JPH0226212Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a pump motor, and more particularly to a pump motor having a vibration-proofing mechanism for preventing resonance in a support portion with respect to a stationary side.

[Technical background of the invention and its problems]

Generally speaking, in rotating machines, it is 1/2 of the rotational speed of the shaft.
Vibration having a frequency component of (generally called oil whirl) cannot be avoided. The main cause of this is the bearing, but when the natural frequency of the shaft or casing matches the frequency of the oil whirl, the amplitude of the vibration becomes extremely large, significantly reducing the reliability of the rotating machine and its peripheral equipment. For example, an internal pump is installed directly in the reactor core, and for reasons such as thermal insulation and vibration resistance, the nozzle 4 installed at the opening of the reactor 1 as shown in FIG. has a cantilever shape with only the upper end fixed. Water inside the nuclear reactor 1 is circulated by an impeller 2. A motor 3 that provides rotational force to this impeller is located outside the furnace, and its rotating shaft passes through the opening of the furnace. Since the temperature of the furnace is very high, various measures have been taken to prevent this heat from being transmitted to the motor 3, one of which is the gap 6 between the motor case 5 and the nozzle. This gap prevents heat conduction. Therefore, it is only the nozzle upper end 7 that supports the motor 3. Therefore, the natural frequency of the motor 3 as a whole becomes low, approximately 10-odd Hz.

This frequency is approximately the rotational synchronous frequency of the shaft (approximately 25
Hz), and the vibrations caused by the oil whirl mentioned above are magnified. This vibration not only increases bearing wear, but can also lead to destruction of the pressure seal within the motor case.

Now, regarding this problem, several countermeasures have been considered so far. Among them, the method shown in Fig. 2 was considered to be an effective countermeasure. By providing a protrusion 8 on a part of the motor case 5 inside the nozzle 4 and bringing the nozzle 4 and the motor case 5 into partial contact, the motor 3's natural frequency is made higher so that it does not match the frequency of the oil whirl. However, in reality, when the temperature rises, the nozzle 4 has a higher temperature and therefore thermal expansion is large, the protrusions 8 no longer contact each other, and the natural frequency of the motor 3 becomes close to the frequency of the oil whirl. FIG. 3 shows a frequency analysis of the vibration waveform measured at this time, where the horizontal axis represents the frequency and the vertical axis represents the amplitude. Because the frequency of the oil whirl and the natural frequency of the motor matched, the amplitude became extremely large at 1/2ωΝ. However, ωΝ is the rotation frequency of the shaft.

[Purpose of invention]

The object of the present invention is to provide a pump motor that increases the natural frequency of the motor without changing the shape of the pump motor, and that does not generate large vibrations even when oil whirl occurs.

[Summary of the idea]

In order to achieve the above object, the present invention is characterized in that a wedge-shaped member is inserted into a part of the gap between the motor case and the nozzle by utilizing the reaction force of the spring. Even if this occurs, both are constrained by this wedge-shaped member to increase the natural frequency of the motor section and prevent the resonance phenomenon.

[Example of idea]

An embodiment of the invention will be described below with reference to FIGS. 4 and 5. A wedge 9 is pressed by a spring 10 to the lowest part of the gap between the nozzle 4 of the nuclear reactor 1 and the motor case 5. A tapered portion 4a matching the shape of a wedge is formed at the lower end of the nozzle 4. FIG. 5 shows an enlarged sectional view of this part. The bolt 11 together with the washer 12 is used to apply a compressive force to the spring 10. That is, bolt 1 passing through wedge 9
1 is fixed to the nozzle 4 and applies a compressive force to the spring 10. The spring 10 tries to push up the wedge 9 due to its reaction force.

As a result, the nozzle 4 expands due to the heat of the reactor,
Even if the gap 6 between the nozzle 4 and the motor case 5 widens, the wedge 9 will be pushed up by the spring reaction force.
The two always maintain contact. On the other hand, when the furnace cools down and expands again, and the gap 6 changes in the direction of narrowing, the wedge 9 overcomes the spring force and is pushed downward, so that no extra stress is generated on the nozzle 4 or the motor case 5. Since the wedge 9 does not follow short-period forces such as vibrations, the natural frequency of the motor 3 is increased in order to maintain strong contact between the nozzle 4 and the motor case 5 against vibrations and increase rigidity. Become. FIG. 6 shows a method of assembling the device shown in FIG. Although the washer 12 and spring 10 are used here, the same effect can be expected even if a spring washer is simply used instead. Furthermore, the wedges 9 are installed at a plurality of locations in the circumferential direction of the nozzle 4, but it is preferable that all of the wedges are point-symmetrical locations. Further, in this embodiment, the wedge 9 is fixed to the reactor nozzle side, but it may be fixed to the motor case 5.

According to this embodiment, conventionally, the frequency of the oil whirl and the natural frequency of the motor part of the cantilevered internal pump were almost the same.
During rated operation, the frequency component of half of the synchronous frequency ωΝ was extremely large, and very large vibrations were generated as a whole. As the natural frequency of the motor becomes higher and falls into the intermediate region between ωΝ and 1/2ωΝ, the vibrations generated are extremely small as shown in Figure 7, and frequency analysis shows that the 1/2ωΝ component is smaller than the conventional one. becomes extremely small.

[Effect of idea]

As explained above, the pump motor according to the present invention significantly reduces vibration by increasing the natural frequency of the entire motor section and preventing the natural frequency from matching the frequency of the oil whirl as in the past. The reliability of the pump motor itself and its peripheral equipment can be dramatically improved. Another advantage is that it is extremely easy to improve existing machines.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional internal pump, Figure 2 is a partially enlarged cross-sectional view of the attachment part with the reactor nozzle in Figure 1, and Figure 3 shows the frequency of motor case vibration that conventionally occurs. Graphs analyzed and shown,
Figure 4 is a partially enlarged view of the attachment part of the internal pump to the reactor nozzle showing one embodiment of the present invention;
The figure is a partially enlarged sectional view of Fig. 4, Fig. 6 is a schematic diagram showing the assembly method, and Fig. 7 is a graph showing the frequency analysis results of motor case vibration waveforms of conventional internal pumps and the present invention. be. DESCRIPTION OF SYMBOLS 1... Nuclear reactor, 2... Impeller, 3... Motor, 4... Nozzle, 4a... Taper part, 5... Motor case, 6... Gap, 7... Nozzle upper end, 9... Wedge, 10...Spring, 11...Bolt, 12...Washer.

Claims (1)

[Scope of utility model registration request] A wedge-shaped member is pushed into the gap between the motor case and the reactor nozzle from the lower end of the insulation gap using the reaction force of a spring, and this wedge-shaped member is attached to the nozzle side or the motor case side. A pump motor characterized by: