JPH0297713A - Rotating machine using five-axis control magnetic bearing - Google Patents

Abstract

PURPOSE:To make high speed, light weight, and high efficiency with natural vibration increased by mounting a radial bearing rotar on the outer periphery of a thrust bearing disk to use as radial bearing, and pivotally supporting three axes including a five-axis middle axis direction at one place. CONSTITUTION:A radial bearing rotar 59 is shrinkage-fitted to the middle small diameter part 50a of a thrust magnetic bearing disk 50, and the stator 58 corresponding to the rotar 59 is fixed to the inner side of a bearing casing 40. Consequently the peripheral velocity of the rotar 59 can be made low, the whole length of a rotar shaft short, bending mode natural vibration increased, and thereby light weight and high efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a five-axis controlled magnetic bearing, that is, an
, A magnetic bearing that controls five degrees of freedom of movement: two degrees of freedom of movement in the Y direction (2 axes x 2) and one degree of freedom of movement in the connecting axis (Z) direction (1 axis). It is particularly suitable for use as radial and thrust bearings in turbo machines such as pumps and compressors.

[Prior Art] Conventionally, a motor pump, which is a type of turbomachine equipped with the above-mentioned five-axis control magnetic bearing, has the following characteristics, as shown in FIG.
A rotor shaft 3 to which an impeller 2 is attached by a shaft end nut 1 has a touchdown bearing 4 which functions as a thrust and radial emergency bearing, a non-thrust side radial magnetic bearing consisting of a stator 5 and a rotor 6, and a thrust side radial touch bearing. A thrust side radial magnetic bearing consisting of a down bearing 7, a stator 8 and a rotor 9, and a disk (rotating disk N
It is supported by a thrust magnetic bearing consisting of an O and excitation coils 11 (two pieces), and is driven by an electric motor consisting of a stator 12 and a stator 13. In the figure, 2a is a balancing hole of an impeller; 14 is a radial sensor on the anti-thrust side, 15 is a radial sensor on the thrust side, 16 is a thrust sensor, 17 is a suction casing of the pump, 18 is a discharge port, 19 is a motor casing, 19a is the same cover, 2
0 is a thrust bearing casing, and 20a is a cover thereof.

During pump operation, the unbalance of the axial thrust caused by the pump discharge pressure that acts on the side plate (shroud) and main plate of the impeller 2 is balanced ( A thrust sensor 16 installed at the end (right end in the figure) of the rotor shaft (pump shaft) 3 detects the displacement behavior of the rotor shaft 3, and the remaining axial thrust is generated by excitation of the thrust magnetic bearing. coil 11
On the other hand, regarding displacement due to radial load, the displacement behavior of the rotor shaft 3 is detected by a non-contact radial sensor 14, 15, and this is input to a negative feedback circuit (not shown). By controlling the excitation current of the load electromagnet 5.8, the rotor shaft 3 is supported in a floating manner, and the pump impeller 2 and the rotor shaft 3 are held at proper positions in the radial direction. The above-mentioned magnetic bearing is of an active type with a large floating blade because it is necessary to support the weight of the rotating body.

[Problem to be solved by the invention]

In a rotating body that uses the conventional 5-axis active magnetic bearing as described above, the natural frequency of the bending mode (first order for bending, but fifth order for rotating body behavior) is sufficiently far from the operating rotational speed. preferably on the higher side than the operating speed.

Although it is of course possible to rotate the rotating body at a rotation speed higher than the natural frequency of the first bending mode, it requires ultra-precise balancing and special consideration must be given to the rotation adjustment, so it is time-consuming. required, and not necessarily advantageous. Particularly when applied to turbomachines such as pumps and compressors, disturbances due to fluid reaction force are applied to the rotating body, so it is desirable that the rotating body be rigid.

On the other hand, there are two factors that reduce the rigidity of the rotating body: (i) a large slenderness ratio of the shaft; and (ii) itt being mounted at a point far from the fulcrum (bearing).

In these respects, a rotating body supported by five-axis magnetic bearings has a relatively small load capacity per unit area of the bearing, so the area of each bearing is relatively large (although it is necessary to Bearings are often installed at the end of the shaft due to various constraints, and are formed as disks with a relatively large diameter, so from the above point of view, the problem is that they have a large effect on the natural frequency of the bending mode of the shaft. There was a point.

The present invention solves the above problems, reduces the influence on the natural frequency of the thrust bearing to almost zero, and thereby provides a five-axis controlled magnetic bearing that relatively easily forms a rotating body with a high natural frequency. The purpose is to provide rotating machines using

[Means to solve problems]

In order to achieve the above object, the present invention provides a rotating machine using a 5-axis control magnetic bearing, in which a radial bearing rotor is attached to the outer periphery of a thrust bearing disk, the rotor is used as a radial bearing, and a 5-axis control magnetic bearing is used. It is characterized in that support for three axes including the central axis direction is concentrated in one location.

The above-mentioned thrust magnetic bearing disk can be made into a prefabricated type, and a radial bearing rotor can be attached to the small diameter portion at the center.

[Function] Since the present invention is configured as described above, the thrust magnetic bearing and the thrust-side radial magnetic bearing configured by attaching the radial bearing rotor to the outer periphery of the thrust magnetic bearing disk provide the following advantages: Support for three axes including the mid-axis direction is concentrated in one location.

As a result, the total length of the rotor shaft is shortened, and by supporting the rotor in the radial direction close to the center of gravity of the thrust bearing disk, the mass effect of the disk can be almost eliminated, and the bending mode characteristic of the entire rotor can be reduced. Thick (can contribute to increasing the vibration frequency.

Therefore, when the shaft diameter is the same, the rotation speed can be high, and when the rotation speed is the same, the shaft can be made thinner, and in either case, it is possible to reduce the weight and increase the efficiency.

Further, in the case where a radial magnetic bearing rotor is attached to the central small diameter portion of the thrust magnetic bearing disk, the circumferential speed of the rotor is reduced, and it is possible to cope with an increase in the speed of the rotor shaft.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG.
3 is a vertical cross-sectional view of a motor pump using a shaft-controlled magnetic bearing; in the figure, the same reference numerals as those shown in FIG. 3 indicate the same or similar parts.

In the figure, a rotor shaft 3 to which an impeller 2 is attached by a shaft end nut 1 is supported by a five-axis control 11fa air bearing consisting of two radial magnetic bearings and one thrust magnetic bearing at the shaft end. The anti-thrust side radial magnetic bearing among the radial magnetic bearings is connected to the motor casing 39.
There is no difference from the conventional one (Fig. 3) in that it consists of a stator 5 fixed inside the rotor shaft 3 and a rotor 6 fixed to the rotor shaft 3, but in this embodiment (the present invention), the thrust side radial magnetic The bearing is different in that the rotor 29 of the bearing is attached to the outer periphery of the air bearing disk 30 by firing or other method, and the rotor 29 and the disk 30 are integrated, and is characterized by this point. .

A stator 28 having an excitation coil corresponding to the rotor 29 is fixed inside a thrust bearing casing 40a, and the thrust magnetic bearing coils 31 facing on both sides of the disk 30 are different from the conventional one (FIG. 3). Similarly, they are fixed to the motor casing cover 39a and the thrust bearing casing cover 40a, respectively. Therefore,
Support for three axes including the five axes in the central axis direction is concentrated in one location.

In the figure, 2a is the balancing hole of the impeller, 4 and 7 are the touchdown bearings, 12 and 13 are the stator and rotor of the electric motor, and 1
4 and 35 are radial sensors, 16 is a thrust sensor
− ゛.

Next, to explain the effect, during pump operation, the unbalance of the axial thrust due to the pump discharge pressure acting on the side plate and main plate of the impeller 2 is balanced by the effect of the balancing hole 2a of the impeller 2, and the remaining The axial thrust of thrust magnetic bearing 3
0.31, and for radial loads, the thrust side consists of an anti-thrust side radial magnetic bearing 5.6, and a radial bearing rotor 29 and stator 28 attached to the outer periphery of the thrust magnetic bearing disk 30. It is supported by a radial magnetic bearing, and support for three axes including the five axes in the axial direction is concentrated at one location at the end of the shaft.

As a result, the total length of the rotor shaft 3 is significantly shortened as compared to the conventional example shown in FIG.
By supporting the disk 30 in the radial direction, the mass effect of the disk 30 can be almost eliminated, and the bending mode natural frequency of the entire rotor of the rotating machine can be increased.

In this type of rotor, another overhanging (cantilevered) mass is the impeller, which is made of low specific gravity material such as A2 alloy or Ti alloy for pumps, blowers, etc. to which the present invention is applied. In addition to the fact that turbomachinery has the property that its diameter decreases in inverse proportion to the square of the number of revolutions, the effect on the problem of natural frequency when increasing speed is not as serious as that shown above. On the other hand, Slus) 61
For the 1-air bearing disk 30, a magnetic material (usually a steel material) must be used, and the diameter is determined only by the magnitude of the axial thrust. There is only a possibility that the outer diameter of the disk 30 can be reduced by the weight reduction of the entire rotor due to the increased rotation speed, and it can be said that the disk itself is almost unrelated to the rotation speed. (In addition, when balancing the fluid thrust using the impeller's balancing hole, it is necessary to increase the size as the head increases.) Therefore, the influence of this type of thrust on the natural frequency of the air bearing disk. can be said to be relatively large, but as mentioned above, with the zero-stroke thrust magnetic bearing disk 30, the above-mentioned influence can be almost eliminated, and as mentioned above, the bending mode of the entire rotor It can increase the vibration frequency.

FIG. 2 is a sectional view of a main part showing another embodiment of the present invention, and in the figure, the same reference numerals as those shown in FIG. 1 indicate the same or similar parts.

In this embodiment, the thrust magnetic bearing disk 50 is of an assembly type, and a radial bearing rotor 59 is attached to the central small diameter portion 50a by firing or other method, and the stator 58 corresponding to the rotor 59 is , is fixed inside the bearing casing 40.

According to this embodiment, the radial magnetic bearing rotor 59 is
Since the thrust [air] is attached to the small diameter portion 50a of the bearing disk 50, the circumferential speed of the rotor 59 is reduced,
Therefore, even if the speed of the rotor shaft 3 is increased, no strength problems occur, and the same effect can be produced while reducing the circumferential speed.

In the above-mentioned embodiment, an example was explained in which the impeller 2 was provided with the balancing hole 2a as a means for reducing fluid thrust. However, a balance piston or a balance disk may be used, or the impeller Even if the structure is made such that one impeller and the other impeller with the suction port in the opposite direction are attached to the above one impeller or the thrust disk side to cancel out the axial thrust, there will be no problem at all. A similar effect is produced.

Further, although an example in which the magnetic bearing according to the present invention is applied to a motor pump has been described, it goes without saying that it can be similarly applied to other rotating machines.

[Effects of the Invention] As explained above, according to the present invention, in a rotating machine using a five-axis controlled magnetic bearing, a radial bearing rotor is attached to the outer periphery of a thrust bearing disk, and the rotor is used as a radial bearing. However, by concentrating the support of 3 axes including the 5 axes in the middle axis direction in one place,
The total length of the rotor shaft can be shortened, and the bending mode natural frequency of the entire rotor can be significantly increased.

Therefore, when the shaft diameter is the same, the rotation speed can be high, and when the rotation speed is the same, the shaft can be made thinner, and in either case, it is possible to reduce the weight and increase the efficiency.

In addition, by making the thrust magnetic bearing disk an assembled type and attaching the radial bearing rotor to the small diameter part in the center, the circumferential speed of the rotor is reduced, so there are no strength problems even when the rotor shaft speeds up. .

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a motor pump using a 5-axis control magnetic bearing showing one embodiment of the present invention, Fig. 2 is a sectional view of main parts showing another embodiment of the invention, and Fig. 3 is a conventional FIG. 2 is a longitudinal cross-sectional view of a motor pump showing an example. 2... Impeller, 2a... Balancing hole, 5... Radial magnetic bearing stator, 6... Radial magnetic bearing rotor,
12... Electric motor stator, 13... Electric motor rotor,
14.35... Radial sensor, 16... Thrust sensor, 28.58... Radial magnetic bearing stator,
29.59...Radial magnetic bearing rotor, 30.50
... Thrust magnetic bearing disk, 31.51... Excitation coil. Foil 1 diagram

Claims (1)

[Claims] 1. The displacement behavior of the rotating body is detected by a non-contact displacement sensor, and this is input to the negative feedback circuit to control the excitation current of the load electromagnet, thereby levitating the rotating body. In rotating machines that use active magnetic bearings as bearings, a radial bearing rotor is attached to the outer periphery of the thrust bearing disk, and the rotor is used as a radial bearing to support three axes, including the five axes in the center axis direction, in one place. A rotating machine using a 5-axis control magnetic bearing, which is characterized by being able to perform operations in a concentrated manner. 2. The thrust bearing disk is an assembly type, and the radial bearing rotor is attached to the outer periphery of the central portion of the disk where the diameter is reduced.
Rotating machinery using axis-controlled magnetic bearings.