JP3578585B2 - underwater pump - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a submersible pump for sewage and the like used for drainage of sewage, for example, installed in an underground drainage tank of a building or a sewage tank of a water treatment apparatus, and particularly relates to a mechanical seal and a mechanical seal chamber. It is about structure.
[0002]
[Prior art]
FIG. 4 shows the structure of a conventional general sewage submersible pump. As shown in FIG. 1, this submersible pump mainly includes a pump unit 1, a motor unit 2, and a mechanical seal unit 3, and a main shaft 4 for transmitting the power of the motor unit 2 to the pump unit 1 is inserted into these. Have been.
[0003]
The pump unit 1 mainly includes a pump casing 5, an intermediate casing 6, and an impeller 7, and the impeller 7 is connected to a lower end of the main shaft 4 so as to rotate integrally therewith. Above the intermediate casing 6, a lower bracket 8 is fixed, and the inside of the lower bracket 8 is a mechanical seal chamber 9.
[0004]
The motor section 2 mainly includes a motor frame 10, a stator 11 fixed in the motor frame 10, and a rotor 12 fixed to the main shaft 4 and installed in the stator 11. An upper bearing 13 and a lower bearing 14 that rotatably support the main shaft 4 are provided vertically above and below the rotor 12.
[0005]
A mechanical seal 20 is provided inside the mechanical seal chamber 9 to prevent the pressure water on the pump section 1 side from leaking and entering the motor section 2. FIG. 5 shows the details of the mechanical seal 20. A lubricating oil for lubricating and cooling the sliding surface of the mechanical seal 20 is sealed in the mechanical seal chamber 9, and the lubricating oil is heated above the lubricating oil by heat generated by sliding of the seal. A space is left to prevent abnormal pressure rise.
[0006]
The mechanical seal 20 employs a so-called monocoil double seal type, and includes a mating ring 22, a seal ring 23 and a bellows 24, as shown in FIG. It has an upper seal portion 21a and a lower seal portion 21b arranged vertically above and below the main shaft 4. Between the two seal portions 21a and 21b, the sliding surfaces of the mating ring 22 and the seal ring 23 face each other. It is configured with a coil spring 25 for applying pressure interposed.
[0007]
Here, in this type of submersible pump for sewage, it is preferable to increase the exit width of the impeller 7 so that foreign substances of a certain size can be discharged even if it is sucked in. When the outlet width is increased, the radial thrust force resulting from the uneven pressure distribution in the impeller 7 and the pump casing 5 increases accordingly.
[0008]
That is, the radial thrust force Fr generally generated by the pump impeller can be expressed by the following equation.
Fr = 0.36 · (1- (Q / Qbep) ² ) · (ρ · g · H) · D ₂ · B ₂ ′ · 10 ^-6
Here, Fr: radial thrust force [N]
Q: Operating point water amount Qbep: Maximum efficiency point water amount ρ: Liquid density = 1000 [kg / m ³ ]
g: gravity acceleration = 9.806 [m / s ² ]
H: Pump head [m]
D ₂ : impeller outer diameter [mm]
B ₂ ': impeller total width [mm]
[0009]
Therefore, as described above, if an impeller 7 having a large passage is adopted so that foreign matter contained in the sewage does not block inside the impeller 7, the impeller width B ₂ ′ generally increases, and in addition, As the vehicle width B ₂ ′ increases, the pumping amount increases and the radial thrust force Fr increases. For this reason, in order to reduce the amount of deflection of the main shaft 4 to a required value or less, the shaft diameter of the main shaft 4 must be necessarily increased.
[0010]
[Problems to be solved by the invention]
However, if the shaft diameter of the main shaft is simply increased so as to withstand the radial thrust force as in the above conventional example, the diameter of the mechanical seal increases with this, and the peripheral speed of this sliding surface increases. As a result, not only heat generation is increased, but also the amount of leakage from the sliding surface is increased, and the life of the pump is shortened.
[0011]
In addition, the lower seal portion is lifted upward by the pressure of the pump portion, and the bellows of the lower seal portion moves while being deformed upward, and the deformation of the bellows causes a sliding abnormality to increase the leakage amount. As a result, it could not be used for high-lift pumps.
[0012]
Further, grease flowing out from the lower bearing flows into the gap between the sliding surfaces of the upper seal portion, and as a result, sliding heat is increased, which may lead to wear. In particular, since the upper seal portion does not come into contact with sewage, it is common to configure the seal ring and mating ring with carbon and ceramics that are relatively inexpensive and have good slidability. The contamination has caused a large abnormality.
[0013]
The present invention has been made in view of the above circumstances, and realizes a highly rigid main shaft without increasing the amount of leakage at the lower seal portion of the mechanical seal, and minimizes deformation of the bellows of the lower seal portion. It is another object of the present invention to provide a submersible pump that can prevent grease flowing out of a bearing from directly reaching a sliding surface of an upper seal portion.
[0014]
[Means for Solving the Problems]
Submersible pumps of the present invention has a motor unit provided with a bearing for supporting the spindle up and down across the motor and the motor rotor on top, having a pump unit in a lower portion, the motor unit and the pump unit In a submersible pump having a mechanical seal installed between the lower bearing and the mechanical seal , a reservoir for grease flowing out of the lower bearing is formed, and the grease flows directly to the sliding surface of the mechanical seal. It is characterized by not being emitted .
[0015]
According to the present invention configured as described above, even if grease sealed in the bearing flows out due to heat generation of the bearing due to the operation of the pump, the grease accumulates in the grease accumulating portion provided on the partition wall, thereby providing mechanical It is possible to prevent grease from entering the sliding surface of the upper seal portion of the seal and causing excessive sliding heat and accompanying abnormal wear of the sliding portion .
[0016]
Further, submersible pumps other aspects of the present invention, the main shaft by increasing the shaft diameter of the upper mechanical seal of the main shaft than the shaft diameter of the lower mechanical seal spindle to form a stepped portion, and the lower mechanical seal The axial distance between the upper end of the bellows and the stepped portion is kept small .
[0017]
According to the present invention configured as described above, by disposing the upper seal portion of the main Kanikarushiru around the large diameter portion of the spindle, ensuring a sufficient rigidity as the main shaft, at the same time, the small diameter of the main shaft of the lower seal portion By arranging around the part, the amount of leakage here can be reduced. In addition, by moving the upper end of the bellows of the lower seal portion close to the step of the main shaft, the upward movement of the bellows is restricted by the step of the main shaft, and this deformation can be prevented as much as possible .
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention applied to a submersible pump for sewage will be described with reference to FIGS. The same parts as those in the conventional example shown in FIGS. 4 and 5 are denoted by the same reference numerals and described.
[0019]
As shown in these drawings, this submersible pump has a pump unit 1 mainly composed of a pump casing 5, an intermediate casing 6, and an impeller 7, and a motor unit composed of a motor frame 10, a stator 11, and a rotor 12. 2 and a mechanical seal portion 3, and a main shaft 4 for transmitting the power of the motor portion 2 to the pump portion 1 is inserted through these components. The interior of a lower bracket 8 fixed above the intermediate casing 6 serves as a mechanical seal chamber 9, and the motor unit 2 includes an upper bearing 13 and a lower bearing 14 that rotatably support the main shaft 4. 12 are provided vertically.
[0020]
Here, the main shaft 4 is provided with a stepped portion 4a located inside the mechanical seal chamber 9, and a large diameter portion 4b having a diameter da above the stepped portion 4a and a small diameter portion having a diameter db below the stepped portion 4a. 4c. A mechanical seal 20 having an upper seal portion 21a and a lower seal portion 21b is accommodated in the mechanical seal chamber 9. The upper seal portion 21a is arranged around the large diameter portion 4b of the main shaft 4. , A lower seal portion 21 b is arranged around the small diameter portion 4 c of the main shaft 4.
[0021]
That is, the upper seal portion 21 a and the lower seal portion 21 b are both formed by the mating ring 21, the seal ring 22 opposed thereto and rotating together with the main shaft 4, the leakage from the surface of the main shaft 4 and the leakage from the back surface of the seal ring 22. The bellows 23 is provided to prevent the lower ring 21 from forming. The mating ring 21, the seal ring 22, and the bellows 23 forming the upper seal 21a are arranged around the large diameter portion 4b of the main shaft 4 to form the lower seal 21b. The ting ring 21, the seal ring 22, and the bellows 23 are arranged around the small diameter portion 4c of the main shaft 4, respectively. Further, the bellows 23 of the lower seal portion 21b is configured such that its upper end is close to the step portion 4a of the main shaft 4, that is, the gap t between the two is 1 mm or less.
[0022]
A coil spring 25 for pressing the seal ring 23 against the mating ring 22 is interposed between the seal portions 21a and 21b, thereby forming the mechanical seal 20. The coil spring 25 is formed in a shape in which a part thereof is formed in a truncated cone shape in accordance with the outer diameters of both the seal portions 21a and 21b.
[0023]
In this way, by using a large-diameter main shaft 4 having sufficient rigidity and arranging the lower seal portion 21b on the small-diameter portion 4c of the main shaft 4, the sliding surface of the lower seal portion 21b is formed. By reducing the diameter, the amount of leakage here can be reduced. That is, for example, by making the diameter db of the small diameter portion 4c of the main shaft 4 equal to the diameter of the main shaft used in the conventional main submersible pump, it is possible to prevent the leakage amount from increasing here, Through the large-diameter portion 4a of the main shaft 4, the rigidity of the main shaft of a conventional general submersible pump of this type can be increased.
[0024]
Here, in the case of a pump with a high head, it is common practice to increase the spring force of the coil spring 25 in accordance with the water pressure, and to use a sliding material capable of withstanding a higher p · v value. However, the bellows 24 of the lower seal portion 21b is pushed upward by water pressure. Then, since the upper end of the bellows 24 is close to the step portion 4a of the main shaft 4, the bellows 24 collides with the step portion 4a to restrict the upward movement, thereby preventing the bellows 24 from being deformed as much as possible. Thus, it is possible to prevent an abnormal sliding and an increase in leakage as a result.
[0025]
A partition wall 8a which is located below the lower bearing 14 of the lower bracket 8 and partitions the mechanical seal chamber 9 is provided with a concave portion 8b which is located immediately below the lower bearing 14 and opened upward. The recess 8b forms a grease reservoir 30 for preventing grease flowing out of the lower bearing 14 from flowing downward.
[0026]
Thus, even if the grease sealed in the lower bearing 14 flows out due to heat generation of the lower bearing 14 due to the operation of the pump, the grease remains in the grease reservoir 30 (recess 8b) provided in the partition wall 8a. Thus, it is possible to prevent the grease from being mixed into the sliding surface of the upper seal portion 21a of the mechanical seal 20 and causing excessive sliding heat and the accompanying abnormal wear of the sliding portion.
[0027]
In this example, an example in which the present invention is applied to a mechanical seal employing a so-called monocoil double seal method is shown. However, the present invention is not limited to this, and is applicable to a mechanical seal employing another method such as a tandem double method. Of course, you can.
[0028]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the spindle of higher rigidity can be implement | achieved, without increasing the amount of leaks in the lower seal part of a mechanical seal. Thereby, the reliability of a pump can be improved, Moreover, The deformation of the bellows of the lower seal portion is suppressed as much as possible, which can contribute to further increasing the pump height.
[0029]
Further, the grease flowing out of the bearing is prevented from directly reaching the sliding surface of the upper seal portion of the mechanical seal, so that the reliability of the mechanical seal can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a submerged sewage pump according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of FIG. 2;
FIG. 3 is a sectional view showing the overall configuration of the pump.
FIG. 4 is a sectional view showing a general structure of a conventional submersible pump for sewage.
FIG. 5 is an enlarged sectional view showing the mechanical seal of FIG. 4;
[Explanation of symbols]
1 Pump part 2 Motor part 3 Mechanical seal part 4 Main shaft,
4a Same step portion 4b Same large diameter portion 4c Same small diameter portion 7 Impeller 8 Lower bracket 8a Same partition wall 9 Mechanical seal chamber 13 Lower bearing 14 Upper bearing 20 Mechanical seal 21a Upper seal portion 21b Lower seal portion 22 Mating ring 23 Seal Ring 24 Bellows 25 Coil spring 30 Oil reservoir

Claims (2)

A motor unit provided with a bearing for supporting the spindle up and down across the motor and the motor rotor on top, having a pump unit in a lower portion, installed mechanical seal between the motor unit and the pump unit In a submersible pump consisting of
A submersible pump , wherein a reservoir for grease flowing out of the lower bearing is formed between the lower bearing and the mechanical seal, so that the grease does not flow directly to the sliding surface of the mechanical seal . A stepped portion is formed on the main shaft by making the shaft diameter of the main shaft of the upper mechanical seal larger than the shaft diameter of the main shaft of the lower mechanical seal, and the axial direction between the upper end of the bellows of the lower mechanical seal and the stepped portion. The submersible pump according to claim 1, wherein the interval is kept small .

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