JPS5920879B2 - Axial thrust balancing method and device for canned motor pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a canned motor pump consisting of a pump section with axial flow vanes and a canned motor.Generally speaking, a canned motor pump has a motor section and a pump section integrally constructed, and the pump Since there is no shaft penetrating portion in the casing, it is not possible to externally support the shaft thrust generated on the common shaft that supports the impeller and the motor rotor.

Conventionally, in a canned motor pump equipped with a pump section that uses a radial flow type or mixed flow type impeller, there is a space between the end plate that defines the pump section and the motor section and the back surface of the impeller, as shown in Fig. 1. A full thrust automatic balance mechanism configured with an axial thrust balance chamber as shown is generally employed.

However, the canned motor pump with the structure shown in Fig. 1 must rotate at a low speed from the viewpoint of suction performance, and therefore, in order to obtain the required pump discharge amount, the impeller must be enlarged, that is, the pump section must be enlarged. However, there is a drawback that manufacturing and maintenance costs increase.

In view of these circumstances, if an axial flow vane is adopted in the configuration of the pump section, high-speed rotation is possible, suction performance can be improved, and the pump section can be made smaller.

However, in canned motor pumps in which the pump part is composed of axial flow vanes, the thrust force always acts strongly in the direction of the pump suction port, and the axial flow vanes themselves cannot be structured to balance this thrust force. , a problem arises in that the normal thrust bearing built into the canned motor pump cannot support the thrust force.

Therefore, the inventors of the present invention conducted various studies in order to overcome the problems with the canned motor pump having the above-mentioned novel configuration. As a result, the inventors of the present invention have found that normally canned motors use pump handling liquid to lubricate the bearings and cool the motor. Since a part of the pump is circulated within the canned motor, an auxiliary pump chamber is provided in the rear motor rotor chamber of the canned motor section, and this auxiliary pump chamber balances the thrust generated by the axial flow blades of the main pump chamber. An auxiliary impeller that generates reverse thrust is installed and attached to the motor rotor shaft, and a portion of the liquid handled by the pump is taken out from the rear end of the axial flow blade in the main pump chamber and introduced into the auxiliary pump chamber. By circulating the flow through the canned motor to the discharge port of the main pump chamber, the axial thrust of the axial flow vanes in the main pump chamber can be easily and reliably balanced, and the above-mentioned problems can be solved. I figured it out.

Therefore, an object of the present invention is to stably balance the axial thrust generated in the axial flow vanes in a canned motor pump consisting of a pump section equipped with axial flow vanes and a canned motor section, thereby achieving a small size and improved suction performance. The purpose of the present invention is to provide a canned motor pump that can achieve smooth pump operation.

In order to achieve the above object, the present invention includes a pump section equipped with axial flow vanes and a canned motor section, and an auxiliary pump chamber is provided at the rear end of the rear motor rotor chamber of the canned motor section. A radial flow type auxiliary impeller is installed on the motor rotor shaft so that it has a suction port in the room opposite to the suction port of the axial flow vanes in the main pump chamber, and the radial flow type auxiliary impeller is installed on the shaft of the motor rotor so that the suction port of the auxiliary pump chamber and the suction port of the axial flow vanes of the main pump chamber are connected to each other. A passage is provided that communicates with the end side, and the front motor rotor chamber is communicated with the discharge part of the main pump chamber near the part of the passage that opens toward the main pump chamber, thereby assisting the liquid discharged by the auxiliary impeller. It is characterized in that it is introduced into the rear motor rotor chamber through the pump chamber, further introduced into the front motor rotor chamber through the gap between the motor rotor and the motor stator, and then circulated to the main pump chamber.

In addition, in the canned motor pump described above, by providing a thrust automatic balance mechanism between the back surface of the auxiliary impeller and the wall surface of the auxiliary pump chamber, the balancing effect of the reverse thrust against the thrust of the axial flow vanes in the main pump chamber is made even smoother. It is possible to achieve this.

Next, embodiments of the canned motor pump according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows an embodiment of a canned motor pump with an internal circulation system.

Reference numeral 10 indicates a pump section, and 12 indicates a canned motor section.

An axial flow vane 16 is disposed in the suction port 14 of the pump section 10, and a passage 22 is provided inside a motor rotor shaft 20 serving as a common shaft supporting the axial flow vane 16 and the motor rotor 18. One end is opened to communicate with the inside of the pump chamber 24 on the rear end side of the axial flow vane 16, while the other end of the passage 22 is opened so as to communicate with the inside of the rear motor rotor chamber 26.

Further, an auxiliary pump chamber 38 is provided in the rear motor rotor chamber 26 where the other end of the passage 22 is open, and an auxiliary impeller 40 of, for example, a semi-open type and a radial flow type is provided in this auxiliary pump chamber 38. is attached to the motor rotor shaft 20.

In this case, the auxiliary impeller 40 is configured and arranged so as to generate a reverse thrust that is balanced against the thrust toward the fluid suction port generated by the axial flow blades 16.

That is, when the auxiliary impeller 40 described in this embodiment is used, the pressure distribution becomes as shown in FIG.
becomes.

With this configuration, in the canned motor pump shown in FIG. 2, during pump operation, a part of the liquid handled by the pump is transferred from the opening at the rear end of the axial flow vane 16 to the rear motor rotor through the passage 22. The pump is introduced into an auxiliary pump chamber 38 formed in the chamber 26 , and within this auxiliary pump chamber 38 , under the action of an auxiliary impeller 40 , a reverse thrust to the thrust of the axial flow vanes 16 is generated.

Next, a part of the pump handling liquid passes through the gap between the motor stator 30 and the motor rotor 18 while suitably lubricating the rear bearing 28 that supports the motor rotor shaft 20, absorbs heat from the motor part during this time, and enters the front motor rotor chamber. You will be guided to 32.

A portion of the pump handling liquid introduced into the front motor rotor chamber 32 is circulated back into the pump chamber 24 while appropriately lubricating the front bearing 36.

In this case, most of the recirculated liquid flows back into the pump chamber 24 through a through hole 34 formed in an end plate that defines the pump section 10 and the motor section 12.

Note that the through hole 34 allows a part of the liquid handled by the pump to pass through the passage 22.
It is preferable to locate the opening in the vicinity of the opening for introduction into the cell.

The pressure distribution characteristics of the circulating fluid flowing from the pump chamber into the canned motor section in the canned motor pump of this embodiment described above are as shown in FIG.

That is, the pressure of the liquid handled by the pump at the opening (2) of the passage 22 is approximately equal to the discharge pressure by the axial flow vane 16, and the pressure drop inside the passage 22 is small, so that the auxiliary impeller 40
The pressure at the suction port (2) does not drop much and is maintained sufficiently higher than the pressure at the suction side (2) of the axial flow vane 16.

Then, at the discharge port of the auxiliary impeller 40 or at the back side (■) of the auxiliary impeller 40, the circulating fluid reaches the highest pressure.
Thereafter, the pressure of the circulating fluid gradually decreases as it passes through the motor rotor chamber V.

Since the pressure in the communication section (2) between the front motor rotor chamber 32 and the pump chamber 24 is approximately equal to the pressure at the opening (2) of the passage 22, the circulating fluid in the motor rotor chamber 32 flows back into the pump chamber 24.

In this way, a certain amount of the pump handling liquid is smoothly circulated within the canned motor section.

In particular, as is clear from the pressure distribution characteristics shown in Figure 4,
In the canned motor pump according to the present invention, the pressure level of the liquid circulating in the canned motor section is much higher than that in the conventional canned motor pump, so cavitation generation force in the front motor rotor chamber 32 can be effectively prevented. , which has the excellent feature of not causing abnormal bearing wear.

In the canned motor pump of this embodiment, since the pump part can be constructed with axial flow vanes, the pump structure can be made smaller.Moreover, in order to effectively achieve the above-mentioned axial thrust balance, the suction can be achieved by high-speed rotation. The performance is improved, and a canned motor pump that is small and has excellent pump performance can be obtained.

Incidentally, when the auxiliary impeller of this example is adopted, it has been confirmed that the highest head can be obtained by setting the outer diameter of the auxiliary impeller to be approximately the same as the outer diameter of the axial flow blade. It is also possible to downsize the entire pump.

As an alternative, as shown in FIG. 5, a fixed orifice 39 and a variable orifice 41 are provided between the back surface of the auxiliary impeller 40 and the wall surface of the auxiliary pump chamber 38, and the pressure is maintained between these orifices 39 and 41. By configuring the conventionally known automatic thrust balance mechanism 42 in which the balance chamber 43 is formed, the thrust of the auxiliary impeller 40 itself can be automatically balanced, and the generation of excessive thrust of the axial flow blades 16 is prevented, and the axial flow blades The balancing action of the reverse thrust against the thrust of 16 can be achieved more smoothly.

In the above-mentioned embodiments, an internal circulation system has been described, but it goes without saying that an external circulation system can also be used.

Furthermore, the canned motor pump according to the present invention can be most suitably applied, especially as a refrigerant circulation pump for an absorption refrigerator.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

Figure 1 is a cross-sectional side view of a conventional canned motor pump, Figure 2 is a partial cross-sectional side view showing an embodiment of the canned motor pump according to the present invention, and Figure 3 is a structure of the auxiliary impeller shown in Figure 2. FIG. 4 is a pressure distribution characteristic curve diagram of the circulating fluid in the pump chamber and canned motor section of the canned motor pump shown in FIG. 2, and FIG. 5 is an explanatory diagram showing the pressure distribution. FIG. 7 is an enlarged cross-sectional view showing another embodiment of the auxiliary impeller. 10...Pump part, 12...Canned motor part, 14...Suction port, 16...
Axial flow vane, 18...Motor rotor, 20-...
...Motor rotor shaft, 22-...Passage, 24...
... Pump chamber, 26 ... Rear motor rotor chamber, 28 ... Rear bearing, 30 ... Motor stator, 32 ... Front motor rotor chamber, 3
4...Through hole, 36...Front bearing, 38
... Auxiliary pump chamber, 40 ... Auxiliary impeller, 42 ... Thrust automatic balance mechanism, 39.
... Fixed orifice, 41 ... Variable orifice, 43 ... Pressure balance chamber.

Claims (1)

[Claims] 1. Consisting of a pump section equipped with axial flow vanes and a canned motor section, an auxiliary pump chamber is provided at the rear end of the rear motor rotor chamber of the canned motor section, and the main pump chamber is located in the auxiliary pump chamber. A radial flow type auxiliary impeller is installed on the motor rotor shaft so that the suction port is in the opposite direction to the suction port of the axial flow vane, and the suction port of the auxiliary pump chamber is communicated with the rear end side of the axial flow vane of the main pump chamber. A passage is provided, and the motor rotor chamber is communicated with the discharge part of the main pump chamber near the part of the passage that opens toward the main pump chamber, and the liquid discharged by the auxiliary impeller is passed through the auxiliary pump chamber to the rear motor rotor chamber. A canned motor pump characterized in that the canned motor pump is configured to be introduced into the front motor rotor chamber through a gap between a motor rotor and a motor stator, and then circulated to the main pump chamber. 2. In the canned motor pump according to claim 1, a fixed orifice and a variable orifice are provided between the back surface of the auxiliary impeller and the wall surface of the auxiliary pump chamber, and a pressure balance chamber is formed between these orifices. A canned motor pump comprising an automatic balance mechanism and configured to generate a thrust opposite to the thrust of an axial flow vane provided in a main pump chamber.