Abstract:
A flash fixing apparatus effectively collect vapor gas produced at the time of fixation while fixing a toner image of medium by means off flashlight. In the flash fixation unit, vapor gas produced in flash fixation flows toward the medium transportation direction. Utilizing this phenomenon, a gas suction face is provided in a gas collector so as to receive the vapor gas flowing toward the medium transportation direction. Otherwise, a gas blast portion is provided at the rear stage of the gas collector. The vapor gas flows to the gas suction face naturally, bringing about improved gas collection efficiency.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a flash fixation apparatus for fixing toners on a medium by means of flash light and a printer using the same, and more particularly a flash fixation apparatus for collecting gas produced from the toners during flash fixation and a printer using the same.  
           [0003]    2. Description of the Related Art  
           [0004]    In a printer for forming toner images in which the electrophotographic scheme of the like is employed, an image is formed by means of a powder toner on a print medium. The toner image is then fixed by fusing the powder toner placed on the print medium. To fix the toner image, it is necessary to apply fixation energy onto the print medium.  
           [0005]    In a high-speed printer, a non-contact type fixation method is employed as a fixation method for applying the fixation energy. It is suitable to use the non-contact type fixation method in the high-speed printer because high fixation energy can be applied without influencing transportation of the print medium.  
           [0006]    As one method of this non-contact type fixation method, a flash fixation method employing flash light produced by a flash lamp. In the flash fixation method, light is emitted from the flash lamp at predetermined intervals corresponding to the transportation of the print medium to fix on each predetermined area of the print medium.  
           [0007]    [0007]FIG. 18 shows a configuration diagram of the conventional flash fixation unit. In a flash fixation unit  13 , a flash lamp  101  and a reflection plate  102  are accommodated in a lamp house  100 . The lamp house  100  on the paper  110  side is covered with a glass plate  103  to isolate the internal portion of the lamp house  100  from outside.  
           [0008]    A toner image  114  is formed on the paper  110  guided by a pair of carrying rollers  112  and  116 . The paper  110  is carried continuously while maintaining a position opposite to the glass plate  103  and is received the flashlight emitted from the flash lamp  101 . The toner  114  on the paper  110  is abruptly heated by the energy applied from the flashlight, producing gas (evaporated gas) C from the toner  114 .  
           [0009]    Gas C adheres onto the flash lamp  101 , the glass plate  103  for protecting the lamp  101 , the print paper  110 , the carrying roller  116  outside the fixation unit, etc. If the gas having adhered is not removed, the gas may cause a failure, such as a decreased fixation ratio, degraded print quality and malfunction of medium transportation.  
           [0010]    Conventionally, in order to circumvent this problem, there has been provided a suction mechanism (or degassing mechanism)  104  on the rear side of the flash fixation unit for collecting the gas (evaporated gas) C to suck and deodorize. This mechanism enables to prevent gas adhesion to the lamp house  100 , the paper  110  and the carrying roller  116 , by which smell diffusion can also be prevented.  
           [0011]    However, as print speed of a printer becomes higher in recent years, transportation speed of the paper  110  becomes higher and, at the same time, higher fixation speed is required. This has required an increased amount of gas generation produced from the toner  114  on the paper  110 , resulting in a tendency of gas leakage in the downstream side of the flash fixation unit, that is the transportation direction of the paper  110 , as shown by arrow B.  
           [0012]    To prevent the gas leakage in the conventional art, it is normally necessary to increase either suction power or suction area so that the produced gas can be sufficiently sucked by suction mechanism  104 , as shown in FIG. 19, and gas collection efficiency can be increased.  
           [0013]    However, when increasing the suction power, pressure to float up out of the transportation plane is produced on the paper  110 , caused by the gas (evaporated gas) suction with an increased wind velocity/pressure. This produces the paper under transportation to flutter easily.  
           [0014]    In the conventional configuration, the paper  110  is guided by the carrying rollers  112  and  116  disposed at the front and rear sides of the flash fixation unit, which produces a reduced tension of the paper  110  between the carrying rollers  112  and  116 . Therefore, when increased suction power is applied, the paper is apt to float up to a large extent, resulting in an unfixed image on the paper  110  possibly contacting to the upper surface of the transportation path (glass plate  103 ). This produces the fixed image on the paper  110  to adhere to a suction duct of the suction mechanism  104 , causing a trouble in the print result such as dimmed print.  
           [0015]    Furthermore, in order to increase the suction power, a large-scale suction blower (having large suction capability) is required. This brings about not only a larger blower in size but also increase of noise and cost. Another method for preventing the paper from fluttering during transportation is to suck the gas from the opposite side of the suction mechanism  104  across the paper  110 . However, it is difficult to conduct air balancing, which makes it difficult to prevent from contacting to the paper  110 . Moreover, the suction from the opposite side requires more suction capability than inherently required for the gas collection in the suction blower. This results in requiring a larger suction blower in size.  
           [0016]    In a yet another method, it may be possible to increase the suction area while maintaining necessary suction time within a limit. This method also brings about larger suction mechanism  104  as well as larger suction blower, resulting in the unit substantially larger in size with increased noise and cost.  
         SUMMARY OF THE INVENTION  
         [0017]    Accordingly, it is an object of the present invention to provide a flash fixation apparatus for improving efficiency in collecting gas (evaporated gas) produced from toner at the time of flash fixation while preventing a medium trouble in printing and a printer using the flash fixation apparatus.  
           [0018]    It is another object of the present invention to provide a flash fixation apparatus for improving efficiency in collecting gas produced from toner at the time of flash fixation without applying large suction power in high-speed printing, and a printer using the flash fixation apparatus.  
           [0019]    It is still another object of the present invention to provide a flash fixation apparatus for improving gas collection efficiency of the gas produced from toner at the time of flash fixation without need of a large unit in size even for high-speed printing, and a printer using the flash fixation apparatus.  
           [0020]    Further, it is still another object of the present invention to provide a flash fixation apparatus for improving gas collection efficiency of the gas produced from toner during flash fixation while preventing a print medium under transportation from flattering, and a printer using the flash fixation apparatus.  
           [0021]    To attain the above-mentioned objects, according to the present invention, a flash fixation apparatus for fixing a toner image on a medium under transportation by means of flash light includes; a flash fixation unit for emitting the flash light; a gas collector being disposed at the downstream side toward the medium transportation direction of the flash fixation unit for collecting vapor gas produced in flash fixation; and a guide being disposed between the flash fixation unit and the gas collector for altering the medium transportation direction. The aforementioned gas collector has a gas suction face disposed along the altered transportation direction.  
           [0022]    Further, according to the present invention, a printer for forming a toner image onto a medium being transported at a predetermined transportation velocity includes; an image forming unit for forming a toner image onto the medium; and a flash fixation unit for fixing the toner image generated on the medium by means of flashlight. The flash fixation unit further includes, a flash fixation device for emitting the flash light;a gas collector being disposed at the downstream side toward the medium transportation direction of the flash fixation device for collecting vapor gas produced in flash fixation; and a guide being disposed between the flash fixation device and the gas collector for altering the medium transportation direction. Here, the gas collector has a gas suction face disposed along the altered transportation direction.  
           [0023]    In the flash fixation apparatus of the present invention, vapor gas produced in flash fixation flows toward the medium transportation direction. Considering this, a guide for altering the medium transportation direction is provided at the entry of the gas collector. Further a gas suction face is provided so as to receive the vapor gas which flows along the altered medium transportation direction. Thus, the vapor gas flows into the gas suction face naturally, bringing about improved gas collection efficiency.  
           [0024]    As a result, higher printing speed can be attained. In addition, it becomes possible, to collect vapor gas without increasing either suction power or suction area of the gas collector even when the vapor gas amount is increased, as well as to avoid medium flattering which may possibly occur at the time of medium transportation. Thus a miniaturized and low-cost flash fixation unit can be obtained.  
           [0025]    According to the present invention, preferably the aforementioned gas suction face is directed to the vapor gas flow direction.  
           [0026]    Further, according to the present invention, preferably a second guide for guiding the medium is provided on the exit (downstream) side of the gas collector. This enables to sustain medium tension at the gas collector so that medium flattering can be avoided even when high-speed printing is carried out, as well as enabling low-tension medium for use.  
           [0027]    Still further, according to the present invention, preferably an angle of the gas suction face is maintained no more than 90 degrees against the medium transportation direction. This enables to guide the vapor gas flow effectively toward the gas suction face.  
           [0028]    Further, the flash fixation apparatus in accordance with the present invention includes; a flash fixation unit for emitting the flash light; a gas suction unit being disposed at the downstream side toward the medium transportation direction of the flash fixation unit for sucking vapor gas produced in flash fixation; and a gas blast mechanism for blasting gas to the medium being disposed at the downstream side of the gas suction unit.  
           [0029]    According to the present invention, the printer for forming a toner image onto a medium being transported at a predetermined transportation velocity includes an image forming unit for forming a toner image onto the medium; and a flash fixation unit for fixing the toner image generated on the medium by means of flashlight. The flash fixation unit further includes; a flash fixation device for emitting the flash light; a gas suction unit being disposed at the downstream side toward the medium transportation direction of the flash fixation device for sucking vapor gas produced in flash fixation; and a gas blast mechanism for blasting gas to the medium being disposed at the downstream side of the gas suction portion.  
           [0030]    In this embodiment of the present invention, there are provided a gas collector for collecting vapor gas which flows in this transportation direction and a gas blast portion at the rear stage of the gas collector in the flash fixing device, considering that vapor gas produced in flash fixation flows toward the medium transportation direction. This constitutes an air curtain at the exit (downstream side) of the gas collector, preventing the vapor gas from leaking out of the gas collector and thus improving gas collection efficiency.  
           [0031]    As a result, higher medium printing speed can be attained. In addition, it becomes possible to collect vapor gas without increasing either suction power or suction area of the gas collector even when the vapor gas amount is increased, as well as to prevent the medium under transportation from flattering. Thus a miniaturized and low-cost flash fixation unit can be obtained.  
           [0032]    Also, according to the present invention, preferably the capacity of the gas blast mechanism is set larger than the capacity of the gas suction portion, which improves gas collection efficiency.  
           [0033]    Further, according to the present invention, preferably a level difference is provided between the outlet of the blast mechanism and the intake of the gas suction portion, which improves gas collection efficiency.  
           [0034]    Still further, according to the present invention, preferably there is further provided a circulation mechanism for filtering the suction gas being sucked in the gas suction portion to circulate to the blast mechanism. This reduces an exhaust gas to be output externally, which contributes to maintain the environment as well as obtains improved gas collection efficiency.  
           [0035]    Further scopes and features of the present invention will become more apparent by the following description of the embodiments with the accompanied drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]    [0036]FIG. 1 shows a configuration diagram of a printer according to one embodiment of the present invention.  
         [0037]    [0037]FIG. 2 shows a cross-sectional view of a flash fixation unit according to a first embodiment shown in FIG. 1.  
         [0038]    [0038]FIG. 3 shows a perspective view of the flash fixation unit shown in FIG. 2.  
         [0039]    [0039]FIG. 4 shows a perspective view of the main portion of the flash fixation unit shown in FIG. 2.  
         [0040]    [0040]FIG. 5 shows a cross-sectional view of a second embodiment of the flash fixation unit according to the present invention.  
         [0041]    [0041]FIG. 6 shows an operation explanation diagram of the configuration shown in FIG. 5.  
         [0042]    [0042]FIG. 7 shows a cross-sectional view of a third embodiment of the flash fixation unit according to the present invention.  
         [0043]    [0043]FIG. 8 shows an operation diagram of the configuration shown in FIG. 7.  
         [0044]    [0044]FIG. 9 shows a cross-sectional view of a fourth embodiment of the flash fixation unit according to the present invention.  
         [0045]    [0045]FIG. 10 shows a cross-sectional view of a fifth embodiment of the flash fixation unit according to the present invention.  
         [0046]    [0046]FIG. 11 shows an operation diagram of the configuration shown in FIG. 10.  
         [0047]    [0047]FIG. 12 shows an explanation diagram illustrating a first simulation result of evaporated gas flow produced by a blast mechanism according to the present invention.  
         [0048]    [0048]FIG. 13 shows an explanation diagram illustrating a second simulation result of evaporated gas flow produced by a blast mechanism according to the present invention.  
         [0049]    [0049]FIG. 14 shows an explanation diagram illustrating a third simulation result of evaporated gas flow produced by a blast mechanism according to the present invention.  
         [0050]    [0050]FIG. 15 shows an explanation diagram illustrating a fourth simulation result of evaporated gas flow produced by a blast mechanism according to the present invention.  
         [0051]    [0051]FIG. 16 shows an explanation diagram illustrating a fifth simulation result of evaporated gas flow produced by a blast mechanism according to the present invention.  
         [0052]    [0052]FIG. 17 shows a cross-sectional view of a sixth embodiment of the flash fixation unit according to the present invention.  
         [0053]    [0053]FIG. 18 shows an explanation diagram of a conventional art.  
         [0054]    [0054]FIG. 19 shows an explanation diagram of air collection operation according to the conventional art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0055]    The preferred embodiment of the present invention is described hereinafter in order of a printer, a flash fixation unit, another flash fixation unit, and the other embodiments referring to the charts and drawings, wherein like numerals or symbols refer to like parts.  
         [0056]    [Printer] 
         [0057]    [0057]FIG. 1 shows a configuration diagram of one embodiment of a printer according to the present invention. In this figure, there is shown the configuration of an electrophotographic printer  1  which handles continuous paper as a printer concerning one embodiment of the present invention.  
         [0058]    Continuous paper  2  loaded on a paper hopper  11  has tractor holes and is continuously carried by a tractor feed system. The continuous paper  2  is then accommodated into a stacker  12  via an image transfer unit  7  and a flash fixation unit  13 . A photosensitive drum  4  rotating clockwise is uniformly charged by a charging unit  3 . Thereafter an image is exposed by an optical system  5 . Thus an electrostatic latent image is produced on the photosensitive drum  4  corresponding to the image. This electrostatic latent image produced on the photosensitive drum  4  is developed by a development unit  6 . Thereafter a toner image on the photosensitive drum  4  is transferred onto the continuous paper  2  by image transfer unit  7 .  
         [0059]    After this image transfer, electric charges on the photosensitive drum  4  are eliminated by a charge eliminator  9 . The residual toner is cleaned up by a cleaning blade  8  and a cleaning brush  10 . The continuous paper  2  on which the toner image is transferred is flash-fixed by flash fixation unit  13  and then is accommodated into the stacker  12 . A non-illustrated flash control unit controls light emission (emission frequency) of a flash lamp provided in the flash fixation unit  13  according to transportation velocity of the continuous paper  2 .  
         [0060]    Namely, first a toner image is formed on the photosensitive drum  4 . The toner image is transferred to the continuous paper  2  to produce the toner image onto the continuous paper  2 . The flash fixation unit  13  irradiates a flashlight onto the continuous paper  2 . The toner of toner image produced on the continuous paper  2  is abruptly heated by flash light energy to fuse the toner to fix. The toner is formed of organic compound such as polyester. Through this abrupt heating, a sublimate (organic gas) is produced from the toner.  
         [0061]    The flash fixation unit  13  is suitable for high-speed printing because of the non-contact toner fixation which enables to avoid additional load for carrying paper, resulting in easy implementation of high-speed paper transportation.  
         [0062]    [Flash Fixation Unit] 
         [0063]    [0063]FIG. 2 shows a cross-sectional view of a first embodiment of flash fixation unit  13  according to the present invention. FIG. 3 shows a perspective view thereof. Also, FIG. 4 shows a perspective view of the main portion of flash fixation unit  3 .  
         [0064]    As shown in FIGS. 2 and 3, the flash fixation unit  13  includes a flash lamp  22  and a reflection plate  24  inside a lamp house  20 . The paper  2  side of the lamp house  20  is covered with a glass plate  26  to isolate the inside of the lamp house  20  from outside. Here, four flash lamps  22  and two reflection plates  24  are employed so as to widen the irradiation area produced by flash light at one time, as well as to produce a unified light energy distribution throughout the irradiation area. However, either the number of flash lamps or the number of reflection plates is not limited to the above description. An arbitrary number can be adopted as required.  
         [0065]    As the flash lamp  22 , there is employed flash lamp of a cylinder-shaped ozoneless silica glass having a predetermined arc length and sealed Xe gas. Also, the glass plate (light transparent plate)  26  is provided between the flash lamp  22  and the continuous paper  2  formed of glass. For this glass plate  26 , preferably a silica glass contained water produced by the VAD method is used. This silica glass contained water produced by the VAD method has an improved transmittance in infrared region (having a wavelength in the vicinity of 200 nm), contributing to improve the fixation ratio against a toner having an absorption wavelength in this region.  
         [0066]    The reflection plate  24  is disposed to cover the flash lamp  22 . Preferably the inside plane of the case thereof is evaporated with aluminum and thereafter reflection intensification process is conducted. By means of the reflection plate  24 , the light emission energy distribution can be formed into the trapezoid shape.  
         [0067]    Because the inside of the lamp house  20  is isolated from outside, the flash lamp  22  can be prevented from being heated by air-cooling the inside with cooled air. Thus it becomes possible to increase light emission frequency of the flash lamp  22  to enable high-speed printing.  
         [0068]    A block  31  is provided oppositely the lamp house  20  across the paper  2 . The block  31  prevents the flashlight emitted from flash lamp  22  from leaking outside the fixation unit. This enables to prevent performance degradation of other units (such as photosensitive drum  4 ) which possibly occurs caused by intense flash light, as well as to avoid influence against a human body such as an operator who is situated in the vicinity of printer  1 . The block  31  is provided with a cooling fin to protect from being heated by the flashlight.  
         [0069]    Suction mechanism  14  is disposed on the exit (downstream) side of the lamp house  20  and includes a suction duct face  15 . The suction duct  14  is connected to a non-illustrated suction blower to suck gas through the suction duct face  15 .  
         [0070]    A guide roller  30  being provided at the entrance of the lamp house (main body of the flash fixation unit)  20  guides the paper  2  produced a toner image thereupon to lead to the position between the flash lamp  22  and the block  31 . A guide roller  32  is provided at the exit (downstream) of the lamp house  20  to alter the transportation direction of the paper  2 . The suction duct face  15  is disposed along this altered transportation direction.  
         [0071]    Namely, as shown by the arrow in FIG. 2, the gas produced by flash fixation flows by inertia to the paper transportation direction. Therefore, by directing the suction duct face  15  toward this gas inertia direction, gas collection efficiency of the suction mechanism  14  can be improved.  
         [0072]    In this case, at the front of the flash lamp  22  in the lamp house  20 , it is important that the paper  2  shall be maintained at a certain distance from the glass plate  26 , keeping at a uniform distance throughout the flash exposure area so as to obtain desired flash fixation performance. In order to direct the suction duct face  15  to the inertia gas flow direction, the guide  32  is disposed between the lamp house  20  and the suction duct  14  at the rear side of the paper fixation face so as to bend paper  2 .  
         [0073]    The paper  2  contacts to this guide  32  to alter the paper transportation direction (for example, to alter from a horizontal direction to an inclined direction). The suction duct face  15  is disposed along this altered paper transportation direction. The suction width of this suction duct face  15  as well as the distance to the paper  2  is determined considering matching with both a paper transportation velocity and suction blower performance.  
         [0074]    With this configuration, gas (evaporated gas) generated on the paper  2  face flows into the suction duct face  15 , resulting in producing high efficient gas collection. Accordingly, gas can be sucked from the suction duct face  15  having narrower width, thus enabling to miniaturize the gas collector. In addition, it is not necessary to increase suction power of the suction blower, and therefore the blower can also be miniaturized.  
         [0075]    With this alteration of paper transportation angle, it is necessary for the suction duct face  15  to direct to the inertia direction of the gas flow. The alteration degree θ is required to be 0 degree &lt;θ&lt;90 degrees against the horizontal flash fixation face. Considering the layouts of a stacker  11  and a hopper  12 , thirty (30) degrees ±10 degrees is desirable.  
         [0076]    Further, a drive roller (or guide)  33  is disposed exactly after the suction duct  14 . Thus the guides for paper  2  are positioned before and after the suction duct  14 . It is possible to shorten the distance between the guides  32  and  33  disposed before and after the suction duct  14 . This enables the paper  2  to resist tightly against suction power of the suction duct  14 , enabling to prevent the paper  2  from contacting to the duct face  15 .  
         [0077]    Accordingly, paper tension can be maintained in the suction duct  14 , and paper flattering can be prevented without providing a suction mechanism on the paper rear side as was required in the conventional art. This contributes to the simplification of the device structure. Moreover, this can prevent the rear face of the paper from contacting to the suction mechanism on the rear face which caused a problem at the time of double-sided printing.  
         [0078]    Furthermore, it becomes hard to broke tractor hole in the tractor portion at the time of paper feeding, enabling to use thinner paper. Also, even when a pre-printed paper having small surface friction resistance, which is difficult to pull by a scuffing roller  34 , paper can be conveyed without occurrence of trouble.  
         [0079]    [Other Flash Fixation Unit] 
         [0080]    [0080]FIG. 5 shows a cross-sectional view of a second embodiment of the flash fixation unit in accordance with the present invention. FIG. 6 shows an operation explanation diagram thereof.  
         [0081]    In FIGS. 5 and 6, like parts having been illustrated in FIG. 2 is referred to by like symbols. Namely, the flash fixation unit  13  accommodates the flash lamp  22  and the reflection plate  24  in the lamp house  20 . The paper  2  side of the lamp house  20  is covered with a glass plate  26  to isolate the inside of the lamp house  20  from outside. Here, four flash lamps  22  and two reflection plates  24  are employed so as to widen the irradiation area produced by flashlight at a time and to unify light energy distribution throughout the irradiation area. However, the number of flash lamps or reflection plates is not limited to the above description. An arbitrary number can be adopted as the need demands.  
         [0082]    The flash lamp  22  is structured by a cylinder-shaped ozoneless silica glass having a predetermined arc length, in which Xe gas is sealed. Also, the glass plate (light transparent plate)  26  is disposed to be sandwiched by the flash lamp  22  and the continuous paper  2 . The reflection plate  24  is disposed to cover the flash lamp  22 . Preferably the inside plane of the case thereof is evaporated with aluminum and thereafter reflection intensification process is conducted. By means of this reflection plate  24 , the light emission energy distribution can be formed into the trapezoid shape.  
         [0083]    Because the inside of the lamp house  20  is isolated from outside, the flash lamp  22  can be prevented from being heated by internally air-cooling with cooled air. Thus it becomes possible to increase light emission frequency of the flash lamp  22  to enable high-speed printing.  
         [0084]    A block  31  is provided oppositely to the lamp house  20  across the paper  2 . The block  31  prevents the flashlight emitted from the flash lamp  22  from leaking outside the fixation unit. The suction mechanism  14  is disposed on the exit (downstream) side of the lamp house  20  and has a suction duct face. The suction duct  14  is connected to a non-illustrated suction blower to suck gas from the suction duct face.  
         [0085]    A guide roller  30  provided at the entrance of the lamp house (main body of the flash fixation unit)  20  guides the paper  2  on which a toner image  28  is formed to the position between the flash lamp  22  and the block  31 . A transportation roller  33  conveys the paper  2  at the exit of the flash fixation unit.  
         [0086]    In order to prevent gas C having been produced by the fixation from leaking to transportation downstream side, a blast mechanism  16  for blasting gas toward the paper  2  is disposed at the downstream side of the suction mechanism  14 . The blast mechanism  16  plays a roll of an air seal by blasting air onto the paper face. Thus leakage of gas C toward downstream side of the transportation can be avoided.  
         [0087]    Further, by configuring the blast mechanism  16  so as to blast air with a variable velocity and thus by increasing the intensity of air onto the paper  2  in case of either high density printing or high speed printing, air-sealing capability can be increased.  
         [0088]    Accordingly, flattering of the paper  2  can be avoided by providing the air suction mechanism  14  for collecting gas (evaporated gas) C produced from the toner  28  at flash-fixation, as well as the blast mechanism  16  at the rear thereof for blasting air. Moreover, blasting air onto the paper functions as air sealing, which can improve gas collection efficiency by the suction mechanism  14 .  
         [0089]    [0089]FIG. 7 shows a cross-sectional view of a third embodiment of the flash fixation unit in accordance with the present invention. FIG. 8 shows an operation explanation diagram thereof.  
         [0090]    In FIGS. 7 and 8, like parts shown in FIG. 5 are referred to by like symbols. In this example, air is blasted with an angle against the paper face. More specifically, a blast mechanism  16 - 1  is provided at the downstream of the suction mechanism  14  with an angle of θ against the paper face.  
         [0091]    As shown in FIG. 8, blasted air has an angle so as to push back gas C flowing from the suction mechanism  14  actively toward the duct face of the suction mechanism. Thus gas collection efficiency of the suction mechanism  14  is improved as well as preventing paper from flattering. To blast air in an oblique way, the blasting outlet is provided obliquely.  
         [0092]    [0092]FIG. 9 shows a cross-sectional view of a fourth embodiment of the flash fixation unit in accordance with the present invention. In FIG. 9, like parts shown in FIG. 5 are referred to by like symbols. In this example, there is provided a level difference ‘t’ in the positional relation between an outlet of the blast mechanism  16 - 2  and an intake of the suction mechanism  14 . Because the outlet of the blast mechanism  16 - 2  is positioned nearer to paper  2  than the intake of the suction mechanism  14 , the seal effect is generated at the portion of level difference ‘t’, enabling to improve collection ratio of gas (evaporated gas) C.  
         [0093]    [0093]FIG. 10 shows a cross-sectional view of a fifth embodiment of the flash fixation unit in accordance with the present invention. FIG. 11 shows a diagram illustrating evaporated gas flow for explaining the operation thereof. In FIGS. 10 and 11, like parts shown in FIG. 5 are referred to by like symbols. In this embodiment, the capacity of the blast mechanism  16 - 3  and the capacity of the suction mechanism  14  are different. Namely, the blast width S 2  of the blast mechanism  16 - 3  is set greater than the suction width S 1  of the suction mechanism  14 . As shown in FIG. 11, evaporated gas flow with capacity difference is sealed. Namely, even when evaporated gas has large viscosity, greater sealing effect can be obtained by increasing the capacity of the blast mechanism  16 - 3 .  
         [0094]    FIGS.  12  to  16  show diagrams of simulation experiment results on evaporated gas flow in the flash fixation unit. FIG. 12 shows the case of blast width S 2  of the blast mechanism  16  being set identical to suction width S 1  of the suction mechanism  14 . FIG. 13 shows the case of blast width S 2  of the blast mechanism  16  being set twice as large as suction width S 1  of the suction mechanism  14 . Also, FIG. 16 shows the case of blast width S 2  of the blast mechanism  16  being set half as large as suction width S 1  of the suction mechanism  14 . Additionally, in FIGS. 14 and 15, the cases that distance ‘th’ between the blast mechanism  16  and the paper  2  as well as distance ‘tk’ between the suction mechanism  14  and the paper  2  is varied.  
         [0095]    In FIGS.  12  to  16 , each parameter in simulation denotes as follows:  
         [0096]    S 1 : capacity (width) of the suction mechanism  14   
         [0097]    S 2 : capacity (width) of the blast mechanism  16 ,  16 - 2 ,  16 - 3   
         [0098]    Vs: paper transportation velocity  
         [0099]    Vh: blast wind velocity  
         [0100]    Vk: suction wind velocity  
         [0101]    th: transportation gap on blast mechanism face  
         [0102]    tk: transportation gap on suction mechanism face  
         [0103]    [0103]FIG. 12 represents a wind velocity distribution in the case of S 1 =S 2 , Vh=Vk, th=tk=4 mm, and Vs=1500 mm/sec. The gas produced by the flash fixation flows toward a paper transportation direction as a whole. Nevertheless, it is understood that the gas flow is blocked by the blast mechanism  16 . In other words, the gas flowing in the downstream direction of transportation is blocked by the blast from the blast mechanism.  
         [0104]    [0104]FIG. 13 represents the wind velocity distribution in the case of  2 ×S 1 =S 2 , Vh=Vk, th=tk=4 mm, and Vs=1500 mm/sec. By the effect of the blast mechanism  16 - 3 , the gas flow is blocked. However, as compared to the case shown in FIG. 12, the gas becomes hard to flow in the downstream direction of transportation. Namely, because the capacity of the blast mechanism  16 - 3  (or the length in the downstream direction of transportation) has been increased, the evaporated gas becomes hard to flow in the downstream direction of transportation, and less leakage is produced even if the transportation velocity is increased.  
         [0105]    [0105]FIG. 16 represents the wind velocity distribution in the case of S 1 =2×S 2 , Vh=Vk, th=tk=4 mm, and Vs=1500 mm/sec. Similar to the cases shown in FIGS. 12 and 13, a blocking effect of gas flow is exhibited. However, as compared to the case shown in FIG. 13, fewer margins are produced.  
         [0106]    [0106]FIG. 14 represents the wind velocity distribution in the case of S 1 =S 2 , Vh=Vk, th=2 mm, tk=4 mm, and Vs=1500 mm/sec. By narrowing transportation gap (distance to the paper) ‘th’ of the blast mechanism  16 - 2 , evaporated gas becomes hard to flow in the downstream direction of transportation.  
         [0107]    [0107]FIG. 15 represents the wind velocity distribution in the case of S 1 =S 2 , Vh=Vk, th=4 mm, tk=2 mm, and Vs=1500 mm/sec. Though gas-blocking effect is exhibited, fewer margins are produced as compared to the case shown in FIG. 14.  
         [0108]    [0108]FIG. 17 shows a cross-sectional view of a sixth embodiment of the flash fixation unit in accordance with the present invention. In FIG. 17, like parts shown in FIG.  5  is referred to by like symbols. In this example, the suction mechanism  14  and the blast mechanism  16  is connected by an identical pipe line  17 . In the pipe line (circulation hose)  17 , a blower  19  and a degassing filter  18  are disposed at appropriate positions. The gas (evaporated gas) having been collected by the suction mechanism  14  is deodorized by degassing filter and reaches to the blast mechanism  16  through the blower  19 .  
         [0109]    In such a way, it becomes possible to decrease an exhaust gas amount flowing outward by circulating the sucked air. Conventionally, there has been a problem of polluting environment in high-speed printing because of impossibility in discharging completely scrubbed air outside of the unit. The aforementioned method can solve this problem.  
         [0110]    Thus, according to the present invention, paper fluttering can be avoided by providing an air suction mechanism for collecting gas (evaporated gas) produced from toner at the time of fixation, as well as a blast mechanism being disposed at the rear of the suction mechanism for blasting air onto the paper. Blasting air onto the paper plays a role of air seal, enabling to increase collection rate by the suction mechanism. Further, an air amount being discharged outward from the unit can be reduced by circulating sucked air.  
         [0111]    [Other Embodiments] 
         [0112]    In the foregoing embodiments of the present invention, the flash fixation unit having four flash lamps has been illustrated. However, the method can also be applied to a flash fixation unit having a single flash lamp or more. Further, though the foregoing description is based on the electrophotographic printer, the method is also applicable to any printer printed by other printing schemes. Still further, though continuous paper is used in the foregoing description, other cut media such as cut form can be used. In addition, the method can be applied for not only paper medium but also other media such as film.  
         [0113]    To summarize, the present invention produces the following effects:  
         [0114]    In a flash fixation unit, considering that vapor gas produced by flash fixation flows in the direction of medium transportation, a gas suction face is provided in a gas collector for receiving the vapor gas which flows in this medium transportation direction. Otherwise, a gas blast portion is provided at the rear stage of the gas collector. By such means the vapor gas flows in a natural manner onto the gas suction face, bringing about increased gas collection efficiency.  
         [0115]    As a result, higher printing speed can be attained. In addition, it becomes possible to collect vapor gas without increasing either suction power or suction area of the gas collector even when the vapor gas amount is increased, as well as to avoid medium flattering which may possibly occur at the time of medium transportation. Thus a miniaturized and low-cost flash fixation unit can be obtained.  
         [0116]    The foregoing description of the embodiments is not intended to limit the invention to the particular details of the examples illustrated. Any suitable modification and equivalents may be resorted to the scope of the invention. All features and advantages of the invention which fall within the scope of the invention are covered by the appended claims.