JP5506532B2 - Image forming apparatus and method for correcting relative phase shift of image carrier - Google Patents

Description

  The present invention relates to an image forming apparatus that includes a plurality of image carriers that respectively form a plurality of images, and superimposes the plurality of images on a recording medium such as an intermediate transfer member, and a method for correcting a relative phase shift of the image carrier. .

  A plurality of image carriers such as a photoconductor corresponding to each of a plurality of images (for example, toner images) are respectively rotated at a constant peripheral speed, and formed by an image forming process such as an electrophotographic method. Conventionally, an image forming apparatus that superimposes images, a so-called tandem type image forming apparatus is known. For example, when forming a full color image, toner images of different colors (usually, yellow (Y), magenta (M), cyan (C), and black (K) color components) are displayed as a plurality of corresponding images. The toner image is formed on the carrier in synchronization with each other, and each toner image is transferred onto a recording medium such as an intermediate transfer body or a recording material (for example, paper). When the recording medium is an intermediate transfer body, the toner image is further transferred to the recording material. .

  By the way, even if a plurality of images are formed on the plurality of image carriers in synchronization with each other, the images may be shifted when the images of the respective image carriers are superimposed. In order to prevent the occurrence of such image shift, it is important to accurately overlay the images on the image carriers.

  The causes of image misalignment include, for example, the peripheral speed caused by the eccentricity of each image carrier, the eccentricity of a rotation member for driving transmission such as a drive gear that transmits rotational driving from the drive unit to each image carrier, and the like. The relative phase shift (relative phase shift) due to the periodic fluctuation (so-called rotation unevenness) can be exemplified.

  In this regard, Patent Document 1 discloses that a plurality of lines for reference colors are formed at equal time intervals in the transport direction as a pattern for reference colors, and a plurality of lines for detection colors are formed as patterns for detection colors. It is formed so as to be arranged alternately with the reference color line at equal time intervals in the transport direction, and the interval between the reference color line and the corresponding detection color line is detected, and the detected reference color line And a color image forming apparatus that calculates a positional deviation amount of the detected color with respect to the reference color based on the interval of the corresponding detection color line and adjusts the rotational phase of the image carrier based on the calculation result. Yes.

  Japanese Patent Laid-Open No. 2004-228688 also counts the time required for the black phase signal and the non-black phase signal to change respectively by simultaneously starting the timing by the black phase timing means and the non-black phase timing means. Each value of the black phase signal and the non-black phase signal at the start is stored, and the black photosensitive member driving means and the non-black photosensitive member driving means are controlled based on the measured time value and the signal value, and the black photosensitive member and A color image forming apparatus that adjusts the rotational phase difference of a non-black photoconductor within a predetermined allowable range is disclosed.

JP 2006-78850 A JP 2005-181787 A

  However, in the conventional image forming apparatuses described in Patent Documents 1 and 2, at least one of the plurality of image carriers is stopped in a state where the plurality of image carriers are mounted on the apparatus main body. In order to correct the relative phase shift due to the periodic fluctuation of the peripheral speed of the image carrier while controlling the drive by changing at least one rotational speed of the plurality of image carriers. The apparatus configuration such as the control configuration for correcting the phase shift becomes complicated.

  In addition, the conventional image forming apparatus includes motors that individually drive the image carriers. When the motors are individually adjusted, the reference color image carrier (specifically, the black photosensitive member). Relative phase shift between the periodic fluctuation of the peripheral speed of the photosensitive drum and the periodic fluctuation of the peripheral speed of the image bearing members for the detection colors (specifically, the photosensitive drums for yellow, magenta, and cyan). Although each can be corrected to an optimum one, there are the following inconveniences when a plurality of detection color image carriers rotate in conjunction with each other.

  That is, in the conventional image forming apparatus, among the plurality of image carriers that respectively form a plurality of images, the first group image carrier including the first image carrier and the plurality of second images among the remaining image carriers. The second group image carrier including the carrier may be driven independently.

  Specifically, a black image is normally formed independently without forming an image of another color when a monochrome image is formed. In this case, a first image carrier (for example, a black photosensitive drum) corresponding to black and an image forming member (a member including a black developing device) for forming an image on the first image carrier are used. A plurality of second image carriers (for example, yellow, magenta, and cyan photosensitive drums) corresponding to the respective images (yellow, magenta, and cyan images) and images formed on the plurality of second image carriers. And a first driving unit that is different from a second driving unit that drives an image forming member (a member that includes yellow, magenta, and cyan developing devices).

  On the other hand, it is necessary to drive an image other than black (for example, an image of yellow, magenta, and cyan). However, in order to reduce the number of driving components and realize downsizing of the image forming apparatus, they are linked with each other. A plurality of rotating second image carriers (for example, photosensitive drums for yellow, magenta, and cyan) and an image forming member corresponding to the second image carrier are simultaneously driven by a common (one) second driving unit. By doing so, the number of parts can be reduced.

  As described above, in the image forming apparatus configured such that the plurality of second image carriers rotate in conjunction with each other as described above, the eccentricity of the first image carrier and the respective deviations of the plurality of second image carriers. Core, eccentricity of a drive transmission rotating member such as a drive gear for transmitting rotational drive from the first drive unit to the first image carrier, and rotational drive from the second drive unit to the plurality of second image carriers. When a circumferential displacement occurs due to periodic fluctuations in the peripheral speed caused by the eccentricity of each of the drive transmission rotating members such as the drive gears, a plurality of second image carriers (for example, Since the photosensitive drums for yellow, magenta, and cyan) rotate in conjunction with each other, the relative phase shift due to the periodic fluctuation of the peripheral speed cannot be adjusted between the plurality of second image carriers. 1 image carrier (for example, photosensitive drum for black) If, it is impossible to adjust each of the relative phase shift even while the each of the plurality of second image bearing member.

  Accordingly, the present invention is an image forming apparatus that includes a plurality of image carriers that respectively form a plurality of images, and superimposes the plurality of images on a recording medium, and a method for correcting a relative phase shift of the image carrier, An object of the present invention is to provide an image forming apparatus capable of correcting a relative phase shift caused by periodic fluctuations in the peripheral speed of the plurality of image carriers with a simple apparatus configuration and a method for correcting a relative phase shift of the image carriers. .

  In order to solve the above problems, the present invention provides the following image forming apparatus and method for correcting the relative phase shift of the image carrier.

(1) Image forming apparatus An image forming apparatus comprising a plurality of image carriers that respectively form a plurality of images, and superimposing the plurality of images on a recording medium, wherein the plurality of image carriers are arranged at a constant peripheral speed. A drive unit that is rotated by a plurality of image carriers, a pattern forming unit that forms a plurality of patterns respectively corresponding to the plurality of image carriers on the recording medium at each circumferential pitch, and any of the plurality of image carriers The phase shift amount indicating the relative phase shift of the periodic fluctuation of the peripheral speed of the image carrier to be adjusted other than the image carrier to be adjusted with respect to the periodic fluctuation of the peripheral speed of the one image carrier to be adjusted. A measurement unit that measures based on a plurality of patterns, an attachment / detachment detection unit that detects attachment / detachment states of the plurality of image carriers with respect to the apparatus main body, and any one of the image carriers to be adjusted. Image to be corrected As the carrier, the drive unit is controlled based on the measurement result of the measurement unit, and the periodic fluctuation of the peripheral speed of the correction target image carrier with respect to the periodic fluctuation of the peripheral speed of the image carrier to be adjusted is controlled. and a correcting unit for correcting the relative phase shift, the correction unit, an image forming apparatus which is characterized that you start a correction operation based on the detection result by the detachable detection unit.

(2) Method for correcting relative phase shift of image carrier A plurality of image carriers that respectively form a plurality of images, and a relative phase of the image carrier in an image forming apparatus that superimposes the plurality of images on a recording medium A method for correcting misalignment, comprising: a driving step of rotating the plurality of image carriers at a constant peripheral speed by a driving unit; and a plurality of patterns respectively corresponding to the plurality of image carriers in a circumferential direction by a pattern forming unit. A pattern forming step formed on the recording medium for each pitch, and the adjustment target image carrier other than the adjustment target image carrier with respect to the periodic fluctuation of the peripheral speed of any one of the plurality of image carriers. A measurement step of measuring a phase shift amount indicating a relative phase shift of the periodic variation of the peripheral speed of the image carrier to be adjusted by the measurement unit based on the plurality of patterns ; An attachment / detachment detection step for detecting an attachment / detachment state of the plurality of image carriers with respect to the apparatus main body, and the measurement using any one of the image carriers to be adjusted as a correction object image carrier. Based on the measurement result by the unit, the drive unit is controlled to correct a relative phase shift of the periodic fluctuation of the peripheral speed of the correction target image carrier with respect to the periodic fluctuation of the peripheral speed of the adjustment target image carrier. look including a correction step of correcting the parts, the correction step, the correction method of the relative phase shift of the image bearing member, characterized in that to start the correcting operation by the correcting unit based on the detection result by the detachable detection unit .

In the image forming apparatus and the method for correcting the relative phase shift of the image carrier according to the present invention, the periodic fluctuation of the peripheral speed of the image carrier to be adjusted with respect to the periodic fluctuation of the peripheral speed of the image carrier to be adjusted. a phase shift amount indicating the relative phase shift Ru Teisu measured by the measuring unit based on the plurality of patterns. Then, the image carrier to be adjusted is detached from the apparatus main body by an operator such as a user or a service person. At this time, the rotation of the image carrier to be adjusted can be stopped regardless of the drive control of the drive unit. As a result, the measurement result by the measurement unit is automatically or artificially set as any one of the image carrier to be adjusted that is detached from the apparatus main body and in a stopped state as the image carrier to be corrected. The adjustment object image carrier can be rotated based on the above. Accordingly, it is possible to correct the relative phase shift of the periodic fluctuation of the peripheral speed of the correction target image carrier with respect to the periodic fluctuation of the peripheral speed of the adjustment target image carrier, with a simple apparatus configuration.

In addition, in the image forming apparatus according to the present invention, one of the attachment / detachment detection unit for detecting the attachment / detachment state of the plurality of image carriers with respect to the apparatus body and the image carrier to be adjusted is corrected. As the target image carrier, the operation of the drive unit is controlled based on the measurement result by the measurement unit, and the peripheral speed of the correction target image carrier is periodically changed with respect to the periodic variation of the peripheral speed of the adjustment target image carrier. and a correcting unit for correcting the relative phase shift variations, the correction unit, start a correcting operation based on the detection result by the detachable detection unit. In the method for correcting the relative phase shift of the image carrier according to the present invention, an attachment / detachment detecting step for detecting an attachment / detachment state of the plurality of image carriers with respect to the apparatus main body by an attachment / detachment detection unit; and the image carrier to be adjusted The correction to the periodic variation of the peripheral speed of the image carrier to be adjusted by controlling the operation of the drive unit based on the measurement result of the measurement unit using any one of the image carrier as a correction object image carrier. A correction step of correcting a relative phase shift of the periodic fluctuation of the peripheral speed of the target image carrier by a correction unit, and the correction step performs a correction operation by the correction unit based on a detection result by the attachment / detachment detection unit. you start.

In this way, when it is determined that the image carrier to be adjusted is detached from the apparatus main body based on the detection result by the attachment / detachment detection unit, the correction operation by the correction unit can be started. Thereby, the relative phase shift of the periodic fluctuation of the peripheral speed of the correction target image carrier with respect to the periodic fluctuation of the peripheral speed of the adjustment target image carrier can be automatically corrected.

An example in which the image forming apparatus according to the present invention further includes a notification unit that notifies that the image carrier to be adjusted is an image carrier to be detached from the apparatus main body based on a measurement result by the measurement unit. it can. Further, in the method for correcting the relative phase shift of the image carrier according to the present invention, notification that the image carrier to be adjusted is an image carrier to be detached from the apparatus main body based on the measurement result by the measurement unit. An aspect further including a notification step of notifying by the unit can be exemplified.
In the image forming apparatus according to the present invention, the notification unit is an image carrier to be attached to the apparatus main body as the adjustment target image carrier after the correction operation by the correction unit is completed. A mode of notifying that there is an example can be exemplified. In the correction method for the relative phase shift of the image carrier according to the present invention, the notifying step may be configured such that after the correction operation by the correction unit is completed, the correction target image carrier is used as the adjustment target image carrier. A mode in which the notification unit notifies that the image carrier is a target to be attached to the camera can be exemplified.

  In this specific matter, after the correction operation by the correction unit is completed, the correction target image carrier (the correction target image carrier that is the adjustment target image carrier) is used as the adjustment target image carrier to the apparatus main body. Is notified by the notification unit. Then, the operator attaches the correction target image carrier (the correction target image carrier that is the adjustment target image carrier) to the apparatus main body as the adjustment target image carrier. At this time, the correction target image carrier mounted as the adjustment target image carrier can be rotated together with the existing adjustment target image carrier by the drive control of the drive unit. Therefore, when it is determined that the correction target image carrier (the correction target image carrier that is the adjustment target image carrier) is attached to the apparatus main body based on the detection result by the attachment / detachment detection unit. Furthermore, a correction operation by the correction unit can be performed. Thereby, even if the image carrier to be adjusted is a plurality of image carriers to be adjusted, the periodic fluctuations in the peripheral speed of the plurality of image carriers to be adjusted are adjusted. It is possible to sequentially correct the periodic fluctuation of the peripheral speed.

  In the image forming apparatus and the method for correcting the relative phase shift of the image carrier according to the present invention, the image carrier includes at least two image carriers among the plurality of image carriers, and the at least two image carriers rotate in conjunction with each other. A group image carrier, and the drive unit rotates a group of image carriers other than the group image carrier at a peripheral speed, and the group image carrier. A mode provided with the 2nd drive part which rotates a body at the peripheral speed can be illustrated.

  In this particular matter, even if the at least two image carriers rotate in conjunction with each other, the mounted image carrier can rotate independently with respect to the detached image carrier, Relative phase shifts due to periodic fluctuations in the peripheral speed can be corrected between the at least two image carriers.

  In the image forming apparatus according to the present invention, the correction unit corrects a relative phase shift of the group image carrier among the plurality of image carriers, and then relative phase of an image carrier other than the group image carrier. A mode of correcting the deviation can be exemplified. Further, in the correction method for the relative phase shift of the image carrier according to the present invention, the correction step includes correcting the relative phase shift of the group image carrier among the plurality of image carriers by the correction unit, A mode in which the relative phase shift of image carriers other than the group image carriers is corrected by the correction unit can be exemplified.

  In this specific matter, the drive of the image carrier other than the group image carrier and the drive of the image carrier of the group image carrier are separate drives, and therefore, the image carrier other than the group image carrier is attached to the first image carrier. It is not necessary to drive one drive unit, and accordingly, the driving load on the members involved in the first drive unit and the power consumption of the first drive unit can be reduced. The operation of detaching the carrier from the apparatus main body can be omitted.

  In the image forming apparatus and the method for correcting the relative phase shift of the image carrier according to the present invention, in forming an image, black is often a color on which characters are printed. It is preferable that a black image is formed on an image carrier other than the group image carrier and a color image is formed on the group image carrier. That is, among the plurality of image carriers, the group image carrier is for performing color image formation, and image carriers other than the group image carrier are for performing black image formation. It is preferable.

  The image forming apparatus and the method for correcting the relative phase shift of the image carrier according to the present invention may include a display unit that displays characters, and the notification by the notification unit may be a message displayed on the display unit.

  In this specific matter, the notification by the notification unit can be displayed as a text message on the display unit, and thereby the notification by the notification unit can be clearly and reliably transmitted to the worker.

  As described above, according to the present invention, the phase shift amount indicating the relative phase shift of the periodic fluctuation of the peripheral speed of the image carrier to be adjusted with respect to the periodic fluctuation of the peripheral speed of the image carrier to be adjusted. Is measured by the measurement unit based on the plurality of patterns, and the notification unit indicates that the image carrier to be adjusted is an image carrier to be detached from the apparatus main body based on a measurement result by the measurement unit. This makes it possible to correct the relative phase shift caused by the periodic fluctuations in the peripheral speeds of the plurality of image carriers with a simple apparatus configuration.

1 is a side view schematically showing a color image forming apparatus according to an embodiment of the present invention. FIG. 2 is a system configuration diagram schematically showing a drive transmission system of a drive device in the color image forming apparatus shown in FIG. 1, and a gear train for transmitting rotational drive from the first and second drive units to the photosensitive drum, and the first It is a figure which shows a phase sensor, a 2nd phase sensor, a 3rd phase sensor, and a 4th phase sensor. FIG. 2 is a perspective view showing in detail a driving device in the color image forming apparatus shown in FIG. 1. FIG. 2 is a block diagram schematically showing a system configuration in the color image forming apparatus shown in FIG. 1. It is a block diagram which shows the control part shown to FIG. 4A in detail. FIG. 4 is a plan view showing an example in which a black pattern, a cyan pattern, a magenta pattern, and a yellow pattern are formed on an intermediate transfer belt. FIG. 6 is a plan view showing a positional relationship between each pattern formed on both ends of the intermediate transfer belt in the width direction on the intermediate transfer belt and a pattern detection sensor. FIG. 7 is an explanatory diagram for explaining a relative phase shift of rotation unevenness of a black photoconductor drum with respect to rotation unevenness of a cyan photoconductor drum, in which (a) is a black photoconductor with respect to rotation unevenness of a cyan photoconductor drum; FIG. 4B is a diagram illustrating an example of a cyan pattern and a black pattern in a state where there is no relative phase shift of drum rotation unevenness, and FIG. 5B is a diagram illustrating rotation unevenness of a black photosensitive drum with respect to rotation unevenness of a cyan photoconductor drum. FIG. 6 is a diagram illustrating an example of a cyan pattern and a black pattern in a state where there is a relative phase shift. It is a graph which shows a cyan density wave, a magenta density wave, a yellow density wave, and a black density wave. It is a timing chart which shows the detection signal of the 3rd phase sensor, the detection signal of the 4th phase sensor, and the detection signal of the 1st phase sensor with respect to the detection signal of the 2nd phase sensor. FIG. 2 is a plan view showing a first notification screen displayed on a display unit in an operation unit of the color image forming apparatus shown in FIG. 1. FIG. 6 is a plan view showing a second notification screen displayed on the display unit in the operation unit of the color image forming apparatus shown in FIG. 1. 2 is a flowchart illustrating an example of a relative phase shift correction operation process performed by a control unit in the color image forming apparatus illustrated in FIG. 1. FIG. 6 is a state transition diagram showing a correction process for correcting relative rotation of the rotational unevenness of the magenta photosensitive drum, the yellow photosensitive drum, and the black photosensitive drum in this order with respect to the rotational unevenness of the cyan photosensitive drum. FIGS. 9A to 9H are views showing the first correction state to the eighth state, respectively.

  Embodiments according to the present invention will be described below with reference to the drawings. The following embodiments are examples embodying the present invention, and are not of a nature that limits the technical scope of the present invention.

  FIG. 1 is a side view schematically showing a color image forming apparatus D according to an embodiment of the present invention.

  A color image forming apparatus D shown in FIG. 1 is a document reading device B1 that reads an image of a document, and records an image of the document read by the document reading device B1 or an image received from the outside in color or single color on plain paper or the like. The apparatus main body A which records and forms on a material is provided.

  In the document reading device B1, when the document is set on the document setting tray 41, the pickup roller 44 is pressed against the surface of the document and rotated, the document is pulled out from the tray 41, and passes between the suction roller 45 and the separation pad 46. After being separated one by one, it is transported to the transport path 47.

  In the conveyance path 47, the leading edge of the document contacts the registration roller 49 and is aligned in parallel with the registration roller 49, and then the document is conveyed by the registration roller 49 and passes between the document guide 51 and the reading glass 52. To do. At this time, the light from the light source of the first scanning unit 53 is irradiated on the surface of the document through the reading glass 52, and the reflected light is incident on the first scanning unit 53 through the reading glass 52. Reflected by the mirrors of the first and second scanning units 53 and 54 and guided to the imaging lens 55, an image on the surface of the document is formed on a CCD (Charge Coupled Device) 56 by the imaging lens 55. The CCD 56 reads an image on the surface of the document and outputs image data indicating the image. Further, the document is transported by the transport roller 57 and discharged to the document discharge tray 59 via the discharge roller 58.

  The document reading device B1 can read a document placed on the document table glass 61. The registration roller 49, the document guide 51, the document discharge tray 59, and the like and the members above them form an integrated cover body, and an axis line along the sub-scanning direction on the back side of the document reading apparatus B1. It is pivotally supported so that it can be opened and closed. When the upper cover body is opened, the document table glass 61 is opened, and a document can be placed on the document table glass 61. The document placed on the document table glass 61 is held by the cover body when the cover body is closed. When a document reading instruction is issued, the surface of the document on the document table glass 61 is exposed by the first scanning unit 53 while the first and second scanning units 53 and 54 are moved in the sub-scanning direction. The reflected light from the document surface is guided to the imaging lens 55 by the first and second scanning units 53 and 54, and is imaged on the CCD 56 by the imaging lens 55, where the document image is read. At this time, the first and second scanning units 53 and 54 are moved while maintaining a predetermined speed relationship with each other, and reflection of the document surface → the first and second scanning units 53 and 54 → the imaging lens 55 → the CCD 56 is performed. The positional relationship between the first and second scanning units 53 and 54 is always maintained so that the length of the optical path of the light does not change, and thereby the focus of the image on the original surface on the CCD 56 is always accurately maintained.

  The entire original image read in this way is sent and received as image data to the apparatus main body A of the color image forming apparatus D, and the image is recorded on the recording material in the apparatus main body A.

  On the other hand, the apparatus main body A of the color image forming apparatus D includes a photoreceptor unit 20 (20a, 20b, 20c, 20d). The photosensitive unit 20 (20a, 20b, 20c, 20d) has a photosensitive drum 3 (3a, 3b, 3c, 3d) that functions as an image carrier, and is detachable from the apparatus main body A. Has been. The apparatus main body A includes an exposure device 1, a developing device 2 (2a, 2b, 2c, 2d), a photosensitive drum 3 (3a, 3b, 3c, 3d) arranged in parallel along the recording material conveyance direction, and a charger. 5 (5a, 5b, 5c, 5d), cleaner device 4 (4a, 4b, 4c, 4d), intermediate transfer belt device 8 including intermediate transfer roller 6 (6a, 6b, 6c, 6d) acting as a transfer unit, A fixing device 12, a transport device 18, a paper feed tray 10 that functions as a paper feed unit, and a paper discharge tray 15 that functions as a paper discharge unit are provided.

  The image data handled in the apparatus main body A of the color image forming apparatus D is one corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color ( For example, it corresponds to a monochrome image using black). Accordingly, the developing device 2 (2a, 2b, 2c, 2d), the photosensitive unit 20 (20a, 20b, 20c, 20d) having the photosensitive drum 3 (3a, 3b, 3c, 3d), and the charger 5 (5a, 5d). 5b, 5c, 5d), four cleaner devices 4 (4a, 4b, 4c, 4d) and four intermediate transfer rollers 6 (6a, 6b, 6c, 6d) so as to form four types of images corresponding to the respective colors. Among the end codes a to d, four image stations are configured by associating the code a with black, the code b with cyan, the code c with magenta, and the code d with yellow. Yes. Hereinafter, the description will be made with the suffixes a to d omitted.

  The photoconductor drum 3 is disposed at substantially the center in the vertical direction of the apparatus main body A. The charger 5 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential, and a charger type charger is used in addition to a contact type roller type or brush type charger. .

  Here, the exposure apparatus 1 is a laser scanning unit (LSU) provided with laser light sources 42a to 42d (not shown in FIG. 1, see FIG. 4A described later) and a scanning optical system 43, and is a charged photosensitive drum. The surface of 3 is exposed according to the image data, and an electrostatic latent image according to the image data is formed on the surface.

  The developing device 2 develops the electrostatic latent image formed on the photosensitive drum 3 with (K, C, M, Y) toner. The cleaner device 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  In addition to the intermediate transfer roller 6, the intermediate transfer belt device 8 disposed above the photosensitive drum 3 includes an intermediate transfer belt (an example of an intermediate transfer member) 7 that acts as a recording medium, an intermediate transfer belt driving roller 21, A driven roller 22, a tension roller 23, and an intermediate transfer belt cleaning device 9 are provided.

  Roller members such as the intermediate transfer belt drive roller 21, the intermediate transfer roller 6, the driven roller 22, and the tension roller 23 stretch and support the intermediate transfer belt 7, and the intermediate transfer belt 7 is moved in a predetermined moving direction (arrow in the figure). Move around in the C direction).

  The intermediate transfer roller 6 is rotatably supported inside the intermediate transfer belt 7 and is pressed against the photosensitive drum 3 via the intermediate transfer belt 7, and transfers the toner image on the photosensitive drum 3 to the intermediate transfer belt 7. A transfer bias is applied.

  The intermediate transfer belt 7 is provided so as to be in contact with each photoconductive drum 3, and a color toner image (each color is transferred by sequentially superimposing and transferring the toner image on the surface of each photoconductive drum 3 onto the intermediate transfer belt 7. Toner image). Here, the transfer belt 7 is formed in an endless belt shape using a film having a thickness of about 100 μm to 150 μm.

  The transfer of the toner image from the photosensitive drum 3 to the intermediate transfer belt 7 is performed by the intermediate transfer roller 6 that is in pressure contact with the inner side (back surface) of the intermediate transfer belt 7. A high voltage transfer bias (for example, a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 6 in order to transfer the toner image. Here, the intermediate transfer roller 6 is a roller based on 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 material.

  The apparatus main body A of the color image forming apparatus D further includes a secondary transfer apparatus 11 including a transfer roller 11a that functions as a transfer unit. The transfer roller 11a is in contact with the opposite side (outside) of the intermediate transfer belt 7 from the intermediate transfer belt drive roller 21.

  As described above, the toner images on the surface of the respective photosensitive drums 3 are stacked on the intermediate transfer belt 7 and become a color toner image indicated by the image data. The stacked toner images of the respective colors are transported together with the intermediate transfer belt 7 and transferred onto the recording material by the secondary transfer device 11.

  The intermediate transfer belt 7 and the transfer roller 11a of the secondary transfer device 11 are pressed against each other to form a nip region. Further, a voltage (for example, a polarity (+) opposite to the toner charging polarity (−)) is applied to the transfer roller 11a of the secondary transfer device 11 to transfer the toner image of each color on the intermediate transfer belt 7 onto the recording material. Is applied). Further, in order to constantly obtain the nip region, either the transfer roller 11a of the secondary transfer device 11 or the intermediate transfer belt drive roller 21 is made of a hard material (metal or the like), and the other is a soft material such as an elastic roller. (Elastic rubber roller, foaming resin roller, etc.).

  In addition, the toner image on the intermediate transfer belt 7 may not be completely transferred onto the recording material by the secondary transfer device 11, and the toner may remain on the intermediate transfer belt 7. Causes color mixing. Therefore, the residual toner is removed and collected by the intermediate transfer belt cleaning device 9. The intermediate transfer belt cleaning device 9 includes, for example, a cleaning blade that comes into contact with the intermediate transfer belt 7 as a cleaning member, and residual toner can be removed and collected by the cleaning blade. The driven roller 22 supports the intermediate transfer belt 7 from the inner side (back side), and the cleaning blade is in contact with the intermediate transfer belt 7 so as to press it toward the driven roller 22 from the outer side.

  The paper feed tray 10 is a tray for storing recording materials, and is provided below the image forming unit of the apparatus main body A. The paper discharge tray 15 provided on the upper side of the image forming unit is a tray for placing printed recording materials face down.

  Further, the apparatus main body A is provided with a conveying device 18 for sending the recording material of the paper feed tray 10 to the paper discharge tray 15 via the secondary transfer device 11 and the fixing device 12. The transport device 18 has an S-shaped transport path S, and along this transport path S, a pickup roller 16, each transport roller 13, a pre-registration roller 19, a registration roller 14, a fixing device 12, and a paper discharge. A conveying member such as a roller 17 is arranged.

  The pickup roller 16 is a pull-in roller that is provided at the downstream end of the paper feed tray 10 in the recording material conveyance direction and supplies the recording material from the paper feed tray 10 to the conveyance path S one by one. Each conveyance roller 13 and the pre-registration roller 19 are small rollers for promoting and assisting the conveyance of the recording material. Each transport roller 13 is provided at a plurality of locations along the transport path S. The pre-registration roller 19 is provided in the immediate vicinity upstream of the registration roller 14 in the conveyance direction, and conveys the recording material to the registration roller 14.

  The registration roller 14 temporarily stops the recording material conveyed by the pre-registration roller 19, aligns the leading end of the recording material, and is on the intermediate transfer belt 7 in the nip region between the intermediate transfer belt 7 and the secondary transfer device 11. The recording material is conveyed with good timing in accordance with the rotation of the photosensitive drum 3 and the intermediate transfer belt 7 so that the color toner image is transferred onto the recording material.

  For example, the registration roller 14 performs recording so that the front end of the color toner image on the intermediate transfer belt 7 matches the front end of the image forming range on the recording material in the nip region between the intermediate transfer belt 7 and the secondary transfer device 11. Transport material.

  The fixing device 12 includes a heat roller 31 and a pressure roller 32. The heat roller 31 and the pressure roller 32 sandwich and transport the recording material.

  The temperature of the heat roller 31 is controlled so as to reach a predetermined fixing temperature, and the recording material is thermocompression-bonded together with the pressure roller 32 to melt, mix, and press the toner image transferred to the recording material. On the other hand, it has a function of heat fixing.

  The recording material after the fixing of the toner images of the respective colors is discharged onto the paper discharge tray 15 by the paper discharge roller 17.

  It is also possible to form a monochrome image using at least one of the four image forming stations and transfer the monochrome image to the intermediate transfer belt 7 of the intermediate transfer belt device 8. Similarly to the color image, this monochrome image is also transferred from the intermediate transfer belt 7 to the recording material and fixed on the recording material.

  Further, in the case of forming not only the front (front) surface of the recording material but also double-sided image formation, the recording material is fixed on the surface of the recording material by the fixing device 12, and then the recording material is discharged on the material conveyance path S. In the middle of conveying by the above, the paper discharge roller 17 is stopped and then reversely rotated, the recording material is passed through the front / back reversing path Sr, the recording material is reversed, and the recording material is guided to the registration roller 14 again. Similarly to the front surface of the recording material, an image is recorded and fixed on the back surface of the recording material, and the recording material is discharged to the paper discharge tray 15.

[Configuration of pattern detection sensor]
The color image forming apparatus D further includes a pattern detection sensor 34. In the following description, the reference numeral 3 for the photosensitive drum, the photosensitive unit 20, the reference numeral 2 for the developing device, and the trailing reference numeral of the transfer unit 6 are not omitted, and the photosensitive drums 3 a, 3 b, 3 c, 3 d, Reference numerals 20a, 20b, 20c, 20d, developing devices (here, developing units) 2a, 2b, 2c, 2d, and transfer portions (here, intermediate transfer rollers) 6a, 6b, 6c, 6d are used.

  The pattern detection sensor 34 is arranged downstream of the photosensitive drum (here, the black photosensitive drum 3a) in the moving direction C of the endless intermediate transfer belt 7. Specifically, the pattern detection sensor 34 is disposed so as to face the surface of the intermediate transfer belt 7.

  Here, the pattern detection sensor 34 is a reflective optical sensor (photo interrupter) having a light emitting unit 341 and a light receiving unit 342. As will be described later, the pattern detection sensor 34 detects each pattern Pa to Pd (see FIGS. 5 and 6 described later) formed on the intermediate transfer belt 7. Specifically, the pattern detection sensor 34 detects incident light reflected from the light emitting unit 341 on the surface of the intermediate transfer belt 7 or each of the patterns Pa to Pd by the light receiving unit 342.

[Configuration of drive unit]
The color image forming apparatus D includes a driving device 100 (not shown in FIG. 1 and described later in FIG. 2 and FIG. 2) that drives the photosensitive drums 3a, 3b, 3c, and 3d provided in the photosensitive units 20a, 20b, 20c, and 20d. (See FIG. 3).

  FIG. 2 is a system configuration diagram schematically showing a drive transmission system of a drive device (an example of a drive unit) 100 in the color image forming apparatus D shown in FIG. 1, from the first and second drive units 110 and 120. It is a figure which shows the gear train which transmits the rotational drive to the photosensitive drums 3a, 3b, 3c, 3d, and the 1st phase sensor 170a, the 2nd phase sensor 170b, the 3rd phase sensor 170c, and the 4th phase sensor 170d. FIG. 3 is a perspective view showing in detail the driving device 100 in the color image forming apparatus D shown in FIG.

  The color image forming apparatus D includes a first photosensitive group including a first photosensitive drum (here, the black photosensitive drum 3a) among the photosensitive drums 3a, 3b, 3c, and 3d for black, cyan, magenta, and yellow. And a plurality of second photosensitive drums (here, cyan photosensitive drum 3b, magenta photosensitive drum 3c, yellow photosensitive drum 3d) and second photosensitive drums 3b, 3c, 3d. Are provided with a second group photoconductor 30b (an example of a group image carrier) that rotates in conjunction with each other. Here, the first group photoreceptor 30a is for performing monochrome image formation (monochrome printing), and the second group photoreceptor 30b cooperates with the first group photoreceptor 30a to form a full color image. Is for doing. The photosensitive drums 3a, 3b, 3c, and 3d have the same diameter.

  The driving device 100 includes a first driving unit 110, a second driving unit 120, a first rotating member (here, a first driving transmission rotating member) 150, and a second rotating member (here, a second driving transmission rotation). Member) 160 and first to fourth phase sensors 170a to 170d.

  The first drive unit 110 is for driving the first group photoconductor 30a. The second drive unit 120 is for driving the second group photoconductor 30b. Here, the first driving unit 110 and the second driving unit 120 are stepping motors.

  The first driving transmission rotating member 150 transmits rotational driving from the first driving unit 110 to the first group photoconductor 30a, and here, the first shaft gear 111, the first intermediate gear 112, It comprises a black photosensitive member driving gear 130. The second drive transmission rotation member 160 transmits the rotation drive from the second drive unit 120 to the second group photoconductor 30b. Here, the second shaft gear 121 and the second to fourth intermediate gears. 122 to 124, and color (for cyan, magenta, and yellow) photosensitive member driving gears 140 (140b to 140d). Note that these gears are parallel to each other in the direction of the rotation axis.

  Specifically, the black photoconductor drive gear 130 is coaxially connected to the rotation shaft of the black photoconductor drum 3 a and meshes with the first intermediate gear 112. A first shaft gear 111 provided on the rotation shaft of the first drive unit 110 meshes with the first intermediate gear 112. As a result, when the first driving unit 110 is driven to rotate, the black shaft connected to the black photosensitive member driving gear 130 via the first shaft gear 111, the first intermediate gear 112, and the black photosensitive member driving gear 130. The photosensitive drum 3a can be rotated.

  The cyan photoconductor drive gear 140 b is coaxially connected to the rotation shaft of the cyan photoconductor drum 3 b and meshes with the third intermediate gear 123. The magenta photoconductor drive gear 140c is coaxially connected to the rotation shaft of the magenta photoconductor drum 3c, and meshes with the second intermediate gear 122, the third intermediate gear 123, and the fourth intermediate gear 124. The yellow photoconductor drive gear 140 d is coaxially connected to the rotation shaft of the yellow photoconductor drum 3 d and meshes with the fourth intermediate gear 124. A second shaft gear 121 provided on the rotation shaft of the second drive unit 120 meshes with the second intermediate gear 122. As a result, the second driving unit 120 is driven to rotate, whereby the magenta connected to the magenta photosensitive member driving gear 140c via the second shaft gear 121, the second intermediate gear 122, and the magenta photosensitive member driving gear 140c. The cyan photosensitive drum 3b connected to the cyan photosensitive drum driving gear 140b is connected to the cyan photosensitive drum 3c via the magenta photosensitive drum driving gear 140c, the third intermediate gear 123, and the cyan photosensitive drum driving gear 140b. Further, the yellow photosensitive drum 3d connected to the yellow photosensitive drum driving gear 140d can be rotated via the magenta photosensitive drum driving gear 140c, the fourth intermediate gear 124, and the yellow photosensitive drum driving gear 140d. it can.

  As a result, the second driving unit 120 of each of the color photosensitive drums 3b, 3c, and 3b can be made common. The photosensitive drums 3b, 3c, and 3d for cyan, magenta, and yellow are rotated in conjunction with each other by the common second driving unit 120. Thus, the first driving unit 110 can rotate the photosensitive drum 3a independently during monochrome printing.

  Photosensitive drum side gears 31a, 31b, 31c, and 31d (see FIG. 3) that mesh with the photosensitive member driving gears 130, 140b, 140c, and 140d are provided on the rotation shafts of the photosensitive drums 3a, 3b, 3c, and 3d, respectively. When the photoconductor units 20a, 20b, 20c, and 20d are attached to the apparatus main body A, the photoconductor drive gears 130, 140b, 140c, and 140d and the photoconductor side gears 31a, 31b, 31c, and 31d are engaged with each other. It is like that.

  The first drive unit 110 also drives the black development unit 2a, and the second drive unit 120 also drives the cyan development unit 2b, the magenta development unit 2c, and the yellow development unit 2d. It is like that.

[Configuration of phase sensor]
Here, each of the first to fourth phase sensors 170 a to 170 d is a transmissive optical sensor (photo interrupter) having a light emitting unit 171 and a light receiving unit 172.

  The first to fourth phase sensors 170a to 170d are respectively protrusions or cutouts (in this case, along the circumferential direction of the drive gears 130 and 140b to 140d) that rotate by rotation of the photosensitive drums 3a to 3d. Cutout portions 131a and 141a) in which the formed ring-shaped rib portions 131 and 141 are cut out are detected.

  Specifically, the first to fourth phase sensors 170a to 170d are configured such that incident light incident on the light receiving portion 172 from the light emitting portion 171 is a protrusion or notch portion (here, the rotation portion of the driving gears 130 and 140b to 140d). The light receiving unit 172 detects the presence or absence of incident light by blocking or passing through the protrusions or notches (here, the notches 131a and 141a) by the circular movement of the notches 131a and 141a). Yes.

  The first to fourth phase sensors 170a to 170d may be reflective optical sensors.

[Control system configuration]
The color image forming apparatus D further includes a control unit 300 that controls the entire apparatus.

  4A is a block diagram schematically showing a system configuration in the color image forming apparatus D shown in FIG.

  The control unit 300 controls the driving load of the control device 100 shown in FIG. 4A. The drive device 100 further includes a drive control circuit 200 that acts as a drive control unit, a first drive unit control circuit 210, a second drive unit control circuit 220, and a belt drive unit 28.

  As described above, the first drive unit 110 is a motor that drives the black photoconductor 3a and the black development unit 2a of the first group photoconductor 30a. The second drive unit 120 is a motor that drives the color photoconductors 3b, 3b, 3d and the color developing units 2b, 2c, 2d of the second group photoconductor 30b.

  The drive control circuit 200 controls the operation of the first drive unit 110 and the second drive unit 120 based on an instruction signal from the control unit 300.

  The first drive unit control circuit 210 is connected between the drive control circuit 200 and the first drive unit 110. The second drive unit control circuit 220 is connected between the drive control circuit 200 and the second drive unit 120.

  The drive control circuit 200 gives commands to start and stop the first drive unit 110 to the first drive unit control circuit 210. The first drive unit control circuit 210 is a circuit that controls the start, stop, and drive speed of the first drive unit 110 under the instruction of the drive control circuit 200. Here, the target speed commanded from the drive control circuit 200 is used. And a servo control circuit for controlling the drive speed of the first drive unit 110 to coincide with each other. Then, the drive control circuit 200 instructs the first drive unit control circuit 210 to drive the first drive unit 110 at a predetermined process speed (image formation drive speed) during image formation. Yes.

  In addition, the drive control circuit 200 gives commands to start and stop the second drive unit 120 to the second drive unit control circuit 220. The second drive unit control circuit 220 is a circuit that controls the start, stop, and drive speed of the second drive unit 120 under the instruction of the drive control circuit 200. Here, the target speed commanded by the drive control circuit 200 is used. And a servo control circuit for controlling the driving speed of the second driving unit 120 to coincide with each other. The drive control circuit 200 instructs the second drive unit control circuit 220 to drive the second drive unit 120 at the process speed during image formation.

  The first drive unit 110 is controlled to operate under the instruction of the drive control circuit 200 and rotationally drives the black photosensitive drum 3a at a constant peripheral speed V. The second drive unit 120 is controlled under the instruction of the drive control circuit 200 to rotate in conjunction with each other in the second group photoconductor 30b, the cyan photoconductor drum 3b, the magenta photoconductor drum 3c, and the yellow photoconductor drum 30c. The photosensitive drum 3d is rotationally driven at a peripheral speed V.

  The belt drive unit 28 is a drive motor that drives the intermediate transfer belt drive roller 21. The belt drive unit 28 rotationally drives the intermediate transfer belt 7 via the intermediate transfer belt drive roller 32. The belt drive unit 28 is controlled to operate under the instruction of the drive control circuit 200 so as to move the intermediate transfer belt 7 around at a peripheral speed V.

  In the drive control circuit 200, a first phase sensor 170a, a second phase sensor 170b, a third phase sensor 170c, and a fourth phase sensor 170d are connected to an input system.

  The first phase sensor 170a, the second phase sensor 170b, the third phase sensor 170c, and the fourth phase sensor 170d indicate the rotation timings of the black photoconductor drum 3a, the cyan photoconductor 3b, the magenta photoconductor 3c, and the yellow photoconductor 3d. Detect each.

[Configuration of detachable sensor]
The color image forming apparatus D further includes a black attachment / detachment sensor 35a, a cyan attachment / detachment sensor 35b, a magenta attachment / detachment sensor 35c, and a yellow attachment / detachment sensor 35d.

   The black attachment / detachment sensor 35a detects whether or not the apparatus body A is mounted with the black photosensitive unit 20a, that is, the black photosensitive drum 3a). The cyan attachment / detachment sensor 35a detects whether or not a cyan photosensitive unit 20b, that is, a cyan photosensitive drum 3b) is attached to the apparatus main body A. The magenta attachment / detachment sensor 35c detects whether or not the magenta photosensitive unit 20c, that is, the magenta photosensitive drum 3c) is attached to the apparatus main body A. The yellow attachment / detachment sensor 35d detects whether or not the yellow photoconductor unit 20d, that is, the yellow photoconductor drum 3d) is attached to the apparatus main body A.

  The attachment / detachment sensors 35a to 35d output attachment signals when the respective photoreceptor units 20a to 20d are attached to the apparatus main body A, while they are detached when the respective photoreceptor units 20a to 20d are detached from the apparatus main body A. Any device can be used as long as it can output a signal. As each of the attachment / detachment sensors 35a to 35d, for example, a micro switch that is turned on (or turned off) when each of the photoconductor units 20a to 20d is mounted and turned off (or turned on) when the photoconductor units 20a to 20d are detached, An optical sensor (a transmissive optical sensor or a reflective optical sensor) that shields (or receives light) when the body units 20a to 20d are mounted and detects (or does not detect) light when the photoreceptor units 20a to 20d are detached is used. An optical switch can be mentioned.

  In the control unit 300, the attachment / detachment sensors 35a to 35d are connected to an input system. Then, the controller 300 detects the attachment / detachment state of each of the photoconductor units 20a to 20d detected by the attachment / detachment sensors 35a to 35d using the attachment / detachment detection unit 305.

[About the control unit]
The control unit 300 is also a component of the color image forming apparatus D and controls the operation of each unit not shown.

  In the control unit 300, the image input unit 62 and the pattern detection sensor 34 are connected to the input system, and the LSU 1 is connected to the output system.

  The image input unit 62 acquires image data of an image to be output from the outside. A source for providing image data is a device connected to the color image forming apparatus D via a communication line. An example of this device is a host such as a personal computer. Another example is an image scanner. The acquired image data is stored in a RAM of storage means 320 (see FIG. 4B) described later for printing processing. Information indicating the attribute is given to the image data acquired from the image input unit 62. The assigned attributes include the vertical and horizontal sizes of each image, the type of monochrome image and color image, and the like.

  The LSU 1 includes a black laser diode 42a, a cyan laser diode 42b, a magenta laser diode 42c, and a yellow laser diode 42d.

  The LSU 1 receives a signal (pixel signal) based on image data stored in an image memory area in the RAM of the storage unit 320 from an image processing unit (not shown). The image processing unit processes the image data and provides a modulation signal corresponding to each pixel of the image to be output to the LSU 1.

  Note that a modulation signal is provided for each color component of black, cyan, magenta, and yellow. The black, cyan, magenta, and yellow modulation signals are used to modulate the light emission of the laser diodes 42a, 42b, 42c, and 42d in the LSU 1, respectively.

  When forming electrostatic latent images on the photosensitive drums 3a to 3d for black, cyan, magenta, and yellow, the control unit 300 includes a black laser diode 42a, a cyan laser diode 42b that is a color laser diode, The magenta laser diode 42c and the yellow laser diode 42d are each caused to emit light, and the uniformly charged black, cyan, magenta, and yellow photosensitive drums 3a to 3d are respectively controlled to be exposed.

  In addition, the control unit 300 obtains a deviation by comparing the detection timing of each pattern Pa to Pd (see FIGS. 5 and 6) read by the pattern detection sensor 34 with a normal timing. The timing deviation can be converted into a position deviation by using the peripheral speed V of the intermediate transfer belt 7.

  FIG. 4B is a block diagram showing in detail the control unit 300 shown in FIG. 4A. As shown in FIG. 4B, the control unit 300 includes a processing unit 310 including a microcomputer such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a data rewritable nonvolatile memory. And storage means 320 including a storage device.

  The control unit 300 controls the operation of various components by causing the processing unit 310 to load a control program stored in advance in the ROM of the storage unit 320 onto the RAM of the storage unit 320 and execute it. . The RAM of the storage unit 320 provides the control unit 300 with a work area for work and an area as an image memory for storing image data.

  Specifically, the control unit 300 stores the acquired image data in the RAM in association with the assigned attribute. The image data is stored in the RAM in units of jobs, and further stored in units of pages when one job consists of a plurality of pages. When the image data is input from an external host in the page description language format, the control unit 300 expands the input image data and stores it in the image memory area. The ROM of the storage unit 320 stores a program that defines the processing procedure executed by the control unit 300.

  The storage unit 320 stores various data and arithmetic expressions used by the pattern forming unit 301, the pattern detection unit 302, the calculation unit 303, the notification unit 304, the attachment / detachment detection unit 305, and the correction unit 306, which will be described later.

[Correction of relative phase shift]
By the way, periodic fluctuations in the peripheral speed due to eccentricity of a plurality of photosensitive drums, eccentricity of a rotation member for driving transmission such as a driving gear that transmits rotational driving from the driving unit to the plurality of photosensitive drums (hereinafter, referred to as a rotational speed). In a conventional color image forming apparatus, at least one of the plurality of photosensitive drums is stopped in a state where the plurality of photosensitive drums are mounted on the apparatus main body. Or changing the rotational speed of at least one of the plurality of photosensitive drums to correct relative phase shift due to periodic fluctuations in the peripheral speed of the photosensitive drum while controlling the drive. Is complicated.

  In the color image forming apparatus, the cyan photoconductor drum, the magenta photoconductor drum, and the yellow photoconductor drum are configured to rotate in conjunction with each other. Eccentricity of the photosensitive drum for magenta, the photosensitive drum for magenta and the photosensitive drum for yellow, and the eccentricity of the rotation member for driving transmission such as a driving gear for transmitting rotational driving from the first driving unit to the photosensitive drum for black. Rotation caused by the eccentricity of each of the rotation members for driving transmission such as a driving gear for transmitting the rotational driving from the core and the second driving unit to the photosensitive drum for cyan, the photosensitive drum for magenta and the photosensitive drum for yellow When a circumferential position shift due to unevenness occurs, the cyan photosensitive drum, the magenta photosensitive drum, and the yellow photosensitive drum in the second group photosensitive member are detected. Are rotated in conjunction with each other, so that relative phase shift due to rotation unevenness cannot be adjusted between the cyan, magenta, and yellow photosensitive drums, and the black photosensitive drum, cyan, magenta, and yellow The relative phase shift due to rotation unevenness cannot be adjusted between each photosensitive drum.

  For this reason, the color image forming apparatus D according to the present embodiment has the following relative phase shift adjustment mode.

  That is, the control unit 300 is configured to function as a pattern forming unit 301, a pattern detection unit 302, a calculation unit 303, and a notification unit 304. The pattern detection unit 302 and the calculation unit 303 constitute a measurement unit 307.

  The execution of the relative phase shift adjustment mode is performed by, for example, a setting screen such as a service simulation screen displayed on the display unit 117 capable of displaying characters in the image forming apparatus D (see FIGS. 10 and 11 to be described later) This is started by a selection operation on the mode key 118 provided in the operation unit 115 (see FIGS. 10 and 11) in D. The user may perform a relative phase shift adjustment mode by performing a user simulation or a mode key selection operation to correct the relative phase shift.

[Pattern forming part]
5 shows black patterns Pa (Pa1, Pa2, Pa3 in the illustrated example), cyan patterns Pb (Pb1, Pb2, Pb3 in the illustrated example), magenta patterns Pc (Pc1, in the illustrated example) on the intermediate transfer belt 7. FIG. 5 is a plan view showing an example in which Pc2, Pc3) and a yellow pattern Pd (Pd1, Pd2, Pd3 in the illustrated example) are formed.

  In the present embodiment, the pattern forming unit 301 forms a black pattern Pa, which is a black image, and a cyan pattern Pb, a magenta pattern Pc, and a yellow pattern Pd, which are color images.

  That is, the pattern forming unit 301 applies the black pattern Pa formed on the black photosensitive drum 3a to the intermediate transfer belt 7 (the recording medium) at every predetermined constant pitch in the circumferential direction (here, the rotation angle θp = 120 °). One example) formed above.

  The pattern forming unit 301 also uses the cyan pattern Pb, the magenta pattern Pc, and the yellow pattern Pd formed on the cyan, magenta, and yellow photosensitive drums 3b to 3d, respectively, as the black pattern Pa. It is formed on the intermediate transfer belt 7 for each pitch (here rotation angle θp = 120 °).

  Specifically, the pattern forming unit 301 forms electrostatic latent images corresponding to the respective patterns Pa to Pd with the LSU 1 on the photosensitive drums 3a to 3d for black, cyan, magenta, and yellow. The latent images are developed into toner images by developing devices (here, developing units) 2a to 2d, and the developed toner images are formed as patterns Pa to Pd at intermediate transfer belts 6a to 6d as transfer portions (here, intermediate transfer rollers). 7 is electrostatically transferred.

  Specifically, the pattern forming unit 301 acquires pattern data of each pattern Pa to Pd stored in advance in the storage unit 320 when forming each pattern Pa to Pd. The pattern forming unit 301 prepares the patterns Pa to Pd by expanding the acquired pattern data in the image memory area. Thereafter, the pattern forming unit 301 transfers the data of the developed patterns Pa to Pd to the LSU 1.

  In the LSU 1, the laser diodes 42a to 42d that have received the data form electrostatic latent images corresponding to the patterns Pa to Pd on the photosensitive drums 3a to 3d, respectively.

  The developing units 2a to 2d develop the electrostatic latent image formed by the LSU 1 to form toner images of the patterns Pa to Pd. The toner images of the patterns Pa to Pd are transferred onto the intermediate transfer belt 7 by the intermediate transfer rollers 6a to 6d, respectively. Thus, the black pattern Pa, the cyan pattern Pb, the magenta pattern Pc, and the yellow pattern Pd are formed on the intermediate transfer belt 7.

  The patterns Pa to Pd are formed on the intermediate transfer belt 7 in a straight line extending in the width direction (main scanning direction) E of the intermediate transfer belt 7 and aligned in the movement direction C. In the present embodiment, the patterns of different colors are formed at different positions in the moving direction (sub-scanning direction) C of the intermediate transfer belt 7, and the interval between the patterns (distance h, for example, about 3 mm, FIG. Open).

  From the downstream side to the upstream side in the moving direction C of the intermediate transfer belt 7, the patterns are in the same order. Here, the cyan patterns Pb1, Pb2, Pb3, the black patterns Pa1, Pa2, Pa3, the magenta. The patterns Pc1, Pc2, and Pc3 for yellow and the patterns Pd1, Pd2, and Pd3 for yellow are formed in this order. Each pattern Pa to Pd may be detected at a plurality of locations in the width direction E of the intermediate transfer belt 7. For example, each of the patterns Pa to Pd may be formed at one end in the width direction E of the intermediate transfer belt 7 or may be formed at both ends.

  FIG. 6 shows patterns Pa to Pd formed on both ends in the width direction E of the intermediate transfer belt 7 on the intermediate transfer belt 7 and pattern detection sensors 34 (first and second pattern detection sensors 34a and 34b in the illustrated example). FIG.

  The pattern detection sensors 34 are provided corresponding to the patterns Pa to Pd formed at different positions in the width direction (main scanning direction) E of the intermediate transfer belt 7. In the example shown in FIG. 6, the pattern detection sensor 34 includes first and second pattern detection sensors 34 a and 34 b. A plurality of patterns Pa to Pd in the width direction E on the intermediate transfer belt 7 are arranged so as to be opposed to positions where the patterns Pa to Pd are to be formed. When the patterns Pa to Pd are detected at a plurality of locations in the width direction E of the intermediate transfer belt 7, the value can be an average value of the values detected at the plurality of locations.

  Each of the patterns Pa to Pd formed on the intermediate transfer belt 7 includes a pitch variation component due to uneven rotation of each of the photosensitive drums 3a to 3d. If there is a mismatch in this pitch variation, it is recognized as a color shift of the image.

   FIG. 7 is an explanatory diagram for explaining the relative phase shift of the rotation unevenness of the black photoconductor drum 3a with respect to the rotation unevenness of the cyan photoconductor drum 3b. FIG. 7A shows an example of the cyan pattern Pb and the black pattern Pa in a state where there is no relative phase shift of the rotation unevenness of the black photosensitive drum 3a with respect to the rotation unevenness of the cyan photosensitive drum 3b. FIG. 7B shows an example of the cyan pattern Pb and the black pattern Pa in a state where there is a relative phase shift of the rotation unevenness of the black photosensitive drum 3a with respect to the rotation unevenness of the cyan photosensitive drum 3b. Yes.

  FIG. 7 shows the relative phase shift caused by the rotation unevenness between the cyan photosensitive drum 3b and the black photosensitive drum 3a. However, the cyan photosensitive drum 3b and the magenta and yellow patterns Pc are shown. , Pd can also be described in the same manner for relative phase shifts due to rotational unevenness between the two.

  As shown in FIG. 7, the cyan photosensitive drum 3b and the black pattern Pa periodically have a wide pitch state and a narrow state when there is rotation unevenness.

   In the cyan pattern Pb, the rotation unevenness is a cyan dense wave α (1) (refer to FIG. 8) that represents a periodic change in a positional shift amount indicating a positional shift in the circumferential direction due to the peripheral speed V in the cyan pattern Pb. In the magenta, yellow, and black patterns Pc, Pd, and Pa, the change in the amount of positional deviation that indicates the positional deviation in the circumferential direction due to the circumferential speed V in the magenta, yellow, and black patterns Pc, Pd, and Pa can be expressed. Can be represented by magenta, yellow and black dense waves α (2), α (3), αa (see FIG. 8).

  FIG. 8 is a graph showing a cyan dense wave α (1), a magenta dense wave α (2), a yellow dense wave α (3), and a black dense wave αa.

  As shown in FIG. 8, if there is a relative phase shift among the cyan dense wave α (1), the magenta dense wave α (2), the yellow dense wave α (3), and the black dense wave αa, a color shift occurs. , Image quality deteriorates. That is, as the relative phase shift between the cyan dense wave α (1), the magenta dense wave α (2), the yellow dense wave α (3), and the black dense wave αa increases, the cyan pattern Pb becomes larger. The difference between the magenta pattern Pc, the yellow pattern Pd, and the black pattern Pa increases, and the influence on the image increases accordingly.

[About the pattern detector]
The pattern detection unit 302 detects a cyan dense wave α (1), a magenta dense wave α (2), a yellow dense wave α (3), and a black dense wave αa.

  The cyan dense wave α (1), the magenta dense wave α (2), the yellow dense wave α (3), and the black dense wave αa are sine curves of the invention already filed by the present applicant (Japanese Patent Laid-Open No. 2009-251109). It can be obtained by a fitting calculation formula. Therefore, detailed description of the detection of the cyan dense wave α (1), the magenta dense wave α (2), the yellow dense wave α (3), and the black dense wave αa is omitted here.

  Note that the detection of the cyan dense wave α (1), the magenta dense wave α (2), the yellow dense wave α (3), and the black dense wave αa is not limited to detection by the sine curve fitting calculation formula. Any known method may be used.

[Calculation section]
The calculation unit 303 uses the data for cyan based on the result detected by the pattern detection unit 302 (data relating to the cyan density wave α (1), magenta density wave α (2), yellow density wave α (3), and black density wave αa). Rotation unevenness of any one of the photosensitive drums 3 to be adjusted (here, the cyan photosensitive drum 3b) among the photosensitive drum 3b, the magenta photosensitive drum 3c, the yellow photosensitive drum 3d, and the black photosensitive drum 3a. The phase shift indicating the relative phase shift of the rotation unevenness of the image carrier to be adjusted other than the cyan photosensitive drum 3b (here, the magenta photosensitive drum 3c, the yellow photosensitive drum 3d, and the black photosensitive drum 3a). Measure the amount.

  Specifically, the calculation unit 303a performs magenta with respect to cyan dense wave α (1) based on data regarding cyan dense wave α (1), magenta dense wave α (2), yellow dense wave α (3), and black dense wave αa. The magenta relative phase angle θ (1) of the dense wave α (2), the yellow relative phase angle θ (2) of the yellow dense wave α (3) with respect to the cyan dense wave α (1), and the cyan dense wave α ( The black relative phase angle θ (3) of the black dense wave αa with respect to 1) is calculated. The relative phase angles θ (1), θ (2), θ (3) are stored in the storage unit 320a.

  FIG. 9 is a timing chart showing the states of the detection signal of the third phase sensor 170c, the detection signal of the fourth phase sensor 170d, and the detection signal of the first phase sensor 170a with respect to the detection signal of the second phase sensor 170b. . In addition, in FIG. 9, these timing charts are shown with one figure.

  As shown in FIG. 9, the correction unit 306 performs a magenta photosensitive drum in response to the detection signal Tb of the second phase sensor 170b that detects the phase of the adjustment target image carrier (here, the cyan photosensitive drum 3b). The detection timing Tbc for magenta of the detection signal Tc of the third phase sensor 170c that detects the phase of 3c, and the detection timing Tbd of yellow for the detection signal Td of the fourth phase sensor 170d that detects the phase of the yellow photosensitive drum 3d The black detection timing Tba of the detection signal Ta of the first phase sensor 170a for detecting the phase of the black photosensitive drum 3a is detected. Accordingly, the phase of the magenta coarse / fine wave α (2) is set to the cyan coarse / fine wave α (1) by the magenta relative phase angle θ (1), and the yellow coarse / fine wave α (2) by the yellow relative phase angle θ (2). The phase of 3) and the phase of the black dense wave αa can be adjusted by the relative phase angle θ for black (3).

[Notification]
FIG. 10 is a plan view showing a first notification screen G1 displayed on the display unit 117 in the operation unit 115 of the color image forming apparatus D shown in FIG.

  As shown in FIG. 10, here, the operation unit 115 is an operation panel provided in the upper front portion of the exterior cover of the color image forming apparatus D. The operation unit 115 is configured to receive various setting information of the entire apparatus and information for operating each function at the input unit 116. In addition, the operation unit 115 is configured to display the input content and the operation status of the entire apparatus on the display unit 117. Here, the input unit 116 has a plurality of input keys 116a and is a key input operation unit that can be operated by the operator.

   When the notification unit 304 determines that the relative phase shift of the rotation unevenness of the photosensitive drum should be adjusted based on the measurement results by the pattern detection unit 302 and the calculation unit 303 (specifically, the relative phase angle θ ( 1) to θ (3) (when it is determined that at least one of them exceeds a predetermined angle), the image carrier to be adjusted (here, the magenta photosensitive drum 3c, the yellow photosensitive drum 3d, and the black photosensitive drum). A first message M1 indicating that the photosensitive drum 3a is a photosensitive drum to be detached from the apparatus main body A (here, a message "Please pull out the magenta, yellow and black photosensitive drums"). Is displayed on the first notification screen G1 of the display unit 117.

  In addition, the control part 300 will complete | finish the adjustment mode of a relative phase shift, if the pressing operation by the operator of the cancellation button BT in the 1st notification screen G1 is received. The same applies to the second notification screen G1 described later.

[Removal detection unit]
In addition to the above configuration, the control unit 300 is configured to function as an attachment / detachment detection unit 305.

  Specifically, the attachment / detachment detection unit 305 indicates the attachment / detachment state of each photoreceptor unit 20a-20d detected by the attachment / detachment sensors 35a-35d (whether each photoreceptor unit 20a-20d is attached to the apparatus main body A). To detect. Specifically, the attachment / detachment detection unit 305 recognizes that each of the photoreceptor units 20a to 20d is attached to the apparatus main body A when an attachment signal is sent from the attachment / detachment sensors 35a to 35d. When the separation signals are sent from the attachment / detachment sensors 35a to 35d, it is recognized that each of the photoreceptor units 20a to 20d is detached from the apparatus main body A.

[About correction unit]
In addition to the above configuration, the control unit 300 is configured to function as the correction unit 306.

  The correction unit 306 selects one of the image carriers to be adjusted (here, the black photoconductor drum 3a, the magenta photoconductor drum 3c, and the yellow photoconductor drum 3d) as a correction target image carrier. As a result of measurement by the pattern detection unit 302 and the calculation unit 303 (specifically, a relative phase angle for magenta θ (1), a relative phase angle for yellow θ (2), and a relative phase angle for black θ (3)). The operation of the driving device 100 (specifically, the second driving unit 120) is controlled so that the relative phase shift of the rotational unevenness of the correction target image carrier with respect to the rotational unevenness of the adjustment target image carrier (here, the cyan photosensitive drum 3b). Correct.

  Specifically, the correction unit 306 determines the magenta photosensitive drum 3c and the yellow relative phase angle θ (1), the yellow relative phase angle θ (2), and the black relative phase angle θ (3), respectively. The relative phase shift of the rotation unevenness of the photosensitive drum 3d and the black photosensitive drum 3a is corrected in this order.

  The correction unit 306 starts the correction operation when it is determined that the image carrier to be adjusted is detached from the apparatus main body A based on the detection result by the attachment / detachment detection unit 305.

  FIG. 11 is a plan view showing a second notification screen G2 displayed on the display unit 117 in the operation unit 115 of the color image forming apparatus D shown in FIG.

  As shown in FIG. 11, the notification unit 304 indicates that the correction target image carrier is a photosensitive drum to be mounted on the apparatus main body A as the adjustment target image carrier after the correction operation by the correction unit 306 is completed. A second message M2 of characters (here, a message “Please insert a photoconductor drum”) is displayed on the second notification screen G2 of the display unit 117.

   In the XX on the second notification screen G2, any one of “magenta”, “yellow”, and “black” is entered in accordance with the correction state described later.

  When the correction unit 306 determines that the image carrier to be corrected is attached to the apparatus main body A based on the detection result by the attachment / detachment detection unit 305 (specifically, the photosensitive drum corresponding to the message is inserted). When it is detected that a correction has been made, a correction operation can be performed.

[Example of control by the control unit]
Next, an example of correcting the relative phase shift by the control unit 300 in the color image forming apparatus D will be described with reference to FIGS.

  FIG. 12 is a flowchart showing a flow of an example of a relative phase shift correction operation process by the control unit 300 in the color image forming apparatus D shown in FIG. Further, FIG. 13 corrects the relative phase shift of rotational irregularities of the magenta photosensitive drum 3c, the yellow photosensitive drum 3d, and the black photosensitive drum 3a in this order with respect to the rotational irregularity of the cyan photosensitive drum 3b. It is a state transition diagram which shows the correction process to do. FIG. 13A to FIG. 13H show the first correction state to the eighth correction state, respectively. In FIG. 13, diagonal lines indicate a state in which the photoconductor units 20a to 20d (that is, the photoconductor drums 3a to 3d) are mounted on the apparatus main body A.

(First correction state)
In the relative phase shift correction operation processing shown in FIG. 12, first, the process waits until the operator gives an instruction to start the relative phase shift adjustment mode (step S1: No), and the operator starts the relative phase shift adjustment mode. When instructed (step S1: Yes), the pattern forming unit 301 forms patterns Pb, Pc, Pd, Pa for cyan, magenta, yellow, and black, respectively (step S2). Next, the pattern detection unit 302 detects the black dense wave αa, the cyan dense wave α (1), the magenta dense wave α (2), and the yellow dense wave α (3) (step S3), and further calculates the calculation unit 303. As a result, the relative phase shift of the rotation unevenness of the photosensitive drums 3c, 3d, 3a for magenta, yellow, and black with respect to the rotation unevenness of the photosensitive drum 3b for cyan (that is, the relative phase angle θ for magenta, yellow, and black). (1) to θ (3)) are respectively calculated (step S4).

  In the first correction state shown in FIG. 13A, the photosensitive drums 3b, 3c, 3d, and 3a for cyan, magenta, yellow, and black are mounted on the apparatus main body A. Here, the relative phase shift of the rotation unevenness of the magenta photoconductor drum 3c with respect to the rotation unevenness of the cyan photoconductor drum 3b is advanced by 90 ° with respect to the cyan photoconductor drum 3b. The yellow photosensitive drum 3d has a relative phase shift caused by the rotation unevenness of the yellow photosensitive drum 3d, and the yellow photosensitive drum 3d is advanced by 180 ° with respect to the cyan photosensitive drum 3b. The relative phase shift of the rotation unevenness of the drum 3a is a position where the black photosensitive drum 3a is advanced by 270 ° with respect to the cyan photosensitive drum 3b. That is, the relative phase angles θ (1) to θ (3) are 90 °, 180 °, and 270 °, respectively.

  Next, the rotational unevenness of the magenta, yellow, and black photosensitive drums 3c, 3d, and 3a that are the adjustment target image carrier with respect to the rotational unevenness of the cyan photosensitive drum 3b that is the adjustment target image carrier. It is determined whether or not the relative phase shift should be adjusted, specifically, whether or not at least one of the relative phase angles θ (1) to θ (3) for magenta, yellow, and black exceeds a predetermined angle. (Step S5) When it is determined that the angle is equal to or smaller than the predetermined angle (Step S5: No), the display unit 117 displays that the relative phase shift need not be adjusted (not shown), and the process is terminated. On the other hand, if it is determined that the angle exceeds the predetermined angle (step S5: Yes), the notifying unit 304 uses the magenta, yellow, and black photosensitive drums 3c that are the adjustment target image carriers. , 3d, and 3a are displayed on the display unit 117 as a first message M1 (see FIG. 10) indicating that the photosensitive drum is a detachable photosensitive drum pulled out from the apparatus main body A (step S6).

(Second correction state)
Next, the attachment / detachment detection unit 305 determines whether or not the magenta, yellow, and black photosensitive drums 3c, 3d, and 3a, which are the adjustment target image carriers, have been pulled out from the apparatus main body A (step). S7). Then, it waits until the photosensitive drums 3c, 3d, 3a for magenta, yellow, and black are pulled out from the apparatus main body A (step S7: No), and when they are pulled out (step S7: Yes), the process proceeds to step S8. .

  That is, in the second correction state shown in FIG. 13B, the cyan photosensitive drum 3b as the adjustment target image carrier is mounted on the apparatus main body A, and the magenta as the adjustment target image carrier. The photosensitive drums 3c, 3d, 3a for yellow and black are pulled out by the operator and detached from the apparatus main body A.

(Third correction state)
Next, with respect to the cyan photosensitive drum 3b that is the adjustment target image carrier remaining in the apparatus main body A by the correction unit 306, any one correction target image carrier of the adjustment target image carrier. The relative phase shift of the determined magenta photosensitive drum 3c is corrected (step S8).

  That is, in the third correction state shown in FIG. 13C, in the second correction state shown in FIG. 13B, the current relative phase angle of the image carrier to be corrected (here, the magenta relative phase angle θ (1)). ) = 90 °) as the adjustment angle θc (1), and the cyan photosensitive drum 3b which is the adjustment target image carrier by driving the second drive unit 120 by the adjustment angle θc (1) (90 ° in this case). The relative phase shift of the rotation unevenness of the magenta photosensitive drum 3c, which is a correction target image carrier for the rotation unevenness, is corrected.

  Next, a second message M2 (notifying unit 304 indicates that the magenta photosensitive drum 3c, which is a correction target image carrier, is a photosensitive drum to be mounted on the apparatus main body A as an adjustment target image carrier. 11) is displayed on the display unit 117 (step S9).

(4th correction state)
Next, the attachment / detachment detection unit 305 determines whether or not the magenta photosensitive drum 3c, which is the correction target image carrier, is attached to the apparatus main body A as the adjustment target image carrier (step S10). Then, the process waits until the magenta photosensitive drum 3c is mounted on the apparatus main body A as an adjustment target image carrier (step S10: No), and when it is mounted (step S10: Yes), the process proceeds to step S11.

  That is, in the fourth correction state shown in FIG. 13D, the magenta photosensitive drum 3c that is the correction target image carrier is inserted by the operator as the adjustment target image carrier, and the adjustment target image carrier is obtained. The photosensitive drums 3b and 3c for cyan and magenta are mounted on the apparatus main body A.

  Next, it is determined whether or not the image carrier to be adjusted exists (step S11). If the image carrier to be adjusted does not exist (step S11: No), the relative phase shift is adjusted. Is displayed on the display unit 117 (not shown), and the process ends. On the other hand, if the image carrier to be adjusted exists (step S11: Yes), the process proceeds to step S8. In the fourth correction state shown in FIG. 13D, since the image carrier to be adjusted is the photosensitive drums 3d and 3a for yellow and black, the process proceeds to step S8.

(5th correction state)
Next, any one of the image carrier to be adjusted is applied to each of the cyan and magenta photoconductor drums 3b and 3c which are the image carrier to be adjusted remaining in the apparatus main body A by the correction unit 306. The relative phase shift of the yellow photoconductive drum 3d, which is one of the correction target image carriers, is corrected (step S8).

  That is, in the fifth correction state shown in FIG. 13E, in the fourth correction state shown in FIG. 13D, the current relative phase angle of the image carrier to be corrected (here, the yellow relative phase angle θ (2)). ) = 180 °) and the adjustment angle θc (2) (90 ° here) obtained by subtracting the relative phase angle (here magenta relative phase angle θ (1) = 90 °) of the previous image carrier to be corrected. 2 Rotation unevenness of the yellow photosensitive drum 3d as the correction target image carrier against the rotational unevenness of the cyan and magenta photosensitive drums 3b and 3c which are driven as the adjustment target image carrier by driving the driving unit 120. Correct the relative phase shift.

  Next, a second message M2 (notifying unit 304 indicates that the yellow photosensitive drum 3c, which is a correction target image carrier, is a photosensitive drum to be attached to the apparatus main body A as an adjustment target image carrier. 11) is displayed on the display unit 117 (step S9).

(Sixth correction state)
Next, the attachment / detachment detection unit 305 determines whether or not the yellow photoconductor drum 3d as the correction target image carrier is mounted on the apparatus main body A as the adjustment target image carrier (step S10). Then, the process waits until the yellow photosensitive drum 3d is mounted on the apparatus main body A as an adjustment target image carrier (step S10: No). When the yellow photosensitive drum 3d is mounted (step S10: Yes), the process proceeds to step S11.

  That is, in the sixth correction state shown in FIG. 13 (f), the yellow photosensitive drum 3c, which is the correction target image carrier, is inserted by the operator as the adjustment target image carrier to be the adjustment target image carrier. The photosensitive drums 3b, 3c, 3d for cyan, magenta, and yellow are mounted on the apparatus main body A.

  Next, it is determined whether or not the image carrier to be adjusted exists (step S11). If the image carrier to be adjusted does not exist (step S11: No), the relative phase shift is adjusted. Is displayed on the display unit 117 (not shown), and the process ends. On the other hand, if the image carrier to be adjusted exists (step S11: Yes), the process proceeds to step S8. In the sixth correction state shown in FIG. 13 (f), the image carrier to be adjusted is the black photosensitive drum 3a, and the process proceeds to step S8.

(Seventh correction state)
Next, the adjustment target image carrier is applied to the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d that are the adjustment target image carriers remaining in the apparatus main body A by the correction unit 306. The relative phase shift of the black photosensitive drum 3a, which is one of the correction target image carriers, is corrected (step S8).

  That is, in the seventh correction state shown in FIG. 13G, in the sixth correction state shown in FIG. 13F, the current relative phase angle of the image carrier to be corrected (here, the black relative phase angle θ (3)). ) = 270 °) and the adjustment angle θc (3) (here 90 °) obtained by subtracting the relative phase angle of the previous image carrier to be corrected (here, yellow relative phase angle θ (2) = 180 °). (2) The black photosensitive drum 3a as the correction target image carrier for the rotation unevenness of the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d that are driven as the adjustment target image carrier by driving the driving unit 120. The relative phase shift of the rotation unevenness is corrected.

  Next, a second message M2 (notifying unit 304 indicates that the black photosensitive drum 3c, which is the correction target image carrier, is a photosensitive drum to be mounted on the apparatus main body A as the adjustment target image carrier. 11) is displayed on the display unit 117 (step S9).

(8th correction state)
Next, the attachment / detachment detection unit 305 determines whether or not the black photosensitive drum 3a as the correction target image carrier is mounted on the apparatus main body A as the adjustment target image carrier (step S10). Then, the process waits until the black photosensitive drum 3a is mounted on the apparatus main body A as the adjustment target image carrier (step S10: No). When the black photosensitive drum 3a is mounted (step S10: Yes), the process proceeds to step S11.

  That is, in the eighth correction state shown in FIG. 13 (h), the black photosensitive drum 3a, which is the correction target image carrier, is inserted by the operator as the adjustment target image carrier to be the adjustment target image carrier. The photosensitive drums 3b, 3c, 3d, and 3a for cyan, magenta, yellow, and black are mounted on the apparatus main body A.

  Next, it is determined whether or not the image carrier to be adjusted exists (step S11). If the image carrier to be adjusted does not exist (step S11: No), the relative phase shift is adjusted. Is displayed on the display unit 117 (not shown), and the process ends. On the other hand, if the image carrier to be adjusted exists (step S11: Yes), the process proceeds to step S8. In the eighth correction state shown in FIG. 13 (h), the process is completed because there is no image carrier to be adjusted.

  In the process of step S8 described above, when the adjustment angle for driving the second drive unit 120 becomes a negative value, the second drive unit 120 may be rotated in the reverse direction. When reverse rotation is not possible, such as when reverse rotation is not possible, a value obtained by adding 360 ° to the negative value can be used as the adjustment angle. For example, in the fifth correction state shown in FIG. 13E, when the yellow relative phase angle θ (2) is 90 ° and the previous magenta relative phase angle θ (1) is 180 °, the second drive unit Since the adjustment angle of 120 is 90 ° −180 ° = −90 °, 270 ° obtained by adding 360 ° to this value −90 ° can be set as the adjustment angle.

  In the present embodiment, the first driving unit 110 that drives the black photosensitive drum 3a and the second driving unit 120 that drives the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d are described. Since the operation is performed independently, in the relative phase shift correction operation process shown in FIG. 12, if the first drive unit 110 is not operated when the second drive unit 120 is operated, the black photosensitive drum 3b is moved. It can be left attached to the apparatus main body A. In this case, in the process of “Step S6”, the first magenta and yellow photoconductor drums 3c and 3d that are the image carrier to be adjusted are the first photoconductor drums to be detached from the apparatus main body A. The message M1 is displayed on the display unit 117. Further, in the process of "Step S9", the display unit of the second message M2 indicating that the black photosensitive drum 3c is the photosensitive drum to be mounted on the apparatus main body A. In the display process to 117 and the process of “Step S10”, the determination process for determining whether or not the black photoconductor drum 3a is attached to the apparatus main body A can be omitted.

  Further, in the present embodiment, the first image bearing member to be adjusted is the cyan photosensitive drum 3b, but other color photosensitive drums 3c and 3d may be used. Although the adjustment target image carrier may be the black photosensitive drum 3a, in this case, since both the first drive unit 110 and the second drive unit 120 need to be driven, the adjustment target image carrier is the first group. The cyan photosensitive drum 3a, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d in the photosensitive member 30b are preferably used.

  As described above, in the color image forming apparatus D according to the present embodiment, magenta, yellow, and yellow as the adjustment target image carrier with respect to the rotation unevenness of the cyan photosensitive drum 3b as the adjustment target image carrier. The measuring unit 307 determines the phase shift amount indicating the relative phase shift of the rotation unevenness of the photosensitive drums 3c, 3d, 3a for black based on the patterns Pb, Pc, Pd, Pa for cyan, magenta, yellow, and black. Based on the measurement result of the measurement unit 307, the notification unit 304 notifies that each of the photoconductor drums 3c, 3d, and 3a for magenta, yellow, and black is a photosensitive drum to be detached from the apparatus main body A. . Then, the magenta, yellow, and black photosensitive drums 3c, 3d, and 3a are detached from the apparatus main body A by an operator such as a user or a service person. At this time, the rotation of the photosensitive drums 3c, 3d, and 3a for magenta, yellow, and black can be stopped regardless of the drive control of the drive device 100. As a result, the measuring unit 307 uses one of the magenta, yellow, and black photoconductor drums 3c, 3d, and 3a that has been detached from the apparatus main body A and is in a stopped state as the correction target image carrier. The cyan photosensitive drum 3b can be rotated based on the measurement result. Accordingly, it is possible to correct the relative phase shift of the rotation unevenness of the magenta photoconductor drum 3c with respect to the rotation unevenness of the cyan photoconductor drum 3b with a simple apparatus configuration.

  Further, in the present embodiment, the magenta, yellow, and black photosensitive drums 3c, 3d, and 3a, which are the adjustment target image carriers based on the detection result by the attachment / detachment detection unit 305, are detached from the apparatus main body A. Therefore, the correction unit 306 starts the correction operation. Therefore, the relative phase of the rotation unevenness of the magenta, yellow, and black photoconductor drums 3c, 3d, and 3a with respect to the rotation unevenness of the cyan photosensitive drum 3b. A phase shift amount indicating a shift can be automatically corrected.

  Further, in the present embodiment, after the correction operation by the correction unit 306 is completed, the magenta photosensitive drum 3c, which is the image carrier to be adjusted, is the photoconductor to be mounted on the apparatus main body A as the image carrier to be adjusted. The notification unit 304 notifies that it is a drum. As a result, the operator mounts the photosensitive drum 3c for the adjustment target image carrier on the apparatus main body A as the adjustment target image carrier. At this time, the magenta photosensitive drum 3c mounted as the adjustment target image carrier is used as an existing adjustment target image carrier by the drive control of the driving device 100 (here, the second driving unit 120). It can be rotated with 3b. Therefore, when it is determined that the magenta photosensitive drum 3c, which is the image carrier to be adjusted, is attached to the apparatus main body A based on the detection result by the attachment / detachment detection unit 305, the correction operation by the correction unit 306 is further performed. It can be carried out. As a result, even if the image carrier to be adjusted is a plurality of magenta, yellow and black photosensitive drums 3c, 3d and 3a as in the present embodiment, each of magenta, yellow and black The rotation unevenness of the photosensitive drums 3c, 3d, and 3a can be sequentially corrected with respect to the rotation unevenness of the cyan photosensitive drum 3b.

  Further, even if the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d rotate in conjunction with each other as in the present embodiment, the mounted photosensitive drum (for example, the cyan photosensitive drum). 3b) can be rotated independently with respect to the separated photosensitive drums (for example, the photosensitive drums 3c and 3d for magenta and yellow), so that the photosensitive drums for cyan, magenta and yellow can be rotated. It is possible to correct the relative phase shift caused by the rotation unevenness between the drums 3b and 3c3d.

  Further, in the present embodiment, the driving of the first group image carrier 30a and the driving of the second group image carrier 30b are separate drives, so that cyan, magenta, and yellow for the second group image carrier 30b are used. After correcting the relative phase shift of each of the photosensitive drums 3b, 3c, and 3d by the correction unit 306, the correction unit 306 corrects the relative phase shift of the black photosensitive drum 3a of the first group image carrier 30a. It is not necessary to drive the black photosensitive drum 3a of the first group image carrier 30a by the first driving unit 110, and accordingly, the driving load on the members involved in the first driving unit 110 and the power consumption of the first driving unit 100 are increased. Therefore, the operation of detaching the black photosensitive drum 3a from the apparatus main body A can be omitted.

  In the present embodiment, since the notification by the notification unit 304 is displayed on the display unit 117 as the first and second messages M1 and M2 as characters, the notification by the notification unit 304 is clearly and reliably transmitted to the worker. Can do.

  The black photosensitive drum 3a is for forming a black image, and the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d are for forming a color image. Therefore, it is possible to effectively improve the image quality of a black text original on which characters are normally printed. The number of color photosensitive drums may be two, or four or more.

3a Photosensitive drum for black (an example of an image carrier)
3b Cyan photoreceptor drum (an example of an image carrier)
3c Photosensitive drum for magenta (an example of an image carrier)
3d yellow photosensitive drum (an example of an image carrier)
7 Intermediate transfer belt (an example of a recording medium)
30a First group photoconductor 30b Second group photoconductor (an example of a group image carrier)
100 Drive device (an example of a drive unit)
110 First drive unit 117 Display unit 120 Second drive unit 301 Pattern formation unit 302 Pattern detection unit 303 Calculation unit 304 Notification unit 305 Attachment / detachment detection unit 306 Correction unit 307 Measurement unit A Device body D Color image forming device Pa Black pattern Pb Cyan pattern Pc Magenta pattern Pd Yellow pattern V

Claims (9)

An image forming apparatus comprising a plurality of image carriers that respectively form a plurality of images, and superimposing the plurality of images on a recording medium,
A drive unit that rotates the plurality of image carriers at a constant peripheral speed;
A pattern forming section for forming a plurality of patterns respectively corresponding to the plurality of image carriers on the recording medium for each circumferential pitch;
Of the plurality of image carriers, the periodic fluctuation of the peripheral speed of the adjustment target image carrier other than the adjustment target image carrier with respect to the periodic fluctuation of the peripheral speed of any one of the adjustment target image carriers A measurement unit that measures a phase shift amount indicating a relative phase shift based on the plurality of patterns;
An attachment / detachment detection unit for detecting an attachment / detachment state of the plurality of image carriers with respect to the apparatus main body;
The peripheral speed of the image carrier to be adjusted is controlled by operating the drive unit based on the measurement result of the measurement unit using any one of the image carrier to be adjusted as an image carrier to be corrected. and a correcting unit for correcting the relative phase shift of the said corrected image bearing member for periodic variation of the peripheral speed of the periodic variation,
Wherein the correction unit includes an image forming apparatus characterized that you start a correction operation based on the detection result by the detachable detection unit. The image forming apparatus according to claim 1,
An image forming apparatus, further comprising: a notification unit that notifies that the image carrier to be adjusted is an image carrier to be detached from the apparatus main body based on a measurement result by the measurement unit. The image forming apparatus according to claim 2,
The notifying unit notifies that the correction target image carrier is an image carrier to be attached to the apparatus main body as the adjustment target image carrier after the correction operation by the correction unit is completed. Image forming apparatus. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:
A group image carrier that includes at least two image carriers among the plurality of image carriers and the at least two image carriers rotate in conjunction with each other;
The drive unit includes: a first drive unit that rotates an image carrier other than the group image carrier among the plurality of image carriers at the peripheral speed; and a first drive unit that rotates the group image carrier at the peripheral speed. An image forming apparatus comprising two drive units. The image forming apparatus according to claim 4,
The correction unit corrects a relative phase shift of an image carrier other than the group image carrier after correcting a relative phase shift of the group image carrier among the plurality of image carriers. Image forming apparatus. The image forming apparatus according to claim 4, wherein:
Among the plurality of image carriers, the group image carrier is for performing color image formation, and the image carrier other than the group image carrier is for performing black image formation. An image forming apparatus, comprising: An image forming apparatus according to any one of claims 2 to 6,
It has a display that displays characters,
The notification by the notification unit is a message to be displayed on the display unit. A method of correcting a relative phase shift of the image carrier in an image forming apparatus that includes a plurality of image carriers that respectively form a plurality of images and superimposes the plurality of images on a recording medium,
A driving step of rotating the plurality of image carriers at a constant peripheral speed by a driving unit;
A pattern forming step of forming a plurality of patterns respectively corresponding to the plurality of image carriers on the recording medium by a pattern forming unit for each circumferential pitch;
Of the plurality of image carriers, the periodic fluctuation of the peripheral speed of the adjustment target image carrier other than the adjustment target image carrier with respect to the periodic fluctuation of the peripheral speed of any one of the adjustment target image carriers A measurement step of measuring a phase shift amount indicating a relative phase shift by the measurement unit based on the plurality of patterns ;
An attachment / detachment detection step of detecting an attachment / detachment state of the plurality of image carriers with respect to the apparatus main body by an attachment / detachment detector;
The peripheral speed of the image carrier to be adjusted is controlled by operating the drive unit based on the measurement result of the measurement unit using any one of the image carrier to be adjusted as an image carrier to be corrected. the correction the peripheral velocity relative phase shift of the periodic variation of the target image bearing member for periodic variation seen including a step of correcting by the correction unit of,
In the correction step, a correction operation by the correction unit is started based on a detection result by the attachment / detachment detection unit, and the relative phase shift of the image carrier is corrected. A method for correcting a relative phase shift of an image carrier according to claim 8,
An image carrier comprising: a notification step of notifying, by a notification unit, that the image carrier to be adjusted is an image carrier to be detached from the apparatus main body based on a measurement result by the measurement unit; Relative phase shift correction method.

Images