JPS635371A - Magnet roll - Google Patents

Abstract

PURPOSE:To highly accurately form a desired magnetic force distribution pattern in a low cost, by providing recessed or projecting section over the longitudinal direction of a roll and controlling the magnetic force distribution by means of the recessed or projecting section. CONSTITUTION:The magnet roll M has a four-pole constitution and is formed by injection molding a resin (nylon 12) dispersing about 80pts.wt. of a magnetic substance (ferrite) and magnetization-oriented with the magnetic substance at the same time. Since projecting section 111 and recessed sections 121 are provided on the peripheral surface of the magnet roll M, a sharp distribution is obtained at the N1 pole and a magnetic force distribution which is asymmetrically reduced in intensity on the downstream side of a developing section is obtained at the S1 pole. Therefore, the toner layer on a sleeve stably becomes thinner and, since the magnetic force suddenly drops at the downstream side of the developing section, the sharpness of developing and fog-free pictures can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnet roll applicable to the field of recording such as electrophotographic copying machines, printers, printing machines, and recording equipment.

The present invention is particularly effective for a plastic magnet roll in which magnetic powder is dispersed in a binder resin and has a plurality of magnetic poles.

[Background technology]

In recent years, magnet rolls used in various fields such as electrophotographic equipment, electrostatic recorders, and display devices have been desired to be smaller and smaller in diameter, as well as those that have strong magnetic force and are suitable for high-precision mass production. Despite these expectations, there has never been anything that meets these expectations.

In particular, the magnetic rollers used to carry and transport the developer include those that are used alone, and those that are fixed or rotated inside a developer carrier such as a non-magnetic sleeve or belt. However, it is important to form a thin layer for developing an electrostatic image by imparting sufficiently charged toner to the developer, and to satisfy conditions for good development.

Recently, there are magnet rollers that are integrally molded into a columnar or cylindrical shape, but if you want to have magnetic poles and you want to reduce the diameter, you need 9
The limit is to provide four poles at 0 degree intervals. Even if the spacing between the poles is changed forcibly, the magnetic force will not only weaken, but also the magnetic force distribution will tend to have a symmetrical pattern with respect to the center of the magnetic pole, where the maximum magnetic force of the magnetic pole is generated.

In the development area, if the development magnetic poles with such a symmetrical pattern are placed closest to the electrostatic image, or placed before and after it, the image developed by the developer may become unclear, and problems such as trailing and density unevenness may occur. There is a strong tendency for developing defects to occur, especially when an alternating electric field (general field such as AC or AC/DC) is applied to the developing section.As a solution to this problem, an asymmetric pattern achieves good development. This was confirmed.

However, the above-mentioned integrally molded magnet roll cannot achieve the above-mentioned effects because it forms a symmetrical pattern of magnetic force distribution even if the magnetic poles are shifted.

In addition, in the developer regulating section, the magnetic force distribution may be symmetrical or asymmetrical, but if the magnetic force distribution forms a gentle slope and widens greatly, the layer thickness due to developer regulation will change. This may lead to poor development. On the other hand, conventional methods reduce the distribution by reducing the width of the bonded magnets, but this is easily affected by bonding accuracy, and the magnetic force distribution changes due to manufacturing variations, resulting in the desired You won't get anything, and it will only weaken the magnetic force.

Furthermore, in the case of bonding, in addition to the drawback that manufacturing costs are inherently high, it is extremely difficult to form a small-diameter magnet roller to be accommodated in a small-diameter sleeve. When simultaneously attaching separated magnets to the shaft, the symmetry of the magnetic force pattern described above cannot be changed, making it difficult to obtain a desired distribution pattern.

[Object of the Invention] As mentioned above, the object of the present invention is to create a BII force distribution pattern at a low cost, with high precision, and with a desired BN force, as opposed to the conventional method of bonding, which has poor density and is expensive. To provide a magnet roller that can reliably form a distribution pattern.

More preferred of the present invention is a magnet roller that can form a good distribution of magnetic force toward the developer regulating section, and a magnet roller that can form a good distribution of magnetic force toward the developing section; It is combined.

The invention provides a magnetic roller that is particularly effective for developing devices, but is not limited thereto.

[Summary of the Invention] The present invention achieves the above object, and uses the magnetic force of magnetic poles provided on a magnet roller that is integrally formed (including the case where the shaft is integral or separate), rather than something like pasted together. It is characterized by having a concave or convex portion for controlling the distribution (preferably at the center of the magnetic pole or in a region of the magnetic pole where the magnetic force is present).

In a preferred embodiment, the magnet roll is a plastic molded magnet roll, has only four magnetic poles, and has a configuration in which the concave portions or convex portions asymmetric the symmetry of the magnetic force pattern with respect to the magnetic force peak position created by the magnetic poles. , the pole III that forms the magnetic force pattern is a magnetic pole around the developer regulating member or a developing magnetic pole in the developing section, and the magnet roll is a fixed magnetic field generating means fixed within the non-6a developer carrier. The present invention brings about extremely effective special effects in both the structure and the structure in which the above-mentioned magnet roll has an apparent diameter of 30 mm or less without having any recesses or projections.

The present invention can be applied to all the configuration examples explained in the background art, eliminates the cost increase due to bonding and the difficulty in controlling the magnetic force pattern in integral molding, and is lightweight and cost-effective. This provides a low magnetic roller.

(Example) Examples of the invention are shown in FIGS. 1 and 6. The magnet roll shown in FIG. ), in which 80 parts of a magnetic material (ferrite) was dispersed in a resin (nylon 12), which was injection molded, and at the same time the magnetic material was oriented upon arrival.

In the conventional integrally molded magnet roll, a symmetrical magnetic force pattern as shown in FIG. 7 and 9 was obtained, but the convex portion 111 shown in FIG. By providing the recess 121, FIG.
In the Nl pole as shown in Figure 1, a sharp distribution with reduced divergence was obtained, and in the S pole, a magnetic force pattern was obtained that was asymmetrically reduced on the downstream side of the developing section. When the Mabnettrol thus obtained is used in a developing device, the toner layer on the sleeve becomes a stable thin layer, and the magnetic force on the downstream side of the developing section decreases rapidly, resulting in sharp images with no fogging. was able to obtain. In addition, the rotating type magnet roll shown in Fig. 6 has numerous convex portions, making the overall magnetic force distribution highly conveyable, and is suitable for use in the developing device shown in Fig. 8. When used, toner particle transportability was improved and fogging could be reduced.

The convex portions and concave portions may be of varying shape and do not need to be symmetrical. Various magnetic patterns can be obtained depending on the shape. For example, when a concave portion is provided at the center of the pole, the width of the tip of the 6n force distribution can be increased, and when a convex portion is provided here, a sharp distribution can be formed as described above. Also, if a convex part is provided on the right side at the center of the magnetic pole,
The magnetic force distribution on the left side can be made sharp and asymmetrical.
If a recess is provided here, the magnetic force distribution on the right side becomes a sharp distribution and becomes asymmetrical with respect to the 6fi force distribution on the left side.

Figure 2 shows a prismatic magnet 2 attached to the circumferential surface of an axial roll made of magnetic or non-EH material. angle) can be achieved by changing the vertical and horizontal lengths of the magnets to be pasted, but it is difficult to change the symmetry of the magnetic pattern, and the disadvantage is that the manufacturing cost increases due to precise pasting. there were.

Figure 3 shows a type in which a rubber magnet 3 is attached to a prismatic shaft core, and the symmetry of the magnetic pattern can be controlled by
This can be easily done by changing the shape of the rubber magnet to be pasted, but it must be pasted with high precision, as in the case shown in Figure 2. The one shown in Figure 3 has a magnetic material 4 such as ferrite sintered and magnetized around the shaft core 1, and since it is integrally magnetized, the process of attaching it is omitted, but the weight is large. It is difficult to control. Recently, it has been considered to use plastic magnets instead of sintered magnets to reduce weight, but it is not easy to control the symmetry of the magnetic pattern.

The magnetic roll example of the present invention is generally used in a developing device of an image device such as a copying machine, and one of the configurations thereof is as follows.
An example is shown in FIG. Here, M is 18. The developer 8, which has a concave groove 112 and a convex portion 121 at the illustrated position of the developing pole using an identification magnet roll with a diameter of -5 mm, is conveyed by the rotation of a non-magnetic sleeve 7 (20 mm in diameter in this example), and is conveyed to the latent image carrier. Develop the image. The sleeve 7 and the carrier 6 rotate in the direction of the arrow. Here, the developer 8 is a magnetic one-component toner, and an alternating current bias of 1,800 Hz and 1.200 Vpp is applied to the sleeve, which is a so-called Chambink developing system.

In such a system, N+'! 4 requires a magnetic force pattern with a narrow half width, and the S2 pole requires an asymmetric magnetic force pattern where the magnetic force rapidly decreases downstream of development, but this is not the case with conventional integrally molded plastic magnet rolls. It was extremely difficult to create a magnetic pattern.

In the embodiment of the present invention shown in FIG. 5, a convex portion 112 and a concave portion 121 are provided to sharply reduce the magnetic force pattern on the downstream side of the developing section in the sleeve direction. However, as an example of the present invention,
Only the convex portion 112 or only the concave portion 121 may be used. Convex portion 112
In the case of forming the recessed part 121, it is preferable in terms of manufacturing because it is sufficient to protrude by a smaller amount than the amount of chipping in the case of forming the recessed part 121.

As explained above, by providing convex portions and concave portions on the circumferential surface of the integrally molded plastic magnet roll, it has become possible to easily control the 6n pattern. This has the following effects on the developing device of the image forming apparatus.

1) N, pole (cut pole, polarity N): More uniform stabilization of sleeve coat toner 2) S1 pole (development pole, polarity S): Image quality stabilization (sharpness, fog, etc.) 3) N2, S2 (transport pole) , polarity N.S) ・Tribo stabilization The present invention eliminates the drawbacks of bonding, preferably of an integrally molded type, preferably a brass stick 7 magnet roll or sintered metal, and is ideal for things such as integral parts or separate shafts. is installed inside a non-magnetic rotating body, especially a small diameter sleeve,
For magnetic rolls with diameter 1 of 30 mm or less,
Since it is possible to obtain a strong magnetic force and to make the symmetrical distribution asymmetrical, it is possible to provide a high-performance magnet roll that solves the problem. The present invention can be applied to any one of magnetic one-component development, two-component development using a magnetic carrier and toner particles, and contact or non-contact development.

〔effect〕

According to the present invention, the drawbacks of conventional integrally molded magnet rolls can be solved, and a desired magnetic force distribution can be reliably formed without being affected by manufacturing variations, and an inexpensive magnet roll can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a preferred embodiment of the magnet roll of the present invention, FIGS. 2 to 4 are explanatory diagrams of conventional magnet rolls, and FIG. 5 is a perspective view of a preferred embodiment using another magnet roll of the present invention. 6 is an explanatory diagram of another embodiment of the present invention, FIG. 7 is an explanatory diagram of an example of controlling the 6n force distribution according to the example in FIG. 1, and FIG. 8 is a developing device using a magnet roll as shown in FIG. It is an explanatory diagram of an example. 1 is the axis, 11.12 is the magnetic pole center, 111, A, 112 are the convex parts, 121, B are the concave parts, dan is the magnet roll diameter, M
is a magnetic roll.

Claims (4)

[Claims] (1) An integrally molded magnet roll having magnetic poles in the longitudinal direction of the roll, characterized in that it has recesses or protrusions in the longitudinal direction of the roll, and the magnetic force distribution is controlled by the recesses or protrusions. (2) The magnet roll is a plastic molded magnet roll and has only four magnetic poles, and the recesses or protrusions make the symmetry of the magnetic force pattern with respect to the peak position of the magnetic force created by the magnetic poles asymmetrical. The magnetic roll described in item 1. (3) The magnetic poles forming the magnetic force pattern are magnetic poles around the developer regulating member or developing magnetic poles in the developing section, and the magnet roll is a fixed magnetic field generating means fixed within a non-magnetic developer carrier. A magnetic roll according to claim 2. (4) The magnet roll according to any one of claims 1 to 3, wherein the magnet roll has an apparent diameter of 30 mm or less without having any concave portions or convex portions.