JP2019157817A - Stationary bush of centrifugal impeller and centrifugal pump including the same - Google Patents

Abstract

To provide a stationary bush of a centrifugal impeller, capable of suppressing occurrence of a stagnated vortex region of the centrifugal impeller to prevent a pump from being blocked or constrained due to foreign matters in sewage water.SOLUTION: A stationary bush of a centrifugal impeller is arranged so as to be at least partially fitted into a boss hole of the centrifugal impeller through which a rotational shaft is passed. The stationary bush comprises a cylindrical bush body having an open hole through which a fastener screwed to the rotational shaft is inserted, and a bush blade fixed to an outside surface of the bush body. In the fitting state, a bush blade extends along a direction in which at least one impeller blade of the centrifugal impeller extends toward a central axial line of the centrifugal impeller.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fixed bush of a centrifugal impeller. The present invention also relates to a centrifugal pump.

  As an example of a conventional centrifugal pump, the structure of a general vortex pump is shown in FIG. The vortex pump has a large gap between the lower edge of the centrifugal impeller blade and the bottom surface of the pump casing that houses the impeller. Therefore, the vortex pump is widely used as a sewage / dirt pump that can prevent the occurrence of a clogging accident in the pump due to foreign matter. In FIG. 3, only the configuration of the pump portion of the vortex pump is shown in a sectional view, and the internal structure of the motor portion is not shown.

  The vortex pump shown in FIG. 3 includes a motor unit 2 that drives a rotating shaft and a pump unit 3 that pumps water by rotating the rotating shaft. And the rotating shaft is sealed with the mechanical seal 104 between the pump part 3 and the motor part 2 so that the pressure water of the pump part 3 may not leak to the motor part 2 side. In FIG. 3, the rotating shaft is not shown. The motor chamber inside the motor unit 2 accommodates a rotor that rotates integrally with the rotating shaft and a stator that includes a stator winding. The motor chamber is sealed in a watertight manner by a substantially cylindrical motor frame 110 opened upward and a motor cover 111 connected to the upper end of the motor frame 110. On the upper surface of the motor cover 111, there is provided a handle 116 for suspending and moving the pump to a spring water site or the like.

  On the other hand, the pump unit 3 includes a centrifugal impeller 141 that has a plurality of blades 140 and is connected to the tip of a rotating shaft (not shown in FIG. 3) so as to rotate integrally therewith. The centrifugal impeller 141 includes a main plate 148 in which a boss portion 144 is formed, and a plurality of blades 140 connected to the main plate 148 and arranged around the boss hole 146 of the boss portion 144 at intervals. . The boss hole 146 is configured to penetrate the main plate 148 in the axial direction (in other words, the direction along the central axis C of the impeller 141) and receive the rotation shaft. The boss hole 146 includes a small diameter portion 146a having substantially the same diameter as the distal end portion of the rotation shaft, and a large diameter portion 146b having a diameter larger than that of the small diameter portion 146a. The small-diameter portion 146a receives the tip of the rotating shaft, and the large-diameter portion 146b receives a bush (not shown in FIG. 3) disposed in contact with the axial tip surface of the rotating shaft. FIG. 3A is a partial view of FIG. 3, in which the tip of the rotating shaft 1 and the bush 200 disposed in the boss hole 146 (not shown in FIG. 3A) are shown. FIG. 4 is a bottom view of the centrifugal impeller 141 shown in FIG. 3A. As shown in FIG. 3A, a fastener 500 such as a bolt is screwed into the screw hole at the tip of the rotating shaft 1 through the through hole of the bush 200. The bush 200 only needs to be fitted at least partially into the large diameter portion 146b of the boss hole 146. In other words, the bush 200 may include a truncated cone shape as shown in FIG. 3A, the lower surface of which protrudes downward from the boss hole 146. Alternatively, the lower surface of the bush 200 may be disposed so as to form substantially the same plane as the surface of the main plate 148. By tightening the fastener 500, the impeller 141 is fixed to the rotating shaft 1.

The pump unit 3 further includes a pump casing 150 that is divided into a lower casing 142 and an intermediate casing 130. The lower casing 142 has a discharge port 142a and a suction port 142b, and forms a pump chamber 143. The centrifugal impeller 141 is covered with a lower casing 142, and sucks spring water and sewage from the lower portion and discharges them from the side surface. A pump base 145 that allows the pump to stand on its own is attached to the lower casing 142. The back surface of the centrifugal impeller 141 is covered with an intermediate casing 130.

  As indicated by the arrow F1, the sewage sucked from the suction port 142b flows from the inner peripheral side of the centrifugal impeller 141 to the outer peripheral side through a flow path between the blades 140 of the rotating centrifugal impeller 141. As described above, the vortex pump forms a large gap between the lower surface of the blades 140 of the centrifugal impeller 141 and the bottom surface of the pump casing 150 so that even a relatively large foreign object can be easily discharged. It is configured.

  However, a stagnation vortex region where a stagnation vortex is generated as indicated by an arrow F2 exists between the suction port 142b of the pump casing 150 and the central portion of the centrifugal impeller 141. In the stagnant vortex region, the foreign substances are entangled and formed into a lump, and the inlet of the flow path between the blades 140 of the centrifugal impeller 141 is likely to be blocked. When the flow path of the centrifugal impeller 141 is blocked, normal operation of the pump is hindered. Moreover, the lump-like foreign matter may cause wear or damage to the wing 140.

  In order to suppress the formation of the stagnant vortex F2, it is preferable that the front edge portion (in other words, the inner peripheral side end portion) 140a of each blade 140 be as close as possible to the central axis C of the impeller 141. Thereby, the sewage flowing from the suction port 142b can be smoothly guided to the flow path between the blades 140. Although it is conceivable to extend the blade 140 so that the diameter of the large diameter portion 146b of the boss hole 146 is reduced and the leading edge portion 140a is moved to the inner peripheral side by that amount, the large diameter portion 146b of the boss hole 146 is considered. The bush 200 to be fitted into the outer diameter needs to have a large outer diameter so as to ensure a sufficient strength. Accordingly, there is a limit to reducing the outer diameter of the large diameter portion 146b, and it is difficult to extend the blade 140 toward the inner peripheral side.

  Patent document 1 describes the crushing pump which provided the stirring protrusion in the fixing nut which fixes an impeller. The stirring protrusion has a tip portion protruding toward the suction path. Patent Document 2 describes an occlusion prevention device having a baffle plate that substantially matches the inner diameter of an impeller of a vortex centrifugal pump. By the blocking prevention device, the sewage flowing into the pump casing is guided from the periphery of the baffle plate to the flow path between the blade plates.

Japanese Patent Laid-Open No. 8-135587 JP 2000-205168 A

  According to one embodiment of the present invention, a stationary bush of a centrifugal impeller that can suppress the occurrence of a stagnant vortex region of the centrifugal impeller and prevent the pump from being closed or restrained by foreign matter in sewage. Can be provided. In addition, according to one embodiment of the present invention, there is provided a centrifugal pump that can suppress the occurrence of a stagnant vortex region of a centrifugal impeller and prevent the occurrence of a clogged or constrained state of the pump due to foreign matter in sewage. can do.

  According to an embodiment of the present invention, there is provided a fixed bushing of a centrifugal impeller that is at least partially fitted in a boss hole of a centrifugal impeller through which the rotation shaft passes, and is screwed to the rotation shaft. A cylindrical bush main body having a through-hole through which a fastener to be inserted is inserted, and a bush blade fixed to the outer surface of the bush main body. A stationary bushing is provided that extends at least one impeller blade along a direction extending toward the central axis of the centrifugal impeller.

It is a figure which shows an example of the principal part of the centrifugal pump by one Embodiment of this invention. It is a bottom view of the centrifugal impeller shown in FIG. It is the elements on larger scale of FIG. It is a figure which shows the fixed bush used for one Embodiment of this invention single-piece | unit. It is a figure which shows an example of the centrifugal pump by a prior art. FIG. 4 is a partial view of FIG. 3. It is a bottom view of the centrifugal impeller shown in FIG. 3A.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the following description shows an example to the last and is not the meaning which limits the technical scope of this invention to the following embodiment. In the drawings, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted. In the following description, terms indicating directions such as “up” and “down” mean directions in the installed state of the centrifugal pump shown in FIG.

  The embodiment of the present invention to be described below is characterized by a structure for attaching a rotary shaft of a centrifugal pump and a centrifugal impeller (specifically, a structure of a fixed bush). Therefore, in the following description, only the components of the pump unit will be described, and the description of the motor unit will be omitted. The configuration of the motor unit of the centrifugal pump in the embodiment of the present invention may be any conventionally known configuration. In the following description, a vortex pump is described as an example of a centrifugal pump. However, the centrifugal pump may not be a vortex pump.

  FIG. 1 is a diagram showing a pump unit 30 of a centrifugal pump (vortex pump in the illustrated example) according to an embodiment of the present invention. As shown in FIG. 1, the centrifugal pump of the present embodiment includes a pump unit 30 including a centrifugal impeller (hereinafter simply referred to as an impeller) 341 and a pump casing 150 that houses the impeller 341. The pump casing 150 has a discharge port 142a and a suction port 142b, and is formed of a lower casing 142 that forms a pump chamber 143, and an intermediate casing 130 that is fixed to the lower casing 142 by fastening or the like. A motor unit (not shown) is disposed above the intermediate casing 130, and the rotating shaft 1 driven by the motor unit so as to rotate the impeller 341 is received and fixed to the boss portion 344 of the impeller 341. The motor unit and the pump unit 30 are sealed by a mechanical seal 104 disposed around the rotating shaft 1 so that the pressure water of the pump unit 30 does not leak to the motor unit side.

  As shown in FIG. 1, the impeller 341 includes a main plate 348 having a front surface 346 and a back surface 347, and a plurality of impeller blades 340 fixed to the front surface 346 of the main plate 348. FIG. 1A is a view of the impeller 341 as viewed from the suction port 142b side (downward in FIG. 1). As shown in FIG. 1A, a plurality of flow paths 349 that allow a handling liquid (hereinafter, liquid) of the centrifugal pump to pass therethrough are formed between the plurality of impeller blades 340. The liquid sucked from the suction port 142b flows through the flow path 349 from the inner peripheral side of the impeller 341 toward the outer peripheral side by the action of centrifugal force generated by the rotation of the impeller 341.

Similar to the conventional centrifugal impeller 141 described with reference to FIG. 3, the impeller 341 has a boss portion 344 in which a boss hole 345 (see FIG. 2) for receiving the rotating shaft 1 and the bush 400 is formed. ing. As shown in FIG. 1A, the impeller blades 340 are arranged around the boss hole 345 of the boss portion 344 (the bush 400 in FIG. 1A) at intervals. The boss hole 345 penetrates the main plate 348 in the axial direction (in other words, the direction along the central axis C of the impeller 341). The boss hole 345 has a small-diameter portion (reference numeral omitted) having a predetermined diameter and a diameter larger than the small-diameter portion, and the bush body 40 of the bush 400 disposed in contact with the axial front end surface of the rotary shaft 1.
2 includes a large diameter portion (reference numeral omitted). The small diameter portion is formed to have substantially the same diameter as the tip portion of the rotating shaft 1, and the large diameter portion is formed to have a diameter sufficient to receive the bushing body 402. A fastener 500 such as a bolt is screwed into the screw hole at the tip of the rotary shaft 1 through the through hole 450 (see FIG. 2 and the like) of the bush 400. The impeller 341 is fixed to the rotating shaft 1 by tightening the fastener 500.

  FIG. 2 is a partially enlarged view of FIG. In FIG. 2, the fastener 500 and the rotating shaft 1 disposed in the through hole 450 of the bush 400 are not shown. FIG. 2A is a perspective view of the bush 400 alone. In FIG. 2A, the bush 400 is shown in a state where it is inverted in the vertical direction with respect to the mounting direction shown in FIG.

  As shown in FIGS. 2 and 2A, the bush 400 includes a substantially cylindrical bush body 402 having a through-hole 450 penetrating the central portion in the axial direction. The through hole 450 is configured to receive a fastener 500 for fixing the impeller 341 to the rotary shaft 1. Specifically, the through hole 450 includes a small diameter portion 450 a that receives a shaft portion of a fastener (bolt in the illustrated example) 500 and a large diameter portion 450 b that receives a head portion of the fastener 500. The dimensions of the bush main body 402 are determined so that sufficient strength is secured to the bush main body 402 against the fastening of the fastener 500 and the like. The bush main body 402 may be disposed at least partially in the boss hole 345 (in other words, fitted). Specifically, the bush main body 402 may include a truncated cone shape as illustrated, for example, whose lower surface protrudes downward from the boss hole 345. Alternatively, the lower surface of the bushing body 402 may be disposed so as to be substantially flush with the surface 346 of the adjacent main plate 348.

  The bush 400 includes at least one (in the illustrated example, two) bush blades 404 fixed to the outer surface of the bush main body 402. As shown in FIG. 1A, when the bush 400 is attached to the impeller 341, that is, when the bush main body 402 is fitted in the boss hole 345 of the impeller 341, the bush blade 404 is at least one of the impeller 341. The two impeller blades 340 (in the illustrated example) extend substantially along a direction extending toward the central axis C of the centrifugal impeller 341 (hereinafter, the extending direction of the impeller blades 340). As a result, the impeller blade 340 is substantially extended to the inner peripheral side of the impeller 341, and as shown in FIG. 2, a substantially single combination in which the bush blade 404 and the impeller blade 340 are combined. A vane 600 can be formed. Therefore, the liquid sucked from the suction port 142b is used for the front edge portion 404a of the bush blade 404 located on the inner peripheral side of the front edge portion 340a of the impeller blade 340 (in other words, the front edge portion of the combined blade 600). To the flow path 349 between the impeller blades 340 (see FIG. 1A). Thereby, generation | occurrence | production of the stagnant vortex area | region in the conventional centrifugal pump can be suppressed, and generation | occurrence | production of the obstruction | occlusion state of a pump and the restraint state by the foreign material in a liquid can be prevented.

  When the bush main body 402 is fitted into the boss hole 345 of the impeller 341, the rear edge portion 404b of the bush blade 404 is preferably disposed at or near the front edge portion 340a of the impeller blade 340. Here, “the rear edge 404b of the bushing blade 404 is disposed at the front edge 340a of the impeller blade 340” means that the rear edge 404b of the bushing blade 404 is at least partially in front of the impeller blade 340. It means contacting the edge 340a. Further, “the rear edge portion 404b of the bush blade 404 is disposed in the vicinity of the front edge portion 340a of the impeller blade 340” means that the rear edge portion 404b of the bush blade 404 is the front edge portion 340a of the impeller blade 340. A gap is formed with the front edge portion 340a of the impeller blade 340 without having a portion in contact with the blade, but the size of the gap can substantially ignore the hydraulic loss that can be caused by the gap. Means about. For example, a gap of about the dimensional tolerance defined in JIS (JISB0403 when bushing blade 404 is a cast product) is preferable.

  In the example of FIG. 2, the trailing edge 404b of the bushing blade 404 is disposed in the vicinity of the leading edge 340a of the impeller blade 340, and therefore, substantially between the bushing blade 404 and the impeller blade 340. The gap is small enough to cause a negligible hydraulic loss. This eliminates the possibility of causing interference between the bushing blades 404 and the impeller blades 340 at the time of attachment, and between the rear edge 404b of the bushing blades 404 and the front edge 340a of the impeller blades 340. Thus, hydraulic loss that can occur in the flow toward the flow path 349 can be reduced as much as possible. However, the rear edge 404b of the bushing blade 404 has a portion that contacts the front edge 340a of the impeller blade 340 as long as there is no interference between the bushing blade 404 and the impeller blade 340. May be. That is, the rear edge portion 404b of the bush blade 404 may be disposed on the front edge portion 340a of the impeller blade 340.

  The bush blades 404 can be formed integrally with the bush main body 402, for example, by casting. When the bush 400 is attached to the boss hole 345, the coupling blade 600 can be formed by rotating the bush 400 so that the rear edge portion 404b of the bush blade 404 is positioned in the extending direction of the impeller blade 340.

  The extension direction of the bush blades 404 from the inner peripheral side to the outer peripheral side of the impeller 341 is preferably set so that the impeller blades 340 smoothly extend toward the central axis C of the impeller 341. Thereby, the liquid can be smoothly guided into the flow path 349 between the impeller blades 340, and a large hydraulic loss is prevented from occurring in the liquid flow from the inner peripheral side to the outer peripheral side of the impeller 341. Can do. For example, the bushing blade 404 and the impeller blade 340 are adjacent to each other (in other words, the portion including the trailing edge 404b and the leading edge 340a) on the blade pressure surface and the blade suction surface, respectively. The blade angle is preferably configured so that the blade angle of the impeller blade 340 substantially matches. Here, the “blade angle” means an angle between a tangent of the surface of the wing and a tangent of a concentric circle with the impeller on the surface. When viewed in the direction along the central axis C of the impeller 341 as shown in FIG. 1A, the bush blades 404 may extend linearly toward the central axis C, or may extend in a curved manner. Further, when the bush blades 404 extend while being curved, the blade angle may be determined by the pump performance of the centrifugal pump.

  Further, as shown in FIG. 2, when the bush 400 is fitted into the boss hole 345 of the impeller 341, the base end surface 404 c of the bush blade 404 is configured to be disposed at or near the main plate 348 of the impeller 341. It is preferable. Here, “the base end surface 404c of the bush blade 404 is disposed on the main plate 348 of the impeller 341” means that the base end surface 404c of the bush blade 404 is at least partially in contact with the main plate 348 of the impeller 341. means. Further, “the base end surface 404c of the bush blade 404 is disposed in the vicinity of the main plate 348 of the impeller 341” means that the base end surface 404c of the bush blade 404 does not have a portion that contacts the main plate 348 of the impeller 341. A gap is formed between the main plate 348 of the impeller 341 and the size of the gap means that hydraulic loss that can be caused by the gap is substantially negligible. For example, a gap of about the dimensional tolerance defined in JIS (JISB0403 when bushing blade 404 is a cast product) is preferable.

In the example of FIG. 2, the base end surface 404 c of the bush blade 404 is disposed in the vicinity of the main plate 348 of the impeller 341, and therefore, substantially between the bush blade 404 and the main plate 348 of the impeller 341. The gap is small enough to cause negligible hydraulic power loss. This eliminates the possibility of interference during installation, and reduces hydraulic loss that may occur in the flow toward the flow path 349 between the base end surface 404c of the bush blade 404 and the main plate 348 of the impeller 341. It can be made as small as possible. However, the base end surface 404c of the bush blade 404 may have a portion that contacts the main plate 348 of the impeller 341 as long as interference does not occur during installation. That is, the base end surface 404 c of the bush blade 404 may be disposed on the main plate 348 of the impeller 341.

  When the bush 400 is fitted into the boss hole 345 of the impeller 341, the distance between the tip (in other words, the lower end) 406 of the rear edge 404b and the bottom surface of the pump casing 150 (see FIG. 1) is The distance between the front end 408 of the front edge 340a and the bottom surface of the pump casing 150 is substantially the same (in other words, the front end surface of the bush blade 404 (in other words, the lower surface) 404d and the impeller blade 340. It is preferable that no step is generated between the front end surface 340d and the front end surface 340d. Thereby, the liquid sucked from the suction port 142b can be efficiently guided into the flow path 349.

  Further, it is preferable that the bush blade 404 has a thickness that is equal to or smaller than the thickness t (see FIG. 1A) of the front edge 340a of the impeller blade 340 at least at the rear edge 404b. Here, the “thickness” means the shortest distance between the pressure surface and the suction surface of the blade. If the thickness of the rear edge portion 404b of the bush blade 404 is larger than the thickness of the front edge portion 340a of the impeller blade 340, the inlet area of the flow path 349 is reduced and the thickness is increased by a step in the thickness direction. Hydraulic loss occurs. Therefore, the thickness of the rear edge 404b of the bush blade 404 is preferably set to be equal to or smaller than the thickness of the front edge 240a of the impeller blade 340. In this case, it is preferable to adjust the position at the time of attachment so that the rear edge portion 404b of the bush blade 404 does not protrude from the front edge portion 240a of the impeller blade 340 in the thickness direction.

  In the example of FIG. 1A, bush blades 404 are provided only on some impeller blades 340. However, by providing the bush blades 40 on all the impeller blades 340, all the impeller blades 340 can be extended to the inner peripheral side. When it is desired to suppress the entrance area of all the inter-blade flow paths of the impeller 341 from decreasing, for example, as illustrated in FIG. 1A, the bush blades 404 are provided only on one of the adjacent impeller blades 340. It is preferable to be provided.

  Thus, according to the embodiment of the present invention, at least one of the plurality of impeller blades 340 of the impeller 341 has a front edge portion (in other words, an inner circumference) disposed in the vicinity of the boss hole 345 of the main plate 348. A coupling blade 600 having a side end portion 404a can be formed. Therefore, according to the embodiment of the present invention, the front edge portion of the impeller blade 340 can be disposed substantially near the center axis C of the impeller 341 as compared with the prior art. Thereby, the liquid flowing in from the suction port 142b can be smoothly guided into the flow path 349 between the impeller blades 340. Therefore, it is possible to prevent the stagnant vortex region from being formed at the inlet portion of the flow path 349, so that the pump can be prevented from being blocked by foreign matter in the liquid.

  Although the embodiments of the present invention have been described above, the above-described embodiments of the present invention are for facilitating the understanding of the present invention and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof. In addition, any combination or omission of each constituent element described in the claims and the specification is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect is achieved. It is.

The present invention includes the following aspects.
1. A fixed bushing of the centrifugal impeller disposed at least partially in a boss hole of the centrifugal impeller through which the rotation shaft is passed,
A cylindrical bush body having a through-hole through which a fastener screwed to the rotating shaft is inserted;
A bush wing fixed to the outer surface of the bush body,
In the fitted state, the bush blades are fixed bushes that extend along a direction in which at least one impeller blade of the centrifugal impeller extends toward the central axis of the centrifugal impeller.
2. In the fitted state, the rear edge of the bushing blade is disposed at or near the front edge of the impeller blade. Fixed bushing as described in.
3. The bush blades have a base end surface arranged in the main plate of the centrifugal impeller or in the vicinity thereof in the fitted state. Or 2. Fixed bushing as described in.
4). 1. The thickness at the trailing edge of the bushing blade is equal to or smaller than the thickness at the leading edge of the impeller blade. ~ 3. A fixed bush according to any one of the above.
5). In the fitted state, at least the distance between the bottom surface of the pump casing that houses the centrifugal impeller and the tip of the rear edge of the bushing blade is between the bottom surface of the pump casing and the front edge of the impeller blade. Which is substantially the same as the distance of 1. above. ~ 4. A fixed bush according to any one of the above.
6). A rotation axis;
A centrifugal impeller fixed to a rotating shaft;
Above 1. ~ 5. A centrifugal pump comprising the fixed bush according to any one of the above.

  The present invention can be widely applied to a fixed bush and a centrifugal pump of a centrifugal impeller.

C ... impeller center axis t ... thickness 1 ... rotating shaft 2 ... motor unit 3, 30 ... pump unit 104 ... mechanical seal 110 ... motor frame 111 ... motor cover 116 ... handle 130 ... intermediate casing 140 ... blade 140a ... front Edge 141 ... Impeller 142 ... Lower casing 142a ... Discharge port 142b ... Suction port 143 ... Pump chamber 144 ... Boss part 145 ... Pump stand 146 ... Boss hole 146a ... Small diameter part 146b ... Large diameter part 148 ... Main plate 150 ... Pump casing DESCRIPTION OF SYMBOLS 200 ... Bush 340 ... Impeller blade | wing 340a ... Front edge part 340d ... Tip end surface 341 ... Impeller 344 ... Boss part 345 ... Boss hole 346 ... Front surface 347 ... Back surface 348 ... Main plate 349 ... Flow path 400 ... Bush 402 ... Bush main body 404 ... Bush wings 404a ... Front edge 404b ... Rear edge 404c ... Base end surface 404d ... tip end surface 406 ... tip end 408 ... tip end 450 ... through hole 450a ... small diameter portion 450b ... large diameter portion 500 ... fastener 600 ... coupling blade

Claims (6)

A fixed bushing of the centrifugal impeller disposed at least partially in a boss hole of the centrifugal impeller through which the rotation shaft is passed,
A cylindrical bush body having a through-hole through which a fastener screwed to the rotating shaft is inserted;
A bush wing fixed to the outer surface of the bush body,
In the fitted state, the bush blades are fixed bushes that extend along a direction in which at least one impeller blade of the centrifugal impeller extends toward the central axis of the centrifugal impeller. 2. The fixed bush according to claim 1, wherein in the fitted state, a rear edge portion of the bush blade is disposed at or near a front edge portion of the impeller blade. The said bush blade is a fixed bush of Claim 1 or 2 which has a base end surface arrange | positioned in the main plate of the said centrifugal impeller, or its vicinity in the said fitting state. The fixed bush according to any one of claims 1 to 3, wherein a thickness at a rear edge portion of the bush blade is equal to or smaller than a thickness at a front edge portion of the impeller blade. In the fitted state, at least the distance between the bottom surface of the pump casing that houses the centrifugal impeller and the tip of the rear edge portion of the bush blade is the bottom surface of the pump casing and the front edge of the impeller blade. The fixed bushing according to any one of claims 1 to 4, wherein the fixed bushing is substantially the same as a distance between the tips of the parts. A rotation axis;
A centrifugal impeller fixed to the rotating shaft;
A centrifugal pump comprising: the fixed bush according to any one of claims 1 to 5.

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