JP2010121713A - Magnetic bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing usable even in an environment where a permanent magnet cannot be used, and capable of generating large bearing force in a predetermined direction. <P>SOLUTION: This magnetic bearing 100 is provided for supporting a substantially cylindrical rotary body 2 rotating to a fixed shaft 1 in a noncontact state. The magnetic bearing 100 is provided by arranging a void between an outer surface of a stator 3 and the rotary body 2 by winding a plurality of bias coils 4 on the stator 3 integrally arranged with the fixed shaft 1 so as to be opposed in close vicinity to an inner peripheral surface of the rotary body 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic bearing, and more particularly to a magnetic bearing that supports a rotating body that rotates while receiving a load mainly from a predetermined direction in a non-contact manner.

  Currently, mechanical bearings such as roller bearings are used as bearings for various large rolls such as papermaking rolls and rolling rolls. However, mechanical bearings need to be regularly maintained and replenished with lubricants such as grease, and the production line must be stopped during maintenance, so there is a limit to the continuous operation time. It is a hindrance. However, it is very difficult to remove the vibration during rotation of the large roll by the mechanical bearing and further improve the rotation accuracy of the large roll, which hinders quality improvement including the accuracy of the final product. .

  Considering these, it is conceivable to use a magnetic bearing instead of a mechanical bearing as a large roll bearing. Since the magnetic bearing supports the rotating body in a non-contact state and does not require a lubricant, regular maintenance can be omitted and the continuous operation time can be greatly extended. In addition, the magnetic bearing can be actively controlled for the position and inclination during rotation by providing an automatic position adjustment function, and the rotation accuracy of the large roll can be improved.

For example, Non-Patent Document 1 discloses a magnetic bearing 900 having an automatic position adjustment function. The magnetic bearing 900 is a hybrid type magnetic bearing including a permanent magnet 901 and an electromagnet, as shown in a schematic axial sectional view in FIG. The magnetic bearing 900 supports the rotating shaft 903 that rotates with respect to the fixed portion 902 in a non-contact manner, and a permanent magnet 901 is fixed to the outer cylinder of the fixed portion 902. As shown in FIG. 6, the electromagnet is provided by winding a control coil 905 around a protrusion 904 that protrudes from the fixed portion 902 so as to face and oppose the rotation shaft 903. The bias magnetic flux generated by the permanent magnet 901 passes evenly as shown by the arrows in FIG. 6, and a bearing force is generated that supports the rotating shaft 903 in a non-contact manner in all directions with respect to the fixed portion 902. The position and inclination of the rotating shaft 903 can be controlled by adjusting the current supplied to the control coil 905 according to the displacement of the rotating shaft 903 detected by the sensor 906.
"IEEE / ASME TRANSACTIONS ON MECHATONICS, VOL.6, No.4, DECEMBER 2001" 521-524

  However, since the conventional hybrid magnetic bearing 900 generates a bias magnetic flux by the permanent magnet 901, there is a problem that it cannot be used in an environment where the permanent magnet cannot perform its function such as a high temperature environment. In addition, since the bias magnetic flux passes evenly, a large bearing force cannot be effectively generated even when receiving a high load from one direction. Therefore, there was a problem that it was not possible to cope with a large roll for which further enlargement was requested in order to increase production efficiency.

  The present invention has been made in view of the above problems, and provides a magnetic bearing that can be used even in an environment where a permanent magnet cannot be used and can generate a large bearing force in a predetermined direction. With the goal.

  In order to achieve the above object, a magnetic bearing according to claim 1 is a magnetic bearing that supports a substantially cylindrical rotating body that rotates with respect to a fixed shaft in a non-contact manner, and is provided integrally with the fixed shaft. A plurality of bias coils are wound around the stator so as to be close to and opposed to the inner peripheral surface of the rotating body, and a gap is provided between the outer surface of the stator and the rotating body.

  A magnetic bearing according to a second aspect is the magnetic bearing according to the first aspect, wherein the stator has a semi-cylindrical outer peripheral surface that faces and opposes the inner peripheral surface of the rotating body, and the outer peripheral surface includes the outer peripheral surface. A part of the bias coil is accommodated in the formed recess.

  According to a third aspect of the present invention, there is provided the magnetic bearing according to the second aspect, wherein an annular groove is formed on an inner peripheral surface of the rotating body that is in close proximity to the bias coil.

  A magnetic bearing according to a fourth aspect of the invention is the magnetic bearing according to any one of the first to third aspects, wherein the displacement of the rotating body is detected in a gap between the outer surface of the stator and the rotating body. It is characterized by providing a sensor.

  A magnetic bearing according to a fifth aspect is the magnetic bearing according to any one of the first to fourth aspects, wherein a plurality of pairs of salient poles each having a control coil wound around the stator are provided, The position of the rotating body is controlled by controlling the generated control magnetic flux.

  A magnetic bearing according to a sixth aspect is the magnetic bearing according to the fifth aspect, wherein a bias magnetic flux density substantially equal to a saturation magnetic flux density of the stator is generated by the bias coil.

  According to the magnetic bearing of the first aspect of the present invention, since the bias magnetic flux is generated by the bias coil, unlike the conventional magnetic bearing 900 in which the bias magnetic flux is generated by the permanent magnet, the permanent magnet such as a high temperature environment is The magnetic bearing can be satisfactorily used even in an environment where the function cannot be exhibited. In addition, since a gap is provided between the outer surface of the stator and the rotating body, the bias magnetic flux generated by the bias coil cannot exceed the gap. Bearing force (bias attractive force) in the predetermined direction is generated by the magnetic flux. Therefore, unlike the conventional magnetic bearing 900 in which the bias magnetic flux is uniformly passed by the permanent magnet and the bearing force is generated uniformly, the bearing force is effectively generated as a counter force against the load received from the direction opposite to the predetermined direction. Therefore, it is possible to obtain a magnetic bearing that can handle a high load with low power consumption. In addition, since a plurality of bias coils are wound, it is possible to obtain a magnetic bearing that can generate a large bearing force while being small in size.

  According to the magnetic bearing of claim 2, the stator has a semi-cylindrical outer peripheral surface that is close to and opposed to the inner peripheral surface of the rotating body, and a part of the bias coil is formed in the concave portion formed on the outer peripheral surface. Is housed. For this reason, the bias magnetic flux can pass through the side where the outer surface of the semi-cylindrical surface is formed, but there is a gap between the stator and the rotating body on the opposite side, so the bias magnetic flux exceeds the gap and I can't pass. Therefore, the bias magnetic flux is biased toward the side on which the outer peripheral surface is formed, and a bearing force directed to the side on which the outer peripheral surface is formed is generated by the bias magnetic flux. In addition, the region where the bias magnetic flux can pass can be maximized on the side where the semicircular cylindrical surface is formed, and the bearing force generated toward the side can be increased. It should be noted that, on the side opposite to the side on which the outer peripheral surface of the semi-cylindrical surface is formed, the area where the bias magnetic flux can be passed can be reduced by widening the gap. The bearing force to be generated can be reduced, and the bearing force to be generated toward the side on which the semi-cylindrical outer peripheral surface is formed can be increased.

  According to the magnetic bearing of the third aspect, since the annular groove is formed on the inner peripheral surface of the rotating body that is in close proximity to the bias coil, the convex portion is formed between the formed annular grooves on the inner peripheral surface of the rotating body. Arise. Therefore, the convex portion and the convex portion generated between the concave portions formed on the outer peripheral surface of the stator are opposed to each other, and the rotating body is axially moved by the attraction action generated by the bias magnetic flux concentrated on the convex portions. It is possible to obtain a large restoring force to be held at a predetermined position. Moreover, since these convex parts are formed in multiple in the axial direction, the said restoring force can be obtained more favorably. Therefore, the axial position variation of the rotating body is stabilized, the thrust bearing can be omitted or downsized, and the manufacturing cost of the magnetic bearing can be reduced.

  According to the magnetic bearing of the fourth aspect, since the sensor is provided in the gap between the outer surface of the stator and the rotating body, it is not necessary to provide a sensor outside as in the conventional magnetic bearing 900. The magnetic bearing can be downsized.

  According to the magnetic bearing of the fifth aspect, since the position of the rotating body is controlled by controlling the control magnetic flux generated by the control coil, the control force changes according to the current supplied to the control coil. By adjusting the current supplied to the control coil, the position of the rotating body can be easily actively controlled, and the position accuracy of the rotating body can be improved.

  According to the magnetic bearing of claim 6, since the bias coil generates a bias magnetic flux density substantially equal to the saturation magnetic flux density of the stator, the change in the bias magnetic flux due to the gap fluctuation between the rotating body and the stator is reduced, The fluctuation of the bearing force generated by the bias magnetic flux can be reduced. Therefore, it is possible to reduce the control force required to absorb the fluctuation of the bearing force, to reduce the size of the control unit, and to reduce the size and manufacturing cost of the magnetic bearing.

  A magnetic bearing 100 according to an embodiment of the present invention supports a substantially cylindrical rotating body 2 in a non-contact manner with respect to a fixed shaft 1, as shown in a schematic axial sectional view in FIG. 1, a stator (stator) 3 is integrally fixed. The stator 3 is fixed to the fixed shaft 1 in the order of the first stator 31, the second stator 32, and the third stator 33 along the axial direction of the fixed shaft 1. Although not shown, the fixed shaft 1 is fixed to the base by a support shaft.

  The stator 3 constitutes a bias magnetic path through which a bias magnetic flux passes, and a plurality (three) of bias coils 4 are wound around the inner peripheral surface of the rotating body 2 so as to face each other. As shown in FIGS. 2A and 2B, the stator 3 is formed so as to provide a gap between the rotor 3 and the lower side of each figure. Specifically, as shown in FIG. 2A, the cross section of the stator 3 in the direction orthogonal to the rotation axis direction is substantially fan-shaped. In more detail, the cross-sectional outer shape is a semicircle whose upper side has a diameter substantially equal to the diameter of the inner peripheral surface of the rotating body 2, and whose lower side has a semicircle having a diameter shorter than the diameter of the upper semicircle, and the semicircle. It consists of tangents from both ends of the upper semicircle to the circle. On the outer peripheral surface of the stator 3, as shown in FIG. 1, recesses 5 in which a part of each bias coil 4 is accommodated are formed. As shown in FIG. 2 (b), the stator 3 in the portion where the concave portion 5 is formed has a circular outer peripheral surface centering on the rotation center, and a part of the outer peripheral surface is the lower surface. It is connected to the surface formed by the semicircle on the side. Thereby, the bias coil 4 is disposed so as to be close to and opposed to the inner peripheral surface of the rotating body 2 over the entire circumference thereof. Moreover, since the several recessed part 5 is formed, a convex part will be formed in the meantime, respectively. Since the stator 3 forms a magnetic path through which the bias magnetic flux passes, the stator 3 is preferably a laminated iron core, but is not necessarily laminated.

  Further, the stator 3 constitutes a control magnetic path through which the control magnetic flux passes. As shown in FIG. 3, two pairs are respectively provided on the outer sides in the axial direction of the first and third stators 31 and 33. (Four) salient poles 6 are provided. Each salient pole 6 is provided by winding a control coil 62 around a projecting portion 61 formed so as to extend equally in four directions around the rotation axis, that is, in a cross shape as a whole. Yes.

  The rotating body 2 has a substantially cylindrical shape, and annular grooves 7 are respectively formed on the inner peripheral surface facing the bias coil 4. The rotating body 2 includes a cylindrical outer cylinder 24 in which three substantially short cylindrical rotors (rotors) 21, 22, 23 corresponding to the first to third stators 31, 32, 33 are divided. Is fixed by a fixing tool (not shown) such as a bolt. Since the plurality of annular grooves 7 are formed, convex portions are respectively formed between them. These convex portions are in close proximity to the convex portions formed on the outer peripheral surface of the stator 3.

  A pair of displacement sensors 7 are provided at two locations in the gap between the stator 3 and the rotating body 2. The displacement sensors 8 are fixed to the fixed shaft 1 while being separated as much as possible in the axial direction within the gap. The pair of displacement sensors 8 detect displacement (gap) in two directions with respect to the rotating body 2. A detection unit (not shown) obtains a deviation of the rotating body 2 from the predetermined position with respect to the fixed shaft 1 based on the detection signals output from the displacement sensors 8.

  When the bias coil 4 and the control coil 62 of the magnetic bearing 100 configured as described above are energized, a bias magnetic flux is generated by the bias coil 4, and a control magnetic flux is generated by the control coil 62. The magnetic bearing 100 generates a bearing force so as to be supported in a non-contact manner with respect to the fixed shaft 1.

  As shown in FIG. 4, the bias magnetic flux generated by energizing the bias coil 4 is formed so as to go around the rotor 2 from the stator 3. Since the bias magnetic flux cannot cross the gap provided between the stator 3 and the rotating body 2 and cannot reach the rotating body 2, the bias magnetic flux is biased to the side where no gap is provided (upper side in the figure). The bearing force (bias attractive force) generated by the magnetic flux is directed in a predetermined direction opposite to the side where the air gap is provided. Therefore, unlike the conventional magnetic bearing 900 shown in FIG. 5, unlike the case where the bias magnetic flux is generated uniformly, it is possible to generate a bearing force as a counter force against the load received from the direction opposite to the predetermined direction.

  Since the stator 3 has a semi-cylindrical outer peripheral surface that is close to and opposed to the inner peripheral surface of the rotating body 2 and a part of the bias coil 4 is accommodated in the recess 5 formed on the outer peripheral surface, the bias magnetic flux Can pass through the side where the semicircular cylindrical surface is formed (upper side in the figure), but there is a gap between the stator 3 and the rotating body 2 on the opposite side. I can't pass. Therefore, the bias magnetic flux is biased toward the side where the outer peripheral surface is formed, and a bearing force is generated in the side direction (upward in the figure) where the outer peripheral surface is formed by the bias magnetic flux. Further, the region through which the bias magnetic flux can pass is maximized on the side where the outer surface of the semi-cylindrical surface is formed, and a large bearing force can be generated toward the side. Further, on the side opposite to the side on which the semi-cylindrical outer peripheral surface is formed, the gap is widened to such an extent that the bias coil 4 can be wound appropriately, and the region through which the bias magnetic flux can pass is reduced. Therefore, the bearing force generated toward the opposite side is reduced, and the bearing force generated toward the side where the semi-cylindrical outer peripheral surface is formed is increased as a whole.

  As described above, since the bias magnetic flux is generated by the bias coil 4, unlike the conventional magnetic bearing 900 shown in FIG. 5 in which the bias magnetic flux is generated by the permanent magnet, the permanent magnet such as a high temperature environment exhibits its function. The magnetic bearing 100 can be used satisfactorily even in an unobtainable environment. Therefore, the magnetic bearing 100 can be suitably used for various large rolls such as a papermaking roll and a rolling roll. Although the fixed shaft 1 is illustrated as being solid, the fixed shaft 1 may be provided with a cavity in which a signal line or the like from the displacement sensor 8 is disposed.

  Moreover, since the convex part produced between the recessed parts 5 formed in the outer peripheral surface of the stator 3 and the convex part produced between the annular grooves 7 formed in the inner peripheral surface of the rotating body 2 are close to each other, these A large restoring force for holding the rotating body 2 at a predetermined position in the axial direction can be obtained by the attraction action generated by the bias magnetic flux concentrated on the convex portion. Moreover, since these convex parts are formed in multiple in the axial direction, the said restoring force can be obtained more favorably. Therefore, the axial position variation of the rotating body 2 is stable, and the thrust bearing can be omitted or downsized.

  Further, since the displacement sensor 8 is provided in the gap between the stator 3 and the rotating body 2, it is not necessary to provide an external sensor unlike the conventional magnetic bearing 900, so the magnetic bearing 100 can be downsized. Is possible.

  Further, the position of the rotating body 2 is controlled by controlling the control magnetic flux generated by adjusting the current supplied to the control coil 62. Therefore, since the control force changes in proportion to the current supplied to the control coil 62, the position of the rotating body 2 can be easily actively controlled by adjusting the current supplied to the control coil 62. It is possible to improve the positional accuracy of the.

  Further, it is preferable that the bias coil 4 generate a bias magnetic flux density substantially equal to the saturation magnetic flux density of the stator 3. Since the change of the bias magnetic flux due to the gap fluctuation between the rotating body 2 and the stator 3 can be reduced and the fluctuation of the bearing force generated by the bias magnetic flux can be reduced, the control force necessary to absorb the fluctuation of the bearing force can be reduced. .

  Further, by appropriately changing the number of the stators 31, 32, 33, it is possible to easily provide the bias coil 4 appropriately according to the required bearing force. Therefore, it is possible to generate a large bearing force while being small, and the expandable magnetic bearing 100 can be easily obtained.

  The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the present embodiment, a mode in which a rotating body that rotates while receiving a high load from a predetermined direction is described as a magnetic bearing that supports the fixed shaft in a non-contact manner has been described. Needless to say, the embodiment can be changed without departing from the gist of the present invention, such as a magnetic bearing for supporting the rotating body rotating with respect to the contactless contact.

1 is a schematic axial sectional view of a magnetic bearing 100 according to an embodiment of the present invention. 2A and 2B are schematic cross-sectional views of the magnetic bearing 100, in which FIG. 1A shows a cross section taken along the line AA shown in FIG. 1, and FIG. It is a schematic sectional drawing of the magnetic bearing 100, and shows the cross section in CC shown in FIG. 3 is an explanatory diagram for explaining a magnetic path through which a bias magnetic flux passes in a magnetic bearing 100. FIG. FIG. 6 is a schematic axial sectional view showing a conventional magnetic bearing 900. It is explanatory drawing explaining the magnetic path through which the bias magnetic flux in the conventional magnetic bearing 900 passes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed shaft 2 Rotating body 3 Stator 4 Bias coil 5 Recess 6 Salient pole 7 Annular groove 8 Displacement sensor 100 Magnetic bearing

Claims (6)

A magnetic bearing that supports a substantially cylindrical rotating body that rotates with respect to a fixed shaft in a non-contact manner,
A plurality of bias coils are wound around a stator provided integrally with the fixed shaft so as to be close to and opposed to the inner peripheral surface of the rotating body, and a gap is formed between the outer surface of the stator and the rotating body. A magnetic bearing characterized by being provided.   The stator has a semi-cylindrical outer peripheral surface close to and opposed to the inner peripheral surface of the rotating body, and a part of the bias coil is accommodated in a recess formed in the outer peripheral surface. The magnetic bearing according to claim 1.   The magnetic bearing according to claim 2, wherein an annular groove is formed on an inner peripheral surface of the rotating body that is in close proximity to the bias coil.   4. The magnetic bearing according to claim 1, wherein a sensor that detects a displacement of the rotating body is provided in a gap between an outer surface of the stator and the rotating body. 5.   2. The position of the rotating body is controlled by providing a plurality of pairs of salient poles each having a control coil wound around the stator, and controlling the control magnetic flux generated by the control coil. 5. The magnetic bearing according to any one of 4 above.   6. The magnetic bearing according to claim 5, wherein a bias magnetic flux density substantially equal to a saturation magnetic flux density of the stator is generated by the bias coil.

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