JP5213889B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a plurality of image carriers that respectively form a plurality of images, and superimposing the plurality of images on a recording medium.

  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 a plurality of different colors (for example, each color component of yellow (Y), magenta (M), cyan (C), and black (K)) are converted into 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. .

  In a conventional image forming apparatus, when driving a plurality of image carriers at a constant peripheral speed, a plurality of image carriers corresponding to a plurality of images (for example, black, yellow, magenta, and cyan images), respectively. In addition, an image forming member (for example, a member including black, yellow, magenta, and cyan developing devices) for forming an image on the image carrier may be driven by a driving unit such as a motor.

  The conventional image forming apparatus includes a first group image carrier including at least one image carrier among the plurality of image carriers, and a plurality of image carriers among the remaining image carriers. In some cases, the image carrier is driven independently from the second group image carrier that rotates in conjunction with each other.

  Specifically, a black image is normally formed independently without forming an image of another color when a monochrome image is formed. In this case, an image carrier corresponding to black and an image forming member (for example, a member including a black developing device) for forming an image on the image carrier are used as other images (eg, yellow, magenta, cyan). A plurality of image carriers corresponding to the image) and image forming members for forming images on the image carriers (for example, members including yellow, magenta, and cyan developing devices) It is driven by the drive unit.

  On the other hand, it is necessary to drive images for images other than black (for example, images of yellow, magenta, and cyan), but they are driven simultaneously to reduce the number of drive components and achieve downsizing of the image forming apparatus. If the yellow, magenta, and cyan image carriers and the image forming members corresponding to the image carriers are driven by one drive unit, the number of components can be reduced.

  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 phase shift of the rotation unevenness due to the periodic fluctuations can be illustrated.

  In this regard, Patent Document 1 discloses an image carrier or an endless carrier itself or an image carrier of an image forming unit in order to reduce the influence of eccentricity caused by attachment thereof, eccentricity due to a clearance error of a rotating shaft, and the like. At least one rotational phase of the endless carrier is detected, and at least one rotational phase of the image carrier and the endless carrier of the image forming unit is individually adjusted based on the detected phase information. An image forming apparatus is disclosed.

JP-A-9-146329

  However, in the image forming apparatus described in Patent Document 1, although the influence of the eccentricity due to the image carrier or the endless carrier itself or its attachment, the eccentricity due to the clearance error of the rotating shaft, etc. can be reduced, various noises, etc. For example, in the case where the relative phase shift is suddenly affected by the influence, incorrect (accidental) phase information is detected. Then, the relative phase shift is adjusted with the control value based on the phase information that is not appropriate, and therefore the reliability of the adjustment of the relative phase shift is lacking.

  Therefore, 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 provides a relative phase shift with a highly reliable control value. An object of the present invention is to provide an image forming apparatus capable of correcting.

In order to solve the above problems, 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. A drive unit for rotating the body at a constant peripheral speed, and a plurality of patterns corresponding to the plurality of image carriers on the recording medium every correction execution period (for example, every fixed number of image formations or every fixed time) The correction is performed on the relative phase shifts of the plurality of dense waves, each of which represents a periodic change of the positional shift amount indicating the positional shift in the circumferential direction due to the peripheral speed in the plurality of patterns. A detection unit that periodically detects each period; a calculation unit that periodically calculates a calculation value for correcting the relative phase shift based on a result detected by the detection unit; A correction unit that corrects the relative phase shift by operating the drive unit based on a control value that controls the drive unit, and a storage unit that stores the control value. When the relative phase shift is periodically corrected for each correction execution period using the calculated value as the control value and the calculated value can be regarded as not changing, the relative phase shift is set with the same control value as the calculated value. It is configured to shift to a control value holding state to be corrected, and in the control value holding state, when an external factor that can be considered to change the relative phase shift occurs, the control value holding state is canceled, and the external factor is An image forming apparatus including at least one of maintenance of the image carrier, maintenance of the driving unit, and forced execution of the relative phase shift correction operation is provided.

According to the present invention, in the initial state in which the relative phase shift is periodically corrected for each correction execution period using the calculated value as the control value, the correction unit can determine that the calculated value does not change. Shifts to the control value holding state in which the relative phase shift is corrected with the same control value as the calculated value, and in the control value holding state, the reliable calculated value is reflected as the control value. I can say that. Accordingly, even when the noise is suddenly affected by various noises, it is possible to eliminate inappropriate (accidental) phase information, and thereby the relative phase can be obtained with a highly reliable control value. The deviation can be corrected.
In addition, when an external factor that can be considered that the relative phase shift changes in the control value holding state, the correction unit cancels the control value holding state, and thus the relative phase shift obviously changes due to the external factor. If it can be considered, the control value holding state can be promptly released and the initial state can be shifted. Furthermore, the external factor includes at least one of maintenance of the image carrier, maintenance of the driving unit, and forced execution of the correction operation of the relative phase shift, thereby changing the relative phase shift. On the other hand, it is possible to change the control value to an appropriate value at the time of maintenance such as replacement of the image carrier and the drive unit that directly affects the correction, or forced execution of the correction operation.

  In the present invention, when the calculation value is different from the control value in the control value holding state, the correction unit can be regarded as a change due to the change in the relative phase shift. A mode in which the control value is changed to the calculated value and the control value holding state is maintained with the same control value as the calculated value can be exemplified.

  In this aspect, the correction unit performs the calculation value until it is determined that the calculation value is reliable again in the control value holding state that can be said to be a state in which the calculation value that is reliable is reflected as the control value. The relative phase shift can be corrected with the control value having high reliability at the present time while confirming the reliability at present.

  In this invention, the said memory | storage part memorize | stores beforehand the some division angle range which divided the angle of the 1 period of the said rough wave, and the said calculated value is any one division angle of the said some division angle range A first specified number of times that defines the number of times of continuous entry into the range is stored in advance, and the correction unit continuously outputs the calculated value within the plurality of segment angle ranges in the initial state. When entering the same segment angle range, a mode of shifting to the control value holding state can be exemplified.

  In this aspect, in the initial state, the reliability of the control value can be defined with a simple control configuration that counts that the calculated value is within the same segment angle range among the plurality of segment angle ranges. it can.

  In the present invention, the first specified number of times can be exemplified as a setting changeable.

  In this aspect, it is possible to change the first specified number of times according to the frequency of sudden influences in which the relative phase shift changes due to influences of various noises, such as differences in user environments.

  In the present invention, the storage unit stores in advance a second specified number of times that defines the number of times that the calculated value continuously enters any one of the plurality of segment angle ranges, and the correction unit When the calculated value is different from the control value in the control value holding state, the calculated value falls within the same segment angle range for the second specified number of times in the plurality of segment angle ranges. A mode in which the control value is changed to the calculated value and the control value holding state is maintained with the same control value as the calculated value can be exemplified. Here, the second specified number of times may be the same as the first specified number of times.

  In this aspect, in the control value holding state, the reliability of the control value is defined with a simple control configuration in which the calculated value is counted within the same segment angle range among the plurality of segment angle ranges. be able to.

  In the present invention, the second specified number of times can be exemplified as a setting changeable.

  In this aspect, it is possible to change the second specified number of times according to the frequency of sudden influences in which the relative phase shift changes due to influences of various noises, such as differences in user environments.

  In the present invention, the storage unit stores the calculated value, a history of the number of times that the calculated value is within the same segment angle range among the plurality of segment angle ranges, the initial state, and the control value holding A mode of storing state information indicating which state is currently in the state can be exemplified.

  In this aspect, it is possible to compare the calculated value and the reliability of the control value with each numerical value.

  In the present invention, all the past information or the latest or neighboring information is stored as the calculated value, the number history, and the state information stored in the storage unit, and the average of the latest or neighboring calculated values is stored. It is possible to take a value, but in this case, the memory capacity increases.

  From this viewpoint, it is preferable that the correction unit overwrites and updates the calculation value, the number history, and the state information stored in the storage unit.

  In this aspect, since it is not necessary to store all the past information or the latest or neighboring information, the memory capacity of the storage unit can be reduced.

  In the present invention, it is possible to exemplify an aspect in which the correction unit returns the state information to the initial state and clears the frequency history when an external factor that can be regarded as a change in the relative phase shift occurs.

  In this aspect, the control value can be changed to an appropriate value when the relative phase shift can be clearly changed due to the external factor.

  As a specific aspect of the present invention, the drive unit includes a plurality of drive units that rotate the plurality of image carriers at a constant peripheral speed, and the pattern forming unit includes the plurality of image carriers. Then, the reference pattern corresponding to any one of the reference image carriers is corrected on the recording medium at every pitch in the circumferential direction, and the detection patterns corresponding to the remaining detection image carriers are corrected at the pitch. The detection unit is formed periodically for each period, and the detection unit includes a reference dense wave that represents a periodic change in a positional deviation amount indicating a circumferential positional deviation due to the peripheral speed in the reference pattern, A detected coarse / fine wave representing a periodic change in a positional deviation amount indicating a positional deviation in the circumferential direction due to the peripheral speed is periodically detected for each correction execution period, and the calculation unit detects the detection of the reference coarse / fine wave. Close wave phase The phase angle is periodically calculated as the calculated value for each correction execution period, and the correction unit drives the reference image carrier in the plurality of drive units and the detection image carrier. Actuation control of at least one of the detection drive units corrects a relative phase shift between the periodic fluctuation of the peripheral speed corresponding to the reference image carrier and the periodic fluctuation of the peripheral speed corresponding to the detection image carrier. The mode to do can be illustrated.

  In this aspect, the relative phase shift of the detection image carrier with respect to the reference image carrier can be phase-controlled while separately comparing the reliability. For this reason, it is possible to correct individual relative phase shifts with the control values having high reliability, and as a result, it is possible to realize reduction of image misalignment.

  Further, as another specific aspect of the present invention, a first group image carrier including a reference image carrier among the plurality of image carriers, and a plurality of detection image carriers among the remaining image carriers, and The plurality of detection image carriers include a second group image carrier that rotates in conjunction with each other, and the drive unit includes a reference drive unit that rotates the first group image carrier at a constant peripheral speed, A detection driving unit that rotates the second group image carrier at the peripheral speed, and the pattern forming unit generates a reference pattern corresponding to the reference image carrier for each pitch in the circumferential direction and the plurality of patterns. A plurality of detection patterns respectively corresponding to the detected image carrier are periodically formed on the recording medium for each correction execution period for each pitch, and the detection unit is configured according to the peripheral speed in the reference pattern. Indicates circumferential misalignment A reference coarse / fine wave representing a periodic change in the displacement amount, and a plurality of detected dense waves each representing a periodic change in a displacement amount indicating a circumferential displacement due to the circumferential speed in the plurality of detection patterns. Is periodically detected for each correction execution period, and the calculation unit corrects the relative phase angle with respect to the reference coarse wave as the calculation value based on a relative deviation amount of the plurality of detected coarse waves with respect to the reference coarse wave. The correction unit periodically calculates for each implementation period, and the correction unit controls the operation of at least one of the reference drive unit and the detection drive unit to periodically change the peripheral speed corresponding to the reference image carrier and the correction unit. An example of correcting the relative phase shift with the periodic fluctuation of the peripheral speed corresponding to the second group image carrier can be exemplified.

  In this aspect, even if there are a plurality of detection patterns, the control value of the plurality of detected coarse / fine waves with respect to the reference coarse / fine wave can be made one value, and the memory capacity of the storage unit can be reduced accordingly. Can do.

  In the present invention, when forming an image, since black is often a color on which characters are printed, in consideration of improving the image quality of a character document, black image formation is performed with the reference image carrier, It is preferable to form a color image with the detection image carrier. That is, it is preferable that the reference image carrier is for performing black image formation, and the detection image carrier is for performing color image formation.

  As described above, according to the image forming apparatus of the present invention, the calculated value changes in the initial state in which the relative phase shift is periodically corrected for each correction execution period using the calculated value as the control value. In the case where it can be regarded as not, even if the control value is shifted to the control value holding state in which the relative phase shift is corrected with the same control value as the calculated value, even when suddenly affected by various noises, etc. Inappropriate (accidental) phase information can be eliminated, and the relative phase shift can be corrected with the control value having high reliability.

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 first drive 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. FIG. 2 is a system configuration diagram schematically showing a drive transmission system of a second drive 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 in FIG.3 and FIG.5 in detail. FIG. 5 is a plan view showing an example in which a black reference pattern, a cyan detection pattern, a magenta detection pattern, and a yellow detection 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. It is explanatory drawing for demonstrating the relative phase shift by the rotation nonuniformity between the photosensitive drum for black and the cyan photosensitive drum, Comprising: (a) is the photosensitive drum for black, and the photosensitive drum for cyan | cyan. FIG. 5B is a diagram illustrating an example of a black reference pattern and a cyan detection pattern in a state where there is no relative phase shift due to rotation unevenness between the black photosensitive drum and the cyan photosensitive drum; It is a figure which shows the example of the pattern for black reference | standard, and the pattern for cyan detection in the state with a relative phase shift by rotation nonuniformity between. It is a graph which shows a black reference | standard rough wave and cyan, magenta, and yellow detection rough wave. It is a timing chart which shows a detection signal of a standard detection phase sensor and a detection phase sensor. 2 is a timing chart showing the operation timing of an output signal to a detection drive unit with respect to an output signal to a reference drive unit that drives a black photoconductive drum, and (a) is a photoconductor drum for cyan, magenta, and yellow. FIG. 6B is a diagram showing a state in which the phase of each of the photosensitive drums for cyan, magenta, and yellow is the photosensitive layer for black. FIG. 6C is a diagram illustrating a state in which the phase is delayed by an optimum relative phase angle with respect to the phase of the body drum, and (c) is a rotation unevenness of the photosensitive drum for black and rotations of the photosensitive drums for cyan, magenta, and yellow. It is a figure which shows the state after correct | amending the relative phase shift | offset | difference with a nonuniformity. It is the schematic which shows the detail of the storage area of a memory | storage part, Comprising: (a) is a figure which shows the memory | storage part in the case of the structure of a 1st drive device, (b) is the structure of a 2nd drive device. It is a figure which shows the memory | storage part in a case. FIG. 2 is a plan view showing a reset screen displayed on a display unit in an operation unit of the color image forming apparatus shown in FIG. 1. FIG. 2 is a plan view showing a correction forced execution screen displayed on a display unit in an operation unit of the color image forming apparatus shown in FIG. 1. FIG. 2 is a plan view showing a specified number of times setting input screen displayed on a display unit in an operation unit of the color image forming apparatus shown in FIG. 1. 3 is a flowchart illustrating an example of a flow of a relative phase shift correction operation process by a control unit in the case of the configuration of the first drive device in the color image forming apparatus illustrated in FIG. 1. FIG. 18 is a data table showing, in a time series, changes in data in the storage unit in the relative phase shift correction operation processing shown in FIG. 17, and is a data table for correcting relative phase shift between a black reference coarse wave and a cyan detection coarse wave. . FIG. 18 is a data table showing, in a time series, changes in data in the storage unit in the relative phase shift correction operation processing shown in FIG. 17, and is a data table for correcting the relative phase shift with the magenta detected coarse / fine wave with respect to the black reference coarse / fine wave. . FIG. 18 is a data table showing, in a time series, changes in data in the storage unit in the relative phase shift correction operation processing shown in FIG. 17, and is a data table for correcting the relative phase shift between the black reference coarse wave and the yellow detected coarse wave. .

  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 parallel to 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. 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 forms a plurality of images using the photosensitive drums 3 (3a, 3b, 3c, 3d) that act as a plurality of image carriers corresponding to the respective images. These images are superimposed. 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, fixing The apparatus 12 includes 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.

  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 drum 3 (3a, 3b, 3c, 3d), the charger 5 (5a, 5b, 5c, 5d), and the cleaner device 4 (4a, 4b, 4c, 4d) and four intermediate transfer rollers 6 (6a, 6b, 6c, 6d) are provided so as to form four types of images corresponding to the respective colors. Four image stations are configured such that a is associated with black, b is associated with cyan, c is associated with magenta, and d is associated with yellow. 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 FIGS. 3 and 5 described later) and a scanning optical system 43, and is charged. The surface of the photosensitive drum 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 of the photosensitive drum, the reference numeral 2 of the developing device, and the end code of the transfer unit 6 are not omitted, and the photosensitive drums 3a, 3b, 3c, 3d, the developing device (here, the developing unit) 2a, 2b, 2c, 2d and transfer portions (here, intermediate transfer rollers) 6a, 6b, 6c, 6d.

  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. The pattern detection sensor 34 detects each pattern Pa, Pb, Pc, Pd (see FIGS. 7 and 8 described later) formed on the intermediate transfer belt 7, as will be described later. More specifically, the pattern detection sensor 34 detects incident light reflected from the light emitting portion 341 on the surface of the intermediate transfer belt 7 or each pattern Pa, Pb, Pc, Pd by the light receiving portion 342.

[Configuration of drive unit]
In the present embodiment, the color image forming apparatus D is a first driving device 100a (see FIGS. 2 and 3) or a second driving device 100b (see FIGS. 4 and 4) as a driving device for driving the photosensitive drum 3. (See FIG. 5).

  2 is a system configuration diagram schematically showing a drive transmission system of the first driving device 100a in the color image forming apparatus D shown in FIG. 1, and FIG. 3 is a system configuration in the color image forming apparatus D shown in FIG. FIG. 4 is a system configuration diagram schematically showing a drive transmission system of the second driving device 100b in the color image forming apparatus D shown in FIG. 1, and FIG. 5 is a system configuration in the color image forming apparatus D shown in FIG. FIG. In FIG. 5, the same components as those of the first drive device 100a are denoted by the same reference numerals.

  The color image forming apparatus D shown in FIG. 1 can use the first driving device 100a or the second driving device 100b as a driving device.

  The first driving device 100a individually drives the black photosensitive drum 3a, the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d at a constant peripheral speed. The photosensitive drum 3a for black is an example of a reference image carrier, and the photosensitive drums 3b, 3c, and 3d for cyan, magenta, and yellow are examples of a detection image carrier.

  In the second driving device 100b, the first group photoconductor 30a including the black photoconductor drum 3a, the cyan photoconductor drum 3b, the magenta photoconductor drum 3c, and the yellow photoconductor drum 3d rotate in conjunction with each other. The second group photoconductor 30b is driven independently. The first group photoconductor drum 30a is an example of a first group carrier, and the second group photoconductor 30b is an example of a second group image carrier.

  In the following description of the configuration of the drive device, the configuration of the first drive device 100a and the configuration of the second drive device 100b will be described separately.

(Configuration of the first driving device)
The first driving device 100a shown in FIGS. 2 and 3 includes a black photosensitive drum 3a and a cyan drum from the reference driving unit 110, the first detection driving unit 120b, the second detection driving unit 120c, and the third detection driving unit 120d, respectively. Rotational drive to the photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d is transmitted by a drive transmission unit.

  Specifically, the black photosensitive drum 3a is for performing monochrome image formation (monochrome printing), and the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d are In order to form a color image. The images formed on the black photosensitive drum 3a, the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d are superposed on the intermediate transfer belt 7, so that a full-color image is obtained. Can be formed. The diameters of the photosensitive drums 3a, 3b, 3c, and 3d for black, cyan, magenta, and yellow are all the same.

  The first drive device 100a includes a reference drive unit 110, a first detection drive unit 120b, a second detection drive unit 120c, a third detection drive unit 120d, a reference drive transmission rotating member 150, and a first detection drive. Transmission rotation member 160b, second detection drive transmission rotation member 160c, third detection drive transmission rotation member 160d, reference phase detection sensor 170a, detection first phase detection sensor 170b, and detection first A two-phase detection sensor 170c and a detection third phase detection sensor 170d are provided. Note that the reference drive transmission rotation member 150, the first detection drive transmission rotation member 160b, the second detection drive transmission rotation member 160c, and the third detection drive transmission rotation member 160d all act as rotation members here. To do.

  The reference driving unit 110, the first detection driving unit 120b, the second detection driving unit 120c, and the third detection driving unit 120d are respectively a black photosensitive drum 3a, a cyan photosensitive drum 3b, a magenta photosensitive drum 3c, and the like. This is for driving the photosensitive drum 3d for yellow. Here, the reference drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d are all stepping motors.

  The reference drive transmission rotation member 150 transmits the rotation drive from the reference drive unit 110 to the black photosensitive drum 3a. Here, the first shaft gear 111, the first intermediate gear 112, and the black use are transmitted. It comprises a photosensitive member driving gear 130. The first detection drive transmission rotation member 140b transmits rotation drive from the first detection drive unit 120b to the cyan photosensitive drum 3b. Here, the second shaft gear 121b and the second intermediate gear 122b are transmitted. And a cyan photoconductor driving gear 140b. The second detection drive transmission rotation member 140c transmits the rotation drive from the second detection drive unit 120c to the magenta photosensitive drum 3c. Here, the third shaft gear 121c and the third intermediate gear 122c are transmitted. And a magenta photosensitive member driving gear 140c. The third detection drive transmission rotation member 140d transmits the rotation drive from the third detection drive unit 120d to the yellow photosensitive drum 3d. Here, the fourth shaft gear 121d and the fourth intermediate gear 122d. And a photoreceptor driving gear 140d for yellow. Note that these gears are parallel to each other in the direction of the rotation axis.

  Specifically, the black photosensitive drum driving gear 130, the cyan photosensitive drum driving gear 140b, the magenta photosensitive drum driving gear 140c, and the yellow photosensitive drum driving gear 140d are respectively the black photosensitive drum 3a and the cyan photosensitive drum driving gear 140d. The first intermediate gear 112, the second intermediate gear 122b, the third intermediate gear 122c and the fourth intermediate gear 3b, the magenta photosensitive drum 3c and the yellow photosensitive drum 3d are coaxially connected to the rotation shaft. It meshes with the gear 122d. The first shaft gear 111, the second shaft gear 121b, and the third shaft gear 121c provided on the rotation shafts of the reference drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d, respectively. And the fourth shaft gear 121d mesh with the first intermediate gear 112, the second intermediate gear 122b, the third intermediate gear 122c, and the fourth intermediate gear 122d, respectively. As a result, the reference shaft 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d are driven to rotate, so that the first shaft gear 111, the first intermediate gear 112, and the black use are driven. The black photosensitive drum 3a connected to the black photosensitive member driving gear 130 via the photosensitive member driving gear 130 is connected to the black photosensitive drum driving gear 130b via the second shaft gear 121b, the second intermediate gear 122b, and the cyan photosensitive member driving gear 140b. The cyan photosensitive drum 3b coupled to the cyan photosensitive drum driving gear 140b is connected to the magenta photosensitive drum driving gear 140c via the third shaft gear 121c, the third intermediate gear 122c, and the magenta photosensitive drum driving gear 140c. The magenta photosensitive drum 3c coupled to the fourth shaft gear 121d, the fourth intermediate gear 122d, and the yellow photosensitive drum drive. Via the gear 140d, connected to the yellow photosensitive body drive gear 140d it was a yellow photosensitive drum 3d can be rotated, respectively.

  The reference driving unit 110 also drives the black developing unit 2a. The first detection driving unit 120b, the second detection driving unit 120c, and the third detection driving unit 120d are respectively cyan developing units. 2b, the magenta developing unit 2c and the yellow developing unit 2d are also driven.

[Configuration of Phase Detection Sensor when First Driving Device is Applied]
Here, the reference phase detection sensor 170a, the detection first phase detection sensor 170b, the detection second phase detection sensor 170c, and the detection third phase detection sensor 170d all include a light emitting unit 171 and a light receiving unit 172. Type optical sensor (photo interrupter).

  The reference phase detection sensor 170a, the detection first phase detection sensor 170b, the detection second phase detection sensor 170c, and the detection third phase detection sensor 170d are respectively a black photoconductor 3a, a cyan photoconductor drum 3b, The protrusions or notches of the rotating members rotated by the rotation of the magenta photosensitive drum 3c and the yellow photosensitive drum 3d (here, the black photosensitive member driving gear 130, the cyan photosensitive member driving gear 140b, the magenta photosensitive member). A notch (not shown) obtained by notching a ring-shaped rib (not shown) formed along the circumferential direction of the drive gear 140c and the yellow photoconductor drive gear 140d is detected. Yes.

  Specifically, the reference phase detection sensor 170a, the detection first phase detection sensor 170b, the detection second phase detection sensor 170c, and the detection third phase detection sensor 170d are incident on the light receiving unit 172 from the light emitting unit 171. Projections are produced by the circumferential movement of the projections or notches associated with the rotation of the black photoreceptor drive gear 130, cyan photoreceptor drive gear 140b, magenta photoreceptor drive gear 140c, and yellow photoreceptor drive gear 140d. Alternatively, the presence or absence of incident light is detected by the light receiving unit 172 by blocking or passing through the notch.

  The reference phase detection sensor 170a, the detection first phase detection sensor 170b, the detection second phase detection sensor 170c, and the detection third phase detection sensor 170d may be reflective optical sensors.

[Configuration of control system when first drive unit is applied]
As shown in FIG. 3, the color image forming apparatus D further includes a control unit 300 a that controls the entire color image forming apparatus D.

  The controller 300a controls driving of the driving load of the first driving device 100a. The first drive device 100a further includes a drive control circuit 200a that acts as a drive control unit, a reference drive unit control circuit 210, a first detection drive unit control circuit 220b, a second detection drive unit control circuit 220c, 3 detection drive part control circuit 220d and the belt drive part 28 are provided.

  The drive control circuit 200a controls the operation of the reference drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d based on an instruction signal from the control unit 300a. Yes.

  The reference drive unit control circuit 210 is connected between the drive control circuit 200a and the reference drive unit 110. The first detection drive unit control circuit 220b is connected between the drive control circuit 200b and the first detection drive unit 120b. The second detection drive unit control circuit 220c is connected between the drive control circuit 200b and the second detection drive unit 120c. The third detection drive unit control circuit 220d is connected between the drive control circuit 200b and the third detection drive unit 120d.

  The drive control circuit 200a is connected to the reference drive unit 110, the first detection drive unit control circuit 220b, the second detection drive unit control circuit 220c, and the third detection drive unit control circuit 220d, respectively. Commands for starting and stopping the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d are given.

  The reference drive unit control circuit 210, the first detection drive unit control circuit 220b, the second detection drive unit control circuit 220c, and the third detection drive unit control circuit 220d are each under the instruction of the drive control circuit 200a, and the reference drive unit 110, respectively. , A circuit for controlling the start, stop, and drive speed of the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d. Here, the reference speed is set based on the target speed commanded from the drive control circuit 200a. The servo control circuit controls the drive speeds of the drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d to coincide with each other.

  In addition, the drive control circuit 200a sets the reference drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d at a predetermined process speed (drive speed for image formation) during image formation. ) To drive the reference drive unit control circuit 210, the first detection drive unit control circuit 220b, the second detection drive unit control circuit 220c, and the third detection drive unit control circuit 220d.

  The reference drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d are controlled to operate under the instruction of the drive control circuit 200a, and each of the black photosensitive drums. 3a, the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d are driven to rotate at a constant 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 200a, and moves the intermediate transfer belt 7 at a peripheral speed V.

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

  The reference phase detection sensor 170a, the detection first phase detection sensor 170b, the detection second phase detection sensor 170c, and the detection third phase detection sensor 170d are respectively a black photosensitive drum 3a and a cyan photosensitive drum 3b. The rotation timing of the magenta photosensitive drum 3c and the yellow photosensitive drum 3d is detected.

(Configuration of second driving device)
The second drive device 100b shown in FIGS. 4 and 5 transmits the rotational drive from the reference drive unit 110 and the detection drive unit 120 to the black photoconductor drum 3a and the second group photoconductor 30b, respectively, by drive transmission means.

  In the color image forming apparatus D, the first group photoconductor 30a including the black photoconductor drum, the cyan photoconductor drum 3b, the magenta photoconductor drum 3c, and the yellow photoconductor drum 3d rotate in conjunction with each other. 2 group photoconductor 30b. Specifically, the first group photoconductor 30a is for performing monochrome image formation (monochrome printing), and the second group photoconductor 30b is for performing color image formation. Then, the images formed on the second group photoconductor 30b and the first group photoconductor 30a are superimposed on the intermediate transfer belt 7, whereby a full color image can be formed. The diameters of the photosensitive drums 3a, 3b, 3c, and 3d for black, cyan, magenta, and yellow are all the same.

  The second drive device 100b includes a reference drive unit 110, a detection drive unit 120, a reference rotation member 150, a detection rotation member 160, a reference phase detection sensor 170a, and a detection phase detection sensor 170e. Here, both the reference drive transmission rotating member 150 and the detection drive transmission rotating member 160 act as rotating members.

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

  The reference drive transmission rotation member 150 transmits the rotation drive from the reference drive unit 110 to the first group photoconductor 30a. Here, the first shaft gear 111, the first intermediate gear 112, and the black drive are used. It comprises a photosensitive member driving gear 130. The detection drive transmission rotation member 160 transmits the rotation drive from the detection drive unit 120 to the second group photoconductor 30b, and here, the second shaft gear 121, the second intermediate gear 122, and the third group gear. The intermediate gear 123, the fourth intermediate gear 124, the cyan photoconductor drive gear 140b, the magenta photoconductor drive gear 140c, and the yellow photoconductor drive gear 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 reference drive unit 110 meshes with the first intermediate gear 112. As a result, when the reference driving unit 110 is rotationally driven, the black photoconductor driving gear 130 is connected to the black photoconductor driving gear 130 via the first shaft gear 111, the first intermediate gear 112, and the black photoconductor 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 detection drive unit 120 meshes with the second intermediate gear 122. As a result, when the detection drive unit 120 is driven to rotate, the magenta gear connected to the magenta photoconductor drive gear 140c via the second shaft gear 121, the second intermediate gear 122, and the magenta photoconductor drive gear 140c. The cyan photosensitive drum 3b connected to the cyan photosensitive drum driving gear 140b through the magenta photosensitive drum driving gear 140c, the third intermediate gear 123, and the cyan photosensitive drum driving gear 140b is connected to the photosensitive drum 3c. The yellow photosensitive drum 3d connected to the yellow photosensitive drum drive gear 140d can be rotated via the magenta photosensitive drum drive gear 140c, the fourth intermediate gear 124, and the yellow photosensitive drum drive gear 140d. .

  As a result, the detection drive unit 120 of each of the photosensitive drums 3b, 3c, and 3b for cyan, magenta, and yellow can be made common (single). In addition, the photosensitive drums 3b, 3c, and 3d for cyan, magenta, and yellow are rotated in conjunction with each other by a common detection driving unit 120. In this way, the black photosensitive drum 3a can be rotated independently by the reference driving unit 110 during monochrome printing.

  The reference driving unit 110 also drives the black developing unit 2a, and the detection driving unit 120 drives the cyan developing unit 2b, the magenta developing unit 2c, and the yellow developing unit 2d. It has become.

[Configuration of Phase Detection Sensor when Second Driving Device is Applied]
Here, each of the reference phase detection sensor 170a and the detection phase detection sensor 170e is a transmissive optical sensor (photo interrupter) having a light emitting unit 171 and a light receiving unit 172.

  The reference phase detection sensor 170a and the detection phase detection sensor 170e are respectively a protrusion or a cutout portion (here, a black photoconductor) of a rotating member that is rotated by the rotation of the first group photoconductor 30a and the second group photoconductor 30b. A notch (not shown) obtained by notching a ring-shaped rib (not shown) formed along the circumferential direction of the drive gear 130 and the yellow photoconductor drive gear 140d is detected. Yes.

  Specifically, the reference phase detection sensor 170a and the detection phase detection sensor 170e turn incident light incident on the light receiving portion 172 from the light emitting portion 171 into rotation of the black photosensitive member driving gear 130 and the yellow photosensitive member driving gear 140d, respectively. The presence or absence of incident light is detected by the light receiving unit 172 by blocking or passing the projection or notch by the circumferential movement of the accompanying projection or notch.

  The reference phase detection sensor 170a and the detection phase detection sensor 170e may be reflective optical sensors.

[Configuration of Control System when Second Drive Device is Applied]
As shown in FIG. 5, the color image forming apparatus D further includes a control unit 300 b that controls the entire color image forming apparatus D.

  The controller 300b controls driving of the driving load of the second driving device 100b. The second drive device 100b further includes a drive control circuit 200b that acts as a drive control unit, a reference drive unit control circuit 210, a detection drive unit control circuit 220, and a belt drive unit 28.

  The drive control circuit 200b performs operation control of the reference drive unit 110 and the detection drive unit 120 based on an instruction signal from the control unit 300b.

  The reference drive unit control circuit 210 is connected between the drive control circuit 200b and the reference drive unit 110. The detection drive unit control circuit 220 is connected between the drive control circuit 200b and the detection drive unit 120.

  The drive control circuit 200b gives commands for starting and stopping the reference drive unit 110 and the detection drive unit 120 to the reference drive unit control circuit 210 and the detection drive unit control circuit 220, respectively.

  The reference drive unit control circuit 210 and the detection drive unit control circuit 220 are circuits for controlling the start, stop, and drive speed of the reference drive unit 110 and the detection drive unit 120, respectively, under the instruction of the drive control circuit 200b. The servo control circuit controls the drive speeds of the reference drive unit 110 and the detection drive unit 120 to coincide with the target speed commanded from the drive control circuit 200b.

  In addition, the drive control circuit 200b includes a reference drive unit control circuit 210 and a detection drive unit so as to drive the reference drive unit 110 and the detection drive unit 120 at a predetermined process speed (drive speed for image formation) during image formation. Each control circuit 220 is instructed.

  The reference driving unit 110 is controlled to operate under the instruction of the drive control circuit 200b, and rotationally drives the black photosensitive drum 3a at a constant peripheral speed V. The detection drive unit 120 is controlled under the instruction of the drive control circuit 200b, and rotates 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. The body 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 21. The belt drive unit 28 is controlled to operate under the instruction of the drive control circuit 200b, and moves the intermediate transfer belt 7 at a peripheral speed V.

  In the drive control circuit 200b, a reference phase detection sensor 170a and a detection phase detection 170e are connected to an input system.

  The reference phase detection sensor 170a and the detection phase detection sensor 170e detect the rotation timings of the black photoconductor drum 3a and the second group photoconductor 30b, respectively.

[About the control unit]
The control units 300a and 300b shown in FIGS. 3 and 5 are further components of the color image forming apparatus D, and control the operation of each unit (not shown).

  In the control units 300a and 300b, 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 the RAMs of the storage units 320a and 320b (see FIG. 6) 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 units 320a and 320b 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, 3b, 3c, and 3d for black, cyan, magenta, and yellow, the control units 300a and 300b are a black laser diode 42a and a color laser diode. The cyan laser diode 42b, the magenta laser diode 42c, and the yellow laser diode 42d emit light, respectively, on the uniformly charged black, cyan, magenta, and yellow photoconductive drums 3a, 3b, 3c, and 3d. Are controlled to be exposed.

  Further, the control units 300a and 300b compare the detection timings of the patterns Pa, Pb, Pc, and Pd (see FIGS. 7 and 8) read by the pattern detection sensor 34 with the normal timings to obtain deviations. The timing deviation can be converted into a position deviation by using the peripheral speed V of the intermediate transfer belt 7. This timing deviation will be described in detail later.

  FIG. 6 is a block diagram showing in detail the control units 300a and 300b shown in FIGS. In FIG. 6, the control units 300a and 300b are shown in one figure, and the same components as those of the control units 300a and 300b are denoted by the same reference numerals.

  As shown in FIG. 6, the control units 300a and 300b are capable of rewriting data, such as processing units 310 and 310 including microcomputers such as a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and the like. Storage units 320a and 320b including a storage device such as a non-volatile memory.

  The control units 300a and 300b are configured such that the processing units 310 and 310 load and execute control programs stored in advance in the ROMs of the storage units 320a and 320b on the RAMs of the storage units 320a and 320b, respectively. Operation control is performed. The RAMs of the storage units 320a and 320b provide a work area for work and an area as an image memory for storing image data to the processing units 310 and 310, respectively.

  Specifically, the control units 300a and 300b store the acquired image data in the RAM in association with the assigned attributes. 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 image data is input from an external host in the page description language format, the control units 300a and 300b develop the input image data and store it in the image memory area. The ROMs of the storage units 320a and 320b store programs that define processing procedures executed by the control units 300a and 300b, respectively.

  The storage units 320a and 320b store various data and arithmetic expressions used in pattern forming units 301 and 301, detection units 302 and 302, calculation units 303a and 303b, and correction units 304a and 304b, which will be described later.

[Correction of relative phase shift]
By the way, in the color image forming apparatus D, the eccentricity of the black photosensitive drum 3a, the eccentricity of the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d, Eccentricity of a rotation member for driving transmission such as a driving gear for transmitting rotational driving to the black photosensitive drum 3a, the cyan photosensitive drum 3b and the magenta photosensitive drum 3c from the detection driving units 120b, 120c, 120d, 120. And circumferential fluctuations due to periodic fluctuations in the circumferential speed V (hereinafter referred to as rotation unevenness) caused by the eccentricity of each of the drive transmission rotating members such as the drive gear for transmitting the rotational drive to the yellow photosensitive drum 3d. Misalignment may occur. For this reason, in the first driving device 100a, the relative phase shift due to rotation unevenness between the black photosensitive drum 3a and the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d is adjusted. . Further, the second driving device 100b adjusts the relative phase shift due to rotation unevenness between the black photosensitive drum 3a and the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d that are linked to each other.

  That is, the color image forming apparatus D according to the present embodiment has the following control configuration.

  The control units 300a and 300b are configured to function as pattern forming units 301 and 301, detection units 302 and 302, calculation units 303a and 303b, and correction units 304a and 304b, respectively.

[Pattern forming part]
FIG. 7 shows a black reference pattern Pa (Pa1, Pa2, Pa3 in the illustrated example), a cyan detection pattern Pb (Pb1, Pb2, Pb3 in the illustrated example), and a magenta detection pattern Pc (illustrated example) on the intermediate transfer belt 7. FIG. 6 is a plan view showing an example in which Pc1, Pc2, Pc3) and a yellow detection pattern Pd (Pd1, Pd2, Pd3 in the illustrated example) are formed.

  In the present embodiment, the pattern forming unit 301 forms a black reference pattern Pa, which is a black image, as a reference pattern for a reference color, and a cyan detection pattern Pb, which is a color image, as a detection color detection pattern. The magenta detection pattern Pc and the yellow detection pattern Pd are respectively formed periodically every preset correction execution period (for example, every fixed number of image formations or every fixed time). Here, the correction execution period is a common (identical) period among cyan, magenta, and yellow.

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

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

  Specifically, the pattern forming unit 301 forms electrostatic latent images corresponding to the patterns Pa to Pd with the LSU 1 on the photosensitive drums 3a to 3d for black, cyan, magenta, and yellow. The electrostatic latent image is developed into a toner image by developing devices (here, developing units) 2a to 2d, and the developed toner images are transferred as transfer patterns (here, intermediate transfer rollers) 6a to 6d as patterns Pa to Pd. It is electrostatically transferred to the belt 7. In this embodiment, the color of the reference pattern is black. However, any other color, that is, yellow, magenta, or cyan may be used as the reference pattern color.

  Specifically, the pattern forming unit 301 acquires the pattern data of the patterns Pa to Pd stored in advance in the storage units 320a and 320b when forming the patterns 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 reference pattern Pa, the cyan detection pattern Pb, the magenta detection pattern Pc, and the yellow detection 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 movement 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 detection patterns Pb1, Pb2, Pb3, the black reference patterns Pa1, Pa2, Pa3, Each magenta detection pattern Pc1, Pc2, Pc3 and each yellow detection pattern Pd1, Pd2, Pd3 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. 8 shows patterns Pa to Pd formed on both ends of the intermediate transfer belt 7 in the width direction E 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 illustrated in FIG. 8, 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 a periodic variation of the peripheral speed V 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. 9 is an explanatory diagram for explaining a relative phase shift due to uneven rotation between the black photosensitive drum 3a and the cyan photosensitive drum 3b. FIG. 9A shows an example of the black reference pattern Pa and the cyan detection pattern Pb in a state where there is no relative phase shift due to rotation unevenness between the black photosensitive drum 3a and the cyan photosensitive drum 3b. FIG. 9B shows a black reference pattern Pa and a cyan detection pattern in a state where there is a relative phase shift due to rotation unevenness between the black photosensitive drum 3a and the cyan photosensitive drum 3b. An example of Pb is shown.

  In FIG. 9, the relative phase shift due to the rotation unevenness between the black photosensitive drum 3a and the cyan photosensitive drum 3b is shown. However, the black photosensitive drum 3a, magenta and yellow detection patterns are shown. The relative phase shift due to the rotation unevenness between Pc and Pd can be explained in the same manner.

  As shown in FIG. 9, when the black reference pattern Pa and the cyan photosensitive drum 3b have rotation irregularities, a state where the pitch is wide and a state where the pitch is narrow are periodically generated.

   In the black reference pattern Pa, the rotation unevenness is a black reference dense wave αa (see FIG. 10) that represents a periodic change in the amount of positional deviation indicating the positional deviation in the circumferential direction due to the peripheral speed V in the black reference pattern Pa. In the cyan, magenta, and yellow detection patterns Pb, Pc, and Pd, the period of the displacement amount that indicates the circumferential displacement due to the circumferential speed V in the cyan, magenta, and yellow detection patterns Pb, Pc, and Pd. Cyan, magenta, and yellow detection coarse / fine waves α (1), α (2), α (3) (see FIG. 10) representing the change in the image.

  FIG. 10 is a graph showing black reference dense waves αa and cyan, magenta, and yellow detected dense waves α (1), α (2), α (3).

  As shown in FIG. 10, when there is a relative phase shift among the black reference dense wave αa, the cyan detected coarse wave α (1), the magenta detected dense wave α (2), and the yellow detected coarse wave α (3), Color misregistration occurs and image quality deteriorates. That is, as the relative phase shift between the black reference dense wave αa, the cyan detected dense wave α (1), the magenta detected dense wave α (2), and the yellow detected dense wave α (3) increases, Deviations among the black reference pattern Pa, the cyan detection pattern Pb, the magenta detection pattern Pc, and the yellow detection pattern Pd increase, and the influence on the image increases accordingly.

[About the detector]
The detection unit 302 periodically detects the black reference density wave αa, the cyan detection density wave α (1), the magenta detection density wave α (2), and the yellow detection density wave α (3) every correction execution period.

  The black reference density wave αa, cyan detection density wave α (1), magenta detection density wave α (2), and yellow detection density wave α (3) are inventions already filed by the present applicant (Japanese Patent Laid-Open No. 2009-251109). ) Sine curve fitting calculation formula. Therefore, detailed description of the detection of the black reference dense wave αa, the cyan detected coarse wave α (1), the magenta detected coarse wave α (2), and the yellow detected coarse wave α (3) is omitted here.

  The detection of the black reference dense wave αa, the cyan detection coarse wave α (1), the magenta detection coarse wave α (2), and the yellow detection coarse wave α (3) is limited to detection by a sine curve fitting calculation formula. Instead, other known methods may be used.

[Calculation section]
(Regarding the arithmetic unit in the case of the configuration of the first drive unit)
In the case of the configuration of the first driving device 100a, the calculation unit 303a detects the results detected by the detection unit 302 (black reference density wave αa, cyan detection density wave α (1), magenta detection density wave α (2), and yellow detection density). Calculation values θe (1), θe (2), θe (3) for correcting the relative phase shift based on the data on the wave α (3) are periodically calculated every correction execution period. The calculated values θe (1), θe (2), and θe (3) are stored in the storage unit 320a.

  Specifically, the calculation unit 303a uses the relative phase angle θ (1) of the cyan detected dense wave α (1) with respect to the black reference dense wave αa as the calculated value θe (1), and the magenta detected dense wave α with respect to the black reference dense wave αa. The relative phase angle θ (2) of (2) is the calculated value θe (2), and the relative phase angle θ (3) of the yellow detected coarse / fine wave α (3) with respect to the black reference dense wave αa is the calculated value θe (3). The calculation is periodically performed for each correction period.

(Regarding the arithmetic unit in the case of the configuration of the second drive unit)
Further, in the case of the configuration of the second driving device 100b, the calculation unit 303b detects the results detected by the detection unit 302 (black reference density wave αa, cyan detection density wave α (1), magenta detection density wave α (2), and yellow. A calculation value θe (see FIG. 11) for correcting the relative phase shift is periodically calculated every correction execution period on the basis of the data on the detected dense wave α (3). The calculated value θe is stored in the storage unit 320b.

  Specifically, since the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d in the second group photosensitive member 30b rotate in conjunction with each other, the cyan, magenta, and yellow photosensitive members are rotated. The relative phase shift due to rotation unevenness cannot be adjusted between the drums 3b, 3c, and 3d, and between the black photosensitive drum 3a and the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d. The relative phase shift due to the rotation unevenness cannot be adjusted. Therefore, the calculation unit 303b determines the reference density based on the relative deviation amounts of the cyan detection density wave α (1), the magenta detection density wave α (2), and the yellow detection density wave α (3) with respect to the black reference density wave αa. A single relative phase angle θ with respect to the wave αa is calculated as a calculated value θe periodically every correction execution period. Here, the calculated value θe is the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the second group photoconductor 30b (the rotations of the cyan, magenta, and yellow photoconductor drums 3b, 3c, and 3d that cannot be adjusted to each other). Each relative phase shift (relative shift amount) with respect to (unevenness) can be a value for specifying an optimum one.

[About correction unit]
[Regarding Correction Unit in Case of Configuration of First Driving Device]
In the case of the configuration of the first drive device 100a, the correction unit 304a controls the operation of at least one of the reference drive unit 110 and the first detection drive unit 120b based on the control value θc (1) (see FIG. 18). At least one of the reference drive unit 110 and the second detection drive unit 120c is controlled based on θc (2) (see FIG. 19), and the reference drive unit 110 and the second detection drive unit 120c are controlled based on the control value θc (3) (see FIG. 19). At least one of the three detection drive units 120d is controlled to correct the relative phase shift. The control values θc (1), θc (2), and θc (3) are stored in the storage unit 320a.

  Specifically, the correction unit 304a controls the operation of at least one of the reference driving unit 110 and the first detection driving unit 120b based on the control value θc (1) to be used as the black photosensitive drum 3a (reference image photosensitive drum). Relative phase shift between the periodic fluctuation of the corresponding peripheral speed V and the periodic fluctuation of the peripheral speed V corresponding to the cyan photosensitive drum 3b (detection image photosensitive drum) is corrected. The correction unit 304a controls the operation of at least one of the reference driving unit 110 and the second detection driving unit 120c based on the control value θc (2), and the periodic variation of the peripheral speed V corresponding to the black photosensitive drum 3a. The relative phase shift from the periodic fluctuation of the peripheral speed V corresponding to the magenta photosensitive drum 3c is corrected. Further, the correction unit 304a periodically controls at least one of the reference drive unit 110 and the third detection drive unit 120d based on the control value θc (3) to periodically rotate the peripheral speed V corresponding to the black photosensitive drum 3a. The relative phase shift between the fluctuation and the periodic fluctuation of the peripheral speed V corresponding to the yellow photosensitive drum 3d is corrected.

[Correction unit in the case of the configuration of the second drive unit]
In the case of the configuration of the second drive device 100b, the correction unit 304b corrects the relative phase shift by controlling the operation of at least one of the reference drive unit 110 and the detection drive unit 120 based on the control value θc. The control value θc is stored in the storage unit 320b.

  Specifically, the correction unit 304b controls the operation of at least one of the reference driving unit 110 and the detection driving unit 120 based on the control value θc, and periodically changes the peripheral speed V corresponding to the black photosensitive drum 3a. The relative phase shift from the periodic fluctuation of the peripheral speed V corresponding to the two group photoreceptors 30b is corrected. The control value θc is stored in the storage unit 320b.

(Rotation phase adjustment of photosensitive drum)
FIG. 11 is a timing chart showing detection signals of the reference detection phase sensor 170a and the detection phase sensors 170b, 170c, 170d, and 170e. FIG. 12 is a timing chart showing the operation timing of the output signals to the detection drive units 120b, 120c, 120d, 120 with respect to the output signal to the reference drive unit 110 that drives the black photosensitive drum 3a. FIG. 12A shows relative phase angles θ (1), θ (2) in which the phases of the cyan, magenta, and yellow photoconductor drums 3b, 3c, and 3d are optimum with respect to the phase of the black photoconductor drum 3a. ), Θ (3), and θ are advanced. FIG. 12B shows relative phase angles θ (1), θ (2) in which the phases of the cyan, magenta, and yellow photoconductor drums 3b, 3c, and 3d are optimum with respect to the phase of the black photoconductor drum 3a. ), Θ (3), and θ are delayed. FIG. 12C shows a state after correcting the relative phase shift between the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d. Show. In FIGS. 11 and 12, the configuration of the first drive device 100a and the configuration of the second drive device 100b are shown in one view.

(Rotational phase adjustment of the photosensitive drum in the case of the configuration of the first driving device)
In the case of the configuration of the first driving device 100a, as shown in FIG. 11, the correction unit 304a includes a detection signal Tk of the reference phase detection sensor 170a that detects the phase of the black photoconductor 3a, and the cyan photoconductor drum 3b. By adjusting the detection timing Tpb with the detection signal Tcb of the first phase detection sensor 170b for detecting the phase of the black, the relative phase shift between the rotation unevenness of the black photoconductor drum 3a and the rotation unevenness of the cyan photoconductor drum 3b. And the detection timing Tpc of the detection signal Tk and the detection signal Tcc of the second phase detection sensor 170c are adjusted, so that the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the magenta photosensitive drum 3c are reduced. And the detection timing Tpd between the detection signal Tk and the detection signal Tcd of the third phase detection sensor 170d is adjusted. It is to correct the relative phase shift between the rotation unevenness of the rotational irregularity and yellow photosensitive drum 3d of the black photosensitive drum 3a.

  Specifically, the correction unit 304a adjusts the stop timings of the reference drive unit 110, the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d after the image formation illustrated in FIG. Execute stop operation.

   For example, as shown in FIG. 12A, the phases of the cyan, magenta, and yellow photoconductive drums 3b, 3c, and 3d are respectively relative phase angles θ (1), θ to the phase of the black photoconductive drum 3a. If the state is advanced by (2), θ (3), the stop operation of the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d is set to θ by the stop operation of the reference drive unit 110, respectively. By advancing (1), θ (2), and θ (3), as shown in FIG. 12C, the rotation unevenness of the black photosensitive drum 3a and the cyan, magenta, and yellow photosensitive drums 3b and 3c are obtained. , 3d and relative phase shift with the rotation unevenness can be corrected appropriately.

  Conversely, as shown in FIG. 12B, the phases of the cyan, magenta, and yellow photoconductor drums 3b, 3c, and 3d are respectively relative phase angles θ (1) and θ1 with respect to the phase of the black photoconductor drum 3a. If the state is delayed by θ (2) and θ (3), the stop operation of the first detection drive unit 120b, the second detection drive unit 120c, and the third detection drive unit 120d is respectively less than the stop operation of the reference drive unit 110. By delaying by θ (1), θ (2), θ (3), as shown in FIG. 12C, the rotation unevenness of the black photosensitive drum 3a and the cyan, magenta, and yellow photosensitive drums 3b, The relative phase shift from the rotation unevenness of 3c and 3d can be corrected, respectively.

  One of the black photosensitive drum 3a and the cyan photosensitive drum 3b, one of the black photosensitive drum 3a and the magenta photosensitive drum 3c, the black photosensitive drum 3a, and the yellow photosensitive drum. After stopping any one of the body drums 3d, the relative phase angles θ (1), θ (2), and θ (3) are similarly corrected after k rotations (k is an integer of 2 or more). By applying and stopping each, the correction of the relative phase shift between the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d may be performed.

  If the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d are in an optimum relative phase angle with respect to the black photosensitive drum 3a, as shown in FIG. , Stop both at the same time. Alternatively, one of the black photosensitive drum 3a and the cyan photosensitive drum 3b, one of the black photosensitive drum 3a and the magenta photosensitive drum 3c, the black photosensitive drum 3a, and the yellow photosensitive drum. One of the photosensitive drums 3d is stopped and then the other is stopped after rotating k times, so that the black photosensitive drum 3a and the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d are relative to each other. Both can be stopped without changing the phase relationship.

(Rotational phase adjustment of the photosensitive drum in the case of the configuration of the second driving device)
In the case of the configuration of the second drive device 100b, the correction unit 304b detects the detection signal Tk of the reference phase detection sensor 170a that detects the phase of the black photoconductor 3a and the phase of the second group photoconductor 30b. By adjusting the detection timing Tp with the detection signal Tc of the detection phase detection sensor 170e, the relative phase shift between the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the second group photoconductor 30b is corrected.

  Specifically, the correction unit 304b performs a stop operation for adjusting the stop timing of the reference drive unit 110 and the detection drive unit 120 after the image formation illustrated in FIG.

  For example, as shown in FIG. 12A, if the phase of the second group photoconductor 30b is advanced by an optimum relative phase angle θ with respect to the phase of the black photoconductor drum 3a, the detection drive unit 120 is used. By stopping the stop operation of the reference driving unit 110 by θ, the relative rotation between the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the second group photoconductor 30b as shown in FIG. The phase shift can be corrected appropriately.

  Conversely, as shown in FIG. 12B, if the phase of the second group photoconductor 30b is delayed by an optimum relative phase angle θ with respect to the phase of the black photoconductor drum 3a, the detection drive unit By delaying the stop operation of 120 by θ from the stop operation of the reference drive unit 110, as shown in FIG. 12C, the rotation unevenness of the black photosensitive drum 3a and the rotation unevenness of the second group photoconductor 30b. Relative phase shift can be corrected.

  The black photosensitive drum 3a and the second group photosensitive member 30b are stopped, and then the relative phase angle θ is similarly corrected and stopped after the k-th rotation, so that the black photosensitive drum is stopped. The relative phase shift between the rotation unevenness 3a and the rotation unevenness of the second group photoconductor 30b may be corrected.

  If the second group photoconductor 30a has an optimum relative phase angle with respect to the black photoconductor drum 3a, both are stopped simultaneously as shown in FIG. Alternatively, either one of the black photosensitive drum 3a and the second group photosensitive member 30b is stopped, and then the other is stopped after rotating k times, whereby the black photosensitive drum 3a and the second group photosensitive member 30b are stopped. Both of them can be stopped without changing the relative phase relationship.

(Control configuration of correction unit)
(Control configuration of the correction unit in the case of the configuration of the first drive unit)
In the case of the configuration of the first drive device 100a, the correction unit 304a, in the initial state, uses the calculated values θe (1), θe (2), and θe (3) as control values θc (1), θc (2), and θc, respectively. As (3), when the relative phase shift is periodically corrected every correction execution period and the calculated values θe (1), θe (2), and θe (3) can be regarded as unchanged, the calculated value θe (1) , Θe (2), θe (3) are shifted to a control value holding state in which the relative phase shift is corrected with the same control value.

(Control configuration of the correction unit in the case of the configuration of the second drive unit)
In the case of the configuration of the second drive device 100b, in the initial state, the correction unit 304b periodically corrects the relative phase shift for each correction execution period with the calculated value θe as the control value θc, and the calculated value θe does not change. In the control value holding state in which the relative phase shift is corrected with the same control value as the calculated value θe.

(Details of control configuration of correction unit)
Specifically, the storage units 320a and 320b store in advance a plurality (here, eight) of divided angle ranges R (1) to R (8), a first specified number of times Na, and a second specified number of times Nb described later. To do. Here, the first specified number of times Na and the second specified number of times Nb are set to the same number here. For this reason, the first prescribed number Na and the second prescribed number Nb are not distinguished, and will be described simply as the prescribed number N.

  FIG. 13 is a schematic diagram showing details of the storage areas of the storage units 320a and 320b. FIG. 13A shows the storage unit 320a in the case of the configuration of the first drive device 100a, and FIG. 13B shows the storage unit 320b in the case of the configuration of the second drive device 100b. Yes.

  The storage units 320a and 320b shown in FIG. 13 have a storage area M1 that stores a plurality of segment angle ranges R (1) to R (8) and a storage area M2 that stores a prescribed number N. doing.

  As shown in FIG. 13, the plurality of segment angle ranges R (1) to R (8) in the storage area M1 include a black reference density wave αa, a cyan detection density wave α (1), and a magenta detection density wave α (2). In addition, the angle (360 °) of one cycle of the yellow detected coarse / dense wave α (3) is equally divided into j pieces (here, divided every 45 °).

  In the example of FIG. 13, the segment angle range R (1) is greater than −22.5 ° and less than or equal to 22.5 ° (calculated value θe (1) = 0 °: median value), and the segment angle range R ( 2) is greater than 22.5 ° and 67.5 ° or less (calculated value θe (2) = 45 °), and the segment angle range R (3) is greater than 67.5 ° and 112.5 °. (Calculation value θe (3) = 90 °), and the segment angle range R (4) is greater than 112.5 ° and 157.5 ° or less (calculation value θe (4) = 135 °). The segment angle range R (5) is greater than 157.5 ° and 202.5 ° or less (calculated value θe (5) = 180 °), and the segment angle range R (6) is greater than 202.5 °. 247.5 ° or less (calculated value θe (6) = 225 °), and the segment angle range R (7) is greater than 247.5 ° and 92.5 ° or less (calculated value θe (7) = 270 °), and the segment angle range R (8) is greater than 292.5 ° and not more than 337.5 ° (calculated value θe (8) = 315 °).

  Further, the specified number N of times in the storage area M2 is that the calculated values θe (1), θe (2), θe (3), θe are any one of a plurality of segment angle ranges R (1) to R (8). It defines the number of times of entering the segment angle range continuously.

  Then, in the initial state, the correction unit 304a has the calculated values θe (1), θe (2), and θe (3) N consecutive times a predetermined number of times in the plurality of segment angle ranges R (1) to R (8). Then, when it falls within the same segment angle range, it shifts to the control value holding state. Further, in the initial state, the correction unit 304b holds the control value when the calculated value θe falls within the same segment angle range N consecutive times N times among the plurality of segment angle ranges R (1) to R (8). Transition to the state.

  In the present embodiment, in the control value holding state, the correction unit 304a has the calculated values θe (1), θe (2), and θe (3) as the control values θc (1), θc (2), and θc (3), respectively. If the calculated values θe (1), θe (2), and θe (3) can be regarded as changes due to changes in relative phase shift, the control values θc (1), θc ( 2) and θc (3) are changed to operation values θe (1), θe (2), and θe (3), respectively, and the same control values as the operation values θe (1), θe (2), and θe (3) are used. Maintain the control value holding state. Further, when the calculated value θe is different from the control value θc in the control value holding state, the correction unit 304b determines that the calculated value θe is a change caused by a change in relative phase shift. Is changed to the calculated value θe, and the control value holding state is maintained with the same control value as the calculated value θe.

  Specifically, in the control value holding state, the correction unit 304a determines that the calculated values θe (1), θe (2), and θe (3) are the control values θc (1), θc (2), and θc (3), respectively. If they are different, the calculated values θe (1), θe (2), and θe (3) are within the same segment angle range N times a predetermined number of times among the plurality of segment angle ranges R (1) to R (8). Then, the control values θc (1), θc (2), θc (3) are changed to the calculated values θe (1), θe (2), θe (3), respectively, and the calculated values θe (1), θe ( 2) The control value holding state is maintained with the same control value as θe (3). In addition, when the calculated value θe is different from the control value θc in the control value holding state, the correction unit 304b has the calculated value θe N times the predetermined number of times in the plurality of segment angle ranges R (1) to R (8). Then, when it falls within the same segment angle range, the control value θc is changed to the calculated value θe, and the control value holding state is maintained with the same control value as the calculated value θe.

  In the storage unit 320a, the frequency history H (1), H (2), H (3) is further stored in the storage area M5, and the state information G (1), G (2), G (3) is stored in the storage area M6. ) Is stored. Further, in the storage unit 320b, the number history H is stored in the storage area M5, and the state information G is stored in the storage area M6.

  The frequency histories H (1), H (2), H (3), and H are calculated values θe (1), θe (2), θe (3), and θe are divided into angular ranges R (1) to R ( 8) and counting within the same segment angle range. Each state information G (1), G (2), G (3), G indicates which state is currently in the initial state or the control value holding state.

  In the control value holding state, the correction units 304a and 304b cancel the control value holding state when an external factor that can be considered that the relative phase shift is changed occurs.

  Specifically, the correction unit 304a returns the state information G (1), G (2), G (3) to the initial state when an external factor that can be regarded as a change in the relative phase shift occurs, and the count history H (1), H (2), H (3) are cleared (to zero). Further, when an external factor that can be considered that the relative phase shift changes is generated, the correction unit 304b returns the state information G to the initial state and clears the count history H (to zero).

  Here, the external factors include maintenance such as replacement of at least one of the black photosensitive drum 3a, the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d, and reference driving. Maintenance of at least one of the unit 110 and the detection drive units 120b, 120c, 120d, and 120 and at least one of forcibly executing a correction operation for relative phase shift.

  Specifically, when external factors are recognized by the control units 300a and 300b, a black photosensitive drum 3a, a cyan photosensitive drum 3b, a magenta photosensitive drum 3c, and a yellow photosensitive drum are set by an operator such as a serviceman. When at least one of the photosensitive drum and the detection driving units 120b, 120c, 120d, and 120 is replaced, a reset signal SN1 as an input operation from the operation unit 115 (see FIG. 6) by an operator such as a serviceman is generated. When the signal is input to the processing unit 310 or when the relative phase shift correction operation is forcibly executed, the correction forcible execution signal SN2 notifying that the correction operation has been forcibly executed is processed by the processing units 310 of the control units 300a and 300b. The case where it inputs to can be illustrated.

  FIG. 14 is a plan view showing a reset screen displayed on the display unit 117 in the operation unit 115 of the color image forming apparatus D shown in FIG. FIG. 15 is a plan view showing a forced correction execution screen displayed on the display unit 117 in the operation unit 115 of the color image forming apparatus D shown in FIG.

  As shown in FIGS. 14 and 15, 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 here. 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 user.

  The reset signal SN1 sets the state information G (1), G (2), G (3), G to the “initial state” and sets the frequency history H (1), H (2), H (3), H to “ In this state, as shown in FIG. 14, the control units 300a and 300b are instructed by an operator's instruction in the state in which the mode is shifted to the simulation mode by the input operation of the input key 116a provided in the operation unit 115. To the processing unit 310.

  That is, on the reset screen displayed on the display unit 117, the first display button BT1 that transmits the reset signal SN1 to the processing unit 310 or the second display button BT2 that does not transmit the reset signal SN1 to the processing unit 310 is displayed on the screen. Selected by touch operation. FIG. 14 shows a state where the first display button BT1 is selected. When the reset signal SN1 is transmitted to the processing unit 310, the reset signal SN1 is transmitted to the processing unit 310 by operating the execution key EXE when the first display button BT1 is in the reverse display state. This reset screen is a replacement of at least one of the black photosensitive drum 3a, the cyan photosensitive drum 3b and the magenta photosensitive drum 3c, the yellow photosensitive drum, and the detection drive units 120b, 120c, 120d, and 120. Can be operated during

  Note that the reset signal SN1 may be a signal that automatically notifies the replacement from the photosensitive unit or the drive unit.

  The correction forced execution signal SN2 (see FIG. 6) is a signal indicating that the relative phase shift correction operation is forcibly executed. Here, as shown in FIG. 15, the input key provided on the operation unit 115 is input. In the state where the operation mode is shifted to the simulation mode by the input operation 116a, it is transmitted to the processing unit 310 of the control units 300a and 300b according to the instruction of the operator.

  That is, on the correction forced execution screen displayed on the display unit 117, the third display button BT3 that forcibly executes the correction operation of the relative phase shift and transmits the correction forced execution signal SN2 to the processing unit 310, or the relative phase shift The fourth display button BT4 that does not forcibly execute the correction operation and does not transmit the correction forcible execution signal SN2 to the processing unit 310 is selected by a touch selection operation on the screen. FIG. 15 shows a state where the third display button BT3 is selected. When the compulsory execution of the relative phase shift correction operation is performed and the correction compulsory execution signal SN2 is transmitted to the processing unit 310, the execution key EXE is operated when the third display button BT3 is in the reverse display state. The correction forced execution signal SN2 is transmitted to the processing unit 310.

   Note that the reset screen and the forced correction execution screen shown in FIGS. 14 and 15 are normally used in the production process during maintenance work by a service person, but are not limited thereto.

(About the storage unit)
As shown in FIG. 13, in the storage unit 320a, the storage area M1 stores in advance the segment angle ranges R (1) to R (8), and the storage area M2 stores the specified number of times N in advance. Calculation values θe (1), θe (2), and θe (3) are stored in M3, and control values θc (1), θc (2), and θc (3) are stored in the fourth storage area M4. In the storage unit 320b, the storage area M1 stores the segment angle ranges R (1) to R (8), the storage area M2 stores the specified number of times N, and the control value θc in advance. The calculated value θe is stored in the area M3, and the braking / controlling value θ is stored in the fourth storage area M4.

  In the present embodiment, in the case of the configuration of the first drive device 100a, the correction unit 304a has the calculated values θe (1), θe (2), θe (3), and control values stored in the storage unit 320a. θc (1), θc (2), θc (3), number history H (1), H (2), H (3) and state information G (1), G (2), G (3) are overwritten Update. Further, the correction unit 304b overwrites and updates the calculated value θe, the control value θc, the number history H, and the state information G stored in the storage unit 320b.

  In the present embodiment, the specified number of times N can be changed. FIG. 16 is a plan view showing a specified number of times setting input screen displayed on the display unit 117 in the operation unit 115 of the color image forming apparatus D shown in FIG.

  Here, the prescribed number N is transmitted to the control units 300a and 300b in accordance with an instruction from the operator in a state where the simulation mode has been entered by an input operation of the input key 116a provided on the operation unit 115.

  That is, in the specified number of times setting input screen displayed on the display unit 117, the setting is changed by an input operation to the input key 116a or an arrow key on the screen (increase +1 with the upper key KY1 or decrease -1 with the lower key KY2). Is done. When the specified number N is set to a value displayed on the screen, the specified number N is stored in the storage area M2 of the storage units 320a and 320b by operating the execution key EXE.

  The specified number N is usually set to 2 or more. However, when it is necessary to correct the calculated value as the control value every time, the specified number N can be set to 1. In addition, the specified number of times input screen shown in FIG. 16 is normally used in the production process during maintenance work by a service person, but is not limited thereto.

[Example of control by the control unit]
Next, a control example of the control unit 300a in the case of the configuration of the first driving device 100a in the color image forming apparatus D will be described with reference to FIGS.

  FIG. 17 is a flowchart illustrating a flow of an example of a relative phase shift correction operation process by the control unit 300a in the case of the configuration of the first driving device 100a in the color image forming apparatus D illustrated in FIG. In addition, although the control part 300a in the case of the structure of the 1st drive device 100a is demonstrated here, calculated value (theta) e (1), (theta) e (2) also about the control part 300b in the case of the structure of the 2nd drive device 100b. ), Θe (3) and the control values θc (1), θc (2), θc (3) can be described in the same manner by simply setting the calculated value θe and the control value θc.

  18 to 20 are data tables that show changes in data in the storage unit 320a in time series in the relative phase shift correction operation processing shown in FIG. FIG. 18 shows a data table of relative phase shift correction with cyan detected dense wave α (1) for black reference dense wave αa, and FIG. 19 shows magenta detected dense wave α (2) for black reference dense wave αa. FIG. 20 shows a data table for correcting the relative phase shift between the black reference dense wave αa and the yellow detected coarse / fine wave α (3).

  In FIGS. 18 to 20, “Free” and “Lock” in the state information G (1), G (2), and G (3) mean “initial state” and “control value holding state”, respectively. . 18 to 20, the determination results of the step S5, S7, S10, and S12 of the condition determination shown in FIG. 17 are also shown in time series.

  In this processing example, the predetermined number N stored in advance in the storage area M2 of the storage unit 320 will be described as “5”.

  As shown in FIG. 17, first, the processing state of the correction operation is set to the initial state. At this time, the operation values θe (1), θe (2), θe (3) are “reset”, and as shown in the first row of the tables of FIGS. 18 to 20, the frequency histories H (1), H ( 2), H (3) are set to “0”, the state information G (1), G (2), G (3) is set to “Free”, and their calculated values θe (1), θe (2), θe (3), frequency history H (1), H (2), H (3) and status information G (1), G (2), G (3) are stored in storage areas M3, M5, M6 of the storage unit 320a, respectively. To remember.

  Next, the reference pattern Pa and the detection patterns Pb, Pc, and Pd are formed by the pattern forming unit 301 (step S2), and the reference dense wave αa of the reference pattern Pa and the detection patterns Pb, Pc, and P are detected by the detection unit 302. Pd detection coarse waves α (1), α (2), α (3) are detected (step S3), and the arithmetic operation unit 303a detects the detected coarse waves α (1), α (2), The relative phase angles θ (1), θ (2), θ (3) of α (3) are calculated as calculated values θe (1), θe (2), θe (3) (step S4).

  Next, it is determined whether or not the number history H (1), H (2), H (3) is “0” (step S5).

  If the number history H (1), H (2), H (3) is “0” in step S5 (step S5: YES (see, for example, the first row (S5) in the tables of FIGS. 18 to 20) )), “1” is added to the frequency history H (1), H (2), H (3) (step S6), and the process proceeds to step S9.

  On the other hand, when the frequency history H (1), H (2), H (3) is not “0” in step S5 (step S5: NO (for example, the second level of the table of FIGS. 18 to 20 (S5)). Calculated values θe (1), θe (2), θe (3) (refer to the calculated values θe (1), θe (2), θe (3) (refer to FIG. That is, it is determined whether or not it is the same as the previous calculation value (step S7).

  In step S7, the calculated values θe (1), θe (2), and θe (3) are stored in the storage area M3 of the storage unit 320a, and the previous calculated values θe (1), θe (2), and θe (3). (Step S7: YES (see, for example, the fifth level (S7) in the table of FIG. 18, the third level (S7) in the table of FIG. 19), and the eighth level (S7) in the table of FIG. 20). )), The process proceeds to step S6. On the other hand, the calculated values θe (1), θe (2), and θe (3) are the previous calculated values θe (1), θe (2), and θe (3) stored in the storage area M3 of the storage unit 320a. Are different (step S7: NO (for example, refer to the second row (S7) in the tables of FIGS. 18 to 20)), the frequency history H (1), H (2), and H (3) are set to “ 1 "(step S8), the process proceeds to step S9.

  Next, the calculation values θe (1), θe (2), θe (3) and the number history H (1), H (2), H (3) are overwritten on the storage areas M3, M5 of the storage unit 320a. It is updated (step S9), and it is determined whether or not the number of times history H (1), H (2), H (3) is the prescribed number N (step S10).

  If the number of times history H (1), H (2), H (3) is not the prescribed number N in step S10 (step S10: NO (for example, refer to the first stage (S10) in the tables of FIGS. 18 to 20)) ), Without updating the state information G (1), G (2), G (3) (step S11), the state information G (1), G (2), G (3) is “Free” (initial It is determined whether or not (state) (step S12).

  If the state information G (1), G (2), G (3) is not “Free” (initial state) in step S12 (ie, “Lock” (control value holding state)) (step S12: NO (for example, refer to the 9th step (S12) in the table of FIG. 18, the 7th step (S12) of the table of FIG. 19 and the 16th step (S12) of the table of FIG. 20)), the control values θc (1), θc (2) Without changing θc (3) (step S13), the process proceeds to step S16.

  Further, when the state information G (1), G (2), G (3) is “Free” (initial state) in step S12 (step S12: YES (for example, 1 in the tables of FIGS. 18 to 20). Step (see S12))), and the process proceeds to step S15.

  Further, when the number of times history H (1), H (2), H (3) is the prescribed number N in step S10 (step S10: YES (for example, the eighth row (S10) in the table of FIG. 18) 19) (see Table 6 (S10) and Table 15 in FIG. 20 (S10))), status information G (1), G (2), G (3) is “Lock” (holds control value) State), the number of times history H (1), H (2), H (3) is overwritten and updated in the storage area M5 of the storage unit 320a (step S14), and the process proceeds to step S15.

  Next, the calculated values θe (1), θe (2), and θe (3) are set as control values θc (1), θc (2), and θc (3), and the control values for the storage area M4 of the storage unit 320a. θc (1), θc (2), and θc (3) are overwritten and updated (step S15), and the correction unit 304a corrects the relative phase shift based on the control values θc (1), θc (2), and θc (3). (Step S16).

  Next, it is determined whether or not the correction execution period has arrived (step S17). If the correction execution period has arrived (step S17: YES), the process proceeds to step S2, while the correction execution period has arrived. If not (step S17: NO), it is determined whether or not there is a reset signal SN1 or a correction forced execution signal SN2 (step S18).

  If there is the reset signal SN1 or the correction forced execution signal SN2 in step S18 (step S18: YES), the state information G (1), G (2), G (3) is set to “Free” (initial state), The count history H (1), H (2), H (3) is set to “0”, and the state information G (1), G (2), G (3) is stored for the storage areas M6, M5 of the storage unit 320a. In addition, the frequency history H (1), H (2), and H (3) are overwritten and updated (step S19), and the process proceeds to step S2.

  Further, when there is no reset signal SN1 or forced correction execution signal SN2 in step S18 (step S18: NO), the processing from step S17 to step S20 is executed until an instruction to end the processing (step S20: NO). If there is an instruction to end the process (step S20: YES), the process ends.

  As described above, according to the color image forming apparatus D according to the present embodiment, the calculated values θe (1), θe (2), θe (3), θe are used as the control values θc (1), θc (2 ), Θc (3), θc, in the initial state in which the relative phase shift is periodically corrected every correction execution period, the correction units 304a, 304b are operated values θe (1), θe (2), θe (3). , Θe can be regarded as unchanged, the control value shifts to a control value holding state in which the relative phase shift is corrected with the same control value as the calculated values θe (1), θe (2), θe (3), θe. In the control value holding state, reliable calculation values θe (1), θe (2), θe (3), and θe are reflected as control values θc (1), θc (2), θc (3), and θc. A state. Therefore, even if it is affected by sudden various noises and the like, it is possible to eliminate inappropriate (accidental) phase information, and thereby the control value θc (1), The relative phase shift can be corrected by θc (2), θc (3), and θc.

  In the present embodiment, the correction units 304a and 304b, in the initial state, have the calculated values θe (1), θe (2), θe (3), and θe in the divided angle ranges R (1) to R (8). Since the control value holding state is entered when entering the same segment angle range N times the specified number of times, in the initial state, the calculated values θe (1), θe (2), θe (3), θe are Control values θc (1), θc (2), θc (3), θc with a simple control configuration that counts within the same segment angle range among the segment angle ranges R (1) to R (8). Can be defined.

  Further, in the present embodiment, the correction units 304a and 304b have the calculated values θe (1), θe (2), θe (3), and θe as the control values θc (1) and θc (2) in the control value holding state. ), Θc (3), and θc are different from each other when the calculated values θe (1), θe (2), θe (3), and θe can be regarded as a change caused by a change in relative phase shift. The control values θc (1), θc (2), θc (3), θc are changed to the calculated values θe (1), θe (2), θe (3), θe, and the calculated value calculated values θe (1), Since the control value holding state is maintained with the same control values as θe (2), θe (3), and θe, the reliable calculation values θe (1), θe (2), θe (3), and θe are the control values θc. (1), θc (2), θc (3), in the control value holding state that can be said to be reflected as θc, the operation value θe (1), Until it is determined that e (2), θe (3), and θe, the current reliability is confirmed with the calculated values θe (1), θe (2), θe (3), and θe. Thus, the relative phase shift can be corrected by the highly reliable control values θc (1), θc (2), θc (3), and θc.

  Further, in the present embodiment, the correction units 304a and 304b have the calculated values θe (1), θe (2), θe (3), and θe as the control values θc (1) and θc (2) in the control value holding state. ), Θc (3), and θc are different from the calculated values θe (1), θe (2), θe (3), and θe by the specified number of times N in the divided angle ranges R (1) to R (8). When continuously entering the same segment angle range, the control values θc (1), θc (2), θc (3), θc are changed to the calculated values θe (1), θe (2), θe (3), θe. Since the control value holding state is maintained with the same control value as the calculated values θe (1), θe (2), θe (3), and θe, the calculated values θe (1), θe ( 2), a simple control structure for counting that θe (3) and θe are within the same segment angle range among the segment angle ranges R (1) to R (8). In the control value θc (1), θc (2), θc (3), it is possible to define the reliability of .theta.c.

  Further, in the present embodiment, the correction units 304a and 304b cancel the control value holding state when an external factor that can be considered that the relative phase shift is changed in the control value holding state. When the deviation can be considered to change, the control value holding state can be quickly released and the initial state can be shifted.

  In the present embodiment, the storage units 320a and 320b store the calculated values θe (1), θe (2), θe (3), and θe, and the count history H (1), H (2), H (3 ), State information G (1), G (2), G (3) and control values θc (1), θc (2), θc (3), θc are stored. ), Θe (2), θe (3), θe and the reliability of the control values θc (1), θc (2), θc (3), θc can be compared with each numerical value.

  In the present embodiment, the correction units 304a and 304b return the state information to the initial state when an external factor that can be regarded as a change in the relative phase shift occurs, and the frequency histories H (1), H (2), Since H (3) is cleared, the control values θc (1), θc (2), θc (3), and θc should be changed to appropriate values when it can be considered that the relative phase shift clearly changes due to external factors. Is possible.

  In the present embodiment, the external factor is maintenance such as replacement of at least one of the black photosensitive drum 3a, the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, and the yellow photosensitive drum 3d. And at least one of performing maintenance such as replacement of at least one of the reference driving unit 110 and the detection driving units 120b, 120c, 120d, and 120, and forcibly executing the correction operation of the relative phase shift. Therefore, the black photosensitive drum 3a, the cyan photosensitive drum 3b, the magenta photosensitive drum 3c, the yellow photosensitive drum 3d, and the reference driving unit 110 that directly influence the change in relative phase shift. And maintenance such as replacement of the detection drive units 120b, 120c, 120d, 120, and strong correction operation Possible to change the control value to a proper value to run become.

  In the present embodiment, since the specified number N can be changed, the frequency of sudden influences in which the relative phase shift changes due to the influence of various noises, such as differences in the user environment, etc. Accordingly, the prescribed number N can be changed.

  In the present embodiment, the correction units 304a and 304b are operated values θe (1), θe (2), θe (3), θe, and a frequency history H (1) stored in the storage units 320a and 320b. , H (2), H (3) and state information G (1), G (2), G (3) are overwritten and updated, so that it is not necessary to store all past information or the latest or neighboring information. Therefore, the memory capacity of the storage units 320a and 320b can be reduced.

  In the present embodiment, in the case of the configuration of the first driving device 100a, the relative phase shifts of the cyan, magenta, and yellow photosensitive drums 3b, 3c, and 3d with respect to the reference image photosensitive drum 3a are separately determined. The phase can be controlled while comparing the reliability. For this reason, it is possible to correct individual relative phase shifts with highly reliable control values, and as a result, it is possible to reduce image misalignment.

  Further, in the present embodiment, in the case of the configuration of the second driving device 100b, even if there are a plurality of detection patterns, the detected dense waves α (1), α (2), α (3 ) Can be set to one value, and the memory capacity of the storage unit can be reduced accordingly.

  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 a reference image carrier)
3b Cyan photoreceptor drum (an example of a detection image carrier)
3c Photosensitive drum for magenta (an example of a detection image carrier)
3d yellow photosensitive drum (an example of a detection image carrier)
7 Intermediate transfer belt (an example of a recording medium)
30a First group photoconductor (an example of a first group image carrier)
30b Second group photoconductor (an example of a second group image carrier)
110 Reference drive unit 120 Detection drive unit 120b First detection drive unit 120c Second detection drive unit 120d Third detection drive unit 301 Pattern forming unit 302 Detection unit 303a Calculation unit 303b Calculation unit 304a Correction unit 304b Correction unit 320a Storage unit 320b Storage Part D Image forming apparatus G Status information G (1) Status information G (2) Status information G (3) Status information H Count history H (1) Count history H (2) Count history H (3) Count history N Specified count Pa Black reference pattern (an example of reference pattern)
Pb Cyan detection pattern (an example of a plurality of detection patterns)
Pc Magenta detection pattern (an example of multiple detection patterns)
Pd yellow detection pattern (an example of a plurality of detection patterns)
R (1) Section angle range R (2) Section angle range R (3) Section angle range R (4) Section angle range R (5) Section angle range R (6) Section angle range R (7) Section angle range R (8) Division angle range V Peripheral velocity αa Black reference dense wave α (1) Cyan detected dense wave α (2) Magenta detected dense wave α (3) Yellow detected dense wave θ Relative phase angle θ (1) Relative phase angle θ (2) Relative phase angle θ (3) Relative phase angle θe Calculated value θe (1) Calculated value θe (2) Calculated value θe (3) Calculated value θc Control value θc (1) Control value θc (2) Control value θc (3) Control value

Claims (12)

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 periodically forming a plurality of patterns corresponding to the plurality of image carriers on the recording medium every correction execution period;
A detector that periodically detects a relative phase shift of a plurality of coarse and dense waves, each representing a periodic change in a positional shift amount indicating a positional shift in a circumferential direction due to the peripheral speed in the plurality of patterns, for each correction execution period; ,
A calculation unit that periodically calculates a calculation value for correcting the relative phase shift based on a result detected by the detection unit for each correction execution period;
A correcting unit that corrects the relative phase shift by controlling the driving unit based on a control value for controlling the driving of the plurality of driving units;
A storage unit for storing the control value,
In an initial state, the correction unit periodically corrects the relative phase shift for each correction execution period using the calculated value as the control value, and when the calculated value can be regarded as not changing, The control value is held in the control value holding state for correcting the relative phase shift with the same control value. When an external factor that can be considered that the relative phase shift changes in the control value holding state, the control value holding state is generated. And
The image forming apparatus according to claim 1, wherein the external factor includes at least one of maintenance of the image carrier, maintenance of the driving unit, and forced execution of the relative phase shift correction operation . The image forming apparatus according to claim 1,
In the control value holding state, when the calculated value is different from the control value, the correction unit determines that the calculated value is a change caused by a change in the relative phase shift. The image forming apparatus is characterized in that the control value holding state is maintained with the same control value as the calculated value by changing the value to the calculated value. An image forming apparatus according to claim 1 or claim 2,
The storage unit stores in advance a plurality of segment angle ranges obtained by segmenting one cycle angle of the dense wave, and the calculated value is continuously within one of the plurality of segment angle ranges. Pre-store the first specified number of times that defines the number of times to enter,
In the initial state, the correction unit shifts to the control value holding state when the calculated value falls within the same segment angle range for the first predetermined number of times among the plurality of segment angle ranges. An image forming apparatus. The image forming apparatus according to claim 3 , wherein
The image forming apparatus, wherein the first specified number of times can be set and changed. The image forming apparatus according to claim 3 or 4 , wherein:
The storage unit stores in advance a second specified number of times that defines the number of times that the calculated value continuously enters any one of the plurality of segment angle ranges.
When the calculated value is different from the control value in the control value holding state, the correction unit has the calculated value within the same segment angle range for the second specified number of times in the plurality of segment angle ranges. Upon entering the image forming apparatus, the control value is changed to the calculated value, and the control value holding state is maintained at the same control value as the calculated value. The image forming apparatus according to claim 5 , wherein
The image forming apparatus, wherein the second specified number of times can be set and changed. An image forming apparatus according to any one of claims 3 to 6 ,
The storage unit includes the calculated value, a history of the number of times that the calculated value is within the same segment angle range among the plurality of segment angle ranges, and the current state among the initial state and the control value holding state. An image forming apparatus that stores state information indicating in which state. The image forming apparatus according to claim 7 ,
The image forming apparatus, wherein the correction unit overwrites and updates the calculation value, the frequency history, and the state information stored in the storage unit. The image forming apparatus according to claim 7 or 8 , wherein
The image forming apparatus according to claim 1, wherein the correction unit returns the state information to the initial state and clears the frequency history when an external factor that can be considered to change the relative phase shift occurs. An image forming apparatus according to any one of claims 1 to 9 , wherein
The drive unit has a plurality of drive units that respectively rotate the plurality of image carriers at a constant peripheral speed,
The pattern forming unit is configured to detect a reference pattern corresponding to any one of the plurality of image carriers at each circumferential pitch and corresponding to the remaining detection image carriers. A pattern is periodically formed on the recording medium for each pitch for each correction execution period,
The detection unit includes a reference dense wave representing a periodic change in a displacement amount indicating a displacement in the circumferential direction due to the circumferential velocity in the reference pattern, and a circumferential displacement due to the circumferential velocity in the detection pattern. Detecting detected dense and dense waves that represent periodic changes in the amount of misregistration periodically detected for each correction execution period,
The calculation unit periodically calculates a relative phase angle of the detected coarse / fine wave with respect to the reference coarse / fine wave as the calculation value for each correction execution period,
The correction unit controls the operation of at least one of a reference drive unit that drives the reference image carrier and a detection drive unit that drives the detection image carrier in the plurality of drive units, and corresponds to the reference image carrier. An image forming apparatus that corrects a relative phase shift between the periodic fluctuation of the peripheral speed and the periodic fluctuation of the peripheral speed corresponding to the detected image carrier. An image forming apparatus according to any one of claims 1 to 9 , wherein
Among the plurality of image carriers, a first group image carrier including a reference image carrier and a plurality of detection image carriers among the remaining image carriers, and the plurality of detection image carriers are interlocked with each other. A rotating second group image carrier,
The drive unit includes a reference drive unit that rotates the first group image carrier at a constant peripheral speed, and a detection drive unit that rotates the second group image carrier at the peripheral speed.
The pattern forming unit records the reference pattern corresponding to the reference image carrier for each pitch in the circumferential direction and the plurality of detection patterns respectively corresponding to the plurality of detection image carriers for the pitch. It is regularly formed on the medium for each correction period,
The detection unit includes a reference dense wave that represents a periodic change in a displacement amount indicating a displacement in the circumferential direction due to the circumferential velocity in the reference pattern, and a circumferential direction due to the circumferential velocity in the plurality of detection patterns. A plurality of detected dense and dense waves each representing a periodic change in a positional deviation amount indicating a positional deviation are periodically detected for each correction execution period,
The calculation unit periodically calculates a relative phase angle with respect to the reference coarse wave as the calculation value based on a relative deviation amount of the plurality of detected coarse waves with respect to the reference coarse wave, for each correction execution period,
The correction unit controls the operation of at least one of the reference driving unit and the detection driving unit to periodically change the peripheral speed corresponding to the reference image carrier and the second group image carrier. An image forming apparatus that corrects a relative phase shift from a periodic variation in peripheral speed. The image forming apparatus according to claim 1 0 or claim 1 1,
The reference image carrier is for performing black image formation,
The image forming apparatus, wherein the detection image carrier is for performing color image formation.

Images