Vertical shaft pump

Abstract

To provide a technology that ensures wear resistance and strength of a sliding member used in a vertical pump to improve a service life of the sliding member.SOLUTION: A vertical shaft pump 100 of the present invention comprises: a rotational shaft 1 extending vertically; an impeller 2 fixed to a lower end part of the rotational shaft 1 and rotating together with the rotational shaft 1; and a bearing device 7 supporting the rotational shaft 1. The bearing device 7 comprises a bearing sliding member 21 made of a material that uses pumped water as lubricant during pumping operation and can operate in non-lubrication sliding without lubrication during idling operation. An inner surface of the bearing sliding member 21 is provided with a sliding surface 25 that comes into sliding contact with the rotational shaft 1, and a solid lubricant, which is a low-friction material, is fixed to the sliding surface 25.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vertical shaft pump provided with a bearing device for supporting a rotating shaft, and more particularly to a vertical shaft pump provided with a bearing device in which dry sliding and sliding in pumped water containing foreign matters and the like are repeated.

Background Art

[0002] In recent years, during heavy rainstorms occurring in urban areas, the inflow of rainwater into drainage pump stations (hereinafter, also simply referred to as drainage stations) has been large and rapid, and the risk of urban floods has increased. In order to avoid the occurrence of such urban floods, a drainage pump that operates promptly even in an emergency is required. Therefore, during normal times when no flood has occurred, an idling operation of a drainage pump such as a vertical shaft pump installed in a drainage station is carried out to check its operation.

[0003] In addition, in order to prevent waterlogging damage due to a delay in starting the drainage pump against a rapid and large inflow of rainwater into the drainage pump station, the drainage pump is idled and standby operation is performed before the rainwater flows into the drainage station so that drainage can be performed immediately when water is discharged. A pre-standby operation is strongly required.

[0004] In a pre-standby operation type vertical shaft pump that performs this pre-standby operation, since the idling operation time during which pumping is not performed becomes long, as a bearing device of the pump, in the case of using pumped water of the pump as a lubricating fluid, dry sliding without lubricating fluid in the bearing device continues for a long time. As a result, there is a high risk of problems such as damage to the bearing device due to heat generation caused by frictional sliding.

[0005] In order to avoid such problems, for example, there is the technology described in Patent Document 1. In the vertical shaft pump described in Patent Document 1, as a sliding member of a bearing disposed opposite to the outer peripheral surface of the rotating shaft of the vertical shaft pump, it is made of a resin material containing at least one of PEEK, PI, PAI, PBI, PTFE, and PPS that is less likely to be damaged even in dry sliding. Further, on the outer peripheral surface of the rotating shaft, a shaft sleeve having grooves provided on the inner peripheral surface is provided.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the vertical shaft pump described in Patent Document 1, although it is possible to suppress the bending of the shaft due to the frictional heat of the sliding portion, the wear resistance and strength of the sliding member have not been sufficiently considered. For this reason, when continuously operated for a long time, there has been a problem that the bearing sliding member reaches the end of its life early. In particular, PTFE has low wear resistance and weak strength.

[0008] An object of the present invention is to provide a technique for ensuring the wear resistance and strength of a sliding member used in a vertical shaft pump and improving the life of the sliding member.

Means for Solving the Problems

[0009] In order to achieve the above object, the present invention provides a vertical shaft pump including a rotating shaft extending in the vertical direction, an impeller fixed to the lower end side of the rotating shaft and rotating together with the rotating shaft, and a bearing device for supporting the rotating shaft. The bearing device includes a bearing sliding member made of a material that can be operated by using pumped water as a lubricant during pumping operation and by non-lubricated sliding without lubricant during idling operation. A sliding surface that slidably contacts the rotating shaft is provided on the inner peripheral surface of the bearing sliding member, and a fixed lubricant serving as a low friction material is fixed to the sliding surface.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a technique for ensuring the wear resistance and strength of a sliding member used in a vertical shaft pump and improving the life of the sliding member.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, for the same elements, the same reference numerals are generally given in all the drawings. Also, for parts having the same function, the description will be omitted. Note that the configurations described below are merely examples, and the embodiments of the present invention are not intended to be limited to the following specific forms.

[0013] FIG. 1 is an overall configuration diagram of a vertical pump according to an embodiment of the present invention.

[0014] This vertical pump 100 includes a rotating shaft 1 that extends and rotates in the vertical direction, an impeller 2 (impeller) fixed to the lower end of the rotating shaft 1 and rotating together with the rotating shaft 1, a pump casing 3 provided so as to cover the outer peripheral portion of the impeller 2, a lift pipe 4 connected to the upper part of the pump casing 3 and extending further upward, a discharge elbow portion 5 that bends the flow path in the horizontal direction, and the like.

[0015] Further, the rotating shaft 1 is supported by bearing devices 6 and 7, and is configured to be rotationally driven by a prime mover such as a motor 10 installed on a support base 15 provided on the floor portion 9a of the suction tank 9 via a coupling 8. Note that a suction bellmouth 3a is provided on the suction port side of the pump casing 3.

[0016] The bearing device 6 is arranged near the impeller 2, rotatably supports the lower end side of the rotating shaft 1, and is fixed to the pump casing 3 via a guide vane 11 or the like. The bearing device 7 rotatably supports the rotating shaft 1 at a portion below the floor portion 9a of the suction tank 9 which is the installation surface of the vertical shaft pump 100 (the central side in the vertical direction of the rotating shaft 1), and is fixed to the lift pipe 4 via a support member 12. By configuring in this way, the rotating shaft 1 is rotatably supported inside the lift pipe 4 via the bearing devices 6 and 7.

[0017] The vertical shaft pump 100 of the present embodiment is a vertical shaft pump that performs an idling operation for operation confirmation or the like, or a vertical shaft pump of a pre-waiting operation type. For the bearing devices 6 and 7, a type that can use the pumped water as a lubricant during the pumping operation and operate with non-lubricated sliding without a lubricant (dry operation) during the idling operation is used.

[0018] Further, as a vertical shaft pump of the pre-waiting operation type, for example, as described in Japanese Patent Laid-Open No. 6-213190, when the water level during the pump operation is below the minimum water level at which air is sucked from the suction bellmouth 3a of the pump casing 3, the impeller 2 is positioned below the water level, and a plurality of air introduction portions (not shown) are provided in the pump casing 3 below the impeller 2. It is preferable to have a configuration in which an intake pipe (not shown) having one end connected and the other end open to the atmosphere is provided in the air introduction portion.

[0019] Next, the configuration of the bearing device 6 or the bearing device 7 will be described. FIG. 2 is an enlarged cross-sectional view of the main part of the bearing device 6 or the bearing device 7 in the vertical shaft pump shown in FIG. 1. In the following description, the case where the bearing device shown in FIG. 2 is the bearing device 7 shown in FIG. 1 will be described, but the bearing device 6 has the same configuration. In FIG. 2, only the right half of the bearing device 7 is shown, but since the left half has the same configuration, the illustration of the left half is omitted.

[0020] In FIG. 2, a shaft sleeve 13 is fitted and fixed to the outer peripheral surface of a rotating shaft 1 of a portion supported by a bearing device 7. When the rotating shaft 1 has a shaft sleeve 13, the rotating shaft shall include the shaft sleeve.

[0021] The bearing device 7 includes a bearing sliding member 21 provided on the inner peripheral side and in sliding contact with the shaft sleeve 13, a back metal 22 provided on the back side (outer peripheral side) of the bearing sliding member 21 for holding the bearing sliding member 21, and a bearing housing 23 provided on the back side (outer peripheral side) of the back metal 22 for holding the back metal 22. The bearing housing 23 is fixed to a support member 12 (see FIG. 1). The bearing sliding member 21 is in sliding contact with the rotating shaft 1 via the shaft sleeve 13.

[0022] The bearing sliding member 21 is made of a material that can be operated by using the pumped water as a lubricant during the pumping operation and by non-lubricated sliding without a lubricant during the idling operation without the pumping operation. As the bearing sliding member 21, for example, a PEEK (polyetheretherketone)-based resin material or a composite resin made by reinforcing a PEEK-based resin material with carbon fiber may be used. In addition to PEEK, PI (polyimide), PAI (polyamideimide), PBI (polybenzimidazole), PPS (polyphenylene sulfide), etc. may also be used as the resin material of the bearing sliding member 21.

[0023] In this embodiment, a plurality of sliding surfaces 25 (25a, 25b, 25c) that contact the rotating shaft 1 via the shaft sleeve 13 are provided on the inner peripheral surface of the bearing sliding member 21, and a sliding surface low friction material 26 (26a, 26b, 26c) that serves as a low friction material is provided on the surface of the sliding surface 25. Further, on the inner peripheral surface of the bearing sliding member 21, stepped portions 27 (27a, 27b, 27c) that are recessed toward the outer peripheral side from the position of the sliding surface 25 so that the inner diameter becomes larger are provided, and a stepped portion low friction material 28 (28a, 28b, 28c) that serves as a low friction material is provided on the surface of the stepped portion 27. A plurality of stepped portions 27 are formed in the axial direction (stepped portions 27a, 27b, 27c). The stepped portion low friction material 28 is provided so as to fill the stepped portion 27, and the stepped portion low friction materials 28a and 28b provided on the stepped portions 27a and 27b are provided so as to be flush with the sliding surface 25 on the inner periphery of the bearing sliding member 21. In other words, the sliding surface low friction material 26 is provided so as to protrude to the inner peripheral side (rotating shaft 1 side) from the stepped portion low friction material 28.

[0024] Here, the sliding surface low friction material 26 and the stepped portion low friction material 28 are formed by fixing a solid lubricant containing at least one of polytetrafluoroethylene (PTFE), molybdenum disulfide, silicon, etc. to the inner peripheral surface that slidably contacts the rotating shaft 1 of the bearing sliding member 21 using a binder. As the binder, for example, one mainly composed of acrylic is used. The sliding surface low friction material 26 and the stepped portion low friction material 28 are applied to cover the inner peripheral surfaces of the sliding surface 25 and the stepped portion 27 by spraying or brushing. For improving work efficiency, it is preferable that the sliding surface low friction material 26 and the stepped portion low friction material 28 are formed of the same material. Further, in this embodiment, the radial thickness of the sliding surface low friction material 26 is made thinner than the radial thickness of the stepped portion low friction material 28. Furthermore, the sliding surface low friction material 26 and the stepped portion low friction material 28 may be formed in layers on the sliding surface 25 and the stepped portion 27 so that a plurality of layers overlap.

[0025] The stepped portion 27a is provided below the bearing sliding member 21 in the axial direction, and there is a sliding surface 25a between the stepped portion 27a and the lower end portion of the bearing sliding member 21. The stepped portion 27b is provided at the center in the axial direction of the bearing sliding member 21.

[0026] Further, the stepped portion 27c is provided at the upper axial end of the bearing sliding member 21. The inner diameter of the stepped portion 27c increases upward in the axial direction. Here, it increases in two steps, but it may have more steps or may increase continuously.

[0027] The reason for the above configuration will be described below. In the vertical shaft pump 100, due to the misalignment (assembly error) in the assembly of the vertical shaft pump 100 and the radial fluid force acting on the impeller 2 attached to the lower end of the rotating shaft 1, the axis of the shaft sleeve 13 and the axis of the bearing sliding member 21 are not necessarily parallel, and they are in a slightly inclined positional relationship due to the inclination and deflection of the rotating shaft 1. When the positional relationship between the shaft sleeve 13 and the bearing sliding member 21 is in such a state, a situation where the upper or lower axial end of the bearing sliding member 21 and the shaft sleeve 13 come into particularly strong contact occurs. During the idling operation without lubricating fluid, which is peculiar to the prior standby type pump, the amount of sliding friction heat generated at this strongly contacting portion is particularly large, and the temperature of the bearing sliding member 21 at this portion rises particularly high, increasing the risk of causing bearing damage such as seizure.

[0028] In this embodiment, corresponding to the position where the shaft sleeve 13 and the bearing sliding member 21 come into strong contact and the amount of sliding friction heat generated is particularly large, stepped portions 27a and 27c are provided on the inner peripheral surfaces of the lower and upper axial ends of the bearing sliding member 21, respectively, and low friction materials 28a and 28c are provided on their respective surfaces.

[0029] Therefore, for example, even when the shaft sleeve 13 and the bearing sliding member 21 come into strong contact in the axial downward direction, the shaft sleeve 13 contacts the sliding surface low friction material 26a provided on the surface of the sliding surface 25a, so that the sliding friction heat can be suppressed to a low level. Therefore, it is possible to suppress causing bearing damage such as seizure and melting.

[0030] However, if the sliding surfaces 25a of the shaft sleeve 13 and the bearing sliding member 21 continue to come into repeated contact, the sliding surface low-friction material 26a wears away as if it were scraped off from the lower end portion in the axial direction. When the sliding surface low-friction material 26a is completely worn out, the bearing sliding member 21 is exposed. However, since the worn surface is also inclined so as to match the inclined shaft sleeve 13, the contact force is relaxed and the sliding frictional heat is also reduced. As the wear progresses further, the shaft sleeve 13 also comes into contact with the step low-friction material 28a on the surface of the step portion 27a, so that the frictional heat can be further suppressed to a lower level. In this way, as wear progresses while suppressing the generation of sliding frictional heat during idling operation, the inner peripheral surface of the bearing sliding member 21 assumes a shape that conforms to the inclination of the shaft sleeve 13, that is, a so-called conforming state. If the conforming shape is achieved initially, then the wear during subsequent operation also progresses while maintaining that shape. Therefore, the maximum value of the contact pressure can be kept low, and the sliding frictional heat is also reduced, making damage less likely to occur and enhancing the reliability of the bearing.

[0031] Similarly, when the shaft sleeve 13 and the bearing sliding member 21 come into strong contact in the upper part in the axial direction, the shaft sleeve 13 comes into contact with the step low-friction material 28c. The step low-friction material 28c is provided on the surface of the step portion 27c. Among the plurality of step portions 27, the inner diameter of the step portion 27c increases as it goes upward in the axial direction (toward the axial end portion). Therefore, the contact area with the shaft sleeve 13 can be increased, and the contact pressure can be reduced.

[0032] In this embodiment, there is also a step portion 27b at the center in the axial direction, and a step low-friction material 28c and a low-friction material 28b are provided on its surface. Also, there are sliding surfaces 25b and 25c below and above the step portion 27b in the axial direction, and sliding surface low-friction materials 26b and 26c are provided on their respective surfaces.

[0033] When the inclination of the shaft sleeve 13 is small, the shaft sleeve 13 contacts the sliding surface low-friction materials 26b and 26c, so that the sliding friction heat can be suppressed. When the operation is repeated, the sliding surface low-friction materials 26b and 26c are worn, and the bearing sliding member 21 is exposed. Then, due to the sliding friction heat, the bearing sliding member 21 expands and bulges inward on the inner peripheral side at the central portion in the axial direction. In the configuration of the present embodiment, there is a stepped portion 27b at the central portion in the axial direction, and a stepped portion low-friction material 28b is provided on the surface thereof. Therefore, when the bearing sliding member 21 bulges inward on the inner peripheral side at the central portion in the axial direction, the stepped portion low-friction material 28b contacts the shaft sleeve 13. When the operation is repeated, the stepped portion low-friction material 28b is worn, and the surface of the bearing sliding member 21 is worn so that the central portion in the axial direction becomes concave. By wearing initially in this way, it becomes possible to avoid strong contact thereafter, and damage does not occur.

[0034] Here, the sliding surface low-friction materials 26a, 26b, and 26c are thinner than the stepped portion low-friction materials 28a, 28b, and 28c. One of the reasons is that the bearing clearance cannot be made thick because it is strictly controlled on the sliding surface. Another reason is that the contact pressure when the shaft sleeve 13 contacts the sliding surface is low, so it takes time for wear to progress.

[0035] By the way, in the prior standby type pump, drainage operation is also performed. The drainage flows from the lower part to the upper part in the axial direction. The drainage contains foreign matters such as earth and sand. When such foreign matters enter the bearing clearance, the low-friction material that is easily worn is quickly worn. In the present embodiment, among the plurality of sliding surfaces 25, one sliding surface 25a is provided at the end portion in the lower part in the axial direction. Since this portion is difficult to wear, it is possible to maintain a small clearance, and the wear of the low-friction material due to the intrusion of foreign matters can be reduced.

[0036] As described above, according to this embodiment, even if contact occurs on the bearing sliding member 21, the contact force can be reduced to suppress the amount of sliding friction heat generated, and the heat dissipation of the friction heat generated by the sliding between the rotating shaft side and the bearing sliding member 21 can be enhanced. Therefore, it is possible to reduce the temperature rise of the bearing sliding member 21. Accordingly, heat generation due to contact of the rotating shaft 1 with the bearing device can be suppressed, and heat dissipation can be improved, thereby suppressing bearing damage due to excessive temperature rise of the bearing sliding member 21, and realizing a vertical shaft pump such as a highly reliable pre-waiting operation type vertical shaft pump.

[0037] Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, in the above-described embodiments, the bearing device is described as including a back metal, but the present invention can be similarly applied to a bearing device without a back metal.

[0038] Further, the present invention is not limited to a pre-waiting operation type vertical shaft pump, and any vertical shaft pump including a bearing device having a bearing sliding member that can use pumping water as a lubricant during pumping operation and can operate with non-lubricated sliding without a lubricant during idling operation can similarly apply the present invention.

[0039] Furthermore, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

Explanation of Reference Numerals

[0040] 1... Rotating shaft, 2... Impeller, 3... Pump casing, 3a... Suction bellmouth, 4... Discharge pipe, 5... Discharge elbow section, 6, 7... Bearing devices, 8... Coupling, 9... Suction tank, 9a... Floor section, 10... Motor, 11... Guide vanes, 12... Support member, 13... Shaft sleeve, 15... Support base, 21... Bearing sliding member, 22... Back metal, 23... Bearing housing, 24... Bearing case, 25a, 25b, 25c... Sliding surfaces, 26, 26a, 26b... Sliding surface low friction materials, 27, 27a, 27b... Step sections, 28, 28a, 28b... Step section low friction materials, 100... Vertical shaft pump.

Claims

1. In a vertical shaft pump comprising a rotary shaft extending in the vertical direction, an impeller fixed to the lower end side of the rotary shaft and rotating together with the rotary shaft, and a bearing device for supporting the rotary shaft, the bearing device includes a bearing sliding member made of a material that can be operated by non-lubricated sliding without lubricating fluid during idling operation and uses the pumped water as a lubricating fluid during pumping operation, a sliding surface that slidably contacts the rotary shaft is provided on the inner peripheral surface of the bearing sliding member, and a vertical shaft pump characterized in that a fixed lubricant serving as a low friction material is fixed to the sliding surface.

2. The vertical shaft pump according to claim 1, wherein the fixed lubricant contains at least one of polytetrafluoroethylene (PTFE), molybdenum disulfide, and silicon.

3. The vertical shaft pump according to claim 2, wherein the bearing sliding member is made of a PEEK (polyetheretherketone)-based resin material or a composite resin obtained by reinforcing a PEEK-based resin material with carbon fibers.

4. The vertical shaft pump according to claim 1, wherein the inner peripheral surface of the bearing sliding member is provided with a stepped portion recessed from the position of the sliding surface toward the outer peripheral side so that the inner diameter increases.

5. The vertical shaft pump according to claim 4, wherein a fixed lubricant serving as a low friction material is fixed to the stepped portion.

6. The vertical shaft pump according to claim 5, wherein the low friction material of the sliding surface protrudes to the inner peripheral side more than the low friction material of the stepped portion.

7. The vertical shaft pump according to claim 5, wherein the radial thickness of the low friction material of the sliding surface is thinner than the radial thickness of the low friction material of the stepped portion.

8. The vertical shaft pump according to claim 5, wherein the low friction material of the stepped portion is provided flush with the sliding surface.

9. The vertical shaft pump according to claim 5, wherein a plurality of sliding surfaces are provided in the axial direction, and one of the plurality of sliding surfaces is provided at the lower end in the axial direction.

10. The vertical shaft pump according to claim 9, wherein a plurality of stepped portions are provided in the axial position, and the inner diameter of one of the plurality of stepped portions increases as it approaches the upper end in the axial direction of the bearing sliding member.

11. In the vertical shaft pump according to any one of claims 5 to 10, The vertical shaft pump is characterized in that the low-friction material of the sliding surface and the low-friction material of the stepped portion fix the fixed lubricant to the sliding surface and the stepped portion by spraying or brushing.

12. In the vertical shaft pump according to claim 11, The vertical shaft pump is characterized in that the low-friction material of the sliding surface and the low-friction material of the stepped portion are formed in layers on the sliding surface and the stepped portion.

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