JPH0416653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic bearing that supports a supported object with respect to a stationary part by magnetic force. [Technical background of the invention and its problems] Magnetic bearings that support rotating bodies and the like using magnetic force have been known as bearings that support rotating bodies and the like. A magnetic bearing is a supported object (hereinafter referred to as a "floating object").
Because it is supported in a completely non-contact state, it has great features such as no mechanical wear, extremely high durability, and no mechanical noise. Such a magnetic bearing is constructed by, for example, fixing a cylindrical body made of a magnetic material to a floating body, and arranging a yoke made of a magnetic material so as to fit into the cylindrical body in a non-contact manner. For example, an annular permanent magnet magnetized in the radial direction is attached to the circumferential surface of the yoke, and a plurality of magnetic poles for radial position control and a plurality of magnetic poles for axial position control are provided protrudingly. A magnetic flux is passed through a magnetic circuit composed of these permanent magnets, magnetic poles, a cylindrical body, and a yoke to generate magnetic force for supporting the floating body. Furthermore, a coil is wound around the plurality of magnetic poles, and by controlling the current applied to the coil, the amount of magnetic flux passing through the cylinder and the yoke is adjusted, thereby controlling stable support of the floating body. ing. Incidentally, in a conventional magnetic bearing of this type, the size, shape, etc. of each magnetic pole and each magnet are set approximately uniformly with respect to the control direction. For this reason, magnetic saturation may occur in the magnetic pole that controls the direction in which the largest load is applied, and problems may arise due to insufficient ability of the magnet to apply magnetic force at positions where the bearing load is large. Therefore, in order to avoid such problems, if the size, shape, etc. of each magnetic pole and each magnet are set to match the one that is expected to have the largest load, this will cause the problem of increasing the size of the entire magnetic bearing. It was hot. [Object of the Invention] The present invention has been made in view of the above-mentioned problems, and its purpose is to provide highly efficient magnetic bearing with no waste, thereby reducing the overall size and weight. The objective is to provide a magnetic bearing that can contribute to the development of [Summary of the Invention] The present invention provides a first magnetic element included on a floating body side, and a second magnetic element included on the fixed body side for supporting the floating body with a magnetic force with respect to a fixed body. and a plurality of radial position control elements protruding in the circumferential direction on the circumferential surface of the second magnetic element facing the first magnetic element, for controlling the radial position of the floating body. In order to support the floating body with magnetic force with respect to the fixed body by supplying magnetic flux through the magnetic poles for controlling the radial direction, and the first and second magnetic elements as magnetic paths. A magnet means for generating a magnetic force, a coil means wound around the magnetic pole, and a current applied to the coil means is controlled to adjust the amount of the magnetic flux to perform stable support control of the floating body. A magnetic bearing comprising at least a control means for
At least one of the cross-sectional area through which the magnetic flux of each of the radial position control magnetic poles passes or the magnetic flux generation capacity of the magnet means is set in accordance with the amount of load determined by the circumferential position of the floating body, The present invention is characterized in that a larger amount of magnetic flux is allowed to pass through the magnetic path corresponding to a large amount of load than at least one of the magnetic paths corresponding to another small amount of load. Note that the load amount herein refers to an amount that includes a load applied in a stationary state and a load applied continuously or instantaneously in an operating state. [Effects of the Invention] As described above, in the present invention, at least one of the cross-sectional area through which the magnetic flux of each magnetic pole for radial position control passes or the magnetic flux generating ability of the magnet means is adjusted to the circumferential position of the floating body. The magnetic flux is set in accordance with the amount of load determined by the above method, and is configured to allow more magnetic flux to pass through the magnetic path corresponding to the large amount of load than at least one other magnetic path corresponding to the other small amount of load. ing. Therefore, each magnetic pole is neither larger nor smaller than necessary, and the magnetic flux generation ability of the magnet means can be made efficient. Therefore, extremely highly efficient magnetic bearing can be performed, which ultimately contributes to miniaturization and weight reduction of the entire magnetic bearing. [Embodiments of the Invention] Details of the present invention will be described below based on illustrated embodiments. FIG. 1 shows an example in which the present invention is applied to a magnetic bearing for a grinder, and numeral 1 in the figure is a cylindrical case whose both ends are closed with, for example, a magnetic shielding material that blocks external magnetism. Inside the case 1, a cylindrical body 2, which is a supported side supporting element and is formed into a bottomed cylindrical shape made of, for example, a magnetic material, has a bottom wall 2a.
is housed facing left in the figure. Above bottom wall 2
One end side of the rotating shaft 3 is coaxially coupled to the central portion of a. The rotating shaft 3 extends outward through a hole provided in the left end wall of the case 1 in the figure.
It is connected to the grinder plate 4. The cylindrical body 2 has a groove 5 formed in the inner peripheral surface along the circumferential direction. The groove 5 is formed at a position substantially facing an axial position control magnetic pole 11, which will be described later, and the inner wall of the groove 5 serves as a path for magnetic flux used for axial position control. Thus, inside the cylindrical body 2, a stationary side support element is arranged. This bearing element is constructed as follows. That is, the yoke 6 made of a high magnetic permeability material is disposed within the cylindrical body 2 so as to fit into the cylindrical body 2 without contacting it. The yoke 6 is fixed to a support column 1a that projects from the inner surface of the right end wall of the case 1 toward the left in the figure. York 6
On the outer circumferential surface of the cylindrical body 2, at positions facing the inner circumferential surface of the cylindrical body 2, there are, in order from the left side in the figure, a magnetic pole group 10 for radial position control, a magnetic pole group 11 for axial position control, and a magnetic pole group 11 for radial position control. Each of the magnetic pole groups 12 is integrally provided in a protruding manner. As shown in FIG .
It is composed of three magnetic poles 10a, 10b, 10c and 10d. The magnetic pole 11 is formed to protrude from the yoke 6 in an annular shape. Further, the magnetic pole group 12 has a third
As shown in the figure, four magnetic poles 12a, 12b, 12c protrude in the same relationship as each magnetic pole of the magnetic pole group 10.
and 12d. Above, magnetic pole group 1
Each of the magnetic poles 10a to 10d constituting the magnetic pole group 1
The width in the axial direction is wider than that of each of the magnetic poles 12a to 12d constituting the magnetic poles 12a to 12d. Moreover, as shown in FIGS. 2 and 3, the magnetic pole group 10
In the figure, 10a and 10c protruding in the vertical direction are
It is formed so that its width in the circumferential direction is wider than each of the other magnetic poles. These magnetic poles 10a to 10d,
Radial stabilizing coils 13a to 13d and 14a to 14d are wound around the coils 12a to 12d, respectively. In addition, on the left and right sides of the magnetic pole 11 in FIG.
Axial stabilizing coils 15a and 15b wound around the respective axes are attached. Further, on the outer periphery of the yoke 6, annular permanent magnets 16, 1 magnetized in the radial direction are located between the magnetic pole group 10 and the magnetic pole group 11 and between the magnetic pole group 11 and the magnetic pole group 12.
7 are fitted together. The permanent magnet 16 is formed to have a wider width in the axial direction than the permanent magnet 17. On the other hand, a projecting peripheral wall 2b that slightly protrudes to the left in the figure is formed at the end edge of the bottom wall 2a located at the left end in FIG. 1 of the cylindrical body 2. A bearing 20 that mechanically supports the cylindrical body 2 in an emergency or the like is mounted on the left end wall of the case 1 facing the inner circumferential surface of the projecting peripheral wall 2b. Similarly, a projecting peripheral wall 2c is also provided at the right end of the cylindrical body 2 in the drawing. A bearing 21 is also mounted on the right end wall of the case 1, which faces the inner peripheral surface of the projecting peripheral wall 2c. A stator 26 of a motor 25 that generates a rotating magnetic field for applying rotational force to the cylindrical body 2 is fixed to the inner circumferential surface of the case 1 at the center in the figure.
A rotor 28 made of a highly conductive ring made of, for example, copper is attached to the outer peripheral surface of the cylindrical body 2 facing the stator 26. Furthermore, each of the magnetic poles 10a to 10d, 12a to 12d is attached to the case 1 via the cylindrical body 2.
Displacement detectors 30a, 30 for detecting displacement of the cylindrical body 2 in the radial direction are located at positions facing each other.
b, 30c and 30d and 31a, 31
b, 31c and 31d are provided, respectively. Further, in the case 1, displacement detectors 32a, 32b, and 32 for detecting displacement of the cylindrical body 2 in the axial direction are provided at positions facing the right end of the cylindrical body 2 in the figure.
c and 32d are provided. The magnetic bearing configured in this way has a permanent magnet 1
The magnetic flux generated at points 6 and 17 is expressed as P ₁ , P ₂ ,
As shown by P ₃ , P ₄ and P ₅ , P ₆ , P ₇ , P ₈ , the magnetic flux is caused to pass through each permanent magnet - yoke 6 - each magnetic pole - cylindrical body 2 - each permanent magnet. The cylindrical body 2 is supported in a non-contact manner by the generated magnetic force. The radial displacement and axial displacement of the cylindrical body 2 are detected by the displacement detectors 30a to 30d, 31a to 31d and 32a to 32d, respectively. displacement detector 30
The outputs of a to 30d and 31a to 31d are input to a known radial stabilization control device (not shown). This radial stabilization control device controls the radial stabilization coil 1 of the cylindrical body 2 based on the above input.
3a to 13d and 14a to 14d are energized. On the other hand, the output of the displacement detector 32 is input to a known axial stabilization control device (not shown). This axial stabilization control device energizes the axial stabilization coils 15a and 15d based on the above input in order to control the axial position of the cylindrical body 2 to an appropriate position.
In this way, the magnetic force acting on the cylindrical body 2 is adjusted by biasing each coil to correct the above displacement. When the motor 25 is connected to a power source (not shown) in this state, the cylindrical body 2 rotates in a non-contact state. Thus, the rotational driving force of the cylindrical body 2 is transmitted to the grinder plate 4 via the rotating shaft 3. By the way, when installed in the state shown in FIG.
As shown by arrow G in the figure, the magnetic pole group 10 and the permanent magnet 1
It is located approximately midway between 6 and 6. Therefore, in this case, the path requires the greatest magnetic force.
is the magnetic force caused by the magnetic flux at P ₂ .
According to this embodiment, the axial width of each of the magnetic poles 10a to 10d constituting the magnetic pole group 10 is increased, and the circumferential width of the magnetic poles 10a and 10c is increased. That is, of all the magnetic poles, 10a and 10c are formed to be the largest. Further, the permanent magnet 16 that generates magnetic flux in the path P ₂ is made larger than the other permanent magnets 17. Therefore, path P ₂ and path P ₁
can pass the most magnetic flux,
This allows the magnetic force to be maximized. On the other hand, a route that does not require particularly large magnetic force,
For example, in _P5 to _P8 , the permanent magnets 17 that supply magnetic flux to the magnetic poles forming the magnetic circuit and the paths _P5 to _P8 are formed in a small size, so that the entire bearing can be made small. As explained above, the present invention is characterized by a configuration that efficiently balances the magnetic force with the load (external force), but when the magnetic bearing of the present invention is applied to a grinder as in the above embodiment, The amount of load (including load during static and operating conditions) is defined as: In other words, the load exerted in a stationary state is
As shown in FIG. 1, in a grinder that is usually used horizontally, the load is mainly exerted by gravity. In addition, the load that is continuously or instantaneously applied in the operating state is the load that is mainly caused by gravity and the pressing force that presses the grinder plate against the workpiece. is defined as the vector sum of these external forces. As described above, according to this embodiment, highly efficient magnetic bearing can be performed without waste, and the above-mentioned effects can be fully exhibited. Note that the present invention is not limited to the above embodiments. In the embodiment described above, the permanent magnet 16 and the permanent magnet 17 are made to have a difference in thickness in the axial direction so as to have a difference in their ability to supply magnetic force. A magnet 40 may also be used. In this case, the radial thickness of the lower side of the permanent magnet 40 in the figure is made thicker than the upper radial thickness of the permanent magnet 40, so that the self-demagnetizing field of the lower side of the permanent magnet 40 can be minimized. can. Therefore, the magnetic flux density of the magnetic flux supplied from the lower side of the permanent magnet 40 to the cylindrical body 2 can be maximized, and as a result, the vector sum of the magnetic force can be efficiently balanced with the external force F. Furthermore, it is possible to achieve the effect of reducing the size of the bearing in the radial direction. Further, as shown in FIG. 5, the magnetic pole group 10 is arranged such that only the magnetic pole 41 extending downward in the figure is connected to the other magnetic poles 41a and 4.
It is clear that if it is configured to be larger than 1b and 41d, it can contribute to further reduction in size and weight than the above-mentioned embodiment. Moreover, it goes without saying that such aspects of the magnetic poles and the magnets serving as the magnetic force supply source are effective even if only one of them is used. Further, in the above explanation, the grinder shown in FIG. 1 was taken as an example, and an example of the type of magnetic bearing was explained. At least one of the passing cross-sectional area or the magnetic flux generation capacity of the magnet means is set in accordance with the amount of load determined by its circumferential position, and the magnetic path corresponding to a large amount of load is connected to another small amount of load. It is characterized by being configured to allow more magnetic flux to pass through than at least one corresponding magnetic path, and the field of application of magnetic bearings is of course not limited to grinders; The type of magnetic bearing is also applicable to all conventionally known magnetic bearings.
The point is that various modifications can be made without departing from the gist of the invention. Furthermore, the present invention is applicable to devices in which the axis is vertical and an external force is applied from a specific direction, devices in which the floating body makes reciprocating motion or rocking motion, and devices in which the floating body is located inside a group of magnetic poles. It can also be applied to things like this.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a magnetic bearing of a grinder according to an embodiment of the present invention, FIG. 2 is a view of the same magnetic bearing cut along line A-A in FIG. Figure 3 is a view of the same magnetic bearing cut along line B-B in Figure 1 and viewed in the direction of the arrow, Figures 4 and 5.
The figures are partial cross-sectional views of magnetic bearings according to other embodiments of the present invention. 1... Case, 2... Cylindrical body (floating body and first magnetic body), 3... Rotating shaft, 4... Grinder plate, 5... Groove, 6... Yoke (second magnetic body),
10, 12 ... Magnetic pole group, 10a-10d... Magnetic pole (magnetic pole for radial position control), 11... Magnetic pole (magnetic pole for axial position control), 12a-12d... Magnetic pole (magnetic pole for radial position control) , 41a to 41d...
Magnetic pole (magnetic pole for radial position control), 13a-13
d, 14a to 14d... Radial stabilization coil, 15a, 15b... Axial stabilization coil,
16, 17, 40...Permanent magnet (magnet means), 2
0, 21...Bearing, 25...Motor, 30
a~30d, 31a~31d, 32a~32d...
…Displacement detector, P ₁ to _{P 8} …path.

Claims (1)

[Scope of Claims] 1. A first magnetic element included on the floating body side; A second magnetic element included on the fixed body side for supporting the floating body with magnetic force with respect to the fixed body; A plurality of protrusions are provided in the circumferential direction on the circumferential surface of the second magnetic element facing the first magnetic element,
a radial position control magnetic pole for controlling the radial position of the floating body; each of the radial position control magnetic poles and the first
and magnet means for supplying magnetic flux through each of the second magnetic elements as a magnetic path to generate a magnetic force for magnetically supporting the floating body with respect to the fixed body, and controlling the radial position of each of the above. a coil means wound around a magnetic pole; and a control means for controlling the stable support of the floating body by adjusting the amount of the magnetic flux by controlling the current flowing through the coil means. In the magnetic bearing, at least one of the cross-sectional area through which the magnetic flux of each of the radial position control magnetic poles or the magnetic flux generation capacity of the magnet means corresponds to the amount of load determined by the circumferential position of the floating body. A magnetic bearing, characterized in that the magnetic bearing is configured to allow more magnetic flux to pass through the magnetic path corresponding to a large amount of load than at least one of the magnetic paths corresponding to another small amount of load.