JP4431709B2 - Canned motor pump - Google Patents

Description

  The present invention relates to a canned motor pump in which a rotor of a motor for driving a pump is accommodated in a can, and the inside of the can is filled with a handling liquid of the pump, and more particularly to a structure relating to a reflux of the handling liquid in the can.

  There is known a canned motor pump in which a rotor of a motor for driving a pump is housed in a can and the inside of the can is filled with a pump handling liquid. In the canned motor pump, all rotating parts such as the pump impeller and motor rotor are housed in the pump casing and can, so there is no need to seal the handling liquid by the sliding part, so that the handling liquid does not leak out. It is relatively easy to do. A part of the can is introduced into the can from the discharge side of the pump, and the handling liquid lubricates and cools the bearings and the like in the can. The handling liquid is returned from the can to the suction side of the pump, and sent again to the pump together with a new handling liquid.

  In order to return the handling liquid in the can to the pump suction side, a configuration is known in which the shaft of the motor that drives the impeller is a hollow shaft and returned to the boss portion of the impeller, that is, the suction port through the hollowed portion. .

Also known is a configuration in which a pipe is connected to the rear end of the motor shaft, that is, near the end opposite to the end where the impeller is provided, and returned to the suction tank that stores, for example, the handling fluid before being sucked through the outside of the motor. It has been.
Japanese Patent No. 3118336 Japanese Patent No. 545420

  When returning the handling liquid through the inside of the motor using the hollow shaft described above, when the handling liquid is a low-boiling point fluid, the warmed liquid after cooling the motor is guided to the low-pressure impeller suction port. There was a problem such as.

  Also, when returning from the rear end of the motor to the suction tank through the outside, the refluxed liquid is mixed with a large amount of cold liquid, so that the occurrence of cavitation as described above can be suppressed, but a separate pipe must be provided. The device becomes larger. Moreover, when installing the said pump, piping must be installed each time according to the installation position of a pump or a suction tank, and workability | operativity is bad.

  The canned motor pump of the present invention has an impeller and a return passage formed in a shaft that drives the impeller, and an extension pipe that extends upstream from the impeller suction port by extending the return passage in the suction pipe. Yes. The handling liquid in the can is refluxed by the return flow path formed by the return flow path and the extension pipe. Since the liquid from the inside of the pipe is discharged away from the impeller suction port, vaporization and cavitation in the impeller can be prevented.

  The extension pipe can have a length that is at least twice the inner diameter of the suction pipe from the impeller suction port. Furthermore, it is also preferable to reach the suction tank.

  The extension tube can rotate integrally with the shaft. Moreover, it is fixed with respect to the suction pipe and can be slid with respect to the shaft. In the case of fixing to the suction pipe, the extension pipe can be arranged without considering the rotation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a canned motor pump 10 of the present embodiment. The canned motor pump 10 includes a centrifugal pump 12 and a motor 14 that drives the centrifugal pump 12. In the centrifugal pump 12, an impeller 18 is rotatably disposed in a casing 16. The impeller 18 includes a plurality of blades 20, and the blades 20 send out the handling liquid sucked from the suction port 22 in the central portion from the outer periphery of the impeller. A suction pipe 24 is connected to the front surface of the casing 16, and a discharge pipe 26 is connected to the side surface.

  The impeller 18 is coupled to a shaft 28 of the motor 14, and the shaft 28 is rotatably supported by bearings 30 and 32 in the vicinity of both ends thereof. Further, the rotor 28 of the motor 14 is coupled to the shaft 28, and both the shaft 28 and the rotor 34 are accommodated in a can 36 formed of a thin plate material in a cylindrical shape. The front end of the can 36 is coupled to the back plate 38 of the casing 16, the rear end is coupled to the rear end surface plate 40, and each coupling portion is sealed. In addition, the back plate 38 is formed with an introduction channel 42 that guides the handling fluid into the can 36. As a result, the can 36 communicates with the centrifugal pump 12 but is sealed from the others. A motor stator 46 is disposed around the rotor 34 via a can 36.

  The shaft 28 is a hollow shaft, and this hollow portion serves as an in-shaft channel 44 extending over the entire length of the hollow portion. Further, the impeller 18 is provided with an in-impeller channel 48 extending to the front end of the blade 20, that is, the suction port 22 along the axis of the impeller 18 so as to be connected to the in-shaft channel 44. An extension pipe 50 is connected to the impeller 18 and communicates with the flow path 48 in the impeller and extends forward from the suction port 22, that is, upstream into the suction pipe 24.

  A part of the handling liquid sent out by the impeller 18 is sent around the back surface of the impeller and through the introduction flow path 42 into the can 36. The liquid handled by the can 36 enters the in-shaft channel 44 from the rear end of the shaft 28 after lubricating and cooling the bearings 30 and 32 and cooling the rotor. Then, the handling liquid is returned to the suction side of the pump by the in-shaft flow path 44 and the impeller flow path 48 and further sent to the upstream side of the suction pipe 24 by the flow path in the extension pipe 50.

  Since the handling liquid returned from the can 36 absorbs heat generated in the rotor 34 and the bearings 30 and 32, the temperature is high. If the liquid to be handled is a low-boiling point fluid such as a refrigerant for an air conditioner, when the liquid having a high temperature is sucked into the centrifugal pump 12 as it is, it boils at a portion where the pressure near the suction port 22 is low. Prone to cavitation. In the present embodiment, the handling liquid returned from within the can 36 is sent to a position that is further back in the suction pipe 24 from the vicinity of the suction port 22 of the centrifugal pump 12. As a result, the handling liquid returned from inside the can 36 flows through the suction pipe 24 and is sucked into the centrifugal pump 12, so that the handling liquid is mixed with a new, that is, a cold handling liquid to eliminate temperature unevenness and Is lowered to prevent boiling.

  Since the new liquid and the returned liquid are mixed while flowing through the suction pipe 24, it is preferable that the returning position is a position in consideration of sufficient mixing. In the present embodiment, if the length L of the extension pipe 50, that is, the length from the suction port 22 to the position where the handling liquid is returned is twice or more the inner diameter D of the suction pipe 24, a sufficient effect can be obtained. It was confirmed. However, this does not mean that the effect cannot be obtained if it is less than 2 times.

  Further, the canned motor pump 10 of the present embodiment has a configuration in which the centrifugal pump 12 is disposed on the upper side and the motor 14 is disposed on the lower side. As a result, the flow path for returning the handling liquid from the can 36 is in the vertical direction, and the gas mixed in the handling liquid is easy to escape from the flow path and the can 36. Further, it is also effective to arrange the canned motor pump 10 obliquely instead of vertically and to give an upward gradient to the flow path.

  FIG. 2 is a diagram showing a schematic configuration of a canned motor pump 60 and a suction tank 62 for storing a handling liquid according to another embodiment. The canned motor pump 60 includes a centrifugal pump 64 and a motor 66 that drives the centrifugal pump 64. These are the same in basic structure as the centrifugal pump 12 and the motor 14 of the canned motor pump 10 shown in FIG. Is omitted. The canned motor pump 60 is disposed obliquely as shown in the figure.

  What is characteristic of the canned motor pump 60 is that an extension pipe 68 for returning the handling liquid from the can to the upstream side of the suction side extends to the suction tank 62 through the suction pipe 70. The extension pipe 68 reaches the upper part of the bent tank in the suction tank 62. Since the position where the suction pipe 70 is connected to the suction tank 62 is generally at the bottom of the tank, the returned handling liquid immediately enters the suction pipe 70 by positioning the end of the extension pipe 68 at the top of the tank. Can be prevented.

  As described above, since the extension pipe 68 is bent, it cannot be configured to be fixed to the impeller and rotated together with it as in the case of the canned motor pump 10 of FIG. Therefore, the extension pipe 68 is fixedly supported by a stay provided in the suction pipe 70. The connection with the impeller 74 is achieved by press-fitting a receiving bush 76 into the impeller 74, and the receiving bush 76 slidably receives and supports the end of the extension pipe 68.

  In addition, by arranging the canned motor pump 60 at an angle, the flow path for returning the liquid to be handled has an ascending gradient throughout and improves the outgassing.

  3-5 is a figure which shows the modification of arrangement | positioning of the canned motor pump 60, the suction tank 62, etc. of FIG. Since there is no change about each structure, the description is abbreviate | omitted. FIG. 3 is an example in which the suction tank 62 is arranged in a direction orthogonal to FIG. FIG. 4 is an example in which the canned motor pump 60 and the suction pipe 70 are arranged horizontally. FIG. 5 shows a state in which the canned motor pump 60 is set up vertically, and the suction tank 62 is positioned immediately above.

  As described above, an extension pipe is provided inside the suction pipe, and by returning the liquid from the can to a position away from the impeller suction port, vaporization in the impeller can be prevented when handling a low boiling point liquid. it can. Moreover, since it returns with piping inside a pump, the countermeasure with respect to a liquid leak can be reduced compared with the case where it returns through piping outside a pump. Further, heat input from the piping can be suppressed as compared to the external piping. Further, since there is no pipe for returning the handling liquid outside, the outer shape can be reduced in size.

  Moreover, when providing the extension pipe | tube fixed to the suction pipe, the wall fixed to the suction inlet vicinity of an impeller will be located. Since the swirling speed of the handling liquid decreases near the wall, the action of the centrifugal force is reduced, and the gas mixed in the handling liquid is prevented from collecting in the center. Therefore, even if gas is generated, it is discharged early.

It is sectional drawing which shows schematic structure of the canned motor pump of this embodiment. It is a figure which shows schematic structure of other embodiment. It is a figure which shows the other example of arrangement | positioning of a canned motor pump and a suction tank. It is a figure which shows the further another example of arrangement | positioning of a canned motor pump and a suction tank. It is a figure which shows the further another example of arrangement | positioning of a canned motor pump and a suction tank.

Explanation of symbols

  10 Canned motor pump, 12 Centrifugal pump, 14 Motor, 16 Casing, 18 impeller, 20 vanes, 22 Suction port, 24 Suction pipe, 28 Shaft, 36 can, 44 Shaft flow path (return flow path), 48 Impeller flow Road (return channel).

Claims (4)

A can motor pump in which a rotor of a motor that drives a pump is placed in a can, and the inside of the can is filled with a pump handling liquid,
A return passage formed in the shaft of the impeller of the pump and the motor that drives the impeller;
An extension pipe connected to the return flow path and extending from the impeller suction port to the suction tank storing the handling liquid provided upstream of the pump suction side ,
The handling fluid is returned from the can to the upstream side of the suction side of the motor by the return channel and the extension pipe.
Canned motor pump. The canned motor pump according to claim 1 , wherein the extension pipe rotates integrally with the shaft. 2. The canned motor pump according to claim 1 , wherein the extension pipe is fixed to a suction pipe and is slidably connected to the shaft. It is a canned motor pump of any one of Claims 1-3 , Comprising: The canned motor pump by which the said return flow path and the extension pipe | tube were arrange | positioned so that a climbing gradient might be attached to a perpendicular direction.

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