Patent Publication Number: US-9411310-B1

Title: Cooling device, image forming apparatus, and cooling method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2015-014595 filed Jan. 28, 2015. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a cooling device, an image forming apparatus, and a cooling method. 
     SUMMARY 
     According to an aspect of the invention, there is provided a cooling device that cools a continuous resin film, which is transported and onto which a toner image is transferred, after the toner image is heated so that the toner image is fixed to the resin film, the resin film to which the toner image is fixed being cooled in such a manner that an image surface side of the resin film is convexly curved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figure, wherein: 
         FIG. 1  illustrates the structure of a cooling device according to a first exemplary embodiment of the present invention and other devices; 
         FIG. 2  illustrating the structure of the cooling device according to the first exemplary embodiment of the present invention and other devices; 
         FIG. 3  is a side view of a support member included in the cooling device according to the first exemplary embodiment of the present invention; 
         FIG. 4  is a perspective view of the support member included in the cooling device according to the first exemplary embodiment of the present invention; 
         FIGS. 5A and 5B  illustrate the manner in which a film warps in the case where the cooling device according to the first exemplary embodiment of the present invention is used; 
         FIGS. 6A and 6B  illustrate the manner in which a film warps in the case where the cooling device according to the first exemplary embodiment of the present invention is not used (in the case of comparative example); 
         FIG. 7  is a diagram illustrating an image forming device included in the image forming apparatus according to the first exemplary embodiment of the present invention; 
         FIG. 8  is a schematic diagram illustrating the image forming apparatus according to the first exemplary embodiment of the present invention; and 
         FIG. 9  is a perspective view of a support member included in a cooling device according to a second exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     First Exemplary Embodiment 
     A cooling device  80  and an image forming apparatus  10  according to a first exemplary embodiment of the present invention will be described with reference to  FIGS. 1 to 8 . In the drawings, the arrow H shows the up-down direction of the apparatus (vertical direction), the arrow W shows the width direction of the apparatus (horizontal direction), and the arrow D shows the depth direction of the apparatus (horizontal direction). 
     Overall Structure 
     As illustrated in  FIG. 8 , the image forming apparatus  10  includes a feeder device  12  and an image forming section  14 . The feeder device  12  feeds a shrink film F (hereinafter referred to as a “film F”), which is an example of a continuous resin film that serves as a recording medium. The image forming section  14  forms a toner image on the shrink film F fed by the feeder device  12 . The image forming apparatus  10  also includes a container device  16  that contains the film F on which the toner image has been formed, and a controller  18  that controls each of the devices. The film F is a packaging material that shrinks when heated and that is used to pack, for example, a PET bottle. In the present exemplary embodiment, the film F is, for example, a 50 μm thick resin film made of polystyrene. 
     Feeder Device 
     The feeder device  12  feeds the film F to the image forming section  14 . The feeder device  12  includes a feed roller  20  around which the film F is wound into a roll. 
     Container Device 
     The container device  16  contains the film F having the toner image formed thereon by the image forming section  14 . The container device  16  includes a take-up roller  22  that is rotated by a driving unit (not shown) and around which the film F having the toner image formed thereon is wound into a roll, and a dancer roller  23  that adjusts the tension applied to the film F. The take-up roller  22  is an example of a transport unit that transports the film F. 
     Image Forming Section 
     The image forming section  14  forms a toner image on the film F on the basis of image information by using toners of four colors, which are yellow (Y), magenta (M), cyan (C), and black (K). 
     The image forming section  14  includes image forming devices  24 , which are examples of image forming units that form a toner image, and an intermediate transfer device  26 , which is an example of a transfer unit. The toner images formed by the image forming devices  24  are transferred onto the intermediate transfer device  26  in a first transfer process, and are then transferred onto the film F by the intermediate transfer device  26  in a second transfer process. The image forming section  14  also includes a fixing device  28  that fixes, by applying heat and pressure, the toner images that have been transferred onto the film F by the intermediate transfer device  26  in the second transfer process, and a cooling device  80  that cools a portion of the film F to which the toner images have been fixed. 
     Image Forming Devices 
     Four image forming devices  24 Y,  24 M,  24 C, and  24 K that form the toner images of the respective colors, which are yellow (Y), magenta (M), cyan (C), and black (K), are provided as the image forming devices  24 . The image forming devices  24  of the respective colors have similar structures except for the toner that is used. In the following description, when it is not necessary to distinguish the image forming devices, the letters “Y”, “M”, “C”, and “K” appended to the reference numeral  24  will be omitted. 
     As illustrated in  FIG. 7 , each image forming device  24  includes a cylindrical image carrier  30  that rotates in the direction of arrow R 1  in  FIG. 1  and that carries a toner image. A charging device  32  that charges the image carrier  30 , an exposure device  34  that irradiates the charged image carrier  30  with exposure light to form an electrostatic latent image, and a developing device  36  that develops the electrostatic latent image into a toner image are arranged around the image carrier  30  in that order from the upstream side in a direction in which the image carrier  30  is rotated. 
     The image forming device  24  also includes a transfer roller  40  and a cleaning device  42 . The transfer roller  40  transfers the toner image on the image carrier  30  onto a transfer belt  46  in the first transfer process. The transfer belt  46  is included in the intermediate transfer device  26 , and rotates in the direction of arrow B in  FIG. 7 . The cleaning device  42  removes the toner or the like that remains on the image carrier  30  after the first transfer process. 
     As illustrated in  FIG. 8 , the image forming devices  24 Y,  24 M,  24 C, and  24 K are arranged in that order from the upstream side in a direction in which the transfer belt  46  is rotated. 
     With this structure, the toner images formed by the image forming devices  24  are successively transferred onto the transfer belt  46  that rotates in the first transfer process, so that the toner images are superposed on the transfer belt  46 . 
     Intermediate Transfer Device 
     As illustrated in  FIG. 8 , the intermediate transfer device  26  includes the above-described transfer belt  46  and rollers  48 A,  48 B, and  48 C around which the transfer belt  46  extends. The roller  48 A receives a rotating force from a driving unit. 
     The roller  48 C is arranged so that the transfer belt  46  is in contact with the film F that is transported. The intermediate transfer device  26  also includes a transfer roller  50  that transfers the toner images formed on the transfer belt  46  onto the film F in the second transfer process. 
     In this structure, the intermediate transfer device  26  transfers the toner images formed on the transfer belt  46  onto the film F in the second transfer process. 
     Fixing Device 
     As illustrated in  FIG. 1 , the fixing device  28  includes a heating unit  54  that is heated to a predetermined temperature and that comes into contact with an image surface of the film F, and a pressing roller  56  that presses the film F that has been transported to the heating unit  54  at a non-image surface side of the film F. The non-image surface of the film F is a surface on which the toner images are not formed. 
     The heating unit  54  includes a pair of rollers  54 A and a fixing belt  54 C arranged so as to extend around the rollers  54 A. At least one of the rollers  54 A has a halogen heater (not shown) disposed therein. In addition, at least one of the rollers  54 A receives a rotating force from a driving member (not shown). 
     In this structure, the fixing device  28  fixes the toner images that have been transferred onto the film F in the second transfer process to the film F while the film F is nipped and transported. At this time, the film F is heated to a temperature higher than the softening temperature of the film F. 
     Operation of Overall Structure 
     Next, an operation performed by the image forming apparatus  10  to form a toner image on the film F will be described. 
     The controller  18  controls each of the devices so that the image forming devices  24  form toner images of the respective colors. The toner images formed by the image forming devices  24  are successively transferred onto the transfer belt  46  that rotates in the first transfer process, so that the toner images are superposed on the transfer belt  46 . 
     The intermediate transfer device  26  transfers the toner images formed on the transfer belt  46  onto the film F fed from the feeder device  12  in the second transfer process. The fixing device  28  fixes the toner images to the film F, and the cooling device  80  cools the film F. 
     The container device  16  receives the film F that has been cooled by the cooling device  80 . Thus, the process of forming a toner image on the film F is completed. 
     Structure of Components 
     The cooling device  80  and other devices will now be described. 
     As illustrated in  FIG. 1 , the cooling device  80  includes a support member  82  that supports the film F, to which the toner image is fixed, at the non-image surface side of the film F, a cooling member  90  that cools the film F through the support member  82 , and a pressing member  92  that presses the film F against the support member  82 . The pressing member  92  is an example of a contact member. 
     Support Member 
     As illustrated in  FIGS. 3 and 4 , the support member  82  includes a support plate  84  having a support surface  84 A that supports the film F at the non-image surface side (back side), and plural heat dissipation plates  86 . 
     The support surface  84 A is convexly curved upward when viewed in the depth direction of the apparatus (width direction of the film F). When viewed in the depth direction of the apparatus, the curvature of the support surface  84 A gradually decreases from the upstream side to the downstream side in a transporting direction in which the film F is transported. 
     The heat dissipation plates  86 , which have surfaces that face in the width direction of the apparatus, are connected to the back surface of the support plate  84  (surface opposite the support surface  84 A) at the proximal ends thereof. The heat dissipation plates  86  are arranged with constant intervals therebetween in the width direction of the apparatus. 
     Cooling Member 
     As illustrated in  FIG. 1 , the cooling member  90  includes a fan  91  that is disposed below the support member  82  and that blows air toward the heat dissipation plates  86  of the support member  82 . By blowing air toward the heat dissipation plates  86 , the fan  91  cools the film F from the side of the support member  82  at the non-image surface side of the film F. 
     More specifically, the fan  91  cools the film F at the non-image surface side of the film F to a temperature lower than or equal to the softening temperature of the film F. The softening point of the film F is close to the glass transition point of the film F. 
     Pressing Member 
     The pressing member  92  is located downstream of the support member  82  in the transporting direction of the film F, and includes a roller  94  capable of rotating while being in contact with the film F at the upper side of the film F. 
     In this structure, when the roller  94  is at a pressing position, which will be described below, the roller  94  presses the film F downward so that the non-image surface side of the film F comes into contact with the support surface  84 A of the support plate  84  and the film F is supported by the support plate  84 . Accordingly, the image surface side of the film F is convexly curved when viewed in the depth direction of the apparatus. 
     Others 
     The image forming apparatus  10  includes a switching unit  88  that switches a path of a recording medium between a first transport path (see  FIG. 1 ) along which the recording medium is transported while being supported by the support member  82  and a second transport path (see  FIG. 2 ) along which the recording medium is transported while being separated from the support member  82 . 
     The switching unit  88  includes rails  96  that are disposed on both sides of the roller  94  and that support the roller  94  such that the roller  94  is movable in the vertical direction, and a driving member  98  that moves the roller  94  along the rails  96 . The operation of the driving member  98  is controlled by the above-described controller  18  (see  FIG. 8 ). 
     In this structure, the controller  18  operates the driving member  98  so as to move the roller  94  between the pressing position illustrated in  FIG. 1 , at which the roller  94  presses the film F, and a separating position illustrated in  FIG. 2 , at which the pressing force is eliminated and the support plate  84  is separated from the film F. When the roller  94  is at the pressing position, the recording medium is transported along the first transport path. When the roller  94  is at the separating position, the recording medium is transported along the second transport path. 
     The image forming apparatus  10  also includes an input unit  62  (see  FIG. 8 ) through which the user inputs a medium type when a recording medium other than the film F (label paper, normal paper, etc.) is used. 
     In this structure, when the medium type input through the input unit  62  differs from the film F, and when the roller  94  is at the pressing position, the controller  18  operates the driving member  98  to move the roller  94  to the separating position, as illustrated in  FIG. 2 . When the medium type input through the input unit  62  is the film F and the roller  94  is at the separating position, the controller  18  operates the driving member  98  to move the roller  94  to the pressing position, as illustrated in  FIG. 1 . 
     Operation 
     The operation will now be described. In the initial state, the roller  94  is at the pressing position, and the film F is transported along the first transport path. 
     The fixing device  28  fixes the toner image that has been transferred onto the film F in the second transfer process to the film F by applying heat and pressure. More specifically, the film F is transported while being nipped between the fixing belt  54 C that is heated and the pressing roller  56 , so that the toner image is fixed to the film F. Since the film F is heated by the fixing device  28  at the image surface side thereof, the temperature of the film F at the image surface side becomes higher than that at the non-image surface side. 
     After the toner image has been fixed to the film F, the roller  94  causes the non-image surface side of the film F to come into contact with the support surface  84 A, as illustrated in  FIG. 3 , and the film F is supported such that the image surface side of the film F is convexly curved when viewed in the depth direction of the apparatus. In this state, the fan  91  cools the film F from the side of the support member  82  at the non-image surface side of the film F. A portion of the film F that has been cooled by the fan  91  is wound around the take-up roller  22  (see  FIG. 8 ). 
     A case in which a recording medium of the type other than the film F (label paper) is used will now be described. A label paper is a sheet in which backing paper, an adhesive layer, and a surface material are stacked together. 
     In the case where the medium type input through the input unit  62  is label paper R, which differs from the film F, the controller  18  controls the driving member  98  so as to move the roller  94  to the separating position, as illustrated in  FIG. 2 . Accordingly, the label paper R that is transported is separated from the support member  82 . Accordingly, the label paper R is transported along a second transport path. 
     The controller  18  does not activate the cooling member  90 . 
     Evaluation 
     An image forming apparatus including the cooling device according to the present exemplary embodiment is evaluated. In addition, an image forming apparatus which does not include the cooling device is also evaluated as an image forming apparatus according to a comparative example to be compared with the present exemplary embodiment. 
     Evaluation Specification 
     1. Color 1000 Press manufactured by Fuji Xerox Co., Ltd. is used as each of the image forming apparatuses. The cooling device  80  is disposed downstream of a fixing device in the image forming apparatus according the present exemplary embodiment, and the cooling device  80  is not included in the image forming apparatus according to the comparative example. The fixing device heats the toner image on the film F (recording medium) at 160° C. 
     2. The film F used as the recording medium is Bonset (EPS45T) manufactured by C.I. Kasei Co., Ltd., which is a 50 μm thick polystyrene resin film having a softening point of 100° C. Here, Bonset (EPS45T) is a shrink film that shrinks in a transporting direction (longitudinal direction) when heated. 
     3. With regard to the shape of the support plate  84  of the support member  82 , in  FIG. 3 , the dimension L 1  is set to 300 mm and the dimension L 2  is set to 60 mm. The curvature of the support surface  84 A gradually varies from 1/700 (upstream side) to 1/900 (downstream side) when viewed in the depth direction of the apparatus. 
     4. In the state in which the film F that is transported is supported by the support member  82 , the fan  91  cools the support member  82  such that the temperature of the support surface  84 A is 120° C. in an upstream region thereof and 90° C. in a downstream region thereof. 
     5. A black solid image (area coverage (image density) 100%) is formed on the film F as the toner image. 
     6. The speed at which the film F is transported is 60 m/min. 
     Evaluation Items 
     The shrinkage ratio in the transporting direction and warping of the film F output from each image forming apparatus are evaluated. The shrinkage ratio is determined by cutting out a portion of the film F that has been output and measuring the distance between predetermined two points. 
     Evaluation Criterion and Evaluation Results 
     When the shrinkage ratio of the film F output from the image forming apparatus is less than 3.0% in the transporting direction of the film F, the film F is evaluated as “Good” since the commercial value thereof is not affected. When the shrinkage ratio is 3.0% or more, the film F is evaluated as “Bad” since the commercial value thereof is affected. Warping of the film F output from the image forming apparatus is visually evaluated. 
     In the image forming apparatus according to the present exemplary embodiment, the shrinkage ratio is 1.5% and the result of the evaluation is “Good”. In the image forming apparatus according to the comparative example, the shrinkage ratio is 4.0% and the result of the evaluation is “Bad”. 
     With regard to warping of the film F output from each image forming apparatus, warping of the film F output from the image forming apparatus according to the present exemplary embodiment is smaller than warping of the film F output from the image forming apparatus according to the comparative example. 
     Consideration 
     In the image forming apparatus according to the comparative example, as illustrated in  FIG. 6A , the film F is flat in the state in which the toner image T is transferred onto the film F. 
     Since the film F is heated by the fixing device at the image surface side thereof, the temperature of the film F is higher at the image surface side than at the non-image surface side. Therefore, as illustrated in  FIG. 6B , the image surface side of the film F shrinks by a larger amount than the non-image surface side of the film F, and the film F warps such that the image surface side thereof is concavely curved when viewed in the depth direction of the apparatus. 
     In the image forming apparatus according to the present exemplary embodiment, similar to the comparative example, since the film F is heated by the fixing device at the image surface side thereof, the temperature of the film F is higher at the image surface side than at the non-image surface side. However, in this state, as illustrated in  FIG. 5A , the film F is supported by the support member  82  such that the image surface side of the film F is convexly curved. In addition, in the state in which the film F is convexly curved, the film F is cooled by the fan  91  (see  FIG. 1 ) through the support member  82 . 
     Therefore, shrinking of the film F is suppressed, and warping of the film F such that the image surface side thereof is concavely curved when viewed in the depth direction of the apparatus is also suppressed (see  FIG. 5B ). 
     Summary 
     In the case where the film F is cooled at the non-image surface side thereof, the film F may be more effectively cooled compared to the case where the film F is cooled at the image surface side thereof. In addition, warping of the film F due to the temperature of the film F being higher at the image surface side than at the non-image surface side is suppressed. 
     Moreover, since the film F is cooled in the state in which the image surface side of the film F is convexly curved, compared to the case in which the film F is not curved, warping of the film F due to the temperature of the film F being higher at the image surface side than that at the non-image surface side is more effectively suppressed. 
     The support surface  84 A of the support member  82  is convexly curved when viewed in the depth direction of the apparatus. Therefore, in the case where the film F that shrinks in the transporting direction (longitudinal direction) when heated is used, compared to the case in which the support surface is convexly curved when viewed in the transporting direction of the film F, warping of the film F is more effectively suppressed. 
     The curvature of the support surface  84 A gradually decreases from the upstream side to the downstream side in the transporting direction of the film F. Therefore, compared to the case in which the support surface has a constant curvature, warping of the film F along the support surface  84 A is reduced. 
     In the image forming apparatus  10 , when a recording medium of the type other than the film F (for example, label paper R) is used, the label paper R that is transported is separated from the support member  82 . Therefore, in the case where, for example, an adhesive layer of the label paper R is partially exposed at the backing-paper side, the risk that the adhesive layer of the label paper R will adhere to the support member  82  is reduced. 
     Second Exemplary Embodiment 
     A cooling device  100  and an image forming apparatus according to a second exemplary embodiment of the present invention will now be described with reference to  FIG. 9 . Components similar to those in the first exemplary embodiment are denoted by the same reference numerals, and the description thereof is thus omitted. Structures different from those in the first exemplary embodiment will be described. 
     As illustrated in  FIG. 9 , the cooling device  100  according to the second exemplary embodiment includes a support member  102  including a support plate  104  having a support surface  104 A that supports the film F at the non-image surface side, and plural heat dissipation plates  106 . 
     The support surface  104 A is convexly curved when viewed in the transporting direction of the film F. The curvature of the support surface  104 A gradually decreases from the upstream side to the downstream side in the transporting direction of the film F. 
     The heat dissipation plates  106 , which have surfaces that face in the width direction of the apparatus, are connected to the back surface of the support plate  104  (surface opposite the support surface  104 A) at the proximal ends thereof. The heat dissipation plates  106  are arranged with constant intervals therebetween in the width direction of the apparatus. 
     In this structure, in the case where the film F that shrinks in the width direction of the film F when heated is used, compared to the case in which the support surface is convexly curved when viewed in the depth direction of the apparatus, warping of the film F is more effectively suppressed. 
     The effects of the second exemplary embodiment are similar to those of the first exemplary embodiment except for the effect provided because the support surface is convexly curved when viewed in the depth direction of the apparatus. 
     Although specific exemplary embodiments of the present invention have been described in detail, the present invention is not limited to the above-described exemplary embodiments. It is obvious to a person skilled in the art that various exemplary embodiments are possible within the scope of the present invention. For example, in the above-described first and second exemplary embodiments, the recording medium cooled by the cooling device  80  is the film F (shrink film). However, the recording medium is not limited to a shrink film as long as the recording medium is a resin-made film (resin film). 
     In addition, although the support member  82 ,  102  includes plural heat dissipation plates  86 ,  106  in the first and second exemplary embodiments, the heat dissipation plates may be omitted when a support member having a high thermal conductivity is used. 
     Although not described in the first and second exemplary embodiments, a member that directly presses the film F against the support surface  84 A,  104 A from above the support member  82 ,  102  by nipping the film F between itself and the support surface  84 A,  104 A may be additionally provided. 
     In addition, although not described in the first and second exemplary embodiments, the support surface  84 A,  104 A of the support member  82 ,  102  may be convexly curved not only when viewed in the depth direction of the apparatus but also when viewed in the transporting direction of the film F. Such a structure is effective in the case where the recording medium is a shrink film that shrinks in all directions when heated. 
     Although the roller  94  is moved by the driving member  98  in the above-described exemplary embodiments, the roller  94  may instead be moved by the user. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.