JPS641288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for applying a multipolar magnetic field to a plurality of cavities defined in a magnetic field injection mold. The present invention relates to a technology that realizes the production of multiple multipolar anisotropic resin magnets from a mold with limited space by adding ingenuity to the magnetic field application means.

There is already a method for manufacturing isotropic resin magnets (or rubber magnets) by mixing ferromagnetic powder such as ferrite magnet powder with thermoplastic synthetic resin (or rubber), molding it into a predetermined shape, and then magnetizing it. It has become widely known and put into practical use. Recently, various studies have been conducted to further improve the magnetic properties of the resin magnets, and as a development of this research, a technology has been developed to orient the axis of easy magnetization of magnet powder in the direction of magnetization to make it anisotropic. There is. Methods for making this magnet anisotropic include applying shear stress mechanically to the particles or creating a magnetic field in an injection mold, and the latter method in particular has been widely implemented industrially. has been done. This method heats and melts a mixture of ferromagnetic powder with a large magnetic anisotropy constant and synthetic resin, injects the molten mixture into a mold cavity in which a magnetic field is created, and aligns the axis of easy magnetization of the magnet powder particles with the magnetic field. The method is to produce an anisotropic resin magnet with excellent magnetic properties by orienting it in a certain direction under the action of.

By the way, when manufacturing anisotropic resin magnets by this so-called magnetic field injection molding, conventionally, as shown in FIG. However, the excitation coil 14 for generating the magnetic field is 1
One magnet is required for one magnetizing yoke, or one magnet is required for two magnetizing yokes. For this reason, there is a mechanical configuration limit to incorporating n or n/2 excitation coils corresponding to the magnetizing yoke in a mold with extremely limited space, and therefore it is difficult to incorporate n or n/2 excitation coils in a single injection molding process. It was extremely difficult to produce a large number of multipolar anisotropic resin magnets from a mold.

The present invention has been devised in order to overcome the above-mentioned difficulties inherent in manufacturing multipolar anisotropic resin magnets by magnetic field injection molding. By adding innovation to the method of applying a multi-pole magnetic field to the magnetic field, the number of excitation coils, which conventionally required at least n/2 to accommodate the magnetizing yoke, can be significantly reduced, making it possible to save money in limited space. The purpose of this invention is to easily realize a large number of multipolar anisotropic resin magnets using a mold, and to reduce manufacturing costs and improve operating efficiency.

In order to achieve the above object, a method for applying a multipolar magnetic field to a plurality of cavities in a mold according to the present invention applies a magnetic field to a plurality of cavities defined in an injection mold. When manufacturing an anisotropic resin magnet by injecting a molten mixture, a common magnetic force generation source placed in the mold excites a magnetic field, and this magnetic field is applied to a common magnetizing yoke that connects adjacent cavities. The magnetic field is distributed and introduced into each cavity by being induced through a magnetic field closed loop, and the magnetic field introduced into each cavity is led out through another magnetizing yoke disposed in the cavity adjacent to the magnetizing yoke. and is characterized in that it is returned to the magnetic field closed loop.

Further, according to another invention of the present application, a device for applying a multipolar magnetic field to a plurality of cavities in a mold, which also achieves the above object, has a plurality of cavities defined in a predetermined arrangement in a movable mold made of a non-magnetic material. At the same time, a first magnetic field inducing yoke made of a ferromagnetic material is arranged on the movable side mold and connected to a common magnetic field generation source, and a first magnetic field inducing yoke made of a ferromagnetic material is installed on the fixed side mold made of a non-magnetic material. A second magnetic field inducing yoke is disposed, and a plurality of magnetizing yokes face the outer periphery of each cavity at a predetermined center angle, and adjacent cavities are commonly connected by the magnetizing yoke, and each cavity A first magnetic field inducing yoke and a second magnetic field inducing yoke are connected alternately correspondingly to the plurality of magnetized yokes facing the magnetized yokes. The present invention is characterized in that a third magnetic field guiding yoke made of a ferromagnetic material is provided which magnetically couples the two magnetic field guiding yokes to form a magnetic field closed loop.

Next, a method and apparatus for applying a multipolar magnetic field to a plurality of cavities in a mold according to the present invention will be described in detail below with reference to the accompanying drawings, using preferred embodiments. FIG. 2 is a perspective view showing a schematic configuration of the device according to the present invention, and illustration of a movable mold and a fixed mold made of a non-magnetic material is omitted. Further, the illustration of the third magnetic field guiding yoke made of ferromagnetic material is also omitted. 3 is a developed sectional view of the end face cut along the - line in FIG. 2, and FIG. 4 is a plan view showing the flow of the applied magnetic field. In FIG. 3, reference numeral 16
shows the overall mold structure of a so-called magnetic field injection molding machine, and this mold 16 is formed from a movable side mold 18 that moves downward and opens with reference to the dividing plane l, and a fixed side mold 20. All of them are made of a non-magnetic material such as austenitic stainless steel. In the movable mold 18, a plurality of cavities 22 are defined in a predetermined arrangement (for example, in a grid pattern) as shown in FIGS. 2 and 4. As shown in FIGS. In this embodiment, the cavities 22 are formed into a cylindrical shape suitable for molding a rotor for a rotating electric machine such as a motor, and a ferromagnetic material is formed on the radial outer circumference of each cavity 22 at a predetermined central angle. A plurality of magnetizing yokes 24 are arranged facing each other.
In this case, the tip of each magnetizing yoke 24 faces the inside of the cavity 22, and the yoke end surface forms a part of the inner circumferential wall surface of the cavity. Furthermore, the magnetizing yoke 24 is composed of an even number of four or more poles in order to impart multipolar anisotropy to the resin magnet formed in the cavity, and the adjacent cavities 22, 22 are connected to each magnetizing yoke. 24 so that they are commonly connected. In other words, as shown in FIGS. 2 and 4, when the cavities 22 are located at each intersection of the grid, the magnetizing yoke 24 disposed on the radial outer circumference of each cavity has one end attached to a specific cavity. 22, and the other end of the yoke also faces the inside of another adjacent cavity 22, thereby commonly connecting both cavities.

Further, a first magnetic field inducing yoke 26 made of a ferromagnetic material is disposed in the movable mold 18, and the yoke 26 is connected to an excitation coil 27 which serves as a common magnetic field generation source.
It is connected to the. Similarly, the stationary mold 20 is also provided with a second magnetic field inducing yoke 28 made of a ferromagnetic material. The first magnetic field inducing yokes 26 and the second magnetic field inducing yokes 28 are connected alternately and correspondingly to the magnetizing yokes 24 facing each cavity 22, as clearly shown in FIG. That is, when considering a specific cavity 22a, in this embodiment, four magnetizing yokes 24
a to 24d face each other at a center angle of 90°, and if the first magnetic field induction yoke 26a is connected to the magnetizing yoke 24a, then the magnetizing yoke 24b facing the adjacent magnetizing yoke 24b clockwise at a phase angle of 90° is connected to the second magnetic field inducing yoke 28a. Similarly, a first magnetic field inducing yoke 26b is connected to the magnetizing yoke 24c adjacent to the magnetizing yoke 24b, and in this manner, the first and second magnetic field inducing yokes are alternately connected to each magnetizing yoke. It's refreshing to be here.
In the case of this embodiment, if the mold is of a vertically open type, the second magnetic field inducing yoke 28 has a thickness smaller than that of the magnetizing yoke 24 compared to the first magnetic field inducing yoke 26, as shown in FIG. This means that the mold is located upward by 90 degrees and is offset by a phase angle of 90 degrees.
Whether or not the magnetic field guiding yokes 26 and 28 are in a vertical relationship is only a relative matter.)

Furthermore, as shown in FIG. 3, when the movable mold 18 is closed toward the fixed mold 20, the first magnetic field inducing yoke 26 and the second magnetic field inducing yoke 2
A third magnetic field guiding yoke 30 made of a ferromagnetic material that magnetically couples the magnetic field elements 8 to form a magnetic field closed loop is provided. This third magnetic field induction yoke 30 is
Various configuration examples can be considered depending on the structure of the mold, but in this embodiment, a movable mold 30a disposed above the stationary mold 20 so as to be movable up and down, and a tie bar 30b.
It is composed of a combination of With this configuration, the magnetic field excited by the exciting coil 27 is transmitted from the first magnetic field inducing yoke 26 → the magnetizing yoke 24 → the magnetizing yoke 24 → the second magnetic field inducing yoke 28 → the movable mold 30a → the tie bar. 30b to form a closed loop of magnetic field.

In FIG. 3, a pinpoint gate 32 for injecting the molten mixture is perpendicularly bored in the portion of the stationary side mold 20 facing the opening top of the cavity 22, and this pinpoint gate 32 is connected to the stationary side mold 20. The movable mold 30a communicates with a runner 34 formed at the mating interface between the movable mold 30a and the movable mold 30a. The runner 34
is connected to a sprue 36 and a nozzle port 38 bored in the movable mold 30a, and the molten mixture is supplied under pressure from the nozzle port 38. Further, a through hole 42 for inserting the rotor rotating shaft 40 is perpendicularly bored in the bottom of the cavity 22, and a hole 42 for removing the resin magnet rotor after molding is provided around the through hole 42. A knockout pin 44 is arranged to be able to move up and down (however, this is a structure for integrally attaching the rotor rotating shaft during molding of the resin magnet, and is of course not an essential component). .

Next, a method of applying a multipolar magnetic field to a plurality of cavities in a mold using the apparatus according to the present invention configured as described above will be explained. Now, a magnetic field is excited by the excitation coil 27, which is a common magnetic force generation source, and this magnetic field is guided to the magnetizing yoke 24 via the first magnetic field induction yoke 26 (this forms part of the magnetic field closed loop). . At this time, for example, the second
In the figure, since the magnetizing yoke 24a commonly connects the adjacent cavities 22a, 22b as described above, the magnetic field induced in the magnetizing yoke 24a is distributed and introduced into each cavity 22a, 22b. Since the magnetic field has the property of being induced in the ferromagnetic material located closest to it in terms of distance, the magnetic field introduced into one cavity 22a is closest to the magnetizing yoke 24a and has a phase angle of 90° left and right. The magnetic field is guided out through the magnetizing yokes 24b and 24d located respectively in the magnetic field, and then returns to the magnetic field closed loop through the third magnetic field induction yoke. As a result, as shown in the magnetic field flowchart in FIG. 4, an induced magnetic field is formed in each cavity 22, so that a molten mixture consisting of ferromagnetic powder with a large magnetic anisotropy constant and synthetic resin is pumped from the nozzle port 38 under pressure. By injecting the resin into the cavity 22 through the sprue 36 and the pinpoint gate 32, magnetic field molding of the resin magnet is performed. At this time, while the mixture of ferromagnetic powder and synthetic resin is in a molten state and the powder array is not solidified, a multi-pole magnetic field is applied, so that the axis of easy magnetization of the powder particles is oriented in the direction of magnetization. A multipolar anisotropic resin magnet with excellent magnetic properties can be obtained. The ferromagnetic powder with a large magnetic anisotropy constant used in this magnetic field injection molding includes, for example,
Ba ferrite magnet powder or Sr magnet powder, or rare earth magnet powder (RCo ₅ type or R ₂ Co ₁₇ type, where R represents one or more rare earth elements) and other anisotropic manganese aluminum (M _o -Al-C) Magnet powder or the like is preferably used. Note that it is desirable that the particle diameter of these ferromagnetic powders be around the single magnetic domain particle diameter.

Synthetic resins are used as organic binders; for example, thermoplastic resins such as polyethylene, nylon, polypropylene, and polyphenylacetate, and thermosetting resins such as phenol and epoxy can be used. Further, a desirable blending ratio of the ferromagnetic powder and the synthetic resin is about 50 to 65% in volume fraction of the magnet powder. Further, the molding temperature of the molten mixture during injection molding is preferably in the range of 150 to 350°C, and the applied magnetic field needs to be 3000 Oe or more.

In this way, by inducing a magnetic field in a common magnetizing yoke that connects adjacent cavities, distributing the magnetic field to each cavity, and then returning it to a closed loop, conventionally, each cavity has at least n/2
(n is the number of magnetizing yokes) The number of excitation coils that were previously required can be significantly reduced. Therefore, it is possible to easily apply a multipolar magnetic field to multiple cavities defined in a mold with limited space, and it is possible to produce a large number of multipolar anisotropic resin magnets. This has many beneficial effects, such as reducing manufacturing costs and improving operating efficiency.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an example of the arrangement of a magnetizing yoke and an excitation coil when manufacturing an anisotropic resin magnet by magnetic field injection molding according to the prior art, and FIG. A partially omitted schematic configuration diagram of a device that applies a multipolar magnetic field to multiple cavities. Figure 3 is a developed cross-sectional view taken along the - line in Figure 2. Figure 4 is a flow of the applied magnetic field. FIG. 18...Movable side mold, 20...Fixed side mold, 2
2... Cavity, 24... Magnetizing yoke, 26...
...Yoke for first magnetic field guidance, 28...Yoke for second magnetic field guidance, 30...Yoke for third magnetic field guidance.

Claims (1)

[Claims] 1. When manufacturing an anisotropic resin magnet by injecting a molten mixture of ferromagnetic powder and synthetic resin while applying a magnetic field to a plurality of cavities defined in an injection mold, Exciting a magnetic field by a common magnetic force generation source disposed therein, guiding this magnetic field to a common magnetizing yoke connecting adjacent cavities via a magnetic field closed loop, and distributing and introducing the magnetic field to each cavity,
A mold characterized in that the magnetic field introduced into each cavity is led out through another magnetizing yoke arranged in the cavity adjacent to the magnetizing yoke, and is returned to the magnetic field closed loop. A method for applying a multipolar magnetic field to multiple cavities inside. 2 A plurality of cavities are defined in a predetermined arrangement in a movable mold made of a non-magnetic material, and a first magnetic field induction yoke made of a ferromagnetic material is arranged in the movable mold to generate a common magnetic field. A second magnetic field inducing yoke made of a ferromagnetic material is arranged on a fixed side mold made of a non-magnetic material, and a plurality of magnetized yokes are made to face the outer periphery of each cavity at a predetermined center angle. Adjacent cavities are commonly connected by the magnetizing yokes, and a first magnetic field inducing yoke and a second magnetic field inducing yoke are connected alternately in a corresponding manner to the plurality of magnetizing yokes facing each cavity. death,
Further, a third magnetic field inducing yoke made of a ferromagnetic material is provided, which magnetically couples the first magnetic field inducing yoke and the second magnetic field inducing yoke to form a magnetic field closed loop when both molds are closed. A device that applies a multipolar magnetic field to multiple cavities in a mold, characterized by: