JPS6147326B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-contact magnetic bearing, and particularly to a structure that increases centripetal force and damping force.

Figure 1 shows the structure of a conventional magnetic bearing. A rotor yoke 2 is attached to a rotatable shaft 1, and inner rotor teeth 2a having diameters D ₁ and D ₂ and a diameter
Outer rotor teeth 2b having D ₃ and D ₄ are integrally formed with the rotor yoke 2 to form a rotor.
A conductor 3 is made of a non-magnetic material and is arranged to surround the rotor teeth 2a and 2b. Stator yokes 5a and 5b are attached to both ends of the permanent magnet 4, and one end of the stator yoke has inner stator teeth 6a having diameters D ₁ and D ₂ and outer stator teeth 6a having diameters D ₃ and D ₄ . The stator teeth 6b face the rotor teeth with the same diameter. The non-magnetic conductor 3 is attached to the stator yoke.

In general, magnetic bearings require a large restoring force in the radial direction in order to operate the rotating body stably at high speeds, and when the rotating body vibrates due to unbalance etc., changes in the magnetic flux passing through the non-magnetic conductor occur. An eddy current is generated and damps the vibration of the rotating body.
The so-called damping force also requires a large value.

In the magnetic bearing shown in Fig. 1, the radial dimensions of the opposing rotor teeth and stator teeth are the same, so the restoring force in the radial direction has a large value, as shown by the dashed-dotted curve in Fig. 6. can get. However, as mentioned above, since the radial dimensions of the rotor teeth and stator teeth are the same,
Since the magnetic flux is concentrated on the opposing tooth portions, less magnetic flux passes through the recessed portions 3a, 3b, 3c, and 3d of the nonmagnetic conductor 3. For this reason, the generated eddy current is small, and its damping force also becomes a small value as shown by the dashed-dotted curve in FIG. 7, making it impossible to suppress the vibration of the rotating body. For this reason, it has not been possible to stably operate the rotating body up to high speeds.

In order to improve the shortcoming of the small damping force shown in Figure 1,
As shown in FIG. 2, the inner stator teeth 6a' facing the inner rotor teeth 2a with a tooth width t ₁ having diameters D ₁ and D ₂ are
Shift in the outer radial direction by more than t ₁ to set D ₁ ′, D ₂ ′
The outer stator teeth _6b ' facing the outer rotor teeth 2b with a tooth width _t2 are shifted in the outer radial direction by the tooth width _t2 or more at D3 _and D4 to have diameters _D3 ' and _D4 '. There is something I did. By configuring the tooth dimensions such that D ₂ < D ₁ ′ and D ₄ < D ₃ ′, the magnetic flux density distribution diagram of the inner tooth portion in Fig. 3 (the magnetic flux distribution of the outer tooth portion has a similar tendency) ), the magnetic flux is distributed radially away from the center of the rotor teeth. Therefore, the non-magnetic conductor 3
Since the magnetic flux passing through the leaning parts 3b and 3d increases, the eddy current generated by the vibration of the rotating body becomes larger than that in Fig. 1, and the damping force is
The value becomes large as shown by the broken line in the figure. In this way, the damping force of the one shown in FIG. 2 is larger than that of the one shown in FIG. , 3c, the magnetic flux is not so distributed in the portions 3a, 3c.
was not working effectively. On the other hand, as for the restoring force in the radial direction in Fig. 2, the magnetic flux distributed from the stator teeth to the tips 7 and 8 of the rotor teeth is small, so the value of the restoring force in the radial direction is the same as that in Fig. 1, as shown by the broken line in Fig. 6. The value was smaller than that of the previous one. For this reason, it was not possible to provide an accurate center position to the rotating body, making the magnetic bearing unsuitable for operation up to high speeds.

An object of the present invention is to provide a magnetic bearing that has large vibration damping force and centripetal force and is suitable for high-speed rotation, while eliminating the drawbacks of the prior art described above.

The magnetic bearing of the present invention comprises: (a) a rotating shaft; (b) a rotor yoke fixed to the shaft and having rotor teeth; and (c) facing the rotor teeth through a gap. stator teeth provided on the stator yoke;
(d) a permanent magnet or an electromagnet provided at the other end of the stator yoke; and (e) a nonmagnetic conductor attached to the stator tooth so as to surround the tip of the rotor tooth. In the magnetic bearing, the stator tooth (c) has an outer diameter larger than the outer diameter of the rotor tooth, and an inner diameter smaller than the inner diameter of the rotor tooth, and It is characterized by having a groove at the tip.

The present invention achieves the following by providing grooves in the stator teeth.
It is possible to distribute a large amount of magnetic flux not only to the upper surface of the tip of the rotor tooth but also to the side surface of the tip. Since a large amount of magnetic flux can be distributed, it is possible to provide a magnetic bearing with a large vibration damping force and a large centripetal force.

An embodiment of the present invention will be described below with reference to FIG. In FIG. 4, parts that are the same as those in FIGS. 1 and 2 are given the same reference numerals, and their explanations will be omitted. The difference between Figure 4 and Figures 1 and 2 is that the diameter
The diameters D _{1 ″} , D ₂ ″ of the inner stator teeth 6a″ facing the inner rotor teeth 2a having D ₁ , D ₂ are set as D ₁ >D ₁ ″, D ₂ <
D ₂ '', and the diameter D _{3 '} ' of the outer stator tooth 6b'' facing the outer rotor tooth 2b having diameters D ₃ and D ₄ ,
D ₄ ″ is configured in the relationship D ₃ > D ₃ ″, D ₄ < D ₄ ″, and the stator teeth 6 a ″, 6 b″ are connected to the rotor teeth 2 a, 2 ″.
This is because grooves S having groove widths W ₁ and W ₂ larger than the tooth widths t ₁ and t ₂ of b are provided.

By doing this, the magnetic flux expands around the rotor teeth 2a, as shown in the magnetic flux density distribution diagram of the inner tooth portion shown in Fig. 5 (the magnetic flux density distribution diagram of the outer tooth portion also shows a similar tendency). is distributed accordingly. Therefore,
A large amount of magnetic flux is also distributed in the recessed portions 3a and 3c of the nonmagnetic conductor 3. In addition, rotor teeth 2a, 2b
A high magnetic flux density can also be obtained at the tip portions 7 and 8 of. Therefore, the restoring force in the radial direction of the device shown in FIG. 4 of the present invention has a larger value than that of the conventional device shown in FIG. 2, as shown by the solid line in FIG. Since it is about the same as that shown in the figure, it is possible to give an accurate center position to the rotating body. On the other hand, as mentioned above, in the conventional device shown in FIG. 2, almost no magnetic flux is distributed in the recessed portions 3a and 3c of the non-magnetic conductor 3, so these portions are not effectively utilized as damping force. In the case of FIG. 4 of the present invention, a large amount of magnetic flux is distributed over all the sagging portions of the nonmagnetic conductor, so that the sagging portions can be used as effectively as possible as vibration damping force. Therefore, as shown by the solid line in FIG. 7, the damping force of the present invention is greater than that of the conventional first
Larger values are obtained compared to those in FIGS. Therefore, the vibration of the rotating body can be suppressed more than ever before, and the reliability of the device is further improved.

In addition, as shown in FIG. 8, the inner stator tooth tip 9a
and 9a' are smaller than the tooth width t ₁ of the inner rotor teeth, and _{W 4 of} the grooves S of the outer stator tooth tips 9b and 9b' are smaller than the tooth width t of the outer rotor teeth 2b. The same effect can be obtained even if the value is smaller than ₂ . moreover,
As shown in FIG. 9, if the inner teeth have the conventional structure shown in FIG. 1 and the outer teeth have the structure of the present invention, an even larger restoring force in the radial direction can be obtained. Further, the shape of the groove may be various shapes such as a triangle or a semicircle as shown in FIG. 10.

Further, even if two stator teeth integral with the stator yoke are provided on the inner side and the outer side as shown in FIG. 11, the same effect as shown in FIG. 4 is obtained.

According to the present invention, the restoring force in the radial direction is increased,
Moreover, since a magnetic bearing with a large vibration damping force can be obtained,
Rotating bodies can be operated stably up to high speeds.
In addition, even if the material of the non-magnetic conductor, which is generally used as the vibration damping material of the magnetic bearing of the present invention, is changed from expensive copper to inexpensive aluminum, the damping force will be greater than that of the conventional one. Due to the relationship of specific resistance<specific resistance of aluminum, aluminum material has a smaller vibration damping force if the volume arrangement is the same.) By using this aluminum material, the cost of the magnetic bearing itself can be significantly reduced. Furthermore, since the process of balancing the rotating body can be shortened, it can contribute to lowering the cost of the entire apparatus. Furthermore, since it is possible to provide a strong magnetic bearing against unstable vibrations caused by earthquakes or disturbances in laminar flow, the reliability of the device is improved.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of conventional magnetic bearings;
Fig. 3 is a magnetic flux density distribution diagram of the inner tooth portion of Fig. 2, Fig. 4 is a cross-sectional view of a magnetic bearing showing an embodiment of the present invention, and Fig. 5 is a magnetic flux density distribution diagram of the inner tooth portion of Fig. 4. Figure 6 is a graph showing the characteristics of the radial restoring force with respect to the magnetic gap, Figure 7 is a graph showing the characteristics of the damping force with respect to the magnetic gap, Figures 8 and 9 are graphs showing the characteristics of the damping force with respect to the magnetic gap.
10 and 11 are partial cross-sectional views of magnetic bearings showing other embodiments. 1... Shaft, 2a... Inner rotor tooth, 2b... Outer rotor tooth, 3a, 3b, 3c, 3d... Recessed portion of non-magnetic conductor, 6a, 6a', 6a''... Inner stator Teeth, 6b, 6b', 6b''...outer stator teeth,
S...Groove, _t1 , _t2 ...Rotor tooth width, _W1 , _W2 ,
W ₃ , W ₄ ...Groove width, 9a, 9a'... Tips of inner stator teeth, 9b, 9b'... Tips of outer stator teeth.

Claims (1)

[Claims] 1. A rotating body consisting of (a) a rotating shaft, (b) a rotor yoke fixed to the shaft and having rotor teeth, and (c) a rotor provided on the stator yoke so as to face the rotor teeth via a gap. (d) a permanent magnet or an electromagnet provided at the other end of the stator yoke; and (e) a permanent magnet or an electromagnet attached to the stator tooth so as to surround the tip of the rotor tooth. In a magnetic bearing comprising a non-magnetic conductor, the stator tooth (c) has an outer diameter larger than the outer diameter of the rotor tooth, and an inner diameter smaller than the inner diameter of the rotor tooth. What is claimed is: 1. A magnetic bearing, characterized in that the stator teeth have grooves at their tips.