Patent Publication Number: US-7896339-B2

Title: Sheet transporting apparatus and sheet processing apparatus using the same

Description:
This is a divisional application of application Ser. No. 10/657,130, filed on Sep. 9, 2003, now U.S. Pat. No. 7,404,557 which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet transporting apparatus disposed in a sheet transportation path. More particularly, the present invention relates to improvements of a sheet transporting apparatus in which, in a mode where the position of a side edge of a sheet is regulated, the sheet regulation position can be adjusted, and a sheet processing apparatus using such a transporting apparatus. 
     2. Background Art 
     A sheet processing apparatus such as a copier or a printer incorporates a sheet transporting apparatus which transports a sheet such as a paper sheet along a predetermined path. In a sheet transporting apparatus of this kind, a predetermined number of transportation rolls are arranged in a sheet transportation path. Each of the transportation rolls is rotatingly driven with using a motor or the like as a drive source. A sheet is transported from the upstream side to the downstream side in the transportation direction in accordance with the rotations of the transportation rolls. 
     In such a sheet transporting apparatus, when a sheet is transported in an inclined state, a so-called skew often occurs in the sheet. When a sheet in a skewed state is fed to a sheet processing section, a predetermined process is applied to the skewed sheet. When a skewed sheet is fed to an image output position of an image forming section, for example, an image which is inclined with respect to the sheet is output. Therefore, a sheet aligning apparatus for deskewing a transported sheet is usually used. 
     As one of aligning systems used in sheet aligning apparatuses, known is a system in which a skew is corrected by regulating the position of a side edge of a sheet. In the aligning system, a side guide is disposed on one side of a sheet transportation path along the transportation direction, and a skew roll is placed in the sheet transportation path. A transported sheet is laterally moved toward the side guide by the skew roll to butt against the side guide, thereby correcting the skew (side skew) of the sheet. 
     JP-A-7-206225 discloses an example of a sheet processing apparatus comprising such a sheet aligning apparatus. The apparatus has a configuration in which a sheet aligning apparatus is configured as one unit, the sheet aligning apparatus is extractably attached to the main unit of the sheet processing apparatus, and, under the attachment state, positioning is performed by butting a side guide of the sheet aligning apparatus against a stopper member of the main unit of the sheet processing apparatus. 
     In order to properly deskew a sheet in a sheet aligning apparatus, a reference line of a side guide must be placed strictly parallel to the sheet transportation direction, and a side edge of the sheet must extend along the reference line. When the reference line of the side guide is inclined with respect to the transportation direction, the sheet is transported with this inclination. As a result, the sheet is improperly deskewed. 
     By contrast, in the apparatus of JP-A-7-206225, since the sheet aligning apparatus is configured as one unit, the whole of the unit (sheet aligning apparatus) must be inclined in order to adjust the inclination of the reference line of the side guide. Therefore, the adjusting work is performed on a large scale and in a complicated manner, and fine adjustment is hardly conducted. 
     In order to eliminate the defects, the inventors of the invention provided a sheet transporting apparatus including: a sheet aligning section which has a reference member (such as a side guide) that is placed parallel to the transportation direction on one side of a sheet transportation path, and which causes a side edge of the sheet to elongate along a reference line set by the reference member; and an inclination adjusting section which has a rotation operating mechanism for rotatably supporting the reference member about a support shaft that is disposed in the transportation direction downstream from the sheet aligning section, and in which the inclination of the reference line with respect to the sheet transportation direction is adjusted by the rotation operating mechanism (see JP-A-2003-081490). 
     According to the configuration, the work of adjusting the inclination may be simplified as compared with the case where the whole unit is inclined. 
     In the configuration, the inclination of the reference member is adjusted by the single adjusting mechanism (rotation operating mechanism). When the adjusting step of the adjusting mechanism is finely set, therefore, fine adjustment after an initialization has been once set can be performed in a relatively simple manner. In a case where, for example, a transportation roll serving as a peripheral part of the sheet aligning apparatus is replaced with another one, when the inclination angle of the reference member is to be reinitialized, the work of adjusting the inclination of the reference member requires a prolonged time period because of the fine adjustment step of the adjusting mechanism, and the workability remains to be poor. 
     In the configuration, before a job, the inclination adjustment of the reference member can be uniquely performed in accordance with the kind of the job, the sheet size, and the environment. In the case where the inclination adjustment of the reference member is to be performed in the middle of the job, however, it is often to hardly cope with such adjustment, particularly when the inclination of the reference member must be adjusted by a large degree. 
     In double-side printing, for example, the same sheet is continuously transported, and the sheet transportation face is changed from a first face to a second face. In this case, the front-rear relationship of the sheet is usually inverted, and hence it is often necessary to change the reference line of the reference member before the regulation of the side edge position of the sheet. 
     In this case, the line of the side edge position of the sheet is inverted. Therefore, the adjustment width of the inclination of the reference member is inevitably increased. Since the adjustment is performed during a job, the time period for the inclination adjustment is restricted. As a result, the inclination of the reference member is hardly adjusted during the process of inversion-transporting a sheet. 
     SUMMARY OF THE INVENTION 
     The invention has been conducted in order to solve the technical problems. It is an object of the invention to provide a sheet transporting apparatus in which a sheet regulation position can be adjusted easily and correctly by a side position regulating mechanism, and a sheet processing apparatus using such a transporting apparatus. 
     To achieve the object, the invention provides a sheet transporting apparatus, including: a sheet transportation path; a predetermined number of transport members disposed in a sheet transportation path; a side position regulating mechanism which regulates a position of a side edge of a sheet in the sheet transportation path, the side position regulating mechanism having a reference member configured to change a sheet regulation position; a base member on which at least the reference member is mounted; a first adjusting mechanism which adjusts a position of the reference member; and a second adjusting mechanism which adjusts a position of a base member. 
     The invention provides a sheet transporting apparatus which transports a sheet to a processing section via a sheet transportation path. The sheet transporting apparatus includes: a sheet aligning mechanism which aligns a transportation posture of the sheet transported toward the processing section; wherein the sheet aligning mechanism includes an adjusting mechanism which automatically adjusts the transportation posture of the sheet in accordance with a deformation degree of the sheet. 
     Further, the invention provides a sheet processing apparatus, including: a sheet transportation path; a sheet processing section disposed in a sheet transportation path; a predetermined number of transport members disposed in a sheet transportation path; a side position regulating mechanism which regulates a position of a side edge of a sheet in the sheet transportation path, the side position regulating mechanism having a reference member configured to change a sheet regulation position; a base member on which at least the reference member is mounted; a first adjusting mechanism which adjusts a position of the reference member; and a second adjusting mechanism which adjusts a position of a base member. 
     The invention provides a sheet processing apparatus, including: a sheet transportation path; a sheet processing section disposed in a sheet transportation path, and a sheet aligning mechanism which aligns a transportation posture of the sheet transported toward the processing section; wherein the sheet aligning mechanism includes an adjusting mechanism which automatically adjusts the transportation posture of the sheet in accordance with a deformation degree of the sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be more readily described with reference to the accompanying drawings; 
         FIG. 1  is a diagram schematically showing the sheet transporting apparatus of the invention. 
         FIG. 2  is a diagram showing the whole configuration of an embodiment of a sheet processing apparatus into which the sheet transporting apparatus of the invention is incorporated. 
         FIG. 3  is a plan view showing main portions of the sheet transporting apparatus used in the embodiment. 
         FIG. 4  is a perspective view showing a transportation unit used in the embodiment. 
         FIG. 5  is a plan view of the transportation unit of  FIG. 4 . 
         FIG. 6  is a plan view showing a state where an upper cover is removed away from the transportation unit of  FIG. 4 . 
         FIG. 7  is a view showing a first adjusting mechanism used in the embodiment. 
         FIG. 8  is a view looking in the direction of VIII in  FIG. 7 . 
         FIG. 9  is a perspective view looking the transportation unit of  FIG. 4  from the rear side. 
         FIG. 10  is a view looking in the direction of X in  FIG. 4 . 
         FIG. 11  is a view showing a driving system of a second adjusting mechanism used in the embodiment. 
         FIG. 12  is a perspective view of the driving system of  FIG. 11 . 
         FIG. 13  is a plan view of the driving system of  FIG. 12 . 
         FIG. 14  is a diagram showing a side shifting mechanism for a registration roll. 
         FIG. 15  is a perspective view of the side shifting mechanism. 
         FIG. 16  is a block diagram showing a control system used in the embodiment. 
         FIG. 17  is a flowchart showing a process of controlling a sheet regulation position used in the embodiment. 
         FIGS. 18A and 18B  are diagrams showing processes of adjusting the sheet regulation position in the embodiment. 
         FIG. 19A  is a diagram showing a state of transporting a sheet in double-side printing. 
         FIG. 19B  is a diagram showing a process of adjusting the sheet regulation position in double-side printing. 
         FIG. 20  is a plan view showing main portions of a sheet transporting apparatus used in an embodiment of the invention. 
         FIG. 21  is a view showing a side position regulating mechanism used in the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the invention will be described in detail referring the accompanying drawings. 
     The apparatus of the invention is a sheet transporting apparatus in which, as shown in  FIG. 1 , a predetermined number of transport members  2  (for example,  2   a  to  2   c ) are disposed in a sheet transportation path  1 , wherein the apparatus includes; a side position regulating mechanism  3  which regulates a position of a side edge of a sheet S in the sheet transportation path  1 ; a first adjusting mechanism  4  which adjusts a position of a reference member  3   a  that can change a sheet regulation position m in the side position regulating mechanism  3 ; and a second adjusting mechanism  6  which adjusts a position of a base member on which at least the reference member  3   a  of the side position regulating mechanism  3  is mounted. 
     In the technical means, the side position regulating mechanism  3  may be selected from a wide variety of mechanisms such as those of the side guide system and the sensor guide system. 
     In the side guide system, the side position regulating mechanism includes: a side guide  8  which is disposed on a side of the sheet transportation path  1  and correspondingly with the side edge position of the sheet S; and a skew member  9  which skew-transports the sheet S toward the side guide  8 . The skew member may have any one of configurations such as that the transportation direction of the sheet S is fixedly determined, and that the transportation direction is changed in accordance with the motion of the sheet S. 
     In the sensor guide system, the side position regulating mechanism comprises: at least two position sensors (not shown) which are disposed correspondingly with the side edge position of the sheet S; and a shift transportation roll (not shown) which nip-transports the sheets, and which is movable perpendicularly to a transportation direction of the sheet S. 
     The first adjusting mechanism  4  may be selected from a wide variety of mechanisms which can adjust the position of the reference member  3   a  of the side position regulating mechanism  3 . The terms “reference member  3   a ” indicate a member which can change the sheet regulation position m, and mean the side guide  8  in the side guide system, or a sensor support member in the sensor guide system. 
     The second adjusting mechanism  6  may be selected from a wide variety of mechanisms which can adjust the position of the base member  5  on which the reference member  3   a  of the side position regulating mechanism  3  is mounted. In this case, it is not required to mount the whole of the side position regulating mechanism  3  on the base member  5 , and at least the reference member  3   a  which is directly related to the sheet regulation position m is requested to be included. 
     The adjusting mechanisms  4 ,  6  may be adjusted by any kind of system. Preferably, a system which swings the mechanism around one swing fulcrum may be preferably employed. 
     The first adjusting mechanism  4  may support the reference member  3   a  that can change the sheet regulation position m in the side position regulating mechanism  3 , in a manner that the reference member is swingable about a swing fulcrum with respect to the base member  5 . The second adjusting mechanism  6  may support the base member  5  on which at least the reference member  3   a  of the side position regulating mechanism  3  is mounted, in a manner that the base member is swingable about a swing fulcrum. 
     The first adjusting mechanism  4  or the second adjusting mechanism  6  may operate in one of manual and automatic manners, or in both of manual and automatic manners. 
     As a typical configuration of the first adjusting mechanism  4  or the second adjusting mechanism  6  in which automatic adjustment is enabled, at least one of the first adjusting mechanism  4  and the second adjusting mechanism  6  may be configured so that a drive source is coupled to the reference member  3   a  or the base member  5  via a driving transmitting mechanism. 
     In a preferred configuration relating to the adjustment steps of the first adjusting mechanism  4  and the second adjusting mechanism  6 , one of the first adjusting mechanism  4  and the second adjusting mechanism  6  can perform the adjustment by a coarse adjustment step, and the other adjusting mechanism can perform the adjustment by a fine adjustment step. According to the configuration, the coarse and fine adjustment steps allow the sheet regulation position m to be adjusted correctly and rapidly. 
     In the configuration, among the first adjusting mechanism  4  and the second adjusting mechanism  6 , the mechanism of the fine adjustment step (for example, the first adjusting mechanism  4 ) operates with being linked with the mechanism of the coarse adjustment step (for example, the second adjusting mechanism  6 ). In this case, the adjusting mechanisms  4 ,  6  can function without interfering with each other. 
     In the configuration, preferably, the first adjusting mechanism  4  and the second adjusting mechanism  6  are combinedly used. However, it is not always required to combine the mechanisms. Of course, under a situation where the adjustment of the sheet regulation position m is very small, for example, only one of the mechanisms may be used. 
     The sheet transporting apparatus is regarded as a control system, the invention can be considered so as to comprise a controlling device  7  which controls the adjusting mechanisms  4 ,  6 . 
     In a specific example of the control by the controlling device  7 , in accordance with usage conditions of the sheet S, the controlling device adjusts at least one of the first and second adjusting mechanisms  4 ,  6 . In the above, “usage conditions of the sheet S” include a wide variety of conditions of using the sheet S, such as the kind of the sheet, the size of the sheet, the environment, the conditions of processing the sheet S, and the direction of the transportation face of the sheet S. In a typical configuration in which the sheet regulation position m must be adjusted during a job, particularly, the usage conditions of the sheet S include the direction of the transportation face of the sheet S. 
     When a change of the transportation posture due to the deformation degree of the sheet (such as the degree of deformation caused in sheet cutting) is considered, the invention may be regarded as follows. 
     In this case, the apparatus of the invention is a sheet transporting apparatus which transports a sheet to a predetermined processing section via a sheet transportation path, wherein the apparatus includes a sheet aligning mechanism which aligns a transportation posture of the sheet transported toward the processing section, and the sheet aligning mechanism comprises an adjusting mechanism which automatically adjusts the transportation posture of the sheet in accordance with a deformation degree of the sheet. 
     In this configuration, when the sheet processing section is to apply a reprocess on a rear face of a sheet in which a front face has been processed, a typical example of the adjusting mechanism of the sheet aligning mechanism automatically adjusts the transportation posture of the sheet in accordance with the deformation degree of the sheet. 
     The apparatus may further includes a controlling device which controls the adjusting mechanism of the sheet aligning mechanism, and the sheet deformation degree may be previously supplied to the controlling device. Alternatively, the controlling device may comprise a measuring section which measures the sheet deformation degree. 
     The invention is not restricted to the sheet transporting apparatus, and may be directed to a sheet processing apparatus using such a sheet transporting apparatus. In this case, as shown in  FIG. 1 , the apparatus of the invention is a sheet processing apparatus having a sheet processing section (not shown) in the sheet transportation path  1 , wherein the above-described sheet transporting apparatus is disposed in the sheet transportation path  1 . 
     Next, embodiments of the invention will be explained. 
     Embodiment 1 
       FIG. 2  is a diagram showing Embodiment 1 of a sheet processing apparatus to which the invention is applied. 
     Referring to the figure, the sheet processing apparatus of the embodiment comprises: an image formation unit  21  incorporating an image forming module  30  which employs a so-called tandem intermediate transfer system; a sheet supply unit  22  which is juxtaposed with the image formation unit  21  to supply a sheet (not shown) such as a paper sheet to the image formation unit  21 ; and a postprocess unit  23  which is juxtaposed with the image formation unit  21  to apply a postprocess on a sheet that has been subjected to the image forming process by the image formation unit  21 . 
     In the embodiment, the image formation unit  21  incorporates the image forming module  30  which forms toner images of color components (for example, yellow (Y), magenta (M), cyan (C), and black (K)) by, for example, the electrophotographic method. In the image forming module  30 , photosensitive drums  31  (specifically,  31 Y,  31 M,  31 C, and  31 K) on which color component toner images are respectively formed and carried are arranged in parallel. The color component toner images formed on the photosensitive drums  31  are sequentially primary-transferred to an intermediate transfer belt  40 . The color component toner images on the intermediate transfer belt  40  are secondary-transferred to a recording sheet supplied from the sheet supply unit  22  by a secondary transfer roll  50 . The sheet is then guided to a fixing device  60 . 
     In the embodiment, electrophotographic devices are sequentially arranged around each of the photosensitive drums  31 . The electrophotographic devices include: a uniform charging device (not shown) which charges the photosensitive drum  31 ; a laser exposing device  33  which writes an electrostatic latent image on the photosensitive drum  31 ; a developing device  34  which houses a toner of the corresponding color component, and which develops the electrostatic latent image on the photosensitive drum  31 ; a primary transfer roll  35  which transfers the color component toner image on the photosensitive drum  31  to the intermediate transfer belt  40 ; and a cleaner  36  which removes away residual toner on the photosensitive drum  31 . 
     The intermediate transfer belt  40  is circularly transported while being stretched by a plurality (in this example, five) of stretch rolls  41  to  45 . For example, the stretch roll  41  is configured as a driving roll, and the other stretch rolls  42  to  45  are configured as driven rolls. One of the stretch rolls  42  to  45 , e.g., the stretch roll  43  functions as a tension roll for applying tension to the intermediate transfer belt  40 . 
     In the embodiment, a portion of the intermediate transfer belt  40  opposed to the stretch roll  44  is set as a secondary transfer position. The secondary transfer roll  50  is disposed in contact with the surface of the intermediate transfer belt  40  at the secondary transfer position. A transfer bias is applied between the secondary transfer roll  50  and the stretch roll  44  (functioning as a backup roll) which is opposed to the secondary transfer roll. 
     In the embodiment, as shown in  FIG. 2 , the sheet supply unit  22  has multiple (in the example, three) sheet supply trays  71  to  73 . The sheet supply trays  71 ,  72  house plain paper sheets of different sizes, and the lowermost large-capacity sheet supply tray  73  houses special sheets including stiff sheets such as coated paper or cardboard. 
     In the embodiment, each of the sheet supply trays  71 ,  72  has a feeder  74  on the side opposite to the image formation unit  21 , and the sheet supply tray  73  has a feeder  74  on the side of the image formation unit  21 . 
     A sheet transportation path from the sheet supply trays  71 ,  72  is configured as a bypass transportation path  77  which is upward directed from the side of the sheet supply unit  22  opposite to the image formation unit  21 , directed toward the image formation unit  21  with using the upper space, and then downward directed. 
     By contrast, a sheet transportation path from the sheet supply tray  73  is configured as a direct transportation path  78  which elongates in a substantially linear manner toward the image formation unit  21 . The direct transportation path  78  and the bypass transportation path  77  are communicatingly joined to a combined transportation path  79  so that a recording sheet is fed through an exit  80  toward the image formation unit  21 . 
     Plural paired transportation rolls  81  are disposed at predetermined intervals in the bypass transportation path  77 , the direct transportation path  78 , and the combined transportation path  79  of the sheet supply unit  22 . 
     In a unit case  220  of the sheet supply unit  22 , a cover  100  which opens and closes the bypass transportation path  77  is disposed in a portion opposite to the image formation unit  21 . 
     The cover  100  swings with using an inner side of the unit case  220  as a swing fulcrum, and rotatably holds one of paired transportation rolls  81  ( 81   a ,  81   b ), or the driven roll  81   b . When the cover is opened, the driving roll  81   a  and the driven roll  81   b  of the transportation rolls  81  are separated from each other. 
     In the embodiment, in a horizontal transportation path portion of the bypass transportation path  77  of the sheet supply unit  22 , a coupling transportation path  101  is formed so as to horizontally elongate toward the side opposite to the image formation unit  21 . The coupling transportation path  101  functions as a transportation path which, in the case where another sheet supply unit (not shown) is placed adjacent to the sheet supply unit  22 , receives a recording sheet supplied from the other sheet supply unit to guide the sheet to the bypass transportation path  77 , or as an insertion portion for manually feeding a recording sheet to the sheet supply unit  22 . 
     In the embodiment, an image reading unit  24  and a user operating unit  25  are disposed above the sheet supply unit  22 . 
     The image reading unit  24  optical reads an image of a document placed on a document table, and is configured by a light source, a reflection mirror, an imaging lens, a CCD sensor, etc. 
     In the embodiment, as shown in  FIG. 2 , the postprocess unit  23  has an entrance opening  231  at a position of a unit case  230  corresponding to a recording sheet discharge port  211  which is opened in a unit case  210  of the image formation unit  21 . An exit opening  232  is opened at a position, of the unit case  230  in the side opposite to the image formation unit  21 . 
     In this example, the entrance opening  231  is disposed at a predetermined position of a lower portion (which is lower in level than one half of the height of the postprocess unit  23 ) of the postprocess unit  23 , the exit opening  232  is disposed at a predetermined position of an upper portion (which is higher in level than one half of the height of the postprocess unit  23 ) of the postprocess unit  23 , and a sheet discharge tray  233  is attached to the unit case  230  corresponding to the exit opening  232 . 
     An inclined transportation path  234  which is obliquely directed is disposed between the entrance opening  231  and the exit opening  232 . The inclined transportation path  234  branches to two paths. The branch transportation paths are provided with decurling devices  235 ,  236  for eliminating upcurls and downcurls, respectively. 
     An adequate number (in this example, three) of paired transportation rolls  237  are disposed in the inclined transportation path  234 . 
     The sheet transportation paths in the image formation unit  21  includes a path which reverses a sheet fed out from the fixing device  60 , and which returns the reversed sheet to the secondary transfer position, in addition to a path along which a sheet supplied from the sheet supply unit  22  is guided to the secondary transfer position and then passed through the fixing device  60  to be discharged toward the postprocess unit  23 . 
     In the sheet transporting apparatus of the embodiment, as shown in  FIGS. 2 and 3 , a sheet aligning device  82  is disposed upstream from the secondary transfer position, a registration roll  83  is disposed between the sheet aligning device  82  and the secondary transfer position, and a transportation belt  84  is disposed downstream from the secondary transfer position. 
     In  FIG. 3 ,  74  denotes a feeder which is disposed in each of the sheet supply trays  71  to  73 , and, for example, comprises a nudger roll  75  which pushes the sheets S, and a feed roll  76  which separates the pushed sheets S and then feeds the separated sheet. The reference numeral  81  denotes a typical one of transportation rolls (takeaway rolls), and  410  denotes a side shift sensor which is disposed immediately downstream from the registration roll  83  to detect a shift amount of the registration roll  83 . 
     A sheet returning mechanism used in the embodiment is used for transferring the sheet S fed from the fixing device  60  to an adequate number of transportation rolls  86  along a loop-like return path  85 . In the mechanism, a reversing portion (in this example, configured by using a lower space of the postprocess unit  23 )  87  is disposed in the middle of the return path  85 , and the sheet S is reversed through the reversing portion  87 . 
     A part of the return path  85  is communicatingly joined to the combined transportation path  79  with using a space in the sheet supply unit  22 . 
     The sheet aligning device  82  used in the embodiment will be described in detail. 
     The sheet aligning device  82  comprises a side position regulating mechanism  300  which regulates the position of a side edge of the sheet S in the sheet transportation path. 
     In the embodiment, the side position regulating mechanism  300  comprises a side guide  310  which is disposed on the side of the sheet transportation path, and a plurality (in this example, three) of skew rolls  321  to  323  disposed in the sheet transportation path. 
     The side guide  310  corresponds to the reference member in the invention. A reference face  311  of the side guide  310  is used for setting a sheet regulation position (reference line) m serving as a reference line for deskewing the sheet S. 
     Each of the skew rolls  321  to  323  is arranged with being inclined to the side guide  310  with respect to the transportation direction of the sheet S, and configured by a driving roll and a pinch roll (driven roll) which pressingly contact each other. The driving roll is inclinedly placed as illustrated. By contrast, the pinch roll is placed along the sheet transportation direction without being inclined. The driving roll and the pinch roll are placed so as to vertically sandwich the sheet transportation path. 
     In the embodiment, the sheet aligning device  82  comprises entrance swing rolls  330  upstream from the skew rolls  321  to  323  in the sheet transportation path. 
     The entrance swing rolls  330  are configured by paired driving rolls and pinch rolls, and arranged along the transportation direction of the sheet S. Unlike the other transportation rolls, at least the driving rolls are configured as split rolls of different diameters and on the same shaft, so that the received sheet S is transported with being slightly skewed in the direction opposite to the side guide  310 , thereby preventing interference between the sheet S and the side guide  310  from occurring. 
     In the embodiment, particularly, the sheet aligning device  82  and the registration roll  83  are incorporated in one transportation unit  340 . 
     In the transportation unit  340 , as shown in  FIGS. 3 to 6 , a unit case  341  is configured by putting a unit cover  343  on a unit base  342 , and the sheet aligning device  82  (the side position regulating mechanism  300  [the side guide  310 , the skew rolls  321  to  323 ], and the entrance swing rolls  330 ) and the registration roll  83  are mounted on the unit base  342  ( FIG. 6  shows a state where the unit cover  343  is detached from the unit case  341 ). 
     A first adjusting mechanism  350  for adjusting the position of the side guide  310  is disposed in the transportation unit  340 . 
     As shown in  FIGS. 6 to 8 , a downstream end in the sheet transportation direction of the side guide  310  is supported as a swing fulcrum (pivot)  351  on the unit base  342 , and a swing operating mechanism  352  is disposed in the vicinity of the other end of the side guide  310 . In the swing operating mechanism  352 , a guide motor  353  serving as a drive source is fixed to the unit base  342 , and the driving force of the guide motor  353  is transmitted to the other end of the side guide  310  through a drive transmission system  354 . 
     The drive transmission system  354  may be configured in the following manner. The driving force of the guide motor  353  is transmitted through a train of bevel gears  355 ,  356  to a drive transmission shaft  357  which is perpendicular to the shaft of the guide motor  353 . An eccentric cam  358  is secured to the drive transmission shaft  357 . A cam follower  359  which butts against the eccentric cam  358  is rotatably attached to the other end of the side guide  310  corresponding to the eccentric cam  358 . An urging spring  360  is attached to a position of the side guide  310  which is separated from the swing fulcrum  351  of the side guide  310 . The eccentric cam  358  and the cam follower  359  are placed so as to pressingly contact each other. 
     In the embodiment, for example, the guide motor  353  is configured by a step motor, and rotatingly driven in a predetermined range by driving pulses, so that the swing free end portion of the side guide  310  is swung by a degree corresponding to the eccentric distance due to the rotation of the eccentric cam  358 . In the embodiment, particularly, the guide motor  353  is set so as to have a fine unit rotation angle for each driving pulse. In  FIG. 8 ,  361  denotes a home sensor for detecting the initial position of the side guide  310 . When the position of a light shielding plate  362  protruded from the drive transmission shaft  357 , the initial position of the side guide  310  is detected. 
     In the embodiment, a second adjusting mechanism  370  for adjusting the position of the unit base  342  is disposed in the transportation unit  340 . 
     In the second adjusting mechanism  370 , as shown in  FIGS. 3 and 9  to  13 , a substantially middle portion of a downstream side in the sheet transportation direction of the bottom of the unit base  342  is swingably supported as a swing fulcrum (pivot)  371  on a frame which is not shown. A swing operating mechanism  372  is disposed in the side opposite to the swing fulcrum  371  of the unit base  342 . A predetermined number (in this example, four) of guide rollers  385  are disposed on the bottom of the unit base  342 . The guide rollers  385  are placed so as to be swingable about the swing fulcrum  371 . 
     In the swing operating mechanism  372 , a unit motor  373  serving as a drive source is fixed to the unit base  342 , and a drive transmission system  374  is interposed between the unit motor  373  and a fixation bracket  375  which is fixed to the frame (not shown). 
     The drive transmission system  374  is configured in the following manner. The driving force of the unit motor  373  is transmitted through a train  376  of several gears to a final drive transmission shaft  377 . An eccentric cam  378  is secured to the final drive transmission shaft  377 . A cam follower  380  is rotatably disposed correspondingly with the eccentric cam  378  on a support pin  379  which upstands from the fixation bracket  375 . An urging spring  383  is interposed between an engagement plate  381  fixed to the unit base  342 , and an engagement pin  382  fixedly formed on the fixation bracket  375 , thereby causing the eccentric cam  378  and the cam follower  380  to pressingly contact each other. 
     In the embodiment, for example, the unit motor  373  is configured by a step motor, and rotatingly driven in a predetermined range by driving pulses, so that the swing free end portion of the unit base  342  is swung by a degree corresponding to the eccentric distance due to the rotation of the eccentric cam  378 . In the embodiment, particularly, the unit rotation angle of the unit motor  373  for each driving pulse is set to be larger than that of the guide motor  353 . In  FIGS. 12 and 13 ,  386  denotes a home sensor for detecting the initial position of the unit base  342 . When the position of a fan-shaped light shielding plate  387  protruded from the final drive transmission shaft  377 , the initial position of the unit base  342  is detected. 
     In the embodiment, as shown in  FIGS. 4 ,  14 , and  15 , the registration roll  83  is supported so as to be laterally shiftable by a side shifting mechanism  400 . 
     In the side shifting mechanism  400 , the driving force of a shift motor  401  is reduction-transmitted to a drive transmission shaft  403  via a reduction gear train  402 , and a pinion  404  is disposed on the drive transmission shaft  403 . A shift rod  405  is coupled to an end portion of the registration roll  83  (in this example, a drive roll  83   a ) in a state where the registration roll  83  is allowed to rotate. A rack  406  is formed on the shift rod  405 . The pinion  404  is meshed with the rack  406 . 
     The reference numeral  408  denotes an urging spring which presses the shift rod  405 , and  409  denotes an urging spring which prevents rattling from occurring during an operation of shifting the registration roll  83 . The reference numeral  411  denotes a side shift home sensor which detects the home position of the registration roll  83 . 
     In the embodiment, the registration roll  83  is caused to perform nipping and releasing operations by a nipping/releasing mechanism  420 . 
     The nipping/releasing mechanism  420  transmits a driving force of a lift-up motor  421  through an eccentric cam (not shown) and a link arm  422  to cause a pinch roll  83   b  (see  FIG. 6 ) of the registration roll  83  to perform nipping and releasing operations. 
     A nipping/releasing mechanism (not shown) which is similar to that in this example is disposed for each of the skew rolls  321  to  323  (see  FIG. 3 ) so that nipping and releasing operations are performed at adequate timings. 
     In the embodiment, as shown in  FIG. 16 , a controlling device  500  is configured by a microcomputer system (a CPU  501 , a ROM  502 , a RAM  503 , and input and output interfaces  504 ,  505 ). The ROM  502  previously stores an image forming program, a sheet transportation program (including a sheet regulation position control program), etc. 
     In the controlling device  500 , the CPU  501  receives via the input interface  504  signals from: various mode selection switches (including a selection switch for initialization)  511 , and numeric keys  512 ; a switch  513  for selecting double side printing which is one of image forming modes; a sheet kind switch  514  for selecting sheets of various basis weights, an OHP sheet, and the like; sheet size sensors  515  which are disposed in the sheet supply trays  71  to  73  (see  FIG. 2 ) and the sheet transportation paths; environment sensors  516  of the humidity, the temperature, and the like; and path sensors  517  (including the side shift sensor  410  (see  FIG. 3 )) which detect the sheet passing state. The CPU  501  executes a predetermined process program to send predetermined control signals to a main transportation motor  520 , the shift motor  401 , the lift-up motor  421 , the guide motor  353 , the unit motor  373 , and the like through the output interface  505 , thereby controlling the corresponding control objects (such as the transportation rolls  81 , the registration roll  83 , the side guide  310 , and the unit base  342 ). 
     Next, the operation of the image forming apparatus of the embodiment will be described (while focusing on the sheet transporting apparatus). 
     As shown in  FIG. 2 , assuming that a sheet is fed from one of the sheet supply trays  71  and  72  of the sheet supply unit  22 , the sheet is fed from the exit  80  toward the image formation unit  21  through the bypass transportation path  77  and the combined transportation path  79 , and then transported to the secondary transfer position through the sheet aligning device  82  and the registration roll  83 . 
     Under this state, a color toner image formed by the image forming module  30  is transferred to the sheet, and the sheet which has undergone the transfer process is passed through the fixing device  60  and then transported toward the postprocess unit  23 . 
     In the postprocess unit  23 , the sheet is transported through the inclined transportation path  234 . During this process, under the condition that the sheet is curled, a postprocess (decurling) is performed in one of the decurling devices  235 ,  236 , and the sheet is then discharged onto the sheet discharge tray  233 . 
     A recording sheet fed from the sheet supply tray  73  is a special sheet such as coated paper or cardboard. Since the sheet is fed from the exit  80  toward the image formation unit  21  through the direct transportation path  78  and the combined transportation path  79 , the sheet can be transported to the secondary transfer position without particularly causing bending deformation or jamming. 
     In such an operation process, the process of transporting the sheet S to the secondary transfer position is performed as shown in  FIGS. 17 and 18 . 
     Referring to  FIG. 17 , when a print start button is depressed, the controlling device  500  receives signals from various switches and sensors such as the mode selection switches  511 , and knows the usage conditions of the sheet S (ST 1 , ST 2 ). Thereafter, the position of the side guide corresponding to the usage conditions of the sheet S is determined by, for example, searching table information which is previously set in accordance with the usage conditions of the sheet S (ST 3 ). It is judged whether the determined side guide position is different from the currently set side guide position or not (ST 4 ). 
     If it is judged that the determined side guide position is different from the current one, the controlling device  500  determines the rotation directions and driving pulses of the guide motor  353  and the unit motor  373  (ST 5 ). 
     At this time, the controlling device  500  determines whether both or one of the guide motor  353  and the unit motor  373  is driven, in accordance with the adjustment amount of the side guide  310 . 
     As a result, the guide motor  353  and/or the unit motor  373  is turned on, and, at a timing when the pulse number reaches the specified one, turned off (ST 6  to ST 8 ). 
     In this state, when only the guide motor  353  is to be driven, for example, the side guide  310  is adjusted by the first adjusting mechanism  350  driven by the guide motor  353  as shown in  FIG. 18A , to be swung about the swing fulcrum  351  from the position of the broken line to that of the solid line, so that the sheet regulation position m of the side guide  310  is determined. 
     By contrast, when both the guide motor  353  and the unit motor  373  are to be driven, for example, the side guide  310  is adjusted by the first adjusting mechanism  350  driven by the guide motor  353  as shown in  FIG. 18B , to be swung about the swing fulcrum  351  from the position of the broken line to that of the solid line, and further adjusted by the second adjusting mechanism  370  driven by the unit motor  373 , so that the unit base  342  on which the side guide  310  is mounted is swung about the swing fulcrum  371 . The sheet regulation position m of the side guide  310  is finally determined by the motions of the side guide and the unit base. 
     In this case, the first adjusting mechanism  350  can perform fine adjustment, and the second adjusting mechanism  370  can perform coarse adjustment. Even when the adjustment amount of the position of the side guide  310  is considerably large, therefore, the adjustment can be performed correctly and rapidly by combinedly using both the mechanisms. 
     When the sheet S thereafter passes over the side shift sensor  410  (see  FIG. 3 ), the processes of ST 2  to ST 10  are repeated until the print job is ended. 
     If it is judged in ST 4  that the side guide position determined by the controlling device  500  is identical with the current one, it is not necessary to change the position of the side guide  310 , and hence the control skips to ST 9 . 
     The case where a double side printing mode is implemented by the double side printing selection switch  513  is assumed as the usage conditions of the sheet S. During printing on one face, as shown in  FIG. 19A , the sheet S is transported while upward directing the sheet transportation face. It is assumed that, at this time, the reference edge Seg of the sheet S is caused by, for example, a cutting error of the sheet to be inclined as shown in the figure. 
     When printing is to be performed on the rear face of the sheet S, the sheet S in which printing has been performed on the front face is reversed, and hence the front-rear relationship of the sheet S is inverted, so that the sheet S is transported while downward directing the sheet transportation face. At this time, the reference edge Seg of the sheet S is inclined as illustrated, but the direction of the inclination is opposite to that in the printing on the front face. 
     When an aligning operation is performed on the sheet S while not changing the sheet regulation position m of the side guide  310  under this state, there is the possibility that the sheet transportation by means of the rear face of the sheet S is performed while being skewed. 
     In the embodiment, therefore, the direction of the transportation face of the sheet S is considered, and a system is employed in which, as shown in  FIG. 19B , the sheet regulation position m of the side guide  310  is changed in accordance with the front and rear faces of the sheet S. 
     When this system is employed, the sheet aligning mechanism configured by the side position regulating mechanism  300 , the first adjusting mechanism  350 , and the second adjusting mechanism  370  performs adjustment of the position of the side guide  310  depending on the front and rear faces of the sheet S to align the transportation posture of the sheet. Therefore, the reduction of the image quality due to a skew of the sheet S can be effectively avoided. 
     In this case, deformation degrees of the sheet S depending on the front and rear faces of the sheet  3  may be previously stored into the memory (the RAM  503 ) of the controlling device  500  shown in  FIG. 16 . Alternatively, a device for measuring the deformation degree of a sheet (such as a sheet edge detector using a line sensor) is disposed in the sheet transportation path, and the deformation degree of the sheet S may be measured in each transportation. 
     It is a matter of course that the adjustment of the transportation posture of a sheet in accordance with the deformation degree of the sheet can be applied also to a configuration in which one of the adjusting mechanisms  350  and  370  is disposed in the side position regulating mechanism  300 . 
     In the embodiment, as shown in  FIGS. 2 and 3 , after the side position of the sheet S is regulated by the sheet aligning device  82 , the sheet is nipped and laterally shifted by a predetermined amount by the registration roll  83 , and then fed to the transfer section. 
     This is performed in order to prevent a damage due to a contact between the side guide  310  and the sheet S from occurring. 
     At this time, the shifting, and nipping and releasing operations of the registration roll  83  are controlled in the following manner. 
     Referring to  FIGS. 3 and 16 , when the tip end of the sheet S is transported to the registration roll  83  to reach the side shift sensor  410  in the downstream of the registration roll  83 , the controlling device  500  controls the shift motor  401  so as to forward rotate, thereby starting the shifting operation of the registration roll  83 . 
     At a timing before the sheet S is nipped by the registration roll  83  and the registration roll  83  starts the shifting operation, the nipping operations of the skew rolls  321  to  323  are canceled. 
     The sheet S nipped by the registration roll  83  is moved in accordance with the shifting operation of the registration roll  83 , and the side shift sensor  410  is turned off. Then, the controlling device  500  stops the shift motor  401  after elapse of a timer time T 1 . 
     Thereafter, the sheet S is transported to the secondary transfer position. After elapse of a timer time T 2 , the controlling device  500  drives the lift-up motor  421  to lift the pinch roll  83   b  (see  FIG. 6 ) of the registration roll  83 , thereby canceling the nipping operation of the registration roll  83 . 
     After an elapse of a timer time T 3  from the cancellation of the nipping operation of the registration roll  83 , the controlling device  500  controls the shift motor  401  so as to reversely rotate, the side shift home sensor  411  is turned off, and the shift motor  401  is stopped after an elapse of a timer time T 4 . 
     By contrast, when the controlling device  500  detects that the sheet S passes over the registration roll  83  (for example, the side shift sensor  410  detects the rear end of the sheet S), the controlling device drives the lift-up motor  421  to cause the registration roll  83  to perform the nipping operation, so that the sheet transporting apparatus is prepared for the next sheet. 
     In the embodiment; when the sheet regulation position of the side guide  310  is to be initialized, as shown in  FIG. 16 , the mode selection switch  511  corresponding to selection of an initializing setting mode is operated, and the amount of initialization by the first adjusting mechanism  350 , and that of initialization by the second adjusting mechanism  370  are then set with using the numeric keys  512 , etc. 
     In the embodiment, the system in which both the first and second adjusting mechanisms  350  and  370  can be automatically operable is structured. Alternatively, at least one of the adjusting mechanisms may be configured so as to be manually operable (for example, an operation knob may be disposed in place of the motor serving as a drive source). 
     For example, the first adjusting mechanism  350  is set to be automatically operable, and the second adjusting mechanism  370  is set to be manually operable. In the process of initialization or maintenance, also the second adjusting mechanism  370  is used in addition to the first adjusting mechanism  350 , and, in a usual job, only the first adjusting mechanism  350  is used. 
     Embodiment 2 
       FIG. 20  is a diagram showing main portions of a sheet transporting apparatus of Embodiment 2. 
     Referring to the figure, the basic configuration of the sheet transporting apparatus has a sheet aligning device  82  which aligns the side edge position of the sheet S in a substantially same manner as Embodiment 1. However, the side position regulating mechanism  300  of the sheet aligning device  82  is different from that of Embodiment 1. The components identical with those of Embodiment 1 are denoted by the same reference numerals, and their detailed description is omitted. 
     In the embodiment, as shown in  FIGS. 20 and 21 , the side position regulating mechanism  300  comprises: two position sensors  601 ,  602  which are disposed on a side of the sheet transportation path and on a reference line corresponding to the sheet regulation position m; and shift transportation rolls  611 ,  612  which nip-transport the sheet S, and which are movable perpendicularly to the sheet transportation direction. 
     The position sensors  601 ,  602  are attached onto a sensor support member  605  corresponding to the reference member in the invention. The first adjusting mechanism  350  is disposed on the sensor support member  605 . The first adjusting mechanism  350  performs a swing operation with using a downstream end portion in the sheet transportation direction of the sensor support member  605  as a swing fulcrum (pivot)  606 , and can be configured in a substantially same manner as that of Embodiment 1. The second adjusting mechanism  370  performs a swing operation with using a downstream end portion in the sheet transportation direction of the unit base  342  as the swing fulcrum  371 , and is configured in a substantially same manner as that of Embodiment 1. 
     The adjusting mechanisms  350 ,  370  are controlled by a controlling device which is substantially similar to that of Embodiment 1. 
     The shift transportation rolls  611 ,  612  are supported by rotation driving mechanisms  621 ,  622  and side shifting mechanisms  631 ,  632 , respectively. 
     Each of the rotation driving mechanism  621 ,  622  is configured so that a driving force of a drive motor  623  is transmitted to a shaft  625  of a shift transportation roll  611  or  612  through a transmission gear train  624 . 
     Each of the side shifting mechanisms  631 ,  632  is configured in the following manner. A shift rod  633  is coupled to an end portion of the shift transportation roll  611  or  612 . A rack  634  is disposed on the shift rod  633 . A pinion  635  is disposed on a shaft of a shift motor  636 , and the pinion  635  is meshed with the rack  634 . 
     According to the embodiment, when the sheet S is transported in a skewed state, as shown in  FIG. 21 , a side portion of the sheet S crosses one or both of the position sensors  601 ,  602 . Then, the corresponding shift transportation roll  611  or  612  is laterally shifted while transporting the sheet, thereby correcting the skewed state of the sheet S. 
     The sheet regulation position m due to the position sensors  601 ,  602  is adjusted by adjusting the position of the sensor support member  605  by the first adjusting mechanism  350 , and by further adjusting the position of the unit base  342  of the transportation unit  340  by the second adjusting mechanism  370 . 
     As described above, according to the sheet transporting apparatus of the invention, the first and second adjusting mechanisms are disposed for the side position regulating mechanism. When the two adjusting mechanisms are efficiently combined with each other, therefore, the sheet regulation position in the side position regulating mechanism can be adjusted easily and correctly. 
     In the invention, when a controlling device for controlling each of the adjusting mechanisms is disposed, the adjusting mechanisms can be efficiently controlled in accordance with, for example, a sheet usage condition. Therefore, the adjustment of the sheet regulation position can be optimized. 
     In a sheet processing apparatus using a sheet transporting apparatus of this kind, the property of transporting a sheet can be stabilized, and hence a process failure due to a skew of a sheet can be surely avoided. 
     According to another mode of the invention, the transportation posture of a sheet by a sheet aligning mechanism can be aligned in accordance with the deformation degree of the sheet. Therefore, a change in the sheet transportation posture caused by a cutting error of a sheet or the like can be surely adjusted.