Developer storage body, image forming unit and image forming apparatus

A developer storage body includes a storage portion in which a developer is stored, a supplying opening through which the developer is ejected, and a conveying member provided in the storage portion. The conveying member is rotatable about a rotation axis so as to convey the developer to the supplying opening. The supplying opening is provided with a plurality of slits extending in a direction substantially perpendicular to the rotation axis of the conveying member.

BACKGROUND OF THE INVENTION

The present invention relates to a developer storage body, an image forming unit and an image forming apparatus such as a printer, a facsimile or a copier.

There is known a developer storage body storing a developer and having a relatively small opening through which the developer is ejected. The developer storage body is externally provided with a slidable shutter for opening and closing the opening (see, Japanese Laid-open Patent Publication No. 2010-237588).

In the conventional developer storage body, a failure in ejection of the developer may occur.

SUMMARY OF THE INVENTION

An aspect of the present invention is intended to provide a developer storage body, an image forming unit and an image forming apparatus capable of suppressing a failure in ejection of a developer.

According to an aspect of the present invention, there is provided a developer storage body including a storage portion in which a developer is stored, a supplying opening through which the developer is ejected, and a conveying member provided in the storage portion. The conveying member is rotatable about a rotation axis so as to convey the developer to the supplying opening. The supplying opening is provided with a plurality of slits extending in a direction substantially perpendicular to the rotation axis of the conveying member.

With such a configuration, it becomes possible to suppress a failure in ejection of a developer.

According to another aspect of the present invention, there is provided an image forming unit including the above described developer storage body.

According to still another aspect of the present invention, there is provided an image forming unit including the above described developer storage body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a schematic view showing a configuration of a printer100including a toner cartridge (i.e., a developer cartridge) according to Embodiment 1 of the present invention.

InFIG. 1, the printer100(i.e., an image forming apparatus) is configured as a color electrophotographic printer capable of printing images of black (K), yellow (Y), magenta (M) and cyan (C). The printer100includes a lower frame28in which a substantially S-shaped sheet transport path15(i.e., a medium transport path) is provided. Sheet transport rollers16,17,18and19are disposed along the sheet transport path15. A feeding cassette20is disposed on an upstream end of the sheet transport path15. The feeding cassette20is configured to store recording sheets (i.e., recording media). A stacker21is disposed on a downstream end of the sheet transport path15. The stacker21is configured so that the printed recording sheets are placed thereon.

A sheet feeding unit22, a detection unit26, a transfer belt unit24, and a fixing unit25are disposed along the sheet transport path15. The sheet feeding unit22is configured to feed the recording sheet from the feeding cassette20into the sheet transport path15. The detection unit26is configured to detect a thickness of the recording sheet. The transfer belt unit24has a transfer belt11that absorbs the recording sheet by electrostatic effect and transports the recording sheet. The fixing unit25is configured to fix the toner to the recording sheet.

Image forming units23K,23Y,23M and23C are disposed on a side (in this example, an upper side) opposite to the transfer belt unit24with respect to the recording sheet transported by the transfer belt11. The image forming units23K,23Y,23M and23C are provided in a main body of the printer100, and are arranged in this order from upstream to downstream in a transport direction of the recording sheet. When the image forming units23K,23Y,23M and23C need not be distinguished from each other, the image forming units23K,23Y,23M and23C are collectively referred to as the image forming units23. The image forming units23K,23Y,23M and23C have the same configurations except toners (developers) stored therein. The configuration of the image forming unit23will be herein described. In this regard, a part of the printer100from which a detachable component (for example, an image forming unit23) is detached is referred to as a main body of the printer100.

InFIG. 1, X direction is defined as the transport direction of the recording sheet when the recording sheet passes the image forming units23, and Y direction is defined as a direction of a rotation axis of a photosensitive body1(described later) of each image forming unit23. Further, Z direction is defined as a direction perpendicular to both of the X direction and Y direction. In the subsequent drawings, the X direction, the Y direction and the Z direction indicate the same directions as those ofFIG. 1. In other words, in the subsequent drawings, the X-axis, the Y-axis and the Z-axis indicate directions of component parts in a state where the component parts are assembled into the printer100shown inFIG. 1. Further, in this example, the Z direction is a substantially vertical direction.

FIG. 2is a schematic view showing the configuration of the image forming unit23(i.e., image forming units23K,23Y,23M and23C), a transfer roller12, an exposure unit3and a recording sheet13.

As shown inFIG. 2, the image forming unit23includes a developing device10detachably mounted to the main body of the printer100, a toner cartridge5(i.e., a developer storage body), and a toner cartridge holding unit41(i.e., a developer storage body holding unit).

The developing device10includes a photosensitive body1, a charging roller2, a developing unit110and a cleaning blade9. The photosensitive body1has a chargeable surface layer whose charge is removed by exposure. The photosensitive body1is rotatable in a direction shown by an arrow. The charging roller2, an exposure unit3, the developing unit110and the cleaning blade9are arranged in this order from upstream to downstream in a rotating direction of the photosensitive body1.

The charging roller2(i.e., a charging member) is pressed against the surface of the photosensitive body1by a predetermined pressure, and uniformly charges the surface of the photosensitive body1. The exposure unit3includes, for example, LED (Light Emitting Diode) head as a light source. The exposure unit3is configured to emit light so as to irradiate the uniformly charged surface of the photosensitive body1so as to form a latent image. The exposure unit3is mounted to an upper frame30(FIG. 1) of the main body of the printer100.

The developing unit110is configured to develop the latent image formed on the surface of the photosensitive body1using a toner4(i.e., a developer) of a predetermined color. The cleaning blade9is configured to scrape the toner (i.e., a residual toner) remaining on the surface of the photosensitive body1after the toner is transferred to the recording sheet13. The cleaning blade9is made of a resilient body. An edge portion of the cleaning blade9is pressed against the surface of the photosensitive body1by a predetermined pressure. The residual toner scraped by the cleaning blade9falls into a waste toner collecting unit111. The respective rotating bodies (rollers and the like) of the image forming units23are driven to rotate by a force transmitted from a driving source (not shown) via gears or the like.

The developing unit110is configured to develop the latent image on the surface of the photosensitive body1. To be more specific, the developing unit110includes a toner reservoir112(i.e., a developer reservoir), a developing roller6(i.e., a developer bearing body), a toner supplying roller8(i.e., a developer supplying member) and a developing blade7(i.e., a developer regulating member). The toner reservoir112is configured to hold the toner4ejected from a toner conveying path27(i.e., a developer conveying path). The toner supplying roller8is configured to supply the toner4to the developing roller6. The developing blade7is configured to form a thin layer of the toner4(i.e., a toner thin layer) on the surface of the developing roller6.

The toner cartridge holding unit41(described later) is configured to hold the detachable toner cartridge5storing the toner4. The toner cartridge holding unit41is configured to guide the toner4ejected from a toner supplying opening39(i.e., a supplying opening) of the toner cartridge5to the toner reservoir112. In this regard, the toner cartridge holding unit41is disposed in the main body of the printer100as described later.

The developing roller6and the toner supplying roller8are disposed in parallel to each other, and are pressed against each other by a predetermined pressure. The developing roller6and the toner supplying roller8rotate in directions shown by arrows inFIG. 2. The developing blade7and the toner supplying roller8are disposed parallel to each other. In this example, a bent portion of the developing blade7is pressed against the surface of the developing roller6by a predetermined pressure.

As shown inFIG. 1, transfer rollers12are provided so as to face the respective photosensitive bodies1of the four image forming units23. Each transfer roller12has a roller portion made of electric conductive rubber or the like. The transfer rollers12are pressed against the respective photosensitive bodies1via the transfer belt11that absorbs and transports the recording sheet13(FIG. 2). Each transfer roller12is applied with a transfer voltage so as to form a potential difference between the transfer roller12and the surface layer of the photosensitive body1. With the potential difference, the toner is transferred from the photosensitive body1to the recording sheet13(FIG. 2).

The fixing unit25includes a heat roller and a backup roller. The fixing unit25is configured to fix a transferred toner14to the recording sheet13by application of heat and pressure. The transport rollers18and19transport the recording sheet13(to which the toner image has been fixed) to the stacker21.

A printing operation of the printer100will be described with reference toFIGS. 1 and 2.

When the printing operation is started, the printer100causes the sheet feeding unit22(FIG. 1) to feed the recording sheet13(FIG. 2) from the feeding cassette20into the sheet transport path15. Further, the transport rollers16and17transport the recording sheet13along the sheet transport path15to the transfer belt unit24. The detection unit26detects a thickness of the recording sheet13transported along the sheet transport path15. In the transfer belt unit24, the transfer belt11holds the recording sheet13by absorption, and transports the recording sheet13through the image forming units23K,23Y,23M and23C. As the recording sheet13passes through the image forming units23K,23Y,23M and23C, toner images (i.e., developer images) are transferred to the recording sheet13(FIG. 2) in an overlapping manner. The toner image is fixed to the recording sheet13by the fixing unit25, and the recording sheet13(i.e., the printed recording sheet) is transported to the stacker21.

In the image forming unit23, the toner4replenished from the toner cartridge5is supplied by the toner supplying roller8to the developing roller6. The developing blade7regulates a thickness of the toner on the surface of the developing roller6. The developing roller6develops the latent image on the surface of the photosensitive body1with the toner formed into a thin layer having a uniform thickness. The developed toner image is transferred to the recording sheet13by the transfer roller12. The toner4remaining on the surface of the photosensitive body1without being transferred to the recording sheet13is scraped by the cleaning blade9, and falls into the waste toner collecting unit111.

Next, a mechanism for detachably mounting the toner cartridge5to the printer100will be described.

FIG. 3is a perspective view showing the printer100in a state where a front cover92is opened.FIG. 4is a perspective view showing the toner cartridge5mounted to the toner cartridge holding unit41of the printer100.FIG. 5is a perspective view showing the toner cartridge5mounted to the toner cartridge holding unit41of the printer100as seen in a different direction fromFIG. 4.FIGS. 6 and 7are a top perspective view and a bottom perspective view showing the toner cartridge5.FIG. 8is a perspective view showing an inner configuration of the toner cartridge5with a cover thereof partially removed.FIG. 9is a perspective view showing the toner cartridge holding unit41.FIG. 10is a perspective view showing the toner cartridge holding unit41as seen in a different direction fromFIG. 9.

As shown inFIGS. 1though3, the toner cartridge holding units41are fixed to the main body of the printer100. Each toner cartridge holding unit41is disposed between the developing device10of each image forming unit23and the toner cartridge5. The front cover29is provided on an upper part of a front part of the printer100. The front cover29is supported by the main body of the printer100so as to be rotatable about a rotation shaft extending in the X direction. The front cover29is rotated so as to open and close respective cartridge mounting portions100a(i.e., insertion-removal portions) formed on the main body of the printer100. Ends of the toner cartridge holding units41protrude outside from the cartridge mounting portions100a. The cartridge mounting portions100ahave openings100bthrough which the toner cartridges5are mounted (inserted) and detached (removed).

InFIG. 3, four toner cartridge holding units41(41K,41Y,41M and41C) are arranged in the X direction. Among the four toner cartridge holding units41, the toner cartridge5C is mounted to the toner cartridge holding unit41C. The toner cartridge5M is being mounted to the toner cartridge holding unit41M. No toner cartridge is mounted to the toner cartridge holding units41Y and41K.

FIGS. 4 and 5are perspective views showing a state where the toner cartridge5is mounted to the toner cartridge holding unit41(like the toner cartridge holding unit41C inFIG. 3). In this state, the toner cartridge holding unit41and the toner cartridge5extend in the Y direction in the main body of the printer100. Hereinafter, a longitudinal direction of the toner cartridge holding unit41and a longitudinal direction of the toner cartridge5indicate the Y direction.

As shown inFIGS. 6,7and8, the toner cartridge5includes a toner storage portion31(i.e., a storage portion) in which the toner4is stored, a toner supplying opening39(i.e., a supplying opening) through which the toner is ejected from the toner storage portion31, and a shutter33(i.e., an opening-and-closing member) for opening and closing the toner supplying opening39. The toner supplying opening39is disposed at a bottom of the toner storage portion31. The shutter33is slidable in a longitudinal direction of the toner cartridge5.

The toner cartridge5further includes a positioning post32, a regulating groove portion52, external ribs50, gears34aand34b, a spiral36(i.e., a conveying member), an agitating member35, a grip portion49, and a handle portion48.

The positioning post32fits into a fitting hole (described later) formed on a driving input gear37(FIG. 11) provided on the main body of the printer100so as to determine a position of the toner cartridge5with respect to the toner cartridge holding unit41. The regulating groove portion52engages a positioning portion44(described later) of the toner cartridge holding unit41to prevent a rotation of the toner cartridge5. The external ribs50slides on guide members43(described later) of the toner cartridge holding unit41so as to allow the toner cartridge5to be slidable with respect to the toner cartridge holding unit41. The gears34aand34bmesh with the driving input gear37(FIG. 11) and receive a driving force. The spiral36rotates together with the gear34ato convey the toner4toward the toner supplying opening39. The agitating member35rotates together with the gear34bto agitate the toner4. The grip portion49is gripped by a user when the user holds the toner cartridge5. The handle portion is operated by the user when the user pulls the toner cartridge5from the main body of the printer100. In this regard,FIG. 7shows the toner cartridge5in a state where the shutter33closes the toner supplying opening39.

Here, the toner supplying opening39is disposed at a substantially center portion of the toner cartridge5in the longitudinal direction. The toner supplying opening39is provided with ribs58(FIG. 13B) as described later. Further, an arrow5ais provided on an external surface of the toner cartridge5. The arrow5aindicates a mounting direction (i.e., an inserting direction) of the toner cartridge5.

As shown inFIGS. 9 and 10, the toner cartridge holding unit41includes a tray42, the guide members43, the positioning portion44, a latch45, a shutter movement restricting portion56, and the toner conveying path27. The tray42is configured so that the toner cartridge5is placed thereon. The guide members43slidably contact the external ribs50of the toner cartridge5so as to guide the toner cartridge5when the toner cartridge5moves (slides) on the tray42. The positioning portion44engages the groove portion52of the toner cartridge5so as to prevent the rotation of the toner cartridge5and restrict an insertion amount of the toner cartridge5. The latch45engages a rear end portion of the shutter33so as to move the shutter33when the toner cartridge5is pulled out (removed). The shutter movement restricting portion56engages the shutter33upon insertion of the toner cartridge5so as to restrict the movement of the shutter33in the inserting direction of the toner cartridge5. The toner conveying path27(i.e., a developer receiving portion) is provided for conveying the toner4ejected from the toner supplying opening39of the toner cartridge5to the toner reservoir112of the developing device10.

An inserting operation of the toner cartridge5into the main body of the printer100will be described.

As shown inFIG. 3, when the user opens the front cover29of the printer100, ends of four toner cartridge holding units41protruding from the opening100bappear. The user places an end portion of the toner cartridge5in the direction indicated by the arrow5a(FIG. 6) on the tray42(FIG. 9), and inserts the toner cartridge5in such a manner that the external ribs50(FIG. 6) slide on the guide members43. In this state, the toner cartridge5slides on the tray42(FIG. 9) in −Y direction.

During the insertion of the toner cartridge5, the shutter33presses the latch45(formed of a resilient member) causing the latch45to be deformed. Then, the shutter33contacts the shutter movement restricting portion56, and a further movement of the shutter33is restricted. When the toner cartridge5is further inserted, the shutter33(contacting the shutter movement restricting portion56) relatively moves with respect to the toner cartridge5to start opening the toner supplying opening39(FIG. 8).

When the toner cartridge5is further inserted, the positioning post32(FIG. 6) fits into the fitting hole (not shown) formed on a center portion (i.e., a rotation center) of the driving input gear37as shown inFIG. 11. At the same time, the positioning portion44(FIG. 9) of the toner cartridge holding unit41engages the groove portion52(FIG. 7) of the toner cartridge5. Therefore, the position of the toner cartridge5is determined with respect to the toner cartridge holding unit41. In this state, the driving input gear37meshes with the gears34aand34bof the toner cartridge5.

In this state, the latch45is released from being pressed, and engages the rear end portion of the shutter33. The latch45also engages a latch-engaging portion (not shown) formed on the main body of the toner cartridge5. Therefore, the shutter33and the toner cartridge5are prevented from moving in +Y direction. In other words, the toner cartridge5is retained on the toner cartridge holding unit41so as not to be dropped, and the toner supplying opening39is kept opened. A position of the toner cartridge5whose toner supplying opening39(FIG. 8) is opened is referred to as a mounting position.

A configuration of the toner cartridge5will be further described.

FIG. 12is a perspective view showing the spiral36(i.e., the conveying member) disposed in the toner storage portion31of the toner cartridge5as shown inFIG. 8. As shown inFIG. 12, the spiral36is configured so that two main parts are symmetrical with each other with respect to an imaginary plane therebetween perpendicular to an axial direction of the spiral36. The spiral36includes an agitating portion36aextending in the axial direction. The agitating portion36ais disposed at a center portion of the spiral36. The agitating portion36aextends along an imaginary cylindrical surface whose diameter is the same as an outer diameter of the spiral36. Further, the agitating portion36ais in the form of a bar. The spiral36further includes a left spiral portion36band a right spiral portion36c(i.e., conveying portions) connected to both ends of the agitating portion36a. The left spiral portion36band the right spiral portion36chave spiral shapes. The left spiral portion36band the right spiral portion36care wound in opposite directions.

When the spiral36is mounted to a predetermined position in the toner storage portion31as shown inFIG. 8, an end of the left spiral portion36bis fixed to the gear34a. In this state, the agitating portion36aof the spiral36faces the toner supplying opening39from above. The toner supplying opening39is formed on a bottom of the toner storage portion31, and is disposed at a substantially center portion of the toner storage portion31. The spiral36rotates together with the gear34ain such a manner that the agitating portion36amoves in proximity to or in contact with a bottom inner circumferential surface38(FIG. 14C) of the toner storage portion31. The bottom inner circumferential surface38has an arcuate cross section, and is formed on a bottom of the toner storage portion31. A direction of the rotation axis of the spiral36is parallel to the longitudinal direction of the toner cartridge5(i.e., the Y direction).

Therefore, when the driving input gear37(meshing with the gear34a) rotates in a predetermined direction, the spiral36rotates in a direction shown by an arrow A (FIG. 12) in the toner storage portion31. As the spiral36rotates in the direction shown by the arrow A, the left and right spiral portions36band36cconveys the toner4toward the center portion (i.e., the toner supplying opening39). To be more specific, the left spiral portion36bconveys the toner4in +Y direction toward the toner supplying opening39, and the right spiral portion36cconveys the toner4in −Y direction toward the toner supplying opening39. The spiral36is made of, for example, a metal wire. To be more specific, the spiral36is made of, for example, a stainless steel (more specifically, SUS304-WPB).

FIG. 13Ais a bottom perspective view showing the toner cartridge5in a state where the toner supplying opening39is opened.FIG. 13Bis an enlarged view showing a part surrounded by a dashed line13B inFIG. 13A.FIG. 14Ais a front view showing the toner cartridge5.FIG. 14Bis a sectional view showing the toner cartridge5taken along line14B-14B inFIG. 14A.FIG. 14Cis an enlarged view showing a part surrounded by a dashed line14C inFIG. 14B.FIG. 15Ais a transparent plan view showing the toner cartridge5.FIG. 15Bis an enlarged view showing a part surrounded by a dashed line15B inFIG. 15A.

The toner supplying opening39is disposed at the substantially center portion of the toner cartridge5in the longitudinal direction of the toner cartridge5. The toner supplying opening39has an opening area39a(FIG. 14C) having a rectangular shape elongated in the longitudinal direction of the toner cartridge5(seeFIGS. 13A,13B and15A). Further, as shown inFIG. 14C, the toner supplying opening39has a depth to reach from the bottom inner circumferential surface38to a connecting portion46connected to the toner cartridge holding unit41(FIG. 9).

The toner supplying opening39is provided with a plurality of ribs58as shown inFIGS. 13B and 14C. The ribs58are disposed at a region in the toner supplying opening39on the same side as the bottom inner circumferential surface38. The ribs58are disposed at a predetermined interval in the direction of the rotation axis of the spiral36. The ribs58extend in a direction perpendicular to the rotation axis of the spiral36so that inner ends of the ribs58are aligned with the bottom inner circumferential surface38. A plurality of slits40are formed between the ribs58. The slits40extend in the direction perpendicular to the rotation axis of the spiral36, and are disposed at a predetermined interval in the direction of the rotation axis of the spiral36.

As shown inFIG. 15B, each slits40has an opening area in the form of an elongated rectangle along the bottom inner circumferential surface38. InFIG. 15B, L1indicates a length of a shorter edge (i.e., a slit width) of each slit40in the direction of the rotation axis of the spiral36. L2indicates a length of an arcuate longer edge (i.e., an edge on a plane perpendicular to the rotation axis of the spiral36) of each slit40. The ribs58are formed so that the length L1of the shorter edge is shorter than the length L2of the longer edge (i.e., L1<L2). For example, the length L1of the shorter edge is preferably in a range from 4 mm to 6 mm, and the length L2of the longer edge is preferably in a range from 10 mm to 15 mm. Further, a width d of each rib58in the direction of the rotation axis of the spiral36is preferably in a range from 1 mm to 2 mm.

The agitating portion36ais disposed at a position facing the slits40of the toner storage portion31. The left spiral portion36band the right spiral portion36c(i.e., conveying portions) are disposed at positions that do not face the slits40of the toner storage portion31.

Hereinafter, description will be made of an operation in which the toner4is supplied from the toner storage portion31of the toner cartridge5to the toner conveying path27(leading to the toner reservoir112of the developing device10shown inFIG. 2) via the toner supplying opening39with reference toFIGS. 2,8,13A through15B.

As shown inFIG. 14B, when the agitating member35rotates in a direction shown by an arrow C, the toner4stored in the toner storage portion31of the toner cartridge5is conveyed toward the spiral36. The toner4is then conveyed from both sides toward the toner supplying opening39at the center portion by the left spiral portion36band the right spiral portion36cof the spiral36rotating in the direction shown by the arrow A inFIG. 8. In this state, a conveying direction of the toner4is the same as the direction of the rotation axis of the spiral36.

Since the toner supplying opening39extends downward, the toner4conveyed by the spiral36to the vicinity of the toner storage opening39is introduced into the toner supplying opening39by gravity of the toner4or by conveying forces of the left and right spiral portions36band36c. The toner4which has not been introduced into the toner supplying opening39is moved by the agitating portion36ain a rotating direction of the spiral36. The agitating portion36aagitates the toner4by changing the conveying direction of the toner4. The agitating portion36arotates in proximity to or in contact with an inner circumferential surface of the toner storage portion31, and conveys the toner4toward the toner supplying opening39.

As the spiral36rotates to convey the toner4toward the toner storage opening39, an excessive amount of the toner4may be collected at the toner supplying opening39. In such a case, a pressure applied to the toner4may increase, and a part of the toner4may be agglomerated. However, in Embodiment 1, the ribs58provided in the toner supplying opening39prevents agglomeration of the toner4.

As shown inFIGS. 14C and 15B, the ribs58are provided along the inner circumferential surface of the toner storage portion31. Further, the ribs58extend in a direction perpendicular to the agitating portion36athat moves in proximity to or in contact with the inner circumferential surface of the toner storage portion31. Therefore, when the agitating portion36arotates to convey the toner4toward the toner supplying opening39, the agitating portion36arotates in proximity to or in contact with the ribs58. Accordingly, the agitating portion36aloosens the agglomerated toner and conveys the toner into the toner supplying opening39via the slits40. The toner4introduced into the toner storage opening39passes the toner conveying path27, and is stored in the toner reservoir112(FIG. 2) of the developing device10. Since the agglomerated toner4is loosened at the toner supplying opening39of the toner cartridge5, the non-agglomerated toner is stably supplied to the developing device10.

Here, a toner cartridge905of Comparison Example will be described. In the toner cartridge905of Comparison Example, the toner supplying opening39has ribs961extending in the direction parallel to the rotation axis of the spiral36.

FIG. 21Ais a perspective view showing the toner cartridge905of Comparison Example in a state where the toner supplying opening39is opened.FIG. 21Bis an enlarged view showing a part surrounded by a dashed line21B inFIG. 21A.FIG. 22Ais a front view showing the toner cartridge905of Comparison Example.FIG. 22Bis a sectional view showing the toner cartridge905taken along line22B-22B inFIG. 22A.FIG. 22Cis an enlarged view showing a part surrounded by a dashed line22C inFIG. 22B.FIG. 23Ais a transparent plan view showing the toner cartridge905of Comparison Example.FIG. 233is an enlarged view showing a part surrounded by a dashed line23B inFIG. 23A.

The spiral36of Comparison Example is the same as the spiral36of the toner cartridge5of Embodiment 1. The toner supplying opening39of Comparison Example has ribs961(i.e., referred to as parallel ribs961) extending in the direction parallel to the rotation axis of the spiral36, in addition to the ribs58extending in the direction perpendicular to the rotation axis of the spiral36. In the toner supplying opening39of Comparison Example, the ribs961and ribs58cross each other in a lattice manner. The provision of the parallel ribs961increases an amount of the toner4moving on the parallel ribs961among the toner4conveyed in the direction of the rotation axis by the left and right spiral portions36band36c. This leads to the same result as when the opening area of the toner supplying opening39decreases.

This results in reduction of the amount of the toner4supplied into the toner supplying opening39by the gravity of the toner4and by the conveying forces of the left and right spiral portions36band36c. Therefore, a pressure applied to the toner4moving toward the toner supplying opening39is likely to increase. That is, the agglomeration of the toner4may occur.

Further, although the agitating portion36aconveys the toner4toward the toner supplying opening39, lengths of the slits940(formed between the ribs58and the ribs961) in the rotating direction of the spiral36decrease because of the provision of the parallel ribs961. Therefore, an amount of the toner4conveyed by one rotation of the agitating portion36adecreases. Further, although the toner4is pushed through between the agitating portion36aand the ribs58and introduced into the toner conveying path27through between the ribs58, the amount of the toner4introduced into the toner conveying path27(by one rotation of the spiral36) decreases since gaps between the ribs58become smaller because of the provision of the parallel ribs61.

For this reason, in Embodiment 1, the ribs58of the toner supplying opening39are arranged at a predetermined interval in the direction of the rotation axis of the spiral36, and extend perpendicular to the rotation axis of the spiral36. Further, each slit40between the ribs58is formed so that the length L1of the shorter edge is shorter than the length L2of the longer edge (i.e., the arcuate longer edge). With such a configuration, the toner4conveyed by the spiral36can be effectively introduced into the toner supplying opening39, and the agglomeration of the toner4(due to the increase in pressure) can be prevented.

Next, a toner cartridge1005of Experimental Example will be described. The toner cartridge1005of Experimental Example has the toner supplying opening39provided with inclined ribs958.FIG. 16Ais a transparent plan view showing the toner cartridge1005of Experimental Example.FIG. 16Bis an enlarged view showing a part surrounded by a dashed line16B inFIG. 16A.

The spiral36of Experimental Example is the same as the spiral36of Embodiment 1. The ribs958of the toner supplying opening39of Comparison Example extend along the bottom inner circumferential surface38(FIG. 14C) of the toner storage portion31. The ribs958are inclined with respect to a circumferential direction B (i.e., the rotating direction) of the spiral36. To be more specific, the ribs958on both sides of a center portion of the toner storage portion31are inclined in opposite directions. In this example, the ribs958on the left side inFIG. 16Bare inclined at −10°, and the ribs958on the right side inFIG. 16Bare inclined at +10°.

In Experimental Example, a contact length over which the ribs958contact the agitating portion36ais larger as compared with a configuration in which the ribs958are not inclined. Therefore, the amount of the toner4which is loosened by one rotation of the spiral36increases. However, a total area of the ribs958relative to the opening area of the toner supplying opening39increases, and therefore the amount of the toner4introduced into the toner supplying opening39decreases.

For this reason, in Embodiment 1, the ribs58(958) of the toner supplying opening39are formed so that inner ends of the ribs58(958) extend along the bottom inner circumferential surface38(FIG. 14C) of the toner storage portion31. Further, if the ribs958are inclined with respect to the circumferential direction B of the spiral36(so that the ribs958on both side of the center portion are inclined in opposite directions), the inclination angle of the ribs958is preferably in a range of ±5°, and more preferably in a range of ±2°. It is experimentally confirmed that the agglomeration of the toner is prevented at a practically non-problematic level when the inclination angle of the ribs958is in these ranges.

In Embodiment 1, the spiral36is made of the metal wire wound in a spiral shape. However, the spiral36is not limited to such a structure. For example,FIG. 17shows a spiral150of Modification 1. The spiral150of Modification 1 is in the form of a screw, and is made of, for example, a molding material such as resin.

FIG. 18shows a toner cartridge of Modification 2.FIG. 19is a perspective view showing an agitating member151according to Modification 2. In Modification 2, the agitating member151is used instead of the spiral36. The agitating member151has a sheet member152. The sheet member152has inclined portions on both sides of a center portion facing the toner supplying opening39. The inclined portions of the sheet member152are inclined with respect to a rotation axis of the agitating member151. When the agitating member151rotates, the sheet member152of the agitating member151conveys the toner4from both sides toward the toner storage opening39. In Modification 2, the same effects as those of Embodiment 1 can be provided. The sheet member152is a flexible member. For example, the sheet member152is made of a polyester film, and has a thickness of 0.1 mm.

In Embodiment 1, the toner cartridge holding units41are formed as separate bodies from the developing device10, and are fixed to the printer100. Further, each toner cartridge holding unit41has a function to introduce the toner to the developing device10via the toner conveying path27. However, the present invention is not limited to such a configuration. For example,FIG. 20shows an image forming unit123(except a toner cartridge5) according to Modification 3. In Modification 3, the image forming unit123is provided with function components having the same function as the toner cartridge holding unit41except the toner conveying path27. The function components are directly provided on an upper side of the image forming unit123, and are integrally formed with the image forming unit123.

As described above, according to the printer of Embodiment 1, the agglomerated toner is loosened at the toner supplying opening. Therefore, a failure in ejection of the toner (caused by the agglomerated toner) can be prevented, and a toner supplying capacity can be maintained. Further, since the non-agglomerated toner can be supplied to the developing device, a high-quality printing can be achieved. Moreover, since the toner stored in the toner cartridge is loosened, the amount of the toner that remains in the toner storage portion when a lifetime of the toner cartridge expires can be reduced. Therefore, the toner stored in the toner cartridge can be effectively used, and a cost performance is enhanced.

FIG. 24Ais a transparent plan view showing a toner cartridge205according to Embodiment 2.FIG. 24Bis an enlarged view showing a part surrounded by a dashed line24B inFIG. 24A.FIG. 25is a perspective showing a spiral236provided in the toner cartridge205according to Embodiment 2.

The printer with the toner cartridge205of Embodiment 2 is different from the printer100(FIG. 1) of Embodiment 1 in a shape of a spiral236. Therefore, components of the printer of Embodiment 2 which are the same as those of the printer100of Embodiment 1 are assigned with the same reference numerals, and duplicate explanations will be omitted. Here, explanations will be focused on differences from Embodiment 1. Since the components of the printer of Embodiment 2 except the spiral236are the same as those of the printer100of Embodiment 1,FIGS. 1 through 15will be referred as necessary.

The spiral236is configured so that two main parts are substantially symmetrical to each other with respect to an imaginary plane at a center portion of the spiral236in a longitudinal direction (i.e., the Y direction). An agitating portion236ais formed at a center region of the spiral236. The agitating portion236ais in the form of a V-shape (i.e., a bent shape), and extends in the substantially longitudinal direction. A left spiral portion236band a right spiral portion236cextend from both ends of the agitating portion236a. The left spiral portion236band the right spiral portion236chave spiral shapes. The left spiral portion236band the right spiral portion236cand are wound in opposite directions.

InFIG. 24B, a portion where the agitating portion236ais connected to the left spiral portion236bis referred to as a left connecting portion236d. A portion where the agitating portion236ais connected to the right spiral portion236cis referred to as a right connecting portion236e.

The agitating portion236aincludes a left half part251and a right half part252. The left half part251extends from the left connecting portion236dat a predetermined angle (for example, 10°) with respect to a straight line parallel to the rotation axis of the spiral236. The straight line is defined on a tangent plane that contacts an imaginary cylindrical surface whose diameter is the same as an outer diameter of the spiral236and also contacts the left connecting portion236d. The right half part252extends from the right connecting portion236eat a predetermined angle (for example, 10°) with respect to a straight line parallel to the rotation axis of the spiral236. The straight line is defined on a tangent plane that contacts the imaginary cylindrical surface whose diameter is the same as an outer diameter of the spiral236and also contacts the right connecting portion236e. The left half part251and the right half part252are connected at a center point250of the agitating portion236ain the form of a V-shape that protrudes in the rotating direction (shown by an arrow A inFIG. 24B) of the spiral236.

Further, the left half part251and the right half part252of the agitating portion236ahave curved shapes along the imaginary cylindrical surface whose diameter is the same as an outer diameter of the spiral236. Therefore, the spiral236has a shape in which the main parts are substantially symmetrical to each other with respect to an imaginary plane passing through the center point250of the agitating portion236aand perpendicular to the rotation axis. In this regard, the inclination angle of each of the left and right half parts251and252is not limited to 10°. It is preferred that the inclination angle each of the left and right half parts251and252is less than or equal to 10°

An operation of the toner cartridge205of Embodiment 2 will be described.

As was described in Embodiment 1 with reference toFIG. 14B, the toner4stored in the toner storage portion31of the toner cartridge205is conveyed toward the spiral236by the rotation of the agitating member35in the direction shown by the arrow C (FIG. 14B). The toner4is then conveyed toward the toner storage opening39by the left spiral portion236band the right spiral portion236cof the spiral236rotating in the direction shown by the arrow A inFIG. 25. In this state, a conveying direction of the toner4is the same as the direction of the rotation axis of the spiral236.

Since the toner supplying opening39extends downward, the toner4conveyed by the spiral236to the vicinity of the toner storage opening39is introduced into the toner supplying opening39by gravity of the toner4or by conveying forces of the left and right spiral portions236band236c. The toner4which has not been introduced into the toner supplying opening39is moved by the agitating portion236ain directions shown by arrows D inclined to the left side and the right side at the predetermined angles (for example, 10°) with respect to the rotating direction of the spiral36. The agitating portion236aagitates the toner4by changing the conveying direction of the toner4. The agitating portion236arotates in proximity to or in contact with an inner circumferential surface of the toner storage portion31, and conveys the toner4toward the toner supplying opening39.

As the spiral236rotates to convey the toner4toward the toner storage opening39, the toner4of an excessive amount may be collected at the toner supplying opening39. In such a case, a pressure applied to the toner4may increase, and a part of the toner4may be agglomerated. However, in Embodiment 2, the ribs58provided in the toner supplying opening39prevents agglomeration of the toner4.

As shown inFIGS. 14C and 15B, the ribs58are provided along the inner circumferential surface of the toner storage portion31. Further, the ribs58extend in a direction almost perpendicular to (i.e., at an angle of 80° with respect to) the agitating portion236athat moves in proximity to or in contact with the inner circumferential surface of the toner storage portion31. Therefore, when the agitating portion236arotates to convey the toner4toward the toner supplying opening39, the agitating portion236arotates in proximity to or in contact with the ribs58. That is, the agitating portion236aloosens the agglomerated toner and conveys the toner into the toner supplying opening39via the slits40. The toner4introduced into the toner storage opening39passes the toner conveying path27, and is stored in the toner reservoir112of the developing device10(FIG. 2). Since the agglomerated toner4is loosened at the toner supplying opening39of the toner cartridge5, the non-agglomerated toner is stably supplied to the developing device10.

Further, in Embodiment 2, the left half part251and the right half part252of the agitating portion236aare inclined at the predetermined angle (in this example, 10°) in opposite directions as shown inFIG. 24B. Therefore, a contact length over which the rib58of the toner storage portion31contact the agitating portion236abecomes larger as compared a configuration in which the left and right half parts251and252are not inclined. Therefore, the amount of the toner4loosened by one rotation of the spiral236increases. In this regard, the inclination angle of each of the half parts251and252is not limited to 10°. It is preferred that the inclination angle of each of the half parts251and252is less than or equal to 10°. It is experimentally confirmed that the agglomeration of the toner is prevented at a practically non-problematic level when the inclination angle is in this range.

Moreover, when the agitating portion236arotates in proximity to or in contact with the ribs58, the toner4moving on the rib58is pushed into the slits40(between the ribs58) by the agitating portion236a. Therefore, the toner4is efficiently supplied to the toner supplying opening39. That is, the amount of the toner supplied by one rotation of the spiral236increases.

In Embodiment 2, the left and right half parts251and252of the agitating portion236aare connected at the center point250in the form of a V-shape (i.e., a bent shape) that protrudes in the rotating direction as shown by the arrow A inFIG. 25. However, the present invention is not limited to such a configuration. For example,FIGS. 26A and 26Bare a perspective view and a front view showing a spiral336according to Modification 4. The spiral336of Modification 4 has an agitating portion336aincluding left and right half parts251and252. The left and right half parts251and252are connected in the form of a V-shape (i.e., a bent shape) that protrudes in a direction opposite to the rotating direction (shown by the arrow A). It is preferred that the inclination angle of each of the half parts251and252is less than or equal to 10°.

Further,FIGS. 27A and 27Bare a perspective view and a front view showing a spiral436according to Modification 5. The spiral436of Modification 5 has an agitating portion436awhich is inclined as a whole at a predetermined angle (for example, 5°) in one direction.FIGS. 28A and 28Bare a perspective view and a front view showing a spiral536according to Modification 6. The spiral536of Modification 6 has an agitating portion536awhich is inclined as a whole at a predetermined angle (for example, 5°) in a direction opposite to the agitating portion436aof Modification 5.

Regarding Modifications 5 and 6, the “inclination angle” indicates, for example, an angle between the connecting portion at which the agitating portion and the left spiral portion are connected and a straight line parallel to the rotation axis of the spiral. The straight line is defined on a tangent plane that contacts an imaginary cylindrical surface whose diameter is the same as the outer diameter of the spiral and also contacts the left connecting portion. Further, the agitating portion is formed along the imaginary cylindrical surface whose diameter is the same as the outer diameter of the spiral. The inclination angle is not limited to 5°. The inclination angle is preferably less than or equal to 5°. It is experimentally confirmed that the agglomeration of the toner is prevented at a practically non-problematic level when the inclination angle is in this range.

As described above, according to Embodiment 2 of the present invention, the agitating portion of the spiral is inclined at the predetermined angle. Therefore, an ability to loosen the agglomerated toner and a toner supplying capacity can be enhanced. Accordingly, it becomes possible to prevent image blurring (caused by insufficient supplying of the toner) or other image failure, and to achieve a high-quality printing. Further, as the toner supplying capacity increases, a time10, period over which the toner stays in the toner cartridge becomes shorter. Therefore, an increase in pressure applied to the toner in the vicinity of the toner storage opening can be suppressed, and the agglomeration of the toner can be retarded. As a result, the printing quality can be maintained for a long time.

In the above described embodiments, the color electrophotographic printers have been described as examples of the image forming apparatus. However, the present invention is also applicable to other type of image forming apparatus such as a copier, a facsimile machine or an MFP (Multi-Function Peripheral). Further, the present invention is also applicable to an image forming apparatus (for example, a monochrome printer) that forms a monochrome image.

While the preferred embodiments of the present invention have been illustrated in detail, it should be apparent that modifications and improvements may be made to the invention without departing from the spirit and scope of the invention as described in the following claims.