Patent Publication Number: US-9897949-B2

Title: Image formation apparatus having lockable and unlockable cover

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority based on 35 USC § 119 from prior Japanese Patent Application No. 2015-256040 filed on Dec. 28, 2015, entitled “IMAGE FORMATION APPARATUS”, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This disclosure relates to an image formation apparatus that includes an image formation device which forms a developer image on a medium, and a fixation device which fixes the developer image to the medium by heating. 
     2. Description of Related Art 
     In general, an electrophotographic image formation apparatus is designed to use a fixation device to heat a developer image transferred to a medium and thus to fix the developer image to the medium. In this regard, there is proposed an image formation apparatus (see Japanese Patent Application Publication No. 2006-106668, for example), which uses a cooling fan to forcibly cool a medium after undergoing a fixation device in order to accelerate fixation of the developer image fused by the heating. 
     SUMMARY OF THE INVENTION 
     Meanwhile, if the medium has low heat resistance, the medium is at risk of being softened or fused by the heat from the fixation device in case the medium gets stuck (so-called a paper jam) in the fixation device during a printing operation. In this case, a possible consequence is that a user fails to adequately remove the stuck medium, and the stuck medium disrupts the subsequent use of the image formation apparatus. 
     An object of one aspect of the invention is to provide an image formation apparatus which enables a quick recovery in case of the occurrence of a stuck medium. 
     An aspect of the invention is an image formation apparatus includes: an image formation device which forms a developer image on a medium; a storage unit having medium information concerning the medium stored therein; a fixation device which fixes the developer image to the medium by heating the developer image while causing the medium to travel; a first detector which detects a stop or a speed reduction of travel of the medium in the fixation device; a second detector which detects a temperature of the fixation device; a cooler; and a controller which, when the first detector detects the stop or the speed reduction of the travel of the medium, stops an operation of the fixation device, and operates the cooler based on the medium information and the temperature of the fixation device, thereby cooling the medium stuck in the fixation device. 
     According to the aspect of the invention, it is possible to achieve a quick recovery even in case of the occurrence of a stuck medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an example of an overall configuration of an image formation apparatus according to embodiments of the invention. 
         FIG. 2  is a partially enlarged perspective view illustrating a partially enlarged fixation device in the image formation apparatus depicted in  FIG. 1 . 
         FIG. 3  is a block diagram illustrating an example of a control mechanism and the like of the image formation apparatus depicted in  FIG. 1 . 
         FIG. 4  is a flowchart illustrating an example of a control operation of the image formation apparatus depicted in  FIG. 1 . 
         FIG. 5A  is a flowchart illustrating a modified example of the control operation of the image formation apparatus depicted in  FIG. 1 . 
         FIG. 5B  is a flowchart illustrating the modified example of the control operation of the image formation apparatus depicted in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the invention are described below in detail with reference to the drawings. It is to be noted that the following description represents an example of the invention, and the invention is not limited only to this aspect. In addition, it is to be also understood that the invention is not limited only to layouts, dimensions, dimensional ratios, and the like of respective constituents as illustrated in the drawings. The description is given in the following order:
     1. Embodiments (an example of an image formation apparatus which determines a possibility of recovery processing by using medium information);   2. Modified Example (an example of an image formation apparatus designed to allow selection of natural cooling or forcible cooling);   3. Experimental Examples; and   4. Other Modified Examples.
 
&lt;1. Embodiments&gt;
 
[Configuration of Image Formation Apparatus]
   

       FIG. 1  schematically illustrates an overall configuration example of image formation apparatus  1  according to embodiments of the disclosure. Image formation apparatus  1  corresponds to a typical example of the “image formation apparatus” of the disclosure, which is a printer that forms an image (such as a color image) by applying an electrophotographic method on medium PM such as a paper sheet or a film. Examples of medium PM include a paper sheet with a relatively high heat resistance such as plain paper, and a film made of a resin such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). 
     As illustrated in  FIG. 1 , image formation apparatus  1  includes paper sheet cassette (paper feed tray)  2 , hopping roller (paper feed roller)  31 , registration sensor (paper sheet detection sensor)  37 , registration roller pair  18 , conveyance roller pair  19 , multiple (such as five) image formation devices  4  ( 4 K,  4 Y,  4 M,  4 C, and  4 W), fixation device  50 , and discharge rollers  36 , all of which are arranged along conveyance path  32 . Image formation apparatus  1  further includes intermediate transfer belt  11 , driving roller  12 , driven roller  13 , backup roller  14 , cleaning blade  15 , cleaner container  16 , density sensor  17 , primary transfer rollers  5  ( 5 K,  5 Y,  5 M,  5 C, and  5 W), secondary transfer roller  21 , LED head or exposure devices  6  ( 6 K,  6 Y,  6 M,  6 C, and  6 W), and cooler  7 . Discharge sensor  38  and conveyance separator  33  are provided on conveyance path  32 . Reconveyance rollers  35 A to  35 C are provided on reconveyance path  34  which branches off from conveyance path  32 . Here, these components are housed inside housing  10 . Opening  10 K is formed in housing  10  at a position corresponding to fixation device  50 . Housing  10  includes: cover  10 C openably and closably provided in such a way as to cover opening  10 K, and lock device  10 R which locks cover  10 C. Lock device  10 R includes a pin, a hole or slit which is formed at the image formation apparatus body and through which the pin is to be inserted, and an actuator, for example. The pin is provided slidably in a direction indicated by arrow Y 10 , for example. When the pin projects from an edge of opening  10 K of the image formation apparatus body by the actuator, cover  10 C is locked. When the pin returns to the edge of opening  10 K by the actuator, the lock on cover  10 C is released (unlocked). 
     Paper sheet cassette  2  is a component that contains media PM in a stacked state, which is detachably attached to a lower part of housing  10 . 
     Hopping roller  31  is a component (a sheet feeder mechanism) which picks up media PM contained in paper sheet cassette  2 , one by one separately from the top, and sends media PM to registration roller pair  18 . 
     Registration roller pair  18  is a component which sandwiches and conveys media PM sent from hopping roller  31  to intermediate transfer belt  11  while correcting a skew of each medium PM. 
     Registration sensor  37  is a sensor which detects the passage of each medium PM sent from hopping roller  31  in a contact or noncontact manner. When the passage of medium PM is detected, registration sensor  37  outputs an output signal to notify of the passage to external I/F  260  of controller control unit  200  (to be described later). 
     As illustrated in  FIG. 1 , image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W are arranged in this order along a direction of conveyance of (the conveyance path for) medium PM (from an upstream side to a downstream side). Note that each of image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W corresponds to an example of an “image formation device” of this disclosure. 
     Image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W form developer images (toner images) on medium PM by using toners (developers) of colors different from one another. 
     Specifically, image formation device  4 K forms a black toner image by using a black (K: blacK) toner. Image formation device  4 Y forms a yellow toner image by using a yellow (Y: Yellow) toner. Image formation device  4 M forms a magenta toner image by using a magenta (M: Magenta) toner. Image formation device  4 C forms a cyan toner image by using a cyan (C: Cyan) toner. Image formation device  4 W forms a white toner image by using a white (W: White) toner. 
     Each of the color toners contains a given colorant, a given release agent, a given charge control agent, a given treatment agent, and the like, and is manufactured by mixing these components as appropriate or subjecting the components to surface treatments. Among them, each of the colorant, the release agent, and the charge control agent functions as an internal additive. In contrast, for example, silica, titanium oxide, or the like is used as an external additive. Meanwhile, polyester resin is used as a binder resin, for example. In the meantime, it is possible to use one or a combination of dyes, pigments, and the like as the colorant. 
     Here, image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W have the same configuration except that the devices form the toner images by using the toners of colors different from one another as described above. Accordingly, a description is given below of image formation device  4 K as a representative of these devices. 
     As illustrated in  FIG. 1 , image formation device  4 K includes toner cartridge  41 , photoconductor drum  42 , charge roller  43 , development roller  44 , and supply roller  45 . 
     Toner cartridge  41  is a container which contains the toner of one of the above-mentioned colors. Specifically, in the example of image formation device  4 K, the black toner is contained in toner cartridge  41 . Likewise, the yellow toner is contained in toner cartridge  41  of image formation device  4 Y, the magenta toner is contained in toner cartridge  41  of image formation device  4 M, the cyan toner is contained in toner cartridge  41  of image formation device  4 C, and the white toner is contained in toner cartridge  41  of image formation device  4 W. 
     Photoconductor drum  42  is a component which carries an electrostatic latent image on its surface (a surface layer portion), and is formed by using a photoconductor (such as an organic photoconductor). Specifically, photoconductor drum  42  includes an electroconductive support and a photoconductive layer covering the outer periphery (a surface) of the electroconductive support. The electroconductive support is formed from a metal pipe made of aluminum, for example. The photoconductive layer has a structure formed by laminating a charge generation layer and a charge transport layer in this order. Photoconductor drum  42  is rotated at a predetermined circumferential speed. 
     Charge roller  43  is a component which charges the surface (the surface layer portion) of photoconductor drum  42 , and is disposed in contact with the surface (a peripheral surface) of photoconductor drum  42 . For example, charge roller  43  includes a metal shaft, and a semi-electroconductive rubber layer (such as a semi-electroconductive epichlorohydrin rubber layer) covering the outer periphery (a surface) of the metal shaft. Here, charge roller  43  described above is rotated in the opposite direction to the rotating direction of photoconductor drum  42 , for example. 
     Development roller  44  is a component which carries the toner on its surface for developing the electrostatic latent image, and is disposed in contact with the surface (the peripheral surface) of photoconductor drum  42 . For example, development roller  44  includes a metal shaft, and a semi-electroconductive urethane rubber layer covering the outer periphery (a surface) of the metal shaft. Here, development roller  44  described above is rotated in the opposite direction to the rotating direction of photoconductor drum  42  at a predetermined circumferential speed, for example. 
     Supply roller  45  is a component for supplying the toner contained in toner cartridge  41  to development roller  44 , and is disposed such that its surface comes into contact with a surface (a peripheral surface) of development roller  44 . For example, supply roller  45  includes a metal shaft, and a foamed silicone rubber layer covering the outer periphery (a surface) of the metal shaft. Here, supply roller  45  described above is rotated in the opposite direction to the rotating direction of development roller  44 , for example. 
     Primary transfer rollers  5 K,  5 Y,  5 M,  5 C, and  5 W are components for electrostatically transferring the toner images of the respective colors formed by image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W onto intermediate transfer belt  11 . Primary transfer rollers  5 K,  5 Y,  5 M,  5 C, and  5 W are disposed opposite to respective photoconductor drums  42  of image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W while interposing intermediate transfer belt  11  in-between. Here, each of primary transfer rollers  5 K,  5 Y,  5 M,  5 C, and  5 W is formed from a foamed semi-electroconductive elastic rubber material, for example. 
     Exposure devices  6 K,  6 Y,  6 M,  6 C, and  6 W are devices, such as LED heads, which irradiate the surfaces of photoconductor drums  42  with irradiation light to perform exposure, and thus form the electrostatic latent images on a surface (surface layer portions) of photoconductor drums  42 . Exposure devices  6 K,  6 Y,  6 M,  6 C, and  6 W are supported by housing  10 . Each of exposure devices  6 K,  6 Y,  6 M,  6 C, and  6 W includes, for example, light sources which emit the irradiation light, and a lens array which focuses the irradiation light on the surface of photoconductor drum  42 . Here, examples of the light sources include light emitting diodes (LEDs), laser elements, and the like. 
     Intermediate transfer belt  11  is a belt which secondarily transfers the toner images to medium PM that is conveyed by registration roller pair  18 , conveyance roller pair  19 , and the like. Intermediate transfer belt  11  is stretched by driving roller  12 , driven roller  13 , and backup roller  14 . Each of driving roller  12  and driven roller  13  is a component for moving intermediate transfer belt  11 . Backup roller  14  and secondary transfer roller  21  collectively constitute a secondary transfer device. Backup roller  14  is provided such that intermediate transfer belt  11  and medium PM are held between backup roller  14  and secondary transfer roller  21 . Cleaning blade  15  is a component which scrapes off the toners remaining on intermediate transfer belt  11 . Cleaner container  16  is a container for storing the toners scraped off with cleaning blade  15 . Density sensor  17  detects a density (a toner amount) of the toner image primarily transferred onto intermediate transfer belt  11 . 
     Fixation device  50  is a device for applying heat and pressure to and thereby fixing the toner images on medium PM, which are transferred from intermediate transfer belt  11 .  FIG. 2  is an enlarged perspective view illustrating a configuration of a substantial part of fixation device  50 . For example, fixation device  50  includes heating roller  51  and pressure roller  52  disposed opposite to each other while interposing conveyance path  32  to convey medium PM. Heating roller  51  includes annular fixation belt  511 , and heater  512  provided inside of heating roller  51  and which heats fixation belt  511 . Pressure roller  52  is pressed against heating roller  51  when fixation processing takes place, thus constituting a nipper. However, pressure roller  52  is made to be detachable from heating roller  51  during stand-by, at the time of removing medium PM when it is stuck in conveyance path  32  inside fixation device  50 , and so forth. Fixation device  50  further includes heating roller temperature sensor  55  to detect a temperature of heating roller  51 , and pressure roller temperature sensor  56  to detect a temperature of pressure roller  52 . Heating roller temperature sensor  55  and pressure roller temperature sensor  56  detect the temperature of heating roller  51  and the temperature of pressure roller  52  either successively or at predetermined time intervals, and send output signals notifying of the temperatures to external I/f  260  (to be described later) of controller control unit  200  (to be described later). Note that heating roller temperature sensor  55  in the embodiment corresponds an example of a “second detector” of this disclosure. Pressure roller temperature sensor  56  may be used as an example of a “second detector” of the disclosure. In fixation device  50 , temperature control of heating roller  51  is conducted by fixation temperature control section  340 . Note that fixation device  50  corresponds to an example of a “fixation device” of this disclosure. 
     Discharge sensor  38  is a sensor which detects the passage of medium PM conveyed from fixation device  50  in a contact or noncontact manner, and corresponds to an example of a “first detector” of the disclosure. When the passage of medium PM is detected, discharge sensor  38  sends an output signal to notify of the passage to external I/F  260  of controller control unit  200 . If no output signal from discharge sensor  38  is inputted to external I/F  260  even after a lapse of a predetermined time period since the detection of the passage of medium PM by registration sensor  37 , for example, then controller control unit  200  determines that medium PM is in a state (a so-called jammed state) of being stuck on conveyance path  32  or the like inside fixation device  50 . Discharge rollers  36  are guide members for discharging medium PM, to which the toner images are fixed by fixation device  50 , to the outside of image formation apparatus  1 . Medium PM discharged through discharge rollers  36  is stacked on stacker  10 Z on an upper part of housing  10 . 
     Cooler  7  includes blower fan  71  and exhaust fan  72 . Blower fan  71  and exhaust fan  72  are disposed opposite to each other in a width direction of medium PM (an X axis direction) orthogonal to a traveling direction of medium PM, while interposing fixation device  50  in-between. Blower fan  71  takes in the air outside housing  10  and sends the air in the X axis direction, for example, to medium PM held between heating roller  51  and pressure roller  52 , thereby cooling medium PM and others. Exhaust fan  72  has a function to discharge the air from blower fan  71  to the outside of housing  10 . Accordingly, as indicated by arrow F in  FIG. 2 , an air flow in the X axis direction is formed in the vicinity of fixation device  50  by blower fan  71  and exhaust fan  72  in cooperation. 
     [Configuration of Control Mechanism, Etc.] 
     Here, a control mechanism of image formation apparatus  1  is described with reference to  FIG. 3  as well as  FIG. 1 .  FIG. 3  is a block diagram which illustrates an example of the control mechanism of image formation apparatus  1  together with control objects. 
     As illustrated in  FIG. 3 , in this example, the control mechanism of image formation apparatus  1  includes controller control unit  200 , process control unit  300 , and display  400 . Display  400  displays internal information on image formation apparatus  1  and provides a user with the information visually. Display  400  corresponds to an example of an “output device” of this disclosure. 
     (Controller Control Unit  200 ) 
     Controller control unit  200  includes, for example, CPU (Central Processing Unit)  210 , ROM (Read Only Memory)  220 , RAM (Random Access Memory)  230 , timer  240 , host I/F  250 , and external I/F  260 . CPU  210 , ROM  220 , RAM  230 , timer  240 , host I/F  250 , and external I/F  260  are connected to one another through internal bus  270 . 
     CPU  210  communicates signals for controlling actions of RAM  230 , timer  240 , host I/F  250 , and external I/F  260  in accordance with a print processing program stored in ROM  220 . CPU  210  further communicates signals for controlling process control unit  300  through external I/F  260 . Note that CPU  210  corresponds to an example of a “controller” of this disclosure. 
     ROM  220  is a domain for storing the print processing program, and is a non-volatile memory which can save data even after image formation apparatus  1  is powered off. For example, ROM  220  stores in advance of a printing operation: information on media PM (brands, thicknesses, material types, heat resistance factors, and the like); information concerning printing conditions including a temperature condition and a nipping pressure of fixation device  50 , an operating speed, and the like. Note that ROM  220  as a memory corresponds to an example of a “storage unit” of this disclosure. 
     RAM  230  is a domain to store print data (print jobs, print commands, and so forth), which are supplied from a host device (an external device) such as a personal computer (PC) via a communication line. RAM  230  is a volatile memory storing the data which are to be erased when image formation apparatus  1  is powered off. Moreover, RAM  230  stores time information measured with timer  240  and used for various control timings. Timer  240  measures the time and outputs time data to CPU  210 . 
     Host I/F  250  transmits and receives various control signals, print data, and the like between external apparatus  100  and CPU  210 . Here, external apparatus  100  includes display  110  and input device  120 , for example. Display  110  is a display device which displays print images created by a variety of application software and instructions from host I/F  250 , and is formed from a liquid crystal display device and the like. Input device  120  is an input device used for creating print image data with the variety of application software, inputting medium information, and inputting response items to the instructions from host I/F  250 . For example, input device  120  is formed from a keyboard, a pointing device, and the like. 
     External I/F  260  receives inputs of density data outputted from density sensor  17 , output signals outputted from registration sensor  37  and discharge sensor  38 , temperature data outputted from heating roller temperature sensor  55  and pressure roller temperature sensor  56 , and the like. 
     (Process Control Unit  300 ) 
     Process control unit  300  includes, for example, high voltage control section  310 , exposure control section  320 , motor control section  330 , fixation temperature control section  340 , and cooling control section  350 , each of which is implemented by a circuit (s). 
     High voltage control section  310  includes image formation device control section  311  and transfer control section  315 . Image formation device control section  311  properly controls high voltages to be applied to components (charge rollers  43 , development rollers  44 , and supply rollers  45 ) in respective image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W in accordance with the control of controller control unit  200 . Transfer control section  315  properly controls voltages to be applied to primary transfer rollers  5 K,  5 Y,  5 M,  5 C, and  5 W and secondary transfer roller  21 , respectively, in accordance with the control of controller control unit  200 . 
     Exposure control section  320  controls exposure amounts and exposure timings concerning exposure devices  6 K,  6 Y,  6 M,  6 C, and  6 W. 
     Motor control section  330  controls actions of motors in image formation apparatus  1 . Specifically, motor control section  330  controls motors which drive: the components (photoconductor drums  42 , charge rollers  43 , development rollers  44 , and supply rollers  45 ) in respective image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W; hopping roller  31 ; registration roller pair  18 ; conveyance roller pair  19 ; lock device  10 R; and the like. 
     Fixation temperature control section  340  performs a temperature control of heating roller  51  by adjusting a voltage to be applied to heater  512  in heating roller  51  in response to output signals from heating roller temperature sensor  55  and pressure roller temperature sensor  56 . 
     Cooling control section  350  controls actions of blower fan  71  and exhaust fan  72  of cooler  7 . Note that cooling control section  350  corresponds to an example of the “controller” of this disclosure. 
     [Operation and Effect] 
     (A. Basic Actions of Image Formation Apparatus  1  as a Whole) 
     In image formation apparatus  1 , the toner images are formed on medium PM as described below. Specifically, as illustrated in  FIG. 3 , when a print job is supplied from external apparatus  100  or the like to controller control unit  200  via the communication line and the like, controller control unit  200  executes print processing based on the print job, so as to cause the components in image formation apparatus  1  to perform actions as described below. 
     Specifically, as illustrated in  FIG. 1 , hopping roller  31  first picks up media PM contained in paper sheet cassette  2  one by one separately from the top, and sends media PM to registration roller pair  18  on the downstream. Each medium. PM sent from hopping roller  31  is subjected to correction of its tilt by registration roller pair  18 , and is then conveyed by conveyance roller pair  19  to the secondary transfer device in which backup roller  14  and secondary transfer roller  21  are disposed opposite to each other while interposing intermediate transfer belt  11  in between. The toner images formed by image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W, respectively, are transferred sequentially onto the surface of the thus conveyed medium PM through intermediate transfer belt  11 . 
     The toner images of the respective colors are formed in image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W each in accordance with the following electrophotographic process. To be more precise, first of all, the surface (the surface layer portion) of each photoconductor drum  42  is uniformly charged by charge roller  43 , to which the voltage is applied from image formation device control section  311 . Subsequently, illumination light is emitted from each of exposure devices  6 K,  6 Y,  6 M,  6 C, and  6 W to the surface of photoconductor drum  42  to perform the exposure. Thus, the electrostatic latent images corresponding to print patterns defined by the above-mentioned print job, are formed on photoconductor drums  42 . 
     In the meantime, each supply roller  45  to which the voltage is applied from image formation device control section  311 , and each development roller  44  to which the voltage is applied from image formation device control section  311  likewise, come into contact with each other and are rotated at predetermined circumferential speeds, respectively. As a consequence of this action, the toner is supplied from supply roller  45  and is carried on the surface of development roller  44 . 
     Subsequently, the toner on development roller  44  is charged by means of friction and the like with a toner control member (not shown) which is in contact with development roller  44 . Here, the thickness of a layer of the toner on development roller  44  is determined depending on the voltage applied to development roller  44 , the voltage applied to supply roller  45 , a pressing pressure of the toner control member (a voltage applied to the above-mentioned toner control member), and the like. 
     Meanwhile, since each development roller  44  is in contact with photoconductor drum  42  corresponding thereto, the toner carried on development roller  44  adheres to the electrostatic latent image on photoconductor drum  42  as a consequence of the voltage application to development roller  44 . 
     Thereafter, the toner (the toner image) on each photoconductor drum  42  is primarily transferred to intermediate transfer belt  11  by means of an electric field between photoconductor drum  42  and a corresponding one of primary transfer rollers  5 K,  5 Y,  5 M,  5 C, and  5 W. 
     Furthermore, the toner images transferred to intermediate transfer belt  11  are secondarily transferred onto medium PM by the secondary transfer device. Here, in the course of the secondary transfer, the toners remaining on the surface of intermediate transfer belt  11  are scraped off and removed by cleaning blade  15 , and are stored in cleaner container  16 . 
     In this way, the toner images of the respective colors are formed by image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W, and are transferred onto medium PM sequentially along the direction of conveyance. To be more precise, as illustrated in  FIG. 1 , image formation devices  4 K,  4 Y,  4 M,  4 C, and  4 W form layers (image layers) of the toner images of the respective colors by using the toners of the corresponding colors (the black toner, the yellow toner, the magenta toner, the cyan toner, and the white toner). 
     Thereafter, fixation device  50  applies the heat and the pressure to the toner images on medium PM, thereby fixing the toner images to medium PM. Specifically, medium PM conveyed from the secondary transfer device to fixation device  50  is nipped by the nipper formed between fixation belt  511  and pressure roller  52 , for example, and receives the heat and the pressure at the same time. Thus, the above-described fixation processing is carried out. 
     Lastly, medium PM thus subjected to the fixation processing is discharged to the outside of image formation apparatus  1  by using discharge rollers  36 , and is stacked on stacker  10 Z. Hence, an image formation operation by image formation apparatus  1  is completed. 
     (B. Concerning Recovery Processing in Case of the Occurrence of a Stuck Medium) 
     Image formation apparatus  1  performs recovery processing in accordance with the following procedures when medium PM stops traveling inside the fixation device  50 , or in other words, when medium PM gets stuck (i.e., causes a paper jam) on conveyance path  32  or the like inside fixation device  50  instead of being discharged from image formation apparatus  1 . A method of the recovery processing by image formation apparatus  1  is described below with reference to  FIG. 4 .  FIG. 4  is a flowchart illustrating an example of a control operation of image formation apparatus  1 . Note that a series of processing surrounded with a dashed line in  FIG. 4  corresponds to the recovery processing. 
     First, prior to a printing operation, the information concerning medium PM (the brand, the thicknesses, the material type, the heat resistance factor, and the like) is inputted with input device  120  of external apparatus  100 , for example, and is sent to host I/F  250  (step S 101 ). The inputted medium information is registered with ROM  220 . Meanwhile, the information concerning the printing conditions including the temperature condition and the nipping pressure of fixation device  50 , the operating speed, and the like is stored in ROM  220 . 
     Next, the printing operation is executed (step S 102 ). Here, the print data is transmitted from input device  120  of external apparatus  100  to controller control unit  200 , and CPU  210  controls the actions of RAM  230 , timer  240 , host I/F  250 , and external I/F  260  in accordance with the print processing program stored in ROM  220 . Meanwhile, by way of external I/F  260 , CPU  210  causes process control unit  300  to execute the printing operation. 
     Next, controller control unit  200  determines the presence of the occurrence of a paper jam (the stop of travel of medium PM) inside fixation device  50  (step S 103 ). Here, if discharge sensor  38  fails to detect the passage of medium PM to be conveyed from fixation device  50  for a predetermined time period, i.e., when the paper jam inside fixation device  50  is detected (step S 103 Y), controller control unit  200  stops the operation of fixation device  50  and determines whether or not medium PM to be printed has a low heat resistance (step S 104 ). The determination in step S 104  is carried out on the basis of the information on medium PM registered with ROM  220  in advance. When controller control unit  200  determines in step S 104  that medium PM has a low heat resistance (step S 104 Y), controller control unit  200  causes display  400  to display a notification that it is not possible to conduct an immediate removal of medium PM (step S 105 ). In this case, motor control section  330  may be also used to lock cover  10 C by using Lock device  10 R so as to make cover  10 C unopenable. By locking cover  10 C as described above, it is possible to prevent a user from an erroneous operation to perform removal processing of medium PM at an inappropriate timing. In addition, controller control unit  200  causes cooling control section  350  to execute an operation of blower fan  71  and exhaust fan  72  of cooler  7  and to cool medium PM (step S 106 ). 
     Thereafter, controller control unit  200  determines whether or not the temperature of fixation device  50  falls to or below a reference temperature (step S 107 ). To be more precise, controller control unit  200 , for example, determines whether or not either one or both of the temperature of heating roller  51  detected by heating roller temperature sensor  55  and the temperature of pressure roller  52  detected by pressure roller temperature sensor  56  fall to or below a reference temperature depending on the type of medium PM. 
     When controller control unit  200  does not determine in step S 107  that the temperature of fixation device  50  falls to or below the reference temperature (step S 107 N), the cooling of medium PM is continued (step S 106 ). When controller control unit  200  determines in step S 107  that the temperature of fixation device  50  falls to or below the reference temperature (step S 107 Y), controller control unit  200  stops cooler  7  (step S 108 ). Here, if cover  10 C is locked by Lock device  10 R, controller control unit  200  causes motor control section  330  to release the lock by Lock device  10 R. Then, controller control unit  200  causes display  400  to display a notification that it is possible to conduct the immediate removal of medium PM (step S 109 ). 
     Thereafter, controller control unit  200  completes the recovery processing upon detection of the removal of stuck medium PM (step S 110 ). Here, the determination as to whether or not the stuck medium PM is removed is carried out, for example, by using a sensor to detect a fact that cover  10 C that is once opened is closed again. Furthermore, when controller control unit  200  determines that the entire printing task is completed (step S 111 Y), controller control unit  200  terminates (ends) the processing as it stands. 
     (C. Operation and Effect of Image Formation Apparatus  1 ) 
     As described above, in the embodiments, when discharge sensor  38  detects the stop of travel of medium PM, controller control unit  200  stops the operation of fixation device  50 , and operates the cooler  7  based on the medium information stored in ROM  220  and the temperature of fixation device  50 , thereby cooling medium PM stuck in fixation device  50 . For this reason, a situation is avoided in which medium PM is torn apart due to the heat from fixation device  50  and remains inside fixation device  50  when the user attempts to remove stuck medium PM. In this way, according to image formation apparatus  1 , the user can conduct the removal processing of medium PM in fixation device  50  at an appropriate timing. Hence, even in case of the occurrence of a stuck medium, it is possible to achieve a quick recovery. 
     &lt;2. Modified Example&gt; 
     Next, a modified example of the above-described embodiments is described. Note that constituents of this modified example which are substantially the same as those of the above-described embodiments are denoted by the same reference numerals and descriptions thereof are omitted as appropriate. 
     In the above-described embodiments, when controller control unit  200  determines that the paper jam occurs in fixation device  50 , controller control unit  200  forcibly cools medium PM by operating cooler  7  (see step S 106  in  FIG. 4 ). On the other hand, this modified example selectively performs the forcible cooling of medium PM in the recovery processing. Details are described below with reference to  FIGS. 5A and 5B .  FIGS. 5A and 5B  are flowcharts illustrating a control operation in the recovery processing of the modified example. 
     As illustrated in  FIG. 5A , in the modified example, mode selection information is inputted together with the input of the medium information prior to the execution of the printing operation (step S 201 ). Specifically, the information concerning medium PM is inputted with input device  120  of external apparatus  100 , for example, and is transmitted to host I/F  250 . In addition, the user selects whether to perform the recovery processing in a normal mode or to perform the recovery processing in a silent mode, and mode selection information on the selected mode is transmitted from input device  120  to host I/F  250 . The pieces of medium information and mode selection information thus inputted are registered with ROM  220 . 
     Thereafter, the printing operation is executed (step S 202 ). When controller control unit  200  determines that a paper jam occurs inside fixation device  50  (step S 203 Y), controller control unit  200  determines whether or not medium PM to be printed has a low heat resistance (step S 204 ). When controller control unit  200  determines in step S 204  that medium PM has a low heat resistance (step S 204 Y), controller control unit  200  causes display  400  to display a notification that it is not possible to conduct an immediate removal of medium PM (step S 205 ). Here, motor control section  330  may be also used to lock cover  10 C by using Lock device  10 R so as to make cover  10 C unopenable. 
     Subsequently, controller control unit  200  determines whether or not the recovery processing in the silent mode is selected, on the basis of the mode selection information registered with ROM  220  in advance (step S 206 ). When controller control unit  200  determines in step  206  that the silent mode is selected (step S 206 Y), controller control unit  200  subjects medium PM to natural cooling (step S 207 ) until controller control unit  200  determines that the temperature of fixation device  50  falls to or below the reference temperature. 
     On the other hand, when controller control unit  200  determines in step S 206  that the silent mode is not selected (step S 206 N), i.e., that the normal mode is selected, controller control unit  200  subjects medium PM to the forcible cooling. Specifically, as illustrated in  FIG. 5B , controller control unit  200  causes cooling control section  350  to execute the operation of blower fan  71  and exhaust fan  72  of cooler  7  and to cool medium PM (step S 211 ). Thereafter, controller control unit  200  determines whether or not the temperature of fixation device  50  falls to or below the reference temperature (step S 212 ). When controller control unit  200  determines in step S 212  that the temperature of fixation device  50  falls to or below the reference temperature (step S 212 Y), controller control unit  200  stops cooler  7  (step S 213 ). 
     When the temperature of fixation device  50  is determined to fall to or below the reference temperature (steps S 207 Y and S 212 Y), controller control unit  200  causes motor control section  330  to release the lock by Lock device  10 R if cover  10 C is locked by Lock device  10 R. Then, controller control unit  200  causes display  400  to display the notification that it is possible to conduct the immediate removal of medium PM (step S 208 ). 
     Lastly, controller control unit  200  completes the recovery processing upon detection of the removal of stuck medium PM (step S 209 ). Here, the determination as to whether or not the stuck medium PM is removed is carried out, for example, by using the sensor to detect the fact that cover  10 C that is once opened is closed again. Furthermore, when controller control unit  200  determines that the entire printing task is completed (step S 210 Y), controller control unit  200  terminates (ends) the processing as it stands. 
     As described above, in this modified example, the operation mode in the recovery processing is selected, and the determination as to whether to perform the forcible cooling or to perform the natural cooling is made on the basis of the selected mode. Thus, it is possible to eliminate any annoyance at night or under a quiet environment, for example, which may be caused by the operating noises of blower fan  71 , exhaust fan  72 , and the like. In the modified example, the mode selection information is inputted together with the input of the medium information, and these pieces of information are stored in ROM  220  prior to the execution of the printing operation. However, the invention is not limited only to this configuration. For example, the mode selection information may be inputted after the start of the printing operation, namely, during the printing operation, at a point of occurrence of a stuck medium (a paper jam) in fixation device  50  or the like device, or the like timing for example. 
     &lt;3. Experimental Examples&gt; 
     Experimental Example 1 
     Next, the recovery processing by image formation apparatus  1  described in the embodiments is conducted as Experimental Example 1. Then, the presence of residues of medium PM inside fixation device  50  is examined. A result is indicated in Table 1. In Table 1, the symbol o in the column titled residues represents that for example, medium PM is not torn so that torn medium PM does not remain inside fixation device. Meanwhile, the symbol x therein represents that for example, medium PM is torn so that torn medium PM remains inside fixation device  50 . 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Fixation 
                 Forc- 
                   
                 Heating 
                   
               
               
                   
                   
                 Temper- 
                 ible 
                 Waiting 
                 Roller 
               
               
                   
                   
                 ature 
                 Cool- 
                 Time 
                 Temperature 
                 Resi- 
               
               
                   
                 Medium 
                 [° C.] 
                 ing 
                 [sec.] 
                 [° C.] 
                 dues 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Experimental 
                 Low 
                 150 
                 YES 
                 120 
                 70 
                 ∘ 
               
               
                 Example 1 
                 Melting 
               
               
                   
                 Point 
               
               
                   
                 Medium 
               
               
                 Experimental 
                 Low 
                 150 
                 NO 
                 1200 
                 70 
                 ∘ 
               
               
                 Example 2 
                 Melting 
               
               
                   
                 Point 
               
               
                   
                 Medium 
               
               
                 Experimental 
                 Plain 
                 150 
                 NO 
                 10 
                 155 
                 ∘ 
               
               
                 Example 3 
                 Paper 
               
               
                 Experimental 
                 Low 
                 150 
                 NO 
                 10 
                 155 
                 x 
               
               
                 Example 4 
                 Melting 
               
               
                   
                 Point 
               
               
                   
                 Medium 
               
               
                   
               
            
           
         
       
     
     Here, a low melting point medium containing polyethylene as its main component and having a heatproof temperature of 90° C. is used as medium PM, and the forcible cooling is performed by cooler  7 . Moreover, fixation device  50  is subjected to the temperature control such that the temperature to be detected by the heating roller temperature sensor  55  becomes equal to 150° C. Here, medium PM is cooled continuously for 120 seconds, then cover  10 C is immediately opened and medium PM is subjected to the removal processing. In this case, for example, medium PM is not torn so that medium PM does not remain inside fixation device  50 . Here, the temperature of heating roller  51  at that point is equal to 70° C. 
     Experimental Example 2 
     Next, as Experimental Example 2, the recovery processing is conducted under the same conditions as those of Experimental Example 1 described above, except that the natural cooling is conducted for 1200 seconds without performing the forcible cooling by use of cooler  7 . Then, the presence of residues of medium PM inside fixation device  50  is examined. Table 1 also indicates a result of this example. Also in Experimental Example 2, for example, medium PM is not torn so that torn medium PM does not remain inside fixation device  50 . Here, the temperature of heating roller  51  at that point is equal to 70° C. as with Experimental Example 1. 
     Experimental Example 3 
     Next, as Experimental Example 3, the recovery processing is conducted under the same conditions as those of Experimental Example 1 described above, except that plain paper is used as medium PM and, the removal processing of medium PM is performed soon (about 10 seconds) after the occurrence of the paper jam without conducting the forcible cooling by use of cooler  7 . Then, the presence of residues of medium PM inside fixation device  50  is examined. Table 1 also indicates a result of this example. Also in Experimental Example 3, for example, medium PM is not torn so that torn medium PM does not remain inside fixation device  50 . Here, the temperature of heating roller  51  at that point is equal to 135° C. 
     Experimental Example 4 
     Next, as Experimental Example 4, the recovery processing is conducted under the same conditions as those of Experimental Example 1 described above, except that the removal processing of medium PM is performed soon (about 10 seconds) after the occurrence of the paper jam without conducting the forcible cooling by use of cooler  7 . Then, the presence of residues of medium PM inside fixation device  50  is examined. Table 1 also indicates a result of this example. In Experimental Example 4, medium PM gets torn inside fixation device  50 , and the residues of medium PM are present between heating roller  51  and pressure roller  52 . Here, the temperature of heating roller  51  at that point is equal to 135° C. 
     From the results of Experimental Examples 1 to 4 described above, it is successfully confirmed that the embodiments can suppress the occurrence of residues of medium PM inside fixation device  50 , by conducting the forcible cooling or providing an appropriate cooling time period depending on the heat resistance property (such as the melting point) of medium PM. 
     &lt;4. Other Modified Examples&gt; 
     The invention is described above with reference to the embodiments, the modified example, and the experimental examples. However, the invention is not limited thereto and various other modifications are possible. For instance, the above-described embodiments and others describe the image formation apparatus which forms color images. However, without limitation to the foregoing, the invention is also applicable to an image formation apparatus which forms black-and-while images by transferring only the black toner, for example. In addition, the above-described embodiments and others describe the image formation apparatus adapted to the secondary transfer method. However, the invention is also applicable to an image formation apparatus adapted to a direct transfer method. 
     In the meantime, the series of processing described in the embodiments and others may be carried out by means of hardware (circuits) or software (programs). If the processing is carried out by the software, then the software includes a group of programs for causing a computer to execute the respective functions. The programs may be used by being preinstalled on the computer, or by being installed on the computer from a network or a storage medium. 
     Meanwhile, in the above-described embodiments, display  400  is provided as an example of the output device, and the notification that it is possible to conduct the removal processing of medium PM is displayed on display  400  based on the control signal from external I/F  260 . However, the invention is not limited to this aspect. For instance, lamps of different colors may be turned on and off depending on the situations so as to allow the user to visually recognize whether or not the removal processing of medium PM is possible. Further, the invention is not limited to the above-mentioned visual communication method. For example, voice guidance, alarms, and the like may be used to allow the user to aurally recognize whether or not the removal processing of medium PM is possible. 
     Moreover, the invention is not limited to the configuration in which the temperature control of fixation device  50  is performed only on the basis of the detection signal from heating roller temperature sensor  55 , but may also be configured to perform such temperature control only on the basis of the detection signal from pressure roller temperature sensor  56 . Alternatively, the temperature control may be performed on the basis of these two types of detection signals. Furthermore, the temperature control may be performed while also taking into account temperature information from any other devices. 
     Meanwhile, the above-described embodiments are configured to input the medium information and the like from external apparatus  100  which is separate from image formation apparatus  1 . However, the invention is not limited to this configuration. For instance, display  400  may be formed from a touch panel so as to function as the input device for inputting the medium information and inputting the response items to the instructions from host I/F  250 . Alternatively, image formation apparatus  1  may be provided with an input device for allowing the user to input various kinds of information, as a constituent that is different from display  400 . 
     Furthermore, the embodiments describe the image formation apparatus provided with the print function as a typical example of the “image formation apparatus” of the disclosure. However, the invention is not limited to this aspect. Specifically, the invention is also applicable to an image formation apparatus that serves as a multifunction machine, which includes a scan function and a facsimile function in addition to the print function, for example. 
     Furthermore, in the above-described embodiments, process control unit including high voltage control section  310 , exposure control section  320 , motor control section  330 , fixation temperature control section  340 , and cooling control section  350  is implemented by circuits. However, each of these control section may be implemented by a hardware, a software, or a combination thereof. 
     Note that the image forming apparatus may stop the operation of fixation device  50  and operate cooler  7  when the speed reduction of the travel of the medium PM is detected by discharge sensor  38  but the complete stop of the travel of the medium PM is not detected. 
     The invention includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention.