Patent Publication Number: US-7905486-B2

Title: Transportation apparatus for transporting transportation target medium, recording apparatus having the same, and control method for controlling the same

Description:
BACKGROUND 
     1. Technical Field 
     The present invention generally relates to a transportation apparatus for transporting a transportation target medium, a recording apparatus that is provided with the transportation apparatus for transporting a transportation target medium, and a control method for controlling the transportation apparatus for transporting a transportation target medium. More particularly, the present invention relates to a transportation apparatus for transporting a sheet-type transportation target medium while holding it between a pair of pinching rollers thereof during transportation. The present invention further relates to a recording apparatus that is provided with such a transportation apparatus, and a control method for controlling such a transportation apparatus. 
     2. Related Art 
     In the related technical fields of the invention, transportation units are built in a variety of apparatuses/equipment such as a recording apparatus, a facsimile machine, and a copying machine, though not limited thereto, for the functional purpose of transporting sheet-shaped transportation target media, sheet-shaped recording target media, or the like. As an example of these transportation units, one known in the art is configured to transport a transportation target medium while holding it between a pair of pinching rollers of the transportation apparatus during transportation, at least one of which is/are driven in a rotational manner. Such a type of transportation unit has a driving roller that is operated rotationally (i.e., rotates actively) and a driven roller that follows the rotary movement of the driving roller (i.e., rotates passively). In such a configuration, the driven roller applies a pressing force onto a transportation target medium toward the driving roller. As the driving roller rotates, the transportation target medium is transported while being pinched therebetween. 
     The patent document JP-A-2002-128314 discloses a paper transportation apparatus that has a driving roller and a driven roller that is urged toward the driving roller. The paper transportation apparatus described in JP-A-2002-128314 transports a sheet of paper in accordance with the rotation of the driving roller. During transportation, the sheet of paper is supported between the driving roller and the driven roller. In addition to these rollers, the paper transportation apparatus according to JP-A-2002-128314 is further provided with an urging member that urges the driven roller toward the driving roller and an arm member that allows the driven roller to move apart from the driving roller against the urging force applied thereto by the urging member. With such a configuration, it is possible to remove, if there occurs any paper jam malfunction between the driving roller and the driven roller, a jammed paper by releasing the pinching force exerted by the driven roller without causing any adverse mechanical stress on each of these rollers. 
     The patent document JP-A-2002-192782 teaches a configuration in which, at an ejection unit of a recording apparatus that is a kind of transportation apparatus, a holder that is configured to be capable of moving in a rotating direction (i.e., drawing/tracing an arc) supports an ejection driven roller. With such a configuration, it is possible to prevent a recording target material/medium from being damaged by moving the ejection driven roller apart from an ejection driving roller. As described above, some of transportation apparatuses that have a pair of pinching rollers provided for transportation of a transportation target medium allow a driving roller and a driven roller to become distanced from (i.e., not in contact with) each other when there is no transportation target medium that is now being transported. 
     A related-art transportation unit such as one described above transports various kinds of sheet-type recording target media that vary in terms of thickness from one to another. Nowadays, it is not infrequent that, in addition to a sheet of recording paper having a thickness of less than 1 mm, which is flexible, a sheet of cardboard paper, information recording medium, printed wiring board, and the like having a thickness of 3 mm of greater is fed as a target of transportation. In a related-art application where a transportation unit having the roller mechanism described above transports such a thick-type recording target medium, as a pre-transportation step, a driven roller is temporarily moved apart from a driving roller so as to form a sufficiently large clearance therebetween; and thereafter, the thick recording target medium is fed therebetween. With such a procedure/configuration, the related-art transportation unit described above ensures the smooth feeding of the recording target medium. In addition, the above-described procedure/configuration makes it possible to reduce any undesirable mechanical stress applied to constituent members that make up the transportation unit. 
     In the roller configuration of the above-described transportation apparatus that has a combination of the driving roller and the driven roller, it is preferable that the driven roller can rotate smoothly as the driving roller rotates. In order to ensure the smooth rotation of the driven roller, an urging force is not directly applied to the driven roller but indirectly thereto via a driven roller holder. The driven roller holder supports the driven roller in such a manner that the driven roller can rotate freely. For the same reason, when the driven roller is moved apart from the driving roller, it is done so by means of the driven roller holder. 
     When the driven roller holder is turned so as to move the driven roller apart from the driving roller, the mechanical stress due to the urging force is applied to the driven roller holder. Disadvantageously, plastic deformation could occur on the driven roller holder, most of which is made of a resin material, if the driven roller continues to be distanced apart from the driving roller for a long time period. As a result of the plastic deformation of the driven roller holder, a gap between the driving roller and the driven roller decreases. Eventually, the gap therebetween decreases into an insufficient level. If the gap between the driving roller and the driven roller is set at a larger value in anticipation of such plastic deformation of the driven roller holder, a wide open space is required in the periphery of the driven roller holder because the moving vector amount of the driven roller becomes larger. For this reason, disadvantageously, the size of a transportation apparatus increases. On the other hand, an expensive deformation-free material must be used in order to avoid the driven roller holder from becoming deformed. Or, it is necessary to increase the size of the driven roller holder itself for the prevention of plastic deformation thereof, which results in an undesirable increase in the size of the transportation apparatus. 
     SUMMARY 
     In order to address the above-identified problem without any limitation thereto, an advantage of a first aspect of the invention is to provide a transportation apparatus for transporting a transportation target medium in a predetermined transportation direction, the transportation target medium transportation apparatus including: a transport driving roller that is operated rotationally; a transport driven roller that is urged against the transport driving roller and follows the rotary movement of the transport driving roller; and a control section that controls the movement of the transport driven roller between a contact position at which the transport driven roller is in contact with the transport driving roller and a non-contact position at which the transport driven roller is not in contact with the transport driving roller, wherein the control section moves the transport driven roller to the non-contact position at which the transport driven roller is not in contact with the transport driving roller when the thickness of the transportation target medium is at least a predetermined value, and then moves the transport driven roller to the contact position at which the transport driven roller is in contact with the transport driving roller when the length of time period in which the transport driven roller continues to be at the non-contact position exceeds a predetermined time period. With the configuration described above, it is possible to prevent the occurrence of plastic deformation of a driven roller holder, which could be caused when the transport driven roller continues to be distanced apart from the transport driving roller for a long time period. In other words, it is possible to manufacture the driven roller holder having a compact configuration by means of low-cost material without any necessity to increase the mechanical strength thereof at the sacrifice of size and/or cost. In addition, since it is not necessary to anticipate any decrease in a gap between the transport driving roller and the transport driven roller due to plastic deformation, it is possible to reduce both the moving vector amount of the driven roller and a space required for moving thereof, which advantageously results in the smaller size of the transportation apparatus. 
     In the configuration of the transportation target medium transportation apparatus according to the first aspect of the invention described above, it is preferable that the control section issues a message for notifying to a user that, in a case where the transport driven roller has been moved to the contact position at which the transport driven roller is in contact with the transport driving roller when the length of time period in which the transport driven roller continues to be at the non-contact position exceeds the predetermined time period, the moving of the transport driven roller to the contact position has been completed; and the control section causes the transport driven roller to stay at the contact position till the reception of the issued message by the user is confirmed. With the configuration described above, the user is notified that the transport driven roller is now in contact with the transport driving roller, and that, for this reason, it is not possible to feed a thick-type recording target medium unless it is moved apart therefrom. 
     In the configuration of the transportation target medium transportation apparatus according to the first aspect of the invention described above, it is preferable that the control section makes a detection as to whether a transportation target medium is present between the transport driving roller and the transport driven roller or not, and issues a message so as to alert the user to remove, if present, the transportation target medium therefrom. With the configuration described above, it is possible to prevent the transportation target medium from remaining not removed between the transport driving roller and the transport driven roller that are not currently in operation. 
     In the configuration of the transportation target medium transportation apparatus according to the first aspect of the invention described above, it is preferable that the control section moves the transport driven roller to a position corresponding to a recording target medium that is most likely to be fed in the next operation in a case where the transport driven roller has been moved to the contact position at which the transport driven roller is in contact with the transport driving roller when the length of time period in which the transport driven roller continues to be at the non-contact position exceeds the predetermined time period and further in a case where it is detected that no transportation target medium is present between the transport driving roller and the transport driven roller. With the configuration described above, it is possible to initiate the next operation of the transportation target medium transportation apparatus in a speedy manner. 
     As another advantage of the invention, the invention provides a recording apparatus having a recording head for forming an image on the surface of a recording target medium, the recording apparatus being provided with the transportation target medium transportation apparatus having the configuration according to the first aspect of the invention. With the configuration described above, it is possible to offer the advantageous effects described above in the transport unit of the recording apparatus. 
     In order to address the above-identified problem without any limitation thereto, the invention provides, as a second aspect thereof, a control method for controlling a transportation apparatus for transporting a transportation target medium in a predetermined transportation direction, the transportation target medium transportation apparatus having a transport driving roller that is operated rotationally and further having a transport driven roller that is urged against the transport driving roller and follows the rotary movement of the transport driving roller, the transportation target medium transportation apparatus being configured so as to be able to control the movement of the transport driven roller between a contact position at which the transport driven roller is in contact with the transport driving roller and a non-contact position at which the transport driven roller is not in contact with the transport driving roller, the control method for controlling the transportation target medium transportation apparatus including: moving the transport driven roller to the non-contact position at which the transport driven roller is not in contact with the transport driving roller when the thickness of the transportation target medium is at least a predetermined value; and moving the transport driven roller to the contact position at which the transport driven roller is in contact with the transport driving roller when the length of time period in which the transport driven roller continues to be at the non-contact position exceeds a predetermined time period. The control method described above offers the advantageous effects described above without any restriction to hardware configuration. 
     In order to address the above-identified problem without any limitation thereto, the invention provides, as a third aspect thereof, a transportation apparatus for transporting a transportation target medium in a predetermined transportation direction, the transportation target medium transportation apparatus including: a transport driving roller that is operated rotationally; a transport driven roller that is urged against the transport driving roller and follows the rotary movement of the transport driving roller; and a control section that selectively controls the movement of the transport driven roller between a contact position at which the transport driven roller is in contact with the transport driving roller and a non-contact position at which the transport driven roller is not in contact with the transport driving roller depending on the thickness of the transportation target medium, wherein the control section moves the transport driven roller to the contact position at which the transport driven roller is in contact with the transport driving roller when the length of time period in which the transport driven roller continues to be at the non-contact position exceeds a predetermined time period. With such a configuration, the transportation apparatus described above offers the advantageous effects described above. 
     It should be noted that the above summary of the invention does not enumerate all features necessary for the implementation of the invention; and thus, needless to say, any subcombination of these features could also constitute the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a front perspective view that schematically illustrates an example of the general appearance of an ink-jet recording apparatus  100 . 
         FIG. 2  is a rear perspective view that schematically illustrates an example of the general appearance of the ink-jet recording apparatus  100  illustrated in  FIG. 1 . 
         FIG. 3  is a front perspective view that schematically illustrates an example of the configuration of an inner mechanical structure  200  inside the ink-jet recording apparatus  100 . 
         FIG. 4  is a sectional view that schematically illustrates, in the above-described inner mechanical structure  200  of the ink-jet recording apparatus  100 , an example of paper transport paths  300  on each route of which a sheet of recording paper  250 , recording paper  254 , and cardboard paper  256 , is transported. 
         FIG. 5  is an enlarged view that schematically illustrates an example of the configuration of a paper transport unit  320  in the inner mechanical structure  200 . 
         FIG. 6  is a perspective view that schematically illustrates an example of the configuration of one of a plurality of driven roller holders  326  that are provided in the paper transport unit  320  illustrated in  FIG. 5 . 
         FIG. 7  is a diagram that schematically illustrates an example of the paper transport unit  320 , including its peripheral components, which is viewed from the rear side of the frame  220 . 
         FIG. 8  is a diagram that schematically illustrates the contact state of the driven roller holder  326 , where a pair of the transport driven rollers  324  is lowered to its contact position. 
         FIG. 9  is a diagram that schematically illustrates the non-contact state of the -driven roller holder  326 , where the pair of the transport driven rollers  324  is raised to its non-contact position. 
         FIG. 10  is a diagram that schematically illustrates an example of the configuration of a system  500  that is configured to operate the ink-jet recording apparatus  100 . 
         FIG. 11  is a flowchart F 100  that illustrates an example of the control procedures executed by the control unit  360 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Although the invention is described below while explaining an exemplary embodiment thereof, the specific embodiment described below is not intended to limit the scope of the invention recited in the appended claims and thus should in no case be understood to restrict thereof; nor is it always necessary to encompass all of features and/or a combination(s) thereof that are discussed in the following embodiment as means for solving the problem identified by the invention. 
       FIG. 1  is a front perspective view that schematically illustrates an example of the general appearance of an ink-jet recording apparatus  100  that is provided with a transportation apparatus that constitutes a transportation unit  320  of the ink-jet recording apparatus  100 . As illustrated in the drawing, the outer body chassis of the ink-jet recording apparatus  100  is configured as a housing case  101  that has the shape of a substantially rectangular parallelepiped. 
     On the upper surface of the housing case  101 , a transportation target material (paper) feeding unit cover  110 , a transportation target material (paper) transport path cover  120 , and an ink cartridge holder cover  130  are provided in the order of appearance herein when viewed from the rear end thereof. A user can open the paper feeder cover  110  in a direction shown by an arrow C in the drawing by hooking their finger(s) on a cover-opening slit  112  and then lifting the finger-hooked portion of the paper feeder cover  110 . As the user raises the finger-hooked portion thereof, the paper feeder cover  110  hinges with its rear end functioning as a turn axis. When the paper-feeding unit cover  110  is opened, a transportation target material feeding unit  310 , which will be described later, appears as its inner component. A user can also open the paper transport path cover  120  and the ink cartridge holder cover  130  in a direction shown in the drawing by arrows B and A, respectively. Each of the paper transport path cover  120  and the ink cartridge holder cover  130  hinges with its rear end functioning as a turn axis. As the paper transport path cover  120  is opened, a paper transport path, which a sheet of recording target medium  250  that is now under recording passes through, appears as its inner component. With such a structure, a user can perform various kinds of troubleshooting and/or maintenance work on the inner transport path. For example, a user can remove a sheet of recording paper that is stuck or jammed on the inner transport path. The ink cartridge holder cover  130  is configured to extend from the upper face of the housing cover  101  to the front face thereof. An inner cartridge holder  230  is exposed when a user opens the ink cartridge holder cover  130 . With such a structure, a user can attach, from the front-face side of the ink-jet recording apparatus  100 , ink cartridges  232  to the cartridge holder  230  in a detachable manner. They can also remove the ink cartridges  232  from the cartridge holder  230  after opening the ink cartridge holder cover  130 . 
     A transportation target material ejecting unit cover  140  is provided at a position under the ink cartridge holder cover  130  on the front face of the housing case  101 . A discarded-ink collection cartridge cover  150  is provided on the right side of the paper-ejecting unit cover  140  on the front face of the housing case  101 . A user can open the paper-ejecting unit cover  140  and the discarded-ink collection cartridge cover  150  in a direction shown in the drawing by arrows D and E, respectively. Each of the paper-ejecting unit cover  140  and the discarded-ink collection cartridge cover  150  hinges with its lower end functioning as a turn axis. When a user opens the paper-ejecting unit cover  140 , a transportation target material ejection unit  340 , which ejects a sheet of recording paper  250  after completion of recording thereon, is exposed as its inner component. On the other hand, a user can replace an old (i.e., filled) discarded-ink collection cartridge  152  with new one after opening the discarded-ink collection cartridge cover  150 . 
     The ink-jet recording apparatus  100  is provided with an operation panel  160 , which is provided at the proximal right end of the upper surface of the housing case  101  thereof. The operation panel  160  has manual operation buttons  162  and a liquid crystal display panel  164 . The manual operation buttons  162  are used for manipulating the ink-jet recording apparatus  100  directly (i.e., not through data communication). The liquid crystal panel  164  displays the manipulation status and other information. With such a configuration, a user can operate the ink-jet recording apparatus  100  as a standalone device while monitoring its operation/manipulation status displayed on the liquid crystal display panel  164 . 
       FIG. 2  is a rear perspective view that schematically illustrates an example of the general appearance of the ink-jet recording apparatus  100  illustrated in  FIG. 1 . As illustrated in the drawing, a cover-opening slit  122  that provides a finger-hold for opening the paper transport path cover  120  is formed in the upper surface of the housing case  101 . A manual-feeding paper transport path cover  170  is provided on the rear surface of the housing case  101 . A user can open the manual-feeding paper transport path cover  170  in a direction shown by an arrow F in the drawing. The manual-feeding paper transport path cover  170  hinges with its lower end functioning as a turn axis. As a user opens the manual-feeding paper transport path cover  170 , an inner path for transporting a sheet of recording paper  254  that is manually fed is exposed. Through the manual-feeding paper transport port, they can insert/feed a sheet of recording paper  254  into the ink-jet recording apparatus  100 . 
       FIG. 3  is a perspective view that schematically illustrates an example of the configuration of an inner mechanical structure  200  that appears when the housing case  101  is removed from the ink-jet recording apparatus  100 .  FIG. 3  takes the same observation angle/point as that of  FIG. 1 . As illustrated in the drawing, the inner mechanical structure  200  is provided both at the front side and at the rear side of a frame  220  that extends in a longitudinal direction of the ink-jet recording apparatus  100 . 
     The paper-feeding unit  310 , which is exposed when the paper-feeding unit cover  110  is opened, is provided at the back of the frame  220 . The paper-feeding unit  310  has a paper support  210 , which is formed on the reverse face of the paper-feeding unit cover  110 , and a hopper  212  that is provided below the paper support  210 . The paper support  210  holds a plurality of sheets of recording paper  250  that are stacked from the backside of the stacked paper  250 . While moving forward and backward, the hopper  212  functions to press the uppermost one of the above-mentioned plurality of sheets of recording paper  250  against a paper-feeding roller  312 , which will be described later. 
     In front of the frame  220 , a paper transport unit  320 , a platen  330 , and a paper-ejecting unit  340  are provided. The paper transport unit  320  is provided at a position closest to the frame  220  among these three components, whereas the paper-ejecting unit  340  is provided at a position remotest to the frame  220  among these three components. A carriage  260  is provided above the platen  330 . The cartridge holder  230  is provided above the paper-ejecting unit  340 . 
     The cartridge holder  230  is fixed to the front end of the frame  220 . A plurality of ink cartridges  232  each of which contains ink is detachably attached to the cartridge holder  230 . As a non-limiting exemplary configuration, for example, each one of nine illustrated ink cartridges  232  that are detachably attached to the cartridge holder  230  contains the corresponding one among nine colors of ink, that is, photo black ink, mat black ink, gray ink, yellow ink, cyan ink, light cyan ink, magenta ink, light magenta ink, and red ink. Each of the ink cartridges  232  that are detachably attached to the cartridge holder  230  is in communication with the carriage  260  through a flexible tube that is not shown in the drawing. With such a configuration, each of the ink cartridges  232  supplies ink to a recording head  262  that is provided at the bottom face of the carriage  260 . 
     The carriage  260  reciprocates along a guide axis  280  so as to travel across the entire length (i.e., width) of the platen  330 . A timing belt  270  is provided in front of the frame  220 . The timing belt  270  is wound around a pair of pulleys (not shown in the drawing) each of which is provided in the proximity of a side end of the frame  220 . The timing belt  270  moves horizontally between the pair of pulleys in accordance with the rotation thereof. The carriage  260  is fixed to the timing belt  270 . As the timing belt  270  moves, so does the carriage  260 . 
     The discarded-ink collection cartridge  152  that is attached at the front portion of the right end of the frame  220  has an ink absorption member. The ink absorption member absorbs ink that has been discarded by the carriage  260  for the purpose of cleaning its nozzles at a home position that is located on the right side of the platen  330 . The amount of ink discarded and accumulated in the discarded-ink collection cartridge  152  increases as the cumulative operation time of the ink-jet recording apparatus becomes longer. A periodical or timely replacement of an old discarded-ink collection cartridge  152  with a new cartridge makes it possible to maintain a high ink absorption capability thereof for a long time period. 
       FIG. 4  is a sectional view that schematically illustrates, in the above-described inner mechanical structure  200  of the ink-jet recording apparatus  100 , an example of a paper transport path  300  on which a sheet of recording paper  250  is transported. As illustrated in the drawing, the ink-jet recording apparatus  100  has a plurality of paper transport channels (i.e., paths/routes) through which recording paper  250 , which is a ink-discharging target medium onto which the recording head  262  mounted on the bottom of the carriage  260  discharges ink drops, can be fed and transported. 
     The main paper transport channel that is likely to be used most frequently among the plurality of paper transport channels takes/offers the following route; that is, recording paper  250  that has been fed at the paper support  210  goes through the paper-feeding unit  310 , the paper transport unit  320 , the paper-ejecting unit  340 , in the order of appearance herein, and then gets ejected out of the paper-ejecting unit  340 . The transport operation of this paper transport channel is explained below. Among a plurality of sheets of recording paper  250  stacked on the paper support, the lower end of the hopper  212  moves forward so as to press the uppermost sheet of the recording paper  250  against the paper-feeding roller  312 . A driving motor that is not shown in the drawing drives the paper-feeding roller  312  so as to rotate the paper-feeding roller  312 . As the paper-feeding roller  312  rotates, the recording paper  250  that is pressed by the hopper  212  against the paper-feeding roller  312  is drawn downward. Then, the recording paper  250  is pinched between the paper-feeding roller  312  and a retard roller  314 . In the course of the above operation, since the lower end of the hopper  212  moves backward, rest of the recording paper  250  is separated from the uppermost sheet of the recording paper  250  by the functioning of the retard roller  314 . In addition, paper-returning hook member  311  functions to return, to the paper support  210 , other recording paper  250  that is drawn together though not intended to be done so when the paper-feeding target recording paper  250  is drawn downward. Then, upon reaching of the paper-feeding target recording paper  250  that has been fed by the paper-feeding roller  312  to the paper transport unit  320 , a contact between the recording paper  250  and the roller contact surface of the paper-feeding roller  312 , which has the shape resembling an alphabet D in its cross section, is released. By this means, the paper transport unit  320  takes over the transportation of the recording paper  250  from the D-shaped paper-feeding roller  312 . 
     The paper transport unit  320  is provided with a transport driving roller  322  and a transport driven roller  324 . A driving motor that is not shown in the drawing rotates the transport driving roller  322 . The transport driven roller  324  is urged against the transport driving roller  322 . The transport driven roller  324  follows the rotary movement of the transport driving roller  322 . The recording paper  250  that is fed between the transport driving roller  322  and the transport driven roller  324  is pressed against the transport driving roller  322  by the transport driven roller  324 . Then, as the transport driving roller  322  rotates, the recording paper  250  is transported onto the platen  330 . 
     While supporting the recording paper  250  that is now under transportation from the reverse side thereof (or, in other words, from a lower side), the platen  330  determines the height of the recording paper  250 . The recording head  262  that is mounted on the bottom of the carriage  260  discharges ink drops downward toward the height-determined target recording paper  250 . By this means, an ink image is formed on the surface of the recording paper  250 . The recording paper  250  with a printed image formed thereon further moves forward. Then, the front edge of the recording paper  250  reaches the paper-ejecting unit  340 . A paper position detection unit  332 , which detects whether the recording paper  250  is present or not, is provided at an upstream position that is immediately before the platen  330 , which is viewed along the transportation direction of the recording paper  250 . Another paper position detection unit  332  having the same function as above is also provided at a downstream position that is immediately after the platen  330 , which is viewed along the transportation direction of the recording paper  250 . With such a configuration, a control unit  360 , which will be described later, is capable of making a detection as to whether any recording paper  250  is actually present on the platen  330  or not. 
     The paper-ejecting unit  340  is provided with an ejection driving roller  342  and a pair of ejection driven rollers  344 . A driving motor that is not shown in the drawing rotates the ejection driving roller  342 . The ejection driven roller  344  is urged against the ejection driving roller  342 . The ejection driven roller  344  follows the rotary movement of the ejection driving roller  342 . The recording paper  250  that is fed between the ejection driving roller  342  and the ejection driven roller  344  is pressed against the ejection driving roller  342  by the ejection driven roller  344 . Then, as the ejection driving roller  342  rotates, the recording paper  250  is ejected out of the ink-jet recording apparatus  100 . 
     The ink-jet recording apparatus  100  is further provided with the control unit  360 , which is responsible for controlling the operations of the ink-jet recording apparatus  100 . The control unit  360  is provided at the rear/reverse side of the lower end of the frame  220 . The control unit  360  performs control on the basis of a command/instruction that is inputted into the ink-jet recording apparatus  100  via an information processing device or the like that is connected to the ink-jet recording apparatus  100  or on the basis of a command/instruction that is inputted through the operation panel  160  in order to ensure the proper operations of the ink-jet recording apparatus  100 . In addition to the above, the control unit  360  further functions as an interface for receiving information on an image that is to be printed. Image information that is received by the control unit  360  may contain, in addition to the image information itself, information on recording quality such as the resolution of an image, the number of colors thereof, though not limited thereto. In addition, it may further contain information on a recording target medium such as paper size and/or material thereof, though not limited thereto. 
     The ink-jet recording apparatus  100  has a manual-feeding paper transport path that has a feeding port inside the manual-feeding paper transport path cover  170 . That is, a user can directly (i.e., manually) feed recording paper  254  just in front of the paper transport unit  320  after opening the manual-feeding paper transport path cover  170  that is provided on the rear face of the housing case  101 . With such a configuration, the ink-jet recording apparatus  100  offers another paper transport channel, which is provided separately from the afore-mentioned main paper transport channel that mechanically feeds the recording paper  250  stacked on the paper support  210 . That is, as done on the recording paper  250  that is fed from the paper support  210  automatically, the second paper transport channel makes it possible to perform image recording on the manually-fed recording paper  254 , which could be used on a temporarily basis, and then to eject the printed paper on the front side of the ink-jet recording apparatus  100 . 
     In addition, the ink-jet recording apparatus  100  has still another paper transport channel that can be used to perform image recording on a thick type of paper that is not flexible, that is, in this example, a cardboard paper  256  that is not bendable. To use this cardboard paper transport path, a user opens the paper-ejecting unit cover  140  so as to expose an inner cardboard paper transport port, which is not shown in the drawing. Then, the user feed the cardboard paper  256  through the opened port. The cardboard paper transport path, which is configured to be a level horizontal route, passes through a clearance/gap between the recording head  262  and the platen  330  to reach the rear face of the ink-jet recording apparatus  100 . 
     Since the thick cardboard paper  256  has high flexural/bending rigidity, the load of transport increases significantly if it is bent somewhere in the middle of the paper transport path. For this reason, it is necessary to retract the transport driven roller  324  upward when the cardboard paper transport path is in use. When the cardboard paper transport port is opened, the control unit  360  detects that the recording operation of the cardboard paper  256  is started. Upon detection thereof, the control unit  360  reverses the operation of the paper-ejecting unit  340 . By this means, the cardboard paper  256  is moved backward until the front edge of the recording surface area of the cardboard paper  256  reaches a point under the recording head  262 . Next, the control unit  360  returns the operation of the paper-ejecting unit  340  to its normal rotation so as to transport the cardboard paper  256  forward while recording an image thereon. As described above, the paper transport path  300  of the ink-jet recording apparatus  100  has a plurality of paper transport channels. Depending on the type and/or character of the transportation target medium, for example, the recording paper  250 , the recording paper  254 , or the cardboard paper  256 , a user can select suitable one for performing recording operation. 
       FIG. 5  is an enlarged view that schematically illustrates an example of the configuration of the paper transport unit  320  in the inner mechanical structure  200 . As illustrated in the drawing, the transport driven roller  324  is attached to one end of a driven roller holder  326 . The transport driven roller  324  is mounted thereto over the transport driving roller  322 , both ends of which ( 322 ) are supported by the frame  220 , so that the transport driven roller  324  applies a contact force (i.e., pressing force) against the transport driving roller  322  from the above. The driven roller holder  326  is supported by the frame  220  in such a manner that it can move in a rotating direction (i.e., draw/trace an arc) around a turn axis  328 . The other end of the driven roller holder  326  is raised/lowered by a cam  321  that turns around a camshaft  323 . The cam  321  and the other end of the driven roller holder  326  are provided at the rear-face side of the frame  220 . As the cam  321  raises/lowers the other end of the driven roller holder  326 , it is possible to lower/raise the transport driven roller  324  that is attached to the above-described one end (i.e., opposite to “cam end”) of the driven roller holder  326 . 
       FIG. 6  is a perspective view that schematically illustrates an example of the configuration of one of a plurality of the driven roller holders  326  that are provided in the paper transport unit  320  illustrated in  FIG. 5 . As illustrated in the drawing, the driven roller holder  326  is configured as a flat-shaped resin component having an integrally molded body as a whole. The turn axis  328  is also formed to constitute a part of the integrally molded body The turn axis  328  is formed to protrude at middle side (left/right) regions between a front region and a back region thereof. The driven roller holder  326  supports, substantially at the front end thereof, a pair of the transport driven rollers  324 . 
     Each of the driven roller holders  326  has a spring  329  that stands in the center region of the driven roller holder  326 . As described later, when the driven roller holder  326  is attached to the frame  220 , the spring  329  is fixed to the frame  220  with its rear end being set in a standing position. The spring  329  applies an urging force to the driven roller holder  326  in a direction to lower the pair of the transport driven rollers  324 . On the other hand, the front end of the spring  329  contacts the central region, or in the proximity thereof, of the front end of the driven roller holder  326 . 
     The driven roller holder  326  has many ribs  327  formed as a part of integrally molded body to have high flexural/bending rigidity. Although the driven roller holder  326  has good flexural/bending stiffness, it is subjected to mechanical stress because, as has already been described above, on one hand, the cam  321  that raises the transport driven roller  324  applies a contact/pressing force to the rear end of the driven roller holder  326 , while on the other hand, the spring  329  applies an urging force to the front end thereof. For this reason, plastic deformation could occur on the driven roller holder  326  if the transport driven roller  324  continues to be raised for a long time period. 
       FIG. 7  is a diagram that schematically illustrates an example of the driven roller holders  326  and their peripheral components illustrated in  FIG. 5 , which are viewed from the rear side of the frame  220 . As illustrated in the drawing, each rear end of the driven roller holder  326  is protruded through the rear face of the frame  220 . A plurality of the driven roller holders  326 , the number of which may be determined arbitrarily depending on the length of the transport driving roller  322 , are provided. A cam  321  is provided for each of the plurality of the driven roller holders  326 . One end of the spring  329  is fixed to the frame  220  for each of the driven roller holders  326 . 
     The plurality of cams  321  is supported by a camshaft  323  above the driven roller holders  326  at the rear side of the frame  220 . As the camshaft  323  turns, so does each of the cams  321 . As each of the cams  321  rotates, the rear end of the corresponding driven roller holder  326  is lowered. When the cams  321  lower the rear ends of the driven roller holders  326 , the transport driven rollers  324  that are attached to the opposite end (i.e., front end) thereof are raised. On the other hand, since each of the springs  329  applies an urging force to the corresponding driven roller holder  326 , the rear ends of the driven roller holders  326  are raised when the cams  321  are oriented in a direction illustrated in the drawing. Since the rear ends of the driven roller holders  326  are raised, the transport driven rollers  324  are lowered. The lowered transport driven rollers  324  contact the transport driving roller  322 . In other words, it is possible to check whether the transport driven rollers  324  are in a raised non-contact position or not by checking the orientation of the cams  321 . 
       FIG. 8  is a diagram that schematically illustrates the “contact state” of the driven roller holder  326  illustrated in  FIGS. 6 and 7 , where a pair of the transport driven rollers  324  is lowered to its contact position. As illustrated in the drawing, the front end (i.e., the left end in the drawing) of the driven roller holder  326  is lowered so that the transport driven rollers  324  are in contact with the transport driving roller  322 . Since the spring  329  is fixed to the rear face of the frame  220  with its rear end being set in a standing position, the front end of the driven roller holder  326  is urged downward by the spring  329 . However, the urging force of the spring  329  is not exerted on the driven roller holder  326  because the spring  329  applies its pressing force right on the transport driven rollers  324 , which contact the transport driving roller  322 . 
       FIG. 9  is a diagram that schematically illustrates the “non-contact state” of the driven roller holder  326 , where a pair of the transport driven rollers  324  is raised to its non-contact position. As illustrated in the drawing, in order to move the transport driven roller  324  to its non-contact position, the cam  321  applies a pressing force of P 2  onto the rear end, or in the neighborhood thereof, of the driven roller holder  326  downward so as to turn the driven roller holder  326 . As the driven roller holder  326  turns, the front end thereof is raised so that the transport driven roller  324  moves apart from the transport driving roller  322 . While the rear end of the driven roller holder  326  is pressed down, the spring  329  continues to apply an urging force Pi onto the front end thereof, intensively. The driven roller holder  326  is supported indirectly from the frame  220  at its approximately center by means of the turn axis  328 . As a result of such static mechanical stress that is applied/exerted onto the driven roller holder  326  for a long time period, a creep strain could occur thereon, which is made of resin. Finally, the creep deformation could eventually cause the front end of the driven roller holder  326  to sag. 
       FIG. 10  is a diagram that schematically illustrates an example of the configuration of a system  500  that is configured to operate the ink-jet recording apparatus  100  described above. As illustrated in the drawing, in the system  500 , the ink-jet recording apparatus  100  is connected to an information processing apparatus  510 , which serves as a host apparatus, via a cable  518  that is connected to the control unit  360  of the ink-jet recording apparatus  100 . The information processing apparatus  510  is provided with a keyboard  512  and a computer mouse  514 , which constitute input means for accepting instructions or the like from a user, and a display apparatus  520  that displays images to the user. 
     The information processing apparatus  510  is further provided with a disc drive  516  for reading/writing information from/into a storage medium and with a telecommunication line (not shown in the drawing) for performing data communication with an external communication device, server, or the like. With such a configuration, in addition to image information that is created by the information processing apparatus  510  by itself, the information processing apparatus  510  is able to acquire image information that is to be recorded (i.e., printed out) by the ink-jet recording apparatus  100  from a storage medium that is inserted in the disc drive  516 , via the communication line, or the like. In addition, the information processing apparatus  510  may read/download, and then install, a program for controlling the ink-jet recording apparatus  100  from an external source. 
       FIG. 11  is a flowchart F 100  that illustrates an example of the control flow applied by the control unit  360  to the cam  321 . As illustrated in the drawing, when a cardboard paper transport port is opened so as to enter the ink-jet recording apparatus  100  into a standby state in which the ink-jet recording apparatus  100  waits for the initiation of the recording operation on the target cardboard paper  256 , the control unit  360  starts the following series of control operations performed on the paper transport unit  320  (step S 101 ). 
     Upon initiation of the series of control operations, as a first step thereof, the control unit  360  makes a judgment as to whether the transport driven roller  324  is currently distanced, that is, raised, at a position apart from the transport driving roller  322  or not (referring to such a non-contact state, the term “non-contact position” is used in the following description as well as the appended claims) (step S 102 ). If it is judged that the transport driven roller  324  is currently in a lowered position to be in contact with the transport driving roller  322  (referring to such a contact state, the term “contact position” is used in the following description as well as the appended claims) (step S 102 : NO), the control unit  360  ends the controlling of the paper transport unit  320  because there is no risk of the plastic deformation of the driven roller holder  326  when it is in the contact state (step S 108 ). 
     On the other hand, if it is judged that the transport driven roller  324  is currently in the non-contact position (step S 102 : YES), the control unit  360  checks the length of time period (i.e., duration) of the non-contact state in which the transport driven roller  324  stays (i.e., continues to be) at the non-contact position. Then, the control unit  360  further makes a judgment as to whether the length of time period in which the transport driven roller  324  continues to be at the non-contact position exceeds a certain predetermined threshold period or not (step S 104 ). If it is judged that the length of time period in which the transport driven roller  324  continues to be at the non-contact position is not more than the certain predetermined threshold period (step S 104 : NO), the process returns to the preceding step S 102 . Then, the above-described judgment process is repeated until the length of time period in which the transport driven roller  324  continues to be at the non-contact position exceeds the certain predetermined threshold time period. 
     On the other hand, if it is judged that the length of time period in which the transport driven roller  324  continues to be at the non-contact position exceeds the certain predetermined threshold period (step S 104 : YES), the control unit  360  causes the cam  321  to turn. As a result thereof, the driven roller holder  326  is turned so as to move the transport driven roller  324  to the contact position (step S 105 ). By this means, it is possible to prevent the occurrence of a creep deformation on/of the stress-applied the driven roller holder  326  by releasing it. 
     Next, after moving the transport driven roller  324  to the contact position, the control unit  360  makes a judgment as to whether there is any cardboard paper  256  on the cardboard paper transport path or not (step S 106 ). If it is judged that a cardboard paper  256  is present on the cardboard paper transport path (step S 106 : YES), the control unit  360  issues an error message so as to alert the user (step S 109 ). When the user removes the detected cardboard paper  256  in response to the alert error message, the control unit  360  confirms the clearance of the error state (step S 110 : YES). Then, the control unit  360  ends the series of control processing (step S 108 ). On the other hand, if the outstanding error state is not cleared (step S 110 : NO), the control unit  360  returns the process to the previous step S 106 . 
     If it is judged that there is no cardboard paper  256  on the cardboard paper transport path (step S 106 : NO), the control unit  360  further checks whether the cardboard paper transport port is opened or not (step S 107 ). If it is judged that the cardboard paper transport port is closed (step S 107 : NO), the control unit  360  ends the positional control of the transport driven roller  324  because, if it is closed, it is in the same state as in a stand-by mode prior to usual recording operations, that is, normal recording in which the cardboard paper transport path is not used. On the other hand, if it is judged that the cardboard paper transport port is opened (step S 107 : YES), the control unit  360  issues an error message so as to alert the user to either close the cardboard paper transport port or move the transport driven roller  324  to the non-contact position (step S 109 ). Then, the control unit  360  waits for the user to clear the error state in response to the issued alert error message (step S 110 ). 
     As explained above, the ink-jet recording apparatus  100  according to an exemplary embodiment of the invention is configured to lower (a pair of) the transport driven roller(s)  324  so as to make it contact the transport driving roller  322  if the length of time period in which the transport driven roller  324  continues to be raised against the urging/pressing force of the spring  329  applied/exerted downward exceeds a certain predetermined threshold time period. With such a configuration, the invention makes it possible to effectively prevent the occurrence of plastic deformation of the driven roller holder  326  due to the mechanical stress applied by the spring  329 . Since it is not necessary to anticipate the plastic deformation of the driven roller holder  326 , it is not necessary to set a gap between the transport driven roller  324  and the transport driving roller  322  at a large distance. Accordingly, it is not necessary to increase the size of the ink-jet recording apparatus  100  just for the purpose of maintaining the gap between the transport driven roller  324  and the transport driving roller  322 . In addition, it is also not necessary to disadvantageously increase the mechanical strength of the driven roller holder  326  by means of costly material or any other similar means. Thus, the invention offers a cost advantage when manufacturing the ink-jet recording apparatus  100 . 
     Although the present invention is described while explaining the exemplary embodiments thereof, the technical scope of the invention is in no case limited to the explicit and implicit description of the above embodiments of the invention. It is clear and obvious for a person skilled in the art that the above embodiments of the invention may be subjected to various alterations, adaptations, modifications, or improvements thereof. From the recitation of the appended claims, it is clear and obvious that such an altered, adapted, modified, or improved mode is also encompassed by the technical scope of the invention.