pump

Abstract

To provide a pump that can suppress vibration of an impeller which is caused by NZ exciting force and suppress excessive vibration which is caused by resonance with the natural vibrations of other components.SOLUTION: A pump 10 includes: a pump casing; an impeller 30 fitted to a rotation shaft 25; a tongue part 20a opposite to a vane 32 of the impeller 30; and a plurality of centrifugal dynamic vibration absorbers 40 installed to a shroud 31 of the impeller 30 around an axis A of the rotation shaft 25 at intervals. The dynamic vibration absorbers 40 includes a plate-like mass body 45 disposed so as to extend along a radial direction of the shroud 31 and pivotally supported on a radial inner end side.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a pump. [Background technology]

[0002] The vertical pump disclosed in Patent Document 1 includes an impeller and a bearing casing within a pump casing. The impeller has a number of blades protruding radially, and is attached to the lower end of the rotating shaft within the pump casing. The bearing casing is disposed above the impeller within the pump casing via a guide vane, and rotatably supports the portion of the rotating shaft protruding from the impeller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-176798 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of pump, when the blades of the impeller pass under the lower end (tongue) of the guide vane, the impeller is excited and vibrates at a period of the blade passing frequency (NZ) obtained by multiplying the impeller rotation speed (N) by the number of impeller blades (Z). The excitation force due to this NZ acts individually on all the passing blades, and the direction of the NZ excitation force varies depending on the direction in which the guide vane extends, but is generally radial for the impeller as a whole. The guide vane is subjected to a force due to NZg, which is the impeller rotation speed (N) multiplied by the number of guide vanes (Zg). However, since the guide vane is fixed to the pump casing, the force acting on the guide vane by NZg is smaller than the excitation force acting on the impeller by NZ. In other words, there is no need to consider the force acting on the guide vane by NZg.

[0005] When the vibration frequency of the impeller caused by the NZ excitation force resonates in synchronization with the natural frequency of other components (particularly the pump casing), excessive vibration occurs. However, the vertical pump of Patent Document 1 does not take into consideration the resonance between the vibration of the impeller caused by the NZ excitation force and the natural vibration of other components, so there is room for improvement in suppressing vibration caused by resonance.

[0006] An object of the present invention is to provide a pump that can suppress vibration of an impeller caused by an NZ excitation force and can suppress excessive vibration caused by resonance with the natural vibration of other components. [Means for solving the problem]

[0007] The present invention provides a pump comprising: a cylindrical pump casing, a shroud attached to a rotating shaft within the pump casing, an impeller having a plurality of blade portions protruding radially from the shroud, a plurality of tongue portions provided on the pump casing so as to face the blade portions and spaced apart around the axis of the rotating shaft, and a plurality of centrifugal dynamic vibration absorbers arranged to extend radially along the shroud and having a plate-shaped mass body journaled at its radially inner end side, and arranged at intervals around the axis of the rotating shaft relative to the shroud.

[0008] The shroud of the impeller is provided with a plate-shaped mass body extending along the radial direction of the shroud, and multiple dynamic vibration absorbers are arranged at intervals around the axis of the rotating shaft in a centrifugal manner. As a result, when a radial excitation force acts on the impeller, the mass body that can rotate and oscillate provided in the dynamic vibration absorber oscillates (turns) in the opposite direction to the excitation force due to inertia. Therefore, it is possible to suppress the vibration of the impeller caused by the NZ excitation force. As a result, it is possible to suppress the vibration frequency of the impeller from resonating in synchronization with the natural frequency of other components such as the pump casing, and to suppress the occurrence of excessive vibration in the pump. Effect of the Invention

[0009] In the present invention, the vibration of the impeller caused by the NZ excitation force can be suppressed, and excessive vibration caused by resonance with the natural vibration of other components can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a vertical pump according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a partial cross-sectional view of the impeller taken along line II-II in FIG. [Diagram 3] FIG. 2 is an enlarged cross-sectional view of part III in FIG. 1 . [Figure 4] FIG. 4 is an exploded perspective view of the impeller shroud and dynamic vibration absorber. [Diagram 5] Cross-sectional view of the impeller in Figure 1 along line II-II, where an excitation force from NZ is applied. [Figure 6] 6 is a cross-sectional view similar to FIG. 5 showing a method for balancing an unbalanced impeller. [Figure 7] FIG. 2 is a diagram showing an outline of a dynamic vibration absorber. [Figure 8] 1 is a graph showing a change in vibration due to a critical damping ratio. [Figure 9] FIG. 4 is a cross-sectional view similar to FIG. 2 of a vertical pump according to a second embodiment. [Figure 10] FIG. 5 is an enlarged cross-sectional view similar to FIG. 3 of a vertical pump according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] (First embodiment) 1, a vertical pump 10 according to a first embodiment of the present invention includes a pump casing 15, a rotating shaft 25, and an impeller 30, and discharges water that has flowed into a suction tank 1 downstream. In this embodiment, vibration of the impeller 30 is suppressed when the impeller 30 rotates, thereby suppressing excessive vibration of the pump casing 15 in resonance.

[0013] The pump casing 15 is cylindrical, and is inserted from above into a mounting hole formed in the installation floor 2 that covers the upper part of the suction tank 1, and is fixed to the installation floor 2. The pump casing 15 includes a lifting pipe 16 and a discharge pipe 23 connected to the upper end of the lifting pipe 16.

[0014] The lift pipe 16 protrudes vertically downward from the installation floor 2. The lift pipe 16 includes a straight pipe 17 of uniform diameter, an elliptical cylindrical vane casing 18 that bulges outward in the radial direction, and a bell mouth 19 that gradually widens toward the lower end. The straight pipe 17, vane casing 18, and bell mouth 19 are joined from top to bottom in this order. The number of straight pipes 17 depends on the total length required for the pump casing 15.

[0015] A bearing casing 21 is integrally provided inside the vane casing 18 with a plurality of guide vanes 20 interposed therebetween.

[0016] Each of the guide vanes 20 is plate-shaped, with an inner end joined to the bearing casing 21 and an outer end joined to the vane casing 18. The guide vanes 20 are provided at intervals around the axis A of the rotating shaft 25. The lower end edge (opposing edge) of each guide vane 20 forms a tongue portion 20a that faces the blade portion 32 of the impeller 30. Referring to Figures 2 and 5, in this embodiment, five guide vanes 20 are provided at intervals of 72 degrees. However, the number of guide vanes 20 may be three or more.

[0017] 1, the bearing casing 21 has a generally conical cylindrical shape that widens downward, and is disposed directly above (downstream of) the impeller 30. The bearing casing 21 includes a cylindrical support member 22 therein. The support member 22 rotatably supports a portion of the rotating shaft 25 that protrudes upward from the impeller 30.

[0018] The discharge pipe 23 is a bent pipe that is bent at approximately 90 degrees, and protrudes upward from the installation floor 2. A water supply pipe (not shown) that is piped to a discharge tank on the downstream side is connected to the discharge pipe 23 via a gate valve (not shown) that can open and close the flow path.

[0019] The rotating shaft 25 has a lower part that passes through the discharge pipe 23 and is disposed inside the lift pipe 16, and an upper part that protrudes outward from the discharge pipe 23. The lower part of the rotating shaft 25 extends in the vertical direction along the axis of the lift pipe 16. In other words, the axis A of the rotating shaft 25 coincides with the axis of the lift pipe 16. An electric motor 35, which is an example of a drive source, is mechanically connected to the upper part of the rotating shaft 25. However, the drive source may be a prime mover instead of the electric motor 35.

[0020] The impeller 30 is attached to the lower end of the rotating shaft 25 so as to be located directly below the bearing casing 21. However, the attachment position of the impeller 30 is not limited to the lower end of the rotating shaft 25, but may be any position below the bearing casing 21 and on the lower end side of the rotating shaft 25. Specifically, the impeller 30 includes a shroud 31 and a plurality of blade portions 32, and is formed by casting.

[0021] The shroud 31 is generally in the shape of an inverted cone cylinder that gradually widens towards the upper side, and is attached to the lower end of the rotating shaft 25 so as to be unable to rotate relative to the rotating shaft 25.

[0022] The plurality of blades 32 protrude radially from the shroud 31 and are positioned below (upstream of) the guide vanes 20 in the pump casing 15 at intervals. With reference to Figs. 2 and 5, in this embodiment, four blades 32 are provided at 90 degree intervals. However, it is preferable that the number of blades 32 is three or more and different from the number of guide vanes 20. This is because, when the number of blades 32 and the number of guide vanes 20 are the same, the blades 32 pass below the guide vanes 20 at the same period.

[0023] 1, in the vertical pump 10 configured as above, the impeller 30 shown in FIG. 2 rotates counterclockwise (rotation direction r) as a unit with the rotary shaft 25 driven by the electric motor 35. As a result, water in the suction tank 1 is sucked in from the suction port at the lower end of the lifting pipe 16 and discharged downstream through the pump casing 15.

[0024] During this drainage operation, when the blade 32 passes under the tongue 20a of the guide vane 20, as in the case of the uppermost blade 32 shown in Fig. 5, the impeller 30 is excited and vibrates at a period of a blade passing frequency (NZ) obtained by multiplying the number (Z) of the blades 32 by the rotation speed (N) of the impeller 30. This excitation force F is generated at positions corresponding to all of the guide vanes 20 by the rotation of the impeller 30, and acts on all of the blades 32 individually. The direction in which the excitation force F acts on the impeller 30 depends on the direction in which the guide vanes 20 extend, and therefore differs for each individual guide vane 20, but is generally radial for the impeller 30 as a whole.

[0025] The impeller 30 vibrates due to the excitation force F, and if the vibration frequency resonates in synchronization with the natural frequency of other components such as the pump casing 15, excessive vibration will result. In order to suppress the vibration of the impeller 30 due to this excitation force F and to balance the impeller 30 made of cast metal, a plurality of dynamic vibration absorbers 40 are arranged on the impeller 30 of this embodiment.

[0026] The configuration of the dynamic vibration reducer 40 will be specifically described below with reference to FIGS.

[0027] The multiple dynamic vibration absorbers 40 each have a mass body 45, and are individually arranged in multiple recesses 42 formed in the shroud 31 of the impeller 30. The number of dynamic vibration absorbers 40 including recesses 42 is the same as the number of blades 32, and the dynamic vibration absorbers 40 are arranged at the same angular positions as the blades 32 in the circumferential direction of the shroud 31. However, the number of dynamic vibration absorbers 40 and the number of blades 32 may be different, and the dynamic vibration absorbers 40 and the blades 32 may be arranged at different angular positions.

[0028] The shroud 31 is provided with an annular base portion 41 that is thicker in the direction along the axis A of the rotating shaft 25. The upper surface of the base portion 41 extends flush with the upper end portion of the shroud 31, and extends in a direction perpendicular to the axis A of the rotating shaft 25 (horizontal direction). However, a plurality of base portions 41 may be partially provided at positions that form the recesses 42 in the shroud 31, and may be arranged at intervals in the circumferential direction.

[0029] The recesses 42 are spaced apart from each other around the axis A of the rotation shaft 25 relative to the base portion 41 so as to correspond to the angular positions of the wing portions 32 when viewed from the direction in which the rotation shaft 25 extends. Each recess 42 includes a fitting portion 42a and a recess body 42b, and is recessed downward. In other words, the recess 42 is recessed in a direction away from the tongue portion 20a of the guide vane 20.

[0030] The fitting portion 42a is a rectangular groove recessed downward from the upper surface of the base portion 41 and extending in the radial direction of the shroud 31. The fitting portion 42a is provided to close the upper end of the recess body 42b by fitting a cover 44 having the same shape into the fitting portion 42a. In other words, the fitting portion 42a is an opening of the recess 42, and is closed by the cover 44.

[0031] The recessed portion main body 42b is a rectangular groove recessed downward from the bottom of the fitting portion 42a and extending in the radial direction of the shroud 31. When viewed from the direction in which the axis A of the rotating shaft 25 extends, the shape of the recessed portion main body 42b is slightly smaller than the shape of the fitting portion 42a, and the centroid of the recessed portion main body 42b coincides with the centroid of the fitting portion 42a. The depth of the recessed portion main body 42b is deeper than the height dimension of the mass body 45. The bottom of the recessed portion main body 42b extends in a direction perpendicular to the axis A of the rotating shaft 25 (horizontal direction).

[0032] A plurality of shaft holes 43 are provided in the bottom of the recess body 42b in order to detachably dispose the mass body 45 and to support it so that it can rotate and swing. The plurality of shaft holes 43 are provided in the recess body 42b, biased toward the radially inner side of the shroud 31, and are arranged at intervals in the radial direction of the shroud 31. In this embodiment, the number of shaft holes 43 is three. However, the number of shaft holes 43 may be one or two, or may be four or more.

[0033] The recess 42 is filled with a liquid 50 for providing fluid resistance together with the mass body 45. A lubricating oil is used as the liquid 50 so that the liquid 50 also has a damping function. However, instead of the lubricating oil, pumped water to be discharged may be used as the liquid 50. In this case, it is preferable to provide a hole in the cover 44 for allowing the pumped water to flow in. Alternatively, the recess 42 may be left open without using the cover 44.

[0034] Each dynamic vibration absorber 40 is of the centrifugal type, and includes a mass body 45 that is rotatably and swingably disposed in the recess 42. The mass body 45 includes a plate-shaped arm portion 46 and a weight 47 attached to the tip (outer end) of the arm portion 46, and is disposed in the recess 42 so as to be detachable and rotatably and swingably.

[0035] The arm portion 46 is disposed in the recess 42 so as to extend along the radial direction of the shroud 31. The total length of the arm portion 46 in the radial direction of the shroud 31 is shorter than the total length of the recess body 42b, and the lateral width of the arm portion 46 in the circumferential direction of the shroud 31 is narrower than the lateral width of the recess body 42b.

[0036] An axle portion 46a is provided at one end (inner end) of the arm portion 46. The axle portion 46a has a through hole 46b through which the axle portion 48a of the pin 48 passes. The axle portion 48a of the pin 48 passes through the axle portion 46a and is inserted into one of the three shaft holes 43 of the recess 42. This causes the axle portion 46a to be sandwiched between the head portion 48b of the pin 48 and the bottom of the recess 42. As a result, the entire mass body 45 including the arm portion 46 is arranged to be freely rotatable and swingable in the horizontal direction around the axle portion 48a of the pin 48 extending along the rotation axis 25. A thrust washer 49 is interposed between the axle portion 46a and the bottom of the recess 42 to ensure sliding properties.

[0037] The weight 47 has a mounting hole 47a for non-detachably mounting to the arm portion 46. The mounting hole 47a is provided so as to extend from one end of the weight 47 in the longitudinal direction to the vicinity of the other end. In this embodiment, with the weight 47 mounted to the arm portion 46, the dimension from the rotation axis Ar of the through hole 46b of the arm portion 46 to the tip surface of the weight 47 is defined as the length L of the mass body 45.

[0038] (Suppression of vibration caused by excitation force) In the impeller 30 equipped with a plurality of dynamic vibration absorbers 40 configured as described above, vibrations caused by the excitation force F shown in FIG. 5 can be suppressed, as will be described in detail below.

[0039] In the following description, of the multiple wing portions 32, the one located at the top in Figures 5 and 6 may be referred to as wing portion 32A, and in clockwise order from wing portion 32A, the following may be referred to as wing portion 32B, wing portion 32C, and wing portion 32D. Also, of the multiple dynamic vibration absorbers 40, the ones corresponding to wing portions 32A, 32B, 32C, and 32D may be referred to as dynamic vibration absorbers 40A, 40B, 40C, and 40D, respectively, and of the multiple mass bodies 45, the ones provided on dynamic vibration absorbers 40A, 40B, 40C, and 40D may be referred to as mass bodies 45A, 45B, 45C, and 45D, respectively.

[0040] First, when the uniformed impeller 30 is rotated under no load, the mass bodies 45A-45D of the multiple dynamic vibration absorbers 40A-40D are all extended from the inside to the outside in the radial direction of the impeller 30 due to centrifugal force (see FIG. 2).

[0041] On the other hand, as shown in FIG. 5, when the blade 32A passes under the uppermost guide vane 20 in FIG. 5, an excitation force F due to the blade passing frequency (NZ) acts on the blade 32A, and the mass bodies 45A to 45D rotate and swing in the direction opposite to the excitation force F due to inertia. In the example of FIG. 5, the mass bodies 45A and 45C do not rotate because they extend in a direction generally parallel to the excitation force F. The mass bodies 45B and 45D extend in a direction intersecting the downward excitation force F in FIG. 5, so they all swing (rotate) upward in FIG. 5. When the blade 32A passes under a guide vane 20 other than the uppermost guide vane 20 in FIG. 5, and when the excitation force F acts on the blades 32B to 32D other than the blade 32A, the mass bodies 45A to 45D also swing (rotate) in the direction opposite to the excitation force F due to inertia.

[0042] In this way, when the excitation force F acts on the blade portions 32A-32D, the mass bodies 45A-45D included in the multiple dynamic vibration absorbers 40A-40D rotate and oscillate in the direction opposite to the excitation force F. This makes it possible to suppress the vibration of the impeller 30 caused by the NZ excitation force F. Therefore, even if the vibration frequency of the impeller 30 resonates in synchronization with the natural frequency of other components such as the pump casing 15, the vertical pump 10 can be prevented from experiencing excessive vibration.

[0043] Here, the principle of vibration suppression of the impeller 30 by the dynamic vibration absorber 40 will be described with reference to FIGS.

[0044] The m1 in the main vibration system shown in Fig. 7 corresponds to the impeller 30 shown in Fig. 1. The secondary vibration system shown in Fig. 7 corresponds to the dynamic vibration absorber 40 shown in Fig. 3. More specifically, m2 in Fig. 7 corresponds to the weight 47 shown in Fig. 3, k2 in Fig. 7 corresponds to the centrifugal force acting on the mass body 45 by the rotation of the impeller 30, and c in Fig. 7 corresponds to the liquid 50 shown in Fig. 3.

[0045] If the dynamic vibration absorber 40 is not provided, the impeller 30 will vibrate when an excitation force F acts on the blade portion 32 that has passed below the guide vane 20. However, since the impeller 30 of this embodiment is provided with multiple dynamic vibration absorbers 40 (secondary vibration system) having a natural frequency ω2, the dynamic vibration absorbers 40 absorb the excitation force F acting on the blade portion 32, and the vibration of the impeller 30 can be rapidly reduced.

[0046] Fig. 8 is a graph showing vibration changes due to critical damping ratios. In Fig. 8, the horizontal axis is frequency and the vertical axis is amplitude. The two-dot chain line in Fig. 8 shows the response of an impeller 30 in which a dynamic vibration absorber 40 is not arranged, and the one-dot chain line in Fig. 8 shows the response of an impeller 30 in which a dynamic vibration absorber 40 without liquid 50 (damping function) is arranged. Two types of dashed lines and a solid line with different pitches in Fig. 8 show the response of an impeller 30 in which a damping-type dynamic vibration absorber 40 with liquid 50 (damping function) is arranged.

[0047] 8, when the dynamic vibration absorber 40 is used for the impeller 30, two resonance peaks appear, with their intersections at P and Q. These points P and Q do not change (are fixed points) regardless of how the damping is changed. By appropriately setting the spring constant K (centrifugal force) of the mass body 45 and the liquid 50 (damping constant), the two resonance peaks passing through points P and Q can be kept low, achieving low vibration over a wide range.

[0048] As shown by the dashed line in Fig. 8, when a non-damping type dynamic vibration absorber 40 is used, the natural frequency of the secondary vibration system (dynamic vibration absorber 40) is matched to the frequency of the excitation force F, thereby making it possible to balance the spring force (the centrifugal force of the mass body 45) and the excitation force F. This makes the response of the primary vibration system (impeller 30) completely zero.

[0049] In the case of a damping type dynamic vibration absorber 40, the dynamic vibration absorber 40 is adjusted so that it resonates with the rotation speed of the main vibration system (impeller 30). Since it is tuned to the main vibration system rather than the excitation force F, it is effective over a wide frequency range and also suppresses free vibration. However, there is an optimum value for damping by the dynamic vibration absorber 40, and if the damping is too small, it will be shown by a dashed line with a wide pitch in FIG. 8, and if the damping is too large, it will be shown by a dashed line with a narrow pitch in FIG. 8. If the dynamic vibration absorber 40 has appropriate damping, it can exert a vibration-damping effect over a wide range of natural frequencies, as shown by the solid line in FIG. 8. In addition, it can exert a vibration-damping effect even if the natural frequency changes due to aging.

[0050] (Impeller balancing using dynamic vibration absorbers) Since the impeller 30 is a casting formed by casting, it is difficult to mold it in a balanced state, and the existence of an inherent imbalance (for example, the portion of the unbalanced weight M shown in FIG. 6) is unavoidable. For this reason, in the past, the impeller 30 was balanced by cutting a part of the shroud 31 or the blade portion 32. However, in this case, the impeller 30 deviates from the specified shape, and the hydraulic performance, such as the pump efficiency, of the vertical pump 10 using this impeller 30 may decrease.

[0051] Therefore, in this embodiment, multiple types of mass bodies 45 with different weights of the weights 47 are prepared in advance, and the impeller 30 can be balanced by arranging mass bodies 45 of appropriate weights. In order to prevent an excessive weight increase, the total weight of one mass body 45 including the weights 47 is set to be 2% or more and less than 5% of the weight of the impeller 30 without the multiple dynamic vibration absorbers 40.

[0052] However, instead of preparing multiple types of mass bodies 45 with different weights of weights 47, multiple types of mass bodies 45 with different lengths L may be prepared. Also, the radius R from the axis A of the rotation shaft 25 to the rotation axis Ar of mass body 45 may be adjusted by arranging mass body 45 rotatably and swingably in an appropriate one of the multiple shaft holes 43. Also, multiple types of mass bodies 45 with different both the weights of weights 47 and the lengths L of mass body 45 may be prepared and arranged in an appropriate shaft hole 43 so as to be rotatably and swingably.

[0053] With reference to FIG. 6, the uniformization of the impeller 30 by using a plurality of types of mass bodies 45 will be specifically described.

[0054] As shown in Fig. 6, when the blade portion 32A of the dynamic vibration absorber 40A has an unbalanced weight M, which is the cause of the imbalance, the impeller 30 vibrates (rotates) due to the rotation. Therefore, in order to eliminate the influence of the unbalanced weight M, the dynamic vibration absorbers 40C and 40D located on the opposite side of the unbalanced weight M are arranged with an appropriate counterweight m C ,m D The masses 45C and 45D are changed to masses 45C and 45D each having a weight 47.

[0055] Specifically, the distance from the axis A of the rotating shaft 25, which is the rotation center of the impeller 30, to the part of the unbalanced weight M is a radius R M Therefore, the excess centrifugal force F caused by the unbalanced weight M is M is the radius R of the unbalanced weight M M (F M =M×R M ). This centrifugal force F M When the vector is resolved based on the direction in which the masses 45C and 45D extend, the mass 45C has a correction force F C mass 45D is subjected to a correction force F D It can be seen that the radius from the axis A of the rotating shaft 25 to the axis Ar of the masses 45C and 45D is R, and the masses 45C and 45D have a length L. Therefore, the balance weight m that satisfies the following formula is C ,m D Mass bodies 45C and 45D including weights 47 are selected and placed in the corresponding recesses 42. Mass bodies 45A and 45B to which weights 47 are not attached are placed in the other dynamic vibration absorbers 40A and 40B.

[0056] [Number 1] m C =F C / (R+L) m D =F D / (R+L) m C : Balance weight of mass 45C m D : Balance weight of mass 45D F C : Corrective force required for mass 45C F D : Corrective force required for mass 45D R: Radius from the axis of the rotating shaft to the axis of the mass L: Length from the axis of rotation of the mass body to the tip

[0057] In order to suppress the vibration of the impeller 30 due to the excitation force F shown in FIG. 5, the dynamic vibration absorbers 40A and 40B are provided with the same weight m A ,m B When it is necessary to dispose mass bodies 45A and 45B each including a weight 47 of weight m A ,m B The counterweight m C ,m D Mass bodies 45C and 45D each including weights 47 each having a weight equal to the sum of the weights are disposed. The same applies when the unbalanced weight M exists in the wings 32B to 32D other than the wings 32A or in a part of the shroud 31.

[0058] In this way, the impeller 30 including the portion of the unbalanced weight M can be balanced. Therefore, it is possible to suppress vibrations caused by the rotation of the unbalanced impeller 30. Moreover, since there is no need to cut the shroud 31 or the blade portion 32, the hydraulic performance of the vertical pump 10 using this impeller 30, such as the pump efficiency, is not reduced.

[0059] As described above, in the vertical pump 10 of this embodiment, multiple dynamic vibration absorbers 40 are arranged at intervals circumferentially on the impeller 30, so that both vibration of the impeller 30 due to the excitation force F acting on the blade portion 32 that has passed below the guide vane 20 and vibration of the impeller 30 due to residual imbalance of the impeller 30 can be effectively suppressed.

[0060] More specifically, the vertical pump 10 of the present embodiment has the following features.

[0061] The shroud 31 of the impeller 30 is provided with a plate-shaped mass body 45 extending along the radial direction of the shroud 31, and a plurality of dynamic vibration absorbers 40 are arranged at intervals around the axis A of the rotating shaft 25 in a centrifugal manner. As a result, when a radial excitation force F acts on the impeller 30, the rotatably swingable mass body 45 provided in the dynamic vibration absorber 40 swings (rotates) in the opposite direction to the excitation force F due to inertia. Therefore, it is possible to suppress the vibration of the impeller 30 due to the NZ excitation force F. Therefore, it is possible to effectively suppress the vibration frequency of the impeller 30 from resonating in synchronization with the natural frequency of other components such as the pump casing 15, and the occurrence of excessive vibration in the vertical pump 10.

[0062] A plurality of types of mass body 45 are prepared so that at least one of the weight of the weight 47 and the length L of the mass body 45 is different, and the mass body 45 is detachable from the shroud 31. As a result, when there is residual unbalance (the portion of the unbalanced weight M) in the impeller 30 which is a cast metal, the impeller 30 can be balanced by changing the mass body 45 of a given dynamic vibration absorber 40. Therefore, the vibration caused by the rotation of the unbalanced impeller 30 can be suppressed. Moreover, since there is no need to cut the shroud 31 or the blade portion 32, the hydraulic performance such as the pump efficiency of the vertical shaft pump 10 using this impeller 30 is not deteriorated.

[0063] The shroud 31 is provided with a plurality of shaft holes 43 spaced apart in the radial direction for supporting the mass body 45. This allows fine adjustment of the dimension from the axis A of the rotating shaft 25 to the outer end of the mass body 45, i.e., the magnitude of the centrifugal force acting by the mass body 45. This ensures that the impeller 30 is uniform.

[0064] The shroud 31 is provided with a plurality of recesses 42 in which a plurality of dynamic vibration absorbers 40 are individually arranged so as to be recessed in a direction away from the tongue portion 20a. This makes it possible to prevent the rotational oscillation of the mass body 45 from being hindered by the fluid resistance caused by the pumped water in the pump casing 15 when the impeller 30 rotates. Therefore, the vibration of the impeller 30 caused by the NZ excitation force F can be effectively suppressed.

[0065] The recess 42 is filled with liquid 50 for providing resistance, and the opening of the recess 42 is closed by a cover 44. This allows the liquid 50 to function as a damper while preventing the rotational oscillation of the mass body 45 from being hindered by fluid resistance due to pumped water in the pump casing 15 during rotation of the impeller 30. Therefore, the vibration of the impeller 30 due to the NZ excitation force F can be effectively suppressed.

[0066] In the radial direction of the shroud 31, the dynamic vibration absorber 40 is disposed at the same angular position as the blade portion 32. As a result, when an NZ excitation force F acts on a certain blade portion 32, the mass body 45 of the dynamic vibration absorber 40 corresponding to the other blade portion 32 can reliably rotate and oscillate in the direction opposite to the NZ excitation force F. Therefore, the vibration of the impeller 30 due to the NZ excitation force F can be suppressed, and the occurrence of excessive vibration in the vertical pump 10 can be effectively suppressed.

[0067] Other embodiments and various modifications of the present invention will be described below, but in these descriptions, points that are not particularly mentioned are the same as those in the first embodiment. In the drawings referred to below, the same elements as those in the first embodiment are given the same reference numerals.

[0068] Second embodiment 9, the vertical pump of the second embodiment differs from the first embodiment in that two dynamic vibration absorber groups are arranged on the impeller 30. However, the number of dynamic vibration absorber groups may be three or more.

[0069] The dynamic vibration absorbers 40 constituting the first dynamic vibration absorber group are arranged near the outer periphery of the base portion 41 of the shroud 31 so as to be uniformly spaced from the axis A of the rotating shaft 25 in the radial direction. The dynamic vibration absorbers 40 constituting the second dynamic vibration absorber group are arranged radially inward of the first dynamic vibration absorbers 40 with respect to the base portion 41 of the shroud 31 so as to be uniformly spaced from the axis A of the rotating shaft 25. The number of the dynamic vibration absorbers 40 in the first dynamic vibration absorber group is the same as the number of the dynamic vibration absorbers 40 in the second dynamic vibration absorber group. The dynamic vibration absorbers 40 in the first dynamic vibration absorber group and the dynamic vibration absorbers 40 in the second dynamic vibration absorber group are arranged at intervals in the circumferential direction with respect to the shroud 31.

[0070] In the vertical pump of the second embodiment configured in this manner, vibrations due to two different types of excitation frequencies can be suppressed by the first set of dynamic vibration absorbers 40 and the second set of dynamic vibration absorbers 40. For example, by setting one of the two sets of dynamic vibration absorbers to match the frequency band during drainage at the design point flow rate, and setting the other to match the frequency band during miniflow (partial flow rate region) when the drainage amount is reduced, it is possible to suppress vibrations under different conditions.

[0071] Third embodiment Referring to FIG. 10, the impeller 30 of the vertical pump of the third embodiment differs from that of the first embodiment in that a plurality of dynamic vibration absorbers 40 are arranged at an inclination inside a shroud 31 having an inverted conical cylindrical shape.

[0072] The recess 42 for disposing the mass body 45 is recessed from the inner surface side toward the outer surface side of the shroud 31. The mass body 45 is disposed such that the axial attachment portion 46a is located below the recess 42, which is inclined upward from the inner side toward the outer side in the radial direction, and is axially attached by a pin 48.

[0073] In the vertical pump 10 of the third embodiment configured as above, it is possible to obtain the same functions and effects as in the first embodiment.

[0074] The present invention is not limited to the configurations of the above-described embodiments, and various modifications are possible.

[0075] For example, the guide vane 20 including the tongue portion 20 a may be configured to be disposed upstream of the impeller 30 .

[0076] The pump may be a horizontal shaft pump other than the vertical shaft pump 10, and may be any pump as long as it has a tongue portion that faces the blade portion 32 of the impeller 30. [Explanation of symbols]

[0077] 1 Water absorption tank 2 Installation floor 10 Vertical pump (pump) 15 Pump casing 16. Lifting pipe 17 straight pipe 18 Vane casing 19 Bellmouth 20 Guide vane 20a Tongue 21 Bearing casing 22 Support member 23 Discharge pipe 25 Rotational Axis 30 Impeller 31 Shroud 32 Wings 35 Electric Motor 40 Dynamic vibration absorber 41 Base 42 Recess 42a Fitting portion (recess opening) 42b Recessed body 43 Shaft hole 44 Cover 45 mass body 46 Arm section 46a Shaft mounting part (inner end side) 46b Through hole 47 Weight 47a Mounting hole 48 pin 48a Shaft 48b Head 49 Washer 50 liquid A Axis of the rotating shaft F Excitation force Ar: axis of rotation of mass L is the length of the mass M Unbalanced weight part

Claims

1. A cylindrical pump casing; an impeller having a shroud attached to a rotating shaft within the pump casing and a plurality of blades protruding radially from the shroud; a plurality of tongue portions provided on the pump casing so as to face the vane portions and spaced apart around an axis of the rotating shaft; a plurality of centrifugal dynamic vibration absorbers each having a plate-shaped mass body that is disposed so as to extend along the radial direction of the shroud and whose inner end side in the radial direction is journaled, the centrifugal dynamic vibration absorbers being disposed at intervals around the axis of the rotating shaft relative to the shroud; A pump comprising:

2. 2. The pump according to claim 1, wherein the mass body includes a weight on an outer end side in the radial direction, the weight is detachable from the shroud, and a plurality of types of the mass body are prepared so that at least one of a weight of the weight and a length from a rotation axis of the mass body to a tip of the weight is different.

3. 3. The pump according to claim 1, wherein the shroud is provided with a plurality of shaft holes for supporting the mass body at intervals in the radial direction.

4. 3. The pump according to claim 1, wherein the shroud is provided with a plurality of recesses in which the dynamic vibration absorbers are individually disposed so as to be recessed in a direction away from the tongue portion.

5. 5. The pump according to claim 4, wherein the recess is filled with a liquid for providing resistance, and an opening of the recess is closed by a cover.

6. The number of the dynamic vibration absorbers is equal to the number of the wing portions, 3. The pump according to claim 1, wherein the dynamic vibration reducer is disposed at the same angular position as the vane in the radial direction of the shroud.

7. the pump casing has a bearing casing that is provided on a downstream side of the impeller via a guide vane and supports a part of the rotating shaft protruding from the impeller, The pump according to claim 1 or 2, wherein the tongue portion is formed by an opposing edge of the guide vane that faces the blade portion.

Images