JPH09319226A - Magnet roll and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to inexpensively obtain a magnet roll for magnetic brush development having an excellent high heat resistant characteristic by forming this roll of a composite resin magnet material compsn. consisting of a block amide resin having polyether groups in the molecular chains as a base material. SOLUTION: A roll-shaped magnet 6 is formed by integrating the composite resin magnet material consisting of the block amide resin having the polyether groups in the molecular chains as the base material resin and a metallic shaft 6a by insert molding in metal molds in which a magnetic field for orientation is formed. As a result, the magnet roll having the high heat resistance is inexpensively provided by the stage of insert molding the magnet shaft 6a. Fatty acid amine polycondensate is added to a mixture mainly composed of a magnetic powder material and a high-polymer compd. material. As a result, the flow property in molding is improved and the strain at the molding is suppressed, by which the linearity of magnetic characteristics is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roll used in an electrophotographic developing device such as a copying machine, a printer and a facsimile, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In general, a magnet roll used for magnetic brush development in an electrophotographic developing device is a cylindrical non-magnetic sleeve and a roll having a plurality of magnetic poles on the surface inside the non-magnetic sleeve. Bearings for rotating at least one of the non-magnetic sleeve and the roll-shaped magnet, or flanges integrated with the bearings, hold the shafts at both ends of the roll-shaped magnet. Fixed to both ends of the non-magnetic sleeve.

In the electrophotographic developing device, at least one of the non-magnetic sleeve and the roll-shaped magnet is rotated to adsorb and convey the developer made of magnetic powder on the non-magnetic sleeve and to charge the surface of the photoreceptor. A magnetic brush developing method is used in which the electrostatic latent image formed on the surface is transferred to be visualized.

A conventional magnet roll for developing a magnetic brush will be described below with reference to the sectional view of FIG. According to the figure, the magnet roll is configured to relatively rotate the roll-shaped magnet 6 in the non-magnetic sleeve 5, but the bearings 7a, 7b and the bearings 7a, 7b are provided at both ends of the non-magnetic sleeve 5. A bearing portion composed of flanges 8a and 8b for holding foreign matter 7b and preventing foreign matter from entering the non-magnetic sleeve 5 from both ends is formed, and the roll magnet 6 and the non-magnetic sleeve 5 are minimized. The flanges 8a and 8b are bonded and fixed to the non-magnetic sleeve 5 with an adhesive in such a manner that the distance 9 is provided and the rotational load is not increased.

A shaft 6a for rotating or fixing the roll-shaped magnet 6 is drawn out to the outside of one flange 8b, but the method in which the roll-shaped magnet 6 is fixed and the non-magnetic sleeve 5 is rotated is the mainstream. In order to regulate the positional relationship between the magnetized pattern and the photoconductor, a reference surface such as a D-cut is provided at the end of the shaft 6a. Further, the shaft 6a is made of a conductive metal material for the purpose of forming an electric path for giving a specific electric characteristic to the surface of the non-magnetic sleeve 5.

The roll-shaped magnet 6 fixed to the outer side of the metal shaft 6a is conventionally made of cylindrical sintered ferrite, but in recent years, nylon (nylon 6,
Nylon 12 etc.), polypropylene, polyethylene,
It is configured by using a composite resin magnet material in which a thermoplastic resin such as chlorinated polyethylene or vinyl acetate is used as a binder.

In the conventional composite resin magnet material, magnetic properties are improved by a method of orienting the easy axis of magnetization of ferrite powder, which is a ferromagnetic powder, by a mechanical means and a method of orienting by the action of a magnetic field. Has been planned.

A method of orienting the easy axis of magnetization of the ferrite powder in a constant direction by using mechanical means is to roll the composite resin magnet material 10 on the rolling roller 1 as shown in FIG. 6 (a).
1 to form a sheet-shaped magnet 13 in which the axis 12 of easy magnetization of the ferrite powder is oriented in a direction perpendicular to the sheet surface, and then the sheet-shaped magnet 13 is formed as shown in FIG. 6 (b). It is wound around the shaft 6a into a roll shape, and then magnetized to form a roll magnet 6.

As another method, as shown in FIG.
In order to improve the orientation efficiency, several sheet-like magnets 13 are stacked, and then a fan-shaped pressure-molded piece 6b is formed into a metal shaft 6a as shown in FIG. 6 (e), as shown in FIG. 6 (d). It is also contrived to cut the outer periphery of the laminated magnet adjacent to the center of the magnet to form a roll shape and magnetize it to form the roll magnet 6.

A method of orienting by the action of a magnetic field is called magnetic field injection molding, and a strong magnetic field is applied to a composite resin magnet material in a plastic state in a mold at the time of injection molding,
As shown in FIG. 7, a magnetic pole piece 6b having a fan-shaped cross section and oriented from the fan-shaped arc portion to the fan-shaped side surface and the inner circumference was obtained by using a roll-shaped magnet in which the easy axis of magnetization of the ferrite powder was oriented in the direction of the magnetic flux lines. After that, a method of joining a plurality of magnetic pole pieces 6b to a metal shaft 6a using an adhesive or the like to form a roll-shaped magnet 6, and a composite resin magnet material in a plastic state during injection molding as shown in FIG. Of the coil 16a and the yoke 16 arranged around the cavity 15 in the mold 14.
There is a magnet which is subjected to the action of a magnetic field from the orienting magnet 16 of b and orients the easy axis of magnetization of the ferrite powder in the direction of the magnetic flux line to form a rolled magnet only by molding.

In any case, the base material resin of the composite resin magnet material is determined by giving importance to the orientation characteristics and molding characteristics of the ferrite powder, and the modified polyethylene resin or rubber elastomer is used in the method of obtaining the sheet magnet by mechanical orientation. Nylon 6 or Nylon 12 is used in the type in which the orienting piece for each pole is formed by magnetic field injection molding and then fixed to the metal shaft with an adhesive, etc. In the type in which the shaft is insert-molded, ethylene / ethyl acrylate resin is used as the base material resin in order to absorb the difference in expansion coefficient between the metal shaft and the composite resin magnet material.

[0012]

In general, an electrophotographic developing apparatus using a dry developer visualizes image information such as characters latently formed on a photoconductor through charge-exposure by an electrostatic attraction effect. Therefore, a roll-shaped magnet having a high magnetic force for the purpose of stirring and charging the developer and adsorbing and transporting the developer is received by a flange via a bearing and incorporated into a non-magnetic sleeve.

Then, the magnet portion is fixed, the flange is driven to rotate the non-magnetic sleeve, and the developer is transferred along the distribution of magnetic force lines on the surface of the non-magnetic sleeve.
Therefore, the function of each magnetic pole of the developing magnet roll, which is composed of multiple poles, is determined according to the configuration of the developing unit and the relationship with the photoconductor, and the optimum magnetic field distribution is required for that function. To be done.

That is, the distribution of magnetic force lines generated from the roll-shaped magnet plays an important role in determining image characteristics.
It is required that a plurality of magnetic poles that are configured can be individually designed and that a complicated magnetization pattern can be realized by an easy process.

The metal shaft of the fixed magnet portion is made of a metal material having conductivity and is used for imparting a certain electric characteristic to the surface of the non-magnetic sleeve.

For the purpose of always controlling the developer to a stable charged state even after long-term use or under specific environmental conditions, a special treatment may be applied to the surface of the non-magnetic sleeve after assembly as a magnet roll. Has been done. Specifically, a conductive fine powder such as carbon black fine particles is dispersed in a binder resin material on the surface of the non-magnetic sleeve 5, and then fixed and applied in a film form. These steps are generally performed at 150 ° C. It is carried out in a hot atmosphere to some extent, and it is required that the magnet roll has the heat characteristics capable of withstanding it. As a base material resin in the conventional composite resin magnet material, nylon 6 is completely deformed, and the initial characteristics cannot be maintained at all.

In other words, except for nylon 6 because of the physical properties of the composite resin magnet material used for these magnet rolls, there is no problem at 60 ° C., which is the normal set use guarantee temperature, but the heat resistance is limited, whereas nylon 6 is only molded. It is not possible to use a method with excellent productivity for orienting with a roll magnet.

The present invention aims to solve the conflicting problems described above, and provides a magnetic roll for developing a magnetic brush excellent in high heat resistance at low cost.

[0019]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a magnet roll which is insert-molded with a metal shaft to obtain a roll-shaped magnet excellent in productivity and has high heat resistance. As a composite resin magnet material capable of performing a special treatment on the sleeve surface after assembly, a block amide resin having a polyether group in the molecular chain is used as a base material resin.

According to the above construction, unlike the conventional composite resin magnet material, it is possible to inexpensively manufacture a magnet roll excellent in high heat resistance by a manufacturing method excellent in productivity.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is
The mixture of ferromagnetic powder material and polymer compound material is melt-injected by placing a metal shaft in a mold in which a plurality of orienting magnets that generate an orienting magnetic field are placed, and then melt-injecting it. In the method of manufacturing a magnet roll having a plurality of magnetic poles, by using a block amide resin having a polyether group in the molecular chain as a polymer compound material, a method with excellent productivity for insert molding of a metal shaft is provided. It is possible to provide a magnet roll excellent in high heat resistance.

According to a second aspect of the present invention, the fatty acid amine polycondensate is contained in an amount of 1% by weight or less in the mixture containing the ferromagnetic powder material and the high molecular compound material according to the first aspect. It improves the fluidity during molding and stabilizes the linearity of the orientation magnetic characteristics.

The invention according to claim 3 of the present invention is the invention according to claim 1.
By containing 80 to 95% by weight of the ferromagnetic powder material described in (1), the characteristics of the magnet roll can be further improved.

The invention according to claim 4 of the present invention is the invention according to claim 1.
When manufacturing the magnet roll described in (1), by using a mold that forms a ring gate by attaching a conical attachment to the end of the metal shaft to be inserted, eccentricity of the metal shaft to be inserted is prevented, and The linearity of the characteristics is secured from the aspect of the construction method.

Prior to the description of the embodiments of the present invention, a general manufacturing method of the present invention will be described.

The mixture mainly composed of the ferromagnetic powder material and the polymer compound material used for molding is a block amide resin having a polyether group in the molecular chain as a base material, and barium ferrite, strontium ferrite, etc. Surface treatment of hard ferrite powder and rare earth magnetic powder with a coupling agent such as titanium or silane,
A kneaded mixture having a content of 80 to 95% by weight is used.

In the developing magnet roll produced by such a manufacturing method, an orienting magnet is arranged around the cavity of the molding die in order to give optimum characteristics to each required magnetic pole. It is important that the strength and the positional relationship between the orienting magnets are designed to have optimum contents according to the magnetization pattern required for each product.

An embodiment of the magnet roll of the present invention will be described below with reference to FIGS.

FIG. 1 is a cross-sectional view of an orientation mold used for magnetic field injection molding of a magnet roll of the present invention, FIG. 2 is a cross-sectional view of the periphery of the gate portion, and FIG. 3 is an eccentric state of a central portion of a shaft. FIG. 4 is a cross-sectional view of the magnet roll, and FIG. 4 shows the same magnetic characteristics.

According to FIG. 1, reference numeral 1 designates a non-magnetic base made of stainless steel, and the vicinity of the cavity 2 in the non-magnetic base 1 corresponds to the number and pole position of the magnet roll to be obtained. Then, the orienting magnet 3 is arranged.
The orienting magnet 3 is configured by integrating a permanent magnet 3a with a front yoke 3b made of a soft magnetic material and a base yoke 3c.

The intervals between the adjacent oriented magnets 3, so-called inter-angle angles θ1, θ2, θ3, θ4, are determined in accordance with the product specifications. The magnetic strength and size of the permanent magnet 3a and the size of the front yoke 3b at the tip are determined by the product. The permanent magnet 3a has a Br of 1070, although it is designed according to the specifications, particularly the magnetic force and the half width.
A rare earth cobalt magnet having 0G and IHC of 10700 Oe is used, and each magnet is magnetized in the diameter direction.

FIG. 2 is a sectional view showing the gate portion of the mold of the present invention. For example, shaft end portions are formed at both ends of the cavity portion having a diameter of 17.4 mm, and one end A is connected to the nozzle port. Although the spool and the runner are connected, the conical attachment 4 is inserted into one end of the shaft 6a to form a ring gate, and the composite resin magnet material is uniformly injection-molded on the outer peripheral surface of the shaft 6a.

For injection molding, the composition of the composite resin magnet roll consisting of various base resins shown in (Table 1) was mixed in advance with a super mixer, and then pelletized using a twin-screw kneading extruder, and plated. The iron shaft 6a thus prepared was inserted, and the conical attachment 4 was mounted in the mold to integrally form the roll magnet 6.

[0034]

[Table 1]

Next, the following comparative tests were conducted. First, the roll magnet 6 is left as it is in a drying oven at 150 ° C. for 1 hour, and a heat shock test at −30 ° C. to room temperature to 60 ° C. for 10 cycles is performed to confirm the appearance shape and the surface magnetic flux density. The measurement was performed with a Gauss meter.

In order to make a state of being used as a magnet roll for measurement, the magnet was incorporated into a sleeve having an outer diameter of 20 mm, and the Hall element of a Gauss meter was brought into contact with the surface of the sleeve to obtain the peak magnetic force at the central portion (C) in the longitudinal direction. The coaxial magnetic property was evaluated by measuring the peak magnetic force at a position (A and B) 20 mm from the end.

After the measurement, the magnet roll was left in a drying oven at 150 ° C. for 1 hour, then taken out and left at room temperature for 24 hours, and similarly the magnetic characteristics were measured to obtain the amount of change before and after, and also after heat shock. The same measurement was performed.

The measured value was an average value of N = 10, and the difference before and after the test was within ± 10, which was the level at which there was no change.

The results of the above appearance confirmation are shown in (Table 2).
The measurement results of the surface magnetic flux density are shown in (Table 3).

[0040]

[Table 2]

[0041]

[Table 3]

As is clear from the above results, the composite resin magnet material using the block amide resin having a polyether group in the molecular chain as the base material resin and the metal shaft 6
By integrating a into a roll magnet 6 by insert molding in a mold in which an orientation magnetic field is formed, a magnet roll having high heat resistance can be provided at low cost by a method of insert molding a metal shaft.

Further, by adding a fatty acid amine polycondensate to a mixture mainly composed of a ferromagnetic powder material and a high molecular compound material, the fluidity at the time of molding can be improved, the distortion at the time of molding can be suppressed, and the magnetic characteristics can be improved. The linearity of is improved.

Even in the case where the ring gate is used, the eccentricity of the shaft 6a is suppressed, so that the variation of the surface magnetic force (the linearity of magnetic characteristics) shown in FIG. 4 due to the eccentricity of the shaft 6a as shown in FIG. 3 is suppressed. It is what is done.

In the above embodiment, the optimum composition should be determined according to a wide range of required product characteristics such as magnetic force characteristics and mechanical characteristics, and the detailed composition ratio is not limited to the above embodiment. Absent.

[0046]

INDUSTRIAL APPLICABILITY As described above, the magnet roll of the present invention has high heat resistance by using a composite resin magnet material composition containing a block amide resin having a polyether group in the molecular chain as a base material. It is possible to inexpensively provide a magnet roll having magnetic characteristics that realizes good image characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold for manufacturing a magnet roll according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a gate portion of the magnet roll manufacturing die.

FIG. 3 is a side sectional view of the comparative example.

[Fig. 4] Same coaxial magnetic characteristic diagram

FIG. 5 is a sectional view of a conventional magnet roll.

FIG. 6 is an explanatory diagram of a conventional magnet roll manufacturing process.

FIG. 7 is a perspective view of another conventional magnet roll.

FIG. 8 is a sectional view of a molding die for forming another conventional magnet roll by injection molding.

[Explanation of symbols]

 1 non-magnetic base 2 cavity 3 oriented magnet 4 conical attachment 6 roll magnet 6a shaft

Claims (4)

[Claims] 1. A mixture composed mainly of a ferromagnetic powder material and a polymer compound material is melt-injected by placing a metal shaft in a mold in which a plurality of orienting magnets for generating an orienting magnetic field are arranged. A magnet roll for forming a plurality of magnetic poles on the outer peripheral surface of a molded body, which uses a block amide resin having a polyether group in the molecular chain as a polymer compound material. 2. The magnet roll according to claim 1, wherein the mixture mainly composed of the ferromagnetic powder material and the polymer compound material contains 1% by weight or less of a fatty acid amine polycondensate. 3. The magnet roll according to claim 1, which contains a ferromagnetic powder material in an amount of 80 to 95% by weight. 4. The method of manufacturing a magnet roll according to claim 1, wherein a die having a ring gate formed by attaching a conical attachment to an end of a metal shaft to be inserted is used.