JP3182063B2 - Developing device toner supply roller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner supply device for a developing device for visualizing an electrostatic latent image in an electrophotographic copying machine or the like.
It relates to a supply roller.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, a printer, a facsimile, and the like, a document image is formed as an electrostatic latent image on the surface of a photosensitive drum, and a toner image is formed by attaching toner to the image. By transferring and fixing, a visible image is formed and an image is output.

A portion for forming the image is referred to as a developing device, and includes a toner tank storing toner, a toner supply roller for supplying toner from the toner tank to a developing roller,
And a developing roller.

As a toner supply roller used in such a developing device, for example, a toner supply roller having a conductive foam structure as disclosed in JP-A-60-229065 and a toner supply roller disclosed in JP-A-5-181352 are disclosed. As described above, the roller itself has a non-conductive inner and outer two-layer structure, the outer layer is formed of a single-cell foam, and the inner layer is formed of an open-cell foam. As shown in the above, there has been proposed one formed of a non-conductive single-cell foam.

[0005]

However, such conventional toner supply roller structures each have advantages and disadvantages, and still have problems in durability and output print quality.

That is, as described in JP-A-5-181352, in a roller having a two-layer structure in which the outer layer is made of a single-cell foam and the inner layer is made of an open-cell foam, an inner portion close to the shaft is used. The lower the hardness, the more appropriate the roller as a whole can be maintained, and the toner can be prevented from clogging in cells (voids) as compared with the case where the surface of the elastic layer is formed of open-cell foam. The advantage of is recognized once. On the other hand, since the inner layer is an open-cell foam, there is a problem of insufficient adhesion to the shaft, and when used for a long time, the elastic body may peel off from the shaft, which is not always satisfactory in terms of durability. Was not .

Further, a roller having a single-cell foam structure as described in JP-A-6-102748 has too high a hardness as compared with a roller having a continuous-cell foam structure, and thus has a high In order to stably press the toner, the pressing force is increased, and as a result, the toner is deteriorated by long-term use, which is not preferable.

Although such inconvenience can be solved by reducing the hardness of the foam, the amount of the plasticizer added to reduce the hardness causes an excessive amount of the plasticizer to bleed from the roller. As a result, the oil adheres to the developing roller to fuse the toner.
This fusion of the toner causes the newly supplied toner to be blocked, resulting in insufficient charging of the toner,
This is undesirable because it induces a defect in output print quality called "fog".

Further, a roller having a conductive foam structure described in Japanese Patent Application Laid-Open No. 60-229065 is disclosed.
It simply made the structure of the foam conductive.
Since the cell structure of the foam is not specified at all, it has the same problems as the above-mentioned other conventional techniques.

The present invention solves the above-mentioned problems of the prior art, and does not adversely affect the developing roller and the toner on the other developing roller even during long-term use. It is an object of the present invention to provide a toner supply roller of a developing device having excellent durability without causing the elastic layer to be separated from the body.

[0011]

According to the present invention, there is provided an image forming apparatus comprising:
Roller to supply toner to the developing roller
Te, conductive elastic layer is formed on the outer periphery of the shaft, the toner supply roller which is formed the elastic layer in two layers of the inner elastic layer and an outer elastic layer, the outer elastic layer is a single foam
And an open cell are formed by the conductive foam in which the conductive foam is mixed, and the open cell rate of the conductive foam is set to 20 to 80%. That is, the conductive foam forming the outer elastic layer has a cell structure in which closed cells and open cells are mixed, and the open cell ratio is set to 20 to 80%.

[0012] In this case, it is desirable that the inner elastic layer is formed of a conductive non-foam having higher hardness than the outer elastic layer.

As described above, according to the present invention, the surface layer of the conductive elastic body layer has a cell structure in which closed cells and open cells are mixed, and the ratio of open cells to closed cells, that is, the open cell rate is 20 to 40%.
By setting it to 80%, the opponent 's current
While being able to come into contact with the image roller, the inner elastic layer in contact with the shaft is made of a conductive non-foam layer so that the conductive elastic layer does not peel off from the shaft, and the conductive material does not Charge injection into the elastic layer can be made more reliable.

[0014]

FIG. 1 shows a typical embodiment of the present invention. As shown in FIGS. 1A and 1B, the toner
The supply roller 1 is formed by integrally forming a conductive elastic layer 3 around a metal shaft 2 as a center. The conductive elastic layer 3 is made of a non-foaming solid elastic material. The conductive inner elastic layer 4 made of a body and the outer elastic layer 5 made of a conductive foam form a two-layer composite elastic structure. The conductive foam referred to here is of a type in which the cell structure of the foam itself is a mixture of closed cells and open cells.

The inner elastic layer 4 and the outer elastic layer 5
As a material of the material, a material mainly containing EPDM (ethylene propylene rubber) is used.
In addition to DM, for example, urethane rubber, silicone rubber, chloroprene rubber, acrylic rubber, hydrin rubber,
It is also possible to use styrene butadiene rubber, isoprene rubber, acrylonitrile butadiene rubber, and composite mixtures thereof.

The material of the inner elastic layer 4 is, for example,
EPDM; 100 parts by weight, zinc white; 5 parts by weight, stearic acid; 1 part by weight, conductive carbon black; 5 parts by weight,
Furnace-based carbon black; 50 parts by weight; paraffin-based process oil; 40 parts by weight; vulcanization accelerator (thiazole-based); 2 parts by weight; sulfur;

The material of the outer elastic layer 5 may be, for example, 100 parts by weight of EPDM, 5 parts by weight of zinc white, 1 part by weight of stearic acid, 5 parts by weight of conductive carbon black, 5 parts by weight of furnace-based carbon black. 50 parts by weight, paraffinic process oil; 40 parts by weight, vulcanization accelerator (thiazole type); 2 parts by weight, blowing agent;
One having a composition such as 1 part by weight is used.

In order to manufacture the toner supply roller 1, for example, first, the shaft 2 is placed in a mold having a cylindrical product space (cavity), and the shaft 2 is surrounded. Is filled with a conductive non-foamed elastic compound to be the inner elastic layer 4 and cured by vulcanization to produce an intermediate molded article in which the shaft 2 and the inner elastic layer 4 are integrated. Thereafter, the obtained intermediate molded product is polished to a predetermined thickness using a cylindrical grinder, and the inner elastic layer 4 is finished to a predetermined thickness.

Next, the intermediate molded product of the toner supply roller 1 thus obtained is placed in a mold having a cylindrical product part space (cavity), and the outer molded body is surrounded by the outer elastic layer 4. The toner supply roller 1 in which the electrically conductive foamed elastic compound to become the elastic layer 5 is filled and cured by vulcanization, and the outer elastic layer 5 is integrally formed on the outer periphery of the inner elastic layer 4 is produced. Finally, the toner supply roller 1
The outer elastic layer 5 is polished to a predetermined thickness using a cylindrical grinder to finish the outer elastic layer 5 to a predetermined thickness.

As another method of manufacturing the toner supply roller 1, the pipe-shaped elastic layer 3 in which the inner elastic layer 4 and the outer elastic layer 5 are integrated is formed by, for example, extrusion molding. Then, the shaft 2 is inserted into the elastic layer 3 to be integrated as the toner supply roller 1, and finally the outer elastic layer 5 of the toner supply roller 1 is formed using a cylindrical grinder. May be polished to a predetermined thickness.

Here, what is important is that the outer elastic layer 5
Is formed of a foam having a cell structure in which closed cells and open cells are mixed, and the open cell rate, which is the ratio of open cells incorporated in the closed cells, is set in the range of 20 to 80%. That is. The open cell rate can be arbitrarily controlled by changing the amount of the foaming agent described above. That is, when the amount of the foaming agent is increased, the open-cell rate increases, and when the amount of the foaming agent is reduced, the open-cell rate decreases.

The open cell rate referred to herein is specifically measured and adjusted as follows.

(A) The specific gravity ρ ₀ of the unvulcanized rubber material in which the rubber material to be the main component of the outer elastic layer 5 is not foamed is measured. When air is mixed in the rubber material, the specific gravity is measured after deaeration. The measuring method is based on JIS K 6220.

(B) The weight Wo and the volume Vo of the rubber foam sample after foam molding are measured. The method of measuring the volume is J
According to IS K 6220.

(C) Next, the above-mentioned sample piece is put in a compression device, compressed by a compression plate from above and below so that the compression rate of the sample piece becomes 50%, and fixed, and then the temperature is 20 ± 5 ° C. Immersed in distilled water, and left for 1 minute with the sample piece being about 50 cm below the water surface.

(D) The compression of the sample piece is released in water, the position of the upper compression plate is raised so that the sample piece floats and is about 25 cm below the water surface, and the sample piece is left in this water state for 5 minutes.

(E) The sample piece is taken out of the water, water droplets adhering to the surface are wiped off, and the weight W _{1 of the} sample piece is measured.

The open cell rate of the rubber foam is calculated by the following equation.

Open cell rate (%) = (W ₁ −W ₀ ) / (ρ × V ₂ ) × 100 closed cell rate (%) = 100−open cell rate (%) where W ₀ ; Weight of sample piece (g) W ₁ ; Weight of sample piece after immersion (g) V ₀ ; Volume of sample piece (cm ³ ) V ₁ ; Volume of rubber portion in sample piece (cm ³ ) V ₁ = W ₀ / ρ ₀ V ₂ ; Volume of the bubble portion in the sample (cm ³ ) V ₂ = V ₀ −V ₁ ρ ₀ ; Specific gravity of unvulcanized rubber material before foaming ρ; Specific gravity of distilled water

[0030]

Example 1 An inner elastic layer 4 was integrally formed around a shaft 2 with a material having the following composition.

EPDM (EP4045, manufactured by Mitsui Petrochemical) 100 (parts by weight) Zinc flower (manufactured by Shirasu Chemical) 5 Stearic acid (manufactured by Kao) 1 Conductive carbon black (Ketjen Black EC, manufactured by Lion) 5 Furnace-based carbon black (Niteron # 10, manufactured by Nippon Steel Chemical) 50-Paraffin-based process oil (P-300, manufactured by Kyodo Sekiyu) 40-Vulcanization accelerator (thiazole-based) (Axel CZ, Kawaguchi Chemical) 1 -Vulcanization accelerator (thiazole type) (Noxeller M, manufactured by Ouchi Shinko Chemical Co., Ltd.) 1-Sulfur 1 Further, the outer elastic layer 5 is integrally formed on the outer periphery of the inner elastic layer 4 with a material having the following composition. Molded.

-EPDM (EP4045, manufactured by Mitsui Petrochemical) 100 (parts by weight)-Zinc flower (manufactured by Shirasu Chemical) 5-Stearic acid (manufactured by Kao) 1-Conductive carbon black (Ketjen Black EC, manufactured by Lion) 5 Furnace-based carbon black (Niteron # 10, manufactured by Nippon Steel Chemical) 50-Paraffin-based process oil (P-300, manufactured by Kyodo Sekiyu) 40-Vulcanization accelerator (thiazole-based) (Axel CZ, Kawaguchi Chemical) 1 Vulcanization accelerator (thiazole type) (Noxeller M, manufactured by Ouchi Shinko Chemical Co., Ltd.) 1-Blowing agent (Vinihole AC3W, manufactured by Eiwa Kasei) 1-Sulfur 1 The open cell rate of the outer elastic layer 5 in Example 1 is 20%
Met.

[0033]

Embodiment 2 The material of the inner elastic layer 4 is the same as that of the first embodiment, but only the compounding amount of the foaming agent (Vinihole AC3W, manufactured by Eiwa Kasei) is increased to 2 parts by weight for the material of the outer elastic layer 5. The outer elastic layer 5 was formed under the same conditions as in Example 1 except for the above. The open cell rate of the outer elastic layer 5 in Example 2 was 40%.

[0034]

Embodiment 3 The material of the inner elastic layer 4 is the same as that of the first embodiment, but only the compounding amount of the foaming agent (Vinihole AC3W, manufactured by Eiwa Kasei) is increased to 3 parts by weight for the material of the outer elastic layer 5. The outer elastic layer 5 was formed under the same conditions as in Example 1 except for the above. The open cell ratio of the outer elastic layer 5 in Example 3 was 80%.

[0035]

Comparative Example 1 The material of the inner elastic layer 4 was the same as that of Example 1, but the material of the outer elastic layer 5 was not mixed with a foaming agent (Vinihole AC3W, manufactured by Eiwa Chemical Co., Ltd.). The outer elastic layer 5 was formed under the same conditions as in Example 1. The open cell rate of the outer elastic layer 5 in Comparative Example 1 was 0%.

[0036]

COMPARATIVE EXAMPLE 2 The material of the inner elastic layer 4 was the same as that of the first embodiment, while the material of the outer elastic layer 5 was only 0.5 part by weight of the foaming agent (Vinihole AC3W, manufactured by Eiwa Kasei). The outer elastic layer 5 was formed under the same conditions as in Example 1 except for the above. The open cell rate of the outer elastic layer 5 in Comparative Example 2 was 10%.

[0037]

COMPARATIVE EXAMPLE 3 The material of the inner elastic layer 4 was the same as that of the first embodiment, but the amount of the foaming agent (Vinihole AC3W, manufactured by Eiwa Kasei) was increased to 4 parts by weight for the material of the outer elastic layer 5 The outer elastic layer 5 was formed under the same conditions as in Example 1 except for the above. The open cell ratio of the outer elastic layer 5 in Comparative Example 3 was 90%.

[0038]

Comparative Example 4 While the material of the inner elastic layer 4 was the same as that of Example 1, the amount of the thiazole vulcanization accelerator (Noxeller M, manufactured by Ouchi Shinko Chemical) was added to the material of the outer elastic layer 5. Was reduced to 0.5 parts by weight, and the amount of the foaming agent (Vinihole AC3W, manufactured by Eiwa Kasei) was increased to 4 parts by weight, and the other conditions were the same as in Example 1 except that the outer elastic layer 5 was formed. did. The open cell ratio of the outer elastic layer 5 in Comparative Example 4 was 100%.

Table 1 summarizes the composition components and open cell ratios in Examples 1 to 3 and Comparative Examples 1 to 4 described above.

[0040]

[Table 1]

[0041] Then, the difference in communication bubble index of the outer elastomer layer 5 of the above, experiments were conducted either affect how the toner supply roller and to Printout quality of the current image device.

That is, the toner supply rollers of the open-cell foam forming the outer elastic layer 5 having the open-cell ratio of 10%, 20%, 40%, 80% and 90% are connected to the developing device .
Incorporating in Table 2 shows the results obtained by continuous printing.

[0043]

[Table 2]

As is clear from Table 2, when the open cell ratio of the foam is 10% or less, since the closed cell ratio becomes relatively high, the repulsive force against the pressing force of the roller at a constant strain increases. As a result, the contact pressure with the toner becomes excessively large, causing toner blocking due to fusion of the toner and delaying the supply of the toner, which is an undesirable result.

On the other hand, when the open cell ratio of the foam is 90% or more, on the contrary, the open cell ratio is too high, the toner is filled in the cells, and the roller itself becomes inevitably hard. As a result, the toner was blocked due to the fusion of the toner, and the toner supply was delayed in the same manner as described above.

From the above experimental results, it is understood that the printing quality is excellent when the open cell ratio of the outer elastic layer 5 is set to 20%, 40% and 80% as in Examples 1, 2 and 3. .

[0047]

COMPARATIVE EXAMPLE 5 An elastic layer made of a material having exactly the same composition as that of the outer elastic layer 5 of Example 3 was made uniform without dividing the elastic layer 3 into an inner elastic layer and an outer elastic layer. The whole was formed. The shaft 2 used was the same as that of the third embodiment.

[0048] Then, the toner supply roller of Comparative Example 5 and the toner supply roller of Example 3, was subjected to a peeling strength test between the shaft member, respectively.

In this peel strength test, both ends of the shaft were supported by both ends with a fixing jig, and the elastic layer was compressed to 30% of the diameter of the roller (elastic layer) while the circumference of the shaft was being reduced. Apply a load with a twist amplitude of 45 degrees in the direction. After applying the load of the twist amplitude several times, the state of peeling of the elastic layer from the shaft was examined. Table 3 shows the results.

[0050]

[Table 3]

As can be seen from Table 3, the non-foamed inner elastic layer 4 in direct contact with the shaft 2 has better peeling durability and can withstand long-term use. all right.

Further, with respect to the toner supply roller of Comparative Example 5 in which the elastic body was separated from the shaft body 2 as described above, the partial resistance value of the separated portion was measured and found to be 10 ⁷ Ω or more. Was done. A printing test was conducted by incorporating the toner supply roller into the developing device. As a result, toner conveyance failure occurred, and clear missing characters were recognized.

Therefore, it has been clarified that, as shown in each comparative example, in the toner supply roller in which the foam layer is in direct contact with the shaft, a problem such as missing characters occurs in long-term use.

[0054]

As described above, according to the first aspect of the present invention, the conductive elastic layer having a two-layer structure including the inner elastic layer and the outer elastic layer is formed on the outer periphery of the shaft. In the toner supply roller, the outer elastic layer has a mixture of closed cells and open cells.
The outer elastic layer is formed of a foam having open-cell characteristics by forming the conductive foam from the conductive foam and setting the open-cell ratio of the conductive foam to 20 to 80%. Therefore, it is possible to maintain an appropriate pressing force without applying excessive pressure to the developing roller on the other side to which the toner supply roller comes into pressure contact, and as a result, it is possible to prevent toner clogging, In addition to preventing toner deterioration and fusing beforehand, it can greatly contribute to the improvement of printing quality, can withstand long-term use, and has a large peel strength between the shaft and the conductive elastic layer. , Which is extremely advantageous in terms of durability. In particular, as in the invention according to claim 2, by forming the inner elastic body layer that comes into direct contact with the shaft body from a conductive non-foamed body,
The adhesive strength between the two is further increased, and the peel strength can be further improved.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of the present invention, wherein (A) is a toner;
FIG. 2B is a perspective view of a main part of a supply roller, and FIG. 2B is a cross-sectional view of the toner supply roller .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Toner supply roller 2 ... Shaft 3 ... Conductive elastic layer 4 ... Inner elastic layer 5 ... Outer elastic layer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Chiho Ikeda 330, Naganuma-cho, Inage-ku, Chiba-shi, Chiba Pref. Seiko Epson Corporation (56) References JP-A-8-179603 (JP, A) JP-A-8-272210 (JP, A) JP-A-5-181352 (JP, A) JP-A-6-102748 (JP, A) JP-A-7-36273 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08 501

Claims (2)

(57) [Claims] An image forming apparatus is provided in a toner tank of a developing device.
Roller to supply toner to the developing roller
Te, conductive elastic layer is formed on the outer periphery of the shaft, the toner supply roller which is formed the elastic layer in two layers of the inner elastic layer and an outer elastic layer, the outer elastic layer is a single It is formed of a conductive foam in which bubbles and open cells are mixed, and the open cell rate of the conductive foam is 20 to
80% of the toner supply roller of the developing device . 2. A developing mounting serial to claim 1, characterized in that the inner elastic layer is formed of a conductive non-foam
The toner supply roller of the device .