JP2012003061A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus having a paper support belt with good paper separability without affecting transfer processing even when a thin paper is used.SOLUTION: A color printer 1 of this invention is an image formation apparatus having an image formation part for forming a toner image on an intermediate transfer belt 11, a secondary transfer part 31 for conveying a sheet of paper and transferring the toner image from the intermediate transfer belt 11 onto the paper, and a fixation part 41 for applying pressure and heat to the paper on which the secondary transfer part 31 transferred the toner image. The secondary transfer part 31 is an endless belt having a paper support belt 32 for supporting and conveying the paper. A surface roughness on a surface supporting the paper of the paper support belt 32 is greater than a center part in at least one end in a width direction with respect to a conveyance direction of the paper.

Description

  The present invention relates to an electrophotographic image forming apparatus. More specifically, the present invention relates to an image forming apparatus that uses a transfer member that transfers a toner image to a recording member while the recording member is carried and conveyed by an endless belt-like paper carrying belt.

  Conventionally, as an image forming apparatus such as a printer or a copier, there is an electrophotographic system that forms an image using toner. In such an apparatus, usually, a toner image is first formed on an image carrier and then transferred from the image carrier to a recording member such as paper. Examples of the image carrier include a photoreceptor and an intermediate transfer material. As a transfer member for transferring a toner image from an image carrier to a sheet, there is an apparatus using an endless belt-like sheet carrier belt. That is, the sheet is attracted to the sheet carrying belt and conveyed, and the toner image is transferred to the sheet at a position where the sheet faces the image bearing member.

  The sheet on which the toner image is transferred by the transfer member is sent out to the fixing member for toner fixing processing. Therefore, in an image forming apparatus using a paper carrying belt, it is necessary to quickly separate the paper after the transfer process from the paper carrying belt. However, conventionally, when thin paper is used in a low temperature and low humidity environment, it has been difficult to separate the paper.

  On the other hand, Patent Document 1 discloses an image forming apparatus in which a difference in electrical resistance value is provided between an end region and a central region with respect to the width direction of the sheet carrying belt. According to this document, by setting the resistance value at the end portion in the width direction to 1/10 to 1/2 of the central portion, paper or the like is not wound, and the apparatus can be easily separated. Further, this document further discloses that a heat treatment is performed as a method of manufacturing such a paper carrying belt.

JP 2007-155987 A

  However, in the conventional image forming apparatus described above, the resistance value of the paper carrying belt varies depending on the location of the belt, which may affect the transfer process. For example, if a difference in resistance value appears as uneven transfer bias value, there is a problem that it may cause image quality failure.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus having a sheet-carrying belt with good sheet separation even when thin sheets are used without affecting the transfer process.

  An image forming apparatus according to the present invention, which has been made for the purpose of solving this problem, includes a toner image forming unit for forming a toner image on an image carrier, and a toner image formed by the toner image forming unit while conveying a recording member. Image forming apparatus comprising: a transfer unit that transfers toner to a recording member; and a fixing unit that fixes the toner by pressurizing and heating the recording member that has received the transfer of the toner image by the transfer unit to form an image on the recording member The transfer unit has an endless belt shape and has a paper carrying belt that carries and conveys a recording member. The surface roughness of the surface of the paper carrying belt that carries the recording member is At least one end in the width direction with respect to the conveying direction of the member is larger than the central portion.

  According to the image forming apparatus of the present invention, the surface roughness of the sheet carrying belt that carries the sheet in the transfer unit differs depending on the position in the width direction with respect to the conveying direction. In particular, the surface roughness is large at one end in the width direction. In a place where the surface roughness of the paper carrying belt is large, it is easy to separate the carrying paper. That is, according to the present invention, the paper is easily peeled from the paper carrying belt at the end portion. The arrangement of the surface roughness does not particularly affect the image transfer process. Therefore, the image forming apparatus has a paper carrying belt that has good paper separation even when thin paper is used without affecting the transfer process.

Further, according to the present invention, the surface roughness of the surface of the paper carrying belt that bears the recording member is the smallest at the central portion, is larger than the central portion at the other end portion in the width direction, and extends from the central portion toward the end portions on both sides. It is desirable that they become larger in order.
In this case, the recording member is most easily peeled off at both end portions.

Alternatively, in the present invention, the surface roughness of the surface carrying the recording member of the paper carrying belt is smaller than the central portion at the other end in the width direction, and gradually decreases from one end toward the other end. It may be.
In this case, the surface roughness of the sheet carrying belt is the largest at one end. Accordingly, the sheets are separated in order from the corner disposed on the side closer to one end of the sheet carrying belt in the leading end.

Furthermore, in the present invention, the ten point average roughness Rz of the largest portion of the surface roughness is in the range of 10 μm or more and 30 μm or less, and the ten point average roughness Rz of the smallest portion is in the range of 5 μm or less. It is desirable.
If the 10-point average roughness Rz of the portion having the largest surface roughness is too small, the effect of separability is reduced. If the 10-point average roughness Rz of the portion having the largest surface roughness is too large, the image quality may be affected. If the ten-point average roughness Rz of the portion having the smallest surface roughness is too large, the effect of separability is reduced.

Furthermore, in the present invention, a cleaning member for cleaning the surface of the paper carrying belt is provided, and the cleaning force by the cleaning member is strong at a portion of the paper carrying belt where the surface roughness is large, and the surface roughness of the paper carrying belt is small. It is desirable that the portion is weaker than the portion having a large surface roughness.
In this way, even if the surface roughness is different, the cleaning effect can be made equivalent.

  According to the image forming apparatus of the present invention, the sheet carrying belt has a good sheet separation property even when a thin sheet is used without affecting the transfer process.

1 is a schematic configuration diagram illustrating a color printer according to an embodiment. It is explanatory drawing which shows the division | segmentation of the paper support belt which concerns on this form.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a so-called tandem type color printer.

  The color printer 1 of this embodiment is a so-called tandem type color printer capable of forming a color image, as shown in FIG. The image forming units 10Y, 10M, 10C, and 10K for each color are arranged in the vertical direction along the intermediate transfer belt 11 around the center in the drawing. The image forming portions for the respective colors are arranged in the order of yellow 10Y, magenta 10M, cyan 10C, and black 10K from the top to the bottom in the drawing. In the lower part of the figure, a detachable paper feed cassette 13 is mounted. A belt cleaner 15 for scraping off the toner remaining on the intermediate transfer belt 11 is provided in the upper part of the drawing.

  As shown in FIG. 1, the yellow image forming unit 10 </ b> Y includes a charging unit 22, an exposure unit 23, a developing unit 24, a primary transfer unit 25, and a cleaner 26 with a photosensitive member 21 at the center. In the drawing, only the yellow image forming unit 10Y is described with reference numerals, but the other colors have the same configuration. Further, a hopper 28 for storing toner of each color is provided on the right side of the intermediate transfer belt 11 in the drawing.

  Further, a secondary transfer portion 31 is provided at the lower left portion of the intermediate transfer belt 11 in FIG. In the present embodiment, the secondary transfer unit 31 includes an endless belt-like sheet carrying belt 32 and a secondary transfer roller 33. Further, a plurality of stretching rollers 34 that stretch and rotate the paper carrying belt 32, a belt cleaner 35 that is attached to a position facing one of the stretching rollers 34 with the paper carrying belt 32 interposed therebetween, have.

  Further, as shown in FIG. 1, a fixing unit 41 is provided on the left side of the secondary transfer unit 31 in the drawing. Further, the intermediate transfer belt 11 is stretched around a plurality of rollers. The belt roller 43, which is one of them, faces the secondary transfer roller 33 with the paper carrying belt 32 and the intermediate transfer belt 11 interposed therebetween. At the time of image formation, as indicated by a broken line P in the drawing, the sheet is pulled out from the sheet feeding cassette 13, passes between the sheet carrying belt 32 and the intermediate transfer belt 11, passes through the fixing unit 41, and is outside the machine. Is discharged.

  Next, the operation of each part when a color image is formed by the color printer 1 will be briefly described. A toner image is formed on each color photoconductor 21 at the same timing. That is, it is uniformly charged by the charging unit 22 and subsequently exposed by the exposure unit 23. As a result, an electrostatic latent image based on the image data of each color is formed on the surface of the photoconductor 21 of each color. Next, the developing unit 24 supplies toner to the electrostatic latent image, and a toner image is formed on the photoreceptor 21.

  At the time of image formation, the intermediate transfer belt 11 is rotated clockwise as shown by an arrow X in FIG. The toner images formed on the photoconductors 21 of the respective colors at the same timing are transferred onto the intermediate transfer belt 11 by the respective primary transfer units 25 and are superimposed on each other. As a result, a color toner image is formed on the intermediate transfer belt 11. Note that the toner remaining on the photosensitive member 21 after passing through the primary transfer region is scraped off by the cleaner 26.

  On the other hand, a sheet as a recording member for forming an image is pulled out from the lower sheet feeding cassette 13 in FIG. 1 one by one and conveyed toward the secondary transfer unit 31. In the secondary transfer unit 31, the paper is attracted to the surface of the paper carrying belt 32 by the electrostatic attraction between the paper carrying belt 32 and conveyed. The toner image superimposed on the intermediate transfer belt 11 is transferred onto the paper between the secondary transfer roller 33 and the belt roller 43.

  The sheet that has received the transfer of the toner image is carried by the sheet carrying belt 32 and further conveyed. The sheet carrying belt 32 has a convex curved surface at a position where it contacts the stretching roller 34. The leading edge of the paper is separated from the paper carrying belt 32 at this convex portion by the strength of the paper itself. The sheet with the leading end peeled off from the sheet carrying belt 32 is conveyed while being sequentially separated toward the trailing end, and reaches the fixing unit 41. The toner is fixed on the paper by the fixing unit 41, and an image is formed on the paper.

  Here, in this embodiment, a member whose surface roughness is not uniform is used as the paper carrying belt 32. This is because even when a very thin sheet is used, the sheet can be easily removed from the state where the sheet is adsorbed by the electrostatic adsorption force as described above only by the stiffness of the sheet itself at the convex portion of the sheet carrying belt 32. It is for peeling. The inventor of the present application has found that the adsorption force between the paper carrying belt 32 and the paper is proportional to the contact area. Furthermore, it has also been found that separation is easy at a portion where the ratio of the area in contact with the sheet carrying belt 32 is small. Hereinafter, the ratio of the true contact area to the apparent contact area is referred to as the contact area ratio.

  In view of this, the sheet carrying belt 32 of the present embodiment has a surface roughness greater than that of the central region in at least one end region in the width direction (the depth direction in FIG. 1). That is, the portion having the largest surface roughness is one of the end regions in the width direction, and at least the central region has a smaller surface roughness. Here, the surface is a surface disposed on the outer peripheral side, and is a surface that contacts the paper during the transfer process. Further, the width direction is a direction intersecting with the traveling direction of the paper, and is an axial direction of the rollers 33 and 34 for driving the paper carrying belt 32.

  The sheet carrying belt 32 of this embodiment is divided into a plurality of regions in the width direction (vertical direction in FIG. 2) as indicated by AG in FIG. Furthermore, the surface roughness is different for each segmented area. Specifically, among the seven regions A to G, the surface roughness of the region A is the largest, and the surface roughness decreases in order from the region B to the region G. Therefore, in the area A, the contact area ratio between the sheet and the sheet carrying belt 32 is small, and increases in order from the area B to the area G. Note that the circumferential direction (lateral direction in FIG. 2), that is, the traveling direction of the paper carrying belt 32, may have a uniform surface roughness for each region.

  Thus, the portion of the paper disposed in the region A has a smaller electrostatic attraction force with the paper carrying belt 32 than the portion disposed in the other region. That is, it is easy to peel off. The electrostatic attraction force gradually increases toward the region G, and is difficult to peel off. In this embodiment, the paper carried on the paper carrying belt 32 is carried over at least two areas regardless of the size. The division of the areas A to G is determined so as to be so. Therefore, the contact area ratio with the paper carrying belt 32 differs depending on the position in the width direction of the paper, and the ease of peeling differs.

  Since the contact area ratio is arranged as described above, the portion of the leading edge of the paper that is transported to the area A of the paper carrying belt 32 or the position closest thereto is most easily peeled off. That is, the end portion disposed on the area A side of the sheet. Since the surface roughness of the paper carrying belt 32 is arranged in this way, one end of the paper is peeled off first. Furthermore, the arrangement is such that the ease of peeling becomes smaller in order from the side closer to the end to the other end. Therefore, it starts to peel off from one end and peels in order toward the other end.

  The arrangement of the surface roughness of the paper carrying belt 32 is not limited to the above. Contrary to the above, the surface roughness of the region G may be the largest and may gradually decrease toward the region A. Alternatively, the surface roughness of the region A and the region G corresponding to both end regions may be the largest, and the surface roughness of the region D that is the central region may be the smallest. In that case, the surface roughness may be decreased in order from the region A to the region D and from the region G to the region D.

  If the center part peels first, even if it partly peels once, it may be attracted again by being pulled to the end parts on both sides. Therefore, an arrangement in which the surface roughness of the central region is large and the both end regions are smaller is not preferable. It is preferable to arrange a portion having the largest surface roughness in at least one of both end regions. And it is preferable to arrange | position so that surface roughness may become small in order toward the center part area | region from the edge part. Note that the other end region may have a larger surface roughness than the center region. Alternatively, the surface roughness of the other end region may be smaller than that of the central region. In any case, the surface roughness is arranged so as to increase or decrease in order from the central region toward the other end.

  Normally, the paper transport path is predetermined for each apparatus. Therefore, in the apparatus in which the sheet transport path in the apparatus is transported with the right end aligned in the transport direction, it is preferable that the surface roughness decreases from the region G toward the region A in order. In the apparatus for aligning the left end, it is preferable that the surface roughness be arranged to the right. By doing in this way, it will become easy to peel from one end part more reliably.

  Also, the method of dividing the area is not limited to that shown in FIG. In this figure, an area that is outside the effective range for the transfer process is left at both end portions in the axial direction, and is equally divided into seven parts. However, it is not always necessary to leave both ends, and it is not essential to divide evenly. Further, the number of divisions may be at least two, but it is desirable to divide them relatively finely. For example, the number of divisions may be in the range of 5 to 11 regions. Even when the smallest size paper that can be transported is used, it is preferable that the paper is transported across at least two areas.

  Further, the surface roughness of the surface of each region is desirably within the following range in terms of a ten-point average roughness Rz value (conforming to JIS0601). That is, in the region having the largest surface roughness, it is desirable that it is 10 μm or more and 30 μm or less. More desirably, it is 15 μm or more and 20 μm or less. In the region with the smallest surface roughness, it is desirable to be 5 μm or less. More desirably, it is 3 μm or less. In addition, if there is a portion having a surface roughness exceeding Rz 30 μm, it is not preferable because defective cleaning tends to occur and the back side of the paper may be stained.

Note that the sheet carrying belt 32 of this embodiment is different in surface roughness depending on the region as described above, but the volume resistivity is uniform. If the volume resistivity of the paper carrying belt 32 is too large, the adsorption rate becomes too strong, and if it is too small, the paper may not be conveyed. Therefore, in this embodiment, the volume resistivity of the paper carrying belt 32 is set to 10 ⁵ Ω / cm or more and 10 ¹² Ω / cm or less. More preferably, it is 10 ⁷ Ω / cm or more and 10 ¹⁰ Ω / cm or less.

  Next, a method for manufacturing the paper carrying belt 32 of this embodiment will be described. When manufacturing by a method in which a space having the shape of the paper-carrying belt 32 is formed in the inner space of the mold and the material is injected into the space, the above-mentioned surface roughness condition is satisfied as the inner surface shape of the mold. Form something. Alternatively, in the case where an endless belt-like product is first manufactured by drawing or the like and then surface treatment is performed, for example, a difference can be provided in the coating on the surface layer. Alternatively, partial polishing or roughening may be performed.

  In this embodiment, since the surface roughness of the paper carrying belt 32 is different depending on the region as described above, the surface contamination is also different. Therefore, the cleaning force of the belt cleaner 35 that cleans the paper carrying belt 32 is also different depending on the facing region. That is, a cleaning member that cleans a region with a large surface roughness is stronger in cleaning power than a cleaning member with a region with a small surface roughness.

  For example, when a blade or a foaming roller is used as the cleaning member of the belt cleaner 35, the pressing force at a location facing a region having a large surface roughness may be increased. Alternatively, the protruding amount of the cleaning member may be increased or the hardness may be increased. In addition, when using a brush member as a cleaning member, increasing the flocking density of the brush (number of brush bristles per area), using a harder brush bristle, or increasing the amount of bite Good.

The inventor of the present application confirmed the effect of the present invention through experiments. As shown in FIG. 2, the effective range is divided into seven regions A to G, and the nine types of paper carrying belts 32 in which the surface roughness Rz (μm) of each portion is set as shown in Table 1 below. Manufactured. Each paper carrying belt 32 was attached to the color printer 1 and a paper passing test was performed using thin paper. In the test, A4 size OK medium quality coated paper (made by Oji Paper Co., Ltd., basis weight 60.2 g / m ² ) in a low temperature and low humidity environment with a temperature of 10 ° C. and a humidity of 15% was 1000 sheets vertically and 1000 sheets horizontally. A total of 2000 sheets were continuously fed.

  The evaluation criteria for separability are as follows. The number of occurrences of paper jams in a total of 2000 sheets was rated as ◎ if it was 2 or less, ○ if it was 3-4, Δ if 5-9, and x if 10 or more. The image quality evaluation criteria are as follows. ◎ when there is no image quality defect that can be found visually, ◎, at first glance, but if you observe in detail, if there is density unevenness, you can see at a glance that there is density unevenness or white spots When there was, it was set as x.

The arrangement of the surface roughness of the paper carrying belt 32 used in this experiment is shown in Table 1 below. That is, the surface roughness of each region is expressed as follows using the segmentation code of the region.
Example 1 falls to the right of A>B>C>D>E>F> G Example 2 falls to the center of A>B>C> D <E <F <G Example 3 shows A> B >C> D <E <F <G Lowering in the Center Example 4 is A>B>C> D <E <F <G Lowering in the Center Example 5 is A>B>C>D>E> F > G to the right. Particularly, in Examples 1 and 2, the maximum value of the surface roughness is in the range of 15 to 30 μm, and the minimum value is in the range of less than 5 μm.

The arrangement of the surface roughness of each comparative example was as follows.
In Comparative Example 1, A≈B≈C≈D≈E≈F≈G
In Comparative Example 2, A≈B≈C≈D≈E≈F≈G
In Comparative Example 3, A≈B≈C≈D≈E≈F≈G
In Comparative Example 4, A <B <C <D>E>F> G was raised in the middle.

  The results of this experiment were as shown in Table 1 above. In Examples 1 to 5, only ◎ and ◯ were obtained, and both had good results in both separation and image quality. However, it was confirmed that there was a more preferable range depending on the value of the surface roughness. In other words, Examples 1 and 2 in which the maximum value of the surface roughness is in the range of 15 to 30 μm and the minimum value is in the range of less than 5 μm are better than other examples. there were.

  Other Examples 3 to 5 are out of the range of the most preferable surface roughness value, but there is no problem in both the separability and the image quality. In Example 3, since the maximum value was smaller than 15 μm, the reliability of separation was not as good as in Examples 1 and 2. In Example 4, since the minimum value was smaller than 5 μm, the reliability of separation was still not as good as in Examples 1 and 2. Example 5 was not as good in image quality as Examples 1 and 2 because the maximum value was larger than 30 μm.

  Further, each of Comparative Examples 1 to 4 does not have the surface roughness arrangement of the present invention. In Comparative Examples 1 to 3, the surface roughness of the entire sheet carrying belt 32 is almost the same. In Comparative Example 1 having a surface roughness value smaller than 5 μm as a whole, the separability was poor. In Comparative Example 2 in which the value of the surface roughness was about 15 μm as a whole, the separability was poor. In Comparative Example 3 having a surface roughness value larger than 30 μm as a whole, both the separability and the image quality were poor. In Comparative Example 4 in which the surface roughness of the central region was large (center rising), the separability was poor.

  Therefore, from the results of this experiment, it was confirmed that both the separability and the image quality can be improved by changing the surface roughness to one side or the center as in this embodiment. Furthermore, it has been confirmed that a satisfactory result can be obtained more reliably by setting the maximum value of the surface roughness within the range of 15 to 30 μm and the minimum value within the range of less than 5 μm.

  As described above in detail, according to the color printer 1 of the present embodiment, the surface roughness of the paper carrying belt 32 is provided with a gradient. Accordingly, the paper having undergone the secondary transfer process is peeled off from the paper carrying belt 32 in order from the end in the width direction. Therefore, even if thin paper is used, it can be reliably peeled off. Further, it is not once peeled off and adsorbed again. Further, the volume resistivity of the paper carrying belt 32 is uniform throughout. The value is almost the same as the value which has been regarded as a preferable range. Therefore, the image forming apparatus has a paper carrying belt that has good paper separation even when thin paper is used without affecting the transfer process.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the arrangement and configuration of the image forming unit in the color printer 1 are not limited to those illustrated. Further, the present invention is not limited to a color printer, and can be applied to any apparatus that transfers a toner image onto a sheet using a sheet carrying belt. For example, the present invention can be applied to a monochrome printer, a copier, a FAX, and a multifunction machine thereof.

DESCRIPTION OF SYMBOLS 1 Color printer 10Y, 10M, 10C, 10K Image formation part 11 Intermediate transfer belt 31 Secondary transfer part 32 Paper support belt 35 Belt cleaner 41 Fixing part

Claims (5)

A toner image forming portion for forming a toner image on the image carrier, a transfer portion for transferring the toner image formed by the toner image forming portion to the recording member while conveying the recording member, and a toner image by the transfer portion. An image forming apparatus having a fixing unit that fixes the toner by pressurizing and heating the recording member that has received the transfer and forms an image on the recording member;
The transfer unit is an endless belt, and has a paper carrying belt that carries and conveys a recording member,
An image characterized in that the surface roughness of the surface carrying the recording member of the paper carrying belt is larger at least at one end in the width direction with respect to the conveying direction of the recording member than at the central portion. Forming equipment. The image forming apparatus according to claim 1,
The surface roughness of the surface carrying the recording member of the paper carrying belt is
Smallest at the central portion, larger at the other end in the width direction than the central portion,
An image forming apparatus, wherein the image forming apparatus increases in size from the central portion toward the end portions on both sides. The image forming apparatus according to claim 1,
The surface roughness of the surface carrying the recording member of the paper carrying belt is
Smaller than the central portion at the other end in the width direction,
An image forming apparatus, wherein the image forming apparatus decreases in order from the one end to the other end. In the image forming apparatus according to any one of claims 1 to 3,
Of the surface roughness,
The ten-point average roughness Rz of the largest portion is in the range of 10 μm to 30 μm,
An image forming apparatus, wherein the ten-point average roughness Rz of the smallest portion is in a range of 5 μm or less. The image forming apparatus according to any one of claims 1 to 4, wherein:
A cleaning member for cleaning the surface of the paper carrying belt;
The cleaning force by the cleaning member is strong at a portion where the surface roughness is large in the paper carrying belt, and is weaker at a portion where the surface roughness is small among the paper carrying belt than a portion where the surface roughness is large. An image forming apparatus.

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