Abstract:
A method and apparatus to control the fusing temperature of an image forming apparatus. This method of controlling the fusing temperature of an image forming apparatus having a fan to exhaust the internal air to the outside includes counting the accumulated number of sheets of paper printed in response to print commands, lowering a set point of the fusing temperature and controlling the fan to increase the amount of air to be exhausted when the accumulated number of sheets of printed paper is greater than a predetermined value. According to the method, without installing an additional temperature sensor inside the image forming apparatus, the temperature therein can be presumed and controlled by controlling the fusing temperature of the fusing roller and a fan flow rate to lower the temperature of the paper, and consequently, preventing the formation of creases in the paper.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the priority of Korean Patent Application No. 2003-81727, filed on Nov. 18, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety and by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present general inventive concept relates to a method and apparatus to control the fusing temperature of an image forming apparatus, and, more particularly, to a method and apparatus to control the fusing temperature of an image forming apparatus that adjusts a fusing temperature and a fan flow rate as the number of sheets of paper printed continuously increases.  
         [0004]     2. Description of the Related Art  
         [0005]     An electrophotographic image forming apparatus includes a fixing apparatus, which heats a sheet of paper having a toner image transferred, fuses the toner image in a powder state, and fixes the toner image on the sheet of paper. The fixing apparatus includes a fusing roller for fixing toner on the sheet of paper and a pressure roller for pressing the sheet of paper against the fusing roller.  
         [0006]      FIG. 1  is a horizontal sectional view of a conventional fusing roller using a halogen lamp as a heat source.  FIG. 2  is a vertical sectional view of a fixing apparatus adopting the fusing roller shown in  FIG. 1 .  
         [0007]     Referring to  FIG. 1 , the fusing roller  10  includes a cylindrical roller  11  and a halogen lamp  12  installed in the middle of the cylindrical roller  11 . A teflon coating layer  11  a is formed on the surface of the cylindrical roller  11 . The halogen lamp  12  generates heat inside the cylindrical roller  11 , and the cylindrical roller  11  is heated by radiant heat from the halogen lamp  11 .  
         [0008]     Referring to  FIG. 2 , a pressure roller  13  facing the cylindrical roller  11  is placed on the bottom of the fusing roller  10  interposing a sheet of paper  14  therebetween. Supported elastically by a spring  13   a , the pressure roller  13  pushes the sheet of paper  14 , which passes between the fusing roller  10  and the pressure roller  13 , toward the fusing roller  10  with predetermined pressure. Here, a powder-state toner image  14   a , which was transferred on the sheet of paper  14 , is fixed on the sheet of paper  14  by predetermined pressure and heat when the sheet of paper  14  passes between the fusing roller  10  and the pressure roller  13 .  
         [0009]     Installed on one side of the fusing roller  10  are a thermistor  15  for measuring the surface temperature of the fusing roller  10  and a thermostat  16  for cutting off the supply of power to the halogen lamp  12  when the surface temperature of the fusing roller  10  exceeds a set value. The thermistor  15  measures the surface temperature of the fusing roller  10  and transmits an electric signal of the measured temperature to a control unit (not shown) of a printer (not shown). Then, the control unit controls power to be supplied to the halogen lamp  12  according to the measured temperature and maintains the surface temperature of the fusing roller  10  within a predetermined range. Furthermore, when the control unit fails to control the surface temperature of the fusing roller  10 , leading the temperature of the fusing roller  10  to a temperature higher than a set limit value, a contact (not shown) of the thermostat  16  is opened to cut off power supplied to the halogen lamp  12 .  
         [0010]     In the meantime, in case of printing continuously while maintaining the fusing temperature of the fusing roller  10  within a predetermined range, the ambient temperature of the fusing roller  10  increases due to the heat generated from the fusing roller  10 . In particular, an increase in the temperature of the pressure roller  13  directly leads to an increase in the temperature of the paper passing over the pressing roller  13 , which is a major cause of paper creases.  
         [0011]     Inside the image forming apparatus is installed a fan, which exhausts hot air to the outside (externally) to lower the internal temperature. The fan cools the inside of the printer to prevent overheating. However, the fan also accelerates the flow of air inside the image forming apparatus, thereby also forming creases in the paper. In particular, more creases in the paper are formed when the temperature of paper is higher than an appropriate fusing temperature.  
         [0012]     In order to control a fusing temperature, there has been proposed a method of measuring the temperature of a fusing roller  10  and adjusting the heat from a halogen lamp  12  being a heat source.  
         [0013]     However, this method, intended to maintain the temperature of a fusing roller  10  steadily, fails to prevent the creasing of paper because the ambient temperature of the fixing apparatus including a pressure roller  13  rises as a result of a continued use of a printer.  
       SUMMARY OF THE INVENTION  
       [0014]     The present general inventive concept provides an apparatus and method of controlling a fusing temperature of an image forming apparatus that counts a number of sheets of paper printed continuously, which is most closely related to an ambient temperature of a fusing roller, and adjusts a speed of a fan and the fusing temperature accordingly.  
         [0015]     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.  
         [0016]     The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing a method of controlling a fusing temperature of an image forming apparatus having a fan to ventilate air from or to an outside (externally) of the apparatus, the method including counting an accumulated number of sheets of paper printed in response to print commands, and lowering a set point of a fusing temperature and controlling the fan to increase an amount of air to be ventilated when the accumulated number of sheets of printed paper is greater than a predetermined value.  
         [0017]     The above method may include counting the accumulated number of sheets of paper printed in response to print commands, setting a set point of the fusing temperature of a fusing roller at a second value when the accumulated number of sheets of printed paper is equal to or less than a first value, and keeping the fan off; and resetting the fusing temperature of the fusing roller to a third value, lower than the second value, and starting the fan and controlling a fan flow rate at a fourth value when the accumulated number of sheets of printed paper is greater than the first value.  
         [0018]     The above method may further include resetting the accumulated number of sheets of printed paper when the image forming apparatus is started or a new print command is received in a power-saving mode, in which the supply of power to a heater of the fusing roller is cut off to save power.  
         [0019]     The above method may further include resetting a set point of the temperature of the fusing roller to a sixth value lower than the third value, and controlling the fan flow rate at a seventh value higher than the fourth value, when the accumulated number of sheets of printed paper is greater than a fifth value higher than the first value.  
         [0020]     The foregoing and/or other aspects and advantages of the present general inventive concept are achieved by providing an apparatus to control a fusing temperature of an image forming apparatus, the fusing temperature controlling apparatus including a fan which ventilates air from or to an outside (externally), a fan-driving unit which drives the fan, a heater which heats a fusing roller, an AC power supply unit which supplies AC power to the heater, a counter which counts an accumulated number of sheets of paper printed in response to print commands, and a control unit which controls the fan-driving unit to reduce AC power supplied to the heater and increase a fan flow rate when the accumulated number of sheets of printed paper counted by the counter is greater than a predetermined value. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     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:  
         [0022]      FIG. 1  is a horizontal sectional view of a conventional fusing roller using a halogen lamp as a heat source;  
         [0023]      FIG. 2  is a vertical sectional view of a fixing apparatus adopting the fusing roller shown in  FIG. 1 ;  
         [0024]      FIG. 3  is a block diagram showing a controlling apparatus to control the fusing temperature of an image forming apparatus according to an embodiment of the present general inventive concept; and  
         [0025]      FIG. 4  is a flow chart of a method of controlling the fusing temperature of an image forming apparatus according to an embodiment of the present general inventive concept. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     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.  
         [0027]      FIG. 3  is a block diagram showing a controlling apparatus to control the fusing temperature of an image forming apparatus, according to an embodiment of the present general inventive concept.  
         [0028]     Referring to  FIG. 3 , the controlling apparatus includes a fan  112 , a fan-driving unit  110 , a heater  122 , an AC power supply unit  120 , a fusing temperature-measuring unit  140 , a counter  130 , and a control unit  100 .  
         [0029]     The fan  112  exhausts air inside an electrophotographic image forming apparatus, such as, for example, a printer (not shown), to lower a temperature inside the image forming apparatus (printer) by indirectly inducing outside air to an inside thereof. One or a plurality of fans can be installed inside the printer. The speed of the fan  112  may be adjusted, depending on printing status of the printer, in order to maintain the temperature inside the printer below an appropriate temperature.  
         [0030]     The fan-driving unit  110  controls the speed of the fan  112 , or a fan flow rate, according to a control value received from the control unit  100 . The control value uses a pulse width modulation (PMW) method, in which a frequency pulse is applied to an element to apply power to the fan-driving unit  110 , and the pulse width of a frequency pulse used to run the fan-driving unit  110  is modulated according to the control value. In addition, a duty control method of controlling the time spent for power supply during a predetermined control period may be used. The flow rate of the fan  112  may easily be controlled using either PWM or the duty control method.  
         [0031]     The heater  122  being a heat source, which applies predetermined heat to a fusing roller (such as the fusing roller  10  illustrated in  FIG. 1 ), corresponds to the halogen lamp  12  shown in  FIG. 1 . Additionally, the heater  122  may be a heating coil (not shown) in an instant fusing roller (not shown) using a heat pump. The heater  122  may be applied in various forms. The heater  122  is heated by a predetermined amount of power supplied from the AC power supply unit  120 . The fusing temperature-measuring unit  140  measures the temperature, i.e., fusing temperature, of the fusing roller (such as the fusing roller  10  illustrated in  FIG. 1 ), heated by the heater  122 . For a precise control of a fusing temperature, one of the above-described PWM and duty control methods may be used as well as an on/off control method.  
         [0032]     The counter  130  counts the number of sheets of paper fed into the printer or the number of sheets of paper printed by the printer. This accumulated number of sheets of printed paper is used as a numerical index indicating a temperature increase inside the printer and in the periphery of the fusing roller, caused by continuous printing. Hence, the accumulated number of sheets of printed paper may be counted from the moment when the printer first starts printing or restarts printing after a conversion from a power-saving mode to a printing mode.  
         [0033]     Table 1 is an example of a control value of a fan flow rate and a set value of fusing temperature in a case of continuous printing.  
                                   TABLE 1                                       Accumulated   1˜100   101˜200   201 or greater           Number of Sheets of           Printed Paper           Fan Flow Rate   Fan off   50%   100%           Control           Fusing Temperature   T   T-ΔT 1     T-ΔT 2                        
 
         [0034]     Referring to Table 1, in the initial printing, printing is performed under the condition that a fusing temperature is set at a predetermined value of T (for example, 180° C.). Here, the fan  112  remains turned off because the temperature inside the printer, as well as that of a pressure roller (such as the pressure roller  13  illustrated in  FIG. 1 ), is low even without running the fan  112 .  
         [0035]     Thereafter, when the accumulated number of sheets of printed paper increases to more than 100 sheets, leading to an increase in the temperature inside the printer and that of the pressure roller (such as the pressure roller  13  illustrated in  FIG. 1 ), the fan  112  runs at a flow rate of about 50 percent to lower the temperature inside the printer, and the set temperature of the fusing roller is lowered by a predetermined value of ΔT 1  (for example, 5° C.).  
         [0036]     Later, when the accumulated number of sheets of printed paper increases to more than 200 sheets, leading to an even higher increase in the temperature inside the printer and that of the pressure roller (such as the pressure roller  13  illustrated in  FIG. 1 ), the fan  112  runs fully at a flow rate of 100 percent, and the fusing temperature is lowered by a predetermined value of ΔT 2  (for example, 10° C.).  
         [0037]     In Table 1, the number of sheets of paper printed continuously is divided into three sections to adjust a fan control value and a set value of fusing temperature accordingly. For each section, a set value of the temperature of the fusing roller and a fan flow rate are adjusted to prevent a temperature increase inside the printer, resulting from continuous printing, and, consequently, to prevent the formation of creases in paper. Although Table 1 has three sections, the number of sheets of paper printed continuously can be divided into less than or more than three sections depending on the type of the heater  122  within the fixing system of the printer, the control method of the fan  112 , and the like.  
         [0038]     Meanwhile, the printing stage is classified into a printing mode, a stand-by mode, and a power-saving mode. The printing mode indicates that printing is in progress. In the stand-by mode, the set temperature of the fusing roller is maintained at a predetermined value (for example, below 120° C.) when there is no print command for a predetermined amount of time. The power-saving mode is when power supplied to the heater  122  of the fusing roller  10  is cut off to cool the fusing roller to the room temperature after a long stand-by mode.  
         [0039]     The counter  130  may restart when power is applied to a printer or in a case of a conversion from a power-saving mode to a printing mode. In other words, the counter  130  is reset when the power of the printer is turned on or in a case of a conversion from a power-saving mode to a printing mode.  
         [0040]      FIG. 4  is a flow chart of a method of controlling the fusing temperature of an image forming apparatus according to an embodiment of the present general inventive concept.  
         [0041]     When power is applied to a printer or in the case of a conversion from a power-saving mode to a printing mode, a count icount of the number of sheets of printed paper is reset to “1” (operation  210 ). Thereafter, the accumulated count of sheets of printed paper icount is compared with a predetermined value of A (operation  220 ). In operation  220 , when the accumulated count icount is less than A, a fusing temperature T f  is set at a predetermined value of T (for example, 180° C.), and a fan motor is kept off (operation  221 ). Then, the accumulated count icount is increased by “1” (operation  240 ), and operation  220  is re-performed.  
         [0042]     In operation  220 , when the accumulated count icount is equal to or greater than A, the accumulated count icount is compared with a predetermined value of B (operation  230 ).  
         [0043]     In operation  230 , when the accumulated count icount is less than B, a fusing temperature T f  is set at a value lowered by ΔT 1  from a predetermined value of T (for example, 180° C.) and a fan motor is kept at a flow rate of 50 percent (operation  231 ). Then, the accumulated count icount is increased by “1” (operation  240 ) and operation  220  is re-performed.  
         [0044]     In operation  230 , when the accumulated count icount is equal to or greater than B, a fusing temperature T f  is set at a value lowered by ΔT 2 , which is greater than ΔT 1 , from a predetermined value of T, and a fan motor is kept at a flow rate of 100 percent (operation  232 ). Then, the accumulated count icount is increased by “1” (operation  240 ), and operation  220  is re-performed.  
         [0045]     As described so far, the present general inventive concept provides a method of controlling the fusing temperature of an image forming apparatus. According to the method illustrated in  FIG. 4 , without installing an additional temperature sensor inside a printer, the temperature inside the printer can be presumed and controlled by controlling the fusing temperature of a fusing roller and a fan flow rate to lower the temperature of paper, and consequently, preventing the formation of creases in paper.  
         [0046]     The present invention can be realized as a method, an apparatus, and a system. When the present invention is manifested in computer software, components of the present invention may be replaced with code segments that are necessary to perform the required action. Programs or code segments may be stored in media readable by a processor, and transmitted as computer data that is combined with carrier waves via a transmission media or a communication network.  
         [0047]     The media readable by a processor include anything that can store and transmit information, such as, electronic circuits, semiconductor memory devices, ROM, flash memory, EEPROM, floppy discs, optical discs, hard discs, optical fiber, radio frequency (RF) networks, etc. The computer data also includes any data that can be transmitted via an electric network channel, optical fiber, air, electro-magnetic field, RF network, etc.  
         [0048]     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.