JP2014081665A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that is shipped with openings formed on a partition wall sealed with sheet members, and prevents application of an excessive load to a motor when the sheet members are automatically taken up.SOLUTION: Openings 107a and 107b on a partition wall 103 partitioning a developing container 101 have sealing sheets 51a and 51b adhered thereto, respectively. At the initial start-up of a developing device 100, the sealing sheets 51a and 51b are taken up into a take-up shaft 600 and removed in association with rotation of a stirring screw 104b. At this time, a reverse conveyance screw 104c conveys a developer accumulated on the downstream side of a stirring chamber 101b in association with the rotation of the stirring screw 104b to alleviate an increase in pressure of the developer, and reduce load torque of a drive motor of the stirring screw 104b. The reverse conveyance screw 104c is arranged at a position higher than the height of the developer when the openings 107a and 107b are opened to form a circulation path of the developer.

Description

  The present invention relates to an image forming apparatus equipped with a developing device that is shipped in a state in which an opening of a partition wall that partitions a first chamber and a second chamber is sealed with a sheet member and a developer is sealed in the second chamber, Specifically, the present invention relates to a structure that reduces the load on the drive motor at the initial startup of the developing device.

  An image forming apparatus in which a developing device or a process cartridge is replaceably mounted, an electrostatic image formed on an image carrier is developed into a toner image by a developing device, and the toner image is transferred to a recording material is widely used ( Patent Document 2). Image forming apparatuses and replacement developing apparatuses are usually shipped in a state where an initial developer used first in the developing apparatus is sealed and filled with nitrogen gas or the like so as not to be exposed to the outside air. This is because if the developer is left in contact with high-temperature and high-humidity air, the developer deteriorates in moisture absorption, and the developer cannot exhibit predetermined performance at the initial startup.

  In Patent Document 1, an output of a drive motor provided in an image forming apparatus is connected to a developing device via a coupling, and input rotation is distributed into a plurality of gear trains so that a developer conveying screw and a developing sleeve are integrated. A developing device to be rotated is shown.

  Patent Document 2 discloses a developing device in which a developer container filled with an initial developer and sealed with a sheet member is incorporated. Here, after the developing device is mounted on the image forming apparatus, the sheet member is manually pulled from the outside to release the seal pack of the developer container, and the developer in the developer container is dropped into the developing apparatus. Filled with developer.

  However, as in Patent Document 2, when the first chamber and the second chamber are shipped in an empty state and the initial developer is filled from the developer container at the first startup, the developer container is stored in the developing device. A large space is required. For this reason, a small-sized developing device cannot accommodate a sufficiently large developer container, and if a sufficiently large developer container is accommodated, the image forming apparatus can be prevented from being miniaturized.

  Therefore, in Patent Document 3, the opening at both ends of the partition partitioning the first chamber and the second chamber is sealed with a sheet member to seal the second chamber, and the required amount of initial developer is sealed in the second chamber. A developing device has been proposed. In this case, since the second chamber functions as a developer container for the initial developer, even if a sufficient capacity of the initial developer is accommodated, the developing device does not need to be increased in size.

JP 2001-75346 A JP 2002-236413 A JP 2004-252174 A

  In the case of the developing device of Patent Document 3, when the image forming apparatus is first operated or when the developing device is replaced with a new one, the sheet member is manually pulled from the outside prior to the start of image formation, and the developing device is moved to the developing device. It is necessary to fill the initial developer. Therefore, as disclosed in Patent Document 1, it is proposed that the input rotation from the coupling is distributed to a plurality of gear trains, and the sheet member is peeled off from the opening of the partition wall using one of them and automatically removed. It was.

  Here, since the configuration of Patent Document 3 has a smaller sheet member sticking area than the configuration of Patent Document 2, it is considered that the peeling torque of the sheet member may be small. However, when the sheet member is automatically wound up by the developing device configured as in Patent Document 3, the torque of the drive motor increases during winding, and the drive motor may be overloaded. found.

  Therefore, when the operation state was observed with a part of the appearance of the developing device being transparent, if the second conveying screw continued to rotate in the second chamber whose opening was blocked by the sheet member, the downstream side of the second chamber It was observed that the developer reached the ceiling. It was found that the developer without escape was pushed into the downstream side of the second chamber, the developer pressure increased, and the conveying screw was overloaded.

  The present invention relates to a developing device that does not cause an overload of a drive motor when the sheet member is automatically wound by a developing device that is shipped with the opening formed in the partition wall sealed with the sheet member. The purpose is to provide.

  The image forming apparatus according to the present invention includes an image carrier that carries an image, a developer carrying a toner and a carrier, and a developer carrier that develops a latent image formed on the image carrier, and the development A developing chamber that supplies the developer to the developer carrying member at a position facing the developer carrying member, a stirring chamber that is connected at both ends of the developing chamber to form a circulation path for circulating the developer, and the developing chamber A first conveying member that is rotatably provided and conveys the developer; and a second conveying member that is rotatably provided in the stirring chamber and conveys the developer in a direction opposite to the conveying direction of the first conveying member; A first opening for transferring the developer from the stirring chamber to the developing chamber, a second opening for transferring the developer from the developing chamber to the stirring chamber, the developing chamber and the stirring chamber A partition wall for partitioning the first opening portion to seal the developer in the stirring chamber A seal portion that seals the second opening portion so as to be openable, an opening mechanism that is provided so as to be able to open the seal portion, and the second transport member is driven during the opening operation of the seal portion. A control unit for controlling. The timing at which the opening of the first opening is started is configured earlier than the timing at which the opening of the second opening is started.

  In the image forming apparatus of the present invention, the timing at which the opening of the first opening of the developing device is started is configured earlier than the timing at which the opening of the second opening is started.

  Therefore, it is not necessary to cause an overload of the motor when the sheet member is automatically wound by the developing device shipped with the opening formed in the partition wall sealed with the sheet member.

1 is an explanatory diagram of a configuration of an image forming apparatus. It is explanatory drawing of the cross-sectional structure of a developing device. It is explanatory drawing of the plane structure of a developing device. It is explanatory drawing of the plane structure which looked at the developing device from the top. It is explanatory drawing of the sealing structure of the initial stage developer of a developing device. It is explanatory drawing of a gear train. It is a flowchart of initial start-up control. It is a diagram of the load torque of the drive motor in the initial startup process. It is explanatory drawing of the opening start of a sealing sheet. It is explanatory drawing of the circulation state of a developing agent.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention replaces part or all of the configuration of the embodiment with an alternative configuration as long as a conveyance screw having a conveyance direction opposite to that of the second conveyance screw is additionally disposed in the second chamber. Other embodiments can also be implemented.

  The developing device of the present invention can be implemented without distinction in a tandem type / 1 drum type, intermediate transfer type / direct transfer type image forming apparatus. The present invention can be implemented in image forming apparatuses for various uses such as a printer, various printing machines, a copying machine, a FAX, and a multifunction machine, in addition to necessary equipment, equipment, and a housing structure.

  In addition, about the general matter of the image development apparatus shown by patent documents 1-3, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. As shown in FIG. 1, the image forming apparatus 200 includes a tandem type intermediate in which yellow, magenta, cyan, and black image forming portions Sa, Sb, Sc, and Sd are exchangeably mounted along the intermediate transfer belt 7. It is a transfer type full-color printer.

  In the image forming unit Sa, a yellow toner image is formed on the photosensitive drum 1 a and transferred to the intermediate transfer belt 7. In the image forming unit Sb, a magenta toner image is formed on the photosensitive drum 1 b and transferred to the intermediate transfer belt 7. In the image forming portions Sc and Sd, a cyan toner image and a black toner image are formed on the photosensitive drums 1c and 1d, respectively, and transferred to the intermediate transfer belt 7.

  The intermediate transfer belt 7 is wound around the primary transfer rollers 5a, 5b, 5c, and 5d, the opposing roller 8, the tension roller 17, and the stretching roller 18, and is driven by the opposing roller 8 that also serves as a driving roller in the direction of arrow R7. Rotate. The four-color toner images transferred to the intermediate transfer belt 7 are transported to the secondary transfer portion T2, and secondarily transferred to the recording material P taken out from the recording material cassette 10 and transported to the secondary transfer portion T2. The recording material P is supplied to the secondary transfer portion T2 by a feeding / conveying device (all not shown) having a paper feed roller, a conveyance roller, a registration roller, and the like.

  The recording material P to which the toner image has been transferred by the secondary transfer portion T2 is heated and pressed by the fixing device 13 in which the pressure roller 15 is brought into pressure contact with the fixing roller 14, and the toner image is fixed on the surface thereof. It is discharged outside.

  The image forming portions Sa, Sb, Sc, and Sd are configured substantially the same except that the colors of toner used in the developing devices 100a, 100b, 100c, and 100d are different. Hereinafter, the image forming unit Sa will be described, and the image forming units Sb, Sc, and Sd will be described by replacing “a” at the end of the reference numerals attached to the components of the image forming unit Sa with “b”, “c”, and “d”. To do.

  In the image forming unit Sa, a charging roller 2a, an exposure device 3a, a developing device 100a, a primary transfer roller 5a, and an auxiliary charging roller 6a are arranged around the photosensitive drum 1a.

  The photosensitive drum 1a is formed with a photosensitive layer having a negative polarity on the outer peripheral surface of an aluminum cylinder, and rotates in the direction of arrow R1 at a predetermined process speed. The charging roller 2a charges the surface of the photosensitive drum 1a to a uniform negative potential. The exposure device 3a scans the laser beam with a rotating mirror and writes an electrostatic image of the image on the surface of the charged photosensitive drum 1a. The developing device 100a develops the electrostatic image formed on the photosensitive drum 1a using a two-component developer composed of toner and carrier, and forms a toner image on the photosensitive drum 1a.

  The primary transfer roller 5 a presses the inner surface of the intermediate transfer belt 7 to form a primary transfer portion T <b> 1 between the photosensitive drum 1 a and the intermediate transfer belt 7. By applying a positive DC voltage to the primary transfer roller 5 a, the negative toner image carried on the photosensitive drum 1 a is primarily transferred to the intermediate transfer belt 7. The auxiliary charging roller 6a charges the transfer residual toner remaining on the photosensitive drum 1a after escaping from the transfer to the recording material P to a negative polarity, and participates in the next development by the developing device 100a.

  A belt cleaner 11 is in contact with a position corresponding to the tension roller 17 of the intermediate transfer belt 7 in order to remove the transfer residual toner attached to the intermediate transfer belt 7.

<Developing device>
FIG. 2 is an explanatory diagram of a cross-sectional configuration of the developing device. FIG. 3 is an explanatory diagram of a planar configuration of the developing device. In the following description, a developing device that is replaceably mounted on the image forming unit will be described with a, b, c, and d at the end of the symbol representing the distinction of the image forming unit omitted.

  As illustrated in FIG. 2, the developing device 100 develops an electrostatic image (latent image) on the photosensitive drum 1 by supporting a developer containing toner and a carrier on a developing sleeve 102 which is an example of a developer carrier. The developing sleeve 102 is rotatably disposed in an opening portion of the developing container 101 that faces the photosensitive drum 1. A layer thickness regulating blade 121 is disposed upstream in the rotation direction of the developing area where the developing sleeve 102 and the photosensitive drum 1 face each other, and regulates the thickness of the developer carried on the developing sleeve 102.

  The developing container 101 is partitioned (divided) into a developing chamber 101a and a stirring chamber 101b by a partition wall (partition wall) 103 provided vertically. In the developing chamber 101a and the stirring chamber 101b (circulation path), a two-component developer in which a nonmagnetic toner, a magnetic carrier, and a small amount of an external additive are mixed is accommodated.

  Inside the developing sleeve 102, a magnet 102m is disposed which is supported non-rotatingly by arranging a plurality of magnetic poles on the surface. In the developer, the magnetic carrier is constrained by the magnetic flux formed between the magnetic poles of the magnet 102m and is carried on the surface of the developing sleeve 102, and the negatively charged toner is electrostatically charged on the surface of the positively charged carrier. To form a magnetic brush. The power source 52 applies an oscillating voltage in which an AC voltage is superimposed on a negative DC voltage, and transfers the toner charged to the negative polarity and carried on the magnetic brush to the electrostatic image on the photosensitive drum 1.

  As shown in FIG. 3, the developing container 101 is partitioned into two parallel spaces by a partition wall 103. The stirring chamber 101b and the developing chamber 101a are configured to be able to store and transport the two-component developer. The developing device 100 is disposed in the vicinity of a stirring chamber 101b having a stirring screw 104b (second conveying member) therein, a developing chamber 101a having a developing screw 104a (first conveying member) therein, and the developing chamber 101a. A developing sleeve 102 is provided.

  Through the openings 107a and 107b formed at both ends of the partition wall 103, the stirring chamber 101b and the developing chamber 101a communicate with each other to form a developer circulation path. The developer is transferred from the stirring chamber 101b to the developing chamber 101a through the opening 107a, and the developer is transferred from the developing chamber 101a to the stirring chamber 101b through the opening 107b.

  In the process in which the developer circulates in the circulation path configured as described above, the toner particles and the carrier particles are rubbed, and the toner is negatively charged and the carrier is positively charged. The developer is conveyed to the downstream side while being stirred by the stirring screw 104b inside the stirring chamber 101b, and then flows into the developing chamber 101a through the opening 107a without the partition wall 103. The developer is carried on the developing sleeve 102 in the course of being conveyed downstream by the developing screw 104a inside the developing chamber 101a.

  A developing screw 104a, which is an example of a first conveying screw, is rotatably mounted inside a developing chamber 101a, which is an example of a first chamber. When the developing screw 104a rotates, the two-component developer is conveyed from the upstream side to the downstream side of the developing chamber 101a as indicated by an arrow B.

  An agitation screw 104b, which is an example of a second conveying screw, is rotatably mounted inside an agitation chamber 101b, which is an example of the second chamber. When the second stirring screw 104b rotates, the two-component developer is conveyed from the upstream side to the downstream side of the stirring chamber 101b as indicated by an arrow A.

  A toner replenishing mechanism 105 is disposed on the upper upstream side of the stirring chamber 101b (see FIG. 5B). The toner contained in a toner bottle (not shown) is conveyed to a toner supply mechanism 105 through a toner conveyance path (not shown), passes through the toner supply port 106, and is dropped and supplied into the stirring chamber 101b. In the developing device 100, the same type of toner as the initial developer is used as a replenishing toner.

  Here, the toner charge amount Q / M of the two-component developer is an important parameter for determining the developed image density. There is a correlation between the weight ratio (toner concentration T / D) of the toner contained in the two-component developer and the toner charge amount Q / M.

  Since the toner is charged by contact friction with the carrier, the toner charge amount Q / M increases as the contact opportunity with the carrier increases. For this reason, in the two-component developer, the smaller the toner density T / D, the larger the toner charge amount Q / M, and the lower the image density when developing the same electrostatic image. For this reason, the toner concentration T / D of the developer circulating through the developing chamber 101a and the stirring chamber 101b is always detected using a magnetic permeability sensor (not shown). Then, the toner supply amount from the toner supply mechanism 105 is adjusted so that the toner density T / D becomes substantially constant.

  Incidentally, as disclosed in JP-A-2001-249544, in a two-component developer, toner and carrier are mixed in advance at a predetermined toner concentration T / D and sealed in a developer container. When the toner and the carrier are mixed and then left for a long time in a high temperature and high humidity environment, the toner charge amount Q / M contained in the two-component developer at the start of the start-up operation of the developing device 100 is desired. Lower than the value of.

  In such a case, as a starting operation of the developing device 100, there is a method in which the developer is stirred and circulated by the developing screw 104a and the stirring screw 104b until the toner charge amount Q / M becomes an appropriate value. However, if the developer is continuously circulated, the developer may be deteriorated and the fluidity may be lowered or the charging performance may not be recovered.

  For this reason, even when the developing device 100 is initially started up, it is preferable that the time for stirring and circulating the developer is as short as possible. Therefore, a method of supplying the initial developer stored in a sealed state in a separate container from the developing device to the developing device, or a method of storing the initial developer in a sealed state in the developing device is adopted.

  Here, the method of replenishing the initial developer from a separate container has a problem that the developer is scattered when the developer is charged and the surroundings are stained. There are also many problems in loss of work time for putting the initial developer, user operability, and skill required for work. Further, when the developing device incorporating the developer is transported, overflow or leakage of the developer becomes a problem.

  Therefore, a method of storing the initial developer in a developing device in a sealed state is becoming mainstream (Patent Documents 1 and 2). Further, as one configuration for sealing the developer in the developing device, in Patent Document 3 (Japanese Patent Laid-Open No. 2004-252174), the opening of the partition wall is sealed with a seal member, and the initial developer is removed. A configuration for hermetically storing in a stirring chamber has been proposed.

<Sealing structure of initial developer>
FIG. 4 is an explanatory diagram of a planar configuration of the developing device as viewed from above. FIG. 5 is an explanatory diagram of an initial developer sealing structure of the developing device. 5, (a) is a vertical section viewed from the EE direction in FIG. 4, and (b) is a vertical section viewed from the FF direction in FIG.

  As shown in FIG. 4, the relationship among the developing device 100, the drive motor 53, the power source 52, the control unit 50, and the operation panel 56 is shown using a block diagram. Further, in the developing device 100, a sealing sheet 51a that is an example of a sealing member is attached to the opening 107a of the partition wall 103 that partitions the developing container 101, and a sealing sheet 51b that is an example of a sealing member is attached to the opening 107b. Is affixed. With this configuration, in the developing device 100 at the time of shipment, the initial developer is filled in only the stirring chamber 101b in a sealed state. At this time, neither the carrier nor the toner exists in the developing chamber 101a.

  As shown to (a) of FIG. 5, sealing sheet 51a, 51b which is an example of a sealing member is a sheet | seat member affixed to the opening part 107a, 107b so that it can peel off (opening is possible). The sealing sheet 51a is affixed to the opening 107a on the downstream side in the second conveyance screw conveyance direction, and the sealing sheet 51b is affixed to the opening 107b on the upstream side in the second conveyance screw conveyance direction.

  The sealing sheet 51a is folded upward from the lower end side while sealing the opening 107a, and the tip is fixed to the common winding shaft 600. Similarly, the sealing sheet 51b is folded upward from the lower end side while the opening 107b is sealed, and the tip is fixed to the common winding shaft 600.

  A take-up shaft (rotating shaft rotatable along the rotation axis direction of the developing sleeve) 600, which is an example of the sealing member moving mechanism (opening mechanism), is sealed with the sealing sheets 51a and 51b as the stirring screw 104b rotates. Is moved (can be driven) to open the openings 107a and 107b. The take-up shaft 600 automatically peels off the sealing sheets 51a and 51b of the developing device 100 from the openings 107a and 107b without depending on the user's work, and starts up the developing device 100 in an operable state.

  The take-up shaft 600 performs the peeling start of the sealing sheets 51a and 51b, and also performs the peeling of the sealing sheets 51a and 51b so that they do not overlap with each other at the end of the peeling. And the peeling start time of the sealing sheet 51a stuck on the opening 107a is set earlier than the peeling start time of the sealing sheet 51b stuck on the opening 107b. That is, the length from the sticking position on the lower end side of the sealing sheet 51b to the attachment to the common take-up shaft 600 is set longer than the length from the folding back of the sealing sheet 51a to the attachment to the take-up shaft 600. Has been.

<Drive mechanism of winding shaft>
FIG. 6 is an explanatory diagram of the gear train. As shown in FIG. 6 with reference to FIG. 4, the developing device 100 is connected to a driving motor 53 installed on the main body side of the image forming apparatus 200 via a coupling 54 in which the developing sleeve 102 is detachable in the axial direction. The The drive motor 53 is driven by the control unit 50 to rotate the developing sleeve 102.

  The rotation of the developing sleeve 102 is distributed by the opposite gear train 160 to which the drive motor 53 is connected, and the stirring screw 104b, the developing screw 104a, the winding shaft 600, and the reverse conveying screw 104c are rotated together. The developing sleeve 102, the developing screw 104a, the stirring screw 104b, the winding shaft 600, and the reverse conveying screw 104c are integrally connected by a gear train 160. When the developing sleeve 102 rotates, the central gear 151 rotates. A gear 150 that meshes with the gear 151 rotates the developing screw 104a. A gear 152 that meshes with the gear 151 rotates the stirring screw 104b.

  The reverse conveying screw 104c rotates through the meshing of the gears 151, 153, and 156. The winding shaft 600 rotates through the meshing of the gears 151, 153, 157, 154, 155. The gears 154 and 155 are configured to greatly decelerate using a worm gear so that the necessary torque can be secured when the winding shaft 600 peels off the sealing sheets 51a and 51b.

  As a result, the developing sleeve 102 rotates at 250 rpm, the developing screw 104a rotates at 300 rpm, and the stirring screw 104b rotates at 400 rpm. This is because the stirring force of the stirring screw 104b is set larger than the stirring force of the developing screw 104a in order to improve the charging performance of the developer. The reverse conveying screw 104c rotates at 300 rpm, and the winding shaft 600 rotates at 20 rpm.

  Further, the winding shaft 600 and the gear 155 are connected at a position close to the sealing sheet 51a out of the two sealing sheets 51a and 51b. Thereby, the setting of the peeling start time is set later as the sheet member is farther from the drive end of the winding shaft 600.

  By the way, when the space between the developing chamber 101a is sealed with the sealing sheets 51a and 51b and the initial developer is sealed and stored in the stirring chamber 101b, the load on the drive motor 53 is heavy when the developing device is operated. There are challenges. If the stirring screw 104b continues to rotate in a state where the sealing sheets 51a and 51b are not removed, the developer cannot move from the stirring chamber 101b to the developing chamber 101a, so that the driving load of the developing device 100 becomes very large.

  The reverse conveying screw 104c, which is an example of the developer reverse feeding means, causes the developer pushed into the second conveying screw conveying direction downstream side of the stirring chamber 101b whose opening 107a is not opened as the stirring screw 104b rotates. 2 conveying screw conveying in the reverse direction. The reverse conveying screw 104c has its height position set so that the developer can be conveyed at a position higher than the height of the developer when the openings 107a and 107b are opened and the developer circulation path is formed. ing. In the inventor's experiment, the diameter of the reverse conveying screw 104c is φ15 mm, and the above effect has been confirmed when the screw length is 9 mm or more.

<Initial startup control>
FIG. 7 is a flowchart of the initial startup control. FIG. 8 is a diagram of the load torque of the drive motor in the initial startup process. FIG. 9 is an explanatory view of the opening of the sealing sheet. FIG. 10 is an explanatory diagram of the circulation state of the developer.

  In the developing device 100 according to the first exemplary embodiment, the sealing members (51a and 51b) are not manually removed by a user or a service person as in Patent Document 3, but the driving motor 53 of the image forming apparatus 200 is used. The sealing members (51a, 51b) are automatically removed. Therefore, the developing device 100 with high usability can be provided.

  As shown in FIG. 7 with reference to FIG. 4, first, the user sets the developing device 100 in the image forming apparatus 200 (S801).

  Subsequently, when the user inputs an initial startup command to the operation panel 56, the control unit 50 operates the drive motor 53 disposed in the image forming apparatus 200 to rotate the developing sleeve 102. By the gear train 160 described above, the stirring screw 104b, the developing screw 104a, the reverse conveying screw 104c, and the take-up shaft 600 (during the opening operation of the seal portion) rotate simultaneously with the rotation of the developing sleeve 102 (S802).

  As shown in FIG. 5B, the stirring screw 104b rotates to transport the developer in the direction of arrow A in the stirring chamber 101b. However, since the sealing sheet 51a has not yet been peeled off (the driving start timing is ahead of the opening start timing during the opening operation), the downstream side in the direction of arrow A (the second chamber of the second chamber in which the opening is not opened). The developer collects on the downstream side of the two conveying screws. However, since the collected developer is conveyed in the direction of arrow C by the reverse conveying screw 104c, the developer is divided vertically and circulated in the stirring chamber 101b. For this reason, excessive torque is not generated in the stirring screw 104b.

  As shown in FIG. 5A, the sealing sheets 51a and 51b are wound up by the rotation of the winding shaft 600 while the developer is circulating in the stirring chamber 101b. And since the folding length of the sealing sheet 51a is shorter than the sealing sheet 51b, the sticking part of the sealing sheet 51a begins to peel off before the sticking part of the sealing sheet 51b, and the opening part (first opening part) ) 107a is opened (S803).

  At this time, as shown in FIG. 8, the resistance applied to peel off the adhesion is added and the torque applied to the drive motor 53 is maximized (S803). Thereafter, the developer gradually leaks into the developing chamber 101a from the gap of the opened opening 107a, but the developer is circulated by the stirring screw 104b and the reverse conveying screw 104c while the gap of the opening 107a is small. .

  The developer pushed out to the developing chamber 101a by the stirring screw 104b gradually increases through the gap where the sealing sheet 51a is peeled off, and is conveyed downstream by the developing screw 104a.

  As shown in FIG. 9, the sealing part of the sealing sheet 51b is peeled off after the sealing sheet 51a, and the opening 107b starts to be opened (S804). The resistance applied to peel off the sticking is added and the torque applied to the drive motor 53 forms a peak again (S804).

  When the developer conveyed by the developing screw 104a reaches the opening 107b, the sealing sheet 51b has also started to peel off and has passed for a while. Therefore, the developer flows from the developing screw 104a into the stirring chamber 101b through the opening 107b without being blocked by the sealing sheet 51b, and is delivered to the stirring screw 104b. At this time, the developer starts to circulate in the developing device 100 (S805).

  When the sealing sheet 51a is peeled off to the end and completely wound on the winding shaft 600, the opening 107a is completely opened (S806). When the sealing sheet 51b is completely wound around the winding shaft 600 with a slight delay, the opening 107b is also completely opened (S807).

  In this state, the control unit 50 rotates the developing sleeve 102, the developing screw 104a, the stirring screw 104b, and the reverse conveying screw 104c after rotating for 120 seconds. As a result, as shown in FIG. 10, the two-component developer filled in the developing container 101 is sufficiently stirred and mixed, and the initial startup of the developing device 100 is completed (S808). If there is an image forming job, image formation is started without stopping.

  During the operation of the developing device 100, the reverse conveying screw 104c and the take-up shaft 600 rotate in conjunction with the developing sleeve 102 and the like. However, since the reverse conveying screw 104c rotates at a position away from the developer surface of the stirring chamber 101b, and the winding shaft 600 only rotates the sealing sheets 51a and 51b, the load is small. For this reason, the rotation of the developing sleeve 102 and the stirring of the developer are not adversely affected.

<Comparative example>
In this embodiment, the initial start-up using the reverse conveying screw 104c has been described. However, when the reverse conveying screw 104c is not used, as shown by the broken line in FIG. 8, the torque of ΔTmax at the timing when the sealing sheet 51a is peeled off. A difference will occur. Therefore, when the reverse conveying screw 104c is not used, it is necessary to increase the capacity of the drive motor 53 on the image forming apparatus 200 side or to provide a separate drive source for the take-up shaft 600, which is not preferable.

  By the way, as shown in FIG. 5A, another sealing method is conceivable as a method of storing the initial developer in the developing device 100 in a sealed state. In this method, the developing sleeve 102 and the developing screw 104a are largely covered with a single sealing sheet, and the developing chamber 101a and the stirring chamber 101b are sealed in a communicating state.

  As long as the openings 107a and 107b are opened to form a circulation path, even if the developing screw 104a continues to rotate, the pressure of the developer does not increase locally and the load on the stirring screw 104b does not increase. For this reason, it is not necessary to provide the reverse conveyance screw 104c.

  However, in this case, it is necessary to secure a passage space for the sealing sheet between the developing sleeve 102 and the developing screw 104a, and there is a problem that the interval between the developing sleeve 102 and the developing screw 104a becomes larger than that in the first embodiment. . In the developing device 100, since the developing sleeve 102 and the developing screw 104a are brought close to each other, the image quality of the output image is improved and the deterioration of the developer is prevented.

  As shown in FIG. 5A, in the developing device 100, the developer is attracted and carried on the surface of the developing sleeve 102 using the magnetic force of the magnet 102 m in the developing sleeve 102. In this case, if the distance between the developing sleeve 102 and the developing screw 104a cannot be made close, it is necessary to increase the magnetic force of the magnet 102m to a certain level or more. When the magnetic force of the magnet 102m is strong, there is a problem that the deterioration of the developer is promoted and the durability of the developer is lowered.

  In order to achieve high image quality of the output image, it is desirable to make the distance T1 between the developing sleeve 102 and the developing screw 104a of the developing device 100 as small as possible. It is desirable to reduce the distance T1 so as not to cause insufficient supply of the developer from the developing screw 104a to the developing sleeve 102.

  In this regard, if a sealing sheet is provided between the developing sleeve 102 and the developing screw 104a, there is a limit to reducing the distance T1. Further, when the sealing sheet is peeled off and removed, the developing sleeve 102 may be damaged.

<Effect of Example>
As shown in FIG. 5A, in Example 1, the reverse conveying screw 104c is arranged above the stirring screw 104b and the central axis is shifted rearward by G1. As a result, while ensuring sufficient clearance with the take-up shaft 600 above the stirring screw 104b, as shown in FIG. Do not touch.

  In Example 1, in order to wind around the winding shaft 600, the sealing sheets 51a and 51b were made of a sheet-like resin containing polyester having a thickness of 0.1 mm. This is basically the same as the manual peeling type sealing sheet disclosed in Patent Document 2. Note that the materials, shapes, and timings used for each are not limited to those described here.

  The load applied when peeling off the sealing sheets 51a and 51b tends to increase at the beginning of peeling and at the end of peeling. Therefore, in Example 1, when a plurality of sealing sheets are peeled off at the same time, the timings at which the peeling start and the peeling end are all different are set. Thereby, the load peak applied to the winding shaft 600 is dispersed, and the maximum load applied to the drive motor 53 is reduced.

  In Example 1, these timings are adjusted by making the folding length of the sealing sheet 51b longer than the folding length of the sealing sheet 51a. However, it is also possible to provide a time difference in the peeling timing by making the shaft diameter of the winding shaft 600 different between the sealing sheets 51a and 51b and increasing the shaft diameter to be peeled off first.

  Further, when the sealing sheets 51a and 51b are peeled off, if a high load is applied to the winding shaft 600, twisting occurs in the rotational direction. For this reason, the winding timing of the sealing sheet tends to be delayed as the distance from the driving end of the winding shaft 600 increases.

  Therefore, in Example 1, the gear 155 and the take-up shaft 600 are connected at a position close to the sealing sheet 51a that starts to be peeled first among the sealing sheets 51a and 51b. For this reason, even when the winding shaft 600 is twisted, the sealing sheet 51b always starts to peel off with a delay from the sealing sheet 51a. For this reason, even if the winding shaft 600 has low rigidity, it is possible to reliably start the sealing sheet 51a before the sealing sheet 51b. Therefore, the first embodiment can be implemented not only when the take-up shaft 600 is made of a material having a relatively low rigidity, such as a resin mold product, but also a material having a high rigidity such as a metal.

  In Example 1, as described in the comparative example, there is no sealing sheet between the developing sleeve 102 and the developing screw 104a. Therefore, as shown in FIG. 5A, the distance T1 is 2 mm, and the distance T1 between the developing sleeve 102 and the developing screw 104a can be made sufficiently close. As a result, it is possible to prevent toner scattering at the initial startup and to further improve the image quality of the output image. The developing sleeve 102 is not damaged by peeling off the sealing sheet.

  In the first embodiment, the developer in the developing chamber 101 a is attracted to the developing sleeve 102 by the magnetic force of the magnet 102 m in the developing sleeve 102. By reducing the distance T1, the magnetic force of the magnet 102m can be weakened.

  Conventionally, for a distance T1 of 2.5 mm, the magnet magnetic force of a pole that attracts the developer in the developing chamber 101a to the developing sleeve 102 (hereinafter referred to as an attracting pole) was 600G. On the other hand, in Example 1, since the distance T1 is 2 mm, the magnet magnetic force of the attracting pole can be 500 G or less. By weakening the magnetic force, the load on the developer can be reduced, and deterioration of the developer can be prevented.

  When the developer is deteriorated, a fogged image appears on a white background. In the first embodiment, the occurrence of fog is prevented by weakening the magnetic force of the magnet 102m and suppressing the deterioration of the developer to the minimum necessary. Therefore, not only toner scattering but also fogging can be prevented, and a high-quality output image can be provided over a long period of time.

<Example 2>
As shown in FIG. 2, when the developing device 100 is started, the developing sleeve 102 starts rotating immediately, and the developer in the developing chamber 101a is carried on the rotating developing sleeve 102. At this time, since the developer in the developing chamber 101a is hardly charged, the toner does not adhere to the magnetic brush of the carrier carried on the developing sleeve 102. However, since a certain amount of toner is actually mixed with the carrier of the magnetic brush, the toner may scatter from the developing sleeve 102 as the developing sleeve 102 rotates.

  Further, in the developing device 100, as shown in FIG. 1, the transfer residual toner is reused by using auxiliary charging rollers 6a, 6b, 6c and 6d which are examples of auxiliary charging means. In the case of a cleaner-less configuration having auxiliary charging means, it is necessary to prevent transfer residual toner from contaminating the auxiliary charging roller and the charging roller by increasing transfer efficiency and reducing transfer residual toner. In order to increase the transfer efficiency, it is effective to keep the toner charge amount Q / M appropriately. Therefore, in order to prevent contamination of the auxiliary charging roller and the charging roller, it is necessary to appropriately maintain the toner charge amount Q / M.

Therefore, as described above, the developing device 100 according to the second exemplary embodiment stirs and mixes the initial developer in a state where the initial developer is confined in the stirring chamber 101b at the time of initial startup, and increases the charged state of the developer to a certain extent. 101a. With the openings 107a and 107b sealed with the sealing sheets 51a and 51b, the stirring screw 104b and the reverse conveying screw 104c
Thus, the developer is circulated while stirring in the stirring chamber 101b to increase the toner charge amount Q / M.

  That is, in the developing chamber 101a, which is an example of the first chamber, the developing screw 104a, which is an example of the first conveying screw, can convey the developer along the developing sleeve 102, which is an example of the developer carrier. The stirring chamber 101b, which is an example of the second chamber, communicates with the developing chamber 101a through the openings 107a, 107b, and the stirring screw 104b, which is an example of the second transport screw, can transport the developer in the opposite direction to the developing chamber 101a. It is.

  Moreover, the sealing sheet 51a which is an example of a sealing member seals the opening part 107a located in the 2nd screw conveyance direction downstream so that opening is possible. The winding shaft 600, which is an example of the sealing member moving mechanism, moves the sealing sheet 51a to open the opening 107a.

  Further, the reverse conveying screw 104c, which is an example of the developer reverse feeding means, conveys the developer in the second conveying screw conveying reverse direction in the stirring chamber 101b whose opening 107a is not opened. As a result, the reverse conveying screw 104c can cooperate with the stirring screw 104b and circulate the developer in the stirring chamber 101b while stirring.

  And the control part 50 which is an example of a control means uses the stirring screw 104b and the reverse conveyance screw 104c for the initial stage developer which sealed the opening part 107a with the sealing sheet 51a first, and was confine | sealed in the stirring chamber 101b. Circulate with stirring. Thereafter, the control unit 50 controls the winding shaft 600 to open the opening 107a and circulate the developer in the developing chamber 101a and the stirring chamber 101b.

  Therefore, in the image forming apparatus 200, the initial developing chamber is empty, and no developer is carried on the developing sleeve 102 no matter how much the developing screw 104a rotates. Until the sealing sheet 51a is peeled off, in the stirring chamber 101b, the developer is stirred and circulated in the longitudinal section by the stirring screw 104b and the reverse conveying screw 104c to be charged. After the opening 107a is opened, a sufficiently charged developer flows into the developing chamber 101a, and the developer surface is raised, and then is carried on the developing sleeve 102. Therefore, the toner charge amount Q / M can be appropriately maintained from the beginning at the initial startup, and even in the cleaner-less configuration, the occurrence of image defects due to toner scattering at the initial startup or contamination of the charging roller or the like can be prevented. Can be prevented.

<Example 3>
The present invention is effective only with a detachable developing device. However, if the developing device 100 described above is used as a process cartridge, it is possible to realize a process cartridge that is maintenance free of toner scattering and has high usability.

1 1a, 1b, 1c, 1d Photosensitive drums 2a, 2b, 2c, 2d Charging devices 3a, 3b, 3c, 3d Exposure device 50 Control unit, 51a, 51b Sealing sheet 52 Power supply, 53 Drive motor, 54 Coupling 56 Operation panel 100 100a, 100b, 100c, 100d Developing device 101 Developing container, 101a Developing chamber, 101b Agitation chamber 102 Developing sleeve, 102m Magnet, 103 Partition wall 104a Developing screw, 104b Agitation screw 104c Reverse conveying screw, 107a, 107b Opening 200 Image Forming device, 600 take-up shaft

Claims (3)

An image carrier for carrying an image;
A developer carrying member that carries a developer including toner and a carrier, and that develops a latent image formed on the image carrier;
A developing chamber for supplying a developer to the developer carrying member at a position facing the developer carrying member;
A stirring chamber connected at both ends of the developing chamber to form a circulation path for circulating the developer;
A first conveying member that is rotatably provided in the developing chamber and conveys the developer;
A second transport member that is rotatably provided in the stirring chamber and transports the developer in a direction opposite to the transport direction of the first transport member;
A first opening for delivering the developer from the stirring chamber to the developing chamber;
A second opening for transferring the developer from the developing chamber to the stirring chamber;
A partition partitioning the developing chamber and the stirring chamber;
A seal part that seals the first opening and the second opening so that the developer is sealed in the stirring chamber;
An unsealing mechanism provided to be drivable and unsealing the seal portion;
A control unit that controls the second conveying member to be driven during the opening operation of the seal unit,
2. The image forming apparatus according to claim 1, wherein a timing at which the opening of the first opening is started is earlier than a timing at which the opening of the second opening is started.   The image forming apparatus according to claim 1, wherein the control unit controls the driving start timing of the second conveying member to be earlier than the opening start timing of the second opening.   The unsealing mechanism includes a rotation shaft that is rotatable along a rotation axis direction of the developer carrier, and the seal portion is wound around the rotation shaft by driving the rotation shaft. The image forming apparatus according to claim 1.

Images