HK1084192B - Image-forming device - Google Patents

Description

Image forming apparatus with a plurality of image forming units

Technical Field

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

Background

In recent years, electrophotographic image forming apparatuses well known in the art have been equipped with separate various cartridges for respectively accommodating the developer and the photosensitive member so that these cartridges can be individually replaced according to their own service lives.

One example of the type of image forming apparatus disclosed in U.S. Pat. No. 6,330,410B 1 includes a photosensitive cartridge accommodating a photosensitive drum and a developing cartridge accommodating a developing roller, wherein the photosensitive cartridge and the developing cartridge can be assembled in or removed from a main casing of the image forming apparatus as an integral unit. In another image forming apparatus disclosed in U.S. patent application publication No. 2003/0161656 a1, a photosensitive cartridge and a developing cartridge may be assembled in or removed from a main casing along separate paths.

However, these two image forming apparatuses simply provide extra space in the main casing for the mounting path of the photosensitive cartridge and the mounting path of the developing cartridge. Therefore, these image forming apparatuses have various limitations in how the apparatuses are made more compact.

Disclosure of Invention

In view of the foregoing, it is an object of the present invention to provide a compact image forming apparatus having first and second cartridges that are detachably assembled, and the space required for the assembly path of these cartridges has been reduced.

Another object of the present invention is to provide a photosensitive cartridge, a developing cartridge, and a process cartridge which can be detachably mounted in an image forming apparatus.

In order to achieve the above and other objects, the present invention provides an image forming apparatus comprising: a housing; and a first cartridge and a second cartridge detachably fitted in the casing and having a process member used in the image forming process. The first cartridge is thicker than the second cartridge in a thickness direction perpendicular to a fitting direction of the first and second cartridges. The housing has a cartridge accommodating portion in which the first and second cartridges are accommodated. The cartridge accommodating section includes first and second accommodating sections which are provided continuously in a fitting direction of the first and second cartridges and are partially displaced from each other in a thickness direction. The first accommodating section defines a first accommodating area in which the first cartridge is accommodated, and the second accommodating section defines a second accommodating area in which the second cartridge is accommodated, the second accommodating section being disposed upstream of the first accommodating section with respect to a fitting direction of the first and second cartridges and being formed thicker than the first cartridge in a thickness direction, the second accommodating section being thinner than a combined thickness of the first and second cartridges when the first and second cartridges are accommodated in the cartridge accommodating section. When the first and second cartridges are accommodated in the cartridge accommodating section, the first accommodating section is thicker in the thickness direction than the combined thickness of the first and second cartridges.

With this structure, even if the second housing portion is thinner than the combined thickness of both the first and second cartridges when the cartridges are housed in the cartridge housing portions, the first and second cartridges can be fitted in the cartridge housing portions by first inserting only the first cartridge through the second housing portion which is wider than the thickness of the first cartridge, then fitting the first cartridge in the first housing portion which is wider than the thickness of both the cartridges when the first and second cartridges are housed in the cartridge housing portions, and then fitting the second cartridge which is thinner than the first cartridge in the second housing portion. Therefore, this configuration can reduce the space required for the assembly path of the first and second cartridges, enabling the apparatus to be made compact.

According to another aspect the present invention provides an imaging apparatus comprising: a housing; and a first cartridge and a second cartridge detachably fitted in the casing and having a process member used in the image forming process. The housing has a cartridge accommodating portion in which the first and second cartridges are accommodated. The cartridge accommodating section includes first and second accommodating sections that are continuously provided along a fitting direction of the first and second cartridges and are partially displaced from each other in a thickness direction perpendicular to the fitting direction of the first and second cartridges. The first accommodating portion defines a first accommodating area in which the first cartridge is accommodated, and the second accommodating portion defines a second accommodating area in which the second cartridge is accommodated, the first accommodating portion being disposed downstream of the second accommodating portion with respect to a fitting direction of the first and second cartridges, and being formed wider than the second accommodating portion in a thickness direction perpendicular to the fitting direction of the first and second cartridges. The first accommodating portion has an expanded region by which the first accommodating portion is made wider than the second accommodating portion. The first cartridge has a projection disposed in the expansion region when the first cartridge is fitted in the first accommodation portion. The cartridge accommodating portion has a shape that restricts the first cartridge from moving in the fitting direction when the protrusion is positioned in the expanded region, but allows the first cartridge to move in the fitting direction when the protrusion is moved away from the expanded region in the thickness direction by a distance equal to the thickness of the second cartridge.

With this structure, when the protrusion is provided in the expanded region, the movement of the first cartridge in the cartridge accommodating section is restricted in the fitting direction, but when the protrusion is moved away from the expanded region in the thickness direction by a distance equal to the thickness of the second cartridge, the movement of the first cartridge is permitted. Therefore, the first cartridge can be fitted in the first housing portion by first inserting the first cartridge through the second housing portion and then positioning the protruding portion in the expanded region. Subsequently, the second cartridge may be fitted in the second receiving portion. This configuration can reduce the space required for the assembly path of the first and second cartridges, enabling the entire apparatus to be made compact.

According to another aspect the present invention provides an imaging apparatus comprising: a housing; and a first cartridge and a second cartridge which are detachably fitted in the casing and are provided with a process member used in the image forming process. The housing includes: a first accommodating portion; a second accommodating portion; and an enlarged portion. The first accommodating portion defines a first accommodating area in which the first cartridge is accommodated. The second accommodating portion is disposed upstream of the first accommodating portion with respect to a fitting direction in which the first cartridge is fitted. The second accommodating portion defines a second accommodating area that allows the first cartridge to pass therethrough when the first cartridge is fitted to or removed from the first accommodating portion, and accommodates the second cartridge therein. The enlarged portion is enlarged toward the second receiving area, and restricts passage of the first cartridge in the second receiving portion when the first cartridge is carried with the second cartridge, and allows passage of the first cartridge through the second receiving area of the second receiving portion when the first cartridge is not carried with the second cartridge.

By forming the enlarged portion to the second housing area in this way, the first and second cartridges can be fitted in the cartridge housing without simply allocating additional space for the fitting path of the first and second cartridges. This can be achieved by first passing the first cartridge through the second receiving region of the second receiving portion without interference from the enlarged portion, then fitting the first cartridge in the first receiving portion so that the first cartridge is received in the first receiving region, and then fitting the second cartridge in the second receiving portion so that the second cartridge is received in the second receiving region. In particular, this configuration makes it impossible for the first cartridge to pass through the second accommodating section together with the second cartridge, avoiding the enlarged portion by utilizing the second accommodating area in which the second cartridge is to be accommodated. Therefore, the space required for the assembly path of the first and second cartridges can be reduced, enabling the entire apparatus to be made compact.

According to another aspect the present invention provides a photosensitive cartridge that can be detachably fitted in a cartridge accommodating section defined in an image forming apparatus. The photosensitive cartridge includes: a first housing; and a photosensitive member and a charger provided in the first housing. The first housing integrally includes: a main body in which the charger and the photosensitive member are accommodated; and an extension disposed upstream of the main body in an assembling direction in which the photosensitive cartridge is assembled.

With this structure, the main body and the extension portion are integrally formed, resulting in a simple configuration. Further, this configuration can improve the positioning accuracy of the photosensitive member and the charger.

According to another aspect the present invention provides a process cartridge comprising: a photosensitive cartridge detachably mountable in a cartridge accommodating portion defined in the image forming apparatus; and a developing cartridge that can be detachably fitted in a cartridge accommodating portion defined in the image forming apparatus. The photosensitive cartridge includes: a first housing; and a photosensitive member and a charger provided in the first housing. The first housing integrally includes: a main body accommodating therein the charger and the photosensitive member; an extension portion is provided upstream of the main body in an assembling direction in which the photosensitive cartridge is assembled. The developing cartridge includes: a second housing; and a developing roller disposed in the second casing with a portion thereof exposed therefrom.

This configuration has the photosensitive cartridge positioned accurately, thus ensuring reliable operation.

The present invention provides a developing cartridge detachably mountable in a cartridge accommodating portion defined by a wall included in an image forming apparatus according to another aspect. The developing cartridge includes: a housing; a developing roller; a pressurization part; and a sliding portion. The developing roller is disposed in the casing with a portion exposed from the casing. The pressure portion is provided on the casing, faces the outer circumferential surface of the developing roller exposed from the casing along the length of the developing roller, and is in pressure contact with the outer circumferential surface of the developing roller to prevent leakage of the developer. The sliding portion projects further downstream than the pressing portion in an assembly direction in which the developing cartridge is assembled in a cartridge accommodating portion defined by a wall included in the image forming apparatus. The sliding part protrudes closer to the wall than the pressing part. When the developing cartridge is assembled, the sliding portion contacts the wall and functions to slide along the wall.

With this structure, when the developing cartridge is assembled, the sliding portion contacts and slides along the wall of the image forming apparatus defining the cartridge accommodating unit, thereby preventing damage to the pressing portion and reliably preventing leakage of the developer from the outer circumferential surface of the developing roller.

According to another aspect the present invention provides a process cartridge comprising: a developing cartridge detachably mountable in a cartridge accommodating portion defined by a wall included in the image forming apparatus; and a photosensitive cartridge that can be detachably fitted in the cartridge accommodating section. The developing cartridge includes: a second housing; a developing roller disposed in the second casing with a portion thereof exposed therefrom; a pressing portion provided on the second casing, facing the outer circumferential surface of the developing roller exposed from the second casing along a length of the developing roller, and in pressure contact with the outer circumferential surface of the developing roller to prevent leakage of the developer; and a sliding portion which projects further downstream in a cartridge accommodating portion than the pressing portion in a fitting direction of the developing cartridge, the sliding portion being closer to the wall than the pressing portion after the projection, the sliding portion contacting the wall when the developing cartridge is fitted and functioning to slide along the wall. The photosensitive cartridge includes a first housing, and a photosensitive member and a charger provided in the first housing.

This configuration includes the developing cartridge capable of reliably preventing leakage of the developer, thus ensuring reliable operation.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent upon reading the following description of the preferred embodiments taken in conjunction with the accompanying drawings in which:

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

fig. 2 is a perspective view from above the front side of a drum cartridge in the color laser printer of fig. 1;

FIG. 3 is a perspective view from below the rear side 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 perspective view from above the front side of the developing cartridge in the color laser printer of fig. 1;

fig. 9 is a perspective view from below the rear side of the developing cartridge;

fig. 10 is a plan view of the developing cartridge;

fig. 11 is a front view of the developing cartridge;

fig. 12 is a right side view of the developing cartridge;

fig. 13 is a left side view of the developing cartridge;

fig. 14 is a perspective view from above the front side of the main casing in the color laser printer;

fig. 15 is a side view showing an assembled state of the drum cartridge in the process accommodating portion (when passing through the developing accommodating portion);

fig. 16 is a side view showing an assembled state of the drum cartridge in the process accommodating portion (when reaching the drum accommodating portion);

fig. 17 is a side view showing an assembled state (when rotated) of the drum cartridge in the process accommodating portion;

fig. 18 is a side view showing an assembled state (when completely assembled) of the drum cartridge in the process accommodating portion;

fig. 19(a) -19(c) are a series of side views showing an operation of engaging the restricting spring with the drum convex portion when the drum cartridge is mounted in the process accommodating portion, in which fig. 19(a) shows the restricting spring before engagement, fig. 19(b) shows the restricting spring being engaged, and fig. 19(c) shows the restricting spring after completion of engagement;

fig. 20 is a sectional view taken along an imaginary horizontal plane showing an assembled state of the drum cartridge in the process accommodating portion (when passing through the developing accommodating portion);

fig. 21 is a sectional view taken along an imaginary horizontal plane showing an assembled state of the drum cartridge in the process accommodating section (when the assembly is completed);

fig. 22 and 23 are a series of side views showing a process of engaging the pressing cam with the drum shaft when the drum cartridge is fitted in the process accommodating portion (an engaging operation is associated with fitting and removal of the drum cartridge), in which fig. 22 shows the pressing cam before engagement and fig. 23 shows the pressing cam after engagement is completed;

fig. 24 is a side view showing an assembled state of the developing cartridge in the process accommodating portion (before the developing boss is inserted into the boss insertion groove);

fig. 25 is a side view showing an assembled state of the developing cartridge in the process accommodating portion (when the developing protrusion contacts the protrusion contacting portion);

fig. 26 is a side view (separated state) showing an assembled state of the developing cartridge in the process accommodating portion;

fig. 27 is a side view (contact state) showing an assembled state of the developing cartridge in the process accommodating portion;

fig. 28 is a plan view showing an assembled state (separated state) of the developing cartridge in the process accommodating portion;

fig. 29 is a front view (separated state) showing an assembled state of the developing cartridge in the process accommodating portion;

fig. 30 is a plan view showing a state of fitting of the developing cartridge in the process accommodating portion (contact state);

fig. 31 is a front view (contact state) showing an assembled state of the developing cartridge in the process accommodating portion;

FIG. 32(a) is a plan view showing a cam driving path structure;

FIG. 32(b) is a side view showing a cam driving path structure;

fig. 33(a) and 33(b) are a series of side views showing a process of engaging the pressing cam with the drum shaft (the engaging operation is associated with the fitting and removal of the developing cartridge) when the drum cartridge is fitted in the process accommodating section according to the modification, in which fig. 33(a) shows the pressing cam before engagement and fig. 33(b) shows the pressing cam after engagement is completed; and

fig. 34 is a side view showing a variation of the second pressing member in the contact/separation mechanism according to another modification of the preferred embodiment.

Detailed Description

An image forming apparatus according to a preferred embodiment of the present invention will be described below with reference to the accompanying drawings, in which like parts and elements are denoted by the same reference numerals to avoid repetitive description.

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

The color laser printer 1 shown in fig. 1 is a transverse tandem type color laser printer having a plurality of processing sections 27 arranged horizontally in parallel. The color laser printer 1 includes a main casing 2 and a feed 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 supplied from the feed unit 4, and a discharge unit 6 for discharging the sheet 3 from the color laser printer 1 after the image is formed on the sheet 3.

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

As shown in fig. 14, the main casing 2 includes a left side plate 8 and a right side plate 9 facing each other in a lateral direction perpendicular to the front-rear direction and the vertical direction and separated by a prescribed interval; and four partition plates 10 and one front plate 11 spanning between the left and right side plates 8 and 9. Partition plates 10 are provided in the main casing 2 at regular intervals in the front-rear direction, and a front plate 11 is further provided in front of the partition plates 10 so as to partition the space between the left and right side plates 8, 9 in the front-rear direction into spaces for each process section 27 (fig. 1) to be described later. Each partition plate 10 has a rear surface 33 on its rear side.

Each of the partition plate 10 and the front plate 11 is inclined with respect to the front-rear direction and the vertical direction which are exactly the same as the direction in which the sheet 3 is conveyed by the color laser printer 1 at the time of image formation, and the top end of the plate is further forward than the bottom end. As shown in fig. 1, the partition plate 10 and the front plate 11 are arranged such that a vertical space is formed between the top ends of the plates 10, 11 and the top cover 7, and another vertical space is formed between the bottom ends of the plates 10, 11 and a transfer section 28 to be described later.

Accordingly, as shown in fig. 14, the four process accommodating sections 12 are partitioned in the main casing 2 by the left side plate 8, the right side plate 9, the adjacent partition plate 10, and the front plate 11. Each process accommodating portion 12 is provided for one process portion 27 corresponding to each print color. Each process accommodating portion 12 includes a drum accommodating portion 13 (see fig. 15) for accommodating a drum cartridge 31 to be described later, and a developing accommodating portion 14 (see fig. 15) for accommodating a developing cartridge 32 to be described later. As shown in fig. 15, the drum cartridge 31 has a holder unit 43 fitted in the drum accommodating portion 13, and the developing cartridge 32 is fitted in the developing accommodating portion 14.

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

The developing accommodating portion 14 is provided on the upstream side of the drum accommodating portion 13 with respect to the direction in which the drum cartridge 31 is assembled, as a continuation of the drum accommodating portion 13. In other words, the developing accommodating portion 14 is provided above the drum accommodating portion 13 in the fitting direction of the drum cartridge 31 and the developing cartridge 32. The developing 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 developing accommodating portion 14 partitioned in this way (excluding the extended accommodating space 18 to be described later) forms the developing accommodating space 16 for accommodating the developing cartridge 32.

As shown in fig. 14 and 15, in each of the development accommodating sections 14, a rail portion 17 is provided on the partition plate 10, extending along both lateral ends of the partition plate 10. The rail portion 17 is formed as a thick belt extending in the assembling direction of the drum cartridge 31. When the drum cartridge 31 is assembled, ridges 51 (to be described later) of the drum cartridge 31 slide against the rail portions 17, respectively.

As shown in fig. 1, the feeding unit 4 includes a paper supply tray 21 detachably fitted to a lower portion of the main casing 2 and capable of being inserted into or removed from the main casing 2 through a front side in a horizontal direction; a pickup roller 22 and a feed roller 23 disposed above the front side of the sheet supply tray 21; a feeding-side U-shaped path 24 provided in front of and above the feeding roller 23; a conveying roller 25 and a registration roller 26 disposed along the feed-side U-shaped path 24.

The sheets 3 are stacked inside the sheet supply tray 21. The pickup roller 22 picks up the uppermost sheet 3 and conveys it forward. Subsequently, the feeding roller 23 feeds the sheet along the feeding-side U-shaped path 24. The feed-side U-shaped path 24 is shaped substantially like a letter U and serves as a conveyance path for the sheet 3. The upstream end of the feeding-side U-shaped path 24 is positioned adjacent to the lower portion of the feeding roller 23 that feeds the sheet 3 forward, while the downstream end is positioned adjacent to the upper portion of a conveyor belt 80 for conveying the sheet 3 backward, which will be described later.

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 3 along the feed-side U-shaped path 24 with the conveying direction of the sheet 3 reversed. The registration rollers 26 first register the sheet 3 and then convey the sheet backward.

The image forming unit 5 includes a processing portion 27, a transfer portion 28, and a fixing portion 29. The process section 27 is provided one for each toner color. Specifically, the color laser printer 1 of the preferred embodiment has four processing sections 27 including a yellow processing section 27Y, a magenta processing section 27M, a cyan processing section 27V, and a black processing section 27K. One processing portion 27 is provided in each processing accommodating portion 12, horizontally aligned with each other in the front-rear direction and separated by a prescribed interval.

Each process portion 27 includes a scanner unit 30, a drum cartridge 31, and a developing cartridge 32 detachably mounted on the drum cartridge 31. The process cartridge is configured by a drum cartridge 31 and a developing cartridge 32 fitted on the drum cartridge 31.

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

As shown in fig. 14, the scanner housing 35 is disposed at the lateral center of each partition plate 10 such that the rail portion 17 of each partition plate 10 is positioned one at each lateral end of the scanner housing 35. Further, the rear wall of the scanner housing 35 contacts the front surface of the partition plate 10 while the front wall 34 of the scanner housing 35 protrudes forward from the partition plate 10. By disposing 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 developing cartridge 32 can be arranged close to each other, thereby enabling a more compact apparatus.

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

As shown in fig. 15, due to the scanner housing 35, the development accommodating portion 14 is formed narrower than the drum accommodating portion 13 in a direction perpendicular to the lateral direction and the fitting direction of the drum cartridge 31 and the development cartridge 32 (hereinafter, referred to as "thickness direction" of the drum cartridge 31 and the development cartridge 32).

More specifically, the development accommodating portion 14 is formed wider than the thickness of the holder unit 43 of the drum cartridge 31 in the thickness direction, and narrower than the thicknesses of the drum cartridge 31 and the development cartridge 32 fitted to each other.

Further, the drum accommodating portion 13 has an expanded space 19 on the downstream side of the scanner housing 35 with respect to the fitting direction of the drum cartridge 31, and the drum accommodating portion 13 is wider than the developing accommodating portion 14 by the expanded space 19. Therefore, the drum accommodating portion 13 is formed wider in the thickness direction than the thickness of the drum cartridge 31 and the developing cartridge 32 assembled together, and is accommodated in the process accommodating portion 12.

As will be described later, when the holder unit 43 of the drum cartridge 31 is disposed in the expanded space 19, that is, when the drum cartridge 31 is accommodated in the drum accommodating space 15 of the drum accommodating portion 13, and when the developing cartridge 32 is accommodated in the developing accommodating space 16 of the developing accommodating portion 14, since the holder unit 43 contacts the scanner housing 35, the drum cartridge 31 is restricted from moving in the direction in which the drum cartridge 31 is removed. After the developing cartridge 32 is removed from the developing accommodating portion 14, the drum cartridge 31 can be removed by first moving the drum cartridge 31 in a direction (forward) away from the scanner housing 35, thereby allowing the drum cartridge 31 to pass from the drum accommodating portion 13 through the developing accommodating portion 14.

As shown in fig. 15, the extended accommodating space 18 is formed in the developing accommodating portion 14 between the upper end and both lateral ends of the scanner housing 35 and near the front wall 34 of the scanner housing 35 (a space between the front wall 34 of the scanner housing 35 and the developing accommodating space 16, in which an intermediate plate 54 to be described later is provided). The extension accommodating space 18 accommodates an extension 44 of the drum cartridge 31 to be described later.

As shown in fig. 1, a window 40 is formed in the front wall 34 of the scanner housing 35 for allowing the laser beam to pass therethrough. The laser emitting unit of the scanning unit 30 emits a laser beam based on the designated image data. This laser beam is deflected by the polygon mirror 36, passes through or is reflected in the lens 37, the reflection mirror 39 and the lens 38, 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 holder unit 43 and an extension 44 extending from the holder unit 43. The holder unit 43 and the extension 44 are integrally formed of synthetic resin.

The drum cartridge 31 will be described below with reference to fig. 2 to 7. In the following description, the region of the drum cartridge 31 above fig. 2 is referred to as the "upper side" of the drum cartridge 31 (the rear side when the drum cartridge 31 is assembled), and the portion of the drum cartridge 31 at the bottom of fig. 2 is referred to as the "lower side" of the drum cartridge 31 (the front side when the drum cartridge 31 is assembled). Further, the side of the drum cartridge 31 where the holder unit 43 is provided will be referred to as the "front side" of the drum cartridge 31 (the lower side when the drum cartridge 31 is assembled), and the side where the extension 44 is provided will be referred to as the "rear side" of the drum cartridge 31 (the upper side when the drum cartridge 31 is assembled).

The holder unit 43 includes two side walls 45 opposed to each other across a prescribed interval in the lateral direction, a top wall 46 spanning between upper edges of the side walls 45, and a front wall 47 extending perpendicularly from a front edge of the top wall 46 along a part of the front edge of the side wall 45. The holder unit 43 is thicker than the developing casing 64 (see fig. 8) of the developing cartridge 32.

The holder unit 43 is formed thicker (longer in the vertical direction) than the extension portion 44. This configuration can reliably accommodate the photosensitive drum 42 and the charger 62.

As shown in fig. 6 and 7, a developing positioning groove 48, which is formed in a substantially U-shape and opens rearward, is formed at a lower portion of each side wall 45. An insertion portion 49 is formed at the front side of the developing positioning groove 48 for inserting the drum shaft 60 of the photosensitive drum 42.

As shown in fig. 2, a cleaner mounting portion 50 is formed in the top wall 46 along the width of the top wall 46. A cleaner 63 to be described later is slidably mounted in the cleaner mounting portion 50. As shown in fig. 6 and 7, the ridges 51 formed on both lateral ends of the top wall 46 are substantially triangular projections that project upward at the front end of the top wall 46 when viewed from the side.

As shown in fig. 2 and 3, the extending portion 44 extends rearward from the holder unit 43 such that the extending portion 44 extends above the upper end of the scanner housing 35 in the developer accommodating portion 14 when the holder unit 43 is fitted in the drum accommodating portion 13.

The extension 44 includes two extension side portions 52 opposed to each other across a space in the lateral direction, an extension rear wall 53 spanning between rear edges of the extension side portions 52, and an intermediate plate 54 provided in an area surrounded by the holder unit 43, the extension side walls 52, and the extension rear wall 53.

As shown in fig. 2 and 3, each extended side portion 52 has a substantially box-shaped cross section open at the bottom. As shown in fig. 2, the outer surfaces of the extended side portions 52 extend rearward from both lateral ends of the holder unit 43 so as to continue rearward from the top of the developing positioning groove 48.

As shown in fig. 3, two reinforcing ribs 55 substantially X-shaped as viewed from the bottom are provided inside the box shape of the extended side portion 52 in the front-rear direction. A bulging protrusion 56 that protrudes outward in the lateral direction is provided on the outer side surface of each extended side portion 52 midway along the longitudinal direction of the extended 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 provided at the lateral center of the extended rear wall 53, making it easier to grasp the drum cartridge 31 and to assemble and remove the drum cartridge 31 with respect to the drum accommodating portion 13.

As shown in fig. 2, the intermediate plate 54 is formed into a substantially rectangular planar shape. The intermediate plate 54 is provided at a portion surrounded by the holder unit 43, the extended side portion 52, and the extended rear wall 53, and is connected to the holder unit 43, the extended side portion 52, and the extended rear wall 53 at a position recessed below the upper surfaces of the extended side portion 52 and the extended rear wall 53. An opening 58 is formed in the intermediate plate 54 to allow passage of the laser beam emitted through the window 40 of the scanner housing 35. As shown in fig. 4, the opening 58 is shaped like a trapezoid in plan view, with a front side wider than a rear side. By forming the opening 58 in a trapezoidal shape in plan view, it is possible to cut off only a portion of the intermediate plate 54 through which the laser beam passes, resulting in a stronger extension 44 than when the intermediate plate 54 is formed in a rectangular shape in plan view.

As shown in fig. 2, the photosensitive drum 42 is accommodated in the holder unit 43 in the lateral direction. The photosensitive drum 42 includes a main drum body 59 having a cylindrical shape and a positively charged photosensitive layer composed of polycarbonate or the like on the outer surface thereof, and a drum shaft 60 extending along the axial center of the main drum body 59. The drum shaft 60 is supported in the side walls 45 by two shaft ends such that each shaft end is inserted into the insertion portion 49 of the respective side wall 45 and projects axially outwardly from each side wall 45. The drum shaft 60 cannot rotate relative to the side wall 45.

A rotation support member 61 is mounted to each shaft end of the main drum body 59 so as not to be rotatable relative to the main drum body 59. The rotation support member 61 is supported on the drum shaft 60 and is rotatable with respect to the drum shaft 60. Therefore, the main drum body 59 is supported to be rotatable with respect to the drum shaft 60. With this structure, as shown in fig. 5, the photosensitive drum 42 is disposed in the holder unit 43 such that the front surface is exposed below the front wall 47.

As shown in fig. 1, the charger 62 is accommodated in the holder unit 43 above (rearward in fig. 2) the ridge 51 and extends in the lateral direction. The charger 62 is a positively charged, gated corona charger including charging wires and a grid for generating a corona discharge. The charger 62 is supported on the top wall 46 behind the photosensitive drum 42 and faces the photosensitive drum 42 at a prescribed distance without contacting it. As shown in fig. 2, the charger 62 is equipped with a cleaner 63 for cleaning the charging wire. The cleaner 63 is slidably mounted in the cleaner mounting portion 50 of the top wall 46.

The developing cartridge 32 shown in fig. 8 to 13 includes a developing housing 64, and a toner accommodating chamber 65, a supply roller 66, a developing roller 67, and a thickness regulating blade 68 provided in the developing housing 64, as shown in fig. 1.

Next, the developing cartridge 32 will be described in detail with reference to fig. 8 to 13. In the following description, the portion of the upper side in fig. 8 of the developing cartridge 32 will be referred to as the "upper side" of the developing cartridge 32 (referred to as the rear side when the developing cartridge is assembled), and the portion of the lower side in fig. 8 of the developing cartridge 32 will be referred to as the "lower side" of the developing cartridge 32 (referred to as the front side when the developing cartridge 32 is assembled). Further, the side of the developing cartridge 32 where the developing roller 67 is provided will be referred to as the "front side" of the developing cartridge 32 (referred to as the lower side when the developing cartridge 32 is assembled), while the side of the developing cartridge 32 where the toner-accommodating chamber 65 is provided will be referred to as the "rear side" of the developing cartridge 32 (referred to as the upper side when the developing cartridge 32 is assembled).

As shown in fig. 8, the developing casing 64 is formed in a box shape with a front-side opening. A jaw portion 69 and a slide guide 70 are provided on a lower front edge of the developing housing 64. The jaw portion 69 is provided across the entire width of the developing housing 64 and projects slightly forward from its lower front edge. As shown in fig. 11, in order to prevent toner from leaking from the developing roller 67, the jaw portion 69 is disposed in a confronting relationship with the developing roller 67 so as to be pressed against the outer peripheral surface of the developing roller 67 from below.

A slide guide 70 is provided at the lower front edge of the developing housing 64, one at each widthwise end of the jaw portion 69. As shown in fig. 12 and 13, the slide guide 70 is formed in a curved L shape in side view and projects forward and downward more than the jaw portion 69.

As shown in fig. 9, the developing boss 71 is provided at the upper rear end of the developing housing 64 and projects outward from both side walls of the developing housing 64 in the width direction. As shown in fig. 9 and 10, the developing handle 72 is provided at the substantially widthwise center on the rear wall of the developing housing 64 so that the user can grasp the developing cartridge 32 when fitting the developing cartridge 32 to the developing accommodating portion 14 or removing the developing cartridge 32 from the developing accommodating portion 14. Further, small contact bumps 91 are formed on the bottom surface of the developing casing 64 at positions close to the rear side, one at each of the widthwise ends.

As shown in fig. 1, a toner containing chamber 65 is formed in an upper portion (rear portion in fig. 8) of the developing housing 64 to contain toners of respective colors for the color laser printer 1. In the preferred embodiment, the toner-accommodating chamber 65 of each process portion 27 accommodates a non-magnetic, one-component polymerized toner having a positive charging characteristic. The toner-accommodating chamber 65 of the yellow process section 27Y accommodates yellow toner, the toner-accommodating chamber 65 of the magenta process section 27M accommodates magenta toner, the toner-accommodating chamber 65 of the cyan process section 27C accommodates cyan toner, and the toner-accommodating chamber 65 of the black process section 27K accommodates black toner.

More specifically, the toners of the respective colors used in the preferred embodiment are polymerized toners of substantially spherical shapes obtained by a polymerization method. The basic component of the polymerized toner is a binder resin obtained by copolymerizing a monomer by a known polymerization method such as suspension polymerization. The polymerized monomer may be, for example, a styrene monomer such as styrene; or acrylic monomers such as acrylic acid, hydrocarbyl (C1-C4) acrylates, and hydrocarbyl (C1-C4) methacrylates. The primary toner particles are formed by mixing the binder resin with a colorant, a charge control agent, paraffin wax or the like. An additive for increasing fluidity is also mixed in the basic toner particles.

The colorant mixed with the binder 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 and a monomer 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 silicon oxide, aluminum oxide, titanium oxide, strontium titanium oxide, cerium oxide, or magnesium oxide, or an inorganic powder such as a carbide powder or a metal salt powder.

An agitator 73 shown in fig. 1 is rotatably supported on both side walls of the developing housing 64 in a lower portion (front side in fig. 8) of the toner containing chamber 65 to agitate the toner. The supply roller 66 is also rotatably supported on both side walls of the developing housing 64 on the lower front side (front lower side in fig. 8) of the toner accommodating chamber 65. The supply roller 66 is constituted by a metal roller shaft covering a roller body portion formed of a conductive sponge material.

The developing roller 67 is disposed below the supply roller 66 (in front of the supply roller in fig. 8) and faces the supply roller 66 in a compressive relationship. As shown in fig. 8, the developing roller 67 is disposed at the front end thereof along the width of the developing housing 64, and the front surface is exposed from the developing housing 64. As described above, the lower portion of the exposed portion is in pressure contact with the jaw portion 69.

The developing roller 67 is constituted by a metal roller shaft 74 covering a roller body portion 75 formed of an elastic material such as a conductive rubber material. More specifically, the roller body portion 75 has a double-layer structure including: an elastic roller body portion formed of conductive urethane rubber, silicone rubber, or EPDM rubber containing fine carbon particles or the like; and a coating layer covering the surface of the roller body portion and having urethane rubber, urethane resin, polyimide resin or the like as a basic component. Both width ends of the roller shaft 74 are rotatably supported on both side walls of the developing housing 64 and project outward from the both side walls in the width direction.

The layer thickness regulating blade 68 is provided at the upper front end of the developing casing 64 across the entire width thereof. As shown in fig. 1, the layer thickness regulating blade 68 is constituted by a blade body formed of a metal leaf spring member and a pressing portion provided at a free end of the blade body. The pressing portion has a semicircular cross section and is formed of an insulating silicone rubber. The base portion of the sheet is supported at the front edge of the upper wall constituting the developing casing 64 so that the pressing portion provided at the free end of the sheet is in pressure contact with the rear surface (upper surface in fig. 1) of the developing roller 67.

As shown in fig. 14, a guide groove 101 is formed in each process accommodating portion 12. The guide grooves 101 guide the drum cartridge 31 when the drum cartridge 31 is fitted into 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. The guide grooves 101 are formed as recesses on the inner surfaces of the left and right side plates 8, 9 at corresponding positions in the width direction, inclining backward from top to bottom in the direction of assembling the drum cartridge 31 as shown in fig. 15.

As shown in fig. 19, the guide groove 101 includes: an upstream guide portion 140 wider in the front-rear direction of the upper end, the upstream guide portion 140 functioning to guide the drum cartridge 31 when the drum cartridge 31 passes through the development accommodating portion 14; and a downstream guide portion 141 formed continuously with the upstream guide portion 140 at a lower portion gradually narrowing toward a bottom end thereof. The downstream guide portion 141 is inclined rearward relative to the upstream guide portion 140 so that the holder unit 43 is guided toward the extension space 19 after the drum cartridge 31 passes through the development accommodating portion 14. Therefore, the downstream guide portion 141 functions to guide the drum cartridge 31 when the drum cartridge 31 is fitted to the drum accommodating portion 13 or removed from the drum accommodating portion 13.

The lower end (deepest end) of each downstream guide portion 141 is a receiving portion 102 that receives the drum shaft 60. The receiving portion 102 is formed as a recess in which the drum shaft 60 is completely fitted in the front-rear direction, and is positioned so that the photosensitive drum 42 is in contact with the conveyor belt 80, which will be described below, when the drum shaft 60 is received in the receiving portion 102.

Drum positioning grooves 103 are formed at respective widthwise positions of the left and right side plates 8 and 9 to receive the drum projections 56. The drum positioning groove 103 is recessed in a rectangular shape when viewed from the side and opened at the front side, and is located midway along the length of the upstream guide portion 140.

As shown in fig. 14, a projection insertion groove 133 is formed on the upper side of the upstream guide 140 as a cut-out portion of the left and right side plates 8 and 9 to receive the developing projection 71 of the developing cartridge 32. As shown in fig. 24, the projection insertion groove 133 is formed as a straight, substantially elongated U-shaped notch at the upper ends of the left and right side plates 8, 9, which is inclined in the fitting direction of the developing cartridge 32, i.e., in the path in which the developing projection 71 moves when the developing cartridge 32 is fitted or removed. Further, the projection insertion groove 133 is formed deep enough so that the bottom of the projection insertion groove 133 is deeper than the position of the developing projection 71 when the developing cartridge 32 is mounted on the drum cartridge 31. The projection insertion groove 133 also has a sufficient width in the front-rear direction so that the developing projection 71 can fit into the projection insertion groove 133 with a certain gap. The upper end of the projection insertion groove 133 has a generally triangular shape gradually widening toward the top so as to receive the developing projection 71.

Provided in the guide groove 101 are: a drum shaft locking mechanism 104 (see fig. 22) that restricts movement of the drum shaft 60 received in the receiving portion 102; a limiting spring 105 (see fig. 19) that limits the rotation of the drum cartridge 31; and a contact/separation mechanism 106 (see fig. 24) that contacts the developing cartridge 32 with the drum cartridge 31 or separates the developing cartridge 32 from the drum cartridge 31.

As shown in fig. 22, the drum shaft locking mechanism 104 is provided at a position where the outer surfaces of the left and right side plates 8 and 9 are close to the receiving portion 102. Each drum shaft locking mechanism 104 includes a pressing cam 107 and a drive spring 108. The pressing cam 107 has a substantially rectangular plate shape. The lower rear end of the pressing cam 107 is rotatably supported on a support shaft 109 that protrudes outward in the width direction from the outer surfaces of the left and right side plates 8, 9. The upper rear corner of the pressing cam 107 is a contact portion 110 for contacting the drum shaft 60. An elliptical hole 111 is formed through the left and right side plates 8, 9 at a position near the upper front corner of the pressing cam 107. The contact shafts 112 protrude inward in the width direction toward the fitting path of the drum cartridge 31 (i.e., the path in which the drum shaft 60 moves) through the respective oblong holes 111.

The drive spring 108 is a coil spring having a coil portion wound on the support shaft 109. One end of the wound portion is fixed to each of the left and right side plates 8 and 9, and the other end is engaged with the bottom end of the pressing cam 107. The urging force of the urging spring 108 constantly urges the pressing cam 107 to rotate in a direction (counterclockwise in fig. 22) in which the contact portion 110 urges the drum shaft 60 into the receiving portion 102 and the contact shaft 112 forward into the fitting path of the drum cartridge 31.

As shown in fig. 19, a restricting spring 105 is provided on the outer surfaces of the left and right side plates 8 and 9 at a position close to the drum positioning groove 103. The restraining spring 105 is a coil spring having a coil portion. The wound portion is wound around a fixing shaft 115 protruding outward in the width direction from the outer surface of each of the left and right side plates 8 and 115. One end of the coiled portion is fixed to each of the left and right side panels 8 and 9. The other end surface of the restriction spring 105 faces the drum positioning groove 103 and is constantly urged toward the drum positioning groove 103 by the urging force of the restriction spring 105, but can be withdrawn from the drum positioning groove 103.

As shown in fig. 24, one contact/separation mechanism 106 is provided on the outer surface of each of the left and right side plates 8 and 9 at a position close to each of the projection insertion grooves 133. The contact/separation mechanism 106 includes a first pressing member 116 that presses the developing boss 71 in the fitting direction, a first drive spring 117 that drives the first pressing member 116, a second pressing member 118 that presses the developing boss 71 in the removal direction, a second drive spring 119 that drives the second pressing member 118, and a cam 120 that is disposed to face the first pressing member 116 and the second pressing member 118.

The first pressing member 116 is substantially V-letter shaped, and one pen of the V is connected to another pen by a bent portion. When the first pressing member 116 is in a separated state, which will be described below with reference to fig. 26, the V-shaped pen of the first pressing member 116 is parallel to the projection insertion groove 133, and the other pen extends in the front-rear direction. The projection contact part 121 is formed at the distal end of the first pen to contact the developing projection 71. The convex contact portion 121 forms an angle with the first pen so that the convex contact portion 121 extends forward from the end of the first pen when the first pressing member 116 is in the separated state. The bottom surface of the projection contact part 121 is formed as an upper pressing surface 134 to press the developing projection 71 from above. The upper pressing surface 134 is formed to contact the developing protrusion 71 obliquely while generating a pressing force to press the developing protrusion 71 in the fitting direction and a pressing force to press the developing protrusion 71 toward a front edge of the protrusion insertion groove 133, which serves as a reference surface. A cam contact portion 122 is formed at the other distal end of the V-shaped second pen of the first pressing member 116 for contacting the cam 120. The cam contact portion 122 protrudes upward from the other end when the first pressing member 116 is in the separated state.

The first pressing member 116 is rotatably supported at its curved portion on the support shaft 123. The support shaft 123 is provided on the outer surfaces of the left and right side plates 8 and 9 and projects outward in the width direction from a position behind the bottom end (deepest portion) of the boss insertion groove 133. With this structure, the first pressing member 116 is provided so that the projection contact part 121 can be pushed into the projection insertion groove 133, i.e., the moving path of the developing projection 71, or withdrawn from the projection insertion groove 133 in the front-rear direction; meanwhile, the cam contact part 122 may contact the bottom side of the cam 120 or be separated from the bottom side of the cam 120 at a side of the support shaft 123 opposite to the protrusion insertion groove 133.

With this arrangement, the fitting direction of the support shaft 123 with respect to the developing convex portion 71 is set downstream of the convex contact portion 121.

The first drive spring 117 is a tension spring having one end fixed to the first fixed shaft 124 protruding from a position on the outer surface of each of the left and right side plates 8 and 9 below the bottom end (deepest portion) of the boss insertion groove 133. The other end of the first drive spring 117 engages with the cam contact portion 121. Therefore, the first driving spring 117 constantly drives the first pressing member 116 in a direction to move the boss contact portion 121 toward the moving path of the developing boss 71 (forward) and to move the cam contact portion 122 closer to the cam 120 (upward).

The second pressing member 118 has a substantially rectangular planar shape. A projection contact claw 125 is provided at an upper front corner of the second presser member 118 to contact the developing projection 71. When the second pressing member 118 is in the separated state, the projection contact pawl 125 projects diagonally upward and forward. Further, a rotation restricting pawl 126 contactable with the first fixed shaft 124 is provided at a lower front corner of the second presser member 118, and the rotation restricting pawl 126 projects diagonally downward and forward when the second presser member 118 is in a separated state. A cam contact protrusion 127 for contacting the cam 120 is also provided on a portion of the upper edge of the second pressing member 118 near the rear end, and the cam contact protrusion 127 protrudes upward when the second pressing member 118 is in the separated state. A spring engaging projection 128 for engaging the other end of the second drive spring 119 is provided at the lower edge of the second presser member 118 near the rear end portion of the second presser member 118, and the spring engaging projection 128 projects downward when the second presser member 118 is in the separated state (fig. 26).

The second presser member 118 is rotatably supported on the support shaft 123 at the midpoint in the front-rear direction. In this way, the projection contact claw portion 125 extends to the midpoint of the projection insertion groove 133, that is, the midpoint of the moving path of the developing projection 71 at a position downstream of the projection contact portion 121 in the fitting direction of the developing projection 71, and is movable in the fitting direction or the removing direction of the developing projection 71. Also, the rotation restricting pawl portion 126 can be brought into contact with or separated from the first fixed shaft 124, and the cam contact protrusion 127 can be brought into contact with or separated from the cam 120 on the opposite side of the support shaft 123 with respect to the projection insertion groove 133.

The second driving spring 119 is a tension spring, one end of which is fixed to a second fixing shaft 129, the second fixing shaft 129 being provided on the outer surfaces of the respective left and right side plates 8 and 9. The second fixing shaft 129 protrudes laterally outward from a position below the first fixing shaft 124. The other end of the second drive spring 119 is engaged on the spring engagement projection 128. With this structure, the second driving spring 119 constantly drives the second pressing member 118 in a direction in which the boss contacting pawl 125 presses (upward) the developing protrusion 71 in the removing direction along the moving path of the developing protrusion 71, the rotation restricting pawl 126 moves (upward) toward the first fixed shaft 124, and the cam contacting protrusion 127 separates (downward) from the cam 120.

The spring constant of the second drive spring 119 is set smaller than the spring constant of the first drive spring 117.

As shown in fig. 28, both the first pressing member 116 and the second pressing member 118 are rotatably supported on the support shaft 123, and the first pressing member 116 is disposed laterally outside the second pressing member 118. The convex contact portion 121 of the first pressing member 116 projects laterally inward, and the convex contact claw portion 125 of the second pressing member 118 projects laterally outward, so that the upper pressing surface 134 of the convex contact portion 121 overlaps the lower pressing surface 135 of the convex contact claw portion 125 in the moving direction of the developing convex portion 71.

As shown in fig. 24, the cam 120 is somewhat fan-like in shape. The cam 120 is coupled to the camshaft 130 but is not rotatable relative to the camshaft 130. The cam shaft 130 is rotatably supported by the left and right side plates 8 and 9 and projects laterally outward from positions above and behind the support shaft 123. The cam 120 forms a continuous circumferential surface including an arcuate contact surface 131 and a separation surface 132, the separation surface 132 being formed on opposite sides of the contact surface 131 and shaped substantially like a letter V with the corners at its center.

By rotating the cam shaft 130, the cam 120 is oriented to selectively position the contact surface 131 or the separation surface 132 to face the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118.

When the developing cartridge 32 is fitted in the developing accommodating portion 14, during the non-image forming operation, the contact surface 131 of the cam 120 comes into contact with the cam contact portion 122 and the cam contact protrusion 127, and the first pressing member 116 and the second pressing member 118 are driven downward in a separated state in which the photosensitive drum 42 is separated from the developing roller 67, as shown in fig. 26, 28, and 29.

Although the first driving spring 117 pulls the projection contact portion 121 of the first pressing member 116 downward, in the separated state, the first pressing member 116 rotates against the driving force of the first driving spring 117, causing the projection contact portion 121 to retreat from the moving path of the developing projection 71. When the projection contact part 121 is moved in the withdrawal direction in the separated state, the projection contact part 121 is slightly pushed forward toward the moving path of the developing projection part 71 within the range allowed for fitting and removing the developing cartridge 32.

Also in the separated state, the second pressing member 118 is rotated in a direction to compress the second drive spring 119 by a pressing force larger than the driving force of the second drive spring 119, the projection contact pawl 125 is moved in a direction to press in the removing direction to the developing convex portion 71, and the rotation restricting pawl 126 is moved toward the first fixed shaft 124. In this separated state, the projection contact pawl portion 125 is provided at a position on the moving path of the developing projection portion 71, which is on the upstream side with respect to the fitting direction of the developing projection portion 71 in a contact state to be described later.

As shown in fig. 32(a), the contact/separation mechanism 106 is provided for each process accommodating portion 12, and, in each process accommodating portion 12, a cam shaft 130 is spanned between the left and right side plates 8 and 9 and rotatably supported by the left and right side plates 8 and 9, and one cam 120 is connected to each end of the cam shaft 130. Although not shown in the drawings, a pair of first pressing members 116 and a pair of second pressing members 118 are provided in each process accommodating portion 12, corresponding to the pair of cams 120.

A cam drive gear 136 is connected to the end of each cam shaft 130 that projects from the outer edge of the left side plate 8. Cam drive gear 136 cannot rotate relative to camshaft 130. The intermediate gear 137 is disposed between the adjacent cam driving gears 136 and is engaged with the cam driving gears 136. With this structure, the gear train is composed of the cam drive gear 136 and the intermediate gear 137, as shown in fig. 32 (b). The motor 138 is provided to generate a driving force to drive each camshaft 130. The driving force generated by the motor 138 is input to the gear train via the pinion 139. The driving force is transmitted to the camshafts 130 through a gear train to rotate each camshaft 130. Accordingly, the cam pair 120 simultaneously rotates to selectively position the contact surface 131 or the separation surface 132 facing the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118.

With the color laser printer 1 according to the present preferred embodiment, each drum cartridge 31 is fitted in the main casing 2 by fitting the drum cartridge 31 of each color into the corresponding drum accommodating section 13 of the corresponding process accommodating section 12. Then, the developing cartridge 32 of each color is fitted into the corresponding developing accommodating portion 14, thereby being fitted on the corresponding drum cartridge 31.

Next, the process of assembling the drum cartridge 31 and the developing cartridge 32 in the main casing 2 will be described with reference to fig. 15 to 23.

To fit the drum cartridge 31 in the drum accommodating space 15 of the process accommodating portion 12, the user grasps 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 shown in fig. 15. By such an operation, the drum projection 56 is inserted into the upstream guide portion 140, and the drum cartridge 31 is guided by the development accommodating portion 14. Next, the drum projection 56 is inserted into the downstream guide portion 141, and the holder unit 43 is guided toward the direction of the expansion space 19 until the drum cartridge 31 is fitted into the drum accommodating portion 13. This structure ensures that the drum cartridge 31 can be smoothly fitted into the drum accommodating portion 13.

When the drum cartridge 31 is assembled and the holder unit 43 of the drum cartridge 31 passes through the development accommodating space 16 of the development accommodating portion 14, the ridge 51 of the drum cartridge 31 frequently slides against the rail portion 17 of the development accommodating portion 14, as shown in fig. 20. In this way, since the ridge 51 protrudes toward the rail portion 17 and the rail portion 17 is composed of a thick strip, the ridge 51 is in contact with the rail portion 17, a space is formed between the front wall 34 of the scanner housing 35 and the top wall 46 opposite to the front wall 34, which prevents the top wall 46 from rubbing against the front wall 34 of the scanner housing 35.

Since the sliding of the ridge 51 against the rail portion 17 when the drum cartridge 31 is assembled can prevent the top wall 46 from sliding against the front wall 34 of the scanner housing 35, the color laser printer 1 of the present preferred embodiment can prevent the drum cartridge 31 from being damaged during the assembly process. In addition, since the ridge 51 and the rail portion 17 are provided at each lateral end of the scanner housing 35, this reliably prevents the holder unit 43 from sliding against the scanner housing 35.

In addition, the charger 62 is disposed behind the ridge 51 of the holder unit 43 in fig. 2, that is, on the upstream side of the ridge 51 in the drum cartridge 31 fitting direction. Therefore, the ridge 51 is always positioned in front of the charger 62 when the drum cartridge 31 is assembled, which reliably prevents damage to the charger 62.

When the holder unit 43 of the drum cartridge 31 reaches the drum accommodating portion 13, the drum shaft 60 is guided along the downstream guide portion 141, and the downstream guide portion 141 is bent obliquely rearward with respect to the upstream guide portion 140. Accordingly, the drum shaft 60 moves diagonally rearward along the downstream guide portion 141, as shown in fig. 16. When the drum shaft 60 reaches the tip of the receiving portion 102, the drum housing 41 is in the inclined orientation, the holder unit 43 is positioned rearward and the extension portion 44 is positioned forward, as shown in fig. 17, 19(a), and 22. In this state, the development accommodating space 16 of the development accommodating portion 14 is closed by the extending portion 44.

When the drum shaft 60 reaches the end of the receiver 102, the user grasps the drum grip 57 and rotates the extension 44 rearward about the drum shaft 60 supported in the receiver 102. By such an operation, the extension portion 44 is retracted from the development accommodating space 16 into the extension accommodating space 18 as shown in fig. 18 and 21, thus emptying the development accommodating space 16 accommodating the developing cartridge 32.

More specifically, when the drum shaft 60 reaches the tip of the receiver 102, the drum projection 56 first opposes the drum positioning groove 103, as shown in fig. 19 (a). Then, the extending portion 44 is withdrawn from the development accommodating space 16 toward the extension accommodating space 18, and the drum projection 56 is received into the drum positioning groove 103, as shown in fig. 19 (b). The drum projection 56 slidingly contacts the other end of the restraining spring 105 until it is accommodated in the deepest portion of the drum positioning groove 103, as shown in fig. 19 (c).

In operation, when the drum projection 56 is pressed against the restraining spring 105, the resilient end of the restraining spring 105 is temporarily pushed out of the drum positioning groove 103 as shown in fig. 19(b) until the drum projection 56 passes into the drum positioning groove 103. Then, the end of the regulating spring 105 is returned into the drum positioning groove 103 by the elastic force of the regulating spring 105, as shown in fig. 19 (c). At this time, the end of the regulating spring 105 regulates the drum projection 56 being accommodated in the deepest portion of the drum positioning groove 103 so that it cannot be separated from the drum positioning groove 103. This arrangement limits forward rotation of the extension 44. Therefore, once the extension 44 moves from the development accommodating space 16 into the extension accommodating space 018, the extension 44 is reliably positioned and prevented from receding into the development accommodating space 16.

To remove the drum cartridge 31, the user grasps the drum handle 57 and rotates the extension 44 forward. At this time, the drum projection 56 presses against the end of the restricting spring 105, causing the elastic restricting spring 105 to be pushed out from the drum positioning groove 103, as shown in fig. 19 (b). When the drum projection 56 is removed from the drum positioning groove 103, the end of the regulating spring 105 is returned to the drum positioning groove 103 by the elastic force of the regulating spring 105, as shown in fig. 19 (a). Thus, the drum projection 56 can be separated from the drum positioning groove 103.

Further, when the drum shaft 60 is at the tip of the receiving portion 102, and the drum housing 41 is in the inclined position, the holder unit 43 is rearward, and the extension portion 44 is forward (fig. 17 and 19(a)), the bottom end of each side wall 45 is pressed against each contact shaft 112 in the drum shaft locking mechanism 104, as shown in fig. 22. In addition, the pressing cam 107 rotates against the driving force of the driving spring 108 in a direction (clockwise in fig. 22) in which the contact shaft 112 is withdrawn from the assembly path of the drum cartridge 31.

After the extension 44 described above with reference to fig. 18, 19(b), and 19(c) is rotated rearward, the urging force of the urging spring 108 causes the pressing cam 107 to rotate in the direction (counterclockwise in fig. 23) in which the contact shaft 112 is urged into the fitting path of the drum cartridge 31. Therefore, the contact portion 110 advances to close the guide groove 101 and press the drum shaft 60 toward the receiving portion 102, thereby restricting the movement of the drum shaft 60 in the receiving portion 102.

To remove the drum cartridge 31, the user grasps the drum handle 57 and rotates the extension 44 forward. As a result, the bottom end of the side wall 45 presses the contact shaft 112, causing the pressing cam 107 to rotate against the driving force of the drive spring 108 in the direction (clockwise in fig. 22) in which the contact shaft 112 is withdrawn from the assembly path of the drum cartridge 31. Therefore, the contact portion 110 is separated from the drum shaft 60 so that the guide groove 101 is opened, thereby allowing the movement of the drum shaft 60 in the receiving portion 102.

Through the above-described process, the drum cartridge 31 is fitted in the main casing 2 such that the drum cartridge 31 is accommodated in the drum accommodating space 15 of the drum accommodating section 13 having the expanded space 19 and the extended portion 44 is accommodated in the extended accommodating space 18 of the developing accommodating section 14.

In the color laser printer 1 of the present preferred embodiment, the front wall 34 of each scanner housing 35 projects forward from the partition plate 10 toward the development accommodating space 16. Therefore, when the developing cartridge 32 is fitted on the drum cartridge 31, the front wall 34 of the scanner housing 35 restricts the passage of the drum cartridge 31 through the development accommodating portion 14. But when the developing cartridge 32 is separated from the drum cartridge 31, the drum cartridge 31 is allowed to pass through the development accommodating space 16.

By forming the front wall 34 of the scanner housing 35 to expand toward the development accommodating space 16, the drum cartridge 31 can pass through the development accommodating space 16 without interfering with the front wall 34 of the scanner housing 35, and, when separated from the development cartridge 32, the drum cartridge 31 can be fitted in the drum accommodating portion 13 and accommodated within the drum accommodating space 15 without simply allocating an additional space for the fitting path of the drum cartridge 31 and the development cartridge 32. Then, as described below, the developing cartridge 32 can be fitted in the developing accommodating portion 14 and accommodated in the developing accommodating space 16, thereby completing the process of fitting the drum cartridge 31 and the developing cartridge 32.

Specifically, the color laser printer 1 of the present preferred embodiment inserts the drum cartridge 31 separated from the developing cartridge 32 over the front wall 34 of the scanner housing 35 with the developing accommodating space 16 of the developing accommodating portion 14 accommodating the developing cartridge 32 in order to fit the drum cartridge 31 in the drum accommodating portion 13. Therefore, the color laser printer 1 of the present preferred embodiment can reduce the amount of space required for the assembly path of the drum cartridge 31 and the developing cartridge 32, thereby making the entire apparatus more compact.

More specifically, in the color laser printer 1 according to the present preferred embodiment, the developing accommodating section 14 may be formed narrower than the thickness of the drum cartridge 31 and the developing cartridge 32 when the drum cartridge 31 and the developing cartridge 32 are accommodated in the process accommodating section 12. In such a case, only the drum cartridge 31 is first inserted through the development accommodating portion 14 and fitted in the drum accommodating portion 13. Then, the developing cartridge 32 having a thickness smaller than that of the holder unit 43 on the drum cartridge 31 is fitted into the development accommodating portion 14, thereby completing the fitting of the drum cartridge 31 and the developing cartridge 32. Therefore, the space required for the assembly path of the drum cartridge 31 and the developing cartridge 32 can be reduced, so that the entire apparatus can be made more compact.

More specifically, when the drum cartridge 31 and the developing cartridge 32 are fitted in the drum accommodating portion 13 and the developing accommodating portion 14, respectively, the holder unit 43 is disposed in the expanded space 19 of the drum accommodating portion 13. Although the movement of the drum cartridge 31 in the removal direction is restricted when the holder unit 43 is positioned in the expanded space 19, the drum cartridge 31 is allowed to be removed by moving the holder unit 43 from the expanded space 19 in the thickness direction by a distance corresponding to the thickness of the developing cartridge 32. Therefore, after the drum cartridge 31 is inserted through the developing accommodating portion 14, the drum cartridge 31 is fitted in the drum accommodating portion 13 and the holder unit 43 is positioned within the expanded space 19, so that the developing cartridge 32 is fitted in the developing accommodating portion 14. In this way, the space required for assembling and removing the drum cartridge 31 and the developing cartridge 32 can be reduced, thereby making the entire apparatus more compact.

Since the drum cartridge 31 is accommodated in the drum accommodating space 15 of the drum accommodating portion 13 and the developing cartridge 32 is accommodated in the developing accommodating space 16 of the developing accommodating portion 14, the drum cartridge 31 and the developing cartridge 32 can be reliably accommodated in the process accommodating portion 12.

Further, when the drum cartridge 31 is assembled in the color laser printer 1 according to the present preferred embodiment, the extension 44 rotates rearward about the drum shaft 60 while the drum shaft 60 is supported in the receiving portion 102, thereby retracting the extension 44 from the development accommodating space 16 into the extension accommodating space 18 to empty the development accommodating space 16 accommodating the development cartridge 32. Therefore, by a simple operation, after the drum cartridge 31 is fitted in the drum accommodating portion 13, the developing cartridge 32 can be accommodated in the developing accommodating space 16.

In addition to serving as a rotation point, the drum shaft 60 also improves the accuracy of positioning the photosensitive drum 42 while assembling the drum cartridge 31, thereby reducing the number of required parts.

Further, when the drum cartridge 31 is fitted into the drum accommodating portion 13, the restricting spring 105 prevents the drum projection 56 from being separated from the drum positioning groove 103, thereby restricting the extension 44 from rotating forward. This structure reliably holds the drum cartridge 31 in its assembled position, preventing the drum cartridge 31 from obstructing the developing cartridge 32 when the developing cartridge 32 is assembled.

Further, when the drum cartridge 31 is assembled (rotated), the contact portion 110 of the pressing cam 107, which has been withdrawn from the assembly path of the drum cartridge 31 to open the guide groove 101, is driven by the drive spring 105, and when the drum shaft 60 is received in the receiving portion 102, the contact portion 110 of the pressing cam 107 presses the drum shaft 60 into the receiving portion 102, thereby restricting the movement of the drum shaft 60 in the receiving portion 102. Therefore, the drum cartridge 31 can be smoothly fitted into the drum accommodating section 13 without receiving a large resistance from the contact portion 110. As a result, the drum cartridge 31 does not need to have strong rigidity and can therefore be made small. Moreover, this structure achieves reliable assembly of the drum cartridge 31 and reliable positioning of the photosensitive drum 42, since the contact portion 110 presses the drum shaft 60 into the receiving portion 102 when the drum cartridge 31 is assembled.

Further, in the drum shaft locking mechanism 104 having the structure as described above, the bottom end of the side wall 45 is pressed against the contact shaft 112, causing the pressing cam 107 to rotate against the driving force of the drive spring 108. Therefore, the contact portion 110 of the pressing cam 107 is advanced into the guide groove 101, i.e., the moving path of the drum shaft 60 in association with the fitting and removal of the drum cartridge 31, or retracted from the guide groove 101, thereby ensuring that the drum cartridge 31 can be reliably fitted and removed.

Since the drum shaft locking mechanism 104 restricts the movement of the drum shaft 60 when the drum shaft 60 is received in the receiving portion 102, the drum shaft locking mechanism 104 can improve the accuracy of positioning the photosensitive drum 42, thereby reducing the number of required parts.

When the holder unit 43 is accommodated in the drum accommodating space 15 of the drum accommodating portion 13, the ridge 51 passes on the rail portion 17 to a position below the scanner housing 35, as shown in fig. 21. At this time, the top of the charger 62 is disposed below the scanner housing 35, as shown in fig. 18. In addition, the photosensitive drum 42 is in contact with a conveyor belt 80, which will be described later.

Further, when the extension portion 44 is accommodated in the extension accommodating space 18 of the development accommodating portion 14, the extension side portion 52 is in contact with the rail portion 17 of the rail on each lateral side of the scanner housing 35, as shown in fig. 21. This configuration prevents the extension 44 from interfering with the scanner housing 35. Also, by forming the reinforcing rib 55 on the extended side portion 52 to improve the strength of the extended side portion 52, the reinforcing rib 55 can prevent the extended side portion 52 from being deformed due to contact with the rail portion 17. Also, an extended rear wall 53 is provided above the track scanner housing 35, as shown in fig. 18. Providing the drum handle 57 on the extended rear wall 53 facilitates grasping the extended rear wall 53 and improves operability. Although not shown in the drawings, the intermediate plate 54 is disposed opposite the front wall 34 of the scanner housing 35, and the opening 58 of the intermediate plate 54 is positioned opposite the window 40 of the scanner housing 35.

Since the drum cartridge 31 includes the holder unit 43 and the extension 44 as the drum housing 41, the drum cartridge 31 can be increased in size while reducing the overall size of the apparatus because the extension 44 can be accommodated in the extension accommodating space 18 when the drum cartridge 31 is assembled.

Further, the holder unit 43 and the extension portion 44 of the drum case 41 are formed integrally of a synthetic resin material. Further, as described later, by positioning the charger 62 and the photosensitive drum 42 and the metal roller shaft 74 that further receives the developing roller 67 in the developing positioning groove, the drum housing 41 can also position the developing cartridge 32 with reference to the metal roller shaft 74. Since the drum housing 41 can position all of the charger 62, the photosensitive drum 42, and the developing cartridge 32, it is possible to improve the accuracy of positioning these components relative to each other by a simple structure. Further, this configuration can improve the accuracy of positioning the developing roller 67 with respect to the photosensitive drum 42 by positioning the developing cartridge 32 with reference to the metal roller shaft 74 of the developing roller 67. Also, by disposing the charger 62 in the holder unit 43, the size of the entire apparatus can be reduced while holding the charger 62 in place.

Next, the operation of fitting the developing cartridge 32 on the drum cartridge 31 after fitting the drum cartridge 31 on the main casing 2 will be described. As shown in fig. 24, the developing protrusion 71 of the developing cartridge 32 is positioned opposite to the protrusion insertion groove 133. The developing cartridge 32 is pushed down as shown in fig. 25, so that the developing boss 71 is inserted into the boss insertion groove 133. The developing boss 71 is in contact with the boss contact part 121 of the first pressing mechanism 116 that slightly protrudes into the moving path of the developing boss 71. As shown in fig. 26, 28, and 29, the developing protrusion 71 slides on the protrusion contact portion 121 and comes into contact with the protrusion contact claw portion 125 waiting on the moving path of the developing protrusion 71. The developing protrusion 71 presses the protrusion contact claw portion 125 downward in the assembly direction. However, the cam contact portion 127 contacts the contact surface 131 of the cam 120, restricting further rotation of the second pressing member 118. Therefore, further movement of the developing convex portion 71 in the fitting direction is restricted and stopped at the contact position with the convex contact pawl portion 125. As a result, as shown in fig. 26, 28, and 29, the developing cartridge 32 is held in a state of being separated from the drum cartridge 31, in which a slight interval is maintained between the photosensitive drum 42 and the developing roller 67. In this way, the developing cartridge 32 is accommodated in the developing accommodating space 16 of the developing accommodating portion 14 and fitted on the drum cartridge 31, the drum cartridge 31 being previously fitted in the main casing 2.

When the color laser printer 1 of the present preferred embodiment performs the non-image forming operation, the developing cartridge 32 is held in a state of being separated from the drum cartridge 31, whereby the developing roller 67 is separated from the photosensitive drum 42. During the image forming operation, the developing cartridge 32 is in a contact state, at which the developing roller 67 is in contact with the photosensitive drum 42.

Specifically, in the separated state, the contact surface 131 of the cam 120 is in contact with the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118. To switch the separated state to the contact state, the cam 120 is rotated until the separation surface 132 of the cam 120 is opposed to the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118.

To rotate the cam 120, as shown in fig. 32(a) and 32(b), the motor 138 inputs a driving force into the camshaft 130 via the pinion 139 and the gear train composed of the cam drive gear 136 and the intermediate gear 137 to rotate the camshaft 130. By this operation, the cam pair 120 is simultaneously rotated until the separation surface 132 of the cam 120 is positioned opposite to the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118.

The separation surface 132 of the rotating cam 120 opposite to the cam contact part 122 and the cam contact protrusion 127 releases the pressure of the contact surface 131, as shown in fig. 27, 30 and 31. As a result, the first driving spring is retracted due to its own restoring force, and therefore, the first pressing member 116 is driven to rotate about the supporting shaft 123, causing the projection contact part 121 to advance into the moving path of the developer projection part 71. In addition, the second driving spring 119 is expanded by its own restoring force, and drives the second pressing member 118 to rotate about the supporting shaft 123, so that the projection contacting claw portion 125 is moved downward in the assembling direction of the developing projection portion 71 from the initial position of their separated state.

When the first pressing member 116 rotates, the upper pressing surface 134 of the projection contact part 121 comes into contact with the developing projection 71 and presses the developing projection 71 toward the front edge of the projection insertion groove 133 in the assembly direction of the developing projection 71. When the second pressing member 118 rotates, the projection contact pawl portion 125 moves downward in the fitting direction of the developing projection 71. The lower side pressing surface 135 of the projection contacting claw 125 is contacted by the developing boss 71 pressed by the upper pressing surface 134, and the second drive spring 119 elastically receives the developing boss 71.

Since the spring constant of the second drive spring 119 is set smaller than that of the first drive spring 117, the pressing force of the upper pressing surface 134 causes the developing boss 71 to move downward in the fitting direction from its initial position in the detached state, and the lower pressing surface 135 receives the developing boss 71, as shown in fig. 30 and 31. When the developing projection 71 moves downward in the fitting direction, the developing roller 67 and the photosensitive drum 42 are brought into contact, and therefore, the photosensitive drum 42 and the developing roller 67 are brought into a contact state.

In the contact state, the developing protrusion 71 is brought into contact with the front edge of the protrusion insertion groove 133 by the pressure of the upper pressing surface 134. In addition, the first and second driving springs 117 and 119 drive the first and second pressing members 116 and 118, respectively, such that a space is formed between the separation surface 132 of the cam 120 and the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118.

Next, a process of switching from the contact state back to the separated state will be described. In the contact state, the separation surface 132 of the cam 120 is opposed to the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118 with a space formed therebetween. As previously described, the cam 120 rotates until the contact surface 131 of the cam 120 is brought into contact with the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118.

When the contact surface 131 is rotated to be opposed to the cam contact portion 122 and the cam contact protrusion 127, as shown in fig. 26, the contact surface 131 of the cam 120 is brought into contact with the cam contact portion 122 of the first pressing member 116 and the cam contact protrusion 127 of the second pressing member 118, and pushes down the first pressing member 116 and the second pressing member 118. As a result, the first pressing member 116 rotates about the supporting shaft 123 against the driving force of the first driving spring 117, and stretches the first driving spring 117, causing the projection contact part 121 to retreat from the moving path of the developing projection 71. Further, the second presser member 118 is rotated about the support shaft 123 by a pressing force larger than the driving force of the second drive spring 119, compressing the second drive spring 119 so that the projection contact pawl 125 is moved to the upstream side with respect to the fitting direction of the developing convex portion 71.

By the rotation of the first pressing member 116, the upper pressing surface 134 of the boss contact part 121 is separated from the developing boss 71, and the boss contact part 121 is retracted to a position protruding only slightly into the moving path of the developing boss 71. By rotating the second pressing member 118, the projection contact pawl 125 is moved to the upstream side with respect to the fitting direction of the developing protrusion 71, and thus the lower side pressing surface 135 of the projection contact pawl 125 presses the developing protrusion 71 in the removing direction, thereby separating the developing roller 67 from the photosensitive drum 42, and thus the photosensitive drum 42 and the developing roller 67 are in the separated state. Since the projection contact part 121 is withdrawn from the moving path of the developing projection 71 and projects only slightly into the path in this separated state, the developing cartridge 32 can be removed from the developing accommodating part 14.

In the contact/separation mechanism 106 of the color laser printer 1 as described above, the projection contact portion 121 is withdrawn from the moving path of the developing projection 71 in the separated state. Therefore, the developing protrusion 71 can move along the moving path without interfering with the protrusion contact part 121, so that the developing cartridge 32 can be assembled and removed.

Since the boss contact part 121 of the first pressing member 116 advances into the moving path of the developing protrusion 71 at the time of the contact state, the boss contact part 121 can be reliably pressed toward the developing protrusion 71 in the fitting direction. As a result, the moving path of the developing protrusion 71 can be formed into a substantially straight effective protrusion insertion groove 133 despite the provision of the protrusion contact portion 121. Also, the boss contact portion 121 can reliably press the developing protrusion 71 in the fitting direction.

By forming the projection insertion groove 133 to be substantially straight, the entire apparatus can be made compact. In addition, the workability of assembling and removing the developing cartridge 32 is improved.

In the separated state, the projection contact part 121 is moved in the direction of withdrawal, but still projects slightly into the moving path of the developing projection part 71, the extent of projection being within a range that allows the mounting and removal of the developing cartridge 32. Therefore, when the developing cartridge 32 is assembled or removed, the projection contact part 121 and the developing projection 71 are elastically contacted to such an extent that the movement of the developing projection 71 is not hindered. This contact provides a clicking feeling to the operator when the developing cartridge 32 is mounted and removed, which ensures that the operator does not leave the developing cartridge 32 midway along the mounting or removing path.

In the contact state where the projection contact portion 121 advances into the moving path of the developing projection 71, if the operator grasps the developing handle 72 and pulls the developing cartridge 32 from the developing accommodating portion 14 with a force greater than or equal to the prescribed pulling force, this force pushes the projection contact portion 121 in the withdrawal direction against the driving force of the first driving spring 117. Therefore, if a power failure or another unforeseen event occurs, the developing cartridge 32 can be forcibly removed without damaging the first pressing member 116.

During the contact state, the upper pressing surface 134 of the projection contact part 121 presses the developing projection 71 toward the front edge of the projection insertion groove 133 in the assembly direction of the developing projection 71. Therefore, the developing protrusion 71 is in contact with the front edge of the protrusion insertion groove 133, ensuring accurate positioning of the developing cartridge 32 in the contact state.

In the separated state, the lower side pressing surface 135 of the projection contact pawl 125 reliably presses the developing protrusion 71 in the removing direction. Therefore, in the non-image forming operation, the developing cartridge 32 can be withdrawn to the upstream side in the fitting direction.

Further, in the middle of the process of assembling the developing cartridge 32, the projection contact claw portion 125 of the second pressing member 118 and the developing projection portion 71 are in contact. Therefore, if strongly assembled, the contact with the projection contact claw portion 125 can moderate the force of assembling the developing cartridge 32. Therefore, this structure can prevent the developing cartridge 32 and the drum cartridge 31 from being damaged.

Further, the projection contact claw portion 125 is provided on the moving path of the developing convex portion 71 on the downstream side of the projection contact portion 121 with respect to the fitting direction of the developing convex portion 71. Therefore, in the contact state, the developing convex portion 71 between the convex contact portion 121 and the convex contact pawl portion 125 is simultaneously subjected to the pressing forces of the convex contact portion 121 in the fitting direction and the convex contact pawl portion 125 in the removing direction. Therefore, the pressing force on the developing boss 71 in the assembling direction of the developing cartridge 32 can be regulated, and thus, the correct assembly of the developing cartridge 32 is ensured.

More specifically, in the contact/separation mechanism 106, in the contact state, the separation surface 132 of the cam 120 is not in contact with the cam contact portion 122 and the cam contact protrusion 127. Therefore, the entire driving force of the first driving spring 117 can be applied to the cam contact portion 122, and the pressing force applied to the developing protrusion 71 in the fitting direction can be adjusted based on the spring constant preset to the first driving spring 117. Also, the entire driving force of the second driving spring 119 can be applied to the projection contact pawl portion 125, and the pressing force acting on the developing projection 71 in the removing direction can be adjusted based on a spring constant preset to the second driving spring 119. Therefore, the convex contact portion 121 is reliably pressed against the developing cartridge 32 in the fitting direction by the preset pressure generated by the first drive spring 117, and the convex contact pawl portion 125 is reliably pressed against the developing cartridge 32 in the removing direction by the preset pressure generated by the second drive spring 119.

As a result, since the spring constant of the second drive spring 119 is set smaller than that of the first drive spring 117, in the contact state, the developing convex portion 71 can be held between the convex contact portion 121 and the convex contact claw portion 125 with a stable and light pressing force exerted on the developing cartridge 32 in the fitting direction, thereby ensuring that the developing cartridge 32 is in a proper fitting state.

More specifically, during the image forming operation, the separation surface 132 of the cam 120 is opposed to, but not in contact with, the cam contact portion 122 and the cam contact protrusion 127. At this time, the driving force of the first driving spring 117 urges the projection contact portion 121 into the fitting and removing path, so that the projection contact portion 121 presses the development convex portion 71, and at the same time, the projection contact claw portion 125 pressing the development convex portion 71 in the removing direction by the driving force of the second driving spring 119 elastically receives the development convex portion 71 pressed by the projection contact portion 121. With this structure, the driving forces of the first and second driving springs 117 and 119 cause the developing roller 67 and the photosensitive drum 42 to contact each other with a stable pressure.

In the non-image forming operation, the contact surface 131 of the cam 120 is opposed to the cam contact portion 122 and the cam contact protrusion 127, and presses down the first pressing member 116 and the second pressing member 118. At this time, the projection contact portion 121 is withdrawn from the fitting and removing path against the driving force of the first drive spring 117, and thus is separated from the developing projection 71, while the projection contact claw portion 125 is pressed in the removing direction toward the developing projection 71 with a pressure greater than the driving force of the second drive spring 119, thereby facilitating the removal of the developing cartridge 32.

Therefore, by rotating the cam 120, the separation surface 132 and the contact surface 131 can be selectively positioned at positions opposite to the cam contact portion 122 and the cam contact protrusion 127. By so doing, it is possible to correctly advance and retract the projection contact portion 121 and the projection contact pawl portion 125 on the moving path of the developing protrusion 71, thereby stabilizing and regulating the pressing force on the developing protrusion 71 in the assembling direction, facilitating the removal of the developing cartridge 32.

In this way, the developing roller 67 and the photosensitive drum 42 can be kept in contact during the image forming operation and kept separated during the non-image forming operation. Since the developing roller 67 and the photosensitive drum 42 are kept in contact only when necessary, the life of these components can be extended.

In the contact/separation mechanism 106, both the first pressing member 116 and the second pressing member 118 are rotatably supported on the support shaft 123, thereby simplifying the structure and reducing the number of required parts.

Further, the support shaft 123 is provided downstream of the position where the developing boss 71 is pressed in the assembly direction from the boss contact portion 121 to the developing boss 71 in the assembly direction. This structure reduces the amount of rotation of the first presser member 116, enabling the entire apparatus to be more compact.

Further, the convex contact portion 121 of the first pressing member 116 is formed to project laterally inward, and the convex contact claw portion 125 of the second pressing member 118 is formed to project laterally outward, so that the upper pressing surface 134 of the convex contact portion 121 and the lower pressing surface 135 of the convex contact claw portion 125 overlap along the moving path of the developing convex portion 71. With this structure, the positions where the upper pressing surface 134 and the lower pressing surface 135 press against the developing protrusion 71 overlap in the moving direction of the developing protrusion 71, thereby ensuring the pressure applied to the developing protrusion 71 by the protrusion contacting portion 121 and the protrusion contacting claw portion 125 to be stable.

When the motor 138 inputs a driving force to the gear train constituted by the cam drive gear 136 and the intermediate gear 137, the pair of cams 120 are simultaneously rotated in the contact/separation mechanism 106. Therefore, the plurality of paired cams 120 corresponding to the plurality of paired first pressing members 116 and the paired second pressing members 118 can be reliably rotated by a simple structure. As a result, the plurality of developing cartridges 32 can be reliably assembled and removed by the proper operation of the first and second pressing members 116 and 118.

Also, as described above, in fig. 8, the slide guide 70 is shown to protrude forward and downward by a larger extent than the jaw portion 69. Therefore, when the developing cartridge 32 is fitted in the developing accommodating portion 14, the slide guide 70 protrudes downward deeper than the jaw portion 69 closer to the rear surface 33 of the partition wall 10 in the fitting direction of the developing cartridge 32. Therefore, the slide guide 70 of the developing casing 64 is in contact with the rear surface 33 of the partition plate 10, and slides along the rear surface 33 when the developing cartridge 32 is assembled. This prevents the jaw portion 69 from contacting the rear surface 33 of the partition plate 10. This structure can prevent damage to the jaw portion 69, and can reliably prevent toner leakage from the outer peripheral surface of the developing roller 67.

When the developing cartridge 32 is fitted on the drum cartridge 31 in the developing accommodating portion 14 such that the developing cartridge 32 can be selectively switched between the separated state and the contact state, in order to determine the position of the developing cartridge 32 with respect to the drum cartridge 31, the metal roller shaft 74 of the developing roller 67 is fitted into the developing positioning groove 48 of the drum housing 41. Further, by the contact projection 91 on the bottom surface of the developing casing 64 being in contact with the rear surface 33 of the partition plate 10, the position of the developing cartridge 32 relative to the developing accommodating portion 14 is determined, as shown in fig. 24, 25, 26 and 27. Specifically, in the color laser printer 1 according to the present preferred embodiment, the drum housing 41 of the drum cartridge 31 is positioned on the rear side by inserting the drum projection 56 into the deepest part of the drum positioning groove 103 and preventing the drum projection 56 from being separated from the drum positioning groove 103 with the restricting spring 105, and at the same time, the developing housing 64 of the developing cartridge 32 is positioned on the front side by bringing the contact projection 91 on the bottom surface of the developing housing 64 into contact with the rear surface 33 of the partition plate 10. In this way, the drum cartridge 31 and the developing cartridge 32 are positioned on both sides opposite to each other in the front-rear direction, and an error is less likely to occur when one of the drum cartridge 31 and the developing cartridge 32 is used to position the other. Therefore, this structure enables more accurate positioning of the drum cartridge 31 and the developing cartridge 32.

In the color laser printer 1 of the present preferred embodiment, since the drum cartridge 31 equipped with the photosensitive drum 42 and the developing cartridge 32 equipped with the toner containing chamber 65 can be individually assembled and removed with respect to the color laser printer 1, the drum cartridge 31 and the developing cartridge 32 can be individually replaced according to the life of the photosensitive drum 42 and the toner containing chamber 65, respectively.

When the drum cartridge 31 is fitted in the drum accommodating portion 13, the photosensitive drum 42 is grounded through connection with a contact point (not shown in the drawing). During an image forming operation, a charging bias is applied to the charger 62. Further, in the image forming operation, the motor 138 inputs a driving force that rotates the photosensitive drum 42 through engagement of gears (not shown in the drawings).

Connection with a contact point (not shown in the drawing) is made when the developing cartridge 32 is fitted in the developing accommodating portion 14, so that a developing bias can be applied to the metal roller shaft 74 of the developing roller 67 during an image forming operation. During an image forming operation, the motor 138 inputs a driving force through a coupling (not shown) to rotate the agitator 73, the supply roller 66 and the developing roller 67.

During the image forming operation, the toner stirrers 73 of each color accommodated in the toner accommodating chambers 65 of the respective process sections 27 shown in fig. 1 are stirred and supplied to the supply roller 66. When rotated, the supply roller 66 supplies toner to the developing roller 67, and at this time, the toner is positively charged by friction between the supply roller 66 and the developing roller 67 to which a developing bias is applied.

When the developing roller 67 rotates, the toner supplied onto the surface of the developing roller 67 passes between the developing roller 67 and the layer thickness regulating blade 68, and thus the layer thickness regulating blade 68 regulates 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, applying a uniform positive charge to the surface of the photosensitive drum 42. When the photosensitive drum 42 rotates, the surface of the photosensitive drum 42 is exposed under high-speed scanning by the laser beam emitted by the scanning unit 30. The scanner unit 30 forms an electrostatic latent image on the surface of the photosensitive drum 42 corresponding to an image formed on the sheet 3.

When 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 onto the latent image on the surface of the photosensitive drum 42, that is, the exposed portion on the surface of the photosensitive drum 42 which has been exposed to the laser beam and thus has a lower potential than other portions on the positively charged surface. In this way, the electrostatic latent image is developed into a visible toner image by the process of reversal development, and the toner image of each color is carried on the surface of the photosensitive drum 42.

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-rear direction below the process accommodating section 12. The transfer section 28 includes a driving roller 78, a driven roller 79, a conveying belt 80, and a transfer roller 81. The driving roller 78 is disposed at a position further forward than the process accommodating section 12 accommodating the yellow process section 27Y. The driven roller 79 is provided at a position further rearward than the process accommodating portion 12 accommodating the black process portion 27K.

The conveyor belt 80 is an endless belt composed of a synthetic resin such as conductive polycarbonate or polyimide containing dispersed charged particles such as carbon. The conveyor belt 80 circulates around the drive roller 78 and the driven roller 79. When the drive roller 78 is driven, the driven roller 79 rotates with the rotation of the drive roller 78, and at the same time, the conveyor belt 80 circulates between the drive roller 78 and the driven roller 79. The belt 80 is opposed to and brought into contact with the photosensitive drum 42 in each process portion 27 at the image forming position, and moves in the same direction as the surface of the photosensitive drum 42 at the point of contact.

The transfer roller 81 is disposed inside the conveying belt 80 at a position opposed to each photosensitive drum 42 with the conveying belt 80 interposed therebetween. The transfer roller 81 is constituted by a metal roller shaft covered with a roller body portion formed of an elastic material such as a conductive rubber material. The transfer roller 81 is rotatably disposed so that the surface of the transfer roller 81 moves in the same direction as the conveying belt 80 at the image forming position. At the time of transfer operation, a transfer bias is applied to the transfer roller 81.

As described above, when the driving roller 78 is driven and the driven roller 79 is driven, the conveying belt 80 circulates around the driving roller 78 and the driven roller 79. When the sheet 3 is supplied from the feeding unit 4, the conveyor belt 80 sequentially conveys the sheet 3 in a backward direction through each image forming position between the conveyor belt 80 and the photosensitive drum 42 of the processing portion 27. When the sheet 3 is conveyed by the conveyor belt 80, the toner image carried on the photosensitive drum 42 of each process section 27 is sequentially transferred onto the sheet 3, thereby forming a color image on the sheet 3.

Specifically, the yellow toner image carried on the surface of the photosensitive drum 42 in the yellow process section 27Y is first 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 to 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-green process section 27C and the black toner image carried on the surface of the photosensitive drum 42 in the black process section 27K, thereby forming a color image of a plurality of colors on the sheet 3.

In order to form a multicolor image in this manner, the color laser printer 1 is constituted as a tandem type apparatus in which a set of a drum cartridge 31 and a developing cartridge 32 is provided in each process section 27, one set for each color. Therefore, the color laser printer 1 of the present preferred embodiment forms the toner images of each color at substantially the same speed as that required for forming a monochrome image, thereby obtaining a color image at high speed. Therefore, the color laser printer 1 of the present preferred embodiment can form a color image while keeping the structure compact.

The fixing portion 29 is provided at a position behind the process accommodating portion 12 accommodating the black process portion 27K in the main casing 2 and aligned with an image forming position at a contact point between the photosensitive drum 42 and the conveyor belt 80 in the front-rear direction. The fixing section 29 includes a heating roller 82 and a pressure roller 83.

The heating roller 82 is composed of a metal pipe, and a release layer is coated on the surface thereof. The metal pipe accommodates a halogen lamp extending along the axis of the heating roller 82. The halogen lamp heats the surface of the heating roller 82 to a fixing temperature. The pressure roller 83 is disposed to face the heating roller 82 to apply pressure.

After the toner image is transferred to the sheet 3, the sheet 3 is conveyed to the fixing section 29. The fixing section 29 fixes the color image onto the sheet 3 with heat when the sheet 3 passes between the heating roller 82 and the pressing roller 83.

The discharge unit 6 includes a U-shaped discharge path 84, a discharge roller 85, and a discharge tray 86.

The discharge path 84 has a curved U-shape and functions as a path for conveying the sheet 3. The upstream end of the discharge path 84 is a lower portion of the discharge path 84 and is positioned adjacent to the fixing portion 29 for feeding the sheet 3 in the backward direction, and the downstream end of the discharge path 84 is an upper portion and is positioned adjacent to the discharge tray 86 for discharging the sheet 3 forward.

The discharge rollers 85 are a pair of rollers provided near the downstream end of the discharge path 84. The drain pan 86 is a surface formed at the top of the main casing 2 and inclined downward from the front side to the rear side.

After the multicolor image is fixed on the sheet 3 at the fixing section 29, the sheet 3 is conveyed to the upstream end of the discharge path 84 in the backward direction. The U-shaped discharge path 84 reverses the conveying direction of the sheet 3, and the discharge roller 85 discharges the sheet 3 forward onto the discharge tray 86.

In the color laser printer 1 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 through the image forming position is opposite to the forward direction in which the sheet 3 is discharged by the discharge rollers 85. This structure makes the apparatus compact while providing a transport path for the sheet 3.

In the color laser printer 1 of the above preferred embodiment, the drum cartridge 31 and the developing cartridge 32 are fitted in the drum accommodating portion 13 and the developing accommodating portion 14 of each process accommodating portion 12 obliquely with respect to the front-rear direction and the vertical direction (the thickness direction of the paper 3). More specifically, the drum cartridge 31 and the developing cartridge 32 are mounted in a direction inclined rearward from the top to the bottom. This structure can improve the workability of assembling and removing the drum cartridge 31 and the developing cartridge 32.

In the color laser printer 1 of the preferred embodiment described above, the plural sets of the drum cartridges 31 and the developing cartridges 32 are alternately arranged with the plural scanner units 30 in the front-rear direction, so that an efficient arrangement is achieved that can produce a more compact apparatus.

In the color laser printer 1 of the preferred embodiment described above, the extension 44 of the drum housing 41 on the drum cartridge 31 is inserted between the scanner unit 30 and the developing cartridge 32 of each process accommodating section 12. However, an opening 58 is formed on the intermediate plate 54 of the extension 44 to allow the laser beam emitted by the scanner unit 30 toward the photosensitive drum 42 to pass therethrough. Therefore, efficient structural arrangement can be ensured by inserting the extension portion 44 between the scanner unit 30 and the developing cartridge 32, while the opening 58 formed on the extension portion 44 can ensure reliable passage of the laser beam emitted from the scanner unit 30 toward the photosensitive drum 42.

As described above, according to the present embodiment, the drum cartridge 31 is formed thicker than the developing cartridge 32 in the thickness direction orthogonal to the fitting direction of the first and second cartridges. That is, the thickness of the drum cartridge 31 is defined in the up-down direction of the drum cartridge 31 (fig. 2). Since the holder unit 43 is formed thicker than the extension portion 44 in the up-down direction (thickness direction), the thickness of the drum cartridge 31 is determined according to the thickness of the holder unit 43. The thickness of the developing cartridge 32 is defined in the up-down direction of the developing cartridge 32 (fig. 8). The thickness of the drum cartridge 31 is larger than that of the developing cartridge 32. The drum cartridge 31 is fitted in the process accommodating portion 12 in an orientation in which the front-rear direction (fig. 2) of the drum cartridge 31 is along the fitting direction, and the front side (fig. 2) of the drum cartridge 31 is on the downstream side in the fitting direction with respect to the rear side (fig. 2) of the drum cartridge 31. Similarly, the developing cartridge 32 is mounted in the process accommodating portion 12 in such an orientation that the front-rear direction (fig. 2) of the developing cartridge 32 is along the mounting direction, and the front side (fig. 8) of the developing cartridge 32 is on the downstream side in the mounting direction with respect to the rear side (fig. 8) of the developing cartridge 32. In the process accommodating portion 12, the drum accommodating portion 13 and the developing accommodating portion 14 are continuously provided in the fitting direction of the drum cartridge 31 and the developing cartridge 32, and are partially displaced from each other in the thickness direction orthogonal to the fitting direction. The developing accommodating portion 14 is provided upstream of the drum accommodating portion 13 with respect to the fitting direction of the drum cartridge 31 and the developing cartridge 32, is formed thicker than the drum cartridge 31 in the thickness direction, and is thinner than the thickness of the drum cartridge 31 and the developing cartridge 32 added together when the drum cartridge 31 and the developing cartridge 32 are accommodated together in the process accommodating portion 12. The drum accommodating portion 13 is formed thicker in the thickness direction than the thickness of the drum cartridge 31 and the developing cartridge 32 added together when the drum cartridge 31 and the developing cartridge 32 are accommodated together in the process accommodating portion 12.

With this structure, even if the thickness of the drum cartridge 31 and the developing cartridge 32 added together is thinner than the thickness of the drum cartridge 31 and the developing cartridge 32 when the developing accommodating portion 14 is accommodated in the process accommodating portion 12 together with the drum cartridge 31 and the developing cartridge 32, the drum cartridge 31 is first fitted into the drum accommodating portion 13 wider than the thickness of the drum cartridge 31 and the developing cartridge 32 added together when the drum cartridge 31 and the developing cartridge 32 are accommodated in the process accommodating portion 12 by inserting only the drum cartridge 31 through the developing accommodating portion 14 wider than the thickness of the drum cartridge 31, and then the developing cartridge 32 thinner than the drum cartridge 31 is fitted into the developing accommodating portion 14, the drum cartridge 31 and the developing cartridge 32 can be fitted into the process accommodating portion 12. Therefore, this structural arrangement can reduce the space required for the assembly path of the drum cartridge 31 and the developing cartridge 32, enabling the apparatus to be more compact.

That is, the drum accommodating portion 13 is formed to be wider than the developing accommodating portion 14 in the thickness direction orthogonal to the fitting direction of the drum cartridge 31 and the developing cartridge 32. The drum accommodating portion 13 has an expanded area 19 so that the drum accommodating portion 13 is wider than the developing accommodating portion 14. When the drum cartridge 31 is fitted in the drum accommodating portion 13, the drum cartridge 31 has a protruding portion 43 provided in the expanded area 19. The process accommodating portion 12 has a shape that restricts the movement of the drum cartridge 31 in the fitting direction when the protruding portion 43 is located in the expanded region 19, but allows the movement of the drum cartridge 31 in the fitting direction when the protruding portion 43 is moved from the expanded region 19 in the thickness direction by a distance equal to the thickness of the developing cartridge 32.

With this structure, when the protruding portion 43 is provided on the expanded area 19, the movement of the drum cartridge 31 in the mounting direction in the process accommodating portion 12 is restricted, and when the protruding portion 43 moves in the thickness direction from the expanded area 19 by a distance equal to the thickness of the developing cartridge 32, the above-described movement of the drum cartridge 31 is permitted. Therefore, the drum cartridge 31 can be fitted on the drum accommodating portion 13 by first inserting the drum cartridge 31 through the development accommodating portion 14 and then positioning the protruding portion 43 on the expanded area 19. Then, the developing cartridge 32 may be fitted into the developing accommodating portion 14. Such a structure can reduce the space required for the assembly path of the drum cartridge 31 and the developing cartridge 32, enabling the entire apparatus to be more compact.

According to the present embodiment, the drum accommodating portion 13 defines the drum accommodating area 15 accommodating the drum cartridge 31. The development accommodating portion 14 defines a development accommodating area 16 that allows the drum cartridge 31 to pass therethrough and accommodates the developing cartridge 32 therein when the drum cartridge 31 is fitted to or removed from the drum accommodating portion 13. The enlarged portion 35 expands toward the development accommodating area 16 to restrict passage of the drum cartridge 31 in the development accommodating area 16 when the drum cartridge 31 carries the developing cartridge 32, and to allow passage of the drum cartridge 31 through the development accommodating area 16 of the development accommodating portion 14 when the drum cartridge 31 does not carry the developing cartridge 3121.

By forming the enlarged portion 35 toward the development accommodating area 16 in this way, both the drum cartridge 31 and the development cartridge 32 can be fitted in the process accommodating portion 12 without simply allocating an additional space for the fitting path of the drum cartridge 31 and the development cartridge 32. This process may be done by first passing only the drum cartridge 31 through the development accommodating area 16 of the development accommodating portion 14 without interference from the enlarging portion 35, then fitting the drum cartridge 31 in the drum accommodating portion 13 to accommodate the drum cartridge 31 in the drum accommodating area 15, and then fitting the development cartridge 32 in the development accommodating portion 14 to accommodate it in the development accommodating area 16. In particular, this structure allows the drum cartridge 31 without the developing cartridge 32 to pass through the development accommodating portion 14 while avoiding the enlarged portion 35 with the development accommodating area 16 to be accommodated with the developing cartridge 32. Therefore, the space required for the assembly paths for the drum cartridge 31 and the developing cartridge 32 can be reduced, enabling the entire apparatus to be more compact.

In the drum shaft locking mechanism 104 described in fig. 22 and 23 above, the contact shaft 112 is provided on the pressing cam 107. By bringing the contact shaft 112 into contact with the bottom end of the side wall 45, the pressing cam 107 can be rotated against the driving force of the driving spring 108. However, as shown in fig. 33(a), the contact shaft 112 may be replaced by a fitting member 113 that can be engaged with or disengaged from the metal roller shaft 74 of the developing roller 67.

In fig. 33(a), parts and elements similar to those of fig. 22 and 23 are denoted by the same reference numerals to avoid repetitive description. As shown in fig. 33, the fitting member 113 is a plate having a substantially U-shape. When the drum cartridge 31 is fitted to the drum accommodating portion 13 and the developing cartridge 32 is fitted to the drum cartridge 31 in the developing accommodating portion 14 or removed from the drum cartridge 31, the fitting member 113 is engaged with or disengaged from the metal roller shaft 74 of the developing roller 67. The engaging member 113 is rotatably supported on a rotating shaft 114 that protrudes outward in the width direction from the outer surfaces of the left and right side plates 8, 9. With such a structure, the fitting member 113 can be rotated forward or reversely when the metal roller shaft 74 is fitted or removed.

The upper edge of the front side of the pressing cam 107 contacts the engaging member 113. The driving force of the driving spring 108 constantly drives the pressing cam 107 to rotate the pressing cam 107 in a direction (counterclockwise in fig. 33 (a)) in which the contact portion 110 pushes the drum shaft 60 into the receiving portion 102 and the upper edge of the pressing cam 107 pushes the fitting member 113 into the fitting path (removing path of the metal roller shaft 74) of the developing cartridge 32 to engage with the metal roller shaft 74, as shown in fig. 33 (b).

Fig. 33(a) shows the developing cartridge 32 in a removed state. When the developing cartridge 32 is switched to this state, the metal roller shaft 74 is retracted, so that the engaging member 113 is rotated against the driving force of the driving spring 108 to be retracted from the moving path of the metal roller shaft 74. In fig. 33(a), the engaging member 113 is held in the withdrawn state.

Fig. 33(b) shows the developing cartridge 32 in an assembled state. Here, the metal roller shaft 74 engages with the fitting member 113, rotating the fitting member 113 (counterclockwise in fig. 33 (b)) into the fitting path of the developing cartridge 32. At this time, the urging force of the urging spring 108 rotates the pressing cam 107 to cause the contact portion 110 to close the guide groove 101 and press the drum shaft 60 into the receiving portion 102, thereby restricting the movement of the drum shaft 60 in the receiving portion 102.

In the drum shaft locking mechanism 104 shown in fig. 33(a) and 33(b), the contact portion 110 of the pressing cam 107 enters and exits forward the guide groove 101, i.e., enters and exits forward and backward, and the assembly and removal of the developing cartridge 32 are associated with the moving path of the drum shaft 60. This structure thus ensures reliable assembly and removal of the drum cartridge 31.

In the contact/separation mechanism 106 described above, the second drive spring 119 is provided on the second pressing member 118. However, the second pressing member 118 may be configured as shown in fig. 34. In this structure, the second presser member 118 is rotatably supported on the support shaft 123 and has a center of gravity that ensures that the rotation restricting pawl 126 is always lowered and the cam contact projection 127 is always raised. This structure does not require the second drive spring 119.

Although the present invention has been described in detail with reference to the specific embodiments, it is apparent to those skilled in the art that various changes or modifications can be made therein without departing from the spirit of the present invention.

For example, although the preferred embodiment describes the tandem type color laser printer 1 that transfers an image directly from the photosensitive drum 42 to the paper 3, the present invention is not limited to this type of apparatus. For example, the present invention can be applied to an intermediate transfer type color laser printer that temporarily transfers toner images of respective colors from a photosensitive member onto an intermediate transfer member and then transfers the entire multicolor image onto a sheet. The invention can also be used in monochrome printers.

Claims (32)

1. An image forming apparatus, characterized by comprising:

a housing; and

a first cartridge and a second cartridge detachably fitted in the housing and having a process member used during an image forming process, the first cartridge being formed thicker than the second cartridge in a thickness direction perpendicular to a fitting direction of the first and second cartridges,

the casing has a cartridge accommodating portion accommodating therein the first and second cartridges,

the cartridge accommodating section includes first and second accommodating sections which are provided continuously in a fitting direction of the first and second cartridges and are partially displaced from each other in a thickness direction,

the first containing portion defines a first containing area in which the first cartridge is contained, and the second containing portion defines a second containing area in which the second cartridge is contained, the second containing portion being provided upstream of the first containing portion with respect to a fitting direction of the first and second cartridges, and being formed thicker than the first cartridge in a thickness direction, thinner than the first and second cartridges together when the first and second cartridges are contained in the cartridge containing portion,

the first containing portion is formed thicker in the thickness direction than the first and second cartridges together when the first and second cartridges are contained in the cartridge containing portion.

2. An image forming apparatus, characterized by comprising:

a housing; and

a first cartridge and a second cartridge detachably fitted in the housing and having a process member used in an image forming process,

the casing has a cartridge accommodating portion accommodating therein the first and second cartridges,

wherein the cartridge accommodating section includes first and second accommodating sections which are provided continuously in a fitting direction of the first and second cartridges and are partially displaced from each other in a thickness direction perpendicular to the fitting direction of the first and second cartridges,

the first housing portion defines a first housing area in which the first cartridge is housed, and the second housing portion defines a second housing area in which the second cartridge is housed, the first housing portion being disposed downstream of the second housing portion with respect to a fitting direction of the first and second cartridges, and being formed wider than the second housing portion in a thickness direction perpendicular to the fitting direction of the first and second cartridges,

the first receiving portion has an expanded area such that the first receiving portion is wider than the second receiving portion,

the first cartridge has a projection portion disposed in the expanded area when the first cartridge is fitted in the first accommodation portion,

the cartridge accommodating portion has a shape that restricts movement of the first cartridge in the fitting direction when the protrusion is positioned in the expanded region, but allows movement of the first cartridge in the fitting direction when the protrusion is moved away from the expanded region in the thickness direction by a distance equal to the thickness of the second cartridge.

3. The image forming apparatus as claimed in claim 2, wherein the housing has a guide portion that guides the first cartridge when the first cartridge is fitted in the cartridge accommodating portion,

wherein the guide portion includes:

an upstream guide portion extending in the first direction and guiding the first cartridge through the second accommodating portion; and

the first cartridge is mounted in the first housing portion so as to be extended in a second direction different from the first direction and guided, thereby allowing the protrusion to enter the downstream guide portion of the expansion region after the first cartridge passes through the second housing portion.

4. An image forming apparatus, characterized by comprising:

a housing; and

a first cartridge and a second cartridge detachably fitted in the housing and equipped with a process member used in an image forming process,

the housing includes:

a first accommodating portion defining a first accommodating area in which the first cartridge is accommodated;

a second accommodating section provided upstream of the first accommodating section with respect to an assembling direction in which the first cartridge is assembled, the second accommodating section defining a second accommodating area that allows the first cartridge to pass therethrough and accommodates the second cartridge therein when the first cartridge is assembled in or removed from the first accommodating section; and

and an enlarged portion enlarged toward the second receiving region, the enlarged portion preventing the first cartridge from passing through the second receiving portion when the second cartridge is brought together with the first cartridge, and allowing the first cartridge to pass through the second receiving region of the second receiving portion when the second cartridge is not brought together with the first cartridge.

5. The imaging apparatus of claim 4,

wherein the first cartridge has a first housing,

the first housing includes:

a main body accommodated in the first accommodation region of the first accommodation portion after passing through the second accommodation region of the second accommodation portion when the first cartridge is not carried with the second cartridge; and

an extension part extending to the second accommodating part when the first cartridge is fitted in the first accommodating part,

wherein the second receiving portion has an extension receiving area receiving the extension.

6. The imaging apparatus of claim 5, wherein said main body and extension are integrally formed with one another.

7. The imaging apparatus of claim 5,

wherein the first housing has a rotation support portion provided on a main body rotatably supported in the first accommodation portion,

the first cartridge is fitted in the first housing portion by supporting the rotation support portion in the first housing portion and rotating the first cartridge about the rotation support portion, and the extension portion is retracted from the second housing region toward the extension portion housing region to allow the second cartridge to be housed in the second housing region of the second housing portion.

8. The image forming apparatus as claimed in claim 7, further comprising a rotation restricting portion which restricts rotation of the first cartridge when the first cartridge is fitted in the first accommodating portion.

9. The imaging apparatus of claim 5,

wherein the housing further has:

a first positioning portion located on a side of the second housing portion where the enlarged portion is provided, the first positioning portion positioning the first cartridge by contacting the extended portion; and

and a second positioning portion located on a side of the second accommodating portion opposite to the side where the enlarged portion is provided, the second positioning portion positioning the second cartridge by contacting the second cartridge.

10. The imaging apparatus of claim 5,

wherein the first housing has a protrusion formed on a side facing the enlarged portion and protruding toward the enlarged portion to prevent the first housing from sliding against the enlarged portion when the first cartridge is fitted in the first accommodation portion.

11. The image forming apparatus as claimed in claim 5, wherein the process member includes a charger provided on the main body of the first housing.

12. The image forming apparatus as claimed in claim 11, wherein the projection is provided on the main body of the first housing on a downstream side of the charger in the first cartridge mounting direction.

13. The imaging apparatus of claim 10, wherein the housing includes a rail portion in the second receiving portion along which the protrusion slides, and

wherein a space is formed between the enlarged portion and the first housing by bringing the protrusion into contact with the rail portion.

14. The imaging apparatus of claim 13,

wherein the rail portion includes a pair of rail members provided in the second accommodating portion and extending in the fitting direction of the first cartridge, facing each other, one on each side of the enlarged portion,

wherein the protrusions include a pair of protrusions provided on the first housing to correspond to the pair of rail members, respectively.

15. The imaging apparatus of claim 5,

wherein the extended portion of the first casing includes a pair of extended side portions extending in the fitting direction of the first cartridge, the pair of extended side portions being opposed to each other, one on each side on the enlarged portion, when the first cartridge is fitted in the first accommodation portion with the extended portion accommodated in the extended portion accommodation region,

wherein each of the extending side portions includes a reinforcing portion that is provided in the mounting direction of the first cartridge and reinforces the corresponding extending side portion.

16. The imaging apparatus of claim 15,

wherein the extension portion of the first housing includes a grip portion for facilitating attachment and detachment of the first cartridge to and from the first accommodating portion.

17. The imaging apparatus of claim 16,

wherein the first casing includes an extended end portion for connecting respective end portions of the pair of extended side portions located upstream in the first cartridge mounting direction,

wherein the grip portion is disposed on the extended end portion.

18. The imaging apparatus of claim 4,

wherein the process member includes a photosensitive member and a developer storage portion,

the photosensitive member is provided in a first cartridge, and the developer storage portion is provided in a second cartridge.

19. The imaging apparatus of claim 18,

wherein the first housing determines relative positions of the charger, the photosensitive member, and the second cartridge.

20. The imaging apparatus of claim 19,

wherein the process member includes a developing roller provided in the second cartridge,

the first casing determines a position of the second cartridge based on a shaft of the developing roller.

21. The imaging apparatus of claim 20,

wherein the first housing has a rotation support portion provided on a main body rotatably supported in the first accommodation portion,

wherein the first cartridge is fitted in the first housing portion by supporting the rotation support portion in the first housing portion and rotating the first cartridge around the rotation support portion, the extension portion is retreated from the second housing area toward the extension portion housing area to allow the second cartridge to be housed in the second housing area of the second housing portion,

wherein the photosensitive member is provided in a main body of the first housing, an

The rotation support portion includes a support shaft that supports the photosensitive member in a main body of the first housing.

22. The imaging apparatus of claim 18,

wherein the first housing includes a shaft protruding in a longitudinal direction of the photosensitive member,

the housing further includes, in the first accommodation portion:

a receiving portion that receives the shaft of the first housing; and

a pressing member provided to be retractable along a path on which the shaft moves when the first cartridge is mounted in or dismounted from the first housing portion, the pressing member advancing into and retracting from the path of the shaft, and pressing the shaft into the receiving portion when the first cartridge is mounted to the first housing portion.

23. The imaging apparatus of claim 22,

wherein the pressing member is advanced into a path of the shaft or retracted from the path of the shaft in association with fitting or removal of the first cartridge in or from the first accommodating portion.

24. The imaging apparatus of claim 22,

wherein the pressing member is advanced into or withdrawn from the path of the shaft in association with fitting or removal of the second cartridge on or from the first cartridge.

25. The imaging apparatus of claim 24,

wherein the shaft includes a support shaft that supports the photosensitive member.

26. The imaging apparatus of claim 18,

wherein the process member includes a developing roller,

the second cartridge includes:

a second housing;

a developing roller disposed in the second casing, a portion of which is exposed from the second casing;

a pressing portion provided on the second casing to face the developing roller from a side thereof facing one wall of the casing on an opposite side of an enlarged portion defining the second accommodating portion when the second cartridge is assembled in the second accommodating portion, along a length direction of the developing roller, the pressing portion pressing the developing roller to the outer circumferential surface to prevent the developer from leaking; and

and a sliding portion that protrudes further downstream than the pressing portion in the fitting direction, is closer to the wall than the pressing portion when the second cartridge is fitted in the second accommodating portion, and contacts and slides along the wall when the second cartridge is fitted in the second accommodating portion.

27. The imaging apparatus of claim 4, further comprising an exposure apparatus fitted in the housing,

wherein the enlarged portion is part of an exposure device.

28. The imaging apparatus of claim 4,

wherein the first cartridge and the second cartridge are formed in one set, and one set is provided for each of a plurality of different colors.

29. The image forming apparatus as claimed in claim 28, further comprising a feeding part picking up and feeding a recording medium; and

a discharge unit for discharging the recording medium from the housing,

wherein the plurality of sets of first and second cartridges are disposed between the feeding section and the discharging section along a conveyance path for conveying the recording medium,

wherein the feeding section and the discharging section are arranged such that a pickup direction in which the feeding section picks up the recording medium is opposite to a conveying direction in which the plurality of sets of first and second cartridges convey the recording medium through the image forming positions for successive image formation; and

wherein a conveying direction of the recording medium through the image forming position is opposite to a discharging direction of the recording medium discharged by the discharging portion.

30. The imaging apparatus of claim 29,

wherein the first and second cartridges are attached and removed in a direction inclined with respect to a conveying direction in which the recording medium is conveyed in the image forming apparatus and a thickness direction of the recording medium perpendicular to the conveying direction.

31. The imaging apparatus of claim 30,

the image forming apparatus further includes a plurality of exposure devices, one for each of the plurality of sets of the first and second cartridges,

wherein the exposure device is disposed alternately with the first and second cassette groups along a conveying direction in which the recording medium is conveyed through the image forming apparatus.

32. The imaging apparatus of claim 31,

wherein the first cartridge has a first housing,

the first housing includes:

a main body accommodated in the first accommodation region of the first accommodation portion after passing through the second accommodation region of the second accommodation portion when the first cartridge is not provided with the second cartridge; and

an extension part extending to the second accommodating part when the first cartridge is fitted in the first accommodating part,

wherein the second receiving portion has an extension receiving area receiving the extension,

the extension portion of the first housing is interposed between each exposure device and each second cartridge,

the extension has an opening that allows passage of a laser beam emitted by the exposure device toward the photosensitive member.