JP3981654B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming method executed by the image forming apparatus.
[0002]
[Prior art]
Conventionally, as a method for recording images on both the front and back sides of a sheet, a method in which a sheet on which toner is placed on one side is reversed after passing through a fixing device and then transferred to another side of the sheet and then fixed. Has been used. This method has many problems in ensuring the reliability of conveyance because the conveyance direction of the sheet is changed and the paper once fixed has curl.
[0003]
For example, Patent Document 1 discloses a method for improving such a problem. In this method, a toner image is formed on both sides of a recording medium (paper) and then fixing is performed once. Specifically, the first image formed on the photoconductor is transferred to the transfer belt by the first transfer unit, and then the second image formed on the photoconductor is transferred to one side of the sheet by the first transfer unit. . Thereafter, the first image on the transfer belt is transferred to the other side of the sheet by the second transfer unit, whereby the image can be transferred to both sides of the sheet and fixed.
[Patent Document 1]
JP-A-1-209470
However, the proposed method forms an image on both sides of a sheet using a belt-shaped intermediate transfer member, and the number of times of transfer is increased by one, and the thickness of the sheet greatly affects the image. It has the disadvantage that image quality cannot be achieved. In addition, the use of a charger as the second transfer means has the disadvantage of generating ozone and soiling the wire.
[0005]
[Problems to be solved by the invention]
In view of the above-described drawbacks of the conventional methods, it is an object of the present invention to provide an image forming apparatus capable of obtaining a high-quality double-sided print without reducing transfer efficiency.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a first image carrier, a second image carrier comprising a first intermediate transfer belt, a third image carrier comprising a second intermediate transfer belt, and the first image. A first transfer means for transferring a visible image from the carrier to the second image carrier, and a second for transferring the visible image from the second image carrier to the third image carrier or a transported recording medium. Transfer means and third transfer means for transferring a visible image to a recording medium conveyed from the third image carrier, and transferring the visible image from the first image carrier to the second image carrier. A step of transferring a visible image from the second image carrier to the third image carrier, and a transfer means from either the second image carrier or the third image carrier by a transfer means. an image forming apparatus for performing the step of transferring the visible image on one side, and the second image carrier and the third image bearing member is mutually pressing The two nips formed continuously in the conveyance direction of the recording medium are the transfer nips of the second transfer unit and the third transfer unit, and images are obtained on both sides of the recording medium by one conveyance. The image to be transferred to one side of the recording medium is repulsively transferred from the second image carrier to the third image carrier in advance, and another image is transferred from the second image carrier to the other side of the recording medium at the first transfer nip. After the repulsive transfer , an image forming apparatus is proposed in which a single-sided image transferred at the next transfer nip is repulsively transferred from a third image carrier to a recording medium .
[0008]
The present invention is effective when the backup roller of the second transfer unit and the backup roller of the third transfer unit are arranged on opposite sides of the recording medium.
[0009]
Furthermore, the present invention is effective when a predetermined nip width is secured by abutting the nip securing member.
[0010]
Furthermore, the present invention is effective when the nip securing member is constituted by a roller.
Furthermore, the present invention is effective when the nip securing member is constituted by a bearing.
Furthermore, the present invention is effective when the nip securing member is insulative.
[0011]
Furthermore, the present invention is effective when the means for executing each transfer step is a roller.
Furthermore, the present invention is effective when the surface resistance (Ω / □) of the second image carrier is in the range of 10 ⁵ to 10 ¹² Ω.
[0012]
Furthermore, the present invention is effective when the thickness of the second image carrier is 50 to 1500 μm.
Furthermore, the present invention is effective when the surface resistance (Ω / □) of the third image carrier is in the range of 10 ⁵ to 10 ¹² Ω.
[0013]
Furthermore, the present invention is effective when the thickness of the third image carrier is 50 to 600 μm.
Furthermore, the present invention is effective when the surface roughness of the third image carrier is 1 μ (Rz) or less.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a configuration of an image forming apparatus according to the present invention capable of forming images on both sides of a recording medium (hereinafter referred to as paper) almost simultaneously. A neutralizing device L, a cleaning device 2, a charging device 3, and a developing device 5 are arranged on the outer periphery of the photosensitive member 1 as a first image carrier that is rotatably supported and rotates in the direction of the arrow. A space for storing optical information emitted from the exposure device 4 is secured between the charging device 3 and the developing device 5. There are four photoconductors 1 (a, b, c, d), but the configuration of the components for image formation provided around each is the same, and only the color of the color material (toner) handled by the developing device 5 is different.
[0015]
The photoreceptor 1 is a photoreceptor in which an organic semiconductor layer that is a photoconductive substance is provided on an aluminum cylindrical surface having a diameter of about 30 to 100 mm. Part of it is in contact with the intermediate transfer belt 10 as the second image carrier. The intermediate transfer belt 10 is supported and stretched between the rotating rollers 11 (11A and 11B), 12 and 13 so as to be movable in the direction of the arrow, and the first transfer means 20 is provided on the back side (inside the loop). Is arranged in the vicinity of the photosensitive member 1, and the second transfer unit 11 </ b> A is arranged so as to be in contact with the second intermediate transfer belt 100 as a third image carrier via the intermediate transfer belt 10.
[0016]
The first intermediate transfer belt (second image carrier) 10 is a belt having a thickness of 50 to 1500 μm using a resin as a base, and a belt having a resistance value capable of transferring toner from the photoreceptor 1, for example, surface resistance ( (Ω / □) is a belt in the range of 10 ⁵ to 10 ¹² Ω. Moreover, it is good also as a two-layer structure of a resin film and a rubber layer. For example, a polyimide layer and a urethane rubber layer.
[0017]
The first transfer unit 20 forms a transfer nip by pressing the first intermediate transfer belt 10 against the photoreceptor 1 by a pressing mechanism (not shown).
A first intermediate transfer belt cleaning device 25 is disposed outside the belt loop of the first intermediate transfer belt 10. After transferring from the first intermediate transfer belt 10 (secondary transfer), unnecessary toner remaining on the surface is wiped off.
[0018]
The exposure device 4 irradiates the uniformly charged surface of the photoconductor as a latent image with optical information corresponding to full color image formation by a known laser system. An exposure apparatus comprising an LED array and an image forming unit can also be employed.
[0019]
A second intermediate transfer belt (third image carrier) 100 disposed on the right side of FIG. 1 is supported and stretched between the rotating rollers 111, 112, and 113 so as to be movable in the direction of the arrow. A third transfer unit 11C is disposed (inside the loop). A second intermediate transfer belt cleaning device 250 is disposed outside the belt loop. The cleaning device 250 is configured to wipe off unnecessary toner remaining from the belt after the toner is transferred to the paper. The first intermediate transfer belt 10 and the second intermediate transfer belt 100 come into contact with each other by the third transfer unit 11C, the roller 11D, and the rollers 11A (also serving as the second transfer unit) and 11B that support the first intermediate transfer belt 10 and 11B. A defined transfer nip is formed.
[0020]
The transfer nip for the secondary transfer is formed by pressing the second intermediate transfer belt 100 against the first intermediate transfer belt 10 with a backup roller 11D facing the second transfer unit 11A by a pressing mechanism (not shown). ing. The width of the transfer nip is desirably 1 mm to 5 mm (FIG. 2), and securing of the nip width is ensured by abutting a nip securing member. The nip securing members are a roller A81 attached to the second transfer unit 11A and a roller B82 attached to the backup roller 11D. By abutting these, an appropriate nip is secured and the nip width is large. In the case of paper wrinkles, the transfer failure when the nip width is small is prevented. In this example, resin roller A81 and roller B82 are used as the nip securing member (FIG. 3). It is also possible to configure with a bearing.
[0021]
The second transfer means 11A and the backup roller 11D are conductive rollers. In this example, a conductive rubber roller is used for the second transfer means 11A, and a metallic one is used for the backup roller 11D. When metal rollers are used as the conductive rollers, the first intermediate transfer belt 10 has a two-layer structure with a rubber base as shown in FIG. 4 to secure a nip.
[0022]
The second intermediate transfer belt 100 is a resin film having a substrate thickness of 50 μm to 600 μm, and a belt having a resistance value capable of transferring toner from the first intermediate transfer belt 10, for example, a surface resistance (Ω / □). The belt is in the range of 10 ⁵ to 10 ¹² Ω. The surface roughness is 1 μ (Rz), for example, polyimide (FIG. 4). The third transfer unit 11C has the same configuration as the second transfer unit 11A.
[0023]
The sheets P are stored in sheet feeding devices (sheet feeding cassettes) 26-1 and 26-2 in the lower part of FIG. 1, and the uppermost sheet is registered by a sheet feeding roller 27 one by one through a plurality of guides 29. It is conveyed to the roller pair 28. In the upper part of the figure, a fixing heating means 30, a paper discharge guide pair 31, a paper discharge roller pair 32, and a paper discharge stack section 40 are arranged.
[0024]
A storage unit TS for storing supply toner is provided above the first intermediate transfer belt 10 and below the paper discharge stack unit 40. The toner has four colors, magenta, cyan, yellow, and black, and is in the form of a cartridge TC. The developing device for the corresponding color is appropriately supplied by a powder pump or the like.
[0025]
The frame 50 (right side of the figure) of the main body has a structure that can be rotated and opened around the opening / closing support shaft 50A, so that the recording medium conveyance path is wide open to handle jammed paper. Making it easy.
[0026]
Next, the operation when images are obtained on both sides of the paper will be described.
First, image formation is performed by the photosensitive member (first image carrier) 1. Due to the operation of the exposure device 4, light from an LD light source (not shown) passes through an optical component (not shown) and reaches a photoconductor 1 a that is uniformly charged by the charging device 3. Then, a latent image corresponding to the writing information (information corresponding to the color) is formed. The latent image on the photoreceptor 1 is developed by the developing device 5, and a visible image with toner is formed and held on the surface of the photoreceptor 1. This toner image is transferred to the surface of the first intermediate transfer belt 10 that moves in synchronization with the photoreceptor 1 by the first transfer means 20. The surface of the photoreceptor 1 is cleaned by the cleaning device 2 with the remaining toner, and is neutralized by the neutralization device L, and is prepared for the next image forming cycle.
[0027]
The first intermediate transfer belt 10 carries the toner image transferred on the surface and moves in the direction of the arrow (counterclockwise). A latent image corresponding to another color is written on the photoconductor 1 marked b, and developed with a toner of the corresponding color to become a visible image. This image is overlaid on the visible image of the previous color already on the first intermediate transfer belt 2, and finally four colors are overlaid. At this time, the second intermediate transfer belt 100 is moved in the direction of the arrow (clockwise) in synchronism, and the second transfer means 11A causes the first intermediate transfer belt 10 to move onto the surface of the second intermediate transfer belt 100. The image created on the surface is transferred.
[0028]
The second and third image carriers (first intermediate transfer belt and second intermediate transfer belt) move while forming images on four photoconductors (first image carriers) in a so-called tandem format. Because the image is advanced, the time can be shortened. When the first intermediate transfer belt 10 moves to a predetermined location, a toner image to be created on the other side of the paper is formed again by the photosensitive member 1 in the process as described above, and paper feeding is started.
[0029]
When the paper feeding roller 27 rotates counterclockwise, the uppermost paper P in the paper feeding device (paper feeding cassette) 26 is drawn out and conveyed to the registration roller pair 28. The toner image on the surface of the first intermediate transfer belt 10 is transferred to the second transfer unit 11A on one side of the sheet fed between the first intermediate transfer belt 10 and the second intermediate transfer belt 100 via the registration roller pair 28. Is transcribed by.
[0030]
Further, the sheet is conveyed upward, and the toner image on the surface of the second intermediate transfer belt 100 is transferred to the other surface of the sheet by the third transfer unit 11C. At the time of transfer, the sheet is conveyed at a timing so that the position of the image is normal.
[0031]
In this example, the polarity of the toner imaged on the photoreceptor 1 is negative. By applying a positive charge to the first transfer unit 20, the toner formed on the photosensitive member is transferred to the first intermediate transfer belt 10. By applying a negative charge to the second transfer unit 11A, the toner formed on the first intermediate transfer belt is pushed out of the first intermediate transfer belt and transferred to the second intermediate transfer belt 100. The toner on the surface of the first intermediate transfer belt is also transferred to one side of the sheet (see FIG. 5). By applying a negative polarity charge from the third transfer unit 11C, the negative polarity toner on the surface of the second intermediate transfer belt 100 is repelled and transferred to the other surface of the sheet (see FIG. 6). Since the transfer method using such repulsive force does not depend on the thickness of the paper, high image quality can be achieved regardless of the paper type.
[0032]
The sheet P on which the toner images are transferred on both sides in the above steps is sent to the fixing and heating means 30, and the toner images (both sides) on the sheet are melted and fixed at one time. As a result, the paper is discharged to the paper discharge stack 40 at the top of the main body frame.
[0033]
As shown in FIG. 1, when the paper discharge unit 40 is configured, the lower surface is a surface (page) of the double-sided image that is transferred to the paper later, that is, the surface that is directly transferred from the first intermediate transfer belt 10 to the paper. In order to align the pages, the second page image is created first, the toner image is held on the second intermediate transfer belt 100, and the first page is stored. These images are directly transferred from the first intermediate transfer belt 10 to a sheet.
[0034]
The image transferred from the first intermediate transfer belt 10 to the paper is a normal image on the surface of the photoconductor, and the toner image transferred from the second intermediate transfer belt 100 to the paper is a reverse image (mirror image) on the surface of the photoconductor. It is exposed as follows. Such an image forming order for page alignment is a known technique for storing image data in a memory, and exposure for switching between a normal image and a reverse image (mirror image) can also be realized by a known image processing technique.
[0035]
After transferring from the second intermediate transfer belt 100 to the paper, unnecessary toner and paper dust remaining on the surface of the second intermediate transfer belt are removed by a cleaning device 250 having a known brush roller, collection roller, blade, and the like inside. Remove.
[0036]
Next, the operation when an image is obtained on one side of a sheet will be described. In the case of single-sided, there are two methods, but the case where the step of transferring toner to the second intermediate transfer belt 100 is omitted and the toner is transferred from the first intermediate transfer belt 10 to a sheet will be described.
[0037]
The toner image formed on the surface of the photoreceptor 1 is transferred to the paper P while being transferred to the first intermediate transfer belt 10. In FIG. 1, paper P is sent between the first intermediate transfer belt 10 and the second intermediate transfer belt 100 in synchronization with the toner image formed on the first intermediate transfer belt 10. The toner is transferred from the first intermediate transfer belt 10 to the paper P by the second transfer unit 11A.
[0038]
The third transfer unit does not operate, and the sheet P moves together with the second intermediate transfer belt 100 and is sent to a region where the fixing heating unit 30 is located, and the toner is fixed. Thereafter, the sheet is separated from the second intermediate transfer belt 100, is discharged in the direction of arrow A through the guide pair 31 and the discharge roller pair 32, and the discharge stack unit 40 is in a state where the image surface is down (face down). Placed on. With such a configuration, even if a document of several pages is processed in order from one page, the printed matter is in page order when it is taken out from the paper discharge stack unit 40.
[0039]
In the above example, the image formation of a color image using a plurality of color toners has been described, but it is natural that the same technical idea can be applied to the creation of a monochrome image.
[0040]
【The invention's effect】
According to the present invention, when the visible image is transferred to one side in the step of transferring the visible image to one side, the step of transferring the visible image to the other side of the recording medium is performed by repulsive transfer. The image quality difference between one side and the other side can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus according to the present invention.
FIG. 2 is a conceptual diagram illustrating a nip between a first intermediate transfer belt and a second intermediate transfer belt.
FIG. 3 is a detailed view showing a configuration for securing the nip.
FIG. 4 is a partial view showing a cross-sectional configuration of a first intermediate transfer belt and a second intermediate transfer belt.
FIG. 5 is a model diagram of transfer from a first intermediate transfer belt to a sheet.
FIG. 6 is a model diagram of transfer from a second intermediate transfer belt to a sheet.
[Explanation of symbols]
A Output direction,
L static elimination lamp,
P recording medium (paper),
TS toner storage,
TC toner (cartridge),
1 first image carrier (photoreceptor),
2 Photoconductor cleaning device,
3 charging device,
4 exposure equipment,
5 Development device,
10 Second image carrier (intermediate transfer belt),
11A Second transfer means,
11C Third transfer means,
11B, 11D Backup roller,
12, 13 rollers (support shaft of the second image carrier),
20 first transfer means,
25 Cleaning device,
26-1, 26-2 paper feeder (paper cassette),
27 Paper feeding roller 28 Registration roller pair,
29 Transport guide,
30 heating device,
31 guide pairs,
32 Paper discharge roller pair,
40 discharge stack part,
50 Opening and closing frame,
50A open / close spindle,
81 Roller A,
82 Coro B,
100 Third image carrier (intermediate transfer belt),
111, 112, 113 rollers (support shafts of the third image carrier),
250 Cleaning device (for third image carrier)

Claims (13)

A first image carrier;
A second image carrier comprising a first intermediate transfer belt;
A third image carrier comprising a second intermediate transfer belt;
First transfer means for transferring a visible image from the first image carrier to the second image carrier;
Second transfer means for transferring a visible image from the second image carrier to the third image carrier or a transported recording medium;
Third transfer means for transferring a visible image to a recording medium conveyed from the third image carrier;
Have
Transferring a visible image from the first image carrier to the second image carrier;
Transferring a visible image from the second image carrier to a third image carrier;
Transferring a visible image from one of the second image carrier and the third image carrier to one side of a recording medium by transfer means;
In an image forming apparatus that performs
Two nips formed continuously in the conveyance direction of the recording medium by the mutual pressing of the second image carrier and the third image carrier are transfer nips of the second transfer unit and the third transfer unit,
When images are obtained on both sides of the recording medium by one transport,
An image to be transferred to one side of the recording medium is transferred in advance from the second image carrier to the third image carrier in advance,
After repulsive transfer of another image from the second image carrier to the other side of the recording medium at the first transfer nip,
An image forming apparatus, wherein a single-sided image previously transferred at a next transfer nip is repulsively transferred from a third image carrier to a recording medium .   The image forming apparatus according to claim 1, wherein the backup roller of the second transfer unit and the backup roller of the third transfer unit are arranged on opposite sides of the recording medium.   The image forming apparatus according to claim 1, wherein a predetermined transfer nip width is secured by abutment of a nip securing member.   The image forming apparatus according to claim 3, wherein the nip securing member includes a roller.   The image forming apparatus according to claim 3, wherein the nip securing member includes a bearing.   The image forming apparatus according to claim 3, wherein the nip securing member is insulative.   2. The image forming apparatus according to claim 1, wherein each of the transfer units is a roller. 2. The image forming apparatus according to claim 1, wherein a surface resistance (Ω / □) of the second image carrier is in a range of 10 ⁵ to 10 ¹² Ω.   The image forming apparatus according to claim 1, wherein the second image carrier has a thickness of 50 to 1500 μm. 2. The image forming apparatus according to claim 1, wherein the surface resistance (Ω / □) of the third image carrier is in the range of 10 ⁵ to 10 ¹² Ω.   The image forming apparatus according to claim 1, wherein the third image carrier has a thickness of 50 to 600 μm.   2. The image forming apparatus according to claim 1, wherein the surface roughness of the third image carrier is 1 [mu] (Rz) or less.   The image forming apparatus according to claim 7, wherein a material of the third image carrier is polyimide.

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