JP2015087603A - Image formation device and calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device 1 capable of both improving precision in calibration and shortening time.SOLUTION: An image formation device 1 includes measuring means 402 which measures length L of one round in rotational direction of an intermediate transfer belt B1, calculation means 403 which, based on the length L of one round in rotational direction of the intermediate transfer belt B1 and a total number S of patches, calculates length L0 in rotational direction of the patch and a patch number N representing position of the patch, base material concentration coping means 404 which measures a base material concentration D0 of the intermediate transfer belt B1 and associates the base material concentration D0 that has been measured with respective patch numbers N, and calibration means 401 which forms a patch corresponding to the length L0 in rotational direction of the patch, and based on a patch concentration D of the patch and the base material concentration D0 corresponding to the patch number N of the patch, makes calibration.

Description

  The present invention relates to an image forming apparatus and a calibration method, and more particularly, to an image forming apparatus and a calibration method capable of both improving calibration accuracy and reducing time.

  In image forming apparatuses such as copiers and printers that employ an electrophotographic process, a standard toner patch image (reference image) is usually used as an intermediate to stabilize the toner image (toner image) corresponding to the image data. The toner image is transferred to a transfer body (for example, an intermediate transfer belt, a photosensitive drum, etc.), and the toner density of the patch image is measured by a measuring unit such as a density detection sensor. Then, the image forming apparatus calculates the toner density (toner amount) of the toner image used for printing by using the measured value (output value), resets the printing output condition based on this calculation, and sets the appropriate value. The toner image is controlled to have a proper density.

  In order to more stably control the density of the toner image, it is necessary to accurately measure (detect) the toner density of the patch image. Therefore, normally, the toner density of the patch image is obtained by subtracting the measured value (density value) of the background (background) of the intermediate transfer body on which the patch image is formed from the measured value (density value) of the measured patch image. The value is calculated as the toner density value of the official patch image.

  Here, in an image forming apparatus that employs the above-described method for calculating the toner density value of a patch image, Japanese Patent Application Laid-Open No. 2000-221738 (Patent Document 1) describes as much productivity as possible during printing (during printing). There is disclosed an image forming apparatus that accurately matches the position of a measured value of a patch image and a measured value of a background corresponding to the patch image without lowering. In this image forming apparatus, a plurality of types of panel areas divided according to the image forming size are set, a toner image for controlling image forming conditions is formed and detected at a predetermined position, and a ground at the same position is set at a predetermined timing. Detect and correct the detection result of the toner image. As a result, the background portion and the toner image portion of the intermediate transfer member or the transfer member holding member can be detected at the same position without increasing the execution time and complicating the image forming sequence. An image forming apparatus capable of image formation can be provided.

JP 2000-221738

  However, in the technique described in Patent Document 1, in order to accurately match the position of the measured value of the patch image and the measured value of the background corresponding to the patch image, the detection timing of the patch image and the detection timing of the background However, if this timing is shifted, the measured value (output characteristics) may vary due to variations in the light amount of the density detection sensor itself, and the measured value of the background may also change during printing. Accordingly, there is a problem that the toner density value of the accurate patch image cannot be calculated, and the density of the toner image cannot be properly stabilized. Further, in order to set the panel area in accordance with the image forming size, the number of sheets output in one rotation of the intermediate transfer member is an integer. For this reason, depending on the type of paper size, it is necessary to unnecessarily increase the length of the paper space (non-image region) between the image regions, and there is a problem that productivity is extremely reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a calibration method capable of both improving calibration accuracy and reducing time.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention is an image forming apparatus that performs calibration by forming a calibration patch, and employs the following configuration. .

  That is, according to the present invention, a measuring unit that measures the length of one rotation in the rotation direction of the intermediate transfer member that forms a toner image at the time of printing, and the length of one rotation in the rotation direction of the intermediate transfer member that are measured are set in advance. Further, based on the total number of patches that can be formed in one rotation length of the intermediate transfer member, the length of the patch in the rotation direction and the length of one rotation in the rotation direction of the intermediate transfer member. Calculation means for calculating a patch number indicating the position of each patch, a background density corresponding means for measuring the background density of the intermediate transfer member, and associating the measured background density with each patch number, A calibration unit that forms a patch corresponding to the length in the rotation direction and calibrates based on the patch density of the patch and the background density corresponding to the patch number of the patch; And features.

  Further, the calibration unit may measure the length of the patch in the rotation direction of the patch in a non-image area other than the image area corresponding to the printing in the intermediate transfer body area during printing. And measure the density of the patch as a measured value, and calculate the patch density as a calculated value using the background density associated with the patch number indicating the position of the patch, and execute the calibration. To do.

  Further, the background density corresponding means measures the background density of the non-image area other than the image area corresponding to the printing among the areas of the intermediate transfer body at the time of printing, and the measured background density is Re-associate with the patch number of the non-image area.

  In addition, the present invention can be provided as a calibration method for an image forming apparatus that executes calibration by forming a calibration patch.

  That is, according to the present invention, a step of measuring the length of one rotation in the rotation direction of the intermediate transfer member that forms a toner image at the time of printing, and the length of one rotation in the rotation direction of the intermediate transfer member measured in advance are set in advance. Based on the total number of patches that can be formed in one rotation length of the intermediate transfer member, the length of the patch in the rotation direction and the length of one rotation in the rotation direction of the intermediate transfer member. A step of calculating a patch number indicating the position of each patch, a step of measuring a background density of the intermediate transfer member, associating the measured background density with each patch number, and a length of the patch in the rotation direction. And a step of calibrating based on the patch density of the patch and the background density corresponding to the patch number of the patch. Even with such a configuration, the same effects as described above can be obtained.

  Further, the present invention can be provided as a program for causing a computer to circulate individually via a telecommunication line or the like. In this case, the central processing unit (CPU) realizes the control operation in cooperation with each circuit other than the CPU according to the program of the present invention. Each means realized by using the program and the CPU can also be configured by using dedicated hardware. The program can also be distributed in a state where it is recorded on a computer-readable recording medium such as a CD-ROM.

  According to the image forming apparatus and the calibration method of the present invention, it is possible to improve both calibration accuracy and time.

1 is a schematic configuration diagram of an image forming apparatus according to an exemplary embodiment. FIG. 3 is a detailed view of one image forming unit. 2 is a schematic configuration diagram relating to control of the image forming apparatus 1 in the present embodiment. FIG. 1 is a functional block diagram of an image forming apparatus of the present invention. It is a flowchart for showing the execution procedure of this invention. FIG. 6 is a schematic diagram showing the relationship between the intermediate transfer belt and the patch of the present invention (FIG. 6A), and a schematic diagram when forming the patch on the intermediate transfer belt of the present invention (FIG. 6B). Schematic diagram (FIG. 7A) when patches are continuously formed in the first and second rounds of the intermediate transfer belt of the present invention, and the patches are formed from the second round of the conventional intermediate transfer belt. It is a schematic diagram at the time (FIG. 7B).

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not. Moreover, the alphabet S added before the number in a flowchart means a step.

<Image forming apparatus>
The image forming apparatus 1 according to the present invention will be described below. FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 of the present embodiment.

  The image forming apparatus 1 transfers a toner image formed by the tandem-type image forming unit A1 that forms a toner image based on image data, a paper storage unit 2 that stores paper, and the image forming unit A1 onto the paper. A next transfer unit 3 is provided. The image forming apparatus further includes a fixing unit 4 that fixes the transferred toner image on the paper, a paper discharge device 5 that discharges the fixed paper, and a paper discharge tray 7 that receives the discharged paper. Further, the image forming apparatus 1 includes a paper transport unit 6 that transports paper from the paper storage unit 2 to the paper discharge device 5.

  The image forming unit A1 includes an intermediate transfer belt B1 (intermediate transfer member), a cleaning unit B2 for cleaning the intermediate transfer belt B1, and each color of yellow (Y), magenta (M), cyan (C), and black (B). Are provided with image forming units FY, FM, FC, and FB, respectively.

  The intermediate transfer belt B1 is a belt-like member having an endless shape, that is, a loop shape, which is wider than a sheet having the maximum length in the direction perpendicular to the usable sheet conveying direction and having conductivity. Circulated around.

  The image forming units FY, FM, FC, and FB are arranged in this order along the intermediate transfer belt B1 in the moving direction of the intermediate transfer belt B1, downstream from the cleaning unit B2 and upstream from the secondary transfer unit 3. . Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image. The image forming units FY, FM, FC, and FB are arranged so that the intervals between the image forming units are equal.

  Next, an image forming operation of the image forming apparatus 1 will be described. FIG. 2 is a detailed view of one of the image forming units FY, FM, FC, and FB. The image forming units FY, FM, FC, and FB have almost the same configuration.

  The image forming unit FY includes a photosensitive drum (image carrier) 10, a charger 11, an exposure device 12, a yellow developing device HY, a primary transfer roller (voltage application unit) 20, a cleaning blade 35 for the photosensitive drum 10, A static eliminator 13 and a carrier removal roller (carrier removal member) 30 are provided.

  The other image forming units FM, FC, and FB include developing devices HM, HC, and HB corresponding to the respective colors. Of the image forming units, the image forming unit FB located on the most downstream side in the moving direction of the intermediate transfer belt B1 is not provided with the carrier removing roller 30 because the image forming unit is not located downstream thereof. Other configurations are the same.

  The photoreceptor drum 10 only needs to be able to carry a toner image including toner charged on its surface (charged positively in this embodiment).

  In the present embodiment, the photosensitive drum 10 is a substantially cylindrical member that is arranged to be rotatable about a rotation axis that is perpendicular to the moving direction of the intermediate transfer belt B1 and parallel to the surface direction of the intermediate transfer belt B1. The photosensitive drum 10 is in contact with the surface of the intermediate transfer belt B1 at a predetermined primary transfer position 10S. The photosensitive drum 10 can rotate so that the moving direction at the primary transfer position 10S is the same as the moving direction of the intermediate transfer belt B1, that is, in FIG.

  The cleaning blade 35, the charge eliminating device 13, the charger 11, the exposure device 12, and the yellow developing device HY are arranged around the photosensitive drum 10 in this order as seen from the primary transfer position along the rotation direction described above. The

  The charger 11 can uniformly charge the surface of the photosensitive drum 10. The exposure device 12 has a light source such as a laser scanner unit (LSU), and irradiates the surface of the charged photosensitive drum 10 with light according to the image data in accordance with the image data from the above-described host device. An electrostatic latent image can be formed on the surface of the drum 10.

  The yellow developing device HY holds a developer containing yellow toner and a carrier so as to face the electrostatic latent image, thereby applying toner to the electrostatic latent image, and converting the electrostatic latent image into a toner image. Can be developed. This toner image is primarily transferred by the primary transfer roller 20 to the intermediate transfer belt B1. Details of the primary transfer roller 20 will be described later.

  The cleaning blade 35 is a blade-like member disposed so as to be in contact with the photosensitive drum 10. The cleaning blade 35 removes the developer remaining on the surface of the photosensitive drum 10 after the primary transfer.

  The neutralization device 13 includes a light source. After the developer is removed by the cleaning blade 35, the surface of the photosensitive drum 10 is neutralized by light from the light source to prepare for the next image formation.

  The primary transfer roller 20 is disposed so as to contact the back surface of the intermediate transfer belt B1 at a voltage application position 20S downstream from the primary transfer position 10S in the moving direction of the intermediate transfer belt B1. A voltage having a polarity opposite to that of the toner in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 from a power source (not shown). That is, the primary transfer roller 20 can apply a voltage having a polarity opposite to that of the toner to the intermediate transfer belt B1 at the voltage application position 20S. Since the intermediate transfer belt B1 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt B1 at the voltage application position 20S and the periphery thereof.

  Therefore, in the present embodiment, the primary transfer position 10S is disposed within a range in which toner is attracted to the intermediate transfer belt B1 side by the applied voltage. As a result, the toner moves from the photosensitive drum 10 to the surface of the intermediate transfer belt B1, and primary transfer is performed.

  As long as primary transfer is possible in this way, the specific configuration of the primary transfer roller 20 is not particularly limited, and the specific configuration can be changed as appropriate. In the present embodiment, the primary transfer roller 20 can rotate in the opposite direction to the photosensitive drum 10 around a rotation axis parallel to the rotation axis of the photosensitive drum 10, that is, the movement direction at the charge application position 20S is intermediate. It is a substantially cylindrical member that can be rotated in the same direction as the transfer belt B1.

  In this embodiment, the carrier removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photosensitive drum 10 around a rotational axis parallel to the rotational axis of the photosensitive drum 10. The carrier is not limited, and it is sufficient that the carrier can be removed from the surface of the intermediate transfer belt B1 downstream of the charge application position 20S and upstream of the secondary transfer position in the moving direction of the intermediate transfer belt B1. Specifically, the carrier removing roller 30 only needs to be able to move the carrier on the surface of the intermediate transfer belt B1 to its own surface by contacting the surface of the intermediate transfer belt B1.

  During primary transfer, a small amount of carrier may be transferred from the photosensitive drum 10 to the intermediate transfer belt B1 together with the toner. This carrier transfer may interfere with primary transfer in the downstream image forming unit and cause image defects such as image blurring and blurring. Providing the carrier removal roller 30 can prevent such an image defect.

  In the present embodiment, the carrier removal roller 30 is disposed so as to contact the surface of the intermediate transfer belt B1 downstream of the charge application position 20S in the moving direction of the intermediate transfer belt B1. The carrier removal roller 30 is incorporated in the cleaning unit 31 together with the cleaning blade 35 described above. The cleaning unit 31 is provided in the image forming unit FY. In addition to the cleaning blade 35 and the carrier removing roller 30, the cleaning unit 31 is in contact with the surface of the carrier removing roller 30 to remove the carrier attached to the surface of the carrier removing roller 30. The carrier removal blade 31b, the carrier removed from the carrier removal roller 30, and the developer (including toner and carrier) removed from the surface of the photosensitive drum 10 by the cleaning blade 35 are conveyed to the outside of the cleaning unit 31. A transport member 31c is provided. The image forming unit FY may further include a separation unit that separates the carrier and the toner in order to reuse the carrier and the toner conveyed by the conveyance member 31c.

  Next, the configuration of the developing device HY will be described. The configurations of the developing devices HY, HM, HC, and HB for the respective colors are the same.

  The developing device HY includes a developing container 40, a developing roller 40a, a magnetic roller (mag roller) 40b, a drawing roller 40c, stirring spirals 40d and 40e, and a magnetic roller doctor blade 40g.

  The developing container 40 stores therein a developer composed of yellow toner (toner particles) and a carrier. The stirring spirals 40d and 40e are provided so as to be entirely immersed in the developer in the developing container 40, and stir the developer. The toner is uniformly dispersed in the carrier by the rotation of the stirring spirals 40d and 40e.

  The drawing-up roller 40c is arranged so that a part of the drawing-up roller 40c is immersed in the developer in the developing container, and the developer is pumped up by adhering to the surface. A magnetic roller 40b is arranged in contact with the pumping roller 40c, and a developer is supplied from the pumping roller 40c. The magnetic roller 40b rotates in the counter direction of the developing roller 40a, and in the vicinity of the nip, a magnetic roller doctor blade 40g is provided that simultaneously peels off the developer and places the developer. The magnetic roller doctor blade 40g regulates the developer layer thickness on the surface of the magnetic roller 40b to a predetermined amount. A developing roller 40a (also referred to as a developing device) is disposed so as to be in contact with the magnetic roller 40b, and a developer is applied to the surface thereof from the magnetic roller 40b. Since the developer layer thickness of the magnetic roller 40b is regulated to a predetermined value, the developer layer thickness formed on the surface of the developing roller 40a is also kept at the predetermined value. The developing roller 40a is in contact with the photosensitive drum 10, and responds to an image instructed to be formed from the host apparatus by the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 10 and the developing bias value applied to the developing roller 40a. A toner image is formed on the surface of the photosensitive drum 10 (development operation).

  The image forming apparatus of the present invention is characterized in that image density correction of a toner image is performed by adjusting a developing bias value (voltage value, simply referred to as a bias value) applied to the developing roller 40a.

  The developer on the surface of the developing roller 40a that has completed the developing operation on the photosensitive drum 10 is removed by the magnetic roller doctor blade 40g via the magnetic roller 40b, and flows down along the surface of the magnetic roller doctor blade 40g. The developer stored in the developer container 40 is mixed with the developer stored in the developing container 40.

  A toner concentration sensor 40h is disposed in the developing container, and detects the toner concentration of the developer in the developing container 40. When it is detected that the toner concentration is lower than a predetermined value, toner (a developer having a toner concentration higher than the predetermined value) is supplied from a toner cartridge (not shown) to the developing container 40, and the toner concentration is higher than the predetermined value. The carrier is supplied to the toner container 40 from a carrier cartridge (not shown).

  Under such a configuration, the image forming apparatus 1 that has received an instruction for image formation from a host device such as a personal computer (PC) or the like forms toner images of each color corresponding to the received image data in the image forming units FY, FM. , FC, and FB. The toner image formed in each image forming unit is transferred to the intermediate transfer belt B1, and is superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is fed to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray section 7 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the cleaning unit B2.

  In addition, two density detection sensors 605 and 606 for detecting the patch density of the patch formed on the intermediate transfer belt B1 at a predetermined timing and the background density of the intermediate transfer belt B1 include a black image forming unit FB and a secondary image sensor. It is provided at a predetermined position between the transfer unit 3. The black image forming unit FB is located on the most downstream side with respect to the rotation direction of the intermediate transfer belt B1 as compared with the other image forming units FY, FM, and FC. Therefore, the density detection sensors 605 and 606 detect the patch density of any of the plurality of image forming units FY, FM, FC, and FB even if the patch is formed on the intermediate transfer belt B1. It is configured to be able to.

  Further, the density detection sensors 605 and 606 are provided in advance at positions corresponding to the positions of the intermediate transfer belt B1 where the patches are formed. In the embodiment of the present invention, two density detection sensors 605 and 606 are provided near both ends of the intermediate transfer belt B1. Provided. The density detection sensors 605 and 606 may have any form as long as they can detect the patch density or the background density of the patch for each color. For example, the background on the patch or the intermediate transfer belt B1 is used as a light source. Reflection type density detection sensors 605 and 606 that irradiate with light from the light source, detect reflected light intensity with a light receiving sensor, and convert light intensity information into density. The density detection sensors 605 and 606 are also used for detecting the toner density of a solid band image to be described later.

  FIG. 3 is a schematic configuration diagram relating to control of the image forming apparatus 1 in the present embodiment.

  The image forming apparatus 1 includes a CPU (Central Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, a HDD (Hard Disk Drive) 304, and a driver 305 corresponding to each driving unit in the printing. They are connected via an internal bus 306. The CPU 301 uses, for example, the RAM 302 as a work area, executes a program stored in the ROM 303, the HDD 304, or the like, and exchanges data and commands with the driver 305 based on the execution result, as shown in FIG. The operation of each driving unit is controlled. Also, each means (shown in FIG. 4) described later other than the drive unit operates as each means when the CPU 301 executes a program.

<Embodiment of the present invention>
Next, the configuration and execution procedure according to the embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a functional block diagram of the image forming apparatus of the present invention. FIG. 5 is a flowchart for showing the execution procedure of the present invention.

  First, when the user turns on the power to the image forming apparatus 1, the image forming apparatus 1 is activated, and the calibration unit 401 of the image forming apparatus 1 determines whether to prepare for calibration ( FIG. 5: S101).

  Here, the calibration can be any calibration as long as the calibration is performed in the image forming apparatus 1, and examples thereof include density adjustment calibration and position adjustment calibration.

  Further, any method may be used as the method for determining whether or not the calibration means 401 prepares for the calibration. For example, when the calibration unit 401 is turned on for the first time in the image forming apparatus 1, when a predetermined number of sheets are printed, when a predetermined amount of toner is consumed, the temperature of a thermometer provided in advance is first. It is possible to adopt a method for determining whether or not a specific time point such as a time point when the temperature is equal to or higher than the set temperature (for example, 35 degrees) or less than the second set temperature (for example, 15 degrees).

  Here, since the image forming apparatus 1 has been activated earlier, the calibration unit 401 determines to prepare for the calibration (FIG. 5: S101 YES), and notifies the measurement unit 402 accordingly. Upon receiving the notification, the measuring unit 402 measures the length of one rotation in the rotation direction of the intermediate transfer belt B1 on which the toner image is formed during printing (FIG. 5: S102).

  Any method may be used for the measuring unit 402 to measure the length of one rotation in the rotation direction of the intermediate transfer belt B1. For example, the measuring unit 402 is configured as follows.

  That is, as shown in FIG. 6A, the intermediate transfer belt B1 usually has a reference at one end in a direction perpendicular to the rotation direction of the intermediate transfer belt B1 in order to determine the timing for forming the toner image. A position member 600 is provided in advance, and a detection member 601 that can detect the reference position member 600 is further provided corresponding to the reference position member 600. Since the reference position member 600 is provided only at one position on the intermediate transfer belt B1, the measurement unit 402 newly starts from the time when the position reference member 600 is detected corresponding to the rotation of the intermediate transfer belt B1. A time T (sec) required until the position reference member 600 is detected is measured, and a multiplication value obtained by multiplying the measured time T (sec) by the rotational speed V (mm / sec) of the intermediate transfer belt B1 is obtained. Thus, the length L (mm) of one rotation in the rotation direction of the intermediate transfer belt B1 can be obtained.

  When the measurement unit 402 completes the measurement of the length L (mm) of one rotation in the rotation direction of the intermediate transfer belt B1, the measurement unit 402 notifies the calculation unit 403 to that effect. Upon receiving the notification, the calculation unit 403 receives the measured length L (mm) of the circumference of the intermediate transfer belt B1 and the preset length of the circumference of the intermediate transfer belt B1 in the rotation direction. On the basis of the total number S (pieces) of patches that can be formed in each of the lengths of the patches in the rotational direction L0 (mm) and the length of one round of the intermediate transfer belt B1 in the rotational direction. A patch number N (−) indicating the position of the patch is calculated (FIG. 5: S103).

  Any method may be used for the calculation means 403 to calculate the length L0 (mm) in the rotation direction of the patch (the length in the rotation direction of one patch) and the patch number N (−). Although it does not matter, for example, it is made as follows.

  For example, when the measured length L (mm) of the circumference of the intermediate transfer belt B1 in the rotation direction is 960 mm and the total number S (number) of patches stored in advance in a predetermined memory is 85, The calculation means 403 calculates a division value (960/85 = 111.294 mm) obtained by dividing the length L (mm) of one rotation in the rotation direction of the intermediate transfer belt B1 by the total number S (number of patches) of the patch. The length in the rotation direction is L0 (mm).

  Here, when the division value is made to correspond to the unit of resolution (600 dpi) of the printing toner image, the calculation unit 403 converts the division value (11.294 mm) into a conversion coefficient (42.33 * 1000 mm / dpi). A value obtained by dividing (266.8 = 266 dpi) can be set as the length L0 (dpi) in the rotation direction of the patch corresponding to the resolution. This makes it easy to form image data of a patch corresponding to the calculated length L0 (dpi) in the rotation direction of the patch during printing.

  Next, the calculation means 403 forms the position of each patch by dividing the length L (mm) in the rotation direction of the intermediate transfer belt B1 by the calculated length L0 (mm) in the rotation direction of the patch. Then, the reference position member 600 of the intermediate transfer belt B1 is set to the first number N (for example, No. 1) with respect to the positions of the formed patches, and sequentially corresponds to the total number S (pieces) of the patches. And number N. The S-th patch corresponding to the total number S of patches is given to the position of the last patch before the reference position member 600 of the intermediate transfer belt B1. Accordingly, it is possible to calculate the patch number N (−) indicating the position of the patch corresponding to the length L (mm) in the rotation direction of the intermediate transfer belt B1.

  When the calculation unit 403 completes the calculation of the length L0 (mm) in the rotation direction of the patch and the patch number N (−), the calculation unit 403 notifies the background density correspondence unit 404 accordingly. Upon receiving the notification, the background density correspondence unit 404 measures the background density D0 (−) of the intermediate transfer belt B1, and associates the measured background density D0 (−) with each patch number N (−).

  The background density correspondence unit 404 measures the background density D0 (−), and associates the background density D0 (−) with each patch number N (−). It is done as follows.

  For example, as shown in FIG. 6 (A), two density detection sensors 605 and 606 are provided in advance corresponding to both ends of the intermediate transfer belt B1 in the direction perpendicular to the rotation direction of the intermediate transfer belt B1, as shown in FIG. First, the background density correspondence unit 404 uses the two density detection sensors 605 and 606 to rotate the patch until the next reference position member 600 appears from the reference position member 600 of the intermediate transfer belt B1. The base density D0 (−) in the rotation direction of the intermediate transfer belt B1 is measured with the length L0 (mm) of one unit as one unit (FIG. 5: S104).

  Here, since the two background densities D0 (−) are measured with respect to one patch number N (−), for example, the average value of the two is determined as the background density D0 (1) with respect to one patch number N (−). -), Or the background density D0 (-) at both ends (left and right) is associated with one patch number N (-), and two patch densities are assigned to one patch number N (-). You may comprise so that it measures as a measured value and calculates two patch density | concentrations as a calculated value using each background density | concentration D0 (-).

  Until the next reference position member 600 appears, in other words, the length of the patch in the rotation direction of the intermediate transfer belt B1 over the entire length L (mm) of the rotation of the intermediate transfer belt B1. When the background density D0 (−) has been measured in units of L0 (mm), the patch number N (−) of the first number corresponding to the reference position member 600 is obtained using the calculated patch number N (−). ) The measured background density D0 (−) is associated in order from (first) (FIG. 5: S105). Note that the last measured background density D0 (−) is associated with the last patch number N (−) (Sth) before the reference position member 600 of the intermediate transfer belt B1. The patch number N (-) and the background density D0 (-) associated therewith are stored in a predetermined memory.

  Thereby, for example, even if the intermediate transfer belt B1 changes in the length L (mm) of one rotation in the rotation direction of the intermediate transfer belt B1 due to an environmental change (for example, a temperature change), the preparation for the calibration is performed. In each case, the length L0 (mm) in the rotation direction of the patch is calculated, and the background density D0 (-) corresponding to this is calculated, so that calibration is executed without being affected by the above-described fluctuation. It becomes possible to improve the accuracy of the calibration.

  In particular, in the intermediate transfer belt B1, it is known that, for example, when the environmental temperature fluctuates by 10 degrees, the length L (mm) of one rotation in the rotation direction of the intermediate transfer belt B1 varies by about 1 mm. Therefore, as in the present invention, as preparation for the calibration, by determining the length L0 (mm) in the rotation direction of the patch each time, it becomes possible to cope with the variation.

  Further, the background density D0 (−) corresponding to the length of one rotation in the rotation direction of the intermediate transfer belt B1 is associated with each patch number N (−), and no matter where the patch is formed on the intermediate transfer belt B1, It is not necessary to measure the background density D0 (-) corresponding to this.

  When the background density correspondence unit 404 completes associating the background density D0 (−) with each patch number N (−), the calibration unit 401 is notified that the calibration preparation has been completed. . Upon receiving the notification, the calibration unit 401 can execute calibration at any time using the background density D0 (−) for each patch number N (−).

  For example, when a user transmits an image formation instruction corresponding to predetermined image data from a host device such as a personal computer (PC) to the image forming apparatus 1, the printing unit 405 of the image forming apparatus 1 The instruction is received (FIG. 5: S106 YES), and execution of printing is started.

  When the printing unit 405 executes the printing, the printing unit 405 notifies the calibration unit 401 of the fact, and the calibration unit 401 that has received the notification corresponds to the printing in the area of the intermediate transfer belt B1. Forming a calibration patch in a non-image area other than the image area to be measured in units of length L0 (mm) in the rotation direction of the patch, and measuring the density D (−) of the patch as a measurement value; Using the background density D0 (−) associated with the patch number N (−) indicating the position of the patch, the patch density is calculated as a calculated value, and the calibration is executed.

  For example, as shown in FIG. 6B, the printing unit 405 forms a toner image corresponding to the printing image data from the reference position member 600 of the intermediate transfer belt B1 (FIG. 5: S107). Here, when there are a plurality of (for example, three) image data for printing, a toner image corresponding to the image data is formed at a predetermined interval along the rotation direction of the intermediate transfer belt B1. To do. An area where the toner image is formed is an image area. Since a predetermined interval is provided between the toner images, a region corresponding to this interval is a non-image region.

  Here, in the above description, since the patch number N (−) and the background density D0 (−) corresponding to the length of one rotation in the rotation direction of the intermediate transfer belt B1 have already been acquired, the calibration unit 401 In conjunction with the printing means 405, as shown in FIG. 6B, the patch 602 is formed in the non-image area (FIG. 5: S108).

  Then, the calibration unit 401 measures the density D (−) of the formed patch 602 as a measurement value by the two density detection sensors 605 and 606 (FIG. 5: S109), and the patch 602 is formed. From the patch number N (−) in the non-image area, the patch density is calculated as a calculated value using the background density D0 (−) corresponding to the patch 602.

  Here, the patch density (−) as the calculated value is normally calculated by subtracting the background density D0 (−) from the patch density (−) as the measured value. The patch density (−) corresponding to this subtraction value is normally used for calibration.

  The calibration unit 401 performs calibration based on the measured patch density (FIG. 5: S110).

  For example, in the case of calibration for adjusting the toner density according to the magnitude of the developing bias value, the calibration unit 401 determines the developing bias value based on a graph in which the developing bias value varies stepwise with respect to the toner density. Different patches are formed in the non-image area, and the patch density is calculated. Then, the calibration means 401 adjusts the development bias value corresponding to the toner density in the graph so as to become the development bias value corresponding to the calculated patch density (−), and the graph is reproduced again. Configure. Here, each graph exists for each color of yellow (Y), magenta (M), cyan (C), and black (B), and the calibration means 401 patches each graph for each color. , Calculate the patch density, and execute calibration (graph adjustment). Thereby, the calibration is completed.

  Thus, since the calibration unit 401 can execute the calibration even during printing, the intermediate transfer belt B1 is rotated for the calibration so that the intermediate transfer is performed. It is not necessary to form a patch on the belt B1, in other words, the calibration can be executed at any time, so that the time required for calibration can be shortened.

  In the present invention, since calibration can be executed in any region of the intermediate transfer belt B1, the following effects are also obtained.

  That is, as shown in FIG. 7A, an integral multiple (total number S times) of the patch length L0 (mm) corresponds to the length L (mm) of the intermediate transfer belt B1 in the rotational direction. The last patch number N (−) (Sth) in the first turn of the intermediate transfer belt B1 and the first patch number N (−) (first) in the second turn of the intermediate transfer belt B1 (reference position) There is no patch boundary with the patch number corresponding to the member 600, and it is continuous. For this reason, the calibration unit 401 continuously applies the calibration patch 602 from the first rotation to the second rotation of the intermediate transfer belt B1 based on the length L0 (mm) in the rotation direction of the patch. It is possible to continuously form and measure the density of each patch 602 as a measured value.

  Conventionally, as shown in FIG. 7B, the length L1 (mm) in the rotation direction of the patch is a preset value, and the length L (in the rotation direction of the intermediate transfer belt B1). mm), the patch formed at the end of the first turn of the intermediate transfer belt B1 overlaps the patch formed at the beginning of the second turn of the intermediate transfer belt B1. End up. Therefore, in this case, in the conventional image forming apparatus, after waiting for detection of the reference position member 600 of the intermediate transfer belt B1, the calibration patch is formed from the start of the second turn of the intermediate transfer belt B1. Inevitably, useless waiting time will occur.

  In the present invention, as shown in FIG. 7A, the above-described waiting time can be deleted, so that the time required for the calibration can be further shortened.

  As described above, according to the present invention, the measuring unit 402 that measures the length L (mm) of the circumference of the intermediate transfer belt B1 that forms the toner image during printing, and the measured rotation direction of the intermediate transfer belt B1. On the basis of the length L (mm) of one circumference and the total number S (pieces) of patches that can be formed to a preset length of one circumference in the rotation direction of the intermediate transfer belt B1. A calculating unit 403 that calculates a length L0 (mm) in the rotation direction and a patch number N (−) indicating the position of each patch with respect to the length of one rotation in the rotation direction of the intermediate transfer belt B1. . Further, the background density D0 (−) of the intermediate transfer belt B1 is measured, the background density correspondence means 404 for associating the measured background density D0 (−) with each patch number N (−), and the rotation direction of the patch. A patch is formed corresponding to the length L0 (mm), and calibration is performed based on the patch density D (-) of the patch and the background density D0 (-) corresponding to the patch number N (-) of the patch. Calibration means 401 for performing the calibration. This makes it possible to improve both calibration accuracy and reduce time.

  In the embodiment of the present invention, after the calculation unit 402 calculates the length L0 (mm) in the rotation direction of the patch and the patch number N (−), the background density correspondence unit 404 calculates the background density. Although D0 (−) is configured to be associated with patch number N (−), other configurations may be used. For example, while the measurement unit 402 is measuring the length L (mm) of one rotation in the rotation direction of the intermediate transfer belt B1, the background density corresponding unit 404 is configured to apply the background density of the intermediate transfer belt B1. You may comprise so that D0 (-) may be measured. This makes it possible to simultaneously measure the length L0 (mm) in the rotation direction of the patch and the background density D0 (−) of the intermediate transfer belt B1 by the idling rotation of the intermediate transfer belt B1. It is possible to further reduce the time required for the operation.

  In the embodiment of the present invention, the calibration unit 401 is configured to execute the calibration at the execution timing of the printing after the calibration preparation is completed. However, other configurations may be used. Absent. For example. The calibration unit 401 forms a patch corresponding to the length L0 (mm) in the rotation direction of the patch immediately after the calibration preparation is completed, and the patch density D (−) of the patch The calibration may be performed based on the background density D0 (−) corresponding to the patch number N (−) of the patch.

  In the embodiment of the present invention, the calibration unit 401 is configured to execute calibration by forming a patch corresponding to the length L0 (mm) in the rotation direction of the patch in the non-image area. However, other configurations may be used. For example, the background density correspondence unit 404 measures the background density D0 (−) of the non-image area at a predetermined timing, and uses the measured background density D0 (−) as the patch number N ( It may be configured to associate (update) with-) again. Accordingly, since the background density D0 (−) varies depending on the number of printings and the like, the background density correspondence unit 404 appropriately updates the background density D0 (−) using the non-image area. Thus, it is possible to calculate a patch density with high accuracy corresponding to the variation.

  In the present invention, the touch-down development method is assumed. However, any image forming apparatus may be used as long as the image forming apparatus executes calibration using a toner image and a patch. In the touchdown development method, a toner thin layer is formed on the developing sleeve by transferring only toner from a magnetic roller carrying a two-component developer containing toner and carrier, and an electrostatic latent image is formed. In other words, the electrostatic latent image is developed as a toner image by flying toner from the thin toner layer onto the surface of the photoreceptor.

  In the present invention, the intermediate transfer belt is an intermediate transfer member on which a toner image is formed. However, for example, this may be a photosensitive drum or the like.

  In the embodiment of the present invention, the image forming apparatus 1 is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. . In this configuration, the image forming apparatus 1 is caused to read the program, and the image forming apparatus 1 realizes the respective units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is possible to provide a method for storing the steps executed by each means in a hard disk.

  As described above, the image forming apparatus and the calibration method according to the present invention are useful not only for multi-function machines but also for copying machines, printers, and the like, and for image formation capable of achieving both improvement in calibration accuracy and reduction in time. It is effective as an apparatus and a calibration method.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 401 Calibration means 402 Measuring means 403 Calculation means 404 Background density corresponding means 405 Printing means

Claims (4)

An image forming apparatus that performs calibration by forming a calibration patch,
Measuring means for measuring the length of one rotation in the rotation direction of the intermediate transfer member for forming a toner image during printing;
Based on the measured length of the circumference of the intermediate transfer member and the preset total number of patches that can be formed to the length of the circumference of the intermediate transfer member in the direction of rotation. Calculating means for calculating a patch number indicating the position of each patch with respect to the length in the rotation direction of the intermediate transfer member and the length of one round in the rotation direction of the intermediate transfer member;
A background density corresponding means for measuring the background density of the intermediate transfer member and associating the measured background density with each patch number;
Calibration means for forming a patch corresponding to the length of the patch in the rotation direction, and performing calibration based on the patch density of the patch and the background density corresponding to the patch number of the patch. An image forming apparatus. The calibration unit forms the patch in a non-image area other than the image area corresponding to the printing as a unit in the rotation direction of the patch during printing. Then, the density of the patch is measured as a measured value, the patch density is calculated as a calculated value using the background density associated with the patch number indicating the position of the patch, and the calibration is executed. Item 2. The image forming apparatus according to Item 1. The background density correspondence unit measures a background density of a non-image area other than an image area corresponding to the printing among the areas of the intermediate transfer member at the time of printing, and the measured background density The image forming apparatus according to claim 1, wherein the image forming apparatus associates again with the patch number of the image area. A calibration method for an image forming apparatus that performs calibration by forming a calibration patch,
Measuring the length of one round of the rotation direction of the intermediate transfer member that forms a toner image during printing;
Based on the measured length of the circumference of the intermediate transfer member and the preset total number of patches that can be formed to the length of the circumference of the intermediate transfer member in the direction of rotation. Calculating the patch number indicating the position of each patch with respect to the length in the rotation direction of the intermediate transfer member and the length of one rotation in the rotation direction of the intermediate transfer member;
Measuring the background density of the intermediate transfer member, and associating the measured background density with each patch number;
Forming a patch corresponding to the length of the patch in the rotation direction, and performing calibration based on the patch density of the patch and the background density corresponding to the patch number of the patch. Calibration method.

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