JP2005157169A - Image forming apparatus and process unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing load fluctuations due to the partial reduction of a surface friction coefficient of an image carrier due to a long time neglect, regarding the image forming apparatus having a plurality of image carriers which are driven by the same driving system at the same cycle, and to provide a process unit used for the image forming apparatus. <P>SOLUTION: The image forming apparatus comprises the plurality of photoreceptor drums 1, a driving motor 11 for rotationally driving the plurality of photoreceptor drums, and a gear train 12 for transmitting the driving force from the driving motor 11 to the plurality of photoreceptor drums, wherein the plurality of photoreceptor drums are rotationally driven by the driving motor 11 through the gear train 12 at the same cycle. The image forming apparatus also comprises a phase shifting means for shifting the phase of at least one photoreceptor drum in rotating out of the plurality of photoreceptor drums to which the driving force is transmitted through the gear train 12 from the phase of another photoreceptor drum in stopping. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image by an electrophotographic system, an electrostatic recording system, or the like, and includes a drive transmission unit that transmits drive from a single drive source to a plurality of image carriers. The present invention relates to an image forming apparatus and a process unit used therefor.

  In recent years, there is a tandem type image forming apparatus in which a plurality of photosensitive drums as image carriers are arranged side by side as a multicolor image forming system suitable for speeding up.

  As shown in FIG. 8, the tandem type image forming apparatus has four photosensitive drums 1Y, 1M, 1C, and 1Bk, which are four image carriers that form yellow, magenta, cyan, and black toner images in a row. Each of the photosensitive drums is rotated to form a toner image of each color and is sequentially transferred to the rotating intermediate transfer belt 30 to form a color image. The color image is then transferred to a secondary transfer roller 32. Secondary transfer is performed on the transfer material 20 conveyed separately in the next transfer section.

  As a driving method of the photosensitive drum in such a tandem type image forming apparatus, each photosensitive drum is driven by a motor as a driving source, as disclosed in JP-A-2003-29492. “Individual motor system” (see FIG. 9A), “One motor system” (see FIG. 9B) in which all the photosensitive drums 1 are driven by one motor, or coloring toner, for example. There is a “multiple motor system” (see FIG. 9C) in which the photosensitive drums 1Y, 1M, and 1C are driven by one motor and the photosensitive drum 1Bk having black toner is driven by another motor.

  In the “1-motor system”, a color mode in which all the photosensitive drums 1 are driven and a black mode in which only the black photosensitive drum 1 is driven include an electronic clutch, a mechanical one-way clutch, and other Japanese Patent Laid-Open No. 7-181773. Some of them can be switched by adopting a drive transmission mechanism as disclosed in Japanese Patent Publication No. Gazette.

  The “1-motor system” has a relatively low number of motors as drive sources compared to other systems, and the control system when there are a plurality of motors (the rotational speed detection mechanism of each motor and its control mechanism) is also 1 Therefore, it is generally advantageous in terms of cost. On the other hand, there is a demerit that it is difficult to control image deterioration factors such as color shift and banding.

  For the above reasons, in general, a color image device that desires a high-definition image often employs the “individual motor method”, and a relatively inexpensive small-sized color image device that does not require a high-definition image is inexpensive. The adoption ratio of “multiple motor system” and “1 motor system” tends to increase.

  In addition, in order to improve cost merit, naturally, there is a tendency to use common parts, and the process members such as the photosensitive drum, the charging device, and the developing device described above are common except for the toner color. Often used. This tendency is particularly strong in an inexpensive small color image device.

JP 2003-29492 A JP-A-7-181773

  In the image forming apparatus of “1-motor system” and “multiple-motor system” as described above, when the photosensitive drum having the same drive system is a common part (having a common outer diameter and a common rotational speed) In the case where the photosensitive drum is driven individually, a streak-like image defect may occur. This is because the toner or external additives remaining on the photosensitive drum were pressed against the photosensitive drum, for example, on the portion where the rubber cleaning blade or the contact charging roller was pressed. It has been found that the surface slipperiness (friction coefficient μ) on the drum changes only in that part. Since the portions where the friction coefficient μ of all the photosensitive drums having the same drive system are reduced appear in the same cycle, the drive load fluctuates when passing through the cleaning blade and the charging roller at the same timing. Therefore, the magnitude of the load fluctuation of the entire drive system is amplified according to the number of photosensitive drums belonging to the same drive system. At this time, the latent image on the photosensitive drum drawn by the exposure apparatus is blurred, and appears on the image as a stripe of the photosensitive drum pitch. Due to such a principle, it occurs remarkably in a halftone pattern.

  In order not to convert the load fluctuations as described above into rotational speed fluctuations, it is necessary to reduce the backlash of the drive system. However, in improving the accuracy of parts, the effect / cost is small and practical. is not.

  In order to reduce the relative load fluctuation ratio, a method of applying a driving load other than a cleaning blade is conceivable. However, a large driving motor that can withstand a sufficient driving load that does not cause streak-like image defects is required. The driving load of the entire image forming apparatus is greatly increased, which is not preferable from the viewpoint of cost and power consumption.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus having a plurality of image carriers that are driven in the same cycle by the same drive system. The present invention provides an image forming apparatus and a process unit used therefor that can reduce load fluctuation due to a partial reduction in surface friction coefficient at a low cost without greatly increasing the driving load of the entire image forming apparatus.

  The first means in the present invention for solving the above problems includes a plurality of image carriers, a drive source for rotationally driving the plurality of image carriers, and the drive source to the plurality of image carriers. And an image forming apparatus in which the plurality of image carriers are rotationally driven from the drive source by the drive transmission means in the same cycle. The drive transmission means transmits the drive force. Among the plurality of image carriers, at least one of the image carriers is provided with phase displacement means for displacing the phase when the other image carriers are stopped.

  The second means is characterized in that, in the first means, the phase displacement means is a clutch means for cutting and connecting the transmission of the driving force.

  A third means is characterized in that, in the first means, the phase displacement means is a delay means for delaying transmission of the driving force.

  The fourth means includes a plurality of image carriers, a drive source for rotationally driving the plurality of image carriers, and a drive transmission means for transmitting a driving force from the drive source to the plurality of image carriers. In the image forming apparatus in which the plurality of image carriers are rotationally driven from the drive source by the drive transmission unit at the same cycle, at least of the plurality of image carriers to which the drive transmission unit transmits the driving force Phase displacement control having phase displacement means for displacing the phase at the time of rotation of one image carrier relative to the phase at the time of stopping the other image carrier, and for controlling the phase displacement by the transfer displacement means It has the means.

  The fifth means is the clutch means for disconnecting and connecting the transmission of the driving force in the fourth means, and the phase displacement control means disconnects and connects the transmission of the driving force by the clutch means. It is characterized by controlling the timing of performing the above.

  In the fourth means, the phase displacement means is a delay means for delaying transmission of the driving force, and the phase displacement control means controls the transmission delay time of the drive by the delay means in the fourth means. Features.

  The seventh means includes an image carrier for forming an image and a drive transmission member provided on a rotation shaft of the image carrier in a process unit that is mounted on the main body of the image forming apparatus and constitutes the image forming unit. And a drive transmission member mounted on the image forming apparatus according to any one of the first to sixth means and having a drive force transmitted by the drive transmission means.

  In the present invention, the phase when rotating at least one of the plurality of image carriers is displaced with respect to the phase when other image carriers are stopped. In an image forming apparatus having a plurality of image carriers driven at the same cycle, load fluctuations due to a partial decrease in the surface friction coefficient of the image carrier due to long-term standing greatly increase the driving load of the entire image forming apparatus. Therefore, the image can be reduced at a low cost, and a good image can always be output without causing a streak-like image defect due to distortion of the latent image or toner image during exposure or transfer.

  Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
(Overall configuration of image forming apparatus)
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the present embodiment, which is basically the same as a conventional tandem image forming apparatus. As image forming means, first to fourth image forming units PY, PM, PC, and PBk that form images of respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk) are provided. . The image forming units for each color have the same configuration except that the color of the image to be formed is different. Therefore, in FIG. 1, members having the same function are given the same reference numerals, and the color of the developer is particularly distinguished. In this case, Y, M, C, Bk (yellow, magenta, cyan, black) are attached.

  As shown in the figure, the photosensitive drum 1Y is driven in the direction of the arrow in the figure by a driving means (not shown) and is uniformly charged by the primary charging roller 2Y. Next, laser light according to a yellow image pattern is irradiated from the exposure device (LED array) 3Y to the photosensitive drum 1Y, and a latent image is formed on the photosensitive drum 1Y. The latent image formed on the photoreceptor drum 1Y is developed by the developing device 4Y containing yellow toner. The toner image visualized by development is transferred onto the intermediate transfer belt 30 rotating in the arrow direction at substantially the same speed as the photosensitive drum 1Y by the primary transfer bias applied to the primary transfer roller 5Y. The untransferred toner remaining on the photosensitive drum 1Y is removed by the cleaning unit 6Y using a cleaning blade.

  Following the yellow image, the charging, exposure, development, and primary transfer processes described above are performed in the same manner for each color of magenta, cyan, and black at a predetermined timing, and the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 30. Thus, a toner image composed of a plurality of color toners is formed.

  The multi-color toner image formed on the intermediate transfer belt 30 is applied to the secondary transfer roller 32 on the transfer material 20 sent at a predetermined timing by the pickup roller 31 constituting the conveying means. Transferred by bias. Transfer transfer residual toner remaining on the intermediate transfer belt 30 is removed by a cleaning means 33 using a blade. The transfer residual toner removed by the cleaning means 33 is sent to a waste toner box 34.

  The transfer material 20 onto which the multicolor toner image has been transferred is sent to the fixing device 7 by the transport belt 35. The multicolor toner image is melted and fixed to the transfer material 20 by applying heat and pressure by the fixing device 7 and sent to the discharge tray 36 to complete the color image formation.

  In this embodiment, the photosensitive drum 1, the charging roller 2, and the cleaning unit 6 are integrated, and a storage unit 8 that stores waste toner collected by the cleaning unit 6 is added as a latent image process unit 9. The developing device 4 is also configured as a developing process unit. The latent image process unit and the developing process unit are integrated to form an image forming unit PY, PM, PC, PBk, which can be easily detached from the image forming apparatus body 10. It became the composition which became. The above process unit can be easily replaced as a latent image process unit 9 or a developing process unit as the developing device 4 as a consumable when the toner is exhausted or when the photosensitive drum 1 is consumed. Thus, the convenience of the user in the maintenance of the image forming apparatus is improved.

(Photosensitive drum drive configuration)
Next, the driving configuration and operation of the photosensitive drum in the image forming apparatus of this embodiment will be described with reference to FIGS. FIG. 2 is a schematic view of the drive transmission means for the photosensitive drum in the image forming apparatus of this embodiment, and FIG. 3 is an explanatory diagram of the configuration of the clutch gear.

  The image forming apparatus of this embodiment is a “one motor system” in which four photosensitive drums are driven by one motor. Each photosensitive drum 1 of the image forming apparatus uses a driving motor 11 as a driving source, and this driving force is a driving transmission member attached to the rotating shaft of each photosensitive drum via a gear train 12 as driving transmission means. Is transmitted to the gear. A clutch gear a which is a clutch means capable of meshing and releasing meshing with adjacent gears c and d is arranged in the gear train 12.

  In this embodiment, by controlling the operation of the clutch gear a, the phase when at least one of the plurality of photosensitive drums is rotated is changed to the phase when the other photosensitive drums are stopped. Phase displacement means for displacing relative to is constructed.

  That is, as shown in FIG. 3, the clutch gear a is provided with an electronic clutch 13. When the electronic clutch 13 is disconnected, the clutch gear a is disengaged from the adjacent gears c and d. The drive transmission between the gear c and the gear d adjacent to the clutch gear a is cut off. For this reason, the driving force of the driving motor 11 is not transmitted from the gear c to the gear a, and as a result, the rotational driving force is not transmitted to the photosensitive drums 1Y, 1M, and 1C.

  On the other hand, when the electronic clutch 13 is connected, the clutch gear a is pushed in the direction of meshing with the adjacent gears c and d and meshes with each other, and the driving force is transmitted. Therefore, the driving force of the drive motor 11 is transmitted to the photosensitive drums 1Y and 1M via gear c → gear a → gear d → gear e → gear f, and to the photosensitive drum 1C via gear a → g. Communicated.

  The drive motor 11 and the electronic clutch 13 are controlled by a CPU 80 as a control unit, and the drive motor 11 is controlled by the CPU 80 to drive, stop, and connect and disconnect the electronic clutch 13.

  When the CPU 80 receives the print signal, it sends a signal to the drive motor 11 so as to start the rotational drive, and starts the pre-multiple rotation. At this time, during the previous multiple rotation, the electronic clutch 13 connects the clutch gear a to the gear train 12 at a predetermined timing from the time when the drive motor 11 starts the rotation drive, and connects the transmission of the rotation drive. The photosensitive drums 1Y, 1M, and 1C can start rotating with a certain phase difference (displacement) with respect to the photosensitive drum 1Bk by this timing. That is, the timing at which the portion where the slip property of the surface of the photosensitive drum 1 is likely to change passes through the charging roller 2 and the cleaning 6 is shifted, and the dynamic load fluctuation can be dispersed.

  Further, since the electronic clutch 13 is controlled to be connected and disconnected by the CPU 80 serving as the phase displacement control means, it is possible to give a desired phase difference by controlling the connection and disconnection timing.

  In the present embodiment, the electronic clutch 13 is installed in the clutch gear a. However, the present invention is not limited to this, and it may be installed in a gear that can shift the transmission timing of at least one of the plurality of photosensitive drums 1.

[Second Embodiment]
Next, an apparatus according to a second embodiment will be described with reference to FIGS. Since the basic configuration of the apparatus of the present embodiment is the same as that of the above-described embodiment, a duplicate description is omitted, and here, a configuration that is a feature of the present embodiment will be described. In addition, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above.

  FIG. 4 is a drive system of the photosensitive drum of the image forming apparatus of the present embodiment. The image forming apparatus of the present embodiment is a “1-motor system”. Drive is transmitted to each photosensitive drum 1 through the gear train 12 using the drive motor 11 as a drive source. In this gear train 12, a mechanical one-way clutch 14 is disposed at the positions of gears f, g, and h. This mechanical one-way clutch 14 transmits drive when it is driven in a constant rotational direction, but does not transmit drive when it is driven in the opposite direction. Further, the gear b and the gear e are a coupling 15 and a coupling 18 which are delay means, and are cut. The coupling 15 and the coupling 18 have different cut amounts.

  In the present embodiment, the drive transmission is delayed by the cut amount of the couplings 15 and 18, so that the phase during rotation of a predetermined photosensitive drum among the plurality of photosensitive drums is changed to another photosensitive member. Phase displacement means for displacing with respect to the phase when the drum is stopped is configured.

  Here, a cross-sectional view of the coupling 15 is shown in FIG. The coupling 15 is configured to have a concave and convex shape in which the coupling concave portion 16 and the coupling convex portion 17 are provided on the same axis and engage with each other. Then, as shown in FIGS. 6A and 6B, the coupling force 17 is engaged with the cut shape of the coupling recess 16 to transmit the driving force. Similarly, the other coupling 18 has a cut-shaped coupling concave portion 16 and a coupling convex portion 17, but differs from the coupling 15 in the cut amount. This is to cause a phase difference in drive transmission. Thus, after the driving is completed, the reverse rotation control is performed so that the two couplings 15 and 18 return to the position where the phase difference is generated. In this embodiment, as shown in FIG. 4, the cut shape of the coupling 15 that transmits the driving force to the photosensitive drum 1Bk is smaller than the cut shape of the coupling 18 that transmits the driving force to the photosensitive drums 1Y and 1M. It is comprised so that it may become.

  Next, the operation of the photosensitive drum drive system of this embodiment will be described in detail. In FIG. 4, when the CPU 80 receives the print signal, it sends a signal to the drive motor 11 so as to start the rotational drive, and starts the pre-multiple rotation. This driving force is transmitted to the gear train 12, and the driving force is transmitted to the couplings 15 and 18. Here, since the coupling 15 and the coupling 18 are provided with the cut shape as described above, even if the driving force is transmitted, there is a backlash of the cut portion, so that the photosensitive drum 1Bk and the photosensitive drums 1Y and 1M are moved. The drive transmission is delayed with a time difference compared to the photosensitive drum 1C. In this embodiment, since the cut amount of one coupling 18 is larger than the cut amount of the other coupling 15, the driving force to the photosensitive drums 1Y and 1M is transmitted with a delay from the photosensitive drum 1Bk. The Thereby, it is possible to disperse fluctuations in the driving load of the entire image forming apparatus.

  When the image formation is completed, the drive motor 11 is temporarily stopped, and the coupling convex portion 17 returns from the predetermined position, that is, the state shown in FIG. 7B to the position shown in FIG. 7A. Further, the CPU 80 is controlled so as to reversely rotate the drive motor 11. At this time, since the mechanical one-way clutch 14 does not transmit driving force in the reverse direction, each photoconductive drum 1 does not rotate, and thus does not cause a rubbing scratch with the intermediate transfer belt 30 or the like.

  By performing this reverse rotation control, it is possible to always distribute the drive load variation at the start of image formation. Further, the phase shift control means for controlling the movement amount of the coupling convex portion 17 by this reverse rotation control can give the desired phase difference by controlling the movement amount to control the drive transmission delay time. Is possible.

  In this embodiment, the one-way clutch 14 is installed in the gear f, the gear g, and the gear h, the coupling 15 having the cut shape is installed in the gear b, and the coupling 18 is installed in the gear e. The timing is configured to generate three time phase differences. However, the present invention is not limited to this, and the configuration is such that a combination of two photosensitive drums or a phase difference is generated in the driving timing of all the photosensitive drums. The effect can be obtained.

  In the present embodiment, the image forming apparatus includes the intermediate transfer belt 30. However, the image forming apparatus can be effective not only in the intermediate transfer belt system but also in an intermediate transfer drum system and a direct paper transfer system.

1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. It is the schematic of the drive transmission means which concerns on the 1st Embodiment of this invention. It is the schematic of the drive transmission by the electronic clutch which concerns on the 1st Embodiment of this invention. It is the schematic of the drive transmission means which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the coupling shape which concerns on the 2nd Embodiment of this invention. The coupling shape which concerns on the 2nd Embodiment of this invention is shown, (a) is a coupling recessed part, (b) is explanatory drawing of a coupling convex part. It is the schematic of the operation | movement mechanism regarding the phase control which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram which shows the conventional image forming apparatus. FIG. 3 is a schematic diagram of an image carrier driving method in a tandem type image forming apparatus, where (a) is an “individual motor method”, (b) is a “one motor method”, and (c) is an explanation of an “individual motor method”. FIG.

Explanation of symbols

P: Image forming unit a: Clutch gear 1 ... Photoconductor drum 2 ... Charging roller 3 ... Exposure device 4 ... Developing device 5 ... Primary transfer roller 6 ... Cleaning means 7 ... Fixing device 8 ... Storage unit 9 ... Latent image process unit
10 ... Image forming device body
11… Drive motor
12 ... Gear train
13… Electronic clutch
14… One-way clutch
15… coupling
16… Coupling recess
17… Coupling convex
18… Coupling
30 ... Intermediate transfer belt
31… Pickup roller
32… Secondary transfer roller
33 Cleaning means
35… Conveyor belt
80… CPU

Claims (7)

A plurality of image carriers, a drive source for rotationally driving the plurality of image carriers, and drive transmission means for transmitting a driving force from the drive source to the plurality of image carriers. In the image forming apparatus in which the image carrier is rotationally driven from the drive source by the drive transmission means in the same cycle,
Phase displacement means for displacing a phase during rotation of at least one image carrier among a plurality of image carriers to which the drive transmission means transmits a driving force with respect to a phase when other image carriers are stopped. An image forming apparatus comprising: The image forming apparatus according to claim 1, wherein the phase displacement unit is a clutch unit that disconnects and connects transmission of driving force. The image forming apparatus according to claim 1, wherein the phase displacement unit is a delay unit that delays transmission of a driving force. A plurality of image carriers, a drive source for rotationally driving the plurality of image carriers, and drive transmission means for transmitting a driving force from the drive source to the plurality of image carriers. In the image forming apparatus in which the image carrier is rotationally driven from the drive source by the drive transmission means in the same cycle,
Phase displacement means for displacing a phase during rotation of at least one image carrier among a plurality of image carriers to which the drive transmission means transmits a driving force with respect to a phase when other image carriers are stopped. And an image forming apparatus comprising phase displacement control means for controlling phase displacement by the transfer displacement means. The phase displacement means is a clutch means for disconnecting and connecting transmission of driving force,
5. The image forming apparatus according to claim 4, wherein the phase displacement control unit controls the timing of disconnecting and connecting the driving force transmitted by the clutch unit. 5. The image forming apparatus according to claim 4, wherein the phase displacement unit is a delay unit that delays transmission of a driving force, and the phase displacement control unit controls a transmission delay time of driving by the delay unit. In the process unit that is mounted on the image forming apparatus main body and forms the image forming unit,
An image carrier for forming an image;
A drive transmission member provided on a rotation shaft of the image carrier, which is mounted on the image forming apparatus according to any one of claims 1 to 6, and a driving force is transmitted by the drive transmission unit. A drive transmission member;
A process unit comprising:

Images