JPH10166561A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink-jet system-employed image forming device having a higher productivity by a method wherein printing starting positions, by starting printing from which the printing can be finished by the shortest period of time, are obtained with a calculating means before printing for starting the printing from the obtained positions. SOLUTION: The printing starting positions of IJU1-IJU4 are represented respectively by SP1-SP4. The printing ranges S1-S3 of the IJU1-IJU3 are ranges, each of which ranges from the printing starting point of each unit to that to next unit. The printing range S4 of the last IJU4 is a range, which ranges from the printing starting point SP4 to the terminal end of a paper. A printing process ends when the terminal end of the paper passes the IJU1. The printing number of lines of the IJUj (j=1-4) is respectively represented by Nj (j=1-4). For example, N1 is an integer, which is obtained by dividing the printing range S1 of the IJU1 by a line feed distance Dcr .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a color copying machine.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus for printing a color image on paper, an ink jet system or
2. Description of the Related Art A color copier employing an electrophotographic method is known.
Color copiers that use the inkjet method are lower in price, smaller in space, and smaller than those that use the electrophotographic method.
And low running cost is realized.

[0003]

Here, the printing speed of a color copying machine employing an electrophotographic method is several tens of sheets per minute, whereas the printing speed of a color copying machine employing an ink jet method is as follows. It takes several minutes to form several images per minute or one image, and the productivity is low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus employing an ink jet system which has higher productivity.

[0005]

An image forming apparatus according to the present invention is provided with a plurality of ink jet units which are provided at predetermined intervals in a paper transport path and print a color image in a direction perpendicular to the paper transport direction. Control means for allocating color image data to the plurality of ink jet units, calculating means for determining a print start position at which printing in all the ink jet units is completed in the shortest time, and color from the print start position obtained by the calculating means. Control means for controlling each inkjet so that printing of an image is started. Before printing is actually performed in the ink jet unit, a printing start position at which printing is completed in the shortest time is calculated by the calculation unit, and printing is started from the obtained position, thereby realizing more rapid color image printing.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus according to an embodiment of the present invention will be described below in the following order with reference to the accompanying drawings. (1) Configuration of color image forming apparatus (1-1) Configuration of copier main body (1-2) Configuration of operation panel (1-3) Description of processing block (1-4) Configuration of inkjet unit (1-5) ) Configuration of intermediate tray (2) Handling of image data (3) Image forming process (3-1) Main routine (3-2) Mode setting process (3-3) Image forming process (3-3-1) First Image data processing (3-3-1-1) Original discrimination processing (3-3-1-2) Printing time calculation processing (3-3-1-3) Example of printing time calculation (3-3-1-4) ) Image rotation processing (3-3-2) Second image data processing (3-3-2-1) Print processing by area (3-3-2-2) Print start position optimization processing (3-3-3 ) Inkjet image forming process

(1) Configuration of Color Image Forming Apparatus (1-1) Configuration of Copying Machine Main Body FIG. 1 is a sectional view of a copying machine 50 according to an embodiment of the present invention. The copier 50 includes an image reading unit 100 including an automatic document feeder 110, and an electrophotographic image forming unit 200.
And an inkjet image forming unit 300.

The reading of image data by the image reading section 100 is performed as follows. Automatic document feeder 110 provided above image reading unit 100
Is automatically set at a predetermined position on the platen glass 107 and irradiated by the exposure lamp 101. The reflected light from the original surface is reflected by three mirror groups 103
The light is guided to the lens 104 by a to 103c and forms an image on the CCD sensor 105. Exposure lamp 101 and mirror 10
3a is moved by the scanner motor 102 in the sub-scanning direction (the direction of the arrow) at a speed V according to the copying magnification, and scans the entire document. The mirrors 103b and 103c move in the same direction at a speed of V / 2 with the movement of the exposure lamp 101 and the mirror 103a. The CCD sensor 105 converts the incident reflected light of the original into an analog electric signal and outputs it. The electric signal output from the CCD sensor 105 is
In the image processing circuit 106, after being converted into 8-bit gradation data of yellow, magenta, cyan, and black subjected to shading correction and line-to-line correction, the interface unit 108 and the electrophotographic image forming unit 200
Alternatively, it is output to the inkjet image forming unit 300.

The development of a black-and-white image in the electrophotographic image forming section 200 is performed as follows. In the electrophotographic image forming unit 200, the image data correction unit 201 performs predetermined MTF correction, gamma correction, and the like on the input 8-bit gradation data, and outputs the data to the exposure head 202. Then, a laser beam is emitted. The laser beam emitted from the exposure head 202 is
The photosensitive drum 209 is exposed through the. The photosensitive drum 209 is charged to a predetermined voltage by the charger 204 before receiving exposure for each copy. When exposure is performed in this state, an electrostatic latent image of the document is formed on the photosensitive drum 209. Then, first, the black toner developing device 205 develops the electrostatic latent image on the photosensitive drum 209. On the other hand, according to the size of the original,
220c, an appropriate sheet is selected,
When the toner image is supplied to the conveyance path via the paper feed rollers 221 to 222c, the developed toner image is transferred onto the conveyed paper by the transfer charger 206.
The toner image transferred to the sheet is heated by the fixing roller pair 224 and is fixed on the sheet. Transport path switching claw 22
Reference numeral 5 switches between a transport path for discharging the sheet after the fixing process to the discharge tray 229 and a transport path for transporting the sheet to the inkjet image forming unit 300 provided at the lower stage. In addition,
The fur brush 207 collects the toner remaining on the photosensitive drum 209 after the transfer. The main eraser 208
The residual potential on the surface of the photosensitive drum 209 is removed.

Next, the structure of the ink jet image forming section will be described. The inkjet image forming unit 300 includes an intermediate tray 301 that temporarily stores the conveyed paper, and an ink jet unit 308 (hereinafter, I) that prints a color image on the paper discharged from the intermediate tray 301.
JU unit 308). IJU unit 308
Has four inkjet units (hereinafter, appropriately referred to as IJUs) IJU1 for printing the upper surface of the conveyed paper.
To IJU4 and four IJU5s for printing the lower side of the paper
~ IJU8 are equally spaced (maximum use size 420m
m, which is 1/4 of a distance of 105 mm).
The IJU1 to IJU8 are configured to be detachable from the copying machine 50, and the number of used units and the mounting location can be selected in accordance with the usage environment of the user. For example, by wearing IJU1 and IJU5, it is possible to perform color printing on both sides of a sheet in one transfer. In addition, IJU1 to IJU
When U4 is mounted, the area to be printed by one IJU is
1/4 when printing only with IJU1
The printing of the entire surface of the paper is completed in the time. The paper on which printing has been performed in the IJU unit 308 is discharged to the paper discharge tray 229 through a vertical conveyance path. The end of printing in the IJU unit 308 is detected when a sheet passes beside the sensor 307.

Printing of a color image in the ink jet image forming section 300 having the above configuration is performed as follows. By the action of the transport path switching claw 225, the sheets carried into the inkjet image forming unit 300 are stored in the intermediate tray 301 so as to be stacked. Sensor 30
Reference numeral 5 indicates that a sheet is carried into the intermediate tray 301. The re-feed roller 302 conveys the sheet to the IJU unit 308 in order from the sheet at the bottom of the intermediate tray 301. Sensor 30
No. 6 detects that the sheet has been discharged from the intermediate tray 301. In the inkjet image forming unit 300, the transport direction (vertical or horizontal) of the paper in which the printing time is the shortest, the direction of the image to be printed on the paper (the case where the image is directly printed on the paper, Print processing is performed at the print start position. Also, when the high image quality mode is set, one color image area is prevented from being shifted by a plurality of ink jet units and printed to prevent a printing position shift and a color shift. The area is printed by one inkjet unit. Configuration of IJU1 to IJU8, and
Processing for calculating the optimal image orientation and the print start position will be described later.

(1-2) Configuration of Operation Panel 400 FIG. 2 is a front view of the operation panel 400 provided in the copying machine 50. The operation panel 400 includes a numeric keypad 401 used to input the number of copies, a start key 402 used to start copying, a liquid crystal panel 403 for displaying a mode setting screen and the number of copies, and only the inkjet image forming unit 300. Mode to perform color printing using
A key 406 for setting a high image quality mode for performing an area-specific printing process in which one inkjet unit is allocated to one color image area, and a high-speed mode for performing high-speed black-and-white copying using only the electrophotographic image forming unit 200 are set. And a key 407. When the high-quality mode or the high-speed mode is not set, the electrophotographic image forming unit 200 and the inkjet image forming unit 300
A composite mode that uses both of them as appropriate is set. The copying operation when each mode is set will be described later.

(1-3) Description of Processing Blocks FIG. 3 shows each processing block centering on the image processing circuit 106. The analog electric signal output from the CCD sensor 105 is converted into a digital signal (hereinafter, referred to as image data) by an A / D converter 601 and then subjected to predetermined shading correction. The first image processing unit 602 converts image data represented by three primary colors of RGB into YCrCb data represented by lightness and chromaticity. This is because the YCrCb data is suitable for encoding even when the value of each data changes due to a calculation error, unlike in the case of RGB data, in which color shift is not conspicuous. The GBTC compression unit 603 includes the first image processing unit 6
02 is subjected to an encoding process using a block truncation (hereinafter, referred to as GBTC) system to reduce the data amount, and the encoded data is stored in the compression memory 604. The encoding process of the image data according to the GBTC method will be described later.
The CPU 607, based on the encoded data in the compression memory 604, converts the data of the black-and-white image area processed by the electrophotographic image forming unit 200 and the data of the color image area processed by the inkjet image forming unit 300. Determine. An attribute map is created based on the determination result, and the created attribute map is stored in the hard disk 612. Here, in the color image area, in order to prevent unnecessary development in the electrophotographic image forming unit 200, the data in the compression memory 604 is replaced with data indicating pixels of a base (white), and The color image data is saved to the hard disk 612 via the SCSI controller 611. The GBTC decompression unit 605 decompresses data stored in the compression memory 604 at a predetermined timing. The second image processing unit 606 performs an MTF correction process, a gradation correction process, and the like on the expanded data, and then outputs the data to the electrophotographic image forming unit 200. Also, CP
The U 607 expands the color image data saved on the hard disk 612 into image-formable data as necessary, and transfers the data to the work RAM 608. The DMA (Direct Memory Access) controller 609
The image data in the AM 608 is appropriately transferred to the IJU controller 6
Transfer to 10. The IJU controller 610 uses the IJU
Appropriate image data is transferred to IJU1 to IJU8 in accordance with the attachment / detachment and operation state of each unit attached to the unit 308, and printing of a color image is controlled. The image data read by the image reading unit 100, that is, a signal input from the CCD, is transmitted via the interface unit 108 to a facsimile machine (represented as FAX in the figure) 650 or a personal computer (PC in the figure). 660) to an external device 800. Further, image data is received from the external device 800, and an image based on the received image data is sent to the inkjet image forming unit 30.
0 can also be printed on paper. In addition, IJ
When no ink jet unit is set in the U section 308, data input from the interface section 108 is invalidated.

(1-4) Configuration of Inkjet Unit IJU1 to IJU8 have the same outer shape and configuration. FIG. 4 shows the case of IJU1. The IJU 1 is mounted on the slide rails 312a and 312b, and is configured to be detachable from the copying machine 50 by moving along the slide rails 312a and 312b.
The IJU1 is provided with handles 313 and 314 to facilitate detachment. IJU1 has a position fixing hole 310
The fixed pins a and 310b are fixed by inserting the fixing pins on the main body side, and the connection between the connector 311 and the connector on the main body side enables transmission and reception of signals with the main body. IJ
At the bottom of U1, there is an opening 315 for ink ejection,
Printing can be performed on the lower sheet. FIG. 5 shows the internal configuration of the IJU1. The ink ejecting section 320 has one end supported by the shaft 319 and the other end connected to the belt 31.
6 is connected. With the rotation of the gear 317 attached to the shaft of the recording head drive motor 318, the belt 316 moves to move the ink ejecting unit 320 in a direction perpendicular to the sheet conveyance direction, that is, as indicated by a double arrow in the drawing. Convey in any direction. Ink is attached to the ink cartridge 321 for each color, and supplied to the ink ejecting unit 320 of each color as appropriate. The ink ejected from the slit 322 of the ink ejection unit 320 is supplied to the opening 3 on the bottom surface.
15 and adheres to the paper. Ink ejection unit 320
After moving from one end of the shaft 319 to the other end in the figure, the sheet is conveyed stepwise according to the width to be printed.
By repeating this, a color image is formed on the sheet.
The IJU5 to IJU8 for backside printing are mounted on the copying machine 50 with the ink jet unit (IJU) having the configuration shown in FIGS. The IJU 1 includes an ink presence / absence detection sensor 323, a circuit for controlling the motor 318 (not shown), and a circuit (not shown) for transmitting and receiving signals to and from the copier 50 via the connection connector 311. I have.

(1-5) Configuration of Intermediate Tray FIG. 6 shows the configuration of the intermediate tray 301. Motor 341
The paper holding lever 342 is connected to the rotating shaft of. The paper holding lever 342 is connected to the motor 3 in FIG.
With the clockwise rotation of 41, the paper in the intermediate tray 301 is pressed. A roller 342a is provided at a portion of the paper pressing lever 342 that comes into contact with the paper in order to smoothly transport the paper. The bottom surface of the intermediate tray 301 is inclined so that the refeed opening 343 is lowered, and the sheet moves to the position of the refeed roller 302 due to the inclination. Paper subjected to black and white development in the electrophotographic image forming unit 200 is carried into the intermediate tray 301 from the upper left side in the drawing. When storing paper, the motor 341
Rotates counterclockwise in this figure, and releases the pressing of the sheet by the sheet pressing lever 342. Meanwhile, IJU
When the preparation for printing in the unit 308 is completed, the motor 34
1 rotates clockwise in the figure, and presses the sheet by the sheet pressing lever 342. Re-feed roller 3
With the rotation of 02, the sheets stored in the intermediate tray 301 are conveyed to the IJU unit 308 through the refeed opening 343 in order from the lowest sheet. The intermediate tray 301 is
The copying machine 5 is controlled by the slide rails 344a and 344b.
0, and by moving back and forth,
It is configured to be detachable from the copying machine 50. If paper is set in the intermediate tray 301 in advance,
It is no longer necessary to pass the paper supplied to any of the paper feed cassettes through the electrophotographic image forming unit 200, and adverse effects in the electrophotographic image forming unit 200 (black toner scattering, wrinkles generated when passing through the fixing roller 224, High-quality color printing can be rapidly performed without receiving paper bending or oil adhesion and shortening the paper transport path. Intermediate tray attachment / detachment sensor 346 provided in copying machine 50 and comprising a light emitting element and a light receiving element
Detects the state of attachment / detachment of the intermediate tray 301 based on whether or not the light emitted from the light emitting element is detected by being reflected by the reflector 345 provided on the side surface of the intermediate tray 301. Copying machine 50 with roller 342a contacting the paper of paper holding lever 342
A predetermined light emitting element 349 is provided on the side facing the light emitting element.
By detecting the light emission position 49, it is determined whether or not the number of sheets stored in the intermediate tray 301 has reached the maximum number of sheets. A light emitting element 347 is provided at the center of the roller 342a.
A sensor 348 provided on the bottom surface of the first tray 301 detects the presence or absence of a sheet in the intermediate tray 301 by detecting the light emitted by the light emitting element.

(2) Handling of Image Data FIG. 7 is an image diagram showing the order of storing one page of data of a color image area in a document image on the hard disk 612. Hereinafter, the data storage order when the data (GBTC encoded data) of the area determined to be a color image is saved to the hard disk 612 will be described with reference to FIG. The hatched area in the figure represents a color image area. The GBTC encoding process is a fixed-length encoding method, and data in the compressed image memory 604 is arranged in the same manner as in FIG. The CPU 607 discriminates a black-and-white image region (a portion other than hatching) and a color image region (a hatched portion) based on data in the compression memory 604, and creates an attribute map based on the discrimination result. Is stored in the hard disk 612. Based on this attribute map, data belonging to a color image is raster-scanned from the main scanning direction of the leading edge of the document in the numerical order shown in FIG. That is, 1 to 2
After storing the line data up to this point, the data of the next lower line is sequentially scanned from the left end to the right end and stored in the hard disk 612. After storing the line data from 3 to 4, 5 to 6 and the left end to the right end of the next line, store the line data on the hard disk 612 from 7 to 8 and 9 to 10 of the color image area on the left side I do.
Hereinafter, data reading for each line is similarly continued.
Data is read from 25 to 26, 27 to 28,..., 29 to 30, and the process ends. Here, the horizontal thin line shown in the figure indicates the printing width by the inkjet unit. The ink ejection head 320 handles image data at intervals of 16 pixels. In the GBTC encoding process, 4 × 4 pixels are defined as one block. Therefore, in the sub-scanning direction, data is handled in units of four blocks. As described later, the GBTC encoding compresses 16 × 3 bytes of data into 6 × 3 bytes per block. When IJU1 to IJU4 are mounted on the copying machine main body, when printing a color image, IJU1 is in charge of color printing in the print range 501, IJU2 is in charge of printing of a color area in the print range 502, and IJU3.
Is responsible for printing the color area in the print range 504,
The IJU 4 prints a color area in the print range 504. As described above, in the inkjet image forming unit 300, printing of a color image is shared by the inkjet units provided in the IJU unit 308. FIG. 8 is an image diagram showing a storage state of data in hard disk 612. At the top of the hard disk 612, a page address table 505 indicating the location of the attribute map in each page and the size of the attribute map determined by the document size is stored. After the page address table 505, the attribute map 506 of page 1 and color image data 507, the attribute map 508 of page 2 and color image data 509, the attribute map 51 of page 3
0 and color image data 511 are stored in order.
As described above, the color image data of each page is stored after the storage area of the attribute map. The CPU 607,
With reference to the page address table 505, an attribute map of a desired page is read. The size of the attribute map is approximately 64 Kbytes for an A3 document. The data size differs from the ratio of the color image on the original screen. If the entire surface of A3-size paper is a color image, the size of the color image data is about 35M.
It becomes bytes. From the page address table 505 in the hard disk 612 and the attribute map of the page specified by the table 505, the position of the color image of the document image can be grasped, and desired data can be supplied to the IJU1 to IJU8. . For example, the data of the color image of the original shown in FIG.
When reading from the first line, when printing the first line, IJ
No data is supplied to U1. 5-6 for IJU2
Are supplied to the IJU3, and 19 to 2
0 line data is supplied, and IJU4
Data of 28 lines is supplied.

Hereinafter, the GBTC encoding process will be described. In the GBTC encoding process, original image data is extracted for each block of a predetermined pixel matrix, and for each block, a parameter P1 determined from data in the block is set.
Average value Q1 of the following data and parameter P2 (however, P
1 <P2 is satisfied. Based on the average value information LA obtained by bisecting the sum of the average values Q4 of the data having the above values and the gradation width index LD which is the difference between the average value Q4 and the average value Q1, each of the blocks in the block is obtained. The pixel data is compression-encoded into code data obtained by quantizing the pixel data to a smaller number of gradation levels than the data within the range of the gradation distribution in the block. The copying machine 50 has a GBT as will be described later.
Average value information LA and gradation width index LD obtained by C encoding
Is used to determine whether the predetermined pixel matrix belongs to a black-and-white image or a color image, and the type of the document is determined based on the determination result. The method of determining the type of the original is not limited to this,
A method of making a determination based on the YCrCb data may be employed. FIG. 9 is a diagram showing the flow of the encoding process of the GBTC system. In the GBTC method, as shown in FIG. 9A, image data of a document image is extracted in units of 4 × 4 pixel blocks. The extracted image data in the 4 × 4 pixel block is subjected to an encoding process according to a method described below with reference to FIG. 10, and for each pixel, 1 byte (= 8 bits) data × 16 pixel image data ( As shown in FIG. 9B, 16 bytes, that is, 128 bits) are allocated by classifying the 1-byte gradation width index LD, the 1-byte average value information LA, and the data of each pixel into four levels. The data is encoded into a total of 6 bytes (= 48 bits) of 2-bit code data × 16 pixels. As a result, the data amount becomes 3
/ 8. FIG. 9C is a diagram illustrating that the amount of encoded data corresponds to six pixels of image data before encoding. Decoding of the encoded data is executed by setting 1-byte image data corresponding to each 2-bit code data based on the gradation width index LD and the average value information LA. In the present embodiment, the image data of the document is extracted in units of 4 × 4 pixel blocks, but the present invention is not limited to this, and the image data is extracted in units of 3 × 3 pixel blocks or 6 × 6 pixel blocks. Is also good. Further, in the present embodiment, 256-level data of each pixel in the block is encoded into 4-level code data. However, the present invention is not limited to this, and 2-level or 8-level code data is encoded. May be used. FIG. 10 is a diagram showing an encoding process and a decoding process of the GBTC system. From image data extracted in units of 4 × 4 pixel blocks, a predetermined feature amount required for encoding is obtained. The feature amount is obtained by the following calculation. FIG. 10A shows a maximum value Lmax and a minimum value Lmin.
And the relationship between the parameters P1 and P2 and the gradation width index LD. First, a maximum value Lmax and a minimum value Lmin of 8-bit image data in a 4 × 4 pixel block are detected. Next, a parameter P1 obtained by adding 1/4 of the difference between the maximum value Lmax and the minimum value Lmin to the value of the minimum value Lmin.
And a parameter P2 obtained by adding 3/4 of the difference to the value of the minimum value Lmin. Note that parameters P1 and P1
2 is obtained by calculation of the following “Equation 1” and “Equation 2”.

P1 = (Lmax + 3Lmin) / 4 (1)

P2 = (3Lmax + Lmin) / 4 (2) Next, an average value Q1 of the image data of the pixels having the parameter P1 or less among the image data of each pixel is obtained. Further, of the image data of each pixel, an average value Q4 of the image data of the pixels having the parameter P2 or more is obtained. Average values Q1 and Q4 obtained
Based on the average value information LA = (Q1 + Q4) / 2,
A gradation width index LD = Q4-Q1 is obtained. Next, "Equation 3"
And the calculation of "Equation 4" is performed, and 1 byte (8 bits) of each pixel, that is, image data of 256 gradations is converted into 2 bits, that is, 4 bits.
The reference value L1, which is used when encoding into gradation code data,
L2 is determined.

L3 = LA-LD / 4 (3)

L2 = LA + LD / 4 (4) FIG. 10B shows the i-th pixel in the 4 × 4 pixel block.
Column (however, i = 1, 2, 3, 4; the same applies hereinafter),
FIG. 10 is a diagram showing the value of code data φ _ij assigned according to the data value of pixel X _ij in the j-th row (where j = 1, 2, 3, and 4; the same applies hereinafter). More specifically, 2-bit code data φ _ij having a value shown in Table 1 below is assigned according to the value of the pixel X _ij .

[Table 1] The data encoded by the GBTC method includes code data for 16 pixels (16 × 2 bits), a gradation width index LD of one byte (8 bits), and average value information LA. FIG. 10C shows data obtained by the decoding process. When decoding the encoded data, the gradation width index LD and the average value information LA are used. Specifically, the value of the gradation range index LD and average value information LA, in accordance with the value of the code data phi _ij assigned to a pixel X _ij in the j-th row of the i-th column, the data of X _ij The data is replaced with 256 gradation data having the values shown in Table 2 below.

[Table 2] In the GBTC method, pixels X _ij (where i and j are 1, 2,
It is one of the values 3 and 4. ) Is replaced with 256 gradation data of four values. In the GBTC method, the parameters Q1 and Q4 are completely restored from the gradation width index LD and the average value LA included in the encoded data. Therefore, in a character image (black and white binary image) in which the black portion is equal to or less than the parameter P1 and the white portion is equal to or more than the parameter P2, the character image can be completely reproduced from the encoded data.

(3) Image formation processing When the composite mode is set, the development of a black and white image
The color image printing is performed in the electrophotographic image forming unit 200, and the printing of the color image is performed in the inkjet image forming unit 300. Therefore, when copying a document including a color image in part or in whole, the paper is stored in the electrophotographic image forming unit 20.
0 and the ink-jet image forming unit 300. On the other hand, when copying a black-and-white original containing no color image, the electrophotographic image forming unit 200 performs black-and-white development and then directly discharges the paper to the paper discharge tray 229. However, before copying the monochrome document, if a color document or a document in which a color image and a monochrome image are mixed is being copied, that is, color printing is being performed in the inkjet image forming unit 300. In this case, the developed paper of the black and white image is also conveyed to the inkjet image forming unit 300. Thereby, the order of the sheets discharged to the sheet discharge tray 229 can be changed by the automatic document feeder 11.
The order of the originals set to 0 is the same. When the high image quality mode is set, the inkjet image forming unit 300 prints one color image area with one inkjet unit (IJU). This eliminates a printing position shift on printing paper and a color shift due to individual differences of the inkjet units, which occur when printing one color image area with a plurality of inkjet units. When paper is set on the intermediate tray 301, printing is performed directly in the inkjet image forming unit 300 using this paper. This prevents the paper from being soiled or bent when passing through the electrophotographic image forming unit 200. In addition, the CPU 607
Is the direction of the image in which the printing time in the inkjet image forming unit 300 is the shortest (0 with respect to the paper conveyance direction).
, 90 °, 180 °, or 270 °), and the image in the inkjet image forming unit 300 is performed after rotating the image in the obtained direction. When the high image quality mode is not set, the printing start position where the printing time in the inkjet image forming unit 300 is the shortest is obtained by calculation, and the image forming process is executed at the obtained printing start position. When the high-speed mode is set, black-and-white development is performed in the electrophotographic image forming unit 200 regardless of the type of the original. Thereby, high-speed copying can be realized. When only the electrophotographic image forming unit 200 is used as in the setting of the mode, the external device 800 is permitted to use the inkjet image forming unit 300.

(3-1) Main Routine FIG. 11 is a flowchart of a main routine of an image forming process executed by the CPU 607. First, initialization of each variable involved in processing and initialization of each element are performed (step S1). Next, key input by the user is accepted,
Various modes are set (step S2). In this mode setting process, when the user presses the start key 402, the process proceeds to the following process. First, in accordance with the mode set by the user, preprocessing such as shading processing for image reading and preparation of each element for image formation is performed (step S3). The automatic document feeder 110 reads the image data of the document placed on the document table 107. The read image data is G
After the BTC encoding, it is stored in the compressed image memory 604 (step S4). Based on the data stored in the compressed image memory 604, a document discriminating process is performed, and an image forming process corresponding to the type of the document is performed (step S5).
This image forming process will be described later. After this image forming process, cleaning of the photoconductor 209 after image formation and cleaning of the ink ejecting unit 320 are not directly related to the copying operation, but
A process required to maintain the condition of the device is performed (step S6). Finally, other processing such as communication control not directly related to the above control is executed (step S).
7). Thereafter, the processes of steps S2 to S7 are repeated.

(3-2) Mode Setting Process FIG. 12 is a flowchart of the mode setting process (FIG. 11, step S2). If the high image quality mode key 406 is pressed (YES in step S10), the high image quality mode is set as the print mode (step S11). In the high image quality mode, printing is performed using only the inkjet image forming unit 300 regardless of the type of the document, and a high quality copy output is obtained. On the other hand, high-speed mode key 4
07 is pressed (YES in step S12), the high-speed mode is set as the print mode (step S1).
3). This high-speed mode means that after performing black-and-white development in the electrophotographic image forming unit 200 regardless of the type of the original,
By immediately discharging the paper to the paper discharge tray 229, a copy output is obtained at high speed. Keys 406 and 4
If none of the keys 07 is pressed (step S
(NO at 12), the composite mode using one or both of the electrophotographic image forming unit 200 and the inkjet image forming unit 300 according to the type of the document is set as the print mode (step S14). Thereafter, the user waits until the start key 402 is pressed (YE in step S15).
S), returning to the main routine.

(3-3) Image Forming Process FIGS. 13 and 14 are flowcharts of the image forming process (FIG. 11, step S5). First, the first image data processing is executed (step S20). In the first image data processing, processing of determining the type of the document, and determining the orientation of the image that minimizes the copy cost and the printing time in the inkjet image forming unit 300 is performed. There are three types of documents determined here: a black-and-white document, a color document, a document in which a black-and-white image and a color image are mixed. When the Intermediate Tray 301 is Not Mounted on the Copier 50 (Step S2
When the electrophotographic image forming unit 200 conveys the processed paper to the intermediate tray 301, a paper jam occurs. Therefore, the paper is supplied from any of the paper cassettes 220a to 220c regardless of the set mode. After the image forming process in the electrophotographic image forming unit 200, the printing process of immediately discharging the paper to the paper output tray 229 without going through the inkjet image forming process 300 (FIG. 14)
(Mode A print processing). On the other hand, when the intermediate tray 301 is mounted on the copying machine 50 (YES in step S21), the process branches depending on the set mode type (step S22). Here, when the composite mode is set, and an output request is made from the external device 800 via the interface unit 108 (YES in step S23), when the high image quality mode described below is set. Perform the same process. This is copier 5
This is because, in the case of 0, only printing in the inkjet image forming unit 300 is permitted in response to an output request from the external device 800. If the composite mode has been set and no output request has been made from the external device 800 (NO in step S23), based on the result (document type) of the document discrimination processing in the first image data processing. To perform an appropriate image forming process (step S24).
Subsequent processing). If it is determined by the document determination performed in the first image data processing that the document is a document in which a color image and a black-and-white image are mixed (mixed document), even if a black-and-white document is copied thereafter, The mode change flag F is set to 1 in order to always pass through the inkjet image forming unit 300 (step S25).
If the intermediate tray 301 is empty (YE in step S26)
S), the print processing in mode C shown in FIG. 14 is executed. In the printing process of mode C, any of the sheet cassettes 220a
Image forming unit 2 on paper supplied from
After black and white development at 00, the paper
It is stored in the intermediate tray 301. Then, while controlling the timing, the sheet is transferred to the inkjet image forming unit 3.
00, and in the inkjet image forming unit 300, cyan, magenta, and yellow color printing is executed, and the sheet is discharged to the sheet discharge tray 229. If there is a sheet in the intermediate tray 301 (N in step S26)
O), print processing in mode B1 shown in FIG. 14 is executed.
In the printing process in the mode B1, the electrophotographic image forming unit 200
The paper is directly conveyed from the intermediate tray 301 to the inkjet image forming unit 300 without going through the
After performing four color printing of yellow and black,
The paper is discharged to the paper discharge tray 229. Also, in step S24, an original (color original) composed entirely of a color image
, The mode change flag F is set to 1 as in the case of the mixed document (step S2).
7). Here, when the intermediate tray 301 is empty (YES in step S28), the printing process in the mode B2 shown in FIG. 14 is executed. In the printing process in the mode B2, the electrophotographic image forming unit 200 does not form an image on a sheet supplied from any one of the sheet feeding cassettes 220a to 220c, passes the sheet, stores the sheet in the intermediate tray 301, and The stored paper is subjected to image forming processing by IJU1 to IJU8. If there is a sheet on the intermediate tray 301 (NO in step S28), the printing process in mode B1 in FIG. 14 is executed. If it is determined in step S24 that the document is a monochrome document, the mode change flag F is checked first. This is because a mode change flag F corresponding to determining whether or not printing has been performed by the inkjet image forming unit 300 prior to the image forming operation of a monochrome document in a group of documents on which image formation is performed continuously is set. If the value is 0 (NO in step S29), it is determined that printing has not been performed in the inkjet image forming unit 300 before, and the printing process in mode A shown in FIG. 14 is executed. If the mode change flag F is 1 (step S2
9), before copying the black-and-white document, it is determined that a copy of a document partially or wholly composed of a color image is performed, and that the inkjet image forming unit 300 has been used. The mode C print process is executed. Thus, the order of the sheets discharged to the discharge tray 229 is made the same as the order of the documents set in the automatic document feeder 110. If the high image quality mode is set in step S22, or if an output request is made from the external device 800 when the composite mode is set (YES in step S23), the color original is copied when the composite mode is set. Execute the same processing as when.
Further, in step S22, when the high-speed mode is set, the same processing as when copying a black-and-white document when the composite mode is set is executed.

Step S32 or step S37
When the copying of all the originals set in the automatic original feeder 110 is completed by the paper ejection in step (YES in step S33), the mode change flag F is reset to 0 (step S34). ). If copying of all originals has not been completed (NO in step S33), the process returns to step S20 in FIG. In this example, when the intermediate tray 301 is not mounted, the printing process of the mode A is automatically executed. However, a warning that the intermediate tray 301 is not mounted is issued.
The mode A may be set after confirmation.

(3-3-1) First Image Data Processing FIG. 15 shows the first image data processing (FIG. 13, step S2).
It is a flowchart of 0). First, a document discriminating process for discriminating the type of the document is executed (step S50). Here, it is determined whether the document is a color document, a black and white document, or a document in which a color image and a black and white image are mixed. In addition, based on this determination result,
An attribute map indicating the distribution of the color image area is formed. This is stored in the hard disk 612. Based on the result of the document discrimination process, the area ratio of the color and black and white images in the document is calculated (step S51). This area ratio is calculated assuming that the ratio of the black-and-white image is what percentage and the ratio of the color image is what percentage when the area of the entire sheet is 100%. In this example, since the image is a GBTC encoding method and a fixed-length encoding method, rotation of an image can be easily performed by setting a read address of a compression memory or a register in a compression circuit. Therefore, the image currently stored in the compression memory is rotated in units of 90 degrees, and the time required to form the image in each direction is calculated (step S52). Then, the rotation angle that requires the shortest time for printing is selected, and the arrangement of the encoded data is changed (step S53). Thereafter, the coded data belonging to the color image is stored in the hard disk 612 (step S5).
4) The data of the color image in the compression memory 604 is replaced with the data of the base (white) (step S55).

(3-3-1-1) Document Discrimination Processing The document discrimination processing (FIG. 15, step S50) will be described below. A black-and-white image is composed of an achromatic color in which the data values of the chromaticity components a * and b * are almost zero. For example, a chromaticity component a of a 4 × 4 pixel block obtained by the GBTC encoding process
If the average value information LA of * and b * is within ± 5, it can be determined that the block is an achromatic image. However, with the above criterion alone, even when the chromaticity component a * of a certain pixel is -120 and the chromaticity component a * of another pixel is 125, the average value information LA may be within ± 5. Can be In such a case, it is erroneously determined that the 4 × 4 pixel block belongs to a monochrome image. Therefore, only when the gradation width index LD is within ± 5, it is determined that the 4 × 4 pixel block belongs to the monochrome image.

FIG. 16 is a flowchart of the document discrimination process. First, the monochrome document flag MONO and the color document flag COL are reset to 0 (step S6).
0). When both the average value information LA and the gradation width index LD of the chromaticity components a * and b * are within ± 5 (step S6)
It is determined that the 4 × 4 pixel block belongs to the monochrome image (step S65), and the flag MON is set.
O is set to 1 (step S66). Flag COL
Is 0, that is, if there is no block determined to be a color image before the block (YES in step S67), it is determined that the document is a monochrome document (step S68). On the other hand, when at least one of the average value information LA and the gradation width index LD of the chromaticity components a * and b * is ± 5 or more (NO in any one of steps S61 to S64), 4 × 4 It is determined that the pixel block belongs to the color image (step S69). Here, if the flag MONO is 0, that is, if there is no block determined to be a monochrome image before the block (YES in step S71), the document is determined to be a color document (step S71). Step S73). Step S6 above
7, if COL = 1 or step S7
In MONO = 1, if MONO = 1, it is determined that both the block belonging to the black-and-white image and the block belonging to the color image are mixed in the document (step S72). Steps S61 to S73 for all blocks in the document
(YE in step S74)
S), and return.

(3-3-1-2) Printing Time Calculation Processing Hereinafter, the printing time calculation processing (FIG. 15, step S52) will be described. When a plurality of ink jet units are mounted, for example, as shown in FIG. 17A, the paper is transported vertically when viewed from the front of the drawing, and IJU1, IJU2,.
17B, the time required to form a triangular mark on the sheet by using
17C, the time required to rotate the image by 180 degrees as shown in FIG. 17C, and the time required to rotate the image by 270 degrees as shown in FIG. 17D. The time required for each case is different. Therefore,
In order to shorten the printing time in the inkjet image forming unit 300 at all, in the printing time calculation processing, the image of the document is shifted by 0 °, 90 °, 180 °, 27 ° with respect to the paper passing direction.
Rotate to 0 degrees, calculate the time required for printing in the inkjet image forming unit 300 with each rotated,
The rotation angle θ that can be printed in the shortest time is determined.

FIG. 18 shows the printing time calculation process (FIG. 1).
5 is a flowchart of step S52). First,
The mounting state of the ink jet unit to the copying machine 50 and the presence or absence of ink are checked using a sensor, and a usable ink jet unit is selected (step S75). If you do not rotate the image, i.e. obtained from calculating the image creation time T ₀ when the rotational angle 0 degrees (Step S7
6). Next, the printing time T ₉₀ when the image is rotated by 90 degrees
Is obtained by calculation (step S77). If the number of ink jet units mounted on the copier 50 is two or more (YES in step S78), one
The print time T ₁₈₀ when rotated 80 degrees, obtained by respectively calculating the printing time T ₂₇₀ when it is rotated 270 degrees (step S79 and S80). IJU for copier 50
If only one is mounted (N in step S78)
O), T ₀ and T ₁₈₀ and T ₉₀ and T ₂₇₀ have the same value. Therefore, the calculations in steps S79 and S80 are not performed. An image rotation angle θ corresponding to the minimum value of the printing times T ₀ , T ₉₀ , T ₁₈₀ , and T ₂₇₀ is obtained (step S81).

Hereinafter, the calculation of the printing time will be described.
FIG. 19 is a diagram for explaining the calculation process (FIG. 18, step S76) of the printing time T when an image is formed on a sheet conveyed in the arrow direction (left direction in the figure). This figure shows a case where IJU1 to IJU4 are mounted on the copying machine 50. The print start position of IJU1 to IJU4 is
In the drawing, they are represented by SP1 to SP4, respectively. IJU1
The print range S1 to S3 of the IJU3 is from the print start point of each unit to the print start point of the next unit, and the print range S4 of the last IJU4 is from the print start point SP4 to the end of the sheet. In the printing process, the end of the paper is IJ
The process ends when passing through U1. In the figure, IJUj (j = 1
To 4) are N _j (j = 1 to 4), respectively.
It is represented by For example, N ₁ is the printing range of IJU1 S1
Is divided by a line feed interval Dcr. IJ
The printing length of the i-th row (1 ≦ i ≦ N _j ) of Uj (j = 1 to 4) is represented by Lij. For example, the print length of the first line of IJU1 is 0 because there is no color image. Also, IJ
The print lengths L1i and L1i + 1 of the i-th line and the (i + 1) -th line of U1 are the same value. The same applies to IJU2 to IJU4. As shown in the first line of IJU2, the print length L21 when there are two or more print areas is the length of both ends of the two or more print areas.

FIG. 20 shows a process for calculating the printing time T ₀ when the image is rotated by 0 degrees (FIG. 18, step S
It is a flowchart of 76). First, IJU1 to IJ
The print start points SP1 to SP4 of U4 are obtained (Step S)
85). Next, the print ranges S1 to S4 of each IJU are obtained (step S86). Set the print range of each IJU to the line feed interval D
The number of print lines N _{1 to} N ₄ is obtained by dividing by cr (step S8)
7). The maximum value of the number of print lines N _{1 to} N ₄ of each IJU is set as the maximum number of print lines N (step S88). The value of the line number i for printing is set to 1 (step S89). The value of the total printing time T _total is set to 0 (step S90). If the line number i for printing is equal to or less than the maximum number N of print lines (YES in step S91), the print length Lij of the i-th line of each IJU
(J = 1 to 4) is obtained (step S92). The maximum value of Lij is set as the maximum print length Li of the i-th line (step S9).
3). The printing time Ti of the i-th row of each IJU is Li / Vp + Tc.
It is obtained by calculating r (step S94). Where Vp
Is the printing speed (line-wise distance per unit time),
Tcr is the time required for a line feed. If the printing speed differs for each IJU, the printing time T for the i-th row for each IJU
ij is calculated by Tij = (Lij / Vpj) + Tcr, and the maximum value of Tij is set as the printing time Ti of the i-th row. Then, after the calculated value of the printing time Ti of the i-th row is accumulated in the _total printing time T _total and 1 is added to the value of the printing row number i (step S95), the process returns to the step S91. This is repeated until the print line number i becomes larger than the maximum value N. If the print line number i is larger than the maximum print line number N (NO in step S91), T _total is IJU
Shows the printing time T ₀ at the time of printing. On the other hand, the length of the paper in the transport direction is divided by the paper transport speed, and the developing time T for electrophotographic printing is calculated.
e is calculated (step S96). Here, when the total printing time T _total is shorter than the developing time Te (step S97)
YES), the total printing time T _total is replaced with the developing time Te (step S98). The transfer speed in the electrophotographic image forming section 200 in the copying machine 50 is 100 mm / se.
c, and for A4 size paper, the development time Te = 2.1
Seconds (vertical feed) or 3.0 seconds (horizontal feed). If the total printing time T _total is equal to or longer than the developing time Te, the process is terminated. Note that the images are 90 degrees, 180 degrees, and 27 degrees.
When the image is rotated by 0 degrees, the printing times T ₉₀ , T ₁₈₀ , and T ₂₇₀ can be calculated by the same processing. Since the same description is repeated, the description of the print time calculation processing when the image is rotated by 90 degrees, 180 degrees, and 270 degrees is omitted.

(3-3-1-3) Example of Calculation of Printing Time Hereinafter, a plurality of combinations are considered for the color image drawn on the original and the number of ink jet units mounted on the copying machine. The times are compared to confirm that the time required for printing changes depending on the direction of the sheet to be conveyed and the direction of the image formed on the sheet. The line printing speed Vp is 0.5 mm / msec, the line feed interval Dcr is 1 mm, the time Tcr required for line feed is 20 ms / line, and the paper size W × H is 2 mm.
10 mm x 297 mm. (First Example) First, in the first example, as shown in FIG. 21, the paper is fed so that the longitudinal direction of the paper is at the top, and two rectangular color image areas indicated by oblique lines on the paper. 7
Consider the case where 10 and 711 are printed using only IJU1. In the figure, W0, W1, W2, h0, h1, h2, h3, h4
Is a constant indicating the length of each part, and in this example, w1 = 2
00 mm, h1 = h3 = 50 mm, and h2 = 100 mm. As shown in the figure, there is no color image area in the section a. Therefore, the printing time T ₀ a of section a is a time required for paper feeding by the line break is calculated by (w0 / Dcr) × Tcr. Also,
In the section b, two color image areas 711 and 712
Exists. The printing time T ₀ b in the section b is (w1 / Dcr) × ((h1
+ h2 + h3) / Vp + Tcr). As in the section a, the section of the color image does not exist in the section c. Therefore, section c
Print time T ₀ c of a time required for paper feeding by the line break is calculated by (w2 / Dcr) × Tcr. As described above, the time T ₀ required for printing in the drawing is T ₀ a + T ₀ b + T ₀ c = (w
1 / Dcr) × ((h1 + h2 + h3) / Vp) + (W / Dcr) × Tcr = 84.2 seconds. Next, as shown in FIG. 22, the paper shown in FIG. 21 is rotated counterclockwise by 90 degrees, the paper is fed so that the short side of the paper is at the top, and printing is performed using IJU1. Consider. W0, W1, W2, h0, h1, h2, h3, h described in the figure
4 has the same length as that of FIG. In this case, the printing time T _{90 of the} sections d, f, and h where the color image area does not exist.
d, T ₉₀ f, T ₉₀ h are (h0 / Dcr) × Tcr, (h2 / Dcr) × Tc
r, (h4 / Dcr) × Tcr. On the other hand, the printing time T ₉₀ e of the section e where the color image area 710 exists is (h1
/ Dcr) × (w1 / Vp + Tcr). Further, the printing time T ₉₀ g of the section g where the color image area 711 exists is:
It is obtained by (h3 / Dcr) × (w1 / Vp + Tcr). In this way, the printing time of each section d to h can be obtained by calculation. Therefore, the printing time T _{90 in} the case of FIG.
₉₀ d + T ₉₀ e + T ₉₀ f + T ₉₀ g + T ₉₀ h = ((h1 + h3) / Dcr) × (w1 / Vp)
+ (H / Dcr) × Tcr = 45.9 seconds. From the above, it can be seen that in the case of the first example, the printing time is shorter when the document image is rotated by 90 degrees counterclockwise and printed.

(Second Example) In the second example, as shown in FIG. 23, the paper is fed so that the longitudinal direction of the paper is first, and one rectangular color image is printed on the paper. Area 712 is printed using two IJU1 and IJU2. As described above, when printing is performed using two or more IJUs, a color image area may exist in another IJU even if there is no color image area to be printed in one IJU. As described above, when two or more IJUs are mounted, the position of the color image area assigned to each IJU must be considered. That is, only when all the IJUs do not have a color image area to be printed, a line feed is performed without doing anything.
In other cases, after printing on the line having the largest color image area is completed, a line feed is performed and the sheet is sent to the next print line. In this figure, IJU1 and IJU2
Is d12. w0 = 5mm, w1 = 200mm, h0 = h1 = 50mm, d1
And 2 = 105mm, w0 <d12 < w1, and, (w0 + w1) <print time T ₀ when satisfying the relation (2 × d12) is determined by the following procedure. In the section 1a assigned to the IJU1, no color image area exists, but in the section 2a assigned to the IJU2, a part of the color image area 712 exists. Therefore, the printing time T ₀ a of this section becomes a time IJU2 is required for printing is calculated by (w0 / Dcr) × (h1 / Vp + Tcr).
On the other hand, a part of the color image area 712 exists in the section 1b. Therefore, the printing time T ₀ b in this section is equal to the IJU
1 is the time required for printing, which is ((d12-w0) / Dcr) × (h1 / Vp
+ Tcr). At this time, in the section 2b, a part of the area 712 of the color image exists, and I
At the same time as the printing operation of section 1b by JU1, the printing operation on the image of section 2b by IJU2 is performed. However, since the image area of section 2b is smaller than the image area of section 1b, the printing time of section 2b is calculated. do not do. IJU
1 is assigned to IJ at the time of printing the previous section 1b.
Printing has been completed by U2, and only a line feed is performed. Therefore, the printing time T ₀ c in this section is obtained by ((W−d12) / Dcr) × Tcr. Therefore, the printing time T _{0 of the} document is T ₀ a
_{+ T 0 b + T 0 c} = (d12 / Dcr) (h1 / Vp) + (W / Dcr) a × Tcr = 14.7 seconds. Next, as shown in FIG. 24, the paper shown in FIG. 23 is rotated 90 degrees counterclockwise to feed the paper so that the short side of the paper is at the top, and printing is performed using IJU1 and IJU2. Consider the case. In this case, (h0 + h
1) Satisfies the relationship <d12. In other words, there is no color image area assigned to IJU2, and the entire color image area 712 is printed by IJU1. Printing time T for section 1d
₉₀ d becomes (h0 / Dcr) × Tcr, and the printing time T _{90 of the} section 1 e is obtained.
e is (h1 / Dcr) × (w1 / Vp + Tcr), and the printing time T ₉₀ f of the section 1f is (h2 / Dr) × Tcr. Therefore, the printing time T _{90 of the} original is T ₉₀ d + T ₉₀ e + T ₉₀ f = (h1 / Dcr) × (w1 / V
p) + H / Dcr) × Tcr = 25.9 seconds. As described above, in the case of the second example, it is understood that the printing time is shorter when the original image is printed as it is without rotating it.

(Third Example) In the third example, as shown in FIG. 25, the paper is fed so that the longitudinal direction of the paper is at the top, and one rectangular color image is printed on the paper. Area 713 is printed using two IJU1 and IJU2. As mentioned earlier, 2
When printing using more than one IJU, one IJU
Even if there is no color image area to be printed by another IJU,
It is also necessary to consider whether or not there is a color image area. In this figure, w0 = w1 = 50mm, h0 = 50mm, h1 = 200mm, d1
2 = 105 mm, which satisfies the relationship of (w0 + w1) <d12. Section 1a in charge of IJU1 and Section 2a in charge of IJU2
Has no color image to be printed. For this reason,
In this area, it takes time only to feed paper by line feed,
Its time T ₀ a is calculated by (w0 / Dcr) × Tcr. In the section 1b, a color image area 713 exists. Print time T ₀ b of this section 1b is obtained by (w1 / Dcr) × (h1 / Vp + Tcr). Since the section 1c there is no color image to be printed, the printing time T ₀ c becomes a time required only to paper feed newline is obtained by (w2 / Dcr) × Tcr. Therefore, the printing time T _{0 of the} original is T ₀ a + T ₀ b +
T ₀ c = (w1 / Dcr) × (h1 / Vp) + (W / Dcr) × Tcr = 24.2 seconds.
Next, as shown in FIG. 26, calculates the printing time T ₉₀ in the case of performing the paper feed to the paper shown in FIG. 25 rotated 90 degrees counter-clockwise lateral direction of the sheet becomes the head . In this case, the relations h0 <d12 and (2 × d12) <(h0 + h1) are satisfied. There is no color image area in the section 1d assigned to the IJU1, but a part of the color image area 713 exists in the section 2d assigned to the IJU2. The printing time T ₉₀ d of the section is the time required for IJU2 to print, (h0 / Dcr)
× (w1 / Vp + Tcr). Color image area 713
The printing time T ₉₀ e of the section 1 e having a part of is ((d12−h0)
/ Dcr) × (w1 / Vp + Tcr). The area of the color image to be printed by the IJU1 after the printing of the section 1e has been printed by the IJU2 when the preceding section 1d is printed. However, a part of the color image area 713 to be printed by the IJU 2 exists in the section 2f. Therefore, the printing time T ₉₀ f of the section 1f is obtained by ((h0 + h1-2 × d12) / Dcr) × (w1 / Vp + Tcr). A part of the color image area 713 in the section 1g has already been printed by IJU2. Therefore,
The time required for paper feed by line feed is the printing time T ₉₀ g, which is obtained by ((h2 + d12) / Dcr) × Tcr. Therefore,
The printing time T5 of the original is T ₉₀ d + T ₉₀ e + T ₉₀ f + T ₉₀ g =
((h0 + h1-d12) / Dcr) × (w1 / Vp) + (H / Dcr) × Tcr = 20.4 seconds. Thus, in the case of the third example, it can be seen that the printing time is shorter when the document image is rotated by 90 degrees counterclockwise.

(3-3-1-4) Image Rotation Processing FIG. 27 is a flowchart of the image rotation processing (step S54). The process branches depending on the value of the image rotation angle θ obtained by the printing time calculation process (step S100). If the angle is 0 degree, the process returns as it is. If the angle is 90 degrees, the encoded data is rotated by 90 degrees (step S101).
If the angle is 0 degree, the encoded data is rotated by 180 degrees (step S102), and if the angle is 270 degrees, the encoded data is rotated by 270 degrees (step S103).

(3-3-2) Second Image Data Processing FIG. 28 shows the second image data processing (FIG. 14, step S3).
It is a flowchart of 5). First, the state of attachment of the inkjet unit to the copying machine 50 is checked (step S110). If the high image quality mode is set (YES in step S111), the printing process for each area is executed (step S112). In this area discrimination printing process, the area of the color image in the document is identified, and the area of one color image is assigned to one inkjet unit (I
JU). On the other hand, when the high image quality mode is not set (NO in step S111), the print start position optimizing process is executed (step S11).
3). In the print start position optimizing process, the print start positions of the inkjet units included in the inkjet image forming unit 300 are sequentially changed, and the position where the print process ends in the shortest time is detected. Step S112, or
After any of the processes in step S113, the sheet is transported stepwise to the set initial printing position (step S11).
4).

(3-3-2-1) Print Processing by Area In print processing by area, each area of a color image on a document is identified and assigned with an identification number, and the ink jet unit is identified for each identified area. (IJU). First, a description will be given of a difference in a method of allocating data of a color image area to each IJU when the high image quality mode is set and when the high image quality mode is not set with reference to the drawings. FIG. 29 is a diagram clearly showing a region of a color image shared by each IJU when the high image quality mode is not set. When the high image quality mode is not set, a color image within the print range of each IJU is printed. For example,
In the area A, the IJU1 prints a portion in the print range (S1) of the IJU1, the IJU2 prints a portion in the print range (S2) of the IJU2, and prints the IJU3 (S3). ), The printing is performed on the IJU3. Thus, each IJ
The processing time is reduced by dividing the area of the document image assigned to U. FIG. 30 is a diagram illustrating a region of a color image assigned to each IJU as a result of the region-specific printing process performed when the high-quality mode is set. IJU1 is assigned printing in area A, IJU2 is assigned printing in area B, and IJU4 is assigned printing in area C. In this way, one color image area corresponds to one area.
By allocating one IJU, it is possible to obtain a high-quality output without color shift or unevenness.

FIG. 31 is a flowchart of the printing process for each area (FIG. 28, step S112). In this process, as shown in FIG.
It is divided by the line feed interval of U, and the number of lines obtained by this division is defined as the last line NLst. First, a color image area in the first row is detected (step S120). A serial number is assigned to each detected color image area (step S1).
21). The line number i is set to 2 (step S122),
The following process is repeatedly executed until the row number i becomes the last row N (step S123). First, an area of the color image in the i-th row is detected (step S124). It is checked whether or not the detected area of each color image in the i-th row is continuous with the area of the color image in the immediately preceding (i-1) -th row (step S125). Here, if there is a color image area to which no area number is assigned in the area (YES in step S125), the color image area and the color image of the color image on the (i-1) th row immediately before are displayed. The relationship with the area is checked (step S126).
Here, a new serial number is assigned to an independent color image area that is not continuous with the color image area in the immediately preceding (i-1) th row (step S127). If it is continuous with the area of one color image in the immediately preceding (i-1) th row, the same number as the number assigned to the area of the color image at the time of the processing of the (i-1) th row is assigned (step S128). ). Further, when the color image is continuous with two or more color image areas in the preceding (i-1) th row, the smallest number among the numbers assigned to the plurality of color image areas in the (i-1) th row is used. Is assigned to the area of the color image (step S129). Such a case occurs when the areas of the color image are distributed in a U-shape. Then, the area numbers of all the continuous areas are set in step S12.
9 is replaced with the minimum number assigned (step S130). After these processes are performed for all the color image areas in the i-th row, 1 is added to the row number i (step S131), and the process returns to step S123. 1
Step 31 is repeatedly executed. When the row number i is larger than NLst (NO in step S123), that is, after the process of numbering each color image area in the image area is completed, the existence of the first numbered row exists. The IJU to perform printing of the area of the color image with the number (step S132). As shown in FIG. 30, the area A starts from the fourth line, and the line is within the print range of IJU1. Therefore, the area A is printed by the IJU1. Similarly, area B is printed by IJU2 and area C is printed.
Causes IJU4 to print.

(3-3-2-2) Printing Start Position Optimization Processing The printing time depends on the IJ in addition to the paper transport direction (rotation angle).
It can also be shortened by optimizing the U print start position. In the document image shown in FIG. 26, when the relationship of h1 <(2 × d12) is further satisfied, the printing process by IJU1 and IJU2 is not started from the leading edge of the sheet, but only the step conveyance of the sheet by line feed is performed. Done, color image area 71
If printing by IJU1 and IJU2 is started at the same time after the leading end of IJU1 reaches the printing position of IJU1, printing time T5 can be reduced from 20.4 seconds to 16.4 seconds.
Therefore, the print start position optimization processing (FIG. 28, step S
113), the area of the color image is I
Until the print position of JU1 is reached, a position where the print time is the shortest is detected, and the detected position is determined as a print start position. FIG. 32 is a diagram for explaining the calculation of the print start position. FIG. 33 is a flowchart of the print start position optimizing process. Hereinafter, the print start position optimizing process will be described with reference to FIG. First, the paper is divided in the paper feed direction by a line feed interval Dcr, and the print length L of each line is calculated (step S140).
For example, in the i-th row, there is a non-print portion that is not a color image area in the middle, but since the ink ejecting unit 320 needs to finally move to both ends of the color image area included in the i-th row, The distance between both ends of the color image area is defined as a print length Li. After the processing in step S140, the first line number whose print length L is not 0 is set to Ns (step S141). The print start line js is set to the first line at the leading end of the sheet (step S142). Then, the printing range of each IJU is obtained from the position of the mounted IJU, and the printing time Tjs is obtained by calculation (step S143). The minimum printing time Tmin is set as the value of the printing time Tjs obtained in step S143 (step S144). Printing start position J
The min is set to js (step S145). One is added to the value of js (step S146). If the print start line js is equal to or smaller than Ns (YES in step S147), the print time Tjs at the print start position js is calculated (step S14).
8). The printing time Tjs calculated here is the minimum printing time Tmin
If it is less than (YES in step S149), the minimum printing time Tmin is replaced with the printing time Tjs (step S149).
150), the print start position Jmin is set to js (step S151). In the above step S147, the value of js is N
When the value becomes larger than s, Tmin set at that time is the minimum printing time, and Jmin is the line number of the printing start position.

(3-3-3) Ink Jet Image Forming Process The ink jet image forming process will be described below. FIG. 34 shows an inkjet image forming process (FIG. 14, FIG.
It is a flowchart of step S36). First, the attribute map of the document image for the paper to be printed is read from the hard disk 612 (step S1).
60). The position of the attribute map of the document image to be printed is stored in the page address table 505. By indexing this table 505, the storage position of the attribute map for the corresponding page in the hard disk 612 can be obtained. When performing simultaneous two-sided printing or printing two pages of images on the same side of a sheet, a plurality of document image information is required for one sheet. Read the map.
If it is determined from the number of mounted IJUs and the positional relationship of the color data area of the attribute map that there is color data in the print line of each IJU (step S161)
Then, the address of the color data to be printed in the hard disk 612 and the data width are calculated from the attribute map (step S162). Data from the calculated address is stored in the hard disk 61 by the data width.
2 and temporarily write it into the working RAM 608 (step S163). After the GBTC decryption of the data written in the work RAM 608 (step S16
4) Convert the YCrCb data into RGB data (step S165). RGB data for cyan, magenta,
The data is converted into yellow and black gradation data (step S166). Error diffusion processing for data of each color of cyan, magenta, yellow, and black (dither processing may be used)
Is converted to binary data (step S167). 2
The data is rearranged so that the data of each color can be easily supplied to the IJU (step S168). That is, 1-bit data for each color of each pixel is cut out in units of 8 pixels in the arrangement direction (sub-scanning direction) of the ink ejecting unit 320 for each color and handled as byte data. The ink ejecting unit 320 for each color has a head for 16 pixels in the sub-scanning direction, and requires data of the number of pixels arranged on a line × 2 bytes at the time of printing. The data of cyan, magenta, yellow, and black are written into the working RAM to prepare for a data request from the IJU controller 610 (step S
169). Note that the processing of steps S74 to S78 is performed by software.
It is also possible to implement hardware as a part of the controller 610. By implementing such fixed processing as hardware, the processing speed can be increased and the processing time load on the CPU 607 can be reduced, so that the CPU 607 can be opened to other controls. The data for one line written in the work RAM 608 in step S79 is supplied to the ink ejection unit (see FIG. 5) of a predetermined IJU via the DMA controller 609 and the IJU controller 610 (step S170). In accordance with the supply of data, each IJU is driven to move the ink ejection unit in the paper transport direction (step S171). Wait for printing of one line to be completed (step S172)
YES), the sheet is transported stepwise by the width of one line (16 pixels) (step S173). The above processing is executed for all data, and after execution (YE in step S174)
S), and return.

[0039]

The ink-jet image forming section of the color image forming apparatus of the present invention uses a plurality of ink-jet units at the same time to share the printing process for the conveyed paper, and further uses the calculating means in the shortest time. A printing start position at which printing ends is obtained, and printing is started from this position, thereby realizing rapid printing of a color image.

[Brief description of the drawings]

FIG. 1 is a sectional view of a copying machine.

FIG. 2 is a front view of an operation panel.

FIG. 3 is a diagram showing each processing block centered on an image processing circuit.

FIG. 4 is an external view of an ink jet unit (IJU).

FIG. 5 is a diagram illustrating a configuration of an inkjet unit (IJU).

FIG. 6 is a diagram illustrating a configuration of an intermediate tray.

FIG. 7 is a diagram illustrating a data storage order of a color image area in a document image;

FIG. 8 is a diagram showing a storage state of data in a hard disk.

FIG. 9 is a diagram showing a flow of an encoding process of the GBTC system.

FIG. 10 is a diagram showing an encoding process and a decoding process of the GBTC system.

FIG. 11 is a flowchart of a main routine of an image forming process.

FIG. 12 is a flowchart of a mode setting process.

FIG. 13 is a flowchart of an image forming process.

FIG. 14 is a flowchart of an image forming process.

FIG. 15 is a flowchart of first image data processing.

FIG. 16 is a flowchart of a document determination process.

FIG. 17 shows an image of a document at 0 °, 90 °, 180 °, and 2 °.
It is a figure which shows each state at the time of rotating to 70 degrees.

FIG. 18 is a flowchart of a printing time calculation process.

FIG. 19 is a diagram illustrating a print time calculation process.

FIG. 20 is a flowchart of a process for calculating a printing time.

FIG. 21 is a diagram illustrating a process of calculating a printing time.

FIG. 22 is a diagram illustrating a process of calculating a printing time.

FIG. 23 is a diagram illustrating a process of calculating a printing time.

FIG. 24 is a diagram illustrating a process of calculating a printing time.

FIG. 25 is a diagram for explaining processing for calculating a printing time.

FIG. 26 is a diagram illustrating a process of calculating a printing time.

FIG. 27 is a flowchart of an image rotation process.

FIG. 28 is a flowchart of a second image data process.

FIG. 29 is a diagram showing a color image area shared by each IJU when the high image quality mode is not set.

FIG. 30 is a diagram illustrating an area of a color image shared by each IJU when a high image quality mode is set.

FIG. 31 is a flowchart of an area-specific printing process.

FIG. 32 is a diagram illustrating print start position calculation.

FIG. 33 is a flowchart of a print start position optimizing process.

FIG. 34 is a flowchart of an inkjet image forming process.

[Explanation of symbols]

 1-8 IJU 50 Copier 100 Image reading unit 200 Electrophotographic image forming unit 300 Inkjet image forming unit 301 Intermediate tray 308 IJU unit 607 CPU

Claims (1)

[Claims] 1. A paper feed path is provided at a predetermined interval in a paper transport path,
A plurality of inkjet units each for printing a color image in a direction perpendicular to the paper transport direction; a control means for allocating the color image data to the plurality of inkjet units; and printing in all inkjet units in the shortest time An image forming apparatus comprising: a calculating unit that determines a printing start position to be performed; and a control unit that controls each inkjet unit so that printing of a color image is started from the printing start position obtained by the calculating unit. .