Pumping device

Abstract

To improve rotor dynamics in a pump system. [Solution] The pump device 1 according to the present invention comprises a motor 3, a rotating shaft 4 that rotates by the drive of the motor, an impeller 6 attached to the rotating shaft that sucks in and discharges the liquid to be handled, a first bearing 51 disposed between the motor and the impeller that rotatably supports the rotating shaft, a second bearing 8 that rotatably supports the impeller, and a pump housing 2 that houses the impeller and the second bearing. The impeller comprises blades 61 that rotate in accordance with the rotation of the rotating shaft, a front shroud 62 that covers the first direction of the blades, and cylindrical supported surfaces 64c, 64k, 66a that are supported by the second bearing.

Description

Technical Field

[0001] The present invention relates to a pump device.

Background Art

[0002] A pump device includes a rotor, a rotating shaft, a pair of bearings, and an impeller. The rotor rotates the rotating shaft, and via the rotating shaft, rotates the impeller. In the axial direction of the rotating shaft, the pair of bearings are arranged on both sides of the rotor and rotatably support the rotating shaft. In the axial direction, one side of the rotating shaft protrudes to one side from the bearing, and an impeller is attached to the end thereof. Such a structure in which the impeller is not arranged between the pair of bearings (so-called overhang structure) is widely used in pump devices (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] The impeller is a heavy object. Therefore, in a centrifugal pump adopting an overhang structure, rotor dynamics are likely to deteriorate. In particular, when an inducer is attached upstream of the impeller, when a plurality of impellers are attached to the rotating shaft (in the case of a multistage structure), or when the rotating shaft rotates at high speed, the deterioration of rotor dynamics becomes remarkable.

[0005] The present invention aims to improve rotor dynamics in a pump system. [Means for solving the problem]

[0006] A pump device in one embodiment of the present invention comprises a motor, a rotating shaft that rotates by the drive of the motor, an impeller attached to the rotating shaft for sucking in and discharging a liquid to be handled, a first bearing disposed between the motor and the impeller to rotatably support the rotating shaft, a second bearing to rotatably support the impeller, and a pump housing that houses the impeller and the second bearing, wherein in the axial direction of the rotating shaft, the direction in which the impeller is positioned relative to the motor is the first direction, and the direction in which the motor is positioned relative to the impeller is the second direction, the impeller comprises blades that rotate in accordance with the rotation of the rotating shaft, a front shroud covering the first direction of the blades, and a suction port disposed adjacent to the front shroud in the first direction of the front shroud, the suction port having a cylindrical outer surface, and the second bearing supporting the outer surface. [Effects of the Invention]

[0007] The present invention improves rotor dynamics in a pump device. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view of a pump device showing an embodiment of the pump device according to the present invention. [Figure 2] This is a partially enlarged cross-sectional view of part A in Figure 1 of the pump device described above. [Figure 3] This is a partially enlarged schematic cross-sectional view of part B in Figure 2 of the pump device described above. [Figure 4] This is a schematic perspective view of the first impeller of the pump device described above. [Figure 5] This is a schematic front view of the first impeller shown above. [Figure 6]This is a schematic cross-sectional view showing the flow of the liquid being handled in the suction port of the pump device when the pump device is in operation. [Figure 7] This is the result of a simulation analysis of the rotor dynamics of a simulated pump device. [Figure 8] This is the Campbell diagram of the above-mentioned dummy pump device. [Figure 9] These are partially enlarged schematic cross-sectional views of the pump device in each modified example, where (a) shows the pump device in the first modified example, (b) shows the pump device in the second modified example, (c) shows the pump device in the third modified example, and (d) shows the pump device in the fourth modified example. [Figure 10] This is a partially enlarged schematic cross-sectional view of the pump device in the fifth modified example. [Figure 11] This is a partially enlarged schematic diagram of the first impeller of the pump, showing the location of the through-hole in the pump device in the fifth modified example. [Figure 12] This is a partially enlarged schematic cross-sectional view of the pump device in the sixth modified example. [Figure 13] This is a partially enlarged schematic cross-sectional view of the pump device in the seventh modified example. [Modes for carrying out the invention]

[0009] Embodiments of the pump device according to the present invention are described below. In the following description, the drawings are referenced as appropriate. In each drawing, the same reference numerals are used for the same members and elements, and redundant explanations are omitted. In addition, the dimensional ratios of each element may be exaggerated for the sake of explanation and are not limited to the ratios shown in each drawing.

[0010] ●Pumping equipment● ● Pump system configuration Figure 1 is a schematic cross-sectional view of a pump device showing an embodiment of the pump device according to the present invention. The figure shows a longitudinal section of the pump device 1 cut along a vertical plane passing through the axial centerline of the rotating shaft 4 (described later). In the figure, some components are shown as non-cross-sectional views for the sake of explanation.

[0011] The pump device 1 sucks in and discharges (delivers) the liquid to be handled. The pump device 1 is, for example, a centrifugal pump. The pump device 1 includes a housing 2, a motor 3, a rotating shaft 4, two bearings 51, 52, a first impeller 6, a second impeller 7, and an impeller bearing 8.

[0012] The "liquid to be handled" is the liquid handled (delivered) by the pump device 1. The liquid to be handled is, for example, a liquid fuel.

[0013] In the following description, the "forward direction" is the direction in which the first impeller 6 is located with respect to the motor 3, and the "backward direction" is the direction in which the motor 3 is located with respect to the first impeller 6. The "axial direction" is the direction (front-rear direction) along the axial center line of the rotating shaft 4, the "radial direction" is the radial direction of the rotating shaft 4, and the "circumferential direction" is the circumferential direction of the rotating shaft 4. The "upstream side" is the upstream side in the flow of the liquid to be handled in the housing 2, and the "downstream side" is the downstream side in the flow of the liquid to be handled in the housing 2. The "rotation direction RD (see FIG. 4)" is the direction in which the rotating shaft 4 rotates. In the present embodiment, it is counterclockwise when viewed from the forward direction. The forward direction is an example of the first direction in the present invention, and the backward direction is an example of the second direction in the present invention.

[0014] The housing 2 houses the motor 3, the rotating shaft 4, the bearings 51, 52, the first impeller 6, the second impeller 7, and the impeller bearing 8. The housing 2 includes two pump chambers 21, 22, a suction hole 23, a motor chamber 24, a suction pipe portion 25, a discharge pipe portion 26, and a connecting flow path 27. The housing 2 is an example of the pump housing in the present invention.

[0015] FIG. 2 is a partially enlarged cross-sectional view of part A in FIG. 1 of the pump device 1. In the following description, FIG. 1 is appropriately referred to together with FIG. 2.

[0016] The pump chamber 21 houses the first impeller 6. The pump chamber 21 has a front inner surface 21a. The front inner surface 21a is the inner surface of the pump chamber 21 that faces rearward. The front inner surface 21a is positioned in front of the front shroud 62 (described later; the same applies hereafter) of the first impeller 6 and faces the front shroud 62. The shape of the front inner surface 21a is a curved surface that is recessed in a roughly frustoconical shape toward the front, following the shape of the front shroud 62.

[0017] Pump chamber 22 houses the second impeller 7. Since the configuration of pump chamber 22 is the same as that of pump chamber 21, a detailed explanation is omitted. Pump chamber 22 is located behind pump chamber 21.

[0018] The suction port 23 guides the handling fluid to the first impeller 6. The suction port 23 is located at the front end of the housing 2. The suction port 23 is located adjacent to the pump chamber 21 in the forward direction of the pump chamber 21 and communicates with the pump chamber 21. The shape of the suction port 23 is a three-stage cylindrical shape along the axial direction. The suction port 23 comprises a large diameter section 23a, a medium diameter section 23b, a small diameter section 23c, a first stage section 23d, a second stage section 23e, a bypass passage 23f, and a female screw surface 23j.

[0019] The inner diameter of the large-diameter portion 23a is larger than the inner diameter of the medium-diameter portion 23b, and the inner diameter of the medium-diameter portion 23b is larger than the inner diameter of the small-diameter portion 23c. In the axial direction, the medium-diameter portion 23b is located in front of the large-diameter portion 23a and adjacent to the large-diameter portion 23a. In the axial direction, the small-diameter portion 23c is located in front of the medium-diameter portion 23b and adjacent to the medium-diameter portion 23b. The first step portion 23d is located between the large-diameter portion 23a and the medium-diameter portion 23b and is a surface facing the rear. The second step portion 23e is located between the medium-diameter portion 23b and the small-diameter portion 23c and is a surface facing the rear. In a rearward view, the shape of the first step portion 23d is ring-shaped. The shape of the second step portion 23e is a planar shape parallel to the vertical direction and is ring-shaped in a rearward view. The second step portion 23e is an example of an opposing surface in the present invention. An internal threaded surface 23j is positioned on the inner circumferential surface of the large-diameter portion 23a.

[0020] The bypass channel 23f is a channel that returns the handling fluid that has flowed from the first impeller 6 into the first cylindrical space S2 (described later; the same applies hereinafter) to the main flow of the handling fluid F0 (see Figure 6; the same applies hereinafter) flowing through the small diameter section 23c. The shape of the bypass channel 23f is, for example, tubular. The bypass channel 23f is provided with a channel inlet 23g and a channel outlet 23h. The channel inlet 23g opens to the medium diameter section 23b and the second stage section 23e. The channel outlet 23h opens to the small diameter section 23c. Of the bypass channel 23f, the front end portion 23i on the channel outlet 23h side is inclined more towards the rear than radially. The front end portion 23i is an example of an open end portion in the present invention.

[0021] In this invention, the number of bypass channels 23f can be set as appropriate and is not limited to "1".

[0022] The motor room 24 houses the motor 3, a portion of the rotating shaft 4, and bearings 51 and 52. The motor room 24 is partitioned by the rear half of the housing 2.

[0023] The front end of the housing 2 extends cylindrically forward so as to be coaxial with the rotation axis 4, forming a suction pipe section 25. The suction pipe section 25 is composed of a front half of a large diameter section 23a, a medium diameter section 23b, a small diameter section 23c, a first stage section 23d, and a second stage section 23e.

[0024] A portion of the housing 2 located radially outward from the second impeller 7 extends tangentially (upward) to the second impeller 7 in an axial view, forming a discharge pipe section 26 for discharging the liquid being handled from the pump chamber 22.

[0025] The connecting passage 27 is a passage that connects the pump chamber 21 and the pump chamber 22, and guides the liquid being handled discharged from the first impeller 6 from the pump chamber 21 to the pump chamber 22. The connecting passage 27 is formed, for example, from a part of the housing 2.

[0026] Motor 3 is a known motor comprising a rotor attached to a rotating shaft 4 and a stator that rotates the rotor.

[0027] The rotating shaft 4 rotates due to the drive (rotation) of the motor 3, transmitting rotational power to the first impeller 6 and the second impeller 7. The rotating shaft 4 is cylindrical in shape. The rotating shaft 4 is attached to the motor 3, and the front part 4a of the rotating shaft 4 protrudes into the pump chambers 21 and 22.

[0028] Bearings 51 and 52 rotatably support the rotating shaft 4. Bearing 51 is located in front of the motor 3, between the motor 3 and the second impeller 7. Bearing 52 is located in rear of the motor 3. Bearings 51 and 52 are, for example, sliding bearings. Bearing 51 is an example of the first bearing in the present invention.

[0029] Figure 3 is a partially enlarged schematic cross-sectional view of part B of the pump device 1 in Figure 2. In the following explanation, Figure 2 will be referred to as appropriate, along with Figure 3.

[0030] The first impeller 6 draws in and discharges the handling fluid. The first impeller 6 is attached to the front part 4a of the rotating shaft 4 and is housed in the pump chamber 21. The first impeller 6 is a so-called closed-type impeller. The first impeller 6 comprises a plurality of blades 61, a front shroud 62, a rear shroud 63, a suction port 64, and a discharge port 65. The first impeller 6 is an example of an impeller in the present invention.

[0031] The blades 61 rotate circumferentially around the rotation axis 4, guiding the liquid being handled, drawn in from the suction port 64, to the discharge port 65. The blades 61 are positioned between the front shroud 62 and the rear shroud 63.

[0032] The front shroud 62 is a plate (so-called side plate) that covers the front of the blade 61. The shape of the front shroud 62 is roughly ring-shaped, with the inner edge being more convex forward than the outer edge.

[0033] The rear shroud 63 is a plate (the so-called main plate) that covers the rearward direction of the blade 61. The rear shroud 63 has a ring-like shape. In an axial view, the central part of the rear shroud 63 protrudes forward in a roughly frustoconical shape.

[0034] The suction port 64 is the inlet for the handling fluid flowing into the first impeller 6. The inner edge of the front shroud 62 extends forward in a two-stage cylindrical shape coaxial with the rotation axis 4, forming the suction port 64. That is, the suction port 64 is located in the forward direction of the front shroud 62 and adjacent to the front shroud 62. The front shroud 62 also includes the suction port 64. The shape of the suction port 64 is a two-stage cylindrical shape along the axial direction. The suction port 64 includes an outer circumferential surface 64a, an inner circumferential surface 64e, a front end surface 64f, a helical groove 64g, and a plurality (4) end face grooves 64h.

[0035] The outer circumferential surface 64a has a two-stage cylindrical shape. The outer circumferential surface 64a comprises a large-diameter portion 64b, a small-diameter portion 64c, and a stepped portion 64d. The outer diameter of the large-diameter portion 64b is larger than the outer diameter of the small-diameter portion 64c. In the axial direction, the small-diameter portion 64c is positioned in front of the large-diameter portion 64b and adjacent to the large-diameter portion 64b. The stepped portion 64d is positioned between the large-diameter portion 64b and the small-diameter portion 64c and is a surface facing forward. The shape of the stepped portion 64d is planar and parallel to the vertical direction, and is ring-shaped when viewed from the front. The small-diameter portion 64c is an example of an outer circumferential surface in the present invention and an example of a supported surface in the present invention.

[0036] The shape of the inner circumferential surface 64e is cylindrical. The inner circumferential surface 64e is an example of an inner circumferential surface in the present invention.

[0037] The front end surface 64f is an opening surface oriented forward. The shape of the front end surface 64f is planar and parallel to the vertical direction, and is ring-shaped when viewed from the front. The front end surface 64f is an example of an end surface in the present invention.

[0038] The portion of the first impeller 6 excluding the suction port 64 is housed in the pump chamber 21. The suction port 64 is housed in the large-diameter section 23a. Between the front inner surface 21a and the large-diameter section 23a and the first impeller 6 (front shroud 62 and suction port 64), a space S1 is formed into which a portion of the liquid being handled discharged from the first impeller 6 flows. In other words, the front inner surface 21a and the large-diameter section 23a, as well as the first impeller 6 (front shroud 62 and suction port 64), define the space S1.

[0039] A cylindrical space (hereinafter referred to as "first cylindrical space S2") is formed between the large-diameter section 23a and the small-diameter section 64c, in which the impeller bearing 8 is located. In other words, the housing 2 and the suction port 64 define the first cylindrical space S2. The first cylindrical space S2 is in communication with space S1. A cylindrical space (hereinafter referred to as "second cylindrical space S3") is formed between the medium-diameter section 23b and the small-diameter section 64c, through which the handling fluid flowing in from the first impeller 6 flows. In other words, the housing 2 and the suction port 64 define the second cylindrical space S3. The second cylindrical space S3 is located in the forward direction of the impeller bearing 8 (downstream in the flow of the handling fluid in space S1). The second cylindrical space S3 is in communication with the internal space of the bypass flow path 23f and the first cylindrical space S2. The second cylindrical space S3 is an example of the first space in the present invention. The second stage portion 23e is positioned in the forward direction of the front end surface 64f, spaced apart from the front end surface 64f, and facing the front end surface 64f. A ring-shaped gap (hereinafter referred to as "end face gap S4") is formed between the second stage portion 23e and the front end surface 64f. In other words, the second stage portion 23e and the front end surface 64f define the end face gap S4. The end face gap S4 communicates with the internal space of the bypass flow path 23f and the second cylindrical space S3. The flow path outlet 23h of the bypass flow path 23f opens at a position further forward (upstream) than the suction port 64. That is, the internal space of the bypass flow path 23f communicates with the space (hereinafter referred to as "upstream space S5") within the internal space of the suction hole 23 that is further forward (upstream) than the first impeller 6.

[0040] Figure 4 is a schematic perspective view of the first impeller 6. For the sake of clarity, the diagram omits the illustration of some of the components of the first impeller 6. In the following explanation, Figures 2 and 3 will be referred to as appropriate, along with Figure 4.

[0041] The helical groove 64g is a spiral groove that, in accordance with the rotation of the rotating shaft 4 (first impeller 6), directs the liquid being handled from the rear to the front (second cylindrical space S3) as it flows into the first cylindrical space S2. The helical groove 64g is positioned from the front end to the center of the small diameter section 64c (outer surface 64a). The helical groove 64g is positioned on the small diameter section 64c (outer surface 64a) such that it spirals along the rotational direction RD of the rotating shaft 4 as the position of the helical groove 64g moves from the front (downstream side in the flow of the liquid being handled in space S1) to the rear (upstream side in the flow of the liquid being handled in space S1).

[0042] Figure 5 is a schematic front view of the first impeller 6. In the following explanation, Figures 2 and 3 will be referred to as appropriate, along with Figure 5.

[0043] The end face groove 64h is a groove (recess) that, in accordance with the rotation of the rotating shaft 4 (first impeller 6), directs the handling fluid that has flowed into the end face gap S4 from the radially inward direction to the radially outward direction. In the circumferential direction, the end face grooves 64h are arranged on the front end face 64f at equal angular (90°) intervals. In a forward view, the end face grooves 64h are arranged on the front end face 64f such that they trace an arc from the forward direction to the rearward direction in the rotational direction RD as the end face grooves 64h move from the inner circumferential surface 64e (radially inward direction) to the outer circumferential surface 64a (radially outward direction). The end face groove 64h is an example of a recess in the present invention.

[0044] In the following explanation, the drawings primarily referenced will return to Figures 1 through 3. The discharge port 65 is the outlet for the liquid being handled that flows through the first impeller 6. The discharge port 65 is located on the outer edge of the first impeller 6.

[0045] The second impeller 7 draws in and discharges the fluid being handled. The second impeller 7 is attached to the front part 4a of the rotating shaft 4 and is housed in the pump chamber 22. The configuration of the second impeller 7 is the same as that of the first impeller 6, except that the second impeller 7 does not have a part corresponding to the small diameter section 64c. Therefore, a detailed explanation thereof is omitted.

[0046] The impeller bearing 8 rotatably supports the first impeller 6 (small diameter portion 64c). The impeller bearing 8 is, for example, a known sliding bearing. The impeller bearing 8 is located in the front half of the first cylindrical space S2. That is, radially, the impeller bearing 8 is located outward from the first impeller 6 (small diameter portion 64c). As a result, behind the impeller bearing 8 is the rear part of the first cylindrical space S2, and is a space defined by the housing 2, the first impeller 6, and the impeller bearing 8 (hereinafter referred to as the "rear space S21"). That is, the rear space S21 is located behind the impeller bearing 8 (upstream in the flow of the handled fluid in space S1). The impeller bearing 8 comprises a bearing housing 81, a bearing body 82, and a pin 83. The impeller bearing 8 is an example of the second bearing in the present invention. The rear space S21 is an example of the second space in the present invention.

[0047] The bearing housing 81 houses the bearing body 82. The bearing housing 81 has a male threaded surface 81a. The male threaded surface 81a corresponds to the female threaded surface 23j and is located on the outer circumferential surface of the bearing housing 81. The bearing housing 81 is attached to the large diameter portion 23a and the first stage portion 23d by the male threaded surface 81a being fitted into the female threaded surface 23j. The bearing body 82 rotatably supports the first impeller 6. The shape of the bearing body 82 is cylindrical. The bearing body 82 has a cylindrical inner circumferential surface 82a. The bearing body 82 is housed in the bearing housing 81 and is located between the bearing housing 81 and the suction port 64 (small diameter portion 64c). The pin 83 fixes the position of the bearing body 82 in the circumferential direction.

[0048] A suction port 64 is inserted through the bearing body 82. A small gap S22 is formed between the outer circumferential surface 64a (small diameter portion 64c) of the suction port 64 and the inner circumferential surface 82a of the bearing body 82. When the rotating shaft 4 (first impeller 6) is rotating, a lubricating film (not shown) of the handling fluid is formed in the gap S22. A helical groove 64g is arranged on the portion of the outer circumferential surface 64a (small diameter portion 64c) that faces the bearing body 82.

[0049] ● Operation of the pump device Next, the operation of the pump device 1 will be explained below, focusing on the flow of the liquid being handled in the suction port 23. Figures 1 to 3 will be referred to as appropriate in the following explanation.

[0050] Figure 6 is a schematic cross-sectional view showing the flow of the liquid being handled in the suction port 23 when the pump device 1 is operating. This figure shows the same cross-section as the pump device 1 in Figure 3. In this figure, the flow of the liquid being handled F0 to F7 (described later) is indicated by arrows.

[0051] When the pump device 1 is operating, the first impeller 6 and the second impeller 7 rotate in accordance with the rotation of the rotating shaft 4. The first impeller 6 draws in the handling fluid introduced into the small diameter section 23c and discharges it into the pump chamber 21. The handling fluid discharged into the pump chamber 21 is sent to the pump chamber 22 via the connecting passage 27. At this time, a portion of the handling fluid discharged into the pump chamber 21 flows into the rear space S21 via space S1 (flow F1). The handling fluid that flows into the rear space S21 returns to the suction hole 23 via the impeller bearing 8 (gap S22), the second cylindrical space S3, and the end face gap S4 (flow F4). This returning flow F4 of the handling fluid disrupts the main flow F0 just before it is drawn into the first impeller 6, and adversely affects the suction performance of the first impeller 6 (pump device 1). Therefore, flows F1 and F4 are generally suppressed by orifices or labyrinth structures. However, as described later, the pump device 1 actively utilizes flow F1 to improve the lubrication (formation of a lubricating film) and cooling effect of the impeller bearing 8.

[0052] In the pump device 1, the first impeller 6 is supported by an impeller bearing 8, which is not present in conventional pumps. Therefore, the pump device 1 is equipped with a structure (hereinafter referred to as the "introduction structure") that actively introduces the handling fluid into the impeller bearing 8 in order to improve the lubrication and cooling effect of the handling fluid on the impeller bearing 8. In this embodiment, the helical groove 64g mainly functions as the introduction structure.

[0053] As described above, the helical groove 64g is formed on the outer circumferential surface 64a (small diameter portion 64c) such that it pivots along the rotational direction RD of the rotating shaft 4 as the position of the helical groove 64g moves from the front to the rear. Furthermore, in the radial direction, the gap S22 between the outer circumferential surface 64a (small diameter portion 64c) and the inner circumferential surface 82a is extremely small (large enough for a lubricating film to form). Therefore, most of the handling fluid (flow F2) that flows into the rear space S21 flows through the helical groove 64g (flow F3). At this time, when the rotating shaft 4 rotates, the helical groove 64g functions as a screw that transports the handling fluid from the rear direction (rear space S21) to the front direction (second cylindrical space S3) of the impeller bearing 8. As a result, the amount of handling fluid (flow F1) flowing into the rear space S21 increases, and the amount of handling fluid (flow F2) flowing into the gap S22 also increases. Therefore, a sufficient amount of handling fluid is available for the lubrication and cooling of the impeller bearing 8. As a result, the lubrication and cooling effects of the impeller bearing 8 are improved.

[0054] The handling fluid delivered to the second cylindrical space S3 flows into the end face gap S4 (flow F4) and the bypass channel 23f (flow F5). The end face groove 64h faces the end face gap S4. As described above, the end face groove 64h is formed on the front end face 64f such that it traces an arc from the front to the rear in the rotational direction RD as the end face groove 64h moves from the inner circumferential surface 64e to the outer circumferential surface 64a. Therefore, when the rotating shaft 4 rotates, the end face groove 64h functions like a wing that directs the handling fluid that has flowed into the end face gap S4 from the inward to the outward direction in the radial direction. As a result, a flow F6 is generated in the handling fluid in the end face gap S4, moving from the inward to the outward direction. This flow F6 becomes stronger the narrower the end face gap S4 is in the front-rear direction (axial direction). The flow F6 suppresses the flow F4 from the second cylindrical space S3 to the end face gap S4. Therefore, most of the liquid being handled that is delivered to the second cylindrical space S3 flows into the bypass channel 23f (flow F5) and is returned to the main flow F0 of the liquid being handled that flows through the small diameter section 23c from the channel outlet 23h (flow F7). As mentioned above, the front end 23i of the bypass channel 23f on the channel outlet 23h side is inclined more in the rear direction than in the radial direction. Therefore, the flow F7 returned to the main flow F0 merges with the main flow F0 along the main flow F0 and does not affect the main flow F0. In addition, the channel outlet 23h is located at a position further forward than the first impeller 6. Therefore, even if the main flow F0 is affected by the flow F7, that effect is absorbed by other flows before the liquid being handled is drawn into the first impeller 6.

[0055] In conventional pump systems (hereinafter referred to as "conventional pumps"), which have a structure in which the impeller is not positioned between the bearings (a so-called overhang structure), the impeller is positioned outside (forward) between the bearings. Therefore, in conventional pumps, the rotating shaft located in front of the bearings deforms and oscillates according to the weight of the impeller. In other words, the rotor dynamics of conventional pumps can be greatly reduced.

[0056] In contrast, in the pump device 1, the first impeller 6, which is positioned forward of the bearing 51, is supported by the impeller bearing 8. That is, the front end (front portion 4a) of the rotating shaft 4 is supported by the impeller bearing 8 via the first impeller 6. Furthermore, the portion of the first impeller 6 excluding the suction port 64 and the second impeller 7 are positioned between the bearing 51 and the impeller bearing 8. Therefore, deformation and vibration of the rotating shaft 4 (front portion 4a) located forward of the bearing 51 are suppressed. In other words, the rotor dynamics of the pump device 1 are improved.

[0057] Figure 7 shows the simulation analysis results of the rotor dynamics of a simulated pump device. Figure 8 is a Campbell diagram of a simulated pump device.

[0058] The "pseudo-pump device" is a pump device 1 in which the hubless inducer replaces the small-diameter portion 64c of the suction port 64 with a large-diameter portion 64b. The shape of the shroud of the hubless inducer is the same as the shape of the small-diameter portion 64c.

[0059] Figure 7 also shows the analysis results of a pump device that mimics a conventional pump (a pseudo-pump device without the impeller bearing 8) as a comparative example. Similarly, Figure 8 also shows the Campbell diagram of a pump device that mimics a conventional pump as a comparative example. The vertical axis in Figure 8 shows the natural frequency of the rotating body (rotating shaft 4), and the horizontal axis shows the rotational speed of the rotating body. In Figure 8, the critical speed for each bending mode is indicated by a circle ("○").

[0060] As shown in Figure 7, when the hubless inducer is not supported by the impeller bearing 8, the rotating shaft 4 deforms significantly, starting near the bearing 51. In particular, the front end (suction port 64) of the rotating body (rotating shaft 4, first impeller 6, and second impeller 7) becomes a free end and is greatly displaced radially outward. The front end of the rotating shaft 4 experiences the maximum displacement, which is 0.0095 mm. On the other hand, when the hubless inducer is supported by the impeller bearing 8, the radial displacement of the front end of the rotating body is restricted by the impeller bearing 8. That is, the free end of the rotating body becomes a fixed end (the simulated pump device does not have an overhang structure). As a result, the rotating shaft 4 deforms, starting near the bearing 51 and the impeller bearing 8. The intermediate portion of the rotating shaft 4 between the bearing 51 and the impeller bearing 8 experiences the maximum displacement, which is 0.0013 mm. Thus, in the simulated pump device, the hubless inducer is supported by the impeller bearing 8, eliminating the need for an overhang structure. As a result, the displacement is significantly reduced, improving rotor dynamics. Consequently, as shown in Figure 8, the natural frequencies of the primary and secondary bending modes in the Campbell diagram increase, and the critical speed increases from approximately 20,000 rpm to approximately 50,000 rpm. The configuration of the simulated pump device is almost identical to that of pump device 1, except for the presence or absence of inducer blades. The presence or absence of inducer blades does not significantly affect rotor dynamics. Therefore, pump device 1 is expected to exhibit rotor dynamics similar to those of the simulated pump device.

[0061] Thus, in the pump device 1, the impeller bearing 8 supports the first impeller 6 (suction port 64), which corresponds to the tip of the overhang structure. As a result, the rotor dynamics are improved compared to conventional pumps with an overhang structure.

[0062] Furthermore, the impeller bearing 8 does not support the rotating shaft 4 and is positioned radially outward from the first impeller 6. That is, in the axial direction, the impeller bearing 8 is not positioned alongside the first impeller 6 and the second impeller 7. In this configuration, in the axial direction, the length of the suction port 64 is extended by the length required for support by the impeller bearing 8 compared to the length of the suction port of a typical impeller. That is, in the axial direction, the length of the pump device 1 may be greater than the length of a conventional pump, depending on the amount of extension of the length of the suction port 64. Here, if the impeller bearing 8 and the first impeller 6 without the small diameter portion 64c are positioned side by side in the axial direction, the length of the area required for the placement of the impeller bearing 8 will be slightly greater than the same extension amount. Therefore, in the axial direction, the length of the pump device 1 will be slightly less than the length when the impeller bearing 8 and the first impeller 6 without the small diameter portion 64c are positioned side by side.

[0063] Furthermore, in the pump device 1, the helical groove 64g actively directs the handling fluid for lubrication and cooling of the impeller bearing 8 into the rear space S21. Therefore, even though the impeller bearing 8 is positioned between the housing 2 and the first impeller 6, there is no shortage of lubrication and cooling for the impeller bearing 8. Consequently, the impeller bearing 8 functions normally. Moreover, in the pump device 1, the handling fluid delivered to the second cylindrical space S3 is returned to the handling fluid in the suction hole 23 without affecting the main flow F0, thanks to the bypass passage 23f and the end face groove 64h. Consequently, the suction performance of the pump device 1 is not reduced.

[0064] ●Summary According to the embodiment described above, the pump device 1 comprises a motor 3, a rotating shaft 4, bearings 51, 52, a first impeller 6, and an impeller bearing 8. In the axial direction, the direction in which the first impeller 6 is positioned relative to the motor 3 is forward, and the direction in which the motor 3 is positioned relative to the first impeller 6 is rearward. The first impeller 6 comprises blades 61, a front shroud 62, and a suction port 64. The suction port 64 is positioned in front of the front shroud 62 and adjacent to the front shroud 62. The suction port 64 has a cylindrical outer surface 64a (small diameter portion 64c). The impeller bearing 8 supports the outer surface 64a (small diameter portion 64c). With this configuration, the radial movement of the front end of the rotating body (rotating shaft 4, first impeller 6, and second impeller 7) is restricted by the impeller bearing 8. As a result, rotor dynamics are improved.

[0065] Furthermore, according to the embodiment described above, the housing 2 and the front shroud 62 define a second cylindrical space S3 in front of the impeller bearing 8 and a rear space S21 in rear of the impeller bearing 8. A portion of the handling fluid discharged from the first impeller 6 flows into the rear space S21. The first impeller 6 is equipped with a helical groove 64g. The helical groove 64g is formed on the outer circumferential surface 64a (small diameter portion 64c) such that the position of the helical groove 64g pivots along the rotational direction RD of the rotating shaft 4 as it moves from the front to the rear. With this configuration, when the rotating shaft 4 rotates, the helical groove 64g functions as a screw that delivers the handling fluid toward the impeller bearing 8 and the second cylindrical space S3. As a result, the flows F1 and F2 increase. Therefore, a sufficient amount of handling fluid necessary for lubrication and cooling of the impeller bearing 8 is secured. In other words, the lubrication and cooling effects of the impeller bearing 8 are improved.

[0066] Furthermore, according to the embodiment described above, the suction port 64 is provided with a front end surface 64f. The housing 2 is provided with a second stage portion 23e. The second stage portion 23e is positioned in the forward direction of the front end surface 64f, spaced apart from the front end surface 64f, and facing the front end surface 64f. In a forward view, the end face groove 64h is positioned on the front end surface 64f such that as the end face groove 64h moves from the inner circumferential end to the outer circumferential end, it draws an arc that moves from the forward direction to the rear direction in the rotational direction RD. With this configuration, the flow F4 is suppressed, and turbulence of the main flow F0 based on the flow F4 is suppressed. As a result, the suction performance of the pump device 1 is improved.

[0067] Furthermore, according to the embodiment described above, the housing 2 is provided with a bypass passage 23f. The internal space of the bypass passage 23f communicates with the end face gap S4 and the upstream space S5 of the suction hole 23, which is located in the forward direction of the first impeller 6. The front end portion 23i of the bypass passage 23f is inclined in the rearward direction rather than the radial direction. With this configuration, the decrease in the suction performance of the pump device 1 based on the flow F7 is suppressed.

[0068] Furthermore, according to the embodiments described above, the impeller bearing 8 is a sliding bearing. The helical groove 64g is located on the outer surface 64a in the portion facing the impeller bearing 8. With this configuration, a sufficient amount of handling fluid necessary for lubrication and cooling of the impeller bearing 8 is ensured. In other words, the lubrication and cooling effects of the impeller bearing 8 are improved.

[0069] ●Variations● Next, a modified version of the pump device 1 will be described below, focusing on the parts that differ from the embodiment described above (hereinafter referred to as the "first embodiment"). In the following description of the modified version, elements that are the same as those in the first embodiment and elements that have common functions are denoted by the same reference numerals as in the first embodiment for the sake of explanation, and their descriptions will be omitted. Figures 1 to 6 will be referred to as appropriate in the following description.

[0070] ●1st variation to 4th variation Figure 9 shows partially enlarged schematic cross-sectional views of the pump device 1 in the first to fourth modified examples, where (a) shows the pump device 1 in the first modified example, (b) shows the pump device 1 in the second modified example, (c) shows the pump device 1 in the third modified example, and (d) shows the pump device 1 in the fourth modified example.

[0071] As shown in Figure 9(a), in the first modified example, the pump device 1 does not have a bypass passage 23f. In this configuration, the handling fluid necessary for lubrication and cooling of the impeller bearing 8 is sufficiently supplied by flow F3, as in the first embodiment. On the other hand, since there is no flow F5 directed toward the bypass passage 23f, the flow rate of flow F4 increases compared to the first embodiment. As a result, flow F4 may slightly disturb the main flow F0.

[0072] As shown in Figure 9(b), in the second modified example, the pump device 1 does not have a bypass passage 23f and a helical groove 64g. In this configuration, the flow F4 increases compared to the first embodiment, similar to the first modified example. Also, because the flow F3 due to the helical groove 64g is eliminated, the flow rates of F1 and F2 decrease compared to the first modified example. Even in this state, flows F1 and F2 are maintained, and the handling fluid necessary for lubrication and cooling of the impeller bearing 8 is ensured.

[0073] As shown in Figure 9(c), in the third modified example, the pump device 1 does not have an end face groove 64h. In this configuration, flow F6 is eliminated except for the flow based on the main flow F0. Therefore, the flow rate of flow F4 is increased compared to the first embodiment, and flow F4 may slightly disturb the main flow F0. On the other hand, the handling fluid necessary for lubrication and cooling of the impeller bearing 8 is sufficiently supplied by flow F3, as in the first embodiment.

[0074] As shown in Figure 9(d), in the fourth modified example, the pump device 1 is equipped with a rolling bearing instead of a sliding bearing as the impeller bearing 8. Furthermore, the helical groove 64g is not located in the region facing the impeller bearing 8, but is located only in the forward direction of the impeller bearing 8 (facing the second cylindrical space S3). If the impeller bearing 8 is a rolling bearing, and the helical groove 64g is formed in the region facing the impeller bearing 8, the fluid being handled that flows into the rear space S21 will flow mostly into the helical groove 64g rather than into the rolling elements. In this case, the lubrication and cooling effects of the impeller bearing 8 may be reduced. In the fourth modified example, the helical groove 64g is located only in the forward direction of the impeller bearing 8 so that the fluid being handled that flows into the rear space S21 flows towards the rolling elements (flow F8).

[0075] In the fourth modified example, the helical groove 64g may also be positioned in the rearward direction of the impeller bearing 8.

[0076] ● Fifth variation Figure 10 is a partially enlarged schematic cross-sectional view of the pump device 1 in the fifth modified example.

[0077] The pump device 1 in the fifth modified example comprises a housing 2, a motor 3, a rotating shaft 4, two bearings 51 and 52, a first impeller 6, a second impeller 7, an impeller bearing 8, and an inducer 9.

[0078] The suction port 64 of the first impeller 6 is provided with an outer circumferential surface 64a, an inner circumferential surface 64e, a front end surface 64f, a helical groove 64g, a plurality (4) end face grooves 64h, and a plurality (3) through holes 64i.

[0079] The through holes 64i are through holes that open into the outer circumferential surface 64a and the inner circumferential surface 64e. In the circumferential direction, the through holes 64i are arranged at equal angular (120°) intervals in front of the suction port 64 (in the axial direction, forward of the impeller bearing 8). The through holes 64i open at positions opposite to the middle diameter portion 23b (positions facing the second cylindrical space S3), and at positions forward of the negative pressure surface 92b (described later) and close to the negative pressure surface 92b. In addition, a portion of some of the through holes 64i open into the helical groove 64g. That is, the internal space of the through holes 64i is in communication with the second cylindrical space S3, the internal space of the helical groove 64g, and the internal space of the suction port 64.

[0080] Figure 11 is a partially enlarged schematic diagram of the first impeller 6, showing the location of the through-hole 64i opening in the inner circumferential surface 64e. For ease of explanation, a portion of the inducer blade 92 (described later) is also shown in the same figure. In the following explanation, Figure 10 will be referred to together with Figure 11 as appropriate.

[0081] The "position close to the negative pressure surface 92b" is a position in which, in a radial view, at least a portion of the opening of the through hole 64i faces the vicinity of the negative pressure surface 92b and the region where the pressure of the liquid being handled is reduced (hereinafter referred to as the "negative pressure region Rn"). In this embodiment, the through hole 64i is located at the position indicated by "P1" in Figure 7.

[0082] In this invention, the through-hole 64i may be located at the positions indicated as "P2" and "P3" in Figure 11. Furthermore, the through-hole 64i may be located adjacent to the wingtip 92c of the negative pressure surface 92b.

[0083] The inducer 9 is a known inducer comprising a hub 91 and a plurality (3) inducer blades 92. The inducer 9 is housed in the suction port 64. The hub 91 is mounted at the front end of the rotating shaft 4 so as to be coaxial with the rotating shaft 4. The inducer blades 92 protrude from the outer circumferential surface of the hub 91 toward the inner circumferential surface 64e of the suction port 64. The inducer blades 92 rotate in accordance with the rotation of the rotating shaft 4. The inducer blades 92 have a positive pressure surface 92a and a negative pressure surface 92b. The positive pressure surface 92a is the surface oriented in the direction of rotation RD. The negative pressure surface 92b is the surface oriented in the opposite direction of rotation RD. That is, the negative pressure surface 92b is the surface opposite to the positive pressure surface 92a. In the circumferential direction, the inducer blades 92 are arranged at equal angular intervals.

[0084] In this configuration, a portion of the handling fluid supplied to the second cylindrical space S3 flows into the internal space of the suction port 64 through the through hole 64i (flow F9). Flow F9 may disturb the main flow F0 of the handling fluid in the internal space of the suction port 64. However, immediately after flowing into the internal space of the suction port 64, flow F4 flows into the negative pressure surface region Rn without flowing into the main flow F0 of the handling fluid in that internal space. At this time, flow F9 disturbs the flow Fn in the negative pressure surface region Rn without disturbing the main flow F0 of the handling fluid. As a result, separation of the handling fluid on the negative pressure surface 92b is suppressed, and the occurrence of cavitation in the internal space of the suction port 64 is suppressed. In addition, the handling fluid in the through hole 64i is drawn into the negative pressure surface region Rn. Therefore, a portion of the handling fluid supplied to the second cylindrical space S3 is drawn into the through hole 64i. As a result, the amount of fluid flowing into the gap S22 (flow F2) increases, and the amount of fluid flowing into the rear space S21 (flow F1) also increases. Therefore, the flow rate of the fluid used for lubrication and cooling of the impeller bearing 8 increases. In addition, a portion of the through hole 64i opens into the helical groove 64g. Therefore, a portion of the fluid delivered by the helical groove 64g (flow F3) flows directly from the helical groove 64g into the through hole 64i (flow F9). Thus, when the inducer 9 is positioned inside the suction port 64, the through hole 64i also functions as an introduction structure.

[0085] In the fifth modified example, the number of through holes 64i is not limited to "3". Preferably, the through holes 64i are arranged in correspondence with the inducer blades 92. Also, the number of through holes 64i for one inducer blade 92 is determined according to the design of the pump device 1 and is not limited to "1".

[0086] Furthermore, in the fifth modified example, some of the multiple through holes 64i do not need to open into the helical groove 64g.

[0087] Furthermore, in the fifth modified example, not all through holes 64i have to open into the helical grooves 64g.

[0088] Furthermore, in the fifth modification, the through-hole 64i may open forward of the negative pressure surface region Rn. In this configuration as well, the handling fluid flowing in from the through-hole 64i flows into the negative pressure surface region Rn immediately after inflow.

[0089] Furthermore, in the fifth modified example, the number of inducer blades 92 can be determined according to the design of the pump device 1, and is not limited to "3".

[0090] ●6th variation Figure 12 is a partially enlarged schematic cross-sectional view of the pump device 1 in the sixth modified example.

[0091] The suction port 23 guides the handling fluid to the first impeller 6. The shape of the suction port 23 is a two-stage cylindrical shape along the axial direction. The suction port 23 comprises a large diameter portion 23a, a small diameter portion 23c, an internal threaded surface 23j, and a stepped portion 23k. In the axial direction, the small diameter portion 23c is located in front of the large diameter portion 23a and adjacent to the large diameter portion 23a. The stepped portion 23k is located between the large diameter portion 23a and the small diameter portion 23c and is a surface facing backward. In a rearward view, the shape of the stepped portion 23k is ring-shaped.

[0092] The intake port 64 of the first impeller 6 has an outer circumferential surface 64a and an inner circumferential surface 64j. The outer circumferential surface 64a is cylindrical in shape. The inner circumferential surface 64j is a two-stage cylindrical shape. The inner circumferential surface 64j has a large diameter section 64k, a small diameter section 64l, and a stepped section 64m. The inner diameter of the large diameter section 64k is larger than the inner diameter of the small diameter section 64l. In the axial direction, the large diameter section 64k is positioned in front of the small diameter section 64l and adjacent to the small diameter section 64l. The stepped section 64m is positioned between the large diameter section 64k and the small diameter section 64l and is a surface facing forward. In a forward view, the shape of the stepped section 64m is ring-shaped.

[0093] The impeller bearing 8 rotatably supports the first impeller 6 (large diameter portion 64k). The impeller bearing 8 is located in the front half of the first cylindrical space S2 and in the large diameter portion 64k. The impeller bearing 8 comprises a bearing housing 81, a bearing body 82, and a pin 83. The impeller bearing 8 is an example of the second bearing in the present invention.

[0094] The bearing housing 81 supports the bearing body 82. The bearing housing 81 comprises a male threaded surface 81a, a large-diameter portion 81b, and a small-diameter portion 81c. The male threaded surface 81a corresponds to the female threaded surface 23j and is located on the large-diameter portion 81b. The outer diameter of the large-diameter portion 81b is larger than the outer diameter of the small-diameter portion 81c. The large-diameter portion 81b is located in front of the small-diameter portion 81c and adjacent to the small-diameter portion 81c. The bearing housing 81 is attached to the large-diameter portion 23a and the stepped portion 23k by the male threaded surface 81a being fitted into the female threaded surface 23j. The bearing body 82 rotatably supports the first impeller 6. The shape of the bearing body 82 is cylindrical. The bearing body 82 comprises a cylindrical outer circumferential surface 82b. The small-diameter portion 81c is inserted into the bearing body 82, and the bearing body 82 is inserted into the suction port 64 (large-diameter portion 64k). Specifically, the bearing body 82 is positioned between the bearing housing 81 (small diameter portion 81c) and the suction port 64 (large diameter portion 64k). Upstream of the impeller bearing 8 in the flow of the handling fluid within space S1, there is a space defined by the housing 2, the first impeller 6, and the impeller bearing 8 (hereinafter referred to as "rear space S23"). Downstream of the same flow, there is a space S24 defined by the stepped portion 64m and the impeller bearing 8. The pin 83 fixes the position of the bearing body 82 in the circumferential direction. A small gap S25 is formed between the inner circumferential surface 64j (large diameter portion 64k) of the suction port 64 and the outer circumferential surface 82b of the bearing body 82. When the rotating shaft 4 (first impeller 6) is rotating, a lubricating film (not shown) of the handling fluid is formed in the gap S25.

[0095] With this configuration, the rotor dynamics are improved, similar to the first embodiment.

[0096] In the sixth modified example, the outer surface 64a may be provided with a helical groove 64g.

[0097] Furthermore, in the sixth modified example, the large-diameter section 64k may be provided with a helical groove (not shown; the same applies hereinafter) having the same function as the helical groove 64g. In this case, the helical groove transports the liquid being handled from the front to the rear. Therefore, the direction of rotation of the helical groove is the opposite direction to the direction of rotation of the helical groove 64g.

[0098] ●7th variation Figure 13 is a partially enlarged schematic cross-sectional view of the pump device 1 in the seventh modified example.

[0099] The pump chamber 21 includes a front inner surface 21a and a bearing retaining portion 21b. A portion of the front inner surface 21a is recessed in a ring shape concentric with the rotating shaft 4 in the forward direction, forming the bearing retaining portion 21b.

[0100] The first impeller 6 includes a supported portion 66. The supported portion 66 is supported by the impeller bearing 8. A portion of the front shroud 62 extends cylindrically forward so as to be coaxial with the rotation axis 4, forming the supported portion 66. That is, the supported portion 66 is positioned in the front direction of the front shroud 62 and adjacent to the front shroud 62. The front shroud 62 also includes the supported portion 66. In a forward view, the shape of the supported portion 66 is cylindrical and concentric with the rotation axis 4 and the intake port 64. The supported portion 66 includes an outer circumferential surface 66a and an inner circumferential surface 66b. The shapes of the outer circumferential surface 66a and the inner circumferential surface are cylindrical. The supported portion 66 is housed in the bearing retaining portion 21b.

[0101] The impeller bearing 8 rotatably supports the first impeller 6 (supported portion 66). The impeller bearing 8 comprises a bearing body 82. The bearing body 82 comprises a cylindrical inner circumferential surface 82a.

[0102] The supported portion 66 and the bearing body 82 are housed in the bearing retaining portion 21b. The bearing body 82 is fixed to the bearing retaining portion 21b, for example, by bolts (not shown). The supported portion 66 is inserted into the bearing body 82. That is, in the radial direction, the impeller bearing 8 is positioned outward from the first impeller 6 (supported portion 66). A small gap S26 is formed between the outer circumferential surface 66a of the supported portion 66 and the inner circumferential surface 82a of the bearing body 82. When the rotating shaft 4 (first impeller 6) is rotating, a lubricating film (not shown) is formed in the gap S26 by the handling fluid. Also, in the radial direction, a cylindrical gap S27 is formed between the bearing retaining portion 21b and the supported portion 66.

[0103] With this configuration, the rotor dynamics are improved, similar to the first embodiment.

[0104] In the seventh modified example, the outer surface 66a may be provided with a helical groove (not shown; the same applies hereinafter) having the same structure as the helical groove 64g. In this case, the space S1 includes the space downstream of the impeller bearing 8 in the flow of the liquid being handled within the space S1, and the space upstream of the impeller bearing 8 in the same flow.

[0105] Furthermore, in the seventh modified example, the impeller bearing 8 may include a bearing housing 81 and a pin 83.

[0106] ●Other Embodiments● In addition, in this invention, the housing 2 may be disassembled into multiple parts.

[0107] Furthermore, in this invention, the number of impellers (first impeller 6, second impeller 7) is not limited to "2". That is, for example, the number of impellers may be "1" or "3" or more. Here, the greater the number of impellers, the greater the effect of improving rotor dynamics.

[0108] Furthermore, in the present invention, the pump device 1 does not need to be equipped with a bypass flow path 23f, as shown in the first and second modified examples.

[0109] Furthermore, in the present invention, the pump device 1 does not need to be provided with an end face groove 64h, as shown in the third modified example.

[0110] Furthermore, in the present invention, the pump device 1 does not need to be equipped with a helical groove 64g and an end face groove 64h. In this configuration, the flow rates of flows F1 and F2 are reduced compared to the first embodiment. However, as mentioned above, the pressure of the fluid being handled that flows into the rear space S21 is high. Therefore, the fluid being handled easily flows into the gap S22. Thus, the fluid being handled necessary for lubrication and cooling of the impeller bearing 8 is secured. Subsequently, the fluid being handled flows into the second cylindrical space S3. A portion of the fluid being handled flows not only into the end face gap S4 but also into the bypass flow path 23f. Therefore, turbulence in the main flow F0 is suppressed.

[0111] Furthermore, in the present invention, the pump device 1 does not necessarily have to be equipped with a bypass passage 23f and an end face groove 64h. In this configuration, the flows F1 and F2 are reduced compared to the first embodiment. Also, all of the handling fluid delivered to the second cylindrical space S3 flows into the end face gap S4. Therefore, the suction performance of the pump device 1 may decrease. On the other hand, sufficient handling fluid necessary for lubrication and cooling of the impeller bearing 8 is ensured.

[0112] Furthermore, in the present invention, the pump device 1 does not necessarily have to be equipped with a helical groove 64g. In this configuration, the flow rates of flows F1 and F2 are reduced compared to the first embodiment. However, as described above, the handling fluid necessary for lubrication and cooling of the impeller bearing 8 is ensured. Also, most of the handling fluid that flows into the second cylindrical space S3 flows into the bypass flow path 23f. Therefore, turbulence in the main flow F0 is suppressed.

[0113] Furthermore, in the present invention, the pump device 1 does not necessarily have to be equipped with a bypass passage 23f, a helical groove 64g, and an end face groove 64h. In this configuration, the effects based on these configurations cannot be obtained. On the other hand, the handling fluid necessary for lubrication and cooling of the impeller bearing 8 is ensured.

[0114] Furthermore, in the present invention, the suction port 64 may have a protrusion projecting forward from the front end surface 64f instead of the end face groove 64h. In this case, when viewed from the front, the protrusion is positioned on the front end surface 64f such that it traces an arc from the front to the rear in the rotational direction RD as the protrusion moves from the inner end to the outer end. Here, the shape of the protrusion when viewed from the front may be the same as the shape of the end face groove 64h.

[0115] Furthermore, in the present invention, the number of end face grooves 64h is not limited to "4".

[0116] Furthermore, in the present invention, the outer peripheral surface 64a does not necessarily have to include a large diameter portion 64b and a stepped portion 64d.

[0117] Furthermore, in the present invention, the size of the second cylindrical space S3 in the radial direction may be about the same as the size of the gap S22 (the second cylindrical space S3 may be narrow). In this case, even in the second cylindrical space S3, the liquid being handled is delivered forward by the helical groove 64g. The same applies to the rear space S21.

[0118] Furthermore, in the present invention, the impeller bearing 8 does not necessarily have to include a bearing housing 81 and a pin 83. In this case, the bearing body 82 may be fixed to the housing 2 by bolts, for example, as shown in the seventh modified example.

[0119] Furthermore, in the present invention, the method of mounting the bearing housing 81 is not limited to a method using the female threaded surface 23j and the male threaded surface 81a. That is, for example, the bearing housing 81 may be attached to the large-diameter portion 23a and / or the first-stage portion 23d with bolts (not shown).

[0120] Furthermore, in the present invention, the pump device 1 is not limited to a centrifugal pump. That is, for example, the pump device 1 may be an axial flow pump or a mixed flow pump.

[0121] ●Embodiments of the present invention● Next, embodiments of the present invention as understood from the embodiments described above will be described below, with reference to the terms and reference numerals used in each embodiment.

[0122] A first embodiment of the present invention comprises a motor (e.g., motor 3), a rotating shaft (e.g., rotating shaft 4) that rotates by the drive of the motor, an impeller (e.g., first impeller 6) attached to the rotating shaft for sucking in and discharging the liquid being handled, a first bearing (e.g., bearing 51) disposed between the motor and the impeller to rotatably support the rotating shaft, a second bearing (e.g., impeller bearing 8) to rotatably support the impeller, and a pump housing (e.g., housing 2) housing the impeller, the inducer, and the second bearing. The pump device (e.g., pump device 1) is configured such that, in the axial direction of the rotating shaft, the direction in which the impeller is positioned relative to the motor is the first direction, and the direction in which the motor is positioned relative to the impeller is the second direction, and the impeller comprises a blade (e.g., blade 61) that rotates in accordance with the rotation of the rotating shaft, a front shroud (e.g., front shroud 62) that covers the first direction of the blade, and a cylindrical supported surface (e.g., small diameter portion 64c, large diameter portion 64k, outer peripheral surface 66a) supported by the second bearing. This configuration improves the rotor dynamics in the pump system.

[0123] A second embodiment of the present invention is a pump device in which, in the first embodiment, the impeller is provided with a suction port (e.g., suction port 64) located adjacent to the front shroud in the first direction of the front shroud, and the suction port is provided with an outer peripheral surface (e.g., outer peripheral surface 64a) that functions as the supported surface. This configuration improves the rotor dynamics in the pump system.

[0124] A third embodiment of the present invention is a pump device in which, in the second embodiment, the pump housing and the suction port define a first space (e.g., rear space S21) in the first direction of the second bearing and a second space (e.g., second cylindrical space S3) in the second direction of the second bearing, into which a portion of the liquid being handled discharged from the impeller flows; the impeller is provided with a helical groove (e.g., helical groove 64g) arranged on its outer circumferential surface, the helical groove being arranged on its outer circumferential surface such that the position of the helical groove rotates along the rotational direction of the rotating shaft (e.g., rotational direction RD) as the direction from the first direction to the second direction. With this configuration, a sufficient amount of handling fluid is ensured to lubricate and cool the impeller bearing.

[0125] A fourth embodiment of the present invention is a pump device in which, in the second or third embodiment, the suction port comprises a cylindrical inner circumferential surface (e.g., inner circumferential surface 64e) and a ring-shaped end face (e.g., front end face 64f) facing the first direction, the pump housing comprises an opposing surface (e.g., second step portion 23e) positioned at a distance from the end face in the first direction of the end face and facing the end face, the end face comprises a recess (e.g., end face groove 64h) or a protrusion, and in a view in the first direction, the recess or the protrusion is positioned on the end face such that the recess or the protrusion traces an arc from the front to the rear in the rotational direction of the rotation axis as the suction port 64 moves from the inner circumferential surface toward the outer circumferential surface. This configuration improves the suction performance of the pump system.

[0126] A fifth embodiment of the present invention is a pump device in which, in the fourth embodiment, the pump housing comprises a bypass passage (e.g., bypass passage 23f) communicating with a gap defined by the end face and the opposing face (e.g., end face gap S4) and an upstream space (e.g., upstream space S5) located in the first direction relative to the impeller within the internal space of the pump housing, wherein the opening end of the bypass passage on the upstream space side (e.g., front end 23i) is inclined towards the second direction side relative to the radial direction of the rotation axis. In this configuration, the flow returned from the bypass channel to the main channel does not affect the main channel.

[0127] A sixth embodiment of the present invention is a pump device in which, in the third embodiment, the second bearing is a sliding bearing, and the helical groove is arranged on the outer surface in a portion facing the second bearing. This configuration improves the lubrication and cooling effects of the impeller bearing.

[0128] A seventh embodiment of the present invention is a pump device comprising, in the third embodiment, an inducer (e.g., inducer 9) attached to the rotating shaft and housed in the suction port, wherein the suction port has a cylindrical inner circumferential surface (e.g., inner circumferential surface 64e), the impeller has an outer circumferential surface and a through hole (e.g., through hole 64i) opening to the inner circumferential surface, the inducer comprises an inducer blade (e.g., inducer blade 92) that rotates in accordance with the rotation of the rotating shaft, the inducer blade has a positive pressure surface (e.g., positive pressure surface 92a) and a negative pressure surface (e.g., negative pressure surface 92b) which is the surface opposite to the positive pressure surface, and in the axial direction, the through hole is positioned in the first direction relative to the second bearing and opens in the first direction relative to the negative pressure surface. This configuration suppresses cavitation within the internal space of the intake port. Furthermore, it ensures a sufficient amount of fluid is available for lubrication and cooling of the impeller bearing.

[0129] An eighth embodiment of the present invention is a pump device in which, in the first embodiment, the impeller is provided with a suction port located adjacent to the front shroud in the first direction of the front shroud, and the suction port is provided with an inner circumferential surface (for example, a large diameter portion 64k) that functions as the supported surface. This configuration improves the rotor dynamics in the pump system.

[0130] A ninth embodiment of the present invention is a pump device in which, in the first embodiment, the impeller comprises a cylindrical suction port positioned adjacent to the front shroud in the first direction of the front shroud, and a cylindrical supported portion (e.g., supported portion 66) positioned adjacent to the front shroud in the first direction of the front shroud, wherein, in a view in the first direction, the supported portion is positioned concentrically with the suction port in the radially outward direction of the rotation axis relative to the suction port, and the supported portion comprises an outer peripheral surface (e.g., outer peripheral surface 66a) that functions as the supported surface. This configuration improves the rotor dynamics in the pump system. [Explanation of Symbols]

[0131] 1. Pumping device 2 enclosures (pump enclosures) 23e Second section 23f Bypass channel 23i Front end (open end) 3 motors 4 rotation axes 51 Bearing (First Bearing) 6. First impeller 62 Front Shroud 64 Inlet 64a Outer surface 64c Small diameter part (supported surface, outer peripheral surface) 64e Inner surface (inner surface of shroud) 64f Front end face (shroud end face) 64g spiral groove 64h End groove 64i through hole 64k Large diameter part (supported surface, inner peripheral surface) 66 Supported part 66a Outer surface (supported surface) 8. Impeller bearing (second bearing) 9 Inducer 92 Inducer Wings 92a Positive pressure side 92b Suction side S21 Rear space (second space) S3 Second cylindrical space (first space) S4 End face gap (gap) S5 upstream space

Claims

1. Motor and, A rotating shaft that rotates due to the drive of the aforementioned motor, An impeller attached to the aforementioned rotating shaft, which sucks in and discharges the liquid being handled, A first bearing is positioned between the motor and the impeller and rotatably supports the rotating shaft, A second bearing that rotatably supports the impeller, A pump housing that houses the impeller and the second bearing, It has, In the axial direction of the rotating shaft, the direction in which the impeller is positioned relative to the motor is the first direction, and the direction in which the motor is positioned relative to the impeller is the second direction. The impeller is, A blade that rotates in accordance with the rotation of the aforementioned rotating shaft, A front shroud covering the first direction of the aforementioned blade, A cylindrical supported surface supported by the second bearing, Equipped with, Pumping device.

2. The impeller is, In the first direction of the front shroud, an intake port is located adjacent to the front shroud. Equipped with, The aforementioned suction port is The outer peripheral surface that functions as the supported surface, Equipped with, The pump device according to claim 1.

3. The pump housing and the suction port are, A first space is defined in the first direction of the second bearing, A second space is defined in the second direction of the second bearing, A portion of the handling fluid discharged from the impeller flows into the second space. The impeller is, A spiral groove is arranged on the outer surface, Equipped with, The helical groove is arranged on the outer circumferential surface such that the position of the helical groove rotates along the rotational direction of the rotation axis as the direction moves from the first direction to the second direction. The pump device according to claim 2.

4. The aforementioned suction port is The cylindrical inner surface, A ring-shaped end face oriented in the first direction, Equipped with, The aforementioned pump housing is A surface positioned in the first direction of the end face, spaced apart from the end face, and facing the end face, Equipped with, The aforementioned end face is Recessed or protruding part, Equipped with, In the first viewing direction, the recess or the protrusion is positioned on the end face such that, as the recess or the protrusion moves from the inner circumferential surface of the suction port toward the outer circumferential surface, it traces an arc that moves from the front direction toward the rear direction in the rotational direction of the rotation axis. The pump device according to claim 2 or 3.

5. The aforementioned pump housing is A bypass channel communicating with the gap defined by the end face and the opposing face, and the upstream space located in the first direction relative to the impeller within the internal space of the pump housing, Equipped with, The open end of the bypass channel on the upstream side is inclined toward the second direction more than the radial direction of the rotation axis. The pump device according to claim 4.

6. The second bearing is a sliding bearing, The helical groove is arranged on the outer surface in the portion facing the second bearing. The pump device according to claim 3.

7. An inducer, which is attached to the rotating shaft and housed in the suction port, It has, The aforementioned suction port is Cylindrical inner surface, Equipped with, The impeller is, Through holes opening in the outer circumferential surface and the inner circumferential surface, Equipped with, The aforementioned inducer is, An inducer blade that rotates in accordance with the rotation of the aforementioned rotation axis, Equipped with, The aforementioned inducer blade is Positive pressure surface and, The negative pressure surface is the surface opposite to the positive pressure surface, Equipped with, In the axial direction, the through hole is positioned in the first direction relative to the second bearing and opens in the first direction relative to the negative pressure surface. The pump device according to claim 3.

8. The impeller is, In the first direction of the front shroud, an intake port is located adjacent to the front shroud. Equipped with, The aforementioned suction port is The inner circumferential surface that functions as the supported surface, Equipped with, The pump device according to claim 1.

9. The impeller is, In the first direction of the front shroud, a cylindrical suction port is provided adjacent to the front shroud, In the first direction of the front shroud, a cylindrical supported portion is provided adjacent to the front shroud, Equipped with, In the first view, the supported portion is arranged concentrically with the suction port in the radially outward direction of the rotation axis relative to the suction port, The supported portion is, The outer peripheral surface that functions as the supported surface, Equipped with, The pump device according to claim 1.

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