JP2003151824A - Magnet roller and developing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet roller which varies in diameter in cross section so as to produce a magnetic pole pattern having a desired and specific shape and is restrained from being warped and to provide a developing device using the same. SOLUTION: A magnet roller is composed of a magnet body circular or nearly circular in cross section and a shaft. A plurality of protrudent stripes formed of the same material as the magnet body are provided symmetrical about a rotating axis on all the surface of the magnet body in a lengthwise direction. A developing device is equipped with a developing roller composed of a sleeve provided in a freely rotatable manner and the magnet roller provided inside the sleeve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roller and a developing device using the magnet roller. More specifically, the present invention relates to an electrophotographic device such as a copying machine, a facsimile, a printer, an electrostatic recording device, etc., including a developing device,
The present invention relates to a magnet roller having a different-diameter cross-sectional shape, which is preferably used for a cleaning device, a toner conveying device, and the like, and a warp is suppressed, and a developing device including the magnet roller.

[0002]

2. Description of the Related Art In electrophotographic devices such as copying machines and printers, electrostatic recording devices, etc., a resin magnet is placed in a rotating sleeve as a developing system for visualizing an electrostatic latent image on a latent image carrier such as a photosensitive drum. The magnet roller formed by the above is arranged to cause the toner carried on the sleeve surface to fly onto the latent image holding member by the magnetic force characteristic of the magnet roller. A developing method for visualizing a latent image is known.

Conventionally, when manufacturing the magnet roller, a resin material in which a magnetic powder such as ferrite is mixed and dispersed in a binder of a thermoplastic resin such as nylon or polypropylene is injected into a magnetic field of a cavity of a mold, It is manufactured by molding a roller-shaped magnet roller and magnetizing it to a desired magnetic force characteristic.

FIG. 4 is a front view and a side view showing an example of a conventional magnet roller. As shown in FIG.
The conventional magnet roller is composed of a magnet main body 11 and a shaft 12 each having a circular cross section or a shape similar to the circular cross section. The magnet roller thus formed has the following problems.

This is because in the situation where the magnetic force pattern in the circumferential direction required for the magnet roller has become complicated, there is a limit to the magnetic force pattern that can be designed by the conventional magnet roller, and it is possible to sufficiently meet this request. The point is that you can't. FIG. 5 is a graph showing the circumferential magnetic force pattern of the magnet roller thus formed, with the horizontal axis indicating the circumferential angular position and the vertical axis indicating the magnetic force. Figure 5
FIG. 5A is a general circumferential magnetic force pattern of a conventional magnet roller for magnetic one-component toner, and FIG.
Is a general circumferential magnetic force pattern of a conventional magnet roller for magnetic two-component toner, and each pattern has a magnetic force peak corresponding to a plurality of magnetic poles.

In such a conventional magnet roller structure, even if an attempt is made to change the peak of the magnetic force pattern corresponding to a specific magnetic pole to a peculiar one, it is limited to the circular shape and becomes a gentle pattern close to a sine curve. Will end up. The main pole (developing pole) of a magnet roller used in a copying machine or the like must have a required half-value width, that is, a peak angular width at a magnetic force height of half the peak magnetic force. It is known that high quality image quality can be obtained by using a so-called asymmetrical circumferential magnetic force pattern with different magnetic forces, but since the magnetic roller position of the conventional magnet roller having a circular cross section or a shape close to it is determined, It is difficult to control the half-value width, and it is necessary to perform another process such as re-magnetization. Further, the control may be impossible depending on the desired circumferential magnetic force pattern.

Therefore, various techniques have been taken so far to form a desired circumferential magnetic force pattern having a special shape. For example, at least a part of the surface of the magnet body is provided with a ridge and / or a groove formed of the same material as the magnet body along the entire axial length to form a magnet body having a different diameter cross section. Attempts have been made to make it. The magnet main body having such a shape is, for example, (a) a method in which a ridge member made of the same material as that is bonded to the roll-shaped magnet main body using an adhesive, and (b) cutting the roll-shaped magnet main body. It can be manufactured by a method of processing to form a groove groove, a method of (c) using a mold, and a method of molding by injection or extrusion molding. However, the above methods (a) and (b) have a problem that it is tedious and unavoidable that the manufacturing cost is high. Further, the method (c) is easy to manufacture and advantageous, but warps are likely to occur after the mold is removed, and particularly when a protrusion is provided, the magnet roller is easily warped in the direction in which the protrusion is present. was there.

FIG. 6 shows a warped state of a magnet roller having one ridge on the surface of the magnet body. FIG. 6A is a front view of a magnet roller in which one protrusion is provided on the surface of the magnet main body over the entire length in the axial direction, and FIG. 6B is a side view showing a warped state. As shown in the figure, the magnet main body 11 having one protrusion 13 on the surface is likely to be warped in the direction in which the protrusion 13 exists after being molded with a mold and demolded. 12
Is the shaft part.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the object of the present invention is to provide an electrophotographic apparatus or electrostatic recording. Which has a different diameter cross-sectional shape capable of forming a circumferential magnetic force pattern of a desired special shape, which can be suitably used for a developing device in a device, a cleaning device, a toner conveying device, etc. It is an object of the present invention to provide a magnet roller in which the magnetic field is suppressed and a developing device provided with the magnet roller.

[0010]

SUMMARY OF THE INVENTION The present invention has been accomplished in order to achieve the above-mentioned object, and its gist structure and operation will be described below.

A magnet roller according to a first aspect of the present invention has a magnet main body having a circular cross section or a shape similar thereto, and a shaft, and the surface of the magnet main body is made of the same material as the magnet main body. The plurality of formed ridges are provided symmetrically about the rotation axis over the entire axial length.

In the magnet roller of the present invention, the plurality of protrusions are provided symmetrically with respect to the rotation axis of the magnet roller, so that the warp of the magnet roller can be effectively suppressed.

According to a second aspect of the present invention, in the magnetic roller according to the first aspect, two to four ridges are provided.

The number of the protrusions is not particularly limited and may be appropriately selected in view of the desired circumferential magnetic force pattern and the effect of preventing warpage, but usually about 2 to 4 is sufficient.

A magnet roller according to a third aspect of the present invention has a magnet main body portion having a plurality of magnetic poles along the circumferential direction and a circular cross section or a shape similar to that, and a shaft portion. Protruding ridges protruding from the surface of the magnet main body at the corresponding circumferential positions and formed of the same material as the magnet main body are provided over the entire axial length, and the heights of these ridges are all the same. Is.

In this magnet roller, since the ridges are provided at the circumferential positions corresponding to all the magnetic poles, the magnetic force of each magnetic pole can be increased. In addition, usually, the arrangement of these magnetic poles on the circumference is such that the gap between two specific magnetic poles does not become extremely narrow or wide, and is well-balanced. The amount of warp can be reduced by making the heights of the ridges uniform.

The magnet roller according to claim 4 is the magnet roller according to any one of claims 1 to 3, in which the protrusion has a height of 0.003 to 0.1 times the roller diameter and 0.0.
It has a width of 5 to 0.4 times.

The shapes of the plurality of ridges are preferably the same in terms of the effect of suppressing the occurrence of warpage. The shape of the ridge is not particularly limited, and the cross section may have any of a quadrangular shape, a semicircular shape, an inverted U shape, and the like. The height of the protrusions is preferably 0.003 to 0.1 times the roller diameter, and more preferably 0.01 to 0.08 times the roller diameter. In addition, the width of the ridge is 0.05 to the roller diameter.
The range of 0.4 times is preferable, and the range of 0.1 to 0.3 times is particularly preferable.

According to a fifth aspect of the present invention, there is provided a developing device including a developing roller including a rotatably disposed sleeve and a magnet roller disposed inside the sleeve, and the magnetic field of the magnet roller is provided on the surface of the sleeve. Depending on the characteristics, a magnetic developer is carried, and a layering blade is used to form a thin layer having a predetermined thickness. A developing device for supplying a developer to the surface of a formed body to form a visible image on the surface of the image formed body, wherein the magnet roller is used as the magnet roller.
The magnet roller according to any one of 1 to 4 is used.

Since the developing device of the present invention uses the magnet roller according to any one of claims 1 to 4, it is possible to bring about the above-described operation.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a magnet roller according to the present invention will be described with reference to FIGS.
FIG. 1A is a front view showing an example of the magnet roller of the present invention, and FIG. 1B is a side view thereof. This magnet roller includes a magnet body 1 and a shaft 2
And as main constituent elements, and the magnet body 1
Has a circular cross section or a shape close to it, and has four ridges 3a, 3b, 3c and 3d on its surface.
Are provided symmetrically about the rotation axis over the entire axial length.

In the magnet roller of the present invention, the magnet main body 1 and the plurality of ridges 3a to 3d provided on the surface thereof are formed of the same material, and as the material, resin and rubber-like elastic body are used. A magnet composition obtained by mixing and dispersing magnetic powder in at least one binder selected from the above is preferably used.

The binder used in the magnet composition is not particularly limited, and any binder can be selected from those conventionally used in magnet rollers. Examples of the resin binder include polyamide resin such as nylon 6 and nylon 12, polystyrene resin, polyethylene terephthalate resin (PET),
Polybutylene terephthalate resin (PBT), polyphenylene sulfide resin (PPS), ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate copolymer resin (EEA), epoxy resin, ethylene-vinyl alcohol copolymer resin (EVOH), and further polyolefins such as polypropylene resin, polyethylene, and polyethylene copolymers, and modification by introducing reactive functional groups such as maleic anhydride group, carboxyl group, hydroxyl group, and glycidyl group into the structure of these polyolefins Examples include polyolefins. Among these, polyamide resin, EVA and EEA are particularly preferable. Examples of the rubber-like elastic binder include nitrile rubber (NBR), chloroprene rubber (CR), chlorosulfonated polyethylene (CSM), and silicone rubber. These resin binders and rubber-like elastic body binders may be used alone or in combination of two or more.

On the other hand, the magnetic powder is not particularly limited, and any one can be selected and used from those conventionally used in magnet rollers. Specifically, strontium ferrite, barium ferrite,
Ferrite powder such as lead ferrite, Sm-Co alloy,
Examples include rare earth alloy powders such as Nd-FB alloys and Ce-Co alloys. These magnetic powders may be used alone or in combination of two or more.

The mixing ratio of the binder and the magnetic powder in the magnet composition is not particularly limited and may be appropriately selected according to the strength of the magnetic force required of the magnet roller.
It is preferable to select in the range of 80 to 95% by weight (density of about 3.0 to 4.0 g / cm ³ ) based on the total amount of the magnet composition.

If desired, mica, talc, fibers such as carbon fibers and glass fibers, and fillers having a large reinforcing effect such as whiskers can be added to the magnet composition. That is, when the magnetic force required for a molded product is relatively low and the filling amount of magnetic powder is small, the rigidity of the molded product tends to be low.In such a case, in order to compensate for the rigidity, mica, whiskers, etc. The filler can be added to reinforce the molded product. In this case, as the filler that is preferably used, mica, whiskers and the like can be mentioned. As this whisker, for example, silicon carbide,
Non-oxide whiskers made of silicon nitride, Zn
Examples thereof include metal oxide type whiskers such as O, MgO, TiO ₂ , SnO ₂ and Al ₂ O _3, and multiple oxide type whiskers such as potassium titanate, aluminum borate and basic magnesium sulfate. Among them, double oxide whiskers are preferable because they can be easily compounded with plastics.

The compounding ratio of these fillers is not particularly limited, but is usually in the range of 2 to 32% by weight, preferably 5 to 20% by weight based on the total amount of the magnet composition.

The method for preparing the magnet composition is not particularly limited, but, for example, a binder, magnetic powder and a filler used as necessary are mixed by a conventional method, melt-kneaded, and then pelletized. A magnet composition can be prepared by molding. At this time, for melt-kneading, a usual method and conditions using a twin-screw kneading extruder, a KCK kneading extruder or the like can be adopted.

The method for producing the magnet roller of the present invention is not particularly limited, and for example, (A) at least the magnet main body is formed by a mold in which a magnetic field is formed around the cavity using the above-mentioned magnet composition. After (injection molding or extrusion molding), a plurality of ridge forming magnet pieces made of the same material as the magnet main body are attached to the surface of the magnet main body with an adhesive or the like, (B) for the magnet A plurality of fan-shaped magnet pieces obtained by using the composition are annularly arranged and fixed to the outer periphery of the shaft with an adhesive or the like to form a magnet main body, and then a plurality of ridges made of the same material as the magnet main body are formed. A method of attaching the part forming magnet piece to the surface of the magnet main body part with an adhesive or the like, (C) using a mold in which a magnetic field is formed around the cavity, Of the magnet composition and molding (injection molding or extrusion), and a plurality of protrusions provided on the surface and the magnet main body can be employed as a method of integrally formed. Among these methods, the method (C) is particularly preferable because the operation is simple and the effects of the present invention are effectively exhibited.

FIG. 2 shows another example of the structure of the magnet roller of the present invention, in which the magnet main body having two ridges on the surface is molded by the method (C).
2A is a cross-sectional view taken along the line II-II of FIG.
Shows a shaft-integrated structure in which the magnet body 1, the protrusions 3a and 3b, and the shaft 2a are integrally molded with the magnet composition. FIG. 2B shows the magnet body 1, the ridges 3a and 3b, and the shaft 2 on one side.
a shows a one-sided shaft insertion type structure in which a and a are integrally molded with the magnet composition and the shaft 2b is inserted into the other side. FIG. 2C shows a double-sided shaft insertion type structure in which the magnet body 1 and the protrusions 3a and 3b are molded from the magnet composition, and the shafts 2b are inserted on both sides thereof. Further, FIG. 2D shows a shaft insertion type structure in which the magnet body 1 and the protrusions 3a and 3b are molded from the magnet composition and the shaft 2b is inserted.

In the magnet rollers shown in FIGS. 2 (b) to 2 (d), the shaft used for insertion and the shaft used in the method (B) are not particularly limited, and the conventional magnet roller is used. In this case, those conventionally used in can be used. As this shaft, for example, a metal solid shaft or hollow shaft,
Examples include shafts made of various resins.

The magnet roller thus obtained may be used as it is, and if desired, it may be demagnetized and then re-magnetized to orient the magnetic powder to form a desired magnetic force pattern. Good. The demagnetizing operation and the magnetizing operation are not particularly limited, and can be performed by a known method using a known device according to the target magnetic force pattern.

The magnet roller of the present invention is preferably used as a magnet roller which constitutes a developing roller, a cleaning roller or the like of an electrophotographic apparatus such as a copying machine, a printer or a facsimile or an electrostatic recording apparatus.
Incidentally, the cleaning roller is for scraping off the toner remaining on the latent image holding member such as a photosensitive drum with a cleaning blade, and then collecting it by magnetic force, and arranging the magnet roller at a suitable place for collecting, The magnetic force causes the toner to be attracted to the magnet roller, and the toner is peeled from the magnet roller by a blade at a predetermined position, and the toner is collected in a predetermined collecting unit.

FIG. 3 is a sectional view showing a magnet roller 4 of another example of the first embodiment. Magnet roller 4
Of the magnet main body 5 has four magnetic poles which are circumferentially spaced from each other by angles α, β, γ and δ, respectively, and each of the ridges 6a, 6b, 6
c and 6d are provided so as to project from the circumference of the magnet body 5 at circumferential positions corresponding to these magnetic poles.
And these ridge parts 6a-6d have the same height h.

In the magnet roller 4 shown in FIG. 3,
The circumferential spacings α, β, γ, and δ of the ridges may be different from each other. Instead, the heights of the ridges are the same to prevent the magnet roller 4 from warping. It is important to do.

The developing device of the present invention comprises a developing roller comprising a sleeve (usually cylindrical) rotatably arranged and a magnet roller having the desired circumferential magnetic force pattern arranged inside thereof. A magnetic developer is carried on the surface of the sleeve according to the magnetic characteristics of the magnet roller, and is laminated into a thin layer having a predetermined thickness by a layering blade. Contact or approach, and depending on the magnetic characteristics of the magnet roller,
By supplying a developer from the sleeve to the surface of the image forming body,
A visible image is formed on the surface of the image forming body.

[0037]

EXAMPLES As examples of the present invention, three types of magnet rollers having different heights of the ridges were made on a trial basis, and the amounts of warpage thereof were measured and compared with those of the conventional example. In the magnet roller of the example, the number of ridges is two, and the relative positions of these are symmetrical with respect to the rotation axis of the magnet roller. The width of the two ridges is 3 mm.
The height of one ridge was 0.5 mm for all three types of magnet rollers, and the height of the other ridge was three types shown in Table 1.

The magnet roller of the conventional example was also prototyped in three types corresponding to those of the embodiment. However, the number of these ridges was one, and the size of the ridge was the other ridge of the embodiment. Same source. That is, the width is 3 mm and the height is shown in Table 1.
There are three types shown in.

The magnet roller of each of the examples and the conventional example was manufactured by the following method. That is, a magnet composition is prepared by blending 10% by weight of an ethylene-ethyl acrylate copolymer as a binder and 90% by weight of strontium ferrite powder as a magnetic powder in a cavity in a mold having a magnetic field formed around it. , Cylinder temperature 245 ℃, mold temperature 65 ℃ and injection pressure 70
A shaft having a shape shown in FIG. 2 (a), which is formed by integrally injecting and injecting under a condition of MPa, a magnet main body having a projecting ridge on the surface and having a circular cross-sectional shape, and a shaft protruding from both ends An integrated magnet roller was produced. The magnet body has a diameter of 14 mm and a length of 310 mm,
The shaft portion has a diameter of 6 mm and a length of 30 mm.

The amount of warpage was measured for each of these magnet rollers. Here, the amount of warp refers to the amount of deflection of the magnet shaft center at the center position in the magnet axial direction when both shaft parts of the magnet roller are supported and rotated.

From Table 1, in the case where the magnet roller is provided with the ridges, one having two ridges at symmetrical positions with respect to the roller rotation axis is more preferable than one having one ridge. Shows that the warp is small and is advantageous, and the one in which the heights of the two ridges are equal is preferable because the warp is the smallest.

[0042]

[Table 1]

[0043]

The magnet roller of the present invention has a structure in which a plurality of ridges are provided on the surface of the magnet main body in the longitudinal direction about the rotation axis, and the occurrence of warpage can be suppressed. A desired magnetic pole pattern can be easily formed, and it is suitable for use in electrophotographic devices such as copiers, facsimiles, printers, and electrostatic recording devices, as well as developing devices, cleaning devices, and toner transport devices. can do.

[Brief description of drawings]

FIG. 1 is a front view and a side view showing an embodiment of a magnet roller according to the present invention.

FIG. 2 is a cross-sectional view of another example of the structure of the magnet roller of the present invention.

FIG. 3 is a cross-sectional view of another example of the structure of the magnet roller of the present invention.

FIG. 4 is a front view and a side view showing an example of a conventional magnet roller.

FIG. 5 is a graph showing a general circumferential magnetic force pattern of a conventional magnet roller.

FIG. 6 is an explanatory view showing a warped state of a magnet roller in which one protrusion is provided on the surface of a conventional magnet main body.

[Explanation of symbols]

1 Magnet body 2 shaft part 3a, 3b, 3c, 3d ridge portion 4 magnets 5 Magnet body 6a, 6b, 6c, 6d ridge portion

Claims (5)

[Claims] 1. A magnet main body having a circular cross section or a shape similar thereto, and a shaft, and a plurality of ridges formed of the same material as the magnet main body on the surface of the magnet main body. Is a magnet roller that is provided symmetrically around the rotation axis over the entire axial length. 2. The method according to claim 1, wherein two to four ridges are provided.
Magnet roller described in. 3. A magnet main body having a plurality of magnetic poles along the circumferential direction and having a circular cross-sectional shape or a shape similar thereto, and a shaft portion, which are provided at circumferential positions corresponding to all the magnetic poles. A magnet roller in which protrusions protruding from the surface of the magnet body are formed of the same material as the magnet body and are provided over the entire length in the axial direction, and the heights of these protrusions are all the same. 4. The protrusion has a roller diameter of 0.003 to 0.1.
2. Double height and 0.05-0.4 times wide width.
The magnet roller according to any one of 1 to 3. 5. A developing roller comprising a rotatably arranged sleeve and a magnet roller arranged inside the sleeve, wherein a magnetic developer is carried on the surface of the sleeve by the magnetic characteristics of the magnet roller. The toner is supplied to the surface of the image forming body from the sleeve due to the magnetic characteristics of the magnet roller by contacting or approaching the surface of the image forming body in this state by forming a thin layer with a predetermined thickness on the image forming body. Then, in the developing device for forming a visible image on the surface of the image forming body, the developing device using the magnet roller according to any one of claims 1 to 4 as the magnet roller.