Patent Grant
7783225
The present invention relates to an electrostatic image forming apparatus such as a printer, a copier or a facsimile. More specifically, the invention relates to an image forming apparatus (particularly, tandem-type color image forming apparatus) comprising a pair of stationary side walls arranged in an image forming apparatus body and a plurality of photosensitive drum units supported between the stationary side walls, and to a photosensitive drum unit applied to the image forming apparatus.
In an electrostatic image forming apparatus such as a printer, a copier or a facsimile, an electrostatic latent image or the like is formed on a photosensitive material, developed into a toner image through a developing device, the toner image is transferred onto a recording paper directly or through an intermediate transfer belt which is a to-be-transferred member, and the transferred image is fixed to obtain a desired record. In recent years, there have been widely used color image-forming apparatuses such as color printers and color copiers, and studies to speed up their operation are under way. As for a system for realizing a color image forming apparatus that operates at high speeds, attention has been given to a so-called tandem-type color image forming apparatus in which a plurality of photosensitive drum units are arranged. Further, in the tandem-type color image forming apparatus, an LED head that requires a relatively compact space for installation is often used as an exposure means. The LED head is constituted by an LED array, a rod lens array and a frame for holding them.
In the tandem-type color image forming apparatus equipped with a plurality of photoconductor units, the exposure means in the photoconductor units must be mounted at positions aligned with each other in the axial direction of the photosensitive drums relative to an intermediate transfer belt that is a to-be-transferred member. Otherwise, a problem occurs that the color image has a color drift. When the LED head is used as the exposure means, further, the depth of a focal point of the rod lens array is shallow. Therefore, there arises a problem with adjustment of the focal point to the peripheral surface of the photosensitive drum, on which the image is to be formed.
There has been known an image forming apparatus of a type in which the LED head is supported by the frame of the photosensitive drum unit (see Japanese Unexamined Utility Model Publication (Kokai) No. 5-15051). In the image forming apparatus disclosed in the above publication, the photosensitive drum unit has a pair of side frames. Photosensitive drums are supported between the side frames so as to freely rotate. Leg portions are formed at both end portions of the LED head, and a positioning hole is formed in each of the leg portions. A placing table is provided for each of the side frames integrally therewith, the placing table having a projection erected upright. Each side frame has a stepped portion formed integrally therewith so as to be mounted on the apparatus body. The legs of the LED head are each placed on the placing tables of the corresponding side frames, and the positioning holes formed in the leg portions of the LED head are fitted to the projections formed on the placing tables. The photosensitive drum unit having the LED head that is thus installed on the side frames is mounted on a predetermined position of the apparatus body by utilizing the stepped portions formed on each of the side frames.
In the thus constituted image forming apparatus, the positional precision of the LED head in the axial direction of the photosensitive drum varies depending upon the precision in the mounting position of the photosensitive drum unit and hence, fluctuation is liable to occur in the positional precision due to tolerance of building-up of parts. When the image forming apparatus is a tandem-type color image forming apparatus, consequently, fluctuation easily occurs in the precision of the mounting position of the LED head between the photosensitive drum units in the axial direction of the photosensitive drum, and color drift is very likely to occur in the color image.
On the other hand, the position in the radial direction relative to the peripheral surface of the photosensitive drum, of the LED head varies depending upon the precision of mounting the leg portions of the LED head on the placing tables of the corresponding side frames and hence, fluctuation easily occurs. As a result, precision in the mounting position in the radial direction relative to the peripheral surface of the photosensitive drum, in other words, precision in the focal point, of the LED head is not maintained as desired, and sharp image may not be guaranteed.
It is an object of the present invention to provide a novel image forming apparatus equipped with photosensitive drum units, which enables to improve precision in the mounting position in the axial direction of the photosensitive drum, of an exposure means; and a photosensitive drum unit applied to the above image forming apparatus.
It is another object of the present invention to provide a novel image forming apparatus equipped with photosensitive drum units, which enables to improve precision in the mounting position in the axial direction relative to the peripheral surface of the photosensitive drum, of an exposure means; and a photosensitive drum unit applied to the above image forming apparatus.
It is a further object of the present invention to provide a novel image forming apparatus equipped with photosensitive drum units, which can improve precision in the mounting position in the axial direction of the photosensitive drum, of an exposure means and precision in the mounting position in the radial direction relative to the peripheral surface of the photosensitive drum, of an exposure means, simultaneously; and a photosensitive drum unit applied to the above imaging forming apparatus.
According to one aspect of the present invention, there is provided an image forming apparatus comprising a pair of stationary side walls arranged in an image forming apparatus body and a plurality of photosensitive drum units supported between the stationary side walls, wherein each of the photosensitive drum units comprises a drum-holding frame for holding a photosensitive drum, an exposure means-holding frame for holding the exposure means, and a pressing means for pressing the exposure means-holding frame from one side toward the other side in the axial direction of the photosensitive drum.
It is desired that the pressing means is disposed on one side of the drum-holding frame so as to press the exposure means-holding frame from one side toward the other side in the axial direction of the photosensitive drum.
It is desired that the pressing means is pushed upon coming in contact with one stationary side wall and a part on the other side of the exposure means-holding frame is press-contacted to the other stationary side wall, so that the exposure means-holding frames are aligned to each other at predetermined positions in an axial direction with the other stationary side wall as a reference.
It is desired that the exposure means-holding frame is supported so as to move in the axial direction relative to the drum-holding frame by fitting the shafts or the fitting holes disposed on both side walls that define both sides of the exposure means-holding frame to the fitting holes or the shafts disposed on both side walls of the drum-holding frame, and axes of the shafts or the fitting holes disposed on both side walls of the exposure means-holding frame and the axes of the fitting holes or the shafts disposed on both side walls of the drum-holding frame, are arranged on a common imaginary axis line in parallel with the axis of the photosensitive drum, which is on a common imaginary axis line on the peripheral surface, on which an image is focused by the exposure means, of the photosensitive drum.
It is desired that first positioning projections are disposed on both side walls of the drum-holding frame and having axes common to the axis of the photosensitive drum, second positioning projections are disposed on both side walls of the exposure means-holding frame in parallel with the axis of the photosensitive drum, and a first positioning groove and a second positioning groove are formed in the stationary side walls for positioning the first positioning projection and the second positioning projection that are inserted therein.
It is desired that the first positioning projections disposed on both side walls of the drum-holding frame are constituted by the shaft of the photosensitive drum.
It is desired that the second positioning projection disposed on the other side wall of the exposure means-holding frame is constituted by a positioning/pushing shaft, positioning surface walls are formed substantially integrally with the stationary side walls on the outer sides of the regions of the stationary side walls where the second positioning grooves are formed, and as the first positioning projections are inserted in the first positioning grooves and as the second positioning projections are inserted in the second positioning grooves thereby enabling the photosensitive drum units to be supported at predetermined positions between the stationary side walls, the pressing means is pushed upon coming in contact with the positioning wall surface of the one stationary side wall, and the front end surface of the positioning/pushing shaft of the exposure means-holding frame is pushed onto the positioning wall surface of the other stationary side wall due to the pressing means.
It is desired that the exposure means-holding frame has a side wall for defining one side of the exposure means-holding frame, the drum-holding frame has one side wall for defining one side of the drum-holding frame, which is positioned on the outer side of one side wall of the exposure means-holding frame, the pressing means comprises a cap-shaped pressing member disposed on one side wall of the drum-holding frame so as to move in the axial direction and a compression coil spring disposed between the pressing member and the one side wall of the exposure means-holding frame, the pressing member is so disposed as to protrude beyond one side wall of the drum-holding frame and is limited at a predetermine position from moving in a direction to separate away from one side wall of the exposure means-holding frame, and, in a state where the photosensitive drum units are supported at predetermined positions between the stationary side walls, the pressing member is pushed upon being contacted to one stationary side wall and, upon bringing part on the other side of the exposure means-holding frame into pressed contact with the other stationary side wall, the exposure means-holding frames are aligned to each other, at predetermined positions in an axial direction, with the other stationary side wall as a reference.
It is desired that the exposure means is held by the exposure means-holding frame so as to adjust the position thereof in the radial direction relative to the peripheral surface of the photosensitive drum.
It is desired that both side portions of the exposure means are supported by the exposure means-holding frame via a radial direction position adjusting means capable of adjusting the positions thereof in the radial direction relative to the peripheral surface of the photosensitive drum.
It is desired that each of the radial direction position adjusting means includes fitting holes formed in the bottom wall portions disposed integrally in the inside of both side portions of the exposure means-holding frame, the fitting holes being such that the ends thereof on the bottom wall side are closed by the closing walls and the other ends thereof are opened, cylindrical portions formed integrally on both side portions of the exposure means and being internally threaded along the inner peripheral surfaces thereof, the cylindrical portions being inserted in the fitting holes from the other ends thereof so as to slide, radial direction position adjusting bolts brought into engagement with the cylindrical portions and into contact at the front ends thereof with the closing walls in the bottom wall portions, and a spring means for urging both side portions of the exposure means toward the bottom wall portions, wherein the fitting holes are so positioned that the axes thereof extend in parallel with each other and at right angles with the axis of the photosensitive drum.
It is desired that the exposure means comprises an LED head.
According to another aspect of the present invention, there is provided a photosensitive drum unit supported between a pair of stationary side walls disposed in the image forming apparatus body, which comprises a drum-holding frame for holding a photosensitive drum, an exposure means-holding frame for holding an exposure means, and a pressing means capable of pressing the exposure means-holding frame from one side toward the other side in the axial direction of the photosensitive drum.
It is desired that the pressing means is disposed on one side of the drum-holding frame so as to press the exposure means-holding frame from one side toward the other side in the axial direction of the photosensitive drum.
It is desired that the exposure means-holding frame has one side wall for defining one side of the exposure means-holding frame; the drum-holding frame has a side wall for defining one side of the drum-holding frame, which is positioned on the outer side of one side wall of the exposure means-holding frame, the pressing means comprises a cap-shaped pressing member disposed on one side wall of the drum-holding frame so as to move in the axial direction and a compression coil spring disposed between the pressing member and the one side wall of the exposure means-holding frame, and the pressing member is so disposed as to protrude beyond one side wall of the drum-holding frame and is limited at a predetermine position from moving in a direction to separate away from one side wall of the exposure means-holding frame.
It is desired that the exposure means-holding frame is supported so as to move in the axial direction relative to the drum-holding frame by fitting the shafts or the fitting holes disposed on both side walls that define both sides of the exposure means-holding frame to the fitting holes or the shafts disposed on both side-walls of the drum-holding frame, and axes of the shafts or the fitting holes disposed on both side walls of the exposure means-holding frame and the axes of the fitting holes or the shafts disposed on both side walls of the drum-holding frame, are arranged on a common imaginary axis line in parallel with the axis of the photosensitive drum, which is on a common imaginary axis line on the peripheral surface where an image is focused by the exposure means, of the photosensitive drum.
It is desired that the exposure means is held by the exposure means-holding frame so as to adjust the position thereof in the radial direction relative to the peripheral surface of the photosensitive drum.
It is desired that both side portions of the exposure means are supported by the exposure means-holding frame via a radial direction position adjusting means capable of adjusting the positions thereof in the radial direction relative to the peripheral surface of the photosensitive drum.
It is desired that each of the radial direction position adjusting means comprises fitting holes formed in the bottom wall portions disposed integrally in the inside of both side portions of the exposure means-holding frame, the fitting holes being such that the ends thereof on the bottom wall side are closed by the closing walls and the other ends thereof are opened, cylindrical portions formed integrally on both side portions of the exposure means and being internally threaded along the inner peripheral surfaces thereof, the cylindrical portions being inserted in the fitting holes from the other ends thereof so as to slide, radial direction position adjusting bolts brought into engagement with the cylindrical portions and into contact at the front ends thereof with the closing walls in the bottom wall portions, and a spring means for urging both side portions of the exposure means toward the bottom wall portions, wherein the fitting holes are so positioned that the axes thereof extend in parallel with each other and at right angles with the axis of the photosensitive drum.
It is desired that the exposure means comprises an LED head.
a) is a disassembled perspective view of a head-holding frame and a drum-holding frame provided in the photosensitive drum unit illustrated in
a) is a perspective view of one side surface of the photosensitive drum unit of
b) is a perspective view illustrating the other side surface thereof; and
A preferred embodiment of an image forming apparatus equipped with photosensitive drum units constituted according to the present invention will now be described with reference to the accompanying drawings.
A conveyer belt mechanism 330 including a conveyer belt 332 is arranged on the lower side of the photosensitive drum units 310 and the developing units 320. A transfer unit 334 is arranged on the lower side of each of the photosensitive drums 2. The conveyer belt 332 is so arranged that part of the regions thereof move in nearly a horizontal direction passing through between the photosensitive drums 2 and the transfer units 334 facing thereto. The conveyer belt mechanism 330 works to convey the recording papers delivered from paper feed cassettes 336 arranged on the lower side thereof so as to pass through between the photosensitive drums 2 and the transfer units 334 facing thereto. The basic constitution of the tandem-type color image forming apparatus maybe constituted in a customary manner and does not pertain to the feature of the present invention, and hence, is not described here in further detail.
Next, described below in detail are the constitution of the photosensitive drum units 310 mounted on the image forming apparatus body 302 illustrated in
Referring to
The drum-holding frame 100 that can be integrally formed by using a suitable synthetic resin has a pair of side walls 12 and 14, and a coupling frame 16 for coupling the side walls 12 and 14 together. Referring to
A driven gear (not shown) is supported by the shaft 26 of the photosensitive drum 2 so as to rotate relative to the shaft 26 of the photosensitive drum 2 neighboring the flange member 24 on the outer side thereof in the axial direction. The driven gear is integrally coupled so will not to rotate relative to the flange member 24. Referring to
Fitting holes 27 and 28 are formed at predetermined edge portions of the side walls 12 and 14 of the drum-holding frame 100. In part of the region in the circumferential direction of the fitting hole 27 formed in the side wall 12, there is formed a notch 27a (see
The head-holding frame 202 that can be integrally molded from a suitable synthetic resin has a pair of side walls 204 and 206, and a coupling frame 208 integrally coupled to the side walls 204 and 206. The LED head 200 is arranged between the side walls 204 and 206. The LED head 200 that is constituted in a known manner comprises an LED array 210, a rod lens array 212 and a frame 214 for holding them. Both side portions of the LED head 200 in the lengthwise direction are supported by the head-holding frame 202 via a radial direction position-adjusting means 200A which capable of adjusting the position in the radial direction relative to the peripheral surface of the photosensitive drum 2.
The radial direction position adjusting means 200A comprise fitting holes 216 formed in the bottom wall portions 215 disposed integrally in the inside of both side portions of the head-holding frame 202, the fitting holes 216 being such that the ends thereof on the bottom wall side being closed by the closing walls 218 and the other ends thereof being opened; cylindrical portions 220 that are formed integrally on both side portions of the LED head 200 and are internally threaded along the inner peripheral surfaces thereof, the cylindrical portions 220 being inserted in the fitting holes 216 from the other ends thereof to be slidably fitted thereto; radial direction position adjusting bolts 222 that are brought into engagement with the cylindrical portions 220 and into contact at the front ends thereof with the closing walls 218 of the bottom wall portion 215; and resilient means or, in this embodiment, compression coil springs 224, for urging both side portions of the LED head 200 toward the bottom wall portion 215.
The bottom wall portion 215 of the head-holding frame 202 is formed by a part of the coupling frame 208 of the head-holding frame 202. In the intermediate region of the bottom wall portion 215 in the lengthwise direction, there is formed an opening 215a which is slender in the lengthwise direction so as not to prevent the exposure to light emitted from the LED head 200 onto the peripheral surface of the photosensitive drum 2. Between the side walls 204 and 206 of the head-holding frame 202, there is arranged a ceiling wall 226 facing the bottom wall portion 215, and the compression coil springs 224 are arranged between the two side portions of the ceiling wall 226 and the two side portions of the frame 214 of the LED head 200. The axes of the fitting holes 216 extend in parallel to each other and are positioned at right angles with the axis of the photosensitive drum 2 (axis of the shaft 26). The radial direction position adjusting means 200A are constituted as described above. By suitably rotating the bolts 222, therefore, the position of the LED head 200 in the radial direction relative to the peripheral surface of the photosensitive drum 2 can be easily and reliably adjusted. As heads of the bolts 222 are exposed on the upper side, the focus-adjusting operation can be easily conducted.
Shafts 230 are integrally formed so as to extend outward from the lower end portions of the side walls 204 and 206 defining both sides of the head-holder frame 202. The shaft 230 of one side only is illustrated in
A positioning shaft 240 is integrally formed so as to extend outward from the central portion of the side wall 204 of the head-holding frame 202. Further, a positioning/pushing shaft 242 is integrally formed so as to extend outward from the central portion of the side wall 206 of the head-holding frame 202. The positioning shaft 240 and the positioning/pushing shaft 242 are longer than the above shaft 230 and exist on a common axis. The axis of the positioning shaft 230 and the positioning/pushing shaft 242 is in parallel with the axis of each of the shafts 230. The positioning shaft 240 and the positioning/pushing shaft 242 constitute second positioning projections in parallel with the shaft 26 of the photosensitive drum 2 disposed on both side walls 204 and 206 of the head-holding frame 202.
The head-holding frame 202 for holding the LED head 200 as described above is supported so as to move in only the axial direction of the photosensitive drum 2 relative to the drum-holding frame 100. If described in further detail with reference to
The coupling is effected in a manner as described below. Namely, the small-diameter portion of the one shaft 230 (see
As shown in
Referring to
Referring to
Referring to
If described in further detail, a cover member 42 that can be integrally molded by using a suitable synthetic resin is mounted on the side wall 12 of the drum-holding frame 100 from the outer side thereof. The cover member 42 is locked with the side wall 12 via suitable locking means 42a, 42b, 42c and 42d so as not to escape in the axial direction and so as not to turn relative thereto (see
In an overhung portion of the cover member 42, there is formed a protruding portion 42e that extends downward. The protruding portion 42e penetrates through the side wall 204 and the cover member 42 and is fitted to a slit 26S formed in one end portion that protrudes outward, of the shaft 26 of the photosensitive drum 2. Thereby, the rotation of the shaft 26 of the photosensitive drum 2 relative to the drum-holding frame 100.is prevented. As will be easily understood from the foregoing description, it can be said that the cover member 42 constitutes part of the one side wall 12 of the drum-holding frame 100. It can therefore be said that the pressing means 40 is arranged on one side wall 12. The region, on which the pressing means 40 is disposed, of the one side wall 12 is located on the outer side of the one side wall 204 of the head-holding frame 200.
The pressing means 40 is disposed on the cover member 42. Namely, in the cover member 42, there is formed a through hole 44 having an axis in parallel with the axis of the photosensitive drum 2. The inner surface of the region where the through hole 44 is formed, of the cover member 42 is positioned to be opposed to part of the region on the outer surface of the holding plate member 250 mounted on the side wall 204 of the head-holding frame 202. In the inner peripheral surface of the through hole 44, there is formed a guide groove 44a which, while maintaining a predetermined width in the circumferential direction, linearly extends from one end of the side facing the holding plate member 250 up to a position close to the other end thereof in the axial direction. A step portion 44b is formed between the other end (the other end on the side in the axial direction opposite to the side facing the holding plate member 250) of the guide groove 44a and the inner peripheral surface of the through hole 44.
A cap-shaped pressing member 46 that comprises a cylindrical portion 46a and a closing wall 46b and is opened at one end in the axial direction, is fitted into the through hole 44 so as to slide in the axial direction but so as not to rotate. Namely, in an end portion in the outer peripheral surface of the pressing member 46 in the axial direction (i.e., in an end portion of the side facing the holding plate member 250 and on the opening side), there is formed a to-be-guided projection 46c that linearly extends in the axial direction toward the other end thereof while maintaining a predetermined width in the circumferential direction. The pressing member 46 is fitted to the through hole 44 in a state where the to-be-guided projection 46c is fitted to the guide groove 44a in the through hole 44 so as to slide. The open end of the pressing member 46 is so positioned as to be opposed to the holding plate member 250. The length of the pressing member 46 in the axial direction is longer than the length of the through hole 44 in the axial direction. A compression coil spring 48 is disposed in the pressing member 46. One end of the compression coil spring 48 is pressed onto, and contacted with, the closing wall 46b of the pressing member 46, and the other end thereof is pressed onto, and contacted with, the outer surface of the holding plate member 250.
In a mounting state where no external force in the axial direction acts on the pressing member 46, the pressing member 46 slides, in the through hole 44, in the axial direction (toward the right in
Referring to
The stationary side wall bodies 410 and the side frames 420 can be each integrally molded together by using a synthetic resin. Each side frame 420 has a first positioning groove 422 and a second positioning groove 424, which extend in substantially a vertical direction. The first positioning grooves 422 are each for holding, at predetermined positions, both ends that are the first positioning projections, of the shaft 26 of the photosensitive drum 2. The second positioning grooves 424 are each for holding, at predetermined positions, the positioning shafts 240 and the positioning/pushing shafts 242, which are the second positioning projections to be inserted, formed on the side walls 204 and 206 of the head-holding frame 202. The positioning shaft 240 is inserted in the second positioning groove 424 of one side frame 420 shown in
The first positioning grooves 422 and the second positioning grooves 424 have each upper ends that are opened upward and lower ends that are closed. In the illustrated embodiment, the first positioning grooves 422 have a relatively short length between the upper ends and the lower ends in the vertical direction, and the closed lower ends have a curved surface expanding downward. The first positioning grooves 422 of one side frame 420 shown in
As viewed in a direction in which the side frames 420 are facing each other (axial direction of the photosensitive drum 2 in a state where the photosensitive drum unit 310 is mounted), the axes at the lower ends of the first positioning grooves 422 are arranged substantially in alignment with the axis of the photosensitive drum 2, and the axes at the lower ends of the second positioning grooves 424 are each arranged substantially in alignment with the axes of the positioning shaft 240 and of the positioning/pushing shaft 242. As will be easily understood from
In the illustrated embodiment, the closed lower ends of the first positioning grooves 422 have curved surfaces expanding downward, and the closed lower ends of the second positioning grooves 424 are forming flat surfaces. The shapes of the closed lower ends, however, are in no way limited. The closed lower end of the first positioning groove 422 in one side frame 420 illustrated in
On the outer sides of the regions where the second positioning grooves 424 are formed in the stationary side walls 400, positioning wall surfaces 410a are formed substantially integrally with the stationary side walls 400 so as to be positioned at a predetermined distance relative to the above regions on the outer sides of the regions where the respective second positioning grooves 424 are formed in the side frames 420 in the illustrated embodiment, the positioning wall surfaces 410a are formed in the stationary side wall bodies 410 so as to be located at a predetermined gap relative to the above regions of the side frames 420. The positioning wall surfaces 410a are substantially vertical surfaces. The function of the positioning wall surfaces 410a will be described later.
The above-mentioned photosensitive drum unit 310 is detachably supported at predetermined positions between the respective stationary side walls 400 after focus adjustment, in other words, after the LED head 200 is adjusted for its position in the radial direction relative to the peripheral surface of the photosensitive drum 2 by using the above-mentioned radial direction position-adjusting means 200A disposed on both sides of the LED head 200. In a state where the photosensitive drum unit 310 is supported at predetermined positions between the respective stationary side walls 400, the drum-holding frame 202 is supported by the respective stationary side walls 400 so as not to move in the axial direction of the photosensitive drum 2, and the pressing means 40 is pushed upon coming in contact with the one stationary side wall 400 illustrated in
If described more specifically, the photosensitive drum unit 310 is lowered in a state where the positioning shaft 240 formed on the side wall 204 of the head-holding frame 202 that is the second positioning projection of the photosensitive drum unit 310, is inserted in the second positioning groove 424 in one side frame 420 illustrated in
When the photosensitive drum unit 310 is further lowered to a small extent, the positioning shaft 240 formed on the side wall 204 of the head-holding frame 202 is placed on, and supported by, the lower end of the second positioning groove 424 in the one side frame 420 illustrated in
During the above-mentioned lowering operation for mounting the photosensitive drum unit 310 on the stationary side walls 400 and after the photosensitive drum unit 310 whose lowering operation has been stopped, has been supported at predetermined positions on the stationary side walls 400, the closing wall 46b of the pressing member 46 protruding outward beyond the outer side surface of the cover member 42 by a predetermined length in the axial direction, comes into contact with the positioning wall surface 410a of the one stationary side wall body 410 and is pushed relatively thereto (see
As a result, the position of the drum-holding frame 100 in the axial direction is determined as the annular groove 26a in the shaft 26 of the photosensitive drum 2 is fitted to, and engaged with, the positioning groove 422 in the other side frame 420 illustrated in
The image forming apparatus body 302 illustrated in
The head-holding frames 202 are supported by the drum-holding frames 100, and the LED heads 200 are supported, at both sides thereof, by the head-holding frames 202 via a radial direction position-adjusting means 200A that are capable of adjusting the positions thereof in the radial direction relative to the peripheral surfaces of the photosensitive drums 2. Therefore, the positions in the radial direction relative to the peripheral surfaces of the photosensitive drums 2, of the LED heads 200 can be easily and correctly adjusted.
Accordingly, the present invention makes it possible to improve the precision in the mounting positions of the LED heads 200 in the axial direction of the photosensitive drums 2. It is further made possible to improve the precision in the mounting positions of the LED heads 200 in the radial direction relative to the peripheral surfaces of the photosensitive drums 2. It is further allowed to improve the precision in the mounting positions of the LED heads 200 in the radial direction relative to the peripheral surfaces of the photosensitive drums 2 as well as to improve the precision in the mounting positions of the LED heads 200 in the axial direction of the photosensitive drums 2.
As will be easily understood from the foregoing description, the photosensitive drum units 310 can be reliably mounted on the side frames 420, i.e., on the predetermined positions of the stationary side walls 400 by simply lowering the photosensitive drums 310 at predetermined positions and hence, it offers easy operability for assembling.
In the above-mentioned embodiment of the invention, the head-holding frame 202 has a constitution to couple it to the drum-holding frame 100 so as to move only in the axial direction of the photosensitive drum 2 by fitting the shafts 230 disposed on both side walls 204 and 206 of the head-holding frame 202 to the fitting holes 27 and 28 formed in both side walls 12 and 14 of the drum-holding frame 100. However, it is also allowable to employ another embodiment for coupling by, conversely, forming the fitting holes 27 and 28 in both side walls 204 and 206 of the head-holding frame 202, and forming the shafts 230 on both side walls 12 and 14 of the drum-holding frame 100 to couple them together. In the above-mentioned embodiment of the invention, further, the first positioning projections disposed on the side walls 12 and 14 of the drum-holding frame 100 are constituted by the shaft 26 of the photosensitive drum 2. However, the first positioning projections may be formed integrally with other members such as the side walls 12 and 14 as far as they have an axis in common with the axis of the photosensitive drum 2. Further, though the above embodiment of the invention has dealt with a tandem-type color image forming apparatus 300 including four photosensitive drum units 310, the photosensitive drum units 310 maybe included in a plural number. In the above embodiment, further, the image forming apparatus 300 is so constituted as to directly transfer a toner image onto a recording paper conveyed by the conveyer belt mechanism 330 through the transfer device 334. However, the image forming apparatus may be of a form in which the toner image is transferred onto an intermediate transfer belt that is a to-be-transferred member and, then, the toner image is transferred onto a recording paper conveyed by the other conveyer mechanism.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-012135 | Jan 2003 | JP | national |
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| Number | Date | Country |
|---|---|---|
| 5-15051 | Feb 1993 | JP |
| 8-30175 | Feb 1996 | JP |
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| Number | Date | Country | |
|---|---|---|---|
| 20040228652 A1 | Nov 2004 | US |
