JP4260616B2 - Color image forming apparatus - Google Patents

Description

  The present invention relates to a color image forming apparatus such as a printer, a copying machine, a facsimile machine, or a plotter capable of forming a multicolor or full color image, and more particularly to a color image forming apparatus having an intermediate transfer member capable of overwriting a plurality of colors. Is.

  Conventionally, a color image forming apparatus has a configuration including a plurality of image forming units in order to form images of a plurality of colors. Then, the registration in the sub-scanning direction is adjusted at the timing until the image forming operation is started with the system operation start signal generated based on the detection signal of the registration sensor for detecting the position of the recording medium (for example, transfer paper). In such a color image forming apparatus, for example, a visible image forming unit such as a photosensitive member is arranged along a conveyance belt called an intermediate transfer belt, and images of the respective colors are overlapped and formed at the same position on the intermediate transfer belt. There is a tandem type color image forming apparatus that transfers the image onto a transfer sheet using a separate transfer device. Here, the intermediate transfer belt has an endless shape and is arranged on a plurality of rollers with a predetermined tension. Then, it is conveyed at a constant speed in a predetermined direction by a driving means for rotating the driving roller.

In such a tandem type color image forming apparatus, the timing of starting image formation by the image forming units of the respective colors is different. Therefore, the operation of the entire system starts based on a detection signal from a registration sensor or the like that detects the transfer paper position. Generate a signal. Then, starting from this system operation start signal, the timing until the start of the image forming operation is adjusted for each color, and the registration amount in the sub-scanning direction is changed.
In a color image forming apparatus having an intermediate transfer member such as an intermediate transfer belt, the distance from the registration sensor to the image forming position differs for each color depending on the arrangement of the image forming system. For this reason, a means for independently adjusting the timing until the start of image formation is provided for each color. As an example, in the invention described in Patent Document 1, a tandem color image forming apparatus has a delay adjustment counter for each color independently and controls image formation start timing.

  The sub-scanning resist needs to be controlled in accordance with the color matching of each color, and is normally controlled based on a synchronization detection signal that is a main scanning writing reference timing signal for each color. However, the synchronization detection signal for each color is input at an independent timing for each color because the image height position is different. Further, the system operation start signal generated based on the registration sensor is an asynchronous input signal with respect to the synchronous detection signal of each color. Therefore, a line period shift occurs between colors in accordance with the timing of the system operation start signal and each color synchronization detection signal, and as a result, the sub-scanning registration position generates a shift corresponding to one line period. Here, in the invention described in Patent Document 2, in the one-drum intermediate transfer type color image forming apparatus, the main scanning writing start that generates the sub-scanning start signal phase for starting the image formation on the photosensitive member from the synchronization detection sensor is started. By synchronizing with the signal phase, the phase of each color is adjusted independently to prevent the registration position shift of one sub-scanning line. However, this cannot be applied to a tandem type color image forming apparatus as it is.

JP-A-9-220825 JP 2000-94739 A

  In the present invention, in order to solve the above problems, the timing adjustment means until the start of the image forming operation of each color is not the system operation start signal based on the detection signal of the registration sensor or the like, but the image after the system operation start signal is detected. By starting from the timing when the sync detection signal of all colors is not detected in the writing optical system that is the forming unit, the starting lines of the sub-scanning resist adjustment for each color are made coincident, and the image formation start timing for each color is unified. It is an object of the present invention to provide a color image forming apparatus that enables color matching that is adjusted and prevents sub-scanning registration position deviation in units of one line.

The present invention has the following features as means for solving the above problems.
The first configuration of the present invention includes a writing optical system that scans light beams from a plurality of light sources with a single deflector to form a plurality of colors of electrostatic latent images, and each color using light beams emitted from the writing optical system. A plurality of image carriers on which each of the electrostatic latent images is formed, a developing device that visualizes the electrostatic latent images formed on each image carrier with a developer of each color, and opposed to the image carriers A color image forming apparatus provided with an intermediate transfer body that is arranged and to which a developed image of each color is sequentially transferred, and a transfer device that collectively transfers an image formed on the intermediate transfer body to a recording medium. Each color has a writing control unit for controlling a light source, one image signal processing unit for inputting an image signal to the writing control unit, and a writing scanning system writing position in the main scanning direction. It has a detection optical sensor of the synchronization detection signal as a reference, before In the color image forming apparatus for outputting a synchronization detection signal for each color, before Kishokomi controller from the image signal processing unit transfer request plurality chromatic of a counter for controlling the delay time or more colors two up image signal to And generating a write control unit operation start signal at a timing not detecting the synchronization detection signal for all colors after detecting the system operation start signal generated from the sheet feeding timing of the recording medium, The counter used for each color is switched for each operation start signal, the count initial value is set for each color of the plurality of counters when the write control unit operation start signal is generated, and the synchronization detection signal is output. The counter value corresponding to each time is subtracted and an image signal transfer request is made at the timing when the counter value becomes 0. (Claim 1)

Here, in the color image forming apparatus according to the present invention , the starting point of the timing adjusting means until the image forming operation of each color is started is not the system operation start signal based on the detection signal of the registration sensor or the like, but the system operation start signal is detected. Later, the writing optical system, which is the image forming unit, is operated starting from the timing at which all color synchronization detection signals are not detected, so that the starting lines of the sub-scanning registration adjustment for each color are matched, and the image formation start timing for each color is set. It is possible to perform color matching that is generally adjusted and prevents sub-scanning resist position deviation in units of one line.
In addition, when only one delay timing control counter for adjusting the sub-scanning registration is provided for each color, the first timing for image formation when a print job for a plurality of pages is requested is the first. A print job for the second page is required after the first color is imaged, the second and third colors are imaged, and the last fourth color is imaged. That is, when the system operation start signal for the second page is detected before the image formation start timing for the first page of the fourth color, it is necessary to wait until the image formation start timing for the first page of the fourth color. That is, the system operation start signal for the second page is received and the control for the second page cannot be started until the fourth color starts image formation. However, according to the present invention, by having two or more delay timing control counters independently for each color, it is possible to reduce the job waiting time between pages over a plurality of pages and reduce the total processing time of the image forming apparatus. .

In the color image forming apparatus according to the present invention , from the timing at which the synchronization detection signals for all colors after the detection of the system operation start signal are not detected, until the transfer request of the image signal from the writing control unit to the image signal processing unit is made. a counter for controlling the delay time, that control is operated as a down counter.

In the color image forming apparatus according to the present invention, since it has a plurality of counters for line delay adjustment to the sub-scanning registration adjustment and the image forming operation start of each color, in normal use by switching for each print job page configuration It has become. However, when the delay timing adjustment means for adjusting the timing until the start of the image forming operation is to be controlled by the counter, the value set in the register or the like as the storage means is counted up using the up counter for each line cycle. When the image formation is started at the same timing as the value, the register setting value cannot be changed during the period until the image forming operation for the same page starts for all colors. In other words, when it is desired to change the sub-scanning registration adjustment value for the next page operation, it is necessary to delay the system operation start timing for the next page until the image forming operation for the previous page starts for all colors. The print job time becomes longer and the productivity is lowered.
Therefore, by operating and controlling a plurality of delay timing control counters as down counters, it is possible to achieve without reducing productivity. In other words, after the system operation start signal is detected, the delay line number setting value is loaded as the counter initial value from the timing when all color synchronization detection signals are not detected, and the decrement operation is performed at the timing of each color synchronization detection signal. The number of sub-scanning delay lines can be controlled by setting the time when the counter value reaches 0 as the image formation start timing. Also, by controlling the downcount, even when the delay line number setting value is changed during the print job operation, the initial value of the downcounter is determined from the output timing of the system operation start signal without worrying about the previous page job operation before the change. It can be changed except for the timing until the value is loaded. As a result, the color matching control result detected in the print job can be reflected in real time on the print job without reducing the productivity of the printing operation.

Further, in the color image forming apparatus according to the present invention , a recording medium (for example, a completely asynchronous operation) in the writing control unit which is the image forming unit in order to make it possible to adjust the color matching of the sub-scanning resist position in units of one line. In order to synchronize the transfer control of the transfer paper), a system operation start signal is generated based on the registration sensor signal detected from the transfer paper transfer control, and the synchronization from the synchronization detection sensor serving as the reference signal of the writing control unit In order to eliminate the asynchronism between the detection signal and the system operation start signal, the control is performed in units of line cycles, and the sub-scan start reference position of each color is controlled according to the synchronization detection signal. It is possible to control color matching in units of one line in the sub-scanning direction.

The second embodiment of the present invention is a color image forming apparatus of the first configuration, according to the result of color matching control made during image forming operation, to change the count initial value during the image forming operation It is characterized (Claim 2 ).
In the second configuration, for the same problem as in the first configuration, by using a down counter as a delay timing adjustment unit, a color matching correction control result detected in a print job over a plurality of pages is used to start system operation. By changing the down-loader initial load value except for the timing from the signal output timing to the down-counter initial value loading, the sub-scanning resist value can be adjusted even during the image formation period, without stopping the print job. It can be reflected in real time.

According to a third configuration of the present invention, in the color image forming apparatus of the first or second configuration, a process cartridge having a storage unit is provided in a unit that stores the image carrier, and the storage unit stores all the colors in advance. The number of delay lines of the image formation timing of each color is stored from the arrangement of the image carrier, and is used as an initial value of the downcount start value of the delay timing control counter (claim 3 ).
In a color image forming apparatus having a process cartridge in which an image carrier, a developer container (for example, a toner bottle) or the like is formed as one unit, the interval between the image carriers of each color is known. Since the interval between the image carriers corresponds to the delay timing amount between the colors of the image formation timing, the initial load value of the delay timing control counter for each color is stored in the process cartridge, so that the interval between the image carriers can be determined. The delay timing can be adjusted to be constant by default. Thereafter, color adjustment can be easily performed by finely adjusting the arrangement of the image forming system in the overall configuration of the apparatus.

Incidentally, in the color image forming apparatus having the above structure, as the plurality of light sources, for example, a semiconductor laser (laser diode: LD) is Ru is used.
Further, as the image bearing member, for example, photoconductive photoreceptor is Ru is used.
Furthermore, as the deflector, for example, a rotary polygon mirror Ru is used.
Further, as the intermediate transfer member, for example, an intermediate transfer belt is used, this along an intermediate transfer belt plurality of image bearing member Ru are juxtaposed at predetermined intervals.

In this onset bright, the color image forming apparatus having an intermediate transfer member are sequentially transferred by the transfer device an image of a plurality of colors, based on the system operation start signal which is a main scanning direction of the write reference signal for each color line synchronization signal System that generates a write control unit operation start signal from the timing of the output and operates a counter for delay timing control of each color in the sub-scanning direction from the write control unit operation start signal as a starting point. The image formation timing in the sub-scanning direction can be controlled regardless of the operation start signal input timing. Further, by providing two or more delay timing control counters independently for each color, it is possible to provide a color image forming apparatus capable of reducing the inter-page job waiting time of a print job over a plurality of pages.

According to the present invention , in the color image forming apparatus configured as described above , a plurality of delay timing control counters that control the number of delay lines in the sub-scanning direction of each color from the system operation start signal are operated as down counters. Even if the sub-scan delay amount is changed during a print job across pages, there is no restriction except for the timing from the system operation start signal output timing to the down counter initial value loading without worrying about the job operation of the previous page. The system can change the sub-scan delay amount. Accordingly, it is possible to provide a color image forming apparatus that can reflect the color matching control result detected in the print job in real time without reducing the productivity of the printing operation.

Furthermore, in this onset bright, the color image forming apparatus of the above configuration, the system operation start signal is completely asynchronous operation in the write control unit is an image forming unit in synchronization detection signal is a reference signal of the write control unit In this way, the color-alignment control for each line in the sub-scanning direction in the tandem color image forming apparatus is performed by controlling the sub-scan start reference position of each color according to the synchronization detection signal. Can be possible.

Furthermore, in this onset bright, the color image forming apparatus of the above configuration, by operating the delay timing control counter for controlling the number of delay lines in the sub-scanning direction of each color from the system operation start signal as a down counter, a plurality Even if the sub-scan delay amount is changed during a print job across pages, there is no restriction except for the timing from the system operation start signal output timing to the down counter initial value loading without worrying about the job operation of the previous page. The system can change the sub-scan delay amount. Accordingly, it is possible to provide a color image forming apparatus that can reflect the color matching control result detected in the print job in real time without reducing the productivity of the printing operation.

Furthermore, in this onset bright, the color image forming apparatus of the above configuration, to form a process cartridge structure in which the one unit of the image bearing member and the developing device or the like, may be provided a storage means in the unit of the process cartridge, The interval between the image carriers of the respective colors is stored in the cartridge. Since the photosensitive drum interval corresponds to the image formation timing delay interval between the respective colors, the sub-scanning color matching control can be easily realized when the process cartridge is replaced by using the stored value as a default value. be able to.

  The present invention relates to a writing optical system that forms a plurality of colors of electrostatic latent images by scanning light beams from a plurality of light sources (for example, semiconductor lasers (laser diodes: LD)) with a single deflector (for example, a rotating polygon mirror). A writing optical unit), a plurality of image carriers (for example, photoconductive photosensitive drums) each of which forms an electrostatic latent image of each color by a light beam (laser beam) irradiated from the writing optical unit, and each image carrier A developing device that visualizes the electrostatic latent image formed on the body with a developer of each color (for example, toner of each color), and a developed image (toner image) of each color that is disposed opposite to the image carrier is sequentially transferred. The present invention relates to a color image forming apparatus including an intermediate transfer member (for example, an intermediate transfer belt) and a transfer device that collectively transfers an image formed on the intermediate transfer member to a recording medium (for example, transfer paper). Hereinafter, the best mode for carrying out the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 2 is a schematic cross-sectional view of the writing optical unit 1 used in the color image forming apparatus of the present invention. Reference numeral 20 in the drawing denotes a rotating polygon mirror (polygon mirror) 21-1, 21-2 as a deflector. fθ lenses, 22M, 22C, 22Y, and 22K are first mirrors, 23M, 23C, 23Y, and 23K are surface tilt correction lenses (such as WTL), 24M, 24C, 24Y, and 24K are second mirrors, and 25M, 25C, and 25Y , 25K are third mirrors. The writing optical unit 1 of the color image forming apparatus forms images of four colors of magenta: M, cyan: C, yellow: Y, and black: BK. In the conventional image forming apparatus, four color images are formed by four independent writing optical units, but in the image forming apparatus of the present invention, four color images are formed by one writing optical unit. A laser beam emitted from a laser diode mounted on each color laser unit (not shown) enters a cylindrical lens (not shown). The cylindrical lens has a refractive index determined in the sub-scanning direction, condenses the parallel beam emitted from the laser unit in the sub-scanning direction, and enters the rotating polygon mirror (polygon mirror) 20 that is a deflector. . The polygon mirror 20 is rotated at a high speed by a motor and deflects the incident laser beam in the main scanning direction. In the writing optical unit 1 of the present invention, the polygon mirror 20 is arranged in the center of the optical unit, and the laser beam of four colors is deflected in the main scanning direction by one polygon mirror 20. Then, a laser unit, mirrors, lenses, and other components are arranged symmetrically with respect to the polygon mirror 20, and the optical paths of the two colors of laser beams are laid out on the left and right, so that one polygon mirror 20 can generate four colors. The laser beam is deflected. In the drawing, magenta: M and cyan: C optical paths are laid out on the left side of the polygon mirror 20, and yellow: Y and black: BK optical paths are laid out on the right side. The laser beams of the respective colors deflected by the polygon mirror 20 are reflected by the first mirrors 22M, 22C, 22Y, and 22K.

  3 and 4 are schematic plan views of the optical system in the writing optical unit of FIG. In the figure, reference numeral 20 denotes a rotating polygon mirror (polygon mirror), 21-1 and 21-2 denote fθ lenses, 22M, 22C, 22Y and 22K denote first mirrors, 24M, 24C, 24Y and 24K denote second mirrors and 26M. , 26C, 26Y, 26K are laser units equipped with laser diodes, 27M, 27C, 27Y, 27K are cylindrical lenses, 28-1, 28-2 are reflection mirrors, 29M, 29C, 29Y, 29K are synchronous detection reflection mirrors, Reference numerals 30-1 and 30-2 denote synchronization detection lenses, and reference numerals 31-1 and 31-2 denote synchronization detection sensors. Note that the surface tilt correction lenses (WTL, etc.) 23M, 23C, 23Y, and 23K and the third mirrors 25M, 25C, 25Y, and 25K are not shown.

  2 to 4, after the laser beams incident on the first mirrors 22M, 22C, 22Y, and 22K are incident on the surface tilt correction lenses (such as WTL) 23M, 23C, 23Y, and 23K, the second mirrors 24M and 24C are obtained. , 24Y, 24K. Surface tilt correction lenses (WTL, etc.) 23M, 23C, 23Y, and 23K are used to correct the surface tilt of the polygon mirror 20. The laser beams reflected by the second mirrors 24M, 24C, 24Y, and 24K are reflected by the third mirrors 25M, 25C, 25Y, and 25K, emitted from the writing optical unit 1, and imaged on a photosensitive drum (not shown). As described above, the writing optical unit 1 has optical parts arranged symmetrically with respect to the polygon mirror 20, and the optical paths are laid out in two colors on the left and right. The line synchronization detection signal detectors for detecting the writing reference position in the main scanning direction are the synchronization detection sensors 31-1 and 31-2 in the drawing. The laser beam reflected by the second mirrors 24M, 24C, 24Y, and 24K at a specific position in the main scanning is reflected by the synchronization detection reflection mirrors 29M, 29C, 29Y, and 29K, and is detected by the synchronization detection lenses 30-1 and 30-2. The light is condensed and incident on the synchronous detection sensors 31-1 and 31-2. The synchronization detection lenses 30-1 and 30-2 are arranged to focus the incident laser beam on the synchronization detection sensors 31-1 and 31-2. The synchronization detection sensors 31-1 and 31-2 are made of optical sensors, one on each of the left and right sides of the optical system, and the timing of the two colors of laser beams can be detected by one sensor. That is, the main scanning reference position of magenta: M and cyan: C is detected by one sensor 31-1, and the yellow: Y and black: BK beams are detected by another sensor 31-2.

  FIG. 5 is a schematic configuration diagram of a color image forming apparatus showing an embodiment of the present invention. In FIG. 5, reference numeral 1 denotes the above-described writing optical unit, 2M, 2C, 2Y, 2K are photosensitive drums which are image carriers. 3M, 3C, 3Y, and 3K are charging devices, 4 is an endless intermediate transfer belt that is an intermediate transfer member, 4a, 4b, and 4c are intermediate transfer rollers that support the intermediate transfer belt, 4dM, 4dC, 4dY, and 4dK are Transfer bias application rollers, 5M, 5C, 5Y and 5K are developing devices for each color, 6 is an intermediate transfer belt cleaning device, 7 is a transfer device using a transfer conveyance belt, 8 is a paper feeding registration roller, 9 is a fixing device, Reference numeral 10 denotes a paper discharge device, and s denotes a transfer paper.

  In FIG. 5, when the start switch of the image forming apparatus (not shown) is pressed or the print job start signal from the printer is validated, the surfaces of the photosensitive drums 2M, 2C, 2Y, 2K are charged by the charging devices 3M, 3C, 3Y, A laser beam charged by 3K and controlled in timing by the laser writing optical unit 1 is emitted and exposed on the surfaces of the photosensitive drums 2M, 2C, 2Y, and 2K, and magenta: M, cyan: C, yellow: Y, Black: An electrostatic latent image corresponding to each color of BK is formed. Then, the corresponding photosensitive drums 2M, 2C, 2Y, and 2K are rotated by the developing devices 5M, 5C, 5Y, and 5K of the respective colors according to the exposed laser beam positions, and the developing devices 5M, 5C, 5Y, and 5K are rotated. The electrostatic latent image is developed with each color toner to form a single color image of magenta: M, cyan: C, yellow: Y, black: BK on each photosensitive drum. In parallel with the developing operation on the photosensitive drum, the intermediate transfer belt 4 is driven to rotate. That is, one of the three intermediate transfer rollers 4a, 4b, 4c shown in the figure is rotationally driven as a drive roller, and the other two are driven rollers, and the intermediate transfer belt 4 is conveyed in the direction of arrow B in the figure. By the developing operation on the photosensitive drum and the conveying operation of the intermediate transfer belt 4, the monochrome images formed on the photosensitive drums 2M, 2C, 2Y, and 2K are sequentially transferred to the intermediate transfer belt 4, and the intermediate transfer belt 4 A composite color image of four colors superimposed is formed on top. On the other hand, when the job start signal is validated, the transfer sheets s are separated one by one from a sheet feeding device (not shown), conveyed and fed against the sheet feeding registration roller 8 and temporarily stopped. Then, the registration roller 8 is rotated in synchronization with the synthesized color image on the intermediate transfer belt 4, the transfer paper s is fed between the intermediate transfer belt 4 and the transfer device 7, and the transfer device 7 synthesizes the transfer paper s. Transfer color image. The transfer sheet s after the transfer is directly conveyed by the transfer conveyance belt of the transfer device 7 and is conveyed to the fixing device 9, and heat and pressure are applied by the heating roller and the pressure roller of the fixing device 9 to fix the transferred image. The paper is discharged by a paper discharge roller attached to the paper discharge device 10 and stacked on a paper discharge tray (not shown).

  FIG. 1 is a block diagram of a control system of a color image forming apparatus showing an embodiment of the present invention. In this control system, an operation mode of each control unit is set by an engine control unit (control device (CPU) 43 including a microcomputer) that controls the entire image forming apparatus. Various settings are also made for each color writing control unit 44M, 44C, 44Y, 44K which is an image forming unit, and a reference color is set out of the four colors. In the drawing, the arrangement shown in FIG. 5 is assumed, and magenta: M that starts image formation first is set as a reference color. The system control start signal STTRIG_N is sent from the engine control unit 43 to each of the write control units 44M, 44C, 44Y, and 44K at the timing when the transfer sheet position is detected by the registration sensor 8A provided at the position of the paper feed registration roller 8. Output. Each color write control unit 44M, 44C, 44Y, 44K determines whether it is a reference color or a dependent color, and in the case of the reference color, STTRIG_N is latched and the write control unit is controlled at a specific timing managed for each color line. Operation start signal: Output STOUT_N. In this example, STTRIG_N is latched using magenta: M as a reference color, and STOUT_N is output for the other three colors. Each color write controller counts the line synchronization signal: lclre with STOUT_N as a trigger. lclre is a timing at the synchronization signal control unit in the writing control unit based on the synchronization detection signal: DETP_N detected by the synchronization detection sensors 31-1 and 31-2 attached to the synchronization detection plate of the writing optical unit 1. This is a line clear signal for generating one pulse on one surface of a controlled polygon mirror.

  Each color write control unit 44M, 44C, 44Y, 44K has a delay line control unit independently, and the number of delay lines is controlled by delay counters for delay timing control: mfcount0-3. Delay counters: mfcount 0 to 3 load the counter initial value at the timing of STOUT_N, count the line synchronization signal: lclre, and control the number of delay lines in the sub-scanning direction. A position in the sub-scanning direction for forming an electrostatic latent image of each color image transferred onto the intermediate transfer belt 4 is detected in advance, and delay timings for forming cyan, yellow, and black from the reference color magenta are calculated. A transport delay time calculated from the positional relationship between the registration position of the registration sensor 8A for detecting the transfer paper position and the transfer position of the reference color magenta is added to the calculated result, and the delay time is replaced with the number of sub-scanning lines. Information obtained by replacing the image formation delay time of each color with the number of delayed sub-scan lines is set in the sub-scan delay line register: mfdly_r from the engine control unit 43 to the write control units 44M, 44C, 44Y, and 44K for each color.

  Write control unit operation start signal: Delay counter selected by STOUT_N: mfcount0 to 3 loads the sub-scan delay line register value as an initial value, decrements every time a line synchronization signal is detected, and the delay counter becomes 0 A request signal: MFSYNC_N for requesting image transfer from the writing control units 44M, 44C, 44Y, 44K for each color to the preceding image processing unit 42 is output at the timing reached. The image processing unit 42 stores image data that has been subjected to various types of image processing based on input image data developed from the preceding scanner unit / printer driver unit 41. The image data accumulated on the basis of MFSYNC_N input to the image processing unit 42 from the write control units 44M, 44C, 44Y, 44K for each color is output to the write control units 44M, 44C, 44Y, 44K as an image signal: IPDATA_N. To do. Then, the writing image developing unit in the writing control unit develops the image signal: IPDATA_N into a two-dimensional image of main scanning and sub-scanning based on the line synchronization signal: lclre, and supplies it to the LD driver unit. The LD driver unit drives laser diodes mounted on the LD units 26M, 26C, 26Y, and 26K of the writing optical unit 1 based on the input two-dimensional image signal.

FIG. 6 shows a timing chart of job start control of the color image forming apparatus used in the present invention. A system operation start signal: STTRIG_N is output from the engine control unit 43 to the writing control unit at the transfer paper position detection timing by the registration sensor 8A. Then, the magenta writing control unit 44M for the reference color outputs a writing control unit operation start signal: STOUT_N at a timing that does not generate the synchronization detection signal: DETP_N and the line synchronization signal: lclre for all colors. In the present invention, since the image is formed in the order of magenta, cyan, yellow, and black, the sub-scan delay line register: mfdly_r value of each color is
mfdly_r (M) <mfdly_r (C) <mfdly_r (Y) <mfdly_r (K)
Is set to the magnitude relationship. When STOUT_N is input / output, the delay line control unit in the write control unit selects a counter to be operated from a plurality of delay counters for delay line control: mfcount0 to mfcount3. This counter selection is used in a configuration that switches in the toggle order for each job transfer sheet. Here, a case where mfcount0 is selected will be described. When mfcount0 is selected as a delay counter at the time of generating STOUT_N, the count value of mfcount0 is loaded with the sub-scan delay line register: mfdly_r value. After loading the counter initial value, the counter is decremented for each surface of the polygon mirror 20 using the line sync signal: lclre of the corresponding color as a counter clock. Delay counter: MFSYNC_N is output to the image processing unit 42 at the timing when the counter value of mfcount0 reaches 0, and an image signal transfer request is issued from the image processing unit 42. In the present invention, based on the system operation start signal input at the asynchronous timing detected by the registration sensor 8A, the image in the sub-scanning direction is written by the writing control unit that develops the image signal two-dimensionally on the transfer paper. In order to form an image without disturbing the writing position, a writing control unit operation start signal is separately generated based on the synchronization detection signal, and in the sub-scanning direction using this line as a main scanning reference signal, the line synchronization signal. By controlling the number of delay lines independently for each color, the color matching timing of each color in the sub-scanning direction can be controlled. This reflects the contents of the first configuration (claim 1).

An example of the operation of the black delay line control unit is shown in the lower part of FIG. When STOU_N is input from the magenta writing control unit 44M as the reference color to the black writing control 44K, the mfdly_r (K) value that is the initial value is loaded into mfcount0 (K). In the figure, mfdly_r = 06h. Black line synchronization signal: Every time lclre (K) is input, mfcount0 (K) is decremented by -1. MFSYNC_N (K) is output when mfcount0 (K) = 00h. After the output of MFSYNC_N (K), mfcount0 (K) finishes the decrement operation, and shifts to the standby state FF00h. Each color has independent sub-scan delay line registers: mfdly_r (M), mfdly_r (C), and mfdly_r (Y). By setting appropriate values for each color, sub-scan from STOUT_N to each color MFSYNC_N output Timing can be adjusted arbitrarily. In the present invention, from the system operation start signal: STTRIG_N, the write control unit operation start signal: STOUT_N that does not detect all the color synchronization signals is used as the starting point until the image signal transfer request signal: MFSYNC_N is generated. The sub-scanning delay timing can be adjusted by loading the initial value of the sub-scanning delay timing with STOUT_N as the starting point and performing the down-counting operation by the control counter independent for each color. This reflects the contents of the first configuration (claim 1 ).

  7 and 8 show timing charts when an image forming operation of a plurality of pages is performed in the color image forming apparatus used in the present invention. In the operation of a plurality of pages, STTRIG_N is output from the engine control unit 43 at the timing when the transfer sheet position of each page is detected by the registration sensor 8A. Based on the output STTRIG_N, the reference color writing control unit (magenta in the drawing) 44M generates STOUT_N and outputs it to the respective color writing control units 44C, 44Y, 44K. After inputting STOUT_N, the delay counter is selected by the means described above to control the number of sub-scan delay lines. There are a plurality of delay counters for each color (four colors for mfcount 0 to 3 in the figure), and the delay counter is switched for each STOUT_N input. In the case of transfer paper (eg, A3 portrait size) long in the sub-scan direction shown in FIG. 7, after the transfer request (MFSYNC (M) output) of the magenta image signal for the first page, the fourth color black is the image signal. Because the STTRIG_N and STOUT_N of the second page are not input before the transfer request (MFSYNC (K) output) is started, the second page is also controlled by the same delay counter as the first page: mfcount0 to control the number of sub-scan delay lines Can do.

  However, in the case of a transfer sheet that is short in the sub-scanning direction as shown in FIG. 8 (e.g., postcard length size), after the magenta image transfer request for the first page, the second color cyan requests the image transfer for the first page. Since the magenta image transfer for the first page has already been completed, the magenta can respond even if the job start signal for the second page is input. The image signal transfer request is not reached due to the image forming position. When each color has only one delay counter, the first color magenta forms the first page image until the fourth color black requests the first page image signal transfer (MFSYNC_N (K) output). Ending and waiting until the second page. Therefore, there are a plurality of delay line control counters for each color in the sub-scanning direction, and the delay counter is switched for each transfer sheet of the job. Until the signal transfer starts, the system operation start signal of the job of the next page can be received. Thereby, the standby state can be reduced and an image forming job between a plurality of pages can be processed efficiently. Further, in FIG. 8, the first color magenta starts transferring the image signal of the third page until the fourth color black starts to transfer the image signal of the first page. Is waiting. In this embodiment, since the delay line control unit for each color has four delay counters (mfcount0 to 3), it is possible to wait for image transfer for a maximum of four pages. In addition, a large amount of color image formation can be realized by toggle-switching from mfcount0 to mfcount3 for a job with four or more pages of transfer paper. This reflects the contents of the first configuration (claim 1).

FIGS. 9 and 10 show other timing charts when the image forming operation of a plurality of pages is performed in the color image forming apparatus used in the present invention. The difference from FIG. 8 is that the number of sub-scan delay lines for each color is changed between the third and fourth pages depending on the result of color matching control. In the example shown in FIG. 9, the delay counter of the delay line control unit is controlled by an up counter or the like. When the sub-scan delay line register for each color: mfdly_r is changed according to the STOUT_N output timing of the 4th page, the changed value is reflected from the 4th page in the 1st magenta, but the 3rd yellow is 3 pages depending on the image formation timing. From the first, black of the fourth color reflects the number of delay lines after the change from the fourth page, and color shift occurs on the third and fourth pages on the final output transfer paper. Therefore, it is necessary to change the reflection of the delay line register for each color, but the timing to change cannot be controlled by STOUT_N, and it is necessary to provide a job waiting time between pages when changing mfdly_r. However, by controlling the delay counter of the delay line control unit by operating the down counter, even if the delay line register: mfdly_r value is changed, the register value before the change is reflected and changed on the page where STOUT_N has already been generated. The register value after the change will be reflected in the page generated by the later STOUT_N. The example shown in FIG. 10 is a case where the delay counter of the delay line control unit is controlled by the down counter. By changing mfdly_r value of each color between STOUT_N of 3rd page and 4th page, when STOUT_N of 4th page is generated, line delay counter of each color: mfdly_r value is changed to mfcount3 By initial loading, the image signal transfer request signal for the fourth page: MFSYNC_N can be generated at the timing after each color change. In this case, since the image signal transfer request timing up to the third page of each color is performed based on the mfdly_r value before the change, the sub-scan line delay number after the change from the fourth page is reflected in the final output image. An image can be obtained. This reflects the contents of the second configuration (claim 2 ).

  Next, FIG. 11 is a schematic configuration diagram of a color image forming apparatus showing another embodiment of the present invention. In FIG. 11, reference numeral 1 denotes a writing optical unit, and 2M, 2C, 2Y, and 2K are photosensitive members that are image carriers. Drum, 4 is an intermediate transfer belt which is an intermediate transfer member, 5M, 5C, 5Y and 5K are developing devices, 6 is an intermediate transfer belt cleaning device, 7 is a transfer device using a transfer conveyance belt, 8 is a paper feeding registration roller, Reference numeral 9 is a fixing device, and 10 is a paper discharge device. The basic configuration of this color image forming apparatus is the same as that shown in FIG. 5, but in this embodiment, there are four photosensitive drums 2M, 2C, 2Y, 2K and a charging device (reference numeral omitted) arranged around them. The developing devices 5M, 5C, 5Y, and 5K are housed in one process cartridge 11.

  In FIG. 11, when the start switch of an image forming apparatus (not shown) is pressed or the print job start signal from the printer is validated, the surfaces of the photosensitive drums 2M, 2C, 2Y, 2K are charged by the charging device, and laser writing is performed. A timing-controlled laser beam is emitted from the optical unit 1 and exposed on the surfaces of the photosensitive drums 2M, 2C, 2Y, and 2K, and corresponds to magenta: M, cyan: C, yellow: Y, and black: BK. An electrostatic latent image is formed. Then, the corresponding photosensitive drums 2M, 2C, 2Y, and 2K are rotated by the developing devices 5M, 5C, 5Y, and 5K of the respective colors according to the exposed laser beam positions, and the developing devices 5M, 5C, 5Y, and 5K are rotated. The electrostatic latent image is developed with each color toner to form a single color image of magenta: M, cyan: C, yellow: Y, black: BK on each photosensitive drum. In parallel with the developing operation on the photosensitive drum, the intermediate transfer belt 4 is driven to rotate. That is, one of the three intermediate transfer rollers shown in the figure is rotationally driven as a driving roller, and the other two are driven rollers, and the intermediate transfer belt 4 is conveyed in the direction of arrow B in the figure. By the developing operation on the photosensitive drum and the conveying operation of the intermediate transfer belt 4, the monochrome images formed on the photosensitive drums 2M, 2C, 2Y, and 2K are sequentially transferred to the intermediate transfer belt 4, and the intermediate transfer belt 4 A composite color image of four colors superimposed is formed on top. On the other hand, when the job start signal is validated, the transfer sheets s are separated one by one from a sheet feeding device (not shown), conveyed and fed against the sheet feeding registration roller 8 and temporarily stopped. Then, the registration roller 8 is rotated in synchronization with the synthesized color image on the intermediate transfer belt 4, the transfer paper s is fed between the intermediate transfer belt 4 and the transfer device 7, and the transfer device 7 synthesizes the transfer paper s. Transfer color image. The transfer sheet s after the transfer is directly conveyed by the transfer conveyance belt of the transfer device 7 and is conveyed to the fixing device 9, and heat and pressure are applied by the heating roller and the pressure roller of the fixing device 9 to fix the transferred image. The paper is discharged by a paper discharge roller attached to the paper discharge device 10 and stacked on a paper discharge tray (not shown).

As described above, the configuration and operation of the color image forming apparatus shown in FIG. 11 are the same as those of the color image forming apparatus shown in FIG. 5 described above. The difference from the apparatus shown in FIG. 2M, 2C, 2Y, 2K, the developing devices 5M, 5C, 5Y, 5K and the charging device are housed in one process cartridge 11 to form an integral cartridge configuration. As described above, the process drums 11 in which the photosensitive drums of the respective colors are integrated into one process cartridge 11 can determine the configuration and arrangement position of the photosensitive drums 2M, 2C, 2Y, and 2K of the respective colors. Then, a storage device (not shown) is provided in the process cartridge 11, and the image forming timing interval of each color determined from the interval between the photosensitive drums of each color is stored in the storage device. It is possible to automatically read without detecting the interval. The image forming timing interval of each color stored in the storage device is read by the engine control unit 43 described above, and a magenta image forming timing delay amount of the first color as a reference from the registration sensor detection is added, so that The number of sub-scan delay lines can be easily derived. The sub-scanning timing of each color can be easily adjusted by using the number of sub-scanning delay lines derived in this way as a default delay counter initial load value and then fine-tuning with control such as color matching. . This reflects the contents of the third configuration described above (claim 3 ).

  As described above, the present invention can be suitably used for color image forming apparatuses such as printers, copiers, facsimiles, and plotters having an intermediate transfer member, and realizes high-quality color image formation without color misregistration. can do.

1 is a block diagram of a control system of a color image forming apparatus showing an embodiment of the present invention. It is a schematic sectional drawing of the writing optical unit which shows one Example of this invention. FIG. 3 is a schematic plan view of an optical system in the writing optical unit shown in FIG. 2. FIG. 3 is a schematic plan view of an optical system in the writing optical unit shown in FIG. 2. 1 is a schematic configuration diagram of a color image forming apparatus showing an embodiment of the present invention. 6 is a timing chart showing job start control timing. 6 is a timing chart illustrating an example of a multi-page image forming operation. 6 is a timing chart showing another example of the image forming operation of a plurality of pages. 6 is a timing chart showing another example of the image forming operation of a plurality of pages. 6 is a timing chart showing another example of the image forming operation of a plurality of pages. It is a schematic block diagram of the color image forming apparatus which shows another Example of this invention.

Explanation of symbols

1: Writing optical unit 2M, 2C, 2Y, 2K: Photosensitive drum (image carrier)
3M, 3C, 3Y, 3K: Charging device 4: Intermediate transfer belt (intermediate transfer member)
4a, 4b, 4c: Intermediate transfer roller 4dM, 4dC, 4dY, 4dK: Roller for applying transfer bias 5M, 5C, 5Y, 5K: Developing device 6: Intermediate transfer belt cleaning device 7: Transfer device 8: Feeding registration roller 8A : Registration sensor 9: Fixing device 10: Paper discharge device 20: Rotating polygon mirror (polygon mirror)
21-1, 21-2: fθ lens 22M, 22C, 22Y, 22K: first mirror 23M, 23C, 23Y, 23K: surface tilt correction lens (WTL, etc.)
24M, 24C, 24Y, 24K: Second mirror 25M, 25C, 25Y, 25K: Third mirror 26M, 26C, 26Y, 26K: Laser unit 27M, 27C, 27Y, 27K: Cylindrical lenses 28-1, 28-2: Reflection mirrors 29M, 29C, 29Y, 29K: synchronization detection reflection mirrors 30-1, 30-2: synchronization detection lenses 31-1, 31-2: synchronization detection sensors (optical sensors)
41: Scanner unit / printer driver unit 42: Image processing unit 43: Engine control unit 44C, 44Y, 44K: Write control unit s: Transfer paper (recording medium)

Claims (3)

A writing optical system that scans light beams from a plurality of light sources with a single deflector to form an electrostatic latent image of a plurality of colors, and an electrostatic latent image of each color is formed by the light beams emitted from the writing optical system. A plurality of image carriers, a developing device that visualizes an electrostatic latent image formed on each image carrier with a developer of each color, and a development image of each color that is arranged opposite to the image carrier and sequentially transfers A color image forming apparatus comprising an intermediate transfer member to be transferred and a transfer device that collectively transfers an image formed on the intermediate transfer member to a recording medium, and a writing control for controlling a light source corresponding to the image formation For each color, and one image signal processing unit for inputting an image signal to the writing control unit, for detecting a synchronization detection signal serving as a reference for the writing position in the main scanning direction of the writing optical system possess an optical sensor, the synchronization detection signal for each color In the color image forming apparatus for outputting,
Before Kishokomi controller the image signal processing unit a plurality of counters to control the delay time until the transfer request more colors two image signals have to from,
Generate a write control unit operation start signal at a timing not detecting the synchronization detection signal of all colors after detecting the system operation start signal generated from the paper feeding timing of the recording medium,
Switch the counter to be used for each color for each write control unit operation start signal, set the initial count value for each color of the plurality of counters when generating the write control unit operation start signal,
A color image forming apparatus, wherein the counter value is subtracted every time the synchronization detection signal is output, and an image signal transfer request is made when the counter value reaches zero . The color image forming apparatus according to claim 1.
A color image forming apparatus , wherein the count initial value is changed during an image forming operation according to a result of color matching control performed during the image forming operation . The color image forming apparatus according to claim 1 or 2,
A process cartridge having a storage means is provided in a unit for storing the image carrier, and the storage means stores in advance the number of delay lines of the image forming timing of each color from the arrangement of the image carriers of all colors, and the delay A color image forming apparatus which is used as an initial value of a down-count start value of a timing control counter.

Images