JP2024081323A - pump - Google Patents

Abstract

To provide a pump which can prevent gas from staying at a bottom part side of a can.SOLUTION: A pump A1 comprises: a cylinder part 31 whose one side x1 in an axial direction is opened; a can 3 having a bottom part 32 for blocking another side x2 in the axial direction; a casing 5 having a suction port 54, a discharge port 55, and a vortex chamber 56, and covering one side x1 end of the can 3 in the axial direction; a shaft 6 extending along the axial direction x, and non-rotatably supported by the casing 5 and the bottom part 32 of the can 3; and a rotor 4 having a magnet 41 and an impeller 42 arranged in the vortex chamber 56, and rotatably supported by the shaft 6. A first clearance G1 is formed between the rotor 4 and the cylinder part 31. The shaft 6 has a hollow hole 61 penetrating in the axial direction x from a first opening end 611 on the one side x1 in the axial direction up to a second opening end 612 on the other side x2 in the axial direction, and the first opening end 611 communicates with the suction port 54 and communicates with the first clearance G1 of the second opening end 612.SELECTED DRAWING: Figure 4

Description

The present invention relates to a pump that sucks and discharges liquid.

It is known that when a large amount of fine bubbles are generated in water, these bubbles slowly rise to the surface while adsorbing dirt and other surrounding matter, exerting a cleaning effect. It is also known that when such fine bubbles are generated in warm water, they exert a warm bath effect. In order to exert this effect effectively, the size of the bubbles generated needs to be 10 to 50 μm in diameter or even smaller. Such fine bubbles are sometimes called fine bubbles. In order to construct a device that generates fine bubbles as described above, a pump capable of discharging liquid at a relatively high pressure is required.

An example of a conventional pump is disclosed in, for example, Patent Document 1. The pump described in Patent Document 1 includes a motor case (1), a stator (2), a can (3), a rotor (4), a casing (5), and a shaft (6) as shown in Figures 4 and 6 of the document. The stator (2) is a cylindrical coil and is provided in the motor case (1). The rotor (4) has a cylindrical holder (40), a cylindrical magnet (41), and an impeller (42). The magnet (41) is concentrically arranged inside the stator (2). The impeller (42) is housed in a spiral chamber (56) of the casing (5). The shaft (6) extends along the axial direction, and both ends are supported by the casing (5) and the can (3) so as not to rotate. Between the shaft (6) and the cylindrical holder (40) is a collar (43) that functions as a bearing, and the rotor (4) is rotatably supported by the shaft (6) via the collar (43). When power is supplied to the stator (2), a rotational driving force is generated in the rotor (4). This causes the impeller (42) to rotate, and a fluid such as water can be caused to flow from the suction port (54) through the volute (56) to the discharge port (55). In the above conventional pump, a gap is provided between the cylindrical portion of the can (3) and the rotor (4), and when the pump is in operation, a part of the fluid passing through the volute (56) also flows into the bottom side of the can (3) (the left side in FIG. 4 of Patent Document 1) through the gap between the can (3) and the rotor (4). As a result, the rotor (4) is submerged inside the can (3), and the sliding portion around the shaft (6) is in contact with the water, preventing wear.

The pump of Patent Document 1 is used, for example, in a fine bubble generator. In a pump used in a fine bubble generator, a gas-liquid multiphase fluid containing a large amount of gas such as air is introduced into a volute chamber (56) from an inlet (54). In the volute chamber (56), gas dissolves in the pressurized liquid in a pressurized state, and this pressurized fluid is discharged to the outside through an outlet (55). However, in a pump used in a fine bubble generator as described above, the gas-liquid multiphase fluid introduced into the volute chamber (56) contains a relatively large amount of gas. For this reason, the excess gas that does not dissolve in the pressurized liquid in the volute chamber (56) may flow into the bottom side of the can (3) through the above-mentioned gap between the can (3) and the rotor (4) and remain there. In this case, the sliding parts around the shaft (6) become dry, resulting in so-called dry operation, which may lead to excessive wear and temperature rise, and may hinder normal operation of the pump.

JP 2018-162744 A

The present invention was conceived under these circumstances, and its main objective is to provide a pump that can prevent gas from accumulating at the bottom of the can.

To solve the above problems, the present invention provides the following technical solutions:

The pump provided by the present invention comprises a cylindrical stator, a can disposed inside the stator, a cylindrical portion that opens on one axial side, and a bottom that closes the other axial side, a casing that has an intake port, a discharge port, and a volute and covers one axial end of the can, a shaft that extends along the axial direction, both ends of which are supported by the casing and the bottom of the can and cannot rotate, a magnet disposed inside the can, and an impeller disposed in the volute, and a rotor that is rotatably supported by the shaft, and a first gap is formed between the rotor and the cylindrical portion of the can, and the shaft has a hollow hole that penetrates in the axial direction from a first open end on one side of the axial direction to a second open end on the other side of the axial direction, and the intake port is located on one side of the shaft in the axial direction, the first open end is connected to the intake port, and the second open end is connected to the first gap.

In a preferred embodiment, the bottom portion has a seat facing one side in the axial direction and a recessed groove recessed from the seat to the other side in the axial direction, the shaft has a first end face located at the other end in the axial direction and capable of abutting against the seat, and the second open end communicates with the first gap via the recessed groove.

In a preferred embodiment, the grooves are arranged radially when viewed along the axial direction.

In a preferred embodiment, the rotor defines a first space that is in contact with the bottom and communicates with the second open end and the first gap, and the suction port.

In a preferred embodiment, the pump is a so-called fine bubble generator pump that is incorporated into a fine bubble generator.

Other features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a plan view showing an example of a pump according to the present invention. FIG. 2 is a front view of the pump shown in FIG. FIG. 2 is a left side view of the pump shown in FIG. 1 . FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2 shows the pump shown in FIG. 1 with the cover plate removed. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. FIG. 2 is a perspective view of the casing as seen from the inside. FIG. 5 is a partially enlarged view of FIG. 4 . FIG. 9 is a partially enlarged cross-sectional view taken along line IX-IX in FIG. 8. FIG. 9 is a partially enlarged cross-sectional view taken along line XX in FIG. 8.

The preferred embodiment of the present invention will now be described in detail with reference to the drawings. In the following description, terms such as "first" and "second" are used merely as labels and are not necessarily intended to assign any order to their objects.

Figures 1 to 10 show an example of a pump according to the present invention. The pump A1 of this embodiment comprises a motor case 1, a stator 2, a can 3, a rotor 4, a casing 5, a shaft 6 and a number of bolts 8, and is intended to be incorporated into a fine bubble generator, for example.

In the description of pump A1, the left-right direction in Figures 3 and 4 is an example of the "axial direction" of the present invention and is referred to as the "axial direction x." Also, the right side in Figures 3 and 4 is an example of the "one axial side" of the present invention and is referred to as the "one axial side x1," and the left side in the figures is an example of the "other axial side" of the present invention and is referred to as the "other axial side x2."

The motor case 1 is formed in a cylindrical shape with a bottom that is open on one axial side x1, and is made of a metal such as aluminum. The motor case 1 houses the stator 2, the can 3, and a part of the rotor 4 (a cylindrical holder 40 and a magnet 41, described later), and is connected to the casing 5 via a number of bolts 8. In addition, a step is formed at the end of the one axial side x1 of the motor case 1 for fixing the can 3. In this embodiment, a connector housing 10 is provided on the upper part of the motor case 1.

As shown in FIG. 5, the connector housing 10 has an internal space surrounded by multiple side walls 11, and a part of the cord 71 and a connector 72 are housed in the internal space. Multiple cables 73 for driving the pump are connected to the connector 72, and these cables 73 are inserted into the cord 71. The multiple cables 73 include, for example, power supply cables. The power supply cables are cables used to supply power to drive the pump A1. The multiple cables 73 may also include control cables. The control cables are cables used for inputting and outputting control signals from a control panel (not shown) and sensors (not shown) that control the rotation speed of the pump A1, etc.

The upper end of the connector housing 10 is formed with an access opening 10a that is open to the outside. As shown in FIG. 4, the access opening 10a is covered by a cover plate 12. The cover plate 12 is attached via a sheet packing 13. Note that the cord 71, connector 72, and cable 73 are omitted from FIG. 4.

As shown in FIG. 5, in this embodiment, the cord 71 is supported on the side wall 11 via a waterproof packing 75. More specifically, an opening 111 is formed in the side wall 11, penetrating in the thickness direction, and the waterproof packing 75 is fitted into this opening 111 while holding the cord 71. This provides moisture protection for the inside of the connector housing 10 from the outside.

As shown in FIG. 4, the stator 2 is composed of an electromagnetic coil installed between the inner wall of the motor case 1 and the can 3, and has an overall cylindrical shape. Driving power is supplied to the stator 2 via the cable 73.

The rotor 4 has a cylindrical holder 40, a magnet 41, and an impeller 42. The cylindrical holder 40 constitutes the main part of the rotor 4. Inside the cylindrical holder 40, two collars 43 made of, for example, polyphenylene sulfide (hereinafter, PPS) resin are provided. The cylindrical holder 40 and the collars 43 are connected in such a way that, for example, the convex portion of one engages with the concave portion of the other, and they rotate together. The collars 43 are rotatably supported by the shaft 6. The shaft 6 is supported at one axial end x1 by the casing 5 (the shaft support tube 52 described later) and at the other axial end x2 by the can 3.

The magnet 41 has a generally cylindrical shape and fits into the gap 40a of the cylindrical holder 40. The magnet 41 is made of, for example, a plastic magnet.

In the illustrated example, the cylindrical holder 40 has a plurality of through holes 40b formed therein. These through holes 40b are provided at regular intervals around the circumference of the cylindrical holder 40 and penetrate the cylindrical holder 40 in the axial direction x. Each of the plurality of through holes 40b communicates with a space on one axial side x1 of the cylindrical holder 40 (rotor 4) and a space on the other axial side x2. In this embodiment, a filler 401 is filled in an appropriate position in each of the plurality of through holes 40b. Each of the plurality of through holes 40b is partially blocked by the filler 401. The material of the filler 401 is not particularly limited, and may be, for example, a synthetic resin putty material.

The impeller 42 is provided at one axial end x1 of the cylindrical holder 40, and is housed in a volute chamber 56 of the casing 5, which will be described later. As shown in Figures 4 and 6, the impeller 42 has a hole 421 penetrating in the axial direction x at the center, and a number of blades 422. Openings 423 are formed between adjacent blades 422. When viewed in the axial direction x, the openings 423 have a spiral shape centered on the hole 421. When the impeller 42 is rotated, the rotational centrifugal force draws fluid from the hole 421, and the fluid is discharged to the outside from the openings 423 between the blades 422.

The can 3 is for preventing hot water flowing into the casing 5 from entering the motor case 1. The can 3 has a cylindrical shape with a bottom, and has a cylindrical portion 31, a bottom portion 32, and an outward flange 33. The cylindrical portion 31 is disposed inside the stator 2. The bottom portion 32 is connected to the other axial side x2 end of the cylindrical portion 31 and blocks the other axial side x2 of the cylindrical portion 31. The outward flange 33 is connected to one axial side x1 of the cylindrical portion 31. The material of the can 3 is not particularly limited, and is, for example, made of PPS resin. A part of the can 3 (mainly the cylindrical portion 31 and the bottom portion 32) is accommodated in the internal space of the stator 2. The cylindrical holder 40 and the magnet 41 of the rotor 4 are accommodated inside the can 3. As shown in FIG. 4, a predetermined first gap G1 is formed between the outer peripheral surface of the cylindrical holder 40 (rotor 4) and the inner peripheral surface of the cylindrical portion 31.

As shown in Figures 4, 8 to 10, in this embodiment, the bottom 32 includes a bottom wall 321 and a cylindrical wall 322. The bottom wall 321 closes the other axial end x2 of the cylindrical portion 31 and is generally disk-shaped. The cylindrical wall 322 is connected to the bottom wall 321 and extends to the one axial side x1. As shown in Figures 8 and 10, the end of the shaft 6 on the other axial side x2 is fitted into the cylindrical wall 322 and is supported by the cylindrical wall 322. As shown in Figure 10, a notch 63 is formed in the end of the shaft 6 on the other axial side x2.

As shown in Figures 8 to 10, the bottom wall 321 has a seating surface 321a and a groove 321b. The seating surface 321a is a surface facing one axial side x1 on the inside of the cylindrical wall 322. The groove 321b is recessed from the seating surface 321a to the other axial side x2. As shown in Figures 9 and 10, in the illustrated example, the grooves 321b are arranged radially when viewed along the axial direction x.

8 and 10, the cylindrical wall 322 has a recess 322a and a vertical groove 322b. The recess 322a is a portion recessed from the end of the cylindrical wall 322 on one axial side x1 to the other axial side x2, and extends radially from the inner peripheral surface to the outer peripheral surface of the cylindrical wall 322. In the illustrated example, a plurality of recesses 322a are formed at regular intervals in the circumferential direction of the cylindrical wall 322. The vertical groove 322b is a portion recessed radially outward from the inner peripheral surface of the cylindrical wall 322, and extends from the end of the cylindrical wall 322 on one axial side x1 to the end of the cylindrical wall 322 on the other axial side x2. In the illustrated example, a plurality of vertical grooves 322b are formed at regular intervals in the circumferential direction of the cylindrical wall 322. Each of the plurality of vertical grooves 322b is connected to one of the plurality of recesses 322a and the recessed groove 321b.

The casing 5 constitutes the part that functions as a pump, and as shown in FIG. 4, has a disk-shaped wall 51, a shaft support tube 52, a cylindrical peripheral wall 53, an intake port 54, an exhaust port 55, and a volute 56. The outer peripheral connection part 57 of the casing 5 covers one axial side x1 (outward flange 33) of the can 3.

The suction port 54 is an opening for sucking warm water, for example, from a bathtub into the pump A1, and penetrates the center of the disk-shaped wall 51. As shown in Figures 2 and 4, the suction port 54 is substantially cylindrical and faces the direction in which the rotation axis Ox of the rotor 4 extends. As shown in Figure 4, the suction port 54 is located on one axial side x1 of the shaft 6.

The shaft support tube 52 is for supporting the end of the shaft 6 on one axial side x1, and is connected to the disk-shaped wall 51 via a connecting piece 521. As shown in Figs. 4 and 7, the inner surface 52a of the shaft support tube 52 has a shape in which a part of a cylinder is cut out, and the end of the shaft 6 is provided with a notch portion 62 corresponding to the inner surface 52a. The end of the shaft 6 on one axial side x1 (notch portion 62) is fitted into the inner surface 52a of the shaft support tube 52. As a result, the shaft 6 is supported in a non-rotatable manner with respect to the casing 5. A through hole 52b is formed in the shaft support tube 52. As shown in Fig. 4, the through hole 52b overlaps with a hollow hole 61 in the shaft 6, which will be described later, when viewed along the axial direction x.

The volute chamber 56 is an internal space defined by the disk-shaped wall 51 and the cylindrical peripheral wall 53, and houses the impeller 42 of the rotor 4. The cylindrical peripheral wall 53 has a substantially cylindrical inner peripheral surface 53a, and the gap between the inner peripheral surface 53a and the outer peripheral edge 42a of the impeller 42 is of a substantially constant size.

The outlet 55 is an opening for discharging warm water, for example, toward a bathtub, and has a generally cylindrical shape as shown in Figs. 1 and 6. The outlet 55 has a base end 551 that penetrates the cylindrical peripheral wall 53, and extends from the base end 551 to the tip end 552 in a generally tangential direction of the cylindrical peripheral wall 53. The material of the casing 5 is not particularly limited, and may be, for example, PPS resin.

In the above configuration, when the impeller 42 rotates, discharge pressure is generated in the volute 56, and the hot water flows from the suction port 54 through the holes 421 and openings 423 of the impeller 42 and the volute 56 to the discharge port 55.

As shown in Figures 4, 6, 8, and 10, the shaft 6 extends along the axial direction x and has a cylindrical shape as a whole. The shaft 6 has a hollow hole 61, a notch 62, and a notch 63. The hollow hole 61 penetrates the shaft 6 in the axial direction x from the first opening end 611 on one axial side x1 to the first opening end 611 on the other axial side x2. The notch 62 has a shape in which a part of the outer periphery is cut off at the end of the one axial side x1 of the shaft 6. The notch 63 has a shape in which a part of the outer periphery is cut off at the end of the other axial side x2 of the shaft 6. As described above, the end of the one axial side x1 of the shaft 6 is supported by the shaft support tube 52, and the other axial side x2 of the shaft 6 is supported by the cylindrical wall 322 (bottom 32). In addition, the end (notch 62) of the shaft 6 on one axial side x1 fits into the inner surface 52a of the shaft support tube 52, so that the shaft 6 is supported in an unrotatable state. The material of the shaft 6 is not particularly limited, and it can be made of PPS resin or sintered carbon, for example.

As shown in FIG. 4, the shaft 6 is supported with both ends sandwiched between the shaft support tube 52 of the casing 5 and the bottom 32 of the can 3. The first open end 611 of the hollow hole 61 is connected to the suction port 54 via the through hole 52b of the shaft support tube 52. The first end face 64 of the other axial end x2 of the shaft 6 can abut against the seat surface 321a of the bottom wall 321 (bottom 32). Here, "the first end face 64 can abut against the seat surface 321a" means that even if the first end face 64 is designed to abut against the seat surface 321a, a small gap may occur between the first end face 64 and the seat surface 321a due to manufacturing errors, etc., and includes such cases.

As shown in Figures 4, 8 to 10, the groove 321b of the bottom wall 321 (bottom 32) overlaps with the hollow hole 61 when viewed along the axial direction x. The second opening end 612 of the hollow hole 61 communicates with the first space S1 that contacts the bottom 32 via the groove 321b, the vertical groove 322b, and the recess 322a. As shown in Figure 4, the first space S1 communicates with both the second opening end 612 and the first gap G1 between the cylindrical holder 40 (rotor 4) and the cylindrical portion 31.

Next, the operation of pump A1 in this embodiment will be described.

The pump A1 is installed, for example, next to a bathtub in a bathroom and is incorporated into a fine bubble generator. When the impeller 42 (rotor 4) is rotated during operation of the pump A1, a gas-liquid mixed phase fluid, mainly the hot water in the bathtub, is introduced from the suction port 54 into the volute chamber 56, and gas is dissolved in the pressurized liquid in a high-pressure state. This pressurized fluid is discharged from the discharge port 55 through a dedicated nozzle into the hot water in the bathtub. The pressure of the pressurized fluid discharged into the hot water is suddenly reduced, and the gas dissolved in the pressurized fluid is discharged into the hot water as fine bubbles. In the pump A1 constituting the fine bubble generator, the rotor 4 (impeller 42) is rotated at high speed to discharge the pressurized fluid in a high-pressure state from the discharge port 55. The rotation speed of the rotor 4 is, for example, about 6,000 rpm.

In the pump A1 used in the fine bubble generator, the gas-liquid mixed phase fluid introduced into the volute chamber 56 contains a relatively large amount of gas. Therefore, the excess gas that does not dissolve in the pressurized liquid in the volute chamber 56 flows into the bottom 32 of the can 3 through the first gap G1 between the cylindrical holder 40 (rotor 4) and the cylindrical portion 31 of the can 3 (see the dotted arrow in Figure 4).

In the pump A1 of this embodiment, the shaft 6 extends along the axial direction x, and both ends are supported by the casing 5 and the bottom 32 (can 3). The shaft 6 is supported in a non-rotatable state, and has a hollow hole 61 penetrating in the axial direction x from the first opening end 611 on one axial side x1 to the first opening end 611 on the other axial side x2. The first opening end 611 is connected to the suction port 54 located at x1 of the shaft 6, and the second opening end 612 is connected to the first gap G1 between the rotor 4 and the cylindrical portion 31. With this configuration, when the pump A1 is in operation, a suction force is generated in the hollow hole 61 of the shaft 6 toward the suction port 54 located on the one axial side x1. Then, the gas that flows into the bottom 32 side through the first gap G1 flows from the second opening end 612 of the shaft 6 through the hollow hole 61 to the one axial side x1, and flows into the suction port 54 through the first opening end 611 (see the dotted arrow in FIG. 4). This prevents gas from accumulating on the bottom 32 side of the can 3, and prevents problems such as pump A1 running dry.

The bottom wall 321 (bottom portion 32) of the can 3 has a seating surface 321a facing one axial side x1 and a recessed groove 321b recessed from the seating surface 321a to the other axial side x2. The shaft 6 has a first end face 64 located at the end of the other axial side x2, and the first end face 64 can abut against the seating surface 321a. The second open end 612 of the shaft 6 communicates with the first gap G1 via the recessed groove 321b.
With this configuration, even when the first end face 64 of the shaft 6, which is supported non-rotatably, is in close contact with the bottom 32, a flow path connecting both the first gap G1 and the hollow hole 61 of the shaft 6 can be secured.

The grooves 321b are radial when viewed along the axial direction x. With this configuration, the gas that has flowed into the bottom 32 side through the first gap G1 can be efficiently introduced into the hollow hole 61 of the shaft 6. This is preferable in terms of preventing gas from accumulating on the bottom 32 side of the can 3.

In this embodiment, the multiple through holes 40b formed in the cylindrical holder 40 of the rotor 4 are filled with a filler 401, and each of the multiple through holes 40b is partially blocked by the filler 401. As a result, the rotor 4 is in contact with the bottom 32 (bottom wall 321 or cylindrical wall 322), and partitions the first space S1 that communicates with the first gap G1 and the second opening end 612 of the shaft 6, and the suction port 54 located on one axial side x1 of the shaft 6. With this configuration, as shown by the dotted arrow in FIG. 4, a single flow path is formed from the first gap G1 through the first space S1 and the hollow hole 61 toward the suction port 54. As a result, a suction force toward the suction port 54 is appropriately generated in the hollow hole 61 of the shaft 6. Therefore, it is possible to more reliably suppress the gas from accumulating on the bottom 32 side of the can 3.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the spirit of the invention. The specific configuration of each part of the pump according to the present invention can be freely designed and modified in various ways.

In the above embodiment, the rotor 4 (cylindrical holder 40) is an example of an existing design, and a configuration has been described in which the multiple through holes 40b formed in the cylindrical holder 40 are filled with the filler 401 to close them, but the present invention is not limited to this. The rotor 4 (cylindrical holder 40) may be configured so as not to have the through holes 40b described in the above embodiment.

In the above embodiment, the pump A1 is described as being applied to a fine bubble generator, but the present invention is not limited to this. The uses of the pump according to the present invention are not particularly limited, and it can be used in a wide range of applications.

A1: Pump 1: Motor case 10: Connector housing 10a: Access opening 11: Side wall 111: Opening 12: Cover plate 13: Sheet packing 2: Stator 3: Can 31: Cylindrical portion 32: Bottom 321: Bottom wall 321a: Seat surface 321b: Groove 322: Cylindrical wall 322a: Recess 322b: Vertical groove 33: Outward flange 4: Rotor 40: Cylindrical holder 40a: Cavity 40b: Through hole 401: Filler 41: Magnet 42: Impeller 42a: Outer periphery 421: Hole 422: Blade 423: Opening 43: Collar 5: Casing 51: Disc-shaped wall 52: Shaft support cylinder 52a: Inner surface 52b: Through hole 521: Connecting piece 53: Cylindrical peripheral wall 53a : Inner peripheral surface 54 : Suction port 55 : Discharge port 551 : Base end portion 552 : Tip portion 56 : Swirl chamber 57 : Peripheral connection portion 6 : Shaft 61 : Hollow hole 611 : First opening end 612 : Second opening ends 62, 63 : Notch portion 64 : First end surface 71 : Cord 72 : Connector 73 : Cable 75 : Waterproof packing 8 : Bolt G1 : First gap S1 : First space Ox : Rotation axis x : Axial direction x1 : One axial side x2 : Other axial side

Claims (4)

A cylindrical stator;
a can disposed inside the stator and having a cylindrical portion that is open on one side in an axial direction and a bottom portion that closes the other side in the axial direction;
a casing having an inlet, a discharge port, and a volute, and covering one end of the can in the axial direction;
a shaft extending along the axial direction, both ends of which are supported by the casing and the bottom of the can, and which is non-rotatable;
a rotor having a magnet disposed inside the can and an impeller disposed in the volute, the rotor being rotatably supported by the shaft;
A first gap is formed between the rotor and the cylindrical portion of the can,
the shaft has a hollow hole passing through in the axial direction from a first open end on one side in the axial direction to a second open end on the other side in the axial direction,
The suction port is located on one side of the shaft in the axial direction,
The first open end communicates with the suction port,
The second open end of the pump communicates with the first gap. The bottom portion has a seat surface facing one side in the axial direction and a recessed groove recessed from the seat surface to the other side in the axial direction,
the shaft has a first end surface located at the other end in the axial direction and capable of abutting on the seat surface,
The pump according to claim 1 , wherein the second opening end communicates with the first gap via the groove. The pump according to claim 2, wherein the grooves are arranged radially when viewed along the axial direction. The pump according to any one of claims 1 to 3, wherein the rotor is in contact with the bottom and defines a first space that communicates with the second open end and the first gap, and the suction port.

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