Abstract:
Disclosed is a magnetic bearing structure including a permanent magnet, levitating a rotation body without a bias current, and easily magnetizing the permanent magnet. The magnetic bearing structure includes a ring-shaped permanent magnet provided on a side of a rotation shaft and magnetized in a direction parallel with a shaft direction of the rotation shaft, a coil installed on a side of the permanent magnet, and a conductor installed on an external side of the coil and used to form a magnetic field path. According to the configuration, when an additional bias current is not supplied to the coil installed in the magnetic bearing, a rotation body levitates according to the magnetic field caused by the permanent magnet, and a magnetized direction of the permanent magnet is in parallel with a shaft direction of the rotation shaft thereby allowing easy magnetization and increasing productivity of the magnetic bearing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (a) Field of the Invention 
         [0002]    The present invention relates to a magnetic bearing structure and a turbo machine having the same, and it particularly relates to a magnetic bearing structure for using a permanent magnet and an electromagnet in a magnetic bearing provided on a side of a rotation body to allow the electromagnet to control a position of the rotation body and allow the permanent magnet to generate a bias magnetic field, and then control a magnetized direction of the permanent magnet to correspond to a shaft direction of a rotation shaft thereby facilitating magnetization, and a turbo machine having the same. 
         [0003]    (b) Description of the Related Art 
         [0004]    A magnetic bearing device has been widely used for various kinds of precision machine devices. The magnetic bearing device levitates a rotation body and supports it according to a magnetic force generated by an electromagnet. With devices using a magnetic bearing, a shaft does not contact the bearing so dust caused by abrasion is suppressed, a lubricant is not used, and noise is reduced. 
         [0005]    A general rigid body has six degrees of freedom (DOF). However, a conventional rotation body rotates the shaft so five DOF excluding a rotation movement of the rotation shaft must be controlled. Therefore, the magnetic bearing applicable to a 5-shaft control device for controlling the entire five DOF is classified as a radial magnetic bearing and an axial magnetic bearing. 
         [0006]    Regarding the magnetic bearing, conductor surfaces facing each other pull the rotation body and increase or reduce a magnetic force depending on a position change of the rotation body to stably support the rotation body. However, in this instance, a predetermined bias magnetic force must be applied to the rotation body according to a load caused by the rotation body. To form the bias magnetic force, a permanent magnet is used as well as an electromagnet. Here, to divide paths of magnetic fields of the electromagnet and the permanent magnet, a magnetic bearing structure for using a method for providing a donut-shaped permanent magnet between a pair of electromagnets has been proposed. 
         [0007]    In the case of the above-structured magnetic bearing, the magnetized direction of the donut-shaped permanent magnet must be perpendicular to the shaft direction of the rotation body, that is, the permanent magnet must be magnetized in a radius direction of the permanent magnet. However, the magnetization method is difficult and production efficiency of the magnetic bearings can be worsened. Therefore, it is required to provide a magnetic bearing structure for easily magnetizing the permanent magnet while dividing the magnetic field paths of the permanent magnet and the electromagnet. 
         [0008]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in an effort to provide a magnetic bearing structure for dividing paths of magnetic fields of an electromagnet and a permanent magnet to intercept interference of the paths thereof and to provide easy magnetization of the permanent magnet, and a turbo machine having the same. 
         [0010]    An exemplary embodiment of the present invention provides a magnetic bearing structure including: a ring-shaped permanent magnet provided on a side of a rotation shaft and magnetized in a direction in parallel with a shaft direction of the rotation shaft; a conductor installed on an external side of the permanent magnet and used to form a magnetic field path; and a coil installed inside the conductor. 
         [0011]    The magnetic bearing structure further includes a support contacting the permanent magnet and connected to the same, and the magnetic field path caused by the permanent magnet is formed through the rotation shaft by the support. 
         [0012]    The rotation shaft further includes a rotation plate, and the magnetic field path is formed through the rotation plate. 
         [0013]    A non-magnetic material is filled in an empty space formed inside the conductor. 
         [0014]    A gap is formed between the rotation plate and the conductor. 
         [0015]    Another embodiment of the present invention provides a turbo machine including: a housing; a rotation shaft installed inside the housing; a power transmitter connected to the rotation shaft and transmitting power; and a magnetic bearing applied to the rotation shaft wherein the magnetic bearing includes: a ring-shaped permanent magnet provided on a side of the rotation shaft and wrapping the rotation shaft; a conductor installed on an external side of the permanent magnet and used to form a magnetic field path; and a coil installed inside the conductor, wherein the permanent magnet is magnetized in a direction parallel with a shaft direction of the rotation shaft. 
         [0016]    The turbo machine further includes a rotation plate connected to the rotation shaft, and a magnetic field path of the permanent magnet is formed through the rotation plate. 
         [0017]    A gap is formed between the rotation plate and the conductor. 
         [0018]    The turbo machine further includes a support contacting the permanent magnet and connected to the same, and a magnetic field path caused by the permanent magnet is formed through the rotation shaft by the support. 
         [0019]    The turbo machine further includes a rotation plate connected to the rotation shaft, and a magnetic field path of the permanent magnet is formed through the rotation plate. 
         [0020]    A gap is formed between the rotation plate and the conductor. 
         [0021]    A non-magnetic material is filled in an empty space formed inside the conductor. 
         [0022]    According to the embodiments of the present invention, the paths of the magnetic fields of the electromagnet and the permanent magnet are divided, an additional bias current is not applied to the electromagnet by the bias magnetic field caused by the permanent magnet, and the magnetized direction of the permanent magnet corresponds to the shaft direction of the rotation body, thereby facilitating magnetization of the permanent magnet and improving productivity of the magnetic bearing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  shows a cross-sectional view of a turbo machine with a magnetic bearing structure according to an exemplary embodiment of the present invention. 
           [0024]      FIG. 2  shows a cross-sectional view of a magnetic bearing shown in  FIG. 1 . 
           [0025]      FIG. 3  and  FIG. 4  show cross-sectional views of a magnetic bearing according to another exemplary embodiment of the present invention. 
           [0026]      FIG. 5  and  FIG. 6  show cross-sectional views of a drive of a magnetic bearing. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0027]    Exemplary embodiments of the present invention will now be described in detail with reference to accompanying drawings. 
         [0028]      FIG. 1  shows a cross-sectional view of a turbo machine  1  with a magnetic bearing structure according to an exemplary embodiment of the present invention. 
         [0029]    The turbo machine  1  according to an exemplary embodiment of the present invention includes a housing  10 , a rotation shaft  20 , a power transmitter  30 , and a magnetic bearing  100 . The turbo machine  1  includes a multi-purpose turbo machine used for a general machine tool, and particularly includes a small turbo machine. 
         [0030]    The housing  10  provides a space for receiving the rotation shaft  20 , and the rotation shaft  20  covers a case in which the rotation shaft is driven while it is set to be perpendicular and a case in which it is driven while it is set to be horizontal. The power transmitter  30  includes a generally-used motor, and the power transmitter  30  can be provided inside or outside the housing  10 . The magnetic bearing  100  is provided on a side of the rotation shaft  20  while supporting the rotation shaft on the side. 
         [0031]    The magnetic bearing  100  includes a permanent magnet  110 , a coil  120 , and a conductor  130 . A further detailed description will now be given with reference to  FIG. 2  to  FIG. 4 .  FIG. 2  shows a cross-sectional view of a magnetic bearing  100  further including a support  140 ,  FIG. 3  shows a cross-sectional view of a modified exemplary variation in which a position of a coil  120  is changed in an exemplary embodiment shown in  FIG. 2 , and  FIG. 4  shows a cross-sectional view of a magnetic bearing  100  without the support  140 . 
         [0032]    The permanent magnet  110  is a ring type, and it is provided on a side of the rotation shaft  20 . A magnetic circuit for biasing the rotation shaft  20  is formed by the permanent magnet  110  while an additional current influencing the bias of the rotation shaft  20  is not supplied, so the rotation shaft  20  floats.  FIG. 2  and  FIG. 3  show a magnetic field formed by the permanent magnet  110 . It is exemplified in this case that a rotation plate  21  is additionally provided to the rotation shaft  20  and the rotation plate  21  levitates, or that the rotation shaft  20  and the rotation plate are integrally formed and they levitate. Also, the rotation shaft  20  or rotation plate  21  is made of a conductor. 
         [0033]    In this instance, the magnetized direction of the permanent magnet  110  is set to be in parallel with the shaft direction of the rotation shaft  20 . That is, the N polarity or the S polarity does not proceed to the rotation shaft because of magnetization of the permanent magnet  110 , so compared to the magnetic bearing having another permanent magnet magnetized perpendicularly with respect to the direction of the rotation shaft, a formation of the magnetic field influencing the bias of the rotation shaft  20  formed by the permanent magnet  110  does not become symmetrical. However, in general, the fact that transmittivity of the conductor  130  is good and the formation of the bias magnetic field does not become symmetrical does not significantly influence levitation of the rotation shaft  20  or the rotation plate  21  caused by the bias magnetic field of the permanent magnet  110 . 
         [0034]    Therefore, a bias flux formed by the permanent magnet  110  passes through the rotation shaft  20  or the rotation plate  21  and the conductor  130 , it returns to the permanent magnet  110 , and the rotation shaft  20  or the rotation plate  21  levitates. 
         [0035]    The coil  120  is provided on a side of the permanent magnet  110 . The coil  120  is exemplified to be formed outside the permanent magnet  110  and have a ring shape for wrapping the rotation shaft  20 , but the shape is not restricted to this. That is, it can be formed as a pair facing each other with respect to the rotation shaft  20 . The current flows to the coil  120  to form a magnetic field so as to control the levitation position of the rotation shaft  20  or the rotation plate  21 . That is, as the position of the rotation shaft  20  or the rotation plate  21  is changed in the shaft direction, a size or direction of the current is changed to control the position change of the shaft direction of the rotation shaft  20  or the rotation plate  21 . A detailed drive will be described later. 
         [0036]    A conductor  130  influencing formation of a path of the magnetic field is provided outside the coil  120  and the permanent magnet  110 . The conductor  130  influences formation of paths of the magnetic field for biasing the rotation shaft  20  or the rotation plate  21 , formed by the permanent magnet  110  and the magnetic field for controlling the position change of the rotation shaft  20  or rotation plate  21 , formed by the coil  120 . A gap is formed between the conductor  130  and the rotation plate  21 . That is, in general, a sensor  40  for sensing the gap is provided inside or outside the magnetic bearing  100 , and as the gap is changed depending on the sensor  40 , the size or direction of the current supplied to the coil  120  is changed to maintain the gap within a predetermined range and control the position change of the rotation shaft  20  or the rotation plate  21 . 
         [0037]    The magnetic bearing  100  further includes a support  140 . The support  140  is exemplified to contact the permanent magnet  110  and be connected thereto. The support  140  is desirably formed with a conductor. The support  140  contacts the permanent magnet  110  and is connected thereto, and the magnetized direction of the permanent magnet  110  is in parallel with the shaft direction of the rotation shaft  20  so the N polarity or the S polarity caused by magnetization contacts the support  140 . In this instance, the path of the magnetic field generated by the permanent magnet  110  is formed by the rotation shaft  20  or the rotation plate  21  through the support  140 . In this case, a form of the magnetic field influencing the bias of the rotation shaft  20  formed by the permanent magnet  110  does not become symmetrical. However, in a like manner of the above description, the fact that the formation of the bias magnetic field does not become symmetrical does not significantly influence the levitation of the rotation shaft  20  or the rotation plate  21  caused by the bias magnetic field of the permanent magnet  110 . 
         [0038]    When the support  140  is provided, a gap is also formed between the conductor  130  and the rotation plate  21 . That is, in general, the sensor  40  for sensing the gap influences the magnetic bearing  100 , and as the gap is changed depending on the sensor  40 , the size or direction of the current supplied to the coil  120  is changed to maintain the gap within a predetermined range and control the position change of the rotation shaft  20  or the rotation plate  21 . 
         [0039]    As shown in  FIG. 3 , the permanent magnet  110  is provided in the space inside the conductor  130 , the support  140  is provided thereon, and the coil  120  is provided thereon. The function of the coil  120  in the case corresponds to the above description. 
         [0040]    Further, by the disposal of the above constituent elements, an empty space surrounded by the coil  120 , the conductor  130 , and the support ( 140 , wherein the support  140  is exchangeable with a rotation plate  21 ) is formed, and it is desirable to fill the empty space with a non-magnetic material such as Cu or Al. In a like manner of the conductor  130 , the filled non-magnetic material is used to form the path of the magnetic field and it supports the coil  120 . 
         [0041]    A drive of a turbo machine  1  using a structure of a magnetic bearing  100  according to the present invention will now be described with reference to  FIG. 2 ,  FIG. 5 , and  FIG. 6 . The drive including the support  140  will be exemplarily described, and the drive case with the support  140  has the same principle. 
         [0042]    The magnetic bearing  100  is used for the rotation shaft  20 , and in this instance, it is desirable for the rotation shaft  20  to exemplarily include the rotation plate  21  and for the magnetic bearing  100  to be used for the rotation plate  21 . In this instance, the rotation plate  21  is formed with a conductor. 
         [0043]    When the magnetic bearing  100  is used for the rotation plate  21 , as shown in  FIG. 2 , the rotation plate  21  levitates by the magnetic field generated by the permanent magnet  110 . In this instance, the magnetized direction of the permanent magnet  110  is in parallel with the shaft direction of the rotation shaft  20  so that the formation of the magnetic field does not become symmetrical. The formation does not significantly influence levitation of the rotation plate  21 . 
         [0044]    When the rotation shaft  20  is rotated according to an operation of the turbo machine  1 , the rotation plate  21  is rotated, and in this instance, the rotation plate  21  is rotated while changing the position in the shaft direction. Therefore, it is needed to control the position change of the rotation plate  21  within a predetermined range. In general, the position change of the rotation plate  21  can be checked by detecting a displacement of the rotation plate  21  through the sensor  40  attached to the inside or the outside of the magnetic bearing  100 . 
         [0045]    When the rotation plate  21  moves downward in the drawing as shown in  FIG. 5 , the magnetic field formed by the permanent magnet  110  is increased or reduced by the magnetic field formed by the coil  120 , the size or the direction of the current flowing to the coil  120  is controlled so that the direction of the magnetic field going downward may be greater than the magnetic field going upward, and the rotation plate  21  is moved upward. 
         [0046]    When the rotation plate  21  is moved upward in the drawing, as shown in  FIG. 6 , the magnetic field formed by the permanent magnet  110  is increased or reduced by the magnetic field formed by the coil  120 , the size or the direction of the current flowing to the coil  120  is controlled so that the direction of the magnetic field going upward may be greater than the magnetic field going downward, and the rotation plate  21  is moved downward. 
         [0047]    By controlling the position of the rotation plate  21  as described, the gap is maintained between the rotation plate  21  and the conductor  130  within a predetermined range. 
         [0048]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
         [0049]    The scope of the present invention should therefore not be construed as limited to the exemplary embodiments set forth herein, and should be defined by the appended claims and equivalents thereof.