JP3206044B2 - Composite superconducting bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A composite superconducting bearing device according to the present invention is used, for example, to support a rotating shaft rotating at an extremely high speed in a non-contact state.

[0002]

2. Description of the Related Art A rotating shaft rotating at an extremely high speed cannot be supported by ordinary bearing devices such as a sliding bearing and a rolling bearing, and it is necessary to support the rotating shaft in a non-contact state. Thus, in recent years, as a bearing device for supporting the rotating shaft in a non-contact state,
A superconducting bearing device that supports the rotating shaft in a floating state by utilizing the pinning effect of the superconductor has been studied.

FIGS. 5 and 6 show superconducting bearing devices that have been proposed in the past, which are described on page 18 of "Summary of 1991 Spring Conference on Low Temperature Engineering and Superconductivity". This conventionally known superconducting bearing device is:
It is intended for a bearing in the thrust direction, and is constituted by a plurality of pellets 2 and 2 made of superconducting material facing a ring-shaped permanent magnet 1 as shown in FIG. The permanent magnet 1 and the pellets 2, 2 are embedded in copper disks 3, 4, respectively. Further, pellets 2 and 2 made of an yttrium-based oxide superconducting material (for example, YBa ₂ Cu ₃ Ox) are arranged concentrically and face the permanent magnet 1.

If the pellets 2 and 2 are brought into a superconducting state by cooling the disk 4 in which the pellets 2 and 2 are embedded, a pinning effect acting between each of the pellets 2 and 2 and the permanent magnet 1 results. Thus, a force is generated in a direction that prevents the distance between each of the pellets 2 and 2 and the permanent magnet 1 from changing. That is, when each of the pellets 2 and 2 is in a superconducting state, the magnetic flux emitted from the permanent magnet 1 is restrained in each of the pellets 2 and 2.
Pinning force occurs.

When the distance between the permanent magnet 1 and the pellets 2 and 2 tends to increase based on this pinning force, an attractive force acts between the two members 1 and 2 and conversely, the permanent magnet 1
When the distance between the pellets 2 and 2 tends to decrease, a repulsive force acts between the members 1 and 2. The distance between the permanent magnet 1 and the pellets 2 and 2 is kept constant by such attraction or repulsion. Further, the positional relationship between the permanent magnet 1 and the pellets 2 and 2 in the plane direction is also prevented based on the pinning force. Therefore, if the permanent magnet 1 is fixed to a rotating shaft, the rotating shaft can be rotatably supported in a floating state.

FIG. 6 shows a state in which the rotating shaft 5 is rotatably supported by the superconducting bearing device having the above-described principle. A pair of circular plates 4a, 4a in which a plurality of pellets 2, 2 are respectively embedded are arranged in parallel with a space therebetween, and can be cooled by liquid nitrogen stored in a cooling jacket 7 of a housing 6. I have. A circular plate 3a is fixed to a portion between the pair of circular plates 4a, 4a at an intermediate portion of the rotary shaft 5 inserted inside the pair of circular plates 4a, 4a. The permanent magnets 1 and 1 embedded on the upper and lower surfaces of the circular plate 3a are opposed to the pellets 2 and 2, respectively. An electric motor 8 is provided at an end of the rotating shaft 5 so that the rotating shaft 5 can be driven to rotate.

Liquid nitrogen is fed into the cooling jacket 7 and the pellets 2, 2 embedded in the circular plates 4a, 4a are introduced.
Is in a superconducting state, the circular plate 3a fixed to the intermediate portion of the rotary shaft 5 does not move toward and away from the circular plates 4a and 4a, and the rotary shaft 5 is in a floating state. And the rotating shaft 5 can be rotated.

[0008]

However, superconducting bearing devices, including those of the structure proposed in the prior art, tend to have lower rigidity in the radial direction than rigidity in the thrust direction. In the case of the conventional structure shown in FIG.
Since the pellets 2 and 2 made of the superconducting material and the permanent magnets 1 and 1 are opposed to each other in the thrust direction, the rigidity and load capacity in the radial direction are particularly low, but the superconductor and the permanent magnet are temporarily displaced in the radial direction. Even when they face each other, it is difficult to obtain sufficient radial rigidity and load capacity (although the radial rigidity and load capacity are improved as compared with the structure shown in FIG. 6).

For this reason, when rotating the rotating shaft inside the bearing housing or rotating the rotor around the pivot, the rotating speed of the rotating shaft or the rotor is increased beyond the critical speed. I can not let it. That is, the rotating members such as the rotating shaft and the rotor always have a unique resonance frequency in consideration of the bearing rigidity and the like. When the rotation speed of the rotating member that has been stopped until then is increased, if the rotation speed matches the resonance frequency, a so-called whirling phenomenon occurs in which the rotating member is severely displaced in the radial direction. The rotation speed at which such a whirling phenomenon occurs is referred to as the critical speed of the rotating system. When the rotation speed of the rotating member is lower than the critical speed or when the rotation speed exceeds the critical speed, the rotating member swings. It does not rotate, and this rotating member rotates smoothly.

Conventionally commonly used bearing devices, such as sliding bearings, fluid bearings, and rolling bearings, have sufficiently high radial rigidity and load capacity, and are located in a rotation region where the critical speed is high. Even if the operating rotational speed was set to be lower than the critical speed, a bearing device that could sufficiently withstand practical use was obtained.
However, in the case of a superconducting bearing having a small rigidity in the radial direction and a small load capacity, the superconducting bearing appears in a rotation region where the critical speed is low. For this reason, when a member that rotates at an extremely high speed is supported by the superconducting bearing, it is necessary to increase the rotation speed of the rotating member beyond the above critical speed.

On the other hand, in the super high speed rotation region, the sliding bearing and the rolling bearing cannot maintain sufficient durability due to heat generation and the like. Composed of a magnetic material and an electromagnet,
In the case of a control type magnetic bearing that maintains the rotating member in a floating state by controlling the amount of electricity to this electromagnet, there is no disadvantage, but a precise displacement sensor and a controller with excellent responsiveness are required There is a problem that the structure is complicated and the production cost increases. The composite superconducting bearing device of the present invention solves all of the above problems.

[0012]

A composite superconducting bearing device according to the present invention comprises a shaft, a mating member provided around the shaft so as to be freely rotatable relative to the shaft, a permanent magnet and a superconductor. A superconducting bearing provided between the mating member and the shaft, and a bearing other than the superconducting bearing, wherein an auxiliary bearing is detachably provided between the shaft and the mating member; And a control circuit for controlling the engagement / disengagement means. The control circuit compares the rotational speed of the shaft with a set value exceeding the critical speed of the superconducting bearing, and automatically engages the auxiliary bearing when the rotational speed of the shaft exceeds the set value. The auxiliary bearing is automatically engaged when the rotational speed of the shaft is equal to or less than the set value.

[0013]

[Action] For composite superconducting bearing device of the present invention constructed as described above, between the rotational speed of the rotating side member until exceeding critical speed N ₀ of the superconducting bearing, based on the instruction of the control unit Then, the auxiliary bearing is engaged between the shaft and the mating member. As a result, the shaft and the mating member are supported to freely rotate relative to each other via the auxiliary bearing. Auxiliary bearing composed of a bearing other than the superconductor bearing, since the stiffness and load capacity in the radial direction is sufficiently large, the critical speed N ₁ based on the bearing rigidity of the auxiliary bearing is made sufficiently higher than the critical speed N ₀ . Therefore, the rotational speed it is possible to exceed the critical speed N ₀ of the superconducting bearing. When the rotation speed exceeds the critical speed N ₀ , the auxiliary bearing is disengaged based on a command from the controller, and the shaft and the mating member are supported by a superconducting bearing. As a result, since the rotating member is supported only by superconducting bearing, the rotating member, it is not possible to encounter critical speed N ₁ of the auxiliary bearing, beyond the critical speed N _1, it can be realized ultra high-speed rotation Becomes

[0014]

1 and 2 show a first embodiment of the present invention, in which a rotating shaft 10 is rotatably supported inside a housing 9. The upper end of the cylindrical wall 11, which constitutes the housing 9 as the mating member, is closed by the top plate 12, and the lower end is closed by the bottom plate 13. Inside the housing 9, two positions on the outer peripheral surface of the rotating shaft 10 held concentrically with the cylindrical wall 11 are spaced apart from each other.
A pair of upper and lower permanent magnets 14a and 14b are fixed.

A pair of superconductors 15a and 15b are fixed on the inner peripheral surface of the cylindrical wall 11 directly above the permanent magnet 14a and directly below the permanent magnet 14b. Then, the lower surface of the upper superconductor 15a and the upper permanent magnet 1
The upper surface of the lower superconductor 15b and the lower surface of the lower permanent magnet 14b are opposed to each other via the bearing gap 16b. Although not shown, a cooling jacket is provided on the inner peripheral surface of the cylindrical wall 11 so as to surround a part of each of the superconductors 15a and 15b. Liquid nitrogen as a coolant can be supplied and discharged freely.

On the upper and lower end surfaces of the rotating shaft 10, conical convex surfaces 17a and 17b concentric with the rotating shaft 10 are formed, respectively. On the other hand, an upper bearing 18a is provided at a central portion of the lower surface of the top plate 12 facing the upper end surface of the rotating shaft 10, and a central portion of the upper surface of the bottom plate 13 facing the lower end surface of the rotating shaft 10. Is provided with a lower bearing 18b. On the lower surface of the upper bearing 18a, a conical concave surface 19a that can be in close contact with the conical convex surface 17a is formed, and on the upper surface of the lower bearing 18b, a conical concave surface 19b that is in close contact with the conical convex surface 17b is formed.

Then, at least one of the conical convex surface 17a and the conical concave surface 19a, which are made freely close to each other,
At least one of the conical convex surface 17b and the conical concave surface 19b is coated or coated with a solid lubricant such as graphite or molybdenum disulfide, or an oil lubricant such as grease, respectively. When the conical concave surfaces 19a, 19b are in close contact with the conical concave surfaces 17a, 17b, a sliding bearing, which is an auxiliary bearing, can be configured freely.

The conical convex surfaces 17a, 17 facing each other
b and at least one of the conical concave surfaces 19a and 19b, a dynamic pressure groove is formed, so that when the rotating shaft 10 rotates,
A so-called hydrodynamic bearing for forming a film of air or oil between 7a, 17b, 19a and 19b,
The above-mentioned both surfaces 17a, 1
A so-called hydrostatic bearing, in which a pressurized fluid is fed between 7b, 19a and 19b to support the rotary shaft 10, can also be constructed.

Of the upper bearing 18a and the lower bearing 18b, the upper bearing 18a is fixed to the lower surface of the top plate 12, while the lower bearing 18b is supported above the bottom plate 13 so as to be able to move up and down. That is, the lower edge of the bellows 20 is connected and supported at the center of the upper surface of the bottom plate 13, and the lower bearing 18 b is connected and supported at the upper edge of the bellows 20. An air supply port 21 and an exhaust port 22 are provided in a central portion of the bottom plate 13 and surrounded by the bellows 20.
The lower bearing 18b can be freely moved up and down by the supply and discharge of compressed air to the inside of the cylinder 0, thereby constituting an engaging / disengaging means for engaging and disengaging the auxiliary bearing. Although not shown, the lower bearing 18b is provided on a guide portion provided inside the housing 9,
The lower bearing 18b is prevented from being displaced in the radial direction by freely engaging only with the vertical movement. Further, a rotor 23 is fixed to the lower outer peripheral surface of the rotary shaft 10 and a stator 24 is provided on a portion of the inner peripheral surface of the cylindrical wall 11 facing the rotor 23, thereby driving the rotary shaft 10 to rotate. Of the electric motor 25 for performing the operation.

Further, the bellows 2 constituting the above-mentioned engaging / disengaging means is provided.
The supply and discharge of the compressed air into 0 are controlled by a control circuit as shown in FIG. For this purpose, a detection signal A of a rotation speed sensor 30 for detecting the rotation speed of the rotation shaft 10 is input to a controller 31. The controller 31 is provided with an engaging / disengaging means 32 for engaging and disengaging the auxiliary bearing, that is, an electromagnetic type provided in a compressed air supply / discharge circuit for supplying / discharged compressed air to / from the bellows 20. The control signal B is output to the switching valve and the like.

The controller 31 sets a speed exceeding the critical speed and stores the speed, and compares the setting signal C sent from the setting device 33 with the detection signal A. When the detection signal A is equal to or greater than the setting signal C (A ≧ C), the comparator 34 outputs a command signal D, and the driving circuit 35 outputs the control signal B based on the command signal D.
It is composed of

In the composite superconducting bearing device of the present invention, the above-described control circuit is incorporated so that the rotating shaft 10
But when to start from a state in which the stop, even without any special operation, without the rotary shaft 10 is whirling in the vicinity of the critical speed N _0, it is possible to increase the rotation speed. That is, during the period from the stop state to the state immediately after the start up and the rotation number is low, the compressed air is fed into the bellows 20 (FIG. 1) constituting the engagement / disengagement means 32, and the rotation speed of the rotary shaft 10 becomes the critical speed N. If it exceeds ₀ , the compressed air in the bellows 20 is automatically discharged, and the sliding bearings (upper,
The engagement between the lower dual bearings 18a and 18b) and the rotating shaft 10 is released.

The composite superconducting bearing device of the present invention as described above constructed acts in the following manner, and thereby it is able rotate the rotary shaft 10 at a high speed exceeding the critical speed N _0. First, prior to energizing the electric motor 25, compressed air is fed into the bellows 20 through the air supply port 21 based on a command from the control circuit, and the rotary shaft 1 is moved together with the lower bearing 18b.
Increase 0. As a result, the conical convex surfaces 17a, 17b provided at the upper and lower ends of the rotary shaft 10 and the upper and lower bearings 1
The conical concave surfaces 19a, 19b of 8a, 18b are in close contact with each other, and the rotating shaft 10 is rotatably supported inside the housing 9 via a pair of upper and lower sliding bearings. In this state, a pair of upper and lower permanent magnets 14a, 14
b and the superconductors 15ab and 15b are concentric with each other, and the upper bearing gap 16a of the bearing gaps 16a and 16b is minimized (close to zero as much as possible), and conversely, the lower bearing gap 16b increases.

Next, energization of the electric motor 25 is started, and the rotating shaft 10 is rotated. The rotation speed of the rotating shaft 10 gradually increases, and the rotating shaft 10 and the rotating shaft 1
Even if the critical speed N ₀ determined by the mass of the member fixed to 0 and the bearing rigidity of the superconducting bearing is reached, the sliding bearing constituted by the upper and lower bearings 18a and 18b has the rigidity in the radial direction and the load capacity. Is sufficiently large, and the critical speed N ₁ determined by the bearing rigidity of the sliding bearing is sufficiently higher than the critical speed N ₀ , so that the rotating shaft 10 does not swing.

When the rotation speed of the rotary shaft 10 further increases and exceeds the critical speed N ₀ , the compressed air in the bellows 20 is discharged through the exhaust port 22 based on a command of the control circuit, The lower bearing 18b is lowered. on the other hand,
After the compressed air is fed into the bellows 20 through the air supply port 21 and before the compressed air is discharged from the exhaust port 22, liquid nitrogen is fed into a cooling jacket (not shown) provided in the housing 9. The pair of upper and lower superconductors 15a and 15b are kept in a superconducting state.

After the superconductors 15a and 15b are brought into the superconductive state, the lower bearing 18b is lowered to remove the supporting force of the lower shaft 18b from the lower bearing 18b. The fixed pair of upper and lower permanent magnets 14a and 14b tend to descend by their own weight, and the upper bearing gap 16a of the bearing gaps 16a and 16b expands, and the lower bearing gap 16b shrinks. However, in this state, each of the superconductors 15
a, 15b, the pair of permanent magnets 14a, 1a
4b is pinned, and between the permanent magnets 14a, 14b and the superconductors 15a, 15b, the two members 14a, 14b, 15a, 15b are prevented from being displaced from each other. Power is added.

That is, when the rotating shaft 10 and the like tend to descend due to their own weight, an attractive force based on a pinning force acts between the upper permanent magnet 14a and the superconductor 15a, and Between the permanent magnet 14b and the superconductor 15b,
A repulsive force based on the pinning force acts. As a result, the lowering of the rotating shaft 10 stops in a state where the own weight is balanced with the suction force and the repulsion force. Also, the displacement of the rotating shaft 10 in the radial direction is prevented by the force based on the pinning force.

Therefore, the rotating shaft 10 is mounted on the lower bearing 18.
b after the loss of bearing capacity
It is supported in a floating state concentrically with zero. Therefore, the rotating shaft 1
No frictional force acts on rotating 0. Further, in this state, since the rotation speed of the rotating shaft 10 has already exceeded the critical speed N ₀ , the rotating shaft 10 does not swing around, and the rotating shaft 10 can be rotated at a very high speed.

The critical speed N ₀ of the rotating shaft 10 determined by the bearing rigidity of the superconducting bearing depends on the material, outer diameter and length of the rotating shaft 10, the weight of the member fixed to the rotating shaft 10, the mounting position, and the like. Although different, for example, it is used as a bearing spindle incorporated in a centrifuge or the like.
It is about 000r.pm. Also, the electric motor 25 is energized while the rotating shaft 10 is stopped, and the time required for the rotating speed of the rotating shaft 10 to exceed the critical speed N ₀ is several seconds to several tens of seconds. It is a short time. Therefore, only until the speed exceeds the critical speed N ₀ ,
Can be easily supported by sliding bearings.

FIG. 3 shows a second embodiment of the present invention. In contrast to the above-described first embodiment in which the conical convex surfaces 17a and 17b are formed on both upper and lower end surfaces of the rotating shaft 10, and the conical concave surfaces 19a and 19b are formed in the upper and lower bearings 18a and 18b, the present embodiment is different from the first embodiment. In the case of this embodiment, spherical convex surfaces 26a and 26b are formed on the lower end surfaces of the upper bearing 18a and the rotating shaft 10, and spherical concave surfaces 27 are formed on the upper end surfaces of the rotating shaft 10 and the lower bearing 18b.
a and 27b are respectively formed.

When the lower bearing 18b rises with the compressed air being sent into the bellows 20, the spherical convex surfaces 26a, 26b and the spherical concave surfaces 27a, 27b are engaged with each other to form a pair of upper and lower permanent magnets. 14a, 14b and superconductor 1
5a and 15b (FIG. 1) are concentric with each other, and constitute a pair of upper and lower sliding bearings. Other configurations and operations, such as forming a dynamic pressure groove on a desired surface as needed, are based on the supply and discharge of compressed air into the bellows 20 from a control circuit including a controller 31 as shown in FIG. This is the same as the above-described first embodiment, including the execution based on the above-mentioned command.

FIG. 4 shows a third embodiment of the present invention. While both the first embodiment described above and the second embodiment described above used a sliding bearing as an auxiliary bearing,
In the case of the present embodiment, a rolling bearing is used as an auxiliary bearing. That is, a rolling bearing capable of supporting a radial load and a thrust load is provided at the center of the lower surface of the top plate 12.
The upper receiving piece 29a is rotatably supported via a deep groove type ball bearing 28a, and the lower receiving piece is also provided via a deep groove type ball bearing 28b on the upper end of the bellows 20 at the center of the upper surface of the bottom plate 13. 29b is rotatably supported.

At the upper and lower ends of the rotating shaft 10, conical convex surfaces 17 are provided.
a, 17b, the lower surface of the upper receiving piece 29a and the lower receiving piece 29b.
Conical concave surfaces 19a, 19b are formed on the upper surface of the bellows 20, respectively, and the compressed air is fed into the bellows 20.
When the lower receiving piece 29b is raised, a pair of upper and lower permanent magnets 1
4a, 14b and superconductors 15a, 15b (FIG. 1)
They are configured to be concentric with each other. Other configurations and operations include the supply and discharge of compressed air into the bellows 20 based on commands from a control circuit including a controller 31 as shown in FIG. This is the same as the second embodiment.

In each of the above-described embodiments, the member driven based on the control signal B sent from the controller 31 is an electromagnetic member provided in a circuit for supplying and discharging compressed air to the bellows 20. Switching valve of the type. On the other hand, when a solenoid is provided in place of the bellows 20 and the engagement / disengagement means 32 is constituted by the solenoid, the solenoid is directly driven by the control signal B. Further, the above description has been made on the case where the rotating shaft 10 is rotated inside the fixed housing 9. However, the present invention is not limited to such a case, and the case where the rotor is rotated around the fixed pivot is described. It can also be applied to

[0035]

Since the composite superconducting bearing device of the present invention is constructed and operates as described above, it is possible to increase the rotational speed of a rotating member such as a rotating shaft beyond a critical speed, and to increase the radial speed. This has a great effect of contributing to the practical use of a superconducting bearing device having a small rigidity and a small load capacity in all directions.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a control circuit.

FIG. 3 is a partial longitudinal sectional view showing a second embodiment of the present invention.

FIG. 4 is a partial longitudinal sectional view showing the third embodiment.

FIG. 5 is a perspective view showing the basic principle of a conventional example.

FIG. 6 is a perspective view showing a specific configuration of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 permanent magnet 2 pellet 3 disk 3a circular plate 4 disk 4a circular plate 5 rotating shaft 6 housing 7 cooling jacket 8 electric motor 9 housing 10 rotating shaft 11 cylindrical wall 12 top plate 13 bottom plate 14a, 14b permanent magnet 15a, 15b Superconductor 16a, 16b Bearing gap 17a, 17b Conical convex surface 18a Upper bearing 18b Lower bearing 19a, 19b Conical concave surface 20 Bellows 21 Air supply port 22 Exhaust port 23 Rotor 24 Stator 25 Electric motor 26a, 26b Spherical convex surface 27a, 27b Spherical concave surface 28a, 28b Ball bearing 29a Upper receiving piece 29b Lower receiving piece 30 Rotation speed sensor 31 Controller 32 Disengagement means 33 Setting device 34 Comparator 35 Drive circuit

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16C 32/00-32/06

Claims (3)

(57) [Claims] 1. A shaft, a mating member provided around the shaft so as to freely rotate relative to the shaft, a permanent magnet and a superconductor, and provided between the mating member and the shaft. A superconducting bearing, a bearing other than the superconducting bearing, an auxiliary bearing provided detachably between the shaft and the mating member, and a disengaging means for disengaging the auxiliary bearing ;
And a control circuit for controlling the engagement / disengagement means.
The control circuit determines the rotational speed of the shaft and the critical speed of the superconducting bearing.
Compared to the set value which is higher than
When the set value is exceeded, the above-mentioned auxiliary bearing is automatically engaged.
Release, and when the rotation speed of the shaft is below this set value,
Composite superconducting bearing device that automatically engages auxiliary bearings . 2. The auxiliary bearing is a plain bearing or a fluid bearing having a conical or spherical concave surface and a convex surface which can be close to or close to each other and whose respective central axes coincide with the central axis of the shaft. 2. The composite superconducting bearing device according to claim 1, wherein one of the concave surface and the convex surface is fixed to the shaft, and the other is supported by a mating member so as to be able to move in and out of the shaft by means of an engaging and disengaging means. 3. The auxiliary bearing is a rolling bearing that constitutes an engagement / disengagement means and rotatably supports a receiving piece that moves toward and away from the shaft while supporting a radial load and a thrust load applied to the receiving piece. The composite superconducting bearing device according to claim 1 .