JPH0672613B2 - Electromagnetic bearing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic bearing device, and more particularly to a rotary machine supported by an electromagnetic bearing, which reduces damage to a rotating body and a protective bearing to improve safety. The present invention relates to an electromagnetic bearing device suitable for extending the life.

[Prior Art] In a conventional rotating machine having a magnetically levitated rotating body using an electromagnetic bearing such as a turbo molecular pump, in the case of power loss (power outage) such as power failure or failure of a control circuit. There are several protective bearings to prevent damage to the rotating body. Normally, the protective bearing gear set is set to about 1/2 of the electromagnetic bearing gear set and 0.1 to 0.5 mm.
Therefore, the rotator rotates in a non-contact state when it floats.
Then, when a power loss or the like occurs, the protective bearing is contacted and rotated. Since the protective bearing has a cap, a large vibration load is applied at the time of high-speed rotation, and the protective bearing is damaged, resulting in damage to the rotating body.

In order to prevent this, the present invention developed by the present inventors
In the electromagnetic bearing device of No. 62-17707, the contact part between the support part of the protective bearing and the rotating body is tapered, and when the electromagnetic force of the electromagnetic bearing disappears, the rotating body moves in the axial direction and becomes By rotating the gear with the protective bearing to zero,
It has low vibration and damage to the bearing is negligible. On the other hand, the taper reduces the vibration of the rotating body, but when the power is restored, the rotating body and the protective bearing must be fixed and decomposed. Also, since the spring constants of the protective bearing and the electromagnetic bearing are different, the critical speed of the rotating body changes, and the critical speed of bending is passed when descending, which may damage the rotating body. That is, no consideration was given to vibration when rotating with the protective bearing.

It is also possible to support the protective bearing with a weak spring that is the same as the spring constant of the electromagnetic bearing so that the vibration characteristics do not change. There was a risk of contact with the fixed part and damage to the wings.

[Problems to be Solved by the Invention] In the above-mentioned prior art, no consideration is given to changes in the vibration characteristics of the rotating system when rotating with the protective bearing, and replacement of parts due to damage to the protective bearing or damage to the rotating body is also possible. There was a problem that it was necessary.

The present invention has been made in order to solve the above-mentioned problems in the prior art, and makes the vibration characteristics when rotating the rotating body by the protective bearing close to the state of being supported by electromagnetic force so that the vibration characteristics of both are the same. An object of the present invention is to provide an electromagnetic bearing device that suppresses vibration of a rotating body by means of the above-mentioned method to provide a protective bearing with a higher degree of safety, and also to reduce the vibration force by reducing the gear gap between the protective bearing and the rotating body. It is what

[Means for Solving the Problems] In order to achieve the above object, the structure of an electromagnetic bearing device according to the present invention is an electromagnetic bearing device in which a rotating body is supported by magnetic radial bearings. In an electromagnetic bearing device comprising a protective bearing that rotates in contact with a rotating body when electromagnetic force is lost, and this protective bearing is elastically supported so as to bend in the load direction, the elastically supported protective bearing is It is provided with a means for canceling the bending.

Further, here, the deflection releasing means of the protective bearing is configured to operate by the output of the failure detection circuit of the control circuit.

[Operation] The operation of the above technical means is as follows.

The protective bearing is elastically supported by a spring whose spring constant is almost the same as that of the electromagnetic bearing.In the case of a horizontal rotating machine, it is normally attracted downward by the same amount as the spring deformation due to the bearing load. The center of rotation and the center of the protective bearing should be aligned when levitating. When the electromagnetic force of the electromagnetic bearing disappears due to, for example, a power failure, the rotating body comes into contact with the protective bearing, and at this time, the downward attraction force is released. Due to such an action, the cap of the protective bearing can be set to a necessary minimum and the vibration characteristic does not change, so that the critical speed of bending is not passed.

Further, since the cap of the protective bearing can be set small, a large exciting force does not act and the returning operation becomes simple.

Embodiments Embodiments of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 is a cross-sectional view showing the main structure of a protective bearing portion of an electromagnetic bearing device according to an embodiment of the present invention, and FIG. 2 is A of FIG.
3A is a cross-sectional view and FIG. 3 is an explanatory diagram showing changes in vibration characteristics of the rotating body of FIG.

In FIG. 1, 1 is a bearing housing, 2 is a radial electromagnetic bearing related to a magnetic radial bearing, 3 is a rotor related to a rotating body, and 4 is in contact with the rotating body when the electromagnetic force of the electromagnetic bearing is lost. Rotating protective bearings 5 (generic names of 5a, 5b, 5c, 5d) are springs for elastic support, and 6 is an attraction electromagnet. That is,
The electromagnetic bearing device shown in FIGS. 1 and 2 has a rotor 3 electromagnetically supported by a radial electromagnetic bearing 2 in a bearing housing 1.
And a protective bearing 4 for maintaining the rotation of the rotor 3 in the event of power failure such as power failure. Protective bearing 4
Is elastically supported by a spring 5 and pulled downward by a force corresponding to a bearing load by an attraction electromagnet 6 so that the center of the radial electromagnetic bearing 2 and the center of the protective bearing 4 are aligned with each other. .

When a power failure such as a power failure occurs, the electromagnetic force of the radial electromagnetic bearing 2 disappears, and at the same time, the attraction force of the attraction electromagnet 6 also disappears. At this time, the rotor 3 contacts the protective bearing 4 and maintains rotation. In the protective bearing 4, instead of the attracting force of the attracting electromagnet 6 that has been acting, the weight of the rotor 3 of the same size acts, and as a result, the center of rotation of the rotor 2 does not change from the center of rotation during normal operation. Although not shown here, it is possible to avoid contact between the annular seal portion or the blade tip of the rotor 3 and the fixed portion (casing or the like).

FIG. 3 shows the vibration characteristics of the rotating body supported by the electromagnetic bearing, and has the amplitude response shown by the solid line. In general, the spring constant of an electromagnetic bearing is smaller than that of a normal bearing, so that it passes through the critical speeds 7 and 8 in the rigid body mode in which the entire rotor vibrates as a rigid body at a low rotation speed. The rated speed is much higher than the critical speeds 7 and 8 and is set lower than the critical speed 9 in the bending mode in which the rotating body vibrates elastically.

When a power failure such as a power failure occurs, the spring constant of a protective bearing that is not elastically supported by springs is 10 to 100 times larger than the spring constant of an electromagnetic bearing. Although it disappears, the critical speed 9 in the bending mode decreases and the critical speed 10 in the bending mode shown by the broken line in the figure
Will be below the rated speed. If the power is cut off at the rated speed, when using the protective bearing to lower the speed,
Since the critical velocity of bending 10 is passed, the vibration width sharply increases, the rotating body comes into contact with the fixed portion, and the rotating body is damaged.

On the other hand, in the elastic support type protective bearing of this embodiment, if the spring constant is set to be substantially equal to the spring constant of the radial electromagnetic bearing 2, the vibration characteristics at the time of normal rotation and at the time of rotation by the protective bearing become equal, and bending It is not necessary to exceed the critical speed of 10 and you can safely descend.

Further, since the protective bearing 4 is normally sucked downward, the gear gap between the protective bearing 4 and the rotor 3 can be reduced. If not sucked downward, the protective bearing 4
Is eccentric downward due to the weight of the rotor 3, so that the rotating body comes into contact with the fixed portion.

When the rotor is supported by two protective bearings, the radial gear gap δ between the protective bearing and the rotor is set as follows.

Now, assuming that the rotor weight is 2 W, the maximum rotational angular velocity of the rotor is ω, and the gravity acceleration is g, when the friction between the protective bearing and the rotor is ignored,
In order to prevent the rotor 3 from swinging in the gear of the protective bearing 4, it is a condition that its own weight is larger than the centrifugal force of the rotor. That is, Should be satisfied. Therefore, the gear σ is Becomes

According to this embodiment, when the rotor 3 is rotated by the protective bearing 4, the rotor 3 is supported by the same spring constant as the radial electromagnetic bearing 2, so that the vibration characteristics of the rotating system do not change and the critical velocity of bending can be passed. Since the protective bearing 4 can be sucked downward, the gear gap of the protective bearing can be reduced, and the value δ
To By setting to 3, the whirling of the rotor 3 can be prevented.

From this, it is possible to suppress the vibration of the rotating body small,
Damage to the protective bearing is a minor sign, and a safe rotating machine can be provided.

Next, FIG. 4 is a partial sectional view of a protective bearing portion according to another embodiment of the present invention. The electromagnetic bearing portion not shown in FIG. 4 is the same as that in FIG. 1, and those having the same reference numerals as those in FIG. 1 are the same portions as the embodiment of FIG. .

The embodiment shown in FIG. 4 employs a hook 12 and a restoring spring 13 as means for bending the protective bearing 4 in the load direction, instead of the attraction electromagnet 6 shown in FIG. This hook 12, restoration spring
What is constituted by 13 is also a means for canceling the bending in the load direction.

That is, normally, the protective bearing 4 is pulled downward by the hook 12, and when the power is cut off, the electromagnetic force disappears and the rotor 3 comes into contact with the protective bearing 4, and the weight of the rotor 3 acts on the protective bearing 4. Move down. Then, the hook 12 is rotated by the restoring spring 13 and is separated from the protective bearing 4, so that the rotor 3 can be kept rotating without the rotational centers of the protective bearing 4 and the rotor 3 being displaced.

According to the embodiment of FIG. 4, the same effect as that of the previous embodiment is expected, and there is an effect peculiar to this embodiment that the hook 12 can be released automatically. Further, although not particularly shown, the hook 12 can be configured to be released in synchronization with a signal from the failure detection circuit of the control circuit.

Next, an embodiment in which the protective bearing is supported by an anisotropic spring will be described. Here, the anisotropic spring means a spring having a different amount of deflection in the vertical direction.

FIG. 5 is a partial sectional view of a protective bearing portion according to still another embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 are the same parts, and the description thereof will be omitted.

In the embodiment of FIG. 5, the protective bearing 4 has one spring 5 on the upper side.
a, the lower side is supported by three springs 5b. in this way,
The lower side receiving the load of the rotor 3 is supported by a large number of springs.

As a result, the normal time when the load does not act on the protective bearing 4,
Since the electromagnetic force disappears due to a power failure such as a power failure and the rotor 3 rotates in the protective bearing 4 and the load of the protective bearing 4 acts on the protective bearing 4, the movement of the center of the protective support 4 can be reduced.
It is possible to reduce the gear gap between the rotor 3 and the rotor 3, and to provide a stable rotating machine with low vibration.

Next, FIG. 6 is a partial sectional view of a protective bearing portion according to still another embodiment of the present invention, and FIG. 7 is a displacement / load diagram of the laminated leaf spring shown in FIG. In the figure, the same symbols as those in FIG.

In the embodiment of FIG. 6, the protective bearing 4 is an arc-shaped laminated spring 14
Is supported by. The laminated leaf spring 14 is a so-called anisotropic spring having a different amount of deflection (displacement) depending on the vertical direction, as shown in the displacement-loading diagram of FIG. This spring has a large spring constant with respect to downward displacement, while there is a dead zone when it is displaced upward, that is, there is a region where a load is not generated even if it is displaced, and when it is further displaced, the spring constant gradually increases. .

Therefore, even if the weight of the rotor 3 acts on the protective bearing 4, its deflection is small, so that the center of the protective bearing is the same as in the normal state, and the gear gap can be recognized as small. Further, the average spring constant of the protective bearing does not increase, and the change in vibration characteristics is small. Therefore, it becomes a safe protective bearing.

If lubricating oil is injected between the laminated leaf springs 14, naturally a damping effect can be expected.

FIG. 8 is a plan view of a protective bearing portion according to still another embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 indicate the same parts. The embodiment shown in FIG. 8 is another embodiment of the anisotropic spring-supported protective bearing described in the embodiment shown in FIG.

The protective bearing 4A is supported by weak springs 5a, 5c, 5d and a strong spring 5b in the load direction.
The notch 4b is formed on the inner circumference of the 4a.

According to this structure, when the rotor 3 rotates with the protective bearing 4A, the contact surface pressure increases, the contact position between the rotor 3 and the inner ring 4a becomes stable, and the rotor 3 does not easily swing around in the inner ring 4a. There is an effect peculiar to this embodiment that the load direction is constant.

[Effects of the Invention] As described above, according to the present invention, the vibration characteristics when the rotating body is rotated by the protective bearing are brought closer to the state of being supported by the electromagnetic force, and the vibration characteristics of both are made to be similar to each other. It is possible to provide an electromagnetic bearing device that suppresses the vibration of the body to form a protective bearing with a higher degree of safety and reduces the gear gap between the protective bearing and the rotating body to reduce the vibration force.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the main structure of a protective bearing portion of an electromagnetic bearing device according to an embodiment of the present invention, and FIG. 2 is A of FIG.
-A sectional view, FIG. 3 is an explanatory view showing changes in vibration characteristics of the rotating body of FIG. 1, and FIG. 4 is a partial sectional view of a protective bearing portion according to another embodiment of the present invention. FIG. 6 and FIG. 6 are partial sectional views of a protective bearing portion according to still another embodiment of the present invention, FIG. 7 is a displacement / load line diagram of the laminated leaf spring of FIG. 6, and FIG. FIG. 7 is a plan view of a protective bearing portion according to still another embodiment of the present invention. 1 ... Bearing housing, 2 ... Radial electromagnetic bearing, 3 ...
… Rotor, 4,4A …… Protective bearing, 5,5a, 5b, 5c, 5d …… Spring, 6 …… Suction electromagnet, 12 …… Hook, 13 …… Restoring spring, 14 …… Layered leaf spring.

Front page continuation (72) Inventor Ikuhiro Saito 502 Jinritsu Machinery Co., Ltd., Tsuchiura City, Ibaraki Pref., Mechanical Research Laboratory, Inc. (72) Inventor Tomoaki Inoue, 502 Jinritsucho, Tsuchiura City, Ibaraki Co., Ltd. (56) References JP-A-62-194025 (JP, A) JP-A-58-65321 (JP, A) JP-B-61-57493 (JP, B1)

Claims (2)

[Claims] 1. An electromagnetic bearing device in which a rotating body is supported by a magnetic radial bearing, and a protective bearing is provided which rotates in contact with the rotating body when the electromagnetic force of the electromagnetic bearing is lost.
In an electromagnetic bearing device elastically supported so as to bend in the load direction, the elastically supported protective bearing includes means for canceling the bend in the load direction. 2. The electromagnetic bearing device according to claim 1, wherein the deflection releasing means of the protective bearing is configured to operate with the output of the failure detection circuit of the control circuit.