JP2001188441A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the overall throughput and the durability of a device even in the case of printing a document in which various colors coexist and also to reduce the printing cost. SOLUTION: A CPU 101 discriminates the size of paper fed from a paper- feeding cassette when both-side printing is specified from a controller 112 and also at least the printing data of two-page portion is inputted, and recognizes color information used at the time of deciding a printing mode from the printing data of each page in the case the size is equal to or smaller than the size A4 and holds it in a RAM 103, and compares the color information corresponding to one surface and the other surface of the same paper used for the printing of two-page portion which is the next object of both-side printing out of it, and changes the color information for a monochromatic mode to that for a color mode in the case that one is the color information for the color mode and the other is that for the monochromatic mode, and then determines the printing mode based on the color information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color image forming apparatus such as a color laser printer, a digital color copying machine, and a digital color multifunction machine.

[0002]

2. Description of the Related Art As a color image forming apparatus such as a color laser printer, a color mode in which printing is performed using four colors of Y (yellow), M (magenta), C (cyan), and K (black), or printing using only K. The print mode is automatically switched to the monochrome (black and white) mode by determining the color information (indicating the type of color and the number of colors) of the print data every time one page (one sheet) is printed. A method has been proposed in which the print mode is switched or the print mode is automatically switched for each job.

[0003] As a printing method in the color mode (however, a printing method using electrophotography), for example, a one-color toner image is formed on one drum-shaped or belt-shaped photoreceptor to form a drum-shaped or belt-shaped photoconductor. There is a method in which a process of transferring a toner image of a plurality of colors is repeatedly performed for each color by repeatedly performing a process of transferring the toner image on the intermediate transfer member, and then the toner images of the plurality of colors are collectively transferred onto one sheet of paper.

In the above-described system (hereinafter, referred to as "one photoconductor system"), in order to perform printing in the color mode, a transfer process (transfer of a toner image from a photoconductor to an intermediate transfer body) is performed.
Need to be performed for the number of colors using the printing process (printing step) that includes.

That is, when printing a monochrome image using only black toner (consisting of white and black) or printing a monocolor image using only a single color toner other than black, a two-color toner is used once. The above-described printing is performed twice when printing a color image using the above-described method, three times when printing a color image using the three-color toner, and four times when printing a full-color image using the four-color toner. Need to go through the process.

Here, a normal document to be printed is a monochrome document composed of monochrome pages (monochrome images), a color document composed of color pages (color images), and a mixture of monochrome pages and color pages. And monochrome mixed color documents (color mixed documents).

[0007]

In the above-described color image forming apparatus using the one-photoconductor method, the print mode is automatically switched by discriminating the color information of the print data every time one page is printed. If you use the method
Depending on the document to be printed, there is a problem that switching the print mode adversely lowers the performance and lowers the durability of the apparatus (parts).

On the other hand, when a method of automatically switching the print mode for each job is used, a color image may be printed as a monochrome image, or a monochrome image may be printed in the color mode. There are problems that the cost increases and the durability of the device decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is intended to provide a color image forming apparatus such as a color laser printer, and more particularly, a color image forming apparatus using a one-photoreceptor system and capable of performing double-sided printing. Even when printing a plurality of pages (mixed color documents) in which monochrome pages are mixed, an object is to improve the overall throughput and the durability of the apparatus and reduce the printing cost.

[0010]

According to the present invention, there is provided a paper feeding means for feeding paper, a printing means for printing a color image or a monochrome image on paper, and a paper feeding means for feeding paper, and Reversing / re-feeding means for reversing and re-feeding the paper on which the color image or monochrome image has been printed on the surface, and the other surface of the paper re-fed by the reversing / re-feeding means In order to achieve the above object, a color image forming apparatus in which a color image or a monochrome image is printed by the printing means is characterized as follows.

According to a first aspect of the present invention, double-sided printing is specified,
And color information recognition and holding means for recognizing and holding color information used when determining a print mode from the print data of each page when print data for at least two pages is input; Of the color information of each page, color information corresponding to one side and the other side of the same sheet used for printing the next two pages to be subjected to double-sided printing is compared, and one is used for color mode. If the other color information is monochrome mode color information, the color information is stored in the color information changing unit for changing the monochrome mode color information to the color mode color information and the color information recognition and holding unit. Print mode determining means for determining a print mode based on color information.

According to a second aspect of the present invention, in the color image forming apparatus of the first aspect, the color information of the next page to be printed is the color information for the color mode.
The next page belongs to the other side of the sheet on which one side has already been printed, and there is print data necessary for feeding the next sheet by the sheet feeding means, and the next page is recognized from the print data. If the color information is the color information for the color mode, the print mode corresponding to the paper re-fed by the reversing / re-feeding means and the paper fed next by the paper feeding means is set to each paper. And a means for determining a two-color printing mode in which the printing processes of the respective colors are performed substantially in parallel.

According to a third aspect of the present invention, in the color image forming apparatus of the first aspect, there is provided a paper size determining means for determining the size of the paper fed by the paper feeding means, and the print mode determining means includes a paper size determining means. Only when the size determined by the means is equal to or smaller than the predetermined size, the color information of the next page to be printed is the color information for the color mode, and the next page is a sheet of paper on which one side has already been printed. If there is print data belonging to the other side and necessary to feed the next sheet by the sheet feeding means, and the color information recognized from the print data is color information for a color mode, A print mode corresponding to a sheet re-fed by the reversing / re-feeding means and a sheet fed next by the sheet feeding means are set in such a manner that the printing processes of the respective colors on the respective sheets are performed substantially in parallel. Single and in those having a means for determining the mode.

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a diagram illustrating a configuration example of a mechanism of a color image forming apparatus embodying the present invention.

In this color image forming apparatus, reference numeral 1 denotes a flexible belt-shaped photoreceptor (hereinafter referred to as a "photoreceptor belt") as an image carrier, which is rotatably supported by rotating rollers 2 and 3. Is driven in the direction of arrow A (clockwise) by the driving of the rotation roller 2. On the outer peripheral portion of the photoreceptor belt 1,
A charging charger 4 as charging means for uniformly charging the surface of the photoreceptor belt 1 is provided.

At the downstream position of the charger 4, there is an optical writing section to which a laser beam emitted from a laser writing unit 5 as an exposure means is irradiated. A color developing device 6 in which a plurality of developing devices (developing means) are supported so as to be switchable is disposed downstream of the optical writing unit. The color developing device 6 includes Y (yellow), M (magenta), C (cyan), and K (black), which will be described later.
The four developing devices having the four color developers (toners) are integrally formed.

Reference numeral 10 denotes an intermediate transfer belt, which is an intermediate transfer member. The intermediate transfer belt is rotatably supported by rotating rollers 11 and 12, and is rotated in the direction of arrow B (counterclockwise) by driving the rotating roller 11. You. The intermediate transfer belt 10 is in contact with the photosensitive belt 1 at the position of the rotating roller 3. A bias roller 13 having conductivity is in contact with the back surface of the intermediate transfer belt 10 at the contact portion under predetermined conditions.

Here, the printing (image forming) operation of the color image forming apparatus will be described. After the surface of the photoreceptor belt 1 is uniformly charged by the charging charger 4,
The laser writing unit 5 performs scanning exposure with laser light modulated according to print data (image data), and forms an electrostatic latent image on the surface. At this time, a laser beam generated by a semiconductor laser (not shown) based on the print data is scanned and adjusted by an optical system including a polygon mirror (not shown).

The print data indicates bitmap image data (video data), and is roughly divided into color print data and monochrome print data, of which full-color print data (separated into four colors) is used as color print data. Single-color image data), color print data (two-color or three-color)
There are monochromatic print data (monochromatic image data other than black) and monochromatic print data (monochromatic image data other than black).

For example, an electrostatic latent image sequentially formed on the surface of the photoreceptor belt 1 by scanning exposure of a laser beam modulated according to full-color print data is Y, M, C, and K by a color developing device 6, respectively. , And a single color toner image is sequentially formed.

Each single-color toner image formed on the surface of the photoreceptor belt 1 is biased on the surface of the intermediate transfer belt 10 in synchronism with the photoreceptor belt 1 for each of Y, M, C, and K single colors. The images are sequentially transferred and superimposed by a predetermined transfer bias applied to the roller 13.

Y, M, C, K toner images (full color toner image) superimposed on the intermediate transfer belt 10
Is supplied from a paper supply cassette 17 constituting a paper supply means by a paper supply roller 18, and passes through a pair of conveyance rollers 19 and a pair of registration rollers 20 to a transfer portion (a contact portion between the intermediate transfer belt 10 and the transfer roller 14). Conveyed paper (transfer paper)
The batch transfer is performed by the transfer roller 14.

After the transfer process is completed, the sheet on which the full-color toner image has been transferred is sent to the fixing device 50, where the full-color toner image is fixed, and the full-color image is completed. The paper is discharged to a paper discharge tray 52 outside the apparatus. Each unit related to a printing operation including the above-described laser writing unit 5, color developing device 6, transfer roller 14, and fixing device 50 constitutes a printing unit.

On the other hand, when double-sided printing is designated, the sheet on which the full-color image has been printed on one side (the sheet that has passed through the discharge roller pair 51) is a double-sided unit serving as a reversing / re-feeding unit. After being inverted and re-fed, the image forming / transfer /
The fixing process is performed in the same manner as described above, and a full-color image is printed on the other surface.

Here, the duplex unit will be described more specifically.
0, a transport unit 70, and a reversing unit 80. When double-sided printing is specified, the paper that has passed through the paper discharge roller pair 51 has its transport path switched by the switching lever 61 in the paper discharge unit 60, passes under the paper discharge tray 52, and passes through the transport unit 7.
0 and is conveyed to the reversing unit 80.

The sheet conveyed to the reversing unit 80 is reversed by the reversing roller 81 and the direction is changed. The sheet which has been the rear end becomes the leading end, and is fed again by the reverse rotation of the reversing roller 81. The sheet is conveyed toward each unit constituting the printing unit so that the full-color image is printed on the surface.

This color image forming apparatus has an electrical equipment / control device 100 mounted thereon. In this embodiment, the operation for obtaining a full-color image (an image in four colors) has been described. However, a color image (an image in two or three colors), a mono-color image (a single-color image other than black),
When a monochrome image is obtained, the same operation as described above is performed for the designated color and the number of colors. Further, in this embodiment, the intermediate transfer belt 10 is used as the intermediate transfer body, but an intermediate transfer drum can be used.

FIG. 3 is an enlarged view showing a part of the color image forming apparatus. For convenience of illustration, the arrangement angle of the intermediate transfer belt 10 and the like is changed. At the end (outside the image area) of the intermediate transfer belt 10, a plurality of light reflector marks 41 (only one is shown) are arranged at regular intervals. The first-color laser writing (electrostatic latent image) is started based on the detection timing of an arbitrary mark by the detection sensor 40, and the second-color laser is generated based on the re-detection timing of the mark after the intermediate transfer belt 10 makes one rotation. Start writing.

For example, when print data (image information) input from an image reader (not shown) separate from the color image forming apparatus is input to the laser writing unit 5, the laser writing unit 5 A laser beam modulated in accordance with the print data is generated from the semiconductor laser 5E, and the laser beam is
A is scanned in the main scanning direction by a polygon mirror 5B rotated by A, and after passing through an fθ lens 5C, the mirror 5
The light path is bent by D, and the light is irradiated onto the peripheral surface of the photosensitive belt 1 uniformly charged by the charging charger 4.

At this time, the laser beam scanned in the main scanning direction by the polygon mirror 5B is detected by the synchronization detecting sensor 5F (outside the image area) before being irradiated on the photosensitive belt 1 in one main scanning. This synchronization detection sensor 5
The detection signal from F is used as a synchronization detection signal for timing the scanning of the laser beam by the polygon mirror 5B.

In this example, the print data input from the image reading device is used. However, print data transmitted from a host device such as a personal computer may be used. However, if the print data transmitted from the host device is code data, it is necessary to develop it into bitmap image data (video data).

FIG. 1 is a block diagram showing an example of the configuration of the electrical equipment / control device 100. The CPU 101, ROM 102, R
AM 103, nonvolatile memory 104, host interface (hereinafter, "interface" is referred to as "I / F") 1
05, image writing circuit 106, phase control circuit 107, various sensor I / Fs 108, various actuator I / Fs 10
9, system bus 110, and image data bus 111
And so on.

The CPU 101 is a central processing unit that operates in accordance with a control program in the ROM 102 to control the entire electric device / control device 100 as a whole. It can function as a change unit, a print mode determination unit, and a paper size determination unit. The ROM 102 includes the CPU 10
1 is a read-only memory that stores various fixed data including a control program for operating 1.

The RAM 103 is a readable / writable memory used as a work memory for processing data by the CPU 101, a bit map memory, a color information memory, and the like.
Here, it is assumed that the bitmap memory has a capacity capable of storing A3 size full-color print data. As a result, it is possible to store two pages of A4 size full-color print data having an area 1/2 of the A3 size. Also, for A4 size monochrome print data, eight pages can be stored. Non-volatile memory 1
Reference numeral 04 denotes a memory for storing device-specific data.

The host I / F 105 is connected to the controller 11
2 controls transmission and reception of commands and status information and reception of print data (image data). Further, the received print data is transferred to the image writing circuit 106 via the image data bus 111. However, if the capacity of the system bus 110 is sufficient, the print data can be transferred to the image writing circuit 106 using the system bus 110 without using the image data bus 111.

The image writing circuit 106 includes a host I / F 10
The print data transferred from the printer 5 is subjected to processes such as gradation conversion and gamma correction, and is transferred to the LD modulation circuit 113 of the laser writing unit 5. LD modulation circuit 1
Reference numeral 13 denotes voltage / voltage data for printing from the image writing circuit 106.
The semiconductor laser 5E is converted into a current and supplied to the semiconductor laser 5E, and the semiconductor laser 5E is modulated (ON / OFF). At this time, the modulation drive is performed in synchronization with the pixel clock sent from the phase control circuit 107 via the image writing circuit 106.

The phase control circuit 107 includes a polygon motor 5
In addition to controlling the phase of the motor synchronization signal output to A,
Processing such as correcting a deviation of a pixel clock given to the LD modulation circuit 113 is performed. The various sensor I / Fs 108 are the synchronization detection sensor 5F and the mark detection sensor 4 shown in FIG.
A signal for detecting the state of the device output from various sensors including 0 is input.

Various actuator I / Fs 109 include ON / OF for operating or stopping a motor or a solenoid.
Outputs F signal. The system bus 110 is a signal line for mutually connecting each unit in the electrical equipment / control device 100. The image data bus 111 is a signal line for directly transferring print data from the host I / F 105 to the image writing circuit 106.

The controller 112 is connected to a printer or a digital copier, and performs predetermined processing on print data sent from a host device such as a personal computer or image data read by an image reading device (scanner). (If the print data from the host device is code data, it includes a process of converting the code data into bitmap image data.)
Transfer to

Next, a printing sequence in full-color printing in the color mode in the color image forming apparatus of this embodiment will be described with reference to FIGS. The numbers described in each of FIGS. 4 to 6 indicate page numbers to be printed.

Further, in the color image forming apparatus of this embodiment configured as shown in FIG. 2, printed paper is discharged to the discharge tray 52 in a face-down manner. Accordingly, at the time of double-sided printing, printing on paper is performed in the order of the back surface (even number pages) → the front surface (odd number pages).

FIG. 4 is a diagram showing an example of a printing sequence at the time of A3-size full-color printing (printing of a plurality of full-color pages) in the color mode (color one-color mode in this example) in the color image forming apparatus.

In this example, a printing process of each color (full color) is performed on the back side (second page) of the sheet first fed from the sheet feeding cassette 17, and the sheet is fed to the duplex unit (the sheet discharging section of FIG. 2). Unit 60, transport unit 70,
After being conveyed to the reversing unit 80 and turned over, the front side (1
The printing process of each color is performed on the page (page), and the paper on which both sides (the first and second pages) have been printed is discharged to the paper discharge tray 52.

Subsequently, a printing process of each color is performed on the back side (fourth page) of the sheet fed next from the sheet feeding cassette 17, and the sheet is conveyed to the duplex unit and turned over. The printing process of each color is performed on the front side (page 3) of the sheet re-fed from the duplex unit, and the sheet on which the printing on both sides (pages 3 and 4) is completed is discharged to the discharge tray 52. You.

By the way, as can be seen from FIG.
When performing full-color printing of a size (larger than A4 size), it is necessary to wait for four colors to be re-fed from the duplex unit until the paper on which the back surface (one surface) has been printed (the back surface is already printed) is re-fed. Since the transfer process needs to be performed, the time T2 required for the transfer process for one color needs to be about ４ or less of the refeeding time T3.

FIG. 5 is a diagram showing an example of a printing sequence at the time of full-color printing of A4 size in a color mode (two-color printing mode in this example) in the color image forming apparatus. In this example, a printing process of each color (full color) is performed on the back surface (second page) of the sheet first fed from the sheet feeding cassette 17.

After the sheet is conveyed to the duplex unit and turned over, the printing process of each color on the front side (page 1) of the sheet re-fed from the duplex unit and the next feeding from the sheet cassette 17 are performed. Back side of paper (4
The printing process of each color for the page is performed substantially in parallel. At this time, sheet feeding from the sheet feeding cassette 17 is performed first, followed by sheet re-feeding from the duplex unit.
Two sheets are continuously fed to the transfer unit.

The sheet on which the printing on the back side (4th page) is completed is conveyed to the duplex unit and inverted, and the sheet on which the printing on both sides (1st and 2nd pages) is completed is ejected to the ejection tray 52.

Next, the printing process of each color on the front side (page 3) of the sheet re-fed from the duplex unit and the printing of each color on the back side (page 6) of the sheet fed next from the sheet cassette 17 are described. The processes are performed substantially in parallel. At this time, re-feeding from the duplex unit is performed first, followed by feeding from the paper feed cassette 17, and
Sheets of paper are continuously fed to the transfer unit.

The sheet on which printing on both sides (pages 3 and 4) has been completed is discharged to the sheet discharge tray 52, and the back side (page 6).
The sheet on which printing has been completed is conveyed to the duplex unit and turned over. Thereafter, a printing process of each color is performed on the front side (fifth page) of the sheet re-fed from the duplex unit. The sheet on which the printing of the (page) is completed is discharged to the discharge tray 52.

Incidentally, in the case of the A4 size having an area occupied by half of the A3 size, the time T1 required for the transfer processing is also A
Only half the time T2 required for the transfer process in the case of three sizes is required. For this reason, when the print data of the front side (odd number page) is to be printed, if the print data of the back side (even number page) of the next sheet is complete, the two pages of print data are used to print two sheets of color. Full-color printing can be performed in the skip mode (a mode in which printing processes of each color on paper re-fed from the duplex unit and paper fed next from the paper feed cassette 17 are performed substantially in parallel).

Even when A4 size paper is used, the sequence for performing full-color printing in the single color printing mode (normal color mode) uses the A3 size paper shown in FIG. It is the same as when

Hereinafter, the processing according to the present invention in the color image forming apparatus will be specifically described with reference to FIGS. FIG. 6 is a diagram illustrating an example of a print sequence in mixed color printing of A4 size (printing of a plurality of pages in which color pages and monochrome pages are mixed) in the color image forming apparatus.

FIG. 7 is a flowchart showing a main routine of a process related to printing by the CPU 101 of FIG. This processing corresponds to print data and paper of A4 size (predetermined size) or less.
If the bitmap memory No. 3 can store two or more pages of A3 size full color print data, it can also handle A3 size print data and paper. However, the processing of FIG. 9 described later can be applied only to print data and paper of A4 size (predetermined size) or less.

When double-sided printing is designated by the controller 112 and print data of at least two pages is input, the CPU 101 stores the print data of each page in the RAM.
After storing the data in the bitmap memory 103, the size of the paper (print data size) fed from the paper feed cassette 17 is determined (however, the bitmap memory of the RAM 103 stores more than two pages of A3 size full-color print data). If the size is smaller than A4 size, the color information (color type and number of colors) used to determine the print mode from the print data of each page is recognized. It is stored in the color information memory of the RAM 103.

For example, when color information is added to the input print data of each page, the color information is sequentially recognized, a page number is assigned, and the color information is stored in the color information memory of the RAM 103. Alternatively, when color information is not added to the input print data of each page, each print data is sequentially analyzed to generate color information, and each color information is assigned a page number and the color information of the RAM 103 is added. Keep in memory.

Further, processing for determining the order of print pages is also performed. Thereafter, the process of FIG. 7 is started, the color information change process is performed in step S1, the print mode determination process is performed in step S2, and the print process is performed according to the print mode determined in step S3.

FIG. 8 is a flowchart showing a subroutine of the color information changing process of FIG. First, in step S11, the CPU 101 sets the color information of each page held in the color information memory of the RAM 103 to the next page to be printed (one of the pages to be printed next) on the same sheet. Which page belongs to the color information of the page belonging to the back side, the color information of the page belonging to the back side is compared with the color information of the page belonging to the front side of the same paper (which is a pair of the color information of the page belonging to the back side). Step S for comparison
Move to 12.

If the color information of the next page to be printed is the color information of a page belonging to the front side, the comparison has already been completed, and the process returns to the main routine of FIG.
In step S12, it is determined whether the color information of the page belonging to the back side is the same as or different from the color information of the page belonging to the front side. If the color information is different, the existence of the color information (monochrome page) for the monochrome mode is determined. The process proceeds to step S13 to confirm the presence or absence.

If the color information of the page belonging to the back side is the same as the color information of the page belonging to the front side, the page shown in FIG.
Returns to the main routine. In step S13, one of the two pages of color information (color information corresponding to one side and the other side of the same sheet used for printing two pages) to be subjected to the next two-sided printing is used for the monochrome mode. It is determined whether or not the color information is color information. If the color information is for monochrome mode, the process proceeds to step S14.

Each of the color information for two pages to be subjected to the next two-sided printing (color information corresponding to one side and the other side of the same sheet used for printing two pages) is color information for monochrome mode. If not, the process returns to the main routine of FIG. In step S14, the color information for the monochrome mode is changed to the color information for the color mode, and the process returns to the main routine of FIG.

FIG. 9 is a flowchart showing a subroutine of the print mode determining process of FIG. CPU101
First, in step S21, it is determined whether the color information of the next page to be printed is color information for the monochrome mode among the color information for the next two pages to be printed on both sides, and the color information for the monochrome mode is determined. If it is information, the print mode is determined to be the monochrome mode in step S27, and the process returns to the main routine of FIG.

If the color information of the next page to be printed is the color information for the color mode, it is determined in step S22 which color information the page belongs to which side of the paper, and the color information belongs to the back side. If it is page color information, step S
At 26, the printing mode is determined to be the single color printing mode, and the process returns to the main routine.

In the color two-sheet printing mode, the printing process of each color on the front side of the sheet (the sheet on which the back side is printed) re-fed from the duplex unit and the next sheet feeding from the sheet feeding cassette 17 are performed. This is because the printing process of each color on the back surface of the sheet is performed in substantially parallel.

If the color information of the next page to be printed is the color information of a page belonging to the front side of the sheet (one side of the sheet already printed is the other side), the bit map of the RAM 103 is read in step S23. It is determined whether there is print data necessary to feed the next sheet from the paper feed cassette 17 in the memory. If there is no print data, the print mode is determined to be the single color printing mode in step S26.
Return to the main routine.

If the bit map memory of the RAM 103 has print data necessary for feeding the next sheet from the paper feed cassette 17, color information recognized from the print data also exists. It is determined whether or not the color information is color mode color information. If not, the printing mode is determined to be the single color printing mode in step S26, and the process returns to the main routine.

If the color information recognized from the print data necessary to feed the next sheet is the color information for the color mode, the printing mode is determined to be the two-color printing mode in step S25, and the main routine is executed. Return to

Here, a printing sequence in A4 size mixed color printing (printing of a plurality of pages in which color pages and monochrome pages are mixed) in the color image forming apparatus will be briefly described with reference to FIG. In the example of FIG. 6, a printing process of each color (full color) is performed on the back surface (second page) of the sheet first fed from the sheet feeding cassette 17.

Then, after the sheet is conveyed to the duplex unit and turned over, the printing process of each color (the print sequence and timing are performed on the front side (page 1)) of the sheet re-fed from the duplex unit. The process is the same as the process, but the printing process for each color (same as the first page) on the back surface (the fourth page) of the paper to be fed next from the paper feed cassette 17 is performed. Perform almost in parallel. At this time, sheet feeding from the sheet feeding cassette 17 is performed first, followed by re-feeding from the duplex unit, and two sheets are continuously fed to the transfer unit.

The sheet on which the printing on the back side (4th page) is completed is conveyed to the duplex unit and inverted, and the sheet on which the printing on both sides (1st and 2nd pages) is completed is discharged to the discharge tray 52.

Next, the printing process of each color on the front side (page 3) of the paper re-fed from the duplex unit (the printing sequence and timing are the same as those of the full-color printing process, but actually the printing process of the YMC printing process). ) And the printing process of each color on the back surface (6th page) of the paper fed next from the paper feed cassette 17 (the printing sequence and timing are the same as those in the full-color printing process, but actually only Y printing is performed). Process) is performed substantially in parallel. At this time, re-feeding from the duplex unit is performed first, followed by feeding from the sheet feeding cassette 17, and two sheets are continuously fed to the transfer unit.

The sheet on which printing on both sides (3rd and 4th pages) has been completed is discharged to the discharge tray 52, and the back side (6th page).
The paper on which printing has been completed is conveyed to the duplex unit, turned over, and then subjected to the printing process of each color (the printing sequence and timing are changed to the full color printing process) on the front side (page 5) of the paper re-fed from the duplex unit. As in the case described above, the printing process of the MC is actually performed, and the paper on which both sides (pages 5 and 6) have been printed is discharged to the paper discharge tray 52.

As described above, in the color image forming apparatus of this embodiment, when double-sided printing is specified and print data of at least two pages is input,
7 to determine the size of the paper to be fed, and when the size is smaller than A4 size, recognizes and retains color information to be used when determining a print mode from the print data of each page. The color information corresponding to one side and the other side of the same sheet of paper used for printing the next two pages of two-sided printing is compared, and one is for color mode and the other is for monochrome mode. If it is color information, the monochrome mode color information is changed to color mode color information, and then the print mode is determined based on the color information.

At this time, the color information of the next page to be printed is the color information for the color mode, and the next page belongs to the other side of the already printed sheet, and If there is print data necessary to feed the next sheet from the cassette 17 and the color information recognized from the print data is color information for the color mode, the sheet is fed again from the duplex unit. The printing mode corresponding to the sheet and the sheet to be fed next from the sheet feeding cassette 17 is determined to be the color two-sheet mode in which the printing process of each color for each sheet is performed substantially in parallel.

Thus, even when printing a plurality of pages in which color pages and monochrome pages are mixed, a series of printing sequences and timing are kept constant, and control is simplified. Accordingly, the overall throughput and the durability of the apparatus are improved, and the printing cost can be reduced. Further, since the number of times of printing in the two-color printing mode is increased, efficient mixed color printing can be performed.

In step S24 of FIG. 9, the color information of the page belonging to the surface of the sheet, which is the color information of the next page to be printed, and the color recognized from the print data necessary for feeding the next sheet. Determine if the information matches,
If they match, the print mode is set to color 2 in step S25.
The mode may be determined to be the retrieving mode.

If the bitmap memory of the RAM 103 can store two pages or more of A3-size full-color print data, the size of the paper fed from the paper feed cassette 17 immediately before starting the processing of FIG. It is preferable to determine whether the size is equal to or smaller than the A4 size (predetermined size), and if the size is equal to or smaller than the A4 size, the determination in step S21 in FIG. 9 is performed.

[0078]

As described above, according to the color image forming apparatus of the present invention, when double-sided printing is specified and at least two pages of print data are input,
Recognizes and holds the color information used when determining the print mode from the print data of each of the above pages, and stores one side of the same paper used for printing two pages of the next two-sided print target. And color information corresponding to the other surface, and if one is color mode color information and the other is monochrome mode color information, the monochrome mode color information is replaced with the color mode color information. After changing to the information, the print mode is determined based on the color information, so even when printing multiple pages where color pages and monochrome pages are mixed, a series of print sequences and timing are kept constant, simplifying control. Be transformed into Accordingly, the overall throughput and the durability of the apparatus are improved, and the printing cost can be reduced.

According to the second aspect of the present invention, the color information of the next page to be printed is the color information for the color mode, and the next page is the other side of the sheet on which one surface has already been printed. If there is print data necessary to feed the next sheet by the sheet feeding means and the color information recognized from the print data is color information for the color mode, -The print mode corresponding to the paper re-fed by the paper re-feeding means and the paper fed next by the paper feeding means is changed to the two-color printing mode in which the printing process of each color for each paper is performed substantially in parallel. Since the determination is made, the number of times of printing in the two-color printing mode increases, and more efficient mixed color printing becomes possible.

Further, according to the third aspect of the present invention, the size of the paper fed by the paper feeding means is determined, and when the size is equal to or smaller than a predetermined size (the condition for realizing the color two-sheet mode), Only the color information of the next page to be printed is the color information for the color mode, and the next page belongs to the other side of the sheet on which one side has already been printed, and If there is print data required to feed the paper and the color information recognized from the print data is color information for the color mode, the paper re-fed by the reversing / re-feeding means Since the printing mode corresponding to the paper fed next by the paper feeding means is determined to be the two-color printing mode in which the printing process of each color on each paper is performed substantially in parallel, the processing is wastefully performed. Lost , Allowing more efficient color mixing printing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of an electric device / control device 100 of FIG.

FIG. 2 is a diagram illustrating a configuration example of a mechanism of a color image forming apparatus embodying the present invention;

3 is an enlarged view showing a part of the color image forming apparatus shown in FIG. 2;

FIG. 4 is a diagram illustrating an example of a print sequence at the time of full-color printing of A3 size in a color mode in the color image forming apparatus illustrated in FIG. 2;

FIG. 5 is a diagram illustrating an example of a printing sequence at the time of full-color printing of A4 size in a color mode in the color image forming apparatus illustrated in FIG. 2;

FIG. 6 illustrates an A4 image in the color image forming apparatus illustrated in FIG. 2;
FIG. 7 is a diagram illustrating an example of a print sequence during mixed color printing of sizes.

FIG. 7 is a flowchart showing a main routine of processing relating to printing by a CPU 101 in FIG. 1;

FIG. 8 is a flowchart showing a subroutine of a color information change process of FIG. 7;

FIG. 9 is a flowchart showing a subroutine of a print mode determination process in FIG. 7;

[Explanation of symbols]

 1: Photoreceptor belt 5: Laser writing unit 60: Discharge unit 70: Transport unit 80: Reversing unit 100: Electrical equipment / control device 101: CPU 102: ROM 103: RAM 104: Non-volatile memory 106: Image writing circuit 107 : Phase control circuit 108: Various sensor I / F 109: Various actuator I / F 112: Controller 113: LD modulation circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H04N 1/46 H04N 1/46 C5C079 F term (Reference) 2H027 DB02 DC19 FA11 FA13 FB11 ZA07 2H028 BB01 2H030 AD08 AD16 5C062 AA05 AB42 AC04 AC09 AC11 AC21 AC24 AC67 AE03 AF00 BA04 5C074 AA12 BB02 DD24 EE20 FF15 HH02 5C079 HA13 KA03 LB11 NA11 NA21 PA02

Claims (3)

[Claims] 1. A paper feeding unit for feeding a sheet, a printing unit for printing a color image or a monochrome image on a sheet, and a color image or a monochrome image fed to one side by the printing unit and fed by the paper feeding unit Reversing / re-feeding means for reversing and re-feeding the paper on which the image printing has been completed, and the other side of the paper re-fed by the reversing / re-feeding means is also provided by the printing means. In a color image forming apparatus capable of printing a color image or a monochrome image, when double-sided printing is specified and at least two pages of print data are input, a print mode is determined from the print data of each page. Color information recognition and holding means for recognizing and holding color information to be used when printing, and for printing two pages of the next two-sided printing target among the color information of each page held by the means. The color information corresponding to one side and the other side of the same paper to be used is compared, and if one is color mode color information and the other is monochrome mode color information, the monochrome mode color information is used. Color information changing means for changing color information into color mode color information; and a print mode determining means for determining a print mode based on the color information held in the color information recognition and holding means. Color image forming apparatus. 2. The color image forming apparatus according to claim 1, wherein the print mode determining unit determines that color information of a next page to be printed is color information for a color mode, and that the next page is already one. Side belongs to the other side of the printed paper,
If there is print data necessary for feeding the next sheet by the sheet feeding means and the color information recognized from the print data is color information for a color mode, The printing mode corresponding to the paper re-fed by the paper means and the paper fed next by the paper feeding means is determined to be a color two-sheet mode in which the printing process of each color on each paper is performed substantially in parallel. 2. A color image forming apparatus according to claim 1, further comprising: 3. The color image forming apparatus according to claim 1, further comprising: a paper size determining unit configured to determine a size of the paper fed by the paper feeding unit, wherein the print mode determining unit includes the paper size determining unit. The color information of the next page to be printed is the color information for the color mode only when the size determined by is equal to or smaller than the predetermined size, and the next page is the other side of the sheet on which one surface has already been printed. And the print data required to feed the next sheet by the sheet feeding means, and the color information recognized from the print data is color information for a color mode, The printing mode corresponding to the paper re-fed by the reversing / re-feeding means and the paper fed next by the paper feeding means are set in substantially parallel with the printing process of each color for each paper. The color image forming apparatus according to claim 1, further comprising a means for determining the Nau two color and in mode.