Abstract:
An image heating apparatus including: a pressure member; a fixing roller to rotate on the pressure member; a heater to heat an external surface of the fixing roller; and a film to be heated by the heater. While passing through a gap between the pressure member and the fixing roller, the film may form a nip with the pressure member. The image heating apparatus may reduce an initial warm-up time through a film heating operation, and may utilize the fixing roller as a heat reservoir by heating the fixing roller.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C §119(a) from Korean Patent Application No. 10-2007-0021861, filed on Mar. 6, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entity by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present general inventive concept relates to an image heating apparatus, and more particularly, to a method and apparatus to fuse an image, which can reduce a warm-up time and also can improve a fusing quality. 
         [0004]    2. Description of the Related Art 
         [0005]    An image heating apparatus generally includes a heating roller and a pressure roller. The image heating apparatus may pass a printing paper, formed with an image, through the heating roller and the pressure roller to fuse the image on the printing paper. Accordingly, the image heating apparatus may be used for a copying machine, a printer, a facsimile, and the like. Also, the image heating apparatus may be used to fuse character or image information on a printing paper as an image. 
         [0006]    A main task of the image heating apparatus may be to fuse an image identical to an original image on the printing paper. Also, the image heating apparatus may reduce an initial warm-up time and power consumption. 
         [0007]      FIG. 1  is a cross-sectional view illustrating an image heating apparatus according to a conventional art. 
         [0008]    Referring to  FIG. 1 , the conventional image heating apparatus includes a pressure roller  10  and a heating roller  12 . In this instance, the heating roller  12  includes a heating element such as a lamp or an electric heating coil, and may be heated up to a predetermined temperature and maintained at the temperature by using the heating element. However, since the heating roller  12  is entirely heated by a lamp  14 , a comparatively greater warm-up time is required. As an example, when the entire heating roller  12  is utilized, it may take more than 30 seconds to raise the temperature of a nip up to about 160° C. 
         [0009]      FIG. 2  is a cross-sectional view illustrating another image heating apparatus according to the conventional art. 
         [0010]    Referring to  FIG. 2 , the image heating apparatus includes a pressure roller  20 , a fixing roller  22 , a belt  24 , and a heating roller  26 . In this instance, the fixing roller  22  is provided above the pressure roller  20 , and the belt  24  passes through a gap between the pressure roller  20  and the fixing roller  22  via the heating roller  26 . The pressure roller  20 , the fixing roller  22 , and the belt  24  form a nip N to fuse a toner image. A pre-fused toner image may be fused on a printing paper while passing through the nip N. 
         [0011]    In the image heating apparatus of  FIG. 2 , the heating roller  26  may be formed in a comparatively smaller size and thus may be quickly heated. Accordingly, an initial warm-up time may be reduced when compared to heating the comparatively larger pressure roller  12  of the image heating apparatus of  FIG. 1 . As an example, when an image heating apparatus similar to the image heating apparatus of  FIG. 2  utilizes a heater with a capacity of about 1.3 kW, it may take about 20 to 22 seconds to raise the image heating apparatus from room temperature up to about 160° C. 
         [0012]    In this instance, heat is indirectly transmitted to the nip N through the belt  24  instead of direct transmission, and thus the initial warm-up time may be slow. Also, while the belt  24  is heated by the heating roller  26  and being moved to the nip N, the temperature of the belt  24  may non-uniformly change due to heat radiation, which may deteriorate a fusing quality. 
       SUMMARY OF THE INVENTION 
       [0013]    The present general inventive concept provides an image heating apparatus which can quickly raise a temperature in a nip and thereby reduce an initial warm-up time. 
         [0014]    The present general inventive concept also provides an image heating apparatus which can reduce an initial heating warm-up time and also can maintain a temperature to be uniform in a nip. 
         [0015]    Additional aspects and utilities 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. 
         [0016]    The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an image heating apparatus including: a pressure member; a fixing roller to rotate on the pressure member; a heater to heat an external surface of the fixing roller; and a film to be heated by the heater. In this instance, the heating temperature of the nip may be raised to a predetermined level and maintained at the level by using the fixing roller and the film as media. Specifically, the heater may simultaneously heat both the external surface of the fixing roller and the film. 
         [0017]    The image heating apparatus may quickly reach a predetermined warm-up temperature by using a significantly rising temperature of the film. Also, the image heating apparatus may uniformly maintain the heating temperature by using the fixing roller, with a comparatively smaller temperature change, as a heat reservoir. 
         [0018]    Also, the pressure member may contact with the fixing roller and the film in a pressurized state and thus may form the nip to fuse an image on a recording medium. A roller with a surface formed using a rubber material may be generally utilized for the pressure member. Also, a different element capable of easing a movement of the recording medium may be utilized for the pressure roller. 
         [0019]    The heater may directly heat the external surface of the fixing roller and also may heat the film at the same time. In this instance, the heater may include a heating element, such as a halogen lamp, a ceramic heating element, and the like. Also, the heater may transmit heat through a heat conduction while directly contacting with the fixing roller. Also, the heater may be provided adjacent to the external surface of the fixing roller and thereby transmit heat through a heat radiation without contacting with the fixing roller. The conventional heating roller may transmit heat to only either a film or a belt while rotating with the film or the belt. However, the heater may simultaneously transmit heat to both the film and the fixing roller. Accordingly, the image heating apparatus may reduce an initial warm-up time and uniformly maintain a heating temperature during an operation, and thereby provide a uniform fusing quality. 
         [0020]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an image heating apparatus including: a pressure roller; a fixing roller to rotate in engagement with the pressure roller; a heater to comprise a protective cover which is provided adjacent to an external surface of the fixing roller and is open towards the fixing roller, and a heating element which is contained in the protective cover and thereby directly heats the external surface of the heating roller; and a belting film to circulate around the fixing roller, form a nip with the pressure roller, and pass through a gap between the pressure roller and the fixing roller while contacting with an external surface of the protective cover. 
         [0021]    The pressure roller and the fixing roller may correspond to each other and thereby rotate. Also, the belting film may circulate around the fixing roller and form the nip with the pressure roller. In this instance, the heater may include the heating element which is provided adjacent to the fixing roller, and the protective cover which contains the heating element. The protective cover has one side open towards the fixing roller so that the heating element may directly heat the external surface of the fixing roller. Also, since the belting film passes through the gap between the pressure roller and the fixing roller while contacting with the external surface of the protective cover, the belting film may receive heat from the heated protective cover. Also, the protective cover may prevent the heating element from being damaged due to the quickly rotating film. 
         [0022]    In this instance, the heating element may be a heating element such as a halogen lamp. Also, the heating element may directly contact with the fixing roller or be provided adjacent to the fixing roller and thereby effectively transmit heat. Also, the heating element may be in a static state, that is, in a motionless state. However, the present general inventive concept is not limited thereto, and thus the heater may be in a dynamic state, that is, in a moving or rotating state with respect to the fixing roller. 
         [0023]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an image heating apparatus including: a pressure roller; a fixing roller to rotate in engagement with the pressure roller; a heater to be provided adjacent to an external surface of the fixing roller, comprise an internal surface which is concavely formed corresponding to the external surface of the fixing roller, and thereby directly heat the external surface of the heating roller; and a belting film to circulate around the fixing roller, form a nip with the pressure roller, and pass through a gap between the pressure roller and the fixing roller while contacting with an external surface of the heater. 
         [0024]    The heater may include a concavely formed internal surface in correspondence to the external surface of the fixing roller, to transmit heat to the fixing roller. Also, a distance between the internal surface of the heater and the external surface of the fixing roller may be maintained at a minimum level and a facing surface area may be maintained at a maximum level. Also, the heater may include an external surface capable of transmitting heat to the belting film. In this instance, since the belting film passes through the gap between the pressure roller and the fixing roller while contacting with the external surface of the heater, the heat may be effectively transmitted from the belting film. 
         [0025]    The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an image heating apparatus including a fixing roller to fix a toner image to a recording medium, a film to enclose the fixing roller to contact an outer surface of the fixing roller with an inner surface of the film and to contact the recording medium including the toner image, and a heater disposed within the film such that the film rotates around both the fixing roller and the heater and heats both an external surface of the fixing roller and the film simultaneously. 
         [0026]    The heater may include a heating element and a protective cover surrounding the heating element on three sides such that the protective cover has an opening facing the fixing roller to radiate heat thereto while at least one of the three remaining sides contacts the film to transfer heat thereto. 
         [0027]    The heating element may include a heating member including a first surface facing the fixing roller to radiate heat thereto, and at least one other surface in contact with the film to transfer heat thereto. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    These and/or other aspects and utilities 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: 
           [0029]      FIG. 1  is a cross-sectional view illustrating an image heating apparatus according to a conventional art; 
           [0030]      FIG. 2  is a cross-sectional view illustrating another image heating apparatus according to the conventional art; 
           [0031]      FIG. 3  is a cross-sectional view illustrating an image heating apparatus according to an embodiment of the present general inventive concept; 
           [0032]      FIG. 4  is a cross-sectional view illustrating an image heating apparatus according to another embodiment of the present general inventive concept; and 
           [0033]      FIG. 5  is a cross-sectional view illustrating an image heating apparatus according to still another embodiment of the present general inventive concept. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    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. 
         [0035]      FIG. 3  is a cross-sectional view illustrating an image heating apparatus  100  according to an embodiment of the present general inventive concept. 
         [0036]    Referring to  FIG. 3 , the image heating apparatus  100  includes a pressure roller  110 , a fixing roller  120 , a belting film  130 , and a heater  140 . The pressure roller  110  is provided below the fixing roller  120 , and forms a nip with the pressure roller  110  by using the belting film  130  as a medium for mutual engagement. The heater  140  is provided adjacent to the fixing roller  120 , and is also provided adjacent to an inlet of the nip around the fixing roller  120 . Accordingly, the belting film  130  is heated by the heater  140  before passing through the nip. Also, the heater  140  may continuously heat an external surface of the fixing roller  120 . 
         [0037]    The external surface of the pressure roller  110  and the fixing roller  120  may be formed using a rubber material, and thus the pressure roller  110  and the fixing roller  120  may rotate in engagement with each other in a pressurized state. In the present embodiment, the pressure roller  110  and the fixing roller  120  exclude a lamp heating element or a conductive heating element. However, the present general inventive concept is not limited thereto, and thus the pressure roller  110  and the fixing roller  120  may have a heating element embedded therein to raise a warm-up temperature or maintain the heating temperature. 
         [0038]    Also, the heater  140  may be formed using a heating element with a heating function capable of uniformly maintaining the heating temperature. In this instance, the heater  140  may have a structure, such as a halogen lamp and a ceramic heating element, to simultaneously heat at least two surfaces, such as surfaces of both the fixing roller  120  and the belting film  130 . 
         [0039]    The heater  140  should heat both the fixing roller  120  and the belting film  130 . Accordingly, the heater  140  may be provided between the fixing roller  120  and the belting film  130 . In this instance, the heater  140  may contact with the fixing roller  120  or the belting film  130  or maintain only a close distance therefrom. Accordingly, the heater  140  may directly heat the fixing roller  120  without a medium by using a heat conduction or a heat radiation. In this instance, the initial warm-up in the nip is progressed by heating of the belting film  130 , and thus it may be desirable that the belting film  130  directly transmits heat through the heat conduction while directly contacting with the external surface of the heater  140 . 
         [0040]    Also, a relative slip may occur between the circulating belting film  130  and the heater  140 . Specifically, the heater  140  may maintain a static state without rotation and the belting film  130  may pass through the gap between the pressure roller  110  and the fixing roller  120 , and thereby the relative slip may occur between the belting film  130  and the heater  140 . Particularly, the heater  140  does not utilize a heating roller surrounded by a rubber material, which is different from the conventional image heating apparatus of  FIG. 2 . Accordingly, the heater  140  may directly heat the external surface of the fixing roller  120  through a heat radiation and the like. 
         [0041]    According to the present embodiment, the belting film  130  has a comparatively smaller heat capacity and thus may be quickly heated. Accordingly, the initial warm-up may be quickly completed by the belting film  130 . Conversely, the fixing roller  120  has a comparatively greater heat capacity and thus may not be quickly heated. However, once the fixing roller  120  is heated up to a desirable temperature, the fixing roller  120  functions as a heat reservoir. Accordingly, the fixing roller  120  may help the heating temperature to be uniformly maintained. Also, a process of heating the belting film  130  and a process of heating the external surface of the fixing roller  120  may be simultaneously performed. Both of the processes may be simultaneously performed while the heating is ongoing. 
         [0042]      FIG. 4  is a cross-sectional view illustrating an image heating apparatus  200  according to another embodiment of the present general inventive concept. 
         [0043]    Referring to  FIG. 4 , the image heating apparatus  200  includes a pressure roller  210 , a fixing roller  220 , a belting film  230 , and a heater  240 . The pressure roller  210  is provided below the fixing roller  220 , and forms a nip with the fixing roller  220  by using the belting film  230  as a medium for mutual engagement. The heater  240  is provided adjacent to the fixing roller  220 , and is also provided adjacent to an inlet of the nip around the fixing roller  220 . Also, the heater  240  includes a heating element  242  and a protective cover  244 , and may heat each of the fixing roller  220  and the belting film  230 . Accordingly, the belting film  230  is heated by the protective cover  244 , which is heated by the heating element  242 , before passing through the nip. Also, the heater  240  may continuously heat an external surface of the fixing roller  220 . 
         [0044]    The external surface of the pressure roller  210  and the fixing roller  220  may be formed using a rubber material, and thus the pressure roller  210  and the fixing roller  220  may rotate in engagement with each other in a pressurized state. In the present embodiment, the pressure roller  210  and the fixing roller  220  exclude a lamp heating element or a conductive heating element. However, the present general inventive concept is not limited thereto, and thus the pressure roller  210  and the fixing roller  220  may have a heating element embedded therein to raise a warm-up temperature or maintain the heating temperature. 
         [0045]    As described above, the heater  240  includes the heating element  242  and the protective cover  244 . Also, the heating element  242  may be formed using a heating element with a heating function capable of uniformly maintaining the heating temperature. As an example, a heating lamp, such as a halogen lamp, may be used for the heating element  242 . Also, the protective cover  244  contains the heating element  242 , and has an open side facing towards the fixing roller  220 . Accordingly, although the heating element  242  is contained in the protective cover  244 , the heating element  242  may directly heat the external surface of the fixing roller  220 . Also, the protective cover  244  may transmit heat generated from the heating element  242  to the belting film  230 , and thus may be formed using a heat conductive material, for example, a metal material such as stainless steel. 
         [0046]    The protective cover  244  covers around the heating element  242 , so that the atmosphere heated from the heating element  242  may remain around the heating element  242  and the heating element  242  may intensively heat the external surface of the fixing roller  220 . Also, the protective cover  244  may protect the heating element  242  from being damaged due to the quickly rotating belting film  230 . 
         [0047]    Since the heater  240  should heat both the fixing roller  220  and the belting film  230 , the heater  240  is provided between the fixing roller  220  and the belting film  230 . In this instance, the heating element  242  may contact with the fixing roller  220  or maintain only a close distance therefrom. Also, the protective cover  244  may supply heat to the belting film  130  through a heat conduction while contacting with the belting film  230 . 
         [0048]    Also, the circulating belting film  230  may transmit heat while passing by the external surface of the protective cover  244 . The heating element  242  and the protective cover  244  of the heater  240  may maintain the static state without rotation. When the belting film  230  passes through the gap between the pressure roller  210  and the fixing roller  220  while contacting with the external surface of the protective cover  244 , the relative slip may occur between the belting film  230  and the external surface of the protective cover  244 . 
         [0049]    According to the present embodiment, the belting film  230  has a comparatively smaller heat capacity and thus may be quickly heated. Accordingly, the initial warm-up may be quickly completed by the belting film  230 . Conversely, the fixing roller  220  has a comparatively greater heat capacity and thus may not be quickly heated. However, once the fixing roller  220  is heated up to a desirable temperature, the fixing roller  220  functions as a heat reservoir. Accordingly, the fixing roller  220  may help the heating temperature to be uniformly maintained. Also, a process of heating the belting film  230  and a process of heating the external surface of the fixing roller  220  may be simultaneously performed. Both of the processes may be simultaneously performed while the heating is ongoing. 
         [0050]    When a lamp with a capacity of about 850 W is utilized in the image heating apparatus of  FIG. 4 , it may generally take about 8 to 10 seconds to raise the image heating apparatus from room temperature up to about 160° C. When considering that the conventional image heating apparatus of  FIG. 2  needs an initial warm-up time of about 20 to 22 seconds, the image heating apparatus of the present general inventive concept is very effective. 
         [0051]      FIG. 5  is a cross-sectional view illustrating an image heating apparatus  300  according to still another embodiment of the present general inventive concept. 
         [0052]    Referring to  FIG. 5 , the image heating apparatus  100  includes a pressure roller  310 , a fixing roller  320 , a belting film  330 , and a heater  340 . The pressure roller  310  is provided below the fixing roller  320 , and forms a nip with the pressure roller  310  by using the belting film  330  as a medium for mutual engagement. The heater  340  is provided adjacent to the fixing roller  320 , and is also provided adjacent to an inlet of the nip around the fixing roller  320 . Also, the heater  340  may include a concavely formed internal surface  342  to face the fixing roller  220 , and an external surface  344  to correspond to the internal surface  342 . The heater  340  may heat each of the fixing roller  320  and the belting film  330 . Accordingly, the belting film  330  is heated by the external surface  344  of the heater  340  before passing through the nip. Also, the heater  340  may continuously heat an external surface of the fixing roller  320 . 
         [0053]    The external surface of the pressure roller  310  and the fixing roller  320  may be formed using a rubber material and thus the pressure roller  310  and the fixing roller  320  may rotate in engagement with each other in a pressurized state. In the present embodiment, the pressure roller  310  and the fixing roller  320  exclude a lamp heating element or a conductive heating element. However, the present general inventive concept is not limited thereto, and thus the pressure roller  310  and the fixing roller  320  may have a heating element embedded to raise a warm-up temperature or maintain the heating temperature. 
         [0054]    As described above, the heater  340  includes the concavely formed internal surface  342  and the relatively protruding external surface  344 . Also, the heater  340  may be formed using a heating element with a heating function capable of uniformly maintaining the heating temperature. As an example, a ceramic heating element may be utilized to heat element. 
         [0055]    The heater  340  includes the internal surface  342  concavely formed in correspondence to the external surface of the fixing roller  320  to transmit heat. Also, a distance between the internal surface  342  of the heater  340  and the external surface of the fixing roller  320  is maintained at a minimum level. In this instance, it is possible to readily transmit heat to the fixing roller  320  by optimally forming the internal surface  342  and external surface  344  of the heater  340 . Also, the heater  340  may include the protruding external surface  344  capable of transmitting heat to the belting film  330 . Also, since the belting film  330  passes while contacting with the external surface  344  of the heater  340 , heat may be effectively transmitted to the belting film  330 . The protruded external surface  344  of the heater  340  may be variously formed. Also, a bottom portion of the external surface  344  of the heater  340  may be variously formed. Through the various adjustments, the shape and length of the nip may be variously adjusted. 
         [0056]    The heater  340  should heat both the fixing roller  320  and the belting film  330 . Accordingly, the heater  340  may be provided between the fixing roller  320  and the belting film  330 . In this instance, the internal surface  342  of the heater  340  may contact with the fixing roller  320  or maintain only a close distance therefrom. Also, the external surface  344  of the heater  340  may transmit heat to the belting film  330  through the heat conduction while contacting with the belting film  330 . 
         [0057]    Also, heat may be transmitted to the circulating belting film  330  while passing the external surface of the heater  340 . In this instance, the heater  340  may maintain the static state without rotation. When the belting film  330  passes through the gap between the pressure roller  310  and the fixing roller  320  while contacting with the external surface of the heater  340 , a relative slip may occur between the belting film  330  and the external surface of the heater  340 . 
         [0058]    According to the present embodiment, the belting film  330  has a comparatively smaller heat capacity and thus may be quickly heated. Accordingly, the initial warm-up may be quickly completed by the belting film  330 . Conversely, the fixing roller  320  has a comparatively greater heat capacity and thus may not be quickly heated. However, once the fixing roller  320  is heated up to a desirable temperature, the fixing roller  320  functions as a heat reservoir. Accordingly, the fixing roller  320  may help the heating temperature to be uniformly maintained. Also, a process of heating the film and a process of heating the external surface of the fixing roller  320  may be simultaneously performed. The both processes may be simultaneously performed while the heating is ongoing. 
         [0059]    The image heating apparatus according to the various embodiments may uniformly maintain a heating temperature in a nip, and provide a quick warm-up time. According to test results, when a lamp with a capacity of about 850 W was used, it generally took about 8 to 10 seconds to raise the image heating apparatus from room temperature up to about 160° C. Specifically, even when using a heater with a comparatively smaller capacity than the conventional image heating apparatus, an initial warm-up time may be reduced to almost half of an initial warm-up time of the conventional image heating apparatus. 
         [0060]    Also, when a protective cover protects a heating element of a heater, the protective cover may cover around the heating element, so that the atmosphere heated from the heating element may remain around the heating element and the heating element may intensively heat the external surface of a fixing roller. Also, the protective cover may protect the heating element from being damaged due to the quickly rotating belting film. 
         [0061]    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.