Patent Publication Number: US-7587153-B2

Title: Cooling device and image forming apparatus having the same installed therein

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of Korean Patent Application No. 2006-11233, filed Feb. 6, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Aspects of the present invention relate to a cooling device, which cools an image development cartridge and laser scanning unit used in forming images on print media, and an image forming apparatus having the same installed therein. 
   2. Description of the Related Art 
   Photocopiers, printers, multifunction apparatuses and similar image forming apparatuses may be broadly divided into color image forming apparatuses and black-and-white image forming apparatuses. The advantages of black-and-white image forming apparatuses compared to other image forming apparatuses are that they are generally smaller and provide faster printing speeds. 
   Generally in black-and-white image forming apparatuses, the print medium (i.e., paper, transparency, etc.) is moved from the paper supply tray by the pick-up roller and follows a predetermined course past an organic photoconductive (OPC drum), on the surface of which the image is formed, and a transfer roller rotating while facing the Organic photoconductor. The image formed on the Organic photoconductor is transferred to the print medium as it passes between the transfer roller and the Organic photoconductor. The print medium, on which the image is printed, then passes through a fuser assembly, where the image is fused to the surface of the print medium by an application of high temperatures and pressures. The print medium is then either discharged from the main body of the image forming apparatus, or is sent back through the main body of the image forming apparatus, via a duplex printing path, so that printing on the other side of the printing medium may occur. 
   The fuser assembly comprises a heating roller maintained at a high temperature, and a pressure roller, which presses the heating roller with high pressure while rotating. A fuser assembly with this structure maintains a high temperature both in a printing mode thereof and a warming-up mode thereof, and, consequently, emits heat for a long period. As a result, other components in the image forming device, such as the Organic photoconductor and the laser scanning unit, also heat up due to the heat emitted by the fuser assembly. 
   The Organic photoconductor is installed in the development cartridge inside the printer housing, and comprises a photosensitive layer on a surface thereof, which is sensitive to heat. Therefore, in general, the Organic photoconductor is unable to maintain a constant temperature due to the heat which the Organic photoconductor itself produces during operation, and the heat generated by the fuser assembly. In this situation, normal printing quality cannot be ensured. 
   Furthermore, structural limitations resulting from the Organic photoconductor being installed on the inside of the development cartridge, surrounded by a charging member, a cleaning blade, and a developer roller, render natural cooling of the Organic photoconductor difficult. 
   Moreover, the laser scanning unit to scan the Organic photoconductor is usually installed on top of the image development part, which comprises the Organic photoconductor. Generally, the laser scanning unit comprises a light source, a polygonal mirror, a spindle motor and a plurality of optical members. It is important to isolate or reduce the heat generated from the fuser assembly, as a minute change in the location or dimensions of laser scanning units, caused by the rise in temperature, may have a significant effect on the precision of components used in scanning the Organic photoconductor. 
   Taking the above factors into consideration, development of an apparatus that effectively cools down the laser scanning unit and the image development part is acutely needed. 
   SUMMARY OF THE INVENTION 
   Aspects of the present invention provide a cooling apparatus with a structure developed in order to cool both the laser scanning unit and the image development part, and an image forming apparatus having the cooling apparatus installed therein to alleviate the above and/or other problems. 
   According to aspects of the cooling apparatus of the present invention, the cooling apparatus is a cooling unit, which cools the laser scanning unit and the image development part. The image forming apparatus comprises an image development part, which transfers the image to the print medium; a laser scanning unit, which scans the surface of the organic photoconductor; and a fuser assembly, which fixes the image transferred from the organic photoconductor on the print medium. The cooling apparatus of the present invention comprises a fan, which generates airflow at the time of operation thereof; a support frame, installed inside the printer housing, to support the laser scanning unit; and a guide member, which guides the air generated by the fan towards the laser scanning unit and the image development part. 
   The guide member may be formed integrally with the support frame. The support frame may be disposed between the laser scanning unit and the fuser assembly. The fan may be installed on one side of the support frame in order to move the air towards the opposite side of the support frame. 
   The guide member may comprise a plurality of support ribs, disposed at predetermined intervals along the length of the support frame, which guide the airflow generated by the fan towards the image development cartridge and the laser scanning unit. The guide ribs may vary in length. The guide ribs may have curved surfaces to allow for efficient guiding of the air. The degree of curvature of the guide surfaces may vary. 
   The support frame may have an opening between an upper and a lower plate, and the guide ribs may be disposed perpendicularly at predetermined intervals around the opening in order to guide the airflow through the opening towards the image development part. The upper plate of the support frame may be formed with a smaller surface area than the lower plate, so the airflow generated by the fan may be directed towards the laser scanning unit. The guide ribs positioned the farthest from the fan may be longer than the other guide ribs. The guide ribs which are longer than the other guide ribs may also be inclined at a greater angle relative to the support frame than the other guide ribs. 
   The image forming apparatus of the present invention, in order to achieve the objectives listed above, comprises an image development part installed on the main body, with an organic photoconductor; a laser scanning unit to scan the organic photoconductor; a fuser assembly to fix the image to the print medium; and a cooling unit to cool the laser scanning unit and the image development part. 
   The cooling unit may be installed between the laser scanning unit and the fuser assembly. 
   The cooling unit may comprise a fan, installed inside the printer housing, which generates airflow at the time of operation; a support frame installed in the housing, which supports the scanning unit; and a guide member, disposed on the support frame, to guide the airflow generated by the fan towards the laser scanning unit and the image development part. 
   Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a cross-sectional diagram showing schematically the image forming apparatus according to an embodiment of the present invention. 
       FIG. 2  is a perspective view schematically showing the image forming apparatus in which the laser scanning unit is supported by the support frame. 
       FIG. 3  is a perspective view showing only the support frame illustrated in  FIG. 2 . 
       FIG. 4  is a sectional side view schematically showing the image forming apparatus in the state in which the airflow between the illustrated support frame and the laser scanning unit is guided towards the image development part. 
       FIGS. 5A and 5B  are graphs contrasting the temperature before and after the installation of the guide member on the support frame, based on experiments. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
   As shown in  FIG. 1 , the image forming apparatus according to an embodiment of the present invention comprises a housing  10 , a image development part  20  installed inside the housing  10 , which prints the image onto the print medium (i.e., paper, transparency, etc.), a fuser assembly  30 , which fixes the image onto the print medium after the print medium has passed the image development part  20 , by an application of high temperature and high pressure; a laser scanning unit  40 , and a cooling unit  50 . 
   A paper supply tray  11  is installed at a bottom of the housing  10 . The print medium is picked up by the pick-up roller  12  from the paper supply tray  11 , and is then moved toward the image development part  20  by an operation of a plurality of paper feed rollers (not displayed). 
   The image development part  20  prints an image onto the print medium, and comprises an organic photoconductive cartridge (Organic photoconductor)  21 , a charge roller  22 , which projects a charge onto the Organic photoconductor  21 , a developer roller  23 , which provides the toner and other materials used in image development, and a cleaning member  24 , which cleans the Organic photoconductor  21 . The Organic photoconductor  21  is installed so as to rotate while remaining in contact with a transfer roller  61 . When the print medium passes between the Organic photoconductor  21  and the transfer roller  61 , the image formed on the Organic photoconductor  21  is transferred to the print medium. 
   The Organic photoconductor  21  is rotatably installed inside the housing  10  of the image development part, and is substantially completely held inside the casing  25 . The surface of the Organic photoconductor  21  receives an electrical charge from the charge roller  22 . The surface of the charged Organic photoconductor  21  is partially scanned by a laser beam emitted by the laser scanning unit  40 . An electrostatic impression corresponding to the desired image is formed on the surface of the Organic photoconductor  21  by the laser scan. The toner materials provided by the developer roller  23  move onto the electrostatic impression area and a visible image forms. 
   The casing  25  may be divided into a first casing  25   a , filled with new print material, and a second casing  25   b , in which residual toner and other materials removed by the cleaning member  24  are stored. A mixer  26 , which mixes the print materials, a print material delivery roller  27 , and a print material volume regulating member  28  are each installed inside the first casing  25   a . The Organic photoconductor  21  is disposed between the first case  25   a  and the second case  25   b . One part of the Organic photoconductor  21  is scanned on an outside surface thereof, which contacts the transfer roller  61 . The other part is exposed in order to be scanned with the laser beam of the laser scanning unit  40 . The laser beam from the laser scanning unit  40  may be delivered to the Organic photoconductor  21  through an opening  25   c  in the top of the casing  25 . The casing  25  is structured such that the casing  25  may be installed in the housing or removed from the housing  10 . Consequently, if the lifespan of the Organic photoconductor  21  is reached, or the print materials are consumed, replacing the cartridge is possible. 
   Of course, it is understood that the image development part  20  may be designed with a diverse range of embodiments in mind in addition to the embodiments described above. However, since this may be easily understood from the related art, a more detailed description thereof has been omitted. 
   The fuser assembly  30  fixes the image transferred from the image cartridge onto the surface of the print medium by an application of high temperature and high pressure. To this end, the fuser assembly  30  comprises a heating roller  31  and a pressure roller  33 . A heater, which heats the heating roller  31  to the high temperature, is installed inside the heating roller  31 . Meanwhile, the pressure roller  33  is rotatably installed in the housing  10 , and presses into the heating roller  31  as a result of a biasing force provided by a pressure member (not shown). Heaters can be installed inside both the heating roller  31  and the pressure roller  33 , and the position of the heating roller  31  and the pressure roller  33  can be swapped. Because this kind of fuser assembly  30  maintains a high temperature both while warming up and while printing, it is the heat source that increases the temperature inside the housing  10 . 
   The laser scanning unit  40  is installed in the housing  10  and is designed to scan the Organic photoconductor  21 . Specifically, the laser scanning unit  40  is disposed above the image development part  20  and the fuser assembly  30 , as shown in  FIG. 2 , while being supported on the support frame  52 , as described below. The laser scanning unit  40  is an optical apparatus comprising a laser diode, a polygonal mirror, and a plurality of optical members, and may be readily understood from the related art, so detailed description thereof is omitted. 
   The cooling unit  50  prevents the laser scanning unit  40  and the image development part  20  from overheating as a result of the heat generated by the fuser assembly  30 . The cooling unit  50 , as shown in  FIGS. 2 and 3 , comprises a fan  51  installed in the housing  10 , a support frame  52 , which supports the laser scanning unit  40 , and a guide member  53 , which is disposed on the support frame  52 , and which guides the air moved by the fan  52  in the direction of the image development part  20  and the laser scanning unit  40 . The fan  51  is disposed on one side of the support frame  52 , and is positioned so as to move air towards the opposite side of the support frame  52 . 
   The support frame  52  is connected to two or more sides of the housing  10 , and supports the laser scanning unit  40 . The support frame  52  is disposed between the fuser assembly  30  and the laser scanning  40 , and prevents heat produced by the fuser assembly  30  from being directly transmitted to the laser scanning unit  40 . The support frame  52  has a lower plate  52   a  and an upper plate  52   b , and an opening  52   c  defined between the upper and lower plates. The upper plate  52   b  has a smaller surface area than the lower plate  52   a . If the laser scanning unit  40  is disposed on the upper plate  52   b , the laser scanning unit  40  is fastened to and supported by the upper plate  52   b  with screws or other fasteners. 
   The guide member  53  may be integrally formed with the support frame  52 . The guide member  53  comprises a plurality of guide ribs  53   a ,  53   b ,  53   c ,  53   d  which are each disposed at predetermined intervals along the length of the support frame  52 . The guide ribs  53   a ,  53   b ,  53   c ,  53   d  vary in length and in their angle of inclination according to their position along the support frame  52 . In more detail, the guide ribs  53   d  located farthest from the fan  51  are longer than the guide ribs  53   a ,  53   b ,  53   c  located closer to the fan  51 , and are inclined at a greater angle relative to the support frame  52 . Also, the guide ribs  53   a ,  53   b ,  53   c ,  53   d  each have a guide surface of a predetermined curvature. The guide surface is formed in order to receive the oncoming airflow generated by the fan  51 , and to then guide the airflow towards the opening  52   c.    
   If the image forming apparatus according to an embodiment of the present invention has the structure described above, air moved by the fan  51  travels towards the side of the support frame  52  opposite the fan  51 . Most of the air moved by the fan  51  contacts the lower side of the laser scanning unit  40  directly, as shown in  FIGS. 3 and 4 . As a result, the laser scanning unit  40  is cooled first. Part of the airflow reflected from the bottom of the laser scanning unit  40  is guided by the guide ribs  53   a ,  53   b ,  53   c ,  53   d  through the opening  52   c , and is directed towards the image development part  20  in order to secondarily cool the image development part  20 . The air, which passes through the opening  52   c , moves towards the top of the image development part  20  and cools the casing  25  of the image development part  20 . A portion of this air moves inside the casing  25  and cools components inside the casing  25  of the image development part  20 . For example, the portion of this air cools the print material volume regulating member  28  inside the casing  25  of the image development part  20 . 
   Additionally, some of the air moved by the fan  51  is not guided by the guide members  53 , but rather, travels in the opposite direction and causes the surrounding air to circulate, so that the temperature inside the housing  10  is distributed evenly. 
     FIG. 5A  is a graph showing measurements over time of the temperature change inside the housing  10  while duplex printing (i.e., double-sided printing), is in progress, in the situation that guide members  53  are not present, and only the fan  51  is used. 
     FIG. 5B  is a graph showing measurements over time of the temperature change inside the housing  10  while the duplex printing is in progress, in an embodiment of the present invention furnished with guide ribs  53 . In  FIGS. 5A and 5B , the term, “OPC,” refers to the Organic photoconductor  21 , and the term, “blade,” refers to the print material volume regulating member  28 . 
   As may be seen in  FIGS. 5A and 5B , if a guide member with the specific structure of the present invention is installed in an image forming apparatus, a drop in an internal temperature of the image forming apparatus of approximately 10 degrees Celsius on average compared to the temperature before the installation of the guide member may be realized. In this manner, the temperature inside the housing  10 , particularly the temperature of the image development part  20 , may be reduced, preventing a deterioration of the functioning of the Organic photoconductor and a deterioration of the printing quality as a result of the rise in temperature. As such, an increase in the printing quality may be realized. 
   By additionally cooling the laser scanning unit  40  using the ventilation, laser errors arising due to a change in the dimensions of the components caused by the rise in temperature may also be prevented. 
   According to the cooling apparatus and the image forming apparatus comprising the cooling apparatus, overheating of the laser scanning unit caused by heat from the fuser assembly may be prevented, by having the cooling unit disposed between the fuser assembly and the laser scanning unit. 
   Moreover, by providing a guide member on the support frame supporting the laser scanning unit, the airflow may be guided directly towards the image development cartridge. As a result of cooling the image development cartridge with the moved air in this manner, the temperature of the image development cartridge may be substantially lowered, and a deterioration of the printing quality caused by the high temperature may be prevented. 
   Also, the air inside the housing may be made to circulate, so the temperature inside the housing may be maintained at a relatively constant level. 
   Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.