JP2007121907A - Image forming apparatus and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform predetermined correction processing without lowering productivity. <P>SOLUTION: An image forming apparatus includes: an image forming part 200 forming a toner pattern on an intermediate transfer belt 208; and a pattern detection sensor 210 detecting the toner pattern. The apparatus controls various printing conditions based on detected results of the toner pattern. The apparatus is equipped with a control part 300 controlling write-in timing by the image forming part 200 when forming the pattern and detection timing by the toner pattern detection sensor 210. The control part 300 sets the write-in timing by the image forming part 200 and the detection timing by the toner pattern detection sensor 210, forms the toner pattern between paper and paper and detects the formed toner pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method for forming a toner pattern and correcting density and positional deviation.

  2. Description of the Related Art Conventionally, a so-called tandem type color image forming apparatus that forms a full-color image by arranging a plurality of electrophotographic writing units and image forming units in parallel to each other is known. In such an image forming apparatus, for example, a full-color copying machine, an image forming station for forming images of each color of cyan, magenta, yellow and black is provided, and a laser modulated by image data of each color is changed from a writing unit to an image forming unit. The photosensitive member is irradiated to form a latent image. Each color image forming unit supplies toner of each color to the formed latent image on the photoconductor, develops the toner, and visualizes the latent image. The visualized toner image is sequentially transferred onto a transfer sheet conveyed on the conveyance belt, and a color image on which the toner images of the respective colors are superimposed is formed on the transfer sheet, fixed, and a color image is output. .

  As described above, in a color image forming apparatus having a plurality of image forming stations, each image forming station is compared with a color image forming apparatus in which only one photoconductor called a one-drum system is provided to form a color image. Since different toner images are sequentially superimposed on the same surface of the same transfer paper to form a color image, if the transfer image position on the transfer paper in each image forming station is shifted, the image formed in each image forming station The intervals are shifted or overlapped, and in the case of a color image, a color difference or a color shift occurs, and the image quality deteriorates. This misalignment includes misalignment caused by inclination and misalignment in the vertical and horizontal directions. That is, in the former, the inclination of the scanning line for each color occurs due to an assembly error inside the writing optical system, an attachment error of each unit to the color image forming apparatus main body, and an attachment error of the photosensitive member to the color image forming apparatus main body. In the latter case, the position of the scanning line is shifted parallel to the reference position, and the four color images are shifted in the vertical or horizontal direction as a whole. Of these misalignments, the misalignment is corrected by finely adjusting the position of the reflecting mirror of the writing unit, and the parallel misalignment is adjusted by adjusting the writing start timing in the main scanning direction or the sub scanning direction. The correction can be performed. The length of the image in the main scanning direction can be adjusted by changing the frequency of the writing pixel, that is, by adjusting the magnification error.

  Such misregistration occurs not only due to replacement of the image forming unit, maintenance of the color image forming apparatus, transportation of the color image forming apparatus, etc. Also due to the temperature expansion of the mechanism after image formation of the sheet, the error varies with time.

  Therefore, if the number of sheets to be fed exceeds a preset number during continuous printing of multiple sheets, an alignment pattern is formed between the recording media to correct misalignment or a simple misalignment pattern between the recording media. Techniques such as forming and performing positional deviation correction are known.

  Among them, for example, Japanese Patent Application Laid-Open No. H10-228667 aims to correct image misalignment appropriately while improving the image formation efficiency, and in continuous printing, image data is provided in each color image forming unit arranged along the conveyor belt. A toner image of a different color is created on the basis of the toner image and sequentially transferred onto a transfer sheet conveyed at a paper interval shorter than one circumference of the photoreceptor on the conveyance belt to form a color image. Exceeds the preset number of alignment executions, the transfer sheet conveyance interval is changed to a sheet interval longer than the circumference of the photosensitive member only during the position detection pattern formation timing, and the changed sheet A position detection pattern is formed on the transport belt between the transfer sheets at intervals, and the position deviation correction process is performed.

In addition, when performing detection and correction by toner pattern image formation in continuous printing, the machine is once stopped (LD extinguishing, polygon stop and photoconductor stop are performed), and various initial settings for pattern image formation are performed. There are also examples in which pattern generation and detection correction are performed.
JP 2001-290327 A

  In the invention described in Patent Document 1, as described above, when creating a misregistration correction pattern during continuous printing, the position detection pattern is formed on the transport belt by changing the sheet interval, so that the productivity of image formation is reduced. I cannot deny it. In addition, when performing detection and correction by toner image formation in continuous printing, once the machine is brought down, the productivity of image formation naturally decreases.

  The present invention has been made in view of such a state of the prior art, and an object of the present invention is to enable a predetermined correction process without reducing productivity.

  In order to achieve the object, the first means comprises pattern forming means for forming a toner pattern on the image carrier and toner pattern detecting means for detecting the toner pattern, and based on the detection result of the toner pattern. In the image forming apparatus for controlling various printing conditions, the image forming apparatus includes control means for controlling the toner pattern formation timing by the pattern forming means and the toner pattern detection timing by the toner pattern detection means. The formation timing and the detection timing are controlled such that the toner pattern is formed and detected without the system being lowered between sheets during continuous printing of sheets. Here, the system shutdown means that the LD in the system is turned off, the polygon motor is stopped, or the photosensitive member is stopped.

  The second means is a light writing means for performing line scanning by a light beam emitted from a light emitting source controlled to be turned on according to image data in the first means, and writing the image on the scanning line. A light beam detecting means for detecting; and a correcting means for correcting at least one of a density correction of an image written by the light writing means and a positional deviation correction of a writing position obtained from a detection result by the light beam detecting means. It is characterized by.

  The third means is characterized in that in the second means, formation of the toner pattern, detection of the toner pattern, and correction by the correction means are performed within the same sheet.

  The fourth means includes a transfer means for transferring an image formed on the image carrier onto a transfer paper in any one of the first to third means, and the control means is configured to transfer the image to the transfer means. The toner pattern is formed at a timing when the toner pattern passes after being separated from the carrier.

  A fifth means is characterized in that, in the fourth means, a misregistration correction pattern is formed after the transfer means is separated from the image carrier.

  The sixth means is characterized in that, in the fourth or fifth means, a cleaning blade wrinkle prevention pattern is formed between the sheets.

  A seventh means is characterized in that, in the sixth means, images are formed in the order of a density correction pattern, a cleaning blade wobbling prevention pattern, and a positional deviation correction pattern.

  The eighth means is characterized in that, in any one of the fourth to sixth means, the image formation timing of the toner pattern is managed by using a negation of an FGATE signal indicating that an image is being created as a trigger.

  The ninth means is characterized in that, in any one of the fourth to eighth means, the image carrier is an intermediate transfer belt, and the transfer means is a secondary transfer device.

  A tenth means includes a plurality of image forming methods in which a toner pattern is formed on an image carrier, the formed toner pattern is detected, and various printing conditions are controlled based on the detected result of the toner pattern. The formation timing and the detection timing are set such that the formation and detection of the toner pattern can be performed without the system being lowered between sheets during continuous printing of sheets.

  The eleventh means is characterized in that, in the tenth means, at least one of density correction of the detected toner pattern image and position deviation correction of the toner pattern writing position is performed.

  A twelfth means is characterized in that, in the eleventh means, the toner pattern is formed, the toner pattern is detected, and the displacement is corrected within the same sheet.

  In an embodiment described later, the image carrier is on the photosensitive member 201 or the intermediate transfer belt 208, the pattern forming unit is on the writing unit 202, the charging unit 201 and the developing unit 203, and the toner pattern detection unit is on the pattern detection sensor 210. The control unit is the control unit 300 and the timing control unit 120, the optical writing unit is the writing unit 202, the light beam detecting unit is the synchronization detection plates 106a and 106b, the correcting unit is the control unit 300, and the transfer unit is the secondary transfer unit. 209, the misregistration correction pattern corresponds to the M pattern, the cleaning blade wobbling prevention pattern corresponds to the B pattern, and the density correction pattern corresponds to the P pattern.

  According to the present invention, it is not necessary to open the sheet because the system is not shut down. As a result, it is possible to perform a predetermined correction process without reducing productivity.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an optical writing device in an image forming apparatus according to an embodiment of the present invention. The optical writing device 1 according to the present embodiment includes a writing optical system 11 and a writing control system 12. The writing optical system 11 is provided outside a writing scanning range to a photoconductor (not shown), a semiconductor laser (hereinafter referred to as LD) 101 as a light source, a polygon mirror 102 as a scanning means, an Fθ lens 103 as a scanning speed conversion means. The first and second reflection mirrors 105a and 105b, the first and second synchronization detecting plates 106a and 106b to which the scanning light reflected by the first and second reflection mirrors 105a and 105b is input, and image formation It is mainly composed of a dust-proof glass 104 that is provided at the boundary to the image forming unit and prevents dust from entering the image forming unit side, and a polygon control unit 108 that controls the driving of the polygon motor that rotationally drives the polygon mirror 102. Yes.

  The writing control system 12 includes a dot position deviation detection / control unit 112 to which position detection signals from the first and second synchronization detection plates 106a and 106b are input, and a control output from the dot position deviation detection / control unit 112. The pixel clock generation unit 111 that generates the pixel clock, the image processing unit 113 that receives the pixel clock generated by the pixel clock generation unit 111, the pixel clock from the pixel clock generation unit 111, the first The synchronization detection signal from the synchronization detection plate 106a and the image data for image writing from the image processing unit 113 are input, and the LD drive data generation unit 110 that generates LD drive data and the LD drive data generation unit 110 generate the LD drive data. An LD drive data is inputted and an LD control unit 107 that performs lighting control of the LD 101 is schematically configured.

  The timing controller 120 generates various timing signals such as FGATE representing an image area in the sub-scanning direction and RGATE representing an image area in the main scanning direction. The image forming timing is generated based on the synchronization detection signal from the synchronization detection plate 106a and is input to the LD drive data generation unit 110 and the pixel clock generation unit 111.

  In the optical writing apparatus schematically configured as described above, the laser light from the LD 101 is scanned in the main scanning direction by the polygon mirror 102, converted from constant angular velocity deflection to constant velocity deflection by the Fθ lens 103, and from the dust-proof glass 104. The light is emitted to the image forming device side. The polygon control unit 108 controls the rotation of the polygon mirror 102, and the effective writing start position and end position of the scanning laser beam scanned by the polygon mirror 102 are detected by the first and second synchronization detection plates 106a and 106b, respectively. The The detected position detection information is input to the dot position deviation detection / control unit 112. The dot position deviation detection / control unit 112 measures the time during which the laser beam scans between the first and second synchronization detection plates 106a and 106b, and compares it with the scanning time when ideal scanning is performed. Thus, the amount of deviation of the scanning time is obtained, phase data for correcting the amount of deviation is generated and output to the pixel clock generation unit 111.

The pixel clock generation unit 111 performs a phase shift that changes the phase of the clock generated by the PLL based on the PLL that generates the clock and the phase data. A detailed description of the PLL is omitted,
F = CLKref × [N set value] / [M set value]
The clock can be set by [N setting value] and [M setting value] in the calculation formulas. The reference frequency CLKref of the PLL is input by a crystal oscillator.

  When the pixel clock generation unit 111 does not include a phase data storage circuit, the dot position deviation detection / control unit 112 outputs phase data to the pixel clock generation unit for each line, but includes a phase data storage circuit. In such a case, the phase data is obtained in advance to the pixel clock generator 111 in advance. In addition, the dot position deviation detection / control unit 112 not only provides phase data (first phase data) for always performing the same correction for each line that corrects scanning unevenness caused by the characteristics of the scanning lens, but also the polygon mirror 102. When phase data (second phase data) corresponding to correction that changes for each line such as rotation unevenness is also generated and the pixel clock generation unit 111 includes a phase data synthesis circuit, the phase data is generated. Are also output to the pixel clock generator 111.

  The pixel clock generation unit 111 generates a pixel clock based on the phase data from the dot position deviation detection / control unit 112 and supplies the pixel clock to the image processing unit 113 and the LD drive data generation unit 110. The image processing unit 113 generates image data based on the pixel clock, and the LD drive data generation unit 110 inputs the image data, and similarly generates laser drive data (modulation data) based on the pixel clock. The LD 101 is driven via the LD driver 107. The LD driving unit 107 has a function (hereinafter referred to as shading) for changing the light amount of each area in the main scanning direction.

  In the write control system 12 having such a configuration, it is possible to shift the phase of the pixel clock PCLK by +1/8 PCLK and −1/8 PCLK by providing phase data in synchronization with the pixel clock PCLK. That is, by shifting the phase of the image clock serving as the reference clock of the image data, the scanning speed unevenness generated by the deflector of the writing optical system 11 including the polygon mirror 102 and the transmission wavelength between the light emitting sources in the multi-beam optical system It is possible to correct a dot position shift in the main scanning direction due to an exposure shift caused by the difference with an accuracy of phase shift (for example, 1/8 PCLK). The method of changing the phase shift and the dot position to an arbitrary position is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-279873, and is a publicly known matter.

  FIG. 2 is an explanatory diagram showing a dot position shift correction operation. The “ideal state” in FIG. 2 indicates the dot position in the ideal state in which the scanning speed unevenness and the exposure deviation as described above do not occur at all. When 1200 dpi (dot diameter is about 21.2 μm), continuous six dots are scanned. It is the result. “Before correction” in FIG. 2 indicates that the dot position accuracy of the first dot is the same, but the dot position shift due to the scanning speed unevenness and the exposure shift has occurred, and the sixth dot is in an ideal state. On the other hand, a dot position shift of 10.6 μm corresponding to 1/2 dots of 1200 dpi occurs. Since the time required for writing one dot in this state is equivalent to one pixel clock = 1PCLK, this means that when the phase shift resolution is 1/8 PCLK, that is, the dot position can be corrected with 1/8 dot accuracy.

  In “after correction” in FIG. 2, when the phase shift resolution is 1/8 dot, that is, 1/8 PCLK, the phase shift of −1/8 PCLK from the state before correction in which a ½ dot position shift has occurred from the ideal state is data. By performing four times in the area, the dot position of the sixth dot can theoretically be shifted by −1/8 PCLK × 4 = −1 / 2 PCLK, and the dot position can be adjusted with an accuracy of 1/8 PCLK with respect to the ideal state. It can be corrected.

  The dot position deviation detection / control unit 112 measures the time difference during which the laser beam is scanned. This measurement method is disclosed in, for example, Japanese Patent Laid-Open No. 9-58053, and includes the first synchronization detection plate 106a. When the second synchronization detection plate 106b receives the laser beam, the detection signals DETP1 and DETP2 are respectively input to the dot position deviation detection and control unit 112, and the dot position deviation detection and control unit 112 receives the detection signals DETP1 and DETP2. Based on this, the number of counts of a predetermined clock from when the first detection plate 106a detects the laser light to when the second detection plate 106b detects the laser light is measured. A time difference is obtained from the measured count.

  FIG. 3 is a block diagram showing details of the LD control unit 107. The LD control unit 107 includes an LD driver 107a and a DAC 107b, and turns on the LD 101 by the LD driver 107a based on the image data from the laser drive data generation unit 110. The light quantity is adjusted with reference to the light quantity reference voltage 107c from the DAC 107b. A light amount reference voltage value is set to the DAC 107b from a CPU (not shown). The DAC 107b also has a function of changing the reference voltage, which is a shading function.

  FIG. 4 is a diagram showing a schematic configuration of the image forming unit. The image forming unit basically includes an image forming unit 200, a writing unit 100, and a control unit 300 for controlling them. In the writing unit 100, four optical writing devices 1 shown in FIG. 1 are provided for each color of YMCK, and optical writing is performed for each color. Hereinafter, one color, K color in the figure, will be described as an example.

  In the case of forming an image, the photosensitive member 201 is charged by the charging unit 202, the LD light modulated according to the image data is irradiated from the writing unit 100 to the photosensitive member 201, and an electrostatic latent image is formed on the surface of the photosensitive member 201. Form. The electrostatic latent image on the photoconductor 201 is developed by the developing unit 203 by attaching toner of a color corresponding to the photoconductor 201, and the visualized toner image is transferred to the intermediate transfer belt 208 by a primary transfer unit (not shown). Primary transfer. In the present embodiment, the image is transferred to the intermediate transfer belt 208 in the order of Y → C → M → K and superimposed to form a full color image. On the other hand, the transfer paper is fed from the paper feed unit 204, and the full-color image is secondarily transferred from the intermediate transfer belt 208 onto the transfer paper in the secondary transfer unit 209. In this embodiment, a secondary transfer roller is used for the secondary transfer unit 209. The color image transferred onto the transfer paper is fixed by the fixing unit 205 at the next stage. Further, an excessive toner image remaining on the surface of the photoconductor 201 is removed by the cleaning unit 207. In the present embodiment, a pattern detection sensor 210 is provided on the downstream side of the secondary transfer unit 209, and the toner pattern is detected by the pattern detection sensor 210.

  The control unit 300 includes a CPU, a ROM, and a RAM (not shown), and controls the entire image forming apparatus including each unit such as the writing unit 100, the image forming unit 200, the fixing unit 205, the paper feeding unit 204, and the image forming unit. The sensor output of the pattern detection sensor 210 is input to the control unit 300. The control unit 300 performs image formation control for position deviation correction, density correction, and cleaning blade wrinkle prevention according to the detected toner density and pattern deviation. Controls such as these are also executed.

  FIG. 5 is a timing chart showing the relationship between the LD lighting and the secondary transfer roller contact / separation timing of the secondary transfer unit 209 in the inter-sheet control (hereinafter, the inter-sheet interval is referred to as a conventionally used inter-sheet interval). . A print start trigger STTRIG is input to the timing control unit 120 of the write control system 12 from a CPU (not shown) that controls the control unit 300. The timing control unit 120 performs XPFGATE_ * (* indicates all of Y, C, M, and K, the same applies hereinafter) indicating the image area in the sub-scanning direction at a predetermined timing based on the linear velocity and resolution, and LD driving that is another module. The data is output to the data generation unit 110 and the pixel clock generation unit 111. The LD drive data generation unit 110 converts input image data from an unillustrated ASIC (not shown) into LD drive data in accordance with the period when XPFGATE_ * is LOW, and the LD control unit 107 is generated by the LD drive data generation unit 110. The LD 101 is turned on based on the LD drive data. Further, the timing control unit 120 rotates the pattern sub-scan counter from the XPFGATE_ * negate of each color, and corrects the density correction pattern (hereinafter referred to as the P pattern), the blade blurring prevention pattern (hereinafter referred to as the B pattern), and the positional deviation correction. The timing of the pattern for use (hereinafter referred to as M pattern) is also output to the LD drive data generation unit 110, and the LD drive data generation unit 110 generates LD drive data for writing the P pattern, B pattern, and M pattern. The generation timing of the P pattern, B pattern, and M pattern can be set at an arbitrary position in units of sub-scanning dots.

  The secondary transfer roller separation timing of the secondary transfer unit 209 is controlled by inputting XPPFGATE_K as an interrupt signal to the CPU, and the CPU rotates the timer based on the input of the interrupt signal to control the secondary transfer roller. It is set after passing (after transferring the image) (period A in FIG. 7... Period from the negation of XPFGATE_K to the start of separation of the secondary transfer roller). Further, the M pattern is set in the timing control unit 120 so that the LD 101 is turned on after exposure of the secondary transfer roller (denoted as secondary point separation in the drawing) (so that the photosensitive member 201 is exposed) (FIG. 7). B period). The contact timing of the secondary transfer roller is set after the M pattern is detected, and is executed by the CPU. Then, after performing various corrections, continuous printing is resumed.

  Here, the density correction pattern (P pattern) and density correction control will be described. Since the formation of the P pattern and the density correction control using the P pattern are known techniques as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-258040, only the outline is given and details are omitted.

  The pattern detection sensor 210 also functions as a means for detecting the toner adhesion amount, and is disposed at a position facing the intermediate transfer belt 208. The pattern detection sensor 210 includes a light emitting element such as a light emitting diode and a light receiving element such as a photodiode. The pattern detection sensor 210 detects the amount of toner attached to a plurality of patch patterns (toner images) formed on the intermediate transfer belt 208 and the amount of toner attached to the background portion on the intermediate transfer belt 208 at a predetermined timing. Is done. Specifically, the pattern detection sensor 210 detects the toner adhesion amount of the patch pattern, and based on the detection result (voltage output corresponding to the amount of received light), the image forming conditions on the intermediate transfer belt 208, that is, the development bias, The charging potential and exposure potential (exposure amount) are optimally adjusted and controlled. The P pattern itself forms a plurality of patterns having different densities by developing bias control. Although details are omitted, this is done by controlling the developing bias by the CPU.

  A power supply unit (not shown) supplies a developing bias to the developing roller of the developing unit 203. The magnitude of the developing bias can be changed by a CPU (not shown) of the control unit 300. The power supply unit supplies a charging voltage to the charging unit 202. The magnitude of the charging voltage can be changed by the CPU. Thereby, the charging potential on the photosensitive member 201 can also be changed. The output of the laser beam emitted from the LD control unit 107 can be changed by the CPU of the control unit 300, and the exposure potential on the photoconductor 201 also changes due to the change in the output of the laser beam. A potential sensor (not shown) is disposed at a position facing the photoconductor 201 in order to detect the surface potential of the surface of the photoconductor 201. The potential sensor detects a latent image potential (exposure potential) in a plurality of patch patterns (latent images) formed on the photoconductor (drum) 201 at a predetermined timing.

  On the other hand, the formed image has a gradation whether it is monochrome or color. Therefore, it is necessary to correct when the gradation (density) does not correspond to the input data. This gradation correction (correcting the density) is performed based on the density detected from a plurality of patch patterns created on the photoconductor 201 through an image forming process such as charging, optical writing, and development. Specifically, the density (strictly, the latent image potential) varies stepwise while changing the output of the laser beam at a position on the photoconductor 201 facing the pattern detection sensor 210 and the potential sensor. A patch pattern is formed. Since the number of patch patterns to be created varies depending on the gradation of the image to be formed, patch patterns having the number of densities corresponding to the number of gradations are formed. Next, a latent image potential on each patch pattern is detected by the potential sensor. The potential data detected by this potential sensor is transmitted to and held by a control unit (not shown). Next, each of the plurality of patch patterns is visualized by the developing unit 203. Then, the reflected light amounts of the plurality of patch patterns that have reached a position facing the pattern detection sensor 210 are respectively detected by the pattern detection sensor 210. The toner adhesion amount is obtained based on a plurality of detection values corresponding to the number of patch patterns at this time.

Specifically, based on the output value of the pattern detection sensor 210, it is compared with data relating to the toner adhesion amount stored in advance in the control unit 300. The data relating to the toner adhesion amount is a table of the relationship between the normalized value of the output of the pattern detection sensor 210 and the toner adhesion amount, and the data is converted into the toner adhesion amount per unit area from this table. Is stored in the control unit 300. Next, a linear approximate expression indicating the relationship between the development potential and the toner adhesion amount is calculated. As shown in FIG.
Y = A × X + B
And obtained from the toner adhesion amount data stored in the RAM of the control unit 300 and the latent image potential (exposure potential) data. In FIG. 6, the X-axis indicates a value obtained by subtracting the developing bias applied at that time from the exposure potential, that is, the developing potential, and the Y-axis indicates the toner adhesion amount per unit area.

  Then, based on the data stored in the control unit, data is plotted on the XY plane by the number corresponding to the number of patch patterns. Then, a section on the XY plane for performing linear approximation is determined from the plurality of plotted data. Thereafter, within the section, the least square method is performed to obtain the linear approximation formula (Y = A × X + B). At this time, the development gamma and the development start voltage VK are calculated based on the linear approximation formula. Specifically, the development gamma γ is calculated as the slope of the linear approximation formula (γ = A), and the development start voltage VK is calculated as the intersection of the linear approximation formula and the X axis (VK = −B / A). In this way, the developing ability (a quantified value) in the image forming apparatus is calculated. Next, the calculated development gamma is stored in the RAM of the control unit 300. Further, the image forming conditions are corrected based on the obtained development gamma. Specifically, each of them is adjusted and controlled so that the charging potential, the exposure potential, and the developing bias are optimum for the obtained development gamma. In this way, P pattern formation and density correction control are performed.

  Next, the blade wobbling prevention pattern (B pattern) and its correction control will be described. The B pattern and its correction control are disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-234358 and are publicly known matters, and therefore only the outline is described here and the details are omitted.

  FIG. 7 is a schematic diagram of a toner image formed for preventing the cleaning blade from curling. For the sake of clarity, the photosensitive member 201 is illustrated as being spaced downward from the intermediate transfer belt 208. The toner image 21 that is normally formed for preventing the cleaning blade from curling is formed at a rate of once for a plurality of copying processes, and is formed during the interval between sheets to fill the maximum image width of the photoconductor (drum) 201. For this reason, the amount of toner on the intermediate transfer belt 208 due to the toner adhering to the non-image portion is smaller in the R2 region, which is the paper passing portion through which the transfer paper S passes, than the R1 and R3 regions for the transfer paper size. The size of the toner image is detected by a transfer paper size detection unit (not shown), and the irradiation time of the light to be written in the R1 and R3 regions is changed by a signal from the control unit 300, so that a toner image (B pattern) for preventing blurring is created. By controlling the image area, the image forming area of the toner image for preventing blurring (B pattern) in the R2 region is increased to a level that can prevent the transfer cleaning blade from curling according to the transfer paper size. Alternatively, control is performed to reduce the image formation area of the toner image (B pattern) for preventing blurring in the R1 and R3 regions to a level at which no cleaning failure occurs according to the transfer paper size. As a result, the amount of toner input to the transfer cleaning blade (not shown) at the end portion and the sheet passing portion on the intermediate transfer belt 208 can be kept constant, and the transfer cleaning blade can be prevented from wobbling and poor cleaning.

  For this purpose, the toner density of the toner adhering to the non-image area is detected by a plurality of P sensors provided on the intermediate transfer belt 208, and the image formation area of the toner image for preventing the transfer cleaning blade from blurring is controlled based on the detected density. To do. For this control, the image formation area of the blade blurring prevention toner image is increased when the amount of toner in the non-image area is small, and the image area of the blade blurring prevention toner image is increased when the amount of toner in the non-image area is large. The transfer efficiency is lowered by changing the transfer current during the transfer of the toner image for preventing the blade blurring.

  Also in this case, the pattern detection sensor 210 is used, a constant voltage is applied to the light emitting element of the sensor, the detection light is emitted to the surface of the photosensitive member 201, the reflected light is received by the light receiving element, and the photoelectrically converted voltage value Thus, the toner amount on the intermediate transfer belt 208 is detected. The control is executed according to a signal from the control unit 300 according to the detected toner amount, and the amount of toner input to the edge of the transfer cleaning blade can be kept constant, thereby preventing poor cleaning and blade curling. it can.

As described above, according to the present embodiment, the following effects can be obtained.
1) Conventionally, when creating a misregistration correction pattern during continuous printing, a position detection pattern is formed on the transport belt by changing the sheet interval, or detection and correction by image formation of a toner pattern is performed during continuous printing. At this time, since the machine (system) was once shut down, the productivity of image formation was lowered. However, according to the present embodiment, when performing detection and correction by image formation of a toner pattern in continuous printing, the system Since the pattern creation, detection, and correction are performed only by setting the timing without performing the fall of, productivity does not decrease.

2) In a system having a secondary transfer roller and no secondary transfer roller cleaning mechanism, when a toner pattern is formed in an area where the secondary transfer roller is in contact with the intermediate transfer belt and is not transferred to transfer paper, Although the transfer roller is soiled with toner and the backing paper is soiled, according to this embodiment, the pattern image is formed at the timing when the toner pattern passes after the separation of the secondary transfer roller. It is possible to prevent the back paper from being soiled by toner stains.

3) If the secondary transfer roller is separated during the image formation of the misregistration correction pattern, a pattern different from the original misregistration correction pattern may be formed due to the shock of the separation. According to the method, since the image for the misalignment correction pattern is formed after the secondary transfer roller is separated, the alignment correction can be performed with high accuracy.

4) Although it is necessary to form an image for preventing the cleaning blade from rolling under certain conditions, if the image is formed independently and the secondary transfer roller is separated, the waiting time increases for the user. However, according to the present embodiment, the gap is formed between the sheets and between the misregistration correction pattern and the density correction pattern, so there is no need to leave a gap between the sheets nor to bring down the machine once. The waiting time of the user does not increase.

5) In a system in which various process conditions such as a developing bias are changed when a density correction pattern is formed, if a position shift correction pattern is formed before the condition is changed to the normal state, the position shift cannot be corrected with high accuracy. Further, when the process conditions are changed to the normal state, it takes time to perform the image forming order of the pattern for preventing positional deviation and blade swell. However, according to the present embodiment, since the pattern image forming order is the density correction pattern, the cleaning blade wobbling prevention pattern, and the positional deviation correction pattern, the positional deviation correction can be performed with high accuracy and correction. Can be shortened.

6) Conventionally, when forming a pattern between sheets, it is difficult to set the pattern formation timing, and it is difficult to accurately manage the pattern formation timing between sheets. However, according to the present embodiment, the timing is managed with the negation of the FGATE signal as a trigger, so that the timing management can be performed with high accuracy.

  In this embodiment, a tandem color image forming apparatus is described as an example. However, the present invention is applied to an optical writing apparatus or a color image forming apparatus that forms a pattern between papers and corrects an image misalignment. Can do. In addition, the present invention can also be applied to those that form density correction and / or a cleaning blade wobbling prevention pattern.

1 is a diagram illustrating a schematic configuration of an optical writing device in an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the correction | amendment operation | movement of a dot position shift in embodiment of this invention. It is a block diagram which shows the detail of the LD control part in embodiment of this invention. It is a figure which shows schematic structure of the image creation part in embodiment of this invention. 6 is a timing chart showing the relationship between the LD lighting and the secondary transfer roller contact / separation timing of the secondary transfer unit in the sheet interval control in the embodiment of the present invention. It is a figure which shows the linear approximation formula which shows the relationship between the developing potential used for density correction, and the toner adhesion amount. FIG. 6 is a schematic diagram of a toner image formed for preventing the cleaning blade from curling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical writing apparatus 11 Writing optical system 12 Writing control system 100 Writing unit 101 LD
DESCRIPTION OF SYMBOLS 102 Polygon mirror 103 F (theta) lens 105a, 105b Reflection mirror 106a, 106b Sync detection board 107 LD control part 110 LD drive data generation part 111 Pixel clock generation part 112 Dot position shift detection, control part 120 Timing control part 200 Image formation part 201 Photosensitive Body 202 charging unit 203 developing unit 204 sheet feeding unit 205 fixing unit 207 cleaning unit 208 intermediate transfer belt 209 secondary transfer unit 210 pattern detection sensor 300 control unit

Claims (12)

Pattern forming means for forming a toner pattern on the image carrier;
Toner pattern detecting means for detecting the toner pattern;
An image forming apparatus that controls various printing conditions based on the detection result of the toner pattern,
Control means for controlling the formation timing of the toner pattern by the pattern formation means and the detection timing of the toner pattern by the toner pattern detection means;
The control means controls the formation timing and the detection timing so that the toner pattern is formed and detected without the system being lowered between sheets during continuous printing of a plurality of sheets. An image forming apparatus. A light writing unit that performs line scanning by a light beam emitted from a light source that is controlled to be turned on according to image data, and writes an image;
A light beam detecting means for detecting the light beam on a scanning line;
Correction means for correcting at least one of density correction of an image written by the light writing means and position shift correction of a writing position obtained from a detection result by the light beam detection means;
The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 2, wherein the toner pattern is formed, the toner pattern is detected, and correction is performed by the correction unit within the same sheet. A transfer means for transferring the image formed on the image carrier to transfer paper;
4. The image according to claim 1, wherein the control unit forms the toner pattern at a timing when the toner pattern passes after the transfer unit is separated from the image carrier. 5. Forming equipment.   The image forming apparatus according to claim 4, wherein the transfer unit forms a misregistration correction pattern after the transfer unit is separated from the image carrier.   6. The image forming apparatus according to claim 4, wherein a pattern for preventing a cleaning blade from curling is formed between the sheets.   7. The image forming apparatus according to claim 6, wherein the image is formed in the order of a density correction pattern, a cleaning blade wobbling prevention pattern, and a positional deviation correction pattern.   7. The image forming apparatus according to claim 4, wherein image forming timing of the toner pattern is managed using a negation of an FGATE signal indicating that an image is being created as a trigger.   The image forming apparatus according to claim 4, wherein the image carrier is an intermediate transfer belt, and the transfer unit is a secondary transfer device. In an image forming method for forming a toner pattern on an image carrier, detecting the formed toner pattern, and controlling various printing conditions based on the detected result of the toner pattern,
The image formation is characterized in that the formation timing and the detection timing are set so that the toner pattern is formed and detected without a system shutdown between a plurality of sheets during continuous printing. Method.   11. The image forming method according to claim 10, wherein at least one of density correction of the image of the detected toner pattern and position deviation correction of the writing position of the toner pattern is performed.   The image forming method according to claim 11, wherein the toner pattern is formed, the toner pattern is detected, and the misregistration is corrected between the same sheets.

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