Patent Grant
12130581
The present invention relates to a process cartridge detachably mountable to an image forming apparatus and an image forming apparatus including the process cartridge. The image forming apparatus forms an image on a recording material using an image forming process. Examples of the image forming apparatus include a printer, a copying machine, a facsimile machine, or word processor and a multi-function combination of these machines.
Conventionally, in an image forming apparatus using an electrophotographic image forming process, a photosensitive drum and process parts actable on the photosensitive drum are not fixed to the apparatus, but rather are provided in a cartridge, for example, as a process cartridge that is detachably mountable to an apparatus main assembly of the image forming apparatus.
With this type of process cartridge, maintenance of the image forming apparatus can be performed by a user himself (herself). As a result, operation of the apparatus is improved, and, thus, process cartridges are widely used in image forming apparatuses.
In a full-color electrophotographic image forming apparatus using a transfer belt (intermediary transfer belt), a constitution is used in which a plurality of process cartridges are arranged below the transfer belt. This is because in the case in which a print is discharged onto an upper surface of the image forming apparatus, by positioning the process cartridges below the transfer belt, the time to a first printing can be shortened. As a process cartridge corresponding to this constitution, an arrangement is used in which a developing chamber is disposed at an upper portion close to the transfer belt and developer is scooped up, to the developing chamber, from a developer accommodating chamber positioned below the developing chamber (Japanese Laid-Open Patent Application 2008-170951).
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 so as to reduce an amount of residual developer.
However, in the constitution of Japanese Laid-Open Patent Application 2008-170951, there was a need to provide the stirring member in the developing chamber at 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 used for disposing the stirring member can be filled, and therefore residual developer can be further suppressed.
The present invention is a further development of the prior art structure.
Accordingly, it is an object of the present invention is to provide a process cartridge and an image forming apparatus 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, such that itis possible to realize reduction of residual developer while reducing the number of parts.
According to the present invention, there is provided process cartridge comprising: (i) a photosensitive drum; (ii) a rotatable developing roller for developing an electrostatic latent image formed on the photosensitive drum; (iii) a developer supplying roller, provided in contact with the developing roller, for supplying a developer to the developing roller; (iv) a driving force receiving portion for receiving a driving force, wherein the driving force receiving portion is provided at a shaft end portion of the developer supplying roller and is movable in a direction crossing a shaft of the developer supplying roller; (v) a first driving force transmitting portion for transmitting the driving force, received by the driving force receiving portion, to the developing roller, wherein the first driving force transmitting portion is provided on the developer supplying roller; and (vi) a second driving force transmitting portion, provided on the developing roller, for transmitting the driving force by engaging with the driving force transmitting portion. A rotational direction of the developing roller is an opposite direction to a rotational direction of the developer supplying roller, and a surface speed of the developer supplying roller is larger than a surface speed of the developing roller.
Further, according to the present invention, there is provided an image forming apparatus including a main assembly and a process cartridge, wherein: (i) the main assembly includes (i-i) a driving portion; and (ii) the process cartridge detachably mountable to the image forming apparatus includes: (ii-i) a photosensitive drum; (ii-ii) a developer supplying roller, provided in contact with a developing roller, for supplying a developer to the developing roller; (ii-iii) a developer supplying roller, provided in contact with the developing roller, for supplying the developer to the developing roller; (ii-iv) a driving force receiving portion for receiving a driving force by being connected with the driving portion, wherein the driving force receiving portion is provided at a shaft end portion of the developer supplying roller and is movable in a direction crossing a shaft of the developer supplying roller; (ii-v) a first driving force transmitting portion for transmitting the driving force, received by the driving force receiving portion, to the developing roller, wherein the first driving force transmitting portion is provided on the developer supplying roller; and (ii-vi) a second driving force transmitting portion, provided on the developing roller, for transmitting the driving force from the first driving force transmitting portion to the developing roller by engaging with the driving force transmitting portion. A rotational direction of the developing roller is opposite to a rotational direction of the developer supplying roller, and a surface speed of the developer supplying roller is larger than a surface speed of the developing roller.
In
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. Accordingly, the scope of the present invention is not limited thereto unless otherwise specified.
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.
(General Structure of Image Forming Apparatus)
First, a general structure of an electrophotographic image forming apparatus (hereinafter referred to as an “image forming apparatus”) 100 will be described using
The process cartridge 70 includes electrophotographic photosensitive drums (hereinafter referred to as “photosensitive drums”) 1 (1a, 1b, 1c, 1d), and at a periphery of the photosensitive drums 1, process means such as charging rollers 2 (2a, 2b, 2c, 2d), developing rollers 25 (25a, 25b, 25c, 25d), and cleaning members 6 (6a, 6b, 6c, 6d) are integrally provided.
The charging roller 2 electrically charges the surface of the photosensitive drum 1 uniformly, and the developing roller 25 develops a latent image, formed on the photosensitive drum 1, with toner to visualize the latent image. The cleaning member 6 removes the toner remaining on the photosensitive drum 1 after a toner image formed on the photosensitive drum 1 is transferred onto a recording material (medium).
Further, below the process cartridges 70, a scanner unit 3 is provided for forming the latent image on the photosensitive drums 1 by subjecting the photosensitive drums 1 to selective exposure to light on the basis of image information.
At a lower portion of the apparatus main assembly 100A, a cassette 17 is mounted in which sheets of the recording material S are accommodated. 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 69 and a fixing portion 74. That is, a feeding roller 54 for separating and feeding the sheets of the recording material S in the cassette 17 in a one-by-one manner, a feeding roller pair 76 for feeding the fed recording material S, and a registration roller pair 55 for synchronizing the latent image formed on the photosensitive drum 1 with the recording material S are provided.
Further, above the process cartridges 70 (70Y, 70M, 70C, 70K), an intermediary transfer unit 5 is provided as an intermediary transfer means onto which the toner image formed on each of the photosensitive drums 1 (1a, 1b, 1c, 1d) is to be transferred. The intermediary transfer unit 5 includes a driving roller 56, a follower roller 57, primary transfer rollers 58 (58a, 58b, 58c, 58d) at positions opposing the photosensitive drums 1 for the respective colors, and an opposite roller 59 at a position opposing the secondary transfer roller 69. Around these rollers, a transfer belt (intermediary transfer belt) 9 is extended and stretched.
Further, the transfer belt 9 is circulated and moved so as to oppose and be contacted to all of the photosensitive drums 1, so that primary transfer (of the toner images) from the photosensitive drums 1 onto the transfer belt 9 is made by applying a voltage to the primary transfer rollers 58 (58a, 58b, 58c, 58d). Then, by voltage application to the secondary transfer roller 69 and the opposite roller 59 disposed inside the transfer belt 9, the toner images are transferred from the transfer belt 9 onto the recording material S.
During image formation, while rotating each of the photosensitive drums 1, the photosensitive drum 1 uniformly charged by the charging roller 2 is subjected to selective exposure to light emitted from the scanner unit 3. By this, an electrostatic latent image is formed on the photosensitive drum 1. The latent image is developed by the developing roller 25. By this, the toner images of the respective colors are formed on the photosensitive drums 1, respectively. In synchronism with this image formation, the registration roller pair 55 feeds the recording material S to a secondary transfer position where the secondary transfer roller 69 opposing the opposite roller 59 is contacted to the transfer belt 9.
Then, by applying a transfer bias voltage to the secondary transfer roller 69, the respective color toner images are secondary-transferred from the transfer belt 9 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 74, so that the toner images are fixed on the recording material S. Thereafter, the recording material S is discharged onto a discharge portion 75 by a sheet-discharging roller pair 72. The fixing portion 74 is disposed at an upper portion of the apparatus main assembly 100A.
(Process Cartridge)
Next, the process cartridge 70 in this embodiment will be described with reference to
The respective process cartridges 70 (70Y, 70M, 70C, 70K) include drum units 26 (26a, 26b, 26c, 26d) as a first unit and developing units 4 (4a, 4b, 4c, 4d) as a second unit. The drum unit 26 includes the photosensitive drum 1 (1a, 1b, 1c, 1d), the charging roller 2 (2a, 2b, 2c, 2d) and the cleaning member 6 (6a, 6b, 6c, 6d). Further, the developing unit 4 includes the developing roller 25.
To a cleaning frame 27 of the drum unit 26, the photosensitive drum 1 is rotatably mounted via a front drum bearing 10 and a rear drum bearing 11. The photosensitive drum 1 is provided with a drum coupling 16 and a flange 19 at an end portion thereof.
On a circumferential surface of the photosensitive drum 1, as described above, the charging roller 2 and the cleaning member 6 are disposed. The cleaning member 6 is constituted by an elastic member formed with a rubber blade and a cleaning supporting member 8. A free end portion of the elastic member is disposed in contact with the photosensitive drum 1 counter directionally to a rotational direction of the photosensitive drum 1. Further, residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls into a removed toner chamber 27a. Still further, a receptor sheet 29 for preventing leakage of the removed toner in the removed toner chamber 27a is contacted to the photosensitive drum 1.
By transmitting a driving force of a main assembly driving motor (not shown) as a driving source to the drum unit 26, the photosensitive drum 1 is rotationally driven in an image forming operation. The charging roller 2 is rotatably mounted to the drum unit 26 via a charging roller bearing 28 and is urged against the photosensitive drum 1 by a charging roller urging member 46, thus being rotated by the rotation of the photosensitive drum 1.
The developing unit 4 includes the developing roller 26, rotating in contact with the photosensitive drum 1 in an arrow B direction, and a developing device frame 31 for supporting the developing roller 25. Further, the developing unit 4 is constituted by a developing chamber 31b in which the developing roller 25 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 31 is positioned below the developing roller 25 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 25 is rotatably supported by the developing (device) frame 31 via a front developing (means) bearing 12 and a rear developing (means) bearing 13 provided in both sides of the developing device frame 31, respectively (
Further, a developer supplying roller 34 rotatable in contact with the developing roller 25 in an arrow E direction, and a developing blade 35 for regulating a toner layer on the developing roller 25 are provided to a peripheral surface of the developing roller 25.
The developer supplying roller 34 is constituted by a metal-made developer supplying roller shaft 34j and a sponge portion 34a that is an elastic portion for covering an outer peripheral surface of the shaft in an exposed state at end portions. The developer supplying roller 34 is disposed so that the sponge portion 34a is contacted to the developing roller 25 with a predetermined penetration amount into the developing roller 25. Further, a leakage-out preventing sheet 33 is provided as a developing (means) contact sheet for preventing the toner from leaking out of the developing frame 31 by contacting the developing roller 25.
Further, in the toner accommodating portion 31c in the developing frame 31, a toner feeding member 36 is provided 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.
As described above, the toner accommodating portion 31c is provided below the developing chamber 31b with respect to the direction of gravity, and the toner feeding member 36 is therefore also positioned below the developing chamber 31b with respect to the direction of gravity. That is, the developing cartridge 70 in this embodiment has a toner scooping-up constitution in which the toner is fed by the toner feeding member 36 against gravity from the toner accommodating portion 31c disposed at a lower position to the developing chamber 31b disposed at an upper position of the toner accommodating portion 31c.
Further, the cleaning frame 27 is provided with a front drum bearing 10 and a rear drum bearing 11 which rotatably support the photosensitive drum 1. The rear drum bearing 11 supports a drum coupling 16 coupled to the photosensitive drum 1. Further, the front drum bearing 10 supports the flange 19. Here, the drum coupling 16 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 1.
The developing frame 31 is provided with the front and rear developing bearings 12 and 13 for rotatably supporting the developing roller 25. Further, the developing unit 4 is constituted so as to be urged against the drum unit 26, during image formation of the process cartridge 70, by an urging spring 32 provided at each of ends of the developing frame 31. By these urging springs 32, an urging force for bringing the developing roller 25 into contact with the photosensitive drum 1 is generated with, as rotation centers, the hang holes 12a and 13a of the front and rear developing bearings 12 and 13.
(Insertion and Mounting Constitution of Process Cartridge into Image Forming Apparatus Main Assembly)
With reference to
In this embodiment, with respect to an insertion direction of the process cartridge 70, 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 100, main assembly upper mounting guide portions 103 (103a, 103b, 103c, 103d), which are first main assembly guide portions, are provided in an upper side. Further, in the image forming apparatus 100, main assembly lower mounting guide portions 102 (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 103 and the main assembly lower guide portions 102 has a guide shape extending along an insertion direction F of each of the process cartridge 70.
The process cartridge 70 is placed in a front side of the main assembly lower mounting guide portion 102 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 102 and 103, thus being inserted into the image forming apparatus 100.
An operation of mounting the process cartridge 70 into the apparatus main assembly 100A will be described.
Then, by the contact of the cartridge positioning portion 10a provided at the upper portion of the rear drum bearing 10 with the main assembly positioning portion 97a that is a main assembly side positioning portion of a front plate 97, the position of the process cartridge 70 relative to the apparatus main assembly 100A is determined. Also in this state, the guide portion 27b of the cleaning frame 27 is spaced from the guide surface of the main assembly lower mounting guide portion 102 such that the process cartridge 70 is pressed by a spring force of the main assembly pressing spring 105 received from the main assembly pressing member 104.
Further, the cleaning frame 27 is provided on a side surface thereof with a boss 27c as a rotation stopper for the process cartridge 70, and the boss 27c engages with a rotation preventing hole (portion) 98b provided in the rear plate 98. Thus, the process cartridge 70 is prevented from rotating in the apparatus main assembly 100A.
(Spacing Mechanism Between Photosensitive Drum and Developing Roller in Process Cartridge)
In the process cartridge 70 according to this embodiment, the photosensitive drum 1 and the developing roller 25 are capable of being contacted to and spaced from each other. Here, a spacing mechanism between the photosensitive drum 1 and the developing roller 25 will be described with reference to
In
Further, as shown in
(Spacing Mechanism when Process Cartridge is Mounted)
A spacing mechanism when the process cartridge 70 is mounted in the apparatus main assembly 100A will be described using
When the process cartridge 70 is mounted in the apparatus main assembly 100A, the developing unit 4 is in the contact position, and the photosensitive drum 1 and the developing roller 25 are in contact with each other. At the completion of the mounting of the process cartridge 70 in the apparatus main assembly 100A and at the end of the image forming operation of the image forming apparatus 100, the developing unit 4 is in the spaced position, and the photosensitive drum 1 and the developing roller 25 are spaced from each other.
Therefore, when the process cartridge 70 is mounted in the apparatus main assembly 100A, there is a need to move the process cartridge 70 from the contact position to the spaced position, and a constitution thereof will be described using
As shown in (a) of
When the process cartridge 70 is caused to further enter the apparatus main assembly, as shown in (c) of
(Constitution of Developer Supplying Roller Supporting and Developing (Means) Driving Force Inputting Portion in Process Cartridge)
Next, a constitution of a developing driving force inputting portion and a supporting constitution of the developer supplying roller 34 in the process cartridge 70 according to this embodiment will be described using
Using
The follower-side engaging portion 21 is fixed and mounted to an end portion (at one end side with respect to an axial direction) of the developer supplying roller shaft 34j. One fixing method is a connection made by a spring pin or a parallel pin. In another method, which as shown in
The driving-side engaging portion 23 (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 23 is rotatably held in a hole 41d of a holding portion 41. Further, the driving-side engaging portion 23 is integrally formed with three projections 23c1, 23c2 and 23c3 engageable with a main assembly side developing (means) coupling 91 (
This Oldham coupling 20 allows a deviation between an axis of the main assembly developing coupling 91 and an axis of the developer supplying roller 34, and transmits a rotational driving force (first rotational driving force) from the apparatus main assembly 100A to the developer supplying roller 34. Further, the Oldham coupling 20 is capable of transmitting a rotational driving force (second rotational driving force) from the apparatus main assembly 100A to the developer supplying roller 34 when the developing unit 4 is in the contact position and when the developing unit 4 is in the spaced position.
In
The intermediary engaging portion 22 engages with the follower-side engaging portion 21 and the driving-side engaging portion 23, and constitutes an intermediary portion for transmitting a driving force, inputted into the driving-side engaging portion 23, to the follower-side engaging portion 21. The intermediary engaging portion 22 is movable in a direction crossing the axial direction of the developer supplying roller 34 while maintaining engagement with each of the engaging portions 21 and 23.
The photosensitive drum 1 is provided, at one end side with respect to the axial direction, with a triangular prism drum coupling 16. A guide portion 41b of the holding portion 41 is movable, in a direction crossing the axial direction of the developer supplying roller 34, along the groove 43a of the side cover 43 fixed on the developing unit with an unshown screw or the like. That is, the driving-side engaging portion 23 is movable in a direction crossing the developing unit 4 (the direction crossing the axial direction of the developer supplying roller).
In
The main assembly drum coupling 90 is urged in a direction of the process cartridge 70 by a drum pressing (urging) member 106 such as a compression spring. Further, the main assembly drum coupling 90 is movable in the axial direction of the photosensitive drum 1. Further, in the case where the drum coupling 16 and the hole 90a of the main assembly drum coupling 90 are out of phase and in contact with each other when the process cartridge 70 is mounted in the apparatus main assembly 100A, the main assembly drum coupling 90 is pushed by the drum coupling 16, thus being retracted. Then by rotation of the main assembly drum coupling 90, the drum coupling 16 and the hole 90a are engaged with each other, and the rotational driving force is transmitted to the photosensitive drum 1.
Further, the main assembly developing coupling 91 is urged toward the process cartridge 70 in a direction parallel to the axial direction of the photosensitive drum 1 by a developing (means) pressing (urging) member 107, such as a compression spring. However, the main assembly developing coupling 91 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 91 rotates for transmitting the drive (driving force), but is only movable in the axial direction.
When the driving-side engaging portion 23 and the main assembly developing coupling 91 are engaged with each other as the process cartridge 70 enters the apparatus main assembly 100A, in some cases the projections 23c1-23c3 and the holes 91a1-91a3 are out of phase. In this case, free ends of the projections 23c1-23c3 contact portions other than the holes 91a1-91a3 such that the main assembly developing coupling 91 is retracted in the axial direction against an urging force of the developing pressing member 107. However, when the main assembly developing coupling 91 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 107.
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 such that the driving-side engaging portion 23 and the axis (rotation center) of the main assembly developing coupling 91 coincide with each other. Then, by rotation of the main assembly coupling 91, 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 34. Next, rotation of the developing roller 25 will be described. The developer supplying roller 34 is provided with the driving-side engaging portion 23 at one end side and is provided with a gear at 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 25 is provided with a gear engageable with the gear of the developer supplying roller. By this constitution, the rotational driving force is transmitted to the developing roller 25 from the developer supplying roller 34 by the gears at the other end side with respect to the longitudinal direction.
Here, the drive transmission to the main assembly drum coupling 90 and the main assembly developing coupling 91 is made by a motor provided in the apparatus main assembly 100A. By this, the photosensitive drum 1 and the developer supplying roller 34 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 70 for the respective colors and a constitution in which the drive is transmitted to multiple process cartridges by the single motor.
(Constitution of Developing Frame and Rotational Directions of Developing Roller and Developer Supplying Roller)
Next, a constitution of the developing frame and the rotational directions of the developing roller and the developer supplying roller will be described using
As described above, the toner accommodating portion 31c of the developing frame 31 is provided with the toner feeding member 36 (
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
In this embodiment, as shown in
In
On the other hand, at a portion where the rotation of the developer supplying roller 34 advances and the state of the developer supplying roller 34 is restored from the deformed state, air pressure inside the sponge portion 34a lowers with the restoration. For that reason, a flow of air is generated for taking in the toner toward the inside of the sponge portion 34a. 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 taking-in portion 34c is a region in a side downstream of the contact portion between the developer supplying roller 34 and the developing roller 25 with respect to the rotational direction of the developer supplying roller 34. 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 34, 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 25 is made. In order to provide a stable supply of the developer to the developing roller 25, it is important to stably supply the toner to the taking-in portion 34c.
As shown in
On the other hand, in this embodiment, with respect to the direction of gravity as shown in
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 31, the level of toner is raised to a position close to the taking-in portion 34c, and therefore such an arrangement is 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 level of toner 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 34 and the developing roller 25 with respect to the rotational direction of the developer supplying roller 34. 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 31f is naturally taken in by the developer supplying roller 34 and is gradually consumed.
Accordingly, unlike the conventional constitution, the circulation of the toner is made even when a developing chamber toner feeding member 37 as shown in
(Surface Speeds and Roller Diameters of Developing Roller and Developer Supplying Roller)
Using
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 rate of rotation of the developing roller 25 has a large influence on the toner supplying property to the photosensitive drum 1, and therefore from the viewpoint of a developing process, it is not desirable that the peripheral speed difference is provided by lowering the rate of rotation of the developing roller 25.
Therefore, in order to increase the peripheral speed of the developer supplying roller 34 while maintaining the rate of rotation of the developing roller 25, a method is used in which the rate of rotation of the developer supplying roller 34 is relatively increased by changing a gear ratio between a developer supplying roller gear 38 and a developing roller gear 39 (
Here, with respect to a surface speed ratio between the developing roller 25 and the developer supplying roller 34 (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 1.3 or more to 1.8 or less. This range is such that the necessary and sufficient toner supplying property and toner peeling off property can be maintained. When the peripheral speed ratio is below 1.3, 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 1.8 or less, the toner supplying property and the toner peeling-off property can be sufficiently maintained. When the peripheral speed ratio exceeds 1.8, friction becomes large, and thus abrasion of the developer supplying roller and the developing roller is liable be generated, and it is therefore not desirable that the surface speed of the developer supplying roller 34 is excessively increased. Here, in this embodiment, by the above-described diameter ratio and gear ratio, the surface speed of the developing roller 25 is set at about 304 mm/s and the surface speed of the developer supplying roller 34 is set at about 487 mm/s, so that the peripheral speed ratio therebetween is about 1.60. In this 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 to herein is a speed on the surface excluding the contact portion between the developing roller 25 and the developer supplying roller 34, and this is similarly applicable to also the peripheral speed ratio.
(Drive Input and Driving System for Developing Unit)
Using
Here, first, the drive input constitution of the developing unit 4 will be described using
As shown in
Using
As shown in
As shown in
(Small Deformation of Developer Supplying Roller)
Using
First,
In the case where the sponge portion 34a of the developer supplying roller 34 is not deformed, as shown in
On the other hand, in the embodiment shown in
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 considered from the viewpoint of the above-described roller peripheral speed difference, a tendency as shown in the Table in
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 34 is opposite 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 34 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 34, whereby it is possible to reduce image defects, e.g., when the developer supplying roller 34 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 that are capable of improving the image quality while reducing the number of parts and decreasing the amount of the residual toner.
According to the present invention, there are provided a process cartridge and an image forming apparatus which are capable of realizing reduction of a residual developer while reducing the number of parts, 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-273204 | Dec 2012 | JP | national |
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