JP2007248547A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of surely preventing the occurrence of failure such as the overflow of toner from a cleaning device and the damage of a toner collecting path even when a large quantity of toner is forcibly consumed such as refreshing a photoreceptor or refreshing developer. <P>SOLUTION: In the image forming apparatus provided with a photoreceptor cleaning device 25 for a photoreceptor 6 and an intermediate transfer body cleaning device 26 for an intermediate transfer body 12 respectively, a controller 27 performs control by switching between photoreceptor side collecting disposal in which the toner in a developing device 7 is forcibly shifted to the photoreceptor 6 so as to be collected by the photoreceptor cleaning device 25 when an image is not formed, and intermediate transfer body side collecting disposal in which the toner in the developing device 7 is forcibly shifted to the intermediate transfer body 12 through the photoreceptor 6 so as to be collected by the intermediate transfer body cleaning device 26 in a time division manner. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine, and more particularly to an intermediate transfer type image forming apparatus.

  In general, some image forming apparatuses such as copying machines, printers, facsimiles, and multifunction machines employ an intermediate transfer method. That is, in this intermediate transfer type image forming apparatus, an electrostatic latent image is exposed and formed on the surface of a photoreceptor, and then a toner is electrostatically attached to the electrostatic latent image by a developing device to form an unfixed toner image. After development, the toner image is primarily transferred to an intermediate transfer member, and the toner image transferred to the intermediate transfer member is secondarily transferred onto the surface of a recording medium such as paper. Thereafter, the recording medium carrying the toner image is fixed as a permanent image by the fixing device.

  This intermediate transfer type image forming apparatus, in particular, when carrying out color printing, once carrying a full color image on the intermediate transfer member and then performing secondary transfer to a recording medium at a time, ensuring high image quality, There is an advantage that color printing can be performed on recording media of various types and sizes.

  In addition, in this intermediate transfer type image forming apparatus, a slight amount of toner remains on the surface of the photosensitive member when the toner image is transferred from the photosensitive member to the intermediate transfer member. A photoconductor cleaning device is provided. Further, even when a toner image is transferred from the intermediate transfer member to a recording medium, a slight amount of toner remains on the surface of the intermediate transfer member, so that the intermediate transfer member cleaning device collects the residual toner by cleaning the intermediate transfer member. Is provided.

  By the way, when this type of image forming apparatus is used for a long period of time, an ion product resulting from corona discharge of a charger such as a corotron adheres to the drum surface of the photosensitive member, and the sharpness of the electrostatic latent image is reduced. Phenomena such as flow may occur. In this case, during non-image formation in which the toner image is not transferred to the recording medium, the toner in which the abrasive is mixed in the developing device is forcibly transferred to the photoconductor and polished (hereinafter referred to as photoconductor refresh). Is done.

  Further, when the image forming apparatus is used for a long period of time, the characteristics of the developer composed of toner and carrier may change in the developing device, or the charging characteristics of the developer may deteriorate due to mixing of paper dust. In that case, during non-image formation, an operation of forcibly transferring the toner in the developing device to the photosensitive member and actively consuming a large amount thereof (hereinafter referred to as developer refresh) is performed.

  When a large amount of toner is forcibly consumed at the same time as in the above-described photoreceptor refresh or developer refresh, the photoreceptor is transferred to the photoreceptor and simply collected by the photoreceptor cleaning device. The collection load is concentrated on the cleaning device. In particular, when collecting a large amount of toner with reduced fluidity, the toner collection and conveyance path is clogged in the middle and cannot be smoothly conveyed to the collection device, and the toner overflows to the outside and adversely affects the printed image. This causes problems such as hardening and damage to the transport path.

  Therefore, conventionally, a technique has been proposed in which a magnetic cleaning roller is provided in the photosensitive member cleaning device and a spiral groove that continuously changes is formed on the cleaning roller to improve toner conveyance (see, for example, Patent Document 1). .

  Conventionally, a technique has also been proposed in which the shape of the toner transport pipe that connects the photoconductor cleaning device and the collection device is devised to reduce the load on the toner transport path (see, for example, Patent Document 2).

As another conventional technique, a technique for performing the above-described photoreceptor refreshing and developer refreshing has been proposed (see, for example, Patent Documents 3 and 4).
JP-A-8-83030 Japanese Patent Laid-Open No. 10-198245 JP 2005-156929 A Japanese Patent Laid-Open No. 2005-134776

  However, when performing photoconductor refreshing and developer refreshing, unlike normal printing, a large amount of toner is forcibly consumed at one time. Even if measures such as forming a spiral groove on the cleaning roller to improve toner transportability or devising the shape of the toner transport pipe to reduce the load on the toner transport path are still insufficient, The toner collected in the photoconductor cleaning device still overflows to the outside and adversely affects the printed image, or the toner collecting / conveying path is clogged and damaged.

  Further, Patent Documents 3 and 4 only propose techniques for performing photoconductor refreshing and developer refreshing, and do not mention any technique on how to reduce the recovery load in the cleaning device at that time. . Therefore, even in this case, there is a possibility that the recovery load concentrates on the photoconductor cleaning device, causing a toner overflow or a failure of the toner recovery path.

  The present invention has been made to solve the above-described problems. Even when a large amount of toner is forcibly consumed, such as a photoreceptor refresh or a developer refresh, a toner overflow from a cleaning device and a recovery path are provided. An object of the present invention is to provide an image forming apparatus capable of reliably preventing the occurrence of problems such as breakage of the image.

  In order to achieve the above object, the present invention is obtained by developing a photosensitive member on which an electrostatic latent image is formed, a developing unit for developing the electrostatic latent image on the photosensitive member with toner, and developing the developing unit. It is assumed that the image forming apparatus includes a transfer device that retransfers the toner image to a recording medium such as paper via an intermediate transfer member.

  In the present invention, the photosensitive member is provided with a photosensitive member cleaning device for cleaning the photosensitive member, the intermediate transfer member is provided with an intermediate transfer member cleaning device for cleaning the intermediate transfer member, and a non-image. The toner on the developing device is forcibly transferred to the photoconductor at the time of formation and is collected by the photoconductor cleaning device, and the toner on the developing device is forcibly passed through the photoconductor and the intermediate transfer member. And a recovery switching means for switching in a time-sharing manner to the intermediate transfer member side recovery process for recovery to the intermediate transfer member cleaning device.

  In this case, the recovery switching unit executes the intermediate transfer member side recovery processing in a time-sharing manner while the photoconductor side recovery processing is being executed, or each of the processes is performed between the photosensitive member side recovery processing and the intermediate transfer member side recovery processing. It can be configured such that it is executed alternately every time it is completed.

  Further, the recovery switching unit can switch between the photoreceptor side recovery process and the intermediate transfer body side recovery process by turning on / off the transfer voltage with respect to the intermediate transfer body.

  In the image forming apparatus of the present invention, when a large amount of toner is forcibly consumed, such as a photoreceptor refresh or a development refresh, the collection switching unit performs a photoreceptor side collection process to the photoreceptor cleaning apparatus side and an intermediate transfer body cleaning. Since switching to the intermediate transfer member side recovery process to the apparatus side is performed in a time-sharing manner, the toner recovery load is evenly distributed between the photosensitive member cleaning device and the intermediate transfer member cleaning device.

  For this reason, the collection load is not concentrated only on one of the photoconductor cleaning devices as in the prior art, and the collected toner overflows outside in the cleaning device, adversely affects the printed image, or the collection path is clogged and damaged. Can be avoided.

  In particular, for developer refresh, if the intermediate transfer member side recovery process is executed in a time-sharing manner while the photoreceptor side recovery process is being executed, the toner recovery load can be evenly distributed during the developer refresh. It is valid. For photoreceptor refresh, if the photoreceptor side collection process and the intermediate transfer body side collection process are executed alternately each time the processes are completed, the photoreceptor can be sufficiently refreshed. It is effective for.

  In addition, switching between the photoconductor side recovery process and the intermediate transfer body side recovery process by turning on / off the transfer voltage for the intermediate transfer body is effective because it can be easily realized without incurring an extra cost. It is.

  FIG. 1 is a schematic configuration diagram showing an entire copying machine as an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a configuration diagram showing an arrangement relationship among a developing device, a transfer device, and a cleaning device provided in the copying machine. It is.

  The copying machine 1 according to this embodiment includes a housing 2. An image reading device 3 for reading an image of a document and R, G, and B read by the image reading device 3 are provided in the housing 2. An image processing device 4 that converts three-color image data into four colors Y, M, C, and K, and an exposure device 5 that exposes a photoconductor 6 described later based on the image data processed by the image processing device 4. A photosensitive member 6 on which an electrostatic latent image is formed by the exposure device 5; a developing unit 7 for developing the electrostatic latent image on the photosensitive member 6 with toner to form a visible toner image; There is provided a transfer unit 8 for transferring a toner image developed by the developing unit 7 onto a paper p as a recording medium, and a fixing device 9 for thermally fixing the toner image transferred onto the paper p by the transfer unit 8. It has been.

  The exposure apparatus 5 includes a laser light source, an optical reflection system, and the like, and the developing device 7 includes a rotary developing unit having toner cartridges of four colors Y, M, C, and K for color printing in this example. .

  The transfer unit 8 includes an intermediate transfer belt 12 as an intermediate transfer body onto which the toner image on the photosensitive member 6 is transferred, a primary transfer roller 13 for transferring the toner image on the photosensitive member 6 to the intermediate transfer belt 12, A driving roller 14 that drives the transfer belt 12, a secondary transfer roller 15 and a contact roller 16 that are arranged opposite to each other to re-transfer the toner image transferred to the intermediate transfer belt 12 to the surface of the paper p, and an intermediate transfer that will be described later An idle roller 17 is provided so as to face the body cleaning device 26.

  The photosensitive member 6 is provided with a charger 21 for charging the photosensitive member 6 in order to form an electrostatic latent image on the surface of the photosensitive member 6, and the charger 21 is connected via a charging switch SW1. A high-voltage power supply is connected. Further, a power supply 24 for applying a charging voltage having a polarity opposite to that of the toner is connected to the primary transfer roller 13 constituting the transfer device 8 via a transfer switch SW2. Here, it is assumed that the toner has a negative charge at the time of frictional charging. Therefore, a positive voltage is applied to the primary transfer roller 13.

  Further, a photosensitive member cleaning device 25 for cleaning the photosensitive member 6 is provided, and an intermediate transfer member cleaning device 26 for cleaning the intermediate transfer belt 12 is provided. Each of the cleaning devices 25 and 26 includes blades 25a and 26a that wipe off the toner, and recovery rollers 25b and 26b that recover the toner.

  FIG. 3 is a block diagram showing the configuration of the control system of the copying machine.

  This control system includes a controller 27 such as a CPU and an input operation unit 28 such as a touch panel for giving a command to the controller 27. The controller 27 performs secondary transfer only when the toner image is secondarily transferred onto the paper p. Only when the transfer roller 15 is moved toward the intermediate transfer belt 12 and the toner on the intermediate transfer belt 12 is collected, the intermediate transfer body cleaning device 26 is brought into contact with the intermediate transfer belt 12. The controller 27 is programmed to turn on / off the charging and transfer switches SW1 and SW2 at a predetermined timing. The controller 27 and the switches SW1 and SW2 correspond to the recovery switching means in the claims.

  Reference numeral 31 denotes an original platen provided on the upper part of the housing 2, 32 denotes a paper feed cassette, and 33 denotes a transport roller for transporting various sizes of paper p stored in the paper feed cassette 32 toward the transfer unit 8.

  In the copying machine 1 configured as described above, when printing on the paper p, for example, an image of a document set on the document table 31 is read by the image reading device 3, and the three color images of R, G, and B are read. The data is converted into image data of four colors Y, M, C, and K by the image processing device 4.

  Subsequently, the charging switch SW1 is turned on and a high voltage is applied from the high-voltage power source 23 to the charger 21, whereby the surface of the photoreceptor 6 is uniformly charged. In this state, the surface of the photoreceptor 6 is exposed by the exposure device 5. Is exposed for each color based on the image data to form an electrostatic latent image, and then the toner is transferred to the photosensitive member 6 for each color by the developing unit 7 to visualize the electrostatic latent image as a toner image. The Each time a toner image for each color is formed on the photoreceptor 6, the transfer switch SW <b> 2 is turned on and a transfer voltage is applied to the primary transfer roller 13, whereby the toner image is primarily transferred to the intermediate transfer belt 12. The

  When the full-color toner image is transferred to the intermediate transfer belt 12 by repeating the above operation, the sheet p is taken out of the paper feed cassette 32 by the transport roller 33 and transported toward the transfer device 8 in accordance with the timing at which the paper p is transported to the transfer device 8. The next transfer roller 15 is moved to the intermediate transfer belt 12 side, and a full-color toner image is secondarily transferred onto the paper p at a time. The sheet p on which the toner image is transferred is fixed as a permanent image by the fixing device 9 and then discharged to a tray or the like outside the housing 2. At the time of secondary transfer, the intermediate transfer body cleaning device 26 is brought into contact with the intermediate transfer belt 12, and excess residual toner on the intermediate transfer belt 12 is removed and collected by the intermediate transfer body cleaning device 26.

  On the other hand, when the conditions for performing the photoreceptor refresh or the developer refresh are satisfied, the controller 27 first separates the secondary transfer roller 15 from the intermediate transfer belt 12 so that printing on the paper p is not performed. After that, the intermediate transfer member cleaning device 26 is brought into contact with the intermediate transfer belt 12.

  In this state, the controller 27 forcibly transfers the toner of the developing device 7 to the photoconductor 6 and collects it by the photoconductor cleaning device 25 (hereinafter referred to as photoconductor-side recovery processing). A recovery process (hereinafter, referred to as an intermediate transfer body side recovery process) in which the toner 7 is forcibly transferred to the intermediate transfer belt 12 through the photoreceptor 6 and recovered by the intermediate transfer body cleaning device 26 is executed in a time-sharing manner.

  That is, as shown in FIG. 4A, the controller 27 turns on the charging switch SW1 for a certain period T1 to apply a high voltage to the charger 21 to charge the surface of the photoreceptor 6, and the exposure device 5 The surface of the photoreceptor 6 is exposed for each color so as to form a printing pattern such as solid printing, and the toner is transferred to the photoreceptor 6 for each color by the developing unit 7. At this time, the controller 27 turns on / off the transfer switch SW2 at a predetermined cycle. Since the transfer voltage is not applied to the primary transfer roller 13 when the transfer switch SW2 is off, the toner on the photoreceptor 6 does not move to the intermediate transfer belt 12, but is wiped off by the blade 25a of the photoreceptor cleaning device 25. It is collected by the collection roller 25b. On the other hand, when the transfer switch SW2 is on, the transfer voltage is applied to the primary transfer roller 13, so that the toner on the photosensitive member 6 is transferred to the intermediate transfer belt 12 and is moved by the blade 26a of the intermediate transfer member cleaning device 26. It is wiped off and collected by the collection roller 26b.

  In FIG. 4A, the intermediate transfer member side recovery process is executed in a time-sharing manner while the photoconductor side recovery process is being executed. However, the present invention is not limited to this. For example, as shown in FIG. When the toner is transferred to the photosensitive member 6 by turning ON, the case where the transfer switch SW2 is turned on and the case where the transfer switch SW2 is turned off are alternately repeated. It can also be executed alternately each time the process is completed. This is effective because the photosensitive member 6 can be sufficiently refreshed when the photosensitive member is refreshed.

  As described above, in this embodiment, when a large amount of toner is forcibly consumed, such as a photoreceptor refresh or a developer refresh, the photoreceptor side collection process and the intermediate transfer body side collection process are time-divisionally divided. Therefore, the toner recovery load is evenly distributed between the photosensitive member cleaning device 25 and the intermediate transfer member cleaning device 26. As a result, the collection load does not concentrate only on the photoconductor cleaning device 25 as in the prior art, and the collected toner overflows to the outside in the cleaning device 25 and adversely affects the printed image, or the toner collection path is clogged and damaged. It is possible to avoid the occurrence of problems such as

  In order to confirm the effectiveness in the above embodiment, the following evaluation experiment was performed.

  As a copying machine, a model of LS-C5016N manufactured by Kyocera Mita is used, and in the first embodiment according to the present invention, as shown in FIG. 4A, when the charging switch SW1 is turned on, the transfer switch SW2 is set to 0.2 sec. The intermediate transfer member side recovery process was executed in a time-sharing manner during the execution of the photosensitive member side recovery process. In Embodiment 2 according to the present invention, as shown in FIG. 4B, when the charging switch SW1 is turned on, the transfer switch SW2 is alternately turned on and turned off, whereby the photoconductor side is repeated. The collection process and the intermediate transfer body side collection process were alternately performed as each process was completed. For comparison with Examples 1 and 2, Comparative Example 1 does not perform the forced toner consumption operation. In Comparative Example 2, the toner is collected by the photoconductor cleaning device 25 only during the forced toner consumption operation. The photoreceptor side recovery process was performed.

  As printing conditions at this time, a solid print pattern is formed every 1000 sheets of toner with a full width in the photoreceptor axis direction and a 540 mm width in the circumferential direction, and 0 for all colors Y, M, C, and K. Continuous printing of 50000 sheets was performed at a printing rate of 1% and 8%. Then, Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated for the experimental results according to each evaluation item and each criterion shown in Table 1. And when the defect generate | occur | produced on the criterion, the experiment on the condition was stopped.

  Among the evaluation items in Table 1, the image density (ID) mainly evaluates the presence / absence of the deterioration of the developer, and the black image streak mainly evaluates the presence / absence of toner overflow of the photoconductor cleaning device. Is mainly used for evaluating the refreshing effect of the photosensitive member, and a cleaning lock is used for evaluating whether the cleaning devices 25 and 26 are clogged with toner.

  Table 2 shows the evaluation results based on Table 1 for Examples 1 and 2 and Comparative Examples 1 and 2.

  As is apparent from the evaluation results, the evaluation results are all good in any of Examples 1 and 2 (Tables 2 (a) and (b)) according to the present invention.

  On the other hand, in Comparative Example 1 (Table 2 (c)), since no forced toner consumption operation is performed, cleaning lock does not occur, but image density (ID) and image flow occur. In particular, when the printing rate is low, it occurs early when the number of printed sheets is small. In Comparative Example 2 (Table 2 (d)), since the toner is forcibly consumed, no image density (ID) or image flow occurs, but the toner is collected only by the photoconductor cleaning device 25. Black streaks or cleaning locks have occurred. In particular, when the printing rate is high, the amount of forced toner consumption increases, and accordingly, black image streaks and cleaning locks occur early when the number of printed sheets is small.

  In the above-described embodiment, the intermediate transfer belt 12 is used as the intermediate transfer body. However, the present invention is not limited to this, and the present invention can be applied even to an apparatus having an intermediate transfer roller.

  The present invention is not limited to a copying machine, and can be widely applied to various image forming apparatuses such as a printer, a facsimile machine, and a multifunction machine.

1 is a schematic configuration diagram illustrating an entire copying machine according to an embodiment of the present invention. FIG. 2 is a configuration diagram illustrating an arrangement relationship between a developing device, a transfer device, and a cleaning device provided in the copier. 2 is a block diagram illustrating a schematic configuration of a control system of the copier. FIG. It is a timing chart with which it uses for operation | movement description in embodiment of this invention.

Explanation of symbols

1 Copying machine (image forming device)
5 Exposure device 6 Photoconductor 7 Developing device 8 Transfer device 12 Intermediate transfer belt (intermediate transfer member)
21 Charger SW1 Charging switch (collection switching means)
SW2 Transfer switch (collection switching means)
25 Photoconductor cleaning device 26 Intermediate transfer member cleaning device 27 Controller (collection switching means)

Claims (4)

A photosensitive member on which an electrostatic latent image is formed, a developing unit that develops the electrostatic latent image on the photosensitive member with toner, a toner image obtained by developing with the developing unit, a sheet or the like via an intermediate transfer member An image forming apparatus including a transfer device that re-transfers to a recording medium of
The photosensitive member is provided with a photosensitive member cleaning device for cleaning the photosensitive member, and the intermediate transfer member is provided with an intermediate transfer member cleaning device for cleaning the intermediate transfer member. Forcibly transfers the toner to the photoconductor and collects it by the photoconductor cleaning device, and forcibly transfers the toner from the developing device to the intermediate transfer body via the photoconductor. An image forming apparatus comprising: a recovery switching unit that switches in time division to an intermediate transfer member side recovery process that is recovered by a body cleaning device.   The image forming apparatus according to claim 1, wherein the recovery switching unit is configured to execute the intermediate transfer member side recovery process in a time division manner during execution of the photosensitive member side recovery process.   The image forming apparatus according to claim 1, wherein the recovery switching unit alternately executes the photoconductor side recovery process and the intermediate transfer body side recovery process every time each process is completed. 4. The recovery switching means switches between the photoreceptor side recovery process and the intermediate transfer body side recovery process by turning on / off a transfer voltage with respect to the intermediate transfer body. The image forming apparatus according to any one of the above.

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