JPH08234564A - Conductive sponge roller, manufacture of the same and device equipped with the same - Google Patents

Abstract

PURPOSE: To make the volume resistivity in the longitudinal direction of a roller uniform and to perform the uniform electrifying treatment in the longitudinal direction of the roller without generating the electrification defect under low temperature and low humidity conditions in a contact electrifying roller, for instance, with respect to a conductive sponge roller having a conductive sponge layer, and being used by applying the voltage. CONSTITUTION: In the roller which has the conductive sponge layer 17 being at least a foamed layer and is used by applying the voltage, the volume resistivity along the longitudinal direction of the roller on the conductive sponge layer 17 or roller surface is almost uniformalized, irrespective of a larger foaming ratio of the conductive sponge layer 117 in the vicinity of both end parts of the roller than that in the vicinity of the central part in the longitudinal direction of the roller because of larger diffused quantity of a conductive material in the conductive sponge layer 17 in the vicinity of both end parts of the roller than that in the vicinity of the central part in the longitudinal direction of the roller, or because of the almost uniformalized foaming ratio along the longitudinal direction of the roller in the conductive sponge layer 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has at least a conductive sponge layer, which is a foamed layer, and is used by applying a voltage, and a method for manufacturing the roller.
The present invention relates to a device equipped with the roller.

[0002]

2. Description of the Related Art For convenience, a contact charging roller will be described as an example.

Contact charging is performed by a charging member (hereinafter, referred to as a charging roller) 20 which is generally a roller body, as shown in FIG.
0 is brought into contact with an object to be charged 100 (for example, an electrophotographic rotary photoconductor), a voltage is applied to the charging roller 200 by a bias power source S, and the surface of the object to be charged 100 is charged to a required polarity and potential (static elimination). The same shall apply hereinafter).

A DC application method in which only a DC voltage is applied to the charging roller 200, and an AC application in which an oscillating voltage (a voltage whose voltage value periodically changes with time) due to superposition of a DC voltage and an AC voltage is applied. There is a method. A
As described in Japanese Patent Application Laid-Open No. 63-149669, the charging roller 200 is applied with an oscillating voltage having a peak-to-peak voltage that is at least twice the charging start voltage of the member to be charged 100 when a DC voltage is applied. The method of applying a voltage to the surface to perform charging is effective because it allows uniform charging processing.

Such contact charging has an advantage over the corona charging device in that a lower applied voltage can be used and the generation of ozone is extremely small. For example, an electrophotographic copying machine, laser beam printer, electrostatic In an image forming apparatus such as a recording apparatus, it has been put to practical use as a charging means for an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, or a chargeable member such as a transfer material.

The charging roller 200 is generally shown in FIGS.
7, a metal rod, which is a conductive material, is used as a cored bar 201, and a solid low-resistance base rubber roller layer (conductive rubber layer) 202 is concentrically formed around the cored bar 201, and the outer peripheral surface of the rubber roller layer is further formed. One or a plurality of coating layers, for example, a medium resistance or high resistance rubber material is thinly coated to form the resistance layer 203.

In FIG. 16, the core metal 2 of the charging roller 200 is shown.
Each end of 01 is rotatably held by a bearing 204, and the bearing 204 is pressed by a pressure spring 205.
The charging roller 200 is pressed against the member 100 to be charged with a predetermined pressing force by being urged in the direction of, and the charging roller 200 is driven to rotate with the rotation of the electrophotographic rotary photosensitive member 100 as the member to be charged. . Application of voltage from the bias power source S to the charging roller 200 applies pressure spring 205 and bearing 20.
4. It is made through the core 201.

By the way, when the oscillating voltage is applied to the solid type charging roller 200 by the AC application method to charge the member 100 to be charged, the charging roller 2 is charged.
00 by the AC electric field applied to the charging roller 20.
0 strikes and vibrates the body to be charged 100 to generate a so-called “charging sound”. Since this charging sound is unpleasant in some frequency regions, a weight is disposed on the inner surface of the image carrier 100 as a member to be charged in an image forming apparatus that performs contact charging processing on an image carrier such as a photoconductor. It suppresses the vibration of the body and reduces the charging noise.

However, in the above-mentioned structure, when the material of the weight and the work of installing the weight on the inner surface of the image carrier 100 are taken into consideration,
The cost will be high.

Therefore, recently, the charging roller 200 itself is made light and soft to weaken the force for hitting the image carrier 100 as a member to be charged, thereby reducing the vibration of the image carrier 100 and reducing the charging noise. The method of doing is adopted.

More specifically, as shown in FIG. 18, the base rubber roller layer is a sponge layer 202A formed by foaming rubber, so that the charging roller 200 is of a light, soft, sponge type.

Such a sponge type charging roller 2
As a manufacturing method of 00, there are a free foaming method and an in-mold foaming method.

.. Free foaming method As shown in (a) of FIG. 19, a non-vulcanized or non-foamed rubber material in which a compounding agent a such as a foaming agent or a conductive material is mixed and uniformly dispersed around a core metal 201. The layer 202a is adhered and formed, and the unvulcanized / unfoamed rubber material layer 202a is heat-treated in a free state to be vulcanized / free-foamed into a conductive rubber sponge layer, and the rubber sponge layer is polished. , (B), the outer diameter of the sponge type base rubber roller layer (conductive sponge layer) 202A having a predetermined outer diameter is shaped, (c)
As described above, it is a method of manufacturing by forming a required coating layer such as the resistance layer 203 on the outer peripheral surface thereof. b is a rubber material layer 202a
Many bubbles are generated in the conductive sponge layer 202A by vulcanization and foaming.

.. In-mold foaming method As shown in FIGS. 20A and 20B, unvulcanized and unfoamed rubber in which a compounding agent a such as a foaming agent or a conductive material is uniformly dispersed around a cored bar 201. Form a layer 202a of material, set it in the molding cavity C of the split mold 18,19,
The unvulcanized / unfoamed rubber material layer 202a is heat-treated to be vulcanized / foamed, and at the same time, is molded as a conductive sponge layer (202A) having a predetermined outer diameter in the molding cavity C and taken out from the mold. After that, a required coating layer such as a resistance layer (203) is formed on the outer peripheral surface of the conductive sponge layer (202A) to produce the conductive sponge layer (202A).

As the manufacturing method, the latter in-mold foaming method which can form a desired roller shape at the same time as foaming is predominant.

[0016]

A layer 202a of an unvulcanized / unfoamed rubber material in which a compounding agent a such as a foaming agent or a conductive material is uniformly dispersed is heat-treated to form the rubber material layer 202.
Although a is vulcanized and foamed to form a large number of bubbles b in the layer to form the conductive sponge layer 202A, in this case, the unvulcanized or unfoamed type is used regardless of the above free foaming method or in-mold foaming method. In the rubber material layer 202a, in the foaming process, the material portion near the surface layer of the material layer is more easily foamed than the material portion inside the layer, and the rubber material layer 202a has many surface layers.
Since the foaming ratio (volume ratio of the bubble portion in the unit volume of the sponge layer) at both ends of the roller in the longitudinal direction of the roller a is higher than that in the central part of the longitudinal direction of the roller, the formed sponge layer 202.
Bubbles b in each part along the roller length in A do not have substantially uniform diameters, and as shown in the model diagrams of FIGS. The diameter of the bubble b in is larger than that of the bubbles inside the layer and in the central portion of the roller longitudinal direction.

As a result, such a conductive sponge layer 2 is formed.
As shown in FIG. 19D, the volume resistance distribution along the length of the charging roller 200 having 02A becomes higher in the vicinity of both end portions of the roller length than in the vicinity of the central portion of the roller length, and in particular, charging failure occurs at low temperature and low humidity. There was a problem that it was easy.

Therefore, the present invention has a conductive sponge roller having such a conductive sponge layer and applied with a voltage to be used as a charging roller or the like to make the volume resistance uniform in the roller longitudinal direction. To aim. Another object of the present invention is to provide a method for manufacturing the roller and an apparatus equipped with the roller.

[0019]

The present invention is a conductive sponge roller, a method for manufacturing the roller, and an apparatus equipped with the roller, which are characterized by the following constitutions.

(1) A roller having at least a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein the conductive material dispersion amount in the conductive sponge layer is the center of the roller in the longitudinal direction. By virtue of the fact that there is more near both ends than near the edges, the conductive sponge layer or the roller surface does not have a greater foaming ratio near both ends than near the longitudinal center of the roller. In the conductive sponge roller, the volume resistance along the roller longitudinal direction is substantially uniform.

(2) In the conductive sponge material layer before the foaming treatment, the foaming agent is dispersed substantially uniformly in each part in the longitudinal direction of the roller, and the conductive material is dispersed in the vicinity of both ends of the conductive material in the longitudinal direction of the roller rather than in the central part thereof. The method for producing the conductive sponge roller according to (1), in which the material layer is subjected to a foaming treatment.

(3) A roller which has at least a conductive sponge layer, which is a foamed layer, around a core bar and which is used by applying a voltage, wherein the core bar has a diameter smaller than that near the central portion in the roller longitudinal direction. Since the vicinity of both ends is larger, the volume ratio of the conductive sponge layer along the roller longitudinal direction on the roller surface is larger regardless of the fact that the foaming ratio of the conductive sponge layer is larger near both ends than near the center in the longitudinal direction of the roller. A conductive sponge roller characterized by being substantially uniform.

(4) A roller having at least a conductive layer and a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein the thickness of the conductive layer is closer to the central portion in the roller longitudinal direction. Also, since the conductive sponge layer is thicker near both ends than near the central portion in the longitudinal direction of the roller, the volume resistance along the roller longitudinal direction on the roller surface is larger than that near the central portion in the longitudinal direction of the roller. Is a substantially uniform conductive sponge roller.

(5) A roller having at least a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein a resistance layer is provided on the outer periphery of the conductive sponge layer near the central portion in the roller longitudinal direction. Is formed so as to be thicker than the vicinity of both ends, and the conductive layer is formed on the outer periphery of the resistance layer so that the roller surface layer has a straight roller shape. A conductive sponge roller, wherein the volume resistance along the roller longitudinal direction on the roller surface is substantially equalized, although the roller is larger near both ends than in the central portion in the longitudinal direction.

(6) A roller which has at least a conductive sponge layer which is a foamed layer and which is used by applying a voltage, wherein the conductive sponge layer has a diameter at both end portions smaller than the longitudinal center portion of the roller. Is formed into a crown shape, a conductive layer is formed on the outer periphery of the conductive sponge layer, and the roller surface layer is formed into a straight roller shape.
Since the resistance layer is formed on the roller, the conductive sponge layer extends along the roller longitudinal direction on the roller surface regardless of the fact that the foaming ratio of the conductive sponge layer is greater in the vicinity of both end portions than in the central portion in the longitudinal direction of the roller. A conductive sponge roller having a substantially uniform volume resistance.

(7) The conductive sponge roller according to (5) or (6), wherein the conductive sponge layer is formed by in-mold foam molding.

(8) A roller having at least a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform. By doing so, the conductive sponge layer or the surface of the roller has a substantially uniform volume resistance along the roller longitudinal direction.

(9) In the conductive sponge material layer before the foaming treatment, the conductive material is dispersed substantially uniformly in each part in the longitudinal direction of the roller, and the dispersed amount of the foam material is nearer to both end portions than to the central portion in the roller longitudinal direction. The method for producing a conductive sponge roller according to (8), in which the material layer is subjected to a foaming treatment to reduce the amount of foaming and the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform.

(10) With respect to the conductive sponge material layer before the foaming treatment, the conductive material and the foaming agent are dispersed substantially evenly in each part in the longitudinal direction of the roller, and the diameter of the material layer is set at both end portions rather than near the central part in the roller longitudinal direction. As the diameter of the material layer is increased in the vicinity of the roller to form a straight roller-shaped sponge layer having a substantially uniform diameter along the roller longitudinal direction, in-mold foaming processing is performed so that the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially equal. The method for producing a conductive sponge roller according to (8), which is homogenized.

(11) As a roller core metal, one having a larger diameter in the vicinity of both end portions than in the vicinity of the central portion in the roller longitudinal direction is used, and a conductive material and a foaming agent are dispersed substantially uniformly around the core metal. The conductive sponge material before the foaming treatment is coated so that the thickness along the roller longitudinal direction is approximately uniform at each part to form a conductive sponge material layer, and the material layer is a straight line having a substantially uniform diameter along the roller longitudinal direction. The method for producing a conductive sponge roller according to (8), wherein the roller-shaped sponge layer is subjected to in-mold foaming treatment to have a substantially uniform foaming ratio in the roller longitudinal direction of the conductive sponge layer.

(12) With respect to the conductive sponge material layer before the foaming treatment, the conductive material and the foaming agent are dispersed substantially uniformly in each part in the roller longitudinal direction, and the diameter of the material layer is substantially uniform in the roller longitudinal direction in a straight roller shape. That is, the material layer is subjected to in-mold foam molding in a crown shape in which the diameters of both end portions are made smaller than the central portion of the roller longitudinal direction so that the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform (8 The manufacturing method of the electroconductive sponge roller of Claim 1).

(13) With respect to the conductive sponge material layer before the foaming treatment, the conductive material and the foaming agent are dispersed substantially uniformly in the longitudinal direction of the roller, and the heat treatment temperature of the material layer is increased from the vicinity of the both longitudinal ends of the roller to the central portion. The foaming ratio along the roller longitudinal direction of the conductive sponge layer is substantially uniform by increasing the vicinity to promote the foaming near the center of the roller length of the material layer and suppressing the foaming near both ends. The method for producing the conductive sponge roller according to (8),

(14) An apparatus comprising the conductive sponge roller according to any one of (1) and (3) to (8).

(15) An image forming apparatus comprising the conductive sponge roller according to any one of (1) and (3) to (8).

(16) The image forming apparatus according to (15), characterized in that the conductive sponge roller is a contact charging roller that comes into contact with the image carrier at least during image formation.

(17) The image forming apparatus according to (15), wherein the conductive sponge roller is a transfer roller, a developing roller, or both.

(18) Attached to and detached from the main body of the image forming apparatus,
A process cartridge comprising the conductive sponge roller according to any one of (1) and (3) to (8).

(19) The process cartridge as described in (18), wherein the conductive sponge roller is a contact charging roller which is brought into contact with the image carrier at least during image formation.

(20) The process cartridge according to (18), wherein the conductive sponge roller is a transfer roller, a developing roller, or both.

(21) The process cartridge is characterized in that the charging means, the developing means or the cleaning means, and the image carrier are integrated into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus. The process cartridge according to (18) to (20).

(22) In the process cartridge, at least one of the charging means, the developing means or the cleaning means and the image carrier are integrally formed into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus. The process cartridge according to any one of (18) to (20) above.

(23) In the process cartridge, at least the developing means and the image carrier are integrated into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus. (20)
The process cartridge described in 1.

[0043]

[Action]

a) Even if the foaming ratio of the conductive sponge layer is greater near both ends of the roller than near the central portion in the longitudinal direction of the roller, the amount of conductive material dispersed in the conductive sponge layer at both ends is greater than that near the central portion of the roller in the longitudinal direction. By increasing the area near the edges, the foaming ratio of the conductive sponge layer is larger near both ends of the roller than near the center in the longitudinal direction of the roller. The non-uniformity of resistance can be compensated / corrected to make the volume resistance of the conductive sponge layer or the roller surface along the roller longitudinal direction substantially uniform.

B) The diameter of the roller core metal is made larger in the vicinity of both end portions than in the vicinity of the central portion in the roller longitudinal direction, or in the case of a roller having a conductive layer and a conductive sponge layer, the thickness of the conductive layer is By making the area near both ends more thick than the area near the center in the longitudinal direction, the distance from the surface of the core metal or conductive layer to the roller surface can be made shorter at both ends than the center of the roller in the longitudinal direction. Even if the foaming ratio of the layer is larger near both ends of the roller than near the center in the longitudinal direction, the foaming ratio of the conductive sponge layer is larger near both ends of the roller than near the center of the roller. Along the roller longitudinal direction on the conductive sponge layer or roller surface, compensates and corrects the non-uniformity of volume resistance along the roller longitudinal direction on the conductive sponge layer or roller surface. It can be the product resistance to substantially uniform.

C) A resistance layer is formed on the outer periphery of the conductive sponge layer so that the thickness in the vicinity of the central portion in the roller longitudinal direction is thicker than in the vicinity of both ends, and the conductive layer and the roller surface layer are straight on the outer periphery of the resistance layer. The conductive sponge layer is formed into a roller shape, or the conductive sponge layer is formed into a crown shape in which both end portions have a diameter smaller than the roller longitudinal center portion, and the conductive layer is formed on the outer periphery of the conductive sponge layer. The roller surface layer is formed in the shape of a straight roller, and the resistance layer is formed on the roller surface layer, so that the foaming ratio of the conductive sponge layer is closer to both end portions than to the central portion in the longitudinal direction of the roller. However, the foaming ratio of the conductive sponge layer is larger in the vicinity of both ends of the roller than in the vicinity of the center in the longitudinal direction of the roller. (1) The non-uniformity of the volume resistance along the longitudinal direction of the roller can be compensated and corrected by the thickness distribution of the conductive layer along the roller longitudinal direction so that the volume resistance along the roller longitudinal direction on the conductive sponge layer or the roller surface can be made substantially uniform. .

D) By making the foaming ratio of the conductive sponge layer along the roller longitudinal direction substantially uniform, the foaming ratio of the conductive sponge layer is greater near the both ends of the roller than near the longitudinal center thereof. It is possible to eliminate the non-uniformity of the volume resistance along the roller longitudinal direction on the conductive sponge layer or the roller surface, and the volume resistance along the roller longitudinal direction on the conductive sponge layer or the roller surface is substantially equalized. The foaming ratio of the conductive sponge layer along the roller longitudinal direction can be made substantially uniform by the methods (9) to (13).

[0047]

【Example】

<Embodiment 1> (FIG. 1) This embodiment shows an example of an image forming apparatus, and FIG. 1 is a schematic diagram thereof. The image forming apparatus of this example is a copying machine or a laser beam printer (LBP) using a process cartridge attachment / detachment method and a transfer type electrophotographic process.

Reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member as an image bearing member, which is rotationally driven in a clockwise direction indicated by an arrow a at a predetermined peripheral speed (process speed) by a drive system (not shown).

Reference numeral 2 is a contact charging roller as a primary charging means for uniformly charging the peripheral surface of the photosensitive member 1 to a predetermined polarity and potential, and like the above-mentioned FIG.
Both ends of the bearing are rotatably held by movable bearings 13, and the bearings 13 are urged toward the photoconductor 1 by a pressure spring 13a so that the charging roller 2 is pressed against the photoconductor 1 with a predetermined pressing force. The charging roller 2 is brought into pressure contact, and the charging roller 2 is driven to rotate in the direction of the arrow c as the photoconductor 1 rotates. The charging roller 2 may be retracted from the surface of the photoconductor 1 in a non-contact manner against the pressure spring 13a by a pulling mechanism (not shown) during non-image formation.

A superimposing voltage (oscillating voltage) of a predetermined DC voltage and a predetermined AC voltage is applied to the charging roller 2 from the charging bias power source S, whereby the outer peripheral surface of the rotary photosensitive member 1 is contact charged. Primary charging is performed to a predetermined polarity and potential.

The primary charging surface of the rotating photosensitive member 1 is exposed with desired image information 12 by image information exposure means (projection exposure means for original image, laser beam scanning exposure means, etc.) not shown. As a result, an electrostatic latent image corresponding to the exposed image information is formed on the surface of the rotating photoconductor 1.

The electrostatic latent image is developed as a toner image by the toner developing device 5. Reference numeral 3 denotes a developing sleeve or developing roller that rotates in the direction of arrow b to convey toner.
Is an elastic blade for controlling the toner coat thickness on the developing sleeve. A predetermined developing bias is applied to the developing sleeve 3 from the developing bias power source 3A.

Then, the toner image on the surface of the photoconductor 1 is fed to the transfer unit, which is a contact nip between the photoconductor 1 and the transfer roller 10, at a predetermined timing from a paper feeding unit (not shown). Transferring is sequentially performed on the transferred transfer material P as a recording material. A predetermined transfer bias is applied to the transfer roller 10 from a transfer bias power source 10A.

The transfer material P which has received the toner image transferred through the transfer portion is separated from the surface of the rotary photosensitive member 1, is conveyed to an image fixing device (not shown), undergoes an image fixing process, and is printed out.

After the transfer of the toner image to the transfer material P, the rotary photosensitive member 1 is cleaned by the cleaning device 8 after removal of residual adherence of transfer residual toner and the like, and is repeatedly used for image formation. Reference numeral 6 is a cleaning blade for scraping off the transfer residual toner and the like from the surface of the photoreceptor 1, 6a is a supporting member for the blade, and 7 is a squeeze sheet for collecting the scraped transfer residual toner and the like.

In the image forming apparatus of this embodiment, the process cartridge 11 is a detachable and replaceable unit for the image forming apparatus main body, which collectively includes the four process devices including the photoconductor 1, the charging roller 2, the developing device 5, and the cleaning device 8. There is. Reference numeral 9 denotes a cartridge housing in which the above-mentioned four process devices 1, 2, 5, and 8 are incorporated in a predetermined arrangement. 1
Reference numeral 1A is a process cartridge insertion / removal guide / holding portion on the image forming apparatus main body side.

In a state where the process cartridge 11 is installed in the image forming apparatus main body in a predetermined manner, the process cartridge 11 side and the image forming apparatus main body side are mechanically
The mutual coupling state is electrically established, and the lower surface of the photoconductor 1 on the process cartridge 11 side is brought into contact with the transfer roller 10 on the image forming apparatus main body side in a predetermined manner, so that the image formation is executable.

The process cartridge is a cartridge in which the charging means, the developing means or the cleaning means and the electrophotographic photosensitive member are integrally formed, and the cartridge can be attached to and detached from the image forming apparatus main body.
Further, at least one of the charging means, the developing means, and the cleaning means and the electrophotographic photosensitive member are integrally made into a cartridge so that it can be attached to and detached from the main body of the image forming apparatus. Further, it means that at least the developing means and the electrophotographic photosensitive member are integrally made into a cartridge so as to be attachable to and detachable from the apparatus main body.

The charging roller 2 is a conductive sponge roller which is the object of the present invention. Examples 2 to 10 below
The present invention is an embodiment of a structure and a manufacturing method of a conductive sponge roller as a charging roller 2 having a uniform volume resistance in the roller longitudinal direction, which is an object of the present invention.

<Embodiment 2> (FIG. 2) FIG. 2A is a schematic vertical sectional view of the charging roller 2 of the present embodiment, in which the amount of conductive material dispersed in the conductive sponge layer is at the center in the longitudinal direction of the roller. By virtue of the fact that the foaming ratio of the conductive sponge layer is greater near the both ends than near the central part, the conductive sponge layer or the roller surface is In the roller, the volume resistance along the roller longitudinal direction is substantially uniform. Reference numeral 14 is a roller core metal, 17 is a conductive sponge layer formed concentrically around the core metal 14, and 16 is a resistance layer as a coating layer roller surface layer on the outer peripheral surface of the conductive sponge layer 17.

The conductive sponge layer 17 is, for example, a conductive material-dispersed foam layer of epichlorohydrin rubber. In addition to epichlorohydrin rubber, various rubbers such as urethane rubber and EPDM may be used, and a conductive material such as carbon is dispersed in the rubber to adjust the volume resistance to about 10 ² to 10 ⁶ Ω · cm for use. ing.

The resistance layer 16 as the roller surface layer is 10 ⁸ Ω
-It is a layer adjusted to have a resistance of about cm. If the resistance layer 16 can be adjusted to the above resistance so as to prevent leakage of electric charges in the roller longitudinal direction at the time of charging, a resin such as nylon or acryl or various rubbers can be prepared as a single substance, or carbon, tin oxide or the like can be dispersed therein. May be.

The conductive sponge layer 17 of the charging roller 2 of this embodiment is an unvulcanized or unfoamed rubber material layer in which a required compound such as a foaming agent and a conductive material is dispersed by a free foaming method or an in-mold foaming method. It is vulcanized and foamed. The foaming agent is substantially uniformly dispersed in the roller longitudinal direction of the unvulcanized / unfoamed rubber material layer. Therefore, as described above, the foaming ratio of both ends of the rubber material layer in the roller length is in the center of the roller length. It will be higher than
The bubbles in each part of the formed sponge layer 17 along the length of the roller do not have substantially uniform diameters, and similar to the roller model diagrams of FIGS. Although the diameter of the bubble b on both ends of the roller length is larger than that of the bubbles inside the layer and in the center of the roller length ,. As for the conductive material, the conductive sponge layer 17 is provided as shown in the conductive material dispersion amount graph in the roller longitudinal direction of FIG.
Since the conductive material dispersion amount in the inside of the roller is larger in the vicinity of both ends of the roller than in the vicinity of the central portion in the longitudinal direction of the roller, this allows the foaming ratio of the conductive sponge layer 17 to be as described above. Even if the vicinity of both ends is larger than the vicinity of the central portion in the longitudinal direction, the conductive material dispersion amount in the conductive sponge layer portion near the both ends is larger than that in the conductive sponge layer portion near the central portion in the longitudinal direction of the roller as described above. The volume resistance along the roller longitudinal direction of the conductive sponge layer 17 is substantially equalized due to the large amount.

That is, in the conductive sponge layer 17, the conductive material is dispersed more in the both ends in the roller longitudinal direction having a higher foaming ratio than in the central part in the roller longitudinal direction, and the conductive material is dispersed even if the foaming ratio is high or low. The volume resistance of the conductive sponge layer 17 along the roller longitudinal direction is made uniform by the amount.

Such a conductive sponge layer 17 is obtained by comparing the unvulcanized / unfoamed rubber material layer of the conductive sponge layer with
The foaming agent is dispersed substantially uniformly in each part in the roller longitudinal direction, and the conductive material is manufactured by foaming the material layer so that the amount of dispersion is larger near the both ends than near the central part in the roller longitudinal direction. You can

Specifically, when the unvulcanized / unfoamed rubber material layer of the conductive sponge layer 17 is formed by extrusion in the shape of a hollow cylinder, the conductive material is immediately before the portion corresponding to the longitudinal end of the roller is extruded. By itself, or by mixing the same rubber material in which the conductive material is excessively kneaded at the above timing, the conductive material dispersion amount is larger in the vicinity of both ends of the roller than in the vicinity of the center in the longitudinal direction of the roller. Use a distribution form. The foaming agent is substantially uniformly dispersed in the roller longitudinal direction. Then, this rubber material layer is vulcanized and foamed by a free foaming method or an in-mold foaming method to obtain a conductive sponge layer 17 in which the conductive material dispersion amount is larger near both ends of the roller than near the longitudinal center thereof. .

When the method of coating the rubber material layers on the cored bar 14 one by one with the width of the longitudinal length while rotating the cored bar 14 is performed, the roller length of the rubber material kneaded for coating is increased. By preliminarily increasing the conductive material dispersion amount for the portions corresponding to both ends in the direction from the central portion in the roller longitudinal direction, the conductive material dispersion amount in the rubber material layer is closer to both end portions than to the central portion in the longitudinal direction of the roller. Use a form with a large amount of dispersion distribution. The foaming agent is substantially uniformly dispersed in the roller longitudinal direction. Then, the rubber material layer is vulcanized and foamed by a free foaming method or an in-mold foaming method,
A conductive sponge layer 17 is obtained in which the conductive material dispersion amount is greater near the both ends of the roller than near the longitudinal center thereof.

In a method other than the above, the amount of conductive material dispersed in the unvulcanized / unfoamed rubber material layer of the conductive sponge layer 17 formed on the cored bar 14 is closer to both end portions than to the central portion in the longitudinal direction of the roller. It suffices if the dispersion amount distribution form can be large.

By the above method, the conductive sponge layer 1
7 has a configuration in which a larger amount of the conductive material is dispersed near both ends of the roller in the roller longitudinal direction so that the volume resistance of the conductive sponge layer 17 itself of the charging roller 2 or the roller surface can be reduced in the roller longitudinal direction. Can be made uniform, and charging can be performed uniformly in the roller longitudinal direction.

<Embodiment 3> (FIG. 3) FIG. 3 is a schematic vertical sectional view of the charging roller 2 of this embodiment.
The diameter of the cored bar 14 is larger near both ends of the roller than near the center in the longitudinal direction of the roller, so that the foaming ratio of the conductive sponge layer 17 is larger near both ends of the roller than near the central part in the longitudinal direction. Despite the above, the roller has a substantially uniform volume resistance along the roller longitudinal direction on the roller surface.

This charging roller 2 uses a cored bar 14 having a diameter larger in the vicinity of both ends than in the vicinity of the central portion in the roller longitudinal direction, and the unvulcanized and unfoamed rubber of the conductive sponge layer 17 is used. A material in which a conductive material and a foaming agent are substantially uniformly dispersed is used as a material, and the rubber material layer is formed by the core metal 14
The conductive sponge layer 1 is formed by surrounding the rubber material layer and vulcanizing and foaming the rubber material layer by a free foaming method or an in-mold foaming method.
7 is formed, and then the conductive sponge layer 17 is coated with the resistance layer 16.

Conductive sponge layer 1 of charging roller 2 of this example
In No. 7 as well, the foaming agent is dispersed substantially evenly in the roller longitudinal direction of the unvulcanized / unfoamed rubber material layer, and as described above, therefore, the foaming ratio of the rubber material layer at both ends of the roller longitudinal direction is the roller longitudinal direction. Since the height is higher than that in the central portion, the diameters of the bubbles in the respective portions in the formed sponge layer 17 along the roller length are not substantially uniform, and the bubbles in FIG.
Similar to the roller model diagram of (c), the diameter of the bubble b on both sides of the roller 17 in the roller longitudinal direction is larger than that in the layer and in the center of the roller longitudinal direction. By making it thicker in the vicinity of both end portions than in the longitudinal center portion, the distance from the surface of the metallic cored bar 14 which is a conductive material to the surface of the charging roller 2 can be made shorter at both end portions than the central portion in the roller longitudinal direction. The volume resistance on the surface of the charging roller 2 having a straight shape can be made uniform in the roller longitudinal direction in the roller longitudinal direction, and the charging can be performed uniformly in the roller longitudinal direction.

In this embodiment, the cored bar 14 is thicker than its normal diameter near both ends so that the charging roller 2 maintains its longitudinal strength.

<Embodiment 4> (FIG. 4) FIG. 4 is a schematic vertical sectional view of the charging roller 2 of this embodiment.
The conductive layer 20 is provided between the core metal 14 and the conductive sponge layer 17, and the conductive layer is thicker near both ends than near the central portion in the roller longitudinal direction. Is a roller in which the volume resistance along the roller longitudinal direction on the roller surface is substantially equalized, though the roller is larger near both ends in the longitudinal direction than near the central portion.

In this charging roller 2, as the core metal 14, the conductive layer 20 is provided around the core metal only at the portions corresponding to both ends in the roller longitudinal direction where the conductive sponge layer 17 has a high foaming ratio and a high volume resistance. When installed, or when installed along the length of the roller, it should be installed thicker in the vicinity of both ends than in the vicinity of the central part in the roller longitudinal direction, and a conductive material or a foaming agent should be used as the unvulcanized / unfoamed rubber material of the conductive sponge layer 17. Using a uniformly dispersed material, this rubber material layer is formed around the core metal 14, and the rubber material layer is vulcanized and foamed by a free foaming method or an in-mold foaming method to form a conductive sponge layer 17. Then, the resistance layer 1 is formed on the conductive sponge layer 17.
6 is coated.

The charging roller 2 of this example is also based on the same concept as in Example 3 described above, and the conductive layer 20 is made more conductive near both end portions than in the central portion in the roller longitudinal direction. The distance from the surface of the layer 20 to the surface of the charging roller 2 can be made shorter at both end portions than at the central portion in the roller longitudinal direction, and as a result, the volume resistance on the surface of the charging roller 2 having a straight shape can be made uniform in the roller longitudinal direction in the roller longitudinal direction. Thus, charging can be performed uniformly in the roller longitudinal direction.

In the case of the charging roller 2 of the third embodiment, since the longitudinal strength of the charging roller 2 is emphasized, the charging roller 2 itself tends to be heavy. There is an advantage that is not possible.

<Embodiment 5> (FIG. 5) FIG. 5 is a vertical sectional model view of the charging roller 2 of the present embodiment.
A resistance layer 16 is formed on the outer periphery of the conductive sponge layer 17 so that the thickness in the vicinity of the central portion in the roller longitudinal direction is thicker than in the vicinity of both ends, and the conductive layer 20 and the roller surface layer are straight rollers on the outer periphery of the resistance layer 16. Since the conductive sponge layer 17 is formed to have a shape, the foaming ratio of the conductive sponge layer 17 is greater in the vicinity of both ends of the roller than in the vicinity of the central portion in the longitudinal direction of the roller, but along the roller longitudinal direction on the roller surface. The roller has a substantially uniform volume resistance.

In the charging roller 2 of this example, a conductive sponge layer 17 is used as an unvulcanized / unfoamed rubber material in which a conductive material and a foaming agent are dispersed substantially uniformly. The rubber material layer is vulcanized and foamed around the periphery by a free foaming method or an in-mold foaming method to form a straight conductive sponge layer 17, and the resistance layer 16 is formed around the conductive sponge layer 17. Is formed so that it is thicker in the vicinity of the central portion in the roller longitudinal direction than in the vicinity of both ends, and the conductive layer 20 is formed on the outer periphery of the resistance layer 16 so that the roller surface layer has a straight roller shape.

With this roller structure, the volume resistance in the surface layer of the charging roller 2 is totaled in the roller longitudinal direction regardless of the fact that the foaming ratio of the conductive sponge layer 17 is higher in the vicinity of both end portions than in the central portion in the roller longitudinal direction. Can be uniform in direction.

As in this example, the volume resistance was made uniform in the roller longitudinal direction, but when the surface layer was the conductive layer 20, if the surface of the image bearing member 1 had defects such as pinholes, leakage would easily occur. In some cases, uniform charging cannot be performed in the longitudinal direction. Therefore, a thin resistance layer having a thickness of several tens of μm may be coated on the conductive layer 20 with a uniform thickness to prevent leakage.

In the case of the present embodiment, the conductive sponge layer 17 has an advantage that it can be finely adjusted to a desired resistance by the thickness and resistance of the coat layers 16 and 20 as in the conventional example.

<Embodiment 6> (FIG. 6) FIG. 6 is a vertical sectional model view of the charging roller 2 of this embodiment.
The conductive sponge layer 17 is formed in a crown shape in which both end portions have a diameter smaller than the longitudinal center portion of the roller, and the conductive layer 20 is formed on the outer periphery of the conductive sponge layer so that the roller surface layer has a straight roller shape. Since the resistance layer 16 is formed on the roller surface, the conductive sponge layer has a higher foaming ratio near both end portions than near the central portion in the longitudinal direction of the roller. The roller has a substantially uniform volume resistance along the roller longitudinal direction.

The crown-shaped conductive sponge layer 17 is
As the unvulcanized / unfoamed rubber material of the conductive sponge layer, a material in which a conductive material and a foaming agent are dispersed almost uniformly is used, and this rubber material layer is formed around the core metal 14 so that the rubber material layer is free. After the vulcanization / foaming by the foaming method or the in-mold foaming method to form the straight conductive sponge layer 17, the sponge layer 17 is polished to reduce the thickness in the vicinity of both end portions from the central portion in the roller longitudinal direction. It was formed into a crown shape.

Then, a conductive layer 20 is coated on the surface of the crown-shaped conductive sponge layer 17 so that the charging roller 2 has a straight shape, and a resistance layer 16 is coated thereon with a substantially uniform thickness. is there.

In this embodiment, since the sponge layer 17 is foamed as in the prior art, the foaming ratio near the both ends of the roller in the longitudinal direction of the roller is higher than that at the center, but both ends are thinned by polishing. In addition to shortening the distance from the surface of the core metal 14 to the surface of the sponge layer 17, the conductive sponge layer 17 is coated with a thick coating at both ends.
However, the total volume resistance is uniform in the longitudinal direction of the roller regardless of the fact that the foaming ratio is higher in the vicinity of both end portions than in the central portion in the longitudinal direction of the roller.

<Embodiment 7> (FIG. 7) FIG. 7A is a vertical sectional model view of the charging roller 2 of this embodiment, in which the foaming ratio of the conductive sponge layer 17 along the roller longitudinal direction is substantially uniform. Since the conductive sponge layer 17 or the roller surface is made uniform, the volume resistance along the roller longitudinal direction is substantially uniform.

The conductive sponge layer 17 in which the foaming ratio along the roller longitudinal direction is substantially uniform is shown in FIGS. 7 (b) and 7 (c).
As described above, in the conductive sponge material layer 17A before the foaming treatment, the conductive material is dispersed substantially uniformly in the roller longitudinal direction, but the foaming agent c has a dispersion amount along the roller longitudinal direction near the central portion in the roller longitudinal direction. The material layer 17A may be formed by vulcanizing and foaming the material layer 17A by a free foaming method or an in-mold foaming method to form a straight conductive sponge layer 17 rather than the both ends. . The resistance layer 1 is formed on the outer peripheral surface of the conductive sponge layer 17.
6 is coated.

In the charging roller 2 of this embodiment, the conductive material is dispersed and mixed in the conductive sponge layer 17 at each portion in the roller longitudinal direction. However, the foaming agent c is added to the conductive sponge material layer 17A before the foaming treatment. As described above, by dispersing a smaller amount on both end sides compared to the central portion in the roller longitudinal direction, originally, both end portions where the foaming ratio becomes high were made in a direction to suppress the foaming by reducing the dispersion amount of the foaming agent. By doing so,
As shown in the model diagram of (a) of FIG. 3, bubbles b formed near both ends in the roller longitudinal direction of the conductive sponge layer 17 after the foaming treatment.
Each is large in size but has few foamed parts. On the other hand, in the vicinity of the central portion of the conductive sponge layer 17 in the roller longitudinal direction, the diameter of the formed bubbles b is small, but there are many foamed portions. Therefore, the foaming ratio of the conductive sponge layer 17 can be made substantially equal near both ends of the roller in the longitudinal direction of the roller and near the center thereof, and the volume resistance of the conductive sponge layer 17 itself or the roller surface is substantially uniform along the roller length. And can be uniformly charged in the roller longitudinal direction.

Conductive sponge material layer 17A before foaming treatment
The method of varying the dispersion amount of the foaming agent c with respect to the central portion and both end portions in the roller longitudinal direction as described above can be performed according to the method of varying the dispersion amount of the conductive material in the above-described Example 1.

Further, by combining this embodiment with the above-mentioned Embodiment 1, the volume resistance of the charging roller 2 can be more effectively made uniform along the length of the roller.

<Embodiment 8> (FIG. 8) In this embodiment as well, since the foaming ratio of the conductive sponge layer along the roller longitudinal direction is made substantially uniform, the conductive sponge layer or the roller surface in the roller longitudinal direction. The roller having a substantially uniform volume resistance along the line.

In this embodiment, as shown in FIG. 8A, in the conductive sponge material layer 17A before the foaming treatment, the conductive material and the foaming agent are substantially uniformly dispersed in each part in the roller longitudinal direction. The material layer 1 is formed such that the diameter of the core metal 14 is larger in the vicinity of both end portions than in the vicinity of the central portion in the longitudinal direction of the core metal 14.
7A is used as a straight roller-shaped sponge layer 17 having a diameter along the roller longitudinal direction that is substantially uniform in each part, and the molds 18 and 19 are formed.
In-mold foam molding process. The outer peripheral surface of the conductive sponge layer 17 is coated with a resistance layer 16 as shown in (b).

As shown in (a), in the conductive sponge material layer 17A before the foaming treatment, the conductive material and the foaming agent are substantially uniformly dispersed in the roller longitudinal direction, and the diameter of the material layer 17A is set to the center in the roller longitudinal direction. When the material layer is made larger in the vicinity of both ends than in the vicinity of the portion and the in-mold foam molding process is performed on the material layer as a straight roller-shaped sponge layer 17 having a substantially uniform diameter along the roller longitudinal direction, the sponge layer 17 after foaming is formed. ,
Since the amount of the rubber material layer 17A before foaming is increased at both ends in the roller longitudinal direction, as shown in the model diagram of (b),
At both ends, the volume ratio of foaming is suppressed as compared with the central part. Therefore, the foamed diameter of the foamed bubbles b in the sponge layer 17 after foaming is small at both ends in the roller longitudinal direction of the sponge layer 17 and larger than the both ends in the central part, and although both ends are slightly larger in the number of foams, As a result, the foaming ratio of the conductive sponge layer 17 can be made substantially equal near both ends in the roller longitudinal direction and near the center, and the volume resistance on the sponge layer 17 itself or on the roller surface becomes uniform in the roller longitudinal direction. As a result, charging can be performed uniformly in the roller longitudinal direction.

As shown in (a), the conductive sponge material layer 17A before foaming is formed into a shape in which the diameter of the material layer 17A is larger in the vicinity of both end portions than in the central portion in the roller longitudinal direction. There is a method of forming by injecting into a mold whose both ends are thickened in advance, or extrusion molding.In the case of extrusion molding, the diameter of the extrusion port of the rubber material is opened like a camera shutter or The thickness of the extruded material layer 17A is made desired by repeating closing and closing. For example, at the timing when the vicinity of the end is extruded, the extrusion opening is made larger than when the central portion passes, and at the timing when the vicinity of the central portion is extruded, the extrusion opening is made smaller so that both end portions as shown in FIG. It is possible to form the thick material layer 17A.

In addition, the method as described above is the same as in the seventh embodiment.
As compared with the above case, the foaming rate of the conductive sponge layer along the roller longitudinal direction can be adjusted more easily and reliably.

<Embodiment 9> (FIG. 9) In this embodiment as well, since the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform, the conductive sponge layer or the roller surface has a roller longitudinal direction. The roller having a substantially uniform volume resistance along the line.

In this embodiment, as shown in FIG. 9A, in the conductive sponge material layer 17A before the foaming treatment, the conductive material and the foaming agent are substantially uniformly dispersed in each part in the roller longitudinal direction, and the material layer is formed. The diameter of 17A is formed in a straight roller shape that is substantially uniform in the longitudinal direction of the core metal 14, and the material layer 17A is formed into a crown shape in which the diameters of both end portions are smaller than the central portion of the roller longitudinal direction, and in-mold foam molding is performed with the molds 18 and 19. The conductive sponge layer 17 is formed by processing.

That is, in the case of this embodiment, the rubber material layer 17 before foaming is installed in a straight shape around the core metal 14.
It is characterized in that A is vulcanized and foamed in the mold cavity 21 having a thick crown shape in the central portion as compared with both end portions in the roller longitudinal direction.

As compared with the above-mentioned Example 6, at the time of foaming of the sponge layer, it is possible to prevent the foaming ratio at both ends from increasing by reducing the volume of foaming at both ends rather than at the central part. Therefore, efficiency is higher than in Example 6 (the difference in the thickness between the both end portions and the central portion in the crown shape is small), and the cost advantage comes out because the polishing step of the sponge layer 17 can be omitted. The coat layers 20 and 16 on the sponge layer 17 formed in the crown shape are the same as in the sixth embodiment.

In this embodiment, since the volume resistance along the roller longitudinal direction can be adjusted substantially uniformly as described above,
In FIG. 9B, it suffices to coat the sponge layer 17 having a crown shape with the resistance layer 16 having a long and uniform thickness. By doing so, the conductive layer 20 can be formed in one step. It becomes possible to omit it, and further, cost reduction becomes possible.

<Embodiment 10> (FIGS. 10 to 15) The length of the conductive sponge layer 17 of the charging roller 2 or the length of the conductive sponge layer 17 in order to substantially equalize the volume resistance along the roller longitudinal direction on the roller surface. As a method of making the foaming ratio along the direction substantially uniform, in the conductive sponge material layer 17A before the foaming treatment, the conductive material and the foaming agent are dispersed substantially uniformly in each part in the roller longitudinal direction, and the foaming treatment temperature of the material layer is adjusted. The conductive sponge after foaming is formed by making the material near the center of the roller longer than that of both ends of the roller to promote foaming of the material layer 17A near the center of the roller longitudinal and to suppress foaming near both ends. The foaming ratio of the layer 17 along the roller longitudinal direction can be made substantially uniform.

(A) FIG. 10 is an explanatory view of the first method.

That is, in the conductive sponge material layer 17A before the foaming treatment, the conductive material and the foaming agent are substantially uniformly dispersed in the roller longitudinal direction, and the diameter of the material layer 17A is substantially uniform in the roller longitudinal direction. It has a shape and is formed substantially concentrically around the core metal 14.

This is inserted into the heating element coil 21, and the material layer 17A is heated by the heat generated by the heating element coil 21 to perform vulcanization / foaming treatment by the free foaming method, or the gold in which the heating element coil 21 is embedded. The heating element coil 2 is set in the mold.
The material layer 17A is heated by the heat generation of No. 1 to perform vulcanization / foaming treatment by the in-mold foaming method. In the case of this example, the heating element coils 21 have substantially equal spiral wire ring intervals. Two
One portion is arranged so as to correspond to only the vicinity of the central portion in the longitudinal direction of the material layer 17A, and has a temperature gradient such that the vulcanization temperature of the material layer 17A is higher in the central portion than both ends in the longitudinal direction of the material layer 17A. The material layer 1
7A promotes the foaming in the vicinity of the central portion in the longitudinal direction and suppresses the foaming at both ends to make the foaming ratio of the conductive sponge layer 17 itself after vulcanization and foaming in the roller longitudinal direction uniform. is there.

The vulcanization temperature of the material layer 17A is set to 140 °, for example.
C is 1 near the center of the material layer 17A in the longitudinal direction.
The vulcanization temperature is varied in the longitudinal direction of the material layer 17A such that the temperature is 60 ° C. and the temperature is 140 ° C. at both ends. It is better to coat the resistance layer 16 and the like on the outer peripheral surface of the conductive sponge layer 17 after foaming.

As described above, the foaming ratio of the material layer 17A in the longitudinal direction is made uniform to make the volume resistance of the conductive sponge layer 17 itself or the roller surface after foaming uniform in the longitudinal direction, and the charging roller makes uniform charging. Can be done.

(B) FIG. 11 is an explanatory diagram of the second method.

In this example, as shown in FIG. 11, the heating element coil 21 for heat-treating the conductive sponge material layer 17A before the foaming treatment has a length substantially extending over the length of the material layer 17A. The vulcanization temperature of the material layer 17A is made different by varying the spacing density so that the spiral wire ring spacing of the heating element coil 21 is narrow near the central portion in the longitudinal direction of the heating element coil 21 and widens toward the ends. By providing a temperature gradient that makes the vicinity of the central portion higher than both ends in the longitudinal direction of the layer 17A, the foaming in the vicinity of the central portion in the longitudinal direction of the material layer 17A is promoted, and the foaming at both ends is suppressed, thereby applying a pressure. This is to make the foaming ratio of the conductive sponge layer 17 itself after sulfurization and foaming in the roller longitudinal direction uniform. It is better to coat the resistance layer 16 and the like on the outer peripheral surface of the conductive sponge layer 17 after foaming.

In this way, the foaming ratio of the material layer 17A in the longitudinal direction is made uniform, and the volume resistance of the conductive sponge layer 17 itself after foaming or the roller surface is made uniform in the longitudinal direction, and is made uniform by the charging roller. Charging can be performed.

Regarding the adjustment of the foaming ratio of the conductive sponge layer 17 along the roller longitudinal direction, the heating element coil 21 is positioned only at the central portion of the material layer 17A in the longitudinal direction as shown in FIG. 10A. In the embodiment, since the temperature difference of the vulcanization temperature along the length of the material layer 17A becomes large at the boundary of the presence or absence of the heating element coil 21, it is difficult to finely adjust the foaming ratio, but in this example, along the length of the material layer 17A. There is no step in the vulcanization temperature, and the vulcanization temperature along the length of the material layer 17A is finely graded by adjusting the spiral wire ring spacing of the heating element coil 21 so that the conductive sponge layer 17 extends in the roller longitudinal direction. It is possible to adjust the foaming ratio along with.

(C) FIG. 12 is an explanatory diagram of the third method.

In this example, as shown in FIG. 12, the heating element coil 21 for heat-treating the conductive sponge material layer 17A before the foaming treatment has a length substantially extending along the length of the material layer 17A. The diameter of the spiral coil of the heating element coil 21 is gradually increased from the central portion in the longitudinal direction of the heating element coil 21 toward the end portion.

That is, the spiral coil at the center of the heating coil 21 in the longitudinal direction is close to the center of the material layer 17A in the longitudinal direction, and the spiral coils at both ends are separated from both ends of the material layer 17A. The vulcanization temperature of the material layer 17A is the material layer 1
In the longitudinal direction of 7A, the temperature gradient becomes higher in the vicinity of the central portion than in the longitudinal end portions of the material layer 17A, which promotes foaming in the vicinity of the central portion in the longitudinal direction of the material layer 17A and suppresses foaming at both end portions, thus vulcanizing and foaming. The foaming ratio of the subsequent conductive sponge layer 17 itself in the roller longitudinal direction is made uniform. It is better to coat the resistance layer 16 and the like on the outer peripheral surface of the conductive sponge layer 17 after foaming.

In this way, the foaming ratio of the material layer 17A in the longitudinal direction is made uniform, and the volume resistance on the surface of the conductive sponge layer 17 itself after foaming or on the roller surface is made uniform in the longitudinal direction. Charging can be performed.

In the present example, the spiral wire ring intervals along the length of the heating element coil 21 are made equal, but by combining the heating element coil configurations of (b) (FIG. 11) described above, the roller of the conductive sponge layer 17 is formed. The foaming ratio along the longitudinal direction can be adjusted more efficiently.

(D) FIG. 13 is an explanatory diagram of the fourth method.

In this example, as shown in FIG. 13, the heating element coil 2
Although the intervals between the spiral wire loops along the length of 1 are uniform, the vulcanization temperature of the material layer 17A may vary depending on the number of windings of the wire loop.
In the longitudinal direction, the temperature gradient is made higher in the central part than in both ends. For example, if the number of turns of the spiral coil in the central portion of the heating element coil 21 in the longitudinal direction is 4, the number of turns of the heating element coil 21 is reduced to 3, 2, 1 toward the end to reduce the amount of heat generated by the heating element coil 21. A temperature gradient is provided by adjusting so as to increase in the central portion in the longitudinal direction and decrease in the end portion so that the foaming ratio in the longitudinal direction of the conductive sponge layer 17 after vulcanization and foaming becomes uniform. It is better to coat the resistance layer 16 and the like on the outer peripheral surface of the conductive sponge layer 17 after foaming.

In this way, the foaming ratio of the material layer 17A in the longitudinal direction is made uniform, and the volume resistance on the surface of the conductive sponge layer 17 itself after foaming or the roller surface is made uniform in the longitudinal direction, and is made uniform by the charging roller. Charging can be performed.

(E) FIG. 14 is an explanatory diagram of the fifth method.

In this example, as shown in FIG. 14, the heating element coil 2
Although the spiral wire loop spacing along the length of 1 is uniform, the thickness (diameter) of the spiral wire loop of the heating element coil 21 is set to the heating element coil 2
1 is thin at the central portion in the longitudinal direction and is thicker toward the end portion, and the amount of heat generated in the longitudinal direction of the heating element coil 21 is large in the central portion and has a small temperature gradient toward the end portion, thereby foaming the material layer 17A. The ratio is made substantially uniform in the longitudinal direction. It is better to coat the resistance layer 16 and the like on the outer peripheral surface of the conductive sponge layer 17 after foaming.

In this way, the foaming ratio in the longitudinal direction of the material layer 17A is made uniform, and the volume resistance of the conductive sponge layer 17 itself or the roller surface after foaming is made uniform in the longitudinal direction, and is made uniform by the charging roller. Charging can be performed.

(F) FIG. 15 is an explanatory view of the fifth method.

In this example, as shown in FIG. 15, a plurality of plate-shaped heat generating elements 22 are used, and a thin plate in the vicinity of the central portion in the longitudinal direction and a thick piece in the vicinity of both ends are embedded in a cylindrical mold 23. The vulcanization temperature in the longitudinal direction in the cylindrical mold 23 has a temperature gradient that is high in the central part and low in both ends.

In the inner space of the cylindrical mold 23, with respect to the conductive sponge material layer 17A before the foaming treatment, the conductive material and the foaming agent are substantially uniformly dispersed in each part in the longitudinal direction of the roller.
7A is formed into a straight roller shape having a substantially uniform diameter in the roller longitudinal direction and is formed substantially concentrically around the core metal 14, and the material layer 17A is heated and vulcanized / foamed by a free foaming method. As a result, the foaming ratio in the longitudinal direction of the conductive sponge layer 17 after vulcanization and foaming is made uniform.
The resistance layer 16 is formed on the outer peripheral surface of the conductive sponge layer 17 after foaming.
It is better to coat etc.

In the above example, the material layer 17A is freely foamed, but as a matter of course, the plate-shaped heating element 22 may be embedded in a mold to be vulcanized and foamed in the mold.

In this example, the heating element 22 extending in the longitudinal direction was used, but the heating element 22 having a plate-like shape with a width of several cm and having a shape as shown in (a) (FIG. 10) is provided only near the central portion. You may arrange.

Such a plate-shaped heating element 22 has a plate width,
Since the number of the heating elements 22 to be arranged can be designed variously, more delicate temperature adjustment can be performed.

By the above method, it is possible to promote the foaming of the central portion of the material layer 17A in the longitudinal direction and suppress the foaming of both end portions thereof, and as a whole, the conductive sponge layer 17 itself has a uniform foaming ratio in the longitudinal direction. Thus, the volume resistance on the conductive sponge layer 17 itself or on the roller surface becomes uniform in the roller longitudinal direction, and the charging roller can perform uniform charging.

<Other Embodiments> Each of the above-described embodiments is effective even if implemented independently, but in order to obtain further effects, it is more effective to combine the respective embodiments.

Further, in each of the embodiments, only the charging roller 2 has been described, but the present invention is not limited to the charging roller 2, and it is necessary to make the volume resistance in the longitudinal direction uniform.
It has a sponge layer and can be applied to all rollers used by applying a voltage. For example, in the image forming apparatus of FIG. 1, the transfer roller 10 having the sponge layer, the developing roller 3
And so on.

In addition, the charging roller 2 in the cartridge 11
However, the charging roller 2 is not limited to the charging roller 2 in the cartridge, and the charging roller 2 of the image forming apparatus is also effective.

It is needless to say that the apparatus provided with the conductive sponge roller is not limited to the image forming apparatus and the process cartridge of the embodiment.

[0134]

As described above, according to the present invention,
A conductive sponge roller having a conductive sponge layer, which is used by applying a voltage, has a uniform volume resistance in the roller longitudinal direction and a uniform volume resistance in the roller longitudinal direction. In the case of a contact charging roller, for example, it is possible to perform uniform charging processing in the roller longitudinal direction without causing charging failure even under low temperature and low humidity.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an example of an image forming apparatus according to a first exemplary embodiment.

FIG. 2A is a vertical cross-sectional model diagram of the charging roller (conductive sponge roller) of Example 2, and FIG. 2B is a distribution graph of conductive material dispersion amount in the conductive sponge layer along the charging roller longitudinal direction.

FIG. 3 is a vertical cross-sectional model diagram of a charging roller of Example 3.

FIG. 4 is a schematic vertical cross-sectional view of a charging roller of Example 4.

FIG. 5 is a vertical cross-sectional model diagram of a charging roller of Example 5.

FIG. 6 is a schematic vertical cross-sectional view of a charging roller of Example 6.

7A is a vertical cross-sectional model view of a charging roller of Example 7, FIG. 7B is a model view of a conductive sponge material layer before foaming formed around a cored bar, and FIG. 7C is a view of the material layer. Foaming agent dispersion amount distribution graph along the longitudinal direction

FIG. 8A is an explanatory diagram of a conductive sponge layer forming procedure of the charging roller of Example 8, and FIG.

FIG. 9A is an explanatory view of a conductive sponge layer forming method of the charging roller of Example 9, and FIG.

FIG. 10 is an explanatory view of a conductive sponge material layer heating vulcanization / foaming treatment procedure (first method) of Example 10.

FIG. 11 is an explanatory diagram of the second method.

FIG. 12 is an explanatory diagram of the third method.

FIG. 13 is an explanatory diagram of the fourth method.

FIG. 14 is an explanatory diagram of the fifth method.

FIG. 15 is an explanatory diagram of the sixth method.

FIG. 16 is a structural schematic diagram of a main part of a contact charging device as a conventional example.

FIG. 17 is a schematic vertical sectional view of the charging roller (solid type)

FIG. 18 is a schematic cross-sectional view of a sponge type charging roller.

FIGS. 19 (a), (b), and (c) are explanatory views of the manufacturing procedure of the sponge type charging roller, and FIG. 19 (d) is a graph of volume resistance change along the longitudinal direction of the charging roller.

20 (a) and 20 (b) are explanatory views of an in-mold foaming method of a conductive sponge material layer.

[Explanation of symbols]

 1 Photoreceptor (Image Carrier) 2 Charging Roller (Conductive Sponge Roller) 3 Developing Sleeve (Developing Roller) 5 Developing Device 8 Cleaning Device 10 Transfer Roller 11 Process Cartridge 14 Charging Roller Core 16 Resistive Layer 17 Conductive Sponge Layer 17A Conductive sponge material layer before foaming 18/19 Heat vulcanization / foaming mold of conductive sponge layer 20 Conductive layer 21 Vulcanization / foaming heater coil of conductive sponge layer

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03G 15/06 G03G 15/16 103 15/16 103 G03G 15/00 556 // B29K 105: 04

Claims (23)

[Claims] 1. A roller having at least a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein the conductive material dispersion amount in the conductive sponge layer is the central portion in the longitudinal direction of the roller. Because there are more near both ends than near,
Despite the fact that the foaming ratio of the conductive sponge layer is larger near both ends of the roller than near the center in the longitudinal direction of the roller, the volume resistance along the roller longitudinal direction on the conductive sponge layer or the roller surface is substantially uniform. Conductive sponge roller characterized by having. 2. The conductive sponge material layer before the foaming treatment is such that the foaming agent is substantially uniformly dispersed in each part in the roller longitudinal direction, and the conductive material is dispersed in the vicinity of both ends of the roller rather than in the center of the roller longitudinal direction. The method for producing the conductive sponge roller according to claim 1, wherein the material layer is foamed to increase the amount of the material. 3. A roller which has at least a conductive sponge layer, which is a foamed layer, around a core metal and which is used by applying a voltage, wherein the diameter of the core metal is at both ends of the roller as compared to the vicinity of the central portion in the roller longitudinal direction. By virtue of the fact that the area around the roller is larger, the foaming ratio of the conductive sponge layer is larger near both ends than near the central portion in the longitudinal direction of the roller, but the volume resistance along the roller longitudinal direction on the roller surface is substantially A conductive sponge roller characterized by being made uniform. 4. A roller which has at least a conductive layer and a conductive sponge layer which is a foamed layer, and which is used by applying a voltage, wherein the thickness of the conductive layer is greater than that near the central portion in the roller longitudinal direction. Since the conductive sponge layer is thicker in the vicinity of both ends than in the vicinity of the central portion in the longitudinal direction of the roller, the volume resistance along the roller longitudinal direction on the roller surface is larger than that in the vicinity of the central portion in the longitudinal direction of the roller. A conductive sponge roller characterized by being substantially uniform. 5. A roller having at least a conductive sponge layer that is a foamed layer and used by applying a voltage, wherein a resistance layer is provided on the outer periphery of the conductive sponge layer in the vicinity of the central portion in the roller longitudinal direction. It is formed so that it is thicker than the vicinity of both ends, and the conductive layer is formed on the outer periphery of the resistance layer so that the roller surface layer has a straight roller shape.
Despite the fact that the foaming ratio of the conductive sponge layer is larger near both ends of the roller than near the center in the longitudinal direction of the roller, the volume resistance along the roller longitudinal direction on the roller surface is substantially uniform. Conductive sponge roller. 6. A roller having at least a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein the conductive sponge layer has a diameter at both end portions smaller than a longitudinal center portion of the roller. The conductive sponge layer is formed in a crown shape, a conductive layer is formed on the outer periphery of the conductive sponge layer, a roller surface layer is formed in a straight roller shape, and a resistance layer is formed on the conductive layer. Despite the fact that the foaming ratio of the sponge layer is higher near the ends of the roller than near the center of the roller in the longitudinal direction, the volume resistance along the roller longitudinal direction on the roller surface is substantially uniform. Sex sponge roller. 7. The conductive sponge roller according to claim 5, wherein the conductive sponge layer is formed by an in-mold foam molding process. 8. A roller having at least a conductive sponge layer which is a foamed layer and used by applying a voltage, wherein the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform. The conductive sponge roller is characterized in that the volume resistance along the roller longitudinal direction on the conductive sponge layer or the roller surface is substantially equalized. 9. In the conductive sponge material layer before foaming treatment, the conductive material is dispersed substantially evenly in each part in the roller longitudinal direction, and the foamed material is dispersed in the vicinity of both end portions in the roller longitudinal direction rather than in the central portion in the roller longitudinal direction. The method for producing a conductive sponge roller according to claim 8, wherein the material layer is subjected to a foaming treatment to reduce the amount of foaming and the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform. 10. The conductive sponge material layer before the foaming treatment, wherein the conductive material and the foaming agent are substantially uniformly dispersed in each part in the roller longitudinal direction, and the diameter of the material layer is near both ends of the roller longitudinal direction rather than near the central part in the roller longitudinal direction. To make the material layer into a straight roller-shaped sponge layer whose diameters along the roller longitudinal direction are substantially uniform in each part, and subjected to in-mold foaming treatment so that the foaming ratio of the conductive sponge layer along the roller longitudinal direction is substantially uniform. The method for manufacturing a conductive sponge roller according to claim 8, wherein the conductive sponge roller is manufactured. 11. A roller core metal having a larger diameter in the vicinity of both end portions than in the vicinity of the central portion in the roller longitudinal direction is used, and a conductive material and a foaming agent are dispersed substantially uniformly around the core metal. A straight roller in which the conductive sponge material before foaming treatment is coated to have a uniform thickness along the roller longitudinal direction to form a conductive sponge material layer, and the material layer has a substantially uniform diameter along the roller longitudinal direction. The foaming ratio in the roller longitudinal direction of the conductive sponge layer is substantially uniformed by performing in-mold foaming treatment as the foam sponge layer.
A method for producing the conductive sponge roller according to item 1. 12. The conductive sponge material layer before the foaming treatment, wherein the conductive material and the foaming agent are substantially evenly distributed in each part in the roller longitudinal direction, and the diameter of the material layer is formed into a straight roller shape having a substantially uniform diameter in the roller longitudinal direction. No, the foaming ratio of the conductive sponge layer in the roller longitudinal direction is substantially uniformized by subjecting the material layer to an in-mold foaming process in a crown shape in which the diameters of both end portions are smaller than the longitudinal center portion of the roller. A method for producing the conductive sponge roller according to item 1. 13. In the conductive sponge material layer before the foaming treatment, the conductive material and the foaming agent are substantially evenly dispersed in each part in the roller longitudinal direction, and the heat treatment temperature of the material layer is changed from the vicinity of both ends of the roller length to the central part. The foaming ratio of the conductive sponge layer along the roller longitudinal direction is made substantially uniform by increasing the height of the conductive sponge layer to promote foaming near the center of the roller length of the material layer and suppress foaming near both ends. 9. A method of manufacturing a conductive sponge roller according to claim 8. 14. The method according to claim 1 and claims 3 to 8.
An apparatus comprising the conductive sponge roller according to any one of 1. 15. The method according to claim 1 and claims 3 to 8.
An image forming apparatus comprising the conductive sponge roller according to any one of the above. 16. The image forming apparatus according to claim 15, wherein the conductive sponge roller is a contact charging roller that contacts the image carrier at least during image formation. 17. The image forming apparatus according to claim 15, wherein the conductive sponge roller is a transfer roller or a developing roller, or both of them. 18. A process cartridge comprising the conductive sponge roller according to claim 1 or claim 3 or claim 8, which is attached to or detached from an image forming apparatus main body. 19. The process cartridge according to claim 18, wherein the conductive sponge roller is a contact charging roller that contacts the image carrier at least during image formation. 20. The process cartridge according to claim 18, wherein the conductive sponge roller is a transfer roller, a developing roller, or both. 21. The process cartridge comprises a charging means,
21. The process cartridge according to claim 18, wherein the developing means or the cleaning means and the image carrier are integrally formed into a cartridge, and the cartridge is detachably mountable to the main body of the image forming apparatus. . 22. The process cartridge comprises a charging means,
At least one of developing means or cleaning means,
21. The process cartridge according to claim 18, wherein the image carrier and the image carrier are integrated into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus. 23. The process cartridge according to claim 18, wherein at least the developing means and the image carrier are integrally formed into a cartridge, and the cartridge can be attached to and detached from the main body of the image forming apparatus. Item 21. The process cartridge according to Item 20.