JP2016126270A - Image formation apparatus and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus and a method of controlling the same that can eliminate a phase difference in a stop state of each image carrier under simple driving control even if phase differences of a plurality of image carriers are accumulated as a printing job is repeated.SOLUTION: An image formation apparatus that comprises a plurality of image carriers forming a plurality of images respectively, and superposes a plurality of images one over another on a recording medium controls and drives the plurality of image carriers to rotate, detects phases of the plurality of image carriers, and determines a speed reduction pattern of speed change up to a stop of the image carriers for each driving means according to differences of the phases detected at the end of printing.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus and a control method thereof.

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

  In the tandem type image forming apparatus, in order to accurately control the position of each color image, the phase of each image carrier is controlled to rotate and stop. In order to always perform such phase control, it is necessary to control the phase of each image carrier at the start of printing. Therefore, if the phase at the time of stopping each image carrier after the end of the print job is different, the waiting time for detecting and controlling the phase of each image carrier at the start of the next printing becomes long.

  Therefore, in Patent Document 1, control is performed such that the phase difference of each image carrier is within a predetermined range by changing the stop start timing of each image carrier at the end of printing. As a result, since the phase of each image carrier in the stopped state is appropriately controlled, it is not necessary to control the phase of the image carrier at the start of the next printing, and the time until the start of printing can be shortened. It was.

Japanese Patent Laying-Open No. 2005-077786

  Even in such a conventional technique, a minute phase difference may occur during the operation of stopping the rotation of the image carrier. In actual use of the image forming apparatus, a difference occurs in the number of operations and the number of rotations of the image carrier while switching between monochrome printing and color printing. Therefore, a minute phase shift accumulates by repeating the print job. It will be. Accumulation of this phase shift may interfere with accurate phase control.

  In particular, a black (K) image carrier for monochrome printing is driven by one driving means, and three image carriers for yellow (Y), magenta (M), and cyan (C) for color printing are combined. In the case of driving with one driving means, the load applied to the monochrome driving means and the color driving means is different, and therefore, the accumulated difference in phase shift tends to increase.

  Therefore, the present invention provides an image formation that can eliminate the phase difference in a stopped state of each image carrier by simple drive control even when the phase differences in a plurality of image carriers are accumulated by repeating a print job. An object is to provide a device and a control method thereof.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a plurality of image carriers that respectively form a plurality of images, and superimposes the plurality of images on a recording medium. A plurality of drive means for rotating the plurality of image carriers, a drive control means for controlling the plurality of drive means, and a phase detection means for detecting the phases of the plurality of image carriers, the drive control means comprising: A deceleration pattern, which is a speed change until the image carrier is stopped, is determined for each of the driving means according to the phase difference detected by the phase detecting means at the end of printing.

  In the image forming apparatus of the present invention, the drive control unit starts the deceleration of the plurality of drive units at substantially the same timing.

In the image forming apparatus of the present invention, the drive control unit selects the deceleration pattern of the combination that eliminates the phase difference in the plurality of image carriers. The image forming apparatus of the present invention Then, the deceleration pattern is selected from a combination of speed changes that cause a phase change of 45 degrees to each other.

  In the image forming apparatus of the present invention, the drive control unit selects a reference deceleration pattern as the deceleration pattern of the one image carrier, and the other image carrier based on the reference deceleration pattern and the phase difference. The deceleration pattern of the body is selected.

  In the image forming apparatus of the present invention, the image carrier on which the reference deceleration pattern is selected is for black printing.

  On the other hand, in the control method of the image forming apparatus of the present invention, the control method of the image forming apparatus includes a plurality of image carriers that respectively form a plurality of images, and superimposes the plurality of images on a recording medium. A plurality of image carriers are controlled and rotated, the phases of the plurality of image carriers are detected, and the speed change until the image carrier is stopped according to the phase difference detected at the end of printing. A certain deceleration pattern is determined for each of the driving means.

  In the image forming apparatus and the control method thereof according to the present invention, the plurality of image carriers are controlled and rotated, the phases of the plurality of image carriers are detected, and according to the phase difference detected at the end of printing, A deceleration pattern, which is a speed change until the image carrier is stopped, is determined for each driving unit. Therefore, by simply selecting a deceleration pattern according to the phase difference, the amount of rotation from the start point to the end point of rotation stop can be made different for each image carrier, and a rotation amount difference corresponding to the phase difference can be generated. it can. Thereby, even when a print job is repeated and phase differences in a plurality of image carriers are accumulated, an image forming apparatus capable of eliminating the phase difference in a stopped state of each image carrier by simple drive control, and The control method can be provided.

1 is a schematic cross-sectional view illustrating a schematic configuration of an image forming apparatus. 2A is a schematic side view showing the configuration of the photosensitive drum 3, and FIG. 2B is a schematic end view showing the configuration of the photosensitive drum 3. The flowchart which shows slow-down control in 1st Embodiment. An example of the table which shows the angle rotated from the deceleration start in each deceleration pattern to a rotation stop. The conceptual diagram explaining the deceleration pattern selection in 1st Embodiment, and elimination of a phase shift. The conceptual diagram explaining the deceleration pattern selection in 2nd Embodiment, and elimination of a phase shift. The conceptual diagram explaining the deceleration pattern selection in 2nd Embodiment, and elimination of a phase shift. The flowchart which shows slow-down control in 3rd Embodiment. The conceptual diagram explaining the deceleration pattern selection in 3rd Embodiment, and elimination of a phase shift.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, a configuration example of an image forming apparatus to which the present invention is applied will be described.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of the image forming apparatus according to the present embodiment. An image forming apparatus 100 shown in FIG. 1 forms a toner image on a sheet P such as recording paper using toner.

  The apparatus main body 110 includes an image carrier (here, a photosensitive drum) 3, a charging unit (here, a charger) 5 for charging the surface of the photosensitive drum 3, and an electrostatic latent image on the photosensitive drum 3. An exposure device (here, an exposure unit) 1 for forming, a developing device (here, a developing device) 2 for visualizing the electrostatic latent image with toner and forming a toner image on the photosensitive drum 3, and an intermediate Transfer is performed by a transfer member (here, an intermediate transfer belt) 61, a primary transfer device (here, an intermediate transfer roller) 64 that temporarily transfers the toner image on the photosensitive drum 3 onto the intermediate transfer belt 61, and an intermediate transfer roller 64. A primary cleaning device (cleaner unit here) 4 that removes residual toner remaining on the surface of the photosensitive drum 3 without being transferred, and a secondary transfer device that transfers the toner image on the intermediate transfer belt 61 onto the sheet P Here, a secondary transfer unit) 10, a secondary cleaning device (here, an intermediate transfer belt cleaning unit) 65 that removes residual toner remaining on the surface of the intermediate transfer belt 61 without being transferred by the secondary transfer unit 10, and a sheet A fixing device 7 is provided that fixes the toner image formed on P by heating and melting and fixing the toner image on the sheet P.

  In addition to the above configuration, the image forming apparatus 100 includes a conveyance path S for a sheet P, a pair of conveyance rollers 12a to 12d disposed along both sides of the conveyance path S, and an original reading apparatus that reads an image of an original. (Scanner device here) 90, a document placing table 92 on which a document is placed, and an automatic document processing device 120.

  A document reading device 90 is provided on the upper portion of the apparatus main body 110. A document placing table 92 made of transparent glass is provided on the upper side of the document reading device 90, and an automatic document processing device 120 is attached on the upper side of the document placing table 92. The automatic document processing device 120 automatically conveys the document onto the document reading device 90. Further, the automatic document processing device 120 is rotatable about a pivot shaft along the document conveyance direction so that the document can be manually placed by opening the document placing table 92. It has become. As a result, the document reading device 90 can read the image of the document conveyed by the automatic document processing device 120 or the image of the document placed on the document placing table 92.

  The image forming apparatus 100 forms multicolor and single color images on the sheet P in accordance with image data corresponding to the document read by the document reading device 90 or image data transmitted from the outside. It is configured.

  More specifically, image data handled in the image forming apparatus 100 corresponds to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a single color ( For example, it corresponds to a monochrome image using black). Accordingly, four each of the developing device 2, the photosensitive drum 3, the charger 5, the cleaner unit 4, and the intermediate transfer roller 64 are provided to form four types of images corresponding to the respective colors.

  That is, these four members are set to black, cyan, magenta, and yellow, respectively, and an image station is configured by these members.

  The charger 5 is a charging unit for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. As the charger 5, a contact type charger (for example, a roller type or a brush type) or a charger type charger as shown in FIG. 1 can be used.

  The exposure unit 1 has a function of forming an electrostatic latent image corresponding to image data on the surface by exposing the surface of the charged photosensitive drum 3 according to input image data. . Specifically, the exposure unit 1 includes a polygon mirror that scans a laser beam and optical elements such as a lens and a mirror for guiding the laser beam reflected by the polygon mirror to the photosensitive drum 3.

  As the exposure unit 1, a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror, or a writing device (for example, a writing head) in which light emitting elements such as EL and LED are arranged in an array can be used.

  The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toners of four colors (Y, M, C, K). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  An intermediate transfer belt unit 6 is disposed above the photosensitive drum 3. The intermediate transfer belt unit 6 includes an intermediate transfer belt driving roller 62 and an intermediate transfer belt driven roller 63 in addition to the intermediate transfer belt 61, the intermediate transfer roller 64, and the intermediate transfer belt cleaning unit 65 described above.

  The intermediate transfer belt driving roller 62, the intermediate transfer roller 64, the intermediate transfer belt driven roller 63, and other rollers stretch and support the intermediate transfer belt 61, and the surface of the intermediate transfer belt 61 is directed in a predetermined direction (in the direction of arrow D in the figure). ) Can be moved.

  The intermediate transfer roller 64 is rotatably supported on the side opposite to the photosensitive drum 3 with the intermediate transfer belt 61 interposed therebetween. The intermediate transfer roller 64 gives a transfer bias to the intermediate transfer belt 61 for the toner image on the photosensitive drum 3.

  The intermediate transfer belt 61 is provided so as to be in contact with each photosensitive drum 3, and each color toner image formed on the photosensitive drum 3 is sequentially superimposed and transferred onto the intermediate transfer belt 61. Thus, a color toner image (multicolor toner image) is formed on the intermediate transfer belt 61. Here, the intermediate transfer belt 61 is formed endlessly using a film having a thickness of about 100 μm to 150 μm.

  The toner image is transferred from the photosensitive drum 3 to the intermediate transfer belt 61 by an intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61 (that is, the side opposite to the photosensitive drum 3 of the intermediate transfer belt 61). Done. The intermediate transfer roller 64 has a high-voltage transfer bias for transferring the toner image to the intermediate transfer belt 61, that is, a high-voltage transfer having a polarity (for example, a positive electrode) opposite to the toner charging polarity (for example, a negative electrode). A bias is applied. Here, the intermediate transfer roller 64 is based on a rotating shaft made of a metal having a diameter of 8 mm to 10 mm (for example, stainless steel), and the surface thereof is made of a conductive elastic material (for example, a material such as EPDM or urethane foam). ). The intermediate transfer roller 64 can apply a high voltage uniformly to the intermediate transfer belt 61 by the conductive elastic material. In this embodiment, a roller-shaped transfer electrode is used. However, the present invention is not limited to this, and a brush-shaped electrode can also be used.

  As described above, the toner images visualized by the toners of the respective colors on the photosensitive drum 3 are stacked on the intermediate transfer belt 61. The toner images of the respective colors stacked in this manner are transferred onto the sheet P by the secondary transfer unit 10 disposed at a transfer portion where the sheet P and the intermediate transfer belt 61 face each other by the rotation of the intermediate transfer belt 61. .

  The intermediate transfer belt 61 and the transfer roller 10a of the secondary transfer unit 10 are pressed against each other to form a nip region. Further, the transfer roller 10a of the secondary transfer unit 10 has a voltage (that is, a polarity opposite to the charging polarity of the toner (for example, a negative electrode) for transferring the toner image of each color on the intermediate transfer belt 61 onto the sheet P, that is, For example, a positive electrode) voltage is applied. Further, in order to constantly obtain the nip region, either the roller of the secondary transfer unit 10 or the intermediate transfer belt drive roller 62 is made of a hard material such as a metal roller, and the other is a soft material such as an elastic roller. (For example, soft materials such as elastic rubber and foamable resin).

  By the way, the toner image of each color on the intermediate transfer belt 61 may not be completely transferred onto the sheet P by the secondary transfer unit 10, and the toner may remain on the intermediate transfer belt 61. This residual toner causes toner color mixing in the next step.

  Therefore, the intermediate transfer belt cleaning unit 65 is configured to remove and collect the residual toner. For example, the intermediate transfer belt cleaning unit 65 includes a cleaning blade that contacts the intermediate transfer belt 61 as a cleaning member. The cleaning blade is supported on the back side of the intermediate transfer belt 61 (that is, the side opposite to the intermediate transfer belt driven roller 63) at a position facing the intermediate transfer belt driven roller 63.

  The image forming apparatus 100 further includes a paper feed cassette 81 and a discharge unit 91. The sheet feeding cassette 81 is for storing sheets P used for image formation, and is a sheet feeding apparatus according to this embodiment provided on the lower side of the apparatus main body 110. In addition, the discharge unit 91 is provided on the upper portion of the apparatus main body 110, and is a discharge tray in the present embodiment. The discharge unit 91 is a tray for loading the image-formed sheet P face down.

  Further, the apparatus main body 110 is provided with a substantially S-shaped main conveyance path S1 for sending the sheet P of the paper feed cassette 81 to the discharge unit 91 via the secondary transfer unit 10 and the fixing device 7. .

  Further, a pickup roller 11a, a registration roller 13, a secondary transfer unit 10, and a fixing device 7 are disposed along the main conveyance path S1 from the paper feed cassette 81 to the discharge unit 91. The pickup roller 11a is pressed against the uppermost recording sheet (sheet P) of the sheet bundle of the paper feed cassette 81, and the uppermost recording sheet is pulled out by rotating the pickup roller 11a, and the recording sheet is moved to the main transport path S1. And carry.

  The conveyance rollers 12 a to 12 d are, for example, small rollers for promoting and assisting the conveyance of the sheet P, and are provided along the conveyance path S. The transport path S includes a switchback transport path S2 and a reverse transport path S3 in addition to the main transport path S1.

  The registration roller 13 temporarily stops the sheet P conveyed from the sheet feeding cassette 81 and aligns the leading end of the sheet P. The registration roller 13 has a function of conveying the sheet P in a timely manner in synchronization with the toner image on the intermediate transfer belt 61.

  The fixing device 7 fixes the unfixed toner image formed on the sheet P on the sheet P by heat-melting and fixing the image.

  In the image forming apparatus 100 described above, when a single-sided image formation is requested, first, the sheet P conveyed from the paper feed cassette 81 is conveyed to the registration roller 13 by the conveyance roller 12a in the main conveyance path S1. . Next, the sheet P is conveyed to the transfer portion in synchronization with the toner image on the intermediate transfer belt 61 by the registration roller 13. The toner image on the intermediate transfer belt 61 is transferred onto the sheet P conveyed to the transfer site by a transfer electric field applied to the secondary transfer unit 10. Thereafter, the sheet P passes through the fixing device 7, whereby the unfixed toner transferred onto the sheet P receives heat and pressure, and is melted, fixed, and fixed on the sheet. Thereafter, the sheet P on which the toner image is fixed is discharged onto the discharge portion 91 via the conveyance roller 12b.

  On the other hand, when requesting double-sided image formation, as described above, the single-sided image formation is completed, and the sheet P that has passed through the fixing device 7 is conveyed while being chucked by the conveyance roller 12b in the switchback conveyance S2. When the roller 12b rotates in the reverse direction, the roller 12b is transported to the reverse transport path S3 by the transport rollers 12c and 12d so that the upstream end in the transport direction before stopping is forward. The sheet P conveyed to the reverse conveyance path S3 is guided to the upstream side in the conveyance direction from the transfer portion by the conveyance rollers 12c and 12d, and then the image is formed on the back surface through the registration roller 13 and discharged to the discharge unit 91. Is done.

  2A is a schematic side view showing the configuration of the photosensitive drum 3, and FIG. 2B is a schematic end view. The photoconductor drum 3 includes a photoconductor portion 3a, a photoconductor drive gear 3b, a rib 3c, and a phase detection sensor 3d.

  The photoreceptor portion 3a is a substantially cylindrical member, and is a portion where an electrostatic latent image is formed by being charged by the charger 5. The photosensitive member driving gear 3b is a gear provided at one end of the photosensitive member portion 3a, and is a portion to which power of driving means such as a motor (not shown) is transmitted by a belt or a gear mechanism. The rib 3c is a protruding portion formed in the vicinity of the outer periphery of the photosensitive member driving gear 3b. The phase detection sensor 3d is a detection sensor including a light emitting element and a light receiving element, and detects the passage of the rib 3c when the light receiving state changes due to the passage of the rib 3c passing through the concave portion.

  When the power of driving means (not shown) is transmitted to the photosensitive member driving gear 3b, the photosensitive member portion 3a and the rib 3c are also rotationally driven together with the photosensitive member driving gear 3b. At this time, the rib 3c is rotated in the circumferential direction and periodically passes through the concave portion of the phase detection sensor 3d, and the phase detection sensor 3d generates a phase detection signal every time the rib 3c passes. Therefore, the combination of the rib 3c and the phase detection sensor 3d constitutes the phase detection means of the present invention. Here, an example is shown in which the phase detection means is configured by the phase detection sensor 3d having the rib 3c and the concave portion, but other configurations may be used as long as the phase of the photoconductor portion 3a can be detected. The phase detection unit may be configured using a reflection unit such as a mirror and a sensor that detects a change in reflectance.

  The rib 3c and the phase detection sensor 3d, which are phase detection means, may be provided on all the photosensitive drums 3 to detect all phases. Further, when the three colors of cyan (C), magenta (M), and yellow (Y) are rotationally driven by power from the same driving means, the CMY photosensitive drums 3 are always driven in the same phase state. Therefore, it is only necessary to detect a cyan (C) phase signal as a representative. Therefore, in such a case, phase detection means may be provided on the two photosensitive drums 3 of cyan (C) and black (K).

  The image forming apparatus of the present invention further includes a drive control unit that controls the rotational drive of the photosensitive drum 3 by the drive unit based on the phase detection signal detected by the phase detection unit. The drive control means includes a processing unit including a microcomputer such as a CPU (Central Processing Unit), and a storage means including a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a rewritable nonvolatile memory. Including.

  When the print job is finished, the drive control unit performs the slow-down control to stop the rotation drive control of the photosensitive drum 3 during the print job and to stop the rotation while gradually changing the rotation speed of the photosensitive drum 3. At this time, a deceleration pattern is determined from a pre-recorded table according to the phase difference of each photosensitive drum 3, and different slowdown control is performed according to the phase of the photosensitive drum 3.

  FIG. 3 is a flowchart showing the slow-down control in the first embodiment. Here, only the steps related to the slow-down control by the drive control means are described, and the description of phase control and the like during a normal print job is omitted.

When a color print job is started, each photosensitive drum 3 is rotated by a driving unit, and a phase detection signal is detected every time the rib 3c passes the phase detection sensor 3d. In step S _c1 , the drive control means recognizes the phase of the photosensitive drum 3 as, for example, a phase of 0 ° at the timing when the phase detection signal becomes the ON signal. The drive control unit counts the elapsed time from the timing when the phase detection signal becomes the on signal, and repeats the operation of resetting the elapsed time at the next on signal timing. The interval of the on-signal generation of the phase detection signal corresponds to a period in which the photosensitive drum 3 makes one round. Therefore, by measuring the elapsed time from the on-signal and calculating based on the rotational speed of the photosensitive drum 3, The phase (rotated angle) of the photosensitive drum 3 can be recognized according to the elapsed time.

In step S _c2 , the phase difference between the cyan (C), magenta (M), and yellow (Y) photosensitive drums 3 is calculated based on the phase detected by the black (K) photosensitive drum 3. To do. At this time, when CMY is rotationally driven by the same driving means, the phase of the representative C photosensitive drum 3 is calculated. When CMY is rotationally driven by individual driving means, phase detection and phase difference calculation are performed for the phase of each photosensitive drum 3.

Next, in step _Sc3 , it is determined whether or not the phase difference between the CMY photosensitive drums 3 with respect to the reference K photosensitive drum 3 is within a predetermined range as a phase control request determination. When the CMY photosensitive drums 3 are rotationally driven by individual driving means, the determination is performed for each driving means based on the phase difference determination result of each photosensitive drum 3. When the phase difference is within the predetermined range, the process _proceeds to step S _c4 , and when the phase difference exceeds the predetermined range, the process _proceeds to step S _c5 . For example, 45 ° is used as a reference phase difference as a criterion for determination, but any number of phase differences may be used as a reference.

In step S _c4 , a reference deceleration pattern is selected for the driving means that rotationally drives the K photoconductor drum 3. The reference deceleration pattern is also selected for the driving means of the photosensitive drum 3 whose phase difference is within an allowable range with respect to K. After storing the deceleration pattern of each driving means, the process _proceeds to step _Sc6 .

In step S _c5 , a reference deceleration pattern is selected for the driving means that rotationally drives the K photoconductor drum 3. For the driving means of the CMY photosensitive drum 3 whose phase difference is outside the allowable range with respect to K, a deceleration pattern different from the reference deceleration pattern is selected. At this time, in order to eliminate the phase difference calculated in step _Sc2 , a deceleration pattern is selected such that the rotation angle from the deceleration start to the rotation stop differs from the reference deceleration pattern by the phase difference. After selecting the deceleration pattern of each driving means and storing the setting, the process _proceeds to step _Sc6 .

In step S _c6 , a motor stop request for stopping the driving means for ending the color print job is determined. In the image forming apparatus 100, an ON signal is continued as a JOB signal during a print job, and the signal is switched to an OFF signal together with an instruction to end the print job. Further, as the JOB signal is switched off, the drum driving signal that has been continued for the driving means is switched off. In step S _c6 , when the drum drive signal is turned off, it is determined that there is a motor stop request, and the process _proceeds to step S _c7 . Judges no motor stop request when an ON signal of the drum drive continues to repeat the control loop of steps S _c6 proceeds to step S _c1. In the repeated control loop, the deceleration pattern selection in step S _c4 or S _c5 is repeated, and when a new deceleration pattern is selected, the latest deceleration pattern is updated and stored.

In step S _c7 , the drive control unit controls the rotation operation of each driving unit based on the deceleration pattern selected in step S _c4 or S _c5 , and slows down control for gradually decreasing the rotation speed of each photosensitive drum 3. I do. When the rotation of each photosensitive drum 3 is stopped, the color print job is completed.

  When the monochrome printing job is started, the black (K) photosensitive drum 3 is rotated by the driving unit, and the phase (rotated angle) of the photosensitive drum 3 is changed according to the elapsed time as in the color printing job. recognize. The drive control means stores the black (K) phase at the start of the monochrome print job as the previous phase.

The drive control means determines a motor stop request in step S _m1 during the color print job. When the drum drive signal is turned off, it is determined that there is a motor stop request, and the process proceeds to step _Sm2 . If the drum drive ON signal continues, it is determined that there is no motor stop request, the monochrome print job is repeated, and the control loop up to step S _m1 is repeated.

In step S _m2 , the drive control unit controls the rotation operation of the black (K) drive unit based on the reference deceleration pattern, and performs slow-down control for gradually decreasing the rotation speed of the black (K) photosensitive drum 3. Do. At this time, the drive control means calculates the rotation angle from the deceleration start to the rotation stop by the reference deceleration pattern, and calculates the deceleration start timing so that the rotation stops at the previous phase stored at the start of the monochrome print job. Then start deceleration. When the rotation of the black (K) photosensitive drum 3 is stopped, the monochrome print job is completed.

  Since the phase when the K photoconductor drum 3 is stopped does not change before and after the monochrome print job, the phase of the KDMY photoconductor drums 3 does not shift even under the condition where the color print job and the monochrome print job are mixed. .

  FIG. 4 is an example of a table showing the angle of rotation from the start of deceleration to the stop of rotation in each deceleration pattern recorded in advance in the drive control means. In this example, the deceleration patterns No. 1 to No. 8 are set to have different angles by 45 degrees. Further, a phase difference within a range of ± 22.5 degrees is set for each, and a deceleration pattern belonging to the range is selected. For example, when the phase difference is 57 degrees, the No. 1 deceleration pattern is selected, and when the phase difference is 118 degrees, the No. 3 deceleration pattern is selected.

  FIG. 5 is a conceptual diagram for explaining deceleration pattern selection and phase shift elimination according to the first embodiment. FIG. 5A shows a deceleration pattern stored in advance in the drive control means, the horizontal axis shows time, and the vertical axis shows the angular velocity in rotation of the photosensitive drum 3. The numbers shown on the horizontal axis are the deceleration pattern numbers shown in FIG. Each of the deceleration patterns No. 1 to 8 gradually decreases the angular velocity from the start of deceleration to the stop of rotation, but the rate of the deceleration is different, and the time required from the start of deceleration to the stop of the rotation and the angle of rotation differ between them. .

  In the first embodiment, the No. 1 deceleration pattern with the shortest time to stop rotation and the smallest rotation angle is used as the reference deceleration pattern. Further, the black (K) photosensitive drum 3 is always selected as the reference deceleration pattern No1, and the CMY photosensitive drum 3 is selected as appropriate deceleration patterns No2 to No.8 that eliminate the phase difference. In the overall drive control of the image forming apparatus, various controls are often performed with the black (K) photosensitive drum 3 as a reference. Therefore, it is preferable to always perform slow-down control of K with a reference deceleration pattern.

If the phase shift between K and CMY is within the set range in step S _c3 , the process _proceeds to step S _c4 and No. 1 of the reference deceleration pattern is selected for K and CMY. In this case, the photosensitive drums 3 for K and CMY start to decelerate at approximately the same timing in step _Sc7 and are decelerated to stop rotating with the No. 1 deceleration pattern. Accordingly, there is no change in the phase difference between the photosensitive drums 3.

If the phase shift is outside the set range in step S _c3 , the process _proceeds to step S _c5 , and No. 1 of the reference deceleration pattern is selected for K as shown in FIG. Further, as shown in FIG. 5C, an appropriate deceleration pattern for CMY is selected according to the phase difference between K and CMY. Here, a case where the phase difference is 180 ° ± 22.5 ° with respect to K is shown, and the No. 5 deceleration pattern is selected for CMY.

The K and CMY photosensitive drums 3 start to decelerate at substantially the same timing in step _Sc7 as shown in FIG. Further, the K photoconductor drum 3 is decelerated to the rotation stop by the No. 1 deceleration pattern, and the CMY photoconductor drum 3 is decelerated to the rotation stop by the No. 5 deceleration pattern. At this time, since the rotation angle from the start of deceleration to the rotation stop is 45 degrees for No1 and 225 degrees for No5, an angle difference of 180 degrees is generated to eliminate the phase difference. In the drawing, time is taken on the horizontal axis and angular velocity is taken on the vertical axis, so the amount of deviation that occurs from the start of deceleration to the stop of rotation corresponds to the area of the triangle shown in FIG.

As described above, a deceleration pattern is determined from a pre-recorded table in accordance with the phase difference of each photosensitive drum 3, and different slow-down control is performed in accordance with the phase of the photosensitive drum 3. The phase difference in the stop state of each image carrier can be eliminated by the control.
(Second Embodiment)
Next, a second embodiment of the present invention will be described. The description of the configuration common to the first embodiment is omitted. 6 and 7 are conceptual diagrams for explaining deceleration pattern selection and phase shift elimination according to the second embodiment.

  In the second embodiment, the No. 2 deceleration pattern with the second fastest time to stop rotation is used as the reference deceleration pattern. Further, the black (K) photosensitive drum 3 is always selected as the reference deceleration pattern No2, and the CMY photosensitive drum 3 is selected as an appropriate deceleration pattern No1 or No3 that eliminates the phase difference.

If the phase shift between K and CMY is within the set range in step S _c3 , the process _proceeds to step S _c4 and No2 of the reference deceleration pattern is selected for K and CMY. In this case, the photosensitive drums 3 K and CMY are decelerated until rotation is stopped at a deceleration pattern of No2 starting decelerated at substantially the same timing in step S _c7. Accordingly, there is no change in the phase difference between the photosensitive drums 3.

If the phase of CMY with respect to K is delayed in the range of 45 ° ± 22.5 ° in step S _c3 , in step S _c5 , K is the reference deceleration pattern as shown in FIG. The No. 2 deceleration pattern is selected, and for CMY, the No. 3 deceleration pattern is selected as shown in FIG.

The photosensitive drums 3 for K and CMY start to decelerate at approximately the same timing in step _Sc7 as shown in FIG. 6 (d). Further, the K photoconductor drum 3 is decelerated to the rotation stop by the No. 2 deceleration pattern, and the CMY photoconductor drum 3 is decelerated to the rotation stop by the No. 3 deceleration pattern. Therefore, the CMY photoconductor drum 3 rotates 45 degrees more than the K photoconductor drum 3 to cancel the phase delay and stop.

If the phase of CMY with respect to K is advanced in the range of 45 ° ± 22.5 ° in step S _c3 , the reference deceleration pattern is used for K in step S _{c5 as} shown in FIG. The No. 2 deceleration pattern is selected, and for CMY, the No. 1 deceleration pattern is selected as shown in FIG.

The K and CMY photosensitive drums 3 start to decelerate at substantially the same timing in step _Sc7 as shown in FIG. Further, the K photoconductor drum 3 is decelerated to the rotation stop by the No. 2 deceleration pattern, and the CMY photoconductor drum 3 is decelerated to the rotation stop by the No. 1 deceleration pattern. Accordingly, the CMY photoconductive drum 3 rotates 45 degrees less than the K photoconductive drum 3 to cancel the phase advance and stop.

The phase shift gradually accumulates as the print job is repeated. Therefore, in the slowdown control shown in FIG. 3, the phase shift determined in step _Sc3 is often the minimum phase difference between the deceleration patterns shown in FIG. Therefore, in the present embodiment, the reference deceleration pattern No. 2 is set as the K deceleration pattern, and the deceleration patterns No. 1 and No. 3 adjacent thereto are set as the CMY deceleration patterns to perform the slow-down control. Thereby, slow down control of K and CMY can be performed using only the deceleration patterns of No. 1 to No. 3, and the time required to stop the rotation can be shortened.
(Third embodiment)
Next, a third embodiment of the present invention will be described. The description of the configuration common to the first embodiment is omitted. FIG. 8 is a flowchart showing the slow-down control in the third embodiment. FIG. 9 is a conceptual diagram for explaining deceleration pattern selection and phase shift elimination according to the third embodiment.

When the color print job is started, each photosensitive drum 3 is rotated by the driving means, and a phase detection signal is detected every time the rib 3c passes the phase detection sensor 3d (step _Sc11 ).

In step Sc _12, based on the detected phase of the photosensitive drum 3 of the black black (K), cyan (C), magenta (M), yellow (Y) calculating a phase difference between the photosensitive drum 3 of each color To do.

Next, in step _Sc13 , as the phase control request determination, it is determined whether the phase difference of the CMY photosensitive drums 3 with respect to the reference K photosensitive drum 3 is within a predetermined range. When the phase difference is within the predetermined range, the _{process proceeds} to step S _c14 , and when the phase difference exceeds the predetermined range, the _{process proceeds} to step S _c15 .

In step S _c14 , No1 is selected as the reference deceleration pattern for the driving means that rotationally drives the K photoconductor drum 3. For the driving means of the photosensitive drum 3 whose phase difference is within an allowable range with respect to K, No1 is selected as the reference deceleration pattern. After storing the deceleration pattern of each driving means, the _{process proceeds} to step _Sc16 .

In step S _c15 , No1 is selected as the reference deceleration pattern and No2 is selected as the deceleration pattern on the phase lag side of the K and CMY photosensitive drums 3 on the phase advance side.

In step S _c16 , a motor stop request for stopping the driving means for ending the color print job is determined. If it is determined that there is a motor stop request, the _{process proceeds} to step S _c17 . If it is determined that there is no motor stop request, the _{process proceeds} to step S _c11 and the control loop up to step S _c16 is repeated. In the repeated control loop, the deceleration pattern selection in step S _c14 or S _c15 is repeated, and when a new deceleration pattern is selected, the latest deceleration pattern is updated and stored.

In step S _c17 , the drive control unit controls the rotation operation of each drive unit based on the deceleration pattern selected in step S _c14 or S _c15 , and slows down control for gradually decreasing the rotation speed of each photosensitive drum 3. I do. When the rotation of each photosensitive drum 3 is stopped, the color print job is completed.

When the monochrome print job is started, the drive control unit determines a motor stop request in step S _m11 during the color print job. If it is determined that there is a motor stop request, the _{process proceeds} to step _Sm12 . If it is determined that there is no motor stop request, the monochrome print job is repeated, and the control loop up to step S _m11 is repeated.

In step S _m12 , the drive control means controls the rotation operation of the black (K) drive means based on the No. 1 deceleration pattern as the reference deceleration pattern, and gradually increases the rotation speed of the black (K) photosensitive drum 3. Slow down control is performed. At this time, the drive control means calculates the rotation angle from the deceleration start to the rotation stop by the reference deceleration pattern, and calculates the deceleration start timing so that the rotation stops at the previous phase stored at the start of the monochrome print job. Then start deceleration. When the rotation of the black (K) photosensitive drum 3 is stopped, the monochrome print job is completed.

When the phase shift between K and CMY is within the set range, No1 of the reference deceleration pattern is selected for K and CMY. In this case, the photosensitive drums 3 for K and CMY start to decelerate at substantially the same timing in step _{Sc 17} and are decelerated to stop rotation with the No. 1 deceleration pattern. Accordingly, there is no change in the phase difference between the photosensitive drums 3.

  When the phase of CMY with respect to K is delayed in the range of 45 degrees ± 22.5 degrees, the No. 1 deceleration pattern as the reference deceleration pattern is selected for K as shown in FIG. In response to this, the deceleration pattern No. 2 is selected as shown in FIG. The photosensitive drums 3 for K and CMY start to decelerate at substantially the same timing as shown in FIG. Further, the K photoconductor drum 3 is decelerated to the rotation stop by the No. 1 deceleration pattern, and the CMY photoconductor drum 3 is decelerated to the rotation stop by the No. 2 deceleration pattern. Therefore, the CMY photoconductor drum 3 rotates 45 degrees more than the K photoconductor drum 3 to cancel the phase delay and stop.

  When the phase of CMY with respect to K is advanced in the range of 45 degrees ± 22.5 degrees, No. 2 of the deceleration pattern is selected for K as shown in FIG. As shown in FIG. 7C, the No. 1 deceleration pattern which is the reference deceleration pattern is selected. The photosensitive drums 3 for K and CMY start to decelerate at substantially the same timing as shown in FIG. Further, the K photoconductor drum 3 is decelerated to the rotation stop by the No. 2 deceleration pattern, and the CMY photoconductor drum 3 is decelerated to the rotation stop by the No. 1 deceleration pattern. Accordingly, the CMY photoconductive drum 3 rotates 45 degrees less than the K photoconductive drum 3 to cancel the phase advance and stop.

In this embodiment, of the K and CMY photosensitive drums 3, the reference deceleration pattern No 1 is selected as the deceleration pattern with the leading phase, and the slow deceleration pattern is selected with No 2 as the slow deceleration pattern. Do. Thereby, slow down control of K and CMY can be performed using only the deceleration patterns of No. 1 and No. 2, and the time required to stop the rotation can be further shortened. (Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. The description of the configuration common to the first embodiment is omitted. In the first to third embodiments, slowdown control is performed with the deceleration start timings of K and CMY being substantially the same.

  In this embodiment, the drive control means selects a deceleration pattern that can eliminate the phase difference from a pre-recorded table, calculates a phase difference that cannot be eliminated only by selecting the deceleration pattern, and corresponds to a phase difference that cannot be eliminated. The deceleration start timing of each photosensitive drum 3 is shifted as much as possible.

  For example, when the phase of K is 60 degrees later than CMY, the slow-down control shown in the first to third embodiments only eliminates the 45-degree phase difference and cannot eliminate the 15-degree phase difference. The photosensitive drum 3 stops. Therefore, the deceleration start timing of K is delayed by 15 degrees from CMY to further eliminate the phase difference.

  As described above, the deceleration pattern is determined from the pre-recorded table according to the phase difference of each photosensitive drum 3, the deceleration start timing is shifted, and different slowdown control is performed according to the phase of the photosensitive drum 3. Thus, the phase difference in the stopped state of each image carrier can be eliminated by simple drive control.

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus 110 ... Apparatus main body 1 ... Exposure unit 2 ... Developing apparatus 3 ... Photoconductor drum 3a ... Photoconductor part 3b ... Photoconductor drive gear 3c ... Rib 3d ... Phase detection sensor 5 ... Charger

Claims (7)

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 plurality of driving means for rotationally driving the plurality of image carriers;
Drive control means for controlling the plurality of drive means;
Phase detection means for detecting the phase of the plurality of image carriers,
The drive control unit determines, for each of the drive units, a deceleration pattern that is a speed change until the image carrier is stopped according to the phase difference detected by the phase detection unit at the end of printing. Image forming apparatus. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the drive control unit starts decelerating the plurality of drive units at substantially the same timing. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the drive control unit selects a combination of the deceleration patterns that eliminates the phase difference in the plurality of image carriers. The image forming apparatus according to claim 3, wherein
The image forming apparatus, wherein the deceleration pattern is selected from a combination of speed changes that cause a phase change of 45 degrees to each other. The image forming apparatus according to claim 3, wherein:
The drive control means selects a reference deceleration pattern as the deceleration pattern of one of the image carriers, and selects the deceleration pattern of another image carrier based on the reference deceleration pattern and the phase difference. An image forming apparatus. The image forming apparatus according to claim 3, wherein:
The image forming apparatus, wherein the image carrier on which the reference deceleration pattern is selected is for black printing. A control method of 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,
Controlling and rotating the plurality of image carriers,
Detecting the phase of the plurality of image carriers,
A control method for an image forming apparatus, wherein a deceleration pattern, which is a speed change until the image carrier is stopped, is determined for each of the driving units in accordance with the phase difference detected at the end of printing.

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