Image forming apparatus in which developing unit is easily detachable to photosensitive member unit

An image forming device has a main casing, a first cartridge, and a second cartridge. The main casing has the image forming portion and an inner surface. The first cartridge is loadable to and unloadable from the image forming portion. The second cartridge detachably is attachable to the first cartridge. The first cartridge further has a receiving portion for receiving the second cartridge; and a first guide for guiding the second cartridge to the receiving portion. The main casing further has a second guide provided in the inner surface for guiding the second cartridge to the first cartridge loaded in the image forming portion. The second guide communicates with the first guide of the first cartridge loaded in the image forming portion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Japanese Patent Application No. 2006-114253 filed Apr. 18, 2006. The entire content of this priority application is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an image forming apparatus including removable photosensitive member and developing cartridges, and more particularly to electrophotographic image forming apparatuses such as a laser printer, a copier, and a facsimile machine.

BACKGROUND

In the conventional image forming apparatus, a pair of guides are provided in a frame of the apparatus so as to guide the parts protruding outwardly from both left and right sides of the photosensitive member cartridge, i.e., rotation shaft of the photosensitive drum. Further, a pair of grooves are provided on the photosensitive member cartridge so as to guide the developing roller shaft of the developing cartridge into a unit accommodating part which accommodates the developing cartridge. In addition, Japanese Patent Application Publication No. 2003-84645 discloses an image forming apparatus which includes a developing cartridge removable without removing the photosensitive member cartridge from a frame.

In the above apparatus, a user is usually required to pay attention to attachment and detachment of the developing cartridge with respect to the photosensitive member cartridge.

An object of the present invention is to provide an image forming device in which a developing cartridge is easily attached to or detached from a photosensitive member cartridge loaded in a main casing.

SUMMARY

The present invention provides an image forming device having a main casing, a first cartridge, and a second cartridge. The main casing has the image forming portion and an inner surface. The first cartridge is loadable to and unloadable from the image forming portion. The second cartridge detachably is attachable to the first cartridge. The first cartridge further has a receiving portion for receiving the second cartridge; and a first guide for guiding the second cartridge to the receiving portion. The main casing further has a second guide provided in the inner surface for guiding the second cartridge to the first cartridge loaded in the image forming portion. The second guide communicates with the first guide of the first cartridge loaded in the image forming portion.

The present invention provides a primary cartridge loadable to and unloadable from an image forming portion in a main casing of an image forming device. The main casing has a primary guide for guiding a secondary cartridge to the primary cartridge loaded in the main casing. The secondary cartridge has a projection to be guided by the primary guide. The primary cartridge has a receiving portion and a secondary guide. The receiving portion receives a secondary cartridge. The secondary guide guides the secondary cartridge to the receiving portion by the projection. The primary guide is configured to connect with the secondary guide, when the secondary cartridge is loaded in the image forming portion.

The present invention provides a secondary cartridge detachably attachable to a primary cartridge loaded in an image forming portion in a main casing of an image forming device. The primary cartridge has a primary guide for guiding the secondary cartridge. The main casing has a secondary guide for guiding the secondary cartridge. The secondary cartridge has a casing and a projection. The casing has a side face. The projection is formed in an upper portion of the side face. The projection is configured to be guided by the primary guide and the secondary guide to a predetermined position in the image forming portion.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the expressions “front”, “rear”, “above”, “below”, “right”, and “left”, are used throughout the description to define the various parts when a laser printer and a process cartridge are disposed in an orientation in which the laser printer and the process cartridge are intended to be used.

Referring toFIG. 1A, a laser printer1includes a main casing2having a feeder unit4which feeds a sheet of paper as a recording medium and an image forming unit5which forms a given image on the fed paper sheet.

The feeder unit4includes a paper tray6removably attached to the bottom of the main casing2, a paper mounting plate7provided in the paper tray6, a feed roller8and a feed pad9provided at an upper end of the paper tray6, and a pair of register rollers12provided downstream of the feed roller8in the sheet feeding direction.

The paper mounting plate7supports a stack of paper sheets. The paper mounting plate7pivots about one end far from the feed roller8so that the closer end is vertically movable. The paper mounting plate7is urged upwardly by a spring (not shown) disposed on the underside of the paper mounting plate7. As the amount of the paper sheets stacked on the paper mounting plate7increases, the paper mounting plate7pivots downward about the one end away from the feed roller8against an urging force of the spring. The feed roller8and the feed pad9are arranged to face each other. The feed pad9is pressed against the feed roller8by a spring13disposed on the underside of the feed pad9. The sheet stack on the paper stack on the paper mounting plate7is urged toward the feed roller8by a spring (not shown) disposed on the underside of the paper mounting plate7so that a topmost sheet can be pinched between the feed roller8and the feed pad9as the feed roller8rotates, thereby feeding each topmost sheet. The fed sheet is then sent to the register rollers12. The register rollers12register the sheet for correcting its orientation and then feed the sheet to the image forming unit5.

The image forming unit5includes a scanner unit16, a process cartridge17, and a fixing unit18.

The scanner unit16is provided in an upper portion of the main casing2below the underside of a discharge tray46. The scanner unit16includes a laser unit (not shown), a polygon mirror19rotatably driven, lens20, and a reflecting mirror21. A beam of laser light based on given image data emitted from the laser unit passes through or reflects at the polygon mirror19, the lens20, and the reflecting mirror21in this order as indicated by a chain line, to scan at high speed across a surface of a photosensitive drum (photosensitive member)27in the process cartridge17.

As shown inFIG. 1A, the process cartridge17includes a photosensitive member cartridge26and a developing cartridge28attached thereto. The photosensitive member cartridge26includes the photosensitive drum27, a scorotron charger (not shown), and a transfer roller30, as shown inFIG. 1B.

In a state where the developing cartridge28is attached to the photosensitive member cartridge26, the photosensitive drum27is rotatably provided to a side of a developing roller31so as to face the developing roller31. The photosensitive drum27includes a grounded drum body, and the surface of the photosensitive drum27is formed of a positively-chargeable photosensitive layer made from a variety of materials. Examples thereof include an amorphous silicon-based material such as α-Si:H, a cadmium sulfide-based material such as CdS, a zinc oxide-based material such as ZnO, a selenium-based material such as AsSe3, and an organic photoreceptor material such as polycarbonate.

A rotation shaft27aof the photosensitive drum27protrudes from both right and left sides of the photosensitive member cartridge26, and the photosensitive drum27is rotatably driven by a driving force transmitted from a main motor (not shown).

The scorotron charger (not shown) is disposed above the photosensitive drum27with a predetermined distance therefrom so as not to make contact with the photosensitive drum27. The scorotron charger is a positively charging charger which generates corona discharge from a charging wire made from tungsten or other material for uniformly and positively charging the surface of the photosensitive drum27. As the photosensitive drum27rotates, the surface of the photosensitive drum27is first uniformly and positively charged by the scorotron charger, and then exposed to the laser light emitted from the scanner unit16by high-speed scanning based on image data so as to form an electrostatic latent image on the surface of the photosensitive drum27.

Below the photosensitive drum27, the transfer roller30is rotatably supported so as to face the photosensitive drum27. The transfer roller30includes a metal roller shaft covered by a roller portion formed of an ion-conductive rubber material. A transfer bias (forward bias) is applied from a transfer bias applying power source to the transfer roller30for transfer. Accordingly, a visible image is formed on the surface of the photosensitive drum27, and the visible image is transferred onto a paper sheet while the sheet passes between the photosensitive drum27and the transfer roller30.

The developing cartridge28shown inFIG. 1Ais detachably attached to the photosensitive member cartridge26. The developing cartridge28includes the developing roller31, a layer thickness regulating blade32(not shown inFIG. 1A), a toner supply roller33(not shown inFIG. 1A), and a toner box34.

The toner box34accommodates a positively chargeable non-magnetic single component toner, as a developing agent. The toner is, for example, a polymerized toner that is obtained by copolymerizing polymerizable monomers using a known polymerization method, such as a suspension polymerization method. The polymerizable monomers may be styrene-based monomers, such as styrene, and acrylic-based monomers, such as acrylic acid, alkyl (C1-C4) acrylate, and alkyl (C1-C4) methacrylate. Polymerized toner particles are spherical in shape, and thus have excellent fluidity. A coloring material such as carbon black and wax are added to the toner. In order to improve the fluidity of the toner, silica is also added to the toner as an external additive. A toner particle size is approximately 6 to 10 μm.

An agitator shaft35is disposed in a substantially central portion of the toner box34. The agitator shaft35supports an agitator (not shown) which agitates the toner in the toner box34as the agitator rotates. The toner is discharged through a toner supply opening (not shown) provided in a side wall of the toner box34.

The toner supply roller33is disposed to a side of the toner supply opening. The developing roller31is rotatably disposed at a position in confrontation with the toner supply roller33. The toner supply roller33and the developing roller31are in pressure contact with each other. The toner supply roller33includes a metal roller shaft covered by a roller portion formed of an electrically conductive foam material.

The developing roller31includes a metal roller shaft31acovered by a roller portion formed of an electrically conductive rubber material. More specifically, the roller portion of the developing roller31is formed of an electrically conductive urethane rubber or silicone rubber including fine carbon particles. A surface of the roller portion of the developing roller31is coated with urethane rubber or silicone rubber those including fluorine. A developing bias is applied to the developing roller31from a developing bias application power source (not shown).

The toner layer thickness regulating blade32is disposed adjacent to the developing roller31. The regulating blade32includes a blade portion formed of a leaf spring and a contact portion attached to one end of the blade portion. The contact portion has a semicircular cross-sectional shape, and is formed of insulating silicone rubber. The toner layer thickness regulating blade32is supported near the developing roller31to the developing cartridge28so that the contact portion presses the developing roller31with the resiliency of the blade portion.

The toner discharged through the toner supply opening is supplied onto the developing roller31by the rotation of the toner supply roller33. At this time, the toner is positively charged through friction charging at a contact portion between the toner supply roller33and the developing roller31. As the developing roller31rotates, the toner supplied onto the developing roller31enters between the contact portion of the layer thickness regulating blade32and the developing roller31, where the toner is again charged through friction charging more sufficiently. The toner which has passed between the contact portion and the developing roller31, is formed into a thin toner layer having a uniform thickness on the developing roller31.

Thereafter, in accordance with the rotation of the developing roller31, the toner carried on the developing roller31and charged with positive polarity is deposited onto the electrostatic latent image formed on the photosensitive drum27, when making contact with the photosensitive drum27from the front. In other words, the toner is selectively supplied to parts on the surface of the photosensitive drum27exposed to the laser light, where the potential level is lower than that of the remaining part of the photosensitive drum surface uniformly positively charged. Thus, a visible toner image is formed in a reversed manner.

The fixing unit18is disposed downstream of the process cartridge17in the sheet feeding direction. The fixing unit18includes a heat roller41, a pressure roller42that is pressed against the heat roller41, and a feeding roller43disposed downstream of the heat roller41and the pressure roller42in the sheet feeding direction. The heat roller41, formed of metal, includes a halogen lamp as a heat source. When the toner which has transferred on the sheet in the process cartridge17passes between the heat roller41and the pressure roller42, the toner is fused by heat to fixedly adhere to the sheet. After that, the sheet is transported by the feeding roller43, to a discharge path44. The sheet fed to discharge rollers45is discharged onto the discharge tray46through the discharge path44by the discharge rollers45.

Referring toFIG. 1A, the laser printer1includes a structure for detachably loading the photosensitive member cartridge26to the main casing2.

A front cover54rotatable about a supporting shaft54ais disposed on the front surface of the main casing2to open and close the main casing2. When the front cover54is in an open position, an internal space3is provided in the main casing2so as to insert the photosensitive member cartridge26and the developing cartridge28therethrough. As shown inFIG. 1A, in the space for attachment3, a pair of photosensitive member cartridge guides55(indicated by the alternate long and short dashed line inFIG. 1A) is formed to extend downward from a starting portion3ato the position for the photosensitive member cartridge26inFIG. 1A. Each of the photosensitive member cartridge guides55is formed as a substantially V-shaped groove having a tapered width to an insertion stop position55ain order to guide the rotating shaft27aof the photosensitive drum27between the upper and lower portions of the guide55. It is noted that the rotating shaft27aof the photosensitive drum27protrudes from the right and left sides of the photosensitive member cartridge26. The rotating shaft27ais positioned so as to be rotatably supported at the lower end of each guide groove, i.e., the insertion stop position55a.

The photosensitive member cartridge26includes a handle (not shown) provided on and above an end plate26bthereof. The developing cartridge28includes a handle (not shown) provided on an opposite side portion to the side portion facing the developing roller31. The handle of the photosensitive member cartridge26is provided at the position for staying away from the side end of the developing roller30in the developing cartridge28, when the developing cartridge28is loaded to the developing member cartridge26.

In the structure described above, by holding the handle (not shown) of the photosensitive member cartridge26, the left and right side ends of the rotating shaft27aare inserted in the guide grooves55with the photosensitive drum27side of the photosensitive member cartridge26facing the internal space3. The photosensitive member cartridge26is then loaded into the position where the rotating shaft27ais supported at the insertion stop position55aalong the photosensitive member cartridge guides55, and then disposed at the image forming position with stability. On the other hand, when the photosensitive member cartridge26is unloaded from the image forming position, by pulling the handle (not shown), the photosensitive member cartridge26is guided and unloaded obliquely upward with the front portion of the photosensitive member cartridge26up. The guides55are available to the process cartridge17in which the developing cartridge28has been assembled to the photosensitive member cartridge26for loading and unloading the process cartridge17to and from the main casing2, respectively. When the handle of the developing cartridge28is merely operated, the process cartridge17is easy to be loaded and unloaded. It should be noted that Japanese Patent Application Publication No. 2000-250310 discloses that each of the photosensitive member cartridge26and the developing cartridge28is loaded in and unloaded from the main casing2alone.

The next description will explain the structure for allowing the developing cartridge28to be detachably loaded to the photosensitive member cartridge26disposed at the image forming position. Referring first toFIG. 1A, the structure of the photosensitive member cartridge26is described as follows.

The photosensitive member cartridge26includes left and right side plates26aand26a. The rotating shaft27aof the photosensitive drum27projects from the side plates26aand26aat the downstream positions in the loading direction of the photosensitive member cartridge26into the main casing2. Upstream portions of left and right side plates26aand26ain the loading direction, and an end plate26bprovides an accommodation site for accommodating the developing cartridge28therein. Each of the left and right side plates26aand26aof the photosensitive member cartridge26has a developing cartridge guide61extending toward the photosensitive drum27. In this embodiment, the developing cartridge guide61is formed as a longitudinal notch in each of the side plates26aand26a. The shape of the developing cartridge guide61is identical to the shape of the bottom portion of the photosensitive member cartridge guide55, as shown inFIG. 1A.

When the developing cartridge28is to be loaded to the accommodating site with the developing roller31facing the internal space3, the roller shaft31aprotruding from both right and left sides of the developing roller31slides along the photosensitive member cartridge guide61of each of the left and right side plates26aand26ainto the position where the developing roller31contacts with the photosensitive drum27(the trailing end61aof the photosensitive member cartridge guide61). In this state, the developing cartridge28is supported by the photosensitive member cartridge26with stability. The roller shaft31aincludes a collar member31bfitted to both ends thereof, as shown inFIG. 2A. In this embodiment, the length of the roller shaft31aof the developing roller31is shorter than the length of the rotating shaft27aof the photosensitive drum27.

As shown inFIG. 1A, the main casing2includes a second developing cartridge guide70which communicates with the photosensitive member cartridge guide61of the photosensitive member cartridge26. The second developing cartridge guide70includes two substantially linear projection guides70A,70B projecting from an internal side face of the main casing2in an axial direction of the developing roller31. The projection guides70A,70B are positioned in parallel to each other in a vertical direction. In particular, an lower face of the projection guide70A and an upper face of the projection guide70B define the developing cartridge guide70to guide the developing cartridge28to the photosensitive member cartridge26.

The second developing cartridge guide70extends on an inner side of the main casing2to connect the starting portion3aof the internal space3to the photosensitive member cartridge guide61of the photosensitive member cartridge26which has been disposed at the image forming position. The vertical distance between the linear projection guides70A,70B is the largest at the starting portion3a, and gradually decreases from the starting portion3ato the image forming position.

In this embodiment, the second developing cartridge guide70has two projection guides70A,70B. When the developing cartridge28is loaded into the main casing2, the upper surface of the lower projection guide70B may be used for guiding the developing cartridge26thereon, or the lower surface of the upper projection guide70A may be used for guiding the developing cartridge26thereon. This structure of the second developing cartridge guide70is advantageous to a user, because the user can select either one of the projection guides70A and70B which is used for guiding the developing cartridge26, depending on the height at which the laser printer1is placed. This facilitates the user's loading operation of the developing cartridge26. In another embodiment, the second developing cartridge guide70may include only one linear projection guide70B.

In order to load the developing cartridge28into the accommodating site of the photosensitive member cartridge26disposed at the image forming position, the roller shaft31aprotruding from both right and left sides of the developing roller31slides along the developing cartridge guide70. As described above, since the developing cartridge guide70has a large width at the starting point3a, the roller shaft31aof the developing roller31is easily put into the developing cartridge guide70.FIG. 2Ais a cross-sectional view taken along lines X-X ofFIG. 1A, showing the roller shaft31aof the developing cartridge28arrives at the position shown inFIG. 1A. In this embodiment, the lower guide surface70aof the lower projection guide70B, which slidably contacts with the lower sliding surface of the roller shaft31a, is positioned slightly above an upstream guide surface61bof the photosensitive member cartridge guide61in the loading direction of the developing cartridge28, as viewed from a side. The lower guide surface70aof the lower projection guide70B comes to be positioned at the same height at the height of the photosensitive member cartridge61at the position A which is closer to the photosensitive member cartridge26from the position X ofFIG. 1Aby a short distance.

When the roller shaft31awhich has been guided by the developing cartridge guide70arrives at the position A shown inFIG. 1A, the photosensitive member cartridge guide61of the photosensitive member cartridge26then guides the roller shaft31a. The projection guide70B is terminated at the position closer to the photosensitive member cartridge26than the position at which the guide of the developing cartridge28is switched from the second developing cartridge guide70to the first developing cartridge guide61. When the roller shaft31aslides along the photosensitive member cartridge guide61formed in the left and right side plates26aand26aof the photosensitive member cartridge26and arrives at the trailing end61aof the photosensitive member cartridge guide61, the roller shaft31ais rotatably supported by the photosensitive member cartridge26.

FIG. 3shows a scheme that the roller shaft31aof the developing cartridge28is first guided by the second developing cartridge guide70, and then guided by the first photosensitive member cartridge guide61, with emphasis for understanding.

As is clear fromFIG. 3, in a section Z, the first photosensitive member cartridge guide61and the second developing cartridge guide70are positioned parallel to each other from the above. Specifically, the upstream guide surface61bof the photosensitive member cartridge guide61and the downstream section of the lower guide surface70aof the developing cartridge guide70overlap each other over a certain length in the attaching direction of the developing cartridge28as viewed from a side. In this section Z, the lower peripheral surface of the roller shaft31ais guided by the second developing cartridge guide70and the first developing cartridge guide61.

In another embodiment, the first developing cartridge guide61may be aligned with the second developing cartridge guide70. In this case, the first developing cartridge guide61may be connected to the second developing cartridge guide70without any gap therebetween. Alternatively, the first developing cartridge guide61may be connected to the second developing cartridge guide70through a gap which is less than a diameter of the roller shaft31a.

Referring now toFIG. 2, the next description will explain a laser printer of a second embodiment. The second embodiment is different from the first embodiment in that the photosensitive member cartridge guide serves as the developing cartridge guide. In this embodiment, a combination guide56is formed in an inner side surface of the main casing2to function as both of the photosensitive member cartridge guide and the developing cartridge guide. The structural member which has a same function as that of the first embodiment has the same reference number. And detailed description thereof is omitted here.

As shown inFIG. 4, a pair of combination guides56are formed on the left and right inner side surfaces of the internal space3to slant downward from a starting portion3a. Each of the combination guides56is provided by an upper projection guide56A having a lower surface, and a lower projection guide56B having an upper surface. The upper projection guide56A and the lower projection guide56B are positioned to sandwich the rotation shaft27aof the photosensitive drum27from above and below, thereby forming a substantially U-shaped groove in the inner side surface of the internal space3. The photosensitive drum27is rotatably supported through the rotation shaft27aat the rearmost end of the combination guide56, i.e., insertion stop position56a.

In the structure described above, by gripping the handle (not shown) of the photosensitive member cartridge26, the left and right side ends of the rotating shaft27aare inserted into the guide grooves55, with the photosensitive drum27side of the photosensitive member cartridge26facing the internal space3. The photosensitive member cartridge26is then loaded along the photosensitive member cartridge guide56to the position where the rotating shaft27ais rotatably supported at the insertion stop position56a, and disposed at the image forming position with stability. The way to unload the photosensitive member cartridge26from the image forming position is the same as that of the first embodiment.

The Next description will explain the structure which enables the developing cartridge28to be detachably attached to the photosensitive member cartridge26disposed at the image forming position.

The combination guides56are formed in the inner side surfaces of the main casing2to function as the photosensitive member cartridge guide and the developing cartridge guide. The roller shaft31ais guided from the starting portion3aof the internal space3by the combination guides56so that the developing cartridge28is loaded in the main casing2. When the roller shaft31aarrives at the position B shown inFIG. 4, the roller shaft31ais then guided by the photosensitive member cartridge guide61of the photosensitive member cartridge26. The roller shaft31athen slides along the photosensitive member cartridge guide61. When the roller shaft31aarrives at the trailing end61aof the photosensitive member cartridge guide61, the roller shaft31ais rotatably supported by the photosensitive member cartridge26.

Described above, since the combination guides56functions as both of the photosensitive member cartridge guide and the developing cartridge guide, the internal structure of the main casing2is made simple. And this structure facilitates the loading of both of the photosensitive member cartridge26and the developing cartridge28to the main casing2.

Referring toFIG. 5A, the next description will explain a laser printer1of a third embodiment. In this embodiment, the process cartridge17includes a photosensitive drum27, a developing roller31, a layer thickness regulating blade32, a supply roller33, a scorotron charger (not shown), and a transfer roller30, as shown inFIG. 5B. A toner cartridge80including a toner box34for accommodating a developing agent is detachably attached to the process cartridge17.

InFIGS. 5A and 5B, the process cartridge17is formed as a single unit. In another embodiment, the process cartridge17may be formed by combining a photosensitive member cartridge including at least a photosensitive drum27, and a developing cartridge including at least a developing roller31. In this case, the photosensitive member cartridge and the developing cartridge may be combined by using a well-known manner.

The next description will explain the structure which enables the toner cartridge80to be attached to the process cartridge17.

The rotation shaft27aof the photosensitive drum27projects from the downstream positions of the left and right side plates17band17bof the process cartridge17in the loading direction to the main casing2. Frontward portions of the left and right side plates17band17band an end plate17cpositioned at the trailing end in the insertion direction define an accommodation site for accommodating the toner cartridge80. The left and right side plates17band17bof the accommodation site has toner cartridge guides81. The process cartridge17has an opening (not shown) on the trailing end through which toner is supplied. When the toner cartridge80is attached to the process cartridge17, a toner supply opening (not shown) formed in the leading end of the toner cartridge80communicates with the opening.

The toner cartridge80includes an agitator (not shown). The toner is agitated in the toner box34, as the agitator rotates. The toner is discharged from the toner supply opening (not shown) to a processing chamber39in the process cartridge17. An agitator shaft35is rotatably provided in a substantially central portion of the toner box34. A toner cartridge protrusion90is provided in both sides of the toner box34and downstream of the agitator shaft35in the attaching direction. The toner cartridge protrusion90is provided in an upper portion of the toner cartridge80and on the opposite side to a handle80A thereof.

The toner cartridge protrusion90has two-level stepped shape, as shown inFIGS. 8A-8D. The toner cartridge protrusion90has a smaller cross section portion at the distal end and a larger cross section portion at the proximal end.FIG. 8Ashows the toner cartridge protrusion90in which two different diameter cylinders are stacked.FIG. 8Bshows the toner cartridge protrusion90in which two different triangular prisms are stacked.FIG. 8Cshows the toner cartridge protrusion90in which two different quadrangular prisms are stacked.FIG. 8Dshows the toner cartridge protrusion90in which a cylinder having a smaller cross section is stacked on a quadrangular prism having a larger cross section. With the above structures of the toner cartridge protrusion90, the larger cross section portion at the proximal end is guided along the toner cartridge guide81. The smaller cross portion at the distal end is guided along a toner cartridge guide93.

The toner cartridge80is loaded to the process cartridge17with the toner cartridge protrusion90being oriented toward the internal space3. The toner cartridge protrusion90slides along the toner cartridge guide81of the left and right side plates17band17b. When the toner cartridge protrusion90arrives at the trailing end81aof the guide on the toner cartridge side81, the toner cartridge80is supported by the process cartridge17with stability.

The next description will explain the structure which enables the process cartridge17to be loaded to the main casing2.

As shown inFIG. 5A, in the internal space3, a pair of process cartridge guides92(indicated by the alternate long and short dashed line inFIG. 5A) is formed in the left and right sides of the internal space3to slant downward from a starting portion3ato an image forming position. The process cartridge guides92are formed as a substantially U-shaped groove as viewed from a side to sandwich the rotating shaft27aof the photosensitive drum27from above and below. The rotating shaft27ais rotatably supported at the lower end of the grooves, i.e., an insertion stop position92a.

In the structure described above, by holding a handle (a portion of the end plate17c) of the process cartridge17, the left and right side ends of the rotating shaft27aare inserted into the process cartridge guide92with the photosensitive drum27side of the process cartridge17facing the internal space3. The process cartridge17is then guided to the position where the rotating shaft27ais supported at the insertion stop position92aof the process cartridge guide92, and disposed at the image forming position with stability. On the other hand, in order to unload the process cartridge17from the mage forming position, by holding the handle (not shown) of the process cartridge17up, the process cartridge17is pulled out obliquely upward with the front end thereof being oriented upward. The above way to load and unload the process cartridge17in the main casing2is also available to the loading of the processing cartridge17, which the toner cartridge80has been attached to the process cartridge17, to the main casing2.

The next description will explain the structure which enables the toner cartridge80to be detachably loaded to the process cartridge17disposed at the image forming position.

As shown inFIG. 5A, the main casing2includes toner cartridge guides93formed in the left and right inner side faces of the internal space3to communicate with the toner cartridge guide81of the process cartridge17. The toner cartridge guide93extends on the inner surface of the main casing2to connect a starting portion3aof the internal space3to the toner cartridge guide81of the process cartridge17disposed at the image forming position.

In order to load the toner cartridge80in the accommodation site of the process cartridge17disposed at the image forming position, the toner cartridge protrusion90is guided with the upper outer circumference surface thereof contacting the toner cartridge guide93. As described above, since the toner cartridge guide93extends from the starting portion3aof the internal space3, the toner cartridge93guide is easily recognized when the front cover54is open. Therefore, it is easy to load the toner cartridge80from the starting portion3a.

When the toner cartridge80is loaded, while guiding the toner cartridge protrusion90along the toner cartridge guide93, and arrives at the position C shown inFIG. 5A, the toner cartridge protrusion90is then guided by the toner cartridge guide81(FIG. 6B). The toner cartridge protrusion90then slides along the guide surface81bof the toner cartridge guide81formed in the left and right side plates17band17b(FIG. 6C). When the toner cartridge protrusion90arrives at the trailing end81aof the toner cartridge guide81, the toner cartridge80is supported by the process cartridge17with stability (FIG. 6D).

As is clear fromFIG. 5A, the toner cartridge guide81and the toner cartridge guide93have adjacent portions which are parallel to each other. In other words, the guide surface81bof the toner cartridge guide81and the portion of the lower guide surface93aof the toner cartridge guide93overlap each other over a certain length as viewed from a side in the attaching direction of the toner cartridge80. In this case, the upper peripheral surface of the toner cartridge projection90is guided by the toner cartridge guide93, and the lower peripheral surface of the toner cartridge projection90is guided by the toner cartridge guide81.

In this embodiment, the toner cartridge projection90has a two-level stepped shape. In another embodiment, as shown inFIGS. 7A-7D, the toner cartridge projection90may be formed from two separate parts. In other words, the toner cartridge projection90may include a small cylinder portion90A projecting from the side of the toner cartridge80to be guided by the toner cartridge guide93, and a collar90B coaxially fitted around the small cylinder portion90A, the collar90B being to be guided by the toner cartridge guide81.

In another embodiment, the toner cartridge guide81may be aligned with the toner cartridge guide93in the loading direction of the toner cartridge80In this case, the toner cartridge guide81may be connected to the toner cartridge guide93without any gap therebetween. Alternatively, the toner cartridge guide81may be connected to the toner cartridge guide93with a small gap therebetween which is shorter than the diameter of the toner cartridge projection90.

Alternatively, the process cartridge guide92may function as the toner cartridge guide93. In this case, the process cartridge guide92is used for guiding the rotation shaft27aof the photosensitive drum27to load the process cartridge17to the image forming position. And, the process cartridge guide92is used for guiding the toner cartridge protrusion90to the toner cartridge guide81. This structure enables both the process cartridge17and the toner cartridge80to be attached in the main casing2easily. The internal structure of the main casing2is formed simple.

In the above embodiments, the rotating shaft27aof the photosensitive drum27is used as an engaging portion of the photosensitive member cartridge to the main casing2. In another embodiment, any type of projection from the side of the photosensitive member cartridge26may be used as the engaging portion to the main casing2.

Similarly, a protrusion member protruding from each side of the developing cartridge28may be employed as the engaging portion of the developing cartridge side as well as the roller shaft31aof the developing roller31.

In addition, a rib protruding upward from the upper surface of the photosensitive member cartridge26is formed. And, a photosensitive member cartridge guide for engaging the rib may be provided in the inner upper surface of the internal space3of the main casing. Alternatively, a developing cartridge guide may be continuously formed from the starting portion of the internal space of the main casing to the photosensitive member cartridge guide.

Furthermore, a rib protruding downward from the bottom surface of the photosensitive member cartridge26is formed. And, a photosensitive member cartridge guide may be formed in the inner bottom surface of the internal space3of the main casing2to be engaged with the rib. In this case, a developing cartridge guide may be formed extending from the starting portion of the inner bottom surface of the main casing to the photosensitive member cartridge guide of the main casing.

FIGS. 2B through 2Dshow modifications of the developing cartridge guide70according to the first embodiment. As shown inFIG. 2B, a single guide protrusion100may be formed on an inner side of the main casing2for guiding the upper sliding surface of the outer periphery of the roller shaft31aof the developing roller31. Further, a guide groove200for slidingly contacting the lower sliding surface of the roller shaft31a. As shown inFIG. 2C, a single guide protrusion300is formed on an inner side of the main casing2. The lower sliding surface of the roller shaft31ais guided by the upper guide surface of the guide protrusion300. As shown inFIG. 2D, a groove is formed in the main casing2to provide an upper guide surface400for guiding the lower sliding surface of the roller shaft31a. Preferably, the developing cartridge guide has at least a guide surface for guiding the lower sliding surface of the roller shaft31a. In addition, if the upper sliding surface of the roller shaft31aincludes a guide surface available to guide the developing cartridge, the developing cartridge28is loaded to the main casing2smoothly without any unexpected movement.

According to the present invention, the developing cartridge which has been guided by the developing cartridge guide of the main casing is continuously guided by the developing cartridge guide of the photosensitive member cartridge. In other words, the developing cartridge is guided smoothly from the starting portion of the main casing to the photosensitive member cartridge loaded in the main casing. Accordingly, damage to the developing cartridge or the main casing is prevented

It is understood that the foregoing description and accompanying drawings set forth the embodiments of the invention at the present time. Various modifications, additions and alternative designs will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the spirit and scope of the disclosed invention. Thus, it should be appreciated that the invention is not limited to the disclosed embodiments but may be practiced within the full scope of the appended claims.