JP2017219708A - Conveying device, imaging device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conveying device, a developing device, and an image forming apparatus that can stabilize the amount of developer inside a developer tank to prevent scattering of toner.SOLUTION: A developing device comprises a developer housing, and the developer housing is provided with a first conveyance path and a second conveyance path. The first conveyance path and second conveyance path are communicated with each other by a slit 142a and a slit 142b provided in a boundary wall 142, and the developer is circulated in the first conveyance path and second conveyance path. The boundary wall 142 includes a second wall part 1422 partitioning the developer housing on the downstream side in a conveyance direction of the first conveyance path with respect to the slit 142b. The second wall part 1422 has a through hole 1428 formed therein for, when the height of the surface of the developer in the first conveyance path becomes higher than a predetermined height, discharging the developer to the second conveyance path.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a transport device, a developing device, and an image forming apparatus, and more particularly, to a transport device, a developing device, and an image forming apparatus that transport a developer in a developing tank, for example.

  An example of a conventional developing device is disclosed in Patent Document 1. The developing device of Patent Document 1 is a developing device adopting a trickle developing method among electrophotographic methods using a developer composed of two components of a toner and a carrier. The trickle development method is simply described. A new carrier is mixed with the toner in the toner cartridge at a constant ratio, and the new carrier is supplied into the developing device at the same time as the toner is supplied. This technique is to sequentially replace a deteriorated carrier in the developing device with a new carrier by discharging the developed developer from the developing device.

  In the developing device disclosed in Patent Document 1, the inside of the developing housing provided in the developing device is partitioned into a pair of linear transport paths by a partition portion, and communication ports are opened at both longitudinal end portions of the partition portion. As a result, a circulation conveyance path through which the developer can be circulated is formed.

Japanese Patent Laying-Open No. 2005-221852

  In the above background art, a discharge unit (developer discharge port) is provided on the downstream side of the developer conveyance direction in one conveyance path, and the conveyed developer flows into the discharge unit more than necessary due to its momentum. End up. In order to prevent such excessive discharge of the developer, a developer discharge port may be provided on the upstream side in the developer transport direction.

  However, even in this case, the developer transported on the opposite transport path may flow directly into the discharge port via the communication port, so the transport path provided with the developer discharge port It is desirable to provide a boundary wall for narrowing the communication port communicating with the upstream end in the developer conveyance direction.

  However, if a boundary wall for narrowing the communication port is provided, the developer discharge port is provided when the toner density fluctuates or the developer fluidity deteriorates due to a high developer temperature. The developer stays excessively at the downstream end in the transport direction of the developer on the transport path opposite to the path. If the developer stays excessively in a part of the transport path, packing occurs in the developing tank, and the mixing performance of the toner and the developer decreases. For this reason, there is a possibility that the developer is not properly discharged, the developer in the developing tank increases, and the toner scatters.

  Therefore, a main object of the present invention is to provide a transport device, a developing device, and an image forming apparatus capable of stabilizing the amount of developer in the developing tank and preventing toner scattering.

  The first invention includes a first conveyance path, a first conveyance member, a second conveyance path, a second conveyance member, a first boundary wall, a first communication path, a second communication path, a third conveyance path, and a third conveyance member. And a second boundary wall, and a conveyance device that circulates the developer between the first conveyance path and the second conveyance path via the first communication path and the second communication path. The first transport path and the second transport path are formed in the developing tank and are arranged in parallel to each other. The first conveying member conveys the developer in the first conveying direction while stirring the developer in the first conveying path. The second conveying member conveys the developer in the second conveying direction opposite to the first conveying member while stirring the developer in the second conveying path, and the developer carrying member such as a developing roller. To supply. The first boundary wall is provided between the first conveyance path and the second conveyance path. The first communication path and the second communication path are slits formed in the first boundary wall. The first communication path connects the first transport path and the second transport path on the downstream side in the first transport direction from the first boundary wall. The second communication path connects the first conveyance path and the second conveyance path upstream of the first boundary wall in the first conveyance direction. The third transport path is connected to the second transport path on the upstream side in the second transport direction. The third conveying member conveys the developer overflowing from the second conveying path to the third conveying path to the discharge port. The second boundary wall is provided between the first conveyance path and the second conveyance path on the downstream side of the first communication path in the first conveyance direction. At the end of the second boundary wall on the downstream side in the first conveyance direction, the first conveyance path and the second conveyance are positioned above the bottom of the first communication path and at a predetermined height from the bottom of the developing tank. A third communication path communicating with the path is formed.

  According to the first invention, since the second boundary wall is provided downstream of the first communication path in the developer conveyance direction by the first conveyance member, the developer is transferred from the first conveyance path to the second conveyance path. It is possible to prevent the developer from being excessively moved and discharged excessively. In addition, at the end of the second boundary wall on the downstream side in the first conveyance direction, the first conveyance path and the first conveyance path are located above the bottom of the first communication path and at a predetermined height from the bottom of the developing tank. Since the third communication path that connects the two transport paths is formed, the developer is moved from the first transport path to the second transport path when the liquid level of the developer exceeds a predetermined height. The For this reason, it is possible to prevent the developer from remaining excessively on the downstream side of the first transport path. As a result, the amount of developer in the developing tank can be stabilized and toner scattering can be prevented.

  The second invention is a transport device subordinate to the first invention, wherein the first transport member has a screw for transporting the developer while stirring, and the third communication path is the first communication path. It is formed above the rotation axis of the screw of the conveying member.

  According to the second invention, it is possible to prevent the developer from being excessively discharged to the second conveyance path by the momentum conveyed through the first communication path.

  3rd invention is a conveying apparatus which depends on 1st or 2nd invention, Comprising: A 3rd communicating path contains the notch or hole provided in the 2nd boundary wall.

  According to the third aspect, the same effect as the first aspect can be obtained, the amount of developer in the developing tank can be stabilized, and toner scattering can be prevented.

  A fourth invention is a transfer device according to any one of the first to third inventions, and the third communication path expands from the first transfer path side toward the second transfer path side.

  According to the fourth aspect of the invention, the third communication path expands in the direction in which the developer is pushed out, so that it is difficult for the developer to clog the third communication path. Therefore, it is possible to prevent as much as possible the loss of the effect obtained by providing the third communication path.

  A fifth invention is a transfer device according to any one of the first to fourth inventions, is arranged to pass through the third communication path, and contacts at least one of the first transfer member and the second transfer member. A loosening member is further provided.

  According to the fifth invention, since the loosening member for loosening the developer adhered or clogged in the third communication path is provided, it is possible to make the third communication path difficult to be clogged with the developer, and even if the developer is clogged. Can be removed. Therefore, it is possible to prevent as much as possible the loss of the effect obtained by providing the third communication path.

  A sixth invention is a developing device including the transport device and the developer carrying member according to any one of the first to fifth inventions.

  A seventh aspect of the invention is an image forming apparatus including the transport device according to any one of the first to fifth aspects.

  According to the sixth and seventh inventions, the same effects as those of the first invention can be obtained, the amount of developer in the developing tank can be stabilized, and toner scattering can be prevented.

  According to the present invention, the amount of developer in the developing tank can be stabilized and toner scattering can be prevented.

FIG. 1 is an illustrative view showing one example of a schematic overall configuration of the image forming apparatus of the first embodiment. FIG. 2 is a perspective view of the specific external configuration of the developing device shown in FIG. 1 as viewed obliquely from above. FIG. 3 is a view of the developing device shown in FIG. 2 as viewed from the left side. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is an illustrative view for explaining the flow of the developer in the developing device shown in FIG. FIG. 6 is a front view of the boundary wall of the first embodiment. FIG. 7 is a view of the boundary wall of the first embodiment as viewed from the left side. FIG. 8 is a perspective view of the developing device shown in FIG. 2 as viewed obliquely from above. FIG. 9 is an enlarged view of a part of the IX-IX cross-sectional view of FIG. FIG. 10 is a perspective view of the developing device in the second embodiment as viewed obliquely from above. FIG. 11 is a perspective view showing an example of the developing device of the third embodiment. FIG. 12 is a perspective view showing another example of the developing device of the third embodiment.

[First embodiment]
FIG. 1 is a schematic configuration diagram of an entire image forming apparatus 10 according to an embodiment of the present invention as viewed from the back side.

  Referring to FIG. 1, an image forming apparatus 10 according to the first embodiment is a color printer, and forms a multicolor or single color image on a sheet (recording medium) by an electrophotographic method. However, the image forming apparatus 10 may be a monochrome printer. The image forming apparatus 10 need not be limited to a printer, and may be a copier, a facsimile machine, or a multifunction machine having these functions.

  First, the basic configuration of the image forming apparatus 10 will be schematically described. As shown in FIG. 1, the image forming apparatus 10 includes a photosensitive drum 12, a developing device 14, a charger 16, a cleaning unit 18, an exposure device 20, an intermediate transfer belt unit 22, a secondary transfer roller 24, a fixing unit 26, and the like. And forming an image on a sheet conveyed from the sheet feed tray 28, and discharging the image-formed sheet to the discharge tray 30. As image data for forming an image on paper, image data input from an external computer is used. However, when the image forming apparatus 10 has a scanner function, not only image data input from the outside but also image data read from a document by a scanner can be used.

  Each of the components described above is accommodated in the housing 10a of the image forming apparatus 10. In addition, a control unit including a CPU and a memory (not shown) is provided in the housing 10a of the image forming apparatus 10. The control unit transmits a control signal to each part of the image forming apparatus 10 to cause the image forming apparatus 10 to execute various operations.

  Here, the image data handled in the image forming apparatus 10 corresponds to four color images of black (BK), magenta (M), cyan (C), and yellow (Y). For this reason, each of the photosensitive drum 12, the developing device 14, the charger 16 and the cleaning unit 18 is provided so as to form four types of latent images corresponding to the respective colors, thereby forming four image stations. Composed. The four image stations are arranged in a line along the running direction (circumferential movement direction) of the surface of the intermediate transfer belt 36, and from the downstream side in the running direction of the intermediate transfer belt 36, that is, to the secondary transfer roller 24. From the near side, black, magenta, cyan and yellow are arranged in this order. However, the arrangement order of the colors can be changed as appropriate.

  In each image station, the charger 16, the developing device 14, and the cleaning unit 18 are arranged in this order around the rotation direction of the photosensitive drum 12 (counterclockwise in FIG. 1). The developing device 14 is arranged so that the rotation shaft of the developing roller 156 (see FIG. 2) is aligned in parallel with the rotation shaft of the photosensitive drum 12. Further, the charger 16 is arranged so that its own rotation axis is aligned in parallel with the rotation axis of the photosensitive drum 12. Further, the cleaning unit 18 is disposed so that the longitudinal direction of the cleaning blade (not shown) coincides with the rotational axis direction of the photosensitive drum 12. However, in FIG. 1, the rotation axis direction of the photosensitive drum 12 is a depth direction (front-rear direction) when the image forming apparatus 10 is viewed from the back.

  The photosensitive drum 12 is an image carrier in which a photosensitive layer (photoconductive layer) is formed on the surface of a conductive substrate, and is supported so as to be rotatable around an axis by a driving unit (not shown). The substrate can take various shapes such as a cylindrical shape, a columnar shape, and a thin film sheet shape. The photosensitive layer is formed of a material that exhibits conductivity when irradiated with light. The photosensitive drum 12 of the first embodiment includes a cylindrical base made of aluminum and amorphous silicon (a-Si), selenium (Se), or organic light formed on the outer peripheral surface of the base. Those including a photosensitive layer made of a semiconductor (OPC) are used.

  The developing device 14 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 12 with toner (forms a toner image). A toner cartridge 32 is connected to the developing device 14 via a toner supply pipe 34. The toner cartridge 32 is a container for storing unused toner and carrier, and is provided above the developing device 14 to supply (supplement) toner to the developing device 14 and replenish the carrier. The toner supply pipe 34 connects (connects) the toner cartridge 32 and a toner supply port 144a (see FIG. 2) formed in the developing device 14. Details of the developing device 14 will be described later.

  The charger 16 is a device that charges the surface of the photosensitive drum 12 to a predetermined polarity and potential. As the charger 16, a brush-type charging device, a roller-type charging device, a corona discharge device, an ion generator, or the like can be used.

  The cleaning unit 18 removes and collects the toner remaining on the surface of the photosensitive drum 12 after the toner image is transferred from the photosensitive drum 12 to the intermediate transfer belt 36, and cleans the surface of the photosensitive drum 12. . Therefore, for example, the cleaning unit 18 includes a cleaning blade that is a plate-like member for scraping off the toner, and a recovery container for recovering the scraped toner.

  The exposure device 20 is provided below the developing device 14. The exposure device 20 is configured as a laser scanning unit (LSU) including a laser emitting unit, a reflection mirror, and the like, and exposes the charged surface of the photosensitive drum 12 to generate an electrostatic latent image corresponding to image data. It is formed on the surface of the photosensitive drum 12.

  The intermediate transfer belt unit 22 includes an intermediate transfer belt 36, a driving roller 38, a driven roller 40, four intermediate transfer rollers (primary transfer rollers) 42, and the like, and is disposed above the photosensitive drum 12.

  The intermediate transfer belt 36 is an endless belt having flexibility, and is formed of a synthetic resin, rubber, or the like appropriately mixed with a conductive material such as carbon black. The intermediate transfer belt 36 is stretched by a plurality of rollers such as a driving roller 38 and a driven roller 40, and the surface (outer peripheral surface) thereof is disposed so as to contact the surface of the photosensitive drum 12. The intermediate transfer belt 36 rotates (circulates) in a predetermined direction (clockwise in FIG. 1) as the driving roller 38 rotates.

  The drive roller 38 is provided so as to be rotatable around its axis by a drive unit (not shown). The driven roller 40 rotates as the intermediate transfer belt 36 rotates and applies a constant tension to the intermediate transfer belt 36 to prevent the intermediate transfer belt 36 from slackening.

  The intermediate transfer roller 42 is disposed at a position facing each of the photosensitive drums 12 with the intermediate transfer belt 36 interposed therebetween. The intermediate transfer roller 42 is in pressure contact with the inner peripheral surface of the intermediate transfer belt 36 and rotates as the intermediate transfer belt 36 rotates. To do. Although not shown, the intermediate transfer roller 42 is connected to a transfer power source for applying a transfer bias. At the time of image formation, a voltage having a polarity opposite to the charging polarity of the toner constituting the toner image formed on the surface of the photosensitive drum 12 is applied to the intermediate transfer roller 42. As a result, a transfer electric field is formed between the photosensitive drum 12 and the intermediate transfer belt 36, and the toner image formed on the photosensitive drum 12 is transferred to the outer peripheral surface of the intermediate transfer belt 36 by the action of the transfer electric field. The For example, when forming a color image, the toner images of the respective colors formed on the respective photosensitive drums 12 are sequentially transferred onto the intermediate transfer belt 36 (primary transfer), and are transferred onto the outer peripheral surface of the intermediate transfer belt 36. A multicolor toner image is formed.

  Further, the secondary transfer roller 24 is disposed at a position facing the driving roller 38 with the intermediate transfer belt 36 interposed therebetween. A transfer power supply (not shown) is connected to the secondary transfer roller 24, and a voltage (secondary transfer voltage) is applied to the secondary transfer roller 24 by the transfer power supply during image formation. The intermediate transfer belt is moved while the sheet passes through the transfer nip region between the intermediate transfer belt 36 and the secondary transfer roller 24 by the action of the transfer electric field formed by the secondary transfer roller 24 to which a voltage is applied. The toner image formed on the outer peripheral surface 36 is transferred (secondary transfer) to the paper. Thereafter, the toner remaining on the surface of the intermediate transfer belt 36 is removed and collected by a transfer belt cleaning unit (not shown).

  The fixing unit 26 includes a heat roller and a pressure roller, and is disposed above the secondary transfer roller 24. The heat roller is set to have a predetermined fixing temperature, and when the paper passes through the fixing nip area between the heat roller and the pressure roller, the toner image transferred to the paper is melted, mixed, and mixed. The toner image is heat-fixed on the sheet by pressure contact.

  Further, a paper conveyance path for sending the paper placed on the paper feed tray 28 to the discharge tray 30 through the secondary transfer roller 24 and the fixing unit 26 is formed in the housing 10 a of the image forming apparatus 10. Is done. In the paper conveyance path, paper conveyance means such as conveyance rollers 44, 46, and 48 and a registration roller 50 are appropriately disposed.

  At the time of image formation, the sheets placed on the sheet feeding tray 28 are guided to the sheet conveying path one by one by a pickup roller (not shown) and conveyed to the registration roller 50 by the conveying roller 44. Then, the registration roller 50 conveys the sheet to the secondary transfer roller 24 at a timing when the leading end of the sheet and the leading end of the toner image on the intermediate transfer belt 36 are aligned, and the toner image is transferred onto the sheet. Thereafter, by passing through the fixing unit 26, unfixed toner on the sheet is melted and fixed by heat, and the sheet is discharged onto the discharge tray 30 through the conveyance rollers 46 and 48.

  In such an image forming apparatus 10, as will be described later, a developer (two-component developer) composed of black, cyan, magenta, or yellow toner and a carrier is stored in a developing housing 140 provided in the developing device 14. However, the carrier is a magnetic material such as iron powder or ferrite. The same applies hereinafter.

  For example, the developing device 14 is a trickle developing type developing device. The trickle developing method is simply described. A new carrier is mixed with the toner in the toner cartridge 32 at a fixed ratio, and a new carrier is supplied (supplemented) into the developing device 14 at the same time as the toner is supplied (supplemented). In addition, it refers to a technique for sequentially replacing the deteriorated carrier in the developing device 14 with a new carrier by discharging the excess developer from the developing device 14.

  In this specification, “developer is discharged” or the like simply means that the deteriorated carrier or the developer in which the deteriorated carrier and the toner are mixed is discharged. Further, although the deteriorated carrier is not necessarily replaced with the unused carrier, the developing device 14 is basically configured such that the deteriorated carrier is replaced with the unused carrier.

  In the developing device 14, when toner is consumed by forming an image on a sheet, toner corresponding to the amount of consumption is replenished. For this reason, for example, a toner density detection sensor (not shown) is provided at the bottom of the development housing 140, and the toner density (T / D: T / D :) in the development housing 140 is determined based on the detection result of the toner density detection sensor. T is toner and D is developer). Then, toner supply is controlled in accordance with the detected toner density.

  As the toner concentration detection sensor, a transmissive optical sensor, a reflective optical sensor, a magnetic permeability sensor, or the like is used. Among these, it is preferable to use a magnetic permeability sensor. The magnetic permeability varies depending on the ratio of the magnetic material in the developer. That is, when the mixing ratio of the magnetic material and the non-magnetic material in the developer, that is, the relative concentration of the magnetic material changes, the output of the magnetic permeability sensor changes. Therefore, by detecting the magnetic permeability of the developer, the concentration of the carrier that is a magnetic material in the developer is measured. Or the density | concentration of the toner which is a nonmagnetic material in a developing agent is measured.

  FIG. 2 is a perspective view of a specific external configuration of the developing device 14 shown in FIG. 1 as viewed obliquely from above. FIG. 3 is a side view of the developing device 14 shown in FIG. 2 as viewed from the left side. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG.

  However, the right side of the developing device 14 shown in FIG. 2 is disposed on the front (front) side of the image forming apparatus 10 shown in FIG. 1, and the left side of the developing device 14 shown in FIG. 2 is the image forming apparatus 10 shown in FIG. It is arranged on the back side.

  As shown in FIG. 2, the developing device 14 includes a developing housing 140, a boundary wall 142, a housing cover 144, a first conveying member 150, a second conveying member 152, a third conveying member 154, and a developing roller (magnet roller) 156. Including.

  However, the housing cover 144 is a member that covers the first conveying member 150, the second conveying member 152, and the developing roller 156 above the developing housing 140 in the vertical direction. In FIG. It is omitted.

  Further, the developing device 14 includes a doctor blade and the above-described toner concentration detection sensor, but in FIG. 2, the doctor blade and the toner concentration detection sensor are omitted together with a part of the housing cover 144.

  As described above, the developing housing 140 stores a developer (two-component developer) in which toner and a carrier are mixed. In addition, the first transport member 150, the second transport member 152, the developing roller 156, and the third transport member 154 are provided inside the developing housing 140.

  However, illustration of each of the toner and the carrier, and the developer mixed therewith is omitted.

  Further, a device obtained by removing the developing roller 156 and the doctor blade from the developing device 14 may be referred to as a conveying device that conveys the developer.

  Further, a developing roller 156 is disposed in the developing housing 140 above the second conveying member 152 in the vertical direction. The developing roller 156 functions as a developer carrying member and is disposed at a position facing the photosensitive drum 12 (see FIG. 1). The developing roller 156 carries the developer in the developing housing 140 on the surface and supplies toner contained in the carried developer to the surface of the photosensitive drum 12. Therefore, as described above, the electrostatic latent image formed on the surface of the photosensitive drum 12 is developed (visualized).

  Although not shown, the doctor blade is fixed to the developing housing 140 with a predetermined gap with respect to the surface of the developing roller 156. However, the doctor blade is a plate-like member extending in the axial direction of the developing roller 156. By this doctor blade, the amount of developer carried on the developing roller 156 is regulated to a predetermined amount.

  As shown in FIG. 2, the developing device 14 has a toner supply port for supplying toner and a carrier from the toner cartridge 32 at one end of the housing cover 144 and above the first conveying member 150. 144a is formed. As described above, the toner supply pipe 34 extending from the toner cartridge 32 is connected to the toner supply port 144a.

  However, one end of the housing cover 144 is an upstream end in the transport direction in which the developer is transported by the first transport member 150.

  Further, in the developing housing 140, the first conveying member 150 and the second conveying member 152 are rotatable, and are arranged so that the respective rotation axes are parallel to each other, as can be seen from FIGS. . Further, the third transport member 154 is integrally formed coaxially with the second transport member 152.

  As shown in FIGS. 2 and 4, the first transport member 150 is an auger screw in which blades (screw blades 150b) for transporting the developer while stirring the developer are formed on a rotating shaft (screw shaft 150a). The first conveying member 150 conveys the developer from the back side of the image forming apparatus 10 toward the front side of the image forming apparatus 10 while stirring the developer. However, in the first conveying member 150, the screw blade 150b is reversely wound at the downstream end in the developer conveying direction (the right end in FIGS. 2 and 4).

  The second conveying member 152 is also an auger screw formed with screw blades 152b for conveying the developer while stirring the developer to the screw shaft 152a. The second conveying member 152 conveys the developer from the front side of the image forming apparatus 10 toward the back side of the image forming apparatus 10 while stirring the developer. That is, the second transport member 152 transports the developer in the opposite direction to the first transport member 150. However, in the second conveying member 152, the pitch of the screw blades 152b is shortened at the upstream end in the developer conveying direction (the right end in FIGS. 2 and 4). Further, in the second conveying member 152, the screw blade 152b is reversely wound at the downstream end portion (left end portion in FIGS. 2 and 4) in the developer conveying direction, and the pitch of the screw blade 152b is shortened. .

  Further, the third transport member 154 is provided integrally with the second transport member 152. The third transport member 154 is coaxial with the second transport member 152 and is provided in the third transport path 140c. The second conveyance path 140b and the third conveyance path 140c are formed in a cylindrical shape or a substantially cylindrical shape (the same applies to the first conveyance path 140a). The third conveyance path 140c is coaxial with the second conveyance path 140b, and is formed so that the diameter of the cylinder is smaller than that of the second conveyance path 140b. Accordingly, a step is formed in the connecting portion (connecting portion) 140d between the second transport path 140b and the third transport path 140c. Since the second conveyance path 140b and the third conveyance path 140c are formed in this way, for example, when the developing device 14 is inclined, a large amount of developer overflows from the second conveyance path 140b to the third conveyance path 140c. It is prevented. Therefore, the developer is not discharged more than necessary from the third transport path 140c.

  Further, the third transport member 154 has a rotating shaft (screw shaft 152a) coaxial with the second transport member 152, and has a screw blade 154b that is reversely wound from the screw blade 152b of the second transport member 152. The third transport member 154 transports the developer from the back side of the image forming apparatus 10 toward the front side of the image forming apparatus 10. However, the outer diameter of the screw blade 154b is made smaller than that of the screw blade 152b.

  Further, in the developing housing 140, the developing housing 140 is partitioned between the first conveying member 150 and the second conveying member 152 in the direction of the rotation axis of the first conveying member 150 and the second conveying member 152. A partition or boundary wall 142 is provided. Accordingly, a first transport path 140 a in which the developer is transported by the first transport member 150 is formed in the developing housing 140, and a second transport path 140 b in which the developer is transported by the second transport member 152 is formed. It is formed. The first transport path 140a and the second transport path 140b are arranged in parallel in the horizontal direction or substantially in the horizontal direction. When the developing device 14 is mounted on the image forming apparatus 10, the first transport path 140a and the second transport path 140b are respectively in the front-rear direction of the image forming apparatus 10. Extend. Further, a third transport path 140 c for discharging the developer by the third transport member 154 is formed in the developing housing 140. The third transport path 140c is connected (coupled) to the second transport path 140b.

  In addition, slits 142 a and 142 b are provided at both ends of the boundary wall 142. The first conveyance path 140a and the second conveyance path 140b are communicated with each other by the slit (second communication portion) 142a and the slit (first communication portion) 142b. The details of the boundary wall 142 will be described later in detail.

  FIG. 5 is an illustrative view showing the developer conveyance direction in the cross-sectional view of FIG. 4. In the first embodiment, the screw shaft 150a of the first transport member 150 and the screw shaft 152a (154a) of the second transport member 152 are rotated in opposite directions. Therefore, as described above, the developer is transported toward the first transport path 140a toward the back side of the image forming apparatus 10 (from the slit 142a side toward the slit 142b side), and the second transport path 140b is transported along the image forming apparatus. The developer is conveyed toward the front surface side of 10 (from the slit 142b side toward the slit 142a side).

  The developer transported along the first transport path 140a is transported in the first transport path 140a by the first transport member 150 (hereinafter referred to as “the transport direction of the first transport path 140a”). The developer collides with the developer staying at the downstream end or the wall (inner wall) of the development housing 140 at the downstream end. Accordingly, the developer is dammed (stayed) at the downstream end of the first conveyance path 140a in the conveyance direction (first conveyance direction), and pushed (moved) from the slit 142b to the second conveyance path 140b. .

  Further, the developer transported through the second transport path 140b is transported in the developer transported along the second transport path 140b by the second transport member 152 (hereinafter referred to as “transport direction of the second transport path 140b”). The developer stays at the downstream end and collides with the wall (inner wall) of the development housing 140. Therefore, the developer is dammed (stayed) at the downstream end of the transport direction (second transport direction) of the second transport path 140b and pushed (moved) from the slit 142a to the first transport path 140a. .

  Thus, in the developing housing 140, the first transport path 140a and the second transport path 140b are communicated with each other by the slit 142a and the slit 142b, so that the first transport member 150 and the second transport member 152 are rotated. The developer is circulated. In FIG. 5, as indicated by arrows A, B, C, and D, the developer is circulated in the development housing 140.

  Further, as described above, the third conveyance path 140c is coaxial with the second conveyance path 140b, and the diameter (size) of the cylinder forming the conveyance path is smaller than that of the second conveyance path 140b. For this reason, in the vertical direction, the bottom of the third transport path 140c is positioned above the bottom of the second transport path 140b. That is, a step is provided in the connection portion 140d between the second conveyance path 140b and the third conveyance path 140c.

  Therefore, in the second transport path 140b, when the second transport path 140b overflows from the second transport path 140b to the third transport path 140c beyond the step between the upstream end in the transport direction of the second transport path 140b and the connection portion 140d, The developer overflowing the third transport path 140c is transported by the third transport member 154 in the direction opposite to the transport direction of the second transport path 140b. Although not shown, a toner discharge port is provided on the downstream side in the transport direction of the developer transported along the third transport path 140c by the third transport member 154 in the third transport path 140c. The developer overflowing from the second conveyance path 140b to the third conveyance path 140c is discharged from the toner discharge port. For example, when the developer level in the second transport path 140b exceeds the level difference of the connecting portion 140d, the developer exceeding the level difference is transported to the toner discharge port in the direction indicated by arrow E in FIG.

  As described above, the developing device 14 according to the first embodiment is configured such that the developer overflowing to the third transport path 140c side is discharged at the upstream end of the second transport path 140b in the transport direction. . More specifically, the sizes of the second conveyance path 140b and the third conveyance path 140c are determined so that the amount of developer stored in the development housing 140 and the toner concentration are kept constant, and the amount of developer is determined. Emissions are adjusted.

  In such a developing device 14, when the developer usage period becomes long, the toner density in the developing housing 140 fluctuates or the developer itself deteriorates, and the fluidity of the developer deteriorates.

  Further, in the developing device 14 of the image forming apparatus 10 (high speed machine) that performs image formation at high speed (for example, the image forming speed is 50 to 75 sheets / min), the developer is circulated at high speed in the developing housing 140. . For this reason, the developer becomes high temperature due to friction between the developer and the developing housing 140, the first transport member 150, and the second transport member 152, and the viscosity of the developer increases. When the viscosity of the developer increases, the fluidity of the developer deteriorates.

  Further, when the use environment (installation location) of the image forming apparatus 10 is high temperature and humidity, similarly, the developer becomes high temperature, the viscosity of the developer becomes high, and the fluidity deteriorates.

  As described above, when the fluidity of the developer deteriorates, it becomes difficult for the developer to circulate in the developing housing 140. For this reason, the developer stays excessively at the downstream end in the transport direction of the first transport path 140a and the downstream end in the transport direction of the second transport path 140b. In this case, packing may occur in the developing housing 140, or the mixing performance of the toner and the developer may deteriorate. For this reason, there is a possibility that the developer in the developing housing 140 is increased and toner scattering occurs.

  In order to solve such a problem, in the developing device 14 of the first embodiment, the amount of the developer in the developing housing 140 increases more than necessary even when the flowability of the developer deteriorates. Is to prevent.

  Briefly, in the developing device 14 of the first embodiment, when the amount of developer (liquid level) in the developing housing 140 exceeds a predetermined height, the downstream end in the transport direction of the first transport path 140a. , A communication path (short-circuit path) 1430 for moving the developer from the first transport path 140a to the second transport path 140b is provided.

  However, the predetermined height is a height from the bottom (bottom surface) of the developing housing 140 and is determined by an experiment or the like.

  FIG. 6 is an illustrative view of the boundary wall 142 in the developing housing 140 as viewed from the front. FIG. 7 is an illustrative view when the boundary wall 142 in the developing housing 140 is viewed from the left side of the developing device 14. FIG. 8 is a perspective view of the developing device 14 of the first embodiment when viewed obliquely from above. FIG. 9 is an enlarged view of a part of the IX-IX cross-sectional view in FIG.

  In FIG. 8, the upper left side corresponds to the right side of the developing device 14 shown in FIG. 8 (similarly in FIGS. 10 to 12), in order to show the structure of the boundary wall 142 in an easy-to-understand manner, the curved shape of the boundary wall 142 when viewed from the front is omitted, and the boundary wall 142 is formed in a flat plate shape It is shown.

  As shown in FIG. 6, the boundary wall 142 of the first embodiment is composed of four parts in the longitudinal direction. Specifically, the boundary wall 142 includes a first wall portion (corresponding to the first boundary wall) 1420, a second wall portion (corresponding to the second boundary wall) 1422, a third wall portion 1424, and a fourth wall portion 1426. Composed.

  As can be clearly seen from FIG. 9, the first wall portion 1420 and the second wall portion 1422 extend from the bottom surface of the developing housing 140 to a position where it contacts the housing cover 144 in the vertical (vertical) direction. Accordingly, the first wall portion 1420 and the second wall portion 1422 divide the first conveyance path 140a and the second conveyance path 140b except for the portion of the through hole 1428 formed in the second wall portion 1422. The through hole 1428 is formed in a rectangular shape in a part of the right end portion of the second wall portion 1422. As can be seen from FIG. 6, the through-hole 1428 is formed above the upper end of the fourth wall portion 1426.

  In the first embodiment, the shape of the through hole 1428 is a horizontally long rectangle when viewed from the front. However, the shape of the through hole 1428 is not necessarily limited to a rectangle. For example, it may be circular or semi-circular when viewed from the front.

  Further, as can be seen from FIGS. 6 and 9, the second wall portion 1422 is located at the right end portion of the boundary wall 142. That is, the second wall portion 1422 is provided at the downstream end (downstream side of the slit 142b) in the transport direction of the first transport path 140a. Therefore, as can be seen from FIG. 8, the developer conveyed in the conveyance direction of the first conveyance path 140a is from the downstream end side in the conveyance direction of the first conveyance path 140a to the upstream end in the conveyance direction of the second conveyance path 140b. Hard to move to the side. For this reason, the developer is retained at the downstream end in the transport direction of the first transport path 140a. Therefore, the developer is prevented from flowing more than necessary into the upstream end in the transport direction of the second transport path 140b. For this reason, the developer is not discharged more than necessary from the third transport path 140c.

  As shown in FIGS. 6, 8, and 9, the third wall portion 1424 and the fourth wall portion 1426 are set to be lower in height in the vertical direction than the first wall portion 1420 and the second wall portion 1422. . The third wall portion 1424 is disposed upstream of the first wall portion 1420 in the transport direction of the first transport path 140a, and the fourth wall portion 1426 is transported in the first transport path 140a than the first wall portion 1420. Arranged downstream in the direction. As described above, the slit 142a is formed above the third wall portion 1424, and the slit 142b is formed above the fourth wall portion 1426. Accordingly, the first transport path 140a and the second transport path 140b are communicated with each other at the position where the third wall portion 1424 and the fourth wall portion 1426 are disposed.

  However, as described above, the first transport path 140a and the second transport path 140b are formed in a cylindrical shape or a substantially cylindrical shape. Therefore, as shown in FIG. 7, the surface of the boundary wall 142 on the first conveyance path 140 a side is curved along the screw blade 150 b of the first conveyance member 150. Similarly, the surface of the boundary wall 142 on the second conveyance path 140 b side is curved along the screw blades 152 b of the second conveyance member 152. As can be seen from FIG. 7, in the first embodiment, the height of the rotational axis of the screw shaft 150 a of the first transport member 150 is different from the height of the rotational axis of the screw shaft 152 a of the second transport member 152. Further, the first transport path 140a and the second transport path 140b have different bottom surface heights. In the first embodiment, the bottom surface of the first transport path 140a is provided to be higher than the bottom surface of the second transport path 140b.

  As shown in FIGS. 8 and 9, the second wall portion 1422 (the right end of the boundary wall 142) abuts on the inner surface of the developing housing 140, so that the developing housing 140 is provided with the boundary wall 142. The through-hole 1428 forms a communication path (third communication path) 1430 that connects the first transport path 140a and the second transport path 140b.

  Further, as shown in FIGS. 7 to 9, the lower end portion of the through hole 1428 (the bottom side (bottom surface) in the vertical direction) is located above the rotation axis of the first transport member 150 and the second transport member 152. Provided. Further, the upstream end of the through hole 1428 in the transport direction of the first transport path 140a (the side on the side not opened in the left-right direction) is from the position where the screw blade 150b of the first transport member 150 is reversely wound. Is also provided on the downstream side in the transport direction of the first transport path 140a.

  This configuration is configured only when the developer liquid level in the developing housing 140 (in the first transport path 140a) is higher than a predetermined height from the bottom (bottom surface) of the developing housing 140. This is because the developer is discharged (moved) to the second transport path 140b through the communication path 1430. Accordingly, even if the through hole 1428 is provided, the developer is not excessively moved from the downstream end portion in the transport direction of the first transport path 140a to the upstream end portion in the transport direction of the second transport path 140b.

  Instead of forming the through hole 1428, it is also conceivable to extend the slit 142b to the inner surface of the developing housing 140. However, in this case, as described above, there is too much developer pushed out from the downstream end in the transport direction of the first transport path 140a to the upstream end in the transport direction of the second transport path 140b, and the first transport path 140a. The developer conveyed is moved from the slit 142b to the connecting portion 140d between the second conveyance path 140b and the third conveyance path 140c with almost no reduction in the momentum to be conveyed. In this case, the developer jumps over the step between the second conveyance path 140b and the connection portion 140d with the momentum as it is and overflows into the third conveyance path 140c. In this case, the developer is excessively discharged. Therefore, in the first embodiment, by adopting the configuration as described above, the developer can be discharged from the first conveyance path 140a to the second conveyance path 140b through the communication path 1430 only when necessary. It is.

  According to the first embodiment, the developer is prevented from being excessively discharged, and when the developer in the developing housing 140 increases and the liquid level of the developer becomes higher than a predetermined height. The developer passes through the communication path 1430 and is discharged from the first transport path 140a to the second transport path 140b. That is, the amount of developer in the developing housing 140 can be stabilized.

  Further, according to the first embodiment, the amount of developer in the developing housing 140 can be stabilized, so that toner scattering can be prevented.

  In the first embodiment, the communication passage 1430 is provided by forming the through hole 1428 in a part of the second wall portion 1422. However, the present invention is not limited to this. For example, the communication path 1430 may be provided by removing (cutting out) the upper right corner of the second wall 1422. Also in such a case, the lower end of the notched portion is formed at a position higher than the bottom of the slit 142b.

  In this way, the size of the communication path 1430 can be made larger than that shown in the first embodiment, so that the developer when the viscosity increases becomes clogged with the communication path 1430. Can be prevented as much as possible.

In the first embodiment, the boundary wall 142 is composed of the first wall portion 1420, the second wall portion 1422, the third wall portion 1424, and the fourth wall portion 1426. Alternatively, all may be independent parts.
[Second Embodiment]
The image forming apparatus 10 of the second embodiment is the same as that of the first embodiment except that the configuration of the developing device 14 is partially changed.

  FIG. 10 is a perspective view of the developing device 14 in the second embodiment when viewed obliquely from above. As shown in FIG. 10, in the second embodiment, the communication path 1430 expands from the first transport path 140a side toward the second transport path 140b side. In the second embodiment, the bottom surface 1426a on the lower side of the through hole 1428 constituting the communication path 1430 is an inclined surface that is inclined downward from the first transport path 140a side toward the second transport path 140b side. That is, the communication path 1430 of the second embodiment is formed such that the developer is easily moved (pushed out) from the first transport path 140a side to the second transport path 140b side and is not easily moved in the reverse direction.

  Of the surface of the through hole 1428 constituting the communication path 1430, the other surface other than the bottom surface 1426a also increases in size as the through hole 1428 (communication path 1430) increases from the first transport path 140a toward the second transport path 140b. You may make it incline so that height may become large. For example, when the shape of the through hole 1428 is circular or semicircular when the boundary wall 142 is viewed from the front, the diameter of the through hole 1428 is changed from the first conveyance path 140a side to the second conveyance path. Increased toward 140b.

According to the second embodiment, the communication path 1430 expands in the direction in which the developer is pushed out, so that the developer can be prevented from clogging the communication path 1430. Therefore, it is possible to prevent the loss of the effect obtained by providing the communication path 1430 as much as possible.
[Third embodiment]
The image forming apparatus 10 of the third embodiment is the same as that of the first embodiment except that the configuration of the developing device 14 is partially changed.

  Briefly, in the third embodiment, the developing device 14 is provided with a loosening member disposed so as to pass through the communication path 1430. Below, the specific example of a loosening member is demonstrated.

  FIG. 11 is a perspective view showing an example of the developing device 14 in the third embodiment. Although omitted in the first embodiment and the second embodiment, as shown in FIG. 11, a flexible sheet 160 is provided at the upstream end in the transport direction of the second transport path 140b. For example, the flexible sheet 160 is bonded to the inner wall at the upstream end in the transport direction of the second transport path 140b. In addition, for example, the flexible sheet 160 is formed of a synthetic resin such as polyethylene terephthalate (PET), polyethylene, polypropylene, polystyrene, polyurethane, and polycarbonate.

  The flexible sheet 160 is formed with a through hole 160a through which the screw shaft 152a of the second conveying member 152 passes. The through-hole 160a has a shape in which semicircles having different diameters are combined in the upper half and the lower half. However, the through hole 160a has a shape in which two semicircles are joined so that the centers of the two semicircles are overlapped and the straight portions are aligned.

  In addition, the diameter of the upper half semicircle is set to be the same as or substantially the same as the diameter of the screw shaft 152 a so that there is no gap with respect to the screw shaft 152 a of the second conveying member 152. That is, the upper half of the connecting portion 140d is covered (closed) by the flexible sheet 160.

  On the other hand, the diameter of the lower half semicircle is set larger than the diameter of the third conveyance path 140c so that a gap is formed with respect to the screw shaft 152a of the second conveyance member 152. Therefore, the lower half part of the connection part 140d is not covered (not blocked) by the flexible sheet 160.

  Since the flexible sheet 160 having the through-hole 160a formed in this manner is provided, only the developer that gets over the step and overflows the third conveyance path 140c is discharged. Therefore, the developer that is about to overflow the third conveyance path 140c from the upper half of the connecting portion 140d without overcoming the step is prevented from being discharged. That is, the developer is prevented from being discharged unintentionally by the developer and the carrier is appropriately replaced.

  Further, the flexible sheet 160 is provided with a protruding piece (unraveling member) 160b that protrudes toward the first conveying path 140a through the communication path 1430. The projecting piece 160 b comes into contact (contact) with the first conveying member 150 at the tip. Therefore, the protruding piece 160b vibrates due to vibration when the first transport member 150 rotates. As a result, the developer adhered or clogged in the communication path 1430 is loosened and removed. Therefore, the protruding piece 160b can also be called a removal member.

  The protruding piece 160b may be integrally formed with the flexible sheet 160 or may be bonded to the flexible sheet 160.

  Further, the protruding piece 160b is provided integrally with the flexible sheet 160, and its tip is in contact with the first conveying member 150, but is not limited thereto. For example, one end may be bonded to the inner wall of the downstream end of the first transport path 140a in the transport direction, and the other end (tip) may be brought into contact with the second transport member 152 through the through hole 1428.

  FIG. 12 is a perspective view showing another example of the developing device 14 of the third embodiment. In the configuration shown in FIG. 12, a wire member (unraveling member) 162 is provided that spans the screw shaft 150 a of the first transport member 150 and the screw shaft 152 a of the second transport member 152.

  The wire member 162 is formed of a single wire and includes a first attachment portion 162a, a second attachment portion 162b, and a connecting portion 162c that connects the first attachment portion 162a and the second attachment portion 162b.

  The first attachment portion 162a and the second attachment portion 162b are formed in a ring shape by winding the ends of the wire in a spiral shape or a spiral shape, respectively. For example, the first mounting portion 162 a is wound around the screw shaft 150 a of the first transport member 150, and the second mounting portion 162 b is wound around the screw shaft 152 a of the second transport member 152. However, the first mounting portion 162a and the second mounting portion 162b are configured such that the ring diameter is larger than the diameters of the screw shafts 150a and 152a so as not to increase the rotational load on the first transport member 150 and the second transport member 152, respectively. The screw shafts 150a and 152a are wound so as to be slightly larger. That is, the first attachment portion 162 a contacts the first transport member 150, and the second attachment portion 162 b contacts the second transport member 152. In addition, the connecting portion 162 c is disposed so as to pass through the communication path 1430.

  Therefore, for example, after a bar-shaped wire is passed through the connecting portion 162c and one end of the wire is wound around one screw shaft 150a (or 152a), the other end of the wire is connected to the other screw shaft 152a (or 150a). ). Then, the wire member 162 is formed, and the wire member 162 is bridged over the screw shaft 150a and the screw shaft 152a.

  However, the inner diameter of the first mounting portion 162a is larger than the outer diameter of the screw shaft 150a of the first conveying member 150, and the inner diameter of the second mounting portion 162b is larger than the screw shaft 152a of the second conveying member 152. Set to That is, there is a gap between the first attachment portion 162a and the screw shaft 150a of the first transport member 150. Further, there is a gap between the second mounting portion 162b and the screw shaft 152a of the second transport member 152. Accordingly, the first mounting portion 162a and the second mounting portion 162b vibrate due to vibrations when the first transport member 150 and the second transport member 152 rotate. Accordingly, the connecting portion 162c also vibrates. That is, the entire wire member 162 vibrates. As a result, the developer adhered or clogged in the communication path 1430 is loosened and removed. Therefore, the wire member 162 can also be called a removal member.

  According to the third embodiment, since the loosening members (160b, 162) for loosening the developer adhering to or clogging the communication path 1430 are provided, it is possible to prevent the developer from clogging in the communication path 1430 and Even if it is clogged, it can be removed. Therefore, it is possible to prevent the loss of the effect obtained by providing the communication path 1430 as much as possible.

  Note that the modification shown in the third embodiment can also be applied to the image forming apparatus 10 of the second embodiment.

  In the above-described embodiment, the first transport path 140a and the second transport path 140b have been described by taking the configuration in which the bottom surface height is different as an example, but it is not necessary to be limited to this. For example, the bottom surface of the first transport path 140a and the bottom surface of the second transport path 140b may be the same height.

  Furthermore, the specific shapes and the like given in the above-described embodiments are examples, and can be appropriately changed according to actual products.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Photoconductor drum 14 ... Developing device 16 ... Charger 18 ... Cleaning unit 20 ... Exposure device 24 ... Secondary transfer roller 32 ... Toner cartridge 36 ... Intermediate transfer belt 42 ... Intermediate transfer roller 140 ... Development housing 140a ... 1st conveyance path 140b ... 2nd conveyance path 140c ... 3rd conveyance path 142 ... Boundary walls 142a, 142b ... Slit (communication path)
144a ... Toner replenishment port 150 ... First conveying member 150a, 152a, 154a ... Screw shaft 150b, 152b, 154b ... Screw blade 152 ... Second conveying member 154 ... Third conveying member 156 ... Developing roller 160 ... Flexible sheet ( Loosening material)
162: Wire member (unraveling member)
1420 ... 1st wall part 1422 ... 2nd wall part 1424 ... 3rd wall part 1426 ... 4th wall part 1428 ... Through-hole 1430 ... Communication path (short circuit)

Claims (7)

A first conveyance path formed in the developing tank;
A first conveying member for conveying the developer in the first conveying direction while stirring the developer in the first conveying path;
A second transport path disposed in parallel with the first transport path in the developing tank;
A second conveying member that conveys the developer to a developer carrying member while conveying the developer in a second conveying direction opposite to the first conveying member while stirring the developer in the second conveying path;
A first boundary wall provided between the first transport path and the second transport path;
A first communication path that connects the first conveyance path and the second conveyance path on the downstream side in the first conveyance direction with respect to the first boundary wall; and the first conveyance path in the first conveyance direction with respect to the first boundary wall. A second communication path that communicates the first conveyance path and the second conveyance path on the upstream side;
A transport device for circulating the developer between the first transport path and the second transport path via the first communication path and the second communication path;
A third conveyance path connected to the second conveyance path on the upstream side in the second conveyance direction;
A third conveying member for conveying the developer overflowing from the second conveying path to the third conveying path to a discharge port; and the first conveying on a downstream side of the first communicating path in the first conveying direction. A second boundary wall provided between a path and the second transport path,
The first transport at the end of the second boundary wall on the downstream side in the first transport direction is above the bottom of the first communication path and has a predetermined height from the bottom of the developing tank. A transfer device that forms a third communication path that communicates the path with the second transfer path. The first conveying member has a screw for conveying the developer while stirring,
The transport apparatus according to claim 1, wherein the third communication path is formed above a rotation axis of the screw of the first transport member.   The transfer device according to claim 1, wherein the third communication path includes a notch or a hole provided in the second boundary wall.   4. The transfer device according to claim 1, wherein the third communication path expands from the first transfer path side toward the second transfer path side. 5.   5. The transport device according to claim 1, further comprising a loosening member disposed so as to pass through the third communication path and in contact with at least one of the first transport member and the second transport member.   A developing device comprising the transport device according to claim 1 and a developer carrier.   An image forming apparatus comprising the transport device according to claim 1.

Images