Abstract:
An image forming apparatus for forming an image including: a photoreceptor; a charging apparatus for charging the photoreceptor; and exposure apparatus for exposing an image onto the charged photoreceptor and forming an electrostatic latent image on the photoreceptor; a development apparatus for developing the electrostatic latent image on the photoreceptor; and a plural kinds of air flow paths for discharging air out of the apparatus by ventilating the air in an axial direction of the photoreceptor; wherein air flow directions in the plural kinds of air flow paths are made to be one and the same direction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is based on Japanese Patent Application No. 2007-213456 filed with Japanese Patent Office on Aug. 20, 2007, the entire content of which is hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming apparatus for forming an image on a sheet by an electrophotographic process, particularly to an image forming apparatus incorporating a plurality of air flow paths. 
   2. Description of the Related Art 
   The image forming apparatus based on electrophotographic process is provided with a passage for guiding the cooling air for cooling a fixing apparatus and development apparatus, the air including the ozone generated in a charging apparatus, and the air containing scattered toner, to ensure that the air, processed with dust protection and ozone elimination measures, is discharged out of the image forming apparatus. 
   Means are devised to ensure that cooling and ozone elimination steps can be taken effectively even when the apparatus is designed in a compact configuration and various forms of components inside the apparatus are packed in compact arrangements. 
   For example, the Japanese Unexamined Patent Application Publication No. 10-115958 (JPA10-115958) discloses an image forming apparatus wherein a ventilation duct is installed between the cleaning apparatus and fixing apparatus and an outer air intake fan is arranged in the vicinity of the charging apparatus. The incoming air is led in the axial direction of the aforementioned photoreceptor inwardly (one way only), and is then led in the axial direction of the aforementioned photoreceptor inside the aforementioned ventilation duct outwardly to be discharged out of the image forming apparatus. 
   In the image forming apparatus of JPA10-115958, the direction of air flowing in the vicinity of the charging apparatus is opposite that of the air flowing through the ventilation duct between the cleaning apparatus and fixing apparatus. 
   Such an airflow path cannot be said to be a rational and effective flow path in an image forming apparatus of compact configuration. 
   To be more specific, air flows through the image forming apparatus in two opposite directions. If two air paths are arranged close to each other in a compact version, two streams of air flowing in opposite directions will interfere with each other. Thus, one air stream will hinder the other air stream, with the result that the effects of cooling, ozone elimination and scattered toner recovery may be reduced. 
   To solve this problem, the air flow paths must be separated from each other. This will make it difficult to design a compact apparatus. 
   Several types of air flow paths arranged around the development apparatus in particular are close to one another, and there will be serious interference among flow paths. 
   The object of the present invention is to solve such a problem and to provide an image forming apparatus of compact design wherein sufficient ozone elimination, recovery of scattered toner and cooling of development apparatus are ensured. 
   SUMMARY 
   The aforementioned object can be achieved by the following image forming apparatus reflecting one aspect of the present invention: 
   An image forming apparatus for forming an image, including: 
   a photoreceptor; 
   a charging apparatus for charging the photoreceptor; 
   an exposure apparatus for exposing an image onto the charged photoreceptor and forming an electrostatic latent image on the photoreceptor; 
   a development apparatus for developing the electrostatic latent image on the photoreceptor; and 
   a plural kinds of air flow paths for discharging air out of the apparatus by ventilating the air in an axial direction of the photoreceptor; 
   wherein air flow directions in the plural kinds of air flow paths are made to be one and the same direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a drawing representing the overall structure of the image forming apparatus A as an embodiment of the present invention; 
       FIG. 2  is a cross sectional view representing the front surface of the image forming apparatus A, wherein the structure in the vicinity of a development apparatus is shown; 
       FIG. 3  is a perspective view taken along arrow line A-A of  FIG. 2 ; 
       FIG. 4  is a perspective view taken along arrow line B-B of  FIG. 2 ; 
       FIG. 5  is a diagram representing the air flow path of the image forming apparatus; and 
       FIG. 6  is a diagram representing that air flows in one and the same direction. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following describes the present invention with reference to the embodiment of the present invention, without the present invention being restricted thereto. 
     FIG. 1  is a drawing representing the overall structure of the image forming apparatus A as an embodiment of the present invention. 
   The image forming apparatus A is what is called the tandem type color image forming apparatus, and includes a plurality of image forming units  10 Y,  10 M,  10 C and  10 K, a belt-like intermediate transfer member  6 , a sheet feed apparatus  20  and a fixing apparatus  30 . 
   An image reading apparatus SC is mounted on the top of the image forming apparatus A. The originals placed on the original platen are exposed and scanned by the optical system of the original image scanning exposure apparatus of the image reading apparatus SC and the image of the original is read by the line image sensor. 
   The analog signal obtained by photoelectric conversion by the line image sensor is subjected to such processing as analog processing, analog-to-digital conversion, shading correction and image compression by the image processing section. After that, the signal is inputted into the exposure apparatuses  3 Y,  3 M,  3 C,  3 K. 
   The image forming unit  10 Y for forming a yellow (Y) toner image includes a charging apparatus  2 Y, an exposure apparatus  3 Y, a development apparatus  4 Y and a cleaning apparatus  5 Y which are arranged around the photoreceptor  1 Y. 
   The image forming unit  10 M for forming a magenta (M) toner image includes a charging apparatus  2 M, an exposure apparatus  3 M, a development apparatus  4 M and a cleaning apparatus  5 M. 
   The image forming unit  10 C for forming a cyan (C) toner image includes a charging apparatus  2 C, an exposure apparatus  3 C, a development apparatus  4 C and a cleaning apparatus SC. 
   The image forming unit  10 K for forming a black (K) toner image includes a charging apparatus  2 K, an exposure apparatus  3 K, a development apparatus  4 K and a cleaning apparatus  5 K. 
   The  4 Y,  4 M,  4 C and  4 K are development apparatuses that accommodate two-component developer containing yellow (Y), magenta (M), cyan (C) and black (K) toners having a small particle diameter, and carriers. 
   An intermediate transfer member  6  is wound with a plurality of rollers, and is rotatably supported. 
   Toner images of various colors formed by image forming units  10 Y,  10 M,  10 C and  10 K are sequentially primarily-transferred onto the rotating intermediate transfer member  6  by the primary transfer apparatuses  7 Y,  7 M,  7 C and  7 K, and are formed into a superimposed color toner image. 
   Paper P stored in the sheet feed cassette  21  of the sheet feed apparatus  20  is fed by a sheet feed section  22 , and is conveyed to a secondary transfer apparatus  9  through the sheet feed rollers  23 ,  24 ,  25  and  26 , registration roller  27 . Then the color toner image is secondarily transferred onto the paper P. 
   The three-step sheet feed cassettes  21  arranged in a single file in the vertical direction below the image forming apparatus A have almost the same structure. The three-step sheet feed sections  22  also have almost the same structure. Including the sheet feed cassette  21  and sheet feed section  22 , this is called the sheet feed apparatus  20 . 
   The paper P with the color toner image transferred thereon is subjected to a step of fixing by heat and pressure in the fixing apparatus  30 . The upper surface of the paper P subsequent to fixing is sandwiched by ejection rollers  28 , and the paper is placed on the ejection tray  29  outside the apparatus. 
   In the meantime, after the color toner image has been transferred onto the paper P by the secondary transfer apparatus  9 , the intermediate transfer member  6  is cleaned by a cleaning apparatus  8  so that the residual toner is removed. 
   The image forming apparatus A is a color image forming apparatus, and the present invention can also be applied to the image forming apparatus for forming a monochromatic image. 
   In the following description, the photoreceptors  1 Y,  1 M,  1 C and  1 K will be collectively called the photoreceptor  1 , and the development apparatuses  4 Y,  4 M,  4 C and  4 K will be collectively called the development apparatus  4 . 
     FIG. 2  is a cross sectional view representing the front surface of the image forming apparatus A, wherein the structure in the vicinity of a development apparatus is shown. 
   The structure in the vicinity of the development apparatuses  4 Y,  4 M,  4 C and  4 K is as shown in  FIG. 2 . A plurality of air flow paths are arranged around the development apparatus. A plurality of air flow paths include an ozone passage as a passage of the air including ozone, a scattered toner passage as a passage of the air including scattered toner, and a cooling air passage allowing passage of cooling air. As “4” is used to denote the development apparatuses  4 Y,  4 M,  4 C and  4 K, the abbreviated symbol of omitting YMCK will be assigned to each part in the following description. 
   The development apparatus  4  incorporates a housing  40 , which further includes a development roller  41 , agitation/conveyance screws  42  and  43 , a regulating member  43  for regulating developer, and a developer recovery roller  44 . 
   The development roller  41  is configured with a rotating development sleeve and a magnetic roll arranged and fixed in the rotating development sleeve, the magnetic roll containing a plurality of magnetic poles. The recovery roller  44  is configured with a rotating recovery sleeve and a magnetic roll, which contains a plurality of magnetic poles, arranged and fixed in the rotating recovery sleeve. 
   In the step of image formation, the photoreceptor  1  rotates in the counterclockwise direction as indicated by the arrow mark W 1 , and the electrostatic latent image on the photoreceptor  1  is developed by the layer of developer on the development roller  41 . 
   In the development apparatus  4 , the agitation/conveyance screws  42  and  43  rotate to agitate and convey the developer so that the developer is supplied onto the development roller  41 . 
   The developer on the development roller  41  is regulated by the regulating member  45  so that a fixed amount of developer is always supplied to the development area. 
   After development, the developer is fed below the development roller  41  and is recovered by the agitation/conveyance screw  43 . Further, the excess developer regulated by the regulating member  45  is recovered by the recovery roller  44 , and is fed to the agitation/conveyance roller  42 . 
   A charging apparatus  2  is arranged below the development apparatus  4 . The ozone having been generated in the charging apparatus  2  passes through the ozone passage  50  arranged below the development apparatus  4 . 
   The ozone passage  50  is made of a duct  51  including a gas inlet  52 , and consists of the passage divided into a plurality of parts as shown in  FIG. 2  by the partition members  53  through  55  for regulating air flow. 
     FIG. 3  is a perspective view taken along arrow line A-A of  FIG. 2 . As shown in  FIG. 3 , the ozone passage  50  is divided into a plurality of parts by the partition members  53  through  55 . 
   As indicated by the arrow mark W 2 , air containing ozone passes through the ozone passage  50 . As will be described later, ozone is removed, and the air is discharged out of the image forming apparatus A ( FIG. 1 ). 
   A cooling air passage  60  is formed on the side of the development apparatus  40 . 
   The cooling air passage  60  is formed by the space surrounded by a plurality of parts constituting the image forming apparatus A. 
   A scattered toner passage  70  is formed above the development apparatus  4 . 
   The scattered toner passage  70  is made up of a duct  71 . As shown in  FIG. 4 , the scattered toner passage  70  is divided into a plurality of parts by the partition members  72  through  74 . The air containing toner passes through each passage flows as indicated by the arrow mark W 3 . As will be described later, the air is discharged out of the image forming apparatus A.  FIG. 4  is a perspective view taken along arrow line B-B of  FIG. 2 . 
   The recovery passage for recovering toner into the scattered toner passage  70  is made up of the housing  40  of the development apparatus and the cover member  75  connected to the duct  71 . 
     FIG. 5  shows the air flow path of the image forming apparatus. 
   The ozone filter  56  and exhaust fan  57  are mounted on the exhaust section of the ozone passage  50 . The ozone generated in the charging apparatus  2  is sucked by the exhaust fan  57 , and the air from which ozone has been removed by the ozone filter  56  is discharged out of the image forming apparatus A. 
   The air supply fan  61  and filter  62  are installed on the outside air inlet section of the cooling air passage  60 , and the exhaust fan  63  is arranged on the exhaust section. 
   The dust protection filter  75  and exhaust fan  76  are mounted on the exhaust section of the scattered toner passage  70 . Toner is sucked by the exhaust fan  76 , and the air from which toner has been removed by the dust protection filter  75  is discharged out of the image forming apparatus A. 
   The exhaust fans  57 ,  63  and  76  can be configured with one or two common fans. 
   In  FIG. 5 , the lower portion indicates the front side of the image forming apparatus A, while the upper portion represents the rear side of the image forming apparatus A. 
   The air flow direction W 2  in the ozone passage  50 , the air flow direction W 3  in the cooling air passage  60 , and the air flow direction W 4  in the scattered toner passage  70  respectively have traveling components in axial direction of the photoreceptor, namely in perpendicular direction to the moving direction of the photoreceptor, which being parallel to the surface of the photoreceptor. 
   The direction W 2 , direction W 3  and direction W 4  are arranged in the same orientation with one another. The symbol W 5  denotes the traveling direction of the photoreceptor. 
   Even in an apparatus wherein passages  50 ,  60  and  70  are arranged close to one another, according to the above direction of air flow, a smooth flow of air in each passages is ensured without the air flow in each passage interfering with that in the other passage, thereby ensuring an effective removal of ozone, cooling of the development apparatus and recovery of scattered toner. 
   That air flow directions W 2  through W 4  are arranged in the same orientation is not restricted to mean that there must be complete agreement among directions W 2  through W 4 . For example, this includes the case wherein the air flows in the direction oblique to the axial direction of the aforementioned photoreceptor as induced by the partition members  53  through  55 , and  72  through  74  shown in  FIG. 3  and  FIG. 4 . 
   Referring to  FIG. 6 , the following describes “flow of air in the axial direction of the photoreceptor” and “two air flows in the same direction”. 
   When the angle θ 1  between the air flow direction WA and axial direction WH of the photoreceptor is less than 45 degrees, air is assumed to flow in the axial direction of the aforementioned photoreceptor. 
   When the angle θ 2  between the arrow mark WB and arrow mark WC is less than 90 degrees, the air flow direction indicated by the arrow mark WB is assumed as the same as that indicated by the arrow mark WC. 
   When the nip angle θ 2  is greater than 90, the air flow indicated by the arrow mark WB interferes with the air flow indicated by the arrow mark WC. If the nip angle θ is less than 90, however, there is no interference. 
   In the present invention, the direction of air flow in a plurality of air flow paths is the same as the axial direction of the photoreceptor. This arrangement ensures an effective removal of ozone, cooling of the development apparatus and removal of scattered toner without any interference among air flows in each flow path, whereby a compact design of the apparatus can be achieved.