JP3750325B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image on a transfer material such as recording paper using a plurality of photosensitive drums, such as a color copying machine and a color printer, and more particularly to a tandem type full color image forming apparatus.
[0002]
[Prior art]
In one of the full-color image forming methods that are becoming mainstream, four photosensitive drums are arranged in parallel in the direction perpendicular to the longitudinal direction of the transfer belt, and cyan, magenta, yellow, and black are arranged on each photosensitive drum. There is a tandem system in which a toner image is formed using toner (hereinafter, C, M, Y, K), and the toner images are sequentially transferred onto a single transfer material conveyed on a transfer belt.
[0003]
By the way, in the case of forming a monochrome image in the tandem method for forming a full-color image in this way, for example, the user sets only the monochrome image original on the apparatus and designates the monochrome copy mode from the operation panel. Thus, image formation is performed only by the photosensitive drum that forms the black toner image. At this time, if all the four photosensitive drums are driven and the three photosensitive drums C, M, and Y are idled without being involved in image formation, a dedicated configuration for monochrome image formation is minimized. This has the advantage that the image forming mechanism can be simplified and the processing speed can be made substantially the same as that during color image formation. Depending on the type of the image forming apparatus, there are those in which such technical measures are taken (first conventional machine).
[0004]
Contrary to these measures, when the monochrome image is formed, the driving of the photosensitive drum of toner color unnecessary for forming the monochrome image is stopped and the drum peripheral surface is separated from the transfer belt surface. The proposed technology has been proposed (JP-A-3-288173, JP-A-6-258194, JP-A-6-102767, etc.) (second conventional machine).
[0005]
However, in the first conventional machine, since all the photosensitive drums are driven in spite of monochrome image formation, the peripheral surfaces of the C, M, and Y photosensitive drums that are not used for toner image formation are also cleaned. Since the members are in sliding contact and the toner is not adhered, excessive frictional resistance is generated on the drum peripheral surface, resulting in a problem that the life of the photosensitive drum is shortened and the cleaning member is turned up.
[0006]
On the other hand, in the case of the second conventional machine, it is necessary to suspend the exposure and transfer operations at the time of transfer belt separation and pressure contact switching, interrupt the paper feeding operation, and perform the separation and pressure contact operations. There was a problem that it was not good.
[0007]
[Problems to be solved by the invention]
By the way, recently, there are monochrome documents such as character documents while document images are becoming multi-colored. Therefore, there is a demand for a copying operation in a so-called mixed loading state in which color documents and monochrome documents are mixed in an unordered manner during copying. There is.
In order to automatically perform the copying operation in such a mixed loading state, it is necessary to determine whether the original image is color or monochrome before the original is read. Therefore, automatic copying in a mixed state is impossible.
[0008]
Even if a function for discriminating whether a manuscript is a color manuscript or a monochrome manuscript is added to the above-mentioned conventional machine so that the color copying mode and the monochrome copying mode can be switched according to the discrimination result, four photosensitive drums are used. In the first conventional machine that performs monochrome copying by driving all three drums C, M, and Y, without making an image, and without making an image, the life of the photosensitive drum is The aforementioned problem of turning over the cleaning member remains as it is.
[0009]
In the second conventional machine that stops driving the photosensitive drum unnecessary for the formation of a monochrome image and separates the photosensitive drum from the surface of the transfer belt, the above-mentioned problems still remain and a series of further steps Even during document copying, the transfer belt is pressed and separated according to the document discrimination result, so that the copying operation is interrupted many times, and the image is accompanied by vibration generated by the transfer belt pressing and separating operations. In order to avoid this, it is necessary to ensure a sufficient work interruption time when the transfer belt is pressed and separated, resulting in a problem that the copying speed is reduced.
[0010]
In view of the above points, the present invention is a new and useful method that can automate a copying operation in a mixed state of a monochrome document and a color document in a state where both the problems with the first conventional machine and the problems with the second conventional machine are solved. It aims to provide a means.
[0011]
[Means for Solving the Problems]
  In order to solve the above problems, the present invention writes original images of different colors on a plurality of image carriers, and superimposes the original images on the image carriers on a transfer belt or a transfer material conveyed on the transfer belt. The transfer belt is relatively spaced from the color print mode for transfer and all other image carriers except the one image carrier, and the original image on the one image carrier is transferred over the transfer belt or above. Image forming apparatus switchable between single color print mode for transfer to transfer material conveyedBecause,During one print operation,Single color printContinuousPrintNumberA means of accumulating results,During the one printing operation,Next, a determination unit that determines whether a document image to be printed is a single color or a color, and the determination unit determines that the document image is a single color, and the accumulation result of the accumulation unit satisfies a predetermined condition Only in some cases, the color print mode is switched to the single color print mode, and when the original image to be printed next is determined to be in color by the determination means, the single color print mode is switched to the color print mode. And a control means for controlling the operation.
[0012]
  The accumulating means isSaidIt may be a counting means for counting the number of continuous prints of a single color print.
  The accumulating means includesSaidAn integrator that integrates the continuous printing operation time of a single color print may be used.
  Further, the present invention provides a color print mode in which original images of different colors are written on a plurality of image carriers, and the original images on the image carriers are transferred while being superimposed on a transfer belt or a transfer material conveyed on the transfer belt. The transfer belt is relatively separated from all other image carriers except the one image carrier, and the original image on the one image carrier is transferred to the transfer belt or a transfer material conveyed thereon. Image forming apparatus switchable between single color print mode for transferBecause,During each print operationColor information acquisition means for capturing color information of the original image before writing the original image on the image carrier, determination means for determining whether each original image is a single color or color from the acquired color information, and the determination A copy number order grasping means for grasping a single color and a color copy number and a copy order for a series of document images determined by the determination result of the means; and a copy number order for the series of document images; Control means for switching from the color print mode to the single color print mode immediately before printing when the single color original image is continuous, and switching from the single color print mode to the color print mode after the single color print is completed; It is characterized by providing.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Hereinafter, a tandem full-color image forming apparatus as an application example of the present invention will be described. FIG. 1 is an internal front view showing a main configuration of the image forming apparatus. The image forming apparatus is roughly classified into an automatic document feeder 10, an image scanner unit 20, a control unit 40, a writing optical system 50, a printer unit 60, a paper feeding unit 90, and the like.
[0014]
As shown in the figure, the automatic document feeder 10 is parallel to the surface of a platen glass 201 to be described later by the peripheral surfaces of the document set tray 101, feed rollers 102 to 116, and a plurality of rollers 107 to 114 from upstream to downstream in the document transport direction. A known document conveying belt 115 that is stretched, a drive motor (not shown) that rotationally drives the belt 115, a document switchback unit 116, a discharge roller 117, a document discharge tray 118, and the like are arranged in this order. It is.
[0015]
The image scanner unit 20 includes a platen glass 201 arranged in a horizontal direction on the paper surface, a first slider unit 204 having an exposure lamp 202 and a mirror 203 immediately below the platen glass 201, and a second slider having mirrors 205 and 206. The unit 207, the equal magnification lens 208, and the CCD scanner 209 are disposed at predetermined positions in the drawing. The first and second slider units 204 and 207 are movable left and right in the drawing along the glass plane. Reference numeral 212 on the right side of the drawing is a drive motor for each slider unit. Further, a white reference plate 210 for shading correction is disposed at the left end of the platen glass 201 in the drawing. A digital signal processing unit 211 (details will be described later) includes a ROM for storing original image data of red, green, and blue (R, G, B) therein, and correction processing is performed on the image data. Built-in control circuit.
[0016]
The control unit 40 is composed of a plurality of substrates, and is connected to drive systems (motors, etc.) of each part of the apparatus. Also, it has a CPU and ROM (not shown) inside, and controls and manages a main routine (FIG. 13) regarding a series of image forming operations of the apparatus. The control unit 40 is also connected to the digital signal processing unit 211 described above, and is disposed in the proximity position of the unit.
[0017]
The writing optical system 50 includes a plurality of mirrors 502a to 511a and 502b to 511b around a polygon mirror 501 and laser diodes 512C to 512K. A detailed configuration of the writing optical system 50 and the printer unit 60 is shown in a front view of the periphery of the printer unit 60 in FIG.
As shown in the figure, the polygon mirror 501 and the mirrors 502a to 511a and 502b to 511b each have four broken lines as light paths of cyan, magenta, yellow, and black (hereinafter referred to as C, M, Y, and K) color components, respectively. The photosensitive drums 601 </ b> C to 601 </ b> K are arranged while maintaining a predetermined angle so as to be able to scan the peripheral surfaces.
[0018]
The printer unit 60 is stretched around the peripheral surface of the driving roller 61, driven rollers 62, 67, 77, and tension roller 63 in the center inside the apparatus housing (lower side of the writing optical system 50 in FIG. 2). The image forming station 600C is mainly composed of a transfer belt 65 that is rotationally driven in the X direction with the 61 side as an upstream, and image forming stations 600C to 600K that are orthogonal to the X direction on the forward path and arranged in parallel with each other. .
[0019]
Photosensitive drums 601C to 601K are built in the image forming stations 600C to 600K while being parallel to the length of each station, and charging devices 602C to 602C are arranged on the peripheral surfaces along the Z direction from the upper left in the drawing. 602K, developing devices 603C to 603K, transfer brushes 604C to 604K, drum cleaners 605C to 605K, and the like are arranged to perform image formation by a known Carlson process. The photosensitive drums 601 </ b> C to 601 </ b> K are driven by being driven in the Z direction by transmitting a driving force by pressing the peripheral surface thereof against the surface of the transfer belt 65. A belt cleaner 68 is disposed on the upstream side of the transfer belt 65, a separation charger 69 is disposed on the downstream side of the forward path, and a static elimination charger 70 is disposed on the belt return path at predetermined positions in the drawing.
[0020]
A frame-like frame 64 is accommodated on the inner peripheral surface of the transfer belt 65 with its longitudinal direction being parallel to the belt. The frame 64 has a structure in which two L-shaped steel plates 641 and 642 are opposed to each other at regular intervals, and are connected to each other by three strip-shaped members 643 to 645 as shown in the frame perspective view of FIG. . On the opposite side surfaces A and B of the frame 64, driven rollers 62 and 67 are rotatably supported on the front side and the back side of the paper, and four transfer brushes 604C to 604K, although not shown, are arranged on the two sides. It is arranged at regular intervals between the rollers.
[0021]
Of these, the shaft 621 of the driven roller 62 extends longer than the width of the frame 64, and is supported by flanges 622 and 623 fixed to the apparatus housing side independently of the frame 64.
Also, springs 69a and 69b are installed between the rear side of the bottom surface of the frame 64 (the back side of the connecting member 644 in the drawing) and the stage 691 fixed to the apparatus housing side, and the frame 64 is arranged around the axis 621. In addition, it is always elastically biased upward.
[0022]
Further, the side surfaces A and B of the L-shaped steel plates 641 and 642 are provided with notches C and D at appropriate positions near the driven roller 67, respectively, and bearing portions 66d and 66e outside the frame 64 are provided in the notches C and D, respectively. The cam shaft 66c pivotally supported by is inserted. Two cams 66a and 66b are fixed to the cam shaft 66c at positions near the inside of the side surfaces A and B, while the front end of the cam shaft 66c is connected to a drive system of a stepping motor (not shown). ing. Therefore, when a constant rotational driving force is applied from the drive system to the cam shaft 66c, the cam surface comes into contact with the bottom surfaces E and F of the L-shaped steel plates 641 and 642, and opposes the elastic force of the springs 69a and 69b. The frame 64 is pushed down around the shaft 621 of the driven roller 62.
[0023]
According to the operation of the frame 64 as described above, when the cams 66a and 66b do not operate, the surfaces of the transfer belt 65 and the transfer belt 65 of the frame 64 are the peripheral surfaces of all the photosensitive drums 601C to 601K as shown in FIG. Pressure contacted. On the other hand, when the cams 66a and 66b are operated, the two rollers 62 and 77 are driven by the driven roller 62 and the driven roller 77 pivotally supported on the apparatus housing side at the position shown in FIG. The surface range of the stretched transfer belt 65 is held in pressure contact with the photosensitive drum 601K, and the other surfaces of the transfer belt 65 are the drum peripheral surfaces of the photosensitive drums 601C to 601Y by the frame 64 being pushed down. Spaced apart. In this embodiment, the state in which the transfer belt 65 is in pressure contact with all the photosensitive drums 601C to 601K is referred to as a color mode, and the state in which only a single photosensitive drum (601K) is in pressure contact with the belt. It will be called monochrome mode. Further, the present apparatus is set to the normal color mode, and can be switched to the monochrome mode according to circumstances.
[0024]
Returning to FIG. 1 again, at the bottom of the apparatus casing, there are paper feed cassettes 91a to 91d for storing recording papers of various sizes, feed rollers 92a to 92d arranged on the upper surface near one end thereof, and the rollers 92a to 92d. Conveying rollers 93 a to 96 d, 93 a to 96 d, 93 a to 96 d, and 93 a to 96 d are arranged along the recording paper conveying direction to constitute a paper feeding unit 90.
[0025]
On the upstream side and downstream side of the forward path of the transfer belt 65 shown in the left-right direction on the paper surface, the manual recording paper tray 70, the feeding rollers 71 to 73, the registration rollers 74 and 75, or the fixing unit 80 and the paper discharge tray 78, respectively. Is arranged at a position in the figure. Further, on the upstream side of the registration rollers 74 and 75, photocouplers 78 and 79 are installed as recording sheet leading edge detection sensors.
[0026]
An operation panel 30 is installed on the upper side surface of the copier housing in which the image scanner unit 20 is housed, at a position (dashed line in FIG. 1) that is easy for the user to use.
The digital signal processing unit 211 is connected and arranged at an intermediate position between the image scanner unit 20 and the writing optical system 50, and is configured by a substrate centering on a CPU, ROM, and IC. The unit 211 generally stores R, G, and B image data of an original image read by the image scanner 20 in a ROM 507B, and sequentially converts the image data into C, M, Y, and K image data. In this embodiment, in addition to this operation, a function for controlling the separation of the frame 64 of the printer unit 60 is also provided. Hereinafter, the block diagram relating to the automatic color selection (ACS) function of the digital signal processing unit of FIG. 6 will be described in detail.
[0027]
As illustrated, the digital signal processing unit 211 includes a CPU 501B, a ROM 507B, a timing control unit 502B, a shading correction unit 503B, an HVC conversion unit 504B, an ACS unit 505B, a UCR-BP unit, a masking unit, a γ correction unit (not shown), and the like. Consists of.
The timing control unit 502B controls the operation timing of the scanning and shading correction of the CCD 209, and is connected to the CPU 501.
[0028]
The shading correction unit 503B has a function of eliminating the irradiation unevenness of the exposure lamp 202 and the sensitivity unevenness of the CCD scanner 209. Specifically, when the white reference plate 210 installed at the edge of the platen glass is read by the CCD scanner 209 during pre-scanning, the multiplication ratio for shading correction for R, G, and B color pixels of the original image is determined from the data. It is determined and stored in the ROM 507B described later. Then, it is taken out from the ROM 507B again at the time of reading the document image, and the document data is corrected using this multiplication ratio. The shading correction unit 503B outputs in two directions. That is, one is a direction related to general image formation, and is a known one in which a UCR-BP portion, a masking portion, a γ correction portion and the like are sequentially connected. On the other hand, the other output direction is connected from the HVC conversion unit 504B to the ACS unit 505B.
[0029]
The HVC conversion unit generally converts the R, G, and B image data corrected by the shading correction unit 503B into a hue angle (H *) that is a color region signal in a known Munsell color space (not shown), The data is converted into lightness (V) and chroma (C *) data. In the HVC conversion unit 504B according to the present embodiment, brightness (V) and color difference (W) in the process of calculating the H, V, and C data._R, W_B) Is output to the ACS unit 505B.
[0030]
The ACS unit 505B includes a saturation calculation unit 5051B, a first comparison unit 5052B, a chromatic pixel counter 5053B, an achromatic pixel counter 5054B, a second comparison unit 5055B, and the like. It has a function of discriminating whether a document is color or monochrome from G and B data.
Among these configurations, the saturation calculation unit 5051B includes the V, W calculated by the HVC conversion unit 504B for each pixel of the document._R, W_BFor each data, the saturation signal W is calculated by the following expression (1).
[0031]
[Expression 1]
W = (W_R ²+ W_B ²)^1/2
The first comparison unit 505B determines whether or not the calculated W is greater than or equal to a preset threshold value. That is, if it is equal to or greater than the threshold value, it is determined as a chromatic pixel, and if it is equal to or less than that, it is determined as an achromatic pixel. The determination result is cumulatively counted by the chromatic pixel counter 5053B and the achromatic pixel counter 5054B connected to the comparison unit 505B.
[0032]
The second comparison unit 5055B divides the counted number of pixels by the total number of pixels of a preset document size, and thereby the ratio of chromatic or achromatic pixels in the total number of pixels per document Are calculated, and it is determined from the result whether the original to be copied is monochrome or color. In this embodiment, the total number of pixels of the original size is set to a value corresponding to the maximum A3 in the normal size, and the ratio of chromatic color pixels is calculated to be 0.1% or more of the total number of pixels of the original size. If so, it is set so as to determine that the original to be copied is in color.
[0033]
The ROM 507B stores the R, G, B color component data of the document, the control program of the CPU 501B (frame separation control program, recording paper interval control program, etc.), setting values set in advance for the monochrome copy count value, The total pixel number setting data and the like of the A3 document are respectively stored and directly connected to the CPU 501B.
[0034]
The CPU 501B has an assistant role to the CPU of the control unit 40. A frame separation control unit 5011B and a monochrome copy counter unit 5012B are included therein, and the operation of each component of the printer unit 60 is integrated.
The monochrome copy counter unit 5012B counts the number of copies when the mode determination unit 506B determines that the document used for image formation is monochrome. The monochrome copy count value is sequentially compared with a set value stored in advance in the ROM 507B every increment of one count, and a control instruction to the separation control unit 5011B is determined by the CPU 501B from the comparison result. In this embodiment, the set value to be compared with the monochrome copy count value is set to three copies.
[0035]
It should be noted that when the document copied during counting shifts from monochrome to color, the counting operation is reset and stopped. On the other hand, when the document is only in color, the counter unit 5012B does not count. It has become.
The separation control unit 5011B performs separation control of the frame 64 through the control unit 40 according to the frame separation control program when the count value of the monochrome copy counter unit 5012B exceeds a set value. Further, before the separation control, a separation control flag is set in the CPU 501B (flag ← 1), and the separation control is continued while this flag is set. The flag is deleted when the monochrome copy that has been continued until now is shifted to color copy or when only color is copied (flag ← 0).
[0036]
Further, as an important function for maintaining a good copying speed, the CPU 501B controls the interval between the continuously conveyed recording sheets by the recording sheet conveyance control program.
Next, the recording paper conveyance control program will be specifically described with reference to FIGS. These figures are image station peripheral views showing the recording paper conveyance state in the color mode or monochrome mode, and further in the monochrome / color mode transition state. In these figures, X is the recording paper interval, L1 is the distance from the exposure position to the transfer position on the peripheral surfaces of the photosensitive drums 601C to 601K, V is the system speed, and T is the time required for the separation operation. The recording sheets to be conveyed are indicated by numbers (1) to (8).
[0037]
When shifting from the color to monochrome mode, the configuration of the periphery of the printer unit 60 shifts from FIG. 7 to FIG. 8 to FIG. That is, the recording sheets {circle around (1)} to {circle around (8)} are fed out by the feeding rollers 95a and 96a, the intervals between the recording papers are adjusted by the timing rollers 74 and 75, and are conveyed on the transfer belt 65, thereby four photosensitive drums 601C. The transfer positions of ˜601K are sequentially passed to perform predetermined image formation. Here, FIG. 7 shows a state in which color copying is performed on recording papers {circle around (1)} to {circle around (4)} before the mode is switched (color mode), FIG. 8 is a time when switching from color to monochrome mode, and FIG. This shows a state in which monochrome copying is performed on recording sheets (5) to (8) after switching (monochrome mode). Here, in FIG. 8, the interval between the recording sheet $ on which the last color copy was made and the recording sheet (5) on which the monochrome copy was made first is expressed by the following equation (2).
[0038]
[Expression 2]
X ≧ L1 + VT
In the above equation, VT is the recording paper conveyance distance (belt rotation driving distance) of the transfer belt 65 during the separation operation. That is, the reason why VT is added to the right side of the above equation is to prevent image formation from being performed until the separation operation is completed in order to avoid an unstable image formation operation due to vibration generated during the separation operation. .
[0039]
On the other hand, the recording paper interval X (FIGS. 7 and 9) in the state before and after the transition from the color mode to the monochrome mode is expressed as in Expression 3 based on Expression 2.
[0040]
[Equation 3]
X <L1 + VT
That is, in this case, X creates a recording paper conveyance control program so as to make it as small as possible according to the performance relating to the processing speed of the image forming station and the conveyance speed of the transfer belt 65, and ensures a high image processing speed. ing.
Next, when the mode returns from the monochrome mode to the color mode, the state of the configuration around the printer unit 60 shifts from FIG. 10 to FIG. 11 to FIG. Here, in FIG. 10, monochrome copying is performed on the recording sheets (1) to (3) before mode switching (monochrome mode), in FIG. 8, when switching from monochrome mode to color, and in FIG. This shows how color copying is performed on recording sheets (4) to (7) after switching (color mode). Among these, in FIG. 11, the interval between the recording sheet {circle around (3)} on which the last monochrome image is formed and the recording sheet {circle around (4)} on which color copying is performed first is expressed by the following equation (4).
[0041]
[Expression 4]
X ≧ L0 + L1 + VT
Here, L0 is the distance between the axes of the photosensitive drums 601C and 601K, and the distance between the transfer position of the photosensitive drum 601K on the most downstream side of the recording paper conveyance of the transfer belt 65 and the transfer position of the upstreammost photosensitive drum 601C. This is a necessary term for securing. Further, the recording paper interval X before and after the separation operation (FIGS. 10 and 12) is expressed as follows using Equation 4.
[0042]
[Equation 5]
X <L0 + L1 + VT
At this time, X is also set by the recording paper conveyance control program in the ROM 507B so as to be as small as possible as in Equation 3.
Summarizing the recording paper conveyance control of the CPU 501B, when the frame 64 is separated, a predetermined recording paper interval is required in accordance with the change of the transfer position. In other cases, the processing speed is increased. In order to increase the speed, the interval is set as narrow as possible.
[0043]
The image forming operation of the apparatus having the above configuration will be described with reference to the main routine in FIG. 13 and the subroutine for frame separation control in FIG. In the present invention, since the operation of the apparatus differs depending on whether the document is color or monochrome, the description will be given separately for each case. First, a case where one color original is set by the user and one copy is made is described. Separately, a monochrome original and a color original are set one by one, and each of these is copied ten times in succession. To state.
[0044]
First, a case where a user designates copying of a color document will be described.
According to this apparatus, first, when the user presses a copy start key (not shown) on the operation panel 30, the first recording sheet is fed from the sheet feeding cassette 91a by the feeding roller 92a, and the feeding roller 74, The leading edge of the recording paper S is positioned immediately before 75 and waits.
[0045]
Further, the programs related to the stepping motor control, recording paper conveyance control, frame separation control, etc. stored in the ROMs of the control unit 40 and the digital signal processing unit 211 are returned to the initial state, and the remaining original image Data is erased. In addition, the count value n of the monochrome image formation counter unit 5012B of the CPU 501B is also reset (n ← 0) (S100).
[0046]
When the initial setting is completed, the internal timer of the control unit 40 starts counting (S101), and is placed on the document set tray 101 of the automatic document reading unit 10 according to the control instruction of the CPU built in the control unit 40. One color document placed thereon is conveyed to a predetermined position on the platen glass 201. The document image is exposed to the exposure lamp 202 through the first slider unit 204 and the second slider unit 207 of the image reader unit, reflected by the mirrors 203 to 206 and the like, and read by the CCD scanner 209. At this time, the document image read by the CCD scanner 209 is appropriately processed by the timing control unit 502B and the shading correction unit 503B of the digital signal processing unit 211, and is temporarily stored in the ROM 507B of the unit 211 (S200).
[0047]
Subsequently, a frame separation control process (S300) is performed. According to the subroutine of FIG. 14, after it is determined whether or not the recording paper leading edge detection sensors (photocouplers 78 and 79) have detected the leading edge of the recording paper (S301), each color of R, G, and B stored in the ROM 507B is determined. The component image data is sequentially extracted, and the HVC conversion unit 504B performs lightness (V) data and color difference data (W for each Munsell color system coordinate)._R, W_B). These data are sent to the ACS unit 505B, where it is determined whether the document is color or monochrome (S302). In other words, in this case, in the ACS unit 505B, the pixels of the document distributed by the first comparison unit 5052B through the saturation calculation unit 5051B are counted by the chromatic / achromatic pixel counters 5053B and 5054B, respectively. In 5055B, it is determined that the number of chromatic pixels with respect to the total number of pixels of the original A3 size is 0.1% or more, and it is recognized that the original is color. The subroutine proceeds to S305, where the count value n of the monochrome copy counter unit 5012B of the CPU 501B is reset, the separation control flag is deleted in the CPU 501B (flag ← 0) in S307, and the position of the frame 64 is maintained in the normal state. The That is, the transfer belt 65 is maintained in contact with the peripheral surfaces of all the photosensitive drums 601C to 601K, and this subroutine is returned.
[0048]
Note that the process of determining whether or not the leading edge of the recording paper has been detected in S301 is necessary in order to perform the processes of S302 to S304 or S302 to S307 only once on one recording paper. That is, if the distinction for each recording sheet is not made clear, the routine circulates many times during the processing for one recording sheet, and the monochrome copy count value n is inadvertently counted up. S301 prevents the occurrence of such a problem.
[0049]
The process returns to the main routine again, and then a copy process is performed in S400. Specifically, each image data output from the shading correction unit 503B is converted into image data of each color component of C, M, Y, and K through each correction process such as UCR-BP, masking, and γ correction unit. . These image data are later sent to the control unit 40, where they are converted into laser beams corresponding to the respective color components, irradiated from the respective laser diodes 512C to 512K of the writing optical system 50 to the polygon mirror 501, and The photosensitive drums 601C to 601K are exposed to the peripheral surface through the optical path. Since the drum peripheral surface is charged in advance by the chargers 602C to 602K, each toner is attached from the developing unit 603M to form a toner image. This toner image is successively multiplex-transferred to a predetermined position of the recording paper S conveyed on the transfer belt 65 by the electric field generated by the transfer brushes 604C to 604K. The transferred recording paper is separated from the belt surface by the electric field generated by the separation charger 69, and the toner is fixed by the fixing unit 80, and then discharged to the discharge tray 71. After the transfer, the transfer belt 65 is neutralized on the inner and outer peripheral surfaces by a neutralization charger 70 and cleaned by a belt cleaner 68. Thereafter, the main routine waits for the end of the internal timer, and finishes one routine after the end (S102).
[0050]
The above is the operation when one copy is made per color document. As described above, when only one copy is made, the copying operation is not continued. Therefore, the same operation is performed when one copy is made in monochrome, and the frame separation control by the CPU 501B is not performed.
Next, a case will be described in which the user sets a color document and a monochrome document one by one in this order on the document tray and inputs to the operation panel 30 to make 10 copies each. In the following description, in order to clarify the difference in the operation of the apparatus, the description of the common part with the above operation is simplified.
[0051]
When the user designates from the operation panel 30 and the copy start key is pressed, the first recording sheet waits immediately before the feeding rollers 74 and 75, and the control unit 40 and the digital signal processing unit 211 are initialized. (S100).
Next, the internal timer starts counting (S101). First, the original is read by the image reader unit 20, and the original image data of each of the R, G, and B color components is subjected to image correction such as shading correction in the digital signal processing unit 211. Once stored in the ROM 507B (S200).
[0052]
Subsequently, the process proceeds to a frame separation control process (S300), and proceeds to a subroutine S301. Here, after it is determined whether or not the recording paper leading edge detection sensors (photocouplers 78 and 79) have detected the leading edge of the recording paper, the ACS unit 505B performs color discrimination on the image data stored in the ROM 507B (S302). ). In this case, since the document is in color, the color mode is set after the monochrome copy count value n is reset (S305) after the ACS section 505B determines this, and one color copy is made in S400. Done. After the main routine is completed, the remaining nine copies are processed in the same manner. At this time, the rotational speeds of the feeding rollers 74 and 75 are controlled by the CPU 501B so that the interval between the recording sheets satisfies Equation 3.
[0053]
When all the 10 color copying processes are completed in this way, monochrome copying is performed continuously. First, in the first monochrome copying, processing similar to the above is performed from S101 to S300, and the process proceeds to frame separation control processing (S300). In the subroutine of S300, after it is determined whether or not the recording paper leading edge detection sensors (photocouplers 78 and 79) have detected the leading edge of the recording paper (S301), when the document is subjected to ACS control, the ACS section The second comparison unit 5055B of 505B determines that the ratio of chromatic color pixels to the total number of pixels of the A3 size document included in this document is 0.1% or less, and recognizes that the document has shifted from color to monochrome. (S302).
[0054]
Thereafter, the subroutine proceeds to S303, where the count value n of the monochrome copy counter unit 5012B of the CPU 501B is compared with the set value (m = 3) stored in the ROM 507B. Since n is still 0 in this case, the process proceeds to S306. After n ← n + 1 is counted (n ← 1 is counted up), the separation control flag of the CPU 501B is erased in S307, and the main routine is executed. To return to monochrome copying in the color mode (S400). After completion of the timer (S102), it is determined whether or not all copies are completed (S103), and this routine is returned.
[0055]
In the subsequent monochrome copying routine, the monochrome copy count value (n = 1) is compared with the set value (m = 3) in subroutine S303, and the condition of n ≧ m is not yet satisfied. Similarly, the process proceeds to S306 to count up (n ← 2), the separation control flag is deleted (S307), the process returns to the main routine, and monochrome copying is performed in the color mode (S400), and the internal timer is ended. (S102) One routine is terminated.
[0056]
In the same manner, the third monochrome copy is made and n is counted up (n ← 2).
Here, the flow in the subroutine of S300 is changed from the fourth monochrome copying operation. In other words, n = 3 = m is recognized from the comparison result of the number of monochrome copies in S303, and the step proceeds to S304 for the first time at this point, and the frame separation control is performed from the frame separation control unit 5011B of the CPU 501B through the CPU of the control unit 40. The That is, the photosensitive drums 601C to 601Y other than 601K are separated from the peripheral surface of the transfer belt 65, and their rotational driving is stopped. Subsequently, the control unit 40 adjusts the rotational speeds of the feeding rollers 74 and 75 so that the recording paper interval satisfies Equation 2, and the fourth recording with the interval from the third recording paper maintained appropriately. Monochrome copying is performed on the paper only by the photosensitive drum 601K. At this time, n is counted up to 4. After copying, the internal timer is ended (S102), it is determined whether or not all copying is completed (S103), and this routine is returned.
[0057]
In the subsequent six-color monochrome copying, the CPU 501B controls the recording paper to be continuously conveyed so that the interval between the three is satisfied, and copying is performed only by the image forming station 600K. If it is determined that all copies have been completed (S103), this routine ends.
Although detailed explanation is omitted, contrary to the above case, when the copying process is shifted from monochrome to color, it is determined in the subroutine of S300 that the next copy is color copying (S302). In step S305, the monochrome copy count value n is reset, and the process proceeds to step S307. Here, the separation control flag is deleted in the CPU 501B (flag ← 0), and since the flag has shifted from 1 to 0 at this time, the separation control unit 5012B in the CPU 501B moves the frame 64 to the normal position through the control unit 40. The transfer belt 65 is pressed against the peripheral surfaces of the photosensitive drums 601C to 601K. At this time, the CPU 501B controls the interval between the recording sheet on which the monochrome copy is made last and the recording sheet on which the color copy is made first to satisfy Equation (4).
[0058]
(Embodiment 2)
Hereinafter, an image forming apparatus which is another application example of the present invention will be described. In this embodiment, the elapsed processing time during monochrome copying is measured, and when this measured time exceeds a predetermined value, the image forming apparatus shifts to the monochrome mode. The main feature of this embodiment is that the internal configuration of the CPU 501B of the digital signal processing unit 211 in Embodiment 1 is equipped with a monochrome copy timer unit (not shown) instead of the monochrome copy counter unit 5011B. is there. Since the other configuration is almost the same as that of the above embodiment, the description of the common parts is simplified.
[0059]
In the subroutine of the frame separation control process S300 of FIG. 15 described later, the monochrome copy timer unit determines that copying is performed on the monochrome image by the ACS unit 505B, and a time count flag is set in the CPU 501B (flag ← 1). Start the time count. This time counting operation is continued until the flag is erased (flag ← 0).
[0060]
The CPU 501B is preset with a comparison count value for the count value of the monochrome copy timer section. This is a time scale for the apparatus to shift from the color mode to the monochrome mode, and is set to 40 seconds in the present embodiment.
Hereinafter, the operation of the image forming apparatus according to the present embodiment will be described with reference to the main routine of FIG. 13 and the S300 subroutine of FIG. The next operation is performed when the user designates 10 copies for one color document and one monochrome document.
[0061]
When the user presses the copy start key on the operation panel 30, the first recording paper is waited immediately before the feed rollers 74 and 75, and the control unit 40 and the digital signal processing unit 211 are initialized (S100). .
Subsequently, the internal timer starts counting (S101), the R, G, B color component image data of the color document is read by the image reader unit 20, and each digital signal processing unit 211 performs each correction process such as UCR-BP. And stored in the ROM 507B (S200).
[0062]
The subroutine for the subsequent frame separation control process (S300) proceeds to S311 in FIG. That is, the ACS unit 505B determines the color of the document, and in this case, since it is a color, the process proceeds to S315, where the time count flag is deleted in the CPU 501B (flag ← 0), and the time count is reset. (Tn ← 0). When the CPU 501B enters this state, the copying process is set and controlled to the color mode (S317), and the process returns to the main routine.
[0063]
In this way, color copying is performed on the first recording sheet. The same applies to the subsequent nine color copies, and the interval between the recording sheets is appropriately adjusted so as to satisfy Equation 3 by the CPU 501B or the like.
When all 10 copies are completed, the copying process shifts to monochrome copying. The operation at this time will be described with reference to FIG.
[0064]
When monochrome copying is performed for the first time, it is determined in the frame separation control process S300 that monochrome copying is first designated (S311), the process proceeds to S312 and a time count flag is set in the CPU 501 ( It is determined whether or not flag = 1). In this case, since this is the first monochrome copy and the flag remains erased (flag = 0), the process proceeds to S316, where the flag is set (flag ← 1). At the same time, the time count Tn by the monochrome copy timer unit 5013B in the CPU 501B is started. Thereafter, the routine proceeds to S318, returns to the main routine while the color mode is set, and monochrome copying is performed in this state.
[0065]
In the second monochrome copying, after the routine proceeds to subroutine S311, the time count flag is confirmed through monochrome determination (S312). When the flag is confirmed, the time count value Tn is compared with the set value T (= 40) to determine whether Tn is equal to or greater than T. Here, it is assumed that about 10 seconds have elapsed from the time counting in S316 in the first monochrome copying routine until the time of reaching S312 in the second monochrome copying routine. Therefore, Tn has not yet reached T, and the color mode is set in the same manner as the first monochrome copying (S317), and the copying process is executed (S400). Thereafter, if Tn becomes equal to or greater than T, that is, if monochrome copying in the color mode takes about 10 seconds per copy, the same copying operation as described above is performed until the fourth copy is completed.
[0066]
Here, the operation of the apparatus is changed when the fifth monochrome copy is made. That is, in the subroutine S313 in the fifth monochrome copying routine, the condition of Tn ≧ T is satisfied for the first time, and the process proceeds to S314. Here, the apparatus is set to the monochrome mode, and monochrome copy in the first monochrome mode is performed on the fifth recording sheet. Subsequent monochrome copying is performed in the monochrome mode in the same manner as described above through steps S311 to S314 of the subroutine.
[0067]
(Embodiment 3)
In the first and second embodiments described above, the number of monochrome copying copies processed in the past or the monochrome copying operation time required in the past is measured, and when these values reach a preset value, a black toner image is formed. The mode in which only the image forming station is brought into contact with the transfer belt to shift to the monochrome mode has been described. This embodiment differs from the above two embodiments in that color determination is made in advance for a series of originals set before copying, the copy order and the number of copies of each original are grasped, and accordingly, the copy mode is switched appropriately. Is what you do.
[0068]
The image forming apparatus will be described below. Note that the configuration of the present apparatus other than the CPU 501B is substantially the same as that of the first embodiment, and thus description of the common parts is omitted.
The CPU 501B has a frame separation control unit 5011B, a copy order storage unit (not shown), and the like inside, thereby controlling the operation of each component of the printer unit.
[0069]
The copy order storage unit is a RAM, and stores color discrimination information and copy order (numbering) information for each copy of recording paper on which a document image is to be copied, for a series of documents set by the user. Specifically, as shown in the copy order storage unit table of FIG. 16, a memory area group 16b for individually storing information relating to n (preferably at least several tens of copies) recording sheets in the copy order storage unit. The address 16a having the mark is continuously secured, and the copy order information R of each recording sheet corresponds to the address 16. The copy order information R is not the order of recording sheets to be copied for one document image, but the order of all recording sheets used for the copying operation for a series of documents set by the user. Refers to information.
[0070]
Further, as shown in the figure, the memory area group 16b corresponding to the address 16a stores information on whether the copying process performed on each recording sheet is monochrome mode or color mode. That is, in the present embodiment, a monochrome mode flag is set when monochrome copying continues for a certain number of copies or more (flag ← 1), and is erased when monochrome copying is less than the certain number of copies or color copying (flag). ← 0). In this embodiment, the fixed number of monochrome copies is set to two, and the monochrome mode flag is set when two or more monochrome copies are continuous.
[0071]
The CPU 501B sets a monochrome mode through the frame separation control unit 5011B immediately before two or more copies are made based on a series of recording paper information stored in the copy order storage unit.
Next, when a user sets color, monochrome, and color originals one by one in this order, and copies one by one, FIG. 17 shows a copy order storage unit table, FIG. 18 main routine, and FIG. A specific description will be given using a subroutine of the image input pre-processing S2000 and a subroutine of the frame separation control process S4000 in FIG.
[0072]
First, when the original is set by the user and the copy start key on the operation panel 30 is pressed, various flags in the CPU 501B are deleted (flag ← 0) in the initial setting S1000 of the main routine of FIG. Information in the memory area 16b in the storage unit is simultaneously erased. In addition, various control programs in the ROM 507B are initialized.
[0073]
Subsequently, an internal timer is started (S1010), and the process proceeds to image input preprocessing S2000. In this image input pre-processing S2000, in the subroutine of FIG. 19, it is first determined whether or not the document prefetch flag is zero. In this case, since prefetching has not yet been performed (flag = 0), the process proceeds to step S2020, the flag is set (flag ← 1), and n sheets set by the user (three sheets in the present embodiment) Is pre-read by the image reader unit 20, and color discrimination is performed by the ACS unit 505B of the digital signal processing unit 211 (S2030). Whether the CPU 501B plans two or more monochrome copy processes in the copy order for all the recording papers to be copied from now on based on the color information of each of the n documents pre-read in this way. It is determined whether or not (S2040). In this case, of the set three originals, the second original is a monochrome image, so that the monochrome copy process is performed twice for the third and fourth copy processes of all six copies. It is scheduled to be continued. Accordingly, the process proceeds to S2050, and the monochrome mode flag is set in the memory area of the recording paper copy order address in the copy order storage unit corresponding to the recording paper to be subjected to the third and fourth copy processing.
[0074]
The copy order storage unit table of FIG. 17 shows the state of the copy order storage unit in which information about six recording sheets to be used for the copying operation is stored for the three original images read by the above operation. Represents. In the memory areas 173b and 174b of the third and fourth recording sheets corresponding to the addresses 173a and 174a in the drawing, a monochrome mode flag is set as shown (flag ← 1). In S2040, it is determined that the set originals are all in color, or that there is only a schedule for monochrome copy processing of less than a certain number of copies (one copy in the present embodiment) in the copy order of the recording paper used for copying. In that case, the process proceeds to S2060, and the all monochrome mode flag is deleted.
[0075]
When the processing of the flag is completed, the subroutine returns, and the image input process S3000 is performed again in the main routine. Here, after the first original image is read and subjected to a predetermined image correction process, the image data is temporarily stored in the ROM 507B.
Subsequently, the process proceeds to the frame separation control process S4000. After it is determined in the subroutine of FIG. 20 whether or not the recording paper leading edge detection sensors (photocouplers 78 and 79) have detected the leading edge of the recording paper (S4010), copying is performed. It is determined whether or not the order count value R is 0 (S4020). Here, since the count has not yet started, R = 0, and the count starts in S4030 (R ← 1).
[0076]
In subsequent S4040, it is determined whether or not the monochrome mode flag is set on the recording sheet having the number corresponding to the copying order count value R (R = 1 in this case) in the ROM in the CPU 501B. Since it is now the first copy, the flag is not raised as apparent from the addresses 171a and 171b in FIG. 17, so the step moves to S4060 where the color mode is set. After the setting, the copying order count value R is counted up again in S4070 (R ← R + 1 = 2), the process returns to the main routine, and color mode copy processing is performed in S5000. After the copy is completed, the internal timer is ended (S1020), and it is determined whether or not all copies are completed (S1030).
[0077]
In the subsequent second copying operation, it is determined in the subroutine S2010 of the image input pre-processing S2000 whether or not the document prefetch flag is 0, and the flag is set at the time of the first copying. Immediately return to the main routine. That is, during the second and subsequent copies, the main image input pre-processing S2000 is similarly avoided. On the other hand, in the subroutine of the frame separation control process S4000, after it is determined whether or not the recording paper leading edge detection sensor (photocoupler 78, 79) has detected the leading edge of the recording paper (S4010), the recording paper number count value R is zero. It is determined whether or not (S4020). Since R = 2 now, the process proceeds to S4040. Here, it is determined whether or not the monochrome mode flag is set at the address of the corresponding R number. As apparent from the addresses 172a and 172b in FIG. 17, the monochrome mode flag is not set on the second copy sheet, so that the color mode is set (S4060), and the copy order count value R is set in S4070. The count is incremented (R ← R + 1 = 3), and the copy process in the color mode is performed in the same manner as the first (S5000). When the second color copy is finished, the internal timer is finished (S1020), it is determined whether all copying is finished (S1030), and the main routine starts the internal timer again to shift to the third copying operation. (S1010).
[0078]
As can be seen from the addresses 173a and 173b in FIG. 17, the third copy operation is monochrome with the subsequent fourth copy, and the monochrome mode flag is set to perform two-part continuous monochrome copy. Therefore, when the flag is confirmed in the address value corresponding to R = 3 in the subroutine S4040 of the frame separation control process S4000, the monochrome mode is set here (S4050). R is counted up (S4070), the subroutine returns to the main routine, and monochrome copy processing in monochrome mode is performed (S5000). Except for the R count-up operation, the fourth copy is similarly monochrome copied.
[0079]
In color copying performed in the fifth copying operation, an address corresponding to R = 4 is referred to in subroutine S4040, the color mode is set again (S4060), R is counted up (S4070), and the color mode is set. A color copy is made (S5000). Regarding the last sixth copying operation, color copying is performed in the same manner as the fifth, except for counting up R.
[0080]
When all copies are completed in this way, this is confirmed in S1030, and the main routine ends.
Although explanation is omitted, it is assumed that the interval between the recording sheets is appropriately controlled in the same manner as in the first embodiment.
In the first to third embodiments, the image formation is performed on the recording paper conveyed on the transfer belt 65. However, the present invention is not limited to this. For example, the image formation is directly performed on the surface of the transfer belt 65. May be performed.
[0081]
【The invention's effect】
  As is apparent from the above description, the present invention writes original images of different colors on a plurality of image carriers, and superimposes the original images on the image carriers on a transfer belt or a transfer material conveyed on the transfer belt. The transfer belt is relatively spaced from the color print mode for transfer and all other image carriers except the one image carrier, and the original image on the one image carrier is transferred to the transfer belt or above. Forming apparatus capable of switching between single color print mode for transferring image to transfer material conveyedBecause,During one print operation,Single color printContinuousPrintNumberAccumulating means for accumulating results, determining means for determining whether a document image to be printed next is a single color or a color, and determining by the determining means that the original image is a single color; Only when the accumulated result satisfies a predetermined condition, the color print mode is switched to the single color print mode. When the determination unit determines that the original image to be printed next is a color, the single color is selected. And a control means for controlling to switch from the print mode to the color print mode. Therefore, it is possible to deal with mixed color / monochrome originals accurately when the predetermined condition is satisfied and when the predetermined condition is not satisfied. This eliminates the need to separate the original image into color and monochrome and switch the print mode accordingly. Thus, there is an effect that high-speed print processing is possible. At the same time, it is possible to limit the driving of the image carrier and the like which are not required depending on the print mode to some extent, so that there is an effect of extending their life.
[0082]
  Further, the present invention provides a color print mode in which original images of different colors are written on a plurality of image carriers, and the original images on the image carriers are transferred while being superimposed on a transfer belt or a transfer material conveyed on the transfer belt. The transfer belt is relatively separated from all other image carriers except the one image carrier, and the original image on the one image carrier is transferred to the transfer belt or a transfer material conveyed thereon. Image forming apparatus switchable between single color print mode for transferBecause,During each print operationColor information acquisition means for capturing color information of an original image before writing the image on the image carrier, determination means for determining whether each original image is a single color or color from the acquired color information, and the determination A copy order grasping means for grasping a single color and the number of color copies and a copy order of a series of document images determined by the determination result of the means; and a single color document of a predetermined number or more in the copy order for the series of document images Control means for switching from the color print mode to the single color print mode immediately before the printing when the images are continuous and controlling to switch from the single color print mode to the color print mode after the single color print is completed. So that you can know the exact print processing schedule ahead of time, Serial effect can be switched lean print mode in addition, it has the effect of allowing more of sustaining both the high-speed print processing and high durability.
[Brief description of the drawings]
FIG. 1 is a front view showing a main configuration of a tandem type full-color image forming apparatus as an application example of the present invention.
FIG. 2 is a detailed configuration diagram centering on a print unit 60;
FIG. 3 is a perspective view of a frame 64. FIG.
FIG. 4 is a diagram illustrating the position of a frame 64 in the color mode.
FIG. 5 is a diagram illustrating the position of a frame 64 in the monochrome mode.
6 is a block diagram of a digital signal processing unit 211. FIG.
FIG. 7 is a peripheral view of a printer unit in a color mode.
FIG. 8 is a peripheral view of a printer unit when shifting from a color mode to a monochrome mode.
FIG. 9 is a peripheral view of the printer unit after the transition from the color mode to the monochrome mode is completed.
FIG. 10 is a peripheral view of the printer unit in a monochrome mode.
FIG. 11 is a peripheral view of the printer unit at the time of transition from the monochrome mode to the color mode.
FIG. 12 is a peripheral view of the printer unit after the transition from the monochrome mode to the color mode.
FIG. 13 is a main routine of the apparatus.
FIG. 14 is a subroutine of a frame separation control process S300.
FIG. 15 is a subroutine of a frame separation control process S300.
FIG. 16 is a table of a copy order storage unit.
FIG. 17 is a table diagram of a copy order storage unit.
FIG. 18 is a main routine of the apparatus.
FIG. 19 is a subroutine of image input preprocessing S2000.
FIG. 20 is a subroutine of a frame separation control process S4000.
[Explanation of symbols]
60 Printer section
64 frames
66a, 66b cam
69a, 69b Spring
501B CPU
507B ROM
505B ACS Department
601C to 601K photosensitive drum
5011B Frame separation control unit
5012B Monochrome copy counter section

Claims (4)

A color print mode in which original images of different colors are written on a plurality of image carriers, and the original images on the respective image carriers are transferred onto a transfer belt or a transfer material conveyed on the transfer belt, and one image carrier A single-color print that transfers the original image on the one image carrier onto the transfer belt or a transfer material conveyed thereon by relatively separating the transfer belt from all other image carriers except the body a switchable image forming apparatus with the mode,
Accumulating means for accumulating the actual number of continuous prints of a single color print during one printing operation ;
Determining means for determining whether the original image to be printed next is a single color or a color during the one printing operation ;
The color printing mode is switched to the single color printing mode only when the determination unit determines that the color is a single color and the accumulation result of the accumulation unit satisfies a predetermined condition, and the determination unit attempts to print next. An image forming apparatus comprising: a control unit that controls to switch from a single color print mode to a color print mode when it is determined that a document image is in color. It said accumulating means includes an image forming apparatus according to claim 1, characterized in that the counting means for counting the continuous printing number of the single color printing. It said accumulating means includes an image forming apparatus according to claim 1, characterized in that the integrator for integrating the continuous printing operation time of the single color printing. A color print mode in which original images of different colors are written on a plurality of image carriers, and the original images on the respective image carriers are transferred while being superimposed on a transfer belt or a transfer material conveyed on the transfer belt;
The transfer belt is relatively separated from all other image carriers except one image carrier, and the original image on the one image carrier is transferred to the transfer belt or a transfer material conveyed thereon. a switchable image forming equipment with the single color print mode,
Color information acquisition means for capturing color information of each original image before writing the original image on the image carrier during one printing operation ;
A determination means for determining whether each document image is a single color or a color from the acquired color information;
Copy number order grasping means for grasping the single color and the number of color copies and the copy order for a series of document images determined by the determination result of the determination means;
In the order of the number of copies relating to the series of document images, when a predetermined number or more of single-color document images are continuous, the color print mode is switched to the single-color print mode immediately before printing, and the single-color print is completed. An image forming apparatus comprising: control means for controlling to switch from the single color print mode to the color print mode later.

Images