JP4459769B2 - Image forming apparatus and adjustment method thereof - Google Patents

Description

  The present invention relates to a method for adjusting an image forming position on a sheet in an electrophotographic image forming apparatus, and an image forming apparatus using the method.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, an image is formed on a recording sheet based on image data input from a peripheral device. The image forming position shift with respect to the sheet is caused by a shift between the sheet transport position by the transport unit that transports the sheet and the position of the image written on the image carrier based on the image data. As a method of correcting this misalignment, a method of adjusting the sheet conveyance position to a predetermined position and further adjusting the image forming position to a predetermined position so that an image is formed at the correct position of the sheet. Alternatively, a method of adjusting an image formed on an image carrier or a sheet conveyed by a sheet conveying unit so that the other position is matched.

  As an example of such an adjustment method, in the image processing apparatus with a recording position adjustment function described in Patent Document 1, first, an image before adjustment is formed, and the image is formed on the sheet by checking the image with a reading unit. Is adjusted.

  In recent years, with the diversification of purposes of use, image forming apparatuses in recent years are equipped with multi-stage sheet storage means so that a plurality of types of sheets can be used efficiently. In such an image forming apparatus, the position of the image relative to the sheet is adjusted for each sheet storage unit. In particular, since the positional relationship between the sheet and the image is not the same as the condition in which the sheet is transported from each sheet storage unit to the image forming unit, the position of the sheet fed to the image forming unit by the used sheet storage unit is Because they are different, each adjustment is made.

For example, Patent Document 2 discloses a configuration in which a cassette is selected and a writing position is adjusted in units of cassettes in a facsimile apparatus having a plurality of paper feeding cassettes.
JP-A-10-186994 (publication date: July 14, 1998) JP 10-4493 A (publication date: January 6, 1998)

  However, in the above-described conventional configuration, in order to accurately read the positional deviation, when the test chart of the reference image is read using the image reading device of the peripheral device, the adjustment is correctly performed and there is no reading deviation. There is a problem that an image reading device is required. Further, many adjustments are required for adjusting the image forming apparatus, and there is a problem that adjustment is troublesome.

  That is, in the conventional configuration, in order to correctly grasp the positional deviation that has occurred, the image formed on the sheet is visually confirmed, for example, and the state and amount of the positional deviation are determined by the image reading apparatus. Then, the image forming apparatus is adjusted based on the result. For this reason, if an image reading apparatus having a reading deviation is used, the positional deviation cannot be correctly grasped and cannot be adjusted. Such adjustment is performed by an assembly adjustment person or service person at the manufacturing stage, the installation stage by a service person, or when parts or units related to image formation are replaced.

  Further, for example, when considering a multifunction peripheral (copying apparatus) in which an image forming apparatus and an image reading apparatus are set, adjustment on the image reading apparatus side is indispensable in order to adjust a formed image of the multifunction peripheral. That is, in an image reading apparatus for inputting image data to the image forming apparatus, when image data that is misaligned is generated when a document is read, the data is input to the image forming apparatus as it is. . For this reason, even an image forming apparatus for which adjustment has been completed forms an image that is misaligned. Since the image reading apparatus also needs to adjust the reading position in this manner, the person in charge of assembly adjustment or a service person makes adjustments.

  For this reason, for example, in a complex machine (copying apparatus) in which an image reading apparatus (reading means) is set in an image forming apparatus, an image is formed and output based on reference data (image formed object: test chart). In general, the image is read by a reading device, and the position and magnification of the image with respect to the sheet of the image forming apparatus are adjusted. For this purpose, an adjusted image reading device is required. That is, when both the image reading apparatus and the image forming apparatus are in the state before adjustment, the adjustment is performed by adjusting the image reading apparatus first and then adjusting the image forming apparatus.

  In this case, a reference document (adjusted image) is necessary to adjust the image reading apparatus, and a serviceman or the like always needs to bring the adjusted image. In addition, there is a problem that adjustment cannot be made when the adjustment image is forgotten.

  The present invention has been made in view of the above-described problems, and the object thereof is stored in advance in an image forming apparatus even if reading means such as a reading apparatus for reading a formed image is not properly adjusted. Image forming apparatus adjustment method capable of correctly adjusting the image forming conditions such as the position and magnification of the image with respect to the sheet of the image forming apparatus using the adjusted image data, and image formation to be adjusted using the method To provide an apparatus.

  Further, according to the present invention, an image forming apparatus that forms an adjusted image that suppresses occurrence of sheet conveyance jam in the fixing unit and suppresses the amount of developer used, and adjustment of the image forming apparatus using the adjusted image Realize the method.

  As a result of intensive studies on the above problems, the inventor of the present application stores adjustment image data serving as a reference in an image forming apparatus in advance, and forms an adjustment image on a sheet based on this data. It has been found that by adjusting the image forming conditions using a sheet, correct adjustment can be performed even when the reading means is not adjusted correctly.

  Then, the present inventor forms an adjustment image larger than the sheet (that is, an adjustment image formed over the entire outer edge of the sheet: see FIG. 12), and performs adjustment based on the size of the sheet. And found that correct adjustment is possible. However, when such an adjusted image is formed, an image is also formed at the two corners at the front end of the sheet conveyance direction (that is, a developer is applied). The sheet becomes difficult to be peeled off, and the sheet is wound around the fixing roller, thereby causing a problem that the sheet is easily jammed.

  Further, when a plurality of sheet cassettes and sheet trays are provided in the image forming apparatus in order to accommodate sheets of a plurality of sizes, adjustment images are formed on the sheets supplied from the respective cassettes and trays. There is a need. For this reason, when an adjusted image larger than the sheet is formed, the amount of developer to be used increases, which is not preferable in terms of cost.

  Therefore, the inventor of the present application assumes that the adjustment image is composed of partial images formed at least one on each side of the quadrilateral sheet, and the two corners at the leading edge in the sheet conveyance direction include the partial image. By not forming an image, it was found that sheet conveyance jams in the fixing unit are less likely to occur, and the present invention has been completed.

  In other words, an image forming apparatus according to the present invention is an image forming apparatus that adjusts an image formed using a reference adjustment image, and is based on a storage unit that stores adjustment image data and the adjustment image data. An image recording unit for forming an adjustment image on the sheet, a conveyance unit for conveying the sheet, a reading unit for reading the adjustment image formed on the sheet, and an image for the sheet from the read data of the adjustment image obtained from the reading unit. And a control unit for controlling the operation of the image writing unit of the image recording unit and the conveying unit based on the correction value, and based on the adjusted image data. The adjustment image formed on the sheet is composed of at least one partial image formed on each side of the rectangular sheet, and the partial image is formed from the sheet. Together have an area out seen, the partial image is characterized in that the portion of the corner of the sheet conveying direction leading end is not formed.

  According to the above configuration, the adjustment image is composed of partial images that protrude from the end portions of the four sides of the sheet. Therefore, a partial image is formed up to the end portion of at least a part of each side of the sheet on which the adjustment image is formed. Has been. Therefore, when the sheet on which the adjustment image printed out is formed is read by the reading unit, the end portion (edge) of the sheet can be clearly read. Accordingly, the relationship between the sheet and the position of the image to be formed can be read with high accuracy on the basis of the sheet size, and a highly accurate correction value can be obtained. Furthermore, since the partial image is not formed at the corner portion at the front end in the sheet conveyance direction, occurrence of sheet conveyance jam in the fixing unit can be reduced.

  In the image forming apparatus of the present invention, the partial images formed on the two opposite sides of the sheet are arranged at positions that are symmetric with respect to the center line of the two opposite sides in the region where the adjustment image is formed. It is preferable.

  According to the above configuration, an accurate correction value can be easily obtained by using the reading result of the partial images arranged at positions symmetrical with respect to the center line of the two opposite sides in the region where the adjustment image is formed. Can be obtained by simple calculation.

  Further, in the partial image, if the end located at the end of the sheet is set as an outer point, the reading unit reads the outer point, and the calculation unit is arranged at a position symmetric with respect to the center line. It is preferable to obtain a correction value for the reading error caused by the reading means from the result of calculating the distance between the outer points of each partial image.

  According to the above configuration, by detecting the distance (interval) between the outer points of each partial image arranged symmetrically with respect to the center line of the sheet and the position of each, it is determined how much from the known sheet size. It is possible to easily detect a reading error (that is, a magnification error and a reading position error in each of the main scanning direction and the sub-scanning direction) in the reading unit as to whether an error has occurred. Then, a correction value for correcting the reading means can be obtained from the reading error.

  Further, in the partial image, if the end located at the end of the sheet is an outer point, and the end opposite to the outer point is an inner point, the reading means reads the outer point and the inner point, The calculation means obtains a correction value for the image forming magnification of the image recording means from the result of calculating the distance between the outer points and the inner points of the partial images arranged at positions symmetrical to the center line. May be.

  In the adjustment image formed on the sheet, the distance (interval) between the outer points of each partial image is known because it depends on the size of the sheet, and the distance (interval) between the inner points is image recording. It is determined by the image data obtained by the means and the image forming magnification (image forming resolution). Therefore, when the position of the image recording unit is adjusted, if the reading magnification of the reading unit is correctly adjusted, the correction value of the image forming magnification in the image recording unit can be obtained only from the reading result of the inner points.

  However, even when the reading magnification in the reading unit is not adjusted, as described above, by using the reading results of both the outer point and the inner point, the correction value of the image forming magnification of the image recording unit is obtained. Thus, accurate correction of the image recording means can be performed.

  Further, in the partial image, if the end located at the end of the sheet is an outer point, and the end opposite to the outer point is an inner point, the reading means reads the outer point and the inner point, The arithmetic means corrects the deviation of the sheet conveyance line from the result of calculating the distance between the outer point and the inner point for the partial images formed at two end portions parallel to the sheet conveyance line. It is preferable to obtain a correction value.

  According to the above configuration, the deviation from the sheet conveyance line is corrected based on the size (length) of the partial image formed at both ends of the sheet parallel to the conveyance direction in the direction orthogonal to the conveyance direction. The correction value can be easily obtained.

  Further, in the partial image, if the end located at the end of the sheet is an outer point, and the end opposite to the outer point is an inner point, the reading means reads the outer point and the inner point, The calculation means calculates the distance between the outer point and the inner point for the partial image formed at the end on the front end side in the sheet conveying direction or the end on the rear end side in the sheet conveying direction. It is preferable to obtain a correction value for correcting the position in the sub-scanning direction of the image writing unit for writing an image on the sheet.

  According to the above configuration, in either one of the partial image formed at the end of the sheet on the leading end side in the transport direction or the partial image formed at the end of the sheet on the rear end side in the transport direction The correction value of the image forming position with respect to the sheet can be easily obtained by obtaining the size (length) of the partial image in the conveyance direction.

  In the image forming apparatus of the present invention, it is preferable that a plurality of partial images of the adjusted image are formed for each side of the sheet.

  According to the above configuration, by forming a plurality of partial images constituting the adjustment image for each side of the sheet, a plurality of distant locations can be detected, and the inclination of the reading means, the bending distortion, the sheet Oblique conveyance (skew) or the like can be detected.

  In the image forming apparatus of the present invention, the reading unit detects an outer point and an inner point for each of the partial images formed on each side of the sheet, and the calculating unit detects the detected outer point. It is preferable to average the inner points and obtain the correction value.

  According to said structure, a more exact correction value can be obtained by averaging the outer point and inner point of the some partial image formed in each edge | side.

  In the image forming apparatus of the present invention, the reading unit detects an outer point for each of the partial images formed on each side of the sheet, and the calculating unit connects the outer points of the partial images. It is preferable to calculate an outer virtual frame and to determine the placement state of the sheet read by the reading unit based on the outer virtual frame.

  According to the above configuration, the outer virtual frame obtained by connecting the outer points of the partial images, the loading state of the sheet reading unit on which the adjustment image is formed on the document table (that is, on the document table) It is possible to easily confirm whether or not the sheet is inclined.

  In addition, the image forming apparatus of the present invention further includes a display unit that displays an operation state of the apparatus, and when it is determined that the outer virtual frame is tilted by a predetermined amount or more, the calculation unit obtains a correction value. It is preferable that the operation is interrupted and the display unit displays a warning that the outer virtual frame is tilted.

  According to the above configuration, when the sheet placed on the document table of the reading unit is tilted by a predetermined amount or more, the operation for obtaining correction can be interrupted and a warning to that effect can be notified. Accordingly, since the user performs the adjustment operation again after placing the sheet again, it is possible to avoid the danger that the adjustment operation is performed in a state where the sheet is largely inclined and an inappropriate correction is obtained.

  In the image forming apparatus according to the aspect of the invention, the reading unit may detect an inner point for each of the partial images formed on each side of the sheet, and the calculating unit may connect the inner points of the partial images. It is preferable to calculate an inner virtual frame and determine the image forming state in the image recording means based on the inner virtual frame.

  In the image forming apparatus of the present invention, even if the sheet on which the adjustment image is formed is read by the reading unit and the correction value for correcting the image forming position on the sheet is obtained, the main scanning line of the image writing unit in the image recording unit If there is an inclination in the sheet or an inclination in the sheet conveyance itself, there is a problem that a good image cannot be formed even if the correction value is obtained.

  Therefore, as described above, the inclination of the image writing unit in the image recording unit is obtained by determining the inner virtual frame obtained by connecting the inner points of the partial images and determining the image forming state based on the inner virtual frame. Further, sheet skew (oblique conveyance) can be easily confirmed.

  The image forming apparatus according to the present invention further includes a display unit that displays an operation state of the apparatus. When it is determined that the inner angle of the inner virtual frame is shifted from 90 degrees by a predetermined angle or more, the calculation is performed. Preferably, the means interrupts the operation for obtaining the correction value, and the display unit displays a warning that the main scanning line of the image writing unit is tilted.

  As described above, when the inner angle of the inner virtual frame is greatly deviated from 90 degrees, the main scanning line of the image writing unit of the image recording unit may be inclined. Therefore, the image writing unit can be adjusted by issuing a warning as described above.

  The image forming apparatus of the present invention further includes a display unit that displays an operation state of the apparatus, and when it is determined that the inner virtual frame is inclined at a predetermined angle or more from the sub-scanning direction of the image writing unit. Preferably, the calculation means interrupts the operation for obtaining the correction value, and the display unit displays a warning that the sheet is conveyed obliquely in the conveyance means.

  As described above, when the inner virtual frame is inclined at a predetermined angle or more from the sub-scanning direction of the image writing unit, it is conceivable that the sheet is fed obliquely because the conveying means is inclined. Therefore, the conveying means can be adjusted by issuing a warning as described above.

  The image forming apparatus of the present invention further includes a plurality of sheet storage units, and the calculation unit preferably obtains a correction value for correcting the position of image formation with respect to the sheet for each of the sheet storage units.

  According to the above configuration, when a plurality of sheet storage units are provided, an optimum correction value can be set for each storage unit by obtaining correction for each sheet storage unit. As a result, it is possible to perform good image formation when the sheet is supplied from any sheet storage means.

  An adjustment method for an image forming apparatus according to the present invention is an adjustment method for an image forming apparatus that adjusts an image formed by an image forming apparatus using a reference adjustment image. The partial image is formed of at least one partial image formed on each side of the rectangular sheet, the partial image has a region protruding from the sheet, and the partial image has a corner at the front end in the sheet conveyance direction. An adjustment image forming step for forming an adjustment image not formed on the portion, a reading step for reading the image formed on the sheet by the reading means, and correcting the image forming conditions on the sheet from the read data read The method includes a calculation step for obtaining a correction value, and an adjustment step for adjusting the image forming apparatus using the correction value.

According to the above method, since the adjustment image is composed of partial images that protrude from the end portions of the four sides of the sheet, a partial image is formed up to the end portion at least on a part of each side of the sheet on which the adjustment image is formed. Has been. Therefore, when the sheet on which the adjustment image printed out is formed is read by the reading unit, the end portion (edge) of the sheet can be clearly read. Accordingly, the relationship between the sheet and the position of the image to be formed can be read with high accuracy on the basis of the sheet size, and a highly accurate correction value can be obtained. Furthermore, the partial image, because it is not formed on the corners of the sheet conveying direction leading end, Ru can also reduce the occurrence of paper jam of the sheet in the fixing means.

  As described above, the image forming apparatus according to the present invention includes a storage unit that stores adjustment image data, an image recording unit that forms an adjustment image on a sheet based on the adjustment image data, and a conveyance unit that conveys the sheet. A reading unit that reads an adjustment image formed on the sheet, a calculation unit that obtains a correction value for correcting an image forming condition for the sheet from the read data of the adjustment image obtained from the reading unit, and a correction value based on the correction value. An adjustment unit formed on the sheet based on the adjustment image data is provided at least on each side of the quadrilateral sheet. It consists of partial images that are formed one by one. The partial image has an area that protrudes from the sheet, and the partial image The part is characterized in that it is not formed.

  The adjustment method of the image forming apparatus according to the present invention includes a partial image formed on each side of a rectangular sheet based on predetermined image data, and the partial image is formed from a sheet. The partial image includes an adjustment image forming step for forming an adjustment image that is not formed at a corner portion at the front end in the sheet conveyance direction, and has an area that protrudes, thereby reading the image formed on the sheet. The correction value for correcting the image forming condition on the sheet is obtained from the read data read by the means, and the image forming apparatus is adjusted using the correction value.

  According to the present invention, the adjustment of image forming conditions such as the position and magnification of an image with respect to a sheet of the image forming apparatus can be performed correctly using adjusted image data stored in advance in the image forming apparatus. Play. In addition, it is possible to suppress the occurrence of a sheet conveyance jam at the fixing unit when conveying the sheet after image formation, and to form an adjusted image with a reduced amount of developer used.

  One embodiment of the present invention will be described below.

  In the present embodiment, as an example of the image forming apparatus of the present invention, a multifunction machine having functions such as a copying machine, a scanner, and a printer will be described. FIG. 2 shows a configuration of the multifunction machine 1 according to the present embodiment. The multi-function device 1 shown in FIG. 2 is roughly composed of an automatic document feeder 210, an image forming unit 100, an image reading unit (reading unit) 200, and a paper feeding desk device 20.

  In the present embodiment, an image reading unit 200 is disposed on the upper part of the multifunction device 1, and a document table 209 made of transparent glass is provided on the upper surface of the image reading unit 200. An automatic document feeder 210 is provided on the document table 209. An image forming unit 100 is disposed below the image reading unit 200, and a sheet feeding desk device 20 is provided below the image forming unit 100.

  The automatic document feeder 210 is a device that automatically conveys a plurality of sheets (documents) set on the document set tray 211 one by one onto the document table 209.

  The image reading unit 200 is a device that scans and reads an image of a sheet placed on the document table 209. The image reading unit 200 of this embodiment is a color reading unit. The image reading unit 200 includes a first scanning unit 201 and a second scanning unit 202, an optical lens 203, and a CCD line sensor 204, which is a photoelectric conversion element, below the document table 209.

  The first scanning unit 201 includes an exposure lamp 205 that exposes the surface of the sheet, a first mirror 206 that reflects a reflected light image from the sheet in a predetermined direction, and the like. The second scanning unit 202 includes a second mirror 207 and a third mirror 208 that guide the reflected light from the sheet reflected from the first mirror 206 of the first scanning unit 201 to the CCD line sensor 204 that is a photoelectric conversion element. It is made up of. The optical lens 203 forms an image of the reflected light from the original on the CCD line sensor 204. The CCD line sensor 204 uses a three-line image sensor of R (red), G (green), and B (blue), and can read an image by separating it into three colors.

  Further, the image reading unit 200 reads an image of a document automatically conveyed by the automatic document conveying device 210 by an operation related to the automatic document conveying device 210, and inputs image data (shown in FIG. 3) as image data. The image processing unit 511 performs predetermined image processing on the image data and then temporarily stores the image data in the memory 512 of the image processing unit 511. The data is read and transferred to the image writing unit 11 of the image forming unit 100.

  Next, the configuration of the image forming unit 100 and the configuration of each unit related to the image forming unit 100 will be described.

  The image forming unit 100 forms multi-color and single-color images on sheets (recording paper) of various sizes according to image data read by the image reading unit 200 or image data transmitted from the outside. It is. As shown in FIG. 2, the exposure unit 10, the developing unit (developing unit) 2, the photosensitive drum 3, the charging unit (charging unit) 5, the cleaner unit 4, the transfer conveyance belt unit 8, the fixing unit (fixing unit). 12, a paper transport path (part of transport means) S, a paper feed tray (sheet storage means) 19, a paper discharge tray (sheet stacking unit, claim sheet stacking device) 15, a paper discharge tray 33, and the like. ing.

  Note that image data handled in the image forming unit 100 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, the exposure unit 10 (10a, 10b, 10c, 10d), the developing device 2 (2a, 2b, 2c, 2d), the photosensitive drum 3 (3a, 3b, 3c, 3d), and the charger 5 (5a, 5b, 5c, 5d), and four cleaner units 4 (4a, 4b, 4c, 3d) are provided so as to form four types of latent images corresponding to the respective colors, a being black (K) and b being Four image stations are configured with cyan (C), c set to magenta (M), and d set to yellow (Y). If it is not necessary to distinguish between the image forming stations, they will be referred to as an exposure unit 10, a developing device 2, a photosensitive drum 3, a cleaner unit 4, and a charger 5 for the sake of simplicity.

  The photosensitive drum 3 is disposed (attached) at substantially the center of the image forming apparatus.

  The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum to a predetermined potential. In addition to a contact type roller type and a brush type charger, as shown in the figure, a charger type charger is used. A vessel is used. The exposure unit 10 constitutes the image writing unit 11 and includes, for example, an EL or LED writing head (not shown) in which light emitting elements are arranged in an array, a laser irradiation unit, and a reflection mirror, and a laser scanning unit. (LSU) is used. The charged photosensitive drum 3 is exposed according to the input image data, thereby forming an electrostatic latent image corresponding to the image data on the surface. The developing unit 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with (K, C, M, Y) toner. The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum after development and image transfer.

  The transfer / conveying belt unit (conveying means) 8 disposed below the photosensitive drum 3 includes a transfer belt 7, a transfer belt driving roller 71, a transfer belt tension roller 72, a transfer belt driven roller 73, a transfer belt supporting roller 74, A transfer roller (transfer section) 6 (6a, 6b, 6c, 6d) and a transfer belt cleaning unit 9 are provided.

  A transfer belt drive roller 71, a transfer belt tension roller 72, a transfer roller 6, a transfer belt driven roller 73, a transfer belt support roller 74, and the like stretch the transfer belt 7 and rotate the transfer belt 7 in the direction of arrow B. It is.

  The transfer roller 6 is rotatably supported by a frame (not shown) inside the transfer belt unit, and a sheet (recording paper) on which the toner image on the photosensitive drum 3 is adsorbed and conveyed on the transfer belt 7. ).

  The transfer belt 7 is provided so as to come into contact with the respective photosensitive drums 3, and the color toner images formed on the photosensitive drums 3 are sequentially superimposed on the sheet and transferred, thereby transferring the color toner. It has a function of forming a toner image (multicolor toner image). This transfer belt is formed endlessly using a film having a thickness of about 100 μm.

  Transfer of the toner image from the photosensitive drum 3 to the sheet is performed by the transfer roller 6 that is in contact with the back side of the transfer belt 7. A high voltage (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the transfer roller 6 in order to transfer the toner image. The transfer roller is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the recording paper (sheet). In this embodiment, the transfer roller 6 is used as the transfer electrode, but a brush or the like is also used.

  Thus, each member of the transfer / conveyance belt unit 8 functions as a transfer unit that transfers the toner image from the photosensitive drum 3 to the sheet. The configuration of the transfer means is not limited to the transfer conveyance belt unit 8. When the transfer means is not a belt, the region shown as the transfer belt 7 in FIG. 1 can be considered as a development view of the photosensitive drum 3 instead.

  Further, the toner adhering to the transfer belt 7 due to contact with the photosensitive drum 3 is set to be removed and collected by the transfer belt cleaning unit 9 in order to cause the back surface of the recording paper to become dirty. The transfer belt cleaning unit 9 includes, for example, a cleaning blade that contacts the transfer belt 7, and the transfer belt 7 that contacts the cleaning blade is supported by a transfer belt support roller 74 from the back side.

  The paper feed tray 19 is a tray for accumulating sheets (recording paper) used for image formation, and is provided below the main image forming unit 100. The paper discharge tray 15 provided on the upper part of the image forming unit 100 is a tray for placing printed sheets face down, and is provided on the side of the image forming apparatus. The paper tray 33 is a tray on which an image-formed sheet is placed face up.

  Further, the main image forming unit 100 is provided with an S-shaped paper conveyance path S for sending the sheets on the paper feed tray 19 to the paper discharge tray 15 via the transfer conveyance unit 8 and the fixing unit 12. ing. Further, in the vicinity of the sheet conveyance path S from the sheet feed tray 19 to the sheet discharge tray 15 and the sheet discharge tray 33, a pickup roller 16, a registration roller 14, a fixing unit 12, a conveyance direction switching gate 34, and a conveyance for conveying a sheet. A roller 25 and the like are arranged.

  The conveyance roller 25 is a small roller for promoting and assisting conveyance of the sheet, and a plurality of conveyance rollers 25 are provided along the sheet conveyance path S. The pickup roller 16 is provided at an end portion of the paper feed tray 19 and is a drawing roller that feeds sheets one by one from the paper feed tray 19 to the paper transport path S.

  The conveyance direction switching gate 34 is rotatably provided on the side cover 35, and separates the sheet from the middle of the conveyance path S by discharging from the state indicated by the solid line to the state indicated by the broken line and discharges the sheet to the paper discharge tray 33. It can be done. In the state indicated by the solid line, the sheet passes through the conveyance unit S ′ (part of the sheet conveyance path S) formed between the fixing unit 12, the side cover 35, and the conveyance switching guide 34, and the upper discharge tray 15. To be discharged.

  Further, the registration roller 14 temporarily holds the sheet being conveyed on the sheet conveyance path S. The sheet has a function of transporting the sheet with good timing in accordance with the rotation of the photosensitive drum 3 so that the toner image on the photosensitive drum 3 can be satisfactorily transferred onto the sheet.

  That is, the registration roller 14 controls the registration clutch (see FIG. 3) at a preset timing based on a detection signal output from a registration sensor (not shown), and the leading edge of the toner image on each photosensitive drum 3 is placed on the sheet. The sheet is set to be conveyed so as to match the leading end of the image forming range.

  The fixing unit 12 includes a heat roller 31, a pressure roller 32, and the like, and the heat roller 31 and the pressure roller 32 rotate with a sheet interposed therebetween.

  Further, the heat roller 31 is set to have a predetermined fixing temperature by a control unit based on a temperature detection value from a temperature detector (not shown), and the sheet is formed by thermocompression bonding the sheet together with the pressure roller 33. The multi-color toner image transferred onto the sheet is melted, mixed and pressed, and thermally fixed to the sheet.

  If the sheet discharge destination is designated as the sheet discharge tray 15, the sheet after the fixing of the multicolor toner image is conveyed to the reverse sheet discharge path of the sheet conveyance path S by the conveyance rollers 25, and reversed. In this state (with the multi-color toner image facing downward), it is discharged onto the discharge tray 15. The image processing board 300 is a circuit board that performs predetermined processing on image data, and the control circuit board 400 is a circuit board that controls an image forming process, and is housed in a control unit (control means) 500 described later. Yes.

  Next, the sheet feeding desk device 20 will be described. The paper feed desk device 20 is provided below the paper feed tray 19 of the image forming unit 100. The paper feed desk device 20 includes three stages of paper feed trays (sheet storage means) 20 a to 20 c, and can supply paper to the image forming unit 100 via the paper transport path S. The multi-function device 1 according to the present embodiment is not limited to the configuration of the paper feed desk device 20, and includes a single-stage paper feed tray or a tandem tray that includes two trays in parallel. Alternatively, it can be mounted according to the user's request, such as a device that simply functions as a desk.

  In this embodiment, the image forming unit 100 is described as a multicolor image forming apparatus that forms a multicolor image. However, an image forming apparatus that forms a monochrome (monochrome) image has a function excluding a part of the present invention. It can be implemented. Further, although the multi-function device 1 has been described as including the automatic document feeder 210, the present invention is not limited to this, and the automatic document feeder may not be mounted.

  In addition, the multifunction device 1 includes a control unit (control means) 500 for controlling the operation of the multifunction device 1. The control unit 500 adjusts control conditions in the image forming unit 100, for example.

  As shown in FIG. 3, the control unit 500 includes a fixing unit 501, a transfer unit 502, a developing unit 503, a charging unit 504, a conveying unit 505, a pattern storage unit 506, a data storage unit 507, and an operation unit (operation panel) 220. A data input / output unit 509, an image data input unit (data input means) 510, an image processing unit 511, a memory 512, and an image writing unit 11 are connected, and the control unit 500 controls them. The transport unit 505 includes a transport motor 514 and a registration clutch 515. A display unit (touch panel liquid crystal display device) 221 is disposed in the operation unit 220.

  Control during image formation in the multifunction machine 1 will be described. The fixing unit 501, the transfer unit 502, the developing unit 503, the charging unit 504, and the image writing unit 11 include a fixing unit 12, transfer rollers 6a to 6d, developing units 2a to 2d, charging units 5a to 5d, and an exposure unit 10a, respectively. -10d and their peripherals. As a result, an image is recorded on the sheet. Therefore, the image writing unit 11, the fixing unit 501, the transfer unit 502, the developing unit 503, and the charging unit 504 are collectively referred to as an image recording unit (image recording unit) 520.

  The control unit 500 controls the surface potential of the photosensitive drums 3a to 3d by controlling the grid bias voltage of the charging chargers as the chargers 5a to 5d with respect to the charging unit 504.

  The control unit 500 controls the writing operation such as the light beam power and writing timing of the image writing unit 11. When the image writing unit 11 (exposure unit 10) is an EL or LED writing head, the writing operation such as the light beam power and writing timing is controlled.

  The control unit 500 controls the developing unit 503 so that proper development is performed by controlling the bias voltage of the developing roller in the developing units 2a to 2d. The control unit 500 controls the voltage applied to the transfer rollers 6 a to 6 d from a high-voltage power supply for transfer (not shown) for the transfer unit 502.

  The control unit 500 controls the heat roller 31 of the fixing unit 501 (fixing unit 12) so as to reach a predetermined fixing temperature based on a temperature detection value from a temperature detector (not shown). The control unit 500 controls the operations of the transport motor 514 and the registration clutch 515 with respect to the transport unit 505.

  Further, in the multifunction device 1, the control means performs the following operation in order to adjust image formation. The control unit 500 controls the pattern storage unit (storage unit) 506 to store a predetermined pattern of adjusted image data. The control unit 500 controls the data storage unit 507 to store the reference value.

  Further, the multifunction device 1 inputs data of a reading result from an external image reading device that is not mounted, or reads data of a reading result read by the image reading unit 200 mounted on the multifunction device. A data input / output unit 509 for outputting to an external device is provided.

  Further, the reading operation in the multifunction device 1 is controlled as follows. The image reading unit 200 reads an image of a document automatically conveyed by the automatic document conveyance device 210 by an operation related to the automatic document conveyance device 210 shown in FIG. Then, the read image is transferred as image data to the image data input unit 510 shown in FIG.

  The control unit 500 controls the image data input unit 510 so that the image data read by the image reading unit 200 is input to the image processing unit 511 of the image forming unit 100. The control unit 500 controls the image processing unit 511 to perform predetermined image processing on the image data input to the image data input unit 510. Thus, the image processing unit 511 performs predetermined image processing on the image data transferred to the image data input unit 510.

  The control unit 500 controls the memory 512 so as to temporarily store the image data processed by the image processing unit 511. The control unit 500 controls the light beam power of the EL, LED writing head, and laser irradiation unit of the exposure units 10 a to 10 d with respect to the image writing unit 11. As a result, the image data subjected to the image processing is temporarily stored in the memory 512, and the image data in the memory 512 is read out and transferred to the image writing unit 11 in accordance with the output instruction.

  Furthermore, in the present embodiment, a calculation unit (calculation unit) 600 is connected to the control unit 500. The arithmetic unit 600 obtains a correction value for correcting the image forming condition for the sheet from the read data obtained by reading the image formed on the sheet by the image reading unit 200. The operation of this calculation unit will be described later.

  In addition, the multifunction device 1 includes an operation unit (operation panel) 220 as a user interface of the multifunction device 1 at the position of the image reading unit 200.

  As shown in FIG. 9, the operation panel 220 is provided with a touch panel liquid crystal display device (referred to as LCD) 221 as a display unit on the left side, and a numeric keypad 231, start key 241, clear key on the right side thereof. 251 and an all release key 261 are arranged.

  Various screens are switched and displayed on the screen of the LCD 221. In these screens, touch keys for setting various conditions are arranged, and various conditions can be set (for example, monochrome / color mode selection, document type selection, automatic operation by directly pressing the touch keys with a finger. / Manual selection, other special function selection, etc.). In addition, operation guidance, warnings, and the like are also displayed on the LCD 221. When a selection key for whether or not to add an additional image (advertisement) or the like is provided on the image forming apparatus side, it is provided as a touch key on the LCD 221 or as a hard key on the operation panel 220 such as a numeric keypad. . In this case, it is preferable to provide as a touch key on the LCD 221. As a result, when this function is incorporated in the image forming unit 100, software is added, and the image forming unit 100 can be used in common.

  Also, between the LCD 221 and the numeric keypad 231, as keys for switching functions when the multifunction device 1 having the image forming unit 100 operates as a multifunction device, a printer key 271, a facsimile / image transmission key 281, a copy key 291, In addition, a job key 311 for confirming the job status registered for each function is arranged.

  Among the keys arranged on the right side of the LCD 221, the numeric keypad 231 is a key used for inputting a numerical value (such as the number of copies) on the LCD 221 screen, and the start key 241 is an image forming operation or reading in each processing mode. This is a key for instructing the start of operation. The clear key 251 is a key for clearing a set value displayed on the LCD 221 or interrupting an operation currently being executed such as an image forming operation. The all cancel key 261 is a reading condition, an image forming condition, or the like. It is a key to return the setting of to the default value. The interrupt key 321 is a key for temporarily interrupting an image forming operation being executed and allowing other image formation.

  FIG. 9 shows a state where the color image forming mode is selected. At this time, the density at the time of image formation and reading such as copy density is automatically controlled according to the document.

  When the operation panel 220 detects an instruction to start an image forming operation or a reading operation input to the multifunction device 1, the control unit 500 causes the image writing unit 11 and the conveying unit 505 of the image forming unit 100 to operate. Control.

  Next, a method for adjusting the image forming conditions (that is, the magnification, position, etc. of the formed image) in the multifunction device 1 will be described in detail.

  The maximum sheet size that can be used in the multifunction machine 1 is A3 size (297 mm × 420 mm). In this case, for example, a correction value for adjusting the image forming conditions can be obtained using sheets of A4 size (210 mm × 297 mm), B5 size (182 mm × 257 mm), B4 size (257 mm × 364 mm), and the like.

  When the adjustment of the image forming condition is started in the multifunction device 1, first, the image recording unit 520 displays the adjusted image on the sheet based on predetermined adjustment image data stored in the pattern storage unit 506. Form.

Here, the shape of the adjustment image to be formed will be described in detail.
Prior to finding the adjustment image according to the present invention, the present inventor forms an adjustment image P ′ formed over the entire outer edge of the sheet N as shown in FIG. It was found that correct adjustment is possible by making adjustments. However, when such an adjusted image is formed, an image is also formed at two corner portions (portions Q1 and Q2 separated by a broken line) at the front end in the sheet conveying direction (that is, a developer is applied). Therefore, it is difficult to peel off the sheet from the roller provided in the fixing unit 501, and the sheet is wound around the roller, so that there is a problem that the sheet is easily jammed.

  Accordingly, the inventors of the present application have devised the shape of the adjustment image, and have come up with an adjustment image composed of partial images formed at least one on each side of the rectangular sheet. Note that this partial image has a region protruding from the sheet, and no partial image is formed at the corner portion at the front end of the sheet conveying direction.

  FIG. 1 shows an example of an adjustment image formed on the sheet N. The adjusted image P is stored as adjusted image data in the pattern storage unit 506 in the multifunction machine 1 according to the present embodiment.

  As shown in FIG. 1, the adjustment image P includes partial images p1, p2, p3, and p4 that are formed one by one on each side of the rectangular sheet N. The partial images p1, p2, p3, and p4 each have a region that protrudes from the edge of the sheet, and approximately the center of each side of the sheet (more precisely, on the center line of the image indicated by the alternate long and short dash line). Is located. The partial images p1, p2, p3, and p4 are formed only in the vicinity of each side of the sheet N, and are not formed in the central portion of the sheet N. That is, it is formed in a part of the frame region surrounding the end portion of the sheet N. Further, the partial images p1, p2, p3, and p4 are located in the image forming area K of the transfer belt 7 as shown in FIG.

  The two partial images p1 and p4 and p2 and p3 formed on the two opposite sides of the sheet are arranged at positions symmetrical with respect to the center line of each of the two sides. In other words, the line connecting the two partial images p1 and p4 formed on the two opposite sides of the sheet is parallel to the transport direction D1 and is formed on the two opposite sides of the sheet. A line connecting the two partial images p2 and p3 is perpendicular to the transport direction D1, that is, parallel to the main scanning direction D2.

  Thus, by calculating the distance between the partial images p1 and p4 and the distance between the partial images p2 and p3 by the calculation unit 600, a correction value for correcting the image forming condition can be easily obtained.

  Note that only one size of the adjusted image may be stored in the pattern storage unit 506, or a plurality of adjusted images may be stored so as to correspond to a plurality of sheet sizes.

  Furthermore, in the present embodiment, as shown in FIG. 1, a rectangular direction indicating the direction of the image at a position offset toward the leading end side of the conveyance direction (sub-scanning direction) D1 inside the partial images p1, p2, p3, and p4. Adjustment image data is stored so that the mark M is formed. As a result, when the sheet on which the adjustment image is formed is set in the image reading unit 200, the image direction is not mistaken.

  Although it is possible to use an arrow-shaped direction mark with emphasis on visibility, this increases the data capacity in the pattern storage unit 506, and also when the image reading unit 200 reads an image formed on a sheet. Since it is complicated to determine the reading result, it is preferable to use a simple rectangular mark as in this embodiment. Further, the direction of the sheet set on the reading unit 200 may be automatically detected without forming the direction mark M.

  In addition, since a sheet output from the image forming unit 100 may be placed on the document table 209 with a large inclination, in order to prevent this, an allowable range of inclination is set and the allowable value is exceeded during reading. In such a case, an error may be generated, and a message to that effect may be displayed on the operation panel 220 of the operation unit 508 and read again. This control method will be described in detail later.

  The data storage unit 507 stores a reference value. In the present embodiment, the vertical and horizontal lengths of A4 size sheets are stored as reference values, and correction values are obtained using the A4 size as a reference.

  FIG. 4 shows an adjustment image formed on the sheet. In the partial images p1, p2, p3, and p4 of the adjustment image formed on the sheet N, end portions located at the end portions of the sheets are set as outer points f1, f2, f3, and f4, respectively, and the outer points f1, f2 , F3, and f4, the ends on the center side of the sheet are denoted by g1, g2, g3, and g4, respectively. Note that the outer point is merely the end of the adjustment image formed on the sheet, and is different from the outermost end of the adjustment image itself.

  At this time, the distance between the opposing f1 and f4 is the sheet length L1 of the transfer belt 7 in the sheet conveyance direction D1. The distance between the opposing f2 and f3 is the sheet length W0 in the direction perpendicular to the sheet conveying direction D1. The distance between the opposing g1 and g4 is L3, and the distance between the opposing g2 and g3 is W3.

  When adjustment is performed using an A4 size sheet, the L0 is 210 mm and the W0 is 297 mm. The outside size of the adjustment image in the main scanning direction (that is, the distance J1 from the outer end portion protruding from the sheet of the adjustment images p1 and p4 in the main scanning direction D2 shown in FIG. 1) is the main scanning. It is formed in a size exceeding 210 mm in the direction and not more than the effective image forming width, for example, 220 mm or 230 mm. Further, the outside size of the adjustment image in the main scanning direction (that is, the distance J2 from the outer end portion protruding from the sheet of the adjustment images p2 and p3 in the sub scanning direction D1 shown in FIG. For example, 307 mm or 317 mm is formed so as to have a length exceeding 297 mm in the scanning direction. However, when the image size is too large, a deviation peculiar to the device to be adjusted may be determined in advance by an experiment or the like. In this way, the image data of the adjustment image is created and stored in the pattern storage unit 506 so that the image can be formed with sufficient allowance in consideration of possible conveyance deviations. Note that if each sheet size or each size is grouped and a common adjustment image is used in each group, the storage capacity of the image data of the adjustment image can be reduced.

  Further, in the present embodiment, when an A4 sheet is used, the distance L3 between the inner points is set to be sufficiently smaller than 210 mm, for example, image data such that the distance is 180 mm (−30 mm). The W3 is image data such that when the used sheet is A4, the interval is sufficiently smaller than 297 mm, for example, 267 mm (−30 mm). However, the present invention is not necessarily limited to this.

  In the image forming apparatus 1 according to the present embodiment, the length of the conveyance direction (sub-scanning direction) is calculated from the result of reading L3 by the image reading unit 200, and compared with 210 mm, thereby reading the image used for reading. The magnification in the sub-scanning direction (D1) of the apparatus can be obtained. Further, the magnification in the main scanning direction can be similarly obtained by calculating the length in the main scanning direction (D2) from the result of reading W3 and comparing it with 297 mm.

  In FIG. 4, the broken line is the center line of the two opposite sides of the sheet, and the alternate long and short dash line is the center line of the two opposite sides in the area where the adjustment image is formed.

  Further, the adjusted image shown in FIG. 4 has one partial image (p1, p2, p3, p4) on each side of the sheet. However, the present invention is not limited to this, and each side of the sheet. A plurality of partial images may be formed.

  FIG. 5 shows an example of an adjusted image having three partial images on each side of the sheet. FIG. 13 is an enlarged view of the adjustment image shown in FIG.

  In the adjustment image P (p1 to p4) shown in FIG. 5 as well, the distance between the opposing f1 and f4 is equal to the sheet length L1 in the sheet conveyance direction D1 on the transfer belt 7, as in the adjustment image shown in FIG. Become. The distance between the opposing f2 and f3 is the sheet length W0 in the direction perpendicular to the sheet conveying direction D1. A virtual frame (corresponding to the end of the sheet) obtained by connecting the outer points f1, f2, f3, and f4 is defined as an outer virtual frame B1. A virtual frame obtained by connecting the inner points g1, g2, g3, and g4 is defined as an inner virtual frame B2 (a frame indicated by a two-dot chain line in FIG. 13).

  In FIG. 5, the broken line is the center line of the two opposite sides of the sheet, and the alternate long and short dash line is the center line of the two opposite sides in the region where the adjustment image is formed. As shown in FIG. 5, when three partial images are formed on each side of the sheet, the distance between the partial images provided on one side (the distance between the centers of the partial images). Are arranged to be about 1/4 of the length (L0 or W0) of the corresponding outer virtual frame B1 (that is, about L0 / 4 or about W0 / 4).

  As described above, since a plurality of partial images are formed for each side, the calculation unit 600 obtains a correction value by averaging each detected outer point and inner point (that is, an adjusted image is formed). The correction value is obtained from the distance between the outer points of each partial image and the average value of the distances between the outer points of each partial image arranged at a position symmetrical to the center line of the two opposite sides of the edge of the area being Can do. Therefore, a more accurate correction value can be obtained.

  In addition to the partial images p1 to p4 and the direction mark M, the adjustment image data may include identification mark information for identifying which paper feed tray has been conveyed.

  As the identification mark, a mark having a different size is prepared for each sheet feeding tray in order to identify the sheet feeding tray, and is added to the sheet corresponding to the sheet feeding tray. Further, the identification marks may be the same size and added with different numbers and positions so that it can be recognized from which paper feed tray. In the case of a color image forming apparatus, the color may be different and the paper feed tray may be identified by the color. Further, a plurality of conditions may be recognized by combining them, and another condition is identification of the sheet size. If the size can be detected, sheets of different sizes are sequentially supplied to the document table 209 of the image reading unit 200 by the automatic document feeder 210 and read together, and then the sheet size can be easily determined when obtaining correction values for each sheet. Since it can be recognized, an efficient reading operation can be performed.

  Next, a specific processing flow for adjusting the image forming conditions in the image forming unit 100 of the multifunction machine 1 will be described with reference to FIG.

  By the way, the image forming apparatus usually includes a plurality of trays and cassettes (sheet storage means) like the image forming apparatus shown in the present embodiment, and the sheet conveyance state for each storage means. In particular, the position of the sheet from the reference transport line (position in the main scanning direction) is often different. In addition, since there is a registration means for the position in the sub-scanning direction, there is no great deviation for each sheet accommodation means, but there are some differences depending on the type of sheet to be accommodated (material, waist strength, thickness, surface condition). A case where a deviation occurs is considered. Therefore, when strict adjustment is performed, it is preferable to set a correction value for each sheet storage unit with respect to an image position shift in the sub-scanning direction with respect to the sheet.

  Therefore, in the present embodiment, first, a paper feed tray (sheet storage unit) 19 provided in the image forming unit 100 and three paper feed trays (sheet storage unit) 20a provided in the paper feed desk device 20 are firstly provided. ˜20c, the tray in which the sheet is to be adjusted is selected, and the sheet is fed from the corresponding tray (S1). Next, an adjustment image is formed by the image forming unit 100, transferred to the sheet, and the sheet on which the adjustment image is formed is output (S2, adjustment image forming step). Here, the adjustment images formed on the photosensitive drum 3 of the image forming unit 100 and transferred to the sheet N and the transfer belt 7 are as partial images p1 to p4 shown in FIG. The sheet on which the image has been transferred and is discharged to, for example, the sheet discharge tray 33 through the fixing unit 12 or the like has an adjustment image formed of four partial images p1 to p4 formed as a sheet N shown in FIG. It has become.

  Then, the output sheet is set on the document table 209 of the image reading unit 200 (S3), and the adjustment image is read (S4, reading step).

  Note that, when the output sheet on which the adjustment image is formed is placed on the document table 9, as shown in FIG. 6, it is read by the document placement guide (document reference member) 810 of the image reading unit 200. If the sheet N is in contact, the sheet can be placed accurately. Further, marks (reference mark T, center position T0) indicating the position and size of the sheet may be provided on the document placement guide 810. If this reference mark T or the like is used, it can be expected that the placement of the sheet becomes more accurate.

  However, depending on, for example, the material of the document placement guide 810, it is difficult to distinguish between the document placement guide 810 and the end of the sheet, and as a result, it becomes difficult to read the image formed at the corner of the sheet, and the reading accuracy. May fall. In such a case, as shown in FIG. 7, the sheet is placed with a gap provided between the document placement guide 810 and the end of the sheet N to be read. In this way, the image formed at the corner of the sheet can be reliably and accurately read.

  Further, as shown as a sheet N in FIGS. 6 and 7, the sheet can be placed in the reading region 800 of the image reading unit 200 so that the longitudinal direction of the sheet is parallel to the main scanning direction of the image reading unit 200. . However, according to this, since the necessary size of the image reading unit 200 is increased, it is necessary to increase the number of reading sensors (not shown) necessary for reading the image, which increases the cost of the image reading unit 200. In addition, in order for the image reading unit 200 to accurately read, a reading error occurs unless the sheet is accurately placed in the reading area 800.

  6 and 7, the sheet is placed on the reading region 800 of the image reading unit 200 so that the longitudinal direction of the sheet is parallel to the sub-scanning direction of the image reading unit 200. According to this, the cost of the image reading unit 200 can be suppressed by minimizing the necessary size of the image reading unit 200. In addition, since the sheet can be placed with a margin in the reading area 800, occurrence of reading errors can be suppressed.

  In S4, as described above, the adjustment image as shown in FIG. 4 on the sheet is read by the image reading unit 200, and the size of the sheet is first obtained therefrom.

  In the present embodiment, the lengths W0 and L0 of the sheet N shown in FIG. 4 are read as the sheet size. Then, the distance between the partial image p1 and the partial image p4 formed in the front and rear of the adjustment image conveyance direction (sub-scanning direction) D1 shown in FIG. 4 (L3 shown in FIG. ), And the distance (W3 shown in FIG. 4, that is, the distance between the inner points) between the partial image p2 and the partial image p3 formed respectively in front and rear in the main scanning direction D2. Further, the distance L1 between the outer point f1 and the inner point g1 of the partial image p1 formed in front of the sheet conveyance direction D1, and the outer point f4 and inner of the partial image p4 formed behind in the sheet conveyance direction D1. A distance L1 from the point g4 and a distance W1 between the outer point f2 (or f3) and the inner point g2 (or g3) of each of the two adjustment images p2 and p3 formed in the direction D2 orthogonal to the sheet conveyance direction; Read W2. These values are calculated by the calculation unit 600 to which the image data is transferred from the image data input unit 510 by the control unit 500 using the image data input from the image reading unit 200 to the image data input unit 510 shown in FIG. To do.

  In this embodiment, the data storage unit 507 stores the length in the longitudinal direction of the A4 size sheet and the length in the direction orthogonal to the longitudinal direction (that is, the length of the A4 size sheet (210 mm)), And the horizontal length (297 mm) is stored.

  As a result of performing the reading as described above in S4, if there is an abnormality in the way the sheet is placed, for example, the sheet placed on the document table is greatly inclined (that is, the outer virtual frame B1 described later is If it is tilted more than a predetermined angle (for example, 0.48 °), the adjustment work is interrupted, and a warning that the seat is tilted is displayed on the LCD 221 of the operation panel 220 to notify the user ( S5).

  By providing S5 as described above, when the output sheet on which the adjustment image is formed is set on the document table 209 with a large inclination, an error is generated and a message indicating this is displayed on the LCD (display) of the operation panel (operation unit) 220. Part) 221 and confirming the output state of the output sheet, it can be read again. As a result, more accurate image forming conditions can be adjusted. The allowable range of the inclination of the sheet placed on the document table 209 can be within ± 0.5 mm, for example. Then, when the predetermined allowable range is exceeded, the adjustment work may be interrupted and a warning to that effect may be displayed on the display unit.

  If it is determined that the inner angle of an inner virtual frame B2, which will be described later, obtained by the reading process is shifted from 90 degrees by a predetermined angle or more, the adjustment operation is interrupted and image writing is performed on the LCD 221 of the operation panel 220. By displaying a warning that the main scanning line of the unit 11 is tilted, the user is notified (S6). FIG. 10 shows an example of an image formed by the image forming unit 100 when the main scanning line is inclined. In this figure, the transfer belt 7 is conveyed with no inclination. In the present embodiment, the allowable inclination range of the inner virtual frame B2 is set such that the deviation of two sides (a1 in FIG. 10) perpendicular to the main scanning direction D2 of the inner virtual frame B2 is within ± 0.5 mm. This inclination indicates the inclination of the main scanning line of the LED head and the laser writing unit constituting the image writing unit 11. Although this value is set in the present embodiment, the present invention is not limited to this value. As another example of the allowable inclination range of the inner virtual frame B2, the inner angle θ1 of the inner virtual frame B2 may be in the range of 88.96 ° to 90.14 °.

  Further, at the same time, in S6, when it is determined that the inner virtual frame B2 is inclined at a predetermined angle or more from the sub-scanning direction of the image writing unit 11, the adjustment operation is interrupted and transferred to the LCD 221 of the operation panel 220. The user is notified by displaying a warning that the belt (conveying means) 7 conveys the sheet diagonally (S6). FIG. 11 shows an example of an image formed by the image forming unit 100 when the sheet is conveyed obliquely on the transfer belt 7. In the present embodiment, as a permissible range of inclination of the inner virtual frame B2, the deviations (a2 or b in FIG. 11) of the two opposing sides of the inner virtual frame B2 are within ± 0.5 mm. Although this value is set in the present embodiment, the present invention is not limited to this value.

  In S5 and S6, when the sheet placed on the document table, the main scanning line, or the inclination of the sheet conveyance on the transfer belt is within the allowable range, and the adjustment operation is not interrupted, Calculation steps (S7 to S10) for obtaining a correction value for correcting the image forming condition for the sheet from the read data read are performed.

  Here, the image reading unit 200 calculates the length in the transport direction (sub-scanning direction) from the result of reading the distance L3 between the two inner points g1 and g4 in the adjustment image, and compares the length with 210 mm to read the image. The magnification in the sub-scanning direction (D1) of the image reading unit used in the above is obtained. Further, the main scanning direction (D2) length is calculated from the result of reading the distance W3 between the two inner points g2 and g3 in the adjusted image, and similarly compared with 297 mm, the magnification in the main scanning direction is similarly obtained. .

  Then, considering the magnification in the main scanning direction, if the width of the image data is obtained from the value obtained by reading W1, the writing timing in the main scanning direction can be obtained, and the writing timing in the main scanning direction set in advance is determined. A correction value for is obtained. Similarly, if the width in the image data is obtained from the value obtained by reading L1 in consideration of the magnification in the sub-scanning direction, the writing timing in the sub-scanning direction can be obtained and the preset writing timing in the sub-scanning direction can be obtained. A correction value can be obtained.

  The specific procedure of the calculation process is shown below.

  In S7, the data stored in the data storage unit 507 is compared with a predetermined size obtained by reading by the reading unit 200, and the calculation unit 600 obtains a magnification correction value in the image reading unit 200.

  First, when the read image data is input to the image data input unit 510, the calculation unit 600 uses the read distance W0 between the two outer points f2 and f3 and the A4 size sheet stored in the data storage unit 507. The length in the direction orthogonal to the longitudinal direction of 210 mm is compared. Thereby, when the magnification of the image reading unit 200 is not adjusted and it is determined that W0 is not 210 mm, the magnification of the image reading unit 200 in the main scanning direction can be obtained. Further, the calculation unit 600 compares L0 with the length 297 mm in the longitudinal direction of the sheet in the A4 size stored in the data storage unit 507. Thereby, the magnification of the image reading unit 200 in the sub-scanning direction can be obtained.

  Subsequently, in S8, a magnification correction value on the image recording unit 520 side of the image forming unit 100 is obtained. For this purpose, first, an accurate size of the image printed on the sheet by the image forming unit 100 is obtained using the magnification correction value in the main scanning direction of the image reading unit 200 obtained in S7 with respect to W3 shown in FIG. Ask. The arithmetic unit 600 compares this size with the size corresponding to the pattern stored in the pattern storage unit 506, and a correction value (magnification correction value) for correcting the magnification in the main scanning direction in the image forming unit 100 is obtained. Ask. Further, for L3 shown in FIG. 4, the image forming unit 100 obtains an accurate size of the image printed on the sheet by using the magnification correction value in the sub-scanning direction of the image reading unit 200 obtained in S7. The arithmetic unit 600 compares this size with the size corresponding to the pattern stored in the pattern storage unit 506, and a correction value (magnification correction value) for correcting the magnification in the sub-scanning direction in the image forming unit 100 is obtained. Ask.

  In the next S9 and S10, the calculation unit 600 obtains a correction value for correcting the timing at which the image writing unit 11 writes the electrostatic latent image. The procedure for obtaining the correction value is not limited to the order of S9 and S10, and may be performed in the order of S10 and S9.

  In S9, the correction value of the write timing in the main scanning direction is determined by determining the width (W2 shown in FIG. 4) of the partial image p3 in the main scanning direction based on the magnification correction value in the main scanning direction obtained in S8. Ask. That is, for example, the value obtained by correcting the reading magnification of the image reading unit 200 and correcting the magnification of the image forming unit 100 with respect to the value of W2 is the original value of the pattern stored in the pattern storage unit 506. Thus, the correction value of the writing timing in the image writing unit 11 can be obtained.

  Further, if W2 shown in FIG. 4 is read at at least two different positions in the sub-scanning direction, the inclination of the image forming position with respect to the sheet can be obtained. The calculation unit 600 also obtains a correction value for correcting this inclination. In this case, a plurality of partial images are formed on at least two sides parallel to the sub-scanning direction of the sheet.

  Further, by comparing the width W2 of the partial image p3 in the main scanning direction and the width W1 of the partial image p2 in the main scanning direction, it is possible to determine how much the sheet is deviated from the conveyance line on the transfer belt 7. Thus, a correction value for correcting the deviation from the sheet conveyance line can be easily obtained.

  In S10, the write timing correction value in the sub-scanning direction is determined by determining the width (L1 shown in FIG. 4) of the partial image p1 in the sub-scanning direction based on the magnification correction value in the sub-scanning direction obtained in S8. Ask. That is, for example, the value obtained by correcting the reading magnification of the image reading unit 200 and correcting the magnification of the image forming unit 100 with respect to the value of L1 is the original value of the pattern stored in the pattern storage unit 506. Thus, the correction value of the writing timing in the image writing unit 11 can be obtained.

  Further, if the width L1 in the sub-scanning direction shown in FIG. 4 is read at at least two positions different in the main scanning direction, the inclination of the image formed on the sheet can be obtained. The calculation unit 600 also obtains a correction value for correcting this inclination. In this case, a plurality of partial images are formed on at least two sides parallel to the sub-scanning direction of the sheet.

  In S <b> 11, the control unit 500 reflects the correction value of the write timing obtained in S <b> 9 and S <b> 10 on the image forming unit 100 of the multifunction machine 1.

  The timing in the main scanning direction is adjusted as follows. When the image writing unit 11 (exposure unit 10) of the image forming unit 100 is a laser beam scanning method, the control unit 500 adjusts the timing after passing the beam detector to correct the writing position in the main scanning direction. To do. Further, when the image writing unit 11 (exposure unit 10) of the image forming unit 100 is a solid scanning method using an LED head or the like, the first light emitting element is determined (shifted) from where in the main scanning direction the light is lit. Thus, write adjustment in the main scanning direction is performed. In the case of the solid scanning method, since the magnification in the main scanning direction is almost determined, it is not usually necessary to adjust it. However, if there is a noticeable deviation, either image data is thinned out or the image data is complemented. The number of light emitting elements to be lit is increased or decreased to adjust.

  The timing in the sub-scanning direction is adjusted as follows. Here, using the correction value of the writing timing in the sub-scanning direction obtained in S10, the control unit 500 adjusts the writing timing in the image writing unit 11 to correct the writing position in the sub-scanning direction. However, the present invention is not limited to this, and the writing position in the sub-scanning direction can be corrected by adjusting the connection timing of the registration clutch 515 of the conveying means 505 shown in FIG.

  Further, magnification correction in the sub-scanning direction is performed by adjusting the conveyance speed of the conveyance motor 514 of the conveyance unit 505 and adjusting the conveyance speed of the sheet. Further, the sheet conveyance speed may be adjusted by rotating the transfer roller 6 of the transfer unit 502 at a predetermined speed. In addition, the present invention is not limited to this. For example, the rotation speed of the photosensitive drum 3 can be adjusted to correct the magnification in the sub-scanning direction. However, for example, a configuration in which the conveyance speed of the conveyance motor 514 is adjusted is preferable because the process conditions for image formation need not be changed.

  In this way, in the adjustment step of S11, the obtained correction value is reflected on the image forming unit 100, and the process is terminated.

  In FIG. 8 described above, the adjustment for each image forming station is not mentioned for the sake of simplicity. However, in the multi function device 1, the adjustment for each image forming station is actually performed as follows. Yes.

  That is, when the image forming unit 100 includes a plurality of image forming stations for forming an image using a plurality of color materials as in the multi-function device 1 of the present embodiment, the data storage shown in FIG. The unit 507 stores registration correction data. Then, an image is formed using one color material, and a correction value for correcting the image forming condition in the image forming station of the color material is obtained. For the remaining color material, the correction value of the remaining color material at the image forming station can be obtained from the correction value and the resist correction data already obtained. According to this, since only one color material needs to be used, it is possible to economically adjust the image forming conditions for the sheet.

  Further, the present invention is not limited to the above-described configuration, and a plurality of image forming stations may perform different adjustments. Specifically, for example, any one of the image forming stations may adjust the position and magnification in the main scanning direction and the sub-scanning direction, and the remaining image forming stations may adjust the magnification in the main scanning direction. Good. According to this, it is possible to adjust the image forming conditions for the sheet more accurately.

  Further, when the image reading unit 200 is a color reading unit as in the present embodiment, an image formed on a sheet using any one of the three color photoelectric conversion elements is displayed. It is preferable to read. Accordingly, reading is facilitated, and the number of data obtained by reading is reduced, so that the time for calculating the read data can be shortened.

  In the image reading unit 200, it is preferable to use a photoelectric conversion element having a color that is a complementary color of a colorant used when an image is formed on a sheet. Therefore, for example, if the colors of the optoelectronic elements used in the image reading unit 200 are B, G, and R, a color image using each of Y, M, and C may be formed. Accordingly, since the image reading unit 200 can perform clear reading, more accurate read data can be obtained.

  As described above, according to the present embodiment, the partial image includes at least one partial image formed on each side of the quadrangular sheet, and the partial image has a region protruding from the sheet and the partial image. By forming an adjustment image that is not formed at the corner at the leading edge of the sheet conveyance direction, the end of the sheet can be easily read when the image formed on the sheet is read by the reading unit. . Since the correction value for correcting the image forming condition for the sheet is obtained from the read data read, the image forming apparatus can be adjusted even if the image reading unit used for reading is not accurately adjusted.

  Further, the image data to be formed on the sheet is stored in the pattern storage unit 506 of the image forming unit 100, and the data stored in the pattern storage unit 506 is printed on the sheet. The reference chart like this can be made unnecessary. In addition, the process of reading the reference chart first in the image reading apparatus is not necessary.

  Furthermore, since the adjustment image is composed of partial images that are not formed at the corners at the leading edge of the sheet conveyance direction as described above, the occurrence of sheet conveyance jams in the fixing unit can be reduced.

  In this embodiment, the correction value is calculated by calculating the image data input from the image reading unit by the calculation unit in the image forming unit and reflecting the result in the image forming unit. However, the present invention is not limited to this, and a configuration is also possible in which the CPU is provided in the image reading unit and the correction value data is transferred to the image forming apparatus as information and adjusted. Is possible. Such a configuration can be appropriately changed depending on the program to be used.

  When the image forming unit and the image reading unit are connected directly or via a computer, the obtained correction data can be directly input to the image forming unit to adjust the image forming unit. The correction value obtained using the operation unit of the image forming unit may be manually input by a serviceman or an administrator. When the image reading unit and the image forming unit are not indirectly connected, the correction value cannot be automatically input, and thus manual input from the operation unit or the like is performed.

  Unlike the multifunction device 1 according to the present embodiment, when the image reading unit is not integrated with the image forming unit, a general-purpose system such as an image reading unit and a computer (personal computer) is used. A program for obtaining a correction value for image adjustment may be created and installed, and the correction value may be obtained using the program. In this case, the correction value is obtained by analyzing and calculating the read data input by a computer such as a personal computer and displayed on the display. Then, the displayed correction value may be input to the target image forming apparatus.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Note that each unit and each processing step of the image forming apparatus according to the above embodiment is a program stored in a storage unit such as a ROM (Read Only Memory) or a RAM by a unit that performs calculations such as a control unit (CPU) and a calculation unit. This is realized by controlling the input means such as the keyboard, the output means such as the display, or the communication means such as the interface circuit. Therefore, various functions and various processes of the image forming apparatus of the present embodiment can be realized simply by a computer having these means reading the recording medium on which the program is recorded and executing the program. In addition, by recording the program on a removable recording medium, the various functions and various processes described above can be realized on an arbitrary computer.

  As the recording medium, a memory (not shown) such as a ROM may be used as a program medium for processing by the microcomputer, and a program reader is provided as an external storage device (not shown). It may be a program medium that can be read by inserting a recording medium therein.

  In any case, the stored program is preferably configured to be accessed and executed by the microprocessor. Furthermore, it is preferable that the program is read out, and the read program is downloaded to a program storage area of the microcomputer and the program is executed. It is assumed that this download program is stored in advance in the main unit.

  The program medium is a recording medium configured to be separable from the main body, such as a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a flexible disk or a hard disk, or a disk such as a CD / MO / MD / DVD. Fixed disk system, card system such as IC card (including memory card), or semiconductor memory such as mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), flash ROM, etc. In particular, there are recording media that carry programs.

  In addition, if the system configuration is capable of connecting to a communication network including the Internet, the recording medium is preferably a recording medium that fluidly carries the program so as to download the program from the communication network.

  Further, when the program is downloaded from the communication network as described above, it is preferable that the download program is stored in the main device in advance or installed from another recording medium.

  The image forming apparatus according to the present invention does not require a test chart, and can correctly print even if the image reading apparatus is not accurately adjusted. Therefore, the image forming apparatus can be used for a personal use printer, a multifunction machine, and the like.

It is a schematic diagram showing an example of an adjustment image formed by the image forming apparatus according to the embodiment of the present invention. 1 is an internal configuration diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration for adjusting control conditions in an image forming apparatus according to an embodiment of the present invention. FIG. It is a schematic diagram which shows the adjustment image formed on the sheet | seat. It is a schematic diagram which shows the other example of the adjustment image formed with the image forming apparatus concerning one Embodiment of this invention. FIG. 3 is a plan view showing a sheet placed on a document table of the image forming apparatus shown in FIG. 2. FIG. 7 is a plan view showing a sheet placed on a document table of the image forming apparatus shown in FIG. 2 in a state different from FIG. 6. 3 is a flowchart illustrating an image forming condition adjustment operation in the image forming apparatus illustrated in FIG. 2. It is a top view which shows the operation panel concerning one Embodiment of this invention. FIG. 3 is a schematic diagram illustrating a state of an image formed when a main scanning line of an image writing unit of the image forming apparatus illustrated in FIG. 2 is inclined. FIG. 3 is a schematic diagram illustrating a state of an image formed when a sheet is conveyed while being inclined on a transfer belt of the image forming apparatus illustrated in FIG. 2. It is a schematic diagram which shows the shape of the adjustment image used as the reference example of this invention. It is a schematic diagram which shows the adjustment image shown in FIG. 5 in detail.

Explanation of symbols

1 MFP (image forming device)
7 Transfer belt (conveying means)
11 Image writing unit (image recording means, image writing unit)
19 Paper feed tray (sheet storage means)
DESCRIPTION OF SYMBOLS 100 Image formation part 200 Image reading part (reading means)
221 LCD (display unit)
500 Control unit (control means)
506 Pattern storage unit (storage unit)
520 Image recording unit (image recording means)
600 Calculation unit (calculation means)
P Adjusted image p1 to p4 Partial image f1 to f4 Outside point g1 to g4 Inside point

Claims (12)

A storage means for storing the adjusted image data; an image recording means for forming an image on the sheet; a reading means for reading an image formed on the sheet; and an arithmetic means; and the image recording means based on the adjusted image data Reads the adjusted image formed on the sheet by the reading unit, obtains a correction value for correcting the image forming condition on the sheet by the image recording unit from the reading result, and forms the image using the correction value An image forming apparatus that adjusts conditions,
The image recording means, based on the adjusted image data, adjusts an image including a quadrangular partial image that is a part of a frame area surrounding an end of the quadrangular sheet, and each partial image has each side of the sheet. At least one is formed on the top, and the partial images have a region protruding from the sheet, and the partial images are formed so as not to exist at the corners at the front end in the sheet conveying direction.
The reading unit reads the adjustment image formed on the sheet,
In the adjusted image, each point for obtaining the sheet length in the sheet conveyance direction or the sheet length in the direction perpendicular to the conveyance direction, which is a point corresponding to the edge of the sheet in each partial image. When the point is an outer point, and the point on the inner edge of the sheet in the partial image, and the point existing on the line connecting the outer points is an inner point,
The calculation means calculates the distance between the outer points based on the reading result of the reading means, compares the distance with the actual length of the sheet corresponding to the distance, and is generated by the reading means. A correction value for the reading error is obtained, and further, the size of the adjustment image read by the reading unit is corrected using the correction value for the reading error, and the inner point existing on a line connecting the outer points after the correction Comparing the distance between each other and the distance between the corresponding internal points in the adjusted image data stored in the storage means, and obtaining a correction value for correcting the image forming magnification of the image recording means. An image forming apparatus.   The partial image is disposed at least on the center line of two opposite sides outside the frame region surrounding the edge of the sheet on which the partial image is partially formed, and is disposed on the center line. The image forming apparatus according to claim 1, wherein the outer point and the inner point in the adjusted image exist on the center line. Further comprising a conveying means for conveying the sheet;
The calculation means calculates the distance between the outer point and the inner point in the partial image for the partial image formed at two end portions parallel to the sheet conveyance line. The distance between the outer point and the inner point in the partial image formed at the end portion is compared with the distance between the outer point and the inner point in the partial image formed at the other end portion. Further find a correction value to correct the deviation of the transport line,
The image forming apparatus according to claim 1, wherein the conveyance unit corrects the deviation of the conveyance line using a correction value for correcting the deviation of the conveyance line of the sheet.   For the partial image formed at the end on the leading end side in the sheet conveying direction or the end on the trailing end side in the sheet conveying direction, the arithmetic means calculates the distance between the outer point and the inner point in the partial image. The calculated distance is corrected using the correction value for the reading error and the correction value for correcting the image forming magnification, and the corrected distance and the adjusted image data stored in the storage unit are corrected. And comparing the distance between the corresponding outer point and the inner point to obtain a correction value for correcting the position of the image writing unit for writing an image on the sheet in the sub-scanning direction. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein a plurality of partial images of the adjusted image are formed for each side of the sheet.   The arithmetic means exists on the line connecting the outer points and the distance between the outer points of the partial images for a plurality of partial images formed on each side of the sheet based on the reading result of the reading means. The distance between the inner points is calculated, and the distance between the obtained outer points and the distance between the inner points are averaged to obtain a correction value. Image forming apparatus. It further includes a display unit that displays the operating state of the device,
The calculation means calculates an outer virtual frame by connecting the outer points of a plurality of partial images formed on each side of the sheet based on the reading result of the reading means, and the reading means uses the outer virtual frame to read the outer virtual frame. When the loaded state of the read sheet is determined and it is determined that the outer virtual frame is tilted by a predetermined amount or more, the calculation means interrupts the operation for obtaining the correction value,
The image forming apparatus according to claim 5, wherein the display unit displays a warning that the outer virtual frame is tilted. It further includes a display unit that displays the operating state of the device,
The arithmetic means calculates an inner virtual frame by connecting the inner points of a plurality of partial images formed on each side of the sheet based on the reading result of the reading means, and the image recording means by the inner virtual frame When the image forming state is determined and it is determined that the inner angle of the inner virtual frame is shifted from 90 degrees by a predetermined angle or more, the operation for obtaining the correction value is interrupted,
The image forming apparatus according to claim 5, wherein the display unit displays a warning that the main scanning line of the image writing unit that writes an image on the sheet is tilted. When the calculation unit determines that the inner virtual frame is inclined at a predetermined angle or more from the sub-scanning direction of the image writing unit, the calculation unit interrupts the operation for obtaining the correction value,
The image forming apparatus according to claim 8, wherein the display unit displays a warning that the sheet is conveyed obliquely in a conveying unit that conveys the sheet. A plurality of sheet storage means,
The image forming apparatus according to claim 1, wherein the calculation unit obtains a correction value for correcting an image forming condition for the sheet for each sheet storage unit. An adjustment method of an image forming apparatus that adjusts image forming conditions using a reference adjustment image,
Based on the adjustment image data stored in the apparatus, an adjustment image including a quadrilateral partial image that is a part of a frame area surrounding the edge of the quadrilateral sheet is displayed on each side of the sheet. An adjustment image forming step in which at least one of the partial images has a region protruding from the sheet and the partial image does not exist at a corner portion at the front end in the sheet conveying direction;
A reading step of reading the adjusted image formed on the sheet;
In the adjusted image, each point for obtaining the sheet length in the sheet conveyance direction or the sheet length in the direction perpendicular to the conveyance direction, which is a point corresponding to the edge of the sheet in each partial image. The point is an outer point, a point on the inner edge of the sheet in the partial image, and a point existing on a line connecting the outer points is an inner point,
Based on the reading result in the reading step, the distance between the outer points is calculated, and the distance is compared with the actual length of the sheet corresponding to the distance to correct the reading error generated in the reading step. A correction value for the reading error is used to correct the size of the read adjustment image, the distance between the inner points existing on a line connecting the outer points after the correction, A calculation step for calculating a correction value for correcting the image formation magnification at the time of image recording by comparing the distance between the corresponding internal points in the stored adjustment image data;
An adjustment step of adjusting image forming conditions using the correction value obtained in the calculation step;
A method for adjusting an image forming apparatus, comprising: The partial image is disposed at least on the center line of two opposite sides outside the frame region surrounding the edge of the sheet on which the partial image is partially formed, and is disposed on the center line. the outer points and the inner points in the adjustment image adjustment how the image forming apparatus according to claim 11, characterized in that present on the central line.

Images