JP2001201971A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of obtaining an excellent double-sided color copy by eliminating failures such as the lowering of durability caused by the wear of a fixing roller and a pressure roller and the occurrence of image irregularity. SOLUTION: This image forming device is equipped with a fixing device 18 constituted by including a pair of upper-side fixing roller 29 and lower-side pressure roller 30, and forms an image on both surfaces of transfer material P by performing first fixing where an unfixed developer image is formed on one surface of the material P and is heated and melted by the upper-side fixing roller 29, and then second fixing where the unfixed developer image is formed on the other surface of the material P and is heated and melted by the upper- side fixing roller 29. The surface roughness Rzu of the upper-side fixing roller 29 of the device 18 and the surface roughness Rzd of the lower-side pressure roller 30 are set to Rzu<10 μm and Rzu<Rzd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as an electrophotographic apparatus for forming an image.

[0002]

2. Description of the Related Art As an example of a conventional image forming apparatus, there is a color electrophotographic apparatus for forming a color image as shown in FIG.

The color electrophotographic apparatus shown in FIG. 2 includes a transfer material transport system I provided from the right side of the apparatus main body 1 (right side in FIG. A transfer drum 15 constituting the transfer material transport system I is provided at the center.
A latent image forming section II provided in the vicinity of
And a rotary developing device III disposed in the vicinity of the rotary developing device III.

The transfer material transport system I is constructed as follows.

That is, an opening is formed in the right wall of the apparatus main body 1, and detachable transfer material supply trays 2 and 3 are provided in the opening so as to partially protrude outside the apparatus. . Paper feed rollers 4 and 5 are disposed substantially directly above the trays 2 and 3, respectively. These paper feed rollers 4 and 5 and a transfer drum rotating in the direction of arrow a disposed to the left. The paper feed roller 6 and the paper feed guides 7 and 8 are provided so as to connect the paper feed roller 15 and the paper feed roller 15.

In the vicinity of the outer peripheral surface of the transfer drum 15, a contact roller 9, a gripper 10, a transfer material separating charger 11, and a separating claw 12 are sequentially arranged from the upstream side to the downstream side in the rotation direction. . A transfer charger 13 and a transfer material separating charger 14 are provided on the inner peripheral side of the transfer drum 15. As shown in FIG. 3, a transfer sheet 92 made of polyvinylidene fluoride or the like is attached to a portion of the transfer drum 15 around which the transfer material is wound. Closely adhered.

Further, on the upper right side of the transfer drum 15, a conveying belt means 16 is provided in proximity to the separation claw 12, and at the end (right) end of the conveying belt means 16 in the transfer material conveying direction, a fixing device 18 is provided. It is arranged. Further, further downstream of the fixing device 18 in the transfer material transport direction, the apparatus main body 1
A discharge tray 17 is provided which is detachable from the tray.

Next, the configuration of the latent image forming section II will be described.

In FIG. 2, reference numeral 19 denotes a photosensitive drum which is an image carrier which rotates in the direction of arrow b, and is arranged with its outer peripheral surface in contact with the outer peripheral surface of the transfer drum 15. Above the photosensitive drum 19, a static eliminator 20, a cleaning unit 21, and a primary charger 23 are sequentially arranged from the upstream side to the downstream side in the rotation direction of the photosensitive drum 19. Above the photosensitive drum 19, an image exposure means 24 such as a laser beam scanner for forming an electrostatic latent image on the photosensitive drum 19 and an image exposure reflection means 25 such as a mirror are provided.

Finally, the structure of the rotary developing device III will be described.

That is, at a position facing the outer peripheral surface of the photosensitive drum 19, a rotating body 26 is rotatably disposed, and four kinds of developing devices 27Y, 27M, 2 are provided in the rotating body 26.
7C and 27BK are mounted at four positions in the circumferential direction so that the electrostatic latent images formed on the outer peripheral surface of the photosensitive drum 19 are developed and visualized by these developing devices 27Y, 27M, 27C and 27BK. Has become. 27Y is a yellow developing device, 27M is a magenta developing device, 27C
Denotes a cyan developing device and 27BK denotes a black developing device.

First, the sequence of the color electrophotographic apparatus configured as described above will be briefly described by taking a full color mode as an example.

That is, the photosensitive drum 19 is positioned in the direction indicated by the arrow b in FIG.
When rotated in the direction, the photosensitive member on the photosensitive drum 19 is uniformly charged by the primary charger 23. The operating speed of each part at this time (hereinafter referred to as process speed) is 16
It is set to 0 mm / sec.

When the photosensitive member of the photosensitive drum 19 is uniformly charged by the primary charger 23 as described above, image exposure is performed by the laser beam E modulated by the yellow image signal of the original 28, and the photosensitive drum 19 is exposed. An electrostatic latent image is formed thereon, and the electrostatic latent image is developed by the rotation of the rotating body 26 by the yellow developing device 27Y previously set at the developing position.

On the other hand, the transfer material conveyed through the paper feed guide 7, the paper feed roller 6, and the paper feed guide 8 is held at a predetermined timing by a gripper 10, and the contact roller 9 and the contact roller 9 is electrostatically wound around the transfer drum 15 by the electrode facing the transfer drum 9. At this time, the transfer drum 15 is rotating in the direction of arrow a in FIG. 2 in synchronization with the photosensitive drum 19, and the developed image developed by the yellow developing device 27 </ b> Y The image is transferred by the transfer charger 13 at a portion where the surface contacts. Then, the transfer drum 15 continues to rotate as it is, and prepares for transfer of the next color (magenta in FIG. 2).

On the other hand, the photosensitive drum 19 is neutralized by the neutralizing charger 20 and is cleaned by a cleaning means 21 using a conventionally known blade method. Then, the photosensitive drum 19 is charged again by the primary charger 23, and is charged by the next magenta image signal. Subject to image exposure as described above. Then, in the rotary developing device III, the rotating body 26 rotates while an electrostatic latent image based on the magenta image signal is formed on the photosensitive drum 19 by the image exposure, and the magenta developing device 27M is moved to a predetermined developing position. After being fixed, predetermined magenta development is performed.

Subsequently, the same process as described above is carried out for the cyan and black colors, respectively. When the transfer of the four colors is completed, the four-color visual image formed on the transfer material is transferred to each charger 20. , 14 and the gripper 1
0 is released, the transfer material is separated from the transfer drum 15 by the separation claw 12, sent to the fixing device 18 by the conveyor belt means 16, and fixed to the fixing device 1.
At 8, the visible image is fixed by heat and pressure, thus ending a series of full-color print sequences and forming a desired full-color print image. The fixing operation of the fixing device 18 is performed at the process speed of 160 mm.
This is performed at 90 mm / sec, which is slower than / sec. This is because a sufficient amount of heating must be given to the toner when the unfixed image on which two to four layers of toner are stacked is to be melted and mixed as described later, and the toner is fixed at a speed lower than the process speed. Is performed to increase the amount of heat applied to the toner.

As described above, since a color image has two to four layers of multicolor toners, a color image electrophotographic apparatus differs from a monochrome apparatus in the following two points. have.

That is, the first characteristic relates to the toner to be used. Since the toner is required to have good melting property and color mixing property when heat is applied, the softening point is low. A sharp melt toner having a low melt viscosity (referred to as a sharp melt toner) is used. By using such a sharp melt toner, the color reproduction range of a copy can be expanded, and a color copy faithful to a multi-color or full-color image of a document can be obtained.

A fixing device 18 which is a second feature of the color electrophotographic apparatus will be described below with reference to FIG.

In the fixing device 18 shown in FIG. 4, reference numeral 29 denotes a fixing roller as a fixing means, which is an HTV (high-temperature vulcanization type) silicone rubber 32 on an aluminum cored bar 31 and an additional type on the outside thereof. It has an LTV (low temperature vulcanization type) silicone rubber 33 and is formed to a thickness of 3 mm and a diameter of 40 mm. In addition, the addition type LTV silicone rubber 33
Is composed of a terminally blocked linear dimethylpolysiloxane having a viscosity of 10 ⁴ poise (40 parts by weight) and a resinous organopolysiloxane (60 parts by weight) as a terpolymer.

On the other hand, a pressing roller 30 serving as a pressing means has an HTV of 1 mm thickness on an aluminum cored bar 34,
Further, the same LTV as the surface material of the fixing roller 29 is provided on the surface thereof.
It is formed by forming a silicone rubber layer 35 and has a diameter of 40 mm.

The fixing roller 29 is provided with a halogen heater 36 which is a heat generating means.
At 0, a heater 37 is similarly disposed in the metal core 34, and heating is performed from both sides. The temperature of the pressure roller 30 is detected by the thermistor 38 in contact with the pressure roller 30, and the halogen heaters 36 and 37 are controlled by the control device 39 based on the detected temperature. The temperature of both rollers 30 is maintained at a constant value of about 170 ° C. The fixing roller 29 and the pressing roller 30 are pressed by a pressing mechanism (not shown) with a total pressure of about 40 kg.

In FIG. 4, O is an oil application device as a release agent application means, C is a cleaning device, and C1 is a cleaning blade for removing oil and dirt from the pressure roller 30.

The oil application device O includes an oil pan 52
dimethyl silicone oil 53 (available from Shin-Etsu Chemical Co., Ltd.
F96-300cs) through an oil pumping roller 54 and an oil application roller 55, and an oil application amount adjusting blade 4.
In step 5, the amount of oil to be applied is regulated and applied to the fixing roller 29. In the example shown in FIG. 4, an amount of 0.08 g / A4 is applied as a coating amount by a measuring method described later.

The amount of the silicone oil 53 applied by the oil application device O is obtained as follows.

That is, first, the weight of 50 sheets of A4 size white paper is set to A1 (g), and the image is not transferred onto this white paper.
Silicone oil 53 to the rubber layer 33 of the fixing roller 29
The weight of 50 blank sheets after passing between the fixing roller 29 and the pressure roller 30 without applying is also assumed to be B (g). Next, similarly, the weight of another 50 sheets of A4 size white paper is set to A2 (g), and the image is not transferred onto this white paper, but the silicone oil 53 is applied to the rubber layer 33 of the fixing roller 29. And the fixing roller 29 and the pressure roller 3
The weight of 50 blank sheets after passing between 0 and 0 is defined as C (g).

Using the above weights A1, B, A2 and C,
The coating amount X (g) of the silicone oil 41 per A4 size white sheet is obtained by the following equation.

X = (C + A1-B-A2) / 50 On the other hand, the cleaning device C presses the non-woven fabric web 57a made of Nomex (trade name) against the fixing roller 29 with the pressing roller 57, and the surface of the fixing roller 29 It is a device for cleaning. The web 57a is appropriately wound by a winding device (not shown) so that toner and the like do not accumulate on a portion where the web 57a contacts the fixing roller 29.

The above-described color electrophotographic apparatus forms a visible image only on one side of a transfer material. However, an apparatus capable of forming this visible image on both the front surface and the back surface of the transfer material is also available. It has already been proposed. Hereinafter, this device will be described with reference to FIG.

The apparatus shown in FIG. 5 is a color electrophotographic apparatus similar to that shown in FIG. 2, except that an image can be formed on both surfaces of a transfer material. The mechanism for forming a two-sided image will be described below. The same elements as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

The present apparatus is provided with a re-feed roller 40 and a conveyance path 41 constituting a conveyance mechanism for forming a two-sided image. The re-feed roller 40 re-transfers the transfer material once placed on the discharge tray 17 below the discharge roller 42 to a latent image forming section.
The transfer material is sent to the latent image forming unit II via the transport path 41.

Next, the operation of double-sided copying of a color image by the color electrophotographic apparatus will be described.

The transfer material developed on the rotary developing device III and carrying the unfixed toner image on the surface thereof is conveyed by the conveying belt means 16 and is fixed by the fixing roller 29 and the pressure roller 30 before being fixed to the paper discharge roller. The sheet is placed on the sheet discharge tray 17 by 42. After that, the discharge tray 17
The upper transfer material is fed again by the re-feed roller 40, passes through the transport path 41, is transported again to the latent image forming section II, and forms a color image on the rear surface in the same manner as the front surface. Thus, the transfer material having the color image already fixed on the front surface and carrying the unfixed color toner image transferred on the back surface is sent to the fixing device 18 by the conveyor belt means 16, where it is carried on the back surface. After the unfixed color toner image is fixed,
Finally, the paper is discharged to the paper discharge tray 17, where a series of double-sided color copying operations is completed.

Further, in the electrophotographic apparatus, a visible image is formed on the surface of the transfer material two or more times and is fixed (that is, the visible image is fixed).
Image forming operation is performed several times in a row)
This will be described with reference to FIG.

That is, in FIG. 5, DP is a transport switching plate for performing a multiplex image forming operation, and the transport switching plate DP is at the position of DP1 in the normal single-sided image formation or double-sided image formation. When forming multiple images, D shown in FIG.
It is in the position of P2. Then, at the time of multiplex image formation, the transfer material having the toner image fixed on one surface (front surface) is transported by the re-feed roller 40 to the latent image forming section II via the transport path 41, and thereafter, the operation is the same. , The same image forming operation is repeated.

[0037]

However, in the conventional image forming apparatus, performing the double-sided color copy as described above has caused the following problems.

That is, since the conventional fixing device assumes single-sided color copying, the pressure roller uses a high-strength rubber such as HTV silicone for its surface layer as described above.
Therefore, the surface roughness Rz of the pressure roller is Rz> 10 μm
Will be. When double-sided copying is performed using such a pressure roller, the final backside image (the surface that passes through the pressure roller at the time of the second fixing) is roughened, and the gloss and touch between the front and back surfaces of the transfer material are reduced. Further, there is a problem that the color is different.

As a fixing roller used in a color electrophotographic apparatus, a roller having a small surface roughness (for example, an average surface roughness R
z <10 μm), and the roller was formed of the above-mentioned material so as to reduce the surface roughness.

It is desirable that the surface material of the pressure roller used in the image forming apparatus for performing double-sided copying has a high releasability like the surface material of the fixing roller.

Therefore, in a color electrophotographic apparatus for performing color double-sided copying, the same material is used as the surface material of the fixing roller and the pressure roller, and both rollers have the same surface roughness so as to reduce the surface roughness. It was molded by the method of.

However, it has been found that when the fixing operation is performed using the fixing roller and the pressure roller having both small surface roughnesses as described above, the two rollers are severely worn and their life is shortened. This is because the surface roughness of both rollers is small, so that the adhesion of the pressure contact portions of both rollers is increased, and a slight difference in peripheral speed between them generates shearing force, which accelerates wear. It is believed that there is. The peripheral speed difference between the two rollers is caused by a peripheral speed error due to a transmission peripheral speed error due to gear driving or a difference in rubber elastic deformation.

When the two rollers are worn, the life of the rollers is shortened, and the pressing pressure of the two rollers becomes non-uniform, causing paper wrinkles. In a normal electrophotographic apparatus that does not assume color double-sided copying, since a pressure roller with high strength and large surface roughness is used,
While the life of the fixing roller can withstand 100,000 copies, the life of the fixing roller is 20,000 sheets in a conventional color electrophotographic apparatus having a fixing roller and a pressure roller of the same material and small surface roughness. I could just endure a copy of it.

When the surface roughness of both rollers is small, if there is nothing between them, the two rollers will surely rotate without slipping due to the adhesion between them, but paper etc. will enter between them. Then, there is also a problem that a slip easily occurs between the roller and the paper. This is because, although the surface roughness of the paper is very large, the conveying force is reduced due to the mirror surface of both rollers.

If the slip occurs between the two rollers, the amount of heat applied to the paper increases instantaneously, causing image irregularities such as uneven gloss and streaks.

The present invention has been made in view of the above problems, and an object thereof is to solve problems such as deterioration of durability due to abrasion of a fixing roller and a pressure roller and occurrence of image disorder and the like. An object of the present invention is to provide an image forming apparatus capable of obtaining a two-sided color copy.

[0047]

In order to achieve the above-mentioned object, the present invention provides a fixing device including a pair of upper and lower fixing rotating members, and an unfixed developer image on one surface of a transfer material. After the first fixing, in which the unfixed developer image is heated and melted by the upper fixing rotator, is performed, an unfixed developer image is formed on the other surface of the transfer material. In an image forming apparatus for forming an image on both surfaces of a transfer material by performing a second fixing by heating and fusing the applied developer image with the upper fixing rotator, the upper fixing rotator of the fixing device is used. The surface roughness Rzu and the surface roughness Rzd of the lower fixing rotating body are set so as to satisfy Rzu <10 μm Rzu <Rzd.

Therefore, according to the present invention, Rzu <10 μm, Rzu <10 μm, between the surface roughness Rzu of the upper fixing rotator and the surface roughness Rzd of the lower fixing rotator of the fixing device.
Since the relationship of <Rzd is satisfied, problems such as deterioration of durability and occurrence of image disturbance due to wear of both fixing rotators are eliminated, and a good double-sided color copy can be obtained.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
It will be described based on. FIG. 1 is a configuration diagram of a fixing device provided in the image forming apparatus according to the present invention. The basic configuration of the fixing device is the same as that of the conventional fixing device shown in FIG. Further, the basic configuration of the image forming apparatus according to the present invention is the same as that of the conventional image forming apparatus shown in FIG.

Embodiment 1 The present invention relates to a fixing roller 2
9 and the surface roughness Rzd of the pressure roller 30
And the following relationship: Rzu <10 μm (1) Rzu <Rzd (2)

In the present embodiment, the surface material and the roughness of the pressure roller 30 are different from those of the prior art. That is,
The same material as the surface material of the fixing roller 29 was used as the surface material of the pressure roller 30, and the pressure roller 30 was polished with a grindstone after molding.

As a result, the surface roughness R of the fixing roller 29
zu is Rzu = 5 μm, whereas the pressure roller 30
Has a surface roughness Rzd of 15 μm.

When a two-sided color copy was performed using the fixing device 18 including the fixing roller 29 and the pressure roller 30, slippage during transfer of the transfer material (paper) was prevented, and 100,000 copies were made. The rollers 29 and 30 are not scraped, and the deterioration of durability and the occurrence of image disturbance due to wear of the fixing roller 29 and the pressure roller 30 are eliminated.
A good two-sided color copy can be obtained.

Second Embodiment Next, a second embodiment of the present invention will be described.

In the present embodiment, the fixing roller 29 and the fixing roller 30 are formed by combining a resin segment having a tetrafunctional functional unit with a resin segment having a tetrafunctionality of 10 ⁵ poise and having a vinyl-terminated end block. Resin-like organopolysiloxane which is a block polymer having an oil segment having the same nature in the same molecule: 40 parts by weight Linear dimethylpolysiloxane having a viscosity of 100 poise and capped with a vinyl end: 20 parts by weight.

When the surface layer of the fixing roller 29 is formed, a mold method for manufacturing with a mold having an inner mirror surface is used, and when the pressure roller 30 is formed, spray coating is used.

In this embodiment, the fixing roller 2
9, the surface roughness Rzd of the pressure roller 30 is 18 μm, whereas the surface roughness Rzud of the pressure roller 30 is 4 μm.
The formula was established.

When a two-sided color copy was performed using the fixing device 18 including the fixing roller 29 and the pressure roller 30, a good two-sided color copy was obtained as in the first embodiment.

<Third Embodiment> Next, a third embodiment of the present invention will be described.

In this embodiment, the same material as that of the first embodiment is used as the surface layer material of the fixing roller 29, and the room temperature vulcanization type RTV (KE1406 manufactured by Shin-Etsu Chemical Co., Ltd.) is used as the material of the pressure roller 30. Then, the pressure roller 30 was polished after being cured by a mold.

In this embodiment, the fixing roller 2
9, the surface roughness Rzd of the pressure roller 30 is 12 μm, whereas the surface roughness Rzu = 9 μm.
The formula was established.

When a two-sided color copy was performed using the fixing device 18 including the fixing roller 29 and the pressure roller 30, a good two-sided color copy was obtained as in the first embodiment.

The surface roughness Rz of the roller used in the above description is based on the average surface roughness measuring method according to JIS-A.

In the above-described embodiment, three examples of the material of the pressure roller 30 have been described. However, in consideration of the releasability and surface roughness of the pressure roller 30 for performing double-sided color copying, additional pressure is required. The material of the pressure roller 30 has a linear dimethylpolysiloxane having a viscosity of 10 ⁵ poise or more and a terminal-blocked linear dimethylpolysiloxane and two or more vinyl groups, and the structural unit contains at least one of tetrafunctional and trifunctional. An addition type silicone rubber elastic body obtained by curing a mixture having a resin-like organopolysiloxane is preferred.

The material of the pressure roller 30 is more preferably the same as the surface material of the fixing roller 29.
This is because a material having a high releasability and a long life is selected as the surface layer material of the fixing roller 29.

[0066]

As is apparent from the above description, according to the present invention, the surface roughness Rz of the fixing rotary member on the upper side of the fixing device is obtained.
u and the surface roughness Rzd of the lower rotating body for fixing, R
Since the relations of zu <10 μm and Rzu <Rzd are satisfied, problems such as deterioration of durability and occurrence of image disorder due to abrasion of both fixing rotating bodies are eliminated, and an excellent double-sided color copy can be obtained. Is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fixing device of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view of a conventional image forming apparatus.

FIG. 3 is a perspective view of a transfer drum.

FIG. 4 is a configuration diagram of a fixing device of a conventional image forming apparatus.

FIG. 5 is a sectional view of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 18 Fixing apparatus 29 Fixing roller (rotating body for fixing) 30 Pressure roller (rotating body for fixing) P Transfer material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuo Kishino, Inventor 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hideo Kawamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo (72) Inventor Jiro Ishizuka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masahiro Ito 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (1)

[Claims] A fixing device including a pair of upper and lower fixing rotators, forming an unfixed developer image on one surface of a transfer material, and using the upper fixing rotator to perform the unfixed development. After the first fixing, in which the developer image is heated and melted, an unfixed developer image is formed on the other surface of the same transfer material, and the unfixed developer image is heated and melted by the upper fixing rotating body. In the image forming apparatus which forms an image on both sides of the transfer material by performing the second fixing, the surface roughness Rzu of the upper fixing rotating body and the surface roughness of the lower fixing rotating body of the fixing device are changed. An image forming apparatus, wherein Rzd is set to Rzu <10 μm Rzu <Rzd.