JPS5951223B2 - rotor - Google Patents

Description

[Detailed description of the invention] The present invention relates to a rotor using anisotropic magnets.

Generally, a rotor surrounded by a stator and fixed to a rotating shaft is formed by an annular magnet.

Although this annular magnet has a multipolar outer peripheral surface, isotropic magnets are often used.

As is well known, in the case of multipolarization, isotropic ferromagnetic materials have the advantage of being easy to magnetize because they do not have any particular directionality.

However, a practical magnet using a relatively inexpensive isotropic ferromagnetic material such as ferrite has a low surface magnetic flux density and a small rotational torque.

For example, in the case of an electric motor used in an electronic sewing machine, it is necessary to reciprocate the rotor within a certain angular range, and naturally a large rotational torque is required.

In fields where such a large rotational torque is required, the isotropic magnet rotor described above is insufficient.

However, if the purpose is only to obtain rotational torque, a method of increasing the number of turns of the field coil provided in the stator may be considered.

However, this method results in an increase in the size of the electric motor itself, which limits the range of application of the electric motor.

Another possible means of increasing the rotational torque is to further narrow the distance between the stator and the rotor, but this method also has practical limitations because extremely high assembly precision is required.

Furthermore, although it is possible to use a magnet such as alnico, which has a high surface magnetic flux density, it is too expensive to be used for practical use on the side bottom.

On the other hand, even if it is an inexpensive ferromagnetic material such as the above-mentioned ferrite, one that has anisotropy generally has a high surface magnetic flux density.

Therefore, since the rotational torque can be set to a large value, it is suitable for miniaturizing electric motors, sensors, etc.

Some rotors are already using anisotropic magnets.

However, because of its anisotropy, magnetization was difficult and the number of magnetic poles was limited to two at most.

Moreover, even in this case, it is difficult to magnetize each magnetic pole to obtain a uniform magnetic field, and even if applied to an electric motor, the performance would be extremely low.

The present invention eliminates the above-mentioned drawbacks and provides a rotor using anisotropic magnets that has stable performance.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a plan view showing a four-pole rotor, and the rotor 1 is made of an anisotropic ferromagnetic material 2 such as ferrite.

Each ferromagnetic body 2 is arranged so that the strong magnetic field direction is exposed on the outer circumferential surface, and faces each magnetic leg M of the magnetizer.

The outer circumferential surface is curved, but the inner circumferential surface is planar, and each ferromagnetic body 2 is formed to have a non-uniform thickness as a whole.

A yoke 3 made of a magnetic material such as pure iron is provided on the back surface, that is, on the inner peripheral surface of the ferromagnetic material 2.

This yoke 3 has a substantially rectangular outer shape common to each ferromagnetic body 2 and is integrally formed.

That is, the inner circumferential surface of the ferromagnetic material 2 is bonded to the outer circumferential surface of the yoke 3.

Further, small corners 31 are formed at each top of the yoke 3 so as to separate and position the respective ends of the inner peripheral surfaces of the adjacent ferromagnetic bodies 2.

This corner 31 is formed to further protrude in the radial direction from the top of the yoke.

Furthermore, a spacer 4 made of a conductive non-magnetic material such as copper, aluminum, or brass is provided outside the corner 31.

This spacer 4 is formed to separate adjacent ferromagnetic bodies 2 from each other.

FIG. 2 is a sectional view taken along the line II--II of FIG. 1, and here the through hole 32' formed in the center of the yoke 3 and the rotating shaft S fitted therein are shown at the same time.

Furthermore, although FIG. 3 is a cross-sectional view taken along the line III-III in FIG. .

Of course, the spacers 4 can be formed independently and the bottom plate part 41 can be omitted, but it is preferable to integrate them in terms of assembly work.

Further, the bottom plate portion 41 has a through hole formed in the center like the yoke 3.

In addition, during the magnetizing operation, the rotating shaft S is made of an expensive magnetic material with excellent magnetic permeability, such as pure iron, like the yoke 3.
When the rotor is assembled, it can be made of a suitable non-magnetic material such as stainless steel, brass, or synthetic resin.

Thus, each ferromagnetic body 2' having anisotropy has a magnetic pole formed on its outer peripheral surface in the direction of a strong magnetic field by each magnetic leg M of a magnetizer provided so as to face the periphery. The magnets 2 are each configured to have an axis of easy magnetization in the radial direction with respect to the rotation axis.

In this case, adjacent magnets 2 are arranged in parallel so that they have different magnetic poles.

Here, in order to make the structure of the present invention more clear, the present invention will be further explained using FIG. 4, which shows a part of the rotor 1 in an enlarged manner.

For example, let us first consider a case where a ferromagnetic material 2 is simply placed in a position as shown in the figure using a non-magnetic material such as a synthetic resin without providing a yoke 3 or a spacer 4, and then magnetized.

In this case, the ferromagnetic body 2 has a curved outer circumferential surface and is formed to have a non-uniform thickness. It is close to.

Therefore, because the anisotropic ferromagnetic material itself has thickness dependence and the mechanical arrangement of each ferromagnetic material, the magnetic flux generated in the magnetic leg M is lower overall and is lower at both ends of the ferromagnetic material 2 than at the center. An energy deviation will be concentrated on the ferromagnetic material side and pass through the adjacent ferromagnetic material.

That is, in FIG. 5, which shows the relationship between the rotational angle of the rotor and the magnetic flux (ω and φ), each magnet 2' has a distorted characteristic that is strong on both sides and weak in the center, as indicated by the dotted line a.

The magnetic flux is also small. Furthermore, a small complementary magnetic pole is generated close to the main magnetic pole, similar to that seen in isotropic magnets, and small opposite polarity portions are generated at both ends.

That is, the magnetic field of each magnetic pole becomes non-uniform and the amount of magnetic flux becomes relatively low, so that the rotational torque is small and stable performance cannot be obtained, making it completely impossible to put it into practical use.

Further, when the entire portion up to the spacer 4 in FIG. 4 is formed of a magnetic material such as the yoke 3, in addition to the characteristics similar to those described above, the characteristics shown by the chain line are exhibited.

This indicates that strong complementary magnetic poles of opposite polarity were generated in the vicinity of each magnet in the space between the magnets, that is, in the area corresponding to the spacer.

The generation of this complementary magnetic pole means that the value of the magnetic pole of each magnetized magnet is reduced to the same limit, and stable performance with rotational torque cannot be obtained, so that it cannot be put to practical use at all.

Therefore, in the present invention as described above, a yoke 3 made of a magnetic material is provided on the inner peripheral surface side of each ferromagnetic material 2, and a conductive non-magnetic material is further provided between each adjacent ferromagnetic material. As a result, as shown by the solid line C in FIG. 5, a strong uniform magnetic field is obtained at each magnetic pole.

Further, a flat magnetic flux-free portion can be obtained over a certain range in the above-mentioned interval portion.

Here, when the conductive spacer 4 is magnetized, the magnetic flux from the magnetic pole M is deviated to both ends due to the thickness dependence of each ferromagnetic body 2, and attempts to create a short loop through a part of the spacer. However, in this case, eddy currents are generated, suppressing the occurrence of the short loop, and controlling excessive magnetic field concentration at the end of the ferromagnetic material 2 to form a large magnetic flux loop.

Therefore, each magnetic pole contributes to generating a uniform magnetic field through interaction with the yoke 3.

Furthermore, the corner portion 31 of the yoke 3 is for controlling the shoulder portion C' of each characteristic peak of the solid line C shown in FIG.
The protrusion size and shape are adjusted as appropriate depending on the thickness and width of the spacer 4, the opening angle of the spacer 4, etc.

In particular, it may be removed if the distance between adjacent ferromagnetic bodies 2 becomes narrow.

In the above embodiment, a four-pole configuration is shown in which the magnets 2 are arranged side by side at a uniform angle, that is, 90 degrees.
As shown in FIG. 6, it is also possible to change the spacer spacing and the magnet shape so that they are symmetrical with respect to the neutral line passing through the axis.

Moreover, it is also possible to provide a substantial notch 33 in a part of the yoke 3 that is in contact with the inner circumferential surface of each magnet 2 to adjust the uniformity of the magnetic field.

Furthermore, it goes without saying that the number of magnetic poles can be changed as appropriate, such as 2 poles or 8 poles, depending on the application and the relationship with the stator.

As described above, the rotor of the present invention can generate a uniform magnetic field at each magnetic pole even if several anisotropic magnets with non-uniform thickness are used, and is stable because a reliable magnetic flux-free range is obtained. It is possible to obtain high rotational performance.

Furthermore, since anisotropic magnets are used, a rotor with extremely high surface magnetic flux density can be obtained at low cost.

Furthermore, large rotational torque can be obtained without affecting the number of turns on the stator side, making it extremely effective in downsizing electric motors and the like.

As is clear from the characteristics shown in FIG. 5, since there is no complementary magnetic pole due to the interposition of the spacer 4, when reciprocating motion is made within a certain angle, the reversal occurs due to the excellent mechanical damping effect.

Furthermore, as the number of magnetic poles increases, the above-mentioned effects of the present invention will be more pronounced. Therefore, in combination with a magneto-electric conversion element, it will be used in various fields such as electronic cam devices and tension controllers. The scope of application of the rotor can be significantly expanded, and the practical effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the rotor according to the present invention, FIG. 2 is a cross-sectional view taken along the line II--II of FIG. 1, FIG. FIG. 1 is an enlarged explanatory view of the main part of FIG. 1, FIG. 5 is an explanatory diagram of rotation angle versus magnetic flux characteristics of various rotors in comparison with the present invention, and FIG. 6 is a plan view illustrating another embodiment of the present invention. 1...Rotor, 2...Ferromagnetic material, 2'...Magnet, 3...Yoke, 4...Spacer.

Claims (1)

[Claims] 1. In a rotor consisting of a yoke made of a magnetic material, an even number of anisotropic magnets fixed to share the yoke, and a conductive non-magnetic spacer provided between the magnets, the anisotropic The rotor is characterized in that the magnetic magnet has a flat surface in contact with the yoke, and an arcuate outer circumferential surface in the direction of the strong magnetic field, giving the rotor an overall non-uniform thickness shape.