JP2010060998A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent motor lock failure even if an abnormal volume distribution of developer in a developing device is caused by handling, in an image forming apparatus provided with a small developing device for continuously performing image formation of an image with high image area ratio without causing toner density deviation on a developing sleeve. <P>SOLUTION: The image forming apparatus provided with a small developing device for continuously performing image formation of an image with high image area ratio includes a door opening and closing detection means which detects opening and closing state of a door provided to access the developing device. When the door is closed, or when the image forming apparatus is power-on, a feed carrying member, a recovery carrying member and an agitation carrying member are rotated reversely to a normal rotating direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a multi-function machine having at least two functions having a developing device using a two-component developer composed of a toner and a carrier.

  In a conventionally known electrophotographic image forming apparatus, an electrostatic latent image is formed by charging and exposing an image carrier. Thereafter, the electrostatic latent image formed on the image carrier is converted into a toner image by a developing device, and after the toner image is transferred to a recording medium such as transfer paper, pressurization and heating are performed using a fixing device. Thus, the toner image is fixed on the recording medium to form an image.

  In the field of this type of electrophotographic method, a two-component development method using a developer composed of a toner and a carrier is widely adopted from the viewpoint of excellent durability and image characteristics. The developer is conveyed and carried from the conveying member such as a conveying screw to the developing sleeve by the magnetic force of the magnet contained in the developer carrying member such as the developing sleeve, and an electrostatic latent image is formed by the rotation of the developing sleeve. It is further conveyed to an image carrier such as a photosensitive member and developed. At this time, since only the toner in the developer is consumed in the development area, the toner density (ratio of the toner contained in the developer) is made uniform to output a stable image. It is necessary to replenish the toner in the developing container for the amount of the toner.

  In general, in a developing device using a two-component developer, new toner replenished in the developer is gradually dispersed in the longitudinal direction of the conveying screw while being conveyed by a conveying member such as a conveying screw. Mixing and stirring with the agent is performed. The toner density is determined by the distribution of the toner consumed in the development and the replenished toner, and the charge amount is determined by the frictional charging at the time of mixing the carrier and the toner. The two-component developer is sufficiently stirred to make the toner density distribution uniform, and the charge amount applied to the toner is saturated, thereby stabilizing the toner image.

  Here, for example, in Patent Document 1, a supply shaft (or auger) that supplies developer to the developing sleeve is provided on the upper side, and a recovery shaft that recovers developer remaining on the developing sleeve is provided on the lower side. A developing device is disclosed in which the shaft is connected to both ends so that the developer once collected on the developing sleeve but not used for development is not immediately transferred to the supply shaft again. ing.

  However, the developing device disclosed in Patent Document 1 does not disclose a place where new toner is replenished. For example, toner replenishment is performed on the upstream side in the transport direction of the recovery shaft or on the downstream side in the transport direction of the supply shaft. In this case, new toner cannot be replenished to the developer supplied to the developing sleeve on the upstream side in the transport direction of the supply shaft and recovered on the downstream side in the transport direction of the recovery shaft. The developer may be supplied again to the supply shaft as it is, and the toner density may be low and density unevenness may occur. Conversely, when toner is replenished downstream of the collection shaft in the transport direction or upstream of the supply shaft in the transport direction, there is a path from when the new toner is replenished until the replenished toner reaches the developing sleeve. The supply toner is short and cannot be supplied to the developing sleeve with sufficient stirring.

  In order to solve this problem, for example, in the developing device disclosed in Patent Document 2, a technique is disclosed in which a stirring shaft for stirring the developer and the toner is provided in addition to the collection shaft and the supply shaft. In this developing device, toner is replenished on the downstream side in the transport direction of the collection shaft or on the upstream side in the transport direction of the agitation shaft. For example, this is the case when images having a high printing rate or a high image area rate are continuously formed. However, it is possible to pass the developer having a constant toner concentration and a sufficiently mixed carrier and toner to the supply shaft.

  However, in the developing device of Patent Document 2, in order to make the bulk of the developer on the supply shaft constant in the axial direction with respect to the developing sleeve, an opening serving as a developer delivery point from the stirring shaft to the supply shaft, And an opening, which is a place where the developer is transferred to the recovery shaft, is located outside the area where the image is formed, that is, outside the width of the development area where the toner is supplied to the image carrier. There is a problem that the size of the apparatus becomes large.

  Therefore, as in the developing device described in Patent Document 3, an image is formed of an opening that is a location where the developer is transferred from the stirring shaft to the supply shaft and an opening that is the location where the developer is transferred from the supply shaft to the collection shaft. There has been proposed a developing device within the region to be formed. In this developing device, the developer is lifted from the end of the stirring chamber to the upper supply chamber. During normal use, the bulkiness distribution of the developer becomes appropriate, and the developer may continuously circulate. The developing device is designed so that the toner density of the developer supplied to the developing sleeve is constant regardless of the image to be formed, and a developing device having a small size can be realized.

  However, in an image forming apparatus in which the developing device is used, after performing a work such as attaching / detaching the developing device for some reason or replacing the developing device, the developing device may be tilted, for example. It is also possible that some impact has been applied. In such a case, the developer bulk distribution in the developing device is biased, and the developer on the supply chamber disposed above is clogged without any gaps in the supply chamber (so-called packing state). It may become. When image formation is performed in this packed state, the torque for lifting the developer from the stirring chamber to the supply chamber becomes very high, and as a result, the ability of the motor to operate the stirring shaft, supply shaft, etc. In some cases, an abnormality (so-called motor lock abnormality) that prevents the developing device from rotating may occur.

Japanese Patent Laid-Open No. 05-333691 JP 2001-290368 A JP 2007-193289 A

  In light of the above problems, the present invention provides an image forming apparatus in which a toner density deviation on the developing sleeve does not occur even when an image having a high image area ratio is continuously formed, and the developing apparatus is small in size. An object of the present invention is to provide an image forming apparatus that does not cause a motor lock abnormality even if the bulk distribution of the developer in the developing apparatus becomes abnormal due to handling.

  According to the present invention, there is provided a developer that is disposed opposite to an image carrier on which an electrostatic latent image is formed and is capable of carrying and rotating a two-component developer having a toner and a carrier on the surface. A carrier, a supply conveyance member that conveys the two-component developer along a rotation axis direction of the developer carrier, and supplies the two-component developer to the developer carrier; and the supply conveyance member A supply / conveying chamber for accommodating the developer developer recovered from the developer carrying member after development from the developer carrying member along a rotation axis direction of the developer carrying member and the supply carrying member; A collecting and conveying member that conveys in the same direction, the collecting and conveying chamber that houses the collecting and conveying member, an excess developer that is conveyed to the supply and conveying member without being used for development in the supply and conveying chamber, and the collecting and conveying chamber With the collection and transport member While stirring the collected developer that has been transported, a stirring transport member that transports in the direction opposite to the supply transport member along the rotation axis direction of the developer carrying member, and the stirring transport member are accommodated. And a stirring and conveying chamber provided below the supply and conveying chamber, and the supply and conveying chamber, the recovery and conveying chamber, and the agitating and conveying chamber are each partitioned by a partition member, and The collection conveyance chamber and the agitation conveyance chamber are provided with openings that communicate with each other in order to transfer the collected developer from the collection conveyance chamber to the agitation conveyance chamber, and the supply conveyance chamber and the agitation conveyance chamber The chamber includes an opening communicating with each other for transferring the excess developer from the supply conveyance chamber to the agitation conveyance chamber, and a developer that agitates and conveys the recovered developer and the excess developer. Front from the agitation transfer chamber In an image forming apparatus provided with a developing device each provided with an opening communicating with each other for delivery to the supply conveyance chamber, the image forming device includes an open / closed state of a door provided to access the developing device Door opening / closing detection means is further provided, and when the door is closed or when the power of the image forming apparatus is turned on, the supply conveyance member, the collection conveyance member, and the stirring conveyance member The image forming apparatus is characterized in that the image forming apparatus is rotated in the direction opposite to the normal rotation direction.

  In the present invention, it is proposed that after the rotation in the reverse direction, the supply conveyance member, the recovery conveyance member, and the agitation conveyance member are further rotated in a normal rotation direction.

  According to the present invention, in an image forming apparatus including a developing device having a small toner size deviation that does not generate a toner density deviation on the developing sleeve even when an image having a high image area ratio is continuously formed. When there is a possibility of working on the developing device, that is, when the door necessary to access the developing device is opened and closed, and when the power is turned on, the supply conveyance member, the recovery conveyance member, and the agitation conveyance By rotating each conveying member of the member in the direction opposite to the normal rotation direction, the developer packing state caused by the bias of the developer is effectively eliminated, and the motor lock abnormality does not occur. It becomes possible. Furthermore, by rotating the conveying members in the normal direction after the rotation in the reverse direction, it is possible to return to an appropriate developer distribution state before the developer is biased, and so-called white-out images can be prevented. become.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  First, an image forming apparatus in which the developing device of the present invention is used will be described with reference to FIG. FIG. 1 is a diagram schematically showing a tandem indirect (intermediate) transfer type electrophotographic apparatus as an embodiment of the image forming apparatus of the present invention. In the image forming apparatus shown in FIG. A plurality of photoconductors arranged in the first to fourth photoconductors 1a, 1b, 1c, and 1d in the illustrated example are provided. Toner images of different colors are formed on the respective photoreceptors. In the example shown in FIG. 1, a black toner image, a magenta toner image, and a cyan toner image are formed on these photoreceptors 1a, 1b, 1c, and 1d. And a yellow toner image are formed.

  An intermediate transfer belt 10 configured as an intermediate transfer member is disposed opposite to the first to fourth photosensitive members 1a, 1b, 1c, and 1d, and each of the photosensitive members 1a, 1b, 1c, and 1d is disposed on the intermediate transfer belt 10. It is in contact with the surface. The intermediate transfer belt 10 shown here is wound around support rollers 12, 13, 14, 15 and is configured as a drive roller in which one of these support rollers is driven by a drive device (not shown), When the drive roller is driven, the intermediate transfer belt 10 is driven to rotate counterclockwise in the drawing.

  The configuration for forming a toner image on the photoreceptors 1a, 1b, 1c, and 1d is substantially the same as the configuration for transferring each toner image onto the intermediate transfer belt 10, and the color of each formed toner image is the same. Is only different. Therefore, only the configuration and operation for forming a black toner image on the first photoreceptor 1a and transferring the toner image onto the intermediate transfer belt 10 will be described. The photoconductor 1a is rotated in the clockwise direction as shown by the arrow in FIG. 1, and at this time, the surface of the photoconductor is irradiated with light from a static eliminator (not shown), and the surface potential of the photoconductor 1a is initialized. The The initialized photoreceptor surface is uniformly charged to a predetermined polarity by the charging device 4. The charged surface is irradiated with a light-modulated laser beam 5 emitted from an exposure apparatus (not shown), and an electrostatic latent image corresponding to writing information is formed on the surface of the photoreceptor 1a. In this embodiment, an exposure apparatus including a laser writing apparatus that emits the laser beam 5 is used. However, an exposure apparatus having an LED array and an image forming unit may be used.

  The electrostatic latent image formed on the photoreceptor 1a is visualized as a black toner image when it passes through the developing device 6. On the other hand, on the inner side of the intermediate transfer belt 10, a transfer roller 11 is disposed so as to face the photoreceptor 1a with the belt interposed therebetween. The transfer roller 11 is in contact with the back surface of the intermediate transfer belt 10 to ensure an appropriate transfer nip between the photoreceptor 1a and the intermediate transfer belt 10.

  A transfer voltage having a polarity opposite to the toner charging polarity of the toner image formed on the photoreceptor 1a is applied to the transfer roller 11. As a result, a transfer electric field is formed between the photosensitive member 1a and the intermediate transfer belt 10, and the toner image on the photosensitive member 1a is electrostatically applied to the intermediate transfer belt 10 that is rotationally driven in synchronization with the photosensitive member 1a. Is transcribed.

  In exactly the same manner, a magenta toner image, a cyan toner image, and a yellow toner image are respectively formed on the second to fourth photoreceptors 1b, 1c, and 1d, and the toner images of the respective colors are transferred to the black toner image. Electrostatic transfer is sequentially performed on the intermediate transfer belt 10 that has been applied.

  On the other hand, as shown in FIG. 1, a paper feeding device is disposed in the lower part of the apparatus main body, and the paper feeding device feeds a recording medium 25, for example, transfer paper, to the registration roller pair 27 by the rotation of the paper feeding roller 26. It is. The recording medium 25 sent out to the registration roller pair 27 that is not driven is a portion of the intermediate transfer belt 10 that is wound around the support roller 12 at a predetermined timing, and a secondary that is an example of a transfer device that is placed on the portion. The sheet is fed to the transfer roller 21 by driving the registration roller pair 27. At this time, a predetermined transfer voltage is applied to the secondary transfer roller 21, whereby the composite toner image on the intermediate transfer belt 10 is secondarily transferred to the recording medium 25.

  The recording medium 25 onto which the composite toner image has been secondarily transferred is further conveyed upward and passes through the fixing device 30. At this time, the toner image on the recording medium 25 is fixed by the action of heat and pressure. The recording medium 25 that has passed through the fixing device 30 is discharged out of the image forming apparatus via a pair of paper discharge rollers 32 provided in the paper discharge unit.

  Further, the transfer residual toner adhering to the intermediate transfer belt 10 after the toner image transfer is removed by a belt cleaning device 19 which is a cleaning device. In the belt cleaning device 19 in this embodiment, a blade-shaped cleaning blade 22 made of urethane or the like is used as a cleaning member, and the cleaning blade 22 is applied in the counter direction with respect to the rotation direction of the intermediate transfer belt 10. Touching. Instead of the cleaning blade 22, a conductive brush or roller may be used as a cleaning member so that it can be electrostatically collected and removed.

  Here, FIG. 2 is a diagram showing the main part of the image forming apparatus shown in FIG. 1 in a simplified manner. In FIG. 2, the rotation direction of the intermediate transfer member is different from FIG. That is, in FIG. 1, image transfer from the intermediate transfer member to the recording medium is performed on the right side of the drawing, while in FIG. 2, image transfer from the intermediate transfer member to the recording medium is performed on the left side of the drawing. In the example of FIG. 1, the support roller is wound around four rollers 12, 13, 14, and 15. In the example of FIG. 2, the intermediate transfer belt 10 is wound around at least two support rollers. In the figure, only the support roller 12 on one side is shown. FIG. 2 is a diagram illustrating the main part of the image forming apparatus more simply than FIG. 1 in order to help the understanding of the invention, and each element used is described in detail by using the same reference numerals as in FIG. Description is omitted.

  Hereinafter, the developing device 6 used in the image forming apparatus whose main part is simply illustrated in FIG. 2 will be described in more detail with reference to FIG. As conventionally known, the image forming apparatus as illustrated in FIGS. 1 and 2 can be accessed by the user or the like in the components or parts inside the image forming apparatus such as the developing device 6. A door (not shown) configured to be openable and closable is provided in the housing or the main body, and the developing device 6 can be accessed by opening the door, or the developing device 6 can be attached and detached. It has a configuration. Further, door opening / closing detection means such as a sensor for detecting the opening / closing state of the door is provided in the image forming apparatus so that the opening / closing state of the door can be monitored.

  The developing device 6 shown in FIG. 3 includes a developing container 61 containing a two-component developer, and develops in an opening provided at a position facing the photoreceptor 1 as an image carrier in the developing container 61. A developing sleeve 60 of a developer carrying member for carrying the developer is disposed to face the photosensitive member 1 so as to be rotatable at a predetermined interval. The developing sleeve 60 is formed of a cylindrical shape of a non-magnetic material, and rotates in a direction in which the developing portion that is a facing portion moves in the same direction with respect to the photosensitive member 1 that rotates in the direction indicated by the arrow in FIG. . Inside the developing sleeve 60, a magnet roller as a magnetic field generating unit is disposed so as not to rotate with respect to the rotation of the developing sleeve 60.

  The magnet roller described above has, for example, five magnetic poles N1, S1, N2, N3, and S2. Further, a regulating blade 40 of a magnetic member is attached to the upper portion of the developing sleeve 60 in the developing container 61, and this regulating blade 40 is developed toward the vicinity of the magnetic pole S2 that is substantially located at the uppermost point in the vertical direction of the magnet roller. The sleeve 60 is disposed in a non-contact manner.

  The developing container 61 of the developing device 6 is provided with a supply conveyance chamber 61 a in which a supply conveyance member 63 is accommodated, and the two-component developer in the supply conveyance chamber 61 a is developed by the supply conveyance member 63 by the developing sleeve. The toner is supplied to the developing sleeve 60 while being conveyed along the rotation axis direction 60 (in a direction toward the back side or the near side from the drawing plane in FIG. 3). The supply / conveyance member 63 in the present embodiment is disposed substantially in parallel along the axial direction of the developing sleeve 60. For example, the supply / conveyance member 63 has a screw structure in which a blade member or the like is provided in a spiral shape around the rotation axis. The component developer is configured to be conveyed. A collection conveyance member 64 and an agitation conveyance member 65, which will be described later, have the same configuration, and these conveyance members 63, 64, and 65 are driven and connected by a connection member such as a gear (not shown), and a motor or the like (not shown). Are integrally rotated by a driving source.

  Further, in the developing container 61 of the developing device 6, the two-component development remaining after development on the developing sleeve 60, downstream of the developing sleeve 60 in the rotation direction of the developing sleeve 60 from the developing portion that is the facing portion of the developing sleeve 60 and the photoreceptor 1. A recovery transport chamber 61b for recovering the agent is provided. In the recovery transport chamber 61b, the recovered two-component developer is disposed along the rotation axis direction of the developing sleeve 60 and in the same direction as the supply transport member 63. A collection conveyance member 64 for conveyance is provided. The collection conveyance chamber 61 b is arranged below the developing sleeve 60.

  In the present invention, the agitating and conveying chamber 61c is further provided below the supply and conveying chamber 61a. In the agitating / conveying chamber 61c, an excess developer that is not supplied to the developing sleeve 60 in the supply / conveying chamber 61a, that is, is not used for development, and is conveyed to the most downstream side in the supplying / conveying chamber by the supply / conveying member 63. In addition, while stirring the recovered developer transported to the most downstream side of the recovery transport chamber 61b by the recovery transport member 64 in the recovery transport chamber 61b, along the rotation axis direction of the developing sleeve 60 and the supply transport member 63 An agitating / conveying member 65 that conveys the two-component developer in the opposite direction is provided.

  The supply conveyance chamber 61a, the collection conveyance chamber 61b, and the agitation conveyance chamber 61c described above are partitioned by a partition member. The collection developer is transferred from the collection conveyance chamber 61b to the collection conveyance chamber 61b and the agitation conveyance chamber 61c. An opening 66 communicating with each other for delivery to the agitation transport chamber 61c is provided on the most downstream side of the recovery transport chamber 61b and on the most upstream side of the agitation transport chamber 61c, and the supply transport chamber 61a and the agitation transport chamber In 61c, an opening 68 is provided on the most downstream side of the supply conveyance chamber 61a so as to transfer the above-described excess developer from the supply conveyance chamber 61a to the agitation conveyance chamber 61c. Further, in order to deliver the developer in which the collected developer and the surplus developer are mixed and the newly replenished new toner from the agitating / conveying chamber 61c to the supplying / conveying chamber 61a, the agitating / developing chamber 61c and the supplying / conveying chamber 61a are provided. An opening 67 communicating with each other is provided on the most downstream side of the agitating and conveying chamber 61c and on the most upstream side of the supply and conveying chamber 61a. In the present embodiment, a replenishment toner opening 70 for replenishing toner consumed by development is provided on the upstream side of the agitation transport chamber 61c. As described above, the new toner replenished on the upstream side of the agitating / conveying chamber 61c is sufficiently agitated and charged while being conveyed in the agitating / conveying chamber 61c together with the excess developer and the collected developer.

  In such a developing device 6, the two-component developer supplied and carried from the supply / conveying chamber 61 a of the developer container 61 to the developing sleeve 60 by the magnetic pole of the magnet roller is accompanied by the rotation of the developing sleeve 60. The top is conveyed in the order of magnetic pole S2, magnetic pole N1, and magnetic pole S1. In the process, the regulating blade 40 cooperates with the magnetic pole S 2 to magnetically regulate the developer layer thickness, and a thin layer of developer is formed on the developing sleeve 60. The magnetic pole S1 of the magnet roller is a developing main pole, and the developer conveyed to the developing unit is brought into a so-called spiked state by the magnetic pole S1, contacts the photoreceptor 1, and is formed on the surface of the photoreceptor 1. Develop the electrostatic latent image. Thereafter, the developer remaining on the developing sleeve 60 even after passing through the developing portion formed as the facing portion between the developing sleeve 60 and the photoreceptor 1 is repelled by the magnetic poles N2 and N3 as the developing sleeve 60 rotates. It is removed from the developing sleeve 60 by the magnetic field and collected in the collecting and conveying chamber 61 b of the developing container 61.

  The two-component developer used in such a development process stirs and conveys the supply conveyance chamber 61a, the recovery chamber 61b, and the stirring chamber 61c using the supply conveyance member 63, the collection conveyance member 64, and the agitation conveyance member 65. Then, the supply and transfer chamber 61a, the recovery chamber 61b, and the stirring chamber 61c are circulated through the openings 66, 67, and 68.

  Next, the flow of the two-component developer will be further described with reference to FIG. 4 which is a development view of the supply conveyance chamber 61a, the collection conveyance chamber 61b, and the agitation conveyance chamber 61c. In FIG. 4, the conveyance members 63, the collection conveyance member 64, and the agitation conveyance member 65 are not shown in order to fully understand the flow of the two-component developer.

  The two-component developer recovered from the developing sleeve 60 is first accommodated in the recovery conveyance chamber 61b. Since the collection conveyance member 64 is provided in the collection conveyance chamber 61b, the collection conveyance member 64 is carried by the collection conveyance member 64 to the downstream side in the conveyance direction indicated by the arrow in FIG. Through the provided opening 66, it is carried to the agitating and conveying chamber 61c.

  As described above, the agitating / conveying chamber 61 c is provided with the toner replenishing port 70 for replenishing new toner, and new toner is appropriately replenished from the opening 70. The replenished new toner is conveyed in the agitating and conveying chamber 61c downstream in the conveying direction by the agitating and conveying member 65 together with the surplus developer conveyed from the supply conveying chamber 61a and the collected developer conveyed from the collecting and conveying chamber 61b.

  In the agitating and conveying chamber 61c, an opening 67 is provided on the most downstream side in the conveying direction, and the two-component developer conveyed and stirred by the agitating and conveying member 65 is downstream in the conveying direction of the agitating and conveying chamber 61c. However, it is lifted through the opening 67 so as to overflow into the supply transfer chamber 61a provided above the stirring transfer chamber 61c by the rotational torque of the stirring transfer member 65. The agitating / conveying member 65 has to lift the two-component developer so as to overflow into the supply / conveying chamber 61a. Therefore, the gap between the agitating / conveying chamber 61c and the agitating / conveying member 65 is narrowed to increase the conveying ability. Yes.

  In the supply conveyance chamber 61a, the developer is supplied to the developing sleeve 60 while the two-component developer is conveyed by the supply conveyance member 63. The supply transfer chamber 61a is provided with an opening 68 on the most downstream side in the transfer direction, and crosses the supply transfer chamber 61a without being supplied to the developing sleeve 60 while being transferred through the supply transfer chamber 61a. Excess developer is returned from the opening 68 to the agitating and conveying chamber 61c. Since the supply conveyance member 63 only serves to horizontally convey the two-component developer existing in the supply conveyance chamber 61a, the gap between the supply conveyance chamber 61a and the supply conveyance member 63 is not stirred. Unlike the gap formed between the transfer chamber 61c and the agitating and conveying member 65, it is made wide. Therefore, the conveying ability of the supply and conveying member 63 is made lower than that of the agitating and conveying member 65. ing.

  Thus, the developer is configured to circulate through the supply conveyance chamber 61a, the collection conveyance chamber 61b, and the agitation conveyance chamber 61c during normal image formation. Therefore, the bulkiness distribution of the developer between the supply conveyance chamber 61a and the agitation conveyance chamber 61c when the developer is normally circulated is as shown in FIG. As can be seen from FIG. 5, in the agitation transport chamber 61 c, the developer is lifted and transported so as to overflow to the supply transport chamber 61 a through the opening 67, so that the developer height gradually increases toward the opening 67. In the opening 67, the developer overflows toward the supply / conveying chamber. On the other hand, in the supply / conveying chamber 61a, the supply / conveying member 63 conveys the two-component developer while supplying the two-component developer to the developing sleeve 60. Therefore, the developer bulk becomes lower as the opening 68 is approached.

  Here, if for some reason, for example, the developing device 6 is subjected to handling or work such as attaching or detaching or replacing the developing device 6, an impact is applied to the developing device 6 or the developing device 6 is tilted. When the component developer is tilted in one direction and the tilt direction or the impact direction is on the opening 67 side, the two-component developer is entirely tilted on the opening 67 side as shown in FIG. The state as shown in FIG. 6 is referred to as a so-called packing state in which the two-component developer is clogged without a gap even to the supply conveyance chamber 61a disposed above the agitation conveyance chamber 61c. If the developing device 6 is to be operated in this packing state, the stirring / transporting member 65 has the transporting capability enhanced by narrowing the gap between the stirring / transporting chamber 61c and the stirring / transporting member 65 as described above. The rotational torque of the conveying member 65 becomes very high. As a result, a so-called motor lock in which the rotational torque exceeds the driving capability of the motors of the conveying members 63, 64 and 65 that are coupled and driven integrally using a gear or the like, and the developing device 6 cannot be rotated. Abnormality will occur. If a motor lock abnormality occurs, the developing device 6 does not operate normally, and it is necessary to eliminate this packing state.

  Here, in the packing state, since the rotational torque of the agitating and conveying member 65 exceeds the driving capability of the motor, even if the agitating and conveying member 65 cannot rotate in the normal conveying direction, as can be seen from FIG. Since there is sufficient space for transporting the two-component developer in the direction opposite to the direction in which the two-component developer is transported, that is, in the left direction as viewed in FIG. , The two-component developer in the packed state can be moved in the direction opposite to the normal conveying direction. In this way, by moving the two-component developer in the agitating / conveying chamber 61c in the reverse direction, the two-component developer in the supply / conveying chamber 61a above the agitating / conveying chamber 61c is subjected to the action of gravity and thus stirred. As a result, the packing state in which the two-component developer is clogged up to the supply conveyance chamber 61a without a gap is eliminated.

  In addition, when the agitating / conveying member 65 is rotated in the direction opposite to the normal conveying direction, the supply / conveying member 63 that is drivingly connected using a connecting member such as a gear must also be rotated integrally. As described above, since the agitating and conveying member 65 must lift the two-component developer so as to overflow into the supply and conveying chamber 61a, the agitating and conveying member 65 conveys the gap between the agitating and conveying chamber 61c and the agitating and conveying member 65 as narrow as possible. Although the capability is enhanced, the supply transport member 63 only serves to transport the two-component developer present in the supply transport chamber 61a in the horizontal direction, and therefore, between the supply transport chamber 61a and the supply transport member 63. The gap is made widely. Therefore, even if the supply conveyance member 63 rotates in the reverse direction, the two-component developer can escape into the gap formed between the supply conveyance chamber 61a and the supply conveyance member 63, so that the conveyance can be performed even in the packing state. It can be rotated in the direction opposite to the direction. Further, when the agitating / conveying member 65 is rotated in the direction opposite to the normal conveying direction, the supply / conveying member 63 that is drivingly connected using a connecting member such as a gear becomes the two-component developer in the supply / conveying chamber 61a. However, since the developer conveying capability of the supply conveying member 63 is lower than the developer conveying capability of the agitating conveying member 65, the two-component developer is brought into the packing state. It does not lead to.

  In this way, the two-component developer is moved to the upstream side in the transport direction of the stirring transport chamber 61c by rotating the supply transport member 63, the recovery transport member 64, and the stirring transport member 65 in the reverse direction for a certain period of time. As a result, the clogged developer falls into the supply conveyance chamber 61a without any gap, and the packing state can be eliminated. FIG. 7 shows the state of the developer in which this packing state has been eliminated. As shown in FIG. 7, the packing state in which the two-component developer on the supply conveyance chamber 61a side is clogged without a gap is eliminated, and therefore, the agitation conveyance member 65 can be rotated again with normal torque. . The time for reverse rotation is sufficient if it is sufficient to eliminate the packing state, and is set by repeating experiments and simulations. However, in a normally used image forming apparatus, each conveyance member 63, It is sufficient to reversely rotate 64 and 65. Specifically, it is preferably set to several msec to several tens msec.

  Regarding the timing of reversely rotating the transport members 63, 64 and 65, the above packing state is considered to occur when some work is performed on the developing device 6, for example, when the developing device 6 is attached or detached or replaced. For this reason, when there is a possibility that the developing device 6 has been accessed, the reverse rotation operation of each of the conveying members 63, 64 and 65 may be performed. Therefore, when the door configured to be openable and closable so that a user or the like can access the components or parts inside the image forming apparatus is once opened and then closed, and when the image forming apparatus main body is turned on In addition, by performing the reverse rotation operation, it is possible to eliminate the packing state. The door opening / closing detection is also performed by the door opening / closing detection means described above, and can be dealt with by detecting when the door is closed.

  As can also be seen from FIG. 7, when the image forming operation is started immediately after the packing state is eliminated, the developer in the supply transfer chamber 61 a is once biased toward the opening 67. There is a concern that no developer is present in the vicinity of the opening 68 in the supply transfer chamber 61a. In such a case, there is a shortage of two-component developer in the opposite portion in the vicinity of the opening 68 of the developing sleeve 60, and a problem of so-called white-out image in which coloring is not performed at a portion to be developed with coloring is considered to occur. It is done.

  Therefore, in order to prevent the above problems, when the respective conveying members 63, 64 and 65 are reversely rotated to cancel the packing state and then further rotated in the normal conveying direction, the bulkiness distribution of the developer is shown in FIG. It is further preferable to return to the normal circulation state.

1 is a cross-sectional view schematically showing an image forming apparatus which is an electrophotographic apparatus of a tandem type indirect (intermediate) transfer system of the present invention. 1 is a diagram schematically illustrating a main part of an image forming apparatus of the present invention. It is sectional drawing for demonstrating the structure of a developing device. FIG. 6 is a development view for explaining the flow of developer in the developing device. It is a figure which shows the bulk distribution of the developer in the supply conveyance chamber and stirring conveyance chamber at the normal time in which the developer is circulating. It is a figure which shows the bulkiness distribution of the developer in the supply conveyance chamber and stirring conveyance chamber at the time of a developer packing state. FIG. 10 is a diagram illustrating a bulk distribution of a developer when each conveying member is rotated in a reverse rotation direction from the packing state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 6 Developing apparatus 60 Developer carrier 61 Developer container 61a Supply conveyance chamber 61b Collection conveyance chamber 61c Agitation conveyance chamber 63 Supply conveyance member 64 Collection conveyance member 65 Agitation conveyance member 66 Opening 67 Opening 68 Opening 70 New toner supply mouth

Claims (2)

A developer carrier that is disposed opposite to an image carrier on which an electrostatic latent image is formed and that can carry and rotate a two-component developer having toner and carrier on the surface, and the developer carrier. A supply conveyance member that conveys the two-component developer along the rotation axis direction of the sheet and supplies the two-component developer to the developer carrier, a supply conveyance chamber that houses the supply conveyance member, and the development A recovery conveyance member that conveys the recovered developer of the two-component developer recovered from the developer carrier on the developer along the rotation axis direction of the developer carrier in the same direction as the supply conveyance member; The recovery transport chamber that houses the recovery transport member, the excess developer transported to the supply transport member without being used for development in the supply transport chamber, and the transport transport member transported by the recovery transport member in the recovery transport chamber The recovered developer is stirred. However, the stirring and conveying member that conveys the developer carrier along the rotation axis direction and in the opposite direction to the supply and conveying member, and accommodates the stirring and conveying member, and below the supply and conveying chamber. An agitating and conveying chamber provided; and the supply conveying chamber, the collecting and conveying chamber, and the agitating and conveying chamber are each partitioned by a partition member, and the collecting and conveying chamber and the agitating and conveying chamber are separated from each other. Is provided with an opening communicating with each other for transferring the recovered developer from the recovery transfer chamber to the agitation transfer chamber, and the supply transfer chamber and the agitation transfer chamber are provided with the excess developer. An opening communicating with each other for delivery from the supply conveyance chamber to the agitation conveyance chamber, and a developer that agitates and conveys the recovered developer and the excess developer from the agitation conveyance chamber to the supply conveyance chamber. To pass each other An image forming apparatus having a developing device and an opening in communication are respectively provided,
The image forming apparatus is further provided with a door open / close detecting means for detecting an open / closed state of a door provided to access the developing device. When the door is closed, or in the image forming apparatus When the power is turned on, the image forming apparatus is characterized in that the supply conveyance member, the recovery conveyance member, and the agitation conveyance member are rotated in a direction opposite to a normal rotation direction.   The image forming apparatus according to claim 1, wherein after the rotation in the reverse direction, the supply conveyance member, the collection conveyance member, and the agitation conveyance member are further rotated in a normal direction.

Images