Abstract:
An image forming apparatus capable of minimizing a temperature rise of a cover by substantially preventing heat emission from a fusing device to an outside is disclosed. The image forming apparatus includes a main body, a fusing device mounted in the main body, the fusing device having an outlet to discharge paper, an opening/closing member opening and closing the outlet of the fusing device, a cam member moving the opening/closing member between a first position in which the opening/closing member closes the outlet to prevent heat in the fusing device from being emitted through the outlet and a second position in which the opening/closing member opens the outlet to permit the paper to pass through the outlet, a driving part rotating the cam member, and a control unit controlling the driving part to determine a rotational position of the cam member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of Korean Patent Application No. 2007-0084104, filed on Aug. 21, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
   BACKGROUND 
   1. Field 
   The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that can substantially prevent heat emission from a fusing device to an outside. 
   2. Description of the Related Art 
   An image forming apparatus is an apparatus that prints an image on a printing medium, e.g., paper, according to an inputted image signal. As one type of image forming apparatus, an electrophotographic type image forming apparatus is configured such that light is scanned to a photosensitive body charged with a predetermined electric potential to form an electrostatic latent image on an outer peripheral surface of the photosensitive body. The electrostatic latent image is developed into a toner image by supplying a toner to the electrostatic latent image, and the toner image is transferred onto paper. 
   The toner image transferred onto the paper is just carried on the paper, but is not fused to the paper. Therefore, an image forming apparatus includes a fusing device to fuse the transferred toner image to the paper. The fusing device generally includes a heating roller having a heat source therein, and a press roller in close contact with the heating roller to form a fusing nip at a contact portion with the heating roller. If the toner image transferred paper passes between the rotating heating roller and the press roller, the toner image is fused to the paper by heat transferred from an interior of the heating roller and pressure generated between the heating roller and the press roller. 
   The image forming apparatus is provided with a cover above the fusing device to permit a user to obtain access to an interior of a main body of the image forming apparatus when intending to inspect the interior of the main body or remove jammed paper from the fusing device. 
   The heat generated from the heating roller mounted in the fusing device is transferred to the cover mounted above the fusing device by radiation, conduction and convection phenomena. Because a user frequently touches the cover whenever inspecting the interior of the apparatus, if the cover becomes hot by the heat transferred from the fusing device, it gives the user an unpleasant feeling when touching the cover. 
   To solve this problem, Korean Patent Registration No. 0463273 discloses an image forming apparatus having a heat shielding member mounted between a fusing device and a cover. The heat shielding member intercepts the heat transferred from the fusing device from reaching the cover by reflecting the heat, thereby preventing a temperature rise of the cover. 
   The above heat shielding member can temporarily intercept the heat emitted from the fusing device from being transferred to the cover, but there is a limitation in maintaining a temperature of the cover low only by the heat shielding member in a circumstance in which the fusing device continuously emits heat. 
   SUMMARY 
   Therefore, it is an aspect of the embodiment to provide an image forming apparatus that can minimize a temperature rise of a cover by substantially preventing heat emission from a fusing device to an outside. 
   Additional aspects and/or advantages 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. 
   The foregoing and/or other aspects are achieved by providing an image forming apparatus, including: a main body; a fusing device mounted in the main body, the fusing device having an outlet to discharge paper; an opening/closing member opening and closing the outlet of the fusing device; a cam member moving the opening/closing member between a first position in which the opening/closing member closes the outlet to prevent heat in the fusing device from being emitted through the outlet and a second position in which the opening/closing member opens the outlet to permit the paper to pass through the outlet; a driving part rotating the cam member; and a control unit controlling the driving part to determine a rotational position of the cam member. 
   The image forming apparatus may further include a cover mounted above the fusing device opening and closing a portion of the main body. 
   The driving part may include a driving source and a power intermittence unit intermitting power transmitted from the driving source to the cam member. The power intermittence unit may be configured as an electronic clutch. 
   The image forming apparatus may further include a first paper sensor to sense a front end of the paper advancing into the fusing device. When the front end of the paper is sensed by the first paper sensor, the control unit may rotate the cam member to move the opening/closing member from the first position to the second position. 
   The image forming apparatus may further include a second paper sensor to sense a rear end of the paper having passed through the fusing device. When the rear end of the paper is sensed by the second paper sensor, the control unit may rotate the cam member to move the opening/closing member from the second position to the first position. The opening/closing member may move from the second position to the first position by its own weight. 
   The foregoing and/or other aspects are achieved by providing an image forming apparatus, including: a main body; a cover opening and closing a portion of the main body; a fusing device mounted below the cover, the fusing device having an outlet to discharge paper; an opening/closing member provided movably between a first position in which the opening/closing member closes the outlet and a second position in which the opening/closing member opens the outlet to permit the paper to pass through the outlet; at least one paper sensor to sense a position of the paper; and a driving device moving the opening/closing member between the first position and the second position. 
   The driving device may include a cam member moving the opening/closing member from the first position to the second position by pushing up the opening/closing member. 
   The driving device may further include a driving source and an electronic clutch intermitting power transmitted from the driving source to the cam member. 
   The at least one paper sensor may include a first paper sensor mounted in an inlet of the fusing device, and a second paper sensor mounted in the outlet of the fusing device. 
   When the first paper sensor senses a front end of the paper, the driving device may move the opening/closing member to the second position. When the second paper sensor senses a rear end of the paper, the opening/closing member may move from the second position to the first position. 
   The foregoing and/or other aspects are achieved by providing an image forming apparatus, including: a paper feeding device feeding paper through the image forming apparatus; a developing device developing images onto the paper fed by the paper feeding device; a fusing device fusing the developed images onto the paper and including an outlet; and an opening/closing member opening and closing the outlet of the fusing device. 
   The image forming apparatus may include at least one paper sensor sensing an end of the paper, wherein the opening/closing member may open or close the outlet of the fusing device based on a result of the sensing the end of the paper. 
   The at least one paper sensor may include a first sensor sensing a front end of the paper entering the fusing device at an inlet of the fusing device and a second sensor sensing a rear end of the paper leaving the fusing device at the outlet of the fusing device, and wherein the opening/closing member may open the outlet of the fusing device when the first sensor senses that the front end of the paper enters the fusing device and close the outlet of the fusing device when the second sensor senses that the rear end of the paper leaves the fusing device. 
   The fusing device may include a paper guide adjacent to the outlet of the fusing device, the opening/closing member may have an inclined end portion, and the inclined end portion of the opening/closing member may contact a guide surface of the paper guide to prevent heat from leaking out of the fusing device. 
   The image forming apparatus may include a cam member proximate to the opening/closing member rotating to cause the opening/closing member to open or close based on the result of the sensing the end of the paper. 
   The foregoing and/or other aspects are achieved by providing a fusing device of an image forming apparatus, including: a plurality of rollers causing a toner image to fuse to paper fed into the fusing device by applying heat and pressure to the paper; at least one paper sensor sensing an end of paper being fed into or out of the fusing device; and an opening/closing member opening and closing the outlet of the fusing device based on a result of the sensing the end of the paper. 
   The at least one paper sensor may include a first sensor sensing a front end of the paper entering the fusing device at an inlet of the fusing device and a second sensor sensing a rear end of the paper leaving the fusing device at the outlet of the fusing device, and wherein the opening/closing member may open the outlet of the fusing device when the first sensor senses that the front end of the paper enters the fusing device and close the outlet of the fusing device when the second sensor senses that the rear end of the paper leaves the fusing device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages 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 sectional view illustrating a constitution of an image forming apparatus in accordance with the present embodiment; 
       FIG. 2  is an enlarged view of a portion of the image forming apparatus shown in  FIG. 1 ; 
       FIG. 3  is a view illustrating a state in which an opening/closing member pivots by a cam member to open an outlet of a fusing device in  FIG. 2 ; 
       FIG. 4  is a view illustrating a constitution of a driving device to drive the opening/closing member in the image forming apparatus in accordance with the present embodiment; and 
       FIG. 5  is a view for explaining an operation of opening and closing the outlet of the fusing device by the opening/closing member in the image forming apparatus in accordance with the present embodiment. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Reference will now be made in detail to an embodiment, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiment is described below to explain the present invention by referring to the figures. 
     FIG. 1  is a sectional view illustrating a constitution of an image forming apparatus in accordance with the present embodiment, and  FIG. 2  is an enlarged view of a portion of the image forming apparatus shown in  FIG. 1 .  FIG. 3  is a view illustrating a state in which an opening/closing member pivots by a cam member to open an outlet of a fusing device in  FIG. 2 . 
   As shown in  FIG. 1 , an image forming apparatus according to the present embodiment includes a main body  10  forming an exterior appearance, a paper feeding device  20  to supply a printing medium, i.e., paper S, a developing device  30  to develop an image on the paper, a fusing device  40  to fuse an image to the paper by applying heat and pressure to the paper, and a paper discharge device  50  to discharge the printed paper to an exterior of the main body  10 . 
   The paper feeding device  20  includes a paper feeding tray  21  to load the paper S thereon, a pickup roller  22  to pick up the paper S on the paper feeding tray  21  sheet by sheet, and a feeding roller  23  to feed the picked-up paper toward the developing device  30 . 
   The developing device  30  includes a photosensitive body  31  on which an electrostatic latent image is formed by a laser scanning unit  60 , a charge roller  32  to charge the photosensitive body  31 , four developing cartridges  33 Y,  33 M,  33 C and  33 K to develop the electrostatic latent image formed on the photosensitive body  31  into a toner image by using toners of yellow, magenta, cyan and black, an intermediate transfer belt  34 , a first transfer roller  35 , and a second transfer roller  36 . 
   Each of the developing cartridges  33 Y,  33 M,  33 C and  33 K include a developing roller  37  to develop the electrostatic latent image formed on the photosensitive body  31  by supplying the toner thereto, and a supply roller  38  to supply the toner to the developing roller  37  by rotating while contacting the developing roller  37 . 
   The intermediate transfer belt  34  is supported by support rollers  34   a  and  34   b , and runs at the same velocity as a rotational linear velocity of the photosensitive body  31 . The first transfer roller  35  opposes the photosensitive body  31 , and transfers the toner image developed on the photosensitive body  31  onto the intermediate transfer belt  34 . The second transfer roller  36  opposes the intermediate transfer belt  34 . While the toner image is transferred onto the intermediate transfer belt  34  from the photosensitive body  31 , the second transfer roller  36  is spaced apart from the intermediate transfer belt  34 . When the toner image is completely transferred onto the intermediate transfer belt  34 , the second transfer roller  36  is moved into contact with the intermediate transfer belt  34  with a predetermined pressure. 
   The fusing device  40  fuses the toner image to the paper by applying heat and pressure to the paper. As shown in  FIGS. 1 to 3 , the fusing device  40  includes a frame  41  having an inlet  41   a  to introduce the paper into the frame  41  and an outlet  41   b  to discharge the paper from the frame  41 . Inside the frame  41  are mounted a heating roller  42  having a heat source  42   a  to heat the toner image-transferred paper, and two press rollers  43  and  44  in close contact with the heating roller  42  to maintain a constant fusing pressure with the heating roller  42 . 
   A first paper guide  45  and a second paper guide  46  are mounted near the outlet  41   b  of the fusing device  40 . The first paper guide  45  and the second paper guide  46  guide the paper passing through the fusing device  40  to smoothly move the paper toward a paper discharge port  11  formed at a portion of the main body  10 . One end of the first paper guide  45  is hingedly coupled to the frame  41  of the fusing device  40  by a hinge shaft  45   a , and the other end of the first paper guide  45  extends toward the paper discharge port  11 . The second paper guide  46  is mounted opposite to the first paper guide  45  over the outlet  41   b  of the fusing device  40 . The second paper guide  46  has a guide surface  46   a  to guide the movement of the paper. 
   A cover  70  is mounted above the fusing device  40  to open and close a portion of the main body  10 . The cover  70  is hingedly coupled to the main body  10  by a hinge shaft  71 . When intending to remove jammed paper from the main body  10  or inspect internal components, a user pulls the cover  70  to open a portion of the main body  10  and can observe the interior of the main body  10  or take appropriate measures. 
   The paper discharge device  50  includes a discharge roller  51  to discharge the paper passing through the fusing device  40  to the outside of the main body  10 , and a discharge backup roller  52  mounted while opposing the discharge roller  51 . 
   The operation of the above-structured image forming apparatus will now be explained briefly with reference to  FIGS. 1 to 3 . The laser scanning unit  60  irradiates light, for example, corresponding to yellow image information to the photosensitive body  31  charged with a uniform electric potential by the charge roller  32 , and an electrostatic latent image corresponding to the yellow image is formed on the photosensitive body  31 . A developing bias is applied to the developing roller  37  of the yellow developing cartridge  33 Y, and the yellow toner is attached to the electrostatic latent image to develop the electrostatic latent image into a yellow toner image on the photosensitive body  31 . The toner image is transferred onto the intermediate transfer belt  34  by the first transfer roller  35 . 
   After the yellow toner image corresponding to one page is completely transferred, the toner images of magenta, cyan and black are sequentially transferred onto the intermediate transfer belt  34  through the same procedures as above. Accordingly, a color toner image is formed on the intermediate transfer belt  34  by the toner images of yellow, magenta, cyan and black being overlapped. The color toner image is transferred onto the paper S passing between the intermediate transfer belt  34  and the second transfer roller  36 . The image transferred onto the paper is fused to the paper while passing through the fusing device  40 , by heat transferred from the heating roller  42  and pressure generated between the heating roller  42  and the press rollers  43  and  44 . The paper having passed through the fusing device  40  is discharged to the outside of the main body  10  by the discharge roller  51 . 
   In the above process, if heat from the interior of the fusing device  40  is continuously emitted through the outlet  41   b  of the frame  41 , a temperature of the first paper guide  45  mounted above the outlet  41   b  and a temperature of the cover  70  rise, which gives a user an unpleasant feeling when the user touches the cover  70  and the first paper guide  45  to inspect the interior of the apparatus. 
   To cope with this problem, the image forming apparatus according to the present embodiment includes an opening/closing member  100  to open and close the outlet  41   b  of the fusing device  40 , a driving device  200  (refer to  FIG. 4 ) to drive the opening/closing member  100  so that the opening/closing member  100  can move between a first position in which the opening/closing member  100  closes the outlet  41   b  (refer to  FIG. 2 ) and a second position in which the opening/closing member  100  opens the outlet  41   b  (refer to  FIG. 3 ), and a control unit  300  (refer to  FIG. 4 ) to control the driving device  200  so that the opening/closing member  100  can move at an appropriate point of time. 
   The opening/closing member  100  opens the outlet  41   b  of the fusing device  40  only when the paper S passes through the outlet  41   b  during the printing operation, and closes the outlet  41   b  anytime else, thereby preventing the heat from the interior of the fusing device  40  from being transferred to the cover  70  through the outlet  41   b.    
   As shown in  FIGS. 2 and 3 , the opening/closing member  100  is hingedly coupled to the frame  41  at one end portion by a hinge shaft  110 . Therefore, the other end portion of the opening/closing member  100  can pivot in an up/down direction on the hinge shaft  110  and can move between the first position and the second position. When the opening/closing member  100  is located at the first position to close the outlet  41   b  of the fusing device  40 , the other end portion of the opening/closing member  100  extends across the outlet  41   b  and is supported by the second paper guide  46 . The other end portion of the opening/closing member  100  has an inclined portion  120  (shown in  FIG. 3 ) which is inclined along the guide surface  46   a  of the second paper guide  46 . By the inclined portion  120  being closely contacted with the guide surface  46   a  of the second paper guide  46 , the heat in the fusing device  40  does not leak. 
   It is preferred that the opening/closing member  100  is made of a material having an excellent thermal insulation property. Although not illustrated in  FIGS. 2 and 3 , it is possible to install an additional thermal insulation member inside the opening/closing member. 
     FIG. 4  is a view illustrating the constitution of the driving device to drive the opening/closing member in the image forming apparatus according to the present embodiment. As shown in  FIGS. 2 to 4 , the driving device  200  includes a cam member  210  to move the opening/closing member  100  between the first position and the second position, and a driving part  220  to rotation-drive the cam member  210 . 
   The cam member  210  has a cam shaft  211  and a rotating cam  212  provided at an end portion of the cam shaft  211 . During the rotation, the rotating cam  212  interferes with an end portion  100   a  in a side direction of the opening/closing member  100  at a specific region, and pushes up the opening/closing member  100 . Therefore, the opening/closing member  100  pivots from the first position to the second position, and opens the outlet  41   b  of the fusing device  40  as shown in  FIG. 3 . On the other hand, if the rotating cam  212  rotates more from the state shown in  FIG. 3  and is separated from the opening/closing member  100 , the opening/closing member  100  pivots downward by its own weight to the first position, and closes the outlet  41   b  of the fusing device  40  as shown in  FIG. 2 . 
   The driving part  220  to drive the cam member  210  includes a driving motor  221  as a driving source, and a power intermittence unit  222  to intermit the power transmitted from the driving motor  221  to the cam member  210 . In this embodiment, the power intermittence unit  222  is configured as an electronic clutch  222   a , however the embodiment is not restricted thereto. Various types of clutch devices can be applied to the power intermittence unit  222 . 
   The electronic clutch  222   a  is connected with a clutch gear  223  and the cam member  210 . The clutch gear  223  is connected to the driving motor  221  through a gear train (only two gears  224  and  225  of the gear train are illustrated in  FIG. 4  for convenience of illustration). When the electronic clutch  222   a  is turned ON, a rotational force of the clutch gear  223  is transmitted to the cam member  210 . When the electronic clutch  222   a  is turned OFF, the rotational force of the clutch gear  223  is not transmitted to the cam member  210 . Although  FIG. 4  illustrates that the electronic clutch  222   a  is directly connected with the cam member  210 , it is also possible to install a series of power transmission gears between the electronic clutch  222   a  and the cam member  210 . 
   As shown in  FIGS. 2 and 3 , the image forming apparatus of the present embodiment includes a first paper sensor  80  mounted in the inlet  41   a  of the fusing device  40 , and a second paper sensor  90  mounted in the outlet  41   b  of the fusing device  40 . 
   When the first paper sensor  80  senses a front end of the paper, the control unit  300  determines that the paper is advancing into the fusing device  40 , and accordingly controls the driving device  200  so that the opening/closing member  100  opens the outlet  41   b  of the fusing device  40 . Also when the second paper sensor  90  senses a rear end of the paper, the control unit  300  determines that the paper has completely passed through the fusing device  40 , and accordingly controls the driving device  200  so that the opening/closing member  100  closes the outlet  41   b  of the fusing device  40 . 
   Hereinafter, the operation of opening and closing the outlet of the fusing device by the opening/closing member in the image forming apparatus according to the present embodiment will be explained in detail with reference to FIGS.  3  to  5 A-C. 
   While the paper fed in the main body  10  passes between the intermediate transfer belt  34  and the second transfer roller  36 , an image is printed on the paper. The printed paper S, as shown in  FIG. 5A , starts advancing into the fusing device  40 .  FIG. 5A  shows a state in which the paper is positioned close to the first paper sensor  80 . When the front end of the paper is not sensed by the first paper sensor  80 , the opening/closing member  100  is positioned in the first position and keeps closing the outlet  41   b  of the fusing device  40 . Accordingly, the heat in the fusing device  40  is not transferred to the cover  70 . 
   When the paper S is fed more from the state shown in  FIG. 5A  and the front end of the paper S operates the first paper sensor  80  as shown in  FIG. 5B , the control unit  300  determines that the paper is advancing into the fusing device  40 , and accordingly controls the electronic clutch  222   a  of the driving device  200  so that the opening/closing member  100  opens the outlet  41   b  of the fusing device  40 . In other words, the control unit  300  turns ON the electronic clutch  222   a  for a predetermined time. Only while the electronic clutch  222   a  is in the ON state, the power of the driving motor  221  is transmitted to the cam member  210  to rotate the cam member  210  at a predetermined angle, and the rotating cam  212  of the cam member  210  interferes with the opening/closing member  100  to push up the opening/closing member  100  as shown in  FIG. 5B . As a result, the outlet  41   b  of the fusing device  40  is opened. 
   When the outlet  41   b  of the fusing device  40  is opened as shown in  FIG. 5B , the paper S is fed toward the discharge roller  51  via the outlet  41   b . At this time, the front end of the paper fed toward the discharge roller  51  operates the second paper sensor  90  as shown in  FIG. 3 . 
   As shown in  FIG. 5C , when the rear end of the fed paper S passes away from the second paper sensor  90 , the second paper sensor  90  is returned to its original position. In response to the movement of the second paper sensor  90 , the control unit  300  turns ON the electronic clutch  222   a  for a predetermined time. When the electronic clutch  222   a  is turned ON, the power of the driving motor  221  is transmitted to the cam member  210  through the electronic clutch  222   a , and accordingly the cam member  210  is returned to its original position. When the cam member  210  is returned to its original position as shown in  FIG. 5C , the opening/closing member  100  pivots downward by its own weight and closes the outlet  41   b  of the fusing device  40 . 
   Since the opening/closing member  100  keeps closing the outlet  41   b  of the fusing device  40  until the following sheet of paper is introduced into the fusing device  40 , the heat in the fusing device  40  is intercepted by the opening/closing member  100 , and thus cannot be emitted to the outside through the outlet  41   b . As a result, a rise of a temperature of the first paper guide  45  disposed above the fusing device  40  or a temperature of the cover  70  can be minimized. 
   As apparent from the above description, the image forming apparatus according to the present embodiment can minimize the heat emission from the fusing device to the outside of the fusing device, because the outlet of the fusing device is opened only when needed. Accordingly, a temperature rise of the components arranged near the fusing device can be minimized. 
   Further, since heat loss from the interior of the fusing device to the exterior is reduced, a fusing temperature can be efficiently maintained at an appropriate level. 
   Although an embodiment has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.