JPH0332176B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a magnetic bearing device.

[Background technology of the invention]

For example, when classifying X-ray tube devices structurally, they are roughly divided into fixed anode types and rotating anode types. Among these, the rotating anode type has advantages such as the fact that the anode rotates, so the effective area of the heat load applied to the anode can be increased, which allows it to withstand instantaneous large loads, and the fan angle can be increased. It is equipped with

By the way, regarding the rotating anode type X-ray tube device,
The higher the rotation speed of the anode, the more the anode can be protected from heavy loads. Therefore, when applying a large load to the anode, it is necessary to rotate the anode as fast as possible. In this way, a high-speed rotational drive source is required to rotate the anode at high speed, but if the rotating part of this rotational drive source is supported by a mechanical bearing device, the rotation speed is usually at most 10,000 rotations per minute. The extent is the limit. In addition, when a mechanical bearing device is used, not only does it consume a lot of power to increase the rotation speed to the specified speed in a short period of time, but the life of the bearing is short. Because it must be installed inside a vacuum container,
The lifespan of the entire device is short, and furthermore, the device is too noisy to be used for medical purposes.

Therefore, in order to eliminate such problems,
Recently, a device using a so-called magnetic bearing device has been proposed in which a rotor supporting a rotating anode is supported in a completely non-contact manner by magnetic force supplied from outside the vacuum container. In other words, this magnetic bearing type device is
A ring made of a high magnetic permeability material is attached to the rotor, and a permanent magnet for supplying magnetic force for magnetic support is placed outside the vacuum vessel, and the magnetic flux from the permanent magnet is transferred from the permanent magnet to the ring to the vacuum. The rotor is supported in a completely non-contact manner in both the axial and radial directions by passing through a path between a yoke with magnetic poles provided outside the container and a permanent magnet. and,
A coil is attached to the magnetic pole, and the coil is appropriately energized to correct the displacement of the rotor.

[Problems with background technology]

As mentioned above, in the case where the rotor supporting the rotating anode is supported by magnetic force, the rotor is in a so-called floating form within the vacuum container, so energy loss due to friction is reduced. Compared to a device that does not exist and is supported by a mechanical bearing, it consumes less power and can significantly improve the allowable rotational speed. Furthermore, since there are no elements inside the vacuum container that deteriorate due to friction, the life of the entire device can be significantly extended, and noise issues can also be eliminated.

However, as mentioned above, the rotor is always suspended by magnetic force within the vacuum vessel, so when the rotor is rotated, for example, when the When an external force is applied, the support of the rotor tends to become unstable. In order to prevent instability even when such a large external force is applied, it is necessary to increase so-called magnetic rigidity. For this reason, the so-called constant energization method, in which the magnetic restraint force on the rotor is strengthened by constantly passing current through the coils mentioned above, and the This is a so-called instantaneous energization method in which the coil is energized for a certain amount of time to move the rotor against the external force to a new equilibrium position where the attractive force of the permanent magnet and the external force are balanced. A stabilization control method is being considered that selects the appropriate amount depending on the operating conditions.

However, in the case of conventional devices, that is, conventional magnetic bearing devices, if the instantaneous energization method is selected,
It is necessary to move the rotor by a considerable amount in the direction opposite to the direction of the external force against the external force, and as a result, the power consumption required for the movement is large, making the characteristics of the instantaneous energization method effective. There was a problem that I couldn't do. Although it is possible to increase the number of turns of the coil in order to suppress power consumption, this would not only increase the size of the entire device, but also make it difficult to obtain an appropriate current, so that favorable results would not be obtained.

[Purpose of the invention]

The present invention was made in view of these circumstances, and its purpose is to significantly improve the magnetic rigidity of only the permanent magnets that serve as the source of magnetic flux to achieve magnetic bearing force. The object of the present invention is to provide a magnetic bearing device that can significantly reduce the amount of electric power required when an instantaneous energization stabilization control method is selected.

[Summary of the invention]

The magnetic bearing device according to the present invention includes a cylindrical rotor, and an inner ring and an outer ring made of a high magnetic permeability material on the inner and outer peripheral surfaces of the rotor, respectively. Then, an inner yoke and an outer yoke with magnetic poles are arranged concentrically with the rotor inside and outside the rotor, and the inner yoke and outer yoke have magnetic poles on their peripheral surfaces facing the rotor. An inner annular permanent magnet and an outer annular permanent magnet, which are magnetized in the radial direction and serve as a magnetic force supply source for the magnetic bearing, are respectively attached to the peripheral surface other than the part where the magnet is located.
The rotor is magnetically supported on the inner and outer surfaces by the magnetic flux emitted from the inner and outer annular permanent magnets. Further, coils are attached to the magnetic poles of the inner and outer yokes, and means is provided for energizing each coil in accordance with the relative positional deviation between the inner and outer yokes and the rotor in order to correct the deviation. It has become something that was established.

〔Effect of the invention〕

With the above configuration, the rotor receives a centripetal magnetic attraction force inward by the so-called inner magnetic force supply system, and receives a magnetic attraction force in the radial direction by the outer magnetic force supply system. Therefore, the magnetic rigidity can be easily increased compared to a structure in which a magnetic force supply system is simply provided on only one side. That is, if only the rotor portion of the magnetic bearing device according to the present invention is extracted and schematically shown, the inner magnetic force supply system S, the rotor R, and the outer magnetic force supply system T are arranged concentrically as shown in FIG. It is said that it was placed in . The magnetic rigidity of the rotor R is evaluated by the vectorial sum of the amount of movement of the rotor R and the magnetic forces exerted on the rotor R by the inner and outer magnetic force supply systems S and T during this movement. Now, in FIG. 1, let us consider a case where the rotor R is translated by x _d in the positive direction of the x-axis due to an external force. If the attractive force exerted on the rotor R by the inner magnetic force supply system S on the x-axis is _a , - _b considering the direction of the force, then the magnetic stiffness k on the x-axis due to the inner magnetic force supply system S is , qualitatively, k= _a +(- _b )/ _xd ...(1). Now, the rotor R moves in the positive direction on the x-axis x _d
Under the condition that the magnetic gap A is moved by the same amount, the magnetic gap A becomes narrower, and the magnetic gap B becomes wider. Therefore, the magnetic attraction forces _a , _-b exerted by the inner magnetic force supply system S on the rotor R on the x-axis are | _a |>|
− _b |, and k in equation (1) is a positive value.

On the other hand, on the x-axis, the magnetic attraction forces F _a and -F _b exerted on the rotor R by the outer magnetic force supply system T are determined by the fact that the magnetic gap A' becomes wider and the magnetic gap B' becomes narrower. |F _b |>|−F _a |.
Then, the magnetic stiffness K due to the magnetic attraction force exerted on the rotor R by the inner and outer magnetic force supply systems S and T
is qualitatively expressed as k=( _a + _Fb )+(- _b - _Fa )/ _xd ...(2). Here, as mentioned above, | _a | > | −
From the conditions of _b |, |F _b |＞|−F _a |, | _a +F _b
|>|− _b −F _a |, and K is positive. Also,
Now, if _a = F _b , - _b = -F _a , equation (2) becomes k = 2 _a + 2 (- _b )/x _d ... (3). Therefore, if we rewrite the above equation (3), we get K=2k...(4), and by providing the inner and outer magnetic force supply systems S and T, compared to the case where only one of them is provided, The rigidity due to magnetic force can be easily increased. This has the following meaning. That is, when the instantaneous energization stabilization control method is selected, as described above, the rotor R is
When the rotor R deviates from the equilibrium position, it is first necessary to energize the coil to move the rotor R in the opposite direction to the direction of the external force to a new equilibrium position where the attractive force by the magnetic force supply system and the external force are balanced. However, when the magnetic rigidity of the device of the present invention is significantly increased compared to the conventional device, the above-mentioned attraction force is inevitably large, and therefore, it is difficult to reach a new equilibrium position where the attraction force and external force are balanced. The amount of migration is significantly smaller than in conventional devices. Therefore, the amount of electric power required for the transition can be reduced compared to conventional devices, and the fluctuation in the rotor position due to changes in external force can also be reduced.
The rotor can be stably supported. Also,
The critical speed of the rotor R is proportional to the square root of the above-mentioned stiffness. Therefore, in order to increase the critical speed, it is necessary to significantly increase the rigidity, but if the magnetic force supply system is provided inside and outside the cylindrical rotor as in the device of the present invention, the above-mentioned outside magnetic supply By increasing the magnetic supply power of the system, the critical speed can be increased relatively easily without increasing the diameter of the rotor. Furthermore, the constant energization stabilization control method can of course be selected without any restrictions. As an example of these selections, the constant energization stabilization control method and the instantaneous energization stabilization control method are appropriately selected during the period in which the rotor is raised to the specified rotation speed, and the instantaneous energization stabilization control method is selected as appropriate during the subsequent so-called waiting time. Select the energization stabilization method, and also select the constant energization stabilization method during steady operation. These selections may vary.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a rotating anode type X-ray tube device incorporating a magnetic bearing device according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a vacuum container made of insulating material and formed into a cylindrical shape. In the upper part of the vacuum container 1 in the figure, a cathode 2 and, for example, a rotating anode 3 formed in a cylindrical shape are spaced apart in the vertical direction in the figure. are placed facing each other.

A filament (not shown) is attached inside the cathode 2 . The cathode 2 is connected to a conductor 4. The conductor 4 includes a portion 5 that airtightly penetrates the center of the upper wall of the vacuum vessel 1 in the axial direction;
It consists of a portion 6 extending, for example, at right angles from the tip of this portion 5 located inside the vacuum vessel 1, and the cathode 2 is fixed to the tip of the portion 6. Note that both ends of the filament are led to the outside of the vacuum vessel 1 via an insulated wire (not shown) disposed within the conductor 4.

The rotating anode 3 is arranged such that the peripheral part of the upper surface always faces the cathode 2 in the figure, and the upper surface of the peripheral part is formed into a tapered surface that gradually becomes thinner as it approaches the outer periphery. There is. The rotating anode 3 is supported by a rotor 11, which will be described later.

Therefore, in a portion of the wall of the vacuum vessel 1 that faces the lower surface of the rotating anode 3 in the drawing, there is a recessed wall that is recessed in a cylindrical shape with a bottom toward the rotary anode 3. 7 is formed, and furthermore, in the central part of the so-called bottom wall of the recessed wall 7, an inner side is formed by recessing the central part concentrically with the recessed wall 7 toward the side opposite to the rotating anode. A recessed wall 8 is formed. A rotor 11 is rotatably housed within the cylindrical space 10 formed between the recessed wall 7 and the cylindrical wall portion 9 located outside thereof, and within the inner recessed wall 8. .

The rotor 11 is roughly divided into the rotating anode 3
The upper end in the figure is the rotating anode 3.
A conductive auxiliary shaft 12 is connected to the central part of the lower surface in the figure, and the lower end in the figure is fitted into a cavity surrounded by the inner recessed wall 8, and the upper end in the figure is connected to the center part of the lower surface through the annular insulating material 13. The rotor body 14 is connected to the auxiliary shaft 12 and has a cylindrical rotor body 14 whose lower end in the figure is fitted into the cylindrical space 10 . The rotor main body 14 is a cylindrical body 1 made of a non-magnetic material or a paramagnetic material and has an outer diameter smaller than the inner diameter of the wall portion 9 and an inner diameter larger than the outer diameter of the recessed wall 7.
5, and annular grooves 16a, 16 formed on the inner peripheral surface and outer peripheral surface of this cylinder 15 in a two-stage configuration vertically in the figure.
b, 16c, 16d, and these annular grooves 16a, 1
Rings 17a, 17b, 17 made of high magnetic permeability material are mounted and fixed inside 6b, 16c, 16d, respectively.
c, 17d, and a rotor 19 of a motor 18 fixed to the inner peripheral surface of the cylinder 15 at the lower part in the figure. Moreover, on the inner surface of the inner recessed wall 8,
Bearings 21a and 21b, which mechanically support the auxiliary shaft 12 only in an emergency, normally support the auxiliary shaft 12.
It is provided in a non-contact manner. Furthermore, auxiliary shaft 1
A pin 22 is provided protruding from the lower end surface of FIG. The contact plate 23 is connected to the tip of a conductive rod 24 that passes through the so-called bottom wall of the inner recessed wall 8 in an airtight manner.

An inner yoke 25 is inserted into the space surrounded by the recessed wall 7 and concentrically with the recessed wall 7. This inner yoke 25 is constructed by combining a plurality of blocks, for example, and is formed into an annular shape as a whole as shown in FIG. 3, and has a hole 26 in the center into which the inner recessed wall 8 can fit. have. The outer circumferential surface of both ends of the inner yoke 25 is provided with a
Four magnetic poles 27a, 2 protruding at an opening angle of 90 degrees
Two sets of magnetic pole groups 28 and 29, each including 7b, 27c, and 27d, are provided in a two-stage configuration. In addition,
The distance between the magnetic pole surfaces of the magnetic poles protruding on the same line orthogonal to the axial center line of each magnetic pole group 28, 29 is the distance between the magnetic pole surfaces of the recessed wall 7.
It is set to a value approximately equal to the inner diameter of. A coil 30 for radial stabilization control is attached to the outer periphery of each magnetic pole of each magnetic pole group 28, 29. In addition, an annular magnetic pole 31 is protruded around the axis at the center of the portion located between each magnetic pole group 28 and 29, and axial stabilization is provided on the outer periphery of both axial sides around this magnetic pole 31. Coils 32a and 32b used for control are attached. Thus, on the outer periphery of the inner yoke 25, between the magnetic pole group 28 to which the coil 30 is attached and the coil 32a, and between the coil 32b and the magnetic pole group 2 to which the coil 30 is attached.
9, as shown in FIGS. 2 and 5, there are annular permanent magnets 33a, 33 magnetized in the radial direction.
b is attached. Then, as described above, the coils 30, 32a, 32b and the permanent magnet 33a,
The inner yoke 25 to which the inner yoke 33b is attached is inserted into the space surrounded by the recessed wall 7, as shown in FIG.

Therefore, an annular outer yoke 40 is provided on the outer periphery of the wall portion 9 of the vacuum vessel 1 concentrically with the inner yoke 25.
is installed. At a position on the inner peripheral surface of the outer yoke 40 facing each of the magnetic poles 27a, 27b, 27c, and 27d constituting each of the magnetic pole groups 28 and 29 of the inner yoke 25, as shown in FIG. 2
Magnetic poles 43a, 43b, 43c, and 43d constituting magnetic pole groups 41 and 42 corresponding to magnetic poles 8 and 29 are protruded, and an annular magnetic pole 44 is protruded at a position facing the magnetic pole 31 of the inner yoke 25. It is set up. Further, a coil 45 for radial stabilization control is attached to the outer periphery of each magnetic pole constituting each of the magnetic pole groups 41 and 42, and a coil 45 for radial stabilization control is installed on both sides of the magnetic pole 44 in the axial direction. coils 46a, 46b
is installed. Between the magnetic pole group 41 to which the coil 45 is attached and the coil 46a, and between the magnetic pole group 42 to which the coil 45 is attached and the coil 46b, an annular shape magnetized in the radial direction is provided. permanent magnets 47a and 47b are attached.

A cylindrical body 50 formed of a non-magnetic material and having a bottomed cylindrical shape is attached to the outside of the outer yoke 40 so as to cover the outer yoke 40. A gap 5 formed between the cylindrical body 50 and the wall portion 9
1, 52 and the magnetic poles 43a, 43b, 43c, 4
A displacement detector 53 for detecting displacement in a direction orthogonal to the axial direction of the rotor body 14 and a displacement detector 54 for detecting displacement in the axial direction are provided near 3d. Further, a stator 2 of the motor 18 is located at a position facing the rotor 19 on the inner peripheral surface of the recessed wall 7.
0 is attached, and the armature winding of the stator 20 is connected to a motor drive power source (not shown). Further, the output ends of each of the displacement detectors 53 and 54 are connected to a rotor stabilization control device 61. The rotor stabilization control device 61 actually includes:
It consists of one for stabilization in the radial direction and one for stabilization in the axial direction, and both realize a constant energization stabilization control method and an instantaneous energization stabilization control method. It consists of things to do. Now, if we take out one of the methods to realize the instantaneous energization stabilization control method in the radial direction, the second
As shown in the figure, the output of the displacement detector 53 located at the opposite position is applied to a waveform/phase processing device 62, a signal amplification device 63, and a power amplification device 64, and the power amplification device 64 calculates the displacement once and twice. A current containing a current level corresponding to the differentiated value is supplied to the coils 30 and 45 located between the displacement detectors in a direction that increases the magnetic flux to the coils 30 and 45 located in the direction where the magnetic gap length increases, and Magnetic flux is supplied to those located in the direction in which the magnetic gap length decreases. Note that 71 in FIG. 1 indicates an X-ray transmission window.

With such a configuration, the N of the permanent magnet 33a
The magnetic flux emitted from the poles passes through the wall material of the recessed wall 7 on the one hand, reaches the ring 17a attached to the inner surface of the rotor 11, and after passing through this ring 17a in the axial direction, returns to the recess. It penetrates the wall material of the sunken wall 7 to reach each magnetic pole of the magnetic pole group 28, and then passes through the inside of the inner yoke 25 to reach the S pole of the permanent magnet 33a. On the other hand, a ring 1 is attached to the inner surface of the rotor 11 through the wall material of the recessed wall 7.
7a, passes through the inside of this ring 17a in the axial direction, passes through the wall material of the recessed wall 7 again from the end face, reaches the magnetic pole 31, and then passes through the inner yoke 25 to the permanent magnet 33a. It passes along the path that leads to the south pole.
The magnetic flux leaving the N pole of the permanent magnet 33b also passes through two paths as described above. On the other hand, the magnetic flux leaving the N pole of the permanent magnet 47a passes through the wall material of the wall portion 9, reaches the ring 17c attached to the outer surface of the rotor 11, and moves inside this ring 17c in the axial direction. After passing through the wall material of the wall portion 9, the magnetic flux passes through the wall material of the wall portion 9 again to reach each magnetic pole of the magnetic pole group 41, and then passes through the outer yoke 40 on a path to reach the S pole of the permanent magnet 47a. On the other hand, the wall material of the wall part 9 is penetrated to reach a ring 17c attached to the outer surface of the rotor 11, and after passing through this ring 17c in the axial direction, the wall material of the wall part 9 is again penetrated from the end face. After penetrating the wall material and reaching the magnetic pole 44, it passes through the outer yoke 40 and reaches the S pole of the permanent magnet 47a. The magnetic flux leaving the N pole of the permanent magnet 47b also passes through two paths as described above. Therefore, a magnetic attraction force directed toward the rotation center and a magnetic attraction force that restricts the axial position act on the inner peripheral surface of the rotor 11, and a magnetic attraction force directed in the radial direction and a magnetic attraction force that restricts the axial position act on the outer peripheral surface. A magnetic attraction force that restrains the axial position will act, and these attraction forces are limited to each permanent magnet 3.
It is balanced because 2, 33, 46, and 47 are annular and the magnetic poles are equally distributed in the circumferential direction. Therefore, the rotor 11 is supported in a completely non-contact state, that is, in a floating state, by the magnetic attraction force. When a power source is connected to the stator 20 of the motor 18 in this state, the rotor 19 rotates, and accordingly, the rotor 11 to which the rotor 19 is attached starts rotating. Therefore, the rotating anode 3 also starts rotating. Then, when the rotor 11 reaches the specified rotation speed, the coil 32
When the rotor 11 is moved in the axial direction by adjusting the current flowing through a, 32b and 46a, 46b and the anode current introducing device is turned on, the potential difference between the rotating anode 3 and the cathode 2 increases. As a result, electrons generated at the cathode 2 collide with the rotating anode 3, whereby X-rays P are emitted as shown by the arrows in FIG. Therefore, the function as a rotating anode type X-ray tube device is exhibited here.

As described above, the rotor 11 rotates in an equilibrium state while keeping the magnetic gap constant between the rotor 11 and the so-called inner and outer magnetic force supply systems located outside the vacuum vessel. When an excessive external force is applied to the rotor 11 and this external force causes the rotor 11 to shift in a direction perpendicular to the axis, if the instantaneous energization stabilization control method is selected, the following will occur. A new equilibrium state is thus achieved. That is, when the rotor 11 is moved by an external force in a direction perpendicular to the axis and in the direction of the external force, each ring 17a, 17b, attached to the rotor 11 moves.
The magnetic gap length between the magnetic force supply systems 17c, 17d and the so-called inner and outer magnetic force supply systems changes, forming parts that increase and parts that decrease from the magnetic gap length in the equilibrium state. When such a change occurs, the rotor stabilization control device 61 supplies current in the direction of increasing the magnetic flux to the coils 30 and 45 located at the portion where the magnetic gap length has increased based on the output of the displacement detector 53. , and the coil 3 located at the part where the magnetic gap length is reduced.
0 and 45, a current is supplied in the direction of decreasing the magnetic flux. Therefore, the magnetic attraction force increases in the part where the magnetic gap length increases due to external force, and the magnetic attraction force decreases in the part where the magnetic gap length decreases, resulting in a difference in the magnetic attraction force. As a result, the rotor 11 moves in a direction opposite to the direction of the external force against the external force, and its position moves in a short time to a state where it is in equilibrium with the external force. It should be noted that the energization of the coils by the rotor stabilization control device 61 is stopped when the state reaches a state in equilibrium with the external force, and after that, each of the permanent magnets 33a, 3
It is supported only by the magnetic force of 3b, 47a, 47b.

Therefore, in this embodiment, the rotor 11
A magnetic force supply system is provided on the inside and outside of the rotor 11, and the inner and outer surfaces of the rotor 11 are used for magnetic support.As explained in FIG. As a result, when an external force is applied to the rotor 11 under the condition that the instantaneous energization stabilization control method is selected, the rotor 11 resists the external force and The amount of movement to a new equilibrium position where the magnetic attraction force by the permanent magnet and the external force are balanced can be reduced. Therefore, the amount of electric power required for the above-mentioned transition can be reduced compared to conventional devices, the characteristics of the instantaneous energization stabilization control method can be maximized, and the external force can be reduced. Since the amount of movement of the rotor due to fluctuations can be reduced, the rotor can be stably supported.

The above operation description is an example when the instantaneous energization stabilization control method is selected, but the constant energization stabilization control method can be selected without any support by switching the current supply form to each coil. Of course it can be done. Further, in the above-described embodiment, the rings made of high magnetic permeability material are provided in two stages on the inner peripheral surface and the outer peripheral surface of the rotor 11, but they may be arranged in one stage. Further, the cooling fluid may be made to flow through the space between the cylindrical body 50 and the wall portion 9.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the schematic configuration and effects of a magnetic bearing device according to the present invention, and FIG. 2 is a longitudinal sectional view of an X-ray tube device incorporating a magnetic bearing device according to an embodiment of the present invention. Fig. 3 is a perspective view showing the inner yoke portion of the same device, Fig. 4 is a sectional view of the same device taken along line E-E in Fig. 1 and viewed in the direction of the arrow, and Fig. 5 is the same. FIG. 2 is a cross-sectional view of the device taken along line FF in FIG. 1 and viewed in the direction of the arrow. 1... Vacuum vessel, 2... Cathode, 3... Rotating anode, 11... Rotor, 17a, 17b, 17c,
17d...Ring made of high magnetic permeability material, 25...Inner yoke, 40...Outer yoke, 30, 32a, 32
b, 45, 47a, 47b...Coil, 33a,
33b, 47a, 47b...Annular permanent magnet, 61
...Rotor stabilization control device.

Claims (1)

[Claims] 1 A cylindrical rotor, an inner ring and an outer ring made of high magnetic permeability material attached to the inner and outer circumferential surfaces of the rotor, respectively, and a ring concentric with the rotor on the inner and outer sides of the rotor. an inner yoke and an outer yoke each having a plurality of magnetic poles protruding from a circumferential surface facing the inner and outer surfaces of the rotating body; The rotor is rotated by passing a magnetic flux through a magnetic path that includes the rings and the yokes that are attached to the rotor, respectively, on the surface and on the circumferential surface other than the portion where the magnetic poles are located. radially magnetized inner annular permanent magnets and outer annular permanent magnets that serve as magnetic force sources for freely supporting magnetic forces in the axial and radial directions without contact; and magnetic poles of the inner and outer yokes. and a means for energizing each of the coils in order to correct the deviation in accordance with the deviation in relative position between the inner and outer yokes and the rotor. Features magnetic bearing device.