JP2015172715A - image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and program with which displacement of an image in a direction of conveyance of a recording medium can be accurately suppressed compared with the case of correcting displacement of an image in the direction of conveyance of a recording medium by using the existing correction method.SOLUTION: The reference correction amount for correcting the amount of displacement of an image in a direction of conveyance of a recording medium is determined in advance according to the reference image density, and an image forming apparatus approximates the reference correction amount according to the difference between the reference image density and the density of an image to be formed (first difference in image density) (step 408), and controls forming means to form an image to be formed in which the amount of displacement in the direction of conveyance corrected with the approximate correction amount obtained by approximating the reference correction amount (step 412).

Description

  The present invention relates to an image forming apparatus and a program.

  Japanese Patent Application Laid-Open No. 2004-228561 changes the writing timing of each scanning line in the sub-scanning direction according to the thickness information acquisition unit that acquires the thickness information of the recording sheet and the thickness information acquired by the thickness information acquisition unit. An image forming apparatus including a writing timing changing unit is disclosed. In the image forming apparatus described in Patent Document 1, the writing timing corresponding to the thickness information is controlled according to the thickness of the recording sheet.

  Patent Document 2 includes image correction magnification calculation storage means for calculating and storing an image magnification to be recorded on the back surface of a single-side recorded sheet based on the sheet size detected by the detection means and the single-side recorded sheet size. An image forming apparatus is disclosed. Further, the image forming apparatus described in Patent Document 2 outputs an operation control signal for the image recording member at the time of image recording on the back surface of the single-side recorded sheet according to the image magnification stored in the image correction magnification calculation storage unit. Image recording member control means.

  Patent Document 3 discloses an image forming apparatus that corrects a deviation in the conveyance direction of an image formed on a sheet using a positional deviation correction value determined in accordance with a toner amount (a degree of toner use) included in the image. It is disclosed.

Japanese Patent No. 4140250 Japanese Patent No. 4111026 Patent No. 4905517

  An object of the present invention is to provide an image forming apparatus capable of suppressing an image shift in the conveyance direction of a recording medium with high accuracy as compared with a case where an image shift in the conveyance direction of the recording medium is corrected using an existing correction method. And providing a program.

  The image forming apparatus according to claim 1 corrects a deviation of an image in a conveyance direction on a recording medium and a forming unit that forms an image on the recording medium by transferring a developer image performed according to conveyance of the recording medium. The reference correction amount is determined in advance according to the reference image density, and the approximate correction amount approximates the reference correction amount according to the difference between the formation target image density that is the image density of the formation target image and the reference image density. Control means for controlling the forming means so that the image to be formed in which the shift amount in the transport direction is corrected is formed.

  The image forming apparatus according to claim 1, wherein, as in the invention according to claim 2, detection for detecting a shift amount in the transport direction of a reference image formed at a reference image density on a recording medium by the forming unit. And the reference correction amount is a correction amount for correcting the shift amount detected by the detection unit.

  3. The image forming apparatus according to claim 2, wherein the reference image density is determined according to a use record of an image density of an image formed by the forming unit as in the invention according to claim 3. Density.

  In the image forming apparatus according to claim 3, as in the invention according to claim 4, the actual image density is used at a predetermined frequency among the image densities of the images formed by the forming unit. It has a proven image density.

  5. The image forming apparatus according to claim 1, wherein the approximate correction amount is a difference between the image density to be formed and the reference image density as in the invention according to claim 5. , A reference correction amount associated with a predetermined reference image density, and an approximate correction amount derived by an interpolation method based on the standard correction amount.

  6. The image forming apparatus according to claim 5, wherein the reference correction amount is a type of a recording medium on which an image is formed by the forming unit, a performance of the forming unit, and the The reference correction amount is determined according to at least the type of the recording medium in the operating environment of the forming unit.

  A program according to a seventh aspect is a program for causing a computer to function as a control unit in the image forming apparatus according to any one of the first to sixth aspects.

  According to the first and seventh aspects of the present invention, the image shift in the recording medium conveyance direction can be more accurately compared to the case where the image correction in the recording medium conveyance direction is corrected using an existing correction method. Can be suppressed.

  According to the second aspect of the present invention, compared to the case where the reference correction amount is set without detecting the shift amount of the reference image formed at the reference image density, the shift of the image in the transport direction of the recording medium is reduced. It can be suppressed with high accuracy.

  According to the third aspect of the present invention, compared with the case where the image density determined according to the actual use of the image density of the image formed by the forming unit is not used as the actual image density, the image in the conveyance direction of the recording medium The shift can be suppressed with high accuracy.

  According to the fourth aspect of the present invention, image deviation in the recording medium conveyance direction is suppressed with high accuracy compared to a case where an image density with a proven record used at a predetermined frequency is not used as the record image density. be able to.

  According to the fifth aspect of the present invention, the approximate correction amount is calculated by the difference between the formation target image density and the standard image density, the reference correction amount associated with the predetermined reference image density, and the interpolation method based on the standard correction amount. The approximate correction amount can be easily derived as compared to the case where is not derived.

  According to the invention of claim 6, the reference correction amount is not determined according to at least the type of the recording medium among the type of the recording medium, the performance of the forming unit, and the operating environment of the forming unit. In comparison with this, it is possible to correct the shift amount of the image in the conveyance direction of the recording medium with high accuracy.

1 is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment. 1 is a schematic cross-sectional view illustrating an example of a configuration of an inline sensor included in an image forming apparatus according to an embodiment. 1 is a schematic configuration diagram illustrating an example of an external configuration of an image reading unit included in an image forming apparatus according to an embodiment. FIG. 3 is a schematic configuration diagram illustrating an example of a configuration of a document conveying device and a scanning unit of an image reading unit included in an image forming apparatus according to an embodiment. 1 is a block diagram illustrating an example of an electrical hardware configuration of an image forming apparatus according to an embodiment. 2 is a block diagram illustrating an example of a main configuration of an image processing unit included in the image forming apparatus according to the embodiment. FIG. FIG. 3 is a schematic configuration diagram illustrating an example of an intermediate transfer belt and a secondary transfer roll in a sheet non-conveying state. FIG. 3 is a schematic configuration diagram illustrating an example of an intermediate transfer belt and a secondary transfer roll in a paper transport state. FIG. 3 is a schematic configuration diagram illustrating an example of an intermediate transfer belt and a secondary transfer roll that are not yet transferred. It is a graph which shows an example of the change of the conveyance direction magnification with respect to image density. It is a graph which shows an example of the change of the conveyance direction magnification with respect to the image density when an image is formed on 220 gsm ² uncoated paper. It is a graph which shows an example of the change of the conveyance direction magnification with respect to the image density when an image is formed on 82 gsm ² uncoated paper. It is a graph which shows an example of the change of the conveyance direction magnification with respect to the image density when an image is formed on 128 gsm ² coated paper. It is a schematic block diagram which shows an example of a structure of the reference table memorize | stored in the correction information storage part of the image process part contained in the image forming apparatus which concerns on embodiment. It is a flowchart which shows an example of the flow of the reference | standard information setting process which concerns on embodiment. FIG. 10 is a diagram illustrating an example of a mode in which a lattice chart sheet on which a reference image is formed is conveyed by an image forming unit included in the image forming apparatus according to the embodiment, and the reference image is read by an inline sensor. It is a flowchart which shows an example of the flow of the deviation | shift amount correction process which concerns on embodiment. It is explanatory drawing with which it uses for description of the method of deriving | requiring an approximate correction amount by the interpolation method by the deviation amount correction process which concerns on embodiment. 3 is a schematic configuration diagram illustrating an example of storage contents of a secondary storage unit included in the image forming apparatus according to the embodiment. FIG. 6 is a graph showing an example of a correspondence relationship between the image density of each reference image formed for each image density by a different image forming apparatus and the magnification in the conveyance direction. It is a flowchart which shows an example of the flow of the reference table production | generation process which concerns on embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In the following, in the image forming apparatus 10 shown in FIG. 1 as an example, two-component development in which a toner and a carrier that plays a role of transporting the toner using an electrostatic force to adhere the toner to the electrostatic latent image are mixed. A case where an electrostatic latent image is developed with an agent will be described as an example. However, the present invention is not limited to this, and any image forming apparatus can be used as long as it is an electrophotographic image forming apparatus that develops an electrostatic latent image with an electrophotographic developer other than a two-component developer. Also applies.

  Hereinafter, a so-called tandem type intermediate transfer type image forming apparatus 10 will be described as an example, but the present invention is not limited to this. For example, it may be a rotary development type image forming apparatus, and any electrophotographic type image forming apparatus in which a reference information setting process (see FIG. 12) and a deviation amount correcting process (see FIG. 14) described later are executed. Good.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention, and FIG. 2 is an inline sensor (registered trademark) provided in the image forming apparatus 10 according to an embodiment of the present invention. It is a figure which shows an example.

  (overall structure)

  The image forming apparatus 10 according to the present embodiment forms a full color image or a black and white image. As shown in FIG. 1, as an example, an image forming unit 10A (an example of a forming unit according to the present invention), a fixing discharge unit. 10B and an image reading unit 10C. Further, a control system unit 10D is provided above the fixing discharge unit 10B. The control system unit 10D includes a controller 270 (see FIG. 2) and an image processing unit 290 (see FIG. 4) which is an example of a control unit according to the present invention. The controller 270 controls the overall operation of the image forming apparatus 10, and the image processing unit 290 performs various processes on first image information and second image information described later.

  The image forming unit 10A includes a toner cartridge that stores toners of the first special color (V), the second special color (W), yellow (Y), magenta (M), cyan (C), and black (K). 14V, 14W, 14Y, 14M, 14C, and 14K are provided to be replaceable along the horizontal direction.

  The first special color and the second special color are appropriately selected from colors other than yellow, magenta, cyan, and black (including transparency). In the following description, the first special color (V), the second special color (W), yellow (Y), magenta (M), cyan (C), and black (K) are distinguished for each component. Is described with a letter followed by any letter of V, W, Y, M, C, or K. The first special color (V), the second special color (W), yellow (Y), magenta When not distinguishing (M), cyan (C), and black (K), V, W, Y, M, C, and K are omitted.

  Further, under the toner cartridge 14, six image forming units 16 corresponding to the respective color toners are provided along the horizontal direction so as to correspond to the respective toner cartridges 14.

  The image forming unit 10A includes an image forming unit 16 for each color of V, W, Y, M, C, and K. The image forming unit 10 </ b> A includes a transfer unit 32, a recording medium storage unit 48, and an environment sensor 79.

  An exposure device 40 (40V, 40W, 40Y, 40M, 40C) provided for each image forming unit 16 receives image information subjected to image processing by the image processing unit 290, and modulates light according to the image information. It is configured to irradiate an image carrier 18 (18V, 18W, 18Y, 18M, 18C) described later with a beam L.

  Each image forming unit 16 includes an image carrier 18 that is rotationally driven in one direction. By irradiating each image carrier 18 with the light beam L from each exposure device 40, an electrostatic latent image is formed on each image carrier 18.

  Around each image carrier 18, a corona discharge (non-contact charging) scorotron charger that charges the image carrier 18 and an electrostatic latent image formed on the image carrier 18 by the exposure device 40 are developed. A developing device that develops with the agent, a blade that removes the developer remaining on the image carrier 18 after transfer, and a static eliminator that radiates light by irradiating the image carrier 18 after transfer with light. . The scorotron charger, the developing device, the blade, and the charge eliminating device are arranged in this order from the upstream side to the downstream side in the rotation direction of the image carrier 18 so as to face the surface of the image carrier 18.

  A transfer unit 32 is provided below each image forming unit 16. The transfer unit 32 multiplexes an annular intermediate transfer belt 34 in contact with each image carrier 18 and a toner image (an example of a developer image according to the present invention) formed on each image carrier 18 onto the intermediate transfer belt 34. A primary transfer roll 36 to be transferred is included.

  The intermediate transfer belt 34 includes a drive roll 38 driven by a motor (not shown), a tension applying roll 41 that applies tension to the intermediate transfer belt 34, a counter roll 42 that faces a secondary transfer roll 62 described later, and a plurality of rolls. It is wound around the winding roll 44 and is circulated and moved in one direction (counterclockwise direction in FIG. 1) by the drive roll 38.

  Each primary transfer roll 36 is disposed opposite to the image carrier 18 of each image forming unit 16 with the intermediate transfer belt 34 interposed therebetween. The primary transfer roll 36 is applied with a transfer bias voltage having a polarity opposite to the toner polarity by a power supply unit (not shown). With this configuration, the toner image formed on the image carrier 18 is transferred to the intermediate transfer belt 34.

  On the opposite side of the drive roll 38 across the intermediate transfer belt 34, there is provided a removing device 46 that removes residual toner, paper dust and the like on the intermediate transfer belt 34 by bringing the blade into contact with the intermediate transfer belt 34. .

  Below the transfer unit 32, two recording medium storage units 48 that store paper P as an example of a recording medium are provided along the horizontal direction.

  Each recording medium accommodating portion 48 can be pulled out from the housing 12 of the image forming portion 10A. Above one end side (the right side in FIG. 1) of each recording medium accommodating portion 48, a delivery roll 52 that sends out the paper P from each recording medium accommodating portion 48 to the transport path 60 is provided.

  In each recording medium accommodating portion 48, a bottom plate 50 on which the paper P is placed is provided. The bottom plate 50 is lowered according to an instruction from the controller 270 when the recording medium accommodating portion 48 is pulled out from the housing 12. When the bottom plate 50 is lowered, a space in which the user replenishes the paper P is formed in the recording medium accommodating portion 48.

  When the recording medium accommodating portion 48 pulled out from the housing 12 is attached to the housing 12, the bottom plate 50 is raised by an instruction from the controller 270. By raising the bottom plate 50, the uppermost sheet P placed on the bottom plate 50 and the delivery roll 52 come into contact with each other.

  On the downstream side in the recording medium conveyance direction of the delivery roll 52 (hereinafter sometimes simply referred to as “downstream side”), there is a separation roll 56 that separates the sheets P delivered from the recording medium accommodating portion 48 one by one. Is provided. A plurality of transport rolls 54 that transport the paper P downstream in the transport direction are provided on the downstream side of the separation roll 56.

  The conveyance path 60 provided between the recording medium storage unit 48 and the transfer unit 32 is configured to return the sheet P fed from the recording medium storage unit 48 to the left side in FIG. The portion 60B extends to the transfer position T between the secondary transfer roll 62 and the opposing roll 42 so as to be folded back to the right in FIG.

  The secondary transfer roll 62 is applied with a transfer bias voltage having a polarity opposite to the toner polarity by a power feeding unit (not shown). With this configuration, each color toner image transferred onto the intermediate transfer belt 34 is secondarily transferred onto the paper P conveyed along the conveyance path 60 by the secondary transfer roll 62.

  A spare path 66 extending from the side surface of the housing 12 is provided so as to join the second folding portion 60 </ b> B of the transport path 60. A sheet P sent out from another recording medium storage unit (not shown) arranged adjacent to the housing 12 can enter the transport path 60 through the spare path 66.

  On the downstream side of the transfer position T, a plurality of transport belts 70 are provided in the housing 12 for transporting the paper P on which the toner image has been transferred toward the fixing and discharging unit 10B. A conveyor belt 80 that conveys downstream is provided in the casing 13 of the fixing discharge unit 10B.

  Each of the plurality of conveyance belts 70 and the conveyance belt 80 is formed in an annular shape and is wound around a pair of winding rolls 72. The pair of winding rolls 72 are respectively arranged on the upstream side and the downstream side in the transport direction of the paper P, and when one of them is rotationally driven, the transport belt 70 (transport belt 80) is moved in one direction (the timepiece in FIG. 1). Cycle in the direction of rotation).

  The environmental sensor 79 measures the temperature and humidity in the space inside the housing 12. The environmental sensor 79 is connected to the controller 270 and outputs a measurement result to the controller 270.

  The fixing discharge unit 10B includes a fixing unit 82, a cooling unit 110, an in-line sensor 200 (an example of a detection unit according to the present invention), and a discharge unit 196.

  A fixing unit 82 for fixing the toner image transferred onto the surface of the paper P to the paper P with heat and pressure is provided on the downstream side of the conveyance belt 80.

  The fixing unit 82 includes a fixing belt 84 and a pressure roll 88 disposed so as to contact the fixing belt 84 from below. A fixing unit N is formed between the fixing belt 84 and the pressure roll 88 to fix the toner image by pressurizing and heating the paper P.

  The fixing belt 84 is formed in an annular shape and is wound around the drive roll 89 and the driven roll 90. The drive roll 89 faces the pressure roll 88 from above, and the driven roll 90 is disposed above the drive roll 89.

  Each of the driving roll 89 and the driven roll 90 includes a heating unit such as a halogen heater. As a result, the fixing belt 84 is heated.

  As shown in FIG. 1, a conveyance belt 108 is provided on the downstream side of the fixing unit 82 to convey the paper P sent out from the fixing unit 82 to the downstream side. The conveyor belt 108 is formed in the same manner as the conveyor belt 70.

  A cooling unit 110 that cools the paper P heated by the fixing unit 82 is provided on the downstream side of the conveyance belt 108.

  The cooling unit 110 includes an absorption device 112 that absorbs the heat of the paper P, and a pressing device 114 that presses the paper P against the absorption device 112. The absorption device 112 is disposed on one side (upper side in FIG. 1) with respect to the conveyance path 60, and the pressing device 114 is disposed on the other side (lower side in FIG. 1).

  The absorption device 112 includes an annular absorption belt 116 that contacts the paper P and absorbs the heat of the paper P. The absorption belt 116 is wound around a driving roll 120 that transmits a driving force to the absorption belt 116 and a plurality of winding rolls 118.

  A heat sink 122 made of an aluminum material that dissipates heat absorbed by the absorption belt 116 by contacting the absorption belt 116 in a planar shape is provided on the inner peripheral side of the absorption belt 116.

  Further, a fan 128 for removing heat from the heat sink 122 and discharging hot air to the outside is disposed on the back side of the housing 13 (the back side of the paper surface shown in FIG. 1).

  The pressing device 114 that presses the paper P against the absorbing device 112 includes an annular pressing belt 130 that conveys the paper P while pressing the paper P against the absorbing belt 116. The pressing belt 130 is wound around a plurality of winding rolls 132.

  On the downstream side of the cooling unit 110, there is provided a correction device 140 that conveys the paper P with the paper P interposed therebetween and corrects the curl of the paper P.

  An inline sensor 200 that detects a toner density defect, an image defect, an image position defect, and the like of the toner image fixed on the paper P is provided on the downstream side of the correction device 140. Details of the inline sensor 200 will be described later.

  On the downstream side of the inline sensor 200, a discharge roll 198 that discharges the paper P on which an image is formed on one side to a discharge unit 196 attached to the side surface of the housing 13 is provided.

  On the other hand, when images are formed on both sides, the paper P sent out from the inline sensor 200 is conveyed to a reversing path 194 provided on the downstream side of the inline sensor 200.

  The reverse path 194 includes a branch path 194A that branches from the transport path 60, a paper transport path 194B that transports the paper P transported along the branch path 194A toward the housing 12, and a paper transport path 194B. A reversing path 194 </ b> C is provided that folds the conveyed paper P in the reverse direction and reverses the front and back by performing switchback conveyance.

  With this configuration, the paper P that has been switched back in the reverse path 194C is transported toward the first housing 10A, and further enters the transport path 60 provided above the recording medium accommodating portion 48, so that the transfer position T Will be sent again.

  Next, an image forming process of the image forming apparatus 10 will be described.

  Image information subjected to image processing by the image processing unit 290 is sent to each exposure apparatus 40. In each exposure device 40, each light beam L is emitted according to image information, and exposed to each image carrier 18 charged by a scorotron charger, thereby forming an electrostatic latent image.

  The electrostatic latent image formed on the image carrier 18 is developed by the developing device, and the first special color (V), the second special color (W), yellow (Y), magenta (M), and cyan (C). A toner image of each color of black (K) is formed.

  As shown in FIG. 1, the toner images of the respective colors formed on the image carriers 18 of the image forming units 16V, 16W, 16Y, 16M, 16C, and 16K are six primary transfer rolls 36V, 36W, 36Y, and 36M. , 36C, and 36K, multiple transfer is sequentially performed on the intermediate transfer belt.

  The color toner images transferred onto the intermediate transfer belt 34 are secondarily transferred onto the paper P conveyed from the recording medium accommodating portion 48 by the secondary transfer roll 62. The sheet P on which the toner image has been transferred is transported toward the fixing unit 82 provided inside the housing 13 by the transport belt 70.

  Each color toner image on the paper P is fixed on the paper P by being heated and pressurized by the fixing unit 82. Further, the sheet P on which the toner image is fixed is cooled by passing through the cooling unit 110 and then sent to the correction device 140 to correct the curvature generated on the sheet P.

  The paper P whose curvature is corrected is discharged to the discharge unit 196 by the discharge roll 198 after the inline sensor 200 detects an image defect or the like.

  On the other hand, when an image is formed on a non-image surface on which no image is formed (in the case of double-sided printing), after passing through the inline sensor 200, the paper P is reversed by the reversing path 194 and above the recording medium container 48. A toner image is formed on the back surface in the above-described procedure.

  In the image forming apparatus 10 according to the present embodiment, components for forming images of the first special color and the second special color (image forming units 16V and 16W, exposure devices 40V and 40W, toner cartridges 14V and 14W, The primary transfer rolls 36 </ b> V and 36 </ b> W) are configured to be attachable to the housing 12 as additional components according to the user's selection. Accordingly, the image forming apparatus 10 does not include a part for forming the first special color and second special color images, and the image of any one of the first special color and the second special color. It is good also as a structure which has only the components for forming.

  Next, the inline sensor 200 will be described.

  In the following description, the depth direction (main scanning direction) of the image forming apparatus 10 is the X direction, the length direction of the apparatus (sub-scanning direction, which is the conveyance direction of the paper P) is the Y direction, and the height direction of the apparatus is. This is the Z direction.

(Basic configuration and function of inline sensor)

  As shown in FIG. 2, the inline sensor 200 includes an irradiation unit 202 that irradiates light toward the paper P on which an image is recorded, and a CCD sensor 204 that reflects the light emitted from the irradiation unit 202 and reflected by the paper P. The image forming unit 208 includes an image forming optical system 206 that forms an image on the screen, and a setting unit 210 provided with various standards for use of the in-line sensor 200 and calibration. In the present embodiment, the CCD sensor 204 is described as an example of a line sensor, but an area sensor may be applied.

  The irradiation unit 202 is disposed on the upper side of the conveyance path 60 of the paper P and has a pair of lamps 212. Each of the lamps 212 is a xenon lamp that is elongated in the X direction, and the length of the irradiation range is larger than the width of the largest sheet P to be conveyed. The pair of lamps 212 are arranged symmetrically with respect to the optical axis OA (designed optical axis) that is reflected by the paper P and travels toward the image forming unit 208. More specifically, the lamps 212 are arranged symmetrically with respect to the optical axis OA so that the irradiation angles on the paper P are 45 ° to 50 °, respectively.

  Specifically, the pair of lamps 212 are arranged along the conveyance path 60 of the paper P, and the first lamp 212A of the light source disposed upstream in the conveyance direction of the paper P and the paper with respect to the first lamp 212A And a second lamp 212B of a light source disposed on the downstream side in the P transport direction. And it is comprised so that the light irradiated from the 1st lamp 212A and the 2nd lamp 212B may be irradiated to the irradiation position D on the conveyance path | route 60 between the 1st lamp 212A and the 2nd lamp 212B.

  Further, the imaging optical system 206 reflects the light guided along the optical axis OA in the Y direction (in this embodiment, on the downstream side in the transport direction of the paper P), and the first mirror 214 reflects the light. The second mirror 216 that reflects the reflected light upward, the third mirror 218 that reflects the light reflected by the second mirror 216 upstream in the transport direction of the paper P, and the light that is reflected by the third mirror 218 is the CCD sensor 204. The main part is a lens 220 that focuses (images) the light. The CCD sensor 204 is arranged on the upstream side in the transport direction of the paper P with respect to the optical axis OA.

  The length of the first mirror 214 in the X direction is larger than the maximum width of the paper P. The first mirror 214 to the third mirror 218 reflect the reflected light of the paper P incident on the imaging optical system 206 while constricting (condensing) the light in the X direction (main scanning direction). ing. Thus, the reflected light from each part in the width direction of the paper P is made incident on the substantially cylindrical lens 220.

  With the above configuration, in the in-line sensor 200, the CCD sensor 204 outputs (feeds back) the imaged light, that is, a signal corresponding to the image density, to the controller 270 (see FIG. 1) of the image forming apparatus 10. Yes. The controller 270 corrects an image formed in the image forming unit 16 based on a signal from the inline sensor 200. In the image forming apparatus 10, as an example, the intensity of irradiation light by the exposure apparatus 40, the image formation position, and the like are corrected based on a signal from the inline sensor 200.

  In addition, a light amount diaphragm unit 224 (224L, 224S, 224U)) is provided between the third mirror 218 and the lens 220 in the imaging optical system 206. The light amount diaphragm unit 224 narrows the light amount of the light imaged on the CCD sensor 204 across the optical path in the X direction in the Z direction (direction intersecting with the main scanning direction) and adjusts the light amount diaphragm amount by operating from the outside. It is configured to be possible. The light amount stop amount by the light amount stop unit 224 is adjusted so that the light amount imaged on the CCD sensor 204 is equal to or larger than a predetermined amount even if the light emission amount of each lamp 212 changes with time. .

  On the other hand, the setting unit 210 includes a reference roll 226 that is long in the X direction. The reference roll 226 has a detection reference surface 228 that faces the conveyance path 60 when the image detection of the paper P is performed, a retraction surface 230 that faces the conveyance path when the image detection of the paper P by the inline sensor 200 is not performed, It has a white reference surface 232, a color reference surface 234 on which a multicolor pattern is formed along the longitudinal direction, and a composite inspection surface 236 on which a plurality of inspection patterns are formed. In this embodiment, the reference roll 226 is formed in a polygonal cylindrical shape having eight or more surfaces formed in the circumferential direction. Only one detection reference surface 228, retraction surface 230, color reference surface 234, and composite inspection surface 236 are provided, and two white reference surfaces 232 are provided.

  The reference roll 226 is configured to switch the surface facing the conveyance path 60 side by rotating around the rotation shaft 226A. The surface of the reference roll 226 is switched by the control circuit 100 provided on the circuit board 262. Moreover, the reference | standard roll 226 is formed in the polygonal cylinder shape more than an octagon, The distance difference with respect to the rotation center of the circumferential direction center of each surface and the corner | angular part between surfaces is suppressed small. Thus, the corner between the surfaces of the reference roll 226 does not interfere with the irradiation unit 202 while keeping the distance between each surface of the reference roll 226 and the irradiation position (window glass 286 described later) of each lamp 212 small. ing.

  The detection reference surface 228 has a circumferential width smaller than the other surfaces, and the surfaces on both sides in the circumferential direction are guide surfaces 238 that do not have the above-described functions as the respective references. The detection reference surface 228 is a position reference surface for positioning the detected (read) surface of the conveyed paper P at the irradiation position by each lamp 212.

  The retracting surface 230 has a circumferential width larger than that of other surfaces. The retreat surface 230 is a guide surface for guiding the paper P when the inline sensor 200 does not detect the image of the paper P, and the distance from the axis of the rotation shaft 226A is smaller than the detection reference surface 228. ing. Thereby, when the image detection of the paper P by the inline sensor 200 is not performed, a conveyance path having a wider interval with the irradiation unit 202 (window glass 286) than when the image detection of the paper P by the inline sensor 200 is performed. It is supposed to be formed.

  The white reference surface 232 is used for calibration of the illumination unit 202 and the imaging optical system 206, and is configured by adhering a reference white film from which a predetermined signal is output from the imaging optical system 206. . The color reference plane 234 is used for calibration of the illumination unit 202 and the imaging optical system 206, and is a film on which a reference color pattern is output in which a predetermined signal corresponding to each color is output from the imaging optical system 206. Is affixed.

  The composite inspection surface 236 is formed by arranging a position adjustment pattern for calibrating the position of the reference roll 226 in the rotation direction (the conveyance direction of the paper P), a focus detection pattern, and a depth detection pattern on the same surface. ing.

  The image reading unit 10 </ b> C reads an image of the document 331 (see FIG. 3B), and outputs second image information indicating the read image to the controller 270. In the present embodiment, “reading an image” means optically detecting an image density (hereinafter referred to as “image density”). In other words, the image density refers to the density of the image. In the present embodiment, for convenience of explanation, when an image of the document 331 is read by the image reading unit 10C, an image indicated by the second image information obtained by reading is formed on the paper P by the image forming unit 10A. It is assumed that

  As an example, as illustrated in FIGS. 3A and 3B, the image reading unit 10 </ b> C includes a case 313 and a document conveying device 316. As an example, as shown in FIG. 3A, the case 313 accommodates the main body of the image reading unit 10C, and the upper surface of the case 313 has a substantially rectangular opening 321 (in this embodiment, an opening larger than an A3-sized document). Is formed. The opening 321 is shielded by a platen glass 322 on which a document 331 (see FIG. 3B) is placed.

  Fixing portions 344A and 344B are provided on the upper surface of the case 313. A hinge member (not shown) provided on the bottom surface of the document conveying device 316 (see FIG. 3B) is fixed to the fixing portions 344A and 344B. When a bookbinding document or the like that does not use the table 318 (see FIG. 3B) of the document conveying device 316 is directly placed on the platen glass 322 and copied, the document conveying device 316 is opened upward. In the image reading unit 10C according to the present embodiment, a colorless and transparent glass plate is applied as the platen glass 322. However, the present invention is not limited to this, and any platen that has translucency may be used.

  Around the platen glass 322, a document set guide 330 having a substantially rectangular frame is provided. The document set guide 330 has a slightly convex step from the platen glass 322, and the document 331 is easily positioned by aligning the corners of the document 331 so as to contact the step of the document set guide 330. . On the upper surface of the document set guide 330, a registration mark (not shown) is used as a mark when aligning the corner of the document 331 with the corner of the document set guide 330, and the standard size is obtained by aligning the corner with the alignment mark. In the present embodiment, a document size label (not shown) indicating the position of the end of the document 331 when the document 331 of B5, A4, B4, A3 is placed on the platen glass 322 is provided. .

  As an example, as shown in FIG. 3B, the document feeder 316 is provided with a platform 318 on which documents to be copied are stacked (in the case of a plurality of sheets). In addition, below the mounting table 318, a paper discharge receiver 320 is provided for discharging a document fed from the mounting table 318 and read. Here, in the document conveying device 316, the document placed on the placing table 318 (if a plurality of sheets are stacked, the uppermost document) is sent to a document reversing unit (not shown), and the image is read while being reversed. The original 331 is read by passing through the reading area on the platen glass 322 (see FIG. 3A) of the section 10C and discharging onto the paper discharge receiver 320.

  The document feeder 316 is provided with a user interface 324. The user interface 324 includes a reception unit 324A and a display unit 324B. The receiving unit 324A includes input devices such as an operation button for turning on the main power, an operation button for setting various information, and a scroll key. The reception unit 324A is a user of the image forming apparatus 10 or maintenance / repair of the image forming apparatus 10. Accepts instructions from suppliers who perform inspections. The display unit 324B is a liquid crystal display, for example, and displays various types of information including information received by the receiving unit 324A.

  As an example, as shown in FIG. 3B, the case 313 houses a scanning unit 332 that reads a document 331. The scanning unit 332 includes a light irradiation device 334, a reflection unit 336, a light collecting unit 338, and a CCD (Charge Coupled Device) line sensor 340.

  The light irradiation device 334 includes a plurality of LEDs (Light Emitting Diodes) 334a. The LEDs 334a (see FIG. 3A) are arranged in a grid pattern that emits light toward the document 331 with the direction from the front to the back of the image forming apparatus 10 as the longitudinal direction (main scanning direction). The reflection unit 336 reflects the light L reflected by the document 331 when the light irradiation device 334 irradiates the document 331 with a plurality of mirrors. The condensing part 338 condenses the light L reflected by the reflection part 336 with a lens.

  The CCD line sensor 340 receives (images) the light L collected by the light condensing unit 338 and outputs an electrical signal. The reason why the light L is turned back by the plurality of mirrors in the reflection unit 336 is that a predetermined optical path length is required for image formation on the CCD line sensor 340. Note that the scanning range of the light irradiation device 334 according to the present embodiment is wider than that of the A3 size original 331.

  Here, the scanning unit 332 moves in a direction orthogonal to the main scanning direction (sub-scanning direction: arrow X), so that the light from the light irradiation device 334 forms a line on the image recorded on the document 331. Irradiated. Subsequently, the reflected light from the document 331 is received by the CCD line sensor 340 via the reflection unit 336 and the light collection unit 338, and is photoelectrically converted by the CCD line sensor 340. The CCD line sensor 340 is connected to the controller 270 and outputs an electrical signal corresponding to the image density obtained by photoelectric conversion to the controller 270 as second image information.

  As an example, as illustrated in FIG. 6, the image forming apparatus 10 includes a controller 270. The controller 270 includes a CPU (Central Processing Unit) 272, a primary storage unit 274, and a secondary storage unit 276. The primary storage unit 274 is a volatile memory (eg, RAM (Random Access Memory)) used as a work area or the like when executing various programs. The secondary storage unit 276 is a non-volatile memory (for example, a flash memory or an HDD (Hard Disk Drive)) that stores in advance a control program for controlling the operation of the image forming apparatus 10 and various parameters. The CPU 272, the primary storage unit 274, and the secondary storage unit 276 are connected to each other via a bus 278.

  The secondary storage unit 276 stores a standard information setting program 277 and a reference table generation program 279 (hereinafter simply referred to as “program” when there is no need to distinguish between them). The CPU 276 reads the program from the secondary storage unit 276, develops it in the primary storage unit 274, and executes the program. The CPU 276 operates as a control unit according to the present invention by executing the reference table generation program 279.

  Although the case where the program is read from the secondary storage unit 276 is illustrated here, it is not necessary to store the program in the secondary storage unit 276 from the beginning. For example, the program may first be stored in an arbitrary portable storage medium such as an SSD (Solid State Drive), an IC card, a magneto-optical disk, or a CD-ROM that is connected to the image forming apparatus 10 and used. Good. Then, the CPU 272 may acquire a program from these portable storage media and execute the program. Further, the program may be stored in a storage unit of an external electronic computer such as a computer or a server device connected to the image forming apparatus 10 via a communication unit. In this case, the CPU 272 acquires a program from the external electronic computer and executes it.

  The image forming apparatus 10 includes an input / output interface (I / O) 280 that electrically connects the CPU 272 and various input / output devices to control transmission / reception of various information between the CPU 272 and various input / output devices. It has. The image forming apparatus 10 is connected to the I / O 280, and as an input / output device electrically connected to the CPU 272 via the bus 278, the receiving unit 324A, the display unit 324B, and an external interface (I / F) 282 are provided. , And a communication I / F 284. The image forming apparatus 10 includes an image forming unit 10A, a fixing / discharging unit 10B, an image reading unit 10C, and an image processing unit 290 as input / output devices.

  The image reading unit 10C outputs the second image formation request information to the CPU 272. The second image formation request information includes second image information and first instruction information indicating various instructions used for forming an image (an example of a formation target image according to the present invention) indicated by the second image information. The formation target image according to the present invention refers to an image formed on the paper P by the image forming unit 10A.

  The second image formation request information is output from the image reading unit 10C to the CPU 272 for each job (for example, a unit of processing executed in response to one execution instruction (for example, an instruction for requesting image formation)). .

  The CPU 272 stores the second image formation request information input from the image reading unit 10C in the primary storage unit 274. Then, the second image formation request information is acquired from the primary storage unit 274 at a predetermined timing, and the second image information in the acquired second image formation request information (hereinafter referred to as “unprocessed second image information”). ) To the image processing unit 290. The image processing unit 290 performs various processes on the input unprocessed second image information, and processes the processed second image information obtained by performing various processes on the unprocessed second image information (hereinafter, simply “ The processed second image information ”is output to the exposure apparatus 40. Thereby, in the exposure apparatus 40, the image carrier 18 is irradiated with the light beam modulated based on the processed second image information.

  The external I / F 282 is connected to an external device (for example, a USB memory) and controls transmission / reception of various types of information between the external device and the CPU 272.

  The communication I / F 284 is connected to a communication means such as a LAN (Local Area Network) or the Internet, for example, and transmits / receives various information to / from an external device 285 (for example, a personal computer) connected to the communication means. To manage.

  The communication I / F 284 receives first image formation request information from the external device 285. The first image formation request information includes first image information and second instruction information indicating various instructions used for forming an image (an example of an image to be formed according to the present invention) indicated by the first image information. The first image formation request information is transmitted from the external apparatus 162 to the image forming apparatus 10 for each job.

  The CPU 272 acquires first image formation request information via the communication I / F 284 and stores the acquired first image formation request information in the primary storage unit 274. Then, the first image formation request information is acquired from the primary storage unit 274 at a predetermined timing, and the first image information (hereinafter referred to as “unprocessed first image information”) in the acquired first image formation request information. ) To the image processing unit 290. The image processing unit 290 performs various processes on the input unprocessed first image information, and processes the processed first image information obtained by performing various processes on the unprocessed first image information (hereinafter, simply “ The processed first image information ”is output to the exposure apparatus 40. Thereby, in the exposure apparatus 40, the light beam modulated based on the processed first image information is irradiated onto the image carrier 18.

  In the following, for convenience of explanation, when it is not necessary to distinguish between the first image formation request information and the second image formation request information, these will be referred to as “image formation request information”. In the following, for convenience of explanation, when it is not necessary to distinguish between the first image information and the second image information, these will be referred to as “image information”. In the following, for convenience of explanation, when there is no need to distinguish between the unprocessed first image information and the unprocessed second image information that are targets to be processed by the image processing unit 290, these are referred to as “processing target image information”. ". Further, in the following, for convenience of explanation, when it is not necessary to distinguish between the processed first image information and the processed second image information obtained by processing the processing target image information by the image processing unit 290, these are described. This is referred to as “processed image information”.

  As an example, as illustrated in FIG. 5, the image processing unit 290 includes a color conversion unit 592, an edge processing unit 594, and a binarization processing unit 596. Note that the image processing unit 290 is realized by an application specific integrated circuit (ASIC) that is an integrated circuit in which circuits having a plurality of functions related to image processing are integrated into one. However, the hardware configuration is not limited to this, and may be, for example, a programmable logic device or another hardware configuration such as a computer including a CPU, a ROM, and a RAM.

  The color conversion unit 592 performs color conversion on the processing target image information input from the CPU 272. Then, the processing target image information subjected to the color conversion is output to the edge processing unit 594. Here, color conversion refers to, for example, converting an RGB color space to a YMCK color space.

  The edge processing unit 594 performs edge processing on the processing target image information input from the color conversion unit 592. Then, the processing target image information subjected to the edge processing is output to the binarization processing unit 596.

  The binarization processing unit 596 performs binarization processing on the processing target image information input from the edge processing unit 594. Then, the processing target image information subjected to the binarization processing is output to a correction execution unit 602 described later.

  Incidentally, the driving state of the intermediate transfer belt 34 and the secondary transfer roll 62 at the transfer position T is roughly divided into an unexecuted transfer state shown in FIG. 6A and FIG. 6B as an example and a transfer execution state shown in FIG. 6C as an example. The Further, the transfer unexecuted state is roughly classified into a sheet non-conveying state shown in FIG. 6A as an example and a sheet conveying state shown in FIG. 6B as an example.

  The paper non-conveying state shown in FIG. 6A indicates a state where the intermediate transfer belt 34 and the secondary transfer roll 62 are driven without sandwiching the paper P. 6B indicates a state in which the intermediate transfer belt 34 and the secondary transfer roll 62 are driven with the paper P interposed therebetween. The transfer execution state shown in FIG. 6C indicates a state where the toner image is transferred from the intermediate transfer belt 34 to the paper P.

Here, when the conveyance speed of the intermediate transfer belt 34 is “V _belt ”, the rotation speed of the secondary transfer roll 62 is “V _btr ”, and the conveyance speed of the paper P is “V _paper ”, the state is shown in FIG. 6A. In the non-conveyance state, “V _belt = V _btr ”. 6B, “V _belt = V _btr = V _paper ”. In the transfer execution state shown in FIG. 6C, “V _belt > V _paper = V _btr ”.

  That is, when the toner image is secondarily transferred onto the paper P, a speed difference occurs between the paper P and the intermediate transfer belt 34 at the time of secondary transfer due to the image density, and the image is shifted in the transport direction of the paper P. For example, as illustrated in FIG. 7, the image is shifted in the transport direction of the paper P means that the magnification in the transport direction increases as the image density of the image formed on the paper P increases. Here, in the example shown in FIG. 7, “image density (density) (%)” refers to a toner amount when the maximum toner amount for color reproduction with a single color toner is 100%. For example, when the image density is 150%, Y toner amount = 60%, M toner amount = 50%, C toner amount = 30%, and K toner amount = 10%. Point to. The magnification in the conveyance direction refers to a percentage of the ratio of the length in the conveyance direction of the image shifted in the conveyance direction to the length in the conveyance direction of the image not shifted in the conveyance direction. The ideal conveyance direction magnification (ideal magnification change) is 0%.

  Further, it is known that the change mode of the magnification in the conveyance direction with respect to the image density differs for each type of paper P. For example, as shown in FIG. 8, in the case of 220 gsm (gram square meter (weight per square meter)) uncoated paper, it is confirmed that the magnification in the conveyance direction decreases linearly as the image density increases. Has been. For example, as shown in FIG. 9, in the case of 82 gsm uncoated paper, it has been confirmed that the magnification in the transport direction changes nonlinearly with respect to the image density. Further, for example, as shown in FIG. 10, it is confirmed that the magnification in the transport direction changes nonlinearly with respect to the image density even in the case of 128 gsm coated paper.

  Therefore, in order to correct the shift amount of the image in the transport direction on the paper P (hereinafter referred to as “transport direction shift amount”), the image processing unit 290, as an example, as illustrated in FIG. A correction amount calculation unit 600 and a correction execution unit 602 are provided.

  The correction information storage unit 598 stores standard information 604 and a reference table 606. The reference information 604 indicates a reference correction amount 604A and a reference image density 604B that are associated with each other. The reference correction amount 604A refers to a correction amount for correcting the conveyance direction deviation amount. The reference image density 604B refers to an image density at which the reference correction amount is applied to the correction of the conveyance direction deviation amount.

The reference information 604 is set by performing a later-described reference information setting process, but a default correction amount and a default image density are used as the default reference information 604 before the reference information setting process is performed. . The default reference information 604 indicates, for example, reference information 604 used when the power is first turned on after the image forming apparatus 10 is shipped. The default correction amount is, for example, a reference correction amount Y ₂ (see FIG. 11) of a later-described reference table 606, and the default image density is, for example, a reference image density 80% (see FIG. 11) of a later-described reference table 606. is there.

  The reference table 606 is a table that is referred to when deriving a correction amount for correcting the conveyance direction deviation amount, and is stored in the correction information storage unit 598 for each type of paper P. In the reference table 606, for example, the reciprocal of the magnification in the transport direction of a standard image (so-called patch) actually formed at each of a plurality of image densities (hereinafter referred to as “reference image density”) by the image forming unit 10A is a reference correction amount. Is a table associated with each reference image density.

  In this embodiment, for convenience of explanation, 40%, 80%, 120%, 160%, and 200% are adopted as the reference image density stored in the reference table 606, and each of these reference image densities is used. Are associated with different reference correction amounts.

For example, as shown in FIG. 11 as an example, the reference table 606 has reference image densities of 40%, 80%, 120%, 160%, and 200%, and reference correction amounts Y _{1 to} Y ₅ . In the reference table 606, the reference correction amount _{Y 1} is associated with 40% of the reference image density. In the reference table 606, the reference correction amount _{Y 2} is associated with 80% of the reference image density. In the reference table 606, the reference correction amount _{Y 3} are associated with 120% of the reference image density. In the reference table 606, the reference correction amount _{Y 4} is associated with 160% of the reference image density. In the reference table 606, the reference correction amount _{Y 5} is associated with 200% of the reference image density.

  When a reference image (an image indicated by image information common to each of the image forming apparatuses 10) is formed on each of the different image densities on a predetermined type of paper P by each of the different image forming apparatuses 10, the image The conveyance direction magnification for each density differs for each type of image forming apparatus 10. In the example illustrated in FIG. 17, conveyance for each image density is performed when a reference image is formed on 82 gsm uncoated paper for each different image density by each of the first, second, and third image forming apparatuses 10. Direction magnification is shown for each model. As an example, as illustrated in FIG. 17, the conveyance direction magnification for each image density differs for each model, and individual differences appear as differences in the conveyance direction magnification. Therefore, in the image forming apparatus 10 according to the present embodiment, a reference table 606 used for each image forming apparatus 10 is generated by performing a reference table generation process described later.

  The correction amount calculation unit 600 calculates an approximate correction amount (described later) based on the formation target image density and environment information input from the standard information 204, the reference table 606, and the CPU 272 by performing a shift amount correction process described later. The approximate correction amount is output to the correction execution unit 602. Here, the formation target image density refers to the image density of the image indicated by the image information input to the CPU 272. Moreover, environmental information refers to the temperature and humidity measured by the environmental sensor 79, for example.

  The correction execution unit 602 corrects the deviation in the conveyance direction of the image indicated in the processing target image information input from the binarization processing unit 596 with the approximate correction amount input from the correction amount calculation unit 600. Then, the processing target image information obtained by correcting the image conveyance direction deviation amount with the approximate correction amount is output to the CPU 272 as processed image information.

  Next, the operation of the image forming apparatus 10 will be described. First, reference table generation processing performed in the image forming apparatus 10 when the CPU 272 executes the reference table generation program 279 when the power of the image forming apparatus 10 is turned on will be described with reference to FIG. Here, for convenience of explanation, description will be made on the assumption that 40%, 80%, 120%, 160%, and 200% are already set in the reference table 606 as the reference image density. Also, here, for convenience of explanation, the description will be made on the assumption that a default correction amount is set for each reference image density as the reference correction amount.

  In the reference table generation process shown in FIG. 18, first, in step 700, the CPU 272 determines whether or not a start condition is satisfied. Here, the start condition refers to, for example, a condition that an instruction to start the reference table generation process is given by the specific user via the reception unit 324A. The determination as to whether or not the user is a specific user may be performed based on, for example, login information (for example, login information received by the receiving unit 324A).

  The start condition is not limited to this, and may be a condition that the environment information has changed (operating environment condition). The environmental information has changed, for example, the temperature measured by the environmental sensor 79 is ± 10 degrees relative to the reference temperature (for example, 15 degrees), or the humidity measured by the environmental sensor 79 is the reference humidity ( For example, the humidity is ± 30% relative to 40%).

  In addition, the start condition is not limited to this. For example, the condition that the type of the paper P on which the image is formed by the image forming unit 10A (paper condition) or the performance of the image forming unit 10A has changed. (Performance condition). The case where the paper condition is satisfied refers to, for example, a case where an instruction to change the type of paper P on which an image is formed is received by the receiving unit 324A. In addition, when the performance condition is satisfied, for example, when the circulation speed of the intermediate transfer belt 34 is changed, when the driving time of the intermediate transfer belt 34 exceeds a threshold, and when the image forming unit 10A itself or This refers to the case where the specific member included in the image forming unit 10A is replaced. The case where the circulation speed of the intermediate transfer belt 34 is changed refers to, for example, a case where the circulation speed of the intermediate transfer belt 34 is stabilized in a state where it exceeds a predetermined circulation speed. The specific member included in the image forming unit 10A refers to, for example, the intermediate transfer belt 34, the secondary transfer roll 62, or the toner cartridge 14.

  The start condition is not limited to this, and may be, for example, a condition that power is first turned on after the image forming apparatus 10 is shipped, or an instruction to start the reference table generation process is received by the accepting unit. It may be a condition that it is accepted by 324A. In step 700, the CPU 272 may determine that the start condition is satisfied when two conditions of the operating environment condition, the paper condition, and the performance condition are satisfied, or the three conditions are satisfied. It may be determined that the start condition is satisfied.

  If the start condition is satisfied at step 700, the determination is affirmed and the routine proceeds to step 702. In step 700, when the start condition is not satisfied, the determination is negative and the determination in step 700 is performed again.

  In step 702, as shown in FIG. 13 as an example, the CPU 272 causes the image forming unit 10A to form the standard image 722 (so-called solid image) on the lattice chart sheet 620 for each reference image density, and then the step. Move to 704. The lattice chart sheet 620 refers to a sheet P in which a blank area (white background area) is divided into a lattice shape by a line image 620A. The reference image 722 is formed at a predetermined position (hereinafter referred to as “reference position”) of the lattice chart sheet 620 if there is no deviation in the transport direction.

  In this step 702, 40%, 80%, 120%, 160%, and 200% are adopted as the reference image density, and the standard image 722 is formed on the lattice chart sheet 620 that is different for each reference image density. .

  In step 704, the CPU 272 detects the amount of deviation in the transport direction of the reference image 622 by causing the inline sensor 200 to read the line image 620 </ b> A and the reference image 622 of the lattice chart sheet 620 as illustrated in FIG. 13. Then, the process proceeds to step 356. The amount of deviation in the conveyance direction of the reference image 622 includes the position of the line image 620A arranged at a predetermined interval (for example, 10 millimeters) in the conveyance direction on the lattice chart paper 620, the position where the reference image 722 is formed, and the reference Detected based on position.

  In this step 704, the case where the line image 620A and the reference image 622 are read by the inline sensor 200 is illustrated, but the present invention is not limited to this. For example, reading may be performed by the image reading unit 10C, or reading may be performed by another external reading device. In this case, the receiving unit 324A or the external I / F 282 may receive a reading result by an external reading device.

  In step 706, the CPU 272 derives a reference correction amount (a correction amount used for correcting the deviation in the conveyance direction of the image formed at the reference image density) based on the conveyance direction deviation detected in step 704, and then Control goes to step 708. The reference correction amount derived in step 706 is a correction amount determined so that the conveyance direction deviation amount detected in step 704 is corrected, and is, for example, the reciprocal of the conveyance direction deviation amount detected in step 704. .

  In step 708, the CPU 272 stores (overwrites) the reference correction amount derived in step 706 as a new reference correction amount in the correction information storage unit 598 via the correction amount calculation unit 600, and then performs this reference table generation process. Exit. That is, in this step 708, instead of the reference correction amount currently stored in the reference table 606, the reference correction amount derived in step 706 is stored in the reference table 606 as a new reference correction amount. The reference table 606 is updated.

  Next, reference information setting processing performed in the image forming apparatus 10 when the CPU 272 executes the reference information setting program 277 when the setting start condition is satisfied will be described with reference to FIG. Here, the setting start condition refers to, for example, a condition that an instruction to start the reference information setting process is given by the specific user via the receiving unit 324A. Note that the setting start condition is not limited to this. For example, after the image forming apparatus 10 is shipped, the main power of the image forming apparatus 10 is turned on for the first time, or the previous reference information setting process is performed. It may be a condition that a predetermined time (for example, 3 days) has passed since the break.

  In the reference information setting process shown in FIG. 12, first, in step 350, the CPU 272 derives the actual image density, and then proceeds to step 352. Here, the actual image density refers to the image density determined according to the actual use of the image density of the image formed by the image forming unit 10A in a predetermined period. Here, as an example of a period if it is determined in advance, the past three days when the time when the setting start condition is satisfied are used as the starting point are used, but not limited to this, for example, the setting start condition is satisfied It may be a specific time period (for example, a time period from 13:30 to 13:45) on a specific date in the past (for example, every Tuesday) from the time point, or a period other than this.

  In the present embodiment, as an example of the actual image density, an image density that has been used with a predetermined frequency among the image densities of the images formed by the image forming unit 10A is employed. The proven image density used at a predetermined frequency is, for example, the mode value (predetermined value of the image density of the image indicated by the image information input to the image forming unit 10 during a predetermined period. The image density most adopted among the image densities of the images formed during a given period). For example, the actual image density is 90% when the most images having an image density of 90% are formed in a predetermined period. The actual image density is specified based on, for example, the history of the image density (image density of the image indicated by the input image information) calculated by the CPU 272 every time image information is input to the CPU 272. Here, the history of image density refers to, for example, the image density (calculation result by the CPU 272) stored in the secondary storage unit 276 by the CPU 272 every time the image density is calculated by the CPU 272.

  In step 352, as shown in FIG. 13 as an example, the CPU 272 causes the image forming unit 10A to form a reference image 622 (so-called solid image) of the actual image density derived in step 350 on the lattice chart sheet 620, Thereafter, the process proceeds to step 354. The lattice chart sheet 620 refers to a sheet P in which a blank area (white background area) is divided into a lattice shape by a line image 620A. The reference image 622 is formed at a predetermined position (hereinafter referred to as “reference position”) of the lattice chart paper 620 if there is no deviation in the transport direction.

  In step 354, the CPU 272 detects the amount of deviation in the conveyance direction of the reference image 622 by causing the inline sensor 200 to read the line image 620 </ b> A and the reference image 622 of the lattice chart sheet 620 as illustrated in FIG. 13 as an example. Then, the process proceeds to step 356. The amount of deviation in the conveyance direction of the reference image 622 includes the position of the line image 620A arranged at a predetermined interval (for example, 10 millimeters) in the conveyance direction on the lattice chart paper 620, the position where the reference image 622 is formed, and the reference Detected based on position.

  In step 356, the CPU 272 derives a correction amount (a correction amount used for correcting the deviation in the conveyance direction of the image formed with the actual image density) based on the conveyance direction deviation detected in step 354, and then, in step 356 358. The correction amount derived in step 356 is a correction amount determined so that the conveyance direction deviation amount detected in step 354 is corrected, and is, for example, the reciprocal of the conveyance direction deviation amount detected in step 354.

  In step 358, the CPU 272 stores (overwrites) the actual image density derived in step 350 and the correction amount derived in step 356 as new reference information 604 in the correction information storage unit 598 via the correction amount calculation unit 600. Thereafter, the reference information setting process is terminated. That is, in this step 358, instead of the reference image density 604B currently stored in the correction information storage unit 598, the actual image density derived in step 350 is used as the new reference image density 604B as the correction information storage unit 598. Is remembered. In step 358, the correction amount derived in step 356 is used as the new reference correction amount 604 A in the correction information storage unit 598 instead of the reference correction amount 604 A currently stored in the correction information storage unit 598. Remembered.

  Next, the shift amount correction processing performed by the image processing unit 290 when the processing target image information is input to the image processing unit 290 will be described with reference to FIG. In the following description, for the sake of convenience of explanation, it is assumed that the standard image density 604B is different from the formation target image density and the reference image density, and the formation target image density is different from the reference image density.

  In the shift amount correction process shown in FIG. 14, first, in step 400, the correction amount calculation unit 600 forms the formation target image density from the CPU 272 (the formation target image density corresponding to the processing target image information input to the image processing unit 290). And whether or not environmental information has been input.

  In step 402, the correction amount calculation unit 600 acquires the standard information 604 and the reference table 606 from the correction information storage unit 598, and then proceeds to step 404. The reference table 606 acquired in this step 402 is, for example, a reference table 606 corresponding to the type of paper P instructed via the accepting unit 324A as the type of paper P on which an image is to be formed.

  In step 403, the correction amount calculation unit 600 adjusts the reference correction amount of the reference table 606 acquired in step 402 based on the environment information acquired in step 400, and then proceeds to step 404. Here, adjusting the reference correction amount means, for example, multiplying the reference correction amount by an adjustment coefficient determined in advance according to the environment information. The predetermined adjustment coefficient may be derived from a table (not shown) or may be derived from an arithmetic expression.

  In step 404, the correction amount calculation unit 600 determines the absolute value of the difference between the formation target image density input in step 400 and the reference image density 604B included in the reference information 604 acquired in step 402 (hereinafter referred to as “first image”). (Referred to as “density difference”).

  In the next step 406, the correction amount calculation unit 600 calculates the absolute value of the difference between the specific reference image density in the reference table 606 acquired in step 402 and the standard image density 604 B included in the standard information 604 acquired in step 402 ( Hereinafter, referred to as “second image density difference”). Here, the specific reference image density refers to a reference image density closest to the formation target image density among the reference image densities in the reference table 606, for example.

  In the next step 408, the correction amount calculator 600 determines the first image density difference, the second image density difference, the reference correction amount 604 A included in the reference information 604 acquired in step 402, and the reference table adjusted in step 403. An approximate correction amount is derived based on the reference correction amount 606.

In this step 408, the approximate correction amount is calculated by an interpolation method based on the reference correction amount in the reference table 606 and the standard correction amount 604A included in the standard information 604 acquired in step 402, for example. For example, as shown in FIG. 15, the reference correction amount 604A and _{Y S,} a reference image density 604B and 105%, when the formed object image density 95%, see closest to the forming target image density from the reference table 606 80% adjusted reference correction amount Y ₂ of the image density is obtained. In this case, the first image density difference is “| 95% −105% |”, and the second image density difference is “| 80% −105% |”. Here, when the approximate correction amount is Y _A , Y _A is calculated by the following formula (1).

In this step 408, the acquired 80% of the reference image density closest to the forming target image density from the reference table 606 and the adjusted reference correction amount Y _2, the approximate correction amount Y _A is calculated by interpolation Although the case has been illustrated, the present invention is not limited to this. For example, as shown in FIG. 15, 160% and the adjusted reference correction amount of the reference image density Y ₄ may be acquired. In this case, the approximate correction amount Y _A is calculated by extrapolation.

  In the next step 410, the correction execution unit 602 corrects the conveyance direction deviation amount of the image indicated by the processing target image information input from the binarization processing unit 596 with the approximate correction amount derived in step 408, Thereafter, the process proceeds to step 412.

  In step 412, the correction execution unit 602 outputs processed image information obtained by correcting the conveyance direction deviation amount in step 410 to the exposure apparatus 40, and then ends this deviation amount correction process. The exposure apparatus 40 irradiates the image carrier 18 with a light beam modulated based on the input processed image information.

  In this step 412, the case where the processed image information is directly supplied to the exposure apparatus 40 is illustrated, but the present invention is not limited to this, and the exposure apparatus 40 is not limited to this, and the exposure apparatus 40 is connected from the correction execution unit 602 via the CPU 272. Alternatively, the processed image information may be supplied.

  In this step 412, the case where the exposure apparatus 40 corrects the deviation in the transport direction by irradiating the light beam modulated based on the processed image information is exemplified. However, the present invention is not limited to this. Absent. For example, the CPU 272 controls at least one of the polygon rotation speed (including the video clock frequency), the rotation speed of the image carrier 18 and the circulation speed of the intermediate transfer belt 34 based on the processed image information to convey the image. The amount of direction deviation may be corrected.

  In the above embodiment, the case where the approximate correction amount is derived using the reference table 606 is exemplified, but the present invention is not limited to this. For example, as shown in FIG. 8, when using a paper P that reveals a characteristic that the conveyance direction magnification linearly decreases as the image density increases, a predetermined change amount is used without using the reference table 606. The approximate correction amount may be derived using the ratio. The change amount ratio refers to the ratio of the change amount of the correction amount (value corresponding to the reciprocal of the magnification in the conveyance direction) with respect to the change amount of the image density. Therefore, the approximate correction amount (correction amount corresponding to the formation target image density) is uniquely derived from the change amount ratio, the reference information 604, and the formation target image density.

  The predetermined change amount ratio may be an invariable value determined for each type of paper P, or a variable value customized according to an instruction received by the receiving unit 324A. . Further, the predetermined change rate ratio may be a change rate ratio derived based on a shift amount (actually measured value) of each of the reference images 622 having different image densities periodically formed on the paper P. . The change rate ratio used for calculating the approximate correction amount is a change rate ratio determined in advance according to the type of the paper P, and an adjustment coefficient determined in advance according to the temperature and humidity measured by the environmental sensor 79. It may be a change amount ratio obtained by adjustment.

  Further, the method of deriving the approximate correction amount using a predetermined change amount ratio and the method of deriving the approximate correction amount using the reference table 606 may be used in combination. For example, when the first image density difference is less than the threshold value, an approximate correction amount is derived using a predetermined change amount ratio, and when the first image density difference is equal to or greater than the threshold value, the reference table 606 is used for approximation. A correction amount is derived.

  The method of deriving the approximate correction amount using the predetermined change amount ratio is merely an example, and the approximate correction amount may be derived by other methods. For example, when using paper P that is already known to have a correction amount that increases as the image density increases (for example, linearly monotonically increases), the relationship between the formation target image density and the reference image density 604B. The approximate correction amount may be derived according to the above.

  In this case, for example, if “formation target image density <reference image density 604B”, a predetermined value (for example, an invariable value predetermined for each type of paper P) is subtracted from the reference correction amount 604A ( Alternatively, the obtained correction amount is used as an approximate correction amount. Conversely, if “formation target image density> reference image density 604B”, a correction amount obtained by adding (or multiplying) a predetermined value from the reference correction amount 604A is used as an approximate correction amount. Here, the predetermined value, for example, changes in proportion to the first image density difference according to a predetermined value according to the first image density difference (for example, a proportional constant determined for each type of paper P). Value). Further, the predetermined value may be a value adjusted according to the environmental information.

  Further, in the case of using paper P that is known to have a correction amount that changes nonlinearly with respect to the image density, a value obtained by adjusting the predetermined value is added to or subtracted from the reference correction amount 604A. By doing so, the approximate correction amount may be derived. That is, the correction amount obtained by adding a value obtained by multiplying the predetermined value by the adjustment coefficient determined in advance according to the reference image density 604B and the first image density difference to the reference correction amount 604A. Approximate correction amount.

  In the above embodiment, the case where the reference correction amount of the reference table 606 is adjusted based on the environment information acquired in step 400 is exemplified, but the present invention is not limited to this. For example, the reference correction amount may be adjusted by multiplying the reference correction amount by an adjustment coefficient determined according to the performance of the image forming unit 10A. Here, the performance of the image forming unit 10A includes, for example, the material of the toner, the material of the intermediate transfer belt 34, the circulation speed of the intermediate transfer belt 34, the material of the secondary transfer roll 62, and the rotation speed of the secondary transfer roll 62. At least one of the above.

  In the above embodiment, the actual image density has been described by taking the mode value of the image density of the image indicated by the image information input to the image forming unit 10 during a predetermined period as an example. It is not limited to. For example, an average value of image densities of images indicated by image information input to the image forming unit 10 during a predetermined period may be used as the actual image density. Moreover, you may make it use the image density used with the frequency more than a threshold value in a predetermined period as a performance image density. Further, the mode value or average value of the image density of the image formed in accordance with a specific user instruction may be used as the actual image density. In this case, the determination as to whether or not the instruction is made by a specific user may be made based on login information, for example.

  In the above-described embodiment, the case where the reference image 622 having the actual image density is formed is illustrated. However, the present invention is not limited to this, and for example, the reference image 622 is used instead of the reference image 622. A reference image having an image density instructed by a person may be formed.

  In the above embodiment, the case where the inline sensor 200 reads the line image 620A and the reference image 622 of the lattice chart sheet 620 is illustrated, but the line image 620A and the reference image 622 are read by another reading device. Also good. As an example of another reading apparatus, for example, an image reading unit 10C is cited.

  The above embodiment has been described on the assumption that the formation target image density is different from the reference image density. However, if the formation target image density is not different from the reference image density, the reference correction corresponding to the reference image density is performed. What is necessary is just to correct | amend the conveyance direction deviation | shift amount using quantity.

  The above embodiment has been described on the assumption that the formation target image density is different from the reference image density 604B. However, when the formation target image density is not different from the reference image density 604B, the reference correction amount 604A is used. Thus, the conveyance direction deviation amount may be corrected.

  In the above embodiment, the case where the conveyance direction deviation amount is corrected using the approximate correction amount derived using the reference information 604 is illustrated. However, the conveyance direction deviation amount is corrected using the approximate correction amount derived without using the reference information 604. You may do it. For example, when the image density to be formed is different from any of the reference image densities of the reference table 606, the conveyance direction deviation amount is corrected with an approximate correction amount approximated based on a plurality of reference correction amounts included in the reference table 606. It may be. Here, the approximate correction amount approximated based on a plurality of reference correction amounts is formed with, for example, a polynomial curve (approximate curve) defined by a plurality of reference image densities and a plurality of reference correction amounts included in the reference table 606. A correction amount that is uniquely derived from the target image density.

  When the formation target image density exists between two reference images, an approximate correction amount corresponding to the formation target image density is derived by linear interpolation based on adjacent reference image densities and these reference correction amounts. May be.

  The shift amount correction process (see FIG. 14) described in the above embodiment is merely an example. Therefore, it goes without saying that unnecessary steps may be deleted, new steps may be added, and the processing order may be changed within a range not departing from the spirit. In addition, each process included in the deviation amount correction process described in the above embodiment is executed by the image processing unit 290, which is an ASIC, but is realized by a software configuration using a computer by executing the program. May be. In addition, each process included in the shift amount correction process may be realized by a combination of a hardware configuration and a software configuration.

  In order to realize each process included in the deviation amount correction process described in the above embodiment by software configuration, for example, the CPU 272 executes the deviation amount correction program 330 illustrated in FIG. An amount correction process may be performed. Here, the deviation amount correction program 330, the standard information 604, and the reference table 606 may be stored in the secondary storage unit 276, and the CPU 272 reads the deviation amount correction processing program 330 from the secondary storage unit 276 and performs primary processing. What is necessary is just to perform, after expand | deploying to the memory | storage part 274. In this case, the CPU 272 operates as the correction amount calculation unit 600 and the correction execution unit 602 by executing the deviation amount correction program 330.

10 Image forming apparatus 10A Image forming unit 200 Inline sensor 604A Reference correction amount 604B Reference image density 272 CPU
277 Reference information setting program 290 Image processing unit 600 Correction amount calculation unit 602 Correction execution unit 606 Reference table 630 Deviation amount correction program

Claims (7)

Forming means for forming an image on the recording medium by transferring a developer image performed in accordance with conveyance of the recording medium;
A reference correction amount for correcting the shift amount of the image in the conveyance direction on the recording medium is determined in advance according to the reference image density, and the difference between the formation target image density that is the image density of the formation target image and the reference image density is determined. And a control unit that controls the forming unit so that the image to be formed in which the shift amount in the transport direction is corrected with an approximate correction amount that approximates the reference correction amount.
An image forming apparatus including: A detection unit for detecting a shift amount in the transport direction of the reference image formed at the reference image density on the recording medium by the forming unit;
The image forming apparatus according to claim 1, wherein the reference correction amount is a correction amount for correcting a shift amount detected by the detection unit.   The image forming apparatus according to claim 2, wherein the reference image density is a record image density determined according to a record of use of the image density of the image formed by the forming unit.   The image forming apparatus according to claim 3, wherein the actual image density is an image density that has been used with a predetermined frequency among image densities of images formed by the forming unit.   The approximate correction amount is a difference between the formation target image density and the standard image density, a reference correction amount associated with a predetermined reference image density, and an approximation derived by an interpolation method based on the standard correction amount. The image forming apparatus according to claim 1, wherein the image forming apparatus is a correction amount.   The reference correction amount is a reference correction determined according to at least the type of the recording medium among the type of the recording medium on which the image is formed by the forming unit, the performance of the forming unit, and the operating environment of the forming unit. The image forming apparatus according to claim 5, wherein the image forming apparatus is an amount. Computer
The program for functioning as a control means in the image forming apparatus of any one of Claims 1-6.