JP2008137238A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for forming a good image by suppressing generation of defects caused by the fact that a special code is present at a halfway point of video data received at the receiving side in the technique in which synchronization of transmission and reception of the video data between the transmitting side and the receiving side is obtained by using the special code. <P>SOLUTION: A main controller (transmitting side) stores the video data over a plurality of blocks, and inserts a dummy block with dummy data stored therein in the halfway of the plurality of blocks. Moreover, the main controller substitutes the dummy data stored in the dummy block with the special code, thereby generating transmission data. A head controller (receiving side) controls lighting of a line head on the basis of video data reconstructed by removing the dummy block from the received transmission data. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for forming an electrostatic latent image by exposing the surface of a photoreceptor with a line head having a plurality of light emitting elements.

  2. Description of the Related Art Conventionally, there has been known an image forming technique for forming an electrostatic latent image on the surface of a photoconductor by scanning and exposing the surface of the photoconductor with a light beam emitted from a light source. However, in recent years, light-emitting elements such as LEDs (light-emitting diodes) and organic EL (electroluminescence) elements that have a small size and can obtain a sufficient amount of light have been developed, and these light-emitting elements are used as exposure light sources. Therefore, a technique for eliminating the scanning optical system and reducing the size of the apparatus and the process speed has been studied. For example, in the image forming apparatus described in Patent Document 1, a line head having a large number of organic EL elements arranged in a row is arranged opposite to a photoconductor, and each EL element in a row is turned on all at once, thereby forming one line. A latent image of minutes is formed.

JP-A-2005-212291 U.S. Pat. No. 4,486,739

  In the image forming technique using the line head as described above, in order to form a latent image corresponding to a desired image on the surface of the photoreceptor, video data is generated from the image signal by a signal processing circuit, and then based on the video data. The head control circuit controls the lighting of the line head. More specifically, the signal processing circuit performs signal processing such as halftone processing and gradation correction on the image signal to generate video data corresponding to the toner color, and sends the video data to the head control circuit. Send. At this time, video data can be transmitted / received as a unit of a bit string of a predetermined length, which indicates information relating to, for example, the color and gradation value per dot. That is, at this time, the signal processing circuit transmits the bit string for one line of video data, for example, to the head control circuit, and the head control circuit receives the bit string for one line as video data for one line. The lighting control of the line head is executed based on the video data.

  In the image forming technique as described above, in order to meet the recent demand for higher definition and higher image quality of images, it is preferable to transmit and receive video data between the signal processing circuit and the head control circuit at high speed. Therefore, it is conceivable to apply serial communication technology to image forming technology in order to enable high-speed transmission / reception. That is, it can be considered that high-speed transmission / reception is possible by transmitting / receiving video data as a serial signal between the signal processing circuit and the head control circuit.

  However, when the above-described bit string is transmitted continuously to execute serial communication, the head control circuit on the receiving side may not be able to determine from where to where the bit corresponds to the bit string. On the other hand, for example, Patent Document 2 describes a technique using a special code that is a bit string of a code pattern that cannot be generated when data is represented. That is, in this patent document, when data is transmitted / received with a 10-bit bit string as a unit, a special code having a length of 10 bits is added before and after the data to be transmitted / received, for example. Then, with reference to the special code, it is possible to determine where to what bit corresponds to a bit string representing data. That is, the data transmission side and the reception side are synchronized on the basis of the special code.

  However, when a special code is inserted between a bit string indicating video data and the above-mentioned synchronization is taken, the following problem may occur. In other words, when the transmission side (signal processing circuit) generates transmission data by inserting a special code between the bit string indicating the video data and the bit string and outputs the transmission data, the reception side (head control circuit) receives it. The data to be processed is also data in which a special code is inserted between the bit string indicating the video data. That is, on the receiving side (head control circuit), there is a special code in the middle of video data that should be continuous. As described above, the special code has a code pattern that cannot be generated when representing video data. As a result, there is a case where the reception side (head control circuit) does not operate properly and a desired image cannot be obtained due to the presence of such special codes in the middle of video data. there were.

  The present invention has been made in view of the above problems, and an image forming apparatus and an image which use a special code to synchronize transmission / reception of video data between a transmission side (signal processing circuit) and a reception side (head control circuit). An object of the forming method is to suppress the occurrence of problems due to the presence of special codes in the middle of video data received on the receiving side (head control circuit) and to form a good image.

  An image forming apparatus according to a first aspect of the present invention develops an electrostatic latent image formed on the surface of the photosensitive member, the line head for forming the electrostatic latent image on the surface of the photosensitive member, and a toner image by developing the electrostatic latent image. J image forming stations (where J is an integer equal to or greater than 2) having a developing device to form, and forming toner images of different colors on each of the J image forming stations to obtain a J color toner image In addition, an image forming apparatus that forms a color image by superimposing the J color toner images, and in order to achieve the above object, the image signal included in the image formation command is subjected to signal processing to generate a J color toner. A signal processing unit for generating video data of J color corresponding to an image, and a data structure in which a plurality of words are arranged in which J blocks corresponding to J color are arranged in a predetermined order corresponding to J color Send data A main controller having a transmission unit for serial output; and a head controller for receiving transmission data and controlling lighting of the line head. The main controller receives a plurality of video data for one line for each of the J colors. A dummy word having a color corresponding to each of the J blocks is stored in a block corresponding to each color across the word, and a dummy word is inserted in the middle of the plurality of words, and at least the dummy word The dummy data stored in one block is replaced with a special code to generate transmission data, and the head controller removes the word in which the special code exists from the received transmission data and reconstructs the video data of each color. Based on the video data of each color, the lighting of the corresponding line head is controlled. It is characterized by a door.

  The image forming method according to the first aspect of the present invention includes a photosensitive member, a line head for forming an electrostatic latent image on the surface of the photosensitive member, and an electrostatic latent image formed on the surface of the photosensitive member to develop a toner. A toner image of a different color is formed on each of the J image forming stations using an image forming apparatus having J image forming stations (J is an integer of 2 or more) having a developing unit for forming an image. An image forming method for forming a color image by superimposing the J color toner images and forming the color image, and in order to achieve the above object, the image forming apparatus A signal processing unit that performs signal processing on the included image signal to generate J-color video data corresponding to the J-color toner image, and J blocks corresponding to the J-color are stored in a predetermined number of blocks. Words arranged in order A main controller having a transmission unit that serially outputs transmission data having a data structure in which a plurality of data are arranged, and a head controller that receives the transmission data and controls lighting of the line head. Each line of video data is stored in a block corresponding to each color across a plurality of words, and dummy data of a color corresponding to each of J blocks is stored. Inserting in the middle, and replacing the dummy data stored in at least one block of the dummy word with a special code to generate transmission data, and the head controller determines the word containing the special code from the received transmission data. Based on the video data of each color that has been removed and reconstructed, Data is characterized by controlling the lighting of the corresponding line head.

  An image forming apparatus according to a second aspect of the present invention is an image forming apparatus that forms an electrostatic latent image on the surface of a photosensitive member by a line head in which a plurality of light emitting elements are arranged in a row. In order to achieve the above, serially output transmission data having a data structure in which a signal processing unit that generates video data by performing signal processing on an image signal included in an image formation command and a block that stores a bit string of a predetermined length A main controller having a transmission unit for receiving the transmission data and controlling the lighting of the line head. The main controller stores the video data across a plurality of blocks and stores the video data in the plurality of blocks. Insert a dummy block in which dummy data is stored in the middle, and specify the dummy data stored in the dummy block. Replacing the code to generate the transmission data, the head controller is characterized to control the lighting of the line head on the basis of the transmission data received in the video data reconstructed by removing the dummy block.

  The image forming method according to the second aspect of the present invention generates a video data by performing signal processing on an image signal included in an image formation command and a line head in which a plurality of light emitting elements are arranged in a line. An image forming apparatus comprising: a main controller that serially outputs transmission data having a data structure in which blocks storing bit strings of a predetermined length are arranged; and a head controller that receives transmission data and controls lighting of a line head An image forming method for forming an electrostatic latent image on the surface of a photoconductor using the main controller stores video data across a plurality of blocks in order to achieve the above object. Insert a dummy block with dummy data stored in the middle, and also store the dummy data stored in the dummy block. The generated transmission data is replaced with a special code, the head controller is characterized by controlling the lighting of the line head on the basis of the transmission data received in the video data reconstructed by removing the dummy block.

  In the first aspect of the present invention, a toner image of a different color is formed on each of the J image forming stations to obtain a toner image of J color, and a color image is formed by superimposing the toner images of J color. To do. In addition, a main controller that performs signal processing on the image signal included in the image formation command to generate J color video data corresponding to the J toner image, and receives the video data from the main controller to form J images. Transmission / reception of signals to / from the head controller that controls lighting of the line heads of each station is executed by serial communication. That is, the main controller serially outputs transmission data having a data structure in which a plurality of words are arranged in which J blocks corresponding to J color are arranged in a predetermined order corresponding to J colors.

In order to synchronize the serial communication between the main controller and the head controller, a special code is used as follows. That is, the main controller stores video data for one line for each of J colors in blocks corresponding to each color across a plurality of words, and also stores dummy data for colors corresponding to each of the J blocks. A dummy word is inserted in the middle of a plurality of words, and the dummy data stored in at least one block of the dummy word is replaced with a special code to generate transmission data. And
The head controller controls lighting of the line head corresponding to the video data of each color based on the video data of each color which is reconstructed by removing the word having the special code from the received transmission data.

  An image forming apparatus according to the second aspect of the present invention includes a main controller that generates video data by performing signal processing on an image signal included in an image forming command, and receives video data from the main controller. Transmission / reception of signals to / from the head controller that controls lighting is executed by serial communication. That is, the main controller serially outputs transmission data having a data structure in which blocks storing a bit string having a predetermined length are arranged.

  In order to synchronize the serial communication between the main controller and the head controller, the special code is used as follows. That is, the main controller stores the video data across a plurality of blocks, inserts a dummy block in which dummy data is stored in the middle of the plurality of blocks, and uses the dummy data stored in the dummy block as a special code. Replace and generate transmission data. The head controller controls lighting of the line head based on the video data reconstructed by removing the dummy block from the received transmission data.

  That is, in both the first and second aspects of the present invention, the main controller inserts a special code in the middle of the video data to generate transmission data, and the head controller removes the special code to reconstruct the video data. The line head is controlled based on the reconstructed video data. Therefore, it is possible to suppress the occurrence of problems due to the presence of special codes in the middle of video data received by the head controller and to form a good image.

  The image forming apparatus according to the first aspect of the present invention may be configured as follows. That is, the dummy data stored in each block of the dummy word may be configured to be the same as the video data stored in each block of the adjacent word before the dummy word. When configured in this way, the operation of replacing the dummy data with the special code in the main controller has malfunctioned, and the data stored in the block of the word immediately before the dummy word is replaced with the special code Even so, it is preferable in the head controller that video data can be correctly reconstructed by removing words in which special codes exist.

  The image forming apparatus according to the first aspect of the present invention may be configured as follows. In other words, video data stored in two words adjacent to the dummy word before and after is averaged for each color to generate dummy data, and the dummy data is stored in each block of the dummy word. Also good. When configured in this way, the operation of replacing the dummy data with the special code in the main controller has malfunctioned, and the data stored in the block of either word before or after the dummy word is replaced with the special code Even so, it is preferable that the head controller can construct data approximate to the original video data by removing the word having the special code.

  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 of the image forming stations 2Y, 2M, 2C, and 2K is provided with a photosensitive drum 21 (photosensitive body) 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. Thus, in this embodiment, the four image forming stations 2Y, 2M, 2C, and 2K correspond to “J image forming stations” in the present invention.

  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 that carries toner on the surface thereof. 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. Thus, in this embodiment, the developing unit functions as the “developer” in the present invention.

  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 sheet feeding unit 7 includes a sheet feeding unit having a sheet feeding cassette 77 capable of stacking and holding sheets and a pickup roller 79 that feeds sheets one by one from the sheet feeding cassette 77. 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. Although it is conceivable to configure the head controller HC integrally with the main controller MC or the line head 29, the following advantages are produced by configuring them separately.

  First, by making the function of the head controller HC independent of the line head 29, the line head 29 can be significantly downsized, and the engine unit EG and the entire apparatus can be downsized. In addition, by separating the processing function depending on the structure of the line head from the main controller MC and making it a dedicated block, the main controller MC can perform only more versatile signal processing without considering the head configuration. become able to. If the communication between the main controller MC and the head controller HC is standardized, the head controller corresponding to the head to be used can be used without changing the main controller even when using a head having a different configuration. It will be necessary to prepare only. As a result, a common main controller MC can be used in common for apparatuses having differently configured heads, and multi-model development using one controller is facilitated.

  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 a synchronization signal Vsync that triggers the start of the image forming operation to the head controller HC that controls each line head 29 via the UART communication line. To output.

  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. 5 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. 6 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 for transmitting the request signals VREQ and HREQ output from the head controller HC is different for each toner color. 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. Further, as apparent from FIG. 6, there is a timing at which signals of two or more colors are simultaneously transmitted / received, so that it is difficult to adopt a bus communication system via a common bus line.

  Therefore, in this embodiment, the request signal is encoded as described below. 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.

  Hereinafter, the data communication system in the present embodiment will be described in detail. In this embodiment, the request signals for four colors sent from the head controller HC to the main controller MC and the video data for four colors sent from the main controller MC to the head controller HC are both multiplexed and converted into serial signals. Sent and received.

  FIG. 7 is a diagram illustrating the configuration of the head controller. The head controller HC includes a head side communication module 300 and a 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 VD-Y, VD-M, VD-C, and VD-K are respectively input to the corresponding color head control blocks. 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 head side communication module 300 receives the video data multiplexed and transmitted from the main controller MC and receives the video data for each color and restores the video data for each color, and the transmission for multiplexing the request signal and transmitting it to the main controller MC. And block 310. First, the transmission block 310 will be described, and the reception block 320 will be described after the description of the main controller MC.

  FIG. 8 is a diagram illustrating the contents of data output from the serializer. As shown in FIG. 8, in this embodiment, 32-bit data composed of 4 sections each having 8 bits is output from the serializer 311. Each bit of each section is assigned one of Y, M, C, and K vertical request signals VREQ and horizontal request signals HREQ. There are eight types of request signals sent to the serializer 311 for each color, ie, a vertical request signal VREQ and a horizontal request signal HREQ for four colors. 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.

  FIG. 9 is a timing chart showing an example of a request signal. FIG. 10 is a diagram showing a result of encoding the pattern of FIG. The operation of the serializer 311 will be described with reference to these drawings. Note that the patterns shown in FIG. 9 and FIG. 10 are virtual ones created for convenience of explanation, and do not necessarily match the patterns that can actually occur in the operation of the apparatus. When the request signal is encoded, the H level is represented by a value 0 and the L level is represented by a value 1.

  The serializer 311 samples and encodes the request signal at a sampling period corresponding to 1/4 of the transfer period for one word, that is, the transfer period per section. When the time t = 0 is set as the start point, since all the eight types of request signals are at the H level in the first sampling period, this state can be expressed by “00000000d”, that is, “00h”. Here, symbols d and h represent binary notation and hexadecimal notation, respectively. This value becomes the value of the first section (bits 31 to 24) of the first word. Similarly, the second sampling period can be expressed as “00h”, which is the value of the second section (bits 23 to 16).

  Since only the vertical request signal VREQ-Y corresponding to yellow is at the L level in the third sampling period, this state can be represented by “10000000d”, that is, “80h”. Therefore, the value of the third section (bits 15 to 8) is “80h”. In the fourth sampling period, all the signals are again at the L level, and therefore can be represented by “00h”. From the above, the sampling result of the first to fourth sampling periods can be expressed as “00000000h” in one word (32 bits long). In this way, each request signal in this period can be multiplexed and encoded. The encoded request signal is output from the serializer 311.

  Data output from the serializer 311 is input to the 8B10B encoder 312. As described above, the data output from the serializer 311 has four sections as one word, and each section is composed of 8 bits. Then, the 8B10B encoder 312 performs 8B10B conversion on each section. That is, 8-bit data in one section is converted into 10-bit data by the 8B10B encoder. Thus, the length of one word after the 8B10B conversion is 40 bits (= 10 bits × 4 sections). This 8B10B conversion is mainly intended to improve the DC balance of data, and specifically, for example, the technique described in US Pat. No. 4,486,739 can be used.

  The 40-bit data is input to the serializer 314 via the buffer 313 and output as serial data. At this time, the serializer 314 superimposes the transmission clock supplied from the PLL 333 on the data, that is, modulates the transmission clock with the transmission data, and outputs the modulated signal from the TX + and TX− terminals as a differential serial signal. The clock supplied from the PLL 333 is a clock having the same period synchronized with a recovery clock RCCLK described later. In other words, the serializer 311, the encoder 312, and the buffer 313 of the transmission block 310 are supplied with a clock obtained by dividing the recovery clock RCCLK by an appropriate division ratio, and the serializer 314 receives the divided recovery clock RCCLK. A clock that has been multiplied by the PLL 333 and returned to the cycle before frequency division (that is, a clock having the same cycle as the recovery clock RCCLK) is supplied.

  FIG. 11 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 (image signal) 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. . That is, the image processing unit 100 generates four-color video data VD-Y, VD-M, VD-C, and VD-K. As described above, in this embodiment, the image processing unit 100 functions as a “signal processing unit” of the present invention.

  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 and serially transmits them to the head controller HC. A reception block 220 that receives the vertical and horizontal request signals VREQ and HREQ of each color that are multiplexed and sent from the head controller HC, restores the original signals, and outputs them.

  First, 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 a differential signal in which a clock 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. Note that the clock embedded in the signal is demodulated by the clock demodulator 233, and data is received based on the demodulated clock.

  The received 40-bit serial data is input to the 10B8B decoder 223 via the deserializer 222. The 10B8B decoder 223 converts the data into 32-bit data. This 32-bit data is given to the distributor 225.

  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. That is, the request signal multiplexing described with reference to FIGS. 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.

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

  FIG. 12 is a diagram showing the contents of video data output from the FIFO buffer. 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). That is, in this embodiment, video data per dot is stored in each section. In each section, null data or predetermined dummy data is inserted into a section corresponding to a toner color for which a request signal is not output from the head controller HC. Thus, in this embodiment, video data of each color is multiplexed. Such multiplexing will be described in detail below.

  FIG. 13 is an explanatory diagram of how video data is multiplexed. The symbols Ye, Me, Ce, and Ke in the figure represent video data of yellow Y, magenta M, cyan C, and black K, respectively, and the suffix e immediately after the uppercase alphabets Y, M, C, and K representing colors is It represents that the corresponding data is 8 bits. As shown in “Before Multiplexing” in the drawing, before multiplexing, video data is represented in a state in which an 8-bit bit string indicating information for one dot is continuous for each color. Note that the contents of each bit string in FIG. 13 correspond to the contents stored in each section in FIG. On the other hand, in this embodiment, in order to multiplex the video data of each color, the video data of each color corresponding to the same timing is arranged in series with respect to the time series in a predetermined color order. That is, as shown in “after multiplexing” in FIG. 13, for example, video data Ke (n−1), Ce (n−1), Me (n−1) of each color corresponding to the time TM (n−1). ), Ye (n-1) are arranged in this order to form one word Wt (n-1), and video data Ke (n), Ce (n) for each color corresponding to time TM (n) ), Me (n), Ye (n) are arranged in this order to form one word Wt (n), and a plurality of words thus constructed are serially arranged in time series. Deploy.

  That is, each word of this embodiment corresponds to four colors of black K, cyan C, magenta M, and yellow Y, and four sections are black K, cyan C, magenta M, yellow Y from the right in FIG. It is arranged in the order of. Then, as shown in “after multiplexing” in the figure, video data for one line of each of the four colors is stored in a section corresponding to each color across a plurality of words.

  The 32-bit data output from the FIFO buffer 211 is input to the 8B10B encoder 213 via the serializer 212 and converted into 40-bit data. The operation of the 8B10B encoder 213 is the same as that of the 8B10B encoder 312 described above. The 40-bit data is input to the special code insertion circuit 214. Next, the operation of the special code insertion circuit 214 will be described.

  FIG. 14 is a diagram illustrating an operation of inserting a special code in the main controller. As described above, special code insertion circuit 214 receives data having a length of one word of 40 bits. One word is composed of four sections (blocks), and each section can store a bit string having a length of 10 bits. In other words, as described above, each word of the present embodiment corresponds to four colors of black K, cyan C, magenta M, and yellow Y, and four sections are black K, cyan C, magenta M from the right side of FIG. , Yellow Y. Then, as shown in STEP 1 in the figure, video data for one line of each of the four colors is stored in a section corresponding to each color across a plurality of words. Here, symbols Yt, Mt, Ct, and Kt in the figure represent video data of yellow Y, magenta M, cyan C, and black K, respectively, and suffixes immediately after uppercase alphabets Y, M, C, and K representing colors. t represents that the corresponding data is 10 bits. Further, STEP 1 in the figure shows the (n−1) th and nth words Wt (n−1) and Wt (n) of the data input to the special code insertion circuit 214. Then, the special code insertion circuit 214 performs the operations shown in STEP 2 and STEP 3 in FIG.

  In STEP2, a dummy word Wt (dmy) is inserted in the middle of a plurality of words Wt that are continuously arranged. Specifically, in this embodiment, a dummy word Wt (dmy) is inserted between the (n−1) th word Wt (n−1) and the nth word Wt (n). Note that dummy data Yt (dmy), Mt (dmy), Ct (dmy), and Kt (dmy) of the corresponding color are stored in each of the four sections of the dummy word Wt (dmy). Moreover, arbitrary data can be adopted as specific values of the dummy data Yt (dmy), Mt (dmy), Ct (dmy), and Kt (dmy). In the present embodiment, Video data Yt (n-1), Mt (n-1), Ct (n-1), Kt stored in each section of the adjacent word Wt (n-1) before the dummy word Wt (dmy) The same value as (n-1) is adopted. Then, in STEP3, among the four sections of the dummy word Wt (dmy), the 10-bit data Yt (dmy) in the yellow Y section is replaced with a special code SC having the same size of 10 bits. Generate transmission data. The special code SC is a code called a so-called K character or K code, and the content thereof will be described below.

  As described above, in this embodiment, 8B10B conversion is performed to convert 8-bit data into 10-bit data. The special code SC is defined as 10-bit data other than 256 10-bit data corresponding to 8-bit data in the 8B10B conversion. That is, the special code SC is 10-bit data that cannot be generated when 8-bit data is converted according to the conversion rule of 8B10B conversion. Such special code SC is used to establish synchronization of 10-bit data. That is, although the data has a structure in which 10 bits are one section, each section is actually continuous without being interrupted. In addition, each of these sections only has a 0 or 1 signal encoded. Therefore, if there is no mark of any kind, it cannot be determined from where to where 10 bits correspond to one section. Therefore, the special code SC is appropriately inserted into the data, and the special code SC is detected to determine one section. The frequency of inserting the special code SC may be, for example, every 100 words or every 200 words. Nor does it need to be regular. In short, it is sufficient to insert it as often as necessary to establish synchronization.

  The data inserted with the special code SC in this way is input to the serializer 216 via the buffer 215. In addition, a transmission clock TMCLK generated by multiplying the clock generated by the clock generation unit 231 by the PLL 232 is input to the serializer 216. The serializer 216 superimposes the transmission clock TMCLK supplied from the PLL 232 on the input transmission data, that is, modulates the transmission clock TMCLK with the transmission data, and converts the modulated signal from the TX + and TX− terminals as a differential serial signal. Output. 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 on which the transmission clock TMCLK is superimposed. That is, in this embodiment, video data for four colors is transmitted through a pair of differential signal lines.

  FIG. 15 is a diagram schematically showing video data on a signal line. In this embodiment, the frequency of the transmission clock TMCLK is 37.5 MHz, and therefore the transmission period of one word data is about 26.7 nsec. Since the data length is 40 bits, the data transfer rate is 1.5 Gbps (bits per second). Note that the transmission clock TMCLK is superimposed on the data, and the illustrated clock signal is not transmitted separately. Thus, in this embodiment, the transmission block 210 functions as a “transmission unit” in the present invention.

  Next, the operation of the reception block of the head controller will be described using FIG. 7 again. As described above, the signal transmitted from the main communication module 200 is a differential signal on which the transmission clock TMCLK is superimposed. 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 321. The transmission clock TMCLK superimposed on the signal is demodulated as a recovery clock RCCLK by the reception clock demodulator 331, and data is received based on the demodulated recovery clock RCCLK.

  The transmission data transmitted from the main controller MC is received by the reception buffer 321 and then input to the special code detection circuit 323 via the deserializer 322. The special code detection circuit 323 detects the special code SC inserted in the input transmission data and takes the above-described synchronization based on the detection result. That is, the operation of the special code detection circuit 323 synchronizes between the main controller MC that transmits and receives transmission data and the head controller HC. Then, the transmission data is output from the special code detection circuit 323 to the special code extraction circuit 324.

  FIG. 16 is a diagram illustrating the operation of the special code extracting circuit. The special code extraction circuit 324 receives transmission data having a data structure in which a plurality of words composed of four sections capable of storing a bit string having a length of 10 bits are arranged (STEP 1 in the figure). Then, the special code extraction circuit 324 removes the dummy word Wt (dmy), which is a word in which the special code SC exists, and reconstructs video data from the transmission data (STEP 2).

  The reconstructed video data is input to the 10B8B decoder, decoded into 32-bit data, and then input to the distributor 326. The distributor 326 divides the video data into sections, restores 8-bit video data for each color, and outputs the video data to the head control module 400. That is, the head side communication module 300 demultiplexes the four-color video data multiplexed and sent from the main controller MC, and develops the video data for each color.

  As described above, serial data is transmitted and received between the main controller MC and the head controller HC. Here, a signal transmission method used for transmission / reception of such serial data will be described.

  FIG. 17 shows 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 TX + terminal and a TX− terminal for transmission provided in the main communication module 200, and an RX + terminal and an RX− terminal for reception provided in the head communication module 300. 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. That is, the main side communication module 200 and the head side communication module 300 are point-to-point connected. 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. In addition, the wiring from the TX + terminal to the RX + terminal and the wiring from the TX− terminal to the RX− terminal have the same length including the communication cable 700 and the wiring pattern on the board, and stable communication is possible even at high speed. It can be done.

  FIG. 18 is a diagram showing the configuration of the head control block. Here, the Y head control block 410Y for yellow will be described, but the other blocks 410M, 410C, and 410K have the same structure. The Y head control block 410Y drives and controls the driver IC of the line head 29 based on the video data VD transmitted from the head side communication module 300, and lights the LED array 293 at an appropriate timing.

  The Y head control block 410Y includes a request signal generation unit 411. The request signal generation unit 411 generates request signals VREQ-Y and HREQ-Y at appropriate timing based on the synchronization signal Vsync supplied from the engine controller EC. That is, the request signal generation unit 411 starts counting the internal timer 412 when receiving the synchronization signal Vsync, and outputs a vertical request signal VREQ-Y indicating the head of the page when a predetermined waiting time has elapsed. The internal timer 412 receives a recovery clock RCCLK from the head side communication module, and executes a count using the recovery clock RCCLK. That is, in this embodiment, the request signals VREQ-Y and HREQ-Y are generated based on the recovery clock RCCLK. As a result, the request signals VREQ-Y and HREQ-Y are synchronized with the recovery clock RCCLK. Is output. The synchronization signal Vsync from the engine controller EC is simultaneously applied to the head control blocks for each color, but the waiting time is set individually for each toner color. By setting the standby time according to the difference in the primary transfer position, the difference in data transfer timing for each color shown in FIG. 6 can be created.

  In the above embodiment, toner images of different colors are formed on the four image forming stations 2Y, 2M, 2C, and 2K to obtain four color toner images, and these four color toner images are superimposed. A color image is formed. Further, the main controller MC that performs signal processing on the image data (image signal) included in the image formation command to generate four-color video data corresponding to the four-color toner image, and receives the video data from the main controller MC. The transmission / reception of transmission data with the head controller HC that controls the lighting of the line heads 29 of the four image forming stations 2Y, 2M, 2C, and 2K is executed by serial communication.

  Then, in order to synchronize the serial communication between the main controller MC and the head controller HC, the special code SC is used as follows. That is, the main controller MC stores video data for one line of each of the four colors in sections (blocks) corresponding to the respective colors across a plurality of words Wt, and color dummy corresponding to each of the four sections. A dummy word Wt (dmy) in which data is stored is inserted in the middle of a plurality of words Wt, and the dummy data stored in at least one section of the dummy word Wt (dmy) is replaced with a special code SC. Generate transmission data. Then, the head controller HC controls the lighting of the line head 29 corresponding to the video data of each color based on the video data of each color reconstructed by removing the word in which the special code SC exists from the received transmission data. .

  That is, in the above embodiment, the main controller MC inserts the special code SC in the middle of the video data to generate transmission data, and the head controller HC removes the special code SC to reconstruct the video data. The line head 29 is controlled based on the reconstructed video data. Therefore, it is possible to suppress the occurrence of problems due to the presence of the special code SC in the middle of video data received by the head controller HC, and to form a good image.

  In the above embodiment, the dummy word Wt (dmy) is used as the value of the dummy data Yt (dmy), Mt (dmy), Ct (dmy), and Kt (dmy) stored in each section of the dummy word Wt (dmy). ) Before the video data Yt (n-1), Mt (n-1), Ct (n-1), Kt (n-1) stored in each section of the adjacent word Wt (n-1). The same value is adopted. Therefore, a malfunction occurs in the operation of replacing the dummy data with the special code SC in the main controller MC, and the data stored in the section of the word Wt (n−1) immediately before the dummy word Wt (dmy) is stored. Even if the special code SC is replaced, the head controller HC can correctly reconstruct the video data by removing the word Wt (n-1) in which the special code SC exists. It is. This point will be described using a specific example.

  FIG. 19 is an operation explanatory diagram when there is an error in the replacement operation with the special code. For easy understanding, as shown in FIG. 14, the dummy data Yt (dmy) of the dummy word Wt (dmy) should be replaced with the special code SC as “replacement operation” in FIG. As shown, consider a case where the video data Yt (n-1) of the (n-1) th word Wt (n-1) is mistakenly replaced with the special code SC. As described above, the special code extraction circuit 324 extracts a word in which the special code SC exists. Therefore, if there is an error in the replacement operation as described above, the (n-1) th word Wt (n-1) is extracted by the special code extraction circuit 324 as shown in the "extraction operation" in FIG. Is issued. At this time, the video data is reconstructed with the dummy word Wt (dmy) remaining. However, in the above embodiment, the data stored in the sections of the dummy word Wt (dmy) and the (n−1) th word Wt (n−1) are equal to each other. Therefore, the video data reconstructed in the “extraction operation” in FIG. 19 is equal to the video data reconstructed in “STEP 2” in FIG. As described above, the above-described embodiment is suitable because the video data can be correctly reconstructed even if there is an error in the replacement operation with the special code SC.

  By the way, in the above embodiment, as shown in STEP 2 of FIG. 14, in the special code insertion circuit 214, dummy data Yt (dmy), Mt (dmy), Ct stored in each section of the dummy word Wt (dmy). As the values of (dmy) and Kt (dmy), video data Yt (n-1) and Mt (n) stored in each section of the adjacent word Wt (n-1) before the dummy word Wt (dmy). -1), Ct (n-1), and Kt (n-1) are the same values. Then, as shown in STEP 2 of FIG. 16, the special code extracting circuit 324 extracts the dummy word Wt (dmy). Here, a circuit that easily realizes the dummy word extraction / insertion operation will be introduced.

  FIG. 20 is a diagram showing a circuit for inserting a dummy word. FIG. 21 is a diagram illustrating the operation of the circuit of FIG. The circuit shown in the figure includes a count-up counter 2141, a selector 2142, a shift register 2143, a shift register 2144, and a shift register 2145, all of which operate in synchronization with the transmission clock TMCLK. Further, a special command pulse for giving a timing for inserting a dummy word is inputted to the input terminal of the count-up counter 2141. That is, the count-up counter increments the counter value by 1 each time a special command pulse is input. Since the horizontal request signal HREQ is input to the reset terminal of the count up counter 2141, the counter value is reset to 0 each time the horizontal request signal HREQ is input. Then, the output of the count-up counter 2141, that is, the counter value is input to the count input terminal count [1: 0] of the selector 2142.

  Therefore, the selector 2142 outputs a signal input to the input terminal in0 from the output terminal out when the counter value is 0, and outputs a signal input to the input terminal in1 when the counter value is 1. When the counter value is 2, the signal input to the input terminal in2 is output from the output terminal out. When the counter value is 3, the signal input to the input terminal in3 is output from the output terminal out. To do.

  Video data is input to the input terminal in 0 of the selector 2142. Video data shifted by one clock of the transmission clock TMCLK by the shift register 2143 is input to the input terminal in 1 of the selector 2142. Video data shifted by two clocks of the transmission clock TMCLK by the shift register 2143 and the shift register 2144 is input to the input terminal in2 of the selector 2142. Video data shifted by three clocks of the transmission clock TMCLK by the shift register 2143, the shift register 2144, and the shift register 2145 is input to the input terminal in3 of the selector 2142.

  Here, for easy understanding, as shown in FIG. 21, consider a case where 10 words of video data is input to the special code insertion circuit 214 using the horizontal request signal HREQ as a trigger. While the counter value is 0, video data input to the input terminal in0 is output from the selector 2142. That is, words Wt (1) to Wt (4) are output. While the counter value is 1, the data input to the input terminal in1 is output from the selector 2142. That is, words Wt (4) to Wt (7) are output. While the counter value is 2, the selector 2142 outputs data input to the input terminal in2. That is, words Wt (7) to Wt (10) are output. As described above, the word Wt (4) and the word Wt (7) are inserted as dummy data at the timing of the special command pulse by the circuit shown in FIG. In FIG. 21, the underlined word Wt (4) and word Wt (7) correspond to dummy data. Then, the data stored in the predetermined sections (blocks) of the word Wt (4) and the word Wt (7), which are dummy data, are replaced with the special code SC and output from the special code insertion circuit 214 as transmission data. The

  FIG. 22 is a diagram showing a circuit for extracting a dummy word. FIG. 23 is a diagram illustrating the operation of the circuit of FIG. The circuit shown in the figure includes a countdown counter 3241, a selector 3242, a shift register 3243, a shift register 3244, and a shift register 3245, all of which operate in synchronization with the recovery clock RCCLK. Also, a special command pulse that gives the timing at which a dummy word is inserted is input to the input terminal of the countdown counter 3241. That is, the countdown counter decrements the counter value by 1 each time a special command pulse is input. Since the horizontal request signal HREQ is input to the reset terminal of the countdown counter 3241, the counter value is reset to take the value 3 each time the horizontal request signal HREQ is input. The output of the countdown counter 3241, that is, the counter value is input to the count input terminal count [1: 0] of the selector 3242.

  Accordingly, the selector 3242 outputs a signal input to the input terminal in0 from the output terminal out when the counter value is 0, and outputs a signal input to the input terminal in1 when the counter value is 1. When the counter value is 2, the signal input to the input terminal in2 is output from the output terminal out. When the counter value is 3, the signal input to the input terminal in3 is output from the output terminal out. To do.

  Transmission data is input to the input terminal in0 of the selector 3242. Transmission data shifted by one clock of the recovery clock RCCLK by the shift register 3243 is input to the input terminal in 1 of the selector 3242. Transmission data shifted by two clocks of the recovery clock RCCLK by the shift register 3243 and the shift register 3244 is input to the input terminal in2 of the selector 3242. Transmission data shifted by three clocks of the recovery clock RCCLK by the shift register 3243, the shift register 3244, and the shift register 3245 is input to the input terminal in3 of the selector 3242.

  Transmission data is input from the main controller using the horizontal request signal HREQ as a trigger. While the counter value is 3, the data input to the input terminal in3 is output from the selector 3242. That is, words Wt (1) to Wt (4) are output. While the counter value is 2, the selector 3242 outputs data input to the input terminal in2. That is, words Wt (5) to Wt (7) are output. While the counter value is 1, the data input to the input terminal in1 is output from the selector 3242. That is, words Wt (8) to Wt (10) are output. As described above, the circuit shown in FIG. 22 extracts the word Wt (4) and the word Wt (7) as dummy data at the timing of the special command pulse. In FIG. 23, the underlined word Wt (4) and word Wt (7) correspond to dummy data.

  As described above, both the dummy word insertion circuit of FIG. 20 and the dummy word extraction circuit of FIG. 22 are preferably configured inexpensively and simply without having a memory.

  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 values of the dummy data Yt (dmy), Mt (dmy), Ct (dmy), and Kt (dmy) stored in each section of the dummy word Wt (dmy) in the special code insertion circuit 214. Video data Yt (n-1), Mt (n-1), Ct (n-1) stored in each section of the adjacent word Wt (n-1) before the dummy word Wt (dmy) , Kt (n-1) is adopted. However, the data that can be stored in each section of the dummy word Wt (dmy) is not limited to this, and may be configured as follows.

This will be described with reference to FIG. That is, dummy data is generated by averaging the video data stored in two words Wt (n) and Wt (n-1) adjacent to the dummy word Wt (dmy) for each color. Data may be stored in each section (block) of the dummy word. Specifically, at this time, the dummy data of each color is
Yt (dmy) = (Yt (n) + Yt (n-1)) / 2
Mt (dmy) = (Mt (n) + Mt (n-1)) / 2
Ct (dmy) = (Ct (n) + Ct (n-1)) / 2
Kt (dmy) = (Kt (n) + Kt (n-1)) / 2
It becomes. In such a configuration, malfunction occurs in the operation of replacing the dummy data with the special code SC in the main controller MC, and any of the words Wt (n) and Wt (n-1) before and after the dummy word Wt (dmy) Even when the data stored in the section (block) is replaced with the special code SC, the head controller HC removes the word in which the special code SC exists, so that the original video data is restored. It is possible and preferable to construct approximate data.

  In the above embodiment, among the four sections of the dummy word Wt (dmy), the 10-bit data Yt (dmy) in the yellow Y section is replaced with the special code SC having the same size of 10 bits. ing. However, of the four sections of the dummy word, the section to be replaced with the special code SC is not limited to the yellow Y section, and may be a cyan C section. Further, the number of sections to be replaced with the special code SC is not limited to one, and replacement may be performed for all two or four sections.

  Moreover, in the said embodiment, the insertion / extraction operation | movement of a special code is performed as follows. That is, the main controller MC inserts a dummy word Wt (dmy) in which dummy data of a color corresponding to each of the four sections is stored in the middle of the plurality of words Wt, and the dummy word Wt (dmy) The dummy data stored in at least one section is replaced with the special code SC to generate transmission data. Then, the head controller HC controls the lighting of the line head 29 corresponding to the video data of each color based on the video data of each color reconstructed by removing the word in which the special code SC exists from the received transmission data. . However, the operation of inserting / extracting special codes is not limited to this, and may be configured as follows.

  FIG. 24 is a diagram illustrating another example of the special code insertion operation in the main controller. As shown in STEP 1 in the figure, video data stored across a plurality of sections (blocks) arranged side by side is input to the special code insertion circuit. In the special code insertion operation shown in the figure, a dummy section (dummy block) storing dummy data Yt (dmy) is inserted in the middle of the plurality of sections (STEP 2 in the figure). Then, the dummy data Yt (dmy) is replaced with a special code SC to generate transmission data (STEP 3 in the figure). The transmission data generated in this way is transmitted toward the head controller HC.

  FIG. 25 is a diagram illustrating another example of the operation for extracting the special code in the head controller. The special code extraction circuit 324 receives transmission data having a data structure in which a plurality of sections (blocks) capable of storing a 10-bit bit string are arranged (STEP 1 in the figure). Then, the special code extraction circuit 324 removes the dummy section (dummy block) in which the special code SC exists, and reconstructs video data from the transmission data (STEP 2).

  The reconstructed video data is input to the 10B8B decoder, decoded into 32-bit data, and then input to the distributor 326. The distributor 326 divides the video data into sections, restores 8-bit video data for each color, and outputs the video data to the head control module 400. That is, the head side communication module 300 demultiplexes the four-color video data multiplexed and sent from the main controller MC, and develops the video data for each color.

  As described above, also in the embodiment described with reference to FIGS. 24 and 25, the main controller MC inserts the special code SC in the middle of the video data to generate transmission data, and the head controller HC removes the special code SC. To reconstruct the video data. The line head 29 is controlled based on the reconstructed video data. Therefore, it is possible to suppress the occurrence of problems due to the presence of the special code SC in the middle of video data received by the head controller HC, and to form a good image.

  In the present embodiment, the request signals VREQ and HREQ are generated from the recovery clock RCCLK. For example, the request signals VREQ and HREQ are generated on the basis of the request signal generation clock separately. May be. However, in the above embodiment, the transmission clock TMCLK superimposed on the signal output from the main controller MC is restored as the recovery clock RCCLK, and the reception operation of the video data VD and the generation operation of the horizontal request signal HREQ in the head controller HC are performed. By performing both based on the recovery clock RCCLK, it is not necessary to provide a separate clock oscillation source when executing these two operations, and the apparatus configuration is simplified and the cost is reduced.

  Further, in the present invention, when transmitting / receiving a signal between the main controller MC and the head controller HC, a clock communication line is not provided separately from the video data, but a transmission clock TMCLK is superimposed on the video data and transmitted. High-speed communication can be performed stably. Therefore, it is possible to stably form an image, and it is possible to flexibly meet demands for higher speed and higher definition and more colors that lead to an increase in data amount. In addition, the number of communication lines can be reduced by not providing the clock communication line.

  In the above embodiment, the recovery clock RCCLK is supplied to the serializer 314 via the frequency divider 332 and the PLL 333. However, the manner of supplying the recovery clock RCCLK to the serializer 314 is not limited to this, and the recovery clock RCCLK may be directly supplied to the serializer 314.

  Further, in the image processing unit 100 provided in the main controller MC of the above embodiment, image data before image processing is stored in the image memory, and when requested by the head controller HC, each image processing block Is output as video data after performing necessary processing. However, the present invention is not limited to this. For example, when image data is received from an external device, image processing is performed and the processed image data is stored in the image memory. These may be read out sequentially and sent out.

  Furthermore, in the above embodiment, the present invention is applied to a color image forming apparatus using YMCK four-color toner, but the application target of the present invention is not limited to this, and the types of colors and the number of colors The present invention can also be applied to different image forming apparatuses.

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 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 head controller. The figure which shows the content of the data output from a serializer. The timing chart which shows the example of a request signal. The figure which shows the result of having encoded the pattern of FIG. The figure which shows the structure of a main controller. The figure which shows the content of the video data output from a FIFO buffer. Explanatory drawing of the mode of multiplexing of video data. The figure which shows the insertion operation | movement of the special code in a main controller. The figure which shows typically the video data on a signal wire | line. The figure which shows operation | movement of a special code extraction circuit. The figure which shows the connection of a main controller and a head controller. The figure which shows the structure of a head control block. Operation | movement explanatory drawing when there is an error in substitution operation to a special code. The figure which shows the circuit which inserts a dummy word. The figure which shows operation | movement of the circuit of FIG. The figure which shows the circuit which extracts a dummy word. The figure which shows operation | movement of the circuit of FIG. The figure which shows another example of the insertion operation | movement of the special code in a main controller. The figure which shows another example of extraction operation | movement of the special code | symbol in a head controller.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Image processing part (signal processing part), 21 ... Photosensitive drum (photosensitive body), 210 ... Transmission block (transmitting part), 214 ... Special code insertion circuit, 25 ... Developing part (developing device), 29 ... Line head 2Y, 2M, 2C, 2K ... image forming station, 323 ... special code detection circuit, 324 ... special code extraction circuit, EC ... engine controller, HC ... head controller, MC ... main controller, VD ... video data, SC ... Special code

Claims (6)

An image forming station comprising: a photoconductor; a line head that forms an electrostatic latent image on the surface of the photoconductor; and a developing unit that develops the electrostatic latent image formed on the surface of the photoconductor to form a toner image. J (where J is an integer equal to or greater than 2), each of the J image forming stations forms a different color toner image to obtain a J color toner image, and the J color toner images are superimposed. In an image forming apparatus that forms a color image together,
A signal processing unit that performs signal processing on an image signal included in an image formation command to generate J-color video data corresponding to the J-color toner image, and a block that stores a bit string of a predetermined length correspond to the J-color A main controller having a transmission unit that serially outputs transmission data having a data structure in which a plurality of words are arranged in a predetermined order.
A head controller that receives the transmission data and controls lighting of the line head;
The main controller stores video data for one line of each of the J colors in a block corresponding to each color across a plurality of words, and dummy data of a color corresponding to each of the J blocks is stored. Inserting a dummy word in the middle of the plurality of words, and replacing the dummy data stored in at least one block of the dummy word with a special code to generate the transmission data,
The head controller controls lighting of the line head corresponding to the video data of each color based on the video data of each color which is reconstructed by removing the word having the special code from the received transmission data. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the dummy data stored in each block of the dummy word is the same as the video data stored in each block of the word adjacent to the dummy word.   The video data stored in two words adjacent to the dummy word before and after the dummy word is averaged for each color to generate the dummy data, and the dummy data is stored in each block of the dummy word. Image forming apparatus. In an image forming apparatus for forming an electrostatic latent image on the surface of a photoreceptor by a line head in which a plurality of light emitting elements are arranged in a row,
A signal processing unit that performs signal processing on an image signal included in the image formation command to generate video data; and a transmission unit that serially outputs transmission data having a data structure in which blocks storing a predetermined-length bit string are arranged. The main controller,
A head controller that receives the transmission data and controls lighting of the line head;
The main controller stores the video data across a plurality of blocks and inserts a dummy block in which dummy data is stored in the middle of the plurality of blocks, and the dummy controller stores the dummy data stored in the dummy block as a special code. To generate the transmission data,
The image forming apparatus according to claim 1, wherein the head controller controls lighting of the line head based on video data reconstructed by removing the dummy block from the received transmission data. An image forming station comprising: a photoconductor; a line head that forms an electrostatic latent image on the surface of the photoconductor; and a developing unit that develops the electrostatic latent image formed on the surface of the photoconductor to form a toner image. Using the image forming apparatus provided with J (where J is an integer of 2 or more), each of the J image forming stations forms a different color toner image to obtain a J color toner image, and An image forming method for forming a color image by superimposing J toner images,
The image forming apparatus performs signal processing on an image signal included in an image formation command to generate J color video data corresponding to the J color toner image, and a block for storing a bit string of a predetermined length A main controller having a transmission unit that serially outputs transmission data having a data structure in which a plurality of words are arranged in a predetermined order corresponding to the J colors, and receiving the transmission data, A head controller for controlling lighting of the line head;
The main controller stores video data for one line of each of the J colors in a block corresponding to each color across a plurality of words, and dummy data of a color corresponding to each of the J blocks is stored. Inserting a dummy word in the middle of the plurality of words, and replacing the dummy data stored in at least one block of the dummy word with a special code to generate the transmission data,
The head controller controls lighting of the line head corresponding to the video data of each color based on the video data of each color which is reconstructed by removing the word having the special code from the received transmission data. An image forming method. A data structure in which a line head in which a plurality of light emitting elements are arranged in a row and a video data are generated by performing signal processing on an image signal included in an image formation command and a block for storing a bit string of a predetermined length is arranged. An electrostatic latent image is formed on the surface of the photosensitive member by using an image forming apparatus including a main controller that serially outputs transmission data and a head controller that receives the transmission data and controls lighting of the line head. An image forming method for forming,
In the main controller, the video data is stored across a plurality of blocks and a dummy block in which dummy data is stored is inserted in the middle of the plurality of blocks, and the dummy data stored in the dummy block is To generate the transmission data,
In the head controller, lighting of the line head is controlled based on video data reconstructed by removing the dummy block from the received transmission data.

Images