Abstract:
A heating roller and an image forming apparatus including the heating roller. The image forming apparatus can include: an image forming part to apply a developer selectively on a paper to form an image; a paper sensing part to sense the size of the paper fed to the image forming part; a heating roller including a cylindrical roller main body, a first heating part provided in a first area of the roller main body to generate heat, and a second heating part provided in a second area of the roller main body to generate heat; and a controller to control the first heating part and/or the second heating part to selectively heat the paper according to the sensing result of the paper sensing part. Thus, a heating roller capable of controlling a heating range in accordance with a width of object media is possible.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from Korean Patent Application No. 2005-0086487, filed on Sep. 15, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present general inventive concept relates to a heating roller and an image forming apparatus including the heating roller, and more particularly, to a heating roller having a plurality of coils to heat different areas thereof and an image forming apparatus including the heating roller.  
         [0004]     2. Description of the Related Art  
         [0005]     A heating roller as a part used for an image forming apparatus, etc., is used to heat and/or press object media with a pressure roller. Here, the pressure roller is provided along with the heating roller.  
         [0006]      FIG. 1  is a sectional view illustrating a conventional heating roller  10 .  
         [0007]     The heating roller  10  comprises a cylindrical roller main body  11  and a coil  12  provided inside of the roller main body  11 . Electric power is supplied to the coil  12  to operate the heating roller  10 , and heat generated from the coil  12  is transmitted to the outside through the roller main body  11 .  
         [0008]     However, the conventional heating roller  10  has a problem in that the coil  12  is wound with a uniform interval over the whole length in the internal side of the heating roller  10 , and as a result, the whole roller main body  11  is heated uniformly regardless of the size of a transferring media to be heated and/or pressed.  
         [0009]     In this case, when the size of the heated and pressed transferring medium, for example, the width of a printing paper, is smaller than the heating width of the heating roller  10  during a heating operation, an area where the printing paper does not contact the heating roller  10  occurs, and accordingly energy is consumed unnecessarily. Moreover, the temperature difference between a paper passing area and a paper non-passing area increases. In particular, when the paper non-passing area is overheated, a safety device provided in the heating roller  10  is activated, and thus the heating roller  10  stops operating or breaks down.  
         [0010]     Also, in the case that the surface temperature of the heating roller  10  increases above a normal value when heating or pressing toner particles formed on the paper, a “hot offset” of an image occurs.  
         [0011]     The above-mentioned problems with the conventional heating roller  10  occurs frequently in the case that the axial length of the heating roller  10  is long, for example, in the case of a large heating roller used to form an image on a large paper, such as A3 size paper.  
       SUMMARY OF THE INVENTION  
       [0012]     The present general inventive concept provides a heating roller which is capable of controlling a heating range in accordance with a width of object media.  
         [0013]     Additional aspects and advantages of the present general inventive concept 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 general inventive concept.  
         [0014]     The foregoing and/or other aspects and utilities of the present general inventive concept can be achieved by providing an image forming apparatus, comprising: an image forming part to apply selectively a developer on a paper to form an image; a paper sensing part to sense a size of the paper fed to the image forming part; a heating roller comprising a cylindrical roller main body, a first heating part provided in a first area of the roller main body to generate heat, and a second heating part provided in a second area of the roller main body to generate heat; and a controller to control the first heating part and/or the second heating part to selectively heat the paper according to the sensing result of the paper sensing part.  
         [0015]     The first heating part can be provided in a central area of the roller main body, and the second heating part can be provided at both sides of the central area.  
         [0016]     The heating roller can comprise a left area and a right area which are disposed in a lengthwise direction thereof, and the first heating part and the second heating part can be provided in the left area and right area, respectively.  
         [0017]     Each of the first and second heating parts can comprise a plurality of heating areas, and the controller can control the respective heating areas to be separately heated.  
         [0018]     The first heating part and second heating part can comprise the first coil and the second coil, respectively, each of which is provided in the inside of the roller main body, and separately heated according to control of the controller.  
         [0019]     The image forming apparatus may further comprise an insulator interposed between the first coil and the second coil.  
         [0020]     The first coil and the second coil, respectively, can be wound up with different diameters on a central axis in a lengthwise direction of the roller main body.  
         [0021]     The first coil can differ in winding turns from the second coil.  
         [0022]     The image forming apparatus can further comprise a supporting pipe provided inside of the roller main body to support the first and second coils.  
         [0023]     The image forming apparatus can further comprise an insulator interposed among the roller main body, the first coil, the second coil, and the supporting pipe.  
         [0024]     The foregoing and/or other aspects and utilities of the present general inventive concept can also be achieved by providing a heating roller, comprising: a roller main body; a first heating part provided in a first area of the roller main body to generate heat; a second heating part provided in a second area of the roller main body to generate heat; and a controller to control the first heating part and/or the second heating part to selectively heat the paper depending on a size of the paper.  
         [0025]     The foregoing and/or other aspects and utilities of the present general inventive concept can also be achieved by providing a heating roller, comprising: a roller main body having a cylindrical shape; a center coil provided inside of the roller main body to heat a central area of the roller main body; a side coil provided inside of the roller main body to heat side areas of the roller main body; and a plurality of connecting terminals disposed on opposite end parts of the roller main body and having electrodes electrically connected to the center coil and the side coil. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     These and/or other aspects and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
         [0027]      FIG. 1  is a sectional view illustrating a conventional heating roller,  
         [0028]      FIG. 2  is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present general inventive concept,  
         [0029]      FIG. 3  is a sectional view illustrating a heating roller according to the embodiment of  FIG. 2 ,  
         [0030]      FIG. 4  is a schematic view illustrating the configuration of the image forming apparatus to according to the embodiment of  FIG. 2 , and  
         [0031]      FIG. 5  is an exemplary diagram illustrating a configuration of a heating roller according to another embodiment of the present general inventive concept. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     Reference will now be made in detail to the embodiments of the present general inventive concept, 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 general inventive concept by referring to the figures.  
         [0033]      FIG. 2  is a block diagram illustrating a configuration of an image forming apparatus  1  according to an embodiment of the present general inventive concept. As illustrated therein, the image forming apparatus  1  according to the embodiment of  FIG. 2  comprises a paper feeding part  100  feeding a paper to feed paper, a paper sensing part  300  to sense a size of the paper being fed from the paper feeding part  100 , an image forming part  120  to form an image on the paper, an image fixing part  260  (see  FIG. 4 ) to fix the image to the paper, and a power supply  400  to supply power to the image fixing part  260 .  
         [0034]     As illustrated in  FIG. 4 , the paper feeding part  100  may accommodate a plurality of papers on an inside surface thereof. When an image output signal is applied to the image forming apparatus  1 , the paper feeding part  100  feeds a paper to the image forming part  120  by using a pick-up roller  110 .  
         [0035]     The paper sensing part  300 , which is provided between the paper feeding part  100  and the image forming part  120 , senses a size of the fed paper and delivers the sensed result to a controller  500 . The paper sensing part  300  may contact the paper to sense the size of the paper, but is not limited thereto. For example, the paper sensing part  300  may alternatively sense the size of the paper through mutual signals of a light emission part and a light receiving part. The paper sensing part  300  may also be constructed with one of various known ways to sense the size of the paper.  
         [0036]     The image forming part  120  applies selectively a developer on the paper to form an image by using an electrical potential difference. This image forming part  120  has a similar configuration as a conventional image forming part. Accordingly, a detailed description thereof is omitted to keep the detailed description herein brief.  
         [0037]     The image fixing part  260  heats and presses the paper in which the image forming part  120  has applied the developer thereon, so as to fix the developer to the paper. Herein, the image fixing part  260  comprises a pressure roller  250  to press the paper and a heating roller  200  to heat the paper.  
         [0038]     As illustrated in  FIG. 3 , the heating roller  200  according to the present embodiment comprises a first heating part  220  provided in a central area C of a roller main body  210 , and a second heating part  230  provided at both side areas S of the first heating part  220 . Further, the first heating part  220  includes a center coil  221  provided therein and a side coil  231  provided therein. Each second heating part  230  includes the side coil  231  provided therein and the center coil  221  provided therein. Here, each of the center and side coils  221  and  231  heat both the first and second heating parts  220  and  230 . However, the center and side coils  221  and  231  heat both the first and second heating parts  220  and  230  to a different degree, which will be described in more detail infra. Also, each of the center and side coils  221  and  231  is connected to a connecting terminal  240 . Here, the power supply  400  supplies power to the respective center and side coils  221  and  231  through f the connecting terminal  240 .  
         [0039]     The center coil  221  and the side coil  231  are fixably located on different diameters, respectively, based on a central axis A of the roller main body  210 . Between the center coil  221  and the side coil  231  is interposed an insulator  250  to fixably support the coils  221  and  231  and to prevent the coils  221  and  231  from contacting each other.  
         [0040]     In the inside of the center coil  221  and the side coil  231  is a supporting pipe  260  made of a material comprising aluminum. The center coil  221  and the side coil  231  are radially supported by the supporting pipe  260 . The insulator  250  is interposed between the center coil  221  and the roller main body  210  and between the side coil  231  and the supporting pipe  260  to support the coils  221  and  231  and to prevent electric contact among the respective elements.  
         [0041]     As described above, the center and side coils  221  and  231  are in both the first and second heating parts  220  (C) and  230  (S) of the roller main body  210  and heat both the first and second heating parts  220  and  230 . However, in the roller main body  210 , the center coil  221  in the central part C has more winding turns than in the side parts S. Accordingly, when heating the center coil  221 , the heating roller  200  has a higher temperature in the central part C than in the side parts S.  
         [0042]     In contrast with the central coil  221 , the side coil  231  has more winding turns in the side parts S of the roller main body  210  than in the central part A thereof. As a result, when heating the side coil  231 , the temperature of the side parts S of the heating roller  200  becomes higher than that of the central part C.  
         [0043]     On each side of the roller main body  210 , the connecting terminal  240  is positioned and connected with the center coil  221  and the side coil  231 . The connecting terminal  240  comprises a first electrode  241  of a ring shape and a second electrode  242  formed in the central part thereof. The first electrode  241  is electrically connected with the center coil  221  and the second electrode  242  is electrically connected with the side coil  231 . External power supplied from the power supply  400  is provided through the first electrode  241  and the second electrode  242  to the coils  221  and  231 , respectively.  
         [0044]     Further, the first and second heating parts  220  and  230  comprise a first thermistor  223  and a second thermistor  233 , respectively, so as to measure the temperature of the area of each heating part. The first and second thermistors  223  and  233  measure the temperature of each area and can deliver the measured results to the controller  500 .  
         [0045]     A coating layer  270  made of the material comprising PTFE (Poly Tetra Fluoro Ethylene), which is known as the trademark ‘Teflon’ is formed on an external surface of the roller main body  210 .  
         [0046]     The roller main body  210  is divided into the first heating part  220  in the center area C and the second heating parts  230  in two side areas S, but is not limitable thereto. Alternatively, the roller main body  210  may be divided into the first heating part  220  in one left area and the second heating part  230  in one right area, and vice versa. The first and second heating parts  220  and  230 , respectively, may also be divided into a plurality of areas. In another embodiment, as illustrated in  FIG. 5 , the first and second heating parts  220  and  230  are divided into two areas  220   a  and  220   b , and  230   a  and  230   b , respectively. At this time, each of the divided areas  220   a  and  220   b , and  230   a  and  230   b  includes a heating coil to generate heat by power supplied from the power supply  400 , and a thermistor to measure the temperature of the respective areas. In another embodiment, the configuration of dividing the roller main body  210  and the number of the divided areas therein may be varied depending on the size and the type of the fed papers. Also, the configuration of dividing the roller main body  210  and the number of the divided areas therein may be varied according to paper feeding types such as a center feeding and a side feeding.  
         [0047]     The power supply  400  supplies power selectively to the center coil  221  and the side coil  231  provided inside of the heating roller  200  through the first and second electrodes  241  and  242 .  
         [0048]     The controller  500  controls the power supply  400  to heat the first and/or second heating parts  220  and  230  selectively according to the sensed result of the paper sensing part  300 . Also, the controller  500  controls the power supplied from the power supply  400  to the center and side coils  221  and  231 , respectively, depending on the temperature results measured by the first and second thermistors  223  and  233 .  
         [0049]     Hereinafter, an operation of the heating roller  200  of the image forming apparatus  1  having the above described configuration will be described with reference to  FIG. 2  through  4 .  
         [0050]     First, the pick-up roller  110  of the paper feeding part  100  feeds a paper according to an image output signal. At this time, the paper sensing part  300  senses the size of the fed paper and delivers the sensed result to the controller  500 . The image forming part  120  applies the developer selectively on the fed paper by applying a transition voltage between the image forming part  120  and a transfer roller  130  so as to form an image on the paper using the developer.  
         [0051]     The fed paper, which the image forming part  120  applies the developer thereon, is delivered to the image fixing part  260 . At this time, the controller  500  recognizes the sensed result transferred from the paper sensing part  300 , and then controls the power supply  400  to selectively heat the first and second heating part  220  and  230 .  
         [0052]     For example, when the paper sensing part  300  senses that the size (width) of the fed paper corresponds with the width W of the heating roller  200  (referring to  FIG. 3 ), the controller  500  controls the power supply  400  to heat evenly the first and second heating parts  220  and  230  so that the two part  220  (area C) and  230  (areas S) can be heated with the same temperature. That is, the controller  500  controls the power supply  400  to provide even power to both the center coil  221  and the side coil  231 .  
         [0053]     When the paper sensing part  300  senses that the size (width) of the provided paper corresponds with the width C of the first heating part  220 , the controller  500  controls the power supply  400  to provide power to only the center coil  221 .  
         [0054]     On the other hand, in the case in which another paper having a width corresponding to the width W of the heating roller  200  is fed after a paper having a width corresponding to the width C of the first heating part  220  is fed, the temperature of the first heating part  220  measured by the first thermistor  223  will be different (higher) from that of the second heating part  230  measured by the second thermistor  233 . At this time, the controller  500  controls the power supply  400  to make the second heating part  230  be more quickly heated than the first heating part  220  so that the temperature of the second heating part  230  will be the same as the temperature of the first heating part  220 . That is, the controller  500  controls the power supply  400  to supply more power to the side coil  231  than the center coil  221  until the first and second heating parts  220  and  230  have the same temperature.  
         [0055]     According to the foregoing operations, the heating roller  200  heats the paper and the pressure roller  250  presses the paper to fuse the developer to the paper, thereby completing formation of an image. Then, papers are discharged to an outside of the image forming apparatus  1  through a discharging part thereof (not illustrated).  
         [0056]     As described above, according to the embodiments of the present general inventive concept, there is provided a heating roller capable of controlling a temperature thereof by individual areas depending on a size of fed papers and a feeding type thereof.  
         [0057]     As apparent from the above description, according to the embodiments of the present general inventive concept, a heating roller using a center coil and a side coil provided in an inside of a roller main body can control the temperature of a central part and side parts of the heating roller separately. Hence, by selectively operating a center coil and a side coil according to the width of a media being heated by the heating roller, overheating of the heating roller as well as breakdown of the roller can be provided.  
         [0058]     Although a few embodiments of the present general inventive concept have been shown and described, it will 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 general inventive concept, the scope of which is defined in the appended claims and their equivalents.