Image forming device having belt cleaner and drum cleaner both provided in one of drum units

An image forming device includes photosensitive drums, developer cartridges, an endless belt, first collecting units, first conveying units, a second collecting unit, a second conveying unit and communication portions. The photosensitive drums form a drum array including a leading photosensitive drum. Each developer cartridge has a waste developer accommodating chamber. Each first collecting unit collects waste developer on the corresponding photosensitive drum. Each first conveying unit conveys the waste developer toward the waste developer accommodating chamber. The second collecting unit collects waste developer on the endless belt. The second conveying unit conveys the waste developer toward the waste developer accommodating chamber. Each communication portion allows fluid communication between the first conveying unit and the waste developer accommodating chamber. One of the communication portions associated with the leading photosensitive drum also allows fluid communication between the second conveying unit and the waste developer accommodating chamber.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2010-171999 filed Jul. 30, 2010. The entire content of the priority application is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an image forming device such as a color printer.

BACKGROUND

In well-known tandem image forming devices, photosensitive drums for colors of yellow, magenta, cyan and black are juxtaposed, and a toner image of each color is formed on the corresponding photosensitive drum substantially at the same time with one another. In case of a direct transferring system, each toner image formed on each photosensitive drum is sequentially superimposed onto a sheet passing beneath each photosensitive drum due to a circular movement of a conveyor belt. In case of an intermediate transferring system, each toner image is sequentially superimposed on an intermediate transfer belt to form a colored toner image, and the colored toner image is then transferred onto a sheet.

Some of the toner carried on each photosensitive drum may sometimes remain deposited thereon without being transferred onto the sheet or the intermediate transfer belt. To this effect, some tandem image forming devices are provided with a drum cleaner for collecting remaining toner from each photosensitive drum.

A belt cleaner has also been proposed for collecting toner remained on the conveyor belt or the intermediate transfer belt. Such belt cleaner includes a waste toner box in which the toner collected by the belt cleaner (waste toner) is stored.

When both of the drum cleaner and the belt cleaner are provided, the toner collected by the drum cleaner is ejected onto a belt, and the toner on the belt is then collected by the belt cleaner.

SUMMARY

However, conventionally, the photosensitive drums are disposed upward of the belt, while the belt cleaner is disposed below the belt. This configuration inevitably requires a large dimension in height, resulting in a large image forming device. Furthermore, when the waste toner box becomes full, the belt needs to be removed first in order to take out the waste toner box from the image forming device.

In view of the foregoing, it is an object of the present invention to provide a compact image forming device capable of facilitating disposal of waste toner.

In order to achieve the above and other objects, the present invention provides an image forming device including a plurality of photosensitive drums, a plurality of developer cartridges, an endless belt, a plurality of first collecting units, a plurality of first conveying units, a second collecting unit, a second conveying unit, and a plurality of communication portions. The plurality of photosensitive drums is juxtaposedly arrayed in a first direction to form a drum array including a leading photosensitive drum and a trailing photosensitive drum in the first direction, each photosensitive drum extending in a second direction perpendicular to the first direction. Each of the plurality of developer cartridges is detachably mountable on each of the plurality of photosensitive drums, each developer cartridge having a developer accommodating chamber in which developer to be supplied to each photosensitive drum is stored and a waste developer accommodating chamber in which waste developer to be disposed is stored. The endless belt extends in the first direction and in the second direction and facing each of the plurality of photosensitive drums. Each of the plurality of first collecting units is disposed for each of the plurality of photosensitive drums, each first collecting unit collecting the waste developer on the corresponding photosensitive drum. Each of the plurality of first conveying units is disposed for each of the first collecting units and conveys the waste developer collected by the each first collecting unit toward the waste developer accommodating chamber of the corresponding developer cartridge. The second collecting unit is disposed adjacent to the leading photosensitive drum and collects the waste developer on the endless belt. The second conveying unit conveys the waste developer collected by the second collecting unit toward the waste developer accommodating chamber of the developer cartridge corresponding to the leading photosensitive drum. Each of the plurality of communication portions allows fluid communication between the first conveying unit and the waste developer accommodating chamber, wherein among the plurality of communication portions a specific communication portion in association with the leading photosensitive drum also allows fluid communication between the second conveying unit and the waste developer accommodating chamber.

DETAILED DESCRIPTION

First, a general configuration of a tandem color printer1according to an embodiment of the present invention will be described with reference toFIGS. 1 through 4. In the color printer1, a drawer frame3according to the embodiment is mountable.

In the following description, a right side inFIG. 1will be referred to as a front side, while a left side inFIG. 1will be referred to as a rear side. The terms “upward”, “downward”, “upper”, “lower”, “above”, “below”, “beneath”, “right”, “left”, “front”, “rear” and the like will be used assuming that the color printer1is viewed from its front side. Also, directions with respect to the drawer frame3will be referenced based on an assumption that the drawer frame3is accommodated within the color printer1.

As shown inFIG. 1, the color printer1includes a main casing2within which the drawer frame3can be accommodated. The drawer frame3has a square frame shape in a plan view. A front cover4is pivotably movably provided at the front side of the main casing2. When the front cover4is opened, the drawer frame3is movable relative to the main casing2with respect to a horizontal direction. More specifically, the drawer frame3is movable between an accommodated position in which the drawer frame3is accommodated within the main casing2(shown inFIG. 1), and a pull-out position in which the drawer frame3is pulled out from the main casing2(shown inFIG. 2).

In the drawer frame3, four drum units5are supported. The four drum units5are provided respectively for four colors of black, yellow, magenta and cyan to be used in the color printer1. The drum units5are juxtaposed in a front-to-rear direction according to the order of colors given above such that the drum unit5for black is positioned rearmost in the front-to-rear direction.

Each drum unit5is detachably mountable on the drawer frame3from above when the drawer frame3is in the pull-out position, as shown inFIG. 3. More specifically, as shown inFIG. 3, the drawer frame3includes a left side frame (not shown) and a right side frame302disposed in opposition to each other in a left-to-right direction. On inner surfaces of the left side frame and the right side frame302(on a right side surface of the left side frame and a left side surface of the right side frame302), four guide grooves7are formed respectively in correspondence with the four drum units5. Each guide groove7extends diagonally downward and frontward in the front-to-rear direction. A shaft801of a photosensitive drum8(described later) is inserted into the corresponding pair of guide grooves7from upward thereof, such that each drum unit5is being mounted in the drawer frame3along the guide grooves7, while the shaft801is slidingly moved downward within the guide grooves7. Likewise, when the drum unit5is removed from the drawer frame3, the drum unit5is pulled upward along the corresponding guide grooves7.

Each drum unit5includes the photosensitive drum8, a charging roller9, a developing device10and a drum cleaner11. The photosensitive drum8is rotatable about its axis extending in the left-to-right direction and is rotatably supported to the drum unit5. During image formation, the photosensitive drum8is rotated in a counterclockwise direction when viewed from its left side (i.e., in a counterclockwise direction inFIG. 1). The charging roller9, the developing device10and the drum cleaner11are disposed to surround the photosensitive drum8. More specifically, as shown inFIG. 1, the charging roller9is disposed at a position diagonally upward and frontward of the photosensitive drum8and in contact with the photosensitive drum8. The developing device10has a lower end portion that opposes the photosensitive drum8at a position rearward of the same. The drum cleaner11confronts the photosensitive drum8at a position frontward of the photosensitive drum8. The drum unit5for the color of black positioned rearmost in the front-to-rear direction (hereinafter to be referred to as the drum unit5K) is further provided with a belt cleaner12.

A toner cartridge13for storing toner therein is detachably mountable on the developing device10from above. As shown inFIG. 3, when the drawer frame3is in the pull-out position, the toner cartridge13is integrally detachable with the drum unit5relative to the drawer frame3. Further, when the drawer frame3is in the pull-out position, the toner cartridge13alone is also removable from the drawer frame3, while the drum unit5remains mounted on the drum unit5, as shown inFIG. 4.

Within the main casing2, an exposure device14, an intermediate transfer belt15, a sheet feed cassette22and a fixing unit23are also provided, as shown inFIG. 1.

The exposure device14is disposed at an uppermost portion of the main casing2. The exposure device14is configured to irradiate four laser beams corresponding to the four colors used in the color printer1toward surfaces of the photosensitive drums8. Instead of the exposure device14, four LED arrays may be provided for the photosensitive drums8.

As each photosensitive drum8rotates, the corresponding charging roller9applies a uniform charge to the surface of the photosensitive drum8.

Subsequently, the laser beams irradiated from the exposure device14selectively expose the surfaces of the photosensitive drums8to light. As a result of exposure to light, an electrostatic latent image is formed on the surface of each photosensitive drum8. When toner is supplied to the electrostatic latent image from the developing device10, the electrostatic latent image is developed into a toner image.

The intermediate transfer belt15is disposed below the drawer frame3in the accommodated position. The intermediate transfer belt15is an endless belt, and mounted around three rollers16,17and18in a taut state. The two rollers16,17are disposed so as to oppose each other in the front-to-rear direction and at positions identical to each other with respect to a vertical direction. The two rollers16,17are separated from each other in the front-to-rear direction by a prescribed distance that is substantially identical to a length of the drawer frame3in the front-to-rear direction. The remaining roller18is disposed diagonally downward and frontward of the roller17that is positioned at the rear side in the main casing2. The intermediate transfer belt15thus defines a planar portion19between the rollers16,17(upper portion of the endless intermediate transfer belt15), the planar portion19extending in the front-to-rear direction and the left-to-right direction. The planar portion19is in contact with each of the photosensitive drums8and a first cleaning roller75(to be described later).

Four primary transfer rollers20are disposed within a loop of the intermediate transfer belt15such that each primary transfer roller20is in confrontation with each photosensitive drum8via the planar portion19.

During image formation, the intermediate transfer belt15circularly moves in a clockwise direction when viewed from its left side. Due to the primary transfer rollers20, the toner images formed on the surfaces of the photosensitive drums8are superimposed onto the intermediate transfer belt15, sequentially from the black toner image. A colored toner image is thus formed on the intermediate transfer belt15.

A secondary transfer roller21is disposed rearward of the roller17so as to oppose the same via the intermediate transfer belt15. The secondary transfer roller21is in contact with the intermediate transfer belt15.

The sheet feed cassette22is disposed at a lower portion of the main casing2. The sheet feed cassette22accommodates therein sheets of paper P. The paper P accommodated in the sheet feed cassette22is conveyed toward a position where the intermediate transfer belt15is in contact with the secondary transfer roller21by various rollers. Due to the secondary transfer roller21, the colored toner image formed on the intermediate transfer belt15is transferred onto the paper P passing between the intermediate transfer belt15and the secondary transfer roller21.

The fixing unit23is disposed rearward of the drawer frame3in the accommodated position. The paper P on which the colored toner image has been transferred is then conveyed to the fixing unit23whereby the toner image is fixed to the paper P by heat and pressure. After the toner image has been fixed to the paper P in the fixing unit23, various rollers discharge the paper P onto a discharge tray24formed on a top surface of the main casing2.

Next, a detailed configuration of the drum unit5K will be described with reference toFIGS. 5 through 14as an example for explaining a configuration of the drum unit5. The drum unit5K has a configuration identical to those of other three drum units5(for yellow, magenta and cyan) except that the belt cleaner12and a second conveyor unit101(described later) are provided only in the drum unit5K.

As shown inFIGS. 5 and 6, the drum unit5K includes a left side plate31and a right side plate32arranged in opposition to each other in the left-to-right direction. The charging roller9, the developing device10, the drum cleaner11and the belt cleaner12(shown inFIG. 1) are interposed between the left side plate31and the right side plate32and integrally held to the left side plate31and the right side plate32. The left side plate31extends upward and has an upper end portion facing the toner cartridge13from leftward of the same. The right side plate32extends upward and has an upper end portion facing the developing device10from rightward of the same such that a space above the developing device10is exposed rearward so as to be used as a space for accommodating the toner cartridge13therein.

The developing device10includes a developing device frame41extending between the left side plate31and the right side plate32, as shown inFIGS. 5 and 6. A developing chamber42is formed in the developing device frame41, as shown inFIGS. 7 and 8. The developing chamber42has a lower end portion that is open toward the photosensitive drum8.

Within the developing chamber42, a developing roller43, a supply roller46, a thickness-regulating blade49and an auger50are disposed.

The developing roller43is positioned at the lower end portion of the developing chamber42. The developing roller43includes a cylindrical-shaped developing roller main body44and a developing roller shaft45extending in the left-to-right direction. The developing roller main body44has an axis extending in the left-to-right direction, and the developing roller shaft45penetrates through the developing roller main body44along the axis thereof. The developing roller main body44has an outer circumferential surface a portion of which is exposed outside of the developing chamber42and is in contact with the surface of the photosensitive drum8. The developing roller shaft45penetrates through left and right side plates (not shown) of the developing device frame41and is rotatably supported to the same. The developing roller shaft45has widthwise ends in the left-to-right direction that are supported to the left side plate31and the right side plate32respectively.

The supply roller46includes a cylindrical-shaped supply roller main body47and a supply roller shaft48extending in the left-to-right direction. The supply roller main body47has an axis extending in the left-to-right direction, and the supply roller shaft48penetrates through the supply roller main body47along the axis of the supply roller main body47. The supply roller46is disposed diagonally upward and rearward of the developing roller43such that the supply roller main body47is in contact with the developing roller main body44. The supply roller shaft48is rotatably supported to the left and side plates of the developing device frame41.

The thickness-regulating blade49has a thin plate-like shape. The thickness-regulating blade49has a base end held to the developing device frame41and another free end that is movable due to resilient deformation of the thickness-regulating blade49. The free end of the thickness-regulating blade49is in contact with the developing roller main body44from upward of the same.

The auger (feeder screw)50is disposed at a position diagonally upward and frontward of the supply roller46. The auger50includes an auger shaft51extending in the left-to-right direction and an auger screw52formed on and along the auger shaft51in a spiral manner. The auger shaft51is rotatably supported to the left side plate31and the right side plate32.

As the auger50rotates, toner supplied within the developing chamber42from the toner cartridge13is conveyed in the left-to-right direction and dispersed along the auger50. As the supply roller46rotates, the toner is supplied onto the developing roller main body44from the supply roller main body47. As the developing roller43rotates, the toner on the developing roller main body44enters between the free end of the thickness-regulating blade49and the developing roller main body44, and is maintained on the developing roller main body44as a thin layer of uniform thickness.

The developing device frame41is further formed with a plate-shaped partitioning wall53positioned between the developing chamber42and the space for accommodating the toner cartridge13. The partitioning wall53curves in an arcuate shape, with its convex side facing the developing chamber42.

The partitioning wall53is formed with a communication port54at a position circumferentially center of the partitioning wall53. The communication port54penetrates through the partitioning wall53so as to allow the communication port54to be in fluid communication with the developing chamber42. The auger50is positioned within the developing chamber42at a position in confrontation with the communication port54.

A plate-shaped developing-side shutter55is provided on the partitioning wall53. The developing-side shutter55has an accurate shape protruding toward the developing chamber42substantially in conformance with the arcuate-shaped outline of the partitioning wall53. The developing-side shutter55is formed with a shutter opening56at a position corresponding to the position of the communication port54formed on the partitioning wall53. The developing-side shutter55is movable along the partitioning wall53between an open position where the shutter opening56is in communication with the communication port54and a closed position where the shutter opening56is prevented from communicating with the communication port54.

The drum cleaner11includes a drum cleaner casing61extending in the left-to-right direction. The drum cleaner casing61spans across the left side plate31and the right side plate32, as shown inFIG. 9. The drum cleaner casing61includes a cleaner opening62and a waste toner chamber63. The cleaner opening62spans an entire width of the photosensitive drum8in the left-to-right direction so as to face the same. The waste toner chamber63is formed within the drum cleaner casing61and in fluid communication with the cleaner opening62.

As shown inFIGS. 7 through 9, an auger64is disposed within the waste toner chamber63. The auger64includes an auger shaft65extending in the left-to-right direction and an auger screw66provided on and along the auger shaft65in a spiral manner. The drum cleaner casing61has a right side wall67that closes (covers) the waste toner chamber63at a right side thereof, as shown inFIG. 9. The auger shaft65has a right end portion penetrating the right side wall67and is rotatably supported to the same. The auger shaft65has a left end portion that is rotatably supported to an opposing wall92(described later).

The drum cleaner11further includes a scraper69as shown inFIGS. 7 and 8. The scraper69has a plate-like shape extending in the left-to-right direction and in the vertical direction. The scraper69has an upper en portion that is fixed to the drum cleaner casing61, and a lower portion that is in contact with the surface of the photosensitive drum8within the cleaner opening62.

In accordance with the rotation of the photosensitive drum8, the toner remaining deposited on the surface of the photosensitive drum8after the toner image is transferred onto the intermediate transfer belt15is scraped off from the surface of the photosensitive drum8by the scraper69as waste toner. The waste toner scraped off from the photosensitive drum8is received within the waste toner chamber63via the cleaner opening62. Subsequently, as the auger64rotates, the auger64(the auger screw66) conveys the waste toner leftward within the waste toner chamber63.

The belt cleaner12includes a belt cleaner casing71. As shown inFIGS. 7 and 8, the belt cleaner casing71includes a first peripheral wall72and a second peripheral wall73. The first peripheral wall72curves in an arcuate shape in cross-section, with its convex side facing upward. The first peripheral wall72has a front end portion from which the second peripheral wall73extends downward. The second peripheral wall73has a substantially U-shape in cross-section, whose bottom end portion projecting downward. As shown inFIG. 10, each of the first peripheral wall72and the second peripheral wall73has a left end portion connected to the left side plate31. The belt cleaner casing71also includes a right side wall74(seeFIG. 10) defining right end portions of the first peripheral wall72and the second peripheral wall73. The right side wall74is spaced away from the right side plate32of the drum unit5K.

As shown inFIGS. 7 and 8, the first cleaning roller75is disposed within the drum cleaner casing belt cleaner casing71at a position between rear end portions of the first peripheral wall72and the second peripheral wall73. The first cleaning roller75includes a cylindrical-shaped cleaning roller main body76and a cleaning roller shaft77extending in the left-to-right direction. The cleaning roller main body76has an axis extending in the left-to-right direction, and the cleaning roller shaft77penetrates through the cleaning roller main body76along the axis of thereof The cleaning roller shaft77is rotatably supported to the belt cleaner casing71.

The belt cleaner casing71is formed with a roller accommodation chamber78surrounded by the first peripheral wall72, and a waste toner chamber79surrounded by the second peripheral wall73.

A second cleaning roller80is further disposed within the roller accommodation chamber78. The second cleaning roller80includes a cylindrical-shaped cleaning roller main body81and a cleaning roller shaft82extending in the left-to-right direction. The cleaning roller main body81has an axis extending in the left-to-right direction, and the cleaning roller shaft82penetrates through the cleaning roller main body81along the axis thereof The cleaning roller main body81is in contact with the cleaning roller main body76of the first cleaning roller75at a position diagonally upward and frontward of the cleaning roller main body76. As shown inFIG. 10, the cleaning roller shaft82has a right end portion that is rotatably supported to the right side plate32, and a left end portion that is rotatably supported to the belt cleaner casing71.

Within the waste toner chamber79, an auger83is rotatably disposed, as shown inFIGS. 7,8,10. The auger83includes an auger shaft84extending in the left-to-right direction and an auger screw85formed on and along the auger shaft84in a spiral manner. As shown inFIG. 10, the auger shaft84has a right end portion penetrating through the right side wall74and rotatably supported to the right side plate32, and a left end portion rotatably supported to an opposing wall102(described later).

Further, as shown inFIGS. 7 and 8, a scraper86is disposed at a boundary area between the roller accommodation chamber78and the waste toner chamber79. The scraper86has a plate-like shape extending in the left-to-right direction. The scraper86has an upper en portion that is fixed to the belt cleaner casing71, and a lower portion that is in contact with a surface of the cleaning roller main body81of the second cleaning roller80at a position diagonally downward and frontward of the cleaning roller main body81.

The cleaning roller main body76of the first cleaning roller75is in contact with the intermediate transfer belt15, as described earlier (seeFIG. 1). Further, as also shown inFIG. 1, a backup roller87is disposed within the loop of the intermediate transfer belt15at a position in confrontation with the first cleaning roller75via the intermediate transfer belt15.

Toner still remaining on the intermediate transfer belt15after the toner image has been transferred to the paper P (i.e., waste toner) is carried on a surface of the cleaning roller main body76of the first cleaning roller75when the cleaning roller main body76confronts the intermediate transfer belt15in accordance with the circular movement of the intermediate transfer belt15. The waste toner is then transferred from the surface of the cleaning roller main body76of the first cleaning roller75to the surface of the cleaning roller main body81of the second cleaning roller80. The waste toner is scraped off from the surface of the cleaning roller main body81by the scraper86, and is received within the waste toner chamber79. Subsequently, as the auger83rotates, the auger83(the auger screw85) conveys the waste toner leftward within the waste toner chamber79.

Incidentally, instead of the belt cleaner12, a scraper may be provided so as to be in slidingly contact with the intermediate transfer belt15. In this configuration, the waste toner on the intermediate transfer belt15can be scraped off therefrom by the scraper.

As shown inFIG. 11, on an outer surface (left side surface) of the left side plate31of the drum unit5K, a first conveying unit91is provided. The first conveying unit91has an elongated shape, extending diagonally upward and rearward from a lower front end portion to an upper end portion of the left side plate31. The first conveying unit91includes the opposing wall92and a peripheral wall93. The opposing wall92is disposed in opposition to the left side plate31and is spaced away therefrom. The peripheral wall93is formed along an entire periphery of the opposing wall92. As shown inFIGS. 9 and 12, a space94is defined by the outer surface of the left side plate31, the opposing wall92and the peripheral wall93, and serves as a waste toner chamber through which waste toner is conveyed.

Belt shafts95,96are respectively disposed at upper and lower end portions within the waste toner chamber94. The belt shafts95,96extend in the left-to-right direction and are rotatably supported to the opposing wall92. An endless toner conveying belt98is mounted on the belt shafts95,96. The toner conveying belt98has an outer circumferential surface on which a plurality of ribs97is formed at regular intervals. The toner conveying belt98is circularly moved in a clockwise direction in a left side view, as indicated by an arrow inFIG. 12.

The belt shaft95has a left end protruding leftward from the opposing wall92. The left end of the belt shaft95protruding from the opposing wall92is fitted with a gear99, as shown inFIG. 11.

As shown inFIG. 9, the waste toner chamber94is in fluid communication with the waste toner chamber63of the drum cleaner11. Therefore, the waste toner conveyed leftward within the waste toner chamber63by the auger64flows into the waste toner chamber94. The waste toner flowing into the waste toner chamber94is then conveyed upward by the ribs97of the toner conveying belt98in accordance with the circular movement of the toner conveying belt98.

Further, as shown inFIG. 11, on the outer surface (left side surface) of the left side plate31of the drum unit5K, the second conveyor unit101is provided. The second conveyor unit101has an elongated shape, extending diagonally upward and frontward from a lower rear end portion to the upper end portion of the left side plate31.

The second conveyor unit101includes an opposing wall102and a peripheral wall103. The opposing wall102is disposed in opposition to the left side plate31and is spaced away therefrom. The peripheral wall103is formed along an entire periphery of the opposing wall102. As shown inFIGS. 10 and 12, a space104is defined by the outer surface of the left side plate31, the opposing wall102and the peripheral wall103, and serves as a waste toner chamber through which waste toner is conveyed.

Belt shafts105,106are respectively disposed at upper and lower end portions within the waste toner chamber104. The belt shafts105,106extend in the left-to-right direction and are rotatably supported to the opposing wall102. An endless toner conveying belt108is mounted on the belt shafts105,106. The toner conveying belt108has an outer circumferential surface on which a plurality of protrusions107is formed at regular intervals. The toner conveying belt108is circularly moved in a clockwise direction in a left side view, as indicated by an arrow inFIG. 12.

The belt shaft105has a left end protruding leftward from the opposing wall102. The left end of the belt shaft105protruding from the opposing wall102is fitted with a gear109, as shown inFIG. 11.

As shown inFIG. 10, the waste toner chamber104is in fluid communication with the waste toner chamber79of the belt cleaner12. Therefore, the waste toner conveyed leftward within the waste toner chamber79by the auger83flows into the waste toner chamber104. The waste toner flowing into the waste toner chamber104is then conveyed upward by the protrusions107in accordance with the circular movement of the toner conveying belt108.

As shown inFIG. 12, a communication unit111is provided between upper end portions of the first conveying unit91and the second conveyor unit101. The communication unit111has a hollow cylindrical shape, extending in the left-to-right direction and penetrating through the left side plate31, as shown inFIG. 13. That is, the communication unit111has a left-side portion protruding leftward from the left side plate31, and a right-side portion protruding rightward from the left side plate31.

As shown inFIG. 12, the left-side portion of the communication unit111has a peripheral wall on which communication ports112,113are formed, the communication ports112,113penetrating through the peripheral wall. The communication port112is in fluid communication with the waste toner chamber94of the first conveying unit91, while the communication port113is in fluid communication with the waste toner chamber104of the second conveyor unit101.

The right-side portion of the communication unit111has a peripheral wall on whose bottom portion a connecting port114is formed, the connecting port114penetrating through the peripheral wall, as shown inFIG. 13.

As shown inFIGS. 9 and 13, a cylindrical-shaped shutter115is externally coupled to the peripheral wall of the right-side portion of the communication unit111. The shutter115is movable in the left-to-right direction along the peripheral wall of the right-side portion of the communication unit111. The shutter115is biased rightward by a coil spring116disposed between the shutter115and the left side plate31.

Within the communication unit111, an auger117is rotatably disposed. The auger117includes an auger shaft118extending in the left-to-right direction and an auger screw119formed on and along the auger shaft118in a spiral manner. The auger shaft118has a left end portion protruding leftward from the communication unit111. The left end of the auger shaft118protruding from the communication unit111is fitted with a gear120, as shown inFIG. 11.

The gear120is in meshing engagement with the gears99,109. Hence, when a driving fore is inputted to the gear120, the driving force is transmitted to the respective gears99,109, thereby rotating the same. The rotation of the gears99,109enables the toner conveying belts98,108to circularly move.

The waste toner conveyed upward by the toner conveying belt98within the waste toner chamber94flows into the communication unit111via the communication port112. The waste toner conveyed upward by the toner conveying belt108within the waste toner chamber104flows into the communication unit111via the communication port113. As the auger117rotates in response to input of the driving force to the gear120, the auger117(auger screw119) conveys the waste toner rightward within the communication unit111.

As shown inFIGS. 7 and 8, the toner cartridge13includes a hollow cylindrical-shaped inner casing121and an outer casing122that accommodates therein the inner casing121. The outer casing122also has a hollow cylindrical shape.

A partitioning wall123is formed within the inner casing121. The partitioning wall123partitions an internal space of the inner casing121into a toner accommodation chamber124and a waste toner accommodation chamber125. Toner to be supplied to the developing device10is stored within the toner accommodation chamber124, while collected waste toner is stored within the waste toner accommodation chamber125.

On the inner casing121, an inner outlet126is formed for allowing fluid communication between inside and outside of the toner accommodation chamber124. The inner outlet126is positioned such that the inner outlet126is in coincidence with the communication port54of the partitioning wall53when the toner cartridge13is mounted on the partitioning wall53of the developing device frame41.

As shown inFIGS. 13 and 14, the inner casing121has a left end face on which a recessed portion127is formed. The recessed portion127is protruding inward (toward the inner space of the inner casing121) from the left end face of the inner casing121. The recessed portion127has a circular-shaped side view, having an inner diameter greater than an outer diameter of the communication unit111but smaller than an outer diameter of the shutter115. The recessed portion127has a bottom end on which a discharging port128is formed. The discharging port128opens downward and is in fluid communication with the waste toner accommodation chamber125.

Within the recessed portion127, a shutter129is movably disposed for opening and closing the discharging port128. The shutter129is movable in the left-to-right direction, and integrally includes a cylindrical portion130and an abutment portion131. The cylindrical portion130has an outer diameter substantially identical to the inner diameter of the recessed portion127. The abutment portion131covers a left end of the cylindrical portion130. A coil spring132is disposed between the abutment portion131and the recessed portion127such that the shutter129is biased leftward by the coil spring132.

Within the toner accommodation chamber124, an agitator133is disposed, as shown inFIGS. 7 and 8. The agitator133includes an agitator shaft134extending in the left-to-right direction, and an agitating film135held to the agitator shaft134.

Within the waste toner accommodation chamber125, an auger136is rotatably disposed. As shown inFIG. 13, the auger136includes an auger shaft137extending in the left-to-right direction and an auger screw138formed on and along the auger shaft137in a spiral manner.

As shown inFIGS. 7 and 8, on an outer circumferential surface of the outer casing122, an outer outlet139is formed. The outer outlet139is positioned such that the outer outlet139is in coincidence with the inner outlet126with respect to the left-to-right direction. Hence, as the outer casing122is made to rotate (slidingly move) relative to the inner casing121, the inner outlet126takes either a position where the inner outlet126confronts the outer outlet139and is in communication with the same, or another position where the inner outlet126is not in confrontation with the outer outlet139. The outer outlet139is also positioned such that the outer outlet139is in confrontation with the shutter opening56of the developing-side shutter55and in communication with the same when the toner cartridge13is mounted on the partitioning wall53of the developing device frame41.

The toner cartridge13is mounted within the space above the partitioning wall53of the developing device frame41(seeFIG. 6) from a right side of the space. That is, at the time of installation of the toner cartridge13, the toner cartridge13is moved from the right side toward a left side of the space above the partitioning wall53. Subsequently, as shown inFIG. 13, the recessed portion127and the communication unit111are positionally-aligned with each other such that the communication unit111is inserted within the recessed portion127provided on the left end face of the inner casing121. At this time, the shutter115coupled to the communication unit111is in confrontation with a peripheral end portion of the recessed portion127.

As the toner cartridge13moves further leftward, the shutter115is brought into contact with the peripheral end portion of the recessed portion127and is prevented from being inserted within the recessed portion127, while, in the mean time, the communication unit111is inserted into the recessed portion127. As the communication unit111is inserted into the recessed portion127, the communication unit111pushes the shutter129rightward. In response, the shutter129is moved rightward against a biasing force of the coil spring132. When the shutter129moves to reach an inner right end portion of the recessed portion127, the toner cartridge13is stopped from moving further, the installation of the toner cartridge13being completed. At this time, the connecting port114of the communication unit111is in confrontation with the discharging port128of the toner cartridge13. That is, an internal space of the communication unit111and the waste toner accommodation chamber125of the toner cartridge13are in fluid communication with each other via the connecting port114and the discharging port128.

With this configuration, the waste toner conveyed rightward by the auger117within the communication unit111flows into the waste toner accommodation chamber125via the connecting port114and the discharging port128. In accordance with rotation of the auger136disposed within the waste toner accommodation chamber125, the auger136conveys the incoming waste toner rightward. The waste toner is thus uniformly dispersed within the waste toner accommodation chamber125in the left-to-right direction.

As shown inFIG. 8, when the toner cartridge13has just been mounted within the space above the partitioning wall53, the communication port54of the partitioning wall53and the shutter opening56of the developing-side shutter55do not confront each other. Further, the inner outlet126of the inner casing121and the outer outlet139of the outer casing122do not confront each other, either.

From this state, the outer casing122is then made to rotate in a counterclockwise direction inFIG. 8. When the toner cartridge13is mounted on the space above the partitioning wall53, the outer casing122is connected to the developing-side shutter55. Therefore, when the outer casing122is rotated, the developing-side shutter55is also moved in conjunction with the rotation of the outer casing122. The outer casing122is rotated to a position where the outer outlet139opposes the inner outlet126. As a result, as shown inFIG. 7, the outer outlet139is in opposition to the inner outlet126, and the shutter opening56formed on the developing-side shutter55is in opposition to the communication port54formed on the partitioning wall53. Thus, the toner accommodation chamber124and the developing chamber42are brought into fluid communication with each other, and the toner accommodated within the toner accommodation chamber124is supplied to the developing chamber42.

As described above, the drum cleaner11is disposed for each photosensitive drum8for collecting waste toner deposited on the surface of the photosensitive drum8. The belt cleaner12for collecting waste toner on the intermediate transfer belt15is provided rearward of the rearmost photosensitive drum8for black. The toner cartridge13includes the toner accommodation chamber124for accommodating toner to be supplied to the photosensitive drum8, and the waste toner accommodation chamber125for accumulating the waste toner to be disposed.

The waste toner collected at the drum cleaner11is conveyed toward the waste toner accommodation chamber125of each toner cartridge13by the first conveying unit91. The waste toner collected at the belt cleaner12is conveyed toward the waste toner accommodation chamber125of the toner cartridge13corresponding to the rearmost photosensitive drum8positioned adjacent to the belt cleaner12. Each waste toner accommodation chamber125is in fluid communication with the communication unit111of each drum unit5. The communication unit111that is in fluid communication with the waste toner accommodation chamber125of the toner cartridge13corresponding to the rearmost photosensitive drum8for black also serves to allow fluid communication between the first conveying unit91and the waste toner accommodation chamber125, and between the second conveyor unit101and the waste toner accommodation chamber125.

With this configuration, the waste toner collected from the photosensitive drum8for black by the drum cleaner11is conveyed, via the first conveying unit91and the communication unit111, to the waste toner accommodation chamber125that is in fluid communication with the communication unit111. To this waste toner accommodation chamber125, the waste toner collected from the intermediate transfer belt15by the belt cleaner12is also conveyed via the second conveyor unit101and the communication unit111. Therefore, a separate waste toner box for storing the waste toner collected from the intermediate transfer belt15is not necessary. The color printer1can be thus made compact.

Further, the waste toner collected from both of the photosensitive drum8and the intermediate transfer belt15can be disposed at a time just by replacing the toner cartridge13corresponding to the black photosensitive drum8. Furthermore, since the intermediate transfer belt15is not required to be removed for replacing each toner cartridge13, efforts required to dispose the waste toner can be greatly reduced.

Further, the communication unit111is connected to the left end face of the toner cartridge13. The waste toner collected by the drum cleaner11and the belt cleaner12is conveyed first leftward by the augers64,83, then upward by the first conveying unit91and the second conveyor unit101, and finally to the waste toner accommodation chamber125from its left side via the communication unit111.

The auger136provided within the waste toner accommodation chamber125conveys the waste toner flowing from the communication unit111into the waste toner accommodation chamber125rightward. Therefore, the waste toner can be dispersed in the left-to-right direction within the waste toner accommodation chamber125. As a result, the waste toner is prevented from accumulating at an area in the vicinity of the communication unit111within the waste toner accommodation chamber125. The flow of the waste toner from the communication unit111into the waste toner accommodation chamber125can be made smooth and secured.

Further, each photosensitive drum8, the drum cleaner11, the communication unit111, the first conveying unit91and the second conveyor unit101are integrally supported to the left side plate31and the right side plate32. More specifically, the side plates31,32retaining the rearmost photosensitive drum8for black integrally support the drum cleaner11, the belt cleaner12, the first conveying unit91and the second conveyor unit101. The pair of side plates31,32retaining each of the remaining three photosensitive drums8supports the drum cleaner11corresponding to the photosensitive drum8, and the first conveying unit91. Therefore, the black photosensitive drum8, the drum cleaner11, the belt cleaner12, the first conveying unit91and the second conveyor unit101can be treated as an integral unit, while each of the other three photosensitive drums8, its drum cleaner11and first conveying unit91can be treated as an integral unit.

Further, the four toner cartridges13can be integrally pulled out from the main casing2via the drawer frame3. Therefore, replacement of the toner cartridge13for black that is positioned rearmost in the front-to-rear direction can be facilitated.

Although the present invention has been described with respect to the specific embodiment thereof, it will be appreciated by one skilled in the art that a variety of changes may be made without departing from the scope of the invention.