JP4698303B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a color image forming apparatus such as a copying machine, a facsimile machine, or a printer, and more particularly to an image forming apparatus having a color mode for forming a color image and a single color mode for forming a single color image.

  Conventionally, whether an original image is monochrome or color is detected. If the original image is a monochrome image, the image is formed in the monochrome mode. If the original image is a color image, the image is formed in the full color mode. A forming apparatus is known (Patent Document 1). In monochrome mode, image formation is performed by separating the photoreceptor, which is an image carrier unnecessary for monochrome image formation, from the transfer belt, which is a belt member. In full color mode, all photoreceptors are in contact with the transfer belt to form an image. I do. Thereby, it is possible to suppress the deterioration of the Y, M, and C color photoreceptors.

  However, in the image forming apparatus disclosed in Patent Document 1, when continuously copying a mixture of a monochrome document and a color document, it is necessary to perform the above-described separation operation when switching from the full color mode to the monochrome mode. The copying operation is temporarily interrupted, resulting in a reduction in copying speed. If all originals in which monochrome originals and color originals are mixed are performed in the full color mode, the reduction in copying speed can be suppressed. However, since the Y, M, and C photoconductors are in contact with the transfer belt even during monochrome image printing, The deterioration of the Y, M, and C photoconductors proceeds.

  Patent Document 2 describes an image forming apparatus that detects whether a monochrome image or a color image is detected for all originals to be continuously copied in advance, and switches from a full color mode to a monochrome mode when a predetermined number of monochrome images are continuous.

  By making it like patent document 2, compared with what switches to a full color mode and a monochrome mode for every original document, the copying speed at the time of copying continuously what mixed the monochrome original and the color original can be raised. it can. Further, the deterioration of the Y, M, and C photoconductors can be suppressed as compared with a case where all originals in which monochrome originals and color originals are mixed are performed in the full color mode.

JP-A-9-160335 JP-A-11-167238 (Embodiment 3)

  However, in the image forming apparatus disclosed in Patent Document 2, all originals to be continuously copied are stored in advance in a memory serving as a recording unit to detect whether the image is a monochrome image or a color image, and whether a predetermined number of monochrome images are continuous is detected. Since image formation is started after that, there is a problem that it takes time to start image formation. In addition, when there are many originals, the amount of images to be recorded increases, and a memory with a large capacity is required, leading to an increase in cost.

  The present invention has been made in view of the above problems, and the object of the present invention is to increase the image forming speed when continuously forming a mixture of a single-color original and a color original, An object of the present invention is to provide an image forming apparatus capable of accelerating the start of image formation.

In order to achieve the above object, an invention according to claim 1 provides an image forming means including an image carrier on which a latent image is formed and a developing device for converting the latent image on the image carrier into a toner image for each color. The image bearing member of each image forming means is brought into contact with the belt member, and the toner image on each image bearing member is transferred to the belt member and then transferred to the transfer material, or conveyed by the belt member. In the image forming apparatus for transferring to a transfer material, a storage unit that sequentially stores image data to be imaged, a determination unit that determines whether the image data is a single color image, and an image using all the image forming units The color mode for forming the image and the image carrier of all the other image forming means except for one image forming means are relatively separated from the belt member, and the first image forming means is used to form an image. 1 single color mode and all The operation of the developing devices of all other image forming units except one image forming unit is stopped without separating the carrier from the belt member, and an image is formed using the one image forming unit. When the second single color mode and a plurality of document images are continuously formed, when the image data of the first document image is read, image formation is started, and the remaining document images are sequentially displayed during image formation. Image control means for storing in the storage means, and mode selection means for selecting one of the color mode, the first single color mode, and the second single color mode based on the determination result of the determination means. The mode selection unit selects a color mode when the image of the image data determined not to be a monochrome image by the determination unit is formed, and the image of the image data determined to be a monochrome image by the determination unit Formed When the image data stored in the storage means has not yet been formed, it is detected whether or not the number of image data is not more than a predetermined number, and the image data stored in the storage means is less than the predetermined number of image data. In this case, the second monochromatic mode is selected, and when the number of image data that has not been subjected to image formation stored in the storage means exceeds a predetermined number, the image formation stored in the storage means has not been completed. From the image data, it is determined whether or not a plurality of images to be subsequently formed are single-color images. If the single-color images are continuous, the first single-color mode is selected. When there are less than a plurality of monochrome images to be formed, the second monochrome mode is selected.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the colors of the toner images that can be formed on the plurality of image carriers are a plurality of colors including black, and the first single color mode and the above The image formed in the second monochrome mode is a black monochrome image.
According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, a driving force of a driving source for driving the developing device is transmitted to the developing device via a clutch, and the second single color is provided. The stop of the operation of the developing device performed in the mode is performed by disengaging the clutch.
According to a fourth aspect of the present invention, in the image forming apparatus of the first or second aspect, a driving source for driving only the developing device is provided, and the operation of the developing device performed in the second single color mode is stopped in each developing device. This is performed by stopping the drive source for driving the motor.
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect of the present invention, a common driving source is used for the developing devices of the respective colors whose operation is stopped in the second single color mode.
According to a sixth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to fifth aspects, wherein the monochrome selecting mode always forms a monochrome image regardless of whether it is a monochrome image, or an automatic mode selection mode using the mode selecting means. A manual selection means is provided that allows the user to select any one of the color change modes.
According to a seventh aspect of the present invention, in the image forming apparatus of the sixth aspect, the manual selection means can also select the color mode.
According to an eighth aspect of the present invention, in the image forming apparatus according to the sixth or seventh aspect, the single color mode is the first single color mode.
According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, an image reading device capable of reading image information is provided.

According to the first to tenth aspects of the present invention, when the first original image is read, image formation is started. When a predetermined number of image data is stored in the recording means, it is determined whether a predetermined number of single-color images are continuous. Judgment. Thereby, the start of image formation can be accelerated compared to the conventional method in which it is determined whether or not a predetermined number of monochrome images are continuous. In addition, since the first monochrome mode is switched only when a predetermined number of monochrome images are continuous, the monochrome document and the color document are mixed as compared with the one that switches to the first monochrome mode every time the color image changes to the monochrome image. Thus, the image forming speed can be increased when images are continuously formed. Further, it is possible to suppress the deterioration of the color image carrier that is not used at the time of forming a monochromatic image, as compared with the case where all the monochromatic originals and color originals are mixed in the color mode.
In addition, when forming a monochrome image, when the predetermined number of image data for which image formation has not been completed is not stored in the recording means, or when the number of monochrome images subsequently formed is less than the predetermined number, the second monochrome mode To form an image. Thereby, it is possible to suppress the deterioration of the developing devices of other colors and the developer in the developing device. Further, since the operation of the developing device is only stopped, the time required for the image forming operation to be temporarily suspended is shorter than that in the first single color mode. Thereby, it is possible to suppress a decrease in image forming speed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an example of a copying machine as an image forming apparatus to which the present invention is applied. In FIG. 1, reference numeral 100 denotes a copying machine main body, reference numeral 200 denotes a paper feed table on which the copying machine is placed, reference numeral 300 denotes a scanner mounted on the copying machine main body 100, and reference numeral 400 further denotes an automatic document transport mounted thereon. Device (ADF). This copier is a tandem type electrophotographic copier that employs an intermediate transfer (indirect transfer) system.

  In the center of the copying machine main body 100, an intermediate transfer belt 10 including a belt which is an intermediate transfer member serving as an image carrier is provided. The intermediate transfer belt 10 is stretched around support rollers 14, 15, and 16 as three support rotating bodies, and rotates in the clockwise direction in the drawing. An intermediate transfer belt cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is provided on the left side of the second support roller 15 in the drawing among these three support rollers. Further, among the three support rollers, a belt portion stretched between the first support roller 14 and the second support roller 15 has yellow (Y), magenta (M), A tandem image forming unit 20 in which four image forming units 18 of cyan (C) and black (K) are arranged side by side is arranged oppositely. In the present embodiment, the third support roller 16 is a drive roller. An exposure device 21 as a latent image forming unit is provided above the tandem image forming unit 20.

  A secondary transfer device 22 as a second transfer unit is provided on the opposite side of the tandem image forming unit 20 with the intermediate transfer belt 10 interposed therebetween. In the secondary transfer device 22, a secondary transfer belt 24 that is a belt as a recording material conveying member is stretched between two rollers 23. The secondary transfer belt 24 is provided so as to be pressed against the third support roller 16 via the intermediate transfer belt 10. The secondary transfer device 22 transfers an image on the intermediate transfer belt 10 to a sheet as a recording material. A fixing device 25 for fixing the image transferred on the sheet is provided on the left side of the secondary transfer device 22 in the drawing. The fixing device 25 has a configuration in which a pressure roller 27 is pressed against a fixing belt 26 that is a belt. The secondary transfer device 22 described above also has a sheet conveyance function for conveying the sheet after image transfer to the fixing device 25. Of course, a transfer roller or a non-contact charger may be disposed as the secondary transfer device 22, and in such a case, it is difficult to provide this sheet conveying function together. In the present embodiment, a sheet reversing device for reversing the sheet so as to record images on both sides of the sheet is provided below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming unit 20 described above. 28 is also provided.

When making a copy using the copying machine, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it. Thereafter, when a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is conveyed and moved onto the contact glass 32. On the other hand, when an original is set on the contact glass 32, the scanner 300 is immediately driven. Next, the first traveling body 33 and the second traveling body 34 travel. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.
In parallel with this document reading, the drive roller 16 is rotated by a drive motor which is a drive source (not shown). As a result, the intermediate transfer belt 10 moves in the clockwise direction in the drawing, and the remaining two support rollers (driven rollers) 14 and 15 rotate along with the movement. At the same time, the photosensitive drums 40Y, 40M, 40C, and 40K serving as latent image carriers are rotated in the individual image forming units 18 so that yellow, magenta, cyan, and black are separately provided on the photosensitive drums. Each information is exposed and developed to form a single color toner image (visualized image). Then, the toner images on the photosensitive drums 40Y, 40M, 40C, and 40K are sequentially transferred onto the intermediate transfer belt 10 so as to overlap each other, thereby forming a composite color image on the intermediate transfer belt 10.

In parallel with such image formation, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheets are separated one by one and placed in the paper feed path 46, transported by the transport roller 47, guided to the paper feed path in the copying machine main body 100, and abutted against the registration roller 49 and stopped. Alternatively, the sheet feed roller 50 is rotated to feed out the sheets on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, the sheet is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is transferred onto the sheet. The image-transferred sheet is conveyed by the secondary transfer belt 24 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to fix the transferred image, and then the switching roller 55 is used to switch the discharge image. The paper is discharged at 56 and stacked on the paper discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56.
The intermediate transfer belt 10 after the image transfer is removed by the intermediate transfer belt cleaning device 17 to remove residual toner remaining on the intermediate transfer belt 10 after the image transfer, so that the tandem image forming unit 20 can prepare for another image formation. Here, the registration roller 49 is generally used while being grounded, but it is also possible to apply a bias for removing paper dust from the sheet.

  Next, the image forming unit 18 of the tandem image forming unit 20 described above will be described. Here, the K color image forming unit 18K will be described, but the Y, M, and C image forming units have the same configuration. For example, as shown in FIG. 2, the image forming unit 18K includes a charging device 60K, a potential sensor 710K, a developing device 61K, a photoconductor cleaning device 63K, a static elimination device (not shown), and the like around a drum-shaped photoconductor 40K. Yes. The potential sensor 710K detects the surface potential of the photoreceptor 40K.

  At the time of image formation, the photoconductor 40K is rotationally driven by a drive motor (not shown). Then, after being uniformly charged by the charging device 60K, it is exposed by the writing light L from the laser writing device 21 to carry an electrostatic latent image. The color image signal from the scanner 300 is subjected to image processing such as color conversion processing by an image processing unit (not shown), and is output to the laser writing device 21 as an image signal of each color of K, Y, M, and C. The laser writing device 21 converts the K image signal from the image processing unit into an optical signal, and scans and exposes the photoconductor 40K based on the optical signal to form an electrostatic latent image.

  The electrostatic latent image on the photoreceptor 40K is developed by the developing device 61K to become a K toner image, and the K toner image on the photoreceptor 40K is primarily transferred onto the transfer sheet S on the intermediate transfer belt 10 by the primary transfer device 62K. Is done. After the toner image is transferred to the photoreceptor 40K, the residual toner is cleaned by the photoreceptor cleaning device 63K, and the charge is removed by a charge removal device (not shown) to prepare for the next image formation.

  Similarly, the toner image forming units 18Y, 18M, and 18C include a charging device, a potential sensor, a developing device, a photoconductor cleaning device, a static elimination device, and the like around the drum-shaped photoconductors 40Y, M, and C. . Then, Y, M, and C toner images are formed on the photoconductors 40Y, 40M, and 40C, and these images are superimposed on the intermediate transfer belt 10 and primarily transferred.

  The image forming apparatus according to the present embodiment includes a full color mode in which all the photoreceptors 40Y, 40M, 40C, and 40BK are in contact with the surface of the intermediate transfer member 10 when the color of an image to be formed is full color, and black when the color is black. And a monochrome mode in which the other photoreceptors 40Y, 40M, and 40C are separated from the surface of the intermediate transfer member 10. The image forming apparatus of the present embodiment also includes an auto color change mode that detects whether a document image read by the scanner is a monochrome image or a color image and automatically switches between the monochrome mode and the full color mode. . In the monochrome mode, a first monochrome mode in which an image is formed with a photosensitive member other than the K color photosensitive member relatively spaced from the intermediate transfer belt, and a second monochrome mode in which the operation of the developing device other than the K color is stopped. There are two types. The second monochrome mode is a mode that is executed when the auto color change mode is selected. To switch between the monochrome mode, the full color mode, and the auto color change mode, an input unit is provided on an operation panel (not shown) serving as a manual operation means so that the user can determine and input the mode.

  Since the mode can be selected by the user, there are the following advantages. For example, the original image is a color image, but when the user wants to make a monochrome image, the user can operate the operation panel to select the monochrome mode, and a monochrome image as desired by the user can be obtained. In addition, when the user selects the monochrome mode, the Y, M, and C photoconductors are always separated from the intermediate transfer belt 10, so that the deterioration of the Y, M, and C photoconductors can be suppressed.

  When the user selects a color mode, the monochrome mode is not switched to a monochrome image as in the auto color change mode. Therefore, the printing speed when continuously printing a plurality of originals in which color originals and monochrome originals are mixed is faster than in the automatic color change mode. As a result, when the user selects the color mode, the user can quickly obtain print images of a plurality of originals in which color and monochrome are mixed.

FIGS. 3A and 3B are enlarged views of the transfer portion when the full color mode is executed and when the monochrome mode (first monochrome mode) is executed, respectively. The transfer unit 6 according to this embodiment includes a transfer unit 600 that is fixedly arranged with respect to the apparatus main body, and a transfer subunit 601 that can swing around a swing shaft 602 provided on the transfer unit main body side. . The transfer unit main body 600 supports a black primary transfer roller 62K, an eccentric cam 603 for swinging the transfer subunit 601 and the like. On the other hand, the transfer subunit 601 supports primary transfer rollers 62Y, 62M, and 62C for color. Further, as an urging means for urging the transfer subunit 601 to be separated from the color photosensitive drums 40Y, 40M, and 40C, between the swing end portion of the transfer subunit 601 and the transfer unit main body 600. The spring 604 is attached. The eccentric cam 603 is attached so as to be in contact with the lower surface of the swing end portion of the transfer subunit 601 and is rotationally driven by a driving device (not shown).
When the color mode shown in FIG. 3A is executed, the eccentric cam 603 is rotated to a position where the lower surface of the swing end of the transfer subunit 601 is pushed up against the biasing force of the spring 604. As a result, the intermediate transfer belt 10 and all the photosensitive drums come into contact with each other, and the toner images of the respective colors on the respective photosensitive drums are transferred onto the intermediate transfer belt 10 in a superimposed manner.
When the monochrome mode shown in FIG. 3B is executed, the eccentric cam 603 is rotated to a position where the push-up force with respect to the swing end of the transfer subunit 601 is released. As a result, the oscillating end of the transfer subunit 601 is pushed down by the urging force of the spring 604, the intermediate transfer belt 10 and the color photosensitive drums 40Y, 40M, and 40C are separated from each other, and the black on the photosensitive drum 40K. Only the toner image can be transferred onto the intermediate transfer belt 10.

  Next, features of the present embodiment will be described. In the conventional auto color change mode, when copying a mixture of a monochrome document and a color document continuously, it is necessary to perform the above-described separation operation when switching from the full color mode to the monochrome mode. , 40M, 40C must be performed many times, and time and electric power are required. In view of this, there are cases where it is determined whether all originals to be continuously copied are monochrome images or color images, and when a predetermined number of monochrome images continue, the full color mode is switched to the monochrome mode. However, when the number of documents is large, there is a problem that the time until the image forming operation is started becomes long.

Therefore, in the image forming apparatus of the present embodiment, image formation is started immediately after the image of the scanner 300 is read. When N (four in the present embodiment) image data is stored, it is determined whether or not a predetermined number (four in the present embodiment) of monochrome images is continuous. Executes the first monochrome mode. The second monochrome mode is executed when a monochrome image is printed when monochrome images are not continuous or when N (four in this embodiment) image data is not stored.
FIG. 4 is a timing chart showing timing for determining whether or not a predetermined number (four in this embodiment) of monochrome images are continuous. As shown in FIG. 4, the time for the scanner to read an image of one original is shorter than the time for the image forming unit 20 to form one image. As shown in FIG. 4, when the image forming unit 20 completes the printing of the four images, the scanner 300 starts reading the ninth original image. For this reason, four image data from the fifth to the eighth image are stored in the image memory as the storage means. When the fifth image is printed, it is determined whether or not four monochrome images are continuous. Also, when printing the monochrome image for the first to fourth sheets, the second monochrome mode is executed, the drive of the Y, M, and C color developing devices 61 is stopped, and the Y, M, and C color images are stopped. Suppresses developer deterioration. As shown in FIG. 2, since the photosensitive member 40 and the developing roller 61a of the developing device 61 are arranged with a predetermined gap, the rotating photosensitive member 40 is damaged even if the driving of the developing device 61 is stopped. There is hardly anything. In addition, when printing a monochrome image in which the first monochrome mode is not executed on the fifth and subsequent sheets, the driving of the Y, M, and C color developing devices 61 is stopped to perform printing.

FIG. 5 is a diagram showing a driving portion of the developing device 61 for Y, M, and C colors. As shown in the figure, the drive gear 101a fixed to the shaft of the drive source motor 101, which is a drive source, meshes with the photoconductor gear 104 fixed to the photosensitive shaft. The photoconductor gear 104 meshes with the electromagnetic clutch 102 attached to the shaft of the developing roller 61a. A first gear 103 is fixed to the shaft of the developing roller 61a, and meshes with a second gear 105 fixed to the shaft of the conveying screw 61b. When the full color mode is executed, the electromagnetic clutch 102 is ON, and the shaft of the developing roller 61a and the electromagnetic clutch 102 are connected. As a result, the driving force of the driving motor 101 is transmitted from the photosensitive member gear 104 to the shaft of the developing roller 61a via the electromagnetic clutch 102. As a result, the developing roller 61a rotates, and at the same time, the conveying screw 61b in the developing device rotates. On the other hand, when the second monochrome mode is executed, the electromagnetic clutch 102 is turned off. Then, the connection between the shaft of the developing roller 61a and the electromagnetic clutch 102 is released, and the driving force of the driving motor 101 is not transmitted from the photoconductor gear 104 to the shaft of the developing roller 61a. As a result, only the photosensitive member 40 is rotated by the driving force of the motor 101, the developing roller 61a and the conveying screw 61b are not rotated, and the deterioration of the developer in the developing device is suppressed. When the first monochrome mode is executed, the drive motor 101 is stopped, and the operations of the photoconductor 40 and the developing device 61 are stopped.
The drive motor 101 may be provided for each of the Y, M, C, and K image forming units 18 or may be common to the Y, M, C, and K image forming units 18. However, it is preferable in terms of torque balance that each Y, M, C, K image forming unit 18 is provided.
In FIG. 5, the driving source of the photosensitive member 40 and the driving source of the developing device 61 are shared, but the driving source of the photosensitive member 40 and the driving source of the developing device 61 are provided separately, and each drive is provided. The operation of the Y, M, and C color developing devices 61 may be stopped by stopping the source. Increasing the number of motors unnecessarily leads to an increase in cost. However, the drive motor is more durable than the clutch, so the life of the apparatus can be extended. Further, the influence of torque fluctuation on the photoreceptor 40 is reduced, and shock jitter can be suppressed. Alternatively, the drive sources of the Y, M, and C color developing devices 61 may be shared, and the operation of the Y, M, and C color developing devices 61 may be stopped by stopping the drive sources. By sharing Y, M, and C drive sources, the number of drive sources can be reduced.

  FIG. 6 is a control block diagram of the image forming apparatus. In the figure, the control unit 72 controls the entire apparatus. The control unit 72 includes a ROM 72a that stores various control programs, a RAM 72b that is a working memory for executing the control programs, a CPU 72c for executing the programs, and the like. The ROM 72a has a determination program for determining whether the image data stored in the image memory 73 is a monochrome image or a color image, and a mode selection program for selecting one of the color mode, the first monochrome mode, and the second monochrome mode. A control program such as is stored. The determination program and the mode selection program are executed using the CPU 72c and the RAM 72b, and the control unit 72 functions as a mode selection unit and a determination unit. A control program for controlling the image forming unit 20 is stored in the ROM 72 a of the control unit 72. This control program is executed using the CPU 72c and RAM 72b, and the control unit 72 functions as an image control means. The control program for controlling the image forming unit is based on a program for starting image formation based on the read image immediately after the first original image is read, or on a mode selected by an operation unit serving as a manual selection unit. A program for controlling the image forming unit 20 is included.

  Next, the auto color mode of this embodiment will be described in detail. FIG. 7 is a control flow of the auto color change mode. First, it is checked whether the image to be printed is a color image (S1). This determination is made by reading out image data stored in the image memory. If the image is not a color image, that is, a monochrome image (NO in S1), it is checked whether the primary transfer rollers 62 of Y, M, and C are separated from the Y, M, and C photoconductors 40 (S2). When the primary transfer roller 62 is separated from the Y, M, and C photoconductors 40 (S2 YES), it is determined that a monochrome image continues for N consecutive images (four in this embodiment) with the previous image data. Therefore, in the first monochrome mode (S6), a monochrome image is printed. On the other hand, if the Y, M, and C primary transfer rollers 62 are not separated from the Y, M, and C photoconductors 40, is there more than N (4 in the present embodiment) image data in the image memory? A check is made (S3). As shown in FIG. 4, in the case of the first to fourth image data, since there are not more than N (4) image data in the image memory (NO in S3), Y, M, and C color development is performed. The driving of the roller 61 is stopped (S8), and a monochrome image is printed in the second monochrome mode (S14). On the other hand, when there are N (4) or more image data in the memory (YES in S3), it is checked whether or not N monochrome images are continuous (S5). For example, in the case of the fifth image data, it is checked whether the sixth to eighth image data stored in the image memory are monochrome. If even one of the 6th to 8th sheets has a color image, N (4) monochrome images are not continuous (NO in S4), so the driving of the developing roller 61 is stopped (S8). Then, a monochrome image is printed in the second monochrome mode (S14). On the other hand, when N (4) continuous monochrome images continue from the image to be printed (YES in S4), the mode is switched to the first monochrome mode. That is, the drive of the YMC photoconductor is turned off, the drive of the YMC developing roller is turned off, and the primary transfer roller 62 of Y, M, C is separated from the Y, M, C photoconductor 40 (S5). . When the operation of S5 is completed, a monochrome image is printed in the first monochrome mode (S6). When the monochrome image is printed, it is checked whether or not there is a next image. If there is (YES in S7), the flow after S1 is executed. On the other hand, if there is no next image (NO in S7), the process ends.

  On the other hand, if the image to be printed is a color image in S1 (YES in S1), it is checked whether the driving of the Y, M, and C developing rollers 61 is ON (S9). When the driving of the Y, M, and C developing rollers 61 is ON (YES in S9), the color image is printed in the color mode as it is (S12). If the driving of the Y, M, and C developing rollers 61 is not ON (NO in S9), whether or not the primary transfer rollers 62 of Y, M, and C are separated from the Y, M, and C photoconductors 40. Check (S10). When the Y, M, and C primary transfer rollers 62 are not separated from the photoreceptor 40 (NO in S10), the Y, M, and C developing rollers 61 are driven (S13), and then a color image is displayed in the color mode. Is executed (S12). On the other hand, when the primary transfer rollers 62 of Y, M, and C are separated from the photoreceptor 40, step S11 is executed. That is, the Y, M, and C photoconductors 40 and the Y, M, and C developing rollers 61 are turned on, and the Y, M, and C primary transfer rollers 62 are respectively applied to the Y, M, and C photoconductors 40. Touch it. When the step of S11 is completed, printing of a color image is executed in the color mode (S12), it is checked whether there is a next image (S7), and if there is (YES in S7), the flow after S1 is executed. carry out. On the other hand, if there is no next image (NO in S7), the process ends.

  In the above description, the example in which the present invention is applied to the image forming apparatus in which the user can select three modes of the auto color mode, the full color mode, and the monochrome mode has been described. The present invention can also be applied to an image forming apparatus having two modes. In this case, when the user selects the full color mode, the control flow shown in FIG. 7 is executed.

(1)
As described above, according to the image forming apparatus of the present embodiment, image formation is started when the image data of the first original image is stored in the image memory serving as the storage unit. As described above, since the image formation is started as soon as the image data of the first original image is stored in the image memory, it is possible to suppress the problem that it takes time until the image formation is started as in the conventional case. Can do. When a predetermined number of pieces of image data are stored in the image memory, it is determined whether the predetermined number of single-color images are continuous. If they are continuous, the mode is switched to the first single-color mode. As described above, since the first monochrome mode is switched only when a predetermined number of monochrome images are continuous, the monochrome document and the color document are compared with those that switch to the first monochrome mode each time the color image changes to the monochrome image. It is possible to increase the copying speed when continuously copying mixed items. Further, the deterioration of the photoconductors of other colors can be suppressed as compared with a case where all originals in which a single color original and a color original are mixed are performed in the color mode.
Also, when image data that has not undergone image formation is not stored in the recording means, or when a single color image is formed when a predetermined number of single color images are not continuously formed, image formation is performed in the second single color mode. Thereby, it is possible to suppress the deterioration of the developing devices of other colors and the developer in the developing device.
(2)
Deterioration of the Y, M, and C color photoreceptors when printing a document in which a monochrome image and a color image are mixed, by forming the image formed in the first monochrome mode and the second monochrome mode as a black monochrome image. Deterioration of the developing device and the developer can be suppressed.
(3)
Further, according to the image forming apparatus of the present embodiment, since the operation of the developing device that is performed in the second monochrome mode that is the second single color mode is stopped by disengaging the electromagnetic clutch that is the clutch, the developing device can be configured with an inexpensive configuration. Can be stopped.
(4)
In addition, the operation of the developing device that is performed in the second monochrome mode that is the second monochrome mode may be stopped by stopping a drive source that drives only the developing device. By providing a drive source for driving only the developing device, the operation of the developing device can be stopped simply by stopping the drive source, and the drive stop of the developing device can be easily controlled.
(5)
Further, if the driving source of each color developing device whose operation is stopped in the second single color mode is made common, it can be made cheaper than the case where the driving source is provided for each developing device of each color.
(6)
In addition, according to the image forming apparatus of the present embodiment, a monochrome mode in which a monochrome image is always formed regardless of whether the document is a single color image, or an auto color in which a mode is automatically selected by the control unit in the apparatus as the mode selection unit. An operation unit is provided as manual selection means that allows the user to select any one of the change modes. As a result, if the user wants to print a color image in a single color, selecting the single color mode allows the color image to be printed in a single color, thereby providing a user-desired image.
(7)
Further, according to the image forming apparatus of the present embodiment, the operation unit can select the color mode. If the user selects the color mode on the operation unit, even if the document image is a monochrome image, all the image forming means are driven to form a monochrome image. In the auto color change mode, when the original image is switched from a color image to a monochrome image, the driving of the Y, M, and C developing devices is stopped or the primary transfer rollers of Y, M, and C are separated from the photoconductor. Such an operation occurs, and no image is formed until the operation is completed. On the other hand, since the color mode does not switch from the color mode to the monochrome mode even for a monochrome image, the image forming speed is faster than the auto color change mode. Therefore, when the user selects the color mode with the operation unit, it is possible to finish printing a document including a monochrome image and a color image earlier than in the auto color change mode.
(8)
Further, according to the image forming apparatus of the present embodiment, the monochrome mode is the first monochrome mode. As a result, the deterioration of the Y, M, and C photoconductors and the suppression of Y, M, and C can be suppressed.
(9)
Further, according to the image forming apparatus of the present embodiment, since the image reading apparatus that can read image information is provided, an image can be printed based on the image read by the image reading apparatus.

1 is a schematic configuration diagram of an entire copying machine according to an embodiment. FIG. 3 is an enlarged configuration diagram illustrating an image forming unit for K of the copier. (A) is an enlarged view of the transfer unit when the color mode is executed. FIG. 6B is an enlarged view of the transfer unit when the first monochrome mode is executed. 6 is a timing chart showing timing for determining whether or not a predetermined number of monochrome images are continuous. FIG. 3 is a diagram illustrating an example of a driving unit of a developing device. Control block diagram of image forming apparatus Control flow diagram of auto color change mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 6 Transfer unit 10 Intermediate transfer belt 18 Image forming means 20 Image forming unit 40 Photoconductor 61 Developing device 62 Primary transfer roller 72 Control unit 73 Image memory 101 Drive motor 102 Electromagnetic clutch 300 Scanner

Claims (9)

An image forming unit including an image carrier on which a latent image is formed and a developing device that converts the latent image on the image carrier into a toner image is provided for each color, and the image carrier of each image forming unit is used as a belt member. In the image forming apparatus in which the toner image on each image carrier is transferred to the belt member after being contacted and transferred to the transfer material, or transferred to the transfer material conveyed by the belt member.
Storage means for sequentially storing image data to be imaged, determination means for determining whether or not the image data is a single color image, color mode for forming an image using all the image forming means, and one image formation A first monochromatic mode in which the image carrier of all other image forming units except the unit is relatively spaced from the belt member, and an image is formed using the one image forming unit, and all the image carriers are A second single color that stops the operation of the developing devices of all the other image forming means except one image forming means without being relatively separated from the belt member, and forms an image using the one image forming means. When the image data of the first original image is read, the image formation is started and the remaining original images are sequentially stored in the storage means during the image formation. Images to remember A control unit; and a mode selection unit that selects one of the color mode, the first single color mode, and the second single color mode based on a determination result of the determination unit, and the mode selection unit includes: When an image of image data that is determined to be a non-monochromatic image by the determination unit is formed, a color mode is selected, and when an image of an image data that is determined to be a monochromatic image by the determination unit is formed, the image data When it is detected whether or not the image data that has not been subjected to image formation stored in the storage means is equal to or greater than a predetermined number, and the image data that has not been subjected to image formation that is stored in the storage means is less than the predetermined number, When the second monochromatic mode is selected and the number of image data that has not been formed and stored in the storage means is greater than or equal to the predetermined number, the image data that has not been formed and stored in the storage means Therefore, it is determined whether or not a plurality of images to be subsequently formed are single-color images. If the single-color images are continuous, the first single-color mode is selected, and the images are formed continuously thereafter. An image forming apparatus that selects a second monochrome mode when there are less than a plurality of monochrome images. The image forming apparatus according to claim 1.
The toner images that can be formed on the plurality of image carriers are a plurality of colors including black, and the images formed in the first monochrome mode and the second monochrome mode are black monochrome images. Image forming apparatus. The image forming apparatus according to claim 1 or 2,
The driving force of the drive source for driving the developing device is transmitted to the developing device via a clutch, and the operation of the developing device performed in the second single color mode is stopped by disengaging the clutch. An image forming apparatus. The image forming apparatus according to claim 1 or 2,
An image forming apparatus comprising: a driving source that drives only the developing device; and stopping the operation of the developing device performed in the second single color mode by stopping the driving source that drives each developing device. The image forming apparatus according to claim 4.
An image forming apparatus characterized in that a common driving source is used for each color developing device whose operation is stopped in the second single color mode. The image forming apparatus according to claim 1,
There is a manual selection means that allows the user to select either a single-color mode that always forms a single-color image regardless of whether it is a single-color image or an auto color change mode that uses the mode selection means to select a mode. An image forming apparatus. The image forming apparatus according to claim 6.
The image forming apparatus according to claim 1, wherein the manual selection unit can select the color mode. The image forming apparatus according to claim 6 or 7,
The image forming apparatus, wherein the single color mode is the first single color mode. The image forming apparatus according to claim 1,
An image forming apparatus comprising an image reading apparatus capable of reading image information.

Images