JPH04172469A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To prevent failures in image formation on sheets when forming images on sheets again by providing a sheet feed passage with a pair of hard rollers which are made to rotatably abut on each other, a sheet straightening means made by an elastic body roller, and a sheet static eliminating means. CONSTITUTION:To perform e.g. double side copying, a sheet S1 on which first image information is completed is curled when passing through a fixing device and is then allowed to pass through a straightening means 11 and a sheet static eliminating means 12 and stored in a paper refeed unit 17 and so when passing through the straightening means 11 the sheet S1 is curled in a direction favorable for transfer and separation at second image formation. At the same time the sheet S1 is frictionally electrified by the sponge roller of an elastic body roller 11b. However, static electricity is eliminated when the sheet S1 is allowed to pass through a next sheet static eliminating means 12, and so even when a plurality of sheets S1 are loaded on the paper refeed unit 17 the sheets S1 would not attract one another with static electricity and second image formation is smoothly carried out at an image forming portion 5 without any problem in refeeding paper.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an image forming apparatus such as a multifunctional copying machine, a laser beam printer, a printing press, etc. capable of, for example, double-sided copying and the formation of multiple images.

(B) Prior art Conventionally, as this type of image forming apparatus, for example,
There is something like the one shown in the figure. That is, this device is capable of repeatedly forming images on both sides or the same side of a sheet material, and the first conveyance is performed to feed the sheet material 101A to the image forming section 100 for the first image formation. path 102, and a second transport path 103 for refeeding the sheet material 101B to the image forming section 100 for second and subsequent image formation.

In the image forming section 100, a toner image is electrostatically formed on the surface of the image carrier 104, and the toner image is electrostatically formed on the surface of the image carrier 104.
4. The transfer charger 105 charges the back surface of the sheet material 101 that is in contact with the surface with an electric charge having a polarity opposite to that of the toner, and transfers the toner image to the sheet material 101, thereby forming an image on the sheet material 101. It is formed.

After the image has been transferred, the sheet material 101 is charged by the separation charger 106 to neutralize the charges on the back surface of the sheet material 101.
The image carrier 104 is separated from the image carrier 104 by its own elastic force. The transferred sheet material 101B is then sent to a fixing device 108 by a conveyor belt 107, where the image is fixed.

After that, when image formation is to be completed, the transferred sheet material 101B is sent out in the direction A in the figure and placed on the paper output tray 109.
discharged inside. In addition, this transferred sheet material 101B
When performing so-called multiple copying, in which an image is formed again on the surface on which the image was previously formed, or in so-called double-sided copying, in which an image is formed on the back surface, the transferred sheet material 101B is sent out in the direction B in the figure. , is guided to the second conveyance path 103, joins the first conveyance path 102 again, and is sent to the image forming section 100, where image formation is performed.

Here, since the fixing device 108 generally uses a pair of rollers, the transferred sheet material 101B after fixing is curled and deformed. If the material 101B is sent as is to the image forming section 100, image formation may be defective. In particular, if the sheet material 101B is curled in the same direction as the curvature of the image carrier 104, it will wrap around the image carrier 104 and become difficult to separate. Therefore, more static electricity is removed from the image carrier 104 than necessary, and as a result, the toner once transferred to the sheet material 101B is transferred to the image carrier 104 again.
4, a so-called white spot occurs in which the image is missing. On the other hand, if the sheet material 101B is too warped with respect to the image carrier 104, so-called transfer dropout, etc., in which there are parts of the sheet material 101B where the image is not transferred, is likely to occur.
A problem arises in that the quality of the formed image deteriorates.

Therefore, conventionally, in order to correct the curled state of the sheet material 101B, the sheet material 101B is
A curling means 110 as a sheet material straightening means is provided on the second conveying path 103 for conveying the sheet material 10B.
The curl condition of 1B was corrected to an appropriate condition.

This curling device is used, for example, in Japanese Patent Application Laid-Open No. 50-43
A roller pair consisting of a heat roller and a rubber roller with a larger diameter than the heat roller as proposed in Japanese Utility Model Publication No. 936, and a hollow elastic body as proposed in Japanese Utility Model Application No. 57-98453. In addition to a pair of rollers that can change the curl state of the sheet material 101B by changing the internal pressure of each roller, there are also pairs of rollers that include a hard roller and an elastic roller that rotatably abut each other. be.

(C) Problems to be Solved by the Invention However, in the case of the above-mentioned prior art device, one of the pair of rollers composing the device is made of an insulating elastic material, and the roller pair is made of an insulating elastic material. is a total pressure of 1 to 3 k
When the sheet material 101B passes through the pair of rollers, the sheet material 101B is subjected to a pressure of Uploads occur frequently.

In particular, with curling, if the device is installed upstream of the paper refeeding unit used for duplex/multiple copying and double-sided/multiple copying is performed, the charged up paper may be transferred to the paper refeeding unit in low humidity conditions. Because they are housed in the same space, they attract each other electrostatically. If the adsorption force between the sheet materials is greater than the conveying force to the sheet materials, paper feeding becomes impossible, resulting in paper feeding failure. Further, even if the paper can be fed, there is a problem that the paper may be skewed.

A possible solution to this problem is to use a metal roller as the hard roller and ground it, but this is still insufficient as a countermeasure because the charge-up caused by the elastic roller still remains.

Further, for curling, a method can be considered in which the device is provided on the downstream side of the paper refeeding unit or in a common portion of the first conveyance path 102 and the second conveyance path 103. However, although this method can prevent paper feeding errors, if the sheet material 101B enters the transfer/separation process in a charged state, the toner image on the image carrier 104 may not be transferred before the transfer process is performed. Since an electrostatic force acts, problems such as image scattering and other deterioration of image quality occur.

Therefore, the present invention has been made in view of the above-mentioned circumstances, and when a sheet material, which has undergone image formation once, is conveyed through a sheet material conveyance path for performing image formation again, An object of the present invention is to provide an image forming apparatus that can correct curls and eliminate static from a sheet material.

(d) Means for Solving the Problems In order to achieve the above object, the present invention, for example, as shown with reference to FIG.
The present invention relates to an image forming apparatus having a sheet material conveyance path (9) for performing image formation again.

Further, the present invention provides a curl correction means (11) for the sheet material (Sl), which comprises a pair of hard rollers (X1a) and an elastic roller (llb>) rotatably abutting each other on the sheet material conveyance path (9). ), and sheet material static elimination means (12) disposed at the curl correction means (11) or downstream thereof.
It is characterized by having the following.

Further, the sheet material static elimination means (12) includes a sheet material (S
It is characterized in that it also serves as the conveyance guide function of l).

(Phantom effect) According to the above configuration, the sheet material (S
l) or sheet material conveyance path (9) for performing image formation again.
), the curl formed on the sheet material (Sl) is corrected by the curl correction means (11), and then the sheet material (Sl) is neutralized by the sheet material neutralization means (12).

It should be noted that the above reference numerals in parentheses are used to refer to the drawings, and do not limit the structure of the present invention.

(f) Example Embodiments of the present invention will be described below based on the drawings.

<First Embodiment> FIG. 1 shows a schematic configuration of an image forming apparatus according to a first embodiment of the present invention.

This image forming apparatus includes an image forming section 5 including an image carrier 1, a transfer charger 2, a separation charger 3, and a paper feed cassette 6.
A first conveyance path 7 for feeding the sheet material S1 to perform the second image formation, and a second and subsequent image formation on the sheet material S1 after image formation from the downstream side in the conveyance direction with respect to the image forming section 5. A second conveyance path 9 is provided for refeeding the sheet material S1 toward the image forming section 5 in order to perform the following operations.

The first conveyance path 7 and the second conveyance path 9 merge on the upstream side of the image formation 5 and have a common conveyance path (10). Then, all the sheet materials S1 on which image formation is to be performed for the second and subsequent times are fed to the image forming section 5.

The second conveyance path 9 is provided with a curl correction means 11 and a sheet material neutralization means 12 for correcting the curled state of the sheet material S1.

In the image forming section 5, a toner image is electrostatically formed on the surface of the image carrier 1, and the toner image is transferred to the charger 2.
The image is transferred onto the sheet material S1 by the following steps. Then, the sheet material S1 is transferred to the image carrier 1 by the separation charger 3.
separated from Thereafter, although not shown, the sheet material S1 is sent to a fixing device by a conveyor belt as in the conventional example, where the toner image is heated and fixed. As a method for forming an image on the image carrier 1, various methods such as a known electrostatic method and a magnet stylus method can be employed.

FIG. 2 shows the curl correction means 11 and the sheet material static elimination means 1.
2, and the arrow indicates the direction in which the sheet material S1 is conveyed through the second conveyance path 9.

The curl correction means 11 is composed of a pair of hard rollers ILa and an elastic roller 11b that are in rotatable contact with each other. The hard roller lla is a metal roller and is connected to a ground 13. Further, the elastic roller Ilb is a sponge roller having a core metal 15, and the amount of penetration of the hard roller 11a into the elastic roller Ilb is set to about 1 square inch.

Further, the sheet material static eliminating means 12 is a static eliminating brush made of a conductive member, and is provided with a ground 16.

In the image forming apparatus having the above configuration, for example, when performing double-sided copying, the sheet material S1 after the first image formation is curled when passing through a fixing device (not shown); 11. Sheet material static elimination means 1
2 and is stored in the refeeding unit 17, so that the paper is stored in the refeeding unit 17, so that when it passes through the curl correction means]
Curling is done in a direction favorable for separation. At this time,
At the same time, the sheet material S1 is frictionally charged by the sponge roller of the elastic roller llb. However, since the static electricity is removed when the sheet material passes through the subsequent sheet material static eliminator 12, even when a plurality of sheet materials S1 are loaded on the paper refeeding unit 17, each sheet material S1 is attracted to each other by static electricity. There is no interference between the sheets, and the paper is re-feeded without any problem, and the second image formation is smoothly performed in the image forming section 5.

Second Embodiment FIG. 3 shows a curl correction means and a sheet material neutralization means according to a second embodiment of the present invention.

Here, the curl correction means 19 includes a metal roller 19a that is a hard roller and a conductive rubber roller 19b that is an elastic roller. The sheet material static eliminating means 20 includes a ground 20a attached to a metal roller 19a and a ground 20b attached to a rubber roller 19b.

Therefore, there is no charge-up when the sheet material S passes through the curl correction means 19, and the following steps are also performed without problems.

Third Embodiment FIG. 4 shows a curl correction means and a sheet material neutralization means according to a third embodiment of the present invention.

Here, the curl correction means 11 has the same structure as the first embodiment. In addition, sheet material static elimination means 21
In the case of this embodiment, which consists of a pair of grounded conductive rubber rollers or metal rollers 21a and 21a, it is possible to correct curls and remove static electricity from the sheet material S1 in the same manner as in the first embodiment.

Fourth Embodiment FIG. 5 shows a curl correction means and a sheet material neutralization means according to a fourth embodiment of the present invention.

In the same figure, reference numeral 11 indicates a curl correction means configured similarly to the first embodiment, and reference numeral 22 indicates a sheet material S1.
This is a plate-shaped sheet material static elimination means that also functions as a guide to stabilize the conveyance of the sheet material. Reference numeral 17 indicates a paper refeeding section, and reference numeral 23 indicates a member for preventing backflow of the sheet material S1 when stacking the sheet material S1 in the paper refeeding section 17, for example. This backflow prevention member 23 is made of a conductive film. Therefore, the sheet material S1 charged up when passing through the curl correction means 11
Since the static electricity is removed when the sheet material passes through the grounded guide such as the sheet material static eliminating means 22 and the backflow prevention member 23, there will be no paper feeding failure during paper refeeding or scattering during the transfer/separation process.

Note that the above-mentioned stacking means stacking the sheet materials S1 in a stepwise manner in the paper refeeding section 17 for the purpose of reducing the cost of the paper feeding mechanism in the paper refeeding section 17. By doing this, the leading ends of the sheet materials S1 are respectively shifted backward and stacked on the paper refeeding section 17, so that paper feeding at the time of paper refeeding becomes easy.

However, in order to shift the tip of the sheet material S1 by a certain value,
When a plurality of sheet materials S1 are stored, the length of the sheet material S1 required for the paper refeeding section 17 in the feeding direction becomes long. Therefore, in order to ensure the length, the sheet material S1 is switched back using the roller pair 25. At this time, the backflow prevention member 2
3 is required.

(G) As described in detail of the invention, the image forming apparatus of the present invention includes a sheet material curl correction means, which is provided in a sheet material conveyance path and includes a pair of hard rollers and an elastic roller that rotatably abut each other. ,
Since the curl correction means section or the sheet material neutralization means disposed downstream thereof is provided, when the sheet material that has once completed image formation is conveyed through the sheet material conveyance path for performing image formation again, The curl formed on the sheet material is corrected by the curl correction means, and the sheet material is neutralized by the sheet material neutralization means.

Therefore, when images are formed on the sheet material again,
No defective image formation occurs on the sheet material, and the sheet material can be transported smoothly.

[Brief explanation of the drawing]

FIG. 1 shows an image forming bag according to a first embodiment of the present invention.
2 is a side view showing the curl correction means and sheet material static elimination means in the same image forming apparatus, and FIG. 3 is a schematic diagram showing the curl correction means and sheet material static elimination means according to the second embodiment. FIG. 4 is a side view showing the curl correction main stage and sheet material static elimination means according to the third embodiment, and FIG. 5 is a side view showing the curl correction means and sheet material static elimination means according to the fourth embodiment. 6 are schematic side views of conventional image formation defects. 9... Second conveyance path (sheet material conveyance path), 11.1
9... Curl correction means, 11a, 19a... Hard roller,! , 1b, 19b... elastic roller, 12.20,
21.22... Sheet material static elimination means, Sl... Sheet material.

Claims (1)

[Scope of Claims] 1. In an image forming apparatus having a sheet material conveyance path for forming an image again on a sheet material that has undergone image formation once, the image forming apparatus comprises two members rotatably abutting each other on the sheet material conveyance path. An image forming apparatus comprising: a sheet material curl correction means comprising a pair of hard rollers and an elastic roller; and a sheet material static elimination means disposed at the curl correction means section or downstream thereof. 2. The image forming apparatus according to claim 1, wherein the sheet material static elimination means also serves as a conveyance guide function for the sheet material.