JPH04155903A - Magnetic circuit for magnetic levitation using permanent magnet - Google Patents

Abstract

PURPOSE:To increase an attraction force of a permanent magnet by multipolarizing the magnet and by making the magnetized areas of the N pole and S pole on the surface of the magnet nearly the same. CONSTITUTION:A permanent magnet attached firmly to a movable body is multipolarized to lower the average demagnetizing field while making a working point high. By multipolarization of the magnet, the demagnetizing field of each magnetic pole is reduced. However, if the number of poles is increased more than necessary, a magnetic transition region between the poles expands, causing a decline of an attraction force of the magnet since the magnetic transition region between the poles does not exert attraction. The required number of poles is not less than two but not more than 20. Preferablly, not less than three but not more than 10. In order to obtain the maximum attraction force of the magnet, it is important that the magnetized areas of the N pole and S pole on the surface of the permanent magnet are nearly the same.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic circuit for magnetic levitation suitable for application to a device for transporting a moving object by magnetic levitation, such as a linear motor or a moving wall device.

[Prior Art and Problems] Devices for conveying or moving moving objects by magnetically levitating them are well known. However, the magnets used in this type of conventional device are electromagnets, and the use of permanent magnets is extremely rare.

The reason for this is that the magnetic properties of permanent magnets (ferrite magnets such as barium (Ba) ferrite) are low, so permanent magnets are only able to attract their own weight. This is because it was almost impossible to aspirate.

However, since the electromagnet consists of a yoke and a coil, it is large and heavy, and there are problems in that it consumes electric power and requires a so-called uninterruptible power supply in case of a power outage. Furthermore, there is also the problem that a conductor must be connected to the moving body in order to send current to the electromagnet.

In recent years, superconducting magnets have come into use, but the reality is that the use of superconducting magnets is limited to large-scale devices due to the manufacturing cost and maintenance of the devices.

On the other hand, with the development of rare earth permanent magnets, it has become possible to obtain magnets with magnetic properties approximately 10 times higher than those of Ba ferrite magnets. For this reason, magnetic circuits for magnetic levitation using rare earth permanent magnets have been considered.

However, in the magnetization of conventional rare earth permanent magnets, the entire magnet is single-pole magnetized, so the periphery of the magnet has a low demagnetizing field and the operating point is high, so a large amount of magnetic flux can be extracted, but the center of the magnet has a low demagnetizing field. There was a problem in that because the magnetic flux was high, the amount of magnetic flux that could be extracted was small.

[Purpose of the Invention] The purpose of the present invention is to magnetize a rare earth permanent magnet with multiple poles, lower the average demagnetizing field of the magnet, raise the operating point, and increase the attractive force of the magnet.

Another object of the present invention is to provide a suitable braking force to a moving body and prevent the moving body from accelerating more than necessary when a multi-pole magnetized permanent magnet is applied to a magnetic levitation device. The object is to perform multipole magnetization in the traveling direction (that is, the traveling direction of the permanent magnet fixed to the moving body).

[Means and effects for solving the problem] According to the present invention, in a device for levitating a moving body to which a magnetic circuit made of permanent magnets and iron is fixed by using the attractive force of the permanent magnets,
The above object is achieved by magnetizing the permanent magnet into a plurality of magnetic poles and by making the magnetized areas of the N and S poles on the surface of the permanent magnet approximately equal.

[Example 1] Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, according to the present invention, a permanent magnet fixed to a moving body is magnetized with multiple poles, and the average demagnetizing field is lowered to raise the operating point of the magnet. The reason for this is that multipole magnetization reduces the demagnetizing field of each magnetic pole. However, if the number of magnetic poles is increased unnecessarily, the magnetic transition region between the magnetic poles will increase, and since this portion will not contribute to attraction, the attraction force will decrease on the contrary. Therefore, the number of magnetic poles needs to be 2 or more and 20 or less, but preferably 3 or more, which is good for the upper and lower lO poles.

2 for each of (A), (B), (C), (D) and (N) in Figure 1.
A permanent magnet magnetized with multiple poles, 3 poles, 4 poles, 5 poles, and N poles is shown. Reference numbers 10, 12, 14, 16 and 18 indicate multipolar magnetized permanent magnets, respectively.

Note that magnetization must be done so that the attractive force of the magnet is maximized. Therefore, it is important that the magnetized areas of the N and S poles on the surface of the permanent magnet are approximately equal.

Incidentally, a moving object, which is a heavy magnetically levitated object, can be moved with a small amount of force, but since the moving object has a large inertial force, it requires a large force to stop it if it accelerates excessively. The present invention skillfully utilizes the braking force due to eddy currents induced in a conductor (in this case, a ferrous material to which a permanent magnet is attracted).

That is, in the present invention, the permanent magnet is magnetized with multiple poles in the direction of movement, so that the moving body including the permanent magnet can move at a constant speed without excessively accelerating. This will be explained in more detail with reference to FIG.

In FIG. 2 (A), a multipolar magnetized permanent magnet 20
is fixed to a yoke 22 fixed to a structure (a moving body main body (not shown)). 24 is an arrow indicating the moving direction of the moving body (ie, the moving direction of the permanent magnet 20). The magnetic flux from the permanent magnet 20 generates a large number of eddy currents 28 in the conductor 26 provided at intervals above the magnet. In (A) of FIG. 2, a plurality of magnetic poles of the permanent magnet 20 are provided in a direction substantially perpendicular to the direction of movement of the magnet (that is, multipolar magnetization is performed in a direction substantially perpendicular to the direction of movement of the magnet). .

On the other hand, in (B) of Fig. 2, similarly to (A) of Fig. 2,
A multi-pole magnetized permanent magnet 30 is fixed on a yoke 32 fixed to a structure (not shown) such as a moving body, and is shown by an arrow 34.
move in the direction of A large number of eddy currents 38 are generated in the conductor 36 provided at intervals above the magnet. However, in (B) of FIG. 2, the plurality of magnetic poles of the permanent magnet 30 are lined up in the direction of movement of the magnet (that is, multipole magnetized in the direction of movement of the magnet), so that the moving body is not braked. Power is big.

That is, the attractive force of the magnet (the force with which the magnet is attracted to the conductor) is the same in both cases (A) and (B) in FIG. 2. However, in the case of (B) in FIG. 2, the force for braking the moving body is greater. Therefore, in the present invention, the direction in which the permanent magnet is magnetized is the direction in which it moves.

Although it has been described that a large number of permanent magnets are magnetized in the direction of movement, it may also be stated that multi-pole magnetized permanent magnets are arranged in the direction of magnetization or in the direction of movement of the permanent magnets.

The magnetic circuit according to the present invention can be applied to a device in which a permanent magnet is attracted to a conductor to levitate a moving object, such as a linear motor or a partition moving device.

FIG. 3 is a cross-sectional view schematically showing a magnetic circuit when the present invention is applied to a partition moving device, and the left half of the magnetic circuit is omitted because the area around the magnetic circuit is symmetrical. Reference number 40 indicates the center line of bilateral symmetry. The permanent magnet 42 of the embodiment shown in FIG. Rare earth magnets such as Co-based or Nd-Fe-B-based magnets are used.

The permanent magnet 42 is fixed to a back yoke 44 made of iron, and this back yoke 44 is fixed to a partition 46. The magnetic flux from the permanent magnet 42 is transferred to the iron back cork 4.
4 and returns to the permanent magnet 42 again to form a closed magnetic path. The permanent magnet 42 faces the iron rail 50 through a narrow gap 48 and is attracted towards the rail 50.

Note that a stopper wheel (not shown) is provided to prevent the permanent magnet 42 from coming into close contact with the rail 50.

FIG. 4 shows part of the flow of magnetic flux when a permanent magnet is magnetized with four poles. Since the magnetic circuit is symmetrical with respect to the center line 60, only the right half of the magnetic circuit is shown in FIG. The results shown in FIG. 4 were obtained by computer simulation, and the setting conditions were as follows.

(a) Permanent magnet: Nd-Fe- equivalent to 37MGOe
B series magnet (b) Magnet width: 40 mm (however, the left half is omitted, so Wr shown is 20 mm) (c) Magnet thickness: 5 mm (d) Magnet length: infinite length ( perpendicular to the paper) (e)
Gap: G=5mm As can be seen from Fig. 4, there is little magnetic flux going out from the right end of the permanent magnet 62 toward the side of the rail 64 (mostly flowing in the vertical direction,
It can be seen that the magnetic flux of the permanent magnet 62 effectively exerts an attractive force.

As a result of investigating the relationship between the number of poles and the attractive force using the same magnet dimensions, gears, and distance as above, the following results were obtained.

L pole 18. OKgf 2 poles 46. OKgf 3-pole 49.8 Kgf 4-pole 33.2 Kgf As far as the above results are concerned, it was found that 3-pole magnetization is desirable.

[Effects of the Invention] As explained above, according to the present invention, the rare earth permanent magnet is magnetized with multiple poles to lower the average demagnetizing field of the magnet and raise the operating point, thereby increasing the attractive force of the magnet. Can be made larger. Furthermore, since multipole magnetization is performed in the moving direction of the moving object (that is, the moving direction of the permanent magnet fixed to the moving object), it is possible to apply an appropriate braking force to the moving object and prevent the moving object from accelerating more than necessary. It can be done.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining a multi-pole magnetized magnet according to the present invention, Fig. 2 is a diagram showing how eddy current is generated by a permanent magnet, and Fig. 3 is a diagram illustrating a specific example of the present invention. FIG. 4, which is an explanatory diagram, is a diagram showing the flow of magnetic flux in a multi-pole magnetized magnet. In the figure, 20, 30.42 are permanent magnets, 26, 36.50
indicates a conductor, and 22, 32, and 44 indicate a back yoke. Figure 1 Figure 3

Claims (4)

[Claims] (1) A device for levitating a moving body to which a magnetic circuit consisting of a permanent magnet and iron is fixed, by the attractive force of the permanent magnet, wherein the permanent magnet is magnetized with a plurality of magnetic poles, and the surface of the permanent magnet is A magnetic circuit for magnetic levitation, characterized in that the magnetized areas of the north pole and the south pole are approximately equal. (2) The magnetic circuit for magnetic levitation according to claim 1, wherein the permanent magnet is a rare earth magnet. (3) The magnetic circuit for magnetic levitation according to claim 1 or 2, wherein the plurality of magnetic poles is 2 or more and 20 or less. (4) The magnetic circuit for magnetic levitation according to any one of claims 1 to 3, wherein the plurality of magnetic poles are magnetized in the moving direction of the moving body.