WO2011027959A1

WO2011027959A1 - Apparatus and method for manufacturing electro-conductive roller

Info

Publication number: WO2011027959A1
Application number: PCT/KR2010/003346
Authority: WO
Inventors: Jung-Soo Kim; Hyoun-Jin Kim
Original assignee: Jahwa Electronics Co., Ltd.
Priority date: 2009-09-04
Filing date: 2010-05-27
Publication date: 2011-03-10
Also published as: KR101080618B1; KR20110025519A

Abstract

An apparatus and method for manufacturing a conductive roller are provided, in which a tube fixer supports an elastic tube, an air compressor expands an insertion hole of the elastic tube by applying an air pressure to the insertion hole or contracts the insertion hole of the elastic tube by blocking the air pressure from the insertion hole, a shaft transferor transfers a shaft to be inserted into the expanded insertion hole, and a shaft support supports the shaft so that the shaft is transferrable.

Description

APPARATUS AND METHOD FOR MANUFACTURING ELECTRO-CONDUCTIVE ROLLER

The present invention relates to an apparatus and method for manufacturing an electro-conductive roller for use in an image forming apparatus.

In general, an image forming apparatus translates an image signal to a visible image on a printing paper sheet being a recording medium according to a digital signal received from a computer or a scanner. As an image forming apparatus, a laser beam printer is popular, which forms an image using an electrostatic latent image.

A configuration of a laser beam printer being a major image forming apparatus will be described below.

Referring to FIG. 1, a charging roller 2 charges the surface of a photoconductive drum 3 and then a laser scanner 4 forms a latent image on the charged surface of the photoconductive drum 3 in a laser beam printer 1. A developing roller 5 selectively attaches toner 6 onto the static image, thus forming a toner image. The toner image is transferred to a contact surface between a transfer roller 7 and the photoconductive drum 3, that is, a transfer nip by rotation of the photoconductive drum 3. At the same time, a paper sheet 8 is fed from a paper cassette (not shown) by a pick-up roller (not shown) and transferred to the transfer roller 7.

A high voltage having a polarity opposite to the polarity of the toner 6 is applied to the transfer roller 7 so that the toner 6 attached on the photoconductive drum 3 is electrostatically attracted and thus the toner image is transferred onto the paper sheet 8. As a transfer potential having the polarity opposite to the polarity of the toner 6 is applied to the rear surface of the paper sheet 8, the transferred toner 6 is maintained, while the image is transferred onto the paper sheet 8 by attracting the toner 6 electrostatically. A fixer 9 presses the paper sheet 8 with the toner image transferred thereon with heat, thereby permanently fixing the toner image on the paper sheet 8.

There are two kinds of electro-conductive rollers depending on their functions. One is the developing roller 5 for transferring the toner 6 to the photoconductive drum 3 in the image forming apparatus 1, and the other is the charging roller 2 for charging the photoconductive drum 3 in the image forming apparatus 1.

The electro-

conductive rollers

2 and 5 are major components of the image forming apparatus 1, for transferring the toner 6 and charging the photoconductive drum 3, and require fine control of their electrical characteristics. Among them, uniform electrical resistance characteristics of the electro-conductive rollers are significant in printing uniform images.

Unless the electrical resistance characteristics are satisfied, various errors may increase in an image, such as an image smear, a non-uniform concentration, or a low transfer efficiency.

To overcome the above problems, a technique for satisfying a narrow electrical resistance area in an electro-conductive roller and fabricating almost the same electro-conductive rollers is required for mass production.

Referring to FIG. 2 illustrating the structure of the conventional electro-

conductive rollers

2 and 5, each of the electro-

conductive rollers

2 and 5 includes a metal shaft 10, an adhesive 11 coated on the outer circumferential surface of the shaft 10, and an elastic layer 12 attached on the adhesive 11.

A coating layer 13 is formed on the outer surface of the elastic layer 12 in order to enhance durability and reduce friction force.

However, the adhesive layer used for adhesion between the shaft and the elastic layer is difficult to form to a uniform thickness, thus making it difficult to maintain the electrical resistance characteristics of the above electro-conductive roller fabricated with an adhesive to be uniform and to manufacture the electro-conductive roller.

Moreover, the coated adhesive layer causes a change in the electrical resistance characteristics in a low-temperature, low-humidity environment. As a result, an image forming apparatus adopting the conventional electro-conductive roller has limits in its use range in terms of environmental reliability.

Accordingly, there exists a need for an apparatus for manufacturing an electro-conductive roller using an air pressure instead of a non-uniform adhesive coating.

An aspect of exemplary embodiments of the present invention is to address at least the problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of exemplary embodiments of the present invention is to provide an apparatus and method for manufacturing an electro-conductive roller using an air pressure instead of a conventionally used adhesive in order to maintain the electrical resistance characteristics of the electro-conductive roller uniform, facilitate control of the electrical resistance characteristics, prevent changes in environmental characteristics caused by a long term use, and thus increase the reliability of the electro-conductive roller.

In accordance with an aspect of exemplary embodiments of the present invention, there is provided an apparatus for manufacturing an electro-conductive roller, in which a tube fixer supports an elastic tube, an air compressor expands an insertion hole of the elastic tube by applying an air pressure to the insertion hole or contracts the insertion hole of the elastic tube by blocking the air pressure from the insertion hole, a shaft transferor transfers a shaft to be inserted into the expanded insertion hole, and a shaft support supports the shaft so that the shaft is transferrable.

In accordance with another aspect of exemplary embodiments of the present invention, there is provided a method for manufacturing a conductive roller, in which an elastic tube is fixed, the elastic tube is expanded by applying an air pressure into an insertion hole of the elastic tube, a shaft is transferred to be inserted into the expanded insertion hole, and the insertion hole and an outer circumferential surface of the shaft are brought into close contact by blocking the air pressure from the insertion hole, while the shaft is inserted in the insertion hole.

The present invention is to provide an apparatus and method for manufacturing an electro-conductive roller using an air pressure instead of a conventionally used adhesive in order to maintain the electrical resistance characteristics of the electro-conductive roller uniform, facilitate control of the electrical resistance characteristics, prevent changes in environmental characteristics caused by a long term use, and thus increase the reliability of the electro-conductive roller.

FIG. 1 is a schematic view illustrating a configuration of a conventional toner cartridge in a laser beam printer having electro-conductive rollers;

FIG. 2 is a side sectional view of the configuration of the conventional electro-conductive rollers;

FIG. 3 is a schematic view illustrating an apparatus for manufacturing an electro-conductive roller according to an exemplary embodiment of the present invention;

FIG. 4 is a side sectional view of a tube fixer and a tube presser in the apparatus for manufacturing an electro-conductive roller according to an exemplary embodiment of the present invention; and

FIG. 5 is a flowchart illustrating a method for manufacturing an electro-conductive roller according to an exemplary embodiment of the present invention.

The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of exemplary embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

Referring to FIGs. 3 and 4, an electro-conductive roller manufacturing apparatus 100 includes a tube fixer 110, a tube presser 120, an air compressor 130, a shaft transferor 140, and a shaft support 150. The tube fixer 110 functions to fix a later-described elastic tube 200. An insertion hole 201 is formed through the elastic tube 200 to allow a later-described shaft 300 to extend therethrough. The tube presser 120 is placed above the tube fixer 110 to press the fixed elastic tube 200. The air compressor 130 is provided at an end of the elastic tube 200 to expand the insertion hole 201 by applying an air pressure A1 into the insertion hole 201 or to contract the insertion hole 201 by blocking the air pressure A1 from the insertion hole 201. The shaft transferor 140 is provided at the other end of the elastic tube 200 to insert the shaft 300 through the expanded insertion hole 201. The shaft support 150 is disposed under the shaft transferor 140 to support the transfer of the shaft 300.

While the air compressor 130 is used in the present invention, it is a mere exemplary application. Hence, the present invention is not limited to the air compressor 130 and thus any other device that applies the air pressure A1 is available.

An electro-conductive roller is formed by inserting the shaft 300 into the insertion hole 201 of the elastic tube 200.

As illustrated in FIGs. 3 and 4, the insertion hole 201 is formed to be smaller than an outer diameter of the shaft 300 such that when the air pressure A1 is blocked from the air compressor 130, the expanded insertion hole 201 is contracted and thus closely contacts the outer circumferential surface of the shaft 300.

As illustrated in FIGs. 3 and 4, the shaft 300 applies the air pressure A1 into the insertion hole 201 so that an inner diameter of the insertion hole 201 gets larger than the outer diameter of the shaft 300. The shaft 300 is inserted into the insertion hole 201, while blocking the air pressure A1 from the insertion hole 201. Thus the shaft 300 is brought into close contact with the insertion hole 201.

In addition, the air compressor 130 is positioned at a first opening of the insertion hole 201, whereas the shaft transferor 140 and the shaft support 150 are positioned at a second opening of the insertion hole 201 at an opposite side of the first opening.

The electro-conductive roller is supposed to have a total resistance between 10³Ω and 10⁷Ω.

The elastic tube 200 is formed of one or both of epichlorohydrin resin and nitrile butadiene rubber. The elastic tube 200 has a surface electrical resistance between 10³Ω to 10⁷Ω and a shrinkage rate of 3% or below.

As illustrated in FIG. 4, a plurality of

pressing plates

111 or 121 are formed in each of the tube fixer 110 and the tube presser 120. The pressing plates 111 or 112 are combined to a hexagonal tube. Any other shape than the hexagonal tube is also available to the pressing plates 111 or 112. For instance, a rectangular tube or an octagonal tube is also available.

The electro-conductive roller has a surface hardness between 40 and 70 degrees (in case of JIS K6253 (Type A)) and a surface roughness between 4 to 20㎛.

Referring to FIGs. 3 and 4, the electro-conductive roller manufacturing apparatus 100 includes the elastic tube 200 having the insertion hole 201 formed therein, the tube fixer 110, the tube presser 120, the air compressor 130, the shaft transferor 140, and the shaft support 150.

The elastic tube 200 is cut to appropriate dimensions in its crosslinking- completed state.

Then the elastic tube 200 is fixedly mounted on the plurality of pressing plates 111 formed in the tube fixer 110.

In this state, the tube presser 120 over the tube fixer 110 is brought down and presses the elastic tube 200.

The plurality of pressing plates 121 formed in the tube presser 120 are also brought down and engaged with the plurality of the pressing plates 111 formed in the tube fixer 110.

As illustrated in FIG. 4, the pressing plates 111 and 112 form a hexagonal, fixedly surrounding the elastic tube 200.

In this state, the air compressor 130 at an end of the elastic tube 200 as illustrated in FIG. 3 applies the air pressure A1 into the insertion hole 201 of the elastic tube 200, thus expanding the insertion hole 201.

The air compressor 130 is disposed at the first opening of the insertion hole 201, while the shaft transferor 140 and the shaft support 150 are positioned at the second opening opposite to the first opening.

The shaft 300 provided at the other end of the elastic tube 200 is inserted into the expanded insertion hole 201 by the shaft transferor 140.

If the air pressure A1 is blocked from the air compressor 130 with the shaft 300 inserted into the insertion hole 201, the insertion hole 201 shrinks into close contact with the outer circumferential surface of the shaft 300.

Because the insertion hole 201 is formed to be smaller than the outer diameter of the shaft 300, the insertion hole 201 is brought into close contact with the outer circumferential surface of the shaft 300 by blocking the air pressure A1 from the insertion hole 201.

As described above, the electro-conductive roller is manufactured by inserting the shaft 300 into the insertion hole 201 of the elastic tube 200 using the air pressure A1, instead of the conventional non-uniformly coated adhesive. Therefore, the electrical resistance characteristics of the product are maintained uniform and control of the electrical resistance characteristics is facilitated.

While the electro-conductive roller has been described to be used in a laser beam printer, it is a mere exemplary application. Hence, the electro-conductive roller is applicable to any other type of printer.

Printers according to an exemplary embodiment may include all printers using an electro-conductive roller such as an ink jet printer, a dot printer, etc.

With reference to FIG. 5, an electro-conductive roller manufacturing method according to an exemplary embodiment of the present invention will be described in detail.

Referring to FIG. 5, the crosslinking-completed elastic tube 200 having the insertion hole 201 formed therein is cut to appropriate dimensions.

The elastic tube 200 is fixedly mounted on the plurality of pressing plates 111 formed in the tube fixer 110 in step S1.

The tube presser 120 mounted over the tube fixer 110 is brought down and presses the elastic tube 200 in step S2.

Thus the plurality of pressing plates 121 formed in the tube presser 120 are also brought down and engaged with the plurality of pressing plates 111 formed in the tube fixer 110.

When they are engaged, the pressing plates 111 and 112 form a hexagonal, fixedly surrounding the elastic tube 200.

In step S3, the air compressor 130 at one end of the elastic tube 200 applies the air pressure A1 into the insertion hole 201 of the elastic tube 200, thus expanding the insertion hole 201.

The shaft 300 at the other end of the elastic tube 200 is transferred and inserted into the expanded insertion hole 201 by the shaft transferor 140 in step S4.

With the shaft 300 inserted in the insertion hole 201, the air pressure A1 is blocked from the air compressor 130. Thus the insertion hole 201 shrinks to be brought into close contact with the outer circumferential surface of the shaft 300 in step S5.

Because the insertion hole 201 is formed to be smaller than the outer diameter of the shaft 300, the blocking of the air pressure A1 leads to close contact between the insertion hole 201 and the outer circumferential surface of the shaft 300.

The air compressor 130 is provided at one end of the elastic tube 200 in order to expand the insertion hole 201 by applying the air pressure A1 having a force larger than the elastic force of the elastic tube 200, while the shaft transferor 140 and the shaft support 150 are provided at the other end of the elastic tube 200 in order to insert the shaft 300 into the insertion hole 201.

[Embodiment 1]

A method for manufacturing an electro-conductive roller according to an exemplary embodiment of the present invention will be described below.

The electro-conductive roller manufacturing method according to the exemplary embodiment of the present invention includes forming an elastic tube, fixing the exterior of the elastic tube having an insertion hole, expanding the elastic tube (i.e. the inner diameter of the insertion hole) by applying an air pressure into the insertion hole, inserting a shaft into the expanded insertion hole of the elastic tube, and bringing the insertion hole and the shaft into close contact by eliminating the air pressure from the insertion hole.

The elastic tube formation includes forming the elastic tube around a rod with a smaller outer diameter than an outer diameter of the shaft and forming the insertion hole through the elastic tube by removing the rod. The rod is formed of a metal, but when needed, it may be formed of an extruded plastic core.

The rod has an out-of-roundness of 0.1 or below and the shaft 300 has a surface roughness of 15 or below with respect to RM.

The elastic tube is formed by extrusion formation of a blended material for formation of the elastic tube and the rod in an extrusion cylinder heated to more or less 30 to 90 degrees. An appropriate distance should be maintained between a cone and a dice during the extrusion formation to prevent die swell.

The blended material for the elastic tube is a mixture of 40 weight percent of Epichlorohydrin (ECO) and 60 weight percent of Nitrile Butadiene Rubber (NBR), which is blended with non-conductive carbon to thereby achieve an intended resistance. Because ECO contains a low-molecular conducting material, it may contaminate the surface of the photosensitive drum.

While a rubber adhesive used to attach rubber onto a metal surface usually disturbs a current flow, the present invention allows for fabrication of a low-resistance conductive roller in spite of a small amount of ECO because there is no need for an adhesive. Furthermore, due to the use of a small weight percent of ECO, the contamination of the photosensitive drum may be suppressed.

The insertion hole is formed by eliminating the rod from the extruded elastic tube. The elastic tube may be completed by crosslinking at a temperature of 140 to 160 degrees under a pressure of 3.0 to 4.5Kgf. The elastic tube formed in the above operation is cut to appropriate dimensions and brought into close contact with the shaft. Thus the conductive roller is completely formed. The conductive roller with the shaft inserted therein is machined and heated at 150 to 160 degrees in the air, to thereby eliminate the residual shrinkage of the elastic material and reinforce the crosslinking. The elastic tube manufactured in the above manner has a shrinkage rate of 0.5% or below in an air pressure state.

Table 1 below compares a conventional electro-conductive roller with an electro- conductive roller according to the exemplary embodiment, after they are exposed in an N/N (23 degrees, 50%) environment. The conventional electro-conductive rollers and the electro-conductive rollers of the present invention tabulated in Table 1 and Table 2 use respectively an elastic layer and an elastic tube fabricated with a blended material in which 40 weight percent of ECO is mixed with 60 weight percent of NBR. While the present invention does not use an adhesive, the conventional elastic layer is attached onto a shaft with an adhesive.

Table 1

	Exposed to N/N(23℃, 50%) environment for 30 minutes				Exposed to N/N(23℃, 50%) environment for 12 hours
	Conventional (10E, adhesive)		Present Invention		Conventional (10E adhesive)		Present invention
	500V	250V	500V	250V	500V	250V	500V	250V
1	0.5㏁	0.8㏁	0.2㏁	0.2㏁	0.4㏁	0.7㏁	0.2㏁	0.2㏁
2	0.5㏁	0.8㏁	0.2㏁	0.2㏁	0.5㏁	0.7㏁	0.2㏁	0.2㏁
3	0.5㏁	0.8㏁	0.2㏁	0.2㏁	0.5㏁	0.7㏁	0.2㏁	0.2㏁
4	0.6㏁	0.9㏁	0.2㏁	0.2㏁	0.4㏁	0.8㏁	0.2㏁	0.2㏁
5	0.5㏁	0.8㏁	0.2㏁	0.2㏁	0.4㏁	0.7㏁	0.2㏁	0.2㏁
6	0.7㏁	0.8㏁	0.2㏁	0.2㏁	0.4㏁	0.7㏁	0.2㏁	0.2㏁
7	0.4㏁	0.7㏁	0.3㏁	0.3㏁	0.5㏁	0.7㏁	0.2㏁	0.2㏁
8	0.5㏁	0.8㏁	0.2㏁	0.2㏁	0.5㏁	0.6㏁	0.2㏁	0.2㏁

Referring to Table 1, resistance rapidly changes according to a temperature and an applied voltage in the conventional conductive rollers, whereas there is little change in the electro-conductive rollers of the present invention.

Table 2 below compares electro-conductive rollers of the present invention and conventional electro-conductive rollers, which are manufactured in the same condition as listed in Table 1, in terms of resistance change, after they are exposed to an L/L (10 degrees, 30%) environment.

Table 2

	Exposed to L/L environment (10℃,30%) for 30 minutes				Exposed to L/L environment (10℃,30%) for 12 hours
	conventional(10E, adhesive)		Present invention		Conventional (10E adhesive)		Present invention
	500V	250V	500V	250V	500V	250V	500V	250V
1	1.0㏁	3.0㏁	0.5㏁	0.5㏁	1.0㏁	4.0㏁	1.0㏁	1.0㏁
2	1.0㏁	3.0㏁	0.5㏁	0.6㏁	3.0㏁	4.0㏁	0.9㏁	0.9㏁
3	1.0㏁	3.0㏁	0.5㏁	0.6㏁	2.0㏁	4.0㏁	0.9㏁	1.5㏁
4	2.0㏁	1.0㏁	0.5㏁	0.6㏁	2.0㏁	4.0㏁	0.9㏁	1.5㏁
5	2.0㏁	2.0㏁	0.5㏁	0.6㏁	2.0㏁	4.0㏁	0.9㏁	0.9㏁
6	2.0㏁	3.0㏁	0.5㏁	0.5㏁	2.0㏁	4.0㏁	1.0㏁	1.0㏁
7	2.0㏁	3.0㏁	0.5㏁	0.7㏁	3.0㏁	5.0㏁	0.9㏁	1.5㏁
8	2.0㏁	3.0㏁	0.5㏁	0.6㏁	3.0㏁	4.0㏁	0.8㏁	1.0㏁
9	2.0㏁	3.0㏁	0.5㏁	0.6㏁	2.0㏁	4.0㏁	0.7㏁	1.0㏁
10	2.0㏁	4.0㏁	0.5㏁	0.6㏁	2.0㏁	5.0㏁	0.9㏁	1.5㏁

The conventional electro-conductive rollers using an adhesive generally tend to increase resistance under the L/L environment (10 degrees, 30%) and have an increased resistance change according to a change in an applied voltage. On the other hand, the electro-conductive rollers of the present invention can maintain stable resistance characteristics under situations having different voltages and even in the L/L environment.

As is apparent from the above description, since an electro-conductive roller is manufactured using an air pressure instead of a conventionally used adhesive, the electrical resistance characteristics of the electro-conductive roller are maintained uniform and readily controlled. Further, changes in environmental characteristics caused by a long term use are prevented, thus increasing the reliability of the electro-conductive roller.

While the invention has been shown and described with reference to certain exemplary embodiments of the present invention thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents.

Claims

An apparatus for manufacturing an electro-conductive roller, comprising:

a tube fixer for supporting an elastic tube;

an air compressor for expanding an insertion hole of the elastic tube by applying an air pressure to the insertion hole or contracting the insertion hole of the elastic tube by blocking the air pressure from the insertion hole;

a shaft transferor for transferring a shaft to be inserted into the expanded insertion hole; and

a shaft support for supporting the shaft so that the shaft is transferrable.
The apparatus of claim 1, wherein the insertion hole is smaller than an outer diameter of the shaft.
The apparatus of claim 1, wherein the shaft is inserted into the insertion hole by increasing an inner diameter of the insertion hole to be larger than the outer diameter of the shaft by applying the air pressure into the insertion hole, and the shaft is brought into close contact with the insertion hole by blocking the air pressure from the insertion hole.
The apparatus of claim 1, wherein the air compressor is positioned at a first opening of the insertion hole, and the shaft transferor and the shaft support are positioned at a second opening of the insertion hole at an opposite side to the first opening of the insertion hole.
The apparatus of claim 1, wherein each of the tube fixer and the tube presser has a plurality of pressing plates for surrounding the elastic tube and the pressing plates form a hexagonal tube when the pressing plates are engaged with one another.
The apparatus of claim 1, wherein the electro-conductive roller has a surface hardness between 40 and 70 degrees and a surface roughness between 4 and 20㎛.
A method for manufacturing an electro-conductive roller, comprising:

fixing an elastic tube;

expanding the elastic tube by applying an air pressure into an insertion hole of the elastic tube;

transferring a shaft to be inserted into the expanded insertion hole; and

bringing the insertion hole and an outer circumferential surface of the shaft into close contact by blocking the air pressure from the insertion hole, while the shaft is inserted in the insertion hole.
The method of claim 7, further comprising forming the elastic tube.
The method of claim 8, wherein the elastic tube formation comprises:

forming the elastic tube around an outer circumference of a rod having an outer diameter smaller than an outer diameter of the shaft; and

eliminating the rod from the elastic tube.
The method of claim 9, wherein the elastic tube formation further comprises cutting the elastic tube from which the rod is removed, and in which the insertion hole is formed, polishing the cut elastic tube, and machining the polished elastic tube.
The method of claim 10, wherein the elastic tube is formed of one of epichlorohydrin resin and nitrile butadiene rubber, or a mixture of epichlorohydrin resin and nitrile butadiene rubber, and the elastic tube has a surface electrical resistance between 10³Ω to 10⁷Ω and a shrinkage rate of 3% or below.
The method of claim 9, wherein the insertion hole is smaller than an outer diameter of the shaft.
An electro- conductive roller comprising:

a shaft; and

an elastic tube closely contacting an outer circumferential surface of the shaft.
The electro-conductive roller of claim 13, wherein the elastic tube includes a hollow insertion hole formed along a length direction of the elastic tube, the shaft is inserted into the insertion hole, when the insertion hole is expanded by an air pressure, and the insertion hole closely contacts the outer circumferential surface of the shaft by a restoration force of the elastic tube.
The electro-conductive roller of claim 13, wherein the electro-conductive roller has a total resistance between 10³Ω and 10⁷Ω.
The electro-conductive roller of claim 13, wherein the electro-conductive roller has a surface hardness of 40 to 70 degrees and a surface roughness of 4 to 20㎛.