JP2018132654A - Development apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development apparatus that can suppress occurrence of toner scattering due to replenishing of a replenishing agent on the basis of a function separation type constitution.SOLUTION: A disc member 101 is disposed on a down streamside of a second communication port 17 to lower developer conveyance force of an agitation screw 14 to temporarily accumulate developer. When the disc member 101 is disposed in an agitation screw 14, the developer is accumulated by the disc member 101, and a portion of the developer reaches the second communication port 17. That is, it can be easily realized by using the disc member 101 to keep the developer in the second communication port 17 previously before replenishing a replenishing agent at developer conveyance time. Since some quantity of the developer can be kept in the second communication port 17, the replenishing agent replenished from the replenishing port 40 is mixed with the developer in the second communication port 17. Thus, occurrence of toner scattering through the second communication port 17 due to the replenishing of the replenishing agent can be suppressed.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a developing device suitable for an image forming apparatus using electrophotographic technology such as a printer, a copying machine, a facsimile machine, or a multifunction machine.

  2. Description of the Related Art Image forming apparatuses such as printers, copiers, facsimile machines, and multi-function machines are provided with a developing device that develops an electrostatic latent image formed on a photosensitive drum with a developer to make a visible image. In the developing device, a two-component developer (hereinafter also simply referred to as a developer) composed of a nonmagnetic toner and a magnetic carrier is used. As a developing device, a developing chamber for supplying the developer to the developing sleeve and a stirring chamber for collecting the developer separated from the developing sleeve are formed in the developing container, and the developer is circulated between the developing chamber and the stirring chamber. A so-called function-separated configuration has been proposed (Patent Documents 1 and 2). In the function separation type developing device, the developing chamber and the stirring chamber are communicated with each other through a communication port, and a developing screw and a stirring screw for transporting the developer are provided in each chamber. The developer is transferred from the stirring chamber to the developing chamber through the downstream communication port on the downstream side in the developer conveying direction of the stirring screw, and from the developing chamber through the upstream communication port on the upstream side in the developer conveying direction of the stirring screw. It is circulated in the developing container so as to be delivered to the stirring chamber.

  In the case of the above developing device, when the developer reaches a stable state (so-called steady state), the developer surface of the developer gradually decreases from the upstream to the downstream in the developer conveying direction of the developing screw in the developing chamber. ing. On the other hand, in the stirring chamber, the developer surface gradually increases from the upstream to the downstream in the developer conveying direction of the stirring screw. In this specification, the term “upstream” or “downstream” refers to the upstream of the stirring screw in the developer conveyance direction or the downstream of the developer conveyance direction without particular notice.

  In addition, since the carrier deteriorates and the charging performance decreases in accordance with the image formation, a so-called carrier refresh system is used in which a replenisher (mainly toner) is replenished to the developing container and excess developer is discharged out of the developing container. A developing device has been proposed (Patent Document 3).

JP 2010-197539 A JP 2009-192554 A JP 59-1000047 A

  By the way, the replenishment agent is replenished into the agitation chamber from a replenishment port formed on the upstream side of the upstream communication port of the agitation chamber. However, as described above, in the agitation chamber, the developer surface of the developer is lower on the upstream side than on the downstream side, that is, the amount of developer on the upstream communication port side is smaller than the amount of developer on the downstream communication port side. ing. In particular, when the toner consumption is rapid, the amount of developer on the upstream communication port side is extremely reduced until the replenisher is replenished. At this time, when the replenishment agent is replenished, the amount of developer on the upstream communication port side is relatively small with respect to the amount of replenishment agent to be replenished. The portion easily scatters to the developing chamber and thus to the outside of the developing container via the upstream communication port (referred to as toner scattering). When the toner scatters, the inside of the apparatus main body becomes dirty, and the toner stain may occur in the output image.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device that can suppress the occurrence of toner scattering accompanying replenishment of a replenisher with a function-separated configuration.

  The developing device according to the present invention has a carrying region for carrying a developer, and a developer carrying member that carries and rotates the developer, a first chamber that supplies the developer to the developer carrying member, A developer container in which a developer circulation path is formed with the first chamber and a second chamber for collecting the developer from the developer carrier, and a supply port is formed in the second chamber; A first conveying screw that is provided in the first chamber and conveys the developer in the first direction, and is provided in the second chamber and conveys the developer in the second direction opposite to the first direction, and the replenishment A second conveying screw that conveys the replenisher replenished from the mouth in the second direction, the first chamber and the second chamber in the developing container, and the second chamber on the downstream side in the second direction. A first series of openings for delivering the developer from the first chamber to the first chamber; A partition wall having a second communication port for delivering developer from the first chamber to the second chamber on the upstream side in the second direction with respect to the carrying region, and the second conveying screw includes the second conveying screw. A transport force reduction section that lowers the developer transport force from the carrying area on the downstream side in the second direction from the center in the second direction of the communication port and on the upstream side in the second direction from the carrying area; It is characterized by.

  The developing device according to the present invention has a carrying region for carrying a developer, and a developer carrying member that carries and rotates the developer, a first chamber that supplies the developer to the developer carrying member, A developer container in which a developer circulation path is formed with the first chamber and a second chamber for collecting the developer from the developer carrier, and a supply port is formed in the second chamber; A first conveying screw that is provided in the first chamber and conveys the developer in the first direction, and is provided in the second chamber and conveys the developer in the second direction opposite to the first direction, and the replenishment A second conveying screw that conveys the replenisher replenished from the mouth in the second direction, the first chamber and the second chamber in the developing container, and the second chamber on the downstream side in the second direction. A first series of openings for delivering the developer from the first chamber to the first chamber; A partition wall having a second communication port for delivering developer from the first chamber to the second chamber on the upstream side in the second direction with respect to the carrying region, and the second conveying screw includes the second conveying screw. A multi-thread screw having a larger number of threads than the support area is provided on the downstream side in the second direction with respect to the communication port and on the upstream side in the second direction with respect to the support area.

  According to the present invention, with the function separation type configuration, it is possible to suppress the occurrence of toner scattering associated with the replenishment of the replenishment agent, so that the contamination in the apparatus main body and the toner stain of the output image due to replenishment of the replenishment agent are less likely to occur. .

1 is a schematic diagram illustrating a configuration of an image forming apparatus to which a developing device according to an exemplary embodiment is applied. FIG. 3 is a cross-sectional view illustrating the developing device according to the embodiment. FIG. 2 is a top cross-sectional view illustrating the developing device according to the first embodiment. The graph showing the relationship between a screw pitch and the developer conveyance amount per one rotation of a screw. The schematic diagram explaining the force which acts by screw rotation. The graph showing the relationship between the angle of a blade | wing and the force which acts on the orthogonal direction of a developer conveyance direction. FIG. 6 is a top cross-sectional view illustrating a developing device according to a second embodiment. FIG. 10 is a top cross-sectional view illustrating a developing device according to a third embodiment.

<First embodiment>
First, the configuration of an image forming apparatus to which the developing device of this embodiment is applied will be described with reference to FIG. An image forming apparatus 100 shown in FIG. 1 is a tandem intermediate transfer type full-color printer in which image forming units PY, PM, PC, and PK are arranged along an intermediate transfer belt 25.

<Image forming apparatus>
In the image forming unit PY, a yellow toner image is formed on the photosensitive drum 10Y and transferred to the intermediate transfer belt 25. In the image forming unit PM, a magenta toner image is formed on the photosensitive drum 10M and transferred to the intermediate transfer belt 25. In the image forming units PC and PK, a cyan toner image and a black toner image are formed on the photosensitive drums 10C and 10K, respectively, and transferred to the intermediate transfer belt 25. The four-color toner images transferred to the intermediate transfer belt 25 are transported to a secondary transfer portion (secondary transfer nip portion) T2 and are collectively transferred to a recording material S (sheet material such as paper or an OHP sheet). Is done. The recording material S is taken out one by one from a paper feed cassette (not shown) and conveyed to the secondary transfer portion T2.

  The image forming units PY, PM, PC, and PK are configured substantially the same except that the colors of toner used in the developing devices 1Y, 1M, 1C, and 1K are different from yellow, magenta, cyan, and black. Hereinafter, the configuration and operation of the image forming units PY to PK will be described by omitting Y, M, C, and K at the end of the code representing the distinction between the image forming units PY, PM, PC, and PK.

  In the image forming portion P, a charging roller 21, an exposure device 22, a developing device 1, a transfer roller 23, and a drum cleaning device 24 are disposed so as to surround the photosensitive drum 10 as an image carrier. The photosensitive drum 10 has a photosensitive layer formed on the outer peripheral surface of an aluminum cylinder, and is rotated in the direction of arrow R1 in FIG. 1 at a predetermined process speed.

  The charging roller 21 is charged with a charging voltage and contacts the photosensitive drum 10, thereby charging the photosensitive drum 10 to a uniform negative-polarity dark portion potential. The exposure device 22 generates a laser beam obtained by ON-OFF modulation of scanning line image data obtained by developing a separation color image of each color from a laser light emitting element, and scans this with a rotating mirror on the surface of the photosensitive drum 10 that is charged. Write an electrostatic image of the image. The developing device 1 supplies toner to the photosensitive drum 10 to develop the electrostatic image into a toner image. Details of the developing device 1 will be described later (see FIGS. 2 and 3).

  The transfer roller 23 is disposed opposite to the photosensitive drum 10 with the intermediate transfer belt 25 interposed therebetween, and forms a primary transfer portion (primary transfer nip portion) T1 of the toner image between the photosensitive drum 10 and the intermediate transfer belt 25. In the primary transfer portion T1, a toner image is primarily transferred from the photosensitive drum 10 to the intermediate transfer belt 25 by applying a primary transfer voltage to the transfer roller 23 by, for example, a high voltage power source (not shown). That is, when a primary transfer voltage opposite to the toner charging polarity is applied to the transfer roller 23, the toner image on the photosensitive drum 10 is electrostatically attracted to the intermediate transfer belt 25 and transferred. The drum cleaning device 24 rubs the photosensitive drum 10 with a cleaning blade to remove the primary transfer residual toner slightly remaining on the photosensitive drum 10 after the primary transfer.

  The intermediate transfer belt 25 is supported around a tension roller 26, a secondary transfer inner roller 27, a driving roller 28, and the like, and is driven by the driving roller 28 to rotate in the direction of arrow R2 in FIG. The secondary transfer portion T <b> 2 is a toner image transfer nip portion to the recording material S formed by contacting the secondary transfer inner roller 27 with the intermediate transfer belt 25 supported by the secondary transfer outer roller 29. In the secondary transfer portion T2, a predetermined secondary transfer voltage is applied to the secondary transfer inner roller 27, whereby the toner image is transferred to the recording material S that is nipped and conveyed from the intermediate transfer belt 25 to the secondary transfer portion T2. Next transferred. Secondary transfer residual toner remaining on the intermediate transfer belt 25 after the secondary transfer is removed by the belt cleaning device 30 rubbing the intermediate transfer belt 25. The belt cleaning device 30 removes the secondary transfer residual toner by sliding the cleaning blade against the intermediate transfer belt 25.

  The recording material S on which the four-color toner images are secondarily transferred by the secondary transfer portion T2 is conveyed to the fixing device 31. The fixing device 31 melts and fixes the toner image on the recording material S by applying pressure from a roller or a belt (not shown) and a heat source (not shown) such as a heater. The recording material S on which the toner image is fixed by the fixing device 31 is discharged out of the machine body.

  A replenishing device 32 is connected to the developing device 1, and the replenishing device 32 replenishes the developing device 1 with toner (specifically a replenisher) in accordance with the consumption of the toner of the developing device 1 during image formation. As will be described in detail later, a replenishing port is formed in the developing device 1 to connect a replenishing device 32. Further, a discharge port is formed in order to discharge the excess developer generated by the replenishment of the replenisher to the outside.

<Developing device>
The developing device 1 of this embodiment will be described with reference to FIGS. As shown in FIG. 2, the developing device 1 includes a developing container 2 forming a housing, a developing sleeve 3 as a developer carrier, a regulating blade 5, a developing screw 13 as a first conveying screw, and a second conveying screw. A stirring screw 14 and the like are provided.

  The developing container 2 contains a two-component developer containing a nonmagnetic toner and a magnetic carrier. In this embodiment, a two-component development system is used as a development system, and a non-magnetic toner having a negative charge polarity and a magnetic carrier having a positive charge polarity are mixed and used as a developer. The non-magnetic toner is obtained by encapsulating a colorant, a wax component and the like in a resin such as polyester or styrene acryl, and pulverizing or polymerizing the powder. The magnetic carrier is obtained by applying a resin coat to the surface layer of a core made of resin particles kneaded with ferrite particles or magnetic powder. In this embodiment, the toner concentration (ratio of toner weight to the total weight of the developer (TD ratio)) in a new (initial state) developer that has not yet been developed is, for example, 8%. .

  As shown in FIG. 2, the developing container 2 has a part facing the photosensitive drum 10 (see FIG. 1), and a developing sleeve as a developer carrying member is partly exposed in the opening. 3 is rotatably arranged. The developing sleeve 3 is formed in a cylindrical shape from a nonmagnetic material such as an aluminum alloy, and is driven to rotate in the direction of arrow R3 in FIG. The developing sleeve 3 has a coat region M (carrying region, see FIG. 3) capable of carrying the developer on the surface. A magnet roller 4 composed of a plurality of magnetic poles is disposed inside the developing sleeve 3 so as not to rotate.

  The developing sleeve 3 rotates in the direction of the arrow R3 in FIG. 2, and carries the developer adsorbed at the position of the magnetic pole N1 of the magnet roller 4 in the direction of the regulating blade 5. The developer spiked by the regulating magnetic pole S1 is subjected to a shearing force by the regulating blade 5 when passing through the gap between the developing sleeve 3 and the regulating blade 5, and the amount thereof is regulated, and a predetermined layer thickness is formed on the developing sleeve 3. The developer layer is formed. The formed developer layer is carried and conveyed to a development area facing the photosensitive drum 10 and develops the electrostatic latent image formed on the surface of the photosensitive drum 10 with magnetic spikes formed by the development magnetic pole N2. After being subjected to development, the developer is peeled off from the developing sleeve 3 by a non-magnetic band formed by adjoining the same pole between the stripping magnetic pole N3 and the pumping magnetic pole N1.

  In the developing container 2, a developing chamber 11 as a first chamber and a stirring chamber 12 as a second chamber are formed, and the developing chamber 11 and the stirring chamber 12 are partitioned between the developing chamber 11 and the stirring chamber 12. A partition wall 15 is provided. The partition wall 15 separates the developing chamber 11 and the stirring chamber 12 so as to protrude from the bottom surface portion 2 c into the developing container. The partition wall 15 extends in the rotation axis direction of the developing sleeve 3, and the developing chamber 11 and the stirring chamber 12 are formed along the rotating axis direction of the developing sleeve 3. In this embodiment, the developing chamber 11 and the stirring chamber 12 have a difference in height when viewed from the horizontal direction so that the bottom surface portion 12a on the stirring chamber 12 side is above the bottom surface portion 11a on the developing chamber 11 side. Are arranged.

  Above the partition wall 15, a guide member 151 is provided so as to extend close to the developing sleeve 3 and guide the developer peeled off from the developing sleeve 3 to the stirring chamber 12. The guide member 151 is preferably provided over a range including at least a coat region M (see FIG. 3) capable of carrying the developer of the developing sleeve 3. In the present specification, “upper” and “lower” refer to the upper direction of gravity and the lower side of direction of gravity, respectively.

  As illustrated in FIG. 3, the partition wall 15 includes a first communication port 16 and a second communication port 17 that allow the developing chamber 11 and the stirring chamber 12 to communicate with each other on both ends in the rotation axis direction (longitudinal direction) of the stirring screw 14. Have The first communication port 16 allows the developer to be transferred from the stirring chamber 12 to the developing chamber 11 on the downstream side (downstream side in the second direction), and the second communication port 17 develops on the upstream side (upstream side in the second direction). This is a developer delivery section that enables delivery of the developer from the chamber 11 to the stirring chamber 12. The first communication port 16 is formed on the downstream side of the coating region M of the developing sleeve 3, and the second communication port 17 is formed on the upstream side of the coating region M of the developing sleeve 3. In the present embodiment, with respect to the longitudinal direction of the partition wall 15, the width of the first communication port 16 is 30 mm and the width of the second communication port 17 is 10 mm.

  The developing chamber 11 is provided with a developing screw 13 that conveys the developer in a predetermined first direction in the developing chamber 11. The stirring chamber 12 is provided with a stirring screw 14 that conveys the developer in the second direction opposite to the developing screw 13 in the stirring chamber 12. The developing screw 13 and the stirring screw 14 are configured by forming blades 13b and 14b in a spiral shape around the rotary shafts 13a and 14a, respectively. Both ends of the rotation shafts 13a and 14a are rotatably supported by the developing container 2, respectively. In the case of this embodiment, the stirring screw 14 has a disc member 101 on the rotating shaft 14a in addition to the blades 14b. The disk member 101 will be described later.

  The developing screw 13 and the stirring screw 14 are arranged so that at least a part thereof is overlapped when viewed from the horizontal direction. In the present embodiment, as shown in FIG. 2, the lower end 14 e of the stirring screw 14 is disposed so as to be higher than the lower end 13 e of the developing screw 13 when viewed from the horizontal direction.

  Here, a screw pitch is demonstrated using FIG.4 and FIG.5, referring FIG. FIG. 4 is a graph showing the relationship between the screw pitch and the developer conveyance amount per rotation of the screw. Here, the case where the screw outer diameter of the stirring screw 14 is 20 mm was mentioned as an example. As can be understood from FIG. 4, the developer conveyance amount per rotation varies depending on the screw pitch. If all of the developer is conveyed in the same direction following the movement of the blade 14b, the distance traveled by the developer during one rotation of the stirring screw 14 becomes equal to the screw pitch. However, in reality, a part of the developer is moved while sliding on the blade 14b, so that not all of the developer follows the blade 14b and is conveyed in the same direction. That is, as shown in FIG. 5, as the screw pitch G increases, the angle α between the screw conveying surface (specifically, the blade 14b) and the rotating shaft 14a decreases. As the angle α decreases, the amount of developer moved while sliding on the blade 14b increases. As shown in FIG. 4, the developer conveyance amount per rotation becomes maximum when the screw pitch is 40 mm.

  In the case of this embodiment, the screw pitch of the stirring screw 14 is formed to be 40 mm at which the developer transport amount per rotation is maximized in order to transport the developer quickly in the stirring chamber. On the other hand, the screw pitch of the developing screw 13 is 20 mm. That is, the developing screw 13 has a developer conveying speed slower than the conveying speed of the stirring screw 14. This is because the developer is appropriately supplied to the developing sleeve 3 by transporting the developer later in the developing chamber 11 than in the stirring chamber 12. Note that both the developing screw 13 and the stirring screw 14 are formed with a screw shaft having a diameter of 6 mm and a screw outer diameter of 20 mm.

  Returning to FIG. 3, the developing sleeve 3, the developing screw 13, and the agitation screw 14 are configured to be connected and driven by a gear train (not shown), and are respectively rotated through a gear train from a driving motor (not shown). To do. As the developing screw 13 and the agitating screw 14 rotate, the developer is circulated and conveyed in the direction indicated by the arrow R4 in FIG. At this time, the developer is transferred from the stirring chamber 12 to the developing chamber 11 through the first communication port 16, and the developer is transferred from the developing chamber 11 to the stirring chamber 12 through the second communication port 17. As a result, a developer circulation path is formed between the developing chamber 11 and the stirring chamber 12, and the developer is mixed and stirred by circulating through the circulation path.

  The developing chamber 11 supplies the developer to the developing sleeve 3, and the stirring chamber 12 collects the developer peeled from the developing sleeve 3. That is, as shown in FIG. 2, the developer in the developing chamber 11 is attracted to the developing sleeve 3 at the position of the pumping magnetic pole N <b> 1 of the magnet roller 4 while being conveyed by the developing screw 13. On the other hand, the guide member 151 provided on the upper part of the partition wall 15 extends from the upper end of the partition wall 15 so as to be close to the developing sleeve 3 in the vicinity of the no-magnetic band of the developing sleeve 3. Therefore, the developer separated from the developing sleeve 3 by the stripping magnetic pole N3 is accommodated in the stirring chamber 12 without returning to the developing chamber 11. In the stirring chamber 12, the collected developer is conveyed by the stirring screw 14 while collecting the developer.

  By the way, in the developing device 1 that performs development using a two-component developer, the developing characteristics of the developer can change with image formation, such as, for example, the charging performance of the carrier with respect to toner decreases. When the charging performance of the carrier is deteriorated, image defects such as density fluctuation and scattering fogging may occur. Therefore, in order to restore the charging performance of the carrier, for example, a replenisher in which toner and carrier are mixed at a weight ratio of 9: 1 is replenished from a replenishing device 32 (see FIG. 1) connected to the developing device 1. Control for refreshing is performed.

<Supply port>
As shown in FIG. 3, a replenishing port 40 is formed in the developing container 2 upstream of the second communication port 17 of the stirring chamber 12. A supply device 32 (see FIG. 1) is connected to the supply port 40. The replenishing device 32 has a toner bottle (not shown) containing a replenishing agent, and replenishes the stirring chamber 12 from the replenishing port 40 by rotating the toner bottle. The supplied replenisher is sufficiently mixed and stirred with the existing developer by the stirring screw 14 and the developing screw 13 and supplied to the developing sleeve 3. In this way, the development characteristics of the developer contained in the developer container are kept constant.

<Discharge port>
As described above, the replenisher is replenished from the replenishing device 32. However, when the developer is excessively increased in the developing container as the replenisher is replenished, the developer is not sufficiently stirred and the density fluctuation or scattering occurs. Image defects such as fogging are likely to occur. Therefore, a discharge port 50 for discharging the developer to the outside of the developing container is formed in the developing container 2 so that the developer that becomes excessive due to the replenishment of the replenishing agent is discharged from the developing container 2.

  In the present embodiment, the discharge port 50 is formed on the downstream side of the first series port 16 of the stirring chamber 12. This is because, for example, when the discharge port 50 is formed in the wall surface in the middle of the stirring chamber 12, the developer may be discharged more than necessary by the jumping up by the stirring screw 14. That is, the developer is easily discharged regardless of the amount of the developer, and in some cases, the developer becomes too small. As a result, a sufficient amount of developer is not ensured in the developing chamber 11 on the upstream side in the developer conveying direction of the developing screw 13, and the coating region M of the developing sleeve 3 is difficult to be uniformly coated. When such a coating defect occurs, image defects such as image unevenness and white stripes may occur. In order to avoid this, it is preferable that the discharge port 50 is formed on the downstream side of the first series of ports 16 that are less affected by the splashing of the developer by the stirring screw 14.

  The developing device 1 of the present embodiment has a so-called function separation type configuration in which a developer is supplied to the developing sleeve 3 in the developing chamber 11 and the developer is recovered from the developing sleeve 3 in the stirring chamber 12. In the function separation type developing device 1, the developer on the developing sleeve is collected in the longitudinal direction of the stirring chamber 12 (in the rotational axis direction of the stirring screw 14). Therefore, the developer is divided into a first path that is transported from the developing chamber 11 to the stirring chamber 12 without going through the developing sleeve 3, and a second path that is transported directly from the developing sleeve 3 to the stirring chamber 12. The developer is circulated through the two paths, and the distribution of the developer amount tends to be non-uniform in the developing container. Specifically, in the developing chamber 11 and the stirring chamber 12, the developer surface tends to be lower on the upstream side than on the downstream side. Therefore, the amount of developer delivered from the developing chamber 11 to the stirring chamber 12 via the second communication port 17 is the amount of developer delivered from the stirring chamber 12 to the developing chamber 11 via the first communication port 16. Less than.

  By the way, in the case of the function separation type developing device 1, since the developer is circulated faster in the stirring chamber 12 than in the developing chamber 11, the developer is likely to jump up. In particular, since the amount of the developer is small in the upstream of the stirring chamber 12, the developer is likely to jump up. Here, the relationship between the angle α of the blade 14b of the stirring screw 14 and the force acting in the direction in which the developer is flipped up will be described with reference to FIGS.

  When the screw pitch G of the stirring screw 14 shown in FIG. 5 is increased, the angle α of the blade 14b is decreased. And if the angle (alpha) of the blade | wing 14b becomes small, the developer conveyance force F of the stirring screw 14 will become large. An increase in the developer conveying force F means that a force F1 acting in the developer conveying direction of the stirring screw 14 and a force F2 acting in a direction perpendicular to the force F1 are increased. Thus, as shown in FIG. 6, the force F2 increases as the angle α of the blade 14b decreases. Since this force F2 acts on the developer as a centrifugal force, the greater the force F2, the easier it is for the developer to jump up. In addition, when the amount of developer conveyed by the agitating screw 14 is small and the agitating screw 14 is not so much buried in the developer, the developer is likely to jump up.

  As described above, the screw pitch G may be increased in order to circulate the developer quickly in the developing container. However, if the screw pitch G is increased, the force F2 increases and the developer is likely to jump up. In particular, on the upstream side of the stirring chamber 12 with a small amount of developer, the developer is likely to jump up. In spite of such a state, when the replenishment agent is replenished, as already described, the replenishment agent is not sufficiently mixed with the developer, and a part of the replenishment agent passes through the second communication port 17. As a result, toner scattering that scatters outside the developing chamber 11 and the developing container can occur (see FIG. 3).

<Disk member>
Therefore, in this embodiment, a part of the developer conveyed in the stirring chamber 12 is blocked and temporarily stored, so that the developer that can be mixed with the replenished replenishment agent is secured in the second communication portion 171. It was made to be. In order to temporarily store the developer, the agitation screw 14 has a conveyance force lowering portion in which the developer conveyance force is reduced compared to the developer conveyance force in the coating region M. In 1st embodiment, as shown in FIG. 3, the stirring screw 14 has the disc member 101 as a conveyance power fall part. The disc member 101 will be described with reference to FIG.

  As shown in FIG. 3, the disc member 101 is provided on the rotating shaft 14 a so as to rotate in accordance with the rotation of the stirring screw 14. The disk member 101 is disposed downstream of the center of the second communication port 17 (second direction center, indicated by a straight line O in the figure) and upstream of the coating region M of the developing sleeve 3. The disc member 101 is formed so as to intersect the developer conveying direction of the stirring screw 14 and to have an outer diameter that is approximately the same as or slightly larger than the outer diameter of the screw (here, 20 mm) (for example, 19 mm to 22 mm). ing.

  The disc member 101 is a regulating member that regulates a part of the developer conveyed by the stirring screw 14 and temporarily accumulates the developer. When the developer is stored by the disk member 101, a part of the stored developer reaches the second communication portion 171 and the amount of developer in the second communication portion 171 increases compared to the conventional case. Thus, by securing the developer in the second communication portion 171, toner scattering due to the replenishment of the replenisher is less likely to occur. That is, since the replenisher is replenished so as to be mixed with the developer secured in the second communication portion 171, the amount of the developer in the second communication portion 171 is smaller than in the conventional case. A part of the developing chamber 11 is not easily scattered outside the developing container 11 through the second communication port 17.

  If the disk member 101 is disposed upstream of the center of the second communication port 17, the developer (or replenisher) stored by the disk member 101 is likely to return to the developing chamber 11 side. This is because the developer transferred to the stirring chamber 12 from the developing chamber 11 and the replenished replenisher are stored in the second communication portion 171 in a narrow range facing the second communication port 17, so that the second communication portion. This is because the amount of the developer 171 may be excessive. If the amount of the developer in the second communication portion 171 becomes too large, the developer (or replenisher) is likely to jump to the developing chamber 11 side when replenishing the replenisher. When the developer (or replenisher) is sprung up toward the developing chamber 11 by the disk member 101, they are supplied to the developing sleeve 3 and cause image defects such as fogging. Also, toner scattering is likely to occur. For this reason, the disk member 101 may be disposed downstream of the center of the second communication port 17, preferably downstream of the second communication port 17. In the case of this embodiment, the disc member 101 is disposed at a position about 10 mm away from the downstream end of the second communication port 17 on the downstream side.

  As described above, in the developing device 1 of the present embodiment, the disk member 101 is disposed downstream of the second communication port 17 in order to reduce the developer conveying force of the stirring screw 14 and temporarily accumulate the developer. Arranged. When the disc member 101 is disposed on the stirring screw 14, the developer is stored by the disc member 101, and a part of the stored developer reaches the second communication portion 171. In this way, securing the developer in the second communication portion 171 prior to replenishment of the replenishment agent during transport of the developer is easily realized by using the disk member 101. Since a certain amount of developer can be secured in the second communication portion 171, the replenisher is mixed with the developer in the second communication portion 171 when the replenisher is replenished. Thereby, the amount of developer in the second communication portion 171 does not decrease too much, and it is possible to suppress the occurrence of toner scattering due to the replenishment of the replenisher. In addition, since the replenisher is mixed with the developer at a relatively early stage immediately after replenishment and the stirring ability of the developer by the stirring screw 14 is improved, the effect of easily recovering the charging performance of the carrier is also obtained.

<Second embodiment>
As described above, in the first embodiment, the disk member 101 for temporarily storing the developer is disposed in the stirring screw 14 in order to secure the developer in the second communication portion 171, but this is not a limitation. In order to temporarily store the developer, a part of the screw shape of the stirring screw 14 may be a return screw. Even with the return screw, the developer conveying force of the stirring screw 14 can be temporarily reduced to temporarily accumulate the developer. FIG. 7 shows a developing device 1A according to the second embodiment. Hereinafter, in the developing device 1A of the second embodiment shown in FIG. 7, the same components as those of the developing device 1 of the first embodiment shown in FIG.

  As shown in FIG. 7, the agitation screw 140 has a return portion 142 as a conveyance force reducing portion upstream of the first conveyance portion 141 in which the blades 14b are formed around the rotation shaft 14a. The return portion 142 is a return screw 102 in which a return blade 14c wound in a direction opposite to the blade 14b is formed around the rotation shaft 14a, and conveys the developer in a direction opposite to the blade 14b (that is, the first direction). As with the disk member 101 described above, the return screw 102 is coated downstream of the center of the second communication port 17 (straight line O in the drawing) (preferably downstream of the second communication port 17) and the developing sleeve 3. Arranged upstream of the region M. In the case of this embodiment, the return screw 102 is disposed at a position about 10 mm away from the downstream end of the second communication port 17 on the downstream side. The return screw 102 is formed, for example, with a screw pitch of 20 mm, a screw outer diameter of 20 mm, and a length in the rotation axis direction of 20 mm (one turn of the return screw 102).

  The return screw 102 is transferred from the developing chamber 11 to the stirring chamber 12 via the second communication port 17, and pushes back a part of the developer conveyed by the stirring screw 140 to the upstream side, thereby temporarily removing the developer. Can be accumulated. When the developer is accumulated by the return screw 102, a part of the accumulated developer reaches the second communication portion 171, and the amount of developer in the second communication portion 171 increases compared to the conventional case. Thus, in the developing device 1A of the second embodiment, as in the case of the first embodiment, the developer can be secured in the second communication portion 171, and toner scattering occurs due to the replenishment of the replenisher. Can be suppressed.

<Third embodiment>
Next, the developing device of the third embodiment will be described with reference to FIG. In the developing device 1B of the third embodiment shown in FIG. 8, the same components as those of the developing device 1 of the first embodiment shown in FIG.

  As shown in FIG. 8, in the case of this embodiment, the stirring screw 145 has a second transport unit 146 on the upstream side of the first transport unit 141. The second transport unit 146 is adjacent to the first transport unit 141 on the downstream side, and transports the developer in the same direction as the first transport unit 141. The 1st conveyance part 141 is a single screw which has the rotating shaft 14a and the helical blade | wing 14b formed in the rotating shaft 14a. On the other hand, the 2nd conveyance part 146 is the multi-thread screw 103 which has the rotating shaft 14a and the helical blade | wing 14d formed in the rotating shaft 14a, and there are many thread | sleds more than the 1st conveyance part 141. That is, in the developing device 1B, a part of the screw shape of the stirring screw 14 is the multi-thread screw 103. In the case of the present embodiment, the multi-thread screw 103 is, for example, a double thread formed with two blades 14d, a screw pitch of 40 mm, a screw outer diameter of 20 mm, and a length in the rotation axis direction of 20 mm. The angle of the blade 14d of the multi-thread screw 103 is preferably substantially the same as that of the blade 14b of the stirring screw 14.

  The multi-thread screw 103 is disposed on the downstream side of the second communication port 17 (more specifically, on the downstream end of the second communication port 17 (indicated by the straight line Q in the figure)) and on the upstream side of the coating region M of the developing sleeve 3. If it is arranged so that the multi-thread screw 103 enters the second communication portion 171, that is, the upstream end of the multi-thread screw 103 is positioned upstream of the downstream end of the second communication port 17, The developer (or replenisher) can be returned to the developing chamber 11 side by the strip screw 103. In the case of the multiple strip screw 103, this is the radial direction (perpendicular to the longitudinal direction) as compared to the single strip screw (first transport unit 141). This is because the developer (and replenisher) that has returned to the developing chamber 11 side can cause image defects such as fogging and toner scattering. Multi-row It is preferable to arrange the view 103 on the downstream side of the second communication port 17. In the case of this embodiment, the multi-thread screw 103 is disposed at a position about 10 mm away from the downstream end of the second communication port 17 on the downstream side. ing.

  As described above, in the developing device 1 </ b> B of this embodiment, a part of the screw shape of the stirring screw 14 is the multi-thread screw 103 (second conveying unit 146). By using the multi-thread screw 103, the replenishment agent supplied by the multi-thread screw 103 is more easily stirred with the developer even if the developer is smaller than the conventional one, and is quickly conveyed to the downstream side while being stirred. The In this way, the replenisher is transported so as to be quickly taken into the agitating chamber from the second communicating portion 171 while being agitated more times by the multi-thread screw 103, and thus toner scattering occurs due to replenishment of the replenisher. Can be suppressed. In addition, since the developer can be stirred by the multi-thread screw 103, the charging performance of the carrier can be easily recovered.

<Other embodiments>
In each of the above-described embodiments, an intermediate transfer method in which a toner image of each color is primarily transferred from the photosensitive drum 10 of each color to the intermediate transfer belt 25, and then a composite toner image of each color is collectively transferred to the recording material S. Although the image forming apparatus 100 has been described, the present invention is not limited to this. For example, the image forming apparatus may be a direct transfer type that directly transfers from a photosensitive drum to a recording material carried and conveyed by a transfer material conveyance belt.

  In each of the above-described embodiments, the developing container 2 is divided into the developing chamber 11 and the stirring chamber 12 in the horizontal direction, or the developing container 2 is divided into the developing chamber 11 and the stirring chamber 12. The present invention can also be applied to a vertical stirring type developing device partitioned in the vertical direction.

1 (1A, 1B) ... developing device, 2 ... developing container, 3 ... developer carrier (developing sleeve), 11 ... first chamber (developing chamber), 12 ... second Chamber (stirring chamber), 13 ... first conveying screw (developing screw), 14 (140, 145) ... second conveying screw (stirring screw), 15 ... partition wall, 16 ... first series 17 through second communication port, 40 through replenishment port, 100 with image forming apparatus, 101 with reduced conveyance force (regulating member, disk member), 102 with conveyance force Lower part (return screw), 103 ... multi-thread screw, M ... supporting area (coat area)

Claims (6)

A developer carrying body that has a carrying area for carrying the developer, and carries and rotates the developer; and
A first chamber for supplying a developer to the developer carrier, and a second chamber for forming a developer circulation path in the first chamber and collecting the developer from the developer carrier, A developing container in which a supply port is formed in the second chamber;
A first conveying screw provided in the first chamber for conveying the developer in a first direction;
A second conveying screw that is provided in the second chamber, conveys the developer in a second direction opposite to the first direction, and conveys the replenisher replenished from the replenishing port in the second direction;
A first communication port that separates the first chamber and the second chamber in the developing container and delivers developer from the second chamber to the first chamber on the downstream side in the second direction; and the supply port A partition wall having a second communication port for transferring the developer from the first chamber to the second chamber on the downstream side in the second direction and on the upstream side in the second direction with respect to the carrying region.
The second conveying screw has a developer conveying force more than the carrying area on the downstream side in the second direction from the center in the second direction of the second communication port and on the upstream side in the second direction from the carrying area. It has a conveyance power reduction part to reduce,
A developing device. The conveyance force reduction unit is a regulating member that regulates a part of the developer conveyed in the second direction.
The developing device according to claim 1. The transport force reduction unit is a return screw that transports a part of the developer transported in the second direction opposite to the second direction.
The developing device according to claim 1. A developer carrying body that has a carrying area for carrying the developer, and carries and rotates the developer; and
A first chamber for supplying a developer to the developer carrier, and a second chamber for forming a developer circulation path in the first chamber and collecting the developer from the developer carrier, A developing container in which a supply port is formed in the second chamber;
A first conveying screw provided in the first chamber for conveying the developer in a first direction;
A second conveying screw that is provided in the second chamber, conveys the developer in a second direction opposite to the first direction, and conveys the replenisher replenished from the replenishing port in the second direction;
A first communication port that separates the first chamber and the second chamber in the developing container and delivers developer from the second chamber to the first chamber on the downstream side in the second direction; and the supply port A partition wall having a second communication port for transferring the developer from the first chamber to the second chamber on the downstream side in the second direction and on the upstream side in the second direction with respect to the carrying region.
The second conveying screw has a multi-thread screw having a larger number of threads than the supporting area on the downstream side in the second direction than the second communication port and on the upstream side in the second direction than the supporting area.
A developing device. The second conveying screw is disposed below the first conveying screw so that at least a part of the second conveying screw overlaps with the first conveying screw when viewed from the horizontal direction.
The developing device according to claim 1, wherein The first conveying screw has a developer conveying speed slower than that of the second conveying screw,
The developing device according to claim 1, wherein:

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