Patent Publication Number: US-6985165-B2

Title: Toner scattering suppressing apparatus and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority under 35 USC §119 to Japanese Patent Application No. 2001-204546 filed on Jul. 5, 2001, the entire contents of which are herein incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image forming apparatus, such as a copier, a printer, a facsimile, a combined machine combining these apparatuses, etc. capable of subsequently forming toner images on an image bearer by repeating processes of discharging, writing, developing with dry type developer, transferring images onto transfer members, such as sheets, medium transfer members, etc., and cleaning. More particularly, the present invention relates to a toner scattering suppression apparatus capable of suppressing toner scattering from cleaning and developing apparatuses of the electro-photographic image forming apparatus. 
   2. Discussion of the Background 
   In a conventional electro-photographic system using an image forming apparatus, a discharging apparatus uniformly charges a surface of an image bearing member and a writing apparatus and subsequently writes and forms a latent image on the surface by irradiating a light while the image bearing member rotates. Then, a developing device applies toner so as to develop the latent image. The developed toner image is transferred by a transfer apparatus onto a transfer member, such as a sheet, a medium transfer member, etc. Finally, a cleaning apparatus removes toner remaining on the image bearer after image transfer. Then, the image forming apparatus prepares for the next image formation starting from discharging. 
   However, the rotation of the image bearer and of an internal rotation member cause a rising airflow and an internal air pressure increase in the developing and cleaning apparatuses each accommodating toner. As a result, the airflow leaks from slight gaps in the device at joined parts and toner leakage occurs together with the airflow. Thus, the image forming apparatus is contaminated internally and externally. 
   Typically, openings are arranged on the developing and cleaning apparatuses to drain air. Air filters are also attached to the openings so as to prevent toner passage and scattering therefrom. However, the air filter can be choked with the toner during usage, and therefore prevention from an increase in internal air pressure is not effective. Thus, dust collection is not effective and toner scattering likely occurs. 
   Consequently, the air filter requires periodical maintenance. Specifically, the air filter is cleaned by a cleaner or other appropriate substance, or washed to remove toner. Otherwise, the old air filter is replaced with a new filter. 
   However, two types of air filters are needed in the respective developing and cleaning apparatuses in such a conventional image forming apparatus. As a result, the number of replacement parts increases, and the cost of maintenance rises based on an increase in maintenance inventory. 
   Further, intervals of maintenance for air filters in the developing and cleaning apparatuses are different from each other in the conventional toner scattering prevention apparatus. Thus, a frequency of maintenance and accordingly an increase in cost results. In such a case, if an air filter with a long maintenance interval receives maintenance at the same time an air filter with a short maintenance interval, changing the long maintenance interval filter is wasteful. 
   SUMMARY OF THE INVENTION 
   Accordingly, an object of the present invention is to address and resolve the above-noted and other problems and provide a new image forming apparatus. 
   The above and other objects are achieved according to the present invention by providing a novel image forming apparatus including a developing apparatus for developing a latent image formed on an image bearer by applying toner thereto, and a cleaning apparatus for cleaning the image bearer while removing the toner remaining on the image bearer after a toner image is transferred to a transfer medium. A toner scattering prevention apparatus is also included to prevent toner scattering. The toner scattering prevention apparatus includes, for example, a pair of substantially similar air filters which are detachably attached to air draining openings formed on the respective developing and cleaning apparatuses. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a side view illustrating the entire schematic configuration of an interior organization of a digital copier that employs a toner scattering prevention apparatus according to the present invention; 
       FIG. 2  is a side view illustrating surroundings of a PC drum of  FIG. 1 ; 
       FIG. 3  is a chart illustrating a relationship between an area of an air filter used in the toner scattering prevention apparatus and an operational life of the filter; 
       FIG. 4  is a side view illustrating various processing units integrated in a body together with a PC drum and employing a toner scattering prevention apparatus according to the present invention; and 
       FIG. 5  is a side view illustrating a recycle type image forming apparatus employing a toner scattering prevention apparatus according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, wherein like reference numerals and marks designate identical or corresponding parts throughout several views, and in particular in  FIG. 1 , the schematic configuration of an internal organization of a digital copier that includes a toner scattering prevention apparatus according to the present invention is illustrated. 
   Numeral  100  denotes a copier apparatus body. A reading and writing apparatus  200  may be attached above the copier apparatus body. The copier apparatus body may also be set on a table like sheet bank  300 . 
   As shown, the copier apparatus body  100  includes a drum shaped photo-conductive member (PC member)  10  as an image bearer. An upward charger  12 , a developing apparatus  13 , a transfer and transportation apparatus  14 , a cleaning apparatus  15  and a charge removing apparatus  11  (see  FIG. 2 ) is arranged one after another in this order in a clockwise direction “A” around the photo-conductive member  10 . 
   Also, a sheet transportation path B may be formed in the apparatus body so as to transport a sheet (i.e., a transfer member), such as an OHP film, etc., from right to left in the drawing via a gap formed between the PC member  10  and a transfer and transportation apparatus  14 . A register roller  16  is also disposed upstream of the PC member  10  on the sheet transportation path B, and a fixing apparatus  17  is disposed downstream of the PC member  10  along the sheet transportation path B. The fixing apparatus  17  includes a fixing roller  18  with a heater, and a pressure applying roller  19  pressing against the fixing roller  18 . An ejection roller  20  is also disposed in a left side of the fixing apparatus  17 . 
   The reading and writing apparatus  200  also includes a laser writing apparatus  22  and a manuscript reading apparatus  23 . The laser writing apparatus  22  includes a laser light source (not shown), a polygon mirror  24  for scanning, a polygon motor  25 , a scanning optical unit  26  such as an fθ lens. The manuscript reading apparatus  23  includes a light source  28 , a plurality of mirrors  29  and an image sensor  30  such as a CCD. 
   In addition, as shown, an exposure glass  31  is arranged on an upside of the reading and writing apparatus  200 . A document cover  32  is attached to the reading and writing apparatus  200  as is openable to cover the exposure glass  31 . 
   Also, the sheet bank  300  includes a plurality of multistage type sheet cassettes  34 , in which each sheet cassette  34  includes a supplying roller  35  and a separation roller  36 . A sheet feeding passage C is also formed from the right side of the multistage type sheet cassettes  34  to a sheet transportation path B extended in the image forming apparatus body  100 . Further, the sheet feeding passage C has a certain number of transportation rollers  37 . 
   As shown, the image forming apparatus body  100  includes an openable and manually sheet feeding tray  38  for guiding a manually inserted sheet to the sheet transportation passage B on the right side surface thereof Further, a sheet ejection tray  39  is attached to the left side surface so as to receive an image-recorded sheet ejected by an ejection roller  20 . 
   When a document is copied, the document cover is open and the document is set onto the exposure glass  31 . Then, a start switch (not shown) is depressed. The document reading apparatus  23  is driven and the light source  28  is moved along the exposure glass  31 . Simultaneously, a light beam from the light source  28  is reflected by the surface of the document. The reflected light is then reflected by a plurality of mirrors  29  and enters into an image sensor  30 , thereby the document is read by the image sensor  30 . 
   In addition, a PC member driving motor (not shown) rotates the PC member  10 , and the charger  12  may optionally include a charge roller that uniformly charges the surface of the PC member  10 . Subsequently, the laser writing apparatus  22  writes with a laser light in accordance with the contents of the document read by the document reading apparatus  23 , so that a latent image is formed on the surface of the PC member  10 . Next, the developing apparatus  13  affixes toner thereto, and thus the latent image is formed. 
   Further, when the start switch is depressed, an appropriate supply roller  35  is rotated, so that some sheets are supplied from a corresponding sheet cassette  34  among the plurality of multistage type sheet cassettes  34 . A following separation roller  36  separates and guides sheets one by one to the sheet feeding passage C. The transportation roller  37  transfers and guides the sheet to the sheet feeding passage B. The sheet then collides and stops at the register roller  16 . Then, the register roller  16  rotates and feeds the sheet to a section below the PC member in synchronism with rotation of the PC member  10 . 
   Otherwise, the supply roller  41  disposed on the manual sheet feeding section is rotated to bring a sheet manually set on the opening manual sheet inserting tray  38  to the sheet transportation passage B. Then, the register roller  16  similarly feeds the sheet toward the section below the PC member  10  in synchronism with the rotation of the PC member  10 . 
   Subsequently, the transfer and transportation apparatus  14  including a transfer belt  40  transfers a visible image onto the sheet fed to the below section. The cleaning apparatus  15  removes and cleans the toner remaining on the PC member  10  after the image transfer. The charge removing apparatus  11  (see  FIG. 2 ) also removes a potential charge remaining on the PC member  10  in order to prepare for the next image formation started from charging of the charging apparatus  12 . 
   Further, the sheet having received the toner transfer is then fed to the fixing apparatus  17  by the transfer and transportation apparatus  17 . The transferred image is then fixed by the fixing apparatus  17  while the fixing and pressure applying rollers  18  and  19  apply heat and pressure thereto. Then, the ejection roller  20  ejects and stacks the sheet on the sheet ejection tray  39 . 
   Referring to  FIG. 2 , details of the developing apparatus  13  are described. The developing apparatus  13  is formed from a developing tank  43  and a developing hopper  44 . 
   The developing tank  43  includes a developing roller  46 , a paddle wheel  47 , a stirring roller  48 , a transfer screw  49 , a separator  50 , a doctor blade  51  and a toner density sensor  52 , or the like. The developing tank  43  also accommodates two component type developers including at least carrier and toner. 
   The developing roller  46  includes a cylindrical developing sleeve  65  made of nonmagnetic material, such as aluminum, brass, stainless, conductive plastic, etc. Also, the developing roller  46  may be a magnetic roller member  66  disposed in the developing sleeve  65  so as to form a magnetic field so that the developer can form a bristle on the outer surface of the developing sleeve  65 . A rotation driving mechanism (not shown) rotates the developing sleeve  65  counter clockwise. 
   The developer hopper  44  has a gear such as toner replenishment member  54 , a replenishment regulating plate  55  and an agitator  56  or other appropriate apparatuses. The developing hopper  44  also accommodates toner. 
   Further, the stirring roller  48  rotates and frictionally discharges the two component developer in the developing casing of the developing apparatus  13 . The paddle wheel  47  then rotates and chums the developer so that the developer adheres to the developing roller  46 . Thus, the magnetic field lines form a chain like bristle made of the carrier on the developing sleeve  65 . The charged toner simultaneously sticks to the chain like bristle, thereby forming a magnetic brush. 
   Then, the magnetic brush is conveyed while the developing sleeve  65  rotates and is regulated to have a prescribed thickness by the doctor blade  51 . Specifically, the magnetic brush adheres to the PC member  10  and develops the latent image on the PC drum  10  after the excessive amount is scraped. 
   When toner decreases as a result of adhesion to the PC member  10  in the developing apparatus  13 , a toner rate (i.e., toner density) decreases accordingly. Then, if a toner density of the developer is less than a target value thereof, the agitator  56  rotates and stirs the toner. Simultaneously, the toner is transported to the toner replenishment member  54  and is replenished to the developing tank  43  from the developer hopper  44  while the toner replenishment member  54  is rotated and the replenishment regulating plate  55  is swung. Thus, the toner density can be maintained within a prescribed range. 
   A toner density sensor  52  may also be attached to the developing casing  58  so as to detect the toner density of the developer. A value obtained by measuring (a density of) a so called “P” pattern (a measurement use toner image) formed on the PC member  10  with a photo sensor can be preset as a toner density target value. 
   Then, the toner adhering to the PC member  10  is electrostatically transferred onto a sheet by the transfer and transportation apparatus  14  as described above. However, about 10% of the toner remains on the PC member  10  without being transferred. Toner remaining on the PC member  10  is scraped off by the cleaning blade  60  and brush roller  61  disposed in the cleaning apparatus  15  from the PC member  10 . 
   Referring again to  FIG. 2 , details of the cleaning apparatus are now described. The cleaning apparatus  15  forms a recovery tank  62  in the cleaning casing  64  and includes a cleaning blade  60 , a brush roller  61  and a recovery screw  63 . 
   The cleaning blade  60  may be made of rubber, and contact the PC member  10  via its tip with a prescribed pressure and angle. The brush roller  61  may be formed from a metal bar on which brushes are implanted and is rotated by a driving device (not shown) in a direction shown by an arrow in the drawing. The recovery screw  63  may be formed from a metal or plastic mold in a spiral shape. 
   The brush roller  61  initially scrapes off the toner remaining on the PC member  10  after transfer. Subsequently, the toner surviving the initial scraping operation is almost completely removed by the cleaning blade  60 . The toner scraped off from the PC member  10  by the cleaning blade  60  and brush roller  61  then enters into the recovery tank  62 . Then, the toner is transferred to one side of the cleaning apparatus  15  by a recovery screw  63 . 
   Further, an air draining use-opening  70  is formed on the developing casing  58  of the developing apparatus  13 , and a filter holding frame  71  is arranged around the air draining use-opening  70 . Another air draining use-opening  72  is formed in the cleaning casing  64  of the cleaning apparatus  15 , and another filter holding frame  73  is arranged around the air draining use-opening  72 . As shown, a pair of air filters  74  and  75  have substantially the same shape and material and are detachably attached to the respective filter holding frames  71  and  73 . The air filters  74  and  75  may be made from paper, fabric, bonded fiber fabric, or multi porous synthetic plastic, or any other appropriate material, as to remove toner by either physically percolating or using an electrostatic absorption system, or any other appropriate removal system. 
   When the developing sleeve  65  of the developing roller  46  rotates together with the PC member  10  in the developing apparatus  13 , an airflow shown by a dotted line arrow D in  FIG. 2  arises in the developing casing  58 . However, the airflow leaks through the air draining use opening  70 , and the inner air pressure of the developing apparatus  13  does not increase. In addition, floating toner is prevented from leaking from the developing apparatus  13  when trapped by the air filter  74 . 
   Further, when the brush roller  61  rotates together with the PC member  10  in the cleaning apparatus  15 , an airflow shown by a dotted line arrow E in  FIG. 2  arises in the cleaning casing  64 . However, the airflow leaks through the air draining use-opening  72 , and the inner air pressure of the cleaning apparatus  15  does not increase. In addition, floating toner is prevented from leaking from the cleaning apparatus  15  when trapped by the air filter  75 . 
   Such internal air pressure is designed to be substantially the same in the respective developing and cleaning casings. In addition, scattering levels in the developing and cleaning casings is also designed to be substantially the same. Thus, because substantially the same material and shape air filters  74  and  75  are used as air draining use openings  70  and  72  in the developing and cleaning apparatuses  13  and  15 , parts can be commonly used, and maintenance inventory can be decreased. As a result, the cost of maintenance can be decreased. 
   If an amount of toner scattering in the developing and cleaning apparatuses  13  and  15  is taken into account and the maintenance interval for respective air filters  74  and  75  are designed to be substantially equal, the respective air filters  74  and  75  can be either cleaned by a cleaner, washed with water or replaced with new ones, at substantially the same time. As a result, the maintenance labor and cost may accordingly decreased. 
   As illustrated in  FIG. 2 , when substantially the same air filters  74  and  75  are coupled to air draining use openings  70  and  72  of the respective developing and cleaning apparatuses  13  and  15 , and maintenance intervals thereof are designed to be substantially equal, parts may be commonly used, and maintenance inventory may be decreased. In addition, when performance of maintenance occur at substantially the same time, the maintenance labor and cost may be decreased. 
   Further, if a maintenance interval for at least one of parts of the developing and cleaning apparatuses  13  and  15  is designed to be substantially the same as that of the air filters  74  and  75 , and if the maintenance timing for the other parts is substantially the same in addition to that of the respective air filters  74  and  75 , the maintenance labor and cost may be further decreased. 
   Referring now to  FIG. 3 , a relationship between an area of an air filter  74  or  75  and an operational life of the filters is illustrated. As shown, the larger the area of the air filter  74  or  75 , the longer the operational life of the filters. Accordingly, as shown by a dotted line F, if an optimal area of the air filter  74  or  75  is selected to have an operational life corresponding to an operational lifetime of another part, the maintenance intervals for the air filters and other parts may be substantially the same. 
   As a result, the operational lifetimes of the air filters  74  and  75  may be set to not expire before the operational lifetime of the other parts, which are simultaneously to be replaced. In addition, the air filters  74  and  75  having the predetermined operational lives are not prematurely. Thus, the maintenance cost may be decreased. 
   A monochrome copier in which a toner image formed on a PC member  10  is directly transferred to a sheet serving as a transfer member, for example, can be used in the above-described example. However, the present invention is not limited thereto and can be applied to the other types of an image forming apparatus, such as a printer, a facsimile, etc., in a similar manner. Further, a color image forming apparatus, in which a toner image formed on an image bearer is temporary transferred onto a medium transfer member, and is transferred therefrom onto a sheet, may also similarly be used in the present invention. 
   With reference to  FIGS. 4 and 5 , an alternate embodiment is described. As illustrated in  FIG. 4 , the above-described respective processing devices  11 ,  13 ,  14 ,  15  may be integrated together with the PC drum  140  in a casing  101  as a process cartridge so as to be integrally attached and discarded. However, the process cartridge can only include one of the processing devices  11 ,  13 ,  14 ,  15  and the PC drum  10 . The process cartridge may also include the entire PC drum  10 , charging apparatus  12 , developing apparatus  13  and cleaning apparatus  15  in a body. 
     FIG. 5  illustrates a recyclable type image forming apparatus. A recovery screw  63  is provided so as to transfer collected toner in the cleaning tank  62  toward the front side of the cleaning apparatus  15 . A toner recycle pipe  103  is provided to connect at one end the recovery screw  63  and at another end to the developing device  13 . A transfer coil is also provided in the toner recycle pipe  103  so as to receive driving force from a driving device (not shown) and rotate to transfer the collected toner to the developing apparatus  13 . The recycled toner is blended with fresh toner in the developing apparatus and serves as developer used in the developing process. While blending the toner, air can also be transferred in the developing device  13 , and the internal air pressure can further rise. However, the filteres according to the present invention, lower the excessive internal pressure. 
   Obviously, numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.