumferential direction of the shaft portion, and the auxiliary blade is configured to be the inner auxiliary blade and the outer auxiliary blade. The blades are divided into blades and intermediate auxiliary blades, which are sequentially shifted in the circumferential direction of the shaft portion, and the intermediate blades, the intermediate auxiliary blades, the outer blades, and the outer auxiliary blades are arranged around the shaft portion. The intermediate blades are arranged alternately with respect to the inner auxiliary blades and the outer auxiliary blades and shifted around the shaft portion, and the intermediate auxiliary blades are arranged with respect to the inner blades and the outer blades. The drainage pump according to any one of claims 4 to 6, wherein the drainage pump is arranged around the portion.