JP2008207492A - Image forming apparatus, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speedily and efficiently transmit data by effectively using the data transmitting capacity of a communication wire in an image forming apparatus and its method which selectively execute a plurality of motion modes for forming images by operating a plurality of image forming stations, and a single motion mode for forming images by operating the image forming station for a single motion which is one of the image forming stations. <P>SOLUTION: Under a color mode, to each of 8 bit data channels which is time-sharing-multiplied, each video data of Y, M, C and K colors is allotted (Fig.(a)). Under a monochrome mode for which the K color alone is used, in stead of inserting null data to data channels other than that of the K color (Fig.(b)), the K color data is allotted to the data channels corresponding to the Y, M and C colors as well (Fig.(c)). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plurality of operation modes in which a plurality of image forming stations are operated to form an image, and a single operation mode in which one of the plurality of image forming stations is operated to form an image. The present invention relates to an image forming apparatus and method for selectively executing.

  In an image forming apparatus having a plurality of image forming stations, image data given from an external device such as a host computer is given to each image forming station, and each image forming station receiving the image data corresponds to the image data. Form an image. For example, the image forming apparatus described in Patent Document 1 is a so-called tandem type image forming apparatus in which four image forming units having different toner colors are arranged to face a conveyance belt that circulates in a predetermined direction. In this apparatus, image data supplied from a personal computer (PC) is separated into video data for each toner color, stored in an image memory, and transferred to each image forming station via a transfer circuit provided for each toner color. The

Japanese Patent Laying-Open No. 2004-249549 (FIG. 3)

  In the tandem type image forming apparatus, image formation by each image forming station proceeds concurrently with a little time difference corresponding to the difference in position. Therefore, it is necessary to supply image data to each image forming station in parallel. Also in the above-described image forming apparatus described in Patent Document 1, a transfer circuit is provided for each toner color, and image data is sent to each image forming station via an independent signal line.

  However, such data transmission is inefficient. This is because it is necessary to prepare communication means such as a transfer circuit and a communication line corresponding to each image forming station, and only one of the plurality of image forming stations is operated to form an image. This is because the functions of the communication means corresponding to other image forming stations are not used at all.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. A plurality of operation modes in which a plurality of image forming stations are operated to form an image, and one single-operation image forming station among the plurality of image forming stations is operated. It is an object of the present invention to provide an image forming apparatus and method for selectively executing a single operation mode for forming an image, and to transmit data at high speed and efficiently by effectively utilizing the data transmission capability of a communication line.

  In order to achieve the above object, an image forming apparatus according to the present invention generates a plurality of image forming stations for forming an image corresponding to image data, and the image data to be given to each of the plurality of image forming stations. A data generation means for outputting, a data distribution means for receiving the image data output from the image data generation means and distributing the image data to the image forming stations, and a plurality of image forming stations. A plurality of operation modes for allocating the image data to a plurality of data channels and transmitting the image data from the data generation means to the data distribution means; and operating the plurality of image forming stations to form an image. And an image forming station for single operation among the plurality of image forming stations. And a control unit that selectively executes a single operation mode for forming an image by operating the communication unit, and when the plurality of operation modes are executed, the communication unit is configured to transmit the data to each of the plurality of data channels. While the image data to be given to each image forming station corresponding to a channel is allocated and transmitted, when the single operation mode is executed, the image forming station for single operation is assigned to two or more of the plurality of data channels. The image data to be given to the camera is assigned and transmitted.

  In the invention configured as described above, the image data to be given to the image forming station for single operation is allocated and transmitted to the data channel corresponding to the image forming station that is not used in the single operation mode. It can be transmitted well. Therefore, transmission of image data from the data generation unit to the data distribution unit can be performed in a shorter time. Therefore, according to the present invention, high frequency noise caused by data transmission can be suppressed and power consumption can be reduced.

  For example, when the single operation mode is executed, the communication unit may allocate and transmit the image data to be given to the single operation image forming station to all of the plurality of data channels. By doing so, the time required for transmission of the image data is minimized, and the above effect can be maximized.

  Further, the data distribution unit may supply all of the image data transmitted by the communication unit to the single operation image forming station when the single operation mode is executed. In this way, the image forming station for single operation can receive all the image data corresponding to the image to be formed and form a necessary image.

  The communication means may transmit the image data assigned to each data channel via a common signal line by time division multiplexing. By doing so, the signal line and the configuration for driving the signal line can be reduced, and the configuration of the apparatus can be greatly simplified to reduce the cost and size of the apparatus.

  For example, the data structure of the image data transmitted from the communication means is image data corresponding to one of the pixels constituting the image in each of the time slots obtained by dividing one data frame into the number of the image forming stations. Can be assigned. In this way, although there is a difference between whether the data assigned to each time slot corresponds to a plurality of image forming stations or to the same image forming station, it is different from a plurality of operation modes. The apparent data structure can be made equivalent to the operation mode. Therefore, the configuration for realizing communication can be simplified.

  In addition, the present invention further includes an intermediate transfer member that circulates in a predetermined direction, and each of the image forming stations forms a toner image with a different toner color, and the toner image is transferred to each of the intermediate images at different transfer positions. In the multiple operation mode, the image forming apparatus is configured to form a full-color image by superimposing the toner images of the respective colors formed by the image forming stations on the intermediate transfer member in the multiple operation mode. Can be suitably applied. In such an image forming apparatus capable of forming a full color image, a monochrome image is often formed with a single toner color (typically black color) of these full color colors in response to a user's request. The merit of the present invention that can efficiently transmit data during image formation is great.

  In particular, the surface of the intermediate transfer body of the longest image that can be formed in the apparatus has a distance along the surface of the intermediate transfer body between the two closest transfer positions among the transfer positions corresponding to the image forming stations. The effect is remarkable in the image forming apparatus shorter than the length along the line. In the image forming apparatus configured as described above, since the operation period for image formation may overlap between at least two image forming stations, image data is transmitted to two or more image forming stations at the same time. There are times when you have to. Therefore, it is necessary to individually provide data channels for transmitting data to each image forming station. In the apparatus having such a configuration, data transmission can be efficiently performed by transmitting image data using a data channel other than the data channel corresponding to the image forming station for single operation in the single operation mode.

  In order to achieve the above object, the image forming method according to the present invention operates a plurality of image forming stations for forming an image corresponding to image data to form an image, and the plurality of images. A single operation mode in which an image forming station for single operation is operated among the forming stations to form an image, and in the multiple operation mode, the data generation means The image data to be given to each is generated, and the image data is allocated to each data channel of a communication means provided with a plurality of data channels corresponding to each of the plurality of image forming stations. The image data is transmitted to the image forming station and the data distributing means In the single operation mode, the image data to be provided to the single operation image forming station is generated by the data generation means, and the image to be supplied to the single operation image forming station. Data is allocated to two or more of the plurality of data channels and transmitted to the data distribution means.

  In the invention configured as described above, the image data can be transmitted at high speed and efficiently as in the invention related to the image forming apparatus described above.

  FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a view showing the arrangement of image forming stations in the image forming apparatus of FIG. FIG. 3 is a diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus uses a color mode in which four color toners of yellow (Y), magenta (M), cyan (C) and black (K) are superimposed to form a color image, and only black (K) toner. Thus, the image forming apparatus can selectively execute a monochrome mode for forming a monochrome image. In this image forming apparatus, when an image forming command is given from an external device such as a host computer to a main controller MC having a CPU, a memory and the like, the main controller MC gives a control signal to the engine controller EC, and based on this, the engine controller EC The controller EC controls each part of the device such as the engine unit EG and the head controller HC to execute a predetermined image forming operation, and responds to an image forming command on a sheet as a recording material such as a copy sheet, a transfer sheet, a sheet, and an OHP transparent sheet. The image to be formed is formed.

  In the housing main body 3 of the image forming apparatus according to this embodiment, an electrical component box 5 is provided that incorporates a power circuit board, a main controller MC, an engine controller EC, and a head controller HC. An image forming unit 2, a transfer belt unit 8, and a paper feed unit 7 are also disposed in the housing body 3. In FIG. 1, a secondary transfer unit 12, a fixing unit 13 and a sheet guide member 15 are disposed on the right side in the housing body 3. The paper feed unit 7 is configured to be detachable from the housing body 3. The paper feeding unit 7 and the transfer belt unit 8 can be removed and repaired or exchanged.

  The image forming unit 2 includes four image forming stations 2Y (for yellow), 2M (for magenta), 2C (for cyan) and 2K (for black) that form a plurality of images of different colors. In FIG. 1, since the image forming stations of the image forming unit 2 have the same configuration, only some of the image forming stations are denoted by reference numerals for convenience of illustration, and the reference numerals are omitted for other image forming stations. To do.

  Each image forming station 2Y, 2M, 2C, and 2K is provided with a photosensitive drum 21 on which a toner image of each color is formed. Each photosensitive drum 21 is connected to a dedicated drive motor and is driven to rotate at a predetermined speed in the direction of arrow D21 in the figure. A charging unit 23, a line head 29, a developing unit 25, and a photoconductor cleaner 27 are disposed around the photoconductive drum 21 along the rotation direction thereof. Then, a charging operation, a latent image forming operation, and a toner developing operation are executed by these functional units. When the color mode is executed, the toner images formed by all the image forming stations 2Y, 2M, 2C, and 2K are superimposed on the transfer belt 81 provided in the transfer belt unit 8 to form a color image. When the monochrome mode is executed, only the image forming station 2K is operated to form a black monochrome image.

  The charging unit 23 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to rotate in contact with the surface of the photosensitive drum 21 at the charging position, and is driven to rotate as the photosensitive drum 21 rotates. The charging roller is connected to a charging bias generator (not shown). The charging roller is supplied with the charging bias from the charging bias generator and is charged at the charging position where the charging unit 23 and the photosensitive drum 21 come into contact with each other. The surface of 21 is charged to a predetermined surface potential.

  The line head 29 includes a plurality of light emitting elements arranged in the axial direction of the photosensitive drum 21 (a direction perpendicular to the paper surface of FIG. 1), and is disposed to face the photosensitive drum 21. Then, light is emitted from these light emitting elements toward the surface of the photosensitive drum 21 charged by the charging unit 23 to form an electrostatic latent image on the surface.

  FIG. 4 is a diagram showing the structure of the line head. In the following description, the direction from the back of the drawing to the near side in FIG. That is, the X direction is a direction parallel to the rotation axis of the photosensitive drum 21 and is orthogonal to the moving direction of the surface of the photosensitive drum 21 and the moving direction D81 of the transfer belt 81. In the line head 29, an LED array 293 in which a plurality of LED (light emitting diode) elements serving as exposure light sources are arranged in the X direction is held in a long housing. The LED array 293 on the base substrate 294 is driven by a driver IC 295 formed on the same base substrate 294. When a video signal is supplied from the head controller HC, the driver IC 295 is operated based on the video signal, and the LED elements provided in the LED array 293 are turned on. The gradient index rod lens array 296 constitutes an imaging optical system, and a gradient index rod lens 297 arranged in front of the LED element is stacked. The housing covers the periphery of the base substrate 294, and the side facing the photosensitive drum 21 is open. In this way, light is emitted from the gradient index rod lens 297 to the photosensitive drum 21. Thereby, an electrostatic latent image is formed on the photosensitive drum 21 corresponding to the video signal.

  Returning to FIG. 1, the description of the apparatus configuration will be continued. The developing unit 25 has a developing roller 251 on which toner is carried. The charged toner is developed at a developing position where the developing roller 251 and the photosensitive drum 21 come into contact with each other by a developing bias applied to the developing roller 251 from a developing bias generator (not shown) electrically connected to the developing roller 251. Moves from the developing roller 251 to the photosensitive drum 21, and the electrostatic latent image formed on the surface thereof is visualized.

  The toner image made visible at the developing position is conveyed in the rotational direction D21 of the photosensitive drum 21, and then is transferred to the transfer belt 81 at a primary transfer position TR1 where the photosensitive belt 21 comes into contact with the transfer belt 81 described later in detail. Primary transcription.

  A photoreceptor cleaner 27 is provided in contact with the surface of the photoreceptor drum 21 on the downstream side of the primary transfer position TR1 in the rotation direction D21 of the photoreceptor drum 21 and on the upstream side of the charging unit 23. The photoconductor cleaner 27 abuts on the surface of the photoconductor drum to remove the toner remaining on the surface of the photoconductor drum 21 after the primary transfer.

  The transfer belt unit 8 includes a driving roller 82, a driven roller 83 (blade facing roller) disposed on the left side of the driving roller 82 in FIG. 1, and an arrow D81 illustrated in FIG. And a transfer belt 81 that is circulated in the direction (conveyance direction). Further, four transfer belt units 8 are arranged on the inner side of the transfer belt 81 so as to be opposed to each of the photosensitive drums 21 included in the image forming stations 2Y, 2M, 2C, and 2K when the cartridge is mounted. Primary transfer rollers 85Y, 85M, 85C and 85K. Each of these primary transfer rollers is electrically connected to a primary transfer bias generator (not shown).

  When the color mode is executed, as shown in FIGS. 1 and 2, all the primary transfer rollers 85Y, 85M, 85C, and 85K are positioned on the image forming stations 2Y, 2M, 2C, and 2K, so that the transfer belt 81 is imaged. A primary transfer position TR1 is formed between each photosensitive drum 21 and the transfer belt 81 by being pushed and brought into contact with the photosensitive drum 21 included in each of the forming stations 2Y, 2M, 2C, and 2K. Then, by applying a primary transfer bias from the primary transfer bias generating unit to the primary transfer roller 85Y or the like at an appropriate timing, the toner images formed on the surface of each photosensitive drum 21 are respectively transferred to the corresponding primary transfer positions. Transfer is performed on the surface of the transfer belt 81 in TR1. That is, in the color mode, the single color toner images of the respective colors are superimposed on the transfer belt 81 to form a color image.

  In the so-called tandem image forming apparatus, the primary transfer position where the toner image is primarily transferred from the photosensitive drum 21 to the transfer belt 81 is different for each image forming station. In this embodiment, the yellow image forming station 2Y, the magenta image forming station 2M, the cyan image forming station 2C, and the black image forming station 2K are arranged in this order along the moving direction of the transfer belt 81. . Accordingly, the yellow primary transfer position TR1y and the magenta primary transfer position TR1m are the distance Lym, the magenta primary transfer position TR1m and the cyan primary transfer position TR1c are the distance Lmc, and the cyan primary transfer position TR1c and the black primary transfer position TR1k are only the distance Lck. Separated.

  On the other hand, when executing the monochrome mode, among the four primary transfer rollers, the primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations 2Y, 2M, and 2C that face each other, and the primary transfer rollers corresponding to the black color are used. By bringing only 85K into contact with the image forming station 2K, only the monochrome image forming station 2K is brought into contact with the transfer belt 81. As a result, the primary transfer position TR1k is formed only between the primary transfer roller 85K and the image forming station 2K. Then, by applying a primary transfer bias to the primary transfer roller 85K from the primary transfer bias generator at an appropriate timing, a black toner image formed on the surface of the photosensitive drum 21 provided in the image forming station 2K is obtained. A monochrome image is formed by transferring to the surface of the transfer belt 81 at the primary transfer position TR1k.

  Further, the transfer belt unit 8 includes a downstream guide roller 86 disposed on the downstream side of the black primary transfer roller 85K and on the upstream side of the driving roller 82. The downstream guide roller 86 is common to the primary transfer roller 85K and the black photosensitive drum 21 (K) at the primary transfer position TR1 formed by the primary transfer roller 85K contacting the photosensitive drum 21 of the image forming station 2K. It is configured to contact the transfer belt 81 on the tangent line.

  A patch sensor 89 is provided opposite to the surface of the transfer belt 81 wound around the downstream guide roller 86. The patch sensor 89 is composed of, for example, a reflection type photosensor, and optically detects a change in the reflectance of the surface of the transfer belt 81, so that the position and density of the patch image formed on the transfer belt 81 as necessary. Is detected.

  The paper feed unit 7 includes a paper feed cassette 77 capable of stacking and holding sheet-like recording materials (hereinafter simply referred to as “sheets”), and a pickup roller 79 for feeding sheets one by one from the paper feed cassette 77. A paper feed unit is provided. The sheet fed from the sheet feeding unit by the pickup roller 79 is adjusted in sheet feeding timing by the registration roller pair 80, and then the drive roller 82 and the secondary transfer roller 121 abut along the sheet guide member 15. Paper is fed to the secondary transfer position TR2.

  The secondary transfer roller 121 is provided so as to be able to come into contact with and separate from the transfer belt 81 and is driven to come into contact with and separate from a secondary transfer roller drive mechanism (not shown). The fixing unit 13 includes a heating roller 131 that includes a heating element such as a halogen heater and is rotatable, and a pressure unit 132 that presses and biases the heating roller 131. The sheet on which the image is secondarily transferred is guided to the nip formed by the heating roller 131 and the pressure belt 1323 of the pressure unit 132 by the sheet guide member 15, and in the nip, a predetermined value is formed. The image is heat-fixed at temperature. The pressure unit 132 includes two rollers 1321 and 1322 and a pressure belt 1323 stretched between them. A nip portion formed by the heating roller 131 and the pressure belt 1323 is formed by pressing the belt tension surface stretched by the two rollers 1321 and 1322 out of the surface of the pressure belt 1323 against the peripheral surface of the heating roller 131. Is configured to be widely taken. Further, the sheet thus subjected to the fixing process is conveyed to a paper discharge tray 4 provided on the upper surface portion of the housing body 3.

  The drive roller 82 circulates and drives the transfer belt 81 in the direction of the arrow D81 in the figure, and also serves as a backup roller for the secondary transfer roller 121. A rubber layer having a thickness of about 3 mm and a volume resistivity of 1000 kΩ · cm or less is formed on the peripheral surface of the drive roller 82, and secondary transfer is omitted by grounding through a metal shaft. A conductive path of a secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 121 is used. Thus, by providing the driving roller 82 with a rubber layer having high friction and shock absorption, image quality deterioration caused by transmission of the impact to the transfer belt 81 when the sheet enters the secondary transfer position TR2. Can be prevented.

  Further, in this apparatus, a cleaner portion 71 is disposed to face the blade facing roller 83. The cleaner unit 71 includes a cleaner blade 711 and a waste toner box 713. The cleaner blade 711 removes foreign matters such as toner and paper dust remaining on the transfer belt 81 after the secondary transfer by bringing the tip of the cleaner blade 711 into contact with the blade facing roller 83 via the transfer belt 81. The foreign matter removed in this way is collected in a waste toner box 713. Further, the cleaner blade 711 and the waste toner box 713 are integrally formed with the blade facing roller 83.

  In this embodiment, the photosensitive drum 21, the charging unit 23, the developing unit 25, and the photosensitive cleaner 27 of each of the image forming stations 2Y, 2M, 2C, and 2K are unitized as a unit. The cartridge is configured to be detachable from the apparatus main body. Each cartridge is provided with a nonvolatile memory for storing information related to the cartridge. Then, wireless communication is performed between the engine controller EC and each cartridge. Thus, information about each cartridge is transmitted to the engine controller EC, and information in each memory is updated and stored. Based on these pieces of information, the usage history of each cartridge and the lifetime of consumables are managed.

  In this embodiment, the main controller MC, the head controller HC, and each line head 29 are configured as separate blocks, and are connected to each other via a serial communication line as described below.

  FIG. 5 is a diagram showing the connection between the main controller and the head controller. The main controller MC is provided with a 7-pin plug 201 (hereinafter referred to as “host plug”) electrically connected to the main communication module 200. The head controller HC is also provided with a 7-pin plug 301 (hereinafter referred to as “device plug”) that is electrically connected to the head-side communication module 300. The two plugs are connected to each other by a communication cable 700 having 7-pin connectors 701a and 701b fitted to the host plug 201 and the device plug 301, respectively.

  The signal transmission method employs an LVDS (Low Voltage Differential Signaling) interface capable of high-speed transmission, and 2 for transmission from the main controller MC to the head controller HC and vice versa. A differential signal line with a set of books is used. One of the two signal line pairs includes a transmission TX + terminal and a TX− terminal, which will be described later, provided in the main communication module 200 and a reception RX + terminal and RX−, provided in the head communication module 300. The terminals are electrically connected to each other through a connector. The other pair electrically connects the RX + and RX- terminals for reception provided in the main-side communication module 200 and the TX + and TX- terminals for transmission provided in the head-side communication module 300, respectively. Connecting. Each signal line pair is shielded, and the shield conductor and the GND line are also connected to the connectors 701a and 701b, respectively, with the signal line pair interposed therebetween. These shield conductors and the GND line are grounded in both communication modules. As described above, in this embodiment, data transmission from the main controller MC to the head controller HC and data transmission from the head controller HC to the main controller MC are performed bidirectionally by a set of communication cables.

  The cooperative operation of each part of the apparatus configured as described above will be described with reference to FIG. 3 again. When an image formation command is given from the external device to the main controller MC, the main controller MC transmits a control signal for starting the engine unit EG to the engine controller EC via a UART (general purpose asynchronous transmission / reception) communication line. Further, the image processing unit 100 provided in the main controller MC performs predetermined signal processing on the image data included in the image formation command, and generates video data for each toner color.

  On the other hand, the engine controller EC receiving the control signal starts initialization and warm-up of each part of the engine part EG. When these are completed and the image forming operation can be executed, the engine controller EC sends the vertical synchronization signal Vsync that triggers the start of the image forming operation to the head controller HC that controls each line head 29, and the UART communication line. Output via. In addition, in communication between the engine controller EC and the head controller HC via the UART communication line, various control parameters for controlling the line head 29 are exchanged.

  The head controller HC is provided with a head control module 400 that controls each line head and a head-side communication module 300 that controls data communication with the main controller MC. On the other hand, the main communication module 200 is also provided in the main controller MC. From the head-side communication module 300 to the main-side communication module 200, a vertical request signal VREQ indicating the head of an image for one page and a horizontal request for requesting video data for one line among the lines constituting the image. Signal HREQ is transmitted. On the other hand, the video data VD is transmitted from the main communication module 200 to the head communication module 300 in response to these request signals. More specifically, after receiving the vertical request signal VREQ indicating the head of the image, each time the horizontal request signal HREQ is received, video data is sequentially output for each line from the head portion of the image.

  FIG. 6 is a diagram illustrating communication between the main controller and the head controller. An image of one page is positioned little by little in a direction perpendicular to the line in which a large number of dots are arranged in a line along the X direction (the light emitting element arrangement direction of the line head 29), that is, in the moving direction D81 of the transfer belt 81. It is formed while differentiating. A request signal VREQ output from the head controller HC indicates the head of the page. The main controller MC validates the request signal HREQ received after receiving the request signal VREQ, and transmits video data VD for one line to the head controller HC every time the request signal HREQ is received.

  In this embodiment, the maximum number of dots constituting one line is 6828. The resolution is 600 dpi (dots per inch), and the dot pitch is equal to this. Thus, the maximum length of one line is approximately 11.4 inches (289 mm). This length corresponds to the short side dimension of Japanese Industrial Standard A3 size paper. The image data of each dot is represented by 8 bits and multi-gradation, and the video data VD for one line is a predetermined specific value (here 55h) of head data followed by 8 bits × 6828 dots. Image data string. The head data is for indicating the head of the data string, and the head controller that receives the video data can recognize the head of the data from the head data received after the value 00h. In other words, if a value other than 00h received first after receiving the vertical request signal VREQ is different from that determined as the head data, it can be determined that a communication error has occurred.

  After outputting the video data for one line in this way, when the request signal HREQ is subsequently given, the main controller MC outputs the data for the next one line. By repeating this, video data VD corresponding to an image for one page is transferred from the main controller MC to the head controller HC. When there is an image of the next page to be formed, the vertical request signal VREQ is transmitted again from the head controller HC to the main controller MC after the data communication of the previous page is completed.

  In this embodiment, the above-described signals, that is, request signals VREQ and HREQ sent from the head controller HC to the main controller MC and video data VD sent from the main controller MC to the head controller HC correspond to four sets corresponding to each color of YMCK. Exists. In the following, the colors are distinguished by attaching a hyphen and a code representing the color to each signal as necessary. For example, the vertical synchronizing signal, horizontal synchronizing signal, and video data for yellow are represented as VREQ-Y, HREQ-Y, and VD-Y, respectively.

  FIG. 7 is a diagram showing the communication timing for each color. More specifically, this figure shows the exchange of signals between the main controller and the head controller when two pages of color images are continuously formed. As shown in FIG. 2, the primary transfer positions TR1y, TR1m, TR1c and TR1k at which the image forming stations 2Y, 2M, 2C and 2K transfer the toner image onto the transfer belt 81 are different from each other. Therefore, in order to superimpose the toner images formed at the respective image forming stations at the same position on the transfer belt 81, a buffer memory for temporarily storing video data to absorb the difference in the primary transfer position is used as a head. It is necessary to provide the video data transmission timing for each toner color depending on the distance between the primary transfer positions provided in the controller HC. In the former case, a large-capacity memory is required for each toner color, resulting in a significant increase in apparatus cost.

This embodiment employs the latter method that does not require a large-capacity buffer memory. In other words, by providing a time difference in the video data transmission timing in accordance with the arrangement of the image forming stations, the toner image formation positions on the transfer belt 81 are made to coincide between the toner colors. More specifically, the timing at which the request signals VREQ and HREQ output from the head controller HC are transmitted is different for each toner color using the vertical synchronization signal Vsync as a timing reference. For example, the time difference Tym between the yellow vertical request signal VREQ-Y and the magenta vertical request signal VREQ-M is obtained when the moving speed of the transfer belt 81 is Vtb.
Tym = Lym / Vtb
The output timing of the request signal is adjusted so that As a result, a similar time difference is generated between the yellow video signal VD-Y and the magenta video signal VD-M. As a result, the toner image formation positions of both toner colors are the same on the transfer belt 81. . Similarly, the distance between the primary transfer positions is also between the magenta video signal VD-M and the cyan video signal VD-C, and between the cyan video signal VD-C and the black video signal VD-K. The time differences Tmc and Tck according to the above are provided.

  At this time, it is the request signal output from the head controller HC that sets the time difference according to the distance between the primary transfer positions, and the main controller MC simply receives the video signal at the timing requested by the given request signal. Is simply output. In this way, it is not necessary to manage the distance between the primary transfer positions on the main controller MC side, and the main controller MC can perform only processing independent of the configuration of the engine unit EG.

  By the way, in such a communication system, at least three signal lines of request signals VREQ and HREQ and video data VD are required for each color. As the number of colors increases, the number of signal lines also increases. In addition, when the image length in the moving direction D81 of the transfer belt 81 is longer than the shortest distance between the transfer positions, the other image forming station is faster than the image formation at one image forming station is completed. Therefore, the operation of two or more image forming stations is executed in parallel. In the apparatus having such a configuration, as apparent from FIG. 7, there is a timing at which signals of two or more colors are simultaneously transmitted and received, so it is difficult to adopt a bus communication system via a common bus line.

  Therefore, in this embodiment, as will be described later, the request signal is encoded. Thus, the vertical and horizontal request signals VREQ and HREQ for each toner color are multiplexed in a time division manner so that request signals for four colors can be transmitted through one set of serial signal lines. Also, video data VD can be transmitted through one set of serial signal lines by multiplexing four colors into one signal in a time division manner. Therefore, in this embodiment, the number of colors is determined by a set of signal lines including a signal line for transmitting from the main controller MC to the head controller HC and a signal line for transmitting from the head controller HC to the main controller MC. It is possible to perform necessary data communication regardless of the case.

  When data is multiplexed in this way, data transmission at higher speed is required. In this embodiment, a clock for data transmission is generated on the transmission module side, and the clock component is superimposed on the data for transmission, thereby eliminating the clock transmission lines and further reducing the number of signal lines, and at a higher speed. Stable data communication is possible.

  FIG. 8 is a diagram showing the configuration of the main controller. The main controller MC includes an image processing unit 100 that performs signal processing necessary for image data included in an image formation command given from an external device, and a main-side communication module 200. The image processing unit 100 includes a color conversion processing block 101 that develops RGB image data into CMYK image data corresponding to each toner color, and an image memory 102 for temporarily storing the image data. Further, the image processing unit 100 is provided with image processing blocks 103Y, 103M, 103C, and 103K for each toner color, which generate video data VD by performing processing such as screen processing and gamma correction on the image data. Yes. Each image processing block 103Y or the like starts signal processing for the image for one page triggered by the input of the vertical request signal VREQ-Y or the like, and sequentially outputs the generated video data for each line to the main communication module 200. .

  Next, the configuration of the main communication module 200 will be described. The main-side communication module 200 multiplexes four-color video data VD-Y, VD-M, VD-C, and VD-K output from the image processing unit 100 based on the above principle, and serially transmits them to the head controller HC. A receiving block 220 that receives the vertical and horizontal request signals VREQ and HREQ of each color transmitted from the head controller HC after being multiplexed for four colors, and restores and outputs the original signals, respectively, and a block 210; And a clock generation block 230 for generating a clock for this purpose.

  The transmission block 210 is provided with a buffer 211 for aligning the timing for multiplexing the video data VD of each color. The buffer 211 receives 8-bit video data VD-Y, VD output from the image processing block of each color according to the restored vertical request signals VREQ-Y, VREQ-M, VREQ-C, VREQ-K of each color. -M, VD-C, and VD-K are output as 32-bit parallel data while being latched by horizontal request signals HREQ-Y, HREQ-M, HREQ-C, and HREQ-K, respectively.

  FIG. 9 is a diagram showing the contents of data transmitted from the main controller. From the main controller MC to the head controller HC, video data represented by 8 bits for each color is time-division multiplexed into a 32-bit serial signal and transmitted. The 32-bit data is composed of four sections in units of 8 bits, and one toner color is assigned to one section. Each section represents information (2 bits) indicating a position such as whether the dot to be formed is top aligned or bottom aligned, information indicating the type of screen to be applied (1 bit), and the gradation value of the dot to be formed It consists of information (5 bits).

  Returning to FIG. 8, the description of the main communication module 200 will be continued. The 32-bit data output from the buffer 211 is input to an 8b / 10b encoder 212 that adds 2 additional bits to 8 bits of data to form 10-bit data, and is processed into 40-bit data. When an error correction code such as a CRC (Cyclic Redundancy Check) code is used as the additional bit data, the reliability of the transmission data can be further improved, but the present invention is not limited to this.

  The 40-bit data is input to the serializer 214 via the FIFO buffer 213 and sent to the transmission buffer 215 as serial data. The transmission buffer 215 embeds the transmission clock generated by the transmission clock generation unit 232 based on the reference clock (REFCLK) 231 provided in the clock generation block 230, that is, modulates the transmission clock with the transmission data, The modulation signal is output as a differential serial signal from the TX + and TX− terminals. As described above, in this embodiment, the video data for four colors are multiplexed into one serial signal, and the serial signal is output as a differential signal in which the clock component is embedded. That is, in this embodiment, video data for four colors is transmitted through a pair of differential signal lines.

  Next, the configuration and operation of the reception block 220 will be described. As described above, the signal transmitted from the head side communication module 300 is also a differential signal in which a clock component is embedded. This differential signal is input between the RX + terminal and the RX− terminal, and the received 40-bit serial data is input to the reception buffer 221. The clock component embedded in the signal is demodulated by the reception clock demodulation unit 233, and data is received based on the demodulated clock.

  The received 40-bit serial data is parallelized by the deserializer 222. Then, the additional bit data is removed by the 10b / 8b decoder 223 and converted to 32-bit data. At this time, error correction is performed as necessary. The 32-bit data is input to the buffer 224 and supplied to the distributor 225 in synchronization with an output clock 234 provided separately.

  In the distributor 225, each bit information of 32-bit data is cut out and output in time series, thereby restoring eight types of request signals. Among them, the vertical request signals VREQ-Y, VREQ-M, VREQ-C, and VREQ-K are given to the image processing blocks 103Y, 103M, 103C, and 103K, respectively, to notify the start timing of the image processing. The horizontal request signals HREQ-Y, HREQ-M, HREQ-C, and HREQ-K are used as FIFO data signals as data latch timing signals to multiplex the video data VD output from each image processing block at a predetermined timing. The buffer 211 is given.

  FIG. 10 is a diagram showing the configuration of the head controller. The head controller HC includes a head side communication module 300 and a head control module 400. The configuration of the head side communication module 300 is similar to that of the main side communication module 200. That is, the head-side communication module 300 receives the video data multiplexed and transmitted from the main controller MC and restores it to video data for each color, and multiplexes the request signal and transmits it to the main controller MC. The transmission block 310 and the clock generation block 330 are provided. The serial signal transmitted from the main communication module 200 is received based on the clock demodulated from the signal by the reception clock demodulator 333 and input to the reception buffer 321. Then, it is converted into 40-bit parallel data by the deserializer 322, and additional bits are removed by the 10b / 8b decoder 323, converted into 32-bit parallel data, and input to the buffer 324. The 32-bit data input to the buffer 324 is given to the distributor 325 in synchronization with the output clock 334. The distributor 325 divides the data into sections, restores 8-bit video data for each color, and outputs the video data to the head control module 400.

  The head control module 400 includes a Y head control block 410Y, an M head control block 410M, a C head control block 410C, and a K head that individually control the line heads 29 provided in the image forming stations 2Y, 2M, 2C, and 2K. A control block 410K is provided. The video data divided for each color is input to the corresponding color head control block. Further, the vertical request signal VREQ and the horizontal request signal HREQ are input to the head side communication module 300 from each head control block at independent timings.

  The transmission block 310 of the head side communication module 300 encodes and multiplexes request signals input from each head control block as needed, and outputs them to the main side communication module 200. The multiplexer 311 provided in the transmission block 310 outputs a total of eight types of request signals VREQ and HREQ output from each head control block as 32-bit data of 8 bits × 4 sections.

  FIG. 11 is a diagram showing the contents of data transmitted from the head controller. The 32-bit data transmitted from the head controller HC is composed of four sections of data in units of 8 bits, and each bit of each section includes Y, M, C, and K color vertical request signals VREQ and horizontal requests. One of the signals HREQ is assigned. There are eight types of request signals sent from the head controller HC to the main controller MC for two colors, that is, a vertical request signal VREQ and a horizontal request signal HREQ for each color. These 8 types of signals are assigned to each of 8 bits constituting one section. Here, it is assumed that the request signals VREQ-Y, HREQ-Y, VREQ-M, HREQ-M, VREQ-C, HREQ-C, VREQ-K, and HREQ-K are assigned in order from the upper bit. The main controller MC that has received this information can restore the request signal for each color that has been multiplexed into the serial signal by taking out each bit information and rearranging it in time series.

  Returning to FIG. 10, the description of the head side communication module 300 will be continued. Thus, the 8-bit / 10b encoder adds 2 bits of additional data per 8 bits to the 32-bit data obtained by multiplexing the request signals of the respective colors, and converts the data into 40 bits. The 40-bit data obtained in this way is sent to the serializer 314 via the FIFO buffer 313, and the serially converted data is sent to the transmission buffer 315.

  The transmission buffer 315 performs differential communication on the 40-bit serial data in which the clock component is embedded based on the transmission clock generated by the transmission clock generation unit 332 in synchronization with the reference clock (REFCLK) 331 provided in the clock generation block 330. Output to line. In this way, the eight types of request signals are multiplexed into one serial signal and transmitted through a pair of differential communication lines.

  As described above, the communication between the main controller MC and the head controller HC in this embodiment is bidirectional serial communication based on the LVDS method. Since the data of each color is multiplexed into one data, the transmission data from both can be transmitted only by one differential signal line pair. Therefore, only a minimum of four signal lines are required to connect the controllers, and the number of signal lines can be greatly reduced. In this embodiment, a 7-wire signal cable including a GND wiring and a shield conductor is used. This type of cable is a SATA (Serial Advanced Technology Attachment) which is one of the standards for interconnection between computer peripheral devices. ) It is also adopted in the standard and can be obtained at a low price on the market as the standard product. In addition, the use of the differential signal line enables high-speed transmission and is hardly affected by noise.

  Next, in the apparatus configured as described above, data communication between the main controller MC and the head controller HC will be described in more detail.

  FIG. 12 is a diagram showing a data structure in the data communication of this embodiment. More specifically, FIG. 12A shows the structure of data sent from the head controller HC to the main controller MC. FIG. 12B shows the structure of data sent from the main controller MC to the head controller HC.

  Data sent from the head controller HC to the main controller MC consists of a total of eight types of vertical request signals VREQ and horizontal request signals HREQ for four colors. As shown in FIG. 12A, these signals are time-division multiplexed by serial multiplexing into serial data having 8 bits as one data frame.

  On the other hand, data sent from the main controller MC to the head controller HC is video data of each color. The video data of each color is represented by 8 bits per dot. As shown in FIG. 12 (b), the serial data has 8 bits as 1 data channel and 4 data channels (32 bits in total) as 1 data frame. It is time-division multiplexed with word multiplexing. That is, in the data transmission from the main controller MC to the head controller HC in this embodiment, one data frame is divided into four time slots equal to the number of image forming stations, and video data of each color for one dot is divided into each time slot. This is realized by assigning them one by one.

  FIG. 13 is a diagram showing a video data string transmitted from the main controller. As described above, the video data of each color is multiplexed with 8 bits corresponding to one dot as one data channel. When the color mode is executed, as shown in FIG. 13A, Y, M, C, and Data for one dot is assigned to each data channel corresponding to each toner color and transmitted.

  On the other hand, when the monochrome mode is executed, the video data to be transmitted is only the data corresponding to the black color. In this case, when data transmission is performed in the same manner as in the color mode, dot-unit image data K1, K2,... Are assigned to the data channel corresponding to the K toner color, as shown in FIG. On the other hand, all data channels corresponding to Y, M, and C toner colors are assigned null data (00h). Such a transmission method is essentially capable of transmitting only 8 bits of data per frame over a communication line having a data transmission capacity of 32 bits per frame. I can not say. Therefore, in this embodiment, as shown in FIG. 13C, by assigning K toner color image data K1, K2,... To the data channels originally provided for Y, M, and C toner colors, The communication function is used effectively.

  FIG. 14 is a diagram showing a comparison of data transmission times. More specifically, it is a diagram showing a difference in data transmission time when transmitting N-dot K-color video data per line. First, as shown in FIG. 13B, a case is considered in which null data is allocated to data channels for Y, M, and C toner colors without data and transmitted. In this case, since K-color video data of 1 dot is assigned to each data frame, as shown in FIG. 14A, N frames of data need to be transmitted to transmit N dots of data. For this purpose, time T1 is required.

  On the other hand, when K color video data is also allocated to the data channels for Y, M and C colors as shown in FIG. 13C, 4 dots per data frame as shown in FIG. 14B. Therefore, in order to transmit data for N dots, it is only necessary to transmit data of N / 4 frames, and the required time T2 is also set to about 1/4 of the time T1. It is possible. On the other hand, if the data transmission time is made equal, more data can be transmitted. For example, if the generation cycle of the horizontal request signal HREQ is the same, video data for four lines can be transmitted.

  In this way, the amount of data transmission per unit time can be increased and the time required for data transmission can be shortened. As a result, it is possible to increase the time T3 from the transmission of video data for one line until the start of transmission of the next data. As shown in FIG. 14 (a), when data is intermittently transmitted as shown in FIG. 14 (b), it is radiated from the communication line as compared to the case where data is almost always transmitted on the communication line. It is possible to keep high frequency noise low. In addition, since the period during which data is not output is known in advance, power consumption can be suppressed by stopping the operation of each circuit during this period.

  Although the generation cycle of the horizontal request signal HREQ, which is a data request signal for each line from the head controller HC, has been described here as being the same, the time required for data transmission for one line is greatly reduced. It is also possible to shorten the generation cycle of the request signal HREQ. In this way, the time required to transmit one page of video data is greatly shortened, and the above effect is further increased. However, in this case, since video data is sent in a shorter cycle, the head controller HC needs to be provided with a buffer memory for temporarily storing the received data.

  Next, a hardware configuration for enabling data transmission as described above will be described. Such a data transmission method is properly used between the color mode and the monochrome mode, for example, by using the buffer 211 (FIG. 8) provided in the main communication module 200 and the distributor 325 provided in the head communication module 300 as follows. This can be realized by configuring.

  FIG. 15 is a diagram showing the configuration of the buffer 211 of the main communication module. The 8-bit video data VD-Y, VD-M, VD-C, and VD-K output from the image processing blocks 103Y, 103M, 103C, and 103K are input to the FIFO buffers 2111, 2112, 2113, and 2114, respectively. Accumulated. Each of the FIFO buffers 2111 to 2114 starts outputting the accumulated data with the input of the corresponding horizontal request signal HREQ-Y or the like as a trigger. Further, each of the FIFO buffers 2111 to 2114 outputs video data for one dot in synchronization with a shift clock SCLK1 output from a shift clock generation circuit (not shown).

  The 8-bit video data output from the FIFO buffers 2111 to 2114 is input to the selector switch group 2116. When the color mode is executed, outputs from these FIFO buffers 2111 to 2114 are selected and supplied to the latch circuit 2117. The latch circuit 2117 outputs the 8-bit data for these four channels as 32-bit parallel data synchronized with the shift clock SCLK1. This 32-bit output data is input to the 8b / 10b encoder 212 (FIG. 8). As a result, the data string transmitted from the main-side communication module 200 has a structure in which the video data of the toner color is assigned to the data channel provided corresponding to each of Y, M, C, and K. It becomes.

  The output of the FIFO buffer 2114 corresponding to the K toner color is also input to the 4-channel demultiplexer 2115. The demultiplexer 2115 distributes the input K-color video data to the four channels corresponding to Y, M, C, and K colors while sequentially switching the data output destination according to the shift clock SCLK1.

  When the monochrome mode is executed, the selector switch group 2116 selects the output from the demultiplexer 2115 and inputs it to the latch circuit 2117. By doing so, four dots of 8-bit video data corresponding to the K toner color are converted into 32-bit data and input to the 8b / 10b encoder 212. As a result, in the data mode transmitted from the main communication module 200, video data of K color is assigned to each data channel to which data corresponding to each of Y, M, C, and K is assigned in the color mode. It will be. The arrangement of data assigned to each data channel is obtained by rearranging the dot arrangement in one line in time series.

  FIG. 16 is a diagram showing the configuration of the distributor of the head side communication module. The 32-bit data received and demodulated by the head side communication module 300 is input to a data splitter 3251 provided in the distributor 325. The data splitter 3251 divides 32-bit data into 4-channel data in 8-bit order from the MSB and outputs the data. As shown in FIG. 9, video data of Y, M, C, and K colors are assigned to the 32-bit data in order from the MSB side. It is divided into.

  Each 8-bit data divided in this way is input to the selector switch group 3253. When the color mode is executed, the selector switch group 3253 selects the output of the data splitter 3251 and inputs it to the FIFO buffers 3254 to 3257. Accordingly, video data VD-Y corresponding to each toner color is output from the FIFO buffers 3254 to 3257.

  Of the data divided by the data splitter 3251, data corresponding to K color is also input to the 4-channel multiplexer 3252. The multiplexer 3252 selects and outputs four inputs in order according to the shift clock SCLK2 output from a shift clock generation circuit (not shown). Thereby, the four input data input in parallel are output in order along the time series.

  When the monochrome mode is executed, the selector switch group 3253 selects the output from the multiplexer 3252 and inputs it to the FIFO buffer 3257 corresponding to the K color in the FIFO buffer. Further, no data is given to the FIFO buffers 3254 to 3256 corresponding to other toner colors. By doing so, the K video data arranged in chronological order according to the dot arrangement is sequentially given to the K head control block 410K (FIG. 10).

  As described above, in this embodiment, each of the image forming stations 2Y, 2M, 2C, and 2K functions as an “image forming station” of the present invention. The image processing unit 100 functions as the “data generating unit” of the present invention, while the head side communication module 300 functions as the “data distributing unit” of the present invention. Further, the main communication module 200 that controls data transmission between the two, the head communication module 300, and the communication cable 700 that connects them together function as a "communication means" of the present invention. In this embodiment, the transfer belt 81 functions as an “intermediate transfer member” of the present invention.

  In this embodiment, the engine controller EC functions as the “control means” of the present invention, and the “color mode” and “monochrome mode” in the present embodiment are the “multiple operation modes” and “single mode” of the present invention. This corresponds to “operation mode”. The black image forming station 2K functions as the “single-operation image forming station” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the data length of data exchanged between the main controller MC and the head controller HC is 32 bits, but the data length is not limited to this and is arbitrary.

  Further, for example, in the communication between the main controller MC and the head controller HC in the above embodiment, data transmission is performed after converting 32-bit data into 40-bit data by adding 2 additional bits per 8 bits. . However, whether or not to perform such data conversion is arbitrary in the present invention, and data may be transmitted without adding additional bits. Further, error correction is also optional, and error correction may not be performed or other error correction methods may be employed.

  Furthermore, in the above-described embodiment, the present invention is applied to a tandem color image forming apparatus using YMCK four-color toners, but the application target of the present invention is not limited to this, and a rotatable development is possible. The present invention can also be applied to a rotary developing type image forming apparatus in which a plurality of developing devices are mounted on a rotary, and to image forming apparatuses having different types and numbers of colors.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an arrangement of image forming stations in the image forming apparatus of FIG. 1. FIG. 2 is a diagram illustrating an electrical configuration of the image forming apparatus in FIG. 1. The figure which shows the structure of a line head. The figure which shows the connection of a main controller and a head controller. The figure which shows the communication between a main controller and a head controller. The figure which shows the communication timing for every color. The figure which shows the structure of a main controller. The figure which shows the content of the data transmitted from a main controller. The figure which shows the structure of a head controller. The figure which shows the content of the data transmitted from a head controller. The figure which shows the data structure in the data communication of this embodiment. The figure which shows the video data sequence transmitted from a main controller. The figure which shows the comparison of data transmission time. The figure which shows the structure of the buffer of the main side communication module. The figure which shows the structure of the distributor of a head side communication module.

Explanation of symbols

  2Y, 2M, 2C ... image forming station, 2K ... image forming station (image forming station, image forming station for single operation), 81 ... transfer belt (intermediate transfer member), 100 ... image processing unit (data generating means), 200 ... main side communication module (communication means), 300 ... head side communication module (data distribution means, communication means), 700 ... communication cable (communication means), EC ... engine controller (control means)

Claims (8)

A plurality of image forming stations that form images corresponding to the image data;
Data generating means for generating and outputting the image data to be given to each of the plurality of image forming stations;
Data distribution means for receiving the image data output from the image data generation means and distributing the image data to the image forming stations;
Communication means for allocating the image data to a plurality of data channels provided corresponding to each of the plurality of image forming stations and transmitting the image data from the data generation means to the data distribution means;
A plurality of operation modes for forming an image by operating the plurality of image forming stations and a single operation mode for forming an image by operating one image forming station for single operation among the plurality of image forming stations are selectively used. And a control means for executing
When the plurality of operation modes are executed, the communication unit allocates and transmits the image data to be provided to each of the image forming stations corresponding to the data channel to each of the plurality of data channels. An image forming apparatus, wherein when the operation mode is executed, the image data to be given to the single operation image forming station is assigned to two or more of the plurality of data channels and transmitted.   2. The image forming apparatus according to claim 1, wherein when the single operation mode is executed, the communication unit assigns and transmits the image data to be provided to the single operation image forming station to all of the plurality of data channels.   The image forming apparatus according to claim 2, wherein the data distribution unit provides all the image data transmitted by the communication unit to the image forming station for single operation when the single operation mode is executed.   4. The image forming apparatus according to claim 1, wherein the communication unit transmits the image data assigned to each data channel via a common signal line by time division multiplexing. 5.   The data structure of the image data transmitted from the communication means assigns image data corresponding to one of the pixels constituting the image to each of the time slots obtained by dividing one data frame into the number of the image forming stations. The image forming apparatus according to claim 4, wherein An intermediate transfer member that moves in a predetermined direction;
Each of the image forming stations is configured to form a toner image with different toner colors and transfer the toner image to the intermediate transfer member at different transfer positions, respectively.
6. The image forming apparatus according to claim 1, wherein in the plurality of operation modes, a toner image of each color formed by each image forming station is superimposed on the intermediate transfer member to form a full color image.   The distance along the surface of the intermediate transfer body between the two closest transfer positions among the transfer positions corresponding to the image forming stations is longer than the length along the surface of the intermediate transfer body of the longest image that can be formed. The image forming apparatus according to claim 6, which is shorter. A plurality of operation modes in which a plurality of image forming stations that form images corresponding to image data are operated to form an image, and one single operation image forming station among the plurality of image forming stations is operated to generate an image. Selectively execute the single operation mode to be formed,
In the multiple operation mode, each of the communication means that generates the image data to be given to each of the plurality of image forming stations by a data generation means, and has a plurality of data channels corresponding to each of the plurality of image forming stations. Assigning the image data to a data channel and transmitting the image data from the data generation means to the data distribution means, and distributing the image data to the image forming stations by the data distribution means,
In the single operation mode, the image data to be supplied to the single operation image forming station is generated by the data generating means, and the image data to be supplied to the single operation image forming station is output from two of the plurality of data channels. An image forming method characterized by allocating to at least one and transmitting to the data distribution means.

Images