Process cartridge and image forming apparatus

A process cartridge detachably mountable to the main body of an image forming apparatus includes an electrophotographic photosensitive drum, at least one process device for acting on the drum, a cartridge frame holding the drum and the process device and exposing a portion of the drum, a shutter member provided for movement between a position to protect and a position to permit exposure the of the drum, and a shutter opening and closing link mechanism for moving the shutter member in operative association with the opening and closing operation of an openable and closable door when the process cartridge is mounted on the cartridge mounting portion of the main body of the image forming apparatus.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process cartridge detachably mountable to an image forming apparatus, and to an image forming apparatus.

Herein, the image forming apparatus is an apparatus for forming an image on a recording medium such as recording paper, an OHP sheet, or cloth by the use of an electrophotographic image forming process, and covers, for example, an electrophotographic copying machine, an electrophotographic printer (such as an LED printer or a laser beam printer), a facsimile apparatus and a word processor.

The term “process cartridge” refers to an electrophotographic photosensitive drum and at least one process means for acting on the electrophotographic photosensitive drum integrally made into a cartridge detachably mountable to the main body of the image forming apparatus, or an electrophotographic photosensitive drum and at least developing means integrally made into a cartridge detachably mountable to the main body of the image forming apparatus. The process means include, in addition to developing means for supplying a developer to the electrophotographic photosensitive drum, charging means for charging the electrophotographic photosensitive drum, cleaning means for cleaning the electrophotographic photosensitive drum, etc.

2. Description of Related Art

In an image forming apparatus using the electrophotographic image forming process, selective exposure is effected on an electrophotographic photosensitive drum (hereinafter simply referred to also as the photosensitive drum) uniformly charged by charging means to thereby form a latent image on the surface of the photosensitive drum. The latent image is then visualized by a developer supplied from developing means, and thereafter the visualized image is transferred to a recording medium and further, the image is fixed by heat and pressure or the like to thereby effect image recording on the recording medium.

Also, any residual developer on the photosensitive drum after the transfer is removed by cleaning means, such as a cleaning blade and is contained as a removed developer in a cleaning container and therefore, the next development operation can be effected without any residual developer remaining on the surface of the photosensitive drum.

There has been adopted a process-cartridge system whereby of these portions concerned with image formation, the photosensitive drum and the process means (such as the charging means, the developing means and the cleaning means) for acting on the photosensitive drum are integrally made into a cartridge, which is made detachably mountable to the main body of the image forming apparatus. In this case, a user himself can effect the interchange of the cartridge to thereby interchange the photosensitive drum and consumables, such as the developer, without maintenance by a serviceman.

As the construction of an image forming apparatus for forming a multicolor (color) image by the use of such a process cartridge, a plurality of process cartridges containing developers of different colors therein are arranged in parallel to thereby constitute an image forming portion.

The process cartridge of this type may be left outside the main body of the image forming apparatus, or even if it is mounted in the main body of the image forming apparatus, the openable and closable door of the main body of the apparatus may sometimes be opened. In such a state, the photosensitive drum of the process cartridge may be exposed to external daylight and a characteristic thereof may deteriorate. Also, in case of the handling of the process cartridge outside the main body of the apparatus, the process cartridge may be damaged or foreign substances may adhere to the surface of the photosensitive drum. In order to eliminate the possibility of such deterioration or damage, there is provided a shutter member functioning as a protective member for protecting an exposed portion of the photosensitive drum, which is exposed out of a cartridge frame. When the process cartridge is outside the main body of the apparatus, the shutter member is closed, and when the process cartridge is mounted in the main body of the apparatus, the shutter member is opened to thereby expose the photosensitive drum, and during the operation of the image forming apparatus, it is retracted to a position in which it does not hamper image formation.

Now, in the image forming apparatus, in recent years, there has been a strong desire for the downsizing of the image forming apparatus on the part of the user, and there has been the problem that it is difficult to secure a great stroke for opening and closing the shutter member. There has further been a strong desire for the simple mounting and dismounting of the process cartridge, and it has been necessary to open and close the shutter member in operative association with the mounting and dismounting of the process cartridge. Moreover, the provision of a complicated mechanism on the opening and closing means of the shutter member leads to an increase in the cost of parts and the failure rate and therefore, it has been necessary for the opening and closing means to be a simple mechanism.

Further, in a full-color image forming apparatus of the in-line type, process cartridges of respective colors must be disposed in a limited space, and with regard also to the retraction position and retraction path of the shutter member of the photosensitive drum, the limitation in space is great. Also, not only in the full-color image forming apparatus, but also from the viewpoint of space saving, it is desirable that the space necessary for the retraction of the shutter member of the photosensitive drum be as small as possible.

SUMMARY OF THE INVENTION

So, it is an object of the present invention to provide a process cartridge and an image forming apparatus provided with a shutter member openable and closable in operative association with the mounting and dismounting of the process cartridge with respect to the main body of the image forming apparatus and retractable by a simple construction and a limited space.

It is another object of the present invention to provide a process cartridge and an image forming apparatus in which that portion of an electrophotographic photosensitive drum which is exposed out of a cartridge frame can be reliably protected by a shutter member.

It is another object of the present invention to provide a process cartridge and an image forming apparatus in which a shutter member can be retracted to a retraction position in a smaller space.

It is another object of the present invention to provide a process cartridge and an image forming apparatus in which a shutter member can be moved between a protection position and a retraction position in a smaller space.

It is another object of the present invention to provide a process cartridge and an image forming apparatus in which a shutter member can be reliably moved between a protection position and a retraction position.

It is another object of the present invention to provide a process cartridge detachably mountable to the main body of an image forming apparatus having a cartridge mounting portion for mounting the process cartridge thereon, and an openable and closable door, the process cartridge having an electrophotographic photosensitive drum, at least one process means for acting on the electrophotographic photosensitive drum, a cartridge frame holding the electrophotographic photosensitive drum and the process means and exposing a portion of the electrophotographic photosensitive drum therefrom, a shutter member provided for movement between a protection position in which it protects an exposed portion of the electrophotographic photosensitive drum that is capable of being exposed out of the cartridge frame and a retraction position in which it is retracted from the protection position to expose the exposed portion of the electrophotographic photosensitive drum that is exposed out of the cartridge frame, and a shutter opening and closing link mechanism for moving the shutter member in operative association with the opening and closing operation of the openable and closable door when the process cartridge is mounted on the cartridge mounting portion of the main body of the image forming apparatus, and an image forming apparatus on which the process cartridge is detachably mountable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The general construction of an image forming apparatus according to the present invention and image formation thereby will first be schematically described with reference to FIG.1.FIG. 1is a cross-sectional view showing the general construction of a full-color laser beam printer which is an embodiment of the image forming apparatus of the present invention.

The image forming apparatus P shown inFIG. 1is such that a plurality of (inFIG. 1, four) cartridge mounting portions (30a,30b,30c,30d) for mounting thereon process cartridges (hereinafter simply referred to also as the cartridges)7(7a,7b,7c,7d) provided with electrophotographic photosensitive drums (hereinafter simply referred to as the photosensitive drums) (1a,1b,1c,1d), functioning as image bearing members, are juxtaposed in a vertical direction. In the respective process cartridges7(7a,7b,7c,7d), the photosensitive drums (1a,1b,1c,1d) are driven in a counterclockwise direction as viewed inFIG. 1by driving means (not shown). Around the photosensitive drums (1a,1b,1c,1d), there are disposed, in succession in accordance with the direction of rotation thereof, charging devices (2a,2b,2c,2d) for uniformly charging the surfaces of the photosensitive drums (1a,1b,1c,1d), scanner units (3a,3b,3c,3d) for applying laser beams onto the photosensitive drums on the basis of image information to thereby form electrostatic latent images thereon, and developing devices (4a,4b,4c,4d) for causing developers to adhere to the electrostatic latent images to thereby develop the electrostatic latent images. Also, there is disposed an electrostatic transfer device5for transferring the developer images on the photosensitive drums to a recording medium S. This electrostatic transfer device5has an electrostatic transport belt11and transfer rollers (12a,12b,12c,12d). Also, there are disposed cleaning devices (6a,6b,6c,6d) for removing any developers remaining on the surfaces of the photosensitive drums after the transfer.

The photosensitive drums (1a,1b,1c,1d), the charging devices (2a,2b,2c,2d), the developing devices (4a,4b,4c,4d), the cleaning devices (6a,6b,6c,6d) and developer containing portions (8a,8b,8c,8d) are made integral with one another to thereby constitute the process cartridges7(7a,7b,7c,7d). The construction of the process cartridges7is shown in detail in FIG.4. These cartridges7(7a,7b,7c,7d) are detachably mounted on the cartridge mounting portions (30a,30b,30c,30d) of the main body25of the image forming apparatus (hereinafter simply referred to also as the main body of the apparatus). The scanner units (3a,3b,3c,3d) are attached to the main body25of the apparatus so as to correspond to the cartridges7(7a,7b,7c,7d) mounted on the cartridge mounting portions (30a,30b,30c,30d).

The respective constructions will hereinafter be described in succession. The constructions of the respective cartridges7are schematically similar to one another.

Each of the photosensitive drums (1a,1b,1c,1d) is comprised, for example, of an aluminum cylinder having a diameter of 30 mm and a photoconductive layer provided on the outer peripheral surface thereof. Each of the photosensitive drums has the opposite end portions of its drum shaft rotatably supported by support members such as bearings. A driving force from a driving motor (not shown) provided on the main body side of the apparatus is transmitted to one end portion of each of the photosensitive drums, whereby each of the photosensitive drums1is driven to rotate in a counterclockwise direction as viewed in FIG.1.

As the charging devices (2a,2b,2c,2d), use is made of ones of the contact-charging type. Each of the charging devices has an electrically conductive roller formed into a roller shape. This charging roller is brought into contact with the surface of each of the photosensitive drums. By a charging bias voltage being applied to the charging roller, the surface of each of the photosensitive drums is uniformly charged. In the present embodiment, a discharged area developing system is used and therefore, the surface of each of the photosensitive drums is charged to the negative polarity.

The scanner units (3a,3b,3c,3d) are disposed substantially in the horizontal direction of the respective photosensitive drums (1a,1b,1c,1d) of the process cartridges7mounted on the cartridge mounting portions (30a,30b,30c,30d). The scanner units (3a,3b,3c,3d) apply image light corresponding to an image signal to polygon mirrors (9a,9b,9c,9d) rotated by a scanner motor (not shown), by laser diodes (not shown). The image light reflected by the polygon mirrors (9a,9b,9c,9d) selectively exposes the charged surfaces of the photosensitive drums (1a,1b,1c,1d) thereto through imaging lenses (10a,10b,10c,10d). As a result, electrostatic latent images corresponding to respective colors are formed on the photosensitive drums.

The developing devices (4a,4b,4c,4d) have developer containing portions (8a,8b,8c,8d) containing yellow, magenta, cyan and black developers therein. The developing devices cause the developers of the respective colors to adhere to the electrostatic latent images formed on the corresponding photosensitive drums (1a,1b,1c,1d) to thereby develop those electrostatic latent images as developer images. The yellow developer is contained in the developer containing portion8aof the cartridge7a, and likewise, the magenta developer, the cyan developer and the black developer are contained in the developer containing portion8bof the cartridge7b, the developer containing portion8cof the cartridge7cand the developer containing portion8dof the cartridge7d. respectively.

The cleaning devices (6a,6b,6c,6d) are for scraping off and removing any residual developers remaining on the photosensitive drums (1a,1b,1c,1d) after the developer images formed thereon are transferred to the recording medium S by the electrostatic transfer device5. The photosensitive drums (1a,1b,1c,1d) cleaned by the cleaning devices (6a,6b,6c,6d) become capable of effecting the next image-forming process again.

The electrostatic transfer device5has an electrostatic transport belt11for electrostatically attracting and transporting the recording medium S so as to bring the recording medium S into contact with the plurality of photosensitive drums (1a,1b,1c,1d) It also has transfer rollers (12a,12b,12c,12d) disposed at locations opposed to the respective photosensitive drums (1a,1b,1c,1d) to transfer the developer images formed on the photosensitive drums to the recording medium S.

As the electrostatic transport belt11, use is made of a multi-layer film-like member comprising resin film or a rubber base layer and a resin layer provided thereon. The electrostatic transport belt11is moved round so as to contact all of the photosensitive drums1(1a,1b,1c,1d). In the present embodiment, the electrostatic transport belt11is a belt having a circumferential length of about 700 mm and a thickness of about 150 μm, and is passed over a drive roller13, driven rollers14a,14band a tension roller15. The electrostatic transport belt11is rotatably driven (in the direction indicated by the arrow inFIG. 1) by the driving force of the drive roller13. Also, an electrostatic attraction roller22is disposed at a region opposed to the driven roller14aat the lower end. This attraction roller22is urged against the outer periphery of the electrostatic transport belt11so as to sandwich the recording medium S between itself and the electrostatic transport belt11. A voltage is applied to between the electrostatic transport belt11and the attraction roller22. As a result, charges are induced in the dielectric material layers of the recording medium S, which is a dielectric material and the electrostatic transport belt11, and the recording medium S is electrostatically attracted to the outer periphery of the electrostatic transport belt11.

Also, the transfer rollers (12a,12b,12c,12d) are disposed at locations opposed to the photosensitive drums (1a,1b,1c,1d) and contact with the inner side of the electrostatic transport belt11. A bias voltage of the positive polarity is applied to these transfer rollers (12a,12b,12c,12d) during transfer, and charges of the positive polarity are applied to the recording medium S through the electrostatic transport belt11. By an electric field created at this time, the developer images of the negative polarity on the photosensitive drums1are transferred to the recording medium S which is in contact with the photosensitive drums1.

In the transfer device5constructed as described above, the electrostatic transport belt11attracts the recording medium S to the left outer peripheral surface thereof as viewed inFIG. 1by the attraction roller22. The electrostatic transport belt11is moved round to bring the recording medium S into contact with the respective photosensitive drums (1a,1b,1c,1d). By the action of the transfer rollers (12a,12b,12c,12d) opposed to the photosensitive drums (1a,1b,1c,1d), the developer images on the respective photosensitive drums (1a,1b,1c,1d) are transferred to the recording medium S while it is transported from the roller14aside to the roller13side.

A feeding portion16transports the recording medium S to the image forming portion. A cassette17contains a plurality of recording mediums S therein. A feed roller18and a pair of registration rollers19are rotatably driven in conformity with the image forming operation. Thereby, during image formation, the recording media S in the cassette17are separated and fed one by one. The leading edge of each recording medium S hits against the pair of registration rollers19and is once stopped thereby, and forms a loop. Thereafter, the pair of registration rollers19are rotated with the rotation of the electrostatic transport belt11synchronized with the image writing start position. The recording medium S is then fed to the electrostatic transport belt11.

A fixing portion20fixes the developer images of plural colors transferred to the recording medium S on the recording medium S. It has a rotatable heat roller21aand a pressure roller21burged against it and imparting heat and pressure to the recording medium S. That is, the recording medium S to which the developer images on the photosensitive drums1have been transferred is transported by the pair of fixing rollers (21a,21b) and is given heat and pressure by the pair of fixing rollers when it passes through the fixing portion20. As a result, the developer images of plural colors are fixed on the surface of the recording medium S.

The image forming process by the image forming apparatus of the present invention will be further described with reference to FIG.1. The process cartridges7(7a,7b,7c,7d) mounted on the respective cartridge mounting portions (30a,30b,30c,30d) of the main body25of the apparatus are successively driven in timed relationship with image formation. In conformity with the driving, the photosensitive drums (1a,1b,1c,1d) are rotatably driven in the counterclockwise direction. The scanner units (3a,3b,3c,3d) corresponding to the respective cartridges7(7a,7b,7c,7d) are successively driven. By this driving, the charging devices (2a,2b,2c,2d) impart uniform charges to the peripheral surfaces of the photosensitive drums (1a,1b,1c,1d). The scanner units (3a,3b,3c,3d) effect exposure on the peripheral surfaces of the photosensitive drums (1a,1b,1c,1d) in conformity with an image signal. As a result, electrostatic latent images of respective colors are formed on the peripheral surfaces of the photosensitive drums (1a,1b,1c,1d). The developing rollers of the developing devices (4a,4b,4c,4d) supply the developers contained in the developer containing portions (8a,8b,8c,8d) and cause the developers to shift to the low potential portions of the electrostatic latent images. As a result, developer images are formed on the peripheral surfaces of the photosensitive drums (1a,1b,1c,1d). That is, the electrostatic latent images formed on the photosensitive drums (1a,1b,1c,1d) are developed.

The pair of registration rollers19start to be rotated in accordance with the timing at which the leading edge of the developer image on the peripheral surface of the most upstream photosensitive drum1ais rotatably transported to a point opposed to the electrostatic transport belt11so that the image-formation starting position of the recording medium S may coincide with the opposed point. They feed the recording medium S to the electrostatic transport belt11.

The recording medium S is urged against the outer periphery of the electrostatic transport belt11by the attraction roller22and the electrostatic transport belt11. A voltage is then applied to between the electrostatic transport belt11and the attraction roller22. Thereby, the recording medium S is electrostatically attracted to the outer periphery of the electrostatic transport belt11. The recording medium S is stably attracted to the electrostatic transport belt11and is transported to the most downstream transfer portion.

As described above, the recording medium S is transported by the electrostatic transport belt11, and in this transporting process, the developer images of respective colors formed on the photosensitive drums1a,1b,1c,1dare successively transferred to the recording medium S by electric fields formed between the corresponding photosensitive drums1a,1b,1c,1dand transfer rollers12a,12b,12c,12d.

The recording medium S to which the developer images of respective colors have been transferred is self-stripped from the electrostatic transport belt11by the curvature of the belt drive roller13. Thereafter, it is carried into the fixing portion20. The recording medium S has the developer images thereon heat-fixed by the heat roller21aand the pressure roller21bin the fixing portion20. Thereafter, the recording medium S is delivered from a delivery portion24to the outside of the main body of the apparatus by a pair of delivery rollers23with its image bearing surface facing downward.

On the other hand, any untransferred residual developer on the surfaces of the photosensitive drums (1a,1b,1c,1d) is scraped off by the respective cleaning devices (6a,6b,6c,6d). The thus cleaned photosensitive drums (1a,1b,1c,1d) again become capable of carrying out the next image forming process.

A description will now be provided of the construction of the cartridge mounting portions of the main body of the apparatus and a method of mounting and dismounting the cartridges with respect to the cartridge mounting portions.

The process cartridges 7 (7a,7b,7c,7d) are designed to be interchanged with new ones after a predetermined amount of image formation with the service lives of the photosensitive drums1and the respective process means, such as the charging devices, the developing devices and the cleaning devices and the amounts of developers contained in the developer containing portions, taken into account. When, depending on the service life of each process means and the consumption of each developer, the interchange of each cartridge is required or a new cartridge is to be mounted on the main body of the apparatus, each process cartridge is mounted to or dismounted from the cartridge mounting portion of the main body25of the apparatus in a direction perpendicular to the axial direction of each photosensitive drum1.

The main body25of the apparatus, as shown inFIGS. 1to3, is provided with an insertion port having a width greater than the width of the cartridge7in the lengthwise direction thereof (the lengthwise direction of the photosensitive drum), and is provided therein with a plurality of (inFIG. 1, four) cartridge mounting portions (30a,30b,30c,30d). A front door (openable and closable door)26is mounted in the insertion port of the main body25of the apparatus so as to be openable and closable about a rotary shaft26arelative to the main body25of the apparatus. The front door26is provided with the electrostatic transport belt11and the transfer rollers (12a,12b,12c,12d) of the electrostatic transfer device5, and the rollers13to15for supporting the electrostatic transport belt11. The front door26is usually closed as shown inFIG. 1, and is opened by an operator as shown inFIG. 2in case of the new mounting or interchange of the cartridges7. Simultaneously with the opening of the front door26, the electrostatic transfer device5is also moved and the cartridge mounting portions (30a,30b,30c,30d) are opened.

As shown inFIG. 3, first main body guide portions (31a,31b,30c,30d) and second main body guide portions (32a,32b,32c,32d) for guiding the cartridges7to the cartridge mounting portions are provided in juxtaposed relationship at equal intervals on a first side plate27and a second side plate28, respectively, of the main body25of the apparatus. Also, at the regions of the first side plate27which correspond to the respective cartridge mounting portions, there are provided dash surfaces (33a,33b,33c,33d) and (34a,34b,34c,34d) abutting against the outer peripheral surfaces of bearings67rotatably supporting the photosensitive drums of the cartridges7and protruding outwardly from the sides thereof. At the regions of the second side plate28which correspond to the respective cartridge mounting portions, there are provided dash surfaces (35a,.35b,35c,35d) and (36a,36b,36c,36d) abutting against the outer peripheral surfaces of bearings68rotatably supporting the photosensitive drums1of the cartridges7and protruding outwardly from the side thereof. As a result, the cartridges7are positioned with respect to the respective cartridge mounting portions through the bearings67and68rotatably supporting the photosensitive drums1. Resilient members (not shown) such as pressure springs for pressing the cartridges7against predetermined positions are disposed on the respective cartridge mounting portions. The cartridges are also pressed against one side plate to position the photosensitive drums1.

The process cartridges7(7a,7b,7c,7d), as shown inFIG. 3(and FIG.4), are provided with grip portions66protruding to the side opposite to the mounting direction of the cartridges7on the opposite end portions thereof in the widthwise direction of the cartridge frames thereof (the lengthwise direction of the photosensitive drums). When mounting the cartridge7on the cartridge mounting portion of the main body25of the apparatus, the operator grasps the grip portions66by his hands, and inserts the cartridge7horizontally along the main body guide portions and (FIG. 3) provided on the opposite side plates27and28of the main body,25of the apparatus, with the photosensitive drum (inFIG. 4,5) disposed on this side. Then, the operator causes the bearings67and68rotatably supporting the photosensitive drum1of the cartridge7to abut against the dash surfaces (33a,33b,33c,33d,34a,34b,34c,34d,35a,35b,35c,35d,36a,36b,36c,36d) respectively, and ram them against these dash surfaces. Thereby, the cartridge7is positioned and mounted on each cartridge mounting portion of the main body25of the apparatus. After the cartridge7has been mounted on the cartridge mounting portion, the operator closes the front door26. Thereby, the cartridge7is set at a predetermined position by the pressing of the resilient member such as a pressure spring, not shown. At the same time, as shown inFIG. 1, the electrostatic transport belt11of the electrostatic transfer device5provided on the front door26comes into contact with the photosensitive drum1of each cartridge7.

The construction of the process cartridges and a shutter member as a protective member for protecting the photosensitive drum will now be described in detail with reference toFIGS. 4to7.

The cartridge7of the present embodiment, as shown inFIG. 4, has a drum unit41as an upper unit (a first frame) and a developing unit42as a lower unit (a second frame). The two units41and42are pivotally coupled together by a rocking movement center43, as will be described later.

The photosensitive drum51(corresponding to the photosensitive drum inFIG. 1) is rotatably supported on the upper unit (drum unit)41at the opposite side walls of the frame41aof the upper unit41. The drum shaft51A of the photosensitive drum51is rotatably journalled through bearings67and68(one bearing67only being shown in FIG.6). The upper unit41further has the charging member (charging roller)52of the charging device, the cleaning member (cleaning blade)56of the cleaning device, a removed developer containing portion55for containing therein the developer removed by the blade56, and removed developer transporting means57. On the photosensitive drum51, a flexible sheet member63is disposed upstream of the cleaning blade56. Any untransferred developer on the photosensitive drum51passes that portion of the flexible sheet member63which is in contact with the photosensitive drum51and arrives at the position of the cleaning blade56, but the contacting condition of the flexible sheet member63is set so that the developer removed from the photosensitive drum51by the blade56may not leak to the outside of the frame41aof the upper unit41. Also, the removed developer transporting means57has a crank rotatably provided on the removed developer containing portion55, and a removed developer transporting member57rotatably supported on this crank. The transporting member57is reciprocally moved by the crank being rotatively driven and transports the removed developer from the vicinity of the blade56to the removed developer containing portion55.

The lower unit (developing unit)42is provided with the developing member (developing roller)54of the developing device, a developing frame58and a developer containing portion59(corresponding to the developer containing portion inFIG. 1) containing the developer of each color therein. The developer containing portion59is located below the removed developer containing portion55. The interior of the developer containing portion59is provided with agitating members60aand60bserving also as a developer feeding mechanism. The developer in the developer containing portion59is fed to a developer supply roller61in the developing frame58while being agitated by the agitating members60aand60b. The developer adheres to the outer periphery of the developing roller54by a developing blade62abutting against the developer supply roller61rotated in the direction indicated by the arrow and the outer periphery of the developing roller54rotated in the direction indicated by the arrow, and charges are imparted thereto.

Also, bearing members48and49to be coupled to the upper unit41are provided on the opposite walls of the frame of the lower unit42(the lengthwisely opposite ends of the developing roller54). The bearing members48and49have through-holes coaxially with the rocking movement center43, and positioning pins are fitted into these through-holes and holes formed in the upper unit41. Thereby, the upper unit41and the lower unit42are rockably coupled together through the rocking movement center43.

Also, by the resilient forces of pressure springs64disposed on the lengthwisely opposite end portions of the photosensitive drum51which are the end portions of the two units41and42opposite to the photosensitive drum51, the two units41and42are biased so that the developing roller54may be pressed against the photosensitive drum51about the rocking movement center43. Thereby, the photosensitive drum51and the developing roller54reliably contact each other over the entire lengthwise area thereof. InFIG. 4, the reference numeral65designates an exposure opening portion formed between the upper unit41and the lower unit42, and the photosensitive drum51is exposed to an optical image applied from the scanner unit3through this exposure opening portion65to thereby form an electrostatic latent image on the photosensitive drum51.

When the electrostatic latent image is to be developed by the use of the process cartridge, the developer contained in the developer containing portion59is fed to the developer supply roller61in the developing frame58while being agitated by the agitating members60aand60b. The developer supply roller61rotated in the direction indicated by the arrow supplies the developer to the developing roller54by the rubbing thereof against the developing roller54rotated in the direction indicated by the arrow and causes the developer to be borne on the developing roller54. The developer borne on the developing roller54comes to the developing blade62with the rotation of the developing roller54, and the developing blade62regulates the developer and forms a developer layer of a predetermined thickness, and a desired amount of charge is imparted thereto. The developer made into a thin layer on the developing roller54is transported to a developing portion in which the photosensitive drum51and the developing roller54are in contract with each other, with the rotation of the developing roller54in the direction indicated by the arrow, and in the developing portion, the developer adheres to the electrostatic latent image formed on the surface of the photosensitive drum51, by a DC developing bias applied from a power source (not shown) to the developing roller54, thereby developing the latent image. Any residual developer on the surface of the developing roller54without contributing to the development of the electrostatic latent image is returned into the developing frame58with the rotation of the developing roller54, and is stripped and collected from the developing roller54at the frictional contact portion thereof with the developer supply roller61. The thus collected developer is agitated and mixed with the remaining developer by the agitating members60aand60b.

In the contact developing system of the present embodiment, in which the photosensitive drum51and the developing roller54are in contact with each other and effect development, it is preferable that the photosensitive drum51be a rigid member and that the surface layer of the developing roller54(the contact portion thereof with the photosensitive drum51) be an elastic member. As this elastic member, use is made of a solid rubber single layer or a solid rubber layer subjected to resin coating thereon with a charge imparting property to the developer taken into account.

Now, a characteristic of the photosensitive drum51in the process cartridge7will deteriorate if exposed to external daylight for a long time, and if the photosensitive drum51is exposed in case of the handling thereof outside the image forming apparatus, it may be damaged or foreign substances may adhere to its surface. In order to eliminate such possibility of deterioration or damage, provision is made of a drum shutter (shutter member)100functioning as a protective member for opening and closing the opening portion for exposing a portion of the photosensitive drum51in the frame of the process cartridge7to thereby protect the photosensitive drum, and when the process cartridge7is mounted on the cartridge mounting portion of the main body25of the apparatus, the drum shutter100is opened and exposes the photosensitive drum51, but the drum shutter100is designed to be closed in the other cases.

As shown inFIGS. 4 and 5, in the frame opening portion from the distal end portion58aof the developing frame to the contact portion of the flexible sheet member63in the frame of the process cartridge7, there is disposed the drum shutter100which is retractable to a position in which it does not hinder the transfer of the developer image to the recording medium during image formation. That is, the drum shutter100is provided for movement between a protection position (shielding position) in which it shields the opening portion of the cartridge frame for exposing a portion of the photosensitive drum51therethrough and protects the exposed portion of the photosensitive drum51(a position indicated by solid line inFIGS. 4 and 5) and a retraction position in which it is retracted from the protection position and opens the opening portion (a position indicated by double-dotted line in FIGS.4and5).

The drum shutter100, as shown inFIG. 5, is movably mounted through a shutter opening and closing link mechanism103comprising a shutter shaft member101and a shutter opening and closing arm102pivotably supported on the frame of the cartridge7(the side wall surface of the frame41aof the upper unit41). The shutter shaft member101of the shutter opening and closing link mechanism103which comprises a substantially U-shaped metal bar or the like has its opposite end portions110arotatably journalled to the right and left side wall surfaces of the frame41aof the cartridge7, and its central portion101bis rotatably mounted on the vertically central portion of the drum shutter100along the widthwise direction thereof. The shutter opening and closing arm102is a transmitting member for performing the opening and closing operation of the drum shutter100in operative association with the opening and closing operation of the front door (openable and closable door)26of the main body25of the apparatus which will be described later, and is rotatably supported by a rotary shaft102adisposed on the left wall surface of the frame41aof the cartridge7, and one end portion102bthereof is rotatably mounted on the lower end portion of the drum shutter100, and on the other end portion thereof, a convex member102cis provided while leftwardly protruding through an arcuate groove106. This convex member102cis provided with an abutting portion102dabutting against a shutter interlocking plate111(seeFIGS. 8to10) operatively associated with the opening and closing operation of the front door26of the main body25of the apparatus. It is preferable that at least the abutting portion102dprotrudes from the side wall surface of the frame41aof the cartridge7through the arcuate groove106. Also, the shutter opening and closing arm102of the shutter opening and closing link mechanism103is biased in a counterclockwise direction by a shutter spring (not shown) so as to maintain the protection position indicated by solid line in FIG.5. Accordingly, in a state in which no force is applied to the convex member102cand the abutting portion102dof the shutter opening and closing arm102, such as a state in which the cartridge7has been taken out of the main body25of the apparatus, the drum shutter100is positioned in the protection position indicated by solid line inFIGS. 4 and 5, by the biasing force of the shutter spring (not shown). The shutter opening and closing arm102then performs the opening and closing operation of the drum shutter100in operative association with the vertical movement of the shutter interlocking plate111, which will be described later.

On the main body25side of the image forming apparatus P, as shown inFIGS. 8to10, there is provided a (main body side) shutter opening and closing mechanism110for vertically moving the shutter interlocking plate111for performing the opening and closing operation of the drum shutter100of each cartridge7in operative association with the opening and closing operation of the front door26of the main body25of the apparatus. The shutter opening and closing mechanism110is disposed on the inner surface side of the side wall27of the main body25of the apparatus, and is comprised of the shutter interlocking plate111extending substantially vertically along each cartridge mounting portion30and disposed for movement in the vertical direction, a cam member112against which the lower end portion of the shutter interlocking portion111abuts a cam gear113provided integrally with the cam member112, and a rotary member115having a gear portion115ameshing with the cam gear113and a pressed portion115bengaged with the pressed by a pressing portion116provided on the front door26, and disposed for rotation about a rotary shaft115c.In the present embodiment, the pressing portion116provided on the front door26is provided by the circumferential portion of the shaft portion of the driven roller14aof the electrostatic transport belt11located in the lower portion of the front door26being protruded toward a side. Also, the shutter interlocking portion111is provided with a projected portion111afor abutting against and vertically moving the abutting portion102dof the shutter opening and closing arm102of the cartridge in each cartridge mounting portion.

The relation between the opening and closing operation of the front door of the main body of the apparatus and the movement of the drum shutter will now be described with reference toFIGS. 8to10.

In case of the new mounting or interchange of the cartridge7, the front door26of the main body25of the apparatus is opened and the cartridge7is inserted into and mounted on a predetermined cartridge mounting portion. Thereafter, the front door26is closed. The state in which the cartridge7is mounted on the predetermined cartridge mounting portion is shown inFIGS. 8 and 9. In this state, the drum shutter100of the cartridge7is still positioned in the protection position (see also FIG.6). In case of the closing operation of pivotally moving the front door26in the direction indicated by the arrow about the rotary shaft26afrom this state, the pressing portion116of the front door26is moved and abuts against the pressed portion115bof the rotary member115, thereby pivotally moving the rotary member115in the direction indicated by the arrow about the rotary shaft115c. This pivotal movement of the rotary member115in the direction indicated by the arrow pivotally moves the gear portion115ato thereby rotate the cam gear113meshing with the gear portion115ain the direction indicated by the arrow. By this rotation of the cam gear113, the cam member112is also rotated at the same time to thereby upwardly move the shutter interlocking plate111abutting against the cam member112. By this upward movement of the shutter interlocking plate111, the projected portion111ais also upwardly moved to thereby push up the abutting portion102dof the shutter opening and closing arm102against which the projected portion111ais abutting. Thereby, the shutter opening and closing arm102is pivotally moved clockwise about the rotary shaft102a, and by the downward movement of one end portion102bof the shutter opening and closing arm102, the drum shutter100is pivotally moved about the opposite end portions111aof the shutter shaft member101and is moved to the retraction position shown inFIG. 10, and a portion of the photosensitive drum51is exposed through the opening portion (see also FIG.7). When the front door26is completely closed in this manner, the drum shutter100is moved to the retraction position, as shown in FIG.10. This retraction position of the drum shutter100is a position in which it does not hinder the image formation by the process cartridge between the cartridge frame41aand the openable and closable door26and between adjacent cartridges. The electrostatic transport belt11contacts with the photosensitive drum51exposed through the opening portion of the cartridge frame41aand the transfer roller12is positioned at a position corresponding to the photosensitive drum51. In this manner, there is brought about a state in which image formation becomes possible.

Also, when the front door26is to be opened for the interchange or the like of the cartridge7, the main body side shutter opening and closing mechanism110and the shutter opening and closing link mechanism103are operated conversely to the aforedescribed operation, by the opening operation of the front door26. That is, when inFIG. 10, the front door26is pivotally moved in the clockwise direction about the shaft26a, the rotary member115is pushed by the pressing member116and begins to be rotated in the clockwise direction about the rotary shaft115. The cam gear113meshing with the gear portion115aof the rotary member115is then rotated in the counterclockwise direction about the shaft113a. Thereby, the shutter interlocking plate111abutting against the cam112is downwardly moved and the projected portion111aof the shutter interlocking plate111releases its abutment against the abutting portion102dof the shutter opening and closing arm102and is downwardly moved. As a result, the drum shutter100is moved from the retraction position indicated by dots-and-dash line inFIG. 5to the protection position indicated by solid line inFIG. 5by the biasing force of the shutter spring (not shown), and is returned to the protection position.

By constructing the drum shutter and the opening and closing means therefore as described above, it is possible to open and close the drum shutter in operative association with the opening and closing operation of the front door associated with the mounting and dismounting operation of the process cartridge. Further, the drum shutter is moved by the use of the shutter opening and closing link mechanism comprising the shutter shaft member and the shutter opening and closing arm rotatably coupled to the drum shutter, whereby the drum shutter can be made retractable by a simple construction and a limited space in the main body of the apparatus.

The aforedescribed embodiment of the present invention will be summarized as follows.

In the aforedescribed embodiment, it is preferable that the grips66to be grasped in case of mounting and dismounting the process cartridge which protrude in the mounting and dismounting direction of the process cartridge, be provided on the lengthwise opposite end portions of the electrophotographic photosensitive drum51and the shutter member100be passed between the grips66and moved between the protection position and the retraction position with its surface side opposed to the electrophotographic photosensitive drum51being opposed to the cartridge frame41aand further, it is preferable that the shutter member100be biased by biasing means so as to be positioned in the protection position.

Also, in the embodiment of the process cartridge, it is preferable that the shutter opening and closing link mechanism103have a shutter shaft member101having its opposite end portions101apivotally supported on the opposite side portions of the cartridge frame41aand having its central portion101bpivotally coupled to the shutter member100, and a shutter opening and closing arm102having one end portion102bthereof pivotally coupled to the shutter member100, and be designed such that the other end portion102cof the shutter opening and closing arm102is moved to thereby pivotally move the shutter opening and closing arm102, thereby moving the shutter member100between the protection position and the retraction position, and it is preferable that at least a portion of the other end portion102cof the shutter opening and closing arm102be designed to protrude from the side wall surface of the cartridge frame41aand be engaged with a main body side member moved in operative association with the opening and closing operation of the openable and closable door26of the main body25of the image forming apparatus.

Further, in the embodiment of the image forming apparatus, it is preferable that the retraction position of the shutter member100of the process cartridge7be set at a position in which between the cartridge frame41aand the openable and closable door26and between adjacent cartridge mounting portions, it does not hinder the image formation by the process cartridge.

Also, in the embodiment of the image forming apparatus, it is preferable that the main body side shutter opening and closing mechanism110have a rotary member115having a pressed portion115bagainst which a pressing member116provided on the openable and closable door26abuts and a gear portion115a, a cam gear113meshing with the gear portion115aof the rotary member115, a cam member112provided integrally with the cam gear113, and a shutter interlocking plate111abutting against the cam member112and substantially vertically extending along the plurality of cartridge mounting portions and disposed for movement in the vertical direction, and be designed such that the shutter interlocking plate111is moved up and down in conformity with the opening and closing operation of the openable and closable door26, and further, it is preferable that the shutter opening and closing link mechanism103have a shutter shaft member101having its opposite end portions110apivotally supported on the opposite sides of the cartridge frame41aand having its central portion101bpivotally coupled to the shutter member100, and a shutter opening and closing arm102having its central portion102apivotally supported on the cartridge frame41aand having one end portion102bthereof pivotally coupled to the shutter member100, and be designed such that the other end portion102cof the shutter opening and closing arm102is moved to thereby pivotally move the shutter opening and closing arm102, thereby moving the shutter member100between the protection position and the retraction position, and it is preferable that at least a portion of the other end portion102cof the shutter opening and closing arm102be designed to protrude from the side wall surface of the cartridge frame41aand be engaged with the shutter interlocking plate111of the main body side shutter opening and closing link mechanism110moved in operative association with the opening and closing operation of the openable and closable door26of the main body25of the image forming apparatus.

According to the aforedescribed embodiment, in the process cartridge detachably mountable to the main body of the image forming apparatus, the shutter member (drum shutter) for protecting the electrophotographic photosensitive drum is designed to be moved between the protection position and the retraction position in operative association with the opening and closing operation of the openable and closable door of the main body of the image forming apparatus. Also, as the opening and closing mechanism for the shutter member, use is made of a shutter opening and closing link mechanism comprising a shutter shaft member and a shutter opening and closing arm rotatably coupled to the shutter member to thereby realize a shutter member retractable by a simple construction and a limited space in the main body of the apparatus.

As described above, according to the present embodiment, the shutter member (drum shutter) for protecting the photosensitive drum in the process cartridge detachably mountable to the main body of the image forming apparatus can be moved by the shutter opening and closing mechanism operated in operative association with the opening and closing operation of the openable and closable door of the main body of the image forming apparatus. Further, the shutter member is moved by the use of the shutter opening and closing link mechanism comprising the shutter shaft member and the shutter opening and closing arm rotatably coupled to the shutter member, whereby there can be realized a shutter member retractable by a limited space in the main body of the image forming apparatus.

As described above, according to the present invention, the shutter member can be retracted in a smaller space.

While the invention has been described with reference to the structure disclosed therein, 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 purposes of the improvements or the scope of the following claims.