JP3657417B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus capable of simultaneously forming images on a plurality of surfaces, for example, with a digital color copying machine, a printer device, or the like, and particularly to prevention of useless printing.
[0002]
[Prior art]
In order to increase the color image forming efficiency in an image forming apparatus that forms a multicolor image of a document read by a document reading device or image information sent from a host device, for example, as disclosed in JP-A-4-175774 In addition, a two-screen color image having a reference image size can be formed on a photosensitive belt having a reference image size, for example, a length that is at least twice as long as the A4 size, as disclosed in JP-A-7-152259. As shown in the figure, the toner image formed on the photosensitive member is transferred onto two transfer sheets adsorbed on a transfer drum having a circumference of at least twice the reference image size to form a two-screen color image. So-called two-chamfering is adopted.
[0003]
A color copying machine or the like has an automatic color selection function that automatically determines whether a document is color or black and white without pre-scanning and switches between color copying and black and white copying to improve the copying speed. This automatic color selection function determines whether a document is a color image or a monochrome image in the first scan, and switches between color image formation processing and monochrome image formation processing accordingly.
[0004]
[Problems to be solved by the invention]
In the image forming process, the image forming interval and various operations are different between the color image forming process and the monochrome image forming process. For this reason, when the next operation is determined after one scan by the automatic color selection function, there is a case where the switching of the operation of the second sheet cannot be performed in the case of performing two-sided cutting.
[0005]
In addition, the color image formation process has more settings such as color settings and image quality settings than the black and white image formation process. When the start button is pressed, a setting error is noticed and copying is immediately stopped. Many. However, in the image forming process for forming a color image, a four-color toner image is created from when the start button is pressed until the printed transfer paper is discharged, and the image forming process is interrupted in order to superimpose the toner images. Doing so increases the load on the imaging system. For this reason, even if the stop button is pressed, it is not stopped immediately, but is often stopped after the image copy operation during image formation is completed. For this reason, when performing two-sided chamfering, two sheets of transfer paper on which a color image is printed are discharged, and the two-screen image forming process and two sheets of transfer paper are wasted even though the stop button is pressed. turn into.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that improves such disadvantages and can stably form a color image and prevent waste of transfer paper.
[0007]
[Means for Solving the Problems]
The image forming apparatus according to the present invention has an intermediate transfer belt capable of simultaneously transferring a plurality of toner images having a reference image size formed on a photosensitive member onto a transfer sheet, and transferring the toner image transferred to the intermediate transfer belt onto a transfer sheet. In an image forming apparatus for secondary transfer , when a document is a black and white image, it is selected that a toner image for a plurality of surfaces is formed on the intermediate transfer belt from the start of reading the document, and reading is started when the document is a color image. The image forming apparatus includes transfer mode selection means for forming a toner image of the first document on the intermediate transfer belt for one side and selecting forming a plurality of toner images on the intermediate transfer belt for the second and subsequent pages of the document. And
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The image forming apparatus of the present invention includes a document reading unit, an image forming unit, a primary transfer unit, a secondary transfer unit, a paper feed unit, and a fixing unit. The image forming unit forms an electrostatic latent image on the photosensitive member with a laser beam from the image writing unit, and visualizes the formed electrostatic latent image with a color developing unit to form a toner image. The primary transfer unit includes an intermediate transfer belt wound around a plurality of tension rollers, a primary transfer unit, a secondary transfer roller, a reference position sensor, and a cleaning unit. The toner image formed on the photosensitive member is transferred to the intermediate transfer belt. Primary transfer. The intermediate transfer belt has a length equal to or more than twice the length of the standard A4 size, and can transfer toner images for two surfaces at the same time. Two fiducial marks are provided at a certain interval in the image portion. The secondary transfer unit secondarily transfers the toner image transferred to the intermediate transfer belt onto the transfer paper. The control unit includes a central control unit that processes image information of the document read by the document reading unit and manages the operation of the entire apparatus, an automatic color selection unit, and a transfer mode selection unit.
[0011]
When a plurality of documents are set in the automatic document feeder, the start button is pressed, the first first of the set documents is sent to the document reading unit, and the first scan is started. From the image information obtained by scanning, it is determined whether the document set is a color image or a monochrome image. When the set original is a monochrome image, the transfer mode selection means selects a two-sided chamfering mode in which toner images for two sides are formed on the intermediate transfer belt of the primary transfer unit from the start of reading the original as the transfer mode. When the two-chamfer mode is selected, the central control unit transfers the toner image of the first document to the intermediate transfer belt at a predetermined timing after transferring the toner image of the first document to the intermediate transfer belt. Two toner images are formed on the intermediate transfer belt. The toner images for these two surfaces are transferred to transfer paper that is sequentially fed, fixed, and discharged.
[0012]
Further, the transfer mode selection means selects the special two-chamfer mode when the set original is a color image. When the special two-chamfering mode is selected, the central control unit 201 sequentially forms black (BK), cyan (C), magenta (M), and yellow (Y) toner images of the first document on the photosensitive member. Then, after transferring the formed full-color toner image on the intermediate transfer belt, the transfer of the second and subsequent original toner images to the intermediate transfer belt is performed in the two-chamfer mode.
[0013]
【Example】
FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. As shown in the figure, the image forming apparatus includes an image forming unit 100 including an image forming unit 1, a primary transfer unit 2, a secondary transfer unit 3, a paper feed unit 4, and a fixing unit 5, and a document reading unit 6. A display unit 7 and a control unit 200; The control unit 200 includes a central control unit 201 that processes image information of a document read by the document reading unit 6 and manages the operation of the entire apparatus, an automatic color selection unit 202, and a transfer mode selection unit 203.
[0014]
As shown in the configuration diagram of the image forming unit 100 in FIG. 2, the image forming unit 1 includes a charging charger 12 and an image writing unit 13 arranged around the photoconductor 11, black (BK), cyan (C), It has a rotary or fixed color developing unit 14 and a drum cleaning unit 15 made of magenta (M) and yellow (Y), and an electrostatic latent image is formed on the photosensitive member 11 by a laser beam from the image writing unit 13. And the formed electrostatic latent image is visualized by the color developing unit 14 to form a toner image. The primary transfer unit 2 includes an intermediate transfer belt 21, a primary transfer unit 22, a plurality of tension rollers 23, a secondary transfer roller 24, a reference position sensor 25, and a cleaning unit 26, and a toner image formed on the photoreceptor 11. Is primarily transferred to the intermediate transfer belt 21. The intermediate transfer belt 21 has a circumferential image length L that is at least twice as large as the reference image size, for example, A4 size, and can transfer toner images for two surfaces at the same time. A reference mark 27 is provided. The intermediate transfer belt 21 is separated from the surface of the photoconductor 11 by a contact / separation mechanism (not shown) except when the toner image on the photoconductor 11 is primarily transferred, and is pressed against the surface of the photoconductor 11 only when the toner image is primarily transferred. Is done. The secondary transfer unit 3 secondarily transfers the toner image transferred to the intermediate transfer belt 21 onto the transfer paper 8. The paper feed unit 4 includes a plurality of paper feed trays 41a to 41c.
[0015]
The image forming unit 100 configured as described above sets the reference mark 27 of the intermediate transfer belt 21 of the primary transfer unit 2 to the reference position as shown in the time chart of FIG. The toner image detected by the sensor 25 is primarily transferred onto the intermediate transfer belt 21 with reference to the mark detection signal. The secondary transfer unit 3 secondarily transfers the toner image onto the transfer paper 8 fed from, for example, the paper feed tray 41 a in accordance with the tip of the toner image transferred to the intermediate transfer belt 21, and the fixing unit 5 transfers the transfer paper 8. The toner image transferred to is fixed by heating and pressing. The toner remaining on the intermediate transfer belt 21 is collected by the cleaning unit 26.
[0016]
When two or more images are to be formed, the toner image formed on the photoconductor 11 is superimposed on the intermediate transfer belt 21 so that there is no color misregistration when the toner image is primarily transferred to the intermediate transfer belt 21. A reference mark 27 on 21 is detected by a reference position sensor 25, and the toner image formed on the photoconductor 11 is primarily transferred to the intermediate transfer belt 21 based on the mark detection signal. This primary transfer is repeated for each color. That is, when forming a two-color image, the intermediate transfer belt 21 is rotated twice, and when forming a full-color image, the intermediate transfer belt 21 is rotated four times as shown in the time chart of FIG. The black (BK), cyan (C), magenta (M), and yellow (Y) toner images formed on the photoconductor 11 with reference to the mark detection signal for each rotation are primarily transferred to the intermediate transfer belt 21. Then, the images of the respective colors are overlaid without misalignment. When the toner image of a predetermined color is primarily transferred to the intermediate transfer belt 21, the toner image is transferred to the transfer paper 8 fed in accordance with the front end of the toner image transferred to the intermediate transfer belt 21 by the secondary transfer unit 3. Next, the fixing unit 5 fixes the toner image transferred onto the transfer paper 8 by heating and pressing.
[0017]
The automatic color selection unit 202 of the control unit 200 sends a document set in an automatic document feeder (not shown) to the document reading unit 6 and scans the document with the document reading unit 6 for the first time. Determine whether. Whether the transfer mode selection unit 203 forms toner images for a plurality of surfaces on the intermediate transfer belt 21 of the primary transfer unit 2 from the start of reading the document, based on the determination result of the automatic color selection unit 202 and the instruction from the operation display unit 7. Then, it is selected whether the toner image of the first document on which the reading of the document has been started is formed on one surface of the intermediate transfer belt 21 and whether the toner images of a plurality of surfaces are formed on the intermediate transfer belt 21 after the second document. .
[0018]
An operation when a toner image of a reference size, for example, an A4 size image is simultaneously transferred to the intermediate transfer belt 21 by the image forming apparatus configured as described above will be described.
[0019]
When a plurality of documents are set on the automatic document feeder and the start button of the operation display unit 7 is pressed, the first one of the documents set on the automatic document feeder is sent to the document reading unit 6. The document reading unit 6 starts the first scan based on the mark detection signal of the reference mark 27 on the intermediate transfer belt 21. The automatic color selection unit 202 of the control unit 200 determines whether the set document is a color image or a monochrome image from the image information obtained by the first scan, and sends the determination result to the transfer mode selection unit 203. When the original set by the automatic color selection unit 202 is sent from the automatic color selection unit 202 to the transfer mode selection unit 203, the toner image for two sides from the start of reading the document is transferred to the intermediate transfer of the primary transfer unit 2 as the transfer mode. A two-chamfer mode to be formed on the belt 21 is selected and sent to the central control unit 201. When the two-chamfering mode is selected as the transfer mode, the central control unit 201 transfers the toner image 9a of the first original to the intermediate transfer belt 21 with reference to the reference mark 27 as shown in FIG. The toner image 97b of the second original is transferred to the intermediate transfer belt 21 at a predetermined timing, and the toner images 7a and 7b transferred to the intermediate transfer belt 21 are fed to the paper feed tray 41a on which the A4-size transfer paper 8 is set. To the transfer paper 8 continuously fed from the second transfer.
[0020]
Further, when the automatic color selection unit 202 sends that the original set as a color image is sent from the automatic color selection unit 202, the transfer mode selection unit 203 uses the intermediate transfer belt 21 as a transfer mode to transfer the toner image of the first original that has been read. A special two-chamfering mode in which the second and subsequent documents are formed in the two-chamfering mode is selected and sent to the central control unit 201. When the special two-chamfer mode is selected as the transfer mode, the central control unit 201 forms a black (BK) toner image of the first original on the photosensitive member 11 as shown in the time chart of FIG. The transferred toner image is transferred to the intermediate transfer belt 21, and subsequently, cyan (C), magenta (M), and yellow (Y) toner images of the first document are formed on the photoconductor 11 and then transferred to the intermediate transfer belt 21. Overlapping. When a full-color toner image is formed on the intermediate transfer belt 21, it is transferred to the transfer paper 8, fixed, and discharged. Subsequently, after the two-sided chamfering mode, toner images for two sides of the second document and the third document are transferred to the intermediate transfer belt 21, and from the paper feed tray 41a on which the A4 size transfer paper 8 is set. Secondary transfer is performed on transfer paper 8 that is continuously fed.
[0021]
As described above, when the document is a color image, the toner image of the first document is transferred to the intermediate transfer belt 21 by one side. Therefore, there is a setting error such as color setting or image quality setting, and the operation display unit 7 When the stop button is pressed, only the transfer sheet 8 onto which the first image is transferred is discharged, and it is possible to prevent waste of the transfer sheet 8 when there is a setting error.
[0022]
In the above embodiment, the case where it is determined whether the original set by the automatic color selection unit 202 is a color image or a black-and-white image has been described. However, when forming a color image, the operation display unit 7 sets a color image of an odd number of documents. Is selected, or when it is selected to form an odd number of color images with one original, the transfer mode selection unit 203 may select the special two-chamfer mode. Thus, even when the special two-chamfering mode is selected when forming an odd number of color images, the toner image to be transferred to the intermediate transfer belt 21 at last is only for two surfaces, and all the images are recorded. The formation time is almost the same as when the two-chamfer mode is selected, and a high-quality color image can be stably formed without reducing the image forming speed.
[0023]
【The invention's effect】
As described above, according to the present invention, a toner image of the first document that is read when the document is a color image is formed on one surface of the intermediate transfer belt, and a plurality of toner images are formed on the second and subsequent pages of the document. By selecting to form the image on the intermediate transfer belt, the first image was transferred when the stop button was pressed due to a setting error such as color setting or image quality setting when forming a color image. Since only the transfer sheet is discharged, it is possible to prevent the transfer sheet from being wasted when there is a setting error.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a configuration diagram of an image forming unit in the embodiment.
FIG. 3 is a time chart showing an image forming process of a one-color document.
FIG. 4 is a time chart showing image forming processing of a full-color original.
FIG. 5 is a layout diagram illustrating a toner image transferred to an intermediate transfer belt by two chamfering.
FIG. 6 is a time chart showing image forming processing in a special two-chamfer mode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Primary transfer unit 3 Secondary transfer unit 4 Paper feed unit 5 Fixing unit 6 Document reading unit 7 Operation display unit 100 Image forming unit 200 Control unit 201 Central control unit 202 Automatic color selection unit 203 Transfer mode selection unit

Claims (1)

In an image forming apparatus having an intermediate transfer belt capable of simultaneously transferring a plurality of toner images of a reference image size formed on a photosensitive member onto a transfer sheet, and secondarily transferring the toner image transferred to the intermediate transfer belt onto a transfer sheet.
When the original is a black and white image, it is selected to form a toner image for a plurality of surfaces on the intermediate transfer belt from the start of reading the original, and when the original is a color image, the toner image of the first original that has been read is intermediate An image forming apparatus comprising transfer mode selecting means for forming one surface on a transfer belt and selecting to form toner images on a plurality of surfaces on an intermediate transfer belt for the second and subsequent sheets of a document.

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