Patent Application
20060072936
The present invention relates to a process cartridge and an electrophotographic image forming apparatus.
The electrophotographic image forming apparatus forms an image on a recording material through an electrophotographic image formation type process. The electrophotographic image forming apparatus may be an electrophotographic copying machine, an electrophotographic printer (a LED printer, a laser beam printer or the like), an electrophotographic printer type facsimile machine, an electrophotographic printer type word processor or the like.
In the field of an electrophotographic image forming apparatus using an electrophotographic image process, a process cartridge type is known in which an electrophotographic photosensitive member i.e. an electrophotographic photosensitive drum and process means actable on the electrophotographic photosensitive drum are integrally contained in a cartridge which is detachably mountable to a main assembly of an electrophotographic image forming apparatus as a unit. Such is process cartridge type is advantageous in that maintenance operation of the apparatus can be performed by the user without relying on a serviceman, and therefore, the operativity is good. Therefore, the process cartridge type is widely used in the field of image forming apparatus.
In an electrophotographic image forming apparatus, the light corresponding to image information is projected from a laser, LED or a lamp onto an electrophotographic photosensitive drum (photosensitive drum). This forms an electrostatic latent image on the photosensitive drum. The electrostatic latent image thus produced is developed by a developing member which is build in the process cartridge. The developed image formed on the photosensitive drum is transferred onto the recording is material. In this manner, an image is formed on a recording material.
In a conventional example, a developing device 1 includes a developing roller 3 swingably supported on a supporting shaft 8 provided in the main assembly of the image forming apparatus, and a follow gear 6 for transmitting the driving to the developing roller 3 (Japanese Laid-open Patent Application Sho 55-15177). The follow gear 6 is rotatably supported on an outside of a side plate supporting the developing roller 3, and it is brought into meshing engagement with a driving gear 7 provided in the main assembly of the image forming apparatus to transmit the driving force. The developing device 1 is correctly positioned relative to the main assembly of the image forming apparatus by the side plate abutting to a stopper 9 provided in the main assembly of the image forming apparatus. With this arrangement, the position where the driving force is transmitted to the follow gear 6 and the position where the side plate is abutted to the stopper 9 are different in the longitudinal direction of the developing device 1. Therefore, when the driving is transmitted from the driving gear 7, the developing device 1 is subjected to a moment about the position where the side plate is abutted to the stopper 9 with respect to the longitudinal direction of the developing device 1. There is a possibility that moment adversely affect the positional accuracy of the developing roller 3 and so on.
Accordingly, it is a principal object of the present invention to provide, a process cartridge and an electrophotographic image forming apparatus, in which the process cartridge are subjected to less bending moment and less deformation thereof when the process cartridge set in place in the main assembly of the electrophotographic image forming apparatus receives the driving force from the main assembly of the apparatus.
It Is another object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus in which the deformation of the process cartridge is suppressed, the deformation being otherwise caused by the force received by the driving input gear within the engagement range between the driving input gear and the main assembly driving gear when the process cartridge set in place in the main assembly of the electrophotographic image forming apparatus receives the driving force from the main assembly of the apparatus.
It is a further object of the present invention to provide a developing cartridge, a process cartridge and an electrophotographic image forming apparatus in which even when the rotational driving force is transmitted from the main assembly of the electrophotographic image forming apparatus, the developing roller is kept positioned with high accuracy relative to the main assembly of the apparatus.
It is a further object of the present invention to provide a developing cartridge, a process cartridge and an electrophotographic image forming apparatus which are downsized.
Accordint to an aspect of the present invention, there is provided a process cartridge detachably mountable to an electrophotographic image forming apparatus, said process cartridge comprising an electrophotographic photosensitive drum extending in a longitudinal direction of said process cartridge; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum; a first cartridge positioning portion which is provided at each of one and the other longitudinal end portion of said process cartridge and which is abuttable to a first main assembly positioning portion provided in the main assembly of the apparatus to position said process cartridge with respect to a direction crossing with the longitudinal direction, when said process cartridge is mounted to the main assembly of the apparatus; a second cartridge positioning portion which is provided at one longitudinal end portion of said process cartridge and which is abuttable to a second main assembly positioning portion provided in the main assembly of the apparatus to limit rotation of said process cartridge about said first cartridge positioning portion, when said process cartridge receives a rotational driving force for rotating said developing roller from the main assembly of the apparatus; a first drive input gear, provided at said one longitudinal end portion, for engagement with a main assembly driving gear provided in the main assembly to transmit a rotational driving force to said developing roller; a range of engagement, with respect to the longitudinal direction, between the main assembly driving gear and said input gear when said input gear is engaged with said main assembly gear, overlaps with said second cartridge positioning portion as seen in a direction which is perpendicular to the longitudinal direction and which passes through said second cartridge positioning portion.
According to another aspect of the present invention, there is provided a An electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, said apparatus comprising (a) a main assembly positioning portion: (b) a main assembly positioning portion; (c) a main assembly driving gear; (d) a mounting means for detachably mounting a process cartridge, said process cartridge including, an electrophotographic photosensitive drum extending in a longitudinal direction of said process cartridge; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum; a first cartridge positioning portion which is provided at each of one and the other longitudinal end portion of said process cartridge and which is abuttable to a first main assembly positioning portion provided in the main assembly of the apparatus to position said process cartridge with respect to a direction crossing with the longitudinal direction, when said process cartridge is mounted to the main assembly of the apparatus; a second cartridge positioning portion which is provided at one longitudinal end portion of said process cartridge and which is abuttable to a second main assembly positioning portion provided in the main assembly of the apparatus to limit rotation of said process cartridge about said first cartridge positioning portion, when said process cartridge receives a rotational driving force for rotating said developing roller from the main assembly of the apparatus; a first drive input gear, provided at said one longitudinal end portion, for engagement with a main assembly driving gear provided in the main assembly to transmit a rotational driving force to said developing roller; a range of engagement, with respect to the longitudinal direction, between the main assembly driving gear and said input gear when said input gear is engaged with said main assembly gear, overlaps with said second cartridge positioning portion as seen in a direction which is perpendicular to the longitudinal direction and which passes through said second cartridge positioning portion; said apparatus further comprising (e) feeding means for feeding the recording material.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
The description will be made as to a developing unit, a process cartridge and an electrophotographic image forming apparatus according to an embodiment of the present invention.
(General Arrangement of Image Forming Apparatus)
Referring to
The multi-color image forming apparatus 100 shown in this Figure includes four photosensitive drums 1a, 1b, 1c, 1d which are arranged substantially vertically. The photosensitive drum 1 is rotated in the counterclockwise direction in the Figure by a driving means (unshown). Around the photosensitive drum 1, there are provided charging means 2 (2a, 2b, 2c, 2d) for electrically charging the associated photosensitive drum 1 to a uniform potential, a scanner unit 3 (3a, 3b, 3c, 3d) for forming an electrostatic latent image on the photosensitive drum 1 by exposing it with a laser beam modulated in accordance with image information, and a developing unit 4 (4a, 4b, 4c, 4d) for developing the electrostatic latent image with a developer, electrostatic transferring means 5 for transferring the toner image provided by the development from the photosensitive drum 1 onto a recording material S, and cleaning means 6 (6a, 6b, 6c, 6d) for removing untransferred toner remaining on the surface of the photosensitive drum 1 after the image transfer, in the order named.
In this embodiment, the photosensitive drum 1, the charging means 2 developing unit 4 and the cleaning means 6 are contained in a cartridge 7 as a unit.
The photosensitive drum 1 has a photosensitive layer on an outer surface of an aluminum cylinder, for example. The photosensitive drum 1 is rotatably supported on a cleaning frame 51 (first frame) by end supporting members ((unshown) at the opposite ends. At one axial end of the photosensitive drum 1 (longitudinal end of the cartridge 7), there is provided a coupling member 25 mounted thereto as shown in
In this embodiment, a contact charging type charging means 2 (2a, 2b, 2c, 2d) is used. The charging means 2 is in the form of an electroconductive roller, which is contacted to the peripheral surface of the photosensitive drum 1. The roller 2 is supplied with a charging bias voltage. By this, the peripheral surface of the photosensitive drum 1 is uniformly charged. In this embodiment, the use is made with a reverse development, and therefore, the peripheral surface of the photosensitive drum 1 is charged to the negative polarity.
The scanner unit 3 (3a, 3b, 3c, 3d) is disposed substantially at the same levels as the associated photosensitive drum 1 and is extended substantially in a horizontal direction. The image light produced by a laser diode (unshown) correspondingly to an image signal is projected onto a polygonal mirror 9 which is rotated at a high speed by a scanner motor (unshown). The image light reflected by the polygonal mirror 9 is projected on the surface of the photosensitive drum 1 which has been electrically charged, through an imaging lens 10 (10a, 10b, 10c, 10d). By the imagewise exposure of the photosensitive drum to the image light, an electrostatic latent image is formed in accordance with the image signal.
As shown in
On the other hand, as shown in
A transfer roller 12 (12a, 12b, 12c, 12d) is disposed in the electrostatic transfer belt 11 which is an endless belt, and is contacted to the inside of the electrostatic transfer belt 11 at a position opposed to the associated photosensitive drum (1a, 1b, 1c, 1d). The transfer roller 12 applies charge of positive polarity to the recording material S through the electrostatic transfer belt 11. By this, the toner image is transferred from the photosensitive drum 1 onto the recording material S.
A feeding portion 16 functions to feed the recording material S to such an image forming station. Here, a cassette 17 accommodates a plurality of recording materials S. During the image forming operation, a paper feeding roller 18 (crescent roller) and registration roller 19 are rotated in accordance with the image forming operation. By this, the recording material S in the cassette 17 is fed out one by one. A leading end of the recording material S is abuted to the registration roller 19, and is temporarily stops to form a loop. The recording material S is fed to the electrostatic transfer belt 11 in timed relation with the rotation of the electrostatic transfer belt 11 and the image writing position by the registration roller 19.
The fixing portion 20 functions to fix the toner images of different colors having been transferred onto the recording material S. The fixing portion 20 includes a rotatable heating roller 21a and a pressing roller 21b press-contacted thereto to apply heat and pressure to the recording material S. The recording material S having the toner image transferred from the photosensitive drum 1, is fed by the pressing roller 21b in the nip of the fixing portion 20, provided by the heating and pressing rollers 21a and 21b. In t fixing portion 20, the recording material is pressed and heated by the pressing roller 21b and the heating roller 21a. By doing so, the toner image comprising toner particles having a plurality of colors is fixed on the surface of the recording material S.
The image forming operation is as follows.
The cartridges 7a, 7b, 7c, 7d are sequentially rotated in timed relation with the image forming operation. By this, the photosensitive drum (1a, 1b, 1c, 1d) are rotated in response thereto. The scanner unit 3 is sequentially actuated corresponding to the cartridges. By the actuation, the charging roller 2 applies uniform charge on the peripheral surface of the photosensitive drum 1. The scanner unit 3 exposes the peripheral surface of the photosensitive drum 1 in accordance with image signal to form an electrostatic latent image on the peripheral surface of the photosensitive drum 1. The developing roller 40 in the developing unit 4 transfers the toner to a low potential portion of the electrostatic latent image, thus forming a toner image on the peripheral surface of the photosensitive drum 1.
As described in the foregoing, the toner image is sequentially transferred from the photosensitive drums 1 onto the recording material S by the electric fields formed between the photosensitive drums 1 and the transfer rollers 12.
4 the recording material S onto which the toner image has been transferred, is separated from electrostatic transfer belt 11 by the belt driving roller 13 using the curvature of the belt driving roller 13, and is fed into the fixing portion 20. The recording material S is subjected to the heat fixing operation of the fixing portion 20 so that said toner image is fixed, and then is discharged from a discharging portion 24 onto the tray 28 with the image side facing down.
(Structure of Process Cartridge)
Referring to
In the cleaner unit 50, the photosensitive drum 1 is rotatably mounted to the cleaning frame 51 (first frame) through bearing members 31 (31a, 31b). The photosensitive drum 1 has a photosensitive layer on the outer surface thereof. Around the photosensitive drum 1, there are provided a charging means 2 for electrically charging the photosensitive layer to a uniform potential, a cleaning blade 60 for removing the toner remaining on the photosensitive drum 1 after the image transfer, and a flexible sheet 80. The charging means 2, the cleaning blade 60 and the flexible sheet 80 are support by the cleaning frame 51. The toner removed from the surface of the photosensitive drum 1 by the cleaning blade 60 is sequentially fed to a residual toner chamber 55 provision at a rear side of the cleaning frame 51.
The developing unit 4 contains a developing roller 40 rotating with a small gap from the photosensitive drum 1 and a developing device frame 45 (second frame). The developing roller 40 is rotatable in the direction indicated by arrow D2.
The developing device frame 45 comprising an upper frame 45a and a lower frame member 45b. The upper frame 45a and the lower frame member 45b are welded by ultrasonic welding to constitute a toner accommodating portion 46 for accommodating the toner. The developing roller 40 is rotatably supported by the developing device frame 45 through bearing members (unshown).
To the developing roller 40, the toner supplying roller 43 and the developing blade 44 are contacted. The toner supplying roller 43 is rotatable in the direction indicated by arrow D3. In the toner accommodating container 46, there is provided a toner feeding mechanism 42 for stirring and feeding the toner to the toner supplying roller 43.
The developing unit 4, as shown in
Similarly, as shown in
During the developing operation, the toner accommodated in the toner accommodating container 46 is fed to the toner supplying roller 43 by the toner stirring mechanism 42. The toner supplying roller 43 rotating in the direction indicated by an arrow D3 is in rubbing relation with the developing roller 40 rotating in the direction indicated by arrow D2, so that toner is supplied to the developing roller 40 to deposit the toner on the peripheral surface of the developing roller 40. The toner deposited and carried on the peripheral surface of the developing roller 40 is moved to the developing blade 44 with the rotation of the developing roller 40. The developing blade 44 regulates t toner to form a predetermined thin toner layer while applying desired amount of the charge to the toner. The thin layer of the toner thus provided on the developing roller 40 is fed to the developing zone where the developing roller 40 is close to the photosensitive drum 1. The toner is deposited onto the electrostatic latent image formed on the surface of the photosensitive drum 1 by a developing bias applied to the developing roller 40 from a voltage source (unshown) in the developing zone, thus forming a developed image.
The toner not used for the development and remaining on the surface of the developing roller 40 is returned into the developing device with the rotation of the developing roller 40. The toner is removed from the developing roller 40 at the sliding portion which the developing roller 40 is in sliding relation with the toner supplying roller 43 and is collected. The collected toner is stirred and mixed with the other toner by the toner stirring mechanism
(Mounting and Demounting of the Process Cartridge Relative to the Main Assembly of the Image Forming Apparatus)
Referring to
(Positioning of Process Cartridge)
As shown in
Thus, the rotational driving force from the driving gear 70 rotates the developing roller 40, the toner supplying roller 43 and the toner feeding mechanism 42, and the torque required for rotating them all is quite large. Therefore, as shown in
Referring to
(Positional Relation Between the Driving Input Gear and Positioning Portion)
In other words, the positional relation between the driving input gear 76 and the positioning portion 51a is as follows. As shown in
In further words, the positional relation is described as follows. The longitudinal engagement range Z shown in
Furthermore, the driving input gear 76, as seen in the direction V1, overlaps at least a part of the positioning portion 51a, with respect to the longitudinal direction of the cartridge 7.
With this structure, even when the cartridge 7 received t rotational driving force at the driving gear 70, the cleaning frame 51 is not subjected to a moment about the positioning portion 51a, as shown in
In this manner, the positioning accuracies of the developing roller 40 and the toner supplying roller 43 relative to the photosensitive drum 1 is improved. This is effective to improve the image quality of the image provided by the apparatus. In addition, the positioning accuracy of the cleaning blade 60 supported on the cleaning frame 51 relative to t photosensitive drum 1 is improved, so that removal property of the residual toner from the surface of the photosensitive drum 1 improved.
In this embodiment, as described hereinbefore, the cartridge positioning portion 51a is included in the engagement range Z with respect to the direction perpendicular to the longitudinal direction of the cartridge 7. However, only a part of the positioning portion 51a may overlap the engagement width Z. On the contrary, the width of the positioning portion 51a may be larger than the engagement width Z.
In the case that driving input gear 76 is a helical gear, the force Y is inclined correspondingly to the angle of twist of the gear teeth. However, when the deformation of the cleaning frame 51 by the moment about the positioning portion 51a, it will suffice if the component in the direction perpendicular to the supporting portion 72 (reference surface HP) is considered. That is, it is sufficient that component in the direction of the force Y shown
The positioning portion 51a is disposed above the driving input gear 76 when the cartridge 7 is set in place in the main assembly 100 of the apparatus. With this structure, the driving gear 70 and the second supporting portion 72 can be at different positions in the main assembly 100 of the apparatus, the main assembly 100 of the apparatus can be downsized, and the cartridge 7 can be downsized.
Moreover, the positioning portion 51a is provided by the peripheral surface of a cylindrical projection which is coaxial with the supporting hole supporting the pin 49. The projected portion is projected from the cleaning frame 51. The pin 49 is supported inside the projected portion. With this feature, the main assembly 100 of the apparatus can be downsized, and the cartridge 7 can be downsized.
The second cartridge positioning portion 51a may be provided only at one end side of the cartridge 7 with respect to t longitudinal direction. With the above-described positional relation between the engagement range Z and the cartridge positioning portion 51a, the deformation of the cleaning frame 51 can be suppressed, and the cartridge 7 can be correctly positioned to the main assembly 100 of the apparatus, even if the cartridge positioning portion is not provided at the other longitudinal end. This eliminates the necessity of the space for providing the positioning structure at the other side, so that main assembly 100 of the apparatus and the cartridge 7 can be downsized. This advantage is significant particularly when the cartridges 7 are arranged substantially in the vertical direction in the main assembly of the multi-color image forming apparatus 100 as in this embodiment.
(Checking)
The mounting structure of the developing device is frame 45 relative to the cleaning frame 51 may be as shown in
When they are seen in the direction V1 in
With this structure, the cleaning frame 51 is not subjected to a moment about positioning portion 51a. The deformation of the developing device frame supported rotatable Lines on the cleaning frame 51 can be suppressed, and therefore, the positioning accuracies of the developing roller 40 and the toner supplying roller 43 relative to t photosensitive drum 1 can be improved, so that image quality can be improved. The positioning accuracy of the cleaning blade 60 supported on the direction relative to the photosensitive drum 1 can be improved, so that removal property of the residual toner from the photosensitive drum 1 can be improved, too. In addition, the cartridge 7 and the main assembly 100 of the apparatus can be downsized.
In the first and second embodiments, the material of the cleaning frame 51 and the developing device frame 45 is a styrene material such as high impact polystyrene (HIPS), acrylic nytril butadiene polymer (ABS) or the like. From the standpoint of moldability and the cost, the thicknesses of the cleaning frame 51 and the developing device frame 45 are small. However, in order to assure a mechanical strength of the frame, a certain degree of thickness (approx. 2 mm) is required even when such a material is used. According to the present invention, the thickness can be reduced (for example, to degree 1.5 mm). In some cases, in order to reinforce the frame, a metal plate has been used at an upper part of the cartridge. However, according to the present invention, there is no need of using such a metal plate. This accomplishes cost reduction, downsizing, lightening, and better assembling properties.
As described in the foregoing, according to the present invention, the deformation of the developing cartridge or the process cartridge is suppressed when the rotational driving force is transmitted from the main assembly of the electrophotographic image forming apparatus. The positional accuracy of the developing roller is improved when the rotational driving force is transmitted from the main assembly of the electrophotographic image forming apparatus in the developing cartridge, the process cartridge and the electrophotographic image forming apparatus. In addition, the developing cartridge, the process cartridge and the electrophotographic image forming apparatus can be downsized.
While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims
This application claims priority from Japanese Patent Application No. 293846/2004 filed Oct. 6, 2004, which is hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 293846/2004(PAT.) | Oct 2004 | JP | national |
