JP2005091604A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of being realized by stabilized processes and also stabilizing positioning precision in a transfer system in a serial system in an electrophotographic system. <P>SOLUTION: In an image forming apparatus of a cross transfer system which has a first image holding member which holds and rotates visible images and a second image holding member which is provided so as to be transferred in a direction to cross a transfer direction of the first image holding member and transfers the visible images by arranging the visible images on the first image holding member on the second image holding member or on a transfer material supported by the second image holding member by combination of transfer and stop operations of the first image holding member and transfer of the second image holding member, it is constituted that image width of the first image holding member in the width direction has a larger value than the value obtained by dividing image width of the second image holding member in the feeding direction by a natural number. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a fax machine. In particular, in an electrophotographic serial transfer system, an image that can be realized by a stable process and can have a stable alignment accuracy. The present invention relates to a forming apparatus.

Generally, in the image forming apparatus, the relationship between the operation direction of the image forming body and the image forming member in the portion where an image is formed on the image forming body is roughly divided into two methods. Here, the direction in which the image forming surface of the image forming body is conveyed and the direction in which the image forming member is conveyed are different from the same.
For example, in a general electrophotographic image forming apparatus, an image formed on a photoconductor is brought into contact with a transfer material (transfer paper) as an image forming body, and the transfer material and the photoconductor operate in the same direction. doing.
In contrast, in general dot printers, thermal printers, and inkjet printers, the head member, which is an image forming member, transports the surface of the image forming body while the recording paper, thermal paper, etc., that are the image forming body are stationary. Scanning in a direction perpendicular to the direction. Hereinafter, this latter is referred to as a serial type image forming apparatus.
The merit of the serial type image forming apparatus is that the configuration can be simplified by the downsizing of the image forming member, and it is economically superior. The disadvantage is that it is not suitable for high speed because of the scanning operation.
Also in the electrophotographic image forming apparatus, a serial type image forming apparatus has been proposed in order to realize the above merits. The present invention also provides a new configuration of a serial type image forming apparatus.
As a prior art, Japanese Patent Laid-Open No. 4-69254 (when the transfer state is selected, the guide shaft is moved to the right by the driving means. At this time, the developing object on which the toner image is formed and the recording paper 1 Then, the transfer roll is pressed against the platen, and the carriage is pulled by the right wire and moves in the right direction, and the transfer roll rotates by contact with the platen as the right direction moves. The contact position of the recording sheet with respect to the transfer roll is sequentially moved to the right by the carriage spacing operation, and at the same time, the contact position of the developing member with respect to the recording sheet 1 is newly changed), Japanese Patent Laid-Open No. 9-230715 The toner image carried on the toner image carrier stretched in a direction orthogonal to the conveyance direction of the printing paper by the roller is transferred to the conveyance direction of the printing paper by the transfer counter roller. An orthogonal transfer type image forming apparatus that transfers toner images transferred to the printing paper in the intersecting direction and fixes the toner image transferred to the printing paper. And at least one of the rollers closest to the transfer counter roller at the start point and end point of the longest movement path of the roller is arranged at a height that does not contact the transfer counter roller.
JP-A-4-69254 JP-A-9-230715

However, the serial type electrophotographic image forming apparatus has various problems due to the serial operation that is the basic configuration thereof.
One problem is the joint of images in the transfer paper feeding direction.
This occurs because the transfer material repeats the feeding operation and the stop operation (for the transfer process operation) by performing the serial operation, and there are problems of position accuracy and image forming process.
The second is a problem of the fixing process.

The above problem will be described in detail below.
The joint of images in the feed direction is a problem common to all serial image forming apparatuses. Therefore, technical improvements are progressing with respect to position accuracy. However, there is a wide range of transfer material support required for an image forming apparatus in an electrophotographic process, and there is a problem in achieving high positional accuracy for various transfer materials.
In addition, the image forming process also has a problem that image problems such as dust and a han image generated particularly in the transfer process occur. In other words, when transfer is performed by the serial method, the transfer process always occurs on or at the boundary of the image transferred by the previous transfer process (the image transferred to the transfer material and transported by the transfer material). Therefore, the transfer process occurs again for the image transferred in the previous transfer process, and the image is disturbed. This phenomenon is called “Chile”.
Further, in the serial method, the transfer material is stationary and the transferred member is scanned, so that when the transfer material and the transferred member are separated, the image transferred to the transfer material is returned to the transferred member again. An abnormal image due to this is called a Han image.
Furthermore, when forming a single image by superimposing a plurality of images, for example, an image forming apparatus that transfers a black image and a red image to the same transfer material with a two-color image or a full-color image using yellow, magenta, cyan, black, etc. An image forming apparatus that transfers images onto the same transfer material is required.
In this case, even in an image forming apparatus that is not a serial system, a slight shift leads to a difference in color of the image or missing. Here, the color difference occurs when each image has a uniform halftone, and when the images are interspersed to express the halftone, colors are formed by overlapping each color. Therefore, the manner in which the dots are scattered in each color is constant, but it is a phenomenon that appears as a different color due to the difference in color overlap. With the serial method, when transferring from a holding member that is orthogonal to the transfer material, the color is superimposed each time the image is transferred to the transfer material, so the slight displacement of the transfer position is likely to vary from image area to image area. The taste will change.
In addition, image omission occurs in the solid image color switching section, and in an image in which monochromatic yellow and magenta are alternately continued, originally yellow and magenta should be alternately continued. As a result, a gap is generated between yellow and magenta, and it looks as if the image is missing (reversely, the overlapping portion appears to have generated red).
In addition, since the electrophotographic fixing process applies a certain amount of heat to the transfer material, if the feeding and stopping are repeated in the transfer portion, the transfer material is repeatedly sent and stopped in the fixing portion, and the fixing temperature is set. The problem of making it constant and the problem of fixing nip marks and poor cleaning of the fixing roller due to the stopping operation at the fixing unit occur.
In other words, in the fixing process, a constant amount of heat is supplied and a constant pressure is applied to the transfer material, and it is composed of normal rollers. Therefore, when the roller stops, the pressure at the stopped and non-stop portions differs. As a result, unevenness occurs. In the stopped state, the image quality is different only in the portion (nip portion) where the roller abuts on the transfer material. In addition, when a contact is made by a roller in the fixing process, an image is also transferred to the roller side (fixing offset), but the roller is cleaned so as not to re-fix the transferred image. There may be a mechanism, and in the stop portion, a defect occurs in this cleaning, which is referred to as fixing roller cleaning defect.

In Japanese Patent Laid-Open No. 4-69254, the transfer process and the fixing process are simultaneously performed to solve the problem of the transfer process.
However, since the transfer material expands when heat is applied to the transfer material, a position accuracy mechanism including thermal expansion for each characteristic of the transfer material is necessary. In addition, it is necessary to cope with toner fixation due to overheating in the photoreceptor process.
Japanese Patent Laid-Open No. 9-230715 solves the problem by using a non-contact fixing process for an image transferred by a transfer plate and a transfer counter roller, but reduces the roughness of the non-contact fixing process. A mechanism was needed. Furthermore, it is necessary to construct a stable transfer process for each characteristic of the transfer material.
The present invention has been made to solve the above-mentioned problems, and the object thereof can be realized in a stable process in the serial transfer method in the electrophotographic method, and the alignment accuracy can be stabilized. An image forming apparatus is provided.

In order to achieve the above-described object, the invention according to claim 1 is directed to a first image holding member that rotates while holding a visible image, and a direction that intersects a moving direction of the first image holding member. A second image holding member provided so as to move, and the second image holding member is combined with the movement and stop operation of the first image holding member and the movement of the second image holding member. In the cross transfer type image forming apparatus for transferring the visible images on the first image holding member side by side onto the transfer material supported on the image holding member or the second image holding member, the first image holding The image width in the width direction of the member is larger than a value obtained by dividing the image width in the feeding direction of the second image holding member by a natural number.
According to a second aspect of the present invention, a first image holding member that rotates while holding a visible image and a moving direction of the first image holding member are provided. A second image holding member, on the second image holding member or the second image holding member by a combination of movement and stop operation of the first image holding member and movement of the second image holding member. In the cross transfer type image forming apparatus for transferring the visible images on the first image holding member side by side onto the transfer material supported by the image holding member, the image width in the width direction of the first image holding member Is a value larger than a value obtained by dividing a predetermined value obtained from the image width in the width direction of the second image holding member by a natural number.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the predetermined value is a ratio of an image width in the width direction to an image width in the feeding direction of the second image holding member and an image in the width direction. It is a value obtained by multiplying the width.
According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the ratio is √2.

According to the first aspect of the present invention, by adopting the intermediate transfer mechanism, transfer conditions of the transfer process in the serial type image formation are limited, so that it can be realized in a stable process, and the alignment accuracy is also stable. can do. Further, the serial image forming apparatus that determines the image width of the first image holding member by the value obtained by dividing the image width of the second image holding member in the feeding direction by a natural number has an easy mechanism for conveying the image with high accuracy. In addition, the marking mechanism is incorporated on the intermediate transfer belt, and the detection of the marking makes it easy to configure the alignment mechanism.
According to a second aspect of the present invention, the image width in the width direction of the first image holding member is a value obtained by dividing a predetermined value obtained from the image width in the width direction of the second image holding member by a natural number. Since the value is large, the image width in the width direction of the first image holding member can be set to an optimum width from a predetermined value obtained from the image width in the width direction of the second image holding member.
According to the invention of claim 3, the predetermined value is a value obtained by multiplying the ratio of the image width in the width direction to the image width in the feed direction of the second image holding member and the image width in the width direction. The optimum width of the image width in the width direction of the photosensitive belt 1 can be determined.
According to the fourth aspect of the present invention, since the ratio is √2, the optimum width of the image width in the width direction of the photosensitive belt 1 can be determined.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of an embodiment relating to a main part of a digital copying machine as an image forming apparatus according to the present invention.
As shown in FIG. 1, a photosensitive belt (first image holding member) 1 that is a belt-like photosensitive body having a mechanism for charging, exposure, a plurality of developments, cleaning, and charge removal in an electrophotographic process is a first photosensitive member. , And are supported by the second and third rollers 3, 5, and 7. The third roller 7 has a mechanism in which a belt-shaped intermediate transfer belt (second image holding member) 9 and the photosensitive belt 1 come in contact with and separate from each other, and the photosensitive belt 1 scans and contacts the intermediate transfer belt 9. doing. Further, the intermediate transfer belt 9 is configured to come into contact with the transfer paper 11 as the second transfer material at a position different from the position in contact with the photosensitive belt 1. Note that the moving direction of the photosensitive belt 1 and the moving direction of the intermediate transfer belt 9 intersect each other.
Now, the photosensitive belt 1 is continuously driven to form a uniform potential on the photosensitive member by the charging mechanism 13, and a latent image is formed by the exposure mechanism 15 on the surface of the photosensitive member on which the charging potential is formed. When a latent image is formed by the exposure mechanism 15, a mechanism for making the latent image position constant by marking on the photosensitive member, and when the exposure mechanism 15 is an LD scanning mechanism, the exposure mechanism 15 includes a plurality of LD pitch adjustment mechanisms and pixels. A mechanism that enables uniform exposure by providing an interval adjusting mechanism is provided. An image is formed by an electrophotographic process on the surface of the photoreceptor through a developing mechanism 17 that forms a toner image as an image on the latent image. Further, the photosensitive belt 1 is configured such that the toner remaining on the surface of the photosensitive member after the transfer process is removed by the cleaning mechanism 19 and the charging process is performed in a state in which the residual potential on the surface of the photosensitive member is removed by the static eliminating mechanism 21. Yes.
At this time, the operation of the photosensitive belt 1 is driven by the first roller 3, and the second and third rollers 5 and 7 rotate by being driven. The second roller 5 has a mechanism for making the tension of the photosensitive belt 1 constant on the support member. The third roller 7 is held at a position where the photosensitive belt 1 and the intermediate transfer belt 9 do not contact each other.

Next, when the toner image on the photoreceptor surface is conveyed to a predetermined position where the transfer process to the intermediate transfer belt 9 is performed, the conveyance of the photoreceptor belt 1 is stopped. With the conveyance of the photosensitive belt 1 stopped, the conveyance of the intermediate transfer belt 9 in the transfer section is stopped, and the support member of the third roller 7 is driven so that the toner image on the surface of the photosensitive belt 1 is transferred to the intermediate transfer belt. Scanning is performed so as to sequentially contact the image holding surface 9. At this time, since there is a transfer mechanism 23 that supplies a transfer bias to the surface of the intermediate transfer belt 9 that faces the image holding surface, the portion that is in contact with the intermediate transfer belt 9 by the third roller 7 is subjected to toner by a transfer process. Images are sequentially transferred from the photoreceptor belt 1. The photosensitive belt 1 and the intermediate transfer belt 9 are each provided with a mechanism for detecting the position, and the transfer is performed after the position is corrected. After the transfer of the predetermined area is completed, the third roller 7 is held at a position where the photosensitive belt 1 and the intermediate transfer belt 9 do not contact each other.
Further, the photoreceptor belt 1 is continuously driven to form a uniform potential on the photoreceptor by the charging mechanism 13, and a latent image is formed by the exposure mechanism 15 on the photoreceptor surface on which the charged potential is formed. An image is formed by an electrophotographic process on the surface of the photoreceptor through a developing mechanism 17 that forms a toner image as an image on the latent image.
At this time, as shown in FIG. 2, development is performed using a development mechanism 17a different from the initial development mechanism. FIG. 2 is a schematic diagram of an embodiment relating to a main part of a color image forming apparatus having a plurality of developing mechanisms.

The photosensitive belt 1 is subjected to a charging process with the cleaning mechanism 19 removing the toner remaining on the surface of the photosensitive member after the transfer process and the charge removing mechanism 21 removing the residual potential on the surface of the photosensitive member, and the same as the first time. When the toner image on the photoreceptor surface is conveyed to a predetermined position where the transfer process to the intermediate transfer belt 9 is performed, the conveyance of the photoreceptor belt 1 is stopped, and the conveyance of the intermediate transfer belt 9 in the transfer unit 23 is stopped. In this state, the supporting member of the third roller 7 is driven to scan so that the toner image on the surface of the photoreceptor belt 1 is in contact with the image holding surface of the intermediate transfer belt 9 sequentially. The toner images are sequentially transferred from the photoreceptor belt 1 by the transfer process at the portion in contact with the intermediate transfer belt 9 by the third roller 7. After the transfer of the predetermined area is completed, the third roller 7 is held at a position where the photosensitive belt 1 and the intermediate transfer belt 9 do not contact each other.
By performing the above serial image forming sequence a plurality of times, a plurality of images are formed on the intermediate transfer belt 9 in a superimposed manner.

As shown in FIG. 3, the intermediate transfer belt 9 is provided with a first transfer mechanism for transferring a toner image from the photosensitive belt 1 at a position facing the photosensitive belt 1, and the intermediate transfer belt 9. The second transfer mechanism for transferring the toner to the transfer paper 11 is provided at a position facing the fourth roller 25. FIG. 3 is a schematic view of an embodiment relating to an intermediate transfer belt of a digital copying machine as an image forming apparatus according to the present invention.
The fourth roller 25 conveys the intermediate transfer belt 9 by continuous driving. The fifth roller 27 and the sixth roller 29 are driven rollers, and each of the roller support members has a mechanism for making the tension of the intermediate transfer belt 9 constant. The seventh roller 31 has a mechanism for driving and conveying the intermediate transfer belt 9 and a mechanism for stopping conveyance at the position of the seventh roller 31.
Now, the rotation of the seventh roller 31 is stopped, and the image is transferred to the intermediate transfer belt 9 by the serial image forming sequence described above. At this time, the fifth roller 27 has a mechanism that makes the tension constant according to the conveying force of the fourth roller 25, and the distance between the fifth roller 27 and the fourth roller 25 on the belt and the seventh roller The distance between the belt 31 and the fifth roller 27 on the belt decreases. Further, the sixth roller 29 also has a mechanism for making the tension constant, and the distance between the fourth roller 25 and the sixth roller 29 on the belt and the distance between the sixth roller 29 and the seventh roller 31 on the belt. Move in the direction that becomes longer.
When the serial image forming sequence is completed and the third roller 7 is positioned in a state where the photosensitive belt 1 and the intermediate transfer belt 9 are not in contact with each other, the seventh roller 31 is faster than the speed at which the sixth roller 29 is conveyed. Transport at speed. At this time, the sixth roller 29 has a mechanism that makes the tension constant with the conveying force of the seventh roller 31, and the distance between the fourth roller 25 and the sixth roller 29 on the belt and the sixth roller 29. The distance between the belt 29 and the seventh roller 31 on the belt is shortened. Further, the fifth roller 27 also has a mechanism for making the tension constant, and the distance between the fifth roller 27 and the fourth roller 25 on the belt and the distance between the seventh roller 31 and the fifth roller 27 on the belt. Move in the direction that becomes longer.
With the intermediate transfer belt 9 moved to a predetermined position where the rear end of the image formed immediately before the serial image formation sequence and the front end of the image newly formed in the serial image formation sequence are connected, the seventh roller 31 again The conveyance of the intermediate transfer belt 9 at the position is stopped. At this time, the fifth roller 27 and the sixth roller 29 return to the same predetermined positions as when the seventh roller 31 was stopped last time.
Since the intermediate transfer belt 9 is continuously conveyed at the position of the fourth roller 25, the transfer paper conveyance mechanism (not shown) causes the image on the intermediate transfer belt 9 to reach a desired position on the transfer paper. By transferring the transfer paper, a transfer bias is applied to the transfer paper by the transfer mechanism 23, and the toner image can be transferred from the intermediate transfer belt to the transfer paper. Further, the toner image is fixed on the transfer paper 11 by a fixing mechanism (not shown).
In the transfer process and the fixing process, an image conveyance speed conversion mechanism is used. Here, the image conveyance speed conversion mechanism is a mechanism that can control the conveyance speed at a plurality of different positions of the image holding unit while holding the image in the same image holding unit, etc. It has a transport stop position for image formation and a continuous transport position for continuous transfer onto a transfer material (transfer paper), and does not hinder the operation of the continuous transport unit. Here, this is realized by a mechanism that adjusts the transport distance between the transport stop unit and the continuous transport unit, and a system with higher productivity is provided.

Next, the relationship between the image width in the width direction of the photoreceptor belt 1 and the image width in the feed direction of the intermediate transfer belt 9 which is the main part of the present invention will be described.
In this apparatus, the width of the intermediate transfer belt 9 depends on the width of the transfer material. For example, in order to form a 420 mm image on a paper having a maximum width of 420 mm, the width of the intermediate transfer belt 9 needs to be at least 420 mm. Actually, the width is a width obtained by adding a width that does not affect the end of the belt to 420 mm and a width that does not affect the image near the belt.
However, the width of the photosensitive belt 1 does not depend on it. This is because, by repeating the serial operation to the intermediate transfer belt 9 and further continuously transferring from the intermediate transfer belt 9 to the transfer material, it is possible to continue to form an image regardless of the width of the photosensitive belt 1. Because.
However, considering the efficiency of serial operation, there is an optimum value for the width of the photosensitive belt 1. That is, since the serial operation is an intermittent operation, the serial operation time for one time with respect to the intermediate transfer belt 9 is constant even if the image width is different in the width direction of the photosensitive belt 1. Therefore, increasing the image area in the width direction of the photosensitive belt 1 to reduce the number of serial operations increases the efficiency of the entire system.

Here, in the configuration of the image forming apparatus in which the maximum adaptive size in the width direction of the intermediate transfer belt 9 is 813 mm and the maximum adaptive size in the width direction of the photosensitive belt 1 is 200 mm, a predetermined size (see FIG. 4, 813 mm × A case where an image of 546 mm) is formed will be described as an example.
FIG. 4 is an explanatory diagram of image formation when the maximum adaptive size in the width direction of the intermediate transfer belt 9 and the maximum adaptive size in the width direction of the photosensitive belt 1 are predetermined sizes. Since the maximum size in the width direction of the intermediate transfer belt 9 is adapted to 813 mm, in order to form an image of a predetermined size, the image in the longitudinal direction (813 mm) with respect to the width direction of the intermediate transfer belt 9 is used. Naturally, the efficiency differs between the case of forming the image and the case of forming the image in the short direction (546 mm).
Now, when an image in the short direction is formed in the width direction of the intermediate transfer belt 9, the serial operation of the photosensitive belt 1 can be obtained from a natural number n satisfying 200 mm × n> = 813 mm, which is 5 times (FIG. 5). FIG. 5 is an explanatory diagram for forming an image in the short direction in the width direction of the intermediate transfer belt 9.
Here, considering the optimization of the maximum adaptive size of the photosensitive belt 1 when an image in the short direction is formed in the width direction of the intermediate transfer belt 9, if the width of the photosensitive belt 1 is W, W × What is necessary is just to obtain W that satisfies n> = 813 mm. That is, assuming that the image size L in the feed direction of the intermediate transfer belt 9 is W> = L ÷ n, and considering W> = 813 mm ÷ n, W is 813 mm when n = 1, and 406. 5 mm, 271 mm when n = 3, 203.25 mm when n = 4, etc., and the photosensitive belt 1 corresponding to an image size of 203.25 mm or more which is slightly longer than the width 200 mm of the current photosensitive belt 1 is used. This shows that the serial operation can be shortened to four times. It can also be seen that if the width of the photosensitive belt 1 corresponds to an image size of 162.6 mm or more, the same five operations as the width of 200 mm are sufficient.
Further, considering the optimization of the photosensitive belt 1 in the case where an image in the longitudinal direction is formed in the width direction of the intermediate transfer belt 9 with the previous image size, when n = 1, W> = 546 mm and n = 2. It can be seen that the optimum width can be obtained by W> = 273 ÷ m regardless of the image feeding direction (m is a natural number).
The 273 mm is a predetermined value obtained from the image width of the intermediate transfer belt 9.

As described above, according to the first aspect of the present invention, by adopting the intermediate transfer mechanism, the transfer condition of the transfer process in the serial type image formation is limited, so that a stable process can be realized. The accuracy can also be stabilized. Further, the serial image forming apparatus that determines the image width of the first image holding member by the value obtained by dividing the image width of the second image holding member in the feeding direction by a natural number has an easy mechanism for conveying the image with high accuracy. In addition, the marking mechanism is incorporated on the intermediate transfer belt, and the detection of the marking makes it easy to configure the alignment mechanism. In addition, by adopting the conventional technology for the transfer process of the photoreceptor and the intermediate transfer belt, the quality becomes stable against transfer dust, and the transfer process to the transfer paper and the fixing process by using the image conveyance speed conversion mechanism. It is possible to use a mechanism having a technology that has been integrated conventionally, and the optimum width shape of the first image holding member can be determined so as to be effective for problems such as fixing nip marks and fixing roller cleaning failure.
Note that the transfer material (transfer paper or the like) on which an image is formed by the image forming apparatus can be classified into those whose size information is not preliminarily grasped. Here, a pre-held size is defined as a standard size, and an unheld size is defined as an irregular size.
In the case of a standard size, for example, in the case of 813 mm × 546 mm, when the short direction is formed in the width direction of the second image holding member (intermediate transfer belt), the longitudinal direction is the first image holding member (photosensitive belt). ) In the width direction as described in the first aspect. Accordingly, in order to optimize the width of the photosensitive belt 1 in the image formation, the length in the longitudinal direction can be specified from the length in the short side direction = the width of the intermediate transfer belt 9. The width of the photosensitive belt 1 suitable for image formation can be obtained (claim 1).
Thus, in the case of the standard size, the width of the photosensitive belt 1 can be optimized from the width of the intermediate transfer belt 9. Therefore, the image width in the width direction of the first image holding member can be set to an optimum width from the predetermined value obtained from the image width in the width direction of the second image holding member.

Further, in the standard size, the size obtained by folding the longitudinal direction in half may be the standard size (see FIG. 6). FIG. 6 is an explanatory diagram of image formation in a case where the standard size is a size in which the longitudinal direction is folded in half. For example, the standard size is 813 mm x 546 mm, and the folded size is 546 mm x 406.5 mm, the folded size is 406.5 mm x 273 mm, and the folded size is 273 mm x 203.25 mm. If the image width in the width direction of the intermediate transfer belt 9 is 813 mm, 406.5 mm, and 203.25 mm, the image width in the width direction of the photosensitive belt 1 is Wk> = 203.25 mm ÷ n. , Both can be optimized. That is, the image width Wk in the width direction of the photosensitive belt 1> = the image width Wt of the intermediate transfer belt 9 × (Wk / Wt) ÷ n, so that the optimum width of the image width in the width direction of the photosensitive belt 1 is satisfied. Can be determined (Claim 3).
In the above standard size, there are two ratios of Wk / Wt: 813 mm / 546 mm≈1.49 and 546 mm / 406.5 mm≈1.34. This is because the ratio of the length and the short length of the original size is different from the ratio of the length and the short length of the folded size. It is known that the ratio is set to √2 in order to make the ratio of the long side to the short side constant even when folded in half. This is the ratio of the square root because the size of repeating the folding twice is reduced to half the original size. Therefore, in the standard size in which the ratio of long to short is √2, the width of the photosensitive belt is satisfied by satisfying the image width Wk in the width direction of the photosensitive belt> = the image width Wt of the intermediate transfer belt × √2 ÷ n. The optimum width of the image width in the direction can be determined (claim 4).
In this case, of course, since it is a serial system, a color image forming apparatus that realizes space saving in each process of charging, exposure, development, cleaning, and static elimination is provided.

FIG. 7 is a schematic view of a modification in which the present invention is applied to an image forming apparatus constituted by the photosensitive drum 33, the first intermediate transfer belt 35, and the second intermediate transfer belt 37.
FIG. 8 is a schematic view of a modification in which the present invention is applied to an image forming apparatus constituted only by the photosensitive drum 33 and the intermediate transfer belt 35.

1 is a schematic diagram of an embodiment relating to a main part of a digital copying machine as an image forming apparatus according to the present invention. 1 is a schematic view of an embodiment relating to a main part of a color image forming apparatus having a plurality of developing mechanisms according to the present invention. 1 is a schematic view of an embodiment relating to an intermediate transfer belt of a digital copying machine as an image forming apparatus according to the present invention. 5 is an explanatory diagram of image formation when a maximum adaptive size in the width direction of the intermediate transfer belt 9 and a maximum adaptive size in the width direction of the photosensitive belt 1 are predetermined sizes. FIG. 5 is an explanatory diagram when an image in a short direction is formed in the width direction of the intermediate transfer belt 9. FIG. FIG. 10 is an explanatory diagram of image formation when a size obtained by folding the longitudinal direction in half is a standard size. FIG. 6 is a schematic view of a modification in which the present invention is applied to an image forming apparatus including a photosensitive drum 33, a first intermediate transfer belt 35, and a second intermediate transfer belt 37. FIG. 6 is a schematic view of a modification in which the present invention is applied to an image forming apparatus constituted only by a photosensitive drum 33 and an intermediate transfer belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photosensitive belt, 3 ... 1st roller, 5 ... 2nd roller, 7 ... 3rd roller, 9 ... Intermediate transfer belt, 11 ... Transfer paper, 13 ... Charging mechanism, 15 ... Exposure mechanism, 17 ... Development mechanism, 17a ... development mechanism, 19 ... cleaning mechanism, 21 ... static elimination mechanism, 23 ... transfer mechanism, 23 ... transfer portion, 25 ... fourth roller, 27 ... fifth roller, 29 ... sixth roller, 31 ... Seventh roller, 33 ... photosensitive drum, 35 ... intermediate transfer belt, 35 ... first intermediate transfer belt, 37 ... second intermediate transfer belt

Claims (4)

A first image holding member that rotates while holding a visible image; and a second image holding member that is provided so as to move in a direction that intersects a moving direction of the first image holding member. The transfer material supported on the second image holding member or on the second image holding member by a combination of the movement and stop operation of the first image holding member and the movement of the second image holding member An image forming apparatus of a cross transfer method that transfers a visible image on the first image holding member side by side,
An image forming apparatus, wherein an image width in a width direction of the first image holding member is larger than a value obtained by dividing an image width in a feeding direction of the second image holding member by a natural number. A first image holding member that rotates while holding a visible image; and a second image holding member that is provided so as to move in a direction that intersects a moving direction of the first image holding member. The transfer material supported on the second image holding member or on the second image holding member by a combination of the movement and stop operation of the first image holding member and the movement of the second image holding member An image forming apparatus of a cross transfer method that transfers a visible image on the first image holding member side by side,
The image width in the width direction of the first image holding member is larger than a value obtained by dividing a predetermined value obtained from the image width in the width direction of the second image holding member by a natural number. Forming equipment.   3. The image forming apparatus according to claim 2, wherein the predetermined value is a value obtained by multiplying a ratio of an image width in the width direction to an image width in the feed direction of the second image holding member and an image width in the width direction. An image forming apparatus.   The image forming apparatus according to claim 3, wherein the ratio is √2.

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