JPH0630540A - Canned motor pump - Google Patents

Abstract

PURPOSE:To provide a canned motor pump in which axial thrust to be exerted onto a rotary body is balanced perfectly, axial bearing is sustained in noncontact state, and friction thereof is eliminated. CONSTITUTION:An axial bearing is constituted of a bearing retainer 2 secured to an end cover 3 on the opposite side to an impeller, and a thrust disc 1 for self-balancing secured to a main shaft 20 wherein the thrust disc 1 is arranged in a space defined by the bearing retainer 2 and the end cover 3. High pressure liquid is then introduced into a space defined by a motor rotor and a bearing member 6 on the opposite side to the impeller and a pressure relief means (piping 11) is provided in order to reduce pressure in a space defined by the thrust disc 1 and the end cover 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a canned motor pump, and more particularly to a canned motor pump having a long bearing life.

[0002]

BACKGROUND OF THE INVENTION Conventionally, sliding bearings have been used as bearings for canned motor pumps of this type. As the material of the plain bearing, metal is usually used on the rotating side and carbon is used on the fixed side. FIG. 3 is a diagram showing the structure of a conventional canned motor pump of this type.

[0003]

2. Description of the Related Art In a conventional canned motor pump, as shown in FIG. 3, bearing members 5 and 6 are arranged on both sides of a motor rotor 4, that is, on the side of an impeller 7 and on the opposite side of the impeller 7. Thrust plates 15 and 16 slidingly contacting the ends of the
Is fixed to the main shaft 20. Thrust generated from a pump or the like is divided into radial thrust and axial thrust depending on the direction. The radial thrust is received by a radial bearing composed of the bearing member 5 and the shaft sleeve 8 and a radial bearing composed of the bearing member 6 and the shaft sleeve 9. Further, the axial thrust is received by an axial bearing composed of the bearing member 5 and the thrust plate 15 and an axial bearing composed of the bearing member 6 and the thrust plate 16.
In FIG. 3, 24 is a motor casing, 25 is a can, and the motor stator 4 ′ is sealed in a space formed by the motor casing and the can 25.

[0004]

However, in the above-described conventional canned motor pump, the shaft sleeves 8 and 9 and the thrust plates 15 and 1 which are the rotating side during operation are in operation.
Since the bearing 6 rotates while contacting the bearing members 5 and 6 on the fixed side, the bearing members 5 and 6 are mainly worn.

Both the radial thrust and the axial thrust magnitudes depend on the operating point of the pump. The radial thrust is constant unless the operating point of the pump changes.
On the other hand, the axial thrust also depends on the magnitude of the pressure acting on the surface of each component even if the operating point of the pump does not change.

For the purpose of lubricating the bearing and cooling the canned motor, the discharge port 22 of the pump, which is a high-pressure portion for circulation, is used.
The liquid introduced from the above enters the inside of the bearing cover 17 through the pipe 14, passes through the canned motor, and flows to the suction part of the pump, which is the low pressure part. Therefore, the pressure of the discharge port 22 is P1, the pressure inside the bearing cover 17 is P2, the pressure on the side opposite the impeller of the canned motor is P3, and the side of the impeller of the canned motor is related to the magnitude of the pressure during pump operation. Pressure of P
4, the pressure near the balance hole 7a of the pump is P5,
If the pressure of the suction port 21 is P6, then P1>P2>P3>P4>P5> P6.

At this time, the axial thrust acts on the stop plate 18, the stop bolt 19, the thrust plate 16, the motor rotor 4, and the thrust plate 15, respectively, and all of them act in the direction of the suction port 21 of the pump. Therefore, since the rotating body is pushed toward the suction port of the pump, all the axial thrust is received by the bearing member 5 and the thrust plate 15 on the impeller 7 side.

When the operating point does not change, the pressure P1 at the discharge port 22 is constant and the balance hole 7 of the pump is
Since the pressure P5 near a is equal to the suction pressure because the impeller 7 is provided with the balance hole 7a, the magnitude of the axial thrust is substantially determined by the magnitude of the pressure P2 in the bearing cover 17. As the operation time elapses, the holes in the orifice 23 become larger due to wear of the orifice 23, the loss in the orifice 23 portion decreases, and the pressure P2 gradually increases. When considering the operation for a long time, the radial thrust is constant unless the operating point of the pump changes, while the axial thrust increases. As a result, there is a drawback in that the surface pressure between the bearing member 5 and the thrust plate 15 that receives the axial thrust is further increased, and their wear is promoted.

The present invention has been made in view of the above points, and an object of the present invention is to provide a canned motor pump capable of removing the wear of the axial bearing among the above-mentioned drawbacks.

[0010]

In order to solve the above-mentioned problems, the present invention comprises an axial bearing composed of a bearing retainer fixed to an end cover on the side opposite to the impeller, and a self-balancing thrust disk fixed to the main shaft. Then, the thrust disk is arranged in a space formed by the bearing retainer and the end cover, high-pressure liquid is introduced into the space between the motor rotor and the bearing on the side opposite to the impeller, and the space formed by the thrust disk and the end cover. Is provided with pressure relief means so that the pressure becomes low.

[0011]

As described above, the thrust disk is arranged in the space formed by the bearing retainer and the end cover, high-pressure liquid is introduced into the space between the motor rotor and the bearing on the side opposite to the impeller, and the thrust disk and the end cover are connected. By providing pressure relief means so that the space formed by becomes low pressure,
As will be described later in detail, the axial thrust applied to the rotating body can be perfectly balanced, and the gap S between the thrust disc and the bearing retainer can be set to S> 0. Therefore, the thrust disc and the bearing retainer are different from each other. Can be completely contactless.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a canned motor pump according to the present invention. In FIG. 1, the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. The same applies to other drawings. Reference numeral 2 is a bearing retainer, and the bearing retainer 2 is fixed to an end cover 3 on the opposite side of the impeller 7. Reference numeral 1 is a self-balancing thrust disk, and the thrust disk 1 is fastened and fixed with a stop bolt 19 with a stop plate 18 interposed on a main shaft 20.
The thrust disk 1 and the bearing retainer 2 constitute an axial bearing.

In the canned motor pump having the above structure, the high pressure liquid is supplied from the discharge port 22 of the pump to the pipe 1
0 is introduced. This liquid is also used to lubricate bearings and cool canned motors. The liquid flows in two paths after passing through the pipe 10 from the discharge port 22 of the pump. The first path is a path that flows through the outer peripheral portion of the motor rotor 4, passes through the inner peripheral portion of the bearing member 5, passes through the balance hole 7a of the impeller 7, and returns to the suction port 21 of the pump, which is the low pressure portion.
The second path flows through the inner peripheral portion of the bearing member 6, passes through the gap between the bearing retainer 2 and the sliding portion of the shaft sleeve 9, passes through the gap between the thrust disk 1 and the bearing retainer 2, and then the pipe 11
It is a path that passes through and returns to the portion of the suction port 21 of the pump, which is the low pressure portion.

Regarding the pressure relationship between the two paths, the pressure at the discharge port 22 is P1, and the pressure on the side opposite to the impeller of the canned motor is P.
3, the pressure on the impeller side of the canned motor is P4, the pressure near the balance hole 7a of the pump is P5, and the pressure at the suction port is P6, the first path is P1>P3>P4>P5> P6. , The second path is P1>P3>Pf>Pb> P6. Here, Pf is the pressure between the thrust disk 1 and the bearing retainer 2, and Pb is the pressure inside the end cover 3.

The axial thrusts of these two paths act in exactly opposite directions to each other. The first path mainly acts on the motor rotor 4, and its axial thrust is T1. In the second path, mainly thrust disk 1 and stop plate 1
8 and the set bolt 19, and the total sum of those axial thrusts is T2. The size of the thrust T2 mainly depends on the gap S between the sliding surfaces of the thrust disc 1 and the bearing retainer 2.

When the thrust T1 and the thrust T2 are such that T1> T2, the rotating body is pushed toward the suction port 21 side, the gap S becomes smaller, and the sliding surface between the thrust disc 1 and the bearing retainer 2 becomes smaller. Will increase the loss. Therefore, the pressure Pf acting on the surface of the thrust disc 1 on the bearing retainer 2 side is
However, since the pressure Pb on the back surface is almost the same as the suction pressure and is constant, the thrust T2 increases, and this time the rotor is pushed back in the direction opposite to the suction port 21 side. Then, since T1 <T2, the gap S becomes larger and the pressure Pf becomes smaller, and the rotating body is returned to the suction port 21 side again.

Once the operating point of the pump is determined, thrust T1
Is constant and the thrust T that balances the thrust T1
The pump is operated while maintaining the gap S of 2 in an instant. Even when the operating point changes, the gap S that becomes the thrust T2 balanced with each thrust T1 is secured in an instant. In this way, a so-called self-balancing mechanism that follows the change of the thrust T1 and automatically settles in the gap S where T1 = T2 is established.

Utilizing such a self-balancing mechanism, from the various dimensions and pressure conditions of the canned motor pump,
T1 = T2, that is, S when the axial thrust is balanced is calculated in advance, and the outer diameter of the thrust disc 1 is determined so that S> 0 in the entire operating flow rate range of the pump.

FIG. 2 is a sectional view showing another structure of the canned motor pump of the present invention. 2 is different from the canned motor pump of FIG. 1 in that the canned motor pump of FIG.
In the above, the high-pressure liquid is introduced from the outside through the pipe 12 into the space between the motor rotor 4 and the bearing member 6, and the escape from the space between the thrust disk 1 and the end cover 3 to the low-pressure portion is also introduced through the pipe 13 to the outside. The other points are exactly the same as those in FIG.

[0020]

As described above, according to the present invention, the thrust disk is arranged in the space formed by the bearing retainer and the end cover, and high-pressure liquid is introduced into the space between the motor rotor and the bearing on the side opposite to the impeller. In addition, by providing the pressure relief means so that the space formed by the thrust disc and the end cover has a low pressure, the axial thrust applied to the rotating body can be perfectly balanced, and the thrust disc and the bearing retainer can be balanced. Since the gap S can be set to S> 0, the thrust disk and the bearing retainer can be completely brought into non-contact with each other, and an excellent effect that the life of the axial bearing is dramatically lengthened is obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a canned motor pump of the present invention.

FIG. 2 is a cross-sectional view showing another structure of the canned motor pump of the present invention.

FIG. 3 is a view showing the structure of a conventional canned motor pump of this type.

[Explanation of symbols]

 1 Thrust Disc 2 Bearing Retainer 3 End Cover 4 Motor Rotor 5 Bearing Member 6 Bearing Member 7 Impeller 8 Shaft Sleeve 9 Shaft Sleeve 10 Piping 11 Piping 12 Piping 13 Piping 20 Main Spindle 21 Suction Port 22 Discharge Port

Claims (1)

[Claims] 1. A canned motor pump in which radial bearings are arranged on both sides of an impeller side and an opposite impeller side of a motor rotor, and an axial bearing is arranged at a predetermined position of a main shaft, wherein the axial bearing is opposite to the impeller side. Of the bearing retainer fixed to the end cover and a thrust disc for self-balancing fixed to the main shaft, and the thrust disc is arranged in a space defined by the bearing retainer and the end cover, and the motor rotor and the rotor A canned motor pump, characterized in that a high pressure liquid is introduced into a space between the impeller side bearing and a pressure relief means is provided so that a space formed by the thrust disk and the end cover has a low pressure.