JPH11327328A - Roller for electrophotographic printer and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a toner shifter from a photoreceptor drum from sticking to the surface of a roller and to prevent a printing medium from being soiled by forming the surface of the surface layer part of the roller into a recessed and projecting shape and holding the toner shifted from the photoreceptor drum by the recessed part. SOLUTION: A tube 17 is constituted by superposing one on another tubes using different electronic conduction mechanisms such as ionic conduction and electronic conduction in a layer state, and its surface is engraved to be recessed and projecting part by using a file such as sand paper, etc., so that the projecting part 19 and the recessed part 18 are formed. Since the toner whose particle size is about 7 μm and which is shifted from the photoreceptor drum gets into the recessed part 18 whose width is about several μm to 100 μm and whose height is about several μm to 20 μm and which is formed on the semiconductive resin tube 17, the toner shifter from the photoreceptor drum does not stick to the projecting part 19 being the surface of the transfer roller. Therefore, the toner is prevented from adhering to the back surface of paper, so that the back surface of the paper is not soiled. Furthermore, the toner accumulated in the recessed part 18 is restored to a toner storing part again, thereby, the toner is not wasted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a roller used in an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printer, a toner is superimposed on an electrostatic latent image on a photosensitive drum to form a visible image, and a photosensitive drum and a transfer roller provided opposite to the photosensitive drum are used. The printing medium is conveyed in between, and a potential difference of several hundred volts to several thousand volts having a polarity opposite to that of the toner is applied to the transfer roller. Then, the toner moves from the photosensitive drum to the print medium in a uniform electric field formed between the photosensitive drum and the transfer roller, and the transfer is performed.

Here, the structure of a transfer unit for moving toner from a photosensitive drum to a medium will be described. The transfer roller is usually made of a metal shaft and a sponge-like rubber, such as urethane or silicone, attached around the metal shaft, and is elastic enough to make sufficient contact with the photoconductor drum. It is a body, and the surface of the rubber is uneven. Even when the toner remaining on the photosensitive drum surface moves to the transfer roller when the print medium is not interposed, the concave portion retains the toner, and when the print medium is interposed, the toner is pressed and printed. It prevents movement to the medium.

Further, it is necessary to secure a clearance when paper passes between the photosensitive drum and the fluctuation of the contact amount (pressing amount) between the transfer roller and the photosensitive drum due to the variation in the outer diameter of the transfer roller and the photosensitive drum. To prevent this, the transfer roller is pressed toward the photosensitive drum by a spring.

The transfer roller has a certain degree of conductivity so that a necessary transfer current flows through the sheet when a high voltage is applied. The transfer roller has a certain degree of conductivity between the metal shaft serving as an electrode when the transfer roller is applied and the surface of the transfer roller. The electrical resistance value at about 10 ⁶ Ω (1M
Ω) to 10 ⁹ Ω (1000 MΩ). Generally, this resistance value band is said to be a very difficult region to stabilize the resistance value. That is, in a region smaller or larger than this, the resistance value changes slowly with respect to the amount of conductivity contained in the rubber, whereas this region is very sensitive. Therefore, even if the roller is manufactured in the same manner, there are problems that the resistance value varies between rollers, and a portion having a high or low resistance value is formed in one roller. In addition, there has been a problem that the resistance value increases due to deterioration due to oxidation or the like of the roller surface due to repeated application of a high voltage during use.

In order to solve these problems, a transfer roller of a type in which a semiconductive resin film or a semiconductive resin tube is mounted on the surface of the roller in recent years has been devised. Since the film or tube does not fire or flow as seen in rubber, there is no variation in resistance due to manufacturing, there is little electrical change, chemical reaction with the photoreceptor drum does not easily occur, and sealing performance is strong. The rubber roller alone has characteristics that are difficult to realize, such as a fluorine-based resin that is resistant to oxidation can be used as a tube base material. This is heat-shrinked to the roller-shaped rubber, integrated with an adhesive, and used as a transfer roller.

Next, a description will be given of a method of manufacturing a transfer roller of a type equipped with this tube (hereinafter, the tube also includes a film) (excluding a metal shaft).

[0008] First, rubber is sponged into a sponge shape so as to form a roller shape, and then finished to a predetermined roller diameter by polishing or the like. Next, an adhesive is applied to the rubber surface so that the tube is adhered and adhered. Then, the rubber is covered with a tube slightly larger than the rubber, and heat treatment is performed to shrink the tube and at the same time expand the rubber to start bonding. The roller is completed after further cooling for a certain period of time.

[0009]

In the above-mentioned conventional transfer roller, since the above-mentioned tube has a large sealing property and a dense structure and is stiffer than rubber, these follow the uneven shape formed on the surface of the conventional rubber. It is difficult to form an uneven shape on the surface, and there is almost no unevenness on the surface as compared with a conventional solid transfer roller or a transfer roller coated with a coating agent.

Therefore, if the toner remaining on the photosensitive drum shifts and adheres to the surface of the transfer roller when the print medium is not interposed, the toner is pressed against the print back surface of the print medium during printing, and stains on the print back surface. This causes a problem of lowering print quality.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a roller-shaped rubber, which is provided opposite to a photosensitive drum for holding toner and is fixed around a shaft, has a semiconductive material. In a roller for an electrophotographic printer formed by fixing a surface layer of a toner, the surface of the surface layer is made uneven, and the concave portion holds the toner transferred from the photosensitive drum.

According to the present invention, since the toner transferred from the photosensitive drum is held in the concave portion, the toner does not adhere to the surface of the roller which is the convex portion.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Elements common to the drawings are assigned the same reference numerals.

[0014] First Embodiment FIG. 1 cross section illustration of the surface of the tube of the first embodiment, FIG. 2 is an explanatory view showing the structure of a printing process unit of the first embodiment, FIG. 3 is a cross-sectional view showing the transfer roller of the first embodiment, and FIG. 4 is an explanatory diagram of a cross-sectional shape of the surface of the tube before processing according to the first embodiment. Note that FIG.
In FIG. 4, the cutting direction is a direction parallel to the axial direction of the transfer roller 11.

First, the structure of the printing process unit 1 built in the electrophotographic printer will be described. FIG.
In this printing process unit 1, a photosensitive drum 2 for carrying a toner image is provided. Around the photosensitive drum 2, a charging roller 3 for applying electrostatic to the surface of the photosensitive drum 2, an LED head 4 for performing exposure to form an electrostatic latent image on the photosensitive drum 2, and a toner cartridge 5 through a toner container 6, and is conveyed by a stir bar and a sponge roller 7 (not shown).
The toner image formed on the surface of the photosensitive drum 2 by pressing the toner 8 charged to (−) onto the photosensitive drum 2 with a constant force and the developing roller 9 for attaching the toner 8 to the electrostatic latent image is fed to the feed roller 13. A bias voltage having a polarity opposite to the charging polarity of the toner 8 is applied to the transfer roller 11 for transferring to the paper 10 which is a printing medium conveyed by the printer, and the residual toner remaining on the surface of the photosensitive drum 2 after the transfer is removed. At the same time, a cleaning roller 12 for removing electricity from the surface of the photosensitive drum 2
Is provided. Further, a fixing device (not shown) for fixing the transferred toner 8 to the paper 10 is provided downstream of the print process unit 1 in the paper 10 transport direction.
The fixing device has a built-in heat roller.

In FIG. 3, the transfer roller 11 has a certain degree of conductivity so that a necessary transfer current flows through the paper 10 when a high voltage is applied, and serves as an electrode when a voltage is applied to the transfer roller 11. A metal shaft 15, a semi-conductive rubber 16 such as urethane or silicone, etc., which has been spun into and sprinkled around the metal shaft 15, and a semi-conductive resin which is a surface layer covering the surface of the rubber 16. And a tube (hereinafter, referred to as a tube 17). Note that the tube 17 is formed to have a thickness of several μm to several hundred μm by arbitrarily layering tubes using different electric conduction mechanisms such as ion conduction and electron conduction. The material of the tube 17 is nylon or fluororesin, and is formed of the same material as the tube of the conventional example.
The transfer roller 11 is an elastic body so that the transfer roller 11 can make sufficient contact with the photosensitive drum 2. Also, the clearance between the transfer roller 11 and the photosensitive drum 2 due to variations in the outer diameter of the transfer roller 11 and the photosensitive drum 2 is ensured when the paper 10 passes between the photosensitive drum 2 and the contact amount (push amount) between the transfer roller 11 and the photosensitive drum 2.
Transfer roller 11 is provided with a spring 1
4 is pressed toward the photosensitive drum 2.

FIG. 4 shows an unprocessed tube 17.
3 is a cross-sectional view of the surface of FIG. As can be determined from FIG. 4, the state is almost flat, and the uneven shape cannot be confirmed. Therefore, in the present embodiment, irregularities as shown in FIG. 1 are carved on the surface of the tube 17 using a file such as sandpaper to form convex portions 19 and concave portions 18. That is, the convex portion 19 and the concave portion 18 are formed by applying sandpaper to the surface of the tube 17 and rotating the shaft 15 while applying a uniform force to the sandpaper. This is a simple method for forming the recess 18 in a direction perpendicular to the axis 15. Note that the file side may be rotated instead of rotating the shaft 15.

The concave part 18 and the convex part 19 are several μm to about 100 μm.
It has a width of about m and a height of about several μm to about 20 μm. The concave portion 18 is a place where the concave portion
Are convex portions where the meat of the concave portion 18 is extruded and rises. The recess 18 has a particle size of about 7 μm.
The m toner 8 is held and accumulated. The width and height of the concave portion 18 are taken into consideration in consideration of the fact that the current printing resolution of the electrophotographic printer does not adversely affect the printing and the current toner particle size of about 7 μm. It is set under.

Next, an operation for preventing the toner 8 remaining on the photosensitive drum 2 in the above configuration from adhering to the surface of the transfer roller 11 when the paper 10 is not interposed will be described.

Here, in the electrophotographic printer, a cleaning process for removing the toner 8 attached to the transfer roller 11 after printing is introduced. In this case, a voltage opposite to the transfer voltage at the time of printing is applied between the photosensitive drum 2 and the transfer roller 11 shown in FIG. 2, and the transfer roller 11 is transferred via the photosensitive drum 2, the developing roller 9 and the sponge roller 7.
The toner 8 on the upper side is carried to the toner storage section 6 and reused. In the case of continuous printing, this process is performed once every several sheets of printing.

Assume that the toner 8 remaining on the photosensitive drum 2 moves to the surface of the transfer roller 11 when the paper 10 is not interposed. However, the toner 8 enters the concave portion 18 of the tube 17 and is held and accumulated there, and the photosensitive drum 2 comes into contact with the convex portion 19. Therefore, even if the sheet 10 is conveyed between the photosensitive drum 2 and the transfer roller 11, it is possible to prevent the toner 8 from moving from the surface of the transfer roller 11 to the back side of the sheet 10 and attaching thereto.

The toner 8 held and accumulated in the concave portion 18 moves from the concave portion 18 onto the photosensitive drum 2 by a cleaning process, and is again conveyed to the toner containing portion 6.

Although the surface layer is described using the tube 17, the same effect can be obtained even with a semiconductive resin film.

As described above, in the first embodiment, the width formed on the semiconductive resin film or the semiconductive resin tube 17 is about several μm to about 100 μm, and the height is about several μm to about 20 μm. Since the toner 8 having a particle diameter of about 7 μm transferred from the photosensitive drum 2 enters the concave portion 18 of FIG.
The toner 8 transferred from the photosensitive drum 2 is transferred to the transfer roller 11
The toner 8 does not adhere to the convex portion 19, which is the surface of the paper 10, and therefore, the toner 8 is prevented from adhering to the back surface of the paper 10, and as a result, the back surface of the paper 10 is not stained. Further, the toner 8 accumulated in the concave portion 18 returns to the toner storage section 6 again, so that the toner 8 is not wasted.

In the present embodiment, the transfer roller has been described as the roller. However, the surface of the roller in contact with the photosensitive drum 2, for example, the charging roller 3 may be made uneven.

Second Embodiment Next, a second embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. FIGS. 5 and 6 are partial perspective views showing a transfer roller according to the second embodiment.

In the second embodiment, the recess 18
The method of forming the projections 19 is different from that of the first embodiment.
And a convex portion 19 are formed.

Here, a method of forming the tube 21 will be described. The material of the tube 21 that is not yet in the shape of the tube 21 is extruded by penetrating the inside of a ring (not shown) having irregularities formed therein in a direction parallel to the shaft 15. As a result, the tube 21 shown in FIG. 5 having the uneven surface is formed. Thereafter, an adhesive is applied to the surface of the rubber 16 to adhere and adhere the tube 21. Then, a tube 21 slightly larger than the rubber 16 is put on the rubber 16 and heat treatment is performed to shrink the tube 21 and at the same time expand the rubber 16 to start bonding as shown in FIG.
After further cooling for a certain period of time, the transfer roller 22 is completed. Moreover, the width of the concave portion 20 becomes smaller than that before the heat contraction due to the heat contraction of the tube 21.

As described above, in the second embodiment, the first
In addition to the same effects as in the embodiment of FIG.
The molding of the concave portion 20 and the convex portion 30 into one is more simplified, and the cost is reduced by shortening the manufacturing process.

Third Embodiment Next, a third embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. FIG. 7 is a partial perspective view showing a transfer roller according to the third embodiment.

In the manufacturing process of the transfer roller 23 in the above embodiment, when an adhesive is used for bonding the tube 17 and the rubber 16, the tube 17 contracts and the rubber 16 expands during the heat treatment. When the tube 17 is bonded, the bonding is fixed. But,
Since the degree of contraction and the degree of expansion are not always constant, the sizes of the rubber 16 and the tube 17 at the time of bonding are not always constant. Therefore, it is conceivable that the roller diameter varies, and the roller diameter varies after cooling.

If the tube 17 and the rubber 16 are brought into close contact only by shrinkage without bonding, such variations can be eliminated. However, as described above, the transfer roller 11 applies a constant force to the photosensitive drum 2. Is pressed against
Further, mechanical stress such as the surface of the tube 17 being twisted due to rubbing between the photosensitive drum 2 and the tube 17 due to the rotation due to the small adhesion between the rubber 16 and the tube 17 is repeatedly applied. For this reason, it is conceivable that the phenomenon that the tube 17 is twisted and the wrinkles are distorted or shifted may occur.

Therefore, in the third embodiment, the rubber 24 and the tube 25 can be adhered to each other without using an adhesive.

The tube 25 is made of the same material as that of the first embodiment, but has a different shape, and a plurality of stripe-like projections 26 are formed on the inner surface thereof as shown in FIG. The streaks 26 are formed by grooves formed in advance in a molding cylinder (not shown) when the resin tube 25 is extruded, and the same streaks are formed along the longitudinal direction of the shaft 15. Exists. The size of the projection 26 is arbitrary, but the effect can be sufficiently exerted if irregularities of about several tens of μm are generated.

When the transfer roller 23 is manufactured, a tube 25 slightly larger than the rubber 24 is placed on the rubber 24 so as to shrink the tube 25 by heat treatment. Since it is a resin system, it is harder than the rubber 24, and the portion of the rubber 24 corresponding to the protrusion 26 is deformed by shrinkage, and the protrusion 2
6 sinks into rubber 24 like a wedge. Therefore, the tube 25 is fixed to the rubber 24 without using an adhesive.
The tube 25 can rotate integrally with the tube 4. Then, the protrusion 26 becomes a resistance against the sliding force, whereby the adhesive force is increased, and the mechanical resistance between the tube 25 and the rubber 24 in the rotation direction is increased. As a result, the rotation of the transfer roller 23 causes the tube 2 to rotate.
Even if the mechanical stress is repeatedly applied to the tube 5, the tube 25 is prevented from being twisted by the mechanical stress.

In the third embodiment, the step of bonding the tube 25 and the rubber 24 using an adhesive can be eliminated, and the possibility of affecting the diameter of the transfer roller 23 is eliminated.

Fourth Embodiment Next, a fourth embodiment will be described. The same parts as those in the third embodiment are denoted by the same reference numerals, and description thereof will be omitted. FIG. 8 is a partial perspective view showing a transfer roller according to the fourth embodiment.

As shown in FIG. 8, a projection 31 is formed on the inner surface of the tube 30 of the transfer roller 27 in the fourth embodiment as in the third embodiment.
The projection 31 is formed in a direction non-parallel to the axis 15, that is, in a state of extending in a spiral shape in the present embodiment.

The molding of the tube 30 has the disadvantage that the molding apparatus and the molding technique are advanced and difficult to extrude while rotating a molding cylinder (not shown) with respect to the third embodiment. When the transfer roller 27 is manufactured by the same manufacturing method as in the third embodiment, the degree of adhesion between the rubber 24 and the tube 30 increases, that is,
In addition to the mechanical stress in the rotation direction of the transfer roller 27, the mechanical stress in the longitudinal direction is increased.

In the fourth embodiment, since the tube 30 is resistant to mechanical stress in the longitudinal direction, even if the transfer roller 27 moves in the longitudinal direction during printing,
The tube 30 does not move while twisting and comes off the rubber 24. As a result, the tube 30 is prevented from being twisted further than the tube 25 of the third embodiment.

In the third and fourth embodiments, an example in which the present invention is applied to a transfer roller has been described. However, the present invention can be applied to other rollers such as a developing roller 9, a charging roller 3, and a heat roller (not shown). is there.

[0042]

As described above in detail, according to the present invention, the surface of the roller is made uneven, and the toner transferred from the photosensitive drum is held in the concave portion. Does not adhere to the surface of the roller, thus preventing toner from adhering to the print media, and as a result, the print media is not soiled.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a cross-sectional shape of a surface of a tube according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating a structure of a printing process unit according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating a transfer roller according to the first embodiment.

FIG. 4 is an explanatory diagram of a cross-sectional shape of a surface of a tube before processing according to the first embodiment.

FIG. 5 is a partial perspective view illustrating a transfer roller according to a second embodiment.

FIG. 6 is a partial perspective view illustrating a transfer roller according to a second embodiment.

FIG. 7 is a partial perspective view illustrating a transfer roller according to a third embodiment.

FIG. 8 is a partial perspective view illustrating a transfer roller according to a fourth embodiment.

[Explanation of symbols]

 2 Photoconductor drum 11 Transfer roller 15 Shaft 16 Rubber 17 Tube 18 Concave portion 19 Convex portion 21 Tube 22 Transfer roller 23 Transfer roller 24 Rubber 25 Tube 26 Projection 27 Transfer roller 30 Tube 31 Projection

Claims (6)

[Claims] 1. An electrophotographic printer, comprising a semiconductive surface layer fixed on a surface of a roller-shaped rubber fixed around a shaft and provided on a photosensitive drum holding toner. A roller for an electrophotographic printer, wherein the surface of the surface layer has an irregular shape, and the concave portion holds the toner transferred from the photosensitive drum. 2. A method of manufacturing a roller for an electrophotographic printer formed by fixing a semiconductive surface layer to a surface of a roller-shaped rubber fixed around a shaft, wherein a file is applied to the surface of the surface layer. A method of manufacturing a roller for an electrophotographic printer, wherein the surface of the surface layer is made uneven by rotating the file or the shaft. 3. A method of manufacturing a roller for an electrophotographic printer formed by fixing a semiconductive surface layer on a surface of a roller-shaped rubber fixed around a shaft, wherein a ring having irregularities formed therein is provided. A method of manufacturing a roller for an electrophotographic printer, wherein a surface layer portion is formed by penetrating the inside of the material of the surface layer portion, and the surface of the surface layer portion is made uneven. 4. A roller for an electrophotographic printer formed by fixing a semiconductive surface layer on a surface of a roller-shaped rubber fixed around a shaft, wherein the surface layer has a surface in contact with the rubber. And a protrusion extending in a direction parallel to the axial direction, wherein the protrusion is recessed into the rubber, and the surface layer is fixed to the rubber. 5. A roller for an electrophotographic printer formed by fixing a semiconductive surface layer on the surface of a roller-shaped rubber fixed around a shaft, wherein the surface layer has a surface in contact with the rubber. And a protrusion extending in a direction non-parallel to the axial direction, wherein the protrusion is recessed into the rubber and the surface layer is fixed to the rubber. 6. The roller for an electrophotographic printer according to claim 4, wherein the projection is formed integrally with the surface layer.