JPH0224110B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a permanent magnet field DC machine and a method for manufacturing the same, and particularly to a permanent magnet field DC machine and a method for manufacturing the same. The present invention relates to a permanent magnet field DC machine equipped with field magnetic poles and a manufacturing method thereof.

[Prior art]

Figure 1 is a sectional view showing an example of a motor equipped with field magnetic poles made of permanent magnets, and Figure 2 is
-X sectional view.

The motor of this example consists of a stator 1 and a rotor 2. The stator 1 has two permanent magnets 4, 4' fixed to the inner circumference of a cylindrical yoke 3, and end brackets 5 are attached to both ends of the motor. is attached to support the bearing 6. The rotor 1 has an armature core 8 around which an armature winding 7 is wound and a commutator 9 fixed to a shaft 10.

As mentioned above, in motors that use permanent magnets as field magnetic poles, a demagnetizing force acts on the field permanent magnets due to armature reaction, so the field magnetic poles require a large permanent demagnetization resistance. . on the other hand,
In view of the output characteristics of this motor, a large magnetic flux density is required for the field magnetic poles.

However, in a ferrite magnet having the basic formula MO・nFe ₂ O ₃ (M=Sr, Ba, Pb), which is suitable as a permanent magnet material for field magnetic poles, the residual magnetic density Br and coercive force iHc are generally approximately equal. Because of the tendency to be inversely proportional, there are difficult technical problems with design in rotating electrical machines, especially material selection for the field poles.

FIG. 3 is an analytical diagram of a mechanism in which a ferrite magnet is demagnetized by an external magnetic field, with the vertical axis representing the magnetic flux density B and the horizontal axis representing the magnetic field strength H.

The illustrated curve B-H and 4πI-H curve are characteristic curves that exhibit different shapes depending on the respective magnetic materials.

Pc is an operating line obtained from the magnetic circuit, and the intersection A with the B-H curve is the operating point.

Now, when a demagnetizing field ΔH is applied to the magnet, the magnet operating point is parallel to the operating line Pi, which is found graphically.
After the demagnetizing field ΔH disappears due to Pi' via point D on the BH curve corresponding to point C on the 4πI curve, the operating point shifts to A'.

The ordinate Bd ₁ of the initial operating point A is the initial magnetic flux density, and the ordinate Bd ₂ of the operating point A' after demagnetizing field loading is the magnetic flux density after demagnetizing field loading; This means that irreversible demagnetization of ΔBd has occurred.

As is clear from the above analysis, the demagnetization strength of a permanent magnet can be determined by the BH-curve, and when a demagnetization field iHc corresponding to the left end of the curve is applied, the magnetization strength becomes zero. , within the range of the straight part at the top of the curve, the magnetization strength does not decrease even when a demagnetizing field is applied.

FIG. 4 shows examples F and G (both not shown) of ferrite magnets as magnetic materials.
This is a chart comparing the B-H curves, where F' is the B-H curve of ferrite magnet F, and G' is the B-H curve of ferrite magnet G.

Ferrite magnet G has a higher magnetic flux density than Ferrite magnet F, so if it is used for the field magnetic pole, it can construct a rotating electrical machine with excellent operating characteristics, but its coercive force is inferior, so the performance will be affected by demagnetization. It is easy to cause a decline.

In order to solve the above-mentioned trade-off problems regarding magnetic materials, a structure of field magnetic poles as shown in FIG. 5 has been proposed (Japanese Patent Laid-Open No. 55-56456 (for electric machines such as small motors). This figure shows two semi-circular arcs.
The field magnets 4, 4' are shown expanded in the horizontal direction,
This is a diagram with a diagram of curve C showing the magnetomotive force distribution of armature reaction added thereto. The horizontal axis of the chart represents the circumferential direction, and the vertical axis of the chart represents the strength of the magnetic field.

When considering the field magnet 4, the area to the right of the center portion 4m in the circumferential direction of the magnetic pole face in the figure is a demagnetizing field, and the area to the left is an increasing field.

Therefore, the coercive force of the field magnet is not required in the increased field region J on the left side of the figure. Therefore, the left-side portion including the center of the field magnet 4 uses the magnetic material G (having a large magnetic flux density and a small coercive force) described in FIG. 4.

In the demagnetizing field region K on the right side of the figure, it is necessary to have a large coercive force. Therefore, the above-mentioned magnetic material F is used to provide demagnetization resistance while sacrificing the magnetic flux density slightly.

When the field magnet is composed of two types of magnetic materials as described above, compared to the case where it is composed of one type of magnetic material, a relatively large coercive force and a relatively large residual magnetic flux density can be achieved depending on the required location. It is possible to improve the output characteristics and durability of the permanent magnet rotating electric machine.

However, as is clear from a comparison of the configuration of the field magnet and the armature countermotive force curve C in FIG. 5, the changes in the curve C are continuous in the circumferential direction, whereas the changes in the magnetic material is gradual. Therefore, naturally, the required magnetic properties and the actual magnetic properties cannot completely match.

Although there is some degree of freedom left in the design, no matter how you set it, the part of the magnetic material F that is close to the same G tends to have excess coercive force and insufficient magnetic flux density. The part of G that is close to F tends to have insufficient coercive force. In the end, there remains the question of how much margin for demagnetization tolerance should be cut in order to improve output characteristics, which must be left to a design decision.

It is possible to improve the two-stage field magnet shown in Figure 5 to have three or four stages, but the conventional construction technology for ferrite magnets involves injection molding of a paste-like material into a mold. There is no suitable method other than this method, and attempting to construct a multi-stage magnetic material using this method would significantly increase production costs as the number of stages increases, and furthermore, the stability of product quality would decrease, making it impractical. .

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a permanent magnet field DC machine having field magnetic poles with a perfectly balanced coercive force and magnetic flux density as required, and a method for manufacturing the same. .

[Summary of the Invention] In order to achieve the above object, the permanent magnet field DC machine of the present invention smoothly changes the magnetic properties of an arc-shaped permanent magnet made of fired magnetic material in the circumferential direction to achieve desired properties. In order to achieve this, the fired body is characterized in that the density of the fired body is made coarser steplessly from the magnetizing field side to the demagnetizing field side.

As a method for controlling the density of the fired body mentioned above, (a) adjusting the consolidation ratio when pressing the firing raw material;

(b) Adjust the particle size distribution of the firing raw materials.

(c) Adjust the mixing ratio of firing raw materials.

Both methods are effective. Among these, the most effective is the so-called impregnation method, which is employed in the method of manufacturing the permanent magnet field DC machine of the present invention.

For example, a part of a molded body made of a magnetic material having a basic composition of MOnFe ₂ O ₃ (M=Sr, Ba, Pb) is treated with at least one additive selected from Al, Cr, Pb, and borax. The molded product is immersed in a solution containing the additive and gradually pulled up, or the molded product is gradually suspended in the solution, and the impregnation concentration of the additive is varied steplessly in the direction of movement of the molded product. A permanent magnet is manufactured by firing.

In such permanent magnets, the denser the additive impregnation concentration, the more the crystal grain growth of the magnetic material during firing is suppressed and the shrinkage rate becomes smaller, resulting in a lower fired body density (density after water is removed). becomes smaller. When fixing this permanent magnet to a stator, the coarse side of the additive concentration should be the front side in the rotation direction of the rotor, and the dense side should be the rear side, that is, the dense side of the fired body density of the permanent magnet. is on the front side in the rotational direction of the rotor (magnetizing field side), and the coarser fired body density side is on the rear side in the rotor rotational direction (demagnetizing field side). As a result, the permanent magnet has a high residual magnetic flux density on the side of the increasing field, a high coercive force on the side of the demagnetizing field, and has smooth desired magnetic properties in between, depending on the change in firing density. It becomes possible to manufacture DC machines.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, among the permanent magnet field DC machine and the manufacturing method thereof of the present invention, the field magnetic pole and the manufacturing method thereof relating to the embodiments relating to the characteristic parts will be described in detail.

FIG. 6 shows a field magnet 4'' according to an embodiment of the present invention.
This is a diagram in which the graph is expanded in the horizontal direction and compared with the magnetomotive force curve C of the armature reaction, and corresponds to the left half of FIG. 5 explaining the conventional field magnet 4. The degree of shading shown with spots represents the degree of density of the field magnetic pole 4'' according to the embodiment of the present invention, and corresponds to the increased field area J to the left of the center point 4m in the rotation direction. The portion is densely constructed, and the portion corresponding to the demagnetizing field region K on the right side is the polar arc portion end 4 on the demagnetizing field side.
The density is changed steplessly so that the density becomes smaller as it approaches e.

As a result, the magnetic flux density Br uniformly shows the highest value in the increased magnetic field region J, and the opposite arc-shaped part end 4
It gradually decreases as it approaches e.

Moreover, contrary to the above, the coercive force iHc shows a uniformly low value in the increasing field region J, and the coercive force iHc shows a uniformly low value in the increasing field region J, and
, it increases as it approaches the polar arc-shaped end 4e, and shows the highest value at the polar arc-shaped end 4e.

The above curve of coercive force iHc is proportional to the armature counter-motive force curve C within the demagnetizing field region, so it is possible to minimize the decrease in magnetic flux density Br while achieving the required holding strength. can demonstrate.

One embodiment of a method for constructing field poles with density gradients as described above will now be described.

MO・ which is the raw material for firing ferrite magnets
An appropriate binder is added to a powder material having a composition according to the basic formula nFe ₂ O ₃ (M=Sr, Ba, Pb), and the mixture is press-molded into a predetermined shape. However, this predetermined shape must be appropriately set in consideration of shrinkage during firing.

On the other hand, an aqueous solution containing Al ions, Cr ions, Pb ions, or borax is prepared in advance. This aqueous solution may contain any one of the four types of additives described above, but may contain any plurality of additives.

One part of the molded body, specifically, the half of the side that is to be the polar arc-shaped end 4e on the demagnetizing field side is immersed in this aqueous solution. Then, raise it gradually over an appropriate amount of time. As a result, the additive penetrates into the demagnetizing field side, and the amount of impregnation is distributed only on the demagnetizing field side.
Furthermore, the impregnated amount distribution shows a slope such that the amount is maximum at the polar arc-shaped end portion 4e.

When implementing the present invention, it may be suspended gradually and then pulled up suddenly. You can also suspend it gradually and then pull it up gradually. In short, the above-mentioned additive distribution may be formed by giving different immersion times to each part.

When a molded body impregnated with an additive in this manner is fired, the additive acts to prevent shrinkage due to firing, so that the density distribution of the fired body tends to be inversely proportional to the impregnation rate of the additive. As a result, a residual magnetic flux density distribution Br almost proportional to the density distribution and a coercive force iHc distribution almost inversely proportional to the density distribution are obtained, and the field magnetic pole 4'' having the magnetic characteristics shown in Fig. 6 is constructed. .

As is clear from the above description, the method of the present invention can be easily carried out using simple equipment, and the desired magnetic properties can be obtained by controlling the immersion time, resulting in easy product quality.

When a motor of the type shown in Figs. 1 and 2 was constructed using the field magnet constructed as described above, it had a practically sufficient coercive performance, and the average We were able to increase magnetic flux density by 15%. This has improved the output characteristics of the motor, and has made it possible to make the motor smaller and lighter.

〔Effect of the invention〕

As described above, since the permanent magnet field DC machine of the present invention uses field magnetic poles having magnetic properties that take armature reaction into consideration, it is possible to achieve improved performance and reduction in size and weight.

Furthermore, according to the manufacturing method of the present invention, it is possible to easily make the magnetic properties of the field magnetic poles desired characteristics, so that a high-performance, high-quality permanent magnet field DC machine can be efficiently manufactured. It has the effect of being able to.

[Brief explanation of drawings]

1 and 2 show an example of a permanent magnet type motor, with FIG. 1 being a sectional view perpendicular to the axis, and FIG. 2 being a sectional view including the axis. Figure 3 is an analysis diagram of the demagnetization effect of a ferrite magnet due to an external magnetic field.
Fig. 4 is a chart showing the magnetic characteristics of ferrite magnets, Fig. 5 is a developed diagram of a conventional field magnetic pole with a magnetomotive force distribution curve of armature reaction added, and Fig. 6 is a diagram showing an example of the present invention. It is a diagram in which a magnetomotive force distribution curve of armature reaction and a magnetic characteristic curve of the magnetic poles are added to a developed view of the field magnetic poles. 1...Stator, 2...Rotor, 3...Yoke,
4, 4', 4''... Field magnetic pole, 5... End plate, 6... Bearing, 7... Armature winding, 8... Armature core, 9... Commutator, 10... Armature shaft.

Claims (1)

[Claims] 1. A permanent magnet field DC machine comprising a stator having arc-shaped permanent magnets made of a plurality of fired bodies, and a rotor rotatably provided inside these arc-shaped permanent magnets. , as each arc-shaped permanent magnet,
A permanent magnet field DC machine characterized by using arc-shaped permanent magnets whose fired body density is steplessly coarsened from the magnetizing field side to the demagnetizing field side. 2. In a method for manufacturing a permanent magnet field DC machine comprising a stator having arc-shaped permanent magnets made of a plurality of fired bodies and a rotor rotatably provided inside these arc-shaped permanent magnets, a magnetic material The molded product is gradually suspended in a solution containing an additive, or the molded product immersed in the solution is gradually pulled up, so that the impregnation concentration of the additive changes steplessly in the direction of movement. and firing the molded body to produce the arc-shaped permanent magnet, and when fixing the arc-shaped permanent magnet to the stator, the side with the coarser additive concentration is placed on the front side with respect to the rotation direction of the rotor. A method for manufacturing a permanent magnet field DC machine, characterized in that it is fixed with the dense side facing the rear.