JPH10142845A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which forms images on both sides of a transfer paper sheet by means of a simple structure. SOLUTION: The color image forming device 1 feeds a plurality of transfer paper sheets from a sheet feed cassette onto a transfer belt 2, onto a circulation path 2, at specific sheet-intervals as one unit, and abased on the image information of memories 11 and 12, it records yellow(Y), magenta(M), cyan(C), and black (K) images onto the surface of each transfer sheet 5 by means of developing units 10Y-10K. The recording sheets 5 with images recorded on them are inverted by inverting units 6 and 7 alternately, and they are carried to the developing units 10Y-10K again, and images are recorded on the backs of the transfer sheets 5. Also, after the last transfer sheet 5 of the one block passes the position of the sheet feed cassette 4, the transfer sheets 5 of the following block are successively fed from the sheet feed cassette 4 onto the transfer belt 2. The transfer sheets 5 subjected to two-sided recording are separated from the transfer belt 2 with the aid of a separating member 9, and placed onto a sheet-ejection tray 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus capable of forming an image on both sides of a transfer sheet with a simple structure.

2. Description of the Related Art Recently, in an image forming apparatus, an image has been recorded on both sides of a recording sheet (transfer sheet) in order to save resources. Conventionally, there is a method for controlling a double-sided recording apparatus described in Japanese Patent Application Laid-Open No. 63-313172. The control method of the double-sided recording apparatus includes a storage unit for storing and reading recording information successively for each page, and a recording information for two pages of the recording information on the first surface and the second surface of the recording medium. In a method for controlling a double-sided recording apparatus, comprising: a recording unit for separately recording on both sides, a control unit for controlling the storage unit and the recording unit, the first recording medium recorded on the first side is introduced into the recording unit again. Until the mouth is reached, recording continues on the first side of the new recording medium, then recording on the second side of the first recording medium, and thereafter recording on the first side of another new recording medium. And recording on the second surface of the recording medium recorded on the first surface is performed alternately. That is, according to this conventional double-sided recording, at the start of recording, the recording on the front surface is continued,
When the first recording paper arrives at the back recording paper feed port, the back recording of the recording paper fed first is performed, and thereafter, the recording is alternately performed on the front surface and the back surface, thereby improving the throughput.

However, in such a conventional image forming apparatus, when recording is started, the recording on the front surface is continued, and when the first recording paper reaches the rear recording paper feed port, Perform back side recording of the recording paper that was fed first,
Thereafter, since the front and back sides are alternately recorded, only the front side is continuously recorded at the start of recording, and only the back side is continuously recorded before the end of recording. The gap between the recording paper and the recording paper when recording only the front side and the recording only on the back side before the end of recording is twice the interval between the recording paper and recording paper during intermediate recording where the front and back sides are alternately recorded And there is a problem that the efficiency of image recording is low. Further, when the toner is fixed by the fixing unit as the image recording method of the image forming apparatus, the recording paper shrinks when passing through the fixing unit. The image recording start timing is different from the case of forming an image, and it is necessary to change the image recording start timing on the front side and the back side of the recording paper. As a result, the conventional image forming apparatus has a problem that the structure of the image forming apparatus becomes complicated and the image forming apparatus becomes expensive. Therefore, the invention according to claim 1 is to provide a plurality of transfer papers which can be simultaneously circulated on a circulation path having a length capable of simultaneously transporting a plurality of transfer papers, by setting the paper interval between the transfer papers to a predetermined equal interval. The paper is sent out from the paper feeding section to the circulation path as a single block, and images are continuously formed on the surfaces of all the transfer papers in one block by the image forming means. By successively inverting by the reversing means and continuously forming an image on the back surface of the inverted transfer paper of one block, without providing a mechanism for storing the transfer paper having the image formed on the front surface, It is another object of the present invention to provide an inexpensive image forming apparatus that can appropriately form an image on both sides of a transfer sheet without frequently controlling the image writing start timing, has a simple structure, and is inexpensive. According to a second aspect of the present invention, the paper feeding unit and the paper discharging unit are arranged at a distance of not more than half of the length of the circulation path, so that a plurality of transfer papers sent out to the circulation path as a block are formed. When more than half of the transfer paper remains in the circulation path, the supply of the next block of transfer paper to the circulation path can be started. It is an object of the present invention to provide an image forming apparatus capable of forming an image. According to a third aspect of the present invention, in the paper supply unit, the last transfer paper in one block in which the image formation on the front surface is completed is transferred from the paper supply unit to the circulation path and merged with the circulation path. When the sheet passes through the position, the transfer paper is continuously fed at a predetermined interval by starting to feed the first transfer paper of the next block at a predetermined paper interval from the last transfer paper in one block. It is an object of the present invention to provide an image forming apparatus which can be conveyed, is even smaller, and can form an image on both sides of transfer paper efficiently. According to a fourth aspect of the present invention, two memories for storing the image information for the front side and the image information for the back side of one transfer sheet are provided, and the two memories are alternately used by the image forming means, and are sequentially used. By forming an image on the conveyed transfer paper, the image can be appropriately formed on both sides of the transfer paper even if the paper interval between the transfer papers is shortened. It is an object of the present invention to provide an image forming apparatus capable of forming an image on both sides of a transfer sheet. According to a fifth aspect of the present invention, two reversing means for reversing the transfer paper on the circulation path are provided, and the transfer paper sequentially conveyed on the circulation path is alternately reversed by the two reversing means, so that the transfer paper and the transfer paper are alternately reversed. Even if the paper interval of the transfer paper is shortened, the transfer paper can be properly inverted without providing a mechanism to accumulate the transfer paper on which the image is formed on the surface. It is an object of the present invention to provide an image forming apparatus capable of forming an image on both sides of paper. According to a sixth aspect of the present invention, the circulation path has a length obtained by multiplying the length obtained by adding the length of the transfer paper and the paper interval between the transfer papers to the number of transfer papers conveyed simultaneously. When the number of transfer papers that can be simultaneously conveyed on the circulation path is conveyed as one block, the paper interval between the last transfer paper of one block and the first transfer paper of the next block is determined by the transfer within the block. By setting the paper interval to be the same as the paper interval between the paper and the transfer paper, it is possible to further facilitate the control of the image writing start timing, to provide a simpler structure and a lower cost image forming apparatus. It is intended to provide.

According to the first aspect of the present invention, there is provided an image forming apparatus, wherein a transfer sheet is fed from a paper supply unit onto a circulation path of a predetermined length, and the transfer paper is conveyed along the circulation path. An image is formed on the front surface of the transfer paper by the image forming means disposed along the circulation path, and the front and back surfaces of the transfer paper on the circulation path having the image formed on the front surface are reversed by a reversing means. Transported again on the circulation path to the image forming unit, forms an image on the reverse side of the transfer sheet by the image forming unit, and transfers the transfer sheet having the image formed on the front and back sides to a sheet discharging unit. An image forming apparatus for discharging, wherein the circulating path is formed to have a length capable of simultaneously transporting a plurality of the transfer sheets, and the transfer sheet and the transfer sheet are transferred by the number of transfer sheets that can be simultaneously circulated on the circulating path. Make sure that all paper gaps are equal One block poured into,
The paper is sequentially sent out from the paper supply unit onto the circulation path, images are continuously formed on the surfaces of all the transfer papers of the one block by the image forming unit, and the transfer papers on which the image formation is completed are sequentially performed. By inverting by the inverting means and continuously forming an image by the image forming means on the back surface of the inverted transfer paper of the one block,
The above objective has been achieved. According to the above configuration, the number of transfer papers that can be simultaneously circulated on the circulation path having a length capable of simultaneously transporting a plurality of transfer papers is set such that all the paper gaps between the transfer papers are spaced at a predetermined regular interval. As one block, the paper is sent out from the paper feeding unit onto the circulation path, an image is continuously formed on the surface of all the transfer paper in one block by the image forming means, and the transfer paper on which the image has been formed is sequentially turned over by the reversing means. Since the image is formed continuously on the reverse side of the transfer paper of the inverted one block, the mechanism for storing the transfer paper having the image formed on the front surface is not provided, and the image is frequently formed. It is possible to appropriately form an image on both sides of the transfer paper without controlling the writing start timing of the image forming apparatus, thereby making the image forming apparatus simple and inexpensive. In the above case, for example, as described in claim 2, the paper feeding unit and the paper discharging unit may be arranged at a distance of not more than half the length of the circulation path. According to the above configuration,
Since the paper feed unit and the paper discharge unit are arranged at a distance of less than half the length of the circulation path, of the multiple transfer papers sent to the circulation path as blocks, With the transfer paper remaining in the circulation path, the supply of the transfer paper of the next block to the circulation path can be started, and the image forming apparatus can be reduced in size and the image forming efficiency can be improved. it can. Further, for example, as described in claim 3, the paper feeding unit is configured such that the last transfer paper in the one block in which the formation of the image on the front surface is completed is transferred from the paper feeding unit to the circulation path. When the transferred transfer paper passes through a position where the transfer paper merges with the circulation path, the transfer of the first transfer paper of the next block is started at a predetermined paper interval from the last transfer paper in the one block. It may be something. According to the above configuration, the paper feed unit is located at a position where the last transfer paper in one block on which the image formation on the front surface is completed is where the transfer paper sent from the paper feed unit to the circulation path merges with the circulation path. , The first transfer paper in the next block starts to be sent out at a predetermined paper interval from the last transfer paper in one block, so that the transfer paper is continuously transported at a predetermined interval. And the image forming apparatus is more compact,
The image forming efficiency can be further improved. Further, for example, as described in claim 4, the image forming apparatus includes two memories for storing image information for the front side and image information for the back side for one transfer sheet, and the image forming unit However, the two memories may be alternately used to form an image on the transfer paper that is sequentially conveyed. According to the above configuration, two memories for storing image information for the front side and image information for the back side for one transfer sheet are provided,
Since the two memories are used alternately by the image forming means, an image is formed on the transfer paper sequentially conveyed.
Even if the paper interval between transfer papers is shortened, images can be appropriately formed on both sides of the transfer paper, and the image forming apparatus is further reduced in size and the image forming efficiency is further improved. Can be. Further, for example, as described in claim 5, the image forming apparatus includes two of the reversing means, and the transfer paper sequentially conveyed on the circulation path is alternately reversed by the two reversing means. It may be. According to the above configuration, two reversing means for reversing the front and back of the transfer paper on the circulation path are provided, and the transfer paper sequentially conveyed on the circulation path is alternately reversed by the two reversing means. Even if the paper interval is shortened, the transfer paper can be properly inverted without providing a mechanism for storing the transfer paper on which the image is formed on the surface, and the image forming apparatus can be made smaller and more compact. Good image forming efficiency can be achieved. Further, for example, as set forth in claim 6, the circulation path multiplies the number of the transfer papers conveyed simultaneously by a length obtained by adding the length of the transfer paper and the paper interval between the transfer papers. May have a predetermined length. According to the above configuration, the circulation path has a length obtained by multiplying the length obtained by adding the length of the transfer paper and the paper interval between the transfer papers to the number of transfer papers to be simultaneously conveyed. When transporting a number of transfer papers that can be simultaneously transported on a road as one block, the paper interval between the last transfer paper of one block and the first transfer paper of the next block is set to the transfer paper in the block. With the same paper interval as the paper interval, the control of the image writing start timing can be further facilitated, and the image forming apparatus has a simpler structure and is more inexpensive. be able to.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified. 1 to 3 are diagrams showing an embodiment of an image forming apparatus according to the present invention, and the present embodiment is applied to a color image forming apparatus for forming a color image. FIG. 1 is a schematic configuration diagram of a color image forming apparatus 1 to which an embodiment of the image forming apparatus of the present invention is applied. In FIG. 1, a color image forming apparatus 1 includes a transfer belt 2 having a predetermined length.
Is formed in a ring shape over a roller (not shown) to form a circulation path 3 having a predetermined length. The transfer belt 2 is rotated by a motor (not shown) so that the transfer belt 2 is guided by the roller. It rotates counterclockwise as indicated by the arrow in FIG. The transfer belt 2 includes a paper feed cassette (paper feed unit) 4
Transfer paper 5 is fed out from a paper feed roller or the like (not shown), and two reversing units (reversing means) 6 and 7 are provided near the paper feeding cassette 4 in the rotation direction upstream of the transfer belt 2.
Are arranged. The reversing units 6 and 7 reverse the front and back surfaces of the transfer paper 5 conveyed on the transfer belt 2,
It is sent out onto the transfer belt 2 again. The transfer belt 2 has a length capable of simultaneously transporting a plurality of transfer papers 5,
In the color image forming apparatus 1 of the present embodiment, the length is such that eight transfer papers 5 can be simultaneously conveyed at a predetermined paper interval. Then, the paper feed cassette 4 sends out the transfer papers 5 onto the transfer belt 2 at predetermined intervals by the number of sheets that can be simultaneously transferred by the transfer belt 2, and the paper gap between the transfer papers 5 and the transfer paper 5 is sequentially transferred. This interval is suitable for the transfer paper 5 conveyed on the belt 2 to be alternately turned over by the reversing unit 6 and the reversing unit 7 and conveyed to the transfer belt 2. Therefore, the transfer belt 2 has a predetermined length of the transfer paper 5.
When the transfer paper 5 is conveyed by the number of conveyed sheets with a space between the transfer paper 5 and the transfer paper 5, that is, when eight transfer papers 5 are conveyed simultaneously, the length of the transfer paper 5 and the next transfer paper 5 Is multiplied by the value obtained by adding the interval of “1” to “8” which is the number of transfer sheets 5 to be transferred at the same time. Transfer belt 2
On the upstream side of the paper feed cassette 4 of the
Further, a paper discharge tray (paper feed unit) 8 is disposed further upstream than the paper discharge tray 7. The paper discharge tray 8 is at least half the length of the transfer belt 2 from the paper feed cassette 4. It is located at the location. A separation member 9 is provided at a position corresponding to the paper discharge tray 8 of the transfer belt 2. The separation member 9 separates the transfer paper 5 on which the image recording is completed from the transfer belt 2, and discharges the paper. The sheet is discharged to the tray 8. At a predetermined position of the transfer belt 2 between the paper feed cassette 4 and the discharge tray 8, images of yellow (Y), magenta (M), cyan (C), and black (K) images are formed on the transfer paper 5. A yellow developing unit 10Y as an image forming unit for performing recording,
Magenta developing unit 10M, cyan developing unit 10
C and black developing units 10K are arranged side by side in the rotation direction of the transfer belt 2, and each developing unit 10K
Y, 10M, 10C, and 10K are, for example, an image writing unit that forms an electrostatic latent image on a photoconductor based on image information by an electrophotographic method, and a photoconductor on which an electrostatic latent image is formed is formed by a wet development method. An image of each color is formed on the transfer paper 5 by providing a wet developing unit that develops a toner image to form a toner image, a transfer unit that transfers the toner image of the photoconductor to the transfer paper 5 conveyed by the transfer belt 2, and the like. Each developing unit 10Y, 10M, 1
0C and 10K each include two image information memories 11 and 12 for storing image information, respectively.
Reference numeral 12 stores image information for the front side and image information for the back side of the transfer paper 5 of each color. The image information memory 11 stores, for example, image information for odd-numbered transfer sheets 5 of the transfer sheet 5 conveyed on the transfer belt 2, and stores the image information memory 12.
Stores image information for the even-numbered transfer paper 5. The color image forming apparatus 1 includes developing units 10Y, 10M, 10M.
Although not shown, a fixing unit is disposed downstream of the transfer belt 2 of C and 10K in the rotation direction, and the fixing unit transfers the toner images transferred by the developing units 10Y, 10M, 10C and 10K to the transfer paper 5. To be established. Next, the operation of the present embodiment will be described. When performing double-sided recording (images are stored on both sides of the transfer paper 5), the color image forming apparatus 1 sequentially transfers a number of transfer papers 5 that can be simultaneously conveyed on the circulation path 3 as one block, as shown in FIG. The paper is fed from the paper feed cassette 4 onto the transfer belt 2 at predetermined intervals, and is stored in the memories 11 of the yellow developing unit 10Y, the magenta developing unit 10M, the cyan developing unit 10C, and the black developing unit 10K. The image information of the front and back sides for the even-numbered transfer paper 5 is stored in the memory 12 as follows.
Each of the memories 11 and 1 is written in accordance with the timing at which the transfer paper 5 is conveyed on the transfer belt 2 to each of the developing units 10Y, 10M, 10C and 10K.
(2) formation of an electrostatic latent image on the photoconductor by the image writing unit, formation of a toner image on the photoconductor on which the electrostatic latent image has been formed by the wet developing unit, and The transfer of the toner image to the transfer paper 5 is performed, and the recording of each color image on the transfer paper 5 is performed. At this time, the transfer paper 5 is sent out to the transfer belt 2 so that the transfer paper 5 sent out from the paper feed cassette 4 onto the transfer belt 2 and the transfer paper 5 have the same space. The memory 11 and the memory 12 store the image information of the odd-numbered and even-numbered transfer sheets 5 of the transfer sheet 5 conveyed on the transfer belt 2, and store the transfer sheet 5 and the transfer sheet 5 on the transfer belt 2. The image is appropriately formed on the transfer paper 5 even if the paper is conveyed at a short interval. That is, the color image forming apparatus 1 is capable of simultaneously transporting the transfer paper 5 from the paper feed cassette 4 onto the transfer belt 2, that is, the first transfer paper 5.
When the eighth transfer paper 5 (shown in FIG. 1) from the first transfer paper 5 (shown in FIG. 1) is sequentially sent out at a predetermined paper interval, the transfer paper 5 is transferred from the paper feed cassette 4 onto the transfer belt 2. And the formation of a front surface image on the transfer belt 5, and the first transfer paper 5 (the transfer paper 5) moves on the transfer belt 2 to the developing units 10 Y, 10 M, 10 C, and 10 K.
, Each developing unit 10Y, 10M,
Images of yellow (Y), magenta (M), cyan (C), and black (K) are sequentially recorded on the surface of the transfer paper 5 by 10C and 10K. Thereafter, similarly, the developing units 10Y, 10M, 10C,
The image of each color of yellow (Y), magenta (M), cyan (C) and black (K) is sequentially formed on the surface of the transfer paper 5 conveyed to 10K by the developing units 10Y, 10M, 10C and 10K. Record At this time, an image is recorded on the odd-numbered transfer paper 5 based on the image information stored in the memory 11, and an image is stored on the even-numbered transfer paper 5 based on the image information stored in the memory 12. Record Therefore, even if the paper interval between the transfer sheets 5 is shortened, the odd-numbered transfer sheets 5 are stored in the two memories 11 and 12.
And the image information of the even-numbered transfer paper 5 are stored alternately, so that each of the developing units 10Y, 10M, 10M
By C and 10K, an image can be appropriately formed,
The length of the transfer belt 2 is reduced and the color image forming apparatus 1
Can be reduced in size. In addition, since the interval between all the transfer sheets 5 and the transfer sheet 5 is the same, the timing of recording an image on the transfer sheet 5 by each of the developing units 10Y, 10M, 10C, and 10K can be made constant. Control at the time of image formation can be easily performed. Thereafter, the recording paper 5 on which the toner image has been transferred is fixed by a fixing unit (not shown) by the developing units 10Y, 10M, 10C, and 10K, and the transfer paper 5 on which the fixing is completed is conveyed to the reversing units 6 and 7. After the color image forming apparatus 1 reverses the transfer paper 5 with the reversing unit 6 or the reversing unit 7,
Again, the transfer paper 5 is sent out onto the transfer belt 2 with the back surface facing upward, and is conveyed by the transfer belt 2. The transfer paper 5 whose back surface is turned upside down is the developing unit 10Y, 10M, 10M.
C and 10K, the developing units 10Y, 10M, 10C, and 10K sequentially perform the same operation as described above.
Images of each color of yellow (Y), magenta (M), cyan (C) and black (K) are recorded on the back surface of the transfer paper 5. At this time, when an image is recorded on the back surface of the transfer paper 5, the transfer paper 5 is slightly shrunk when the toner image is transferred to the front surface and then fixed by a fixing unit. In consideration of the shrinkage of No. 5, each developing unit 10Y, 10Y
The recording timing on the transfer paper 5 at M, 10C, and 10K is shifted. The adjustment of the recording timing is performed by setting the transfer paper 5 to 8
Since one sheet is conveyed at the same sheet interval as one block, once adjusted, eight sheets can be recorded at the same timing, and the recording timing does not need to be adjusted frequently. As a result, the adjustment of the recording timing can be simplified, and the control of the color image forming apparatus 1 can be simplified. Also, at this time, since the image information for the front side and the image information for the back side are stored in the memories 11 and 12, the transfer paper 5 for the front side recording and the transfer paper 5 for the back side recording of the same block are continuously arranged. Even if the transfer paper 5 has been conveyed, the developing units 10Y, 10M, 1M
With 0C and 10K, an image can be appropriately formed. Therefore, the length of the transfer belt 2 can be reduced, and the color image forming apparatus 1 can be downsized. And
When the last transfer paper 5 of one block (the transfer paper 5 shown in FIG. 1) passes through the position of the paper feed cassette 4, the color image forming apparatus 1 transfers the transfer paper 5 from the paper feed cassette 4 as shown in FIG. 5 is sent out onto the transfer belt 2, and the transfer paper 5 of the next block is sequentially sent out to the transfer belt 2 in the same manner as described above.
At this time, the next space between the last transfer paper 5 of the previous block and the first transfer paper 5 of the next block is set to be the same as the space between the transfer paper 5 and the transfer paper 5 in the block. The first transfer sheet 5 in the block is sent out from the sheet cassette 4.
When the transfer paper 5 on which the image formation on the back surface of the transfer paper 5 of the first block is completed comes to the position of the separation member 9, the color image forming apparatus 1 transfers the transfer paper 5 by the separation member 9 to the transfer belt. 2, the block is placed on a discharge tray 8 with the back side facing up from the first transfer sheet 5 of the block, as shown in FIG. Thereafter, the same process is performed on the transfer paper 5 of the next block as in the transfer paper 5 of the first block. Therefore, the color image forming apparatus 1
As shown in FIG. 3, the first transfer paper 5 of the first block
Eighth transfer paper (transfer paper 5) to (transfer paper 5)
To the transfer belt 2 from the paper supply cassette 4 at the same paper interval, and sequentially to the yellow developing unit 10Y,
Magenta developing unit 10M, cyan developing unit 10
An image is recorded (image-formed) on the surface of the transfer paper 5 by the C and black developing unit 10K, and the transfer paper 5 on which the image on the surface is completed is sequentially alternately reversed by the reversing unit 6 and the reversing unit 7. The transfer paper 5 with the front and back reversed is placed on the back surface of the first transfer paper 5 (the transfer paper 5) to the back side of the eighth transfer paper (the transfer paper 5), in order, the yellow developing unit 10Y, the magenta developing unit 10M, Cyan developing unit 10C
And an image is recorded by the black developing unit 10K. As described above, according to the present embodiment, the number of transfer papers 5 that can be simultaneously circulated on the circulation path 3 having a length capable of simultaneously transporting a plurality of transfer papers 5 is determined. The paper is sent out from the paper supply cassette 4 onto the circulation path 3 as one block with all the paper intervals spaced at predetermined equal intervals, and the yellow developing unit 10Y, the magenta developing unit 10M, Cyan developing unit 10C
Then, an image is continuously formed by the black developing unit 10K. Then, the transfer paper 5 on which the formation of the image is completed is sequentially reversed by the reversing units 6 and 7, and an image is continuously formed on the reverse surface of the transfer paper 5 of one inverted block. Therefore, an image can be appropriately formed on both sides of the transfer paper 5 without providing a mechanism for accumulating the transfer paper 5 on which an image is formed on the front surface, and without frequently controlling the timing of starting image writing. Thus, the color image forming apparatus 1 can have a simple structure and be inexpensive. Further, in the color image forming apparatus 1, since the paper feed cassette 4 and the paper discharge tray 8 are arranged at a distance equal to or less than half the length of the circulation path 3, they are sent out to the circulation path 3 as blocks. With half or more of the transfer sheets 5 remaining in the circulation path 3 among the plurality of transfer sheets 5, supply of the transfer paper 5 of the next block to the circulation path 3 can be started,
The color image forming apparatus 1 can be small and have good image forming efficiency. Further, in the color image forming apparatus 1, the last transfer paper 5 in one block in which the formation of the image on the front surface is completed is transferred from the paper feed cassette 4 to the circulation path 3. When the sheet passes the merging position, the transfer of the first transfer sheet 5 of the next block is started at a predetermined interval from the last transfer sheet 5 in one block. The color image forming apparatus 1 can be opened and transported continuously.
Can be further reduced in size and the image forming efficiency can be further improved. Further, the color image forming apparatus 1 includes:
There are provided memories 11 and 12 for storing image information for the front side and image information for the back side for 51 sheets of transfer paper. Since the images are formed on the transfer paper 5 that is sequentially conveyed by using the memories 11 and 12 alternately, even if the space between the transfer paper 5 and the transfer paper 5 is shortened, the image is appropriately formed on both sides of the transfer paper 5. An image can be formed, and the color image forming apparatus 1 can be made smaller and more excellent in image forming efficiency. Further, the color image forming apparatus 1 includes two reversing units 6 and 7 for reversing the front and back of the transfer paper 5 on the circulation path 3, and the transfer paper 5 sequentially conveyed on the circulation path 3.
Are alternately reversed by the two reversing units 6 and 7, so that a mechanism for accumulating the transfer paper 5 having an image formed on its surface even when the paper interval between the transfer papers 5 is shortened. The transfer paper 5 can be appropriately reversed without providing the color image forming apparatus 1, and the color image forming apparatus 1 can be made smaller and more excellent in image forming efficiency. Also,
Since the circulation path 3 is formed by multiplying the length obtained by adding the length of the transfer paper 5 and the paper interval between the transfer papers 5 by the number of transfer papers 5 to be conveyed at the same time, When the number of transfer papers 5 that can be simultaneously conveyed is conveyed as one block, the paper interval between the last transfer paper 5 of one block and the first transfer paper 5 of the next block is set to the transfer paper in the block. 5
And the paper interval between the transfer paper 5 and
Control of the image writing start timing can be further facilitated. Therefore, the color image forming apparatus 1 can be made simpler in structure and more inexpensive. As described above, the invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and can be variously modified without departing from the gist thereof. Needless to say. For example, in the above-described embodiment, as the image forming unit, an image writing unit that forms an electrostatic latent image on a photosensitive member based on image information by an electrophotographic method, and a photosensitive member on which an electrostatic latent image is formed is a wet type. The image forming unit includes a wet developing unit that forms a toner image by developing with a developing method and a transfer unit that transfers a toner image of a photoconductor to transfer paper conveyed by a transfer belt. The image forming method
It is not limited at all. Further, in the above embodiment, the present invention is applied to a color image forming apparatus for forming a color image. However, the present invention is not limited to a color image forming apparatus, but may be a monochrome image forming apparatus.

According to the image forming apparatus of the first aspect of the present invention, a plurality of transfer papers that can be simultaneously circulated on a circulation path having a length capable of simultaneously transporting a plurality of transfer papers are transferred to the transfer paper and the transfer paper. The paper is sent out from the paper supply unit onto the circulation path at intervals of predetermined equal intervals, and the image is continuously formed on the surface of all the transfer paper in one block by the image forming unit. The transfer paper on which the image has been formed is sequentially inverted by the reversing means, and an image is continuously formed on the back surface of the inverted transfer paper of one block. Therefore, the transfer paper having the image formed on the front surface is accumulated. It is possible to appropriately form an image on both sides of a transfer sheet without providing a mechanism for storing the image, and without frequently controlling the timing of starting writing of the image. Things. According to the image forming apparatus of the present invention, since the paper feeding unit and the paper discharging unit are arranged at a distance of not more than half the length of the circulation path, they are sent out to the circulation path as blocks. The transfer of the next block of transfer paper to the circulation path can be started with more than half of the transfer paper remaining in the circulation path among the plurality of transfer papers. It is possible to achieve a small size and good image forming efficiency. According to the image forming apparatus of the third aspect of the present invention, the paper feed unit transfers the last transfer paper in one block in which the image formation on the front surface is completed from the paper feed unit to the circulation path. When the sheet passes through the position where it merges with the circulation path, it starts feeding the first transfer sheet of the next block at a predetermined sheet interval from the last transfer sheet in one block. The image forming apparatus can be continuously opened and conveyed, so that the image forming apparatus can be further reduced in size and the image forming efficiency can be further improved. According to the image forming apparatus of the present invention, the memory for storing the image information for the front side and the image information for the back side for one transfer sheet is provided with two memories.
Since the two memories are alternately used by the image forming means to form an image on the transfer paper that is sequentially conveyed, the transfer paper can be properly formed even if the paper interval between the transfer papers is shortened. An image can be formed on both sides of the image forming apparatus, and the image forming apparatus can be further reduced in size and the image forming efficiency can be further improved. According to the image forming apparatus of the present invention, two reversing means for reversing the transfer paper on the circulation path are provided, and the transfer paper sequentially conveyed on the circulation path is alternately reversed by the two reversing means. Therefore, even if the paper interval between the transfer papers is shortened, the transfer paper can be appropriately reversed without providing a mechanism for storing the transfer paper on which the image is formed on the surface. Can be further reduced in size and the image forming efficiency can be further improved. According to the image forming apparatus of the present invention, the length of the circulation path is obtained by multiplying the length obtained by adding the length of the transfer paper and the paper interval between the transfer papers by the number of transfer papers to be simultaneously conveyed. Since the number of transfer papers that can be simultaneously conveyed on the circulation path is conveyed as one block,
The interval between the last transfer sheet in one block and the first transfer sheet in the next block is set to be the same as the interval between the transfer sheets in the block and the transfer sheet. Can be made easier, and the image forming apparatus can be made simpler in structure and more inexpensive.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color image forming apparatus to which an embodiment of the image forming apparatus of the present invention is applied.

FIG. 2 is a schematic configuration diagram of the color image forming apparatus in a state where the color image forming apparatus of FIG. 1 has started conveying a transfer sheet of a next block.

FIG. 3 is a timing chart showing processing timing of image forming processing by the color image forming apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Color image forming apparatus 2 Transfer belt 3 Circulation path 4 Paper cassette 5 Transfer paper 6, 7 Reversing unit 8 Discharge tray 9 Separation member 10Y Yellow developing unit 10M Magenta developing unit 10C Cyan developing unit 10K Black developing unit 11, 12 Memory

Claims (6)

[Claims] 1. A transfer sheet is fed from a paper feeding section onto a circulation path of a predetermined length, and while the transfer paper is conveyed on the circulation path,
An image is formed on the front surface of the transfer paper by the image forming means disposed along the circulation path, and the front and back surfaces of the transfer paper on the circulation path having the image formed on the front surface are reversed by a reversing means. Transported again on the circulation path to the image forming unit, forms an image on the reverse side of the transfer sheet by the image forming unit, and transfers the transfer sheet having the image formed on the front and back sides to a sheet discharging unit. An image forming apparatus for discharging, wherein the circulating path is formed to have a length capable of simultaneously transporting a plurality of the transfer sheets, and the transfer sheet and the transfer sheet are transferred by the number of transfer sheets that can be simultaneously circulated on the circulating path. The paper is sequentially sent out from the paper supply unit onto the circulation path as one block with all paper intervals at predetermined equal intervals, and is continuously formed on the surface of all the transfer paper of the one block by the image forming unit. Image Forming the image, and sequentially inverting the transfer paper on which the image has been formed by the inverting means, and continuously forming an image on the back surface of the inverted transfer paper of the one block by the image forming means. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the paper feeding unit and the paper discharging unit are arranged at a distance of not more than half the length of the circulation path. 3. The paper feeding section, wherein the last transfer paper in the one block in which the image formation on the front surface is completed is sent from the paper feeding section to the circulation path, and the transfer paper is circulated in the circulation path. 2. The method according to claim 1, wherein when the sheet passes through a position where it joins a road, a first sheet of the next block is fed out at a predetermined sheet interval from the last transfer sheet in the one block. Alternatively, the image forming apparatus according to claim 2. 4. An image forming apparatus according to claim 1, wherein said image forming apparatus has two memories for storing image information for the front side and image information for the back side of one sheet of transfer paper.
4. The image forming apparatus according to claim 1, wherein the image forming unit forms an image on the transfer paper conveyed sequentially by using the two memories alternately. Image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus includes two reversing means, and the transfer paper sequentially conveyed on the circulation path is alternately reversed by the two reversing means. The image forming apparatus according to claim 4. 6. The circulation path has a length obtained by multiplying the length obtained by adding the length of the transfer paper and the paper interval between the transfer papers to the number of the transfer papers conveyed simultaneously. The image forming apparatus according to any one of claims 1 to 5, wherein: