JPS62689A - Double centrifugal pump - Google Patents

Abstract

PURPOSE:To obtain seal pressure corresponding to discharge pressure by so supporting a driven shaft that it can be turned freely and moved axially by a radial ring disposed between a primary and a secondary impeller and mounting a seal ring which restrains the axial movement of said shaft. CONSTITUTION:When a driving magnet 31 is turned by an electric motor, a driven magnet 24, a driven shaft 21 and a primary impeller 20 are turned o that liquid may be absorbed from a primary intake hole 35 and then discharged from a primary discharge hole 37, and a secondary impeller 23 is also turned so that liquid is discharged from a secondary discharge hole 39. The impellers 20 and 30 generate discharge pressure corresponding to the rotational speed thereof, thrust force proportional to the discharge pressure acts on the driven shaft 21 in the right direction and a seal ring 34 is subjected to axial compression force via the side face of a radial ring 30, whereby increasing seal face pressure. The startability is thus improved and the sealing effect corresponding to discharge pressure is obtained so that liquid may be prevented from leaking between the case 29 and the driven shaft 21 which are disposed between the primary and the secondary pump case 36 and 38.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dual centrifugal pump, and relates to a mechanical seal in a pump rotationally driven by a magnetic coupling having a driving magnet and a driven magnet. .

[Conventional technology]

In the conventional centrifugal pump, as shown in FIG.
4 and the packing 12 to seal the pump casing 10 and the main shaft 14.

In the above configuration, the coil packing is expensive and requires space for its installation. Furthermore, since the surface pressure between the seal 12 and the main shaft 14 does not change when the pump is stopped and when it is running, when the pump is stopped (when the possibility of leakage is small)
The same surface pressure as when driving is applied. Therefore, since this surface pressure acts as a rotational load on the main shaft 14, there is a problem of poor starting performance when starting the pump. Particularly, in a type of pump in which the main shaft is rotated using a magnetic coupling, the above-mentioned startability is extremely poor.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above points, and therefore, in a centrifugal pump having a magnetic coupling, by changing the seal surface pressure at pump startup and operation, the pump starting torque is reduced and the durability of the seal ring is improved. , and to reduce the installation space for seal rings.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides two impellers in which the first impeller and the second impeller rotate integrally with the driven shaft by the magnetic rotation of the driven magnet accompanying the rotation of the drive magnet, thereby drawing in and pumping fluid. In the type centrifugal pump, the driven shaft is supported so as to be movable in the axial direction by an axial propulsive force generated by the rotation of the impeller, and is provided in a housing between the first impeller and the second impeller, and is provided in the housing between the first impeller and the second impeller. a radial ring that rotatably supports a driven shaft; and a radial ring that restricts movement of the driven shaft in the axial direction;
and a seal ring provided at a position pressed against a side surface of the radial ring by movement of the driven shaft due to the propulsive force.

[Effect]

When the driven shaft and impeller are stopped, no propulsive force is generated, but when the impeller rotates, the impeller receives a propulsive force toward the suction side. This increases the surface pressure between the seal ring and the radial ring, improving the sealing performance between the driven shaft and the housing. Furthermore, during operation when the rotation of the impeller increases, the discharge pressure in the pump chamber increases, but the driving force of the driven shaft by the impeller also increases.
The sealing surface pressure of the seal ring and the radial ring increases, and the sealing surface pressure can be made to correspond to the discharge pressure of the pump chamber.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 is a longitudinal sectional view of a dual centrifugal pump showing an embodiment of the present invention. The first impeller 20 is connected to one end of a driven shaft 21, and a second impeller 23 is integrally fixed to the center of the driven shaft 21. Further, a driven magnet 24 is provided on the outer periphery near the other end of the driven shaft 21, and is made liquid-tight by a cover 25 of the second impeller 23. The driven shaft 21 is rotatably supported via a bearing 28 at the bottom of a bottomed cylindrical body 27 that is provided integrally with a case 26 of the pump body.
It is rotatably supported by a radial ring 30 attached to a case 29 provided at the rear of the impeller 2o. Further, the driven shaft 21 is supported so as to be movable by a minute amount in the axial direction by the propulsive force generated by the rotation of the first impeller 20 and the second impeller 23.

A rotating body 32 has a driving magnet 31 attached to the outer periphery of the bottomed cylindrical body 27 so as to face the driven magnet 24.
The rotating body 32 and the rotating shaft 33 are rotationally driven by an electric motor (not shown).

The driven shaft 21 at the rear of the first impeller 20 has a stepped portion 2.
1a is formed on the outer periphery, and a seal ring 34 is provided between this stepped portion 21a and the radial ring 30 described above. Therefore, the movement of the seal ring 34 in the left direction in FIG. 1 is restricted by the stepped portion 21a of the driven shaft 21.

Note that a small gap is provided between the side surface of the radial ring 30 and the seal ring 34 when the pump is stopped.

Next, the operation will be explained based on the above-described configuration.

When the drive magnet 31 rotates in response to the rotational force of an electric motor (not shown), the driven magnet 24, the driven shaft 21, the first impeller 20, and the second impeller 23 begin to rotate together.

Then, the first impeller 20 sucks fluid into the first pump chamber 36 from the first suction hole 35 in the axial direction of the driven shaft 21,
The fluid is discharged from the first discharge hole 37 , and the second impeller 23 similarly sucks fluid into the second pump chamber 38 from a suction hole (not shown) and discharges fluid from the second discharge hole 39 .

Here, the first impeller 20 and the second impeller 23 are
Since a discharge pressure corresponding to the rotational speed is generated and discharged from the first discharge hole 37 and the second discharge hole 39, the driven shaft 21 receives a driving force proportional to the discharge pressure in the right direction in FIG. act. Therefore, the driven shaft 21 moves rightward in FIG. 1, and the seal ring 34 receives an axial compressive force on the side surface of the radial ring 30, increasing the seal surface pressure. For this reason,
Case 2 between the first pump chamber 36 and the second pump chamber 38
9 and the driven shaft 21 is prevented from leaking and sealed.

According to the above-described embodiment, the axial position of the driven shaft 21 changes between when the pump is in operation and when it is stopped,
When the pump is stopped, the seal surface pressure between the radial ring 30 and the seal ring 34 is low, or a gap is provided, so that the pump starts easily. Further, during pump operation, the seal surface pressure increases due to the propulsive force generated by the impeller 20.23, and the seal surface pressure increases between the first pump chamber 36 and the second pump chamber 38.
The respective fluids are prevented from leaking between the two.

〔Effect of the invention〕

As described above, according to the present invention, the following effects can be obtained.

First, since the driving torque of the driven shaft at the time of starting the pump is reduced, starting performance is improved even in a pump having a magnetic coupling. Secondly, during pump operation, the sealing surface pressure of the seal ring increases as the impeller rotates by 8 degrees, so that a sealing effect is achieved that corresponds to the discharge pressure.

Third, the present invention has superior seal ring durability compared to conventional O-rings for seals, and is simpler in structure and cheaper to install than conventional coil packings, mechanical seals, etc. It has the effect of requiring less space.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a two-barrel centrifugal pump that is an embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a conventional centrifugal pump. 20... First impeller, 21... Driven shaft, 21a.
...Stepped portion, 23...Second impeller, 24...Driver magnet, 25...Cover, 26...Case, 2
7... Bottom cylindrical body, 28... Bearing, 29... Case, 30... Radial ring, 31... Drive magnet, 32... Rotating body, 33... Rotating shaft, 34...
- Seal ring, 35... first suction hole, 36... first pump chamber, 37... first discharge hole, 38... second pump chamber, 39... second discharge hole. Representative Patent Attorney Takashi Okabe Figure 1

Claims (2)

[Claims] (1) In a dual centrifugal pump in which a first impeller and a second impeller are rotated together with a driven shaft to draw in and pressure feed fluid by magnetic rotation of a driven magnet accompanying rotation of a drive magnet, the driven shaft is connected to the impeller. a radial ring that is movably supported in the axial direction by an axial propulsive force generated by the rotation of the impeller, and is provided in a housing between the first impeller and the second impeller and rotatably supports the driven shaft; and a seal ring provided to restrict movement of the driven shaft in the axial direction, and a seal ring provided at a position pressed against a side surface of the radial ring by movement of the driven shaft due to the propulsive force. (2) The dual centrifugal pump according to claim 1, wherein the seal ring is restricted in movement by a stepped portion provided on the outer periphery of the driven shaft.