JP2003097555A - Voice coil type thrust magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voice coil type thrust magnetic bearing having a smaller coil inductance and improved controllability for quick and highly accurate position control by adopting voice coils not using a magnetic material such as an iron core. SOLUTION: The thrust bearing comprises permanent magnets 1a, 1b fixed to a rotating shaft 3, at least a portion of the rotating shaft 3 being formed as a yoke portion of a magnetic material, and the voice coils 5a, 5b not requiring the magnetic material such as the iron core, fixed to the inner periphery face of a ring yoke 6 of a magnetic material concentrically spaced from the rotating shaft 3 as predetermined, the voice coils 5a, 5b being located in a magnetic field formed in a space by the permanent magnets 1a, 1b, wherein a current is carried in the voice coils 5a, 5b to generate Lorentz force for giving force to the thrusting direction. The highly accurate position control in the thrusting direction is enabled by the control of the current in the voice coils.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust magnetic bearing for supporting a rotating shaft rotating at high speed in a high-precision processing machine, a turbo molecular pump device for vacuum, etc. The present invention relates to a voice coil type thrust magnetic bearing that can be used.

[0002]

2. Description of the Related Art Spindle bearings used in high precision processing machines and bearings used in turbo molecular pump devices for vacuum use high precision ball bearings, high precision static pressure bearings or high precision magnetic bearings. It supports the shaft. In recent years, high precision processing machines are required to have higher precision and higher processing precision, and in turbo molecular pumps for vacuum, higher rotation speeds of shafts are strongly required to increase exhaust efficiency. There is. Especially in high precision processing machines,
Spindle speed from 10,000 rpm to 30,000
If you try to maintain high accuracy by rotating at a speed as high as rpm or more, problems will occur in accuracy. In particular, it has been known that self-excited vibration of several nanometer level occurs in the thrust direction of the shaft. Conventionally, it was not a problem even if there was self-excited vibration in the thrust direction at this level,
In high-precision machine tools that have been required in recent years, such self-excited vibration in the thrust direction affects the surface roughness of the machined surface, etc., so it is required to eliminate the self-excited vibration in the thrust direction of the shaft. It's starting to happen. In addition, in the turbo molecular pump for vacuum, it is important to remove the self-excited vibration of the shaft and stably rotate the turbine in order to achieve high-speed rotation and high durability in order to increase the exhaust efficiency and speed. .

Conventionally, a thrust magnetic bearing has been used as a means for eliminating self-excited vibration. A magnetic circuit in which a magnetic flux flows from an electromagnet of the bearing portion to a rotary shaft is formed, and magnetic attraction is provided between the bearing portion and the rotating body. Generate force and use it as control force,
The force is used to hold the rotary shaft in the thrust direction and control its position.

A conventional electromagnet type thrust magnetic bearing of this type is constructed as shown in FIG. In the figure, 101 is a face plate made of a magnetic material, which is formed in a brim shape around the rotary shaft 102 and is fixed to the rotary shaft 102,
The pair of yokes 103a and 103b and the coil 1 fixed to the respective yokes 103a and 103b so as to sandwich the flange-shaped face plate 101 with a predetermined distance from both sides.
04a and 104b are fixed to another member and arranged, and these constitute a ring-shaped electromagnet. That is,
The ring-shaped electromagnet is a brim-shaped face plate 101 made of a magnetic material.
Are arranged so as to be sandwiched at a certain distance, and a current is passed through each of these electromagnets to form a magnetic circuit shown by an arrow in FIG. 4 to form an electromagnet type thrust bearing. At this time, the face plate 101 is attracted to the right side or the left side in FIG. Position control is possible.

[0005]

However, in the above-mentioned conventional electromagnet type thrust bearing, the amount of magnetic flux flowing inside the coil is large because the magnetic material such as the iron core is combined inside the coil to form the electromagnet. Therefore, the inductance of the coil becomes large, the load of the coil power source for position control of the thrust direction becomes large, and the force applied by the electromagnet to control the thrust direction of the rotating shaft is 2 times the value of the current flowing in the coil. The characteristic of being proportional to the power makes the control system system of the thrust magnetic bearing complicated,
There is a problem that high-speed rotation makes it difficult to control with high precision.

Therefore, the present invention has been made in view of the above-mentioned problems of the thrust magnetic bearing of the prior art, and reduces the inductance of the coil by using a voice coil which does not use a magnetic material such as an iron core. It is an object of the present invention to provide a voice coil type thrust magnetic bearing which has improved controllability, is highly responsive and highly controllable, and enables highly accurate position control.

[0007]

To achieve the above object, in a voice coil type thrust magnetic bearing of the present invention, a yoke made of a magnetic material and a permanent magnet are fixed to a rotating shaft, and the yoke and the permanent magnet are provided in a space. It is characterized in that a voice coil is arranged in the magnetic field to be formed and a force in the thrust direction is applied to the rotating shaft.

In the voice coil type thrust magnetic bearing of the present invention, when the rotating shaft is made of a magnetic material, the rotating shaft can be used as a yoke of a permanent magnet.

In the voice coil type thrust magnetic bearing of the present invention, it is preferable that the own weight of the rotary shaft is supported by another bearing, and a ball bearing, a static pressure bearing or a magnetic bearing is used as the other bearing. You can

[0010]

According to the present invention, a yoke made of a magnetic material and a permanent magnet are fixed to a rotary shaft, and a voice coil which does not use a magnetic material such as an iron core is provided in a magnetic field formed by the yoke and the permanent magnet in a space. Then, a voice coil type thrust magnetic bearing is constructed which generates a Lorentz force and gives the force in the thrust direction of the rotary shaft to support and control the position of the rotary shaft. The voice coil has a small coil inductance, and the force applied to control the rotating shaft has characteristics that are directly proportional to the value of the current that flows in the coil, so the control characteristics are good, and high-speed rotation provides high accuracy and high responsiveness. A thrust magnetic bearing having high controllability can be realized.

Further, by using the voice coil type thrust magnetic bearing of the present invention in a high precision processing machine, a turbo molecular pump for vacuum, etc., the control characteristic in the spindle thrust direction is improved and the self-excited vibration of the shaft is removed with high precision. It becomes possible to do. Therefore, with a high-precision machine, it is possible to control the position with high accuracy even at high-speed rotation, it is possible to eliminate self-excited vibration in the thrust direction of the shaft, and it is possible to smooth the surface roughness of the machined surface. In addition, in the turbo molecular pump for vacuum, it is possible to remove the self-excited vibration of the shaft and rotate it stably, the operation of the bearing becomes smooth, and high speed rotation and high durability can be realized. Since the pump has a long life and can be driven at a higher rotational speed, there are great advantages such as increased exhaust efficiency.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

An embodiment of a voice coil type thrust magnetic bearing according to the present invention will be described with reference to FIG.

In FIG. 1, 1a and 1b are ring-shaped permanent magnets, which are fixed to the rotary shaft 3 and
Is made of a magnetic material so as to form the yokes of the permanent magnets 1a and 1b. A ring-shaped yoke 6 made of a magnetic material is fixedly held by a member (not shown), and is arranged along the outer peripheral surface of the rotating shaft 3 at a predetermined interval and concentrically with respect to the rotating shaft 3. The voice coils 5a and 5b, which do not use a magnetic material such as an iron core, are fixed to the inner peripheral surface of the ring-shaped yoke 6, and the voice coils 5a and 5b are fixed to the rotary shaft 3. The magnets 1a and 1b are opposed to each other at a predetermined interval and are concentrically arranged with respect to the rotating shaft 3. The rotary shaft 3 needs to be formed of a magnetic material in order to form the yokes of the permanent magnets 1a and 1b, but it is not necessary to form the entire rotary shaft 3 of a magnetic material, and at least the yoke is formed. Only the constituent part may be made of a magnetic material, and the parts other than the part constituting the yoke part may be made of a non-magnetic material, which can be appropriately combined and formed. Further, the yoke 6 does not have to have a ring-shaped integral structure, and may have a structure in which it is divided into, for example, four pieces or eight pieces, and the voice coil is fixed to each of the divided pieces. At this time, the voice coil may be arranged concentrically with respect to the rotating shaft 3. Further, it is desirable that the own weight of the rotary shaft 3 is supported by another bearing (not shown), such as a ball bearing, a static pressure bearing, or a magnetic bearing.

In the present embodiment configured as described above, in the magnetic field formed in the space by the permanent magnets 1a, 1b fixed to the rotating shaft 3 and the yoke portion formed of the magnetic material of the rotating shaft 3, By arranging the voice coils 5a and 5b, a voice coil type thrust magnetic bearing is constructed, and the magnetic circuit by the permanent magnets 1a and 1b is shown in FIG.
Is formed as indicated by an arrow, and a current is passed through the voice coils 5a and 5b in the magnetic field to generate a Lorentz force to give a force in the thrust direction. Here, the voice coils 5a and 5b, which do not use a magnetic material such as an iron core, have a small coil inductance and have a characteristic that the force applied to control the rotating shaft is directly proportional to the current value flowing in the coil. Since the control characteristics are straightforward, the position control in the thrust direction can be performed with high precision by controlling the currents flowing through the voice coils 5a and 5b, and the self-excited vibration of the shaft can be removed with high precision. It is possible to control with high precision by high-speed rotation.

Therefore, by using the voice coil type thrust magnetic bearing of the present embodiment as a spindle bearing of a high precision processing machine, it becomes possible to perform position control with high precision even at high speed rotation and self-excitation in the thrust direction of the shaft. Vibration can be eliminated, and the surface roughness of the processed surface can be made smooth. In addition, in the turbo molecular pump for vacuum, it is possible to remove the self-excited vibration of the shaft and rotate it stably, the operation of the bearing becomes smooth, and the rotation speed and high durability can be realized. Since it has a long life and can be driven at a higher rotational speed, it can improve exhaust efficiency.

Next, a second embodiment of the voice coil type thrust magnetic bearing according to the present invention will be described with reference to FIG.

In FIG. 2, reference numeral 11 is a ring-shaped permanent magnet, and a yoke 12 for fixing the permanent magnet 11 is made of a magnetic material and is fixed coaxially to the rotating shaft 13, and A ring-shaped tubular portion 12a and a central portion 12b are formed at one end by an annular groove 12c,
The ring-shaped permanent magnet 11 is fixed to the inner peripheral surface of the cylindrical portion 12 a of the yoke 12. The voice coil 15 is fixed to the outer peripheral surface of the ring-shaped portion 16a at the tip of the bobbin 16, and by placing the ring-shaped portion 16a of the bobbin 16 in the annular groove 12c of the yoke 12, the voice coil 1
5 are arranged concentrically with the ring-shaped permanent magnet 11 so as to face each other at a predetermined interval. When the material of the rotary shaft 13 is a magnetic material, the yoke 12 and the rotary shaft 13 do not have to be separate bodies, and a part of the rotary shaft 13 can be formed as an integral body that is used as a yoke. Is. Further, the own weight of the rotary shaft 13 is preferably supported by another bearing (not shown) such as a ball bearing, a static pressure bearing, or a magnetic bearing.

In the present embodiment configured as described above, the permanent magnet 11 is fixed to the rotary shaft 13 or the yoke 12 made of a magnetic material and the inner peripheral surface of the cylindrical portion 12a of the yoke 12. By arranging the voice coil 15 in the magnetic field formed by the space, the voice coil type thrust magnetic bearing is constructed, and the magnetic circuit by the permanent magnet 11 is formed as shown by the arrow in FIG. By applying an electric current to the voice coil 15 in the magnetic field, a Lorentz force can be generated to give a force in the thrust direction.

Therefore, also in this embodiment, similarly to the above-described embodiments, the position control in the thrust direction can be performed with high accuracy by controlling the current flowing in the voice coil that does not use a magnetic material such as an iron core. Thus, the same operational effects as those of the above-described embodiment are exhibited.

Further, a third embodiment of the voice coil type thrust magnetic bearing according to the present invention will be described with reference to FIG.

In FIG. 3, reference numeral 21 is a rod-shaped permanent magnet, and the yoke 22 for fixing the permanent magnet 21 is
It is made of a magnetic material and is coaxially fixed to the rotating shaft 23. The yoke 22 has a ring-shaped cylindrical portion 2 at one end thereof.
2a is formed, and the rod-shaped permanent magnet 21 is fixed to the central shaft portion of the internal space of the cylindrical portion 22a, and is arranged coaxially with the rotating shaft 23. A member 22b made of a magnetic material is arranged at one end of the permanent magnet 21. Voice coil 25
Is fixed to the outer peripheral surface of the ring-shaped portion 26a at the tip of the bobbin 26. By arranging the ring-shaped portion 26a of the bobbin 26 inside the tubular member 22a of the yoke 22, the voice coil 25 becomes a rod-shaped permanent magnet. 21 are arranged concentrically. When the material of the rotating shaft 23 is a magnetic material, it is not necessary to separate the yoke 22 and the rotating shaft 23, and it is possible to form a part of the rotating shaft 23 as an integrated body that is used as a yoke. Is. Also, the rotary shaft 23
The weight of the other bearing is not shown, for example, a ball bearing,
It is desirable to support by a hydrostatic bearing or a magnetic bearing.

Also in the present embodiment configured as described above, a ring-shaped yoke 22 made of a magnetic material fixed to the rotary shaft 23 or integral with the rod-shaped permanent magnet 21 fixed to the central shaft portion of the yoke 22. By arranging the voice coil 25 in the magnetic field formed by the space, the voice coil type thrust magnetic bearing is constructed, and the magnetic circuit by the permanent magnet 21 is formed as shown by the arrow in FIG. By applying an electric current to the voice coil 25 in the magnetic field, the Lorentz force is generated and the force is applied in the thrust direction.

Therefore, also in this embodiment, similarly to the above-described embodiments, the position control in the thrust direction can be performed with high accuracy by controlling the current flowing in the voice coil that does not use a magnetic material such as an iron core. Thus, the same operational effects as those of the above-described embodiment are exhibited.

[0025]

As described above, according to the present invention,
By installing a magnet and a yoke on the rotating shaft, arranging a voice coil in a magnetic field formed in the space by the magnet and the yoke, and generating a Lorentz force to apply a force in the thrust direction of the rotating shaft, A voice coil type thrust magnetic bearing having high accuracy, high responsiveness and high controllability can be realized.

By using the voice coil type thrust magnetic bearing of the present invention, in a high precision processing machine, a turbo molecular pump for vacuum, etc., the control characteristics in the spindle thrust direction are improved and the self-excited vibration of the shaft is removed with high precision. It becomes possible to smooth the surface roughness of the machined surface with a high-precision machine, and to eliminate the self-excited vibration of the shaft in the turbo molecular pump for vacuum and rotate it stably. This enables the bearing to operate smoothly, achieves high speed rotation and high durability, and enables the pump to have a long life and drive at a high rotational speed, thereby improving exhaust efficiency.

[Brief description of drawings]

FIG. 1 is a configuration diagram schematically showing an embodiment of a voice coil type thrust magnetic bearing according to the present invention.

FIG. 2 is a configuration diagram schematically showing a second embodiment of a voice coil type thrust magnetic bearing according to the present invention.

FIG. 3 is a configuration diagram schematically showing a third embodiment of a voice coil type thrust magnetic bearing according to the present invention.

FIG. 4 is a configuration diagram schematically showing a conventional thrust magnetic bearing.

[Explanation of symbols]

1a, 1b Permanent magnet 3 rotation axes 5a, 5b voice coil 6 York 11, 21 Permanent magnet 12, 22 York 13, 23 rotation axis 15, 25 voice coils 16, 26 bobbins

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3J102 AA01 BA03 CA02 CA11 CA27                       DA09 DB11 GA06                 5H607 AA00 AA04 FF06 GG02 GG19                       GG20 GG21

Claims (4)

[Claims] 1. A yoke made of a magnetic material and a permanent magnet are fixed to a rotary shaft, and a voice coil is arranged in a magnetic field formed by the yoke and the permanent magnet in a space to apply a thrust direction force to the rotary shaft. A voice coil type thrust magnetic bearing having a structure. 2. The voice coil type thrust magnetic bearing according to claim 1, wherein when the rotating shaft is made of a magnetic material, the rotating shaft is a yoke of a permanent magnet. 3. The voice coil type thrust magnetic bearing according to claim 1, wherein the weight of the rotary shaft is supported by another bearing. 4. The voice coil type thrust magnetic bearing according to claim 3, wherein the other bearing that supports the own weight of the rotating shaft is a ball bearing, a static pressure bearing, or a magnetic bearing.