JPS60202913A - Manufacture of anisotropic magnet roll - Google Patents

Abstract

PURPOSE:To obtain an anisotropic composite magnet having excellent dimensional stability and magnetic characteristics by fitting a plurality of injection ports on a circumference concentric to a molding space in the end surface thereof and arranging the injection ports among magnetic poles for a magnetic circuit in the periphery of the molding space. CONSTITUTION:A plurality of injection ports 81-83 are mounted on a circumference concentric to a molding space 1 in the end surface of the molding space 1. The injection ports 81-83 are disposed where corresponding to sections among magnetic poles for a magnetic circuit consisting of yokes 71-73 fitted around the molding space 1 and a core 2 at that time. A kneaded material is introduced into the molding space 1 from the injection ports 81-83, thus manufacturing an anisotropic magnet roll.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an anisotropic magnet roll, which includes a step of injection molding a mixed material containing a ferromagnetic powder and a polymer compound in a magnetic field.

In image reproducing devices (dry type) such as electrophotographic copiers, facsimiles, and printers, it is a means for transporting magnetic developer (two-component developer that is a mixed powder of magnetic carrier and toner, or one-component magnetic toner, etc.) A permanent magnet member having a plurality of magnetic poles is installed inside a non-magnetic sleeve as a developing roll or cleaning roll, etc.
A magnetic roll configured to rotate both relative to each other is generally used.

The above magnetic rolls also have various structures,
For example, as described in Utility Model Publication No. 57-9798, a permanent magnet is formed by fixing a long anisotropic block magnet obtained by press-molding ferrite powder in a magnetic field and then sintering it around a shaft. Those using a magnetic member, or those using a permanent magnet member formed by fixing a cylindrical permanent magnet made of hard ferrite to a shaft (for example,
907, and Japanese Patent Publication No. 53-47043).

However, in the former case, there are problems such as assembly failure and low-temperature demagnetization, while in the case of joints, magnetic material is also used in the part between the magnetic poles, and the density of the sintered body is about 5 (
]/cm, so there is a problem that the weight is large. In addition, ferrite magnets generally have a problem in that since the particles themselves are fragile, they tend to crack or break during or after sintering, resulting in poor yields.

On the other hand, ferromagnetic powder (generally ferrite powder is used) and polymer compounds (
A magnet roll using a so-called composite magnet, which is made by integrally molding a mixed material (generally made of rubber or plastic material) into a cylindrical shape by extrusion molding or injection molding, and then magnetizing it after cooling and solidifying it. was proposed, and practical application was carried out.
No. 08207, No. 57-130407, No. 57-16
(Refer to various publications such as No. 450) When manufacturing this cylindrical magnet, since the composite magnet has a lower density than sintered magnet 6, in order to obtain the same magnetic properties as a ferrite magnet, it is necessary to wait until cooling solidification is completed. In the meantime, the axis of easy magnetization of the ferromagnetic powder is aligned with the direction of the lines of magnetic force inside the magnet after magnetization. It is well known that a so-called anisotropy process is necessary. (For example, see Japanese Patent Application Laid-Open No. 51-62396.) When manufacturing anisotropic composite magnets by injection molding, raw materials are generally mixed from the nozzle opening through the sprue, runner, and injection port (as in plastic injection molding). The molded product is obtained by injecting into the molding space (cagoty) of the mold from the mold gate. (For example, JP-A No. 51-21198 and No. 5
(Refer to each publication No. 1-21199) In that case, if the shape of the molded product is complex, various gates (for example, film gate, ring gate, or direct gate) may be used to uniformly fill each part of the cavity with the raw material contaminants. It has been proposed. Furthermore, when a molded product is used, the gate position is usually located at a position that does not pose problems in terms of physical properties such as dimensional accuracy and magnetic properties.

However, since the anisotropic cylindrical composite magnet incorporated into the magnet roll is long (usually with a length/diameter of 5 or more), in order to uniformly fill the magnet, a film gate is placed on the outer circumferential surface of the cylindrical molding space (cavity). It is effective to introduce the kneaded raw material by installing an injection port such as a multi-point pinpoint gate, but it is effective to introduce anisotropy to the outer circumference of the cavity! Since a magnetic circuit for generating a vA field is installed to generate a cylindrical composite magnet, there are problems such as damaging the magnetic properties of the cylindrical composite magnet, making it difficult to implement this method. Therefore, it is more advantageous to install a gate on the end face of the mold molding space (kitobiti) for introducing the crosstalk.In this case, 1, ring goo 1 ~ or bottle point gate can be considered, but it is difficult to uniformly fill ring goo 1. Although it is effective, it is difficult to cut the gate during mold release, and 1
In the point bin point gate, insufficient filling and welding lines occur, making it difficult to fill uniformly and making it impossible to obtain sufficient magnetic properties.

An object of the present invention is to solve the problems of the prior art described above and obtain an anisotropic composite magnet with good dimensional stability and magnetic properties, particularly an anisotropic magnet roll equipped with an anisotropic cylindrical composite magnet. The objective is to provide a manufacturing method that can

The present invention provides a method for manufacturing an anisotropic magnet roll, which includes a step of injection molding a mixed material mainly consisting of ferromagnetic powder and a polymer compound in a mold having a cylindrical molding space in the presence of a magnetic field. A plurality of inlets are provided on the end face of the molding space on a circumference concentric with the molding space, and the inlets are arranged at positions corresponding to between the magnetic poles of a magnetic circuit provided around the molding space. This method of manufacturing an anisotropic magnet roll is characterized in that the mixed material is introduced into the molding space through an injection port.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of an injection mold used in the present invention, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1.

In both figures, the mold has a cylindrical molding space 1 in which a core 2 is provided concentrically.

Permanent magnets 3 magnetized in the radial direction are arranged around the molding space 1.
1 to 33, permanent magnets 41 to 44 magnetized in the circumferential direction, and a nonmagnetic spacer 5 are installed. Further, their outer peripheries are surrounded by a yoke 6 made of a soft magnetic material, and yokes 71 to -/-+ made of a soft magnetic material are also provided inside 73 of the permanent magnets 31 to 33. In this way, the combination of the permanent magnet and the yoke effectively converges the magnetic flux of the permanent magnet within the molding space, making it possible to achieve sufficient magnetic field orientation.

(For an explanation of the magnetic circuit, please refer to Japanese Patent Application No. 58-117
857) One end of the nozzle opening 16 is a magnetic pole formed by the mold magnetic circuit, that is, a bin point gate 81.82.83 located in the middle of the yoke 71.72.73 and ]A2.
is connected to. When injection molding is performed using the above-mentioned mold, when the raw material contaminant is injected into the mold heated to a predetermined temperature, the contaminant is injected from the nozzle port 16 and is inserted into the sprue 12.
, through runner 13, to 3-point bin point gate 81.
The molding space 1 is filled from 82.83. While the kneaded material advances to the molding space 1, it is oriented by a magnetic field, and is cooled and solidified by spinning. Thereafter, the mold plate 10 and the mold plate 11 are protruded and the molded body is taken out from the mold. In this case, there are 3 points (8+, 8+,
82.83), the molding space 1 is filled uniformly, and the gate position is located at a position corresponding to the poles of the mold magnetic circuit, so that the mixed material solidifies appropriately, and the ferromagnetism in the kneaded material is The powder can be oriented appropriately in the magnetic field. Therefore, the difference in the density of the compact between the magnetic poles and the magnetic poles is small, and there is no cracking.
Moreover, a molded article with good dimensional accuracy can be obtained.

In FIG. 2, 15 is a protruding bottle, and a lower stand 9 is fixed to the tip thereof. Further, on the opposite side of the lower stand 9, templates 10 and 11 are provided, and the templates 10 and 11 are provided with a nozzle port 16 and a sprue 12. On the other hand, the mold plate 10 is provided with a runner 13 that communicates with the sprue 12 and communicates with the three bin point gates 81 to 83, so that uniform filling is possible and good magnetic field orientation is obtained.

The molded body thus obtained is processed to have a predetermined outer diameter as required, and then the shaft is fixed and then magnetized in the same direction as the anisotropic direction, as shown in Figure 3. You can get a magnetic roll. In FIG. 3, C11G is a cylindrical magnet having three poles on the outer periphery, and 17 is a shaft.

In addition, in FIG. 2, by erecting the shaft of the magnet roll on the lower stand 9 instead of the core 2, it is also possible to manufacture an integral molded magnet roll.

In the above explanation, we talked about manufacturing a cylindrical magnet with 3 pole magnetization, but it is of course possible to manufacture 5 or more poles by increasing the number of magnets in the mold. By changing the number of poles, even number poles such as 4 poles, 6 poles, 8 poles, etc. can be obtained.
(Patent application D: (58-1559)
(See No. 75). Note that the present invention is not limited to permanent magnet type molds, but can also be applied to molds using permanent magnets and pulsed magnets A, and electromagnet type molds. A type mold is most suitable.

Further, in the present invention, the raw material mixed material may be prepared using the following materials used in ordinary composite magnets.

Examples of the ferromagnetic powder include ferrite powder having a magnetic brambite crystal structure such as 3a ferrite or 3r ferrite, Aα-Ni-CO magnetic powder, Fe
-Cr-Go magnet powder, rare earth cobalt magnet powder,
Known magnet powders such as rare earth iron magnet powders can be used. Further, as the polymer compound, various thermoplastic resins such as polyamide resin, polyethylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, polypropylene, etc. can be used. Additionally, in order to improve moldability, a small amount of lubricant such as calcium stearate (
Furthermore, in order to improve the wettability of the ferromagnetic powder, the surface of the ferromagnetic powder can be pretreated with an organosilicon compound or an organotitanate compound. The blending ratio of the ferromagnetic powder is ferromagnetic powder:resin -80 to 94:20
It is preferable to have a gravity ω ratio of ˜6. This is because if the amount of ferromagnetic powder is less than the above range, the magnetic properties will deteriorate, and if the amount is more than the above range, molding will become substantially difficult.

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto.

<Example> 1.35 kg of polyamide resin (nylon 6) was added to 7.65 kQ of 3a ferrite powder with an average particle size of 1 μm.
The mixture was kneaded using a kneader at 50°C. When this crosstalk is handled using a mold with the magnetic circuit shown in Figure 1 (A) and three bin point gates are used at positions corresponding to each magnetic pole (
B) When three bin point gates are used at positions corresponding to each magnetic pole (C) When a ring gate is used (D>
Close the bin point gates 82 and 83 in Figure 1 and use one bin point gate [2 in each case]
Each piece was injection molded under the same conditions. The injection molding conditions at this time are shown in Table 1. Also, the permanent magnet of the mold used here was 3r9. The magnet was a rare earth cobalt magnet (H-22A manufactured by Hitachi Metals) of OKG, 1 ton, 1 c, 10 KOe, and the magnetic flux density distribution on the surface of the molding space was as shown in FIG. The obtained molded body (outer diameter 30n+mφ, inner diameter 12mmφ
, a length of 260111 m>, and then magnetized in the same direction as the anisotropic direction during molding to obtain a magnet roll as shown in FIG. Table 2 shows the measurement results (average values) of surface magnetic flux density at the N pole of magnet rolls prepared using these four types of gates, as well as cracks and warpage of molded bodies. When the ring gate shown in Table 2 (C) is used, the magnetic properties are good and the molded product has no cracks and warpage is small, but there is a problem that all the cuts cannot be made at the gate part when releasing the mold. .

As shown in Table 2, by arranging the bin point gates at positions corresponding to the respective magnetic poles of the magnetic circuit according to the method of the present invention, the magnetic properties are good, there is no cracking, there is no warpage, and the dimensional stability is excellent. I was able to obtain a directional magnet roll.

Table 1 Molding condition

[Brief explanation of the drawing]

Fig. 1 is a poly sectional view showing an example of the position of the mold used in the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, Fig. 3 is a perspective view of the magnet roll, and Fig. 4 is a It is a figure which shows the magnetic flux density distribution on the inner surface of the metal mold|die shown in a figure. 1: Molding space, 2: Core, 3.4: Permanent magnet, 81.8
2.83: Pinpoint gate No. 1 Lacquer 2 @ No. 3 Figure 7

Claims (1)

[Claims] 1. Manufacture of an anisotropic magnet roll including the step of injection molding a mixed material mainly composed of ferromagnetic powder and a polymer compound in a mold having a cylindrical molding space in the presence of a magnetic field. In the method, a plurality of injection ports are provided on an end surface of the molding space on a circumference concentric with the molding space, and the injection ports are positioned at positions corresponding to between magnetic poles of a magnetic circuit provided around the molding space. A method for manufacturing an anisotropic magnet roll, characterized in that the mixed wire is introduced into the molding space through the injection port. 2. The method for manufacturing an anisotropic magnet roll according to claim 1, which involves injection molding in a magnetic field of permanent magnets.