Abstract:
Apparatus and methods for fusing developer are disclosed. A developer fuser may comprise a first heating element for transferring energy for fusing developer to a media. The developer fuser may have a controller for controlling the power applied to the first heating element. Upon initiation of a copy process, the power applied to the first heating element may be set to a set-up power level determined, at least in part, by a physical characteristic of the media. The power applied to the first heating element may be further varied in response to a first temperature sensor to maintain a fixing temperature during the copy process. The fixing temperature may be determined, at least in part, by the physical characteristic of the media.

Description:
RELATED APPLICATION INFORMATION  
       [0001]     This application is a continuation of U.S. application Ser. No. 10/782,281 filed Feb. 19, 2004 which, in turn, claims priority from U.S. Provisional Application No. 60/492,869 filed Aug. 6, 2003 
     
    
     NOTICE OF COPYRIGHTS AND TRADE DRESS  
       [0002]     A portion of the disclosure of this patent document contains material which is subject to copyright protection. This patent document may show and/or describe matter which is or may become trade dress of the owner. The copyright and trade dress owner has no objection to the facsimile reproduction by any one of the patent disclosure as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright and trade dress rights whatsoever.  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field Of The Invention  
         [0004]     This invention relates to a fixing device of an image forming apparatus such as a copier or a printer.  
         [0005]     2. Description Of Related Art  
         [0006]     An image forming apparatus using digital technology may include a fixing device which fixes developer by applying pressure to images heat fused on a media such as paper.  
         [0007]     In an electronic copier, the catoptric light from an original is photo electrically converted by the photoelectric conversion element, such as a CCD (charge coupled device), and an electrostatic latent image corresponding to an acquired image signal is formed on a photo conductor. The electrostatic latent image is generated by adhering a developer (toner) selectively. A developer image on the photo conductor is transferred to medias supplied at the predetermined timing, and fixed with the fixing device.  
         [0008]     Fixing devices are equipped with a heating member which fuses a developer, such as a toner, and a pressurizing member which provides this heating member with a predetermined pressure. The developer images on a media are melted between the heating and pressurizing members with heat from the heating member, and fixed on the media by pressure from the pressurizing member.  
         [0009]     Induction-heating is one method of heating a fixing device. The induction-heating method uses a coil. By applying high frequency current to the coil, a predetermined magnetic field is generated, and the joule heat caused by the eddy current generated from the magnetic field heats the heating member.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of a compound-type electronic copier including a fixing device of this invention.  
         [0011]      FIG. 2  is a perspective view of a fixing device in accordance with this invention.  
         [0012]      FIG. 3  is a block diagram of a control system of the compound-type electronic copier in accordance with this invention.  
         [0013]      FIG. 4  is a block diagram of a control system of a fixing device in accordance with this invention.  
         [0014]      FIG. 5 ( a ) is a perspective view of a heating unit embodiment in accordance with this invention.  
         [0015]      FIG. 5 ( b ) is a circuit diagram of the heating unit of  FIG. 5 ( a ).  
         [0016]      FIG. 6 ( a ) is a perspective view of a heating unit embodiment in accordance with this invention.  
         [0017]      FIG. 6 ( b ) is a circuit diagram of the heating unit of  FIG. 6 ( a ).  
         [0018]      FIG. 6 ( c ) is a circuit diagram of the heating unit of  FIG. 6 ( a ).  
         [0019]      FIG. 7  is a flowchart of a control process embodiment in accordance with this invention.  
         [0020]      FIG. 8  is a flowchart of a control process embodiment in accordance with this invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than limitations on the apparatus and methods of the present invention.  
         [0022]     Referring now to  FIG. 1 , there is shown a compound-type electronic copier  1 , an embodiment of an image forming apparatus. An original stand (glass plate)  2 , to which an original D may be set, may be prepared at the upper surface of the compound-type electronic copier  1 . The original D put on the original stand  2  may be illuminated by an illumination light from an exposure lamp  5  of a carriage  4  prepared with the original stand  2 .  
         [0023]     A catoptric light from the original D may be photo electrically converted by a CCD (charge coupled device)  10 , which is a photoelectric conversion element. Thereby, an image signal corresponding to an image information on the original D is obtained. The image signal outputted from the CCD  10  may be converted into a digital signal in an image-processing portion, and may be supplied to a laser unit  27  after a predetermined image processing is performed.  
         [0024]     A laser beam B may illuminate a photoconductive drum  20  by the laser unit  27  according to an output signal to which an image processing was performed in the image-processing portion. The photoconductive drum  20  may be prepared in a predetermined position in the copier  1  so that a latent image can be held by being irradiated by light while charging. A charger  21 , a developing unit  22 , a transfer unit  23 , a separator  24 , a cleaner  25 , and a discharger  26  may be disposed in the circumference of the photoconductive drum  20  sequentially. Although it is not explained in detail, the latent images may be formed in the photoconductive drum  20  by the laser beam B from the laser unit  27 . The latent images formed on the photoconductive drum  20  may be developed with a toner, selectively supplied from the developing unit, and may be transferred to a media supplied at a predetermined timing. The media may be a paper, a transparency, a metal film, canvas, plastic, hybrid or other.  
         [0025]     Referring now to  FIG. 2 , there is shown an embodiment of a fixing device  100 . The fixing device  100 , mentioned later, may fix the toner transferred to the media. A fixing device  100  may contact a surface where the toner has adhered to the media S. The fixing device  100  may comprise a heating roller  101  which heats the toner T and the media S, and a pressurizing roller  102  which gives predetermined pressure to the heating roller  101 . A contact portion of the heating roller  101  and the pressurizing roller  102  may have a deformation field, known as nip width.  
         [0026]     The heating roller  101  may comprise a roller, formed cylindrically with a conductive material, such as a ferrite, whose periphery may be covered with a fluoro-resin which may comprise a copolymer of polytetra fluoroethylene and perfluoro alkyl vinyl ether, a copolymer of tetra fluoroethylene and hexa fluoroethylene, a copolymer of tetra fluoroethylene and ethylene, a polytetra fluoroethylene, a tetra fluoroethylene, a hexa fluoroethylene, a poly-tetra fluoroethylene, or a copolymer of chloro-tri-fluoroethylene and ethylene. The heating roller  101  may rotate in the arrow direction (in this embodiment, in the clockwise direction) by drive motors, which are not illustrated. The pressurizing roller  102  may rotate in the arrow direction (in this embodiment, in the counter-clockwise direction) by contacting with the heating roller  101 .  
         [0027]     A developer image T on the media S guided at the contact portion of the heating roller  101  and the pressurizing roller  102  may be fused by heat from the heating roller  101 , and may be fixed on the media S by pressure from the pressurizing roller  102 . The heating roller  101  may comprise an exfoliation nail  103  for exfoliating the media S from the heating roller  101 , a cleaning member  104  for removing a portion of the toner or a waste which may remain on the heating roller  101 , and an application roller  105  for applying a release agent to the surface of the heating roller  101 .  
         [0028]     The heating roller  101  may include a heating unit  110 . The heating unit  110  may transfer energy in the form of heat. The heat may be generated by a magnetic inductance source, an infrared, a visual or an ultraviolet light source, an electrical resistance source, a heat exchanger, a chemical reaction source, or otherwise. The heating unit  110  may be disposed within the heating roller  101 .  
         [0029]     The heating unit  110  may comprise a heating element support  110 A. The heating element support  110 A may comprise a ceramic material, a composite material, a metal, or otherwise. The choice of what material to manufacture the heating element support  110 A may be based on the method of energy transferred by the heating unit  110 . For example, if the heating unit  110  transfers energy via infrared light, the heating element support  110 A may comprise a ceramic material. Alternatively, if the heating unit  110  transfers energy via inductive resonance, the heating element support  110 A may comprise a ferrite bobbin core. The heating element support  110 A may be secured to the heating unit  110  by a holding member  110 B.  
         [0030]     The heating unit  110  may comprise a single heating element or a plurality of heating elements. If the heating unit  110  comprises a plurality of heating elements, it may also comprise a plurality of heating element supports  110 A corresponding to the quantity of heating elements  111 . The heating element supports  110 A may support the heating elements  111 . For example, the heating elements  111  may comprise copper coil windings around the heating element supports  110 A, for example, ferrite core bobbins. Alternatively, the heating elements  111  may comprise electric resistors which are fused to the heating element supports  110 A, for example, a ceramic tube.  
         [0031]     Power may be provided to each of the heating elements  111  of the heating unit  110 . Power may be provided via an electric power source. Alternatively, power may be provided by a chemical reaction, such as oxidation of ferrite particulate matter. Moreover, power may be provided via a heat exchanger. If the heating elements  111  comprise coils for inductive heating, and high frequency electric power is provided to each heating element  111  of the heating unit  110 , a high frequency magnetic field for induction heating may be generated. If a high frequency magnetic field is generated, an eddy current may result in transferring Joule heat energy to the heating roller  101 .  
         [0032]     Referring now to  FIG. 3 , there is shown a control circuit block diagram of the compound-type electronic copier. The control circuit may comprise a main CPU  50 , connected to a first ROM  51  for control program memory, a first RAM  52  for data memory, a pixel counter  53 , the image-processing portion  55 , a page memory controller  56 , a hard disk unit  58 , a network interface  59 , and a FAX-transceiver-unit  60 . In addition, the main CPU  50  may be connected to a scan CPU  70 , a control panel CPU  80 , and a print CPU  90 .  
         [0033]     The main CPU  50  may control the scan CPU  70 , the control panel CPU  80 , and the print CPU  90 . The main CPU  50  may function as a control means during a copy mode responding to an operation of a copy key, a control means during a printer mode responding to an image input to a network interface  59 , and a control means during a facsimile mode responding to an image reception by the FAX transceiver unit  60 .  
         [0034]     The page memory controller  56  may control a writing and a read-out of an image datum to a page memory  57 . In addition, the page memory controller  56  may be connected with the image-processing portion  55 , the page memory controller  56 , a page memory  57 , the hard disk unit  58 , the network interface  59 , and the FAX transceiver unit  60  by an image data bus  61 .  
         [0035]     The network interface  59  may function as an input portion at the printer mode when the image (image data), transmitted from external equipment, is inputted. A communication network  201 , such as a LAN or the Internet, may be connected to the network interface  59 , and external equipment, for example, at least one personal computer  202 . A personal computer  202  may be equipped with a controller  203 , a display  204 , and an operation unit  205 . The FAX transceiver unit  60  may be connected to a telephone line  210 . The FAX transceiver unit  60  may receive an image datum via the telephone line  210 .  
         [0036]     The scan CPU  70  may be connected to a second ROM  71  for control program memory, a second RAM  72  for data memory, a signal-processing portion  73  that processes and supplies an output of the CCD  10  to the image data bus  61 , a CCD driver  74 , a scanning motor driver  75 , the exposure lamp  5 , an automatic document feeder  40 , and an original sensor  11 . The CCD driver  74  may drive the CCD  10 . The scanning motor driver  75  may drive a scanning motor  76  for carriage driving. The automatic document feeder  40  may include the original sensor  43  for detecting if the original D is set to a first tray  41 , and the size of the original D.  
         [0037]     The control panel CPU  80  may be connected to a touch-sensitive liquid crystal display  14  for a control panel, a ten key  15 , an all reset key  16 , a copy key  17 , and a stop key  18 . The print CPU  90  may be connected to a third ROM  91  for control program memory, a third RAM  92  for data memory, a print engine  93 , a media feeding unit  94 , a process unit  95 , and the fixing device  100 . The print engine  93  may include the laser unit  27  and its drive circuit. The media-feeding unit  94  may include a media-feeding mechanism applied from a media feed cassette  30  to a second tray  38 , and its drive circuit. The process unit  95  may include the photoconductive drum  20  and its circumference. An image-processing portion  55  may process an image. A print portion may print the image to the media P by making the print CPU  90  and its peripheral construction as the subject.  
         [0038]     Referring now to  FIG. 4 , there is shown a block diagram of a control system of the fixing device  100 . The embodiment of the heating unit  110  as described in  FIG. 4  is a coil unit. In this embodiment, the heating unit  110  is disposed within the heating roller  101 . The heating unit  110  of this embodiment may have a plurality of heating elements  111 . Each heating element  111  of this embodiment is an inductive coil. It is not required that heating elements  111  be inductive coils. Alternate embodiments may comprise heat generating resistors, enclosures for chemical reactions, heat exchangers, infrared lights, visual lights, and ultraviolet lights.  
         [0039]     The heating element  111  of this embodiment may comprise three coils,  111   a ,  111   b , and  111   c . The coil  111   a  may be disposed in the central part of the heating roller  101 , and coils  111   b  and  111   c  may be disposed at opposite sides of the coil  111   a  in the heating roller  101 , respectively. The coils  111   a ,  111   b , and  111   c  may be electrically connected to a high frequency generating circuit  120 .  
         [0040]     A temperature sensor  112  may be disposed in a central part of the heating roller  101 . It is not required that the temperature sensor  112  be disposed in the central part of the heating roller  101 . The temperature sensor  112  may be disposed close to the central part of the heating roller  101 . Alternatively, if the temperature sensor  112  is an infrared type temperature sensor, the temperature sensor  112  may be positioned relative to the heating roller  101  such that the temperature sensor  112  has an unobstructed view of the heating roller  101 . The temperature sensor  112  may detect the temperature of the central part of the heating roller  101 . The temperature sensor  112  may detect the temperature of coil  111   a . Alternatively, the temperature sensor  112  may detect the temperature of the heating roller  101  near the coil  111   a.    
         [0041]     The method of determining the temperature of the heating roller  101  near the coil  11   a  is not important. An alternative embodiment may include the temperature of the central part of the heating roller  101  being determined indirectly. For example, the temperature sensor  112  may be disposed exterior to the heating roller  101  and may sense the temperature of the central part of the pressurizing roller  102  (i.e. near the coil  111   a ) at or near the nip width. Alternatively, the temperature sensor  112  may be disposed within the pressure roller and may sense the temperature of the central part of the pressurizing roller  102  at or near the nip width. Since heat may be transferred via conductive heat transfer and/or convective heat transfer from the heating roller  101  to the pressurizing roller  102  at or near the nip width, the temperature of the central part of the pressurizing roller  102  at or near the nip width may have a direct correlation to the temperature of the central part of the heating roller  101 . Therefore, the temperature of the central part of the heating roller  101  may be obtained indirectly by performing a heat transfer function on the datum of the temperature of the central part of the pressurizing roller  102  at or near the nip width.  
         [0042]     A temperature sensor  113  may be disposed in an end of the heating roller  101 . It is not required that the temperature sensor  113  be disposed in an end of the heating roller  101 . The temperature sensor  113  may be disposed close to an end of the heating roller  101 . Alternatively, if the temperature sensor  113  is an infrared type temperature sensor, the temperature sensor  113  may be positioned relative to the heating roller  101  such that the temperature sensor  113  has an unobstructed view of the heating roller  101 . The temperature sensor  113  may detect the temperature of the end portion of the heating roller  101 . The temperature sensor  113  may detect the temperature of the coil  111   c . Alternatively, the temperature sensor  113  may detect the temperature of the heating roller  101  near the coil  111   c . The temperature sensors  112  and  113  may be electrically connected to the print CPU  90 , together with a drive unit  160 . The drive unit  160  may be used to rotate the heating roller  101 .  
         [0043]     The method of determining the temperature of the heating roller  101  near the cloil  111   c  is not important. An alternative embodiment may include the temperature of an end portion of the heating roller  101  being determined indirectly. For example, the temperature sensor  113  may be disposed exterior to the heating roller and may sense the temperature of the end part of the pressurizing roller  102  (i.e. near the coil  111   c ) at or near the nip width. Alternatively, the temperature sensor  113  may be disposed within the pressure roller and may sense the temperature of the end part of the pressurizing roller  102  at or near the nip width. Since heat may be transferred via conductive heat transfer and/or convective heat transfer from the heating roller  101  to the pressurizing roller  102  at or near the nip width, the temperature of the end part of the pressurizing roller  102  at or near the nip width may have a direct correlation to the temperature of the end part of the heating roller  101 . Therefore, the temperature of the end part of the heating roller  101  may be obtained indirectly by performing a heat transfer function on the datum of the temperature of the end part of the pressurizing roller  102  at or near the nip width.  
         [0044]     The print CPU  90  may control the drive unit  160 . The print CPU  90  may also control at least one of power to, current through, frequency to, resonance of, inductance of, voltage across, and temperature at a first heating element  111  and a second heating element  111 . If the heating elements  111  provide heat via inductive resonance, the print CPU  90  may generate a P 1 /P 2  switch signal for specifying the operations of a first resonance circuit and a second resonance circuit. The first resonance circuit may comprise a switching circuit  122 , a power supply  130  and the coil  111   a . The second resonance circuit may comprise the switching circuit  122 , the power supply  130 , and the coil  111   c . The second resonance circuit may also comprise the coil  111   b . The print CPU  90  may control the fuser according to the output power of each resonance circuit and the temperature detected by the temperature sensors  112  and  113 .  
         [0045]     The high frequency generating circuit  120  may generate a high frequency electric power for generating a high frequency magnetic field. The high frequency generating circuit  120  may comprise the switching circuit  122  connected to a rectification circuit  121 . The rectification circuit  121  may rectify AC voltage of the commercial AC power supply  130 .  
         [0046]     The first resonance circuit and second resonance circuit may be excited selectively by a switching element (not shown), such as at least one transistor or FET, disposed inside the switching circuit  122 . The first resonance circuit may have a resonance frequency f 1  based on the inductance of the coil  111   a , and electrostatic capacity of a capacitor in the switching circuit  122  (not illustrated). The second resonance circuit may have a resonance frequency f 2  based on the inductance of the coils  111   b  and  111   c , and electrostatic capacity of the capacitor in the switching circuit  122  (not illustrated).  
         [0047]     The controller  140  may control the on/off drive of the switching circuit  122  based on a P 1 /P 2  switching signal provided by the print CPU  90 . The controller  140  may include an oscillation circuit  141  and a CPU  142 . The oscillation circuit  141  may generate a drive signal of a predetermined frequency to the switching circuit  122 . The CPU  142  may control an oscillation frequency, and a drive signal frequency of the oscillation circuit  141 .  
         [0048]     Referring now to  FIG. 5 ( a ), there is shown an embodiment of the heating unit  110  comprising the heating elements  111   a ,  111   b , and  111   c . The heating elements  111   a ,  111   b , and  111   c  may comprise electric wire of a predetermined cross-section area that are coiled around the heating element supports  110 Aa,  110 Ab, and  110 Ac, respectively. The heating element support  110 Aa may be longitudinally longer than either heating element support  110 Ab or  110 Ac. The numbers of coil turns of the heating element  111   a  may be greater than the heating elements  111   b  or  111   c.    
         [0049]     Referring now to  FIG. 5 ( b ), there is shown a circuit diagram of the heating element of  FIG. 5 ( a ). A first edge P 2  of the heating element  111   a , a first edge P 3  of the heating element  111   
         [0050]     b and a first edge P 6  of the heating element  111   c  may be connected to a junction C 11 . A second edge P 4  of the heating element  111   a  may be connected to a terminal P 11 . A second edge P 1  of the heating element  111   b  and a second edge P 5  of the heating element  111   c  may be connected to a junction P 12 .  
         [0051]     The junction C 11  may comprise a low voltage common node of an output power P 1  and an output power P 2 . A high voltage node of the output power P 1  and the output power P 2  may be supplied to the terminals P 11  and P 12 , respectively.  
         [0052]     Referring now to  FIG. 6 ( a ), there is shown an embodiment of the heating unit  110  with a plurality of inductive heating elements. A coil unit  210  comprises a plurality of coils arranged in the longitudinal direction. The coil unit  210  may include twelve elements, a coil  221 -a coil  232 , to which a predetermined electric wire may be coiled around a coil bobbin  221 CB-a coil bobbin  232 CB, respectively. The quantity of elements is not important. For example, an embodiment may include three, five, twenty-seven or more element. The set of coils  221 - 232  may be held in a predetermined arrangement by a holding member  110 B, and may be divided into predetermined coil groups.  
         [0053]     Referring now to  FIG. 6 ( b ), there is shown a circuit diagram of the heating unit  110  of  FIG. 6 ( a ). The set of coils  221 - 232  may be divided into four coil groups of three coils connected in parallel. One example of the grouping may be a coil group P comprising the coils  221 - 223 , a coil group Q comprising the coils  224 - 226 , a coil group R comprising the coils  227 - 229 , and a coil group S comprising the coils  230 - 232 . The coil group P may comprise an end P 21  and an end P 22 , the coil group Q may comprise an end P 23  and an end P 24 , the coil group R may comprise an end P 25  and an end P 26 , and the coil group S may comprise an end P 27  and an end P 28  respectively.  
         [0054]     Referring now to  FIG. 6 ( c ), there is shown a circuit diagram of the heating unit of  FIG. 6 ( a ). The coil groups Q and R may be electrically connected as the first coil group, and the coil groups P and S may be electrically connected as the second coil group. An electric power of the same magnitude or a different magnitude may be supplied to the first and second coil groups. The electric power supplied to the first and second coil groups may receive the same low voltage common at a junction C 31 .  
         [0055]     Each end P 22 , P 23 , P 26 , and P 27  of the coil groups P, Q, R, and S, respectively, may be connected to the junction C 31 . The ends P 24  and P 25  of the coil groups Q and R, respectively, which comprise the first coil group, may be connected to the junction C 31 . The electric power at the high voltage side, which is supplied to the first coil group, may be supplied to the junction C 31 . Similarly, the ends P 21  and P 28  of the coil groups P and S, respectively, which comprise the second coil group, may be connected to the junction P 32 . The electric power at the high voltage side, which may be supplied to the second coil group, may be supplied to the junction P 32 .  
         [0056]     Referring now to  FIG. 7 , there is shown a process of changing the electric power setting for the fuser based on the physical characteristics of the media, physical characteristics of the toner and environmental conditions. Various physical characteristics that may be utilized to determine the electric power fuser setting may include one or more of media weight, media thickness, media width, media length, media material composition, media moisture content, media hardness, media gloss, media temperature, chemical and physical characteristics of the toner, air temperature and relative humidity.  
         [0057]     At step S 10 , a media setting may be established via an operation panel. Alternatively, the media itself may have an embedded passive sensor that enables an image forming apparatus to retrieve and utilize the physical characteristics data of the media. Another embodiment may include a physical characteristic analyzer that is integral to the image forming apparatus. Such a physical characteristic analyzer may sense one or more of the media&#39;s weight, thickness, width, length, chemical composition, moisture content, hardness, gloss and temperature.  
         [0058]     At step S 20 , a start copy process may be initiated. The start copy process may be initiated by a user input on the operation panel. Alternatively, the copy process may be initiated by a signal over a computer network. Another embodiment may include an automated sensor that detects when a media is inputted to the image forming apparatus.  
         [0059]     If the media setting of step S 10  is a standard media, at step  30 , a fuser power setup may be increased from 700 W to 1000 W. The choice of 700 W and 1000 W are used for example purposes only. The definition of regular media may change over time and therefore a regular media may require an increase from 600 W to 850 W. Alternatively, the increase for a regular media may be from 400 W to 1300 W.  
         [0060]     If the toner can be easily fixed on a set-up media, at step S 40  the power may be increased from 700 W to 800 W and at step S 50  a fixing temperature may be decreased from 200 degrees C. to 190 degrees C. Easily fixed may be defined as requiring only a short amount of time and a reduced amount of energy to fix toner on a set-up media. The actual magnitude of the power is not important. For example, the increase may be from 450 W to 455 W at step S 40  and the fixing temperature may be decreased from 180 degrees C. to 178 degrees C. The actual magnitude of the power control and temperature control may depend on the chemical composition and physical characteristics of the toner, the chemical composition and physical characteristics of the media, and environmental conditions such as the composition of the fluid which the media and toner are surrounded by such as fluid temperature and moisture content.  
         [0061]     If the toner cannot be easily fixed on the set-up media, at step S 60  the power may be increased from 700 W to 1200 W and at step S 70  the fixing temperature may be increased from 200 degrees C. to 210 degrees C. A toner not easily fixed on the set-up media may be where more than a reduced amount of energy is required to fix toner on a set-up media. The actual magnitude of the power control is not important. For example, the power may be increased from 600 W to 1150 W at step S 70  and the fixing temperature may be increased from 185 degrees C. to 189 degrees C. The actual magnitude of the power control and temperature control may depend on the chemical composition and physical characteristics of the toner, the media and the environment.  
         [0062]     At step S 80  a copy is performed according to the setup. The setup may be based on the chemical composition and physical characteristics of the toner, the chemical composition and physical characteristics of the media, and environmental conditions such as air temperature and relative humidity. After the main CPU checks that the copy has been completed, the print CPU may change the electric power to READY, and the fixing device may be in standby. Alternatively, the copy controls may be integrated and performed by a single master CPU. Moreover, the copy controls may be distributed and performed over a shared network of processors, located locally and/or remotely.  
         [0063]     Referring now to  FIG. 8 , there is shown a process of controlling the fixing electric power based on monitoring the fixing temperature. It is not required that control of the fixing electric power be based on the fixing temperature. Alternatively, the control process of fixing electric power may include monitoring the toner temperature at the nip width. An alternative process of monitoring the fixing temperature may include utilizing a sensor which monitors thermal expansion of the heating unit  110 . A person skilled in the art would know of methods to utilize the physical expansion of the heating unit  110  and the coefficient of thermal expansion of the material of the heating unit  110  to calculate the temperature of the heating unit  110 . Alternatively, a sensor may monitor the thermal expansion of the heating roller  101  or the pressurizing roller  102 . A sensor to monitor the thermal expansion may be laser based, infrared based or ultraviolet based. Alternatively, linear transducers may be utilized to monitor thermal expansion.  
         [0064]     Another embodiment to indirectly calculate the temperature of the heating unit  110  may include submerging at least one of the heating unit  110 , the heating roller  101 , and the pressurizing unit  102  in a fluid which resides in a non-sealed vessel. The fluid utilized may be water, glycol, air, nitrogen, or any other suitable fluid. The choice of fluid is not important. The choice of fluid may be based on the fluid&#39;s physical properties such as coefficient of thermal expansion, density and conductivity. As the temperature of the heating unit  110 , heating roller  101  or pressurizing unit changes, the volume of the heating unit  110 , heating roller  101  or pressurizing unit will proportionally change resulting in the fluid level rising or dropping. A person skilled in the art would be able to calculate the temperature based on the change in volume.  
         [0065]     Alternatively, the fluid may reside in a sealed vessel. As the temperature of the heating unit  110 , heating roller  101 , or pressurizing unit  102  changes, a proportional change in pressure of the fluid may result. One skilled in the art would be able to correlate the pressure in the fluid to the temperature of the heating unit  110 , heating roller  101  or pressurizing unit  102 .  
         [0066]     If a copy is commenced, the fixing device may start operation at a set-up fixing power of 1000 W (Step S 200 ). The set-up fixing power is not important. Alternate set-up fixing powers may include 800 W, 850 W, 100 W, or 900 W. The choice of the set-up fixing power may depend on the physical characteristics of the media, the toner, and the environmental conditions.  
         [0067]     A controller may monitor the fixing temperature (Step S 210 ). The controller may monitor the fixing temperature directly via sensors or indirectly. If the fixing temperature decreases while being monitored, the controller may cause a fuser electric power to be increased by 50 W so that the decrease of the fixing temperature stops (Step S 220 ). The magnitude of the power increase is not limited to 50 W. Depending on the characteristics of the system, the fuser electric power may be increased by 0.5 W, 5 W, or 35 W.  
         [0068]     If the temperature of the fuser continues to fall, the controller may cause the fuser electric power to be increased by an additional 50 W (Step S 230 ). The magnitude of the power increase is not limited to 50 W. Depending on the characteristics of the system, the fuser electric power may be increased by 0.5 W, 5 W, or 35 W.  
         [0069]     If the fixing temperature is stable at Step S 210 , the controller may cause the fuser power setup to be reduced by 50 W (Step S 240 ). The magnitude of the power decrease is not limited to 50 W. Depending on the characteristics of the system, the fuser electric power may be decreased by 0.5 W, 5 W, or 35 W.  
         [0070]     If the fuser temperature remains stable at Step  250 , the controller may cause the fuser power setup to be decreased by an additional 50 W. The magnitude of the power decrease is not limited to 50 W. Depending on the characteristics of the system, the fuser electric power may be decreased by 0.5 W, 5 W, or 35 W.  
         [0071]     If it is detected that the temperature of the fuser has decreased at Step S 250 , the controller may cause the power supplied to the fuser to be increased by 50 W. The magnitude of the power increase is not limited to 50 W. Depending on the characteristics of the system, the fuser electric power may be increased by 0.5 W, 5 W, or 35 W.  
         [0072]     If the copy finishes (Step S 270 ), the controller may cause a reduction in electric power being provided to the fuser to 700 W at READY mode. The READY mode power is not important. Alternate READY mode powers may include 600 W, 650 W, 100 W, or 900 W. The choice of the READY mode power may depend on the physical characteristics of the media, the toner, and the environmental conditions.  
         [0073]     According to the fixing device by this invention, electric power of a fuser may be controlled based on first temperature sensor associated with the first heating element, a humidity sensor, a second temperature sensor associated with the second heating element, a media thickness sensor, a media moisture content sensor, a media temperature sensor, and a developer temperature sensor.  
         [0074]     Since setup of the fixing temperature may be changed while the power consumption is modified, fixing may be performed with appropriate conditions, which suits each type.  
         [0075]     Although exemplary embodiments of the present invention have been shown and described, it will be apparent to those having ordinary skill in the art that a number of changes, modifications, or alterations to the invention as described herein may be made, none of which depart from the spirit of the present invention. All such changes, modifications and alterations should therefore be seen as within the scope of the present invention.