Developing device, process cartridge and electrophotographic image forming apparatus having developer supply member passing through the developing opening

A developing device includes a developer carrying member for developing an electrostatic image with a developer, a developer container including a developer accommodating portion, a developing opening, and a developing chamber, and a developer supplying member that includes a shaft member, a first feeding member, and a second feeding member. The first feeding member has a length L1 measured in an axial direction of the developer carrying member and has a rotational radius R1 measured from a rotation center of the shaft member, and the second feeding member has a length L2. When a length of the developing opening is L3, a shortest length from the developing opening to the shaft member is L4, and a length from the developer carrying member to the shaft member is L5, the following relationships are satisfied: L1<L3<L2, and L4<R1<L5.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to an electrophotographic image forming apparatus, a developing device used in a main assembly of the electrophotographic image forming apparatus, and a process cartridge. The electrophotographic image forming apparatus forms an image on a recording material by using an electrophotographic image forming process. For example, the electrophotographic image forming apparatus includes an electrophotographic copying machine, an electrophotographic printer (LED printer, laser beam printer or the like), an electrophotographic facsimile machine, an electrophotographic word processor, or the like.

Further, the developing device is mounted in the main assembly of the electrophotographic image forming apparatus, and develops an electrostatic image formed on an electrophotographic photosensitive member. This developing device has a mounted constitution in which the developing device is mounted and used in the main assembly of the electrophotographic image forming apparatus or a developing cartridge constitution in which the developing device is detachably mountable to the main assembly of the electrophotographic image forming apparatus.

Further, the process cartridge is prepared by integrally assembling the electrophotographic photosensitive member and the developing device actable on the electrophotographic photosensitive member into a cartridge (unit), and is made detachably mountable to the main assembly of the electrophotographic image forming apparatus.

A conventional electrophotographic image forming apparatus using the electrophotographic image forming process employs a cartridge type. According to this cartridge type, a user can perform maintenance of the electrophotographic image forming apparatus by himself (herself) without relying on a service person, and therefore operativity of the maintenance can be remarkably improved.

In the process cartridge and the developing device which are used in the cartridge type, as a means for feeding a developer from a developer container to a developing means and for stirring the developer, a method of rotating an elastic sheet50as shown inFIG. 18is used. Specifically, in a developer accommodating portion21a, a stirring means26rotatable in an arrow RR direction is provided. Further, the stirring means26is constituted by a shaft member60as a base member and the elastic sheet50as a developer feeding member. Then, the shaft member60and the elastic sheet50are integrally rotated in the arrow RR direction, so that a toner T is fed from the developer accommodating portion21ato a developing chamber21athrough a developing opening21d. With respect to this stirring means, a constitution in which in order to prevent high density of the toner T in the developing chamber21c, an elastic sheet free end portion50aenters the developing chamber21cwhen it reaches the developing opening21d, and stirs the toner in the developing chamber21chas been known (Japanese Laid-Open Patent Application (JP-A) 2005-070363). The high density of the toner T in the developing chamber21cis referred to as a “toner packing”.

Further, in a constitution in which the developer accommodating portion21ais upsized to accommodate the toner T in a larger amount in the developer accommodating portion21a, a constitution in which a plurality of stirring means are provided in the developer accommodating portion21ahas been known (JP-A 2006-208433).

However, in the case where the developer accommodating portion is upsized, according to the constitution in JP-A 2005-070363, in order to stir the toner in the upsized developer accommodating portion by a single stirring means, there is a need to elongate the elastic sheet. As a result, the case where the elastic sheet free end portion enters the developing chamber to contact a developer carrying member exists, so that there was a liability that an image defect was caused. Therefore, in the conventional constitution, a dimension of the elastic sheet free end portion was strictly controlled. Further, according to the constitution of JP-A 2006-208433, the plurality of stirring means are provided, so that a cost is increased.

SUMMARY OF THE INVENTION

A principal object of the present invention is not only to feed a developer, accommodated in an upsized developer accommodating portion, to a developing chamber but also to stir the developer in the developing chamber with an inexpensive constitution.

According to an aspect of the present invention, there is provided a developing device comprising: a developer carrying member for developing an electrostatic image with a developer; a developer container including a developer accommodating portion for accommodating the developer, a developing opening and a developing chamber; and a developer supplying member for supplying the developer to the developing chamber through the developing opening, wherein the developer supplying member includes a shaft member rotatably supported by the developer accommodating portion and a feeding member, wherein the feeding member includes a first feeding portion which has a length L1measured in an axial direction of the developer carrying member and a radius R1measured from a rotation center of the shaft member, and includes a second feeding portion which has a length L2measured in the axial direction of the developer carrying member and a radius R2measured from the rotation center of the shaft member, and wherein when a length of the developing opening with respect to the axial direction of the developer carrying member is L3, a shortest length from the developing opening to the rotation center of the shaft member is L4, and a length from the developer carrying member to the rotation center of the shaft member is L5, the following relationships are satisfied:
L1<L3<L2, and
L4<R1<L5.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described specifically with reference to the drawings. However, with respect to functions, materials, shapes, relative arrangements and the like of constituent elements described in the following embodiments, the scope of the present invention is not intended to be limited to only the embodiments unless otherwise specified. Further, the materials, the shapes and the like of members which have already been described in the following description are the same as those first described in the following embodiment unless otherwise specified again.

A developing device, a process cartridge and an electrophotographic image forming apparatus according to the present invention will be described with reference to the drawings.

In the following description, a longitudinal direction of the process cartridge coincides with a rotational direction of an electrophotographic photosensitive member as an image bearing member and an axial direction of a developer carrying member. Further, a short direction of the process cartridge is a direction crossing a rotation shaft of the electrophotographic photosensitive member and coincides with a laser irradiation direction. Further, above and below the process cartridge mean those in a state the process cartridge is mounted in a main assembly of the image forming apparatus.

[General Structure of Image Forming Apparatus]

First, a general structure of an electrophotographic image forming apparatus1in this embodiment will be described with reference toFIG. 2.FIG. 2is a sectional view showing a structure of the image forming apparatus1. The image forming apparatus1shown inFIG. 2forms an image with a developer on a recording material P (such as recording paper, OHP sheet or cloth) depending on image information from an external device, such as a personal computer, communicatably connected with the image forming apparatus1.

A drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum)2is rotated in an arrow A direction, so that a surface of the photosensitive drum2is electrically charged uniformly by a charging roller3as a charging means. The photosensitive drum2is irradiated with laser light L emitted from an optical means (exposure means)4depending on image information, so that an electrostatic image depending on the image information is formed in the photosensitive drum2. The electrostatic image formed on the photosensitive drum2is developed with a toner T as a developer by a developer carrying member22described later, so that a toner image is formed.

On the other hand, in synchronism with formation of the toner image, the recording material P set in a feeding cassette6is separated and fed one by one by a pick-up roller7and a press-contact member9press-contactable to the pick-up roller7. Then, the recording material P is fed toward a transfer10as a transfer means along a feeding guide8. Then, the recording material P passes through a transfer nip N1formed by the photosensitive drum2and the transfer roller10to which a certain voltage is applied. At this time, the toner image formed on the photosensitive drum2is transferred onto the recording material P. The recording material P on which the toner image is transferred is fed along a feeding guide11into a fixing means12consisting of a driving roller12aand a fixing roller12cincorporating a heater12b. Then, heat and pressure are applied to the recording material P passing through a nip N2formed by the fixing roller12cand the driving roller12a, so that the transferred toner image is fixed on the recording material P. Thereafter, the recording material P is fed by a discharging roller pair13and is discharged onto a discharge tray14.

A process cartridge5detachably mountable to the image forming apparatus1in this embodiment will be described with reference toFIGS. 3 and 4.FIG. 3is a sectional view showing a structure of the process cartridge5, andFIG. 4is an exploded perspective view of the process cartridge5.

As shown inFIG. 3, the process cartridge5is constituted by a photosensitive unit30and a developing unit20as a developing device. The photosensitive unit30includes the photosensitive drum2, the charging roller3, a cleaning means (cleaning blade)31and the like. Further, the developing unit20includes a developer container21, a developer carrying member22, a developer layer thickness regulating means23and the like.

The electroconductive photosensitive drum2having the surface coated with a photosensitive layer is rotatably mounted in a cleaning (device) frame32of the photosensitive unit30via drum bearings37and positioning pins38(FIG. 4). Then, when a driving force is transmitted, depending on an image forming operation, to the photosensitive unit30from a driving motor (not shown) provided in the image forming apparatus1, the photosensitive drum2is rotated in an arrow A direction. Further, the charging roller3is urged by a spring34so that the charging roller3is contacted to the photosensitive drum2at a certain pressure with respect to a rectilinear line passing through centers of the charging roller3and the photosensitive drum2. In addition, the charging roller3electrically charges the surface of the photosensitive drum2uniformly by a voltage applied from the image forming apparatus1. Then, the charged photosensitive drum2is exposed to the laser light L from the optical means4, so that the electrostatic image is formed on the photosensitive drum2.

On the other hand, the developer container21constituting the developing unit20is formed by fixing the developing chamber24and a developing chamber cover29by ultrasonic welding or the like. The developing chamber21includes a developer accommodating portion21aaccommodating the toner T, a developing chamber21c, a partition wall portion21bpartitioning an inside of the developer container21into the developer accommodating portion21aand the developing chamber21c, and a developing opening21dthrough which the developer accommodating portion21aand the developing chamber21ccommunicate with each other. Further, a stirring means26as a developer supplying member is rotatably supported by the developer container21, and by rotation of the stirring means26, the toner T is fed from the developer accommodating portion21ainto the developing chamber21cthrough the developing opening21d. The developer carrying member22is rotatably supported by the developer container21as specifically described later. The developer carrying member22incorporates a fixed magnet27, and by a magnetic force of the fixed magnet27, the toner T in the developing chamber21cis attracted to the surface of the developer carrying member22. Further, the regulating means23is fixed to the developer container21so as to elastically contact the developer carrying member22at a certain contact pressure. Then, the regulating means23regulates an amount of the toner T deposited on the developer carrying member22and imparts triboelectric charges to the toner T. As a result, a developer layer is formed on the surface of the developer carrying member22. Further, a blow-off preventing sheet25is mounted on the developer container21so as to contact the developer carrying member22to prevent leakage-out of the toner T from between the developing chamber21cand the developer carrying member22. The developer carrying member22to which a voltage is applied from the image forming apparatus1rotates in an arrow B direction, so that the toner T is transferred therefrom onto the photosensitive drum2depending on the electrostatic image to visualize the electrostatic image on the photosensitive drum2, and thus forms a developer image.

Further, a cleaning blade31is fixed and supported by the cleaning frame32and is provided so that a free end31bof the cleaning blade31is elastically contacted to the photosensitive drum2at a certain contact pressure. Then, the cleaning blade31scrapes off the developer T remaining on the photosensitive drum2after the developer image is transferred onto the recording material P. The developer T which is scraped off is accommodated in a residual toner accommodating portion32a. Further, a receptor sheet39is mounted on the cleaning frame32so as to be contacted to the photosensitive drum2to prevent leakage-out of the developer T from between the residual toner accommodating portion32aand the photosensitive drum2.

As shown inFIG. 4, the developer carrying member22is rotatably supported by the developer container21via developing bearings28aand28cmounted at longitudinal end portions of the developer container21.

Further, the developer carrying member22is provided with spacer rollers40aand40bwhich are gap holding members rotatably supported at ends thereof with respect to a longitudinal direction (axial direction) in order to keep a certain clearance from the photosensitive drum2.

The developing bearing28aand28bare provided with holes28a1and28b1, respectively. Thus, the developing unit20is provided with holes28a1and28b1. The photosensitive unit30is provided with holes30aand30bat longitudinal ends thereof. Further, the holes28a1and30aare rotatably connected by a connecting shaft35aas a connecting member, and the holes28b1and30bare rotatably connected by a connecting shaft35bas the connecting member. As a result, the developing unit20is supported by the photosensitive unit30rotatably about the connecting shafts35aand35b. To the supporting portions20aand20bprovided at the longitudinal end portions of the developing unit20, one end portion36a1of a pressing spring36aand one end portion36b1of a pressing spring36bare mounted, respectively. Further, when the developing unit20and the photosensitive unit30are connected by the connecting shafts35aand35b, the other end portion36a2of the pressing spring36acontacts a receiving surface30cof the photosensitive unit30. Similarly, the other end portion36b2of the pressing spring36bcontacts a receiving surface30dof the photosensitive unit30. Then, the pressing springs36aand36bare compressed between the receiving surfaces30cand30dof the photosensitive unit30and the supporting portions20aand20bof the developing unit20. For this reason, the developing unit20is urged toward the photosensitive drum2by moment D around the connecting shafts35aand35b. At that time, the above-mentioned spacer rollers40aand40bcontact the photosensitive drum2, so that the photosensitive drum2and the developer carrying member22are held with the certain clearance.

In this embodiment, a gear portion (not shown) of the photosensitive drum2and a drive transmitting portion (not shown) such as a gear provided to the developing unit20are engaged with each other, so that the driving force is transmitted from the photosensitive drum2to the developer carrying member (developing roller)22and the stirring means26. The developing roller22and the like may also be rotated by a means for directly driving the developing roller22and the like from the image forming apparatus1or by the like means.

A structure of the stirring means26in this embodiment will be described with reference toFIGS. 1 and 5.FIG. 1is a sectional view, of the developing unit20, showing the structure of the stirring means26.FIG. 5is a schematic view showing structures of the stirring means26and the developing opening21dand a positional relationship between the stirring means26and the developing opening21d.

As shown inFIG. 1, the stirring means26is constituted by a shaft member60as a base member (substrate) and a feeding member fixed on the shaft member60. The feeding member is constituted by a first elastic sheet51as a first feeding portion and a second elastic sheet52as a second feeding portion. A free end portion51aof the first elastic sheet51passes through the developing opening21dand feeds the toner T in the developing chamber21c. A free end portion52aof the second elastic sheet52feeds the toner in the developer accommodating portion21a. Specifically, the first elastic sheet51has the first elastic sheet free end portion51ahaving a distance R1as a radius from a rotation center Z of the shaft member60, and the second elastic sheet52has the second elastic sheet free end portion52ahaving a distance R2as a radius from the rotation center Z. The first elastic sheet51is rotated by rotation of the shaft member60about the rotation center Z in a rotational direction RR, and can feed and stir the toner T in a feeding region D1which is a locus drawn by the elastic sheet free end portion51a.

The developer accommodating portion21aand the developing chamber21care partitioned by a side21f, of the developer accommodating portion21, connected with the developing opening21dand an accommodating portion-side opening region21d3, of the developer accommodating portion21, which is a region overlapping with the developing opening21d. The side21fand the opening region21d3constitute a boundary between the developer accommodating portion21aand the developing chamber21c. A length from the rotation center Z of the shaft member60to an opening downstream end portion21d2, in the accommodating portion-side opening region21d3, which is a downstream end portion with respect to the rotational direction is a distance L4, and length from the rotation center Z to the developer carrying member22is a distance L5. The distance L4is the shortest distance from the rotation center Z to the region21d3. The distance L4may also be a distance from the rotation center Z of the shaft member60to an edge, of the developer container21, defining the developing opening21dor a distance from the rotation center Z to a center of a space of the developing opening21d. The above-mentioned distances are set to satisfy the following relationship:
(distance L4)<(distance R1)<(distance L5)<(distance R2)

Further, as shown inFIG. 5, when a longitudinal length of the first elastic sheet51is a distance L1, a longitudinal length of the second elastic sheet52is a distance L2, and a longitudinal length of the developing opening21dis a distance L3, these distances are set to satisfy the following relationship:
(distance L1)<(distance L3)<(distance L2).

By satisfying the above relationships, the first elastic sheet free end portion51acan pass through the developing opening21dand therefore can enter the developing chamber21c. Then, the free end portion51acan loosen the toner T in the developing chamber21cwithout contacting the developer carrying member22, so that a degree of the toner packing can be reduced. On the other hand, the second elastic sheet free end portion52acannot pass through the developing opening21d, and therefore cannot enter the developing chamber21a. Therefore, also the free end portion52adoes not contact the developer carrying member22.

Behavior of the stirring means26in this embodiment will be described with reference toFIGS. 6 to 12.FIGS. 6, 7 and 9are sectional views, of the developing unit20, showing the behavior of the stirring means26relative to the developing opening21d.FIG. 8is a perspective view showing a relationship between the second elastic sheet52and the developing opening21d.FIG. 10is a perspective view showing a relationship among the first elastic sheet51, the second elastic sheet52and the developing opening21d.FIG. 11is an illustration showing the structures of the stirring means26and the developing opening21dand a longitudinal positional relationship between the stirring means26and the developing opening21d.FIG. 12is a sectional view, taken along a line S-S inFIG. 11, showing a relationship between the first elastic sheet51and the second elastic sheet52.

First, the behavior of the first elastic sheet51will be described with reference toFIGS. 6 and 7.

As shown in (a) ofFIG. 6, by the rotation of the shaft member60in the rotational direction RR, the first elastic sheet51contacts a bottom shape29bwhen being positioned at a lower portion of the developer accommodating portion21a. Then, the first elastic sheet51stirs and feeds the toner T deposited in the developer accommodating portion21ain a flexed state, and approaches the developing opening21d. Then, the first elastic sheet free end portion51aof the first elastic sheet51passes through the opening upstream end portion21d1which is an upstream end portion of the developing opening21dwith respect to the rotational direction RR of the stirring means26, the first elastic sheet51is released from the flexed state. As a result, as shown in (b) ofFIG. 6, the first elastic sheet free end portion51aenters the developing chamber21c. The first elastic sheet free end portion51aenters the developing chamber21c, whereby the first elastic sheet free end portion51acan also stir the toner T in the developing chamber21c, so that the toner packing in the developing chamber21ccan be prevented. Thereafter, as shown in (a) ofFIG. 7, the shaft member60further rotates in the rotational direction RR, so that the first elastic sheet51contacts the opening downstream end portion21d2wand then moves into the developer accommodating portion21awhile being flexed again.

Then, when the first elastic sheet free end portion51apasses through the opening downstream end portion21d2, the first elastic sheet51is released from the flexed state, and then returns to the developer accommodating portion21aas shown in (b) ofFIG. 7.

Thereafter, by repeating this operation, the first elastic sheet51feeds the toner T, in the feeding region D1in the developer accommodating portion21a, to the developing chamber21c, and stirs the toner T in the developing chamber21cwithout contacting the developer carrying member22.

Next, with reference toFIGS. 6 to 9, the behavior of the second elastic sheet52relative to the developing opening21dwill be described.

As shown in (a) ofFIG. 6, the shaft member60rotates in the rotational direction RR, so that the second elastic sheet52contacts the bottom shape29bwhen the second elastic sheet52is positioned at the lower portion of the developer accommodating portion21a. Then, in a flexed state of the second elastic sheet52, the second elastic sheet52sandwiches the toner T, outside the feed region D1of the first elastic sheet51, between itself and the bottom shape29b, and then approaches the developing opening21d.

However, when the second elastic sheet52passes through the opening upstream end portion21d1, as shown inFIG. 8, the second elastic sheet52contacts end portion walls21eprovided at longitudinal end portions of the developing opening21d. As a result, the second elastic sheet free end portion52acannot enter the developing chamber21c, so that the second elastic sheet52continuously rotates in the developer accommodating portion21atogether with the rotation of the shaft member60in the rotational direction RR.

Therefore, as shown in (b) ofFIG. 7, the second elastic sheet52does not enter the developing chamber21cand does not contact the developer carrying member22, so that the second elastic sheet52can feed the toner T, outside the feeding region D1of the first elastic sheet51, into the feeding region D1.

As shown in (b) ofFIG. 7, when a length from the rotation center Z of the shaft member60to the opening upstream end portion21d1of the developing opening21dis a distance L7, the distances L7and R1are set to satisfy the relationship of: (distance L7)<(distance R1). By setting the relationship of: (distance L7)<(distance R1), all the toner T fed into the feed region D1by the second elastic sheet52in the developer accommodating portion21acan be fed into the developing chamber21cby the first elastic sheet free end portion51aof the first elastic sheet51.

Further, as shown inFIG. 9, when a length from the rotation center Z to a lowest rear surface point21f1, which is a remotest point of the developer accommodating portion21a, is a distance L6, the distances L6and R2are set to satisfy the relationship of: (distance L6)<(distance R2). By setting the relationship of: (distance L6)<(distance R2), all the toner T in the developer accommodating portion21acan be fed into the feeding region D1of the second elastic sheet52.

Further, in order to cause the first elastic sheet51to enter the developing chamber21c, with respect to the rotational direction RR of the shaft member60, there is a need to provide the first elastic sheet51in a downstream side and the second elastic sheet52in an upstream side. As shown inFIG. 10, in the case where the first elastic sheet51is set in the upstream side and the second elastic sheet52is set in the downstream side, when the shaft member60rotates in the rotational direction RR, the second elastic sheet52contacts the end portion walls21e, thus blocking the developing opening21d. As a result, the first elastic sheet51cannot enter the developing chamber21c. Therefore, in the case where the first elastic sheet51and the second elastic sheet52are mounted on the same surface of the shaft member60, as in this embodiment, it is desirable that the first elastic sheet51is positioned in the downstream side relative to the toner T and the second elastic sheet52is positioned in the upstream side relative to the toner T.

Further, in the case where the second elastic sheet52is set in the downstream side relative to the toner T, as shown inFIGS. 11 and 12, the second elastic sheet52may also be provided with a hole58through which the first elastic sheet51can pass through the second elastic sheet52. As a result, when the shaft member60rotates in the rotational direction RR, the second elastic sheet52does not block the developing opening21d. Further, the first elastic sheet51and the second elastic sheet52may also be mounted on different surfaces of the shaft member60so that the second elastic sheet52does not block the developing opening21dwhen the shaft member60rotates in the rotational direction RR. In this embodiment, the first elastic sheet51and the second elastic sheet52are provided on the same surface of the shaft member60, but the present invention is not limited thereto, and the first elastic sheet51and the second elastic sheet52may also be fixed on different surfaces, respectively. Further, in the case where the shaft member60has a circular shape in cross-section, the first elastic sheet51and the second elastic sheet52may also be provided at different phases, respectively.

As described above, the distances are set to satisfy the relationships of: (distance L4)<(distance R1)<(distance L5), and (distance L1)<(distance L3)<(distance L2). As a result, with an inexpensive constitution, it is possible to not only cause the stirring means to contact the developer carrying member to permit stirring of the toner in the upsized developer accommodating portion and feeding of the toner into the developing chamber but also stir the toner in the developing chamber.

In this embodiment, the relationship of: (distance L4)<(distance R1)<(distance L5)<(distance R2) is set, but the relationship is not particularly limited to this relationship.

Next, with reference toFIGS. 13 to 15, other shapes of the second elastic sheet52will be described.FIG. 13is a cross-sectional view of the developing unit20for illustrating a structure of a second elastic sheet55.FIG. 14is an illustration showing structures of a second elastic sheet56and the developing opening21dand a longitudinal positional relationship between the second elastic sheet56and the developing opening21d.FIG. 15is a cross-sectional view, of the developing unit20, showing feeding of the toner T when the second elastic sheet56is cut along U-U cross-section inFIG. 14.

As shown inFIG. 13, in order to enhance a toner feeding property of the second elastic sheet55, a second elastic sheet free end portion55awhich is a free end of the second elastic sheet55may also be provided with a bent shape55b. By providing the bent shape55b, a surface55b1of the bent shape55bcan contact the toner T, and therefore compared with a constitution in which the bent shape55bis not provided, a contact area between the second elastic sheet (feeding portion)55and the toner T is increased, so that the toner T feeding property can be improved.

Further, the shape for enhancing the toner T feeding property is not limited to the bent shape55b, but as shown inFIG. 14, the second elastic sheet56may also be provided with holes56b. By providing the second elastic sheet56with the holes56b, as shown inFIG. 15, a surface56b1defined by the holes56bcan contact the toner T. For that reason, compared with the constitution in which the holes56bare not provided, a contact area between the second elastic sheet56and the toner T is increases, so that the toner T feeding property can be improved. The shape of the holes56bis not limited to a rectangular shape, but may also be a circular shape or the like.

Further, as shown inFIG. 14, at end portions of the holes56b, inclined surfaces56c1and56c2along which the toner T is to be moved toward a central portion of the developer carrying member22may also be provided. By providing the inclined surfaces56c1and56c2, when the shaft member60is rotated in the rotational direction RR, with respect to the toner T contacting each of the inclined surfaces56c1and56c2, a feeding force FF in a direction perpendicular to the associated inclined surface56c1or56c2generates. This feeding force FF includes a feed component force FF2which is a component force, of the feeding force FF, in a direction substantially parallel to the longitudinal direction, and therefore the toner T is moved from longitudinal end portions toward the longitudinal central portion. Therefore, also the toner T outside the developing opening21dwith respect to the longitudinal direction can be fed through the developing opening21dby the first elastic sheet51, so that it is possible to prevent the toner T from remaining at the longitudinal end portions.

Further, inFIGS. 14 and 15, as the shape of the holes provided in the second elastic sheet, the structure having the through holes56bis illustrated, but the shape of the holes provided in the second elastic sheet is not limited thereto. For example, a structure in which a non-through hole portion (recessed portion) is provided on the downstream surface of the second elastic sheet with respect to the rotational direction may also be employed, and also by this structure, a similar effect can be obtained.

A structure of a stirring means in a developing device according to Embodiment 2 will be described with reference toFIGS. 16 and 17.FIGS. 16 and 17are schematic views showing structures of an elastic sheet150and a developing opening121dand a longitudinal positional relationship between the elastic sheet150and the developing opening121d.

In Embodiment 1, the first elastic sheet51and the second elastic sheet52are described as the separate members, but the present invention is not limited thereto. In this embodiment, the stirring means is constituted by a flexible single sheet member including a first feeding portion and a second feeding portion. Specifically, as shown inFIG. 16, the elastic sheet150is provided with a cut-away portion K2to define a first elastic sheet portion151as the first feeding portion and a second elastic sheet portion152as the second feeding portion which are formed with the same member (flexible single sheet member). By forming the first elastic sheet portion151and the second elastic sheet portion152with the same member, the present invention can be carried out with an inexpensive constitution compared with the case of the separate members.

Further, as shown inFIG. 17, at a longitudinal central portion of an elastic sheet150, a connecting portion155is provided, so that rigidity of a second elastic sheet portion152can be improved. Therefore, the toner feeding force of the second elastic sheet portion152during rotation of a shaft member160can be improved.

By the above-described constitution, with an inexpensive constitution compared with Embodiment 1, it is possible to not only stir the toner in the upsized developer accommodating portion and feed the toner into the developing chamber but also stir the toner in the developing chamber without bringing the stirring means into contact with the developer carrying member.

In the above-described embodiments, as the process cartridge detachably mountable to the main assembly of the image forming apparatus, the process cartridge integrally including the photosensitive drum, and the charging means, the developing means and the cleaning means which are the process means actable on the photosensitive drum was described as an example. However, the process cartridge is not limited thereto. For example, a process cartridge including, in addition to the photosensitive drum, either one of the charging means, the developing means and the cleaning means may also be used.

Further, in the above-described embodiments, the constitution in which the process cartridge including the photosensitive drum is detachably mountable to the main assembly of the image forming apparatus was described as an example. For example, it is also possible to use an image forming apparatus in which respective constituent members are incorporated or an image forming apparatus in which each of the constituent members is detachably mounted.

Further, in the above-described embodiments, the printer was described as an example, but the present invention is not limited thereto. For example, other image forming apparatuses such as a copying machine, a facsimile machine and a multi-function machine having functions of these machines may also be used. By applying the present invention to these image forming apparatuses, it is possible to obtain a similar effect.

According to the present invention, it is possible to not only feed the developer, in the upsized developer accommodating portion, into the developing chamber but also stir the developer in the developing chamber with an inexpensive constitution.

This application claims priority from Japanese Patent Applications Nos. 014167/2014 filed Jan. 29, 2014 and 228903/2014 filed Nov. 11, 2014, which are hereby incorporated by reference.