Patent Description:
Conventionally, in an image forming apparatus using an electrophotographic image forming process, a photosensitive drum and process parts actable on the photosensitive drum are unfixed into a cartridge. Further, a process cartridge type in which this cartridge is detachably mountable to an apparatus main assembly of the image forming apparatus is employed.

According to this process cartridge type, maintenance of the image forming apparatus can be performed by a user himself (herself). As a result, an operationality can be improved remarkably and the process cartridge type is widely used in image forming apparatuses.

In a full-color electrophotographic image forming apparatus using a transfer belt (intermediary transfer belt), a constitution in which a plurality of process cartridges are arranged below the transfer belt is used. This is because in the case of a constitution in which a print is discharged onto an upper surface of the image forming apparatus, by disposing the process cartridges below the transfer belt, a first print time can be shortened. As a process cartridge corresponding to this constitution, a constitution in which a developing chamber is disposed at an upper portion close to the transfer belt and a developer is scooped up, to the developing chamber, from a developer accommodating chamber disposed below the developing chamber is used (<CIT>).

In this process cartridge, by providing a stirring member in the developing chamber, circulation of the developer in the developing chamber is improved, so that the developer is efficiently supplied to the developing roller above the developing chamber to reduce an amount of a residual developer.

However, in the constitution of <CIT>, there was a need to provide the stirring member in the developing chamber in a side below a contact portion between a developing roller and a developer supplying roller in the developing chamber. Therefore, the developer supplying roller for supplying the developer to the developing roller is rotated in a rotational direction opposite to rotational direction of the developing roller, so that circulation of the developer is made equivalent to or more than a conventional level without providing the stirring member in the developing chamber, and a supplying property of the developer from the developer supplying roller to the developing roller can be satisfied. According to this constitution, a space conventionally ensured for disposing the stirring member can be filled, and therefore a residual of the developer can be further suppressed.

<CIT> shows a generic process cartridge according to the preamble of claim <NUM>. The process cartridge is detachably mountable to a main assembly of an image forming apparatus, the process cartridge comprising: a rotatable developing roller a rotatable developer supplying roller provided in contact with the developing roller and configured to supply a developer to the developing roller; a developer accommodating chamber configured to accommodate the developer; a developing chamber in which the developer supplying roller is provided; a rotatable feeding member provided in the developer accommodating chamber and configured to feed the developer from the developer accommodating chamber into the developing chamber by moving the developer upwardly against a gravity; and a driving force receiving portion configured to receive a driving force for rotating the developer supplying roller, the developing roller and the feeding member.

Further process cartridges according to the prior art are shown in <CIT> and <CIT>.

It is the object of the present invention to further develop a generic process cartridge according to the preamble of claim <NUM> such that a developer peeling-off property from a developing roller is improved.

The object of the present invention is achieved by a process cartridge having the features of claim <NUM>.

It is an advantage of the present invention to provide a process cartridge in which in a constitution that a developer is scooped up from a developer accommodating chamber, provided below a developing chamber, to the developing chamber above the developer accommodating chamber, it is possible to realize reduction of a residual developer while reducing the number of parts.

Hereinbelow, preferred embodiments of the present invention will be exemplarily and specifically described with reference to the drawings. However, dimensions, materials, shapes, relative arrangements and the like of constituent elements described in the following embodiments are appropriately changed depending on constitutions or various conditions of devices (apparatuses) to which the present invention is applied, i.e. the scope of the present invention is defined by the appended claims.

In the following, an image forming apparatus according to an embodiment of the present invention and a process cartridge used therein will be described in accordance with the drawings.

First, a general structure of an electrophotographic image forming apparatus (hereinafter referred to as an "image forming apparatus") <NUM> will be described using <FIG>. As shown in <FIG>, detachably mountable four process cartridges <NUM> (70Y, <NUM>, 70C, <NUM>) are detachably mounted by mounting members (unshown). Further, an upstream side of the process cartridge <NUM> with respect to a mounting direction to the image forming apparatus <NUM> is defined as a front (surface) side, and a downstream side of the process cartridge <NUM> with respect to the mounting direction is defined as a rear (surface) side. In <FIG>, the respective process cartridges <NUM> are inclined and juxtaposed in an apparatus main assembly 100A with respect to a horizontal direction ht.

The process cartridge <NUM> includes electrophotographic photosensitive drums (hereinafter referred to as "photosensitive drums") <NUM> (1a, 1b, 1c, 1d), and at a periphery of the photosensitive drums <NUM>, process means such as charging rollers <NUM> (2a, 2b, 2c, 2d), developing rollers <NUM> (25a, 25b, 25c, 25d), and cleaning members <NUM> (6a, 6b, 6c, 6d) are integrally provided.

The charging roller <NUM> electrically charges the surface of the photosensitive drum <NUM> uniformly, and the developing roller <NUM> develops a latent image, formed on the photosensitive drum <NUM>, with a toner to visualize the latent image. The cleaning member <NUM> removes the toner remaining on the photosensitive drum <NUM> after a toner image formed on the photosensitive drum <NUM> is transferred onto a recording material (medium).

Further, below the process cartridges <NUM>, a scanner unit <NUM> for forming the latent image on the photosensitive drums <NUM> by subjecting the photosensitive drums <NUM> to selective exposure to light on the basis of image information is provided.

At a lower portion of the apparatus main assembly 100A, a cassette <NUM> in which sheets of the recording material S are accommodated is mounted. Further, a recording material feeding portion is provided so that the recording material S can be fed to an upper portion of the apparatus main assembly 100A by being passed through a secondary transfer roller <NUM> and a fixing portion <NUM>. That is, a feeding roller <NUM> for separating and feeding the sheets of the recording material S in the cassette <NUM> in a one-by-one manner, a feeding roller pair <NUM> for feeding the fed recording material S, and a registration roller pair <NUM> for synchronizing the latent image formed on the photosensitive drum <NUM> with the recording material S are provided.

Further, above the process cartridges <NUM> (70Y, <NUM>, 70C, <NUM>), an intermediary transfer unit <NUM> as an intermediary transfer means onto which the toner image formed on each of the photosensitive drums <NUM> (1a, 1b, 1c, 1d) is to be transferred is provided. The intermediary transfer unit <NUM> includes a driving roller <NUM>, a follower roller <NUM>, primary transfer rollers <NUM> (58a, 58b, 58c, 58d) at positions opposing the photosensitive drums <NUM> for the respective colors, and an opposite roller <NUM> at a position opposing the secondary transfer roller <NUM> are provided. Around these rollers, a transfer belt (intermediary transfer belt) <NUM> is extended and stretched.

Further, the transfer belt <NUM> is circulated and moved so as to oppose and be contacted to all of the photosensitive drums <NUM>, so that primary transfer (of the toner images) from the photosensitive drums <NUM> onto the transfer belt <NUM> is made by applying a voltage to the primary transfer rollers <NUM> (58a, 58b, 58c, 58d). Then, by voltage application to the secondary transfer roller <NUM> and the opposite roller <NUM> disposed inside the transfer belt <NUM>, the toner images are transferred from the transfer belt <NUM> onto the recording material S.

During image formation, while rotating each of the photosensitive drums <NUM>, the photosensitive drum <NUM> uniformly charged by the charging roller <NUM> is subjected to selective exposure to light emitted from the scanner unit <NUM>. By this, an electrostatic latent image is formed on the photosensitive drum <NUM>. The latent image is developed by the developing roller <NUM>. By this, the toner images of the respective colors are formed on the photosensitive drums <NUM>, respectively. In synchronism with this image formation, the registration roller pair <NUM> feeds the recording material S to a secondary transfer position where the secondary transfer roller <NUM> opposing the opposite roller <NUM> is contacted to the transfer belt <NUM>.

Then, by applying a transfer bias voltage to the secondary transfer roller <NUM>, the respective color toner images are secondary-transferred from the transfer belt <NUM> onto the recording material S. By this, a color image is formed on the recording material S. The recording material S on which the color image is formed is heated and pressed by the fixing portion <NUM>, so that the toner images are fixed on the recording material S. Thereafter, the recording material S is discharged onto a discharge portion <NUM> by a (sheet-) discharging roller pair <NUM>. The fixing portion <NUM> is disposed at an upper portion of the apparatus main assembly 100A.

Next, the process cartridge <NUM> in this embodiment will be described with reference to <FIG>.

<FIG> is a principal sectional view of the process cartridge <NUM> in which the toner is accommodated. Incidentally, the process cartridge 70Y accommodating the toner of yellow, the process cartridge <NUM> accommodating the toner of magenta, the process cartridge 70C accommodating the toner of cyan, and the process cartridge <NUM> accommodating the toner of black have the same constitution.

The respective process cartridges <NUM> (70Y, <NUM>, 70C, <NUM>) include drum units <NUM> (26a, 26b, 26c, 26d) as a first unit and developing units <NUM> (4a, 4b, 4c, 4d) as a second unit. The drum unit <NUM> includes the photosensitive drum <NUM> (1a, 1b, 1c, 1d), the charging roller <NUM> (2a, 2b, 2c, 2d) and the cleaning member <NUM> (6a, 6b, 6c, 6d). Further, the developing unit <NUM> includes the developing roller <NUM>.

To a cleaning frame <NUM> of the drum unit <NUM>, the photosensitive drum <NUM> is rotatably mounted via a front drum bearing <NUM> and a rear drum bearing <NUM>. The photosensitive drum <NUM> is provided with a drum coupling <NUM> and a flange <NUM> at an end portion thereof.

On a circumferential surface of the photosensitive drum <NUM>, as described above, the charging roller <NUM> and the cleaning member <NUM> are disposed. The cleaning member <NUM> is constituted by an elastic member formed with a rubber blade and a cleaning supporting member <NUM>. A free end portion of the elastic member disposed in contact with the photosensitive drum <NUM> counter directionally to a rotational direction of the photosensitive drum <NUM>. Further, a residual toner removed from the surface of the photosensitive drum <NUM> by the cleaning member <NUM> falls into a removed toner chamber 27a. Further, a receptor sheet <NUM> for preventing leakage of the removed toner in the removed toner chamber 27a is contacted to the photosensitive drum <NUM>.

By transmitting a driving force of a main assembly driving motor (not shown) as a driving source to the drum unit <NUM>, so that the photosensitive drum <NUM> is rotationally driven depending on an image forming operation. The charging roller <NUM> is rotatably mounted to the drum unit <NUM> via a charging roller bearing <NUM> and is urged against the photosensitive drum <NUM> by a charging roller urging member <NUM>, thus being rotated by the rotation of the photosensitive drum <NUM>.

The developing unit <NUM> includes the developing roller <NUM>, rotating in contact with the photosensitive drum <NUM> in an arrow B direction, and a developing device frame <NUM> for supporting the developing roller <NUM>. Further, the developing unit <NUM> is constituted by a developing chamber 31b in which the developing roller <NUM> is disposed and by a toner accommodating portion 31c, disposed below the developing chamber 31b with respect to the direction of gravity in a state in which the process cartridge is mounted in the image forming apparatus, as a developer accommodating container for accommodating the toner. These chambers (portions) are partitioned by a partition wall 31d. The toner accommodating portion <NUM> is positioned below the developing roller <NUM> and the developer supplying roller with respect to the direction of gravity. Further, the partition wall 31d is provided with an opening 31e through which the toner passes when the toner is fed from the toner accommodating portion 31c to the developing chamber 31b. The developing roller <NUM> is rotatably supported by the developing (device) frame <NUM> via a front developing (means) bearing <NUM> and a rear developing (means) bearing <NUM> provided in both sides of the developing device frame <NUM>, respectively (<FIG>).

Further, on a peripheral surface of the developing roller <NUM>, a developer supplying roller <NUM> rotatable in contact with the developing roller <NUM> in an arrow E direction, and a developing blade <NUM> for regulating a toner layer on the developing roller <NUM> are provided.

The developer supplying roller <NUM> is constituted by a metal-made developer supplying roller shaft 34j and a sponge portion 34a which is an elastic portion for covering an outer peripheral surface of the shaft in an exposed state at end portions. The developer supplying roller <NUM> is disposed so that the sponge portion 34a is in contacted to the developing roller <NUM> with a predetermined penetration amount into the developing roller <NUM>. Further, a leakage-out preventing sheet <NUM> as a developing (means) contact sheet for preventing leakage-out of the toner from the developing frame <NUM> contacting the developing roller <NUM> is provided.

Further, in the toner accommodating portion 31c in the developing frame <NUM>, a toner feeding member <NUM> which is a feeding means for feeding the toner into the developing chamber 31b through the opening 31e while stirring the toner accommodated in the toner accommodating chamber 31c is provided.

As described above, the toner accommodating portion 31c is provided below with respect to the direction of gravity, and therefore also the toner feeding member <NUM> is positioned below the developing chamber 31b with respect to the direction of gravity. That is, the developing chamber <NUM> in this embodiment has a toner scooping-up constitution in which the toner is fed by the toner feeding member <NUM> against gravitation from the toner accommodating portion 31c disposed at a lower portion with respect to the direction of gravity to the developing chamber 31b disposed at an upper portion of the toner accommodating portion 31c with respect to the direction of gravity.

<FIG> is a general perspective view of the process cartridge <NUM>. <FIG> is a general perspective view of the developing unit <NUM>. To the drum unit <NUM>, the developing unit <NUM> is rotatably mounted. A front supporting pin <NUM> and a rear supporting pin <NUM> which are press-fitted in the cleaning frame <NUM> are engaged with hang holes 12a and 13a, respectively, of the rear developing bearing <NUM>. As a result, the developing unit <NUM> is rotatably supported by the cleaning frame <NUM> with the front supporting pin <NUM> and the rear supporting pin <NUM> as rotation shafts.

Further, the cleaning frame <NUM> is provided with a front drum bearing <NUM> and a rear drum bearing <NUM> which rotatably support the photosensitive drum <NUM>. The rear drum bearing <NUM> supports a drum coupling <NUM> coupled to the photosensitive drum <NUM>. Further, the front drum bearing <NUM> supports the flange <NUM>. Here, the drum coupling <NUM> is a drum coupling member for transmitting a rotational driving force (first rotational driving force) from the apparatus main assembly 100A to the photosensitive drum <NUM>.

The developing frame <NUM> is provided with the front and rear developing bearings <NUM> and <NUM> for rotatably supporting the developing roller <NUM>. Further, the developing unit <NUM> is constituted so as to be urged against the drum unit <NUM>, during image formation of the process cartridge <NUM>, by an urging spring <NUM> provided at each of ends of the developing frame <NUM>. By these urging spring <NUM>, an urging force for bringing the developing roller <NUM> into contact with the photosensitive drum <NUM> with, as rotation centers, the hang holes 12a and 13a of the front and rear developing bearings <NUM> and <NUM> is generated.

In <FIG>, a constitution in which the process cartridge <NUM> is inserted into the image forming apparatus <NUM> will be described. In this embodiment, a constitution in which the process cartridges <NUM> (70Y, <NUM>, 70C, <NUM>) are inserted through openings <NUM> (101a, 101b, 101c, 101d) of the image forming apparatus <NUM> is a constitution in which the process cartridges <NUM> are inserted from the front side to the rear side in a direction (arrow F direction in the figure) parallel to an axial direction of the photosensitive drums <NUM> (1a, 1b, 1c, 1d).

In this embodiment, with respect to an insertion direction of the process cartridge <NUM>, an upstream side is defined as a front side, and a downstream side is defined as a rear side. Further, in the image forming apparatus <NUM>, main assembly upper mounting guide portions <NUM> (103a, 103b, 103c, 103d) which are first main assembly guide portions are provided in an upper side. Further, in the image forming apparatus <NUM>, main assembly lower mounting guide portions <NUM> (102a, 102b, 102c, 102d) which are second main assembly mounting guide portions are provided in a lower side. Each of the main assembly upper guide portions <NUM> and the main assembly lower guide portions <NUM> has a guide shape extending along an insertion direction F of each of the process cartridge <NUM>.

The process cartridge <NUM> is placed in a front side of the main assembly lower mounting guide portion <NUM> with respect to a mounting direction and then is moved in the insertion direction F along the main assembly upper and lower mounting guide portions <NUM> and <NUM>, thus being inserted into the image forming apparatus <NUM>.

An operation of mounting the process cartridge <NUM> into the apparatus main assembly 100A will be described. <FIG> is a schematic view for illustrating a state before mounting of the process cartridge <NUM> into the apparatus main assembly 100A.

<FIG> is a schematic view for illustrating a state during the mounting of the process cartridge <NUM> into the apparatus main assembly 100A. The main assembly lower mounting guide portion <NUM> provided in the apparatus main assembly 100A is provided with a main assembly(-side) pressing member <NUM> and a main assembly(-side) pressing spring <NUM> which press and position the process cartridge <NUM> against the apparatus main assembly. When the process cartridge <NUM> is mounted in the apparatus main assembly 100A, a guide portion 27b of the cleaning frame <NUM> runs on the main assembly pressing portion <NUM>, so that the process cartridge <NUM> moves in an upward direction. Then, the guide portion 27b of the cleaning frame <NUM> is in a state in which the guide portion 27b is spaced from a guide surface of the main assembly lower mounting guide portion <NUM>.

<FIG> is a schematic view for illustrating a state in which the process cartridge <NUM> is mounted into the apparatus main assembly 100A until the process cartridge <NUM> abuts against a rear(-side) plate <NUM>. In the state in which the guide portion 27b of the cleaning frame <NUM> runs on the main assembly pressing member <NUM>, when the mounting of the process cartridge <NUM> is further continued, a longitudinal abutting portion provided on the rear drum bearing <NUM> contacts the rear plate <NUM> of the apparatus main assembly 100A.

<FIG> and <FIG> are schematic views for illustrating a state in which the process cartridge <NUM> is positioned relative to the apparatus main assembly 100A. In a state of (c) of <FIG>, in interrelation with closing of a front door <NUM> of the apparatus main assembly 100A, the main assembly lower mounting guide portion <NUM> including the main assembly pressing member <NUM> and the main assembly pressing spring <NUM> moves in the upward direction. With the movement, also the process cartridge <NUM> contacts a main assembly(-side) positioning portion 98a of the rear plate <NUM> at a cartridge(-side) positioning portion 11a provided at an upper portion of the rear drum bearing <NUM>.

Then, by the contact of the cartridge positioning portion 10a provided at the upper portion of the rear drum bearing <NUM> with the main assembly positioning portion 97a which is a main assembly(-side) positioning portion of a front plate <NUM>, the position of the process cartridge <NUM> relative to the apparatus main assembly 100A is determined. Also in this state, the guide portion 27b of the cleaning frame <NUM> is spaced from the guide surface of the main assembly lower mounting guide portion <NUM>, so that the process cartridge <NUM> is in a state in which the process cartridge <NUM> is pressed by a spring force, of the main assembly pressing spring <NUM>, received from the main assembly pressing member <NUM>.

Further, the cleaning frame <NUM> is provided on a side surface thereof with a boss 27c as a rotation stopper for the process cartridge <NUM>, and the boss 27c engages with a rotation preventing hole (portion) 98b provided in the rear plate <NUM>. Thus, the process cartridge <NUM> is prevented from rotating in the apparatus main assembly 100A.

In the process cartridge <NUM> according to this embodiment, the photosensitive drum <NUM> and the developing roller <NUM> are capable of being contacted to and spaced from each other. Here, a spacing mechanism between the photosensitive drum <NUM> and the developing roller <NUM> will be described with reference to <FIG> and <FIG>.

In <FIG>, the apparatus main assembly is provided with a spacing member <NUM> at a predetermined position with respect to a longitudinal direction of the process cartridge <NUM>. In the developing unit <NUM> of the process cartridge <NUM>, a spacing force receiving portion 31a of the developing frame <NUM> receives a force from the spacing member <NUM> moving in an arrow N direction, thus moving the developing roller <NUM> to a spaced position where the developing roller <NUM> is spaced from the photosensitive drum <NUM>.

Further, as shown in <FIG>, when the spacing member <NUM> moves in an arrow P direction away from the spacing force receiving portion 31a, the developing unit <NUM> is rotated in an arrow T direction about the holes 12a and 13a of the front and rear developing bearings <NUM> and <NUM> by the urging force of the urging springs <NUM> (<FIG>) provided at the ends of the developing frame <NUM>. Then, the developing unit <NUM> is moved to a contact position, so that the developing roller <NUM> and the photosensitive drum <NUM> are in contact with each other. At least during the image formation, the developing unit <NUM> is held at a contact position of <FIG>. Then, at timing, set in advance, such as during stand-by other than during image formation, the developing unit <NUM> is held at the spaced position of <FIG>. By that, an effect of suppressing the influence of deformation of the developing roller <NUM> on an image quality is obtained.

A spacing mechanism when the process cartridge <NUM> is mounted in the apparatus main assembly 100A will be described using <FIG> and <FIG>.

When the process cartridge <NUM> is mounted in the apparatus main assembly 100A, the developing unit <NUM> is in the contact portion, and the photosensitive drum <NUM> and the developing roller <NUM> are in contact with each other. At the time of completion of the mounting of the process cartridge <NUM> in the apparatus main assembly 100A and at the time of end of the image forming operation of the image forming apparatus <NUM>, the developing unit <NUM> is in the spaced position, and the photosensitive drum <NUM> and the developing roller <NUM> are spaced from each other.

Therefore, when the process cartridge <NUM> is mounted in the apparatus main assembly 100A, there is a need to move the process cartridge <NUM> from the contact position to the spaced position, and a constitution thereof will be described using <FIG>. As shown in <FIG>, the apparatus main assembly 100A is provided with an image forming apparatus opening <NUM> for permitting mounting of the process cartridge <NUM>. Further, as shown in <FIG> and <FIG>, the apparatus main assembly 100A is provided with a spacing guide portion <NUM> contacting a spacing force receiving portion 31a provided on the developing unit <NUM> of the process cartridge <NUM>.

As shown in (a) of <FIG> and <FIG> of <FIG>, before the process cartridge <NUM> enters the apparatus main assembly 100A, the developing unit <NUM> is in the contact position, and the photosensitive drum <NUM> and the developing roller <NUM> are in contact with each other. Then, as shown in (b) of <FIG> and <FIG> of <FIG>, when the process cartridge <NUM> is mounted into the apparatus main assembly 100A, first, the guide portion 27b provided integrally with the cleaning is mounted on the main assembly lower mounting guide portion <NUM> provided in the apparatus main assembly 100A. Then, the spacing force receiving portion 31a provided on the developing frame <NUM> contacts a chamfered portion 93a which is an inclined surface obliquely inclined relative to the spacing guide portion <NUM>.

When the process cartridge <NUM> is caused to further enter the apparatus main assembly, as shown in (c) of <FIG> and <FIG> of <FIG>, the developing unit <NUM> rotates in an arrow J direction about a rear supporting pin <NUM> as a rotation center. Then, the developing unit <NUM> moves in an arrow K direction to the spaced position. Then, when the process cartridge <NUM> is positioned in the apparatus main assembly 100A, as shown in (d) of <FIG> and <FIG> of <FIG>, the spacing force receiving portion 31a is in a contact state with the spacing member <NUM> disposed downstream of the spacing guide portion <NUM> with respect to the mounting direction. At that time, the developing unit <NUM> is in the spaced position, so that the process cartridge <NUM> can be mounted in the apparatus main assembly 100A while keeping the developing roller <NUM> in the spaced state from the photosensitive drum <NUM>.

Next, a constitution of a developing driving force inputting portion and a supporting constitution of the developer supplying roller <NUM> in the process cartridge <NUM> according to this embodiment will be described using <FIG>.

<FIG> is an illustration showing a longitudinal one end side (rear side) of a supporting portion for the developing roller <NUM> and the developer supplying roller <NUM>. In <FIG>, a developing roller shaft 25j of the developing roller <NUM> and a developer supplying roller shaft 34j of the developer supplying roller <NUM> are rotatably engaged with an inner peripheral surface of the rear developing bearing <NUM>. Here, the supporting constitution in the longitudinal one end side of the developing roller <NUM> and the developer supplying roller <NUM> was described, but also in the other longitudinal one end side, similarly, the bearing portion is integrally provided with the bearing member, and the developing roller shaft 25j and the developer supplying roller shaft 34j are rotatably engaged in the other end side. Further, at the developing driving force inputting portion, an Oldham coupling <NUM> which is a shaft coupling member is used.

Using <FIG>, a constitution of the Oldham coupling <NUM> will be described. Here, in order to describe the constitution of the Oldham coupling <NUM>, the rear developing bearing <NUM> is not shown. As shown in <FIG>, the Oldham coupling <NUM> is constituted by a follower-side engaging portion <NUM> which is a driven portion, an intermediary engaging portion which is an intermediary portion, and a driving-side engaging portion <NUM> which is a drive receiving portion.

The follower-side engaging portion <NUM> is fixed and mounted to an end portion (in one end side with respect to an axial direction) of the developer supplying roller shaft 34j. As a fixing method, there are a method in which connection is made by a spring pin or a parallel pin and a method in which as shown in <FIG>, the developer supplying roller shaft 34j is provided with a cut portion <NUM> at an end surface thereof and also a hole in the follower-side engaging portion <NUM> side is similarly shape and is engaged with the cut portion <NUM>.

The driving-side engaging portion <NUM> (first drive receiving portion) is a portion for receiving a driving force of a driving source of the main assembly. Further, in this embodiment, an H direction and an I direction are in a substantially perpendicular relationship. A shaft portion 23d of the driving-side engaging portion <NUM> is rotatably held in a hole 41d of a holding portion <NUM>. Further, the driving-side engaging portion <NUM> is integrally formed with three projections 23c1, 23c2 and 23c3 engageable with a main assembly(-side) developing (means) coupling <NUM> (<FIG>) which is a second main assembly(-side) drive transmitting member of the 100A described later.

This Oldham coupling <NUM> allows a deviation between an axis of the main assembly developing coupling <NUM> and an axis of the developer supplying roller <NUM>, and transmits a rotational driving force (first rotational driving force) from the apparatus main assembly 100A to the developer supplying roller <NUM>. Further, the Oldham coupling <NUM> is capable of transmitting a rotational driving force (second rotational driving force) from the apparatus main assembly 100A to the developer supplying roller <NUM> in a state in which the developing unit <NUM> is in the contact position and in the spaced position.

In <FIG>, a constitution of the Oldham coupling <NUM> will be described in further detail using sectional views. <FIG> is a sectional view of the Oldham coupling <NUM> cut in an arrow H direction in <FIG>, and <FIG> is a schematic view of the Oldham coupling <NUM> cut in an arrow I direction in <FIG>. In (a) of <FIG>, the follower-side engaging portion <NUM> is integrally provided with a rib 21a. The intermediary engaging portion <NUM> is provided with a groove 22a, and the rib 21a and the groove 22a are engaged with each other so as to be movable in the arrow H direction of <FIG>. In (b) of <FIG>, the driving-side engaging portion <NUM> is integrally provided with a rib 23b. The intermediary engaging portion <NUM> is provided with a groove 22b, and the rib 23b and the groove 22b are engaged with each other so as to be movable in the arrow I direction of <FIG>. In this embodiment, the H direction and the I direction are in the substantially perpendicular relationship.

The intermediary engaging portion <NUM> engages with the follower-side engaging portion <NUM> and the driving-side engaging portion <NUM>, and constitutes an intermediary portion for transmitting a driving force, inputted into the driving-side engaging portion <NUM>, to the follower-side engaging portion <NUM>, and is movable in a direction crossing the axial direction of the developer supplying roller <NUM> while maintaining engagement with each of the engaging portions <NUM> and <NUM>.

<FIG> is an illustration showing a constitution including the coupling provided on the process cartridge <NUM> and the coupling provided in the apparatus main assembly 100A. At the end surface of the driving-side engaging portion <NUM> of the Oldham coupling <NUM> provided on the developing chamber <NUM>, the three projections 23c1, 23c2 and 23c3 projecting in the axial direction are formed. Further, a centering boss 23a for being aligned with the axis (rotation enter) of the main assembly developing coupling <NUM> projects in the axial direction from the end surface of the driving-side engaging portion <NUM>.

The photosensitive drum <NUM> is provided, in one end side with respect to the axial direction, with a triangular prism drum coupling <NUM>. A guide portion 41b of the holding portion <NUM> is movable, in a direction crossing the axial direction of the developer supplying roller <NUM>, along the groove 43a of the side cover <NUM> fixed on the developing unit with an unshown screw or the like. That is, the driving-side engaging portion <NUM> is movable in a direction (the direction crossing the axial direction of the developer supplying roller) crossing the developing unit <NUM>.

In <FIG>, the main assembly drum coupling <NUM> which is a first main assembly drive transmitting member for transmitting the drive of the apparatus main assembly 100A to the photosensitive drum <NUM> is provided with a hole 90a having a substantially triangular shape in cross section. The main assembly developing coupling <NUM> which is a second main assembly drive transmitting member for transmitting the rotational driving force (second rotational driving force) from the apparatus main assembly 100A to the developer supplying roller <NUM> is provided with three holes 91a1, 91a2 and 91a3.

The main assembly drum coupling <NUM> is urged in a direction of the process cartridge <NUM> by a drum pressing (urging) member <NUM> such as a compression spring. Further, the main assembly drum coupling <NUM> is movable in the axial direction of the photosensitive drum <NUM>. Further, in the case where the drum coupling <NUM> and the hole 90a of the main assembly drum coupling <NUM> are out of phase and in contact with each other when the process cartridge <NUM> is mounted in the apparatus main assembly 100A, the main assembly drum coupling <NUM> is pushed by the drum coupling <NUM>, thus being retracted. Then by rotation of the main assembly drum coupling <NUM>, the drum coupling <NUM> and the hole 90a are engaged with each other, the rotational driving force is transmitted to the photosensitive drum <NUM>.

Further, the main assembly developing coupling <NUM> is urged in the direction of the process cartridge <NUM> toward a direction parallel to the axial direction of the photosensitive drum <NUM> by a developing (means) pressing (urging) member <NUM> such as a compression spring. However, the main assembly developing coupling <NUM> has no play with respect to the direction crossing the axial direction and is provided in the apparatus main assembly 100A. That is, the main assembly developing coupling <NUM> not only rotates for transmitting the drive (driving force) but also in movable only in the axial direction.

When the driving-side engaging portion <NUM> and the main assembly developing coupling <NUM> are engaged with each other by causing the process cartridge <NUM> to enter the apparatus main assembly 100A, the projections 23c1 - 23c3 and the holes 91a1 - 91a3 are out of phase in some cases. In this case, free ends of the projections 23c1 - 23c3 contact portions other than the holes 91a1 - 91a3, so that the main assembly developing coupling <NUM> is retracted in the axial direction against an urging force of the developing pressing member <NUM>. However, when the main assembly developing coupling <NUM> rotates and the projections 23c1 - 23c3 and the holes 91a1 - 91a3 are in phase, the main assembly developing coupling 91a advances by the urging force of the developing pressing member <NUM>.

Then, the projections 23c1 - 23c3 and the holes 91a1 - 91a3 engage with each other, and also the centering boss 23a which is an engaging portion positioning portion and the centering hole 91b which is a transmitting member positioning portion engage with each other, so that the driving-side engaging portion <NUM> and the axis (rotation center) of the main assembly developing coupling <NUM> coincide with each other. Then, by rotation of the main assembly coupling <NUM>, the projections 23c1 - 23c3 and the holes 91a1 - 91a3 engage with each other, respectively, so that the rotational driving force is transmitted to the developer supplying roller <NUM>. Next, rotation of the developing roller <NUM> will be described. The developer supplying roller <NUM> is provided with the driving-side engaging portion <NUM> in one end side and is provided with a gear in the other end side with respect to the longitudinal direction (the axial direction of the developer supplying roller). On the other hand, the developing roller <NUM> is provided with a gear engageable with the above gear. By this constitution, the rotational driving force is transmitted to the developing roller <NUM> drive-connected to the developer supplying roller <NUM> by the gears in the other end side with respect to the longitudinal direction.

Here, the drive transmission to the main assembly drum coupling <NUM> and the main assembly developing coupling <NUM> is made by a motor provided in the apparatus main assembly 100A. By this, the photosensitive drum <NUM> and the developer supplying roller <NUM> receive the driving force from the image forming apparatus main assembly independently of each other. Incidentally, the motor may employ a constitution using a single motor per each of the process cartridges <NUM> for the respective colors and a constitution in which the drive is transmitted to some process cartridges by the single motor.

Next, a constitution of the developing frame and the rotational directions of the developing roller and the developer supplying roller will be described using <FIG>, <FIG>, <FIG> and <FIG>. <FIG> is an illustration showing a driving force inputting portion and a driving system of the developing unit in this embodiment. <FIG> is an illustration showing the cartridge mounted in the image forming apparatus. <FIG> is an illustration showing a constitution of the developing chamber in this embodiment. <FIG> is an illustration showing a comparison example in which the developing chamber toner feeding member is provided in the developing chamber.

As described above, the toner accommodating portion 31c of the developing frame <NUM> is provided with the toner feeding member <NUM> (<FIG>) for not only stirring the accommodated toner but also feeding the toner to the developing chamber 31b via the toner opening 31e. Incidentally, in this embodiment, a constitution in which the developing roller <NUM> and the developer supplying roller <NUM> are provided in the developing chamber 31b is employed. Further, the toner accommodating portion 31c is provided below the developing chamber 31b with respect to direction of gravity, and therefore the toner feeding member <NUM> is positioned below the developing chamber 31b with respect to the direction of gravity. That is, the process cartridge <NUM> in this embodiment has a scooping-up constitution in which the toner is fed by the toner feeding member <NUM> against the gravity from the toner accommodating portion 31c disposed below the developing chamber 31b with respect to the direction of gravity to the developing chamber 31b disposed above the toner accommodating portion 31c with respect to the direction of gravity.

The developer fed from the toner accommodating portion 31c to the developing chamber 31b stagnates at a developing chamber bottom (portion) 31f as shown in <FIG>. In order to feed the developer stagnating at the developing chamber bottom 31f to the developer supplying roller, as the comparison example, as shown in <FIG>, a developing chamber toner feeding member <NUM> is provided at the developing chamber bottom 31f, and the a developing chamber toner feeding member <NUM> is moved, so that the developer stagnating at the developing chamber 31f was supplied to the developer supplying roller <NUM>.

In this embodiment, as shown in <FIG>, the developer supplying roller <NUM> is set so as to rotate in a direction (arrow E direction) opposite to the rotational direction (arrow B direction) of the developer supplying roller <NUM>. That is, at the contact portion between the developing roller <NUM> and the developer supplying roller <NUM>, the respective surfaces thereof are in a direction of movement in the same direction. Incidentally, as shown in <FIG>, the rotational direction of the photosensitive drum <NUM> is an opposite direction to the rotational direction of the developing roller. Further, the rotational direction of the photosensitive drum <NUM> is the same direction as the rotational direction of the developer supplying roller <NUM>.

In <FIG>, the developer supplying roller <NUM> has a constitution in which a sponge portion (elastic layer having an inner porous portion) 34a is provided. Further, in <FIG>, the developing roller <NUM> has an elastic layer 25a. A surface hardness of the developer supplying roller <NUM> is lower than a surface hardness of the developing roller <NUM>, and therefore when both rollers are in contact with each other, as shown in <FIG>, the developer supplying roller is dented (deformed). Here, as shown in <FIG>, the developer supplying roller <NUM> is in a state in which the surface of the sponge portion 34a is deformed correspondingly to a penetration amount at the contact portion with the developing roller <NUM>. At this time, from the sponge portion 34a, the toner contained in the sponge portion 34a is discharged. Hereinafter, a portion where the toner is discharged by deformation of the sponge portion 34a is referred to as a discharging portion 34b and will be described. This discharging portion 34b is a region in a side upstream of the contact portion between the developer supplying roller <NUM> and the developing roller <NUM> with respect to the rotational direction of the developer supplying roller <NUM>.

On the other hand, at a portion where the rotation of the developer supplying roller <NUM> advances and the state of the developer supplying roller <NUM> is restored from the deformed state, air pressure inside the sponge portion 34a lowers with the restoration. For that reason, a flow of air for taking in the toner toward the inside of the sponge portion 34a generates. Hereinafter, a portion where the state of the sponge portion 34a is restored from the deformed state and the toner is taken in is referred to as a taking-in portion 34c and will be described. This taken-in portion 34c is a region in a side downstream of the contact portion between the developer supplying roller <NUM> and the developing roller <NUM> with respect to the rotational direction of the developer supplying roller <NUM>. The toner taken in this region is discharged again at the discharging portion 34b.

In this way, during the rotational drive of the developer supplying roller <NUM>, the toner is circulated by continuously performing the above-described taking-in and discharging, and in this process, supply of the developer to the developing roller <NUM> is made. In order to effect stable supply of the developer to the developing roller <NUM>, it is important to stably supply the toner to the taking-in portion 34c.

As shown in <FIG>, the rotational direction (arrow C direction) of the developer supplying roller <NUM> in the comparison example is set at the same direction as the rotational direction (arrow B direction) of the developing roller <NUM> in many cases. In this case, as in this embodiment, in the constitution in which the toner is fed from the lower toner accommodating portion 31c to the upper developing chamber 31b, the taking-in portion 34c is positioned above the developing roller <NUM> and the developer supplying roller <NUM>. Accordingly, in order to stably supply the toner to the taking-in portion 34c, there is a need to provide such an arrangement relationship that the toner which passes through the toner opening 31e and which moves toward the taking-in portion 34c positioned above the developer supplying roller <NUM> is not blocked by the developer supplying roller <NUM> itself. Further, at the bottom 31f of the developing chamber 31c, a state in which the toner discharged from the discharging portion 34b, the toner fallen by regulation with a developing blade <NUM> and the toner fed from the toner accommodating portion 31c are accumulated is formed. In order to stir and circulate these toners, at the bottom 31f of the developing chamber 31b, the developing chamber toner feeding member <NUM> which is a stirring member is provided, and there was a need to supply the toner to the developer supplying roller <NUM> by the developing chamber toner feeding member <NUM>.

On the other hand, in this embodiment, with respect to the direction of gravity as shown in <FIG>, the taking in portion 34c is positioned below the developing roller <NUM> and the developer supplying roller <NUM> and is close to the bottom 31f of the developing chamber 31b. That is, the toner fed to the developing chamber 31b moves toward the rear portion by the airflow generated at the taking-in portion 31c, so that the taking-in portion is located at a position where the toner easily reaches the taking-in portion 31c naturally. Accordingly, constraint of an arrangement relationship between the toner opening 31e and the developer supplying roller <NUM> as in the conventional constitution is alleviated, and therefore a degree of flexibility in design of the arrangement of the toner opening 31e and the developer supplying roller <NUM> becomes high.

Here, with respect to the direction of gravity, when a lower end 31e2 of the toner opening 31e is disposed at a position higher than the bottom 31f of the developing chamber <NUM>, the toner surface is raised to a position close to the taking-in portion 34c, and therefore such an arrangement is further desirable. Particularly, when the position of the lower end 31e2 of the toner opening 31e is set at a position higher than the taking-in portion 34c with respect to the direction of gravity, the toner surface in the developing chamber 31b always reaches a height of the taking-in portion 34c, and therefore a toner supplying property to the developing chamber 31c is further stabilized. In this embodiment, the height of the lower end 31e2 of the toner opening 31e is disposed at a position higher than a downstream end of the contact portion between the developer supplying roller <NUM> and the developing roller <NUM> with respect to the rotational direction of the developer supplying roller <NUM>. Further, the taking-in portion 34c is positioned close to the bottom 31f of the developing chamber 31b, and therefore the toner accumulated at the bottom <NUM> is naturally taken in the developer supplying roller <NUM> and is gradually consumed.

Accordingly, as in the conventional constitution, the circulation of the toner is made even when the developing chamber toner feeding member <NUM> shown in <FIG> is not used, and therefore a space in which the developing chamber toner feeding member <NUM> has been conventionally disposed can be filled, so that it is possible to reduce the residual toner.

Using <FIG>, surface speeds of the developing roller <NUM> and the developer supplying roller <NUM> will be described. As shown in <FIG>, the developing roller <NUM> and the developer supplying roller <NUM> rotates in opposite directions. Incidentally, at the contact portion, the respective surfaces move in the same direction. Here, the surface speed of the developer supplying roller <NUM> is set so as to be higher than the surface speed of the developing roller <NUM>. This is because the toner supplying property to the developing roller <NUM> and a property of peeling off the toner, on the developing roller <NUM>, which is not used for development are taken into consideration. The surface speed of the developer supplying roller <NUM> is higher than the surface speed of the developing roller <NUM>, so that a portion, where the toner is contained in a sufficient amount, of the sponge portion 34a always contacts the developing roller <NUM>, and therefore stable toner supply to the developing roller <NUM> can be effected. Further, with respect to the toner peeling-off property, the surface speed of the developer supplying roller <NUM> is higher than the surface speed of the developing roller <NUM> and therefore a frictional force due to a peripheral speed driving force generates, so that the toner on the developing roller <NUM>, which is not used for development, can be peeled off.

Incidentally, with respect to the toner supplying property and the toner peeling-off property, it has been known that an effect is larger when the peripheral speed difference is larger. However, the number of rotation of the developing roller <NUM> has a large influence on the toner supplying property to the photosensitive drum <NUM>, and therefore from the viewpoint of a developing process, it is not desirable that the peripheral speed difference is provided by lowering the number of rotation of the developing roller <NUM>.

Therefore, in order to increase the peripheral speed while maintaining the number of rotation of the developing roller <NUM>, a method in which the number of rotation of the developer supplying roller <NUM> is increased relatively by changing a gear ratio between a developer supplying roller gear <NUM> and a developing roller gear <NUM> (<FIG>) which are described later and a method in which a diameter 34r of the sponge portion 34a is increased are used. In the case where the number of rotation of the developer supplying roller <NUM> is increased relatively while maintaining the number of rotation of the developing roller <NUM>, there is a need to increase an output from the main assembly driving motor (unshown) which is a driving source, and therefore much electric power is required. Accordingly, also in order to suppress electric power consumption, the diameter 34r of the sponge portion 34a may desirably be large, and in this embodiment, a diameter 25r of the developing roller <NUM> is set at <NUM> and the diameter 34r of the developer supplying roller <NUM> is set at <NUM>, so that a diameter ratio therebetween is about <NUM>. However, it is not necessarily required that the diameter 34r of the sponge portion 34a is made larger than the diameter 25r of the developing roller <NUM>, but a desired peripheral speed difference may also given by the gear ratio. Incidentally, although a driving system in this embodiment will be described later, with respect to the number of teeth of the developer supplying roller gear <NUM> and the developing roller gear <NUM> (<FIG>) which are directly connected to each other, the number of teeth of the developer supplying roller gear <NUM> is set at <NUM> teeth, and the number of teeth of the developing roller gear <NUM> is set at <NUM> teeth, so that the gear ratio therebetween is about <NUM>.

Here, with respect to a surface speed ratio between the developing roller <NUM> and the developer supplying roller <NUM> (i.e., (developer supplying roller surface speed)/(developing roller surface speed), hereinafter referred to as a "peripheral speed ratio"), it is desirable that the peripheral speed ratio is set in a range of <NUM> or more and <NUM> or less. This set range is such a range that necessary and sufficient toner supplying property and toner peeling off property can be maintained. When the peripheral speed ratio is below <NUM>, there is a liability that a good toner peeling-off property cannot be maintained, so that there is a liability of the influence of a ghost or the like on an image quality. Further, when the peripheral speed ratio is <NUM> or less, the toner supplying property and the toner peeling-off property can be sufficiently maintained. For that reason, when the peripheral speed ratio exceeds <NUM>, friction becomes large and thus abrasion of the developer supplying roller and the developing roller is liable to generate, and therefore it is not desirable that the surface speed of the developer supplying roller <NUM> is excessively increased. Here, in this embodiment, by the above-described diameter ratio and gear ratio, the surface speed of the developing roller <NUM> is set at about <NUM>/s and the surface speed of the developer supplying roller <NUM> is set at about <NUM>/s, so that the peripheral speed ratio therebetween is about <NUM>. In the setting, it has already been confirmed that a sufficient effect with respect to the toner supplying property and the toner peeling-off property can be obtained. Incidentally, the surface speed referred herein is a speed on the surface excluding the contact portion between the developing roller <NUM> and the developer supplying roller <NUM>, and this is similarly applicable to also the peripheral speed ratio.

Using <FIG> and <FIG>, a drive input constitution and a constitution of the driving system for the developing unit <NUM> will be described. As described above, the driving force outputted from the main assembly driving motor (unshown) which is the driving source of the apparatus main assembly 100A is inputted into the developing unit <NUM> by engagement of the main assembly developing coupling <NUM> of the apparatus main assembly 100A with the driving-side engaging portion <NUM> of the Oldham coupling <NUM> provided at the end portion of the shaft portion 34j of the developer supplying roller <NUM>.

Here, first, the drive input constitution of the developing unit <NUM> will be described using <FIG> is an illustration showing the driving system for the developing unit <NUM>, and for simplification of explanation, only the developing roller <NUM>, the developer supplying roller <NUM> and the driving system relating to these rollers are extracted and shown.

As shown in <FIG>, the shaft portion 34j of the developer supplying roller <NUM> is provided with the developer supplying roller gear <NUM> which is an upstream drive transmitting member (first drive transmitting portion). Similarly, the shaft portion 25j of the developing roller <NUM> is provided with the developing roller gear <NUM> which is a downstream drive transmitting member (second drive transmitting portion) provided so as to directly engage with the developer supplying roller gear <NUM>. Incidentally, in this embodiment, a gear train such as the developer supplying roller gear <NUM> is provided in a side (the other side) opposite from the driving force inputting portion of the developing unit <NUM> with respect to the axial direction from the viewpoint of the space or the like, but the gear train and the driving force inputting portion may also be provided in the same side. Here, the rotational directions of the developing roller <NUM> and the developer supplying roller <NUM> are opposite to each other, and therefore there is no need to provide an <NUM> between the developer supplying roller gear <NUM> and the developing roller gear <NUM>, so that the number of parts can be reduce. The driving force inputted onto the shaft of the developer supplying roller <NUM> is transmitted from the developer supplying roller gear <NUM> to the developing roller <NUM> via the developing roller gear <NUM>. Incidentally, as described above, in this embodiment, the number of teeth of the developer supplying roller gear <NUM> is set at <NUM> teeth, and the number of teeth of the developing roller gear <NUM> is set at <NUM> teeth.

Using <FIG>, the driving system for the developing unit will be described. <FIG> is an illustration showing the driving system in a side downstream of the developing roller <NUM>.

As shown in <FIG>, in a side downstream of the developing roller gear <NUM>, a developing (means) idler gear <NUM>, a stirring idler gear <NUM> and a stirring gear <NUM> which are used for transmitting the drive to the toner feeding member <NUM> are provided in the listed order. The developing idler gear <NUM> and the stirring idler gear <NUM> are rotatably supported by the front developing bearing <NUM>, and the stirring gear <NUM> is rotatably supported by the developing frame <NUM> in a state in which the stirring gear <NUM> is connected to the toner feeding member <NUM> by an unshown connecting means such as snap-fit means and an engaging portion. The driving force inputted onto the shaft of the developer supplying roller <NUM> is transmitted in the order of the developer supplying roller gear <NUM>, the developing roller gear <NUM>, the developing idler gear <NUM>, the stirring idler gear <NUM> and the stirring gear <NUM> and is finally transmitted to the toner feeding member <NUM>.

Using <FIG> and <FIG>, small deformation generating at the sponge portion 34a of the developer supplying roller <NUM> will be described. The developer supplying roller <NUM> is always supported in the contact state with the developing roller <NUM>, but when the developer supplying roller <NUM> is left standing for a long time in a high-temperature environment or the like, at the contact portion with the developing roller <NUM>, small plastic deformation as shown in <FIG> generates in some cases. Hereinafter, with respect to the developer supplying roller <NUM>, a region where the small plastic deformation generates is referred to as a small deformation portion 34n and will be described.

First, <FIG> is an illustration showing a constitution in which different from this embodiment, the driving force from the main assembly is not inputted into the developer supplying roller <NUM>, but is inputted into the developing roller <NUM>. In this constitution, the developing roller gear <NUM> drive the developer supplying roller gear <NUM>. Here, <FIG> is an illustration showing one tooth of each of the developer supplying roller gear and the developing roller gear at an engaging portion between a tooth 38a of the developer supplying roller gear and a tooth 39a of the developing roller gear. <FIG> is an illustration showing a state in which the sponge portion 34a which is not deformed reaches the contact position with the developing roller <NUM>, and <FIG> is an illustration showing a state in which the small deformation portion 34n reaches the contact position with the developing roller <NUM>. A broken line 39b shown in (b) of <FIG> represents a behavior of the developing roller gear tooth 39a in a state in which a load from the developer supplying roller gear <NUM> is decreased. Using <FIG> and <FIG>, the influence due to the small deformation of the developer supplying roller <NUM> will be described.

In the case where the sponge portion 34a of the developer supplying roller <NUM> is not deformed, as shown in (a) of <FIG>, the developing roller gear tooth 39a rotates in a state in which it receives a certain load from the developer supplying roller gear tooth 38a. However, when the small deformation portion 34n of the developer supplying roller <NUM> reaches the contact position with the developing roller <NUM>, a frictional force generating between the developing roller <NUM> and the developer supplying roller <NUM> decreases instantaneously. By this, the developer supplying roller <NUM> is in a state in which the developer supplying roller <NUM> easily rotates instantaneously, and therefore, as shown in (b) of <FIG>, the load received from the developer supplying roller gear tooth 38a by the driven developing roller gear tooth 39a decreases instantaneously. By this, the rotational speed of the developing roller <NUM> instantaneously increased. Therefore, the surface speed of the driving-side <NUM> instantaneously increases relative to the surface speed of the photosensitive drum <NUM>, and therefore there is a possibility that non-uniformity generates in toner supplying property from the developing roller <NUM> to the photosensitive drum <NUM> and thus a phenomenon such as a lateral stripe generates on the image. Incidentally, it is known that this phenomenon is liable to generate as the peripheral speed difference between the surface speed of the developing roller <NUM> and the surface speed of the developer supplying roller <NUM> becomes larger.

On the other hand, in this embodiment shown in <FIG>, the developer supplying roller <NUM> is in a state in which the developer supplying roller <NUM> readily rotates instantaneously by passing of the small deformation portion 34n of the developer supplying roller <NUM> through the contact portion with the developing roller <NUM>. However, as shown in <FIG>, there is no large fluctuation in load for rotating the developing roller <NUM>, and therefore there is no generation of the influence on the behavior of the developing roller <NUM>. Accordingly, even when the small deformation generates at the sponge portion 34a of the developer supplying roller <NUM>, the non-uniformity does not readily generate in toner supplying property from the developing roller <NUM> to the photosensitive drum <NUM>. For that reason, the constitution in which the driving force in inputted into the developer supplying roller <NUM> is capable of suppressing a lowering in image quality compared with a constitution in which the driving force is inputted into the developing roller <NUM>.

Here, when the toner peeling-off property, the electric power consumption and the influence of the small deformation of the sponge portion 34a on the image are summarized from the viewpoint of the above-described roller peripheral speed difference, a tendency as shown in a Table of <FIG> is obtained from an experimental result. That is, the peripheral speed difference between the surface speed of the developing roller <NUM> and the surface speed of the developer supplying roller <NUM> may desirably be set at (developer supplying roller/developing roller) = <NUM> or more and <NUM> or less also from the viewpoint of the influence of the small deformation of the sponge portion 34a on the image.

As described above, according to this embodiment, in the developing device of the constitution in which the toner is scooped up from the toner accommodating chamber disposed below the developing chamber 31b to the upper developing chamber 31b, the rotational direction (arrow C direction) of the developer supplying roller <NUM> is made the opposite direction to the rotational direction (arrow B direction) of the developing roller. By this, it is possible to suppress the stagnation of the toner without providing the stirring member in the developing chamber 31b, and therefore it is possible to reduce the number of parts and to decrease the amount of the residual toner. Further, the surface speed of the developer supplying roller <NUM> is set so as to be higher than the surface speed of the developing roller, whereby it becomes possible to stably supply the toner to the developing roller. Further, the driving force from the image forming apparatus main assembly is inputted onto the shaft of the developer supplying roller <NUM>, whereby it is possible to reduce an image defect generating, e.g., when the developer supplying roller <NUM> is left standing in the high-temperature environment or the like. From the above, in the developing device having the scooping constitution including the toner accommodating chamber below the developing chamber 31c, it is possible to provide a process cartridge and an image forming apparatus which are capable of improving the image quality while reducing the number of parts and decreasing the amount of the residual toner.

Claim 1:
A process cartridge (<NUM>) detachably mountable to a main assembly (100A) of an image forming apparatus (<NUM>), said process cartridge (<NUM>) comprising:
a photosensitive drum (<NUM>);
a rotatable developing roller (<NUM>);
a rotatable developer supplying roller (<NUM>) provided in contact with said developing roller (<NUM>) and configured to supply a developer to said developing roller (<NUM>);
a developer accommodating chamber (31c) configured to accommodate the developer;
a developing chamber (31b) in which said developer supplying roller (<NUM>) is provided;
a rotatable feeding member (<NUM>) provided in said developer accommodating chamber (31c) and configured to feed the developer from said developer accommodating chamber (31c) into said developing chamber (31b) by moving the developer upwardly against a gravity; and
a driving force receiving portion (<NUM>) provided at a shaft end portion of said developer supplying roller (<NUM>) and configured to receive a driving force for rotating said developer supplying roller (<NUM>), said developing roller (<NUM>) and said feeding member (<NUM>);
characterized in that
the process cartridge (<NUM>) further comprises:
a first driving force transmitting portion (<NUM>) provided on said developer supplying roller (<NUM>) and configured to transmit the driving force received by said driving force receiving portion (<NUM>) to said developing roller (<NUM>); and
a second driving force transmitting portion (<NUM>) provided on said developing roller (<NUM>) and configured to transmit the driving force from said first driving force transmitting portion (<NUM>) to said developing roller (<NUM>),
wherein, when said process cartridge (<NUM>) is mounted to the main assembly (100A), said developer supplying roller (<NUM>) and said developing roller (<NUM>) are rotatable such that surfaces of said developer supplying roller (<NUM>) and said developing roller (<NUM>) move at a contact portion between said developer supplying roller (<NUM>) and said developing roller (<NUM>) in the same direction and toward a bottom (31f) of said developing chamber (31b), and
wherein a peripheral speed of the surface of said developer supplying roller (<NUM>) is higher than that of said developing roller (<NUM>).