JP5565217B2 - Optical writing apparatus, image forming apparatus, and optical writing control method - Google Patents

Description

  The present invention relates to an optical writing device, an image forming apparatus, and an optical writing control method.

  In recent years, there has been a tendency to digitize information, and image processing apparatuses such as printers used for outputting digitized information, facsimiles, scanners used for digitizing documents have become indispensable devices. Yes. Such an image processing apparatus is often configured as a multifunction machine that can be used as a printer, a facsimile machine, a scanner, or a copier by providing an imaging function, an image forming function, a communication function, and the like.

  Among such image processing apparatuses, an electrophotographic system is widely adopted in image forming apparatuses used for outputting digitized documents. In an electrophotographic image forming apparatus, an electrostatic latent image is formed by exposing a photoreceptor, and the electrostatic latent image is developed using a developer such as toner to form a toner image. Paper output is performed by transferring the image to paper.

  In such an electrophotographic image forming apparatus, adjustment is made so that an image is formed in the correct range of the paper by aligning the timing of forming the electrostatic latent image by exposing the photoconductor to the timing of transporting the paper. Is done. Also, in a tandem image forming apparatus that forms a color image using a plurality of photoconductors, the exposure timing of each color photoconductor can be adjusted so that the images developed on the photoconductors of each color are accurately superimposed. (For example, refer to Patent Document 1).

  The electrophotographic image forming apparatus described above includes an intermediate transfer system in which a toner image developed on a photoconductor is transferred to an intermediate transfer belt and then transferred and fixed on a sheet, and a toner developed on the photoconductor There is a direct transfer method in which an image is directly transferred to a sheet. In either case, the toner image is transferred in a state where the photosensitive member is in contact with the transfer object to be transferred. In the following description, the intermediate transfer belt in the intermediate transfer system and the transport belt that transports paper in the direct transfer system are collectively referred to as a transport body.

  Further, in a tandem type color image forming apparatus, when performing monochrome image formation, a photosensitive drum for forming a color other than black is separated from the above-described conveyance body. This is to prevent image disturbance due to toner leaking from a photoconductor other than black adhering to the conveyance body.

  In this type of image forming apparatus, the conveyance body expands and contracts due to a change in the internal temperature of the apparatus, resulting in a difference in the conveyance timing of the conveyance body. Therefore, in Patent Document 1, the timing adjustment process is repeatedly executed at a predetermined timing. However, in the timing adjustment process of Patent Document 1, the difference between the case where the photoconductor and the conveyance body are in contact with each other and the case where they are separated from each other is not taken into consideration.

  That is, in the timing adjustment process, as described above, the positional deviation correction between the photoconductors of the respective colors is also performed. Therefore, the adjustment process is often performed in a state where all the photoconductors are in contact with the conveyance body. . The result of executing the adjustment process in this manner is effective when all the photoconductors are in contact with the transport body.

  However, the result of the adjustment process executed in a state where all the photoconductors are in contact with the conveyance body is inappropriate in a state where some of the photoconductors are in contact (some photoconductors are separated). It may have become. On the other hand, the result of the adjustment process executed with some of the photoconductors in contact with each other may be inappropriate when all the photoconductors are in contact with the transport body. Furthermore, since the transport body may expand and contract due to heat or the like, it is desirable to consider the expansion and contraction of the transport body.

  Therefore, the present invention adjusts the position of an image in the sub-scanning direction in an image forming apparatus having a function of abutting and separating a plurality of photosensitive members and a conveying member that transfers an image developed on the photosensitive member. One of the purposes is to perform with higher accuracy.

  In one aspect of the present invention, there is provided an optical writing device that forms an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with a light beam, and the light source includes: A light source control unit for controlling and irradiating a light beam, and an image transferred on the surface of the carrier by an output signal of a sensor for detecting the surface of the carrier on which the image developed on the photosensitive member is transferred An image detection unit that detects that the image sensor is in a position facing the sensor, and the image detection unit starts the first drawing after the light source control unit starts processing to form a first drawing pattern on the carrier. A first detection period counting unit that counts a first detection period as a period until a pattern is detected, and a first reference value as a reference of the first detection period and the first detection period. Calculate offset as difference An offset calculation unit, a second detection period counting unit that counts a second detection period as a period in which the image detection unit has detected two locations of the second drawing pattern drawn on the carrier, An expansion / contraction rate calculation unit that calculates an expansion / contraction rate of the transport body by comparing the second detection period and a second reference value as a reference of the second detection period, and a part of the plurality of photoconductors The contact / separation difference as a difference between the first detection period in a state where the toner is in contact with the transport body and the first detection period in a state where all of the plurality of photosensitive members are in contact with the transport body The contact / separation difference calculating unit for calculating the difference between one of the plurality of photoconductors and the state where all of the plurality of photoconductors are in contact with the transfer body. The corresponding offset, the calculated contact / separation difference, and the calculation Based on the scaling factor, and one comprising the, a correction control unit for correcting the timing for irradiating a light beam to the light source in the other state.

  According to another aspect of the present invention, there is provided an optical writing device for forming an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with a light beam, and a light source for irradiating the light beam; A light source control unit that controls the light source to emit a light beam and an output signal of a sensor that detects the surface of the carrier on which the image developed on the photosensitive member is transferred are transferred to the surface of the carrier. An image detection unit that detects that an image is located at a position facing the sensor, and the image detection unit that has started the process of forming a first drawing pattern on the transport body by the light source control unit. A first detection period counting unit that counts a first detection period as a period until one drawing pattern is detected; a temperature detection unit that detects a temperature inside or around the optical writing device; Before The first detection period, or an offset as a difference between the first detection period and the first reference value as a reference of the first detection period, the predetermined temperature, the detected temperature and the A data accumulation processing unit that stores a plurality of photoconductors in association with the contact state of the photoconductors, and a predetermined storage unit that refers to one of the plurality of photoconductors corresponding to the detected temperature. Contact and separation as a difference between the first detection period when the portion is in contact with the transport body and the first detection period when all of the plurality of photoconductors are in contact with the transport body One of a contact / separation difference calculating unit that calculates a difference, a state where a part of the plurality of photosensitive members is in contact with the transport body, and a state where all of the plurality of photosensitive members are in contact with the transport body The offset corresponding to and the calculated contact / separation difference Based on, and one comprising the, a correction control unit for correcting the timing for irradiating a light beam to the light source in the other state.

  According to the present invention, the adjustment of the position of the image in the sub-scanning direction can reflect the expansion / contraction state of the conveyance body in addition to the contact state of the plurality of photosensitive members with respect to the conveyance body. The position of the image can be adjusted with higher accuracy.

FIG. 1 is a block diagram showing a hardware configuration of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating a functional configuration of the image forming apparatus. FIG. 3 is a diagram illustrating a configuration of a print engine included in the image forming apparatus. FIG. 4 is a top view illustrating a configuration of an optical writing device included in the image forming apparatus. FIG. 5 is a side sectional view showing the configuration of the optical writing device. FIG. 6 is a block diagram illustrating a control unit of the optical writing device. FIG. 7 is a schematic diagram illustrating an example of a relationship between a first reference value, a first detection period, an offset, and a contact / separation difference. FIG. 8 is a schematic explanatory diagram illustrating an example of the relationship between the second reference value, the second detection period, and the expansion / contraction rate. FIG. 9 is a diagram illustrating an example of a drawing pattern drawn by the positional deviation correction processing of the optical writing device. FIG. 10 is a diagram illustrating another example of the drawing pattern drawn by the positional deviation correction processing of the optical writing device. FIG. 11 is a diagram illustrating a configuration of the print engine, and is a diagram illustrating an example of a state in which all the photoconductors are in contact with the conveyance body. FIG. 12 is a diagram illustrating a configuration of the print engine, and is a diagram illustrating an example of a state in which one photoconductor is in contact with the conveyance body. FIG. 13 is a diagram illustrating a configuration of the print engine, and is a diagram illustrating another example of a state in which one photoconductor is in contact with the conveyance body. FIG. 14 is a diagram illustrating a configuration of the print engine, and is a diagram illustrating an example of a state in which two photoconductors are in contact with the conveyance body. FIG. 15 is a diagram illustrating the configuration of the print engine, and is a diagram illustrating still another example of a state in which one photoconductor is in contact with the conveyance body. FIG. 16 is a flowchart illustrating an example of misalignment correction processing in the optical writing device. FIG. 17 is a diagram illustrating an example of a determination criterion for the misregistration correction process in the optical writing device. FIG. 18 is a flowchart illustrating an example of a positional deviation correction process in the optical writing device of the image forming apparatus according to the first embodiment of the present invention. FIG. 19 is a graph schematically showing an example of the correlation between the detected temperature and the offset stored in association with the temperature. FIG. 20 is a diagram showing a configuration of a print engine according to another embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an image forming apparatus as an MFP (Multi Function Peripheral) will be exemplified. The image forming apparatus according to the present embodiment is an electrophotographic image forming apparatus, and the gist thereof is correction of an image writing position in the sub-scanning direction in an optical writing apparatus for forming an electrostatic latent image on a photoreceptor. is there. Moreover, the same component is contained in several embodiment shown below. Therefore, in the following, common reference numerals are given to those similar components, and redundant description is omitted.

<First Embodiment>
FIG. 1 is a block diagram illustrating a hardware configuration of an image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, an image forming apparatus 1 according to the present embodiment includes an engine that executes image formation in addition to the same configuration as an information processing terminal such as a general server or a PC (Personal Computer). That is, the image forming apparatus 1 according to the present embodiment includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 11, a ROM (Read Only Memory) 12, an engine 13, an HDD (Hard Disk Drive) 14, and an I / F15, an NVRAM (Non Volatile RAM) 19 as a nonvolatile storage unit, and the like are connected via a bus 18. In addition, an LCD (Liquid Crystal Display) 16 and an operation unit 17 are connected to the I / F 15.

  The CPU 10 is a calculation unit and controls the operation of the entire image forming apparatus 1. The RAM 11 is a volatile storage medium capable of reading and writing information at high speed, and is used as a work area when the CPU 10 processes information. The ROM 12 is a read-only nonvolatile storage medium, and stores programs such as firmware. The NVRAM 19 is a non-volatile storage unit that can read and write information, and stores correction values, differences, and the like (detailed later) used in the positional deviation correction processing. The engine 13 is a mechanism that actually executes image formation in the image forming apparatus 1.

  The HDD 14 is a nonvolatile storage medium capable of reading and writing information, and stores an OS (Operating System), various control programs, application programs, and the like. The interface (I / F) 15 connects and controls the bus 18 and various hardware and networks. The LCD 16 is a visual user interface for the user to check the state of the image forming apparatus 1. The operation unit 17 is a user interface such as a keyboard and a mouse for the user to input information to the image forming apparatus 1.

  In such a hardware configuration, a program stored in a recording medium such as the ROM 12, the HDD 14, or an optical disk (not shown) is read into the RAM 11, and operates according to the control of the CPU 10, thereby configuring a software control unit. A functional block for realizing the functions of the image forming apparatus 1 according to the present embodiment is configured by a combination of the software control unit configured as described above and hardware.

  Next, an example of a functional configuration of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating an example of a functional configuration of the image forming apparatus 1 according to the present embodiment. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment includes a controller 20, an ADF (Auto Document Feeder) 21, a scanner unit 22, a paper discharge tray 23, a display panel 24, and a paper feed. A table 25, a print engine 26, a paper discharge tray 27, a network I / F 28, and the like are included.

  The controller 20 includes a main control unit 30, an engine control unit 31, an input / output control unit 32, an image processing unit 33, an operation display control unit 34, and the like. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment is configured as a multifunction machine having a scanner unit 22 and a print engine 26. In FIG. 2, the electrical connection is indicated by solid arrows, and the flow of paper is indicated by broken arrows.

  The display panel 24 is an output interface that visually displays the state of the image forming apparatus 1 and is an input when the user directly operates the image forming apparatus 1 or inputs information to the image forming apparatus 1 as a touch panel. It is also an interface (operation unit). The network I / F 28 is an interface for the image forming apparatus 1 to communicate with other devices via the network, and an Ethernet (registered trademark), a USB (Universal Serial Bus) interface, or the like is used.

  The controller 20 is configured by a combination of software and hardware. Specifically, for example, a control program such as firmware stored in a ROM 12, a nonvolatile memory, and a nonvolatile recording medium such as the HDD 14 or an optical disk is loaded into a volatile memory (hereinafter referred to as a memory) such as the RAM 11, and the CPU 10. The controller 20 is configured by a software control unit configured according to the above control and hardware such as an integrated circuit. The controller 20 functions as a control unit that controls the entire image forming apparatus 1.

  The main control unit 30 plays a role of controlling each unit included in the controller 20 and gives a command to each unit of the controller 20. The engine control unit 31 serves as a drive unit that controls or drives the print engine 26, the scanner unit 22, and the like. Further, the engine control unit 31 includes a function of calculating the scanning position of the light beam in the optical writing device included in the print engine 26.

  The input / output control unit 32 inputs a signal or a command input via the network I / F 28 to the main control unit 30. The main control unit 30 controls the input / output control unit 32 and accesses other devices via the network I / F 28.

  The image processing unit 33 generates drawing information based on the print information included in the input print job under the control of the main control unit 30. Here, the drawing information is information for drawing an image to be formed in the image forming operation by the print engine 26 as an image forming unit. The print information included in the print job is image information converted into a format that can be recognized by the image forming apparatus 1 by a printer driver installed in an information processing apparatus such as a personal computer. The operation display control unit 34 displays information on the display panel 24 or notifies the main control unit 30 of information input via the display panel 24.

  When the image forming apparatus 1 operates as a printer, first, the input / output control unit 32 receives a print job via the network I / F 28. The input / output control unit 32 transfers the received print job to the main control unit 30. When receiving the print job, the main control unit 30 controls the image processing unit 33 to generate drawing information based on the print information included in the print job.

  When drawing information is generated by the image processing unit 33, the engine control unit 31 performs image formation on the paper conveyed from the paper feed table 25 based on the generated drawing information. That is, the print engine 26 functions as an image forming unit. A document on which an image has been formed by the print engine 26 is discharged to a discharge tray 27.

  When the image forming apparatus 1 operates as a scanner, the operation display control unit 34 or the input / output is operated according to a user operation on the display panel 24 or a scan execution instruction input from an external PC or the like via the network I / F 28. The control unit 32 transfers a scan execution signal to the main control unit 30. The main control unit 30 controls the engine control unit 31 based on the received scan execution signal.

  The engine control unit 31 drives the ADF 21 and conveys the document to be imaged set on the ADF 21 to the scanner unit 22. Further, the engine control unit 31 drives the scanner unit 22 and images a document conveyed from the ADF 21. If no document is set on the ADF 21 and a document is set directly on the scanner unit 22, the scanner unit 22 takes an image of the set document under the control of the engine control unit 31. That is, the scanner unit 22 operates as an imaging unit.

  In the imaging operation, an imaging element such as a CCD included in the scanner unit 22 optically scans the document, and imaging information generated based on the optical information is generated. The engine control unit 31 transfers the imaging information generated by the scanner unit 22 to the image processing unit 33. The image processing unit 33 generates image information based on the imaging information received from the engine control unit 31 under the control of the main control unit 30. Image information generated by the image processing unit 33 is stored in a storage medium attached to the image forming apparatus 1 such as the HDD 40. That is, the scanner unit 22, the engine control unit 31, and the image processing unit 33 work together to function as a document reading unit.

  The image information generated by the image processing unit 33 is stored in the HDD 14 or the like as it is according to a user instruction or transmitted to an external device via the input / output control unit 32 and the network I / F 28. That is, the ADF 21 and the engine control unit 31 function as an image input unit.

  On the other hand, when the image forming apparatus 1 operates as a copying machine, the image processing unit 33 generates drawing information based on the imaging information received by the engine control unit 31 from the scanner unit 22 or the image information generated by the image processing unit 33. To do. Based on the drawing information, the engine control unit 31 drives the print engine 26 as in the case of the printer operation.

  Next, the configuration of the print engine 26 according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, the print engine 26 according to the present embodiment includes a configuration in which image forming units 106 of respective colors are arranged along a conveyor belt 105 that is an endless moving unit, which is a so-called tandem type. It is what is said. That is, along the transport belt 105 that transports the paper (recording paper) 104 separated and fed by the paper feed roller 102 and the separation roller 103 from the paper feed tray 101, the transport belt 105 is sequentially transported from the upstream side in the transport direction. A plurality of image forming units (electrophotographic process units) 106BK, 106M, 106C, and 106Y are arranged.

  The plurality of image forming units 106BK, 106M, 106C, and 106Y have the same internal configuration except that the color of the toner image to be formed is different. The image forming unit 106BK forms a black image, the image forming unit 106M forms a magenta image, the image forming unit 106C forms a cyan image, and the image forming unit 106Y forms a yellow image. In the following description, the image forming unit 106BK will be described in detail. However, since the other image forming units 106M, 106C, and 106Y are the same as the image forming unit 106BK, the image forming units 106M, 106C, and 106Y are similar to the image forming unit 106BK. For these components, only the symbols distinguished by M, C, and Y are displayed in the drawing in place of the BK attached to each component of the image forming unit 106BK, and detailed description thereof is omitted.

  The conveyor belt 105 is an endless belt, that is, an endless belt that is stretched between a driving roller 107 and a driven roller 108 that are rotationally driven. The drive roller 107 is driven to rotate by a drive motor (not shown), and the drive motor, the drive roller 107, and the driven roller 108 function as a drive unit that moves the conveyance belt 105 that is an endless moving unit. .

  At the time of image formation, the paper 104 stored in the paper feed tray 101 is sent out in order from the top, and the first image forming unit 106BK is conveyed by the conveyance belt 105 that is attracted to and rotated by the conveyance belt 105 by electrostatic adsorption action. Where the black toner image is transferred. That is, the conveyance belt 105 functions as a conveyance body that conveys a sheet that is an image transfer target.

  The image forming unit 106BK includes a photosensitive drum 109BK as a photosensitive member, a charger 110BK arranged around the photosensitive drum 109BK, an optical writing device 111, a developing device 112BK, a photosensitive cleaner (not shown), a removal unit. It is composed of an electric device 113BK and the like. The optical writing device 111 is configured to irradiate the respective photoconductive drums 109BK, 109M, 109C, and 109Y with light beams (laser beams as an example) 114Y, 114C, 114M, and 114BK.

  At the time of image formation, the outer peripheral surface of the photosensitive drum 109BK is uniformly charged by the charger 110BK in the dark, and then written by the light beam 114BK corresponding to the black image from the optical writing device 111. A latent image is formed. The developing device 112BK visualizes the electrostatic latent image with black toner, thereby forming a black toner image on the photosensitive drum 109BK.

  This toner image is transferred onto the sheet 104 by the action of the transfer unit 115BK at a position (transfer position) where the photosensitive drum 109BK and the sheet 104 on the conveying belt 105 contact each other. By this transfer, an image of black toner is formed on the paper 104. After the transfer of the toner image is completed, unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 109BK is wiped off by the photosensitive cleaner, and then the charge is removed by the charge eliminator 113BK, and waits for the next image formation.

  As described above, the sheet 104 on which the black toner image is transferred by the image forming unit 106BK is transported to the next image forming unit 106M by the transport belt 105. In the image forming unit 106M, a magenta toner image is formed on the photosensitive drum 109M by a process similar to the image forming process in the image forming unit 106BK, and the toner image is superimposed on the black image formed on the paper 104. And is transcribed.

  The sheet 104 is further conveyed to the next image forming units 106C and 106Y, and a cyan toner image formed on the photoconductive drum 109C and a yellow toner image formed on the photoconductive drum 109Y by the same operation. Are superimposed on the sheet 104 and transferred. In this way, a full color image is formed on the sheet 104. The sheet 104 on which the full-color superimposed image is formed is peeled off from the conveying belt 105 and fixed on the image by the fixing device 116, and then discharged to the outside of the image forming apparatus 1.

  In such an image forming apparatus 1, an error in the distance between the axes of the photosensitive drums 109BK, 109M, 109C, and 109Y, a parallelism error in the photosensitive drums 109BK, 109M, 109C, and 109Y, a deflection mirror in the optical writing device 111, The toner images of the respective colors do not overlap at positions where they should overlap each other due to an installation error of the electrostatic latent image, an electrostatic latent image writing timing error on the photosensitive drums 109BK, 109M, 109C, and 109Y. May occur.

  For the same reason, the image may be transferred to a range that is outside the range where the image is originally transferred on the paper to be transferred. As such misregistration components, skew, sub-scan registration error, magnification error in the main scanning direction, registration error in the main scanning direction, and the like are mainly known. Further, the expansion and contraction of the conveyor belt 105 due to the temperature change in the apparatus and deterioration with time are known.

  A pattern detection sensor 117 is provided to correct such positional deviation. The pattern detection sensor 117 is an optical sensor that reads (for example, images) the misregistration correction pattern transferred onto the conveyance belt 105 by the photosensitive drums 109BK, 109M, 109C, and 109Y. As shown in FIG. 3, the pattern detection sensor 117 is supported on the same substrate along the direction orthogonal to the conveyance direction of the conveyance belt 105 on the downstream side of the photosensitive drums 109BK, 109M, 109C, and 109Y. .

  Next, the optical writing device 111 according to the present embodiment will be described. FIG. 4 is a view of the optical writing device 111 according to the present embodiment as viewed from above. FIG. 5 is a cross-sectional view of the optical writing device according to the present embodiment as viewed from the side. As shown in FIGS. 4 and 5, light beams to be written on the photosensitive drums 109BK, 109M, 109C, and 109Y of the respective colors are light source devices 281BK, 281Y, 281M, and 281C as light sources (hereinafter collectively referred to as light source devices 281). Irradiated from. Note that the light source device 281 according to the present embodiment includes a semiconductor laser, a collimator lens, a slit, a prism, a cylinder lens, and the like.

  The light beam emitted from the light source device 281 is reflected by the reflecting mirror 280. Each light beam is guided to mirrors 282BK, 282Y, 282M, and 282C (hereinafter collectively referred to as 282) by an optical system such as an fθ lens (not shown), and further, the photosensitive drums 109BK, 109M, and 109C are further advanced by the optical system. , 109Y is scanned.

  The reflecting mirror 280 is a hexahedral polygon mirror, and can rotate by scanning the light beam corresponding to the line in the main scanning direction per one surface of the polygon mirror. The optical writing device 111 according to the present embodiment divides the four light source devices into light source devices of two colors 281BK and 281Y and 281M and 281C, and performs scanning using different reflecting surfaces of the reflecting mirror 280. It is possible to write on four different photosensitive drums at the same time with a more compact configuration than the scanning method using only one reflecting surface.

  Further, a horizontal synchronization detection sensor 283 is provided in the vicinity of the scanning start position in the range where the light beam is scanned by the reflecting mirror 280. When the light beam emitted from the light source device 281 enters the horizontal synchronization detection sensor 283, the timing of the scanning start position of the main scanning line is detected, and the control device that controls the light source device 281 and the reflecting mirror 280 are synchronized. Be taken.

  Next, a control block of the optical writing device 111 according to the present embodiment will be described with reference to FIG. FIG. 6 is a diagram illustrating a functional configuration of the optical writing device control unit 120 that controls the optical writing device 111 according to the present embodiment and a connection relationship with each unit.

  As illustrated in FIG. 6, the optical writing device control unit 120 according to the present embodiment includes, for example, a writing control unit 121, a counting unit 122, a sensor control unit 123, a correction control unit 124 </ b> A, an expansion / contraction rate calculation unit 124 </ b> B, an offset. It includes a calculation unit 124C, a contact / separation difference calculation unit 124D, a data storage processing unit 124E, a temperature detection unit 125, and the like. The optical writing device 111 according to the present embodiment includes an information processing / mechanism such as the CPU 10, the RAM 11, the ROM 12, the NVRAM 19, and the HDD 14 described with reference to FIG. Similarly to the controller 20 of the image forming apparatus 1, the control program 120 is configured by loading a control program stored in the ROM 12 or the HDD 14 into the RAM 11 and operating according to the control of the CPU 10.

  The writing control unit 121 controls the light source device 281 according to a synchronization detection signal from the horizontal synchronization detection sensor 283 based on image information input from the engine control unit 31 of the controller 20. In the present embodiment, the writing control unit 121 corresponds to a light source control unit. The writing control unit 121 controls the light source device 281 based on the image information input from the engine control unit 31, and also draws a drawing pattern 400 for correcting misalignment (see 400A, 400B, FIGS. 9 and 10). Therefore, the light source device 281 is controlled.

  In the misalignment correction process, the count unit 122 starts counting at the same time as the writing control unit 121 controls the light source device 281 to start exposure of the photosensitive drum 109BK. The count unit 122 stops counting when the sensor control unit 123 detects the pattern based on the output signal of the pattern detection sensor 117. As a result, in the positional deviation correction process, the count unit 122 controls the light source device 281 to start exposure of the photosensitive drum 109BK, and then the pattern detection sensor 117 performs the first drawing pattern ( As an example, it functions as a first detection period counting unit that counts a detection period (first detection period) until the drawing pattern 411A or the drawing pattern 411B) is detected. Hereinafter, this count value is referred to as a write start timing count value. Further, the count unit 122 counts the detection timing of the intermittently drawn drawing pattern 412 (see FIGS. 9 and 10) in the positional deviation correction process for correcting the deviation of the toner images of the respective colors. Hereinafter, this count value is referred to as a drum interval count value. Furthermore, the count unit 122 performs a second detection period (in this embodiment, the drawing pattern 411A and the drawing pattern) by the pattern detection sensor 117 with respect to the second drawing pattern 411 (see FIGS. 9 and 10) drawn on the conveyance belt 105. It also functions as a second detection period counting unit that counts (detection timing interval with the pattern 411B). Hereinafter, this count value is referred to as a reference pattern count value.

  The sensor control unit 123 is a control unit that controls the pattern detection sensor 117, and as described above, based on the output signal of the pattern detection sensor 117, the first drawing pattern (for example, formed on the conveyor belt 105). It is detected that the drawing pattern 411A or the drawing pattern 411B) has reached a position facing the pattern detection sensor 117. In the present embodiment, the sensor control unit 123 corresponds to an image detection unit. When the sensor control unit 123 detects that each drawing pattern 400 has reached the position of the pattern detection sensor 117, the sensor control unit 123 inputs a detection signal to the count unit 122.

  The correction control unit 124A controls the writing control unit 121 based on the detection result of the pattern detection sensor 117 to correct the drawing timing. Here, the concept of the correction processing in the present embodiment will be described with reference to FIGS. FIG. 7 is a schematic diagram illustrating an example of a relationship between a first reference value, a first detection period, an offset, and a contact / separation difference. FIG. 8 is a schematic diagram illustrating an example of the relationship between the second reference value, the second detection period, and the expansion / contraction rate. Here, as an example, in the optical writing device 111, one of a plurality of photosensitive drums 109BK, 109M, 109C, and 109Y is in contact with the conveying belt 105 (hereinafter referred to as a separated state), and a plurality An example in which the image forming process is executed with all of the photosensitive drums 109BK, 109M, 109C, and 109Y in contact with the conveyance belt 105 (hereinafter referred to as contact state) will be described.

  The writing start timing may be different from the initial design value due to an initial error of the conveyor belt 105 or the like. Further, the writing start timing may deviate from the initial value as the transport belt 105 stretches over time. The separation offset is a difference between the first detection period at the separation and the first reference value as the reference value of the write start timing corresponding to the first detection period. The contact offset is a difference between the first detection period at the time of contact and the first reference value as the reference value of the write start timing corresponding to the first detection period. In other words, the correction control unit 124A performs write control so as to correct the write start timing corresponding to the first reference value to the write start timing corresponding to the first detection period (offset at separation or offset at contact). The unit 121 is controlled. As a result, highly accurate drawing is possible. Note that the first reference value is common between the separated state and the contacted state.

  Here, as shown in FIG. 7, even in the same image forming apparatus 1, the first detection period may change between separation and contact. As an example, the pattern detection sensor 117 changes the position, posture, and the like of the conveyor belt 105 as the contact state of the photosensitive drums 109BK, 109M, 109C, and 109Y with the conveyor belt 105 changes. This is because, for example, the distance corresponding to the first detection period in the image forming apparatus 1 changes due to the change in the position of. In the present embodiment, the difference between the first detection periods at the time of separation and at the time of contact, that is, the difference between the offset at the time of separation and the offset at the time of contact is referred to as a contact / separation difference. In the present embodiment, the case where the offset at the time of separation is longer than the offset at the time of contact is illustrated, but the offset at the time of contact may be longer than the offset at the time of separation.

  If the optical writing device 111 can always detect the first detection period and calculate the offset at the timing immediately before executing the image formation, and execute the process of correcting the writing timing based on the offset, the accuracy can be improved. High image formation processing may be possible. However, in this case, there are disadvantages such as an increase in toner consumption and a time required for the image forming process as a whole. In this respect, the drawing pattern is drawn, the offset is calculated, the timing for executing a series of processes for correcting the writing timing based on the offset is limited, and further, the contact / separation difference acquired in advance is used. Thus, it is advantageous to execute a process for estimating the other from the detection results (first detection period or offset) at the time of separation and contact.

  In other words, as an example, the optical writing device control unit 120 is in the full color mode, and the monochrome drawing pattern 400A (see FIG. 5) is in contact with the plurality of photosensitive drums 109BK, 109M, 109C, and 109Y in contact with the transport belt 105. 9) Alternatively, a full-color drawing pattern 400B (FIG. 10) is drawn to obtain a contact-time offset based on the drawing patterns 400A and 400B, and this is stored in the storage unit 126. After that, in the monochrome mode, only one of the plurality of photosensitive drums 109BK, 109M, 109C, and 109Y is in a separated state in which only one photosensitive drum 109BK (black photosensitive drum) comes into contact with the conveyance belt 105. In this case, the optical writing device control unit 120 does not newly draw the monochrome drawing pattern 400A and acquires the offset at the time of contact, but acquires the contact at the time of contact and stores it in the storage unit 126. The time offset is added to the contact / separation difference (corrected contact / separation difference) stored in advance in the storage unit 126 to obtain the separation offset.

  As another example, the following processing is also possible. That is, the optical writing device control unit 120 has only one photosensitive drum 109BK (black photosensitive drum) of the plurality of photosensitive drums 109BK, 109M, 109C, and 109Y in contact with the conveyance belt 105 in the monochrome mode. At the time of separation, a monochrome drawing pattern 400A (FIG. 9) is drawn to obtain a separation offset based on the drawing pattern 400A, and this is stored in the storage unit 126. After that, in the full color mode, when all of the plurality of photosensitive drums 109BK, 109M, 109C, and 109Y come into contact with the conveyance belt 105, the optical writing device control unit 120 again performs the full color. The drawing pattern 400B (FIG. 10) is not drawn to obtain the contact offset, but is stored in the storage unit 126 in advance from the separation offset acquired and stored in the storage unit 126 during the separation. The contact offset is obtained by subtracting the contact / separation difference (modified contact / separation difference). As described above, in the present embodiment, it is possible to realize more accurate image formation while reducing the labor for drawing the drawing pattern 400. Note that the addition and subtraction change depending on the specifications of the apparatus and the like, and may be reversed depending on the magnitude relationship between the contact offset and the separation offset.

  However, the contact / separation difference may change over time. Therefore, the optical writing device control unit 120 appropriately obtains the first detection period or offset at the time of separation and contact, and from these, the contact / separation difference, that is, the first detection period at the time of contact and the separation time. It is preferable to calculate the difference from the first detection period and update the contact / separation difference stored in the storage unit 126. The update of the contact / separation difference may be performed at a predetermined time interval, may be performed every predetermined number of image formations, or the time interval and the number of image formations may be variably set. In that case, the user (operator) can change the setting by operating the operation unit 17 or the like.

  Further, the contact / separation difference may change due to expansion / contraction of the conveyance belt 105 (for example, expansion / contraction due to a temperature change) other than a factor over time. Therefore, in this embodiment, the optical writing device control unit 120 appropriately calculates the expansion / contraction rate of the transport belt 105 at a predetermined timing and reflects it in the contact / separation difference. Specifically, as illustrated in FIG. 9, drawing patterns 411 (411 </ b> A and 411 </ b> B) are formed on the conveyance belt 105 at two positions with a predetermined interval L therebetween. Then, the optical writing device control unit 120 acquires, as the second detection period D2, a value obtained by counting the timing at which the pattern detection sensor 117 detects these drawing patterns 411 at the two locations by the counting unit 122. As shown in FIG. 8, the optical writing device control unit 120 calculates the expansion / contraction rate Re as a ratio corresponding to the second reference value S2 of the second detection period D2 (reference pattern count value). As an example, the optical writing device control unit 120 stores the corrected contact / separation difference in the storage unit 126 as a value obtained by multiplying the base contact / separation difference by the expansion / contraction rate Re. In this case, the contact / separation difference corresponds to a value under the condition that the interval between the drawing patterns 411 is L (for example, when the temperature is a predetermined value). This corresponds to the contact / separation difference in a state extending from L. Then, the corrected contact / separation difference is used for the calculation of the offset.

  That is, in this embodiment, the expansion / contraction rate calculation unit 124B included in the optical writing device control unit 120 calculates the expansion / contraction rate, and the offset calculation unit 124C included in the optical writing device control unit 120 performs the offset (during separation). Offset and contact offset), and the contact / separation difference calculation unit 124D calculates the contact / separation difference. In addition, the data storage processing unit 124E stores the calculated offset, the contact / separation difference, the corrected contact / separation difference, and the like in the storage unit 126. The calculated offset is stored in association with a parameter indicating the contact state (for example, the separated state: 0, the contact state: 1). Thereby, the optical writing device control unit 120 can distinguish the offset at the time of contact and the offset at the time of separation.

  The interval L between the drawing patterns 411A and 411B is an integral multiple of the circumference of the photosensitive drums 109BK, 109M, 109C, and 109Y, an integral multiple of the circumference of the drive roller 107 that drives the conveyance belt 105, or the photosensitive drum 109BK. , 109M, 109C, 109Y and an integral multiple of the circumference of the drive roller 107, that is, a common multiple of the circumference of the photosensitive drums 109BK, 109M, 109C, 109Y and the circumference of the drive roller 107 Is preferred. In this embodiment, as an example, the interval L between the drawing patterns 411A and 411B is one time the circumference of the photosensitive drums 109BK, 109M, 109C, and 109Y. By doing so, it is possible to suppress the occurrence of an error in the expansion / contraction rate due to periodic fluctuations of the photosensitive drums 109BK, 109M, 109C, 109Y, the driving roller 107, and the like. That is, the calculation accuracy of the expansion / contraction rate can be further improved.

  Further, the correction control unit 124A compares the drum interval count value with the corresponding drum interval reference value among the count values obtained by the counting unit 122, and calculates a drum interval correction value based on the difference between the two values. The correction value calculated in this way is stored in the storage unit 126 as described above. As described above, by storing the correction value in the storage unit 126, the writing control unit 121 can drive the light source device 281 with reference to the correction value.

  In this embodiment, as shown in FIGS. 9 and 10, a drawing pattern 400A (hereinafter also referred to as a correction pattern A) and a drawing pattern 400B (hereinafter also referred to as a correction pattern B) formed on the conveyor belt 105 are sub-patterns. A plurality of (three in this embodiment) pattern rows 401A and 401B in which various patterns are arranged in the scanning direction are configured.

  As shown in FIGS. 9 and 10, the pattern detection sensor 117 has a plurality (three in this embodiment) of sensor elements 170 in the main scanning direction, and the pattern rows 401 </ b> A and 401 </ b> B have their respective sensor elements 170. Is drawn at a position opposite to. As a result, the optical writing device control unit 120 can detect a pattern at a plurality of positions on the transport belt 105 in the main scanning direction, and calculate the average value of each to increase the accuracy of the misregistration correction operation. Can be improved.

  As shown in FIG. 9, the pattern row 401A includes a pair of drawing patterns 411A and 411B (411) arranged at a predetermined interval L in the sub-scanning direction. As described above, the drawing patterns 411A and 411B function as the second drawing pattern, and one of the drawing patterns 411A and 411B functions as the first drawing pattern.

  On the other hand, as shown in FIG. 10, the pattern row 401 </ b> B includes an all-drum contact pattern 410 and a drawing pattern 411 by the photosensitive drum 109 </ b> BK, respectively. The all-drum contact pattern 410 is a pattern drawn in a state where all of the photosensitive drums 109BK, 109M, 109C, and 109Y are in contact with the transport belt 105. In FIG. 10, the solid line represents the pattern drawn by the photosensitive drum 109BK, the dotted line represents the photosensitive drum 109Y, the broken line represents the photosensitive drum 109C, and the alternate long and short dash line represents the pattern drawn by the photosensitive drum 109M.

  The all drum contact pattern 410 includes a drawing pattern 411 for starting position correction and a drawing pattern 412 for drum interval correction. The drawing pattern 412 for drum interval correction is drawn repeatedly.

  The drawing pattern 411 for starting position correction has drawing patterns 411A and 411B parallel to the main scanning direction. The second drawing pattern 411B can be used as a backup when the detection of the first drawing pattern 411A fails.

  The drawing interval 412 for correcting the drum interval is a pattern drawn for counting the drum interval count value described above. As shown in FIG. 10, the drawing pattern 412 for correcting the drum interval includes a drawing pattern 413 for correcting the sub-scanning direction and a drawing pattern 414 for correcting the main scanning direction. The optical writing device controller 120 corrects misalignment in the sub-scanning direction of each of the photosensitive drums 109BK, 109M, 109C, and 109Y based on the read signal of the drawing pattern 413 for correcting the sub-scanning direction by the pattern detection sensor 117. Based on the read signal of the drawing pattern 414 for correcting the main scanning direction, the positional deviation correction of the photosensitive drums in the main scanning direction is performed.

  That is, the drum interval reference value stored in the storage unit 126 is the drum interval drawn after the light source device 281 starts drawing the drawing pattern 412 for drum interval correction under the control of the writing control unit 121. Each pattern included in the correction drawing pattern 412 is a value serving as a reference for a period from when the pattern detection sensor 117 reads the pattern until it is detected by the sensor control unit 123.

  9 and 10, when all the photosensitive drums are in contact with the conveyance belt 105, and when only the photosensitive drum 109 </ b> BK is in contact with the conveyance belt 105, the drawing pattern 400 for correcting misalignment is used. At both times, it is possible to execute a positional deviation correction of the drawn image.

  As described above, in this embodiment, the pair of drawing patterns 411A and 411B constituting the monochrome drawing pattern (correction pattern A) 400A shown in FIG. 9 functions as the first drawing pattern and the second drawing pattern. It also functions as a drawing pattern. The same applies to the pair of drawing patterns 411A and 411B included in the full-color drawing pattern (correction pattern B) 400B shown in FIG. Further, the drawing pattern 411B in FIG. 10 is a part of the drawing pattern 413 for correcting the drum interval in the sub-scanning direction.

  In this embodiment, in addition to a state in which all the photosensitive drums are in contact with the conveyance belt 105, a monochrome printing state in which only the photosensitive drum 109BK is in contact with the conveyance belt 105 is used. A case where the position is corrected will be described as an example. In addition to this, monochromatic printing is not limited to monochrome, and in consideration of the case of using other colors, only the photosensitive drums other than the photosensitive drum 109BK may be brought into contact with the transport belt 105.

  Even in the case of monochromatic printing, for example, when monochromatic printing is performed in colors such as red, green, and blue, two of the photosensitive drums 109M, 109C, and 109Y may be brought into contact with the conveyance belt 105. . The same applies not only to monochrome printing but also to printing that is not full color. Even in these cases, in constructing the drawing pattern 400 for correcting misregistration, the pattern is drawn in a state corresponding to each, that is, in a state where only the photosensitive drum to be brought into contact is drawn, By storing the reference values corresponding to the respective patterns in the storage unit 126, it is possible to execute misalignment correction in the same manner as described above.

  Next, in the configuration of the print engine 26 according to the present embodiment, the photosensitive drums 109BK, 109M, 109C, and 109Y (hereinafter, sometimes collectively referred to as the photosensitive drum 109) are brought into contact with and separated from the conveyance belt 105. The mechanism to be performed will be described. FIG. 3 shows a state in which all the photosensitive drums 109 are separated from the transport belt 105 as illustrated. FIG. 11 shows a state in which all the photosensitive drums 109 and the transport belt 105 are in contact with each other.

  In order to transition between the state shown in FIG. 3 and the state shown in FIG. 11, the photosensitive drum 109 may be moved up and down, or the driving roller 107 and the driven roller 108 holding the conveying belt 105 are moved up and down. May be.

  FIG. 12 is a diagram illustrating an aspect in which only the photosensitive drum 109BK is brought into contact with the conveyance belt 105. In the embodiment shown in FIG. 12, the driving roller 107 and the driven roller 108 are made different in height so that the surface of the conveying belt 105 facing the photosensitive drum 109 is held in an inclined state, and only the photosensitive drum 109BK is conveyed. It arrange | positions so that it may contact | abut to the belt 105. FIG. This is a mode that is possible when the photosensitive drum 109BK is arranged at the end in the sub-scanning direction as in the print engine 26 according to the present embodiment.

  FIG. 13 is a diagram illustrating another aspect in the case where only the photosensitive drum 109BK is brought into contact with the conveyance belt 105. In the embodiment of FIG. 13, similarly to FIG. 12, the driving roller 107 is disposed at a position lower than the driven roller 108, and the belt height adjusting roller 118 is provided between the photosensitive drum 109BK and the photosensitive drum 109M. Further, the upper height of the belt height adjusting roller 118 and the upper height of the driven roller 108 are arranged to be equal. As a result, the conveyor belt 105 is supported by the belt height adjusting roller 118 and the driven roller 108, and is disposed so as to be in contact with the photosensitive drum 109BK.

  FIG. 14 is a diagram showing an example in which two photosensitive drums are brought into contact with the conveyance belt 105 as a modification of FIG. In the embodiment of FIG. 14, similarly to FIG. 12, the driving roller 107 is disposed at a position lower than the driven roller 108, and a belt height adjusting roller 118 is provided between the photosensitive drum 109M and the photosensitive drum 109C. Further, the upper height of the belt height adjusting roller 118 and the upper height of the driven roller 108 are arranged to be equal. As a result, the conveyor belt 105 is supported by the belt height adjusting roller 118 and the driven roller 108 and is disposed so as to contact only the photosensitive drums 109BK and 109M.

  FIG. 15 is a diagram showing still another aspect in the case where only the photosensitive drum 109BK is brought into contact with the transport belt 105. In FIG. In the embodiment of FIG. 15, the driving roller 107 and the driven roller 108 are arranged as in the case of FIG. 3, and between the photosensitive drum 109BK and the driven roller 108, and between the photosensitive drum 109BK and the photosensitive drum 109M. A belt height adjustment roller 118 is provided between the two belt height adjustment rollers 118 so that the heights of the upper sides of the two belt height adjustment rollers 118 are equal and higher than those of the driving roller 107 and the driven roller 108. As a result, the conveying belt 105 is supported by the two belt height adjusting rollers 118 and disposed so as to contact the photosensitive drum 109BK.

  By such a contact / separation mechanism between the photosensitive drum 109 and the conveying belt 105, for example, when the state of FIG. 11 is changed to the state of FIG. 12, the arrangement of the driving roller 107 and the driven roller 108 changes. As a result, the conveyor belt 105 may slightly expand and contract. As a result, a shift occurs in the timing at which the image formed on the photosensitive drum 109 is transferred to the paper transported by the transport belt 105, resulting in a positional shift of the image transferred on the paper.

  Further, when the conveyance speed of the conveyance belt 105 changes due to the expansion and contraction of the conveyance belt 105, in addition to the above-described image misalignment, the images formed on the photosensitive drums 109BK, 109M, 109C, and 109Y are transferred to a sheet. As a result, a color shift occurs in the image transferred onto the paper, that is, a color shift.

  In the state of FIG. 11, the photosensitive drum 109BK and the conveyance belt 105 are in contact with each other at the lowest point in the vertical direction of the photosensitive drum 109BK, but in the state of FIG. 12, the conveyance belt 105 is inclined. Therefore, the contact position between the photosensitive drum 109BK and the transport belt 105 changes. This also causes a shift in the timing at which the image formed on the photoconductive drum 109 is transferred to the sheet transported by the transport belt 105, resulting in a positional shift of the image transferred on the sheet.

  The deviation due to the change in the contact position between the photosensitive drum 109BK and the conveyance belt 105 as in the case of FIG. Therefore, the positional deviation correction mechanism according to the present embodiment is particularly effective in the print engine 26 that employs the contact / separation mechanism as shown in FIG. The contact / separation mechanism of the print engine 26 as shown in FIG. 11 can be realized, for example, by providing a mechanism that raises or lowers only the height of the drive roller 107, which is advantageous in terms of cost compared to other aspects. It is.

  Further, since the frictional force when the conveying belt 105 is conveyed changes due to the change in the number of the photosensitive drums 109 in contact with the conveying belt 105, the conveying speed of the conveying belt 105 may change. . As a result, there is a possibility that the above-described image position shift and image color shift occur. Further, in the case of FIGS. 13 and 14, since the conveyor belt 105 is expanded and contracted by the belt height adjusting roller 118, there is a possibility that image misregistration and color misregistration occur as described above.

  In response to such a problem of misregistration and color misregistration, performing a correction operation using a drawing pattern 400 for misregistration correction as shown in FIGS. This is one gist of the optical writing device control unit 120). In the present embodiment, a correction operation (hereinafter referred to as “correction operation”) performed by drawing only the drawing pattern 411 (400A) by the photosensitive drum 109BK in FIG. 9 among the drawing patterns 400 for correcting misalignment shown in FIGS. Any one of a misalignment correction A) and a correction operation (hereinafter referred to as misalignment correction B) executed by drawing the drawing pattern 400B of FIG. 10 is selectively executed.

  As shown in FIG. 6, as described above, the storage unit 126 stores at least one of the first reference value, the second reference value, the drum interval reference value, and the offset (separation offset and contact offset). Any one), (basic) contact / separation difference, corrected contact / separation difference, contact state, etc. are stored. Further, the storage unit 126 may store at least one of the first detection period and the second detection period, temperature, expansion / contraction rate, and the like. In the situation where the first reference value is stored, the offset can be calculated from the first detection period, and in the situation where the second reference value is stored, the second This is because the contact / separation difference and the expansion / contraction rate corrected from the detection period can be calculated. The optical writing device 111 includes a temperature sensor 127, and the optical writing device control unit 120 can include a temperature detection unit 125 that acquires a temperature based on a detection result of the temperature sensor 127. In addition, instead of the temperature, the storage unit 126 can store parameters that change in conjunction with the temperature (such as device operation parameters). In addition, the storage unit 126 can store the date and time when the offset or the contact / separation difference is acquired. It is preferable to store the temperature, the expansion / contraction rate, the parameter, the date and time, etc., in association with the offset, the corrected contact / separation difference, and the like. The storage unit 126 does not store all the parameters illustrated in FIG. 6 but can select and store the minimum necessary parameters that do not hinder each process. The storage unit 126 is preferably a nonvolatile rewritable storage unit, and can be configured as the HDD 14 or the NVRAM 19 as an example.

  Next, acquisition of parameters for the misregistration correction operation of the image forming apparatus 1 according to the present embodiment will be described. As shown in FIG. 16, the optical writing device control unit 120 executes different processing depending on whether color printing is in progress or before color printing. Specifically, as shown in FIG. 17, before or during the execution of color printing, the processing is executed using the correction pattern B of FIG. 10, while the color printing is executed after the color printing is executed. Before, during, and after execution, the process is executed using the correction pattern A shown in FIG. The correction pattern A after color printing is not drawn when all of the plurality of photosensitive drums 109BK, 109M, 109C, and 109Y are in contact with the conveyance belt 105, and only the black photosensitive drum 109BK is applied. It is drawn after being in contact. Further, at the time of warming up when the power is turned on (ON), the processing by the correction pattern A is executed with only the black photosensitive drum 109BK in contact.

  As shown in FIG. 16, in step S10, when color printing has not been performed or is not in progress (No in step S10), the write control unit 121 of the optical writing device control unit 120 controls the light source device 281 and the like. Then, as an example, a monochrome correction pattern A as shown in FIG. 9 is printed on the conveyor belt 105 (step S11). Next, the sensor control unit 123, the count unit 122, and the like of the optical writing device control unit 120 detect the correction pattern A as described above (step S12). Next, the expansion / contraction rate calculation unit 124B of the optical writing device control unit 120 calculates the expansion / contraction rate as described above from the detection result of the second drawing pattern 411 included in the correction pattern A (step S13). Next, the contact / separation difference calculation unit 124D of the optical writing device control unit 120 obtains the basic contact / separation difference stored in the storage unit 126, and multiplies the difference by the expansion / contraction rate to reflect the expansion / contraction rate. The obtained contact / separation difference is calculated (step S14). Next, the offset calculation unit 124C of the optical writing device control unit 120 calculates the offset at the time of separation, and subtracts the corrected contact / separation difference from the offset at the time of separation to calculate the offset at the time of contact (step S15). . Then, the data storage processing unit 124E of the optical writing device control unit 120 stores the separation offset and the contact offset in the storage unit 126 (step S16). Steps S11 to S16 are processes for calculating the offset at the time of separation using the correction pattern A and calculating (estimating) the offset at the time of contact using the contact / separation difference. By executing steps S11 to S16, the contact offset can be updated in addition to the separation offset at the time of separation. Therefore, even when the state shifts from the separated state to the contact state, the optical writing device control unit 120 does not perform steps S17 to S21 described later in the contact state, and updates the contact state. Based on the offset (estimated offset), the misalignment correction process can be executed.

  On the other hand, if color printing has been performed before or during color printing in step S10 (Yes in step S10), the writing control unit 121 of the optical writing device control unit 120 controls the light source device 281 and the like to convey the conveyance belt. For example, a correction pattern B as shown in FIG. 10 is printed on 105 (step S17). Next, the sensor control unit 123, the count unit 122, and the like of the optical writing device control unit 120 detect the correction pattern B as described above (step S18). Next, the expansion / contraction rate calculation unit 124B of the optical writing device control unit 120 calculates the expansion / contraction rate as described above from the detection result of the second drawing pattern 411 included in the correction pattern B (step S19). Next, the contact / separation difference calculation unit 124D of the optical writing device control unit 120 obtains the basic contact / separation difference stored in the storage unit 126, and multiplies the difference by the expansion / contraction rate to reflect the expansion / contraction rate. The calculated contact / separation difference is calculated (step S20). Next, the offset calculation unit 124C of the optical writing device control unit 120 calculates the contact offset, and adds the corrected contact difference to the contact offset to calculate the contact offset (step S21). ). Then, the data storage processing unit 124E of the optical writing device control unit 120 stores the separation offset and the contact offset in the storage unit 126 (step S16). Steps S <b> 17 to S <b> 21 and S <b> 16 are processes for calculating the offset at the time of contact using the correction pattern B and calculating (estimating) the offset at the time of separation using the contact / separation difference. By executing steps S17 to S21 and S16, the offset at the time of separation can be updated in addition to the offset at the time of contact at the time of contact. Therefore, even when the contact state shifts to the separated state, the optical writing device control unit 120 does not perform steps S11 to S15 in the separated state, but updates the updated offset (estimated). Misalignment correction processing can be executed on the basis of the offset).

  Then, the writing control unit 121 and the correction control unit 124A of the optical writing device control unit 120 use the parameters (such as an offset) updated in step S16 when the light source device 281 performs the printing process. The timing for irradiating the light beam is controlled.

  As described above, in the image forming apparatus 1 including the optical writing device 111 according to the present embodiment, the optical writing control unit 121 as an example of the light source control unit has the first on the conveyance belt 105 as an example of the conveyance body. After starting the process of forming at least one of the drawing pattern 411A and the drawing pattern 411B as an example of the drawing pattern, the sensor control unit 123 as an example of the image detection unit performs at least one of the drawing pattern 411A and the drawing pattern 411B. A counting unit 122 as an example of a first detection period counting unit that counts a first detection period as a period until detecting the first detection period, and a first as a reference for the first detection period and the first detection period Offset calculation unit as an example of an offset calculation unit that calculates an offset as a difference from the reference value of 24C and the second detection as a period when the sensor control unit 123 as an example of the image detection unit detects two places of the drawing patterns 411A and 411B as an example of the second drawing pattern drawn on the conveyance belt 105. An example of the carrier by comparing the counting unit 122 as an example of a second detection period counting unit that counts the period, the second detection period and a second reference value as a reference of the second detection period. An expansion / contraction rate calculation unit 124B as an example of an expansion / contraction rate calculation unit that calculates the expansion / contraction rate of the conveyance belt 105 as the first detection in a state where a part of the plurality of photosensitive drums 109 is in contact with the conveyance belt 105 The contact / separation difference as an example of the contact / separation difference calculation unit that calculates the contact / separation difference as a difference between the period and the first detection period when all of the plurality of photosensitive members 109 are in contact with the conveyance belt 105. The offset corresponding to one of the exit portion 124D and a state in which a part of the plurality of photosensitive drums 109 is in contact with the conveyance belt 105 and a state in which all of the plurality of photosensitive drums 109 are in contact with the conveyance belt 105 Based on the calculated contact / separation difference and the calculated expansion / contraction ratio, the correction control unit as an example of a correction control unit that corrects the timing of irradiating the light source device 281 as an example of the light source in the other state with the light source 124A.

  That is, according to the present embodiment, the offset and contact / separation acquired in one of the state in which a part of the photoconductor is in contact with the transport body and the state in which all of the plurality of photoconductors are in contact with the transport body. Since the timing including irradiating the light source as an example of the light source in the other state can be corrected using the parameter including the difference, the drawing pattern is drawn or drawn before executing the printing in each state. Printing can be executed in a state where the positional deviation is corrected with relatively high accuracy without performing pattern detection, offset calculation, or the like. Furthermore, according to the present embodiment, since the expansion / contraction rate of the carrier can be reflected in the contact / separation difference, the accuracy of the positional deviation correction can be further improved.

  In the image forming apparatus 1 including the optical writing device 111 according to the present embodiment, the correction control unit 124A as an example of a correction control unit includes one of the photosensitive drums 109 as an example of a plurality of photosensitive members (as an example). Are all the photosensitive drums 109 as an example of the plurality of photosensitive members based on the offset calculated in a state where the black photosensitive drum 109BK is in contact with the conveying belt 105 as an example of the conveying member. The timing of irradiating the light source device 281 as an example of the light source while being in contact with the conveyance belt 105 as an example is corrected. In the image forming apparatus 1 including the optical writing device 111 according to the present embodiment, the correction control unit 124A as an example of the correction control unit is configured such that all of the photosensitive drums 109 as an example of a plurality of photosensitive members are transported. Based on the offset calculated in a state of being in contact with the conveyance belt 105 as an example, one of the photosensitive drums 109 as an example of a plurality of photosensitive members is in contact with the conveyance belt 105 as an example of the conveyance body. The timing for irradiating the light source device 281 as an example of the light source with the light beam is corrected. Therefore, for the monochrome mode and full-color mode that are often set by the image forming apparatus, the processing in the other mode can be performed more efficiently by using the parameters including the offset and the contact / separation difference acquired in one mode. Can perform well.

  In the present embodiment, a part of the drawing patterns 411A and 411B as an example of the second drawing pattern is used as the first drawing pattern. Therefore, compared with the case where the first drawing pattern and the second drawing pattern are drawn separately, the amount of toner can be further reduced and the processing effort can be further reduced.

  In the present embodiment, at least one of the drawing pattern 411A and the drawing pattern 411B as an example of the second drawing pattern is drawn in black by a black photosensitive drum 109BK as an example of a black photosensitive member. It is a pattern. Therefore, the monochrome mode and the monochrome mode of the full color mode that are often set in the image forming apparatus are used, and the parameter including the offset and the contact / separation difference acquired in one of the modes is used in the other mode. This process can be executed more efficiently.

  In the present embodiment, the drawing patterns 411A and 411B as examples of the second drawing pattern include two drawing patterns 411A and 411B, and the interval L between the two drawing patterns 411A and 411B is one photoconductor. An integer multiple of the circumference of the photoconductive drum 109 as an example, an integer multiple of the circumference of the drive roller 107 as an example of a drive roller for driving the conveyance belt 105 as an example of the conveyance body, or an example of the photoconductor It is set to an integral multiple of the circumference of the photosensitive drum 109 and to an integral multiple of the circumference of the drive roller 107 as an example of the drive roller. Therefore, it is possible to suppress the occurrence of an error in the expansion / contraction ratio due to the periodic fluctuation of the photosensitive drums 109BK, 109M, 109C, 109Y, the driving roller 107, and the like. That is, the calculation accuracy of the expansion / contraction rate can be further improved.

  In this embodiment, during the warm-up operation of the optical writing device 111, the photosensitive drum 109BK as an example of some of the plurality of photosensitive members is provided on the surface of the conveyor belt 105 as an example of the conveyor. The drawing patterns 411A and 411B as examples of at least the first drawing pattern are drawn, and the correction control unit 124A as an example of the correction control unit uses the drawing patterns 411A and 411B as examples of the first drawing pattern. The timing for irradiating the light source device 281 as an example of the light source is corrected based on the offset calculated based on at least one of them and the contact / separation difference. That is, according to the present embodiment, it is possible to reduce the amount of color toner consumed as compared with the case where the drawing pattern is formed using all of the photosensitive drum 109 as an example of the photosensitive member during warm-up. It is.

Second Embodiment
In the present embodiment, acquisition of parameters for the misregistration correction operation of the image forming apparatus 1 is performed according to the flowchart shown in FIG. That is, as shown in step S22, when the data storage processing unit 124E of the optical writing device control unit 120 stores the offset at the time of separation and the offset at the time of contact in the storage unit 126, the temperature is detected by the temperature detection unit 125. Store it in association. That is, as an example, as shown in FIG. 19, the contact offset and the separation offset associated with the detected temperature are stored in the storage unit 126. As shown in FIG. 19, the difference between the offset at the time of contact and the offset at the time of separation is a contact / separation difference. Therefore, in this embodiment, the contact / separation difference also substantially corresponds to the temperature in the storage unit 126. It will be remembered. In the present embodiment, the data storage processing unit 124E corresponds to the data accumulation processing unit.

  Then, when executing the printing process, the writing control unit 121 and the correction control unit 124A of the optical writing device control unit 120 correspond to the temperature detected at that time from the data stored in the storage unit 126. The contact offset or the offset at the time of separation and the contact / separation difference are acquired directly or by estimation such as interpolation or least square approximation, and the timing at which the light source device 281 emits the light beam can be controlled. Thereby, the influence of the temperature with respect to position shift can be made smaller. In the present embodiment, the processing of the writing control unit 121 and the correction control unit 124A of the optical writing device control unit 120 at the time of executing the printing described above, the processing in step S16 by the data storage processing unit 124E, and the storage in the storage unit 126 Except for the form and the like, it is exactly the same as the first embodiment. Further, the optical writing device control unit 120 executes interpolation and least square approximation in advance at a predetermined timing. For example, the optical writing device control unit 120 acquires data as indicated by a broken line in FIG. I can leave. In this way, the writing control unit 121 and the correction control unit 124A can more quickly and more easily obtain the parameter corresponding to the temperature detected at the time when the printing process is executed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made. Also, an image forming device, an optical writing device, a light source, a light source control unit, an image detection unit, a first detection period count unit, an offset calculation unit, a second detection period count unit, an expansion / contraction rate calculation unit, and a contact / separation difference calculation The part, the temperature detection part, the data accumulation processing part, the transport body, the drawing pattern, etc. can be changed as appropriate.

  For example, in the present invention, as shown in FIG. 20, an image formed by being transferred from a photosensitive drum 109 as an example of a photosensitive member onto a conveying belt 105 as an example of a conveying member is further transferred onto the paper surface of a sheet. The intermediate transfer type optical writing apparatus or image forming apparatus can be implemented, and similar effects can be obtained. In this case, the conveyance belt 105, which is an intermediate transfer belt, conveys an image as a conveyance body. Alternatively, the second drawing pattern may be formed as one drawing pattern, and the count from the detection start to the detection end of the drawing pattern may be counted as the second detection period.

1. Image forming apparatus (example)
107: Driving roller (example)
109 ... Photosensitive drum (an example of a photosensitive member)
111 ... Optical writing device (an example)
122... Count unit (an example of a first detection period count unit and a second detection period count unit)
123 ... Sensor control unit (an example of an image detection unit)
124B ... Expansion rate calculation unit (an example)
124C ... Offset calculation unit (an example)
124D ... Contact / separation difference calculation unit (an example)
124E: Data storage processing unit (an example of a data storage processing unit)
125... Temperature detector (an example)
281 ... Light source (an example of a light source device)
411A, 411B... First drawing pattern (example), second drawing pattern (example)

JP 2008-299311 A

Claims (11)

An optical writing device that forms an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with a light beam,
A light source that emits a light beam;
A light source controller that controls the light source to irradiate a light beam on the photosensitive member;
Image detection for detecting that the image transferred to the surface of the carrier is in a position facing the sensor by the output signal of the sensor for detecting the surface of the carrier to which the image developed on the photoconductor is transferred And
A first detection period is counted as a period from when the light source control unit starts the process of forming the first drawing pattern on the carrier to when the image detection unit detects the first drawing pattern. A first detection period counting unit to perform,
An offset calculation unit that calculates an offset as a difference between the first detection period and a first reference value as a reference of the first detection period;
A second detection period counting unit that counts a second detection period as a period in which the image detection unit detects two locations of the second drawing pattern drawn on the carrier;
An expansion / contraction rate calculation unit that calculates the expansion / contraction rate of the transport body by comparing the second detection period and a second reference value as a reference of the second detection period;
The first detection period in a state in which a part of the plurality of photoconductors is in contact with the transport body and the first detection period in a state in which all of the plurality of photoconductors are in contact with the transport body A contact / separation difference calculation unit for calculating a contact / separation difference as a difference between
The offset corresponding to one of the state in which a part of the plurality of photoconductors is in contact with the conveyance body and the state in which all of the plurality of photoconductors are in contact with the conveyance body, and the calculated contact A correction control unit that corrects the timing of irradiating the light source with the light beam in the other state based on the separation difference and the calculated expansion / contraction rate;
An optical writing device comprising: An optical writing device that forms an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with a light beam,
A light source that emits a light beam;
A light source controller that controls the light source to irradiate a light beam on the photosensitive member;
Image detection for detecting that the image transferred to the surface of the carrier is in a position facing the sensor by the output signal of the sensor for detecting the surface of the carrier to which the image developed on the photoconductor is transferred And
A first detection period is counted as a period from when the light source control unit starts the process of forming the first drawing pattern on the carrier to when the image detection unit detects the first drawing pattern. A first detection period counting unit to perform,
A temperature detector for detecting the temperature inside or around the optical writing device;
In the predetermined storage unit, the detected first detection period or a difference between the first detection period and a first reference value as a reference of the first detection period is detected in the predetermined storage unit. A data storage processing unit for storing the temperature and the contact state of the plurality of photoconductors with respect to the conveyance body,
Referring to the predetermined storage unit, the first detection period and the plurality of photoconductors corresponding to the detected temperature in a state where a part of the plurality of photoconductors is in contact with the transport body A contact / separation difference calculation unit that calculates a contact / separation difference as a difference from the first detection period in a state where all of the
The offset corresponding to one of the state in which a part of the plurality of photoconductors is in contact with the transport body and the state in which all of the plurality of photoconductors are in contact with the transport body, and the calculated A correction control unit that corrects the timing of irradiating the light source with the light source in the other state based on the approaching and separating difference;
An optical writing device comprising:   The correction control unit is configured so that, based on the offset calculated in a state where one of the plurality of photoconductors is in contact with the transport body, the plurality of photoconductors are in contact with the transport body. The optical writing apparatus according to claim 1, wherein timing for irradiating the light source with the light beam is corrected.   The correction control unit is configured so that one of the plurality of photoconductors is in contact with the transport body based on the offset calculated in a state where all of the plurality of photoconductors are in contact with the transport body. The optical writing device according to claim 1, wherein timing for irradiating the light source with the light beam is corrected.   The optical writing apparatus according to claim 1, wherein a part of the second drawing pattern is used as the first drawing pattern.   The optical writing apparatus according to claim 1, wherein the second drawing pattern is a black drawing pattern drawn by the black photosensitive member. The second drawing pattern includes two drawing patterns,
The interval between the two drawing patterns is an integral multiple of the circumference of one of the photoconductors, an integral multiple of the circumference of a driving roller that drives the transport body, or an integral multiple of the circumference of the photoconductor, and The optical writing apparatus according to claim 1, wherein the optical writing apparatus is set to an integral multiple of a circumference of the driving roller. During the warm-up operation of the optical writing device,
At least the first drawing pattern is drawn on a surface of the transport body using a part of the plurality of photoconductors,
The correction controller corrects the timing of irradiating the light source with a light beam based on the offset and the approach / separation difference calculated based on the first drawing pattern. The optical writing device according to any one of the above.   An image forming apparatus comprising the optical writing device according to claim 1. An optical writing control method in an optical writing apparatus for forming an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with an optical beam,
A light source control step of controlling the light source to irradiate a light beam on the photoreceptor;
Image detection for detecting that the image transferred to the surface of the carrier is in a position facing the sensor by the output signal of the sensor for detecting the surface of the carrier to which the image developed on the photoconductor is transferred Steps,
A first detection period as a period from the start of the process of forming the first drawing pattern on the carrier in the light source control step to the detection of the first drawing pattern in the image detection step A first detection period counting step to count;
An offset calculating step for calculating an offset as a difference between the first detection period and a first reference value as a reference of the first detection period;
A second detection period counting step for counting a second detection period as a period during which two locations of the second drawing pattern drawn on the carrier are detected in the image detection step;
An expansion / contraction rate calculating step of calculating the expansion / contraction rate of the transport body by comparing the second detection period and a second reference value as a reference of the second detection period;
The first detection period in a state in which a part of the plurality of photoconductors is in contact with the transport body and the first detection period in a state in which all of the plurality of photoconductors are in contact with the transport body A contact / separation difference calculating step for calculating a contact / separation difference as a difference between;
The offset corresponding to one of the state in which a part of the plurality of photoconductors is in contact with the conveyance body and the state in which all of the plurality of photoconductors are in contact with the conveyance body, and the calculated contact A correction control step of correcting the timing of irradiating the light source with the light source in the other state based on the separation difference and the calculated expansion / contraction rate;
An optical writing control method comprising: An optical writing control method in an optical writing apparatus for forming an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with an optical beam,
A light source control step of controlling the light source to irradiate a light beam on the photoreceptor;
Image detection for detecting that the image transferred to the surface of the carrier is in a position facing the sensor by the output signal of the sensor for detecting the surface of the carrier to which the image developed on the photoconductor is transferred Steps,
A first detection period as a period from the start of the process of forming the first drawing pattern on the carrier in the light source control step to the detection of the first drawing pattern in the image detection step A first detection period counting step to count;
A temperature detecting step for detecting a temperature inside or around the optical writing device;
In the predetermined storage unit, the detected first detection period or a difference between the first detection period and a first reference value as a reference of the first detection period is detected in the predetermined storage unit. Data storage processing step for storing the temperature and the contact state of the plurality of photoconductors with respect to the conveyance body,
Referring to the predetermined storage unit, the first detection period and the plurality of photoconductors corresponding to the detected temperature in a state where a part of the plurality of photoconductors is in contact with the transport body A contact / separation difference calculating step for calculating a contact / separation difference as a difference from the first detection period in a state where all of the
The offset corresponding to one of the state in which a part of the plurality of photoconductors is in contact with the transport body and the state in which all of the plurality of photoconductors are in contact with the transport body, and the calculated A correction control step for correcting the timing of irradiating the light source with the light source in the other state, based on the contact / separation difference;
An optical writing control method comprising:

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