JP6418955B2 - Image forming apparatus and control method thereof - Google Patents

Description

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

  An image carrier such as a plurality of photosensitive drums corresponding to each of a plurality of images (for example, toner images) is rotated at a constant peripheral speed, and formed by an image forming process such as an electrophotographic method. 2. Description of the Related Art 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, a sheet). .

  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. However, if the photosensitive drum, which is an image carrier, is stopped at the same phase each time when the print job is finished, there is a problem that the same region facing the charging unit at the start of the print job is deteriorated.

  In order to solve this problem, in Patent Document 1 and Patent Document 2, the period from when the phase of the photosensitive drum is detected after the end of the print job to when the rotation of the photosensitive drum is stopped is changed to change the photosensitive drum. Is controlled so as to shift the phase at which printing stops at every print job.

JP 2008-076546 A JP 2012-018247 A

  FIG. 8 is a timing chart showing stop control of the photosensitive drum in the prior art. The time from the phase detection when the previous print job is stopped to the rotation stop is stored in advance as a stop timer. When the current print job ends and an OFF signal is generated, a phase detection signal is detected by a sensor or the like provided on each photosensitive drum. Thereafter, a current stop timer is generated by adding a predetermined time to the previous stop timer, and when the stop timer is turned off, the driving of the photosensitive drum is stopped. At this time, a stop timer which is a time from phase detection to drum drive stop is stored and used in the next print job end operation.

  By performing the rotation stop control of the photosensitive drum shown in FIG. 8, the stop position of the photosensitive drum after the end of the print job is gradually shifted, and even if the print job is repeated, the stop position is uniformly distributed over the entire circumference. In other words, the deterioration of the photoconductor can be prevented from proceeding locally at the same location.

  However, if such rotation stop control is performed, the phase detection is performed after the print job is completed, and the photosensitive drum drive is stopped after the stop timer elapses, and the idle rotation from the end of the print job to the drum drive stop is performed. The time t becomes long. In particular, the period from the end of the print job to the phase detection can be a maximum of nearly one revolution, and since the phase detection until the stop timer elapses, it can be a maximum of nearly one revolution. Could occur. In such a conventional technique, since the idling time from the end of the print job becomes long, it is difficult to stop the image forming apparatus quickly and power consumption increases.

  Therefore, the present invention can reduce the idling time from the end of the print job to the stop of rotation of the image carrier while controlling the phase so that the stop position of the image carrier is uniform and not locally biased. An object of the present invention is to provide an image forming apparatus and a control method thereof.

In order to solve the above problems, the image forming apparatus of 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. Drive means for rotationally driving the plurality of image carriers, drive control means for controlling the drive means, and detecting phases of the plurality of image carriers during a period in which the plurality of image carriers are rotationally driven. Phase detection means, and the drive control means generates a stop prohibition signal for prohibiting rotation stop of the drive means after a predetermined time has elapsed from the detection timing of the phase detection means, and avoids the stop prohibition signal. lasts for t _0, the drive control unit, said stopping said driving means at a timing when stop prohibition signal is not generated after the completion of printing, the drive control means, the detection data Storing period from timing until the rotation stop of the drive means as the previous stop angle, and sets the predetermined time based on the previous stop angle at the next drive.

  In the image forming apparatus according to the aspect of the invention, the drive control unit may stop the drive unit at the first time when the stop prohibition signal is not generated after the end of printing.

  In the image forming apparatus according to the aspect of the invention, the drive control unit may stop the drive unit at the time when the first stop prohibition signal is completed after printing is completed.

The image forming apparatus according to the present invention further includes a charging unit that charges the image carrier, and the avoidance time t ₀ corresponds to a period required for the region of the image carrier facing the charging unit to pass. It is characterized by doing.

In the image forming apparatus of the present invention, the avoidance time t ₀ is continued around the previous stop angle .

On the other hand, in the control method of the image forming apparatus according to 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. The plurality of image carriers are controlled and rotated, and the phases of the plurality of image carriers are detected during a period in which the plurality of image carriers are rotationally driven. After a lapse of time, a stop prohibiting signal for prohibiting rotation stop of the image carrier is generated, the stop prohibiting signal is continued for an avoidance time t ₀ , and the stop prohibiting signal is not generated after printing is completed. stopping the rotation of the image bearing member at the timing, the store period from the detection timing to the rotation stop of the image bearing member as the previous stop angle, based on the previous stop angle at the next drive And sets the serial predetermined time.

  In the image forming apparatus and the control method thereof according to the present invention, the phase of the image carrier is detected during a period in which the plurality of image carriers are rotationally driven, and after a predetermined time has elapsed from the phase detection timing, A stop inhibition signal for inhibiting rotation stop is generated. As a result, it is possible to reduce the idling time from the end of the print job to the stop of rotation of the image carrier while controlling the phase so that the stop position of the image carrier is uniform and not locally biased. An apparatus and a control method thereof 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. FIG. 4 is a timing chart showing drive control of the photosensitive drum 3 by a drive control unit. The timing chart which shows the case where the JOB signal turns off after the stop prohibition signal of the first embodiment. The timing chart which shows the case where the JOB signal turned off before the stop prohibition signal of 1st Embodiment. 6 is a flowchart for explaining a color print job and a monochrome print job of the image forming apparatus according to the first embodiment. The timing chart which shows the case where the JOB signal turns off after the stop prohibition signal of the second embodiment. The timing chart which shows the case where the JOB signal turned off before the stop prohibition signal of 2nd Embodiment. 9 is a flowchart for explaining a color print job and a monochrome print job of the image forming apparatus according to the second embodiment. 9 is a timing chart showing stop control of a photosensitive drum in the prior art.

(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 A transfer body (here, an intermediate transfer body 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 (here, a cleaner unit) 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, A fixing device 7 for fixing the toner image formed on the sheet P by heating and melting and fixing the toner image is provided.

  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 only for black (K) as a representative of the photosensitive drum 3, but may be provided for all the photosensitive drums 3 to detect all phases. Good. 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.

  3 and 4 are timing charts showing drive control of the photosensitive drum 3 by the drive control means. As shown in FIG. 3A, the JOB signal that has been continuously on during the print job is switched to the off signal together with the print job end instruction.

  As shown in FIG. 3 (b), the phase detection means continuously detects the passage of the rib 3c regardless of whether the JOB signal is on or off, and the phase detection signal becomes an on signal every time the rib 3c passes. Become. The drive control means recognizes the phase of the photosensitive drum 3 based on the timing when the phase detection signal becomes the ON signal, and uses it as a reference of timing for generating other signals, for example, with a phase of 0 °. 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, the phase of the photosensitive drum 3 according to the elapsed time ( Can be recognized.

As shown in FIG. 3 (c), the drive control means, recorded beforehand phase stopping of the photosensitive drum 3 in the previous print job as the previous stop angle theta _1, last stop angle theta ₁ at the stop prohibit timer A stop prohibition signal is generated only during a period of avoidance time t ₀ centering on. Therefore, the time that has elapsed from the phase detection signal on only (θ ₁ -t _0/2) to the predetermined time, only the avoidance time t ₀ from a predetermined time stop prohibition signal continues. Here, although in the generating the stop prohibition signal about the last stop angle theta _1, the period of avoidance time t ₀ may be generated as a stop prohibition signal based on the previous stop angle theta _1. For example, the center of the stop prohibition period may be set slightly before the previous stop angle θ ₁ or may be set slightly after.

Here, the avoidance time t _{0 that} is the period of the stop prohibition signal is determined by the area where the charger 5 as the charging means faces the photosensitive drum 3 and the rotational driving speed. The region where the charger 5 is opposed is a range where the photosensitive drum 3 deteriorates due to the influence of electrostatic radiation or the like. Therefore, the avoidance time t ₀ is set to twice the time required for the angle corresponding to the region, for example, a range of 43 °, to pass through the rotation drive. Here, an example of 43 ° is shown, but it may be set as appropriate depending on the configuration and size of the charging means.

  The timing chart shown in FIG. 3 shows a case where the timing when the JOB signal is turned off is within the period in which the stop prohibition signal is generated. At this time, as shown in FIG. 3D, the drive control means continues to drive the photosensitive drum 3 until the stop prohibiting signal of the stop prohibiting timer is turned off, and the drum driving is performed at the timing when the stop prohibiting signal is turned off. Switch off the signal.

  The drive control means stores the period from the phase detection signal until the drum drive signal is turned off as a new previous stop angle θ2, and sets the stop prohibit timer in the next print job as shown in FIG. Used for. For this reason, the period of the stop prohibition signal in the current print job is different from the period of the stop prohibition signal in the next print job.

The previous stop angles θ ₁ and θ ₂ are phases in which the photosensitive drum 3 is stopped in the print job, and the avoidance time t ₀ corresponds to twice the region where the charger 5 faces the photosensitive drum. Therefore, the region of the photosensitive drum 3 that faces the charger 5 at the rotation stop position does not overlap at the current stop and the next stop, and the deterioration of the photosensitive drum 3 can be prevented.

  FIG. 4A is a timing chart showing a case where the JOB signal is turned off after the stop prohibition signal. FIG. 4B is a timing chart showing a case where the JOB signal is turned off before the stop prohibition signal. As shown in FIG. 4, in the first embodiment, if the timing when the JOB signal is turned off is the stop inhibition signal off period, the drum drive signal is turned off.

The drive control means stores the period from the phase detection signal until the drum drive signal is turned off as a new previous stop angle θ ₂ and uses it for setting the stop prohibit timer in the next print job. For this reason, the period of the stop prohibition signal in the current print job and the period of the stop prohibition signal in the next print job do not overlap by more than half. Therefore, the region of the photosensitive drum 3 that faces the charger 5 at the rotation stop position does not overlap at the current stop and the next stop, and the deterioration of the photosensitive drum 3 can be prevented.

  Further, the phase detection means generates the phase detection signal and the stop prohibition signal regardless of whether the JOB signal is on or off, and the time from when the JOB signal is turned off until the phase detection can be omitted. Therefore, in the image forming apparatus of the present invention, it is possible to reduce the idling time until the photosensitive drum 3 stops rotating.

FIG. 5 is a flowchart illustrating a color print job and a monochrome print job of the image forming apparatus. When color image printing (color JOB) is selected as the printing mode of the image forming apparatus, the drive control means performs phase detection by means of the phase detection means of the photosensitive drums 3 for K, C, M, and Y in step S _c1. A detection signal is generated, and a stop prohibition signal of a stop prohibition timer is set based on the previous stop angle θ ₁ and the avoidance time t ₀ . This step S _c1 is repeatedly executed until there is a color print job end instruction.

When the end of the color print job is instructed, the process _proceeds to step _Sc2 , where the JOB signal is switched from on to off, and a request for stopping the motor as the driving means is issued. Next, the process proceeds to step _Sc3 , and it is determined whether the stop prohibition signal is on or off. When the stop prohibition signal is on, the process _proceeds to step S _c4 , and when it is off, the process _proceeds to step S _c5 .

In step S _c4 , the process waits until the stop prohibition signal of the stop prohibition timer is turned off. If the stop prohibition signal is turned off, the process _proceeds to step S _c5 . In step S _c5 , the drum driving signal is turned off to stop driving of the driving means, and the process _proceeds to step S _c6 . In step _Sc6 , the period from the phase detection signal ON to the drum drive signal OFF is stored as a new previous stop angle, and the color print job is completed.

When monochrome image printing (monochrome JOB) is selected as the print mode of the image forming apparatus, a print job is performed by the K photoconductor drum 3 until a monochrome print job end instruction is issued. When the end of the monochrome print job is instructed, the process _proceeds to step S _m1 , where the JOB signal is switched from on to off, and a request for stopping the motor as the driving means is issued. Next, the process proceeds to step S _m2 where the drum drive signal is turned off at the same phase as the previous stop position to stop the drive means and the monochrome print job is completed. In the case of a monochrome print job, since the previous stop angle and the current stop angle are in phase, the previous stop angle is not updated.

In an actual operation using the image forming apparatus, a color print job and a monochrome print job are selected and executed as needed. In the case of a monochrome print job, printing using only the black (K) photosensitive drum 3 is executed, so that the rotational driving is performed independently of the phase of the CMY photosensitive drums 3. In the monochrome print job, the stop prohibition period as shown in FIGS. 3 and 4 is not provided, and the stop position of the photosensitive drum 3 is set to the same position as the previous time, so that even in the condition where the color print job and the monochrome print job are mixed, The phase of the photosensitive drum 3 for each color of KCMY is not shifted. Further, since it is not necessary to control the phase of each CMY color during a monochrome print job, it is possible to prevent the photoconductive drums 3 for each CMY color from idling, reducing power consumption and the photoconductive drums 3 for each CMY color. Can be prevented.
(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. In the first embodiment, if the timing when the JOB signal is turned off is the period when the stop prohibition signal is turned off, the drum driving signal is switched off. However, in this embodiment, after the JOB signal is turned off, the drum driving signal is turned off at the timing when the stop prohibition signal is first switched from on to off. Also in the present embodiment, when the timing when the JOB signal is turned off is within the generation period of the stop prohibition signal, the drum drive signal is turned off at the timing when the stop prohibition signal is switched from on to off. Therefore, the timing chart is the same as that of the first embodiment shown in FIG.

  FIG. 6A is a timing chart showing a case where the JOB signal is turned off after the stop prohibition signal. FIG. 6B is a timing chart showing a case where the JOB signal is turned off before the stop prohibition signal.

  In the timing charts shown in FIGS. 6A and 6B, the timing when the JOB signal is turned off is outside the period in which the stop prohibition signal is generated. At this time, even if the JOB signal is turned off, the drive control means continues to drive the photosensitive drum 3 until the timing when the stop prohibition signal of the stop prohibition timer switches from the on signal to off, and at the timing when the stop prohibition signal turns off. Switch off the drum drive signal.

  As shown in FIG. 6A, when the JOB signal is turned off after the stop inhibition signal, the phase detection signal is turned on after the JOB signal is turned off, and then the stop inhibition signal is turned on and turned off again. The drum drive signal continues until

  However, as shown in FIG. 6B, when the JOB signal is turned off before the stop prohibition signal, the stop prohibition signal is turned on after the JOB signal is turned off. When the JOB signal is turned off again, the drum drive signal is turned off. Become. At this time, the time from the JOB signal being turned off to the phase detection can be omitted, and the idling time until the photosensitive drum 3 stops rotating can be shortened.

In the present embodiment, the period of the stop prohibition signal in the current print job and the period of the stop prohibition signal in the next print job are always different by half. Therefore, the region of the photosensitive drum 3 that faces the charger 5 at the rotation stop position does not overlap at the current stop and the next stop, and the deterioration of the photosensitive drum 3 can be prevented. Further, since the phase shift between the current print job and the next print job is always controlled so that half of the avoidance time t ₀ is shifted backward, the deterioration of the photosensitive drum 3 can be made uniform.

FIG. 7 is a flowchart illustrating a color print job and a monochrome print job of the image forming apparatus. When color image printing (color JOB) is selected as the print mode of the image forming apparatus, the drive control means performs phase detection by means of the phase detection means of the photosensitive drum 3 for each color of K, C, M, and Y in step _Sc11. A detection signal is generated, and a stop prohibition signal of a stop prohibition timer is set based on the previous stop angle θ ₁ and the avoidance time t ₀ . This step S _c11 is repeatedly executed until there is an instruction to end the color print job.

When the end of the color print job is instructed, the process _proceeds to step _Sc12 , where the JOB signal is switched from on to off, and a request for stopping the motor as the driving means is issued. Next, the process proceeds to step S _c13 and waits until the stop prohibition signal of the stop prohibition timer is turned from on to off. If the stop prohibition signal is switched from on to off, the _{process proceeds} to step S _c14 . In step S _c14 , the drum driving signal is turned off to stop driving of the driving means, and the _{process proceeds to} step S _c15 . In step _Sc15 , the period from the phase detection signal ON to the drum drive signal OFF is stored as a new previous stop angle, and the color print job is completed.

When monochrome image printing (monochrome JOB) is selected as the print mode of the image forming apparatus, a print job is performed by the K photoconductor drum 3 until a monochrome print job end instruction is issued. When the end of the monochrome print job is instructed, the process _proceeds to step S _m1 , where the JOB signal is switched from on to off, and a request for stopping the motor as the driving means is issued. Next, the process proceeds to step S _m2 where the drum drive signal is turned off at the same phase as the previous stop position to stop the drive means and the monochrome print job is completed. In the case of a monochrome print job, since the previous stop angle and the current stop angle are in phase, the previous stop angle is not updated.

In an actual operation using the image forming apparatus, a color print job and a monochrome print job are selected and executed as needed. In the case of a monochrome print job, printing using only the black (K) photosensitive drum 3 is executed, so that the rotational driving is performed independently of the phase of the CMY photosensitive drums 3. In the monochrome print job, the stop prohibition period as shown in FIGS. 3 and 6 is not provided, and the stop position of the photosensitive drum 3 is set to the same position as the previous time, so that even in the condition where the color print job and the monochrome print job are mixed, The phase of the photosensitive drum 3 for each color of KCMY is not shifted. Further, since it is not necessary to control the phase of each CMY color during a monochrome print job, it is possible to prevent the photoconductive drums 3 for each CMY color from idling, reducing power consumption and the photoconductive drums 3 for each CMY color. Can be prevented.
(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. In the present embodiment, the drive control when the timing when the JOB signal is turned off is the stop inhibition signal off period is switched by selecting either the first embodiment or the second embodiment.

  The image forming apparatus is provided with an input device such as a switch or a touch panel. Further, in the drive control means, control for switching the drum drive signal to OFF is set as the speed priority mode during the period in which the stop prohibition signal shown in FIG. 4 is OFF, and the stop prohibition signal shown in FIG. Control for switching off the drum drive signal at the timing of switching off is set as the uniform priority mode.

  A user or maintenance worker of the image forming apparatus selects and inputs whether the speed priority mode is the uniform priority mode using the input device. The drive control means controls the timing chart shown in FIG. 3 and FIG. 4 in the speed priority mode as the timing control when the JOB signal is turned off, and in FIG. 3 and FIG. 6 in the uniform priority mode. The timing chart shown is controlled.

Accordingly, it is possible to select whether to give priority to shortening the idling period until the rotation of the photosensitive drum 3 is stopped or to give priority to uniform deterioration of the photosensitive drum 3.
(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 embodiment and the second embodiment, when switching between a monochrome print job and a color print job, as shown in FIGS. 5 and 7, in the monochrome print job, the photosensitive drum 3 is placed at the same position as the previous phase. It has stopped.

  In the present embodiment, the drive control for generating the stop prohibition signal shown in FIGS. In this case, since the rotation stop position of the black (K) photosensitive drum 3 is different from the phase of the CMY photosensitive drum 3, the phase of the CMY photosensitive drum 3 is changed to the phase of the K photosensitive drum after the monochrome print job is completed. An adjustment step for adjusting the phase of the drum 3 is provided.

  The drive control for generating the stop prohibition signal in the monochrome print job may be performed every time the monochrome print job is executed. Further, normally, drive control for stopping at the same phase as the previous time as shown in FIGS. 5 and 7 is performed, and drive control for generating a stop prohibition signal only once every predetermined number of monochrome print jobs is executed. Also good.

Accordingly, it is possible to prevent the deterioration of only the K photosensitive drum 3 in the monochrome print job.
(Fifth embodiment)
Next, a fifth embodiment of the present invention will be described. The description of the configuration common to the first embodiment is omitted. In the first embodiment and the second embodiment, the example in which the drum driving signal is turned off at the same time when the JOB signal is turned off is shown. However, the period of the stop prohibition signal in the current print job and the period of the stop prohibition signal in the next print job do not have to be the same as long as they do not overlap by more than half. For example, a delay period may be provided from when the JOB signal is turned off to when the drum drive signal is turned off.

  As a result, it is possible to provide a margin in the current print job and the next print job so that the area of the photosensitive drum 3 facing the charger 5 does not overlap at the rotation stop position.

DESCRIPTION OF SYMBOLS 1 ... Exposure unit 100 ... Image forming apparatus 110 ... Apparatus main body 2 ... Developing apparatus 3 ... Photoconductor drum 3a ... Photoconductor part 3b ... Photoconductor drive gear 3c ... Rib 3d ... Phase detection sensor 5 ... Charger 7 ... Fixing device 90 ... Document reader t ₀ ... Avoidance time θ ₁ , θ ₂ ... Previous stop angle

Claims (6)

An image forming apparatus comprising a plurality of image carriers for forming a plurality of images, and superimposing the plurality of images on a recording medium,
Drive means for rotationally driving the plurality of image carriers;
Drive control means for controlling the drive means;
Phase detection means for detecting phases of the plurality of image carriers in a period in which the plurality of image carriers are rotationally driven;
The drive control unit generates a stop prohibition signal for prohibiting rotation stop of the drive unit after a predetermined time has elapsed from the detection timing of the phase detection unit, and continues the stop prohibition signal for an avoidance time t _0. ,
The drive control means stops the drive means at a timing when the stop prohibition signal is not generated after the printing is finished ,
The drive control means stores a period from the detection timing to the rotation stop of the drive means as a previous stop angle, and sets the predetermined time based on the previous stop angle at the next drive time. Forming equipment. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the drive control unit stops the drive unit at the first time when the stop prohibition signal is not generated after the end of printing. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the drive control unit stops the drive unit at the time when the first stop prohibition signal ends after the end of printing. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:
A charging means for charging the image carrier,
The avoidance time t ₀ corresponds to a period required for the region of the image carrier facing the charging unit to pass through .   An image forming apparatus according to any one of claims 1 to 4, wherein
  The avoidance time t around the previous stop angle ₀ An image forming apparatus characterized in that A control method of an image forming apparatus comprising a plurality of image carriers that form each of a plurality of images, and superimposing the plurality of images on a recording medium,
Controlling and rotating the plurality of image carriers,
Detecting phases of the plurality of image carriers in a period in which the plurality of image carriers are rotationally driven;
After a predetermined time has elapsed from the detection timing of the phase, a stop prohibiting signal for prohibiting rotation stop of the image carrier is generated, and the stop prohibiting signal is continued for an avoidance time t ₀ ,
Stop the rotation of the image carrier at the timing when the stop prohibition signal is not generated after the end of printing,
A control method for an image forming apparatus, wherein a period from the detection timing to a rotation stop of the image carrier is stored as a previous stop angle, and the predetermined time is set based on the previous stop angle at the next drive. .

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