JP2006259614A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of considerably suppressing deviation of rotation phases between a plurality of photoreceptors. <P>SOLUTION: The image forming apparatus includes; first and second image carriers 1C and 1K which carry toner images to be transferred to a transfer object medium 51 and are disposed along a movement path of the transfer object medium 51; first and second independent driving sources 30C and 30K for driving the first and the second image carriers 1C and 1K respectively; and first and second drive transmission means 11C and 11K for transmitting driving forces of the first and the second driving sources 30C and 30K to the first and second image carriers 1C and 1K respectively. The image forming apparatus has a driving coupling means 20CK for selectively coupling and decoupling the first drive transmission means 11C and the second drive transmission means 11K. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to so-called tandem image formation in which toner images formed on a plurality of image carriers can be superimposed on a transfer material on an intermediate transfer member or a transfer material carrier to form, for example, a full-color image. It relates to the device.

  2. Description of the Related Art Conventionally, so-called tandem image forming apparatuses such as copiers, printers, and facsimiles in which a plurality of image carriers are arranged in a line have been proposed. This is formed on a plurality of image carriers, which are generally drum-type electrophotographic photosensitive members (photosensitive drums), on a transfer material carried on an intermediate transfer member or a transfer material carrier. For example, four color toner images of yellow (Y), magenta (M), cyan (C), and black (K) are sequentially transferred, and a color image is formed by superimposing the respective colors. The intermediate transfer member or the transfer material carrier is, for example, a belt that is stretched around a plurality of rollers and moves endlessly. The tandem type image forming apparatus has an image forming unit for each color, which is advantageous in that printing can be performed at high speed.

  However, in the tandem type image forming apparatus, each color toner image is formed on a plurality of photosensitive drums. In order to suppress (shift), higher accuracy is required for rotational driving of each photosensitive drum than in an image forming apparatus that forms toner images of a plurality of colors on one photosensitive drum.

  Therefore, conventionally, as a countermeasure against positional deviation (color misregistration) of toner images formed on each photosensitive drum and superimposed on a transfer medium (such as an intermediate transfer member or a transfer material on a transfer material carrier), By adjusting the rotational phase of the drum to a desired state, the relative positional deviation of each color toner image is reduced.

  In a tandem image forming apparatus, the following two means are roughly used as means for adjusting the rotational phase of each photosensitive drum.

  As a first means, there is a method in which a plurality of photosensitive drums are driven by a single drive source and assembled by matching the phases of the drive gears.

  As a second means, as disclosed in Patent Document 1 and Patent Document 2, a plurality of photosensitive drums driven by different driving sources are used, and a result of detecting a phase difference between the photosensitive drums is used. Thus, there is a method of adjusting the phase of the drive gear for transmitting the drive from each drive source to the corresponding photosensitive drum.

  However, as the speed of the apparatus increases, the torque required for the driving source of the photosensitive drum increases, and it is difficult to adopt a method of driving all the photosensitive drums using one driving source as in the past. There is.

In addition, when using a method for adjusting the phase between the photosensitive drums by detecting the phase difference between the photosensitive drums driven by independent driving sources, the phase between the photosensitive drums at the start / stop of the apparatus main body. May shift. For this reason, it is necessary to match the phase between the photosensitive drums before image formation. For this reason, it takes time for the preparation operation until image formation is started, resulting in a problem that the printing time becomes long.
JP 2001-305820 A JP 2003-66676 A

  An object of the present invention is to provide an image forming apparatus capable of greatly suppressing a rotational phase shift between a plurality of photoconductors.

  One of the more detailed objects of the present invention is that the rotational phase shift between the plurality of image carriers is greatly reduced at the start / stop of rotation of the image carrier where the rotation phases between the plurality of image carriers are likely to be shifted. An object of the present invention is to provide an image forming apparatus that can be suppressed.

  One of the more detailed objects of the present invention is to provide an image forming apparatus capable of shortening the time from receipt of a print command to completion of printing.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to first and second image carriers that carry a toner image to be transferred to a transfer medium, arranged along a movement path of the transfer medium, and the first and second images. Independent first and second driving sources for driving the first and second image carriers and driving forces of the first and second driving sources are transmitted to the first and second image carriers, respectively. 1. An image forming apparatus having first and second drive transmission means, comprising drive connection means for selectively connecting and releasing the connection between the first drive transmission means and the second drive transmission means. An image forming apparatus characterized by the above.

  According to the present invention, it is possible to significantly suppress a rotational phase shift between a plurality of photoconductors. In addition, as one of the operational effects obtained by the present invention, the rotational phase shift between the plurality of image carriers can be reduced at the start / stop of rotation of the image carrier, in which the rotational phases between the plurality of image carriers are likely to be shifted. It can be significantly suppressed. In addition, as one of the operational effects obtained by the present invention, it is possible to shorten the time from receipt of a print command to the end of printing.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
FIG. 1 shows a sectional view of this embodiment. The image forming apparatus 100 according to the present exemplary embodiment is configured to perform electrophotography in response to an image information signal from an external device such as a personal computer, a document reading apparatus, or a digital camera connected to the image forming apparatus main body (apparatus main body) A in a communicable manner. A four-color full-color image of yellow (Y), magenta (M), cyan (C), and black (K) can be formed on a transfer material (recording paper, OHP sheet, cloth, etc.) S using the method. This is a so-called tandem full-color laser beam printer.

  The image forming apparatus 100 includes first, second, third, and fourth image forming units PY, PM, and PC that respectively form yellow, magenta, cyan, and black images as a plurality of image forming units serving as image forming units. , PK. Further, the image forming apparatus 100 includes an intermediate transfer unit 5 for transferring the image formed in each image forming unit PY, PM, PC, PK to the transfer material S. The intermediate transfer unit 5 includes an endless moving belt as an intermediate transfer member, that is, an intermediate transfer belt 51.

  In the present embodiment, the configurations of the image forming units PY, PM, PC, and PK are substantially the same except that the colors of the developers are different. The subscripts Y, M, C, and K given to the reference numerals to indicate that the element belongs to any one of the image forming units for any color will be omitted for general description.

  Each image forming portion P has a drum-type electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 1 along the moving direction of the intermediate transfer belt 51 as a transfer medium. Around the photosensitive drum 1, a charging roller 2 as charging means for uniformly charging the surface of the photosensitive drum 1, and an electrostatic image (latent image) formed on the photosensitive drum 1 is visualized with toner. A developing device 4 as a developing means and a cleaner 6 as a cleaning means for removing toner remaining on the photosensitive drum 1 after the primary transfer step are arranged. A laser scanner 3 is disposed as an exposure unit (latent image forming unit) for forming an electrostatic image corresponding to an image of a specific color on the surface of the photosensitive drum 1 charged in each image forming unit P. ing. Further, as described above, the image forming apparatus 100 includes the intermediate transfer unit 5, and the toner images of each color formed on the photosensitive drum 1 in each image forming unit P are sequentially superimposed on the intermediate transfer unit 5. An intermediate transfer belt 51 to be transferred is provided.

  In this embodiment, the intermediate transfer belt 51 is stretched around a plurality of rollers including a driving roller 52 to which a driving force is transmitted and a driven roller 53. When the driving roller 52 is driven to rotate, the intermediate transfer belt 52 rotates in the direction of the arrow in FIG. On the inner peripheral surface side of the intermediate transfer belt 51, a toner image formed on the photosensitive drum 1 is transferred to the intermediate transfer belt 51 at a position facing the photosensitive drum 1 of each image forming unit P via the intermediate transfer belt 51. A primary transfer roller 54 is disposed as a primary transfer means for transferring to the camera. The intermediate transfer belt 51 and the photosensitive drum 1 come into contact with each other at the position of the primary transfer roller 54, and a primary transfer portion (primary transfer nip) is formed. Further, a secondary transfer roller 55 as a secondary transfer unit is disposed facing the drive roller 52 of the two rollers on which the intermediate transfer belt 51 is stretched. At a position facing the secondary transfer roller 55, the secondary transfer roller 55 contacts the intermediate transfer belt 51, and a secondary transfer portion (secondary transfer nip) is formed.

  In addition, a toner replenishing container 40 serving as a toner accommodating means for accommodating toner to be replenished to each developing device 4 is provided independently. Toner is supplied from each toner supply container 40 to each developer 4 via toner supply means (not shown) such as a screw.

  In addition, the image forming apparatus 100 includes a transfer material supply unit 7 that supplies the transfer material S to the intermediate transfer belt 51, a fixing device 8 as a fixing unit that fixes the toner image formed on the transfer material S, and the like. It has been.

  In each of the image forming units PY, PM, PC, and PK, the photosensitive drum 1 and the charging roller 2 and the cleaner 6 as process means acting on the photosensitive drum 1 are integrally formed into a cartridge so that the apparatus main body A It may be a process cartridge that can be attached to and detached from.

  Next, an image forming operation will be described. When an image formation start instruction is input to the apparatus main body A, the photosensitive drum 1 is rotated in the direction indicated by the arrow (clockwise) in synchronization with the rotation of the intermediate transfer belt 51. In this embodiment, the surface of the photosensitive drum 1 is uniformly charged to a negative polarity by the charging roller 2. Then, the charged surface of the photosensitive drum 1 is exposed by the laser scanner 3, and an electrostatic image (latent image) corresponding to the image information signal is formed on the photosensitive drum 1.

  The electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the developing device 4. That is, the developing device 4 includes a developer storage container (container) that stores toner, and a developer carrier (development roller) that supports and conveys the developer in the container and supplies the developer to the photosensitive drum 1. In this embodiment, a negatively chargeable non-magnetic one-component developer (toner) is accommodated in the developing device 4 as a developer. Then, when a developing bias is applied to the developing roller, toner on the developing roller is transferred onto the photosensitive drum 1 in accordance with the electrostatic image at a facing portion (developing region) between the developing roller and the photosensitive drum 1. The electrostatic image is visualized as toner.

  The toner image formed on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 51 by the action of a primary transfer bias applied to the primary transfer roller 54.

  For example, when a four-color full-color image is formed, the above-described operation is performed by the image forming unit P for each color of yellow, magenta, cyan, and black, and is formed on the photosensitive drum 1 of each image forming unit P at a predetermined timing. The toner images of the respective colors are sequentially superimposed and transferred on the intermediate transfer belt 51, and a full color toner image is formed on the intermediate transfer belt 51.

  Thereafter, the toner image primarily transferred onto the intermediate transfer belt 51 has been conveyed from the transfer material supply unit 7 by the action of the secondary transfer bias applied to the secondary transfer roller 55 in the secondary transfer unit. Secondary transfer is performed collectively on the transfer material S.

  Here, a method for supplying the transfer material S will be described. When the image forming operation is started, the transfer material S is supplied from the transfer material supply unit 7 to the secondary transfer unit. In the transfer material supply unit 7, the transfer material S is stored in a cassette 71 and is pressed by a transfer material pick-up means (not shown) by a transfer material lifting / lowering means 71a. The transfer material S transported by the transfer material pick-up means is transported separately by the transport roller 72 and the retard roller 73 one by one. Next, the transfer material S is temporarily stopped by a registration roller 74 as registration means. The registration roller 74 resumes feeding of the transfer material S toward the secondary transfer unit in accordance with the timing of the full-color toner image formed on the intermediate transfer belt 51.

  The transfer material S that has passed through the secondary transfer portion is then conveyed to the fixing device 8. The fixing device 8 includes a heat roller 81 with a built-in heater as a heating unit, and a pressure roller 82 that is in pressure contact with the heat roller 81. The transfer material S is heated and pressed by passing through a contact portion (fixing nip portion) between the heat roller 81 and the pressure roller 82, and the toner image is fixed thereon. Then, the transfer material S on which the toner image is fixed is discharged onto a discharge portion 10 formed on the upper surface of the apparatus main body A by a discharge roller pair 9 as discharge means.

  On the other hand, deposits such as toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred to the intermediate transfer belt 51 are removed by the cleaner 6. In addition, deposits such as toner remaining on the surface of the intermediate transfer roller 51 after the toner image is transferred to the transfer material S are removed by a belt cleaner (not shown).

[Drive transmission means]
Next, the most characteristic drive transmission configuration of the photosensitive drum 1 in this embodiment will be described.

  First, a conventional drive transmission structure of a photosensitive drum will be described with reference to FIG. Conventionally, a configuration in which a plurality of photosensitive drums 1 are driven independently includes the following. That is, an independent driving source (not shown) is provided for each photosensitive drum 1, and the driving force of each driving source is transmitted to the driving gear 11 provided coaxially with the photosensitive drum 1. Further, driving is transmitted to each photosensitive drum 1 through a coupling (not shown) fixed to the rotating shaft of the photosensitive drum 1 that engages with a coupling portion of the driving gear.

  At this time, rotation unevenness (speed unevenness) occurs in the rotation cycle of the photosensitive drum 1 due to an angle of deviation between each drive gear 11 and the rotation shaft of the photosensitive drum 1 and the eccentricity of the drive gear 11 itself. This causes color misregistration of the image.

  Therefore, conventionally, as shown in FIG. 7, the drive gear 11 is provided with a phase indicating member 13 that rotates (typically integrally) in synchronization with the rotation period of the drive gear 11, and is provided at a specific position. The optical sensor 14 serving as the phase detection means detects a groove 13a serving as a target that acts on the sensor 14 at a rotation period of the drive gear 11 provided in a part of the phase indicating member 13. Then, the phase position of the drive gear 11 is calculated from the detection result of the optical sensor 14, and the drive source provided corresponding to each photosensitive drum 1 is controlled based on the calculation result of the phase position of each drive gear 11. In addition, phase control means is provided for controlling the phase of each drive gear so as to cancel out the speed unevenness component of one cycle of each photosensitive drum 1.

  However, if the phase of the drive gear 11 with respect to the photosensitive drum 1 for each color is adjusted before image formation by the conventional method, image formation cannot be performed until the phase adjustment control is completed. There is a problem that the time until image output is completed, that is, the initial printing speed is slow.

  Therefore, in this embodiment, a plurality of photosensitive drums 1 are arranged on the image forming path, and at least two independent drive sources (drive motors) for driving the photosensitive drum 1 are provided. In the case where drive transmission means (drive gear) for transmitting drive force to the photosensitive drum 1 is provided, drive connection means for connecting / releasing drive gears 11 to which drive force is transmitted from different drive sources is provided. Thereby, when the drive transmission means are connected, the phases of the photosensitive drums 1 corresponding to the respective drive transmission means are not shifted.

  Further description will be made with reference to FIGS. 2 and 3 as well. In the present embodiment, as in the conventional configuration shown in FIG. 9, the first photosensitive drive 1 is driven as a drive source for independently driving each of the four photosensitive drums 1. Second, third, and fourth drive motors 30Y, 30M, 30C, and 30K are provided. The driving force of each drive motor 30 is transmitted to first, second, third, and fourth drive gears 11Y, 11M, 11C, 11M, and 11K as drive transmission means provided coaxially with the respective photosensitive drums 1. The In the present embodiment, the driving force of the driving motor 30 is transmitted to the driving gear 11 via the gear portion 11 a of each driving gear 11.

  Further, first, second, and third coupling means fixed to the rotating shaft of the photosensitive drum 1 that engages with a coupling portion 11b formed at the end of the driving gear 11 on the photosensitive drum 1 side. The driving force is transmitted to each photosensitive drum 1 via the fourth couplings 12Y, 12M, 12C, and 12K. The coupling portion 11b of the drive gear 11 appears only for the second and fourth drive gears 11M and 11C in FIG. 2, but is similarly provided for all the drive gears 11.

  In this embodiment, as the drive connecting means, the first drive connecting means 20YM for selectively connecting and releasing the drive between the first drive gear 11Y and the second drive gear 11M. , Second drive connection means 20MC for selectively connecting and releasing the drive between the second drive gear 11M and the third drive gear 11C, and the third drive gear 11C and the fourth drive. There is a third drive connecting means 20CK for selectively connecting and releasing the drive with the gear 11K.

  In the present embodiment, each drive connecting means 20 includes a rotatable idler gear that meshes with the gear portion 11a of the upstream drive gear 11 in the image forming path, that is, the surface movement direction of the intermediate transfer belt 51 as a transfer medium. A rotatable idler gear meshing with the gear portion 11a of the downstream drive gear 11 in the same direction, a clutch as a switching means for selectively connecting and releasing the drive between these idler gears, Have

  More specifically, in the present embodiment, the first drive coupling means 20YM meshes with the first idler gear 21Y and the second drive gear 11M that are rotatably provided to mesh with the first drive gear 11Y. And a second idler gear 22M provided rotatably. The first idler gear 21Y and the second idler gear 22M are arranged on the same axis, and the first clutch means 23YM can connect and release the drive between the idler gears 21Y and 23M. When the first clutch 23YM is connected, the first drive gear 11Y and the second drive gear 11M are connected to each other, so that the phases are not shifted from each other.

  Similarly, the second drive connecting means 20MC has a third idler gear 21M, a fourth idler gear 22C, and a second clutch 23MC. The third drive connecting means 20CK includes a fifth idler gear 21C, a sixth idler gear 22K, and a third clutch 23CK. Then, by connecting the second clutch 23MC, the second drive gear 11M and the third drive gear 11C are connected to each other. Further, the third drive gear 11C and the fourth drive gear 11K are connected to each other by connecting the third clutch 23CK.

  Thus, by connecting the first, second, and third clutches 23YM, 23MC, and 23CK, all the drive gears 11Y, 11M, 11C, and 11K can be connected to each other. In this state, it is possible to prevent the drive gears 11Y, 11M, 11C, and 11K from being out of phase.

  Next, the operation method of the drive connecting means 20 as described above will be described.

  The phases of the photosensitive drums 1 are most likely to deviate when the driving of the photosensitive drums 1 is started (when activated) or when the photosensitive drums 1 are stopped.

  Therefore, in the present embodiment, before the driving of the photosensitive drum 1 is started, the driving gears 11 to which driving is transmitted from different driving motors 30 are connected by the drive connecting means 20. Then, after the rotation of the photosensitive drum 1 is stabilized in a predetermined state, the drive coupling means 20 releases the connection between the drive gears 11 to which the drive is transmitted from different drive motors 30. On the other hand, after the image formation, before the drive of the photosensitive drum 1 is stopped (before the stop operation is started), the drive gears 11 to which drive is transmitted from different drive motors 30 are connected by the drive connecting means 20. . Until at least the photosensitive drum 1 is stopped, the drive connecting means 20 does not release the connection between the drive gears 11 to which the drive is transmitted from the different drive motors 30. Typically, after the photosensitive drum 1 is stopped, the connection of the drive gears 11 to which the drive is transmitted from the different drive motors 30 is released by the drive connection unit 20. Accordingly, it is possible to prevent the phase shift between the photosensitive drums 1 when the photosensitive drums 1 having the different driving sources are most likely to shift in phase when the photosensitive drum 1 is stopped or started.

  Further description will be made with reference to FIG. 4 as well. First, second, third, and fourth provided independently at the time of image formation, before each photosensitive drum 1Y, 1M, 1C, and 1K is activated. Before starting the driving motors 30Y, 30M, 30C, 30K, all the driving gears 11Y, 11M, 11C, 11K are connected by connecting the first, second, third clutches 23YM, 23MC, 23CK. Are connected to each other. Thereby, it can start, maintaining the phase of each photosensitive drum 1 of the stopped state.

  However, when one drive gear train is controlled using a plurality of drive motors 30, the behavior may not be stabilized due to the interaction. For this reason, after the activation of the photosensitive drum 1, that is, the first, second, third, and fourth drive motors 30Y, 30M, 30C, and 30K, that is, after the rotation of the photosensitive drum 1 (drive motor 30) is stabilized. The image is formed after the mutual connection of the drive gears 11 is released.

  On the other hand, before stopping the driving of the photosensitive drum 1, that is, before starting the stopping operation of the first, second, third, and fourth driving motors 30Y, 30M, 30C, and 30K, the first, second, By connecting the third clutches 23YM, 23MC, and 23CK, all the drive gears 11Y, 11M, 11C, and 11K are connected to each other. Then, after the rotation of the photosensitive drum 1 is completely stopped, the first, second, and third clutches 23YM, 23MC, and 23CK are released.

  In this embodiment, as shown in FIG. 3, a controller 110 having a storage unit, a control unit, and a calculation unit that comprehensively controls the operation of the image forming apparatus 100 includes first, second, and third drives. It controls the switching function of connection / release of the first, second, and third clutches 23YM, 23MC, and 23CK of the connecting means 20YM, 20MC, and 20CK. The storage unit of the controller 110 stores a program that defines the connection / release operation of the first, second, and third clutches 23YM, 23MC, and 23CK as described above. The controller 110 switches connection / release of the first, second, and third clutches 23YM, 23MC, and 23CK by sending a control signal to the clutch driver 112 at a predetermined timing in accordance with such a program.

  Note that the time until the photosensitive drum 1, that is, the drive motor 30 is stabilized in a predetermined state (predetermined rotation measurement) may be determined by comparison with a value obtained in advance, or a separate rotation speed is detected. Means to do this may be provided. Similarly, the time from when the drive of the drive motor 30 is stopped until the rotation of the photosensitive drum 1 is completely stopped may be determined by comparison with a value obtained in advance, or a separate rotational speed is detected. Means may be provided.

  By operating the drive connecting means 20 as described above, it is possible to prevent the phases of the photosensitive drums 1 from being shifted at the start / stop of the rotation at which the phases of the photosensitive drums 1 are most likely to be shifted. Therefore, after the photosensitive drum 1 is started, after the rotation of the photosensitive drum 1 is stabilized, the image can be formed immediately when the connection of the drive transmission means 20 is released. As a result, a high-quality image can be formed, and the time from the receipt of a print command to the end of printing, that is, the initial print time can be shortened.

  By the way, during image formation, there is a possibility that the phase between the drive gears gradually shifts. For this reason, the image forming apparatus 100 further controls a phase detection unit that detects the phase of the photosensitive drum 1 driven by different drive rollers 30, and controls each drive motor 30 based on the detection result of the phase detection unit. Phase adjusting means for adjusting the phase between the photosensitive drums 1 can be provided.

  For example, in the present embodiment, as described above with reference to FIG. 7, the phase indicating member 13 and the optical sensor 14 shown in FIG. 7 are provided for each drive gear 11, and the output of each sensor 14 is sent to the controller 110. Try to enter. The controller 110 calculates the phase position of each photosensitive drum 1, that is, the drive gear 11, based on the detection result of the sensor 14. Then, the controller 110, for example, decreases the rotational speed of the photosensitive drum 1 whose phase has advanced from the calculated phase position of each photosensitive drum 1, increases the rotational speed of the photosensitive drum 1 whose phase has been delayed, Alternatively, a control signal is sent to the motor driver 111 to drive each drive motor 30 so that the phases of the respective photosensitive drums 1 are aligned by using both of them together. The motor driver 111 controls each drive motor 30 in accordance with a control signal from the controller 110 to adjust the phase of each photosensitive drum 1. The storage unit of the controller 110 stores a program that defines the phase matching operation. The controller 110 controls the phase matching operation according to such a program. Thus, in the present embodiment, the phase indicating member 13, the optical sensor 14 as the phase detection means, and the controller 110 constitute a phase detection mechanism, and the controller 110 and the motor driver 111 constitute a phase adjustment means. . These phase detection mechanisms and phase matching means constitute phase control means for the photosensitive drum 1. The phase detection means is not limited to the optical sensor as in the present embodiment, and may be one that magnetically detects the phase position of the target, for example.

  More specifically, during the phase matching operation, the drive connecting means 20 operates as follows. For example, at a predetermined timing (regularly or every execution of the image forming operation), after the end of image formation, that is, the connection of each drive gear 11 by the drive connecting means 20 is released, and each photosensitive drum 11 rotates. In this state, the phase of each photosensitive drum 1 is matched using the phase matching control means. At this time, the first, second, and third clutches 23YM, 23MC, 23CK, and 23K are connected to each other before the driving of the photosensitive drum 1 is stopped, so that all the driving gears 11Y, 11M, 11C, and 11K are mutually connected. Connect them so that the combined phase does not shift during the stop operation. Then, after the rotation of the photosensitive drum 1 is completely stopped, the first, second, and third clutches 23YM, 23MC, and 23CK are released.

  Alternatively, the phase matching operation can be performed at the time of so-called initial operation when the apparatus main body A is turned on or after the opening / closing member (main body door) that opens the apparatus main body A is opened / closed. In this case, first, the driving of the photosensitive drums 1 is started, and then the phases of the photosensitive drums 1 are matched by the phase matching means, and then the drive gears 11 are connected by the drive connecting means 20. Then, after the rotation of each photosensitive drum 1 is completely stopped, the connection between the drive gears 11 is released by the drive connection means 20.

  As described above, the phase alignment control of the plurality of photosensitive drums 1 is performed before the driving of the photosensitive drums 1 is stopped, so that a minute phase shift that occurs during image formation is accumulated and a large phase shift is prevented. it can. Therefore, it is possible to stop the photosensitive drum 1 in a state where the phases are always in phase. Accordingly, stable image formation can be performed at the same time, and at the same time, the start of printing is not hindered, so that the time from the receipt of the print command to the end of printing can be kept short.

  As described above, according to the present embodiment, it is possible to significantly suppress the rotational phase shift between the plurality of photosensitive drums 1. In other words, the rotational phase shift between the plurality of photosensitive drums 1 can be significantly suppressed when the rotation of the photosensitive drum 1 where the rotational phases between the plurality of photosensitive drums 1 are likely to be shifted, and the print command It is possible to shorten the time from the reception to the end of printing.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are substantially the same as those of the image forming apparatus of the first embodiment. Accordingly, elements having substantially the same or corresponding functions as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, the first, second, and third drive gears 11Y, 11M, and 11C that transmit driving to the photosensitive drums 1Y, 1M, and 1C for yellow, magenta, and cyan, respectively, are connected to each other and are always the same. It is driven to rotate by phase. Therefore, in the present embodiment, the fourth, fourth, and third drive gears 11Y, 11M, and 11C (hereinafter referred to as “drive gear group”) and the fourth photosensitive drum 1K that transmits driving are transmitted. The drive connecting means 20 is provided between the drive transmission gear 11K and the drive gears 11Y, 11M, 11C, and 11K are connected / released at a predetermined timing.

  More specifically, FIG. 5 shows a drive transmission configuration of a plurality of photosensitive drums 1 in this embodiment. In this embodiment, a driving force is transmitted to a gear group drive transmission gear 17 from a first drive source (drive motor) (not shown), and a belt (drive gear group interlocking belt) 16 and pulleys 15Y, 15M, 15C. The drive is transmitted to the drive gear groups 11Y, 11M, and 11C via. This driving force is transmitted to the photosensitive drums 1Y, 1M, and 1C through the first, second, and third couplings 12Y, 12M, and 12C, respectively, as in the first embodiment. Since the first, second, and third drive gears 11Y, 11M, and 11C are connected to each other by the belt 16, the phases are not shifted thereafter by assembling with the respective phases matched.

  On the other hand, a driving force is transmitted from a second driving source (driving motor) (not shown) to the fourth driving gear 11K, and similarly to the first embodiment, the photosensitive drum 1K is passed through the fourth coupling 12K. Is driven.

  In this embodiment, since the first drive motor and the second drive motor are driven independently, the phase between the drive gear groups 11Y, 11M, 11C and the fourth drive gear 11K is shifted. there is a possibility.

  Therefore, in this embodiment, the phase of the specific drive gear (the third drive gear 11C in this embodiment) in the drive gear groups 11Y, 11M, and 11C and the phase of the fourth drive gear 11K are respectively Detection is performed by the same phase detection means as in the first embodiment. Then, the phase between the drive gear groups 11Y, 11M, and 11C and the fourth drive gear 11K is matched by controlling the first drive motor and the second drive motor by the phase matching means.

  Further, between the third drive gear 11C and the fourth drive gear 11K, the drive connection means 20CK having the same configuration as the first, second and third drive connection means 20YM, 20MC, 20CK in the first embodiment. Is provided. That is, among the drive gear groups 11Y, 11M, and 11C, the first idler gear 21C that meshes with the gear portion 11aC of the third drive gear 11C and the gear portion of the fourth drive gear 11K. A second idler gear 22K that meshes with 11aK and is rotatably provided is provided, and these idler gears 21C and 22K are arranged coaxially. The idler gears 21C and 22K are mutually connected and released by the clutch 23CK.

  In the present embodiment, by connecting the clutch 23CK and connecting the idler gears 21C and 22K, the drive gear groups 11Y, 11M, and 11C and all the drive gears of the fourth drive gear 11K can be connected to each other. it can.

  With regard to the operation of the drive connecting means 20, the connection / release timing of the clutch 23CK may be the same as in the first embodiment, and the drive connecting means 20 is only between the third drive gear 11C and the fourth drive gear 11K. The control mode is the same as that of the first embodiment except for the above. The operation of adjusting the phases of the drive gear groups 11Y, 11M, 11C and the fourth drive gear 11K is performed by the controller 110, the phase detection member 13 provided only for the third and fourth drive gears 11C, 11K, and The same control method as that in the first embodiment may be used by the phase control means constituted by the sensor 14.

  As described above, according to the present exemplary embodiment, the same effects as those of the first exemplary embodiment can be obtained, and in the image forming apparatus having a monochrome image forming mode such as black, the phase alignment (drive transmission) configuration of the photosensitive drum 1 can be achieved. It can be simplified.

Example 3
Next, still another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of the present embodiment are substantially the same as those of the image forming apparatus of the first embodiment. Accordingly, elements having substantially the same or corresponding functions as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 6 shows a driving configuration of a plurality of photosensitive drums 1 in this embodiment. The present embodiment is a modification of the first embodiment. As drive coupling means, first drive coupling means 20YM for coupling / releasing the first drive gear 11Y and the second drive gear 11M, second drive. Second drive connection means 20MC for connecting / releasing the gear 11M and the third drive gear 11C, and third drive connection means 20CK for connecting / releasing the third drive gear 11C and the fourth drive gear 11K Have.

  In the present embodiment, each drive connecting means 20 includes a clutch gear 24 provided coaxially with the drive gear 11, an upstream side in the image forming path (that is, a conveyance direction of the intermediate transfer belt 51 as a transfer medium), and And a rotatable idler gear 25 that meshes with the gear portion 24a of the clutch gear 24 provided in the downstream drive gear 11.

  More specifically, in this embodiment, the image forming apparatus 100 includes first, second, third, and fourth drive gears 11Y, 11M, 11C, and 11K that are driven by independent drive sources (drive motors). The first, second, third, and fourth clutch gears 24Y, 24M, 24C, and 24K are provided on the same axis so as to be rotatable. Also, adjacent clutch gears 24, that is, the first clutch gear 24Y and the second clutch gear 24M, the second clutch gear 24M and the third clutch gear 24C, the third clutch gear 24C and the fourth clutch gear. First, second, and third idler gears 25YM, 25MC, and 25CK that mesh with the respective gear portions 24a of 24K are provided.

  The gear portions 24a of the first, second, third, and fourth clutch gears 24Y, 24M, 24C, and 24K are respectively connected to the clutch portions (not shown) of the clutch gears 24Y, 24M, 24C, and 24K. The drive can be connected / released with the first, second, third, and fourth drive gears 11Y, 11M, 11C, and 11K corresponding to the above.

  In such a configuration, the first, second, third, and fourth clutch gears 24Y, 24M, 24C, and 24K, and the first, second, third, and fourth drive gears 11Y, 11M, By connecting 11C and 11K, it is possible to connect all the drive gears 11Y, 11M, 11C, and 11K to each other and prevent the phases of the photosensitive drums 1 from shifting.

  With regard to the operation of the drive connecting means 20, the connection / release timing of the clutch gear 24 may be the same as that in the first embodiment, and the drive connection / release switching means, which is a clutch gear, corresponds to all the drive gears 11. The control mode is the same as that of the first embodiment except that the control mode is provided. Further, the operation for adjusting the phases of the drive gears 11Y, 11M, 11C, and 11K may be performed by the same control method as in the first embodiment.

  As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the aspect of each said Example.

  For example, in each of the embodiments described above, the image forming apparatus 100 has been described as adopting the intermediate transfer method, but the present invention is not limited to this. As an image forming apparatus of the tandem system, an image forming apparatus having an endlessly moving belt stretched around a plurality of rollers as a transfer material carrier, that is, an image forming apparatus having a transfer material conveying belt 151 as shown in FIG. Is well known. In FIG. 8, elements having substantially the same or corresponding functions as those in FIG. In such an image forming apparatus, the transfer material S supplied from the recording material supply unit 7 is held and conveyed on the transfer material conveyance belt 151 by an electrostatic action or the like. Then, a transfer bias applied to a transfer member 154 such as a transfer roller provided on the inner peripheral surface of the transfer material conveyance belt 151 so as to face the photosensitive drum 1 is applied to the transfer material S on the transfer material conveyance belt 151. Thus, the toner images formed on the respective photosensitive drums 1 are sequentially superimposed and transferred. Thereafter, by fixing the toner image on the transfer material S, for example, a full-color image can be output. The present invention can be equally applied to such an image forming apparatus having a transfer material carrier, and the same effects as those of the above embodiments can be obtained.

1 is an overall configuration diagram of an example of an image forming apparatus to which the present invention can be applied. It is a principal part schematic perspective view for demonstrating one Example of the drive transmission structure of a photosensitive drum. FIG. 3 is a block diagram for explaining an embodiment of a photosensitive drum drive control method. FIG. 6 is a chart for explaining an embodiment of a photosensitive drum drive control method; It is a principal part schematic perspective view for demonstrating the other Example of the drive transmission structure of a photosensitive drum. It is a principal part schematic perspective view for demonstrating the further another Example of the drive transmission structure of a photosensitive drum. It is a principal part schematic perspective view which shows one Example of a phase detection means. It is a principal part schematic block diagram of the other example of the image forming apparatus which can apply this invention. It is explanatory drawing for demonstrating the drive transmission structure of the conventional photosensitive drum.

Explanation of symbols

1 Photosensitive drum (image carrier)
11 Drive gear (drive transmission means)
14 Optical sensor (phase detection means)
20 Drive connection means 51 Intermediate transfer belt (intermediate transfer member)
54 Primary transfer roller (primary transfer means)

Claims (8)

A first image carrier and a second image carrier arranged along a movement path of the transfer medium, which carries a toner image to be transferred to the transfer medium;
Independent first and second drive sources for driving the first and second image carriers, respectively.
First and second drive transmission means for transmitting driving forces of the first and second drive sources to the first and second image carriers, respectively.
In an image forming apparatus having
An image forming apparatus comprising drive connection means for selectively connecting and releasing the connection between the first drive transmission means and the second drive transmission means.   Before the driving of the first and second image carriers is started, the first and second drive transmission units are connected by the drive connecting unit, and the rotation of the image carrier is in a predetermined state. The connection of the first and second drive transmission means is later released by the drive connection means, and before the drive of the first and second image carriers is stopped, the drive connection means causes the first and second drive connections to be stopped. The first and second drive transmission means are not released by the drive connection means until the first and second image bearing members are stopped. 1. An image forming apparatus according to 1.   3. The image forming apparatus according to claim 2, wherein after the first and second image carriers are stopped, the connection of the first and second drive transmission means is released by the drive connection means.   Furthermore, the first and second drive sources are controlled by controlling the first and second drive sources based on the detection results of the phase detection means and the phase detection means for detecting the phases of the first and second image carriers. 4. The image forming apparatus according to claim 1, further comprising: a phase adjusting unit that adjusts the phase of the image carrier.   In the phase alignment of the first and second image carriers, the connection of the first and second drive transmission means is released by the drive connecting means, and the first and second image carriers are rotated. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is performed before the driving of the first and second image carriers is stopped in a state where the first and second image carriers are in contact with each other.   The phase alignment of the first and second image carriers is performed when the apparatus main body is turned on or after the opening / closing member that opens the inside of the apparatus main body is opened and closed. The driving of the carrier is started, and after the phases of the first and second image carriers are adjusted by the phase adjusting means, the first and second drive transmission means are connected by the drive connecting means, 5. The image forming apparatus according to claim 4, wherein the first and second drive transmission means are disconnected after the first and second image carriers are stopped.   The drive coupling means includes a first gear driven by the first drive transmission means, a second gear driven by the second drive transmission means, the first gear, and a second gear. The image forming apparatus according to claim 1, further comprising: a clutch that selectively connects and releases the connection.   A third image carrier disposed along a movement path of the transfer medium that carries a toner image to be transferred to the transfer member; and a driving force transmitted to the third image carrier. 3. The third drive transmission means coupled to the second drive transmission means, wherein the third image carrier is driven by the second drive means. 8. The image forming apparatus according to any one of items 7.

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