JPH03186880A - Transfer roller device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of the wrinkle of a paper which is being conveyed for transfer and to accomplish excellent transfer by providing a tensile force adding means which allows the paper incorporated in a transfer press- contact part to have tension in a feeding direction. CONSTITUTION:A paper conveying roller 9 is combined with the tensile force adding means which allows the paper 15 incorporated in the transfer press- contact part Y to have the tension in the feeding direction. Namely, a paper conveying speed a by the roller 9 is set to be a little lower than the surface moving speed b of a transfer intermediate body 5 and the conveyance of the paper 15 is braked by the use of such a speed difference to allow the paper 15 to have 'tension'. Thus, the occurrence of the wrinkle of the paper which is being conveyed for transfer is prevented and the excellent transfer is made possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a method that prevents wrinkles from forming on paper (not limited to paper, but in the form of a sheet) when an image is transferred to paper (sheet-like material, not limited to paper) by a transfer roller. This invention relates to a transfer roller device that has been improved to minimize the occurrence of transfer defects, and is applied to electrophotographic copying machines, printers, and the like.

[Conventional technology]

Conventionally, two typical methods are known as methods for transferring a toner image on an image forming body (photoreceptor or transfer intermediate) onto paper. One is a method in which transfer is performed under pressure using a bias roller to which a negative voltage is applied, and the other is a method in which the bonding force between the paper and toner is increased by negative corona discharge from a transfer charger. A method is known in which the toner is attracted to the paper by increasing the pressure.

Compared to transfer roller devices that use the latter method, transfer roller devices that use the former method are able to achieve faster transfer speeds, and are less affected by changes in paper resistance due to paper thickness, type, and environmental changes. It has the advantages of being able to transfer a large amount of toner at once because it is mechanically pressurized. especially,
It can be said that the air gap between the toner and the paper is narrowed by performing the transfer under pressure, which greatly contributes to improving the transfer performance.

[Problem to be solved by the invention]

However, in the above-mentioned conventional transfer roller device, since the transfer roller applies pressure to the paper as described above, if the paper is not accurately supplied to the transfer roller, there is a risk that the transfer will be hindered. There is. For example, if the paper is taken into the transfer roller with some waves at the leading edge of the paper, or if the timing at which the paper is taken in by the transfer roller is different between the edges of the paper and the center, as shown in Figure 3(a), Furthermore, wrinkles 31a are formed on the sheet 3 while it is being conveyed by the transfer roller 30 and the photoreceptor 32. In the area where the wrinkles 31a are formed, an air gap χ is formed between the area and the circumferential surface of the transfer roller 30, as shown in FIG. 3B, resulting in a transfer failure. It is known that wrinkles 31a are particularly likely to form on paper that has just been opened and placed in a low humidity environment (20 to 30%).

As a solution to the above-mentioned drawbacks, the transfer roller 30 is processed into an inverted crown shape, as shown in FIG. 4, to apply force to the paper in the direction of the arrow in the figure, thereby making wrinkles less likely to occur. A method is known, but in this method, an accuracy of several μm is required for the crown amount of the transfer roller 30,
If this accuracy is not satisfied, transfer defects are more likely to occur.

That is, if the amount of crown is too large, the pressing force on both sides of the transfer roller 30 will become small, resulting in poor transfer in those areas. Further, the transfer roller 30 has both ends 30a.
- Since the transfer roller 30 is supported by the transfer roller 30a and rotates while being pressurized with a force of several kilograms, it is necessary to manufacture the transfer roller 30 from a relatively expensive material in order to accurately maintain the above-mentioned crown amount over a long period of time. This causes the problem of high costs.

(Means for Solving the Problems) In order to solve the above problems, a transfer roller device according to the present invention transfers paper fed from a paper conveying means to a transfer pressure contact portion between a transfer roller and an image forming body. The transfer roller device transfers the image on the image forming body to the paper while applying pressure to the paper, the transfer roller device comprising a tension applying means for imparting tension in the feeding direction to the paper taken into the transfer pressure part. It is characterized by the presence of

[For production]

In the above configuration, the "tension" applied to the paper taken into the conveyance contact section is applied in the direction (from the center of the paper to both sides) to straighten the wrinkles of the paper, like the inverted crown type transfer roller mentioned earlier. Although it does not actively apply force (in the direction toward It becomes possible to prevent this.

Note that when the paper is conveyed so as to be wrapped around the roller surface of the transfer roller, the above-mentioned "tension" acts to make the paper follow the roller surface of the transfer roller before the transfer pressure area. In this conforming state, the paper is taken into the transfer pressure section after corrugations and the like that cause wrinkles are reliably removed. Therefore, in this case, wrinkles can be prevented more reliably by the "tension" and "conformity" that act on the paper.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 and 2. In this embodiment, a case where the transfer roller device is used in a color copying machine is exemplified.

In an electrostatic transfer type color copying machine, as shown in FIG. 2, below the document table glass 1 on which the document 11 is placed,
An optical system 2 for exposure is provided. Optical system 2 is
An exposure lamp 2a that irradiates light toward the original 11, a plurality of reflective mirrors 2b that guide the reflected light from the original 11 onto the photoreceptor 3 as shown by the dotted chain line in the figure, Imaging lens 2c and three primary colors (red, green, blue) placed on the road
The color separation filter 2d has a color filter.

The photoreceptor 3 is rotationally driven by two rollers 12a and 12b, and developing tanks 4a to 4c are arranged near the center of the upper surface of the photoreceptor 3 in a non-contact manner. A cleaning mechanism 13 for removing toner remaining on the photoreceptor 3 on the lower surface of the photoreceptor 3 is disposed around the photoreceptor 3 on the 10th line 12a side, in addition to charging means such as a charger 7. It is set up. - On the 20th line 12b side of the photoreceptor 3, there is a transfer intermediate (image forming body).
5 are arranged.

The transfer intermediate body 5 is rotationally driven by three rollers 14a to 14C. The photoreceptor 3 on the 20th roller 12b side is pressed against one side of the transfer intermediate 5.
An intermediate transfer roller 6 for transferring the monochromatic toner image formed on the photoreceptor 3'2 onto the transfer intermediate 5 is disposed on the back side of the transfer intermediate 5 at this pressure contact portion. The transfer intermediate body 5 is placed on the roller 14c side of the transfer intermediate body 5.
A transfer roller 8 is provided for transferring the color toner image formed thereon onto the paper I5. The transfer roller 8 is a driven roller that rotates with the movement of the transfer intermediate body 5, and one roller is rotated toward the transfer intermediate body 5 side at both end support portions.
The toner image is brought into pressure contact with the paper 15 by applying a pressing force of about 2 kg. Further, while the transfer roller 8 is made of metal, the roller 14c, which functions as a backup roller for the transfer roller 8, is made of an elastic material. This prevents the adhesion between the layers from decreasing.

A paper guide member 20 is provided at the right position of the transfer roller 8 in the figure. The paper discharge port of the paper guide member 20 is open close to the transfer pressure contact portion Y between the transfer roller 8 and the transfer intermediate 5, while the paper receiving port of the paper guide member 20 is opened close to the transfer pressure contact portion Y between the transfer roller 8 and the transfer intermediate 5. means) roller 9a in 9;
The opening is close to the conveyance abutment part Z of 9a. The paper conveyance roller 9 is for feeding the paper 15 taken out from the paper feed cassette 22 toward the transfer pressure contact portion Y, and is configured to move the conveyance contact portion Z a little further than the transfer pressure contact portion Y. It is located at the bottom.

Further, the paper conveyance roller 9 also serves as a tension applying means for imparting tension in the feeding direction to the paper 15 taken into the transfer pressure contact section Y.

That is, the paper conveyance speed a by the paper conveyance roller 9 is set to be somewhat lower than the surface movement speed a of the transfer intermediate body 5 (
The speed a is set as the speed b, and this speed difference applies a brake to the conveyance of the paper 15 to make the paper 15 taut.

A paper conveyance belt 16 is disposed at the left position of the transfer roller 8 in the figure, and a fixing belt 16 for fixing the color toner image on the paper 15 is provided at the terminal end of the paper conveyance belt 1G. Means 10 are provided.

To briefly explain the operation of color copying in the above configuration, light emitted from the exposure lamp 2a is reflected by the original 11, and this reflected light is transmitted to the imaging lens 2c and the color copying by the reflecting mirror 2b... The light passes through a separation filter 2d, and the color separation filter 2d extracts only light of a specific color component corresponding to each color filter, and irradiates it onto the photoreceptor 3. By this exposure operation, a latent image is formed on the photoreceptor 3, and development layers 4a to 4 having a complementary color to the specific color light are formed in areas not irradiated with light.
A monochrome toner image is formed by developing with one of the developers c, and this monochrome toner image is intermediately transferred to the transfer intermediate 5 by the intermediate transfer roller 6. By performing the above operations of exposure using a color filter → monochrome development → intermediate transfer for each color filter (red, green, blue), the transfer intermediate 5 can be processed three times (
Intermediate transfer of colors (yellow, magenta, cyan) is performed, and a color toner image is formed on the transfer intermediate 5 by overlapping monochromatic toner for each color component.

When the color toner image is formed on the transfer intermediate 5, the paper 15, which has been taken out from one of the paper feed cassettes 22 and 22 and has been waiting at a predetermined position, is brought into the transfer pressure contact by the paper conveyance roller 9. It is sent onto part Y at the right time,
A color toner image is transferred onto the paper 15 when passing through the transfer pressure contact portion Y. Paper 15 on which the color toner image has been transferred
is fed into the fixing means 10 by the paper conveying belt 16,
The color toner image is fixed.

Here, during the transfer conveyance by the transfer roller 8 described above, a brake is applied to the conveyance of the paper 15 due to the difference between the paper conveyance speed a and the zero surface movement speed of the transfer intermediate 5. A “tension” is formed on the paper 15 in the section between the transfer pressure contact portion Y and the conveyance contact portion Z. This “tension” is caused by Direction to straighten wrinkles (
Although it does not actively apply a force (direction from the center side of the paper toward both sides), it applies a force that opposes the force in the direction that wrinkles the paper 15 (direction from the paper side side to the center side). By increasing the amount of skin, wrinkles can be prevented as much as possible.

In addition, as in this embodiment, the conveyance contact portion Z is connected to the transfer pressure contact portion Y.
By keeping it lower than , as shown in Figure 1,
The paper 15 is conveyed so as to wrap around the transfer roller 8 in a predetermined section A on the circumferential surface of the transfer roller 8 . At this time, the above-mentioned "tension" is applied to the paper 1 on the roller surface of the transfer roller 8 before the transfer pressure contact portion Y.
The paper 15 is taken into the transfer pressure contact portion Y after being reliably removed from corrugations and the like that cause wrinkles in this conforming state. Therefore, in such a case, it is possible to more reliably prevent wrinkles by the "stretching" and "warping" that act on the paper 15.

Note that in this embodiment, a brake is applied to the conveyance by lowering the paper conveyance speed a of the paper conveyance roller 9, and the paper 15 is made to have some tension, but the paper conveyance speed a is reduced. As specific measures, measures such as (1) lowering the number of rotations of the roller 9a and (2) reducing the diameter of the roller 9a can be considered.

The paper conveyance speed a should be lower than the surface movement speed of the transfer intermediate body 5, but if it is too low, slippage will occur between the paper sheet 15 and the transfer intermediate body 5, causing blurring in the transferred image. It ends up. In order to prevent bleeding, it is desirable to set the speed a to 99% or more of the speed D. In addition,
Experiments using paper that had just been opened and had been left in a low-humidity environment for a long time (4 to 5 hours) showed that if the speed a was set to about 99.5% of the speed, wrinkles would almost certainly be eliminated. It was confirmed that it is possible to prevent the occurrence of However, in the stage actually applied to a copying machine, various factors such as the pressure balance by the transfer roller, the stiffness of the paper, the environment in which the paper is placed, the resistance value of the paper, the type of original, and Since the type of transfer unit has an effect, approximately -99.5% is not suitable. Also, in view of these circumstances,
The speed a may be made variable so that it can be adjusted.

In addition to the above-mentioned method of lowering the paper conveyance speed a, methods for making the paper 15 have "tension" include, for example,
5 is taken into the transfer pressure contact portion Y, the rollers 9a, 9
A method is to stop the drive of the roller a and switch it to the driven state, and to make the paper 15 sticky with the driven rollers 9a, or to transfer the transfer pressure contact part Y and the conveyance contact part. There is a method of applying a load to the paper 15 from the top to the bottom between the paper 15 and the paper Z to give the paper 15 tension.In addition, when applying the above-mentioned load, this load application means is used to apply tension. take measures.

3 [Effects of the Invention] As described above, the transfer roller device according to the present invention is configured to include a tension applying means for imparting tension in the feeding direction to the paper taken into the transfer pressure contact portion.

This has the effect of preventing wrinkles from forming on the paper during transfer and conveyance, thereby enabling good transfer.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention. FIG. 1 is an explanatory diagram showing the main parts of the transfer roller device and the relationship between the surface movement speed of the transfer intermediate and the paper conveyance speed. FIG. 2 is a diagram showing a simplified internal structure of the color copying machine. FIG. 3(a) is an explanatory view showing how the paper wrinkles during transfer and conveyance, and FIG. 3(b) is an enlarged sectional view of the portion indicated by arrow E. 4 FIG. 4 is a front view of a transfer roller having an inverted crown shape. 3 is a photoreceptor, 5 is a transfer intermediate (image forming means), 8 is a transfer roller, 9 is a paper transport roller (paper transport means: tension applying means), and 15 is paper.

Claims (1)

[Claims] 1. Paper fed from a paper conveying means is taken into a transfer pressure contact portion between a transfer roller and an image forming member, and the image on the image forming member is transferred to the paper while being pressed. A transfer roller device according to the present invention, further comprising a tension applying means for imparting tension in the feeding direction to the paper taken into the transfer pressure section.