HK1085545B - Process cartridge in image-forming device - Google Patents

Description

Process cartridge in image forming apparatus

Technical Field

The present invention relates to an image forming apparatus, such as a laser printer, and a process cartridge detachably mountable in the image forming apparatus.

Background

Some conventional electronic image forming apparatuses, such as laser printers, often have various members for performing image forming processes provided in a process cartridge detachably mounted on a main body of the image forming apparatus. In this way, the process cartridge can be replaced individually as needed, depending on the service life of the components housed therein. An image forming apparatus of the type disclosed in U.S. patent No. 6,385,414B 1 is provided with a process cartridge in which a toner accommodating chamber for accommodating toner is provided.

The toner-accommodating chamber is hollow so as to accommodate as much toner as possible. When the chamber is hollow, the chamber walls must be thickened or made non-planar to maintain the stiffness of the toner chamber and prevent the toner chamber from being easily deformed. If the toner-accommodating chamber is deformed, the toner accommodated in the chamber may be ejected, causing toner leakage and other problems.

With the recent demand for more compact image forming apparatuses, the process cartridge must also be made more compact. However, since the toner-accommodating chamber wall must be thickened or made non-planar to maintain the hardness of the toner chamber, the process cartridge inevitably becomes large, making it difficult to meet the demand for a more compact volume.

Disclosure of Invention

As described above, an object of the present invention is to provide a process cartridge which can improve the hardness of a developer accommodating portion. It is another object of the present invention to provide an image forming apparatus to which the process cartridge is detachably mountable.

To achieve the above and other objects, the present invention provides a cartridge detachably mountable to an image forming apparatus. The box includes: a first wall; a second wall opposed to the first wall with a gap formed therebetween, the first wall and the second wall defining therebetween a developer accommodating portion accommodating a developer; and a reinforcing portion that spans between the first wall and the second wall; the reinforcing portion includes a support column member provided on one of the first wall and the second wall and protruding toward the other; and a fitting member on the other of the first wall and the second wall for fitting the support column member.

With this structure, the reinforcing portion provided between the second wall and the first wall in the developer accommodating section can absorb the force applied to the second wall and the first wall from the compression direction, thereby enhancing the hardness of the developer accommodating section. Further, since the reinforcing member is provided between the second wall and the first wall, that is, inside the developer accommodating section, the hardness of the developer accommodating section can be enhanced regardless of the outer shape of the process cartridge.

In another aspect, the present invention provides an image forming apparatus comprising: a housing; and the above-mentioned cartridge detachably mounted in the housing.

By providing the above-described cartridge in the image forming apparatus, the image forming apparatus can still be made compact.

Drawings

The specific features and advantages of the invention, as well as other objects, will be described in detail below with reference to the accompanying drawings, in which,

FIG. 1 is a side sectional view of a color laser printer according to a preferred embodiment of the present invention;

FIG. 2 is a front-top side perspective view of the color laser printer drum cartridge shown in FIG. 1;

FIG. 3 is a rear-bottom side perspective view of the drum cartridge;

FIG. 4 is a top view of the drum cartridge;

fig. 5 is a front view of the drum cartridge;

FIG. 6 is a right side view of the drum cartridge;

FIG. 7 is a left side view of the drum cartridge;

fig. 8 is a front-top perspective view of the color laser printer developer cartridge shown in fig. 1;

fig. 9 is a rear-bottom side perspective view of the developer cartridge;

fig. 10 is a front view of the developer cartridge;

fig. 11 is a right side view of the developer cartridge;

fig. 12 is a left side view of the developer cartridge;

fig. 13 is a plan view of the developer cartridge;

fig. 14 is a bottom view of the developer cartridge;

fig. 15 is an exploded perspective view of the developer cartridge;

fig. 16 is a side sectional view of the developing cartridge;

fig. 17 is a perspective view of the upper front side of the main casing in the color printer;

fig. 18 is a side view illustrating a process of mounting the drum cartridge and the developer cartridge in the main casing;

FIG. 19 is an exploded perspective view showing how the toner cartridge is filled with toner;

fig. 20 is a perspective view of a developer cartridge according to a comparative embodiment;

fig. 21 is an exploded perspective view of the developer cartridge of the color laser printer shown in fig. 1 according to the second embodiment;

fig. 22 is an exploded perspective view of the developer cartridge according to the third embodiment of the color laser printer shown in fig. 1;

fig. 23 is a top-front perspective view of a developer cartridge according to a fourth embodiment of the color laser printer shown in fig. 1;

fig. 24 is a side sectional view of the developer cartridge according to the fourth embodiment;

fig. 25 is an exploded perspective view of the developer cartridge according to the fourth embodiment;

fig. 26 is an exploded perspective view of the developer cartridge according to the fifth embodiment of the color laser printer shown in fig. 1; and

fig. 27 is an exploded perspective view of the developer cartridge according to the fifth embodiment.

Detailed Description

A cartridge and an image forming apparatus according to a preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

Fig. 1 is a side sectional view of a color laser printer as a preferred embodiment of an image forming apparatus according to the present invention.

The color laser printer shown in fig. 1 is a transverse tandem color laser printer, and includes a plurality of processing units 27 arranged horizontally in parallel. The color laser printer 1 includes a main casing 2 and a feeding unit 4 for feeding a sheet 3 in the main casing 2, an image forming unit 5 for forming an image on the sheet 3 fed by the feeding unit 4, and a discharging unit 6 for discharging the sheet 3 from the color laser printer 1 after the image is formed on the sheet 3.

The main casing 2 is substantially shaped like an open-topped rectangular box when viewed from the side. The top cover 7 is located above the main housing 2. The top cover 7 is rotatably supported by a shaft (not shown) provided on the rear side of the main casing 2 (hereinafter, the left side in fig. 1 is referred to as the rear side, and the right side in fig. 1 is referred to as the front side) and can be opened and closed on the main casing 2.

As shown in fig. 17, the main casing 2 includes a left side plate 8 and a right side plate 9 facing each other in the lateral direction, which are orthogonal in the front-rear direction and in the vertical direction, and which are spaced by a certain gap; 4 partition plates 10 and a front plate 11 bridged between the left and right side plates 8 and 9. The partition plates 10 are provided in the main casing 2 at intervals in the front-rear direction, and the front plate 11 is located further forward of the partition plates 10 so as to partition spaces for the respective processing sections 27 (to be described later, see fig. 1) in the front-rear direction in the space between the left and right side plates 8, 9. Each partition plate 10 has a rear surface 33 (see fig. 17) on its rear side.

The partition plate 10 and the front plate 11 are inclined with respect to the front-rear direction, which coincides with the direction in which the sheet 3 is conveyed through the laser printer 1 at the time of image formation, and the vertical direction, respectively, in such a manner that the top end is more forward than the bottom end. As shown in the drawing, the partition plate 10 and the front plate 11 are arranged so as to form a vertical gap between the top ends of the plates 10, 11 and the top cover 7, and another gap is formed between the bottom ends of the plates 10, 11 and a transfer member 28 to be described later.

Accordingly, as shown in fig. 17, four process accommodating portions 12 are partitioned by the left side plate 8, the right side plate 9, the adjacent partition plate 10, and the front plate 11 in the main casing 2. Each process accommodating portion 12 is provided for each process portion 27 corresponding to each print color. Each process accommodating portion 12 includes a drum accommodating portion 13 for accommodating a drum cartridge 31 (described later), and a developer accommodating portion 14 for accommodating a developer cartridge 32 (described later). The drum cartridge 31 has a fixing unit 43 mounted in the drum accommodating portion 13, and the developer cartridge is mounted in the developer accommodating portion 14.

As shown in fig. 18, in a space divided by the left side plate 8 and the right side plate 9 in the lateral direction, and in the front-rear direction by an imaginary oblique line extending from the partition plate 10 to the front plate 11 along the same plane, the drum accommodating portion 13 is lower than the partition plate 10. Each space partitioned in this way in the drum accommodating portion 13 is a drum accommodating space 15 for accommodating the fixing unit 43 of the drum cartridge 31.

The developer accommodating portion 14 is provided upstream of the drum accommodating portion 13 as a continuation of the drum accommodating portion 13 in a direction of mounting with respect to the drum cartridge 31. In other words, the developer accommodating portion 14 is located above the drum accommodating portion in the mounting direction of the drum cartridge 31 and the developer cartridge 32. The developer accommodating portion 14 is partitioned by the partition plate 10 and the front plate 11 in the front-rear direction and partitioned by the left side plate 8 and the right side plate 9 in the lateral direction. The internal space of the developer accommodating portion 14 partitioned in this way (not counting the extension accommodating space 18, which will be described later) forms the developer accommodating space 16 for accommodating the developer cartridge 32.

As shown in fig. 17 and 18, in each developer accommodating section 14, rail portions 17 are provided on the partition plate 10, extending along both ends in the lateral direction of the partition plate. The rail portion 17 is formed as a thick strip extending in the mounting direction of the drum cartridge 31. At the time of mounting the drum cartridges 31, ridges 51 (described later) of the drum cartridges 31 slide against the rail portions 17, respectively.

As shown in fig. 1, the feeding unit 4 includes: a paper supply tray 21 detachably mounted on a lower portion of the main casing 2, insertable into or removable from the main casing 2 through a front side in a horizontal direction; a pickup roller 22 and a feed roller 23 located above the front side of the paper feed tray 21; a feed-side U-shaped channel 24 located above and in front of the feed roller 23; and a conveying roller 25 and a resist roller 26 provided along the feed-side U-shaped passage 24.

The sheets 3 are stacked in the sheet feed tray 21. The pickup roller 22 picks up the uppermost one of the sheets 3 and conveys it upward. Next, the feed roller 23 feeds the sheet along the feed-side U-shaped path 24. The feed-side U-shaped path is substantially in the shape of letter U, which is a conveyance path of the sheet 3. The upstream end of the feed-side U-shaped path 24 is adjacent to a lower portion of the feed roller 23 to feed the sheet forward, and the downstream end is adjacent to a conveyor belt 168 to be described later to convey the sheet 3 backward.

After the feed roller 23 feeds the sheet 3 forward along the upstream end of the feed-side U-shaped path 24, the conveying roller 25 continues to convey the sheet along the feed-side U-shaped path 24 as the conveying direction of the sheet 3 is reversed. The registration roller 26 registers the sheet 3 first and then conveys the sheet backward.

The image forming unit 5 includes a processing portion 27, a transfer portion 28, and a fixing portion 29. Each process section 27 is provided with toner of one color. Specifically, the color laser printer 1 as the preferred embodiment has four processing sections 27 including one yellow processing section 27Y, one magenta processing section 27M, one cyan processing section 27C, and one black processing section 27K. The processing portions 27 are located in the respective processing accommodating portions 12, and are horizontally arranged one after another with a certain gap therebetween in the front-rear direction.

Each process section 27 includes a scanner unit 30, a drum cartridge 31, and a developer cartridge 32 detachably mounted on the drum cartridge 31. The process cartridge is provided with a drum cartridge 31, and a developer cartridge 32 mounted on the drum cartridge 31.

The scanning unit 30 includes a scanner housing 35 and a laser light emitting unit (not shown) in the scanner housing 35, a polygon mirror 36, two lenses 37 and 38, and a reflecting mirror 39.

As shown in fig. 17, the scanner housing 35 is located at the center in the lateral direction of each partition plate 10, so that the rail portions 17 of each partition plate 10 are located at both ends in the lateral direction of the scanner housing 35, respectively. Further, the rear wall of the scanner housing 35 contacts the front surface of the partition plate 10, and the front wall 34 of the scanner housing 35 projects forward from the outside of the partition plate 10. By arranging the scanner housing 35 in such a manner as to project forward from the partition plate 10, the scanner unit 30, the drum cartridge 31, and the developer cartridge 32 can be positioned closer, making it possible to realize a more compact apparatus.

Since the scanner housing 35 projects forward from the partition plate 10, when the developer cartridge 32 is mounted on the drum cartridge 31, the drum cartridge 31 is restricted from passing through the developer accommodating section 14. However, when the developer cartridge 32 is detached from the drum cartridge 31, the drum cartridge 31 may pass through the developer accommodating space 16.

As shown in fig. 18, the developer accommodating section 14 is narrower than the drum accommodating section 13 in the lateral direction and the perpendicular direction to the mounting direction of the drum cartridge 31 and the developer cartridge 32 (hereinafter referred to as the "thickness" direction of the drum cartridge 31 and the developer cartridge 32) due to the scanner housing 35.

More specifically, the developer accommodating section 14 is wider in the thickness direction than the thickness of the fixing unit 43 of the drum cartridge 31 and narrower than when the drum cartridge 31 and the developer cartridge 32 are mounted together.

As shown in fig. 18, the extended accommodating space 18 is located in the developer accommodating portion 14 between the upper end and both ends in the lateral direction of the scanner housing 35, and is close to the front wall 34 of the scanner housing 35 (a space is provided between the scanner housing 35 and the developer accommodating space 16, and an intermediate plate 54 to be described later is provided therein). The extended accommodating space 18 accommodates an extended portion 44 of the drum cartridge 31, which will be described later.

As shown in fig. 1, the front wall 34 of the scanner housing 35 has a window 40 for the laser beam to pass through. The laser emitting unit of the scanning unit 30 emits a laser beam according to certain image data. The laser beam is deflected by the polygon mirror 36, passes through or is reflected by the lens 37, the reflecting mirror 39 and the lens 30, and is emitted through the window 40.

As shown in fig. 2 and 3, the drum cartridge 31 includes a drum housing 41; and a photosensitive drum 42 and a scorotron charger 62 (see fig. 1) provided in the drum housing 41.

The drum housing 41 includes a fixing unit 43, and an extending portion 44 extending from the fixing unit 43. The fixing unit 43 and the extension portion 44 are integrally made of synthetic resin.

The drum cartridge 31 will be described below with reference to fig. 2 to 7. In the following description, when the drum cartridge 31 is in a state of being mounted in the color laser printer 1, a side located facing the rear side of the color laser printer 1 in the thickness direction is referred to as a top surface side or an upper side of the drum cartridge 31; the side located facing the front of the color laser printer 1 is referred to as the bottom surface side or lower side of the drum cartridge 31; the side of the drum cartridge 31 downstream in the mounting direction is referred to as the front side of the drum cartridge 31; and the side of the drum cartridge 31 upstream in the mounting direction is referred to as the rear side of the drum cartridge 31. The width direction of the drum cartridge 31 is defined to be perpendicular to both the top-bottom direction and the front-rear direction of the drum cartridge 31.

The fixing unit 43 includes two side walls 45 facing with a certain gap in a lateral direction, a top wall 47 bridging upper ends of the side walls 45, and a front wall 47 extending perpendicularly from a front edge of the top wall 46 along a portion of the front edge of the side walls 45. The fixing unit 43 is thicker than the developer housing 64 of the developer cartridge 32.

The fixing unit 43 is thicker than the extension portion 44. This structure can surely accommodate the photosensitive drum 42 and the charger 62.

As shown in fig. 6 and 7, the lower portion of each side wall 45 has a developer positioning groove 48 formed substantially in a U-shape with the rear portion open. The developer positioning groove 48 is provided at the front side with an insertion portion 49 for inserting a drum shaft 60 of the photosensitive drum 42.

As shown in FIG. 2, the cleaner mounting portion 50 is located on the top wall 46 along a lateral edge of the top wall 46. A cleaner 63 (described below) is slidably fitted into the cleaner fitting portion 50. As shown in fig. 6 and 7, the ridges 51 at both lateral ends of the top wall 46 are substantially triangular projections projecting upward at the upper end of the top wall 46 as viewed from the side.

As shown in fig. 2 and 3, when the fixing unit 43 is mounted in the drum accommodating portion 13, the extending portion 44 extends rearward from the fixing unit 43 so as to extend above the upper end of the scanner housing 35 in the developer accommodating portion 14.

The extension portion 44 includes two extension side portions 52 facing each other with a gap in a lateral direction, an extension rear wall 53 bridging between rear ends of the extension side portions 52, and an intermediate plate 54 located in an area surrounded by the fixing unit 43, the extension side portions 52, and the extension rear wall 53.

As shown in fig. 2, each of the extension side portions 52 has a substantially box-shaped cross member that is open at the bottom. As shown in fig. 2, the outer surface of the extension side portion 52 extends rearward from both lateral ends of the fixing unit 43 so as to continue rearward from the top of the developer positioning groove 48.

As shown in fig. 3, two reinforcing brackets 55 having substantially X-shaped bottom surfaces are located inside the box shape of the extension side portion 52 in the front-rear direction. Drum projections 56 projecting outward in the lateral direction are located on the outer side surfaces of the extension side portions 52 from the middle along the longitudinal direction of each extension side portion 52.

As described above, the extended rear wall 53 extends in the lateral direction, connecting the rear edges of the extended side portions 52. The drum handle 57 is located at the widthwise middle of the extended rear wall 53 to catch the drum cartridge 31, and to mount and remove the drum cartridge 31 with respect to the drum accommodating portion 13.

As shown in fig. 2, the intermediate plate 54 is located on a plane formed substantially in a rectangular shape. The intermediate plate 54 is located at a portion surrounded by the fixing unit 43, the extension side portion 52, and the extension rear wall 53, and is connected to the fixing unit 43, the extension side portion 52, and the extension rear wall 53 at a recessed position lower than the extension side portion 52 and the extension rear wall 53.

The intermediate plate 54 has an opening 58 therein for passing the laser beam emitted from the window 40 of the scanner housing 35. As shown in fig. 4, the opening 58 is shaped like a trapezoid that is wide at the front and narrow at the back when viewed in a plan view. By such an opening 58 having a trapezoidal shape in plan view, only the portion of the intermediate plate 54 through which the laser beam passes can be cut, making the extension portion 44 stronger than when the planar shape of the intermediate plate is rectangular.

As shown in fig. 2, the photosensitive drum 42 is accommodated in the fixing unit 43 in the lateral direction. The photosensitive drum 42 includes a main drum body 59 having a cylindrical shape, a positively charged photosensitive layer made of polycarbonate or the like as an outer layer, and a drum shaft 60 extending along the central axis of the main drum body 59. The drum shaft 60 is supported by two shaft ends on the side walls 45, each of which is inserted into the insertion portion 49 on the respective side wall 45 and projects axially outward from the respective side wall 45. The drum shaft 60 cannot rotate relative to the side wall 45.

The rotation support members 61 are mounted on both axial ends of the main drum 59 so as not to be rotatable with respect to the main drum 59. The rotation support member 61 is supported by the drum shaft 60 and is rotatable with respect to the drum shaft 60. Thus, the main shell 59 is supported for rotation relative to the drum shaft 60. With this structure, as shown in fig. 5, the photosensitive drum is disposed in the fixing unit 43 so that the front surface is exposed below the front wall 47.

As shown in fig. 1, the charger 62 is housed in the fixed unit 43 above the ridge 51 (at the rear in fig. 2) and extends laterally. The charger 62 is a positively charged scorotron charger including wires and grids for generating a corona discharge. The charger is supported on a top wall 46 at the rear of the photosensitive drum 42 (above in fig. 2) and faces the photosensitive drum at a distance so as not to contact it. As shown in fig. 2, the charger 62 is provided with a cleaner for cleaning the electric wire. The cleaner 63 is slidably mounted in the cleaner mounting portion 50 of the top wall 46.

The developer cartridge 32 shown in fig. 1, 8 and 16 includes a developer housing 64, and, disposed in the developer housing 64, an agitator 69, a supply roller 66, a developing roller 67 and a thickness regulating blade 68.

Next, the developer cartridge 32 will be described in detail with reference to fig. 8 to 16.

In the following description, when the developer cartridge 32 is in a state of being mounted in a color laser printer, the side of the developer cartridge 32 located toward the rear side of the color laser printer in the thickness direction is referred to as a top surface side or an upper side of the developer cartridge 32; the side located toward the front of the color laser printer 1 is referred to as the bottom surface side or lower side of the developer cartridge 32; the side of the developer cartridge downstream in the mounting direction is referred to as the front side of the developer cartridge 32; and the side of the developer cartridge upstream in the mounting direction is referred to as the rear side of the developer cartridge 32. The width direction of the developer cartridge 32 is defined to be perpendicular to both the top-bottom direction and the rear direction of the developer cartridge 32.

As shown in fig. 8, the developer housing 64 is located in a thin box with a front opening. As shown in fig. 15, the developer housing 64 includes a housing member 70 whose top surface side is open; and a cover member 71 separated from the case member for covering the opened top surface side of the case member 70.

The housing member 70 includes a pair of spaced apart and laterally facing side walls 72; a rear wall 73 connected to the rear edge of the side wall 72; and a bottom wall 74 connecting bottom edges of the side wall 72 and the rear wall 73 so as to cover a side of an area enclosed by the side wall 72 and the rear wall 73.

As shown in fig. 14, both side walls are plate-shaped and extend in the front-rear direction. Each side wall 72 integrally includes a front side wall 75, an inclined wall 76 and a rear side wall 77 seamlessly connected in the front-rear direction.

These front side walls 75 are parallel to each other opposite to the thickness regulating blade 68, the supply roller 66, and the agitator 69, and are located at the front of the developer cartridge 32, extending rearward from the front edge to an intermediate position in the front-rear direction.

The rear side walls 77 are located at the rear of the developer cartridge 32, opposite the developing roller 67 to the agitator 69, and are also parallel to each other, and extend forward from the rear edge of the developer cartridge 32 to an intermediate position in the front-rear direction, so that a gap is formed in the front-rear direction between the front sections of the rear side walls 77 and the rear ends of the front side walls 75. The rear side walls 77 are spaced apart from each other by a distance greater than the distance between the front side walls 75.

The inclined wall 76 is inclined with respect to the front-rear direction so that the distance therebetween gradually increases from the front edge to the rear edge. The inclined wall 76 is located between the front side wall 75 and the rear side wall 77, and the inclined wall 76 is connected at a front end thereof to the front side wall 75 and at a rear end thereof to the rear side wall 77. As shown in fig. 15, the inner surface of the inclined wall 76 is an inclined wall 178 for guiding discharged toner, which will be described later.

As shown in fig. 9, a developer projection 95 projects laterally from the rear side wall 77 at the side near the top surface.

As shown in fig. 9 and 5, the rear side wall 73 is formed as a thin rectangular plate extending laterally.

As shown in fig. 16, the bottom wall 74 has a plate shape. The front end of the bottom wall 74 (the portion downstream in the mounting direction of the developer cartridge 32, between the front side walls 75) and the discharge wall 78, the supply roller accommodating wall 79, and the tongue-shaped wall 80 are provided in this order from the rear side to the front side. The discharge wall 78 protrudes toward the top surface and has a cross section curved along the rotation locus of the agitator 69. The cross section of the supply roller accommodating wall 79 is curved along the outer surface of the supply roller 66. The tongue-shaped wall 80 is inclined downward toward the front so as to expose the developing roller 67.

As shown in FIG. 14, a bottom gripping portion 96 is provided on the outer surface of the bottom wall 74 to provide a gripping area for a user. The bottom grip portion 96 is located at a position laterally intermediate the bottom wall 74, and extends from a rear portion of the bottom wall 74 (a portion of the bottom wall 74 located between the rear side walls 77 on the upstream side in the mounting direction of the developer cartridge 32) to a position intermediate the front and rear ends of the bottom wall 74 (a portion of the bottom wall 74 located between the inclined walls 76 in the middle in the mounting direction of the developer cartridge 32). The bottom gripping portion 96 is substantially rectangular in bottom view and has an irregular or corrugated surface for gripping. The bottom grip portion 96 serves as a mark indicating where the user grips the developer cartridge 32.

As shown in fig. 9, the contact projections 94 are located on the outer surfaces of the bottom wall 74 near the rear lateral ends and project slightly upward from the bottom wall.

As shown in fig. 15, the support column member 81 stands upright from the inner surface of the bottom wall 74 at the widthwise center of the bottom wall 74 between the front and rear ends.

The support post member 81 is disposed on an inner surface of the bottom wall 74 opposite the bottom gripping portion 96 on an outer surface of the bottom wall 74. As shown in fig. 16, the supporting column member 81 stands upright in the thickness direction of the developer cartridge 32, and has substantially the same height as the rear wall 73. As shown in fig. 15, the supporting column member 81 is disposed at the center in the lateral direction and the front-rear direction of a toner containing chamber 92 (described later) so as to be spaced apart from two side walls 72, a rear wall 73, and a partition wall 83 (described later). The support column member 81 is formed substantially in a cylindrical shape having a cross section like a tear-drop shape with a conical tip of the tear-drop shape directed rearward and a circular bottom end of the tear-drop directed forward. A substantially V-shaped tapered surface formed along the rear side of the supporting column member 81 serves as a guide surface 82a for guiding the toner in the discharging direction (downward direction when the developer cartridge 32 is mounted).

As shown in fig. 16, the partition wall 83 spans between the front side walls 75 and is located at the midpoint in the front-rear direction of the front side walls 75. The partition wall 83 has a thin rectangular shape extending in the lateral direction, and extends from the top surface side edge portion of the front side wall 75 toward the bottom surface side in the developer cartridge thickness direction. The edge of the partition wall 83 facing the bottom surface side and the connecting portion between the discharge wall 78 and the rear edge of the developing roller accommodating wall 79 (protruding toward the top surface) form a gap in the thickness direction. The partition wall 83 closes a top surface side (to be described later) of the discharge opening 84 in a lateral direction of the developer cartridge 32, that is, a longitudinal direction of the discharge opening 84.

An elongated discharge opening 84 extending in the lateral direction of the developer cartridge 32 is located between one end of the partition wall 83 facing the lower surface side and a connecting portion connecting the front end of the discharge wall 78 and the rear end of the supply roller accommodating wall 79.

As shown in fig. 15, a frame portion 85 for contacting the peripheral edge of the cover member 71 is provided along the edge portions on the top surface side of the side walls 72, the partition wall 83 and the rear wall 73.

The cover member 71 is substantially plate-shaped corresponding to the space surrounded by the partition wall 83, the side wall 72 and the rear wall 73. The cover member 71 is integrally formed of: a contact portion 86 provided on the same plane as the cover member 71 along a peripheral edge thereof to contact the rim portion 85 of the case member 70; and a top wall 87 surrounded by the contact portion 86 and pressed downward to the top surface side.

The top wall 87 integrally includes: a front ceiling wall 88 of a rectangular plate shape on the front side of the cover member 71; a rear ceiling wall 89 of a rectangular plate shape on the rear side of the cover member 71, which is wider and depressed deeper than the front ceiling wall 88; and a substantially trapezoidal intermediate ceiling wall 90 located between the front ceiling wall 88 and the rear ceiling wall 89 in the front-rear direction.

As shown in fig. 8, a top side gripping portion 97 is located on the outer surface of the top wall 87 for gripping by a user. The top side grip portion 97 is located on the transverse center of the portion of the top wall 87 from the rear top wall 89 to the center top wall 90. The top side grip portion 97 is substantially rectangular in plan and has an irregular or corrugated surface. The top side grip portion 97 serves as a sign indicating where the user grips the developer cartridge 32.

As shown in fig. 15, a cylindrical fitting portion 91 is provided on the inner surface of the top wall 87 at the center of the top wall in the lateral direction for fitting one end of the support column member 81 to the top surface side. The cylindrical fitting portion 91 is located on the inner surface of the top wall 87 at a position corresponding to the top side grip portion 97 on the outer surface of the top wall 87. As shown in fig. 16, the depth to which the cylindrical fitting portion 91 extends from the intermediate top wall 90 toward the bottom wall 74 is greater than the depth to which the rear top wall 89 is depressed from the contact portion 86. The cylindrical fitting portion 91 is substantially cylindrical and has a cross-section substantially in the form of a tear-drop similar to the cross-section of the support column member 81, but slightly larger than it for receiving the support column member 81. The cylindrical fitting portion 91 has a guide surface 82b corresponding to the guide surface 82a of the support column member 81.

The developer cartridge 64 is formed by covering the housing member 70 with the cover member 71, the contact portion 86 of the cover member 71 being in contact with the frame portion 85 of the housing member 70, and the top end of the support post member 81 being fitted into the cylindrical fitting portion 91 to tightly couple the contact portion 86 with the frame portion 85. The developer cartridge 64 is thin in structure, and the bottom grip portion 96 and the top grip portion 97 are opposed in the thickness direction, so that the user can grip and grasp the bottom grip portion 96 and the top grip portion 97 with one hand.

As shown in fig. 16, when the support column member 81 is fitted into the cylindrical fitting portion 91, the support column member 81 and the cylindrical fitting portion 91 constitute a reinforcing column 65 bridged between the bottom wall 74 and the top wall 87.

In the developer housing 64 having the above-described structure, the toner accommodating chamber 92 is defined by the top wall 87, the middle rear portion of the bottom wall 74 (including the discharge wall 78 and opposed to the top wall 87 at a distance in the thickness direction), the side wall 72 (specifically, the portion at the midpoint in the front-rear direction from the rear side wall 77 to the front side wall 75), the rear wall 73, and the partition wall 83 between the top wall 87 and the bottom wall 74.

The developing chamber 93 is located further forward of the toner accommodating chamber 92, and is constituted by a front portion of the bottom wall 74 including the supply roller accommodating wall 79 and the tongue-shaped wall 80, a side wall 72 (specifically, a portion from a front edge to a midpoint of the front side wall 75 in the front-rear direction) constituted continuously by a front side of the bottom wall 74, and a partition wall 83.

In the toner accommodating chamber 92, the front ceiling wall 88 and the rear ceiling wall 89 are disposed parallel to the bottom wall 74, and the spacing between the rear ceiling wall 89 and the bottom wall 74 is larger than the spacing between the front ceiling wall 88 and the bottom wall 74. The intermediate top wall 90 is sloped relative to the bottom wall 74, sloping from front to back to the top surface side.

A toner filling hole 98 is located on one rear side wall of the toner accommodating chamber 92. As shown in fig. 11, the toner filling hole is substantially circular in side view and penetrates the rear side wall 77 in the thickness direction.

As shown in fig. 19, the toner filling nozzle 99 is constituted by a straight pipe, and is insertable into the toner filling hole 98 to fill the toner containing chamber 92 with toner. The toner filling nozzle 99 guides the toner along an X-ray extending from the toner filling nozzle 99 in the filling direction. The reinforcing column 65 is disposed at a position distant from the extension line X, and does not overlap the extension line X.

As shown in fig. 8, the toner filling hole 98 is normally covered with a cover 165.

As shown in fig. 11 and 12, the detection windows 100 are located at corresponding positions in the lateral direction of each front side wall 75 of the toner-accommodating chamber 92. The detection window 100 allows detection light to pass from one front side wall 75 to the other to detect the amount of toner accommodated in the toner-accommodating chamber 92.

As shown in fig. 16, the position of the reinforcement pillar 65 does not laterally overlap with the optical path of the detection light passing through the detection window 100, but is located further rearward of the optical path.

The agitator 69 is located inside the toner accommodating chamber 92 near the discharge opening 84. As shown in fig. 18, the agitator 69 includes a rotary shaft 151 rotatably supported between the front side walls 75, and a pair of agitating members 152 provided on the rotary shaft. In fig. 15, 16 and 19, only one of the pair of stirring members 152 is shown for clarity of illustration. Each stirring member is in the form of a grid (see fig. 15) and projects radially therefrom. As shown in fig. 19, more specifically, each stirring member 152 includes: a plurality of plates 152a arranged along the axis of the rotary shaft 151 with gaps therebetween, each protruding radially outward from the rotary shaft 151; and a coupling plate 152b extending parallel to the axis of the rotary shaft 151, coupling tips of the plates 152b one by one. The agitator 69 is disposed adjacent the discharge opening 84 to rotate the agitating member 152 along the discharge wall 78. An outer annular path region projected onto each side wall 77 in the axial direction of the rotary shaft 151 is referred to as an agitator projection region. The detection windows 100 are located at laterally opposite positions on the front side wall 75 so as to overlap with the agitator projection area in the front-rear direction. In other words, detection window 100 is located within the agitator projection area on front sidewall 75.

The reinforcement column 65 is located behind the agitator 69 at a position not overlapping the outer annular path of the rotation locus of the agitating member 152 so that the reinforcement column does not contact the rotating member 152 in rotation. In other words, assuming that the reinforcement column 65 is projected onto each side wall 72 in a direction parallel to the axis of the rotary shaft 151, the region thus formed is referred to as a column projection region which does not overlap with the agitator projection region on each side wall 72. As shown in fig. 15, the toner filling hole 98 is also located on the side wall 72 at a position rearward of the agitator 69 so as not to overlap with the agitator projection area on the side wall 72.

As shown in fig. 1, when the developer cartridge 32 is mounted in the color laser printer 1, a toner-accommodating chamber for accommodating toner of each color used in the color laser printer is located in an upper portion (rear portion in fig. 8) of the developer housing 64. In the preferred embodiment, the toner-accommodating chamber 92 of each process section 27 accommodates a positively charged nonmagnetic mono-component polymerized toner. The toner-accommodating chamber of the yellow process section 27Y accommodates yellow toner, the toner-accommodating chamber of the magenta process section 27M accommodates magenta toner, the toner-accommodating chamber of the cyan process section 27C accommodates cyan toner, and the toner-accommodating chamber of the black process section 27K accommodates black toner.

More specifically, each toner used in the preferred embodiment is a polymerized toner having a substantially spherical shape obtained by a polymerization method. The polymerized toner is a synthetic resin obtained by copolymerizing a polymerizable monomer by a common polymerization method such as suspension polymerization. The polymerizable monomer may be a styrene-based monomer, such as styrene or an acrylic-based monomer, such as acrylic acid, alkyl (C1-C4) acrylate, or alkyl (C1-C4) methacrylate. The base fine particles are obtained by combining these synthetic resins with a coloring agent, a charge control agent, paraffin, and the like. Additives for improving fluidity are also added to the primary toner particles.

The coloring agent compounded with the synthetic resin provides one of yellow, magenta, cyan and black. The charge control agent is a charge control resin obtained by copolymerizing an ionic monomer having an ionic functional group such as an ammonium salt with those copolymerizable with the ionic monomer such as a styrene monomer or an acrylic monomer. The additive may be a powder of a metal oxide such as silica, alumina, titanium oxide, strontium titanate, cerium oxide, or magnesium oxide, or an inorganic powder such as a calcine powder or a metal salt powder.

As shown in fig. 16, the developing chamber 93 is adjacent to and in front of the toner accommodating chamber 92, and is in liquid communication with the accommodating chamber 92 through the discharge port 84.

The developer cartridge 32 is provided at the front end with an opening 159 to open the developing chamber 93 in a region from the upper surface side to the front side. As shown in fig. 8, the front section of the tongue-shaped wall 80 across the entire width of the developer cartridge 32 is provided with a jaw portion 153. The jaw portion 153 opposes the peripheral surface of the developing roller 67 located in the developing chamber 93, and its bottom surface side contacts to prevent toner from leaking outward.

As shown in fig. 11 and 12, a guide plate (runner)154 is located at a front portion of the bottom surface side of the front side wall 75 at a position laterally opposite to the jaw portion 153. The guide plate 154 is shaped like a curved L on the side, as shown, with the arm jaw portion 153 projecting more in the anterior-posterior direction. As shown in fig. 16, the supply roller 66 is located in the developing chamber 93 in front of the discharge opening 84 and extends in the lateral direction to be accommodated in the supply roller accommodating wall 79.

The supply roller 66 includes a metal supply roller shaft 155 rotatably supported between the front side walls; and a supply roller layer 156 made of a conductive sponge member, which covers the surface of the supply roller shaft 155.

The developing roller 67 is located in the developing chamber 93 obliquely forward from the supply roller 66 to the top wall surface side, and extends laterally to face the tongue-shaped wall 80. The developing roller 67 includes a metal supply roller shaft 157 rotatably supported between the front side walls and a developing roller layer 158 made of a conductive rubber material covering the surface of the developing roller shaft 157.

More specifically, the developing roller layer 158 has a two-layer structure including an elastic roller layer made of conductive urethane rubber containing fine carbon particles, silicone rubber, EPDM rubber or the like, and a coating layer covering the surface of the roller layer, the main components being urethane rubber, urethane resin, polyimide resin or the like.

The developing roller 67 and the supply roller 66 are in press contact with each other. As shown in fig. 16, the developing roller 67 is located at the front end of the developing chamber 93 such that the front surface of the developing roller is exposed through the opening 159. As described above, the jaw portion 153 is in press contact with the developing roller 67 on the bottom surface of the exposed front portion.

The thickness regulating blade 68 is located on the front surface of the partition wall 83 across the entire width thereof. As shown in fig. 16, the thickness-adjusting blade 68 includes a blade 160 composed of a metal spring blade; a fixing member 161 for sandwiching one end of the top surface side of the blade 160 and fixing the blade 160 to the front surface of the partition wall 83; and a pressing portion 162 at one end of the bottom surface side of the blade 160. The pressing portion 162 has a semicircular cross section and is formed of an insulating silicon rubber. The thickness regulating blade 68 is provided such that the blade 160 extends in the developer cartridge thickness direction, the top surface side end is fixed to the front surface of the partition wall 83 by a fixing member 161, and the pressing portion 162 at the bottom surface side end is pressed against the rear side of the developing roller layer 158 on the developing roller 67 by the elastic force of the blade 160.

As shown in fig. 8 and 11, a gear train (not shown), an agitator drive gear (not shown), a supply roller drive gear (not shown), and a developing roller drive gear (not shown) are provided on the outer surface of the front side wall 75 of one side wall 72. The gear set transmits the driving force to an agitator driving gear (not shown), a supply roller driving gear (not shown), and a developing roller driving gear (not shown). An agitator drive gear (not shown) is located at one end of the rotating shaft 151 that protrudes from the outer surface of the same side wall 72. A supply roller driving gear (not shown) is located at one end of the supply roller shaft 155 protruding from the outer surface of the same side wall 72. A developing roller driving gear (not shown) is located at one end of the developing roller shaft 157 that protrudes from the outer surface of the same side wall 72. A female coupling portion 163 for inputting a driving force to the gear train is also provided on the outer surface of the front side wall 75 on the same side wall 72. The gear combination female coupling part 163 is received in and supported by the gear cover 164 on the outer surface of the front side wall 75.

The cover detection hole 179 is formed in the gear cover 164 at a position laterally corresponding to the detection window 100. In a side view, the lid detection hole 179 has a substantially elliptical shape corresponding to the detection window 100 extending in the front-rear direction.

As shown in fig. 17, a guide groove 101 is provided in each process accommodating portion 12. The guide grooves 101 guide the drum cartridge 31 to be mounted in or removed from the main casing 2 by inserting both ends of the drum shaft 60 in the drum cartridge 31 into the corresponding guide grooves 101. As shown in fig. 18, the guide groove 101 is constituted by a groove at a corresponding position on the inner surface of the left and right side plates 8 and 9, and is inclined rearward from top to bottom in the mounting direction of the drum cartridge 31.

The lower end (deepest end) of each guide groove 101 is a receiving portion 102 for receiving the drum shaft 60. The receiving portion 102 is constituted by a recess into which the drum shaft 60 is just fitted in the front-rear direction, and is provided at a position where the photosensitive drum 42 is in contact with a conveyor belt 168 (described later) when the drum shaft 60 is received by the receiving portion 102.

The drum cartridge positioning grooves 103 are located at laterally corresponding positions of the left and right side plates 8 and 9. The drum cartridge positioning groove 103 is located at an intermediate position of the length of the guide groove 101. The drum cartridge positioning groove 103 is a rectangular recess in side view, the front being open to receive the drum projection 56.

As shown in fig. 17, the projection insertion groove 133 is located on the upper side of the guide groove 101 as a cutout portion on the left and right side plates 8 and 9 for receiving the developer projection 95 of the developer cartridge 32. The projection insertion grooves 133 are straight substantially elongated U-shaped grooves at the upper ends of the left and right side plates 8 and 9, and are inclined rearward from top to bottom in the mounting direction of the developer cartridge 32, that is, along the moving path of the developer projections 95 when the developer cartridge 32 is mounted or removed.

In the color laser printer according to the preferred embodiment shown in fig. 18, each drum cartridge is mounted in the main casing 2 by mounting the drum cartridge 31 of each color into the corresponding drum housing 13 of the corresponding process housing 12. Also, the developer cartridges 32 of the respective colors are mounted into the corresponding developer accommodating portions 14, and thus, into the corresponding drum cartridges 31.

More specifically, as shown in fig. 18, in order to mount the drum cartridge 31 into the drum accommodating space 15 of the process accommodating portion 12, the user grips the drum handle 57, inserts the drum projections 56 of the drum cartridge 31 into the corresponding guide grooves 101, and pushes down the drum cartridge 31. As a result, the drum cartridge 31 passes through the developer accommodating portion 14 to be finally mounted into the drum accommodating portion 13.

When the drum cartridge 31 is mounted, the ridge 51 of the drum cartridge 31 often slides on the rail portion 17 of the developer accommodating portion 14 when the fixing unit 43 of the drum cartridge 31 passes through the developer accommodating space 16 of the developer accommodating portion 14. In this way, since the ridge 51 protrudes toward the rail portion 17 while the rail portion 17 is constituted by a thick strip, the ridge 51 is in contact with the rail portion 17 to form a gap between the front wall 34 of the scanner housing 35 and the top wall 46 opposite to the front wall 34, thereby preventing mutual friction between the top wall 46 and the front wall 34 of the scanner housing 35.

Next, the drum projections 56 are inserted into the corresponding drum cartridge positioning grooves 103. As a result, the drum cartridge 31 is accommodated in the drum accommodating space 15 while the extending portion 44 thereof is accommodated in the extending accommodating space 18 of the developer accommodating portion 14. In this way, the drum cartridge 31 is mounted in the main casing 2.

In the color laser printer 1 having the above-described structure, the front wall 34 of the scanner housing 35 projects toward the developer accommodating space 16 to the process accommodating portion 12. When the developer cartridge 32 is mounted to the drum cartridge 31 in the developer accommodating portion 14, the passage of the drum cartridge 31 can be restricted by the developer accommodating portion 14. However, when the developer cartridge 32 is separated from the drum cartridge 31, the drum cartridge 31 is allowed to pass through the developer accommodating space 16.

By forming the front wall 34 of the scanner housing 35 to expand toward the developer accommodating space 16, the drum cartridge 31 can pass through the developer accommodating space 16 without abutting against the front wall 34 of the scanner housing 35, and can be mounted in the drum accommodating portion 13 and accommodated in the drum accommodating space 15 when separated from the developer cartridge 32, without allocating an additional space only for the mounting path of the drum cartridge 31 and the developer cartridge 32. Subsequently, as described below, the developer cartridge 32 may be mounted on the developer accommodating portion 14 and accommodated in the developer accommodating space 16, thereby completing the mounting process of the drum cartridge 31 and the developer cartridge 32.

When the fixing unit 43 is accommodated in the drum accommodating space 15 of the drum accommodating portion 13, the ridge 51 passes over the rail portion 17 to a position below the scanner housing 35, as shown in fig. 18. At this time, the top of the charger 62 is placed below the scanner housing 35. The photosensitive drum 42 is in contact with a conveyor belt 168 described later.

Next, the user aligns the developer protrusions 95 with the corresponding protrusion insertion grooves 133 in the bottom grip portion 96 and the top grip portion 97 of the developer cartridge 32 as shown in fig. 17, and pushes down the developer cartridge 32. The developer protrusions 95 are inserted into the corresponding protrusion insertion grooves 133, and the developer cartridge 32 is accommodated in the developer accommodating space 16 and mounted on the drum cartridge 31 that has been previously mounted in the main casing 2.

Further, when the developer cartridge 32 is mounted in the manner as described above, the guide plate (runners)154 of the developer housing 64 is in contact with the rear surface 33 of the partition plate 10 in front of the jaw-like portion 153, and when the developer cartridge 32 is mounted, the guide plate 154 slides along the rear surface 33 of the partition plate 10. This structure can prevent damage to the jaw portion 153 and can effectively prevent toner from leaking from the outer surface of the developing roller 67.

When an image forming operation is not performed in the laser printer 1, a separation mechanism (not shown) holds the developer cartridge 32 in a state of being separated from the drum cartridge 31, so that the developing roller 67 is separated from the photosensitive drum 42. In the image forming operation, the developer cartridge 32 is moved to the contact position, so that the photosensitive drum 42 and the developing roller 67 are in contact with each other.

When the developer cartridge 32 is mounted to the drum cartridge 31, the developer cartridge 32 is positionable relative to the drum cartridge 31 by fitting the developing roller shaft 157 of the developing roller 67 into the developer positioning groove 48 of the drum housing 41, so that the developer cartridge 32 can be selectively switched between the detached position and the contact position in the developer accommodating portion 14. Further, by placing the contact projection 94 on the bottom wall 74 of the developer housing 64 in contact with the rear surface 33 of the partition plate 10, the developer cartridge 32 can also be positioned with respect to the developer accommodating portion 14.

When mounted and positioned in this manner, each developer cartridge 32 is placed on a slope inclined from the vertical direction as shown in fig. 18, so that the openings 159 are positioned on the rear walls 73 on the lower rear side and the upper front side. More specifically, the discharge opening 84 is positioned below the toner accommodating chamber 92, and the agitator 69 is positioned above the discharge opening 84. Further, the supply roller 66 and the developing roller 67 are both disposed below the toner accommodating chamber 92 so that a straight line Z extending vertically downward from the rotary shaft 151 of the agitator 69 intersects a line segment Y connecting the supply roller shaft 155 of the supply roller 66 and the developing roller shaft 157 of the developing roller 67.

When the drum cartridge 31 is mounted in the drum housing 13, the photosensitive drum 42 is electrically grounded through connection with a contact (not shown). In the image forming operation, a charging bias is applied to the charger 62. Also, in the image forming operation, a driving force input from a motor (not shown) rotates the photosensitive drum 42 through engagement of gears (not shown).

When the developer cartridge 32 is mounted in the developer accommodating portion 14, a connection with a contact (not shown) is formed so that a developing bias acts on the developing roller shaft 157 of the developing roller 67 in an image forming operation. Further, a male coupling portion (not shown) is engaged with the female coupling portion 163, so that a driving force of a motor (not shown) can be input to rotate the agitator 69, the supply roller 66, and the developing roller 67 in an image forming operation.

In the image forming operation, the toner of each color in the toner-accommodating chamber 92 of each developer cartridge 32 is vertically moved downward toward the discharge opening 84 by its own weight, and is discharged from the discharge opening 84 as the agitator rotates. The toner discharged from the discharge opening 84 is supplied to the supply roller 66, and further supplied to the developing roller 67 when the supply roller 66 rotates. At this time, a developing bias is applied to the developing roller 67, and the toner is charged with the static electricity of the positive electrode between the supply roller 66 and the developing roller 67.

As the developing roller 67 rotates, the toner supplied to the surface of the developing roller 67 passes between the developer layer 158 of the developing roller 67 and the pressing portion 162 of the thickness-adjusting blade 68, so that the thickness-adjusting blade 68 can adjust the toner carried on the surface of the developing roller 67 into a fixed thin layer.

At the same time, a charging bias is applied to the charger 62 in the drum cartridge 31, causing the charger 62 to generate corona discharge to provide the same positive charge to the surface of the photosensitive drum 42. As the photosensitive drum 42 rotates, the surface of the photosensitive drum 42 is exposed to a high-speed scan of the laser light emitted by the scanner unit 30. The scanner unit 30 forms an electrostatic latent image on the surface of the photosensitive drum 42, corresponding to an image to be on the sheet 3.

As the photosensitive drum 42 further rotates, the electrostatic latent image formed on the surface of the photosensitive drum 42 comes into contact with the positively charged toner carried on the surface of the developing roller 67. The toner on the surface of the rotating developing roller 67 is supplied to the electrostatic latent image on the surface of the photosensitive drum 42, i.e., to the exposed portion of the surface of the photosensitive drum 42, which has been exposed to the laser beam and thus has a lower potential than other positively charged portions of the surface. In this way, the electrostatic latent image is developed into a visible toner image by a reverse developing process, and the toner image is carried on the surface of the photosensitive drum 42 for each color.

As shown in fig. 1, the transfer section 28 is disposed above the feeding unit 4 in the main casing 2, and extends in the front-to-rear direction below the process accommodating section 12. The transfer section 28 includes a driving roller 166, a driven roller 167, a conveying belt 168, and a transfer roller 169. The driving roller 166 is disposed further forward than the process accommodating portion 12 accommodating the yellow process portion 27Y. The driven roller 167 is provided further rearward than the process accommodating portion 12 accommodating the black process portion 27K.

The conveyor belt 168 is an endless belt made of synthetic resin such as conductive polycarbonate or polyimide in which conductive particles such as carbon are dispersed. The conveyor belt 168 is wound around the driving roller 166 and the driven roller 167. When the driving roller 166 is driven, the driven roller 167 follows the rotation of the driving roller 166, while the conveying belt 168 moves in a loop between the driving roller 166 and the driven roller 167. The outer surface of the conveyor belt 168 is opposed to the photosensitive drum 42 and is in contact with the photosensitive drum 42 at the image forming position in each process portion 27, and moves in the same direction as the photosensitive drum surface at the contact point.

A transfer roller 169 is disposed in the conveying belt 168 at a position opposed to each photosensitive drum 42 with the conveying belt 168 sandwiched therebetween. The transfer roller 69 is provided so as to be constituted by a metal roller shaft on which a roller portion made of a conductive rubber material is covered. The transfer roller 69 is rotatably provided so that the surface of the transfer roller 69 moves in the same direction as the conveyance belt at the image forming position. In the transfer operation, a transfer bias is applied to the transfer roller 169.

As described above, when the driving roller 166 is driven and the driven roller 167 follows, the conveying belt 168 moves in a loop between the driving roller 166 and the driven roller 167. When the sheet 3 is supplied from the feeding unit 4, the conveyor belt 168 conveys the sheet 3 in a backward direction sequentially through each image forming position between the conveyor belt 168 and the photosensitive drum 42 in the process portion 27. When the sheet 3 is conveyed by the conveyor belt 168, the toner image of each color conveyed on the photosensitive drum 42 of each process section 27 is sequentially transferred onto the sheet 3, thereby forming a multicolor image on the sheet 3.

Specifically, first, the yellow toner image carried on the surface of the photosensitive drum 42 in the yellow process section 27Y is transferred onto the sheet 3. Next, the magenta toner image carried on the surface of the photosensitive drum 42 in the magenta process section 27M is transferred onto the sheet 3 and superimposed on the yellow toner image. This operation is repeated to transfer and superimpose the cyan toner image carried on the surface of the photosensitive drum 42 in the cyan process section 27C and the black toner image carried on the surface of the photosensitive drum 42 in the black process section 27K, thereby generating a multicolor image on the sheet 3.

In order to form a multicolor image by this method, the color laser printer 1 is provided as a tandem type apparatus in which the drum cartridges 31 and the developer cartridges 32 are provided in sets, one set for each color, in each process section 27. Accordingly, the color laser printer 1 in the preferred embodiment forms the toner image of each color at a speed required for forming a monochrome image, thereby forming a color image at high speed. Therefore, the color laser printer 1 in the preferred embodiment can form a color image while maintaining a compact shape.

The fixing portion 29 is disposed in the main casing 2 behind the process accommodating portion 12 accommodating the black process portion 27K, and is aligned with the image forming position in a contact point between the photosensitive drum 42 and the conveyor belt 168 in the front-rear direction. The fixing section 29 includes a heating roller 17C and a pressure roller 171.

The heating roller 170 is discharged from a configuration of a metal pipe whose surface is covered with a discharge layer. The metal pipe is provided with a halogen lamp extending along the axis of the heating roller 170. The halogen lamp heats the surface of the heating roller 171 to a fixed temperature. The pressing roller 171 is located opposite to the heating roller 170 to provide pressure.

After the toner image is transferred onto the sheet 3, the sheet 3 is conveyed to the fixing section 29. The fixing section 29 fixes the color image on the sheet 3 by heating when the sheet 3 passes between the heating roller 170 and the pressure roller 171.

The sheet discharge unit 6 includes a U-shaped sheet discharge path 172, a sheet discharge roller 173, and a sheet discharge tray 174.

The sheet discharge path has a curved U-shape and functions as a path for conveying the sheet 3. The upstream end of the sheet discharge path 172 is a lower portion of the sheet discharge path 172, and is placed against the fixing section 29 so as to convey the sheet 3 in the backward direction. And the downstream end of the sheet discharge path 172 is an upper portion disposed next to the sheet discharge tray 174 to discharge the sheet 3 forward.

The sheet discharge roller 173 is a pair of rollers disposed near the downstream end of the sheet discharge path 172. The sheet discharge tray 174 is a surface formed on the top of the main casing 2, and is inclined downward from the front side to the rear side.

After the multicolor image is fixed on the sheet 3 in the fixing section 29, the sheet 3 is conveyed to the upstream end of the sheet discharge path 172 in the backward direction. The U-shaped sheet discharge path 172 reverses the transfer direction of the sheet 3, and the sheet 3 is discharged forward onto the sheet discharge tray 174 by the sheet discharge roller 173.

In the color laser printer 1 as described above, the forward direction in which the pickup roller 22 picks up the sheet 3 is opposite to the backward direction in which the sheet 3 is conveyed through the image forming position. Further, the backward direction in which the sheet 3 is conveyed past the image forming position is opposite to the forward direction in which the sheet 3 is discharged by the discharge roller 173. This structure can make the apparatus compact while providing a conveyance path for the sheet 3.

In the color laser printer 1 of the preferred embodiment described above, the drum cartridge 31 and the developer cartridge 32 are mounted in the drum accommodating section 13 and the developer accommodating section 14 of each process accommodating section 12 on slopes at an oblique angle to the front-rear direction (the direction in which the paper 3 is conveyed at the time of image formation) and the vertical direction (the thickness direction of the paper 3 conveyed at the time of image formation). More specifically, the drum cartridge 31 and the developer cartridge 32 are mounted in a direction inclined rearward from the top to the bottom. This structure can improve the workability of mounting and dismounting the drum cartridge 31 and the developer cartridge 32.

In the color laser printer 1 of the preferred embodiment described above, the sets of the drum cartridges 31 and the developer cartridges 32 are arranged alternately with the plurality of scanner units 30 in the front-rear direction, and this arrangement makes the apparatus more compact.

In the developer cartridge 32, the reinforcing columns 65 provided in the toner accommodating chamber 92 bridge between the top wall 87 and the bottom wall 74, and can absorb the pressure applied in the pressing direction between the top wall 87 and the bottom wall 74, thereby improving the rigidity of the toner accommodating chamber 92. Further, because the reinforcing columns 65 are provided between the top wall 87 and the bottom wall 74 in the toner-accommodating chamber 92, the reinforcing columns 65 can increase the rigidity of the toner-accommodating chamber 92 while maintaining the thickness of the developer cartridge 32 regardless of the external shape of the developer cartridge 32, thereby enabling a compact apparatus.

In the developer cartridge 32 having such a structure, the reinforcing column 65 is provided at a position separated from the side wall 72, the rear portion 73 and the partition wall 83 at the lateral center and the front-to-rear center of the toner-accommodating chamber 92, thereby reinforcing the space in the toner-accommodating chamber 92 further inward from the side wall 72, the rear portion 73 and the partition wall 83. This structure further improves the rigidity of the toner-accommodating chamber 92.

The reinforcing column 65 is also provided at a position rearward of the agitator 69 where the column projection area and the agitator projection area do not overlap on the side wall 72, so that the reinforcing column 65 does not contact the rotary stirring member 152. If the reinforcing column 65 is disposed in a position in contact with the agitator 69 such that the rotating agitating member 152 deforms as it slides over the reinforcing column 65, such contact would place an excessive load on the agitator 69 and generate noise.

However, by disposing the reinforcing column 65 so as not to contact the rotary stirring member 152 as in the preferred embodiment, it is possible to prevent the stirrer 69 from being excessively loaded and from generating noise.

In the comparative embodiment, as shown in fig. 20, a cutout portion 175 is formed at the lateral center of each member 152 and the reinforcing column 65 is placed in this cutout portion 175. However, in this embodiment, the stirring action of the stirring member 152 in the axial direction of the rotating shaft 151 will become irregular.

However, in the preferred embodiment (fig. 15), the reinforcing posts 65 are disposed at positions where the post projection areas do not overlap with the agitator projection areas, thereby maintaining the efficiency of the agitating member 152 without irregular agitation.

Even if the agitator 69 is disposed close to the discharge opening 84, the reinforcement column 65 reinforces the space of the toner-accommodating chamber 92 portion on the opposite side of the agitator 69 from the discharge opening 84. Accordingly, it is also possible to enhance the rigidity of the toner containing chamber 92 and ensure that toner can be smoothly discharged from the discharge opening 84.

Because the developer cartridge 32 is thin, the operator can grasp the bottom grip portion 96 and the top grip portion 97 thereof with one hand when mounting or dismounting the developer cartridge 32. This gripping action applies pressure to the top wall 87 and the bottom wall 74 of the developer cartridge 32 in the compression direction in the area where the bottom gripping portion 96 and the top gripping portion 97 are provided.

However, the reinforcing column 65 is bridged between the inner surface of the bottom wall 74 facing the bottom grip portion 96 and the inner surface of the top wall 87 facing the top grip portion 97, thereby reliably absorbing the compressive force in the compression direction. Therefore, this structure enhances the rigidity of the toner-accommodating chamber 92 and prevents the toner-accommodating chamber 92 from being deformed when the developer cartridge 32 is gripped by the operator.

When the support column member 81 is fitted to the cylindrical fitting portion 91, the resulting reinforcing column 65 exhibits a tear-drop shaped cross section in which the conical point of the tear-drop shape is directed upstream in the toner discharge direction. The reinforcing column 65 has a substantially V-shaped tapered surface 82 along its rear side (upward when the developer cartridge 32 is mounted). The surface 82 runs from the guide surface 82a to the guide surface 82 b. The surface 82 serves to guide the toner in the discharge direction.

Therefore, the guide surface 82 can smoothly guide the toner downward in the discharging direction (downward when the developer cartridge 32 is mounted), preventing the toner from accumulating around the reinforcing column 65. Moreover, since the guide surface 82 is conical toward the upstream in the toner discharging direction, the toner is smoothly guided along the conical guide surface 82 to the downstream in the toner discharging direction, thereby effectively preventing the toner from being accumulated around the reinforcing column 65.

The support column members 81 of the bottom wall 74 are placed in the cylindrical fitting portions 91 provided on the top wall 87, forming the reinforcing columns 65 that span between the bottom wall 74 and the top wall 87. Therefore, by placing the supporting column member 81 in the cylindrical fitting portion 91, the reinforcing column 65 can be reliably disposed between the bottom wall 74 and the top wall 87, thereby effectively enhancing the rigidity of the toner containing chamber 92.

As described above, the reinforcement column 65 is placed at a position in front of the extension line X and does not overlap the extension line X. The extension line X is a line extending from the toner filling nozzle 99 inserted in the toner filling through-hole 98 in the toner filling direction, i.e., the direction in which the filling nozzle 99 fills toner into the toner accommodating chamber 92. In other words, the extension line X extends from the center of the toner filling through hole 98 in the direction perpendicular to the side wall 72. This structure reduces the proportion of toner that the toner filling nozzle 99 directly contacts the reinforcing column 65 when filling the toner containing chamber 92 with toner, so that the toner containing chamber 92 is smoothly filled with toner.

The toner filling through hole 98 is disposed behind the agitator 69 so as not to overlap with the agitator projection area on the side wall 72. This structure reduces the proportion of toner that directly contacts the agitator 69 when the toner-accommodating chamber 92 is filled with toner, so that the toner-accommodating chamber 92 is smoothly filled with toner. Further, by forming the toner filling through-holes 98 on the rear side wall 77 having a pitch larger than that of the front side wall 75, the efficiency of toner filling can be improved.

By providing the support column member 81 on the disk-shaped bottom wall 74 and the cylindrical fitting portion 91 on the disk-shaped center top wall 90, the shape of the toner containing chamber 92 can be made narrower.

Further, the reinforcement column 65 is disposed at a position behind but not overlapping with the optical path of the detection light transmitted between the detection windows 100. Therefore, the detection light can be efficiently transmitted from the detection window 100, thereby relatively easily and efficiently detecting the amount of toner remaining.

In the developer cartridge 32 as described above, the gear train (not shown) and the female coupling portion 163 are disposed on the outer surface of the front side wall 75 so as to transmit the driving force to the agitator 69, the supply roller 66, and the developing roller 67. If the axial length of the rotary shaft 151 of the agitator 69 is increased, the gear train and the female coupling portion 163 will extend further outward in the width direction, which is disadvantageous in producing the developer cartridge 32 in a compact structure.

Therefore, by making the distance between the positions where the agitator 69 is provided by the front side wall 75 larger than the distance between the positions where the rear side wall 77 is located on the opposite side of the agitator 69 from the discharge opening 84, such an arrangement can increase the capacity of accommodating the developer by increasing the distance between the positions where the rear side wall 77 is located on the opposite side of the agitator 69 from the discharge opening 84. The gear cover holds the gear (not shown) and the female coupling portion 163 in a small and compact space on the outer surface of the front side wall 75.

By forming the inclined surface 188 on the inner surface of the inclined wall 76 to guide the toner in the discharge direction, the step portion between the front sidewall 75 and the rear sidewall 77 can be omitted even if the pitch of the front sidewall 75 is smaller than the pitch of the rear sidewall 77. Accordingly, the inclined surface 178 prevents toner from being accumulated between the front side wall 75 and the rear side wall 77, and smoothly guides the toner to be discharged from the toner accommodating chamber 92.

In the toner accommodating chamber 92, the front ceiling wall 88 and the rear ceiling wall 89 are disposed parallel to the bottom wall 74 such that the spacing between the rear ceiling wall 89 and the bottom wall 74 is larger than the spacing between the front ceiling wall 88 and the bottom wall 74. This structure increases the capacity of toner at the rear of the developer cartridge 32, and is relatively unobstructed when mounting or dismounting the developer cartridge 32 due to its position relative to the scanner unit 30 and the like. Therefore, the toner capacity of the developer cartridge 32 can be increased while ensuring that the mounting and dismounting operations are smoothly completed.

In the above-described developer cartridge 32, the developing roller 67 is disposed at the front end of the developing chamber 93 that is in liquid communication with the toner accommodating chamber 92, so that the front surface of the developing roller 67 is exposed through the opening 159. Accordingly, the toner in the toner-accommodating chamber 92 can be efficiently discharged into the developing chamber 93 and efficiently carried by the developing roller 67. Further, since the toner in the toner accommodating chamber 92 is turned downward by its own weight when the developer cartridge 32 is mounted to the developer accommodating section 24, and moves toward the discharge opening 84, the toner can be smoothly discharged by this simple structure.

When the developer cartridge 32 is mounted to the developer accommodating section 14, since the agitator is disposed above the discharge opening close thereto, the agitator 69 can discharge the toner moving toward the discharge opening 84 by its own weight in a uniform amount through the discharge opening 84. Therefore, this structure can ensure that a stable amount of toner can be carried on the developing roller 67, and reliable image formation can be achieved.

When the developer cartridge 32 is mounted in the developer accommodating section 14, the supply roller 66 and the developing roller 67 are disposed below the toner accommodating chamber 92, so that the developer cartridge 32 can be made thin. Further, the supply roller 66 and the developing roller 67 are disposed below the toner accommodating chamber 92, so that a vertical line Z extending vertically downward from the rotary shaft 151 of the agitator 69 intersects with a line segment Y connecting the supply roller shaft 155 of the supply roller 66 and the developing roller shaft 157 of the developing roller 67, enabling the developer cartridge 32 to be made thinner.

In the preferred embodiment described above, only a single reinforcing column 65 is provided in the toner-accommodating chamber 92. However, in the second embodiment of the present invention, a plurality of reinforcing columns 65 are provided in the toner-accommodating chamber 92. Fig. 21 shows a developer cartridge 32 according to a second embodiment, in which like parts and elements are denoted by the same reference numerals to avoid repetitive description.

As shown in fig. 21, three support column members 81 spaced apart in the width direction are interposed between the front and rear ends of the inner surface of the bottom wall 74. Three cylindrical fitting portions 91 spaced apart in the width direction are disposed at opposite positions on the inner surface of the center top wall 90 of the top wall 87.

In the developer cartridge 32 shown in fig. 21, when the cover member 71 is covered over the housing member 70, the three support column members 81 are fitted into the three cylindrical fitting portions 91, thereby forming the three reinforcing columns 65. Providing a plurality of reinforcing columns 65 in this way further increases the rigidity of the toner accommodating chamber 92.

In the second embodiment described above, the reinforcing column 65 is provided on the inner surface of the bottom wall 74 at a position separated from the side wall 72, the rear wall 73 and the partition wall 83. However, the reinforcing portion may be formed continuously with any one of the side wall 72, the rear wall 73 and the partition wall 83.

For example, in the third embodiment of the present patent shown in fig. 22, three reinforcing plates 186 formed continuously with the rear wall 73 are disposed on the inner surface of the bottom wall 74, and three reinforcing plate receiving members 187 are disposed on the inner surface of the rear top wall 89, opposite to the positions of the reinforcing plates 186.

The reinforcing plates 186 are disposed at the rear end of the bottom wall 74 rising toward the top surface side and spaced apart from each other at a prescribed interval in the width direction. The reinforcing plate 186 is also formed continuously with the inner surface of the rear wall 73 extending in the front-rear direction.

The reinforcing-plate receiving member 187 is disposed at the rear end of the rear top wall 89, extends in the front-rear direction, and projects downward toward the bottom surface side. The reinforcing plate receiving members 187 are spaced apart from each other at a prescribed interval in the width direction so as to correspond to the reinforcing plates 186. Each reinforcing plate receiving member 187 is constituted by two clamping plates 186 facing each other with a gap therebetween for receiving and clamping the respective reinforcing plate 186.

In the developer cartridge 32 shown in fig. 22, when the cover member 71 is covered over the housing member 70, the reinforcing portion is formed to span between the bottom wall 74 and the top wall 87 with the three reinforcing plates 186 sandwiched between the three reinforcing plate receiving members 187.

Fig. 23 to 25 show a developer cartridge 32 according to a fourth embodiment of the invention, in which like parts and elements are denoted by the same reference numerals to avoid repetitive description. In the fourth embodiment of the present invention, the reinforcing ribs 200 are provided in parallel in the discharge opening 84.

In particular, as shown in fig. 24 and 25, the reinforcing bracket 200 protrudes in the thickness direction near the discharge opening 84. In the preferred embodiment, three reinforcing ribs 200 are arranged in parallel at predetermined intervals in the width direction.

Each reinforcement rib 200 includes a bottom surface-side end 201 and a top surface-side end 202. The top surface side end 201 stands on the inner surface of the discharge wall 78 and is continuously formed along the discharge wall 78, which projects toward the top surface side and has an arc-shaped cross section. Each top surface side end 202 is erected from the rear surface of the partition wall 83 and is continuously formed along the rear surface of the partition wall 83.

The reinforcing rib 200 further includes: a center portion 203 located between the bottom surface-side end 201 and the top surface-side end 202 and passing through the discharge opening 84 in a thickness direction of the developer cartridge 32, i.e., at right angles to a width direction of the developer cartridge 32 in which the discharge opening 84 extends; and an insertion portion 204, which is located on the central portion 203 and is placed into the discharge opening 84. The end surface of the partition wall 83 on the bottom surface side is inclined forward from the rear toward the top surface side. Each insertion portion 204 is formed integrally with the corresponding center portion 203, with the top surface-side end of the insertion portion 204 being in surface contact with the entire bottom surface-side end of the partition wall 83, and the bottom surface-side end of the insertion portion 204 being in contact with the connecting portion between the front end of the discharge wall 78 and the rear end of the supply roller accommodating wall 79. The front side surface of the center portion 203 has a structure in which the top surface side end thereof is flush with the front surface of the partition wall 83, and the bottom surface side end thereof is flush with the front surface of the rear end of the supply roller accommodating wall 79.

As shown in fig. 25, three reinforcing-rib engaging portions 205 are provided on the contact portion 86 of the front surface of the cover member 71 at positions corresponding to the reinforcing ribs 200. Each of the reinforcing-rib engaging portions 205 includes a pair of support pieces 206 for sandwiching the corresponding reinforcing rib 200 on the width-direction side. In the developer cartridge 32 shown in fig. 24 and 25, when the cover member 71 is covered over the case member 70, a reinforcing portion formed by the reinforcing ribs 200 and bridged between the bottom wall 74 and the top wall 87 is formed, and the top surface side ends of the reinforcing ribs 200 are inserted between the pair of support pieces 206 of the corresponding reinforcing rib engagement portions 205. With this structure, the discharge opening 84 is divided into a plurality of openings spaced in the width direction by the reinforcing ribs 200, as shown in fig. 23.

Since the toner-accommodating chamber 92 and the developing chamber 93 are both formed in the developer cartridge 32, the discharge opening 84 is formed to make the toner-accommodating chamber 92 and the developing chamber 93 in liquid communication.

The reinforcing ribs 200 juxtaposed to the discharge opening 84 reinforce the discharge opening 84 and allow toner to be smoothly discharged from the discharge opening 84. Accordingly, the reinforcing ribs 200 can absorb the pressing force applied to the top wall 87 and the bottom wall 74 in the pressing direction, thereby improving the rigidity between the toner containing chamber 92 and the developing chamber 93. This structure can prevent the developer cartridge 32 from being concaved or deformed, and prevent toner in the toner-accommodating chamber from being accidentally ejected from the discharge opening 84 to the developing roller 67.

In the fourth embodiment described above, the reinforcing portion is formed by reinforcing ribs provided in parallel in the discharge opening 84. Fig. 26 and 27 show a developer cartridge 32 according to a fifth embodiment of the invention, in which like parts and elements are denoted by the same reference numerals to avoid repetitive description. As shown in fig. 26 and 27, the reinforcing portion is composed of a partition wall 83 and a connecting wall 207 provided at the front end of the discharge opening 84, connecting the partition wall 83 and the discharge wall 78.

More specifically, as shown in fig. 26 and 27, each of the connecting walls 207 has a cylindrical shape, and extends in the thickness direction of the developer cartridge 32. In the preferred embodiment, three connecting walls 207 are spaced apart from each other in the width direction. Each connecting wall 207 has a structure of: the top surface side end of the connecting wall 207 is connected to the end surface of the partition wall 83 on the bottom surface side, and the lower surface side end of the connecting wall 207 is connected to the end surface on the top surface side of the connecting portion between the front end of the discharge wall 78 and the rear end of the supply roller accommodating wall 79. The front surface structure of the connecting wall 207 is: the top surface side end thereof is flush with the front surface of the partition wall 83, and the bottom surface side end thereof is flush with the front surface of the rear end of the supply roller accommodating wall 79.

In the developer cartridge 32 shown in fig. 26 and 27, when the cover member 71 is covered over the housing member 70, a reinforcing portion composed of the partition wall 83 and the connecting wall 207 and bridging between the bottom wall 74 and the top wall 87 is formed such that the contact portion 86 on the front side of the cover member 71 is in contact with the top surface of the partition wall 83.

The connecting wall 207 formed on the partition wall 83 in this way can reinforce the discharge opening 84 while allowing toner to be smoothly discharged from the discharge opening 84. Therefore, as described above, the connecting wall 207 can absorb the pressing force applied to the top wall 87 and the bottom wall 74 in the pressing direction, thereby improving the rigidity between the toner containing chamber 92 and the developing chamber 93. Therefore, this structure can prevent the developer cartridge 32 from being crushed or deformed, and prevent toner in the toner-accommodating chamber from being accidentally ejected from the discharge opening 84 to the developing roller 67.

In the above-described fifth embodiment, the top surface side of the discharge opening 84 is closed by the partition wall 83 in the width direction while the connection wall 207 partitions the discharge opening 84 in the width direction. Accordingly, the discharge opening 84 can be further reinforced to prevent deformation and ensure smooth discharge of toner.

While various aspects of the invention have been described with reference to specific embodiments, those skilled in the art will recognize that changes may be made thereto without departing from the scope of the invention.

For example, in the first embodiment described above, the support column member 81 is provided on the bottom wall 74, and the cylindrical fitting portion 91 is provided on the top wall 87 to be fitted over the support column member 81. However, the support post member 81 may be provided on the top wall 87 with the cylindrical fitting portion 91 provided on the bottom wall 74 to be fitted over the tip end of the support post member 81.

In the above embodiment, the toner filling through-hole 98 is located on one of the two opposing side walls 72. However, one fill via 98 may be provided on both opposing sidewalls 72.

The above-described embodiment relates to the front-rear type color laser printer 1 that can directly transfer the toner image from each photosensitive drum 42 onto the sheet 3, but the present invention is not limited to this device. For example, the present invention is applicable to a laser printer of an intermediate conveyance type that temporarily conveys toner images of each color from respective photosensitive members onto an intermediate conveyance member, and then conveys the complete color image onto a sheet of paper. The present invention is also applicable to monochrome printers.

Claims (26)

1. A cartridge detachably mountable to an image forming apparatus, characterized in that the cartridge comprises:

a first wall;

a second wall opposed to the first wall with a gap formed therebetween, the first wall and the second wall defining therebetween a developer accommodating portion accommodating a developer; and

a reinforcing portion bridging between the first and second walls;

the reinforcing portion includes a support column member provided on one of the first wall and the second wall and protruding toward the other; and

a fitting member on the other of the first wall and the second wall for fitting the support column member.

2. The cartridge of claim 1, wherein the first wall and the second wall have an outer periphery;

the case further includes a side peripheral wall between an outer peripheral edge of the first wall and an outer peripheral edge of the second wall, and

the reinforcing portion is located at a position separated from the side peripheral wall.

3. The cartridge according to claim 1, further comprising an agitator which is located in the developer accommodating portion and is driven to rotate to agitate the developer,

wherein the reinforcing portion is positioned so as not to contact the rotary agitator.

4. The cartridge of claim 3, wherein the agitator rotates about its axis to form a rotational trajectory and the reinforcing portion is positioned so as not to overlap a projected area of the rotational trajectory of the agitator projected along the axis.

5. The cartridge according to claim 3, wherein the developer accommodating portion has a discharge opening for discharging the developer; and is

The agitator is positioned proximate to the discharge opening.

6. The cartridge of claim 1, wherein the first wall and the second wall each have an inner surface and an outer surface;

the outer surfaces of the first wall and the second wall each have a grip area indicating portion that informs a user of where to grip the developer accommodating portion; and is

The reinforcing portion spans between an inner surface of the first wall opposite the grip area indicator portion disposed on the outer surface of the first wall and an inner surface of the second wall opposite the grip area indicator portion disposed on the outer surface of the second wall.

7. The cartridge according to claim 1, wherein the developer accommodating portion has a discharge opening for discharging the developer; and is

The reinforcing portion has a guide surface at an upstream portion in a direction in which the developer is discharged through the discharge opening, for guiding the developer downstream in the discharge direction.

8. The cartridge according to claim 7, wherein the reinforcing portion is tapered toward an upstream side in the discharge direction.

9. The cartridge according to claim 1, wherein the developer accommodating portion has a filling through-hole for guiding the developer to the developer accommodating portion in a filling direction; and is

The reinforcing portion is positioned so as not to overlap an extension line extending from the filling through-hole to the developer accommodating portion in the filling direction.

10. The cartridge of claim 9, further comprising an agitator, the fill through hole being positioned in an axial direction of the agitator so as not to overlap a projected area of the agitator.

11. The cartridge of claim 1, wherein the first wall and the second wall are substantially plate-shaped.

12. The cartridge according to claim 1, wherein said developer accommodating portion has a detection window through which a detection light is transmitted for detecting an amount of the developer remaining in said developer accommodating portion; and is

The enhancing portion is positioned so as not to overlap with the optical path of the probe light.

13. The cartridge according to claim 1, wherein a distance between an inner surface of said first wall and an inner surface of said second wall in an upstream portion of said developer accommodating portion in said cartridge mounting direction is larger than a distance between said first wall and said second wall inner surface in a downstream portion of said developer accommodating portion.

14. The cartridge according to claim 1, wherein said second wall and said first wall further define a developing portion adjacent to and in liquid communication with said developer accommodating portion;

further comprising a developing roller carrying the developer supplied from the developer accommodating portion, a part of the developing roller being exposed through an opening formed between the second wall and the first wall.

15. The cartridge according to claim 1, wherein the developer accommodating portion has a discharge opening for discharging the developer; and is

The reinforcing portion is adjacent to the discharge opening.

16. The cartridge according to claim 1, wherein the developer accommodating portion has a discharge opening for discharging the developer; and is

The reinforcing portion is located in the discharge opening.

17. The cartridge of claim 16, wherein the reinforcing portion comprises:

a partition wall that closes a top surface side of the discharge opening in a longitudinal direction of the discharge opening; and

and a connecting wall provided at a prescribed interval in a length direction of the discharge opening for connecting the partition wall to the first wall.

18. An image forming apparatus comprising:

a housing; and

a cartridge removably mounted in the housing, the cartridge comprising:

a first wall;

a second wall opposed to the first wall with a gap formed therebetween, the first wall and the second wall defining therebetween a developer accommodating portion accommodating a developer; and

a reinforcing portion bridging between the first and second walls;

the reinforcing part includes:

a support column member provided on one of the first wall and the second wall and protruding toward the other; and

a fitting member provided on the other of the first wall and the second wall for fitting the support column member.

19. The image forming apparatus as claimed in claim 18, wherein said developer accommodating portion has a discharge opening for discharging the developer; and is

The cartridge is mounted in the housing in a direction such that the developer accommodated in the developer accommodating portion moves toward the discharge opening by its own weight.

20. The image forming apparatus as claimed in claim 19, wherein said cartridge includes an agitator in said developer accommodating portion which is urged to rotate to agitate the developer accommodated in the developer accommodating portion, said agitator being disposed above the discharge opening when said cartridge is mounted in the housing.

21. The image forming apparatus as claimed in claim 20, wherein the cartridge includes a developing roller carrying a developer; and

a supply roller that supplies the developer accommodated in the developer accommodating portion to the developing roller,

wherein the developing roller and the supply roller are disposed below the developer accommodating portion when the cartridge is mounted in the casing.

22. The image forming apparatus as claimed in claim 21, wherein the agitator includes a rotation shaft and an agitation member provided on the rotation shaft; it is characterized in that

When the cartridge is mounted in the housing, a vertical line extending downward from the rotation shaft intersects a line segment connecting the developing roller shaft and the supply roller shaft.

23. The imaging apparatus of claim 18, wherein the cartridge comprises a plurality of cartridges corresponding to a plurality of colors, respectively.

24. The imaging apparatus of claim 23, further comprising:

a feeding unit that picks up and feeds a recording medium;

a conveying unit that conveys the recording medium along a conveying path; and

a discharge unit that discharges the recording medium from the casing;

wherein a plurality of cartridges are provided between the feeding unit and the discharging unit along the conveying path;

a pickup direction in which the feeding unit picks up the recording medium is opposite to a conveying direction in which the conveying unit conveys the recording medium through the housing to sequentially form images with the plurality of cartridges; and is

The conveying direction is opposite to a discharge direction in which the discharge unit discharges the recording medium from the image forming apparatus.

25. The image forming apparatus as claimed in claim 24, wherein a direction in which the cartridge is attached to and detached from the housing is inclined with respect to both the conveying direction and a thickness direction of the recording medium orthogonal to the conveying direction.

26. The image forming apparatus as claimed in claim 24, further comprising a plurality of exposure devices respectively corresponding to the plurality of cartridges, the plurality of cartridges and the corresponding exposure devices being alternately arranged in a conveying direction to convey the recording medium through the image forming apparatus.