JPH1184810A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten image processing time when monochrome and color images coexist by changing image formation order, so as to shorten an image formation processing time, in the case that a coexistent mode is set and two sheets of paper can be held. SOLUTION: A transfer drum 12 has such a size that two A4-horizontal-size papers can be held (wound) by a chucking mechanism. It can be judged whether two papers are simultaneously held (double chucking) or not by the fact that the length of the paper is <= A4-horizontal-size or not. For instance, two A- and B-surface papers 18 and 19 are simultaneously held. When the monochrome image exists besides the color image, the monochrome and color images coexist and then, it is decided whether the double chucking is attained or not. When the double chucking is attained, a coexistent double chucking mode is set and when the double chucking is not attained, a single chucking mode is set. Thus, the contents of a printing job are confirmed and the image formation order is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as an electrophotographic printer.

[0002]

2. Description of the Related Art Some electrophotographic color printers wind a sheet around a transfer drum and transfer a toner image formed on a photoreceptor to the sheet. In the electrophotographic process, in the case of a monochrome image, development with black toner is performed, and the toner image is transferred to paper. In the case of a color image, development with cyan, magenta, yellow, and black toners is sequentially performed, and four color toner images are sequentially transferred to a sheet to form a color image. Therefore,
In the case of a monochrome document, the transfer is performed only once, but in the case of a color image, four transfers are required.

[0003]

There is a transfer drum of a two-chuck type which can hold two sheets of paper at the same time. When a print job including image data for a plurality of sheets is sent from a computer, two sheets are held on a transfer drum if possible, and an image is sequentially printed on each sheet. For example, if the first image is a color image and the second image is a monochrome image, the color image is printed on the first sheet and the monochrome image is printed on the second sheet. Printing is performed in the order of images sent from the computer. For example, if the first image is a color image and the second image is a monochrome image, the color image is printed on the first sheet of the two sheets held at the same time, and the second sheet is printed. A monochrome image is printed. However, a monochrome image is formed by one electrophotographic process, while a color image is formed by one electrophotographic process.
A single image is formed. The inventor has found that when monochrome images / color images are mixed, the image forming processing time can be reduced by taking the image forming order into consideration.

An object of the present invention is to provide a color image forming apparatus capable of reducing the image forming processing time when a monochrome image and a color image are mixed.

[0005]

According to the present invention, there is provided a color image forming apparatus for forming a toner image of an image by an electrophotographic process and transferring the toner image to a sheet, and a transfer for holding the sheet to which the toner image is transferred. A transfer drum that can hold two sheets of paper at the same time, a mode setting unit that sets a mixed mode when a monochrome image and a color image are mixed, and a transfer drum that can hold two sheets of paper If the mixed mode is set by the paper holding determination unit and the mode setting unit that determines whether or not two sheets can be held by the paper holding determination unit, the image forming process is performed so as to reduce the image forming processing time. Print control means for switching the order of image formation by the forming means. For example, when the mixed mode is set by the mode setting unit and it is determined that two sheets can be held by the sheet holding unit, the print control unit sets the monochrome image on one sheet and the color image on the other sheet. The image forming order is switched so that images are formed within the same rotation of the transfer drum. One of the two color images that requires time to form one image
Since the image is formed on a sheet, an image can be efficiently formed when there are many monochrome images before a color image. For example, when the mixed mode is set by the mode setting unit and it is determined that the two sheets can be held by the sheet holding unit, if the number of color images is even, The image forming order is switched so that a color image is formed on the same sheet within the same rotation of the transfer drum. Since two color images are formed at the same time, a color image can be formed without waste.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the overall configuration of the color image forming apparatus. The color image forming apparatus includes a printer 10, a printer controller 20, and a computer 30. The printer 10 is an electrophotographic printer. Computer 30 is monochrome /
Data such as a color image is created and sent to the controller 20 of the printer. The controller 20 converts the data into print data for the printer 10 and controls the printer 10 to perform printing.

FIG. 2 schematically shows the printer 10. In the printer 10, in the electrophotographic process,
In the case of a monochrome image, black toner is developed. In the case of a color image, development of cyan, magenta, yellow, and black toners is sequentially performed, and a color image is formed. More specifically, the image processing unit 1
00 processes the image data of the monochrome image or the color image received from the controller 20,
01 to the laser drive signal. The photosensitive drum 102
Charger 1 irradiated by eraser lamp 103
04 is uniformly charged. The laser beam emitted from the laser device 101 scans the photosensitive drum 102 to form an electrostatic latent image. Cyan, magenta, yellow,
The four black toner developing units 105 to 108 are sequentially selected to develop the electrostatic latent image on the photosensitive drum 102.
Appropriate paper is conveyed from the paper supply cassettes 110 to 112, and is supplied via the paper supply roller 122 to the paper holding rollers 11.
6 is attracted to and wound around the transfer drum 109 by an electrostatic attraction charger 115 provided opposite to the transfer drum 6. The transfer drum 109 can chuck two sheets of paper at the same time. In this embodiment, the transfer drum 109
Can be chucked at the same time for A4
It can be up to the size of the paper placed horizontally. Photoconductor drum 101
The toner image developed above is transferred to a sheet on the transfer drum 109 by the transfer charger 117. In the case of full-color copying, the above-described charging / exposure / development / transfer process is repeatedly performed for four colors of magenta, cyan, yellow, and black. That is, the transfer drum 109
Rotates four times. Thereafter, the sheet is discharged by the separation / discharge chargers 118 a and 118 b, and the transfer drum 109 is operated by the action of the separation claw 119.
Separated from The sheet is then discharged to the tray 114 after the toner image is fixed through the fixing device 113.

FIG. 3 is a diagram showing C controlling the controller 20.
The PU 21 is shown. Control data such as the paper size and the number of color images / monochrome images is input from the computer 30 to the CPU 21. Further, a memory (not shown)
A signal for handling image data to be drawn / read out is also input. In addition, a transfer drum suction signal is sent to the suction charger 115 to the printer 10, and a print control signal for performing printing based on image data read from a memory (not shown) is sent to the image forming system. Further, other input signals not specifically described are input, and other output signals are transmitted. As described later, when two sheets are wound on the transfer drum 109 at the same time, the controller 20 checks the contents of the print job and changes the order of image formation.

The transfer drum 12 is moved by a chuck mechanism.
This is a size capable of holding (winding) two sheets of A4 landscape size paper. Holds two sheets at the same time depending on whether the length of the paper is less than the length of A4 horizontal size (double chuck)
Can be determined. In the single-sheet chuck (single chuck) mode, one sheet of paper is wound around the transfer drum. One color copy is completed by four rotations of the transfer drum. In the two-sheet chuck mode, two sheets having a short sheet size are wound around the transfer drum. FIG.
Shows a state in which two sheets 18 and 19 of the A side and the B side are held at the same time. In this mode, two color copies are completed by four rotations of the transfer drum, so that copy productivity is improved.

FIG. 5 shows an example of an image forming order. The conventional processing is also shown on the right for comparison. Here, an example of printing three monochrome images (K1, K2, K3) and one color image will be described. Three monochrome images (K1, K2, K3) are successively sent from the computer 30, and then one color image is sent. If the image forming order is not switched as in the conventional case, A
Monochrome images K1 and K2 are formed on the surface and the surface B, respectively. Both sides A and B are separated from the transfer drum. 2
At the rotation, a monochrome image K3 is formed on the new A surface, and a color cyan image (C) is formed on the new B surface.
Side A is separated from the transfer drum. Side B remains. At the third rotation, only the magenta image (M) of the same color image is formed on the surface B. Similarly, only the yellow image (Y) of the same color image is formed at the fourth rotation, and only the black image (K) of the same color image is formed at the fifth rotation.
Therefore, this job requires a total of five rotations.

On the other hand, in the present embodiment, the contents of the print job are confirmed, the order of image formation is changed, and the job is completed in a shorter rotation time than in the conventional case. The order of image formation is switched so that a monochrome image and a color image are formed within the same rotation. In the example of FIG. 5, the first monochrome image K1 is formed on the surface A during the first rotation, and the cyan image (C) of the color image is formed on the surface B. The A side is separated from the transfer drum, but the B side remains as it is. At the second rotation, a second monochrome image K2 is formed on the new A side,
A magenta image (M) of the same color image is formed on the B side. The A side is separated from the transfer drum, but the B side remains as it is. At the third rotation, a third monochrome image K3 is formed on the new A side, and a yellow image (Y) of the same color image is formed on the B side. The A side is separated from the transfer drum, but the B side remains as it is. At the fourth rotation, only the black image (K) of the same color image is formed. Thus, the image formation is completed in a total of four rotations. Therefore, the processing time can be reduced by one rotation.

FIG. 6 shows a flow of mode selection of the CPU 21 of the controller 20. When the job starts,
First, it is determined whether there is a color image in the job (step S10). If there is no color image, it is a monochrome image, and then it is determined whether or not it is a double chuck (step S80). The double chuck means that two sheets are simultaneously held on the transfer drum, and is determined based on the size of the sheet. Also, a single chuck is
This means that only one sheet of paper is held on the transfer drum at the same time. In this embodiment, if the length of the sheet is A4 horizontal size, double chucking is possible. If it is a double chuck, a monochrome double chuck mode is set (step S90), and a monochrome image is printed by the double chuck.
If it is not the double chuck, the single chuck mode is set (step S50), and the monochrome image is printed with the single chuck. If it is determined that there is a color image in the job (YES in step S10), it is next determined whether monochrome images are mixed (step S20). If there is no monochrome image, since it is only a color image, it is next determined whether or not it is a double chuck (step S60). If it is a double chuck, set the color double chuck mode (step S
70), a color image is formed by a double chuck. If it is not a double chuck, a single chuck mode is set (step S50), and a color image is formed with a single chuck. If there is a monochrome image in addition to the color image (YES in step S20), the monochrome image and the color image are mixed, and it is determined whether the image is a double chuck (step S30). If it is a double chuck, a mixed double chuck mode is set (step S40). If it is not a double chuck, a single chuck mode is set (step S50). The present invention relates to the mixed double chuck mode of step S40, and includes a single chuck mode (step S50).
The description of the color double chuck mode (step S70) and the monochrome double chuck mode (step S90) is omitted.

FIG. 7 shows the flow of the mixed double chuck mode (FIG. 5, step S40). Here, the image forming order is switched. First, for the first rotation, A
The paper 18 on the side is a monochrome image, and the paper 19 on the side B is a color image (step S42), and an image is formed. This corresponds to the first rotation in FIG. After image formation,
It is determined whether a combination of a monochrome image / color image is possible (step S44). If the combination is possible, the process returns to step S200 again, the second rotation,
Continue turning and processing. In the example of FIG. 5, since the monochrome image / color image cannot be combined at the end of the third rotation (NO in step S44), a mode other than the mixed double chuck mode is set according to the flow of FIG. 5 (step S46). ). That is, one of the single chuck mode (step S50), the color double chuck mode (step S70), and the monochrome double chuck mode (step S90) is executed.

Assume that the number of color images is m and the number of monochrome images is n. The number M of color image formations is four times the number m of color images in order to form C, M, Y, and K four times in color images. The image formation frequency N of the monochrome image is the same as the number n. M
When either one of N and N becomes 0, the mixed double chuck mode is stopped. In the example of FIG. 5, in the first rotation, M = 1 ×
4 = 4, N = n = 3. At the end of the first rotation, M =
3, N = 2, and after the second rotation, M = 2,
N = 1. At the end of the third rotation, M = 1, N =
0, which corresponds to N = 0 of M = 1 or N = 0 in the determination of step S44, and proceeds to the processing of step S46.

Next, a second embodiment will be described. The second embodiment differs from the first embodiment only in the control of the image forming order. FIG. 8 shows a flow of mode selection of the CPU 21 of the controller 20 in the second embodiment. In this flow, when the number of colors is an even number, two color images are simultaneously formed, and a monochrome image is also formed.
Create images simultaneously. When the number of colors is an odd number, one of them uses color image formation in the mixed processing. When the job starts, first, the number of colors is recognized (step S1).
10). Next, the number of monochrome images is recognized (step S12).
0). Next, it is determined from the paper size whether or not the double chuck is used (step S130). If it is a double chuck, it is next determined whether or not the number of colors is an odd number (step S140). If it is an odd number, a mixed double chuck mode is set (step S150). If the number is not an odd number, the color double chuck mode is set (step S160).
Set the monochrome double chuck mode (step S
170). If it is not a double chuck, a single chuck mode is set (step S180).

[0016]

According to the present invention, when a monochrome image and a color image are mixed in a print job, the image forming processing time can be reduced. The efficiency of image formation is improved, and the job time is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color image forming apparatus.

FIG. 2 is a schematic sectional view of the printer.

FIG. 3 is a diagram of a controller.

FIG. 4 is a view showing a state of a double chuck.

FIG. 5 is a diagram illustrating an image forming order.

FIG. 6 is a flowchart of mode selection.

FIG. 7 is a flowchart of a mixed double chuck mode.

FIG. 8 is a flowchart of mode selection in the second embodiment.

[Explanation of symbols]

Reference Signs List 10 printer, 20 controller, 30 computer, 100 image data processing unit, 102 photosensitive drum, 109 transfer drum.

Claims (3)

[Claims] 1. An image forming means for forming a toner image of an image by an electrophotographic process and transferring the toner image to a sheet, and a transfer drum for holding a sheet to which the toner image is transferred, and a transfer capable of holding two sheets at the same time A drum, a mode setting unit for setting a mixed mode when a monochrome image and a color image are mixed, a sheet holding determining unit for determining whether two sheets can be held on the transfer drum, and a mode setting When the mixed mode is set by the means and the paper holding determination means determines that two sheets can be held, the print control means for switching the order of image formation by the image forming means so as to shorten the image forming processing time is provided. Color image forming apparatus. 2. The print control unit according to claim 1, wherein the mixed mode is set by the mode setting unit, and when it is determined that the two sheets can be held by the sheet holding unit, the monochrome image is printed on one sheet and the other is printed on the other sheet. 2. The color image forming apparatus according to claim 1, wherein the image forming order is switched so that a color image is formed on the paper within the same rotation of the transfer drum. 3. The print control unit according to claim 2, wherein the mixed mode is set by the mode setting unit, and if it is determined by the sheet holding unit that two sheets can be held, if the number of color images is even, 2. The color image forming apparatus according to claim 1, wherein the image forming order is switched so that a color image is formed on any one of the sheets within the same rotation of the transfer drum.