Patent Publication Number: US-7590370-B2

Title: Image forming apparatus having openings and a cover

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Japanese Patent Application No. 2006-160985 filed on Jun. 9, 2006 in the Japan Patent Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND 
   This invention relates to an image forming apparatus in which an image is formed on a recording sheet, such as a recording paper, by applying developer (for example, toner) thereon. 
   In an image forming apparatus (for example, a laser printer), various noise is generated. For example, mechanical noise is generated when movable members of such image forming apparatus are operated. Friction noise is generated when a recording paper is conveyed and friction is caused thereby. The noise generated inside of an image forming apparatus leaks outside through openings, such as attachment/detachment opening for a paper placement tray (a paper feed tray) on which sheets of recording paper are disposed. 
   In a conventional image forming apparatus, noise leak through a gap between a paper placement tray and an attachment/detachment opening is avoided by providing a sound insulating member made of a resilient member to a dust-proof cover of the paper placement tray. 
   In a general image forming apparatus, (for example, an electrographic image forming apparatus), in order to replenish expendable developer (such as toner), a development cartridge, in which developer is contained, is installed so as to be attachable/detachable with respect to the body of the apparatus. 
   An attachment/detachment opening provided for attaching/detaching the development cartridge to/from the apparatus body therethrough is closed by a front cover. On the other hand, an attachment/detachment opening provided for attaching/detaching a placement tray therethrough is closed by a cover portion integrated with the placement tray. 
   SUMMARY 
   However, for example, in an image forming apparatus wherein a placement tray and a development cartridge are installed in the apparatus body so as to be detachable approximately in a uniform direction, a gap is made between a front cover for the development cartridge and a cover portion of the placement tray. Such gap is made because an attachment/detachment opening for the placement tray and an attachment/detachment opening for the development cartridge are adjacently disposed, and the placement tray and the development cartridge are both detachably installed in the apparatus body. Consequently, noise leaks outside of the apparatus body through the gap. 
   In order to prevent such noise leak, a technique, such as the technique adopted in the above-described conventional image forming apparatus, is introduced. However, providing complete blockage of the gap is difficult by using the noise insulating portion made of a resilient member. Therefore, noise cannot be adequately inhibited from leaking outside of the body of an image forming apparatus. 
   In an image forming apparatus wherein a placement tray and a development cartridge are installed in the apparatus body so as to be detachable, noise is preferably inhibited from leaking outside of the apparatus body. 
   In one aspect of the present invention, an image forming apparatus may include a development cartridge, a placement tray, an apparatus body, and a cover member. The development cartridge contains developer to be applied onto a recording sheet. The placement tray is configured so as to place recording sheets thereon. In the apparatus body, the development cartridge and the placement tray are detachably installed. The apparatus body includes a first opening and a second opening. Through the first opening, the development cartridge is attached/detached. Through the second opening, the placement tray is attached/detached. The cover member has a portion integrally and continuously extending over the first opening and the second opening so as to cover the first opening and the second opening. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described below, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a sectional side view showing a substantial portion of a laser printer according to a first embodiment of the present invention; 
       FIG. 2  is a sectional view showing a paper placement tray removed (pulled out) from a housing of the laser printer according to the first embodiment; 
       FIG. 3  is a sectional view showing a development cartridge removed from the housing of the laser printer according to the first embodiment; 
       FIG. 4  is a sectional view showing a paper placement tray pulled out from a laser printer according to a second embodiment of the present invention; 
       FIG. 5  is an enlarged sectional view showing a guide member of a laser printer according to a third embodiment of the present invention; and 
       FIG. 6  is an enlarged sectional view showing a characterizing portion of a laser printer according to a fourth embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the following embodiments, the image forming apparatus according to the present invention is adopted to a so-called laser printer. 
   First Embodiment 
   1. Overall Structure of Laser Printer 
   As shown in  FIG. 1 , a laser printer  1  includes a housing  10  formed approximately in a box shape (a rectangular parallelepiped shape including a cubical shape). On the top surface of the housing  10 , a paper discharge tray  20  is disposed wherein paper, on which image formation (printing) is performed, is discharged from the housing  10  and placed thereon. For the paper mentioned in the present embodiment, print paper or a recording sheet, such as a OHP sheet, are used. 
   2. Internal Structure of Laser Printer (See  FIG. 1 ) 
   The housing  10  includes an image formation unit  100 , a feeder unit  200 , a discharge chute  300 , and a discharge roller mechanism  310 . The image formation unit  100  forms an image on paper. The feeder unit  200  supplies paper to the image formation unit  100 . The discharge chute  300  guides paper, on which image formation is performed, toward a discharge unit  11 . The discharge roller mechanism  310  discharges paper guided by the discharge chute  300 , and straightens a curl of the paper. 
   2.1. Feeder Unit 
   The feeder unit  200  includes a paper placement tray (paper feed cassette)  201 , a paper feed roller (pickup roller)  202 , a separation roller  203 , and a separation pad  204 . The paper placement tray  201  is detachably installed in the lowest portion of the housing  10 . The paper feed roller  202  is disposed above the front end portion of the paper placement tray  201 , and conveys paper to the image formation unit  100 . The separation roller  203  and the separation pad  204  separate paper to be conveyed by the paper feed roller  202  in a sheet by sheet manner. 
   On the paper placement tray  201 , a plurality of sheets of paper, to be conveyed to the image formation unit  100 , is placed in a stacked manner in an up-and-down direction. The paper placement tray  201  is attached/detected with respect to the housing  10  by being moved in a front-to-back direction (in the left-to-right direction in the drawing). 
   A first and a second pressure rollers  205 ,  206  are rotated while the rollers  205 ,  206  are in contact with a sheet of paper so as to press the sheet of paper against the separation roller  203 . A sheet of paper, discharged upward from the paper placement tray  201 , is conveyed so as to be winded around the outer periphery of the separation roller  203 . The direction of the conveyance of the sheet of paper is thereby changed approximately 180 degrees by a turning unit. Then, the sheet of paper is conveyed toward the image formation unit  100 . 
   Specifically, a sheet of paper discharged from the paper placement tray  201  is pressed against the separation roller  203  by the first pressure roller  205 . The conveyance direction of the paper is changed approximately 90 degrees and directed upward. While the sheet of paper slidingly contacts with a guide surface  207 A of a first guide member  207  formed in an inner wall side of a front cover  15  (to be described hereinafter), the sheet of paper is guided toward the second pressure roller  206 . 
   The sheet of paper guided toward the second pressure roller  206  is guided by the second pressure roller  206  while the paper slidingly contacts with a guide surface  208 A of a second guide member  208  disposed in the housing  10 . The sheet of paper is pressed by the second pressure roller  206  against the upper side of the separation roller  203 . The conveyance direction of the paper is changed toward the left side in the drawing. Then, the sheet of paper is conveyed toward the image formation unit  100 . 
   That is, in the present embodiment, the conveyance direction of paper conveyed from the paper placement tray  201  is changed by a turning unit including the first and the second guide members  207 ,  208 . 
   In the present embodiment, the first pressure roller  205  and the first guide member  207  are attached to the front cover  15 . The second pressure roller  206  and the second guide member  208  are attached to the housing  10 . 
   In the paper conveyance path formed between the paper placement tray  201  and the image formation unit  100 , a pair of resist rollers  209  are disposed in vicinity of an entrance to the image formation unit  100 . The pair of resist rollers  209  adjust conveyance condition of paper by applying predetermined conveyance resistance to a sheet of paper being conveyed. 
   2.2. Image Formation Unit 
   The image formation unit  100  includes a scanner unit  110 , a development cartridge  120 , and a fixation unit  130 . 
   2.2.1. Scanner Unit 
   The scanner unit  110  is disposed in an uppermost portion of the housing  10 , and forms a latent image on the surface of a photoreceptor drum  121  to be described later. Specifically, the scanner unit  110  includes a laser beam source (not shown), a polygon mirror (not shown), a fθ lens (not shown), and a reflection mirror (not shown). 
   Laser beam emitted from the laser beam source is deflected by the polygon mirror based on image data and passes through the fθ lens. The beam path of the laser beam is then returned by the reflection mirror. The beam path is bent downward such that laser beam is directed on the surface of the photoreceptor drum  121  so as to form a latent image thereon. 
   2.2.2. Development Cartridge 
   The development cartridge  120  is disposed above the paper placement tray  201  and below the scanner unit  110 . The development cartridge  120  is located inside of the housing  10  so as to be detachable in the same direction as the detachment direction of the paper placement tray  201 . The development cartridge  120  includes a photoreceptor drum  121 , a charger  122 , and a toner containing portion  123 . 
   The photoreceptor drum  121  holds an image to be transferred on a sheet of paper. The cylindrical outer peripheral of the photoreceptor drum  121  is formed by positively charged photoreceptor layers, made of polycarbonate and the like. The charger  122  charges the surface of the photoreceptor drum  121 . The charger  122  is disposed above and behind the photoreceptor drum  121  so as to face but not to contact the photoreceptor drum  121 . A predetermined interval is provided between the charger  122  and the photoreceptor drum  121 . 
   A scorotron type charger is adopted for the charger  122  according to the present embodiment wherein positive electric is charged approximately in a uniform manner on the surface of the photoreceptor drum  121  by using corona discharge. 
   The toner containing portion  123  contains toner (developer). Between the toner containing portion  123  and the photoreceptor drum  121 , a toner supply roller  124  and a development roller  125  are disposed so as to supply toner, provided from the toner containing portion  123 , to the photoreceptor drum  121 . 
   Specifically, toner provided from the toner containing portion  123  is supplied toward the development roller  125  by rotation of the toner supply roller  124 . Once the toner is supplied to the development roller  125 , the toner is maintained on the surface of the development roller  125 , and the thickness thereof is evenly adjusted to a predetermined thickness by a thickness restriction blade  126 . Subsequently, the toner is supplied to the surface of the photoreceptor drum  121  exposed to laser beam emitted from the scanner unit  110 . 
   In a position opposite to the photoreceptor drum  121  across a sheet of paper being conveyed, a transfer roller  140  is disposed. The transfer roller  140  is rotated in conjunction with the rotation of the photoreceptor drum  121 . When a sheet of paper passes in vicinity of the photoreceptor drum  121 , the transfer roller  140  transfers toner adhered on the surface of the photoreceptor drum  121  onto a printing surface of the sheet of paper. Toner is transferred by applying an electric charge opposite to the electric charge by which the photoreceptor drum  121  is charged (a negative electric charge, in the present embodiment) to the sheet of paper from a surface of the transfer roller  140  located in an opposite side of the printing surface of the sheet of paper. 
   As shown in  FIG. 1 , a contact point between the transfer roller  140  and the photoreceptor drum  121  is located below a contact point between the pair of resist rollers  209 . That is, the contact point between the transfer roller  140  and the photoreceptor drum  121  is located more toward the paper placement tray  201  in comparison with the contact point between the pair of resist rollers  209 . A conveyance path L 1  extends from the side of the second pressure roller  206  and the resist rollers  209  to the side of the transfer roller  140 . The conveyance path L 1  is declined with respect to a horizontal direction such that the portion of the conveyance path L 1  becomes closer to the paper placement tray  201  as the portion of the conveyance path L 1  gets closer toward the side of the transfer roller  140  from the side of the resist rollers  209 . 
   2.2.3. Fixation Unit 
   The fixation unit  130  is disposed in a downstream side of the photoreceptor drum  121  in the conveyance direction of paper. The fixation unit  130  heats and melts toner transferred onto a sheet of paper so as to fix the toner on the sheet of paper. Specifically, the fixation unit  130  includes a heat roller  131  and a pressure roller  132 . The heat roller  131  is disposed in the printing surface side of a sheet of paper, and heats toner. The pressure roller  132  is disposed in an opposite side of the heat roller  131  across a sheet of paper, and presses a sheet of paper toward the heat roller  131 . 
   2.3. Housing and Front Cover 
   As described above, the development cartridge  120  and the paper placement tray  201  are installed in the housing  10  so as to be detachable with respect to the housing  10  approximately in a uniform direction (the left-to-right direction in  FIG. 1 ). The housing  10  is provided with a first opening  12  and a second opening  13 . The development cartridge  120  is attached/detached through the first opening  12 . The paper placement tray  201  is attached/detached through the second opening  13 . 
   In the present embodiment, the first and the second openings  12 ,  13  are integrated so as to form one opening  14 . 
   The opening  14  (the first and the second openings  12 ,  13 ) is closed by the front cover  15  continuously extending over the first and the second openings  12 ,  13 . In the present embodiment, the front cover  15  is provided so as to be integrated with the paper placement tray  201 . 
   The front cover  15  and the paper placement tray  201  according to the present embodiment are respectively and separately manufactured with resin, and combined by a mechanical fastener, such as a screw or a rivet, or engagement members respectively provided to the front cover  15  and the paper placement tray  201 . 
   In the front side of the front cover  15  (in the right side in the drawing), a handle portion  16  is provided so as to pull the front cover  15  (the paper placement tray  201 ). The handle portion  16  and the front cover  15  are integrally formed by resin. 
   An end portion of the housing  10  adjacent to the opening  14 , and an outer peripheral portion of the front cover  15  are respectively provided with overlapping portions  17 ,  18  so that the outer peripheral portion of the front cover  15  and the end portion of the housing  10  adjacent to the opening  14  overlap when the opening  14  (the fist and the second openings  12 ,  13 ) is closed by the front cover  15 . 
   In the present embodiment, the overlapping portion  17  of the front cover  15  is formed into a step shape so as to be subsided toward inside of the housing  10 . In this way, when the opening  14  is closed by the front cover  15 , the outer surfaces of the housing  10  and the front cover  15  form a smooth surface without any bump formed therebetween. 
   The first and the second guide members  207 ,  208 , which change the conveyance direction of paper conveyed from the paper placement tray  201 , are disposed in a position so as to face the inner wall of the front cover  15 , more specifically, in a “gap, formed between the front cover and the cover portion of the placement tray” as described earlier in the section “Background”. In addition, in the present embodiment, the first and the second guide members  207 ,  208  are disposed in a position between the first and the second openings  12 ,  13 . 
   In the above-described configuration, in order to remove the development cartridge  120  from the housing  10 , as shown in  FIG. 2 , firstly, the paper placement tray  201  is pulled out so that the opening  14  (the first and the second openings  12 ,  13 ) becomes uncovered. Then, as shown in  FIG. 3 , the development cartridge  120  is pulled and taken out of the housing  10 . 
   3. Feature of Laser Printer According to Present Embodiment 
   In the present embodiment, the front cover  15  is provided so as to extend over the first and the second openings  12 ,  13 . This configuration enables the first opening  12  through which the development cartridge  120  is attached/detached, and the second opening  13  through which the paper placement tray  201  is attached/detached to be covered by the single front cover  15 . 
   Therefore, “the gap between the front cover and the cover portion of the placement tray” described in the section “Background” does not exit in this configuration. As a result, noise can be effectively inhibited from leaking outside of the housing  10 , and the noise generated by the laser printer  1  can be reduced. 
   The front cover  15  is integrally configured so as to extend over the first and the second openings  12 ,  13 . This configuration enables to form a smooth surface without any gap or a bump in the front side of the laser printer  1 , and to provide a good appearance to the laser printer  1 . 
   The development cartridge  120  is removed from the housing  10  mainly when the amount of toner contained therein becomes small. On the other hand, the paper placement tray  201  is removed from the housing  10  so as to mainly replenish recording sheets. 
   Generally, the maximum amount of toner capable of being contained in the development cartridge  120  is larger than the amount of toner necessary for image formation performed on all the paper stored in the paper placement tray  201 . Therefore, the number of times the paper placement tray  201  is attached/detached is much larger than the number of times the development cartridge  120  is attached/detached. 
   In a case wherein the front cover  15  and the paper placement tray  201  are separately formed, in order to remove the paper placement tray  201  from the housing  10 , the front cover  15  needs to be opened (removed) prior to a removal of the paper placement tray  201  from the housing  10 . Replenishment of paper is likely to become troublesome, if the paper placement tray  201 , which is frequently attached/detached, and the front cover  15  are separately formed. 
   With respect to this issue, the front cover  15  is integrally formed with the paper placement tray  201  in the present embodiment. Replenishment of paper can be inhibited from being troublesome, since opening the front cover  15  and removing the paper placement tray  201  from the housing  10  can be simultaneously done. 
   In a portion of a laser printer, wherein the conveyance direction of paper is changed, friction force applied onto paper becomes large. Therefore, friction noise, which is one of the causes of noise generated in a laser printer, becomes large in this portion of a laser printer. 
   Concerning this problem, in the present embodiment, the first and the second guide members  207 ,  208 , which change the conveyance direction of paper, are disposed in a position so as to face the inner wall of the front cover  15 . The front cover  15  is disposed in vicinity of the first and the second guide members  207 ,  208  where large friction noise is generated. In the present embodiment, the vicinity of the noise source can be covered by the front cover  15 . Therefore, noise can be effectively inhibited from leaking outside of the housing  10 . 
   Moreover, the laser printer  1  (housing  10 ) according to the present embodiment is provided with the overlapping portions  17 ,  18  so that the outer peripheral of the front cover  15  and the end portion of the housing  10  in vicinity of the opening  14  overlap when the opening  14  is closed by the front cover  15 . Therefore, noise leakage from inside of the laser printer  1  (housing  10 ) to outside thereof can be reliably inhibited. 
   Furthermore, in the present embodiment, the portion of the conveyance path L 1  extending from the resist rollers  209  to the transfer roller  140  is declined with respect to the horizontal direction such that the portion of the conveyance path L 1  becomes closer to the paper placement tray  201  as the portion of the conveyance path L 1  gets closer toward the side of the transfer roller  140  from the side of the resist rollers  209 . Therefore, the distance between the transfer roller  140  and the paper placement tray  201  can be reduced, and the size of the laser printer  1  in the up-and-down direction can be reduced. 
   In the laser printer  1  according to the present embodiment, a sheet of paper sent from the paper placement tray  201  is conveyed in a distinctly curved state. Large noise is likely to be caused inside of the housing  10  (laser printer  1 ). 
   However, the laser printer  1  according to the present embodiment is configured such that noise can be sufficiently inhibited from leaking from the housing  10 , and that noise generated in vicinity of the first and the second guide members  207 ,  208  can be reduced. Therefore, noise of the laser printer  1  can be reduced, even if paper is conveyed in a distinctly curved state. 
   As a result, in the present embodiment, the size of the laser printer  1  in the up-and-down direction can be reduced, and noise of the laser printer  1  can be also reduced. 
   Second Embodiment 
   In the first embodiment, the first pressure roller  205  and the first guide member  207  are attached to the front cover  15 , and the second pressure roller  206  and the second guide member  208  are attached to the housing  10 . In the present embodiment, all of the first and the second pressure rollers  205 ,  206  and the first and the second guide members  207 ,  208  are attached to the front cover  15 . 
   That is, in the present embodiment, as shown in  FIG. 4 , all of the first and the second pressure rollers  205 ,  206  and the first and the second guide members  207 ,  208  are disposed in a position so as to face the inner wall of the front cover  15 . 
   The following describes the feature of the laser printer  1  according to the present embodiment. 
   In a case wherein a distinct bump exists between the first and the second guide members  207 ,  208 , a trailing end of a conveyed paper is flipped by the bump and hits the second guide member  208 . When a conveyed paper hits the second guide member  208 , loud noise (hitting noise) is generated. 
   The portion of a conveyed paper more distinctly curved hits the second guide member  208  faster, and makes loud noise (hitting noise). That is, noise is more likely to be generated in a portion of the laser printer  1  wherein the first and the second guide members  207 ,  208  are disposed. 
   With respect to this issue, both of the first and the second guide members  207 ,  208  are fixed to the front cover  15  in the present embodiment. Therefore, a bump formed between the first and the second guide members  207 ,  208  can be configured small. 
   In a case, as in the first embodiment, wherein the first guide member  207  is disposed in the side of the front cover  15  (the paper placement tray  201 ), and the second guide member  208  is disposed in the side of the housing  10 , a bump formed between the first and the second guide members  207 ,  208  is likely to become large, because variation of the size of the front cover  15  with respect to the housing  10  is added to the size of the bump. 
   In order to keep such bump small in the above-described configuration, variations caused in the sizes of the front cover  15  and the housing  10  themselves, and size variation caused in attaching the front cover  15  to the housing  10  need to be kept small. For this purpose, the number of manufacturing steps of the laser printer  1  is likely to be increased. 
   Considering this issue, both of the first and the second guide members  207 ,  208  are fixed to the front cover  15  in the present embodiment. Therefore, the variations caused in the size of the front cover  15  with respect to the housing  10 , and the size variation caused in attaching the front cover  15  to the housing  10  are not added to the size of the bump formed between the first and the second guide members  207 ,  208 . 
   Since the bump formed between the first and the second guide members  207 ,  208  can be small, noise generated by the bump can be reduced. 
   Third Embodiment 
   In the second embodiment, the first and the second guide members  207 ,  208  are individual members. In the present embodiment, as shown in  FIG. 5 , the first and the second guide members  207 ,  208  are integrally formed as a single guide member  210 . The guide member  210  is formed into an arc shape having a smooth guide surface  210 A which slidingly contacts a sheet of paper, and extends along the conveyance direction of paper. 
   Therefore, the guide member  210  is configured without any bump in the present embodiment. As a result, noise generated in vicinity of the guide member  210  can be further reduced, and noise of the laser printer  1  can be further reduced. 
   Fourth Embodiment 
   In the above-described embodiments, the front cover  15  is integrated with the front end portion of the paper placement tray  201 , and does not have mobility with respect to the paper placement tray  201 . In the present embodiment, as shown in  FIG. 6 , the front cover  15  is rotatably attached to the paper placement tray  201  by a hinge mechanism (not shown). 
   Therefore, in the present embodiment, when the front cover  15  is inclined so as to rotate with respect to the paper placement tray  201  for replenishing (placing) paper on the paper placement tray  201 , the front cover  15  can be inhibited from interrupting the replenishment. Paper can be easily replenished on the paper placement tray  201 . 
   Moreover, since the front cover  15  is rotatably attached to the paper placement tray  201  in the present embodiment, the first opening  12  can be opened simply by opening the front cover  15  without pulling out the paper placement tray  201  in order to attach/detach the development cartridge  120  to/from the housing  10 . 
   As a result, operationability in attaching/detaching the development cartridge  120  can be improved, because the development cartridge  120  can be attached/detached while the paper placement tray  201  is installed in the housing  10  (laser printer  1 ). 
   Although  FIG. 6  shows an example wherein the present embodiment is applied to the configuration according to the first embodiment, the application of the present embodiment is not limited to this example. The present embodiment may be applied to the configuration according to the second or the third embodiment. 
   Other Embodiment 
   In the above-described embodiments, the first and the second openings  12 ,  13  constitute the single opening  14 . The present invention is not limited to the above-described configuration. The first and the second openings  12 ,  13  may be individually provided. 
   Moreover, in the above-described embodiments, the front cover  15  is provided to the paper placement tray  201 . However, the present invention is not limited to this configuration. The front cover  15  can be, for example, rotatably attached to the housing  10 , or can be detachably attached to the laser printer  1  (housing  10 ). 
   Furthermore, the overlapping portions  17 ,  18 , by which the outer peripheral of the front cover  15  and the end portion of the housing  10  adjacent to the opening  14  overlap, are provided in the above-described embodiments. The present invention is not limited to this configuration. The outer peripheral of the front cover  15  and the end portion of the housing  10  adjacent to the opening  14  may be formed so as to abut each other, so that the overlapping portions  17 ,  18  may be omitted. 
   Still furthermore, although the overlapping portion  17  of the housing  10  is provided with a step portion in the above-described embodiments, the present invention is not limited to this configuration. The step portion of the overlapping portion  17  of the housing  10  may be omitted, or the step portion may be provided to the overlapping portion  18  of the front cover  15 . 
   Moreover, in the above-described embodiments (for example, in the first embodiment), the first guide member  207  is disposed in the side of the front cover  15 . However, the present invention is not limited to this configuration. Both of the first and the second guide members  207 ,  208  may be, for example, disposed in the side of the housing  10 . 
   Additionally, the present invention is applied to a monochrome laser printer in the above-described embodiments. However, the application of the present invention is not limited to this application. The present invention may be applied to a color laser printer, a monochrome or a color copier. 
   Moreover, the present invention is not only applicable to a laser printer, but may also be applicable to a so-called LED printer. In a LED printer, a photosensitive layer surface of a photoreceptor drum is exposed to light by a plurality of LEDs disposed in parallel along a rotational shaft of the photoreceptor drum. The present invention may be furthermore applicable, for example, to other types of image forming apparatus, such as a multifunction apparatus and so on. 
   Furthermore, the above-described embodiments describe examples wherein toner (for example, powdery toner) is used as the developer. However, the present invention may be also applicable to an image forming apparatus wherein liquid developer is used as the developer. 
   Although specific embodiments have been illustrated and described herein, it is to be understood that the above description is intended to be illustrative, and not restrictive. Combinations of the above embodiments and other embodiments will be apparent to those of skilled in the art upon reviewing the above description. The scope of the invention includes any other applications in which the above structures are used. Accordingly, the scope of the invention should only be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.