JP4485719B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a printer, a copying machine, and a FAX apparatus, and more particularly to an image forming apparatus that can be extended to a copying machine and a FAX apparatus based on a printer.
[0002]
[Prior art]
In recent years, an image forming unit (printer unit or plotter unit), an image reading unit (scanner unit), a FAX communication unit, an image processing unit (controller), etc. are combined to form a copying function, a printer function, a scanner function, a facsimile function, etc. Multifunctional image forming apparatuses such as digital multifunction peripherals that can be freely selected and used are used by many users.
Such a conventional multi-function image forming apparatus is generally configured on a copying machine base, and can be operated as a printer or a scanner by using a part of all the functions, or by adding a FAX communication unit. It could be used as a facsimile machine. For this reason, a dedicated controller capable of comprehensively controlling these functions is provided.
[0003]
[Problems to be solved by the invention]
In such a conventional multi-function image forming apparatus, control of paper feed timing, delay control of exposure scanning timing due to a difference in resolution by each function, and accurate overlay of images of each color in the case of an apparatus having a color copying function. Therefore, it is possible to optimally perform control of delaying the image data of each color in order to form each color, and to use each function in a preferable state.
[0004]
However, such a conventional multifunctional image forming apparatus is large in size and expensive. In addition, there are problems such as lack of versatility, such as the use of controllers from other companies, and inability to easily cope with various extended applications.
The present invention has been made to solve such a problem. By connecting various application boards based on a printer, various functions such as a copy function and a facsimile function can be realized at low cost. An object of the present invention is to provide a high-quality image device that is excellent in versatility and expandability and that does not cause color misregistration.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, an image forming apparatus according to the present invention has a photosensitive member, an exposure unit that scans the photosensitive member to form an electrostatic latent image on the photosensitive member, and a scanning timing by the unit. Synchronous detection means to detectAn image forming apparatus main body comprising:
  The image data of the image to be formedIn the exposure meansAn application board having image data transfer means for transferring;An image forming apparatus comprising:
  In the image forming apparatus main body,Transfer trigger signal generating means for generating a main scanning line trigger signal and a sub-scanning effective area trigger signal, which are signals for designating the transmission timing of the image data from the application board based on the detection signal from the synchronization detecting means; WithThe exposure means includes an LD unit and an LD unit control circuit that controls turning on / off of the LD unit, and an optical unit that deflects a laser beam emitted from the LD unit and scans the photoconductor.ing.
[0006]
  The application board generates a main scanning synchronization signal from the main scanning line trigger signal, and a sub scanning effective area signal generates a sub scanning effective area signal from the sub scanning effective area trigger signal. Generating means,
  The image data transfer means transmits the image data of the image to be formed in synchronization with the main scanning synchronization signal and the sub-scanning effective area signal through the transfer trigger signal generation means of the image forming apparatus main body and the LD unit control circuit. Is a means of forwarding to
  The sub-scanning effective area signal generation means activates the sub-scanning effective area signal at a predetermined timing after the sub-scanning effective area trigger signal is input to the application board, and ends the transfer of the image data Means for deactivating the sub-scanning effective area signalIs.
[0007]
  In addition, the aboveWhen the preparation for transferring the image data of the image to be formed is not completed before the sub-scanning effective area signal becomes active, the image data transfer means performs the formation after the sub-scanning effective area signal becomes active. Means for transferring white image data that does not form an image during the period until image data transfer preparation for the image to be completed is completed.Have.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
First, a color copying machine according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic sectional view showing the configuration of the image forming means of the color copying machine, FIG. 2 is a schematic plan view showing the configuration of the optical unit viewed from above, and FIG. 3 is a control of the color copying machine. FIG. 4 to FIG. 6 are timing charts showing the control timing of the color copying machine.
This color copying machine is a color image forming apparatus provided with an image forming means called a tandem type in which four image forming units are arranged along a conveying belt 2 as shown in FIG.
[0009]
In this color copying machine, a yellow image forming unit 20Y, a magenta image forming unit 20M, and a cyan image forming unit 20C that form images of different colors (yellow: Y, magenta: M, cyan: C, black: K), The black image forming unit 20K is arranged in a line along the conveying belt 2 that conveys the transfer paper 1 at a predetermined interval.
The conveyor belt 2 is stretched between a pair of conveyor rollers 3 and 4, one of which is a driving roller and the other is a driven roller, and is rotated in the direction of arrow A by the rotation of the driving roller. A paper feed tray 5 in which the transfer paper 1 is stored is provided below the conveyor belt 2.
[0010]
The yellow image forming unit 20Y includes a photosensitive drum 6Y that is a photosensitive member, a charger 7Y disposed around the photosensitive drum 6Y, an exposure unit 8 that is an exposure unit common to the image forming units, and a developing unit. 9Y and a photoreceptor cleaner 10Y. Further, a transfer device 12Y is provided at a position facing the photosensitive drum 6Y with the conveyance belt 2 interposed therebetween.
The magenta image forming unit 20M, the cyan image forming unit 20C, and the black image forming unit 20K are also configured in the same manner as the yellow image forming unit 20Y. Each photoconductor drum, charger, developer, photoconductor cleaner, The transfer unit is given the same reference numerals with M, C, and K added to Y in place of the same reference numerals as those assigned to the respective parts of the yellow image forming unit 20Y.
[0011]
In this color copying machine, the transfer sheet at the uppermost position among the transfer sheets stored in the sheet feeding tray 5 is fed by a sheet feeding mechanism such as a sheet feeding roller (not shown) during image formation, When detected by the sensor 14, it is temporarily stopped, timed with each image forming unit, and sucked onto the transport belt 2 by electrostatic suction. The adsorbed transfer paper 1 is conveyed to the yellow image forming unit 20Y, where yellow image formation is performed.
That is, the surface of the photosensitive drum 6Y is uniformly charged by the charger 7Y, and then scanned and exposed by the exposure device 8 with the laser beam 11Y corresponding to the yellow image, and the surface of the photosensitive drum 6Y is electrostatically charged. A latent image is formed. The electrostatic latent image is developed with yellow toner by the developing unit 9Y, and a yellow toner image is formed on the photosensitive drum 6Y. This toner image is transferred to the transfer paper 1 by the transfer device 12Y at the transfer position where the photosensitive drum 6Y contacts the transfer paper 1 on the conveyor belt 2 to form a monochrome yellow image.
[0012]
After the transfer, the photoreceptor drum 6Y is cleaned with unnecessary toner remaining on the surface thereof by the photoreceptor cleaner 10Y to prepare for the next image formation.
In this way, the transfer sheet 1 on which the yellow image is transferred by the yellow image forming unit 20Y is conveyed by the conveying belt 2 to the magenta image forming unit 20M.
Here, similarly to the above-described case, the surface of the charged photosensitive drum 6M is scanned and exposed with the laser beam 11M corresponding to the magenta image by the exposure device 8 to form an electrostatic latent image. The electrostatic latent image is developed with magenta toner by the developing unit 9M, and a magenta toner image is formed on the photosensitive drum 6M. The magenta toner image is transferred onto the transfer paper 1 so as to overlap the yellow image.
[0013]
The transfer sheet 1 is further transported to the cyan image forming unit 20C and the black image forming unit 20K, and similarly corresponds to a cyan image or a black image by the exposure unit 8 on the surface of the photosensitive drums 6C and 6K, respectively. The cyan toner image and the black toner image that have been scanned and exposed to the laser beams 11C and 11K and developed by the developing devices 9C and 9K are sequentially superimposed and transferred to form a color image.
Then, the transfer paper 1 that has passed through the black image forming unit 20K is peeled off from the conveyor belt 2, passes through the fixing device 13, and the transferred toner image of each color is fixed, and then discharged.
[0014]
The exposure device 8 in this image forming means includes an optical unit having the configuration shown in FIG.
This optical unit is a laser beam emitted from four LD units: a black LD unit 31, a yellow LD unit 32, a cyan LD unit 33, and a magenta LD unit 34 each having a laser diode (LD) as a light source. Is a unit that scans the corresponding photosensitive drum. The laser beams from the black LD unit 31 and the yellow LD unit 32 pass through the cylinder lenses 41 and 42, are reflected by the reflecting mirrors 45 and 46, and are incident on different lower reflecting surfaces of the polygon mirror 50.
The polygon mirror 50 rotates in the direction indicated by the arrow B, thereby rotating and deflecting each incident laser beam. The laser beams 11K and 11Y reflected by the polygon mirror 50 pass through the fθ lenses 51 and 52, respectively, and are turned back by the first mirrors 53 and 54, so that the corresponding photosensitive drums 6K and 6K, as shown in FIG. Irradiate on 6Y.
[0015]
  On the other hand, the laser beams from the cyan LD unit 33 and the magenta LD unit 34 are incident on different upper reflective surfaces of the polygon mirror 50 through the cylinder lenses 43 and 44, respectively. The polygon mirror 50 rotates in the direction indicated by the arrow B, thereby rotating and deflecting each incident laser beam. The laser beams 11C and 11M reflected by the polygon mirror 50 pass through the fθ lenses 51 and 52, respectively, and are folded back by the first mirrors 55 and 56, as shown in FIG.likeThe corresponding photosensitive drums 6C and 6M are irradiated.
  By controlling on / off of each LD unit 31 to 34 in this optical unit according to the image data and timing signal of each color to be formed, a desired electrostatic latent on each photosensitive drum 6Y, 6M, 6C, 6K. An image can be formed. The image data is generated by reading an image of a document by an image reading unit (scanner) (not shown).
[0016]
Further, in this optical unit, cylinder mirrors 61 and 62 and synchronization detection sensors 63 and 64 are arranged on the upstream side from the writing position in the main scanning direction, and the laser beam passing through the fθ lenses 51 and 52 is The light is reflected and collected by the cylinder mirrors 61 and 62, and enters the synchronization detection sensors 63 and 64, respectively.
These synchronization detection sensors 63 and 64 are synchronization detection sensors for synchronizing in the main scanning direction, and are synchronization detection means for detecting the scanning timing of the exposure unit 8.
[0017]
Here, for each laser beam from the black LD unit 31 and the cyan LD unit 33, the common cylinder mirror 61 and the synchronous detection sensor 63 are used. Similarly, the common cylinder mirror 62 and the synchronous detection sensor 64 are used for the laser beams from the yellow LD unit 32 and the magenta LD unit 34.
In this configuration, two laser beams are incident on the same synchronization detection sensor. By making the incident angles of the respective laser beams to the polygon mirror 50 different, the respective laser beams are synchronized detection sensors. The synchronization detection signal is output as a pulse train in time series by changing the timing at which the light enters the signal.
[0018]
Further, as can be seen from FIG. 2, the black laser beam 11K and the cyan laser beam 11C are scanned in the arrow D direction by the rotation of the polygon mirror 50 in the arrow B direction, and the yellow laser beam 11Y and the magenta laser are scanned. The beam 11M is scanned in the direction of arrow E (reverse direction).
Note that, when two laser beams are incident on a common synchronous detection sensor, a known technique may be used as appropriate for a method of separating the output signal into the components of each beam. Omitted.
[0019]
  Next, the control circuit of this color copying machine will be described with reference to FIG.
  The control circuit shown in FIG. 3 includes a copy application 100, a reference selection circuit 106, timing generation circuits 102 to 105 for Y, C, M, and K colors, synchronization separation circuits 107 to 110, and LD unit control. Circuits 111-114 are provided.
  The copy application 100 is an application board. Color image data to be formed by the color copying machine is divided into image data for each color, and timing generation circuits 102, 103, 104, and 105 for each color.Through the LD unit control circuit 111, 112, 113, 114 for each colorForward toHas image data transfer meansIs a unit. Here, the application board is a circuit for providing various functions to the image forming apparatus provided with the image forming means or a circuit serving as an interface with an external apparatus. In this embodiment, the application board provides a color copier function. A copy application 100 is installed. The portion other than the copy application 100 is referred to as an image forming apparatus main body for convenience.
[0020]
The synchronization separation circuits 107 and 108 are circuits for separating the output signals of the synchronization detection sensor 64 shown in FIG. 2 into Y and M synchronization detection signals, respectively. The synchronization separation circuit 107 is a Y synchronization detection signal DETP_Y. Is output to the Y LD unit control circuit 111, and the synchronization separation circuit 108 outputs the M synchronization detection signal DETP_M to the M LD unit control circuit 112.
[0021]
Similarly, the synchronization separation circuits 109 and 110 are circuits that separate the output signal of the synchronization detection sensor 63 into C and K synchronization detection signals, respectively. The synchronization separation circuit 109 converts the synchronization detection signal DETP_C for C into The synchronization separation circuit 110 outputs the K synchronization detection signal DETP_K to the K LD unit control circuit 114.
The Y LD unit control circuit 111 is built in the Y LD unit 32 and is a circuit for controlling lighting / extinguishing of the LD unit 32. Similarly, the M LD unit control circuit 112 is built in the M LD unit 34, the C LD unit control circuit 113 is built in the C LD unit 33, and the K LD unit K control circuit 114 is built in the K LD unit 31, respectively. The LD unit is controlled to be turned on / off.
[0022]
Hereinafter, the operation of this control circuit will be described in more detail using the timing charts of FIGS.
At the timing when the synchronization detection sensors 63 and 64 detect the laser beams respectively emitted from the LD units 31 to 34, the synchronization detection circuit DETP_Y from the synchronization separation circuit 107, the synchronization detection signal DETP_M from the synchronization separation circuit 108, and the synchronization separation. The circuit 109 outputs a synchronization detection signal DETP_C, and the synchronization separation circuit 110 outputs a pulse of the synchronization detection signal DETP_K.
These synchronization detection signals DETP_Y, DETP_M, DETP_C, and DETP_K are asynchronous signals. This is because the same mirror surface of the polygon mirror 50 is not used on the Y, M side and the C, K side, This is because the position of the laser beam emitted from each LD unit is different.
[0023]
However, as indicated by an arrow X in FIG. 4, there is a period in which no pulse of the synchronization detection signal is output. The position and length of this period can be derived from the configuration of the optical system and the component accuracy.
On the other hand, the Y LD unit control circuit 111 outputs a synchronization signal DPSYNC_Y synchronized with the Y write clock from the synchronization detection signal DETP_Y to the reference selection circuit 106. Similarly, the M LD unit control circuit 112 outputs the synchronization signal DPSYNC_M, the C LD unit control circuit 113 outputs the synchronization signal DPSYNC_C, and the K LD unit control circuit 114 outputs the synchronization signal DPSYNC_K to the reference selection circuit 106, respectively.
The reference selection circuit 106 arbitrarily selects one of the Y, M, C, and K synchronization signals DPSYNC, and generates a pulse of the reference signal CNT_LD in an arbitrary period of the synchronization signal DPSYNC. This selection and setting of the period may be arbitrary, but are determined in advance. Then, each synchronization signal and this reference signal CNT_LD are output to the corresponding timing generation circuits 102 to 105.
[0024]
  The Y timing generation circuit 102 counts the synchronization signal DPSYNC_Y for the number of lines set in the PFGDY_Y register from the rising timing of the reference signal CNT_LD after the pulse of the start signal XSTART is input from the registration sensor 14, and after the count ends, the sub timing signal DPSYNC_Y is counted. The scan effective area trigger signal XFSYNC_Y is asserted (a pulse is output). Then, it is output to the copy application 100 together with the main scanning line trigger signal XWRSYNC_Y generated from the line synchronization signal XLDSYNC_Y that is asserted thereafter.
  Similarly, the other timing generation circuits 103, 104, and 105 generate sub-scanning effective area trigger signals XFSYNC_M, XFSYNC_C, XFSYNC_K, and main scanning line trigger signals XWRSYNC_M, XWRSYNC_C, XWRSYNC_C, XWRSYNC_C, and XLDSYNC_M, XLDSYNC_C, XLDSYNC_K. Output to the copy application 100. Therefore, each of the timing generation circuits 102 to 105 isTransfer trigger signal generation meansIt is.
[0025]
  As shown in FIG. 5, the copy application 100 receives each sub-scanning effective area signal (F gate signal) XIPUFGT_Y, at a predetermined timing after the pulses of the sub-scanning effective area trigger signals XFSYNC_Y, M, C, and K are input. M, C, and K are made active (LOW), and corresponding to each main scanning line trigger signal XWRSYNC_Y, M, C, and KEach main scanning synchronization signal XIPULSYC_Y, M, C, KIs generated. Therefore, the copy application 100 includes main scanning synchronization signal generation means and sub-scanning effective area signal generation means.
[0026]
  Further, the copy application 100 includes the sub-scanning effective area signals XIPUFGT_Y, M, C, and KMain scanning synchronization signal XIPULSYC_Y, M, C, KIn synchronization with the image data IPUDAT_Y, IPUDAT_M, IPUDAT_C, and IPUDAT_K of the images of the respective colors to be formed, the sub-scanning effective area signals XIPUFGT_Y, M, C, K andEach main scanning synchronization signal XIPULSYC_Y, M, C, KAt the same time, the data is transferred to the LD unit control circuits 111, 112, 113, 114 for each color through the timing generation circuits 102, 103, 104, 105 for each color.Has image data transfer means. Although not shown in FIG. 5, when the copy application 100 finishes transferring all image data in the sub-scanning direction for each color, the sub-scanning effective area signal XIPUFGT for that color is inactive (HIGH). Return to.
[0027]
If the copy application 100 can start transfer of image data immediately after receiving the pulse input of each sub-scanning effective area trigger signal XFSYNC_Y, M, C, K by the processing as described above, each LD unit control circuit 111, 112, 113, and 114 control the turning on / off of the laser diode (LD) in accordance with the image data signals IPUDAT_Y, M, C, and K, so that the latent images of the respective color images to be formed become the respective photosensitive drums. It will be formed on 6Y, 6M, 6C, 6K. Each LD unit control circuit 111, 112, 113, 114 controls the turning on / off of the LD only while the corresponding sub-scanning effective area signal XIPUFGT sent from the copy application 100 is active (LW). The color image can be aligned corresponding to various application boards without taking the end timing on the image forming apparatus main body side.
[0028]
However, the copy application 100 normally performs various image processing depending on the content of the image to be formed. For example, in the case of a text original, MTF correction processing (improvement of resolution) for emphasizing the amplitude of the read image with respect to the image read by the scanner, and smoothing for smoothing the amplitude of the read image on the contrary to the photo original. Processing (reducing moire) is generally performed well. These processes are performed by storing image information for a plurality of lines using a line buffer memory and performing a digital filter operation.
In order to perform such processing, the image information is actually transferred after receiving the input of the sub-scanning effective area trigger signal XFSYNC for performing color matching of Y, M, C, K without using the copy application 100. Until the transfer is completed (until the preparation for transfer is completed), the timing is delayed by the number of lines in the line buffer memory to be used.
[0029]
Next, data transfer when such a delay occurs will be described with reference to FIG. FIG. 6 shows a case where one laser diode is provided in each of the LD units of the LD unit control circuits 111 to 114 shown in FIG. 3, and a delay of one line occurs in image data transfer from the copy application 100. An example is shown.
Here, only transfer of image data for yellow (Y) will be described, but the same processing is performed for transfer of image data for other colors.
In this color copying machine, after the pulse of the sub-scanning effective area trigger signal XFSYNC_Y is input, the copy application 100 outputs the sub-scanning effective area signal (F gate signal) XIPUFGT_Y at the rise timing of the first main scanning line trigger signal XWRSYNC_Y. Activate. XIPULGT_Y indicates a main scanning effective area signal (L gate signal).
[0030]
  However, there is a delay of one line for image data transfer.AriseTherefore, at this point in time, preparation for transferring image data of an image to be formed has not been completed. Therefore, as the image data IPUDAT_Y at the time of the first line transfer, that is, when the main scanning effective area signal XIPULGT_Y becomes active (LOW), white image data that does not form an image is transferred.
  At the time of transfer after the next line, the image data preparation is completed, so the image data of the image to be actually formed is sequentially transferred, and when the transfer of the image data of all the lines is completed, the sub-scan is enabled. The area signal XIPUFGT_Y is deactivated.
[0031]
By performing such processing, a line of white data is added to the head of the image, but for correcting the difference in exposure position between the Y, M, C, and K photoconductor drums. Since the relative time of the number of delay lines for each color does not change, color matching can be performed properly. On the image forming apparatus main body side, if image formation is performed in accordance with each sub-scanning effective area signal XIPUFGT sent from the application board (in this case, the copy application 100), it is not necessary to particularly deal with the transfer delay of the image data. Therefore, even when the application board is changed to another one, there is no need to adjust the main body, and the configuration of the main body can be simplified and the cost can be reduced. Conversely, the application board also activates each sub-scanning effective area signal XIPUFGT with a predetermined trigger pulse even when transfer preparation is delayed, and deactivates it after the transfer is completed, so that image data can be obtained regardless of the configuration on the main body side. Therefore, the versatility of the application board can be improved.
[0032]
Next, a modification of this embodiment will be described. In this modification, the present invention is applied to a color copying machine in which two laser diodes are mounted in the LD units of the LD unit control circuits 111 to 114 shown in FIG. 3 and two lines are written in one scan. It is applied. In this case, image data for two lines is input to each LD unit control circuit 111 to 114 for each scan, and the data is distributed to each laser diode and driven. Other points are the same as those of the color copying machine described above.
Image data transfer control in this color copier will be described with reference to the timing chart of FIG. Here, only the transfer of image data for yellow (Y) will be described here, but the same processing is performed for the transfer of image data for other colors.
[0033]
The color copying machine of this modified example is different from the color copying machine of the above-described embodiment in which one laser diode is provided for each LD unit, because the two laser beams pass through the synchronous detection sensor once. Two pulses exist as the synchronization detection signal DETPO_Y during the scanning period, and the rotation speed of the polygon mirror 50 shown in FIG. 2 is adjusted so that image information for two lines can be written in one rotation. It is that you are.
As in the case of the above-described embodiment, the LD unit Y control circuit 111 generates the synchronization signal DPSYNC_Y and the line synchronization signal XLDSYNC_Y from the synchronization detection signal DETP_Y.
[0034]
In the previous embodiment with one laser diode for each LD unit, the period of the synchronization signal DPSYNC_Y and the line synchronization signal XLDSYNC_Y was 1: 1, but in this variant with two LDs, The period of the signal DPSYNC_Y is unchanged, but the period of the line synchronization signal XLDSYNC_Y is shortened to ½ during the period in which the sub-scanning effective area signal XIPUFGT_Y is ON (LOW).
This is because at least a period during which valid image information is transferred to the application board, one line for one pulse of the main scanning line trigger signal XWRSYNC_Y, regardless of the situation on the main body side (LD unit control circuit). This is a necessary procedure for providing a clear interface (I / F) regulation for transferring image information.
[0035]
Then, the timing Y generation circuit 102 shown in FIG. 3 generates a main scanning line trigger signal XWRSYNC_Y based on the line synchronization signal XLDSYNC_Y and sends it to the copy application 100. Based on the main scanning line trigger signal XWRSYNC_Y, the copy application 100 generates the sub-scanning effective area signal XIPULSYC_Y and the main scanning synchronization signal XIPULGT_Y, and transfers the image data signal XIPUDAT_Y to the engine side in accordance with these signals to form an image. Do.
Again, after the sub-scanning effective area trigger signal XFSYNC_Y is input, the sub-scanning effective area signal XIPUFGT_Y is made active (LOW) at the timing when the main scanning line trigger signal XWRSYNC_Y is first input. When the transfer of all the image data is completed, it is returned to inactive (HIGH).
[0036]
FIG. 7 shows the transfer timing when the transfer of the image data is delayed by one line as in FIG. 6, and white data that does not form an image is transferred as the first yellow image data IPUDAT_Y. Since the image data transfer preparation is completed at the time of transfer after the next line, the image data of the yellow image to be actually formed is sequentially transferred, and when the transfer is completed, the sub-scanning effective area signal XIPUFGT_Y is deactivated. To do.
In summary, image delay performed for color matching of each color is performed by each synchronization signal DPSYNC, and each line synchronization signal XLDSYNC is used to receive image data from each application board. In this way, it is possible to form an appropriate image without the application board having any knowledge of the configuration (number of LDs) of the LD unit control circuit on the main body side or the circumstances due to the writing density of the LD. .
[0037]
Here, with regard to the LD writing density, for example, printer controllers are mainly 1200, 600, and 300 dpi, but the copy application is 600 dpi, and the fax application is not the dpi resolution, but the main / mm resolution is the mainstream. There are various types of pixel density. In order for the main body to cope with these, it is necessary to variably control the rotational speed of the polygon motor 50 shown in FIG.
Therefore, the writing density on the main body side is set to 1200 dpi, which is the least common multiple of the pixel density, and the difference between the pixel density and the writing density is adjusted by doubling processing (double density processing) in which the same image is written twice using a line memory or the like. The method is commonly used.
[0038]
When this doubling process is supported, the period during which valid image data is transferred is defined to transfer one line of image information to one pulse of each line synchronization signal XLDSYNC by thinning out each line synchronization signal XLDSYNC. It is protected.
For example, when transferring image information having a pixel density of 600 dpi from a copy application to an LD unit having one LD and a writing density of 1200 dpi, the cycle of each synchronization signal DPSYNC is set to each line synchronization signal XLDSYNC. When transferring image information with a pixel density of 400 dpi from a copy application to an LD unit having two LDs and a writing density of 1200 dpi, each synchronization signal DPSYNC May be set to 2/3 times the period of each line synchronization signal XLDSYNC.
[0039]
Even in such a case, even if the main body does not know the image delay generated on the application board side, it is possible to always perform high-quality image formation without color misregistration. Accordingly, since a close cooperative operation is not required on the image forming apparatus main body side and the application board side, the range of application boards that can be used in the image forming apparatus can be increased.
In the above description, the color copying machine having the copy application installed in the color image forming apparatus has been described. However, the present invention can be achieved by replacing the application board with a printer controller, a FAX application, or the like, or by mounting a plurality of application boards. Needless to say, the present invention can also be applied to a printer, a facsimile machine, a digital multifunction machine having a plurality of these functions, and the like. Of course, the present invention can also be applied to a one-drum type color image forming apparatus and a monochrome image forming apparatus.
[0040]
The color image forming apparatus to which the present invention is applied has no image delay means for correcting the difference in exposure position by the laser beam for each color in the image forming apparatus main body, and an application board such as a copy application, a printer controller, or a FAX application. By sharing the functions of these functions and notifying the timing of transferring image information for each color from the main unit, it is possible to easily handle various pixel densities depending on the circumstances between application boards, and share image memory. Can be used effectively.
[0041]
For example, when filter processing (MTF processing or smoothing processing) is performed on image information read by a scanner with a copy application, an image delay of several lines always occurs. Therefore, it is possible to accurately perform the color matching control by the difference in the exposure position by the laser beam.
Further, when image data is transferred to the engine, the sub-scanning effective area signal becomes active even if the image data preparation for the image to be formed is not completed before the sub-scanning effective area signal becomes active. Then, transfer of image data is started immediately, and white image data is transferred until preparation for transfer of image data of the image to be formed is completed, so that the engine side is always appropriate without being aware of the processing on the application board. Image formation can be performed.
[0042]
【The invention's effect】
  As described above, the image forming apparatus according to the present invention performs a printer function.Image forming device bodyBy connecting to various application boards, various functions such as a copy function and a facsimile function can be realized, and a high-quality image that is inexpensive, has excellent versatility and expandability, and does not cause color misregistration can be formed. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of image forming means of a color copying machine which is an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a schematic plan view showing the configuration of the optical unit.
FIG. 3 is a block diagram showing a configuration of a control circuit of the color copying machine.
4 is a timing chart showing generation timing of each signal shown in FIG. 3. FIG.
FIG. 5 is a timing chart showing the generation of each signal and the transfer timing of image data.
FIG. 6 is a timing chart showing the generation of signals and the transfer timing of image data when there is a delay in the transfer of image data.
FIG. 7 is a timing chart showing generation of signals and transfer timing of image data in a control circuit of a modification of the color copying machine according to the present invention.
[Explanation of symbols]
1: Transfer paper 2: Conveyor belt
3,4: Conveying roller 5: Paper feed tray
6Y, 6M, 6C, 6K: photosensitive drum
7Y, 7M, 7C, 7K: Charger
8: Exposure unit 9Y, 9M, 9C, 9K: Development unit
10Y, 10M, 10C, 10K: Photoconductor cleaner
11Y, 11M, 11C, 11K: Laser beam
12Y, 12M, 12C, 12K: Transfer device
13: Fixing device 14: Registration sensor
20Y, 20M, 20C, 20K: image forming unit
41-44: Cylinder lens
45, 46: Reflection mirror 50: Polygon mirror
51, 52: fθ lens 53-56: first mirror
61, 62: Cylinder mirror
63, 64: Synchronization detection sensor 100: Copy application
102 to 105: timing generation circuit
106: Reference selection circuit 107-110: Sync separation circuit
111-114: LD unit control circuit

Claims (1)

An image forming apparatus main body comprising: a photoconductor; an exposure unit that scans the photoconductor to form an electrostatic latent image on the photoconductor; and a synchronization detection unit that detects a scanning timing of the exposure unit;
An application board having an image data transfer means for transferring image data of an image to be formed to the exposure means,
In the image forming apparatus main body, a main scanning line trigger signal and a sub-scanning effective area trigger signal which are signals for designating the transmission timing of the image data from the application board based on the detection signal from the synchronization detection unit A transfer trigger signal generating means for generating
The exposure means includes an LD unit and an LD unit control circuit that controls turning on / off of the LD unit, and includes an optical unit that deflects a laser beam emitted from the LD unit and scans the photoconductor. And
The application board generates a main scanning synchronization signal from the main scanning line trigger signal, and a sub scanning effective area signal generating means generates a sub scanning effective area signal from the sub scanning effective area trigger signal. And
The image data transfer means controls the LD unit through the transfer trigger signal generation means of the main body of the image forming apparatus in accordance with the main scanning synchronization signal and the sub-scanning effective area signal. Means to transfer to the circuit,
The sub-scanning effective area signal generation means activates the sub-scanning effective area signal at a predetermined timing after the sub-scanning effective area trigger signal is input to the application board, and finishes the transfer of the image data And means for deactivating the sub-scanning effective area signal,
If the image data transfer means is not ready to transfer image data of the image to be formed before the sub-scanning effective area signal becomes active, the image data transferring means An image forming apparatus comprising: means for transferring white image data that does not form an image during a period until image data transfer preparation for an image to be formed is completed.

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